JPH06140077A - Electrochemical element, lithium secondary battery and set battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a highly reliable battery for which positioning of positive and negative electrodes becomes unnecessary, whose assembling becomes simple and whose performance failure can be reduced as well as providing a high voltage and large capacity lithium secondary battery. CONSTITUTION:A positive electrode 1 is formed on one surface of a separator 3, and a negative electrode 2 is formed on the other surface, continuously respectively so as to become smaller than separator width, and an electrode - separator integrated material is formed. This is laminated, and a battery is formed. A flexible electrode of a soft binder is adopted, and a material formed by arranging the positive electrode 1 and the negative electrode 2 oppositely to each other through the separator 3 is folded up even number times, and an electrically insulating sealing material 4 is arranged around it, and the superimposed directional both end parts are sandwiched between electrically conductive plate materials 5, and a plate-like battery is constituted and realized. A high voltage and large capacity lithium secondary battery can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical element for electrochemically moving ions into and out of an electrode, particularly the structure of a lithium secondary battery and its electrode, an assembled battery using the battery and a method for producing them. Is. In the present specification, a battery will be described as an example of the electrochemical element.

[0002]

2. Description of the Related Art An electrochemical device for electrochemically transferring ions into and out of an electrode is, for example, a battery. In a normal battery, a positive electrode that takes in electrons from an external circuit and cations from an electrolyte or discharges electrons from an external circuit and releases anions into the electrolyte during discharge, and a negative electrode that operates opposite to the positive electrode, The structure is such that they are opposed to each other with a layer called a separator containing an electrolyte having no electron conductivity.

If the electrode is a so-called manganese dry battery, the positive electrode is a positive electrode mixture prepared by kneading manganese dioxide as an active material, carbon as a conductive agent and an electrolytic solution with a carbon rod for current collection. The negative electrode is a can of zinc, which is the active material.

In a battery having such a structure, when a large current is attempted to be obtained, the current density is increased and only the active material in the vicinity of the current collecting rod is used, so that the practical battery capacity is reduced. This phenomenon was particularly remarkable in the case of a non-aqueous electrolyte battery using lithium ions, which has a low electric conductivity of the electrolyte.

Since the lithium secondary battery is lightweight and can obtain a high voltage, it has been actively developed not only for small portable electronic devices but also for large storage batteries.

In this lithium secondary battery, lithium metal alone was used as a negative electrode material before.
There was a problem such as an internal short circuit due to the dendritic deposition of lithium metal. Therefore, in recent years, a method of using carbon as a negative electrode material and inserting and desorbing lithium ions is becoming mainstream. By using this electrode, a battery having a voltage similar to that when using lithium metal and having high safety without dendrite was made possible. The negative electrode is composed of a carbon material such as pyrolytic carbon, carbon black, coke and graphite, and is bound by a binder for molding.

As a positive electrode material for a lithium secondary battery, a battery having a high voltage and a high energy density is possible, and a substance capable of inserting and removing lithium ions while maintaining its structure is required, and various substances are proposed. Has been done. For example, T
iS2, MnO2, V2O5, LiCoO2, LiNiO2,
Examples thereof include LiMn2O4. As the constituent material of the positive electrode, these positive electrode active materials are the main components, and graphite or the like is added to improve conductivity. Also, in order to have moldability similar to the negative electrode, a binder is added and bonded. There is.

In the conventional lithium secondary battery, a separator is interposed between the both electrodes and a non-aqueous organic solvent is used as an electrolytic solution. The battery structure is a coin type or a cylindrical type.

Generally, when trying to obtain a large current in a battery, it has been attempted to make the electrode area as large as possible. Especially in a lithium secondary battery, since an organic solvent having a relatively low conductivity is used as an electrolytic solution,
Increasing the area of the electrode is especially important.

FIG. 12 is a half sectional side view showing a conventional coin type battery shown on page 124 of "Battery Handbook" (edited by Battery Handbook Editing Committee, published by Maruzen 1990).
Reference numeral 1 is a positive electrode, 2 is a negative electrode, 3 is a separator, and 4 is a sealing material.

In the flat battery having such a structure, there is a limit in increasing the electrode area. Therefore, in order to obtain a large electric current even in the case of an electrolyte having a low electric conductivity, a cylindrical battery having a large electrode area has been produced by winding a strip-shaped electrode as a battery of a large electric current type. For example, as described in Japanese Patent Application Laid-Open No. 2-51875, it has been devised to reduce the substantial current density by forming a structure in which a strip-shaped electrode and a separator are laminated and rolled up. In addition, it has been a usual assembly method to manufacture and laminate the strip-shaped electrode and the separator separately.

Further, in order to obtain a large area by using a flat plate-shaped electrode, the conventional method is to adopt a structure in which so-called strip-shaped electrodes are connected. Figure 13 is also the "Battery Handbook"
188 (Edited by Battery Handbook Editorial Committee, published by Maruzen 1990)
FIG. 7 is an exploded perspective view showing a structure of a conventional clad lead-acid battery shown on a page. Both the strip-shaped positive electrode 1 and the negative electrode 2 are connected like a comb by a current collecting tab and a connecting rod, arranged via a separator, and put in one container.

On the other hand, even a lithium secondary battery boasting a high voltage is at most 3-4V. Therefore, when a higher voltage is required, a method of connecting batteries in series is adopted.

When a battery such as a lead-acid battery for an automobile appears to output 12 V, for example, a cell is divided into a plurality of cells, and a positive electrode plate and a negative electrode plate are combined for each division via a separator and an electrolytic cell. It contains liquid, and one of the separators is a unit cell, which is connected in series via a collector tab and a collector rod. There is also a so-called pack battery in which a cylindrical battery or a square battery assembled as a single battery and connected in series by spot welding are put in a container. On the other hand, there is a method of connecting cells in series while forming a single cell with a so-called bipolar structure as seen in a fuel cell or a redox flow battery for storing electric power.

In the conventional secondary battery, it is general to remove the heat generated by charging and discharging by natural heat dissipation. Therefore, when a large number of batteries are put in one room for use such as power storage, Pay attention to ventilation and temperature in the room.

In a conventional sealed secondary battery, when an abnormal increase in internal pressure due to gas generation due to charge / discharge reaction or side reaction occurs, a weak portion is provided in a part of the battery container to release the internal pressure. The method of destroying the lever part is adopted.

In this case, the electrolytic solution also flows out when the internal pressure is released, so that the battery becomes useless. In the open-type secondary battery, the gas can always escape, but since the electrolytic solution also scatters at the same time, the electrolytic solution can be injected from the outside in a timely manner.

[0018]

Since most of the conventional practical secondary batteries have an aqueous electrolyte,
The ionic conductivity resistance of the electrolyte is small, and the electrode is stable even in the air. On the other hand, the performance of the lithium secondary battery is brought out only in an internal environment in which moisture is sufficiently removed. That is, there is a problem in that a stable and high-performance lithium secondary battery cannot be made with the structure and materials used in the conventional secondary battery.

For example, the maximum current drawn from a lead storage battery having the same electrode area reaches several ten times that of a lithium secondary battery. Therefore, in the lithium secondary battery, it is necessary to increase the electrode area by several tens of times so that the same current can be taken out. Therefore, it is necessary to compactly pack the large area electrode in the battery container.

Further, in the conventional method, since the electrode and the separator are separately manufactured and laminated, it is necessary to position the positive electrode and the negative electrode through the separator, which is important in terms of performance, and highly accurate assembly is required. If this alignment is neglected, the reaction area will be insufficient and the capacity will be insufficient. Further, in the worst case, there is a problem that the positive electrode and the negative electrode come into contact with each other at the end portion, and the function as a battery is impaired.

When connecting the cells in series in order to obtain a high voltage, the cells connected by a current collector or connected by spot welding have a fixed connection between the cells.
If a trouble such as an internal short circuit occurs, the battery cannot be protected by disconnecting the external circuit. The lithium secondary battery has a high energy density, which may cause a serious accident.

Even if there is no trouble, it is conceivable that the electrolytic solution may be decomposed and exhausted due to heat generation due to charging and discharging. Since the lithium secondary battery is vulnerable to the infiltration of moisture in the air, it is necessary to prevent the need to replenish the electrolytic solution from the outside.

The present invention was invented in order to solve various problems associated with these lithium secondary batteries.

That is, the present invention provides an electrochemical device and a battery which can simplify the assembly by eliminating the alignment of the positive electrode and the negative electrode at the time of assembly and can reduce the defective performance due to the reduction of the reaction area due to the defective assembly. It is intended to provide a suitable manufacturing method. Another object of the present invention is to provide a safe, high-voltage, large-capacity flat-plate lithium secondary battery, a flexible electrode suitable for it, an assembled battery using the above single battery, and a manufacturing method thereof.

[0025]

The electrochemical device of the present invention is an electron conducting device comprising an active material layer having the ability to electrochemically store and discharge ions with a porous body holding an ion conductive substance sandwiched therebetween. Conductive electrodes are opposed to each other, and the active material layer is formed on the surface of the porous body so as to have a width narrower than the width of the active material layer except the edges thereof. The opposite side) or the one with a current collector inside.

The battery of the present invention has a separator holding a lithium ion conductive electrolyte, and uses an inorganic oxide that absorbs and discharges lithium ions as a positive electrode active material and carbon as a negative electrode active material. A positive electrode active material layer containing a positive electrode active material on one surface of the separator, a negative electrode active material layer containing a negative electrode active material on the other surface, which is formed narrower than the separator width except the separator edge. is there.

In the production of the electrochemical device, the band-shaped porous body is relatively moved, and a paste containing an electrochemically active material is applied to one surface and the other surface of the band-shaped porous body to form an active material layer on the porous body. To form.

Further, the band-shaped porous body is made to hold the ion conductive substance in advance, and then the paste is applied to the porous body.

Further, in the flat lithium secondary battery of the present invention, the positive electrode and the negative electrode are arranged so as to face each other via the separator, and the battery element is formed by folding the positive and negative electrodes evenly and is surrounded by an electrically insulating material. The battery element has a structure in which a sealing material is provided and the battery elements are sandwiched by conductive plate materials provided at both ends in the overlapping direction.

Further, a heat dissipation mechanism is installed on the outer periphery of the battery.

The flexible electrode uses a soft fluororesin composed of the following monomer units A and B obtained by graft-polymerizing a crystalline fluororesin on fluororubber as a binder. _{A: -CH 2 -CF 2 - B} : -CFCl-CF 2 -

Further, the ratio of the binder made of a soft fluororesin to the active material is in the range of 0.1% by weight to 20% by weight, and 5 to 30 parts by weight of the coating material is applied to 1 part by weight of the binder when preparing the electrode. It was made to disperse in a solvent.

Further, the assembled battery of the present invention is formed by stacking the flat plate-shaped lithium secondary batteries and applying a surface pressure in the stacking direction so that the flat plate-shaped batteries are fixed to each other and electrically connected to each other. is there.

Further, a spring is inserted between the flat plate batteries to be stacked so that the flat plates are electrically disconnected from each other when the surface pressure in the stacking direction is loosened.

Further, the flat battery to be stacked is formed in a leaf spring shape, and the flat batteries are electrically disconnected from each other when the surface pressure in the stacking direction is relaxed.

Further, a heat collecting plate is attached to each lithium secondary battery, for example, one or several lithium secondary batteries, and a heat radiating mechanism is provided on the outer periphery of the assembled battery to electrically insulate the heat collecting plate from the heat radiating mechanism. Connected

An electrolyte solution reservoir made of a porous body containing an electrolyte solution is provided on the outer periphery of the assembled battery, and a liquid conducting section made of a porous body connecting the reservoir and the separator of the lithium secondary battery. An electrolytic solution replenishing mechanism is provided.

Further, the liquid absorbing power of the electrolyte reservoir is equal to or less than the liquid absorbing power of the separator and the electrode of the battery,
In addition, it was formed so as to be larger than the liquid absorbing force of the liquid conducting portion.

Further, in a lithium secondary battery using an electrolyte in which a lithium salt is dissolved in an organic solvent, lithium carbonate is contained in at least one of the negative electrode, the separator and the electrolyte.

Carbon dioxide was contained in the container for accommodating the battery, and lithium oxide was contained in at least one of the negative electrode, the separator and the electrolyte.

Then, in manufacturing the lithium secondary battery,
A process of sealing the battery container was performed in a carbon dioxide atmosphere or while blowing carbon dioxide gas to the battery parts.

Carbonate was added to the positive electrode, and after assembling the battery, charging or heating was performed to decompose the carbonate to generate carbon dioxide gas.

[0043]

In the electrochemical device of the present invention, for example, the battery, the positive electrode is formed on one surface of the porous body, that is, the separator, and the negative electrode is formed on the other surface of the porous body. Positioning of the positive electrode and the negative electrode is unnecessary, which simplifies the assembly. When the electrode-separator integrated body thus formed is folded once, for example, with the positive electrode surface facing inward, a battery sheet having a positive electrode inside and a negative electrode surface outside is obtained. A battery can be easily obtained by winding up or stacking. The obtained battery undergoes the same battery reaction as the battery by the conventional method.

For example, in a battery in which lithium cobaltate is used as the active material for the positive electrode and carbon is used as the negative electrode active material, during the charging reaction, lithium ions dissolve into the electrolyte at the same time that electrons are emitted from the positive electrode active material to the external circuit. On the other hand, at the negative electrode, carbon simultaneously absorbs electrons from an external circuit and at the same time absorbs lithium ions from the electrolyte. The discharge reaction proceeds in the opposite direction to charging.

Since both the positive electrode and the negative electrode are formed on the separator with a width narrower than the width of the separator, the positive electrode and the negative electrode are inside the separator even if the end faces are misaligned when they are rolled up or laminated, and thus contact each other. Never,
It does not hinder the progress of the battery reaction.

Further, since the positive electrode active material and the negative electrode active material are surely opposed to each other via the separator, there is no generation of an active material that does not contribute to the reaction due to the electrode displacement, and as a result, the battery capacity is not insufficient.

The positive electrode active material layer and the negative electrode active material layer can be easily formed on the separator by applying a paste containing an electrochemically active material to one surface and the other surface of the porous body, that is, the separator.

Even in the case of a high-viscosity substance such as a polymer electrolyte or a solid ionic conductive substance, which is difficult to retain in the porous separator after forming the active material layer, the ions are previously added to the porous separator. It can be applied by holding a conductive substance.

Further, in the flat lithium secondary battery of the present invention, by configuring as described above, a high-performance battery can be obtained in which a large electrode area electrode can be compactly packed in a battery container and a large current can be obtained. To be Further, it has a flat plate shape and is suitable for forming an assembled battery.

Since the heat radiating mechanism including the heat radiating fins and the pin assembly is provided on the outer peripheral portion of the battery, heat generated during charging and discharging can be quickly removed. It is possible to reduce excessive rise in battery temperature.

By using the above-mentioned soft fluororesin as the binder, a flexible electrode having high performance and high flexibility can be obtained, so that the workability is improved and the degree of freedom of the electrode structure is increased. It facilitates the production of cylindrical spirals and folding electrodes.

The ratio of binder to active material is 0.1.
By adjusting the amount to be in the range of 20% by weight to 20% by weight, the battery performance becomes good, and since it is dispersed in 5 to 30 parts by weight of the coating solvent with respect to 1 part by weight of the binder, coating (electrode preparation) is easy become.

Further, since the battery pack of the present invention is constructed by stacking the flat plate lithium secondary batteries and applying a surface pressure in the stacking direction, the flat plate batteries are fixed to each other and electrically connected to each other. In case of trouble, the connection can be easily broken by loosening the surface pressure, and the battery can be protected.

Further, by inserting a spring between the stacked flat-plate batteries and forming the stacked flat-plate batteries in the shape of a leaf spring, the restoring force of the springs causes a gap between the batteries to facilitate electrical connection. You can come to Japan.

Further, since a heat collecting plate is attached to the lithium secondary battery and a heat radiating mechanism is provided on the outer peripheral portion of the assembled battery, and the heat collecting plate and the heat radiating mechanism are electrically insulated and connected, it is generated inside the battery. The heat generated can be removed, and an excessive rise in battery temperature in the assembled battery, which is difficult to reduce only by natural heat dissipation from the surface of the assembled battery, can be reduced.

Then, an electrolyte solution reservoir is provided on the outer periphery of the assembled battery.
Since the electrolytic solution replenishing mechanism including the liquid conducting section that connects the reservoir and the separator of the lithium secondary battery is provided, the exhaustion of the electrolytic solution can be prevented. The life can be extended.

Further, the liquid absorbing power of the electrolytic solution reservoir is equal to or less than the liquid absorbing power of the battery separator and the electrode,
In addition, since it is formed so as to be larger than the liquid absorption force of the liquid guiding portion, the electrolyte solution is replenished when the electrolyte solution is insufficient, and the decrease in battery efficiency can be prevented.

Further, in the lithium secondary battery, the negative electrode,
Since lithium carbonate is contained in at least one of the separator and the electrolyte, it is possible to suppress gas generation due to decomposition of the organic solvent of the electrolytic solution and suppress increase in battery internal pressure. Safety is improved. In a closed system like a battery,
It is considered that when a large amount of lithium carbonate, which is a reaction product, is present in the system, equilibrium transfer occurs and the reaction becomes difficult to proceed.

Further, since carbon dioxide is contained in the container for accommodating the battery and lithium oxide is contained in at least one of the negative electrode, the separator and the electrolyte, the gas generation rate can be reduced and the internal pressure of the battery can be increased. Can be suppressed.
Since carbon dioxide gas, lithium oxide and lithium carbonate are in an equilibrium relationship, when the carbon dioxide concentration is high, lithium carbonate is produced,
It is considered that the same effect as when adding lithium carbonate was exhibited.

In the production of batteries, in a carbon dioxide gas atmosphere,
Alternatively, by sealing the battery container while blowing carbon dioxide gas to the battery parts, the carbon dioxide gas can be sealed in the container, the decomposition of the electrolytic solution can be suppressed, and the rise in the battery internal pressure can be suppressed.

Further, since carbonate is added to the positive electrode and the battery is assembled and then charged or heated to decompose the carbonate to generate carbon dioxide gas, the concentration of carbon dioxide gas in the battery is adjusted to the electrolytic solution. It can be raised without disassembling, and the rise in battery internal pressure can be suppressed.

[0062]

EXAMPLE The battery of the present invention is one in which a positive electrode is continuously formed on one surface of a separator and a negative electrode is continuously formed on the other surface in order to eliminate alignment between the positive electrode and the negative electrode during assembly. When forming the electrode, the width of the positive electrode and the negative electrode is made smaller than the width of the separator. When the electrode-separator integrated body thus formed is folded once, for example, with the positive electrode side facing inward, a battery sheet having a positive electrode inside and a negative electrode side outside is obtained. If this sheet is rolled up as it is and inserted into a cylindrical can, a cylindrical battery is obtained. Also, if you stack this sheet in the shape of a strip and insert it into a square can,
A prismatic battery can be obtained. Then, the obtained battery undergoes the same battery reaction as the battery by the conventional method. Specific examples will be described below with reference to examples.

Example 1. FIG. 1 is a perspective view showing a battery sheet according to an embodiment of the present invention. In the figure, 51 is a current collecting net with a tab, 52 is a positive electrode active material layer, 53 is a copper foil for current collection, 55 is a negative electrode active material layer, and 3 is a separator. 87 wt% lithium cobaltate, graphite powder (LON
ZA) KS-6) 8 wt%, binder (polyvinylidene fluoride) 5 wt% adjusted positive electrode active material paste on the separator 3, in this case, porous polyethylene film (thickness 50 μm) by the doctor blade method. The thickness was adjusted to 200 μm and applied. Then flip it over,
On the back surface, a negative electrode active material paste adjusted to 95 wt% of mesophase microbead carbon (manufactured by Osaka Gas) and 5 wt% of a binder (polyvinylidene fluoride) was applied to a thickness of 200 μm by the same doctor blade method. The positive electrode and negative electrode active material pastes were applied narrower than the width of the porous polyethylene film 3, excluding the edges. After drying, the positive electrode surface of the battery sheet is placed inside and the tabbed current collector 5
1. In this case, fold in the longitudinal direction of the sheet so as to sandwich a stainless steel net with a tab for current collection, and a copper foil for current collection 5 on the outside.
3 (thickness 20 μm) was applied and the total thickness was adjusted to 150 μm by a roller press to prepare the battery sheet shown in FIG.

The prepared battery sheet was wrapped around a copper bobbin, inserted into a stainless steel can, a stainless steel tab was welded to the positive electrode terminal, and then lithium perchlorate was dissolved in a mixed solvent of ethylene carbonate, dimethoxyethane, and benzene. The electrolyte solution was injected, and sealing treatment was performed.

Through the above steps, 500 cells were continuously produced, but none of them had a defect due to an internal short circuit. In the present invention, the positive electrode is formed on one surface of the separator 3 and the negative electrode is formed on the other surface. Unlike the case of manufacturing and stacking separately, it is not necessary to position the positive electrode and the negative electrode via the separator. A battery could be manufactured without causing a defect due to an internal short circuit even if it was assembled without being assembled. Also, since the number of parts is reduced, the assembling process can be simplified and the production can be easily performed. Further, the battery of the present invention is formed on the separator with a narrower width for both the positive electrode and the negative electrode than the width of the separator. They did not come into contact with each other and did not hinder the progress of the cell reaction. Further, since the positive electrode active material and the negative electrode active material were positively opposed to each other via the separator, no active material that did not contribute to the reaction due to electrode displacement was generated, and the battery capacity was not insufficient.

Example 2. FIG. 2 is a perspective view showing a battery sheet according to another embodiment of the present invention, and 54 is a copper foil for collecting current with a tab. A positive electrode active material paste having a composition of 87 wt% lithium cobaltate, 8 wt% graphite powder (KS-6 made by Lonza), and 5 wt% binder (polyvinylidene fluoride) was placed on the porous polyethylene film (thickness 50 μm) of the separator 3. 2 thickness by doctor blade method
It was adjusted to 00 μm and applied. Next, turn it over and, on the back surface, mesophase microbead carbon (manufactured by Osaka Gas) 95
wt%, binder (polyvinylidene fluoride) 5 wt%
The negative electrode active material paste prepared in step 1 above was also applied to a thickness of 200 μm by the doctor blade method. The positive electrode and negative electrode active material pastes were applied narrower than the width of the porous polyethylene film 3, excluding the edges. After drying, the positive electrode surface of the battery sheet is placed inside and folded in the lengthwise direction of the sheet so as to sandwich the stainless steel net 51 with tabs for current collection, and a copper foil 53 for peripheral electricity with tabs (thickness 20 μm) is provided on the outside. Applying a roller press to adjust the total thickness to 150 μm,
A strip-shaped battery sheet shown in was prepared.

The prepared strip-shaped battery sheets were bundled, the positive electrode tabs were welded to each other, the negative electrode tabs were welded to each other, and then inserted into a square can.
After the sealing treatment was performed except for the electrolytic solution inlet, the electrolytic solution obtained by dissolving lithium perchlorate in a mixed solvent of ethylene carbonate, dimethoxyethane and benzene was injected, and the inlet was welded and sealed.

Through the above steps, 500 cells were continuously produced, but none of them had a defect due to an internal short circuit. The same effect as that of the above embodiment was obtained.

Example 3. Lithium cobaltate 87wt
%, Graphite powder (KS-6 made by Lonza) 8% by weight, binder (polyvinylidene fluoride) 5% by weight, the positive electrode active material paste was adjusted, and 70% by volume of this paste and polyethylene oxide were solid-solved with lithium perchlorate. A positive electrode paste was prepared by well mixing 30% by volume of the polymer electrolyte. Similarly, a negative electrode paste in which 70% by volume of the negative electrode active material paste adjusted to 95% by weight of mesophase microbead carbon (manufactured by Osaka Gas) and 5% by weight of a binder (polyvinylidene fluoride) and 30% by volume of the polymer electrolyte were prepared. Porous polyethylene film (thickness: 50 μm) of separator 3 pre-soaked with polyelectrolyte
The thickness of the positive electrode paste is 20
It was adjusted to 0 μm and applied. Next, turn over and apply a negative electrode paste on the back side with a doctor blade method to a thickness of 200 μm.
Painted on The positive electrode and negative electrode active material pastes were applied narrower than the width of the porous polyethylene film 3, excluding the edges. After drying, the positive electrode surface of the battery sheet is placed inside and folded in the longitudinal direction of the sheet so as to sandwich a net 51 made of stainless steel with a tab for collecting current, and a copper foil with a tab 54 provided outside.
(Thickness of 20 μm) was applied to make the total thickness uniform to 150 μm by a roller press to prepare a strip-shaped battery sheet shown in FIG.

The prepared strip-shaped battery sheets were bundled, the positive electrode tabs were welded to each other, the negative electrode tabs were welded to each other, and then inserted into a square can.
Welded and sealed.

Through the above steps, 500 cells were continuously produced, but none of them had a defect due to an internal short circuit. Further, the same effect as that of the above-mentioned embodiment was shown.

Comparative Example 87 wt% lithium cobaltate and 8 wt% graphite powder (KS-6 made by Lonza) on both sides of an aluminum foil with a tab (20 μm).
%, A positive electrode active material paste adjusted to a composition of 5 wt% of binder (polyvinylidene fluoride) was formed by a doctor blade method, dried and then a roller press was used to form a positive electrode having a thickness of 100 μm.

95 wt% of mesophase microbead carbon (manufactured by Osaka Gas) on both sides of the tabbed copper foil (20 μm)
%, A negative electrode active material paste adjusted to 5 wt% of binder (polyvinylidene fluoride) was similarly formed by the doctor blade method, and after drying, a negative electrode having a thickness of 100 μm was formed by a roller press.

As shown in the schematic view of FIG. 11, a positive electrode 1, a band-shaped porous polyethylene film (thickness 25 μm) separator 3, a negative electrode 2 and a separator 3 are laminated in this order by passing a laminating guide 58 around a stainless bobbin 56. It was wound around, and inserted into a stainless steel can, and after welding a stainless tab to the positive electrode terminal, an electrolytic solution in which lithium perchlorate was dissolved in a mixed solvent consisting of ethylene carbonate, dimethoxyethane and benzene was injected, and a sealing treatment was performed. 57 is an electrode separator laminated roll-up body.

Through the above steps, 500 cells were continuously produced, but 10 of them were defective due to an internal short circuit.

In the above-mentioned embodiment, a battery was used as an example of the electrochemical element, but the same effect can be obtained by applying it to a capacitor.

On the other hand, another lithium secondary battery of the present invention is
In order to realize a high-voltage, large-capacity battery, a flexible electrode using a soft fluororesin as a binder is adopted to form a flat battery having a folding electrode structure. Also, by stacking these, a safe and high-performance assembled battery can be easily obtained.
Furthermore, a heat dissipation mechanism and a pressure release mechanism are provided, and the gas composition in the battery is made to be sufficient for carbon dioxide gas to suppress an increase in pressure and improve safety. In addition, an electrolyte replenishment mechanism is provided to extend the service life.

Example 4. FIG. 3 is a sectional view showing an embodiment of the flat lithium secondary battery of the present invention. A positive electrode 1 and a negative electrode 2 that face each other with a separator 3 in between are folded evenly to form a battery element, and an electrically insulating seal material 4 is arranged around this and sandwiched between two conductive plate materials 5. A flat cell is formed. By doing so, a large electrode area electrode can be compactly packed in a battery container, and a high voltage, large capacity battery can be obtained.

The material of the electrically insulating sealing material and the electrically conductive plate material is not particularly limited, but polypropylene, polyethylene or the like is preferred as the sealing material. Examples of the conductive plate material include copper, aluminum, nickel, iron, and stainless steel.

The reason why the number of times of folding the battery element is set to be an even number is that if the number of times of folding is set to an odd number, only the positive electrode or the negative electrode is provided on both the front and back surfaces of the folded battery element. If the number of times is odd, if the back of the battery element is the positive electrode, the surface will always be the negative electrode. Both the positive and negative electrodes and the separator may be overlapped and folded as separate parts, but it is manufactured as an integrated battery element in which the positive electrode is formed on one surface of one separator and the negative electrode is formed on the opposite surface. You may fold. By using the electrode-separator integral body of the above-mentioned embodiment, it is possible to easily form it with less performance defects.

The number of folds is not specified at all, but it is preferably about 4 to 16 times in consideration of complexity of assembly. The width and length of the battery element are determined by the electrode area to be created and the number of folds. Regarding the thickness of the battery element, the thickness of the separator is about 25 to 50 μm, and the thickness of the positive electrode and the negative electrode is 50 to 500 μm.

Example 5. Next, a flexible electrode which is suitable for the flat lithium secondary battery having the folding electrode structure of the present invention and which can be easily folded will be described. It is a flexible electrode characterized by using a soft fluororesin composed of the following monomer units A and B, which is obtained by graft-polymerizing a crystalline fluororesin on fluororubber as a binder. Moreover, you may use what added the said fluororesin and 1 or more types of other fluororesins as a binder. . _{A: -CH 2 -CF 2 - B} : -CFCl-CF 2 -

Conventionally, such a soft fluororesin has the same level of performance as the fluororesin most favorably used in the electrodes for lithium secondary batteries, and has been improved to improve the mechanical strength. Which is disclosed in JP-A-5
8-206615 discloses the manufacturing method and performance. Since such a soft fluororesin is a fluorocopolymer obtained by graft-polymerizing a crystalline fluororesin to a fluororubber, while maintaining the same level of performance as a conventional fluororesin, the fluororubber also has flexibility. It is a combined fluororesin. When this soft fluororesin is used as a binder, it is possible to produce an electrode having high performance and high flexibility, which is not available in conventional binders.

Such a soft fluororesin can be used not only alone, but also by being mixed with another crystalline fluororesin or the like, the flexibility of the soft fluororesin can be imparted while leaving the properties of the base resin. The resin to be mixed is not particularly limited, but among the fluororesins, polyvinylidene fluoride (PV
It is particularly compatible with dF).

In a flexible electrode using such a binder, if the ratio of the binder to the active material is small, the active material cannot be bound and the battery capacity is lowered. Since it will be covered and hinders the electrode reaction, 0.1% to 20% by weight,
It is preferably in the range of 1% by weight to 10% by weight.
In addition, in the case of making by dispersing in a coating solvent in making the electrode, from the viewpoint of the hardness of the paste at the time of coating,
The ratio of the coating solvent to 1 part by weight of the binder is 5 to 30.
It is desirable that the amount is parts by weight, preferably 8 to 20 parts by weight. As an example of the production method, there is a method in which the binder is dissolved in a coating solvent to prepare a binder solution, and an active material and the like are dispersed in the solution to be molded on a substrate or an electrode current collector.

For example, 33 parts by weight of an N-methylpyrrolidone (NMP) solution as a coating solvent, and a soft fluororesin (Cefural Soft: Central Glass) as a binder
Co., Ltd. 3 parts by weight was dissolved into a binder solution, and 58 parts by weight of LiCoO2 powder as a positive electrode active material and 6 parts by weight of graphite powder as a conductive agent were dispersed in the solution to prepare a coating solution. Liquid with a thickness of 20 which is a current collector
An electrode sheet of one example of the flexible electrode of the present invention having a thickness of about 300 μm was obtained by applying a 30 cm width on an aluminum foil of μm and drying. This sheet is about 80 × 10mm
It was used as a sample for cutting test.

Tensile strength and elongation strain were measured with a tensile strength measuring instrument using the prepared sample, and the mechanical strength thereof was evaluated. The result is the characteristic curve a of the characteristic diagram of FIG.
Shown in. The vertical axis represents load and the horizontal axis represents elongation. Similarly, the characteristic curve c of FIG. 4 shows the evaluation results of an electrode sheet (conventional example) prepared in the same manner except that PVdF was used as the binder. In addition, the characteristic curve b of FIG. 4 shows the evaluation results of the electrode sheets of other examples which were prepared in the same manner except that the binder was changed to the mixed powder (1: 1) of PVdF and the soft fluororesin.

FIG. 4 shows an electrode for a non-aqueous electrolyte battery,
Regarding the electrode to which the electrode active material is adhered by the binder, by using the soft fluororesin obtained by graft-polymerizing the crystalline fluororesin with the fluororubber as the binder, the electrode flexibility which cannot be obtained by the conventional binder is obtained. Show that you can now.

The solvent is not particularly limited as long as it can dissolve the binder, and examples thereof include N-methylpyrrolidone (NMP) and N, N dimethylformamide (DMF). The active material is not particularly limited, but examples thereof include graphite, glassy carbon, carbon black, coke, pyrolytic carbon, carbon materials such as carbon fiber, TiS2, MoS2, MnO.
2, V2O5, V6O13, LiCoO2, LiNiO2, Li
Inorganic compounds such as Mn2O4 are listed. Examples of the current collector include foils such as copper, aluminum, nickel, iron, and stainless steel, mesh, expanded metal, and the like.

When the electrode prepared as described above using the binder is used in a non-aqueous electrolyte battery, it can also be used as a negative electrode or a positive electrode, and the electrolyte or electrolyte of such a battery is also not particularly limited. Instead, a conventional one can be used.

As described above, in an electrode in which a powdery active material is bound by a binder, not only its performance but also its mechanical properties often depend on the performance of the binder. Therefore, in the present invention, by paying attention to the binder for adhering the active material and the like, by finding a binder that does not affect the battery performance and is also excellent in mechanical strength, a flexible electrode having excellent processability is produced. It shows that you can do it.

By applying the above-mentioned binder to the binder for adhering the active material in the electrode for non-aqueous electrolyte battery, it is possible to obtain the electrode flexibility which cannot be obtained by the conventional binder. By using the electrode thus manufactured, it becomes easy to manufacture a folded electrode or a wound electrode in a large electrode area, which brings a beneficial result for improving battery performance.

Example 6. The assembled battery of the present invention is formed by stacking the flat lithium secondary batteries to obtain a high voltage. At this time, the planar batteries are fixed to each other and electrically connected by applying a surface pressure in the stacking direction, but this connection can be cut by loosening the surface pressure.

FIG. 5 is a schematic view showing an embodiment of the assembled battery of the present invention. As shown in FIG. 5, the spring 12 is inserted between the stacked flat plate-shaped batteries 11 shown in FIG. When the surface pressure is applied by the tightening rod 13, the spring 12 contracts to maintain the electrical connection between the flat plate batteries 11. It is when a short circuit occurs inside the assembled battery that it is necessary to loosen the surface pressure to disconnect the flat battery 11 from electrical connection. In this case, an electric current that is several times to several tens of times larger than usual flows, causing abnormal heat generation and causing the battery temperature to rise rapidly. At the same time, the pressure inside the unit cell, which is generating heat abnormally, also rises sharply. By detecting these sudden changes in temperature and pressure and loosening the tightening rod 13, the restoring force of the spring 12 allows a space between the flat plate-shaped batteries 11 to be opened and electrical connection to be cut off.

For example, when the cut-off portion 14 which is a part of the tightening rod 13 is made of a material that melts by the ambient temperature, the tightening rod is broken and the surface pressure can be relaxed when the temperature around the tightening rod abnormally rises. Tightening rod 13
The ambient temperature at which the cut-off portion 14 of the battery melts is set to a temperature above the normal temperature of the battery, but is about 60 ° C.
It is preferable to cut off as described above. As a material that melts at such a temperature, a so-called wood alloy (melting region 60 ° C.
There is a low melting point alloy such as (about 72 ° C.).

Example 7. Further, in the sixth embodiment, the surface pressure is loosened by fusing the cut-off portion 14 of the tightening rod 13, but a part of the tightening rod 13 may be thinned or the material may be changed to obtain a tensile strength. The tightening rod may be broken and the surface pressure may be relaxed by increasing the surface pressure due to the abrupt increase in the internal pressure of the battery by forming the weak portion. As for the surface pressure at which the tightening rod cuts, it is desirable that the internal pressure of the unit cell does not exceed 1 MPa. Therefore, it is desirable to cut at the pressure of 0.8 to 0.9 MPa.

Example 8. Further, the surface pressure can be loosened against a sudden temperature rise or pressure rise by a method that is not a method of destructively loosening the surface pressure such that the tightening rod is cut. That is, a part of the tightening rod is connected by an electromagnet, and a sensor attached to the battery, for example, a temperature sensor such as a thermocouple or a strain gauge detects temperature rise and pressure rise, and a signal current is given to the electromagnet to connect the tightening rod. Is to solve.
It is desirable that the temperature at which the tightening rod is disconnected is about 60 ° C. or higher, and the pressure is about 0.8 to 0.9 MPa.

Example 9. In addition, the assembled battery of the above embodiment,
Although the one in which the spring 12 is inserted between the flat plate-shaped batteries 11 is shown, the flat plate-shaped battery may be formed in a plate spring shape and this may be used, and the same effect is obtained.

The heat generation inside the battery is determined by the current flowing during charging or discharging and the internal resistance of the battery. The current flowing varies depending on how the battery is used, and the internal resistance of the battery is not always constant, and the amount of heat generated is not constant because it changes depending on the current. However, in the case of a lithium secondary battery, on average, the ratio of the electric energy required for charging to the electric energy that can be taken out by discharging, that is, the charging / discharging energy efficiency is about 80% or more, so the heat generation amount is at most the charging energy amount. 20%. However, the energy per kg of battery, that is, the weight energy density, is about 12
Since it is as high as 0 W / kg, if the specific heat of the battery is 0.8,
The battery temperature will rise by 0.12 ° C per second,
In the adiabatic state, the temperature rises by 7.2 ° C in 1 minute of charging and discharging. Since the surface area of a small unit cell is relatively large, it is cooled by natural heat dissipation from the surface, but for a large battery, it is difficult to use only natural heat dissipation from the surface. Further, in the assembled battery, it is difficult to lower the temperature of the battery arranged inside the assembled battery only by natural heat dissipation from the surface of the assembled battery even in the combination of small batteries.

Example 10. Thus, the large battery of the present invention,
In order to increase the area of the electrode, a heat dissipating mechanism including, for example, a heat dissipating fin and an assembly of pins is provided on the outer peripheral portion of the battery of the folding electrode or the winding electrode so that the heat generated due to charging and discharging can be quickly removed. ing. It prevents the battery temperature from rising excessively.

Example 11. FIG. 6 is a schematic view showing another embodiment of the assembled battery of the present invention. As shown in FIG. 6, since the heat dissipation mechanism 21 for removing the heat generated inside the battery is installed on the outer peripheral portion of the assembled battery, it is possible to suppress an excessive rise in the battery temperature. The heat dissipation mechanism 21 is similar to a general heat exchanger, a so-called radiator.

Example 12. FIG. 7 is a partially enlarged schematic view showing still another embodiment of the assembled battery of the present invention, in which a heat collecting plate 31 for effectively removing heat in the central portion of the battery is attached to the unit cell 11. For example, as shown in FIG.
Is a flat battery, the heat collecting plates 31 are stacked so as to be located between the unit cells 11. Then, the heat collecting plate 31 is attached to the heat dissipation mechanism 2
1 through the electrically insulating layer 32. The reason for interposing the electrical insulating layer 32 is to prevent an internal short circuit in the assembled battery between the unit cells 11. Of course, it is an unnecessary layer when the heat collecting plate 31 itself has electric insulation. However,
It is customary that a material having a good thermal conductivity suitable for the heat collecting plate, for example, a material such as carbon, aluminum or copper also has a good electric conductivity. For the electric insulating layer 32, a metal oxide such as alumina having a relatively high thermal conductivity is used.

Example 13. An embodiment of the electrolyte replenishing mechanism provided in the battery pack to prevent the exhaustion of the electrolyte will be described. The electrolyte replenishing mechanism is an electrolyte solution reservoir made of a porous body placed in contact with the assembled battery in a battery container, and a liquid conducting section made of a porous body having a different liquid absorption force for connecting the electrolyte solution reservoir and the separator of the unit cell. Composed of and. The porous body has a property of sucking a liquid into a hollow portion (pore) therein, like a sponge. On the other hand, some force is required to remove the liquid in the pores. This is because there is an inlet radius when the pore is assumed to be cylindrical, the surface tension of the liquid, and the liquid absorption force of the pore that is defined by the contact angle between the liquid and the porous body.
This is determined as shown in the equation below. Since the separator and the electrode are porous, in order to spontaneously absorb liquid when the electrolyte is insufficient, from the electrolyte reservoir which is also porous,
The liquid absorption force of the porous body of the reservoir must be set smaller than that of the separator and the electrode. This is because the liquid in the pores with strong liquid absorption does not move unless external force is applied to the pores with weak liquid absorption. The most common method of controlling the liquid absorption force is to think from the following formula. Therefore, in the electrolyte replenishing mechanism of the present invention, the radius of the pores of the porous body is adjusted to make the liquid absorption force of the porous body of the reservoir smaller than the liquid absorption force of the porous bodies of the separator and the electrode, thereby depleting the electrolyte solution. It is preventing. It has a long life. P = 2σ cos θ / r P: Liquid absorption force (N / m ² ) σ: Surface tension (N / m) θ: Contact angle (degree) r: Radius (m)

When a plurality of batteries stacked in series are replenished with an electrolytic solution from a common reservoir, in a liquid junction state in which the battery and the reservoir are constantly connected by the electrolytic solution, the cells between the stacked batteries are transmitted through the liquid junction. Since a short-circuit current flows through the battery and self-discharge of the battery occurs, it is not preferable to have a liquid junction at all times.

Example 14. In the electrolyte replenishing mechanism of this embodiment, in order to solve the above-mentioned problems, the liquid absorption force of the connecting portion between the reservoir and the separator and the liquid conducting portion is made smaller than that of the reservoir, the separator and the electrode. By configuring in this way, unless an excessive amount of electrolytic solution is included,
The liquid introducing portion is in a liquid-free state, and no liquid junction occurs. When the electrolyte solution is insufficient, the electrolyte solution is replenished, and the decrease in battery efficiency can be prevented. The pore diameter of the separator is preferably less than 1 μm from the viewpoint of preventing an internal short circuit. Therefore, it is desirable that the pore diameter of the liquid introducing portion is 1 μm or more. In this embodiment, the separator is a porous body in which the volume of pores having a pore diameter of less than 1 μm is 50% or more of the total pore volume, and the liquid introducing portion has a volume of pores having a pore diameter of 1 μm or more 50% of the total pore volume. It is composed of the above porous body.

The lack of the electrolytic solution in the battery is mainly caused by the decomposition of the electrolytic solution. The decomposition of the electrolytic solution causes the internal pressure of the battery to rise.
It is considered that the lack of electrolyte causes an increase in internal resistance, so there is a correlation between lack of electrolyte and increase in internal pressure.

When the internal pressure of the battery is applied to the reservoir so that the pressure is equal to or more than the difference between the liquid absorbing force of the connecting portion and the liquid absorbing force of the reservoir, the electrolytic solution is pushed into the connecting portion from the reservoir to cause the liquid junction. Is formed. When the liquid junction is formed, the electrolytic solution is supplied from the reservoir to the separator and the electrode lacking. When the internal pressure release mechanism operates and the internal pressure of the battery decreases, the liquid junction is eliminated again due to the difference in the liquid absorption force between the connection portion and the reservoir.

In order to prevent the internal pressure of the unit cell from rising, the sealing portion of the unit cell should be permeable to gas,
A container for accommodating the assembled battery is prepared to prevent water in the atmosphere from mixing in, but a valve for adjusting the internal pressure release mechanism so that the pressure inside the battery container does not rise too much is attached to the battery container.

A conventional releasing mechanism is to provide a portion that is destroyed by an increase in internal pressure in a part of the container, and is based on the idea of a so-called rupture disc. Since this method is a self-destructive action, once it works, it becomes difficult to reuse it as a whole. In particular, it is a fatal action in a lithium secondary battery that is reluctant to mix water from the atmosphere, and should be called a final safety device.

On the other hand, there are so-called check valves and relief valves, which operate at a predetermined pressure and stop when the pressure falls below that pressure to maintain the internal pressure. Its basic structure is one that produces a force that antagonizes internal pressure,
For example, a valve body connected to a compressed spring presses the opening. If only to release the internal pressure so that the pressure is equal to or lower than a predetermined pressure, such a conventionally known check valve may be attached to the container.

However, as described above, in order to operate the electrolyte replenishing mechanism by utilizing the rise in the battery internal pressure, the internal pressure is released at a certain pressure A, and then the internal pressure is released to a pressure B smaller than the pressure A. You have to make it over.
The pressure B and the pressure A are set so as to sandwich the pressure C at which the electrolyte replenishing mechanism starts operating. The pressure A is a safety upper limit pressure. As a relief valve that operates in this way, the inventors have invented that a valve as shown in the schematic view of FIG. 8 is attached to a battery container.

The operation will be described with reference to FIG. The pressure inside the battery is applied to the valve body 41, and
It is held by a spring A42 that produces a force equivalent to
The spring A42 is housed in the spring case 43, and is supported by the retaining pin 44 together with the spring case 43. Fastening pin 44
Interlocks with the valve body 41. Further, the spring case 43 has a pressure B
It is held by a spring B45 that produces a force equivalent to

When the battery internal pressure exceeds the pressure A, the valve body 41 is lowered, and the internal pressure is released from the release port 46. Valve body 4 at the same time
When the retaining pin 44 interlocked with 1 is removed, the valve body 41 retracts together with the spring case 43 and compresses the spring B45. When the internal pressure of the battery drops below the pressure B, the spring B45 returns,
Push the valve body 41 back together with the spring case 43, and
And the opening 46 is closed again. By acting in this way, the internal pressure of the battery can be prevented from rising too much. It is desirable that the pressure A is less than 1 MPa, which does not produce so-called high-pressure gas. The pressure B may be equal to or lower than the pressure A, but the so-called atmospheric pressure is 0.1MP.
It is preferably between a and 0.3 MPa.

Next, suppression of increase in battery internal pressure will be described. In the case of a lithium secondary battery, the increase in battery internal pressure is the decomposition of an organic solvent that is an electrolytic solution. The organic solvent is, for example,
The decomposition reaction of propylene carbonate, which is often used in the electrolytic solution of a lithium secondary battery, is as shown in Chemical formula 1. In this case, the propene gas generated when decomposing propylene carbonate is the source of increasing the pressure in the battery container.

[0115]

[Chemical 1]

Example 15. This invention was found to have the effect of suppressing this gas generation when lithium carbonate was added to the electrolytic solution, and was made. In a lithium secondary battery using an electrolyte in which a lithium salt is dissolved in an organic solvent, the electrolytic solution is By containing lithium carbonate in the composition, gas generation due to decomposition of the organic solvent of the electrolytic solution is suppressed. As a result, it is possible to suppress an excessive rise in the internal pressure of the battery and improve the safety. Although the details are not clear, it is considered that in a closed system such as a battery, when a large amount of reaction product lithium carbonate is present in the system, equilibrium transfer occurs and the reaction becomes difficult to proceed.

Example 16. It was also found that the gas generation rate decreased similarly when lithium oxide and carbon dioxide coexist. Therefore, carbon dioxide was included in the container for accommodating the battery, and the electrolytic solution was made to contain lithium oxide. As a result, the gas generation rate could be reduced, and the increase in the battery internal pressure could be suppressed. Further, as shown in the characteristic diagram of FIG. 9, the time-dependent change in the internal pressure of the battery differs depending on the difference in carbon dioxide concentration. The vertical axis represents the battery internal pressure, the horizontal axis represents time, and the characteristic curve d
Is a battery internal pressure increase curve of 100% carbon dioxide, a characteristic curve e is a battery internal pressure increase curve of 50% carbon dioxide, and a characteristic curve f is a battery internal pressure increase curve of carbon dioxide 0%. It can be seen that when the carbon dioxide concentration is low, the internal pressure of the battery rises quickly. This is
Since carbon dioxide gas, lithium oxide, and lithium carbonate are in an equilibrium relationship as shown by, it is considered that when the carbon dioxide gas concentration is high, lithium carbonate is produced and the same effect as when lithium carbonate is added is exhibited.

[0118]

[Chemical 2]

Example 17 Therefore, even if carbon dioxide gas is sealed in the battery container, lithium carbonate is generated and the decomposition reaction of the electrolytic solution is suppressed, so that the increase in the battery internal pressure is suppressed. Therefore, the process of sealing the battery container is performed in a carbon dioxide gas atmosphere so that the surrounding carbon dioxide gas is sealed at the same time. Alternatively, the carbon dioxide gas may be blown onto the battery parts so that the battery container is closed, and the blown carbon dioxide gas may be simultaneously enclosed in the container.

Further, the battery prepared by increasing the internal pressure of the battery higher than the constant pressure by carbon dioxide gas has a limit in result as compared with the battery containing no carbon dioxide gas as shown in the characteristic diagram of FIG. It takes a long time to reach the pressure. This is also due to the effect of inhibiting decomposition of the electrolytic solution by carbon dioxide gas. In FIG. 10, the vertical axis represents the battery internal pressure, the horizontal axis represents time, the characteristic curve g represents the battery internal pressure increase curve at 0% carbon dioxide, and the characteristic curve h represents the battery internal pressure increase curve after decomposing the carbonate of the positive electrode. .

In the present specification, the decomposition of propylene carbonate has been described as an example, but the same effect can be obtained for ethylene carbonate which is decomposed in the same manner. Further, the same effect can be obtained even if lithium carbonate or lithium oxide is not directly added to the electrolytic solution but is contained in components such as the negative electrode and the separator inside the battery.

Example 18. However, in the case where the positive electrode contains lithium carbonate, conversely, it is known that the internal pressure rises rapidly during overcharge. This is because lithium carbonate decomposes into carbon dioxide gas and lithium oxide by overcharging.
In this example, by utilizing this, lithium carbonate was added to the positive electrode, and after assembled into a battery, the lithium carbonate was decomposed by intentionally overcharging or heating, and carbon dioxide gas was stored in the battery container. Is being generated. As a result, the carbon dioxide concentration inside the battery can be increased without decomposing the electrolytic solution. If the amount of lithium carbonate added to the positive electrode is 1% by weight or less, the effect of addition is not substantially seen. Further, it is preferable that the amount added is small, and if 2% by weight is added, it is practically sufficient. Weight percent is suitable. It should be noted that the same effect can be obtained not only by using lithium carbonate but also by using another carbonate.

A more specific example will be described below. Example 19. 33 parts by weight of NMP solution as a coating solvent,
3 parts by weight of a soft fluororesin was dissolved as a binder to prepare a binder solution, and Li was used as a positive electrode active material in this solution.
A coating solution was prepared by dispersing 58 parts by weight of CoO2 powder and 6 parts by weight of graphite powder as a conductive agent. This coating solution was applied on an aluminum foil having a thickness of 20 μm and serving as a current collector so as to have a width of 30 cm, and dried to prepare an electrode sheet having a thickness of about 300 μm. The length was 151 cm.

33 parts by weight of NMP solution as a coating solvent,
62 parts by weight of mesophase microbead carbon (hereinafter abbreviated as MCMB) powder (manufactured by Osaka Gas) and 2 parts by weight of lithium carbonate were dispersed in this solution as a binder solution by dissolving 3 parts by weight of a soft fluororesin as a binder. Then, a coating liquid was prepared. This coating solution was applied onto a copper foil having a thickness of 20 μm, which is a current collector, and dried to prepare an electrode sheet having a thickness of about 300 μm. The width of the electrode was 31 cm and the length was 151 cm.

The positive electrode and the negative electrode thus prepared are arranged such that the active material layers face each other with a porous polypropylene film (thickness 50 μm) as a separator sandwiched therebetween, and the end of the positive electrode in the width direction does not extend beyond the end of the negative electrode in the width direction. Then, a battery element was prepared by folding the battery element in a lengthwise direction every 30 cm four times. The length of the separator was 155 cm, and about 2 cm at the beginning and the end of folding, respectively, were projected from the positive electrode and the negative electrode.

The prepared 30 cm square battery element was fitted in two polyethylene frames having a thickness of 1.5 mm and a width of 5 mm, and the separator protruding from the battery element and the liquid conducting part for connecting this to the electrolyte reservoir ( Porous polypropylene film (thickness 50 μm) of reservoir connection porous body is sandwiched between polyethylene frames, and further sandwiched between two 0.1 mm thick stainless steel plates, and heat-bonded while pressing the periphery to form a rectangular flat plate. A single cell was created.

The polyethylene frame has a width of 3 mm and a depth of 0.5 mm.
The groove is formed every 3 mm so as to connect the inside and the outside of the frame, and the separator and the liquid conducting portion are sandwiched in the groove. The heat fusion temperature is preferably 135 to 160 ° C. at which polyethylene is fused and polypropylene is not melted. The separator used had a pore volume of about 0.1 μm or less and 50% of the total pore volume. As the liquid introducing part (reservoir connection porous body), one having a pore volume of about 1 μm or less and 50% of the total pore volume was used.

Forty flat flat cells were laminated in series, and a brass leaf spring was sandwiched between the flat cells to form a battery assembly using a hard polyethylene plate as a pressing plate. The tightening rod used was an aluminum pipe connected with a wood alloy.

An aluminum plate having a thickness of 1 mm was sandwiched as a heat collecting plate for every five unit cells. A heat radiating mechanism connected to the aluminum heat collecting plate via an alumina layer was installed on the two opposite sides of the four outer sides of the battery. The heat radiation mechanism is made of aluminum, and heat radiation fins having a width of 10 mm and a length of 12 cm are arranged at intervals of 10 mm along the stacking direction of 31 sheets on one side.

Electrolyte reservoirs are arranged on the remaining two sides. The electrolyte reservoir is made of a polypropylene case filled with polypropylene non-woven fabric, and the liquid conducting part (reservoir connection porous sheet) that comes out from each battery.
Is sandwiched.

The assembled battery in which the heat dissipation mechanism and the electrolyte reservoir are arranged is housed in a stainless steel battery container, and the positive electrode terminal and the negative electrode terminal are attached to the container lid equipped with the pressure control valve via the insulating layer. After the positive electrode lead and the negative electrode lead that have been taken out are respectively welded, the liquid inlet of the container lid is aligned with the position of the electrolyte reservoir, and the container lid is welded to the battery container.

Vacuum the entire container (-750 mmHg or less)
After that, an electrolytic solution in which 1 mol / l of lithium perchlorate is dissolved in a 1: 1 mixed solvent of ethylene carbonate and dimethoxyethane is poured into the injection port. Injection is performed in a dry box in a dry carbon dioxide atmosphere. After the injection is completed, the injection port is welded and sealed.

The battery thus assembled was charged to an initial cell voltage of 4.2 V, and then the average cell voltage was 3.
It operated at 6 V and an average assembled battery voltage of 144 V, and obtained an output of 1.3 kW.

Example 20. PV electrode binder
A battery was assembled in the same manner as in Example 19 except that the mixed powder of dF and the soft fluororesin (1: 1) was used.

The battery thus assembled had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 as in Example 19.
It operated at 44V and obtained an output of 1.3 kW.

Example 21. A battery was assembled in the same manner as in Example 19 except that 3 parts by weight of lithium oxide was added instead of 3 parts by weight of lithium carbonate during the production of the negative electrode.

The battery thus assembled had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 as in Example 19.
It operated at 44V and obtained an output of 1.3 kW.

Example 22. A battery was assembled in the same manner as in Example 19 except that carbon dioxide gas was blown around the injection port in a dry box in a dry air atmosphere when the electrolytic solution was injected.

The battery thus assembled was operated at an average cell voltage of 3.6 V and an average assembled battery voltage of 144 V as in Example 19, and an output of 1.3 kW was obtained.

Example 23. NMP solution 3 as a coating solvent
3 parts by weight of soft fluororesin as a binder was dissolved in 3 parts by weight to prepare a binder solution, and 58 parts by weight of LiCoO2 powder as a positive electrode active material, 6 parts by weight of graphite powder as a conductive agent and 1 part by weight of lithium carbonate were dispersed in the solution. Then, a coating liquid was prepared. This coating solution was applied on an aluminum foil having a thickness of 20 μm and serving as a current collector so as to have a width of 30 cm, and dried to prepare an electrode sheet having a thickness of about 300 μm. The length was 151 cm.

The following steps are carried out in the same manner as in Example 19, the liquid injection step is carried out in a dry box in a dry air atmosphere to assemble the battery, and then the initial charge is carried out to 4.5 V to generate carbon dioxide gas in the battery container. Was generated and the pressure control valve was operated to make the inside of the battery container a sufficient carbon dioxide gas atmosphere.

The batteries thus assembled had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 as in Example 1.
It operated at 44V and obtained an output of 1.3 kW.

[0143]

Since the present invention is constructed as described above, it has the following effects.

In an electrochemical device having a structure in which electron-conductive electrodes composed of active material layers having the ability to electrochemically store and discharge ions are opposed to each other with a porous body holding an ion-conductive substance sandwiched therebetween, Since the active material layer is formed on the surface of the porous body so as to be narrower than its width excluding the edge thereof, and a current collector is provided on the back surface or the inside of the active material layer, so that the active material layer is assembled at the time of assembly. Since there is no need to align the electrodes facing each other, the assembly can be simplified, and the performance defect due to the reduction of the reaction area due to the assembly defect can be reduced.

Further, in a battery having a separator holding a lithium ion conductive electrolyte, using an inorganic oxide for occluding and discharging lithium ions as a positive electrode active material and carbon as a negative electrode active material, one of the above separators is used. Since the positive electrode active material layer containing the positive electrode active material on the surface and the negative electrode active material layer containing the negative electrode active material on the other surface are formed to be narrower than the separator width except for the separator edge, Since there is no need to align the negative electrode and the negative electrode, and the number of parts is reduced, the assembly process is simplified and simplified, and the shortage of reaction area and short circuit due to the positional deviation between the positive electrode and the negative electrode can be suppressed. There is an effect that defects are eliminated and a highly reliable battery is obtained.

In the production of this electrochemical device, the band-shaped porous body is relatively moved, and a paste containing an electrochemically active material is applied to one surface and the other surface of the band-shaped porous body to form an active material in the porous body. Since the layers are formed, the positive electrode active material layer and the negative electrode active material layer can be easily formed on the separator.

Further, in a flat lithium secondary battery, a positive electrode and a negative electrode are arranged so as to face each other with a separator interposed therebetween, and this is folded evenly to form a battery element, and an electrically insulating sealing material is provided around the battery element. Since the battery elements are arranged and the battery elements are sandwiched by the conductive plate materials arranged at both ends in the overlapping direction, a large electrode area electrode can be compactly packed in a battery container, and high voltage and large current can be obtained. , Performance can be improved.
Further, it has a flat plate shape and is suitable for forming an assembled battery.

Further, since the heat dissipation mechanism is installed on the outer peripheral portion of the battery, heat can be quickly removed and an excessive rise in battery temperature can be prevented. Be safe.

Since a soft fluororesin composed of the following monomer units A and B obtained by graft-polymerizing a crystalline fluororesin on fluororubber was used as the binder, A: --CH ₂ --CF ₂ - B: -CFCl-CF ₂ - high-performance, and highly flexible flexible electrode is obtained. Therefore, the workability is improved and the degree of freedom of the electrode structure is increased. It facilitates the manufacture of wound electrodes and folded electrodes.

Further, since the ratio of the binder made of the soft fluororesin to the active material is set in the range of 0.1% by weight to 20% by weight, the battery performance becomes good, and 5 to 30 parts by weight relative to 1 part by weight of the binder. Since it is dispersed in the coating solvent, the coating (electrode preparation) becomes easy.

Since the plate-shaped lithium secondary batteries are stacked, surface pressure is applied in the stacking direction, and the plate-shaped batteries are fixed and electrically connected to each other to form an assembled battery,
When trouble occurs, this connection can be easily broken by loosening the surface pressure to protect the battery.

Further, since a spring is inserted between the stacked flat plate-shaped batteries or the stacked flat plate-shaped batteries are formed in the shape of leaf springs, when the surface pressure in the stacking direction is relaxed, the restoring force of the springs causes the batteries to be separated from each other. Since there is an interval, the electrical connection can be quickly cut.

Further, since a heat collecting plate is attached to the lithium secondary battery and a heat radiating mechanism is provided on the outer peripheral portion of the assembled battery, and the heat collecting plate and the heat radiating mechanism are electrically insulated and connected, it is generated inside the battery The heat generated can be removed, and an excessive rise in battery temperature in the assembled battery, which is difficult to reduce only by natural heat dissipation from the surface of the assembled battery, can be reduced. .

An electrolyte solution reservoir made of a porous body containing an electrolyte solution is provided at the outer periphery of the assembled battery, and a liquid conducting section made of a porous body connecting the reservoir and the separator of the lithium secondary battery. Since the electrolyte replenishing mechanism is provided, the electrolyte can be prevented from being depleted and the life can be extended.

Further, the liquid absorbing power of the electrolytic solution reservoir is equal to or less than the liquid absorbing power of the separator and the electrode of the battery,
In addition, since it is formed so as to be larger than the liquid absorption force of the liquid guiding portion, the electrolyte solution is replenished when the electrolyte solution is insufficient, and the decrease in battery efficiency can be prevented.

Furthermore, in a lithium secondary battery using an electrolyte in which a lithium salt is dissolved in an organic solvent, since lithium carbonate is contained in at least one of the negative electrode, the separator and the electrolyte, gas is generated by decomposition of the organic solvent in the electrolytic solution. Can be suppressed, and an increase in battery internal pressure can be suppressed. Safety is improved.

Further, since carbon dioxide is contained in the container for accommodating the battery and lithium oxide is contained in at least one of the negative electrode, the separator and the electrolyte, the gas generation rate can be reduced and the internal pressure of the battery can be reduced. The rise can be suppressed.

Then, in manufacturing the lithium secondary battery,
Since the process of sealing the battery container is performed in a carbon dioxide atmosphere or while blowing carbon dioxide gas to the battery parts, carbon dioxide gas can be sealed in the container, decomposition of the electrolytic solution can be suppressed, and the battery internal pressure can be reduced. The rise can be suppressed.

Further, since carbonate is added to the positive electrode and the battery is assembled and then charged or heated to decompose the carbonate to generate carbon dioxide gas, the concentration of carbon dioxide gas in the battery is adjusted to the electrolytic solution. It can be raised without disassembling, and the rise in battery internal pressure can be suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view of a battery sheet according to an embodiment of the present invention.

FIG. 2 is a perspective view of a battery sheet according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing an example of the flat lithium secondary battery of the present invention.

FIG. 4 is a characteristic diagram showing the elongation rate of an electrode showing the effect of the embodiment of the flexible electrode of the present invention.

FIG. 5 is a schematic view showing an example of an assembled battery of the present invention, which is an assembled battery in which the plate-like unit cells shown in FIG. 5 are stacked.

FIG. 6 is a schematic view showing another embodiment of the assembled battery of the present invention, which is an assembled battery incorporating a heat dissipation mechanism.

FIG. 7 is a partially enlarged schematic view showing still another embodiment of the assembled battery of the present invention.

FIG. 8 is a schematic view of a pressure control valve of a battery internal pressure release mechanism according to the present invention.

FIG. 9 is a characteristic diagram showing changes with time in the internal pressure of the battery depending on the carbon dioxide concentration according to the present invention.

FIG. 10 is a characteristic diagram showing changes with time in the battery internal pressure according to the present invention.

FIG. 11 is a schematic view of a battery assembling method in a comparative example.

FIG. 12 is a half sectional side view showing a conventional coin battery.

FIG. 13 is an exploded perspective view showing the structure of a conventional clad lead-acid battery.

[Explanation of symbols]

 1 Positive Electrode 2 Negative Electrode 3 Separator 4 Electrical Insulation Sealing Material 5 Conductive Plate Material 11 Flat Single Cell 12 Spring 13 Tightening Rod 14 Cut-Out Part 21 Heat Dissipation Mechanism 31 Heat Collection Plate 32 Electrical Insulation Layer 41 Valve Body 42 Spring A 43 Spring Case 44 Fastening Pin 45 Spring B 46 Opening port 51 Current collecting net with tab 52 Positive electrode active material layer 53 Copper foil for current collection 54 Copper foil for current collecting with tab 55 Negative electrode active material layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Takashi Nishimura 8-1-1 Tsukaguchi Honcho, Amagasaki City Mitsubishi Electric Corporation Central Research Institute (72) Inventor Shigeru Aihara 8-1-1 Tsukaguchi Honmachi, Amagasaki Mitsubishi Electric Central Research Institute Co., Ltd.

Claims (18)

[Claims] 1. A structure in which electron-conductive electrodes composed of an active material layer containing an active material having an ability of electrochemically absorbing and discharging ions are opposed to each other with a porous body holding an ion conductive material sandwiched therebetween. In the electrochemical element, the active material layer is formed on the surface of the porous body so as to be narrower than its width excluding its edges, and a current collector is provided on the back surface or inside of the active material layer. And electrochemical device. 2. An active material layer is formed on the porous body by moving the strip-shaped porous body relative to each other and applying a paste containing an electrochemically active material to one surface and the other surface of the strip-shaped porous body. A method for manufacturing an electrochemical device, comprising: 3. The method for manufacturing an electrochemical element according to claim 2, wherein the band-shaped porous body is made to hold an ion conductive substance in advance, and then the paste is applied to the porous body. 4. A battery having a separator that holds a lithium ion conductive electrolyte, wherein an inorganic oxide that occludes and discharges lithium ions is used as a positive electrode active material and carbon is used as a negative electrode active material. A positive electrode active material layer containing a positive electrode active material on the surface, a negative electrode active material layer containing a negative electrode active material on the other surface, a lithium secondary characterized by being formed narrower than the separator width except the separator edge. battery. 5. A positive electrode and a negative electrode are arranged so as to face each other with a separator interposed therebetween, which are folded evenly to form a battery element, and an electrically insulating sealing material is arranged around the battery element, and the stacking direction thereof is provided. A flat plate-shaped lithium secondary battery, characterized in that the battery element is sandwiched between conductive plate materials arranged at both ends. 6. The plate-shaped lithium secondary battery according to claim 5, wherein a heat dissipation mechanism is installed on the outer periphery of the battery. 7. An electrode for a non-aqueous electrolyte battery comprising a binder and an active material, wherein the binder is composed of monomer units A and B shown below, in which a fluororubber is graft-polymerized with a crystalline fluororesin. A flexible electrode characterized by being a fluorocarbon resin. _{A: -CH 2 -CF 2 - B} : -CFCl-CF 2 - 8. The ratio of the binder composed of a soft fluororesin to the active material is in the range of 0.1% by weight to 20% by weight, and when the electrode is prepared, 5 parts by weight of the binder are used.
The flexible electrode according to claim 7, wherein the flexible electrode is dispersed in about 30 parts by weight of the coating solvent. 9. The flat-plate lithium secondary battery according to claim 5 is stacked, and a surface pressure is applied in the stacking direction so that the flat-plate batteries are fixed to each other and electrically connected to each other. And assembled battery. 10. A structure in which a spring is inserted between the flat plate batteries to be stacked so that the flat plate batteries can be electrically disconnected from each other when the surface pressure in the stacking direction is loosened. The assembled battery according to the item. 11. The flat plate battery to be stacked is formed in a leaf spring shape, and when the surface pressure in the stacking direction is relaxed, the flat plate batteries are electrically disconnected from each other. The assembled battery according to the item. 12. An assembled battery formed by stacking lithium secondary batteries, wherein a heat collecting plate is attached to the lithium secondary battery, and a heat radiating mechanism is provided on an outer peripheral portion of the assembled battery, and the heat collecting plate and the heat radiating mechanism are provided. An assembled battery characterized by being electrically insulated and connected. 13. An assembled battery formed by stacking the flat-plate lithium secondary batteries according to claim 5, wherein an electrolytic solution reservoir made of a porous body containing an electrolytic solution is provided at an outer peripheral portion of the assembled battery, and An assembled battery characterized in that an electrolytic solution replenishing mechanism including a liquid conducting part made of a porous body that connects the reservoir and the separator of the battery is provided. 14. The electrolytic solution replenishing mechanism is formed so that the liquid absorbing force of the electrolytic solution reservoir is equal to or less than the liquid absorbing force of the separator and the electrode of the battery, and is larger than the liquid absorbing force of the liquid conducting section. The assembled battery according to claim 13, wherein: 15. A lithium secondary battery using an electrolyte in which a lithium salt is dissolved in an organic solvent, wherein at least one of a negative electrode, a separator and an electrolyte contains lithium carbonate. 16. A lithium secondary battery using an electrolyte in which a lithium salt is dissolved in an organic solvent, wherein a container for housing the battery contains carbon dioxide gas, and at least one of the negative electrode, the separator and the electrolyte is oxidized. A lithium secondary battery containing lithium. 17. A method of manufacturing a lithium secondary battery, comprising a step of sealing a battery container in a carbon dioxide atmosphere or while blowing carbon dioxide gas to battery parts. 18. A method for assembling a lithium secondary battery, wherein carbonate is added to the positive electrode, and after assembling the battery, charging or heating decomposes the carbonate to generate carbon dioxide gas. .