Suppressing lattice expansion via Ta5+ doping in Ni-rich LiNi0.9Co0.05Mn0.05O2 cathodes for electrochemical performance

Nickel-rich layered ternary cathode materials have attracted extensive attention due to the high specific capacity and excellent cost-effectiveness. However, severe issues including irreversible phase transitions and progressive lattice expansion are observed during cycling. These issues lead to rapid capacity fading and limited cycling lifespan, severely restricting their large-scale commercial application. In this study, high-valent tantalum (Ta 5+ ) was employed as a dopant to simultaneously enhance Li + diffusion kinetics and structural stability. The Ta 5+ -doped LiNi 0.9 Co 0.05 Mn 0.05 O 2 cathode material was successfully synthesized via a combination of uniform co-precipitation and high-temperature solid-state methods. The results demonstrate that Ta 5+ doping can effectively suppress irreversible phase transitions and lattice distortion during cycling, thus improving the reversible specific discharge capacity and capacity retention. Electrochemical measurements indicate that the 0.3%Ta-NCM exhibits the outstanding performance. The specific discharge capacity of 219.32 mAh/g is obtained for the 0.3%Ta-NCM at 0.1C, which is 24.83 mAh/g higher than that of the NCM (194.49 mAh/g). The 0.3%Ta-NCM delivers a capacity retention of 89.35% after 100 cycles at 0.2C, which is significantly higher than the 85.97% of the pristine NCM. The retention rate surpasses that of the pristine NCM (66.74%) by 23.52% after 100 cycles at 1C. This work provides a feasible modification strategy for the structural regulation and performance optimization of nickel-rich ternary cathode materials.