JP4403594B2 - Cathode active material for alkaline storage battery and method for producing the same - Google Patents

Description

【００７９】
（実験例５）
実験例４における金属酸化物の製造において、ＮｉＳＯ₄とＭｎＳＯ₄の濃度比を変えた混合液を用い、Ｍｎ固溶量を０〜１６モル％となるように合成した。
【００８０】
得られたＭｎ固溶の金属酸化物粉末は、いずれも平均粒径１０μｍの球状粉末であり、タップ密度１．７ｇ／ｃｃ以上であった。また、いずれもβ−Ｎｉ（ＯＨ）₂型の単相であり、Ｍｎの平均価数は３．５〜３．６価の範囲内であった。また、ＣｕのＫα線を用いたＸ線回折パターンを記録したところ、２θ＝３７〜４０゜付近のピークの半価幅は０．６〜０．９ｄｅｇ．の範囲内であり、２θ＝３７〜４０゜付近に位置するピークの積分強度Ａに対する２θ＝１８〜２１゜付近に位置するピークの積分強度Ｂとの比Ｂ／Ａの値は１．０〜１．２の範囲内であった。さらに、窒素ガス吸着による細孔分布測定を実施したところ、全細孔体積に対する４０Å以下の細孔半径を有する空間体積の割合は、６５〜７３％の範囲内の値を示した。
【００８１】
これらの金属酸化物を活物質として用い、実験例４と同様にして円筒密閉型電池を作製し、２０℃で２４０ｍＡでの放電電気量から利用率を求めた。さらに、それぞれの電極充填密度と前記利用率から、電極の体積エネルギー密度（実容量密度）を求めた。なお、電極充填密度については電極の体積と、充填した活物質および添加剤の真比重から計算した空間体積比率（多孔度）が２５％になるよう、電極作製時の圧延率を調整した。
【００８２】
図９は、これらの実験の結果を表す図であって、Ｍｎ固溶量に対する利用率および電極の体積エネルギー密度との関係を示す特性図である。この図から、Ｍｎ固溶量が１．０モル％以上で著しく高い利用率を示すことがわかる。また、Ｍｎ固溶量が１．０モル％以上で高い体積エネルギー密度を示し、１２．０モル％より多くなると逆に低下することがわかる。体積エネルギー密度は、利用率以外に電極充填密度とも大きく関係し、また、充填密度は活物質のタップ密度に大きく影響する。そのため、Ｍｎ固溶量が多いと、ＮｉとＭｎのイオン半径の違いから結晶中に歪みが生じやすく、タップ密度が減少し、電極充填密度が低下する。そのことが起因して体積エネルギー密度が減少したものと考えられる。従って、Ｍｎ固溶量としては、１．０モル％以上１２．０モル％以下が適切であると考えられる。
【００８３】
（実験例６）
実験例４の製造法において、出発原料として、２．１ｍｏｌ／ｌのＮｉＳＯ₄
および０．２ｍｏｌ／ｌのＭｎＳＯ₄および０．１ｍｏｌ／ｌのＡｌ₂（ＳＯ₄）₃を含む混合水溶液を用いた以外は、同様にしてＮｉを主としＭｎとＡｌを含む金属酸化物を合成した。
【００８４】
得られた金属酸化物は、平均粒径１０μｍの球状粉末であった。また、組成分析を実施した結果、得られた金属酸化物のＭｎ、Ａｌ固溶量はそれぞれ８モル％、４モル％であり、β−Ｎｉ（ＯＨ）₂型の単相であった。また、ヨードメトリー法により全金属のトータル価数を求め、その値よりＭｎの平均価数を算出したところ３．６価であった。また、ＣｕのＫα線を用いた粉末Ｘ線回折パターンを記録したところ、２θ＝３７〜４０゜付近のピークの半価幅は０．８１ｄｅｇ．であり、２θ＝３７〜４０゜付近に位置するピークの積分強度Ａに対する、２θ＝１８〜２１゜付近に位置するピークの積分強度Ｂとの比Ｂ／Ａの値は１．２２であった。さらに、窒素ガス吸着による細孔分布測定を実施したところ、全細孔体積に対する４０Å以下の細孔半径を有する空間体積の割合は、６５％を示した。
【００８５】
この金属酸化物を活物質として用い、実験例４と同様にして円筒密閉型電池を作製し、電池特性を評価した。その評価結果については、下記実験例７においていっしょにまとめる。
【００８６】
（実験例７）
実験例４の製造法において、出発原料として、２．１ｍｏｌ／ｌのＮｉ（ＮＯ₃）₂および０．２ｍｏｌ／ｌのＭｎ（ＮＯ₃）₂および０．１ｍｏｌ／ｌのＣａ（ＮＯ₃）₂を含む混合水溶液を用いた以外は、同様にしてＮｉを主としＭｎとＣａを含む金属酸化物を合成した。
【００８７】
得られた金属酸化物は、平均粒径１０μｍの球状粉末であった。また、組成分析を実施した結果、得られた金属酸化物のＭｎ、Ｃａ固溶量はそれぞれ８モル％、４モル％であり、β−Ｎｉ（ＯＨ）₂型の単相であった。また、ヨードメトリー法により全金属のトータル価数を求め、その値よりＭｎの平均価数を算出したところ３．６価であった。また、ＣｕのＫα線を用いた粉末Ｘ線回折パターンを記録したところ、２θ＝３７〜４０゜付近のピークの半価幅は０．７３ｄｅｇ．であり、２θ＝３７〜４０゜付近に位置するピークの積分強度Ａに対する２θ＝１８〜２１゜付近に位置するピークの積分強度Ｂとの比Ｂ／Ａの値は１．１７であった。さらに、窒素ガス吸着による細孔分布測定を実施したところ、全細孔体積に対する４０Å以下の細孔半径を有する空間体積の割合は、７１％を示した。
【００８８】
この金属酸化物を活物質として用い、実験例４と同様にして円筒密閉型電池を作製し、電池特性を評価した。
【００８９】
また、同様に比較のため、実験例４の製造法において、出発原料として、２．４ｍｏｌ／ｌのＮｉＳＯ₄を用いた以外は、同様にしてニッケル酸化物を合成した。得られたニッケル酸化物は、平均粒径１０μｍの球状粉末であった。
【００９０】
このように得られたニッケル酸化物粉末を用い、実験例４と同様にして第２の比較例として円筒密閉型電池を作製した。
【００９１】
実験例４、６、７および比較例２として作製した円筒密閉型電池を用い、実験例１と同様にして活物質の利用率を求めた。また、同実験における放電時において、実放電容量の１／２の電気量に相当する放電深度（ＤＯＤ＝５０％）にて電圧を測定した。また、同実験における充電時において、試験温度を４５℃に設定し、それ以外は同様にして活物質の利用率を求めた。表２に、それらの結果を示す。
【００９２】
【表２】

【００９３】
表２から明らかなように、Ａｌを固溶させることで、放電電圧の向上を図ることができ、また、Ｃａを固溶させることで、高温における充電効率を向上させることができる。
【００９４】
ここでは、ＮｉとＭｎのほかに、Ｃａが含まれた酸化物の例を示したが、Ｃａ以外に、Ｍｇ、Ｔｉ、Ｚｎ、Ｓｒ、Ｂａ、Ｙ、Ｃｄ、Ｃｏ、Ｃｒ、希土類金属、Ｂｉにおいても同様に高温における充電効率を向上させることができた。また、前記固溶元素とＡｌを組み合わせた酸化物においては、放電電圧の向上と充電効率の向上の相乗効果を確認することができた。
【００９５】
（実験例８）
実験例４の製造法において、酸化処理後に得られた金属酸化物粉末を水中に入れて攪拌しながら、２０重量％の硫酸コバルト水溶液と、２５重量％の水酸化ナトリウム水溶液とを滴下することで、Ｃｏ酸化物による表面層で被覆されている金属酸化物粉末を合成した。
【００９６】
得られた酸化物は、平均粒径１０μｍの球状粉末であった。組成分析を実施した結果、粉末内部層の金属酸化物と表面層のＣｏ酸化物との比は１０：１重量％であった。
【００９７】
このようにして得られた金属酸化物粉末を用い、実験例４と同様にして円筒密閉型電池を作製した。
【００９８】
実験例４および実験例８にて作製した円筒密閉型電池を用い、実験例４と同様にして活物質の利用率を測定した。さらに、同実験における放電時の電流を１２００ｍＡとしたときの利用率を測定した。表３に、それらの結果を示す。
【００９９】
【表３】

【０１００】
表３から明らかなように、Ｃｏ酸化物による表面層で被覆されている金属酸化物を用いた場合においても、同様に高い利用率を示し、特に、高率放電時において利用率を向上させる効果があることを確認することができた。
【０１０１】
なお、Ｃｏ酸化物以外に、他の導電性を有する金属酸化物もしくは金属による表面層で被覆されている金属酸化物を用いた場合においても、同様な効果が得られた。
【０１０２】
（実験例９）
実験例４の製造法において、Ａｒガス流量を０〜１２００ｍｌ／ｍｉｎとし、溶存酸素濃度を０．０３〜９．００ｍｇ／ｌに変化させた以外は、同様にして金属酸化物粉末を得た。
【０１０３】
このときの溶存酸素濃度に対する得られた金属酸化物粉末のタップ密度との関係を図１０に示す。この図から溶存酸素濃度が５ｍｇ／ｌ以下で高いタップ密度を示すことがわかる。従って、溶存酸素濃度は５ｍｇ／ｌ以下が適切であると考えられる。
【０１０４】
なお、ここではＡｒガスを供給したが、窒素、ヘリウム等の他の不活性ガスを用いても同様に溶存酸素濃度を５ｍｇ／ｌ以下に保つことができ、同様な特性の金属酸化物を得ることができた。また、これらを組み合わせた場合においても、あるいは、ヒドラジン等の還元剤を用いても同様な結果が得られた。
【０１０５】
比較のため実験例９の製造法において、金属酸化物を水洗させた後、真空下で乾燥させることで、酸化を抑制した以外は、同様にして金属酸化物粉末を得た。
【０１０６】
得られた金属粉末のＭｎの平均価数を測定したところ、２．４価を示した。また、同活物質の利用率は９２％と著しく低かった。従って、酸化処理を施すことでＭｎ価数を高める必要がある。
【０１０７】
（実験例１０）
実験例４の製造法において、大気中で０〜１３０℃で、２０分〜２４時間保持し酸化処理を施した以外は、同様にして金属酸化物粉末を得た。
【０１０８】
このときの各酸化温度での酸化時間に対する金属酸化物のＭｎの平均価数との関係を図１１に示す。この図から、Ｍｎの平均価数３．３価以上の金属酸化物を得るためには、２０℃以上で１時間以上保持することが適切であると考えられる。しかし、１１０℃より高い温度で酸化処理を施した場合、利用率が低下する傾向があった。これは、同処理により金属酸化物の分解反応が進行したためと考えられる。従って、酸化温度としては２０℃〜１１０℃が適切であると考えられる。
【０１０９】
なお、ここでは酸化処理を行うために大気中にて保持したが、酸素、または、過酸化水素、過塩素酸ナトリウム、過塩素酸カリウム等の酸化剤においても同様に、Ｍｎの平均価数を３．３価以上とすることができた。
【０１１０】
（実験例１１）
実験例４の製造法において、合成槽内のｐＨ値が１０〜１３の範囲内で変化させて合成した以外は、同様にして金属酸化物粉末を得た。
【０１１１】
これらの金属酸化物において、ＣｕＫα線を使用するＸ線回折測定を実施したところ、２θ＝３７〜４０゜付近に位置するピークの半価幅を１．２ｄｅｇ．以下とするためには、ｐＨ値が１２．５以下となるようにする必要があった。また、ｐＨ値が１１より低いとき、高密度に成長させることが困難となり、タップ密度が１．７ｇ／ｃｃより小さくなった。
【０１１２】
（実験例１２）
実験例４の製造法において、合成槽内の温度が１０〜８０℃の範囲内で変化させて合成した以外は、同様にして金属酸化物粉末を得た。
【０１１３】
これらの金属酸化物において、ＣｕＫα線を使用するＸ線回折測定を実施したところ、２θ＝３７〜４０゜付近に位置するピークの積分強度Ａに対する、２θ＝１８〜２１゜付近に位置するピークの積分強度Ｂとの比Ｂ／Ａの値を１．２５以下にするためには、温度を６０℃以下に保持する必要であった。また、温度が２０℃より低くなると温度制御が困難になるばかりでなく、スケールの生成が著しくなることから、高密度に成長させることが困難となり、タップ密度が１．７ｇ／ｃｃより小さくなった。
【０１１４】
（実験例１３）
実験例４の製造法において、金属塩水溶液に含まれる全金属イオンの供給速度が５×１０^-5〜５×１０^-2ｍｏｌ／ｍｉｎの範囲内で変化させて合成した以外は、同様にして金属酸化物粉末を得た。
【０１１５】
これらの金属酸化物において、窒素ガス吸着による細孔分布測定を実施したところ、全細孔体積に対する４０Å以下の細孔半径を有する空間体積の割合を６０％以上にするためには、全金属イオンの供給速度を２×１０^-4以上にすることが必要であった。また、供給速度が２×１０^-2より速くなると、滞留時間の著しい低下により、高密度に成長させることが困難となり、タップ密度が１．７ｇ／ｃｃより小さくなった。
【０１１６】
【発明の効果】
以上のように本発明によれば、正極活物質の利用率を高めることができ、エネルギー密度を大きく向上させることができる。さらに、寿命特性、高率放電特性の向上を図ることができる。
【０１１７】
これによって、エネルギー密度の優れたアルカリ蓄電池を提供する。
【図面の簡単な説明】
【図１】 本発明の一実施の形態における密閉アルカリ蓄電池の一部を切り欠いた斜視図
【図２】 本発明の一実施の形態による金属酸化物粉末を充填したニッケル正極のを模式的図
【図３】 本発明の一実施の形態による金属酸化物製造装置を示す図
【図４】 本発明の一実験例によるＮｉを主たる元素とする金属酸化物のＸＲＤチャート
【図５】 本発明の実験例による金属酸化物のＭｎ平均価数に対する利用率の変化を示す図
【図６】 本発明の実験例による金属酸化物のＣｕＫα線を使用するＸ線回折の２θ＝３７〜４０゜付近のピーク半価幅に対する利用率の変化を示す図
【図７】本発明の実験例による金属酸化物のＣｕＫα線を使用するＸ線回折の２θ＝３７〜４０゜付近に位置するピークの積分強度Ａに対する、２θ＝１８〜２１゜付近に位置するピークの積分強度Ｂの比Ｂ／Ａの変化に伴う容量維持率の変化を示す図
【図８】本発明の実験例による金属酸化物の全細孔体積に対する４０Å以下の細孔半径を有する空間体積の割合に対する、放電容量比率の変化を示す図
【図９】 本発明の実験例による金属酸化物のＭｎ固溶量に対する利用率、体積エネルギー密度の変化を示す図
【図１０】 同金属酸化物の製造課程において、反応槽内の溶存酸素濃度に対する合成物のタップ密度の変化を示す図
【図１１】 本発明による製造過程において、大気雰囲気下での各温度（酸化温度）における保持時間（酸化時間）に対するＭｎの平均価数の変化を示す図
【符号の説明】
１ 基板
２ 基板空孔部
３ 活物質粉末
４ 導電性金属酸化物層
５ 空隙部
１０ 極板群
１１ 負極板
１２ 正極板
１３ セパレータ
１４ 電池ケース
１５ 絶縁板
１６ 封口板
１７ ガスケット
１８ 安全弁
１９ キャップ
２０ 正極リード片
２１ 反応槽
２２ 金属塩水溶液供給ライン
２３ アンモニウムイオン供給ライン
２４ ＮａＯＨ水溶液供給ライン
２５ ｐＨスタット
２６ 恒温槽
２７ 金属酸化物粒子含有液取り出しライン
２８ 不活性ガス供給ライン
２９ 攪拌装置
３０ 攪拌翼[0001]
BACKGROUND OF THE INVENTION
  TECHNICAL FIELD The present invention relates to a high-capacity positive electrode active material for alkaline storage batteries mainly composed of a metal oxide containing Ni as a main metal element and a method for producing the same.
[0002]
[Prior art]
With recent advances in semiconductor technology, electronic devices are becoming smaller, lighter and more multifunctional, and personalization of small portable devices such as mobile phones and laptop computers is rapidly progressing. For this reason, there is an increasing demand for smaller and lighter alkaline storage battery secondary batteries widely used as power sources.
[0003]
  To date, nickel oxide (NiOOH) has been used as the main active material of the positive electrode for alkaline storage batteries, but the electrode base has a higher porosity instead of a conventional sintered electrode using a sintered substrate. An electrode (foamed metal electrode) in which nickel oxide powder is densely packed in a three-dimensional foamed nickel porous body (about 95%) is industrialized (for example, Japanese Examined Patent Publication No. 62-54235, US Pat. No. 4,251,603) As a result, the energy density of the nickel positive electrode was dramatically improved.
[0004]
  In order to increase the energy density of the nickel positive electrode, improvement of a method for producing a nickel oxide powder as an active material has been one of important techniques. The conventional nickel oxide powder manufacturing method employs a method in which a nickel salt aqueous solution is allowed to act in an alkaline aqueous solution such as sodium hydroxide to cause precipitation, and then ripened to grow crystals and then pulverized by a mechanical method. However, there is a problem that it is difficult to obtain a high packing density because the manufacturing method is complicated and the powder shape is irregular. However, as disclosed in Japanese Patent Publication No. 4-80513, as another production method, ammonia is allowed to act on a nickel salt aqueous solution to form an ammonium complex of nickel, and nickel hydroxide is grown in an alkaline aqueous solution. A method has been proposed, and a continuous production method can be realized, and the cost can be reduced. Further, since the particle shape is close to a spherical shape, high-density filling is possible.
[0005]
  However, in this advancement, since high-density particles having a large particle size grown to several tens of μm are used as the active material, there is a problem that the charge / discharge efficiency is lowered due to the decrease in the electronic conductivity of the active material itself. It was. For this, Co, its oxide, Ni and the like are added to supplement the electron conductivity (Japanese Patent Publication No. 61-37733, Electrochemistry, Vol. 54, No. 2, p. 159 (1986). , Power Sources 12, p203 (1988)), and also in the active material itself, the charge / discharge efficiency was improved by dissolving a metal element other than Ni such as Co.
[0006]
  In addition, attempts to improve the charge / discharge efficiency by dissolving different metal elements in the crystal as described above are disclosed in Japanese Patent Publication Nos. 3-26903 and 3-50384, Electrochemistry, Vol. 54, no. 2, p164 (1986), Power Sources, 12, p203 (1988), a method of adding Cd and Co into the active material has been conventionally employed. However, from the environmental aspect, cadmium is used. A free battery is demanded, Zn is proposed as an example of a metal element replacing cadmium, and a solid solution of three elements such as Co, Zn and Ba is also proposed (US Pat. No. 5,366,681). It is to be noted that the dissimilar metal solid solution in nickel oxide for the purpose of improving the efficiency of the charge / discharge characteristics is an old technique, and is also known in Japanese Patent Application Laid-Open No. 51-122737.
[0007]
  By improving the substrate shape, active material shape, active material composition, additive, and the like as described above, the energy density of the positive electrode has been dramatically improved, and a positive electrode having an energy density of about 600 mAh / cc is now in practical use. However, as described above, the demand for improving the energy density as a power source for small portable devices is increasing. In order to improve the energy density of the battery, approaches from the aspects of positive / negative electrode, electrolyte, separator, and their constitution method can be considered, but for the negative electrode, instead of the conventional cadmium negative electrode, high energy density As a result of the practical application of metal hydrides (Power Sources 12, p. 393 (1988)), volume energy density more than double that of the positive electrode has been reached. In addition, with regard to the battery construction method, rapid high energy density has been promoted by technological progress such as thinning of the separator and high-density filling of the electrode plate, and now it is almost reaching its limit. Therefore, in order to realize further improvement in energy density, higher energy density of the positive electrode occupying almost half the volume ratio in the battery is becoming an important position as the most effective elemental technology.
[0008]
  In order to improve the energy density of the positive electrode, approaches for improving the electrode packing density such as improving the tap density of the active material, reducing the amount of additive, and reducing the amount of metal in the foamed nickel base can be considered. The limit is being reached. Therefore, it is necessary to attempt to improve the reactivity and the reaction order by modifying the active material itself. Nickel oxide, the current cathode active material, is β-type Ni (OH) when filled₂It is said that a one-electron reaction (utilization rate: 100%) proceeds with β-type NiOOH (trivalent) in normal charging and discharging. However, β-NiOOH in this charged state is oxidized to γ-NiOOH (valence of 3.5 to 3.8), which is partially a high-order oxide, by overcharging. Note that at least γ-NiOOH is a non-stoichiometric material and is known to be disordered in terms of crystallinity (J. Power Sources, 8, p229 (1982), etc.). Conventionally, this γ-NiOOH is electrochemically inactive and causes not only a voltage drop and a capacity drop, but also a conductive agent due to the volume expansion of the electrode due to the expansion of the layers, contact failure with the substrate, dropout, Since it causes many harmful effects such as depletion of the electrolyte due to the incorporation of water molecules, attempts have been made to suppress the production.
[0009]
  However, in order to further increase the energy density using an active material based on nickel oxide, it is extremely important to make full use of the higher-order oxide γ-NiOOH. For this reason, a part of Ni is similar to α-type hydroxide in which dissimilar metals such as Mn (III), Al (III), Fe (III) are dissolved, and anion and water molecules are taken in between layers. Structural materials have been proposed (Solid State Ionics, 32/33, p. 104 (1989), J. Power Sources, 35, p. 249 (1991), US Pat. No. 5,348,822 (1994), US Patent No. 5569562 (1996), JP-A-8-225328, etc.). This oxide is said to be easily charged and discharged with a higher-order oxide having a structure similar to that of γ-NiOOH. However, in reality, this oxide has a wide interlayer and the material itself becomes very bulky, so that high density filling is difficult and practicality is considered to be poor.
[0010]
  On the other hand, we are paying attention to an active material which has a β-type crystal structure at the time of electrode filling and which is charged and discharged with a higher-order oxide γ-NiOOH. As an example, we have proposed the modification of nickel oxide by solid solution of different metals aiming at high density and higher order reactions. In addition, it has been proposed that a dissimilar metal that dissolves in particular has a promising composition mainly composed of Mn (for example, JP-A-8-222215, JP-A-8-222216, and JP-A-9). -115543). The above proposal discloses that Mn is dissolved in nickel oxide to improve proton mobility and electron conductivity and improve utilization. Nickel oxides in which Mn is dissolved are already proposed in Japanese Patent Laid-Open Nos. 51-122737, 4-17956, and 5-41212.
[0011]
[Problems to be solved by the invention]
  As described above, several attempts have been proposed to improve the charge / discharge efficiency by reforming nickel oxide by dissolving different kinds of metals in solid solution. However, the effect may not be sufficiently obtained depending on the type and amount of dissimilar metals to be dissolved. On the other hand, in the nickel oxide in which Mn is dissolved as described above, the effect of improving the charge / discharge efficiency and the reaction order is extremely large, and the improvement of the energy density can be expected. However, in JP-A-4-179056 and JP-A-5-41212, since the purpose is mainly to improve the cycle life, it is not intended to improve the reaction order.
[0012]
  In JP-A-8-222215, JP-A-8-222216, and JP-A-9-115543, appropriate values such as Mn valence, crystal structure, pore distribution and the like that greatly affect the battery characteristics are set. This is not disclosed, and there is room for improvement in order to further increase the energy density. Further, in producing the nickel oxide in which Mn is dissolved, since Mn (II) is unstable and easily oxidized, it is extremely difficult to grow into high-density particles. However, the proposal does not include a description on an improvement method for this problem, and it is difficult to realize a high energy density. U.S. Pat. No. 5637423 also includes Ni (OH) containing Mn.₂However, there is no disclosure regarding a method for producing a powdered metal oxide for the purpose of increasing the energy density.
[0013]
  In light of the above, an object of the present invention is to provide a positive electrode active material for an alkaline storage battery that achieves a dramatic increase in energy density and is excellent in charge / discharge efficiency and life characteristics, and a method for producing the same.
[0014]
[Means for Solving the Problems]
  In order to solve this problem, in the present invention, various physical properties of nickel oxide having at least Mn as a solid solution or in a eutectic state, that is, an average valence of Mn, a tap density, and an X-ray diffraction using CuKα rays. The peak intensity ratio is optimized.
[0015]
  And the manufacturing method of the nickel oxide which has the above various favorable physical properties as a positive electrode active material for alkaline storage batteries is embodied.
[0016]
  By using the nickel oxide having the above configuration as a positive electrode active material for an alkaline storage battery, it is possible to dramatically increase energy density, improve cycle stability, and improve high rate discharge characteristics.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  The present inventionΒ-Ni (OH) containing at least Mn in a solid solution or eutectic state₂Type positive electrode active material for alkaline storage batteries mainly composed of nickel oxide, wherein Mn has an average valence of 3.3 or more, a tap density of 1.7 g / cc or more, and uses CuKα radiation The half width of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction is 1.2 deg. As the dissimilar metal that is solid-dissolved in the nickel oxide, Mn having a remarkable effect for increasing the reaction order is preferable. Further, the average valence of Mn is preferably 3.3 or more. When the average valence is lower than 3.3, the charge / discharge efficiency in the initial cycle is remarkably lowered due to a decrease in electron conductivity or a decrease in γ production efficiency. Further, the tap density is preferably 1.7 g / cc or more, and if it is 1.7 g / cc or less, the filling density of the electrode is lowered and it is difficult to achieve a high energy density. Further, the half width of a peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction using CuKα ray is 1.2 deg. It is particularly desirable that That is, the charge / discharge efficiency can be significantly improved in the case where the half width is small and the crystallinity is high.
[0018]
  The nickel oxide usually means nickel hydroxide.
[0019]
  The present invention also provides:Β-Ni (OH) containing at least Mn in a solid solution or eutectic state₂A positive electrode active material for alkaline storage batteries mainly composed of nickel oxide, wherein the Mn has an average valence of 3.3 or more, a tap density of 1.7 g / cc or more, and uses CuKα radiation. The ratio B / A of the integrated intensity B of the peak located in the vicinity of 2θ = 18 to 21 ° to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction is 1.25 or less. Features.
[0020]
  When the peak intensity ratio B / A is 1.25 or less, the effect is not clear, but the discharge efficiency of the γ phase at the end of the cycle is remarkably improved and the cycle stability is improved.
[0021]
  Furthermore, the present invention providesΒ-Ni (OH) containing at least Mn in a solid solution or eutectic state₂A positive electrode active material for an alkaline storage battery mainly composed of a nickel oxide, wherein the Mn has an average valence of 3.3 or more, a tap density of 1.7 g / cc or more, and a pore size of 40 mm or less The space volume having a radius is characterized by 60% or more of the total pore volume, and the presence of many pores (grain boundaries between crystallites) of 40 mm or less, It becomes possible to alleviate the stress accompanying expansion and contraction. Moreover, these pores have a great influence on the specific surface area, and can significantly improve the charge / discharge efficiency during high rate charge / discharge. Further, sufficient effects cannot be obtained unless the ratio is 60% or more with respect to all pores.
[0022]
  Claims of the invention1The invention described in [3] includes at least Mn in a solid solution or eutectic state, β-Ni (OH)₂A positive electrode active material for alkaline storage batteries mainly composed of nickel oxide, wherein the Mn has an average valence of 3.3 or more, a tap density of 1.7 g / cc or more, and uses CuKα radiation. The half width of a peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction is 1.2 deg. The ratio B / A of the integrated intensity B of the peak located in the vicinity of 2θ = 18 to 21 ° to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° is 1.25 or less, and 40Å The space volume having the following pore radius is 60% or more with respect to the total pore volume.The surface of the nickel oxide powder is coated with a conductive metal oxide or metal.This improves the charge / discharge efficiency with the high-order oxide with a high density, and thus a high energy density can be achieved. Furthermore, as described above, it is possible to simultaneously improve cycle stability and high rate discharge characteristics.
[0023]
  The oxide powder containing Ni as a main metal element is characterized in that the surface of the powder is mainly coated with a conductive metal oxide or metal surface layer. Since the distribution of the conductive material such as metal oxide or metal becomes more uniform and the conductivity is improved, the filling amount of the conductive material can be reduced. In addition, the high-rate discharge characteristics can be improved by improving the conductivity. Furthermore, since the conductive material is uniformly distributed, stability in an aqueous solution is improved, and storage characteristics after discharge can be remarkably improved.
[0024]
  Claims of the invention2The invention described in (2) is characterized in that the Mn content in a solid solution or a eutectic state in the nickel oxide according to the present invention is 1 mol% or more and 12 mol% or less with respect to the total of all metal elements. Is. If the amount is less than 1 mol%, the effect is small. If the amount is more than 12 mol%, the crystal tends to be distorted due to the difference in ionic radius between Ni and Mn, making it difficult to grow at a high density. Accordingly, the Mn content is preferably 1 mol% or more and 12 mol% or less.
[0025]
  Claims of the invention3In the invention described in (2), the nickel oxide according to the present invention is characterized in that it is a powder having a spherical shape or a shape similar thereto, whereby the packing density of the electrode can be improved.
[0026]
  Claims of the invention4The invention described in 1 is characterized in that the oxide containing Ni as a main metal element contains at least Al in addition to Ni and Mn. According to the first aspect of the present invention, the nickel oxide containing Mn as a solid solution undergoes a higher order reaction and can be filled with high density, so that the energy density can be improved. However, on the other hand, it has a problem that the voltage during discharge is slightly low. On the other hand, the discharge voltage can be improved by dissolving Al in the oxide.
[0027]
  Claims of the invention5In the invention described in the above, in addition to Ni and Mn, the oxide containing Ni as a main metal element includes at least Ca, Mg, Ti, Zn, Sr, Ba, Y, Cd, Co, Cr, rare earth metal, One or more elements selected from Bi are included, and by dissolving the metal element in solid solution, the oxygen overvoltage is increased and the charging efficiency is improved.
[0028]
  Claims of the invention6The invention described in [3] includes at least Mn in a solid solution or eutectic state, β-Ni (OH)₂A positive electrode active material for alkaline storage batteries mainly composed of a nickel oxide type, wherein the Mn has an average valence of 3.3 or more and a tap density of 1.7 g / cc or more A method of manufacturing, wherein a dissolved oxygen concentration in an aqueous solution in a reaction vessel is maintained at 5 mg / l or less, an Ni salt is a main component, and an aqueous metal salt solution containing at least an Mn salt and an alkaline aqueous solution. The positive electrode active material is obtained by oxidizing after continuously acting to grow nickel oxide. Here, if the dissolved oxygen is more than 5 mg / l, the oxidation reaction of Mn proceeds during the growth process of the metal oxide, and the crystal lattice is distorted due to the remarkable decrease in the Mn ion radius, making it difficult to grow at high density. become. Therefore, by setting the dissolved oxygen concentration in the reaction vessel to 5 mg / l or less, the oxidation reaction of Mn can be suppressed and high-density growth is possible. Further, by continuously acting an aqueous solution mainly containing Ni salt containing at least Mn salt and an alkaline aqueous solution, an oxide mainly containing Ni containing at least Mn as a solid solution can be grown at a high density. . Further, by taking out the grown metal oxide powder and oxidizing it, the average valence of Mn can be increased to 3.3 or more, and an active material having high density and high charge / discharge efficiency can be obtained. it can.
[0029]
  Further, the present invention is characterized in that the pH value in the synthesis tank is 11 to 12.5, and if the pH value is smaller than 11, it becomes difficult to uniformly dissolve Mn. If it is larger than 5, it becomes an aggregate of fine particles and high density growth becomes difficult. Further, by making the pH value smaller than 12.5, the half width of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction using CuKα ray is 1.2 deg. It can be: Accordingly, a pH value of 11 to 12.5 is suitable.
[0030]
  And this invention is characterized by the temperature in the said synthesis tank being 20-60 degreeC, and it is easy to produce | generate a scale on the wall surface of a reaction tank in temperature lower than 20 degreeC, and more than 60 degreeC. At high temperatures, it tends to be agglomerates of fine particles, and high density growth is difficult in all cases. Further, by synthesizing at 60 ° C. or lower, the integrated intensity of the peak located in the vicinity of 2θ = 18 to 21 ° with respect to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction using CuKα ray. The ratio A / B of B can be 1.25 or less, and the cycle life can be improved. Therefore, 20-60 degreeC is suitable for the temperature in a synthesis tank.
[0031]
  Further, according to the present invention, the supply rate of all metal ions contained in the aqueous metal salt solution is 2 × 10. ^-Four ~ 2x10 ^-2 The aqueous solution is supplied so as to be mol / min, and the supply rate is 2 × 10. ^-2 If it is faster than mol / min, it cannot grow to a high density, and 2 × 10 ^-Four When it is slower than mol / min, the fine pores on the particle surface disappear and the surface area is remarkably lowered. 2 × 10 ^-Four By supplying faster than mol / min, the space volume having a pore radius of 40 mm or less can be made 60% or more with respect to the total pore volume, and the charge / discharge efficiency at the time of high rate charge / discharge is remarkably improved. It becomes possible to make it. Therefore, the supply rate of all metal ions is 2 × 10. ^-Four ~ 2x10 ^-2 It is preferable to supply the metal salt aqueous solution so as to be mol / min.
[0032]
  Claims of the invention7The invention described in (3) is characterized in that an inert gas and / or a reducing agent is continuously supplied into the reaction vessel, thereby reducing the dissolved oxygen concentration in the reaction vessel. The metal oxide powder having a high density can be taken out stably.
[0033]
  Claims of the invention8In the invention described in item 3, the inert gas is characterized by using at least one selected from nitrogen, helium, and argon, so that the dissolved oxygen concentration in the reaction vessel can be lowered relatively easily. And the metal oxide powder having a high density can be taken out stably.
[0034]
  Claims of the invention9The described invention is claimed.7In this method, hydrazine is used as the reducing agent in the metal oxide, whereby the oxidation reaction of Mn can be suppressed and the high-density metal oxide powder can be taken out stably.
[0035]
  Claims of the invention10The invention described is characterized in that an aqueous sodium hydroxide solution or an aqueous solution containing ammonium ions in the aqueous sodium hydroxide solution is used as the alkaline aqueous solution, and an aqueous metal salt solution mainly comprising an Ni salt containing at least a Mn salt. Thus, the oxide particles can be grown at a high density.
[0036]
  Claims of the invention11The described invention proposes to keep in the air atmosphere as an oxidation method in the production method according to the present invention, whereby the average valence of Mn of the metal oxide is increased to 3.3 or more. Can be pulled up easily.
[0037]
  Claims of the invention12The described invention is characterized in that it is maintained at 20 to 110 ° C. for 1 hour or more in the air atmosphere, and the oxidation reaction of Mn does not proceed sufficiently at a temperature lower than 20 ° C., and an average of 3 .It cannot be increased to more than 3 valences. In addition, at a temperature higher than 110 ° C., the decomposition reaction of the oxide proceeds and the charge / discharge efficiency is lowered. In addition, regarding the time of the oxidation treatment, it is difficult to oxidize the inside of the metal oxide particles within 1 hour or less.
[0038]
  Claims of the invention13The described invention proposes a method of reacting with oxygen or an oxidizing agent as a method of oxidizing, and raising the average valence of Mn of the metal oxide to 3.3 or more in a short time. Can do.
[0039]
  Claims of the invention14The invention described is characterized in that at least one selected from hydrogen peroxide and perchlorate is used as the oxidizing agent, whereby the average valence of Mn of the metal oxide is 3. It is possible to raise it to 3 or more.
[0040]
  Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS.3Will be described.
[0041]
  (Embodiment 1)
  FIG. 1 shows an embodiment of the present invention.Embodiment2 shows a cylindrical sealed nickel-hydrogen storage battery using a positive electrode active material by In FIG. 1, the electrode plate group 10 is configured by winding a separator 13 between a negative electrode plate 11 and a positive electrode plate 12 in a spiral shape. The negative electrode 11 is a hydrogen storage alloy MmNi_3.55Co_0.75Mn_0.4Al_0.3Is an active material. The positive electrode 12 uses nickel oxide as an active material. Electrolyte is K⁺, Na⁺, Li⁺It consists of a high concentration alkaline aqueous solution of 10 mol / l in total consisting of hydroxides of The separator 13 is made of sulfonated polypropylene and separates the negative electrode plate 11 and the positive electrode plate 12. The electrode plate group 10 is inserted into a nickel-plated steel battery case 14 and holds an electrolytic solution. The opening of the battery case 14 is sealed with a sealing plate 16 and a gasket 17 each having a safety valve 18 between the cap 19 serving also as a positive electrode terminal. An insulating plate 15 is interposed between the electrode plate group 10 and the bottom of the battery case 14. A nickel lead piece 20 connects the positive electrode plate 12 to the sealing plate 16. The safety valve 18 releases the battery case when oxygen gas or hydrogen gas is generated in the battery and prevents the battery from bursting. The valve operating pressure is 15 to 20 kgf / cm.²Degree. The lead piece of the negative electrode plate is connected to the battery case 14 (not shown).
[0042]
  In this example, the negative electrode is MmNi-based AB._FiveMade of hydrogen storage alloy, but LaNi_FiveOther ABs such as_Five-Based hydrogen storage alloy, Zr-Ti-Mn-Ni-based AB, etc.₂-Based hydrogen storage alloy, Mg-Ni type A, etc.₂The same can be done when a B-based hydrogen storage alloy, a cadmium negative electrode, or a zinc negative electrode is used. Although the cylindrical sealed battery has been described here, the present invention can be similarly applied to a rectangular sealed battery or a large sealed battery for an electric vehicle or a stationary type.
[0043]
  FIG. 2 schematically shows an electrode in which a foamed nickel substrate is filled with an active material mixture as an example of the positive electrode according to the present invention. The substrate 1 is made of foamed nickel. The substrate hole portion 2 is filled with an active material powder 3. The active material powder 3 is nickel oxide particles in which Mn having an average valence of 3.3 or higher is solid-solved at an atomic ratio of Ni: Mn = 9: 1. The conductive metal oxide layer 4 is made of a highly conductive Co oxide, and is present on the surface of the active material particles and / or between the active material particles, between the active material and the substrate, and is a powder of the active material. And has an effect of compensating for conductivity between the active material and the substrate. Reference numeral 5 denotes a gap.
[0044]
  In the above description, the substrate is made of foamed nickel. However, the present invention can be similarly implemented by using a three-dimensional metal porous body such as nickel felt or a two-dimensional metal porous plate such as punching metal. The active material powder is an oxide containing Ni as a main metal element. In addition to Ni and Mn, Al, Ca, Ti, Zn, Sr, Ba, Y, Cd, Co, Cr, rare earth metal The present invention can be similarly applied even when a metal oxide powder of a plurality of metal elements in which at least one element selected from Bi is dissolved is used.
[0045]
  FIG. 3 shows an example of a reaction apparatus for carrying out the method for producing a positive electrode active material of the present invention. In a reaction vessel 21, a metal salt aqueous solution supply line 22 made of nickel salt and manganese salt, and an ammonium ion supply line are shown. 23 and a NaOH aqueous solution supply line 24 are introduced, and the NaOH supply line 24 is provided with a pH stat 25 to adjust the supply amount of the NaOH aqueous solution.
[0046]
  In addition to nickel salt and manganese salt, the metal salt aqueous solution supply line 22 includes at least one selected from Al and / or Ca, Ti, Zn, Sr, Ba, Y, Cd, Co, Cr, rare earth metal, and Bi. A line for supplying an aqueous metal salt solution may be used.
[0047]
  The reaction tank 21 is provided with a thermostatic chamber 26, and the temperature in the reaction tank 21 is kept constant. The upper part is provided with a line 27 for taking out the grown metal oxide particle-containing liquid, and it can be continuously taken out by overflowing.
[0048]
  An inert gas supply line 28 is introduced at the lower part of the reaction tank, so that nitrogen can be continuously supplied and dissolved oxygen can be removed.
[0049]
  Note that argon gas and helium gas may be continuously supplied through the inert gas supply line 28. In addition to the inert gas supply line 28, a reducing agent supply line may be provided so that hydrazine or the like can be continuously supplied.
[0050]
  A stirring blade 30 connected to a stirring device 29 is provided inside the reaction tank 21, and various conditions in the reaction tank 21 are kept uniform.
[0051]
  In addition, as a structure of a reaction apparatus, you may employ | adopt the type which belongs to the magma type | mold apparatus which provided the part which has a classification function other than the type which belongs to the said stirring tank type | mold apparatus.
[0052]
  A metal oxide powder grown using the above reaction apparatus was subjected to an oxidation treatment to obtain a positive electrode active material for an alkaline storage battery according to the present invention.
[0053]
【Example】
  Next, it was obtained by changing various conditions of the production method according to the present invention.Specific experimental exampleWill be explained.
[0054]
  (Experimental example1)
  First, NiSO_FourAnd MnSO_FourMixed aqueous solution, NaOH aqueous solution, NH_ThreeAn aqueous solution was prepared and continuously supplied at a flow rate of 0.5 ml / min into a reactor having the same configuration as that shown in FIG. At the same time, Ar gas was continuously supplied at a flow rate of 800 ml / min, and the dissolved oxygen concentration in the apparatus was maintained at 0.05 mg / l. Here, the concentration of the aqueous solution is NiSO._FourConcentration is 2.2 mol / l, MnSO_FourConcentration 0.2 mol / l, NH_ThreeThe concentration was 5 mol / l, and the NaOH concentration was changed within the range of 4.2 to 7 mol / l. In addition, the pH value showed the different value in the range of 11-13 by the difference in the said NaOH density | concentration. Further, the supply rate of Ni and Mn ions at this time is 1.2 × 10 4 from the concentration of the aqueous solution and the supply flow rate.^-3It was calculated as mol / min.
[0055]
  Subsequently, the pH in the reaction apparatus becomes constant, the balance between the metal salt concentration and the oxide particle concentration becomes constant, and when it reaches a steady state, the suspension obtained by overflow is collected and precipitated by decantation. The thing was separated. After this was washed with water, the metal oxide powder moistened with water was kept in the atmosphere to be dried and oxidized at the same time. Here, the oxidation treatment conditions were kept constant in the range of 20 to 130 ° C. for 20 minutes to 24 hours in the atmosphere. In this way, a powder having an average particle size of 10 μm was obtained.
[0056]
  As a result of conducting the composition analysis, the Mn solid solution amount of the obtained metal oxide was about 8 mol% in all cases. Also, when XRD patterns were recorded, both were β-Ni (OH)₂It was confirmed to be a single phase of the mold. FIG. 4 shows a typical XRD pattern. Moreover, when the tap density was measured, all showed 1.7 g / cc or more, and it was confirmed that it was a material suitable for high energy density (a material excellent in filling property to the electrode support). .
[0057]
  Furthermore, when the total valence of all metals was obtained by the iodometry method and the average valence of Mn was calculated from the value, it varied in the range of 2.8 to 3.7 depending on the temperature and time of the oxidation treatment. . That is, when it was held at 20 ° C. for 20 minutes, it showed 2.8 valence, and when it was kept at 130 ° C. for 24 hours, it showed 3.7 valence. Further, since a correlation (Vegard's law) was observed between the average valence or content of Mn and the lattice constant, it was confirmed that Mn was substituted and dissolved in a part of Ni.
[0058]
  Further, when an X-ray diffraction pattern using Cu Kα rays was recorded, the half width of the peak around 2θ = 37 to 40 ° was different depending on the pH in the reactor, and 0.85 to 1.34 deg. Met. That is, as the pH is higher, the half width tends to be larger, and when the pH is 11, the half width is 0.85 deg. When the pH is 13, 1.34 deg. It became.
[0059]
  Thus, 10 g of Co (OH) was added to 100 g of the metal oxide powder obtained under various production conditions.₂Powder and 40 g of water were added and kneaded into a paste. This paste was filled in a foamed nickel substrate having a porosity of 95%, dried and then pressure-molded to obtain a nickel positive electrode plate. The positive electrode plate thus obtained was cut, and the electrode lead was spot welded to obtain a nickel positive electrode having a theoretical capacity of 1200 mAh. However, the capacity density of the nickel electrode shown here is calculated assuming that Ni in the active material has a one-electron reaction.
[0060]
  Moreover, the well-known negative electrode for alkaline storage batteries was used for the negative electrode. Here, hydrogen storage alloy MmNi_3.55Co_0.75Mn_0.4Al_0.3The negative electrode which consists of was used. Mm, Ni, Co, Mn, and Al mixed at a desired ratio were melted in an arc melting furnace to obtain a hydrogen storage alloy having a desired composition. This alloy lump was mechanically pulverized in an inert atmosphere to obtain a powder having a particle size of 30 μm. Water and a binder carboxymethylcellulose were added thereto and kneaded into a paste. This paste was pressure filled into the electrode support to obtain a hydrogen storage alloy negative electrode plate. This negative electrode plate was cut into a negative electrode having a capacity of 1920 mAh.
[0061]
  A spiral electrode group was formed with the positive electrode and the negative electrode interposed between separators made of a sulfonated polypropylene nonwoven fabric having a thickness of 0.15 mm. After inserting this electrode group into the battery case and injecting 2.2 ml of 10 mol / l KOH aqueous solution, the operating valve pressure was about 20 kgf / cm.²The opening of the battery case was sealed with a sealing plate having a safety valve, and an AA size cylindrical sealed nickel-hydrogen storage battery was produced.
[0062]
  First, cylindrical sealed batteries were produced using samples having different average Mn valences as active materials, and their battery characteristics were evaluated. At 20 ° C., the battery was charged with a current of 120 mA for 18 hours and discharged at a current of 240 mA to a battery voltage of 1.0 V. After the discharge capacity was stabilized, the utilization rate of the active material was determined from the measured discharge capacity. Asked. In addition, the utilization factor was calculated with respect to the theoretical amount of electricity when Ni in the active material reacted with one electron.
[0063]
  FIG. 5 is a characteristic diagram showing the results of these experiments and showing the relationship between the average valence of Mn and the utilization rate. From this figure, it can be seen that, in the range where the average valence of Mn is lower than 3.3, the utilization rate tends to improve as the Mn valence increases, and almost reaches the peak at 3.3 or more. Therefore, it is considered that the average valence of Mn is 3.3 or more. Next, cylindrical sealed batteries were fabricated using samples with different half-value widths of peaks near 2θ = 38.5 ° of the X-ray diffraction pattern using the above-mentioned Cukα rays as active materials, and the battery characteristics were evaluated. did. In the evaluation method, the utilization rate was obtained in the same manner as described above.
[0064]
  FIG. 6 is a diagram showing the results of these experiments, and is a characteristic diagram showing the relationship between the half-value width and the utilization rate. From this figure, it can be seen that in the range where the half-value width is larger than 1.2, the utilization rate tends to decrease as the half-value width increases, and a high utilization rate is exhibited at 1.2 or less. Therefore, the half width of the peak around 2θ = 38.5 ° of the X-ray diffraction pattern using the Cukα ray is preferably 1.2 or less.
[0065]
  (Experimental example2)
  Experimental example1, the NaOH aqueous solution concentration is 5.5 mol / l, the pH value is controlled to be constant around 12.0, and the temperature in the reactor is 20 to 80 ° C. It was synthesized by changing within the range. Further, the oxidation treatment conditions were maintained in the atmosphere at 80 ° C. for 24 hours. Other than thisExperimental exampleIn the same manner as in Example 1, metal oxide powder was obtained.
[0066]
  All of the obtained metal oxide powders were spherical powders having an average particle diameter of 10 μm and had a tap density of 1.7 g / cc or more. In both cases, β-Ni (OH)₂It was a single phase of the mold, and the Mn solid solution amount was about 8 mol%. Also,Experimental exampleWhen the average valence of Mn was calculated in the same manner as in Example 1, all were 3.6. Further, when an X-ray diffraction pattern using CuKα rays was recorded, it was found that 2θ = 18 to 21 ° with respect to the integrated intensity A of the peak located near 2θ = 37 to 40 ° due to the temperature difference in the reactor. The value of the ratio B / A of the integrated intensity B of the peak located was different and varied within the range of B / A = 1.1 to 1.3. That is, the higher the temperature in the reaction tank, the higher the B / A tends to be, and it was 1.1 at 20 ° C. and 1.3 at 80 ° C.
[0067]
  Samples having different integrated intensity ratios B / A of the peaks of the X-ray diffraction pattern using the above-mentioned Cukα rays are used as active materials.Experimental exampleIn the same manner as in Example 1, cylindrical sealed batteries were produced and their battery characteristics were evaluated. The evaluation method was as follows. First, charging and discharging cycles were repeated for 10 hours at 20 ° C. with a current of 120 mA and discharged to a battery voltage of 1.0 V with a current of 240 mA. After the discharge capacity was stabilized, The battery was charged at a current of 6 A for 3 hours, and a charge / discharge cycle of discharging at a current of 0.6 A to a battery voltage of 0.8 V was repeated. Ratio U (300th) / U (1st) between the utilization rate U (1st) of the first cycle of the charge / discharge cycle at 45 ° C. and the utilization rate U (300th) of the 300th cycle (hereinafter referred to as capacity maintenance rate) Cycle stability (lifetime characteristics) was evaluated.
[0068]
  FIG. 7 is a characteristic diagram showing the relationship between the capacity retention ratio (U (300th) / U (1st)) with respect to the ratio B / A of the integrated intensity. From this figure, it can be seen that a high capacity retention ratio is exhibited when the ratio B / A of the integrated intensity is 1.25 or less. Therefore, in order to improve cycle stability, the integration of the peak located in the vicinity of 2θ = 18 to 21 ° with respect to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° of the X-ray diffraction using the CuKα ray. The ratio B / A with the strength B is preferably 1.25 or less.
[0069]
  (Experimental example3)
  Experimental example1, the NaOH aqueous solution concentration is 5.5 mol / l, the pH value is controlled to be constant around 12.0, and the supply rate of Ni and Mn ions is 5 × 10 5.^-Five~ 2x10^-2It was changed within the range of mol / min. The oxidation treatment conditions were maintained at 80 ° C. for 24 hours in the atmosphere. Other than thisExperimental exampleIn the same manner as in Example 1, metal oxide powder was obtained.
[0070]
  All of the obtained oxide powders were spherical powders having an average particle diameter of 10 μm and had a tap density of 1.7 g / cc or more. In both cases, β-Ni (OH)₂It was a single phase of the mold, and the Mn solid solution amount was about 8 mol%. Also,Experimental exampleWhen the average valence of Mn was calculated in the same manner as in Example 1, all were 3.6. Moreover, when the pore distribution measurement by nitrogen gas adsorption was performed, the ratio of the space volume having a pore radius of 40 mm or less with respect to the total pore volume (hereinafter referred to as 40 mm or less) due to the difference in the supply rate of the Ni and Mn ions. (Referred to as pore volume ratio) of 40-80%.
[0071]
  That is, the higher the supply rate, the higher the pore volume ratio tends to be, and 5 × 10 5^-Five40% when mol / min, 2 × 10^-2When mol / min, it was 80%.
[0072]
  Samples having different pore volume ratios of 40 mm or less are used as active materials.Experimental exampleIn the same manner as in Example 1, cylindrical sealed batteries were produced and their battery characteristics were evaluated. The evaluation method is as follows. First, a charge / discharge cycle of charging at 120 ° C. for 18 hours at 20 ° C. and discharging to a battery voltage of 1.0 V at a current of 240 mA is repeated 10 cycles. After the discharge capacity has stabilized, 120 mA at 20 ° C. Then, the battery was discharged to a battery voltage of 0.8 V with current values of 240 mA and 1.2 A. Ratio U (1.2 A) / U (240 mA) between the utilization rate U (240 mA) when discharged at 240 mA and the utilization rate U (1.2 A) when discharged at 1.2 mA (hereinafter referred to as discharge) The high rate discharge characteristic was evaluated by obtaining a capacity ratio).
[0073]
  FIG. 8 is a characteristic diagram showing the relationship between the discharge capacity ratio (U (1.2 A) / U (240 mA)) with respect to the pore volume ratio of 40 μm or less. From this figure, it can be seen that a high discharge capacity ratio is exhibited when the pore volume ratio is 60% or more. Therefore, in order to improve the high rate discharge characteristics, the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume is preferably 60% or more.
[0074]
  (Experimental example4)
  Experimental exampleIn the production conditions described in 1, the concentration of the NaOH aqueous solution is 5.5 mol / l, the pH value is controlled to be constant around 12.0, and the oxidation treatment conditions are maintained at 80 ° C. in the atmosphere for 24 hours. It was. Other than thisExperimental exampleIn the same manner as in Example 1, metal oxide powder was obtained.
[0075]
  All of the obtained metal oxide powders were spherical powders having an average particle diameter of 10 μm and had a tap density of 1.7 g / cc or more. And both are β-Ni (OH)₂It was a single phase of the mold, and the Mn solid solution amount was about 8 mol%.Experimental exampleIn the same manner as in Example 1, when the average valence of Mn in the metal oxide was measured, it showed 3.6. Further, when an X-ray diffraction pattern using Cu Kα ray was recorded, the half width of the peak around 2θ = 37 ° to 40 ° was 0.75 deg. The ratio B / A of the peak integrated intensity B located near 2θ = 18 to 21 ° to the integrated intensity A of the peak located near 2θ = 37 to 40 ° was 1.15. Furthermore, when pore distribution measurement by nitrogen gas adsorption was performed, the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume was 68%.
[0076]
  Using the sample,Experimental exampleIn the same manner as in Example 1, a cylindrical sealed nickel-hydrogen storage battery was produced and the battery characteristics were evaluated. Evaluation contentsExperimental exampleIn the same manner as in 1, 2, and 3, the utilization rate, the discharge capacity ratio (U (1.2 A) / U (240 mA)) and the capacity maintenance ratio (U (300 th) / U (1 st)) were measured. For comparison, a known nickel oxide powder in which Co 1% by weight and Zn 4% by weight used in the current product are dissolved is used as an active material, and a cylindrical sealed nickel-hydrogen storage battery is similarly manufactured. As a comparative example 1, battery characteristics were evaluated.
[0077]
  Table 1 shows the results of these experiments. From this table, the metal oxide of the present invention is the current Ni (OH)₂It can be seen that it has a high utilization rate as compared with the above, and that the high rate discharge characteristics and life characteristics are almost the same level.
[0078]
[Table 1]

[0079]
  (Experimental example5)
  Experimental exampleIn the production of the metal oxide in No. 4, NiSO_FourAnd MnSO_FourUsing a mixed solution in which the concentration ratio was changed, the Mn solid solution amount was synthesized to be 0 to 16 mol%.
[0080]
  Each of the obtained Mn solid-solution metal oxide powders was a spherical powder having an average particle diameter of 10 μm and had a tap density of 1.7 g / cc or more. In both cases, β-Ni (OH)₂It was a single phase of the mold, and the average valence of Mn was in the range of 3.5 to 3.6. Further, when an X-ray diffraction pattern using Cu Kα rays was recorded, the half width of the peak around 2θ = 37 ° to 40 ° was 0.6 to 0.9 deg. The ratio B / A of the peak integrated intensity B located in the vicinity of 2θ = 18 to 21 ° to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° is 1.0 to It was within the range of 1.2. Furthermore, when the pore distribution measurement by nitrogen gas adsorption was performed, the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume showed a value in the range of 65 to 73%.
[0081]
  Using these metal oxides as active materials,Experimental exampleA cylindrical sealed battery was produced in the same manner as in No. 4, and the utilization factor was determined from the amount of electricity discharged at 240 mA at 20 ° C. Furthermore, the volume energy density (actual capacity density) of the electrode was determined from each electrode packing density and the utilization factor. In addition, about the electrode packing density, the rolling rate at the time of electrode preparation was adjusted so that the space volume ratio (porosity) calculated from the volume of the electrode and the true specific gravity of the filled active material and additive may be 25%.
[0082]
  FIG. 9 is a diagram showing the results of these experiments, and is a characteristic diagram showing the relationship between the utilization rate with respect to the Mn solid solution amount and the volume energy density of the electrode. From this figure, it can be seen that when the Mn solid solution amount is 1.0 mol% or more, the utilization rate is extremely high. Also, it can be seen that when the Mn solid solution amount is 1.0 mol% or more, a high volume energy density is exhibited, and when it exceeds 12.0 mol%, the volume decreases. The volume energy density is greatly related to the electrode packing density in addition to the utilization factor, and the packing density greatly affects the tap density of the active material. Therefore, if the Mn solid solution amount is large, distortion is likely to occur in the crystal due to the difference in ionic radius between Ni and Mn, the tap density is reduced, and the electrode filling density is lowered. It is considered that the volume energy density has decreased due to this. Accordingly, it is considered that the Mn solid solution amount is suitably 1.0 mol% or more and 12.0 mol% or less.
[0083]
  (Experimental example6)
  Experimental exampleIn the production method of No. 4, 2.1 mol / l NiSO as a starting material_Four
And 0.2 mol / l MnSO_FourAnd 0.1 mol / l Al₂(SO_Four)_ThreeA metal oxide mainly containing Ni and containing Mn and Al was synthesized in the same manner except that a mixed aqueous solution containing was used.
[0084]
  The obtained metal oxide was a spherical powder having an average particle size of 10 μm. Moreover, as a result of conducting the composition analysis, the Mn and Al solid solution amounts of the obtained metal oxide were 8 mol% and 4 mol%, respectively, and β-Ni (OH)₂It was a single phase of the mold. Moreover, when the total valence of all metals was calculated | required by the iodometry method and the average valence of Mn was computed from the value, it was 3.6 valence. Further, when a powder X-ray diffraction pattern using Cu Kα rays was recorded, the half width of the peak around 2θ = 37 ° to 40 ° was 0.81 deg. The ratio B / A of the peak integrated intensity B located near 2θ = 18 to 21 ° to the integral intensity A of the peak located near 2θ = 37 ° to 40 ° was 1.22. . Furthermore, when pore distribution measurement by nitrogen gas adsorption was performed, the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume was 65%.
[0085]
  Using this metal oxide as an active material,Experimental exampleA cylindrical sealed battery was produced in the same manner as in Example 4, and the battery characteristics were evaluated. About the evaluation result, the followingExperimental examplePut together in 7.
[0086]
    (Experimental example7)
  Experimental exampleIn the production method of No. 4, 2.1 mol / l Ni (NO_Three)₂And 0.2 mol / l Mn (NO_Three)₂And 0.1 mol / l Ca (NO_Three)₂A metal oxide mainly containing Ni and containing Mn and Ca was synthesized in the same manner except that a mixed aqueous solution containing was used.
[0087]
  The obtained metal oxide was a spherical powder having an average particle size of 10 μm. Moreover, as a result of conducting the composition analysis, the Mn and Ca solid solution amounts of the obtained metal oxide were 8 mol% and 4 mol%, respectively, and β-Ni (OH)₂It was a single phase of the mold. Moreover, when the total valence of all metals was calculated | required by the iodometry method and the average valence of Mn was computed from the value, it was 3.6 valence. Further, when a powder X-ray diffraction pattern using Cu Kα rays was recorded, the half width of the peak around 2θ = 37 ° to 40 ° was 0.73 deg. The ratio B / A of the peak integrated intensity B located near 2θ = 18 to 21 ° to the integrated intensity A of the peak located near 2θ = 37 to 40 ° was 1.17. Furthermore, when pore distribution measurement by nitrogen gas adsorption was performed, the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume was 71%.
[0088]
  Using this metal oxide as an active material,Experimental exampleA cylindrical sealed battery was produced in the same manner as in Example 4, and the battery characteristics were evaluated.
[0089]
  Similarly, for comparison,Experimental exampleIn the production method of No. 4, 2.4 mol / l NiSO as a starting material_FourA nickel oxide was synthesized in the same manner except that was used. The obtained nickel oxide was a spherical powder having an average particle size of 10 μm.
[0090]
  Using the nickel oxide powder obtained in this way,Experimental exampleIn the same manner as in Example 4, a cylindrical sealed battery was produced as a second comparative example.
[0091]
  Experimental exampleUsing the cylindrical sealed battery produced as 4, 6, 7 and Comparative Example 2,Experimental exampleThe utilization factor of the active material was determined in the same manner as in 1. Further, during the discharge in the same experiment, the voltage was measured at a discharge depth (DOD = 50%) corresponding to a half of the actual discharge capacity. Further, at the time of charging in the same experiment, the test temperature was set to 45 ° C., and otherwise the utilization rate of the active material was determined in the same manner. Table 2 shows the results.
[0092]
[Table 2]

[0093]
  As is apparent from Table 2, the discharge voltage can be improved by dissolving Al, and the charging efficiency at a high temperature can be improved by dissolving Ca.
[0094]
  Here, an example of an oxide containing Ca in addition to Ni and Mn is shown, but in addition to Ca, Mg, Ti, Zn, Sr, Ba, Y, Cd, Co, Cr, rare earth metal, Bi Similarly, the charging efficiency at high temperatures could be improved. Moreover, in the oxide which combined the said solid solution element and Al, the synergistic effect of the improvement of discharge voltage and the improvement of charging efficiency was able to be confirmed.
[0095]
  (Experimental example8)
  Experimental exampleIn the production method of No. 4, the metal oxide powder obtained after the oxidation treatment was placed in water and stirred, and then a 20 wt% aqueous solution of cobalt sulfate and a 25 wt% aqueous solution of sodium hydroxide were added dropwise, whereby Co A metal oxide powder coated with an oxide surface layer was synthesized.
[0096]
  The obtained oxide was a spherical powder having an average particle size of 10 μm. As a result of the composition analysis, the ratio of the metal oxide in the powder inner layer to the Co oxide in the surface layer was 10: 1% by weight.
[0097]
  Using the metal oxide powder thus obtained,Experimental exampleIn the same manner as in Example 4, a cylindrical sealed battery was produced.
[0098]
  Experimental example4 andExperimental exampleUsing the cylindrical sealed battery produced in 8,Experimental exampleThe utilization factor of the active material was measured in the same manner as in Example 4. Furthermore, the utilization factor was measured when the current during discharge in the experiment was 1200 mA. Table 3 shows the results.
[0099]
[Table 3]

[0100]
  As is apparent from Table 3, even when a metal oxide coated with a surface layer of Co oxide is used, it shows a high utilization factor, and in particular, an effect of improving the utilization factor during high-rate discharge. I was able to confirm that there is.
[0101]
  In addition to the Co oxide, the same effect was obtained when using another metal oxide having conductivity or a metal oxide coated with a surface layer of metal.
[0102]
  (Experimental example9)
  Experimental exampleA metal oxide powder was obtained in the same manner except that the Ar gas flow rate was changed to 0 to 1200 ml / min and the dissolved oxygen concentration was changed to 0.03 to 9.00 mg / l in the production method of No. 4.
[0103]
  FIG. 10 shows a relationship between the tap density of the obtained metal oxide powder and the dissolved oxygen concentration at this time. From this figure, it can be seen that a high tap density is exhibited when the dissolved oxygen concentration is 5 mg / l or less. Therefore, it is considered that the dissolved oxygen concentration is appropriately 5 mg / l or less.
[0104]
  Although Ar gas was supplied here, the dissolved oxygen concentration can be kept at 5 mg / l or less similarly using other inert gases such as nitrogen and helium, and a metal oxide having similar characteristics can be obtained. I was able to. Similar results were obtained when these were combined or when a reducing agent such as hydrazine was used.
[0105]
  For comparisonExperimental exampleIn the production method of 9, the metal oxide powder was obtained in the same manner except that the metal oxide was washed with water and then dried under vacuum to suppress oxidation.
[0106]
  When the average valence of Mn of the obtained metal powder was measured, it showed 2.4. Moreover, the utilization factor of the active material was remarkably low at 92%. Therefore, it is necessary to increase the Mn valence by performing oxidation treatment.
[0107]
  (Experimental example10)
  Experimental exampleA metal oxide powder was obtained in the same manner except that the oxidation treatment was carried out in the production method of 4 at 0 to 130 ° C. in the atmosphere for 20 minutes to 24 hours.
[0108]
  FIG. 11 shows the relationship between the average valence of Mn of the metal oxide and the oxidation time at each oxidation temperature. From this figure, in order to obtain a metal oxide having an average valence of 3.3 or more of Mn, it is considered appropriate to hold at 20 ° C. or more for 1 hour or more. However, when the oxidation treatment is performed at a temperature higher than 110 ° C., the utilization rate tends to decrease. This is presumably because the decomposition reaction of the metal oxide progressed by the same treatment. Therefore, it is considered that an oxidation temperature of 20 ° C. to 110 ° C. is appropriate.
[0109]
  Note that although the oxidation treatment is performed in the atmosphere here, oxygen or an oxidizing agent such as hydrogen peroxide, sodium perchlorate, or potassium perchlorate similarly has an average valence of Mn. 3. It could be more than 3 valences.
[0110]
  (Experimental example11)
  Experimental exampleA metal oxide powder was obtained in the same manner except that the synthesis was carried out by changing the pH value in the synthesis tank within the range of 10 to 13 in the production method of No. 4.
[0111]
  When X-ray diffraction measurement using CuKα rays was performed on these metal oxides, the half width of a peak located near 2θ = 37 to 40 ° was 1.2 deg. In order to make it below, it was necessary to make the pH value 12.5 or less. Further, when the pH value was lower than 11, it was difficult to grow at a high density, and the tap density was smaller than 1.7 g / cc.
[0112]
  (Experimental example12)
  Experimental exampleA metal oxide powder was obtained in the same manner except that the synthesis was carried out by changing the temperature in the synthesis tank in the range of 10 to 80 ° C. in the production method of No. 4.
[0113]
  When X-ray diffraction measurement using CuKα rays was performed on these metal oxides, the peak of the peak located near 2θ = 18 to 21 ° with respect to the integrated intensity A of the peak located near 2θ = 37 to 40 °. In order to make the value of the ratio B / A with the integrated intensity B 1.25 or less, it was necessary to keep the temperature at 60 ° C. or less. Further, when the temperature is lower than 20 ° C., not only temperature control becomes difficult, but also scale generation becomes remarkable, so that it is difficult to grow at a high density, and the tap density becomes smaller than 1.7 g / cc. .
[0114]
  (Experimental example13)
  Experimental exampleIn the production method of No. 4, the supply rate of all metal ions contained in the aqueous metal salt solution is 5 × 10^-Five~ 5x10^-2A metal oxide powder was obtained in the same manner except that the synthesis was carried out by changing within the range of mol / min.
[0115]
  In these metal oxides, pore distribution measurement by nitrogen gas adsorption was carried out. In order to increase the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume to 60% or more, the total metal ions Supply speed of 2 × 10^-FourIt was necessary to do more. Also, the supply speed is 2 × 10^-2At higher speeds, it was difficult to grow at a high density due to a significant decrease in residence time, and the tap density was less than 1.7 g / cc.
[0116]
【The invention's effect】
  As described above, according to the present invention, the utilization factor of the positive electrode active material can be increased, and the energy density can be greatly improved. Further, the life characteristics and high rate discharge characteristics can be improved.
[0117]
  Thus, an alkaline storage battery having an excellent energy density is provided.
[Brief description of the drawings]
FIG. 1 is one of the present inventionEmbodimentThe perspective view which notched some sealed alkaline storage batteries in
FIG. 2 is one of the present inventionEmbodimentSchematic diagram of nickel positive electrode filled with metal oxide powder by
FIG. 3 is a diagram showing a metal oxide production apparatus according to an embodiment of the present invention.
FIG. 4 shows one aspect of the present invention.Experimental exampleXRD chart of metal oxides with Ni as the main element
FIG. 5 shows the present invention.Experimental exampleOf change in utilization rate with respect to Mn average valence of metal oxides
FIG. 6 of the present inventionExperimental exampleOf change in utilization rate with respect to the peak half-value width in the vicinity of 2θ = 37 ° to 40 ° in X-ray diffraction using CuKα ray of a metal oxide by means of
FIG. 7 shows the present invention.Experimental exampleOf the integrated intensity B of the peak located near 2θ = 18 to 21 ° to the integrated intensity A of the peak located near 2θ = 37 to 40 ° of X-ray diffraction using CuKα ray of the metal oxide by B / The figure which shows the change of the capacity maintenance rate accompanying the change of A
FIG. 8 shows the present invention.Experimental exampleOf the discharge capacity ratio with respect to the ratio of the space volume having a pore radius of 40 mm or less to the total pore volume of the metal oxide by
FIG. 9 shows the present invention.Experimental exampleOf change in utilization rate and volumetric energy density with respect to Mn solid solution of metal oxide
FIG. 10 is a graph showing changes in the tap density of the composite with respect to the dissolved oxygen concentration in the reaction vessel in the production process of the metal oxide.
FIG. 11 is a graph showing a change in average valence of Mn with respect to holding time (oxidation time) at each temperature (oxidation temperature) in an air atmosphere in the manufacturing process according to the present invention.
[Explanation of symbols]
    1 Substrate
    2 Substrate hole
    3 Active material powder
    4 Conductive metal oxide layer
    5 gap
  10 plate group
  11 Negative electrode plate
  12 Positive electrode plate
  13 Separator
  14 Battery case
  15 Insulation plate
  16 Sealing plate
  17 Gasket
  18 Safety valve
  19 cap
  20 Positive lead piece
  21 reaction tank
  22 Metal salt aqueous solution supply line
  23 Ammonium ion supply line
  24 NaOH aqueous solution supply line
  25 pH stat
  26 Thermostatic bath
  27 Metal oxide particle-containing liquid removal line
  28 Inert gas supply line
  29 Stirrer
  30 Stirring blade

Claims (14)

A positive electrode active material for an alkaline storage battery mainly containing β-Ni (OH) ₂ type nickel oxide containing at least Mn in a solid solution or eutectic state, wherein the average valence of Mn is 3.3 or more The peak half-width of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction using CuKα rays is 1.2 deg. Or less, 2 [Theta] = relative integrated intensity A of a peak located 37-40 near °, the ratio B / A of integrated intensity B of a peak located in the vicinity of 2 [Theta] = 18 to 21 ° is 1.25 or less, 40 Å The space volume having the following pore radius is 60% or more based on the total pore volume , and the surface layer of the nickel oxide powder is coated with a conductive metal oxide or metal. A positive electrode active material for an alkaline storage battery. 2. The positive electrode active material for an alkaline storage battery according to claim 1, wherein the Mn content in a solid solution or eutectic state is 1 mol% or more and 12 mol% or less with respect to the total of all metal elements in the nickel oxide. . The positive electrode active material for an alkaline storage battery according to claim 1, wherein the nickel oxide is a powder having a spherical shape or a shape similar thereto. Nickel oxide, in addition to Ni and Mn, a positive electrode active material for an alkaline storage battery according to claim 1, characterized in that it contains at least Al. In addition to Ni and Mn, the nickel oxide contains at least one element selected from Ca, Mg, Ti, Zn, Sr, Ba, Y, Cd, Co, Cr, rare earth metal, and Bi. The positive electrode active material for an alkaline storage battery according to claim 1 , wherein: A positive electrode active material for an alkaline storage battery mainly containing β-Ni (OH) ₂ type nickel oxide containing at least Mn in a solid solution or eutectic state, wherein the average valence of Mn is 3.3 or more The peak half-width of the peak located in the vicinity of 2θ = 37 to 40 ° of X-ray diffraction using CuKα rays is 1.2 deg. The ratio B / A of the integrated intensity B of the peak located in the vicinity of 2θ = 18 to 21 ° to the integrated intensity A of the peak located in the vicinity of 2θ = 37 to 40 ° is 1.25 or less, and 40Å The space volume having the following pore radius is 60% or more based on the total pore volume, and the surface layer of the nickel oxide powder is coated with a conductive metal oxide or metal. A method for producing a positive electrode active material for an alkaline storage battery, comprising:
In a state where the dissolved oxygen concentration in the aqueous solution in the reaction vessel is maintained at 5 mg / l or less, the pH value in the reaction vessel is 11 to 12.5, and the temperature in the reaction vessel is 20 to 60 ° C. The supply rate of the total metal ions contained in the metal salt aqueous solution is 2 × 10 ⁻⁴ to 2 × 10 ⁻² mol / min. The method for producing a positive electrode active material for an alkaline storage battery is characterized in that, by supplying the aqueous solution, the nickel oxide is grown by continuous action and then oxidized. The method for producing a positive electrode active material for an alkaline storage battery according to claim 6 , wherein an inert gas and / or a reducing agent is continuously supplied into the reaction vessel. The method for producing a positive electrode active material for an alkaline storage battery according to claim 7 , wherein the inert gas is at least one selected from nitrogen, helium, and argon. The method for producing a positive electrode active material for an alkaline storage battery according to claim 7 , wherein hydrazine is used as the reducing agent. The method for producing a positive electrode active material for an alkaline storage battery according to claim 6 , wherein an aqueous sodium hydroxide solution or an aqueous solution containing an aqueous sodium hydroxide solution and ammonium ions is used as the alkaline aqueous solution. The method for producing a positive electrode active material for an alkaline storage battery according to claim 6 , wherein the material is oxidized by being held in an air atmosphere. The method for producing a positive electrode active material for an alkaline storage battery according to claim 11 , wherein the positive electrode active material is held at 20 to 110 ° C. for 1 hour or longer in an air atmosphere. The method for producing a positive electrode active material for an alkaline storage battery according to claim 6 , wherein oxidation is performed by acting with oxygen or an oxidizing agent. The method for producing a positive electrode active material for an alkaline storage battery according to claim 13 , wherein the oxidizing agent is at least one selected from hydrogen peroxide and perchlorate.

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