Surface-Bulk Phase Differentiated Modification via CeO2 Coating and Fe3+ Doping for High-Voltage Stable Ni-Rich Cathodes

Ni-rich layered oxides, benefiting from their superior specific capacity, have emerged as pivotal cathode candidates for high-energy-density lithium-ion batteries (LIBs). Nevertheless, these materials suffer from severe intrinsic interfacial and structural degradation under high-voltage operation, which severely compromises their practical electrochemical performance. Herein, we developed a surface-bulk phase differentiated modification strategy integrating CeO2 coating and Fe3+ doping, leveraging the divergent diffusion behaviors induced by the different ionic radii of Ce3+ and Fe3+ ions. This targeted modification approach effectively mitigated the interfacial degradation and bulk structural deterioration of Ni-rich cathode materials. Specifically, the surface CeO2 coating inhibited parasitic reactions at the cathode-electrolyte interface, and its rich oxygen vacancies efficiently suppressed lattice oxygen release during long-term cycling. Meanwhile, bulk Fe3+ doping reduced Li+/Ni2+ cation mixing, alleviated internal lattice strain, and reinforced the crystal framework. The synergistic effect of CeO2 coating and Fe3+ doping endowed the cathode with optimized interfacial integrity and structural durability. Taking LiNi0.83Co0.11Al0.06O2 as a representative material, the CeO2-coated and Fe3+-doped cathode demonstrated significantly improved cycling performance at conventional 4.3 V and elevated 4.5/4.6 V. Specifically, after 200 cycles at 1 C within 3.0-4.6 V, the modified cathode retained a capacity retention of 76.9%, which was much higher than the 61.7% retention of the pristine sample. This study highlights the great potential of surface-bulk phase differentiated engineering for stabilizing Ni-rich cathodes, providing a feasible pathway for the development of high-energy-density LIBs.