Oxygen- and Dendrite-Resistant Ultra-Dry Polymer Electrolytes for Solid-State Li-O2 Batteries

Abstract Utilizing polymer electrolytes in Li-O2 batteries could effectively solve safety issues caused by flammable liquid electrolytes. However, the effect of polymer matrixes and additional liquid electrolytes on the cycle performance of Li-O2 batteries is still not clear. Herein, free-standing, Li-ion conducting ultra-dry polymer electrolytes (UDPEs) without additional liquid electrolytes are synthesized by a simple tape-casting and vacuum-drying method. The long-term cycle performance (over 800 h) of the UDPE-based symmetric Li-Li cells in O2 atmosphere demonstrates that the UDPEs significantly resist O2 crossover and Li dendrite penetration. Moreover, side reactions caused by the degradation of liquid electrolytes can be alleviated and a stable LiF-containing solid electrolyte interface is formed between the UDPEs and Li metal. Meanwhile, the cycle life of the UDPE-based catalyst-free Li-O2 batteries under a high current density of 0.4 mA cm-2 is improved by more than twofold in comparison with that of the liquid electrolyte-based Li-O2 batteries. The replacement of liquid electrolytes by UDPEs does not change the fundamental reaction of the solid-state Li-O2 batteries, which is still the formation and decomposition of typical Li2O2 crystals. The outstanding comprehensive performance of UDPEs may trigger further studies towards multifunctional polymer electrolytes in Li-O2 batteries and even other alkali metal-based O2 (air) batteries.