JPS62100942A - Secondary cell - Google Patents

Abstract

PURPOSE:To improve the property of a cell, by coating with carbon the contact surface of a positive electrode made of a polyaniline type compound contacting to a collector. CONSTITUTION:A cell is composed of a negative electrode 3, a separator 4, a positive electrode 5, and collectors 2 and 6, for example. The positive electrode 5 is formed of a polyaniline type compound, and its contact surface to the collector 6 is coated with carbon. On the other hand, the negative electrode 3 is made of (i) an alkaline metal such as Li, (ii) an alkaline metallic alloy such as Li/Al, (iii) a conductive high polymer such as polyacetylene, or (iv) a compound of (i) or (ii), and (iii). In such a composition, a cell of a high energy density, a low self-discharge, a long cycle life, and a good charge and discharge efficiency can be obtained.

Description

[Detailed Description of the Invention] 1. Field of Industrial Application] The present invention is characterized by:
This invention relates to a secondary battery with a long life and good charge/discharge efficiency (Coulombic efficiency).

[Prior Art] So-called polymer batteries used as electrodes are expected to be used as high-energy density secondary batteries.

Many reports have already been made regarding polymer batteries, for example, P. G. Nigley et al., General of the Chemical Society, Chemical Communication, 1979.

Page 594 (P, J, Ntgrcy et al., J, C, S,
, Chcm.

COlColu, 1979.594), Situnal Engineering [Noct U Chemical Society, 198.
1, p. 1651 (J, EIectrochem,
Soc,, 1981.1651), Japanese Patent Application Publication No. 1986-
13646'3 bow, 57-1211G8, 59-
No. 3870, No. 1i159-3872, No. 1i159-387
No. 3, No. 59-196566, No. 59-196573
No. 59-203368, No. 59-203369, etc. can be partially returned.

In addition, there have already been proposals to use polyaniline, which is obtained by oxidative polymerization of aniline, a type of conjugated polymer, as electrodes for aqueous or non-aqueous batteries (A.G. Mac Diarmid et al. , Polymer Preprinz 4 Volume 25, Nan Polymer Preprin
ts, Wataru No. 2.248 (1984)], Sasaki et al., Proceedings of the 50th Conference of the Electrochemical Society, 123 (1983)
), Abstracts of the 51st Conference of the Electrochemical Society, 228 (19
84) ).

[Problems to be Solved by the Invention] However, polymer batteries using conventionally known polymers as electrodes have problems such as (i) high energy density, (ii) low self-discharge, (iii) high charge/discharge efficiency, and (iv) ) It has not been possible to obtain a product that satisfies the cycle life at the same time.

[Means for Solving the Problems] As a result of various studies on electrode materials that simultaneously satisfy the above four battery performances, the present inventors found that a polyaniline compound was used for the positive electrode, and that the polyaniline compound electrode By applying a carbon coating to the area that comes into contact with the current collector,
The present invention has been achieved by devising the ability to obtain a secondary battery that can simultaneously satisfy the above four performances.

That is, in the present invention, the positive electrode is made of a polyaniline compound, and the negative electrode is made of (1) an alkali metal, (ii) an alkali metal alloy, (iii) a conductive polymer, or (iv) an alkali metal or an alkali metal alloy and a conductive polymer. The present invention relates to a secondary battery comprising a composite with molecules, characterized in that the surface of the polyaniline compound electrode that comes into contact with the current collector is coated with carbon.

The polyaniline compound used in the positive electrode of the secondary battery of the present invention has the following general formulas (1) and (2), and the structural formula (
It is obtained by oxidative polymerization or oxidative copolymerization of at least one aniline compound selected from 3).

[However, in the formula, R+ and R2 are an alkyl group having 5 or less carbon atoms or an alkoxy group having 5 or less carbon atoms, and X and Y are 0
．． 1 or 2. ] Specific examples of the aniline compound represented by the general formula (1) or (2) include aniline, 2-methyl-aniline, 2,5-dimethylaniline, 2-methoxy-aniline, 2.5- Examples include dimethoxy-aniline, O-phenylenediamine, 3-methyl-1,2-diamino-benzene, and the like. Among the aniline compounds represented by formulas (1) to (3), aniline, O
Examples include -phenylenediamine and triphenylamine, with aniline being particularly preferred.

The polyaniline compound used in the present invention can be produced by either an electrochemical polymerization method or a chemical polymerization method.

When electrochemical polymerization is used, the aniline compound is polymerized by anodic oxidation. For that purpose, for example 1
A current density of ~201 rLA/cIII2 is used.

In most cases, a voltage of 1 to 300 volts is applied. The polymerization is preferably carried out in the presence of an auxiliary liquid in which the aniline compound is soluble. Water or polar organic solvents can be used for this purpose. When using a water-miscible solvent, a small amount of water may be added.

Suitable organic solvents are alcohols, ethers such as dioxane or tetrahydrofuran, acetone or acetonitrile, benzonitrile, dimethylformamide or N-methylpyrrolidone.

Polymerization is carried out in the presence of a complexing agent. This includes BFi, As Fi, and Δ5Fii as anions.

SbFi, SbC,Q-,PFii,C
jO: .

means a salt containing a group of

These salts have cations such as protons (H”)
, quaternary ammonium cation, lithium ion, sodium ion or potassium ion. The use of compounds of this type is known and is not the subject of the present invention.

These compounds are usually used in an amount such that the polyaniline compound contains 20 to 100 mol% of the anionic complexing agent.

When producing polyaniline compounds by chemical methods, it is possible, for example, to polymerize the aniline compounds in aqueous solution with strong acids such as hydrochloric acid and free peroxides such as potassium persulfate. In this method, a polyaniline compound can be obtained in the form of a fine powder. Since a salt is present in these methods, the polyaniline compound is a complex compound with the corresponding anion.

Molded bodies that can be used as electrodes can be obtained by various methods. For example, in the case of anodic oxidation of an aniline compound, a polyaniline compound is complexed with anions and takes the form of the anode used. If the anode has a flat shape, a flat layer of polyaniline compound is formed. When using a method for producing fine powder of a polyaniline compound, this fine powder can be compression molded into a molded body under pressure and heat by a known method. In many cases T='
Temperature of lfA~300℃ and 10~10,000Ky
A pressure of /cjI2 is used. According to this known method for producing anionic complexed polyaniline compounds, molded bodies of arbitrary shapes can be obtained.

That is, for example, a thin film, a plate or a three-dimensional shaped molding is used.

The polyaniline compound obtained by forming a complex compound with an anion may be used as it is as the positive electrode of the secondary battery of the present invention, or the compound obtained by chemically or electrochemically removing the complexed anion may be used as the positive electrode. Good too.

In the present invention, a polyaniline compound is coated with carbon on the surface of the electrode that comes into contact with the current collector. be done.

There are no particular limitations on the method of coating carbon on the surface of the polyaniline compound electrode that comes into contact with the current collector, but coating is usually performed by vacuum evaporation, ion sputtering, ion blating, or the like. There are no particular restrictions on the thickness of the carbon film to be coated, and it is generally in the range of 10 to 105. The current collecting effect is improved by coating the carbon layer in contact with the current collector of the polyaniline compound vIJ electrode. ,
It is presumed that this improves battery performance.

An alkali metal salt is used as the supporting electrolyte of the electrolytic solution of the secondary battery of the present invention. Alkali metal JZ! Examples of the alkali metal include Li, Na and K metals, preferably l-i metals.

Typical anion components of the supporting electrolyte include, for example, C
, QOi, PFii, As Fii, △sFi.

Examples include SO3CF, BF, and BR'4 (wherein R is an alkyl group or aryl group having 1 to 10 carbon atoms).

Specific examples of alkali metal salts as supporting electrolytes include:
Li[)Fe, liSbFo.

LiCfJOi, 1-iAsFa, cFasO3Li.

Li BFI, l-i +3 (BLI) 4.

Li B (Et12(Buz2゜Na PFa, Na BF4, Na As Fo
.

Na B (Bu14. KB (Btl)4', K
Examples include ΔSFa, but are not necessarily limited to these. These alkali metals
may be used alone or in combination of two or more.

The m degree of the alkali metal salt cannot be unconditionally defined because it varies depending on the type of polyaniline compound used in the positive electrode, the type of cathode, charging conditions, operating temperature, type of supporting electrolyte, type of organic solvent, etc. Generally 0.5
It is preferably within the range of ~10 mol/1. The electrolyte may be homogeneous or heterogeneous.

As the solvent for the electrolyte of the secondary battery of the present invention, the following solvents may be used alone or in combination.

Alkylene nitrile: Examples, chloro1henitrile (liquid range, -51.1°C to 120°C) trialkyl borate 7 examples, 1 to trimethyl boric acid, (CH30)3B (liquid range, -293°C to 67°C) ]~Raalkyl silicate: e.g., tetrahedyl silicate, (CI-130)
4 Si (boiling point, 121°C) two ditroalkanes, nitromethane, CH3NO2 (liquid range, -17°C to 100.8°C) alkyl nitrile: e.g., acetonitrile, Ctl: +C
N (liquid range, -45°C to 81.6°C) two dialkylamides, dimethylformamide, HCON (Cto13) 2 (liquid range, -[30,48°C to 149°C) two monocarboxylic acid esters, Ethyl acetate (liquid range, -83,6
~77.06°C) Two orthoesters, trimethyl orthoformate, HC(OCH3)3 (boiling point, 10
3℃) (Liquid range, -42~・206℃) Dialkylnate, QC (OCH3)2 (Liquid range, 2~
90°C) Alkylene carbonates: e.g., propylene carbonate: e.g., diethyl ether (liquid range, -116 to 34.5°C) Polyethers: e.g., 1,1- and 1,2-dimethoxyethane (liquid range, respectively) -113.2~64,5
°C and -58-83 °C) Cyclic ethers: e.g., tetrahydrofuran (liquid range, -
65-67°C): 1,3-dioxolane (liquid range, -
95-78°C) Nitroaromatics: Examples, nitrobenzene (liquid range, 5, 7-210.8°C) Two examples of aromatic carboxylic acid halides, benzoyl chloride (
Liquid range, 0 to 197°C), benzoyl bromide (liquid range, -24 to 218°C) Aromatic sulfonic acid halogenated vA 2 examples, benzenesulfonyl chloride (liquid range, 14.5 to 251°C) Aromatic phosphonic acid Two dihalides, benzenephosphonyl dichloride (boiling point, 258°C), two aromatic thiophosphonic acid dihalides, benzene thiophosphonyl dichloride (boiling point, 124°C at 5IIlli) (melting point, 22°C) 3-methylsulfolane (melting point, -1℃) 2 examples of alkyl sulfonic acid halides, methane sulfonyl chloride (boiling point, 161℃) 2 examples of alkyl carboxylic acid halides, acetyl chloride (liquid range, -112 to 50.9℃), acedel bromide (
Liquid range, -96 to 76°C), Propionyl chloride (Liquid range, -94 to 80°C) Two saturated heterocyclic compounds, Tetrahydrothiophene (Liquid range, -96 to 121°C): 3-Methyl-2-oxazolidone (Melting point, 15.9°C) Dialkyl sulfamic acid halide: e.g., dimethyl sulfamyl chloride (boiling point, 80°C at 16 g) Alkyl halosulfonate: e.g., ethyl chlorosulfonate (boiling point, 151°C) Unsaturated heterocyclic carbonate Acid halide 2 side, chloride 2-7
0yl (liquid range, -2 to 173°C) five-membered unsaturated heterocyclic compounds: e.g., 1-methylvirol (boiling point, 114°C)
, 2,4-dimethyldeazole (boiling point, 144°C), furan (liquid range, -85.65 to 31.36°C), dibasic carboxylic acid Nisdel d3 and/or two halides, ethyl Oxalyl chloride (boiling point, 135°C) Mixed alkylsulfonic acid halide/two carboxylic acid halides, chlorosulfonylacedel chloride (boiling point, 10III11 at 98°C) Dialkyl sulfoxide: e.g., dimethyl sulfoxide (liquid range, 18
．． 4-189℃) Two dialkyl sulfates, dimethyl sulfate (liquid range, -31.75-188.5
°C) Dialkyl lylphite: e.g., dimethyl sulfide (boiling point, 126°C)) Alkylene lylphite: e.g., ethylene glycol
Sulfide (liquid range, -11 to 113°C) Genated alkanes: e.g., methylene chloride (liquid range,
-95 to 40°C), 1,3-dichloropropane (liquid range, -99.5 to 1204°C) Among the above, preferred organic solvents are sulfolane, crotonitrile, nitrobenzene, tetrahydrofuran, methyl-substituted tetrahydrofuran, 1.3-dichloropropane (liquid range, -99.5 to 1204°C) -Dioxolane, 3-methyl-2-oxazolidone, propylene or ethylene carbonate, sulfolane, γ-butyrolactone, ethylene glycol
sulfide, dimethyl sulfide, dimethyl sulfoxide, and 1,1- and 1,2-dimethoxyethane, particularly preferred are buOpyrene carbonate and 1,2-dimethoxyethane, and sulfolane and 1.2-dimethoxyethane.
A mixed solvent of 2-dimethoxyethane can be mentioned. This is because they are believed to be the most chemically inert towards battery components and have a wide liquid range, especially since they make the cathode material highly and efficiently available. be.

The negative electrode used in the secondary battery of the present invention includes (i) an alkali metal, (it) an alkali metal alloy, (iii) ffll
(iv) a composite of an alkali metal or an alkali metal alloy and a conductive polymer.

(11) Examples of alkali metals include Li, Na, etc.; (11) Examples of alkali metal alloys include Li/A1 alloy, Li/H(J alloy, Li/Zn alloy, cr/
Examples include CD alloy, Li/Sn alloy, Li/PB alloy, and alloys of three or more metals including alkali metals used in these alloys.

Examples of the conductive polymer (iii) include polypyrrole and polypyrrole derivatives, polythiophene and polythiophene derivatives, polyquinoline, boriacene, polyparaphenylene and polyparaphenylene derivatives, polyacetylene, and the like.

Furthermore, as (iv) a complex of an alkali metal or an alkali metal alloy and a conductive polymer, a complex of Li//1 alloy and each of the above-mentioned yuzu conductive polymers, such as polyparaphenylene or boria-propylene, is used. can give. Among these, preferred are polyacetylene, polyparaphenylene, Li/Δhair alloy, and a composite of Li/Δ cross alloy and polyparaphenylene. The complex herein refers to a homogeneous mixture of an alkali metal or an alkali metal alloy and a conductive polymer, a laminate J3, and a modified product in which a base component is modified with another component.

As well known to those skilled in the art, other suitable conductive materials such as carbon black, acetylene black, metal powder, Metal fibers, carbon fibers, etc. may be mixed.

Further, it may be reinforced with a thermoplastic resin such as polyethylene, modified polyethylene, polypropylene, poly(tetrafluoroethylene), ethylene-propylene interpolymer (EPI), or sulfonated EPDM cap.

In the secondary battery of the present invention, the amount of the dopant doped into the polyaniline compound is 02 to 1.5 mol, preferably 0.2 to 1 mol, per 1 N atom in the polyaniline compound. .0 mol.

Dope suspension can be freely controlled QD-j by measuring tourmaline flowing during electrolysis. - The doping can be carried out in any way, under constant current, constant voltage or under conditions of changes in current and voltage.

In the present invention, if necessary, a porous membrane made of synthetic resin such as polyethylene or polypropylene or natural fiber paper may be used as the diaphragm.

Additionally, some of the electrodes used in the secondary battery of the present invention may react with oxygen or water and reduce the performance of the C battery, so the battery should be sealed and substantially oxygen-free and water-free. It is desirable that the condition is as follows.

[Effects of the Invention] The secondary battery of the present invention has high energy density, high charge/discharge efficiency, long cycle life, low self-discharge rate, and good voltage flatness during discharge. Furthermore, the secondary battery of the present invention is lightweight, compact, and has a high energy density, so it is suitable for use in portable devices, electric vehicles, gasoline vehicles, and power storage batteries.

[Example] Hereinafter, the present invention will be explained in more detail by referring to Examples and Comparative Examples.

Example 1 [Manufacture of polyaniline] Distilled water, HBF4, and aniline were added to a glass container, and HB
The concentration of F4 was adjusted to 1.5 mol, and the concentration of aniline was adjusted to 0.7 mol. 6 each at intervals of 21 in aqueous solution
After charging two platinum electrodes of clI2, electrolysis was carried out with a current of 120 ampere-seconds while stirring. At this time, black-purple polyaniline was deposited on the anode plate. The coated anode was repeatedly washed three times with distilled water and then, after vacuum drying at 10° C., the resulting polyaniline film was peeled off from the platinum plate. One side of the obtained film was coated with carbon to a thickness of about 100 mm by ion sputtering.

[Production of film-like acetylene polymer]

In a glass reaction vessel with an internal volume of 500 d under nitrogen atmosphere.
1. Add 1-titanium tetrabutoxide and add 30
A catalyst solution was prepared by dissolving d in anisole and then adding 2.7 d of triedylaluminum with stirring.

This reaction vessel was cooled with liquid nitrogen, and the nitrogen gas in the system was exhausted using a vacuum pump. Next, this reaction vessel was
After cooling to 0.degree. C. and keeping the catalyst solution stationary, purified acetylene gas at a pressure of 1 atmosphere was bubbled through.

Polymerization immediately occurred on the surface of the catalyst solution, producing a film-like acetylene high polymer. Thirty minutes after the introduction of aretylene, the acetylene gas in the reaction vessel system was exhausted to stop the polymerization.

After removing the catalyst solution with a pourer under nitrogen M atmosphere, -
Washing was repeated five times with 100 d of purified toluene while maintaining the temperature at 78°C. The film-like acetylene polymer swollen with toluene was a uniform film-like swollen product in which fibrils were tightly intertwined. Next, this swollen product was vacuum dried to give a reddish-purple color with a metallic luster, a thickness of 180 μm, and a cis content of 98%.
A film-like ahydylene high polymer was obtained. In addition, the bulk density of this film-like acetylene high polymer is 0.30/CC,
Its electrical conductivity (DC four terminal method) is 3.2×1 at 20℃
It was 0-9Ω-1・C scrap-1.

[Battery experiment]

Disks each having a diameter of 20 M were cut out from the polyaniline film and the membranous acetylene polymer obtained by the above method, and a battery was constructed using the disks as positive and negative electrode active materials. However, the polyaniline of the positive electrode was set so that the carbon coated surface was in contact with the current collector.

The figure is a schematic cross-sectional view of a battery cell for measuring the characteristics of a secondary battery, which is an integral example of the present invention, and 1 is a platinum lead wire for the negative electrode;
2 is a platinum wire mesh current collector for the negative electrode with a diameter of 20 mm and a mesh of 80;
3 is a disc-shaped negative electrode with a diameter of 20 mm, 4 is a circular multi-flowered polypropylene diaphragm with a diameter of 20 mm, and is thick enough to be sufficiently impregnated with the electrolyte, 5 is a disc-shaped positive electrode with a diameter of 20#,
Reference numeral 6 indicates a platinum wire mesh current collector for the positive electrode with a diameter of 20 am and 80 meshes, 7 indicates a positive electrode lead wire, and 8 indicates a screw-in type Teflon container.

First, the platinum wire mesh current collector 6 for the positive electrode is placed in a Teflon container 8.
The positive electrode 5 is placed in the lower part of the concave part of the positive electrode, and the positive electrode 5 is placed on the platinum wire mesh current collector 6 for the positive electrode, and the porous bolyb 1]pyrene diaphragm 4 is placed on top of the positive electrode 5, and after sufficiently impregnated with the electrolytic solution, the negative electrode 3 were stacked on top of each other, and the negative electrode platinum wire current collector 2 was further placed thereon, and a Teflon container B8 was tightened to produce a battery.

As the electrolytic solution, a 1 mol/hour solution of 1i3F4 dissolved in an equal volume mixed solvent of 1-cobylene carbonate and 1,2-dimethoxyethane, which had been distilled and dehydrated according to a conventional method, was used.

Using the battery thus prepared, in an argon atmosphere, an amount of electricity corresponding to a doping load of 50 mol% and 6 mol% to the positive and negative electrodes was passed under a constant current (2.5 mΔ/cm2). I charged it. After charging is finished,
A repeated charge/discharge test was conducted by immediately discharging the battery under a constant current (3,077 LA/cm2), and then charging again under the same conditions when the battery voltage reached 0.5V. However, the number of charging/discharging cycles was recorded as 569 times until the value decreased to 70%.

The theoretical energy density at the fifth repetition is 16
7W-hr/Ky T:, maximum charge/discharge efficiency is 10
It was 0%. Furthermore, when the battery was left charged for 62 hours, its self-discharge rate was 3.6%.

Comparative Example 1 [Battery experiment] was conducted in exactly the same manner as in Example 1 except that polyaniline was not coated with carbon in Example 1, but the number of repetitions was 441 times, and the theoretical energy density was 163 W -hr/ h, maximum charge/discharge efficiency is 98%
, the self-discharge rate was 7.8%.

Example 2 In Example 1, instead of the acetylene high polymer used for the negative electrode, Plutin of the Chemical Society of DiV Pan, Vol. 51, p. 2091 (1978
Year) (Bull, Chell, Soc,
Japan.

51, 2091 (1978)) at 1 ton/cix.
A battery experiment was carried out in exactly the same manner as in Example 1, except that a negative electrode formed into a 20mm φ disc shape at a pressure of - The number of repetitions until the discharge efficiency decreased to 70% was recorded as 591 times. The theoretical energy density of this battery was 178 W-hr/Kg, and the maximum charge/discharge efficiency was 100%. Furthermore, when the battery was left charged for 62 hours, its self-discharge rate was 4.5%.

Example 3 In Example 1, except that Li/Δ1 alloy (atomic ratio 1:1) was used as the negative electrode instead of the acetylene high polymer used in the negative electrode, and the utilization rate was 20%. [Battery experiment] was conducted in exactly the same manner as in Example 1. As a result, the number of repetitions until the charging/discharging efficiency drops to 70% is 599.
times were recorded. The theoretical energy density of this battery is 241
W -hr/K'J, and the maximum charge/discharge efficiency is 10
It was 0%. When the battery was left charged for 62 hours, the self-discharge rate was 3.6%.

Comparative Example 2 [Battery experiment] was conducted in the same manner as in Example 3, except that polyaniline was not coated with carbon in Example 3, but the number of repetitions was 424, and the 11p energy density was 236 W. -hr/K9, the highest charge/discharge efficiency was 98%, and the self-discharge rate was 80%.

Example 4 J3 and 5 Example 1. In place of the aniline used in [Production of polyaniline], the aniline compounds shown in the table were used to prepare a polyaniline compound. ! '! One side of the polyaniline compound was coated with carbon to a film thickness of approximately 100 mm (battery experiment) using the same U strip 1'1 as in Example 3, except that the coated material was used for the positive electrode.
The results are 11 and shown in the table.

table

[Brief explanation of drawings]

tel is a cross section of a battery cell for measuring the characteristics of a secondary battery which is an example of the present invention. ... Negative electrode 4 ... Porous polypropylene diaphragm 5 ... Positive electrode 6 ... Platinum wire mesh current collector for iE electrode 7 ... Positive electrode lead wire 8 ... Teflon container Patent applicant Showa Denko Co., Ltd. Hitachi, Ltd.

Claims (1)

[Claims] The positive electrode is made of a polyaniline compound, and the negative electrode is made of (i) an alkali metal, (ii) an alkali metal alloy, (iii) a conductive polymer, or (iv) a composite of an alkali metal or an alkali metal alloy and a conductive polymer. A secondary battery characterized in that a surface of the polyaniline compound electrode that comes into contact with a current collector is coated with carbon.