JP3349191B2 - Battery electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a battery using a conductive polymer, and more specifically, a backup power supply such as a power supply for driving electronic products such as a computer and a telephone, a backup power supply for a memory, an automobile and a motorcycle, and the like. Mobile power, or nuclear power, solar cells, wind power,
The present invention relates to a battery electrode used for a power storage power supply for storing power obtained by hydroelectric power generation or the like.

[0002]

2. Description of the Related Art Conventionally, as a battery using a conductive polymer as a positive electrode active material, a lithium secondary battery using lithium as a negative electrode active material is well known. In the battery, in the positive electrode using the conductive polymer, the supporting electrolyte ions are taken in at the time of charging, and the supporting electrolyte ions are released at the time of discharging. In the case of a lithium negative electrode, lithium is reduced and precipitated during charging, and lithium ions are eluted during discharging. Therefore, since the supporting electrolyte is accumulated in the electrolyte between the two electrodes as the battery is discharged, the electrolyte needs to have an ability to dissolve the same amount of the supporting electrolyte as the electric capacity of the battery. .

However, since the organic solvent used for dissolving the supporting electrolyte generally has poor ability to dissolve the electrolyte, the dissolving of the supporting electrolyte requires a large amount of the organic solvent. In addition, since the electrolytic solution in which the supporting electrolyte is dissolved has a large electric resistance, the use of a large amount of the electrolytic solution inevitably increases the internal resistance of the battery. For the above reasons, it has been difficult to obtain a lightweight and large-capacity battery in a lithium secondary battery using a conductive polymer as a positive electrode active material.

As a countermeasure against the above problems, a method has recently been found in which a composite of a conductive polymer and an anionic polymer electrolyte is used as an electrode. In this method, a complex comprising a conductive polymer and an anionic polymer electrolyte is charged and charged.
It pays attention to the property of so-called cation mobility in which cations are released and taken in with discharge, and the invention of JP-A-63-285864 is known, for example. When the composite is used as a positive electrode in a lithium secondary battery, lithium ions generated by discharge are taken into the composite, so that the supporting electrolyte does not accumulate in the electrolytic solution, and compared with a conventionally known battery. It has become possible to reduce the amount of the electrolyte.

A composite of a conductive polymer and an anionic polymer electrolyte is usually prepared by immersing an electrode substrate in a solution containing a monomer of a conductive polymer and an anionic polymer electrolyte to conduct electrolytic polymerization. Alternatively, it can be obtained by a method in which an oxidizing agent is introduced into a solution containing a monomer of a conductive polymer and an anionic polymer electrolyte to carry out chemical polymerization. In either method, when the monomer of the conductive polymer is polymerized, the anionic polymer electrolyte is taken in as a dopant, and a complex in which the anionic polymer electrolyte is taken in the conductive polymer is formed.

[0006]

By the way, when a battery electrode using a conductive polymer is manufactured by the above method,
It is known that the difference in polymerization method and polymerization conditions changes the microstructure of the resulting conductive polymer, which affects battery performance such as capacity density, which is the capacity per electrode weight. For example, when producing polyaniline, which is often used as an electrode for a battery, by electrolytic polymerization, depending on the type of the supporting electrolyte anion incorporated as a dopant during polymerization, a granular structure, a fibril structure, or the like, polyaniline having a different fine structure is obtained. It is known that polyaniline having a fibril structure having a larger specific surface area than a granular structure exhibits excellent battery performance.

In view of the influence of the fine structure of the conductive polymer on the battery performance, the present inventors have developed a battery for a battery having a composite of a conductive polymer and an anionic polymer electrolyte supported on an electrode substrate. Electrodes were fabricated, and the microstructure of the composite and battery performance were examined. As a result, the composite became a dense and smooth composite having a structure with a small specific surface area. Therefore, a battery electrode having a large capacity density could not be obtained. Further, in order to increase the capacity, the amount of the composite supported on the electrode substrate was increased, and in the battery electrode in which the thickness of the electrode was increased, the composite was dense and inferior in the electrolytic solution. The composite did not function sufficiently as an active material, and the above-mentioned tendency of capacity reduction became even more remarkable.

The cause of this problem is that a composite of a conductive polymer and an anionic polymer electrolyte cannot provide a fine structure having a large specific surface area.
An object of the present invention is to solve such a problem and to obtain a battery electrode capable of realizing cation mobility while maintaining a fine structure having a large specific surface area of a conventional conductive polymer.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present inventors have developed an electrode structure different from a conventional battery electrode using a composite of a conductive polymer and an anionic polymer electrolyte. As a result of diligent studies on battery electrodes having a structure, a battery electrode characterized by a structure in which a conductive polymer supported on an electrode substrate is coated with an anionic polymer electrolyte membrane has a large specific surface area and a high battery performance. It has been found that the resulting electrode for a battery exhibits cation mobility while maintaining an excellent microstructure. The present invention is intended to solve the problem of a conventional battery electrode using a composite of a conductive polymer and an anionic polymer electrolyte.

In the present invention, the conductive polymer is a polymer having a π-conjugated main chain and exhibiting electronic conductivity. For example, polyacetylene, polythiophene, polypyrrole, polyaniline, polyparaphenylene, polyphenylene sulfide, polyphenylene oxide, polyphenylenevinylene, polyacene, and derivatives thereof are given. Among these, polyaniline, polypyrrole, and derivatives thereof, which are known to exhibit excellent battery performance, are particularly preferable. The method for polymerizing the conductive polymer is generally roughly classified into electrolytic polymerization and chemical polymerization. However, the battery electrode according to the present invention does not limit the method for polymerizing the conductive polymer. It can also be used with the conductive polymer produced in the method.

In the present invention, the anionic polymer electrolyte membrane is a solid membrane containing an anionic polymer electrolyte as a component, and the anionic polymer electrolyte is a polymer which becomes an anion by ion dissociation. For example,
Examples include a polyacrylic acid film, a polymethacrylic acid film, a polystyrene carboxylic acid film, a polyfluorocarbon carboxylic acid film, a polyvinyl sulfonic acid film, a polystyrene sulfonic acid film, a polyvinyl sulfate film, and a polyfluorocarbon sulfonic acid film. Above all, compared to hydrocarbon-based anionic polymer electrolyte membranes which are glassy and have close permeability to non-aqueous electrolytes for batteries, plastics having plasticity and flexibility and excellent permeability to non-aqueous electrolytes for batteries Such as a fluorocarbon carboxylate anion and a polyfluorocarbon sulfonate anion;
An anionic polymer electrolyte membrane having an anionic functional group on the side chain of the cationic polyfluorocarbon is particularly preferred.

The method of applying the anionic polymer electrolyte membrane to the conductive polymer supported on the electrode substrate is not particularly limited. In the case of an anionic polymer electrolyte capable of forming a membrane by itself, for example, Dissolve the anionic polymer electrolyte in a suitable solvent, using the solution, spin coating, spraying, brushing, etc., apply an appropriate amount on the conductive polymer, heat drying or drying under reduced pressure, etc. And the like. In the case of an anionic polymer electrolyte that does not form a film by itself, in the above method, an ionic conductive polymer such as polyethylene oxide capable of forming a film is further added to a solution in which the anionic polymer electrolyte is dissolved. There is a method of adding and using. An appropriate method may be used depending on the properties of the anionic polymer electrolyte, solvent, conductive polymer, and the like.

In the present invention, the electrode substrate functions as a current collector for the conductive polymer supported on the surface thereof.
It is a material having electrical conductivity. For example, a metal plate, a carbon plate, a metal net, an expanded metal, a punching metal, a multi-porous conductor made of metal or carbon, and the like can be given. Above all, it is preferable to use a multi-porous conductor, which is an electric conductor having a large number of gaps and pores on the surface and / or inside thereof, because of its large specific surface area. Examples of the multi-porous conductor include, for example, carbon or metal sheets or bulk compacts such as knitted fabrics, nonwoven fabrics, papers and felts made of fibers and whiskers, and sheet sheets made of powder. Alternatively, there is a lump formed body or the like, and among them, a multi-porous conductor made of carbon fiber, carbon whisker, carbon powder, or the like having a very large specific surface area and excellent adhesion to a conductive polymer is particularly preferable.

[0014]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but it should be understood that the present invention is by no means restricted to the details of the Examples.

Comparative Example 1 A carbon plate (W2 cm
X L6cm, thickness 1mm, but liquid contact part w2cm X
L2cm), Platinum plate (w5cm X L8c)
m, thickness 1 mm). Each was used as an anode and a cathode, and a mixed aqueous solution of 0.5 M aniline and 1 g equivalent / dm3 polystyrene sulfonic acid was used as a polymerization solution, and 4 m
Electrolysis was performed at a constant current of A for 17 minutes, and 2 mg of a polyaniline-polystyrene sulfonic acid complex was supported on the electrode substrate. FIG. 2 shows the structure of the carrier used in this operation, which comprises an anode 1, a cathode 2, a polymer solution 3, and a DC power supply 4. After washing the composite with pure water, it was vacuum-dried at 100 ° C. for 180 minutes to obtain a battery electrode. The thickness of the obtained battery electrode was about 0.1 mm.

As shown in FIG. 3, the battery electrode is
SUS net (W5cm XL 8cm, φ50
μm, 200 mesh) on a metallic lithium foil (W5cm
(L5 cm, thickness 500 μm) was pressed to form a negative electrode 6, a battery was assembled in an argon gas atmosphere using a 1M-LiC104 propylene carbonate solution as an electrolyte 7, and a charge / discharge power supply 9 was connected. The battery had a lithium plate electrode (W2cm X L1c) as a reference electrode 8.
m, thickness 0.1 mm). The charge / discharge current of the battery was 0.1 mA, and the upper potential of the positive electrode based on the reference electrode
When charge and discharge were repeated at 0 V and a lower potential of the positive electrode of 2.5 V, the capacity density was 28 Ah / kg based on the electrode weight excluding the electrode substrate. Table 1 shows the results.

Comparative Example 2 An SUS net (W
5cm X L8cm1φ50μm, 200 mesh,
However, the liquid-contact part W5cm X L5cm), and a platinum-plated titanium plate (W5cm X L8cm, plating thickness 2μ)
m) Two sheets were used. As shown in FIG. 4, the counter electrodes are arranged on both surfaces of the electrode base, and the counter electrodes are respectively provided with an anode 10 and a cathode 11
a, 11b, 0.5 M aniline and 1 g equivalent / d
m3 polystyrene sulfonic acid mixed aqueous solution
Was electrolyzed at 365 mA for 155 minutes, and 1.4 g of a polyaniline-polystyrene sulfonic acid complex was supported on both surfaces of the electrode substrate. Thereafter, a battery electrode was prepared in the same manner as in Comparative Example 1. The thickness of the obtained battery electrode was 3 mm. A battery was formed using the battery electrode in the same manner as in Comparative Example 1, and the battery was repeatedly charged and discharged at a charge / discharge current of 10 mA and a positive electrode upper potential of 4.0 V and a positive electrode lower potential of 2.5 V with respect to the reference electrode. And the capacity density was 1 Ah / kg. Table 1 shows the results.

Example 1 In FIG. 2, a carbon plate (W2 cm.times.L6 cm, thickness 1 mm, W2cm.times.L2 cm in liquid contact portion) was used as an electrode substrate, and a platinum plate (W5 cm.sup.2) was used as a counter electrode.
XL8 cm, thickness 1 mm), and used as an anode 1 and a cathode 2, respectively. 1M aniline and 2M-HC10
Using the mixed aqueous solution of No. 4 as the polymerization solution 3, electrolysis was performed at a constant current of 4 mA for 17 minutes, and polyaniline was applied on the electrode substrate for 1 minute.
mg supported. Thereafter, the operation of immersing the polyaniline in a 5 wt% polystyrene sulfonic acid aqueous solution and heating and drying at 50 ° C. for 60 minutes was repeated three times, and 1 mg of the anionic polymer electrolyte membrane was coated on the polyaniline. Finally, it was vacuum-dried at 100 ° C. for 180 minutes to obtain a battery electrode. The thickness of the obtained battery electrode was about 0.1 mm. As in Comparative Example 1, the battery shown in FIG. 3 was constructed and repeatedly charged and discharged. As a result, the capacity density was 49 Ah / kg. Table 1 shows the results.

<Example 2> A solution in which polyaniline was immersed was replaced with a polyfluorocarbon sulfonic acid of 5 wt% N
afion solution (Aldrich Chemical Co.)
An electrode for a battery was obtained in the same manner as in Example 1. The thickness of the obtained battery electrode was about 0.1 mm. As in Comparative Example 1, when the battery shown in FIG. 3 was configured and charged and discharged repeatedly, the capacity density was 71 Ah / kg. Table 1 shows the results.

Example 3 An SUS net (W
5cm X L8cm, φ50μm, 200 mesh,
However, two platinum-plated titanium plates (5 cm × 8 cm) were used for the counter electrode, with the liquid contact part W5 cm × L5 cm). The counter electrodes are arranged on both sides of the electrode substrate, and each of them is an anode 10,
As the cathodes 11a and 11b, 1M aniline and 2M-
Using a mixed aqueous solution of HC104 as the polymerization liquid 12, 365 m
A was electrolyzed for 155 minutes, and 0.7 g of polyaniline was supported on both surfaces of the electrode substrate. Then, 5 wt% of the polyaniline
% Nafion solution (manufactured by Aldrich Chemical Co., Ltd.), and repeated by heating and drying at 70 ° C. for 60 minutes.
0.7 g of Naftion was coated. Finally 100 ° C
For 180 minutes to obtain a battery electrode. The thickness of the obtained battery electrode was about 3 mm. When the battery electrode was repeatedly charged and discharged in the same manner as in Comparative Example 2,
The capacity density was 70 Ah / kg. Table 1 shows the results.

Example 4 A carbon felt (W5 cm × L8 cm, φ10
μm, thickness 3mm, porosity 85%, but liquid contact part W5cm
XL5cm), Platinum-plated titanium plate (W5c)
mx L8 cm, plating thickness 2 μm).
As shown in FIG. 4, the counter electrodes are arranged on both surfaces of the electrode base, and the respective electrodes are provided as an anode 10 and cathodes 11a and 11b.
Using a mixed aqueous solution of 1M aniline and 2M-HC104 as the polymerization liquid 12, electrolysis was performed at 885 mA for 65 minutes, and 700 mg of polyaniline was held on both surfaces of the electrode substrate. Thereafter, a battery electrode was obtained in the same manner as in Example 3. The thickness of the obtained battery electrode was about 4 mm. When the battery electrode was repeatedly charged and discharged in the same manner as in Comparative Example 2, the charge and discharge curve shown in FIG. 1 was obtained. The capacity density at this time is 139 A
h / kg. Table 1 shows the results. In the first to fifth embodiments, a mountain-shaped charge / discharge curve similar to that of FIG. 1 is obtained. The upward curve is the charge curve, the downward curve is the discharge curve, and the capacity density is calculated by dividing the discharge time obtained from the figure by the discharge current time, and dividing the sum by the weight of polyaniline and the mass of the anionic polymer electrolyte. .

[0022]

According to the battery electrode of the present invention, the fine structure of the conductive polymer supported on the electrode substrate can be maintained as a fine structure having excellent specific characteristics and a large specific surface area, and the conductive polymer can be maintained. Because of the function of the anionic polymer electrolyte membrane coated on the substrate to release and take in cations in response to oxidation and reduction of the battery electrode, a battery electrode with a large capacity density can be obtained. Moreover, even in a battery electrode in which the thickness of the electrode is increased in order to increase the capacity, the electrolyte sufficiently penetrates into the electrode, and the conductive polymer inside the electrode functions sufficiently as an active material. Can be suppressed.

[Brief description of the drawings]

FIG. 1 shows a charge / discharge curve of a battery in Example 4 of the present invention.

FIG. 2 shows a configuration of a supporting device for a polyaniline-polystyrene sulfonic acid composite in Comparative Example 1 of the present invention.

FIG. 3 shows a configuration of a battery in Comparative Example 1.

FIG. 4 shows a configuration of a supporting device of a polyaniline-polystyrene sulfonic acid composite in Comparative Example 2.

[Explanation of symbols]

 1 10 Anode of composite supporting device 2 11a, 11b same cathode 3 12 same polymer plate 4 15 same DC power supply 5 battery positive electrode 6 same negative electrode 7 same electrolyte 8 same reference electrode 9 same charge / discharge power supply

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiko Nagai 1-1, Akunouramachi, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory (56) References JP-A-2-174076 (JP, A) JP JP-A-61-211963 (JP, A) JP-A-63-285864 (JP, A) JP-A-63-160154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4 / 60 H01M 4/02 H01M 4/62 H01M 10/40

Claims (3)

(57) [Claims] 1. A battery electrode comprising a conductive polymer supported on an electrode substrate, wherein the conductive polymer is formed by coating with an anionic polymer electrolyte membrane. . 2. The battery electrode according to claim 1, wherein the anionic polymer electrolyte membrane is made of an anionic polymer electrolyte having an anionic functional group on a side chain of polyfluorocarbon. 3. The battery electrode according to claim 1, wherein said electrode substrate is a multi-porous conductor.