6 Application of Oxygen Reduction Catalysts
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can prolong the cycle life of battery. In order to meet the above requirements, lithiumair battery electrolyte is generally a multicomponent mixed solution. Adding some
fluorine substituted solvents (methyl nonafluorobutyl ether and trifluoroethyl phosphonic acid) can improve the solubility of O 2 , while adding tri (pentafluorophenyl)
borane (TPFPB) and crown ether can enhance Li 2 O and the solubility of Li 2 O.
(3) Porous carbon material and oxygen permeable selective membrane for air
electrode.
Research shows that the overpotential of the lithium cathode can be basically ignored
during the charging and discharging process of the lithium-air battery, and the overpotential of the battery mainly comes from the air cathode. Unlike the air electrode of
a fuel cell, the air electrode of a lithium-air battery not only catalytically reduces O 2
but also contains discharge products LiO 2 , Li 2 O 3 , Li 2 O and even byproduct Li 2 CO 3 .
The preparation method and physical characteristics of air electrode deeply affect the
specific discharge capacity, rate performance and cycle performance of the battery.
Therefore, higher requirements are put forward for the specific surface area, porosity,
pore size distribution, carbon loading and electrode thickness of carbon materials as
catalyst carriers, with higher requirements for pore size distribution. During the
battery discharge process, lithium oxide is deposited on the electrode surface, and
smaller pores are easily blocked, thus affecting the transmission of electrolyte and air;
On the contrary, mesoporous and macroporous materials can accommodate a certain
amount of discharge products without affecting the diffusion of O 2 . As the amount
of discharge products tend to saturate in the pores, the battery stops discharging.
Water in the air permeates into the battery through the air electrode and will react
with the negative electrode of lithium metal to corrode the negative electrode of
lithium metal. Organic electrolyte in the battery volatilizes and absorbs water through
the air electrode, which will affect the discharge capacity, cycle performance and
service life of the battery. Therefore, it is necessary to choose a membrane material
that can not only prevent or delay water infiltration and volatilization of organic
electrolyte but also ensure O 2 diffusion into the battery in the air. Teflon-coated glass
fiber membrane (TCFC) can effectively prevent the infiltration of water. The air
environment test for 40 days shows that the volatilization rate of electrolyte is only
2%, the negative electrode of metal lithium is bright as new, and its overpotential
increases by only 13 ~ 24 mV. In addition, the film prepared by adding polyaniline
(PAn) with good conductivity also has good waterproof and air permeability.
6.2.2.2 Aluminum-Air Battery
Aluminum-air battery has always attracted people’s attention because of its theoretical energy density second only to lithium-air battery, low price of negative electrode material and its ability to discharge in aqueous electrolyte. In the 1970s,
the USA developed aluminum-air batteries for navigation beacon lights and mine
lighting. In the 1980s, Canadian Aluminum Power Company developed battery
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can prolong the cycle life of battery. In order to meet the above requirements, lithiumair battery electrolyte is generally a multicomponent mixed solution. Adding some
fluorine substituted solvents (methyl nonafluorobutyl ether and trifluoroethyl phosphonic acid) can improve the solubility of O 2 , while adding tri (pentafluorophenyl)
borane (TPFPB) and crown ether can enhance Li 2 O and the solubility of Li 2 O.
(3) Porous carbon material and oxygen permeable selective membrane for air
electrode.
Research shows that the overpotential of the lithium cathode can be basically ignored
during the charging and discharging process of the lithium-air battery, and the overpotential of the battery mainly comes from the air cathode. Unlike the air electrode of
a fuel cell, the air electrode of a lithium-air battery not only catalytically reduces O 2
but also contains discharge products LiO 2 , Li 2 O 3 , Li 2 O and even byproduct Li 2 CO 3 .
The preparation method and physical characteristics of air electrode deeply affect the
specific discharge capacity, rate performance and cycle performance of the battery.
Therefore, higher requirements are put forward for the specific surface area, porosity,
pore size distribution, carbon loading and electrode thickness of carbon materials as
catalyst carriers, with higher requirements for pore size distribution. During the
battery discharge process, lithium oxide is deposited on the electrode surface, and
smaller pores are easily blocked, thus affecting the transmission of electrolyte and air;
On the contrary, mesoporous and macroporous materials can accommodate a certain
amount of discharge products without affecting the diffusion of O 2 . As the amount
of discharge products tend to saturate in the pores, the battery stops discharging.
Water in the air permeates into the battery through the air electrode and will react
with the negative electrode of lithium metal to corrode the negative electrode of
lithium metal. Organic electrolyte in the battery volatilizes and absorbs water through
the air electrode, which will affect the discharge capacity, cycle performance and
service life of the battery. Therefore, it is necessary to choose a membrane material
that can not only prevent or delay water infiltration and volatilization of organic
electrolyte but also ensure O 2 diffusion into the battery in the air. Teflon-coated glass
fiber membrane (TCFC) can effectively prevent the infiltration of water. The air
environment test for 40 days shows that the volatilization rate of electrolyte is only
2%, the negative electrode of metal lithium is bright as new, and its overpotential
increases by only 13 ~ 24 mV. In addition, the film prepared by adding polyaniline
(PAn) with good conductivity also has good waterproof and air permeability.
6.2.2.2 Aluminum-Air Battery
Aluminum-air battery has always attracted people’s attention because of its theoretical energy density second only to lithium-air battery, low price of negative electrode material and its ability to discharge in aqueous electrolyte. In the 1970s,
the USA developed aluminum-air batteries for navigation beacon lights and mine
lighting. In the 1980s, Canadian Aluminum Power Company developed battery