Reactions in the Rechargeable Lithium-O_2 Battery with Alkyl Carbonate Electrolytes

摘要

The nonaqueous rechargeable lithium-O_2 battery containing an alkyl carbonate electrolyte discharges by formation of C_3H_6(OCO_2Li)_2, Li_2CO_3, HCO_2Li, CH_3CO_2Li, CO_2, and H_2O at the cathode, due to electrolyte decomposition. Charging involves oxidation of C_H_6OCC_2LO_2, Li_2CO_3) HCO_2Li, CH_3CO_2Li accompanied by CO_2 and H_2O evolution. Mechanisms are proposed for the reactions on discharge and charge. The different pathways for discharge and charge are consistent with the widely observed voltage gap in Li- O_2 cells. Oxidation of C_3H_6(OCO_2Li)_2 involves terminal carbonate groups leaving behind the OC_3H_6O moiety that reacts to form a thick gel on the Li anode. Li_2CO_3, HCO_2Li, CH_3CO_2Li, and C_3H_6(OCO_2Li)_2 accumulate in the cathode on cycling correlating with capacity fading and cell failure. The latter is compounded by continuous consumption of the electrolyte on each discharge.