Structure heterogeneity in polycrystalline and single-crystal high-nickel cathode materials by synchrotron radiation XAS

High-nickel Li-ion cathode materials experience rapid capacity decay during battery cycling. To address the issues of stability and cycle life, single crystallization and surface coating treatments have been explored as viable solutions. Our previous research indicated that the formation of NiO-like phases is the main cause of deterioration in high-nickel cathode materials. In this study, lithium-ion conductor Li 4 Ti 5 O 12 is coated on single-crystalline Li(Ni 0.83 Co 0.12 Mn 0.05 )O 2 . Through comprehensive characterization, including morphology, structure, elemental valence states, and electrochemical performance, we find that the layered structure in the bulk of single-crystalline particles is less susceptible to phase transitions, and the coating treatment further suppresses side reactions on surface, resulting in fewer NiO-like phases. Compared to polycrystalline materials, single-crystalline materials exhibit improved structural stability, particularly under high-voltage cycling conditions, and appropriate coating treatments also enhance the electrochemical performance of the materials.