(De)Sodiation Mechanisms and Cycling Stability of Entropy‐Engineered Sodium‐Ion Battery Alloy Anodes by Operando X‐ray Diffraction

Alloy anodes represent a high‐capacity alternative to the prevalent hard carbon‐based anodes for sodium ion‐batteries. The major challenge is their large volumetric changes during (de)sodiation, consuming electrolyte and ultimately leading to pulverization of the anode and hence limited cycle life of the battery. To overcome this fundamental challenge, a proof‐of‐concept solution is introduced in SnSbBiSe _1.5 Te _1.5 , a high‐entropy alloy, as shown by comparing its cycling performance with those of its low‐entropy (Sb ₂ Te ₃ ) and medium‐entropy (SbBiSe _1.5 Te _1.5 ) analogs. Using operando synchrotron X‐ray diffraction, major differences are revealed during the (de)sodiation as function of configurational entropy, and by cross‐sectional SEM further insight is gained on the roles of particle size and distribution, both initially and after cycling. Overall, this study highlights the importance of entropy‐engineered and controlled particle size alloy anodes to limit volumetric changes and render stable cycling.