Gradient Boracic Polyanion Doping-Derived Surface Lattice Modulation of High-Voltage Ni-Rich Layered Cathodes for High-Energy-Density Li-Ion Batteries

The utilization of high-voltage Ni-rich cathodes can cost-effectively push lithium-ion batteries toward higher energy density but suffers from major challenges with severe structural and interfacial degradation and compromised thermal robustness. Herein, a multifunctional modification strategy (i.e., gradient engineering and surface lattice modulation) is rationally devised to establish a chemomechanically reliable single-crystal boracic polyanion-doped LiNi0.6Co0.2Mn0.2O2 (B-NCM) cathode that operates stably under high voltage (≥4.5 V vs Li/Li+). It is found that introduction of a boron-based polyanion into Ni-rich cathodes could form a boron–polyanion gradient-doped structure and disordered layer phase on the surface of NCM particles, further inhibiting parasitic reactions and irreversible phase transition. As a result, the B-NCM cells demonstrate capacity retention of 88.5% after 200 cycles at 4.5 V and stable operation at 60 °C. The current strategy employing gradient engineering and a surface disorder phase affords an effective and facile approach to boost the development of high-voltage Ni-rich cathodes and beyond.