Carbon-Rich Silicon Oxycarbide - a Promising Anode Material: Recent Findings Related to Microstructural, Electrochemical and Electroanalytical Characterization

The electrochemical properties of silicon oxycarbide ceramics (SiOC), in view of application as anode material for Li-ion batteries, were first studied in the middle of the 1990’s by Dahn et al. [1,2]. Since that time SiOC compounds with various chemical compositions have been examined and stoichiometries with an exceptionally high content of free carbon were identified as perspective anode materials, with respect to gravimetric capacity, rate capability and cycling behavior [3-6].

Within this work, the comprehensive characterization of carbon-rich SiOC derived from commercially available polyorganosiloxane RD-684a (Starfire Systems Inc., USA) is presented. The overview includes the correlation of electrochemical properties with microstructural features in dependence of the ceramization temperature of the Si-based polymer [6]. The dependency of the Li-ion diffusion coefficient on the potential is determined by electroanalytical methods PITT, GITT and EIS and analyzed with respect to the microstructural features of the ceramic [7]. In addition, the benefits of chemical modification of the precursor with Sn(ac)₂, in order to enhance the lithium storage properties of SiOC by in-situ precipitation of metallic Sn as additional electrochemically active phase, is highlighted [8]. Finally, our newest results from ex-situ and in-situ Raman-spectroscopy measurements are presented, which directly trace and verify the Li-ion uptake within the free carbon phase in the SiOC microstructure.

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