Decrypting the antisolvent-modulating mechanism in localized high-concentration electrolytes

Antisolvents are one of the main components in localized high-concentration electrolytes (LHCEs), which are considered merely as diluents to control the macro properties and preserve the anion-dominated solvation structure, but their role in shaping the micromicelle-like structure and interface chemistry remains poorly understood. Here, we utilize LHCEs with trifluorobenzene isomer as antisolvent to investigate the antisolvent polarity-dependent solvation structure, interface chemistry and Li deposition behavior in lithium metal batteries (LMBs). The 'dragging effect' of antisolvents on anions can alter the solvation environment, correcting the existing micelle-like solvation structure model of LHCEs. Additionally, the interface adsorption of polar antisolvent negatively impacts the formation of solid electrolyte interphase and ion transport dynamics, thereby influencing the Li deposition behavior. The Li deposition/stripping efficiency in ester-based LHCEs using low-polarity antisolvents is enhanced to 98.55%, as evidenced by the Li||LiFePO₄ full cell (N/P = 3) achieving 90% capacity retention after 250 cycles. Furthermore, the significant role of high-polarity antisolvent in enhancing the ion conductivity of bulk electrolyte, especially at low temperatures, cannot be ignored. This work provides valuable insights into the intricate role of antisolvents in LHCEs, highlighting their pivotal influence on battery performance and contributing to the advancement of electrolyte design for high-energy-density LMBs.