JP3116643B2 - Electrochemical element, assembled battery, and method of manufacturing electrochemical element - Google Patents

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, and more particularly to a structure of a lithium secondary battery, an electrode thereof, an assembled battery using the battery, and a method of manufacturing the same. It is. In this specification, a battery will be described as an example of an electrochemical element.

[0002]

2. Description of the Related Art As an electrochemical element for electrochemically transferring ions into and out of an electrode, there is, for example, a battery. In a normal battery, a positive electrode that takes in electrons from an external circuit during discharge and a cation from the electrolyte or takes in electrons from an external circuit and releases an anion to the electrolyte, and a negative electrode that operates in the opposite direction to the positive electrode, It has a structure in which the electrodes are opposed to each other via a layer called a separator having no electron conductivity and containing an electrolyte.

[0003] If the electrode is a so-called manganese dry battery, the positive electrode is obtained by piercing a positive electrode mixture prepared by kneading manganese dioxide as an active material, carbon as a conductive agent and an electrolyte with a carbon rod for current collection. The negative electrode is a can of zinc as an active material.

In the battery having such a structure, when an attempt is made to obtain a large current, the current density is increased and only the active material near the current collector is used, so that the practical battery capacity is reduced. In particular, this phenomenon was remarkable in the case of a non-aqueous electrolyte battery using lithium ions, in which the electric conductivity of the electrolyte was small.

[0005] Since a lithium secondary battery is lightweight and can obtain a high voltage, it has been actively developed not only for a small portable electronic device but also for a large storage battery.

In this lithium secondary battery, lithium metal alone was used as a negative electrode material before.
There are problems such as an internal short circuit caused by lithium metal dendritic precipitation. Therefore, in recent years, a method of using carbon as a negative electrode material and inserting and removing lithium ions has become mainstream. The use of this electrode has made it possible to provide a highly safe battery having a voltage equivalent to that of the case of using lithium metal and having no dendritic deposition. The structure of this negative electrode is such that a carbon material such as pyrolytic carbon, carbon black, coke, and graphite is used, and a binder is used for molding to bind the carbon material.

[0007] As a positive electrode material for a lithium secondary battery, a material capable of high voltage and high energy density and capable of inserting and removing lithium ions while maintaining the structure is required. Various materials have been proposed. Have been. For example, T
iS2, MnO2, V2O5, LiCoO2, LiNiO2,
LiMn2O4 and the like. As a constituent material of the positive electrode, these positive electrode active materials are used as main components, graphite and the like are added to improve conductivity, and a binder is added and adhered to give moldability similarly to the negative electrode. I have.

In a conventional lithium secondary battery, a separator is interposed between the two electrodes, and a non-aqueous organic solvent is used as an electrolyte. The battery has a coin type or a cylindrical prism type.

In general, when obtaining a large current in a battery, attempts have been made to increase the electrode area as much as possible. Particularly in lithium secondary batteries, since an organic solvent having relatively low conductivity is used as the electrolyte,
It is particularly important to increase the area of the electrode.

FIG. 12 is a half sectional side view showing a conventional coin-type battery shown on page 124 of, for example, "Battery Handbook" (edited by Battery Handbook Editing Committee, published by Maruzen 1990).
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, a cylindrical battery having a large electrode area by winding up a strip-shaped electrode has been manufactured as a battery of a type that takes a large current so that a large current can be obtained even in the case of an electrolyte having a small electric conductivity. For example, as described in Japanese Patent Application Laid-Open No. 2-51875, a method has been devised to substantially reduce the current density by laminating and winding up a strip-shaped electrode and a separator. In addition, the usual assembling method has been to separately manufacture and laminate a strip-shaped electrode and a separator.

Further, in order to obtain a large area by using a flat electrode, a conventional method has been to adopt a structure in which so-called strip electrodes are connected. Fig. 13 is also the "Battery Handbook"
(Battery Handbook Editing Committee, published by Maruzen 1990) 188
It is a disassembled perspective view which shows the structure of the conventional clad type lead battery shown in the page. Both the strip-shaped positive electrode 1 and the strip-shaped negative electrode 2 are connected like a comb with a current collecting tab and a connecting rod, arranged via a separator, and put in one container.

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

In the case where, for example, one battery appears to output 12 V like a lead battery for an automobile, the inside of the tank is divided into a plurality of cells, and each cell is combined with a single cell element in which a positive electrode plate and a negative electrode plate are combined via a separator and an electrolytic cell. Liquid is contained, and one of the separators is a single cell, and the single cells are connected in series via a current collecting tab and a current collecting rod. As in a so-called pack battery, there is also a type in which a cylindrical battery or a square battery assembled as a unit cell and connected in series by spot welding are put in a container. On the other hand, there is a method in which cells are connected in series while forming cells in a so-called bipolar structure, such as that found in a fuel cell or a redox flow battery for power storage.

In a conventional secondary battery, it is general to remove heat generated by charging / discharging to natural heat radiation. Therefore, when a large number of batteries are used in a single room for power storage or the like, they are used. Pay attention to room ventilation and temperature.

In the conventional sealed secondary battery, when an internal pressure is abnormally increased due to gas generation accompanying a charge / discharge reaction or a side reaction, a weak portion is provided in a part of the battery container to release the internal pressure. A method is used to destroy the leverage.

[0017] In this case, the battery becomes unusable because the electrolyte flows out together with the release of the internal pressure. In the open type secondary battery, the gas can always escape, but at the same time, the electrolyte is also scattered, so that the structure is such that the electrolyte can be injected from the outside in a timely manner.

[0018]

Most of the conventional practical secondary batteries have a water-based electrolyte.
Electrodes have low ionic conduction resistance and use electrodes that are stable in air. On the other hand, the performance of a lithium secondary battery is brought out only in an internal environment from which moisture is sufficiently removed. In other words, there is a problem that a stable and high-performance lithium secondary battery cannot be manufactured with the structure and material used for the conventional secondary battery.

For example, the maximum current drawn from a lead-acid battery having the same electrode area reaches several tens of times that of a lithium secondary battery. Therefore, in a 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 pack large-area electrodes compactly in a 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 via the separator, which is important in performance, and requires high-precision assembly. If this alignment is neglected, a capacity shortage occurs due to a short reaction area. Further, in the worst case, there is a problem that the contact between the positive electrode and the negative electrode occurs at the ends, and the function as a battery is impaired.

When cells are connected in series in order to obtain a high voltage, the cells connected by current collector rods or connected by spot welding are fixed in the cells.
When a trouble such as an internal short circuit occurs, the battery cannot be protected by disconnecting the external circuit. In the case of a lithium secondary battery, there is a problem that a serious accident may occur due to a high energy density.

Even if there is no trouble, it is conceivable that the electrolyte is decomposed and depleted due to heat generated by charging and discharging. Since a lithium secondary battery is vulnerable to the intrusion of moisture in the air, it is necessary to avoid the need to externally supply an electrolytic solution.

The present invention has been invented in order to solve the problems relating to these lithium secondary batteries.

That is, the present invention provides an electrochemical device and a battery which can simplify the assembly by eliminating the positioning of the positive electrode and the negative electrode during the assembly, and reduce the performance failure due to the reduction of the reaction area due to the assembly failure. An object is to provide a suitable manufacturing method. It is another object of the present invention to provide a safe, high-voltage, large-capacity flat lithium secondary battery, and a flexible electrode suitable for the same, an assembled battery using the above-described unit cell, and a method of manufacturing the same.

[0025]

According to a first aspect of the present invention, there is provided a first electrochemical device comprising an active material layer having an ability to electrochemically occlude and discharge ions with a porous body holding an ion conductive material interposed therebetween. Having a structure in which electron-conductive electrodes made of at least one active material layer and a porous body are opposed to each other.
Are integrally bonded with a binder, and a current collector is provided on the back surface (the surface opposite to the porous body attachment surface) or inside the active material layer.

Further, a second electrochemical device according to the present invention
Is a binder for the first electrochemical device according to the present invention.
Contains polyvinylidene fluoride.

Also, a third electrochemical device according to the present invention
The porous body of the first electrochemical device according to the present invention is
Titanium ion conductive electrolyte holds lithium ion
Inorganic oxides that occlude and release carbon are used as positive electrode active materials, and carbon is
As a negative electrode active material, a positive electrode active material is coated on one surface of the porous body.
Negative electrode containing a negative electrode active material on the other surface
It has an active material layer.

Further, the first electrochemical device of the present invention
The manufacturing method consists of a porous body, a current collector,
An active material layer containing an active material capable of inserting and extracting
Bonding the electrolyte with a binder, and applying the electrolyte solution to the porous body,
Injected into at least one of the active material layer and the adhesive
It is provided with a step of

Further , the second electrochemical device according to the present invention
The production method includes a strip-shaped porous body and a small number of the strip-shaped porous body.
At least one side of the paste or paste containing the electrochemically active material
A current collector with an
It forms a laminated monolith.

Further, the fourth electrochemical device according to the present invention forms a positive electrode on one surface of the porous body, forms a negative electrode on the other surface, and forms an integrated body in which the electrode and the porous body are bonded with a binder. , Which is wound or folded to form a battery element,
At least two conductive plate members connected to the positive terminal and the negative terminal, respectively, are provided.

The fifth electrochemical device according to the present invention is characterized in that the battery element is formed by at least two conductive plates connected respectively to the positive electrode terminal and the negative electrode terminal of the fourth electrochemical device according to the present invention. Sandwiching the conductive plate connected to the positive terminal and the conductive plate connected to the negative terminal with an electric insulating material, surrounding the battery element, and connecting the conductive plate and the electric insulating material to each other; In which the above-described battery element is sealed.

A sixth electrochemical device according to the present invention is a device in which a heat dissipation mechanism is provided on the outer peripheral portion of the battery element of the fourth electrochemical device according to the present invention.

In the first assembled battery according to the present invention, the fourth electrochemical device according to the present invention is laminated, a surface pressure is applied in the laminating direction, and the electrochemical devices are fixed to each other and electrically connected. It is intended to be connected to.

Further, the second assembled battery according to the present invention is characterized in that
A spring is inserted between the electrochemical elements to be stacked of the first assembled battery according to the present invention, and when the surface pressure in the stacking direction is relaxed, the electrochemical
Which was constructed as an electrical connection between the elements deviate
is there.

Further , the third assembled battery according to the present invention has
The electrochemical element to be laminated of the first assembled battery according to the present invention is formed in a leaf spring shape, and when the surface pressure in the laminating direction is relaxed, the electrochemical
Which was constructed as an electrical connection between the elements deviate
is there.

Further, a fourth assembled battery according to the present invention is an assembled battery obtained by attaching a heat collecting plate to the electrochemical element of the first assembled battery according to the present invention and laminating the electrochemical element. A heat dissipating mechanism is provided on the outer periphery, and the heat collecting plate and the heat dissipating mechanism are electrically insulated and connected.

Further, the fifth assembled battery according to the present invention is characterized in that
An electrolytic solution reservoir formed of a porous body containing an electrolytic solution and disposed on an outer peripheral portion of the first assembled battery according to the present invention , and an electrolytic solution replenishment comprising a liquid conducting portion connecting the reservoir and the electrochemical element. A mechanism is provided .

Further, the sixth assembled battery according to the present invention is characterized in that
According to a fifth aspect of the present invention, there is provided an electrolyte replenishing mechanism for an assembled battery, wherein the liquid absorbing force of the electrolytic solution reservoir is equal to or less than the liquid absorbing force of the porous body and the electrode of the electrochemical element , and the liquid absorbing portion of the liquid conducting portion is used. It is formed to be larger than the force .

[0039]

[0040]

[0041]

[0042]

[0043]

In the electrochemical device of the present invention, for example, a battery, the porous body, that is, the positive electrode is formed on one side of the separator and the negative electrode is continuously positioned on the other side. The positioning of the positive electrode and the negative electrode is unnecessary, and the assembly is simplified. Then, when the electrode-separator integrated body thus formed is folded once, for example, with the positive electrode surface inside, a battery sheet having a positive electrode on the inside and a negative electrode surface on the outside is obtained. Can be rolled up or laminated to easily obtain a battery. In the obtained battery, a battery reaction similar to that of the battery according to the conventional method occurs.

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

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

Further, since the positive electrode active material and the negative electrode active material surely face 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, there is no shortage of battery capacity.

The positive electrode active material layer and the negative electrode active material layer can be easily formed on the separator by coating a paste containing an electrochemically active material on one surface and the other surface of the separator.

Even in the case of a high-viscosity material or a solid ionic conductive material such as a polymer electrolyte which is difficult to be retained on the porous separator after the formation of the active material layer, the porous separator is required to 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 large electrode area electrode can be compactly packed in a battery container, and a high performance battery capable of obtaining a large current can be obtained. Can be Further, it has a flat plate shape and is suitable for forming an assembled battery.

Since a heat dissipating mechanism composed of, for example, an assembly of heat dissipating fins and pins is provided on the outer peripheral portion of the battery, heat generated due to charging and discharging can be quickly removed. Excessive rise in battery temperature can be reduced.

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 processability is improved and the degree of freedom of the electrode structure is increased. The manufacture of cylindrical spirals and folded electrodes is facilitated.

The ratio of the binder to the active material is 0.1
When the content is in the range of 20% by weight to 20% by weight, the battery performance is improved, and the coating (electrode preparation) is easy because the solvent is dispersed in 5 to 30 parts by weight with respect to 1 part by weight of the binder. become.

Further, the battery pack of the present invention is formed by stacking the above-mentioned flat lithium secondary batteries, applying surface pressure in the stacking direction, and fixing and electrically connecting the flat batteries to each other. When a trouble occurs, the connection can be easily broken by relaxing the surface pressure, and the battery can be protected.

Also, by inserting a spring between the stacked flat batteries and forming the stacked flat batteries in a leaf spring shape, the restoring force of the spring allows a space between the batteries to be increased, thereby making the electrical connection quick. You can come to

Further, a heat collecting plate is attached to the lithium secondary battery, and a heat radiating mechanism is provided on the outer periphery of the assembled battery, and the heat collecting plate and the heat radiating mechanism are electrically insulated and connected, so that the heat is generated inside the battery. This can remove excessive heat of the battery inside the battery pack, which is difficult to lower only by natural heat radiation from the surface of the battery pack.

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

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

Further, in the lithium secondary battery, a negative electrode,
Since lithium carbonate is contained in at least one of the separator and the electrolyte, gas generation due to 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. In a closed system such as a battery,
It is considered that when there is a large amount of lithium carbonate, which is a reaction product, in the system, equilibrium transfer occurs, and the reaction hardly proceeds.

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, lithium oxide and lithium carbonate are in an equilibrium relationship, lithium carbonate is generated when the carbon dioxide gas concentration is high,
It is considered that the same effect as when lithium carbonate was added was exhibited.

[0060]

Further, a carbonate is added to the positive electrode, and after assembling the battery, charging or heating is performed to decompose the carbonate to generate carbon dioxide gas. It can be raised without disassembly, and the rise in battery internal pressure can be suppressed.

[0062]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a battery according to the present invention, a positive electrode is continuously formed on one surface of a separator and a negative electrode is continuously formed on the other surface of the separator in order to eliminate the alignment between the positive electrode and the negative electrode during assembly. When forming the electrodes, the width of the positive electrode and the negative electrode is smaller than the width of the separator. When the electrode-separator integrated body thus formed is folded once, for example, with the positive electrode surface inside, a battery sheet having the positive electrode inside and the negative electrode outside is obtained. If this sheet is rolled up as it is and inserted into a cylindrical can, a cylindrical battery can be obtained. Also, by laminating this sheet as a strip and inserting it into a square can,
A prismatic battery is obtained. Then, the obtained battery undergoes the same battery reaction as the battery according to the conventional method. Hereinafter, a specific description will be given with reference to examples.

Embodiment 1 FIG. 1 is a perspective view showing a battery sheet according to one embodiment of the present invention. In the figure, 51 is a current collector network with tabs, 52 is a positive electrode active material layer, 53 is a current collector copper foil, 55 is a negative electrode active material layer, and 3 is a separator. 87 wt% lithium cobaltate, graphite powder (Lonza (LON
A positive electrode active material paste adjusted to a composition of KS-6) 8 wt% and a binder (polyvinylidene fluoride) 5 wt% manufactured by ZA) was placed on a separator 3, in this case, a porous polyethylene film (thickness 50 μm) by a doctor blade method. And adjusted to a thickness of 200 μm. Then flip it over,
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 similarly applied to a thickness of 200 μm on the back surface by the doctor blade method. In addition, the positive electrode and the negative electrode active material paste were applied narrower than the width of the porous polyethylene film 3 except for the edge. After drying, the positive electrode side of the battery sheet is turned inside,
1. In this case, the sheet is folded in the longitudinal direction of the sheet so as to sandwich a stainless steel net with a current collecting tab, and a current collecting copper foil 5
3 (thickness: 20 μm) was applied, and the total thickness was adjusted to 150 μm by roller pressing to prepare a battery sheet shown in FIG. 1.

The prepared battery sheet was wound around a copper bobbin, inserted into a stainless steel can, and a stainless steel tab was welded to the positive electrode terminal. Then, lithium perchlorate was dissolved in a mixed solvent consisting of ethylene carbonate, dimethoxyethane and benzene. The electrolytic solution was injected and sealed.

In the above steps, 500 batteries were continuously formed, but none of them failed 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 where the separator 3 is separately manufactured and laminated, it is not necessary to position the positive electrode and the negative electrode via the separator. The battery could be manufactured without causing a defect due to an internal short circuit even when assembled without the battery. Also, since the number of parts is reduced, the assembling process can be simplified, and the device can be easily created. Also, in the battery of the present invention, both the positive electrode and the negative electrode are formed on the separator with a smaller width than the width of the separator, and when wound up, even if the end faces are shifted, both the positive electrode and the negative electrode are inside the separator. There was no contact and did not hinder the progress of the battery reaction. In addition, since the positive electrode active material and the negative electrode active material surely face each other via the separator, there was no generation of an active material that did not contribute to the reaction due to electrode displacement, and there was no shortage of battery capacity.

Embodiment 2 FIG. FIG. 2 is a perspective view showing a battery sheet according to another embodiment of the present invention, and 54 is a tab-collected copper foil for current collection. A positive electrode active material paste adjusted to a composition of 87 wt% of lithium cobaltate, 8 wt% of graphite powder (KS-6 manufactured by Lonza), and 5 wt% of binder (polyvinylidene fluoride) is placed on a porous polyethylene film (thickness: 50 μm) of the separator 3. By doctor blade method, thickness 2
It was adjusted to 00 μm and painted. Next, the plate is turned over, and on the back surface, mesophase microbead carbon (manufactured by Osaka Gas) 95
wt%, binder (polyvinylidene fluoride) 5wt%
The negative electrode active material paste adjusted as above was applied to a thickness of 200 μm by the same doctor blade method. In addition, the positive electrode and the negative electrode active material paste were applied narrower than the width of the porous polyethylene film 3 except for the edge. After drying, the positive electrode surface of the battery sheet is placed inside, the sheet is folded in the longitudinal direction of the sheet so as to sandwich a stainless steel net 51 with a tab for current collection, and a copper foil 53 (with a thickness of 20 μm) with a tab is provided on the outside. The total thickness was adjusted to 150 μm by applying a roller press.
Were prepared.

The prepared strip-shaped battery sheets are bundled, and the positive electrode tabs and the negative electrode tabs are welded to each other.
After closing the opening except for the electrolyte injection port, an electrolyte in which lithium perchlorate was dissolved in a mixed solvent of ethylene carbonate, dimethoxyethane and benzene was injected, and the injection port was welded and sealed.

In the above steps, 500 continuous batteries were prepared, but none of them had a defect due to an internal short circuit. The same effect as in the above embodiment was obtained.

Embodiment 3 FIG. Lithium cobaltate 87wt
%, Graphite powder (KS-6 manufactured by Lonza) 8 wt%, and binder (polyvinylidene fluoride) 5 wt%, and the positive electrode active material paste was adjusted to 70% by volume of the paste and polyethylene oxide to form a solid solution with lithium perchlorate. A positive electrode paste in which 30% by volume of the polymer electrolyte was well mixed was prepared. Similarly, a negative electrode paste in which 70% by volume of a 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 a polymer electrolyte were prepared. Porous polyethylene film (thickness: 50 μm) of separator 3 pre-soaked with polymer electrolyte
The positive electrode paste is applied to a thickness of 20
It was adjusted to 0 μm and painted. Next, the film was inverted and the negative electrode paste was coated on the backside with a thickness of 200 μm by the same doctor blade method.
I painted it. In addition, the positive electrode and the negative electrode active material paste were applied narrower than the width of the porous polyethylene film 3 except for the edge. After drying, the battery sheet is folded in the longitudinal direction of the sheet so that the positive electrode surface is on the inside, and a stainless steel net 51 with a tab for current collection is sandwiched, and a copper foil 54 with a tab is formed on the outside.
(Thickness: 20 μm), and the entire thickness was adjusted to 150 μm by a roller press to prepare a strip-shaped battery sheet shown in FIG.

The prepared strip-shaped battery sheets are bundled, and the positive electrode tabs and the negative electrode tabs are welded to each other.
Sealed by welding.

In the above steps, 500 batteries were continuously formed, but none of the batteries caused a failure due to an internal short circuit. In addition, the same effects as those of the above embodiment were obtained.

COMPARATIVE EXAMPLE 87 wt% of lithium cobaltate and 8 wt% of graphite powder (KS-6 manufactured by Lonza) on both sides of an aluminum foil with tabs (20 μm).
% And a binder (polyvinylidene fluoride) having a composition of 5 wt% were formed by a doctor blade method, and dried to obtain a positive electrode having a thickness of 100 μm by a roller press.

Mesophase microbead carbon (manufactured by Osaka Gas) 95 wt.% On both sides of tabbed copper foil (20 μm)
%, And a binder (polyvinylidene fluoride) adjusted to 5 wt%, a negative electrode active material paste was similarly formed by a 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 diagram of FIG. 11, the positive electrode 1, a strip-shaped porous polyethylene film (thickness: 25 μm) separator 3, the negative electrode 2, and the separator 3 are laminated in this order while passing through a lamination guide 58. And inserted into a stainless steel can, and a stainless steel tab was welded to the positive electrode terminal. Then, an electrolytic solution in which lithium perchlorate was dissolved in a mixed solvent consisting of ethylene carbonate, dimethoxyethane and benzene was injected, and sealing treatment was performed. Reference numeral 57 denotes a rolled-up body of the electrode separator.

In the above steps, 500 batteries were continuously formed, but 10 batteries having a defect due to an internal short circuit occurred.

In the above embodiment, a battery was described as an example of an electrochemical element. However, similar effects can be obtained by applying the present invention to a capacitor.

On the other hand, another lithium secondary battery of the present invention
In order to realize a high-voltage, large-capacity battery, a flat battery having a folded electrode structure is formed by employing a flexible electrode using a soft fluororesin as a binder. In addition, by stacking them, a safe and high-performance battery pack can be easily obtained.
Furthermore, a heat release mechanism and a pressure release mechanism are provided, and the gas composition in the battery is made sufficient for carbon dioxide to suppress a pressure rise and enhance safety. In addition, an electrolyte supply mechanism is provided to achieve a longer life.

Embodiment 4 FIG. FIG. 3 is a sectional view showing one embodiment of the flat lithium secondary battery of the present invention. Positive on one side of one separator 3
Electrode-separator having pole 1 and negative electrode 2 formed on opposite surface
The integrated element is folded even-numbered to form a battery element, an electrically insulating sealing material 4 is disposed around the battery element, and a flat cell is formed by being sandwiched between two conductive plates 5. By doing so, the large electrode area electrode can be compactly packed in the battery container, and a high voltage, large capacity battery can be obtained. Also, the electrode and separator are integrated
Because it is formed, it is easy to form with less performance defects
Wear.

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

The reason why the number of times of folding of the battery element is defined as an even number is that if the number of times is odd, both the front and back surfaces of the folded battery element will have only one of the positive electrode and the negative electrode. Be sure to surface if the back of the battery element is a positive electrode if an even number of times is a negative electrode. In addition, a positive electrode, a negative electrode,
Although high assembly accuracy is required for the positioning of the battery , the positive and negative electrodes and the separator may be overlapped and folded as separate parts to manufacture a battery element.

The number of times of folding is not specified at all, but is preferably about 4 to 16 times in consideration of the complexity of assembly. The width and length of the battery element are determined by the electrode area to be formed and the number of times of folding. 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.

Embodiment 5 FIG. Next, an easily foldable flexible electrode suitable for the flat lithium secondary battery having the above-mentioned folded electrode structure of the present invention will be described. A flexible electrode characterized by using a soft fluororesin composed of the following monomer units A and B obtained by graft polymerizing a crystalline fluororesin on a fluororubber as a binder. Further, a binder obtained by adding the above-mentioned fluororesin and one or more kinds of fluororesins as a binder may be used. . _{A: -CH 2 -CF 2 - B} : -CFCl-CF 2 -

Such a soft fluororesin has the same performance as that of a fluororesin which has been most popularly used in an electrode for a lithium secondary battery, and has been improved to improve the mechanical strength. And Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 8-206615 discloses a production method and performance thereof. Since such a soft fluororesin is a fluorocopolymer obtained by graft-polymerizing a crystalline fluororesin to a fluororubber, the flexibility of the fluororubber can be improved while maintaining the same performance as a conventional fluororesin. It is a fluororesin that combines. When this soft fluororesin is used as a binder, it is possible to produce a high-performance and highly flexible electrode not available in the conventional binder.

Such a soft fluororesin can be used not only alone but also by mixing with another crystalline fluororesin or the like, while retaining the properties of the base resin, and imparting flexibility. 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 bonded, resulting in a decrease in battery capacity. It will cause the electrode reaction to be hindered.
Preferably, it is in the range of 1% by weight to 10% by weight.
In addition, in the case of preparing by dispersing in a coating solvent in preparing 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 be part by weight, preferably 8 to 20 parts by weight. As an example of a manufacturing method, there is a method in which the binder is dissolved in a coating solvent to prepare a binder solution, and an active material or the like dispersed in the solution is formed 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 (Cefral Soft: Central Glass) as a binder
3 parts by weight were dissolved to form 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 this solution to prepare a coating solution. The liquid is collected to a thickness of 20
An electrode sheet of about one example of the flexible electrode of the present invention having a thickness of about 300 μm was obtained by coating a 30 μm-wide aluminum foil with a width of 30 cm and drying. This sheet is about 80 × 10mm
This was used as a sample for a cutting test.

Using the prepared sample, tensile strength and elongation strain were measured by a tensile strength measuring device, and the mechanical strength was evaluated. The result is shown by the characteristic curve a in the characteristic diagram of FIG.
Shown in The vertical axis represents load, and the horizontal axis represents elongation. Also, the evaluation result of the electrode sheet (conventional example) similarly prepared except that the binder was changed to PVdF is similarly shown in a characteristic curve c of FIG. The characteristic curve b of FIG. 4 shows the evaluation results of the electrode sheet of another example prepared in the same manner except that the binder was changed to a mixed powder (1: 1) of PVdF and a soft fluororesin.

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

The solvent is not particularly limited as long as it can dissolve the binder, but examples thereof include N-methylpyrrolidone (NMP), N, N dimethylformamide (DMF) and the like. Although the active material is not particularly limited, examples thereof include carbon materials such as graphite, glassy carbon, carbon black, coke, pyrolytic carbon, and carbon fiber, TiS2, MoS2, and 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, meshes, and expanded metals.

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

As described above, in the electrode in which the powdered active material is bound by the binder, not only the performance but also the mechanical properties are often influenced by the performance of the binder. Therefore, in the present invention, by paying attention to the binder for bonding the active material and the like, a flexible electrode excellent in processability is produced by finding a binder excellent in mechanical strength without affecting the battery performance. Indicates that you can do it.

By applying the above binder to a binder for bonding an active material in an electrode for a non-aqueous electrolyte battery, it is possible to obtain electrode flexibility that cannot be obtained with a conventional binder. By using the electrode manufactured in this manner, it is easy to manufacture a folded electrode or a wound electrode in a large electrode area, and a useful result for improving battery performance is brought.

Embodiment 6 FIG. The assembled battery of the present invention is formed by stacking the above-mentioned flat lithium secondary batteries to obtain a high voltage. At this time, the flat batteries are fixed to each other by applying a surface pressure in the stacking direction and are electrically connected to each other, but this connection is configured to be cut off by relaxing the surface pressure.

FIG. 5 is a schematic diagram showing one embodiment of the battery pack of the present invention. As shown in FIG. 5, are inserted spring 12 between the plate-shaped battery 11 shown in FIG. 3 to be stacked. When the surface pressure is applied by the fastening rod 13, the spring 12 contracts, and the electrical connection between the flat batteries 11 is maintained. It is necessary to loosen the surface pressure to cut off the electrical connection of the flat battery 11 when a short circuit occurs inside the assembled battery. In this case, a current several times to several tens times that of a normal current flows, so that abnormal heat generation occurs and the battery temperature rises rapidly. At the same time, the pressure inside the unit cell, which is abnormally heated, also rises rapidly. By detecting these sudden changes in temperature and pressure and loosening the tightening rod 13, the interval between the flat batteries 11 is increased by the restoring force of the spring 12, and the electrical connection can be cut off.

For example, if the cut-off portion 14 which is a part of the tightening rod 13 is made of a material which is blown off by the ambient temperature, when the temperature around the tightening rod abnormally rises, the tightening rod breaks and the surface pressure can be reduced. Tightening rod 13
The ambient temperature at which the cut-off portion 14 is blown is set at a temperature exceeding the normal temperature of the battery.
It is preferable to cut off at the above. As a material that melts at such a temperature, a so-called wood alloy (melting range of 60 ° C.) is used.
(.About.72.degree. C.).

Embodiment 7 FIG. Further, in the sixth embodiment, the surface pressure is relaxed by fusing off the cut-off portion 14 of the tightening rod 13, but a part of the tightening rod 13 is made thinner or the material is changed to increase the tensile strength. The weakening portion may be formed so that the fastening rod is cut off due to an increase in surface pressure due to a sudden increase in abnormal internal pressure of the battery, and the surface pressure can be reduced. It is desirable that the internal pressure of the unit cell does not exceed 1 MPa as the surface pressure at which the fastening rod cuts, and therefore it is preferable to cut at 0.8 to 0.9 MPa.

Embodiment 8 FIG. Further, the surface pressure can be relaxed against a sudden temperature rise or a pressure rise by a method other than a method of destructively relaxing the surface pressure such that the clamping rod is broken. That is, a part of the tightening rod is connected with an electromagnet, a temperature sensor and a strain gauge 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 supplied to the electromagnet to connect the tightening rod. Is to solve.
It is desirable that the temperature at which the connection of the fastening rod is cut off is about 60 ° C. or higher, and the pressure is about 0.8 to 0.9 MPa.

Embodiment 9 FIG. Also, the battery pack of the above embodiment is
Although the case where the spring 12 is inserted between the flat batteries 11 is shown, the flat battery may be formed in a leaf spring shape and used, and the same effect is exerted.

The heat generated 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 the use of the battery, and the internal resistance of the battery is not always constant. However, in the case of a lithium secondary battery, on average, the ratio of the electric energy required for charging to the electric energy obtained by discharging, that is, the charging / discharging energy efficiency is about 80% or more. 20%. However, the energy per kg of the battery, that is, the weight energy density is about 12
Since the specific heat of the battery is 0.8 because it is as high as 0 W / kg,
The battery temperature will rise by 0.12 ° C per second,
In the adiabatic state, the temperature rises by 7.2 ° C. in one minute of charging and discharging. A small cell has a relatively large surface area and is cooled by natural heat radiation from the surface. However, a large battery is difficult only by natural heat radiation from the surface. Further, in the battery pack, it is difficult to lower the temperature of the battery disposed inside the battery pack only by natural heat radiation from the battery pack surface even in a combination of small batteries.

Embodiment 10 FIG. Thus, the large battery of the present invention,
At the outer periphery of the battery of the folded electrode or the wound electrode in the large electrode area, for example, a heat radiating mechanism composed of an assembly of heat radiating fins and pins is provided so that heat generated by charging and discharging can be quickly removed. ing. Excessive rise in battery temperature is prevented.

Embodiment 11 FIG. FIG. 6 is a schematic view showing another embodiment of the battery pack of the present invention. As shown in FIG. 6, a heat radiation mechanism 21 for removing heat generated inside the battery is provided on the outer peripheral portion of the battery pack, so that an excessive rise in battery temperature can be reduced. The heat dissipating mechanism 21 is similar to a general heat exchanger so-called radiator.

Embodiment 12 FIG. FIG. 7 is a partially enlarged schematic view showing still another embodiment of the assembled battery according to the present invention, in which a heat collecting plate 31 for effectively removing heat at the center 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 enter between the cells 11. Then, the heat collecting plate 31 is connected to the heat radiating mechanism
1 via an electrical insulating layer 32. The reason why the electric insulating layer 32 is provided is to prevent an internal short circuit between the unit cells 11 in the assembled battery. Of course, this layer is unnecessary when the heat collecting plate 31 itself has electrical insulation. However,
A material having good thermal conductivity suitable for a heat collecting plate, for example, a material such as carbon, aluminum, or copper generally has good electric conductivity. For the electrical insulating layer 32, a metal oxide such as alumina having relatively good thermal conductivity is used.

Embodiment 13 FIG. An embodiment of an electrolyte replenishing mechanism provided in the battery pack to prevent the exhaustion of the electrolyte will be described. The electrolyte replenishment mechanism is a liquid electrolyte reservoir made of a porous body placed in contact with the assembled battery in the battery container, and a liquid guide part made of a porous body having a different liquid absorbing power connecting the electrolyte reservoir and the separator of the unit cell. It is composed of The porous body has a property of sucking a liquid into a hollow portion (pore) therein, for example, like a sponge. On the other hand, some force is required to take out the liquid in the pore. This is because there is an inlet radius and surface tension of the liquid when the pore is assumed to be cylindrical, and there is a liquid absorption power of the pore determined by the contact angle between the liquid and the porous body,
This is determined as shown in the following equation. Since the separator and the electrode are porous, in order to absorb spontaneously from the electrolyte reservoir which is also porous, when the electrolyte is insufficient,
The liquid absorbing power of the porous body of the reservoir must be set smaller than the liquid absorbing power of the separator and the electrode. This is because the liquid in the pore having a strong liquid absorption does not move unless an external force is applied to the pore having a low liquid absorption. The most common method of controlling the liquid absorption is to consider the following equation. Therefore, in the electrolyte replenishment mechanism of the present invention, the radius of the pores of the porous body is adjusted so that the liquid absorbing power of the porous body of the reservoir is smaller than the liquid absorbing power of the porous body of the separator and the electrode, and the exhaustion of the electrolyte is reduced. I'm preventing. Long life. P = 2σ cos θ / r P: Liquid absorption (N / m ² ) σ: Surface tension (N / m) θ: Contact angle (degree) r: Radius (m)

When a plurality of batteries stacked in series are supplied with electrolyte from a common reservoir, in a liquid-junction state where the battery and the reservoir are always connected by the electrolyte, the battery between the stacked batteries transmitted through the liquid-junction part Since a short-circuit current flows and self-discharge of the battery occurs, it is not preferable that there is a liquid junction at all times.

Embodiment 14 FIG. In the electrolytic solution replenishing mechanism of this embodiment, in order to solve the above-mentioned problem, the connecting portion between the reservoir and the separator and the liquid absorbing force of the liquid conducting portion are made smaller than those of the reservoir, the separator and the electrode. By configuring in this way, as long as the excess electrolyte is not included,
The liquid guide section is in a state where there is no liquid, and no liquid junction occurs. When the electrolyte is insufficient, the electrolyte is replenished, and a decrease in battery efficiency can be prevented. The pore diameter of the separator is desirably less than 1 μm from the viewpoint of preventing internal short circuit. Therefore, the pore diameter of the liquid guide is desirably 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. It is composed of the porous body described above.

The shortage of the electrolyte in the battery is mainly caused by the decomposition of the electrolyte. Decomposition of the electrolyte causes an increase in the internal pressure of the battery.
Since it is considered that the shortage of the electrolyte causes an increase in the internal resistance, it is considered that there is a correlation between the shortage of the electrolyte and the increase of the internal pressure.

When the internal pressure of the battery is applied to the reservoir and the pressure is equal to or greater than the difference between the liquid absorbing power of the connecting portion and the liquid absorbing force of the reservoir, the electrolytic solution is pushed into the connecting portion from the reservoir, and the liquid junction is formed. Is formed. When a liquid junction is formed, the electrolyte is supplied from the reservoir to the separators and the electrodes that are insufficient. When the internal pressure release mechanism operates to lower the internal pressure of the battery, 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 cell from rising, the sealing portion of the cell is made permeable to gas.
A container for storing and sealing the assembled battery is prepared so that moisture in the atmosphere is not mixed in, but a valve for adjusting the internal pressure release mechanism so that the pressure in the battery container is not excessively increased is attached to the battery container.

A conventional release mechanism is provided with a portion destroyed by an increase in the internal pressure in a part of the container, and is based on a so-called rupture disk. Since this method is self-destructive, it is difficult to reuse the whole once it works. This is a fatal effect, especially for lithium secondary batteries that do not like the incorporation of moisture from the atmosphere, and should be said to be the ultimate safety device.

On the other hand, there are so-called check valves and relief valves, which operate at a predetermined pressure and stop at a pressure lower than the predetermined pressure to maintain the internal pressure. Its basic structure is to produce a force that antagonizes internal pressure,
For example, a release port is held by a valve body connected to a compressed spring. To release the internal pressure and reduce the pressure to a predetermined pressure or less, it is only necessary to attach such a conventionally known check valve to the container.

However, as described above, in order to operate the electrolyte replenishment mechanism using the increase in the internal pressure of the battery, after releasing the internal pressure at a certain pressure A, the internal pressure is reduced to a pressure B smaller than the pressure A, and the internal pressure is released. It must end.
Pressure B and pressure A are set so as to sandwich pressure C at which the electrolyte replenishment mechanism starts operating. The pressure A is a safety upper limit pressure. As a relief valve that operates as described above, a valve as shown in the schematic diagram of FIG. 8 was mounted on the battery container.

The operation will be described with reference to FIG. The pressure inside the battery is applied to the valve element 41, and the valve element 41
Are held down by a spring A42 that generates a force corresponding 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. Retaining pin 44
Is interlocked with the valve body 41. The spring case 43 has a pressure B
Is held down by a spring B45 that generates a force corresponding to

When the battery internal pressure exceeds the pressure A, the valve body 41 drops, and the internal pressure is released from the release port 46. At the same time valve body 4
When the retaining pin 44 interlocked with 1 comes off, the valve element 41 retracts together with the spring case 43 and compresses the spring B45. When the battery internal pressure decreases and becomes equal to or less than the pressure B, the spring B45 returns,
The valve body 41 is pushed back together with the spring case 43, and the retaining pin 44
Is returned, and the release port 46 is closed again. By acting in this manner, it is possible to prevent the battery internal pressure from rising too much. The pressure A is desirably less than 1 MPa, which does not become a so-called high-pressure gas. The pressure B may be lower than the pressure A, but is so-called atmospheric pressure 0.1MP.
It is desirable to be 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 electrolyte. The organic solvent is, for example,
The decomposition reaction of propylene carbonate, which is often used as an electrolyte for a lithium secondary battery, is as shown in Chemical formula 1. In this case, propene gas generated when propylene carbonate is decomposed is a source of increasing the pressure in the battery container.

[0115]

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Embodiment 15 FIG. The present invention has found that the addition of lithium carbonate to the electrolytic solution has the effect of suppressing this gas generation, and has been achieved.In a lithium secondary battery using an electrolyte obtained by dissolving a lithium salt in an organic solvent, the present invention relates to an electrolytic solution. By containing lithium carbonate, gas generation due to decomposition of the organic solvent in the electrolytic solution is suppressed. As a result, an excessive increase in the battery internal pressure can be suppressed, and safety is improved. Although the details thereof are not clear, in a closed system such as a battery, it is considered that when a large amount of lithium carbonate, which is a reaction product, exists in the system, equilibrium transfer occurs and the reaction hardly proceeds.

Embodiment 16 FIG. It was also found that when lithium oxide and carbon dioxide gas coexist, the gas generation rate was similarly reduced. Therefore, carbon dioxide was contained in the container for storing the battery, and lithium oxide was contained in the electrolytic solution. As a result, the gas generation rate was able to be reduced, and an increase in the internal pressure of the battery was suppressed. Further, as shown in the characteristic diagram of FIG. 9, the time-dependent change of the battery internal pressure differs depending on the carbon dioxide gas concentration. The vertical axis represents the battery internal pressure, the horizontal axis represents time, and the characteristic curve d
Is a battery internal pressure rise curve of 100% carbon dioxide, a characteristic curve e is a battery internal pressure rise curve of 50% carbon dioxide, and a characteristic curve f is a battery internal pressure rise curve of 0% carbon dioxide. It can be seen that the lower the carbon dioxide gas concentration, the faster the internal pressure of the battery rises. This is
Since carbon dioxide, lithium oxide, and lithium carbonate are in an equilibrium relationship as indicated by, lithium carbonate is generated when the carbon dioxide gas concentration is high, and it is considered that the same effect as in the case where lithium carbonate is added appears.

[0118]

Embedded image

Embodiment 17 FIG. Therefore, also by enclosing the carbon dioxide gas in the battery container, lithium carbonate is generated and the decomposition reaction of the electrolytic solution is suppressed, so that an increase in the internal pressure of the battery is suppressed. Therefore, the step of sealing the battery container is performed in a carbon dioxide gas atmosphere, and the surrounding carbon dioxide gas is simultaneously sealed. Alternatively, the battery container may be hermetically sealed while spraying carbon dioxide gas on the battery parts, and the sprayed carbon dioxide gas may be simultaneously sealed in the container.

Further, as shown in the characteristic diagram of the internal pressure of the battery which was made higher than the constant pressure by the carbon dioxide gas as shown in FIG. The time required to reach pressure is long. This is also due to the effect of suppressing 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, a characteristic curve g represents a battery internal pressure rise curve of 0% carbon dioxide gas, and a characteristic curve h represents a battery internal pressure rise curve after decomposition of the positive electrode carbonate. .

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

Embodiment 18 FIG. However, in the case where the positive electrode contains lithium carbonate, it has been found that the internal pressure rises quickly during overcharge. This is because lithium carbonate is decomposed into carbon dioxide and lithium oxide by overcharging.
In this embodiment, by utilizing this, lithium carbonate is added to the positive electrode, and after assembling into a battery, the lithium carbonate is decomposed by intentionally overcharging or heating to decompose the carbon dioxide gas in the battery container. Is occurring. Thereby, the concentration of carbon dioxide in the battery can be increased without decomposing the electrolytic solution. When the amount of lithium carbonate added to the positive electrode is 1% by weight or less, the addition effect is not substantially observed, and the addition amount is preferably small, and when 2% by weight is added, it is practically sufficient. % By weight is appropriate. It should be noted that not only lithium carbonate but also other carbonates can provide similar effects.

Hereinafter, a more specific example will be described. Embodiment 19 FIG. To 33 parts by weight of NMP solution as a coating solvent,
Dissolve 3 parts by weight of a soft fluororesin as a binder to form a binder solution, and add Li as a positive electrode active material to this solution.
A coating liquid 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 liquid was applied to a 20 μm-thick aluminum foil as a current collector to a width of 30 cm, and dried to prepare an electrode sheet having a thickness of about 300 μm. The length was 151 cm.

As a coating solvent, 33 parts by weight of an NMP solution
Dissolve 3 parts by weight of a soft fluororesin as a binder to form a binder solution, and disperse 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 as a negative electrode active material in this solution. Then, a coating liquid was prepared. This coating solution was applied on a copper foil having a thickness of 20 μm as 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 prepared positive electrode and negative electrode are arranged so that the active material layers face each other with a porous polypropylene film (thickness: 50 μm) serving as a separator therebetween, and the widthwise positive electrode end does not protrude beyond the widthwise end of the negative electrode. Then, the battery element was folded four times in a length direction every 30 cm. The length of the separator was 155 cm. At the start and end of the folding, the separator protruded by about 2 cm from the positive electrode and the negative electrode.

The 30 cm square battery element thus prepared was fitted into two 1.5 mm thick, 5 mm wide polyethylene frames, and a separator protruding from the battery element and a liquid conducting portion (for connecting the electrolyte reservoir with the separator). A porous film made of polypropylene (50 μm thick) with a polyethylene frame, sandwiched between two stainless steel plates with a thickness of 0.1 mm, and heat-sealed while pressing the periphery to form a square plate A single cell was prepared.

A polyethylene frame has a width of 3 mm and a depth of 0.5 mm.
Are formed at intervals of 3 mm so as to connect the inside and the outside of the frame, and the separator and the liquid guide portion are sandwiched between the grooves. The heat fusion temperature is desirably set to 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 with a pore volume of 50% of the total pore volume. The liquid conducting portion (reservoir connection porous body) used had a pore volume having a pore diameter of about 1 μm or less and 50% of the total pore volume.

Forty flat plate cells were stacked in series, and a brass leaf spring was interposed between the flat plate cells to form a battery pack using a hard polyethylene plate as a holding plate. The fastening rod used was an aluminum pipe connected with a wood alloy.

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

The remaining two sides are provided with an electrolyte reservoir. The electrolyte reservoir is made of a hard polypropylene case packed with a nonwoven fabric made of polypropylene, and a liquid conducting portion (reservoir connection porous sheet) coming out of each battery.
Is sandwiched.

The assembled battery in which the heat radiating mechanism and the electrolyte reservoir are arranged is housed in a battery container made of stainless steel, and the assembled battery is connected to the positive electrode terminal and the negative electrode terminal which are attached to the container lid provided with the pressure control valve via an insulating layer. After welding out the positive electrode lead and the negative electrode lead, the inlet of the container lid is aligned with the position of the electrolyte reservoir, and the container lid is welded to the battery container.

The whole container is vacuumed (-750 mmHg or less)
After that, an electrolyte obtained by dissolving lithium perchlorate at 1 mol / l in a 1: 1 mixed solvent of ethylene carbonate and dimethoxyethane is poured into the liquid inlet. The 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 charged to an average cell voltage of 3.2 V.
It operated at 6 V and an average assembled battery voltage of 144 V, and obtained an output of 1.3 kW.

Embodiment 20 FIG. PV binder for electrode production
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 assembled as described above had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 as in Example 19.
Operating at 44 V, an output of 1.3 kW was obtained.

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

The battery assembled in this manner had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 as in Example 19.
Operating at 44 V, an output of 1.3 kW was obtained.

Embodiment 22 FIG. A battery was assembled in the same manner as in Example 19, except that the injection of the electrolyte was performed in a dry box in a dry air atmosphere while blowing carbon dioxide gas around the injection port.

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

Embodiment 23 FIG. NMP solution 3 as coating solvent
In 3 parts by weight, 3 parts by weight of a soft fluororesin as a binder are dissolved to form 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 are dispersed in this solution. Then, a coating liquid was prepared. This coating liquid was applied to a 20 μm-thick aluminum foil as a current collector to 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 were performed in the same manner as in Example 19. The battery was assembled by performing the liquid injection step in a dry box in a dry air atmosphere, and then the first charge was performed up to 4.5 V, and carbon dioxide gas was charged in the battery container. Was generated and the pressure control valve was operated to make the inside of the battery container an atmosphere sufficient for carbon dioxide gas.

The battery assembled as described above had an average cell voltage of 3.6 V and an average assembled battery voltage of 1 in the same manner as in Example 1.
Operating at 44V, an output of 1.3 kW was obtained.

[0143]

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

In an electrochemical device having a structure in which an electron conductive electrode formed of an active material layer having the ability to electrochemically occlude and discharge ions sandwiches a porous body holding an ion conductive material, The at least one active material
The layer and the porous body are integrally bonded with a binder.
In addition, since the current collector is provided on the back or inside of the active material layer, it is not necessary to align the electrodes facing each other at the time of assembly, which simplifies the assembly and reduces the reaction area due to the assembly failure. This has the effect of reducing performance defects due to the decrease.

The binder is polyvinylidene fluoride
To reduce the performance of the electrochemical device.
Instead, the porous body and the electrode can be bonded and integrated.

Further, the porous body has a lithium ion conductive property.
Inorganic acid that retains decomposition and stores and discharges lithium ions
Is used as the positive electrode active material and carbon is used as the negative electrode active material.
A positive electrode active material layer containing a positive electrode active material on one surface of
To provide a negative electrode active material layer containing a negative electrode active material on one side
As a result, lightweight, high-voltage lithium secondary batteries
Can be produced.

Further, in the method of manufacturing an electrochemical device,
And the porous body, the current collector, and electrochemically occluded ions,
An active material layer containing an active material capable of discharging
Bonding step, the porous body, the active material layer,
A step of injecting an electrolyte into at least one of the bonded bodies.
The positioning of the electrodes facing each other during assembly is
Required, assembling is simplified, and due to defective assembly
With reduced performance defects due to reduced reaction area
There is an effect that an element can be obtained.

Further, in the method of manufacturing an electrochemical device,
A strip-shaped porous body, and at least one surface of the strip-shaped porous body
Distribute paste and binder containing electrochemical active material
The current collector is laminated and the band-shaped laminated monolithic body is bonded.
Because it was formed, the bonded strip-shaped porous body-
It is easy to manufacture pole-integrated products and has large area electrodes.
Can be manufactured.

A positive electrode is provided on one side of the porous body, and the other side is provided with a positive electrode.
A negative electrode is formed on the electrode, and the electrode and the porous body are bonded with a binder.
Formed into a single unit, which is wound or folded
Form an element and attach it to the positive terminal and the negative terminal, respectively.
With at least two conductive plates connected and connected
To obtain a compact electrochemical device with large area electrodes
Can be

The positive terminal and the negative terminal are connected to each other.
The battery element is sandwiched between at least two successive conductive plates.
The conductive plate connected to the positive terminal and the negative terminal
Connected to the conductive plate material connected to
Surrounds the battery element, and connects the conductive plate with the electrical insulator.
Since the above battery element was sealed in the rim material,
Thus, an electrochemical device suitable for forming an assembled battery can be obtained.

A heat radiating mechanism is provided on the outer periphery of the battery element.
As a result, heat can be removed quickly and the battery temperature
The rise can be prevented. Be safe. Also, at least two
Electrochemical elements with conductive plates
High voltage and high current, and
Can be improved. Further, the at least two conductive plate members are
Laminate the provided electrochemical elements , apply surface pressure in the lamination direction,
Since the assembled battery is configured such that the electrochemical elements are fixed to each other and electrically connected to each other, when a trouble occurs, the connection can be easily broken by relaxing the surface pressure, and the battery can be protected. .

[0152] Also, to insert a spring between the electrochemical device to be stacked, or since the electrochemical device to be stacked to form a leaf spring shape, the surface pressure in the lamination direction to loosen the battery between the restoring force of the spring The interval is large, and the electrical connection can be quickly established.

[0153] Further, while attaching a heat collecting plate in the electrochemical device, the heat radiation mechanism in the assembled battery outer peripheral portion formed by laminating the electrochemical device is provided, electrically insulates the radiation mechanism and the heat collecting plate Since the connection is made, heat generated inside the battery can be removed, and an excessive rise in battery temperature in the assembled battery, which is difficult to reduce only by natural heat radiation from the surface of the assembled battery, can be reduced.

Then, an electrolyte reservoir made of a porous body containing an electrolyte and disposed around the outer periphery of the battery pack, and a liquid supply section connected to the reservoir and the electrochemical element are connected. Since the mechanism is provided, the exhaustion of the electrolyte can be prevented, and the life can be extended.

[0155] In addition, the liquid absorbing power of the electrolyte reservoir electrochemical
It is formed so as to be equal to or less than the liquid absorbing power of the porous element and the electrode of the element , and to be larger than the liquid absorbing power of the liquid conducting part. it can.

[0156]

[0157]

[0158]

Also, a carbonate is added to the positive electrode, and after assembling the battery, charging or heating is performed to decompose the carbonate to generate carbon dioxide gas. It can be raised without disassembly, and the rise in battery internal pressure can be suppressed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a battery sheet according to one 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 one embodiment of the flat lithium secondary battery of the present invention.

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

FIG. 5 is a schematic view showing an embodiment of the assembled battery of the present invention, which is an assembled battery in which the flat plate 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 battery pack of the present invention.

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

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

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

FIG. 11 is a schematic diagram of a battery assembly method in a comparative example.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electric insulating sealing material 5 Conductive plate material 11 Flat cell 12 Spring 13 Tightening rod 14 Cut off part 21 Heat dissipation mechanism 31 Heat collecting plate 32 Electric insulating layer 41 Valve body 42 Spring A 43 Spring case 44 Fastening Pin 45 Spring B 46 Release port 51 Tabbed current collector network 52 Positive electrode active material layer 53 Current collecting copper foil 54 Tabbed current collecting copper foil 55 Negative electrode active material layer

Continued on the front page (72) Inventor Takashi Nishimura 8-1-1 Tsukaguchi Honcho, Amagasaki City Mitsubishi Electric Corporation Central Research Laboratory (72) Inventor Shigeru Aihara 8-1-1 Tsukaguchi Honmachi Amagasaki City Mitsubishi Electric Corporation (56) References JP-A-2-262274 (JP, A) JP-A-2-66855 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10 / 40 H01M 4/62

Claims (14)

(57) [Claims] 1. A structure in which an electron conductive electrode formed of an active material layer containing an active material having the ability to electrochemically occlude and discharge ions sandwiches a porous body holding an ion conductive material. In the electrochemical device, the at least one
Active material layers and porous body are integrally bonded with a binder
And a current collector provided on the back or inside of the active material layer. 2. The binder contains polyvinylidene fluoride.
2. The electrochemical device according to claim 1, wherein: 3. The porous body holds a lithium ion conductive electrolyte, uses an inorganic oxide that absorbs and discharges lithium ions as a positive electrode active material, uses carbon as a negative electrode active material, and forms a positive electrode on one surface of the porous body. A positive electrode active material layer containing an active material and a negative electrode active material layer containing a negative electrode active material on the other surface are provided.
The electrochemical device according to claim 1, wherein 4. A porous body, a current collector and an electrochemically
Active material layer containing active material capable of occluding and discharging gas
Bonding with a binder, the porous body, the active material
Electrolyte into at least one of the porous layer and the adhesive
Of manufacturing an electrochemical device, comprising a step of performing
Method. 5. A strip-shaped porous body , a paste containing an electrochemically active material on at least one surface of the strip-shaped porous body, and
Laminated with current collector with binder
A method of manufacturing an electrochemical device, comprising forming a laminated monolithic product of the above . 6. A positive electrode is formed on one side of the porous body, and a negative electrode is formed on the other side of the porous body to form an integrated body in which the electrode and the porous body are bonded with a binder, and this is wound or folded. To form a battery element, and contact the positive terminal and the negative terminal respectively.
At least two conductive plates connected to each other.
Electrochemical element to be featured. 7. A terminal connected to a positive terminal and a negative terminal, respectively.
The battery element is sandwiched between at least two conductive plates
The conductive plate material connected to the positive terminal and the negative terminal
Connect the electrically conductive material with the conductive plate
Surrounding the battery element, and within the conductive plate material and the electrical insulating material.
7. The battery device according to claim 6, wherein the battery element is encapsulated in the battery.
The electrochemical element according to the above item. 8. The electrochemical device according to claim 6 wherein, wherein it has established a radiation mechanism on the outer periphery of the battery element. 9. An assembled battery, wherein the electrochemical devices according to claim 6 are laminated, and the electrochemical devices are electrically connected to each other . 10. A spring is inserted between the electrochemical elements to be laminated, and is electrically connected by a surface pressure. When the surface pressure in the laminating direction is relaxed, an electric connection between the electrochemical elements is made. 10. The battery pack according to claim 9, wherein the connection is disconnected. 11. The electrochemical device to be stacked is formed on the plate spring, claim the surface pressure in the stacking direction loosening is characterized by being configured to electrically connect between the electrochemical device is disengaged 9 Item. As well as attached to the heat collecting plate 12. A electrochemical device, a heat radiation mechanism in the assembled battery outer peripheral portion formed by laminating the electrochemical device is provided, electrically insulates the radiation mechanism and the heat collecting plate 10. The connection according to claim 9, wherein the connection is established.
The battery pack as described . 13. An electrolytic solution reservoir formed of a porous body containing an electrolytic solution and provided at an outer peripheral portion of the battery pack, and an electrolytic solution replenishing mechanism including a liquid guide portion connecting the reservoir and the electrochemical element. The battery pack according to claim 9, wherein: 14. An electrolytic solution replenishing mechanism, wherein the liquid absorbing force of the electrolytic solution reservoir is equal to or less than the liquid absorbing force of the porous body and the electrode of the electrochemical element , and is larger than the liquid absorbing force of the liquid conducting portion. The thirteenth aspect of the present invention, wherein:
Item.