JP2018198111A - MANUFACTURING METHOD FOR HYDROGEN STORAGE ALLOY WITH INCREASED SURFACE Ni CONCENTRATION - Google Patents
MANUFACTURING METHOD FOR HYDROGEN STORAGE ALLOY WITH INCREASED SURFACE Ni CONCENTRATION Download PDFInfo
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Abstract
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本発明は、表面のＮｉ濃度が増加された水素吸蔵合金の製造方法に関するものである。 The present invention relates to a method for producing a hydrogen storage alloy having an increased Ni concentration on the surface.
ニッケル金属水素化物電池は、正極活物質として水酸化ニッケルなどのニッケル酸化化合物を有する正極と、負極活物質として水素吸蔵合金を有する負極と、アルカリ金属水溶液からなる電解液とを具備する二次電池である。 A nickel metal hydride battery is a secondary battery comprising a positive electrode having a nickel oxide compound such as nickel hydroxide as a positive electrode active material, a negative electrode having a hydrogen storage alloy as a negative electrode active material, and an electrolyte comprising an aqueous alkali metal solution. It is.
水素吸蔵合金の負極活物質としての性能を向上させるため、様々な技術が提案されている。例えば、特許文献１には、ＣａＣｕ５型の結晶構造を有し、かつ、希土類元素並びにＮｉ、Ｃｏ、Ｍｎ及びＡｌを含む合金からなる水素吸蔵合金を、水酸化ナトリウム水溶液に浸漬処理した後に、水洗する技術が記載されている。そして、同文献には、上述の水素吸蔵合金を水酸化ナトリウム水溶液に浸漬処理することで、水素吸蔵合金はニッケルで被覆されたような状態になることが記載されている。 In order to improve the performance of the hydrogen storage alloy as a negative electrode active material, various techniques have been proposed. For example, in Patent Document 1, a hydrogen storage alloy having a CaCu 5 type crystal structure and made of an alloy containing a rare earth element and Ni, Co, Mn, and Al is immersed in an aqueous sodium hydroxide solution. A technique for washing with water is described. The document describes that the above-described hydrogen storage alloy is immersed in an aqueous sodium hydroxide solution so that the hydrogen storage alloy is in a state of being coated with nickel.
さて、産業界は、優れた特性を示すニッケル金属水素化物電池を切望している。そして、優れた特性を示すニッケル金属水素化物電池を提供するために、負極活物質である水素吸蔵合金に対する優れた製造技術が求められている。 Now, the industry is eager for a nickel metal hydride battery that exhibits excellent characteristics. And in order to provide the nickel metal hydride battery which shows the outstanding characteristic, the outstanding manufacturing technique with respect to the hydrogen storage alloy which is a negative electrode active material is calculated | required.
本発明はかかる事情に鑑みて為されたものであり、水素吸蔵合金の好適な製造方法を提供することを目的とする。 This invention is made | formed in view of this situation, and it aims at providing the suitable manufacturing method of a hydrogen storage alloy.
本発明者は、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金に対して、特許文献１に記載された技術を適用したところ、水酸化ナトリウム水溶液処理後の水洗時の濾過工程において、フィルターの目詰まりが生じたため、同工程が円滑に進行しないとの不具合を知見した。本発明者は、かかる目詰まりの原因は、水酸化ナトリウム水溶液処理で溶出された希土類元素が、中性の水と接触したことで、水酸化物となって析出したことにあると考察した。これらの知見及び考察に基づき、本発明者は本発明を完成させた。 The inventor applied the technique described in Patent Document 1 to an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni. In the filtration process, since the filter was clogged, it was found that the process did not proceed smoothly. The present inventor has considered that the cause of the clogging is that the rare earth element eluted by the treatment with the aqueous sodium hydroxide solution is precipitated as a hydroxide by contacting with neutral water. Based on these findings and considerations, the present inventor has completed the present invention.
本発明の製造方法は、
ａ）希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を、アルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理する工程、
ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程、
を含むことを特徴とする、表面のＮｉ濃度が増加された水素吸蔵合金の製造方法である。
The production method of the present invention comprises:
a) a step of treating an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni with a first alkaline aqueous solution in which an alkali metal hydroxide is dissolved;
b) After the step a), separating the hydrogen storage alloy from the first alkaline aqueous solution and treating with a second alkaline aqueous solution in which an alkali metal hydroxide is dissolved,
Is a method for producing a hydrogen storage alloy having an increased Ni concentration on the surface.
本発明の製造方法においては、ｂ）工程で、水素吸蔵合金の表面から希土類元素を除去するので、希土類元素の水酸化物の析出が抑制される。そのため、ｂ）工程後に水洗を行う場合でも、フィルターの目詰まりは抑制される。 In the production method of the present invention, since the rare earth element is removed from the surface of the hydrogen storage alloy in step b), precipitation of the rare earth element hydroxide is suppressed. Therefore, clogging of the filter is suppressed even when washing with water after step b).
以下に、本発明を実施するための形態を説明する。なお、特に断らない限り、本明細書に記載された数値範囲「ａ〜ｂ」は、下限ａ及び上限ｂをその範囲に含む。そして、これらの上限値及び下限値、ならびに実施例中に列記した数値も含めてそれらを任意に組み合わせることで数値範囲を構成し得る。さらに、これらの数値範囲内から任意に選択した数値を、新たな上限や下限の数値とすることができる。 Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.
本発明の製造方法は、
ａ）希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を、アルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理する工程、
ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程、
を含むことを特徴とする、表面のＮｉ濃度が増加された水素吸蔵合金の製造方法である。
本発明の製造方法を経て製造された水素吸蔵合金を、本発明の水素吸蔵合金といい、本発明の水素吸蔵合金を具備するニッケル金属水素化物電池を、本発明のニッケル金属水素化物電池という。
The production method of the present invention comprises:
a) a step of treating an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni with a first alkaline aqueous solution in which an alkali metal hydroxide is dissolved;
b) After the step a), separating the hydrogen storage alloy from the first alkaline aqueous solution and treating with a second alkaline aqueous solution in which an alkali metal hydroxide is dissolved,
Is a method for producing a hydrogen storage alloy having an increased Ni concentration on the surface.
The hydrogen storage alloy manufactured through the manufacturing method of the present invention is referred to as the hydrogen storage alloy of the present invention, and the nickel metal hydride battery including the hydrogen storage alloy of the present invention is referred to as the nickel metal hydride battery of the present invention.
まず、ａ）希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を、アルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理する工程（以下、単に「ａ）工程」という。）について、説明する。 First, a) a step of treating an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni with a first alkaline aqueous solution in which an alkali metal hydroxide is dissolved (hereinafter simply referred to as “a” step ”). That's it. ) Will be described.
ここで、一般に、ニッケル金属水素化物電池の負極活物質として使用される水素吸蔵合金とは、基本的に、容易に水素と反応するものの、水素の放出能力に劣る金属Ａと、水素と反応しにくいものの、水素の放出能力に優れる金属Ｂとの合金である。一般に、Ａとしては、Ｍｇなどの第２族元素、Ｓｃ、ランタノイドなどの第３族元素、Ｔｉ、Ｚｒなどの第４族元素、Ｖ、Ｔａなどの第５族元素、複数の希土類元素を含有するミッシュメタル（以下、Ｍｍと略すことがある。）、Ｐｄなどを例示できる。また、一般に、Ｂとしては、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｐｔ、Ｃｕ、Ａｇ、Ｍｎ、Ｚｎ、Ａｌなどを例示できる。 Here, in general, a hydrogen storage alloy used as a negative electrode active material of a nickel metal hydride battery basically reacts with hydrogen, but reacts with hydrogen with metal A which is inferior in hydrogen release ability. Although it is difficult, it is an alloy with metal B, which is excellent in hydrogen releasing ability. In general, A includes a Group 2 element such as Mg, a Group 3 element such as Sc and a lanthanoid, a Group 4 element such as Ti and Zr, a Group 5 element such as V and Ta, and a plurality of rare earth elements. Mish metal (hereinafter sometimes abbreviated as Mm), Pd, and the like. In general, examples of B include Fe, Co, Ni, Cr, Pt, Cu, Ag, Mn, Zn, and Al.
ａ）工程に用いられる水素吸蔵合金は、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金である。希土類元素及びＭｇは金属Ａに属し、Ｎｉは金属Ｂに属すると考えられる。希土類元素としては、Ｓｃ、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕを例示できる。ａ）工程に用いられる水素吸蔵合金には、その他の金属元素が存在してもよく、その他の金属元素として、Ｍｎ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｃｒ、Ｐｔ、Ｃｕ、Ａｇ、Ｔｉ、Ｚｒ、Ｖ、Ｔａを例示できる。ａ）工程に用いられる水素吸蔵合金としては、Ｎｉを６０〜７０質量％で含有する水素吸蔵合金が好ましい。 The hydrogen storage alloy used in the step a) is an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni. Rare earth elements and Mg are considered to belong to metal A and Ni belongs to metal B. Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. a) Other metal elements may be present in the hydrogen storage alloy used in the step, and as other metal elements, Mn, Fe, Co, Cu, Zn, Al, Cr, Pt, Cu, Ag, Ti , Zr, V, and Ta. As the hydrogen storage alloy used in the step a), a hydrogen storage alloy containing Ni at 60 to 70% by mass is preferable.
水素吸蔵合金は、粉砕して、一定程度の粒子径に調製した粉末状のものが好ましい。水素吸蔵合金の平均粒子径としては１〜１００μｍの範囲内が好ましく、３〜７０μｍの範囲内がより好ましく、５〜５０μｍの範囲内がさらに好ましく、５〜３０μｍの範囲内が特に好ましく、５〜１５μｍの範囲内が最も好ましい。なお、本明細書において、平均粒子径とは、一般的なレーザー回折式粒度分布計を用いた測定におけるＤ５０の値を意味する。 The hydrogen storage alloy is preferably in the form of a powder that is pulverized and adjusted to a certain particle size. The average particle size of the hydrogen storage alloy is preferably in the range of 1 to 100 μm, more preferably in the range of 3 to 70 μm, further preferably in the range of 5 to 50 μm, particularly preferably in the range of 5 to 30 μm, Most preferably within the range of 15 μm. In the present specification, the average particle diameter means a value of D 50 in the measurement using a conventional laser diffraction particle size distribution meter.
ａ）工程で水素吸蔵合金をアルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理すると、アルカリ水溶液に対して溶解性の高い希土類元素が水素吸蔵合金の表面から溶出することになる。ここで、Ｎｉはアルカリ水溶液に対して溶解性が低いため、結果的に、水素吸蔵合金の表面のＮｉ濃度は、水素吸蔵合金の内部と比較して高くなる。以下、水素吸蔵合金において、Ｎｉ濃度が内部と比較して高い部分を、Ｎｉ濃縮層という。Ｎｉ濃縮層の存在に因り、負極活物質の性能が向上すると考えられる。 In the step a), when the hydrogen storage alloy is treated with the first alkaline aqueous solution in which the alkali metal hydroxide is dissolved, the rare earth element having high solubility in the alkaline aqueous solution is eluted from the surface of the hydrogen storage alloy. Here, since Ni has low solubility in an alkaline aqueous solution, as a result, the Ni concentration on the surface of the hydrogen storage alloy is higher than that in the hydrogen storage alloy. Hereinafter, in the hydrogen storage alloy, a portion where the Ni concentration is higher than the inside is referred to as a Ni enriched layer. It is considered that the performance of the negative electrode active material is improved due to the presence of the Ni concentrated layer.
アルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示でき、中でも、水酸化ナトリウムが好ましい。第１アルカリ水溶液として水酸化ナトリウム水溶液を用いることで、第１アルカリ水溶液として水酸化リチウムや水酸化カリウムを用いる場合と比較して、本発明のニッケル金属水素化物電池の電池特性が好適化する場合がある。 Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Of these, sodium hydroxide is preferable. When the battery characteristics of the nickel metal hydride battery of the present invention are optimized by using an aqueous sodium hydroxide solution as the first alkaline aqueous solution, compared to the case of using lithium hydroxide or potassium hydroxide as the first alkaline aqueous solution. There is.
第１アルカリ水溶液としては強塩基のものが好ましい。第１アルカリ水溶液におけるアルカリ金属の水酸化物の濃度として、１０〜６０質量％、２０〜５５質量％、３０〜５０質量％、４０〜５０質量％を例示できる。 The first alkaline aqueous solution is preferably a strong base. As a density | concentration of the hydroxide of the alkali metal in 1st alkali aqueous solution, 10-60 mass%, 20-55 mass%, 30-50 mass%, 40-50 mass% can be illustrated.
ａ）工程は、水素吸蔵合金を第１アルカリ水溶液に浸ける方法で行うのが好ましい。その際には、撹拌条件下で行うのが好ましく、また、加熱条件下で行うのが好ましい。加熱温度の範囲としては、５０〜１５０℃、７０〜１４０℃、９０〜１３０℃を例示できる。加熱時間は、第１アルカリ水溶液の濃度や加熱温度に応じて適宜決定すればよいが、０．１〜１０時間、０．２〜５時間、０．５〜３時間を例示できる。 The step a) is preferably performed by a method in which the hydrogen storage alloy is immersed in the first alkaline aqueous solution. In that case, it is preferable to carry out on stirring conditions, and it is preferable to carry out on heating conditions. Examples of the heating temperature range include 50 to 150 ° C, 70 to 140 ° C, and 90 to 130 ° C. Although what is necessary is just to determine a heating time suitably according to the density | concentration and heating temperature of 1st alkaline aqueous solution, 0.1 to 10 hours, 0.2 to 5 hours, and 0.5 to 3 hours can be illustrated.
水素吸蔵合金と第１アルカリ水溶液の量の関係は、質量比で１：０．５〜１：１０が好ましく、１：０．７〜１：５がより好ましく、１：０．９〜１：３がさらに好ましい。第１アルカリ水溶液の量が過少であれば、水素吸蔵合金の表面にＮｉ濃縮層が十分に形成されない場合があり、他方、第１アルカリ水溶液の量が過多であれば、コスト面で不利になる。 The relationship between the amount of the hydrogen storage alloy and the first alkaline aqueous solution is preferably 1: 0.5 to 1:10, more preferably 1: 0.7 to 1: 5, and 1: 0.9 to 1: 3 is more preferable. If the amount of the first alkaline aqueous solution is too small, the Ni concentrated layer may not be sufficiently formed on the surface of the hydrogen storage alloy. On the other hand, if the amount of the first alkaline aqueous solution is excessive, it is disadvantageous in terms of cost. .
次に、ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程（以下、単に「ｂ）工程」という。）について、説明する。 Next, after step b) a), the hydrogen storage alloy is separated from the first alkaline aqueous solution and treated with a second alkaline aqueous solution in which an alkali metal hydroxide is dissolved (hereinafter, simply referred to as “b) step”. ) Will be described.
ａ）工程が終了した時点における第１アルカリ水溶液には、水素吸蔵合金から溶出した希土類元素が存在する。そして、当該希土類元素は、第１アルカリ水溶液と水素吸蔵合金の分離時に、水素吸蔵合金の表面に、希土類元素の水酸化物として付着し得る。
ｂ）工程は、第１アルカリ水溶液から分離した水素吸蔵合金の表面に付着した、希土類元素の水酸化物を、第２アルカリ水溶液で除去する工程であるといえる。希土類元素の水酸化物は中性条件下においては析出するものの、塩基性水溶液には溶解しやすいとの性質を示す。ｂ）工程は、この性質を利用したものである。
a) The rare earth element eluted from the hydrogen storage alloy is present in the first alkaline aqueous solution at the end of the step. And the said rare earth element can adhere as a hydroxide of rare earth elements on the surface of a hydrogen storage alloy at the time of isolation | separation of 1st alkaline aqueous solution and a hydrogen storage alloy.
Step b) can be said to be a step of removing the rare earth element hydroxide adhering to the surface of the hydrogen storage alloy separated from the first alkaline aqueous solution with the second alkaline aqueous solution. Although rare earth element hydroxide precipitates under neutral conditions, it exhibits the property of being easily dissolved in a basic aqueous solution. The step b) utilizes this property.
第１アルカリ水溶液から水素吸蔵合金を分離する方法としては、濾過や遠心分離が好ましく、特に吸引濾過が好ましい。水素吸蔵合金を第２アルカリ水溶液で処理する方法としては、水素吸蔵合金を第２アルカリ水溶液に浸ける方法、第２アルカリ水溶液を水素吸蔵合金に浴びせる方法を例示できる。上述した濾過に引き続き又は濾過を行いつつ、第２アルカリ水溶液を水素吸蔵合金に浴びせる方法を選択するのが合理的である。 As a method for separating the hydrogen storage alloy from the first alkaline aqueous solution, filtration and centrifugation are preferable, and suction filtration is particularly preferable. Examples of the method for treating the hydrogen storage alloy with the second alkaline aqueous solution include a method in which the hydrogen storage alloy is immersed in the second alkaline aqueous solution, and a method in which the second alkaline aqueous solution is bathed in the hydrogen storage alloy. It is reasonable to select a method in which the second alkaline aqueous solution is bathed in the hydrogen storage alloy following or after the filtration described above.
第２アルカリ水溶液に溶解したアルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示でき、中でも、水酸化ナトリウムが好ましい。 Examples of the alkali metal hydroxide dissolved in the second alkaline aqueous solution include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and among these, sodium hydroxide is preferable.
また、第１アルカリ水溶液のアルカリ金属の水酸化物の濃度Ｃ１と、第２アルカリ水溶液のアルカリ金属の水酸化物の濃度Ｃ２の関係が、Ｃ１＞Ｃ２を満足する条件でｂ）工程を行うのが好ましい。濃度が低いアルカリ水溶液は粘度が低いため、Ｃ１＞Ｃ２を満足する条件においては、ｂ）工程の作業が円滑に進行する。第２アルカリ水溶液におけるアルカリ金属の水酸化物の濃度として、０．０１〜１０質量％、０．０３〜５質量％、０．０５〜１質量％、０．１〜０．５質量％を例示できる。 Further, b under the conditions and concentration C 1 of alkali metal hydroxide in the first aqueous alkaline solution, the relationship of the concentration C 2 of an alkali metal hydroxide in the second aqueous alkaline solution, which satisfies C 1> C 2) It is preferable to carry out the process. Since the aqueous alkaline solution having a low concentration has a low viscosity, the operation in the step b) proceeds smoothly under the conditions satisfying C 1 > C 2 . Examples of the alkali metal hydroxide concentration in the second aqueous alkali solution include 0.01 to 10% by mass, 0.03 to 5% by mass, 0.05 to 1% by mass, and 0.1 to 0.5% by mass. it can.
製造コストなどの観点から、ｂ）工程はａ）工程よりも低温条件下で行うのが好ましい。ｂ）工程の温度範囲としては、０〜１００℃、１０〜７０℃、２０〜５０℃を例示できる。ｂ）工程の温度は、水素吸蔵合金の温度で規定してもよいし、第２アルカリ水溶液の温度で規定してもよい。 From the viewpoint of production cost and the like, the step b) is preferably performed under a lower temperature condition than the step a). b) As a temperature range of a process, 0-100 degreeC, 10-70 degreeC, 20-50 degreeC can be illustrated. The temperature of b) process may be prescribed | regulated with the temperature of a hydrogen storage alloy, and may be prescribed | regulated with the temperature of 2nd alkaline aqueous solution.
水素吸蔵合金と第２アルカリ水溶液の量の関係は、質量比で１：０．５〜１：５０が好ましく、１：１〜１：３０がより好ましく、１：１．５〜１：１０がさらに好ましい。第２アルカリ水溶液の量が過少であれば、希土類元素の水酸化物の除去が不十分となる場合があり、他方、第２アルカリ水溶液の量が過多であれば、コスト面で不利になる。 The relationship between the amount of the hydrogen storage alloy and the second alkaline aqueous solution is preferably 1: 0.5 to 1:50, more preferably 1: 1 to 1:30, and more preferably 1: 1.5 to 1:10 in terms of mass ratio. Further preferred. If the amount of the second alkaline aqueous solution is too small, the removal of the rare earth element hydroxide may be insufficient. On the other hand, if the amount of the second alkaline aqueous solution is excessive, it is disadvantageous in terms of cost.
ｂ）工程においては、第２アルカリ水溶液での処理に引き続き、水素吸蔵合金に対する水での洗浄を行ってもよい。水での洗浄を行うことで水素吸蔵合金の表面に付着する第２アルカリ水溶液を除去できる。水での洗浄時における水素吸蔵合金と水の量の関係は、質量比で１：１〜１：５０が好ましく、１：２〜１：３０がより好ましく、１：３〜１：１０がさらに好ましい。 In the step b), the hydrogen storage alloy may be washed with water following the treatment with the second alkaline aqueous solution. By performing the washing with water, the second alkaline aqueous solution attached to the surface of the hydrogen storage alloy can be removed. The relationship between the hydrogen storage alloy and the amount of water at the time of washing with water is preferably 1: 1 to 1:50, more preferably 1: 2 to 1:30, and more preferably 1: 3 to 1:10 in terms of mass ratio. preferable.
さらに、ｃ）ｂ）工程後の水素吸蔵合金の表面を酸化する工程（以下、単に「ｃ）工程」という。）を実施してもよい。敢えてｃ）工程を実施することで、以後の工程における水素吸蔵合金の急激な表面酸化による発熱を防止することができる。 Furthermore, the step of oxidizing the surface of the hydrogen storage alloy after step c) b) (hereinafter simply referred to as “step c”). ) May be carried out. By carrying out the step c), heat generation due to rapid surface oxidation of the hydrogen storage alloy in the subsequent steps can be prevented.
ｃ）工程としては、空気中に水素吸蔵合金を曝して、空気中の酸素で酸化させる方法でもよいし、水素吸蔵合金を過酸化水素などの酸化物と接触させて酸化させる方法でもよい。ただし、いずれの方法においても、水素吸蔵合金の過剰な発熱を抑制するために、水素吸蔵合金を冷却しながら実施するのが好ましい。具体的には、水素吸蔵合金に水を浴びせて水素吸蔵合金を冷却しながら実施するか、水中に水素吸蔵合金を配置した上で、又は、過酸化水素などの酸化物の水溶液中に水素吸蔵合金を配置した上で実施するのが好ましい。上述したｂ）工程における第２アルカリ水溶液での処理後に実施され得る水素吸蔵合金に対する水での洗浄を、大気下で実施することで、ｃ）工程としてもよい。 The step c) may be a method of exposing the hydrogen storage alloy to the air and oxidizing it with oxygen in the air, or a method of oxidizing the hydrogen storage alloy by contacting with an oxide such as hydrogen peroxide. However, in any method, in order to suppress excessive heat generation of the hydrogen storage alloy, it is preferable to carry out the cooling while cooling the hydrogen storage alloy. Specifically, it is carried out while bathing the hydrogen storage alloy in water and cooling the hydrogen storage alloy, or after placing the hydrogen storage alloy in water, or in an aqueous solution of an oxide such as hydrogen peroxide. It is preferable to carry out after placing the alloy. It is good also as c) process by implementing the washing | cleaning with water with respect to the hydrogen storage alloy which can be implemented after the process by the 2nd aqueous alkali solution in b) mentioned above in air | atmosphere.
本発明の水素吸蔵合金は、本発明の製造方法で製造される水素吸蔵合金であり、表面のＮｉ濃度が、内部のＮｉ濃度と比較して増加された水素吸蔵合金である。内部のＮｉ濃度とは、ａ）工程で用いる処理前の水素吸蔵合金におけるＮｉ濃度と同義である。また、本発明の水素吸蔵合金は、表面にＮｉ濃縮層を具備する水素吸蔵合金と表現することもできる。 The hydrogen storage alloy of the present invention is a hydrogen storage alloy manufactured by the manufacturing method of the present invention, and is a hydrogen storage alloy in which the Ni concentration on the surface is increased compared to the internal Ni concentration. The internal Ni concentration is synonymous with the Ni concentration in the hydrogen storage alloy before treatment used in step a). The hydrogen storage alloy of the present invention can also be expressed as a hydrogen storage alloy having a Ni enriched layer on the surface.
Ｎｉ濃縮層の厚みとしては、５〜２００ｎｍ、１０〜１５０ｎｍ、３０〜１００ｎｍを例示できる。Ｎｉ濃縮層の厚みは、本発明の水素吸蔵合金の粒子の断面を各種の電子顕微鏡で観察して確認できる。 As thickness of Ni concentration layer, 5-200 nm, 10-150 nm, and 30-100 nm can be illustrated. The thickness of the Ni enriched layer can be confirmed by observing the cross section of the particles of the hydrogen storage alloy of the present invention with various electron microscopes.
本発明の製造方法においては、まず、ａ）工程で、アルカリ水溶液に溶解しやすい希土類元素が溶出するため、ａ）工程後の水素吸蔵合金の表面にはＮｉ濃縮層が形成される。次に、ｂ）工程で、水素吸蔵合金の表面に付着した、希土類元素の水酸化物を、第２アルカリ水溶液で除去するため、ｂ）工程後の水素吸蔵合金の表面のＮｉ濃度はさらに増加するといえる。 In the production method of the present invention, since a rare earth element that is easily dissolved in an alkaline aqueous solution is eluted in step a), a Ni concentrated layer is formed on the surface of the hydrogen storage alloy after step a). Next, since the rare earth element hydroxide adhering to the surface of the hydrogen storage alloy in step b) is removed with the second alkaline aqueous solution, the Ni concentration on the surface of the hydrogen storage alloy after step b) further increases. That's right.
実際に、本発明者が本発明の水素吸蔵合金の表面をＸ線光電子分光法で測定したところ、ａ）工程で用いた処理前の水素吸蔵合金の組成よりも、大幅にＮｉ比率が高くなっていることが確認された。そこで、本発明の水素吸蔵合金の一態様として、以下のものを把握できる。 Actually, when the inventor measured the surface of the hydrogen storage alloy of the present invention by X-ray photoelectron spectroscopy, the Ni ratio was significantly higher than the composition of the hydrogen storage alloy before treatment used in step a). It was confirmed that Then, the following can be grasped | ascertained as one aspect | mode of the hydrogen storage alloy of this invention.
本発明の水素吸蔵合金の一態様は、Ｌａ、Ｍｇ及びＮｉを含有し、Ｎｉを６０〜７０質量％で含有するＡ２Ｂ７型の水素吸蔵合金であって、内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値が１．３以上であることを特徴とする。
ここで、内部のＮｉ／Ｌａ元素比とは、本発明の水素吸蔵合金の内部、例えば本発明の水素吸蔵合金の粒子の中心におけるＮｉ／Ｌａ元素比を意味し、また、内部のＮｉ／Ｌａ元素比とは、ａ）工程で用いる処理前の水素吸蔵合金におけるＮｉ／Ｌａ元素比と同義である。
One aspect of the hydrogen storage alloy of the present invention is an A 2 B 7 type hydrogen storage alloy containing La, Mg, and Ni, and containing Ni at 60 to 70% by mass, and has an internal Ni / La element ratio. The value of the Ni / La element ratio of the surface with respect to is 1.3 or more.
Here, the internal Ni / La element ratio means the Ni / La element ratio in the interior of the hydrogen storage alloy of the present invention, for example, the center of the particles of the hydrogen storage alloy of the present invention. The element ratio is synonymous with the Ni / La element ratio in the hydrogen storage alloy before treatment used in step a).
内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値としては、１．３〜２、１．３１〜１．５、１．３４〜１．４の範囲を例示できる。内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値が大きいほど、表面からの希土類元素の除去が好適に行われたことを意味する。 Examples of the value of the Ni / La element ratio on the surface with respect to the internal Ni / La element ratio include ranges of 1.3 to 2, 1.31 to 1.5, and 1.34 to 1.4. The larger the value of the Ni / La element ratio on the surface relative to the internal Ni / La element ratio, the better the removal of the rare earth elements from the surface.
本発明の水素吸蔵合金の平均粒子径としては１〜１００μｍの範囲内が好ましく、３〜７０μｍの範囲内がより好ましく、５〜５０μｍの範囲内がさらに好ましく、５〜３０μｍの範囲内が特に好ましく、５〜１５μｍの範囲内が最も好ましい。 The average particle size of the hydrogen storage alloy of the present invention is preferably in the range of 1 to 100 μm, more preferably in the range of 3 to 70 μm, further preferably in the range of 5 to 50 μm, and particularly preferably in the range of 5 to 30 μm. The most preferable range is 5 to 15 μm.
本発明のニッケル金属水素化物電池用負極は、本発明の水素吸蔵合金を具備する。また、本発明のニッケル金属水素化物電池は、本発明のニッケル金属水素化物電池用負極を具備する。具体的には、本発明のニッケル金属水素化物電池は、正極と本発明のニッケル金属水素化物電池用負極と電解液とセパレータを具備する。 The negative electrode for nickel metal hydride batteries of the present invention comprises the hydrogen storage alloy of the present invention. The nickel metal hydride battery of the present invention includes the negative electrode for a nickel metal hydride battery of the present invention. Specifically, the nickel metal hydride battery of the present invention includes a positive electrode, a negative electrode for a nickel metal hydride battery of the present invention, an electrolyte, and a separator.
正極は、集電体と集電体の表面に形成された正極活物質層とを含む。本発明のニッケル金属水素化物電池用負極は、集電体と、集電体の表面に形成された本発明の水素吸蔵合金を含む負極活物質層とを具備する。以下、正極の構成から説明するが、負極の構成と重複するものについては、正極との限定を付さずに説明する。 The positive electrode includes a current collector and a positive electrode active material layer formed on the surface of the current collector. The negative electrode for nickel metal hydride batteries of the present invention comprises a current collector and a negative electrode active material layer containing the hydrogen storage alloy of the present invention formed on the surface of the current collector. Hereinafter, although it demonstrates from the structure of a positive electrode, about the thing which overlaps with the structure of a negative electrode, it demonstrates without attaching | limiting with a positive electrode.
集電体は、ニッケル金属水素化物電池の放電又は充電の間、電極に電流を流し続けるための化学的に不活性な電子伝導体をいう。集電体の材料は、使用する活物質に適した電圧に耐え得る金属であれば特に制限はない。集電体の材料としては、銀、銅、金、アルミニウム、タングステン、コバルト、亜鉛、ニッケル、鉄、白金、錫、インジウム、チタン、ルテニウム、タンタル、クロム、モリブデンから選ばれる少なくとも一種、並びにステンレス鋼などの金属材料を例示することができる。集電体は公知の保護層で被覆されていても良い。集電体の表面を公知の方法で処理したものを集電体として用いても良い。集電体の材料としては、ニッケル、又は、ニッケルめっきを施した金属材料が好ましい。 The current collector refers to a chemically inert electronic conductor that keeps current flowing through the electrodes during the discharge or charging of the nickel metal hydride battery. The material of the current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. The current collector material is at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector. As a material for the current collector, nickel or a metal material plated with nickel is preferable.
集電体は箔、シート、フィルム、線状、棒状、メッシュ、スポンジ状などの形態をとることができる。集電体が箔、シート、フィルム形態の場合は、その厚みが１μｍ〜１００μｍの範囲内であることが好ましい。 The current collector can take the form of a foil, a sheet, a film, a line, a rod, a mesh, a sponge, and the like. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.
正極活物質層は、正極活物質を含み、必要に応じて正極添加剤、結着剤及び導電助剤を含む。 The positive electrode active material layer includes a positive electrode active material, and includes a positive electrode additive, a binder, and a conductive additive as necessary.
正極活物質としては、ニッケル金属水素化物電池の正極活物質として用いられるものであれば限定されない。具体的な正極活物質として、水酸化ニッケル、金属をドープした水酸化ニッケルを例示できる。水酸化ニッケルにドープする金属として、マグネシウム、カルシウムなどの第２族元素、コバルト、ロジウム、イリジウムなどの第９族元素、亜鉛、カドミウムなどの第１２族元素を例示できる。 The positive electrode active material is not limited as long as it is used as a positive electrode active material for a nickel metal hydride battery. Specific examples of the positive electrode active material include nickel hydroxide and nickel hydroxide doped with metal. Examples of the metal doped into nickel hydroxide include Group 2 elements such as magnesium and calcium, Group 9 elements such as cobalt, rhodium and iridium, and Group 12 elements such as zinc and cadmium.
正極活物質の表面は公知の方法で処理されてもよい。正極活物質は粉末状態が好ましく、また、その平均粒子径としては１〜１００μｍの範囲内が好ましく、３〜５０μｍの範囲内がより好ましく、５〜３０μｍの範囲内がさらに好ましい。 The surface of the positive electrode active material may be treated by a known method. The positive electrode active material is preferably in a powder state, and the average particle size thereof is preferably in the range of 1 to 100 μm, more preferably in the range of 3 to 50 μm, and still more preferably in the range of 5 to 30 μm.
正極活物質層には、正極活物質が正極活物質層全体の質量に対して、７５〜９９質量％で含まれるのが好ましく、８０〜９７質量％で含まれるのがより好ましく、８５〜９５質量％で含まれるのがさらに好ましい。 The positive electrode active material layer preferably contains 75 to 99% by mass, more preferably 80 to 97% by mass, and more preferably 85 to 95% by mass of the positive electrode active material with respect to the total mass of the positive electrode active material layer. More preferably, it is contained in mass%.
正極添加剤は、ニッケル金属水素化物電池の電池特性を向上させるために正極に添加されるものである。正極添加剤としては、ニッケル金属水素化物電池の正極添加剤として用いられるものであれば限定されない。具体的な正極添加剤として、Ｎｂ２Ｏ５などのニオブ化合物、ＷＯ２、ＷＯ３、Ｌｉ２ＷＯ４、Ｎａ２ＷＯ４及びＫ２ＷＯ４などのタングステン化合物、Ｙｂ２Ｏ３などのイッテルビウム化合物、ＴｉＯ２などのチタン化合物、Ｙ２Ｏ３などのイットリウム化合物、ＺｎＯなどの亜鉛化合物、ＣａＯ、Ｃａ（ＯＨ）２及びＣａＦ２などのカルシウム化合物、並びに、その他の希土類酸化物を例示できる。 The positive electrode additive is added to the positive electrode in order to improve the battery characteristics of the nickel metal hydride battery. The positive electrode additive is not limited as long as it is used as a positive electrode additive for nickel metal hydride batteries. Specific positive electrode additives include niobium compounds such as Nb 2 O 5 , tungsten compounds such as WO 2 , WO 3 , Li 2 WO 4 , Na 2 WO 4 and K 2 WO 4, and ytterbium compounds such as Yb 2 O 3 . And titanium compounds such as TiO 2 , yttrium compounds such as Y 2 O 3 , zinc compounds such as ZnO, calcium compounds such as CaO, Ca (OH) 2 and CaF 2 , and other rare earth oxides.
正極活物質層には、正極添加剤が正極活物質層全体の質量に対して、０．１〜１０質量％で含まれるのが好ましく、０．５〜５質量％で含まれるのがより好ましい。 The positive electrode active material layer preferably contains the positive electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the total mass of the positive electrode active material layer. .
結着剤は活物質などを集電体の表面に繋ぎ止める役割を果たすものである。結着剤としては、ニッケル金属水素化物電池の電極用結着剤として用いられるものであれば限定されない。具体的な結着剤として、ポリフッ化ビニリデン、ポリテトラフルオロエチレン及びフッ素ゴムなどの含フッ素樹脂、ポリプロピレン及びポリエチレンなどのポリオレフィン樹脂、ポリイミド及びポリアミドイミドなどのイミド系樹脂、カルボキシメチルセルロース、メチルセルロース及びヒドロキシプロピルセルロースなどのセルロース誘導体、スチレンブタジエンゴムなどの共重合体、並びに、（メタ）アクリル酸誘導体をモノマー単位として含有する、ポリアクリル酸、ポリアクリル酸エステル、ポリメタクリル酸及びポリメタクリル酸エステルなどの（メタ）アクリル系樹脂を例示できる。 The binder plays a role of binding an active material or the like to the surface of the current collector. The binder is not limited as long as it is used as a binder for electrodes of nickel metal hydride batteries. Specific binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, polyolefin resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and hydroxypropyl. Cellulose derivatives such as cellulose, copolymers such as styrene butadiene rubber, and polyacrylic acid, polyacrylic acid ester, polymethacrylic acid and polymethacrylic acid ester containing (meth) acrylic acid derivatives as monomer units ( An example is a (meth) acrylic resin.
活物質層には、結着剤が活物質層全体の質量に対して、０．１〜１５質量％で含まれるのが好ましく、１〜１０質量％で含まれるのがより好ましく、２〜７質量％で含まれるのがさらに好ましい。結着剤が少なすぎると電極の成形性が低下し、また、結着剤が多すぎると電極のエネルギー密度が低くなるためである。 The active material layer preferably contains 0.1 to 15% by mass, more preferably 1 to 10% by mass, and more preferably 2 to 7% by mass of the binder based on the total mass of the active material layer. More preferably, it is contained in mass%. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.
導電助剤は、電極の導電性を高めるために添加される。そのため、導電助剤は、電極の導電性が不足する場合に任意に加えればよく、電極の導電性が十分に優れている場合には加えなくても良い。導電助剤は、粉末状態で活物質層に添加されてもよいし、活物質粒子の表面を被覆した状態で用いられてもよい。導電助剤としては化学的に不活性な電子伝導体であれば良い。具体的な導電材としては、コバルト、ニッケル、銅などの金属、コバルト酸化物などの金属酸化物、及びコバルト水酸化物などの金属水酸化物、カーボンブラック、黒鉛、炭素繊維などの炭素材料が例示される。 The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be added to the active material layer in a powder state, or may be used in a state where the surfaces of the active material particles are coated. The conductive auxiliary agent may be an electronic conductor that is chemically inert. Specific conductive materials include metals such as cobalt, nickel, copper, metal oxides such as cobalt oxide, metal hydroxides such as cobalt hydroxide, carbon materials such as carbon black, graphite, and carbon fiber. Illustrated.
活物質層には、導電助剤が活物質層全体の質量に対して、０．１〜２０質量％で含まれるのが好ましい。正極活物質層には、導電助剤が正極活物質層全体の質量に対して、１〜１５質量％で含まれるのが好ましく、３〜１２質量％で含まれるのがより好ましく、５〜１０質量％で含まれるのがさらに好ましい。負極活物質層には、導電助剤が負極活物質層全体の質量に対して、０．１〜５質量％で含まれるのが好ましく、０．２〜３質量％で含まれるのがより好ましく、０．３〜１質量％で含まれるのがさらに好ましい。導電助剤が少なすぎると効率のよい導電パスを形成できず、また、導電助剤が多すぎると活物質層の成形性が悪くなるとともに電極のエネルギー密度が低くなるためである。 The active material layer preferably contains the conductive additive in an amount of 0.1 to 20% by mass with respect to the mass of the entire active material layer. The positive electrode active material layer preferably contains 1 to 15% by mass, more preferably 3 to 12% by mass, more preferably 5 to 10% by mass of the conductive additive relative to the total mass of the positive electrode active material layer. More preferably, it is contained in mass%. The negative electrode active material layer preferably contains 0.1 to 5% by mass, more preferably 0.2 to 3% by mass of the conductive additive with respect to the total mass of the negative electrode active material layer. More preferably, the content is 0.3 to 1% by mass. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.
負極活物質層は、負極活物質として本発明の水素吸蔵合金を含み、必要に応じて負極添加剤、結着剤及び導電助剤を含む。結着剤及び導電助剤については上述したとおりである。 A negative electrode active material layer contains the hydrogen storage alloy of this invention as a negative electrode active material, and contains a negative electrode additive, a binder, and a conductive support agent as needed. The binder and the conductive aid are as described above.
負極活物質層には、負極活物質が負極活物質層全体の質量に対して、８５〜９９質量％で含まれるのが好ましく、９０〜９８質量％で含まれるのがより好ましい。 The negative electrode active material layer preferably contains the negative electrode active material in an amount of 85 to 99% by mass, more preferably 90 to 98% by mass with respect to the mass of the entire negative electrode active material layer.
負極添加剤は、ニッケル金属水素化物電池の電池特性を向上させるために負極に添加されるものである。負極添加剤としては、ニッケル金属水素化物電池の負極添加剤として用いられるものであれば限定されない。具体的な負極添加剤として、ＣｅＦ３及びＹＦ３などの希土類元素のフッ化物、Ｂｉ２Ｏ３及びＢｉＦ３などのビスマス化合物、Ｉｎ２Ｏ３及びＩｎＦ３などのインジウム化合物、並びに、正極添加剤として例示した化合物を挙げることができる。 The negative electrode additive is added to the negative electrode in order to improve the battery characteristics of the nickel metal hydride battery. The negative electrode additive is not limited as long as it is used as a negative electrode additive for nickel metal hydride batteries. Specific negative electrode additives include rare earth fluorides such as CeF 3 and YF 3 , bismuth compounds such as Bi 2 O 3 and BiF 3 , indium compounds such as In 2 O 3 and InF 3 , and positive electrode additives Can be mentioned as examples.
負極活物質層には、負極添加剤が負極活物質層全体の質量に対して、０．１〜１０質量％で含まれるのが好ましく、０．５〜５質量％で含まれるのがより好ましい。 The negative electrode active material layer preferably contains the negative electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the mass of the entire negative electrode active material layer. .
集電体の表面に活物質層を形成させるには、ロールコート法、ダイコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いて、集電体の表面に活物質を塗布すればよい。具体的には、活物質、溶剤、並びに必要に応じて結着剤、導電助剤及び添加剤を混合してスラリーにしてから、当該スラリーを集電体の表面に塗布後、乾燥する。溶剤としては、Ｎ−メチル−２−ピロリドン、メタノール、メチルイソブチルケトン、水を例示できる。電極密度を高めるべく、乾燥後のものを圧縮しても良い。 In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, an active material, a solvent, and if necessary, a binder, a conductive additive and an additive are mixed to form a slurry, and the slurry is applied to the surface of the current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.
電解液はアルカリ金属の水酸化物が溶解した水溶液である。アルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示できる。電解液には、１種類のアルカリ金属の水酸化物を含んでいてもよいし、複数種類のアルカリ金属の水酸化物を含んでいてもよい。電解液における、アルカリ金属の水酸化物の濃度としては、２〜１０ｍｏｌ／Ｌが好ましく、３〜９ｍｏｌ／Ｌがより好ましく、４〜８ｍｏｌ／Ｌがさらに好ましい。 The electrolytic solution is an aqueous solution in which an alkali metal hydroxide is dissolved. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. The electrolytic solution may contain one kind of alkali metal hydroxide or may contain plural kinds of alkali metal hydroxides. The concentration of the alkali metal hydroxide in the electrolytic solution is preferably 2 to 10 mol / L, more preferably 3 to 9 mol / L, and even more preferably 4 to 8 mol / L.
電解液にアルカリ金属の水酸化物として水酸化リチウムのみを用いる場合には、水酸化リチウムの濃度としては、１．５〜５ｍｏｌ／Ｌが好ましく、２〜５ｍｏｌ／Ｌがより好ましく、３〜５ｍｏｌ／Ｌがさらに好ましい。電解液にアルカリ金属の水酸化物として水酸化ナトリウムのみを用いる場合には、水酸化ナトリウムの濃度としては、１．５〜１５ｍｏｌ／Ｌが好ましく、３〜１０ｍｏｌ／Ｌがより好ましく、４〜８ｍｏｌ／Ｌがさらに好ましい。電解液にアルカリ金属の水酸化物として水酸化カリウムのみを用いる場合には、水酸化カリウムの濃度としては、１．５〜１５ｍｏｌ／Ｌが好ましく、３〜１０ｍｏｌ／Ｌがより好ましく、４〜８ｍｏｌ／Ｌがさらに好ましい。 When only lithium hydroxide is used as the alkali metal hydroxide in the electrolyte, the concentration of lithium hydroxide is preferably 1.5 to 5 mol / L, more preferably 2 to 5 mol / L, and more preferably 3 to 5 mol. / L is more preferable. When only sodium hydroxide is used as the alkali metal hydroxide in the electrolyte, the concentration of sodium hydroxide is preferably 1.5 to 15 mol / L, more preferably 3 to 10 mol / L, and 4 to 8 mol. / L is more preferable. When only potassium hydroxide is used as the alkali metal hydroxide in the electrolytic solution, the concentration of potassium hydroxide is preferably 1.5 to 15 mol / L, more preferably 3 to 10 mol / L, and 4 to 8 mol. / L is more preferable.
電解液には、ニッケル金属水素化物電池用電解液に採用される公知の添加剤が添加されていてもよい。 The electrolyte may be added with known additives that are employed in electrolytes for nickel metal hydride batteries.
セパレータは、正極と負極とを隔離して、両極の接触による短絡を防止しつつ、電解液の貯留空間及び通路を提供するものである。セパレータとしては、公知のものを採用すればよく、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン、ポリイミド、ポリアミド、ポリアラミド（Ａｒｏｍａｔｉｃ ｐｏｌｙａｍｉｄｅ）、ポリエステル、ポリアクリロニトリル等の合成樹脂、セルロース、アミロース等の多糖類、フィブロイン、ケラチン、リグニン、スベリン等の天然高分子、セラミックスなどの電気絶縁性材料を１種若しくは複数用いた多孔体、不織布、織布などを挙げることができる。また、セパレータは多層構造としてもよい。 The separator separates the positive electrode and the negative electrode, and provides a storage space and a passage for the electrolyte while preventing a short circuit due to contact between the two electrodes. A known separator may be employed, such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile or other synthetic resin, cellulose, amylose or other polysaccharide, fibroin. And porous materials, nonwoven fabrics, woven fabrics, and the like using one or more electrical insulating materials such as natural polymers such as keratin, lignin, and suberin, and ceramics. The separator may have a multilayer structure.
セパレータは、表面に親水化処理が施されていることが好ましい。親水化処理としては、スルホン化処理、コロナ処理、フッ素ガス処理、プラズマ処理を例示できる。 The separator is preferably subjected to a hydrophilic treatment on the surface. Examples of the hydrophilic treatment include sulfonation treatment, corona treatment, fluorine gas treatment, and plasma treatment.
本発明のニッケル金属水素化物電池の具体的な製造方法について述べる。
正極及び負極に必要に応じてセパレータを挟装させ電極体とする。正極の集電体及び負極の集電体から外部に通ずる正極端子及び負極端子までを、集電用リード等を用いて接続した後に、電極体に電解液を加えてニッケル金属水素化物電池とする。
A specific method for producing the nickel metal hydride battery of the present invention will be described.
If necessary, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using current collecting leads, etc., an electrolyte is added to the electrode body to form a nickel metal hydride battery. .
本発明のニッケル金属水素化物電池の形状は特に限定されるものでなく、角型、円筒型、コイン型、ラミネート型等、種々の形状を採用することができる。 The shape of the nickel metal hydride battery of the present invention is not particularly limited, and various shapes such as a square shape, a cylindrical shape, a coin shape, and a laminate shape can be adopted.
本発明のニッケル金属水素化物電池は、車両に搭載してもよい。車両は、その動力源の全部あるいは一部にニッケル金属水素化物電池による電気エネルギーを使用している車両であればよく、例えば、電気車両、ハイブリッド車両などであるとよい。車両にニッケル金属水素化物電池を搭載する場合には、ニッケル金属水素化物電池を複数直列に接続して組電池とするとよい。ニッケル金属水素化物電池を搭載する機器としては、車両以外にも、パーソナルコンピュータ、携帯通信機器など、電池で駆動される各種の家電製品、オフィス機器、産業機器などが挙げられる。さらに、本発明のニッケル金属水素化物電池は、風力発電、太陽光発電、水力発電その他電力系統の蓄電装置及び電力平滑化装置、船舶等の動力及び／又は補機類の電力供給源、航空機、宇宙船等の動力及び／又は補機類の電力供給源、電気を動力源に用いない車両の補助用電源、移動式の家庭用ロボットの電源、システムバックアップ用電源、無停電電源装置の電源、電動車両用充電ステーションなどにおいて充電に必要な電力を一時蓄える蓄電装置に用いてもよい。 The nickel metal hydride battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy generated by a nickel metal hydride battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a nickel metal hydride battery is mounted on a vehicle, a plurality of nickel metal hydride batteries may be connected in series to form an assembled battery. Examples of the device on which the nickel metal hydride battery is mounted include various home electric appliances, office devices, industrial devices, and the like driven by batteries, such as personal computers and portable communication devices, in addition to vehicles. Furthermore, the nickel metal hydride battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power for power sources such as ships, and / or power supply sources for auxiliary equipment, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.
以上、本発明の実施形態を説明したが、本発明は、上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.
以下に、実施例及び比較例などを示し、本発明をより具体的に説明する。なお、本発明は、これらの実施例によって限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples.
（実施例１）
Ｌａなどの希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を粉砕して、平均粒子径が２５μｍである水素吸蔵合金の粉末を準備した。
ａ）工程
第１アルカリ水溶液として、水酸化ナトリウムを４８質量％で含有する水酸化ナトリウム水溶液を準備した。
撹拌条件下、第１アルカリ水溶液５０質量部に水素吸蔵合金の粉末５０質量部を加えて懸濁液とした。この懸濁液を１１０℃に加熱して１時間保持し、その後、室温に冷却した。
Example 1
An A 2 B 7 type hydrogen storage alloy containing rare earth elements such as La, Mg and Ni was pulverized to prepare a hydrogen storage alloy powder having an average particle size of 25 μm.
a) Step A sodium hydroxide aqueous solution containing 48% by mass of sodium hydroxide was prepared as the first alkaline aqueous solution.
Under stirring conditions, 50 parts by mass of hydrogen storage alloy powder was added to 50 parts by mass of the first alkaline aqueous solution to form a suspension. The suspension was heated to 110 ° C. and held for 1 hour and then cooled to room temperature.
ｂ）工程
第２アルカリ水溶液として、水酸化ナトリウムを０．４質量％で含有する水酸化ナトリウム水溶液を準備した。
ａ）工程終了後の懸濁液を吸引濾過して、第１アルカリ水溶液から水素吸蔵合金を分離した。吸引濾過を継続した状態で、水素吸蔵合金の上から第２アルカリ水溶液５０質量部を注ぎ、水素吸蔵合金を洗浄した。
b) Step As a second alkaline aqueous solution, a sodium hydroxide aqueous solution containing 0.4% by mass of sodium hydroxide was prepared.
a) The suspension after completion of the step was subjected to suction filtration to separate the hydrogen storage alloy from the first alkaline aqueous solution. With the suction filtration continued, 50 parts by mass of the second alkaline aqueous solution was poured from above the hydrogen storage alloy to wash the hydrogen storage alloy.
ｃ）工程
ｂ）工程の吸引濾過を継続した状態で、水素吸蔵合金の上から水３００質量部を注ぎ、水素吸蔵合金を水洗した。水洗は、濾過のフィルターとして用いた濾紙が目詰まりを起こすこと無く、円滑に実施された。水洗後の水素吸蔵合金を実施例１の水素吸蔵合金とした。ｃ）工程は大気中で実施されたため、水素吸蔵合金の表面は、空気に含まれる酸素によって、酸化される。
c) Process In the state which continued the suction filtration of b) process, 300 mass parts of water was poured from on the hydrogen storage alloy, and the hydrogen storage alloy was washed with water. The water washing was carried out smoothly without causing clogging of the filter paper used as a filter for filtration. The hydrogen storage alloy after washing with water was used as the hydrogen storage alloy of Example 1. c) Since the step was carried out in the atmosphere, the surface of the hydrogen storage alloy was oxidized by oxygen contained in the air.
以下のとおり、実施例１のニッケル金属水素化物電池用負極及びニッケル金属水素化物電池を製造した。 The negative electrode for nickel metal hydride batteries and the nickel metal hydride battery of Example 1 were manufactured as follows.
正極活物質として水酸化ニッケル粉末を９３．３質量部、導電助剤としてコバルト粉末を３質量部、結着剤としてアクリル系樹脂エマルションを固形分として２質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、正極添加剤としてＹ２Ｏ３を１質量部、及び適量のイオン交換水を混合して、スラリーを製造した。正極用集電体として厚み２０μｍのニッケル箔を準備した。このニッケル箔の表面に、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスして、集電体上に正極活物質層が形成された正極を製造した。 93.3 parts by mass of nickel hydroxide powder as a positive electrode active material, 3 parts by mass of cobalt powder as a conductive additive, 2 parts by mass of an acrylic resin emulsion as a binder as a solid content, and 0 of carboxymethyl cellulose as a binder 0.7 parts by mass, 1 part by mass of Y 2 O 3 as a positive electrode additive, and an appropriate amount of ion-exchanged water were mixed to produce a slurry. A nickel foil having a thickness of 20 μm was prepared as a positive electrode current collector. The slurry was applied in a film form on the surface of the nickel foil. The nickel foil coated with the slurry was dried to remove water, and then the nickel foil was pressed to produce a positive electrode having a positive electrode active material layer formed on a current collector.
負極活物質として、実施例１の水素吸蔵合金を９７．８質量部、結着剤としてアクリル系樹脂エマルションを固形分として１．５質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、及び、適量のイオン交換水を混合して、スラリーを製造した。負極用集電体として厚み２０μｍのニッケル箔を準備した。このニッケル箔の表面に、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスして、集電体上に負極活物質層が形成された実施例１のニッケル金属水素化物電池用負極を製造した。 As a negative electrode active material, 97.8 parts by mass of the hydrogen storage alloy of Example 1, 1.5 parts by mass as a solid content of an acrylic resin emulsion as a binder, 0.7 parts by mass of carboxymethyl cellulose as a binder, And an appropriate amount of ion-exchanged water was mixed to produce a slurry. A nickel foil having a thickness of 20 μm was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the nickel foil. The nickel foil to which the slurry was applied was dried to remove water, and then the nickel foil was pressed to form the negative electrode for the nickel metal hydride battery of Example 1 in which the negative electrode active material layer was formed on the current collector. Manufactured.
電解液として、水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液を準備した。 As an electrolytic solution, an aqueous solution having a potassium hydroxide concentration of 5.5 mol / L, a sodium hydroxide concentration of 0.5 mol / L, and a lithium hydroxide concentration of 0.5 mol / L is prepared. did.
セパレータとして、スルホン化処理が施されたポリオレフィン繊維製不織布を準備した。正極と実施例１のニッケル金属水素化物電池用負極とでセパレータを挟持し、極板群とした。樹脂製の筐体に、極板群を配置して、さらに上記電解液を注入し、筐体を密閉することで、実施例１のニッケル金属水素化物電池を製造した。 As the separator, a nonwoven fabric made of polyolefin fiber subjected to sulfonation treatment was prepared. A separator was sandwiched between the positive electrode and the negative electrode for the nickel metal hydride battery of Example 1 to form an electrode plate group. A nickel metal hydride battery of Example 1 was manufactured by placing an electrode plate group in a resin casing, injecting the electrolyte, and sealing the casing.
（実施例２）
ａ）工程において、平均粒子径が８μｍである水素吸蔵合金の粉末を準備し、これを用いた以外は、実施例１と同様の方法で、実施例２の水素吸蔵合金、ニッケル金属水素化物電池用負極、及びニッケル金属水素化物電池を製造した。
実施例２におけるｃ）工程の水洗も、濾過のフィルターが目詰まりを起こすこと無く、円滑に実施された。
(Example 2)
In the step a), a hydrogen storage alloy powder and nickel metal hydride battery of Example 2 are prepared in the same manner as in Example 1 except that a hydrogen storage alloy powder having an average particle size of 8 μm is prepared and used. Negative electrode and nickel metal hydride battery were manufactured.
The water washing in step c) in Example 2 was also carried out smoothly without causing clogging of the filter for filtration.
（比較例１）
実施例１で準備した平均粒子径が２５μｍである水素吸蔵合金の粉末を、ａ）工程、ｂ）工程及びｃ）工程を行うことなく、そのままで比較例１の水素吸蔵合金とした。以後、実施例１と同様の方法で、比較例１のニッケル金属水素化物電池用負極、及びニッケル金属水素化物電池を製造した。
(Comparative Example 1)
The hydrogen storage alloy powder having an average particle size of 25 μm prepared in Example 1 was used as the hydrogen storage alloy of Comparative Example 1 as it was without performing the steps a), b) and c). Thereafter, the negative electrode for nickel metal hydride battery and the nickel metal hydride battery of Comparative Example 1 were manufactured in the same manner as in Example 1.
（比較例２）
ｂ）工程を行わなかった以外は、実施例１と同様の方法で、比較例２の水素吸蔵合金、ニッケル金属水素化物電池用負極、及びニッケル金属水素化物電池を製造した。
比較例２におけるｃ）工程の水洗においては、濾過のフィルターが目詰まりを起こしたため、ｃ）工程の時間が著しく長くなった。
実施例１及び実施例２のｃ）工程においては水洗を円滑に実施できたことから、ｂ）工程に因り、水素吸蔵合金の製造方法が好適化されたといえる。本発明の製造方法の技術的意義が裏付けられたといえる。
(Comparative Example 2)
b) A hydrogen storage alloy, a negative electrode for nickel metal hydride battery, and a nickel metal hydride battery of Comparative Example 2 were produced in the same manner as in Example 1 except that the step was not performed.
In the water washing in step c) in Comparative Example 2, the filter was clogged, and the time in step c) was significantly increased.
In the c) step of Example 1 and Example 2, since the water washing could be carried out smoothly, it can be said that the method for producing the hydrogen storage alloy was optimized due to the b) step. It can be said that the technical significance of the production method of the present invention was supported.
（評価例１）
各実施例及び各比較例の水素吸蔵合金の表面をＸ線光電子分光法で測定し、表面のＮｉ／Ｌａ元素比を算出した。また、対内部値として、比較例１の水素吸蔵合金のＮｉ／Ｌａ元素比に対する各水素吸蔵合金の表面のＮｉ／Ｌａ元素比の値を算出した。これらの結果を、各水素吸蔵合金の特徴とともに、表１に示す。
(Evaluation example 1)
The surface of the hydrogen storage alloy of each example and each comparative example was measured by X-ray photoelectron spectroscopy, and the Ni / La element ratio of the surface was calculated. Moreover, the value of Ni / La element ratio of the surface of each hydrogen storage alloy with respect to Ni / La element ratio of the hydrogen storage alloy of the comparative example 1 was computed as an internal value. These results are shown in Table 1 together with the characteristics of each hydrogen storage alloy.
表１の結果から、ａ）工程を経ることで、水素吸蔵合金の表面からＬａなどの溶解性の高い元素が溶出して、水素吸蔵合金の表面にＮｉ濃縮層が形成されることがわかる。さらに、実施例１と比較例２の結果から、ｂ）工程を経ることで、水素吸蔵合金の表面からのＬａのさらなる除去が行われたといえる。好適なＮｉ濃縮層の形成の点からも、本発明の製造方法の有用性が裏付けられたといえる。
また、実施例１と実施例２の結果から、粒子径の小さい水素吸蔵合金を用いた方が、Ｎｉ濃縮層のＮｉの濃度が高くなることがわかる。
From the results of Table 1, it can be seen that through the step a), a highly soluble element such as La elutes from the surface of the hydrogen storage alloy and a Ni concentrated layer is formed on the surface of the hydrogen storage alloy. Furthermore, from the results of Example 1 and Comparative Example 2, it can be said that further removal of La from the surface of the hydrogen storage alloy was performed through the step b). It can be said that the usefulness of the production method of the present invention was supported also from the viewpoint of forming a suitable Ni enriched layer.
Further, the results of Example 1 and Example 2 show that the Ni concentration in the Ni concentrated layer is higher when the hydrogen storage alloy having a smaller particle size is used.
（評価例２）
実施例１及び実施例２の水素吸蔵合金の粒子の断面を、電界放射型走査型電子顕微鏡（ＦＥ−ＳＥＭ）を用いて観察した。
実施例１の水素吸蔵合金の粒子におけるＮｉ濃縮層の厚みは、１０〜１００ｎｍ程度と観察され、実施例２の水素吸蔵合金の粒子におけるＮｉ濃縮層の厚みは、８０〜１００ｎｍ程度と観察された。
(Evaluation example 2)
The cross section of the particles of the hydrogen storage alloy of Example 1 and Example 2 was observed using a field emission scanning electron microscope (FE-SEM).
The thickness of the Ni-enriched layer in the hydrogen storage alloy particles of Example 1 was observed to be about 10 to 100 nm, and the thickness of the Ni-enriched layer in the hydrogen storage alloy particles of Example 2 was observed to be about 80 to 100 nm. .
（評価例３）
ＳＯＣ（Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ）６０％に調整した実施例１、実施例２、比較例１及び比較例２のニッケル金属水素化物電池について、０℃及び２５℃の条件下、１Ｃレートで５秒間放電させた。放電前後の電圧変化量及び放電時の電流値から、オームの法則に基づき、各放電抵抗を算出した。結果を表２に示す。
(Evaluation example 3)
The nickel metal hydride batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 adjusted to SOC (State of Charge) 60% were discharged at 1C rate for 5 seconds under the conditions of 0 ° C. and 25 ° C. It was. Each discharge resistance was calculated based on Ohm's law from the amount of voltage change before and after discharge and the current value during discharge. The results are shown in Table 2.
表２から、いずれの温度条件下においても、実施例のニッケル金属水素化物電池の放電抵抗は、比較例のニッケル金属水素化物電池の放電抵抗よりも、低いことがわかる。評価例３の結果からも、本発明の製造方法の有用性が裏付けられたといえる。
また、評価例１及び評価例３の結果から、水素吸蔵合金の表面のＮｉ／Ｌａ元素比が高い方が、電池特性が優れる傾向にあるといえる。
From Table 2, it can be seen that the discharge resistance of the nickel metal hydride battery of the example is lower than that of the nickel metal hydride battery of the comparative example under any temperature condition. From the result of Evaluation Example 3, it can be said that the usefulness of the production method of the present invention was supported.
Moreover, it can be said from the results of Evaluation Examples 1 and 3 that the battery characteristics tend to be superior when the Ni / La element ratio on the surface of the hydrogen storage alloy is higher.
Claims (11)
ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程、
を含むことを特徴とする、表面のＮｉ濃度が増加された水素吸蔵合金の製造方法。 a) a step of treating an A 2 B 7 type hydrogen storage alloy containing rare earth elements, Mg and Ni with a first alkaline aqueous solution in which an alkali metal hydroxide is dissolved;
b) After the step a), separating the hydrogen storage alloy from the first alkaline aqueous solution and treating with a second alkaline aqueous solution in which an alkali metal hydroxide is dissolved,
A method for producing a hydrogen storage alloy with an increased Ni concentration on the surface, comprising:
を含む請求項１〜５のいずれか１項に記載の水素吸蔵合金の製造方法。 c) b) a step of oxidizing the surface of the hydrogen storage alloy after the step;
The manufacturing method of the hydrogen storage alloy of any one of Claims 1-5 containing this.
内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値が１．３以上であることを特徴とする水素吸蔵合金。 A 2 B 7 type hydrogen storage alloy containing La, Mg and Ni and containing Ni at 60 to 70% by mass,
A hydrogen storage alloy characterized in that the value of the Ni / La element ratio on the surface with respect to the internal Ni / La element ratio is 1.3 or more.
A nickel metal hydride battery comprising the negative electrode for a nickel metal hydride battery according to claim 10.
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| JP2010007177A (en) * | 2008-05-30 | 2010-01-14 | Panasonic Corp | Hydrogen storage alloy powder, surface treatment method therefor, negative electrode for alkali storage battery, and alkali storage battery |
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