JP2810105B2 - Electrodes for secondary batteries - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrode for a secondary battery using a conductive polymer.

[Related Art] Conventionally, secondary batteries using a mixture type electrode made of a conductive polymer are disclosed in JP-A-62-243248, JP-A-62-193061,
JP-A-62-176068, JP-A-62-93865, JP-A-62-16834
8 and the like are known.

Conventionally, a powdery or particulate conductive polymer is kneaded with a binder such as polytetrafluoroethylene and a conductive material such as carbon black in the form of a mixture-type electrode made of a conductive polymer. A pellet type formed by pressure molding is generally used, but this type is suitable for a small capacity type such as a button type battery. On the other hand, when the present mixture type electrode is applied to a so-called large-capacity type in which a large current is taken out, the kneaded material is applied to a current collector such as a metal mesh, and then formed into a sheet by integrating the current collector with a pressure. It is common to use it as an agent electrode, in a spiral shape with a separator and a counter electrode.

However, in this case, when wound in a spiral shape, the mixture-type electrode cracks, falls off, breaks, etc., and is not practically practical. In order to improve this point, for example, Japanese Patent Application Laid-Open No. 62-93
865 describes that a low-boiling water-soluble organic compound is further added to an aqueous dispersion of an aniline-based polymer or a fluororesin, but it is still unsatisfactory. Therefore, there has hitherto been no satisfactory form of a mixture electrode suitable for extracting a large current.

[Problems to be Solved by the Invention] In view of such circumstances, the present invention has the advantage that a contact area with an electrolyte and an area opposed to a counter electrode can be widened like a spiral type electrode, and is molded into a flat plate. It is an object of the present invention to provide a secondary battery electrode of a novel form in which cracking, falling off, breaking, and the like when winding the prepared mixture are prevented.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have formed an electrode material using a conductive material and a conductive polymer as a binding material into a cylindrical shape. The present inventors have found that a pressure-formed form is effective, and have reached the present invention.

That is, the present invention is an electrode for a secondary battery in which an electrode material using a conductive polymer and a conductive polymer as a binder material is pressure-formed in a cylindrical shape. In this case, the shape of the tube is preferably a cylindrical shape, but may be a triangular, square, hexagonal, or other rectangular tube if necessary.

According to the cylindrical mixture type electrode of the present invention, it is possible to contact the electrolytic solution on the two surfaces, the outer peripheral surface and the inner peripheral surface, and similarly, the two surfaces can be opposed to the counter electrode. If necessary, arrange cylindrical mixture type electrodes of different sizes concentrically or concentrically, without any difference from the spiral type which can take a substantially large area if a separator and counter electrode are arranged between each, and There is no problem such as cracking, falling off or breaking when winding the sheet-form mixture type electrode.

There are various current collection methods in this case, but as an example, if a comb-shaped current collector is used and the teeth of each comb are attached to each cylindrical electrode, the current from all cylindrical electrodes can be concentrated and extracted. Is easy.

Examples of the conductive polymer used in the present invention include polypyrrole, polythiophene, polythiazyl, polyacetylene, polyparaphenylene, polyparaphenylene sulfide, polyaniline, polyparaphenylene vinylene,
Polyisothianaphthene, polypyridazine, polyazulene, polyselenophene, polypyridine, polyacene, polyperinaphthalene and the like are appropriately used.

The dopants for these conductive polymers include BF ₄ ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ , AsF ₅ , SbF ₅ , Na, I ₂ , K, Br _{2 and the} like.

The cylindrical electrode of the present invention desirably does not use a resin binder in order to improve the ratio of the conductive polymer per unit amount of the positive electrode.

As the conductive material, carbon-based materials such as Ketjen Black, acetylene black, graphite, and the like, SU
Examples include S short fibers, fine metal particles such as platinum, gold, and silver, and short metal fibers, and more preferably a carbon-based material.

Next, a method for producing the cylindrical mixture-type electrode of the present invention using the conductive polymer and the conductive material will be described below.

A conductive polymer (preferably powder) and a conductive material are kneaded, molded under pressure using a cylindrical mixture molding machine, and then vacuum dried (if the resin binder is a powder, vacuum drying is not necessary). Just do it.

The weight ratio of the conductive polymer to the conductive material is 60 to 100% by weight, preferably 80 to 95% by weight, and the conductive material is 40% by weight or less, preferably 5 to 20% by weight.

The conductive polymer used in the present invention may be either an electrolytic polymerization method or a chemical polymerization method. However, a chemical polymerization method is more preferable from the viewpoints of easy powdery production and easy mass production during kneading.

When the cylindrical mixture type electrode of the present invention is used as a positive electrode in a secondary battery, zinc, aluminum, magnesium, lithium, cadmium, and the like and a conductive polymer different from the positive electrode can be used as the negative electrode.

Further, when the cylindrical mixture type electrode of the present invention is used as a negative electrode in a secondary battery, manganese dioxide, silver oxide, graphite fluoride, thionyl chloride, activated carbon, titanium disulfide,
A different kind of conductive polymer from molybdenum disulfide and the negative electrode can be used. Of course, both the positive electrode and the negative electrode may be cylindrical mixture-type electrodes made of the conductive polymer of the present invention.

An aqueous solution of a metal halide or a solution of an organic solvent can be suitably used as the electrolytic solution. However, when the negative electrode is lithium, it is selected from organic solvents such as γ-butyrolactone, propylene carbonate, dimethylformamide, dimethoxyethane and the like. As a supporting salt, ammonium chloride in an aqueous solution system, lithium perchlorate in an organic solvent, etc.,
Lithium borofluoride or the like is used.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 (1) Synthesis of Chemically Polymerized Polyaniline 20.4 g (0.219 mol) of aniline was dissolved in 300 ml of a 1M aqueous solution of HCl, and (NH ₄ ) ₂ S ₂ O ₈ 11.5
g (0.0504 mol) in 200 ml of 1M aqueous HCl was added dropwise and stirred. After completion of the dropwise addition, stirring was continued at the same temperature for 2 hours, and the precipitated polyaniline (powder) was collected by filtration. The polyaniline obtained was washed three times with 200 ml of water, then twice with 100 ml of methanol and dried.

Next, the polyaniline was stirred in 300 ml of a 20% methanol solution of hydrazine at room temperature for 2 hours, dedoped and reduced, and filtered. This polyaniline is replaced with hydrazine 20
The treatment was performed in 300 ml of a 30% methanol solution. This dedope reduction treatment was repeated 5 times, and the collected matter was washed twice with 100 ml of methanol to obtain 10.0 g of light blue polyaniline.

(2) Preparation of cylindrical mixture type electrode 1.56g of polyaniline synthesized above and 0.1 of graphite
6 g (KS-6 manufactured by Lonza) is sufficiently kneaded, and a pressure molding machine is used to produce a cylindrical electrode having an outer diameter of 9.5 mm, an inner diameter of 6 mm and a height of 40 mm at a pressure of 100 kg / cm ² as shown in FIG. did.

(3) Evaluation said cylindrical electrodes of the battery characteristics as a positive electrode, lithium foil [Honjo Metal Co., 50 [mu] m thick] separator (Polyplastics Co. Jura guard), and propylene carbonate 70Vol of LiBF ₄ as the electrolyte %, Dimethoxyethane 30Vol%
Using a 3M solution of the above, an evaluation cell shown in FIG. 2 was prepared.
The charge / discharge characteristics were examined.

 The evaluation method is as follows.

Charge end voltage 3.8V, discharge end voltage 2.3V, charge / discharge current 20
mA was set and a charge / discharge test was performed. The positive electrode energy density was 348 Wh / kg. In addition, no change was observed in the shape of the positive electrode even after 100 charge / discharge cycles, and no cracking or falling off was observed.

Comparative Example 1 2.81 g of polyaniline, graphite (KS- manufactured by Lonza)
6) 0.28 g was sufficiently kneaded, and a columnar electrode having a diameter of 9.5 mm and a height of 40 mm was prepared at a pressure of 100 kg / cm ^{2 using} a pressure molding machine.
This columnar electrode is used as a positive electrode, a separator (Polyplastics Co., Ltd. Duraguard) is wound around this electrode, and a lithium foil (Honjo Metal Co., Ltd., 50 μm thick) is further wound therearound. A charge / discharge test was performed using the evaluation cell.

The positive electrode energy density was 23 / Wh / kg. After 100 charge / discharge tests, cracks were observed in the positive electrode in the vertical direction.

Comparative Example 2 Thickness 0.1 mm, mesh size 2 mm × 1 mm stainless steel (S
US316) expanded metal cut into a size of 100 mm in length and 40 mm in width, and the kneaded material of Example 2 was applied to a thickness of 2 m when applied.
m and pressurized at 100 kg / cm ² with a pressure molding machine to obtain a sheet-form mixture type electrode. The sheet-form mixture electrode is dried at 100 ° C. for 5 hours under vacuum, and the dried sheet-form mixture-type electrode is wound around a 5 mmφ round bar to generate cracks and adherence to expanded metal. Observed. As a result, cracks occurred during drying after coating, and large cracks occurred in the winding test. In addition, peeling from the expanded metal also occurred.

[Effects of the Invention] As described above, the secondary battery using the cylindrical mixture-type electrode of the present invention has cracks in the electrode at the time of manufacture or use.
It is a highly reliable electrode that shows sufficient energy capacity, charge / discharge characteristics, and stability without causing defects such as peeling.

[Brief description of the drawings]

FIG. 1 is a view for explaining a cylindrical electrode used for a secondary battery of the present invention, and FIG. 2 is a view for explaining cells for evaluating the secondary battery of the present invention. 1 ... Platinum lead wire for positive electrode, 2 ... Platinum wire lead for negative electrode, 3 ... Teflon stopper, 4 ... Electrolyte, 5 ... Lithium foil (negative electrode), 6 ... Duraguard (separator), 7 ... ... cylindrical positive electrode, 8 ... glass bottle.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-243248 (JP, A) JP-A-62-93865 (JP, A) Fully open Showa 60-13672 (JP, U) Really open Showa 56- 112772 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01M 4/02-4/04, 4/62, 10/40

Claims (1)

(57) [Claims] An electrode for a secondary battery in which an electrode material using a conductive material and a conductive polymer as a binder material is pressure-formed into a cylindrical shape.