Reliable liquid electrolytes for lithium metal batteries

Lithium metal is considered a promising anode material because of its high specific capacity and low redox potential. However, there are two factors that prevent a lithium metal anode from being used, a safety issue caused by dendrite formation and a low Coulombic efficiency caused by the formation of a solid electrolyte interface. Solving these problems by designing reliable liquid electrolytes is an appropriate strategy for two reasons. First, it is the only method that has good compatibility with the current industrial fabrication techniques for lithium ion pouch cells, compared with other strategies such as the use of 3D current collectors or solid-state electrolytes. Second, liquid electrolytes can achieve good kinetics and avoid an energy density loss caused by non-active materials in 3D current collectors. To better understand the benefits which can be realized by designing reliable liquid electrolytes, this review discusses state-of-art electrolyte modification strategies and the mechanisms for improving the performance of a lithium metal anode by the proper selection, design and combination of solvents, solutes, and additives. Furthermore, the problems related to electrolyte modification, and advanced characterization techniques for the anode/electrolyte interface and for solvent-ion interactions are introduced. It is expected that this review will stimulate scientists and engineers to design promising electrolyte components for developing reliable lithium metal batteries.