JPH09231968A - Positive plate for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reduction of an open circuit voltage in a battery caused by its shelf state for a long period of time by a method where in the surface of a Ni porous member having a passive state oxide film is provided with a specified Co/Ni mixed compound and active substance is held on it. SOLUTION: A passive state oxide film is applied to a Ni porous member acting as a supporting member. In addition, a Co/Ni mixed compound with a mole ratio of 20:80 to 97:3 of Co and Ni is formed on the surface of the film. After this state, active substance having as its major element nickel hydroxide is held to make a positive plate. The alkaline storage battery having the positive plate with such a configuration as above has a feature that a reduction of an open-circuited voltage and also a reduction in an irreversible electrical discharging capacity are low even if the battery is left for a long period of time. In the case that the mixed compound in respect to the active substance is converted into hydroxide, an effect of improvement in reduction in performance in the shelf state of long period of time is remarkably increased when 1 to 15wt.% is contained.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、負極にカドミウ
ム、水素吸蔵合金、亜鉛あるいは鉄等を用いたアルカリ
蓄電池用正極板に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode plate for an alkaline storage battery which uses cadmium, a hydrogen storage alloy, zinc, iron or the like as a negative electrode.

【０００２】[0002]

【従来の技術】近年の携帯電話、ビデオカメラあるいは
ヘッドホンステレオ等の種々の小型携帯機器の普及にと
もない、それらの電源としてアルカリ蓄電池は重要な役
割を果たしている。アルカリ蓄電池の正極板には、主と
して焼結式およびペースト式の極板が用いられている。
焼結式正極板は、ニッケル粉末を穿孔鋼板に焼結した支
持体である焼結基板に水酸化ニッケルを主体とする活物
質を含浸して製作される。またペースト式正極板は、発
泡ニッケル等の３次元多孔体の支持体に、粉末状の水酸
化ニッケルを種々の添加物と混合した活物質ペーストを
充填して製作される。一般に、発泡ニッケルは焼結基板
に比べて高多孔度であるので、それを用いたペースト式
正極板には高容量化が図れる利点があるが、高率放電性
能の面では焼結式正極板の方が優れている等、双方とも
いくつかの利点を有している。2. Description of the Related Art With the recent widespread use of various small mobile devices such as mobile phones, video cameras and headphone stereos, alkaline storage batteries play an important role as their power source. Sintered and pasted electrode plates are mainly used as the positive electrode plate of the alkaline storage battery.
The sintered positive electrode plate is manufactured by impregnating a sintered substrate, which is a support body obtained by sintering nickel powder into a perforated steel plate, with an active material mainly containing nickel hydroxide. The paste-type positive electrode plate is manufactured by filling a support of a three-dimensional porous body such as foamed nickel with an active material paste in which powdered nickel hydroxide is mixed with various additives. In general, foamed nickel has a higher porosity than a sintered substrate, so a paste-type positive electrode plate using it has the advantage of achieving higher capacity, but in terms of high rate discharge performance, a sintered positive electrode plate. Both have some advantages, such as better.

【０００３】これらの正極板においては、焼結基板ある
いは発泡ニッケル等のニッケル多孔体に関連した種々の
性能改善がおこなわれている。たとえば焼結式正極板で
は、特開昭５９−９６６５９号公報に示されるような焼
結基板を酸素雰囲気中で加熱処理して酸化皮膜を形成さ
せる方法や、特開昭６３−４８７４７号公報に示される
ように焼結基板上に水酸化ニッケルと水酸化コバルトの
モル比が７：３〜５：５である固溶体層を形成する方法
が提案されている。これらの手段には、放電特性の向上
や活物質充填操作をおこなった際の焼結基板の腐食を防
止する効果がある。In these positive electrode plates, various performance improvements have been made in relation to sintered substrates or nickel porous bodies such as nickel foam. For example, in the case of a sintering type positive electrode plate, a method of forming a oxide film by heating a sintered substrate in an oxygen atmosphere as disclosed in JP-A-59-96659 and JP-A-63-48747 are disclosed. As shown, a method of forming a solid solution layer in which the molar ratio of nickel hydroxide and cobalt hydroxide is 7: 3 to 5: 5 is proposed on a sintered substrate. These means have the effects of improving the discharge characteristics and preventing the corrosion of the sintered substrate during the operation of filling the active material.

【０００４】また、特開昭６３−１９７６２号公報に示
されるように、表面層がニッケルよりなる金属支持体の
表面層に活物質化されたニッケル酸化物を有し、かつそ
の酸化物の内部にコバルトまたはカドミウムの単独か、
あるいは混合物を混在させることにより、電子伝導性を
改善し、高率放電特性や活物質利用率を向上させる方法
が提案されている。Further, as disclosed in Japanese Patent Laid-Open No. 63-19762, the surface layer of a metal support made of nickel has nickel oxide as an active material, and the inside of the oxide is formed. Cobalt or cadmium alone,
Alternatively, a method has been proposed in which a mixture is mixed to improve electron conductivity and improve high rate discharge characteristics and active material utilization rate.

【０００５】[0005]

【発明が解決しようとする課題】一般に、アルカリ蓄電
池を長期間使用しないで放置すると、正極活物質のエー
ジング現象すなわち水酸化ニッケルの結晶の整順化が進
行し、充電効率が低下することが知られている。そのた
め、放置後には充放電を数サイクル繰り返さないと放置
前の放電容量まで回復しない。この場合、電池の開路電
圧の低下をともなうが、その度合いが大きい場合には不
可逆な容量低下がおこり、充放電を繰り返しても放置前
の容量が得られなくなるという問題がある。It is generally known that when an alkaline storage battery is left unused for a long period of time, the aging phenomenon of the positive electrode active material, that is, the ordering of the nickel hydroxide crystals progresses and the charging efficiency decreases. Has been. Therefore, the charge capacity cannot be restored to the discharge capacity before being left unless it is repeatedly charged and discharged for several cycles after being left. In this case, the open circuit voltage of the battery is lowered, but if the degree is large, irreversible capacity reduction occurs, and there is a problem that the capacity before being left cannot be obtained even if charging and discharging are repeated.

【０００６】また最近では、使用上の安全を考慮して、
電池電圧がたとえば１Ｖ程度の設定値に満たないと電池
の充電が開始されないように制御する等の保護回路を設
けた充電器もみられるようになった。これは、たとえば
微小短絡によって開路電圧が低下した電池が充電された
場合の異常加熱等による火災や、電池が正確にセットで
きていない状態での充電や逆充電等を防止することを目
的としている。そのため、長期間放置されて開路電圧が
設定値より低い電池は、このタイプの充電器では充電す
ることができないという問題も生じている。そこで、ア
ルカリ蓄電池を長期放置したときに生ずるこれらの問題
点に対する有効な解決手段が求められていた。Recently, in consideration of safety in use,
Some chargers have been provided with a protection circuit for controlling the charging of the battery so that the charging of the battery does not start unless the battery voltage falls below a set value of about 1V. This is intended to prevent fire due to abnormal heating when a battery whose open circuit voltage has dropped due to a micro short circuit is charged, or charging or reverse charging when the battery is not set correctly. . Therefore, a battery having an open circuit voltage lower than a set value after being left for a long period of time cannot be charged by this type of charger. Therefore, there has been a demand for an effective solution to these problems that occur when the alkaline storage battery is left for a long time.

【０００７】[0007]

【課題を解決するための手段】本発明は前記課題を解決
するべく、不働態酸化物皮膜を有するニッケル多孔体表
面に、コバルトとニッケルのモル比が２０：８０〜９
７：３であるコバルト・ニッケル混合化合物を具備し、
その上に水酸化ニッケルを主体とする活物質が保持され
て成るアルカリ蓄電池用正極板を提供するものである。
なお、前記水酸化ニッケルを主体とする活物質に対する
前記コバルト・ニッケル混合化合物の割合は、前記混合
化合物を水酸化物として換算した場合に１〜１５ｗｔ％
含まれることが望ましい。In order to solve the above problems, the present invention has a molar ratio of cobalt to nickel of 20:80 to 9 on the surface of a nickel porous body having a passive oxide film.
Comprising a 7: 3 mixed cobalt-nickel compound,
The present invention provides a positive electrode plate for an alkaline storage battery, in which an active material mainly composed of nickel hydroxide is held on the positive electrode plate.
The ratio of the cobalt-nickel mixed compound to the active material mainly composed of nickel hydroxide is 1 to 15 wt% when the mixed compound is converted into hydroxide.
It is desirable to be included.

【０００８】[0008]

【発明の実施の形態】本発明では、支持体であるニッケ
ル多孔体に、不働態酸化物皮膜を付与する。さらに、そ
の表面にコバルトとニッケルのモル比が２０：８０〜９
７：３であるコバルト・ニッケル混合化合物を形成させ
る。その後、水酸化ニッケルを主体とする活物質を保持
させて正極板を製作するものである。このような構成の
水酸化ニッケル正極板を用いたアルカリ蓄電池は、長期
間放置されても開路電圧および不可逆な放電容量の低下
が小さいという特徴がある。なお前記水酸化ニッケルを
主体とする活物質に対する前記コバルト・ニッケル混合
化合物の割合は、前記混合化合物を水酸化物に換算した
場合において、１〜１５ｗｔ％含まれる場合に、長期間
放置における性能低下の改善に特に効果が大きくかつ実
用的である。BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a passive oxide film is applied to a nickel porous body which is a support. Furthermore, the molar ratio of cobalt and nickel on the surface is 20: 80-9.
A 7: 3 mixed cobalt-nickel compound is formed. Then, the positive electrode plate is manufactured by holding an active material mainly containing nickel hydroxide. The alkaline storage battery using the nickel hydroxide positive electrode plate having such a configuration is characterized in that the open circuit voltage and the irreversible discharge capacity are not significantly reduced even if the battery is left for a long time. When the ratio of the cobalt-nickel mixed compound to the active material mainly containing nickel hydroxide is 1 to 15 wt% when the mixed compound is converted into hydroxide, the performance is deteriorated after being left for a long time. Is particularly effective and practical for improving

【０００９】[0009]

【実施例】以下、本発明の詳細を実施例を用いて説明す
る。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below using embodiments.

【００１０】多孔度が約８５％の焼結基板を、空気中４
００℃で２０分間加熱処理して緻密な酸化ニッケルの不
働態酸化物皮膜を付与した。これに、コバルトとニッケ
ルのモル比が７０：３０の２．５Ｍ硝酸塩水溶液を減圧
含浸したのちアルカリ性水溶液に浸漬し、次いで湯洗お
よび乾燥をおこなうことにより、焼結基板表面にコバル
ト・ニッケル混合化合物を形成した。さらに、硝酸ニッ
ケルを主成分とする５．５Ｍ硝酸塩水溶液を減圧含浸し
たのち、アルカリ性水溶液に浸漬し、次いで湯洗および
乾燥するという操作を数回繰り返すことにより、水酸化
ニッケルを主体とする活物質を充填して本発明によるア
ルカリ蓄電池用正極板を製作した。このとき、焼結基板
表面のコバルト・ニッケル混合化合物は水酸化物であ
り、水酸化ニッケルを主体とする活物質に対する割合は
約１０ｗｔ％であった。A sintered substrate having a porosity of about 85% was placed in air 4
It heat-processed at 00 degreeC for 20 minutes, and provided the dense passive oxide film of nickel oxide. This was impregnated with a 2.5 M nitrate aqueous solution having a molar ratio of cobalt and nickel of 70:30 under reduced pressure, immersed in an alkaline aqueous solution, and then washed with hot water and dried to give a cobalt-nickel mixed compound on the surface of the sintered substrate. Was formed. Furthermore, the active material mainly composed of nickel hydroxide was obtained by repeating several times the operation of impregnating with a 5.5 M nitrate aqueous solution containing nickel nitrate as a main component under reduced pressure, immersing in an alkaline aqueous solution, and then washing with water and drying. To prepare a positive electrode plate for an alkaline storage battery according to the present invention. At this time, the cobalt-nickel mixed compound on the surface of the sintered substrate was a hydroxide, and the ratio to the active material mainly containing nickel hydroxide was about 10 wt%.

【００１１】この正極板と、正極より充分大きな容量を
もち化成処理によって部分充電済みの公知の焼結式カド
ミウム負極板とを、親水性を付与したポリプロピレン製
セパレータを介して渦巻状に捲回し、電解液として７Ｍ
水酸化カリウムを主体とする水溶液を用いて公称容量１
６００ｍＡｈ、ＫＲ−ＳＣサイズの密閉式ニッケル−カ
ドミウム電池Ａ（以下、本発明電池Ａ）を製作した。This positive electrode plate and a known sintered cadmium negative electrode plate having a capacity sufficiently larger than that of the positive electrode and partially charged by a chemical conversion treatment are spirally wound with a hydrophilic polypropylene separator interposed therebetween. 7M as electrolyte
Nominal capacity of 1 using an aqueous solution containing potassium hydroxide
A sealed nickel-cadmium battery A (hereinafter referred to as battery A of the present invention) of 600 mAh and KR-SC size was manufactured.

【００１２】また、正極の焼結基板表面にコバルト・ニ
ッケル混合化合物を形成後、３００℃で３０分間加熱処
理して水酸化物であるコバルト・ニッケル混合化合物を
酸化物に変換したこと以外は本発明電池Ａと同様にして
本発明電池Ｂを製作した。After forming the cobalt / nickel mixed compound on the surface of the sintered substrate of the positive electrode, the cobalt / nickel mixed compound, which is a hydroxide, was converted into an oxide by heat treatment at 300 ° C. for 30 minutes. The invention battery B was manufactured in the same manner as the invention battery A.

【００１３】比較として、正極板に加熱処理をおこなわ
ない焼結基板を用いたこと以外は本発明電池Ａと同様に
した比較電池Ｃ、コバルト・ニッケル混合化合物を形成
することなしに、加熱処理した焼結基板表面に水酸化ニ
ッケルを主体とする活物質を充填した正極板を用いたこ
と以外は本発明電池Ａと同様にした比較電池Ｄ、および
正極板に加熱処理をおこなわない焼結基板を用いたこと
以外は比較電池Ｄと同様にした比較電池Ｅを製作した。For comparison, the comparative battery C, which was the same as the battery A of the present invention except that the sintered substrate which was not subjected to the heat treatment was used for the positive electrode plate, was subjected to the heat treatment without forming the cobalt-nickel mixed compound. Comparative battery D, which was the same as battery A of the present invention except that a positive electrode plate in which an active material mainly containing nickel hydroxide was filled on the surface of the sintered substrate was used, and a sintered substrate on which the positive electrode plate was not heat-treated. A comparative battery E was manufactured in the same manner as the comparative battery D except that it was used.

【００１４】つぎに、ｐＨが一定に保たれるように制御
されたアルカリ性水溶液を攪拌しながら、これにコバル
トとニッケルのモル比が７０：３０の１．５Ｍ硫酸塩水
溶液を徐々に投入し、コバルト・ニッケル混合化合物を
沈澱させた。これを濾過・洗浄・乾燥することにより粉
末とし、０．４ｗｔ％カルボキシメチルセルロース水溶
液に分散させてペーストを調製した。多孔度９５％の発
泡ニッケル（住友電工製、商品名セルメット）を、空気
中４００℃で２０分間加熱処理して緻密な酸化ニッケル
の不働態酸化物皮膜を付与した後、前記ペーストを充
填、乾燥することにより、コバルト・ニッケル混合化合
物を発泡ニッケル表面に形成した。Next, while stirring the alkaline aqueous solution whose pH was kept constant, a 1.5M aqueous solution of sulfate having a molar ratio of cobalt to nickel of 70:30 was gradually added thereto, A cobalt-nickel mixed compound was precipitated. This was filtered, washed, and dried to give a powder, which was dispersed in a 0.4 wt% carboxymethylcellulose aqueous solution to prepare a paste. Foamed nickel with a porosity of 95% (Sumitomo Denko, trade name Celmet) is heat-treated in air at 400 ° C. for 20 minutes to give a dense nickel oxide passive oxide film, and then the paste is filled and dried. By doing so, the cobalt-nickel mixed compound was formed on the surface of the foamed nickel.

【００１５】さらに、水酸化ニッケルを主体とする活物
質粉末を添加物である水酸化コバルトおよび金属ニッケ
ルと混合した活物質ペーストを充填、乾燥、プレスして
本発明によるアルカリ蓄電池用正極板を製作した。発泡
ニッケル表面のコバルト・ニッケル混合化合物は水酸化
物であり、水酸化ニッケルを主体とする活物質に対する
割合は約１０ｗｔ％であった。Further, an active material paste obtained by mixing an active material powder mainly containing nickel hydroxide with an additive cobalt hydroxide and metallic nickel is filled, dried and pressed to manufacture the positive electrode plate for an alkaline storage battery according to the present invention. did. The cobalt-nickel mixed compound on the surface of the foamed nickel was a hydroxide, and its ratio to the active material mainly containing nickel hydroxide was about 10 wt%.

【００１６】この正極板と、正極より充分大きな容量を
もち化成処理によって部分充電済みの公知の焼結式カド
ミウム負極板とを、親水性を付与したポリプロピレン製
セパレータを介して渦巻状に捲回し、電解液として７Ｍ
水酸化カリウムを主体とする水溶液を用いて公称容量１
６００ｍＡｈ、ＫＲ−ＳＣサイズの密閉式ニッケル−カ
ドミウム電池Ｆ（以下、本発明電池Ｆ）を製作した。The positive electrode plate and a known sintered cadmium negative electrode plate having a capacity sufficiently larger than that of the positive electrode and partially charged by a chemical conversion treatment are spirally wound with a hydrophilic polypropylene separator interposed therebetween. 7M as electrolyte
Nominal capacity of 1 using an aqueous solution containing potassium hydroxide
A 600 mAh, KR-SC size sealed nickel-cadmium battery F (hereinafter, referred to as battery F of the present invention) was manufactured.

【００１７】比較として、正極板に酸化ニッケルの不働
態酸化物皮膜を付与するための加熱処理をおこなわず、
また表面にコバルト・ニッケル混合化合物を形成しない
発泡ニッケルを用いたこと以外は本発明電池Ｆと同様に
して比較電池Ｇを製作した。For comparison, the positive electrode plate was not subjected to heat treatment for applying a passive oxide film of nickel oxide,
Further, a comparative battery G was manufactured in the same manner as the battery F of the present invention except that the foamed nickel that did not form the cobalt-nickel mixed compound on the surface was used.

【００１８】これらの電池を、２５℃において０．１Ｃ
ｍＡ（１６０ｍＡ）で１５時間初充電したのち、１Ｃｍ
Ａ（１６００ｍＡ）で１Ｖまで放電した。さらに、１Ｃ
ｍＡ（１６００ｍＡ）で１．２時間充電し、０．２Ｃｍ
Ａ（３２０ｍＡ）で放電するという充放電を５サイクル
おこなった。放電状態の電池を４５℃の恒温室中に９０
日間放置した。放置後、電池を２５℃の雰囲気に戻し、
３時間経過してから再び放置前と同じ条件で充放電を５
サイクルおこなった。These batteries were tested at 0.1 ° C. at 25 ° C.
First charge for 15 hours at 1mA (160mA)
It was discharged to 1 V with A (1600 mA). Furthermore, 1C
Charged for 1.2 hours with mA (1600mA), 0.2Cm
Five cycles of charging / discharging of discharging at A (320 mA) were performed. 90 in a thermostatic chamber at 45 ℃
Left for days. After leaving it, return the battery to the atmosphere of 25 ° C,
After 3 hours, charge and discharge again under the same conditions as before leaving for 5 hours.
Cycle.

【００１９】電池Ａ、Ｂ、Ｃ、ＤおよびＥの４５℃にお
ける放置中の開路電圧の変化を図１に示す。焼結基板の
ニッケル焼結体に不働態酸化物皮膜を付与した後に、そ
の表面にコバルト・ニッケル混合化合物を形成した正極
板を用いた本発明電池ＡおよびＢの放置中の開路電圧の
低下は小さく、放置９０日目においても１Ｖ以上の高い
値を示した。FIG. 1 shows the change in open circuit voltage of the batteries A, B, C, D and E at 45 ° C. during standing. After the passive oxide film was applied to the nickel sintered body of the sintered substrate, the open circuit voltage of the batteries A and B of the present invention using the positive electrode plate having the cobalt / nickel mixed compound formed on the surface of the sintered substrate was lowered during standing. It was small and showed a high value of 1 V or more even after 90 days of standing.

【００２０】これに対して、不働態酸化物皮膜が付与さ
れていないニッケル焼結体の表面にコバルト・ニッケル
混合化合物を形成した正極板を用いた比較電池Ｃの開路
電圧は、放置５０日目付近で大きく低下し、放置９０日
目には約０．２Ｖになった。また、正極の焼結基板のニ
ッケル焼結体表面にコバルト・ニッケル混合化合物を形
成していない比較電池ＤおよびＥの開路電圧は、放置２
０日目付近から大きく低下した。それらの放置９０日目
の開路電圧は、正極の焼結基板のニッケル焼結体に不働
態酸化物皮膜のみが付与されている比較電池Ｄでは約
０．６Ｖ、不働態酸化物皮膜もコバルト・ニッケル混合
化合物も形成されていない比較電池Ｅでは約０．２Ｖで
あった。On the other hand, the open circuit voltage of the comparative battery C using the positive electrode plate having the cobalt-nickel mixed compound formed on the surface of the nickel sintered body to which the passive oxide film was not applied was 50 days after leaving. It drastically dropped in the vicinity, and became about 0.2 V on the 90th day of standing. Further, the open circuit voltage of Comparative Batteries D and E in which the cobalt-nickel mixed compound was not formed on the surface of the nickel sintered body of the sintered substrate of the positive electrode was 2
It decreased significantly from around day 0. The open-circuit voltage on the 90th day of storage was about 0.6 V in Comparative Battery D in which only the passive oxide film was applied to the nickel sintered body of the positive electrode sintered substrate, and the passive oxide film was also cobalt. The voltage was about 0.2 V in the comparative battery E in which the nickel mixed compound was not formed.

【００２１】すなわち、正極の焼結基板のニッケル焼結
体に不働態酸化物皮膜を付与することのみによる放置中
の開路電圧の低下を抑制する効果は小さく、また、正極
の焼結基板のニッケル焼結体表面にコバルト・ニッケル
混合化合物を形成した場合でも、不働態酸化皮膜が付与
されていないと電圧低下を抑制することはできなかっ
た。これに対し、不働態酸化皮膜を付与したニッケル焼
結体表面にコバルト・ニッケル混合化合物を形成した正
極板を用いることによって、初めて放置中の開路電圧の
低下を長期間にわたって抑制することが可能となった。That is, the effect of suppressing the decrease in the open circuit voltage during standing only by applying the passive oxide film to the nickel sintered body of the positive electrode sintered substrate is small, and the nickel of the positive electrode sintered substrate is small. Even when the cobalt-nickel mixed compound was formed on the surface of the sintered body, the voltage drop could not be suppressed unless the passive oxide film was provided. On the other hand, by using a positive electrode plate with a cobalt-nickel mixed compound formed on the surface of a nickel sintered body provided with a passive oxide film, it is possible to suppress the drop in open circuit voltage during standing for a long time for the first time. became.

【００２２】電池ＦおよびＧの４５℃における放置中の
開路電圧の変化を図２に示す。発泡ニッケルに不働態酸
化物皮膜を付与した後に、その表面にコバルト・ニッケ
ル混合化合物を形成した正極板を用いた本発明電池Ｆの
放置中の開路電圧の低下は小さく、放置９０日目におい
ても１Ｖ以上の高い値を示した。これに対して、発泡ニ
ッケルに不働態酸化物皮膜を付与せず、その表面にコバ
ルト・ニッケル混合化合物を形成していない正極板を用
いた比較電池Ｇの放置９０日目の開路電圧は約０．８Ｖ
であった。FIG. 2 shows changes in the open circuit voltage of the batteries F and G at 45 ° C. during standing. After the passive oxide film was applied to the foamed nickel, the decrease in the open circuit voltage of the battery F of the present invention using the positive electrode plate having the cobalt-nickel mixed compound formed on the surface was small, and even after 90 days of standing, A high value of 1 V or more was shown. On the other hand, the open circuit voltage of the comparative battery G using the positive electrode plate in which the passive oxide film was not applied to the nickel foam and the cobalt-nickel mixed compound was not formed on the surface of the battery was 90 days after leaving for about 90 days. .8V
Met.

【００２３】ペースト式正極板を用いた場合にも、不働
態酸化物皮膜を付与した発泡ニッケルの表面にコバルト
・ニッケル混合化合物を形成することによって、放置中
の開路電圧の低下を抑制する効果が大きいことが確認さ
れた。Even when the paste type positive electrode plate is used, by forming the cobalt-nickel mixed compound on the surface of the nickel foam provided with the passive oxide film, the effect of suppressing the decrease in the open circuit voltage during standing can be obtained. It was confirmed to be large.

【００２４】つぎに、放置性能に及ぼすコバルト・ニッ
ケル混合化合物の組成の影響を検討すべく、コバルトと
ニッケルのモル比を適宜調整した２．５Ｍ硝酸塩水溶液
を用いて、種々の組成のコバルト・ニッケル混合化合物
を形成したこと以外は本発明電池Ａと同様にして種々の
電池を製作した。これらの電池を用いて、前述と同様の
実験をおこなった際の各電池の４５℃・９０日間放置後
の開路電圧を図３に示す。Next, in order to study the influence of the composition of the cobalt / nickel mixed compound on the leaving performance, cobalt / nickel of various compositions was prepared by using 2.5M aqueous nitrate solution in which the molar ratio of cobalt and nickel was appropriately adjusted. Various batteries were manufactured in the same manner as the battery A of the present invention except that a mixed compound was formed. FIG. 3 shows the open-circuit voltage of each battery after leaving it to stand at 45 ° C. for 90 days in the same experiment as described above using these batteries.

【００２５】正極の焼結基板のニッケル焼結体の表面に
形成した化合物がニッケル単独あるいはコバルト単独で
ある場合、放置後の開路電圧はそれぞれ約０．５３Ｖお
よび約０．７２Ｖと低い値であった。これに対して、コ
バルト・ニッケル混合化合物を形成させた場合には電圧
低下は抑制され、特に混合化合物中のコバルトとニッケ
ルのモル比が２０：８０〜９７：３の場合に４５℃・９
０日間放置後の開路電圧が１Ｖ以上を示すという顕著な
効果が得られた。この理由は定かではないが、ニッケル
焼結体表面の化合物中にニッケルを添加したことによっ
て、いわゆるオキシ水酸化コバルトによるネットワーク
の形成効果が増幅されたためと思われる。When the compound formed on the surface of the nickel sintered body of the positive electrode sintered substrate is nickel alone or cobalt alone, the open circuit voltages after being left are as low as about 0.53 V and about 0.72 V, respectively. It was On the other hand, when the cobalt / nickel mixed compound is formed, the voltage drop is suppressed, and particularly when the molar ratio of cobalt and nickel in the mixed compound is 20:80 to 97: 3, 45 ° C. · 9.
The remarkable effect that the open circuit voltage after standing for 0 days is 1 V or more was obtained. The reason for this is not clear, but it is considered that the effect of so-called cobalt oxyhydroxide forming a network was amplified by adding nickel to the compound on the surface of the nickel sintered body.

【００２６】この試験における焼結基板のニッケル焼結
体の表面に形成したコバルト・ニッケル混合化合物の組
成と容量回復率との関係を図４に示す。ここで、各電池
の容量回復率は容量回復率（％）＝｛放置後５サイクル
目の放電容量（ｍＡｈ）／放置前の放電容量（ｍＡ
ｈ）｝×１００と定義した。コバルト・ニッケル混合化
合物中のコバルトの割合が２０モル％以上の場合には、
容量回復率は９５％を越える高い値を示し、放置による
不可逆な容量低下が小さい電池を得ることができた。FIG. 4 shows the relationship between the composition of the cobalt-nickel mixed compound formed on the surface of the nickel sintered body of the sintered substrate and the capacity recovery rate in this test. Here, the capacity recovery rate of each battery is the capacity recovery rate (%) = {discharge capacity (mAh) at 5th cycle after leaving / discharge capacity before leaving (mA)
h)} × 100. When the proportion of cobalt in the cobalt-nickel mixed compound is 20 mol% or more,
The capacity recovery rate showed a high value of over 95%, and a battery having a small irreversible capacity decrease due to standing could be obtained.

【００２７】さらに、放置性能に及ぼすニッケル焼結体
表面へのコバルト・ニッケル混合化合物の形成量の影響
を調査するために、コバルトとニッケルのモル比を７
０：３０に固定して種々の濃度に調製した硝酸塩水溶液
を用い、これ以外は本発明電池Ａと同様にして正極の焼
結基板のニッケル焼結体表面へのコバルト・ニッケル混
合化合物の形成量が異なる種々の電池を製作した。な
お、各電池において水酸化ニッケルを主体とする活物質
の理論容量がほぼ等しくなるように、含浸回数を適宜調
整した。Further, in order to investigate the influence of the formation amount of the cobalt-nickel mixed compound on the surface of the nickel sintered body on the leaving performance, the molar ratio of cobalt and nickel was set to 7
Amounts of cobalt / nickel mixed compound formed on the surface of the nickel sintered body of the sintered substrate of the positive electrode were used in the same manner as the battery A of the present invention except that the aqueous nitrate solution fixed at 0:30 and adjusted to various concentrations was used. Various batteries with different characteristics were manufactured. In addition, the number of impregnations was appropriately adjusted so that the theoretical capacities of the active materials containing nickel hydroxide as a main component were approximately equal in each battery.

【００２８】これらの電池を用いて、前述と同様の実験
をおこなった際の４５℃・９０日間放置後の各電池の開
路電圧を図５に示す。この場合のニッケル焼結体表面の
コバルト・ニッケル混合化合物は水酸化物であり、水酸
化ニッケルを主体とする活物質に対して、その割合が１
ｗｔ％以上の場合には、放置後の開路電圧は１Ｖ以上の
高い値を示した。しかしながら、コバルト・ニッケル混
合化合物の形成量が多くなり過ぎると正極板の残留多孔
度が減少するため、充分な放電容量を得るための活物質
を充填できなくなる等の問題があるので実用的でない。
したがって、水酸化ニッケルを主体とする活物質に対し
て、ニッケル焼結体表面に形成されるコバルト・ニッケ
ル混合化合物の割合は、水酸化物に換算した場合におい
て、実用上１〜１５ｗｔ％に限られる。FIG. 5 shows the open circuit voltage of each battery after leaving it to stand at 45 ° C. for 90 days in the same experiment as described above using these batteries. In this case, the cobalt-nickel mixed compound on the surface of the nickel sintered body is a hydroxide, and its ratio is 1 with respect to the active material mainly containing nickel hydroxide.
In the case of wt% or more, the open circuit voltage after standing showed a high value of 1 V or more. However, if the amount of the cobalt-nickel mixed compound formed is too large, the residual porosity of the positive electrode plate decreases, and there is a problem that the active material cannot be filled to obtain a sufficient discharge capacity, which is not practical.
Therefore, the ratio of the cobalt-nickel mixed compound formed on the surface of the nickel sintered body to the active material mainly containing nickel hydroxide is practically limited to 1 to 15 wt% when converted to hydroxide. To be

【００２９】なお、実施例に示した本発明による正極板
では、ニッケル多孔体への不働態酸化物皮膜の付与方法
として空気中で加熱処理する方法を示したが、電気化学
的あるいは化学的な方法を用いて酸化しても良いし、あ
るいは酸化物を付着させても良い。In the positive electrode plate according to the present invention shown in the examples, a method of heat treatment in air was shown as a method of applying the passive oxide film to the nickel porous body, but it is electrochemical or chemical. A method may be used to oxidize or an oxide may be deposited.

【００３０】また、言うまでもなく、本発明の効果はニ
ッケル・カドミウム電池に限定されるものではなく、負
極に水素吸蔵合金、亜鉛あるいは鉄等を用いたアルカリ
蓄電池においても有効である。Needless to say, the effect of the present invention is not limited to the nickel-cadmium battery, but is also effective for an alkaline storage battery using a hydrogen storage alloy, zinc, iron or the like for the negative electrode.

【００３１】[0031]

【発明の効果】本発明によるアルカリ蓄電池用正極板
は、長期間の放置による電池の開路電圧の低下を抑制で
き、かつ不可逆な容量低下の小さい放置性能の優れた電
池を提供するものであり、その工業的価値は極めて大き
い。The positive electrode plate for an alkaline storage battery according to the present invention is capable of suppressing a decrease in the open circuit voltage of the battery due to being left for a long period of time, and provides a battery having excellent leaving performance with a small irreversible capacity decrease. Its industrial value is extremely high.

【図面の簡単な説明】[Brief description of drawings]

【図１】各電池の放置中の開路電圧の変化を示した図FIG. 1 is a diagram showing a change in open circuit voltage of each battery during standing.

【図２】各電池の放置中の開路電圧の変化を示した図FIG. 2 is a diagram showing changes in open circuit voltage of each battery while being left unattended.

【図３】正極板中のコバルト・ニッケル混合化合物の組
成と電池の放置後の開路電圧との関係を示した図FIG. 3 is a diagram showing the relationship between the composition of the cobalt / nickel mixed compound in the positive electrode plate and the open circuit voltage of the battery after being left unattended.

【図４】正極板中のコバルト・ニッケル混合化合物の組
成と放置後の容量回復率との関係を示した図FIG. 4 is a diagram showing the relationship between the composition of the cobalt-nickel mixed compound in the positive electrode plate and the capacity recovery rate after standing.

【図５】活物質に対する正極板中のコバルト・ニッケル
混合化合物の割合と電池の放置後の開路電圧との関係を
示した図FIG. 5 is a diagram showing the relationship between the ratio of the cobalt / nickel mixed compound in the positive electrode plate to the active material and the open circuit voltage of the battery after being left standing.

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 不働態酸化物皮膜を有するニッケル多孔
体表面に、コバルトとニッケルのモル比が２０：８０〜
９７：３であるコバルト・ニッケル混合化合物を具備
し、その上に水酸化ニッケルを主体とする活物質が保持
されていることを特徴とするアルカリ蓄電池用正極板。1. A molar ratio of cobalt to nickel on the surface of a nickel porous body having a passive oxide film is 20:80 to.
A positive electrode plate for an alkaline storage battery, which comprises a 97: 3 mixed compound of cobalt and nickel and on which an active material mainly composed of nickel hydroxide is retained. 【請求項２】 前記水酸化ニッケルを主体とする活物質
に対する前記コバルト・ニッケル混合化合物の割合が、
前記混合化合物を水酸化物として換算した場合に１〜１
５ｗｔ％であることを特徴とする請求項１記載のアルカ
リ蓄電池用正極板。2. The ratio of the cobalt-nickel mixed compound to the active material mainly composed of nickel hydroxide is
1 to 1 when the mixed compound is converted into hydroxide
It is 5 wt%, The positive electrode plate for alkaline storage batteries of Claim 1 characterized by the above-mentioned.