A stable nanoporous silicon anode prepared by modified magnesiothermic reactions

Porous silicon prepared by low-cost and scalable magnesiothermic reactions is a promising anode material for Li-ion batteries; yet, retaining good cycling stability for such materials in electrodes of practical loading remains a challenge. Here, we engineered the nanoporous silicon from a modified magnesiothermic reaction by controlled surface oxidization forming a <5 nm oxide layer on the 10–20 nm Si nanocrystallites. High loading electrodes of ~3 mAh/cm2 demonstrates stable cycling with ~80% capacity retention over 150 cycles. The specific discharge capacity based on the total electrode weight is ~1000 mAh/g at the lithiation/delithiation current density of 0.5/0.75 mA/cm2. This work reveals the importance of the surface treatment on nanostructured Si, which will lead to a well-controlled ratio of silicon and surface oxide layer and provide guidance on further improvement on silicon-based anode materials.