JP4443135B2

JP4443135B2 - Alkaline storage battery

Info

Publication number: JP4443135B2
Application number: JP2003090535A
Authority: JP
Inventors: 誠越智; 尊之矢野
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2003-03-28
Filing date: 2003-03-28
Publication date: 2010-03-31
Anticipated expiration: 2023-03-28
Also published as: JP2004296395A

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−カドミウム蓄電池などのアルカリ蓄電池に係り、特に、水酸化ニッケルを主体とする正極活物質を含有するニッケル正極を備えたアルカリ蓄電池に関するものである。
【０００２】
【従来の技術】
近年、二次電池（蓄電池）の用途が拡大して、携帯電話、パーソナルコンピュータ、電動工具、電動自転車、ハイブリッド車（ＨＥＶ）、電気自動車（ＥＶ）など広範囲にわたって蓄電池が用いられるようになった。このうち、特に、電動工具、電動自転車、ハイブリッド車（ＨＥＶ）、電気自動車（ＥＶ）などの高出力が求められる機器の電源としては、ニッケル−水素蓄電池やニッケル−カドミウム蓄電池などのアルカリ蓄電池が用いられるようになった。これに伴い、アルカリ蓄電池は高温雰囲気下で使用される機会が増大するようになった。
【０００３】
このような背景にあって、高温の雰囲気下で充放電を行っても、充放電特性、充放電効率が劣化しにくいアルカリ蓄電池が求められるようになった。そこで、特許文献１（特開平８−２２２２１３号公報）において、水酸化ニッケルを主体とする正極活物質粒子の表面に、金属コバルトやコバルト化合物からなる導電剤層を形成するとともに、この正極活物質を備えた正極中に、ジルコニウム化合物、ニオブ化合物、モリブデン化合物およびタングステン化合物から選ばれる１種を添加したアルカリ蓄電池が提案されるようになった。
【０００４】
このように正極中にジルコニウム化合物、ニオブ化合物、モリブデン化合物およびタングステン化合物から選ばれる１種の化合物が添加されていると、水酸化ニッケルを主体とする正極活物質層の表面を被覆するコバルト化合物が、アルカリ電解液中に溶解して析出する速度を遅らせることができるようになる。これにより、ニッケル正極中に良好な導電ネットワークを維持できるようになる。
【０００５】
【発明が解決しようとする課題】
しかしながら、充放電時には電極群の内部の方が高温になって、電極群の内部と外側とで温度差が生じることとなる。さらに、高温の雰囲気で使用されるアルカリ蓄電池にあっては、電池内部の温度は著しく上昇することとなる。このため、電極群の内部に配置された正極の温度が上昇することにより、電極群の内部に配置された正極の劣化速度と、電極群の外側に配置された正極の劣化速度が異なるという問題を生じた。このことは、上述した金属コバルトやコバルト化合物からなる導電剤層を形成した正極活物質を備えた正極中に、ジルコニウム化合物、ニオブ化合物、モリブデン化合物、タングステン化合物などの化合物が添加されていても同様である。
【０００６】
ここで、電極群の内部に配置された正極が、高温に起因して劣化速度が速くなると、この正極の劣化速度が速いことが原因となって、電池全体としての高温でのサイクル寿命が短くなるという問題点が生じた。
そこで、本発明はこのような問題点を改善するためになされたものであって、電極群の内部に配置された正極の劣化を抑制して、電極群の内部と外側で温度差が生じても、電極群の内部と外側での劣化速度をバランスさせるようにして、高温でのサイクル寿命に優れたアルカリ蓄電池を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、本発明のアルカリ蓄電池に用いられる正極は、コバルト化合物の被覆層を有する水酸化ニッケルを主体とする正極活物質にニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物が添加されているとともに、電極群の内部に配置された正極は電極群の外側に配置された正極よりも、これらの化合物の添加量が多く、かつ電極群の内部に配置された正極に添加されたこれらのニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量は、コバルト化合物の被覆層を有する水酸化ニッケルを主体とする正極活物質の質量に対して０．２質量％以上であることを特徴とする。
【０００８】
このように、ニッケル正極中にニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物が添加されていると、水酸化ニッケルを主体とする活物質層の表面を被覆するコバルト化合物が、電解液中に溶解して析出する速度を遅らせることができる。これにより、ニッケル正極中に良好な導電ネットワークを維持できるようになる。この場合、ニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物が添加された正極の配置位置としては、電極群の内部にした方が効果的である。このことにより、電極群の内部と外側で温度差が生じても、電極群の内部と外側での劣化速度をバランスさせるようにして、高温でのサイクル寿命に優れたアルカリ蓄電池を提供することが可能となる。
【０００９】
さらに、電極群の外側に配置された正極においては、ニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量が増大すると高率放電特性において悪影響を与えるため、電極群の外側に配置された正極に添加するニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量を抑制する必要があることが分かった。
【００１０】
また、電極群の内部に配置された正極に添加されるニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことから、電極群の内部に配置された正極に添加されるニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量は０．２質量％以上とするのが望ましい。
【００１１】
しかしながら、電極群の内部に配置される正極板に添加されたニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量が増大しすぎると、室温高率放電特性が低下する。このため、電極群の内部に配置される正極に添加されたニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量は、サイクル寿命を維持するのに必要な最小限の量に調整することが望ましい。
【００１２】
この場合、コバルト化合物層にアルカリカチオンが含有されていると、コバルト化合物層の導電性がさらに向上するので、コバルト化合物層はアルカリカチオンが含有するコバルト化合物層とするのが望ましい。
【００１３】
【発明の実施の形態】
以下に、本発明の実施の形態を図１を参照して詳細に説明するが、本発明はこれに限定されるものではなく、その要旨を変更しない範囲で適宜変更して実施することが可能である。なお、図１は本発明のアルカリ蓄電池の断面を模式的に示す断面図である。
【００１４】
１．ニッケル正極板の作製
質量比で金属ニッケル１００に対して亜鉛３質量％、コバルト１質量％となる硫酸ニッケル、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、反応溶液中のｐＨが１３〜１４になるように維持させて粒状の水酸化ニッケルを析出させた。この粒状の水酸化ニッケルが析出した溶液に対して、硫酸コバルト水溶液を添加し、この反応溶液中のｐＨが９〜１０になるように維持させて、主成分が水酸化ニッケルである球状水酸化物粒子を結晶核として、この核の周囲に水酸化コバルトを析出させた。
【００１５】
このようにして表面に水酸化コバルト被覆層を有する粒状の水酸化ニッケル（正極活物質粒子）を得た。この後、この正極活物質粒子を熱気流中でアルカリ溶液を噴霧するアルカリ熱処理を行った。なお、このアルカリ熱処理において、正極活物質粒子の温度が６０℃になるように温度調節し、コバルト量に対して５倍量の３５質量％のアルカリ溶液（水酸化ナトリウム水溶液）を噴霧した。この後、水酸化ニッケル粒子の温度が９０℃に達するまで昇温した。ついで、これを水洗した後、６０℃で乾燥させて正極活物質とした。これにより、水酸化ニッケル粒子の表面にナトリウム（アルカリカチオン）含有コバルト化合物の高導電性被膜が形成された水酸化ニッケル粉末（正極活物質）を得た。
【００１６】
ついで、上述のように調製した正極活物質にニオブ化合物（例えば、Ｎｂ₂Ｏ₅）を添加して混合物とした後、この混合物５００ｇに対して０．２５質量％のＨＰＣ（ヒドロキシルプロピルセルロース）ディスパージョン液を２００ｇ混合して活物質スラリーを作製した。なお、ニオブ化合物（Ｎｂ₂Ｏ₅）を添加する際に、正極活物質の質量に対して０．１質量％となるように添加したものを活物質スラリーａ１とした。同様に、０．２質量％となるように添加したものを活物質スラリーｂ１とし、０．５質量％となるように添加したものを活物質スラリーｃ１とした。また、ニオブ化合物（Ｎｂ₂Ｏ₅）が無添加のものを作製し、これを活物質スラリーｄ１とした。なお、ニオブ化合物としては、Ｎｂ₂Ｏ₅以外に、Ｎｂ₂Ｏ₃，ＮｂＯ，ＮｂＯ₂，ＮａＮｂＯ₃，ＬｉＮｂＯ₃，ＫＮｂＯ₃，Ｎｂ₂Ｏ₅・ｘＨ₂Ｏを用いるようにしてもよい。
【００１７】
ついで、上述のようにして作製した活物質スラリーａ１〜ｄ１を、厚みが１．７ｍｍの発泡ニッケルからなる電極基板に、所定の充填密度となるように充填した。この後、乾燥させて、厚みが０．９５ｍｍになるまで圧延し、所定の寸法に切断してニッケル正極板１１（ａ，ｂ，ｃ，ｄ）をそれぞれ作製した。なお、活物質スラリーａ１を用いたものをニッケル正極板ａとし、活物質スラリーｂ１を用いたものをニッケル正極板ｂとし、活物質スラリーｃ１を用いたものをニッケル正極板ｃとし、活物質スラリーｄ１を用いたものをニッケル正極板ｄとした。
【００１８】
２．水素吸蔵合金負極板の作製
ミッシュメタル（Ｍｍ）、ニッケル（Ｎｉ：純度９９．９％）、コバルト（Ｃｏ）、マンガン（Ｍｎ）およびアルミニウム（Ａｌ）を所定のモル比になるようにそれぞれ混合し、この混合物をアルゴンガス雰囲気の高周波誘導炉で誘導加熱して合金溶湯とした。この合金溶湯を公知の方法で鋳型に流し込み、冷却して、組成式がＭｍＮｉ_aＣｏ_bＭｎ_cＡｌ_dで表される水素吸蔵合金のインゴットを作製した。この水素吸蔵合金インゴットを機械的粉砕法により、平均粒子径が約６０μｍになるまで粉砕した。
【００１９】
ついで、水素吸蔵合金粉末１００質量部に対して、結着剤としての５質量％のポリエチレンオキサイド（ＰＥＯ）の水溶液を２０質量部混合して水素吸蔵合金ペーストを作製した。この水素吸蔵合金ペーストをパンチングメタルからなる芯体の両面に塗布し、室温で乾燥させた後、所定の厚みに圧延し、所定の寸法に切断して水素吸蔵合金負極板１２を作製した。
【００２０】
３．ニッケル−水素蓄電池の作製
ついで、上述のように作製したニッケル正極板１１（ａ，ｂ，ｃ，ｄ）を４枚と、水素吸蔵合金負極板１２を５枚ずつ用いて、これらの間にポリプロピレン製不織布からなるセパレータ１３を介在させてニッケル正極板１１と水素吸蔵合金負極板１２が対向するように交互に積層した。ついで、ニッケル正極板１１に配設された正極導電タブ１１ａ同士を溶接するとともに、水素吸蔵合金負極板１２に配設された負極導電タブ１２ａ同士を溶接した。そして、正極導電タブ１１ａの溶接部に正極集電体１４を溶接して電極群を作製した。ついで、電極群を箱状の外装缶１５内に挿入した後、封口体１６の正極端子部材１６ｃの下端部に正極集電体１４を溶接した。この後、外装缶１５内に所定の濃度のアルカリ電解液を充填し、外装缶１５の開口部に封口体１６により封止して公称容量が９００ｍＡｈの角形のニッケル−水素蓄電池を作製した。
【００２１】
なお、封口体１６は、中央部に開孔部を備えた略長方形状で金属製の蓋体１６ａと、この蓋体１６ａの下面に配置されて中央部に開孔部を備えた略長方形状で合成樹脂製の絶縁板１６ｂと、これらの開孔部内に挿入された略箱状の正極端子部材１６ｃと、蓋体１６ａと正極端子部材１６ｃとの間に配置されて、蓋体１６ａと正極端子部材１６ｃとを絶縁するとともに、蓋体１６ａと正極端子部材１６ｃとの間を液密にするガスケット１６ｄと、正極端子部材１６ｃの上部に配置されて正極端子部材１６ｃの上端部に溶接された正極キャップ１６ｅとから構成されている。
【００２２】
そして、このように構成される封口体１６を外装缶１０の開口部に配置した後、蓋体１６ａの外周部と外装缶１０の上部内周面とをレーザ溶接することにより、外装缶１０内は液密に封口されることとなる。また、正極キャップ１６ｅ内には弾性を有する弁体１６ｆが配置されており、電池内にガスが発生して電池内が所定の圧力より上昇すると、弁体１６ｆが弾性変形して正極キャップ１６ｅに設けられたガス抜孔１６ｇを通して、電池内で発生したガスを放出するようになされている。これにより、弁体１６ｆは安全弁の作用をして電池内の圧力上昇を防止することができるようになる。
【００２３】
ここで、電極群の外側（外装缶１５側）の正極板１１−１にはニオブ化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にも同様な正極板ｄが配置された電極群を用いたものを電池Ａ１とした。同様に、電極群の外側の正極板１１−１にはニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の内部の正極板１１−２にはニオブ化合物が無添加の正極板ｄが配置された電極群を用いたものを電池Ａ２とした。また、電極群の外側の正極板１１−１にはニオブ化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはニオブ化合物が０．１質量％添加された正極板ａが配置された電極群を用いたものを電池Ａ３とした。
【００２４】
また、電極群の外側の正極板１１−１にはニオブ化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはニオブ化合物が０．２質量％添加された正極板ｂが配置された電極群を用いたものを電池Ａ４とした。また、電極群の外側の正極板１１−１にはニオブ化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはニオブ化合物が０．５質量％添加された正極板ｃが配置された電極群を用いたものを電池Ａ５とした。また、電極群の外側の正極板１１−１にはニオブ化合物が０．１質量％添加された正極板ａが配置され、電極群の内部の正極板１１−２にはニオブ化合物が０．５質量％添加された正極板ｃが配置された電極群を用いたものを電池Ａ６とした。
【００２５】
また、電極群の外側の正極板１１−１にはニオブ化合物が０．２質量％添加された正極板ｂが配置され、電極群の内部の正極板１１−２にはニオブ化合物が０．５質量％添加された正極板ｃが配置された電極群を用いたものを電池Ａ７とした。さらに、電極群の外側の正極板１１−１にはニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の内部の正極板１１−２にもニオブ化合物が０．５質量％添加された正極板ｃが配置された電極群を用いたものを電池Ａ８とした。
【００２６】
４．試験
（１）室温高率放電放電特性の測定
ついで、上述のように作製した電池Ａ１〜Ａ８を用いて、これらの各電池を周囲温度が室温（約２５℃）の雰囲気中で、９００ｍＡ（１ＩｔｍＡ）の充電電流で正極が完全に充電された後に生じる電池電圧の低下（−ΔＶ）が１０ｍＶになるまで充電した後、１時間休止し、９００ｍＡ（１ＩｔｍＡ）の放電電流で、電池電圧が１．０Ｖになるまで放電させるという１Ｉｔ放電を行って、放電時間から各電池の放電容量Ｘ（ｍＡｈ）を求めた。
【００２７】
ついで、周囲温度が室温（約２５℃）の雰囲気中で、９００ｍＡ（１ＩｔｍＡ）の充電電流で正極が完全に充電された後に生じる電池電圧の低下（−ΔＶ）が１０ｍＶになるまで充電した後、１時間休止し、３６００ｍＡ（４ＩｔｍＡ）の放電電流で、電池電圧が１．０Ｖになるまで放電させるという４Ｉｔ高率放電を行って、放電時間から各電池の放電容量Ｙ（ｍＡｈ）を求めた。この後、求めたＸとＹの比率［（Ｙ／Ｘ）×１００％］を室温高率放電特性として算出すると、下記の表１に示すような結果が得られた。
【００２８】
（２）高温サイクル寿命の測定
また、上述のように作製した電池Ａ１〜Ａ８を用いて、これらの各電池を周囲温度が６０℃の高温雰囲気下で、９００ｍＡ（１ＩｔｍＡ）の充電電流で２時間充電した後、４５０ｍＡ（０．５ＩｔｍＡ）の放電電流で電池電圧が１．０Ｖになるまで放電させて、これを１サイクルとする充放電サイクル試験を行った。そして、その放電容量が６０℃の高温雰囲気下で１サイクル目の放電容量の８０％以下に低下するまでのサイクル数を求めて、これを高温サイクル寿命として求めると下記の表１に示すような結果が得られた。
【００２９】
【表１】

【００３０】
上記表１の結果から明らかなように、電極群の外側の正極板１１−１および内部の正極板１１−２に、ニオブ化合物が無添加の正極板ｄが配置された電池Ａ１においては、高温サイクル寿命が１００サイクルと著しく低下していることが分かる。また、電極群の外側の正極板１１−１にニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の内部の正極板１１−２にニオブ化合物が無添加の正極板ｄが配置された電池Ａ２においても、高温サイクル寿命が２５０サイクルと低下していることが分かる。
【００３１】
これに対して、電極群の内部の正極板１１−２にニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の外側の正極板１１−１にニオブ化合物が無添加の正極板ｄが配置された電池Ａ５においては、高温サイクル寿命が４１０サイクルと著しく向上していることが分かる。このことは、ニオブ化合物が添加された正極板ｃを用いることにより、高温サイクル寿命が向上するが、ニオブ化合物が添加された正極板ｃの配置位置としては、電極群の内部にした方が効果的であることを示している。
【００３２】
これは、電極群の内部に配置された正極板１１−２にニオブ化合物が添加されていないと、電極群の内部よりは温度が低い外側（外装缶１５側）に配置された正極板１１−１よりも劣化の速度が速くなる。このため、電極群の外側に配置された正極板１１−１が寿命に至る前に、電極群の内部に配置された正極板１１−２が寿命に至ることで、電池全体としては短寿命となったためと考えられる。
【００３３】
一方、温度が高くなる電極群の内部に配置された正極板１１−２にニオブ化合物が添加されていると、この正極板１１−２が高温で劣化されることが抑制されるようになる。これにより、電極群の内部に配置された正極板１１−２と、外側に配置された正極板１１−１の劣化速度のバランスが保たれるようになる。この結果、ニオブ化合物が添加された正極板ｃを、電極群の内部の正極板１１−２として配置することにより、高温サイクル寿命を向上させることが可能となったと考えられる。
【００３４】
また、電極群の外側の正極板１１−１にニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の内部の正極板１１−２にもニオブ化合物が０．５質量％添加された正極板ｃが配置された電池Ａ８においては、高温サイクル寿命が４５０サイクルと大きい反面、室温高率放電特性が５５％と著しく低下していることが分かる。これに対して、電極群の内部の正極板１１−２にニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の外側の正極板１１−１にニオブ化合物の添加量が０．２質量％と低減された正極板ｂが配置された電池Ａ７においては、高温サイクル寿命が４４０サイクルと大きく、かつ室温高率放電特性も７５％と向上していることが分かる。
【００３５】
また、電極群の内部の正極板１１−２にニオブ化合物が０．５質量％添加された正極板ｃが配置され、電極群の外側の正極板１１−１にニオブ化合物が無添加の正極板ｄが配置された電池Ａ５においては、高温サイクル寿命が４１０サイクルと大きく、かつ室温高率放電特性は８０％とさらに向上していることが分かる。
これらのことから、電極群の外側に配置される正極板１１−１においては、ニオブ化合物の添加量が増大すると室温高率放電特性において悪影響を与えるため、電極群の外側に配置される正極板１１−１に添加するニオブ化合物の添加量を抑制する必要があるといえる。
【００３６】
さらに、電極群の内部の正極板１１−２にニオブ化合物が０．１質量％添加された正極板ａが配置され、電極群の外側の正極板１１−１にニオブ化合物が無添加の正極板ｄが配置された電池Ａ３においては、室温高率放電特性は８０％と大きいのに対して、高温サイクル寿命が２９０サイクルと低下していることが分かる。これに対して、電極群の内部の正極板１１−２にニオブ化合物が０．２質量％添加された正極板ｂが配置され、電極群の外側の正極板１１−１にニオブ化合物が無添加の正極板ｄが配置された電池Ａ４においては、室温高率放電特性は８１％と大きく、かつ高温サイクル寿命も４００サイクルと向上していることが分かる。
【００３７】
このことは、電極群の内部に配置される正極板１１−２に添加されるニオブ化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことを示している。このことから、電極群の内部に配置される正極板１１−２に添加されるニオブ化合物の添加量は０．２質量％以上とするのが望ましい。しかしながら、電極群の内部に配置される正極板１１−２に添加されるニオブ化合物の添加量が増大しすぎると、室温高率放電特性が低下するため、その添加量はサイクル寿命を維持するのに必要最小限の量に調整することが望ましい。
【００３８】
これらのことを総合すると以下のようにいうことができる。即ち、ニオブ化合物が添加された正極板を用いることにより、高温サイクル寿命が向上するが、ニオブ化合物が添加された正極板の配置位置としては、電極群の内部にした方が効果的である。この場合、電極群の外側に配置された正極板１１−１においては、ニオブ化合物の添加量が増大すると室温高率放電特性において悪影響を与えるため、電極群の外側に配置された正極板１１−１に添加するニオブ化合物の添加量を抑制する必要がある。
【００３９】
また、電極群の内部に配置された正極板１１−２に添加されるニオブ化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことことから、電極群の内部に配置された正極板１１−２に添加されるニオブ化合物の添加量は０．２質量％以上とするのが望ましい。しかしながら、電極群の内部に配置される正極板１１−２に添加されたニオブ化合物の添加量が増大しすぎると、室温高率放電特性が低下する。このため、電極群の内部に配置される正極板１１−２に添加されたニオブ化合物の添加量はサイクル寿命を維持するのに必要最小限の量に調整することが望ましい。
【００４０】
５．添加化合物の検討
上述した例においては、ニオブ化合物を正極板中に添加する例について説明したが、チタン化合物（例えばＴｉＯ₂）、タングステン化合物（例えばＷＯ₂）、モリブデン化合物（例えばＭｏＯ₃）を正極板中に添加した場合についても検討した。
【００４１】
（１）チタン化合物について
上述と同様にして調製した正極活物質（コバルト化合物を被覆した水酸化ニッケル）の質量に対してチタン化合物としてのＴｉＯ₂の添加量が０．１質量％となるように添加した活物質スラリーを調製して、これを活物質スラリーｅ１とした。同様に、０．２質量％となるように添加したものを活物質スラリーｆ１とし、０．５質量％となるように添加したものを活物質スラリーｇ１とした。なお、チタン化合物としては、ＴｉＯ₂以外に、Ｔｉ₂Ｏ₃，ＴｉＯ，Ｎａ₂Ｔｉ₃Ｏ₇，Ｌｉ₂ＴｉＯ₃，Ｋ₂ＴｉＯ₃を用いるようにしてもよい。
【００４２】
ついで、これらの活物質スラリーｅ１〜ｇ１を、上述と同様に発泡ニッケルからなる電極基板に充填し、乾燥させ、圧延した後、所定の寸法に切断してニッケル正極板ｅ〜ｇを作製した。なお、活物質スラリーｅ１を用いたものを正極板ｅとし、活物質スラリーｆ１を用いたものを正極板ｆとし、活物質スラリーｇ１を用いたものを正極板ｇとした。ついで、このニッケル正極板ｅ〜ｇと、上述のように作製した水素吸蔵合金負極板を用いて、上述と同様にして、公称容量が９００ｍＡｈの角形のニッケル−水素蓄電池を作製した。
【００４３】
なお、電極群の外側の正極板１１−１にはチタン化合物が０．５質量％添加された正極板ｇが配置され、電極群の内部の正極板１１−２にはチタン化合物が無添加の正極板ｄが配置された電極群を用いたものを電池Ｂ２とした。また、電極群の外側の正極板１１−１にはチタン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはチタン化合物が０．１質量％添加された正極板ｅが配置された電極群を用いたものを電池Ｂ３とした。また、電極群の外側の正極板１１−１にはチタン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはチタン化合物が０．２質量％添加された正極板ｆが配置された電極群を用いたものを電池Ｂ４とした。
【００４４】
また、電極群の外側の正極板１１−１にはチタン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはチタン化合物が０．５質量％添加された正極板ｇが配置された電極群を用いたものを電池Ｂ５とした。また、電極群の外側の正極板１１−１にはチタン化合物が０．１質量％添加された正極板ｅが配置され、電極群の内部の正極板１１−２にはチタン化合物が０．５質量％添加された正極板ｇが配置された電極群を用いたものを電池Ｂ６とした。
【００４５】
また、電極群の外側の正極板１１−１にはチタン化合物が０．２質量％添加された正極板ｆが配置され、電極群の内部の正極板１１−２にはチタン化合物が０．５質量％添加された正極板ｇが配置された電極群を用いたものを電池Ｂ７とした。さらに、電極群の外側の正極板１１−１にはチタン化合物が０．５質量％添加された正極板ｇが配置され、電極群の内部の正極板１１−２にもチタン化合物が０．５質量％添加された正極板ｇが配置された電極群を用いたものを電池Ｂ８とした。
【００４６】
ついで、上述のように作製した電池Ｂ２〜Ｂ８を用いて、上述と同様に、室温高率放電特性および高温サイクル特性（容量維持率）を求めると、下記の表２に示すような結果が得られた。なお、表２には上述した電池Ａ１の結果も併せて示している。
【００４７】
【表２】

【００４８】
上記表２の結果から明らかなように、上述した表１の結果とほぼ同様な傾向であることが分かる。このことから、チタン化合物が添加された正極板を用いることにより、高温サイクル寿命が向上するが、チタン化合物が添加された正極板の配置位置としては、電極群の内部にした方が効果的である。この場合、電極群の外側に配置された正極板１１−１においては、チタン化合物の添加量が増大すると室温高率放電特性において悪影響を与えるため、電極群の外側に配置された正極板１１−１に添加するチタン化合物の添加量を抑制する必要があるといえる。
【００４９】
また、電極群の内部に配置された正極板１１−２に添加されるチタン化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことことから、電極群の内部に配置された正極板１１−２に添加されるチタン化合物の添加量は０．２質量％以上とするのが望ましい。しかしながら、電極群の内部に配置される正極板１１−２に添加されたチタン化合物の添加量が増大しすぎると、室温高率放電特性が低下する。このため、電極群の内部に配置される正極板１１−２に添加されたチタン化合物の添加量はサイクル寿命を維持するのに必要最小限の量に調整することが望ましい。
【００５０】
（２）タングステン化合物について
上述と同様にして調製した正極活物質（コバルト化合物を被覆した水酸化ニッケル）の質量に対してタングステン化合物としてのＷＯ₂の添加量が０．１質量％となるように添加した活物質スラリーを調製して、これを活物質スラリーｈ１とした。同様に、０．２質量％となるように添加したものを活物質スラリーｉ１とし、０．５質量％となるように添加したものを活物質スラリーｊ１とした。なお、タングステン化合物としては、ＷＯ₂以外に、ＷＯ₃，Ｎａ₂ＷＯ₄，Ｌｉ₂ＷＯ₂，Ｋ₂ＷＯ₄を用いるようにしてもよい。
【００５１】
ついで、これらの活物質スラリーｈ１〜ｊ１を、上述と同様に発泡ニッケルからなる電極基板に充填し、乾燥させ、圧延した後、所定の寸法に切断してニッケル正極板ｈ〜ｊを作製した。なお、活物質スラリーｈ１を用いたものを正極板ｈとし、活物質スラリーｉ１を用いたものを正極板ｉとし、活物質スラリーｊ１を用いたものを正極板ｊとした。ついで、このニッケル正極板ｈ〜ｊと、上述のように作製した水素吸蔵合金負極板を用いて、上述と同様にして、公称容量が９００ｍＡｈの角形のニッケル−水素蓄電池Ｃ２〜Ｃ８を作製した。
【００５２】
なお、電極群の外側の正極板１１−１にはタングステン化合物が０．５質量％添加された正極板ｊが配置され、電極群の内部の正極板１１−２にはタングステン化合物が無添加の正極板ｄが配置された電極群を用いたものを電池Ｃ２とした。また、電極群の外側の正極板１１−１にはタングステン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはタングステン化合物が０．１質量％添加された正極板ｈが配置された電極群を用いたものを電池Ｃ３とした。また、電極群の外側の正極板１１−１にはタングステン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはタングステン化合物が０．２質量％添加された正極板ｉが配置された電極群を用いたものを電池Ｃ４とした。
【００５３】
また、電極群の外側の正極板１１−１にはタングステン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはタングステン化合物が０．５質量％添加された正極板ｊが配置された電極群を用いたものを電池Ｃ５とした。また、電極群の外側の正極板１１−１にはタングステン化合物が０．１質量％添加された正極板ｈが配置され、電極群の内部の正極板１１−１にはタングステン化合物が０．５質量％添加された正極板ｊが配置された電極群を用いたものを電池Ｃ６とした。
【００５４】
また、電極群の外側の正極板１１−１にはタングステン化合物が０．２質量％添加された正極板ｉが配置され、電極群の内部の正極板１１−２にはタングステン化合物が０．５質量％添加された正極板ｊが配置された電極群を用いたものを電池Ｃ７とした。さらに、電極群の外側の正極板１１−１にはタングステン化合物が０．５質量％添加された正極板ｊが配置され、電極群の内部の正極板１１−２にもタングステン化合物が０．５質量％添加された正極板ｊが配置された電極群を用いたものを電池Ｃ８とした。
【００５５】
ついで、上述のように作製した電池Ｃ２〜Ｃ８を用いて、上述と同様に、室温高率放電特性および高温サイクル特性（容量維持率）を求めると、下記の表３に示すような結果が得られた。なお、表３には上述した電池Ａ１の結果も併せて示している。
【００５６】
【表３】

【００５７】
上記表３の結果から明らかなように、上述した表１および表２の結果とほぼ同様な傾向であることが分かる。このことから、タングステン化合物が添加された正極板を用いることにより、高温サイクル寿命が向上するが、タングステン化合物が添加された正極板の配置位置としては、電極群の内部にした方が効果的である。この場合、電極群の外側に配置された正極板１１−１においては、タングステン化合物の添加量が増大すると室温高率放電特性において悪影響を与えるため、電極群の外側に配置された正極板１１−１に添加するタングステン化合物の添加量を抑制する必要があるといえる。
【００５８】
また、電極群の内部に配置された正極板１１−２に添加されるタングステン化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことことから、電極群の内部に配置された正極板１１−２に添加されるタングステン化合物の添加量は０．２質量％以上とするのが望ましい。しかしながら、電極群の内部に配置される正極板１１−２に添加されたタングステン化合物の添加量が増大しすぎると、室温高率放電特性が低下する。このため、電極群の内部に配置される正極板１１−２に添加されたタングステン化合物の添加量はサイクル寿命を維持するのに必要最小限の量に調整することが望ましい。
【００５９】
（３）モリブデン化合物について
上述と同様にして調製した正極活物質（コバルト化合物を被覆した水酸化ニッケル）の質量に対してモリブデン化合物としてのＭｏＯ₃の添加量が０．１質量％となるように添加した活物質スラリーを調製して、これを活物質スラリーｋ１とした。同様に、０．２質量％となるように添加したものを活物質スラリーｌ１とし、０．５質量％となるように添加したものを活物質スラリーｍ１とした。なお、モリブデン化合物としては、ＭｏＯ₃以外に、ＭｏＯ₃・Ｈ₂Ｏ，ＭｏＯ₃・２Ｈ₂Ｏ，Ｎａ₂ＭｏＯ₄・２Ｈ₂Ｏ，Ｌｉ₆Ｍｏ₇Ｏ₂₄・１２Ｈ₂Ｏ，Ｋ₂ＭｏＯ₄を用いるようにしてもよい。
【００６０】
ついで、これらの活物質スラリーｋ１〜ｍ１を、上述と同様に発泡ニッケルからなる電極基板に充填し、乾燥させ、圧延した後、所定の寸法に切断してニッケル正極板ｋ〜ｍを作製した。なお、活物質スラリーｋ１を用いたものを正極板ｋとし、活物質スラリーｌ１を用いたものを正極板ｌとし、活物質スラリーｍ１を用いたものを正極板ｍとした。ついで、このニッケル正極板ｋ〜ｍと、上述のように作製した水素吸蔵合金負極板を用いて、上述と同様にして、公称容量が９００ｍＡｈの角形のニッケル−水素蓄電池Ｄ２〜Ｄ８を作製した。
【００６１】
なお、電極群の外側の正極板１１−１にはモリブデン化合物が０．５質量％添加された正極板ｍが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が無添加の正極板ｄが配置された電極群を用いたものを電池Ｄ２とした。また、電極群の外側の正極板１１−１にはモリブデン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が０．１質量％添加された正極板ｋが配置された電極群を用いたものを電池Ｄ３とした。また、電極群の外側の正極板１１−１にはモリブデン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が０．２質量％添加された正極板ｌが配置された電極群を用いたものを電池Ｄ４とした。
【００６２】
また、電極群の外側の正極板１１−１にはモリブデン化合物が無添加の正極板ｄが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が０．５質量％添加された正極板ｍが配置された電極群を用いたものを電池Ｄ５とした。また、電極群の外側の正極板１１−１にはモリブデン化合物が０．１質量％添加された正極板ｋが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が０．５質量％添加された正極板ｍが配置された電極群を用いたものを電池Ｄ６とした。
【００６３】
また、電極群の外側の正極板１１−１にはモリブデン化合物が０．２質量％添加された正極板ｌが配置され、電極群の内部の正極板１１−２にはモリブデン化合物が０．５質量％添加された正極板ｍが配置された電極群を用いたものを電池Ｄ７とした。さらに、電極群の外側の正極板１１−１にはモリブデン化合物が０．５質量％添加された正極板ｍが配置され、電極群の内部の正極板１１−２にもモリブデン化合物が０．５質量％添加された正極板ｍが配置された電極群を用いたものを電池Ｄ８とした。
【００６４】
ついで、上述のように作製した電池Ｄ２〜Ｄ８を用いて、上述と同様に、室温高率放電特性および高温サイクル特性（容量維持率）を求めると、下記の表４に示すような結果が得られた。なお、表４には上述した電池Ａ１の結果も併せて示している。
【００６５】
【表４】

【００６６】
上記表４の結果から明らかなように、上述した表１、表２および表３の結果とほぼ同様な傾向であることが分かる。このことから、モリブデン化合物が添加された正極板を用いることにより、高温サイクル寿命が向上するが、モリブデン化合物が添加された正極板の配置位置としては、電極群の内部にした方が効果的である。この場合、電極群の外側に配置された正極板１１−１においては、モリブデン化合物の添加量が増大すると室温高率放電特性において悪影響を与えるため、電極群の外側に配置された正極板１１−１に添加するモリブデン化合物の添加量を抑制する必要があるといえる。
【００６７】
また、電極群の内部に配置された正極板１１−２に添加されるモリブデン化合物の添加量が少ないと、高温サイクル寿命向上効果が発揮できないことことから、電極群の内部に配置された正極板１１−２に添加されるモリブデン化合物の添加量は０．２質量％以上とするのが望ましい。しかしながら、電極群の内部に配置される正極板１１−２に添加されたモリブデン化合物の添加量が増大しすぎると、室温高率放電特性が低下する。このため、電極群の内部に配置される正極板１１−２に添加されたモリブデン化合物の添加量はサイクル寿命を維持するのに必要最小限の量に調整することが望ましい。
【００６８】
【発明の効果】
上述したように、本発明においては、表面にコバルト化合物の被覆層を有する水酸化ニッケルを主体とする正極活物質を備えたニッケル正極中にニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物が添加されている。このため、水酸化ニッケルを主体とする活物質層の表面を被覆するコバルト化合物が、アルカリ電解液中に溶解して析出する速度を遅らせることができる。
【００６９】
これにより、ニッケル正極中に良好な導電ネットワークを維持できるようになる。この場合、ニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量は、電極群の内部に配置された方が多くなるように添加されているので、電池温度が上昇しやすい電極群の内部に配置された正極のサイクル寿命が向上する。この結果、電池全体としてのサイクル寿命も向上することとなる。
【００７０】
なお、上述した実施の形態においては、ニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量を、電極群の外側に配置された正極板１１−１は少なくし、電極群の内部に配置される正極板１１−２には多くした例について説明した。しかしながら、正極板の配置枚数を多くした電極群を用いる場合は、電極群の外側から内部に向けて、順次これらの化合物の添加量が増大するような構成となるように配置するようにしてもよい。
【００７１】
また、上述した実施の形態においては、板状の正極板１１と、板状の負極板１２をセパレータ１３を介して対向させ、これらを積層した電極群を用いてアルカリ蓄電池を構成した例について説明した。しかしながら、本発明はこの例に限られず、帯状の正極板と帯状の負極板をセパレータを介して対向させ、これらを渦巻状に巻回した渦巻状電極群を円筒形外装缶内に挿入して形成する円筒形電池にも適用することが可能である。
【００７２】
この場合、ニオブ化合物、チタン化合物、タングステン化合物、モリブデン化合物から選択される少なくとも１種の化合物の添加量が異なる正極板を作製して、これらの化合物の添加量が異なる正極板同士を接合して、１枚の帯状正極板とし、これと帯状に形成された水素吸蔵合金負極板をセパレータを間にして渦巻状に巻回して作製した電極群を円筒形外装缶内に挿入して作製すればよい。
【図面の簡単な説明】
【図１】本発明のアルカリ蓄電池の断面を模式的に示す断面図である。
【符号の説明】
１０…ニッケル−水素蓄電池、１１…ニッケル正極板、１１−１…電極群の外側に配置されたニッケル正極板、１１−２…電極群の内部に配置されたニッケル正極板、１２…水素吸蔵合金負極板、１３…セパレータ、１４…正極集電体、１５…外装缶、１６…封口体、１６ａ…蓋体、１６ｂ…絶縁板、１６ｃ…正極端子部材、１６ｄ…ガスケット、１６ｅ…正極キャップ、１６ｆ…弁体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, and more particularly to an alkaline storage battery including a nickel positive electrode containing a positive electrode active material mainly composed of nickel hydroxide.
[0002]
[Prior art]
In recent years, the use of secondary batteries (storage batteries) has expanded, and storage batteries have come to be used over a wide range such as mobile phones, personal computers, electric tools, electric bicycles, hybrid vehicles (HEV), and electric vehicles (EV). Among these, alkaline storage batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries are used as power sources for devices requiring high output such as electric tools, electric bicycles, hybrid vehicles (HEV), and electric vehicles (EV). It came to be able to. Along with this, the opportunities for alkaline storage batteries to be used in a high temperature atmosphere have increased.
[0003]
Against this background, there has been a demand for an alkaline storage battery in which charge / discharge characteristics and charge / discharge efficiency are unlikely to deteriorate even when charge / discharge is performed in a high-temperature atmosphere. Therefore, in Patent Document 1 (Japanese Patent Laid-Open No. 8-222213), a conductive agent layer made of metallic cobalt or a cobalt compound is formed on the surface of positive electrode active material particles mainly composed of nickel hydroxide, and this positive electrode active material. An alkaline storage battery in which one kind selected from a zirconium compound, a niobium compound, a molybdenum compound, and a tungsten compound is added to a positive electrode equipped with a battery has been proposed.
[0004]
As described above, when one compound selected from a zirconium compound, a niobium compound, a molybdenum compound and a tungsten compound is added to the positive electrode, a cobalt compound covering the surface of the positive electrode active material layer mainly composed of nickel hydroxide is obtained. The rate of dissolution and precipitation in the alkaline electrolyte can be delayed. Thereby, a favorable conductive network can be maintained in the nickel positive electrode.
[0005]
[Problems to be solved by the invention]
However, during charging / discharging, the temperature inside the electrode group becomes higher, and a temperature difference occurs between the inside and the outside of the electrode group. Furthermore, in an alkaline storage battery used in a high temperature atmosphere, the temperature inside the battery will rise significantly. For this reason, when the temperature of the positive electrode arranged inside the electrode group rises, the deterioration rate of the positive electrode arranged inside the electrode group is different from the deterioration rate of the positive electrode arranged outside the electrode group. Produced. This is the same even when a compound such as a zirconium compound, a niobium compound, a molybdenum compound, or a tungsten compound is added to the positive electrode including the positive electrode active material in which the conductive agent layer made of the above-described metallic cobalt or cobalt compound is formed. It is.
[0006]
Here, when the deterioration rate of the positive electrode arranged inside the electrode group increases due to high temperature, the cycle life at high temperature as a whole battery is shortened due to the high deterioration rate of the positive electrode. The problem of becoming.
Therefore, the present invention has been made to remedy such problems, and suppresses the deterioration of the positive electrode disposed inside the electrode group, resulting in a temperature difference between the inside and outside of the electrode group. Another object of the present invention is to provide an alkaline storage battery having excellent cycle life at a high temperature by balancing the deterioration rates inside and outside the electrode group.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the positive electrode used in the alkaline storage battery of the present invention is selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound as a positive electrode active material mainly composed of nickel hydroxide having a coating layer of a cobalt compound. At least one kind of compound is added, and the positive electrode disposed inside the electrode group has an added amount of these compounds higher than that of the positive electrode disposed outside the electrode group. The addition amount of at least one compound selected from the niobium compounds, titanium compounds, tungsten compounds, and molybdenum compounds added to the positive electrode disposed inside the electrode group in a large amount has a coating layer of a cobalt compound. It is 0.2% by mass or more based on the mass of the positive electrode active material mainly composed of nickel hydroxide. It is characterized by that.
[0008]
As described above, when at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound is added to the nickel positive electrode, the surface of the active material layer mainly composed of nickel hydroxide is covered. The rate at which the cobalt compound dissolves and deposits in the electrolyte can be delayed. Thereby, a favorable conductive network can be maintained in the nickel positive electrode. In this case, the arrangement position of the positive electrode to which at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound is added is more effective within the electrode group. Thus, even if a temperature difference occurs between the inside and outside of the electrode group, it is possible to provide an alkaline storage battery excellent in cycle life at a high temperature by balancing the deterioration rate between the inside and outside of the electrode group. It becomes possible.
[0009]
Furthermore, in the positive electrode arranged outside the electrode group, when the addition amount of at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound is increased, the high rate discharge characteristics are adversely affected. It has been found that it is necessary to suppress the addition amount of at least one compound selected from niobium compounds, titanium compounds, tungsten compounds, and molybdenum compounds added to the positive electrode disposed outside the electrode group.
[0010]
Moreover, if the addition amount of at least one compound selected from niobium compounds, titanium compounds, tungsten compounds, and molybdenum compounds added to the positive electrode disposed inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exhibited. Therefore, the addition amount of at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound added to the positive electrode disposed inside the electrode group is 0.2% by mass or more. desirable.
[0011]
However, if the amount of at least one compound selected from the niobium compound, titanium compound, tungsten compound, and molybdenum compound added to the positive electrode plate disposed inside the electrode group is excessively increased, the room temperature high rate discharge characteristics Decreases. For this reason, the addition amount of at least one compound selected from niobium compounds, titanium compounds, tungsten compounds, and molybdenum compounds added to the positive electrode disposed inside the electrode group is necessary to maintain the cycle life. It is desirable to adjust to the minimum amount.
[0012]
In this case, when the alkali cation is contained in the cobalt compound layer, the conductivity of the cobalt compound layer is further improved. Therefore, the cobalt compound layer is preferably a cobalt compound layer containing the alkali cation.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the following, an embodiment of the present invention will be described in detail with reference to FIG. 1. However, the present invention is not limited to this, and can be implemented with appropriate modifications without departing from the scope of the present invention. It is. In addition, FIG. 1 is sectional drawing which shows the cross section of the alkaline storage battery of this invention typically.
[0014]
1. Production of nickel positive electrode plate
While stirring a mixed aqueous solution of nickel sulfate, zinc sulfate, and cobalt sulfate that is 3% by mass of zinc and 1% by mass of cobalt with respect to metal nickel 100 by mass ratio, an aqueous sodium hydroxide solution is gradually added, Granular nickel hydroxide was precipitated by maintaining the pH at 13-14. An aqueous cobalt sulfate solution is added to the solution in which the particulate nickel hydroxide is precipitated, and the pH in the reaction solution is maintained at 9 to 10, so that the spherical hydroxide whose main component is nickel hydroxide is added. Cobalt hydroxide was precipitated around the core using the product particles as crystal nuclei.
[0015]
Thus, granular nickel hydroxide (positive electrode active material particles) having a cobalt hydroxide coating layer on the surface was obtained. Thereafter, an alkaline heat treatment was performed on the positive electrode active material particles by spraying an alkaline solution in a hot air stream. In this alkaline heat treatment, the temperature of the positive electrode active material particles was adjusted so as to be 60 ° C., and an alkaline solution (sodium hydroxide aqueous solution) of 35 mass%, which is five times the amount of cobalt, was sprayed. Thereafter, the temperature was raised until the temperature of the nickel hydroxide particles reached 90 ° C. Next, this was washed with water and dried at 60 ° C. to obtain a positive electrode active material. As a result, a nickel hydroxide powder (positive electrode active material) in which a highly conductive coating of a sodium (alkali cation) -containing cobalt compound was formed on the surface of the nickel hydroxide particles was obtained.
[0016]
Next, a niobium compound (for example, Nb) is added to the positive electrode active material prepared as described above. ₂ O _Five ) Was added to prepare a mixture, and 200 g of a 0.25 mass% HPC (hydroxylpropylcellulose) dispersion was mixed with 500 g of the mixture to prepare an active material slurry. Niobium compounds (Nb ₂ O _Five ) Was added so as to be 0.1% by mass with respect to the mass of the positive electrode active material, which was defined as an active material slurry a1. Similarly, what was added so that it might become 0.2 mass% was made into the active material slurry b1, and what was added so that it might become 0.5 mass% was made into the active material slurry c1. Niobium compounds (Nb ₂ O _Five ) Was added, and this was used as the active material slurry d1. Niobium compounds include Nb ₂ O _Five In addition to Nb ₂ O _Three , NbO, NbO ₂ , NaNbO _Three , LiNbO _Three , KNbO _Three , Nb ₂ O _Five XH ₂ O may be used.
[0017]
Subsequently, the active material slurries a1 to d1 produced as described above were filled into an electrode substrate made of foamed nickel having a thickness of 1.7 mm so as to have a predetermined filling density. Thereafter, it was dried, rolled to a thickness of 0.95 mm, and cut into predetermined dimensions to produce nickel positive plates 11 (a, b, c, d), respectively. In addition, what used the active material slurry a1 was made into the nickel positive electrode plate a, what used the active material slurry b1 was made into the nickel positive electrode plate b, and what used the active material slurry c1 was made into the nickel positive electrode plate c, and active material slurry What used d1 was used as the nickel positive electrode plate d.
[0018]
2. Preparation of hydrogen storage alloy negative electrode plate
Misch metal (Mm), nickel (Ni: purity 99.9%), cobalt (Co), manganese (Mn), and aluminum (Al) were mixed in a predetermined molar ratio, and the mixture was mixed with an argon gas atmosphere. Inductive heating was performed in a high frequency induction furnace to obtain a molten alloy. The molten alloy is poured into a mold by a known method, cooled, and the composition formula is MmNi. _a Co _b Mn _c Al _d An ingot of a hydrogen storage alloy represented by This hydrogen storage alloy ingot was pulverized by a mechanical pulverization method until the average particle size became about 60 μm.
[0019]
Next, 20 parts by mass of an aqueous solution of 5% by mass polyethylene oxide (PEO) as a binder was mixed with 100 parts by mass of the hydrogen storage alloy powder to prepare a hydrogen storage alloy paste. This hydrogen storage alloy paste was applied to both sides of a core made of punching metal, dried at room temperature, rolled to a predetermined thickness, and cut to a predetermined size to produce a hydrogen storage alloy negative electrode plate 12.
[0020]
3. Preparation of nickel-hydrogen storage battery
Next, four nickel positive plates 11 (a, b, c, d) and five hydrogen storage alloy negative plates 12 produced as described above are used, and a separator 13 made of a polypropylene nonwoven fabric is interposed between them. The nickel positive electrode plates 11 and the hydrogen storage alloy negative electrode plates 12 were alternately stacked so as to interpose each other. Next, the positive electrode conductive tabs 11 a disposed on the nickel positive electrode plate 11 were welded together, and the negative electrode conductive tabs 12 a disposed on the hydrogen storage alloy negative electrode plate 12 were welded together. And the positive electrode electrical power collector 14 was welded to the welding part of the positive electrode conductive tab 11a, and the electrode group was produced. Next, after the electrode group was inserted into the box-shaped outer can 15, the positive electrode current collector 14 was welded to the lower end portion of the positive electrode terminal member 16 c of the sealing body 16. Thereafter, the outer can 15 was filled with an alkaline electrolyte having a predetermined concentration, and the opening of the outer can 15 was sealed with the sealing body 16 to produce a prismatic nickel-hydrogen storage battery having a nominal capacity of 900 mAh.
[0021]
The sealing body 16 has a substantially rectangular shape with an opening at the center and a metal lid 16a, and a substantially rectangular shape with an opening at the center disposed on the lower surface of the lid 16a. The insulating resin plate 16b made of synthetic resin, the substantially box-shaped positive electrode terminal member 16c inserted into the opening, and the lid body 16a and the positive electrode terminal member 16c are disposed between the lid body 16a and the positive electrode terminal member 16c. A gasket 16d that insulates the terminal member 16c and liquid-tightens between the lid 16a and the positive electrode terminal member 16c, and is disposed on the positive electrode terminal member 16c and welded to the upper end of the positive electrode terminal member 16c. It is comprised from the positive electrode cap 16e.
[0022]
And after arrange | positioning the sealing body 16 comprised in this way to the opening part of the armored can 10, the outer peripheral part of the cover body 16a and the upper inner peripheral surface of the armored can 10 are laser-welded, and thereby the interior of the exterior can 10 Will be sealed liquid-tight. In addition, an elastic valve body 16f is disposed in the positive electrode cap 16e. When gas is generated in the battery and the inside of the battery rises above a predetermined pressure, the valve body 16f is elastically deformed to form the positive electrode cap 16e. The gas generated in the battery is discharged through the provided gas vent hole 16g. As a result, the valve body 16f can act as a safety valve to prevent an increase in pressure in the battery.
[0023]
Here, a positive electrode plate d to which no niobium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group (on the outer can 15 side), and the same positive electrode plate is also applied to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which d was arranged was designated as battery A1. Similarly, a positive electrode plate c to which 0.5% by mass of a niobium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group, and no niobium compound is added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate d was disposed was designated as battery A2. Further, a positive electrode plate d to which no niobium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group, and 0.1% by mass of the niobium compound is added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate a was disposed was designated as a battery A3.
[0024]
Further, a positive electrode plate d to which no niobium compound was added was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.2% by mass of the niobium compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate b was disposed was designated as a battery A4. Further, a positive electrode plate d to which no niobium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group, and 0.5% by mass of the niobium compound is added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate c was disposed was designated as a battery A5. A positive electrode plate a to which 0.1% by mass of a niobium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and 0.5% of the niobium compound is present on the positive electrode plate 11-2 inside the electrode group. A battery A6 was prepared using an electrode group in which the positive electrode plate c added with mass% was disposed.
[0025]
A positive electrode plate b to which 0.2% by mass of a niobium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a niobium compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery A7 was prepared using an electrode group in which the positive electrode plate c added with mass% was disposed. Further, a positive electrode plate c to which 0.5% by mass of a niobium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group, and the niobium compound is also added to the positive electrode plate 11-2 inside the electrode group. A battery A8 was prepared using an electrode group in which the positive electrode plate c added with mass% was disposed.
[0026]
4). test
(1) Measurement of room temperature high rate discharge characteristics
Next, using the batteries A1 to A8 produced as described above, the positive electrodes were completely charged with a charging current of 900 mA (1 ItmA) in an atmosphere where the ambient temperature was room temperature (about 25 ° C.). After charging until the battery voltage drop (−ΔV) that occurs later becomes 10 mV, the battery is rested for 1 hour and discharged at a discharge current of 900 mA (1 ItmA) until the battery voltage reaches 1.0 V. The discharge capacity X (mAh) of each battery was determined from the discharge time.
[0027]
Next, after charging in a atmosphere of ambient temperature of room temperature (about 25 ° C.) with a charging current of 900 mA (1 ItmA) until the battery voltage drop (−ΔV) that occurs after the positive electrode is fully charged reaches 10 mV, The battery was discharged for 1 hour and discharged at a rate of 3600 mA (4 ItmA) until the battery voltage reached 1.0 V, and the discharge capacity Y (mAh) of each battery was determined from the discharge time. Thereafter, when the obtained ratio of X and Y [(Y / X) × 100%] was calculated as the room temperature high rate discharge characteristics, the results shown in Table 1 below were obtained.
[0028]
(2) Measurement of high-temperature cycle life
In addition, using the batteries A1 to A8 manufactured as described above, each of these batteries was charged with a charging current of 900 mA (1 ItmA) for 2 hours in a high-temperature atmosphere having an ambient temperature of 60 ° C., and then 450 mA (0. The battery was discharged at a discharge current of 5 ItmA) until the battery voltage reached 1.0 V, and a charge / discharge cycle test was performed in which the battery voltage was 1 cycle. Then, when the number of cycles until the discharge capacity is reduced to 80% or less of the discharge capacity at the first cycle in a high temperature atmosphere of 60 ° C. is obtained as the high temperature cycle life, it is as shown in Table 1 below. Results were obtained.
[0029]
[Table 1]

[0030]
As is clear from the results in Table 1 above, in the battery A1 in which the positive electrode plate 11-1 to which no niobium compound is added is arranged on the outer positive electrode plate 11-1 and the inner positive electrode plate 11-2, the high temperature is high. It can be seen that the cycle life is significantly reduced to 100 cycles. A positive electrode plate c to which 0.5% by mass of a niobium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a positive electrode plate to which no niobium compound is added to the positive electrode plate 11-2 inside the electrode group. It can be seen that also in the battery A2 in which d is arranged, the high-temperature cycle life is reduced to 250 cycles.
[0031]
On the other hand, the positive electrode plate c added with 0.5 mass% of the niobium compound is disposed on the positive electrode plate 11-2 inside the electrode group, and the niobium compound is not added to the positive electrode plate 11-1 outside the electrode group. It can be seen that in the battery A5 in which the positive electrode plate d is disposed, the high-temperature cycle life is remarkably improved to 410 cycles. This is because the high-temperature cycle life is improved by using the positive electrode plate c to which the niobium compound is added, but the arrangement position of the positive electrode plate c to which the niobium compound is added is more effective when it is in the electrode group. It shows that
[0032]
This is because, when the niobium compound is not added to the positive electrode plate 11-2 arranged inside the electrode group, the positive electrode plate 11- arranged on the outer side (the outer can 15 side) whose temperature is lower than that inside the electrode group. The rate of degradation is faster than 1. For this reason, before the positive electrode plate 11-1 arrange | positioned on the outer side of an electrode group reaches lifetime, the positive electrode plate 11-2 arrange | positioned inside an electrode group reaches lifetime. It is thought that it became.
[0033]
On the other hand, when the niobium compound is added to the positive electrode plate 11-2 arranged inside the electrode group whose temperature increases, the positive electrode plate 11-2 is prevented from being deteriorated at a high temperature. Thereby, the balance of the deterioration rate of the positive electrode plate 11-2 arrange | positioned inside an electrode group and the positive electrode plate 11-1 arrange | positioned outside comes to be maintained. As a result, it is considered that the high-temperature cycle life can be improved by arranging the positive electrode plate c to which the niobium compound is added as the positive electrode plate 11-2 inside the electrode group.
[0034]
A positive electrode plate c to which 0.5% by mass of a niobium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and 0.5 mass of niobium compound is also present on the positive electrode plate 11-2 inside the electrode group. In the battery A8 in which the positive electrode plate c to which% is added is arranged, the high temperature cycle life is as large as 450 cycles, but the room temperature high rate discharge characteristic is remarkably lowered to 55%. On the other hand, the positive electrode plate c to which 0.5% by mass of the niobium compound is added is arranged on the positive electrode plate 11-2 inside the electrode group, and the amount of the niobium compound added to the positive electrode plate 11-1 outside the electrode group. It can be seen that, in the battery A7 in which the positive electrode plate b in which is reduced to 0.2% by mass is arranged, the high-temperature cycle life is as long as 440 cycles and the room temperature high-rate discharge characteristics are also improved to 75%.
[0035]
Further, a positive electrode plate c to which 0.5% by mass of a niobium compound is added is arranged on the positive electrode plate 11-2 inside the electrode group, and a positive electrode plate to which no niobium compound is added to the positive electrode plate 11-1 outside the electrode group. In battery A5 in which d is arranged, the high-temperature cycle life is as long as 410 cycles, and the room temperature high-rate discharge characteristics are further improved to 80%.
For these reasons, in the positive electrode plate 11-1 arranged outside the electrode group, an increase in the amount of niobium compound adversely affects room temperature high rate discharge characteristics. Therefore, the positive electrode plate arranged outside the electrode group It can be said that it is necessary to suppress the addition amount of the niobium compound added to 11-1.
[0036]
Further, a positive electrode plate a to which 0.1% by mass of a niobium compound is added is arranged on the positive electrode plate 11-2 inside the electrode group, and a positive electrode plate to which no niobium compound is added to the positive electrode plate 11-1 outside the electrode group. In the battery A3 in which d is arranged, the room temperature high rate discharge characteristic is as high as 80%, whereas the high temperature cycle life is reduced to 290 cycles. On the other hand, the positive electrode plate b to which 0.2% by mass of the niobium compound is added is arranged on the positive electrode plate 11-2 inside the electrode group, and the niobium compound is not added to the positive electrode plate 11-1 outside the electrode group. In the battery A4 in which the positive electrode plate d is disposed, the room temperature high rate discharge characteristic is as large as 81%, and the high-temperature cycle life is improved to 400 cycles.
[0037]
This indicates that if the amount of the niobium compound added to the positive electrode plate 11-2 disposed inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exhibited. Therefore, it is desirable that the amount of niobium compound added to the positive electrode plate 11-2 disposed inside the electrode group is 0.2% by mass or more. However, if the addition amount of the niobium compound added to the positive electrode plate 11-2 disposed inside the electrode group is excessively increased, the room temperature high rate discharge characteristic is deteriorated, so that the addition amount maintains the cycle life. It is desirable to adjust to the minimum amount necessary.
[0038]
When these things are put together, it can be said as follows. That is, by using a positive electrode plate to which a niobium compound is added, the high-temperature cycle life is improved, but it is more effective to place the positive electrode plate to which the niobium compound is added within the electrode group. In this case, in the positive electrode plate 11-1 arranged outside the electrode group, an increase in the amount of niobium compound adversely affects room temperature high rate discharge characteristics. Therefore, the positive electrode plate 11-arranged outside the electrode group. It is necessary to suppress the amount of niobium compound added to 1.
[0039]
Further, if the amount of the niobium compound added to the positive electrode plate 11-2 arranged inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exerted. Therefore, the positive electrode plate arranged inside the electrode group The addition amount of the niobium compound added to 11-2 is desirably 0.2% by mass or more. However, if the addition amount of the niobium compound added to the positive electrode plate 11-2 disposed inside the electrode group is excessively increased, the room temperature high rate discharge characteristic is deteriorated. For this reason, it is desirable to adjust the addition amount of the niobium compound added to the positive electrode plate 11-2 arranged inside the electrode group to a minimum amount necessary for maintaining the cycle life.
[0040]
5). Study of additive compounds
In the above-described example, the example in which the niobium compound is added to the positive electrode plate has been described. ₂ ), Tungsten compounds (e.g. WO ₂ ), Molybdenum compounds (eg MoO) _Three ) Was also added to the positive electrode plate.
[0041]
(1) About titanium compounds
TiO as a titanium compound with respect to the mass of the positive electrode active material (nickel hydroxide coated with a cobalt compound) prepared as described above ₂ An active material slurry was prepared so that the amount added was 0.1% by mass, and this was used as an active material slurry e1. Similarly, what was added so that it might become 0.2 mass% was made into the active material slurry f1, and what was added so that it might become 0.5 mass% was made into the active material slurry g1. In addition, as a titanium compound, TiO ₂ In addition to Ti ₂ O _Three , TiO, Na ₂ Ti _Three O ₇ , Li ₂ TiO _Three , K ₂ TiO _Three May be used.
[0042]
Then, these active material slurries e1 to g1 were filled in an electrode substrate made of foamed nickel in the same manner as described above, dried, rolled, and then cut into predetermined dimensions to produce nickel positive electrode plates e to g. In addition, the thing using the active material slurry e1 was made into the positive electrode plate e, the thing using the active material slurry f1 was made into the positive electrode plate f, and the thing using the active material slurry g1 was made into the positive electrode plate g. Subsequently, using the nickel positive electrode plates e to g and the hydrogen storage alloy negative electrode plate manufactured as described above, a rectangular nickel-hydrogen storage battery having a nominal capacity of 900 mAh was manufactured in the same manner as described above.
[0043]
A positive electrode plate g added with 0.5% by mass of a titanium compound is disposed on the positive electrode plate 11-1 outside the electrode group, and a titanium compound is not added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate d was disposed was designated as a battery B2. Further, a positive electrode plate d to which no titanium compound was added was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.1% by mass of the titanium compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group on which the positive electrode plate e was disposed was designated as a battery B3. Further, a positive electrode plate d without addition of a titanium compound was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.2% by mass of the titanium compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate f was disposed was designated as a battery B4.
[0044]
Further, a positive electrode plate d to which no titanium compound was added was arranged on the positive electrode plate 11-1 outside the electrode group, and 0.5% by mass of the titanium compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate g was disposed was designated as a battery B5. A positive electrode plate e to which 0.1% by mass of a titanium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a titanium compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery B6 was prepared using the electrode group in which the positive electrode plate g added with mass% was disposed.
[0045]
A positive electrode plate f to which 0.2% by mass of a titanium compound is added is arranged on the positive electrode plate 11-1 outside the electrode group, and a titanium compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery B7 was prepared using the electrode group in which the positive electrode plate g added with mass% was disposed. Further, a positive electrode plate g to which 0.5% by mass of a titanium compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and the titanium compound is also 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery B8 was prepared using the electrode group in which the positive electrode plate g added with mass% was disposed.
[0046]
Next, using the batteries B2 to B8 produced as described above, the room temperature high rate discharge characteristics and the high temperature cycle characteristics (capacity retention ratio) were obtained in the same manner as described above, and the results shown in Table 2 below were obtained. It was. Table 2 also shows the results of the battery A1 described above.
[0047]
[Table 2]

[0048]
As is apparent from the results in Table 2, it can be seen that the tendency is almost the same as the results in Table 1 described above. For this reason, the use of a positive electrode plate to which a titanium compound is added improves the high-temperature cycle life. However, the position of the positive electrode plate to which the titanium compound is added is more effective in the electrode group. is there. In this case, in the positive electrode plate 11-1 arranged outside the electrode group, an increase in the addition amount of the titanium compound has an adverse effect on the room temperature high rate discharge characteristics. Therefore, the positive electrode plate 11-arranged outside the electrode group. It can be said that it is necessary to suppress the addition amount of the titanium compound added to 1.
[0049]
In addition, if the amount of the titanium compound added to the positive electrode plate 11-2 arranged inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exerted. Therefore, the positive electrode plate arranged inside the electrode group The addition amount of the titanium compound added to 11-2 is desirably 0.2% by mass or more. However, when the addition amount of the titanium compound added to the positive electrode plate 11-2 disposed inside the electrode group is excessively increased, the room temperature high rate discharge characteristics are deteriorated. For this reason, it is desirable to adjust the addition amount of the titanium compound added to the positive electrode plate 11-2 disposed inside the electrode group to a minimum amount necessary for maintaining the cycle life.
[0050]
(2) About tungsten compounds
WO as a tungsten compound with respect to the mass of the positive electrode active material (nickel hydroxide coated with a cobalt compound) prepared in the same manner as described above ₂ An active material slurry was prepared so that the amount added was 0.1% by mass, and this was used as an active material slurry h1. Similarly, what was added so that it might become 0.2 mass% was made into active material slurry i1, and what was added so that it might become 0.5 mass% was made into active material slurry j1. In addition, as a tungsten compound, WO ₂ In addition to WO _Three , Na ₂ WO _Four , Li ₂ WO ₂ , K ₂ WO _Four May be used.
[0051]
Then, these active material slurries h1 to j1 were filled in an electrode substrate made of foamed nickel in the same manner as described above, dried and rolled, and then cut into predetermined dimensions to produce nickel positive plates h to j. In addition, the thing using the active material slurry h1 was made into the positive electrode plate h, the thing using the active material slurry i1 was made into the positive electrode plate i, and the thing using the active material slurry j1 was made into the positive electrode plate j. Next, using the nickel positive electrode plates h to j and the hydrogen storage alloy negative electrode plate produced as described above, square nickel-hydrogen storage batteries C2 to C8 having a nominal capacity of 900 mAh were produced in the same manner as described above.
[0052]
A positive electrode plate j to which 0.5% by mass of a tungsten compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a tungsten compound is not added to the positive electrode plate 11-2 in the electrode group. A battery using the electrode group in which the positive electrode plate d was disposed was designated as a battery C2. Further, a positive electrode plate d to which no tungsten compound was added was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.1% by mass of a tungsten compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate h was arranged was designated as a battery C3. Further, a positive electrode plate d to which no tungsten compound was added was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.2% by mass of a tungsten compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate i was arranged was designated as a battery C4.
[0053]
Further, a positive electrode plate d to which no tungsten compound was added was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.5% by mass of a tungsten compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate j was disposed was designated as a battery C5. A positive electrode plate h to which 0.1% by mass of a tungsten compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a tungsten compound is 0.5% on the positive electrode plate 11-1 inside the electrode group. A battery C6 was prepared using an electrode group in which the positive electrode plate j added with mass% was disposed.
[0054]
Further, a positive electrode plate i to which 0.2% by mass of a tungsten compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a tungsten compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery C7 was prepared using an electrode group in which the positive electrode plate j added with mass% was disposed. Further, a positive electrode plate j to which 0.5% by mass of a tungsten compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and the tungsten compound is also 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery C8 was prepared using an electrode group in which the positive electrode plate j added with mass% was disposed.
[0055]
Then, using the batteries C2 to C8 produced as described above, the room temperature high rate discharge characteristics and the high temperature cycle characteristics (capacity retention ratio) were obtained in the same manner as described above, and the results shown in Table 3 below were obtained. It was. Table 3 also shows the results of the battery A1 described above.
[0056]
[Table 3]

[0057]
As is apparent from the results in Table 3, it can be seen that the tendency is almost the same as the results in Table 1 and Table 2 described above. From this, the high temperature cycle life is improved by using the positive electrode plate to which the tungsten compound is added. However, it is more effective to place the positive electrode plate to which the tungsten compound is added in the electrode group. is there. In this case, in the positive electrode plate 11-1 arranged outside the electrode group, an increase in the addition amount of the tungsten compound adversely affects room temperature high rate discharge characteristics. It can be said that it is necessary to suppress the addition amount of the tungsten compound added to 1.
[0058]
In addition, if the addition amount of the tungsten compound added to the positive electrode plate 11-2 arranged inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exerted. Therefore, the positive electrode plate arranged inside the electrode group The addition amount of the tungsten compound added to 11-2 is desirably 0.2% by mass or more. However, if the added amount of the tungsten compound added to the positive electrode plate 11-2 arranged inside the electrode group is excessively increased, the room temperature high rate discharge characteristic is deteriorated. For this reason, it is desirable to adjust the addition amount of the tungsten compound added to the positive electrode plate 11-2 disposed inside the electrode group to a minimum amount necessary for maintaining the cycle life.
[0059]
(3) About molybdenum compounds
MoO as a molybdenum compound with respect to the mass of the positive electrode active material (nickel hydroxide coated with a cobalt compound) prepared as described above _Three An active material slurry was prepared so that the amount added was 0.1% by mass, and this was used as an active material slurry k1. Similarly, what was added so that it might become 0.2 mass% was made into the active material slurry l1, and what was added so that it might become 0.5 mass% was made into the active material slurry m1. As the molybdenum compound, MoO _Three Besides, MoO _Three ・ H ₂ O, MoO _Three ・ 2H ₂ O, Na ₂ MoO _Four ・ 2H ₂ O, Li ₆ Mo ₇ O _{twenty four} ・ 12H ₂ O, K ₂ MoO _Four May be used.
[0060]
Then, these active material slurries k1 to m1 were filled in an electrode substrate made of foamed nickel in the same manner as described above, dried, rolled, and then cut into predetermined dimensions to produce nickel positive plates k to m. In addition, the thing using the active material slurry k1 was made into the positive electrode plate k, the thing using the active material slurry 11 was made into the positive electrode plate 1, and the thing using the active material slurry m1 was made into the positive electrode plate m. Next, using the nickel positive electrode plates k to m and the hydrogen storage alloy negative electrode plate manufactured as described above, prismatic nickel-hydrogen storage batteries D2 to D8 having a nominal capacity of 900 mAh were manufactured in the same manner as described above.
[0061]
The positive electrode plate 11-1 added with 0.5% by mass of a molybdenum compound is disposed on the positive electrode plate 11-1 outside the electrode group, and the molybdenum compound is not added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate d was disposed was designated as a battery D2. Further, a positive electrode plate d to which no molybdenum compound was added was arranged on the positive electrode plate 11-1 outside the electrode group, and 0.1% by mass of the molybdenum compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate k was disposed was designated as a battery D3. Further, a positive electrode plate d without addition of a molybdenum compound was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.2% by mass of a molybdenum compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate l was disposed was designated as a battery D4.
[0062]
Further, a positive electrode plate d without addition of a molybdenum compound was disposed on the positive electrode plate 11-1 outside the electrode group, and 0.5% by mass of a molybdenum compound was added to the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate m was disposed was designated as a battery D5. Further, a positive electrode plate k added with 0.1% by mass of a molybdenum compound is disposed on the positive electrode plate 11-1 outside the electrode group, and a molybdenum compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery D6 was prepared using an electrode group in which the positive electrode plate m added with mass% was disposed.
[0063]
Further, a positive electrode plate l to which 0.2% by mass of a molybdenum compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and a molybdenum compound is 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate m added with mass% was disposed was designated as a battery D7. Further, a positive electrode plate m to which 0.5% by mass of a molybdenum compound is added is disposed on the positive electrode plate 11-1 outside the electrode group, and the molybdenum compound is also 0.5% on the positive electrode plate 11-2 inside the electrode group. A battery using the electrode group in which the positive electrode plate m added with mass% was disposed was designated as a battery D8.
[0064]
Then, using the batteries D2 to D8 produced as described above, the room temperature high rate discharge characteristics and the high temperature cycle characteristics (capacity retention ratio) were obtained in the same manner as described above, and the results shown in Table 4 below were obtained. It was. Table 4 also shows the results of the battery A1 described above.
[0065]
[Table 4]

[0066]
As is clear from the results in Table 4, it can be seen that the tendency is almost the same as the results in Table 1, Table 2, and Table 3 described above. From this, the high-temperature cycle life is improved by using the positive electrode plate to which the molybdenum compound is added, but it is more effective to place the positive electrode plate to which the molybdenum compound is added inside the electrode group. is there. In this case, in the positive electrode plate 11-1 arranged outside the electrode group, an increase in the amount of molybdenum compound adversely affects the room temperature high rate discharge characteristics. Therefore, the positive electrode plate 11-arranged outside the electrode group. It can be said that it is necessary to suppress the amount of molybdenum compound added to 1.
[0067]
In addition, if the addition amount of the molybdenum compound added to the positive electrode plate 11-2 arranged inside the electrode group is small, the effect of improving the high-temperature cycle life cannot be exerted. Therefore, the positive electrode plate arranged inside the electrode group The addition amount of the molybdenum compound added to 11-2 is desirably 0.2% by mass or more. However, when the addition amount of the molybdenum compound added to the positive electrode plate 11-2 disposed inside the electrode group is excessively increased, the room temperature high rate discharge characteristic is deteriorated. For this reason, it is desirable to adjust the addition amount of the molybdenum compound added to the positive electrode plate 11-2 disposed inside the electrode group to a minimum amount necessary for maintaining the cycle life.
[0068]
【The invention's effect】
As described above, in the present invention, a nickel positive electrode including a positive electrode active material mainly composed of nickel hydroxide having a coating layer of a cobalt compound on the surface is selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound. At least one compound is added. For this reason, the speed | rate which the cobalt compound which coat | covers the surface of the active material layer which has nickel hydroxide as a main component melt | dissolves in an alkaline electrolyte and precipitates can be delayed.
[0069]
Thereby, a favorable conductive network can be maintained in the nickel positive electrode. In this case, since the addition amount of at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound is added so as to be larger in the electrode group, the battery temperature As a result, the cycle life of the positive electrode disposed inside the electrode group that tends to increase is improved. As a result, the cycle life of the entire battery is also improved.
[0070]
In the above-described embodiment, the positive electrode plate 11-1 disposed outside the electrode group has a small amount of addition of at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound. And the example which increased the positive electrode plate 11-2 arrange | positioned inside an electrode group was demonstrated. However, when using an electrode group in which the number of positive electrode plates is increased, the electrodes may be arranged so that the amount of addition of these compounds increases sequentially from the outside to the inside of the electrode group. Good.
[0071]
Moreover, in embodiment mentioned above, the plate-shaped positive electrode plate 11 and the plate-shaped negative electrode plate 12 were made to oppose through the separator 13, and the example which comprised the alkaline storage battery using the electrode group which laminated | stacked these is demonstrated. did. However, the present invention is not limited to this example, and a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are opposed to each other via a separator, and a spiral electrode group obtained by winding them in a spiral shape is inserted into a cylindrical outer can. The present invention can also be applied to the formed cylindrical battery.
[0072]
In this case, positive plates with different addition amounts of at least one compound selected from niobium compounds, titanium compounds, tungsten compounds, and molybdenum compounds are produced, and positive electrode plates with different addition amounts of these compounds are joined together. A single strip-shaped positive electrode plate, and a group of electrodes formed by winding the strip and the hydrogen-absorbing alloy negative electrode plate formed in a spiral shape with a separator in between are inserted into a cylindrical outer can. Good.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a cross section of an alkaline storage battery of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Nickel-hydrogen storage battery, 11 ... Nickel positive electrode plate, 11-1 ... Nickel positive electrode plate arrange | positioned outside the electrode group, 11-2 ... Nickel positive electrode plate arrange | positioned inside the electrode group, 12 ... Hydrogen storage alloy Negative electrode plate, 13 ... separator, 14 ... positive electrode current collector, 15 ... outer can, 16 ... sealing body, 16a ... lid, 16b ... insulating plate, 16c ... positive electrode terminal member, 16d ... gasket, 16e ... positive electrode cap, 16f ... Valve

Claims

An alkaline storage battery comprising an electrode group formed such that a positive electrode containing a positive electrode active material mainly composed of nickel hydroxide and a negative electrode face each other with a separator interposed therebetween,
The positive electrode has at least one compound selected from a niobium compound, a titanium compound, a tungsten compound, and a molybdenum compound added to a positive electrode active material mainly composed of nickel hydroxide having a coating layer of a cobalt compound,
The positive electrode arranged inside the electrode group has a larger amount of addition of at least one compound selected from the niobium compound, titanium compound, tungsten compound, and molybdenum compound than the positive electrode arranged outside the electrode group , The addition amount of at least one compound selected from the niobium compound, titanium compound, tungsten compound, and molybdenum compound added to the positive electrode disposed inside the electrode group is water having a coating layer of the cobalt compound. An alkaline storage battery comprising 0.2% by mass or more based on the mass of the positive electrode active material mainly composed of nickel oxide .

2. The alkaline storage battery according to claim 1, wherein the cobalt compound covering the nickel hydroxide is a cobalt compound containing an alkali cation.