Controlled swelling behavior and stable cycling of silicon/graphite granular composite for high energy density in lithium ion batteries

Abstract

The severe swelling behavior of silicon-based electrodes caused by the large volume expansion of Si associated with Li still prevents the practical implementation of Si. Here, we report the amorphous carbon coated silicon/graphite granule (C@SGG) as an attractive anode material to control the swelling behavior and achieve improved electrochemical properties. With the structural uniqueness including inner buffer space, large contact area of silicon and graphite, and the uniform surface carbon coating layer, the C@SGG electrode exhibits stable cycling performance and regulated electrode swelling behavior. C@SGG shows high reversible capacity of 1150 mA h g−1 and improved initial Coulombic efficiency of 85%. We evaluate C@SGG from a practical point of view through the characterization of pouch full cells prepared with LiCoO2 as a cathode with a high areal capacity of 3.4 mA h cm−2. The electrode prepared with the C@SGG of 10% and graphite of 90% (C@SGG 10% electrode) exhibits a stable cycling performance with a capacity retention of 71% over 500 cycles at 1 C-rate. Furthermore, the C@SGG 10% electrode exhibits stable electrode swelling behaviors comparable to the graphite electrode, indicating an initial expansion of 16.0% at a charged state and a cycling expansion of 6.7% over 50 cycles.