JPS63198256A - Secondary battery - Google Patents

Abstract

PURPOSE:To obtain battery performance of high energy density, low self- discharge, high charge and discharge efficiency and long cycle life by obtaining a conductive polymer used for a positive electrode in such a way that a composite polymer is synthesized in the presence of polymer electrolyte and the polymer electrolyte is removed from the synthesized composite polymer. CONSTITUTION:A conductive polymer sued for positive electrode is synthesized in the presence of polymer electrolyte, which is included in the synthesized conductive polymer/polymer electrolyte composite and removed from it. By the arrangement, a secondary battery with high energy density, small self- discharge rate, high charge and discharge efficiency and long cycle life can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a secondary battery that has high energy density, low self-discharge rate, long cycle life, and good charge/discharge efficiency (Coulombic efficiency). Regarding.

[Prior Art] A so-called polymer battery, which uses a polymer compound (conjugated polymer) having a conjugated double bond in its main chain as an electrode, is expected to be a secondary battery with high energy density. There have already been many reports regarding polymer batteries.
For example, P. G. Nigley et al., Journal of the Chemical Society, Chemical Communication, 1979, p. 594 CP, J.
Nigrey et al., J.C.S., Chem, C.
ommun,, 1979.594: l, Journal 0 Electrochemical ψ Society.

1981, p. 1651 (J, Electroch.
em, Soc, 1981゜1B511, A.
G. MacDiarmid et al.

Polymer Preprint, Volume 25, Number 2゜No. 2
48 pages (i984) (A, G, MacDia
rmid et al.

Polyn+er Preprints, 25.
ffi, 2.248 (i984):l, Sasaki et al.
Proceedings of the 50th Conference of the Electrochemical Society, 123 (i983)
, Electrochemical Society Box 50th Conference Abstracts, 228 (i984
), JP 56-138489, JP 59-3870, JP 59-3872, JP 59-3873, JP 59-
2033 [F9 Publication etc. can be mentioned as part of this.

In addition, reports on increasing the functionality of conjugated polymers by polymerizing them in the presence of polymer electrolytes have recently begun to attract attention; for example, Shimizu et al., Proceedings of the 53rd Electrochemical Society of Japan Conference, D121
(i98G), a polymer of polypyrrole and a polymer electrolyte, Hyodo, etc., in the Proceedings of the Society of Polymer Science and Technology.

35, ND, 3.612 (i98B), reports on a polymer of polyaniline and polystyrene sulfonic acid.

[Problems to be solved by the invention] Polymer batteries using conjugated polymers as electrodes have problems such as (i) high energy density, (i1) low self-discharge, (iii) commercial/discharge efficiency, and (IV) long cycle. I haven't been able to find anything that satisfies longevity at the same time.

In order to obtain a secondary battery that satisfies the above four battery performances at the same time, the present inventors conducted various studies on electrode materials, and as a result, synthesized a conductive polymer in the presence of a polymer electrolyte.
We have discovered that a conductive polymer/polyelectrolyte composite polymer from which the polymer electrolyte has been removed is extremely effective as an electrode material.

The present invention was made based on the above-mentioned discovery, and has excellent battery characteristics including (i) high energy density, (i1) low self-discharge, (+11) commercial/discharge efficiency, and (IV) long cycle life. The purpose is to provide secondary batteries.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the gist thereof is that the positive electrode is made of a conductive polymer, the negative electrode is made of (i) an alkali metal, (it) an alkaline earth metal. In a secondary battery consisting of an alloy, (iii) a conductive polymer, or (iv) a composite of a conductive polymer and an alkali metal or alkaline earth alloy, and a non-aqueous electrolyte, the conductive polymer of the positive electrode is The secondary battery is synthesized in the presence of a polymer electrolyte, and the polymer electrolyte is removed from the synthesized conductive polymer/polymer electrolyte composite polymer.

[Specific structure and operation of the invention] The present invention will be explained in detail below.

The conductive polymer used in the positive electrode of the secondary battery of the present invention is not particularly limited as long as it has a conjugated double bond in its main chain, but specific examples include polyacene, polyacenoacene, polyacetylene, polyaniline. , polycarbazole, polydiacetylene, polyfuran, poly(i
, 6-hebutadiene), polyisothianaphthene, polyparaphenylene, polyparaphenylene sulfide, poly-berynaphthalene, polypyridazine, polypyrrole,
Mention may be made of polyquinoline, polyselenophene, polythiophene, poly-(triphenylmethane) and derivatives thereof.

The above conductive polymer is synthesized in the presence of a polymer electrolyte, and the polymer electrolyte used has a number average molecular weight of 20
There is no particular restriction as long as it is 0 or more and contains at least one carboxyl anion, sulfoxyl anion and/or sulfate anion in the molecule.

Generally, those expressed by the following general formula are used.

(Left space below) = 5- or -so -, and a and b are 0 or to Specific examples of these polymer electrolytes include polyacrylic acid anions, polymethacrylic acid anions, and polymethacrylic acid anions having a number average molecular weight of 200 or more. Examples include polyvinylsulfonate anion, polyallylsulfonate anion, polystyrenesulfonate anion, and the like.

The conductive polymer used in the positive electrode of the secondary battery of the present invention can be obtained by chemically or electrochemically polymerizing a monomer solution by a known method in the presence of a polymer electrolyte.

There is no particular limit to the amount of the above-mentioned polymer electrolyte used during the synthesis of the conductive polymer, but it is usually 10% of the conductive polymer monomer.
When adding 1 to 500 parts by weight, preferably 2 to 200 parts by weight, of the polymer electrolyte to the polymerization solution based on 0 parts by weight, it is preferable that the polymer electrolyte is dissolved in the polymerization solution, but it is preferable that the polymer electrolyte be dissolved in the polymerization solution. It doesn't matter if it's in any condition.

The conductive polymer synthesized by the above method is obtained in a composite state with a polymer electrolyte. In the present invention, it is necessary to remove the entrapped polyelectrolyte again. Although various methods can be considered for removing the polymer electrolyte, it is usually carried out by compensating the obtained conductive polymer/polymer electrolyte composite with a basic solution.

As the base used for this compensation, inorganic bases such as aqueous ammonia, sodium carbonate, potassium hydroxide, and sodium hydroxide, and organic bases such as lower aliphatic amines such as triethylamine can be used.

After compensation, the conductive polymer is thoroughly washed with distilled water and then dried.

It is preferable to use the conductive polymer obtained in this way after washing it in advance with a nonaqueous solvent used in an electrolytic solution, such as 1,2-dimethoxyethane or 2-methyltetrahydrofuran.

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

(i) Examples of alkali metals include Li, Na, etc. (i1) Examples of alkali metal alloys include Li/Aj
) alloy, Li/Hg alloy, Li/Zn alloy, Li/
Cd alloy, Li/Sn alloy, L1/pb alloy, Na/P
b alloys and alloys of three or more metals containing alkali metals used in these alloys, such as Ll/Aρ/Mg
, Li/AΩ/Sn, Li/AΩ/Pb, LI/A
Ω/Zn.

Examples include Ll/Aρ/Hg.

These alloys may be manufactured by either an electrochemical method or a chemical method, but those alloyed electrochemically are more preferable.

Examples of the conductive polymer (iii) include polypyrrole, polypyrrole derivatives, polythiophene, polythiophene derivatives, polyquinoline, polyacene, polyparaphenylene, polyparaphenylene derivatives, polyacetylene, and the like. Furthermore, (iv) as a complex of an alkali metal or an alkali metal alloy and a conductive polymer, L
Examples include composites of i/AN alloys, Na/Pb alloys, and the various conductive polymers described above, such as polyparaphenylene or polyacetylene. Among these, preferred examples include a composite of polyacetylene and Li/AΩ alloy, a composite of polyparaphenylene and Lj/Al11 alloy, and a composite of polyparaphenylene and Na/pb alloy. The composite referred to here is a homogeneous mixture of an alkali metal or alkali metal alloy and a conductive polymer.
It means a modified product in which a component forming a laminate and a group-9= body 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, and carbon fibers, as is well known to those skilled in the art. . In addition, polyethylene, modified polyethylene, polypropylene, polytetrafluoroethylene, ethylene-propylene-diene terpolymer (EP
DM) or a thermoplastic resin such as sulfonated EPDM.

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 Ll, Na and K, with the metal L1 being particularly preferred.

Typical anion components of the supporting electrolyte include, for example, C
I! O-1PF6-1AsF6-1AsF-1SO
Examples thereof include CF-1BF-5 and BR4 (wherein R is an alkyl group or aryl group having 1 to 10 carbon atoms).

As the alkali metal salt as a supporting electrolyte, for example, L
i PF6, Li Sb F6, Li CΩ04, Li
AsF6, CF35O3L1, LiBF4, Li B
(Bu)4, LI B (Et)2 (Bu)2, N
a P F e , N a B F 4 , N a
A s F e , Na B (Bu)4, K B
Examples include (Bu)4, K As Fe, 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 unconditionally defined because it varies depending on the type of material used for the positive and negative electrodes, the type of cathode, charging conditions, operating temperature, type of supporting electrolyte, type of organic solvent, etc., but in general is preferably within the range of 0.5 to 10 mol/g. The electrolyte may be homogeneous or heterogeneous.

Examples of organic solvents that can be used alone or in combination as a solvent for the electrolytic solution of the secondary battery of the present invention include the following.

Alkylene nitrile, crotonitrile, (liquid range -51.1°C to 120°C) trialkyl borate, trimethyl borate, (CH30)3B (liquid range -29.3°C to 67°C) tetraalkyl silicate side, tetramethyl silicate, (CH30) 4St
(boiling point 121°C) nitroalkane side, nitromethane, CH3NO2 (liquid range -17°C to 100.8°C) alkyl nitrile: e.g., acetonitrile, CH3CN (liquid range -45°C to 81.6°C) dialkylamide side, Dimethylformamide, HCON(CH3)2 (liquid range -80,48℃~149℃) (liquid range
-16℃~202℃) Monocarboxylic acid esters: e.g., ethyl acetate (liquid range)
-83,6 to 77.06℃) Orthoester: e.g., trimethyl orthoformate, Lactone: e.g., γ-butyrolactone, dialkyl carbonate, dimethyl carbonate, OC(OCH3)2 (liquid range 2℃ to 90℃) Alkylene carbonate side, propylene carbonate, (liquid range -48℃~242℃) Monoether: e.g., diethyl ether, (liquid range -
1168C~34.5℃) Polyether: Example, 1,1-
and 1,2-dimethoxyethane (liquid range -113,2°C to 64,5°C and -58°C to 83°C, respectively)
°C) Cyclic ether diside, tetrahydrofuran (liquid range -65°C to 67°C) = 1.3-dioxolane (liquid range -95°C to 78°C) nitroaromatic diside, nitrobenzene (liquid range 5.7°C) ℃～210.8℃) Aromatic carboxylic acid halide side, benzoyl chloride (
Liquid range: 0°C to 197°C), benzoyl bromide (liquid range: -24°C to 218°C) Aromatic sulfonic acid halide: e.g., benzenesulfonyl chloride (liquid range:
14.5°C to 251'C) Aromatic phosphonic acid halide: e.g., benzenephosphonyl dichloride (boiling point 258°C) aromatic thiophosphonic acid dino-10 halide, benzene thiophosphonyl dichloride (melting point 22°C), 3- Methylsulfolane (melting point -1°C) Alkyl sulfonic acid halides: Examples, methane sulfonyl chloride (boiling point 181°C) Alkyl carboxylic acid halides Examples, acetyl chloride (liquid range -1129°C to 50.9°C), acetyl bromide ( liquid range -966C to 76C), propionyl chloride (liquid range -94C to 80C) saturated heterocyclic compounds: e.g., tetrahydrothiophene (liquid range -96C
~121°C): 3-Methyl-2-oxazolidone (melting point 15.9°C) -15= dialkyl sulfamic acid halide: e.g., dimethyl sulfamyl chloride alkyl halosulfonate diside, ethyl chlorosulfonate (boiling point 151°C) Two unsaturated heterocyclic carboxylic acid halides, 2-furoyl chloride (liquid range -2°C to 173°C), two three-membered unsaturated heterocyclic compounds, 1-methylpyrrole (boiling point 114°)
C), 2,4-dimethylthiazole (boiling point 144°C)
, furan (liquid range - 85.85°C to 31.36°C), esters and/or dibasic carboxylic acid esters: e.g., ethyl oxalyl chloride (boiling point 135°C), mixed alkylsulfonic acid halides/carboxylic acids Acid halides; e.g., chlorosulfonylacetyl chloride (boiling point 98°C at pressure 10r++ mHg) dialkyl sulfoxide diside, dimethyl sulfoxide (liquid range 18.4°C to 189°C) dialkyl sulfate diside, dimethyl sulfate (liquid range -
31.75℃~188.5℃) Dialkyl sulfite side, dimethyl sulfide (boiling point 126℃) Alkylene sulfide: e.g., ethylene glycol
Sulfide (liquid range -11℃~173℃) Halogenated alkane diside, methylene chloride (liquid range -
95°C to 40°C) 1,3-dichloropropane (liquid range -99,58°C to 120.4°C) Among the above, preferred organic solvents are sulfolane, crotonitrile, nitrobenzene, tetrahydrofuran, methyl-substituted tetrahydrofuran, = 17 - 1.3-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 preferably propylene carbonate and 1.
Examples include 2-dimethoxyethane and a mixed solvent of sulfolane and 1,2-dimethoxyethane.

Because they appear to be the most chemically inert toward battery components and have a wide liquid range, they particularly allow for highly and efficient use of cathode active materials. It is from.

The charging method for the secondary battery of the present invention is not particularly limited, but usually methods such as (i) constant current method, (i1) constant voltage method, (ii>pulsed current method, and (i■) pulsed voltage method) A method combining these methods is also used.

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 reduce 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.

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

Example 1 Production of conductive polymer used for positive electrode> 40 ml of deoxygenated distilled water was placed in an electrolytic cell equipped with a reference electrode in advance.
．． 2 g of aniline, polyvinyl sulfate (number average molecular weight approximately 1
0,000) 15 cc of 30% aqueous solution was added. Two platinum electrodes of 25 ct each were inserted into this aqueous solution at an interval of 2 cm, and then electrolyzed at 0.90 V based on a saturated calomel electrode. At this time, a dark green oxidized polymer was deposited on the anode plate. The coated anode was repeatedly washed three times with distilled water;
After air drying, the produced aniline oxidized polymer was peeled off from the platinum plate. This exfoliated oxidized aniline polymer was crushed in a mortar, stirred in 28% ammonia water overnight, and then the ammonia water was removed and washed with excess distilled water.
It was vacuum dried at 'C for 5 hours.

The obtained blue-violet powder was heated under a nitrogen atmosphere with an excess of 1.2-
It was washed with dimethoxyethane and vacuum dried at 150°C for 5 hours.

Elemental analysis values of the oxidized polymer before and after ammonia compensation revealed that 23% by weight of polyvinyl sulfate was removed during polymerization by ammonia compensation.

<Battery experiment> The polyaniline powder obtained by the above method was pressure-molded into a disc shape with a diameter of 20 mm by a known method, and a disc shape with a diameter of 20 m cut out from lithium foil (thickness 200 μm) was used.
A battery was constructed using the disk-shaped disks of m as positive and negative electrode active materials, respectively.

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, in which 1 is a nickel lead wire for the negative electrode, 2 is a negative electrode nickel network aggregate with a diameter of 20+ nm and 80 meshes. , 3 is a negative electrode with a diameter of 20 mm, 4 is a diameter of 2
A circular porous polypropylene membrane with a diameter of 0 mm is thick enough to be sufficiently impregnated with an electrolytic solution, 5 is a disk-shaped positive electrode with a diameter of 20 mm, and 6 is a diameter of 20 mm.

80 mesh positive electrode platinum wire mesh current collector, 7 is positive electrode lead wire,
8 indicates a screw-type polytetrafluoroethylene container.

First, the positive electrode platinum wire mesh current collector 6 is placed in the lower part of the recess of the container 8, the positive electrode 5 is stacked on top of the positive electrode platinum wire mesh current collector 6, and the porous polypropylene diaphragm 4 is stacked on top of the positive electrode platinum wire mesh current collector 6. After sufficiently impregnating with the liquid, the negative electrode 3 was stacked, the negative electrode nickel mesh current collector 2 was further placed on top of the negative electrode 3, and the container 8 was tightened to produce a battery.

The electrolyte was 2 mol/ρ of Li As F6 dissolved in propylene carbonate distilled and dehydrated according to a conventional method.
A solution was used.

Using the battery prepared in this way, under a constant current (i,
25mA/cJ), battery voltage 2.0V to 4. Charge and discharge were repeated within the OV range.

As a result, the discharge capacity per unit weight of positive and negative electrode active materials was 46
0Wφhr/kg, and the number of cycles until the discharge capacity decreased to 50% of the maximum discharge capacity (hereinafter referred to as 'cycle life') was 350.Furthermore, when the battery was left charged for one week, , its self-discharge rate is 3.
It was 8%.

Comparative Example 1 42% by weight HBF instead of polyvinyl sulfuric acid aqueous solution
Polyaniline was synthesized in exactly the same manner as in Example 1, except that 10 ml of the 4 aqueous solution was added, and this was similarly compensated with ammonia to form an electrode and conduct a battery experiment. As a result, the maximum discharge capacity of the battery is 280 W-hr/kg,
The cycle life is 230 times, and the self-discharge rate after 1 week is 1
It was 0.4%.

Example 2 Instead of the polyvinyl sulfuric acid aqueous solution, a 30% aqueous solution of polystyrene sulfonic acid (number average molecular weight approximately 20,000) 3
A battery experiment was conducted in exactly the same manner as in Example 1 except that 0 cc was used.

As a result, the maximum discharge capacity of the battery is 420W・hr/k
The g-cycle life was 380 times, and the self-discharge rate after one week was 3.5%.

Example 3 The procedure was exactly the same as Example 1, except that in <manufacture of conductive polymer used for the positive electrode>, pyrrole was used instead of aniline, and a 30% aqueous solution of potassium polyvinyl sulfate was used instead of a 30% aqueous solution of polyvinyl sulfate. We produced polypyrrole and conducted battery experiments.

As a result, the maximum discharge capacity is 380 W-hr/kg1
Cycle life 280 times, self-discharge rate after 1 week is 7.3
%Met.

Comparative Example 2 Polypyrrole was produced in the same manner as in Example 1 except that pyrrole was used instead of aniline and 5 g of sodium chloride was used instead of the polyvinyl sulfuric acid aqueous solution in <Production of conductive polymer used for positive electrode>, and a battery was prepared. We conducted an experiment.

As a result, the maximum discharge capacity is 200 W-hr/kg-
Cycle life is 270 times, self-discharge rate after 1 week is 20.
It was 8%.

-23 = Examples 4 to 6 Battery experiment> A battery experiment was conducted in exactly the same manner as in Example 1 except that the negative electrode material shown in Table 1 was used instead of lithium. The results are shown in Table 1.

(Left below) [Effects of the Invention] As described above, the secondary battery of the present invention has a positive electrode made of a conductive polymer, a negative electrode made of (i) an alkali metal, (i1) an alkali metal alloy, and (iii) a conductive polymer. In a secondary battery consisting of a molecule or (IV) a complex of a conductive polymer and an alkali metal or an alkali metal alloy, and a non-aqueous electrolyte, the conductive polymer of the positive electrode is synthesized in the presence of a polymer electrolyte. Since the polymer electrolyte is removed from the synthesized conductive polymer/polymer electrolyte composite polymer, it is a good battery with high energy density, low self-discharge rate, and long cycle life. In addition, the secondary battery of the present invention is lightweight,
Because it is small and has high energy density, it is ideal for 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 for measuring characteristics of a secondary battery, which is a specific example of the present invention. 1... Nickel lead wire for negative electrode 2... Nickel mesh current collector for negative electrode = 26- 3... Negative electrode 4... Porous polypropylene diaphragm 5... Positive electrode 6... For positive electrode Platinum mesh current collector 7...positive electrode lead wire

Claims (1)

[Claims] 1. The positive electrode is a conductive polymer, the negative electrode is (i) an alkali metal,
(ii) alkali metal alloy, (iii) conductive polymer,
or (iv) in a secondary battery comprising a composite of a conductive polymer and an alkali metal or an alkali metal alloy, and a non-aqueous electrolyte, the conductive polymer of the positive electrode is synthesized in the presence of a polymer electrolyte, A secondary battery characterized in that the polymer electrolyte is removed from the synthesized conductive polymer/polymer electrolyte composite polymer.