Air electrode for electrochemical accumulators - has active mass contg. graphitised carbon, nickel, and polymer binder, used esp. in zinc air accumulator

摘要

Air electrode has an active mass contg. a binder; carbon powder (I) with a graphitisation index above 0.2 and a specific surface (SS) of 10-60 sq.m/g.; 15-25 wt.% Ni and 15-25 wt.% C (II) with a low density. (I) is pref. obtd. by pyrolysing CO contg. 0-30 vol.% CO2 at 550-700 deg.C on an Ni or Fe-Ni catalyst; or by using the same process to pyrolise CH4 contg. 0-30 vol.% H2; or by milling graphite. The air electrode is pref. coated on one surface with 10-30 g/sq.m. of Ni providing protection, and on the other surface with a porous hydrophobic layer of PTFE. Two such electrodes are pref. used in a sec. cell with a middle Zn electrode and an outer polymer frame. This electrode resists anodic corrosion caused by the release of oxygen, and also expansion during repeated charging and discharging.