JP4663451B2 - Hydrogen storage alloy for alkaline storage battery, method for producing hydrogen storage alloy for alkaline storage battery, and alkaline storage battery - Google Patents
Hydrogen storage alloy for alkaline storage battery, method for producing hydrogen storage alloy for alkaline storage battery, and alkaline storage battery Download PDFInfo
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Description
この発明は、アルカリ蓄電池の負極に使用するアルカリ蓄電池用水素吸蔵合金及びその製造方法、またこのようなアルカリ蓄電池用水素吸蔵合金を負極に使用したアルカリ蓄電池に係り、特に、アルカリ蓄電池の負極に使用するアルカリ蓄電池用水素吸蔵合金を改善し、充放電サイクル特性が低下することなく、低温での高率放電特性に優れたアルカリ蓄電池が得られるようにした点に特徴を有するものである。 The present invention relates to a hydrogen storage alloy for an alkaline storage battery used for a negative electrode of an alkaline storage battery, a method for producing the same, and an alkaline storage battery using such a hydrogen storage alloy for an alkaline storage battery as a negative electrode. It is characterized by improving the hydrogen storage alloy for alkaline storage batteries to obtain an alkaline storage battery excellent in high-rate discharge characteristics at low temperatures without deteriorating charge / discharge cycle characteristics.
従来、アルカリ蓄電池としては、ニッケル・カドミウム蓄電池が広く使用されていたが、近年においては、ニッケル・カドミウム蓄電池に比べて高容量で、またカドミウムを使用しないため環境安全性にも優れているという点から、負極に水素吸蔵合金を用いたニッケル・水素蓄電池が注目されるようになった。 Conventionally, nickel-cadmium storage batteries have been widely used as alkaline storage batteries, but in recent years they have a higher capacity than nickel-cadmium storage batteries and are superior in environmental safety because they do not use cadmium. Therefore, nickel-hydrogen storage batteries using a hydrogen storage alloy for the negative electrode have come to attract attention.
そして、このようなニッケル・水素蓄電池からなるアルカリ蓄電池が各種のポータブル機器等に使用されるようになり、このアルカリ蓄電池をさらに高性能化させることが期待されている。 And the alkaline storage battery which consists of such a nickel-hydrogen storage battery comes to be used for various portable apparatuses, etc., and it is anticipated that this alkaline storage battery will be further improved in performance.
ここで、このようなアルカリ蓄電池においては、その負極に使用する水素吸蔵合金として、一般にＡＢ5型の結晶を主相とする希土類−ニッケル系水素吸蔵合金や、Ｎｉ，Ｚｒ，Ｔｉ，Ｖ等を含みＡＢ2型の結晶を主相とするラーベス相系の水素吸蔵合金等が一般に使用されている。 Here, in such an alkaline storage battery, as a hydrogen storage alloy used for the negative electrode, generally a rare earth-nickel hydrogen storage alloy having a main phase of AB 5 type crystal, Ni, Zr, Ti, V or the like is used. In general, a Laves phase-type hydrogen storage alloy having an AB 2 type crystal as a main phase is generally used.
しかし、上記のような水素吸蔵合金を用いたアルカリ蓄電池の場合、ニッケル・カドミウム蓄電池に比べて低温での高率放電特性が悪いという問題、すなわち低温下において大電流で放電させた場合に十分な放電容量が得られなくなるという問題があった。 However, in the case of an alkaline storage battery using a hydrogen storage alloy as described above, the problem is that the high-rate discharge characteristics at low temperatures are worse than that of a nickel-cadmium storage battery, that is, sufficient when discharged at a large current at low temperatures. There was a problem that the discharge capacity could not be obtained.
そして、近年においては、上記のような水素吸蔵合金粒子に対して酸処理などの化学的表面処理を行い、上記の水素吸蔵合金粒子の表面にニッケルが多く含まれる層を形成し、これによって高率放電特性等を改善するようにしたものが提案されている（例えば、特許文献1及び特許文献２参照。）。
In recent years, the hydrogen storage alloy particles as described above are subjected to a chemical surface treatment such as acid treatment to form a nickel-rich layer on the surface of the hydrogen storage alloy particles. A device that improves the rate discharge characteristic has been proposed (see, for example,
ここで、上記のように水素吸蔵合金粒子に対して酸処理などの化学的表面処理を行って、水素吸蔵合金粒子の表面にニッケルが多く含まれる層を形成するようにした場合、この水素吸蔵合金粒子の表面にひび割れが生じて、その比表面積が増大し、これによりこの水素吸蔵合金粒子の活性度が向上して、高率放電特性等が改善されるようになる。 Here, when the hydrogen storage alloy particles are subjected to a chemical surface treatment such as acid treatment as described above to form a layer containing a large amount of nickel on the surfaces of the hydrogen storage alloy particles, the hydrogen storage alloy particles. Cracks are generated on the surface of the alloy particles, and the specific surface area is increased. This increases the activity of the hydrogen storage alloy particles, thereby improving the high rate discharge characteristics and the like.
しかし、このような水素吸蔵合金粒子を用いたアルカリ蓄電池を繰り返して充放電させると、上記の水素吸蔵合金粒子が微粉化して、この水素吸蔵合金粒子の酸化が進み、アルカリ蓄電池のサイクル寿命が低下するという問題があり、また低温での高率放電特性を十分に向上させることも困難であった。
この発明は、負極に水素吸蔵合金を使用したアルカリ蓄電池における上記のような問題を解決することを課題とするものであり、アルカリ蓄電池における低温での高率放電特性を十分に向上させると共に、充放電により水素吸蔵合金粒子にひび割れが生じて微紛化するのを抑制し、サイクル寿命が低下するのを防止することを課題とするものである。 An object of the present invention is to solve the above-described problems in an alkaline storage battery using a hydrogen storage alloy for the negative electrode, and sufficiently improve the high-rate discharge characteristics at low temperatures in the alkaline storage battery. An object of the present invention is to prevent the hydrogen storage alloy particles from cracking due to electric discharge to be pulverized and prevent the cycle life from being reduced.
この発明においては、上記のような課題を解決するため、アルカリ蓄電池の負極に使用するアルカリ蓄電池用水素吸蔵合金として、一般式Ｌｎ 1-x Ｍｇ x Ｎｉ y-a-b Ａｌ a Ｚｒ b （式中、Ｌｎは希土類元素から選択される少なくとも1種の元素であり、０．０５≦ｘ＜０．３０、２．８≦ｙ≦３．９、０．１０≦ａ≦０．２５、０≦ｂ≦０．５の条件を満たす。）で表され、かつ、その結晶構造がＣｅ ２ Ｎｉ ７ 型構造である水素吸蔵合金を用いたアルカリ蓄電池用水素吸蔵合金において、水素吸蔵合金の最表面の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合が、水素吸蔵合金の内部の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合に比べて多くなったものを用いるようにした。
In the present invention, in order to solve the above problems, as a hydrogen storage alloy for an alkaline storage battery used for the negative electrode of an alkaline storage battery, a general formula Ln 1-x Mg x Ni yab Al a Zr b (where Ln is At least one element selected from rare earth elements, 0.05 ≦ x <0.30, 2.8 ≦ y ≦ 3.9, 0.10 ≦ a ≦ 0.25, 0 ≦ b ≦ 0. 5 meet the.) is represented by and, in the alkaline storage battery for the hydrogen absorbing alloy using the hydrogen storage alloy crystal structure is Ce 2 Ni 7 type structure, the total amount of rare earth elements on the outermost surface of the hydrogen storage alloy using nickel, the ratio of each element of the aluminum and magnesium, nickel to total internal rare earth elements of the hydrogen storage alloy, those increasingly compared to the proportion of each element in the aluminum and magnesium to It was.
また、上記のようなアルカリ蓄電池用水素吸蔵合金を製造するにあたっては、一般式Ｌｎ 1-x Ｍｇ x Ｎｉ y-a-b Ａｌ a Ｚｒ b （式中、Ｌｎは希土類元素から選択される少なくとも1種の元素であり、０．０５≦ｘ＜０．３０、２．８≦ｙ≦３．９、０．１０≦ａ≦０．２５、０≦ｂ≦０．５の条件を満たす。）で表され、かつ、その結晶構造がＣｅ ２ Ｎｉ ７ 型構造である水素吸蔵合金を酸溶液に浸漬させて、この水素吸蔵合金の表面に、水素吸蔵合金の最表面の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合が、水素吸蔵合金の内部の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合に比べて多くなった層を形成させるようにすることができる。
尚、前記酸溶液には塩酸溶液を用いることができる。
Further, in producing the hydrogen storage alloy for alkaline storage battery as described above, the general formula Ln 1-x Mg x Ni yab Al a Zr b (wherein Ln is at least one element selected from rare earth elements). And 0.05 ≦ x <0.30, 2.8 ≦ y ≦ 3.9, 0.10 ≦ a ≦ 0.25, and 0 ≦ b ≦ 0.5. Then, a hydrogen storage alloy whose crystal structure is a Ce 2 Ni 7 type structure is immersed in an acid solution, and nickel, aluminum and magnesium with respect to the total amount of rare earth elements on the outermost surface of the hydrogen storage alloy are immersed on the surface of the hydrogen storage alloy. It is possible to form a layer in which the ratio of each element is larger than the ratio of each element of nickel, aluminum, and magnesium to the total amount of rare earth elements in the hydrogen storage alloy .
In addition, a hydrochloric acid solution can be used for the acid solution.
そして、この発明におけるアルカリ蓄電池においては、その負極における水素吸蔵合金に、上記のようなアルカリ蓄電池用水素吸蔵合金を用いるようにした。 And in the alkaline storage battery in this invention, the above hydrogen storage alloy for alkaline storage batteries was used for the hydrogen storage alloy in the negative electrode.
この発明におけるアルカリ蓄電池においては、上記のように負極におけるアルカリ蓄電池用水素吸蔵合金として、一般式Ｌｎ 1-x Ｍｇ x Ｎｉ y-a-b Ａｌ a Ｚｒ b （式中、Ｌｎは希土類元素から選択される少なくとも1種の元素であり、０．０５≦ｘ＜０．３０、２．８≦ｙ≦３．９、０．１０≦ａ≦０．２５、０≦ｂ≦０．５の条件を満たす。）で表され、かつ、その結晶構造がＣｅ ２ Ｎｉ ７ 型構造である水素吸蔵合金であって、水素吸蔵合金の最表面の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合が、水素吸蔵合金の内部の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合に比べて多くなったものを用いるようにしたため、このようにニッケルとアルミニウムとマグネシウムの割合が多くなった水素吸蔵合金の表面において水素拡散速度が高くなり、低温での高率放電特性が十分に向上されるようになる。
In the alkaline storage battery according to the present invention, as described above, as the hydrogen storage alloy for alkaline storage battery in the negative electrode, the general formula Ln 1-x Mg x Ni yab Al a Zr b (wherein Ln is at least one selected from rare earth elements) It is a seed element and satisfies the following conditions: 0.05 ≦ x <0.30, 2.8 ≦ y ≦ 3.9, 0.10 ≦ a ≦ 0.25, and 0 ≦ b ≦ 0.5. A hydrogen storage alloy whose crystal structure is a Ce 2 Ni 7 type structure, wherein the ratio of each element of nickel, aluminum and magnesium to the total amount of rare earth elements on the outermost surface of the hydrogen storage alloy is hydrogen storage because as adapted to use those increasingly compared to the proportion of the interior of the nickel to the total amount of rare earth elements, aluminum and the elements of magnesium alloy, thus nickel, aluminum, and Mug Proportion of Siumu hydrogen diffusion rate is high at the surface of many became the hydrogen storage alloy, so that high-rate discharge characteristics at low temperature can be sufficiently improved.
また、上記の水素吸蔵合金を酸処理して、この水素吸蔵合金の表面に、水素吸蔵合金の最表面の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合が、水素吸蔵合金の内部の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合に比べて多くなった層を形成するようにした場合、この水素吸蔵合金の表面にひび割れなどが生じて、その比表面積が増大するということがない。
Further, the upper Symbol acid treatment of the hydrogen absorbing alloy, the surface of the hydrogen-absorbing alloy, nickel to the total amount of rare earth elements on the outermost surface of the hydrogen storage alloy, the proportion of each element in the aluminum and magnesium, of the hydrogen storage alloy When a layer that is larger than the ratio of nickel, aluminum, and magnesium to the total amount of internal rare earth elements is formed, the surface of this hydrogen storage alloy is cracked, increasing its specific surface area. There is nothing to do.
このため、このようなアルカリ蓄電池用水素吸蔵合金を負極に用いたアルカリ蓄電池を繰り返して充放電させた場合に、このアルカリ蓄電池用水素吸蔵合金が微粉化して酸化が進むということがなく、アルカリ蓄電池のサイクル寿命が低下するということもない。 For this reason, when an alkaline storage battery using such a hydrogen storage alloy for alkaline storage batteries is repeatedly charged and discharged, the hydrogen storage alloy for alkaline storage batteries is not pulverized and oxidation does not proceed. The cycle life is not reduced.
また、上記の水素吸蔵合金として、特に、その結晶構造がＣｅ２Ｎｉ７ 型構造のものを用いると、この水素吸蔵合金を酸処理した場合に、その表面に、水素吸蔵合金の最表面の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合が、水素吸蔵合金の内部の希土類元素の総量に対するニッケル、アルミニウム及びマグネシウムの各元素の割合に比べて多くなった層が適切に形成されるようになり、またこの水素吸蔵合金における水素吸蔵能力が高く、低温での高率放電特性が優れると共に、高容量でサイクル寿命に優れたアルカリ蓄電池が得られるようになる。
Further, as the hydrogen absorbing alloy, in particular, when the crystal structure used as the Ce 2 Ni 7 type structure, when the acid treatment of this hydrogen-absorbing alloy on its surface, the outermost surface of the hydrogen storage alloy Proper formation of layers in which the ratio of nickel, aluminum, and magnesium to the total amount of rare earth elements is higher than the ratio of nickel, aluminum, and magnesium to the total amount of rare earth elements in the hydrogen storage alloy In addition, the hydrogen storage capacity of the hydrogen storage alloy is high, the high rate discharge characteristics at low temperatures are excellent, and the alkaline storage battery having a high capacity and excellent cycle life can be obtained.
以下、この発明の実施例に係るアルカリ蓄電池用水素吸蔵合金及びその製造方法、またこのようなアルカリ蓄電池用水素吸蔵合金を用いたアルカリ蓄電池について具体的に説明すると共に、比較例を挙げ、この発明の実施例に係るアルカリ蓄電池においては、低温での高率放電特性が向上されると共に、水素吸蔵合金が微粉化するのも抑制されて、サイクル寿命が低下するのも防止されることを明らかにする。なお、この発明におけるアルカリ蓄電池用水素吸蔵合金及びその製造方法並びにアルカリ蓄電池は、下記の実施例に示したものに限定されず、その要旨を変更しない範囲において適宜変更して実施できるものである。 Hereinafter, the hydrogen storage alloy for an alkaline storage battery according to an embodiment of the present invention, a method for producing the same, and an alkaline storage battery using such a hydrogen storage alloy for an alkaline storage battery will be specifically described, and a comparative example will be given. In the alkaline storage battery according to this example, it is clear that the high-rate discharge characteristics at low temperature are improved, the hydrogen storage alloy is also prevented from being pulverized, and the cycle life is also prevented from being reduced. To do. In addition, the hydrogen storage alloy for alkaline storage batteries in this invention, its manufacturing method, and an alkaline storage battery are not limited to what was shown in the following Example, It can implement by changing suitably in the range which does not change the summary.
（実施例）
この実施例においては、負極に用いるアルカリ蓄電池用水素吸蔵合金を製造するにあたり、希土類元素のＬａ，Ｐｒ及びＮｄと、Ｚｒと、Ｍｇと、Ｎｉと、Ａｌとを所定の合金組成になるように混合し、これを高周波誘導溶解炉により溶融させた後、これを冷却させて、水素吸蔵合金のインゴットを得た。なお、この水素吸蔵合金の組成を高周波プラズマ分光分析法（ＩＣＰ）によって分析した結果、この水素吸蔵合金の組成は（Ｌａ0.20Ｐｒ0.39Ｎｄ0.40Ｚｒ0.01）0.84Ｍｇ0.16Ｎｉ3.15Ａｌ0.20になっていた。
(Example)
In this embodiment, when producing a hydrogen storage alloy for an alkaline storage battery used for the negative electrode, the rare earth elements La, Pr, and Nd, Zr, Mg, Ni, and Al are made to have a predetermined alloy composition. This was mixed and melted in a high frequency induction melting furnace, and then cooled to obtain a hydrogen storage alloy ingot. As a result of analyzing the composition of the hydrogen storage alloy by high frequency plasma spectroscopy (ICP), the composition of the hydrogen storage alloy was (La 0.20 Pr 0.39 Nd 0.40 Zr 0.01 ) 0.84 Mg 0.16 Ni 3.15 Al 0.20 . .
そして、この水素吸蔵合金のインゴットをアルゴン雰囲気中において９５０℃で熱処理して均質化させた後、この水素吸蔵合金のインゴットを不活性雰囲気中において機械的に粉砕し、これを分級して、体積平均粒径が３０μｍになった上記の組成の水素吸蔵合金の粉末を得た。なお、上記の水素吸蔵合金の粉末の体積平均粒径は、レーザ回折式粒度分布測定装置を用いて測定した。 Then, the hydrogen storage alloy ingot was heat treated in an argon atmosphere at 950 ° C. to homogenize, and then the hydrogen storage alloy ingot was mechanically pulverized in an inert atmosphere, and this was classified into a volume. A hydrogen storage alloy powder having the above composition with an average particle size of 30 μm was obtained. The volume average particle size of the hydrogen storage alloy powder was measured using a laser diffraction particle size distribution analyzer.
また、このようにして得た水素吸蔵合金の粉末について、Ｃｕ−Ｋα管をＸ線源とするＸ線回折装置を用い、スキャンスピード１°／ｍｉｎ，管電圧４０ｋＶ，管電流４０ｍＡ，スキャンステップ０．０２°でＸ線回折測定を行った。この結果、上記の水素吸蔵合金は、Ｃｅ2Ｎｉ7型の結晶構造のものとピークの位置が略一致しており、この水素吸蔵合金はＣｅ2Ｎｉ7型の結晶構造或いはこれに近い結晶構造になっていると考えられる。 Further, the hydrogen storage alloy powder thus obtained was subjected to a scan speed of 1 ° / min, a tube voltage of 40 kV, a tube current of 40 mA, a scan step of 0 using an X-ray diffractometer using a Cu—Kα tube as an X-ray source. X-ray diffraction measurement was performed at .02 °. As a result, the above hydrogen storage alloy has a Ce 2 Ni 7 type crystal structure whose peak position is substantially the same, and this hydrogen storage alloy has a Ce 2 Ni 7 type crystal structure or a crystal structure close thereto. It is thought that.
次いで、上記のようにして得た水素吸蔵合金粉末２．０ｋｇを、２リットルの塩酸溶液（ｐＨ１）中に浸漬させて、ｐＨ７に達するまで約６分間酸処理を行って、アルカリ蓄電池用水素吸蔵合金の粉末を得た。 Next, 2.0 kg of the hydrogen storage alloy powder obtained as described above was immersed in 2 liters of hydrochloric acid solution (pH 1) and subjected to acid treatment for about 6 minutes until pH 7 was reached. An alloy powder was obtained.
そして、上記のように酸処理したアルカリ蓄電池用水素吸蔵合金の粉末１００重量部に対して、結着剤のポリエチレンオキシドを０．５重量部、ポリビニルピロリドンを０．６重量部加え、これらを均一に混合してスラリーを調製した。そして、このスラリーをニッケル鍍金を施したパンチングメタルからなる導電性芯体の両面に均一に塗布し、これを乾燥させてプレスした後、所定の寸法に切断して、負極に用いる水素吸蔵合金電極を作製した。 Then, 0.5 parts by weight of polyethylene oxide as a binder and 0.6 parts by weight of polyvinyl pyrrolidone are added to 100 parts by weight of the powder of the hydrogen storage alloy for alkaline storage batteries that has been acid-treated as described above, and these are uniformly added. To prepare a slurry. Then, the slurry is uniformly applied to both surfaces of a punching metal made of nickel plating, dried, pressed, cut into a predetermined size, and a hydrogen storage alloy electrode used for the negative electrode Was made.
一方、正極を作製するにあたっては、正極活物質の水酸化ニッケル１００重量部に対して、０．２重量％のヒドロキシプロピルセルロース水溶液を５０重量部加え、これらを混合させてスラリーを調整した。そして、このスラリーをニッケル発泡体に充填し、これを乾燥させて圧延させた後、所定の寸法に切断して、非焼結式ニッケル極からなる正極を作製した。 On the other hand, in preparing the positive electrode, 50 parts by weight of a 0.2% by weight hydroxypropylcellulose aqueous solution was added to 100 parts by weight of nickel hydroxide as the positive electrode active material, and these were mixed to prepare a slurry. Then, the slurry was filled in a nickel foam, dried and rolled, and then cut into a predetermined size to produce a positive electrode composed of a non-sintered nickel electrode.
また、セパレータとしては、耐アルカリ性の不織布を使用し、アルカリ電解液としては、ＫＯＨとＮａＯＨとＬｉＯＨ・Ｈ2Ｏとが８：０．５：１の重量比で含まれ、これらの総和が３０重量％になったアルカリ水溶液を使用し、設計容量が３Ａｈになった、図１に示すような円筒型のＳＣサイズのアルカリ蓄電池を作製した。 In addition, an alkali-resistant non-woven fabric is used as a separator, and KOH, NaOH, and LiOH.H 2 O are included at a weight ratio of 8: 0.5: 1 as an alkaline electrolyte, and the total of these is 30. A cylindrical SC-sized alkaline storage battery as shown in FIG. 1 having a design capacity of 3 Ah was prepared using an alkaline aqueous solution having a weight%.
ここで、上記のアルカリ蓄電池を作製するにあたっては、図１に示すように、正極１と負極２との間にセパレータ３を介在させ、これらをスパイラル状に巻いて電池缶４内に収容させ、上記の負極２の一端を電池缶４内部の底面に取り付けられた負極集電体５に接続させる一方、上記の正極１の一端を正極集電体６に接続させると共にこの正極集電体６のリード部６ａを正極外部端子７と反対側における正極蓋８の面に接続させ、この電池缶４内に上記のアルカリ電解液（図示せず）を注液した後、この電池缶４と正極蓋８との間に絶縁パッキン９を配して封口し、この絶縁パッキン９により電池缶４と正極蓋８とを電気的に分離させた。また、上記の正極蓋８に設けられたガス放出口８ａを閉塞させるようにして、この正極蓋８と正極外部端子７との間にコイルスプリング１０によって付勢された閉塞板１１を設け、電池の内圧が異常に上昇した場合には、このコイルスプリング１０が圧縮されて、電池内部のガスが大気中に放出されるようにした。
Here, in producing the alkaline storage battery, as shown in FIG. 1, the
（比較例）
比較例においては、負極に用いるアルカリ蓄電池用水素吸蔵合金を製造するにあたり、水素吸蔵合金の粉末に対して酸処理を行わないようにし、それ以外は上記の実施例の場合と同様にして、アルカリ蓄電池用水素吸蔵合金の粉末を得た。
(Comparative example)
In the comparative example, in producing the hydrogen storage alloy for an alkaline storage battery used for the negative electrode, acid treatment was not performed on the powder of the hydrogen storage alloy. A hydrogen storage alloy powder for a storage battery was obtained.
そして、このように酸処理を行っていないアルカリ蓄電池用水素吸蔵合金の粉末を用いる以外は、上記の実施例の場合と同様にして、負極を作製すると共に、設計容量が３Ａｈになった円筒型のアルカリ蓄電池を作製した。 Then, except for using the hydrogen storage alloy powder for an alkaline storage battery that has not been subjected to acid treatment in this way, a negative electrode was produced and a cylindrical shape with a design capacity of 3 Ah was produced in the same manner as in the above example. An alkaline storage battery was prepared.
次に、上記のようにして作製した実施例及び比較例の各アルカリ蓄電池を、２５℃の温度条件下において、それぞれ０．３Ａの電流で１６時間充電させた後、０．６Ａの電流で電池電圧が１．０Ｖになるまで放電させ、次いで、０．３Ａの電流で１６時間充電させた後、３．０Ａの電流で電池電圧が１．０Ｖになるまで放電させた。さらに、上記の各アルカリ蓄電池を３Ａの電流で電池電圧が最大値に達した後、１０ｍＶ低下するまで充電させて、０．５時間放置した後、９Ａの電流で電池電圧が１．０Ｖになるまで放電させ、これを３サイクル行って、各アルカリ蓄電池を活性化させた。 Next, each of the alkaline storage batteries of Examples and Comparative Examples produced as described above was charged at a current of 0.3 A for 16 hours under a temperature condition of 25 ° C., and then charged at a current of 0.6 A. The battery was discharged until the voltage reached 1.0 V, then charged with a current of 0.3 A for 16 hours, and then discharged with a current of 3.0 A until the battery voltage reached 1.0 V. Further, after each of the above alkaline storage batteries reaches a maximum value at a current of 3 A, the battery voltage is charged until it decreases by 10 mV, and after being left for 0.5 hours, the battery voltage becomes 1.0 V at a current of 9 A. Each of the alkaline storage batteries was activated by performing three cycles.
そして、上記のように活性化させた実施例及び比較例の各アルカリ蓄電池を解体して、それぞれ負極を取り出し、各負極を水洗し、真空乾燥させた後、各負極からそれぞれ水素吸蔵合金粒子を採取し、各水素吸蔵合金粒子について、その表面を透過型電子顕微鏡（ＴＥＭ）により観察した。 Then, the alkaline storage batteries of Examples and Comparative Examples activated as described above were disassembled, the negative electrodes were taken out, the negative electrodes were washed with water, and vacuum-dried, and then the hydrogen storage alloy particles were respectively removed from the negative electrodes. The surface of each hydrogen storage alloy particle was collected and observed with a transmission electron microscope (TEM).
この結果、実施例の水素吸蔵合金粒子の最表面には、比較例の水素吸蔵合金粒子の最表面に比べて、厚く均一な黒い層が形成されていた。 As a result, a thick and uniform black layer was formed on the outermost surface of the hydrogen storage alloy particles of the example compared to the outermost surface of the hydrogen storage alloy particles of the comparative example.
次に、上記の各水素吸蔵合金粒子について、電子分散Ｘ線分光（ＥＤＳ）により、各水素吸蔵合金粒子における上記の最表面と合金内部とにおける元素分析を行い、それぞれ希土類元素の総量に対するＮｉ，Ａｌ，Ｍｇの各元素の原子比を求め、水素吸蔵合金粒子の内部に対する最表面におけるＮｉ，Ａｌ，Ｍｇの各元素の増減率を下記の式によって求め、その結果を下記の表１に示した。なお、最表面におけるＮｉ，Ａｌ，Ｍｇの各元素の原子比が、水素吸蔵合金粒子の内部より少ないと、１００％未満になる。
各元素の増減率（％）＝（最表面における希土類元素の総量に対する各元素の原子比／合金内部における希土類元素の総量に対する各元素の原子比）×１００
Next, for each of the hydrogen storage alloy particles, elemental analysis is performed on each of the hydrogen storage alloy particles at the outermost surface and inside the alloy by electron dispersive X-ray spectroscopy (EDS). The atomic ratio of each element of Al and Mg was determined, and the rate of increase / decrease of each element of Ni, Al, and Mg on the outermost surface with respect to the inside of the hydrogen storage alloy particles was determined by the following formula, and the results are shown in Table 1 below. . In addition, when the atomic ratio of each element of Ni, Al, and Mg on the outermost surface is less than the inside of the hydrogen storage alloy particles, it becomes less than 100%.
Rate of change (%) of each element = (atomic ratio of each element to the total amount of rare earth elements on the outermost surface / atomic ratio of each element to the total amount of rare earth elements inside the alloy) × 100
この結果、比較例の水素吸蔵合金粒子においては、その最表面におけるＮｉ，Ａｌ，Ｍｇの各元素の割合が合金内部よりも少なくなっていたのに対して、実施例の水素吸蔵合金粒子においては、その最表面におけるＮｉ，Ａｌ，Ｍｇの各元素の割合が合金内部よりも大きく増加しており、実施例の水素吸蔵合金粒子においては、その最表面にＮｉ，Ａｌ，Ｍｇの各元素が多く含まれる厚い均一な層が形成されていることが分かった。 As a result, in the hydrogen storage alloy particles of the comparative example, the proportion of each element of Ni, Al, Mg on the outermost surface was smaller than the inside of the alloy, whereas in the hydrogen storage alloy particles of the example, The ratio of each element of Ni, Al, Mg on the outermost surface is greatly increased from the inside of the alloy, and in the hydrogen storage alloy particles of the example, there are many elements of Ni, Al, Mg on the outermost surface. It was found that a thick uniform layer was formed.
また、上記の各水素吸蔵合金粒子について、それぞれＢＥＴ比表面積を測定し、その結果を下記の表２に示した。 Further, the BET specific surface area was measured for each of the above hydrogen storage alloy particles, and the results are shown in Table 2 below.
この結果、実施例の水素吸蔵合金粒子におけるＢＥＴ比表面積は、比較例の水素吸蔵合金のＢＥＴ比表面積と同程度か、むしろ小さくなっており、前記のように酸処理をしても、この水素吸蔵合金粒子にひび割れが生じていないことが分かった。 As a result, the BET specific surface area of the hydrogen storage alloy particles of the example is approximately the same as or slightly smaller than the BET specific surface area of the hydrogen storage alloy of the comparative example. It was found that the storage alloy particles were not cracked.
このため、このような水素吸蔵合金粒子を用いた実施例のアルカリ蓄電池においては、充放電を繰り返して行った場合においても、従来のように水素吸蔵合金粒子が微粉化して酸化が進むということがなく、アルカリ蓄電池のサイクル寿命が低下するのが防止される。 For this reason, in the alkaline storage battery of the example using such hydrogen storage alloy particles, even when charging and discharging are repeated, the hydrogen storage alloy particles are pulverized and oxidation proceeds as in the past. Therefore, the cycle life of the alkaline storage battery is prevented from being lowered.
なお、上記の水素吸蔵合金粒子を酸処理した場合に、この水素吸蔵合金粒子のＢＥＴ比表面積が増加しない理由については、必ずしも明確ではないが、Ｃｅ2Ｎｉ7型の結晶構造又はこれに近い結晶構造の結晶格子内において、希土類元素と同じサイトを占めるマグネシウムが存在することにより、酸処理時にこの水素吸蔵合金にひび割れが生じたり、微紛化したりするのが抑制されるためであると考えられる。 The reason why the BET specific surface area of the hydrogen storage alloy particles does not increase when the above hydrogen storage alloy particles are acid-treated is not necessarily clear, but the Ce 2 Ni 7 type crystal structure or a crystal close thereto is not clear. It is considered that the presence of magnesium occupying the same site as the rare earth element in the crystal lattice of the structure suppresses the hydrogen storage alloy from being cracked or micronized during acid treatment. .
次に、上記のように活性化させた実施例及び比較例の各アルカリ蓄電池を、２５℃の温度条件下において、それぞれ３Ａの電流で電池電圧が最大値に達した後、１０ｍＶ低下するまで充電させ、これらを−１０℃の恒温槽内で３時間放置させた後、１０Ａの高い電流で電池電圧が０．６Ｖになるまで放電させ、その時の放電曲線を図２に示すと共に、その時の放電容量（Ａｈ）を低温高率放電特性として、下記の表３に示した。 Next, the alkaline storage batteries of Examples and Comparative Examples activated as described above were charged until the battery voltage reached a maximum value at a current of 3 A under a temperature condition of 25 ° C. until the voltage decreased by 10 mV. These were allowed to stand in a thermostatic bath at -10 ° C. for 3 hours, and then discharged at a high current of 10 A until the battery voltage reached 0.6 V. The discharge curve at that time is shown in FIG. The capacity (Ah) is shown in Table 3 below as a low temperature high rate discharge characteristic.
この結果、比較例のアルカリ蓄電池においては、上記の低温高率放電特性が０．３６Ａｈと非常に低くなっていたのに対して、実施例のアルカリ蓄電池においては、上記の低温高率放電特性が２．５７Ａｈとなっており、低温高率放電特性が大幅に向上していた。 As a result, in the alkaline storage battery of the comparative example, the low-temperature high-rate discharge characteristic was as low as 0.36 Ah, whereas in the alkaline storage battery of the example, the low-temperature high-rate discharge characteristic was The low-temperature high-rate discharge characteristics were greatly improved.
なお、図２に示す比較例のアルカリ蓄電池の放電曲線を見ると、放電開始直後から急激に電圧が低下しているのではなく、放電が少し進んだ時点で、電圧が急激に低下していることから、この電圧の低下は水素吸蔵合金粒子の表面での水素の拡散が遅く、水素の供給が遅れているためであると考えられる。 In addition, when the discharge curve of the alkaline storage battery of the comparative example shown in FIG. 2 is seen, the voltage is not suddenly decreased immediately after the start of the discharge, but the voltage is suddenly decreased when the discharge is slightly advanced. From this, it is considered that this voltage drop is caused by the slow diffusion of hydrogen on the surface of the hydrogen storage alloy particles and the delay in the supply of hydrogen.
この結果、上記の実施例のアルカリ蓄電池において、低温高率放電特性が向上したのは、上記のように水素吸蔵合金粒子の表面に形成されたＮｉ，Ａｌ，Ｍｇの各元素が合金内部よりも大きく含まれる層により、この水素吸蔵合金粒子の表面における水素拡散速度が大幅に向上したためであると考えられる。 As a result, in the alkaline storage battery of the above example, the low temperature high rate discharge characteristics were improved because the Ni, Al and Mg elements formed on the surface of the hydrogen storage alloy particles as described above were more than the inside of the alloy. This is presumably because the hydrogen diffusion rate on the surface of the hydrogen storage alloy particles was greatly improved by the layer that was largely contained.
１ 正極
２ 負極
３ セパレータ
４ 電池缶
５ 負極集電体
６ 正極集電体
６ａ リード部
７ 正極外部端子
８ 正極蓋
８ａ ガス放出口
９ 絶縁パッキン
１０ コイルスプリング
１１ 閉塞板
DESCRIPTION OF
Claims (4)
An alkaline storage battery comprising a positive electrode, a negative electrode using a hydrogen storage alloy, and an alkaline electrolyte, wherein the hydrogen storage alloy for an alkaline storage battery according to claim 1 is used as the hydrogen storage alloy of the negative electrode. Alkaline storage battery.
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| JPH1079249A (en) * | 1996-09-03 | 1998-03-24 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy for electrode |
| JPH10116611A (en) * | 1996-10-11 | 1998-05-06 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy electrode |
| JPH11283619A (en) * | 1998-03-30 | 1999-10-15 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy for alkaline storage battery |
| JP2000080429A (en) * | 1998-08-31 | 2000-03-21 | Toshiba Corp | Hydrogen storage alloy and secondary battery |
| WO2001048841A1 (en) * | 1999-12-27 | 2001-07-05 | Kabushiki Kaisha Toshiba | Alloy for hydrogen storage, secondary battery, hybrid car and electric vehicle |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH1079249A (en) * | 1996-09-03 | 1998-03-24 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy for electrode |
| JPH10116611A (en) * | 1996-10-11 | 1998-05-06 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy electrode |
| JPH11283619A (en) * | 1998-03-30 | 1999-10-15 | Sanyo Electric Co Ltd | Manufacture of hydrogen storage alloy for alkaline storage battery |
| JP2000080429A (en) * | 1998-08-31 | 2000-03-21 | Toshiba Corp | Hydrogen storage alloy and secondary battery |
| WO2001048841A1 (en) * | 1999-12-27 | 2001-07-05 | Kabushiki Kaisha Toshiba | Alloy for hydrogen storage, secondary battery, hybrid car and electric vehicle |
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