LiBF₄ Induced Unique Surface Modification Enables Improved Electrochemical Performance of LiNi_0.8Co_0.1Mn_0.1O₂ Cathode

AbstractLiNi0.8Co0.1Mn0.1O2 (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 LiBF4 as the precursor. The homogeneous hybrid LiF‐Li2B4O7 coating layers can be obtained due to the reaction between LiBF4 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 LiBF4‐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.