Kara Evanoff

Atomic layer deposition of vanadium oxide on carbon nanotubes for high-power supercapacitor electrodes

Vanadium oxides may offer high pseudocapacitance but limited electrical conductivity and specific surface area. Atomic layer deposition allowed uniform deposition of smooth nanostructured vanadium oxide coatings on the surface of multi-walled carbon nanotube (MWCNT) electrodes, thus offering a novel route for the formation of binder-free flexible composite electrode fabric for supercapacitor applications with large thickness, controlled porosity, greatly improved electrical conductivity and cycle stability. Electrochemical measurements revealed stable performance of the selected MWCNT–vanadium oxide electrodes and remarkable capacitance of up to ∼1550 F g−1 per active mass of the vanadium oxide and up to ∼600 F g−1 per mass of the composite electrode, significantly exceeding specific capacitance of commercially used activated carbons (100–150 F g−1). Electrochemical performance of the oxide layers was found to strongly depend on the coating thickness.

Towards Ultrathick Battery Electrodes: Aligned Carbon Nanotube – Enabled Architecture

Vapor deposition techniques were utilized to synthesize very thick (∼1 mm) Li-ion battery anodes consisting of vertically aligned carbon nanotubes coated with silicon and carbon. The produced anode demonstrated ultrahigh thermal (>400 W·m(-1) ·K(-1)) and high electrical (>20 S·m(-1)) conductivities, high cycle stability, and high average capacity (>3000 mAh·g(Si) (-1)). The processes utilized allow for the conformal deposition of other materials, thus making it a promising architecture for the development of Li-ion anodes and cathodes with greatly enhanced electrical and thermal conductivities.

Ultra Strong Silicon-Coated Carbon Nanotube Nonwoven Fabric as a Multifunctional Lithium-Ion Battery Anode

Materials that can perform simultaneous functions allow for reductions in the total system mass and volume. Developing technologies to produce flexible batteries with good performance in combination with high specific strength is strongly desired for weight- and power-sensitive applications such as unmanned or aerospace vehicles, high-performance ground vehicles, robotics, and smart textiles. State of the art battery electrode fabrication techniques are not conducive to the development of multifunctional materials due to their inherently low strength and conductivities. Here, we present a scalable method utilizing carbon nanotube (CNT) nonwoven fabric-based technology to develop flexible, electrochemically stable (∼494 mAh·g(-1) for 150 cycles) battery anodes that can be produced on an industrial scale and demonstrate specific strength higher than that of titanium, copper, and even a structural steel. Similar methods can be utilized for the formation of various cathode and anode composites with tunable strength and energy and power densities.

Nanostructured composites for high energy batteries and supercapacitors

High power energy storage devices, such as Li-ion batteries and supercapacitors, are critical for the development of zero-emission electric vehicles, large scale smart grid, energy efficient ships and locomotives, wearable devices and portable electronics. This review will focus on our progress with the developments of nanocomposite electrodes capable to improve both the energy and power storage characteristics of the state of the art devices. We review recent advancements in ultra-high capacity conversion-type anodes and cathodes for Li ion batteries as well as carbon-metal oxide and carbon-conductive polymer (nano)composite electrodes for supercapacitors. Various routes to overcome existing challenges will be discussed, including various solution deposition techniques, atomic layer deposition (ALD), chemical vapor deposition (CVD) and electro-deposition. Several designs and implementations of multi-functional electrodes will also be presented.