Rambutan-Inspired Yolk-Shell Silica@Carbon Frameworks from Biomass for Long-Life Anode Materials

SiO₂ is regarded as one of the most promising anode materials for Li-ion batteries due to its high capacity, low cost and other merits. However, the poor conductivity and the volume change are still hindering its practical applications. In this work, a rambutan-inspired structure is designed to fabricate amorphous SiO₂@N, P co-doped porous carbon frameworks from biomass. The carbon shell could connect with each other, providing good conductivity. After partially etching of the SiO₂, the yolk-shell structure could buffer the volume changes of SiO₂ during the charge/discharge processes without destroying the conducting shell. Besides, N, P doping and graphite nano crystallites in the frameworks could also offer more active sites for Li⁺ storage. As a result, the composite can not only exhibit excellent rate performance nearly 300 mAh g⁻¹ at a current density of 2000 mA g⁻¹, but also deliver a surprisingly stable reversible capacity of 373 mAh g⁻¹ over 1000 cycles at the current density of 500 mA g⁻¹ with the Coulombic efficiency beyond 99%. Considering the facile preparation and satisfactory lithium storage abilities, this composite design could be able to extend for practical battery application.