Improved cyclability of high-voltage LiCoO₂ by the coating of medium-entropy nanomaterials

Although improving the charging cutoff voltage is an effective strategy to increase its capacity, LiCoO₂ ("LCO") undergoes rapid capacity decay due to severe structural and interface degradations at high voltages. Herein, we proposed a multifunctional surface modification by coating nano-sized entropy materials (Li-La-Ti-Zr-Co-O, Nano-MEO). Nano-MEO rivets were constructed on the surface of LCO, which stabilized the fragile surface. Besides, Ti enriched on the surface induced a stable and thin CEI, promoting Li⁺ diffusion across the interface. Meanwhile, the diffusion of La and Zr into the LCO bulk phase improved the transportation of Li⁺ and suppressed the irreversible phase transition. Consequently, LCO modified by Nano-MEO exhibited excellent capacity retention of 84% after 100 cycles at 4.55 V. Therefore, the coating of high-entropy materials that have multi-element synergy increases the degree of freedom for the modulation of electronic and crystal structures, which is instructive for the development of high-voltage LCO.