Supercritical fluid-assisted preparation of Si/CNTs@FG composites with hierarchical conductive networks as a high-performance anode material

Abstract

Considering the high theoretical specific capacity (4200 mAh/g), silicon is perceived as one of the most promising anode materials for lithium-ion battery, but the large volume change during the process of de/lithiation affects its cycle performance and practical application. With the assist of supercritical CO2 fluid (scCO2), graphite is exfoliated to folded graphite (FG) flakes. Meanwhile, the composite of Si/CNTs@FG with a hierarchical conductive network structure was constructed, where the silicon nanoparticles and carbon nanotubes (CNTs) were homogenously attached to the interlayer of FG. The hierarchical conductive network composed of FG and CNTs not only promotes the electrons transfer process but also relieves volume expansion stress of silicon. The Si/CNTs@FG exhibits remarkable Li storage performance, delivering high specific reversible capacity (1204 mAh/g at the current density of 0.2A/g), high capacity retention (970 mAh/g after 100 cycles) and excellent rate performance (635.2 mAh/g at 2 A/g). This study provides a facile and scalable approach to prepare a silicon-based anode material with excellent electrochemical performance.