Radical‐Scavenging Lithium Salt for Stable High‐Voltage Li||LiCoO2 Batteries.

High‐voltage cathodes improve the energy density of the batteries, which satisfies the pursuit of high‐energy‐density lithium metal batteries (LMBs). However, layered lithium cobalt oxide (LiCoO2) cathodes suffer from severe interfacial side reactions under high voltage (4.6 V), which is detrimental for practical applications. Herein, a functional lithium salt, 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl‐4‐sulfate lithium (TEMPO‐OSO3Li) is developed that possesses radical‐scavenging anion TEMPO‐OSO3−. The anion accumulates at the cathode interface and effectively scavenges free radicals under the electric field at high voltage, thereby, inhibiting the electrolyte decomposition and interfacial side reactions. As a result, the Li||LiCoO2 batteries with dual‐salt (TEMPO‐OSO3Li (0.02 m) and LiPF6 (1 m)) electrolyte exhibit high capacity retention of 92% after 100 cycles at 4.6 V and maintain 81% after 200 cycles, which is superior to that of the baseline electrolyte (26%). The work demonstrates a promising strategy for designing electrolyte salts to realize the practical application of LiCoO2 at high voltage. [ABSTRACT FROM AUTHOR]