Thesis presented March 02, 2023

Abstract:
Embedded electrochemical energy storage is essential to meet the growing demand for low-power portable devices such as micro-electromechanical systems (MEMS), autonomous sensor arrays, radio-frequency identification (RFID) tags or biomedical devices. The elaboration of composite electrodes is an important lever to improve performance in terms of energy density and device durability. CVD grown SiNWs are compatible with a purely capacitive supercapacitor system, but their capacity can be improved with the addition of conducting polymers. This research presents the development of flexible nanocomposite electrodes for micro-supercapacitors based on silicon nanowires (SiNWs) and conducting polymers as PEDOT and his derivates. Conducting polymers can be deposited through aqueous micellar medium, which allows better morphology control as a thin film on the SiNWs surface. This morphological optimization results in better performances during electrochemical cycling. These new SiNWs nanocomposites and conductive polymers are then transferred to a flexible substrate based on carbon felts. The electropolymerization of EDOT on the flexible electrodes allows the nanocomposite electrode to provide a capacitance of 22 mF.cm^-2 with electrochemical stability limiting the loss of capacity to 18% after 100,000 cycles in aqueous electrolyte. To overcome the constraints of a liquid electrolyte, a polymer electrolyte is also developed, based on functionalized polysiloxanes. It is deposited on the SiNWs for the evolution towards an all-solid-state device. The all-solid state system exhibits near 98% stability for 100,000 cycles at a voltage of 3.0 V.

Keywords:
Flexible, supercapacitor, silicon, nanowires, conducting polymers

On-line thesis. ​