Design of Localized High Concentration Electrolytes for Fast-Charging Lithium-Ion Batteries

Localized high-concentration electrolytes (LHCEs) have emerged as a promising class of electrolytes to improve the cycle life and energy density of lithium-ion batteries (LIBs). While their application in batteries with lithium-metal anodes is extensively investigated, their behavior in systems with graphite anodes has received less research attention. Herein, the behaviors of four electrolytes in Graphite | LiNiO2 cells are compared. By systematically varying the electrolyte compositions, the impacts of the solvation structure, solvent composition, and salt composition of LHCEs are identified on the rate capability, stability, and propensity for lithium plating in LIB full-cells. It is found that while the solvation structure and solvent composition each play an important role in determining rate capability, the substitution of LiPF6 salt with LiFSI maximizes the rate capability and suppresses irreversible lithium plating. It is now demonstrated via constant-potential cycling, that an appropriately formulated LHCE can, therefore, maintain high reversible capacity and safety under arbitrarily fast charging conditions. By appropriately designing for solvation structure, solvent, and salt, localized high-concentration electrolytes can be developed to support fast charging with minimal risk of lithium plating on the graphite anode. Replacement of LiPF6 salt with LiFSI salt with optimized solvents maximizes the rate capability and suppresses irreversible lithium plating. image