Composition-structure-mechanism correlation in (XCoNiCuZn)O (X = Li, Na, Mg) high-entropy oxides: From cationic modulation to electrochemical performance

High-entropy oxides (HEOs) represent promising anode materials for lithium-ion batteries, yet understanding the intricate relationship between their multi-element composition, crystal structure, and lithium storage mechanism remains a fundamental challenge. This study systematically investigates this relationship in (XCoNiCuZn)O (X = Li, Na, Mg) HEOs by modulating the fifth element. While all compositions form a single rock-salt structure, the cationic radius and valence state of X dictate both the lattice parameters and the electrochemical reaction pathway. It is revealed that (LiCoNiCuZn)O and (MgCoNiCuZn)O undergo a conversion-dominated phase transition mechanism, whereas (NaCoNiCuZn)O follows a solid-solution reaction. This mechanistic divergence, elucidated through in-situ EIS, ex-situ XRD/XPS, and kinetic analysis, directly governs the electrochemical performance. The Li-based HEOs (LiCoNiCuZn)O demonstrates exceptional performance, delivering a high capacity of 549.7 mAh g −1 with 83.4% retention after 300 cycles at 0.5 A g −1 , attributable to its effective charge compensation and superior ion conductivity. This work establishes a clear correlation from cationic modulation to storage performance, offering critical guidance for the rational design of HEOs for energy storage.