Improved cyclability of high-voltage LiCoO2 by 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 structure and interface degradation at high voltages. Herein, we proposed a multifunctional surface modification by coating nano-sized high-entropy materials (Li-La-Ti-Zr-Co-O, Nano-MEO). Nano-MEO rivets are constructed on the surface of LCO, which stabilizes 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 effectively improves the transportation of Li+ and suppresses irreversible phase transition. Consequently, LCO modified by Nano-MEO exhibits excellent capacity retention of 84% after 100 cycles at 4.55 V. Therefore, the coating of high-entropy materials with the advantages of multi-element synergy, increases the degree of freedom for the modulation of electronic and crystal structure, which is instructive for the development of high-voltage LCO.