Rational Design of Multinary Metal Chalcogenide Bi0.4Sb1.6Te3 Nanocrystals for Efficient Potassium Storage

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.