Enhanced Electrochemical Performance of Ni-Rich Cathode Materials with an In Situ-Formed LiBO₂/B₂O₃ Hybrid Coating Layer

Surface Li residues on Ni-rich cathode materials lead to adverse interfacial side reactions, which in turn gives rise to rapid structural and capacity degradations during long-term cycling. Washing is a direct and effective method to remove the residual Li compounds but tends to change the surface structure of the Ni-rich cathode, increasing its air sensitivity. Herein, we report a facile single-step method to prepare an in situ-formed LiBO₂/B₂O₃ hybrid coating layer on the surface of LiNi_0.8Co_0.1Mn_0.1O₂. The fast ion conductor, LiBO₂, is generated via the consumption of surface Li impurities by H₃BO₃, forming a hybrid coating layer together with the cogenerated B₂O₃. Such an optimized hybrid coating layer combines the functions of removing surface Li residues, promoting Li⁺-ion transport, and isolating the cathode material and electrolyte, resulting in a modified Ni-rich cathode material that exhibits superior cycling stability and rate capability compared with the unmodified Ni-rich cathode material. The results demonstrate the feasibility of this hybrid coating strategy to remove the surface Li residues without adversely affecting the performance of Ni-rich cathode materials.