Nanocomposites as anode materials for lithium ion batteries: Synthesis, thermodynamic characterization and modeling of nanoparticular silicon dispersed in SiCN(O) and SiCO-based matrices

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In this project we will investigate amorphous and crystalline silicon nanoparticles homogeneously dispersed in a SiCN(O)- and SiCO-based ceramic derived from polysilazane and polysiloxane. The electrochemical performance of the resulting SiCN(O)/Si and SiCO/Si material will be studied in combination with commercial electrolytes and metallic lithium as reference/counter electrode material. For further studies of the new anode material in a complete battery, commercial cthode material (LiCoO2, LiFePO4) will be used.By means of total energy calculations based on density functional theory we will study the kinetics of the lithium ions in the Si nanoparticles and ceramic matrices and compare them with experimental findings. The existence of intermediate compounds of the constituents is explored by a combination of quantum mechanical calculations, calorimetric measurements and thermodynamic modeling. We will investigate the thermodynamics of the aforementioned materials by using computational methods (Calphad approach) for clarifying phase reactions. Additionally, we will perform high temperature solution calorimetry to measure enthalpies of formation for the materials of interest. Finally, the mechanical stability of the composite will be investigated by molecular dynamics simulations of intercalated and deintercalated structures.