Synergistic bulk–interface stabilization of single-crystal cobalt-free high-nickel cathodes via a fast-ionic-conductor coating

Abstract

Single-crystal, cobalt-free, high-nickel LiNi_0.9Mn_0.1O₂ cathodes represent one of the most promising candidates for next-generation batteries, offering both high energy density and low cost. However, the cathodes suffer from rapid capacity decay in the highly delithiated state due to detrimental phase transitions, interfacial degradation, and oxygen loss. This work demonstrates a multifunctional Li_1.3W_0.15Ti_1.7(PO₄)₃ (LWTP) coating strategy that simultaneously addresses bulk and interfacial instability. The optimized 0.3 wt% LWTP-coated cathode delivers exceptional electrochemical performance, including an initial capacity of 214.1 mA h g⁻¹ at 4.5 V (compared to 208.2 mA h g⁻¹ for the bare cathode) and 15.9% improved capacity retention after 100 cycles, along with outstanding rate capability of 167.8 mA h g⁻¹ at 4.3 V and at a high rate of 3C (compared to 140.2 mA h g⁻¹ for the bare cathode). Comprehensive structural characterization reveals the coating's stabilization effects, including reduced Li⁺/Ni²⁺ cation mixing and suppression of rock-salt phase formation. Interfacial analyses demonstrate substantially lower charge transfer resistance and the formation of a stable cathode–electrolyte interphase. Mechanistic investigations demonstrate that the LWTP coating functions as an efficient ion-conductive network, strengthens metal–oxygen bonds through W/Ti doping, mitigates oxygen release, and prevents microcrack propagation via strain regulation. This multifunctional coating strategy provides a scalable materials engineering solution for developing ultra-stable, high-energy-density cathodes for next-generation lithium-ion batteries.