One-pot sol-gel synthesis of Si/C yolk-shell anodes for high performance lithium-ion batteries

Abstract

Silicon (Si) materials are promising anodes for lithium-ion batteries (LIBs) due to their high theoretical capacity and low discharge potential. Nevertheless, their actual use is seriously restricted by their low conductivity and huge volumetric change. Developing a Si/C composite with a yolk-shell structure is an effective method to overcome the issues including the low electrical conductivity and poor cycling stability caused by Si. In this work, a facile one-pot sol-gel approach is developed to synthesize a Si/C yolk-shell composite in the presence of cost-effective resorcinol-formaldehyde (RF) and tetraethyl orthosilicate (TEOS) as precursors. In this structure, Si nanoparticles (NPs, ∼80–100 nm) are well encapsulated in a ∼12 nm thick hollow carbon shell (HC). There is a 60 nm-thick void space between the silicon core and outer carbon layer. The as-prepared Si@HC sample showed a high charge capacity of 1807.4 mA h g −1 and retained 999.5 mA h g −1 at 100 mA g −1 beyond 100 cycles. Furthermore, this material exhibited a reversible capacity of 500 mA h g −1 after 2000 cycles at 1 A g −1 . • The Si@SiO 2 @RF core-shell precursor can be synthesized by a one-step sol-gel approach. • The size of the thickness of the carbon shell can be adjusted conveniently. • Si@HC anodes exhibit high reversible capacities as well as excellent cycle stability.