Non‐Sacrificial Additive Enables a Non‐Passivating Cathode Interface for 4.6 V Li||LiCoO2 Batteries

Abstract Various electrolyte additives are developed to construct a cathode electrolyte interphase (CEI) layer for high‐voltage LiCoO 2 since the cathode suffers severe interfacial degradation when increasing the cut‐off voltage over 4.55 V. However, the CEI derived from the additive sacrificial reaction faces the risk of rupture due to the corrosion reaction and the volumetric variation of the cathode. Herein, a non‐passivating cathode interface is realized for 4.6 V LiCoO 2 with a non‐sacrificial electrolyte additive (TBAClO 4 ) by regulating the solvent environment at the interface rather than the preferential decomposition for CEI formation. Owing to the novel protection mechanism, the cell performance shows little dependence on the CEI‐formation process. Therefore, an ultra‐high initial coulombic efficiency (96.63%) and excellent cycling stability (81% capacity retention after 300 cycles) are achieved in Li||LiCoO 2 batteries. Moreover, even with the electrolyte containing 1000 ppm H 2 O, the remarkable water capture ability of the additive together with its interfacial regulation enables the 4.6 V Li||LiCoO 2 battery to retain 80% capacity after 200 cycles. This non‐sacrificial strategy provides new insights into high‐voltage electrolyte additive design for high‐energy‐density lithium metal batteries.