Enabling 5 V-class lithium metal batteries via an aggregation-enhanced solvation electrolyte

High-voltage lithium metal batteries (LMBs) utilizing lithium-rich manganese oxide (LRMO) cathodes offer a promising way towards high energy densities yet remain impractical when operating at high voltages, primarily due to electrolyte instability at interfaces of LRMO and Li metal electrodes. In this study, we report stable cycling of LRMO-based LMBs under ultra-high voltage conditions of 5 V by employing an aggregation-enhanced solvation electrolyte (AESE). The AESE features a solvation structure dominated by anion-wrapped aggregates, in which Li⁺ ions are in a coordination environment surrounded by numerous anions. With such a solvation structure, the AESE concurrently stabilizes the Li metal anode and LRMO cathode. It promotes a protective cathode–electrolyte interphase on LRMO and an inorganic-rich interphase on Li metal, collectively suppressing electrolyte oxidation and transition metal dissolution. Thereby, Li||LRMO cells can deliver exceptional cycling stability at 5 V, retaining > 87% capacity after 200 cycles. It also sustains stable operation for 100 cycles at −20 °C. This work demonstrates the electrolyte design for 5 V-class LMBs capable of reliable operation under low-temperature conditions.