JP3587213B2

JP3587213B2 - Negative electrode active material for air-Ga primary battery and air-Ga primary battery using the same

Info

Publication number: JP3587213B2
Application number: JP22419494A
Authority: JP
Inventors: 清史荒木; 利哉北村; 文洋佐藤; 典也石田; 陵坂本; 真樹子柳沢
Original assignee: Dowa Holdings Co Ltd; Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 1994-08-25
Filing date: 1994-08-25
Publication date: 2004-11-10
Anticipated expiration: 2019-11-10
Also published as: JPH0864204A

Description

【０００１】
【産業上の利用分野】
本発明は、空気−Ｇａ１次電池に関し、更に詳しくは負極活物質としてＧａまたはＧａを主とする合金を主成分として使用することにより高容量電池として構成した空気−Ｇａ１次電池に関する。
【０００２】
【従来の技術】
空気電池は、正極活物質として空気中の酸素を使用することから、電池内に正極活物質を充填する必要がなく、密閉型電池として最もエネルギー密度の高い電池となる。さらに対エネルギー当りの経済性が高いことから近年ボタン型の空気電池が補聴器用の電源として用いられている。
【０００３】
従来の空気電池は、正極に酸素還元用触媒を担持した酸素透過膜（空気極）を用い、一方、負極には活物質として亜鉛を用いている。現存の空気−Ｚｎ電池は１次電池であり、充放電の可能な２次電池は未だない。
【０００４】
【発明が解決しようとする課題】
しかしながらこのような従来の空気電池においては、正極が膜の形態で、活物質の酸素が空気中から無限に供給されるために、その電池容量は負極活物質の理論容量によって上限が決まってしまう。
【０００５】
空気電池用負極活物質としては一般に亜鉛が用いられているが、この場合の空気電池の公称電圧は１．４Ｖ（理論電圧：１．６５Ｖ）であり、電気化学等量は６５．３９／２＝３２．７，理論エネルギー密度は１４００Ｗｈ／ｋｇである。
【０００６】
したがって亜鉛より高電位で、かつ低化学等量の活物質の開発が望まれ、今までに、鉄、アルカリ金属、アルカリ土類金属、アルミニウム等の物質が研究されているが活物質の不活性化の問題が解決できず、実用化まで至らないのが実状であった。
【０００７】
上述のように従来の亜鉛に代る新規な空気電池用負極活物質を用いて、高容量電池として知られる従来の空気−亜鉛電池を上回る容量の空気電池の開発が望まれていた。
【０００８】
【課題を解決するための手段】
本発明者等は斯かる課題を解決するために鋭意研究したところ、周期表第３１番元素であるＧａが、原子量６９．７２、価数変化３、電気化学当量２３．２４と亜鉛に対して有利な性質を有し、かつ空気電池用負極活物質となり得ることを見いだし、本発明を提供することができた。
【０００９】
すなわち本発明の第１は、ＧａまたはＧａを主とする合金からなることを特徴とする空気−Ｇａ１次電池用負極活物質であり、第２は、空気極を正極とし、ＧａまたはＧａを主とする合金からなる負極活物質を負極体の中に充填したものを負極として成ることを特徴とする空気−Ｇａ１次電池である。
【００１０】
【作用】
本発明において使用するＧａは、周期表中Ｚｎの隣に位置し、化学的にも似た性質をもつ元素であり、酸・アルカリのどちらにも溶解する両性元素である。特にアルカリ性水溶液中においては、ＧａＯ_３ ^３−やＨＧａＯ_３ ^２−などのイオンとなり、あるいはＧａ_２Ｏ_３、Ｇａ（ＯＨ）_３、ＧａＯＯＨ等の酸化物や水酸化物となって０から３価の価数変化を起こす。そこでこれらの反応を電極反応として利用することでＺｎと同様、Ｇａを空気−Ｇａ１次電池用活物質として用い得ることを予測して研究を進め、本発明に到達した。
【００１１】
Ｇａが有する重要な特性として、低融点金属（融点２９．８℃）であることが挙げられるが、Ｇａの液体状態、固体状態の違いは電池特性に大きな影響を及ぼさない。さらにＩｎ、Ｚｎ、Ｓｎ、Ｐｂ，Ｂｉ、Ｔｌ等の金属と適当な比率で合金化することによって融点をさらに下げることができる。さらにＧａは従来の活物質であるＨｇのように環境上問題とされるような毒性を有していない。このような特性を有しているため、Ｇａは空気−Ｇａ１次電池用負極活物質として有用であることが確認された。
【００１２】
Ｇａの使用形態としては、Ｇａ単独でも合金でもよく、また粉末状でも固体状でも構わないが、粉末状で用いる場合には電解液中に浸漬して用いるとよいことを見いだした。
【００１３】
一方、空気極は触媒のＰｔを含むアセチレンブラックに結着剤や撥水剤の作用を持つＰＴＦＥ（ポリテトラフルオロエチレン）を加えて混合し、次いで該混合粉を適当な大きさに圧延して集電体のＮｉ網に圧着して空気極を構成した。
【００１４】
以下、実施例をもって詳細に説明するが、本発明の範囲はこれらに限定されるものではない。
【００１５】
【実施例１】
図１に示すような正極１として空気極を、負極２としてＰｔ線（−極）３を挿入したＧａＩｎ合金１０からなる負極を用いた電池を構成し、放電試験を行った。この場合の負極活物質としてはＧａ（同和鉱業製純度６Ｎ）９５ｗｔ％とＩｎ（同和鉱業製純度６Ｎ）５ｗｔ％とからなるＧａＩｎ合金３ｇを用いた。空気極としては触媒のＰｔを含むアセチレンブラックに、結着剤や撥水剤の作用を持つＰＴＦＥを適量加えて混合し、次いでこの混合粉を適当な大きさに圧延し、集電体のＮｉ網に圧着して電極としたものを用いた。
【００１６】
電解液４には、３０ｗｔ％水酸化カリウム水溶液を用い、温度２５℃で５ｍＡの放電試験を行った。試験の結果は図２に示すように放電電圧は１．４３Ｖで非常に平坦な放電挙動を示した。
【００１７】
負極活物質であるＧａＩｎ合金は測定温度２５℃で液体であるが、測定温度を１５℃に変えて固体状態で放電試験を行った場合も、上記とほぼ同様な放電挙動を示した。
【００１８】
また上記ＧａＩｎ合金に代え、純ＧａあるいはＺｎ、Ｓｎ、Ｐｂとの合金を用いた場合でも同様な結果が得られ、Ｇａを主成分とする本発明の負極活物質がいずれも充分に有用であることが確認できた。用いた合金はそれぞれＺｎ５ｗｔ％、Ｓｎ５ｗｔ％、Ｐｂ５ｗｔ％を含むＧａ−Ｚｎ、Ｇａ−Ｓｎ、Ｇａ−Ｐｂ合金であった。
【００１９】
【比較例１】
実施例１との比較のため負極活物質として亜鉛を用いた空気−Ｚｎ１次電池を構成し、放電試験を行った。この場合、亜鉛（同和鉱業製純度４Ｎ）３ｇを圧延により板状にして負極材とした他は、実施例１と同一条件で放電試験を行った。その結果は図２中に別の曲線で示した。
【００２０】
図２に見るように、放電電圧１．３４Ｖの平坦な電位が得られたが、実施例１のＧａＩｎ合金の負極材を用いた場合に比較して負極活物質質量当りの容量は少ないことが判明した。
【００２１】
【実施例２】
図３に示すように電解液にＧａ粉（粒径２００μｍアンダー）を負極活物質として充填して、（Ｇａ粉＋電解液）１１とした空気電池を構成した。この場合、Ｇａ粉はまず純度４ＮのＧａを液体窒素中で冷却し固体にした後、液体窒素温度に近い極低温の状態で粉砕し、この粉が液体にならない温度（１５℃程度）の水中でふるいにかけ、２００μｍアンダーのＧａ粉を得た。
【００２２】
次いでこのＧａ粉にポリアクリル酸ナトリウムを１ｗｔ％溶解させた３０ｗｔ％水酸化カリウムを適量混ぜ、これを負極に充填した後、セパレーター８、空気極としての正極１（＋極リード線６）を取り付けて測定セルとした。
【００２３】
実施例１と同様に温度２５℃、５ｍＡの条件で放電試験を行ったところ、放電電圧は１．２８Ｖであり、実施例１よりも若干低いものの充分に空気電池として利用できることが確認できた。
【００２４】
【発明の効果】
上述のように本発明は、主成分として金属ＧａまたはＧａ合金を負極活物質として用いた空気−Ｇａ１次電池を提供するものである。本発明の空気−Ｇａ１次電池は従来の空気−Ｚｎ１次電池より高容量化を図れるものである。
【図面の簡単な説明】
【図１】実施例１における測定用セルの構造図。
【図２】実施例１および比較例１における放電特性図。
【図３】実施例２における測定用セルの構造図。
【符号の説明】
１正極
２負極
３Ｐｔ線（−極）
４電解液
５ＰＰセル
６＋極リード線
７フタ
８セパレーター
９Ｐｔ板
１０Ｇａ／Ｉｎ合金
１１Ｇａ粉＋電解液[0001]
[Industrial applications]
The present invention relates to an air-Ga primary battery, and more particularly, to an air-Ga primary battery configured as a high capacity battery by using Ga or an alloy mainly containing Ga as a main component as a negative electrode active material.
[0002]
[Prior art]
Since an air battery uses oxygen in the air as a positive electrode active material, there is no need to fill the positive electrode active material into the battery, and the air battery has the highest energy density as a sealed battery. In addition, a button-type air battery has recently been used as a power supply for hearing aids because of its high economy per energy consumption.
[0003]
A conventional air battery uses an oxygen-permeable membrane (air electrode) carrying a catalyst for oxygen reduction on a positive electrode, while using zinc as an active material for a negative electrode. The existing air-Zn battery is a primary battery, and there is no chargeable / dischargeable secondary battery yet.
[0004]
[Problems to be solved by the invention]
However, in such a conventional air battery, since the positive electrode is in the form of a film and the oxygen of the active material is supplied infinitely from the air, the upper limit of the battery capacity is determined by the theoretical capacity of the negative electrode active material. .
[0005]
In general, zinc is used as a negative electrode active material for an air battery. In this case, the nominal voltage of the air battery is 1.4 V (theoretical voltage: 1.65 V), and the electrochemical equivalent is 65.39 / 2. = 32.7, theoretical energy density is 1400 Wh / kg.
[0006]
Therefore, the development of an active material with a higher potential and a lower stoichiometric amount than zinc is desired, and materials such as iron, alkali metals, alkaline earth metals, and aluminum have been studied. In reality, it was not possible to solve the problem of commercialization and not to commercialize it.
[0007]
As described above, there has been a demand for the development of an air battery having a capacity higher than that of a conventional air-zinc battery known as a high-capacity battery by using a novel negative electrode active material for an air battery instead of the conventional zinc.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve such a problem, and found that Ga, which is the 31st element of the periodic table, has an atomic weight of 69.72, a valence change of 3, an electrochemical equivalent of 23.24, and zinc. The present inventors have found that they have advantageous properties and can be used as a negative electrode active material for an air battery, and have provided the present invention.
[0009]
That is, the first invention is a negative electrode active material for air -Ga1 battery, characterized by comprising an alloy consisting mainly of Ga or Ga, the second is an air electrode as a positive electrode, mainly Ga or Ga those filled with anode active material made of an alloy and in the negative electrode body is an air -Ga1 battery, characterized by comprising as a negative electrode.
[0010]
[Action]
Ga used in the present invention is an element that is located next to Zn in the periodic table and has chemically similar properties, and is an amphoteric element that is soluble in both acids and alkalis. In particular, in an alkaline aqueous solution, it becomes an ion such as GaO ₃ ^3- or HGaO ₃ ^2- or an oxide or hydroxide such as Ga ₂ O ₃ , Ga (OH) ₃ , GaOOH, etc. Causes a valence change. Therefore, by utilizing these reactions as an electrode reaction, it was predicted that Ga could be used as an active material for an air-Ga primary battery, as in the case of Zn.
[0011]
An important characteristic of Ga is that it is a low melting point metal (melting point: 29.8 ° C.), but the difference between the liquid state and the solid state of Ga does not significantly affect battery characteristics. Further, the melting point can be further lowered by alloying with a metal such as In, Zn, Sn, Pb, Bi and Tl at an appropriate ratio. Further, Ga does not have toxicity that is environmentally problematic, unlike Hg which is a conventional active material. Because of these characteristics, it was confirmed that Ga was useful as a negative electrode active material for an air-Ga primary battery.
[0012]
As a usage form of Ga, Ga alone or an alloy may be used, and it may be in a powder form or a solid form. However, when it is used in a powder form, it has been found that it is better to immerse it in an electrolytic solution.
[0013]
On the other hand, for the air electrode, PTFE (polytetrafluoroethylene) having a function of a binder and a water repellent is added to acetylene black containing Pt as a catalyst and mixed, and then the mixed powder is rolled to an appropriate size. An air electrode was formed by pressure bonding to a Ni net of a current collector.
[0014]
Hereinafter, the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.
[0015]
Embodiment 1
A battery using an air electrode as the positive electrode 1 and a negative electrode made of a GaIn alloy 10 into which a Pt wire (-electrode) 3 was inserted as the negative electrode 2 as shown in FIG. In this case, as the negative electrode active material, 3 g of a GaIn alloy composed of 95 wt% of Ga (purity 6N manufactured by Dowa Mining) and 5 wt% of In (purity 6N manufactured by Dowa Mining) was used. As an air electrode, a suitable amount of PTFE having a function of a binder or a water repellent is added to acetylene black containing Pt as a catalyst and mixed, and then the mixed powder is rolled to an appropriate size to obtain a Ni of the current collector. An electrode which was pressed to a net to form an electrode was used.
[0016]
A discharge test of 5 mA at a temperature of 25 ° C. was performed using a 30 wt% aqueous solution of potassium hydroxide as the electrolyte solution 4. As a result of the test, as shown in FIG. 2, the discharge voltage was 1.43 V and showed a very flat discharge behavior.
[0017]
The GaIn alloy as the negative electrode active material is a liquid at a measurement temperature of 25 ° C., but when the measurement temperature was changed to 15 ° C. and a discharge test was performed in a solid state, almost the same discharge behavior as described above was exhibited.
[0018]
Similar results are obtained when pure Ga or an alloy of Zn, Sn, and Pb is used instead of the GaIn alloy, and any of the negative electrode active materials of the present invention containing Ga as a main component is sufficiently useful. That was confirmed. The alloys used were Ga-Zn, Ga-Sn, and Ga-Pb alloys containing 5 wt% of Zn, 5 wt% of Sn, and 5 wt% of Pb, respectively.
[0019]
[Comparative Example 1]
For comparison with Example 1, an air-Zn primary battery using zinc as a negative electrode active material was formed, and a discharge test was performed. In this case, a discharge test was performed under the same conditions as in Example 1 except that 3 g of zinc (purity 4N, manufactured by Dowa Mining Industry) was rolled to form a negative electrode material. The result is shown by another curve in FIG.
[0020]
As shown in FIG. 2, a flat potential of 1.34 V was obtained, but the capacity per mass of the negative electrode active material was smaller than that of the case where the GaIn alloy negative electrode material of Example 1 was used. found.
[0021]
Embodiment 2
As shown in FIG. 3, an air battery was prepared in which an electrolyte was filled with Ga powder (under a particle size of 200 μm) as a negative electrode active material to make (Ga powder + electrolyte) 11. In this case, first, Ga powder having a purity of 4N is cooled in liquid nitrogen to form a solid, and then pulverized at an extremely low temperature close to the liquid nitrogen temperature. To obtain Ga powder under 200 μm.
[0022]
Next, an appropriate amount of 30 wt% potassium hydroxide obtained by dissolving 1 wt% of sodium polyacrylate in this Ga powder was mixed and filled in the negative electrode, and then the separator 8 and the positive electrode 1 (+ electrode lead wire 6) as an air electrode were attached. To obtain a measurement cell.
[0023]
When a discharge test was performed under the conditions of a temperature of 25 ° C. and 5 mA in the same manner as in Example 1, the discharge voltage was 1.28 V. Although it was slightly lower than that of Example 1, it was confirmed that the battery could be sufficiently used as an air battery.
[0024]
【The invention's effect】
As described above, the present invention provides an air-Ga primary battery using metal Ga or a Ga alloy as a main component as a negative electrode active material. The air-Ga primary battery of the present invention can achieve higher capacity than the conventional air-Zn primary battery.
[Brief description of the drawings]
FIG. 1 is a structural diagram of a measurement cell in Example 1.
FIG. 2 is a discharge characteristic diagram in Example 1 and Comparative Example 1.
FIG. 3 is a structural diagram of a measuring cell in Example 2.
[Explanation of symbols]
1 Positive electrode 2 Negative electrode 3 Pt wire (-pole)
4 Electrolyte 5 PP cell 6 + Lead wire 7 Lid 8 Separator 9 Pt plate 10 Ga / In alloy 11 Ga powder + Electrolyte

Claims

Negative active material for air -Ga1 battery, characterized by comprising an alloy consisting mainly of Ga or Ga.

An air-Ga primary battery characterized in that an air electrode is used as a positive electrode and a negative electrode body is filled with a negative electrode active material made of Ga or an alloy mainly containing Ga as a negative electrode.