Nano-confined Si@C composites with excellent lithium-ion storage performance derived from a POSS-based covalent framework and low-temperature reduction method.

Silicon-based anode materials experience significant volume changes and low conductivity during the lithiation process, which severely hinders their successful application in lithium-ion batteries. Reducing the size of silicon particles and effectively combining them with carbon-based materials are considered the main strategies to enhance the lithium-ion storage performance of silicon-based anodes. In this study, we employed a "bottom-up" strategy to synthesize Si@C anode materials by cross-linking octa-aminopropyl polyhedral oligomeric silsesquioxane (NH-POSS) with terephthalaldehyde and subsequent high-temperature treatment and low-temperature liquid reduction. The obtained nanospheres consist of ultra-thin silicon stripes embedded in a continuous carbon framework, forming a carbon-protected silicon-based anode material suitable for lithium-ion batteries. The Si@C nanospheres exhibit excellent lithium-ion storage performance. After 1000 cycles at a current density of 0.5 A g, it retains an impressive capacity of 1363 mA h g, which is more than three times the theoretical capacity of graphite and 182% of the first cycle capacity after activation (750 mA h g). This work not only provides new possibilities for the application of POSS but also broadens the design and application of advanced silicon-based anode materials in the energy storage field.