Hydrothermal Assembly of Submicron Si Recovered from Si Waste with Graphene and Carbon for Scalable Lithium Battery Anodes

Despite its high theoretical capacity of 4200 mAh/g, the application of Si has been limited for lithium-ion battery (LIB) anode. This is because Si suffers from large volume change during charge and discharge processes, resulting in poor cycling stability. To address this issue, researchers have proposed Si nanoparticles, especially less than 150nm, and their composite with various carbonaceous materials for LIB anodes. Although these electrodes have demonstrated improved cycling stability, it is still far-off from fulfillment for practical LIB anodes. To date, the Si nanoparticles have been synthesized costly processes, such as CVD and magnesiothermic reduction. In addition, their composites were prepared through complex fabrication process requiring toxic chemicals such as silane (SiH4) and hydrofluoric acid (HF). Therefore, it is highly desirable to develop cost-effective Si source and scalable fabrication process for the composite. Today, a large amount of Si is being consumed in photovoltaic and semiconductor industries. Surprisingly, more than 40% of the Si is being dumped as kerf-loss generated during the slicing of high purity Si ingots into Si wafers. The Si waste consists of Si, SiC, and the other impurities. We simply recovered Si and SiC through mild centrifugation using the differences of their specific gravities. The recovered Si particles were slightly ground to homogenize size distributions, resulting in submicron Si. The recovered submicron Si particles were coated with graphene and carbon through a hydrothermal one-pot process, yielding submicron Si@C/Graphene. The submicron Si@C/Gr electrode delivered a reversible capacity of 1192 mAh/g at 100th cycle, showing 84% of initial capacity. This composite electrode assembled from cost-effective Si source can provide cost-effective and high-performance anode materials for the next-generation LIBs.