JPH06318466A - Sheet secondary battery - Google Patents

Abstract

PURPOSE:To enhance energy capacity and improve reliability by filling a frame partitioned by a sealing material on a current collector base with a prescribed coating material solution followed by drying. CONSTITUTION:A coating material solution in which an active material 2 is uniformly dispersed in an uniform solution consisting of an active material 1 and an organic solvent. In the coating material solution, in this case, the active material 2 with a specified particle size is homogeneously dispersed in the active material 1. The uniform coating material solution is continuously applied onto a current collector, whereby an electrode film for secondary battery positive electrode in which the active material 2 is uniformly dispersed in the active material 1 can be prepared. As the active material 1, for example, conductive polymer materials such as polyanilines and polyanilinoanilines are used, and as the active material 2, those having densities of 2.5 g/cm<2> or more are preferred to enhance volume energy density. Thus, energy capacity is enhanced, and reliability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet type secondary battery.

[0002]

2. Description of the Related Art In recent years, a secondary battery using lithium as a negative electrode active material has attracted attention as a secondary battery having a high energy density, and its shape has been reduced in size as electronic devices have become smaller and lighter. Particularly in sheet type lithium secondary batteries, the cycle characteristics of the positive electrode material, moldability, and high energy density are important issues. Generally, examples of the positive electrode active material include transition metal chalcogen compounds and conductive polymers. Inorganic active materials such as transition metal chalcogen compounds have poor electrical conductivity and do not have self-forming property, so it is necessary to add a large amount of conductive aids and binders, but this is not suitable for obtaining flexible and high-strength electrodes. It is enough. For this reason, various kinds of slurry paint preparations, electrode preparation methods, and the like are being studied. As a flexible electrode, for example, a positive electrode made of a material having excellent moldability such as a conductive polymer having advantages such as light weight and workability is being developed. 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 Conference of the Institute of Electrical Science, Proceedings, P2281 / 1984).
Have been reported. These conductive polymers have 10
There is an advantage that it exhibits high cycle characteristics even with a discharge depth of 0%, and when it is soluble, an electrode can be formed by coating. On the other hand, a composite electrode of a conductive polymer and an inorganic active material has been proposed for increasing energy (for example, Japanese Patent Laid-Open No. 63-102162). As the method for producing this composite electrode, (1) 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. A method, (2) a method of chemically or electrically polymerizing a conductive polymer in the presence of a powdery inorganic active material to form a composite, and the like have been proposed. However, no specific proposal has been shown in the battery mounting method using such electrodes. In the above method (1), it is difficult to manufacture a flexible sheet electrode, and it is not possible to achieve the expected volume energy density. Further, in the above method (2), the amount of the inorganic oxide that can be incorporated into the composite is limited, and a sufficient volume energy density cannot be obtained.
As described above, it is very difficult to produce a desired positive electrode for a secondary battery having a high volume energy density by a conventional method.

[0003]

An object of the present invention is to solve the above-mentioned problems of the prior art and to improve the reliability of a sheet-shaped secondary battery having a large energy capacity.

[0004]

[Structure] One of the features of the present invention is to coat a substrate with a uniform coating solution containing a mixture of an active material (1), an active material (2) and an organic solvent, and dry it to form a positive electrode film for a secondary battery. In order to obtain a smooth film in the case of producing, the coating liquid is filled in a frame partitioned by a sealing material on the current collector substrate,
It is to dry. The electrode base material is preferably copper, aluminum or the like, which is inexpensive, has high spreadability and conductivity, and has excellent adhesion to the coating liquid or slurry. However, copper or aluminum has excellent adhesion to the active material in the battery, but with repeated charging and discharging,
Easy to corrode. Therefore, when copper or aluminum is used as the substrate, direct contact with the electrolytic solution must be prevented. (1) When the liquid is poured into the partitioned frame and dried as it is, the film shrinks, and a bare part of copper or aluminum appears at the interface between the frame and the film, resulting in corrosion of copper or aluminum. There is.
Therefore, in order to solve these problems, the present inventors have
As shown in FIGS. 2 and 3, the sealing material forming the frame has a lower width (a contact surface with the substrate) having a width dimension (a) larger than an upper (non-contact surface) width dimension (b). It has been found that the appearance of exposed portions of copper or aluminum does not occur due to shrinkage when the coating liquid is dried. Another feature of the present invention is that at least one kind of polymer material that exhibits an electrochemical redox reaction and is soluble in an organic solvent [hereinafter, active material (1)], and particles insoluble in an organic solvent. A film made of a battery-shaped battery active material [hereinafter, active material (2)] is used as a positive electrode for a secondary battery. That is, a coating solution is prepared by uniformly dispersing the active material (2) in a uniform solution of the active material (1) and an organic solvent, and the active material (1) is added to the active material (1) prepared from the coating solution. It was found that the film in which 2) was homogeneously dispersed with a specific particle size was charged and discharged at a high charge and discharge rate. In particular, an electrode film for a secondary battery positive electrode in which the active material (2) is uniformly dispersed in the active material (1) can be produced by continuously applying the above-mentioned uniform coating liquid onto the current collector. . Examples of the active material (1) include conductive polymer materials such as polyanilines, polyanilinoanilines, polypyrroles, and polyacetylenes. Among these, polyaniline is preferable because it has a relatively large electric capacity per weight and can be charged and discharged relatively stably. These polymeric materials are
Polyalkylthiophene, dimethylformamide, N-
It is used by dissolving it in an organic solvent such as methylpyrrolidone or tetrahydrofuran. The active material (2) preferably has a density of 2.5 g / cm ³ or more in order to increase the volume energy density. For example, if this condition is met,
Further, vanadium pentoxide having a flat portion of the discharge curve in the vicinity of the potential for causing the electrochemical redox reaction of the conductive polymer is preferable. Further, in order to have sufficient adhesion to the active material (1) to increase energy density and homogeneity of the coating solution, the average particle diameter and the maximum particle diameter are 3 μm or less and 10 μm or less, respectively, preferably, respectively. It is 1 μm or less and 3 μm or less.

The composition of a uniform and high-concentration coating liquid obtained by mixing the active material (1), the active material (2) and the above-mentioned organic solvent used for preparing the electrode film of the sheet-shaped secondary battery of the present invention is The solid content is 20% or more in the weight ratio to the solvent, and the weight ratio of the active material (1) and the active material (2) is 4: 6.
It is desirable that the viscosity of the coating solution is 1000 cpm or more and 10000 cpm or less. As a method for dispersing the solid content in the solvent, a method using a ball mill, a barren mill or the like can be mentioned. The polyaniline concentration is particularly preferably 8% to 11%, and the viscosity is 1000 cpm to 10000 cpm in this concentration range. When the viscosity is 1000 cpm 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 cpm or more, the viscosity is too large to be used as a coating liquid. In addition, it is desirable that the preparation of this coating liquid is performed in an inert gas atmosphere in order to avoid alteration of the conductive polymer in the solution. This homogeneous coating solution is applied to any substrate, preferably a current collector substrate, by a wire bar method, a blade coater method, a spray method, or the like, and dried to activate the active material (1). It is possible to obtain a positive electrode film for a secondary battery in which the substance (2) is uniformly dispersed. By controlling the viscosity of the coating liquid, that is, the solid content concentration in the coating liquid within the above range, at least 10 μm or more and 300 μm or more
Although an electrode film having a thickness of m or less can be obtained, it is preferable to form a film having a thickness of 20 to 100 μm. The sheet-shaped thin secondary battery positive electrode manufactured as described above can be used as it is as the current collector substrate as at least a part of the battery exterior material, and the thickness of the members constituting the battery can be reduced. In addition, it has succeeded in significantly improving the energy density and reliability of the battery.

The structure of the sheet-shaped thin secondary battery of the present invention will be specifically described below. Examples of the positive electrode active material (1) include the above-mentioned conductive polymers, and examples of the positive electrode active material (2) are transition metal chalcogen compounds.
_{TiO 2, Cr 3 O 8,} V 2 O 5, V 3 O 6, NiO 2, MnO
₂ , oxides such as CoO ₂ and MoO ₃ , TiS ₂ , V
Sulfides such as S ₂ , FeS, and MoS ₃ and Nb
Examples thereof include selenium compounds such as Se ₃ and composite oxides of V, Mn, Co, Ni and an alkali metal dispersed in a liquid to form a sheet. A conductive auxiliary agent can be further added to the positive electrode forming component, if necessary. As such a conductive auxiliary agent, acetylene black, aniline black, activated carbon, conductive carbon powder such as graphite powder,
Carbon materials starting from PAN, pitch, cellulose, phenol, etc., carbon fibers, metal oxide powders of Ti, Sn, In, etc., metal powders of stainless steel, nickel, etc.,
Fibers. As the properties required for these conductive aids, in addition to high electrical conductivity, an effect with a small addition amount is required. A sheet formed of a composite of a transition metal chalcogenide and a conductive polymer can also be used. As the negative electrode active material constituting the negative electrode, Li, K, N
Alkali metals such as a, Li and Al, Pb, Cd, Si,
Examples thereof include alloys with Ca, In, Zn and Mg, polymer materials such as polyacetylene, polythiophene, polyparaphenylene, polypyridine, polyphenylene vinylene, polyphenylene xylylene, and a reduction polymer of hexachlorobutadiene, carbon bodies and graphite.

As the electrolyte, an electrolyte solution and a solid electrolyte composed of an electrolyte salt and a solvent can be exemplified, but it is preferable to use a polymer solid electrolyte in order to prevent liquid leakage, adhere between positive and negative electrodes, and keep a constant interval. When the electrolytic solution is used, it is preferable to use the electrolytic solution in the separator. As the electrolyte salt of the electrolytic solution, PF is used as an anion.
_{6 (-), SbF 6 (} -), AsF 6 (-), SbCl
Ha-anion anion of Group Va element such as ₆ (-): Hafion anion of Group IIIa element such as BF ₄ (-), BR ₄ (-) (R: phenyl group, alkyl group); ClO ₄ Perchlorate anion such as (-); Cl
Examples thereof include halogen anions such as (−), Br (−), and I (−), CF ₃ SO ₃ (−), and the like. As cations, alkali metal ions such as Li (+), Na (+) and K (+), (R ₄ N) (+) [R: carbon number 1 to 20]
Carbon hydrogen group] and the like. [The above (+) and (-) represent a positive ion and a negative ion, respectively. The same applies hereinafter. ] As a specific example of the compound which gives the above dovant, Li
_{PF 6, LiSbF 6, LiAsF 6} , LiClO 4, Na
ClO ₄ , KI, KPF ₆ , KSbF ₆ , KAsF ₆ , KC
10 ₄ , [(n-Bu) ₄ N] (+) CF ₃ SO
₃ (-), [(n-Bu) ₄ N] (+) · ClO
₄ (−), [(n−Bu) ₄ N] (+) · BF ₄ (−),
LiAlCl _4, LiBF _4, and the like LiCF ₃ SO _3. As the solvent constituting the electrolyte solution,
Although not particularly limited, a solvent having a relatively large polarity is preferably used. Specifically, propylene carbonate,
Ethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, triethyl phosphate, triethyl phosphite, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulfolane, Examples thereof include one kind or a mixture of two or more kinds of organic solvents such as dichloroethane, chlorobenzene, and nitrobenzene.

As the separator, one having a low resistance to the movement of ions of the electrolyte solution and an excellent solution holding property is used. For example, a glass fiber filter; a polymer pore filter such as polyester, Teflon, polyflon, or polypropylene; a non-woven fabric; or a non-woven fabric composed of glass fiber and these polymers can be used.
The separator can also serve as the fusible film as described above.

Examples of the solid electrolyte include inorganic and organic ones, and organic ones are exemplified in terms of flexibility and the like. For example, in an inorganic system, for example, AgC
1, metal halides such as AgBr, AgI and LiI, RbAg ₄ I ₅ and RbAg ₄ I ₄ CN.
In organic systems, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide, etc. are used as the polymer matrix, and the electrolyte salt described above is dissolved in the polymer matrix to form a composite.
Or these crosslinked products, low molecular weight polyethylene oxide, polymer electrolytes ion-dissociating groups such as crown ether grafted to the polymer main chain or polymer solid electrolytes containing a high molecular weight polymer containing an electrolytic solution, solid The electrolyte may be used alone, but it is preferably used in combination with a separator for the purpose of making the current density uniform and preventing a short circuit.

As the current collector, nickel, titanium, copper,
It is preferable to use a metal film such as stainless steel or aluminum as a substrate together with the current collector.
In particular, copper is most preferable because it is inexpensive and has high spreadability and conductivity.

As the partition wall (frame) used in the battery of the present invention, an insulating material which has no reactivity with the battery element and can be adhered to the current collector or the exterior is used. Specifically, it is composed of a resin layer of polyethylene, polypropylene, nylon, polyester or the like and an adhesive layer. Examples of the adhesive layer include heat-fusible resins such as modified polyethylene and modified polypropylene, epoxy-based, acrylic-based, and ceramic-based adhesives. Of these, polyethylene as the resin layer,
The combination of polypropylene and modified polyethylene or modified polypropylene as the adhesive layer is the most preferable from the viewpoint of adhesiveness to the current collector and stability.

[0012]

An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, 140 × 140 mm, thickness 30μ
A polypropylene partition wall (5) having an outer diameter of 140 × 140 mm and a thickness of 350 μm was adhered onto the copper foil (4) having a thickness of m by heat fusion. At this time, as shown in the cross-sectional views of the bonding surfaces of (4) and (5) in FIGS. 2 and 3, the width dimension of the frame was set to 7 mm at (a) and 5 mm at (b). Next, polyaniline powder (hereinafter PAN1) was dissolved in N-methylpyrrolidone to a concentration of 13 wt%, and vanadium pentoxide powder (hereinafter V ₂ O ₅ ) having an average particle size of 1 μm was mixed with PAN1 / V ₂ A mixture of the above solutions in a weight ratio of O ₅ = 3/7 was used as an electrode film forming coating solution (1). This coating solution (1) was poured onto the substrate partitioned by the frame so that the thickness of the solution was 300 μm, and after confirming that the surface of the solution became flat, it was dried at 100 ° C. for 30 minutes to obtain a positive electrode ( 6) was obtained. 80% electrolyte solution of 3M LiBF ₄ / (propylene carbonate + dimethoxyethane) (volume ratio 7: 3), 19.2% ethoxydiethylene glycol acrylate, 0.8% methylbenzoyl formate
After permeating the mixed polymer solid electrolyte composition into the positive electrode (6), a 25 μm polypropylene pore filter (trade name Celgard) was laminated, irradiated with a high pressure mercury lamp, and the electrolyte was laminated on the positive electrode (6). The member (7) was used. On the other hand, 100 μm Li (9) was attached to a copper plate (8) having a thickness of 140 × 140 mm and a thickness of 30 μm with a conductive adhesive, and the polymer solid electrolyte composition described above was applied onto Li, and then a high pressure mercury lamp was used. Irradiation was performed to stack an electrolyte on Li. As shown in FIG. 4, a positive electrode member (7) having a positive electrode / electrolyte layer laminated thereon and a negative electrode (Li) / a negative electrode with a current collector substrate (10) having an electrolyte layer laminated together are heat-sealed to seal the partition wall portion. Then, a sheet-shaped thin battery of 140 mm × 140 mm × 0.50 mm was prepared. This battery was charged to 3.7V and then discharged to 50mA 2.5V.
A discharge capacity of 0 mAh was obtained. After that, a bending test of this battery was conducted, but no particular change was observed in its performance.

[0013]

According to the present invention, a positive electrode for a secondary electrode having excellent workability, high volume energy density and high energy capacity is used, and a current collector substrate constituting the positive electrode is used as at least a part of a battery exterior material. As a result, a sheet-shaped thin battery having a significantly improved energy density was obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a copper foil 4 and a polypropylene partition wall 5 that seals a peripheral portion thereof.

FIG. 2 is a cross-sectional view of a copper foil 4 and a sealing member 5 provided on the copper foil.

FIG. 3 is a cross-sectional view of a copper foil 4 and a sealing member 5 provided on the copper foil.

FIG. 4 is a diagram showing a positive electrode member 7 and a negative electrode 10 with a collector substrate that is bonded to the positive electrode member.

[Explanation of symbols]

 4 Copper foil 5 Polypropylene partition wall 7 Positive electrode member 8 Current collector substrate 9 Li 10 Negative electrode with current collector substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Katagiri 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Kouri Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (4)

[Claims] 1. A sheet-shaped secondary battery comprising at least a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises a conductive polymer film and a current collector substrate which constitutes at least a part of an exterior material of the battery. The secondary battery is characterized in that the substrate is provided with a frame serving as a sealing portion by a sealing material in the peripheral portion so that the substrate and the electrolyte do not come into direct contact with each other. 2. A secondary battery, which is a film in which a particulate battery active material is uniformly dispersed in the conductive polymer film of the positive electrode for a secondary battery according to claim 1. 3. The width dimension (a) of the lower portion (contact surface with the substrate) of the sealing material forming the frame provided on the current collector substrate is
The secondary battery according to claim 1, which is larger than the width dimension (b) of the upper portion. 4. The secondary battery according to claim 1, wherein the current collector substrate is made of copper or aluminum.