Developing lithium ion battery silicon/cobalt core-shell electrodes for enhanced electrochemical properties

In this work, core-shell Si/Co composite powders were produced using an electroless deposition process. The effect of different concentrations of CoSO4 in the plating bath was studied to provide the Co deposition and to reveal the structure on the surface of silicon powders. The surface morphology and the composition of the produced Si/Co composite powders were characterized using scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). X-ray diffraction (XRD) analysis was performed to investigate the structure of the Si/Co composite powders. The discharge capacities of Si/Co composite electrodes were determined with cyclically testing, and resistivity of the produced Si/Co composite electrodes were studied using electrochemical impedance spectroscopy (EIS). The silicon/cobalt composite electrode produced using 40 g/L CoSO4 exhibited the most stable capacity retention, and a discharge capacity of approximately 220 mAh/g was obtained after 15 cycles for this electrode. This study demonstrated that the conductivity of the electrodes was improved and the capacity retention of the Si/Co composite electrodes was increased by increasing the shell structured cobalt content on the surface of silicon powders due to the buffering effect of cobalt against huge volume changes during the lithiation and delithiation process.