Phosphate and Borate-Based Composite Interface of Single-Crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 Enables Excellent Electrochemical Stability at High Operation Voltage.

The application of nickel-rich cathodes in lithium-ion batteries has been hampered by its rapid capacity/voltage fading and limited performance of rate. In this work, a passivation technique is used to create a stable composite interface on single-crystal LiNiCoMnO (NCM811) surface, which greatly improves the cycle life-span and high-voltage constancy of cathode with 4.5 and 4.6 V cut-off voltage. The improved Li conductivity of the interface enables a firm cathode-electrolyte interphase (CEI), which reduces interfacial side reactions, lowers the risk of safety hazards, and improves irreversible phase transitions. As a result, the electrochemical performance of single-crystal Ni-rich cathode are remarkably enhanced. The specific capacity of 152 mAh g can be delivered at a charging/discharging rate of 5 C under 4.5 V cut-off voltage, much higher than 115 mAh g of the pristine NCM811. After 200 cycles at 1 C, the composite interface modified NCM811 demonstrates outstanding capacity retention of 85.4% and 83.8% at 4.5 V and 4.6 V cut-off voltage, respectively.