Fabrication of porous Si/nitrogen doped carbon composite and its enhanced lithium storage capability

With the aim to stabilize the structure of Si then improve the lithium storage performance, in this study a facile way is applied to deposit a layer of nitrogen-doped-carbon (NDC) on porous Si surface by carbonizing melamine, and the porous Si is easily prepared by etching SiAl alloy with HCl solution. After NDC coating, the cycling performance has been improved from 585.3 mAh g−1 for pure porous Si in the 100th cycle at 200 mA g−1 to 1496 mAh g−1 for Si/NDC composite, and the rate capability is also enhanced from 47.1 mAh g−1 for pure porous Si at 3200 mA g−1 to 499.6 mAh g−1 for Si/NDC composite. TEM images show the coating layer helps to stabilize the porous structure of Si during cycling. XPS analysis indicate Si has chemically acted with N and C during the calcination step, and the theoretical calculation based on density function theory indicates these chemical interactions benefit for the electron transferring between Si and the coating layer of NDC, thus enhancing the rate capability.