JPH01272048A - Secondary battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (1) Industrial Application Field The present invention relates to a secondary battery that has high energy density, low self-discharge rate, long cycle life, and good charge/discharge efficiency (Coulombic efficiency). It is something.

(2) Conventional technology A so-called polymer battery, in which a polymer compound having a conjugated double bond in its main chain is used as an electrode, is expected to be a high energy density secondary battery. Many reports have already been made regarding polymer batteries, for example, P.J.
Nigrey et al., Journal of the Chemical Society, Chemical Communication, 1979, p. 594 [P, J, Nigrey et al., J, C, S,
, Chem, Commun, +1979 +59
4), Journal Electrochemical Society, 1981, p. 1651 (J, Electr.
ochem.

Soc, 1981.1651), JP-A-56-1
No. 36469, No. 57-121168, No. 59-38
No. 70, No. 59-3872, No. 59-3873, No. 59-196566, No. 59-196573, No. 5
No. 9-203368, No. 59-203369, etc. can be mentioned as some of them.

In addition, there have already been proposals to use polyaniline, which is obtained by electrolytic oxidation polymerization of aniline, which is a type of conjugated polymer, as an electrode for aqueous or non-aqueous batteries [A.G. Matsuku Diamide et al. Polymer pre-puri-fu. Volume 25.

Number 2. Page 248 (19,84) (A, G.

MacDiarmid etc., Polymer Prepr
ints+25, hh2+248 (1984
), Sasaki et al., Proceedings of the 50th Annual Conference of the Electrochemical Society, 123 (1983), Collected Proceedings of the 51st Annual Conference of the Electrochemical Society, 228 (1984)).

(3) Problems to be solved by the invention However, polymer batteries using conventionally known polymers as electrodes have the following problems: (i) high energy density, (ii) low self-discharge, (iii) high charge/discharge efficiency, and ( iv) A product that simultaneously satisfies long cycle life has not been obtained.

In addition, the polyaniline used in conventionally known documents is obtained by electrolytic oxidation polymerization, and it is preferable to use polyaniline obtained by chemical oxidation polymerization, which is more economical. However, the electrode performance of polyaniline obtained by chemical oxidative polymerization was inferior to that of polyaniline obtained by electrolytic oxidative polymerization.

The biggest reason for this is thought to be that when polyaniline obtained by chemical oxidative polymerization is used as a battery active material, some of it does not work as an actual active material, or some of it dissolves into the electrolyte when left unused. .

(4) Means for Solving the Problems As a result of various studies on electrode materials that simultaneously satisfy the above-mentioned four battery performance requirements and are more economical, the inventors have developed a chemically oxidized polymer of aniline compounds. By washing with an organic solvent under heating in advance, it is possible to efficiently remove substances that cannot function as active materials in a short time, and to obtain a secondary battery that can satisfy the above four performances at the same time. I found it.

That is, the present invention uses a polyaniline compound for the positive electrode, and (i) 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 for the negative electrode. In a secondary battery using a composite of
The present invention also relates to a secondary battery characterized in that the chemically oxidized polymer has been washed in advance with an organic solvent under heating.

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

[However, in the formula, R+ and Rz 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 aniline compounds whose general formulas are represented by (1) and (2) include aniline, 2-methyl-aniline, 2,5-dimethyl-aniline, 2-methoxy-aniline, 2,5-dimethoxy -aniline, 0-phenylenediamine, 3-methyl-1,2-diamino-benzene and the like. Among the aniline compounds represented by formulas (1) to (3), aniline,
Examples include 0-phenylenediamine and triphenylamine, with aniline being particularly preferred.

Chemically oxidized polymers or chemically oxidized copolymers of aniline compounds (hereinafter both are collectively referred to as oxidized polymers)
Any conventionally known chemical oxidative polymerization method can be used.

A specific example of producing an oxidized polymer of an aniline compound by a chemical method is a method in which an aniline compound is polymerized in an aqueous solution with a strong acid such as hydrochloric acid and an inorganic peroxide such as potassium persulfate. can. According to this method, the oxidized polymer is obtained in the form of a fine powder. Since a salt is present in this method, the oxidized polymer is complexed with the corresponding anion.

The oxidized polymer obtained by forming a complex compound with an anion may be used as a positive electrode after removing the complexed anion chemically or electrochemically and washing with an organic solvent under heating. After washing with an organic solvent, the complexed anions may be removed chemically or electrochemically, and then used as a positive electrode. As a method for electrochemically removing a complexed anion, any conventionally known method may be employed, and as a method for chemically removing a complexed anion, KO) 1. NaOH, NH40)
A method of treating with an alkali such as J.

The shape of the oxidized polymer of the aniline compound when cleaning with an organic solvent under heating may be a fine powder obtained by oxidative polymerization, or it may be formed into an electrode. Also good.

Molded bodies that can be used as electrodes can be obtained by various methods. For example, a molded article can be produced by compression molding a fine powder of an oxidized polymer of an aniline compound under pressure using a known method. Often temperatures from room temperature to 300 °C and pressures from 10 to 10,000 kg/cIa are used.

Furthermore, it is more preferable to use a reduced polyaniline compound as the battery active material, and the reduction method may be electrochemical or chemical, but is not particularly limited.

The type of organic solvent used for washing the oxidized polymer of the aniline compound is not particularly limited, but it is preferably an ether solvent or a mixed system of an ether solvent and another solvent, and the ether solvent is at least 30 vol 1% or more. Something is good. Examples of ether solvents include monoethers, polyethers, and cyclic ethers, and among these, preferable examples include diethyl ether, 1,1-dimethoxyethane, 2-dimethoxyethane, tetrahydrofuran, and 1,3-dioxolane. can be mentioned.

The temperature for washing with an organic solvent is in the range of 50°C to 150°C, preferably 70°C to 100°C. On the other hand, in order to further increase the cleaning efficiency, cleaning may be performed under pressure.

The method of washing with an organic solvent is a method of washing until the organic solvent for washing is no longer colored. The presence or absence of stirring, the number of times of washing, the time, etc. vary depending on the amount of polymer to be washed and the difference in the washing liquid.

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

(i) Examples of alkali metals include Li+ Na, K, etc.; (ii) Examples of alkali metal alloys include Li/
A1 alloy, Li/Hg alloy, Li/Zn alloy, Li/C
Examples include d 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, polyacene, polyvaraphenylene and polyvaraphenylene derivatives, polyacetylene, and the like. Furthermore, (iv) as a composite of an alkali metal or an alkali metal alloy and a conductive polymer, Li/A7! Examples include composites of alloys and the various conductive polymers mentioned above, such as polyvaraphenylene or polyacetylene. Among these, preferred are polyacetylene, polyvaraphenylene, and Li/Aj! Alloy, Li/Aj! Examples include composites of alloys and polyvaraphenylene. The complex herein refers to a homogeneous mixture of an alkali metal or an alkali metal alloy and a conductive polymer, a laminate, and a modified product in which a base component is modified with another component.

The electrodes of the secondary battery of the present invention may be mixed with other suitable conductive materials, such as carbon black, acetylene black, metal powder, metal fibers, carbon fibers, etc., as is well known to those skilled in the art.

In addition, polyethylene, modified polyethylene, polypropylene, poly(tetrafluoroethylene), engineered ethylene-propylene rubber ([!PR), ethylene-propylene-diene polymer (EPDM), sulfonated EPD
It may be reinforced with a thermoplastic resin such as M.

The supporting electrolyte of the electrolytic solution of the secondary battery of the present invention is an alkali metal salt. As the alkali metal of the alkali metal salt,
Mention may be made of the metals Li, Na and K, preferably L
i Metals can be mentioned.

Typical anion components of the supporting electrolyte include, for example, C
1o4-I PFa-+ ASF&-I AgF2-I
5OiCFa-+BP,-, and BR#- (however,
R is an alkyl group or aryl group having 1 to 10 carbon atoms)
etc. can be mentioned.

Specific examples of alkali metal salts as supporting electrolytes include:
LiPF4. Li5bPb, LiCl 041 L
iAsFa.

CF35OiLt, LiBFn, LiB(Bu)
*+ LiB(Et)z(Bu)z.

NaPF6+ NaBF4+ NaAsF&+ NaB
(Bu)*, to B(Bu)a.

KAsF, etc., but are not necessarily limited to these. These alkali metal salts may be used alone or in combination of two or more.

The concentration of the alkali metal salt cannot be categorically defined as it varies depending on the type of oxidized polymer of the aniline 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/l. The electrolyte may be homogeneous or heterogeneous.

Examples of organic solvents used alone or in combination as a solvent for the electrolyte of the secondary battery of the present invention include lactone solvents such as γ-butyl lactone, carbonate solvents such as propylene carbonate, ethylene carbonate, and ether solvents such as 1,2-dimethoxy. Examples include ethane and tetrahydrofuran.

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.

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

(5) Examples Hereinafter, the present invention will be explained in more detail by referring to Examples and Comparative Examples.

Example 1 [Manufacture of oxidized polymer] 400 cc of distilled water that had been deoxygenated in advance and 100 cc of an aqueous solution of 42% HBF were placed in an 11 three-necked flask, and nitrogen gas was bubbled through the flask for about 1 hour while stirring. After that, put the inside of the system under a nitrogen atmosphere, attach a thermometer and a condenser,
The flask was then cooled with water and ice to bring the solution temperature to 15°C. To this was added 2 Q, Q g of aniline. After the succulents were dissolved, 22 g of ammonium persulfate was added at once, and the mixture was reacted for 5 hours while stirring and keeping the inner bath at 25° C. or lower.

After the reaction was completed, the greenish-brown reaction liquid was filtered and dried under vacuum to obtain 15 g of a dark green product.

100 1,2-dimethoxyethane per 1 g of product
After adding cc and stirring at 70°C for 1 hour, the slurry liquid was filtered to collect solid content. Then add a new 100 cc
of 1,2-dimethoxyethane was added and the same operation as above was repeated. When this operation was repeated three times, the coloring of the filtrate almost disappeared.

In this operation, the amount of components dissolved in 1,2-dimethoxyethane was 20% by weight.

[Battery experiment]

The aniline oxidation polymer powder obtained by the above method was treated with NH,O
After removing the BF4 anion by impregnating it in an aqueous H solution, it was press-molded into a disk shape with a diameter of 20 mm by a known method, with lithium as the counter electrode and propylene carbonate distilled and dehydrated according to a conventional method as the electrolyte. , 1.2
- A battery was constructed using a solution of LiPF dissolved in a mixed solvent of dimethoxyethane (volume ratio: 1:1) at a concentration of 2 mol/l.

FIG. 1 is a schematic cross-sectional view of a battery cell for measuring the characteristics of a secondary battery, which is a specific example of the present invention, where 1 is a platinum lead wire for the negative electrode, and 2 is a platinum wire mesh for the negative electrode with a diameter of 20mm and an 8o mesh. Current collector, -3 is a disc-shaped negative electrode with a diameter of 2 (1 + m), 4 is a diameter of 20 m
A circular porous polypropylene diaphragm with a thickness that allows sufficient impregnation with the electrolyte; 5 is a disk-shaped positive electrode with a diameter of 2 Q mm; 6 is a platinum wire mesh current collector for the positive electrode with a diameter of 20 ts and 80 mesos; 7 8 indicates a positive electrode lead wire, and 8 indicates a screw-type Teflon container.

First, the platinum wire mesh current collector 6 for the positive electrode is placed in a Teflon container 8.
Further, the positive electrode 5 is placed on the platinum wire mesh current collector 6 for the positive electrode, the porous polypropylene diaphragm 4 is placed on top of it, and after sufficiently impregnated with the electrolyte, the negative electrode 3 is placed on top of the positive electrode 5.
Further, a platinum wire mesh current collector 2 for a negative electrode was placed on top of the current collector 2, and a Teflon container 8 was tightened to produce a battery.

Using this battery, the polyaniline electrode plate was heated until the lithium ratio reached 1. When the battery was charged with a constant current of On+A and then discharged with a constant current of 1.0 mA until it reached 2■ compared to lithium, the discharge capacity reached the maximum capacity (
The number of repetitions of charging and discharging was 810 times until the cycle life decreased by 70%.

Also, the energy density at the fifth repetition is 138
-・hr/kg, the highest light/discharge efficiency was 100%. When the battery was left charged at room temperature for one month, its self-discharge rate was 6.8%.

[Comparative Example 1] Same as Example 1 except that the aniline oxidized polymer obtained in [Production of oxidized polymer] of Example 1 was washed at 20°C instead of washing with 1,2-dimethoxyethane at 70°C. As a result of conducting a [battery experiment] using exactly the same method, the cycle life was 7
It was 52 times.

Also, the energy density at the fifth repetition is 133 W.
The highest light/discharge efficiency was 98% at hr/kg. Furthermore, when the battery was left charged at room temperature for one month, its self-discharge rate was 12.7%.

[Example 2] Instead of washing the aniline oxidized polymer obtained in [Production of oxidized polymer] in Example 1 with 1,2-dimethoxyethane, a mixed solvent of 1,2-dimethoxyethane and propylene carbonate was used. After washing with (volume ratio 1:1) 1.2-
Electrode molding and [battery experiment] were carried out in exactly the same manner as in the example except for cleaning with dimethoxyethane. Cycle life is 830 times, energy density is 138 Whr
/ kg, the highest light/discharge efficiency was 100%, and the self-discharge rate for one month at room temperature was 5.1%.

Example 3 The aniline oxidized polymer obtained in [Production of Oxidized Polymer] of Example 1 was heated to 140° C. at a pressure of 5 kg/crA and washed, and [Battery Experiment] was conducted. The cycle life was 840 times, the energy density was 138 Whr/kg, the maximum light/discharge efficiency was 100%, and the self-discharge rate for one month at room temperature was 4.9%.

(6) Effects 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 ideal for use in portable devices, electric vehicles, gasoline vehicles, and power storage batteries.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a battery cell for measuring characteristics of a secondary battery, which is a specific example of the present invention.

Claims (1)

[Claims] A polyaniline compound is used for the positive electrode, and (i) an alkali metal, (ii) an alkali metal alloy, (iii) a conductive polymer, (iv) a composite of an alkali metal or an alkali metal alloy and a conductive polymer, or a negative electrode. (v) In a secondary battery using an intercalation compound, the polyaniline compound of the positive electrode is a chemically oxidized polymer of an aniline compound, and the chemically oxidized polymer is washed in advance with an organic solvent under heating. A secondary battery featuring: