Water-soluble-template-derived nanoscale silicon nanoflake and nano-rod morphologies: Stable architectures for lithium-ion battery anodes

Earth abundant and economical rock salt (NaCl) particles of different sizes (<3 μm and 5–20 μm) prepared by high energy mechanical milling were used as water-soluble templates for generation of Si with novel nanoscale architectures via low pressure chemical vapor deposition (LPCVD). Si nanoflakes (SiNF) comprising largely amorphous Si (a-Si) with a small volume fraction of nanocrystalline Si (nc-Si), and Si nanorods (SiNR) composed of a larger volume fraction of crystalline Si (c-Si) and a small volume fraction of a-Si resulted from modification of the NaCl crystals. SiNF yielded first-cycle discharge and charge capacities of ∼2,830 and 2,175 mAh·g−1, respectively, at a current rate of 50 mA·g−1 with a first-cycle irreversible loss (FIR loss) of ∼15%–20%. SiNR displayed first-cycle discharge and charge capacities of ∼2,980 and ∼2,500 mAh·g−1, respectively, at a current rate of 50 mA·g−1 with an FIR loss of ∼12%–15%. However, at a current rate of 1 A·g−1, SiNF exhibited a stable discharge capacity of ∼810 mAh·g−1 at the end of 250 cycles with a fade rate of ∼0.11% loss per cycle, while SiNR showed a stable specific discharge capacity of ∼740 mAh·g−1 with a fade rate of ∼0.23% loss per cycle. The morphology of the nanostructures and compositions of the different phases/phase of Si influence the performance of SiNF and SiNR, making them attractive anodes for lithium-ion batteries.