High Rate Capability of SiOC Ceramic Aerogels with Tailored Porosity as Anode Materials for Li-ion Batteries

Porous carbon-rich SiOC ceramic aerogels have been synthesized from a linear polysiloxane cross-linked with divinylbenzene (DVB) via hydrosilylation reaction in presence of a Pt catalyst and acetone as a solvent. The obtained wet gels are aged in solvent followed by drying under supercritical conditions using liquid carbon dioxide. The resulting pre-ceramic aerogels are subjected to pyrolysis at 1000 °C under controlled argon atmosphere to form the desired SiOC aerogel. The synthesized SiOC ceramics contain 43 wt% of free carbon, which is segregated within amorphous SiOC matrix. The high BET surface area up to 230 m2g−1 of preceramic aerogels is only slightly diminished to 180 m2g−1 after pyrolysis at 1000 °C. The electrochemical characterization reveals a high specific capacity of more than 600 mAh g−1 at a charging rate of C (360 mA g−1) along with a good cycling stability. At a rate of 10C (3600 mA g−1) the specific capacities as high as 200 mAh g−1 are recovered. The excellent properties of the materials are discussed with respect to their structural features. The porous nature of the carbon rich ceramics allows for fast ionic transport and helps to accommodate the structural changes which in turn allow a stable performance during repeated lithiation/delithiation.