Accelerated Diffusion Kinetics in ZnTe/CoTe_2 Heterojunctions for High Rate Potassium Storage

摘要

Potassium-ion batteries hold practical potential for large-scale energy storageowing to their appealing cell voltage and cost-effective features. The developmentof anode materials with high rate capability and satisfactory cyclelifespan, however, is one of the key elements for exploiting this electrochemicalenergy storage system at practical levels. Here, a template-assistedstrategy is reported for acquiring a bimetallic telluride heterostructure whichis supported on N-doped carbon shell (ZnTe/CoTe_2@NC) that promotesdiffusion of K+ ions for rapid charge transfer. It is shown that in telluride heterojunctions,electron-rich Te sites and built-in electric fields contributed byelectron transfer from ZnTe to CoTe_2 concomitantly provide abundant cationadsorption sites and facilitate interfacial electron transport during potassiation/depotassiation. The relatively fine ZnTe/CoTe_2 nanoparticles impartedby the heterojunction result in high structural stability, together with a highlyreversible capacity up to 5000 cycles at 5 A g~(?1). Moreover, using judiciouslycombined experiment and theoretical computation, it is demonstrated thatthe energy barrier for K+ diffusion in telluride heterojunctions is significantlylower than that in individual counterparts. This quantitative design for fastand durable charge transfer in telluride heterostructures can be of immediatebenefit for the rational design of batteries for low-cost energy storage andconversion.