Engineering Si-on-Graphite High-Capacity Anodes for Li-ion Battery Applications Fabricated by Fluidized Bed Process

Abstract Composite powders consisting of graphite and small portions of silicon have been considered as potential high-capacity anode materials for the next-generation high-energy Li-ion batteries (LIBs). The choice of a synthesis method is critical for determining the powder microstructure, which has a direct consequence on the material performance and the cost-efficiency for making commercial electrode materials. Herein, we report the fabrication of silicon-on-graphite (Si@Gr) composites by fluidized bed granulation (FBG) for the first time. The FBG process is shown to produce composite powders comprising a uniform layer of nano-sized Si particles lodged onto the surface of micron-sized graphite particles to possess a core-shell microstructure. Adopting a suitable binder during the FBG process is found to be critical to enable firm adhesion of the Si nanoparticles on graphite surface during a subsequent carbon-coating process, where the composite particles are coated with pitch and then carbonised to form a highly electronically conductive and mechanical stabilizing layer of amorphous carbon for further improving their electrochemical performance. The carbon-coated composite powders exhibit a very high capacity reaching over 600 mAh g-1, high rate capability and illustrates the potentially of long-cycle stability in Si@Gr || Li metal cells, showing more than 70% capacity retention after 400 charge-discharge cycles even without electrolyte optimization. Furthermore, a significantly improved cycling stability is found for the carbon-coated Si@Gr materials in NCM-622 || Si@Gr full-cells.