JPH0770319B2 - Electrode for non-aqueous secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel secondary battery, and further to a small and lightweight secondary battery.

[Prior Art] In recent years, electronic devices have been remarkably reduced in size and weight, and accordingly, there has been a great demand for reduction in weight and weight of batteries serving as power sources. In the field of primary batteries, small and lightweight batteries such as lithium batteries have already been put into practical use, but since they are primary batteries, they cannot be repeatedly used, and their fields of use have been limited. On the other hand, lead batteries and nickel-cadmium batteries have been conventionally used in the field of secondary batteries, but both have serious problems in terms of size reduction and weight reduction.
From this viewpoint, non-aqueous secondary batteries have received a great deal of attention, but they have not yet been put to practical use. One of the reasons is that no electrode active material used for the secondary battery has been found to satisfy practical physical properties such as cycle characteristics and self-discharge characteristics.

Meanwhile, a new group of electrode active materials utilizing intercalation of a layered compound or a doping phenomenon, which is a reaction mode which is essentially different from that of conventional nickel-cadmium batteries, lead batteries and the like, has been attracting attention.

Such a new electrode active material is expected to have an extremely excellent charge / discharge cycle property because it does not cause a complicated scientific reaction in the electrochemical reaction during charging and discharging.

One of the factors preventing the practical use of such an electrode active material is a decrease in current collecting performance of the current collector. If the current collecting performance is low, even if an active material having excellent basic characteristics is used, the performance cannot be efficiently obtained. It is generally considered that the active material is separated from the current collector and the contact resistance is increased as a cause of lowering the current collecting performance. Improving is a very important issue from the viewpoint of making excellent electrodes.

[Problems to be Solved by the Invention] The present invention has been made to solve the above problems and provide an electrode for a non-aqueous battery having excellent performance.

[Means and Actions for Solving Problems] According to the present invention, at least an electrode active material as a component,
A non-aqueous battery electrode comprising a current collector coated with a conductive coating comprising a binder and a conductive filler, wherein the conductive coating uses an acrylonitrile polymer or a copolymer thereof as a binder. An electrode for a non-aqueous secondary battery is provided.

As described above, it is extremely important to improve the current collecting performance of the current collector, that is, to minimize the contact resistance with the active material layer in order to bring out the basic performance of the active material.

The present inventors have found that a conductive coating film using an acrylonitrile polymer or a copolymer thereof as a binder significantly enhances the final charge ability of the metal current collector. The acrylonitrile polymer in the present invention refers to a homopolymer obtained by radical polymerization or anionic polymerization of an acrylonitrile monomer. The copolymer referred to in the present invention is not particularly limited, but preferably at least 40% by mol of acrylonitrile unit,
For example, it means a copolymer obtained by copolymerizing at least one of styrene, butadiene, ethylene, propylene, vinyl chloride, vinylidene chloride, acrylic acid ester, methacrylic acid ester, acrylic acid, ethylene oxide and the like. The structure of the copolymer is random consisting of the monomer units,
It may have either a block structure or a graft structure. The amount of the acrylonitrile unit is preferably 40 or more in mol%. If it is less than 40%, the current collecting performance in the conductive coating film is lowered due to the characteristics of the acrylonitrile unit. The conductive coating film in the present invention is mainly composed of the binder and the conductive filler. Examples of the conductive filler include carbon and metal powder, but preferably graphite and
Acetylene black, carbon black and mixtures thereof. The weight ratio of the conductive filler to the binder (x = weight of conductive filler / weight of binder) is not particularly limited, but is 0.
5 ≦ x ≦ 0.2 is preferable. The current collector is mainly a metal current collector, and examples thereof include metal foils such as steel, aluminum, titanium, stainless steel and nickel, nets, expanded metals, punching metals and the like.

The current collector covered with a conductive coating film in the present invention,
When the current collector is a metal foil, it can be easily obtained by coating with a coater, and when it is a metal net, expanded metal, punching metal or the like, it can be easily obtained by dipping or spraying.

As described above, by using the current collector coated with the conductive coating film of the present invention, it is possible to reduce the contact resistance with the active material layer and further improve the electrode performance.

The electrode active material used in the present invention is not particularly limited, but as an example, MnO ₂ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ , Fe
₂ O ₃ , Fe ₃ O ₄ , Li _(1-X) CoO ₂ , Li _(1-X)・ NiO ₂ , TiS ₂ , TiS ₃ , Mo
Inorganic compounds such as S ₃ , FeS ₂ , CuF ₂ , and NiF ₂ , carbon fluoride,
Carbon materials such as graphite, vapor-grown carbon fibers and / or pulverized products thereof, PAN-based carbon fibers and / or pulverized products thereof, pitch-based carbon fibers and / or pulverized products thereof, and conductivity of polyacetylene, poly-p-phenylene, etc. And the like.

When the electrode active material is in the form of powder, it is formed by mixing it with a binder solution and then coating and drying it on the current collector of the present invention.

The non-aqueous battery electrode of the present invention is used as a positive electrode with an electrode active material.
It may be used as a negative electrode. Of the present invention
When assembling batteries using non-aqueous battery electrodes, non-aqueous electrolyte solution
The electrolyte of is not particularly limited, but if one example is shown,
LiClO_Four, LiBF_Four, LiAsF₆, CF₃SO₃Li, LiPF₆, LiI, LiAlCl_Four, NaC
lO_Four, NaBF_Four, NaI, (n-Bu)_FourN ClO_Four, (N-Bu)_FourN B
F_Four, KPF₆Etc. Also, the organic solution used
Examples of the solvent include ethers, ketones, lactones
, Nitriles, amines, amides, sulfur compounds, salts
Oxidized hydrocarbons, esters, carbonates, nitro
Compounds, phosphate ester compounds, sulfolane compounds
Etc., but among these, ether
, Ketones, nitriles, chlorinated hydrocarbons, carbo
Nates and sulfolane compounds are preferred.

Typical examples of these are tetrahydrofuran, 2-methyl etrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyl nitrile, valeronitrile, benzonitrile, 1 , 2-Dichloroethane, γ-butyrolactone, dimethoxyethane, methyl formate, propylene carbonate, ethylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate and these. Examples of the mixed solvent include, but are not necessarily limited to these.

Further, if necessary, a battery is constructed by using parts such as a separator, a terminal and an insulating plate. The structure of the battery is not particularly limited, but a positive electrode, a negative electrode, and if necessary, a paper-type battery in which the separator is a single layer or multiple layers,
Alternatively, a positive electrode, a negative electrode, and if necessary, a form of a cylindrical battery in which a separator is wound in a roll shape or the like can be given.

The non-aqueous battery electrode of the present invention is extremely useful as a small-sized, lightweight and high-power type non-aqueous battery electrode as described above.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Experimental Example 1 Carbon black powder with a particle size of 70 mμ (Industrial carbon black Colvenyan RAVEN 410)
1 part by weight of polyacrylonitrile (weight average separator 10
10,000 parts of DMF solution (10 wt% concentration) was mixed with 10 parts by weight to prepare a coating solution. Apply this coating liquid to a 10 μm thick copper foil 10 cm × 10
Coating was applied on both sides of 00 cm with a thickness of 2 μm on each side.

Experimental Example 2 Commercially available graphite powder having a particle size of 5 μm or less (Lonza graphite
KS2.5 Lonza Co., Ltd.) 2 parts by weight of polyacrylonitrile (weight average molecular weight 100,000) in DMF (10 wt% concentration) 10
A coating liquid was prepared by mixing with 1 part by weight. Thickness of this coating liquid
A 15 μm aluminum foil 10 cm × 1000 cm was coated on both sides with a thickness of 2 μm on each side.

Example 1 1 part by weight of Li _1.03 Co _0.95 Sn _0.042 O ₂ powder having an average particle size of 2 μm was mixed with 0.075 part by weight of graphite having an average particle size of 5 μm and 0.025 part by weight of acetylene black having an average particle size of 0.03 μm, and fluorine was further added. 0.5 parts by weight of a solution of rubber in methyl isobutyl ketone (concentration: 4 wt%) was added and mixed and stirred to prepare a coating liquid. This coating liquid was applied to one surface of the conductive coated aluminum foil 19 μm obtained in Experimental Example 2 as a base material and dried to obtain an electrode having a film thickness of 100 μm. 1 cm x 5 cm from this electrode membrane
Was cut out to obtain a positive electrode.

Commercial petroleum-based needle coke (KOA-S manufactured by Koa Oil Co., Ltd.
J CoKe) was crushed with a ball mill to an average particle size of 10 μm, and 1.0 part by weight of the above-mentioned fluororubber methyl isobutyl ketone solution (concentration 5 wt%) was added to 1 part by weight of this pulverized product, and mixed and stirred to form a coating solution. did. The conductive coating copper foil 14 μm obtained in Experimental Example 1 was used as a base material and this coating liquid was applied and dried to 60 μm.
An electrode having a film thickness of 1 cm x 5 from this electrode membrane
cm was cut out and used as a negative electrode. The battery shown in FIG. 1 was assembled using 0.6M LiClO ₄ propylene carbonate as the electrolytic solution. The overvoltage of this battery during charging and discharging at 10 mA (current density ² mA / cm ² ) was 0.02V.

Example 2 Example 1 except that a current collector in which polyacrylonitrile was replaced by Barex 210 (manufactured by Monsanto) in Experimental Example 1 was used.
The battery was assembled and evaluated in the same manner as in. The results are shown in Table 1.

Example 3 Electric assembly was carried out in exactly the same manner as in Example 1 except that a current collector was used in Example 1 in which polyacrylonitrile was replaced with a polymer composed of a copolymer acrylonitrile monomer unit of 95 mol% and an acrylic acid monomer unit of 5 mol%. And evaluation was performed. The results are shown in Table 1.

Example 4 A battery was prepared in the same manner as in Example 1 except that a current collector was used in Example 1 in which polyacrylonitrile was replaced with a polymer composed of a copolymer acrylonitrile monomer unit of 85 mol% and a methyl acrylate monomer unit of 15 mol%. Assembly and evaluation were performed.

The results are shown in Table 1.

Comparative Example 1 A battery was assembled and evaluated in the same manner as in Example 1 except that the current collector in which the polyacrylonitrile was replaced by polyvinyl chloride was used in Experimental Examples 1 and 2. As a result, the overvoltage is 0.21
It was V.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of batteries used in Examples and Comparative Examples of the present invention. 1 ... Positive electrode and electrolyte solution, 2 ... Negative electrode and electrolyte solution, 3 ... Aluminum foil, 4 ... Copper foil, 5,5a ... Current collector rod, 6 ... Separator and electrolyte solution, 7 ... Battery case

Claims (1)

[Claims] 1. A non-aqueous battery electrode comprising a current collector coated with a conductive coating film comprising at least an electrode active material, a binder and a conductive filler as constituent elements, the conductive coating film serving as a binder. An electrode for a non-aqueous secondary battery, which is characterized by using an acrylonitrile polymer or a copolymer thereof.