A spray deposition manufacturing route has been developed for the fabrication of carbon nano-structured and micro-structured energy storage devices in a thin film format, with controlled film thickness, homogeneous film surface morphology and high electrochemical performance for both supercapacitors and lithium ion battery anodes. Three types of low cost commercially available carbon materials (graphite, activated carbon and carbon black) have been investigated, and electrodes characterised in terms of surface morphology, surface chemistry, microstructure and electrochemical properties. By using ball milling, CO<sub>2</sub> activation and adding suitable carbon conductive additives, nano-graphite-based film electrodes (one meter long and ~ 3 µm thickness) have been fabricated, with excellent ion transport and low electrical resistance (< 1.8 Ω). Specific capacitance of 110 F/g at a scan rate of 100 mV/s in 1 M H<sub>2</sub>SO<sub>4</sub> was achieved. The high rate performance of activated carbon-based electrodes ( ~2 µm thickness) has been enhanced by reducing the contact resistance of electrode/current collector interface and building a well-interconnected and hierachical meso/macro-porous structure. A specific capacitance of over 120 F/g at a scan rate of 600 mV/s or 20 A/g current density in 1 M H<sub>2</sub>SO<sub>4</sub> was achieved. The performance of carbon black-based electrodes (~4 µm thickness) in different electrolytes has been studied in both two- and three-electrode cells. High specific capacitances of 260 F/g at 1 A/g was achieved in 6 M KOH, together with energy and power densities of 21 kW/kg and 18 Wh/kg in 1 M Na<sub>2</sub>SO<sub>4</sub>. Finally, graphite-based electrodes for rechargeable lithium-ion batteries have also been fabricated with controlled film thickness from ~ 900 nm to ~ 40 µm and 98% capacity retention of 371 mA/g after 20 cycles. Spray deposition has been demonstrated to have the potential for scalability in the manufacture of carbon-based thin film electrodes with competitive properties.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:581266 |
| Date | January 2013 |
| Creators | Jiang, Meng |
| Contributors | Grant, Patrick |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:e651c635-6d92-4217-8442-43b2619c9c82 |
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