Multifunctional Electrolyte Additive for High-Nickel LiNi0.8Co0.1Mn0.1O2 Cathodes of Lithium-Metal Batteries

LiNi00.8Co0.1Mn0.1O2 (NCM811) is perceived as a promising cathode material in lithium-ion batteries for its high specific capacity and low cost. However, the catalytic surface between the cathode and electrolyte leads to intensive interfacial reactions and gas generation, ultimately causing rapid capacity fading and a great threat to the safety performance of the battery, which hinders its applications at high voltages. Herein, ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as the electrolyte additive is applied to alleviate the above problems by constructing a solid electrolyte interphase on the cathode and anode. PFPN can be decomposed preferentially over basic electrolytes to shape the thin and stable interface film between the electrolyte and NCM811 cathode for restraining the production of gas and the corrosion of NCM811. The wettability of the separator can be enhanced by PFPN to promote uniform Li deposition. Also, PFPN has a flame-retardant effect due to its phosphoronitrile functional group. Moreover, the Li||Li symmetrical cells can achieve long-cycling stability with the PFPN-electrolyte (cycling performance of 800 h at 0.5 mA cm–2). Last, the capacity retention of NCM811||Li reaches 89.5% after 200 cycles at 1 C and 4.5 V.