Bi-coordinating solvent in EC-free electrolyte to inhibit electrode crosstalk in high-voltage lithium-ion batteries

Abstract

Elevating the cut-off voltage is a pragmatic way to boost the energy density of lithium-ion batteries (LIBs), which nevertheless is plagued by the vulnerable electrolyte chemistry and parasite reactions at interphase. Herein, we proposed a new electrolyte design based on dicarbonyl solvents, which decreases HOMO energy level of 0.95 eV by forming bi-coordinating Li⁺ solvates. Moreover, dicarbonyl solvents facilitate hydrogen-transfer reaction with PF₆⁻ in the solvent-dominated chemistry, constructing an LiF-rich interphase for kinetic passivation. This peculiar coordination geometry contributes to less transition metal dissolution (>60 % reduction) and improved capacity retention (from 48 % to 71 %) after cycling at 4.5 V. Consequently, the designed electrolyte shows wide-liquid range (−60∼60 °C) and oxidative tolerance (4.8 V vs. Li/Li⁺), validated in the 4.5 V-charged NCM811/graphite pouch cells at practical conditions. This work provides a new electrolyte design for advancing LIBs.