Multifunctional Electrolyte Additive for High-Nickel LiNi_0.8Co_0.1Mn_0.1O₂ Cathodes of Lithium-Metal Batteries

LiNi0(0.8)Co(0.1)Mn(0.1)O(2) (NCM811) isperceived as a promising cathode material in lithium-ionbatteries for its high specific capacity and low cost. However, thecatalytic surface between the cathode and electrolyte leads to intensiveinterfacial reactions and gas generation, ultimately causing rapidcapacity fading and a great threat to the safety performance of thebattery, which hinders its applications at high voltages. Herein,ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as the electrolyte additiveis applied to alleviate the above problems by constructing a solidelectrolyte interphase on the cathode and anode. PFPN can be decomposedpreferentially over basic electrolytes to shape the thin and stableinterface film between the electrolyte and NCM811 cathode for restrainingthe production of gas and the corrosion of NCM811. The wettabilityof the separator can be enhanced by PFPN to promote uniform Li deposition.Also, PFPN has a flame-retardant effect due to its phosphoronitrilefunctional group. Moreover, the Li||Li symmetrical cells can achievelong-cycling stability with the PFPN-electrolyte (cycling performanceof 800 h at 0.5 mA cm(-2)). Last, the capacity retentionof NCM811||Li reaches 89.5% after 200 cycles at 1 C and 4.5 V.