Improving High‐Voltage Performance of a LiNi0.5Co0.2Mn0.3O2 Cathode with Triallyl Phosphite as an Electrolyte Additive

Abstract

AbstractTriallyl phosphite (TAPi) is studied as an electrolyte additive for high‐voltage LiNi0.5Co0.2Mn0.3O2 cathodes. Theoretical calculations combined with linear sweep voltammetry (LSV) tests demonstrate that TAPi tends to be preferentially oxidized and suppresses the decomposition of traditional carbonate‐based electrolytes. In addition, the hydrolysis of LiPF6 salt in the electrolyte is investigated by 19F nuclear magnetic resonance spectra, which prove that TAPi inhibits the decomposition of LiPF6. The results of charge/discharge measurements show that TAPi is effective to improve the capacity retention of LiNi0.5Co0.2Mn0.3O2/Li half‐cell and LiNi0.5Co0.2Mn0.3O2/graphite full‐cell. The mechanism of TAPi is studied by a series of physical characterizations, the results indicate that TAPi forms a protective interphase film on the cathode surface after cycling. The TAPi‐derived film protects the cathode structure from destruction to improve the electrochemical performance of the LiNi0.5Co0.2Mn0.3O2 cathode at high voltage.