Universal Phase Engineering of High-Entropy Sulfides for Stable Sodium-Ion Storage With Ultra-High Capacity and...

High-entropy transition metal sulfides (HESs) exhibit great potential as anodes for sodium-ion batteries owing to their synergistic entropy stabilization, lattice distortion and cocktail effects. However, potential phase separation caused by multi-component incompatibility severely limits their performance. Herein, we propose a low-mixing-enthalpy strategy through regulation of element chemical compatibility to precisely design high-performance HES anodes. This strategy enables the successful synthesis of a single-phase Co-Fe-Ni-Mn-Cr HES solid solution (HES-Cr). In contrast, inferior compatibility among components in Co-Fe-Ni-Mn-Mo HES (HES-Mo) leads to its phase separation. The electron delocalization in HES-Cr enhances conductivity and metal-sulfur bond covalency, while moderate lattice distortion alleviates volume changes and stress concentration during Na⁺ insertion/extraction and lowers the Na⁺ migration barrier. Consequently, the HES-Cr delivers excellent Na⁺ storage performance, including a high reversible capacity of 845.2 mAh g^-1 at 0.2 A g^-1 and ultra-high rate property of 497.5 mAh g^-1 even at 40.0 A g^-1 along with long stability, outperforming HES-Mo and most HES-based anodes. Furthermore, we propose a three-parameter descriptor to predict single-phase high-entropy materials across a broader compositional range. This work provides a new approach for rational design of single-phase HESs and deepens understanding of their composition-phase-performance relationships.