Extremely High Yield Conversion from Low‐Cost Sand to High‐Capacity Si Electrodes for Li‐Ion Batteries

Although magnesiothermic reduction has attracted immense attention as a facile route for the fabrication of mass‐scale Si nanostructures for high‐capacity lithium‐ion battery applications, its low conversion yield (<50%) and the discovery of a sustainable and low‐cost precursor remain challenging. Here, an unprecedentedly high final conversion yield (>98%) of magnesiothermic reduction based on control of reaction pressure is reported. The successful use of sand as a nearly infinite and extremely low‐cost source for the high‐yield fabrication of nanostructured Si electrodes for Li‐ion batteries is demonstrated. On the basis of a step‐by‐step analysis of the material's structural, morphological, and compositional changes, a two‐step conversion reaction mechanism is proposed that can clearly explain the phase behavior and the high conversion yield. The excellent charge–discharge performance (specific capacities over 1500 mAh g ‐1 for 100 cycles) of the hierarchical Si nanostructure suggests that this facile, fast, and high‐efficiency synthesis strategy from ultralow‐cost sand particles provides outstanding cost‐effectiveness and possible scalability for the commercialization of Si electrodes for energy‐storage applications.