Surface-modified spinel high entropy oxide with hybrid coating-layer for enhanced cycle stability and lithium-ion storage performance.

High-entropy oxide (HEO) has emerged as a promising anode material for high-energy lithium-ion batteries (LIBs) due to its high theoretical specific capacity. However, the further application of HEO is restricted by its complicated interface problems and inevitable expansion effect. In this work, a simple approach to coat spinel HEO (FeCoNiCrMn)O with a hybrid layer of lithium titanate (LTO) and carbon is presented. The coating is applied through a solution-chemistry method followed by calcination under an inert atmosphere. This hybrid layer significantly improves the electrochemical kinetics and stability at the electrode/electrolyte interface. Additionally, the diffusion of Ti into the HEO bulk during synthesis provides an inactive metal skeleton, potentially improving cycle stability. Electrochemical test results show that the HEO@LTO/C achieved a reversible specific capacity of 1090 mA h g at 0.5 A g and remained stable after 800 cycles. Moreover, the first-coulomb efficiency was increased from 63.7% to 72.8%, and rate performance has improved by at least 100 mA h g. This work demonstrates that hybrid surface-modifying of HEO is an effective measure to improve and stabilize its electrochemical properties.