KR20160037803A - Energy storage device and method of producing the same - Google Patents

Abstract

When manufacturing an energy storage device of a lithium ion battery or the like, the present invention provides an energy storage device which can solve a problem of modification or insulation that can be occurred in a separator, and has excellent durability and reliability. The energy storage device (100) comprises: a positive electrode (10) having a positive composite layer (12) including a positive electrode active material; a negative electrode (20) having a negative electrode composite layer (22) including a negative electrode active material; and a separator (30) for separating the positive electrode (10) and the negative electrode (20). The separator (30) includes: a sheet substrate (31) uniaxially elongated; and a cladding layer (32) for cladding any one surface of the substrate (31). The cladding layer (32) has an anisotropic structure aligned in a direction different from an elongation direction of the substrate (31).

Description

FIELD OF THE INVENTION [0001] The present invention relates to a capacitor device,

The present invention provides a positive electrode comprising a positive electrode in which a positive electrode mixture layer containing a positive electrode active material is formed, a negative electrode in which a negative electrode material mixture layer containing a negative electrode active material is formed, To a capacitor element having a separator for isolating the capacitor element and a method of manufacturing the capacitor element.

A lithium ion battery, which is a typical battery element, has a structure in which a positive electrode and a negative electrode are formed by coating a band-shaped base material with a positive electrode mixture or a negative electrode mixture to form a positive electrode and a negative electrode, And a stacked body in which layers are stacked separately. Here, in the step of manufacturing a lithium ion battery, a layered body that becomes a positive electrode, a separator, and a negative electrode is wound up by a winding device to form a power generating element. At this time, the separator is subjected to a tensile force by the winding work. Therefore, the separator is required to have a strength higher than a certain level that can withstand the winding work.

As the separator of the capacitor element, a resin material which is uniaxially stretched may be used. Therefore, in the separator, the resin is usually oriented in the longitudinal direction which is the stretching direction. Therefore, the separator has a relatively high strength in the MD direction in the stretching direction. On the other hand, with respect to the TD direction (width direction) orthogonal to the stretching direction, since the resin is not oriented, the strength tends to be lowered as compared with the MD direction. In the winding operation of the laminated body, for example, when the tension balance at both end portions of the TD is slightly broken at the time of winding by the winding device, the balance of the tensile force acting on the separator in the laminated body is collapsed from the left and right , A tensile force (stress) may be generated not only in the MD direction but also in the TD direction. In this case, there was a fear that the uniaxial stretching separator would be torn in parallel in the MD direction by the tension in the TD direction.

In manufacturing a capacitor element, it is necessary to improve the strength of the separator in order to prevent deformation and insulation of the separator. As one of such means, for example, it is conceivable to make the separator multi-layered. As a separator used for a conventional lithium ion battery, for example, there has been formed a second porous layer containing a filler and a fibrous material on a porous resin layer made of a base material (see, for example, Patent Document 1) . Patent Document 1 discloses that since the fibrous material is added to the second multi-axial dense layer together with the filler, the shape stability and flexibility of the separator are ensured.

Further, in the separator having a two-layer structure, the first layer is made of a porous resin and the second layer is formed of a porous film containing particles and fibrils (see, for example, Patent Document 2 Reference). Patent Document 2 discloses that the fibrillation contained in the second layer has a three-dimensional network structure connected to each other in a mutually continuous manner, so that flexibility and the like can be imparted to the separator.

Japanese Laid-Open Patent Publication No. 2011-146365 Japanese Patent Application Laid-Open No. 2010-205719

However, the second porous layer described in Patent Document 1 prevents short-circuiting by suppressing heat shrinkage of the separator during charging and discharging of the lithium ion battery, thereby improving the stability of the lithium ion battery. The second layer described in Patent Document 2 has flexibility in the separator even when the separator is broken due to contamination or generation of dendrite at the time of charging and discharging, And is formed so as to improve the safety of the lithium ion battery by securing the insulating property by following the shape of the indenter. As described above, the conventional technique has been developed with the aim of improving the stability of the separator mainly in the use of the lithium battery, paying attention to the problem of the separator that can occur in the production step of the lithium ion battery, The concept of improving durability and reliability has not been shown.

Disclosure of the Invention The present invention has been made in order to solve the above problems, and in particular, it is an object of the present invention to solve the problems of deformation and thermal insulation that may occur in a separator in manufacturing a capacitor element such as a lithium ion battery and to provide a capacitor element having excellent durability and reliability The purpose is to provide. Another object of the present invention is to provide a manufacturing method of a capacitor element which is excellent in such durability and reliability.

In order to solve the above-described problems, a characteristic configuration of a battery device according to the present invention is as follows.

A positive electrode formed with a positive electrode mixture layer containing a positive electrode active material;

A negative electrode formed with a negative electrode mixture layer containing a negative electrode active material; And a separator for isolating the positive electrode and the negative electrode from each other;

And a power storage device,

Wherein the separator comprises a base material of a sheet type which is uniaxially stretched and a coating layer which covers at least one side of the base material,

And the coating layer has an anisotropic structure oriented in a direction different from the stretching direction of the substrate.

As described above, the deformation and the heat insulation of the separator are related to the stretching direction of the substrate. In the uniaxially stretched sheet-like base material, a certain strength can be maintained in the MD direction in the stretching direction, but sufficient strength can not be maintained in the TD direction orthogonal to the stretching direction. Thus, as a result of intensive studies, the present inventors have succeeded in improving the strength of the whole separator by studying the constitution of the coating layer formed on the substrate, and have completed the present invention.

That is, according to the storage of this constitution, at least one surface of the base material constituting the separator is provided with a coating layer having an anisotropic structure oriented in a direction different from the stretching direction of the base material. In this case, since the coating layer functions to reinforce the base material in a direction other than the MD direction, even if stress acts on the separator in a direction other than the MD direction, the anisotropic structure of the coating layer imposes the above stress, . As a result, it becomes possible to provide a battery element excellent in durability and reliability.

In the battery element according to the present invention,

It is preferable that the coating layer has the vertical alignment structure oriented in a direction perpendicular to the stretching direction of the substrate as the anisotropic structure.

According to the capacitor element of this configuration, since the coating layer has the vertical alignment structure oriented in the direction perpendicular to the stretching direction of the substrate, when the tensile force acts in the TD direction of the separator, The tensile force is reliably burdened, and deformation and heat insulation of the separator can be prevented.

In the battery element according to the present invention,

It is preferable that the coating layer has the symmetric alignment structure in which the anisotropic structure is line-symmetrical when viewed from the stretching direction of the substrate.

According to the capacitor element of the present configuration, since the coating layer has a symmetrical alignment structure in which it is line-symmetrical when viewed from the drawing direction of the substrate, when the stress acts in a direction other than the MD direction of the separator, It is dispersed on both sides of the separator, and it can be burdened with good balance. As a result, deformation and thermal insulation of the separator can be prevented.

In the battery element according to the present invention,

The ratio (S _{TD /} S _MD ) of the tensile strength S _TD in the direction perpendicular to the stretching direction of the substrate to the tensile strength S _MD in the stretching direction of the substrate is adjusted to 0.3 or more .

According to the capacitor element of this configuration, since the tensile strength S _TD / tensile strength S _MD is adjusted to 0.3 or more, the tensile strength S _TD is maintained at a certain level or higher. Therefore, the TD direction of the separator, It is possible to prevent the deformation and the heat insulation of the separator.

In the battery element according to the present invention,

It is preferable that the separator is adjusted so that the tensile strength S _TD in the direction perpendicular to the stretching direction of the substrate is 40 N / mm 2 or more.

According to the capacitor element of this configuration, by adjusting the tensile strength S _TD to 40 N / mm < 2 > or more, the TD direction of the separator, which is difficult to maintain the strength with only the substrate, is reliably reinforced by the covering layer, .

In the battery element according to the present invention,

The coating layer is composed of a composite material including fibers having orientation, a filler, and a binder

.

According to the capacitor element of this configuration, by making the constituent material of the covering layer a composite material including fibers having orientation, a filler, and a binder, the base material can be effectively reinforced and the strength of the whole separator can be improved. In particular, by blending fibers having an orientation property, an anisotropic structure can be reliably expressed in the coating layer.

In the battery element according to the present invention,

It is preferable that the negative active material (active material) is a hard carbon having a particle diameter (d50) of 2 탆 to 8 탆.

According to the capacitor element of this configuration, by using hard carbon having a particle diameter (d50) of 2 to 8 占 퐉 as the negative electrode active material contained in the negative pole mixture layer of the negative pole, the volume of the negative pole The flatness of the electrode surface can be maintained not only at the time of manufacture but also at the time of use. Therefore, even if the separator and the negative electrode are stacked to face the coating layer and the negative electrode mixture layer, undue stress does not act on the separator from the negative electrode. As a result, deformation and thermal insulation of the separator can be surely prevented from being synergistically with the reinforcement of the substrate by the anisotropic structure of the coating layer.

In order to solve the above-described problems, a characteristic configuration of a method for manufacturing a battery element,

1. A method of manufacturing a capacitor element which comprises a positive electrode in which a positive electrode mixture layer containing a positive electrode active material is formed and a negative electrode in which a negative electrode mixture layer containing a negative electrode active material is formed,

The separator comprising: a base material forming step of forming a sheet-like base material by uniaxially stretching the porous material; And a coating layer forming step of coating a material including a resin on at least one side of the base material to form a coating layer, wherein in the coating layer forming step, the material containing the resin is different from the stretching direction of the base material As shown in FIG.

According to the manufacturing method of the capacitor element of the present configuration, since the material including the resin is coated in a direction different from the stretching direction of the substrate in the covering layer forming step, the covering layer is oriented in a direction different from the stretching direction of the substrate, As a result, it functions to reinforce the substrate in a direction other than the MD direction. Therefore, even if stress acts on the separator in a direction other than the MD direction, the oriented coating layer is liable to bear the stress, so that deformation and heat insulation of the separator can be suppressed. As a result, it becomes possible to provide a battery element excellent in durability and reliability.

1 is a partially cutaway perspective view of a lithium ion battery.
2 is a perspective view of a power generating element accommodated in a battery case in the lithium ion battery shown in Fig.
3 is a cross-sectional view schematically showing a configuration of a power generating element which is a main part of a lithium ion battery.
Fig. 4 is an enlarged view of the broken line circle of Fig. 3, and is a sectional view schematically showing the structure of the separator.
5 is an exploded perspective view schematically showing the structure of the separator according to the first embodiment.
6 is an exploded perspective view schematically showing the structure of the separator according to the second embodiment.
7 is an exploded perspective view schematically showing the structure of the separator according to the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a battery element according to the present invention will be described with reference to Figs. The method of manufacturing the capacitor element of the present invention will be described in parallel with the description of the embodiment of the capacitor element. In the following embodiments, a lithium ion battery will be described as an example of a battery element. However, the present invention is not limited to the configurations described in the following embodiments and drawings.

[Lithium ion battery]

1 is a partially cut-away perspective view of a lithium ion battery 100 of the present embodiment. 2 is a perspective view of a power generation element 50 housed in a battery case 60 in the lithium ion battery 100 shown in Fig. In Fig. 2, the power generation element 50 in a wound state is partially rewound to clearly illustrate the configuration of the power generation element 50. As shown in Fig. 1 and 2 are all schematically shown, and the details of the structure unnecessary for the description of the present invention are omitted.

1, the lithium ion battery 100 includes a battery case 60 as a casing having a positive electrode terminal 61 and a negative electrode terminal 62, And filling the case (60) with an electrolyte (E) containing a non-aqueous electrolyte. 2, the power generation element 50 is constituted by stacking a separator 30, a positive electrode 10, a separator 30, and a negative electrode 20 in this order to form a laminate, . The positive electrode 10 and the negative electrode 20 are separated from each other by the adjacent separator 30 so that the positive electrode 10 and the negative electrode 20 can be electrically connected to each other They are not grounded, and both are physically insulated. The positive electrode 10 is connected to the positive electrode terminal 61 and the negative electrode 20 is connected to the negative electrode terminal 62 respectively. The electrolytic solution E filled in the battery case 60 is absorbed by the positive electrode 10, the negative electrode 20 and the separator 30 constituting the power generation element 50, And becomes a wet state. As a result, Li ions in the electrolytic solution E are allowed to move between the positive electrode 10 and the negative electrode 20 through the separator 30. The charging amount of the electrolytic solution E to the battery case 60 may be at least enough to absorb the electrolytic solution E at least to the power generating element 50 to be almost completely wetted. And the negative electrode 20 may follow the volume change by the charging and discharging process so that the degree to which a part of the power generating element 50 is immersed in the battery case 60 It is preferable to fill the surplus electrolytic solution (E). The amount of the electrolyte solution E charged into the battery case 60 can be appropriately adjusted in consideration of the prevention of liquid scattering in the power generation element 50 and the balance with the pressure in the battery case. Hereinafter, the configuration of the lithium ion battery 100 will be described in detail.

[Elements of development]

3 is a cross-sectional view schematically showing a configuration of a power generation element 50 which is a main part of the lithium ion battery 100. As shown in Fig. The power generation element 50 is provided with a positive electrode 10, a negative electrode 20, and a separator 30 as a basic structure.

<Positive pole>

The positive electrode 10 is formed by forming the positive electrode material mixture layer 12 on the surface of the positive electrode collector 11. As the positive electrode current collector 11, a foil or film made of a conductive material is used. Examples of the conductive material include aluminum, titanium, nickel, tantalum, silver, copper, platinum, gold, iron, stainless steel, carbon, and conductive polymers. A preferred form of the positive pole collector 11 is an aluminum foil. The aluminum foil is normally in a stable state in which its surface is covered with an oxide (alumina) and is easily processed such as bending and winding, and therefore, it is preferable as a positive electrode member of a lithium ion battery. The positive electrode current collector 11 may be surface-treated with another conductive material. The thickness of the positive electrode collector 11 is 10 mu m to 30 mu m, preferably 12 to 20 mu m. If the thickness of the positive electrode current collector 11 is less than 10 mu m, there is a possibility that the mechanical strength of the positive electrode 10 is insufficient. If the thickness of the positive electrode current collector 11 exceeds 30 占 퐉, the capacity and weight of the entire lithium ion battery increase, and the package efficiency decreases.

The positive electrode material mixture layer 12 includes a positive electrode active material and a binder. As the positive electrode active material, a material capable of absorbing or adsorbing Li ions and capable of releasing Li ions is used. Examples of the positive electrode active material include an olivine type lithium phosphate compound represented by the general formula LiMPO ₄ [M is at least one selected from transition metals], a spinel type lithium transition metal And LiMn ₂ O ₄ which is a compound. Examples of olivine-type lithium phosphate compounds include transition metal lithium phosphate compounds such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCoPO ₄ . Of these, LiFePO ₄ can be preferably used as a positive electrode active material because it can be expected to have an energy density equivalent to that of a conventional lithium ion battery while using iron, which is abundant as a resource, as a part of the material. Further, it may be a positive electrode active material composed of, for example, a composition formula Li _x Mn _a Ni _b Co _c O _d (0 <x <1.3, a + b + c = 1, 1.7? D?

The binder is a binder that binds the positive electrode active material, and a hydrophilic binder or a hydrophobic binder may be used. Examples of the hydrophilic binder include polyacrylic acid (PAA), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and salts or derivatives of these polymers. The above-mentioned hydrophilic binder may be used alone, but it may be used as a mixture of two or more kinds. Examples of the hydrophobic binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ethylene propylene diene terpolymer (EPDM), sulfonated ethylene propylene Rubber, styrene butadiene rubber (SBR), fluorine rubber, and salts or derivatives of these polymers. The hydrophobic binder may be used alone, but it may be used as a mixture of two or more kinds.

In forming the positive electrode material mixture layer 12 on the surface of the positive electrode current collector 11, the binder is dissolved or dispersed in a solvent, the binder solution (dispersion material) is mixed with the positive electrode active material, A positive electrode paste is used. The solvent used for preparing the positive electrode paste is determined depending on the type of the binder to be combined with the positive electrode active material. When a hydrophilic binder is used in the preparation of the positive electrode paste, a water-soluble solvent such as water, alcohol, or acetic acid is used as the solvent. When a hydrophobic binder is used, as the solvent, for example, a lipophilic solvent such as N-methyl-2-pyrrolidone (NMP), xylene, and toluene is used.

In order to increase the conductivity of the positive electrode 10, a conductive auxiliary material may be added to the positive electrode paste. As the conductive agent, an electron conductive material which does not adversely affect the cell performance is used. Examples of such a conductive agent include acetylene black, ketjen black, carbon black, carbon whisker, carbon fiber, natural graphite, artificial graphite, metal powder, and conductive ceramics. The above-mentioned conductive additive can be used singly, but it can be used as a mixture of two or more kinds.

The coating of the positive electrode paste on the surface of the positive electrode current collector 11 can be performed by using a coating device such as a bar coater, a roll coater, a die coater, and a gravure coater. When the viscosity of the paste is sufficiently small, it may be applied by spraying a positive electrode paste on the surface of the positive electrode current collector 11 using an atomizer. By drying the coated positive electrode paste, the solvent contained in the paste is removed by volatilization. Thereafter, the positive electrode 10 is rolled to a predetermined thickness using a press machine or the like.

<Minus pole>

The negative electrode 20 is formed by forming a negative electrode material mixture layer 22 on the surface of the negative electrode collector 21. The material and thickness of the negative electrode current collector 21 are the same as those of the positive electrode current collector 11 used for the positive electrode 10. Therefore, detailed description is omitted.

The negative electrode material mixture layer 22 includes a negative electrode active material and a binder. As the negative electrode active material, a material capable of absorbing or adsorbing Li ions and capable of releasing Li ions is used. Examples of the negative electrode active material include hard carbon, soft carbon, graphite, and lithium titanate having a spinel type crystal structure. In the present invention, from the viewpoint of suppressing the volume expansion of the negative electrode as described later, it is preferable to use hard carbon as the negative electrode active material. Here, in the measurement of the particle diameter, for example, it is measured by a laser diffraction scattering method (scattering method), and D50 corresponds to a volume of 50% on the volume distribution of particles measured by a laser diffraction scattering method Lt; / RTI &gt;

The binder is a binder for binding a negative electrode active material, and a hydrophilic binder or a hydrophobic binder can be used. The type and the selection of the binder are the same as those used for the positive electrode 10. Therefore, detailed description is omitted.

In forming the negative electrode material mixture layer 22 on the surface of the negative electrode current collector 21, a negative electrode paste prepared by adding a solvent to a mixture of a negative electrode active material and a binder and mixing them is used. The solvent used for preparing the negative electrode paste is determined depending on the kind of the binder to be combined with the negative electrode active material and is the same as that used for preparing the positive electrode paste. Therefore, detailed description is omitted.

The negative electrode paste may be applied to the surface of the negative electrode current collector 21 by using a device such as a coating device used for coating the positive electrode paste. Therefore, detailed description is omitted.

<Separator>

The separator 30 has a function of isolating the positive electrode 10 and the negative electrode 20 from each other and transmitting a non-aqueous electrolyte included in the electrolyte solution E. Fig. 4 is an enlarged view of the broken wave source X of Fig. 3, and is a sectional view schematically showing the structure of the cross section of the separator 30. As shown in Fig. The separator 30 has a sheet-like base material 31 and a covering layer 32 covering the base material 31. [

In order to improve the strength in the longitudinal direction (that is, on the MD side), the substrate 31 is uniaxially stretched. The stretching ratio of the base material 31 is adjusted to, for example, 110% to 300%, preferably 150% to 200%. The base material 31 is made of a porous material such as a porous sheet or a nonwoven fabric. The porous material preferably has a performance of not less than 150 sec / cc as a degree of permeability measured in accordance with JIS P 8117 in order to sufficiently secure the ability of the separator (30) to absorb the electrolyte (E) . As the material of the substrate 31, a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a polyester resin such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), a polyacrylonitrile Based resin, a polyphenylene sulfide-based resin, a polyimide-based resin, and a fluororesin. The substrate 31 may be surface-treated with a surfactant or the like.

The coating layer 32 has a function of reinforcing the base material 31 and is formed on at least one side of the base material 31. [ 4 illustrates that the coating layer 32 is formed on the side of the substrate 31 which faces the negative electrode 20. In Fig. The reinforcement of the base material 31 by the coating layer 32 will be described in detail in the item of &quot; anisotropic structure of separator &quot; which will be described later. The coating layer 32 is composed of a composite material including a fiber 32a, a filler 32b, and a binder 32c. By using the composite material, the base material 31 is effectively reinforced, and the strength of the entire separator 30 can be improved. The fiber 32a having an orientation property is used. Here, the term &quot; orientation &quot; means that the fiber 32a has a fiber length larger than the fiber diameter (the aspect ratio is large: the aspect ratio is the length of the long side and the short side of the two- ], And the property that the direction of the fiber length can be arranged in a substantially ordered state. For example, when the fibers 32a are mixed with a resin and the resin is uniaxially stretched at a draw ratio of 120%, if 30% or more of the fibers 32a in the resin are arranged with the lengths of the fibers approximately parallel to each other, The fibers 32a may be considered to have an orientation. (For example, it may be considered that a fiber has an aspect ratio of not less than a predetermined value (for example, 5 or more) as fibers, and 30% or more of the fibers have an angle of 30 degrees or more with respect to the MD direction of the substrate. The average fiber diameter of the fiber 32a is preferably 2 nm to 200 nm, more preferably 20 nm to 150 nm. If the fiber diameter is less than 2 nm, the strength of the fiber itself is insufficient, and even if the fiber 32a is oriented, there is a possibility that sufficient strength is not expressed in the alignment direction. On the other hand, if the fiber diameter exceeds 200 nm, the rigidity of the fiber 32a becomes high, and it may be difficult to orient the fiber 32a. Examples of the fiber 32a having an orientation property include cellulose fiber, aramid fiber, glass fiber, and the like. Since these fibers 32a increase the affinity with the binder 32c, they may be subjected to surface treatment such as surface modification. The filler 32b is added to suppress excessive slippage of the fibers 32a in the coating layer 32. [ When a filler 32b is made to exist between the fibers 32a, an appropriate resistance is generated between the fibers 32a when the fibers 32a are oriented, and the resistance of the fibers 32a through the filler 32b The bonding force can be increased. As a result, the strength of the coating layer 32 itself can be improved. As the filler 32b, for example, inorganic particles are preferable. For example, oxide particles, nitride particles, ionic crystal grains, covalent crystal grains, clay particles, mineral resource-derived materials, or particles of these synthetic materials can be cited. As the fine oxide particles, e.g., iron oxide, SiO _2, Al ₂ O _3, TiO _2, BaTiO _2, ZrO, alumina-silica, etc. may be mentioned particles of the complex oxide. Examples of the nitride particles include particles of aluminum nitride, silicon nitride and the like. Examples of the ionic crystal grains include particles of calcium fluoride, barium fluoride, barium sulfate and the like. Examples of the covalent crystal particles include particles of silicon, diamond, and the like. Examples of the clay particles include particles such as talc and montmorillonite. Examples of the particles of the mineral resource-derived material or the artificial material thereof include inorganic particles such as mite (alumina hydrate), zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite , Mica, and the like. The size of the filler 32b is preferably 2 nm to 3000 nm as the average particle diameter, and more preferably 10 nm to 500 nm. When the size of the filler 32b is less than 2 nm, the filler 32b tends to escape between the fibers 32a when the fibers 32a are oriented, and the bonding force between the fibers 32a may not be sufficiently increased . On the other hand, when the size of the filler 32b exceeds 3,000 nm, the dispersibility of the filler 32b is deteriorated, and there is a fear that a uniform coating layer 32 can not be formed. In addition, when the filler 32b enters the porous structure of the base material 31, there is a possibility that the permeation of the electrolyte solution E may be interrupted. The binder 32c may be one which can adhere the fibers 32a and the filler 32b and therefore the same hydrophilic binder or hydrophobic binder as used for the production of the positive electrode 10 or the negative electrode 20 can be used. As a method for orienting the fiber with the MD direction and angle, for example, a part of the roller is immersed in a container in which the oriented fiber is present, and the oriented fiber is picked out and coated with gravure. . For example, the fibers in the coating solution may be oriented in the container, and the dimension of the plate concave portion may be slightly longer in the transverse direction, but the present invention is not limited thereto. Although an example in which the constitution of the separator is constituted by the substrate and the covering layer is described, from the operation and the effect of the present invention, the constitution is not limited to the constitution. For example, a three-layer structure separator (a separator which is joined to each other) in which polyethylene is sandwiched from above and below with polypropylene may be used. Further, the substrate may be coated with aramid (the covering layer may be aramid fiber). Further, the separator may be an adhesive separator in which the separator is bonded to the electrode. Even when the separator is a single layer, the case where the electrolyte is a polymer or a polymer gel includes the case where the orientation of the separator and the electrolyte becomes anisotropic structurally by the combination of the separator and the electrolyte. The separator may be produced by either wet process using a solvent or dry process without using a solvent.

[Electrolytic solution]

The electrolytic solution (E) mediating the migration of Li ions is obtained by dissolving an electrolytic salt in a non-aqueous solvent. Examples of the nonaqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate, cyclic carbonates such as? -Butyrolactone,? -Valerolactone and the like And chain carbonates such as esters, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. These nonaqueous solvents can be used alone, but they can also be used as a mixture of two or more kinds. As the electrolyte salt, a Li ion salt is used, and for example, LiPF ₆ , LiC ₁ O ₄ , LiBF ₄ , LiAsF ₆ , and LiSbF ₆ can be given. These electrolytic salts can be used alone, but they can also be used as a mixture of two or more kinds.

[Anisotropic Structure of Separator]

In producing the lithium ion battery 100, the stacked body obtained by laminating the positive electrode 10 and the negative electrode 20 separated by the separator 30 is wound up by a winding device to form the power generation element 50 . The separator 30 is formed by a base material forming step of uniaxially stretching a porous material to form a sheet-like base material 31 and a step of forming a base material 31 on at least one surface of the base material 31 ), And a binder 32c) to form a coating layer 32. The coating layer 32 is formed by a coating layer forming step in which the coating layer 32 is formed. The reason why the separator 30 is deformed or insulated at this time is that the base material 31 used for manufacturing the separator 30 is stretched in a specific direction. When the porous material is uniaxially stretched to form the sheet-like base material 31 in the base material forming step, the strength of the base material 31 in the MD direction, which is the stretching direction, becomes high, and the base material 31 can withstand the winding work. However, in the TD direction orthogonal to the stretching direction of the base material 31, the effect of stretching can not be obtained, so that sufficient strength can not be maintained.

The present inventors have conducted intensive studies in order to develop sufficient strength even in the TD direction of the base material 31. The inventors of the present invention have found that a coating material for forming a coating layer 32 is formed by coating a composite material on a base material 31, (MD direction) of the base material 31, the coating layer 32 is oriented, and the base material 31 and the coating layer 32 are oriented in the same direction, It is possible to improve the strength of the separator 30 provided with the separator 30 as a whole. At this time, it was confirmed that the coating layer 32 formed on the base material 31 had a specific structure oriented in a direction different from the stretching direction of the base material 31. In this specification, the specific structure of the coating layer 32 is referred to as &quot; anisotropic structure &quot;. The anisotropic structure of the coating layer 32 is mainly expressed by orienting the fibers 32a contained in the composite material. Therefore, fibers having the above-described orientation property are preferably used for the fibers 32a used for the composite material.

The separator 30 in which the substrate 31 and the coating layer 32 having an anisotropic structure are laminated is reinforced in good balance by the coating layer 32 in the TD direction of the separator, . The ratio (S _TD / S _TD ) of the tensile strength S _TD in the direction perpendicular to the stretching direction (TD direction) of the base material 31 to the tensile strength S _MD in the stretching direction (MD direction) S _MD ) is adjusted to 0.3 or more. It is also preferable that the tensile strength S _TD is adjusted to 40 N / mm 2 or more. By adjusting the tensile strength in this way, the tensile strength S _TD of the separator 30 in the TD direction is maintained at a certain level or more, so that deformation and heat insulation of the separator can be reliably prevented.

Three representative embodiments will be described for a separator 30 having an anisotropic structure having unique characteristics in the capacitor element of the present invention.

&Lt; First Embodiment >

5 is an exploded perspective view schematically showing the structure of the separator 30 according to the first embodiment. The separator 30 has a uniaxially stretched base material 31 and a covering layer 32 covering the surface of the base material 31. [ As shown in Fig. 5, the base material 31 is stretched in the MD direction (longitudinal direction of the paper surface). Therefore, although the strength of the base material 31 is increased in the MD direction, deformation and heat insulation are likely to occur in the TD direction. The coating layer 32 is formed by coating a composite material containing fibers 32a, a filler 32b and a binder 32c in the direction of arrow D1. The D1 direction is a direction different from the MD direction which is the stretching direction of the substrate. Therefore, the fibers 32a in the coating layer 32 are oriented substantially in the direction D1. Therefore, the coating layer 32 has an anisotropic structure oriented in the direction D1.

Here, a case is described in which the tensile force P1 in the TD direction acts on the base material 31, for example, in the separator 30 of the first embodiment. The tensile force P1 in the TD direction acts on the coating layer 32 together with the base material 31. However, the tensile force P1 can be partially alleviated by the fibers 32a of the coating layer 32. [ In the case of the first embodiment, assuming that the angle formed by the D1 direction and the TD direction is? 1, the fibers 32a of the cover layer 32 bear the force of P1 cos? 1 which is a vector component in which the tensile force P1 is dispersed in the D1 direction . Therefore, all of the tensile force P1 does not act on the base material 31. [ Thus, the coating layer 32 having an anisotropic structure functions to reinforce the base material 31 in a direction other than the MD direction, so that deformation and heat insulation of the separator 30 can be suppressed.

&Lt; Second Embodiment >

6 is an exploded perspective view schematically showing the structure of the separator 30 according to the second embodiment. The separator 30 has a uniaxially stretched base material 31 and a covering layer 32 covering the surface of the base material 31. [ The substrate 31 has the same structure as that of the first embodiment, and a detailed description thereof will be omitted. The coating layer 32 is formed by coating a composite material containing fibers 32a, a filler 32b and a binder 32c in the direction of arrow D2. The D2 direction almost coincides with the direction perpendicular to the MD direction, i.e., the TD direction, of the substrate. Therefore, the fibers 32a in the coating layer 32 are oriented substantially in the D2 direction. Therefore, the coating layer 32 has an anisotropic structure oriented in the D2 direction. The anisotropic structure in this case is referred to as &quot; vertical alignment structure &quot;.

Here, a case in which the tensile force P2 in the TD direction acts on the base material 31 in the separator 30 of the second embodiment as in the first embodiment will be examined. The tensile force P2 in the TD direction acts on the coating layer 32 together with the base material 31. However, the tensile force P2 can be largely reduced by the fibers 32a of the coating layer 32. [ In the case of the second embodiment, since the D2 direction and the TD direction are almost the same, the fibers 32a of the covering layer 32 can bear the tensile force P2 as it is. Therefore, most of the tensile force P2 does not act on the base material 31. [ As described above, the covering layer 32 having a vertically aligned structure can reliably reinforce the base material 31 in the TD direction, so that deformation and heat insulation of the separator 30 can be prevented.

&Lt; Third Embodiment >

7 is an exploded perspective view schematically showing the structure of the separator 30 according to the third embodiment. The separator 30 has a uniaxially stretched base material 31 and a covering layer 32 covering the surface of the base material 31. [ The substrate 31 has the same structure as that of the first embodiment, and a detailed description thereof will be omitted. The coating layer 32 is formed by coating the composite material including the fibers 32a, the filler 32b, and the binder 32c in two divided portions. In the first coating, the composite material is coated in the direction of arrow D3, and in the second coating, the composite material is coated in the direction of arrow D4. As a result, the first coating layer 32A and the second coating layer 32B are formed on the base material 31. Therefore, the fibers 32a in the first coating layer 32A are oriented substantially in the D3 direction, and the fibers 32a in the second coating layer 32B are oriented substantially in the D4 direction. Therefore, the coating layer 32 has an anisotropic structure in which the first coating layer 32A is oriented in the D3 direction and a second coating layer 32B is oriented in the D4 direction. Here, the D3 direction and the D4 direction are in a line-symmetrical relationship when viewed from the MD direction, which is the stretching direction of the base material 31. [ Therefore, the anisotropic structure in this case is referred to as a &quot; symmetric alignment structure &quot;.

In the separator 30 of the third embodiment, a case in which tensile force P3 in the TD direction acts on the base material 31 as in the first embodiment will be examined. The tensile force P3 in the TD direction acts on the coating layer 32 together with the base material 31. However, the tensile force P3 can be partially alleviated by the fibers 32a of the coating layer 32. [ In the case of the third embodiment, when the angle formed between the D3 direction and the TD direction is? 2 and the angle formed by the D4 direction and the TD direction is? 3, the fibers 32a of the first coating layer 32A have a tensile force P3 of D3 It is possible to bear the force of P3 占 θ o? 2, which is a vector component dispersed in a direction. Further, the fibers 32a of the second coating layer 32B can bear the force of P3 占 θ o? 3, which is a vector component obtained by dispersing the tensile force P3 in the D4 direction. Since the directions D3 and D4 are in a line-symmetrical relationship when viewed from the MD direction which is the stretching direction of the base material 31 as described above, the sides on which the angles are formed are opposite to each other, but the sizes are the same. Therefore, P3 占 θ o? 2 and P3 占 θ o? 3 have the same size, and both are dispersed with good balance to both sides of the separator 30. Therefore, most of the tensile force P3 does not act on the base material 31. [ As described above, the coating layer 32 having a symmetrical alignment structure can reinforce the base material 31 in a good balance in the TD direction, so that deformation and heat insulation of the separator 30 can be prevented.

In the third embodiment, the coating layer 32 is composed of two layers, but it is also possible to have three or more layers of the coating layer 32. [ Even if the coating layer 32 has three or more layers, a composite material may be coated on the base material 31 so as to have a symmetrical alignment structure between two or more layers.

<Other Embodiments>

The separator 30 described in the first to third embodiments can be obtained by reinforcing the base material 31 by laminating the coating layer 32 having an anisotropic structure on the base material 31 and by deforming the separator 30, But it is also possible to prevent deformation and thermal insulation of the separator 30 by the research on the electrode side. The separator 30 and the negative electrode 20 are disposed so that the coating layer 32 on the side of the separator 30 faces the negative electrode material mixture layer 22 on the negative electrode 20 side However, the volume expansion of the negative electrode 20, which may occur when the lithium ion battery 100 is used, can be suppressed, and the flatness of the surface of the negative electrode 20 can be maintained. Therefore, Is not excessively pressed by the negative electrode 20 and is effective for preventing deformation and heat insulation of the separator 30. [ When various investigations have been made on this point, it has been found that when the hard carbon having a particle diameter d50 of 2 m to 8 m is used as the negative electrode active material of the negative electrode 20, the volume expansion of the negative electrode 20 It can be effectively inhibited. Therefore, even if the negative electrode 20 including the hard carbon having the particle diameter d50 of 2 탆 to 8 탆 is laminated on the separator 30 and the coating layer 32 and the negative electrode material mixture layer 22 face each other, Excessive stress does not act on the separator 30 from the negative electrode 20 and the reinforcement of the base material 31 by the anisotropic structure of the coating layer 32 described in the first to third embodiments, It is possible to reliably prevent the deformation and the heat insulation of the separator 30 from occurring.

The present invention can be applied mainly to a secondary battery (such as a lithium ion battery) used as an in-vehicle power source such as an electric vehicle (EV), a hybrid car (HEV), a plug-in hybrid car (PHEV) , A mobile communication terminal such as a smart phone, a tablet type computer, a secondary battery (such as a lithium ion battery) used as a driving power source for an information terminal such as a notebook computer.

10; Positive pole
12; The positive electrode material mixture layer
20; Negative pole
22; The negative polar compound layer
30; Separator
31; materials
32; Coating layer
32a; fiber
32b; filler
32c; bookbinder
100; Lithium ion battery (charge accumulator)

Claims (9)

A positive electrode formed with a positive electrode mixture layer (positive electrode layer) containing a positive electrode active material (active material);
A negative electrode formed with a negative electrode mixture layer containing a negative electrode active material; And
A separator separating the positive electrode and the negative electrode from each other;
And a power storage device,
Wherein the separator has a sheet type base material which is uniaxially stretched and a coating layer which covers at least one side of the base material,
Wherein the coating layer has an anisotropic structure oriented in a direction different from a stretching direction of the substrate,
Charging device. The method according to claim 1,
Wherein the coating layer has the vertical alignment structure oriented in a direction perpendicular to the stretching direction of the substrate as the anisotropic structure. The method according to claim 1,
Wherein the coating layer has the symmetric orientation structure in which the anisotropic structure is line-symmetrical when viewed from the drawing direction of the substrate. 4. The method according to any one of claims 1 to 3,
Wherein the separator, and the tension (引張) S _TD strength in the direction perpendicular to the stretching direction of the base material, at least the _MD tensile strength S ratio (S _TD / S _MD) with in the stretching direction of the base material O.3 Adjusted capacitive elements. 5. The method according to any one of claims 1 to 4,
Wherein the separator has a tensile strength S _TD adjusted to 40 N / mm 2 or more in a direction perpendicular to the stretching direction of the substrate. 6. The method according to any one of claims 1 to 5,
Wherein the coating layer is composed of a composite material including fibers having orientation, a filler and a binder. 7. The method according to any one of claims 1 to 6,
Wherein the negative electrode active material is a hard carbon having a particle diameter (d50) of 2 탆 to 8 탆. 1. A method of manufacturing a capacitor element comprising: forming a positive electrode having a positive electrode mixture layer containing a positive electrode active material and a negative electrode having a negative electrode mixture layer containing a negative electrode active material,
Wherein the separator comprises: a substrate forming step of forming a sheet-like base material by uniaxially stretching; And
A coating layer forming step of coating a material containing a resin on at least one side of the substrate to form a coating layer;
Lt; / RTI &gt;
In the coating layer forming step, the material including the resin is coated in a direction different from the stretching direction of the substrate,
A method of manufacturing a capacitor element. A positive electrode formed with a positive electrode mixture layer containing a positive electrode active material;
A negative electrode formed with a negative electrode mixture layer containing a negative electrode active material; And
And a separator for isolating the positive electrode and the negative electrode from each other,
Wherein the separator comprises a sheet-like base material and a coating layer covering at least one surface of the base material,
Wherein the coating layer has an anisotropic structure oriented in a direction different from a stretching direction of the substrate,
Charging device.

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