Localized asymmetric dipole electrolyte engineering for high-performance lithium-metal batteries

Abstract

The practical application of lithium metal batteries is severely hampered by lithium-ion disordered multi-phase interface transfer. In this work, a local asymmetric dipole solvent of methyl difluoroacetylsulfonyl fluoride (MDFSA) is proposed by incorporating a partially fluorinated methyl group (–CF2H) into methyl acetate (MA) to reduce the electron cloud density of the carbonyl group and introducing a fluorosulfonyl group (–SO2F) to provide additional solvation sites. This strategy exhibits the high oxidation resistance and interfacial stability characteristic of fluorinated electrolytes, overcoming the limitations of weak solvation ability and poor bulk-phase transport. As a result, it simultaneously enhances both the thermodynamic properties of Li⁺ transport and the interfacial kinetics. Accordingly, Li||NCM811 cells using the MDFSA electrolytes have achieved capacity retention of 70.0% after 400 cycles at 4.3 V. This work provides valuable molecular-level localized dipole design principles for solvation chemistry and interfacial engineering in high-performance lithium metal batteries.