JPS63285863A - Conductive polymer electrode material and lithium secondary battery - Google Patents

Abstract

PURPOSE:To increase the utilization of an electrode material and to increase the capacity of a battery by combining specific conductive polymers, and stacking them for use as electrode material. CONSTITUTION:A conductive polymer composite (A) is obtained by forming a conductive support (a) such as graphite fibers and a conductive polymer (b) such as conductive polyaniline in one film. A conductive polymer (B) is a film of the conductive polymer (b). A conductive polymer electrode material is obtained by stacking a plurality of the composite (A), alternately stacking the polymers (B) and the supports (a), or alternately stacking the composites (A) and the polymers (B). By using this electrode material in a battery, an electrolyte penetrates between layers and the utilization of the electrode material is increased. A lithium battery using this electrode material in a positive electrode is made compact and lightweight and the capacity of the battery is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a conductive polymer electrode material with significantly improved utilization rate per unit weight, and a lithium secondary battery using the same.

<Prior art> Polymer compounds are originally insulators, but some compounds,
It is known that conductivity is developed by adding a so-called doping agent (dopant) (hereinafter referred to as doping). Such a polymer compound is polyaniline.

Conductive polymers such as polypyrrole, polythiophene, and polyacetylene, which are made by adding doping agents, have conductivity comparable to that of semiconductors or metals, and various studies are being conducted with the aim of putting them into practical use. The inventors also
We discovered that a polyaniline film made by directly molding polyaniline into a sheet using a casting method has excellent conductivity, strength, and flexibility, and is effective as a variety of conductor materials and battery materials, and filed a patent application (Japanese Patent Application 1983- No. 31602).

When such conductive polymers are used as battery positive electrodes, they generally have a high operating potential of around 3.0V, and especially when polyaniline, polypyrrole, etc. are used, a relatively flat potential can be obtained. Moreover, because of its long cycle life of several hundred cycles or more, it has begun to attract attention as a material for electrode materials.

<Problems to be Solved by the Invention> However, even if a lithium secondary battery is constructed using a conductive polymer material such as polyaniline as described above,
In reality, only about 1/2 to 1/3 of the theoretical capacity can be obtained, so it has been impossible to manufacture a lithium secondary battery with a capacity that can be put to practical use in the past. Note that this seems to be due to the extremely low utilization rate of the conductive polymer used in the positive electrode of the battery.

In view of these circumstances, an object of the present invention is to provide a conductive polymer electrode material whose utilization rate is significantly improved, and a lithium secondary battery using the same which has a significantly increased capacity.

Measures to solve these problems> Therefore, as a result of various studies on how to effectively use conductive polymer materials as electrodes, we found that using conductive polymer materials as electrodes is effective for electrode reactions. It is only the surface layer that is involved in the reaction, and the further inside the layer, the lower the rate of involvement in the battery reaction, so the utilization rate of the electrode material as a whole decreases, meaning that the full capacity close to the theoretical value cannot be obtained. In addition, even if a thin film with a high utilization rate per unit weight is used and an attempt is made to obtain an electrode material with a high utilization rate by stacking these thin films, if a battery is constructed using this electrode material, It has been found that because the thin films come into close contact with each other, the electrode material has a low utilization rate, similar to when a thick film is used.

As a result of further studies based on this knowledge, we found that when using an electrode material in which conductive polymer thin films are laminated, for example, when constructing a battery, electrolyte solution should be allowed to enter between the thin films. The present invention was completed based on the finding that the utilization rate can be improved by using the above method.

That is, the structure of the conductive polymer electrode material according to the present invention is such that a conductive support such as graphite m fibers or metal mesh 3 metal fibers and a conductive polymer such as conductive polyaniline or conductive polypyrrole are integrally formed into a film. A conductive polymer composite material formed into a shape and a conductive polymer material such as a conductive polyaniline film p-conductive polypyrrole film are laminated individually or in a mixture of the two, and the conductive polymer When molecular materials are stacked on top of each other, the conductive support is interposed between these conductive polymer materials. Mesh 3 metals! A conductive polymer composite material in which a conductive support such as At and a conductive polymer such as conductive polyaniline or conductive polypyrrole are integrally formed into a film, and conductive polyaniline film-4'R $
When a conductive polymer material such as Livirol film is laminated singly or in a mixture of both, and when the conductive polymer materials are laminated together, there is a gap between these conductive polymer materials. The present invention is characterized in that a conductive polymer electrode material in which the above-mentioned conductive support is interposed is used as a positive electrode.

As described above, the conductive polymer electrode material of the present invention can be made by laminating a plurality of conductive polymer composites, or by alternately laminating conductive polymer materials and conductive support materials, or by laminating a conductive polymer material and a conductive support material alternately, or The polymer composite material and the conductive polymer material are alternately laminated, but these laminated materials may be further laminated.

In the present invention, the conductive polymer composite material is one in which a conductive polymer and a conductive support are integrally formed into a film or a sheet (hereinafter referred to as a film), and as mentioned above, it has a high utilization rate. It is preferable that the relationship be as thin as possible.

Here, the conductive polymer is mainly composed of polyaniline and its derivatives, or polypyrrole and its derivatives,
If necessary, the polyaniline or polypyrrole resin containing polypyrrole, polythiophene, polyacetylene, etc. is made to contain a doping agent to make it conductive.

This conductive polymer is generally produced by electrochemical polymerization.
It is produced by a so-called electrolytic polymerization method, but it can also be produced by chemically treating and doping the polyaniline or polypyrrole resin obtained by a chemical polymerization method. These manufacturing methods are detailed in Japanese Patent Application No. 62-31602.

In addition, examples of the above-mentioned polyaniline derivatives include poly(0-anisidine), poly(m-anisidine),
Poly(0-1-luidine), poly(m-toluidine), poly(N-methylaniline), poly(N-ethylaniline)polydiphenylamine, polytriphenylamine.

Examples include polyphenylene diamine.

Conductive supports include metal fibers such as graphite fibers, nickel a fibers, and aluminum fibers; 5. nickel mesh; It may be a metal mesh such as an aluminum mesh, as long as it has conductivity itself and is stably held within the conductive polymer.

The conductive polymer composite material of the present invention may be in the form of a film in which such a conductive support is integrally held within the conductive polymer. It is better to adopt the stretching method. That is, the above-mentioned conductive polymer is dissolved or mixed and dispersed in a suitable solvent, and the h solution (including a semi-dissolved slurry) is applied and impregnated onto a conductive composite material placed on a substrate, and then heated at room temperature or A conductive polymer composite can be obtained by heating and removing the solvent if necessary, but a polymer composite can also be obtained in the same manner using the above polyaniline or polypyrrole resin and a conductive support. After it is made into a material, it can also be made into a conductive polymer composite material by adding post-treatment and doping. Note that doping performed as a post-treatment may be performed, for example, by adding 12% of the polyaniline resin. Br2. This is carried out by a chemical treatment method in which the polyaniline resin is exposed to halogen vapor such as CI2, or by a method in which the polyaniline resin is electrochemically doped with a doping agent such as an inorganic acid salt or a quaternary ammonium salt.

Solvents that can be used in the casting method in the present invention include: (1) Hydrocarbon compounds such as benzene and toluene; (2) Chlorinated hydrocarbon compounds such as dichloromethane and 1,1,1-trictetraloethane; (2) Acetonitrile and benzonitrile. ■ Ketone compounds such as acetone and methyl ethyl ketone ■ Ether compounds such as anisole, tetrahydrofuran, and butyl cellosolve ■ Nitro compounds such as nitroethane and nitrobenzene ■ Ester compounds such as ethyl acetate and propylene carbonate ■ Methanol, ethanol, etc. Alcohol compounds ■ Organic acid compounds such as acetic acid and propionic acid [Phase] Aromatic amine compounds such as pyridine and aniline ■ N,N-dimethylformamide, dimethyl sulfoxide 1. Examples include aprotic polar organic compounds such as sulfolane, N-methylpyrrolidone, and hexamethylphosphoramide. When using such a solvent to dissolve or mix and disperse a conductive polymer or polyaniline or polypyrrole resin to create a solution (including a semi-dissolved slurry; the same applies hereinafter) for use in casting molding. may be heated and stirred or a ball mill or the like may be used as necessary. Among the above solvent groups, if the solvents listed in (1), [Phase], and (2) are used, a solution can be formed at approximately room temperature, while other solvents require heating. Further, among the compounds (1) to (2), when the aprotic polar organic compound of (1) is used as a solvent, the solubility is particularly excellent and it is particularly preferable.

In addition, the method of coating and impregnating the conductive support placed on the substrate with the solution obtained in this way is not particularly limited, but
Solution coating.

dip coach ink, reverse roll coating,
Among various coating methods such as doctor blade coating, the most suitable one may be adopted depending on the state of the solution.

The thickness of the conductive polymer composite obtained in this manner is approximately determined by the thickness of the conductive support disposed on the substrate. As mentioned above, the thickness of the conductive polymer composite is preferably as small as possible in view of the utilization rate, but it is preferably 10 to 500-1, preferably 20 to 300-1.

Therefore, the diameter of the conductive support must also be determined in accordance with the thickness of the conductive polymer composite to be obtained. Note that examples of the substrate used in the casting method include glass, polyethylene terephthalate film (PET film), and the like.

Unit capacity when a battery is constructed using the conductive polymer composite material of the present invention [When using conventional conductive polymer powder or the conductive polymer film proposed in Japanese Patent Application No. 62-31602] Compared to the unit capacity of 30 to 70 Ah/kg, this is significantly improved to 90 to 100 Ah/kg, and the stability is also good.

Furthermore, even when the conductive polymer composite material of the present invention is laminated in multiple layers to improve the overall capacitance, as shown in conventional test examples, Get capacity. In this case, the conductive support serves as a current collector, and the adhesion between the conductive polymer and the current collector is good.

Incidentally, when the conductive polymer films proposed in Japanese Patent Application No. 62-31602 are stacked in multiple layers, the total unit capacity is only 2/3 to 1/2 of the unit capacity of each film. Ta.

On the other hand, the conductive polymer material used in the present invention is a film made of the above-mentioned conductive polymer, but as mentioned above, it is preferable to have a thin film from the viewpoint of utilization rate.
077 m, preferably 30 to 3007 n. This conductive polymer material is preferably manufactured by the casting method similarly to the conductive polymer composite material described above, but the polypyrrole-based conductive polymer material may be manufactured by the electrolytic polymerization method.

As mentioned above, if such a conductive polymer material is simply laminated to form an electrode material, it will only be 2/3 of the unit capacity of each film.
Although only ~1/2 of the unit capacity can be obtained, by alternately laminating the above-mentioned conductive supports, a large capacity can be obtained without decreasing the unit capacity as in the case of laminating conductive polymer composites. Obtainable.

The conductive polymer electrode material of the present invention may be one in which conductive polymer composites are laminated, a conductive polymer material and a conductive support are alternately laminated, or a suitable combination thereof. However, a combination in which the conductive polymer composite material and the conductive support are overlapped is not very preferable because it just wastes space.

When the conductive polymer electrode material of the present invention is used in various batteries, etc., the electrolyte solution penetrates between the layers, resulting in a very high utilization rate. Therefore, this conductive polymer′
When the IA electrode material is used as a positive electrode of a lithium secondary battery, the electric capacity can be greatly improved compared to the conventional one. Moreover, since the unit capacity is extremely high, it is possible to make a lightweight and small lithium secondary battery, so it can be expected to be put to practical use in various fields. Furthermore, since the conductive polymer electrode material of the present invention is in the form of a film, it can be formed into a cylindrical shape by, for example, having a spiral structure, and its industrial utility value is great.

The lithium secondary battery according to the present invention may have a conventionally known configuration except for using a conductive polymer electrode material as the positive electrode. In other words, lithium, sodium, aluminum, etc. may be used as the active material of the negative electrode, but
In order to prevent dendrites, it is preferable to use an alloy of lithium and aluminum (Li-A1 alloy) or a wood alloy with lithium adsorbed as the negative electrode material. In addition, as an electrolyte, lithium perchlorate (Li CI
O,), lithium borofluoride (LiBF,),
Phosphorus fluoride A (KP'F6), e-element fluoride Qi, A (LIA sF6)? An electrolyte consisting of a Lewis acid salt such as sodium phosphorous fluoride (NaPF) dissolved in a solvent at a concentration of 1 mol/l may be used. As the solvent used at this time, tetrapyrene carbonate, γ-butyrolactone ethylene carbonate, etc., tetrahydrofuran, dimethoxyethane, etc., or a mixture of these two, etc. are used.

The lithium secondary battery of the present invention configured as described above has a significantly larger electric capacity of 330h/kg (100Ah/kg) than the conventional lead-acid battery (175W) 17kg.
kg). This value is for electrodeposited polyaniline niocare, ideal value 350Wh/kg
(100Ah/kg) (Electrochemistry, See, 1985.
592-596).

As described above, the lithium secondary battery according to the present invention is lightweight and
Since it can obtain much greater output per unit weight than conventional lead-acid batteries, it can be expected to be used for various electric power applications, especially for road leveling and electric vehicles.

It is thought to be ideal for hybrid applications with solar cells and as a backup power source for IC memories, VTRs, and other devices. In other words, a lightweight and simple home-use secondary mAIM,
Therefore, it is effective for load leveling, and
It is suitable for electric vehicles because it is lightweight and has a large output per unit weight, and when hybridized with solar cells, it is suitable not only for large-scale power storage but also as a power source for wristwatches.
Furthermore, it can be used as a power source for minute currents, which is increasingly being used as the field of microelectronics grows.

Kumi 1/! 1 case and test example> (Manufacture of conductive polymer) Add lithium perchlorate (16.0 g) to the reaction vessel.

0.15 mol), perchloric acid (22.0 g, 0
．． 15moj), 7=phosphorus (14.0g, 0.15
mol ) and 95% acetonitrile aqueous solution (500
ml) and mix. Into this solution, a platinum metski titanium electrode (2cm x 2cmXo, 1cm thickness) was used as an anode and a carbon electrode (10cm x 5cnn
3cm thick) and lowered the temperature to -10°C under an Ar atmosphere.
℃ and stirred at 3 mA (0.75 mA/
React for 12 hours at a constant current of cd). After the reaction is complete,
The polymer was removed from the anode, washed with water, and vacuum dried at room temperature overnight to obtain a conductive polyaniline resin.

(Manufacture of conductive polymer composite material) 17.5 g of N,N-dimethylformamide was added to 7.5 g of the above conductive polyaniline resin, and uniformly dispersed on a roll using a ball mill to obtain a solution. This solution was applied and impregnated onto a graphite fiber material having a diameter of 150 tones using a doctor blade method. Next, the solvent was removed by vacuum drying at about 50° C., and the graphite fiber-polyaniline composite material was obtained by washing with pure water and drying.

The above solution was applied and impregnated onto nickel fibers, nickel mesh and aluminum fibers using a doctor blade method, respectively, and nickel fiber-polyaniline composites, nickel mesh polyaniline composites, and aluminum mesh polyaniline composites were obtained in the same manner. Ta.

(Manufacture of conductive polymer material) 17.5 g of N,N-dimethylformamide was added to 7.5 g of the above conductive polyaniline resin, and a solution was obtained in the same manner. This solution was applied to a thickness of 70 mm on a glass substrate by a doctor blade method. Next, the solvent was removed by vacuum drying at about 50° C., and after washing with pure water, the film was removed from the glass substrate to form a conductive polyaniline film.

Test Example 1 Various conductive polyaniline composites obtained as described above, laminated materials of these as shown in Table 1, and conductive polyaniline films and conductive polyaniline composites or conductive supports were As shown in Table 1, the performance was determined when the alternately laminated materials were used as positive electrode materials for batteries.

(Battery Configuration) As shown in Figure 1, the test cell used in the test consists of a positive electrode terminal 1, a Teflon tube 2 that is fitted to the positive terminal 1, and a Teflon tube 2 that is screwed into the inside of the Teflon tube 2. A positive electrode material 5 with a diameter of 10.6 m, a separator 6 containing an electrolytic solution, and a negative electrode material 7 are placed inside the Teflon tube material 2 in this order, and then the Teflon material 4 has a negative electrode terminal 3. By screwing the material 4 into the Teflon tube material 2, a hand R structure is formed in which the positive electrode terminal 1 and the Teflon material 4 hold the positive electrode material 5, the separator 6, and the negative electrode material 7.

In addition, as the positive electrode material 5, the above-mentioned various electrode materials are used in 10.6+n
It was punched with a +aφ punch and then dried under reduced pressure at 50°C. Further, as the negative electrode material 7, a sheet of Li-
The amount used was sufficient for the amount of anions in the positive electrode of Al alloy (115% Al). Furthermore, as an electrolyte, 1: of propylene carbonate and 1,2-dimethoxyethane is used.
1 m of lithium perchlorate in a mixed solvent of 1 (volume ratio)
・0.4 mj of ol/I solution was used. In preparing this electrolytic solution, each reagent was dried using a conventional method.

(Test conditions) Using the above-mentioned battery, 10
01JA was repeatedly charged and discharged.

The unit capacity was determined from the discharge value at the third cycle at this time.

The results are shown in Table 1 along with the amount of polyaniline in each positive electrode material.

(Comparative Example) For comparison, the conductive polyaniline film used alone and the film laminated with three films were similarly tested. The results are also shown in Table 1.

Table 1 As shown in Table 1, when only three conductive polyaniline films are laminated, the unit capacity is approximately 2/3 that of one conductive polyaniline film, but the conductive polyaniline composite (No. 2 & 4. Na6) and when conductive polyaniline films and conductive polyaniline composites or conductive supports are alternately laminated (No. 2. & 4. Na6).
, 12), it was recognized that it was possible to obtain a unit capacity equivalent to that obtained when a single conductive polyaniline composite material or a single conductive polyaniline film was used. Furthermore, it was also observed that a larger unit volume i can be obtained with the conductive polyaniline composite material than with the conductive polyaniline film.

Test Example 2 A test run similar to Test Example 1 was conducted using conductive polypyrrole instead of conductive polyaniline.

(Sample for electrode material) (1) 80. A conductive polypyrrole film with a thickness of ca, f2) A conductive polypyrrole graphite TA fiber composite material prepared by applying and impregnating graphite fibers using the doctor blade method using the conductive polypyrrole of (1), (31 (21 and Conductive polypyrrole nickel mesh composite prepared in the same manner When the same test as in Test Example 1 was conducted using these samples, the results shown in Table 2 were obtained.As shown in Table 2, polyaniline A similar effect was observed when polypyrrole was used instead of .That is, when conductive polypyrrole composites were laminated (No.
2.

No. 4) When a polypyrrole composite material and a conductive polypyrrole film or conductive support are laminated, the unit capacity is the same as when only one conductive polypyrrole composite material or conductive polypyrrole film is used. was obtained, and it was also observed that a larger unit capacity could be obtained with the conductive polypyrrole composite material compared to the conductive polypyrrole film.

<Effects of the Invention> As specifically explained above with Examples and Test Examples, the conductive polymer electrode material of the present invention has a significantly improved utilization rate compared to conventional ones, and furthermore, Lithium secondary batteries using conductive polymer electrode materials as positive electrodes are lightweight, compact, and large-capacity, and can be expected to be used in a variety of fields.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a test cell used for testing the present invention. In the drawing, 1 is a positive electrode terminal, 3 is a negative electrode terminal, 5 is a positive electrode material, 6 is a separator (containing electrolyte), and 7 is a negative electrode material.

Claims (1)

[Claims] 1) A conductive polymer composite material in which a conductive support such as graphite fibers or metal mesh 3 metal fibers and a conductive polymer such as conductive polyaniline or conductive polypyrrole are integrally formed into a film. and a conductive polymer material such as a conductive polyaniline film or a conductive polypyrrole film, either singly or in combination, and when the conductive polymer materials are laminated together, A conductive polymer electrode material characterized in that the conductive support is interposed between these conductive polymer materials. 2) The conductive polymer electrode material according to claim 1, which is made by laminating a plurality of conductive polymer composite materials. 3) The conductive polymer electrode material according to claim 1, which is made by alternately laminating a conductive polymer material and a conductive support. 4) The conductive polymer electrode material according to claim 1, which is obtained by alternately laminating a conductive polymer composite material and a conductive polymer material. 5) A conductive polymer composite material in which a conductive support such as graphite fiber, metal mesh, or metal fiber and a conductive polymer such as conductive polyaniline or conductive polypyrrole are integrally formed into a film, and a conductive polyaniline film. , a conductive polymer material such as a conductive polypyrrole film, either alone or in combination, and when the above-mentioned conductive polymer materials are laminated together, these conductive polymer materials A lithium secondary battery characterized in that the positive electrode is a conductive polymer electrode material with the conductive support interposed therebetween. 6) The lithium secondary battery according to claim 5, wherein the positive electrode is a conductive polymer electrode material made by laminating a plurality of conductive polymer composite materials. 7) Claim 5 in which a conductive polymer electrode material in which a conductive polymer material and a conductive support are alternately laminated is used as a positive electrode.
Lithium secondary battery as described in section. 8) The lithium secondary battery according to claim 5, wherein the positive electrode is a conductive polymer electrode material in which a conductive polymer composite material and a conductive polymer material are alternately laminated.