Composite Structural Supercapacitors: High-Performance Carbon Nanotube Supercapacitors through Ionic Liquid Localisation.

Composite structural supercapacitors (SSC) are an attractive technology for aerospace vehicles; however, maintaining strength whilst adding energy storage to composite structures has been difficult. Here, SSCs were manufactured using aerospace-grade composite materials and CNT mat electrodes. A new design methodology was explored where the supercapacitor electrolyte was localised within the composite structure, achieving good electrochemical performance within the active region, whilst maintaining excellent mechanical performance elsewhere. The morphologies of these localised SSC designs were characterised with synchrotron X-ray fluorescence microscopy and synchrotron X-ray micro-computed tomography and could be directly correlated with both electrochemical and mechanical performance. One configuration used an ionogel with an ionic liquid (IL) electrolyte, which assisted localisation and achieved 2640 mW h kg-1 at 8.37 W kg-1 with a corresponding short beam shear (SBS) strength of 71.5 MPa in the active area. A separate configuration with only IL electrolyte achieved 758 mW h kg-1 at 7.87 W kg-1 with SBS strength of 106 MPa in the active area. Both configurations provide a combined energy and strength superior to results previously reported in the literature for composite SSCs.

Zero valence iron nanocube decoration of graphitic nanoplatelets.

Graphitic nanoplatelets (GNPs) have been treated using an ultrasonicated ozonolysis procedure to produce stable aqueous dispersions that facilitate deposition of thin films using electrophoretic deposition. The thin GNP films were then coated with zero valence (ZV) iron nanocubes using a pulsed electrodeposition technique. Characterization of the ZV-iron coating with deposition time revealed that the changing magnetic character of the ferromagnetic-graphitic hybrid material was related to the nucleation density and growth of the ZV-iron nanocubes. Density functional theory calculations show a preference for ZV-iron adsorption at the oxygen sites of the GNPs, with ZV-iron displacement of oxygen groups favored in some configurations. Transmission electron microscopy studies confirm ZV-iron growth nucleates preferentially at the graphite nanoplatelet edges and the hybrid material magnetism is affected by the convergent crystalline grain boundaries formed between adjacent ZV-iron nanocubes.

Generation of highly porous silver nanowire networks by plasma treatment and their direct application as supercapacitor electrodes.

Exposure to plasma can significantly increase the surface area of silver species and their resistance to oxidation. While some work investigating plasma-treated silver has been done, limited morphologies and applications have been explored. We hereby explore this effect on silver nanowires (AgNWs) through medium-vacuum air plasma exposure time ranging between 30 s to 60 min. These plasma-treated AgNW networks are directly applied as supercapacitor electrodes, without any carbon or polymer additives that are typically employed alongside silver in energy storage applications. The plasma treatment consequently affected the electrochemical performance of AgNWs, where longer treatment times resulted in higher energy storage capacity. An increase in resistance was observed for plasma treatment times greater than or equal to 5 min, due to the switch from the percolation threshold of the metallic Ag phase to the Ag2O phase. Despite an initial drop in stored energy, an overall improvement in energy storage capacity was observed throughout cycling, where the optimal plasma treatment time of 5 min resulted in an increase of 320% of its starting value with near 100% coulombic efficiency, through the development of stable redox-active surface nanostructures.

Development of Stable Boron Nitride Nanotube and Hexagonal Boron Nitride Dispersions for Electrophoretic Deposition.

Boron nitride nanotubes (BNNTs) represent a relatively new class of materials that provides alternative electrical and thermal properties to the carbon analogue. The high chemical and thermal stability and large band gap combined with high electrical resistance make BNNTs desirable in several thin-film applications. In this study, stable BNNT and hexagonal boron nitride (hBN) particle dispersions have been developed using environmentally friendly advanced oxidation processing (AOP) that can be further modified for electrophoretic deposition (EPD) to produce thin films. The characterization of the dispersions has revealed how the hydroxyl radicals produced in AOP react with BNNT/hBN and contaminant boron nanoparticles (BNPs). While the radicals remove the carbon contaminant present on BNNT/hBN and increase dispersion stability, they also oxidize the BNPs and the boron oxide produced, which, conversely, reduces the dispersion stability. The use of high- or low-powered ultrasonication in combination with the AOP affects the rate of the competing reactions, with low-powered sonication and AOP providing the best combination for producing stable dispersions with high concentrations. BNNT/hBN dispersions were functionalized with polyethyleneimine to facilitate EPD, where films of several micrometer thickness were readily deposited onto stainless steel and glass-fiber fabrics. BNNT/hBN films produced on glass fabrics by EPD exhibited a consistent through-thickness macroporosity that was facilitated by platelet and nanotube stacking. The film macroporosity present on the coated fabrics was suitable for use as separator layers in supercapacitors and provided improved device robustness with a minimal impact on electrochemical performance.