Thermally fabricated cobalt telluride in nitrogen-rich carbon dodecahedra as high-rate potassium and sodium ion battery anodes

Abstract

Cobalt telluride anchored to nitrogen-rich carbon dodecahedra (CoTe@NCD) was synthesized by simultaneous pyrolysis-tellurium melt impregnation of ZIF-67 MOFs. The purely thermal method involved no secondary chemicals and no waste byproducts. The result is a microstructure consisting of nanoscale 86 wt% CoTe intermetallic nanoparticles contained within a thin N-rich carbon matrix. During electrochemical cycling, the 21 nm average diameter CoTe provides short diffusion paths for Na⁺/K⁺ ions, which in conjunction with the electrically conducting carbon matrix allow for rapid potassiation or sodiation. As potassium ion battery (PIB and KIB) and sodium ion battery (NIB and SIB) anodes, CoTe@NCD demonstrates attractive reversible capacity, promising cycling stability, and state-of-the-art rate performance. For example, as a KIB anode, the CoTe@NCD electrode exhibits a reversible capacity of 380 mA h g⁻¹ at 50 mA g⁻¹ and a fast charge capacity of 136 mA h g⁻¹ at 1000 mA g⁻¹. As a NIB anode, it also displays excellent rate capability achieving 620 mA h g⁻¹ at 50 mA g⁻¹ and 345 mA h g⁻¹ at 1000 mA g⁻¹.