Effects of carbon coating on calendered nano-silicon graphite composite anodes of LiB

Recently, silicon has attracted attention as anode material for lithium-ion batteries, but the periodic volume change leads to poor cycling stability. Two promising strategies to overcome this are the use of nanoparticles and the combination with graphite. In our previous study, a process route for production of silicon-on-graphite composites (Si@Gr) with 10 wt% silicon via fluidized bed granulation and carbon coating (Si@Gr/C) was pre-sented. Within this study, the process has been scaled up to pilot scale and the effects of carbon coating on particle level combined with a comprehensive calendering study were investigated in more detail. It could be shown, that the carbon coating reduces the surface area, stabilizes the composite and enhances electrical con-ductivity. Based on porosity measurements, a disintegration of the composites most likely occurred as a consequence of the high shear stresses. The electrochemical performance revealed a significantly enhanced ca-pacity retention after 125 cycles (Si@Gr: 82.2% vs. Si@Gr/C: 91.9%). After calendering, the positive impact of carbon coating was even more pronounced. While Si@Gr suffered from accelerated degradation with increasing electrode density, calendering had only minor impact on Si@Gr/C. This study advances the understanding of the positive effects of carbon coating for the calendering of nano-Si containing electrodes.

Automated summary

This study scaled up the production process of silicon/graphite composites and investigated the effects of carbon coating and calendering on the particle level. The study found that carbon coating reduces surface area, stabilizes the composite, and enhances electrical conductivity. The electrochemical performance of the composites showed improved capacity retention with carbon coating, especially after calendering.