Molten Salt-Assisted Synthesis of Single-Crystalline Nonstoichiometric Li_1+xNi_1-xO2 with Improved Structural Stability

Cobalt-free LiNiO2 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 Li1+xNi1-xO2 with submicron particle size and superior rate performance. The slightly Li-rich and single-crystalline characters inhibit Li+/Ni2+ anti-site defects and mitigates the undesirable phase evolution. Remarkably, single-crystalline Li1.045Ni0.955O2 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 LiNiO2. Furthermore, the particulate morphology of Li1.045Ni0.955O2 remains intact at charge voltages up to 4.8 V, whereas near stoichiometric LiNiO2 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.