JP4706163B2 - Hydrogen storage alloy electrode and nickel metal hydride storage battery using the same - Google Patents

Description

【００９４】
高平衡圧水素吸蔵合金粉末の水素平衡解離圧が０．６５ＭＰａ以上であり、低平衡圧水素吸蔵合金粉末の水素平衡解離圧が０．１ＭＰａ以下であり、さらにニッケル粉末を含有する水素吸蔵合金電極を負極として有する実施例１〜１４のニッケル水素蓄電池は、前記条件を満たさない比較例１〜４のニッケル水素蓄電池と比較して高率放電性能に優れた。
【００９５】
比較例３のように、高平衡圧水素吸蔵合金粉末と低平衡圧水素吸蔵合金粉末とを混合したのみでは、優れた高率放電性能を得ることはできないのに対して、実施例１のように、これらの水素吸蔵合金粉末にニッケル粉末を添加した場合には優れた高率放電性能を得ることができた。
これは、比較例３にても高平衡圧水素吸蔵合金粉末が低平衡圧水素吸蔵合金粉末の水素を受け取り、速やかに合金の活性面に移動せしめることが出来るものの、活性場そのものが不足していることによって、高率放電特性が不十分であるのに対して、実施例１では、ニッケル粉末の添加によって、活性場が充分に存在し、高率放電特性が大幅に向上したものと推定される。
【００９６】
また、比較例４と実施例６と実施例９とを比較して分かるように、優れた高率放電性能を得るためには、高平衡圧水素吸蔵合金粉末は、０．６５Ｍｐａ以上の水素平衡解離圧を有する必要があり、０．９Ｍｐａ以上である場合は、極めて高い高率放電特性を示すことが確認された。
これは、より高い水素平衡解離圧を有する合金を添加することによって、水素を速やかに活性場に移動させる駆動力を高めることができ、高率放電特性が向上するものと推定される。
なかでも、実施例１、実施例２、実施例４を比較して分かるように、ニッケルが金属ニッケルの粉末で構成され、その比表面積が１．５ｍ²／ｇ以上、嵩密度が０．８ｇ／ｍｌ以下である場合、特に優れた高率放電特性が得られた。ニッケルの活性はニッケルの量だけではなく、表面場の多さ、即ち、表面積にも大きく依存するものと考えられ、表面積を大きく有するニッケル粉末を添加することによって、高率放電特性の大幅な改善が出来た。
【００９７】
また、比較例３、実施例１，５，３，７を比較してわかるように、水素吸蔵合金を１００重量部に対してニッケル粉末の含有量が、２重量部以上１０重量部以下で有る場合、特に、優れた高率放電性能と、優れた充放電サイクル性能とを合わせ持つことが確認された。ニッケル粉末は、２重量部添加すれば十分であり、多く添加しすぎると水素吸蔵合金の存在割合が低下することによって、充放電サイクル性能が低下するものと考えられる。
【００９８】
また、実施例１と実施例８とを比較して分かるように、高平衡圧水素吸蔵合金粉末、及び、低平衡圧水素吸蔵合金粉末に関して、希土類元素としてＬａを主成分とし、Ｎｉ，Ｃｏ，Ｍｎ及びＡｌからなる群から選択される１種以上の元素を含有し、さらに、高平衡圧水素吸蔵合金粉末を、Ｎｉ元素に対してＬａが５ｍｏｌ％以上、Ｎｉ元素に対してＭｎとＡｌとの総モル量が５ｍｏｌ％以下となるように構成することによって、優れた高率放電性能を示しながら、より優れた充放電サイクル性能を示した。
なかでも、実施例８，１０，１１，１２を比較して分かるように、高平衡圧水素吸蔵合金粉末が、水素吸蔵合金電極の全重量に対して１０重量％以上３０重量％以下である場合、極めて優れた充放電サイクル性能が得られた。
【００９９】
希土類元素としてＬａを主成分とし、遷移元素としてＮｉ，Ｃｏ，Ｍｎ及びＡｌからなる群から選択される１種以上の元素を主成分とする水素吸蔵合金粉末を用いると、優れた充放電サイクル性能を示す。また、特に高平衡圧水素吸蔵合金粉末が前記水素吸蔵合金粉末とされることによって、高い水素平衡解離圧を有することができたとともに、さらに、高い水素平衡解離圧を得るための方策として、Ｎｉ元素に対して（Ｎｉを１００ｍｏｌ％とした時）、Ｌａを５ｍｏｌ％以上とし、かつ、ＭｎとＡｌの総含有量が５ｍｏｌ％以下とした場合、高い水素平衡圧を有しながら耐食性に優れた水素吸蔵合金を得ることができ、これによって、優れた高率放電特性に加えて、極めて優れた充放電サイクル性能が得られたものと考えられる。
【０１００】
また、高平衡圧水素吸蔵合金粉末と低平衡圧水素吸蔵合金粉末との混合比に関し、高平衡圧水素吸蔵合金粉末の量が多すぎる場合、充放電電圧曲線が、高平衡圧水素吸蔵合金と低平衡圧水素吸蔵合金の有する個別の電位を示して２段階のカーブとなって、電池性能が所望のものに制御されにくいばかりでなく、高平衡圧水素吸蔵合金粉末の利用率が低下してしまう。高平衡圧水素吸蔵合金粉末の含有量が、水素吸蔵合金電極の全重量に対して３０重量％以下の場合、高平衡圧水素吸蔵合金粉末を有する合金の利用率は単独で用いる合金の利用率よりも非常に高いものと考えられる。これは、高平衡圧水素吸蔵合金粉末を単独で用いる場合の利用率の低下は、充電を行なうことができないことによるのに対し、高平衡圧水素吸蔵合金粉末と低平衡圧水素吸蔵合金とを混合して用いた場合における、高平衡圧水素吸蔵合金粉末の利用率の向上は、高平衡圧水素吸蔵合金粉末が低平衡圧水素吸蔵合金粉末より水素を貰うことによって充電を行なうことができるとともに、ニッケル粉末が共存することによるものと考えられる。
【０１０１】
また、実施例１，１３，１４を比較して分かるように、高平衡圧水素吸蔵合金粉末の平均粒径が大きくなると高率放電性能が低下する傾向となるため、２５μｍ以下が好ましく、低平衡圧水素吸蔵合金粉末の平均粒径が小さくなると、充放電サイクル性能が低下する傾向となるため、３０μｍ以上が好ましいことが確認された。水素吸蔵合金は粒径が大きいほど反応場が減少するため、高率放電性能に優れないが、充放電サイクル性能が優れることが一般に知られている。低平衡圧水素吸蔵合金粉末の平均粒径を大きくする事によって、優れた充放電サイクル性能を維持しつつ、高率放電性能の向上に必要とされる高平衡圧水素吸蔵合金粉末の平均粒径を２５μｍ以下とすることによって、優れた高率放電特性と優れた充放電サイクル性能とを両立することが出来た。
【０１０２】
本発明に係る水素吸蔵合金電極によれば、高率放電性能に優れたニッケル水素蓄電池を提供できる。このようなニッケル水素蓄電池によれば、大電流放電性能に優れた電池とすることができるので、電気自動車や電動工具に対する電源として利用できる。
【０１０３】
ニッケル粉末の比表面積が１．５ｍ ^２ ／ｇ以上、ニッケル粉末のかさ密度が０．８ｇ／ｍｌ以下である本発明に係る水素吸蔵合金電極によれば、特に、高率放電性能に優れたニッケル水素蓄電池を提供できる。
また、水素吸蔵合金粉末１００重量部に対して、ニッケル粉末を２重量部以上１０重量部以下で含有してなる本発明に係る水素吸蔵合金電極によれば、特に、高率放電性能及び充放電サイクル性能に優れたニッケル水素蓄電池を提供できる。
【０１０４】
高平衡圧水素吸蔵合金粉末、及び、低平衡圧水素吸蔵合金粉末は、希土類元素としてＬａを主成分とし、Ｎｉ，Ｃｏ，Ｍｎ及びＡｌからなる群から選択される１種以上の元素を含有するとともに、高平衡圧水素吸蔵合金粉末の含有量は、水素吸蔵合金電極の全重量に対して１０重量％以上３０重量％以下であり、高平衡圧水素吸蔵合金粉末は、Ｎｉ元素に対してＬａが５ｍｏｌ％以上、Ｎｉ元素に対してＭｎとＡｌとの総モル量が５ｍｏｌ％以下となるように構成されたこと、及び、高平衡圧水素吸蔵合金粉末の平均粒径が２５μｍ以下であり、低平衡圧水素吸蔵合金粉末の平均粒径が３０μｍ以上であることに係る本発明の水素吸蔵合金電極によれば、耐食性が優れ、特に良好な充放電サイクル性能を得ることができるとともに、高率放電特性にも優れた密閉型ニッケル水素蓄電池が提供できる。よって、この電池を電源とする機器の性能が向上し、それらの用途をさらに広げることができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係るニッケル水素蓄電池の破断斜視図である。
【符号の説明】
１ ニッケル水素蓄電池
２ ケース
２ａ 上部開口部
３ 正極
４ 負極
５ ニッケル水素蓄電池用セパレータ
６ 絶縁ガスケット
７ 封口板
８ 正極端子
９ 集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen storage alloy electrode and a nickel metal hydride storage battery using the same, and more particularly to a nickel metal hydride storage battery excellent in high rate discharge performance and charge / discharge cycle performance.
[0002]
[Prior art]
In recent years, electric devices such as electric vehicles and electric tools that require large current discharge tend to increase rapidly. As a power source for these devices, a sealed nickel-metal hydride storage battery has recently attracted particular attention as a clean power source for the environment in addition to higher energy per unit volume and unit mass than a nickel cadmium storage battery or a lead storage battery. In addition, the nickel-metal hydride storage battery can absorb oxygen generated at the positive electrode during overcharge by the negative electrode containing the hydrogen storage alloy, so the charge control method is simpler than the lithium ion battery, and the charging circuit is also Has the advantage of being simplified.
[0003]
However, since the hydrogen storage alloy has a slow charge transfer on the surface of the alloy, it has a disadvantage that the high rate discharge performance is inferior to that of the nickel cadmium battery. Also known is a hydrogen storage alloy that contains rare earth elements, nickel, and other transition metal elements as a main component and absorbs and desorbs hydrogen, and a battery equipped with an electrode containing this hydrogen storage alloy is sufficient. It takes a long time for the initial activation until a satisfactory discharge characteristic is exhibited, and charging / discharging for activation from several tens of times to several hundred times is necessary.
[0004]
Among these problems, many proposals have been made in order to solve the problem that the activation of the hydrogen storage alloy is slow and is not excellent in high rate discharge. For example, a method is known in which surface treatment is performed on a hydrogen storage alloy to reduce the number of charge / discharge cycles for the activation and to improve high-rate discharge performance. However, in this method, not only the cost required for the surface treatment is high, but also the high rate discharge characteristics cannot be sufficiently improved.
[0005]
For this reason, in order to obtain a battery having excellent high rate discharge performance, a negative electrode containing two or more types of hydrogen storage alloys having different characteristics has been proposed.
More specifically, it is disclosed that the negative electrode includes three or more types of hydrogen storage alloys having different plateau pressures (hydrogen equilibrium dissociation pressures) at a constant temperature (refer to Conventional Example 1: Patent Document 1). .
The negative electrode contains at least two types of hydrogen storage alloys a and b having different hydrogen equilibrium dissociation pressures when the hydrogen storage amount at 45 ° C. is 0.5% by weight, and the hydrogen storage amount at 45 ° C. is 0.5% by weight. An example is described in which the hydrogen equilibrium dissociation pressure is 0.35 MPa for hydrogen storage alloy a and 0.02 MPa for hydrogen storage alloy b (conventional example 2: refer to Patent Document 2).
[0006]
[Patent Document 1]
JP-A-10-199522 (paragraphs [0009] to [0011])
[Patent Document 2]
JP 2000-149933 A (paragraph [0020])
[Patent Document 3]
JP-A-53-103541
[Patent Document 4]
Japanese Examined Patent Publication No. 58-46827
[Patent Document 5]
JP-A 61-64069
[0007]
[Problems to be solved by the invention]
However, the nickel-metal hydride storage batteries having the negative electrodes of Conventional Examples 1 and 2 are not sufficient, although the high-rate discharge performance tends to be improved by the hydrogen storage alloy having a high hydrogen equilibrium dissociation pressure. The number of charge / discharge cycles required is not sufficiently reduced. This is presumably because the hydrogen storage alloy has a high hydrogen dissociation pressure, so that hydrogen is easily desorbed, but the hydrogen storage alloy does not have sufficient active fields required for the reaction.
Moreover, the nickel hydride storage battery which has the negative electrode of the prior art examples 1 and 2 is also inadequate charge / discharge cycle performance. This is because, as described above, in addition to the fact that the hydrogen storage alloy does not have enough active fields required for the reaction, in general, an alloy having a high hydrogen equilibrium dissociation pressure is charged more than an alloy having a low hydrogen equilibrium dissociation pressure. It is considered that an alloy having a low discharge capacity, a small Co content ratio, and a high hydrogen equilibrium dissociation pressure is not excellent in corrosion resistance.
[0008]
Further, in general, the hydrogen storage alloy powder has low conductivity, and when used as an active material for an electrode, there is a drawback that the working area is small. For this reason, the nickel-metal hydride storage battery having a hydrogen storage alloy electrode as a negative electrode has a drawback that the high rate discharge performance is inferior. As means for improving the conductivity of the electrode, addition of carbon black to the hydrogen storage alloy powder has been proposed (see Patent Document 3), but a sufficient effect cannot be obtained. Further, a method of adding nickel powder to a hydrogen storage alloy powder and sintering (see Patent Document 4) and a method of coating the surface of the hydrogen storage alloy with nickel (see Patent Document 5) have been proposed. However, no effect is obtained for improving the high rate discharge performance. Although these additives reduce the contact resistance of the alloy, it is considered that the effect as an active field cannot be sufficiently exhibited because the diffusion rate of hydrogen in the alloy is slow. Such drawbacks are difficult by improving the hydrogen-absorbing alloy powder itself or improving only the additive as an active field, and yet another effective solution has been required, but no effective proposal has been made.
[0009]
The present invention has been made to solve the above problems, and its purpose is to provide high-rate discharge.NohThe object is to provide an excellent nickel metal hydride storage battery.
[0010]
[Means for Solving the Problems]
The present inventors have confirmed that the negative electrode occupies a large portion of resistance during high rate discharge by performing a high rate discharge resistance component of the sealed nickel-metal hydride battery. Therefore, the present inventors have conducted intensive studies to improve the charge transfer rate on the surface of the hydrogen storage alloy contained in the negative electrode during high rate discharge, and as a result, the hydrogen parallel dissociation pressures each having a specific value are obtained. Surprisingly, when a negative electrode is obtained by mixing two or more types of hydrogen storage alloy powders and nickel powders having different valences, a nickel-metal hydride storage battery with excellent high-rate discharge performance and charge / discharge cycle performance can be obtained. The headline, the present invention has been reached.
[0011]
That is, the technical configuration and operational effects of the present invention are as follows. However, the action mechanism includes estimation, and the correctness of the action mechanism does not limit the present invention.
[0012]
  That is,The present inventionThe hydrogen storage alloy electrode according to the present invention contains nickel powder and “hydrogen storage alloy powder containing rare earth elements and transition elements as main components and capable of storing and desorbing hydrogen”. A high equilibrium pressure hydrogen storage alloy powder consisting of two or more types of hydrogen storage alloy powders with different dissociation pressures, and having the highest hydrogen equilibrium dissociation pressure, is hydrogen equilibrium dissociation under the conditions of 60 ° C and hydrogen storage capacity of 0.5 wt%. The low equilibrium pressure hydrogen storage alloy powder having a pressure of 0.65 MPa or more and the lowest hydrogen equilibrium dissociation pressure has a hydrogen equilibrium dissociation pressure of 0.1 MPa or less at 60 ° C. and a hydrogen storage amount of 0.5 wt%. It is characterized by being.
[0013]
According to such a configuration, when the hydrogen storage alloy electrode is used as, for example, a negative electrode of a nickel metal hydride storage battery, the hydrogen equilibrium dissociation pressure contains a high equilibrium pressure hydrogen storage alloy powder of 0.65 MPa or more. Can be easily desorbed from the hydrogen storage alloy, and the hydrogen storage alloy electrode contains nickel powder, so that the active field required for the reaction can be sufficiently supplied to improve the charge / discharge capacity, and the high storage pressure hydrogen storage Since the decrease in charge / discharge capacity caused by the alloy powder can be compensated, excellent high rate discharge performance can be exhibited. In addition, by including the low equilibrium pressure hydrogen storage alloy powder having a hydrogen equilibrium dissociation pressure of 0.1 MPa or less, an excellent charge / discharge cycle performance can be exhibited, probably because a sufficient negative electrode capacity can be obtained. By the above, it can be set as the hydrogen storage alloy electrode which can obtain the nickel hydride storage battery excellent in the high-rate discharge performance and charging / discharging cycling performance. In order to improve the high rate discharge characteristics, a noble metal element such as Pd or Pt can be added to the hydrogen storage alloy powder instead of the nickel powder, but there is a disadvantage that it is expensive.
[0014]
  The present inventionThe hydrogen storage alloy electrode according to the present invention has a specific surface area of nickel powder of 1.5 m.²/ G or more and the bulk density of the nickel powder is 0.8 g / ml or lessIs preferred. Here, the specific surface area is a value measured by the BET method (nitrogen adsorption method), and the bulk density is A.D. S. T.A. It is a value measured by the standard measurement method of the apparent density of the powder defined in M specification B329.
[0015]
According to such a configuration, the specific surface area of the nickel powder is 1.5 m.²Since the active field is sufficiently present with respect to the unit weight of the nickel powder, the high-rate discharge performance can be more reliably improved. Further, when the bulk density of the nickel powder is 0.8 g / ml or less, an excellent high rate discharge performance can be exhibited because the nickel powder can be highly dispersed inside the electrode.
By the above, it can be set as the hydrogen storage alloy electrode which can obtain the nickel hydride storage battery excellent in especially high rate discharge performance.
[0016]
  The present inventionThe hydrogen storage alloy electrode according to the present invention comprises nickel powder in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy powder.Is preferred.
[0017]
According to such a configuration, if the hydrogen storage alloy electrode is used as, for example, a negative electrode of a nickel metal hydride storage battery, nickel powder is contained in 2 parts by weight or more with respect to 100 parts by weight of the hydrogen storage alloy powder. It is possible to have a sufficient field, more reliably high rate discharge performance can be ensured, and nickel powder is contained so as not to exceed 10 parts by weight. It is possible to obtain an excellent charge / discharge cycle performance because a sufficient negative electrode capacity can be obtained.
By the above, it can be set as the hydrogen storage alloy electrode which can obtain the nickel hydride storage battery excellent in especially high rate discharge performance and charging / discharging cycling performance.
[0018]
  The present inventionIn the hydrogen storage alloy electrode according to the present invention, the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder are selected from the group consisting of La as a main component, Ni, Co, Mn and Al as a rare earth element. In addition to containing one or more elements, the content of the high equilibrium pressure hydrogen storage alloy powder is 10% by weight to 30% by weight with respect to the total weight of the hydrogen storage alloy electrode. Is configured such that La is 5 mol% or more with respect to Ni element and the total molar amount of Mn and Al is 5 mol% or less with respect to Ni element.Is preferred.
[0019]
The high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder are one or more elements selected from the group consisting of La as a rare earth element and Ni, Co, Mn and Al as transition elements. As a main component, the sufficient discharge capacity is surely expressed and the high-rate discharge performance tends to be excellent, and the charge / discharge cycle performance tends to be excellent. Further, the high equilibrium pressure hydrogen storage alloy powder is configured so that La is 5 mol% or more with respect to Ni element and the total molar amount of Mn and Al is 5 mol% or less with respect to Ni element. Equilibrium dissociation pressure can be reliably achieved, excellent high-rate discharge performance can be reliably expressed, and corrosion resistance (particularly corrosion resistance to alkaline electrolyte) is excellent, so that excellent charge / discharge cycle performance can be reliably expressed.
[0020]
Further, since the content of the high equilibrium pressure hydrogen storage alloy powder is 10% by weight or more with respect to the total weight of the hydrogen storage alloy electrode, it is possible to exhibit excellent high rate discharge performance and not to exceed 30% by weight. Therefore, it is possible to sufficiently contain the low equilibrium pressure hydrogen storage alloy powder and to obtain a sufficient negative electrode capacity, so that excellent charge / discharge cycle performance can be exhibited.
By the above, it can be set as the hydrogen storage alloy electrode which can obtain the nickel hydride storage battery excellent in especially high rate discharge performance and charging / discharging cycling performance.
[0021]
  The present inventionIn the hydrogen storage alloy electrode according to the present invention, the average particle size of the high equilibrium pressure hydrogen storage alloy powder is 25 μm or less, and the average particle size of the low equilibrium pressure hydrogen storage alloy powder is 30 μm or more.Is preferred.
[0022]
According to such a configuration, the low equilibrium pressure hydrogen storage alloy powder having a large average particle diameter can be encased in the high equilibrium pressure hydrogen storage alloy powder having a small average particle diameter, and hydrogen transfer between the hydrogen storage alloys can be quickly performed. In addition, since the average particle size of the low equilibrium pressure hydrogen storage alloy powder does not become too small and the specific surface area of the alloy does not become too large, corrosion resistance (particularly corrosion resistance against alkaline electrolyte) can be sufficiently secured.
By the above, it can be set as the hydrogen storage alloy electrode which can obtain the nickel hydride storage battery excellent in especially high rate discharge performance and charging / discharging cycling performance.
[0023]
  The present inventionThe nickel metal hydride storage battery according to the present invention includes a positive electrode containing a positive electrode active material, a negative electrode composed of a hydrogen storage alloy electrode according to the present invention, and an electrolyte.
According to such a configuration, since the hydrogen storage alloy electrode according to the present invention is used as the negative electrode, a nickel-metal hydride storage battery excellent in high rate discharge performance and charge / discharge cycle performance can be obtained.
[0024]
  The present inventionIn the nickel metal hydride storage battery according to the present invention, the positive electrode active material is mainly composed of nickel hydroxide, and the electrolytic solution is mainly composed of an alkali metal hydroxide aqueous solution.Is preferred.
According to such a configuration, a nickel-metal hydride storage battery excellent in high-rate discharge performance and charge / discharge cycle performance can be obtained more reliably.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The hydrogen storage alloy electrode according to the embodiment of the present invention contains nickel powder and “hydrogen storage alloy powder capable of occluding and desorbing hydrogen containing a rare earth element and a transition element as main components”. Here, the hydrogen storage alloy powder is composed of two or more kinds of hydrogen storage alloy powders having different hydrogen equilibrium dissociation pressures. The high equilibrium pressure hydrogen storage alloy powder with the highest hydrogen equilibrium dissociation pressure has a hydrogen equilibrium dissociation pressure of 0.65 MPa or more at 60 ° C. and a hydrogen storage amount of 0.5 wt%, and the hydrogen equilibrium dissociation pressure is the highest. The low low equilibrium pressure hydrogen storage alloy powder has a hydrogen equilibrium dissociation pressure of 0.1 MPa or less at 60 ° C. and a hydrogen storage amount of 0.5 wt%.
[0026]
Here, the hydrogen equilibrium dissociation pressure was measured by accurately weighing 0.5 gram of the sample hydrogen storage alloy powder with an accuracy of 0.1 milligram, filled in the sample holder, and manufactured by Toyobo Engineering Co., Ltd. PCT-A02 type) can be measured by adding 0.5 parts by weight of hydrogen to 100 parts by weight of the hydrogen storage alloy (Examples were measured according to this method). .
[0027]
When the hydrogen storage alloy electrode contains the high equilibrium pressure hydrogen storage alloy powder and the nickel powder, excellent high rate discharge performance can be exhibited. This is because the high equilibrium pressure hydrogen storage alloy powder during high rate discharge can be preferentially discharged by obtaining a sufficient amount of nickel powder as an active field, in addition to improving the high rate discharge characteristics. The hydrogen in the low equilibrium pressure hydrogen storage alloy powder moves to the high equilibrium pressure hydrogen storage alloy powder, dissociates from the high equilibrium pressure hydrogen storage alloy at high speed with high hydrogen equilibrium dissociation pressure, and exists in a sufficient amount. This is considered to be because the discharge reaction can be carried out with nickel powder as an active field.
[0028]
In addition, since the hydrogen storage alloy electrode contains the low equilibrium pressure hydrogen storage alloy powder, a sufficient negative electrode capacity can be obtained.
[0029]
When the hydrogen equilibrium dissociation pressure of the high equilibrium pressure hydrogen storage alloy powder having the highest hydrogen equilibrium dissociation pressure is less than 0.65 MPa, it becomes difficult for hydrogen to desorb from the hydrogen storage alloy, and excellent high rate discharge performance cannot be obtained. .
If the hydrogen storage alloy electrode does not contain nickel powder, a decrease in charge / discharge capacity due to the high equilibrium pressure hydrogen storage alloy powder becomes obvious, and excellent high rate discharge performance cannot be obtained.
Moreover, when the hydrogen equilibrium dissociation pressure of the low equilibrium pressure hydrogen storage alloy powder having the lowest hydrogen equilibrium dissociation pressure exceeds 0.1 MPa, sufficient negative electrode capacity cannot be obtained, and excellent charge / discharge cycle performance is obtained. I can't.
[0030]
Nickel powder has a specific surface area of 1.5m²/ G and a bulk density of 0.8 g / ml or less is preferable, and in particular, excellent high rate discharge performance can be exhibited. The bulk density of nickel powder is thought to contribute to the dispersed state of nickel, and the specific surface area is 1.5 m.²Even when the bulk density exceeds 0.8 g / ml, even if the bulk density exceeds 0.8 g / ml, it tends to be agglomerated particles even in the electrode, and nickel tends not to be highly dispersible, so that the high rate discharge characteristics tend not to be excellent.
[0031]
Nickel powder has a specific surface area of 4.0 m²/ G and a bulk density of 0.8 g / ml or less is more preferable, and thereby an extremely excellent high rate discharge performance can be exhibited. Since nickel powder can act as a reaction active field catalyst, it is considered that the higher the specific surface area, the higher the rate of discharge characteristic can be improved.
[0032]
The hydrogen storage alloy electrode preferably contains 2 to 10 parts by weight of nickel powder with respect to 100 parts by weight of the hydrogen storage alloy powder. When the hydrogen storage alloy electrode contains 2 parts by weight or more of nickel powder with respect to 100 parts by weight of the hydrogen storage alloy powder, the high-rate discharge performance can be more reliably improved, and the nickel powder is reduced to 10 parts. Since it contains so that it may not exceed weight part, the outstanding charge / discharge cycle performance can be expressed.
[0033]
In addition, by making the physical properties and amount of nickel powder as described above, a sealed nickel-metal hydride battery can be obtained with high rate discharge characteristics from the beginning even if the activation step (charge / discharge cycle step) is simplified. . In addition, what was obtained by the carbonyl nickel method can be used conveniently for nickel powder.
[0034]
The high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder are mainly composed of La (lanthanum) as a rare earth element, and include Ni (nickel), Co (cobalt), Mn (manganese), and Al (aluminum). It is preferable to contain one or more elements selected from the group consisting of (Ni, Co, and Mn are transition metals).
Here, La preferably occupies 60 mol% or more of rare earth elements, and is usually 90 mol% or less. Examples of rare earth elements other than La include Ce, Pr, and Nd.
In addition, one or more elements selected from the group consisting of Ni, Co, Mn, and Al, among elements other than rare earth elements, Ni is 60 mol% to 85 mol%, Co is 10 mol% to 30 mol%, and Mn is 0 mol. % To 10 mol%, and Al is preferably 0 to 10 mol%. Examples of elements other than Ni, Co, Mn, and Al (elements other than rare earth elements) include Fe and Cu.
The hydrogen equilibrium dissociation pressure of the hydrogen storage alloy powder can be adjusted by changing the type and weight ratio of elements constituting the alloy.
[0035]
The hydrogen storage alloy powder (high equilibrium pressure hydrogen storage alloy powder) having a hydrogen equilibrium dissociation pressure of 0.65 MPa or more under the conditions of 60 ° C. and hydrogen storage amount of 0.5 wt% is not particularly limited. However, an alloy powder configured such that La is 5 mol% or more with respect to Ni element and the total molar amount of Mn and Al with respect to Ni element is 5 mol% or less can be preferably exemplified. More specifically, an alloy powder that satisfies the following composition range can be suitably exemplified. Here, the amount of each element is mol% when the total amount of elements other than rare earth elements is 100 mol%.
La: 5 mol% to 20 mol%
Ni: 70 mol% to 85 mol%
Co: 15 mol% to 30 mol%
Mn: 0 mol% to 5 mol%
Al: 0 mol% to 5 mol%
[0036]
As a hydrogen storage alloy powder (low equilibrium pressure hydrogen storage alloy powder) having a hydrogen equilibrium dissociation pressure of 0.1 MPa or less at 60 ° C. and a hydrogen storage amount of 0.5 wt%, the following composition range is satisfied. An alloy powder can be preferably exemplified. Here, the amount of each element is mol% when the total amount of elements other than rare earth elements is 100 mol%.
La: 5 mol% to 20 mol%
Ni: 65 mol% to 75 mol%
Co: 10 mol% to 20 mol%
Mn: 5 mol% to 10 mol%
Al: 5 mol% to 10 mol%
[0037]
The method for producing the hydrogen storage alloy powder is not particularly limited, but each metal constituting the hydrogen storage alloy (the above-mentioned predetermined molar ratio) is arc-melted in an argon atmosphere to form a mold. After casting, it is preferable to perform heat treatment (aging) at 900 ° C. to 1050 ° C. for 30 minutes, perform cooling, and mechanically wet pulverize in water using an attritor ball mill or the like. At this time, if another method such as a rapid cooling method is used, segregation in the alloy is reduced, and an equivalent or higher charge / discharge cycle performance is easily obtained.
[0038]
As described above, the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder are one or more selected from the group consisting of La, a rare earth element, and Ni, Co, Mn, and Al. And the content of the high equilibrium pressure hydrogen storage alloy powder is 10% by weight or more and 30% by weight or less based on the total weight of the hydrogen storage alloy electrode. A hydrogen storage alloy electrode configured such that La is 5 mol% or more with respect to the element and the total molar amount of Mn and Al with respect to the Ni element is 5 mol% or less can be mentioned as a particularly preferable form, Excellent high rate discharge performance and charge / discharge cycle performance can be realized.
[0039]
This is because the composition of the high equilibrium pressure hydrogen storage alloy powder and that of the low equilibrium pressure hydrogen storage alloy powder are similar so that “the hydrogen moves quickly between the alloy powders” and “La has an excellent discharge. Performance and charge / discharge cycle performance can be expressed "," High-rate discharge performance extremely high during high-rate discharge by suppressing the amount of Mn and the amount of Al for high equilibrium pressure hydrogen storage alloy powder "With regard to the high equilibrium pressure hydrogen storage alloy powder, the amount of La and the total amount of Mn and Al are defined as described above, thereby providing corrosion resistance (particularly corrosion resistance to alkaline electrolyte). ) Is excellent, and the charge / discharge cycle performance can be reliably expressed.
[0040]
Further, in the particularly preferred embodiment described above, the content of the high equilibrium pressure hydrogen storage alloy powder is 10% by weight or more based on the total weight of the hydrogen storage alloy electrode, whereby excellent high rate discharge performance can be expressed. At the same time, by containing it so as not to exceed 30% by weight, the low equilibrium pressure hydrogen storage alloy powder can be sufficiently contained, and a sufficient negative electrode capacity can be obtained, so that excellent charge / discharge cycle performance can be exhibited.
[0041]
Further, when the average particle size of the high equilibrium pressure hydrogen storage alloy powder is 25 μm or less, excellent high rate discharge characteristics can be obtained. This is because the high equilibrium pressure hydrogen storage alloy powder has a small particle size, so that the low equilibrium pressure hydrogen storage alloy powder is encased in the alloy of the high equilibrium pressure hydrogen storage alloy powder and the hydrogen transfer between the alloys can be performed quickly. it is conceivable that. In addition, the average particle size of the high equilibrium pressure hydrogen storage alloy powder is generally higher, the higher rate discharge performance is better, but the charge / discharge cycle performance tends to decrease, and the hydrogen storage alloy powder is difficult to grind. Therefore, it is preferably 10 μm or more.
When the average particle size of the low equilibrium pressure hydrogen storage alloy powder is 30 μm or more, excellent charge / discharge cycle performance can be obtained. Here, when the average particle size is less than 30 μm, the specific surface area of the alloy is large, so that the low equilibrium pressure hydrogen storage alloy powder tends to be corroded quickly by the alkaline electrolyte. The average particle size of the low equilibrium pressure hydrogen storage alloy powder is usually preferably 50 μm or less.
When the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder having different particle sizes are used, the high rate discharge characteristics and the charge / discharge cycle performance can be further improved.
[0042]
The hydrogen storage alloy electrode according to the embodiment of the present invention described above has an advantage that it can be obtained at low cost since the raw material cost is not high.
[0043]
A nickel metal hydride storage battery according to an embodiment of the present invention includes a positive electrode containing a positive electrode active material, a negative electrode composed of a hydrogen storage alloy electrode according to an embodiment of the present invention, and an electrolyte.
[0044]
As the positive electrode active material contained in the positive electrode, a material mainly composed of nickel hydroxide is preferable. More specifically, a material obtained by mixing nickel hydroxide with zinc hydroxide and cobalt hydroxide is used. The use of nickel hydroxide composite hydroxide obtained by uniformly dispersing by coprecipitation is particularly preferred. For additives other than nickel hydroxide composite oxide, cobalt hydroxide, cobalt oxide or the like is used as a conductive modifier, but the nickel hydroxide composite oxide is coated with cobalt hydroxide, or these water. Part of the nickel oxide composite oxide is oxygen or oxygen-containing gas, or K₂S₂O₈Those oxidized with a chemical such as hypochlorous acid can be used. Further, as an additive, an oxide or hydroxide of rare earth elements such as Y and Yb can be used as a substance for improving oxygen overvoltage.
The higher the weight ratio of nickel hydroxide to the total weight of the positive electrode active material, the better the energy density, but Co (OH)₂Zn (OH)₂If there is little content of Co, there is a tendency that the charging efficiency at high temperature tends to be low, and in order to suppress the formation of γ nickel hydroxide at the time of charging, Co (OH)₂Zn (OH)₂Therefore, it is preferable to be 82% by weight to 90% by weight.
Here, the average oxidation number of the transition metal element contained in the positive electrode active material is 2.03 to 2 by being chemically oxidized by an oxidizing agent or electrochemically oxidized by electrolysis. .4 is preferred. As a result, in particular, since the capacity of the irreversible reaction of the positive electrode is not charged during the initial charge, a charge capacity corresponding to the irreversible reaction of the positive electrode is not easily formed on the negative electrode, and the chargeable capacity of the negative electrode is Since it can be increased, charge / discharge cycle performance can be improved.
[0045]
The negative electrode (hydrogen storage alloy electrode according to an embodiment of the present invention) can contain gadolinium, cerium oxide or hydroxide in addition to yttrium, ytterbium, and erbium as a corrosion-resistant additive. Moreover, you may make these hydrogen storage alloys contain these elements as a metal previously.
[0046]
The positive electrode active material is preferably a powder having an average particle size of 50 μm or less, and the preferable average particle sizes of the hydrogen storage alloy powder and the nickel powder which are constituent members of the negative electrode are as described above. Various pulverizers and classifiers are used to obtain the powder in a predetermined shape. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, or the like is used. At the time of pulverization, wet pulverization may be used using water or an aqueous solution of an alkali metal hydroxide. The classification method is not particularly limited, and a sieve or an air classifier can be used. Both dry and wet methods are used as necessary.
[0047]
Further, the positive electrode and the negative electrode may further contain a conductive agent, a binder, a thickener, a filler, and the like.
[0048]
The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect battery performance. As the conductive agent, natural graphite such as scaly graphite, scaly graphite, earthy graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, vapor grown carbon, metal (copper, (Nickel, gold, etc.) One type of conductive material such as powder or metal fiber or a mixture thereof may be mentioned.
[0049]
Among these conductive agents, acetylene black is desirable from the viewpoints of electron conductivity and coatability. The addition amount of the conductive agent is preferably 0.1% by weight to 10% by weight with respect to the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black after being pulverized into ultrafine particles of 0.1 μm to 0.5 μm because the necessary carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, or a planetary ball mill can be used in a dry or wet manner.
[0050]
As the binder, usually, thermoplastic resins such as polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber Such polymers having rubber elasticity can be used as one kind or a mixture of two or more kinds. The addition amount of the binder is preferably 0.1 to 3% by weight with respect to the total weight of the positive electrode or the negative electrode.
[0051]
As said thickener, polysaccharides, such as carboxymethylcellulose and methylcellulose, can be normally used as 1 type, or 2 or more types of mixtures. The addition amount of the thickener is preferably 0.1 to 3% by weight with respect to the total weight of the positive electrode or the negative electrode.
[0052]
The filler is not particularly limited as long as it does not adversely affect battery performance. Usually, olefinic polymers such as polypropylene and polyethylene, carbon and the like are used. The addition amount of the filler is preferably 5% by weight or less with respect to the total weight of the positive electrode or the negative electrode.
[0053]
The positive electrode and the negative electrode are mixed with main constituent materials (positive electrode active material in the positive electrode, nickel powder and hydrogen storage alloy powder in the negative electrode), a conductive agent and a binder in an organic solvent such as water, alcohol and toluene. The obtained mixture is applied on a current collector described in detail below, and dried, and is preferably produced. About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. Is not to be done.
[0054]
As the positive electrode current collector, there is no particular choice as long as it is an electronic conductor that does not adversely affect the constructed battery. For example, nickel or a nickel-plated steel plate can be suitably used, and a two-dimensional device such as a punched steel plate can be used in addition to a foam, a formed fiber group, and a three-dimensional device subjected to uneven processing. The thickness is not particularly limited, but a thickness of 5 to 700 μm is used. Among these current collectors, it is preferable to use, as the positive electrode, a porous structure foam made of Ni, which has excellent corrosion resistance and oxidation resistance against alkali, and has a structure excellent in current collection. .
[0055]
As the current collector for the negative electrode, it is preferable to use a porous plate which is punched with an iron or steel foil or plate which is inexpensive and excellent in electrical conductivity and plated with Ni for improving reduction resistance. The punching hole diameter of the steel sheet is preferably 1.7 mm or less and the opening ratio is 40% or more, so that the adhesion between the hydrogen storage alloy powder and the current collector is excellent even with a small amount of binder. In addition to the calcined carbon fiber and conductive polymer, the nickel surface of the current collector should be treated with Ni powder, carbon, platinum, etc. attached for the purpose of improving adhesion, conductivity and oxidation resistance. Can do. The surface of these materials can be oxidized.
[0056]
In the hydrogen storage alloy powder contained in the negative electrode (hydrogen storage alloy electrode according to the embodiment of the present invention), it is considered that hydrogen is transferred by the contact portion between the alloy powders. For this reason, although the one where the space density of the hydrogen storage alloy powder with respect to the whole negative electrode is higher is preferable, when it is too high, a crack will generate | occur | produce at the time of entrainment and frequent short circuit will occur. Here, since the density of the hydrogen storage alloy powder varies depending on the specific gravity of the alloy and the density of the filler, it is appropriate to represent the remaining space. The negative electrode is the entire negative electrode space excluding the current collector. Is preferably 25% or less, and is preferably 15% or more in order to suppress the occurrence of the short circuit described above.
[0057]
Further, as a nickel metal hydride storage battery, a form in which a nickel metal hydride battery separator is interposed between a positive electrode and a negative electrode can be suitably exemplified, and as such a nickel metal hydride battery separator, a known excellent high rate discharge can be used. A porous film or a non-woven fabric exhibiting characteristics can be used alone or in combination. Examples of the material constituting the separator include polyolefin resins typified by polyethylene and polypropylene, and nylon. The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength and gas permeability. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics. The separator is preferably subjected to a hydrophilic treatment. For example, a hydrophilic group graft polymerization treatment, sulfonation treatment, corona treatment, PVA treatment may be applied to the surface of a polyolefin resin fiber such as polyethylene, or a sheet obtained by mixing fibers that have already undergone these treatments may be used. .
[0058]
As the electrolytic solution, those generally proposed for use in alkaline batteries and the like can be used. Examples of solutes that use water as a solvent and solutes such as potassium, sodium, lithium, and other alkali metal hydroxides or a mixture of two or more of these include, but are not limited to. Yttrium, ytterbium, erbium, calcium, sulfur Compounds such as zinc can be added alone or in admixture of two or more.
[0059]
The concentration of the electrolyte salt in the electrolyte solution is an aqueous solution containing 5 to 7 mol / l potassium hydroxide and 0.5 to 0.8 mol / l lithium hydroxide in order to reliably obtain a battery having high battery characteristics. Is preferred.
[0060]
The battery according to the embodiment of the present invention preferably has a mode in which the positive electrode active material is mainly composed of nickel hydroxide and the electrolytic solution is mainly composed of an alkali metal hydroxide aqueous solution. It can be set as the nickel hydride storage battery excellent in performance and charging / discharging cycle performance.
[0061]
The nickel metal hydride storage battery according to the embodiment of the present invention, for example, injects the electrolyte before or after stacking the nickel metal hydride battery separator, the positive electrode, and the negative electrode, and finally seals with an exterior material. Therefore, it is preferable to manufacture as a sealed nickel-metal hydride storage battery. Further, in a nickel metal hydride storage battery in which a power generation element in which a positive electrode and a negative electrode are stacked via a nickel hydrogen storage battery separator is wound, the electrolyte is injected into the power generation element before and after the winding. preferable. As the injection method, it is possible to inject at normal pressure, but a vacuum impregnation method, a pressure impregnation method, and a centrifugal impregnation method can also be used.
[0062]
Examples of the material of the exterior body of the nickel-metal hydride battery include nickel-plated iron, stainless steel, polyolefin resin, and the like, or a composite thereof.
[0063]
The configuration and shape of the nickel-metal hydride storage battery are not particularly limited, and a coin battery, a button battery, a square battery, a flat battery, and a roll-shaped positive electrode having a positive electrode, a negative electrode, and a single-layer or multi-layer separator. An example is a cylindrical battery having a negative electrode and a separator.
As a cylindrical battery, for example, as shown in a broken perspective view of FIG. 1, a nickel-metal hydride storage battery 1 is formed by winding a power generation element in which a positive electrode 3 and a negative electrode 4 are stacked via a nickel-hydrogen storage battery separator 5. A form in which the product is a roll and is housed in the cylindrical case 2 can be exemplified. Here, the case 2 is provided with an upper opening 2a through an insulating gasket 6, and a positive electrode terminal 8 is provided at a substantially central portion of the upper opening 2a. Further, a current collector 9 is provided on the upper surface of the roll-like material, and a sealing plate 7 is provided between the current collector 9 and the upper opening 2a.
[0064]
【Example】
Hereinafter, the present invention will be described in more detail on the basis of examples. However, the present invention is not limited to the following description, and the positive electrode active material, the negative electrode material, the positive electrode, the negative electrode, and the electrolyte of the test method and constituting battery are not limited thereto. The separator and battery shape are arbitrary.
[0065]
<Example 1>
[Creation of positive electrode]
(Synthesis of nickel hydroxide particles)
In an aqueous solution in which nickel sulfate, zinc sulfate, and cobalt sulfate are dissolved so that the weight ratio of the hydroxides of the respective metals (ie, nickel hydroxide: zinc hydroxide: cobalt hydroxide) is 93: 5: 2. Then, ammonium sulfate and an aqueous caustic soda solution were added to form an ammine complex. Caustic soda was further added dropwise with vigorous stirring of the reaction system, and the temperature of the reaction system was controlled to 45 ± 2 ° C. and the pH was controlled to 12 ± 0.2 to synthesize spherical high density nickel hydroxide particles as the core layer base material. .
[0066]
(Formation of surface layer on nickel hydroxide particle surface)
The high-density nickel hydroxide particles were put into an alkaline aqueous solution whose temperature was controlled to 45 ± 2 ° C. and pH 12 ± 0.2 with caustic soda. While stirring the solution, an aqueous solution containing cobalt sulfate and ammonia at predetermined concentrations was added dropwise. During this time, an aqueous caustic soda solution was appropriately added dropwise to maintain the pH of the reaction bath in the range of 12 ± 0.2. For about 1 hour, the temperature was maintained in the range of 45 ± 2 ° C. and the pH in the range of 12 ± 0.2, and a surface layer made of a mixed hydroxide containing cobalt was formed on the nickel hydroxide surface. The ratio of the surface layer of the mixed hydroxide was 7% by weight with respect to the core layer mother particles (hereinafter simply referred to as the core layer).
[0067]
(Oxidation treatment of positive electrode active material particles)
100 g of nickel hydroxide particles having a surface layer made of the mixed hydroxide was put into 400 g of NaOH aqueous solution having a temperature of 60 ° C. and a concentration of 10 wt%, and sufficiently stirred. Subsequently, 45 ml of a sodium hypochlorite solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirring was continued for 30 minutes. The active material particles were filtered, washed with water and dried. To the obtained active material particles, 20 g of an aqueous NaOH solution having a concentration of 30 wt% and a temperature of 80 ° C. was added, kept at a temperature of 80 ° C. for 2 hours, washed with water and dried. The average oxidation number of the transition metal elements (Ni, Co) contained in the obtained active material particles is determined by a known method (the active material particles are reacted with ferrous ammonium sulfate and then redox using potassium permanganate. Titration). As a result, the average oxidation number of the transition metal elements (Ni, Co) was 2.15.
[0068]
(Preparation of positive electrode plate)
A carboxymethyl cellulose (CMC) aqueous solution is added to the active material particles to form a paste of the active material particles: CMC solute = 99.5: 0.5, and the paste is 450 g / m.²Of nickel porous material (trade name: Nickel Celmet # 8, manufactured by Sumitomo Electric Industries, Ltd.). Then, after drying at 80 ° C., it was pressed to a predetermined thickness, and the surface was coated with Teflon (registered trademark) to produce a nickel positive electrode plate with a capacity of 3000 mAh having a width of 34 mm (including 1 mm of uncoated portion) and a length of 260 mm .
[0069]
[Production of negative electrode]
AB5-type rare earth LaNi with a particle size of 20 μm_Five20 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.3580 parts by weight of a hydrogen storage alloy having the following composition (Mm: Misch metal) was mixed for 30 minutes, and 95 parts by weight of the obtained alloy mixed powder and 5 parts by weight of nickel powder produced by the carbonyl nickel method were mixed for 30 minutes. Thus, an alloy powder mixture was obtained. The “hydrogen equilibrium dissociation pressure under the conditions of 60 ° C. and a hydrogen storage amount of 0.5% by weight” of the two types of hydrogen storage alloys were 0.65 Mpa and 0.10 Mpa, respectively. The specific surface area of nickel powder by BET method is 1.5m.²/ G, bulk density was 0.8 g / ml.
[0070]
The alloy powder mixture thus obtained and the styrene-butadiene copolymer emulsion were mixed in a mass ratio of 99.35: 0.65 on a dry basis, dispersed in water to form a paste, and blade Using a coater, it was applied to a punched steel plate having a hole diameter of 1.0 mm and an aperture ratio of 42.5%, which was nickel-plated on iron, dried at 80 ° C., pressed to a predetermined thickness, and a width of 34 mm (inside, A hydrogen-absorbing alloy negative electrode plate having a coating length of 1 mm and a length of 260 mm and a capacity of 4800 mAh was produced.
[0071]
The hydrogen storage alloy negative electrode plate, a sulfonated polypropylene nonwoven separator with a thickness of 120 μm, and the nickel positive electrode plate were combined and wound in a roll shape. An alkaline electrolytic solution in which 8 mol / l lithium hydroxide was dissolved was injected to produce a subC-type sealed nickel-metal hydride storage battery having a check valve with a valve opening pressure of 2.4 Mpa. This battery is referred to as a nickel-metal hydride storage battery of Example 1.
[0072]
<Example 2>
A nickel metal hydride storage battery of Example 2 was manufactured in the same manner as in Example 1 except that nickel powder obtained by pulverization by a ball mill was used. Specific surface area of nickel powder in negative electrode by BET method is 1.0m²/ G, bulk density was 1.2 g / ml.
[0073]
<Example 3>
The nickel-metal hydride storage battery of Example 3 was manufactured in the same manner as in Example 1 except that 90 parts by weight of the alloy powder mixture and 10 parts by weight of nickel powder manufactured by the carbonyl nickel method were mixed for 30 minutes. did.
[0074]
<Example 4>
Specific surface area of nickel powder produced by carbonyl nickel method by BET method is 4.0m²The nickel-metal hydride storage battery of Example 4 was manufactured in the same manner as in Example 1 except that the bulk density was 0.8 g / ml.
[0075]
<Example 5>
The nickel-metal hydride storage battery of Example 5 was manufactured in the same manner as in Example 1 except that 98 parts by weight of the alloy powder mixture and 2 parts by weight of nickel powder manufactured by the carbonyl nickel method were mixed for 30 minutes. did.
[0076]
<Example 6>
AB5-type rare earth LaNi with a particle size of 20 μm_Five20 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.60Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 6 was manufactured in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
MmNi_3.60Co_0.6Al_0.3Mn_0.35The hydrogen storage alloy having the following composition had a hydrogen equilibrium dissociation pressure of 60 ° C. and a hydrogen storage amount of 0.5% by weight: 0.07 MPa.
[0077]
<Example 7>
A nickel-metal hydride storage battery of Example 7 was manufactured in the same manner as in Example 1 except that 80 parts by weight of the alloy mixed powder and 20 parts by weight of nickel powder manufactured by the carbonyl nickel method were mixed for 30 minutes. .
[0078]
<Example 8>
AB5 type rare earth MmNi with particle size of 20μm_4.11Co_0.685Al_0.091Mn_0.11420 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 8 was manufactured in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes. MmNi_4.11Co_0.685Al_0.091Mn_0.114The “hydrogen equilibrium dissociation pressure under the conditions of 60 ° C. and a hydrogen storage amount of 0.5 wt%” of the hydrogen storage alloy having the following composition was 0.70 MPa.
[0079]
<Example 9>
AB5 type rare earth MmNi with particle size of 20μm_4.19Co_0.698Al_0.058Mn_0.05820 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 9 was manufactured in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes. MmNi_4.19Co_0.698Al_0.058Mn_0.058The “hydrogen equilibrium dissociation pressure under the conditions of 60 ° C. and a hydrogen storage amount of 0.5 wt%” of the hydrogen storage alloy having the following composition was 0.90 MPa.
[0080]
<Example 10>
AB5 type rare earth MmNi with particle size of 20μm_4.11Co_0.685Al_0.091Mn_0.11430 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 10 was manufactured in the same manner as in Example 1 except that 70 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
[0081]
<Example 11>
AB5 type rare earth MmNi with particle size of 20μm_4.11Co_0.685Al_0.091Mn_0.11410 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 11 was manufactured in the same manner as in Example 1 except that 90 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
[0082]
<Example 12>
AB5 type rare earth MmNi with particle size of 20μm_4.11Co_0.685Al_0.091Mn_0.11450 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 12 was manufactured in the same manner as in Example 1 except that 50 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
[0083]
<Example 13>
AB5 type rare earth LaNi with a particle size of 30 μm_Five20 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 20 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 13 was produced in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
[0084]
<Example 14>
AB5 type rare earth LaNi with a particle size of 25 μm_Five20 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Example 14 was manufactured in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes.
[0085]
<Comparative Example 1>
AB5 type rare earth MmNi with particle size of 30μm_3.75Co_0.6Al_0.3Mn_0.35Comparative Example 1 was carried out in the same manner as in Example 1, except that the mixture was mixed for 30 minutes using only a hydrogen storage alloy having the following composition and mixed for 30 minutes without adding nickel powder to the obtained alloy powder. A nickel metal hydride storage battery was manufactured.
[0086]
<Comparative example 2>
AB5 type rare earth MmNi with particle size of 30μm_3.75Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Comparative Example 2 was manufactured in the same manner as in Example 1 except that only a hydrogen storage alloy having the composition of 30 was used and mixed for 30 minutes.
[0087]
<Comparative Example 3>
A nickel-metal hydride storage battery of Comparative Example 3 was manufactured in the same manner as in Example 1 except that mixing was performed for 30 minutes without adding nickel powder.
[0088]
<Comparative example 4>
AB5 type rare earth MmNi with particle size of 20μm_3.75Co_0.6Al_0.3Mn_0.3520 parts by weight of a hydrogen storage alloy having the following composition: AB5 type rare earth MmNi with a particle size of 30 μm_3.60Co_0.6Al_0.3Mn_0.35A nickel-metal hydride storage battery of Comparative Example 4 was manufactured in the same manner as in Example 1 except that 80 parts by weight of a hydrogen storage alloy having the following composition was mixed for 30 minutes. The “hydrogen equilibrium dissociation pressures under the conditions of 60 ° C. and 0.5% by weight of hydrogen storage” of the two types of hydrogen storage alloys were 0.10 Mpa and 0.07 Mpa, respectively.
[0089]
<Battery evaluation>
The nickel-metal hydride storage batteries of Examples and Comparative Examples were stored at 40 ° C. for 12 hours, charged at 600 ° C. at 20 ° C. and 0.02 ItA, and further charged at 0.1 ItA for 12 hours. Further, after discharging to 0.2V at 1 It, charging for 12 hours at 0.1 ItA and discharging to 0.2V at 0.2 ItA were repeated 4 times. The discharge capacity at the fourth time is defined as the initial discharge amount at 20 ° C.
[0090]
After that, the battery was charged at 0.1 ItA for 12 hours, allowed to cool at 5 ° C. for 5 hours, and then discharged at 10 It to 0.8 V. The discharge capacity was the initial discharge at 20 ° C. It shows in Table 1 as 5 degreeC 10 ItA discharge capacity with respect to 100% of quantity. It means that it is excellent in high rate discharge performance, so that this 5 degreeC10ItA discharge capacity is high.
[0091]
Further, a cycle of charging at 25 ° C. at 2 ItA to ΔV 5 mV, resting for 10 minutes, discharging to 1.0 V at 2 ItA, resting for 10 minutes, and the number of cycles reaching 80% of the discharge capacity is shown in Table 1. The greater the number of cycles, the better the charge / discharge cycle performance.
[0092]
In Table 1, in the hydrogen storage alloy powder, “equilibrium pressure” indicates “hydrogen equilibrium dissociation pressure under the conditions of 60 ° C. and hydrogen storage amount of 0.5 wt%”, the unit of which is Mpa, “particle size”. The unit is μm, and “content” indicates the weight ratio with respect to the total weight of the hydrogen storage alloy electrode. In nickel powder, the unit of “specific surface area” is m.²/ G, unit of “bulk density” is g / ml, “amount relative to alloy powder” indicates an amount relative to 100 parts by weight of hydrogen storage alloy powder, and the unit is parts by weight.
[0093]
[Table 1]

[0094]
Hydrogen equilibrium dissociation pressure of high equilibrium pressure hydrogen storage alloy powder is 0.65 MPa or more, hydrogen equilibrium dissociation pressure of low equilibrium pressure hydrogen storage alloy powder is 0.1 MPa or less, and further a hydrogen storage alloy electrode containing nickel powder The nickel hydride storage batteries of Examples 1 to 14 having the negative electrode as a negative electrode were excellent in high rate discharge performance as compared with the nickel hydride storage batteries of Comparative Examples 1 to 4 that did not satisfy the above conditions.
[0095]
As in Comparative Example 3, excellent high rate discharge performance cannot be obtained only by mixing the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder. In addition, when nickel powder was added to these hydrogen storage alloy powders, excellent high rate discharge performance could be obtained.
This is because, even in Comparative Example 3, the high equilibrium pressure hydrogen storage alloy powder can receive the hydrogen of the low equilibrium pressure hydrogen storage alloy powder and quickly move to the active surface of the alloy, but the active field itself is insufficient. Therefore, in Example 1, it is estimated that in Example 1, the active field was sufficiently present by the addition of nickel powder, and the high rate discharge characteristics were greatly improved. The
[0096]
Further, as can be seen by comparing Comparative Example 4, Example 6 and Example 9, in order to obtain an excellent high rate discharge performance, the high equilibrium pressure hydrogen storage alloy powder has a hydrogen equilibrium of 0.65 Mpa or more. It was necessary to have a dissociation pressure, and when it was 0.9 Mpa or more, it was confirmed that extremely high rate discharge characteristics were exhibited.
This is presumed that by adding an alloy having a higher hydrogen equilibrium dissociation pressure, the driving force for rapidly moving hydrogen to the active field can be increased, and the high rate discharge characteristics are improved.
Among them, as can be seen by comparing Example 1, Example 2, and Example 4, nickel is composed of metallic nickel powder, and its specific surface area is 1.5 m.²When the bulk density is 0.8 g / ml or less, particularly excellent high rate discharge characteristics are obtained. The activity of nickel is considered to depend not only on the amount of nickel but also on the surface area, that is, the surface area. By adding nickel powder with a large surface area, the high-rate discharge characteristics are greatly improved. I was able.
[0097]
Further, as can be seen by comparing Comparative Example 3 and Examples 1, 5, 3, and 7, the content of nickel powder is 2 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the hydrogen storage alloy. In particular, it was confirmed that it has both excellent high rate discharge performance and excellent charge / discharge cycle performance. It is considered sufficient to add 2 parts by weight of nickel powder. If too much nickel powder is added, it is considered that the charge / discharge cycle performance is lowered due to a decrease in the proportion of the hydrogen storage alloy.
[0098]
Further, as can be seen from a comparison between Example 1 and Example 8, with respect to the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder, the rare earth element is mainly composed of La, Ni, Co, One or more elements selected from the group consisting of Mn and Al are contained. Further, the high equilibrium pressure hydrogen storage alloy powder is made of 5 mol% or more of La with respect to the Ni element, and Mn and Al with respect to the Ni element. By configuring so that the total molar amount of the water was 5 mol% or less, the battery exhibited better charge / discharge cycle performance while exhibiting excellent high rate discharge performance.
In particular, as can be seen by comparing Examples 8, 10, 11, and 12, when the high equilibrium pressure hydrogen storage alloy powder is 10 wt% or more and 30 wt% or less with respect to the total weight of the hydrogen storage alloy electrode An extremely excellent charge / discharge cycle performance was obtained.
[0099]
Excellent charge-discharge cycle performance when using a hydrogen storage alloy powder containing La as a main component as a rare earth element and one or more elements selected from the group consisting of Ni, Co, Mn and Al as a transition element It is shown. Further, in particular, the high equilibrium pressure hydrogen storage alloy powder was used as the hydrogen storage alloy powder, so that it was possible to have a high hydrogen equilibrium dissociation pressure, and as a measure for obtaining a high hydrogen equilibrium dissociation pressure, Ni With respect to the element (when Ni is 100 mol%), when La is 5 mol% or more and the total content of Mn and Al is 5 mol% or less, the corrosion resistance is excellent while having a high hydrogen equilibrium pressure. It is considered that a hydrogen storage alloy can be obtained, and in this way, in addition to excellent high rate discharge characteristics, extremely excellent charge / discharge cycle performance is obtained.
[0100]
In addition, regarding the mixing ratio of the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder, when the amount of the high equilibrium pressure hydrogen storage alloy powder is too large, the charge / discharge voltage curve is the same as that of the high equilibrium pressure hydrogen storage alloy powder. It shows the individual electric potential of the low equilibrium pressure hydrogen storage alloy to form a two-stage curve, which not only makes it difficult to control the battery performance to the desired level, but also reduces the utilization rate of the high equilibrium pressure hydrogen storage alloy powder. put away. When the content of the high equilibrium pressure hydrogen storage alloy powder is 30% by weight or less based on the total weight of the hydrogen storage alloy electrode, the utilization rate of the alloy having the high equilibrium pressure hydrogen storage alloy powder is the utilization rate of the alloy used alone. Is considered to be much higher. This is because, when the high equilibrium pressure hydrogen storage alloy powder is used alone, the decrease in the utilization rate is due to the fact that charging cannot be performed, whereas the high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy When the mixture is used, the utilization rate of the high equilibrium pressure hydrogen storage alloy powder can be improved by allowing the high equilibrium pressure hydrogen storage alloy powder to charge more hydrogen than the low equilibrium pressure hydrogen storage alloy powder. It is considered that the nickel powder coexists.
[0101]
Further, as can be seen by comparing Examples 1, 13, and 14, since the high rate discharge performance tends to decrease as the average particle size of the high equilibrium pressure hydrogen storage alloy powder increases, it is preferably 25 μm or less, and low equilibrium. When the average particle size of the pressurized hydrogen storage alloy powder is reduced, the charge / discharge cycle performance tends to be reduced, and therefore it was confirmed that 30 μm or more is preferable. It is generally known that the hydrogen storage alloy is not excellent in high-rate discharge performance because the reaction field decreases as the particle size increases, but the charge / discharge cycle performance is excellent. By increasing the average particle size of the low equilibrium pressure hydrogen storage alloy powder, the average particle size of the high equilibrium pressure hydrogen storage alloy powder required to improve the high rate discharge performance while maintaining excellent charge / discharge cycle performance. By controlling the thickness to 25 μm or less, it was possible to achieve both excellent high rate discharge characteristics and excellent charge / discharge cycle performance.
[0102]
According to the hydrogen storage alloy electrode according to the present invention, high rate discharge performance.NohAn excellent nickel metal hydride storage battery can be provided. According to such a nickel-metal hydride storage battery, it can be used as a power source for an electric vehicle or an electric tool because it can be a battery having excellent large current discharge performance.
[0103]
The specific surface area of nickel powder is 1.5m ² / G or more and the bulk density of the nickel powder is 0.8 g / ml or lessAccording to the hydrogen storage alloy electrode according to the present invention, it is possible to provide a nickel metal hydride storage battery particularly excellent in high rate discharge performance.
Also,Nickel powder is contained in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy powder.The hydrogen storage alloy electrode according to the present invention can provide a nickel-metal hydride storage battery that is particularly excellent in high-rate discharge performance and charge / discharge cycle performance.
[0104]
The high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder contain La as a main component as a rare earth element and contain one or more elements selected from the group consisting of Ni, Co, Mn, and Al. At the same time, the content of the high equilibrium pressure hydrogen storage alloy powder is 10% by weight or more and 30% by weight or less with respect to the total weight of the hydrogen storage alloy electrode. Is 5 mol% or more, the total molar amount of Mn and Al with respect to Ni element is 5 mol% or less, and the average particle size of the high equilibrium pressure hydrogen storage alloy powder is 25 μm or less, The average particle size of the low equilibrium pressure hydrogen storage alloy powder is 30 μm or more.According to theOf the present inventionAccording to the hydrogen storage alloy electrode, it is possible to provide a sealed nickel-metal hydride storage battery having excellent corrosion resistance, particularly good charge / discharge cycle performance, and excellent high-rate discharge characteristics. Therefore, the performance of a device using this battery as a power source is improved, and the applications can be further expanded.
[Brief description of the drawings]
FIG. 1 is a cutaway perspective view of a nickel metal hydride storage battery according to an embodiment of the present invention.
[Explanation of symbols]
1 Nickel metal hydride storage battery
2 case
2a upper opening
3 positive
4 negative
5 Nickel metal hydride battery separator
6 insulating gasket
7 sealing plate
8 positive terminal
9 current collector

Claims (4)

  Two or more kinds of nickel storage powders and “hydrogen storage alloy powders capable of occluding and desorbing hydrogen containing rare earth elements and transition elements as main components” and having different hydrogen equilibrium dissociation pressures The high equilibrium pressure hydrogen storage alloy powder having the highest hydrogen equilibrium dissociation pressure has a hydrogen equilibrium dissociation pressure of 0.65 MPa or more at 60 ° C. and a hydrogen storage amount of 0.5 wt%. The low equilibrium pressure hydrogen storage alloy powder having the lowest hydrogen equilibrium dissociation pressure is a hydrogen storage alloy having a hydrogen equilibrium dissociation pressure of 0.1 MPa or less at 60 ° C. and a hydrogen storage amount of 0.5 wt%. electrode. 2. The hydrogen storage alloy electrode according to claim 1 , wherein the high equilibrium pressure hydrogen storage alloy powder has an average particle size of 25 μm or less, and the low equilibrium pressure hydrogen storage alloy powder has an average particle size of 30 μm or more. . The high equilibrium pressure hydrogen storage alloy powder and the low equilibrium pressure hydrogen storage alloy powder are one or more elements selected from the group consisting of La, Ni, Co, Mn, and Al as the rare earth element. And the content of the high equilibrium pressure hydrogen storage alloy powder is not less than 10% by weight and not more than 30% by weight with respect to the total weight of the hydrogen storage alloy electrode. 3. The composition according to claim 1 , wherein La is 5 mol% or more with respect to the element, and the total molar amount of Mn and Al is 5 mol% or less with respect to the Ni element. Hydrogen storage alloy electrode. A nickel-metal hydride storage battery comprising a positive electrode containing a positive electrode active material, a negative electrode comprising the hydrogen storage alloy electrode according to claim 1 , and an electrolyte.

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