JPH053137A - Solid electrode composition - Google Patents

Abstract

PURPOSE:To increase the electric capacity of the title electrode composition making an application of an electrical dual layer comprising an active carbon and a polymer solid electrolyte for the improvement of the workability making the composition flexible. CONSTITUTION:The title solid electrode is composed by compounding of an active carbon and a solid electrolyte comprising a non-protonic organic solvent melting down alkalic metal salt or ammonium salt gelated using a copolymer of acrylonitrile, acrylic methyl or methaacrylic methyl. At this time, the copolymer is affected by the hydroxyl group on the active carbon surface and a carbonic acid group so as to accelerate the gelation of the solid electrolyte for wetting the surfaces inside the pores of the active carbon with the organic solvent melting down the salt inside the pores of the active carbon so that an electric dual layer may be effectively formed along the surfaces inside the pores of the active carbon in large area thereby enabling the large electric dual layer capacity to be obtained. Furthermore, the gelated copolymer can firmly bond the active carbon particles together so that the title electrode composition having the characteristics such as high mechanical strength, excellent workability and flexibility may be formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a solid or solid form,
The present invention relates to an electrode composition comprising activated carbon and an organic polymer electrolyte, which is used in an electrochemical device such as an electric double layer capacitor or a secondary battery.

[0002]

2. Description of the Related Art Activated carbon electrodes are expected to be lightweight and high energy density capacitors, electrochromic devices, and electrochemical devices such as biochemical sensors using microelectrodes. Therefore, research and development have been actively studied in recent years. There is.

Conventionally, a liquid electrolyte has been exclusively used as the electrolyte, and a representative one is an organic solvent solution such as propylene carbonate in which sulfuric acid or a salt is dissolved. It has also been proposed to use a solid electrolyte at room temperature, such as a copper ion conductive solid electrolyte or a silver ion conductive solid electrolyte. If a solid electrolyte is used, the entire element can be solidified, and a highly reliable element without electrolyte leakage can be configured. In particular, a flexible sheet-like activated carbon electrode can be obtained by using a flexible polymer electrolyte represented by polyethylene oxide among solid electrolytes. By using this electrode, a solid electric double layer capacitor having a large area and excellent flexibility can be formed.

[0004]

However, the polymer electrolyte used as a mixture with the activated carbon is not limited to any polymer electrolyte, and can sufficiently penetrate into the pores of the activated carbon so that the surface of the activated carbon is sufficiently filled. You need something to cover. Polyethylene oxide, which has been known from the past,
A polymer electrolyte in which a salt is dissolved in polyethyleneimine, polyether or polyphosphazene has a problem that it has a high viscosity and does not sufficiently penetrate into the pores of the activated carbon, making it difficult to obtain a large capacity. Furthermore, the solubility of salts in these polyelectrolytes is as low as about 0.05 mol / l, and in order to form an electric double layer, a large amount of polyelectrolytes must be mixed in the electrode, and the unit volume or unit weight It has a drawback that the capacity of each electrode is one tenth or less as compared with the one using a liquid electrolyte, and the advantage of using a flexible solid polymer electrolyte is not necessarily utilized. There was a problem that there was not.

The present invention solves such a problem, and uses a solid electrolyte capable of sufficiently penetrating into the pores of an activated carbon electrode, and a solid electrode composition capable of realizing an electrochemical device having an electrode capacity close to that of a liquid electrolyte. It is intended to provide goods.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem, and takes advantage of the characteristics of a polymer electrolyte, which is flexible and solid, and has a capacitance comparable to that of a capacitor using a liquid electrolyte. The present invention provides an electrode composition used in an electric double layer capacitor having the same. The electrode composition of the present invention is a solid electrolyte and activated carbon obtained by gelling an aprotic organic solvent in which an alkali metal salt or an ammonium salt is dissolved using a copolymer of acrylonitrile and methyl acrylate or methyl methacrylate. It is a composite of and.

[0007]

In the solid electrode composition having this structure, the hydroxyl groups and carboxylic acid groups on the surface of activated carbon act on the polymer electrolyte to promote gelation of the polymer electrolyte. As a result, inside the pores of the activated carbon, the organic solvent in which the salt is dissolved is effectively retained inside the pores, and the inner surface of the pores can be sufficiently wetted with the organic solvent.
An electric double layer is effectively formed along the inner surface of the pores. On the outer surface of activated carbon, the copolymerization polymer firmly bonds the activated carbon particles to each other by the gelling reaction between the hydroxyl group or carboxylic acid group on the activated carbon particle surface and the polymer electrolyte, and has excellent mechanical strength and processability, and flexibility. An electrode composition having good properties will be formed.

[0008]

EXAMPLE An example of the present invention will be described below.

The activated carbon used in this embodiment is preferably powdered or fibrous having an average particle size of 5 μm or less, a specific surface area of 1000 m ² / g and a pore volume of about 0.5 ml / g. .. Natural palm oil activated, synthetic resin such as phenolic resin activated,
Either can be used.

The copolymer of acrylonitrile and methyl acrylate or methyl methacrylate can be obtained by polymerizing an acrylonitrile monomer and methyl acrylate or methyl methacrylate by a conventional polymerization method. The copolymer has a molecular weight of 30,000 to 100,00.
0 is desirable. The copolymerization ratio (AN / MA) of acrylonitrile (AN) and methyl acrylate or methyl methacrylate (MA) is preferably about 50: 1 to 2: 1 (molar ratio).

As the aprotic organic solvent, ethylene carbonate (EC), propylene carbonate (P
C), butylene carbonate (BC), diethylene carbonate (DEC), sulfolane (SL), methyl sulfolane (MSL), tetrahydrofuran (THF),
Dioxane (DOX), dioxolane (DOS), etc. may be used alone or in combination. Especially EC and S
It is preferable to use a mixed solvent of L or EC and PC because the conductivity is relatively high and the oxidation stability is good.

Salts MX which are soluble in aprotic organic solvents include lithium iodide (LiI), lithium perchlorate (LiClO ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium borofluoride (LiB).
F ₄ ), such as a lithium salt in which M is an alkali metal Li, tetraethylammonium perchlorate [(C ₂ H ₅ ) ₄ NClO ₄ ] in which M is tetraalkylammonium,
Tetrabutylammonium perchlorate _{[(n-C 4 H 9} ) 4
NClO ₄ ] or tetraethylammonium borofluoride [(C ₂ H ₅ ) ₄ NBF ₄ ] and the like.

The solid electrolyte composition of the present invention is manufactured, for example, as follows. First, lithium trifluoromethanesulfonate as a salt is heated and dissolved in an aprotic mixed solvent composed of EC and PC to obtain an organic solvent solution of the salt. Next, a powder of a copolymer of acrylonitrile and methyl acrylate or methyl methacrylate is added to this solution and heated at 150 ° C to 180 ° C to dissolve the powder to obtain a uniform and transparent solution. This solution is diluted with acetonitrile to 2-3 times by weight. The diluted solution and the powder of activated carbon which has been heated and dried in advance are mixed in a slurry in a mortar. The obtained slurry is cast on a glass plate. After drying at room temperature, the solid electrolyte composition having lithium ion conductivity is obtained by vacuum drying under vacuum of 1 Torr at 60 ° C to 80 ° C.

(Embodiment 1) An embodiment of the present invention will be specifically described below. Lithium trifluorosulfonate 3.
58 g, 10.47 g of propylene carbonate and 7.86 g of ethylene carbonate were mixed and heated to 120 ° C. to obtain a uniform solution. Into this solution, a copolymer of polyacrylonitrile having a molecular weight of 60,000 and methyl acrylate (AN / M
(A = 10/1, molar ratio) 3 g of powder were mixed and sealed 1
The copolymer powder was completely dissolved by heating to 150 ° C. in a 00 ml Erlenmeyer flask to obtain a viscous transparent liquid. 30 g of acetonitrile was added to this liquid to obtain a diluted solution.

Separately, BE obtained by activating a phenol resin
T specific surface area is 2500 m ² / g, pore volume is 0.86 ml / g,
1.25 g of activated carbon powder having an average particle diameter of 3.0 μm and 10 g of the diluted solution were mixed in a mortar to obtain an electrode slurry. About 3 g of the electrode slurry was cast on a glass petri dish having a diameter of 90 mm, dried in an atmosphere of dry argon at 40 ° C. for 1 hour, and further vacuum dried at 80 ° C. for 5 hours to give a thickness of about 200.
A flexible sheet-like solid electrode composition A having a thickness of μm was obtained. The electrode composition thus obtained was in an apparently dry state with no exudation of liquid, and a radius of 10 mm.
It showed good flexibility and mechanical strength without being damaged even after 100 times of repeated bending test. As an electrolyte for forming the electric double layer capacitor A for measuring electrode characteristics, only 10 g of the diluted solution was cast on a glass dish having a diameter of 90 mm, dried in a dry argon gas stream at 40 ° C. for 1 hour, and further 80 By vacuum-drying at 5 ° C. for 5 hours, a sheet-like solid electrolyte having a thickness of about 300 μm was obtained.

Comparative Example 1 A solid electrode composition B having a thickness of about 200 μm was prepared in the same manner as in Example 1 except that polyacrylonitrile having a molecular weight of 55,000 was used in place of acrylonitrile and methyl acrylate copolymer. Got The electrode composition thus obtained is apparently in a dry state and does not exude any liquid. Further, when the same bending test as in Example 1 was carried out, it was broken at a radius of 20 mm or less.
In the same manner as in Example 1, as an electrolyte for forming the electric double layer capacitor B for measuring the electrode characteristics, only 10 g of the diluted solution was cast on a glass petri dish having a diameter of 90 mm and 4
Dry for 1 hour in a dry argon stream at 0 ° C, then add 80
Vacuum drying at ℃ for 5 hours, thickness of about 300μm
A sheet-shaped solid electrolyte of was obtained.

Comparative Example 2 Polyethylene oxide having a molecular weight of about 3,000 was dissolved in 6.6 g, tolylene diisocyanate 0.5 ml and lithium trifluoromethanesulfonate 0.3 g and dissolved in 10 ml methyl ethyl ketone. A solid electrode composition C having a thickness of about 180 μm and comprising a crosslinked polyethylene oxide polymer solid electrolyte in which a lithium salt was dissolved and activated carbon was prepared in the same manner as in Example 1 except that 10 g of the solution was used instead of the diluted solution of Example 1. Got Further, when the bending test similar to that of Example 1 was performed, it was broken at a radius of 25 mm or less. As in Example 1, as an electrolyte for constructing the electric double layer capacitor C for measuring electrode characteristics, only 10 g of the solution was cast on a glass dish having a diameter of 90 mm and dried in a stream of dry argon at 40 ° C. After drying for an hour and further vacuum drying at 80 ° C. for 5 hours, a sheet-like solid electrolyte having a thickness of about 250 μm was obtained.

(Evaluation of Electrode Characteristics) The electrode compositions and the solid electrolytes obtained in Example 1 and Comparative Examples 1 and 2 were punched into a disk having a diameter of 13 mm. A solid electrolyte disc was sandwiched between two electrode composition discs, the whole was further sandwiched between two platinum discs, and the discs were placed in a cylinder made of Teflon having an inner diameter of 13 mm to form an electric double layer capacitor. The electrode characteristics were evaluated while the entire device was pressed from above and below via a spring by a stainless steel rod having a diameter of 13 mm for an electrode terminal. Regarding the electric double layer capacitor assembled in this way,
Charging and discharging were repeated between 0 and 3.5 V at a constant current of 0.27 mA. Table 1 shows the weight of activated carbon per electrode and the capacity calculated from the linear portion of the voltage of 1.5V to 2.5V. All evaluations were performed at 20 ° C.

[0019]

[Table 1]

As shown in (Table 1), the electric double layer capacitor A of the embodiment gives an extremely large capacitance as compared with the capacitors B and C of the comparative example.

In this example, the application to the electric double layer capacitor was explained, but by using the solid electrode composition of the present invention as the counter electrode, in addition to the electric double layer capacitor,
It is possible to obtain a secondary battery having excellent charge / discharge cycle characteristics, an electrochromic element having a fast coloring / fading speed, a biochemical sensor such as a glucose sensor having a fast response speed, and the like. Further, it is also possible to construct an electrochemical analog memory having a high writing / reading speed.

[0022]

As is apparent from the above examples, according to the present invention, activated carbon, an alkali metal salt or an ammonium salt, a copolymer of acrylonitrile and methyl acrylate or methyl methacrylate, In a solid electrode composition that is complexed with a protic organic solvent,
Compared with conventional electrodes using polymer solid electrolytes, they have an extremely large electric capacity and are excellent in mechanical strength and workability. By using this solid electrode composition, it is possible to construct a large-capacity electric double layer capacitor that does not leak in a solid state. In addition to the electric double layer capacitor, it is possible to obtain a secondary battery having excellent charge / discharge cycle characteristics, an electrochromic element having a fast coloring / fading speed, a biochemical sensor such as a glucose sensor having a fast response speed, and the like. Further, it is also possible to construct an electrochemical analog memory having a high writing / reading speed.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroshi Uemachi Hiroshi Uemachi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenichi Takeyama, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. An activated carbon, a salt represented by MX (M is an alkali metal ion or ammonium ion, and X is a counter anion thereof), acrylonitrile and methyl acrylate or methyl methacrylate. A solid electrode composition mainly composed of a copolymer and an aprotic organic solvent.