JPH1012216A - High polymer solid electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain improvement of a charge/discharge characteristic, reliability and stability, by coating a peripheral part and/or a bending part of a surface in contact with a high polymer solid electrolyte of at least one electrode of the positive/negative electrodes, with an ion non-permeable material. SOLUTION: A peripheral part and/or bending part of a surface in contact with a high polymer solid electrolyte of a battery in at least one of positive/ negative electrodes are coated with an ion non-permeable material, without containing a metal material and electron conductive material, of 1×10<-8> S/cm or less electron conductivity and 10<-7> S/cm or less ion conductivity. In this way, in the case of cutting work of the battery, performance decrease according to a cut peripheral part and bending work is lessened, an outflow of a plasticizer and electrolyte, from a side surface of a laminated electrode/high polymer solid electrolyte layered product, can be impeded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery using a solid polymer electrolyte.

[0002]

2. Description of the Related Art A battery using a solid polymer electrolyte as an ion transfer medium has less liquid leakage than a conventional battery using an electrolyte as an ion transfer medium, thereby improving the reliability and safety of the battery and reducing the thickness of the battery. And the ease of forming a stacked body, a high degree of freedom in battery form, and simplification and weight reduction of a package are expected.

[0003] As the polymer solid electrolyte material, a material obtained by adding an electrolyte and a plasticizer to an ion conductive polymer such as a polyacrylonitrile or polyvinylidene fluoride material such as a material mainly composed of polyalkylene oxide such as polyethylene oxide and polypropylene oxide. Has been proposed. A battery using a polymer solid electrolyte is formed by cutting and / or bending a laminate in which a sheet-shaped electrode and a polymer solid electrolyte are laminated, or a laminate in which a polymer solid electrolyte layer is formed by applying a polymer solid electrolyte layer on the electrode surface. It can be manufactured by processing into a predetermined shape. A method of forming each layer of the electrode / polymer solid electrolyte / electrode by coating has also been proposed. As described above, since a method such as sheet lamination or coating can be adopted, it is expected that the production process is excellent in mass productivity. Further, since the liquid leakage which can occur in the conventional electrolyte battery does not substantially occur, the production process can be easily controlled, and a higher voltage is expected by the series connection lamination of the electrode / polymer solid electrolyte / electrode laminate. As a battery using a solid polymer electrolyte, a structure in which a window-like electric insulator layer is provided on the electrode surface of a sheet battery has been proposed (Japanese Patent Laid-Open No. 7-2).
49403). However, there is a problem that ions may diffuse into the electric insulating layer only in the electric insulating seal in the stacked battery, thereby causing an electrochemical short circuit between the stacked electrodes.

[0004]

However, this cutting process causes problems such as deterioration of battery performance due to structural deformation of the electrode stack at the cut portion, structural destruction, and battery operation failure due to short circuit between the electrodes. Further, when a battery is formed with a bent structure of an electrode laminate, stress is concentrated on a bent portion or a portion having a large curvature to cause a deformation of the laminated structure, or a non-uniform current density of the electrodes due to ion transfer between the electrodes. There were also problems such as.

In addition, since the liquid leakage that can occur in the conventional electrolyte battery does not substantially occur, the production process can be easily controlled, and the voltage can be increased by the series connection of the electrode / polymer solid electrolyte / electrode laminate. Although it is expected, when a high voltage battery is manufactured by serially connecting and laminating the electrode / polymer solid electrolyte / electrode laminate as a unit, the voltage of the laminate unit is unevenly distributed due to the above problem, and the battery performance is deteriorated. There were also problems that led to a decline.

When a plasticizer-added material is used as the polymer solid electrolyte, an electrolyte solution of the plasticizer is extruded and leaked due to stress applied during processing, or leaks out in a high-voltage battery in which the laminates are connected in series. There is also a problem that ion transfer occurs between the electrodes that do not cause a voltage drop. As a battery using a polymer solid electrolyte, a structure in which a window-like electric insulator layer is provided on an electrode surface of a sheet battery has been proposed (Japanese Patent Application Laid-Open No. 7-249403). However, in a laminated battery, there is a problem that ions may diffuse into the electrically insulating layer only with the electric insulating seal, and there is a risk that an electrochemical short circuit may occur between the electrodes of the laminated body.

An object of the present invention is to solve the above-mentioned problems of the polymer solid electrolyte battery, to provide a battery having excellent reliability and stability, and to efficiently manufacture a high-performance battery.

[0008]

Means for Solving the Problems The present inventors have conducted research on a solid battery using a solid polymer electrolyte and completed the battery of the present invention. That is, the present invention provides: (1) In a battery in which a positive electrode and a negative electrode are joined via a solid polymer electrolyte, at least one of the positive electrode and the negative electrode has a peripheral portion and / or a bent portion of a surface in contact with the solid polymer electrolyte. Has a structure coated with an ion-impermeable material. (2) It has a laminated structure in which a positive electrode and a negative electrode whose peripheral portions are coated with an ion-impermeable material are joined via a solid polymer electrolyte such that the sides coated with the ion-impermeable material face each other. A battery characterized in that an ion-impermeable material covering the positive electrode and an ion-impermeable material covering the negative electrode are in close contact with each other around the laminated structure. (3) The battery according to (1) or (2) above, wherein the polymer solid electrolyte contains a vinylidene fluoride-based polymer.

Hereinafter, the present invention will be described in detail. The battery of the present invention is constituted by a laminate in which a peripheral portion and / or a bent portion of the electrode surface are covered with a material that does not transmit ions (an ion-impermeable material) and are laminated with a solid polymer electrolyte. . In the present invention, the portion of the electrode surface that covers the ion-impermeable material is a peripheral portion and / or a bent portion of the electrode. The definition of the coating area is not limited because it differs depending on the manufacturing method, constituent materials, and battery structure of the battery to be manufactured.However, if the coating area is too large, the charge / discharge capacity of the battery is reduced, and the electrode coating area has the effect of the present invention. It is preferable to keep it to the minimum necessary.

The ion-impermeable material used in the present invention does not include a metal material or an electronic conductive material, and has an electron conductivity of 1 × 1.
0 ^-8 S / cm or less and ionic conductivity is 10 ^-7 S / cm or less. Since the ion-impermeable material of the present invention is used as a barrier material for suppressing ion permeation, it is necessary that the material does not exhibit ion permeability even when it is in contact with the electrolyte contained in the polymer solid electrolyte for a long time. Although it is preferable that the material does not swell with the electrolytic solution, even a material that swells in a trace amount in the electrolytic solution can be used as the material of the present invention as long as it satisfies the above-mentioned ion conductivity and electron conductivity. By cutting and bending the laminate at the portion covered with this material, it is possible to reduce or eliminate battery performance deterioration or battery operation failure due to structural deformation or structural destruction.

In the battery of the present invention, this material coating is performed on the positive electrode and the negative electrode in a monopolar or bipolar manner. The positive electrode and the negative electrode do not necessarily have the same ion-impermeable material coating area. It is preferable to cut and bend the portion where the ion-impermeable material-covered portion of the negative electrode is coincident. On the other hand, when a laminate with a polymer solid electrolyte is formed using an electrode sheet that has been cut into a predetermined shape in advance, there is a possibility that structural deformation or structural destruction has occurred in the periphery of the already cut electrode portion. After coating the peripheral portion with the ion-impermeable material, a laminate is formed to obtain the battery of the present invention. In addition, in the case where a positive / negative electrode sheet is laminated on a polymer solid electrolyte sheet to produce a laminated battery, a peripheral portion and / or a bent portion of the surface of the polymer solid electrolyte are coated with an ion-impermeable material, A structure in which the surface of the electrode is coated with an ion-impermeable material can be formed by forming a laminate, which is included in the present invention.

Further, a solid polymer electrolyte is bonded to a portion of the electrode covered with the ion-impermeable material which is not covered with the ion-impermeable material, and at least a part of the portion covered with the ion-impermeable material is bonded. There is no polymer solid electrolyte, and a structure in which the ion-impermeable material-coated portions of the positive electrode and the negative electrode are directly adhered to each other is also possible. The contact portion of the non-permeable material not only does not transmit ions and electrons but also functions as a plasticizer outflow barrier of the plasticizer-added polymer solid electrolyte. Therefore, the outflow of the plasticizer can be prevented by providing an ion-impermeable material adhered portion in the peripheral portion of the laminate.

Examples of the ion-impermeable material used in the present invention include polyolefin-based polymers such as polyethylene, polypropylene, polyisoprene and poly (ethylene / vinyl alcohol) copolymer, and polyoxymethylene and poly (phenylene oxide). Ether-based polymers, polystyrene, poly (styrene-butadiene) copolymer, poly (styrene-butadiene-acrylonitrile) copolymer, polyvinylnaphthalene, resole resin, novolak resin, aromatic ring-based polymer such as urushi, polytetrafluoroethylene, Organic polymer materials such as fluorine-containing polymers such as polyhexafluoropropylene oxide; ceramic materials such as silica, magnesia, calcium fluoride, and magnesium fluoride; and mixtures of these materials. It can be. Further, a case where these materials are laminated and coated with another material to satisfy the above-described ionic conductivity and electronic conductivity is also included in the coating material of the present invention.

As a coating method of the ion-impermeable material, there are pressure bonding, melting and solidification, application of a solution or a dispersion, heat compression,
Known methods such as vapor deposition, plasma polymerization, electrolytic polymerization, and sputtering can be used. If necessary, after coating, radiation energy such as electron beam, γ-ray, ultraviolet ray, infrared ray or the like can be irradiated to improve the adhesiveness, the stability and the solvent impregnation.

The solid polymer electrolyte used in the battery of the present invention is characterized by having an electron conductivity of 10 ^-8 S / cm or less and an ionic conductivity of 10 ^-5 S / cm or more. This material is required to have high ionic conductivity, high strength, heat resistance, electrochemical stability, and the like. It is a mixture composed of a matrix polymer, an electrolyte and a plasticizer as a polymer solid electrolyte, and various polymers can be applied as the matrix polymer (for example, by Gray, So
lid Polymer Electronics
(VCH Publisher: 1991). In particular, a polymer solid electrolyte material using a vinylidene fluoride-based polymer such as polyvinylidene fluoride or a vinylidene fluoride-based copolymer as a matrix polymer is preferable because it is excellent in any respects. The polymer solid electrolyte of the present invention preferably contains this vinylidene fluoride-based polymer. As the polymer matrix, either a vinylidene fluoride-based polymer alone or a mixture with another polymer can be used. The content of the vinylidene fluoride unit in the polymer matrix of the polymer solid electrolyte of the present invention is 20% by weight or more, preferably 50% by weight or more.

Further, a structure in which the polymer matrix constituting the polymer solid electrolyte is crosslinked is more preferable because it provides a polymer solid electrolyte having excellent heat resistance and dimensional stability. In addition, a polymer solid electrolyte formed by impregnating an electrolyte solution into a foam polymer has an independent liquid phase domain in the structure, which is a composite structure solid electrolyte sealed with a polymer phase, and a porous polymer having through holes. It is also possible to use a solid polymer electrolyte impregnated with an electrolytic solution.

In the battery of the present invention, when the battery is cut using a solid polymer electrolyte, the performance is not significantly reduced due to the cutting peripheral portion and the bending process, and the plasticizer and the plasticizer from the side of the laminated electrode / polymer solid electrolyte laminate are removed. Since the outflow of the electrolyte can be prevented, the stability and reliability of the battery can be improved, which is preferable. The battery of the present invention is particularly suitable for a lithium ion battery, but is not limited to this and is industrially useful because it can be applied to various batteries such as a lead battery, an alkaline battery, and a nickel hydrogen battery.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

[0019]

Example 1 A needle coke powder having an average particle size of 10 μm was dispersed in a mixture of a carboxymethyl cellulose solution and a styrene butadiene latex (trade name: L1571 manufactured by Asahi Kasei Kogyo Co., Ltd.) to prepare a slurry, and a metal copper sheet (18 μm) was prepared. Thick) and dried to form a coating film (single-sided coating) having a thickness of 120 μm. The composition in the coating film was needle coke (NC) / carboxymethyl cellulose / styrene butadiene = 100 / 0.8 / 2.

On the other hand, a slurry was prepared by mixing and dispersing LiCoO ₂ powder having an average particle size of 10 μm and carbon black in an N-methylpyrrolidone solution of polyvinylidene fluoride (5% by weight). This slurry is transferred to an aluminum foil (film thickness 20μ).
m) (single-side coating) and dried to prepare a coating film having a thickness of 100 μm. The solid content weight composition of the slurry is LiC
oO ₂ (85%), carbon black (8%), and polymer (7%).

After the NC electrode was cut into a 5 cm square, styrene-butadiene latex used as a binder was applied to a width of 2 mm around the cut portion, filled in the electrode holes, and a surface-coated electrode was produced. Then LiCoO
₂ After cutting the electrode into 5 cm square, 2 mm around the cut part
Then, a polyethylene sheet was arranged, and heated and press-bonded to produce an electrode bonded together.

A poly (hexafluoropropylene-vinylidene fluoride) copolymer (hexafluoropropylene content: 5% by weight) was melt-extruded and formed into a sheet having a thickness of 110 μm. After irradiating the polymer sheet with an electron beam (irradiation amount: 10 Mrad), Freon (HFC134a)
(Impregnation weight: 7%) and heated in an impregnated state to produce a foam (film thickness after foaming: 220 μm). LiBF ₄ 1 of a mixed solvent of ethylene carbonate (EC) / propylene carbonate (PC) / γ-butyl lactone (γ-BL) (EC / PC / γ-BL = 1/1/2) is added to the foam.
It was immersed in a mol / liter solution at a temperature of 100 ° C. for 2 hours to prepare a polymer solid electrolyte sheet. 3. The sheet
After cutting into an 8 mm square, and bonding the styrene-butadiene latex to the latex-uncoated portion of the NC electrode, a LiCoO ₂ electrode partially coated with polyethylene was bonded to prepare a battery laminate. After joining a stainless steel sheet to the surface of the metal copper sheet and the aluminum sheet as an electrode for taking out the electrode from the laminate, a sheet battery was produced by packaging with a polyethylene / aluminum / polyethylene terephthalate laminated sheet.

The battery was charged to a charge / discharge tester (Hokuto Denko, 10
(1SM6 type) for charging and discharging. Charging and discharging conditions were as follows: charging was 25 mA, and 4.2 V after constant current.
The constant potential charging and discharging were performed at a current of 25 mA with a 2.7 V cut. Charge / discharge efficiency (electricity) is 80% for the first and 98 for the second
%, And the initial discharge amount is 2% per carbon weight of the negative electrode.
It was 10 mAh / g.

NC electrode sheet and LiC separately cut
Each oO ₂ electrode sheet was coated in the same manner as described above, and the stainless steel sheet was pressed onto the coated surface to measure the electrical resistance and ionic conductivity between the stainless sheet and copper or aluminum. (The electrical resistance was measured by a DC two-terminal method, and the ion conductivity was measured by an AC impedance method. The styrene-butadiene latex coating layer had an electron conductivity of 1 × 10 ⁻⁹ S / cm or less, and the ion conductivity was 1 ×. ^10-8 was less than S / cm. Further, the electron conductivity of the polyethylene-coated layer is 1 × 10 ^-11 S / cm or less, ionic conductivity was less than 1 × 10 ^-8 S / cm.

[0025]

EXAMPLE 2 The needle coke electrode (negative electrode) and the LiCoO ₂ electrode sheet (positive electrode) prepared in Example 1 were each slit to a width of 40 mm to produce a long sheet. 50 in the longitudinal direction of each of the long sheets of the positive electrode and the negative electrode
After arranging polyethylene strips (film thickness 100 μm) having a width of 2 mm and a length of 50 mm at right angles to the longitudinal direction for each mm, a surface-coated electrode sheet was produced by pressing with a heating roll (maximum temperature 140 ° C.).

A polymer solid electrolyte sheet (ethylene carbonate) prepared by melting and extruding the poly (hexafluoropropylene-vinylidene fluoride) copolymer (hexafluoropropylene content: 5% by weight) prepared in Example 1 and foaming the sheet. (EC) / Propylene carbonate (P
C) / γ-butyllactone (γ-BL) mixed solvent (EC
/ PC / γ-BL = 1/1/2) 1 mol of LiBF ₄
/ Liter solution at a temperature of 100 ° C. for 2 hours. ) (Width 42 mm, length 50 mm, film thickness 28)
0 μm). The cut sheet was placed on the uncoated portion of the surface-coated electrode prepared above, laminated in such a manner that the uncoated portions of the positive electrode and the negative electrode faced each other, and then thermocompressed with a heating roll to produce a laminate. Next, a battery stack was bent four times at the portion covered with the polyethylene strip to produce a battery stack. The laminate has a structure in which aluminum, which is a positive electrode current collector, is exposed on the upper surface, and metal copper, which is a negative electrode current collector, is exposed on the lower surface, and a stainless steel sheet (10
(mm width, length 60 mm), and the whole was packaged with a polyethylene / aluminum / polyethylene terephthalate laminated sheet to produce a battery.

The battery was connected to a terminal of a charge / discharge tester and charged / discharged in the same manner as in Example 1. As charging and discharging conditions, charging was performed at a current of 100 mA, followed by 4.2 V constant potential charging after a constant current.
Discharge was performed at a current of 100 mA and a 2.7 V cut. The charge and discharge efficiency (electricity) is 81% for the first time and 99% for the second time,
The initial discharge amount was 212 mAh / g per carbon weight of the portion of the negative electrode where the surface was not coated.

The electrode surface covering portion of the electrode laminate has a width of 1.
It was cut into 5 mm, and a stainless steel sheet was pressed against the surface of each current collector to measure the electric resistance between the electrodes and the ionic conductivity. As a result, the electron conductivity was 1 × 10 ⁻¹¹ S / cm or less, and the ionic conductivity was 1 ×. It was 10 ⁻⁸ S / cm or less (calculated assuming that the film thickness of the polyethylene in the coating portion was 200 μm).

[0029]

Comparative Example 1 Sheets were prepared by cutting the needle coke electrode (negative electrode) and the LiCoO ₂ electrode sheet (positive electrode) prepared in Example 1 into 50 mm × 50 mm, respectively. Then, the polymer solid electrolyte sheet used in Example 1 was
After cutting into an m-square and sandwiching and laminating between the positive electrode and the negative electrode, a stainless steel sheet was arranged on the current collector side as an external extraction terminal of the electrode, and then a polyethylene / aluminum / polyethylene terephthalate laminated sheet was used as in Example 1. A battery was fabricated by packaging.

The battery was connected to the terminal of a charge / discharge tester and charged / discharged in the same manner as in Example 1. As charging and discharging conditions, charging was performed at a current of 25 mA, constant-current charging at a constant potential of 4.2 V, and discharging was performed at a current of 25 mA at a 2.7 V cut. The charge / discharge efficiency (electrical amount) was 70% at the first time and 12% at the second time, and a sudden drop in potential occurred during the third charge, and no discharge was observed. Thereafter, the resistance between the electrodes was measured, and as a result, 10 m
It is expected that a short circuit between the electrodes has occurred, which is less than ohm. The initial discharge amount was 175 mAh / g per carbon weight of the portion of the negative electrode where the surface was not coated. A battery was manufactured in the same manufacturing procedure, but the charge / discharge battery characteristics were not stable.

[0031]

Comparative Example 2 Using a long electrode sheet (width 40 mm) produced in the same manner as in Example 2, a long polymer solid electrolyte sheet (width 42 mm) was prepared without coating the electrode strip with a polyethylene strip sheet. 50 laminates produced by lamination
The battery was folded at every mm to produce a battery laminate. Further, a battery package was manufactured in the same manner as in Example 2. A charge / discharge test was attempted by connecting the battery to the external take-out terminal. However, a short circuit occurred between the electrodes before the charge / discharge test, and charge / discharge was not performed.

[0032]

According to the present invention, it has become possible to provide a solid polymer electrolyte battery having excellent charge / discharge characteristics, reliability of characteristics and stability.

Claims (3)

[Claims] In a battery in which a positive electrode and a negative electrode are joined via a solid polymer electrolyte, at least one of the positive electrode and the negative electrode has a peripheral portion and / or a bent portion on a surface in contact with the solid polymer electrolyte, and has a non-ionic structure. A battery having a structure covered with a permeable material. 2. A laminated structure in which a positive electrode and a negative electrode whose peripheral portions are coated with an ion-impermeable material are joined via a solid polymer electrolyte such that the sides coated with the ion-impermeable material face each other. And a non-permeable material covering the positive electrode and a non-permeable material covering the negative electrode are closely adhered around the laminated structure. 3. A solid polymer electrolyte containing a vinylidene fluoride-based polymer.
The battery as described.