A 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. The zirconia (ZrO 2 ) coating effectively enhances the surface stability of the cathode owing to its excellent chemical durability; however, the insulating electrical conductivity of ZrO 2 increases the electrode resistance and triggers efficiency decay. Here, we propose highly conductive oxygen-deficient black ZrO 2− x as a charge-conductive coating material. The black ZrO 2− x is uniformly coated onto the Ni-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC) surface via a solvent-free mechanochemical shearing process. Benefiting from the black ZrO 2− x coating layer, black ZrO 2− x coated NMC shows improved cycling characteristics and better rate capability than both bare NMC and ZrO 2 coated NMC. The enhanced electrochemical performance by the conformal coating of black ZrO 2− x mainly results from enhanced charge transfer, reduced gas evolution, and mitigated microstructural cracking. Density functional theory calculations confirm that the defective structure of black ZrO 2− x lowers the energy barrier for Li ion transfer, and strong hybridization between Zr in black ZrO 2− x and O in NMC mitigates oxygen evolution. Black ZrO 2− x is coated onto a Ni-rich cathode via solvent-free shearing, enhancing charge transfer, reducing gas evolution, and preventing cracking. It lowers Li-ion transfer barriers and mitigates oxygen release through strong Zr-O hybridization.