Tailoring anion-dominant solvation environment by steric-hindrance effect and competitive coordination for fast charging and stable cycling lithium metal batteries

Abstract

The properties of electrolytes are critical for fast-charging and stable-cycling applications in lithium metal batteries (LMBs). However, the slow kinetics of Li⁺ transport and desolvation in commercial carbonate electrolytes, coupled with the formation of unstable solid electrolyte interphases (SEI), exacerbate the degradation of LMB performance at high current densities. Herein, we propose a versatile electrolyte design strategy that incorporates cyclohexyl methyl ether (CME) as a co-solvent to reshape the Li⁺ solvation environment by the steric-hindrance effect of bulky molecules and their competitive coordination with other solvent molecules. Simulation calculations and spectral analysis demonstrate that the addition of CME molecules reduces the involvement of other solvent molecules in the Li⁺ solvation sheath and promotes the formation of Li⁺–PF₆⁻ coordination, thereby accelerating Li⁺ transport kinetics. Additionally, this electrolyte composition improves Li⁺ desolvation kinetics and fosters the formation of inorganic-rich SEI, ensuring cycle stability under fast charging. Consequently, the Li||LiNi_0.8Co_0.1Mn_0.1O₂ battery with the modified electrolyte retains 82% of its initial capacity after 463 cycles at 1 C. Even under the extreme fast-charging condition of 5 C, the battery can maintain 80% capacity retention after 173 cycles. This work provides a promising approach for the development of high-performance LMBs by modulating solvation environment of electrolytes.