Constructing a Grape-like Silicon/Mildly Expanded Graphite Microsphere Composite as a High-Performance Anode Material for Lithium-Ion Batteries

This work reports that the use of a high-performance and low-cost micron carrier material with abundant load-bearing pores and stable conductive networks for silicon/carbon (Si/C) nanoparticles (NPs) could be an effective strategy to increase the practical use of Si/C anode materials for lithium-ion batteries (LIBs). It proposed for the first time mildly expanded graphite microspheres (MEGMs) as a micron carrier for yolk–shell structured Si/C (Si@void@C) nanospheres to construct a Si@void@C-MEGMs nano/microcomposite. Si@void@C nanospheres disperse on the nanosheets and pores of MEGMs, which is like bunches of grapes hanging between the branches and leaves of the grape. Accordingly, compared with Si@void@C nanospheres, this nano/microcomposite electrode exhibits a reversible specific capacity of 851.2 mAh/g after the rate test and the following 135 cycles at 100 mA/g. The microstructure and composition analysis indicates that the great electrochemical properties could be because the abundant pores and excellent conductivity of the MEGM carrier effectively improve the structure and cycling stability of Si@void@C nanospheres. This work has not only provided a high-performance Si@void@C-MEGMs nano/microcomposite but also verified that MEGMs are an effective and low-cost carrier for the Si@void@C NPs, which will benefit the commercial use of Si/C anode materials for LIBs.