Low Concentration Electrolyte with Non-Solvating Cosolvent Enabling High-Voltage Lithium Metal Batteries

SUMMARY 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 an 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.