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J. Zhu et al.
lithium-air battery, and the conventional air electrode can be satisfied, except that
different catalysts can be used according to different battery uses. This type of air
electrode has been discussed many times before and will not be described here.
6.2.2.3 Zinc-air Battery
Zinc-air battery has become another important metal-air battery besides lithium-air
battery and aluminum-air battery due to its advantages of cheap and easily available
cathode material, capability of charging and discharging cycle in aqueous solution
system, stable working voltage, low pollution, safety and reliability, etc. Although
the theoretical energy density of zinc-air battery is lower than that of lithium,
aluminum and magnesium-air battery, it is still three times that of lithium ion battery.
Unlike lithium-air and aluminum-air batteries, zinc-air batteries can be charged and
discharged in aqueous electrolyte, that is, zinc-air batteries can be charged in aqueous
electrolyte. This is because in neutral or alkaline electrolyte, the hydrogen evolution
overpotential on the zinc surface is very large, Zn
2+ near the negative electrode preferentially obtains electrons to form metal Zn than H
+ during charging, which makes
it possible for the aqueous zinc-air battery to be used as a secondary battery, and it is
precisely this characteristic that the discharge product ZnO of the zinc-air battery can
also be regenerated by electrolysis. As secondary zinc-air uses aqueous electrolyte,
the risk of fire or explosion caused by leakage of organic electrolyte can be reduced,
making it safer than secondary lithium-air battery.
Since 1995, Israel Electric Fuel Co., Ltd. used zinc-gas battery for electric vehicles for the first time, bringing zinc-gas battery into practical stage. Since then, the
USA, Germany, France, Sweden and other countries have also actively promoted
the application of electric vehicles. The zinc-air batteries developed mainly include
secondary batteries and mechanical rechargeable batteries. EOS Energy Storage
Company claimed that the secondary zinc-air battery developed in the USA can
realize 2700 cycles of charge and discharge [59]. The key points of its technology
are as follows: (1) A new neutral electrolyte is used to overcome the problem of pore
blockage caused by carbonate deposition on the air electrode due to absorption of
CO 2 by alkaline electrolyte; (2) The horizontal cell structure design is adopted, and
the electrolyte is separated from the electrode by gravity, thus overcoming the difficult problem that the zinc electrode is oxidized to form dendrites and the diaphragm
is broken, thereby causing the cell to fail. The zinc-air battery for vehicles developed by Sweden and Israel is a mechanical rechargeable battery. This mechanical
zinc refilling-air adopts the design of metal particle replacement and electrolyte
circulation: automatically adding metal particles-discharging-pumping electrolyte,
renewing electrolyte and discharging waste materials. The recovered zinc oxide can
be regenerated into zinc particles by electrolysis for recycling. Figure 6.9 shows the
structure of a metal particle replacement type single cell. The negative electrode is
the matrix of zinc particles and is connected with the current collector. When the
zinc particles are dissolved, the volume of the zinc particles in the battery shell is
J. Zhu et al.
lithium-air battery, and the conventional air electrode can be satisfied, except that
different catalysts can be used according to different battery uses. This type of air
electrode has been discussed many times before and will not be described here.
6.2.2.3 Zinc-air Battery
Zinc-air battery has become another important metal-air battery besides lithium-air
battery and aluminum-air battery due to its advantages of cheap and easily available
cathode material, capability of charging and discharging cycle in aqueous solution
system, stable working voltage, low pollution, safety and reliability, etc. Although
the theoretical energy density of zinc-air battery is lower than that of lithium,
aluminum and magnesium-air battery, it is still three times that of lithium ion battery.
Unlike lithium-air and aluminum-air batteries, zinc-air batteries can be charged and
discharged in aqueous electrolyte, that is, zinc-air batteries can be charged in aqueous
electrolyte. This is because in neutral or alkaline electrolyte, the hydrogen evolution
overpotential on the zinc surface is very large, Zn
2+ near the negative electrode preferentially obtains electrons to form metal Zn than H
+ during charging, which makes
it possible for the aqueous zinc-air battery to be used as a secondary battery, and it is
precisely this characteristic that the discharge product ZnO of the zinc-air battery can
also be regenerated by electrolysis. As secondary zinc-air uses aqueous electrolyte,
the risk of fire or explosion caused by leakage of organic electrolyte can be reduced,
making it safer than secondary lithium-air battery.
Since 1995, Israel Electric Fuel Co., Ltd. used zinc-gas battery for electric vehicles for the first time, bringing zinc-gas battery into practical stage. Since then, the
USA, Germany, France, Sweden and other countries have also actively promoted
the application of electric vehicles. The zinc-air batteries developed mainly include
secondary batteries and mechanical rechargeable batteries. EOS Energy Storage
Company claimed that the secondary zinc-air battery developed in the USA can
realize 2700 cycles of charge and discharge [59]. The key points of its technology
are as follows: (1) A new neutral electrolyte is used to overcome the problem of pore
blockage caused by carbonate deposition on the air electrode due to absorption of
CO 2 by alkaline electrolyte; (2) The horizontal cell structure design is adopted, and
the electrolyte is separated from the electrode by gravity, thus overcoming the difficult problem that the zinc electrode is oxidized to form dendrites and the diaphragm
is broken, thereby causing the cell to fail. The zinc-air battery for vehicles developed by Sweden and Israel is a mechanical rechargeable battery. This mechanical
zinc refilling-air adopts the design of metal particle replacement and electrolyte
circulation: automatically adding metal particles-discharging-pumping electrolyte,
renewing electrolyte and discharging waste materials. The recovered zinc oxide can
be regenerated into zinc particles by electrolysis for recycling. Figure 6.9 shows the
structure of a metal particle replacement type single cell. The negative electrode is
the matrix of zinc particles and is connected with the current collector. When the
zinc particles are dissolved, the volume of the zinc particles in the battery shell is