Molten Salt‐Assisted Synthesis of Single‐Crystalline Nonstoichiometric Li1+xNi1–xO2 with Improved Structural Stability

Abstract Cobalt‐free LiNiO 2 is an attractive cathode material with high energy density and low cost but suffers from severe structural degradation and poor performance. Here, a molten salt‐assisted synthesis combined with a Li‐refeeding strategy is proposed to obtain nonstoichiometric Li 1+ x Ni 1‐ x O 2 with submicron particle size and superior rate performance. The slightly Li‐rich and single‐crystalline characters inhibit Li + /Ni 2+ anti‐site defects and mitigates the undesirable phase evolution. Remarkably, single‐crystalline Li 1.045 Ni 0.955 O 2 exhibits a high specific capacity (218.7 mAh g −1 at 0.1 C), considerable rate capability (187.0 mAh g −1 at 5 C), and an initial Coulombic efficiency (89.62% at 0.1 C) in the 1.27 Ah pouch full cell employing the graphite anode, significantly outperforming near stoichiometric LiNiO 2 . Furthermore, the particulate morphology of Li 1.045 Ni 0.955 O 2 remains intact at charge voltages up to 4.8 V, whereas near stoichiometric LiNiO 2 features intragranular cracks and irreversible lattice distortion. This study underscores the value of molten salt‐assisted synthesis and Li‐refeeding modification to upgrade Ni‐based layered oxide cathode materials for advanced Li‐ion batteries.