Alleviating the Kinetic Hindrance of Ni-Rich Single-Crystal Cathode Materials Driven by Local Structural Realignment

Crack-free Ni-rich single-crystal cathodes exhibit exceptional stability; however, they encounter challenges pertaining to kinetic hindrance, low capacity, and low initial Coulombic efficiency. Herein, we present a melt infiltration-dispersion method for synthesizing a small-sized single-crystal LiNi_0.90Co_0.06Mn_0.04O₂ (N90-SC) material at lower temperatures, enabling kilogram-scale production. The inclusion of low-melting LiOH-Li₂SO₄ eutectic salt enhances uniform mass and heat transfer while penetrating the grain boundaries of secondary particles, thereby inhibiting particle growth and resulting in small single crystals after washing. The elevated lithium potential effectively minimizes Li⁺/Ni²⁺ disorder and facilitates the doping of a small amount of Li ions into the transition metal layers. Under a high state of charge, Ni ions migrate and occupy the lithium layer, resulting in the formation of a localized superlattice structure. This dynamic superlattice exerts a stabilizing pillar effect through robust Ni interlayer superexchange interactions, thus reinforcing the deintercalated structure and promoting a reversible H2-H3 phase transition. At the end of discharge, lithium doping reduces the lithium diffusion barrier by mitigating the electrostatic repulsion effect, enhancing the lithium diffusion coefficient and alleviating the kinetic hindrance of Ni-rich single-crystal cathodes. Consequently, the N90-SC material achieves a high capacity of 227.7 mAh g^-1 and an impressive initial Coulombic efficiency of 94.8%. The pouch-type N90-SC||Graphite full cell demonstrates an ultrahigh initial Coulombic efficiency of 93.3% and maintains 88.2% capacity after 500 cycles. This work offers a dual-benefit strategy that concurrently addresses kinetic hindrance and structural stability, while localized atomic-scale engineering provides further insights into the design of next-generation lithium-ion batteries.