Solution-catalyzed carbothermal reduction of argo-waste SiO2 enables low-temperature and fast synthesis of Si(II)-C anode

Divalent silicon composite materials are becoming increasingly important in the anode industry of lithium-ion battery. However, the preparation of silicon(II) composite materials based on traditional carbothermal reduction and comproportionation faces high operation temperature, high energy consumption, and relatively slow reaction rate due to strong Si-O covalent bonds and solid-state reaction process. Here, we report an efficient carbothermal reduction strategy to achieve low-temperature synthesis of carbon-based silicon(II) composite from argo-waste SiO2 by introducing molten alloys as solution-catalytic reaction media. During the reaction process, the selected Sn-based molten alloys simultaneously extract SiO2 and highly active carbon from straws, thus facilitating the dissociation of Si-O bonds and further catalyzing the carbothermal reduction. Importantly, compared with traditional solid phase reaction, the Sn-based solution-catalytic environment can greatly accelerate the reaction rate. Without using highly reactive metal such as Al and Mg, low oxygen-potential Sn-based molten alloy catalyst can be easily separated from the product, recycled and regenerated, thus significantly simplifying the preparation process. Benefitting from the structure merits of biomass, the resulting carbon silicon (II) composite as a LIB anode exhibits high reversible capacity, good rate capability and excellent cycling stability.