Accelerated Diffusion Kinetics in ZnTe/CoTe2 Heterojunctions for High Rate Potassium Storage

Potassium-ion batteries hold practical potential for large-scale energy storage owing to their appealing cell voltage and cost-effective features. The development of anode materials with high rate capability and satisfactory cycle lifespan, however, is one of the key elements for exploiting this electrochemical energy storage system at practical levels. Here, a template-assisted strategy is reported for acquiring a bimetallic telluride heterostructure which is supported on N-doped carbon shell (ZnTe/CoTe2@NC) that promotes diffusion of K+ ions for rapid charge transfer. It is shown that in telluride heterojunctions, electron-rich Te sites and built-in electric fields contributed by electron transfer from ZnTe to CoTe2 concomitantly provide abundant cation adsorption sites and facilitate interfacial electron transport during potassiation/depotassiation. The relatively fine ZnTe/CoTe2 nanoparticles imparted by the heterojunction result in high structural stability, together with a highly reversible capacity up to 5000 cycles at 5 A g−1. Moreover, using judiciously combined experiment and theoretical computation, it is demonstrated that the energy barrier for K+ diffusion in telluride heterojunctions is significantly lower than that in individual counterparts. This quantitative design for fast and durable charge transfer in telluride heterostructures can be of immediate benefit for the rational design of batteries for low-cost energy storage and conversion.