JPH07302586A - Battery electrode and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To increase the adhesion of a conductive polymer with a current collector by forming a conductive adhesive layer. CONSTITUTION:A conductive adhesive layer is formed on a metallic current collector and an active material layer, containing a conductive polymer is put on the adhesive layer to form a battery electrode. The active material layer is formed by applying a coating solution prepared by dispersing an active material in a solvent to the conductive adhesive layer and drying. The coating solution is prepared by uniformly dispersing at least one kind of powdery inorganic active material 2 in a paint solution containing one kind of a conductive polymer having electrical oxidation/reduction property and a solvent, for forming a film. The coating solution is continuously applied onto the current collector with the adhesive layer. The coating solution has the active material 2 uniformly dispersed in the polymer 2 and forms an electrode film with lightweight, high energy density, and high strength. The coating solution is stuck to fine portions on the surface of the adhesive layer, and by drying, the active material is stuck to the adhesive layer. In addition, when the adhesive layer is a pattern shape, anchor effect is added to obtain the electrode with strong adhesion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a battery with a current collector and a method for manufacturing the electrode.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries using lithium as a positive electrode material have attracted attention as secondary batteries having high energy density. Cycle characteristics, molding processability, and high energy density of the negative electrode material are important issues for making a lithium battery into a secondary battery. Generally, examples of the positive electrode active material include transition metal chalcogen compounds and conductive polymers. However, since only a inorganic active material such as a transition metal chalcogen compound has poor conductivity and has no self-forming property, it is necessary to add a large amount of a conductive aid and a binder. Therefore, it is difficult to obtain the expected energy density. Therefore, development of a positive electrode made of a conductive polymer, which has advantages such as light weight and workability, is under way. Examples of the conductive polymer include polyacetylene (for example, JP-A-56-136489) and polypyrrole (for example, 25th Battery Symposium, Abstracts, P25).
61/1984), polyaniline (for example, 50th Annual Meeting of the Electrochemical Society of Japan, Proceedings, P2281 / 1984).
Have been reported. These conductive polymers have 10
Although it has an advantage that it exhibits high cycle characteristics even at a discharge depth of 0%, it also has the following problems. It is common to use a smooth metal foil as the current collector of the battery electrode, but since the adhesion between the smooth current collector and the conductive polymer active material is not good, the conductivity of the current collector is high. The molecular film is easily detached, and there is a problem in cycle characteristics.
In order to solve this problem, a device for reducing the weight of the electrode and increasing the adhesion between the current collector and the conductive polymer active material by using a porous current collector for the production of the electrode has been proposed.
132046. In this method, a porous current collector is used as the current collector in order to improve the adhesion of the conductive polymer electrode to the current collector. A conductive polymer is grown in the holes by an electrolytic polymerization method to maintain the adhesiveness. However, when a porous metal current collector is used, it is preferable that the pore size of the porous metal be 50 μm or more. For that purpose, a current collector having a thickness of several hundred μm is required. A decrease in energy density is inevitable. Further, although the electrolytic polymerization method is used for manufacturing the electrode, the productivity is poor and it is not practical. An electrode using only a conductive polymer as an active material has a low energy density per volume because of its low density. A composite electrode of a conductive polymer and an inorganic active material has been proposed as a method of compensating for the disadvantages of the inorganic active material and the conductive polymer and making the most of their advantages (for example, JP-A-63).
-102162). As a method for producing this composite electrode,
(1) A method in which an appropriate amount of powdery conductive polymer and powdery inorganic active material are sampled, a binder is added and mixed, and pressure molding is performed on a current collector, (2) powdery inorganic active material A method of chemically or electrically polymerizing a conductive polymer in the presence of a substance to form a composite has been proposed. However, in the above method (1), since it is a mixture of powdery substances, it is not possible to form a composite electrode that is sufficiently uniform down to the details, and it is possible to obtain a flexible sheet-like electrode that has sufficient strength. Difficult to make. The expected volumetric energy density cannot be achieved due to the need to add even more binder. Further, in the above method (2), the amount of the inorganic oxide that can be incorporated into the composite is limited, and sufficient volume energy cannot be obtained. As described above, the production of a secondary battery electrode having a high target volume and weight energy density and good adhesion between the current collector and the conductive polymer active material is very difficult by the conventional method. there were.

[0003]

An object of the present invention is to provide an electrode for a battery with a current collector, which solves the above-mentioned problems of the conventional art.

[0004]

[Structure] The inventors of the present invention can solve the above-mentioned problems of the prior art by providing a layer made of a conductive adhesive between an electrode active material layer containing a conductive polymer and a current collector. Found out. That is, the present invention has an electrode active material layer containing a conductive polymer, a current collector, and a conductive adhesive layer provided therebetween, and a method for producing the electrode. Regarding The battery electrode of the present invention can be prepared by providing an adhesive layer made of a conductive adhesive on a metal current collector, and laminating an active material layer containing a conductive polymer on the adhesive layer. The active material layer may be formed in advance by stacking it on a current collector having an adhesive layer, but in order to obtain higher adhesion, it is preferable to use a coating solution prepared by dispersing the active material in a solvent as an adhesive. It is preferable to manufacture by coating on a current collector having a layer, drying and laminating. As the coating solution, a coating solution containing at least one kind of electrode active material, preferably at least one kind of electroconductive polymer showing an electrochemical redox property [hereinafter, active material (1)
] And at least one kind of particulate inorganic active material [hereinafter referred to as the active material (2)] in a coating solution containing a solvent, and more preferably, it is homogeneously dispersed to form a coating solution. You can In particular, the active material (2) is uniformly dispersed in the active material (1) by continuously applying the coating liquid in which the active material (2) is uniformly dispersed onto the current collector having the adhesive layer. An electrode film that is dispersed, lightweight, high in energy density, and high in strength can be easily produced. On the current collector having the conductive adhesive layer as described above,
By applying a coating liquid composed of an active material and a solvent, particularly a homogeneous coating liquid, the coating liquid adheres to the surface details of the adhesive layer. By drying it, the active material layer is brought into close contact with the adhesive layer, and in the case of a patterned adhesive layer, the anchor effect is added, so that an electrode having stronger adhesiveness can be obtained.

Examples of the active material (1) include polyanilines, polyanilinoanilines, polypyrroles,
A conductive polymer material such as polyacetylene can be exemplified. Among these, polyanilines having a relatively large electric capacity per weight and capable of relatively stable charging and discharging are particularly preferable. These polymer materials are used after being dissolved in a solvent such as dimethylformamide, N-methylpyrrolidone and tetrahydrofuran. The active material (2) preferably has a density of 2.5 g / cm ³ or more in order to increase the volumetric energy density of the electrode. For example, manganese dioxide, vanadium oxide, cobalt oxide, nickel oxide and the like can be exemplified, but the flat portion of the discharge curve is satisfied near the potential that satisfies the above conditions and causes the electrochemical redox reaction of the conductive polymer. With vanadium pentoxide being preferred. Further, in order to have sufficient adhesion to the active material (1) to increase the energy density and homogeneity, the average particle diameter and the maximum particle diameter are 3 μm or less and 10 μm or less, preferably 1 μm each.
Hereafter, it is 3 μm or less. Further, in order to improve the adhesiveness to the adhesive layer, particularly to the patterned adhesive layer, the active material (2) preferably has an average particle diameter and a maximum particle diameter of 3 μm or less and 10 μm or less, respectively. Further, in order to maintain the adhesiveness between the active material layer and the current collector, the particulate inorganic active material is preferably 80% by weight or less based on the total amount of the conductive polymer and the inorganic active material. The composition of the coating solution preferably has a solid content of 20% or more in the weight ratio with respect to the solvent. As a method for dispersing the solid content in the solvent in the preparation of the coating liquid, a method using a ball mill, a barren mill or the like can be mentioned. In addition, the concentration of the conductive polymer such as polyaniline is particularly preferably 8% to 11%, and in this concentration range, the viscosity is 1000 cp to
It is 10,000 cp. When the viscosity is 1000 cp or less, the filler of the active material (2) precipitates in the solution, and a uniform coating liquid cannot be obtained. When the viscosity is 10,000 cp or more, the viscosity is too high to be used as a coating liquid.

As the material of the current collector used in the present invention,
A metal having high strength and high electric conductivity is preferable. Among them, stable stainless steel, nickel, and
It is more preferable to use aluminum or the like after roughening the surface. As the conductive adhesive used in the present invention, one having high electric conductivity and high adhesion to metal and polymer materials is used. To satisfy this condition, an epoxy resin adhesive containing a good conductor filler such as metal or carbon,
Examples thereof include urethane resin adhesives and acrylic resin adhesives. Epoxy resin adhesives are more preferred because of their resistance to organic solvents such as electrolytes. The conductive adhesive layer provided on the current collector in the present invention can be made smooth on the entire active material laminated surface, but in order to further enhance the current collecting effect and adhesion, it is not a whole surface but a partial surface. And / or it is preferable to form in a pattern rather than smooth, and it is more preferable to form in an island pattern. The area where the conductive adhesive layer is provided is 15 to 15 mm of the collector substrate.
70% is preferable. If it is 15% or less, the adhesive effect is insufficient, and if it is 70% or more, the current collecting efficiency is remarkably reduced and the resistance of the electrode is high, which is not practical. When the conductive adhesive layer is composed of a large number of island-shaped adhesives on the current collector, an electrode having higher adhesion can be obtained by the anchor effect in addition to the adhesive effect of the adhesive. In this case, since the anchor effect is obtained and the current collecting action is not significantly reduced, the area to which the adhesive is attached is preferably 15 to 70%, more preferably 15 to 50%. Moreover, in order to further enhance the anchor effect, the width of the island of the adhesive is preferably 50 μm or less. Further, the height of the island is preferably 30 μm or less.

If necessary, a conductive auxiliary agent can be added to the electrode active material of the present invention. As such a conductive aid, acetylene black, aniline black,
Activated carbon, conductive carbon powder such as graphite powder, PA
Examples thereof include carbon bodies starting from N, pitch, cellulose, phenol and the like, carbon transitions, metal oxide powders such as Ti, Sn and In, metal powders such as stainless steel and nickel, fibers and the like. As the properties required for these conductive aids, in addition to high electrical conductivity, an effect with a small addition amount is required. The thickness of the positive electrode is 1 to 1000 μm, preferably 5 to 500 μm. If it is 1 μm or less, it is disadvantageous in terms of energy density, and if it is 1000 μm or more, it is disadvantageous in terms of current collection efficiency. Number 1 on the substrate for coating
A flexible layer can be obtained by forming a film with a thickness of 0 μm or less. In addition, the electrode composed of the active material (1) and the active material (2) in the present invention has excellent workability and flexibility, and thus is suitable for producing a sheet-like electrode, and is suitable for producing a paper-like battery. It was confirmed that the electrode exhibited excellent performance.

Next, a secondary battery using the above electrode will be described. A secondary battery using the battery electrode of the present invention basically comprises a positive electrode, a negative electrode and an electrolyte. The electrode is used as the positive electrode. As the negative electrode, in addition to the above electrodes, L
Alkali metals such as i, Na and K, Li and Al, Mn and P
Alloys such as b, carbon bodies and the like can be used. The following anions or cations are used as the electrolyte. Examples of anions include PF ₆ ⁻ , SbF ₆ ⁻ , A
sF ₆ ^- Va group element halide anions such as, BF
₄ ^-, BR ₄ ^- (R is a phenyl group, an alkyl group) IIIa such as
Examples thereof include anions of group elements, halogen anions such as Cl ⁻ , Br ⁻ , and I ⁻ , perchlorate anion, and trifluoromethanesulfonate anion. Examples of the cation include alkali metal cations such as Li ⁺ , Na ⁺ , and K ⁺ , (R ₄
N) ⁺ (R is a hydrocarbon group having 1 to 20 carbon atoms) and the like. Examples of the compound that provides the electrolyte include Li
_{PF 6, LiSbF 6, LiAsF 6} , LiBF 4, LiC
lO ₄ , LiCF ₃ SO ₃ , LiI, KPF ₆ , KCl
O ₄ , NaPF ₆ , [(n-Bu) ₄ N] BF ₄ , [(n-
Examples thereof include Bu) ₄ N] ClO ₄ and LiAlCl _4, but the present invention is not limited thereto. The solvent constituting the electrolyte solution is not particularly limited,
A solvent having a relatively large polarity is preferably used. Specifically, propylene carbonate, ethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyl lactone, dioxolane, triethylphosphite, dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, dimethoxyethane, polyethylene glycol. , A mixed solution of two or more kinds of organic solvents such as sulfolane, dichloroethane, chlorobenzene, nitrobenzene and diethyl carbonate. As the separator, one having a low resistance to the movement of ions of the electrolyte solution and having excellent solution holding property is used. Examples thereof include glass fiber filters, polymeric pore filter non-woven fabrics such as polyester, Teflon, polyflon and polypropylene, or non-woven fabrics made of glass fibers and these polymers. A solid electrolyte is used as a substitute for the electrolytic solution and the separator. For example, in an inorganic system, AgCl, AgB
Metal halides such as r, AgI and LiI, RbAg
₄ I ₅ , RbAg ₄ I ₄ CN and the like can be mentioned. Further, in the organic system, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide and the like as a polymer matrix, a complex in which the electrolyte salt is dissolved in the polymer matrix, or a gel cross-linked product thereof, a low molecular weight polyethylene oxide, Examples thereof include a polymer solid electrolyte in which an ionic dissociative group such as crown ether is grafted on the polymer main chain, or a gel polymer solid electrolyte in which the electrolyte solution is contained in a high molecular weight polymer. The form of the battery using the electrode of the present invention is not particularly limited, but it can be mounted on various batteries such as a coin type, a sheet type, a cylindrical type, and a gum type.

[0009]

The present invention will be described in more detail with reference to the following examples. Example 1 13 g of polyaniline synthesized by chemical polymerization using sulfuric acid and ammonium persulfate as an oxidizing agent and 87 g of N-methylpyrrolidone were mixed and dispersed in an inert gas atmosphere using a roll mill method to prepare a coating solution. This coating solution was applied onto a current collector with a sprayer to a thickness of 150 μm, and this was dried in the atmosphere at a temperature of 100 ° C. for 15 minutes,
An electrode with a thickness of μm is obtained. As the current collector, stainless steel foil (thickness: 22 μm) whose surface is roughened with sandpaper
On top of it, a conductive adhesive [FA-70 manufactured by Fujikura Kasei Co., Ltd.
7] was uniformly applied with an applicator, cured, and a conductive adhesive layer having a thickness of about 5 μm was attached thereto. This electrode is used as a positive electrode, a Li plate is used as a negative electrode, and the electrolytic solution is
The charge / discharge characteristics were measured using a solution prepared by dissolving LiBF ₄ at a ratio of 3 mol with respect to 1 liter of a mixed solution of propylene carbonate: DME = 7: 3. The measuring method is HJ-201B type charge / discharge measuring device manufactured by Hokuto Denko Co., Ltd.
First, the battery is charged with a current of 0.2 mA / cm ² from the charging direction until the battery voltage reaches 3.7 V, and after a rest time of 1 hour, the battery voltage is increased to 2.8 V with a current of 0.2 mA / cm ^2. After that, the battery was repeatedly charged and discharged, the battery characteristics were evaluated, and the discharge capacities after 10 cycles and 50 cycles are shown in Table 1.

Example 2 13 g of polyaniline synthesized by chemical polymerization using sulfuric acid and ammonium persulfate as an oxidizing agent, and the average particle diameter is 2.5 μm.
m, the maximum particle size is 8 μm, crystalline vanadium pentoxide 30.3
87 g of N-methylpyrrolidone and 87 g of N-methylpyrrolidone were mixed and dispersed in an inert gas atmosphere using a roll mill method, and an electrode was prepared in the same manner as in Example 1 except that it was used as a coating solution, and the battery characteristics were evaluated.

Example 3 An electrode was prepared in the same manner as in Example 2 except that manganese dioxide powder (average particle size 2 μm, maximum particle size 8 μm) was used instead of vanadium pentoxide, and battery characteristics were evaluated.

Example 4 As a current collector, a conductive adhesive [FA-707 manufactured by Fujikura Kasei Co., Ltd.] was sprayed on a stainless steel foil (thickness: 22 μm) whose surface was roughened with sandpaper. Other than using the one coated with the above, cured, and having an island-shaped random pattern with a maximum diameter of 50 μm (the area where the conductive adhesive adheres is approximately 35% of the current collector surface) An electrode was prepared in the same manner as in Example 2 and the battery characteristics were evaluated.

Example 5 As a collector, a conductive adhesive [FA-707 manufactured by Fujikura Kasei Co., Ltd.] was silk-coated on a stainless foil (thickness: 22 μm) whose surface was roughened with sandpaper. Apply with a screen, cure, and have an island-shaped regular pattern with a diameter of about 45 μm (the actual area where the conductive adhesive is attached is about 60% of the surface area of the current collector). An electrode was prepared in the same manner as in Example 2 except that it was used, and the battery characteristics were evaluated.

Example 6 An electrode was prepared and battery characteristics were evaluated in the same manner as in Example 2 except that 4.8 g of graphite powder was added as a conductive agent.

Comparative Example 1 An electrode was prepared in the same manner as in Example 1 except that a stainless foil (22 μm) roughened with sandpaper was used as a current collector, and battery characteristics were evaluated.

Comparative Example 2 An electrode was prepared and battery characteristics were evaluated in the same manner as in Example 2 except that a stainless foil (22 μm) roughened only with sandpaper was used as a current collector.

Comparative Example 3 An island-shaped random pattern having an average diameter of the conductive adhesive of 90 μm (the area of the conductive adhesive adhered is 75 of the collector area).
%) To prepare an electrode in the same manner as in Example 4,
The battery characteristics were evaluated.

Comparative Example 4 Example 2 was repeated except that vanadium pentoxide having an average particle diameter of 10 μm and a maximum particle diameter of 100 μm was used as the particulate active material.
An electrode was produced in the same manner as in 1. and the battery characteristics were evaluated.

Comparative Example 5 An electrode was prepared in the same manner as in Example 2 except that 37 g of vanadium pentoxide having an average particle size of 2.5 μm and a maximum particle size of 8 μm was used as the particulate active material, and the battery characteristics were evaluated.

[0020]

[Table 1] * ¹ Energy capacity per total volume of positive electrode including current collector * ² 90 degree folding endurance test was performed 100 times and adhesion between current collector at bent part and film ○ No peeling from current collector × Current collection There is peeling from the body

[0021]

【effect】

1. Effect of Electrode for Battery of Claim 1 By providing the conductive adhesive layer, the adhesion between the conductive polymer and the current collector is improved. 2. Effect of Battery Electrode of Claim 2 By using polyaniline as the conductive polymer, stable charging and discharging can be performed. 3. Effect of the battery electrode of claim 3 By using the particulate inorganic substance, the energy density of the electrode can be increased. 4. Effect of Battery Electrode of Claim 4 By using a particulate inorganic substance having an average particle diameter of 3 μm or less, the adhesion between the electrode active material layer and the adhesive layer can be improved. 5. Effect of battery electrode of claim 5 Keeping the adhesion between the current collector and the electrode active material by setting the amount of the particulate inorganic substance to 80% by weight or less based on the total amount of the conductive polymer and the inorganic active material. can do. 6. Effect of Battery Electrode of Claim 6 By setting the actual adhesion area of the conductive adhesive layer to 15 to 70%, the adhesive effect of the adhesive is maintained and the current collecting efficiency is less likely to decrease. 7. Effect of Battery Electrode of Claim 7 By forming the conductive adhesive layer in a pattern, the current collecting effect and the adhesiveness can be further improved as compared with the case where the conductive adhesive layer is formed on the entire surface. 8. Effect of Battery Electrode of Claim 8 By forming the pattern of the conductive adhesive layer in an island shape, the adhesiveness can be further improved in the effect described in the above item 7. 9. Effect of the battery electrode according to claim 9 In the effect according to the above 7 or 8, by setting the width of the pattern of the conductive adhesive layer to 50 μm or less, the pattern of the adhesive layer exhibits an anchor effect, and Adhesion can be improved. 10. Effect of battery electrode according to claim 10 The battery electrode according to any one of claims 1 to 9 can be manufactured.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Toshiyuki Kabata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Toshige Fujii 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (11)

[Claims] 1. An electrode for a battery with a current collector, wherein a conductive adhesive layer is provided between an electrode active material layer, at least a part of which is made of a conductive polymer, and a current collector substrate. 2. The battery electrode according to claim 1, wherein the conductive polymer is polyaniline. 3. The electrode active material layer is one in which at least one kind of particulate inorganic active material is dispersed in at least one kind of electroconductive polymer matrix exhibiting electrochemical redox. Alternatively, the battery electrode according to 2 above. 4. The battery electrode according to claim 3, wherein the particulate inorganic active material has an average particle size of 3 μm or less and a maximum particle size of 10 μm or less. 5. The particulate inorganic active material is 80% by weight or less based on the total amount of the conductive polymer and the inorganic active material.
Alternatively, the battery electrode according to item 4. 6. The battery electrode according to claim 1, wherein the actual adhesion area of the conductive adhesive layer is 15 to 70% of the current collector substrate. 7. The battery electrode according to claim 1, wherein the conductive adhesive layer is formed in a pattern. 8. The battery electrode according to claim 7, wherein each pattern of the conductive adhesive layer is formed in an island shape. 9. The width of each pattern of the conductive adhesive layer is 50.
The battery electrode according to claim 7, which has a thickness of not more than μm. 10. An electrode active material layer is formed by applying a coating solution containing at least one kind of electrode active material onto a current collector having a conductive adhesive layer and drying the coating solution. Item 1. A method for producing a battery electrode according to items 1, 2, 3, 4, 5, 6, 7, 8 or 9. 11. The method for producing a battery electrode according to claim 10, wherein the coating solution has at least one kind of particulate inorganic active material uniformly dispersed.