Quenching-Induced LaxCayNiO3−δ Multifunctional Integrated Structure Realizes High-Nickel Cathode Material with High Cutoff Voltage and High Cycling Stability

Abstract

High-nickel layered oxide LiNi_xCo_yMn_1-x-yO₂ (NCM, x ≥ 0.8) materials are considered optimal cathodes for lithium-ion power batteries owing to their high energy density, commendable cycling performance, and cost-effectiveness. However, structural collapse and interface instability during cycling result in diminished cycling stability, significantly hindering their commercial viability. Consequently, this study proposes inducing a multifunctional integrated structure via the quenching process, successfully synthesizing a modified NCM cathode with an inner La/Ca-doped layered structure and a near-surface Li-deficient La_xCa_yNiO_3−δ structure. A series of tests, complemented by density functional theory (DFT) calculations, demonstrated that inner La/Ca doping effectively increases the lattice spacing, enhancing the Li⁺ diffusion coefficient and lattice stability. The external La_xCa_yNiO_3-δ structure offers a stable interface and abundant oxygen vacancies, significantly suppressing side reactions and oxygen evolution reactions at the interface. More importantly, DFT calculations analyzed the doping preference of La³⁺/Ca²⁺ in NCM, revealing that La³⁺/Ca²⁺ predominantly occupy Li sites, with some La³⁺ also occupying Ni sites, which further confirming the feasibility of ion exchange. Additionally, electronic effects of La 3d and Ca 2p orbitals effectively enhance the electrical conductivity of NCM cathodes. Subsequent electrochemical tests demonstrated that the multifunctional integrated structure significantly enhanced the rate performance and cycling stability of high-nickel NCM cathodes. At a 4.3 V cutoff voltage, the LCNCM cathode exhibited significant improvements in cycling stability at 0.5, 1.0, and 2.0C rates. Even at the higher cutoff voltage of 4.4 V, the LCNCM cathode maintained a reversible capacity of 185.0 mAh g^–1 and a capacity retention rate of 89.7% after 100 cycles at 1.0C, demonstrating substantial improvements in electrochemical performance.