JP5455297B2 - Nickel metal hydride storage battery and manufacturing method thereof - Google Patents
Nickel metal hydride storage battery and manufacturing method thereof Download PDFInfo
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Description
本発明は、水素吸蔵合金を負極材料に使用してなるニッケル水素蓄電池その製造方法に関する。 The present invention relates to a nickel-metal hydride storage battery using a hydrogen storage alloy as a negative electrode material and a method for producing the same.
水素吸蔵合金を負極材料に使用したニッケル水素蓄電池は、（ａ）高容量であること、（ｂ）過充電及び過放電に強いこと、（ｃ）高効率充放電が可能であること、（ｄ）クリーンであることなどの特長を有しており、種々の用途において使用されている。 Nickel metal hydride storage batteries using a hydrogen storage alloy as a negative electrode material are (a) high capacity, (b) strong against overcharge and overdischarge, (c) capable of high-efficiency charge / discharge, (d ) It has features such as cleanliness and is used in various applications.
このようなニッケル水素蓄電池の負極材料としては、これまでＣａＣｕ5型結晶構造を有するＡＢ5系希土類−Ｎｉ系合金が実用化されており、優れたサイクル特性を発揮することが知られている。
しかしながら、該ＡＢ5系希土類−Ｎｉ系合金を電極材料として用いた場合、該放電容量は約３００ｍＡｈ／ｇが概ね上限となっており、該合金を用いた放電容量の更なる改善は困難な状況となっている。
As a negative electrode material for such a nickel metal hydride storage battery, an AB 5 rare earth-Ni alloy having a CaCu 5 type crystal structure has been put into practical use and is known to exhibit excellent cycle characteristics.
However, when the AB 5 rare earth-Ni alloy is used as an electrode material, the discharge capacity is generally about 300 mAh / g, and it is difficult to further improve the discharge capacity using the alloy. It has become.
一方、新たな水素吸蔵合金として希土類−Ｍｇ−Ｎｉ系合金が注目されており、このような希土類−Ｍｇ−Ｎｉ系合金を電極材として使用することにより、ＡＢ5系合金を上回る放電容量が得られることが報告されている（特許文献１等）。 On the other hand, attention has been focused on rare -Mg-Ni-based alloy as a new hydrogen absorbing alloy, the use of such a rare earth--Mg-Ni based alloy as an electrode material, the discharge capacity obtained above the AB 5 type alloy (Patent Document 1 etc.).
しかしながら、従来の希土類−Ｍｇ−Ｎｉ系合金を用いたニッケル水素蓄電池では、水素の吸蔵及び放出（即ち、充電及び放電）を繰り返し行った場合に合金の水素吸蔵容量が低下しやすく、ＡＢ5系希土類−Ｎｉ系合金を電極材料として用いた場合と比べてサイクル特性が悪いという問題がある。 However, in a nickel-metal hydride storage battery using a conventional rare earth-Mg-Ni alloy, the hydrogen storage capacity of the alloy is likely to decrease when hydrogen storage and release (that is, charging and discharging) are repeated, and the AB 5 system There is a problem that cycle characteristics are poor as compared with the case where a rare earth-Ni alloy is used as an electrode material.
本発明は、上記のような従来技術の問題点に鑑み、放電容量が大きく且つサイクル特性にも優れたニッケル水素蓄電池を提供することを一の目的とする。 An object of the present invention is to provide a nickel-metal hydride storage battery having a large discharge capacity and excellent cycle characteristics in view of the above-described problems of the prior art.
上記課題を解決するべく、本発明者らが鋭意研究を重ねた結果、希土類−Ｍｇ−Ｎｉ系合金の表面部分にＳｎ原子及びＭｇ原子を含むように構成した水素吸蔵合金粒子を負極の材料として使用することにより、希土類−Ｍｇ−Ｎｉ系合金を用いたニッケル水素蓄電池のサイクル特性を顕著に改善しうることを見い出し、本発明を完成するに至った。 As a result of intensive studies by the present inventors to solve the above-mentioned problems, hydrogen storage alloy particles configured to include Sn atoms and Mg atoms in the surface portion of the rare earth-Mg-Ni alloy are used as the material of the negative electrode. It has been found that the cycle characteristics of nickel-metal hydride storage batteries using rare earth-Mg-Ni alloys can be remarkably improved by using them, and the present invention has been completed.
即ち、本発明は、Ｌａ−Ｍｇ−Ｎｉ系の水素吸蔵合金粒子を含む負極を備えたニッケル水素蓄電池であって、前記水素吸蔵合金粒子の組成は、Ｌｎ1-xＭｇx（Ｎｉ1-yＴy）z（ここで、Ｌｎは希土類元素からなる群より選ばれた少なくとも１種の元素であってＬａを希土類元素の郡内でその過半数の割合で含み、ＴはＣｏ、Ｍｎ、Ａｌ、Ｃｒ、Ｆｅ、ＣｕおよびＺｒからなる群より選ばれた少なくとも１種の元素、ｘ、ｙおよびｚは、それぞれ０．０７≦ｘ≦０．３、０．０２≦ｙ≦０．２５、および３≦ｚ≦４を満たす数である。）であり、前記負極にはＳｎ原子を含む添加剤が、Ｓｎ金属に換算して、前記水素吸蔵合金１００質量部に対して０．４４質量部以上１．７６質量部以下含まれ、前記水素吸蔵合金粒子の表面部分には、Ｓｎ原子およびＭｇ原子が含まれることを特徴とするニッケル水素蓄電池を提供するものである。 That is, the present invention is a nickel-metal hydride storage battery having a negative electrode containing La—Mg—Ni-based hydrogen storage alloy particles, wherein the composition of the hydrogen storage alloy particles is Ln 1-x Mg x (Ni 1-y T y ) z (where Ln is at least one element selected from the group consisting of rare earth elements and contains La in a majority proportion within the group of rare earth elements , and T is Co, Mn, Al, At least one element selected from the group consisting of Cr, Fe, Cu, and Zr, x, y, and z are 0.07 ≦ x ≦ 0.3, 0.02 ≦ y ≦ 0.25, and 3 respectively. ≦ z ≦ 4.) In the negative electrode, an additive containing Sn atoms is 0.44 parts by mass or more and 100 parts by mass with respect to 100 parts by mass of the hydrogen storage alloy in terms of Sn metal. .76 parts by mass or less, and the surface portion of the hydrogen storage alloy particles includes Sn. A nickel-metal hydride storage battery comprising atoms and Mg atoms is provided.
尚、本発明において、Ｌａ−Ｍｇ−Ｎｉ系の水素吸蔵合金粒子とは、希土類元素、Ｍｇ、およびＮｉを含み、且つ、Ｎｉ原子の数が希土類元素の数およびＭｇ原子の数の合計の３倍より大きく５倍未満である合金を含む粒子を意味するものである。また、本発明において、粒子の表面部分とは、粒子表面から粒子内部へ向かって２０ｎｍ以内の領域を意味するものである。 In the present invention, La—Mg—Ni-based hydrogen storage alloy particles include rare earth elements, Mg, and Ni, and the number of Ni atoms is 3 which is the sum of the number of rare earth elements and the number of Mg atoms. It means a particle containing an alloy that is greater than twice and less than five times . In the present invention, the surface portion of the particle means a region within 20 nm from the particle surface toward the inside of the particle.
斯かる構成のニッケル水素蓄電池によれば、Ｌａ−Ｍｇ−Ｎｉ系の水素吸蔵合金の特徴である優れた放電容量を維持しつつ、同時にサイクル特性が大幅に改善されることとなる。
これは、電解質であるアルカリ溶液に対して溶解しやすい性質を有していたＬａ−Ｍｇ−Ｎｉ系水素吸蔵合金が、その合金粒子表面部分にＳｎ原子を含むことにより該アルカリ溶液への溶解が防止され、サイクル特性が顕著に向上したものと推測される。
また、本発明に係るニッケル水素蓄電池においては、水素の吸蔵および脱離反応を阻害するというＳｎ原子の悪影響がＭｇ原子によって補われ、放電容量が維持されたものと推測される。
According to the nickel-metal hydride storage battery having such a configuration, the cycle characteristics are significantly improved while maintaining the excellent discharge capacity that is characteristic of the La—Mg—Ni-based hydrogen storage alloy.
This is because the La-Mg-Ni-based hydrogen storage alloy, which has a property of being easily dissolved in an alkaline solution as an electrolyte, contains Sn atoms in the surface of the alloy particles, so that the dissolution into the alkaline solution is prevented. It is estimated that the cycle characteristics are significantly improved.
In the nickel-metal hydride storage battery according to the present invention, it is presumed that the discharge capacity is maintained because the adverse effect of Sn atoms, which inhibits the hydrogen storage and desorption reaction, is compensated by Mg atoms.
以上のように、本発明によれば、放電容量が大きく且つサイクル特性にも優れたニッケル水素蓄電池が提供される。 As described above, according to the present invention, a nickel-metal hydride storage battery having a large discharge capacity and excellent cycle characteristics is provided.
本発明に係るニッケル水素蓄電池は、Ｌａ−Ｍｇ−Ｎｉ系の水素吸蔵合金粒子を含む負極を備えたニッケル水素蓄電池であって、前記水素吸蔵合金粒子が、粒子表面部分にＳｎ原子及びＭｇ原子を含むものである。 A nickel metal hydride storage battery according to the present invention is a nickel metal hydride storage battery including a negative electrode containing La—Mg—Ni based hydrogen storage alloy particles, wherein the hydrogen storage alloy particles contain Sn atoms and Mg atoms on the particle surface portion. Is included.
粒子表面部分とは、上述の如く粒子表面から粒子内部へ向かって２０ｎｍ以内の領域を意味するものであるが、粒子の表面に被膜が形成されている場合には、この被膜も前記粒子に含まれるものとする。したがって、粒子の表面に被膜が形成されている場合には、粒子表面部分とは、その被膜の表面から２０ｎｍ以内の領域を意味するものである。
粒子の表面に被膜が形成された水素吸蔵合金粒子としては、例えば、表面にＳｎ金属、Ｓｎを含む合金、またはＳｎを含む化合物が被膜として存在し、かつ、Ｍｇ金属、Ｍｇを含む合金またはＭｇを含む化合物が被膜として存在するものが挙げられる。
より具体的には、Ｓｎを含む化合物が被膜として存在している場合として、例えば、粒子本体部分を構成するＬａ−Ｍｇ−Ｎｉ系水素吸蔵合金の原料を焼成して合金粉末粒子を作製した後、該合金粉末粒子の表面にＳｎ化合物を被膜として析出させたものが挙げられる。また、Ｓｎ金属またはＳｎ合金が被膜として存在している場合として、例えば、合金粉末粒子の表面にＳｎ金属またはＳｎ合金を溶融させるなどして付着させたものが挙げられる。
中でも、製造が容易である等の観点から、本発明においては、合金粒子の表面に形成される被膜は、Ｓｎを含む化合物およびＭｇを含む化合物であることが好ましい。斯かる構成の水素吸蔵合金粒子は、ニッケル水素蓄電池の負極を製造する際に、該電極材料にＳｎ原子を含む添加剤を混合することにより得ることができる。これは、添加剤中のＳｎが溶解して過飽和状態になり、その結果、Ｓｎの一部が合金粒子の表面に析出するという現象に基づくものと推測される。
The particle surface portion means a region within 20 nm from the particle surface to the inside of the particle as described above. When a film is formed on the particle surface, this film is also included in the particle. Shall be. Accordingly, when a film is formed on the surface of the particle, the particle surface portion means a region within 20 nm from the surface of the film.
Examples of the hydrogen storage alloy particles having a film formed on the surface of the particles include Sn metal, an alloy containing Sn, or a compound containing Sn on the surface as a film, and Mg metal, an alloy containing Mg, or Mg. The thing which the compound containing this exists as a film is mentioned.
More specifically, as a case where a compound containing Sn exists as a film, for example, after the raw material of the La—Mg—Ni-based hydrogen storage alloy constituting the particle main body portion is fired to produce alloy powder particles , And Sn powder deposited on the surface of the alloy powder particles as a coating. Moreover, as a case where Sn metal or Sn alloy exists as a film, for example, there may be a case where Sn metal or Sn alloy is adhered to the surface of alloy powder particles by melting.
Among these, from the viewpoint of easy production and the like, in the present invention, the coating formed on the surface of the alloy particles is preferably a compound containing Sn and a compound containing Mg. The hydrogen storage alloy particles having such a structure can be obtained by mixing an additive containing Sn atoms with the electrode material when manufacturing a negative electrode of a nickel metal hydride storage battery. This is presumed to be based on the phenomenon that Sn in the additive dissolves and becomes supersaturated, and as a result, a part of Sn precipitates on the surface of the alloy particles.
尚、Ｍｇについては、粒子本体部分を構成する水素吸蔵合金中のＭｇを、溶解析出反応により粒子表面部分へと移行させたものであってもよい。 In addition, about Mg, the thing in which Mg in the hydrogen storage alloy which comprises a particle | grain main-body part was moved to the particle | grain surface part by melt | dissolution precipitation reaction may be used.
また、本発明に係るニッケル水素蓄電池は、前記粒子表面部分に、さらにＣｏ原子が含まれていることが好ましい。粒子表面部分に前記Ｓｎ原子及びＭｇ原子に加えて、さらにＣｏ原子が含まれている場合には、電極を構成する該ニッケル水素蓄電池のサイクル特性がより一層優れたものとなる。 In the nickel-metal hydride storage battery according to the present invention, it is preferable that the particle surface portion further contains Co atoms. When the Co particles are contained in addition to the Sn atoms and Mg atoms in the particle surface portion, the cycle characteristics of the nickel hydride storage battery constituting the electrode are further improved.
前記粒子表面部分に含まれる元素は、Ｓｎ、Ｍｇ、希土類元素、Ｎｉ、Ｃｏ、Ｍｎ，Ａｌ、Ｃｒ、Ｆｅ、Ｃｕ、Ｚｒであることが好ましく、Ｓｎ、Ｍｇ、Ｃｏであることが特に好ましい。 The elements contained in the particle surface portion are preferably Sn, Mg, rare earth elements, Ni, Co, Mn, Al, Cr, Fe, Cu, and Zr, and particularly preferably Sn, Mg, and Co.
本発明におけるＬａ−Ｍｇ−Ｎｉ系の水素吸蔵合金粒子は、希土類元素、Ｍｇ、およびＮｉを含み、且つ、Ｎｉ原子の数が希土類元素の数およびＭｇ原子の数の合計の３倍より大きく５倍未満である合金を含む粒子を意味するものであるが、中でも、組成が、下記一般式
Ｌｎ1-xＭｇx（Ｎｉ1-yＴy）z
で表される合金を含む粒子が好適である。
ここで、前記Ｌｎは希土類元素からなる群より選ばれた少なくとも１種の元素であり、好ましくは、Ｌａ、Ｃｅ、ＰｒおよびＮｄからなる群より選ばれた少なくとも１種の元素である。
また、前記ＴはＣｏ、Ｍｎ、Ａｌ、Ｃｒ、Ｆｅ、ＣｕおよびＺｒからなる群より選ばれた少なくとも１種の元素であり、好ましくは、Ｃｏ、ＭｎおよびＡｌからなる群より選ばれた少なくとも１種の元素である。
また、ｘは、０．０７≦ｘ≦０．３０、好ましくは０．１０≦ｘ≦０．２０、ｙは、０．０２≦ｙ≦０．２５、好ましくは０．０２≦ｙ≦０．０５、ｚは、３≦ｚ≦４、好ましくは３．３≦ｚ≦３．８を満たす数である。
The La—Mg—Ni-based hydrogen storage alloy particles in the present invention contain rare earth elements, Mg, and Ni, and the number of Ni atoms is larger than 3 times the total of the number of rare earth elements and the number of Mg atoms. It means a particle containing an alloy that is less than twice, among which the composition is represented by the following general formula Ln 1-x Mg x (Ni 1-y T y ) z
The particle | grains containing the alloy represented by these are suitable.
Here, Ln is at least one element selected from the group consisting of rare earth elements, and preferably at least one element selected from the group consisting of La, Ce, Pr and Nd.
The T is at least one element selected from the group consisting of Co, Mn, Al, Cr, Fe, Cu and Zr, and preferably at least one element selected from the group consisting of Co, Mn and Al. It is a seed element.
Also, x is 0.07 ≦ x ≦ 0.30, preferably 0.10 ≦ x ≦ 0.20, and y is 0.02 ≦ y ≦ 0.25, preferably 0.02 ≦ y ≦ 0. 05 and z are numbers satisfying 3 ≦ z ≦ 4, preferably 3.3 ≦ z ≦ 3.8.
前記水素吸蔵合金粒子は、結晶相として、六方晶Ｐｒ5Ｃｏ19型結晶構造を有する結晶相（以下、単にＰｒ5Ｃｏ19相ともいう）、菱面体晶Ｃｅ5Ｃｏ19型結晶構造を有する結晶相（以下、単にＣｅ5Ｃｏ19相ともいう）、及び六方晶Ｃｅ2Ｎｉ7型の結晶構造を有する結晶相（以下、単にＣｅ2Ｎｉ7相ともいう）の少なくとも何れかを含むことが好ましい。 The hydrogen storage alloy particles include, as a crystal phase, a crystal phase having a hexagonal Pr 5 Co 19 type crystal structure (hereinafter also simply referred to as a Pr 5 Co 19 phase), a crystal having a rhombohedral Ce 5 Co 19 type crystal structure. It is preferable to include at least one of a phase (hereinafter simply referred to as Ce 5 Co 19 phase) and a crystal phase having a hexagonal Ce 2 Ni 7 type crystal structure (hereinafter also simply referred to as Ce 2 Ni 7 phase). .
ここで、Ｐｒ5Ｃｏ19型結晶構造とは、Ａ2Ｂ4ユニット間に、ＡＢ5ユニットが３ユニット挿入された結晶構造であり、Ｃｅ5Ｃｏ19型結晶構造とは、Ａ2Ｂ4ユニット間に、ＡＢ5ユニットが３ユニット挿入された結晶構造であり、Ｃｅ2Ｎｉ7型の結晶構造とは、Ａ2Ｂ4ユニット間に、ＡＢ5ユニットが２ユニット挿入された結晶構造である。 Here, the Pr 5 Co 19 type crystal structure is a crystal structure in which three AB 5 units are inserted between A 2 B 4 units, and the Ce 5 Co 19 type crystal structure is an A 2 B 4 unit. A crystal structure in which 3 units of AB 5 units are inserted in between, and a Ce 2 Ni 7 type crystal structure is a crystal structure in which 2 units of AB 5 units are inserted between A 2 B 4 units.
尚、Ａ2Ｂ4ユニットとは、六方晶ＭｇＺｎ2型結晶構造（Ｃ１４構造）又は六方晶ＭｇＣｕ2型結晶構造（Ｃ１５構造）を持つ結晶格子であり、ＡＢ5ユニットとは、六方晶ＣａＣｕ5型結晶構造を持つ結晶格子である。
また、Ａは、希土類元素とＭｇからなる群より選択される何れかの元素を表し、Ｂは、遷移金属元素とＡｌからなる群より選択される何れかの元素を表すものである。
The A 2 B 4 unit is a crystal lattice having a hexagonal MgZn 2 type crystal structure (C14 structure) or a hexagonal MgCu 2 type crystal structure (C15 structure), and the AB 5 unit is a hexagonal CaCu 5 unit. It is a crystal lattice with a type crystal structure.
A represents any element selected from the group consisting of rare earth elements and Mg, and B represents any element selected from the group consisting of transition metal elements and Al.
また、前記各結晶構造を有する結晶相は、例えば、粉砕した合金粉末についてＸ線回折測定を行い、得られたＸ線回折パターンをリートベルト法により解析することによって結晶構造を特定することができる。 The crystal phase having each crystal structure can be identified by, for example, performing X-ray diffraction measurement on the pulverized alloy powder and analyzing the obtained X-ray diffraction pattern by the Rietveld method. .
次に、本発明に係るニッケル水素蓄電池の製造方法について説明する。
まず、一実施形態としての水素吸蔵合金の製造方法は、上述のような所定の組成比となるように配合された合金原料を溶融する溶融工程と、溶融した合金原料を１０００Ｋ／秒以上の冷却速度で急冷凝固する冷却工程と、冷却された合金を加圧状態の不活性ガス雰囲気下で８６０℃以上１０００℃以下の温度範囲で焼鈍する焼鈍工程とを備えるものである。
Next, the manufacturing method of the nickel hydride storage battery which concerns on this invention is demonstrated.
First, a method for producing a hydrogen storage alloy as one embodiment includes a melting step of melting an alloy raw material blended so as to have a predetermined composition ratio as described above, and cooling the molten alloy raw material to 1000 K / second or more. A cooling step of rapidly solidifying at a rate, and an annealing step of annealing the cooled alloy in a pressurized inert gas atmosphere in a temperature range of 860 ° C. or higher and 1000 ° C. or lower.
より具体的に説明すると、まず、目的とする水素吸蔵合金の化学組成に基づいて、原料インゴッド（合金原料）を所定量秤量する。
溶融工程においては、前記合金原料をルツボに入れ、不活性ガス雰囲気中又は真空中で高周波溶融炉を用い、例えば、１２００℃以上１６００℃以下に加熱して合金原料を溶融させる。
More specifically, first, a predetermined amount of raw material ingot (alloy raw material) is weighed based on the chemical composition of the target hydrogen storage alloy.
In the melting step, the alloy raw material is put in a crucible and heated to, for example, 1200 ° C. or higher and 1600 ° C. or lower in an inert gas atmosphere or in a vacuum to melt the alloy raw material.
冷却工程においては、溶融した合金原料を冷却して固化させる。冷却速度は、１０００Ｋ／秒以上（急冷ともいう）が好ましい。１０００Ｋ／秒以上で急冷することにより、合金組成が微細化し、均質化するという効果がある。また、該冷却速度は、１００００００Ｋ／秒以下の範囲に設定することができる。 In the cooling step, the molten alloy material is cooled and solidified. The cooling rate is preferably 1000 K / second or more (also called rapid cooling). By rapidly cooling at 1000 K / second or more, there is an effect that the alloy composition is refined and homogenized. The cooling rate can be set in a range of 1000000 K / second or less.
該冷却方法としては、具体的には、冷却速度が１０００００Ｋ／秒以上であるメルトスピニング法、冷却速度が１００００Ｋ／秒程度であるガスアトマイズ法などを好適に用いることができる。 As the cooling method, specifically, a melt spinning method having a cooling rate of 100,000 K / second or more, a gas atomizing method having a cooling rate of about 10,000 K / second, or the like can be preferably used.
焼鈍工程においては、不活性ガス雰囲気下の加圧状態において、例えば、電気炉等を用いて８６０℃以上１０００℃以下に加熱する。加圧条件としては、０．２ＭＰａ（ゲージ圧）以上１．０ＭＰａ（ゲージ圧）以下が好ましい。また、該焼鈍工程における処理時間は、３時間以上５０時間以下とすることが好ましい。 In the annealing step, heating is performed at 860 ° C. or higher and 1000 ° C. or lower using, for example, an electric furnace in a pressurized state under an inert gas atmosphere. The pressurizing condition is preferably 0.2 MPa (gauge pressure) or more and 1.0 MPa (gauge pressure) or less. Moreover, it is preferable that the processing time in this annealing process shall be 3 hours or more and 50 hours or less.
次に、作製した水素吸蔵合金とＳｎまたはＳｎ化合物との混合物を合材層として用いた電極を作製し、これをアルカリ性水溶液に浸漬しながら充放電反応させることによって、Ｓｎを含む化合物およびＭｇを含む化合物を合金表面に析出させる。その結果、表面部分にＳｎ原子およびＭｇ原子を含む水素吸蔵合金が得られる。尚、電極の作製は、水素吸蔵合金の粉末と、ＳｎまたはＳｎ化合物および増粘材のペーストを導電性の基板に塗布、乾燥することにより行うことができる。 Next, an electrode using a mixture of the produced hydrogen storage alloy and Sn or Sn compound as a composite layer is prepared, and a charge-discharge reaction is performed while immersing the mixture in an alkaline aqueous solution, whereby a compound containing Sn and Mg are contained. The containing compound is precipitated on the alloy surface. As a result, a hydrogen storage alloy containing Sn atoms and Mg atoms in the surface portion is obtained. The electrode can be produced by applying a hydrogen storage alloy powder, Sn or Sn compound and a thickener paste to a conductive substrate and drying.
水素吸蔵合金の表面にＳｎおよびＭｇの金属の被膜、あるいは合金の被膜を存在させる場合には、先ずＬａ−Ｍｇ−Ｎｉ系水素吸蔵合金粒子を上述のような手順で作製した後、Ｓｎ原子を含む添加剤と、作製されたＬａ−Ｍｇ−Ｎｉ系水素吸蔵合金粒子とを混合し、その混合物を、添加剤のみが溶融する温度、即ち、添加剤の融点よりも高温であり且つ前記Ｌａ−Ｍｇ−Ｎｉ系水素吸蔵合金の融点よりも低温である温度にまで加熱した後、該混合物を冷却することにより、粒子表面部分と粒子本体部分とが別体として構成され、該粒子表面部分にＳｎ原子及びＭｇ原子を含む水素吸蔵合金粒子を得ることができる。 In the case where a Sn or Mg metal film or an alloy film is present on the surface of the hydrogen storage alloy, first, La—Mg—Ni-based hydrogen storage alloy particles are prepared according to the procedure described above, and then Sn atoms are added. The additive containing and the produced La—Mg—Ni-based hydrogen storage alloy particles are mixed, and the mixture is heated to a temperature at which only the additive melts, that is, higher than the melting point of the additive and the La— After heating to a temperature that is lower than the melting point of the Mg—Ni-based hydrogen storage alloy, by cooling the mixture, the particle surface portion and the particle main body portion are configured as separate bodies, and the particle surface portion includes Sn. Hydrogen storage alloy particles containing atoms and Mg atoms can be obtained.
上述の方法において、水素吸蔵合金と混合するＳｎまたはＳｎ化合物の添加量は、Ｓｎ金属に換算して、水素吸蔵合金１００質量部に対し０．４４質量部以上１．７６質量部以下であることが好ましい。また、ＣｏまたはＣｏ化合物を添加する場合、その添加量はＣｏ金属に換算して、水素吸蔵合金１００質量部に対し０．０４質量部以上０．７９質量部以下であることが好ましい。
本発明で使用する水素吸蔵合金の表面部分に含まれるＳｎの濃度は、０．１質量％以上２０質量％以下であることが好ましく、Ｍｇの濃度は０．５質量以上５質量％以下であることが好ましい。Ｓｎ原子およびＭｇ原子は、水素吸蔵合金の表面部分のとくに外側（電解液との界面に近い側）が高濃度になるように存在することが好ましい。
In the above method, the amount of Sn or Sn compound to be mixed with the hydrogen storage alloy is 0.44 parts by mass or more and 1.76 parts by mass or less with respect to 100 parts by mass of the hydrogen storage alloy in terms of Sn metal. Is preferred. Moreover, when adding Co or a Co compound, it is preferable that the addition amount is 0.04 mass part or more and 0.79 mass part or less with respect to 100 mass parts of hydrogen storage alloys in conversion to Co metal.
The concentration of Sn contained in the surface portion of the hydrogen storage alloy used in the present invention is preferably 0.1% by mass or more and 20% by mass or less, and the concentration of Mg is 0.5% by mass or more and 5% by mass or less. It is preferable. Sn atoms and Mg atoms are preferably present so that the concentration of the surface portion of the hydrogen storage alloy is particularly high on the outer side (side closer to the interface with the electrolyte).
また、本発明における水素吸蔵合金粒子は、粒子中心部分のＳｎ原子濃度よりも、前記粒子表面部分のＳｎ原子濃度が高くなるよう構成されていることが好ましい。斯かる構成の水素吸蔵合金粒子を用いることにより、水素吸蔵合金の劣化を抑制するという効果がある。特に、粒子中心部分のＳｎ原子濃度を０とすることがより好ましく、これにより、水素吸蔵放出量および活性を低下させることなく、電池の放電容量および活性を向上させることが可能となる。 Moreover, it is preferable that the hydrogen storage alloy particle in this invention is comprised so that Sn atom concentration of the said particle | grain surface part may become higher than Sn atom concentration of particle | grain center part. By using the hydrogen storage alloy particles having such a configuration, there is an effect of suppressing deterioration of the hydrogen storage alloy. In particular, it is more preferable to set the Sn atom concentration at the center of the particle to 0, which makes it possible to improve the discharge capacity and activity of the battery without reducing the hydrogen storage / release amount and activity.
また、本発明における水素吸蔵合金粒子は、粒子中心部分のＭｇ原子濃度よりも粒子表面部分のＭｇ原子濃度が高くなるよう構成されていることが好ましい。斯かる構成の水素吸蔵合金粒子を用いることにより、水素の吸蔵および放出をスムーズにするという効果がある。 Moreover, it is preferable that the hydrogen storage alloy particle in this invention is comprised so that Mg atom concentration of a particle | grain surface part may become higher than Mg atom concentration of particle | grain center part. By using the hydrogen storage alloy particles having such a configuration, there is an effect of smoothly storing and releasing hydrogen.
本発明に係る水素吸蔵合金電極は、例えば上述のようにして作製した水素吸蔵合金を水素吸蔵媒体として備えたものである。水素吸蔵合金を水素吸蔵媒体として電極に使用する際には、該水素吸蔵合金を粉砕して使用することが好ましい。
電極製作時の水素吸蔵合金の粉砕は、焼鈍の前後のどちらで行ってもよいが、粉砕により表面積が大きくなるため、合金の表面酸化を防止する観点から、焼鈍後に粉砕するのが望ましい。粉砕は、合金表面の酸化防止のために不活性雰囲気中で行うことが好ましい。
前記粉砕には、例えば、機械粉砕、水素化粉砕などが用いられる。
The hydrogen storage alloy electrode according to the present invention comprises, for example, a hydrogen storage alloy produced as described above as a hydrogen storage medium. When the hydrogen storage alloy is used for an electrode as a hydrogen storage medium, the hydrogen storage alloy is preferably used after being pulverized.
The hydrogen storage alloy may be pulverized at the time of electrode fabrication either before or after annealing, but since the surface area is increased by pulverization, it is desirable to pulverize after annealing from the viewpoint of preventing surface oxidation of the alloy. The pulverization is preferably performed in an inert atmosphere to prevent oxidation of the alloy surface.
For the pulverization, for example, mechanical pulverization or hydrogenation pulverization is used.
水素吸蔵合金電極は、上述のようにして得られた水素吸蔵合金粉末を樹脂組成物やゴム組成物などの結着剤と混合し、所定形状に加圧成形することにより作製することができる。そして、該水素吸蔵合金電極を負極とし、別途作製した水酸化ニッケル製電極等を正極とし、電解液として水酸化カリウム水溶液等を充填することにより、本発明に係るニッケル水素蓄電池を作製することができる。 The hydrogen storage alloy electrode can be produced by mixing the hydrogen storage alloy powder obtained as described above with a binder such as a resin composition or a rubber composition and press-molding it into a predetermined shape. Then, by using the hydrogen storage alloy electrode as a negative electrode, a separately prepared nickel hydroxide electrode or the like as a positive electrode, and filling a potassium hydroxide aqueous solution or the like as an electrolyte, a nickel hydrogen storage battery according to the present invention can be manufactured. it can.
以下、実施例および比較例を用いて本発明を更に具体的に説明するが、本発明は、以下の実施例に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, but the present invention is not limited to the following Examples.
（実施例１）
Ｌａ−Ｍｇ−Ｎｉ系水素吸蔵合金の作製
化学組成がＬａ0.6Ｐｒ0.25Ｍｇ0.15Ｎｉ3.35Ｃｏ0.1Ａｌ0.15となるように原料インゴットを所定量秤量してルツボに入れ、減圧アルゴンガス雰囲気下で高周波溶融炉を用いて１５００℃に加熱し、材料を溶融した。溶融後、メルトスピニング法を適用して急冷し、合金を固化させた。
次に、得られた合金を０．２ＭＰａ（ゲージ圧、以下同じ）に加圧されたアルゴンガス雰囲気下で、９１０℃にて熱処理を行った後、得られた水素吸蔵合金を粉砕して平均粒径（Ｄ５０）が２０μｍの水素吸蔵合金粉末とした。
Example 1
Preparation of La-Mg-Ni-based hydrogen storage alloy The raw material ingot is weighed into a crucible so that the chemical composition is La 0.6 Pr 0.25 Mg 0.15 Ni 3.35 Co 0.1 Al 0.15 The material was melted by heating to 1500 ° C. using a furnace. After melting, it was quenched by applying a melt spinning method to solidify the alloy.
Next, after heat-treating the obtained alloy at 910 ° C. in an argon gas atmosphere pressurized to 0.2 MPa (gauge pressure, the same applies hereinafter), the obtained hydrogen storage alloy was pulverized and averaged A hydrogen storage alloy powder having a particle size (D50) of 20 μm was obtained.
ニッケル水素蓄電池の作製
前記水素吸蔵合金粉末を負極に用いることによって開放形および密閉形のニッケル水素蓄電池を製作した。解放形のものは放電容量の評価に用い、密閉形のものはサイクル寿命の評価に用いた。
前記水素吸蔵合金粉末およびこの合金粉末１００質量部に対してＳｎＯ粉末を０．５質量部（Ｓｎ金属に換算した混合量は０．４４質量部）を混合したのちに、増粘剤（メチルセルロース）を溶解した水溶液を加え、さらに、結着剤（スチレンブタジエンゴム）を１．５質量部加え、ペースト状にしたものを厚み４５μｍの穿孔鋼板（開口率６０％）の両面に塗布して乾燥させた後、厚さ０．３６ｍｍにプレスし、負極とした。このようにして作製した負極をセパレータを介して正極で挟み込み、これらの電極に１ｋｇｆ／ｃｍ2の圧力がかかるようにボルトで固定し、開放形セルとして実施例１のニッケル水素蓄電池を作製した。
尚、開放形セルの正極としては、容量過剰のシンター式水酸化ニッケル電極を用いた。また、電解液としては、６．８ｍｏｌ／ＬのＫＯＨ溶液および０．８ｍｏｌ／ＬのＬｉＯＨ溶液からなる混合液を使用した。
Production of Nickel Metal Hydride Battery An open-type and sealed nickel-metal hydride battery was produced by using the hydrogen storage alloy powder as a negative electrode. The open type was used for evaluating the discharge capacity, and the closed type was used for evaluating the cycle life.
After mixing 0.5 parts by mass of SnO powder (mixing amount converted to Sn metal is 0.44 parts by mass) with respect to 100 parts by mass of the hydrogen storage alloy powder and the alloy powder, a thickener (methyl cellulose) is added. Then, 1.5 parts by mass of a binder (styrene butadiene rubber) is added, and the paste is applied to both sides of a 45 μm-thick perforated steel sheet (opening ratio 60%) and dried. Then, it was pressed to a thickness of 0.36 mm to obtain a negative electrode. The negative electrode thus produced was sandwiched between positive electrodes via a separator, and was fixed with bolts so that a pressure of 1 kgf / cm 2 was applied to these electrodes, and a nickel metal hydride storage battery of Example 1 was produced as an open cell.
As the positive electrode of the open cell, a sinter-type nickel hydroxide electrode having an excessive capacity was used. Further, as the electrolytic solution, a mixed solution composed of a 6.8 mol / L KOH solution and a 0.8 mol / L LiOH solution was used.
一方、密閉形セルは、次の手順で作製した。正極と負極とを、正極容量１に対して負極容量が１．３５となる割合でセパレーターを介して渦巻き状に倦回して電極群とし、正極端子部と集電端子とを抵抗溶接したうえで該電極群を円筒状金属ケースに収納した。つぎに、８ｍｏｌ／ｌのＫＯＨと０．８ｍｏｌ／ｌのＬｉＯＨからなる電解液を１．８４ｍｌ注液し、安全弁を備えた金属製蓋体で封口することにより、２０００ｍＡｈＡＡサイズの密閉形セルを作製した。
密閉形セルに用いた負極は、結着剤（スチレンブタジエンゴム）が０．８質量％であること、厚さ３５μｍの穿孔鋼鈑を用いたこと、プレスの所定の厚さ条件が０．３１ｍｍであること以外は開放形のものと同様にした。
密閉形セルに用いた正極は、増粘剤（カルボキシメチルセルロース）を溶解させた水溶液と、活物質とのペーストをニッケル発泡基板に充填し、乾燥させた後、所定の厚さ（０．９０ｍｍ）にプレスすることによって正極を得た。前記活物質には、亜鉛３質量％およびコバルト０．５質量％を固溶状態で含有する水酸化ニッケル表面に、６質量％の水酸化コバルトを被覆したものを使用した。
On the other hand, the sealed cell was produced by the following procedure. The positive electrode and the negative electrode are spirally wound through a separator at a ratio of 1.35 with respect to the positive electrode capacity 1 to form an electrode group, and the positive electrode terminal portion and the current collecting terminal are resistance-welded. The electrode group was housed in a cylindrical metal case. Next, 1.84 ml of an electrolyte solution composed of 8 mol / l KOH and 0.8 mol / l LiOH was injected, and sealed with a metal lid provided with a safety valve to produce a 2000 mAhAA size sealed cell. did.
The negative electrode used in the sealed cell had a binder (styrene butadiene rubber) of 0.8 mass%, a perforated steel plate with a thickness of 35 μm, and a predetermined thickness condition of the press was 0.31 mm. Except for this, it was the same as the open type.
The positive electrode used for the sealed cell is filled with a paste of an aqueous solution in which a thickener (carboxymethylcellulose) is dissolved and an active material in a nickel foam substrate and dried, and then has a predetermined thickness (0.90 mm). To obtain a positive electrode. As the active material, a nickel hydroxide surface containing 3% by mass of zinc and 0.5% by mass of cobalt in a solid solution state and 6% by mass of cobalt hydroxide coated thereon was used.
放電容量の評価
開放形セルを２０℃の水槽に入れて０．１ＩｔＡおよび１５０%の条件で充電し、０．２ＩｔＡおよび終止電圧−０．６Ｖ（vs.Ｈｇ／ＨｇＯ）の条件で放電した。この充放電を１０サイクル繰り返したときの３サイクル目および１０サイクル目放電容量を測定した。
サイクル寿命の評価
密閉形セルを、２０℃、０．０２Ｉｔ（Ａ）（４０ｍＡ）で１０時間の初充電を行った後、０．２５Ｉｔ（Ａ）（５００ｍＡ）で再度５時間充電した。その後、２０℃、０．２Ｉｔ（４００ｍＡ）で終止電圧が１Ｖとなるまでの放電と、２０℃、０．２Ｉｔ（４００ｍＡ）で６時間の充電とを１０回繰り返し、最後に放電を行うことによって化成処理を行った。
そして、０．５Ｉｔ（Ａ）および−ｄＶ＝５ｍＶの条件での充電、３０分間の休止および１Ｉｔ（Ａ）で終止電圧が１Ｖとなるまでの放電（２０℃）を繰り返し、放電容量が初期容量の５０％となったときのサイクル数をサイクル寿命とした。
Evaluation of discharge capacity An open cell was placed in a water bath at 20 ° C. and charged under conditions of 0.1 ItA and 150%, and discharged under conditions of 0.2 ItA and a final voltage of −0.6 V (vs. Hg / HgO). The third and tenth cycle discharge capacities when this charge / discharge cycle was repeated 10 times were measured.
Evaluation of cycle life The sealed cell was charged at 20 ° C. and 0.02 It (A) (40 mA) for 10 hours, and then charged again at 0.25 It (A) (500 mA) for 5 hours. Thereafter, the discharge until the end voltage becomes 1 V at 20 ° C. and 0.2 It (400 mA) and the charge for 6 hours at 20 ° C. and 0.2 It (400 mA) are repeated 10 times, and finally the discharge is performed. Chemical conversion treatment was performed.
Then, charging under the conditions of 0.5 It (A) and −dV = 5 mV, a pause for 30 minutes, and discharging (20 ° C.) until the end voltage becomes 1 V at 1 It (A) are repeated, and the discharge capacity is the initial capacity. The cycle number when 50% of the cycle was taken as the cycle life.
実施例のニッケル水素蓄電池に含まれる水素吸蔵合金粒子について、ＳｎおよびＭｇの原子濃度分布をＸ線光電子分光法（ＥＳＣＡ）基づく測定装置を用いて測定した。測定は、充放電サイクルを１０回繰り返したあとのものについて行った。
具体的には、装置名：日本電子社製、ＪＰＳ−９０１０ＭＸを用い、電極をカーボンテープ上に固定して試料台に載せ、
Ｘ線源：Ｍｇ−Ｋα、
Ｘ線出力：１０ｋＶ、３０ｍＡ、
積算回数：５回、
エッチング条件：Ａｒイオン銃使用、５００Ｖ、８．６ｍＡ、
により、水素吸蔵合金粒子のＸ線光電子スペクトルを得た。
そして、得られたＸ線光電子スペクトルから、各原子のピーク強度を算出することにより、水素吸蔵合金粒子内のＳｎ原子及びＭｇ原子の分布を求めた。
その結果、Ｓｎ原子は粒子表面から２０ｎｍ（ＳｉＯ2換算）以内の領域に存在しており、表面から２０ｎｍを超える粒子中心部分にはほとんど存在していないことがわかった。Ｍｇは、粒子表面から２０ｎｍ以内の範囲の原子濃度が粒子中心部分の原子濃度よりも高いことがわかった。なお、表面部分のＭｇの原子濃度が高かった理由は、合金組成中のＭｇが電解液中に溶解したのちに合金表面に析出したためであると考えられる。
For the hydrogen storage alloy particles contained in the nickel-metal hydride storage battery of the example, the atomic concentration distribution of Sn and Mg was measured using a measuring device based on X-ray photoelectron spectroscopy (ESCA). Measurements were made after 10 charge / discharge cycles were repeated.
Specifically, using an apparatus name: JPS-9010MX manufactured by JEOL Ltd., the electrode was fixed on a carbon tape and placed on a sample table.
X-ray source: Mg-Kα
X-ray output: 10 kV, 30 mA,
Integration count: 5 times
Etching conditions: Ar ion gun used, 500 V, 8.6 mA,
Thus, an X-ray photoelectron spectrum of the hydrogen storage alloy particles was obtained.
Then, the distribution of Sn atoms and Mg atoms in the hydrogen storage alloy particles was determined by calculating the peak intensity of each atom from the obtained X-ray photoelectron spectrum.
As a result, it was found that Sn atoms are present in a region within 20 nm (in terms of SiO 2 ) from the particle surface, and are hardly present in the particle center portion exceeding 20 nm from the surface. Mg was found to have an atomic concentration in the range of 20 nm or less from the particle surface higher than the atomic concentration in the particle central portion. The reason why the atomic concentration of Mg in the surface portion is high is considered to be that Mg in the alloy composition was dissolved in the electrolytic solution and then deposited on the alloy surface.
（実施例２〜６）
下記表１に示すように、Ｓｎの原料として異なる添加剤を用いることを除き、他は前記実施例１と同様にして実施例２〜６のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。なお、各添加剤の添加量は、水素吸蔵合金１００質量部に対して０．５質量部とした。結果を表１に示す。
(Examples 2 to 6)
As shown in Table 1 below, nickel-metal hydride batteries of Examples 2 to 6 were produced in the same manner as in Example 1 except that different additives were used as Sn raw materials, and the cycle characteristics were similarly evaluated. Went. In addition, the addition amount of each additive was 0.5 mass part with respect to 100 mass parts of hydrogen storage alloys. The results are shown in Table 1.
（比較例１〜７）
下記表１に示すように、Ｓｎを含まない添加剤を用いることを除き、他は前記実施例１と同様にして比較例１〜７のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。なお、各添加剤の添加量は、水素吸蔵合金１００質量部に対して０．５質量部とした。結果を表１に示す。
(Comparative Examples 1-7)
As shown in Table 1 below, except that an additive not containing Sn is used, the nickel-metal hydride storage batteries of Comparative Examples 1 to 7 are manufactured in the same manner as in Example 1, and the cycle characteristics are similarly evaluated. went. In addition, the addition amount of each additive was 0.5 mass part with respect to 100 mass parts of hydrogen storage alloys. The results are shown in Table 1.
表１に示すように、Ｌａ−Ｍｇ−Ｎｉ系水素吸蔵合金粒子にＳｎ原子を含む添加剤を用いた実施例１〜６は、Ｌａ−Ｍｇ−Ｎｉ系水素吸蔵合金粒子にＳｎ原子を含まない他の添加剤を用いた比較例１〜７と比較して、サイクル寿命が顕著に改善されていることがわかる。 As shown in Table 1, Examples 1 to 6 using an additive containing Sn atoms in La-Mg-Ni-based hydrogen storage alloy particles do not contain Sn atoms in La-Mg-Ni-based hydrogen storage alloy particles. It can be seen that the cycle life is remarkably improved as compared with Comparative Examples 1 to 7 using other additives.
（比較例８）
化学組成がＬａ0.7Ｃｅ0.2Ｎｄ0.1Ｎｉ3.8Ｃｏ0.7Ｍｎ0.3Ａｌ0.3となるように原料インゴットを調製してＣａＣｕ5型の結晶構造を有するＡＢ5系の結晶構造を有する水素吸蔵合金を使用したことを除き、他は前記実施例１と同様にして比較例８のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。なお、各添加剤の添加量は、水素吸蔵合金１００質量部に対して０．５質量部とした。結果を表２に示す。
(Comparative Example 8)
A raw material ingot was prepared so that the chemical composition was La 0.7 Ce 0.2 Nd 0.1 Ni 3.8 Co 0.7 Mn 0.3 Al 0.3, and a hydrogen storage alloy having an AB 5 type crystal structure having a CaCu 5 type crystal structure was used. The nickel hydride storage battery of Comparative Example 8 was produced in the same manner as in Example 1 except for the above, and the cycle characteristics were similarly evaluated. In addition, the addition amount of each additive was 0.5 mass part with respect to 100 mass parts of hydrogen storage alloys. The results are shown in Table 2.
（比較例９）
化学組成がＬａ0.7Ｃｅ0.2Ｎｄ0.1Ｎｉ3.8Ｃｏ0.7Ｍｎ0.3Ａｌ0.3となるように原料インゴットを調製してＣａＣｕ5型の結晶構造を有するＡＢ5系の結晶構造を有する水素吸蔵合金を使用し、且つ添加剤を使用しないことを除き、他は前記実施例１と同様にして比較例９のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。結果を表２に示す。
(Comparative Example 9)
A raw material ingot was prepared so that the chemical composition was La 0.7 Ce 0.2 Nd 0.1 Ni 3.8 Co 0.7 Mn 0.3 Al 0.3 and a hydrogen storage alloy having an AB 5 type crystal structure having a CaCu 5 type crystal structure was used. The nickel-metal hydride storage battery of Comparative Example 9 was produced in the same manner as in Example 1 except that no additive was used, and the cycle characteristics were evaluated in the same manner. The results are shown in Table 2.
（比較例１０）
添加剤を使用しないことを除き、他は前記実施例１と同様にして比較例１０のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。結果を表２に示す。
(Comparative Example 10)
Except that no additive was used, a nickel-metal hydride storage battery of Comparative Example 10 was prepared in the same manner as in Example 1 above, and the cycle characteristics were similarly evaluated. The results are shown in Table 2.
表２に示すように、ＡＢ5系の水素吸蔵合金粒子にＳｎ原子を含む添加剤を用いた場合には、サイクル特性が大幅に低下しているのに対し、Ｌａ−Ｍｇ−Ｎｉ系の水素吸蔵合金粒子にＳｎ原子を含む添加剤を用いた場合には、サイクル特性が大幅に向上していることがわかる。 As shown in Table 2, in the case of using an additive comprising a Sn atom into hydrogen storage alloy particles of the AB 5 system, whereas the cycle characteristics are significantly reduced, La-Mg-Ni-based hydrogen It can be seen that when the additive containing Sn atoms is used for the storage alloy particles, the cycle characteristics are greatly improved.
（実施例７〜１０）
下記表３に示すように、Ｓｎ原子を含む添加剤の添加量を変更することを除き、他は前記実施例１と同様にして実施例７〜１０のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。結果を表３に示す。
(Examples 7 to 10)
As shown in Table 3 below, except for changing the addition amount of the additive containing Sn atoms, the nickel hydride storage batteries of Examples 7 to 10 were produced in the same manner as in Example 1 above, and the cycle was similarly performed. The characteristics were evaluated. The results are shown in Table 3.
表３に示すように、Ｓｎの添加量が合金１００質量部に対して０．０９質量部以上１．７６質量部以下である場合には、サイクル寿命の改善効果が優れたものとなり、０．４４質量部以上１．７６質量部以下である場合には、サイクル寿命の改善効果が特に顕著となることがわかる。 As shown in Table 3, when the amount of Sn added is 0.09 parts by mass or more and 1.76 parts by mass or less with respect to 100 parts by mass of the alloy, the effect of improving the cycle life is excellent. It can be seen that when the amount is 44 parts by mass or more and 1.76 parts by mass or less, the effect of improving the cycle life is particularly remarkable.
（実施例１２〜１５）
下記表４に示すように、Ｓｎ原子及びＣｏ原子を含む添加剤を用いることを除き、他は前記実施例１と同様にして実施例１２〜１５のニッケル水素蓄電池を作製し、同様にサイクル特性の評価を行った。結果を表４に示す。
(Examples 12 to 15)
As shown in Table 4 below, except that an additive containing Sn atom and Co atom is used, the nickel hydride storage batteries of Examples 12 to 15 are produced in the same manner as in Example 1 above, and the cycle characteristics are similarly obtained. Was evaluated. The results are shown in Table 4.
表４に示すように、Ｃｏ原子のみを含む添加剤を用いた場合のサイクル寿命改善効果（比較例１０と比較例１１との比較）は、２５サイクルの改善であるのに対し、Ｓｎ原子を含む添加剤に更にＣｏ原子を加えた場合のサイクル寿命改善効果（実施例１と実施例１５との比較）は、１７５サイクルの改善となっており、粒子表面部分にＳｎ原子に加えてＣｏ原子が含まれるＬａ−Ｍｇ−Ｎｉ系水素吸蔵合金を用いた場合に該ニッケル水素蓄電池のサイクル特性がより一層優れたものとなることが認められる。 As shown in Table 4, the cycle life improvement effect (comparison between Comparative Example 10 and Comparative Example 11) when using an additive containing only Co atoms is an improvement of 25 cycles, whereas Sn atoms are The cycle life improvement effect (comparison between Example 1 and Example 15) when Co atoms are further added to the additive to be added is an improvement of 175 cycles, and Co atoms in addition to Sn atoms are added to the particle surface portion It is recognized that the cycle characteristics of the nickel-metal hydride storage battery are further improved when a La—Mg—Ni-based hydrogen storage alloy containing is used.
Claims (5)
Ln 1-x Mg x (Ni 1-y T y ) z (where Ln is at least one element selected from the group consisting of rare earth elements, T is Co, Mn, Al, Cr, Fe, Cu and At least one element selected from the group consisting of Zr and containing La in a proportion of the majority of the rare earth elements , and x, y and z are 0.07 ≦ x ≦ 0.3, 0 0.02 ≦ y ≦ 0.25 and 3 ≦ z ≦ 4.) In the hydrogen storage alloy particles having a composition represented by the following formula: A nickel-metal hydride storage battery characterized in that a negative electrode is formed through a step of charging and discharging by immersing a mixture obtained by mixing 0.44 parts by mass or more and 1.76 parts by mass or less with respect to 100 parts by mass of the storage alloy. Manufacturing method.
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