In-situ processing nano-porous silicon into 3D conductive structure as high-capacity anode for lithium-ion batteries

Abstract

The use of high-capacity materials in lithium-ion batteries (LIBs) is critical for achieving higher energy density. In this paper, a highly-dispersed three-dimensional (3D) graphene-wrapped porous nano-silicon composite (P-Si@rGO, where rGO is reduced graphene oxide) is synthesized from SiO2 and graphene oxide through a novel and facile approach that consists of freeze-drying and in-situ magnesium-thermal reduction. The composite is then utilized as a high-capacity anode for LIBs. A number of attractive properties are evident in this new silicon-based composite and include qualities such as individually encapsulated and highly dispersed silicon particles, close Si—O—C interactions between silicon and graphene, a porous design for the silicon structure, and a bulky porosity. These merits significantly enhance the reaction kinetics of the electrode and endow the composite with both a large electrical contact area and a sufficient buffer space to cope with the volume change during the lithiation/delithiation process. Ultimately, the P-Si@rGO sample demonstrates an excellent cycling stability, boasting a capacity of 1123 mAh g−1 at 1000 mA g−1 over 500 cycles. In this paper, materials with different morphologies are prepared by changing the magnesium-thermal reaction time, so as to study the effects of phase composition and microstructure of the composites on their electrochemical performances. Importantly, the reasons for the capacity increase seen in later stages of the cycling process are also investigated. In brief, these findings provide new insights into the future functional evolution of silicon-based anode materials.