Rational Design of Multinary Metal Chalcogenide Bi_0.4Sb_1.6Te₃ Nanocrystals for Efficient Potassium Storage

Abstract Multinary metal chalcogenides hold considerable promise for high‐energy potassium storage due to their numerous redox reactions. However, challenges arise from issues such as volume expansion and sluggish kinetics. Here, a design featuring a layered ternary Bi_0.4Sb_1.6Te₃ anchored on graphene layers as a composite anode, where Bi atoms act as a lattice softening agent on Sb, is presented. Benefiting from the lattice arrangement in Bi_0.4Sb_1.6Te₃ and structure, Bi_0.4Sb_1.6Te₃/graphene exhibits a mitigated expansion of 28% during the potassiation/depotassiation process and demonstrates facile K⁺ ion transfer kinetics, enabling long‐term durability of 500 cycles at various high rates. Operando synchrotron diffraction patterns and spectroscopies including in situ Raman, ex situ adsorption, and X‐ray photoelectron reveal multiple conversion and alloying/dealloying reactions for potassium storage at the atomic level. In addition, both theoretical calculations and electrochemical examinations elucidate the K⁺ migration pathways and indicate a reduction in energy barriers within Bi_0.4Sb_1.6Te₃/graphene, thereby suggesting enhanced diffusion kinetics for K⁺. These findings provide insight in the design of durable high‐energy multinary tellurides for potassium storage.