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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2018)

As interest in renewable energy grows on both research and policy fronts, energy storage likely represents one of the most viable solutions to the problems posed by the intermittency and irregularity of renewable resources. While new classes of materials promise improved performance of energy storage systems, understanding energy storage electrode architecture and fabrication at the micro-scale allows us to fully leverage performance along different dimensions.

This dissertation aims to explore the use of device architecture manipulation to improve energy storage and conversion electrodes, focusing on addressing challenges around manufacturing high-surface area electrodes. Phsyically, our approach to texturizing electrodes consists of synthesizing materials as to create high-surface area templates while physically manipulating the electrode to maximize performance. Chemically, we manipulate performance with Angstrom-level precision, utilizing atomically thin layers to induce chemical enhancement of our devices at the electrode interface.

The principles of leveraging physical and chemical manipulation of electrodes is demonstrated in five unique works: (1) atomic layer deposition of titanium-nitride on carbon nanotubes for supercapacitor applications, (2) two-dimensional iron-phosphate for supercapacitor applications, (3) thiophene-based electrodeposition for photoelectrochemical water splitting, (4) titanium dioxide-coated zinc oxide nanowire arrays for photoelectrochemical water splitting, and (5) development of atomic layer deposited black titania for photoelectrochemical water splitting.

    Cover page: Atomically Thin Processing of High Surface Area Nanomaterials for Electrochemical Energy Devices
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2018)
    While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g-1 in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg-1 -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg-1 with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS2 -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min.
      Cover page: Titanium Disulfide Coated Carbon Nanotube Hybrid Electrodes Enable High Energy Density Symmetric Pseudocapacitors
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