Establishing a long-term stable cathode–electrolyte interphase through multi-cationic competitive coordination for 4.6 V LiCoO2

Abstract

In basic carbonate liquid electrolytes, uncontrolled serious side reactions between the electrolyte and the electrode material occur under high-voltage conditions, resulting in the failure to form a stable and uniform CEI layer on the surface of LCO, accelerating the irreversible phase transformation of LCO and battery failure. Herein, a non-sacrificial additive was proposed to effectively optimize the existing carbonate electrolyte, passivate the uncontrolled side reaction with lithium ions, and avoid the continuous decay of carbonate electrolyte batteries to a great extent. Rubidium fluoride (RbF) was used as an additive to improve the oxidation stability of the carbonate electrolyte via competitive coordination of Rb⁺, anchoring part of the anions and organic solvent to realize a higher Li⁺ transport coefficient and superior electrode interface compatibility. Hence, side reactions between electrodes and the electrolyte were alleviated, and the cathode–electrolyte interphase (CEI) and cathode structure were stabilized. Compared to the base electrolyte, the electrolyte with 2 wt% RbF showed higher capacity retention in Li‖LCO half cells at 0.5C after 200 cycles (90% vs. 72%) and superior performance in LCO‖graphite pouch cells (99% after 180 cycles) under a 4.6 V cut-off voltage.