A Phosphate Thermal Barrier Coating Endows Ni‐Rich Cathode 4.8 V‐Tolerant and Thermal Oxidation Stability Enabling High‐Energy Lithium‐Ion Batteries

Abstract Ni‐rich layered oxide cathode (LiNi _x Co _y Mn _{1‐ x ‐ y} O ₂ , 0.8 < x < 1) possesses a high theoretical specific capacity (≈270 mAh g ⁻¹ ) and stimulated considerable attention for high energy density lithium‐ion batteries (LIBs). However, the unstable cathode electrolyte interfaces (CEI) resulting in terrible thermal endurance and awful high voltage tolerance (>4.5 V) and thermal instability significantly hinder their practical applications. Herein, a thermodynamically stable InPO ₄ interface is constructed on the LiNi _0.83 Co _0.12 Mn _0.05 O ₂ (NCM83@InPO ₄ ), which achieves excellent cyclic stability (≈85.7% capacity retention after 500 cycles at 10 C in 2.7–4.6 V, ≈80.0% after 200 cycles at 1 C in 2.8–4.8 V). Advanced characterizations confirm that the InPO ₄ coating layer stabilizes the Ni ⁴⁺ /O ^α− (α < 2), and forms a stable CEI that prevents side reactions with electrolytes under high‐voltage operation. In situ characterizations reveal that the InPO ₄ layer suppresses the harmful H2‐H3 phase transition and maintains the layered structure under thermal shock from 25 to 400 °C. Density functional theory (DFT) calculation validates that the modified NCM83@InPO ₄ not only enhances mechanical strength but also reduces the Li⁺ migration energy, facilitating rapid Li ⁺ /electron transfer. This polyanionic thermal barrier coating strategy effectively improves cycling stability and enhances thermal stability, thus shedding light on designing reinforced high‐voltage tolerant cathodes for high‐energy LIBs.