Comprehensive Study of Ti and Ta Co‐Doping in Ni‐Rich Cathode Material LiNi_0.8Mn_0.1Co_0.1O₂ Towards Improving the Electrochemical Performance

Abstract

Layered Ni‐rich oxides (LiNi1‐x‐yCoxMnyO2) cathode materials are of current interest in high‐energy‐demanding applications, such as electric vehicles because of high discharge capacity and high intercalation potential. Here, the effect of co‐doping a small amount of Ti and Ta on the crystal structure, morphology, and electrochemical properties of high Ni‐rich cathode material LiNi0.8Mn0.1Co0.1‐x‐yTixTayO2 (0.0 ≤ x+y ≤ 0.2) was systematically investigated. This work demonstrates that an optimum level of Ti and Ta doping is beneficial towards enhancing electrochemical performance. The optimal Ti4+ and Ta5+ co‐doped cathode LiNi0.8Mn0.1Co0.09Ti0.005Ta0.005O2 exhibits a superior initial discharge capacity of 161.1 mAh g‐1 at 1C, and excellent capacity retention of 87.1% after 250 cycles, compared to the pristine sample that exhibits only 59.8% capacity retention. Moreover, the lithium‐ion diffusion coefficients for the co‐doped cathode after the 3rd and 50th cycles are 9.9×10‐10 cm2 s‐1 and 9.3×10‐10 cm2 s‐1 respectively, which is higher than that of the pristine cathode (3.3×10‐10 cm2 s‐1 and 2.5×10‐10 cm2 s‐1 respectively). Based on these studies, we conclude that Ti and Ta co‐doping enhances structural stability by mitigating irreversible phase transformation, improving Li‐ion kinetics by expanding interlayer spacing, and nanosizing primary particles, thereby stabilizing high‐nickel cathode materials and significantly enhancing cyclability.