Boosting rate performance of layered lithium-rich cathode materials by oxygen vacancy induced surface multicomponent integration

The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries, a domain in which Lithium-rich layered cathode (LLO) materials inherently excel. However, these materials face practical challenges, such as low initial Coulombic efficiency, inferior cycle/rate performance, and voltage decline during cycling, which limit practical application. Our study introduces a surface multi-component integration strategy that incorporates oxygen vacancies into the pristine LLO material Li_1.2Mn_0.6Ni_0.2O₂. This process involves a brief citric acid treatment followed by calcination, aiming to explore rate-dependent degradation behavior. The induced surface oxygen vacancies can reduce surface oxygen partial pressure and diminish the generation of O₂ and other highly reactive oxygen species on the surface, thereby facilitating the activation of Li ions trapped in tetrahedral sites while overcoming transport barriers. Additionally, the formation of a spinel-like phase with 3D Li⁺ diffusion channels significantly improves Li⁺ diffusion kinetics and stabilizes the surface structure. The optimally modified sample boasts a discharge capacity of 299.5 mA h g⁻¹ at a 0.1 C and 251.6 mA h g⁻¹ at a 1 C during the initial activation cycle, with an impressive capacity of 222.1 mA h g⁻¹ at a 5 C. Most notably, it retained nearly 70% of its capacity after 300 cycles at this elevated rate. This straightforward, effective, and highly viable modification strategy provides a crucial resolution for overcoming challenges associated with LLO materials, making them more suitable for practical application.