A Novel Electrolyte Additive Enables High-Voltage Operation of Nickel-Rich Oxide/Graphite Cells.

Nickel-rich oxide/graphite cells under high voltage operation provide high energy density but present short cycle life because of the parasitic electrolyte decomposition reactions. In this work, we report a novel electrolyte additive, N,O-bis(trimehylsilyl)-trifluoroacetamide (NOB), which enables nickel-rich oxide/graphite cells to operate stably under high voltage. When evaluated in a nickel-rich oxide-based full cell, LiNi0.5Co0.2Mn0.3O2 (NCM523)/graphite using a carbonate electrolyte, 1 wt % NOB provides the cell with capacity retention improved from 38% to 73% after 100 cycles at 1C under 4.5 V. It is found that NOB is able to eliminate hydrogen fluoride in the electrolyte. The radicals resulting from the interaction of NOB with the fluoride ion can be preferentially oxidized on the cathode compared with the electrolyte solvents, with its reaction products constructing N-containing interphases simultaneously on the cathode and anode, which suppress the parasitic electrolyte decomposition reactions, leading to the significantly improved cycle stability of nickel-rich oxide/graphite cells under high voltage.