Rechargeable Solid-State Li-Air and Li-S Batteries: Materials, Construction, and Challenges

Nonaqueous Li-air and Li-S batteries are attracting considerable interest because of their outstanding theoretical capacities and energy densities. However, despite the substantial progress in their development, safety remains an issue because of the flammability of their organic electrolytes. Moreover, the electrolyte volatilization of Li-air batteries and shuttle effect in Li-S batteries seriously hinder their development. The use of solid-state Li-air and Li-S batteries is one of the best solutions. Nevertheless, many challenges remain in solid electrolytes, electrodes, and interfaces. In this review, a comprehensive discussion on the development of solid-state Li-air and Li-S batteries is provided. The discussion begins with introduction of the progress in solid electrolytes, including their ionic conductivities and chemical stabilities. It then moves on to the cathodes of both batteries and the interface between electrolytes and electrodes. The reaction process inside the cathode is also presented. Suggestions for the optimization of composite cathodes and modification of the electrode-electrolyte interface are provided in the end. Intensive effort is required for the development of solid-state Li-air and Li-S batteries in the future.