JPH056764A - Secondary battery - Google Patents

Abstract

PURPOSE:To provide a secondary battery having a large capacity and a high energy density in which the manufacture of a positive electrode material is easy, compared with other positive electrode materials requiring pressure mold ing, because it can be manufactured with a simple method such as application. CONSTITUTION:A conductive polymer composite consisting of (A) polyaniline and at least one selected from the group consisting of simple polymers, block copolymers, and random copolymers of (B) alkylene oxide monomer, and cross- linked bodies obtained by cross-linking them, and at least one selected from the group consisting of anions, alkali metal salts and alkaline earth metal salts of (C) protonic acid is used as a positive electrode active material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a secondary battery.

[0002]

2. Description of the Related Art Recently, as electronic devices have become smaller, thinner and lighter, similar demands have been made for batteries used as power sources. In particular, a lithium secondary battery with high voltage, which uses an electrochemically active conductive polymer material such as polypyrrole, polyaniline, or polyacetylene as a positive electrode material, is a powerful battery for achieving this demand. Is attracting attention as. Among them, a battery using polyaniline as a positive electrode material has been attracting attention as a battery having a large discharge capacity and an excellent repeated charge / discharge life.

However, in the conventional secondary battery using polyaniline, although a relatively satisfactory result has been obtained for a battery having a small discharge current of several mA, a battery having a discharge current of several tens to several hundreds mA. However, there is a problem in that sufficient capacity cannot be obtained for the size of the positive electrode material in the case of designing. This is considered to be because, when a large-capacity battery is designed, the thickness of the positive electrode material is correspondingly increased, and diffusion of electrolyte anions into the positive electrode material is rate-determining.

An object of the present invention is to provide a secondary battery having a large capacity and a high energy density, which can solve the problems of the conventional positive electrode material as described above.

[0005]

The secondary battery of the present invention comprises:
(A) polyaniline, (B) alkylene oxide monomer homopolymer, block copolymer, random copolymer and at least one selected from the group consisting of crosslinked products obtained by crosslinking them, and ( C) A conductive polymer composition comprising at least one selected from the group consisting of anions of protonic acids, alkali metal salts and alkaline earth metal salts is used as a positive electrode active material.

In the conductive polymer composition used as the positive electrode material in the secondary battery of the present invention, the component (A) and the component (B) are molecularly dispersed to form a polymer alloy,
Further, the component (C) is doped. Therefore, it has a structure in which the positive electrode active material and the electrolyte are substantially molecularly dispersed, has a low interfacial resistance, and promptly diffuses anions. Therefore, the secondary battery of the present invention has a large capacity and high capacity. Energy density is achieved.

In the present invention, "doping" means adding the component (C) to the component (A), the component (B), or the complex of the components (A) and (B) to form a complex.
That.

The polyaniline of the component (A) used in the present invention is obtained by dispersing or dissolving aniline in a solvent such as water or methanol, and ammonium persulfate, hydrogen peroxide, or dioxide in the presence of a protic acid such as sulfuric acid or hydrochloric acid. It can be easily obtained by adding an oxidizing agent such as manganese and polymerizing it to obtain a doped polyaniline, and further dedoping the polyaniline with a base such as ammonia and sodium hydroxide. Furthermore, reduced polyaniline obtained by treating deanidized polyaniline with a reducing agent such as hydrazine, phenylhydrazine, or hydrazine hydrochloride can also be preferably used. In particular, the latter reduced polyaniline is preferable when the secondary battery is composed of a non-aqueous system.

The alkylene oxide polymer as the component (B) or a crosslinked product thereof is a homopolymer, a block copolymer, a random copolymer of an alkylene oxide monomer or a crosslinked product obtained by crosslinking them. Usually, a polymer obtained by subjecting an active hydrogen compound to an alkylene oxide addition (ring-opening) polymerization reaction as described below, or a polymer obtained by subjecting the polymer to a crosslinking reaction using a suitable crosslinking agent. is there.

As the active hydrogen compound, monohydric alcohols such as methanol and ethanol, ethylene glycol,
Propylene glycol, 1,4-butanediol and other dihydric alcohols, glycerin, trimethylolpropane, sorbitol, sucrose, polyglycerin and other polyhydric alcohols, monoethanolamine, ethylenediamine, diethylenetriamine, 2-ethylhexylamine, hexa Examples include amines such as methylenediamine, compounds containing phenolic active hydrogen such as bisphenol A and hydroquinone.

The alkylene oxide monomers include ethylene oxide, propylene oxide, 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane. 2 to 9 carbon atoms such as 1,2-epoxynonane
Α-Olefin oxide, and α having 10 or more carbon atoms
-Olefin oxide, styrene oxide and the like can be used, but ethylene oxide, propylene oxide and 1,2-epoxybutane are particularly preferable.

In the polymerization reaction, basic catalysts such as sodium methoxide, sodium hydroxide, potassium hydroxide, lithium carbonate, triethylamine, potassium-t-butoxide and acidic catalysts such as perchloric acid and boron trifluoride are used. Especially, a basic catalyst is preferably used.

The number average molecular weight of the alkylene oxide polymer is preferably 100 to 20,000.

Examples of the method for crosslinking the alkylene oxide polymer include isocyanate crosslinking and ester crosslinking.

As the cross-linking agent used for each cross-linking, in the case of isocyanate cross-linking, for example, 2,4-tolylene diisocyanate (2,4-TDI) or 2,6-tolylene diisocyanate (2,6-TDI) is used. , 4, 4 '
-Diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, lysine ester triisocyanate, 1,8-diisocyanate-4-isocyanate methyl octane, 1,6,11-undecane triisocyanate, 1,3,6- Hexamethylene triisocyanate, triphenylmethane diisocyanate, tris (isocyanatophenyl) thiophosphate, bicycloheptane triisocyanate, burette-bonded HMD
I, isocyanurate-bonded HMDI, trimethylolpropane TDI 3 mol adduct, or a mixture thereof. In the case of ester crosslinking, for example, malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, phthalic acid Polycarboxylic acids such as acids, isophthalic acid, terephthalic acid, itaconic acid, trimellitic acid, pyromellitic acid and dimer acid; monomethyl ester, dimethyl ester, monoethyl ester, diethyl ester, monopropyl ester of these polyvalent carboxylic acids, Lower alkyl esters such as dipropyl ester, monobutyl ester and dibutyl ester; and acid anhydrides of the above polyvalent carboxylic acids.

When isocyanate crosslinking is carried out, the reaction is carried out, for example, by mixing isocyanates and an alkylene oxide polymer in the NCO / OH equivalent ratio range of 1.5 to 0.5, and at a temperature of 80 to 150 ° C. Do it for 5 hours.

When ester cross-linking is performed, the reaction (for example, esterification reaction or transesterification reaction)
Is, for example, a mixture of an alkylene oxide polymer and a polyvalent carboxylic acid, a lower alkyl ester thereof, or an acid anhydride thereof at a functional ratio of 1: 2 to 2: 1 and a temperature of 120.
It is carried out under the conditions of ˜250 ° C. and 10 ^{−4 -10} Torr.

The conductive polymer composition used as the positive electrode material in the present invention is, for example, the component (A) and the component (B).
Dimethyl sulfoxide, which is a common solvent for these components,
It is obtained by dissolving in dimethylformamide, N-methyl-2-pyrrolidone or the like to form a complex composed of the components (A) and (B), and doping the complex with the component (C). However, the method of doping the component (C) is
As will be described later, various embodiments are possible and can be carried out either before complex formation or after complex formation.

When undoped polyaniline which has not been subjected to reduction treatment is used as the component (A), a complex is formed by the above-mentioned method and then a protic acid such as perchloric acid, sulfuric acid or paratoluenesulfonic acid is used. It is possible to dope the component (C) by immersing this composite in.

Further, in the electroconductive polymer composition used in the present invention, since the alkylene oxide polymer or its crosslinked product is compounded as the component (B), an alkali metal salt or an alkaline earth metal salt ( It is possible to dope the component (B) by using it as the component C). When the component (B) is doped with these salts, either before or after the formation of the complex of the component (A) and the component (B) is possible.

When the alkylene oxide polymer is used as the component (B) and the component (C) is doped before forming the complex, acetone, methanol, tetrahydrofuran or the like,
A method of using a common solvent for the component (B) and the component (C), mixing them, and then distilling the solvent off can be used. (B) a crosslinked product of an alkylene oxide polymer
When the component (C) is doped as a component, it is possible to dissolve the component (C) in the above-mentioned solvent and immerse the component (B) in this solution.

When the component (C) is doped after forming the complex, it can be done by immersing the complex in a solution of the component (C).

The alkali metal salt or alkaline earth metal salt with which the component (B) is doped is not particularly limited, but examples thereof include LiI, LiCl, LiClO ₄ , LiSCN and L.
iBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF
₃ CO ₂ , LiHgI ₃ , NaI, NaSCN, NaB
r, CaCl ₂ , Ca (SCN) ₂ , Ca (ClO ₄ ).
_{2 and the} like are preferable.

As described above, the degree of freedom in the method for producing the conductive polymer composition as the positive electrode material used in the present invention is high. Among these methods, the reduced polyaniline is used as the component (A), the alkylene oxide polymer is used as the component (B), and the components (A) and (B) are dissolved in a common solvent, and the solution is appropriately prepared. After coating the substrate or immersing the substrate in the solution, it is heated and dried to form a composite film of the components (A) and (B), and the composite film is dipped in a solution of an alkali metal salt. The conductive polymer composition obtained by doping becomes a suitable positive electrode material.
Also, if the above-mentioned crosslinking agent is added at the time when the components (A) and (B) are dissolved in a common solvent, the alkylene oxide polymer will be crosslinked in the next drying step. The composition is also a suitable positive electrode material.

The proportion of the component (A) in the conductive polymer composition as the positive electrode material of the present invention is 20 to 95% by weight, preferably 30 to 90% by weight. The proportion of the component (B) is 5 to 80% by weight, preferably 10 to 70% by weight. The ratio of the component (C) to the composite of the component (A) and the component (B) is preferably 0.01 to 20% by weight.

As the cathode material of the secondary battery of the present invention, polyacetylene, polythiophene, metallic lithium, lithium-aluminum alloy and the like are preferably used.

As the electrolyte to be interposed between the electrodes, a solvent such as propylene carbonate, α-butyl lactone, ethylene carbonate, tetrahydrofuran, ethylene carbonate, dimethyl sulfoxide, dioxolane, etc.,
Or liquid substances such as liquid low molecular weight polyethylene oxide, polypropylene oxide or copolymers thereof, L
iI, LiCl, LiClO ₄ , LiSCN, LiBF
₄ , a liquid electrolyte in which a salt such as LiAsF ₆ or LiCF ₃ SO ₃ is dissolved is used. Furthermore, an ion conductive solid polymer electrolyte in which the above salt is dissolved in a polymer substance such as polyethylene oxide, polypropylene oxide, polyethylene sulfide, poly-β-propiolactone, polyethylene succinate, or a cross-linked product thereof is used. ..

In the secondary battery of the present invention, as a positive electrode material, polyaniline and an alkylene oxide polymer or a crosslinked product thereof are molecularly dispersed to form a polymer alloy, and a conductive material further doped with an alkali metal salt or the like. The polymer composition is used. Therefore, it has a structure in which the positive electrode active material and the electrolyte are substantially molecularly dispersed, has a low interfacial resistance, and promptly diffuses anions. Therefore, the secondary battery of the present invention has a large capacity and high capacity. Energy density is achieved.

The composite of polyaniline used in the present invention and the alkylene oxide polymer or a crosslinked product thereof is a film having excellent mechanical strength formed by removing the solvent from the solution by heating or drying. Therefore, the reliability of the positive electrode is also high.

[0030]

EXAMPLE An example of synthesizing polyaniline is shown below.

Synthesis Example 1 (synthesis of dedoped polyaniline) 20 g of aniline and 18 ml of hydrochloric acid were placed in a 1 liter four-necked flask equipped with a stirrer, thermometer, cooling tube and dropping funnel.
And 250 ml of water were added. After cooling this to 0 ° C., a solution prepared by dissolving 49 g of ammonium persulfate in 120 g of water was added dropwise from a dropping funnel over 4 hours. After completion of dropping, the mixture was further stirred for 1 hour, the precipitated solid was separated by filtration, washed with water, and then washed with methanol until the filtrate became transparent. Next, this solid was dispersed in 500 ml of 4N aqueous ammonia and stirred for 4 hours. After completion of stirring, the solid was filtered off, washed with water until the filtrate became neutral, and then washed with methanol until the filtrate became transparent. The filtered solid was dried under vacuum to obtain 10.2 g of dark brown dedoped polyaniline. This was soluble in N-methyl-2-pyrrolidone.

Synthesis Example 2 (Synthesis of Reduced Polyaniline) 2 g of the undoped polyaniline obtained in Synthesis Example 1 was N-
It was dissolved in 98 g of methyl-2-pyrrolidone, and 0.8 g of phenylhydrazine was added to this solution. After the reaction was completed, the solid was reprecipitated with acetone, the precipitated solid was separated by filtration, washed with acetone, and then dried to give the gray title polyaniline 1.6.
g was obtained.

Next, a synthesis example of an alkylene oxide polymer will be shown.

Synthesis Example 3 (Synthesis of alkylene oxide polymer B-2) Using 212 g of diethylene glycol as a starting material and 12 g of potassium hydroxide as a catalyst, ethylene oxide 1,8
94 g and 1,894 g of propylene oxide were reacted in a 5 liter autoclave at 120 ° C. for 8 hours and then desalted and purified to give a number average molecular weight of 4,000.
3,980 g of an ethylene oxide-propylene oxide random copolymer (calculated from a hydroxyl value) was obtained.

Synthesis Example 4 (Synthesis of alkylene oxide polymer B-4) Using 184 g of glycerin as a starting material, 12.0 g of potassium hydroxide as a catalyst, and 3,816 g of ethylene oxide.
Was reacted in a 5 liter autoclave at 130 ° C. for 4 hours and then desalted and purified to give a number average molecular weight of 2.
3,000 (calculated from the hydroxyl value) of ethylene oxide homopolymer (3,940 g) was obtained.

Synthesis Example 5 (Synthesis of alkylene oxide polymer B-6) Using 92 g of glycerin as a starting material and 10 g of potassium hydroxide as a catalyst, 2,454 g of ethylene oxide and 2,454 g of propylene oxide were added to 120 g in a 10-liter autoclave. After reacting at 8 ° C. for 8 hours, desalting and purification were carried out to obtain 4,990 g of an ethylene oxide-propylene oxide random copolymer having a number average molecular weight of 5,000 (calculated from a hydroxyl value).

Synthesis Example 6 (Synthesis of Alkylene Oxide Polymer B-7) Using 92 g of glycerin as a starting material and 21 g of potassium hydroxide as a catalyst, 1,382 g of ethylene oxide and 5,526 g of propylene oxide were added to 120 g in a 10-liter autoclave. After reacting at 8 ° C for 8 hours, desalting and purification were carried out to obtain 6,990 g of an ethylene oxide-propylene oxide random copolymer having a number average molecular weight of 7,000 (calculated from a hydroxyl value).

Table 1 shows examples of alkylene oxide polymers which can be used in the present invention.

[0039]

[Table 1]

Example 1 0.5 g of reduced polyaniline obtained in Synthesis Example 2 and Synthesis Example 4
0.5 g of the alkylene oxide polymer (B-4) obtained in the above was dissolved in 9.5 g of N-methyl-2-pyrrolidone to obtain a uniform solution. This solution was applied to a stainless steel woven fabric (1 cm in diameter) and then dried at 150 ° C. for 30 minutes.
After drying, it was immersed in a methanol solution of LiBF ₄ (2 mol / liter) for 20 hours, and then at 80 ° C. for 10 ⁻² Torr.
And dried for 10 hours to obtain a positive electrode material.

Using this positive electrode material, a polypropylene porous membrane as a separator, Li foil as the negative electrode, and a propylene carbonate solution of LiBF ₄ (3 mol / liter) as the electrolyte, the test cell shown in FIG. 1 was prepared. 5,
Battery characteristics were measured by charging / discharging at a constant current of mA / cm ² .

In FIG. 1, 11 and 15 are current collectors.
Reference numeral 12 is a positive electrode, 13 is a separator and an electrolyte, 14 is a negative electrode, 16 is a positive electrode lead wire, and 17 is a negative electrode lead wire.

Example 2 To prepare a positive electrode material, N-methyl-2-pyrrolidone solution was mixed with tolylene diisocyanate so that NCO was 1 with respect to OH of the alkylene oxide polymer (NCO / OH equivalent ratio 1.0). The battery characteristics were evaluated in the same manner as in Example 1 except that the addition was made.

Example 3 In the same manner as in Example 1 except that the alkylene oxide polymer was changed to B-6 obtained in Synthesis Example 5 and the addition amount was changed to 0.2 g when the positive electrode material was prepared, The battery characteristics were evaluated.

Example 4 When preparing the positive electrode material, 0.5 g of the undoped polyaniline obtained in Synthesis Example 1 and 0.6 g of the alkylene oxide polymer B-7 previously doped with 0.05 g of LiClO ₄ were used. The battery characteristics were evaluated in the same manner as in Example 1 except for the above.

Comparative Example 1 Using a stainless steel woven cloth as an electrode, electrolytic polymerization was carried out in an aqueous solution containing 1 mol / l of aniline and 2 mol / l of HBF ₄ at a constant current of ² mA / cm ² to obtain a polyaniline electrode. The battery characteristics were measured in exactly the same manner as in Example 1 except that this was used as the positive electrode material.

Comparative Example 2 10 mg of 15 mg of the reduced polyaniline powder obtained in Synthesis Example 2 was used.
The battery characteristics were evaluated in the same manner as in Example 1 except that a thin film was formed by pressure molding at 0 kg / cm ² and this was used as the positive electrode material.

Table 2 shows the evaluation results of the battery characteristics in Examples 1 to 4 and Comparative Examples 1 and 2.

[0049]

[Table 2]

[0050]

The secondary battery of the present invention has a large capacity and a high energy density. Further, the positive electrode material of the secondary battery of the present invention,
Since it can be manufactured by a simple method such as coating, it is easier to manufacture than other positive electrode materials that require pressure molding or the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a test cell for evaluating the characteristics of the secondary battery of the present invention.

[Explanation of symbols]

 11 Current collector 12 Positive electrode 13 Separator and electrolyte 14 Negative electrode 15 Current collector 16 Positive electrode lead wire 17 Negative electrode lead wire

Claims (1)

Claims: 1. A polyaniline (A), a homopolymer of (B) an alkylene oxide monomer, a block copolymer, a random copolymer, and a crosslinked product obtained by crosslinking them. At least one selected from the group, and (C) a conductive polymer composition comprising at least one selected from the group consisting of anions of protonic acids, alkali metal salts and alkaline earth metal salts as a positive electrode active material The secondary battery used.