Modifying the Cathode–Electrolyte Interphase by Sulfone-Based Additive to Enhance the Electrochemical Performance of LiNi_0.5Mn_1.5O₄

LiNi0.5Mn1.5O4 (LNMO) is considered one of the most promising cathode materials for high-energy-density lithium-ion batteries (LIBs). However, the practical application of the LNMO cathode is seriously limited by the poor cycling performance. Hence, methyl phenyl sulfone (MPS) is investigated as an electrolyte additive to modify the cathode–electrolyte interphase and furthermore enhance the electrochemical performance of the LNMO cathode at a high voltage (5 V class). Results evidenced that the cycling performance of LNMO/Li cells was improved remarkably and with a high capacity retention of 89.8% after 400 cycles at 1 C in the 0.1 wt % MPS-containing electrolyte. Subsequently, the rate capability is also significantly improved with a high capacity of 110.2 mAh g–1 even at 5 C. Furthermore, the reason for the much-improved electrochemical performance of the LNMO/Li cell is further investigated in detail. Our investigation reveals that MPS additive can alleviate the decomposition of LiPF6 and is oxidized to form a protective layer, which inhibits the decomposition of electrolyte and dissolution of transition metals and then stabilizes the structure of the LNMO cathode during the cycling process. As a result, such a functional additive provides a cost-efficient choice to achieve the high performance of the LNMO cathode in high-voltage LIBs.