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 0.9 Co 0.05 Mn 0.05 O 2 (NCM9055) severely hinders their commercial application. In this work, straightforward high-temperature solid-state methods are utilized to successfully synthesize Nb-doped and Li 3 PO 4 -coated LiNi 0.9 Co 0.05 Mn 0.05 O 2 by combining two niobium sources, NbOPO 4 ·3H 2 O and Nb 2 O 5, for the first time. Studies indicate that Nb doping enhanced the integrity of the layered structure, and the Li 3 PO 4 coating reduced water absorption on the surface and considerably boosted the durability of the interface. The dual-modified cathode Li(Ni 0.9 Co 0.05 Mn 0.05 ) 0.985 Nb 0.015 O 2 @Li 3 PO 4 (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.