Pomegranate-like silicon-based anodes self-assembled by hollow-structured Si/void@C nanoparticles for Li-ion batteries with high performances.

Silicon is considered as one of the most promising alternatives to the graphite anode for lithium-ion batteries due to its high theoretical capacity (4200 mAh g-1). However, its fragile solid electrolyte interphase cannot tolerate the large volume changes of bare silicon induced by the lithium insertion and extraction, resulting in low Coulombic efficiency. In previous reports, a yolk-shell design, such as Si@void@C, in which the well-defined space allows the silicon particles to expand freely without breaking the outer carbon shells, can effectively improve the Columbic efficiency. Here, we design a pomegranate-like silicon-based anodes self-assembled by the hollow-structured Si/void@C nanoparticles, in which silicon and some voids are together sealed in the outer carbon shells, by the magnesiothermic reduction of the colloidal SiO2@PEI nanospheres prepared by the hydrolysis of the tetraethoxysilane under the catalytic effect of polyetherimide (PEI). Due to the tolerance of the presealed void in the carbon shells of the primary hollow-structured Si/void@C nanoparticles, the prepared pomegranate-like silicon-based anodes deliver a high reversible capacity of 1615 mAh g-1 at 0.1 C and long cycle life of 73.5% capacity retention at 2 C after 500 cycles, as well as high Coulombic efficiency of 99%.