JP2542221B2 - Battery using polyaniline composite electrode - Google Patents

Description

TECHNICAL FIELD The present invention relates to a battery using a polyaniline composite electrode.

[Prior Art] A method of synthesizing an organic polymer by electrolytically oxidizing an organic substance has been known for a long time, and various polymers have been developed by electrochemically controlling the synthesis of the organic polymer.

In particular, since each polymer obtained by electrolytically oxidatively polymerizing pyrrole, aniline, thiophene, benzene and their derivatives has basic characteristics as a switching element, a display element and an electrode material, much research has been conducted. ing. [Polypyrrole, AFDiaz.J.Chem.
Commun, 1979, 635 .; Polythiophene JP-A-56-47421; Polyaniline, AFDiaz.J.Electroanal.Chem., 111 , 1524
(1980); Polyparaphenylene, Electrochem. Acta., 2
7 , 61 (1982)].

In particular, among the applications of polymers to these devices, various studies have been made as being suitable for reducing the weight and increasing the energy density of batteries using the above-described polymer material as an electrode active material.

Among them, a secondary battery using polyaniline, which is excellent in chemical stability of the material, as a positive electrode has recently attracted attention as a secondary battery having high Coulomb efficiency and high energy density.

In the case of synthesizing the polyaniline, generally, aniline is dissolved in an aqueous electrolyte solution, and the electrolyte solution is used as an inactive electrode material (for example, platinum) as a cathode and an anode, and H ₂ SO ₄ and HC are used as the electrolyte solution.
An acidic aqueous solution using a protonic acid such as l, HClO ₄ , and HBF ₄ as an electrolyte is used. (JP-A-62-96525, J. Electroanal. Che
m. 161, 419 (1984) , the battery debate 27 times, Preprint P 20
1) As a battery using the polyaniline thus obtained, for example, Polymer preprints 25 No.2 248 (198
4), The 51st Annual Meeting of the Electrochemical Society of Japan, 228 (1984). However, when considering a practical battery, there are many problems in the current collecting method of polyaniline, that is, since polyaniline is generally produced in the form of powder or fragile film, the current collecting method of polyaniline is the same as that of a normal current collecting method. The one that is pressure-bonded on a metal slope or electrolytically polymerized on a current collector metal plate has problems such as the polymer falling off due to charging and discharging, and only the polymer in contact with the current collecting surface is involved in charging and discharging. It was difficult to obtain efficiency and energy density, and there was a problem in reliability as a battery.

Also, a method is generally used in which polyaniline is mixed with a conductive powder such as carbon powder, and a binder such as Teflon powder is added if necessary, and the mixture is pressed and molded. Is greatly influenced by the morphology of the additive and cannot fully utilize the inherent function of polyaniline.

[Objective] Therefore, an object of the present invention is to produce a polyaniline electrode having a high current collecting efficiency in a polyaniline / collector composite electrode, and to provide a battery using the same.

[Structure] In view of the drawbacks of the prior art, the present inventors have made various studies on the production of polyaniline composite electrodes by an electrochemical polymerization method, and as a result, the perchloric acid-containing reaction medium is porous in a medium having a pH of 2.0 or less. The inventors have found that the above-mentioned object can be achieved by using a composite electrode obtained by polymerizing aniline on the amorphous carbon electrode of (1) and completed the present invention.

That is, the present invention, the pH of the reaction medium containing perchloric acid is 2.0
In the following medium, a polyaniline composite electrode obtained by forming polyniline having a high specific surface area by polymerizing aniline by electrochemical polymerization on a reaction electrode made of an irregular or porous amorphous carbon body is obtained. A battery characterized by being used.

As the porous electrode used in the present invention, an amorphous carbon body obtained by firing a molded body of cellulose, pitch, phenol or the like is most preferably used in consideration of weight, mechanical strength and moldability. .

The porosity of the porous electrode is preferably 10% or more, preferably 10 to 70%, more preferably 30 to 60%. The larger the porosity is, the better the energy density and the output density are. However, when the porosity exceeds 70%, the current collecting property is deteriorated and the strength of the porous body is rapidly reduced.

The average pore diameter of the porous electrode is preferably 0.5 to 150 μm,
More preferably, it is 1 to 50 μm. Average pore size 0.5
If it is less than μm, it becomes difficult to incorporate the active material into the pores, and a sufficiently high energy density cannot be obtained. On the other hand, if it exceeds 150 μm, the active material fixed to the inner wall surface of the pores cannot be increased, and the current collecting efficiency also decreases.

The specific resistance of the amorphous carbon body is preferably 10 Ωcm or less,
The lower the value, the lower the internal resistance and the better electrochemical properties.

Polyaniline can be synthesized in a fibril form by electrolytically polymerizing aniline in an acidic medium, but the inventors of the present invention have conducted extensive research, and as a result, the type of electrolyte, pH, electrolysis potential, or electrolysis It was found that the length and thickness of fibrils, the specific surface area of polyaniline and the electrode characteristics were variously changed by the electric current, and various applications to batteries were investigated.

As a result, when a composite electrode obtained by electrolytically polymerizing aniline on the porous electrode was used as a battery electrode, when the specific surface area of the polyaniline by the BET method was 1 to 200 m ² / g, the electrode reaction during charging and discharging was It was found to be preferable because it can be performed smoothly.

Generally, polyaniline is synthesized in a reaction medium containing a protic acid, but as a protic acid that can be used in the polymerization of aniline, hydrochloric acid, sulfuric acid, perchloric acid, borofluoric acid, methanesulfonic acid, trifluoroacetic acid,
Paratoluene sulfonic acid and the like can be mentioned. In the composite electrode of the present invention, when perchloric acid is used as the protonic acid, it is possible to synthesize polyaniline having a fibril thickness of 0.1 μm or less and a very large specific surface area, and a porous material having a small pore size. Even if the body is used, the polymer can enter the pores, and the composite electrode has good electrochemical properties. On the other hand, for example, when polyaniline synthesized with hydrochloric acid is polymerized into fibrils of about 0.4 μm and a porous body with a small pore size is used, it is difficult for the polymer to enter into the pores, so the porous body is used. Cannot take full advantage of The amount of perchloric acid used is 3 or less, preferably 2 at the pH of the polymerization electrolyte.
It is desirable to add it as follows. When it is 3 or more, the growth rate of the polymer is slow, and the resulting polymer also has a portion soluble in a solvent such as dimethylformamide, so that the degree of polymerization is low and the stability of the material against charge / discharge is not good.

In the electrochemical polymerization of the present invention, the polymerization of aniline is performed by anodic oxidation using an aniline concentration of 0.1 mol / or more, preferably 0.4 mol / or more, and the current density is 0.01 to 50 m.
The constant current method, constant voltage method and any other method can be used within a range of A / cm ² and electrolysis voltage of usually 1 to 100 V, but it is preferable to use the constant potential method.

As the reaction medium in the polymerization system, water, a water-miscible organic solvent and a mixture of two or more water-immiscible organic solvents can be used, but usually water, a water-miscible organic solvent or a mixture thereof is used. Used. Examples of the water-miscible organic solvent include acetonitrile, benzonitrile, tetrahydrofuran, nitrobenzene, dimethylformamide, dimethylsulfoxide and the like.

The reaction temperature used is −50 ° C. to 100 ° C. It is preferable to use -30 ° C to 50 ° C. The reaction time must be appropriately set according to the desired amount of polymer, the reaction temperature, the reaction system, and the applied current density.

A battery using the composite electrode of the present invention is basically composed of a positive electrode, a negative electrode and an electrolytic solution, and a separator can be provided between the electrodes. The electrolytic solution is composed of a solvent and an electrolyte, but it is also possible to use a solid electrolyte.

In the battery of the present invention, at least one electrode is doped with anions or cations to store energy, and dedoped to release energy through an external circuit. Further, in the battery of the present invention, since this doping-dedoping is reversibly carried out, it can be used as a secondary battery.

Examples of these dopants include the following anions or cations. The cation-doped polymer complex is an n-type conductive polymer, and the anion-doped polymer complex is a p-type. To give a conductive polymer.
The p-type semiconductor can be used for the positive electrode and the n-type semiconductor can be used for the negative electrode.

(1) _{^{anion: PF 6 -, SbF 6 -}} , AsF 6 -, SbCl 6 - V , such as
halide anion of a Group elements; BF ₄ ^- like III a
Perchlorate anions such as ^- ClO _4; halide anion of a family of elements.

(2) Cations: alkali metal ions such as Li ⁺ , Na ⁺ and K ⁺ , (R ₄ N) ⁺ [R: a hydrocarbon group having 1 to 20 carbon atoms] and the like.

Specific examples of the compound that gives the above dopant include:
_{LiPF 6, LiSbF 6, LiAsF 6} , LiClO 4, NaClO 4, KI, KPF 6, K
_{SbF 6, KAsF 6, KClO 4} , [(n-Bu) 4 N] + · AsF 6 -,
_{[(N-Bu) 4 N} ] + · ClO 4 -, etc. LiAlCl _4, LiBF ₄ is exemplified.

As the solvent of the electrolytic solution of the battery, water or a nonprotonic solvent which is called a polar nonprotonic solvent having a large relative dielectric property is preferable. Specifically, for example, ketones,
Nitriles, esters, ethers, carbonates, nitro compounds, sulfolane compounds and the like or a mixed solvent thereof can be dissolved, and among these, nitriles, carbonates and sulfolane compounds are preferable. Typical examples thereof include acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, ethylene carbonate, propylene carbonate, γ-butyl lactone, sulfolane and 3-methylsulfolane.

The negative electrode in the battery of the present invention, for example, polypyrrole and polypyrrole derivatives, polythiophene and polythiophene derivatives, conductive polymers such as polyquinoline, polyacene, polyparaphenylene, polyacetylene, graphite, interlayer compounds such as TiS ₂ , lithium, sodium, lithium. -Alkali metals such as aluminum or alloys thereof, and alkali metals or metals such as Zn, Cu and Ag can be used.

As the separator, one having a low resistance to the movement of ions of the electrolyte solution and having excellent solution holding property is used. For example, glass fiber filters; polyester,
Polymeric pore filters such as Teflon, polyflon, and polypropylene, non-woven fabrics; or non-woven fabrics made of glass fibers and these polymers can be used.

Further, a solid electrolyte can be used as a component that replaces the electrolytic solution and the separator. For example, in inorganic systems, AgCl, AgBr, AgI, LiI and other metal halides,
Examples include RbAg ₄ I ₅ and RbAg ₄ I ₄ CN. In the organic system, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide or the like is used as a polymer matrix and the above-mentioned electrolyte salt is dissolved in the polymer matrix to form a complex, or a cross-linked product or low molecular weight polyethylene oxide thereof. , A polymer electrolyte in which an ion dissociative group such as crown ether is grafted onto the polymer main chain.

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 (Production of Electrode) 1.5 mol / HClO ₄ aqueous solution containing 0.5 mol / aniline (p
H0) was used as the reaction solution, and a phenolic amorphous carbon body with a diameter of 16 mm, a thickness of 1.4 mm, a porosity of 45%, and a resistivity of 0.1 Ω · cm was used as the reaction electrode, and platinum was used as the counter electrode. Potential electrolysis was performed, and an electric quantity of 200C was passed. This electrode was washed thoroughly with distilled water and further dried under reduced pressure at 80 ° C for 8 hours.
It was added to a propylene carbonate solution containing ol / LiClO ₄ and platinum was used as a counter electrode, and Ag / Ag ⁺ was used as a reference electrode.
A potential of 2 V vs Ag / Ag ⁺ was applied, and after discharging until the natural potential became 0 V, it was washed and dried to obtain a battery electrode. In addition, the specific surface area of the polyaniline synthesized under these conditions by the BET method is 7
It was 2 m ² / g.

Example 2 (Production of electrode) After polymerizing aniline on a porous material in the same manner as in Example 1, the electrode was washed with distilled water, and then placed in an aqueous solution containing 1 mol / LiClO _4, and platinum was used as a counter electrode. After discharging with a constant current of 0.1 mA / cm ² to 0 V with respect to SCE, it was washed and dried to obtain a battery electrode. The specific surface area of polyaniline is
It was 92 m ² / g.

Example 3 (Production of electrode) A polyaniline for producing a battery electrode was produced in the same manner as in Example 1 except that a phenol-based amorphous carbon material having a porosity of 65% was used as a reaction electrode. The specific surface area was 112 m ² / g. there were.

Example 4 (Production of electrode) A battery electrode was produced in the same manner as in Example 3 except that a solution (pH 1.6) containing 0.5 mol / HClO ₄ was used. The specific surface area of polyaniline was 143 m ² / g.

Comparative Example 1 (Production of Electrode) A battery electrode was produced in the same manner as in Example 3 except that a solution (pH 2.2) containing 0.4 mol / HClO ₄ was used. The specific surface area of polyaniline was 77 m ² / g.

Comparative Example 2 (Production of Electrode) The specific surface area of polyaniline used for producing a battery electrode was 22 m ² / g in the same manner as in Example 3 except that a solution containing 1.5 mol / HCl (pH 0 or less) was used.

Comparative Example 3 (Production of Electrode) A battery electrode was produced in the same manner as in Example 3 except that a solution containing 3.5 mol / HCl (pH 0 or less) was used. The specific surface area of polyaniline was 11 m ² / g.

Battery performance test The electrode prepared in the production of the electrode is used as a positive electrode and as a negative electrode Li or Zn as a propylene carbonate containing 1 mol / LiBF ₄ or 0.5 mol / ZnSO ₄ as a electrolytic solution, and polypropylene battery as a separator using a button battery CR2025. Manufactures button type batteries of the same standard size and produces constant current
The battery performance was evaluated by charging and discharging at 1 mA.

[Effect] As is clear from the above description, according to the configuration of the present invention, a polyaniline composite electrode having a highly suppressed morphology and a high current collection efficiency can be manufactured, and a high Coulombic efficiency and a high energy density can be obtained. Batteries are provided.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshiyuki Kabata 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Shoko Yoneyama 1-3-6 Nakamagome, Ota-ku, Tokyo (56) Reference JP 60-221964 (JP, A) JP 59-18578 (JP, A) JP 62-93868 (JP, A) JP 62-20243 (JP, A)

Claims (1)

(57) [Claims] 1. An aniline is polymerized by electrochemical polymerization on a reaction electrode composed of an irregular or porous amorphous carbon body in a medium in which the pH of the perchloric acid-containing reaction medium is 2 or less. A battery characterized by using a polyaniline composite electrode obtained by forming polyaniline having a high specific surface area.