Optimizing carbon coating parameters for obtaining SiO2/C anodes with improved electrochemical performance

In this work, we present a comprehensive and systematic study on the use of low-cost and highly abundant carbon precursors to obtain SiO₂/C anodes with superior electrochemical performance towards Li-ions. Different SiO₂/C composites are prepared by soaking silica nanoparticles in solutions containing 20 wt%, 40 wt%, or 60 wt% of glucose, sucrose, or cornstarch, followed by thermal decomposition of the carbohydrates at 850 °C or 1200 °C. Structural, microstructural, and textural differences on the composites derived from the different carbon coating treatments are related to the electrochemical performance of the anodes. Composites containing final carbon contents close to 15 wt% show a complete coverage of the SiO₂ particles with a nanometric carbon layer and exhibit the best electrochemical results. The increase in the annealing temperature from 850 to 1200 °C reduces the porosity of the carbon layer and increases its level of ordering, both having positive effects on the overall electrochemical performance of the electrodes. SiO₂/C composites coated with 40 wt% sucrose and heat treated at 1200 °C display the best electrochemical performance, delivering a reversible specific capacity of 723 mAhg⁻¹ at 50 mAg⁻¹ after 100 cycles, which is considerably higher than the reversible capacity of 233 mAhg⁻¹ obtained with the uncoated material cycled under the same conditions.