Black Zirconia Cathode Coating Layer Enabling Facile Charge Diffusion and Surface Lattice Stabilization for Lithium-Ion Batteries

The conformal surface coating of Ni-rich layered cathode materials is essential for mitigating their interfacial and subsequent structural degradation. Zirconia (ZrO2) coating effectively enhances the surface stability of the cathode owing to its excellent chemical durability; however, the insulating electrical conductivity of ZrO2 increases the electrode resistance of the electrode and triggers efficiency decay. Here, we propose a highly conductive oxygen-deficient black ZrO2−x as a charge-conductive coating material. The black ZrO2−x is uniformly coated onto the Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC) surface via solvent-free mechanochemical shearing process. Benefiting from the black ZrO2−x coating layer, black ZrO2−x coated NMC shows improved cycling characteristics and better rate capability than both bare NMC and ZrO2 coated NMC. The enhanced electrochemical operations by the conformal coating of black ZrO2−x mainly results from enhanced charge transfer, reduced gas evolution, and mitigated microstructure cracking. Density functional theory calculations confirmed that the defective structure of black ZrO2−x lowers the energy barrier for Li ion transfer, and strong hybridization between Zr in black ZrO2−x and O in NMC mitigates oxygen evolution.