Doping-Induced Surface Passivation Enables High-Voltage Cycling Capability of Ni-Rich Cathodes for Lithium-Ion Batteries

Raising the cutoff voltage of charging is an economically effective strategy to maximize the reversible capacity of Ni-rich cathodes without changing their compositions. However, the high surface reactivity of Ni-rich cathodes at high voltage would trigger harmful interfacial side reactions between the cathodes and the electrolyte, resulting in structural degradation and performance deterioration. In response to this challenge, surface passivation induced by gradient Ce4+ doping was proposed to strengthen the surface/interfacial stability of Ni-rich cathodes and thereby promote their high-voltage cycling capability. Incorporating Ce4+ ions into the surface lattice of Ni-rich cathodes can not only lower the surface reactivity by diluting surface-active Ni3+ species and reducing surface residual lithium impurities, but also stabilize the surface lattice oxygen by strong Ce–O bonds, thereby inhibiting surface degradation under high-voltage operation. Alternatively, large-radius Ce4+ ions doping expands the interlayer distance along the c-axis to provide a beneficial channel for Li+ diffusion, verified by reaction kinetics results. As expected, Ce-doped Ni-rich cathodes deliver a high reversible capacity of 210.3 mAh g–1, excellent cycling stability with a capacity retention of 83.9% after 100 cycles, and superior rate capability at a high cutoff voltage of 4.6 V. This work provides a design idea for stabilizing the surface/interface of Ni-rich cathodes for high-performance lithium-ion batteries.