Self-sacrificial template-directed ZnSe@C as high performance anode for potassium-ion batteries

Potassium-ion batteries (KIBs) have now stimulated considerable attention due to the widely distributed potassium salt and low cost, which become the competitive candidate for Na-/Li-ion batteries and suitable application for large-scale energy systems. Here, we have reasonably designed N-doped carbon encapsulated yolk-shell ZnSe@C anode with carbon-coated Zn2GeO4@C nanorods as the self-sacrificial template. Uniform ZnSe@C nanorods were facilely prepared by the selenidation of carbon-coated Zn2GeO4@C nanorods, which were synthesized via a simple annealing of ploydopamine-coated Zn2GeO4 nanorods. Such N-doped carbon encapsulated ZnSe@C core-shell nanorods could substantially enhance the electronic conductivity, moderate the volume expansion and provide more pathways for K+ diffusion. In detail, these ZnSe@C nanorods achieve stable galvanostatic discharge/charge performance (deliver 360 mA h g(-1) at 0.2 A g(-1) after 60 cycles and 204 mA h g(-1) at 2.0 A g(-1) over 100 repeated cycles) and superior rate capability (achieve a capacities of 389.4, 379.8, 352.2, 285.6, 226.1, and 167.5 mA h g(-1) at 0.1, 0.2, 0.5, 1.0, 2.0, and 4.0 A g(-1), respectively). The charge-discharge mechanism of ZnSe@C was further investigated by in-situ, ex-situ X-ray diffraction XRD and transmission electron microscopy (TEM) measurements.