6 Application of Oxygen Reduction Catalysts
239
the cycle life of the secondary zinc-air battery. EOS Energy Storage Company in the
USA has made progress in this regard.
To solve the problem of dendrite formation in zinc electrodes, quaternary ammonium salt is generally added to the electrolyte to adsorb organic macromolecular
cations on the active center of zinc surface, thus inhibiting zinc deposition at these
locations and generating dendrites. It is found that sulfate, polyvinyl alcohol, etc.
also have the same effect as quaternary ammonium salt. In addition, the generation
of zinc dendrites can be inhibited by changing the charging mode, or the diaphragm
performance can be improved to reduce the influence of dendrites.
6.2.2.4 Other Metal-Air Batteries
(1) Magnesium-air battery [60]
The theoretical energy density of magnesium-air battery is second only to light metal
lithium and aluminum. Magnesium-air batteries hold five times the energy of lithium
batteries of the same size and can be mechanically charged with fast charging speed.
Magnesium is an ideal electrode material for magnesium-air batteries because of its
abundant reserves, low price and no pollution. The Korean Institute of Science and
Technology has successfully completed the road test of a magnesium-air batterypowered vehicle, enabling the electric vehicle to travel 800 km under the drive of a
complete battery.
Electrolytes used in magnesium-air batteries include aqueous solution and organic
solution. Different electrolytes have different reaction mechanisms. In the aqueous
solution system, the battery reaction is:
Mg + 1/2 O 2 + H 2 O = Mg(OH) 2
In the organic system, the battery reaction is:
Mg + 1/2 O 2 = MgO
In practical applications, the response rate of the air cathode is slow due to the
low reaction efficiency of the magnesium cathode. Although the energy density that
the magnesium-air battery can store is large, the battery’s ability to convert energy
into actual power is very limited. Both types of batteries have technical bottlenecks
that need to be overcome.
In organic magnesium-air batteries, the reactivity of metallic magnesium is very
low, and the discharge current can only reach 0.1 mA cm
−2 . Especially when the
surface of magnesium electrode is oxidized to form a dense Mg (OH) 2 passivation
film (the film cannot conduct Mg
2+ ), the electrode can hardly discharge normally. In
the organic electrolyte, the discharge of O 2 in the air electrode can only depend on
the solubility and diffusion rate of O 2 in the organic solution. MgO, the product of the
discharge reaction, is insoluble in the organic solution and is easy to deposit on the
239
the cycle life of the secondary zinc-air battery. EOS Energy Storage Company in the
USA has made progress in this regard.
To solve the problem of dendrite formation in zinc electrodes, quaternary ammonium salt is generally added to the electrolyte to adsorb organic macromolecular
cations on the active center of zinc surface, thus inhibiting zinc deposition at these
locations and generating dendrites. It is found that sulfate, polyvinyl alcohol, etc.
also have the same effect as quaternary ammonium salt. In addition, the generation
of zinc dendrites can be inhibited by changing the charging mode, or the diaphragm
performance can be improved to reduce the influence of dendrites.
6.2.2.4 Other Metal-Air Batteries
(1) Magnesium-air battery [60]
The theoretical energy density of magnesium-air battery is second only to light metal
lithium and aluminum. Magnesium-air batteries hold five times the energy of lithium
batteries of the same size and can be mechanically charged with fast charging speed.
Magnesium is an ideal electrode material for magnesium-air batteries because of its
abundant reserves, low price and no pollution. The Korean Institute of Science and
Technology has successfully completed the road test of a magnesium-air batterypowered vehicle, enabling the electric vehicle to travel 800 km under the drive of a
complete battery.
Electrolytes used in magnesium-air batteries include aqueous solution and organic
solution. Different electrolytes have different reaction mechanisms. In the aqueous
solution system, the battery reaction is:
Mg + 1/2 O 2 + H 2 O = Mg(OH) 2
In the organic system, the battery reaction is:
Mg + 1/2 O 2 = MgO
In practical applications, the response rate of the air cathode is slow due to the
low reaction efficiency of the magnesium cathode. Although the energy density that
the magnesium-air battery can store is large, the battery’s ability to convert energy
into actual power is very limited. Both types of batteries have technical bottlenecks
that need to be overcome.
In organic magnesium-air batteries, the reactivity of metallic magnesium is very
low, and the discharge current can only reach 0.1 mA cm
−2 . Especially when the
surface of magnesium electrode is oxidized to form a dense Mg (OH) 2 passivation
film (the film cannot conduct Mg
2+ ), the electrode can hardly discharge normally. In
the organic electrolyte, the discharge of O 2 in the air electrode can only depend on
the solubility and diffusion rate of O 2 in the organic solution. MgO, the product of the
discharge reaction, is insoluble in the organic solution and is easy to deposit on the