Si Nanocrystal-Embedded SiO x nanofoils: Two-Dimensional Nanotechnology-Enabled High Performance Li Storage Materials.

Silicon (Si) based materials are highly desirable to replace currently used graphite anode for lithium ion batteries. Nevertheless, its usage is still a big challenge due to poor battery performance and scale-up issue. In addition, two-dimensional (2D) architectures, which remain unresolved so far, would give them more interesting and unexpected properties. Herein, we report a facile, cost-effective, and scalable approach to synthesize Si nanocrystals embedded 2D SiO x nanofoils for next-generation lithium ion batteries through a solution-evaporation-induced interfacial sol-gel reaction of hydrogen silsesquioxane (HSiO1.5, HSQ). The unique nature of the thus-prepared centimeter scale 2D nanofoil with a large surface area enables ultrafast Li+ insertion and extraction, with a reversible capacity of more than 650 mAh g-1, even at a high current density of 50 C (50 A g-1). Moreover, the 2D nanostructured Si/SiO x nanofoils show excellent cycling performance up to 200 cycles and maintain their initial dimensional stability. This superior performance stems from the peculiar nanoarchitecture of 2D Si/SiO x nanofoils, which provides short diffusion paths for lithium ions and abundant free space to effectively accommodate the huge volume changes of Si during cycling.