SnO-decorated waste silicon@carbon composites as high-performance anodes for Li-ion batteries

Although silicon-based anode materials offer significantly higher specific capacity than graphite, their practical applications are limited by drawbacks such as large volume expansion, poor cycling stability and high production costs. Integrating transition metal oxides with silicon, coupled with a carbon coating layer, has been proven of effectiveness in enhancing the cycle stability of silicon-based anodes. Here we report the synthesis of a composite anode by combining tin(II) oxide (SnO) with waste silicon powder (wSi) of photovoltaic industry and introducing a carbon coating via in situ polymerization of resorcinol-formaldehyde followed by thermal pyrolysis. The resulting wSi/SnO@C composite anode exhibits improved rate and cycle performance, as characterized by a high reversible capacity of 1590 mAh g −1 at 3 A g −1 and a high retained capacity of 601 mAh g −1 after 500 cycles at 0.5 A g −1 . Mixing the wSi/SnO@C composite with graphite at an appropriate mass ratio yields a practical applicable anode with robust cycle stability. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses reveal that SnO is irreversibly reduced to metallic Sn during the first discharge, which is then partially converted to SnF 2 together with the formation of Li x Sn alloy. The formed SnF 2 is supposed to enhance the stability of the solid-electrolyte interphase (SEI) and reduce the attack of electrolyte to Si particles, both contributing to the improved cycle stability. This work demonstrates that SnO-decorated Si@C composites hold a high promise as anode materials of lithium-ion batteries towards enhanced cycle life and power density.