LiFePO4-coated LiNi0.6Co0.2Mn0.2O2 for lithium-ion batteries with enhanced cycling performance at elevated temperatures and high voltages

Comprehensive Study of Ti and Ta Co-Doping in Ni-Rich Cathode Material LiNi0.8Mn0.1Co0.1O2 Towards Improving the Electrochemical Performance

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 1 C, 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.

Lithium-Ion Conductive Coatings for Nickel-Rich Cathodes for Lithium-Ion Batteries

Nickel (Ni)-rich cathodes are among the most promising cathode materials of lithium batteries, ascribed to their high-power density, cost-effectiveness, and eco-friendliness, having extensive applications from portable electronics to electric vehicles and national grids. They can boost the wide implementation of renewable energies and thereby contribute to carbon neutrality and achieving sustainable prosperity in the modern society. Nevertheless, these cathodes suffer from significant technical challenges, leading to poor cycling performance and safety risks. The underlying mechanisms are residual lithium compounds, uncontrolled lithium/nickel cation mixing, severe interface reactions, irreversible phase transition, anisotropic internal stress, and microcracking. Notably, they have become more serious with increasing Ni content and have been impeding the widespread commercial applications of Ni-rich cathodes. Various strategies have been developed to tackle these issues, such as elemental doping, adding electrolyte additives, and surface coating. Surface coating has been a facile and effective route and has been investigated widely among them. Of numerous surface coating materials, have recently emerged as highly attractive options due to their high lithium-ion conductivity. In this review, a thorough and comprehensive review of lithium-ion conductive coatings (LCCs) are made, aimed at probing their underlying mechanisms for improved cell performance and stimulating new research efforts.