Sublimated Se-Induced Formation of Dual-Conductive Surface Layers for High-Performance Ni-Rich Layered Cathodes

Ni-rich layered oxide cathode materials for Li-ion batteries have received widespread attention owing to their high specific capacity and comparatively low cost. However, owing to Li-containing surface residues, side reactions with the electrolyte and structural rearrangement after long-term cycling leads to severe degradation of the cathode performance. Here, Se coating serves as a novel and simple sublimation-inducing gas reaction method to modify the Ni-rich layered material, resulting in capacity retention and rate performance improvement. The sublimed gaseous Se reacts with residual Li compounds to form a Li₂SeO₄ coating on the surface of the secondary particles, which simultaneously promotes the transmission of Li ions and reduces electrode-electrolyte side reactions. Moreover, gaseous Se penetrates between the primary particles within the secondary particles to promote electron transmission. This dual-conductive surface layer facilitates superior capacity and voltage retentions. Significantly, the proposed method is scalable and applicable to all Ni-rich cathode materials.