JPH03182051A - Battery - Google Patents

Abstract

PURPOSE:To decrease the reduction of a discharge capacity and enables the lengthening of a service life, by containing specific compounds in battery constitution materials in a battery using polyanine as a main electrode active substance for at least one of the two electrodes. CONSTITUTION:A battery, using polyanine as a main electrode active substance for at least one of the two electrodes, contains benzimidazole compounds in battery constitution materials, which compounds are expressed by formulas. For the compounds expressed by formulas, 2-mercapto benzimidazole, 2- mercaptomethyl benzimidazole, zinc salt made therefrom, etc. This decreases the reduction of the discharge capacity under repeated charge and discharge and enables the lengthening of the polyanine battery service life.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to improvements in batteries, particularly polyaniline batteries, and relates to batteries that are rechargeable, have high gravimetric energy density and volumetric energy density, and have excellent cycle charging characteristics. It is something.

(Prior Art) In recent years, with the spread of electronic devices, smaller and lighter batteries have come to be used for various purposes. In particular, since batteries using lithium have a high energy density, the demand for them has increased rapidly recently. Along with this, there is a strong demand for converting lithium batteries, which have conventionally been secondary batteries, into secondary batteries.

Therefore, recently, it has been developed to obtain lightweight and rechargeable batteries by using organic polymer materials such as polyacetylene, polyaniline, polypyrrole, etc. as the active material of the positive electrode. Among these organic polymer materials,
It has been clarified that polyaniline exhibits excellent battery characteristics. In particular, it has been confirmed that when polyaniline is used for the positive electrode and lithium is used for the negative electrode, a secondary battery with high energy density characteristics can be obtained.

(Problems to be Solved by the Invention) However, the above-mentioned batteries were still insufficient in terms of cycle charge/discharge characteristics, which are considered to be an important performance among the performances required for batteries, that is, durability against repeated charging and discharging6. For example, in a battery using polyaniline as the positive electrode, the power consumption is 120 to 140 A per unit weight (kg).
When repeatedly charging and discharging a capacitance of 200 h,
During the cycle, the discharge capacity becomes about 50% of the initial value, which is a significant decrease.

Therefore, polyaniline batteries have not yet reached the stage of practical use, and there is an urgent need to improve their cycle charge and discharge characteristics.

(Objective of the Invention) An object of the present invention is to provide a polyaniline battery that exhibits little decrease in discharge capacity even after repeated charging and discharging many times and can withstand a long service life.

(Means for Solving the Problem) As a result of intensive research in response to such requests, the present inventors have found that the decrease in the discharge capacity of polyaniline batteries is caused by electrochemical oxidation of polyaniline due to repeated charging and discharging. They found that this is due to the fact that polarons or bipolarons are produced within the electrolyte, and this is reduced in molecular weight by reacting with solvent molecules or electrolyte molecules in the electrolyte. It has also been found that the above-mentioned reaction, which tends to occur, can be suppressed by the coexistence of compounds (antioxidants) represented by the following general formulas (1) and (2).

The battery of the present invention was developed based on the above knowledge, and in a battery formed using polyaniline as the main electrode active material of at least one of the two electrodes, the following general materials are included in the constituent materials of the battery: Formula (1) or (2
) is characterized in that it contains the compound represented by.

The above general formula (
Examples of the compounds represented by 1) and (2) include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salts thereof.

There are no particular limitations on the method of incorporating these antioxidants into the battery, and for example, they may be added to the electrolyte of the battery or mixed into the polyaniline electrode, but particularly preferred methods include When producing polyaniline by electrolytic synthesis, the above-mentioned antioxidant is mixed into the electrodeposited solution, or after the antioxidant is mixed with polyaniline powder, it is molded into an electrode, or the same is used. This method involves immersing a polyaniline electrode in an antioxidant solution and then drying it.

Note that polyaniline is obtained by polymerizing aniline by an appropriate electrochemical or chemical method, and aniline may be bonded to any position.

Furthermore, in the present invention, polyaniline is used for at least one of the two electrodes, but in order to obtain a battery with high energy density, it is preferable to use polyaniline as the positive electrode active material and lithium as the negative electrode active material. In this case, the W solute is preferably lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, or a mixture thereof, and the solvent is dimethoxyethane, propylene carbonate, or ethylene carbonate.

Tetrahydrofuran, sulfuran, gamma butyrolactone or mixtures thereof are preferred.

(Effect of the Invention) Since the battery of the present invention contains an antioxidant in its constituent materials, the polyaniline is less likely to be oxidized even after repeated charging and discharging, and the discharge capacity is less likely to decrease. By the way, when lithium is used as the negative electrode active material, the energy density is 45
Wh/kg or more can be obtained, and 500 at 100% depth of discharge.
Even after repeated charge and discharge cycles, the discharge capacity decreases by approximately 2 times.
It remained at 0%.

(Example 1) A. Production of polyaniline electrode Perchloric acid was dissolved in 100 cc of water to a concentration of 0.2 M.
Aniline was added to this to a concentration of 0.1M to prepare an electrodeposition solution, and then two nickel mesh plates with a size of IOXIOcm were placed facing each other in this solution, one of which was used as an anode, and a saturated sweetener was added to this solution. Anodic oxidation was carried out for 10 hours by setting a potential of 700 mV with respect to the electrode, and 202 g of polyaniline was deposited on the anode side. This polyaniline was taken out, washed in pure water for 24 hours, then dried at 80° C. for 24 hours, and then ground into a fine powder of 100 mesh or less.

An active material prepared by adding and mixing 0.1 g of 2-mercaptobenzimidazole powder to 2 g of the polyaniline powder synthesized in this way was mixed to a thickness of 0.05 mm, a width of 4 cm, and a length of 5.0 cm.
A polyaniline electrode containing 1.8 g of polyaniline alone was obtained by pressure bonding to a 6 cm stainless steel expanded metal.

B. Production of polyaniline battery The polyaniline electrode obtained by cutting is used as the positive electrode, and the thickness is 0.2
A lithium plate with a thickness of 0.3 mm is used as the negative electrode, and a 0.3 mm thick
A polypropylene non-woven fabric separator interposed therebetween was wound into a spiral shape, and the resulting product was loaded into a metal type III battery container.
1 dissolved in a mixed solvent at a concentration of 2.5M.
．． 2 cc was injected, leads were taken out from the positive and negative electrode parts by a known method, and the lid was closed to obtain a battery of the present invention.

This battery weighed 13 g and had a volume of 8.3 cc, which was about 1/2 lighter than a nickel cadmium battery. 4.0-2 to measure the characteristics of this battery
．． When charged and discharged at a constant current of 10 mA in the voltage range of OV, a capacity of 197 mAh was obtained, and the average discharge voltage was about 3.5V. Therefore, the gravimetric energy density of this battery is 53 Wh/kg, and the capacitive energy density is 83 Wh/kg.
．． 1Wh/g, and these values were all larger than those of the nickel-cadmium battery. Also,
When the discharge capacity was measured after 500 cycles, it was 155 m.
Ah, and the capacity reduction rate was about 21%.

(Example 2) A. Production of polyaniline electrode Perchloric acid was dissolved in 100 cc of water at a concentration of 0.2 M.
Example 1 A polyaniline electrode was prepared by adding aniline at a concentration of 0.1M to prepare an electrodeposition solution, and then depositing a polyaniline active material on expanded metal in the same manner as in Actual Example 1 above. Lithium tetrafluoroborate and 2-mercaptomethylbenzimidazole as an oxidizing agent were charged at 2.5M and 0.0M respectively in the same container under the same conditions as above. 3 cc of an electrolyte dissolved in a 1:l mixed solvent of propylene carbonate and dimethoxyethane at a concentration of OIM was injected to form a monomer of the present invention.
! Obtained a model battery.

As a result of testing this battery under the same conditions as in Example 1, the energy density was 51 Wh/kg, and the rate of decrease in discharge capacity after 500 cycles was 22.3%.
Met.

(Comparative Example) A comparative battery was obtained in the same manner as in Example 2 except that polyaniline was not added to the electrolyte.

The capacity reduction rate of this battery after 500 cycles was measured and was 88%.

(Effects of the Invention) The battery of the present invention has excellent cycle charging and discharging characteristics, with a decrease in discharge capacity of about 20% even after 500 cycles of charging and discharging at 100% depth of discharge, and has a long life. , is extremely useful industrially.

Furthermore, the performance of the battery of the present invention exceeds that of conventional lead batteries and nickel-cadmium batteries, and its industrial value is extremely great.

Claims (1)

[Claims] A battery in which polyaniline is used as the main electrode active material of at least one of the two electrodes, in which the constituent materials are represented by the following general formula (1) or (2). A battery characterized by containing a benzimidazole compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) (R is an alkyl group) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2) (R is an alkyl group)