Mesoporous silicon nanocubes coated by nitrogen-doped carbon shell and wrapped by graphene for high performance lithium-ion battery anodes

Silicon materials have received widespread attention due to their inherent high theoretical specific capacity. However, large volumetric expansion and poor electrical conductivity hinder the large-scale application of silicon materials. To address these issues, we synthesize mesoporous silicon nanocubes coated by nitrogen-doped carbon shell ([email protected]) and wrapped by graphene ([email protected]) respectively. The ordered mesoporous silica nanocubes are obtained via a hydrolysis reaction of Tetraethyl Orthosilicate (TEOS) and further reduced by a magnesiothermic reduction to prepare mesoporous silicon nanocubes (MSC). The porous structure of MSC not only speeds up the transfer of ions and electrons, but also buffers the internal stress triggered by the volume expansion of the electrode material. Moreover, in addition to providing additional lithium storage sites and high conductivity, the graphene or nitrogen-doped carbon shell also effectively prevents aggregation and cracking of the mesoporous silicon, greatly promoting the stability of the entire electrode structure. Therefore, the electrochemical properties of composite materials are significantly enhanced by the combination of the mesoporous structure and the nitrogen-doped carbon shell or graphene. [email protected] can deliver the initial discharge specific capacity of 2852.7 mAh·g−1 and the initial Coulombic efficiency (CE) of 83.74%. After 100 cycles, the [email protected] and [email protected] composite materials exhibit reversible specific capacities of 1070.5 mAh·g−1 and 738.2 mAh·g−1 at 0.1 A g−1, respectively.