Controlled Synthesis of Sb Nanostructures and Their Conversion to CoSb3 Nanoparticle Chains for Li-Ion Battery Electrodes

Nanostructured Sb was prepared through a simple polyol process. Either Sb nanoparticles (Sb NP) or nanowires (Sb NW) were obtained by adjusting the concentration of surfactant. Electrochemical analyses revealed that the resultant Sb crystals displayed high charge storage capacities as Li-ion battery electrodes and relatively poor cycling retention during the charge discharge process. For instance, the capacity was 560-584 mA h/g during the second cycle, which decreased to 120-200 mA h/g during the 70th cycle at a rate of 0.2 C. Thus, Sb NPs were reacted with Co precursors to form one-dimensional (I-D) NP chains wrapped in a polyvinyl pyridine layer, and the length of the NP chains could be adjusted by varying the concentration of polyvinyl pyridine. Through a controlled annealing process, the polyvinyl pyridine layer was converted to amorphous carbon, which led to the formation of 1-D core shell structures with CoSb3 NP chains entrapped in the carbon layer. Although CoSb3 NP chains with a carbon shell displayed a lower initial charge storage capacity than Sb nanostructures, improved cycling performance was observed. The capacity was 468 mA h/g during the second cycle, which dropped to 421 mA h/g during the 70th cycle at a rate of 0.2 C. Compared to CoSb3 produced via other techniques, CoSb3/C NP chains displayed higher cycling stability, because of the presence of a carbon buffer layer.