JP3869582B2

JP3869582B2 - Nickel electrode active material for alkaline storage battery, method for producing the same, non-sintered nickel electrode using the same, and alkaline storage battery using the non-sintered nickel electrode.

Info

Publication number: JP3869582B2
Application number: JP11396599A
Authority: JP
Inventors: 勝木原; 良貴馬場
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1999-04-21
Filing date: 1999-04-21
Publication date: 2007-01-17
Anticipated expiration: 2019-04-21
Also published as: JP2000306578A

Description

【０００１】
【発明の属する技術分野】
本発明は、ニッケル水素蓄電池、ニッケルカドミウム蓄電池、ニッケル亜鉛蓄電池などのアルカリ蓄電池に関わり、特に、この種のアルカリ蓄電池に用いるニッケル電極活物質、およびこのニッケル電極活物質を用いた非焼結式ニッケル電極ならびにこの非焼結式ニッケル電極を用いたアルカリ蓄電池に関する。
【０００２】
【従来の技術】
近年、携帯機器の急速な普及により従来に増して高性能な蓄電池が要請されるようになった。このような背景にあって、ニッケル水素蓄電池、ニッケルカドミウム蓄電池などのアルカリ蓄電池に用いられるニッケル電極活物質として、活物質利用率、過放電後の容量回復率などを向上させるために、水酸化ニッケル活物質粒子の表面にナトリウムイオン等のカチオンを含有した結晶性が乱れた高次コバルト化合物層を有する水酸化ニッケル複合粒子が、例えば、特開平８−１４８１４５号公報にて提案されている。
【０００３】
この特開平８−１４８１４５号公報にて提案された、ナトリウムイオン等のカチオンを含有した結晶性が乱れた高次コバルト化合物層を有する水酸化ニッケル複合粒子は次のようにして作製されるものである。即ち、水酸化ニッケルが析出した溶液中に硫酸コバルト水溶液と水酸化ナトリウム水溶液を適下して水酸化ナトリウム液含浸ニッケル活物質粒子とし、アルカリ共存下で空気中で加熱して、高次化処理を行う。このようにして、水酸化ニッケル活物質粒子の表面に結晶性が乱れた高次コバルト化合物を有する水酸化ニッケル複合粒子が得られる。
【０００４】
このような水酸化ニッケル複合粒子は、高次コバルト化合物の高導電性効果が発揮されることで活物質利用率が向上した非焼結式ニッケル電極が得られるようになる。また、水酸化ニッケル粒子の表面に存在するコバルト化合物は、水酸化ニッケル粒子の内部との境界において水酸化ニッケルを取り込んだ状態で結晶化するため、コバルト化合物は電解液に対する溶解性が抑制され、過放電後の容量低下が抑制されるようになる。
【０００５】
【発明が解決しようとする課題】
しかしながら、特開平８−１４８１４５号公報にて提案された水酸化ニッケル複合粒子にあっては、作製の過程で水洗、乾燥する必要があり、その際にコバルト化合物の一部が脱落し、コバルト化合物層の被覆が不完全になるという問題があった。また、この水酸化ニッケル複合粒子を用いた電池が長期的に短絡状態に曝された場合、この水酸化ニッケル複合粒子が電解液と接触しているため、高次コバルト化合物が還元されて電解液に溶出し、コバルトの導電性ネットワークが崩壊される。このため、コバルト化合物の高導電性効果が失われ、電池性能が低下するという問題があった。
【０００６】
そこで、本発明は上記問題点に鑑みてなされたものであり、水酸化ニッケルを被覆するコバルト化合物の脱落、電解液への溶出を防止し、単位活物質あたりの容量が高く、特に放電深度の深い充放電サイクルが進行しても電池容量の低下が抑制されたサイクル特性に優れたアルカリ蓄電池を提供しようとすることを本発明の課題とする。
【０００７】
【課題を解決するための手段】
本発明のアルカリ蓄電池用ニッケル電極活物質は、水酸化ニッケルの表面を水酸化コバルト又は水酸化コバルトを加熱酸化したコバルト化合物の層で被覆したアルカリ蓄電池用ニッケル電極活物質であって、前記層の内部にフッ素樹脂を含有させたことを特徴とするものである。
【０００８】
【発明の実施の形態】
[実施例１]
以下、本発明の実施例について説明するが、本発明は下記実施例に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能である。
【０００９】
（ニッケル電極活物質の作製）
金属ニッケルに対して、亜鉛１重量％、コバルト３重量％となるように、硫酸ニッケル、硫酸亜鉛、硫酸コバルトの混合水溶液を攪拌しながら、水酸化ナトリウム水溶液を徐々に添加し、反応中のpHを13〜14に安定させて球状の水酸化ニッケルを析出させる。
【００１０】
この水酸化ニッケルが析出した水溶液を攪拌し、この水溶液中に、反応中のpHを9〜10に維持するようにして、５０重量％のポリテトラフルオロエチレン（以下ＰＴＦＥと云う）を分散させた硫酸コバルト水溶液のディスパージョンを添加して、水酸化ニッケルを主成分とする球状の水酸化ニッケル粒子を結晶核とし、この核の周囲に、主として内部にＰＴＦＥを含有させた水酸化コバルトを、前記水酸化ニッケルに対して１０重量％析出させた。
【００１１】
尚、水酸化コバルト層の表面にも若干ＰＴＦＥの存在を確認した。
【００１２】
この複合粒子粉末に対して、１０倍の重量の純水で３回洗浄した後、脱水、乾燥することにより、内部にPTFEを含有した水酸化コバルト層を有する本発明のニッケル電極活物質ａを作製した。
【００１３】
（非焼結式ニッケル電極の作製）
上述のように作製したニッケル電極活物質ａに0.2重量％のポリエチレンオキサイド（以下ＰＥＯと云う）水溶液を混合して活物質スラリーを作製した。この活物質スラリーを多孔度96％の３次元的に網目構造を有した発泡ニッケルに充填し、乾燥後、圧延して本発明の非焼結式ニッケル正極Ａを作製した。
【００１４】
（ニッケル水素蓄電池の作製）
前記のように作製した本発明の非焼結式正極と、負極として公知の水素吸蔵合金電極を、セパレータとして耐アルカリ性の不織布を、また、電解液として30重量％の水酸化カリウム水溶液をそれぞれ使用して、公称容量1200mAhのAAサイズのニッケル水素蓄電池（Ａ）を作製した。
【００１５】
図１は前記の様に作製した本発明のニッケル水素電池を示す断面図であり、水酸化ニッケル活物質を有する正極４と、水素吸蔵合金粉末を有する負極５と、これら正負両極板４、５間に介装されたセパレータ６とからなる電極群７は渦巻状に巻回されており、電池外装缶１内に配置した後、30重量％の水酸化カリウム水溶液からなる電解液を注入している。そして、上記負極５は負極集電体（図示せず）により電池外装缶１の底面部に接続されている。
【００１６】
他方、電池外装缶１の上部には、ガスケット８を介在させて、中央部が開口された封口板２が配設され、この封口板２に正極端子９が装着されている。また、正極端子９と正極板４は正極集電体３及び前記封口板２を介して接続されている。
【００１７】
[実施例２]
前記実施例１と同様にして、主成分が水酸化ニッケルである球状水酸化ニッケル粒子を結晶核として、この核の周囲に、主として内部にＰＴＦＥを含有させた水酸化コバルトを、前記水酸化ニッケルに対して、１０重量％析出させた。この析出物を採取して水洗、乾燥して、球状水酸化ニッケル粒子の表面にＰＴＦＥを主として内部に含有した水酸化コバルトの被覆層を有した複合粒子粉末を得た。尚、水酸化コバルト層の表面にも若干ＰＴＦＥの存在を確認した。
【００１８】
その後、この複合粒子を１００℃の加熱空気の雰囲気中で、この複合粒子粉末に対して２５重量％の水酸化カリウムを０．５時間噴霧することによって、前記水酸化コバルトを結晶性の乱れた、カリウムカチオンを含有した高次コバルト化合物層に変化させた。その後、純水で３回洗浄した後、脱水、乾燥することにより、ＰＴＦＥを含有した高導電性の高次コバルト被覆層を有した本発明のニッケル電極活物質ｂ作製した。
【００１９】
その後、前記実施例１と同様にして本発明の非焼結式ニッケル電極Ｂ及び本発明の公称容量1200mAh、AAサイズのニッケル水素蓄電池（Ｂ）を作製した。
【００２０】
[実施例３]
前記実施例１の活物質スラリーを作製する際に、0.2重量％のＰＥＯ水溶液の代わりに、３０重量％のPTFE水溶液を混合して活物質スラリーを作製する以外は、前記実施例１と同様にして本発明の非焼結式ニッケル電極C及び本発明の公称容量1200mAh、AAサイズのニッケル水素蓄電池（Ｃ）を作製した。
【００２１】
尚、この本発明の非焼結式ニッケル正極は、結着剤としてＰＴＦＥを使用しているため、水酸化ニッケル粒子を被覆した水酸化コバルト層の内部及び表面にもＰＴＦＥが含有している。
【００２２】
[実施例４]
前記実施例１と同様に、金属ニッケルに対して、亜鉛１重量％、コバルト３重量％となるように、硫酸ニッケル、硫酸亜鉛、硫酸コバルトの混合水溶液を攪拌しながら、水酸化ナトリウム水溶液を徐々に添加し、反応中のpHを13〜14に維持させて、水酸化ニッケルを析出させる。この水酸化ニッケルが析出した水溶液を攪拌し、この水溶液中に、反応中のpHを9〜10に維持するようにして、この水溶液に対して３０重量％のＰＴＦＥと、硫酸コバルト水溶液を添加して、主成分が水酸化ニッケルである球状水酸化物に対して、主として内部にＰＴＦＥを含有させた水酸化コバルトを、前記水酸化ニッケルに対して、１０重量％析出させて、本発明の活物質ｄ、非焼結式電極Ｄ及びニッケル水素蓄電池（Ｄ）を作製した。
【００２３】
尚、本発明の活物質dの水酸化コバルト層の表面にも若干ＰＴＦＥの存在を確認した。
【００２４】
[比較例１]
前記実施例１のニッケル電極活物質の作製において、硫酸コバルト水溶液にＰＴＦＥを添加せずに、水酸化ニッケルを主成分とする粒子の表面に水酸化コバルト層を形成した以外は、比較例のニッケル電極活物質ｘを作製した。
【００２５】
また、前記実施例１の非焼結式電極の作製において、前記ニッケル電極活物質に０．２重量％のＰＥＯ水溶液を混合した活物質スラリーに６０重量％のＰＴＦＥ水溶液を混合する以外は、前記実施例１と同様にして比較例の非焼結式正極Ｘ及びこの非焼結式正極Ｘを備えた公称容量1200mAhのAAサイズのニッケル水素蓄電池（Ｘ）を作製した。
【００２６】
<実験１>
前記のように作製した実施例１〜４のニッケル水素蓄電池（Ａ）〜（Ｄ）及び比較例１のニッケル水素蓄電池（Ｘ）を用いて以下の条件で充放電サイクル試験を行い、その結果を図２に示す。
【００２７】
充電：120mA×16時間
放電：1200mA（放電終止電圧0.5V）
尚、図２には比較例１の初期放電容量を１００とした時の割合を示している。
【００２８】
上記図２の結果から、本発明のニッケル電極活物質を備えたニッケル水素蓄電池（Ａ）〜（Ｄ）は比較例のニッケル電極活物質を備えたニッケル水素蓄電池（Ｘ）よりも放電深度の深い充放電サイクル特性が優れていることがわかる。
【００２９】
これは、本発明のニッケル水素蓄電池（Ａ）〜（Ｄ）は、正極に水酸化ニッケルの表面に水酸化コバルト又は水酸化コバルトを加熱酸化したコバルト化合物の層を被覆した複合粒子であって、前記層の内部には結着力が大きく、撥水性のＰＴＦＥを含有させたことにより、層の水酸化ニッケル粒子表面からの脱落及び、放電深度の深い充放電サイクルを繰り返し行っても、電解液中への溶出が最小限に抑制されたものと考えられる。
【００３０】
<実験２>
前記のように作製した実施例１〜４及び比較例１のニッケル水素蓄電池を用いて以下の条件で試験を行い、単位活物質当たりの容量を求め、その結果を下記表１に示す。
【００３１】
充電：120mA×16時間
放電：600mA（放電終止電圧1.0V）
このときの放電時間から水酸化ニッケル活物質１ｇ当たりの放電容量を求めた。
【００３２】
尚、比較例１のニッケル電極活物質xの単位活物質当たりの容量を１００とした時の指数表示で示す。
【００３３】
【表１】

上記表１の結果から、本発明のニッケル電極活物質ａ〜ｄを備えたニッケル水素蓄電池は比較例のニッケル電極活物質ｘを備えたニッケル水素蓄電池よりも単位活物質当たりの容量が優れていることがわかる。
【００３４】
これは、本発明のニッケル水素蓄電池は、正極に水酸化ニッケルの表面に水酸化コバルト又は水酸化コバルトを加熱酸化したコバルト化合物の層を被覆した複合粒子であって、前記層の内部には結着力が大きく、撥水性のＰＴＦＥを含有させたことにより、電極作製時の層の水酸化ニッケル粒子表面からの脱落及び電解液中への溶出が最小限に抑制されたので、コバルトの導電性マットリクスが崩壊されなかったためであると考えられる。
【００３５】
一方、比較例１の正極活物質ｘには、水酸化ニッケル粒子の表面を被覆した水酸化コバルト層の内部にフッ素樹脂が含有していないため、活物質の水洗、乾燥時に水酸化コバルト層が水酸化ニッケル粒子から脱落及び電池作製後に水酸化コバルト層が電解液中へ溶出し、コバルトの導電性マトリックスが崩壊し、単位活物質当たりの容量が本発明の活物質ａ〜ｄよりも低下したものと考えられる。
【００３６】
尚、本実施例では、アルカリ蓄電池としてニッケル水素蓄電池を例に挙げたが、これに限らず、ニッケルカドミウム蓄電池、ニッケル亜鉛蓄電池に使用しても同様の効果が得られる。
【００３７】
また、本実施例では、フッ素樹脂として、ＰＴＦＥを挙げたが、これに限らず、撥水性合成樹脂、例えば、クロロトリフロルエチレン、テトラフロルエチレン−ヘキサフロルフロピレン共重合体等を使用することもできる。
【００３８】
【発明の効果】
本発明に係るニッケル電極活物質、その活物質を備えた非焼結式電極及びその電極を備えたニッケル水素蓄電池は、単位活物質当たりの容量が優れているので、高容量化が計れる。更に、放電深度を深くした時であっても、充放電サイクルの進行に伴う電池容量の低下が抑制され、その工業的価値は極めて高い。
【図面の簡単な説明】
【図１】本発明のニッケル水素畜電池の一例を示す断面図である。
【図２】本発明のニッケル水素蓄電池及び比較例のニッケル水素蓄電池のサイクル特性を示す図である。
【符号の説明】
４正極板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alkaline storage battery such as a nickel metal hydride storage battery, a nickel cadmium storage battery, and a nickel zinc storage battery. The present invention relates to an electrode and an alkaline storage battery using the non-sintered nickel electrode.
[0002]
[Prior art]
In recent years, due to the rapid spread of portable devices, higher performance storage batteries have been required. Against this background, as a nickel electrode active material used in alkaline storage batteries such as nickel metal hydride storage batteries and nickel cadmium storage batteries, in order to improve the active material utilization rate, capacity recovery rate after overdischarge, etc., nickel hydroxide A nickel hydroxide composite particle having a disordered crystallinity containing a cation such as sodium ion on the surface of the active material particle is proposed in, for example, Japanese Patent Laid-Open No. 8-148145.
[0003]
The nickel hydroxide composite particles proposed in Japanese Patent Application Laid-Open No. 8-148145 and having a high-order cobalt compound layer containing a cation such as sodium ion and having disordered crystallinity are prepared as follows. is there. In other words, a cobalt sulfate aqueous solution and a sodium hydroxide aqueous solution are appropriately dropped into a solution in which nickel hydroxide is precipitated to form nickel hydroxide liquid-impregnated nickel active material particles, and heated in air in the presence of an alkali to increase the degree of treatment. I do. In this way, nickel hydroxide composite particles having a higher-order cobalt compound with disordered crystallinity on the surface of the nickel hydroxide active material particles are obtained.
[0004]
Such nickel hydroxide composite particles are capable of obtaining a non-sintered nickel electrode with improved active material utilization by exhibiting the high conductivity effect of the higher cobalt compound. In addition, since the cobalt compound present on the surface of the nickel hydroxide particles is crystallized in a state in which nickel hydroxide is taken in at the boundary with the inside of the nickel hydroxide particles, the solubility of the cobalt compound in the electrolytic solution is suppressed, Capacity reduction after overdischarge is suppressed.
[0005]
[Problems to be solved by the invention]
However, in the nickel hydroxide composite particles proposed in Japanese Patent Laid-Open No. 8-148145, it is necessary to wash and dry in the process of production, and in that case, a part of the cobalt compound is dropped, and the cobalt compound There was a problem that the coating of the layer was incomplete. Further, when a battery using the nickel hydroxide composite particles is exposed to a short-circuit state for a long time, since the nickel hydroxide composite particles are in contact with the electrolyte, the higher cobalt compound is reduced and the electrolyte And the cobalt conductive network is destroyed. For this reason, there existed a problem that the high electroconductivity effect of a cobalt compound was lost and battery performance fell.
[0006]
Therefore, the present invention has been made in view of the above problems, and prevents the cobalt compound covering nickel hydroxide from falling off and elution into the electrolytic solution, and has a high capacity per unit active material, in particular, the depth of discharge. An object of the present invention is to provide an alkaline storage battery excellent in cycle characteristics in which a decrease in battery capacity is suppressed even when a deep charge / discharge cycle progresses.
[0007]
[Means for Solving the Problems]
Nickel electrode active material for an alkaline storage battery of the present invention is a surface of nickel electrode active material for an alkaline storage batteries covered with a layer of cobalt compound is heated oxidizing cobalt hydroxide or cobalt hydroxide nickel hydroxide, prior SL layer This is characterized in that a fluororesin is contained in the inside.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the following examples, and can be appropriately modified and implemented without departing from the scope of the invention.
[0009]
(Production of nickel electrode active material)
While stirring a mixed aqueous solution of nickel sulfate, zinc sulfate and cobalt sulfate so that the amount of zinc is 1% by weight of zinc and 3% by weight of cobalt with respect to metallic nickel, an aqueous solution of sodium hydroxide is gradually added to adjust the pH during the reaction. Is stabilized to 13 to 14 to deposit spherical nickel hydroxide.
[0010]
The aqueous solution in which the nickel hydroxide was precipitated was stirred, and 50% by weight of polytetrafluoroethylene (hereinafter referred to as PTFE) was dispersed in the aqueous solution so as to maintain the pH during the reaction at 9 to 10. A dispersion of an aqueous cobalt sulfate solution is added, and spherical nickel hydroxide particles mainly composed of nickel hydroxide are used as crystal nuclei. Cobalt hydroxide containing mainly PTFE inside the nuclei is 10% by weight was deposited with respect to nickel hydroxide.
[0011]
The presence of PTFE was also confirmed on the surface of the cobalt hydroxide layer.
[0012]
The composite particle powder is washed three times with 10 times the weight of pure water, and then dehydrated and dried to obtain the nickel electrode active material a of the present invention having a cobalt hydroxide layer containing PTFE inside. Produced.
[0013]
(Preparation of non-sintered nickel electrode)
The nickel electrode active material a prepared as described above was mixed with a 0.2 wt% aqueous polyethylene oxide (hereinafter referred to as PEO) aqueous solution to prepare an active material slurry. This active material slurry was filled in foamed nickel having a three-dimensional network structure with a porosity of 96%, dried and rolled to produce the non-sintered nickel positive electrode A of the present invention.
[0014]
(Production of nickel metal hydride storage battery)
Using the non-sintered positive electrode of the present invention produced as described above, a known hydrogen storage alloy electrode as the negative electrode, an alkali-resistant non-woven fabric as the separator, and a 30% by weight potassium hydroxide aqueous solution as the electrolyte Thus, an AA size nickel metal hydride storage battery (A) having a nominal capacity of 1200 mAh was produced.
[0015]
FIG. 1 is a cross-sectional view showing the nickel-metal hydride battery of the present invention produced as described above. The positive electrode 4 having a nickel hydroxide active material, the negative electrode 5 having a hydrogen storage alloy powder, and these positive and negative

bipolar plates

4, 5 The electrode group 7 including the separator 6 interposed therebetween is wound in a spiral shape, and after being placed in the battery outer can 1, an electrolytic solution composed of a 30 wt% potassium hydroxide aqueous solution is injected. Yes. The negative electrode 5 is connected to the bottom surface of the battery outer can 1 by a negative electrode current collector (not shown).
[0016]
On the other hand, on the upper part of the battery outer can 1, a sealing plate 2 having a central portion opened with a gasket 8 interposed is disposed, and a positive electrode terminal 9 is mounted on the sealing plate 2. The positive electrode terminal 9 and the positive electrode plate 4 are connected via the positive electrode current collector 3 and the sealing plate 2.
[0017]
[Example 2]
In the same manner as in Example 1, spherical nickel hydroxide particles whose main component is nickel hydroxide are used as crystal nuclei, and cobalt hydroxide containing PTFE mainly inside the nuclei is added to the nickel hydroxide. 10% by weight was precipitated. The precipitate was collected, washed with water, and dried to obtain a composite particle powder having a cobalt hydroxide coating layer mainly containing PTFE inside the spherical nickel hydroxide particles. The presence of PTFE was also confirmed on the surface of the cobalt hydroxide layer.
[0018]
Thereafter, the composite particles were sprayed with 25 wt% potassium hydroxide for 0.5 hours in an atmosphere of heated air at 100 ° C. for 0.5 hours, whereby the cobalt hydroxide was disturbed in crystallinity. The higher cobalt compound layer containing potassium cations was changed. Then, after washing | cleaning 3 times with a pure water, the nickel electrode active material b of this invention which had the highly conductive high-order cobalt coating layer containing PTFE was produced by dehydrating and drying.
[0019]
Thereafter, in the same manner as in Example 1, a non-sintered nickel electrode B of the present invention and a nickel-metal hydride storage battery (B) having a nominal capacity of 1200 mAh and AA size of the present invention were produced.
[0020]
[Example 3]
When preparing the active material slurry of Example 1, the same procedure as in Example 1 was performed except that an active material slurry was prepared by mixing 30% by weight of PTFE aqueous solution instead of 0.2% by weight of PEO aqueous solution. Thus, the non-sintered nickel electrode C of the present invention and the nickel-metal hydride storage battery (C) having the nominal capacity of 1200 mAh and AA size of the present invention were prepared.
[0021]
Since the non-sintered nickel positive electrode of the present invention uses PTFE as a binder, PTFE is also contained inside and on the surface of the cobalt hydroxide layer coated with nickel hydroxide particles.
[0022]
[Example 4]
As in Example 1, the sodium hydroxide aqueous solution was gradually added while stirring the mixed aqueous solution of nickel sulfate, zinc sulfate, and cobalt sulfate so that the metal nickel would be 1 wt% zinc and 3 wt% cobalt. To maintain the pH during the reaction at 13-14 to precipitate nickel hydroxide. The aqueous solution in which the nickel hydroxide was precipitated was stirred, and 30 wt% PTFE and an aqueous cobalt sulfate solution were added to the aqueous solution so that the pH during the reaction was maintained at 9-10. Then, 10 wt% of cobalt hydroxide containing mainly PTFE inside the spherical hydroxide whose main component is nickel hydroxide is precipitated with respect to the nickel hydroxide. Material d, non-sintered electrode D and nickel metal hydride storage battery (D) were produced.
[0023]
The presence of PTFE was also confirmed on the surface of the cobalt hydroxide layer of the active material d of the present invention.
[0024]
[Comparative Example 1]
In the preparation of the nickel electrode active material of Example 1, the nickel hydroxide of the comparative example was formed except that the PTFE was not added to the cobalt sulfate aqueous solution, and the cobalt hydroxide layer was formed on the surface of the particles mainly composed of nickel hydroxide. An electrode active material x was produced.
[0025]
Further, in the production of the non-sintered electrode of Example 1, except that a 60 wt% aqueous PTFE solution was mixed with an active material slurry obtained by mixing a 0.2 wt% PEO aqueous solution with the nickel electrode active material. In the same manner as in Example 1, a non-sintered positive electrode X of Comparative Example and a nickel-metal hydride storage battery (X) having a nominal capacity of 1200 mAh and equipped with this non-sintered positive electrode X were produced.
[0026]
<Experiment 1>
Using the nickel hydride storage batteries (A) to (D) of Examples 1 to 4 and the nickel hydride storage battery (X) of Comparative Example 1 produced as described above, a charge / discharge cycle test was performed under the following conditions, and the results were obtained. As shown in FIG.
[0027]
Charging: 120mA x 16 hours Discharging: 1200mA (end-of-discharge voltage 0.5V)
FIG. 2 shows the ratio when the initial discharge capacity of Comparative Example 1 is 100.
[0028]
From the result of FIG. 2, the nickel hydride storage batteries (A) to (D) provided with the nickel electrode active material of the present invention have a deeper discharge depth than the nickel hydride storage battery (X) provided with the nickel electrode active material of the comparative example. It can be seen that the charge / discharge cycle characteristics are excellent.
[0029]
The nickel-metal hydride storage batteries (A) to (D) of the present invention are composite particles in which the surface of nickel hydroxide is coated on the positive electrode with a cobalt compound layer obtained by heating and oxidizing cobalt hydroxide or cobalt hydroxide . before SL layer inside a large binding force of, by which is contained PTFE water-repellent, falling and from nickel hydroxide particles the surface of the layer, be repeated deep discharge cycle of the depth of discharge, the electrolyte It is thought that elution into the inside was suppressed to a minimum.
[0030]
<Experiment 2>
Using the nickel hydride storage batteries of Examples 1 to 4 and Comparative Example 1 produced as described above, tests were performed under the following conditions to determine the capacity per unit active material, and the results are shown in Table 1 below.
[0031]
Charge: 120mA x 16 hours Discharge: 600mA (end-of-discharge voltage 1.0V)
The discharge capacity per 1 g of nickel hydroxide active material was determined from the discharge time at this time.
[0032]
In addition, the nickel electrode active material x of Comparative Example 1 is indicated by an index when the capacity per unit active material is 100.
[0033]
[Table 1]

From the results of Table 1 above, the nickel hydride storage battery provided with the nickel electrode active materials a to d of the present invention is superior in capacity per unit active material than the nickel hydride storage battery provided with the nickel electrode active material x of the comparative example. I understand that.
[0034]
This nickel hydrogen storage battery of the present invention is a composite particle coated with a layer of the positive electrode to the cobalt compound is heated oxidizing cobalt hydroxide or cobalt hydroxide on the surface of nickel hydroxide, inside the previous SL layer By including PTFE, which has a high binding force and water repellency, the dropping of the layer from the nickel hydroxide particle surface and the elution into the electrolyte during the electrode preparation were suppressed to a minimum. This is probably because the matrix was not destroyed.
[0035]
On the other hand, the positive electrode active material x of Comparative Example 1, since the inner fluororesin cobalt hydroxide layer whose surface is coated nickel hydroxide particles are not contained, washing of the active material, cobalt hydroxide layer during drying After dropping from the nickel hydroxide particles and preparing the battery, the cobalt hydroxide layer was eluted into the electrolyte solution, the cobalt conductive matrix collapsed, and the capacity per unit active material was lower than that of the active materials a to d of the present invention. It is considered a thing.
[0036]
In the present embodiment, a nickel metal hydride storage battery is used as an example of the alkaline storage battery.
[0037]
In this example, PTFE was used as the fluororesin, but not limited thereto, a water-repellent synthetic resin such as chlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or the like is used. You can also.
[0038]
【The invention's effect】
Since the nickel electrode active material according to the present invention, the non-sintered electrode provided with the active material, and the nickel metal hydride storage battery provided with the electrode are excellent in capacity per unit active material, the capacity can be increased. Furthermore, even when the depth of discharge is increased, the decrease in battery capacity accompanying the progress of the charge / discharge cycle is suppressed, and its industrial value is extremely high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a nickel metal hydride battery of the present invention.
FIG. 2 is a diagram showing cycle characteristics of a nickel-metal hydride storage battery of the present invention and a nickel-metal hydride storage battery of a comparative example.
[Explanation of symbols]
4 Positive electrode plate

Claims

A surface of nickel electrode active material for an alkaline storage batteries covered with a layer of cobalt compound is heated oxidizing cobalt hydroxide or cobalt hydroxide nickel hydroxide, characterized in that it contained fluororesin inside the prior SL layer Nickel electrode active material for alkaline storage batteries.

A surface of nickel electrode active material for an alkaline storage batteries covered with a layer of cobalt compound is heated oxidizing cobalt hydroxide or cobalt hydroxide nickel hydroxide, a fluorine resin is contained in and its surface before the SL layer A nickel electrode active material for alkaline storage batteries.

The nickel electrode active material for an alkaline storage battery according to claim 1 or 2, wherein the fluororesin is polytetrafluoroethylene.

A nickel electrode active material for alkaline storage batteries, in which the surface of nickel hydroxide is coated with a layer of cobalt hydroxide or a cobalt compound obtained by heating and oxidizing cobalt hydroxide, is used as a slurry, and this slurry is retained as an active material having a three-dimensional network structure. A non-sintered nickel electrode filled in a body, wherein a fluorine resin is contained in a layer formed on the surface of the nickel electrode active material.

A nickel electrode active material for alkaline storage batteries, in which the surface of nickel hydroxide is coated with a layer of cobalt hydroxide or a cobalt compound obtained by heating and oxidizing cobalt hydroxide, is used as a slurry, and this slurry is retained as an active material having a three-dimensional network structure. A non-sintered nickel electrode filled in a body, wherein a fluororesin is contained inside and on the surface of the layer formed on the surface of the nickel electrode active material.

The non-sintered nickel electrode according to claim 4 or 5, wherein the fluororesin is polytetrafluoroethylene.

A nickel electrode active material for alkaline storage batteries, in which the surface of nickel hydroxide is coated with a layer of cobalt hydroxide or a cobalt compound obtained by heating and oxidizing cobalt hydroxide, is used as a slurry, and this slurry is retained as an active material having a three-dimensional network structure. wound or stacked electrode body in a spiral shape and a non-sintered nickel electrodes was charged to the body, the hydrogen storage alloy negative electrode through the separator together with an alkaline electrolyte in an alkaline storage battery comprising in an outer can, before Symbol An alkaline storage battery characterized in that a fluorine resin is contained inside the layer .

A nickel electrode active material for alkaline storage batteries, in which the surface of nickel hydroxide is coated with a layer of cobalt hydroxide or a cobalt compound obtained by heating and oxidizing cobalt hydroxide, is used as a slurry, and this slurry is retained as an active material having a three-dimensional network structure. wound or stacked electrode body in a spiral shape and a non-sintered nickel electrodes was charged to the body, the hydrogen storage alloy negative electrode through the separator together with an alkaline electrolyte in an alkaline storage battery comprising in an outer can, before Symbol An alkaline storage battery characterized in that a fluororesin is contained inside and on the surface of the layer .

The alkaline storage battery according to claim 7 or 8, wherein the fluororesin is polytetrafluoroethylene.

A step of stirring a spherical hydroxide containing nickel hydroxide as a main component in an alkaline solution; and adding a cobalt-containing acidic aqueous solution in which a fluororesin is added to the alkaline aqueous solution; A nickel electrode active material for an alkaline storage battery, comprising a step of forming a layer of cobalt hydroxide containing a fluororesin or a cobalt compound obtained by heating and oxidizing cobalt hydroxide on the surface of a spherical hydroxide Method.

A step of stirring a spherical hydroxide containing nickel hydroxide as a main component in an alkaline solution, a step of adding a fluororesin to the alkaline aqueous solution, and cobalt in the alkaline aqueous solution to which the fluororesin was added. A step of adding an acidic aqueous solution and forming a layer of cobalt hydroxide containing heat-oxidized cobalt hydroxide containing fluororesin or cobalt hydroxide on the surface of the spherical hydroxide mainly composed of nickel hydroxide. The manufacturing method of the nickel electrode active material for alkaline storage batteries characterized by the above-mentioned.

The method for producing a nickel electrode active material for an alkaline storage battery according to claim 10 or 11, wherein the fluororesin is polytetrafluoroethylene.