Structurele hoog-voltage nanodiëlektrische condensatoren: composietmaterialen voor structurele energieopslag

As the electrification of today's society poses a major challenge, the quest for innovative electrical energy storage solutions has received broad attention. Compared with batteries and supercapacitors as conventional energy storage technologies, solid-state dielectric capacitors offer numerous advantages. The (dis)charging of a dielectric capacitor is extremely fast and the lifetime is quasi unlimited as no electrolyte that degrades over time is involved, which also enables the use of higher voltages. However, the (gravimetric) energy density of solid-state dielectric capacitors needs to be significantly improved to compete with conventional electrolyte-based energy storage technologies. Furthermore, for structural applications where energy storage is also required, a reduction in the overall mass of the design could beneficially decrease its energy consumption and hence energy storage requirements. This design challenge has led to the introduction of multifunctional composites, which simultaneously offer good mechanical properties and energy storage. In the concept of multifunctional composites, the structural capacitor uses the same materials design to store energy while offering excellent mechanical performance, for which carbon-fibre-reinforced polymer (CFRP) composites have generally been used. However, the development of effective strategies for enhancing the energy density is paramount for structural dielectric capacitors, despite the excellent specific stiffness and strength they typically display. Therefore, the introduction of nanoparticles in a polymer matrix to achieve a nanodielectric design has been commonly suggested in the literature to date, but this approach has not yet been explored for structural capacitors. The general aim of this PhD research was to develop a structural nanodielectric capacitor comprising a solid-state nanodielectric for high energy density while providing good structural properties. An extensive review on the design, processing and properties of percolation-based nanodielectrics was provided, which allowed the development of a framework for the effective dispersion of nanoparticles in polymer matrices. This constituted a crucial step in the manufacturing and optimisation of percolation-based nanodielectrics in this research. Both 3D and advanced 2D titanium-carbide-based nanoparticle morphologies were studied in polyvinylidene fluoride (PVDF) to obtain nanodielectrics for a wide range of filler loadings. Moreover, a tailored synthesis method was developed to successfully exfoliate 3D Ti3AlC2 MAX particles into advanced multi-layered 2D Ti3C2Tz MXene nanoparticles. Due to the enhanced interfacial polarisation in the multi-layered MXene nanoparticle morphology, the percolation-based PVDF-MXene nanodielectrics displayed a superior energy density compared with the PVDF matrix. In the final step of this research, the developed PVDF-MXene nanodielectrics were integrated in a CFRP to achieve a structural nanodielectric capacitor. Overall, a structural CFRP PVDF-MXene nanodielectric capacitor was designed and successfully manufactured. When using PVDF-MXene as the dielectric layer in the CFRP, good mechanical properties and an improved energy density compared with PVDF as dielectric layer were observed. In this way, this PhD research underlines the added value of structural nanodielectric capacitors for achieving a multifunctional performance by combining structural properties with energy storage.