Enhanced Anion-Coordination Solvation Structure in High-Voltage Electrolyte Enables Wide-Temperature and Fast-Charging Lithium Metal Batteries

High-voltage lithium metal batteries (LMBs) have garnered significant attention for their high energy density, but struggle with high-rate capability and wide-temperature operation. Balancing high-temperature interfacial stability with rapid low-temperature/high-rate desolvation kinetics remains challenging. This study introduces a polyanion-synergized weakly solvating electrolyte strategy. Using fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) as weakly solvating solvents, a ternary anion system (PF₆⁻/TFSI⁻/BOB⁻) modulates the solvation structure. This results in an anion-enhanced solvation structure enriched with contact ion pairs (CIPs) and ion aggregates (AGGs), which significantly reduces the Li⁺ desolvation energy barrier and enhances Li⁺ transport kinetics. Moreover, the electrolyte constructs a stable electrode/electrolyte interphase (EEI) enriched with inorganic components such as LiF, Li₂S, Li₂SO_x, Li₃N, and Li_xBO_y, providing excellent mechanical and thermal stability. Additionally, LiBOB neutralizes harmful HF, further enhancing electrolyte stability. As a result, the Li||NCM811 battery demonstrates excellent cycling stability across a wide temperature range of -10-60 °C at a high cutoff voltage of 4.6 V and achieves stable charge/discharge performance at a high rate of 5C. A 2.7 Ah pouch cell (359 Wh kg⁻¹) also shows excellent cycling stability. This work provides novel perspectives on high-voltage electrolyte engineering and propels LMBs toward expanded practical applications.