LiBF4 Induced Unique Surface Modification Enables Improved Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Cathode

Abstract LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) has been regarded as a potential cathode material for next‐generation lithium‐ion batteries. However, the electrochemical performance of this material is severely affected by structural deterioration and capacity degradation, and the residual lithium is one of the main culprits. Herein, we propose an effective strategy to design ultrathin coatings on the surface of NCM811 by using LiBF 4 as the precursor. The homogeneous hybrid LiF‐Li 2 B 4 O 7 coating layers can be obtained due to the reaction between LiBF 4 and the residual lithium, which can not only effectively reduce the residual lithium, but also improve interfacial lithium‐ion diffusion kinetics and suppress side reactions. Accordingly, the LiBF 4 ‐modified samples exhibited significantly improved electrochemical performance. The coated sample of NCM811@LBF‐0.7 delivers the 127.1 mAh g −1 discharge capacity with 69.8 % capacity retention even after 300 cycles at 1 C. While the pristine sample only shows 97.1 mAh g −1 and the capacity retention decreases to 31.0 %. This method provides a simple and effective strategy to extend the service life and safety characteristics of high‐energy‐density lithium‐ion batteries.