Entropy Contribution and Tunability Effects on High-Entropy Li-Ion Conversion Anodes

High-entropy oxides (HEOs) have emerged as promising Li-ion conversion anodes due to their structural robustness and compositional flexibility. While configurational entropy is known to stabilize multicomponent single-phase structures, its direct influence on electrochemical performance remains unresolved. Here, we systematically decouple entropy and compositional effects in rock salt-type (MgCoNiCuZn)O by selectively removing individual cations to generate medium-entropy derivatives (HEOcMg, HEO−Co, HEO−Ni, HEO−Cu, and HEO−Zn), reducing configurational entropy from 1.61 to 1.39R. Despite this entropy reduction, all compositions retain a single solid-solution phase, demonstrating that entropy primarily governs structural stabilization. In contrast, electrochemical capacity, conversion potential, pseudocapacitive contribution, and redox reversibility are strongly dependent on the transition-metal chemical environment. Element-resolved X-ray absorption spectroscopy reveals composition-dependent redox activity and cooperative metal−metal interactions that dictate reaction dynamics. These findings establish compositional engineering−not entropy magnitude alone−as the dominant design strategy for optimizing high-entropy conversion electrodes.