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 Li1.2Mn0.6Ni0.2O2. 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.