Porous Si spheres encapsulated in carbon shells with enhanced anodic performance in lithium-ion batteries

• In situ magnesiothermic reduction route for the formation of porous Si@C spheres.
• Unique microstructural characteristics of both porous sphere and carbon matrix.
• Enhanced anodic performance in term of cycling stability for lithium-ion batteries.

A novel type of porous Si–C micro/nano-hybrids, i.e., porous Si spheres encapsulated in carbon shells (porous Si@C spheres), has been constructed through the pyrolysis of polyvinylidene fluoride (PVDF) and subsequent magnesiothermic reduction methodology by using SiO2 spheres as precursors. The as-synthesized porous Si@C spheres have been applied as anode materials for lithium-ion batteries (LIBs), and exhibit enhanced anodic performance in term of cycling stability compared with bare Si spheres. For example, the porous Si@C spheres are able to exhibit a high reversible capacity of 900.0 mA h g−1 after 20 cycles at a current density of 0.05 C (1 C = 4200 mA g−1), which is much higher than that of bare Si spheres (430.7 mA h g−1).

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