JP3239374B2 - Electrode composition - 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 composition, and more particularly to an electrode composition having an organic compound used for electrochemical devices such as batteries, electrochromic display devices, sensors, and memories.

[0002]

2. Description of the Related Art Since the discovery of conductive polyacetylene by Shirakawa et al. In 1971, the use of a conductive polymer as an electrode material has made it possible to use lightweight, high energy density batteries, large-area electrochromic devices, and microelectrodes. Since an electrochemical element such as a biochemical sensor used can be expected, conductive polymer electrodes are being actively studied. Polyacetylene is unstable and is not practical as an electrode.
Electron conducting conductive polymers have been studied, and relatively stable polymers such as polyaniline, polypyrrole, polyacene, and polythiophene have been developed, and lithium secondary batteries using these as a positive electrode have been developed. These polymer electrodes take in not only cations but also anions in the electrolyte during the electrode reaction, so that the electrolyte in the battery not only acts as a transfer medium for ions but also participates in the battery reaction, so it matches the battery capacity. It is necessary to supply a quantity of electrolyte into the battery. In addition, there is a problem that the energy density of the battery is reduced accordingly. The energy density is about 20 to 50 Wh / kg, which is about half that of a normal secondary battery such as a nickel cadmium storage battery or a lead storage battery. On the other hand, US Pat. No. 4,833,048 proposes a disulfide compound as an organic material which can be expected to have a high energy density. This compound is most simply represented as R-S-S-R (R is an aliphatic or aromatic organic group and S is sulfur). S-S bond is cleaved by electrolytic reduction, de R-S and cations in the electrolyte bath (M ^{+) -} to produce the salt represented by · M ^+. This salt returns to the original RSSR by electrolytic oxidation. Cation (M
A metal-sulfur secondary battery combining a metal M and a disulfide-based compound for supplying and promoting ⁺ ) is proposed in the aforementioned U.S. Patent. With an energy density of 150 Wh / kg or more, an energy density comparable to or higher than that of a normal secondary battery can be expected.

[0003]

However, the proposed disulfide compound is disclosed in U.S. Pat.
No. 3,048, J. J. Electroche
m. Soc, Vol. 136, No. 9, p. 2570
As reported in ２５2575 (1989), for example, in the electrolysis of [(C ₂ H ₅ ) ₂ NCSS-] ₂ , the potentials for oxidation and reduction are separated by 1 volt or more, and this depends on the teaching of electrode reaction theory. The electron transfer process is extremely slow. Therefore, near room temperature, a large current suitable for practical use, for example, 1 mA / cm ²
It is difficult to extract the above current, and 100-20
There is a problem that the use at a high temperature of 0 ° C. is limited.

[0004] The present invention solves such a problem and provides an electrode having excellent reversibility capable of performing high-current electrolysis (charge / discharge) even at a slight temperature even at room temperature due to the high energy density of the disulfide compound. The purpose is to:

[0005]

Means for Solving the Problems To solve this problem, the electrode composition of the present invention is a composite electrode in which a disulfide compound and activated carbon are combined.

[0006]

With this structure, in the electrode composition of the present invention, the activated carbon complexed with the disulfide compound acts as an electrode catalyst during the electrolytic oxidation and reduction of the disulfide compound. The potential difference between the oxidation reaction and the reduction reaction, which was 1 volt or more, was reduced to 0.5 volt or less to promote the electrode reaction and enable electrolysis (charge / discharge) with a large current even at room temperature. Introducing an electrocatalyst into a disulfide-based compound electrode is described in the aforementioned U.S. Pat. Electrochem. Soc, Vol.
136, p. 2570-2575 (1989), only an organometallic compound is disclosed as an electrode catalyst. Not only that effect is not specifically shown, but it is not shown at all that activated carbon acts as an electrode catalyst in electrolysis of a disulfide compound.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrode compositions of the embodiments of the present invention will be described below with reference to the drawings.

As the disulfide compound of the present embodiment, a compound represented by the general formula (R (S) _y ) _n described in US Pat. No. 4,833,048 can be used. R is an aliphatic group, an aromatic group, S is sulfur, y is an integer of 1 or more, and n is an integer of 2 or more. C ₂ N ₂ S (SH)
Represented by ₂ 2,5-dimercapto-1,3,4-thiadiazole represented by _{C 3 H 3 N 3 S 3} s- triazine -
2,4,6-trithiol and the like are used.

The activated carbon of this embodiment is obtained by activating a natural product such as a coconut shell or a synthetic product such as a phenol resin, and has a specific surface area of 1000 m ² / g and a pore volume of 0.5 ml / g. A powdery or fibrous material of a certain degree is preferably used. Those capable of holding a disulfide compound and an electrolyte in the pores are preferred.

As the metal ions when the disulfide compound is reduced to form a salt, protons can be used in addition to the alkali metal ions and alkaline earth metal ions described in the aforementioned US patents. When using lithium ions as alkali metal ions, use lithium metal or a lithium alloy such as lithium-aluminum as an electrode for supplying and promoting lithium ions,
When an electrolyte that conducts lithium ions is used, the voltage becomes 3 to
A 4-volt battery can be configured. When a proton is used, a metal hydride such as LaNi ₅ is used as an electrode for supplying and capturing the proton, and an electrolyte that conducts the proton is used, a battery having a voltage of 1 to 2 volts can be formed.

The compounding of the disulfide compound with the activated carbon can be performed by a known method such as mixing, impregnation, co-folding, and recoating. For example, a composite electrode can be obtained by impregnating a solution of a salt of a disulfide compound into the pores of activated carbon. Also, by dispersing the disulfide-based compound particles and activated carbon in a solvent and removing the solvent, a layer of activated carbon is formed on the surface of the disulfide-based compound particles, or vice versa, and a layer of disulfide compound is formed on the activated carbon to form a composite. It may be.

[0012] If necessary, an electrolyte can be added to the composite electrode. As such an electrolyte, an electrolytic solution or an electrolytic solution gel in which an acid, an alkali, or a salt is dissolved in water or an organic solvent, a solid electrolyte, or a polymer electrolyte can be used. Among them, a polymer electrolyte in which a salt is dissolved in polyethylene oxide, a gel electrolyte in which an organic solvent electrolyte is gelled with a resin such as polyacrylonitrile, or the like is preferably used.

Example 1 3.58 g of lithium trifluorosulfonate and 10.47 of propylene carbonate
g, 7.86 g of ethylene carbonate, and
Heated to ℃ to obtain a homogeneous solution. 3 g of polyacrylonitrile powder having a molecular weight of 50,000 was mixed with this solution, and the mixture was sealed.
The mixture was heated to 150 ° C. in a 00 ml Erlenmeyer flask to completely dissolve the copolymer powder to obtain a viscous transparent liquid. 30 g of acetonitrile was added to this liquid to obtain a diluted solution.

2.0 g of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) powder and 0.5 powder of PB-25 activated carbon having an average particle size of 3.5 μm manufactured by Kureha Chemical
g (specific surface area: 2000 m ² / g, pore volume: 0.8 m
1 / g) in a mortar and a diluted solution 1
And 0 g to obtain an electrode slurry. The electrode slurry is cast on a glass Petri dish having a diameter of 90 mm, dried for 1 hour in a dry argon stream at 40 ° C., and further vacuum-dried at 80 ° C. for 5 hours to form a flexible sheet having a thickness of about 260 μm. The electrode composition A was obtained.

At room temperature, LiClO ₄ was
In a dissolved dimethylformamide, a potential of 5 to -0.7 to +0.2 volts with respect to an Ag / AgCl reference electrode.
When the electrolysis was performed by linearly increasing and decreasing at a speed of 0 mV / sec, a current-voltage characteristic shown by a curve (a) in FIG. 1 was obtained. Further, as a comparative example, when the electrode composition B using graphite powder instead of activated carbon was similarly electrolyzed, the current-voltage characteristics shown by the curve (b) in FIG. 1 were obtained. Further, the same electrolysis was performed on the electrode composition C containing only the activated carbon and the solid electrolyte to obtain a current-voltage characteristic shown by a curve (c) in FIG.

The curve (a) shows 2,5-dimercapto-
Among the current peaks corresponding to the oxidation-reduction of 1,3,4-thiazol, the position of the current peak particularly corresponding to the reduction reaction is −
Move from 0.6 volt to around -0.3 volt,
It can be seen that the activated carbon promotes the redox of 2,5-dimercapto-1,3,4-thiadiazole.
On the other hand, in the curve (b), the 2,5-dimect
A current peak corresponding to the redox of 1,3,4-thiadiazole is obtained. However, the potential difference between the oxidation peak and the reduction peak is close to 0.6 volt, the redox is quasi-reversible, and the reaction speed is slow. For example, when is used for the positive electrode of a battery, the voltage difference between charging and discharging becomes greater than or equal to 0.6 volt, and the charging and discharging with a large current results in a battery with a large decrease in efficiency.

(Example 2) 1 part by weight of polyethylene triol having a molecular weight of 3000 was dissolved in 20 parts by weight of methyl ethyl ketone, and a polyacrylonitrile fiber was activated in a polyethylene triol solution.
m, 1 part by weight of activated carbon short fiber having a length of 1 mm and 4 parts by weight of 2,5-dimercapto-1,3,4-thiadiazole powder were dispersed. To this dispersion, polyethylenetriol and an equimolar amount of tolylene diisocyanate were added and mixed.
After 2 hours, the mixture was cast on a petri dish having a diameter of 90 mm, and kept at 80 ° C. in a vacuum for 24 hours to obtain an electrode composition D having a thickness of 240 μm. Also, an equimolar amount of tolylene diisocyanate was added to the polyethylene triol solution and mixed,
After reacting at 80 ° C. for 2 hours, the mixture is cast on a Petri dish having a diameter of 90 mm, and kept in vacuum at 80 ° C. for 24 hours to obtain a thickness of about 30 mm.
A 0 μm polymer electrolyte membrane was obtained. A solid battery D having a size of 28 × 28 mm was prepared using the electrode composition D thus obtained as a positive electrode, a polymer electrolyte as an electrolyte membrane, and metal lithium as a negative electrode. The battery was charged at room temperature to 4.0
After charging for 17 hours at a constant voltage of volts, 1 μA at 30 ° C.,
5 μA, 10 μA, 20 μA, 50 μA, 100 μA,
Was discharged for 3 seconds, and the battery voltage at that time was recorded to evaluate current-voltage characteristics. The results are shown by curve (d) in FIG. In addition, as a comparative example, a battery E was manufactured in the same manner using the electrode composition E having a thickness of 250 μm containing graphite powder instead of activated carbon. The current-voltage characteristics of this battery are shown by curve (e) in FIG.

The battery D having the electrode composition D according to Example 2 has a smaller polarization and a larger current than the battery E having the electrode composition E of the comparative example.

[0019]

As is apparent from the above description of the embodiment, according to the electrode composition of this embodiment, it is difficult to form an electrode in which a disulfide compound and an activated carbon are combined with only a conventional disulfide compound. Electrolysis with a large current becomes possible. Then, by using this composite electrode as the positive electrode and using lithium metal or a hydrogen storage alloy as the negative electrode, a high energy density secondary battery in which a large current charge / discharge can be expected can be formed.

Although only a battery using an electrode composition was shown as an example, in addition to a battery, an electrochromic device having a high color-forming / fading speed by using the electrode composition of the present invention as a counter electrode, and a response speed It is possible to obtain a biochemical sensor such as a glucose sensor having a high speed, and to constitute an electrochemical analog memory having a high writing / reading speed.

[Brief description of the drawings]

FIG. 1 is a graph showing current-voltage characteristics of a composite electrode of Example 1 of the present invention and an electrode of a comparative example.

FIG. 2 is a graph showing current-voltage characteristics of a battery using the electrode composition of Example 2 of the present invention for the positive electrode and a battery using the electrode of Comparative Example for the positive electrode.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Teruju Kamihara 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenichi Takeyama 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-3-93169 (JP, A) JP-A-63-301462 (JP, A) US Patent 4833048 (US, A) WO 91/6132 (WO, A1) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/00-4/62 H01M 10/36-10/40

Claims (1)

(57) [Claims] 1. A sulfur-sulfur bond is cleaved by electrolytic reduction to generate a sulfur-metal ion (including proton) bond, and the sulfur-metal ion bond regenerates the original sulfur-sulfur bond by electrolytic oxidation. An electrode composition having an organic compound and activated carbon.