Unlocking 4.7 V LiCoO2 with a Counterintuitive Low-Concentration Fluoroborate Dual-Salt Electrolyte by Anion-Derived Interfacial Chemistry

Abstract

Elevating the charge cutoff voltage of LiCoO₂ (LCO) from 4.4 to 4.7 V can significantly boost energy density. However, conventional electrolyte strategies encountering the viscosity and wettability obstacles for high-voltage LCO cannot tackle the issues of severe electrolyte decomposition, electrode–electrolyte interface degradation, and irreversible phase-transitions simultaneously. Herein, we achieved stable operation of commercial LCO at 4.7 V using a superwettable low-concentration fluoroborate dual-salt electrolyte (LFE). Our elaborated LFE (0.5 M) features an anion-enriched solvation structure that creates ultrathin, stable yet fast ion/electron transfer electrode/electrolyte interphases, significantly alleviating electrolyte decomposition, interface degradation, and injurious lithium dendrites. Consequently, LFE enables LCO to deliver a record capacity retention of 89.5% after 200 cycles and rate capability, far surpassing state-of-the-art 4.7 V-charged Li||LCO batteries. We assembled 1.25 Ah-class graphite||LCO pouch cells using LFE, achieving 100% capacity retention after 300 cycles and showcasing practicality. This work inaugurates an innovative pathway to maximize energy storage devices performance.