JPH08138677A - Alkaline secondary battery - Google Patents

Abstract

PURPOSE: To provide an alkaline secondary battery which excels in shelf life and suppressing self-discharge. CONSTITUTION: In this battery, a positive electrode and a negative electrode are disposed through a separator in an alkali electrolyte. A sulfur compound having a noncovalent electron pair such as thiol, disulfide, sulfide, thiophene, sulfoxide, sulfinic acid salt, thioslfate or sulfide is carried on the positive electrode or either one of thiol, disulfide, sulfite and sulfur dioxide is carried on the separator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline secondary battery, and more particularly to an alkaline secondary battery which suppresses self-discharge and has excellent storage performance.

[0002]

2. Description of the Related Art Recently, nickel-hydrogen secondary batteries have been attracting attention as high-capacity alkaline secondary batteries. This nickel-hydrogen secondary battery operates with hydrogen as a negative electrode active material, and usually has a negative electrode formed by supporting a hydrogen storage alloy capable of reversibly storing and releasing hydrogen on a current collector, A positive electrode made by supporting nickel hydroxide, which is a positive electrode active material, together with nickel powder or cobalt powder as a conductive material on a current collector, is superposed through an electrically insulating and liquid permeable separator. The power generating element is arranged in an alkaline electrolyte such as potassium hydroxide, and then the whole structure has a sealed structure.

In the above structure, as the current collector of the positive electrode, a porous sintered body formed by sintering carbonyl nickel powder or a sponge-like nickel porous body having a three-dimensional network structure is usually used. There is. As the separator, for example, a nonwoven fabric made of polyamide or polyolefin is widely used.

[0004]

By the way, in such an alkaline secondary battery, for example, if the alkaline secondary battery is stored in the atmosphere in an unused state, the negative electrode self-discharges, and the electrolysis of the electrolytic solution proceeds. As a result, free hydrogen gas may be generated in the battery. Then, this free hydrogen gas may diffuse in the electrolytic solution, pass through the separator, and reach the positive electrode.

When such a situation occurs, the positive electrode active material forming the positive electrode is reduced by this hydrogen gas, so that self-discharge occurs and further the battery voltage is lowered. The decrease in the battery voltage may reach the dissolution voltage of the positive electrode active material. In such a state, even if a new charging process is performed, the battery capacity will not be restored, and the cycle life of the battery will decrease.

The above-mentioned inconvenient problems are prominently exhibited in a nickel-hydrogen secondary battery in which the negative electrode is composed of a hydrogen storage alloy which stores hydrogen in the first place. In particular, when the storage temperature of the battery is high, the above phenomenon is remarkably exhibited and the storage performance thereof is significantly reduced. The present invention solves the above-mentioned inconvenient problems that occur in alkaline secondary batteries by reforming the positive electrode and the separator, thereby suppressing self-discharge and improving the storage performance, especially nickel-hydrogen secondary batteries. The purpose is to provide batteries.

[0007]

Means for Solving the Problems In the process of earnestly researching to achieve the above object, the present inventor has the above-mentioned inconvenient problem in alkaline secondary batteries that the free hydrogen gas generated in the negative electrode is caused in the positive electrode. Even if they come into contact with each other, this can be solved by reforming the positive electrode so that the positive electrode active material is not reduced, and free hydrogen gas generated in the negative electrode does not diffuse through the separator to the positive electrode. I had the idea that it could be resolved by taking such measures.

Based on this idea, the present inventor made the following consideration regarding the positive electrode and the separator. First, the positive electrode incorporated in an alkaline secondary battery is usually a current collector made of Ni, and a positive electrode active material such as Ni (OH) ₂ and a conductive material such as Co or CoO. Attention was paid to the fact that the substance mixture was carried. As is clear from the fact that these transition metal compounds such as Ni and Co are used as catalytic reduction catalysts in synthetic chemistry, they have catalytic activity for hydrogen. This catalytic activity is due to the electronic defect (d) at the d-electron level of the transition metal.
-It is believed to be due to the presence of electronic holes).

Therefore, when the hydrogen gas from the negative electrode comes into contact with the positive electrode having the above-mentioned structure, the hydrogen gas supplies electrons possessed by itself to the d-electron hole of Ni constituting the current collector. It is considered to form a coordinate bond.
That is, it is considered that a catalytic reduction reaction occurs on the surface of Ni, and as a result, the reduction of the positive electrode active material proceeds, causing self-discharge in the positive electrode and further lowering of the battery voltage.

Therefore, if a compound that becomes a catalyst poison for the catalytic activity of these transition metals is carried on the positive electrode, even if free hydrogen gas comes into contact with this positive electrode, catalytic reduction by these transition metals is carried out. The reaction is suppressed,
Therefore, it is considered that the reduction of the positive electrode active material is prevented. Next, considering the separator, even if free hydrogen gas is generated in the negative electrode and it becomes a state where it diffuses to the positive electrode, at that time, hydrogen gas always passes through the separator. If a compound having gas capturing ability is carried and the hydrogen gas is captured by the separator, the hydrogen gas will not diffuse to the positive electrode. Therefore, it is considered that the positive electrode active material is not reduced at the positive electrode, its self-discharge is suppressed, and the decrease of the battery voltage is prevented.

Based on the above consideration, the present inventor has studied a compound to be supported on the positive electrode or a compound to be supported on the separator. In that case, these compounds are required to have the following properties. That is, first of all, the alkaline secondary battery is actually used by repeating charging and discharging and has a long service life.Therefore, even in such a state, it may be decomposed and a harmful substance for the battery reaction may be produced as a by-product. Not a compound. Further, in the case of a compound to be carried on the separator, the separator must be an electrically insulating compound because it must be electrically insulating.
Furthermore, the compound to be carried is required to reversibly carry out the oxidation / reduction reaction as the charging / discharging is repeated.

Based on the above consideration, the present inventor has conducted extensive studies on compounds effective for being carried on the positive electrode or the separator, and as a result, it is effective to carry the compounds described below on the positive electrode and the separator, respectively. That is, the present inventors have found out the fact that That is, the alkaline secondary battery of the present invention (hereinafter referred to as the first battery) is an alkaline secondary battery in which a positive electrode and a negative electrode are arranged in an alkaline electrolyte via a separator, and the positive electrode is not It is characterized in that a sulfur compound having a shared electron pair is supported. Further, another alkaline secondary battery of the present invention (hereinafter referred to as a second battery) is an alkaline secondary battery in which a positive electrode and a negative electrode are arranged in an alkaline electrolyte via a separator, wherein the separator is One of thiol, disulfide, sulfite, and sulfur dioxide is carried.

The first battery of the present invention has the same structure as that of the conventional alkaline secondary battery except that the positive electrode carries a sulfur compound, which will be described later, and the second battery.
The structure of the battery is the same as that of the conventional battery except that the separator carries the compound described below. First, the first battery will be described in detail.

The sulfur compound supported on the positive electrode has an unshared electron pair and functions as a catalyst poison for the Ni current collector and the Co conductive material forming the positive electrode. That is,
The transition metal such as Ni or Co, which is a constituent material of the positive electrode, is coordinate-bonded with the d-electron hole to deactivate the transition metal,
Even when free hydrogen gas comes into contact with the transition metal, the transition metal is prevented from causing a catalytic reduction reaction. This prevents reduction of the positive electrode active material.

Examples of the sulfur compound having such a function include thiol, disulfide, sulfide, thiophene, sulfoxide, sulfinate, thiosulfate and sulfide. As a thiol,
It may be either an aliphatic thiol or an aromatic thiol, and examples of the aliphatic thiol include methanethiol, 1-ethanethiol, 1-propanethiol, 1-
Butanethiol, 1-pentanethiol, 1-octanethiol, 1-nonanethiol, 1-decanethiol,
1-undecanethiol, 1-dodecanethiol, etc.
C _n H _2n + 1 SH linear monosubstituted or represented by (n = 1~12), 1,2- ethanedithiol, 1,3-propanedithiol, 1,4-butane dithiol, 1,5 Dithiol, 1,6-hexanedithiol, 1,7-
Heptanedithiol, 1,8-octanedithiol,
1,9-thiol, 1,10-decane thiol, 1,11-undecane thiol, 1,12-dodecane dithiol such _{as, HSC n H 2n SH (n} = 2~1
The linear disubstituted product represented by 2) can be mentioned. Further, a straight chain tri-substituted product and a branched product can also be used.

Examples of aromatic thiols include thiophenol, 1,2-benzenedithiol, 1,3-benzenedithiol, m-thiocresol, p-thiocresol and the like. As a disulfide,
Although not particularly limited, for example, methyl disulfide, ethyl disulfide, propyl disulfide,
Butyl disulfide, pentyl disulfide, hexyl disulfide, heptyl disulfide, octyl disulfide, nonyl disulfide, decyl disulfide, undecyl disulfide, dodecyl disulfide, etc.
A straight-chain mono-substituted product represented by (C _n H _{2n + 1} ) ₂ S ₂ (n = 1 to 12) can be given. In addition, tert-butyl disulfide, dithioglycolic acid ((HOOC-C
H _{2) 2} S _2), dithio acid ((HOOC-C
_{H 2 -CH 2) 2 S 2} ) or the like can be used.
Furthermore, phenyl disulfide, benzyl disulfide,
Aromatic disulfides such as toluene disulfide can also be used.

Examples of the sulfide include methyl sulfide, ethyl sulfide, propyl sulfide, butyl sulfide, pentyl sulfide, hexyl sulfide, heptyl sulfide, octyl sulfide, nonyl sulfide, decyl sulfide, undecyl sulfide, dodecyl sulfide, and the like (C _n H _{2n + 1} ) ₂ S (n
= 1 to 12). Further, a cyclic sulfide such as thiophene, a disubstituted product or isopropyl sulfide can also be used.

[0018]

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Aromatic sulfides such as can also be used. Examples of the sulfoxide include symmetrical sulfoxides such as dimethyl sulfoxide, diethyl sulfoxide, and dipropyl sulfoxide, and tetramethylene sulfoxide.

[0020]

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[0021] can be mentioned. In addition, aromatic sulfoxides such as diphenyl sulfoxide, dibenzyl sulfoxide, p-tolyl sulfoxide can also be used. Examples of the sulfinic acid salt include aliphatic sulfinic acid or aromatic sulfinic acid in which the unend hydrogen atom is substituted with an alkali metal or an alkaline earth metal, and specifically, sodium benzenesulfinate, Examples thereof include potassium benzenesulfinate, potassium p-toluenesulfinate, and sodium p-toluenesulfinate.

Examples of the thiosulfates include thiosulfate alkali metal salts and alkaline earth metal salts,
Specific examples thereof include sodium thiosulfate and potassium thiosulfate. Any sulfide may be used as long as it generates a sulfide ion (S ²⁻ ) when it comes into contact with an alkaline electrolyte, and specifically, sodium sulfide, potassium sulfide, calcium sulfide, magnesium sulfide, etc. I can give you.

Of these sulfur compounds, thiols and disulfides are preferred. When supporting these sulfur compounds on the positive electrode, first, a predetermined amount of the sulfur compound is dissolved in a suitable organic solvent or water to prepare a solution having a predetermined concentration. Then, the precursor of the positive electrode, which is already manufactured with the active material mixture supported on the current collector, is immersed in the solution. The solution permeates into the voids of the active material mixture carried on the positive electrode precursor. Then, the positive electrode precursor is taken out and dried to obtain the positive electrode of the present invention in a state where the voids of the active material mixture carry the sulfur compound.

At this time, if the amount of the sulfur compound supported is too small, the deactivation of the transition metal constituting the positive electrode cannot be sufficiently achieved. By covering the surface of the active material as well, the battery characteristics such as discharge capacity and high capacity are deteriorated. Therefore, the amount of the sulfur compound supported is preferably about 0.01 to 0.5 mmol per unit weight of the active material mixture.

Next, the second battery will be described in detail. In this battery, any one of thiol, disulfide, sulfite, and sulfur dioxide is carried on the separator. In this case, the positive electrode may be the positive electrode having the structure described in the first battery, or may be a normal positive electrode such as a normal nickel electrode.

Among these compounds, as the thiol and disulfide, those described for the first battery can be used. As the sulfite, those obtained by substituting the hydrogen atom of sulfurous acid (H ₂ SO ₃ ) with an alkali metal or an alkaline earth metal are preferable, and specific examples thereof include sodium sulfite, potassium sulfite, calcium sulfite, magnesium sulfite, and sulfite. Barium etc. can be given.

All of the above compounds are electrically insulating. Then, it causes reversible oxidation / reduction reactions. For example, when disulfide is brought into contact with hydrogen gas in the coexistence of an alkaline electrolyte, the following formula: R—S—S—R + H ₂ → 2R—SH (1) (R is an organic group such as an alkyl group or an aryl group) Is represented) and is reduced to thiol.

When the alkaline concentration of the alkaline electrolyte is high, this thiol has the following formula: R-SH + KOH → R-SK + H ₂ O (2) (when the alkaline electrolyte is potassium hydroxide). It exists as an alkali salt of a thiol.

When this alkali salt of thiol is also brought into contact with oxygen gas in the same coexistence with an alkaline electrolyte, the following formula: 2R-SK + 1 / 2O ₂ + H ₂ O → R-S-S-R + KOH. 3) is oxidized to regenerate a disulfide. Therefore, if the separator is loaded with the thiol in the battery, oxygen gas is generated from the positive electrode when the battery is charged, and the oxygen gas acts on the separator to cause the reaction of formula (3). The thiol is present as a disulfide.

When the separator is loaded with disulfide, the reaction of the formula (3) is in a rate-determining state from the beginning in the separator. When free hydrogen gas is generated from the negative electrode during storage of the battery and diffuses into the separator, the disulfide existing in the separator reacts with hydrogen gas as shown in formula (1). Then restore it to thiol again. That is, as a result, the hydrogen gas generated in the negative electrode is captured by the separator and does not diffuse to the positive electrode.

As a result, the self-discharge of the positive electrode is suppressed and further the decrease of the battery voltage is suppressed. Further, when the compound supported on the separator is a sulfite, the following action is exhibited. First, sulfite in an aqueous solution,
Based on the reaction of the following formula: M ₂ SO ₃ → 2M ⁺ + SO ₃ ²⁻ (4) (M represents a monovalent metal), it is converted to sulfite ion. When hydrogen gas comes into contact with the sulfite ion, the sulfite ion is reduced to the sulfide ion based on the reaction of the following formula: SO ₃ ^2- + 3H ₂ → S ^2- + 3H ₂ O (5).

When the sulfide ions are contacted with oxygen gas under the same conditions, some of them are oxidized to sulfate ions, but most of them are represented by the following formula: S ^{2 −} + 3 / 2O ₂ → SO ₃ ^{2 -} …… Sulfite ion is formed based on the reaction of (6). Therefore, when sulfite is carried on the separator as in the case of the above-mentioned thiol or disulfide, sulfite ions are present in the separator after the battery is charged. When the hydrogen gas generated in the negative electrode during storage of the battery comes into contact with the sulfite ion, the sulfite ion captures the hydrogen gas based on the reaction of the formula (5).

Further, when the compound supported on the separator is sulfur dioxide, the following reaction occurs. Sulfur dioxide is converted into sulfite ion in the alkaline electrolyte based on the reaction of the following formula: SO ₂ + 2KOH → 2K ⁺ + SO ₃ ² + + H ₂ O (7).

When the sulfite ion is brought into contact with hydrogen gas in the alkaline electrolyte, the above-mentioned (5)
It becomes a sulfide ion based on the formula. When this sulfide ion comes into contact with oxygen gas under the same conditions, most of it is oxidized to sulfite ion based on the above equation (6). Therefore, this sulfur dioxide-carrying separator can trap hydrogen gas generated from the negative electrode during storage, just like the above-mentioned separator carrying a sulfite salt.

These compounds can be supported on the separator as follows. First, in the case of thiol or disulfide, a predetermined amount of these may be dissolved in an organic solvent to prepare a solution having a predetermined concentration, and the base material of the fibrous separator may be dipped in the solution and then taken out and dried. The solution permeates between the fibers of the separator substrate, and is carried there when the solvent is dried and removed.

At this time, if the supported amount is too small, the above-mentioned effects are not sufficiently exhibited, and if the supported amount is too large, the porosity of the separator is lowered and the permeation of oxygen generated from the positive electrode during overcharge is impeded. In addition, problems such as hindering the operation of ions in the electrolytic solution will start to occur, so that the supported amount is preferably about 0.05 to 2 mmol per unit weight of the separator substrate.

In the case of a sulfite salt, a predetermined amount of the sulfite may be dissolved in water to prepare an aqueous solution having a predetermined concentration, the separator substrate may be dipped in the aqueous solution, and then taken out and dried.
The supported amount at this time is 0.01 to 2 per unit weight of the separator substrate for the same reason as in the case of thiol or disulfide.
It is preferably about mmol. In the case of sulfur dioxide, it can be supported by leaving the separator substrate in the gas of sulfur dioxide. At this time, the supported amount can be adjusted by changing the gas concentration. The amount of sulfur dioxide supported is preferably about 0.01 to 2 mmol per unit weight of the separator substrate.

Further, for example, methyl isobutyl ketone,
A sulfur dioxide gas may be blown into an organic solvent such as acetone or chloroform or a mixed solvent thereof to prepare a saturated solution of sulfur dioxide, and the base material of the separator may be dipped and supported therein. The base material of the separator may be any conventionally used one, and is not particularly limited, and examples thereof include a polyolefin-based nonwoven fabric and a polyamide-based nonwoven fabric.

The alkaline secondary battery of the present invention is manufactured by incorporating the above-mentioned positive electrode and separator. In that case, as the battery to be manufactured, a battery assembled by using the above-mentioned sulfur compound having no shared electron pair for the positive electrode and not supporting the above compound for the separator; Is a battery assembled using the above-mentioned sulfur compound having no shared electron pair and a separator carrying the above-mentioned compound; and the above-mentioned battery having no shared electron pair in the positive electrode. A battery assembled by using one not supporting a sulfur compound and using one supporting the above compound as a separator can be mentioned.

[0040]

Examples of the invention

Examples 1 and 2, Comparative Example 1 (1) Production of Ni Electrode Particle size 1 containing Zn: 5% by weight and Co: 0.75% by weight
Particle size for 90 parts by weight of Ni (OH) ₂ powder of -60 μm
5 parts by weight of CoO powder of 0.1 to 10 μm, specific surface area of 1 to 3 m
5 parts by weight of carbonyl nickel powder having a filament diameter of 1 μm or less at ² / g was mixed, and further 40 parts by weight of a 1.2% aqueous carboxymethyl cellulose solution was added thereto to prepare a positive electrode mixture paste.

A sponge-like nickel porous body having an average pore size of 0.3 mm, a porosity of 93 to 97%, a length of 72 mm, a width of 41 mm, and a thickness of 1.0 mm was prepared, and the above paste was filled therein, and then 8
It was dried at 0 ° C. for 1 hour, and a pressure of 500 kg / cm ^{2 was} further applied to manufacture a positive electrode precursor. (2) Support of sulfur compound 1.0 g of dodecanethiol (C ₁₂ H ₂₅ SH) was dissolved in 123 ml of n-propyl alcohol to prepare a solution (solution 1) having a concentration of dodecanethiol of 1% by weight.

Further, t-butyl disulfide ((C
1.0 g of H ₃ ) ₃ CSSC (CH ₃ ) ₃ ) was dissolved in 123 ml of n-propyl alcohol to prepare a solution (solution 2) having a concentration of t-butyl disulfide of 1% by weight.
The precursor of the positive electrode manufactured in (1) was immersed in each of these two solutions for 30 minutes, taken out, and dried in the atmosphere at a temperature of 20 ° C. to obtain the positive electrode according to the present invention.

The supported amount of dodecanethiol was 0.4 mmol / g with respect to the positive electrode mixture, and the supported amount of t-butyl disulfide was 0.3 mmol / g with respect to the positive electrode mixture. (3) Assembly of battery and its characteristics Using each of the positive electrodes described above, a hydrogen storage alloy electrode was used as the negative electrode, and FT-310 was used as the separator.
Using (trade name, polyolefin non-woven fabric manufactured by Nippon Vilene Co., Ltd.), the rated capacity is 1100 mA by a conventional method.
h, an AA size nickel-hydrogen secondary battery was assembled.

For comparison, the same battery was assembled using the positive electrode produced in (1) as it was. After initial activation of these 3 types of batteries, charge at 0.2C for 6 hours, 0.2
At C, the battery was discharged until the battery voltage became 1V. In addition,
During this process, the capacities of the three types of batteries were the same. Then, these batteries were left in a constant temperature bath at a temperature of 80 ° C. to measure changes in battery voltage.

The results are shown in FIG. 1 as the relationship between the discharge time and the battery voltage. In the figure, a curve A represents a positive electrode carrying dodecanethiol, a curve B represents a positive electrode carrying t-butyl disulfide, and a curve C represents a comparative example. As is clear from FIG. 1, the battery in which the positive electrode supporting dodecane thiol or t-butyl disulfide is incorporated has a higher battery voltage than that of the comparative battery even when left at a high temperature of 80 ° C. The decline is very slow. This is because the action of the above-described sulfur compound suppresses the reduction of the positive electrode active material by the hydrogen gas generated in the negative electrode.

Examples 3 to 8 and Comparative Examples 2 to 5 Nonwoven fabric FT-310 was dipped in each of the solutions (1) and (2), and dodecanethiol was added to 1 g per 1 g of FT-310.
A separator in which an amount of t-butyl disulfide was supported at 0.8 mmol per 1 g of FT-310 (Example 4) was prepared.

Further, an aqueous solution of sodium sulfite having a concentration of 1 wt. FT-310 1g
A separator was produced having an amount of 0.9 mmol per Example (Example 5). Further, in the separator of Example 5, after drying, it was immersed in an aqueous solution of calcium chloride having a concentration of 1% by weight to precipitate calcium sulfite crystals, which was then washed with water and then again in nitrogen gas at a temperature of 80 ° C. for 1 hour. Was dried to obtain a separator (Example 6).

Further, the nonwoven fabric FT-310 was heated at a temperature of 100 ° C.
After being left in the sulfur dioxide gas atmosphere for 1 hour, it is further left in the atmosphere at room temperature for 1 hour, and the sulfur dioxide becomes FT-3.
A separator having 1.2 mmol supported per 101 g was obtained (Example 7). Further, a saturated methyl isobutyl ketone solution of sulfur dioxide was prepared, and the non-woven fabric FT-310 was dipped therein, and in this state, reflux treatment was performed at a temperature of 100 ° C. for 1 hour and then taken out, and subsequently, in an atmosphere at room temperature. After being dried for 10 minutes, the supported amount of sulfur dioxide is FT-310.
A separator having 1.3 mmol supported per 1 g was obtained (Example 8).

Each of the separators of Examples 5, 6, 7 and 8 was sealed and dried and stored in a light-shielded state to prevent decomposition and dissociation of sulfite ions before being assembled in a battery. For comparison, non-woven fabric FT-310 itself and non-woven fabric FT-773 (trade name, polyamide-based non-woven fabric manufactured by Nippon Vilene Co., Ltd.) themselves were prepared as separators of Comparative Examples 2 and 3, respectively.

In addition, sodium dodecane sulfonate
-Dissolving in propyl alcohol to prepare a solution having a concentration of 1% by weight, and immersing the non-woven fabric FT-310 in this solution, the supported amount of sodium dodecanesulfonate is FT-3.
The separator was 0.9 mmol per 1 g (Comparative Example 4). Further, a sodium sulfate aqueous solution having a concentration of 1% by weight was prepared, and the nonwoven fabric FT-310 was immersed therein to obtain a separator having a sodium sulfate supported amount of 1.1 mmol per 1 g of FT-310 (Comparative Example. 5).

The above 10 kinds of separators were used, the positive electrode manufactured by the method of (1) of Example 1 was used as it was, and the rated capacity was 1100 mAh as in Example 1.
AA size nickel-hydrogen battery was assembled. These one
Similar to Example 1, the 0 kinds of batteries were examined for changes in battery voltage when left in a constant temperature layer at a temperature of 80 ° C.

The results are shown in FIG. As is clear from FIG. 2, all the batteries incorporating the separator according to the present invention show a slower decrease in battery voltage and are excellent in storage performance as compared with the batteries incorporating the comparative separator.

[0053]

As is apparent from the above description, in the alkaline secondary battery according to claim 1, the sulfur compound having an unshared electron pair, as shown in claim 2, causes the transition metal constituting the positive electrode to change. Since it is deactivated, the catalytic reduction reaction of the transition metal is suppressed even when the hydrogen gas generated in the negative electrode comes into contact with the positive electrode, and as a result, the reduction of the positive electrode active material is prevented. Therefore, the self-discharge of the positive electrode is suppressed, and the decrease in the battery voltage during storage is effectively suppressed. In particular, incorporating the positive electrode of claim 1 is effective in the case of the nickel-hydrogen secondary battery of claim 3.

In the alkaline secondary battery of claim 4, the separator carries a compound such as thiol, disulfide, sulfite, and sulfur dioxide that reversibly undergoes oxidation / reduction reaction in an alkaline electrolyte. Therefore, the hydrogen gas generated in the negative electrode during storage is supplemented to suppress its diffusion to the positive electrode. Therefore, the self-discharge of the positive electrode is suppressed and the storage performance of the battery is improved.

[Brief description of drawings]

FIG. 1 shows a battery incorporating a positive electrode according to the present invention at a temperature of 80.
It is a graph which shows the state of the fall of the battery voltage when left to stand at ℃.

FIG. 2 is a graph showing a state of decrease in battery voltage when a battery incorporating the separator according to the present invention is left at a temperature of 80 ° C.

Claims (4)

[Claims] 1. An alkaline secondary battery in which a positive electrode and a negative electrode are arranged in an alkaline electrolyte via a separator, wherein the positive electrode carries a sulfur compound having an unshared electron pair. And alkaline secondary battery. 2. The alkaline secondary battery according to claim 1, wherein the sulfur compound is any one of thiol, disulfide, sulfide, thiophene, sulfoxide, sulfinate, thiosulfate and sulfide. 3. The alkaline secondary battery according to claim 1, wherein the positive electrode is a nickel electrode and the negative electrode is a hydrogen storage alloy electrode. 4. In an alkaline secondary battery in which a positive electrode and a negative electrode are arranged in an alkaline electrolyte via a separator, the separator carries any one of thiol, disulfide, sulfite and sulfur dioxide. Alkaline secondary battery characterized by being