JP4894132B2 - Hydrogen storage alloy electrode, manufacturing method thereof, and nickel metal hydride storage battery - Google Patents
Hydrogen storage alloy electrode, manufacturing method thereof, and nickel metal hydride storage battery Download PDFInfo
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- JP4894132B2 JP4894132B2 JP2004127596A JP2004127596A JP4894132B2 JP 4894132 B2 JP4894132 B2 JP 4894132B2 JP 2004127596 A JP2004127596 A JP 2004127596A JP 2004127596 A JP2004127596 A JP 2004127596A JP 4894132 B2 JP4894132 B2 JP 4894132B2
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- Prior art keywords
- hydrogen storage
- storage alloy
- alloy powder
- electrode
- aqueous solution
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Description
本発明は、水素吸蔵合金電極とその製造方法およびニッケル水素蓄電池に関し、さらに詳しくはその負極である水素吸蔵合金電極の高率放電性能およびサイクル性能の向上に関するものである。 The present invention relates to a hydrogen storage alloy electrode, a method for producing the same, and a nickel metal hydride storage battery, and more particularly to an improvement in high-rate discharge performance and cycle performance of a hydrogen storage alloy electrode that is a negative electrode.
近年、モバイルコンピューター、デジタルカメラなどの移動体電子機器をはじめとする小型軽量を求められる電動機器が急速に増加する傾向にある。これらの機器の電源として、密閉型ニッケル水素蓄電池が、ニッケルカドミウム蓄電池や鉛蓄電池等よりも単位体積および単位質量当たりのエネルギーが高い上、環境にクリーンな電源として最近特に注目されている。また、ニッケル水素蓄電池は、過充電時に正極で発生する酸素を水素吸蔵合金負極で吸収する事が可能であるため、充電制御方式がリチウムイオン電池に比べて単純でよく、充電回路も簡単になり安価である利点を有している。 In recent years, there has been a rapid increase in the number of electric devices that are required to be small and light, such as mobile electronic devices such as mobile computers and digital cameras. As a power source for these devices, a sealed nickel-metal hydride storage battery has recently attracted particular attention as a clean power source for the environment in addition to higher energy per unit volume and unit mass than a nickel cadmium storage battery or a lead storage battery. In addition, since the nickel metal hydride storage battery can absorb the oxygen generated at the positive electrode during overcharge by the hydrogen storage alloy negative electrode, the charge control method can be simpler than the lithium ion battery, and the charging circuit can be simplified. It has the advantage of being inexpensive.
しかしながら、水素吸蔵合金は電解液中で腐蝕して容量が低下するなどの理由によって、正極に比べて過剰な容量の水素吸蔵合金を具備しなければならず、エネルギー密度の向上が達成し難いという欠点を有していた。また、耐食性に優れ、長寿命を有する水素吸蔵合金は、活性化が遅く、そのまま電極に用いた場合、充分な放電特性を発揮するまでの初期の活性化に時間を要し、数十回から場合によっては数百回の充放電が必要となっている。 However, the hydrogen storage alloy must be provided with an excess capacity of the hydrogen storage alloy compared to the positive electrode due to corrosion, etc. in the electrolytic solution, resulting in a decrease in capacity, and it is difficult to improve the energy density. Had drawbacks. In addition, the hydrogen storage alloy with excellent corrosion resistance and long life is slow to activate, and when used as an electrode as it is, it takes time for initial activation until it exhibits sufficient discharge characteristics. In some cases, several hundreds of charge / discharge cycles are required.
耐食性の高い水素吸蔵合金の活性化が遅いという欠点を解決するため、その表面処理法について多くの提案がなされている。特許文献１には、ｐＨ値が０．５〜３．５の酸性水溶液により表面処理を行う方法が開示されている。
In order to solve the drawback of slow activation of the hydrogen storage alloy having high corrosion resistance, many proposals have been made on its surface treatment method.
特許文献２には、９０℃以上で、水酸化ナトリウムを３０〜８０重量％含む水溶液に浸漬する方法が開示されている。
特許文献３には、８０〜９０℃以上で、水酸化リチウムを１〜４Ｎ含む水溶液に浸漬する方法が開示されている。 Patent Document 3 discloses a method of immersing in an aqueous solution containing 1 to 4 N of lithium hydroxide at 80 to 90 ° C or higher.
特許文献４や特許文献５には、表面に厚さが５０〜２００ナノメートル（ｎｍ）であり、Ｎｉを主成分とする層を備える水素吸蔵合金粉末あって、水素吸蔵合金粉末をアルカリ溶液に浸漬した後、希薄な酸性水溶液に浸漬する方法が開示されている。
In Patent Document 4 and
本発明は、上記問題点を解決するためになされたものであって、長寿命で活性な水素吸蔵合金電極を負極に適用することによって、長寿命で高率充放電性能に優れたニッケル水素蓄電池を提供することである。 The present invention has been made to solve the above-mentioned problems, and is a nickel-metal hydride storage battery that has a long life and excellent high-rate charge / discharge performance by applying a long-life and active hydrogen storage alloy electrode to the negative electrode. Is to provide.
上記の課題を達成するために、本発明者らは鋭意検討の結果、特定の粒径の水素吸蔵合金粉末を特定の処理液を用いて、その質量飽和磁化を特定の値とし、特定の表面層を具備するものとすることにより、驚くべきことに、優れたサイクル特性と高率放電特性とを備える電池が得られることを見出し、本発明に至った。本発明は、以下の構成とすることによって前記課題を解決する。
質量飽和磁化は、試料である水素吸蔵合金粉末０．３グラムを精秤し、サンプルホルダーに充填して（株）理研電子製、振動試料型磁力計（モデルＢＨＶ−３０）を用いて５キロエルステッドの磁場をかけて測定した値とする。また、ここでいう表面とは、粉末の外面から深さ４００〜５００ｎｍの領域を指す。なお、表面層は粉末の断面を電子顕微鏡や収束イオンビーム装置を用いて観察することによってその存在を確認することができる。ここでいう空洞のない連続した表面層とは、合金粉末の断面を電子顕微鏡や収束イオンビーム装置を用いて拡大して観察したときに、水素吸蔵合金粉末の表面に切れ切れに点在するのではない連続した層であって、層中に空洞（鬆）がないものを指す。また、前記表面層がＮｉおよびＣｏを構成元素として含むことは、粉末の断面を透過形電子顕微鏡を用いた調査によって確認することができる。
In order to achieve the above-mentioned problems, the present inventors have intensively studied, and as a result of using a specific treatment liquid for a hydrogen storage alloy powder having a specific particle size, the mass saturation magnetization is set to a specific value, and a specific surface is obtained. Surprisingly, it has been found that a battery having excellent cycle characteristics and high rate discharge characteristics can be obtained by providing the layer, and the present invention has been achieved. This invention solves the said subject by setting it as the following structures .
Mass saturation magnetization, accurately weighed a hydrogen storage alloy powder 0.3 g is sample was filled in a sample holder Co. Riken Denshi, vibrating sample magnetometer (Model BHV-30) using 5 A value measured by applying a magnetic field of kilo-Oersted. Moreover, the surface here refers to the area | region of depth 400-500 nm from the outer surface of powder. The presence of the surface layer can be confirmed by observing the cross section of the powder using an electron microscope or a focused ion beam apparatus. The continuous surface layer without cavities here means that when the cross section of the alloy powder is enlarged and observed using an electron microscope or a focused ion beam device, the surface of the hydrogen storage alloy powder is scattered in pieces. This refers to a continuous layer having no voids in the layer. The fact that the surface layer contains Ni and Co as constituent elements can be confirmed by examining the cross section of the powder using a transmission electron microscope.
（１）本発明に係る水素吸蔵合金電極の製造方法は、前記希土類元素、ニッケルおよびコバルトを構成元素として含み、且つ、ＬｉＯＨを０．６〜１．０Ｍ／ｄｍ3、ＮａＯＨを６〜８Ｍ／ｄｍ3含むアルカリ水溶液に浸漬処理した水素吸蔵合金粉末を適用することを特徴とする水素吸蔵合金電極の製造方法である。 ( 1 ) The method for producing a hydrogen storage alloy electrode according to the present invention includes the rare earth element, nickel and cobalt as constituent elements, LiOH is 0.6 to 1.0 M / dm 3 , and NaOH is 6 to 8 M / a method for producing a hydrogen-absorbing alloy electrode you characterized by applying the dm 3 hydrogen absorbing alloy powder immersed in an alkaline aqueous solution containing.
（２）本発明に係る水素吸蔵合金電極の製造方法は、前記水素吸蔵合金粉末を浸漬処理する時のアルカリ水溶液の温度が１００℃〜該水溶液の沸点であることを特徴とする前記（１）に記載の水素吸蔵合金電極の製造方法である。 ( 2 ) The method for producing a hydrogen storage alloy electrode according to the present invention is characterized in that the temperature of the alkaline aqueous solution when immersing the hydrogen storage alloy powder is 100 ° C. to the boiling point of the aqueous solution ( 1 ) The method for producing a hydrogen storage alloy electrode as described in 1. above.
（３）本発明に係る水素吸蔵合金電極の製造方法は、前記希土類元素、ニッケルおよびコバルトを構成元素として含み、平均粒径が２０〜３５μｍである水素吸蔵合金粉末を、前記アルカリ水溶液にし、該浸漬中処理浴を撹拌して浸漬処理する第１工程と、該浸漬処理によって発生した希土類元素を主成分とする元素の水酸化物を合金表面から分離する第２工程と、処理された合金を洗浄する第３工程と、水素を脱離する第４工程とを有することを特徴とした、前記（１）に記載の水素吸蔵合金電極の製造方法である。前記第１工程の撹拌の方法、速度は特に限定されるものではなく、処理液中に投入した水素吸蔵合金粉末が沈降せずに処理浴中に均一に分散していればよい。 ( 3 ) The method for producing a hydrogen storage alloy electrode according to the present invention comprises converting the hydrogen storage alloy powder containing rare earth elements, nickel and cobalt as constituent elements and having an average particle size of 20 to 35 μm into the alkaline aqueous solution, A first step in which the treatment bath is stirred and immersed during the immersion; a second step in which the hydroxide of an element mainly composed of rare earth elements generated by the immersion treatment is separated from the alloy surface; and the processed alloy. The method for producing a hydrogen storage alloy electrode according to (1) above, comprising a third step of cleaning and a fourth step of desorbing hydrogen. The method and speed of the stirring in the first step are not particularly limited as long as the hydrogen storage alloy powder charged into the processing liquid does not settle and is uniformly dispersed in the processing bath.
（４）本発明に係る水素吸蔵合金電極の製造方法は、前記第２工程において、水素吸蔵合金粉末の分散液に超音波を当てた後、水素吸蔵合金粉末を流水にさらすことを特徴とする（３）に記載の水素吸蔵合金電極の製造方法である。 ( 4 ) The method for producing a hydrogen storage alloy electrode according to the present invention is characterized in that, in the second step, after applying ultrasonic waves to the dispersion of the hydrogen storage alloy powder, the hydrogen storage alloy powder is exposed to running water. It is a manufacturing method of the hydrogen storage alloy electrode as described in ( 3 ).
（５）本発明に係る水素吸蔵合金電極の製造方法は、前記第３工程において、洗浄液として、濃度が１／１００Ｍ／ｄｍ3以下の濃度を有する塩酸または有機酸の水溶液を用いることを特徴とする前記（３）に記載の水素吸蔵合金電極の製造方法である。 ( 5 ) The method for producing a hydrogen storage alloy electrode according to the present invention is characterized in that, in the third step, an aqueous solution of hydrochloric acid or organic acid having a concentration of 1/100 M / dm 3 or less is used as the cleaning solution. The method for producing a hydrogen storage alloy electrode according to ( 3 ).
（６）本発明に係る水素吸蔵合金電極の製造方法は、前記第４工程において、水素吸蔵合金粉末を８０℃以上、ｐＨ９以下の温水にさらした後、水素吸蔵合金粉末を水中に投入して４５℃以下の分散液を用意し、該分散液に過酸化水素を添加することを特徴とする前記（３）に記載の水素吸蔵合金電極の製造方法である。 ( 6 ) In the method for producing a hydrogen storage alloy electrode according to the present invention, in the fourth step, after the hydrogen storage alloy powder is exposed to warm water of 80 ° C. or higher and pH 9 or lower, the hydrogen storage alloy powder is poured into water. The method for producing a hydrogen storage alloy electrode according to ( 3 ), wherein a dispersion liquid of 45 ° C. or lower is prepared, and hydrogen peroxide is added to the dispersion liquid.
本発明によれば、高率放電性能と充放電サイクル性能に優れたニッケル水素蓄電池用水素吸蔵電極を得ることができる。 According to the onset bright, it is possible to obtain a high-rate discharge performance, the hydrogen storage electrode superior nickel-metal hydride storage battery of the charge and discharge cycle performance.
本発明によれば、短時間の浸漬処理で表面に磁性を有するＮｉおよびＣｏを含み、連続した均一な厚さの表面層を有する水素吸蔵合金粉末を得ることができる。
本発明によれば表面に磁性を有するＮｉおよびＣｏを含み、連続した均一な厚さの表面層を効率よく形成させることができる。
According to the onset bright, include Ni and Co having magnetic to the surface in immersion treatment of a short time, it is possible to obtain a hydrogen absorbing alloy powder having a surface layer of uniform thickness contiguous.
Includes Ni and Co having magnetic on the surface according to the present onset bright, it is possible to efficiently form the surface layer of uniform thickness contiguous.
水素吸蔵合金粉末の表面に、希土類元素やマンガンの化合物の偏析が生じると、水素吸蔵合金粉末の電気抵抗が増大し高率放電において良好な性能が得られない。本発明によれば、表面に希土類元素等の水酸化物の析出が抑制され、且つ、残存アルカリのない清浄な表面を有する水素吸蔵合金粉末を備え、電気抵抗が小さく高率放電性能の優れた水素吸蔵合金電極を得ることができる。 If segregation of rare earth elements or manganese compounds occurs on the surface of the hydrogen storage alloy powder, the electrical resistance of the hydrogen storage alloy powder increases, and good performance cannot be obtained at high rate discharge. According to the onset bright, is suppressed precipitation of hydroxides such as rare earth elements on the surface, and includes a hydrogen absorbing alloy powder having no residual alkali clean surface, excellent high-rate discharge performance electric resistance is small A hydrogen storage alloy electrode can be obtained.
本発明によれば、水素吸蔵合金粉末をアルカリ水溶液中に浸漬処理した際に水素吸蔵合金粉末に取り込まれた水素を除去することによって、水素吸蔵合金粉末が空気に触れても発熱や発火の虞のない水素吸蔵合金粉末となり、変質が抑制された水素吸蔵合金電極を得ることができる。 According to the onset bright, by removing the hydrogen taken in the hydrogen-absorbing alloy powder when the hydrogen storage alloy powder was immersed in an alkaline aqueous solution, the hydrogen-absorbing alloy powder is heat generation or fire exposed to air It becomes a hydrogen storage alloy powder having no fear, and a hydrogen storage alloy electrode in which alteration is suppressed can be obtained.
本発明に係る水素吸蔵合金電極は、希土類元素、ＮｉおよびＣｏを構成元素として含み、平均粒径が２０〜３５μｍ、質量飽和磁化が１〜５ｅｍｕ／ｇであって、その表面に、磁性を有するＮｉおよびＣｏを含み、空洞がなく連続した表面層を備えた水素吸蔵合金粉末を活物質とする水素吸蔵合金電極である。本発明に係る水素吸蔵合金の結晶系、構成元素の構成比は特に限定されるものではない。例えば、ＬａＮｉ5、ＭｍＮｉ5（Ｍｍはミッシュメタルを表す）等のＡＢ5形合金やＬａＮｉ3、ＭｍＮｉ3等の、ＡＢ3形合金のＮｉの一部を少なくともＣｏで置換したものを適用することができる。さらに、前記Ｎｉの一部をＣｏ以外にＭｎ、Ａｌ、Ｆｅ、Ｃｕ、Ｃｒ等の金属元素で置換したものを適用することができる。中でも、ＭｍＮｉ5系合金のＮｉの一部をＣｏ以外にＭｎおよびＡｌで置換した水素吸蔵合金は、容量が大きく、充放電サイクル特性にも優れるので好適である。 The hydrogen storage alloy electrode according to the present invention contains rare earth elements, Ni and Co as constituent elements, has an average particle diameter of 20 to 35 μm, a mass saturation magnetization of 1 to 5 emu / g, and has magnetism on its surface. This is a hydrogen storage alloy electrode using Ni-Co and a hydrogen storage alloy powder having a continuous surface layer without voids as an active material. The crystal system of the hydrogen storage alloy according to the present invention and the constituent ratio of the constituent elements are not particularly limited. For example, an AB 5 type alloy such as LaNi 5 or MmNi 5 (Mm represents misch metal) or a part of Ni of an AB 3 type alloy such as LaNi 3 or MmNi 3 is applied at least with Co. Can do. Furthermore, a material in which a part of the Ni is replaced with a metal element such as Mn, Al, Fe, Cu, Cr in addition to Co can be applied. Among these, a hydrogen storage alloy in which a part of Ni in the MmNi 5 series alloy is replaced with Mn and Al in addition to Co is preferable because of its large capacity and excellent charge / discharge cycle characteristics.
水素吸蔵合金粉末の粒径が小さいと、比表面積が増大して腐蝕し易くなるため寿命性能が低下する虞がある。また、水素吸蔵合金粉末の粒径が小さくなるに従い、充填密度が低下する欠点がある。逆に、平均粒径が大きいと、充填密度が高くなるが、電極の作用面積が小さいためか高率放電性能が低い欠点があり、また、電池に組み込んで充放電を行ったときに、水素吸蔵合金粉末に割れが生じ、その一部が電極から脱離したり、水素吸蔵合金電極の集電機能が低下するためか、充放電サイクルを繰り返し行ったときに容量が大きく低下する虞がある。本発明においては、水素吸蔵合金の平均粒径を２０〜３５μｍとすることによって、充填密度および高率放電特性の低下を防ぎ、且つ、電池に組み込んで充放電を繰り返し行っても水素吸蔵合金粉末の割れ（微細化）が抑制され、サイクル性能の優れた水素吸蔵合金電極を得ることができる。所定の粒径、形状を有する水素吸蔵合金粉末を得るためには粉砕機や分級機が用いられる。例えば乳鉢、ボールミル、サンドミル、振動ボールミル、遊星ボールミル、ジェットミル、カウンタージェトミル、旋回気流型ジェットミルやハンマーミルや篩等が用いられる。粉砕時には水、あるいは本特許の表面処理水溶液を用いて湿式粉砕を用いることもできる。分級方法としては、特に限定はなく、篩や風力分級機などが、乾式、湿式ともに必要に応じて用いられる。 If the particle size of the hydrogen-absorbing alloy powder is small, the specific surface area increases and corrosion tends to occur, so that the life performance may be lowered. In addition, there is a drawback that the packing density decreases as the particle size of the hydrogen storage alloy powder decreases. On the contrary, if the average particle size is large, the packing density increases, but there is a disadvantage that the high-rate discharge performance is low due to the small active area of the electrode. There is a possibility that the capacity of the storage alloy powder is greatly reduced when the charge / discharge cycle is repeated because the storage alloy powder is cracked and part of the storage alloy powder is detached from the electrode or the current collecting function of the hydrogen storage alloy electrode is reduced. In the present invention, by setting the average particle size of the hydrogen storage alloy to 20 to 35 μm, the filling density and the high rate discharge characteristics can be prevented from being lowered, and the hydrogen storage alloy powder can be repeatedly charged and discharged by being incorporated in a battery. Thus, a hydrogen storage alloy electrode having excellent cycle performance can be obtained. In order to obtain a hydrogen storage alloy powder having a predetermined particle size and shape, a pulverizer or a classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, a hammer mill, a sieve, or the like is used. At the time of pulverization, wet pulverization can be used using water or the surface treatment aqueous solution of this patent. There is no particular limitation on the classification method, and a sieve, an air classifier, or the like is used as needed for both dry and wet methods.
前記のように、本発明に係る水素吸蔵合金電極の水素吸蔵合金粉末は、表面に磁性を有するＮｉおよびＣｏを含み、空洞がなく連続した表面層を備え、その質量飽和磁化が、１〜５ｅｍｕ／ｇである。通常（表面に磁性を有するコバルトとニッケルを含む表面層を備えず、質量飽和磁化が０．１ｅｍｕ／ｇ未満の水素吸蔵合金粉末）を活物質として適用した水素吸蔵合金電極の場合、水素の吸蔵放出速度が遅く、急速な充電を行おうとすると、水素の吸蔵が追いつかないために電極表面から気体状の水素が発生して蓄電池の内圧を上昇させる虞がある。また、高率放電性能が劣る欠点がある。前記磁性を有するニッケルとコバルトを含み、空洞がなく連続した表面層は、水素吸蔵合金電極が電気化学反応によって水素を吸蔵したり、水素吸蔵合金粉末に吸蔵した水素をＯＨ-イオンとして電解液中に放出したりするときの触媒の作用をすると考えられる。 As described above, the hydrogen storage alloy powder of the hydrogen storage alloy electrode according to the present invention includes Ni and Co having magnetism on the surface, has a continuous surface layer without a cavity, and has a mass saturation magnetization of 1 to 5 emu. / G. In the case of a hydrogen storage alloy electrode to which a normal material (hydrogen storage alloy powder having no surface layer containing magnetic cobalt and nickel and having a mass saturation magnetization of less than 0.1 emu / g) is applied as an active material, hydrogen storage If the release speed is slow and rapid charging is attempted, hydrogen storage cannot catch up, and gaseous hydrogen is generated from the electrode surface, which may increase the internal pressure of the storage battery. Moreover, there is a disadvantage that the high rate discharge performance is inferior. The surface layer containing nickel and cobalt having magnetism and having no cavities has a hydrogen storage alloy electrode that stores hydrogen by an electrochemical reaction or hydrogen stored in the hydrogen storage alloy powder as OH − ions in the electrolyte. It is thought that it acts as a catalyst when it is released into the atmosphere.
水素吸蔵合金粉末の質量飽和磁化の値は、表面に生成させた前記表面層の生成量を反映している。質量飽和磁化が１ｅｍｕ／ｇ未満では、前記表面層の生成量が少ないためか、その水素吸蔵電極の電極反応に対する触媒作用が不十分である。また、質量飽和磁化が大きくなるに従い水素吸蔵に寄与しない表面層の比率が増大するために、水素吸蔵合金粉末の水素吸蔵能力（水素吸蔵量）が低下する。特に質量飽和磁化が５ｅｍｕ／ｇを超えると、水素吸蔵量が顕著に低下するので、本発明においては水素吸蔵合金粉末の質量飽和磁化を５ｅｍｕ／ｇとするのが良い。本願発明に係る平均粒径が２０〜３５μｍ、質量飽和磁化が１〜５ｅｍｕ／ｇの水素吸蔵合金粉末においては、表面層の厚さが約５０〜４００ｎｍである。さらに、表面層を生成させた場合においても水素吸蔵合金粉末の平均粒径が３５μｍを超えると水素吸蔵合金粉末内の水素の固相内拡散が追いつかなくなるためか、高率放電性能の向上効果が得られない虞がある。本発明に係る水素吸蔵合金電極においては、水素吸蔵合金粉末の質量飽和磁化を１〜５ｅｍｕ／ｇとし、且つ、平均粒径を３５μｍ以下とすることによって高率放電特性に優れ、充放電サイクル性能の優れた水素吸蔵合金電極を得る。 The value of the mass saturation magnetization of the hydrogen storage alloy powder reflects the amount of the surface layer generated on the surface. If the mass saturation magnetization is less than 1 emu / g, the production of the surface layer is small, or the catalytic action of the hydrogen storage electrode for the electrode reaction is insufficient. Further, as the mass saturation magnetization increases, the ratio of the surface layer that does not contribute to hydrogen storage increases, so that the hydrogen storage capacity (hydrogen storage amount) of the hydrogen storage alloy powder decreases. In particular, when the mass saturation magnetization exceeds 5 emu / g, the hydrogen storage amount is remarkably reduced. Therefore, in the present invention, the mass saturation magnetization of the hydrogen storage alloy powder is preferably 5 emu / g. In the hydrogen storage alloy powder having an average particle diameter of 20 to 35 μm and a mass saturation magnetization of 1 to 5 emu / g according to the present invention, the surface layer has a thickness of about 50 to 400 nm. Furthermore, even when the surface layer is generated, if the average particle diameter of the hydrogen storage alloy powder exceeds 35 μm, the diffusion of hydrogen in the hydrogen storage alloy powder cannot catch up with the solid phase, which may improve the high rate discharge performance. There is a possibility that it cannot be obtained. In the hydrogen storage alloy electrode according to the present invention, the mass saturation magnetization of the hydrogen storage alloy powder is set to 1 to 5 emu / g and the average particle size is set to 35 μm or less, so that the high rate discharge characteristics are excellent, and the charge / discharge cycle performance. An excellent hydrogen storage alloy electrode is obtained.
前記水素吸蔵合金電極の表面層の生成量が少ないと、その触媒作用が十分でなく、逆に多いと水素吸蔵合金粉末と電解液の界面において水素の移行が阻害される。１個の水素吸蔵合金粉末に注目したときに、その表面層の形成にむら（表面層が切れ切れに存在したり、表面層に空洞がある状態）があると、表面層の生成量が少ない箇所や多過ぎる箇所、表面層中に空洞がある箇所では電極反応が起き難く、表面層の生成量が適当な箇所のみに電極反応が集中して起きる（該箇所の電流密度が高くなる）こととなり、分極が大きくなる虞がある。本発明に係る水素吸蔵合金粉末における前記表面層は、連続した層をなしており、層中に空洞がない層である。また、表面層の界面が平滑（凹凸がないこと）であって、厚さが均一であることがさらに好ましい。 If the generated amount of the surface layer of the hydrogen storage alloy electrode is small, the catalytic action is not sufficient, and conversely if it is large, the migration of hydrogen is inhibited at the interface between the hydrogen storage alloy powder and the electrolyte. When attention is paid to one hydrogen storage alloy powder, if the surface layer formation is uneven (the surface layer is in a state of being broken or has a void in the surface layer), the generation amount of the surface layer is small. Electrode reaction is unlikely to occur in areas where there are too many or cavities in the surface layer, and electrode reactions are concentrated only in areas where the amount of surface layer formation is appropriate (the current density at that area increases). There is a possibility that the polarization becomes large. The surface layer in the hydrogen storage alloy powder according to the present invention is a layer that is a continuous layer and has no cavities in the layer. It is further preferable that the interface of the surface layer is smooth (no irregularities) and the thickness is uniform.
本発明に係る水素吸蔵合金粉末は、前記希土類元素、ニッケルおよびコバルトを構成元素として含む水素吸蔵合金粉末を、ＬｉＯＨを０．６〜１．０Ｍ／ｄｍ3、ＮａＯＨを６〜８Ｍ／ｄｍ3含むアルカリ水溶液に浸漬処理することによって得ることができる。該アルカリ水溶液に水素吸蔵合金粉末を浸漬すると、ＬｉＯＨを含まないＮａＯＨやＫＯＨの水溶液を用いて浸漬処理する場合に比べて、浸漬処理時にＣｏ、Ｎｉの溶出が抑制され、かつ、水素吸蔵合金に含まれる希土類元素の他、マンガンやアルミニウムの溶出がゆっくり進むためか、連続していて空洞がなく、界面の平滑な表面層が生成する。
ＮａＯＨとＬｉＯＨの両方を含む処理液において、処理液のＮａＯＨの濃度が６Ｍ／ｄｍ3未満では、生成する水素吸蔵合金粉末の質量飽和磁化の値が低く、本発明に係る１ｅｍｕ／ｇ以上の質量飽和磁化を有する水素吸蔵合金粉末を得ることが困難である。処理液のＮａＯＨの濃度を７Ｍ／ｄｍ3以上とすると表面層の生成速度が速くなり、処理時間が短くなるので好ましい。また、処理液のＬｉＯＨの濃度が０．６Ｍ／ｄｍ3未満では本発明に係る空洞のない連続した表面層を備える水素吸蔵合金粉末を得ることが困難である。処理液のＬｉＯＨの濃度を０．８Ｍ／ｄｍ3以上とすると空洞がなく連続した表面層であって、且つ、平滑で厚さの均一な表面層が得られるので好ましい。
ＮａＯＨの濃度が８Ｍ／ｄｍ3を超えると、０．６〜０．７Ｍ／ｄｍ3の濃度のＬｉＯＨを含む液の粘度が高く、また、０．８Ｍ／ｄｍ3以上の濃度のＬｉＯＨを溶解させることが困難であるので処理液に適さない。
また、ＬｉＯＨの濃度が１Ｍ／ｄｍ3を超えると、ＮａＯＨの濃度を所定の質量飽和磁化を得るための最低の濃度である６Ｍ／ｄｍ3に設定したとしても水溶液の粘度が急激に増大し、かつ、前記のように冷却時にＬｉＯＨが水素吸蔵合金粉末表面に析出する虞が生じるので、処理液として適さない。
以上の理由から処理液に含まれるＮａＯＨの濃度を６〜８Ｍ／ｄｍ3に設定するのが好ましく、７〜８Ｍ／ｄｍ3に設定するのがさらに好ましい。また、ＬｉＯＨの濃度を０．６〜１Ｍ／ｄｍ3に設定するのが好ましく、０．８〜１Ｍ／ｄｍ3に設定するのがさらに好ましい。
The hydrogen storage alloy powder according to the present invention includes the above-described hydrogen storage alloy powder containing rare earth elements, nickel and cobalt as constituent elements, and includes LiOH of 0.6 to 1.0 M / dm 3 and NaOH of 6 to 8 M / dm 3. It can be obtained by immersing in an aqueous alkali solution. When the hydrogen storage alloy powder is immersed in the alkaline aqueous solution, elution of Co and Ni is suppressed at the time of the immersion treatment compared to the case of using an aqueous solution of NaOH or KOH not containing LiOH, and the hydrogen storage alloy In addition to the rare earth elements contained, manganese and aluminum may be eluted slowly, or a continuous surface layer with no cavities and a smooth interface is formed.
In a treatment liquid containing both NaOH and LiOH, when the NaOH concentration of the treatment liquid is less than 6 M / dm 3 , the value of the mass saturation magnetization of the produced hydrogen storage alloy powder is low, and the mass of 1 emu / g or more according to the present invention is low. It is difficult to obtain a hydrogen storage alloy powder having saturation magnetization. It is preferable that the NaOH concentration of the treatment liquid is 7 M / dm 3 or more because the generation rate of the surface layer is increased and the treatment time is shortened. Moreover, when the concentration of LiOH in the treatment liquid is less than 0.6 M / dm 3 , it is difficult to obtain a hydrogen storage alloy powder having a continuous surface layer without voids according to the present invention. It is preferable that the concentration of LiOH in the treatment liquid is 0.8 M / dm 3 or more because a continuous surface layer having no cavities and a smooth and uniform thickness can be obtained.
If the concentration of NaOH is more than 8M / dm 3, high viscosity liquid containing LiOH at a concentration of 0.6~0.7M / dm 3, also to dissolve the LiOH in 0.8 M / dm 3 or more concentrations Therefore, it is not suitable for a processing solution.
Further, the concentration of LiOH exceeds 1M / dm 3, the viscosity of the aqueous solution even if setting the concentration of NaOH in 6M / dm 3 is the lowest concentration for obtaining a predetermined mass saturation magnetization increases abruptly, In addition, as described above, LiOH may be deposited on the surface of the hydrogen storage alloy powder during cooling, which is not suitable as a treatment liquid.
For the above reasons, the concentration of NaOH contained in the treatment liquid is preferably set to 6 to 8 M / dm 3, and more preferably set to 7 to 8 M / dm 3 . Further, it is preferable to set the concentration of LiOH in 0.6~1M / dm 3, and more preferably set to 0.8~1M / dm 3.
前記、表面に連続した空洞のない表面層を有する水素吸蔵合金粉末は、前記希土類元素、ニッケルおよびコバルトを構成元素として含む水素吸蔵合金粉末をＬｉＯＨ単独で含む水溶液であって、ＬｉＯＨの濃度が５Ｍ／ｄｍ3以上であるアルカリ水溶液中に浸漬処理することによって得ることができる。但し、浸漬処理にＬｉＯＨのみを溶解させたアルカリ水溶液を用いた場合には、表面層の生成速度が極めて遅く、そのため、浸漬処理に長時間を要する欠点がある。また、浸漬処理によって表面層を形成するには、水溶液中のＬｉＯＨ濃度を５Ｍ／ｄｍ3以上とすることが必要であり、さらには６Ｍ／ｄｍ3以上とすることが好ましいが、該濃度のＬｉＯＨ水溶液は粘度が高く、浸漬処理が難しい欠点がある。また、ＬｉＯＨの水に対する溶解度が低いために、浸漬処理後に水素吸蔵合金粉末の温度が低下したときに水素吸蔵合金に付着した処理液に含まれるＬｉＯＨが水素吸蔵合金表面に析出し、該析出物は、浸漬処理に続く洗浄工程においても除去し難い欠点がある。 The hydrogen storage alloy powder having a surface layer without a continuous cavity on the surface is an aqueous solution containing the rare earth element, nickel and cobalt as constituent elements, and the LiOH alone, and the concentration of LiOH is 5M. / Dm 3 or more can be obtained by immersing in an alkaline aqueous solution. However, when an alkaline aqueous solution in which only LiOH is dissolved is used for the immersion treatment, the surface layer formation rate is extremely slow, and therefore there is a drawback that the immersion treatment requires a long time. In addition, in order to form a surface layer by immersion treatment, the LiOH concentration in the aqueous solution needs to be 5 M / dm 3 or more, and more preferably 6 M / dm 3 or more. Aqueous solutions have high viscosity and are difficult to dip. Further, since the solubility of LiOH in water is low, LiOH contained in the treatment liquid adhering to the hydrogen storage alloy is deposited on the surface of the hydrogen storage alloy when the temperature of the hydrogen storage alloy powder is lowered after the immersion treatment. Has a drawback that it is difficult to remove even in the cleaning process following the dipping process.
さらに、表面層を実用上支障のない程度の速さ（浸漬処理時間が約４０時間、好ましくは２０時間で済む）で生成させるには、ＬｉＯＨ単独よりも、ＮａＯＨとＬｉＯＨ混合水溶液を適用し、且つ、浸漬処理の温度を１００℃〜沸点の範囲内に設定するのが好ましい。処理温度は１００℃以上で処理速度が劇的に向上するので好ましく、沸点以上では反応速度が速くなりすぎ、制御が困難になるため沸点以下が好ましい。また、浸漬処理を浸漬処理液の沸点以上で行うと反応が促進され、処理時間の短縮を図ることが可能となるが、連続した空洞のない表面層が形成出来ない虞があるので好ましくない。さらに、浸漬浴の温度分布を均一に保つために、浸漬槽の加温に際しては、槽を底面、側面の全体から加温することが好ましい。 Furthermore, in order to produce the surface layer at such a speed that there is no practical problem (immersion time is about 40 hours, preferably 20 hours), a mixed aqueous solution of NaOH and LiOH is applied rather than LiOH alone, And it is preferable to set the temperature of immersion treatment in the range of 100 degreeC-boiling point. The treatment temperature is preferably 100 ° C. or more because the treatment speed is dramatically improved. Above the boiling point, the reaction rate becomes too high and control becomes difficult, and the boiling point or less is preferred. Further, if the immersion treatment is performed at a temperature equal to or higher than the boiling point of the immersion treatment liquid, the reaction is promoted and the treatment time can be shortened. However, it is not preferable because a surface layer without a continuous cavity may not be formed. Furthermore, in order to keep the temperature distribution of the immersion bath uniform, it is preferable that the bath is heated from the entire bottom surface and side surfaces when the immersion bath is heated.
また、水素吸蔵合金粉末の浸漬処理に先だって、水素吸蔵合金粉末に予め水素を吸蔵させておくと、水素吸蔵合金の電位が卑な方向にシフトするので、浸漬処理時にＮｉとＣｏの溶出を低減させることが出来ることから好ましい。この際の水素の吸蔵量については特に限定されるものではないが、５％以上の水素を含有させた場合、水素吸蔵合金粉末の電位をＮｉやＣｏが溶解する電位に比べてはるかに卑な電位とすることができ、ＮｉとＣｏの溶出を大幅に低減させることが出来ることから好ましい。また、該方法によれば、効率よく表面層を形成する事が出来、最小限の表面層厚みで十分な活性が得られるため、合金の容量の低下を最小限に止めることができる。 Prior to the immersion treatment of the hydrogen storage alloy powder, if the hydrogen storage alloy powder is preliminarily occluded with hydrogen, the potential of the hydrogen storage alloy shifts in a base direction, thus reducing the elution of Ni and Co during the immersion treatment. It is preferable because it can be made. The amount of hydrogen occluded at this time is not particularly limited, but when 5% or more of hydrogen is contained, the potential of the hydrogen occlusion alloy powder is much lower than the potential at which Ni or Co dissolves. This is preferable because it can be a potential, and the elution of Ni and Co can be greatly reduced. Further, according to this method, the surface layer can be formed efficiently, and sufficient activity can be obtained with the minimum surface layer thickness, so that the decrease in the capacity of the alloy can be minimized.
浸漬処理による反応が進むと、水素吸蔵合金粉末の表面に希土類元素、マンガンやアルミニウムの水酸化物が水素吸蔵合金の表面に堆積したり、処理浴のアルカリ濃度や温度が不均一になり反応にむらが起きる虞がある。水素吸蔵合金粉末の表面に希土類元素、マンガンやアルミニウムの水酸化物が堆積すると、粉体抵抗（粉末の電気抵抗）が増大し、水素吸蔵合金電極の集電機能が損なわれる虞がある。前記水素吸蔵合金表面への水酸化物の堆積を抑制し、且つ、反応のむらをなくすために、浸漬処理中、水素吸蔵合金粉末を投入した処理浴を撹拌し続けることが好ましい。処理浴の撹拌の方法は特に限定されないが、例えばスクリュー形の撹拌機を用いて撹拌することによって処理液に対流を起こさせ、水素吸蔵合金粉末が沈降するのを防ぎ、液が均一に混ざるようにすればよい。このことによって、前記処理液の浴槽を底面や側面から加熱することとあわせて処理浴の温度分布を一層均一にし、簡便にかつ安価に均質な表面層を形成させることができる。 As the reaction by immersion treatment proceeds, rare earth elements, manganese and aluminum hydroxides accumulate on the surface of the hydrogen storage alloy powder, and the alkali concentration and temperature of the treatment bath become non-uniform. There is a risk of unevenness. When a rare earth element, manganese or aluminum hydroxide is deposited on the surface of the hydrogen storage alloy powder, the powder resistance (electrical resistance of the powder) increases, and the current collection function of the hydrogen storage alloy electrode may be impaired. In order to suppress hydroxide deposition on the surface of the hydrogen storage alloy and to eliminate unevenness of the reaction, it is preferable to continue stirring the treatment bath containing the hydrogen storage alloy powder during the immersion treatment. The method of stirring the treatment bath is not particularly limited. For example, by stirring using a screw-type stirrer, convection is caused in the treatment liquid to prevent the hydrogen storage alloy powder from settling, so that the liquid is mixed uniformly. You can do it. This makes it possible to further uniform the temperature distribution of the treatment bath together with heating the bath of the treatment liquid from the bottom and side surfaces, and to form a uniform surface layer easily and inexpensively.
前記のように浸漬処理中、水素吸蔵合金粉末を投入したアルカリ水溶液を撹拌し続けても、水酸化物が水素吸蔵合金の表面に堆積するのを完全になくすことは難しい。従って、洗浄に先だって、これらの水酸化物を除去することが好ましい。水酸化物を除去するのに先だってあらかじめ濾過をして、希土類元素、マンガン、アルミニウム等のイオン含有の処理液を除去しておくと、前記元素が化合物の形で再析出するのを防止できるので好ましい。水素吸蔵合金の表面から水酸化物を除去する方法としては、塩酸の水溶液であって、０．１〜数十分の１Ｍ／ｄｍ3程度の希薄溶液によって希土類酸化物を溶解しつつ濾過する方法が安価であるが、表面層が酸により溶解して組成が変動し電解液に対する耐食性が低下する虞があるので、長寿命を要求される電池に対しては好ましくない。水素吸蔵合金粉末の表面から前記水酸化物を剥落させるには、水素吸蔵合金粉末に水中で超音波を照射するのが好ましい。超音波照射によって希土類不純物の水酸化物を合金から剥離させた後、水溶液中の沈降速度の差を利用する方法（即ち、合金粉末を投入した攪拌タンク下部から流水をフローさせ、沈降しにくい希土類不純物をフロー水と共に除去する方法）は、表面組成が変動せず耐食性が低下しないため好ましい。 As described above, even if the alkaline aqueous solution charged with the hydrogen storage alloy powder is continuously stirred during the immersion treatment, it is difficult to completely eliminate the hydroxide from being deposited on the surface of the hydrogen storage alloy. Therefore, it is preferable to remove these hydroxides prior to washing. Prior to removing the hydroxide, it is possible to prevent the element from reprecipitating in the form of a compound by removing the treatment liquid containing ions such as rare earth elements, manganese, aluminum, etc. in advance. preferable. As a method of removing hydroxide from the surface of the hydrogen storage alloy, a method of filtering an aqueous solution of hydrochloric acid while dissolving the rare earth oxide with a dilute solution of about 0.1 to several tens of 1 M / dm 3. However, it is not preferable for a battery that requires a long life because the surface layer may be dissolved by an acid to change the composition and the corrosion resistance to the electrolytic solution may be reduced. In order to peel off the hydroxide from the surface of the hydrogen storage alloy powder, it is preferable to irradiate the hydrogen storage alloy powder with ultrasonic waves in water. A method that utilizes the difference in settling speed in an aqueous solution after the hydroxide of rare earth impurities is peeled off from the alloy by ultrasonic irradiation (that is, a rare earth that is difficult to settle by flowing flowing water from the bottom of the stirring tank charged with the alloy powder) The method of removing impurities together with flow water is preferable because the surface composition does not change and the corrosion resistance does not deteriorate.
処理によって得られた合金粉末は、アルカリ性の処理液が付着しており、そのまま放置すると酸化され易い。水素吸蔵合金粉末表面に付着したアルカリは除去し難い。従って、浸漬処理によって表面にアルカリが付着した水素吸蔵合金粉末を、除去が容易な酸性溶液を用いて洗浄することによって、前記アルカリを中和除去することが好ましい。具体的には洗浄液に１／１００Ｍ／ｄｍ3以下の濃度の塩酸および蟻酸や酢酸などの有機酸の水溶液を用いることが好ましい。濃度が１／１００Ｍ／ｄｍ3以下の塩酸、蟻酸や酢酸などの有機酸の水溶液は、同濃度の硝酸水溶液や硫酸水溶液などの他の無機酸の水溶液に比べて水素吸蔵合金に対する腐蝕性が低く、且つ、水洗によって除去し易い利点がある。但し、洗浄液の塩酸濃度が１／１００Ｍ／ｄｍ3を超えると折角生成させた遷移金属リッチ層の主構成成分であるニッケルやコバルトを腐蝕する虞があるので、洗浄液の塩酸水溶液の濃度を１／１００Ｍ／ｄｍ3以下とすることが好ましい。洗浄液に前記塩酸や有機酸の水溶液を適用することによって、洗浄水を少量にし、排水量を低減する事ができる。 The alloy powder obtained by the treatment has an alkaline treatment liquid attached thereto, and is easily oxidized when left as it is. Alkali adhering to the surface of the hydrogen storage alloy powder is difficult to remove. Therefore, it is preferable to neutralize and remove the alkali by washing the hydrogen storage alloy powder having the alkali adhered to the surface by an immersion treatment using an acidic solution that is easy to remove. Specifically, an aqueous solution of hydrochloric acid having a concentration of 1/100 M / dm 3 or less and an organic acid such as formic acid or acetic acid is preferably used for the cleaning liquid. Aqueous solutions of organic acids such as hydrochloric acid, formic acid and acetic acid with a concentration of 1/100 M / dm 3 or less are less corrosive to hydrogen storage alloys than aqueous solutions of other inorganic acids such as aqueous nitric acid and sulfuric acid. And there exists an advantage which is easy to remove by water washing. However, if the hydrochloric acid concentration in the cleaning liquid exceeds 1/100 M / dm 3 , nickel or cobalt, which is the main component of the transition metal rich layer generated at the corner, may be corroded. It is preferable to be 100 M / dm 3 or less. By applying the aqueous solution of hydrochloric acid or organic acid to the cleaning liquid, the amount of cleaning water can be reduced and the amount of drainage can be reduced.
前記浸漬処理を行った水素吸蔵合金粉末は、浸漬処理時に発生した水素を内部に取り込んでいる。そのまま大気中に放置すると、大気中の酸素と反応して発熱し、水素吸蔵合金粉末の変質を招いたり、さらには発火の虞がある。従って、浸漬処理後の水素吸蔵合金粉末から水素を除去しておく必要がある。水素吸蔵合金粉末中の水素を脱離させるには、水素吸蔵合金粉末を過酸化水素水等の酸化剤に接触させる方法がある。しかし、浸漬処理後の水素吸蔵合金粉末をいきなり酸化剤に接触させる方法では大量の酸化剤を必要とする欠点がある。該欠点を解消するには、水素吸蔵合金粉末を酸化剤と接触させるのに先だって、温度８０℃以上、ｐＨが９以下、好ましくはｐＨが５〜８の温水にさらすことが好ましい。該温水処理によって、水素吸蔵合金中に取り込まれた水素のうちのかなりの水素を除去することができ、該温水処理に続いて実施する酸化剤との接触に使用する酸化剤の消費量を大幅に削減することができる。前記温水処理に適用する温水の温度が８０℃未満では水素除去効果が得られず、ｐＨが５未満または９を超えると水素吸蔵合金粉末を腐蝕する虞があり好ましくない。 The hydrogen storage alloy powder subjected to the immersion treatment takes in hydrogen generated during the immersion treatment. If left in the air as it is, it reacts with oxygen in the air to generate heat, which may cause the quality of the hydrogen storage alloy powder to change, and may cause ignition. Therefore, it is necessary to remove hydrogen from the hydrogen storage alloy powder after the immersion treatment. In order to desorb hydrogen in the hydrogen storage alloy powder, there is a method in which the hydrogen storage alloy powder is brought into contact with an oxidizing agent such as hydrogen peroxide solution. However, the method in which the hydrogen storage alloy powder after the immersion treatment is suddenly brought into contact with an oxidizing agent has a drawback that a large amount of oxidizing agent is required. In order to eliminate the disadvantage, it is preferable to expose the hydrogen storage alloy powder to warm water having a temperature of 80 ° C. or more and a pH of 9 or less, preferably 5 to 8 prior to contacting with the oxidizing agent. The hot water treatment can remove a significant amount of the hydrogen taken into the hydrogen storage alloy, greatly increasing the consumption of the oxidant used for contact with the oxidant performed following the hot water treatment. Can be reduced. If the temperature of the hot water applied to the hot water treatment is less than 80 ° C., the effect of removing hydrogen cannot be obtained, and if the pH is less than 5 or more than 9, the hydrogen storage alloy powder may be corroded.
酸化剤の種類は特に限定されるものではないが、不純物元素の混入を避け得る点から、水素と酸素のみからなる過酸化水素が好ましい。酸化剤として過酸化水素を用いる場合、
４５℃以上の温度において過酸化水素が水素吸蔵合金粉末の表面に接触すると酸素ガスを放出し自己分解をするので効率が悪く、４５℃以下に冷却して用いると効率よく合金中の水素と反応するのでより好ましい。
The type of the oxidizing agent is not particularly limited, but hydrogen peroxide consisting only of hydrogen and oxygen is preferable from the viewpoint of avoiding contamination with impurity elements. When using hydrogen peroxide as the oxidizing agent,
When hydrogen peroxide comes into contact with the surface of the hydrogen storage alloy powder at a temperature of 45 ° C. or higher, oxygen gas is released and self-decomposes, resulting in poor efficiency. Therefore, it is more preferable.
処理後の水素吸蔵合金粉末は活性であり、酸化され易く、酸化されると合金の活性が低下する。該酸化を防ぐため、処理された水素吸蔵合金粉末の表面を酸化防止機能を持つ被膜でコートすることが好ましい。コート剤として、特定のコート剤を用いることで、水素吸蔵合金粉末を電池に組み込む時に除去の必要が無く、優れた酸化防止作用が得られる。具体的には水素吸蔵合金粉末の表面にＣＭＣ、ＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡの少なくとも１種とスチレンブタジエンゴム（ＳＢＲ）とで構成される被膜を形成する。水素吸蔵合金粉末に前記ＣＭＣ、ＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡの少なくとも１種を溶解し、かつ、粉末状のＳＢＲを分散させた水溶液を添加して混練した後、乾燥することによって前記被膜を形成させる。 The treated hydrogen storage alloy powder is active and easily oxidized, and when oxidized, the activity of the alloy decreases. In order to prevent the oxidation, it is preferable to coat the surface of the treated hydrogen storage alloy powder with a film having an antioxidant function. By using a specific coating agent as the coating agent, there is no need to remove it when the hydrogen storage alloy powder is incorporated into the battery, and an excellent antioxidant action can be obtained. Specifically, a film composed of at least one of CMC, HPMC, xanthan gum, welan gum, PVA and styrene butadiene rubber (SBR) is formed on the surface of the hydrogen storage alloy powder. Forming the coating by dissolving at least one of the CMC, HPMC, xanthan gum, welan gum, and PVA in a hydrogen storage alloy powder, adding an aqueous solution in which powdered SBR is dispersed, and then drying. Let
水素吸蔵合金粉末に対する被膜の比率は特に限定されるものではないが、被膜の水素吸蔵合金粉末に対する比率を０．５〜３重量％とすることが好ましく、１〜２重量％とすることがさらに好ましい。該比率が０．５重量％未満では酸化防止機能が得られず、３重量％を超えると水素吸蔵合金電極の電気抵抗を増大させる虞があるので好ましくない。ＣＭＣとＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡは、水素吸蔵合金粉末の表面に膜を形成し、ＳＢＲ粉末は該膜中に分散して存在する。ＣＭＣ、ＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡおよびＳＢＲは何れもアルカリ電解液との親和性が良いが、ＣＭＣ、ＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡのみで構成される膜は、電解液浸透の妨げになる。該膜中にＳＢＲ粉末を分散させることによって、水素吸蔵合金粉末の表面に向かって電解液が浸透し易くなる。ＣＭＣ、ＨＰＭＣ、キサンタンガム、ウエランガム、ＰＶＡの少なくとも１種とＳＢＲの混合比率は特に限定されるものではないが、重量比で１：２〜１：４が好ましい。該比率が小さいと酸化防止効果を得にくく、該比率が大きいと電解液の浸透が遅くなる虞がある。水素吸蔵合金粉末の表面に、前記被膜を形成させることで長期間の保管が可能となった。但し、前記被膜を形成させた水素吸蔵合金粉末においても、大気中に放置すると非常にゆっくりではあるが徐々に酸化され表面が変質する。長期に亘り保管する場合には、酸素分圧を０．１ｔｏｒｒ以下とした不活性雰囲気または減圧下で保管することが好ましい。また、前記被膜は、水素吸蔵合金粉末を電池に組み込んだ後も、水素吸蔵合金粉末表面に被膜として存在し、結着剤としての作用をする。 The ratio of the coating film to the hydrogen storage alloy powder is not particularly limited, but the ratio of the coating film to the hydrogen storage alloy powder is preferably 0.5 to 3% by weight, and more preferably 1 to 2% by weight. preferable. If the ratio is less than 0.5% by weight, the antioxidant function cannot be obtained, and if it exceeds 3% by weight, the electric resistance of the hydrogen storage alloy electrode may be increased. CMC and HPMC, xanthan gum, welan gum, and PVA form a film on the surface of the hydrogen storage alloy powder, and the SBR powder is dispersed in the film. CMC, HPMC, xanthan gum, welan gum, PVA, and SBR all have good affinity with an alkaline electrolyte, but a membrane composed only of CMC, HPMC, xanthan gum, welan gum, and PVA hinders electrolyte penetration. Dispersing the SBR powder in the film facilitates the penetration of the electrolyte toward the surface of the hydrogen storage alloy powder. The mixing ratio of at least one of CMC, HPMC, xanthan gum, welan gum, PVA and SBR is not particularly limited, but is preferably 1: 2 to 1: 4 by weight. When the ratio is small, it is difficult to obtain an antioxidant effect, and when the ratio is large, there is a possibility that the permeation of the electrolytic solution may be delayed. By forming the coating film on the surface of the hydrogen storage alloy powder, it can be stored for a long time. However, even when the hydrogen storage alloy powder having the coating film formed thereon is left in the atmosphere, it is oxidized very slowly but the surface is altered. When storing for a long period of time, it is preferable to store under an inert atmosphere or reduced pressure where the oxygen partial pressure is 0.1 torr or less. In addition, even after the hydrogen storage alloy powder is incorporated into the battery, the coating exists as a coating on the surface of the hydrogen storage alloy powder and acts as a binder.
本発明に係るニッケル水素蓄電池に適用する正極活物質としては、水酸化ニッケルに水酸化亜鉛、水酸化コバルトを混合したものが用いられるが、共沈法によって均一組成の水酸化ニッケル複合水酸化物が好ましい。水酸化ニッケル複合酸化物以外の添加物には、導電改質剤剤として水酸化コバルト、酸化コバルト、等を用いるが、前期水酸化ニッケル複合酸化物に水酸化コバルトをコートしたものや、これらの水酸化ニッケル複合酸化物の一部を酸素又は酸素含気体、又は、Ｋ2Ｓ2Ｏ8、次亜塩素酸などの薬剤を用いて酸化したものを用いることができる。添加剤としては酸素過電圧を向上させる物質としてＹ、Ｙｂ等の希土類元素の酸化物や水酸化物を用いることが出きる。 As the positive electrode active material applied to the nickel metal hydride storage battery according to the present invention, a mixture of nickel hydroxide with zinc hydroxide and cobalt hydroxide is used, but a nickel hydroxide composite hydroxide having a uniform composition by a coprecipitation method. Is preferred. For additives other than nickel hydroxide composite oxide, cobalt hydroxide, cobalt oxide, etc. are used as conductive modifiers. A part of the nickel hydroxide composite oxide that has been oxidized using oxygen or an oxygen-containing gas, or a chemical such as K 2 S 2 O 8 or hypochlorous acid can be used. As the additive, oxides or hydroxides of rare earth elements such as Y and Yb can be used as substances for improving oxygen overvoltage.
本発明に係るニッケル水素蓄電池の水素吸蔵合金電極には、ＡＢ5型の結晶構造を有し、例えばＭｍＮｉ5（Ｍｍは希土類元素の混合物）で表される合金のＮｉの一部を主としてＣｏ、Ｍｎ、Ａｌで置換した水素吸蔵合金粉末が好適である。Ｎｉに置き換わる置換元素として、前記３種の元素以外に、さらに、Ｃｕ、Ｆｅを加えてもよい。 The hydrogen storage alloy electrode of the nickel metal hydride storage battery according to the present invention has an AB 5 type crystal structure, for example, a part of Ni of an alloy represented by MmNi 5 (Mm is a mixture of rare earth elements), mainly Co, Hydrogen storage alloy powder substituted with Mn and Al is preferred. In addition to the above three elements, Cu and Fe may be further added as a replacement element that replaces Ni.
本発明に係るニッケル水素蓄電池に適用する水素吸蔵合金電極は、前記水素吸蔵合金粉末の他に、該合金粉末のアルカリ電解液に対する耐食性を高めるための添加剤として、イットリウム、イッテルビウム、エルビウム、ガドリウム、セリウムの１種又は２種以上の元素を酸化物や水酸化物あるいは単体の粉末として混合添加したり、予め水素吸蔵合金粉末中に合金の形で含有させておいてもよい。 The hydrogen storage alloy electrode applied to the nickel metal hydride storage battery according to the present invention includes, in addition to the hydrogen storage alloy powder, as an additive for enhancing the corrosion resistance of the alloy powder to an alkaline electrolyte, yttrium, ytterbium, erbium, gadolinium, One or more elements of cerium may be mixed and added as an oxide, hydroxide, or a single powder, or may be previously contained in the hydrogen storage alloy powder in the form of an alloy.
以上、正極（ニッケル電極）及び負極（水素吸蔵合金電極）の主要構成成分である正極活物質および負極活物質について詳述したが、前記正極及び負極には、前記主要構成成分の他に、導電剤、結着剤、増粘剤、フィラー等が、他の構成成分として含有されてもよい。 As described above, the positive electrode active material and the negative electrode active material which are main components of the positive electrode (nickel electrode) and the negative electrode (hydrogen storage alloy electrode) have been described in detail. In addition to the main component, the positive electrode and the negative electrode include conductive materials. Agents, binders, thickeners, fillers and the like may be contained as other components.
導電剤としては、電池性能に悪影響を及ぼさない電子伝導性材料であれば限定されないが、通常、天然黒鉛（鱗片状黒鉛，土状黒鉛等）、人造黒鉛、カーボンブラック、アセチレンブラック、ケッチェンブラック、カーボンウイスカー、炭素繊維、気相成長炭素、金属（銅，ニッケル，金等）粉、金属繊維等の導電性材料を１種またはそれらの混合物として含ませることができる。 The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance. Usually, natural graphite (flaky graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black In addition, conductive materials such as carbon whisker, carbon fiber, vapor grown carbon, metal (copper, nickel, gold, etc.) powder, metal fiber and the like can be included as one kind or a mixture thereof.
これらの中で、導電剤としては、電子伝導性及び塗工性の観点よりケチェンブラックが望ましい。導電剤の添加量を、正極または負極の総重量に対して０．１重量％〜２重量％とすると導電性を有しつつ、電極の容量を大きく低下させないので好ましい。特にケッチェンブラックを０．１〜０．５μｍの超微粒子に粉砕して用いると必要炭素量を削減できつつ、保液性が向上し、電池の内部抵抗の低減を図ることができるため望ましい。これらの混合方法は、物理的な混合であり、その理想とするところは均一混合である。そのため、Ｖ型混合機、Ｓ型混合機、擂かい機、ボールミル、遊星ボールミル、ホモジナイザといったような粉体混合機を乾式、あるいは湿式で混合することが可能である。 Among these, as the conductive agent, Ketjen black is desirable from the viewpoints of electron conductivity and coatability. It is preferable to add the conductive agent in an amount of 0.1% by weight to 2% by weight with respect to the total weight of the positive electrode or the negative electrode because the electrode capacity is not significantly reduced while having conductivity. In particular, ketjen black is preferably used after being pulverized into ultrafine particles of 0.1 to 0.5 μm, because the required carbon amount can be reduced, liquid retention is improved, and internal resistance of the battery can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, a planetary ball mill, or a homogenizer can be mixed dry or wet.
前記結着剤としては、通常、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレンやポリプロピレン等の熱可塑性樹脂、エチレン−プロピレン−ジエンターポリマー（ＥＰＤＭ）、スルホン化ＥＰＤＭ、スチレンブタジエンゴム（ＳＢＲ）、フッ素ゴム等のゴム弾性を有するポリマーを、本発明特許の表面コート剤と組み合わせて合わせて用いることができる。結着剤の添加量は、正極または負極の総重量に対して０．４〜１．５重量％が好ましい。 As the binder, polytetrafluoroethylene (PTFE), thermoplastic resins such as polyethylene and polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoro rubber Such a polymer having rubber elasticity can be used in combination with the surface coating agent of the present invention. The addition amount of the binder is preferably 0.4 to 1.5% by weight with respect to the total weight of the positive electrode or the negative electrode.
前記増粘剤としては、通常、カルボキシメチルセルロース、メチルセルロース等の多糖類等を１種または２種以上の混合物として用いることができる。増粘剤の添加量は、正極または負極の総重量に対して０．１〜０．４重量％が好ましい。 As said thickener, polysaccharides, such as carboxymethylcellulose and methylcellulose, can be normally used as 1 type, or 2 or more types of mixtures. The addition amount of the thickener is preferably 0.1 to 0.4% by weight with respect to the total weight of the positive electrode or the negative electrode.
フィラーとしては、電池性能に悪影響を及ぼさない材料であれば何でも良い。通常、ポリプロピレン，ポリエチレン等のオレフィン系ポリマー、炭素等が用いられる。フィラーの添加量は、正極または負極の総重量に対して添加量は３重量％以下が好ましい。 As the filler, any material that does not adversely affect the battery performance may be used. Usually, olefinic polymers such as polypropylene and polyethylene, carbon and the like are used. The addition amount of the filler is preferably 3% by weight or less with respect to the total weight of the positive electrode or the negative electrode.
正極および負極は、前記活物質、導電剤および結着剤を水やアルコール、トルエン等の有機溶媒に混合させた後、得られた混合液を下記に詳述する集電体の上に塗布し、乾燥することによって、好適に作製される。前記塗布方法については、例えば、アプリケーターロールなどのローラーコーティング、スクリーンコーティング、ドクターブレード方式、スピンコーティング、バーコータ等の手段を用いて任意の厚みおよび任意の形状に塗布することが望ましいが、これらに限定されるものではない。 The positive electrode and the negative electrode are prepared by mixing the active material, the conductive agent and the binder in an organic solvent such as water, alcohol and toluene, and then applying the obtained liquid mixture onto a current collector described in detail below. It is preferably produced by drying. About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. Is not to be done.
集電体は、構成された電池において悪影響を及ぼさない電子伝導体であればよく特に限定されるものではない。例えば、ニッケルやニッケルメッキを行った鋼板を好適に用いることが出来、発泡体、金属繊維からなるスポンジ状成形体、平板に凸凹加工を施した３次元基材の他に、パンチング鋼板等の２次元基材が用いられる。さらに、軽量な焼成炭素、導電性高分子を適用することもできる。厚みの限定は特にないが、１０〜７００μｍのものが用いられる。
これらの中で、正極の集電体としては、アルカリに対する耐食性と耐酸化性に優れているＮｉを、集電機能に優れた構造である発泡体等の多孔体構造としたものを使用することが好ましい。
負極の集電体としては、安価で、且つ電導性に優れる鉄箔に、耐酸化性向上のためにＮｉメッキを施した、パンチング体を使用することが好ましい。さらに、鋼板のパンチング径は１．７ｍｍ以下、開口率４０％以上であることが好ましく、これにより少量の結着剤でも負極活物質と集電体との密着性は優れたものとなる。
集電体と活物質の接着性、導電性を高め、さらに集電体自身の耐酸化性を向上させる目的で、集電体であるニッケルの表面をＮｉ粉末やカーボンや白金等を付着させて処理した集電体を用いることができる。これらの材料については表面を酸化処理することも可能である。
The current collector is not particularly limited as long as it is an electronic conductor that does not have an adverse effect on the constructed battery. For example, nickel or a nickel-plated steel plate can be suitably used, and in addition to a foam, a sponge-like formed body made of metal fibers, a three-dimensional base material with a roughened plate, a punched steel plate or the like 2 A dimensional substrate is used. Furthermore, lightweight baked carbon and a conductive polymer can also be applied. The thickness is not particularly limited, but a thickness of 10 to 700 μm is used.
Among these, as the current collector of the positive electrode, use a material having a porous structure such as a foam having a structure excellent in current collecting function from Ni which is excellent in corrosion resistance and oxidation resistance to alkali. Is preferred.
As the negative electrode current collector, it is preferable to use a punching body in which an iron foil which is inexpensive and excellent in electrical conductivity is plated with Ni to improve oxidation resistance. Furthermore, it is preferable that the punching diameter of the steel sheet is 1.7 mm or less and the opening ratio is 40% or more, so that the adhesion between the negative electrode active material and the current collector is excellent even with a small amount of binder.
For the purpose of improving the adhesion and conductivity between the current collector and the active material, and further improving the oxidation resistance of the current collector itself, Ni powder, carbon, platinum or the like is attached to the surface of nickel as the current collector. A treated current collector can be used. The surface of these materials can be oxidized.
密閉型ニッケル水素電池用セパレータとしては、優れたレート特性を示す多孔膜や不織布等を、単独あるいは併用することが好ましい。密閉型ニッケル水素電池用セパレータを構成する材料としては、例えばポリエチレン，ポリプロピレン等に代表されるポリオレフィン系樹脂や、ナイロンを挙げることができる。
密閉型ニッケル水素電池用セパレータの空孔率は強度、ガス透過性の観点から８０体積％以下が好ましい。また、充放電特性の観点から空孔率は２０体積％以上が好ましい。
As the separator for the sealed nickel-metal hydride battery, it is preferable to use a porous film or a nonwoven fabric exhibiting excellent rate characteristics alone or in combination. Examples of the material constituting the sealed nickel-metal hydride battery separator include polyolefin resins such as polyethylene and polypropylene, and nylon.
The porosity of the sealed nickel-metal hydride battery separator is preferably 80% by volume or less from the viewpoint of strength and gas permeability. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics.
また、密閉型ニッケル水素電池用セパレータは、親水化処理を施す事が好ましい。
例えば、ポリエチレンなどのポリオレフィン系樹脂繊維からなる不織布または織布に、スルフォン化処理、コロナ放電処理、ＰＶＡ処理を施したり、アクリル酸やメタアクリル酸などの親水基を重合させることによって親水性を付与することができる。
Moreover, it is preferable that the separator for a sealed nickel-metal hydride battery is subjected to a hydrophilic treatment.
For example, non-woven fabric or woven fabric made of polyolefin resin fibers such as polyethylene is subjected to sulfonation treatment, corona discharge treatment, PVA treatment, and hydrophilicity is imparted by polymerizing hydrophilic groups such as acrylic acid and methacrylic acid. can do.
電解液としては、一般にアルカリ電池等への使用が提案されているものが使用可能である。水を溶媒とし、溶質としてはカリウム、ナトリウム、リチウムを単独またはそれら２種以上の混合物等を挙げることができるがこれらに限定されるものではない。合金への防食剤や、正極での過電圧向上のためや、負極の耐食性の向上や、自己放電向上の為の電解液への添加剤として、イットリウム、イッテルビウム、エルビウム、カルシウム、硫黄、亜鉛等を単独またはそれら２種以上の混合物等を挙げることができるが、これらに限定されるものではない。
電解液中の電解質塩の濃度としては、高い電池特性を有する電池を確実に得るために、水酸化カリウムの濃度を５〜７Ｍ／ｄｍ3、水酸化リチウムの濃度を０．５〜０．８Ｍ／ｄｍ3とするのが好ましい。
As the electrolytic solution, those generally proposed for use in alkaline batteries and the like can be used. Water may be used as a solvent, and solutes may include, but are not limited to, potassium, sodium, lithium, or a mixture of two or more thereof. Yttrium, ytterbium, erbium, calcium, sulfur, zinc, etc. are added as an additive to the electrolyte to improve the corrosion resistance of the alloy, to improve the overvoltage at the positive electrode, to improve the corrosion resistance of the negative electrode, and to improve self-discharge. These may be used alone or as a mixture of two or more thereof, but are not limited thereto.
As the concentration of the electrolyte salt in the electrolytic solution, the concentration of potassium hydroxide is 5 to 7 M / dm 3 and the concentration of lithium hydroxide is 0.5 to 0.8 M in order to reliably obtain a battery having high battery characteristics. / Dm 3 is preferable.
本発明に係るニッケル水素蓄電池は、電解質を、例えば、ニッケル水素蓄電池用セパレータと正極と負極とを積層する前または積層した後に注液し、最終的に、外装材で封止することによって好適に作製される。また、正極と負極とがニッケル水素蓄電池用セパレータを介して積層された発電要素を巻回してなるニッケル水素蓄電池においては、電解質は、前記巻回の前後に発電要素に注液されるのが好ましい。注液法としては、常圧で注液することも可能であるが、真空含浸方法や加圧含浸方法や遠心含浸法も使用可能である。 The nickel metal hydride storage battery according to the present invention is preferably prepared by injecting an electrolyte before or after stacking a separator for a nickel metal hydride storage battery, a positive electrode, and a negative electrode, and finally sealing with an exterior material. Produced. Further, in a nickel metal hydride storage battery in which a power generation element in which a positive electrode and a negative electrode are laminated via a nickel hydrogen storage battery separator is wound, the electrolyte is preferably injected into the power generation element before and after the winding. . As the injection method, it is possible to inject at normal pressure, but a vacuum impregnation method, a pressure impregnation method, and a centrifugal impregnation method can also be used.
密閉型ニッケル水素蓄電池の外装体の材料としては、ニッケルメッキした鉄やステンレススチール、ポリオレフィン系樹脂等が一例として挙げられる。 Examples of the material of the outer package of the sealed nickel-metal hydride battery include nickel-plated iron, stainless steel, polyolefin resin, and the like.
密閉型ニッケル水素蓄電池の構成、構造は、特に限定されるものではなく、正極、負極および単層又は複数の層からなるセパレータを有するコイン電池やボタン電池、角型電池、扁平型電池、さらに、ロール状の正極、負極およびセパレータを有する円筒型電池等が一例として挙げられる。 The configuration and structure of the sealed nickel-metal hydride storage battery are not particularly limited, and include a coin battery, a button battery, a square battery, a flat battery, a positive battery, a negative battery, and a single-layer or multi-layer separator, An example is a cylindrical battery having a roll-shaped positive electrode, negative electrode and separator.
以下に、好ましい組成であるＭｍＮｉＣｏＡｌＭｎ系の水素吸蔵合金粉末を適用した実施例に基づき本発明をさらに詳細に説明するが、水素吸蔵合金の組成を初めとして本発明は以下の記載により限定されるものではなく、試験方法や構成する電池の正極活物質、水素吸蔵合金以外の負極材料、正極、負極、電解質、セパレータ並びに電池形状等は任意である。 Hereinafter, the present invention will be described in more detail based on examples in which MmNiCoAlMn-based hydrogen storage alloy powder having a preferred composition is applied. However, the present invention is limited by the following description including the composition of the hydrogen storage alloy. Instead, the test method, the positive electrode active material of the battery to be constituted, the negative electrode material other than the hydrogen storage alloy, the positive electrode, the negative electrode, the electrolyte, the separator, the battery shape, and the like are arbitrary.
（実施例１）
(水酸化ニッケル粒子の合成)
硫酸ニッケルと硫酸亜鉛および硫酸コバルトを所定比で溶解した水溶液に硫酸アンモニウムと水酸化ナトリウム水溶液を添加してアンミン錯体を生成させた。反応系を激しく撹拌しながら更に苛性ソーダを滴下し、反応中の反応系の温度を４５±２℃、ｐＨを１２．０±０．２に制御して芯層母材となる球状高密度水酸化ニッケル粒子を水酸化ニッケル：水酸化亜鉛：水酸化コバルト＝８４．６６：５．４６：１．７２の比となるように合成した。
Example 1
(Synthesis of nickel hydroxide particles)
An ammonium complex and an aqueous sodium hydroxide solution were added to an aqueous solution in which nickel sulfate, zinc sulfate and cobalt sulfate were dissolved at a predetermined ratio to form an ammine complex. While the reaction system is vigorously stirred, caustic soda is further added dropwise, and the temperature of the reaction system during the reaction is controlled to 45 ± 2 ° C., and the pH is controlled to 12.0 ± 0.2. Nickel particles were synthesized to have a ratio of nickel hydroxide: zinc hydroxide: cobalt hydroxide = 84.66: 5.46: 1.72.
（水酸化ニッケル粒子表面への表面層の形成）
前記高密度水酸化ニッケル粒子を、水酸化ナトリウムでｐＨ１２．０±０．２に制御したアルカリ水溶液に投入した。該溶液を撹拌しながら、所定濃度の硫酸コバルト、アンモニアを含む水溶液を滴下した。この間、水酸化ナトリウム水溶液を適宜滴下して反応浴のｐＨを１０〜１３の範囲に維持した。約１時間ｐＨを１２．０±０．２の範囲に保持し、水酸化ニッケル粒子表面にＣｏを含む混合水酸化物から成る表面層を形成させた。該混合水酸化物の表面層の比率は芯層母粒子（以下単に芯層と記述する）に対して、６．５ｗｔ％であった。
(Formation of surface layer on nickel hydroxide particle surface)
The high-density nickel hydroxide particles were put into an alkaline aqueous solution controlled to pH 12.0 ± 0.2 with sodium hydroxide. While stirring the solution, an aqueous solution containing cobalt sulfate and ammonia at predetermined concentrations was added dropwise. During this time, an aqueous sodium hydroxide solution was appropriately added dropwise to maintain the pH of the reaction bath in the range of 10-13. The pH was maintained in the range of 12.0 ± 0.2 for about 1 hour, and a surface layer made of a mixed hydroxide containing Co was formed on the surface of the nickel hydroxide particles. The ratio of the surface layer of the mixed hydroxide was 6.5 wt% with respect to the core layer mother particles (hereinafter simply referred to as the core layer).
（表面層の酸化処理）
前記混合水酸化物から成る表面層を有する水酸化ニッケル粒子５０ｇを、温度１１０℃の３０ｗｔ％（１０Ｍ／ｄｍ3）の水酸化ナトリウム水溶液に投入し、充分に攪拌した。続いて表面層に含まれるコバルトの水酸化物の当量に対して過剰のＫ2Ｓ2Ｏ8を添加し、粒子表面から酸素ガスが発生するのを確認した。活物質粒子をろ過し、水洗、乾燥した。
(Oxidation treatment of surface layer)
50 g of nickel hydroxide particles having a surface layer made of the mixed hydroxide was put into a 30 wt% (10 M / dm 3 ) aqueous sodium hydroxide solution at a temperature of 110 ° C. and sufficiently stirred. Subsequently, excess K 2 S 2 O 8 was added to the equivalent of the cobalt hydroxide contained in the surface layer, and it was confirmed that oxygen gas was generated from the particle surface. The active material particles were filtered, washed with water and dried.
（ニッケル電極の作製）
前記活物質粒子にカルボキシメチルセルローズ（ＣＭＣ）水溶液を添加して前記活物質粒子：ＣＭＣ（固形分）＝９９．５：０．５のペースト状とし、該ペーストを３８０ｇ／ｍ2のニッケル多孔体（住友電工株式会社社製ニッケルセルメット＃８）に充填した。その後８０℃で乾燥した後、所定の厚みにプレスし、表面にポリテトラフロロエチレンコーティングを行い、集電リードを溶接し、幅３４ｍｍ長さ２６０ｍｍ（無塗工部２．５×３８０ｍｍ）の容量３０００ｍＡｈのニッケル電極（正極）とした。
(Production of nickel electrode)
A carboxymethyl cellulose (CMC) aqueous solution is added to the active material particles to form a paste of the active material particles: CMC (solid content) = 99.5: 0.5, and the paste is made of a 380 g / m 2 nickel porous body. (Nickel Celmet # 8 manufactured by Sumitomo Electric Co., Ltd.) was filled. Then, after drying at 80 ° C., pressing to a predetermined thickness, coating the surface with polytetrafluoroethylene, welding the current collector leads, capacity of 34 mm in width and 260 mm in length (non-coated part 2.5 × 380 mm) A nickel electrode (positive electrode) of 3000 mAh was used.
（水素吸蔵合金電極の作製）
（第１工程）
平均粒径３０μｍ、ＡＢ5形希土類系のＭｍＮｉ3.6Ｃｏ0.6Ａｌ0.3Ｍｎ0.35（Ｍｍはミッシュメタルを表す）で表される組成を有する水素吸蔵合金粉末１Ｋｇを、ＮａＯＨの濃度が７Ｍ／ｄｍ3、ＬｉＯＨの濃度が１Ｍ／ｄｍ3である１１０℃の浸漬処理水溶液１ｄｍ3中に投入し、角度付ファンタービン形状の攪拌翼を用いて、２００ｒｐｍで攪拌しつつ、混合して処理を行った。浸漬処理時間を１０時間とした。得られた水素吸蔵合金粉末の質量飽和磁化は１ｅｍｕ／ｇであった。処理中に水素吸蔵合金粉末の抜き取りを行い、水素吸蔵合金粉末の質量飽和磁化が１ｅｍｕ／ｇになるまで浸漬処理を行った。該浸漬処理の所要時間は１０時間であった。
(Production of hydrogen storage alloy electrode)
(First step)
The average particle diameter of 30 [mu] m, AB 5 form rare-earth MmNi 3.6 Co 0.6 Al 0.3 Mn 0.35 in (Mm represents a misch metal) hydrogen absorbing alloy powder 1Kg having a composition represented by the concentration of NaOH is 7M / dm 3, the concentration of the LiOH is put in
（第２工程）
その後、加圧濾過して処理液と合金を分離した後、純水を合金重量と同重量添加して２８ＫＨｚの超音波を１０分間かけた。その後、緩やかに攪拌しつつ純水を攪拌層下部より注入し、排水をフローさせて合金より遊離する希土類水酸化物を除去した。
（第３工程）
その後、ＰＨ１０以下になるまで０．０１Ｍ／ｄｍ3の塩酸水溶液を用いて洗浄、加圧濾過を繰り返した後、純水にて水洗した後、加圧濾過した。
(Second step)
Then, after pressure-separating and isolate | separating a process liquid and an alloy, the pure water was added by the same weight as an alloy weight, and the ultrasonic wave of 28 KHz was applied for 10 minutes. Thereafter, pure water was poured from the lower part of the stirring layer while gently stirring, and the rare earth hydroxide released from the alloy was removed by flowing the waste water.
(Third step)
Thereafter, washing and pressure filtration were repeated using a 0.01 M / dm 3 aqueous hydrochloric acid solution until the pH was 10 or less, and then washed with pure water, followed by pressure filtration.
（第４工程）
第３工程の後、ＰＨ約７、８０℃の温水に暴露して水素脱離を行った。その後、温水を加圧濾過して、再度の水洗を行い合金を２５℃に冷却し、攪拌下４％過酸化水素を合金重量と同量加え、水素脱離を行った後、再度水洗を行い、加圧濾過して、含水率２％のウェット状態の水素吸蔵合金粉末を得た。この水素吸蔵合金粉末を減圧下、８０℃で乾燥して乾燥状態の水素吸蔵合金粉末を得た。
(4th process)
After the third step, hydrogen desorption was performed by exposure to warm water having a pH of about 7 and 80 ° C. Then, hot water is filtered under pressure, washed again with water, the alloy is cooled to 25 ° C., 4% hydrogen peroxide is added under stirring with the same amount as the weight of the alloy, hydrogen is desorbed, and then washed again with water. And filtered under pressure to obtain a hydrogen storage alloy powder in a wet state with a moisture content of 2%. This hydrogen storage alloy powder was dried at 80 ° C. under reduced pressure to obtain a dry hydrogen storage alloy powder.
（水素吸蔵合金粉末の表面及び断面の観察）
ＳＥＭにより前記乾燥状態の水素吸蔵合金粉末の表面を、透過形電子顕微鏡と収束イオンビーム装置を用いて水素吸蔵合金粉末の断面を観察した。
(Observation of surface and cross section of hydrogen storage alloy powder)
The surface of the dried hydrogen storage alloy powder was observed by SEM, and the cross section of the hydrogen storage alloy powder was observed using a transmission electron microscope and a focused ion beam apparatus.
（第５工程）
第４工程で得られたウエット状態の水素吸蔵合金粉末とＳＢＲの水性分散液とＨＰＭＣ水溶液をそれぞれの固形量で９８．９３：０．８：０．２７重量％の割合で混合し、適量の水を添加してペースト状にし、ブレードコーターを用いて、４５μｍの鉄に厚み３μｍのニッケルメッキを施した、直径１．０ｍｍ、開口率４３％のパンチング鋼板に塗布した後、８０℃で乾燥して、パンチング鋼板に保持された水素吸蔵合金粉末を得た。本水素吸蔵合金粉末を本発明水素吸蔵合金粉末１とする。
(5th process)
The wet state hydrogen storage alloy powder obtained in the fourth step, the aqueous dispersion of SBR, and the aqueous HPMC solution were mixed in a ratio of 98.93: 0.8: 0.27% by weight in the respective solid amounts, and an appropriate amount was mixed. After adding water to make a paste and applying it to a punched steel plate with a diameter of 1.0 mm and an aperture ratio of 43%, 45 mm iron was plated with 3 μm thick nickel using a blade coater and dried at 80 ° C. Thus, a hydrogen storage alloy powder held on the punched steel plate was obtained. This hydrogen storage alloy powder is referred to as the present hydrogen
前記パンチング鋼板に保持された本発明水素吸蔵合金粉末１を、所定の厚みにプレスして、所定形状に切り出し、幅３４ｍｍ長さ４１０ｍｍ（無塗工部２．５×４１０ｍｍ）の容量４８００ｍＡｈの水素吸蔵合金電極（負極）とした。得られた水素吸蔵合電極を本発明水素吸蔵合金電極１とする。
The hydrogen
（評価電池の作製）
前記本発明水素吸蔵合金電極１とスルフォン化処理を施した厚み１１０μｍのポリプロピレンの不織布状セパレータと前記ニッケル極板とを組み合わせてロール状に巻回し、６．８Ｍ／ｄｍ3の水酸化カリウムと０．８Ｍ／ｄｍ3の水酸化リチウムを溶解したアルカリ電解液を注液し、開弁圧２．４Ｍｐａの弁を具備するｓｕｂＣ形の密閉型ニッケル水素蓄電池を作製した。得られたｓｕｂＣ形の密閉型ニッケル水素蓄電池を本発明電池１とする。
(Production of evaluation battery)
The hydrogen
（放電容量の評価）
この電池を２５℃で１２時間の放置した後、０．０２ＩｔＡにて６００ｍＡｈ充電し、さらに０．１ＩｔＡで１０時間充電した後、０．２ＩｔＡで１Ｖまで放電した。その後、０．１ＩｔＡで１２時間充電、０．２ＩｔＡで１Ｖまで放電する操作を行った。さらに、０．１ＩｔＡで１６時間充電、０．２ＩｔＡで１Ｖまで放電する操作を２回繰り返し、該操作の２回目の放電における放電容量を０．２ＩｔＡ放電における放電容量とした。
(Evaluation of discharge capacity)
The battery was allowed to stand at 25 ° C. for 12 hours, then charged with 0.02 ItA for 600 mAh, further charged with 0.1 ItA for 10 hours, and then discharged at 0.2 ItA to 1 V. Thereafter, an operation of charging for 12 hours at 0.1 ItA and discharging to 1 V at 0.2 ItA was performed. Further, the operation of charging for 16 hours at 0.1 ItA and discharging to 1 V at 0.2 ItA was repeated twice, and the discharge capacity in the second discharge of the operation was defined as the discharge capacity in 0.2 ItA discharge.
（高率放電試験）
続いて、０．１ＩｔＡで１６時間充電し、５℃に５時間放置して十分冷却したのち、０．８Ｖまで２ＩｔＡ放電を行った操作を行い、該放電における放電容量の前記０．２ＩｔＡ放電における放電容量に対する比率（％）を５℃、２ＩｔＡ放電における放電性能を表す指標とした。
（充放電サイクル試験）
この後、２０℃において１０時間の放置を行い、１ＩｔＡの充電にて電池電圧に５ｍＶの−ΔＶが観測されるまで充電し、１．０Ｖまで１ＩｔＡ放電を行った。該充放電操作を繰り返し行い、放電容量が初期容量（該充放電サイクル試験の１サイクル目の放電容量）の６０％に低下した時点を寿命として、寿命に至る充放電の回数をサイクル寿命とした。
(High rate discharge test)
Subsequently, the battery was charged at 0.1 ItA for 16 hours, allowed to stand at 5 ° C. for 5 hours, and then sufficiently cooled. Then, an operation of performing 2 ItA discharge to 0.8 V was performed, and the discharge capacity of the discharge was 0.2 The ratio (%) to the discharge capacity was used as an index representing the discharge performance at 5 ° C. and 2 ItA discharge.
(Charge / discharge cycle test)
Thereafter, the battery was left at 20 ° C. for 10 hours, charged with 1 ItA until the battery voltage was observed as −ΔV of 5 mV, and discharged with 1 ItA up to 1.0V. The charge / discharge operation was repeated, and the time when the discharge capacity decreased to 60% of the initial capacity (discharge capacity at the first cycle of the charge / discharge cycle test) was regarded as the life, and the number of times of charge / discharge reaching the life was defined as the cycle life. .
（単板試験用水素吸蔵電極および開放形セルの作製）
前記水素吸蔵合金極を水素吸蔵合金粉末の重量が１．５８ｇとなるように裁断し、単板試験用水素吸蔵電極とした。活性化処理を施した放電済みのニッケル電極２枚用意し、該２枚のニッケル電極を用い、前記セパレータを介して前記水素吸蔵合金電極を挟み込んだ。なお、前記水素吸蔵電極に対してニッケル電極の容量が大過剰（２枚合わせて２０００ｍＡｈ）になるように設定した。６．８Ｍ／ｄｍ3のＫＯＨ水溶液を電解液として用い、水素吸蔵合金電極の単板試験用開放形セルを作製した。
(Production of hydrogen storage electrode for single plate test and open cell)
The hydrogen storage alloy electrode was cut so that the weight of the hydrogen storage alloy powder was 1.58 g to obtain a hydrogen storage electrode for a single plate test. Two discharged nickel electrodes subjected to activation treatment were prepared, and the hydrogen storage alloy electrodes were sandwiched between the two nickel electrodes through the separator. Note that the capacity of the nickel electrode was set to be excessively large (2000 mAh in total) with respect to the hydrogen storage electrode. A 6.8 M / dm 3 KOH aqueous solution was used as an electrolyte to prepare an open cell for a single plate test of a hydrogen storage alloy electrode.
（水素吸蔵合金電極の単板試験）
前記単板試験用開放形セルを雰囲気温度２５℃において１２時間の保管後、５００ｍＡにて１０時間充電した後、０．２ＩｔＡで０．６Ｖまで放電する操作を５回繰り返した。この５回目の放電容量を水素吸蔵合金の重量で割った値を水素吸蔵合金の単位重量当たりの容量（ｍＡｈ／ｇ）とした。
(Single plate test of hydrogen storage alloy electrode)
The single cell test open cell was stored for 12 hours at an ambient temperature of 25 ° C., charged for 10 hours at 500 mA, and then discharged to 0.6 V at 0.2 ItA for 5 times. The value obtained by dividing the fifth discharge capacity by the weight of the hydrogen storage alloy was taken as the capacity per unit weight (mAh / g) of the hydrogen storage alloy.
（実施例２）
質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末２、水素吸蔵合金電極を本発明水素吸蔵合金電極２、ニッケル水素蓄電池を本発明電池２とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は２０時間であった。
(Example 2)
The hydrogen storage alloy powder obtained in the same manner as in Example 1 except that the processing time was adjusted so that the mass saturation magnetization was 2 emu / g, the hydrogen
（高率放電試験）
実施例１と同様、５℃、２ＩｔＡ放電における放電試験以外に、更に、０．１ＩｔＡで１６時間充電し、５℃に５時間放置して十分冷却したのち、０．８Ｖまで４ＩｔＡ放電を行った。該放電で得られれた放電容量の前記０．２ＩｔＡ放電における放電容量に対する比率（％）を５℃、４ＩｔＡ放電における放電性能を表す指標とした。
(High rate discharge test)
As in Example 1, in addition to the discharge test at 5 ° C. and 2 ItA discharge, the battery was further charged at 0.1 ItA for 16 hours, allowed to stand at 5 ° C. for 5 hours and sufficiently cooled, and then discharged to 0.8 V to 4 ItA. . The ratio (%) of the discharge capacity obtained by the discharge to the discharge capacity in the 0.2 ItA discharge was used as an index representing the discharge performance at 5 ° C. and 4 ItA discharge.
（実施例３）
質量飽和磁化が３ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた合金を本発明合金粉末３、水素吸蔵合金電極を本発明水素吸蔵合金電極３、ニッケル水素蓄電池を本発明電池３とした。尚、処理に必要な時間は２７時間であった。
（実施例４）
質量飽和磁化が４ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた合金を本発明合金粉末４、水素吸蔵合金電極を本発明水素吸蔵合金電極４、ニッケル水素蓄電池を本発明電池４とした。尚、処理に必要な時間は３５時間であった。
（実施例５）
質量飽和磁化が５ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた合金を本発明水素吸蔵合金粉末５、水素吸蔵合金電極を本発明水素吸蔵合金電極５、ニッケル水素蓄電池を本発明電池５とした。尚、処理に必要な時間は３７時間であった。
(Example 3)
The alloy obtained in the same manner as in Example 1 except that the processing time was adjusted so that the mass saturation magnetization was 3 emu / g, the alloy powder 3 of the present invention, the hydrogen storage alloy electrode of the present invention hydrogen storage alloy electrode 3, the nickel The hydrogen storage battery was designated as the battery 3 of the present invention. The time required for the treatment was 27 hours.
Example 4
The alloy obtained in the same manner as in Example 1 except that the processing time was adjusted so that the mass saturation magnetization was 4 emu / g, the alloy powder 4 of the present invention, the hydrogen storage alloy electrode of the present invention hydrogen storage alloy electrode 4, the nickel The hydrogen storage battery was designated as the battery 4 of the present invention. The time required for the treatment was 35 hours.
(Example 5)
The alloy obtained in the same manner as in Example 1 except that the treatment time was adjusted so that the mass saturation magnetization was 5 emu / g, and the hydrogen
（比較例１）
前記で工程１から工程４までの処理しなかったこと以外は、実施例１と同様にして、得られた合金を比較例水素吸蔵合金粉末１、水素吸蔵合金電極を比較例水素吸蔵合金電極１、ニッケル水素蓄電池を比較例電池１とした。尚、比較例水素吸蔵合金粉末１の質量飽和磁化は０．０５ｅｍｕ／ｇであった。
(Comparative Example 1)
The obtained alloy was used as Comparative Example hydrogen
（比較例２）
質量飽和磁化が０．１ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた合金を比較例水素吸蔵合金粉末２、水素吸蔵合金電極を比較例水素吸蔵合金電極２、ニッケル水素蓄電池を比較例電池２とした。尚、処理に必要な時間は１時間であった。
（比較例３）
質量飽和磁化が６ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様
にして得られた合金を比較例水素吸蔵合金粉末３、水素吸蔵合金電極を比較例水素吸蔵合金電極３、ニッケル水素蓄電池を比較例電池３とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は４０時間であった。
(Comparative Example 2)
The alloy obtained in the same manner as in Example 1 except that the processing time was adjusted so that the mass saturation magnetization was 0.1 emu / g, the comparative example hydrogen
(Comparative Example 3)
The alloy obtained in the same manner as in Example 1 except that the treatment time was adjusted so that the mass saturation magnetization was 6 emu / g, the comparative example hydrogen storage alloy powder 3 and the hydrogen storage alloy electrode comparative example hydrogen storage alloy electrode 3 The nickel-metal hydride storage battery was designated as Comparative Example Battery 3. The time required for the immersion treatment of the hydrogen storage alloy powder was 40 hours.
（比較例４）
平均粒径が１０μｍであり、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末４、水素吸蔵合金電極を比較例水素吸蔵合金電極４、ニッケル水素蓄電池を比較例電池４とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は５時間であった。
(Comparative Example 4)
The hydrogen storage alloy powder obtained in the same manner as in Example 1 except that the processing time was adjusted so that the average particle diameter was 10 μm and the mass saturation magnetization was 2 emu / g was referred to as Comparative Example hydrogen storage alloy powder 4, hydrogen The storage alloy electrode was a comparative example hydrogen storage alloy electrode 4, and the nickel hydride storage battery was a comparative example battery 4. The time required for the immersion treatment of the hydrogen storage alloy powder was 5 hours.
（実施例６）
水素吸蔵合金粉末の平均粒径が２０μｍであり、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末６、水素吸蔵合金電極を本発明水素吸蔵合金電極６、ニケル水素蓄電池を本発明電池６とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１０時間であった。
（実施例７）
水素吸蔵合金粉末の平均粒径が３５μｍであり、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末７、水素吸蔵合金電極を本発明水素吸蔵合金電極７、ニケル水素蓄電池を本発明電池７とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は３０時間であった。
(Example 6)
The hydrogen storage alloy powder obtained in the same manner as in Example 1 except that the processing time was adjusted so that the average particle size of the hydrogen storage alloy powder was 20 μm and the mass saturation magnetization was 2 emu / g. The alloy powder 6, the hydrogen storage alloy electrode were designated as the hydrogen storage alloy electrode 6 of the present invention, and the nickel hydrogen storage battery was designated as the present invention battery 6. The time required for the immersion treatment of the hydrogen storage alloy powder was 10 hours.
(Example 7)
The hydrogen storage alloy powder obtained in the same manner as in Example 1 except that the processing time was adjusted so that the average particle size of the hydrogen storage alloy powder was 35 μm and the mass saturation magnetization was 2 emu / g. The alloy powder 7, the hydrogen storage alloy electrode were designated as the present invention hydrogen storage alloy electrode 7, and the Nikel hydrogen storage battery was designated as the present invention battery 7. The time required for the immersion treatment of the hydrogen storage alloy powder was 30 hours.
（比較例５）
水素吸蔵合金粉末の平均粒径が４５μｍであり、浸漬処理時間を４０時間としたこと以外は実施例１の工程１迄の操作を実施した。得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末５、水素吸蔵合金電極を比較例水素吸蔵合金電極５、ニケル水素蓄電池を比較例電池５とした。尚、４０時間に及ぶ浸漬処理によって得られた水素吸蔵合金粉末の質量飽和磁化は０．８ｅｍｕ／ｇであった。
(Comparative Example 5)
The operations up to
（表面層の形成について）
詳細は省くが、収束イオンビーム装置による水素吸蔵合金断面の観察によれば、比較例１、比較例２を除いて、水素吸蔵合金の表面に、空洞がなく連続しており、厚さがほぼ均一な表面層が形成されているのが認められた。透過形電子顕微鏡による観察の結果、形成された表面層が主としてニッケルとコバルトからなることが確認された。該表面層を形成させたものは質量飽和磁化が高いことからも表面層を形成しているＮｉとＣｏが磁性を有するものであることが裏付けられた。１例として本発明合金２の表面のＳＥＭ写真を図１に、収束イオンビーム装置を用いて観察した断面の写真を図２に示す。なお、図２において１が磁性を有するＮｉとＣｏを含む表面層、２が水素吸蔵合金粉末の内部であり、３は、観察用に粉末の表面に析出させたＰｔ層である。
図１に示したように、本発明合金２の表面は、平滑であることが判る。また、図２に示したように、本発明合金２の表面には、均一な厚さ（厚さ：約３００ｎｍ）を持ち、空洞の無い連続した表面層１が形成されていることが判る。
(Regarding the formation of the surface layer)
Although details are omitted, according to the observation of the cross section of the hydrogen storage alloy with a focused ion beam apparatus, except for Comparative Example 1 and Comparative Example 2, the surface of the hydrogen storage alloy is continuous without a cavity, and the thickness is approximately It was observed that a uniform surface layer was formed. As a result of observation with a transmission electron microscope, it was confirmed that the formed surface layer was mainly composed of nickel and cobalt. It was confirmed that Ni and Co forming the surface layer are magnetic because the surface layer formed has high mass saturation magnetization. As an example, an SEM photograph of the surface of the
As shown in FIG. 1, it can be seen that the surface of the
表１に実施例１〜実施例７、比較例１〜比較例５に係るニッケル水素蓄電池および水素吸蔵電極単極の試験結果を示す。
平均粒径が３０μｍの実施例１〜５、比較例１〜３の結果を比較すると、質量飽和磁化が１〜５の範囲にある実施例１〜５が、５℃、２ＩｔＡ放電の放電容量が優れることがわかる。これは、水素吸蔵合金粉末のアルカリ水溶液中への浸漬処理によって、合金に含まれる希土類やアルミニウム、マンガンが溶出し、水素吸蔵合金粉末の表面に触媒活性を有する磁性を有するニッケルとコバルトを含む表面層が生成すること、また、合金表面積が増大したことによるものと考えられる。質量飽和磁化が０．０５から３までの水素吸蔵合金粉末は、６０℃水素気層中で圧力を加えて水素吸蔵させたときの水素吸蔵量（気相法による水素吸蔵量）を測定した結果から算出した合金の水素吸蔵能力に差が無いため、比較例１、比較例２の水素吸蔵合金電極の５℃、２ＩｔＡ放電の放電性能が劣っているのは、水素吸蔵合金粉末の水素吸蔵能力が劣っているのではなく、質量飽和磁化０．０５、０．１ｅｍｕ／ｇと低い値であるところから分かるように、水素吸蔵合金粉末の活物質としての活性が不足しているためと考えられる。
Table 1 shows the test results of the nickel metal hydride storage batteries and the hydrogen storage electrode single electrode according to Examples 1 to 7 and Comparative Examples 1 to 5.
Comparing the results of Examples 1 to 5 and Comparative Examples 1 to 3 having an average particle size of 30 μm, Examples 1 to 5 having a mass saturation magnetization in the range of 1 to 5 have a discharge capacity of 5 ° C. and 2 ItA discharge It turns out that it is excellent. This is because the surface of the hydrogen storage alloy powder contains nickel and cobalt with magnetic properties that have catalytic activity on the surface of the hydrogen storage alloy powder, by immersing the hydrogen storage alloy powder in an alkaline aqueous solution. This is thought to be due to the formation of layers and the increased surface area of the alloy. Hydrogen storage alloy powder with mass saturation magnetization of 0.05 to 3 is a result of measuring hydrogen storage amount (hydrogen storage amount by vapor phase method) when pressure is applied in a hydrogen gas layer at 60 ° C. to store hydrogen. There is no difference in the hydrogen storage capacity of the alloys calculated from the above, so that the hydrogen storage alloy electrodes of Comparative Example 1 and Comparative Example 2 have inferior discharge performance at 5 ° C. and 2 ItA discharge. Is not inferior, it is considered that the activity as an active material of the hydrogen storage alloy powder is insufficient, as can be seen from the low values of mass saturation magnetization 0.05 and 0.1 emu / g. .
（質量飽和磁化とサイクル性能の関係について）
実施例１〜５、比較例３に係る水素吸蔵合金電極単極の放電容量を比較すると、質量飽和磁化が３を超えると合金のグラム当たりの容量が低下していることが分かる。しかしながら、質量飽和磁化が３ｅｍｕ／ｇを超えても質量飽和磁化５ｅｍｕ／ｇ以下であれば、サイクル寿命は大きく低下せず１０００サイクル以上のサイクル寿命を維持している。この理由は、必ずしも明らかではないが、質量飽和磁化が高く、活性化が進んだ水素吸蔵合金粉末を有する水素吸蔵電極を適用した場合、電池に組み込む以前に活性化が進んでいるために、電池内において水素の発生を伴う活性化反応が抑制された結果充電リザーブの減少が抑制され、グラムあたりの容量が小さいにも拘わらず優れたサイクル性能を示したものと考えられる。表１に示したとおり、水素吸蔵合金粉末の質量飽和磁化が１〜５の範囲にある水素吸蔵合金粉末を有する水素吸蔵合金電極を適用した場合に高率放電性能以外に、サイクル性能に於いても優れていることが分かる。
(Relationship between mass saturation magnetization and cycle performance)
When the discharge capacities of the hydrogen storage alloy electrode single poles according to Examples 1 to 5 and Comparative Example 3 are compared, it is found that when the mass saturation magnetization exceeds 3, the capacity per gram of the alloy is lowered. However, even if the mass saturation magnetization exceeds 3 emu / g, if the mass saturation magnetization is 5 emu / g or less, the cycle life is not significantly reduced and the cycle life of 1000 cycles or more is maintained. The reason for this is not necessarily clear, but when a hydrogen storage electrode having a hydrogen storage alloy powder with high mass saturation magnetization and advanced activation is applied, the activation has progressed before incorporation into the battery. As a result, the reduction of the charge reserve was suppressed as a result of the suppression of the activation reaction accompanied with the generation of hydrogen, and it was considered that the cycle performance was excellent despite the small capacity per gram. As shown in Table 1, when a hydrogen storage alloy electrode having a hydrogen storage alloy powder having a mass saturation magnetization of 1 to 5 in the range of 1 to 5 is applied, in addition to high-rate discharge performance, cycle performance It can be seen that it is excellent.
（水素吸蔵合金粉末の平均粒径と質量飽和磁化およびサイクル性能の関係）
水素吸蔵合金粉末の平均粒径が１０μｍと小さい比較例４の場合は、水素吸蔵合金粉末の耐食性が劣るためか、サイクル性能が劣っている。また、水素吸蔵合金粉末の平均粒径が４５μｍと大きい比較例５の場合は、浸漬処理による表面層の形成が進み難く、４０時間で質量飽和磁化が０．８ｅｍｕ／ｇまでしか到達せず、活性が不足しているためか、５℃、２ＩｔＡ放電での放電性能が劣っている。表面処理は短いほど、設備占有時間や加熱エネルギーが少なくて済み、経済的である。４０時間を超えると、現実的な量産に適用するのが難しい。表１に示した結果から、水素吸蔵合金粉末の平均粒径が２０〜３５μｍの水素吸蔵合金粉末を適用することによって良好な結果が得られることが分かった。
(Relationship between average particle size of hydrogen storage alloy powder, mass saturation magnetization and cycle performance)
In the case of Comparative Example 4 in which the average particle size of the hydrogen storage alloy powder is as small as 10 μm, the corrosion resistance of the hydrogen storage alloy powder is inferior, or the cycle performance is inferior. Further, in the case of Comparative Example 5 where the average particle size of the hydrogen storage alloy powder is as large as 45 μm, formation of the surface layer by the immersion treatment is difficult to proceed, and the mass saturation magnetization reaches only 0.8 emu / g in 40 hours, Because of the lack of activity, the discharge performance at 5 ° C. and 2 ItA discharge is inferior. The shorter the surface treatment, the less the equipment occupation time and heating energy, and the more economical. Beyond 40 hours, it is difficult to apply to realistic mass production. From the results shown in Table 1, it was found that good results can be obtained by applying a hydrogen storage alloy powder having an average particle size of 20 to 35 μm.
（実施例８）
水素吸蔵合金粉末の浸漬処理水溶液として、６Ｍ／ｄｍ3のＮａＯＨ水溶液と１Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明合金８、水素吸蔵合金電極を本発明極板８、ニッケル水素蓄電池を本発明電池８とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は４０時間であった。
（実施例９）
水素吸蔵合金粉末の浸漬処理水溶液として、８Ｍ／ｄｍ3のＮａＯＨ水溶液と１Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明合金９、水素吸蔵合金電極を本発明極板９、ニッケル水素蓄電池を本発明電池９とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１８時間であった。
(Example 8)
Example except that an aqueous solution containing 6 M / dm 3 NaOH aqueous solution and 1 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was designated as the present invention alloy 8, the hydrogen storage alloy electrode as the present invention electrode plate 8, and the nickel hydride storage battery as the present invention battery 8. The time required for the immersion treatment of the hydrogen storage alloy powder was 40 hours.
Example 9
Example except that an aqueous solution containing 8 M / dm 3 NaOH aqueous solution and 1 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was designated as the present invention alloy 9, the hydrogen storage alloy electrode as the present invention electrode plate 9, and the nickel hydride storage battery as the present invention battery 9. The time required for the immersion treatment of the hydrogen storage alloy powder was 18 hours.
（比較例６）
水素吸蔵合金粉末の浸漬処理水溶液として、５Ｍ／ｄｍ3のＮａＯＨ水溶液と１Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、浸漬処理時間を４０時間としたこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末６とした。
(Comparative Example 6)
As the immersion treatment aqueous solution of the hydrogen storage alloy powder, an aqueous solution containing a 5 M / dm 3 NaOH aqueous solution and 1 M / dm 3 LiOH was used, and the immersion treatment time was 40 hours. The obtained hydrogen storage alloy powder was designated as Comparative Example hydrogen storage alloy powder 6.
（実施例１０）
水素吸蔵合金粉末の浸漬処理水溶液として、６Ｍ／ｄｍ3のＮａＯＨ水溶液と０．８Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１０、水素吸蔵合金電極を本発明水素吸蔵合金電極１０、ニッケル水素蓄電池を本発明電池１０とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は４０時間であった。
（実施例１１）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨ水溶液と０．８Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１１、水素吸蔵合金電極を本発明水素吸蔵合金電極１１、ニッケル水素蓄電池を本発明電池１１とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は２０時間であった。
（実施例１２）
水素吸蔵合金粉末の浸漬処理水溶液として、８Ｍ／ｄｍ3のＮａＯＨ水溶液と０．８Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１２、水素吸蔵合金電極を本発明水素吸蔵合金電極１２、ニッケル水素蓄電池を本発明電池１２とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１８時間であった。
(Example 10)
Except that a 6 M / dm 3 NaOH aqueous solution and an 0.8 M / dm 3 LiOH aqueous solution were used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder 10 obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 10 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 10 of the present invention, and the nickel hydride storage battery was used as the present invention battery 10. The time required for the immersion treatment of the hydrogen storage alloy powder was 40 hours.
(Example 11)
Except that a 7M / dm 3 NaOH aqueous solution and an aqueous solution containing 0.8M / dm 3 LiOH were used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 11 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 11 of the present invention, and the nickel hydrogen storage battery was used as the present invention battery 11. The time required for the immersion treatment of the hydrogen storage alloy powder was 20 hours.
(Example 12)
Except that an aqueous solution containing 8 M / dm 3 NaOH solution and 0.8 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 12 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 12 of the present invention, and the nickel hydrogen storage battery was used as the present invention battery 12. The time required for the immersion treatment of the hydrogen storage alloy powder was 18 hours.
（実施例１３）
水素吸蔵合金粉末の浸漬処理水溶液として、６Ｍ／ｄｍ3のＮａＯＨ水溶液と０．６Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１３、水素吸蔵合金電極を本発明水素吸蔵合金電極１３、ニッケル水素蓄電池を本発明電池１３とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は４０時間であった。
（実施例１４）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨ水溶液と０．６Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１４、水素吸蔵合金電極を本発明水素吸蔵合金電極１４、ニッケル水素蓄電池を本発明電池１４とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は２０時間であった。
（実施例１５）
水素吸蔵合金粉末の浸漬処理水溶液として、８Ｍ／ｄｍ3のＮａＯＨ水溶液と０．６Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を本発明水素吸蔵合金粉末１５、水素吸蔵合金電極を本発明水素吸蔵合金電極１５、ニッケル水素蓄電池を本発明電池１５とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１８時間であった。
(Example 13)
Except for using a 6 M / dm 3 NaOH aqueous solution and a 0.6 M / dm 3 LiOH aqueous solution as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and adjusting the treatment time so that the mass saturation magnetization becomes 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 13 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 13 of the present invention, and the nickel hydride storage battery was used as the present invention battery 13. The time required for the immersion treatment of the hydrogen storage alloy powder was 40 hours.
(Example 14)
Except for using a 7 M / dm 3 NaOH aqueous solution and a 0.6 M / dm 3 LiOH aqueous solution as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and adjusting the treatment time so that the mass saturation magnetization becomes 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 14 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 14 of the present invention, and the nickel hydrogen storage battery was used as the present invention battery 14. The time required for the immersion treatment of the hydrogen storage alloy powder was 20 hours.
(Example 15)
Except for using an aqueous solution containing 8 M / dm 3 NaOH solution and 0.6 M / dm 3 LiOH as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and adjusting the treatment time so that the mass saturation magnetization becomes 2 emu / g. The hydrogen storage alloy powder 15 obtained in the same manner as in Example 1 was used as the hydrogen storage alloy powder 15 of the present invention, the hydrogen storage alloy electrode was used as the hydrogen storage alloy electrode 15 of the present invention, and the nickel hydrogen storage battery was used as the present invention battery 15. The time required for the immersion treatment of the hydrogen storage alloy powder was 18 hours.
（比較例７）
水素吸蔵合金粉末の浸漬処理水溶液として、９Ｍ／ｄｍ3のＮａＯＨ水溶液と０．６Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末７、水素吸蔵合金電極を比較例水素吸蔵合金電極７、ニッケル水素蓄電池を比較例電池７とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１６時間であった。
（比較例８）
水素吸蔵合金粉末の浸漬処理水溶液として、６Ｍ／ｄｍ3のＮａＯＨ水溶液と０．５Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末８、水素吸蔵合金電極を比較例水素吸蔵合金電極８、ニッケル水素蓄電池を比較例電池８とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は３６時間であった。
（比較例９）
水素吸蔵合金粉末の浸漬処理水溶液として、８Ｍ／ｄｍ3のＮａＯＨ水溶液と０．５Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末９、水素吸蔵合金電極を比較例水素吸蔵合金電極９、ニッケル水素蓄電池を比較例電池９とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１８時間であった。
(Comparative Example 7)
Except for using a 9 M / dm 3 NaOH aqueous solution and an aqueous solution containing 0.6 M / dm 3 LiOH as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and adjusting the treatment time so that the mass saturation magnetization becomes 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as Comparative Example hydrogen storage alloy powder 7, the hydrogen storage alloy electrode was used as Comparative Example hydrogen storage alloy electrode 7, and the nickel hydrogen storage battery was used as Comparative Example battery 7. The time required for the immersion treatment of the hydrogen storage alloy powder was 16 hours.
(Comparative Example 8)
Except that a 6M / dm 3 NaOH aqueous solution and an aqueous solution containing 0.5M / dm 3 LiOH were used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as Comparative Example hydrogen storage alloy powder 8, the hydrogen storage alloy electrode was used as Comparative Example hydrogen storage alloy electrode 8, and the nickel hydrogen storage battery was used as Comparative Example battery 8. The time required for the immersion treatment of the hydrogen storage alloy powder was 36 hours.
(Comparative Example 9)
Except that an aqueous solution containing 8 M / dm 3 NaOH solution and 0.5 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as Comparative Example hydrogen storage alloy powder 9, the hydrogen storage alloy electrode was used as Comparative Example hydrogen storage alloy electrode 9, and the nickel hydrogen storage battery was used as Comparative Example battery 9. The time required for the immersion treatment of the hydrogen storage alloy powder was 18 hours.
（比較例１０）
水素吸蔵合金粉末の浸漬処理水溶液として、５Ｍ／ｄｍ3のＮａＯＨ水溶液と１．５Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、浸漬処理時間を４０時間としたこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１０とした。
（比較例１１）
水素吸蔵合金粉末の浸漬処理用水溶液として、６Ｍ／ｄｍ3のＮａＯＨ水溶液と１．５Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を調整したが、水溶液の粘度が非常に高く、処理に適さないものであった。
(Comparative Example 10)
As an immersion treatment aqueous solution of the hydrogen storage alloy powder, an aqueous solution containing a 5 M / dm 3 NaOH aqueous solution and a 1.5 M / dm 3 LiOH was used, and the immersion treatment time was 40 hours. The obtained hydrogen storage alloy powder was designated as Comparative Example hydrogen storage alloy powder 10.
(Comparative Example 11)
An aqueous solution containing 6 M / dm 3 NaOH solution and 1.5 M / dm 3 LiOH was prepared as an aqueous solution for immersion treatment of the hydrogen storage alloy powder, but the viscosity of the aqueous solution was very high and was not suitable for treatment. It was.
（比較例１２）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨを単独で含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１２、水素吸蔵合金電極を比較例水素吸蔵合金電極１２、ニッケル水素蓄電池を比較例電池１２とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１８時間であった。
(Comparative Example 12)
Obtained in the same manner as in Example 1 except that an aqueous solution containing 7 M / dm 3 NaOH alone was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The obtained hydrogen storage alloy powder was referred to as Comparative Example hydrogen storage alloy powder 12, the hydrogen storage alloy electrode was referred to as Comparative Example hydrogen storage alloy electrode 12, and the nickel hydrogen storage battery was referred to as Comparative Example battery 12. The time required for the immersion treatment of the hydrogen storage alloy powder was 18 hours.
（比較例１３）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＫＯＨを単独で含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１３、水素吸蔵合金電極を比較例水素吸蔵合金電極１３、ニッケル水素蓄電池を比較例電池１３とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は３時間であった。
（比較例１４）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＫＯＨと１Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１４、水素吸蔵合金電極を比較例水素吸蔵合金電極１４、ニッケル水素蓄電池を比較例電池１４とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は３．５時間であった。
(Comparative Example 13)
As an immersion treatment aqueous solution of hydrogen storage alloy powder, an aqueous solution containing 7 M / dm 3 KOH alone was used, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The obtained hydrogen storage alloy powder was used as Comparative Example hydrogen storage alloy powder 13, the hydrogen storage alloy electrode was used as Comparative Example hydrogen storage alloy electrode 13, and the nickel hydrogen storage battery was used as Comparative Example battery 13. The time required for the immersion treatment of the hydrogen storage alloy powder was 3 hours.
(Comparative Example 14)
Example 1 except that an aqueous solution containing 7 M / dm 3 KOH and 1 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as the comparative example hydrogen storage alloy powder 14, the hydrogen storage alloy electrode as the comparative example hydrogen storage alloy electrode 14, and the nickel hydride storage battery as the comparative example battery 14. The time required for the immersion treatment of the hydrogen storage alloy powder was 3.5 hours.
（比較例１５）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨ水溶液と１．０Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を処理液温度９０℃で用い、処理時間を４０時間としたこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１５、水素吸蔵合金電極を比較例水素吸蔵合金電極１５、ニッケル水素蓄電池を比較例電池１５とした。
（実施例１６）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨ水溶液と１．０Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を処理液温度１００℃で用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を参考例水素吸蔵合金粉末１、水素吸蔵合金電極を参考例水素吸蔵合金電極１、ニッケル水素蓄電池を参考例電池１とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は４２時間であった。
(Comparative Example 15)
Example except that 7 M / dm 3 NaOH aqueous solution and 1.0 M / dm 3 LiOH aqueous solution were used as the immersion treatment aqueous solution of the hydrogen storage alloy powder at a treatment liquid temperature of 90 ° C. and the treatment time was 40 hours. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as Comparative Example hydrogen storage alloy powder 15, the hydrogen storage alloy electrode was used as Comparative example hydrogen storage alloy electrode 15, and the nickel hydrogen storage battery was used as Comparative example battery 15.
(Example 16)
As the immersion treatment aqueous solution of the hydrogen storage alloy powder, an aqueous solution containing a 7 M / dm 3 NaOH aqueous solution and 1.0 M / dm 3 LiOH is used at a treatment solution temperature of 100 ° C., and the treatment time is set so that the mass saturation magnetization is 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 except that the hydrogen storage alloy powder was adjusted was referred to as Reference Example Hydrogen
（参考例１）
水素吸蔵合金粉末の浸漬処理水溶液として、７Ｍ／ｄｍ3のＮａＯＨ水溶液と１．０Ｍ／ｄｍ3のＬｉＯＨを含む水溶液を沸点で用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整したこと以外は実施例１と同様にして得られた水素吸蔵合金粉末を参考例水素吸蔵合金粉末１、水素吸蔵合金電極を参考例水素吸蔵合金電極１、ニッケル水素蓄電池を参考例電池１とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は１０時間であった。
（参考例２）
水素吸蔵合金粉末の浸漬処理水溶液として、５Ｍ／ｄｍ3のＬｉＯＨの水溶液を用い、質量飽和磁化が２ｅｍｕ／ｇとなるよう処理時間を調整した。また、浸漬処理後処理液の温度が低下してＬｉＯＨが析出しないうちに処理液を濾別し、熱水で洗浄して付着した処理液を除去した。それ以外は実施例１と同様にして得られた水素吸蔵合金粉末を参考例水素吸蔵合金粉末２、水素吸蔵合金電極を参考例水素吸蔵合金電極２、ニッケル水素蓄電池を参考例電池２とした。尚、水素吸蔵合金粉末の浸漬処理に必要な時間は７０時間であった。
(Reference Example 1)
As the immersion treatment aqueous solution of the hydrogen storage alloy powder, an aqueous solution containing 7 M / dm 3 NaOH solution and 1.0 M / dm 3 LiOH was used at the boiling point, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. The hydrogen storage alloy powder obtained in the same manner as in Example 1 was used as a reference example hydrogen
(Reference Example 2)
As an immersion treatment aqueous solution of the hydrogen storage alloy powder, an aqueous solution of 5 M / dm 3 LiOH was used, and the treatment time was adjusted so that the mass saturation magnetization was 2 emu / g. Moreover, the treatment liquid was filtered off before the temperature of the treatment liquid after the immersion treatment decreased and LiOH was deposited, and the treatment liquid adhered was removed by washing with hot water. Otherwise, the hydrogen storage alloy powder obtained in the same manner as in Example 1 was referred to as Reference Example hydrogen
（比較例１６）
水素吸蔵合金粉末の浸漬処理水溶液として、３Ｍ／ｄｍ3のＬｉＯＨ水溶液を単独で用い、浸漬処理時間を７０時間としたこと以外は実施例１の工程１迄の操作を実施した。得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１６とした。尚、７０時間におよぶ浸漬処理によって得られた水素吸蔵合金粉末の質量飽和磁化は０．４ｅｍｕ／ｇであった。
(Comparative Example 16)
The operation up to
（比較例１７）
水素吸蔵合金粉末の浸漬処理水溶液として、９Ｍ／ｄｍ3のＮａＯＨと０．８Ｍ／ｄｍ3のＬｉＯＨの水溶液を用いたこと以外は実施例１と同様の操作を実施した。水素吸蔵合金粉末の浸漬処理水溶液として、９Ｍ／ｄｍ3のＮａＯＨと０．６Ｍ／ｄｍ3以上の濃度のＬｉＯＨを溶解させた水溶液を適用しようとしたが、常温においてはＬｉＯＨが完全に溶解しなかった。液の温度を１１０℃とすればＬｉＯＨを溶解できるものの洗浄時にＬｉＯＨと思われる結晶が析出し、洗浄が困難となった。
(Comparative Example 17)
The same operation as in Example 1 was performed, except that an aqueous solution of 9 M / dm 3 NaOH and 0.8 M / dm 3 LiOH was used as the immersion treatment aqueous solution of the hydrogen storage alloy powder. An attempt was made to apply an aqueous solution in which 9 M / dm 3 NaOH and 0.6 M / dm 3 or more of LiOH were dissolved as an aqueous solution for immersing the hydrogen storage alloy powder, but LiOH was not completely dissolved at room temperature. It was. When the temperature of the liquid was 110 ° C., LiOH could be dissolved, but crystals thought to be LiOH were precipitated during washing, making washing difficult.
（表面層の形成について）
詳細は省くが、比較例６、比較例７〜９、比較例１０、比較例１２、比較例１３、比較例１４、比較例１６を除き水素吸蔵合金粉末の表面に、磁性を有するニッケルおよびコバルトを含み、空洞が無く連続した表面層が形成されているのが認められた。
比較例６、比較例１０、比較例１６の場合は、表面層の形成速度が遅いためか、表面層の形成が確認されなかった。（表面層の厚さがおよそ５０ｎｍ以下の場合は確実に表面層が形成されているかどうかの確認が困難）。
比較例７〜９、比較例１２の場合は表面層中に空洞は認められないものの、表面層の厚さが極めて不均一であり、ところどころに表面層のと切れが認められた。処理液にＬｉＯＨが存在するとＮｉやＣｏの溶出が抑制され、連続した均一な厚さの表面層形成に有効に作用すると考えられる。比較例１２の場合は処理液中にＬｉＯＨが存在しないためにＮｉやＣｏが溶出し、表面層の厚さが不均一になったものと考えられる。また、比較例７の場合は処理液中のＮａＯＨの濃度が高く、且つ、ＬｉＯＨの濃度が低いために、比較例８、９の場合にはＬｉＯＨの濃度が低いために、ＬｉＯＨのＮｉやＣｏの溶出抑制効果が十分に発揮されずに厚さが不均一であり、と切れがある表面層となったものと考えられる。
(Regarding the formation of the surface layer)
Although details are omitted, except for Comparative Example 6, Comparative Examples 7-9, Comparative Example 10, Comparative Example 12, Comparative Example 13, Comparative Example 14, and Comparative Example 16, the surface of the hydrogen storage alloy powder has nickel and cobalt having magnetism. It was recognized that a continuous surface layer was formed without voids.
In the case of Comparative Example 6, Comparative Example 10, and Comparative Example 16, the formation of the surface layer was not confirmed because the formation speed of the surface layer was slow. (If the thickness of the surface layer is about 50 nm or less, it is difficult to confirm whether or not the surface layer is reliably formed).
In Comparative Examples 7 to 9 and Comparative Example 12, although no cavities were observed in the surface layer, the thickness of the surface layer was extremely nonuniform, and the surface layer was cut off in some places. When LiOH is present in the treatment liquid, elution of Ni and Co is suppressed, and it is considered that it effectively acts on the formation of a continuous and uniform surface layer. In the case of Comparative Example 12, it is considered that Ni and Co were eluted because LiOH was not present in the treatment liquid, and the thickness of the surface layer became non-uniform. In Comparative Example 7, the concentration of NaOH in the treatment liquid is high and the concentration of LiOH is low. In Comparative Examples 8 and 9, the concentration of LiOH is low. It is considered that the surface layer with a non-uniform thickness and a cut is not obtained because the elution suppression effect is not sufficiently exhibited.
比較例１３と１４の場合は表面層の厚さが不均一であって、且つ、表面層中に空洞が生じていた。１例として比較例水素吸蔵合金粉末１４の表面のＳＥＭ写真を図３に、合金粉末の断面を集束イオンビーム装置を用いて観測した写真を図４に示す。図４に示すように、比較例水素吸蔵合金粉末１４の表面には、平均厚さ約３５０μｍの表面層１が形成されている。該表面層にはところどころに空洞４の存在が認められ、また、かさぶた状に表面層が盛り上がっている部分６に隣り合って表面層の厚さが小さい部分５（厚さ１５０ｎｍ）が存在する。ＫＯＨはＮｉやＣｏの溶出を促進すると考えられ、そのために、比較例水素吸蔵合金粉末１４の表面層の厚さが不均一であり、且つ、表面層中に空洞が生成したものと考えられる
In Comparative Examples 13 and 14, the thickness of the surface layer was not uniform, and cavities were generated in the surface layer. As an example, an SEM photograph of the surface of the comparative example hydrogen storage alloy powder 14 is shown in FIG. 3, and a photograph of a cross section of the alloy powder observed using a focused ion beam apparatus is shown in FIG. As shown in FIG. 4, the
また、図３に示すように、比較例合金粉末１４の表面に小さな粒状の物質が存在する。粉末Ｘ線回折による測定によれば、該粒状物質は、Ｍｎの水酸化物であることが確認された。合金粉末を、ＫＯＨを主たるアルカリ成分として含むアルカリ水溶液に浸漬したことによって、合金に含まれているＭｎが溶出した後、水酸化物となって粉末の表面に析出したものと考えられる。 Moreover, as shown in FIG. 3, a small granular substance exists on the surface of the comparative example alloy powder 14. Measurement by powder X-ray diffraction confirmed that the particulate material was a hydroxide of Mn. It is considered that by immersing the alloy powder in an alkaline aqueous solution containing KOH as a main alkali component, Mn contained in the alloy was eluted and then became hydroxide and precipitated on the surface of the powder.
参考例１においては水素吸蔵合金粉末の表面に、空洞がなく、連続した表面層が形成されているが、実施例のように表面層の厚さが均一でなく表面層に凹凸が認められた。 In Reference Example 1, the surface of the hydrogen storage alloy powder has no cavities and a continuous surface layer is formed, but the thickness of the surface layer is not uniform and irregularities are observed in the surface layer as in the example. .
表２に実施例２、実施例８〜実施例１５、参考例１、２及び比較例６〜比較例１６に係る水素吸蔵合金粉末の質量飽和磁化およびニッケル水素蓄電池の試験結果を示す。
（処理液の組成および処理温度と質量飽和磁化との関係）
ＮａＯＨとＬｉＯＨの両方を含む処理液であっても、処理液中のＮａＯＨの濃度が５Ｍ／ｄｍ3の比較例６、比較例１０においては、４０時間におよぶ浸漬処理を行っても得られた水素吸蔵合金粉末の質量飽和磁化が１ｅｍｕ／ｇ未満であった。また、前記表１に示したように、質量飽和磁化が１ｅｍｕ／ｇ未満の場合は良好な高率放電特性（２ＩｔＡ放電時の放電容量）が得られない。このことから、処理液中のＮａＯＨの濃度を６Ｍ／ｄｍ3以上にすることが好ましい。
(Relationship between treatment liquid composition and treatment temperature and mass saturation magnetization)
Even in the treatment liquid containing both NaOH and LiOH, in Comparative Examples 6 and 10 in which the concentration of NaOH in the treatment liquid was 5 M / dm 3 , the treatment liquid was obtained even after immersion for 40 hours. The mass saturation magnetization of the hydrogen storage alloy powder was less than 1 emu / g. As shown in Table 1, when the mass saturation magnetization is less than 1 emu / g, good high rate discharge characteristics (discharge capacity at 2 ItA discharge) cannot be obtained. For this reason, it is preferable that the concentration of NaOH in the treatment liquid is 6 M / dm 3 or more.
本発明においては処理液としてＬｉＯＨ単独の水溶液を適用することも可能であるが、比較例１６に示すように処理液のＬｉＯＨの濃度が３Ｍ／ｄｍ3の場合、７０時間に及ぶ処理を行っても得られる水素吸蔵合金粉末の質量飽和磁化が１ｅｍｕ／ｇ未満である。参考例２に示すように、濃度が５Ｍ／ｄｍ3のＬｉＯＨ単独の水溶液を処理液に適用すると、所定の質量飽和磁化が得られるものの、処理速度が遅く本発明の狙いとする１以上の質量飽和磁化を持った水素吸蔵合金を得ようとすると、処理時間が極めて長時間となり不利である。また、浸漬処理後の処理液の濾別に際してはＬｉＯＨが析出しないように配慮する必要がある。 In the present invention, it is possible to apply an aqueous solution of LiOH alone as the treatment liquid. However, when the LiOH concentration of the treatment liquid is 3 M / dm 3 as shown in Comparative Example 16, the treatment is performed for 70 hours. The mass saturation magnetization of the obtained hydrogen storage alloy powder is less than 1 emu / g. As shown in Reference Example 2, when an aqueous solution of LiOH alone having a concentration of 5 M / dm 3 is applied to the treatment liquid, a predetermined mass saturation magnetization is obtained, but the treatment speed is slow and one or more masses targeted by the present invention is achieved. If a hydrogen storage alloy having saturation magnetization is to be obtained, the processing time is extremely long, which is disadvantageous. In addition, it is necessary to consider that LiOH does not precipitate during the separation of the treatment liquid after the immersion treatment.
また、比較例１３、比較例１４に示すようにでは処理液にＫＯＨを含む水溶液を適用すると極めて短時間で本発明の狙いとする１以上の質量飽和磁化を有する水素吸蔵合金が得られるものの、前記のように本発明の狙いとする水素吸蔵合金に空洞がなく連続した表面層が形成されない欠点がある。 Moreover, as shown in Comparative Example 13 and Comparative Example 14, when an aqueous solution containing KOH is applied to the treatment liquid, a hydrogen storage alloy having one or more mass saturation magnetization targeted by the present invention can be obtained in a very short time. As described above, the hydrogen storage alloy targeted by the present invention has a defect that there is no void and a continuous surface layer is not formed.
以上記述したことから、本発明の狙いとする質量飽和磁化を有し、且つ、空洞が無く連続した表面層を有する水素吸蔵合金を得るための処理液にはＮａＯＨとＬｉＯＨを含む水溶液が好ましい。ＮａＯＨとＬｉＯＨを含む水溶液であっても、ＬｉＯＨの濃度が０．６Ｍ／ｄｍ3未満の場合は連続した表面層が得られない虞があるので、ＬｉＯＨの濃度を０．６Ｍ／ｄｍ3以上とすることが好ましい。また、ＮａＯＨの濃度が６Ｍ／ｄｍ3未満の場合は、浸漬処理によって質量飽和磁化の値を高め、表面層を形成する速度が極めて遅くなるのでＮａＯＨの濃度が６Ｍ／ｄｍ3以上とすることが好ましい。また、ＮａＯＨの濃度を６Ｍ／ｄｍ3とした実施例８、１０、１３に比べて、ＮａＯＨの濃度を７Ｍ／ｄｍ3とした実施例２、１１、１４およびＮａＯＨの濃度を８Ｍ／ｄｍ3とした実施例９、１２、１５においては処理時間が短くて済むので、処理液のＮａＯＨの濃度を７〜８Ｍ／ｄｍ3とすることがさらに好ましい。ＮａＯＨの濃度を６Ｍ／ｄｍ3以上とした場合、ＬｉＯＨの濃度を１Ｍ／ｄｍ3を超える濃度に設定すると処理液の粘度が極めて高くなる欠点が生じるのでＬｉＯＨの濃度を１Ｍ／ｄｍ3以下とすることが好ましい。さらに、ＮａＯＨの濃度を、８Ｍ／ｄｍ3を超える値に設定すると、ＬｉＯＨの濃度として本発明のより好ましい濃度である０．８Ｍ／ｄｍ3以上含む溶液を得ることが難しくなり、さらに、連続した表面層を形成することが出来なくなる虞があるので、ＮａＯＨの濃度を８Ｍ／ｄｍ3以下とすることが好ましい。 As described above, an aqueous solution containing NaOH and LiOH is preferable as a treatment solution for obtaining a hydrogen storage alloy having a mass saturation magnetization and having a continuous surface layer without voids, which is a target of the present invention. Even in an aqueous solution containing NaOH and LiOH, if the LiOH concentration is less than 0.6 M / dm 3, a continuous surface layer may not be obtained, so the LiOH concentration should be 0.6 M / dm 3 or more. It is preferable to do. Further, when the NaOH concentration is less than 6 M / dm 3 , the value of mass saturation magnetization is increased by the immersion treatment, and the rate of forming the surface layer becomes extremely slow, so the NaOH concentration may be 6 M / dm 3 or more. preferable. Further, compared to Examples 8, 10, and 13 in which the NaOH concentration was 6 M / dm 3 , Examples 2, 11, and 14 in which the NaOH concentration was 7 M / dm 3 and the NaOH concentration was 8 M / dm 3 . In Examples 9, 12, and 15, the treatment time is short, and therefore the NaOH concentration of the treatment liquid is more preferably 7 to 8 M / dm 3 . When the concentration of NaOH is set to 6 M / dm 3 or more, if the concentration of LiOH is set to a concentration exceeding 1 M / dm 3 , the viscosity of the treatment liquid becomes extremely high. Therefore, the concentration of LiOH is set to 1 M / dm 3 or less. It is preferable. Furthermore, when the NaOH concentration is set to a value exceeding 8 M / dm 3 , it becomes difficult to obtain a solution containing 0.8 M / dm 3 or more, which is a more preferable concentration of the present invention, as the LiOH concentration, and it is continuous. Since the surface layer may not be formed, the NaOH concentration is preferably 8 M / dm 3 or less.
処理液の温度が９０℃である比較例１５の場合の場合、４０時間処理を行っても、得られた水素吸蔵合金の質量飽和磁化は１未満であった。このことから、処理温度は１００℃以上とするのが良い。但し、実施例１６のように処理液の温度が１００℃の場合は処理時間が４２時間と長時間を要するので、処理温度を、１００℃を超える温度に設定することが好ましい。
また、参考例１のように処理温度を沸点に設定すると処理時間を短縮することはできるが、生成した表面層の厚さが不均一となる虞があるので、浸漬処理を、１００℃を超える温度であって、沸点未満の温度で実施することが好ましい。さらに、浸漬処理を処理液の沸点以上で行おうとすると、オートクレーブのような高価な処理装置が必要となる。このことからも、沸点未満の温度で処理を行うことが好ましい。
In the case of Comparative Example 15 in which the temperature of the treatment liquid was 90 ° C., the mass saturation magnetization of the obtained hydrogen storage alloy was less than 1 even after treatment for 40 hours. For this reason, the processing temperature is preferably 100 ° C. or higher. However, when the temperature of the treatment liquid is 100 ° C. as in Example 16, the treatment time is as long as 42 hours, so the treatment temperature is preferably set to a temperature exceeding 100 ° C.
Further, when the processing temperature is set to the boiling point as in Reference Example 1, the processing time can be shortened, but the thickness of the generated surface layer may be non-uniform, so the immersion processing exceeds 100 ° C. It is preferable to carry out at a temperature below the boiling point. Further, if the immersion treatment is performed at a temperature equal to or higher than the boiling point of the treatment liquid, an expensive treatment device such as an autoclave is required. Also from this, it is preferable to perform the treatment at a temperature lower than the boiling point.
（処理液の組成、温度と放電特性、サイクル性能の関係）
実施例２、実施例８〜１２、実施例１６、参考例２は２ＩｔＡ放電のみでなく４ＩｔＡ放電においても極めて優れた放電性能を示した。これらの電池においては、水素吸蔵合金の表面に、空洞がなく連続した層であって、しかも凹凸が殆どなく厚さの均一な表面層が形成されており、このことによって、水素吸蔵合金電極が優れた高率放電性能を有する電極となり、該優れた性能が電池の性能に反映したものと考えられる。
(Relationship between treatment liquid composition, temperature and discharge characteristics, cycle performance)
Example 2, Examples 8 to 12, Example 16, and Reference Example 2 exhibited extremely excellent discharge performance not only with 2 ItA discharge but also with 4 ItA discharge. In these batteries, the surface of the hydrogen storage alloy is a continuous layer with no cavities, and has a uniform surface layer with almost no unevenness. It is considered that the electrode has excellent high rate discharge performance, and the excellent performance is reflected in the performance of the battery.
実施例１３〜１５、参考例１の４ＩｔＡ放電の放電性能は、比較例を遥かに上回っているが、実施例２、実施例８〜１２、実施例１６、参考例２に比べて劣っている。実施例１３〜１５、参考例１においては、水素吸蔵合金の表面に空洞がなく連続した表面層が形成されてはいるが、表面層に凹凸があり、表面層の厚さが均一ではない。実施例１３〜１５、参考例１の場合には、前記表面層の厚さが不均一であるために放電時の水素吸蔵合金電極の電流分布が不均一になり分極が大きくなり、実施例２、実施例８〜１２、実施例１６、参考例２との間に４ＩｔＡ放電での放電性能に差が生じたものと考えられる。
以上のことから、処理液中のＬｉＯＨの濃度が０．６Ｍ／ｄｍ3以上であることが好ましく、０．８Ｍ／ｄｍ3以上であることがさらに好ましい。
The discharge performance of the 4 ItA discharges of Examples 13 to 15 and Reference Example 1 is far superior to that of the Comparative Example, but is inferior to those of Examples 2, 8 to 12, Example 16, and Reference Example 2. . In Examples 13 to 15 and Reference Example 1, the surface of the hydrogen storage alloy has no cavities and a continuous surface layer is formed, but the surface layer has irregularities and the thickness of the surface layer is not uniform. In Examples 13 to 15 and Reference Example 1, since the thickness of the surface layer is not uniform, the current distribution of the hydrogen storage alloy electrode at the time of discharge becomes non-uniform and the polarization becomes large. It is considered that a difference in discharge performance with 4 ItA discharge occurred between Examples 8 to 12, Example 16, and Reference Example 2.
From the above, the concentration of LiOH in the treatment liquid is preferably 0.6 M / dm 3 or more, and more preferably 0.8 M / dm 3 or more.
前記のように、水素吸蔵合金の表面層の厚さが不均一であって、表面層にと切れが認められた比較例７〜９、比較例１２の、２ＩｔＡ放電、４ＩｔＡ放電における放電性能が実施例に比べて劣るのは、前記同様、放電時の電流分布が不均一であるためのに、分極が大きくなったことによると考えられる。 As described above, the discharge performance in the 2 ItA discharge and the 4 ItA discharge of Comparative Examples 7 to 9 and Comparative Example 12 in which the thickness of the surface layer of the hydrogen storage alloy is non-uniform and the surface layer is broken. The reason why it is inferior to that of the example is considered to be that the polarization is increased because the current distribution at the time of discharge is non-uniform, as described above.
処理液の温度を沸点とした参考例１の場合は、水素吸蔵合金に形成された表面層の形態が実施例１４、１５のそれに類似しており（表面層に凹凸がある）、放電性能においても実施例１４、１５に近い性能を示した。処理液の温度を９０℃とした比較例１５においては質量飽和磁化が１未満であり、水素吸蔵合金の活性化が不十分なために２ＩｔＡ放電、４ＩｔＡ放電ともに放電性能が劣る結果になったと考えられる。実施例２、比較例１５、実施例１６，参考例１を比較すると、実施例２、実施例１６の放電性能が優れ、次いで参考例１であるところから、電池の特性面からも、処理液の温度は１００℃〜沸点とすることが好ましく、１００〜沸点未満とすることがさらに好ましい。 In the case of Reference Example 1 where the temperature of the treatment liquid is the boiling point, the form of the surface layer formed on the hydrogen storage alloy is similar to that of Examples 14 and 15 (the surface layer has irregularities), and in terms of discharge performance Also showed performance close to Examples 14 and 15. In Comparative Example 15 in which the temperature of the treatment liquid was 90 ° C., the mass saturation magnetization was less than 1, and the activation performance of the hydrogen storage alloy was insufficient, which resulted in poor discharge performance for both 2 ItA discharge and 4 ItA discharge. It is done. When Example 2, Comparative Example 15, Example 16, and Reference Example 1 are compared, the discharge performance of Example 2 and Example 16 is excellent, and since it is Reference Example 1, the processing solution is also from the viewpoint of battery characteristics. The temperature is preferably 100 ° C. to boiling point, more preferably 100 to less than boiling point.
比較例１３、比較例１４のように処理液に、ＫＯＨ単独あるいは主たるアルカリ成分がＫＯＨである水溶液を適用した場合、短時間の浸漬処理で実施例同様質量飽和磁化が２ｅｍｕ／ｇの水素吸蔵合金が得られたが、実施例に比べて５℃、４ＩｔＡ放電での放電容量が極端に低く、サイクル性能も劣っていた。この理由は、必ずしも明らかではないが、比較例１１に係る７Ｍ／ｄｍ3のＫＯＨと１Ｍ／ｄｍ3のＬｉＯＨを含む水溶液による処理では、図３に示すように、合金表面にマンガンの水酸化物が析出（図３の粒状の物質）したために合金粉末の粉体抵抗（電気抵抗）が増大したことと、図４に示すように、表面層１中に空洞４が存在したり、表面層の５、６の部分に示したように、表面層の厚さが不均一なために放電に際して電流が局部に集中して分極が大きくなったためと考えられる。
When KOH alone or an aqueous solution whose main alkali component is KOH is applied to the treatment liquid as in Comparative Examples 13 and 14, a hydrogen storage alloy having a mass saturation magnetization of 2 emu / g as in the case of the short-time immersion treatment. However, the discharge capacity at 5 ° C. and 4 ItA discharge was extremely low and the cycle performance was inferior to that of the example. The reason for this is not necessarily clear, but in the treatment with an aqueous solution containing 7 M / dm 3 KOH and 1 M / dm 3 LiOH according to Comparative Example 11, as shown in FIG. Is deposited (granular substance in FIG. 3), the powder resistance (electrical resistance) of the alloy powder is increased, and as shown in FIG. 4, there are cavities 4 in the
また、比較例１３、比較例１４のように、水素吸蔵合金の表面に、層中に空洞があり、厚さが不均一な表面層が形成したり、比較例７〜９、比較例１２のように、と切れのある表面層が形成すると、放電に際して水素吸蔵合金電極の分極が大きくなったり、充電に際して酸素の吸収機能が劣るために合金の腐蝕が速く、そのために、表２に示すように、これらの電池のサイクル性能が劣る結果になったものと考えられる。これに対して表２に示した実施例や参考例においては、放電時の分極が小さく、かつ、酸素吸収能力にも優れているので、優れたサイクル性能を示したものと考えられる。このように、１ＩｔＡによる充電や２〜４ＩｔＡで放電するような高率での充電や放電を必要とする使用に於いて、本発明電池に係る水素吸蔵合金合金電極を適用すると顕著なサイクル性能の向上を示す。 Further, as in Comparative Examples 13 and 14, the surface of the hydrogen storage alloy has cavities in the layer, and a surface layer with a non-uniform thickness is formed, or Comparative Examples 7 to 9 and Comparative Example 12 Thus, when a cut surface layer is formed, the polarization of the hydrogen storage alloy electrode is increased during discharge, or the oxygen absorption function is poor during charging, so that the alloy is rapidly corroded. Therefore, as shown in Table 2 Moreover, it is considered that the cycle performance of these batteries was inferior. On the other hand, in the examples and reference examples shown in Table 2, since the polarization during discharge is small and the oxygen absorption ability is excellent, it is considered that excellent cycle performance was exhibited. As described above, when the hydrogen storage alloy electrode according to the battery of the present invention is applied in use that requires charging or discharging at a high rate such as charging at 1 ItA or discharging at 2 to 4 ItA, the remarkable cycle performance is obtained. Showing improvement.
なお、参考例２の場合は、実施例と同様、水素吸蔵合金粉末の表面に空洞がなく、連続した表面層が形成され、該水素吸蔵合金粉末を用いた水素吸蔵合金電極ニッケル水素蓄電池の特性も表２に示すように良好であったが、水素吸蔵合金粉末の浸漬処理に長時間を要すること、ＬｉＯＨが析出しないように浸漬液の濾別を昇温した状態で行う必要があるなど実用状の欠点がある。 In the case of Reference Example 2, as in the example, the hydrogen storage alloy powder has no cavities on the surface, a continuous surface layer is formed, and the characteristics of the hydrogen storage alloy electrode nickel-metal hydride storage battery using the hydrogen storage alloy powder Although it was good as shown in Table 2, it took a long time to immerse the hydrogen-absorbing alloy powder, and it was necessary to separate the immersion liquid in a heated state so that LiOH did not precipitate. There is a fault of the shape.
本発明に係る水素吸蔵合金電極の製造方法において、前記Ｌ ｉ Ｏ Ｈ 単独またはＬ ｉ Ｏ Ｈ とＮ ａ Ｏ Ｈ の両方を含むアルカリ水溶液からなる処理液は、Ｋ Ｏ Ｈ の混入を完全に排除するものではなない。アルカリ水溶液に含まれるＫ Ｏ Ｈ が約０ ． １ Ｍ ／ ｄｍ 3 未満であれば水素吸蔵合金の表面に空洞がなく連続したＮ ｉ とＣ ｏ 主成分とする表面層が形成される。また、詳細な説明を省くが、合金粉末を、Ｋ Ｏ Ｈ を主たるアルカリ成分として含むアルカリ水溶液に浸漬するに際して水溶液の温度を比較例１ ３ 、１ ４ に比べてもっと高温（ 例えば沸点近傍） にした場合、表面層の形成スピードは増大するものの、生成した表面層は繋がっておらず、海島状またはまだら状であって、このような水素吸蔵合金粉末を適用した水素吸蔵合金電極は、高率放電性能が極めて悪いことが判った。
The method of manufacturing a hydrogen-absorbing alloy electrode according to the present invention, the L i O H alone or consists of an alkaline aqueous solution containing both L i O H and N a O H treatment liquid, complete mixing of K O H It is not something that is excluded. The K O H contained in the alkaline aqueous solution is about 0. If it is less than 1 M / dm 3 , there is no void on the surface of the hydrogen storage alloy, and a continuous surface layer composed mainly of Ni and Co is formed. Although not described in detail, when the alloy powder is immersed in an aqueous alkali
（酸化防止被膜の有無および製造方法の影響）
（実施例１７）
前記実施例２において、第５工程において水素吸蔵合金に被膜コート処理を施した後、得られた水素吸蔵合金粉末を大気中で１４日間放置した。それ以外は実施例２と同じとした。放置後の水素吸蔵合金粉末を実施例水素吸蔵合金粉末１７、水素吸蔵合金電極を実施例水素吸蔵合金電極１７、ニッケル水素蓄電池を実施例電池１７とした。
(Presence or absence of antioxidant coating and influence of manufacturing method)
(Example 17)
In Example 2, after the coating film was applied to the hydrogen storage alloy in the fifth step, the obtained hydrogen storage alloy powder was left in the atmosphere for 14 days. Otherwise, it was the same as Example 2. The hydrogen storage alloy powder after standing as Example hydrogen storage alloy powder 17, the hydrogen storage alloy electrode as Example hydrogen storage alloy electrode 17, and the nickel hydrogen storage battery as Example battery 17.
（比較例１８）
第１工程でのアルカリ溶液浸漬処理において反応浴を撹拌しなかったこと以外は実施例２と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１８、水素吸蔵合金電極を比較例水素吸蔵合金電極１８、ニッケル水素蓄電池を比較例電池１８とした。
（比較例１９）
第２工程での希土類を主な成分とする水酸化物の分離する工程を実施しなかったこと以外は実施例２と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末１９、水素吸蔵合金電極を比較例水素吸蔵合金電極１９、ニッケル水素蓄電池を比較例電池１９とした。
（比較例２０）
第３工程で、処理後の合金を洗浄する工程を実施しなかったこと以外は実施例２と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末２０、水素吸蔵合金電極を比較例水素吸蔵合金電極２０、ニッケル水素蓄電池を比較例電池２０とした。
（比較例２１）
第４工程での水素を脱離する工程を実施しなかったこと以外は実施例２と同様にして得られた水素吸蔵合金粉末を比較例水素吸蔵合金粉末２１、水素吸蔵合金電極を比較例水素吸蔵合金電極２１、ニッケル水素蓄電池を比較例電池２１とした。
（比較例２２）
前記実施例２において第４工程の後乾燥状態にある水素吸蔵合金粉末を大気中で１４日間放置した。該水素吸蔵合金粉末を比較例水素吸蔵合金粉末２２とする。該比較例水素吸蔵合金粉末２２を用いて実施例２の第５工程同様にしてペーストを作製し、該ペーストをを集電体常に塗布乾燥後プレス、裁断して所定の厚さ、大きさを持つ水素吸蔵合金電極をを作製し、該水素吸蔵合金電極を用いてニッケル水素蓄電池を作製した。該水素吸蔵合金電極を比較例水素吸蔵合金電極２２、ニッケル水素蓄電池を比較例電池２２とした。
実施例２、実施例１７、比較例１８〜２２の試験結果を表３に示す。
(Comparative Example 18)
The hydrogen storage alloy powder obtained in the same manner as in Example 2 except that the reaction bath was not stirred in the alkaline solution immersion treatment in the first step was used as a comparative example. The hydrogen storage alloy powder 18 and the hydrogen storage alloy electrode as a comparative example. The hydrogen storage alloy electrode 18 and the nickel metal hydride storage battery were used as the comparative battery 18.
(Comparative Example 19)
The hydrogen storage alloy powder obtained in the same manner as in Example 2 except that the step of separating the hydroxide containing the rare earth as the main component in the second step was not performed was compared with the comparative example hydrogen storage alloy powder 19, The hydrogen storage alloy electrode was used as a comparative example hydrogen storage alloy electrode 19, and the nickel hydrogen storage battery was used as a comparative example battery 19.
(Comparative Example 20)
In the third step, the hydrogen storage alloy powder obtained in the same manner as in Example 2 was compared with the hydrogen
(Comparative Example 21)
The hydrogen storage alloy powder obtained in the same manner as in Example 2 except that the step of desorbing hydrogen in the fourth step was not performed was used as the comparative example hydrogen storage alloy powder 21 and the hydrogen storage alloy electrode as the comparative example hydrogen. The storage alloy electrode 21 and the nickel metal hydride storage battery were used as the comparative example battery 21.
(Comparative Example 22)
In Example 2, the hydrogen storage alloy powder in the dry state after the fourth step was left in the atmosphere for 14 days. The hydrogen storage alloy powder is referred to as Comparative Example hydrogen storage alloy powder 22. The comparative example hydrogen storage alloy powder 22 was used to prepare a paste in the same manner as in the fifth step of Example 2, and the paste was always applied to the current collector, dried, pressed and cut to a predetermined thickness and size. A hydrogen storage alloy electrode was prepared, and a nickel metal hydride storage battery was manufactured using the hydrogen storage alloy electrode. The hydrogen storage alloy electrode was referred to as Comparative Example hydrogen storage alloy electrode 22, and the nickel hydrogen storage battery was referred to as Comparative Example battery 22.
Table 3 shows the test results of Example 2, Example 17, and Comparative Examples 18-22.
表３に示すとおり、比較例１８と実施例２を比較すると、攪拌が無い比較例１８は、５℃、４ＩｔＡ放電による高率放電特性に優れない。比較例１８の高率放電特性が優れないのは、表面処理によって形成された希土類やマンガン、アルミニウムなどの水酸化物が合金表面を覆い、粉体抵抗を増大させた為であると考えられる。また、合金がこれら水酸化物により結着し、大きな２次粒子を形成するため、塗工がし難くなる不具合が生じた。さらに、処理液の温度分布が不均一となり、表面層の形成が均質でないことも影響していると考えられる。このため、合金粉末の浸漬処理時には処理液を攪拌することが好ましい。また、これら水酸化物により、過充電時の負極での酸素ガス吸収が低下し、電池外に酸素ガスや電解液が漏れることが寿命の低下の原因であると考えられる。
As shown in Table 3, when Comparative Example 18 and Example 2 are compared, Comparative Example 18 without stirring is not excellent in high rate discharge characteristics by 5 ° C., 4 ItA discharge. The reason why the high rate discharge characteristic of Comparative Example 18 is not excellent is considered to be that the rare earth, manganese, aluminum, and other hydroxides formed by the surface treatment covered the alloy surface and increased the powder resistance. Moreover, since the alloy is bound by these hydroxides to form large secondary particles, there is a problem that coating becomes difficult. Further, it is considered that the temperature distribution of the treatment liquid becomes non-uniform and the formation of the surface layer is not uniform. For this reason, it is preferable to stir the treatment liquid during the immersion treatment of the alloy powder. Moreover, it is considered that the oxygen gas absorption at the negative electrode during overcharge decreases due to these hydroxides, and the leakage of oxygen gas and electrolyte solution outside the battery causes the lifetime to decrease.
（浸漬処理後の水酸化物の除去および洗浄の効果）
比較例１９、２０は、実施例２を比較して、５℃、４ＩｔＡ放電による高率放電性能に優れない。水酸化物を分離する工程を省いた比較例１９場合は、水素吸蔵合金粉末の表面に希土類やマンガン、アルミニウムなどの水酸化物が残存したことによって、合金粉末の粉体抵抗（電気抵抗）が増大したことによると考えられる。洗浄工程を省いた比較例２０の場合は、残存するアルカリによって水素吸蔵合金粉末が腐蝕したために性能が低下したものと考えられる。
(Effects of hydroxide removal and cleaning after immersion treatment)
Comparative Examples 19 and 20 are not excellent in the high rate discharge performance by 5 ° C., 4 ItA discharge as compared with Example 2. In the case of Comparative Example 19 in which the step of separating the hydroxide was omitted, the powder resistance (electric resistance) of the alloy powder was reduced because hydroxides such as rare earth, manganese, and aluminum remained on the surface of the hydrogen storage alloy powder. This is thought to be due to the increase. In the case of Comparative Example 20 in which the washing process was omitted, it is considered that the performance was lowered because the hydrogen storage alloy powder was corroded by the remaining alkali.
（浸漬処理後の水素吸蔵合金粉末からの水素脱離効果）
過酸化水素による水素脱離をしない場合、加圧濾過後のウェット状態にある水素吸蔵合金粉末を空気に触れさせると水素吸蔵合金粉末の温度が８０℃を超えるまで発熱した。これは、水素吸蔵合金粉末が酸化されたためであると考えられる。このためか、比較例２１の５℃、２ＩｔＡ放電による放電性能にも優れない。また、サイクル寿命性能にも優れない。この理由は明らかではないが、水素吸蔵合金粉末が酸化によって変質したこと、一旦酸化された水素吸蔵合金粉末が電池内において再度活性化されたために、充電リザーブが減少したためであると考えられる。
(Hydrogen desorption effect from hydrogen storage alloy powder after immersion treatment)
When hydrogen desorption by hydrogen peroxide was not performed, when the hydrogen storage alloy powder in a wet state after pressure filtration was exposed to air, heat was generated until the temperature of the hydrogen storage alloy powder exceeded 80 ° C. This is considered to be because the hydrogen storage alloy powder was oxidized. For this reason, it is not excellent in the discharge performance of Comparative Example 21 by 5 ° C. and 2 ItA discharge. In addition, the cycle life performance is not excellent. The reason for this is not clear, but it is considered that the charge storage was reduced because the hydrogen storage alloy powder was altered by oxidation and the oxidized hydrogen storage alloy powder was reactivated in the battery.
（水素吸蔵合金表面の被膜形成効果その１、高率放電性能）
実施例２と実施例１７を比較すると、５℃、２ＩｔＡ放電、５℃、４ＩｔＡ放電共に放電容量の差は極小さい。他方、詳細な記述は省いたが、酸化防止被膜を形成していない水素吸蔵合金粉末を適用し、水素吸蔵合金粉末を大気中で放置しないで電池に組み込んだ場合には実施例２に劣らない放電性能を示したが、比較例２２の場合は、殆ど放電できなかった。比較例２２の場合は、水素吸蔵合金粉末の表面に酸化防止機能を持つ被膜を形成していないために、水素吸蔵合金粉末を大気中に放置した間に水素吸蔵合金が酸化されて合金粉末の内部まで変質したことと、表面に酸化物や水酸化物の被膜が生成して電極反応が阻害されるために放電特性が大きく低下したものと考えられる。このように、水素吸蔵合金粉末表面を、酸化防止被膜でコートすることによって大気に接触した場合の化学的安定性が向上して取り扱いが容易となるので好ましい。また、酸化防止用被膜として、前記ＣＭＣやＨＰＭＣなどのセルロースに替えてキサンタンガム、ウエランガムなどの多糖類やＰＶＡを適用した場合、あるいは前記セルロース、多糖類、ＰＶＡの何れかを混合使用した場合にもセルロースと同様の効果が認められた。
(Effect of forming a film on the surface of the hydrogen storage alloy,
When Example 2 and Example 17 are compared, the difference in discharge capacity is very small for 5 ° C., 2 ItA discharge, 5 ° C., and 4 ItA discharge. On the other hand, although a detailed description is omitted, when a hydrogen storage alloy powder not formed with an antioxidant coating is applied and the hydrogen storage alloy powder is incorporated in a battery without being left in the atmosphere, it is not inferior to Example 2. Although discharge performance was shown, in the case of Comparative Example 22, almost no discharge was possible. In the case of Comparative Example 22, since a film having an anti-oxidation function was not formed on the surface of the hydrogen storage alloy powder, the hydrogen storage alloy was oxidized while the hydrogen storage alloy powder was left in the atmosphere, and the alloy powder It is considered that the discharge characteristics were greatly deteriorated because the inner surface was altered and an oxide or hydroxide film was formed on the surface to inhibit the electrode reaction. Thus, coating the surface of the hydrogen storage alloy powder with an antioxidant coating improves the chemical stability when it comes into contact with the atmosphere and facilitates handling. In addition, as an antioxidant coating, when a polysaccharide such as xanthan gum or welan gum or PVA is applied instead of cellulose such as CMC or HPMC, or when any one of the cellulose, polysaccharide and PVA is mixed and used An effect similar to that of cellulose was observed.
（水素吸蔵合金表面の被膜形成効果その２、長期放置後の低率放電性能）
前記実施例２と同一の組成を持ち実施例２と同様に酸化防止被膜を形成させた本発明水素吸蔵合金粉末と、前記実施例２と同一の組成であって、酸化防止被膜を形成させてない参考例水素吸蔵合金粉末を常温常湿の大気中で１５日間、３０日間、９０日間放置した。無放置および放置後の水素吸蔵合金粉末を適用して実施例２と同様にして幅３０ｍｍ、長さ３２．５ｍｍ、厚さ０．３３ｍｍ、水素吸蔵合金の充填量から算定される容量が５００ｍＡｈの水素吸蔵合金電極を作製した。該水素吸蔵合金電極を真ん中に、両側に化成後放電させたニッケル電極を配置して、前記同様単板試験用開放形セルを作製した。雰囲気温度２５℃において０．０２ＩｔＡで１２．５時間充電した後０．１ＩｔＡで１２時間充電した。１時間休止後０．２ＩｔＡで水素吸蔵合金電極の参照電極（Ｈｇ／ＨｇＯ）に対する電位が−６００ｍＶに至るまで放電した。２回目以降は０．１ＩｔＡで１２時間充電した後、１時間休止しその後０．２ＩｔＡで水素吸蔵合金電極の参照電極（Ｈｇ／ＨｇＯ）に対する電位が−６００ｍＶに至るまで放電した。該充放電操作を１サイクルとして充放電操作を繰り返し行い５サイクル目の放電容量（ｍＡｈ／ｇ）をもって当該水素吸蔵電極の放電容量とした。
(Effect of forming a film on the surface of the hydrogen storage alloy,
The hydrogen storage alloy powder of the present invention having the same composition as in Example 2 and having an antioxidant coating formed in the same manner as in Example 2, and the same composition as in Example 2 with an antioxidant coating formed. No Reference Example Hydrogen storage alloy powder was allowed to stand for 15 days, 30 days, and 90 days in air at normal temperature and humidity. Applying the hydrogen storage alloy powder left and left untreated, the same as in Example 2, the width is 30 mm, the length is 32.5 mm, the thickness is 0.33 mm, and the capacity calculated from the filling amount of the hydrogen storage alloy is 500 mAh. A hydrogen storage alloy electrode was prepared. In the middle of the hydrogen storage alloy electrode, nickel electrodes discharged after chemical conversion were disposed on both sides, and an open cell for single plate test was produced in the same manner as described above. The battery was charged at 0.02 ItA for 12.5 hours at an ambient temperature of 25 ° C. and then charged at 0.1 ItA for 12 hours. After resting for 1 hour, the battery was discharged at 0.2 ItA until the potential of the hydrogen storage alloy electrode with respect to the reference electrode (Hg / HgO) reached −600 mV. From the second time on, the battery was charged with 0.1 ItA for 12 hours, then rested for 1 hour, and then discharged at 0.2 ItA until the potential of the hydrogen storage alloy electrode with respect to the reference electrode (Hg / HgO) reached −600 mV. The charge / discharge operation was repeated as one cycle, and the discharge capacity (mAh / g) of the fifth cycle was defined as the discharge capacity of the hydrogen storage electrode.
試験結果を図５に示す。図５に示したように、酸化防止被膜を設けていない参考例水素吸蔵合金粉末を適用した水素吸蔵合金電極の放電容量は、無放置もしくは放置期間が３０日いないであれば本発明水素吸蔵合金粉末に比べて劣らない放電容量を有している。しかし、水素吸蔵合金粉末を大気中で９０日間放置すると、本発明水素吸蔵合金粉末の放電容量が殆ど低下していないのに対して、参考例水素吸蔵合金粉末においては放電容量が大幅に低下している。本試験のように０．２ＩｔＡ放電のような低率放電で容量が低下するのは、水素吸蔵合金の変質が粉末の表面に止まらずに内部にまで及んでいることを示唆している。本発明に係る水素吸蔵合金粉末においては、水素吸蔵合金の表面に酸化防止用被膜を形成させることによって、水素吸蔵合金粉末の内部にまで変質が生じるのを防いでいるために、放置後の放電容量の低下が抑制されたものと考えられる。 The test results are shown in FIG. As shown in FIG. 5, the hydrogen storage alloy electrode to which the hydrogen storage alloy electrode to which the reference example hydrogen storage alloy powder having no anti-oxidation coating is applied is not left or has not been left for 30 days. It has a discharge capacity not inferior to that of powder. However, when the hydrogen storage alloy powder is left in the atmosphere for 90 days, the discharge capacity of the hydrogen storage alloy powder of the present invention is hardly reduced, whereas in the reference example hydrogen storage alloy powder, the discharge capacity is significantly reduced. ing. The decrease in capacity at a low rate discharge such as 0.2 ItA discharge as in this test suggests that the alteration of the hydrogen storage alloy extends to the inside without stopping on the surface of the powder. In the hydrogen storage alloy powder according to the present invention, by forming an anti-oxidation coating on the surface of the hydrogen storage alloy, it is possible to prevent the deterioration inside the hydrogen storage alloy powder. It is thought that the decrease in capacity was suppressed.
なお、本発明は上記実施例に記載された活物質の出発原料、製造方法、正極、負極、電解質、セパレータ及び電池形状などに限定されるものではない。 In addition, this invention is not limited to the starting material of the active material described in the said Example, the manufacturing method, a positive electrode, a negative electrode, an electrolyte, a separator, a battery shape, etc.
１ 表面層
４ 空洞
1 Surface layer 4 Cavity
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