JP6016015B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a lithium secondary battery and other non-aqueous electrolyte secondary batteries that can be applied to a vehicle-mounted power source.

  A secondary battery such as a lithium secondary battery or a nickel hydride battery is preferably used as a power source mounted on a vehicle using electricity as a driving source or a power source mounted on a personal computer, a portable terminal, or other electrical products. In particular, lithium secondary batteries and other non-aqueous electrolyte secondary batteries that are lightweight and have a high energy density are becoming increasingly important as high-output power supplies for vehicles such as electric vehicles and hybrid vehicles. In such a non-aqueous electrolyte secondary battery, when performing the charging process, for example, when the battery to be charged is a defective battery, or when the charging device breaks down and malfunctions, the battery is more than normal. If an electric current is supplied, it will fall into an overcharge state and there exists a possibility that a malfunction may arise. Therefore, in order to prevent such troubles, a mechanism (current interrupt device: CID: Current Interrupt Device) that detects an overcharge state based on battery temperature, battery internal pressure, etc., and interrupts the current when an overcharge state is detected. The provided battery is adopted.

  In the secondary battery provided with the CID, a gas generating agent such as cyclohexylbenzene (CHB) or biphenyl (BP) is contained in the electrolytic solution. The gas generating agent reacts to generate gas before the electrolyte is decomposed when the battery is overcharged. Utilizing this, the amount of increase in the battery internal pressure and the rate of increase when the battery is overcharged are increased, and the operating accuracy of the CID against overcharge is increased. Patent document 1 is mentioned as literature which is equipped with CID and has disclosed the secondary battery which contains a gas generating agent in nonaqueous electrolyte.

  In addition, the conventional secondary battery has a basic configuration in which a porous separator is disposed between the positive electrode and the negative electrode. In this type of prior art, Patent Document 4 discloses a water-based secondary battery in which an auxiliary separator is disposed at the center of a wound electrode body for the purpose of preventing a short circuit.

JP 2006-324235 A JP 2000-090959 A

When the gas generating agent present in the secondary battery equipped with the CID is overcharged, it emits electrons on the positive electrode side to become radical cations. This radical cation further reacts (for example, radical cations are polymerized), and a large amount of H ⁺ is generated at that time. This H ⁺ moves in the electrode body and is reduced on the surface of the negative electrode, whereby hydrogen gas (H ₂ ) is generated. By this hydrogen gas, the internal pressure in the battery rises and the CID operates. This is a typical example of the action of the gas generating agent in an overcharged state.

However, the radical cation of the gas generating agent may move to the negative electrode side instead of staying on the positive electrode side and be reduced to the original gas generating agent. The reduced gas generant returns to the positive electrode side and can become a radical cation again. As described above, the phenomenon (reaction) in which the gas generating agent or its radical cation moves back and forth between the positive and negative electrodes is called a shuttle reaction of the gas generating agent. When this shuttle reaction occurs, a reaction that generates a large amount of H ⁺ (for example, polymerization of radical cations) is not sufficiently performed, and a sufficient amount of gas may not be generated during overcharge.

  Thus, as a result of intensive studies, the present inventors have found that the shuttle reaction is promoted in a high temperature environment and that the shuttle reaction can be effectively suppressed by increasing the distance between the positive and negative electrodes. did. And based on these discoveries, it came to complete this invention.

  The present invention relates to an improvement in a non-aqueous electrolyte secondary battery that includes a CID and includes a gas generating agent in the non-aqueous electrolyte. The object of the present invention is to improve the operation accuracy of the CID in an overcharged state and to provide battery characteristics. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery in which the decrease in the temperature is suppressed.

In order to achieve the above object, according to the present invention, a wound electrode body formed by winding a positive electrode and a negative electrode, a non-aqueous electrolyte containing a gas generating agent, and a current interruption mechanism that operates when the internal pressure of the battery case increases. A non-aqueous electrolyte secondary battery is provided. In this non-aqueous electrolyte secondary battery, the wound electrode body is located outside a region A including the innermost peripheral portion of the wound electrode body in a cross section perpendicular to the winding axis. And region B. Further, the inter-electrode distance _{D A} between the positive and negative electrodes in the region A, the interelectrode distance _{D B} between the positive and negative electrodes in the region B _satisfy the relationship of D A> _{D B.}

  According to such a configuration, the distance between the positive and negative electrodes in the winding center side region (region A) of the wound electrode body that tends to be in a high temperature state is the distance between the positive and negative electrodes in the wound outer region (region B). Become bigger. Thereby, the shuttle reaction of the gas generating agent on the winding center side that tends to be in a high temperature state is effectively suppressed, and the amount of gas generated in the overcharged state is increased. Due to this increase in the amount of gas generated, the operating accuracy of the CID in the overcharged state is improved. Further, in this configuration, deterioration of battery characteristics is suppressed. Therefore, according to the present invention, a nonaqueous electrolyte secondary battery is provided in which the accuracy of CID operation in an overcharged state is improved and the deterioration of battery characteristics is suppressed. In the present specification, the “distance between electrodes” means the shortest distance between the positive electrode and the negative electrode facing each other, and typically the shortest distance between one surface of the positive electrode and the negative electrode surface facing the one surface. Shall be pointed to.

In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the region A is a region that occupies 10 to 30% of the wound thickness of the wound electrode body. By the thickness of more than 10% Kai wound of the wound electrode body large area A of the inter-electrode distance D _A, the shuttle reaction of the gas generating agent in the prone winding center side to a high temperature state is effectively suppressed In addition, the tendency to increase the amount of gas generated in the overcharged state is increased. By setting the region A to be 30% or less of the wound thickness, the tendency to suppress the deterioration of the battery characteristics (typically the increase in battery resistance) is increased. That is, by setting the thickness of the region A in the above range, it is possible to further increase the gas generation amount while maintaining the battery characteristics at a high level. In the present specification, “winding thickness of the wound electrode body” means from the innermost inner surface (winding inner surface) to the outermost outer surface (winding outer surface) of the wound electrode body. Point to the shortest distance.

In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, a ratio of the interelectrode distance D _{A to} the interelectrode distance D _B (D _A / D _B ) is 1.5 <(D _A / D _B ) <3. By setting the ratio (D _A / D _B ) to 1.5 or more, it is possible to more effectively suppress the shuttle reaction of the gas generating agent on the winding center side that tends to be in a high temperature state. In addition, by setting the ratio (D _A / D _B ) to 3 or less, it is possible to further suppress deterioration in battery characteristics.

In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, a separator is disposed between the positive electrode and the negative electrode, and the relationship of D _A > D _B is the separator in the region A. This is realized by arranging at least two layers. The at least double separators are a first separator disposed from the region A to the region B, and a second separator disposed in the region A but not disposed in the region B. And preferably. By configuring in this way, it is possible to suitably realize a configuration in which the distance between the poles in the winding center side region is larger than that in the winding outer region. The thickness of the second separator is more preferably 20 μm or more and 40 μm or less.

  In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, the porosity of the second separator is larger than the porosity of the first separator. By comprising in this way, the 2nd separator which contributes to the gas generation amount increase at the time of overcharge increases the tendency which does not inhibit the passage property of a charge carrier (for example, Li ion in the case of a lithium ion secondary battery). Further, the second separator improves the retention of the nonaqueous electrolyte on the winding center side.

  In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, the wound thickness of the wound electrode body is 15 mm or more. The larger the wound electrode body, the lower the heat dissipation on the winding center side, and the higher the temperature tends to be. Since the shuttle reaction of the gas generating agent is easily promoted at a high temperature, the large amount of battery tends to decrease the amount of gas generated on the winding center side. According to the present invention, since the shuttle reaction of the gas generating agent on the winding center side is effectively suppressed, the secondary battery using the wound electrode body having a large wound thickness as described above is overcharged. An increase in the amount of gas generated is preferably realized.

  The non-aqueous electrolyte secondary battery disclosed here has improved CID operating accuracy in an overcharged state, and suppressed deterioration of battery characteristics. Moreover, the effect can be suitably exhibited in a large-sized secondary battery in which the winding center of the wound electrode body is likely to become high temperature. Therefore, taking advantage of this feature, it can be suitably used as a large-sized secondary battery such as a drive power source of a vehicle such as a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), and an electric vehicle (EV). According to the present invention, there is provided a vehicle equipped with any of the non-aqueous electrolyte secondary batteries disclosed herein (which may be in the form of an assembled battery in which a plurality of batteries are connected).

It is a figure which shows typically the structure of the lithium secondary battery which concerns on one Embodiment. It is a figure which shows typically the structure of the winding electrode body of FIG. It is a figure which shows typically the cross section orthogonal to the winding axis | shaft of the winding electrode body of FIG. FIG. 5 is a cross-sectional view corresponding to FIG. 3 and schematically showing another configuration example of a wound electrode body. It is a figure which expands and shows a part between positive and negative electrodes in the area | region A of the wound electrode body of FIG. It is a figure which expands and shows a part between positive and negative electrodes in the area | region B of the winding electrode body of FIG. It is a side view showing typically a vehicle (automobile) provided with a lithium secondary battery concerning one embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than the matters specifically mentioned in the present specification and matters necessary for carrying out the present invention (for example, the configuration and manufacturing method of the electrode body including the positive electrode and the negative electrode, the shape of the battery (case), etc., General techniques related to battery construction, etc.) can be grasped as design matters of those skilled in the art based on conventional techniques in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action are described with the same reference numerals, and overlapping descriptions may be omitted or simplified.

  As a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, a lithium secondary battery will be described as an example. However, the application target of the present invention is not intended to be limited to such a battery. For example, the present invention can also be applied to a non-aqueous electrolyte secondary battery that uses a metal ion (for example, sodium ion) other than lithium ion (Li ion) as a charge carrier. In the present specification, “secondary battery” generally refers to a battery that can be repeatedly charged and discharged. In addition to a storage battery (ie, a chemical battery) such as a lithium secondary battery, a capacitor (ie, a physical battery) such as an electric double layer capacitor. ). Further, in this specification, the “lithium secondary battery” refers to a secondary battery that uses Li ions as electrolyte ions and is charged / discharged by the movement of charges accompanying Li ions between the positive and negative electrodes. A battery generally called a lithium ion secondary battery is a typical example included in the lithium secondary battery in this specification.

  FIG. 1 is a diagram schematically illustrating a configuration of a lithium secondary battery according to an embodiment. As shown in FIG. 1, the lithium secondary battery 100 includes a rectangular battery case 50 and a wound electrode body 80 accommodated in the battery case 50. A non-aqueous electrolyte (non-aqueous electrolyte) 90 is also accommodated in the battery case 50. The non-aqueous electrolyte 90 is impregnated in the wound electrode body 80. The battery case 50 includes a flat box-shaped case main body 52 having an opening on the upper surface, and a lid 54 that closes the opening. The opening of the case body 52 is sealed by the lid 54 after the wound electrode body 80 is accommodated in the case body 52 from the opening. Thus, the inside of the battery case 50 is sealed, so that the lithium secondary battery 100 becomes a sealed battery.

  A positive electrode terminal 70 and a negative electrode terminal 72 are provided on the upper surface (lid 54) of the battery case 50. The positive electrode terminal 70 is electrically connected to a positive electrode current collector plate 74 attached to one end in the width direction of the positive electrode (positive electrode sheet) 10. The negative electrode terminal 72 is electrically connected to a negative electrode current collector plate 76 attached to one end of the negative electrode (negative electrode sheet) 20 in the width direction.

  In the battery case 50, a CID 30 that is operated by an increase in the internal pressure of the battery case 50 is provided. The CID 30 is provided between the positive electrode terminal 70 fixed to the lid body 54 and the wound electrode body 80. When the internal pressure of the battery case 50 increases and reaches a predetermined pressure, the CID 30 reaches the positive electrode 10. The conductive path is configured to be electrically disconnected.

  The CID 30 includes a deformed metal plate 32 and a connection metal plate 34 joined to the deformed metal plate 32. The deformed metal plate 32 has an arch-shaped curved portion 33 having a central portion curved downward. The peripheral portion of the curved portion 33 is connected to the lower surface of the positive electrode terminal 70 via the current collecting lead terminal 35. Further, a part (tip) of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34 at a joint point 36. A positive electrode current collector plate 74 is joined to the lower surface (back surface) of the connection metal plate 34, and the positive electrode current collector plate 74 is connected to the positive electrode 10 of the wound electrode body 80. In this way, a conductive path from the positive electrode terminal 70 to the positive electrode 10 is formed.

  The CID 30 also includes an insulating case 38 formed of plastic. The material of the insulating case is not limited to plastic, and any material having insulating properties and airtightness may be used. The insulating case 38 is provided so as to surround the deformed metal plate 32. An opening for fitting the curved portion 33 of the deformed metal plate 32 is formed in the insulating case 38, and the curved portion 33 of the deformed metal plate 32 is fitted into the opening to seal the opening. doing. As a result, since the inside of the insulating case 38 is kept in a sealed state, the internal pressure of the battery case 50 does not act above the sealed curved portion 33. On the other hand, the internal pressure of the battery case 50 acts on the lower surface of the curved portion 33 outside the insulating case 38. In the CID 30 having such a configuration, when the internal pressure of the battery case 50 increases due to the overcharge current, the internal pressure acts to push up the curved portion 33 curved downward of the deformed metal plate 32. This action (force) increases as the internal pressure of the battery case 50 increases. When the internal pressure of the battery case 50 exceeds the set pressure, the curved portion 33 is inverted upside down. That is, the curved portion 33 is deformed so as to bend upward. Due to the deformation of the curved portion 33, the connection at the junction 36 between the deformed metal plate 32 and the connection metal plate 34 is broken. As a result, the conductive path is electrically disconnected and the current is interrupted.

  In this embodiment, the deformed metal plate 32 is deformed in the CID 30 but is not limited to this. When the internal pressure of the battery case rises, it is not the first member (the member disposed at the position of the deformed metal plate 32 of the present embodiment) disposed above but the second member (the member of the present embodiment) disposed below. The member arranged at the position of the connecting metal plate 34) may be deformed and separated from the other to electrically disconnect the conductive path, and both the first member and the second member It may be deformed. The CID as described above may be provided not only on the positive terminal side but also on the negative terminal side. Further, the CID electrically disconnects a conductive path that conducts at least one of the positive and negative electrodes and an external terminal (positive electrode terminal or negative electrode terminal) exposed to the outside of the battery case when the internal pressure of the battery case increases. What is necessary is just to be comprised, and it is not limited to a specific shape and structure. Furthermore, CID is not limited to what performs the mechanical cutting | disconnection accompanied with a deformation | transformation of the 1st member mentioned above and / or the 2nd member. For example, it may be a CID provided with an external circuit that detects the internal pressure of the battery case with a sensor and interrupts the charging current when the internal pressure detected by the sensor exceeds a set pressure.

  FIG. 2 is a diagram schematically showing the configuration of the wound electrode body of FIG. 1, and shows a long sheet structure (electrode sheet) in the previous stage of constructing the wound electrode body 80. As shown in FIG. 2, the wound electrode body 80 includes a long sheet-like positive electrode (positive electrode sheet) 10 and a long sheet-like negative electrode (negative electrode sheet) 20. The positive electrode sheet 10 includes a long positive electrode current collector 12 and a positive electrode mixture layer 14 formed on at least one surface (typically both surfaces) of the positive electrode current collector 12. The negative electrode sheet 20 includes a negative electrode current collector 22 and a negative electrode mixture layer 24 formed on at least one surface (typically both surfaces) of the negative electrode current collector 22.

  The wound electrode body 80 also includes two long sheet-like separators (separator sheets) 40A and 40B. The positive electrode sheet 10 and the negative electrode sheet 20 are stacked via two separator sheets 40A and 40B. In FIG. 2, the positive electrode sheet 10, the separator sheet 40B, the negative electrode sheet 20, and the separator sheet 40A are stacked in this order. . The laminated body is formed into a wound body by being wound in the longitudinal direction, and further formed into a flat shape by crushing and ablating the wound body from the side surface direction. The separator sheets 40 </ b> A and 40 </ b> B have a width that is larger than the width of the laminated portion of the positive electrode mixture layer 14 and the negative electrode mixture layer 24 and smaller than the width of the wound electrode body 80. By arranging this so as to be sandwiched between the laminated portions of the positive electrode mixture layer 14 and the negative electrode mixture layer 24, the positive electrode mixture layer 14 and the negative electrode mixture layer 24 are prevented from contacting each other and causing an internal short circuit. . Further, the wound electrode body is not limited to a flat shape. It can be made into a cylindrical shape or the like according to the shape of the battery and the purpose of use.

  The positive electrode mixture layer 14 formed on the surface of the positive electrode current collector 12 and the surface of the negative electrode current collector 22 are formed at the center in the width direction (direction orthogonal to the winding direction) of the wound electrode body 80. A portion in which the negative electrode composite material layer 24 thus overlapped and densely stacked is formed. In addition, at one end portion in the width direction of the positive electrode sheet 10, a portion where the positive electrode current collector layer 14 is not formed and the positive electrode current collector 12 is exposed (positive electrode mixture layer non-forming portion 16) is provided. . The positive electrode mixture layer non-forming part 16 is in a state of protruding from the separator sheets 40 </ b> A and 40 </ b> B and the negative electrode sheet 20. That is, at one end in the width direction of the wound electrode body 80, the positive electrode current collector laminated portion 15 in which the positive electrode mixture layer non-forming portion 16 of the positive electrode current collector 12 overlaps is formed. Further, similarly to the case of the positive electrode sheet 10 at one end, the negative electrode current collector stack in which the negative electrode mixture layer non-forming portion 26 of the negative electrode current collector 12 is overlapped with the other end in the width direction of the wound electrode body 80. A portion 25 is formed.

<Distance between poles>
FIG. 3 is a diagram (cross-sectional view) schematically showing a cross section perpendicular to the winding axis of the wound electrode body of FIG. 1. As shown in FIG. 3, the wound electrode body 80 includes a region A including the innermost peripheral portion of the wound electrode body 80 (a region indicated by symbol A in FIG. And a region B (region indicated by a symbol B in FIG. 3) located in the direction. In the cross-sectional view, the region A may be a region (winding region) extending outward from the wound inner surface of the wound electrode body 80 a predetermined number of times. In addition, the region B may be a region (winding region) that extends further outward from the outer peripheral end of the region A and reaches the wound outer surface of the wound electrode body 80 in the cross-sectional view. Then, the inter-electrode distance _{D A} between the positive and negative electrodes in this region A, and the inter-electrode distance _{D B} between the positive and negative electrodes in the region _B, satisfy the relation D A> _{D B.} That is, the interelectrode distance D _A in the region _A is larger than the interelectrode distance D _B in the region B. The above-described configuration can also be applied to a cylindrical wound electrode body 80 as shown in FIG. 4, for example.

The technical significance of the above-mentioned distance between electrodes D _A > D _B will be described. As described above, when the shuttle reaction of the gas generating agent occurs, the gas generation amount in the overcharged state may be reduced. This shuttle reaction is promoted in a high-temperature environment where the diffusibility of radical cations and the like is improved, and the above-described shuttle reaction can be effectively suppressed by increasing the distance between the positive and negative electrodes. It became clear by examination of them. Based on these findings, the inter-electrode distance D _A in the winding center side region of the prone wound electrode assembly in a high temperature state (region A), is larger than the interelectrode distance D _B in the winding outer region (region B) Configure as follows. Thereby, the shuttle reaction of the gas generating agent on the winding center side is effectively suppressed, and an increase in the amount of gas generated in the overcharged state is realized. According to the above configuration, a sufficient amount of gas can be generated even in a high temperature environment of 40 ° C. or higher (typically 50 ° C. or higher). Due to this increase in the amount of gas generated, the operating accuracy of the CID in the overcharged state can be improved. In this configuration, a decrease in battery characteristics (typically an increase in battery resistance) is suppressed. Further, since the amount of gas generated can be increased without increasing the amount of addition of the gas generating agent, the amount of gas generating agent used (added amount) can be kept to the minimum necessary. As a result, it is possible to suppress a decrease in battery characteristics (typically an increase in battery resistance) due to the excessive inclusion of the gas generating agent. Hereinafter, a configuration that satisfies the relationship of the interelectrode distance D _A > D _B will be described in detail.

FIG. 5 is an enlarged view showing a part between the positive and negative electrodes in the region A of the wound electrode body 80, and FIG. 6 is an enlarged view of a part between the positive and negative electrodes in the region B of the wound electrode body 80. FIG. As shown in FIGS. 5 and 6, the first separator 41 is disposed between the positive electrode sheet 10 and the negative electrode sheet 20 in the entire winding direction from the region A to the region B. In the region A, the second separator 42 is disposed so as to be stacked on the first separator 41. The second separator 42 is not disposed in the region B. In other words, it can be said that the region A is a region where the second separator 42 is disposed, and the region B is a region where only the first separator 41 is disposed. According to this structure, the inter-electrode distance D _A in the region A, can be larger than the inter-electrode distance D _B in the region B.

  Both the 1st separator 41 and the 2nd separator 42 are comprised from the porous resin sheet. Although not particularly limited and not particularly illustrated, these two separators are each a three-layer sheet made of polypropylene / polyethylene / polypropylene. The first separator 41 and the second separator 42 are members that constitute the separator 40A. The configuration of the separator 40B may be the same as the conventional configuration, that is, a configuration without using the second separator, or may be basically the same configuration as the separator 40A. As the configuration of the separator 40B in that case, the above description of the separator 40A can be appropriately employed independently, and therefore the description will not be repeated here.

The thickness T _A of the region A shown in FIG. 3 may be a region that occupies a predetermined range of the wound thickness T _T of the wound electrode body 80. Here, the winding thickness T _T of the wound electrode assembly, the shortest distance from the innermost periphery of the inner surface of the wound electrode body (wound in the surface) to the outer surface of the outermost periphery (the wound outer surface) Shall point to. Further, the thickness T _A of the region A, the line segment indicating the shortest distance from the innermost periphery of the inner surface of the wound electrode body (wound in the surface) to the outer surface of the outermost periphery (the wound outer surface) , And the length (thickness) occupied by the region A. In the embodiment, in the line segment, the distance from the innermost inner surface of the wound electrode body 80 to the outermost outer surface of the second separator 42 can also be defined.

The thickness T _A of the region A is preferably 5% or more of the wound thickness T _T of the wound electrode body, preferably 10% or more (for example, 20% or more, typically 30% or more). Further preferred. Inter-electrode distance D greater the thickness T _A of the large area A _A, the shuttle reaction of the gas generating agent in the prone winding center side to a high temperature state is effectively inhibited and the gas generation amount in the overcharge state This is because it tends to increase. Especially when emphasis on increasing the amount of gas generation, the thickness T _A of the region A may be 40% or more. On the other hand, as the thickness T _A of the region A is reduced, there is a tendency to decrease in battery characteristics (typically increase in battery resistance) can be suppressed. From this viewpoint, it is preferred that the thickness _{T A} of the region A to be 40% or less of the wound thickness _{T T} of the wound electrode assembly, 30% or less (e.g., 20% or less, typically 10% or less) and More preferably. In the present specification, expressing that the thickness T _A of the region A is X% of the wound thickness T _T of the wound electrode body is expressed as the ratio (T _A / T _T ) being X%. You can also.

The thickness of the inter-electrode distance D _A is not particularly limited for obtaining it depends electrode body size, etc., from the viewpoint of suppressing the shuttle reaction of the gas generating agent, preferably more than 30 [mu] m, 35 [mu] m or more (e.g. 40μm or more, typically More specifically, it is more preferably 45 μm or more. But not the thickness of the upper also particularly limited in the inter-electrode distance D _A, in view of the ion passage resistance, less than 80 [mu] m (e.g. less than 60 [mu] m, typically less than 55 .mu.m) is preferably set to. The thickness of the inter-electrode distance D _A is a plurality of points the distance between electrodes of the positive and negative electrodes in the region A at regular intervals winding direction (at least three points, preferably more than 10 points) were measured, the average thereof measurements However, for convenience, for example, the thickness of a member (separator, heat-resistant layer, etc.) existing between the positive and negative electrodes at the inner end in the winding direction of the region where the positive and negative electrodes face each other is measured. You may calculate from a measured value (typically total thickness).

The thickness of the inter-electrode distance _{D B} is may be the same as conventional secondary battery, approximately 5Myuemu～40myuemu (e.g. 10 m to 30 m, typically 15Myuemu～25myuemu) is suitable to be. The thickness of the inter-electrode distance D _B is a plurality of points the distance between electrodes of the positive and negative electrodes in the region B at a predetermined interval in the winding direction (at least three points, preferably more than 10 points) were measured, the average thereof measurements However, for convenience, for example, the thickness of a member (separator, heat-resistant layer, etc.) existing between the positive and negative electrodes at the outer end in the winding direction of the region where the positive and negative electrodes face each other is measured. You may calculate from a measured value (typically total thickness).

The ratio of the inter-electrode distance D _A to the inter-electrode distance D _B (D _A / D _B ) is preferably 1.1 or more (eg, 1.5 or more, typically 1.8 or more). As a result, the shuttle reaction of the gas generating agent on the winding center side that tends to be in a high temperature state is more effectively suppressed, and the amount of gas generation is further increased. On the other hand, if the ratio (D _A / D _B ) is too large, the ion permeability at the winding center side is lowered, and the battery characteristics may be lowered. From the viewpoint of suppressing this, the ratio (D _A / D _B ) is preferably 4 or less (eg, 3 or less, typically 2.5 or less).

Further, the difference (D _A −D _B ) between the interelectrode distance D _A and the interelectrode distance D _B is not particularly limited because it may vary depending on the electrode body size and the like, but the shuttle reaction suppression and ion passage on the winding center side are not limited. In consideration of the property, it is preferably more than 10 μm, more preferably 15 μm or more (for example, 20 μm or more, typically 22 μm or more and less than 40 μm).

In the above embodiment, the relationship between the distances D _A > D _B has been realized by arranging two separators (first separator and second separator) in the region A, It is not limited to. The relationship of D _A > D _B may be realized, for example, by stacking three or more separators. Alternatively, it can be realized by changing the thickness of one long separator sheet in the longitudinal direction. Further, the relationship of D _A > D _B can be realized by forming a filler layer having a predetermined thickness on the surfaces of the separator and the positive and negative electrodes instead of the separator.

<Positive electrode>
Next, each component which comprises the above-mentioned lithium secondary battery is demonstrated. As a positive electrode current collector constituting a positive electrode (typically, a positive electrode sheet) of a lithium secondary battery, a conductive member made of a metal having good conductivity is preferably used. As such a conductive member, for example, aluminum or an alloy containing aluminum as a main component can be used. The shape of the positive electrode current collector may be various forms such as a sheet shape, a foil shape, and a mesh shape. The thickness of the positive electrode current collector is not particularly limited, and can be, for example, 5 μm to 30 μm. In addition to the positive electrode active material, the positive electrode mixture layer can contain additives such as a conductive material and a binder (binder) as necessary.

As the positive electrode active material, lithium transition metal composite oxide containing lithium (Li) and at least one transition metal element (preferably at least one of nickel (Ni), cobalt (Co) and manganese (Mn)) Is mentioned. Examples of the composite oxide include so-called binary lithium transition metal composite oxides containing one kind of the transition metal element, so-called binary lithium transition metal composite oxides containing two kinds of the transition metal elements, and transition metal elements. Examples thereof include ternary lithium transition metal composite oxides containing Ni, Co, and Mn as constituent elements, and solid solution lithium-excess transition metal composite oxides. These can be used alone or in combination of two or more. As the positive electrode active material, the general formula is LiMAO ₄ (where M is at least one metal element selected from the group consisting of Fe, Co, Ni and Mn, and A is P, Si, S and A polyanionic compound represented by the following formula is also preferably used: an element selected from the group consisting of V. Among these, a ternary lithium transition metal composite oxide containing Ni, Co, and Mn as transition metal elements as constituent elements is preferable. Typical examples of the ternary lithium transition metal composite oxide include a general formula:
Li (Li _a Ni _x Co _y Mn _z ) O ₂
(A, x, y, z in the above general formula is a real number satisfying a + x + y + z = 1).

  Further, the positive electrode active material is selected from the group consisting of Al, Cr, V, Mg, Ca, Ti, Zr, Nb, Mo, Cu, Zn, Ga, In, Sn, La, W, and Ce, or Two or more kinds of metal elements may be further added. The addition amount (blending amount) of these metal elements is not particularly limited, but is 0.01% by mass to 5% by mass (for example, 0.05% by mass to 2% by mass, typically 0.1% by mass to 0.00%). 8 mass%) is appropriate.

  As the conductive material, a conductive powder material such as carbon powder or carbon fiber is preferably used. As the carbon powder, various carbon blacks such as acetylene black, furnace black, ketjen black, and graphite powder are preferable. Also, conductive fibers such as carbon fibers and metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be used singly or as a mixture of two or more. .

  Examples of the binder include various polymer materials. For example, when the positive electrode mixture layer is formed using an aqueous composition (a composition using water or a mixed solvent containing water as a main component as a dispersion medium of active material particles), water-soluble or water-dispersible These polymer materials can be preferably used as the binder. Examples of water-soluble or water-dispersible polymer materials include cellulose polymers such as carboxymethyl cellulose (CMC); polyvinyl alcohol (PVA); fluorine resins such as polytetrafluoroethylene (PTFE); vinyl acetate polymers; styrene butadiene rubber Rubbers such as (SBR) and acrylic acid-modified SBR resin (SBR latex);

  Alternatively, when the positive electrode mixture layer is formed using a solvent-based composition (a composition in which the dispersion medium of active material particles is mainly an organic solvent), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC) Polymer materials such as vinyl halide resins such as polyethylene oxide, polyalkylene oxide such as polyethylene oxide (PEO), and the like can be used. Such a binder may be used alone or in combination of two or more. In addition, the polymer material illustrated above may be used as a thickener and other additives in the composition for forming a positive electrode mixture layer, in addition to being used as a binder.

  The proportion of the positive electrode active material in the positive electrode mixture layer is more than about 50% by mass, and preferably about 70% to 97% by mass (for example, 75% to 95% by mass). Moreover, the ratio of the additive to the positive electrode mixture layer is not particularly limited, but the ratio of the conductive material is about 1 to 20 parts by mass (for example, 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material). , Typically 3 to 7 parts by mass). The ratio of the binder is about 0.8 parts by mass to 10 parts by mass (for example, 1 part by mass to 7 parts by mass, typically 2 parts by mass to 5 parts by mass) with respect to 100 parts by mass of the positive electrode active material. It is preferable.

The basis weight per unit area of the positive electrode mixture layer on the positive electrode current collector (the coating amount in terms of solid content of the composition for forming the positive electrode mixture layer) is not particularly limited, but a sufficient conductive path From the viewpoint of securing (conductive path), it is 3 mg / cm ² or more (for example, 6 mg / cm ² or more, typically 12 mg / cm ² or more) per side of the positive electrode current collector, and 45 mg / cm ² or less (for example, 28 mg / cm ² or less, typically 18 mg / cm ² or less). The density of the positive electrode mixture layer is not particularly limited, but is 1.0 g / cm ^{3 to} 3.8 g / cm ³ (for example, 1.5 g / cm ^{3 to} 3.5 g / cm ³ , typically 2.0 g / cm 3). ^{3 to} 3.0 g / cm ³ ).

<Negative electrode>
As the negative electrode current collector constituting the negative electrode (typically, the negative electrode sheet), a conductive member made of a metal having good conductivity is preferably used as in the case of a conventional lithium secondary battery. As such a conductive member, for example, copper or an alloy containing copper as a main component can be used. The negative electrode current collector may have various shapes such as a sheet shape, a foil shape, and a mesh shape. The thickness of the negative electrode current collector is not particularly limited, and can be, for example, 5 μm to 30 μm.

  The negative electrode mixture layer includes a negative electrode active material that can occlude and release Li ions serving as charge carriers. There is no restriction | limiting in particular in a composition and a shape of a negative electrode active material, The 1 type (s) or 2 or more types of the material conventionally used for a lithium secondary battery can be used. Examples of such a negative electrode active material include carbon materials generally used in lithium secondary batteries. Representative examples of the carbon material include graphite carbon (graphite) and amorphous carbon. A particulate carbon material (carbon particles) containing a graphite structure (layered structure) at least partially is preferably used. Of these, the use of a carbon material mainly composed of natural graphite is preferred. Natural graphite may be a spheroidized graphite. Alternatively, a carbonaceous powder having a graphite surface coated with amorphous carbon may be used. In addition, as the negative electrode active material, it is also possible to use oxides such as lithium titanate, simple substances such as silicon materials and tin materials, alloys, compounds, and composite materials using the above materials in combination.

  In addition to the negative electrode active material, the negative electrode mixture layer requires one or more binders, thickeners, and other additives that can be blended in the negative electrode mixture layer of a typical lithium secondary battery. It can be contained accordingly. Examples of the binder include various polymer materials. For example, what can be contained in the positive electrode mixture layer can be preferably used for an aqueous composition or a solvent-based composition. In addition to being used as a binder, the binder may be used as a thickener or other additive in a composition for forming a negative electrode mixture layer.

  The proportion of the negative electrode active material in the negative electrode mixture layer is suitably about 90% to 99% by mass (for example, 95% to 99% by mass, typically 97% to 99% by mass). . The proportion of the additive in the negative electrode mixture layer is not particularly limited, but is approximately 0.8% by mass to 10% by mass (for example, approximately 1% by mass to 5% by mass, typically 1% by mass to 3% by mass). ).

The basis weight per unit area of the negative electrode composite material layer on the negative electrode current collector (the coating amount in terms of solid content of the composition for forming the negative electrode composite material layer) is not particularly limited, but sufficient conductive paths From the viewpoint of securing (conductive path), it is 2 mg / cm ² or more (for example, 5 mg / cm ² or more, typically 8 mg / cm ² or more) per side of the negative electrode current collector, and 40 mg / cm ² or less (for example, 22 mg / cm ² or less, typically 14 mg / cm ² or less). The density of the negative electrode mixture layer is not particularly limited, but is 1.0 g / cm ^{3 to} 3.0 g / cm ³ (for example, 1.2 g / cm ^{3 to} 2.0 g / cm ³ , typically 1.3 g / cm 3). ^{3 to} 1.5 g / cm ³ ).

<Separator>
The separator (separator sheet) disposed so as to separate the positive electrode and the negative electrode may be a member that insulates the positive electrode mixture layer and the negative electrode mixture layer and allows the electrolyte to move. As said separator, the thing similar to the sheet | seat used as a separator in the conventional lithium secondary battery can be used. Examples of such a member include a porous body, a nonwoven fabric, and a cloth. Especially, the porous sheet (porous resin sheet) which consists of resin can be used preferably.

  Preferable examples of the porous resin sheet include a sheet mainly composed of a thermoplastic resin such as polyolefin (polyethylene (PE), polypropylene (PP), etc.), polyester, and polyamide. As a preferred example, a sheet having a single-layer structure or a multilayer structure (polyolefin-based sheet) mainly composed of one or more kinds of polyolefin-based resins can be given. For example, a PE sheet, a PP sheet, a sheet having a three-layer structure (PP / PE / PP structure) in which a PP layer is laminated on both sides of the PE layer can be suitably used. The PE may be any polyethylene generally referred to as high-density polyethylene (HDPE), low-density polyethylene (LDPE), or linear (linear) low-density polyethylene (LLDPE), or a mixture thereof. May be. Moreover, the said separator can also contain additives, such as various plasticizers and antioxidant, as needed.

  As the resin sheet constituting the separator having a single layer structure or a multilayer structure, for example, a uniaxially stretched or biaxially stretched porous resin sheet can be suitably used. Among these, a porous resin sheet uniaxially stretched in the longitudinal direction is particularly preferable because it has an appropriate strength and has little heat shrinkage in the width direction. When a separator having a uniaxially stretched porous resin sheet is used, thermal contraction in the longitudinal direction can be suppressed in a mode in which the separator is wound together with a long sheet-like positive electrode and negative electrode. Therefore, the porous resin sheet uniaxially stretched in the longitudinal direction is particularly suitable as one element of the separator constituting the wound electrode body.

Separator porosity (porosity) _{P S} is preferably generally about 20% to 70%, and more preferably, for example, about 30% to 60%. When the porosity P _S of the separator is too large, strength is insufficient or the thermal contraction may be or become remarkably. On the other hand, the When the porosity P _S is too small, the less electrolyte volume capable of holding a separator, and reduced ion passage resistance, charge and discharge characteristics may be a downward trend. Incidentally, the porosity P _S of the separator can be calculated by the following method. The apparent volume occupied by the separator of the unit area (surface area) is V1 [cm ³ ], and the mass of the unit area separator is W [g]. The ratio between the mass W and the true density ρ [g / cm ³ ] of the resin material constituting the separator, that is, W / ρ is V0. Note that V0 is a volume occupied by a dense body of resin material having a mass W. Porosity _{P S} of the separator can be calculated from [(V1-V0) / V1 ] × 100. Porosity P _S of the separator may adjust the material of the resin, the stretching strength or the like.

Further, when the relationship between the distances D _A > D _B is realized by arranging two or more separators in the region A including the innermost peripheral portion of the wound electrode body, each separator is independently The above materials, manufacturing methods, porosity, etc. can be employed. For example, when two separators are disposed in the region A, the above-described porosity may be adopted as the porosity P _S1 of the first separator disposed in the entire winding direction (region A and region B). it can. In addition, the porosity _PS2 of the second separator disposed only in the region A is larger than the porosity _PS1 of the first separator from the viewpoint of ion permeability at the winding center side and retention of the nonaqueous electrolyte, and It is preferably about 30 to 70% (for example, 40 to 60%, typically 45 to 55%). It has been confirmed that the amount of gas generated does not decrease even when the porosity _PS2 of the second separator is increased.

In the case where two separators are arranged in the region A, the ratio of the porosity P _S2 of the second separator to the porosity P _S1 of the first separator (P _S2 / P _S1 ) is on the winding center side. From the viewpoint of ion permeability and nonaqueous electrolyte retention, it is preferably greater than 1, and preferably 1.05 or more (eg 1.1 or more, typically 1.2 or more and less than 1.5). . The difference between the porosity P _S1 (%) of the first separator and the porosity P _S2 (%) of the second separator (P _S2 -P _S1 ) is the same as the above ratio (P _S2 / P _S1 ). 3 (%) or more (for example, 5 (%) or more, typically 8 (%) or more and less than 30 (%)) is preferable.

The thickness of the separator _{T S} is not particularly limited, 5μm~40μm (e.g. 10 m to 30 m, typically 15Myuemu～25myuemu) is preferably about. By thickness T _S of the separator is within the above range, the ion passage of the separator becomes better, also rupture is less likely to occur.

When the relationship between the distances D _A > D _B is realized by arranging two or more separators in the region A including the innermost peripheral portion of the wound electrode body, each separator is independently described above. Thickness can be employed. For example, when two separators are arranged in the region A, the above-described thickness can be adopted as the thickness T _S1 of the first separator arranged in the entire winding direction (region A and region B). . Further, the thickness T _S2 of the second separator disposed only in the region A is preferably more than 10 μm in consideration of the shuttle reaction suppression of the gas generating agent and the ion permeability, and is preferably 15 μm or more (for example, 20 μm or more, (Typically, it is more preferably 22 μm or more and less than 40 μm). When the number of separators disposed only in the region A is three or more, the value of the thickness _TS2 can be preferably adopted as the total thickness.

In the case where two separators are arranged in the region A, the ratio of the thickness T _S2 of the second separator to the thickness T _S1 of the first separator (T _S2 / T _S1 ) is From the viewpoint of suppressing the shuttle reaction of the gas generating agent, it is preferably 0.1 or more (for example, 0.5 or more, typically 0.8 or more). In consideration of ion permeability at the winding center side, the ratio (T _S2 / T _S1 ) is preferably 2 or less (for example, 1.5 or less, typically 1.2 or less). When the number of separators arranged only in the region A is three or more, the value of the ratio (T _S2 / T _S1 ) is preferably applied by using the total thickness as the thickness T _S2. it can.

<Heat resistant layer>
Further, it is preferable that at least one of the separator, the positive electrode, and the negative electrode is provided with at least one heat-resistant layer. The heat-resistant layer may be formed over the entire length direction (winding direction) and width direction of at least one surface (one side or both sides) of the separator, the positive electrode, and the negative electrode. Especially, it is preferable that it is formed on one surface of the separator.

  The heat-resistant layer may be mainly composed of an inorganic filler (for example, a filler such as a metal oxide or a metal hydroxide) or an organic filler (for example, resin particles such as polyethylene or polypropylene). The filler that can be the main component of the heat-resistant layer may be either an organic filler or an inorganic filler, but it is preferable to use an inorganic filler in consideration of heat resistance, dispersibility, and stability. The inorganic filler is not particularly limited. For example, inorganic oxides such as alumina, boehmite, silica, titania, zirconia, calcia, magnesia, and iron oxide, inorganic nitrides such as aluminum nitride, carbonates such as magnesium carbonate, and barium sulfate. Such as sulfate, magnesium chloride, fluoride such as barium fluoride, covalent crystal such as silicon, talc, clay, mica, bentonite, montmorillonite, zeolite, apatite, kaolin, mullite, sericite, etc. It may be a mineral-based material or an artificial product thereof. These can be used alone or in combination of two or more. Among these, alumina, boehmite, silica, titania, zirconia, calcia, and magnesia are preferable, and boehmite and alumina are particularly preferable because of high electrochemical stability and excellent heat resistance and mechanical strength.

The form of the filler is not particularly limited, and may be, for example, a particle shape, a fiber shape, a plate shape (flake shape), or the like. The average particle diameter of the filler is not particularly limited, but is suitably 0.1 μm to 15 μm (for example, 0.1 μm to 5 μm, typically 0.2 μm to 1.5 μm) in consideration of dispersibility and the like. . As the average particle diameter of the filler, a median diameter (average particle diameter D ₅₀ : 50% volume average particle diameter) that can be derived from the particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering / diffraction method can be employed. .

  The heat-resistant layer also preferably contains an additive such as a binder. When the heat-resistant layer forming composition is an aqueous solvent (a solution using water or a mixed solvent containing water as a main component as a dispersion medium for the binder), the binder is dispersed or dissolved in the aqueous solvent. Polymers can be used. Examples of the polymer that is dispersed or dissolved in the aqueous solvent include acrylic resins. As the acrylic resin, a single polymer obtained by polymerizing monomers such as methyl methacrylate, 2-ethylhexyl acrylate, butyl acrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate. Coalescence is preferably used. Or the copolymer which superposed | polymerized 2 or more types of the said monomer may be sufficient. Further, a mixture of two or more of the above homopolymers and copolymers may be used. In addition to the acrylic resin described above, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic; polyolefin resin such as polyethylene (PE); carboxymethylcellulose (CMC), Cellulose polymers such as methyl cellulose (MC); polyvinyl alcohol (PVA); fluorine resins such as polytetrafluoroethylene (PTFE); vinyl acetate polymers; polyalkylene oxides such as polyethylene oxide (PEO); it can. These polymers can be used alone or in combination of two or more. Of these, acrylic resins, SBR, polyolefin resins, and CMC are preferable. These water-based binders are preferable in that they do not react or harden with moisture in the atmosphere and can easily adjust the extensibility of the heat-resistant layer (for example, without performing water management during production).

  When the heat-resistant layer forming composition is a solvent-based solvent (a solution in which the binder dispersion medium is mainly an organic solvent), the binder should be a polymer that is dispersed or dissolved in the solvent-based solvent. Can do. Examples of the polymer that is dispersed or dissolved in the solvent-based solvent include vinyl halide resins such as polyvinylidene fluoride (PVDF). As the polyvinylidene fluoride, a homopolymer of vinylidene fluoride is preferably used. Furthermore, the polyvinylidene fluoride may be a copolymer of a vinyl monomer copolymerizable with vinylidene fluoride. Examples of vinyl monomers copolymerizable with vinylidene fluoride include hexafluoropropylene, tetrafluoroethylene, and ethylene trichloride fluoride. Alternatively, polytetrafluoroethylene (PTFE), polyacrylonitrile, polymethyl methacrylate, or the like is preferably used as a polymer that is dispersed or dissolved in a solvent-based solvent. These may be used alone or in combination of two or more.

  The proportion of the filler (eg, inorganic filler) in the entire heat-resistant layer is not particularly limited, but is approximately 90% by mass or more (eg, 92% by mass to 99.5% by mass, typically 95% by mass to 99% by mass). It is preferable. When the heat-resistant layer contains additives such as a binder and a thickener, the proportion of the additive in the heat-resistant layer is about 10% by mass or less (for example, 0.5% to 8% by mass, typically Is preferably 1% by mass to 5% by mass). When the ratio of the filler, if necessary, the binder and other additives is within the above range, the anchoring property of the heat-resistant layer and the strength (shape retention) of the heat-resistant layer itself are improved. Moreover, it becomes easy to adjust the porosity of a heat-resistant layer to a favorable range, and there exists a tendency for ion permeability to improve more. Furthermore, when forming a heat-resistant layer on a separator, it is easy to adjust the intensity | strength and elongation rate of a separator to a suitable range.

The porosity (porosity) of the heat-resistant layer is not particularly limited, but is 40% or more (for example, 45% or more, typically 50% or more) from the viewpoint of improving nonaqueous electrolyte retention and ion passage. Is preferred. The porosity is 75% or less (for example, 70% or less, typically 65% or less) from the viewpoint of suppressing heat shrinkage and obtaining a strength that does not cause defects such as cracks or peeling. preferable. The porosity of the heat resistant layer can be calculated by the same method as calculating the porosity P _S of the separator. In that case, the mass W of the heat-resistant layer can be measured, for example, as follows. That is, a separator, a positive electrode, or a negative electrode on which a heat-resistant layer is formed are cut out to a predetermined area to obtain a sample, and the mass is measured. Next, the mass of the heat-resistant layer having the predetermined area is calculated by subtracting the mass of the separator, positive electrode, or negative electrode having the predetermined area from the mass of the sample. The mass W [g] of the heat-resistant layer can be calculated by converting the mass of the heat-resistant layer thus calculated per unit area. The porosity of the heat-resistant layer can be adjusted by the constituent components, the blending ratio thereof, the application method, the drying method and the like.

  The thickness of the heat-resistant layer is not particularly limited, but is more preferably about 1 μm to 12 μm (for example, 2 μm to 10 μm, typically 3 μm to 8 μm). When the thickness of the heat-resistant layer is within the above range, the effect of preventing a short circuit and the retention of the nonaqueous electrolyte are improved. Moreover, when providing a heat-resistant layer on a separator, it is easy to adjust the intensity | strength and elongation rate of a separator to a suitable range. The thickness of the heat-resistant layer can be obtained by analyzing an image taken with a SEM (Scanning Electron Microscope).

<Filler layer>
Further, the relationship of the interelectrode distance D _A > D _B may be realized by forming a filler layer on at least one of the separator, the positive electrode, and the negative electrode in the region A including the innermost peripheral portion of the wound electrode body. . This filler layer is formed in the region A but not in the region B. The composition, manufacturing method, and physical properties (for example, porosity and thickness) of the filler layer can preferably employ the above-described composition, manufacturing method, and physical properties in the heat-resistant layer, and thus description thereof will not be repeated here. In addition, the said filler layer may be formed together with the above-mentioned heat resistant layer, or may form only a filler layer without forming a heat resistant layer. Moreover, the said filler layer can be used together with the above-mentioned 2nd separator.

The porosity P _F of the filler layer arranged only in the region A, from the viewpoint of retention of the ion passage resistance and the non-aqueous electrolyte in the winding center side, larger than the porosity P _S of the separator, and approximately 40 to 75% (For example, 45 to 70%, typically 50 to 65%) is preferable. The ratio of the porosity P _F of the filler layer to the porosity P _S of the separator (P F _{/ P S),} taking into account the retention of ion passage of the non-aqueous electrolyte in the winding center side, 1 It is preferably larger, and is preferably 1.05 or more (eg, 1.1 or more, typically 1.2 or more and less than 1.5). Further, the porosity _P F (%) porosity _P S (%) and the filler layer of the separator difference _(P F -P _S), from the same viewpoint as the ratio _{(P F / P S),} 3 ( %) Or more (for example, 5 (%) or more, typically 8 (%) or more and less than 30 (%)).

The thickness _TF of the filler layer disposed only in the region A is preferably more than 10 μm, preferably 12 μm or more (for example, 14 μm) in consideration of the suppression of the shuttle reaction of the gas generating agent and the ion permeability on the winding center side. As described above, typically, the thickness is more preferably 16 μm or more and less than 22 μm. The ratio of the thickness T _F of the filler layer to the thickness T _S of the separator (T _F / T _S ) is 0.1 or more (for example, from the viewpoint of suppressing the shuttle reaction of the gas generating agent on the winding center side) 0.3 or more, typically 0.5 or more). In consideration of ion permeability at the winding center side, the ratio (T _F / T _S ) is preferably 2 or less (for example, 1.5 or less, typically 1 or less).

<Nonaqueous electrolyte>
As the non-aqueous solvent and the supporting salt constituting the non-aqueous electrolyte injected into the lithium secondary battery, those conventionally used for lithium secondary batteries can be used without any particular limitation. The nonaqueous electrolyte is typically an electrolytic solution having a composition in which a supporting salt is contained in a suitable nonaqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2- Diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone These may be used alone or in combination of two or more. Of these, a mixed solvent of EC, DMC and EMC is preferable.

Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _3. One or more of lithium compounds (lithium salts) such as LiI can be used. The concentration of the supporting salt is not particularly limited, but is approximately 0.1 mol / L to 5 mol / L (for example, 0.5 mol / L to 3 mol / L, typically 0.8 mol / L to 1.5 mol / L). Concentration.

  The non-aqueous electrolyte can also include a gas generant. Here, the gas generating agent is a compound that can be dissolved or dispersed in the non-aqueous electrolyte, reacts when the battery is overcharged, and gasses before the decomposition of the non-aqueous solvent contained in the non-aqueous electrolyte. Refers to a compound that generates Among these, a gas generating agent that generates hydrogen gas is preferable.

Although the gas generating agent is not oxidized at the operating voltage of the battery, it reacts (oxidizes) prior to the oxidative decomposition of the nonaqueous solvent of the nonaqueous electrolyte when the battery is overcharged. Therefore, the oxidation potential (oxidation start potential) of the gas generating agent is higher than the upper limit potential of the positive electrode corresponding to the maximum operating voltage. Moreover, it is lower than the oxidation potential (oxidation start potential) of the nonaqueous solvent of the nonaqueous electrolyte. From the above viewpoint, the oxidation potential (vsLi / Li ⁺ ) of the gas generating agent is 0.1 V or higher (for example, 0.2 V or higher, typically 0.3 V or higher) from the upper limit potential (vsLi / Li ⁺ ) of the positive electrode. High is preferred. Moreover, it is preferable that it is 0.1 V or more (for example, 0.2 V or more, typically 0.3 V or more) lower than the oxidation potential (vsLi / Li ⁺ ) of the nonaqueous solvent. For example, in the case of a secondary battery in which the upper limit potential of the positive electrode is 4.2 V or less (typically 4.0 V to 4.2 V), the preferable range of the oxidation potential of the gas generating agent is 4.3 V or more (for example, 4 0.4V or more, typically 4.5V or more) and 5.0V or less (for example, 4.9V or less, typically 4.8V or less).

  Preferable examples of the gas generating agent include alkylbenzenes, cycloalkylbenzenes, biphenyls, terphenyls, diphenyl ethers, and dibenzofurans. Examples of the alkylbenzenes include alkylbenzenes having an alkyl group having 3 to 5 carbon atoms. The alkyl group has a structure that does not hinder polymerization during the polymerization of a gas generant (typically a gas generant containing an alkylbenzene), and can be conjugated with the benzene ring of the other alkylbenzene to be polymerized. It is preferable to have. The alkyl group is preferably branched. Specific examples of the alkylbenzenes include alkylbenzenes such as cumene, diisopropylbenzene, sec-butylbenzene, sec-dibutylbenzene, sec-amylbenzene and the like. Examples of the cycloalkylbenzenes include cyclohexylbenzene (CHB) and a group (substituent) in which at least one of hydrogen atoms bonded to carbon atoms constituting the cyclohexylbenzene does not hinder the polymerization of the gas generant compound. Examples include substituted cyclohexylbenzene derivatives. Specific examples of cycloalkylbenzenes include, in addition to CHB, alkylated cycloalkylbenzenes such as isopropylcyclohexylbenzene. Examples of biphenyls include biphenyl (BP) and biphenyl derivatives in which at least one hydrogen atom bonded to the carbon atom constituting BP is substituted with a group that does not hinder the polymerization of the gas generant compound. Specific examples of biphenyls include BP and alkyl biphenyls such as isopropyl biphenyl and sec-butyl biphenyl. As terphenyls, diphenyl ethers and dibenzofurans, terphenyl, diphenyl ether, dibenzofuran and at least one hydrogen atom bonded to the carbon atoms constituting them are substituted with groups that do not hinder the polymerization of the gas generant compound. Each derivative (terphenyl derivative, diphenyl ether derivative, dibenzofuran derivative). Terphenyl may be a partial hydride of terphenyl in which a hydrogen atom is added to a part thereof. The above gas generating agents can be used alone or in combination of two or more. Among them, alkylbenzenes, cycloalkylbenzenes, biphenyls, and diphenyl ethers are preferable, cycloalkylbenzenes (typically CHB), biphenyls (typically BP) are more preferable, and cycloalkylbenzenes (typically The combined use of CHB) and biphenyls (typically BP) is particularly preferred. The amount (addition amount) of the gas generating agent is about 0.1 to 10% by mass (for example, 0.5 to 7% by mass, typically 1 to 5% by mass) in the non-aqueous electrolyte. ) Is preferable.

  The size of the wound electrode body is not particularly limited. However, the larger the wound electrode body, the lower the heat dissipating property at the center of the wound, and there is a tendency to become a high temperature state when overcharged. In order to more effectively suppress the shuttle reaction of the gas generating agent that is easily promoted in a high temperature state, the configuration of the present invention is applied to a wound electrode body having a wound thickness of 10 mm or more (for example, 15 mm or more, typically 20 mm or more). It is preferable to apply. For the same reason, as the battery size (typically battery capacity) is larger, there is a concern that the amount of gas generated due to the shuttle reaction of the gas generating agent is reduced. In order to avoid this more effectively, the configuration of the present invention is preferably applied to a secondary battery having a rated capacity (design capacity) of 5 Ah or more (for example, 10 Ah or more, typically 20 Ah or more).

  As described above, the lithium secondary battery having such a configuration has improved CID operating accuracy in an overcharged state and suppressed deterioration of battery characteristics. Therefore, it can be used as a secondary battery for various applications. Moreover, the effect can be suitably exhibited in a large-sized secondary battery in which the vicinity of the winding center of the wound electrode body is likely to become high temperature. For this reason, for example, as shown in FIG. 7, the lithium secondary battery 100 is mounted on a vehicle 1 such as an automobile and can be suitably used as a power source for a drive source such as a motor that drives the vehicle 1. Therefore, the present invention provides a vehicle (typically an automobile, particularly a hybrid automobile (HV), a plug-in hybrid automobile (including a battery pack typically formed by connecting a plurality of series-connected batteries) 100 as a power source. PHV), an electric vehicle (EV), a vehicle equipped with an electric motor such as a fuel cell vehicle) 1 can be provided.

  Next, some examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Principle verification test>
[Preparation of positive electrode sheet]
A transition metal (Me) hydroxide serving as a precursor of the positive electrode active material was prepared so that the molar ratio of Ni: Co: Mn: Zr was 33: 33: 33: 0.5. The Me hydroxide and Li ₂ CO ₃ were mixed and baked at 900 ° C. for 48 hours to prepare a positive electrode active material. The Li / Me molar ratio of this positive electrode active material was 1.05 as a result of ICP (Inductive Coupled Plasma) analysis. The positive electrode active material thus obtained, acetylene black (AB) and polyvinylidene fluoride (PVDF) were mixed with NMP so that the mass ratio of these materials was 91: 6: 3, A composition for forming a positive electrode mixture layer was prepared. By applying this composition uniformly on both sides of an aluminum foil (positive electrode current collector: thickness 15 μm) so that the total coating amount is 30 mg / cm ² (based on solid content), drying, and then compressing A sheet-like positive electrode (positive electrode sheet) was produced. The density of the positive electrode mixture layer was 2.8 g / cm ³ .

[Preparation of negative electrode sheet]
Graphite powder, styrene-butadiene copolymer (SBR) and carboxymethylcellulose (CMC) are mixed with ion-exchanged water so that the mass ratio of these materials is 98: 1: 1, and the paste-like negative electrode composite is mixed. A material layer forming composition was prepared. The composition was uniformly applied to a copper foil (thickness: 14 μm) so that the application amount was 17 mg / cm ² (solid content basis), dried and then compressed, whereby a sheet-like negative electrode (negative electrode) Sheet). The density of the negative electrode mixture layer was 1.4 g / cm ³ .

[Construction of lithium secondary battery]
The positive electrode sheet and the negative electrode sheet produced as described above were each cut to have a square size of 4.4 cm and having a tab, and the composite material layer of the tab portion was peeled off, and a lead with a seal was attached. An electrode body was produced by superimposing two negative electrode sheets on one positive electrode sheet via a separator sheet. In this electrode body, one separator sheet is disposed between the positive electrode sheet and the negative electrode sheet. As the separator sheet, a three-layer separator sheet (thickness: 24 μm, porosity: 42%) made of polypropylene (PP) / polyethylene (PE) / polypropylene (PP) was used. This electrode body was accommodated in a bag made of an aluminum laminate film, and a non-aqueous electrolyte was poured into the bag. As the non-aqueous electrolyte, a 3: 4: 3 (volume ratio) mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) was used, and about 1 mol / L LiPF ₆ as a supporting salt. Then, an electrolytic solution containing 2% cyclohexylbenzene (CHB) and 2% biphenyl (BP) was used. While the bag was evacuated, the aluminum laminate film and the seal portion attached to the lead were heat welded. Furthermore, the laminated battery A in the state which restrained the compound-material layer part between 2 glass plates and a clip was produced.

  Further, a laminated battery B was produced in the same manner as the laminated battery A, except that two separator sheets were provided between the positive electrode sheet and the negative electrode sheet, and the two sheets were overlapped and used.

[Gas generation measurement]
The manufactured laminated batteries A and B are charged to 4.1 V at a 1 C rate in an environment of 25 ° C., and when the voltage reaches 4.1 V, constant voltage (CV) charging is performed until the current reaches 0.1 C. It was. And it discharged to 3V at 1C rate. After this charge / discharge was repeated three times, an overcharge test described below was performed. First, the glass plate was removed with SOC (State of Charge) 100%, submerged in a beaker filled with water, and the weight (A0) was measured. At this time, it adjusted with tweezers so that a battery might not touch a beaker. The battery was taken out of the beaker and sandwiched again with a glass plate, and then overcharged in an environment of 25 ° C. and an environment of 60 ° C. until the SOC became 160% at a 1C rate. Note that SOC 100% means charging to 4.1V at a 1C rate, and CV charging is performed until the current reaches 0.1C when the voltage reaches 4.1V, and SOC 0% is discharged to 3V at 1C. Defined as state. The glass plate was removed with SOC 160%, submerged in a beaker filled with water, and the weight (A1) was measured. At this time, similarly to the above, adjustment was made with tweezers so that the battery did not touch the beaker. A1-A0 was defined as the volume increased by gas generation, and this was divided by the battery capacity to determine the amount of gas generated during overcharge (cc / Ah) under each temperature condition of 25 ° C. and 60 ° C. The results are shown in Table 1.

  As shown in Table 1, no difference due to the distance between the electrodes was observed for the amount of gas generated in the 25 ° C. environment. However, in an environment of 60 ° C., the gas generation amount of the laminated battery A was significantly reduced. This is probably because the shuttle reaction of the gas generating agent was promoted in a high temperature environment, and the gas generation amount was reduced. On the other hand, in the laminated battery B having a large inter-electrode distance, the amount of gas generated in a 60 ° C. environment was rather increased. From this result, it is considered that by increasing the distance between the electrodes, the shuttle reaction of the gas generating agent under high temperature conditions is effectively suppressed, and the amount of gas generation is increased.

<Example 1>
A paste-like composition for forming a positive electrode mixture layer was prepared in the same manner as in the principle verification test. This composition was uniformly applied to both sides of a long aluminum foil (positive electrode current collector: thickness 15 μm) so that the total coating amount was 30 mg / cm ² (solid content basis), and after drying, The sheet-like positive electrode (positive electrode sheet) was produced by compressing. The density of the positive electrode mixture layer was 2.8 g / cm ³ . Also, a paste-like composition for forming a negative electrode mixture layer was prepared in the same manner as in the principle verification test. Apply this composition uniformly on both sides of a long copper foil (thickness: 14 μm) so that the coating amount per side is 17 mg / cm ² (based on solid content), and after drying, compress Thus, a sheet-like negative electrode (negative electrode sheet) was produced. The density of the negative electrode mixture layer was 1.4 g / cm ³ .

The produced positive electrode sheet and the negative electrode sheet were laminated and wound via a separator sheet, and the wound body was pressed from the side surface direction and ablated to produce a flat wound electrode body. Specifically, two long separator sheets having different lengths were prepared as separator sheets disposed between the positive and negative electrodes. Each of the separator sheets is a three-layer structure sheet (thickness: 24 μm, porosity: 42%) made of PP / PE / PP. One of the two separator sheets (hereinafter also referred to as a first separator) extends from region A to region B in the cross section of the wound electrode body 80 as schematically shown in FIG. Arranged in the whole winding direction. The other separator sheet (hereinafter also referred to as a second separator) shorter than the first separator was disposed in the region A. The second separator is not disposed in the region B. After winding the positive electrode sheet, the negative electrode sheet, the first separator and the second separator, by pressing from the side surface direction, in the cross section as shown in FIG. A flat wound electrode body 80 is manufactured, in which the distance between electrodes D _A in the region _A and the distance D _B between the regions B satisfy the relationship D _A > D _B. The thickness T _A of the region A is 1 mm, the wound thickness T _T of the wound electrode body 80 is 30 mm, and the ratio of the thickness T _A of the region A to the wound thickness T _T of the wound electrode body 80 ( T _A / T _T ) was 3.3%.

Electrode terminals were welded to the ends of the positive and negative electrode current collectors of the wound electrode body, accommodated in a square aluminum case, and sealed with a laser. Thereafter, the non-aqueous electrolyte was injected from the injection port while vacuuming the inside of the aluminum case. The prismatic lithium secondary battery according to Example 1 was produced by sealing the liquid injection port. As a non-aqueous electrolyte, about 1: 1 mol / L LiPF ₆ was dissolved as a supporting salt in a 3: 4: 3 (volume ratio) mixed solvent of EC, DMC, and EMC to contain CHB 2% and BP 2%. An electrolytic solution was used.

<Example 2 to Example 7>
Example 1 was prepared with different second separator lengths and lithium thickness T _A of the area A according to Examples 2 to 7 In the same manner other than the example 1 was formed to be thick as shown in Table 2 two A secondary battery was produced. Table 2, the ratio of the thickness _{T A} of the area A to the winding thickness _{T T} of the wound electrode assembly _(T A / _{T T)} is also shown.

<Example 8>
A lithium secondary battery was produced in the same manner as in Example 1 except that the second separator was not used.

[Battery resistance measurement]
Each manufactured battery was charged to 4.1 V at a 1 C rate in an environment of 25 ° C., and CV charging was performed until the current became 0.1 C when the voltage reached 4.1 V. Thereafter, aging was performed in an environment of 50 ° C. for 6 days. After aging, the battery was discharged to 1 V at 1 C in an environment of 25 ° C., charged to 4.1 V at a 1 C rate, and CV charging was performed until the current became 0.1 C when the voltage reached 4.1 V. And it discharged to 3V at 1C. After repeating this charging and discharging three times, the battery resistance was measured. The battery resistance was measured by adjusting the SOC to 60% in an environment of 25 ° C., then letting the voltage left for 30 minutes to be V0, discharging at a discharge rate of 4C for 10 seconds, and then the reached voltage to be V1, V0− The battery resistance was determined from V1. The obtained battery resistance is shown as a relative value with the value of Example 8 being 100. The smaller the value, the lower the resistance and the better the output characteristics of the battery. The results are shown in Table 2.

[Gas generation measurement]
After measuring the battery resistance, an overcharge test was performed at a 1 C rate in an environment of 25 ° C. The amount of gas generated during overcharge was calculated based on an internal pressure sensor attached to the prismatic battery. The results are shown in Table 2.

As shown in Table 2, the lithium secondary batteries according to Examples 1 to 7 in which the distance between the electrodes on the winding center side of the wound electrode body is larger than in Example 8 in which the distance between the electrodes is constant. Despite the same amount of agent used, gas generation increased. Further, when Examples 1 to 5 are compared with Examples 6 and 7, it can be seen that the effect of increasing the amount of gas generation tends not to be obtained even if the distance between the electrodes is increased at a location away from the winding center. Further, Examples 2 to 6 in which the ratio (T _A / T _T ) is in the range of 5 to 40% achieve both the increase in the amount of gas generation and the suppression of the increase in battery resistance. In particular, Examples 3 to 5 in which the ratio (T _A / T _T ) is in the range of 10 to 30% are highly compatible with an increase in the amount of gas generation and an increase in battery resistance. From these results, the shuttle reaction of the gas generating agent, which is considered to be a cause for reducing the gas generation amount, frequently occurs on the winding center side in the high temperature state, and the interelectrode distance D _A in a predetermined range on the winding center side. It is considered that the shuttle reaction on the winding center side was effectively suppressed by increasing the value of.

<Example 9 to Example 11>
Example 1 was prepared the electrode-constituting member having a different length (positive electrode sheet, negative electrode sheet, a first separator and the second separator) and thickness shown in Table 3 the winding thickness T _T of the wound electrode assembly from 30mm is changed to (mm), example 9 to example 11 in the same manner as other examples 4 was changed to a thickness shown in Table 3 (mm) of the winding thickness T _a of the region a in which the second separator disposed Such a lithium secondary battery was produced. The amount of gas generated was measured in the same manner as in Example 1 for each battery obtained. The results are shown in Table 3. Table 3 also shows the ratio (T _A / T _T ) (%) of the wound electrode body according to each example.

<Example 12 to Example 14>
Electrode-constituting member having a different length to Example 8 (positive electrode sheet, negative electrode sheet and the first separator) was prepared, thickness showing a winding thickness T _T of the wound electrode assembly from 30mm in Table 3 (mm) A lithium secondary battery according to Examples 12 to 14 was produced in the same manner as Example 8 except that the lithium secondary battery was changed to. The amount of gas generated was measured in the same manner as in Example 1 for each battery obtained. The results are shown in Table 3.

Example 9 and Example 12, Example 10 and Example 13, Example 11 and Example 14 have the same wound electrode body size and the same wound thickness. In comparison of these, respectively, as shown in Table 3, the greater the thickness wound of the wound electrode body, it can be seen that there is a tendency that the gas generation amount increases effect of increasing the inter-electrode distance D _A increases . This is because, as the winding thickness of the wound electrode body increases, the heat dissipation on the winding center side decreases and the temperature rises during overcharging, and the shuttle reaction of the gas generating agent easily occurs. effect of increasing the between distance D _a, that is, the effect of suppressing the shuttle reaction of the gas generating agent be because appeared prominently.

<Example 15 and Example 16>
A lithium secondary battery was produced in the same manner as in Example 4 except that the second separator was changed to a separator having the porosity shown in Table 4. The battery resistance and gas generation amount were measured in the same manner as in Example 1 for each battery obtained. The results are shown in Table 4.

  As shown in Table 4, it can be seen that the increase in battery resistance can be suppressed as the porosity of the second separator increases. Moreover, even if the porosity was increased, no demerits such as a decrease in gas generation amount were observed. From this result, it is inferred that the shuttle reaction of the gas generating agent is more dependent on the distance between the electrodes than other conditions such as the porosity of the separator.

<Example 17>
A lithium secondary battery was produced in the same manner as in Example 4 except that the gas generating agent in the non-aqueous electrolyte was changed from CHB 2% and BP 2% to BP 4%. With respect to the obtained battery, the battery resistance and the amount of gas generated were measured in the same manner as in Example 1. The results are shown in Table 5. Table 5 also shows T _A (mm) and the ratio (T _A / T _T ) (%).

<Example 18>
A lithium secondary battery was produced in the same manner as in Example 8, except that the gas generating agent in the non-aqueous electrolyte was changed from CHB 2% and BP 2% to BP 4%. With respect to the obtained battery, the battery resistance and the amount of gas generated were measured in the same manner as in Example 1. The results are shown in Table 5.

  As shown in Table 5, the amount of gas generated increased even if the type of gas generating agent was changed to only BP.

  Thus, according to the present invention, the amount of gas generated in an overcharged state can be increased. Due to this increase in the amount of gas generated, the operating accuracy of the CID in the overcharged state can be improved. Nevertheless, a decrease in battery characteristics (typically an increase in battery resistance) is suppressed. Therefore, according to the present invention, the operation accuracy of the CID in the overcharged state can be improved while suppressing the deterioration of the battery characteristics.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The invention disclosed herein can include various modifications and alterations of the specific examples described above.

1 Automobile (vehicle)
10 Positive electrode sheet (positive electrode)
DESCRIPTION OF SYMBOLS 12 Positive electrode collector 14 Positive electrode compound material layer 15 Positive electrode current collector lamination | stacking part 16 Positive electrode compound material layer non-formation part 20 Negative electrode sheet (negative electrode)
22 Negative electrode current collector 24 Negative electrode composite material layer 25 Negative electrode current collector layered portion 26 Negative electrode composite material layer non-formed portion 30 CID (current blocking mechanism)
32 Deformed metal plate 33 Curved portion 34 Connection metal plate 35 Current collecting lead terminal 36 Joint point 38 Insulating case 40A, 40B Separator 41 First separator 42 Second separator 50 Battery case 52 Case body 54 Lid 70 Positive electrode terminal 72 Negative electrode terminal 74 Positive electrode current collector plate 76 Negative electrode current collector plate 80 Winding electrode body 90 Non-aqueous electrolyte 100 Lithium secondary battery A Region A
B area B
Winding thickness of the thickness T _T wound electrode assembly of the inter-electrode distance T _A region A in inter-electrode distance D _B region B in D _A region A

Claims (9)

A wound electrode body formed by winding a positive electrode and a negative electrode, a non-aqueous electrolyte containing a gas generating agent, and a current interruption mechanism that operates when the internal pressure of the battery case increases,
The wound electrode body has a region A including the innermost peripheral portion of the wound electrode body and a region B located outside the region A in a cross section perpendicular to the winding axis.
The region A is a region that occupies 5 to 40% of the wound thickness of the wound electrode body,
And inter-electrode distance D _A of the positive and negative electrodes in the region A, the interelectrode distance D _B between the positive and negative electrodes in the region B satisfies the relation of D _A> D _B, and the relative said inter-electrode distance D _B The ratio (D _A / D _B ) of the inter-electrode distance D _A is 4 or less,
A separator is disposed between the positive electrode and the negative electrode,
The relationship of D _A > D _B is realized by disposing at least two separators in the region A,
The separators disposed at least twice are a first separator disposed from the region A to the region B, a second separator disposed in the region A but not disposed in the region B, Including
Porosity of the second separator, rather greater than the porosity of said first separator,
The oxidation potential of the gas generating agent (vsLi / Li ^+), the higher than 0.1V than the upper limit potential of the positive electrode (vsLi / Li ^+), the oxidation potential of the nonaqueous solvent of the nonaqueous electrolyte (vs Li / Li ⁺ ) , And a non-aqueous electrolyte secondary battery lower by 0.1V or more . Electrode body Kai wound made by winding a positive electrode and a negative electrode, a nonaqueous electrolyte containing a gas generating agent, and a current interrupting mechanism operated by the internal pressure of the battery case rises, the non-aqueous electrolyte secondary battery comprising a There,
The wound electrode body has a region A including the innermost peripheral portion of the wound electrode body and a region B located outside the region A in a cross section perpendicular to the winding axis.
The region A is a region that occupies 10 to 40% of the wound thickness of the wound electrode body,
And inter-electrode distance D _A between the positive and negative electrodes in the region A, the interelectrode distance D _B between the positive and negative electrodes in the region B satisfies the relation of D _A> D _B, and the relative said inter-electrode distance D _B The ratio (D _A / D _B ) of the inter-electrode distance D _A is 1.5 or more and 4 or less,
The negative electrode has a negative electrode mixture layer containing a carbon material as a negative electrode active material,
The wound electrode body has a flat shape, and the wound thickness is 10 mm or more,
The non-aqueous electrolyte secondary battery Ri lithium ion secondary battery der,
The oxidation potential of the gas generating agent (vsLi / Li ^+), the higher than 0.1V than the upper limit potential of the positive electrode (vsLi / Li ^+), the oxidation potential of the nonaqueous solvent of the nonaqueous electrolyte (vs Li / Li ⁺ ) , And a non-aqueous electrolyte secondary battery lower by 0.1V or more . A separator is disposed between the positive electrode and the negative electrode,
The relationship of D _A > D _B is realized by disposing at least two separators in the region A,
The separators disposed at least twice are a first separator disposed from the region A to the region B, a second separator disposed in the region A but not disposed in the region B, The nonaqueous electrolyte secondary battery according to claim 2, comprising:   The nonaqueous electrolyte secondary battery according to claim 3, wherein the porosity of the second separator is larger than the porosity of the first separator.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the second separator has a thickness of 20 μm or more and 40 μm or less.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the region A is a region that occupies 10 to 30% of a wound thickness of the wound electrode body. The ratio (D _A / D _B ) of the inter-electrode distance D _{A to} the inter-electrode distance D _B satisfies 1.5 <(D _A / D _B ) <3. The non-aqueous electrolyte secondary battery described in 1.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein a wound thickness of the wound electrode body is 15 mm or more.   A vehicle provided with the nonaqueous electrolyte secondary battery according to claim 1.

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