JP3550193B2 - Negative electrode and secondary battery using the same - Google Patents

Description

[0001]
[Industrial applications]
The present invention provides a negative electrode, which is obtained by kneading a mixture of gallium oxide or a combination of gallium oxide and another metal oxide with a conductive carbon-based material and filling the inside of the porous body, and using the negative electrode. Battery.
[0002]
[Prior art]
Conventionally, it has been studied to use various materials alone or in combination of several as a negative electrode active material for a battery, but negative electrode active materials for a battery using an aqueous electrolyte include zinc, lead, cadmium, and hydrogen. It was limited to occlusion alloys.
[0003]
In such a conventional technique, the types of the negative electrode active materials that affect the basic performance of the battery are small as described above. In particular, the types of the secondary batteries that can be charged and discharged include a lead storage battery, a nickel-cadmium battery, and a hydrogen battery. Only three types of occlusion batteries have been put into practical use. As described above, the types of the existing batteries are few, and it is not in a situation where the disadvantages of the other batteries can be sufficiently compensated. Conventional batteries have the following disadvantages.
[0004]
{Circle around (1)} In a zinc battery, dendrite is generated on the electrode surface during charging and discharging, and the cycle life is deteriorated. Therefore, zinc is not suitable as a secondary battery material.
[0005]
(2) A lithium battery is a substance in which lithium is chemically active. Since a non-aqueous electrolyte is used for the battery electrolyte, the battery is apt to spontaneously ignite, and there is a risk of a fire accident or the like occurring at the stage of use. In order to prevent this, it is necessary to use a graphite electrode for the negative electrode or to provide various safety devices, which increases the manufacturing cost.
[0006]
(3) Lead batteries have the toxicity that lead poses an environmental problem, and the electric capacity per unit weight is small due to the large weight of lead.
[0007]
{Circle around (4)} Cadmium batteries have low voltage, and cadmium has toxicity which is environmentally problematic as described above.
[0008]
(5) The battery using the hydrogen storage alloy has a low voltage, and the production cost is high at this stage.
[0009]
[Problems to be solved by the invention]
As described above, in the batteries that have been practically used in the past, since the types of the negative electrode active material are small, it is not possible to compensate for the disadvantages of each battery. As a new substance that can be used, a negative electrode body using a substance mainly composed of gallium oxide has been developed. Accordingly, it is an object to provide a secondary battery having no pollution, high discharge voltage, high electric capacity, high cycle characteristics, and being inexpensive.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve such a problem, and found that instead of Ga, which is a liquid near room temperature, it is difficult to form an electrode plate, and instead of gallium oxide or a combination of gallium oxide and other metal oxides and conductive material. It has been found that a porous carbon-based material can be easily used as a battery negative electrode body by filling a kneaded material obtained by kneading or kneading a combination of gallium oxide with another metal oxide and metal gallium powder, or The present invention could be provided.
[0011]
That is, the present invention firstly mixes gallium oxide or a combination of gallium oxide with SnO ₂ , ZnO, In ₂ O ₃ , Ag ₂ O ₃ , CdO, PbO ₂ or Bi ₂ O ₃ with a conductive carbon-based material. A negative electrode for a secondary battery, wherein the kneaded material obtained by the above is filled in a porous body and the gallium oxide is used as a negative electrode active material; secondly, gallium oxide or gallium oxide and SnO ₂ , ZnO , In ₂ O ₃ , Ag ₂ O ₃ , CdO, PbO ₂ or Bi ₂ O _3, and a kneaded product obtained by mixing the mixture with a metal gallium powder is filled in a porous body. Thirdly, a negative electrode for a secondary battery characterized by using metal gallium as a negative electrode active material; Thirdly, a negative electrode for use in the negative electrode according to the first or second aspect is provided. .
[0012]
[Action]
Generally, metals such as Zn, Cd, and Pb are used as the negative electrode active material. Other metals have the potential to be used for battery electrodes, but it was a problem whether they could be practical batteries.
[0013]
As for the use of gallium as a negative electrode active material for batteries, gallium has been used as a battery material in addition to being liquid at about 30 ° C. or higher, and being easily reacted with other metals and having unstable characteristics as a battery. This is the main reason why it was not done.
[0014]
However, Ga is used as the negative electrode active material in the electrode body of the present invention. Ga is a periodic table 31 th element, accompanied valence change in the electrochemical reaction is 3, is an alkaline aqueous solution ^{_{Ga + 3H 2 O = GaO 3}} 3- + 6H + + 3e - (1)
Is thought to dissolve in the reaction. In addition, the chemical equivalent of Ga is 23.24, which is considerably smaller than the chemical equivalent of Zn of 32.70, indicating that Ga can theoretically be a high-capacity battery material.
[0015]
Therefore, the present inventors wrapped gallium oxide with a porous material and made it so that it did not fall off from the current collector by (1) preventing the negative electrode active material from being deutilized by falling off (2) through the porous material (3) It is possible to prevent the occurrence of side reactions that are not involved in the battery reaction due to the dropped negative electrode active material and to prevent the adverse effects on the battery characteristics caused by these side reactions. Most of the conventional problems could be solved.
[0016]
In this case, it turned out that the presence or absence of the conductivity of the porous substance was not particularly a problem. As the conductive porous material, a carbon-based material such as Ketjen black, acetylene black, and graphite is effective without reacting with gallium, and as a current collector, Ni or Cu mesh having low reactivity with gallium is used. Are effective and practical.
[0017]
As the non-conductive porous material, various plastic materials, separators used in conventional batteries, and the like can also be used.However, these materials are not limited to materials, and when Ga or Ga alloy is liquefied during charging. A material having as high a porosity as possible is suitable as long as the material does not leak.
[0018]
As a negative electrode active material mainly composed of gallium, we initially thought that only metal gallium and its alloys could be used, but later studies showed that gallium compounds, such as gallium oxide or a combination of gallium oxide and other metal oxides It was also found that these compounds function as battery electrodes under specific conditions.
[0019]
Although the above reaction is extremely complicated and cannot be accurately identified, it is presumed to be due to charge transfer between gallium oxide or hydroxide and metal gallium.
[0020]
Incidentally, even if gallium oxide is initially filled in the porous body, the presence of metallic gallium is recognized after the charge / discharge process.This is because the following reaction occurs in which gallium oxide is reduced to metallic gallium. Conceivable.
Ga ₂ O ₃ + 3H ₂ O + 6e ⁻ = 2Ga + 6OH ⁻ (2)
The presence of metallic gallium generated at this time does not only function as a negative electrode active material, but also serves as an extremely good current collector for low-conductivity gallium compounds.Therefore, metallic gallium is intentionally added to gallium oxide. May be used.
[0021]
As a mixture of gallium oxide and another metal oxide in the present invention, SnO ₂ , ZnO, In ₂ O ₃ , Ag ₂ O _3, etc. based on 70 to 100 wt% of Ga ₂ O ₃ , or in addition, It was confirmed that similar results were obtained even when CdO, PbO ₂ , Bi ₂ O _{3 and the} like were added in a total amount of 30 to 0 wt%.
[0022]
Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.
[0023]
Embodiment 1
3 g of gallium oxide (purity: 99.99%, manufactured by Dowa Mining Co., Ltd.) is mixed and kneaded with 0.1 g of ketjen black for the purpose of imparting conductivity, and the bottom shown in FIG. 2 is formed into a bag-shaped cylindrical shape. The separator shown in FIG. 1 was used as a negative electrode by injecting it into a separator, using a stainless steel thin wire as a negative electrode current collector, a 30 wt% -KOH aqueous solution as an electrolytic solution, and nickel hydroxide as a positive electrode. The cell was configured.
[0024]
When a charge / discharge test was performed using the simple cell, it was clearly confirmed visually that gallium oxide inside the negative electrode was partially reduced to metal gallium by the first charge.
[0025]
Further, a high potential of 1.92 V was obtained immediately after charging, and a current of about 250 mA / g was obtained as a current value per gram of the negative electrode active material. Furthermore, it was confirmed that by appropriately adjusting the amount of the electrolyte, the cycle characteristics of the secondary battery could be improved up to about 200 times.
[0026]
Embodiment 2
A mixture of 1.5 g of gallium oxide and an equal amount (1.5 g) of metal gallium mixed with 0.08 g of graphite powder and kneaded was filled into a cylindrical porous carbon electrode shown in FIG. A charge / discharge test was conducted by constructing a simple cell similar to that of Example 1 except that the above-mentioned conditions were satisfied.
[0027]
As a result, although the open circuit voltage and the cycle characteristics were almost the same, the charging current value was about 320 mA / g per gram of the negative electrode active material, which was higher than that of Example 1.
[0028]
Embodiment 3
The same simple cell as in Example 2 was used, except that about 10 wt% of each oxide of Sn, In, Ag, Zn, Pb, Bi, and Cd was added to Ga ₂ O _{3 as} a metal oxide. When a discharge test was performed, no change was observed in the open circuit voltage at the above-mentioned amount of addition.
[0029]
However, when the amount of addition was adjusted, the flatness of the discharge potential when using a mixture of each oxide of 10 wt% of Sn, 8 wt% of In, 5 wt% of Zn, 2 wt% of Bi, and 4 wt% of Cd was used. Was confirmed to be improved.
[0030]
【The invention's effect】
As described above, it was confirmed that the negative electrode of the present invention can be practically used by kneading gallium oxide or a mixture of gallium oxide and another metal oxide with a carbon-based material. The battery of the present invention has no dendrite precipitation accompanying charge / discharge, and when nickel hydroxide is used for the positive electrode, a higher voltage is obtained than a conventional nickel-cadmium battery or hydrogen storage battery, and the toxicity is further reduced. There are advantages such as.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a battery in Example 1.
FIG. 2 is a schematic diagram of a negative electrode used in Example 1.
FIG. 3 is a schematic diagram of a negative electrode used in Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Porous container 2 Negative electrode active material 3 Stainless steel wire (negative electrode)
4 Nickel hydroxide electrode (positive electrode)
5 30 wt% -KOH aqueous solution 6 PP lid 7 PP cell 8 Bottom bag-shaped cylindrical separator 9 Porous carbon electrode

Claims (3)

A porous material is obtained by mixing gallium oxide or a combination of gallium oxide with SnO ₂ , ZnO, In ₂ O ₃ , Ag ₂ O ₃ , CdO, PbO ₂ or Bi ₂ O ₃ with a conductive carbon-based material. A negative electrode for a secondary battery, wherein the negative electrode is filled inside and the gallium oxide is used as a negative electrode active material. A kneaded product obtained by mixing gallium oxide or a combination of gallium oxide and SnO ₂ , ZnO, In ₂ O ₃ , Ag ₂ O ₃ , CdO, PbO ₂ or Bi ₂ O ₃ with metal gallium powder is placed inside the porous body. A negative electrode for a secondary battery, which is filled and uses the gallium oxide and the metal gallium as a negative electrode active material. A secondary battery comprising the negative electrode according to claim 1.

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