Abstract
This project investigated methods for manufacture of electrochemical capacitor, or supercapacitor, -based structural energy storage devices. Investigations were made into introducing structural components to supercapacitor designs, attempting to produce a cell with inherent load-bearing capability and mechanical strength. Design- led developments were also conducted into the combination of supercapacitors with composite materials, in particular embedding energy storage within sandwich panel composites and fibre reinforced polymer composites. Electrochemical and mechanical testing and analysis were performed experimentally on all designs. Electrochemical impedance spectroscopy was carried out at the frequency range 10 mHz to 1 MHz for all manufactured cells. Cyclic voltammetry was undertaken using scan rates in the range 0.5 mV/s to 10 V/s depending on supercapacitor size. Galvanostatic charge-discharge was performed for current densities ranging from 0.5 mA/cm2 to 30 mA/cm2. Together these testing regimes allow for presentation of electrode specific gravimetric capacitance, energy and power, total device specific gravimetric energy and power, and total device volumetric energy and power density. Mechanical testing was undertaken to the three- point bend test standard ASTM.D790, providing results for flexural modulus and strength. Initial investigations were carried out to explore the viability of solid or part-solid electrolytes using epoxy-electrolyte mixes, and mechanically stable electrodes using sulfur-graphene structural coatings doped with carbon nanomaterials. Later developments in the project introduced the incorporation of existing supercapacitor technology with organic liquid electrolytes into composite material panels. Novel contributions were made in the successful design of composite sandwich panels with embedded supercapacitors as structural energy storage devices. These designs used supercapacitor current collectors as multifunctional materials that provide strength to the sandwich panel core. Low and high-density designs were investigated, with additional preliminary work on supercapacitor embedded composite flat panels presented with a view to further development within the subject.