Electrochemical lithiation of thin silic

Thin silicon layers containing approximately 20% carbon and 20% oxygen were potentiostatically deposited on copper substrates from a 1 M SiCl4, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethyl) sulfonimide [BMPTf2N] electrolyte. The electrodeposition process was investigated utilizing voltammetric techniques coupled with in-situ microgravity methods, namely quartz crystal microbalance (QCM). The electrochemical and QCM data revealed contributions from partial Si4+ to Si2+ reduction and potential restructuring of the metallic substrate. Significant side reactions occurred in parallel with the deposition. Energy dispersive X-ray analysis (EDX) confirmed the formation of silicon-based films, while depth profiling X-ray photoelectron spectroscopy (XPS) provided detailed information regarding the chemical composition and elemental distribution of the deposit. The resultant silicon-containing layers demonstrated stable lithiation, achieving capacity values around 1200 mAh/g with 80% capacity retention following 300 cycles in standard E1 M/C electrolytes. In ionic liquid, however, the material exhibited a lower capacity of about 500 mAh/g, likely due to the high viscosity of the electrolyte and the presence of ionic liquid decomposition products during lithiation.