Introducing SiC/C dual-interface on porous silicon anode by a conventional exothermic displacement reaction for improved cycle performance

The poor cyclability and high cost are the two major obstacles to the commercial applications of Si-based anode materials. Porous structure and carbon coating may facilitate the ion and electron conduction and also restrict the huge volume change of Si anodes. In addition, introducing a ceramic interlayer between Si and C can reduce the chemical reaction of Si with fluorine ions in the electrolyte and hence improve the cyclability. In this work, porous Si anode protected by SiC/C dual-interface is prepared by simply heating fine Mg2Si particles in pure CO2 at 650 °C, based on the conventional exothermic displacement reaction between Mg (released from Mg2Si) and CO2. The large amount of heat generated during the displacement reaction leads to sharp temperature rise, resulting in the formation of SiC at such a low temperature. The porous Si/SiC/C powders as well as the spherical sample prepared by subsequent spray-drying and pyrolysis process display much improved rate capability and cyclability as compared to the porous Si/C counterpart, due to the enhanced structural integrity induced synergistically by the porous structure, SiC/C dual-interface and spherical structure during the repeated lithiation/delithiation cycles. •SiC/C dual-interface is introduced on porous Si anode at low temperature.•Fine Mg2Si leads to high exothermic displacement reaction between Mg and CO2.•Porous SiC/C/Si anode exhibits improved rate capability and cyclstability.•Spherical porous SiC/C/Si anode shows the least volume expansion after cycles.