Low concentration electrolyte with non-solvating cosolvent enabling high-voltage lithium metal batteries

Developing low cost, yet high-voltage electrolyte is significant to improve the energy density and practicability of lithium metal batteries (LMBs). Low concentration electrolyte has significant merits in terms of cost and viscosity; however, their poor compatibility with high-voltage LMBs hinders its applications. Here, we develop a diluted low concentration electrolyte by replacing solvating cosolvent with a non-solvating cosolvent to facilitate the interaction between BF₄ ^- and Li⁺, resulting in optimized interfacial chemistry and suppressed side reaction. Thus, the high-loading Li-LiCoO₂ full cells (20.4 mg cm^-2) deliver outstanding cycling stability and rate performance at a cutoff voltage of 4.6 V. More impressively, a Li-LiCoO₂ pouch cell achieves an energy density of more than 400 Wh kg^-1 under practical conditions with thin Li (50 μm) and lean electrolyte (2.7 g Ah^-1). This work provides a rational approach to design a low concentration electrolyte, which can be extended to other high voltage battery systems.