Kinetic investigation of catalytic disproportionation of superoxide ions in the non-aqueous electrolyte used in Li-air batteries

Superoxide reacts with carbonate solvents in Li-air batteries. Tris(pentafluorophenyl)borane is found to catalyze a more rapid superoxide (O₂^-) disproportionation reaction than the reaction between superoxide and propylene carbonate (PC). With this catalysis, the negative impact of the reaction between the electrolyte and O₂^- produced by the O₂ reduction can be minimized. A simple kinetic study using ESR spectroscopy was reported to determine reaction orders and rate constants for the reaction between PC and superoxide, and the disproportionation of superoxide catalyzed by Tris(pentafluorophenyl)borane and Li ions. The reactions are found to be first order and the rate constants are 0.033 s^-1 M^-1, 0.020 s^-1 M^-1 and 0.67 s^-1 M^-1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively.