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

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.