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

Abstract 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 (LiCoO 2 ) 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‐OSO 3 Li) is developed that possesses radical‐scavenging anion TEMPO‐OSO 3 − . 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||LiCoO 2 batteries with dual‐salt (TEMPO‐OSO 3 Li (0.02 m ) and LiPF 6 (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 LiCoO 2 at high voltage.