High-Entropy Metal Sulfides with Enhanced d-Orbital Coupling for Boosted Sodium Storage Performance

Abstract

The advanced high-entropy configuration approach is employed to stabilize the structural integrity of transition metal sulfides during cycling by suppressing volume expansion. This configuration simultaneously preserves abundant active sites and maintains high electronic conductivity. However, the sodium storage mechanism in high-entropy materials remains inadequately understood. In this study, a solvothermal method is employed to synthesize a unique class of (FeCoNiCuW)S2 high-entropy metal sulfides (HEMSs), which exhibit distinct d-orbital coupling characteristics. Density functional theory (DFT) calculations reveal that stronger d-orbital coupling among the metals leads to higher electron density near the Fermi energy (EF), resulting in an upward shift of the entire d-band center relative to EF, thus enhancing the adsorption of the Na2S intermediate. As a result, (FeCoNiCuW)S2 demonstrates superior rate capability, achieving a specific capacity of 518.6 mA·h·g–1 at 5.0 A·g–1. Moreover, ex situ characterization confirms a reversible sodium storage mechanism, further demonstrating that the high-entropy effect stabilizes the conversion reaction reversibility upon prolonged cycling. This work highlights structurally stable HEMSs as promising anode materials for sodium-ion batteries.