High-Rate and Long-Cycle Silicon/Porous Nitrogen-Doped Carbon Anode via a Low-Cost Facile Pre-Template-Coating Approach for Li-ion Batteries

- A low cost facile pre-template-coating approach for Si/p-NC composite is developed.
- Si/p-NC possesses porous structure in both Si core and nitrogen-doped carbon shell.
- 88%Si/p-NC presents over 90% high capacity retention with current density increase.
- 88%Si/p-NC delivers high capacity of 665 mA g−1 even after 600 cycles at 5000 mA g−1.

Exploring low-cost, facile, and scalable fabrication procedure for silicon/carbon composite with excellent electrochemical performance is urgently required to promote the practical application of high-capacity silicon material for Li-ion battery anodes. Using commercial cost-effective AlSi alloy nanopowder as the silicon source, here we present a facile approach via pre-template-coating and chemical acid etching methods for synthesizing silicon/porous nitrogen-doped carbon composite with a unique core-porous shell structure. At the pre-template-coating stage, the AlSi alloy nanopowder is initially coated by carbon via the solution deposition and carbonization of PVP. The Al template is subsequently removed by acid etching, affording silicon nanoparticles wrapped by the highly conductive nitrogen-doped carbon. The escape of hydrogen gas during acid etching leads to the nitrogen-doped carbon shell with a microporous structure. The silicon/porous nitrogen-doped carbon composite with 88% Si delivers a high reversible capacity of 1730 mAh g−1 (based on the total mass of the composite) after 100 cycles at a current density of 1000 mA g−1 with a coulombic efficiency of approximately 100%. Moreover, the rate capability is significantly improved. With the increase in the current density from 200 to 500, 1000, 2000 and 3000 mA g−1, high capacity retention values of 99.7, 97.5, 93.7 and 91.5%, respectively, are obtained. A long cycle life at a high rate is also achieved, with a notable capacity of 665 mAh g−1 after 600 cycles at a high current density of 5000 mA g−1. The low-cost, facile, and scalable synthesis of the approach silicon/porous nitrogen-doped carbon composite with exceptional electrochemical performance from a commercial AlSi alloy powder makes it extremely promising as a practical anode material for high-energy Li-ion batteries.

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