Unlocking 4.7 V LiCoO<sub>2</sub> with a Counterintuitive Low-Concentration Fluoroborate Dual-Salt Electrolyte by Anion-Derived Interfacial Chemistry
Anping Zhang, Endian Yang, Zhihong Bi, Gongrui Wang, Shihao Liao, Xiaofeng Li, Yan Yu, Qi Liu, Xinhe Bao, Zhong‐Shuai Wu
Abstract
Elevating the charge cutoff voltage of LiCoO 2 (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.