Enhancing the Cycling and Rate Performance of Ni-Rich Cathodes for Lithium-Ion Batteries by Bulk-Phase Engineering and Surface Reconstruction

The structural and interfacial instability of Ni-rich layered cathodes LiNi_0.9Co_0.05Mn_0.05O₂ (NCM9055) severely hinders their commercial application. In this work, straightforward high-temperature solid-state methods are utilized to successfully synthesize Nb-doped and Li₃PO₄-coated LiNi_0.9Co_0.05Mn_0.05O₂ by combining two niobium sources, NbOPO₄·3H₂O and Nb₂O₅, for the first time. Studies indicate that Nb doping enhanced the integrity of the layered structure, and the Li₃PO₄ coating reduced water absorption on the surface and considerably boosted the durability of the interface. The dual-modified cathode Li(Ni_0.9Co_0.05Mn_0.05)_0.985Nb_0.015O₂@Li₃PO₄ (NCM-2) exhibits remarkable cycling and rate performance. The initial discharge specific capacity of NCM-2 is 203.33 mAh g^-1 at 0.1 C and 196.04 mAh g^-1 at 1 C, while the capacity retention after 200 cycles is 91.38% at 1 C, which is much higher than that of pristine NCM9055 (49.96%). In addition, it also provides a superior discharge specific capacity of about 175.63 mAh g^-1 even at 5 C. This study emphasizes a feasible approach to enhancing the stability of Ni-rich cathodes at the interfaces and bulk structures.