JPH1140201A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery which maintains contact with an interface between a positive and/or negative electrode and a polymer electrolyte and is good in charging and discharging at a high rate by adhering the positive and/or negative electrode to the polymer electrolyte with an adhesive. SOLUTION: Since a polymer electrolyte is adhered to a positive and/or negative electrode by an adhesive in a lithium battery, the electrolyte can follow expansion and shrinkage of electrode volume, and its cycle characteristic is improved compared to a conventional one. In this case, if the adhesive connecting the positive and/or negative electrode to the polymer electrolyte has ion conductivity, ions can move in the adhesive and food charging and discharging electrolyte is obtained. Furthermore, if this adhesive and the polymer electrolyte are made of a same material, ions can move more uniformly. A polymer which swells or expands through electrolyte, e.g. polyvinyliden fluoride is preferable for the polymer electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art Unlike lithium-ion batteries, nickel-cadmium batteries and nickel-metal hydride batteries which use an aqueous solution for the electrolyte, lithium batteries and lithium-ion batteries use a flammable organic electrolyte for the electrolyte. There's a problem. Therefore, it has been attempted to improve the safety of the battery by using a solid polymer electrolyte having less chemical reactivity instead of the organic electrolyte. Also, application of solid polymer electrolytes has been attempted for the purpose of flexibility of battery shape, simplification of manufacturing process, reduction of manufacturing cost, and the like.

As an ion conductive polymer, a complex of a polyether such as polyethylene oxide or polypropylene oxide with an alkali metal salt has been studied. However, polyether is difficult to obtain high ionic conductivity while maintaining sufficient mechanical strength, and since conductivity is greatly affected by temperature, sufficient conductivity cannot be obtained at room temperature. , A comb polymer having a polyether in a side chain, a copolymer of a polyether chain and another monomer,
Attempts have been made to use polysiloxane or polyphosphazene having a polyether in a side chain, a crosslinked product of polyether, or the like.

Further, it has been attempted to produce a gel-like solid electrolyte by impregnating a polymer with an electrolytic solution and to apply it to a lithium-based battery. Polymers used in the gel solid electrolyte include polyacrylonitrile, polyvinylidene fluoride, polyvinyl chloride and the like. Also, nitrile rubber, styrene butadiene rubber,
Attempts have also been made to produce a polymer membrane by drying a latex such as polybutadiene and polyvinylpyrrolidone, and impregnate the polymer membrane with an electrolyte to produce a lithium ion conductive polymer membrane.

[0005]

In a lithium ion battery, an active material such as LiCoO ₂ , L, which repeatedly expands and contracts in volume by charging and discharging a positive electrode or a negative electrode.
A positive electrode active material of a layered compound such as iNiO ₂ or a spinel compound such as LiMn ₂ O ₄ , and a layered negative electrode active material such as carbon or graphite are used. Therefore, when charge and discharge are repeated, the interface between the positive electrode or the negative electrode and the polymer electrolyte is dissociated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a positive electrode and / or a negative electrode;
It is characterized in that the polymer electrolyte is adhered with an adhesive, so that even when charge and discharge are repeated, contact at the interface between the positive electrode or the negative electrode and the polymer electrolyte is maintained, and charging at a high rate is performed. An object of the present invention is to provide a non-aqueous electrolyte battery having good discharge.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional lithium ion battery using a polymer electrolyte, since the positive electrode or the negative electrode is not bonded to the polymer electrolyte, repeated charging and discharging causes expansion and contraction of the volume of the positive electrode or the negative electrode. There was a drawback that the polymer electrolyte could not follow and the charge / discharge performance was significantly reduced. The battery according to the present invention can follow the expansion and contraction of the volume of the electrode because the polymer electrolyte is bonded to the positive electrode or the negative electrode with an adhesive, and the cycle characteristics are higher than those of the conventional polymer electrolyte lithium ion battery. Is improved. At this time, when the adhesive bonding the positive electrode or the negative electrode and the polymer electrolyte has ionic conductivity, ions can be moved even in the adhesive, and good charge / discharge characteristics are obtained. be able to. Further, when the adhesive for bonding the positive electrode or the negative electrode and the polymer electrolyte and the polymer electrolyte are made of the same material, more uniform ion transfer becomes possible.

[0008]

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

Example 1 Lithium cobaltate (LiC)
A mixture of 70 wt% of oO ₂ ), 6 wt% of acetylene black, 9 wt% of polyvinylidene fluoride (PVdF), and 15 wt% of n-methyl-2-pyrrolidone (NMP) is applied on an aluminum foil having a thickness of 20 μm.
Dry at <RTIgt; C </ RTI> to evaporate the NMP. After the above operation was performed on both surfaces of the aluminum foil, it was pressed to obtain a positive electrode plate. The thickness of the positive electrode plate after pressing was 170 μm.

Next, 76% by weight of graphite, PVd
A mixture of 9 wt% of F9 and 15 wt% of NMP is coated on a 14 μm-thick copper foil, dried at 150 ° C., and dried.
Was evaporated. After performing the above operation on both surfaces of the copper foil, it was pressed to obtain a negative electrode plate. The thickness of the negative electrode after pressing was 190 μm.

The polymer electrolyte layer was manufactured as follows. 12 g of PVdF powder having an average molecular weight of 60,000
Was dissolved in 88 g of NMP. This solution was immersed in water to wash out the NMP, yielding a microporous PVdF membrane having a porosity of 60% and a thickness of 25 μm. This film was swollen with an electrolytic solution to form a polymer electrolyte, as described later.

An ethylene-vinyl acetate copolymer is applied as an adhesive on the positive electrode plate and the negative electrode plate prepared as described above, hot-melted with a microporous PVdF film interposed therebetween, and then wound. , Height 47.0 mm, width 22.
It was inserted into a square stainless steel case having a thickness of 2 mm and a thickness of 6.4 mm. Inside the battery, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 and an electrolyte in which 1 mol / l of LiPF ₆ was dissolved was added by vacuum injection to give a microporous solution. The polymer electrolyte was obtained by swelling the PVdF membrane with the electrolytic solution. Thus, a battery (A) according to the present invention having a nominal capacity of 400 mAh was manufactured.

Example 2 As Example 2, a battery (B) according to the present invention having a nominal capacity of 400 mAh and having the same configuration as that of Example 1 except that polyethylene oxide was used as an adhesive was manufactured.

Example 3 As Example 3, a battery (C) according to the present invention having a nominal capacity of 400 mAh and having the same configuration as that of Example 1 except that PVdF was used as an adhesive was manufactured.

(Comparative Example 1) As Comparative Example 1, except that the adhesive was not used, the microporous PVdF film was interposed between the positive electrode plate and the negative electrode plate, and the film was wound without hot-melt. Nominal capacity is 400 mA, same configuration as 1
h, a conventionally known battery (a) was manufactured.

Using these batteries (A), (B), (C) and (a), the battery was charged to 4.1 V at a current of 1 CA at 25 ° C., and then charged at a constant voltage of 4.1 V to 3 V. After charging for an hour, the battery was discharged to 2.75 V at a current of 1 CA.

FIG. 1 is a diagram showing a discharge curve when charging and discharging are performed under the above conditions using these batteries. From the figure it can be seen that the batteries (A), (B) and (C) according to the invention
It can be understood that shows excellent discharge characteristics as compared with the conventionally known battery (a). In particular, in the battery (C) in which the polymer electrolyte and the adhesive were made of the same material, the best discharge characteristics were obtained because the diffusion of ions was performed uniformly.

FIG. 2 shows a comparison of changes in discharge capacity when charging and discharging are repeated under the same conditions as in FIG. From the figure, it is understood that the batteries (A), (B) and (C) according to the present invention show superior cycle characteristics as compared with the conventionally known battery (a).

In the above embodiment, as a method for producing a microporous polymer membrane, NMP is removed by immersing a solution of a polymer in NMP in water, but the solvent for dissolving the polymer is limited to NMP. What is necessary is just what melt | dissolves a polymer instead of what is performed. Further, the liquid in which the solution in which the polymer is dissolved is immersed is not limited to water, and any liquid that does not dissolve the polymer and is compatible with the solvent in which the polymer is dissolved may be used. When the solvent is removed from the polymer solution using such a combination of the polymer, the solvent for dissolving the polymer, and the liquid for immersing the solution in which the polymer is dissolved, the portion where the removed solvent was present is reduced. The microporous polymer film can be manufactured as a hole.

As a method for producing a porous polymer for producing a porous polymer electrolyte, in addition to the above-mentioned methods, a stretching method, a method of removing fine particles from a polymer to which fine particles are added, and a method of cooling a high-temperature polymer solution are used. A method of solidifying the polymer to remove the liquid and a method of manufacturing a nonporous polymer film and then physically drilling through holes using a fine stainless steel needle were attempted. Among these, batteries manufactured by a method using fine needles of stainless steel exhibited excellent charge / discharge characteristics as in the case of using a wet method, but sufficient porosity was not obtained by other methods. Was.

The polymer used for the porous polymer electrolyte may be polyvinyl chloride (PVD) in addition to the above-mentioned PVdF.
C), using polyacrylonitrile (PAN), polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene imine, polybutadiene, polystyrene and polyisoprene. Attempts were made to produce porous polymer electrolytes and batteries using them, but PVDF, PVC and PAN
Was especially excellent.

In the above embodiment, polyvinylidene fluoride is used as the polymer which swells or wets with the electrolytic solution. However, the polymer is not limited to this, and polyethers such as polyvinyl chloride, polyethylene oxide and polypropylene oxide are used. , Polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene imine, polybutadiene, polystyrene, polyisoprene, or derivatives thereof. May be used alone or as a mixture. Further, a polymer obtained by copolymerizing various monomers constituting the polymer may be used.

In the above embodiment, a mixed solution of EC and DEC is used as the electrolytic solution contained in the polymer. However, the present invention is not limited to this. For example, ethylene carbonate, propylene carbonate, dimethyl Carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,
A polar solvent such as 2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

Further, in the above embodiment, LiPF ₆ is used as the lithium salt to be contained in the electrolytic solution. In addition, LiBF ₄ , LiAsF ₆ , LiClO
₄ , LiSCN, LiI, LiCF ₃ SO ₃ , LiC
1, LiBr, LiCF ₃ CO ₂ , Li (CF ₃ S
A lithium salt such as O ₂ ) ₂ N or a mixture thereof may be used.

Further, in the above embodiment, LiCoO ₂ was used as the positive electrode active material, but the present invention is not limited to this. In addition, as an inorganic compound, a composite represented by a composition formula Li _x MO ₂ or Li _y M ₂ O ₄ (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2) An oxide, an oxide having tunnel-like holes, and a metal chalcogenide having a layered structure can be used. Specific examples thereof include LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O
₄ , Li ₂ Mn ₂ O ₄ , MnO ₂ , FeO ₂ , V
Examples include ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , and TiS ₂ . Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, in the above embodiment, graphite is used as the negative electrode active material.
alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal composite oxides such as LiFe ₂ O ₃ , WO ₂ ,
A transition metal oxide such as MoO _{2, a} carbonaceous material such as graphite and carbon, a lithium nitride such as Li ₅ (Li ₃ N), a metal lithium foil, or a mixture thereof may be used.

Further, in the above embodiment, EVA, polyethylene oxide and PVdF are used as the adhesive, but reactive acrylic resin, amino resin, phenol resin, epoxy resin and the like may also be used. .

In the present invention, by partially or entirely covering the interface between the positive electrode and the negative electrode and the electrolyte with a porous lithium ion conductive polymer, the organic electrolysis using the positive electrode and the negative electrode, which is a problem for a high-voltage battery, is performed. The oxidation and reduction of the solution could be reduced, and the charge storage characteristics could be improved. Also in this case, charge / discharge at a high rate became possible because the lithium ion conductive polymer was porous.

[0029]

As described above, in the battery according to the present invention, since the positive electrode and / or the negative electrode and the polymer electrolyte are adhered with the adhesive, the positive electrode and / or the negative electrode can be repeatedly charged and discharged. It is possible to provide a nonaqueous electrolyte battery that maintains good contact at the interface between the negative electrode and the polymer electrolyte and has good charge / discharge at a high rate.

[Brief description of the drawings]

FIG. 1 is a diagram showing discharge characteristics of batteries (A), (B), (C) according to the present invention and battery (a) of Comparative Example 1.

FIG. 2 is a diagram showing cycle characteristics of batteries (A), (B), (C) according to the present invention and battery (a) of Comparative Example 1.

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery in which a positive electrode and / or a negative electrode and a polymer electrolyte are bonded with an adhesive. 2. The non-aqueous electrolyte battery according to claim 1, wherein the adhesive has ionic conductivity. 3. The non-aqueous electrolyte battery according to claim 1, wherein the polymer electrolyte is a polymer that swells or wets with an electrolytic solution. 4. The non-aqueous electrolyte battery according to claim 1, wherein the polymer electrolyte is a porous lithium ion conductive polymer. 5. The non-aqueous electrolyte battery according to claim 1, wherein the polymer electrolyte and the adhesive are made of the same material.