Design of Preceramic Polymer Derived Nanostructured Anodes for Lithium Ion Batteries

Abstract

Preceramic polymers with their unique nanostructure and phase composition have aided myriads of structural and functional applications of materials. One such important application is their usage as anodes in lithium ion batteries. In the next generation anodes, Siis widely regarded as a leading material due to its high theoretical capacity. However, its practical use is hindered by significant volume expansion (over 300%) during lithiation, leading to mechanical degradation. In this work, we propose the design of a nanostructured silicon–carbon (Si–C) hybrid anode synthesized from Si nanoparticles and a carbon-rich preceramic polymer. The study investigates the phase composition, microstructure, and electrochemical performance of Si–C hybrids synthesized by varying Si:C ratios, pyrolysis temperatures, and etching conditions. A polymer-derived SiOC ceramic is used as the carbon source, offering tunable pore architecture and surface chemistry. A key innovation lies in introducing controlled porosity into the SiOC matrix by tailoring its microstructure, thereby enhancing its functionality as an anode material. Three synthesis routes are explored. In the first, nanocrystalline Si is combined with SiOC-derived carbon synthesized at 1000 °C and 1200 °C, followed by HF etching to introduce porosity. The second route incorporates amorphous SiO₂ fillers as sacrificial pore-forming agents, which are later removed via HF etching. The third approach enhances interfacial bonding between Si and the carbon matrix through the addition of a non-ionic surfactant that facilitates uniform dispersion of Si particles within the amorphous SiCO matrix. All synthesized Si–C hybrids exhibit outstanding electrochemical performance, with the surfactant-assisted hybrids showing the most significant improvement. The SiCO-derived carbon matrix acts as a mechanically resilient and conductive framework, accommodating the volume changes of Si during cycling and promoting efficient electron transport. High mesoporosity and ordered carbon structures further contribute to the superior electrochemical behaviour. These results underscore the potential of SiCO-based Si–C hybrids and suggest the feasibility of extending this strategy to other polymer precursors for advanced lithium-ion battery anodes.