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 LiNi0.9Co0.05Mn0.05O2 (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 LiNi0.9Co0.05Mn0.05O2 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(Ni0.9Co0.05Mn0.05)0.985Nb0.015O2@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.