Material Design and Optimisation of Electrochemical Li-Ion Storage Properties of Ternary Silicon Oxycarbide/Graphite/Tin Nanocomposites

In this work, we present the characterization and electrochemical performance of various ternary silicon oxycarbide/graphite/tin (SiOC/C/Sn) nanocomposites as anodes for lithium-ion batteries. In binary SiOC/Sn composites, tin nanoparticles may be produced in situ via carbothermal reduction of SnO2 to metallic Sn, which consumes free carbon from the SiOC ceramic phase, thereby limiting the carbon content in the final ceramic nanocomposite. Therefore, to avoid drawbacks with carbon depletion, we used graphite as a substitute during the synthesis of precursors. The ternary composites were synthesized from liquid precursors and flake graphite using the ultrasound-assisted hydrosilylation method and pyrolysis at 1000 degrees C in an Ar atmosphere. The role of the graphitic component is to ensure good electric conductivity and the softness of the material, which are crucial for long term stability during alloying-dealloying processes. The presented approach allows us to increase the content of the tin precursor from 40 wt.% to 60 wt.% without losing the electrochemical stability of the final material. The charge/discharge capacity (at 372 mA g(-1) current rate) of the tailored SiOC/C/Sn composite is about 100 mAh g(-1) higher compared with that of the binary SiOC/Sn composite. The ternary composites, however, are more sensitive to high current rates (above 372 mA g(-1)) compared to the binary one because of the presence of graphitic carbon.