Impact of blending with polystyrene on the microstructural and electrochemical properties of SiOC ceramic

In this work, we present the electrochemical behavior and microstructural analysis of silicon oxycarbide (SiOC) ceramics influenced by an addition of polystyrene (PS). Polymer‐derived ceramics were obtained by pyrolysis (1000°C, Ar atmosphere) of different polysiloxanes prepared by sol–gel synthesis. This method is very effective to obtain desired composition of final ceramic. Two alkoxysilanes phenylthriethoxysilane and diphenyldimethoxysilane were used as precursors. Before pyrolysis polysiloxanes were mixed with PS using toluene as a solvent. Blending with PS affects the microstructure and free carbon content in the final ceramic material. Free carbon phase has been confirmed to be a major lithium storage host. Nevertheless, we demonstrate here that capacity does not increase linearly with increasing carbon content. We show that the amount of SiO₄ units in the SiOC microstructure increases the initial capacity but decreases the cycling stability and rate capability of the material. Furthermore, the microstructure of the free carbon influences the electrochemical performance of the ceramic: More ordered graphitic clusters favor better rate capability performance.