Nanostructured silicon for advanced Li-ion storage systems

Abstract

The interest in batteries beyond the present intercalation-type chemistry has been clearly catalyzed by the current environmental issues. On the one hand, transport electrification can considerably reduce the well-to-wheel emission through the use of renewable and low carbon electricity stored in efficient batteries. On the other hand, successful exploitation of intermittent energy sources, such as solar or wind, requires energy storage capability, particularly in managing peak electricity production and demand. Several Li-ion battery (LIB) chemistries are well established; however, they can not satisfy the energy demands nor the environmental policies associated with their production and disposal. High-performance, lighter and safer batteries are possible if Si-based electrodes are adopted. Herein, we explored several routes to solve the key failure modes in Si cycling via optimized material and electrode design. First, we present an accessible, room temperature, silicon nanowires (SiNWs) and kinked SiNWs synthesis based on a metal-assisted chemical etching scheme that allows for the reuse of the Si substrate via a sacrificial porous segment. Secondly, we explored an electrode design that is more realistic and suitable for alloying-type electrodes suffering from the volume variations such as Si. In this sense, we report on the mechanical and electrochemical properties of a self-standing Si-carbon-based electrode with optimized porosity to sustain the volume variations during Li-Si alloying reaction. Also, Si surface passivation is discussed as a possible route for extending the cycling life of Si-based electrodes. We particularly study the lithiation fundamentals in Ni coated Si nanostructures and apply our findings towards achieving high-performance Si-based electrodes. We further show that an aqueous conducting polymer, converted mechanochemically to a hydrogel, meets all the requirements as a binder for Si anodes. Not only it enhances the cycling life of Si anodes but also can deflect the current electrode manufacturing process towards a cleaner, safer path. Finally, this work evaluates possible routes to redirect LIB technology towards an environmentally friendlier, safer, and cost-effective direction by developing accessible material synthesis protocols, within low cost and recycling strategies, as well as aqueous processing of battery electrodes.(FSA - Sciences de l'ingénieur) -- UCL, 201