Constructing a Stabilized Cathode Electrolyte Interphase for High- Voltage LiCoO2 Batteries via the Phenylmaleic Anhydride Additive

Increasing the charge cutoff voltage (>= 4.6 V) is an effective and mainstream strategy to elevate the energy density of LiCoO2 (LCO)-based lithium-ion batteries (LIBs). However, the cycle life is compromised and challenged owing to the vulnerable cathode electrolyte interphase (CEI) and severe structural degradation of LCO at high voltages. In this work, a functional electrolyte additive phenylmaleic anhydride (PMA) is applied to construct a stabilized CEI film with compact and uniform properties, which facilitates preserving the fast Li+ diffusion kinetics during cycling and mitigates the dissolution of Co ions and fragmentation of LCO. As a result, the durability of the LCO battery is significantly improved in the electrolyte with PMA, and the capacity retention is promoted from 55.3 to 78.6% after 300 cycles at 1C at a cutoff voltage of 4.65 V. The electrolyte regulation with a proper additive provides an effective path to enhance the electrochemical performance of LIBs with high energy density and thus realize their practical applications.