Achieving Stable Cycling of Li-Metal Anodes in Li-O_2 Batteries: Optimizing Solvation Environment in Ionic Liquid/Solvent Blend Formulations

摘要

The realization of a truly rechargeable, high capacity lithium-oxygen (Li-O_2) battery faces serious technological barriers relating to material/intermediate stability, electrochemical reversibility of the cathode discharge processes, and gas supply challenges. Furthermore, to maximize energy densities of Li-O_2 cells, the utilization of Li-metal anodes is highly desired, thus introducing additional and serious interfacial challenges in the form of electrolyte degradation and susceptibility to dendrite formation on cycling. These factors ultimately create serious safety issues and further contribute to the reduced cyclability of Li-O_2 cells that is already limited by the poor reversibility of Li_2O_2 formation at the cathode. Without introducing artificial anode protection or isolation of Li from a cathoylte compartment, the electrolyte for a high-performance Li-O_2 device must exhibit complementary stability at both reactive interfacial regions of the two different electrodes. In many cases, the solvents that mediate good performance at the Li-O_2 cathode exhibit poor stability at Li-metal and, consequently, new electrolyte formulations geared towards good stability and performance at both the cathode and the anode are required.