An Ultra‐Long‐Life Lithium‐Rich Li 1.2 Mn 0.6 Ni 0.2 O 2 Cathode by Three‐in‐One Surface Modification for Lithium‐Ion Batteries

Abstract Voltage decay and capacity fading are the main challenges for the commercialization of Li‐rich Mn‐based layered oxides (LLOs). Now, a three‐in‐one surface treatment is designed via the pyrolysis of urea to improve the voltage and capacity stability of Li 1.2 Mn 0.6 Ni 0.2 O 2 (LMNO), by which oxygen vacancies, spinel phase integration, and N‐doped carbon nanolayers are synchronously built on the surface of LMNO microspheres. Oxygen vacancies and spinel phase integration suppress irreversible O 2 release and help lithium ion diffusion, while N‐doped carbon nanolayer mitigates the corrosion of electrolyte with excellent conductivity. The electrochemical performance of LMNO after the treatment improves significantly; the capacity retention rate after 500 cycles at 1 C is still as high as 89.9 % with a very small voltage fading rate of 1.09 mV cycle −1 . This three‐in‐one surface treatment strategy can suppress the voltage decay and capacity fading of LLOs.