JPH06150976A - Thin type battery - Google Patents

Abstract

PURPOSE:To provide a sheet-like thin type battery having high energy density by providing a carbon electrode layer on the metal layer of a sheet-like layered product made of a plastic layer and the metal layer. CONSTITUTION:A sheet-like layered product made of a plastic layer 1 and a metal layer 2 is used as the base material of a carbon electrode layer 3 constituting the negative electrode material of a thin type battery. The strength of a current collector metal can be reinforced by plastic, the thinner current collector metal layer 2 can be used, and the defect on the gas moisture permeability of the plastic layer 1 can be resolved. The resin layer 1 can be used as the outer material of the thin type battery itself in particular in addition to the protecting and reinforcing function of the metal thin film layer 2. The battery can be manufactured thinner and lighter, and the energy density of the battery can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the field of thin batteries.

[0002]

2. Description of the Related Art Recent advances in miniaturization, thinning, and weight reduction of electronic devices have been remarkable, and in the OA field, in particular, desktop devices have been reduced in size and weight to laptop types and notebook types. In addition, the field of new small electronic devices such as electronic notebooks and electronic still cameras will also appear, and in addition to the miniaturization of conventional hard disks and floppy disks, the development of new small memory media, memory cards, will be promoted. ing. In the wave of miniaturization, thinning, and weight reduction of such electronic devices, there is a trend toward development of miniaturization, thinning, and weight reduction of batteries for supporting these electric power regardless of whether they are for driving or memory backup. In particular, in terms of thinning, batteries called paper batteries, thin flat batteries, or plate-shaped batteries have been developed, which were not found in conventional batteries, and batteries that meet the development trends of such electronic devices. Is desired. Conventionally, aqueous batteries such as lead batteries and nickel-cadmium batteries have been the mainstream as secondary batteries for general use.However, although these batteries have excellent cycle characteristics, they are sufficient in terms of battery weight and energy density. It is hard to say that the characteristics are satisfactory. On the other hand, research and development of high energy density non-aqueous electrolyte secondary batteries using lithium or a lithium alloy for the negative electrode have been actively conducted, and some have been commercialized. This battery has the excellent features of high energy density, low self-discharge and light weight, but as the charge-discharge cycle progresses, lithium grows into dendrite-like crystals during charging and reaches the positive electrode, causing an internal short circuit. Due to the drawbacks that increase the possibility and the poor charging and discharging efficiency of lithium itself, it is not possible to have sufficient cycle characteristics,
Further, since lithium is unstable in the air, especially in water, it is necessary to give due consideration to safety.
On the other hand, a non-aqueous electrolyte secondary battery using a carbon material for the negative electrode has lithium that is previously supported on the carbon material by a chemical / physical method, lithium in the positive electrode active material, or the electrolyte solution. It utilizes doping / dedoping of dissolved carbon materials such as lithium, and no dendrite-like precipitation of lithium during charging is observed even if the cycle progresses.
It has been actively researched in recent years because it has excellent cycle performance, does not have the danger of lithium, and has abundant resources. However, in order to use a carbon material as an electrode material in a thin battery, various technical problems arise. One of them is the problem of current collection from carbon materials. Conventionally, in a negative electrode for a thin battery using a lithium metal, it is possible to form a sheet (thin) electrode with 100% lithium, while lithium itself has good conductivity and does not impair the conductivity. On the other hand, in order to process a carbon material (generally powder) into a sheet shape, a binder (plastic) for binding the carbons is added and the carbon material is formed into a sheet shape. This will impair the conductivity of the material. Therefore, it is necessary to give sufficient consideration to the current collection from the carbon material. For example, as a carbon electrode used in a conventional cylindrical battery or the like, a self-holding property is provided as an electrode by binding a carbon material on a collector metal serving as a base (Japanese Patent Laid-Open No. 2-2021). 68855). For this reason, it is impossible to make the current collector metal thin enough to have no self-holding property, and naturally there is a limit in its thickness (strength). Also, when considering the exterior of a thin battery, the conventional tubular type,
Unlike gum type and coin type batteries, it can be made flexible and lightweight by using a plastic exterior. However, plastic is
It has high moisture permeability and is not preferable as an exterior material for non-aqueous batteries. At present, it has been possible to prevent moisture permeation by providing a metal thin film layer in plastic. However,
When such a packaging material is used in combination with the carbon electrode (carbon-collector), it is disadvantageous in terms of thickness (volume) and weight, and as a result, the energy density of the battery is lowered.

[0003]

An object of the present invention is to provide a sheet-shaped thin battery with high energy density, which solves the above-mentioned problems of the prior art.

[0004]

[Structure] The present inventors use a sheet-shaped laminate composed of a plastic layer 1-metal layer 2 as a support for a carbon material 3 which constitutes a negative electrode material of a thin battery as shown in FIG. The strength of the current collector metal can be reinforced with plastic, and a thinner current collector metal layer can be obtained, and the disadvantage of the gas permeability of the plastic layer 1 is that the current collector metal layer is used. I found that can be solved by. That is, the present invention relates to a negative electrode for a thin battery in which a carbon material layer is provided on a sheet-shaped laminate including a plastic layer and a metal layer, and a thin battery using the electrode. In particular, the resin layer has a function of protecting (reinforcing) the metal thin film layer and can be used as an exterior material of the thin battery itself. By adopting such a configuration, the battery can be made thinner and lighter, and the energy density of the battery can be improved. In the present invention, the thickness of the thin film metal layer is 10 μm or less,
More preferably, it is less than 10 μm. The electric resistance of the metal material of the metal layer is 10 ⁻⁴ Ω · c at 0 ° C.
It is preferable to use one having a thickness of m or less, more preferably 2 × 10 ⁻⁵ Ω · cm or less. 10
^{If it is} larger than ^-4 Ω · cm, the electric resistance when the metal layer is thinned is not sufficiently lowered, and the internal impedance of the battery is increased. As a metal material satisfying such conditions, Al (2.5 × 10 ⁻⁵ Ω · cm), Au
(2.05 × 10 ⁻⁵ Ω · cm), Ag (1.47 × 10
^-5 Ω · cm), Cu (1.55 × 10 ⁻⁵ Ω · cm), N
i (6.2 × 10 ⁻⁵ Ω · cm), Pt (9.81 × 10)
^-5 Ω · cm) or the like can be used, but it is most preferable to use copper because it has a low electric resistance, can be made into a thin film, is inexpensive, and has abundant resources.

In order not to impair the characteristic of being light and flexible, which is one of the features of the thin sheet battery of the present invention, a light and flexible conductive polymer material should be used. Is preferred. Such a conductive polymer material is a material that has the ability as an active material, does not dissolve in an electrolytic solution, has a binding property between polymer materials, and exhibits conductivity. For example, a five-membered heterocyclic compound polymer having pyrrole or thiophene as a monomer, an aromatic hydrocarbon compound polymer having benzene or azulene as a monomer, aniline or diphenylbenzidine as a monomer. Amine-based compound polymers can be used. However, since these conductive polymer materials are plastics, the active material itself is electrically conductive as described above, and since it is light and flexible, it has preferable characteristics as an active material of a thin battery. However, it has a drawback that the volume energy density of the electrode is low.

Further, as the positive electrode active material in the present invention,
Titanium (Ti), molybdenum (Mo), niobium (N
b), oxides of metals such as chromium (Cr), manganese (Mn), vanadium (V), and cobalt (Co),
Sulfides, selenides, or composites thereof with lithium can be used, but inorganic active material materials are often hard and moldable, and often lack electrical conductivity themselves, so that they are used as electrodes for thin batteries. Has a drawback that additives such as a binder and a conductive agent must be mixed. As the positive electrode active material in the present invention, a combination of the conductive polymer and the inorganic active material is particularly preferable because a sheet-shaped positive electrode having high energy density and processability and excellent voltage flatness can be obtained. The electric conductivity of the conductive polymer material used in the composite of the conductive polymer and the inorganic active material is preferably 10 ⁻⁴ S / cm, more preferably 10 ⁻² S / cm or more. If it is 10 ⁻⁴ S / cm or less, the current collection efficiency when it is combined with the inorganic active material is not sufficient, and the internal impedance of the battery is increased. As such a conductive polymer material, for example, a substance such as polypyrrole, poly-3-methylthiophene, and polyaniline, which has a small ionization potential and is stable in an anion-doped state, is preferable. Considering the energy density of the active material, polyaniline is most preferably used. As the inorganic active material, those having a flat discharge potential such as spinel type lithium manganese dioxide, cobalt oxide, and crystalline vanadium pentoxide are preferable. Furthermore, insertion of anion of conductive polymer to be complexed, insertion of cation relatively close to electrode potential accompanying release,
Those having an emission potential are preferable, and it is most preferable to use crystalline vanadium pentoxide. The composite amount of the conductive polymer in this composite is 10 to 70% by weight. More preferably, it is 10 to 40% by weight, and if it is less than 10% by weight, there are problems in binding force and conductive ion conductivity.
If it is 0% by weight or more, it is disadvantageous in terms of energy density.

Further, the kind of the polymer material constituting the plastic layer is not particularly limited, but an inexpensive and flexible material which does not deteriorate up to about 100 ° C. is preferable, and specifically, polyester, polypropylene, Polyethylene or the like can be used, but is not limited to this.
It is also conceivable to use it as a laminated structure of various plastic materials. Further, the thickness of the plastic layer also varies depending on the thickness of the metal thin film layer, but when used also as an exterior material, it is about 100 to 1000 μm. The metal thin film layer provided on the plastic layer is
It can be formed by a method such as vapor deposition or sputtering, and usually has a thickness of less than 10 μm.

The carbon material used for the carbon negative electrode in the present invention is petroleum coke, pitch coke, carbon black, glassy carbon, graphite, or phenol resin, polyacrylonitrile resin, furan resin, polyamide resin, polyimide resin. Carbon materials obtained by firing an organic polymer such as, phenol-based, polyacrylonitrile-based, pitch-based carbon fibers, natural graphite and the like can be exemplified, but among them, by using cokes, particularly pitch-based cokes. A negative electrode having excellent capacity, potential holding property and discharge voltage flatness can be obtained. The carbon negative electrode of the present invention comprises the above carbon material and Teflon,
A sheet-like carbon negative electrode can be produced by adding a binder such as polyvinylidene fluoride or polyacrylonitrile and supporting it on the metal thin film layer.

As the electrolyte used in the thin sheet battery of the present invention, a non-aqueous electrolytic solution or a solid electrolyte composed of an electrolyte salt impregnated in a separator and a non-aqueous solvent is used. As a result, it is possible to prevent variations in battery performance, deterioration, and deformation of the battery during heating due to uneven distribution of the solvent. As the electrolyte salt in the present invention, the following anions or cations are used. Examples of the anion include halide anions of Va group elements such as PF ₆ ⁻ , SbF ₆ ⁻ and AsF ₆ ⁻ , and group IIIa elements such as BF ₄ ⁻ and BR ₄ ⁻ (R is a phenyl group or an alkyl group). Anion, C
Examples thereof include a halogen anion such as l ⁻ , Br ⁻ , and I ⁻ , a perchlorate anion, a trifluoromethanesulfonate anion, and a thiocyanate 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 LiPF ₆ , LiSbF ₆ , and LiAs.
F ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , Li
I, KPF ₆ , KClO ₄ , NaPF ₆ , [(n-Bu) ₄
N] BF ₄ , [(n-Bu) ₄ N] ClO ₄ , LiSC
N, NaSCN, KSCN, LiAlCl _{4 and the} like can be exemplified, but the invention is not particularly limited thereto. As the non-aqueous solvent in the present invention, propylene carbonate, γ-butyl lactone, ethylene carbonate,
Diethyl carbonate, sulfolane, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2
-Ethoxymethoxyethane, methyl diglyme,
Examples thereof include glymes such as methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme. For example, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, etc. as a polymer matrix the above-mentioned electrolyte salt is dissolved in the polymer matrix complex or a cross-linked product thereof, low molecular weight polyethylene oxide, crown It is also possible to use a polymer solid electrolyte in which an ion dissociative group such as ether is grafted on the polymer main chain, or a solid electrolyte having a structure in which the electrolyte solution is contained in a high molecular weight polymer. In this method, a polymerizable compound is added to an ordinary electrolytic solution, and polymerization is caused by heat or light to solidify the electrolytic solution. More specifically, an acrylate (eg, methoxydiethylene glycol methacrylate, methoxydiethylene glycol diacrylate) -based compound as a polymerizable compound is benzoyl peroxide, azobisisobutyronitrile, methylbenzoyl formate,
Polymerization is carried out using a polymerization initiator such as benzoin isopropyl ether to solidify the electrolytic solution. As the solid electrolyte in the present invention, AgCl, AgBr, and
Inorganic substances such as AgI, LiI, RbAg ₄ I ₃ and RbAg ₄ I ₃ CN can be used.

A separator may be used when the solid electrolyte is poor in mechanical strength and a short circuit of the positive electrode is feared, or when an electric field is applied more uniformly. As the separator, one having a low resistance to the ionic conduction of the electrolyte and an excellent liquid retaining property is used. For example, a glass fiber filter, a polymer pore filter such as polyester, Teflon, polyethylene, polypropylene or a non-woven fabric, a non-woven fabric such as a glass fiber or a ceramic fiber, or a composite thereof can be used. The present invention produces a high-performance thin battery by combining the above-described battery components, for example, by adopting a laminated structure of resin layer-metal layer-carbon electrode layer-solid electrolyte layer-positive electrode layer. can do.

[0011]

【Example】

Example 1 (1) A sheet-like laminate was prepared by vapor-depositing copper on a heat-fusible modified polypropylene with a thickness of 5 μm (9 × 5.5 cm). Pitch coke 9 at the center (7 × 4.0 cm) of this laminate.
A solvent was added to 0 parts by weight and 10 parts by weight of polyvinylidene fluoride to form a slurry, which was applied and dried. Additional press pressure was applied. The active material was 40 μm. 7 to this
9.9% 3M LiBF ₄ , PC / DME (7/3), 2
0% ethoxydiethylene glycol acrylate, 0.
An electrolytic solution having a composition of 1% benzoyl peroxide was sufficiently impregnated under reduced pressure, and light of a high pressure mercury lamp was irradiated to solidify the electrolytic solution. This was used as a negative electrode member. (2) A positive electrode was produced in the following manner separately from the negative electrode member. 0.9 mmφ that was blasted to 10 μm as a reaction electrode in a 3M HBF ₄ aqueous solution containing aniline
The aniline was polymerized at a constant current of 3 mA / cm ² using a stainless steel sheet 4 × 7.5 cm (polymerization part) having a through hole of 1 (polymerization on only one side). The stainless polyaniline electrode was washed with running water, and then the potential was applied to -0.4 V vs. SCE in 0.2 N sulfuric acid to sufficiently perform the dedoping operation. This was reduced with a 20% aqueous hydrazine solution, washed and dried to obtain a polyaniline electrode (thickness 340 μm). Thickness 20 μm, 5.5 × 9
A frame made of modified polypropylene having a thickness of 200 μm, an outer diameter of 5.5 × 9 cm, and an inner diameter of 4.1 × 7.6 cm is fixed to a SUS sheet having a size of cm. The polyaniline electrode was bonded to the center of the frame using a conductive adhesive. Then, the above-mentioned electrolytic solution composition was sufficiently impregnated with polyaniline. The polyaniline portion was compressed to 150 μm, and a polypropylene pore filter sufficiently impregnated with the mixed solution was laminated on the polyaniline and irradiated with light from a high pressure mercury lamp for 1 hour. The electrolytic solution solidified and did not seep out even when pressure was applied. This was used as a positive electrode member. (3) The positive and negative electrode members were attached to each other, and a copper foil having a thickness of 10 μm was sandwiched between the frame parts of the frame as a carbon electrode side terminal, and four sides were heat-sealed under reduced pressure to produce a thin battery.
The obtained battery had a thickness of 385 μm and an initial discharge capacity of 15 mAh.

Comparative Example 1 A carbon layer was prepared in the same manner as in Example 1 on one surface of a 20 μm thick copper foil (7.5 × 4 cm: by terminal portion). This electrode is A
The heat-fusible plastic sheet (9 × 5.
(5 cm) was fixed by heat pressing to the center, and then the electrolytic solution was solidified in the same manner as in Example 1. Example 1
A positive electrode member was produced in the same manner as in 1. and was laminated with the above electrode to produce a thin battery. The thickness of the battery was 385 μm (385
The thicknesses of the positive electrode active material and the negative electrode active material were adjusted so as to be μm). The initial discharge capacity was 13 mAh.

Example 2 A solvent was added to 50 parts by weight of polyaniline and 50 parts by weight of crystalline vanadium pentoxide, and a blasting treatment was performed at a center portion (7.5 ×) of a SUS foil having a thickness of 20 μm (9 × 5.5 cm).
(4.0 cm) and dried. After pressurization was further applied, the electrolytic solution composition of Example 1 was sufficiently impregnated, and then a separator was placed thereon, and the electrolytic solution was solidified in the same manner as in Example 1.
A negative electrode member similar to that in Example 1 (however, the active material layer was 65 μm) was prepared, and laminated with the positive electrode member, and a thin battery was prepared in the same manner as in Example 1. The thickness of the battery was 410 μm, and the initial discharge capacity was 24.9 mAh.

Comparative Example 2 A negative electrode member similar to Comparative Example 1 and a positive electrode member similar to Example 2 were used to prepare active material layers for positive and negative electrode members so that the total thickness of the battery was 410 μm to prepare a battery. The initial discharge capacity was 22 mAh.

According to the present invention, a thin battery with high energy density is provided.

[Brief description of drawings]

FIG. 1 shows a negative electrode for a thin battery of the present invention.

[Explanation of symbols]

 1 plastic layer 2 metal layer 3 carbon material layer

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

Claims (4)

[Claims] 1. A thin battery in which a carbon electrode layer is provided on a metal layer of a sheet-shaped laminate comprising a plastic layer and a metal layer. 2. A positive electrode member having a positive electrode in which the electrode active material is a conductive polymer material or a composite of the polymer material and an inorganic active material, and the carbon electrode layer according to claim 1 as a negative electrode member. A thin battery characterized by the above. 3. A thin battery according to claim 2, wherein a composite of crystalline vanadium pentoxide and polyaniline is used as a positive electrode in the thin battery. 4. The thin battery according to claim 2, wherein the plastic layer of the negative electrode member also serves as a battery exterior material.