A Designed Durable Electrolyte for High‐Voltage Lithium‐Ion Batteries and Mechanism Analysis

Abstract

Rechargeable lithium‐ion batteries (LIBs) have dominated the energy market from electronic devices to electric vehicles, but pursuing greater energy density remains challenging due to the limited electrode capacity. Although increasing the cut‐off voltage of LIBs (>4.4V vs. Li+/Li) can enhance the energy density, the aggravated electrolyte decomposition always leads to a severe capacity fading and/or expiry of battery. Herein, we present a new durable electrolyte for high voltage LIBs. The designed electrolyte is composed of mixed linear alkyl carbonate solvent with certain cyclic carbonate additives, in which the ethylene carbonate (EC) co‐solvent was successfully avoided in use to suppress the electrolyte decomposition. As a result, an extremely high cycling stability, rate capability and high‐temperature storage performance were demonstrated in the case of graphite | LiNi0.6Co0.2Mn0.2O2 (NCM622) battery at 4.45 V when such electrolyte was used. We confirm that the good compatibility of electrolyte with graphite anode and the mitigated structural degradation of NCM622 cathode are responsible for the high performance at the high potential above 4.4 V. This work presents the promising applications of high voltage electrolytes for pursuing high energy LIBs and provides a straightforward guideline to study the electrodes‐electrolyte interface for higher stability.