Outstanding electrochemical performance of high-voltage LiNi_1/3Co_1/3Mn_1/3O₂ cathode achieved by application of LiPO₂F₂ electrolyte additive

Layered LiNi_1/3Co_1/3Mn_1/3O₂ (LNCM) cathode has received extensive attention because of its high specific capacity at high voltage (4.5 V). While the unsatisfactory electrochemical performance at high voltage hinders its practical application in next generation lithium ion batteries. Herein we demonstrate that simply application of lithium difluorophosphate (LiPO₂F₂) electrolyte additive significantly improves the electrochemical performance of high voltage LNCM/Li cell, at room and low temperature (−10 °C). Capacity retention of high voltage LNCM/Li cell with 3 wt. % LiPO₂F₂ additive achieves 89% after 250 cycles at room temperature and 94% after 200 cycles at low temperature in comparison with that of 61% and 10% without additive. Even discharging at 10 C, the LNCM/Li cell with 3% LiPO₂F₂ still delivers an initial capacity of 144 mAh g⁻¹ and maintains at 69 mAh g⁻¹ after 1000 cycles at room temperature. While the one without additive drops to 0 mAh g⁻¹ after about 350 cycles. The improved cyclic stability and rate capability of high voltage LNCM is mainly ascribed to the steady low impedance cathode electrolyte interphase (CEI) film created by 3% LiPO₂F₂ additive, which greatly hinders the subsequent electrolyte oxidation, electrode structural destruction and increase of electrode polarization during cycling.