Carbon nanotube film based nanocomposites for stretchable energy storage devices
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Stretchable electronics are robust and functional when being mechanically bent, folded, twisted, and even stretched. They are attracting intense attention due to their promising applications in portable electronics and bio-implantable devices with arbitrarily adjustable surfaces. To power them, stretchable energy storage devices are the essential for the fabrication of independent and complete stretchable electronic systems. Material synthesis and structural design are the core of highly stretchable energy storage devices. Utilizing carbon nanotube (CNT) films as stretchable electrodes in supercapacitors has demonstrated excellent functionality and cycling stability. However, the main drawback of such a stretchable electric double-layer supercapacitor suffers from a low specific capacitance and energy density. In this dissertation, research efforts have been focused on three major breakthroughs in CNT film-based stretchable pseudocapacitors, stretchable asymmetric supercapacitors, as well as stretchable lithium-ion batteries, all of them exhibit excellent mechanical property and improved electrochemical performance. ☐ The realization of dynamically stretchable pseudocapacitors using buckled MnO2/CNT hybrid electrodes has been achieved. The stable electrochemical performance of the dynamically stretchable pseudocapacitors under various bending/stretching conditions is attributed to a fast redox reaction at the MnO2/CNT hybrid electrodes, indicated by the extremely small relaxation time constant of less than 0.15 s. To increase the mass loading of the pseudo-capacitive materials in stretchable MnO2/CNT electrodes so as to improve the energy density of the pseudocapacitors, a novel all-solid-state sandwich-like capacitor design has been proposed and constructed, which overcomes the loading limitation of active materials and exhibits excellent structural and electrochemical stabilities. This novel component-level design can also be extended for improving the performance of other stretchable electrochemical systems. Afterward, we devote to developing a high operating voltage stretchable supercapacitor by taking advantage of the asymmetric design with MnO2/CNTs as the positive electrode and Fe2O3/CNTs as the negative electrode. Due to the synergistic effects of the two electrodes with an optimized potential window, the stretchable cell voltage is increased to 2 V, and the energy density is significantly enhanced. ☐ Based on the successes on stretchable supercapacitors, a more challenge task for developing reliable and stretchable lithium-ion battery has been tackled. A bottle neck issue has been resolved by applying a low-temperature hydrothermal synthesis to fabricate the stretchable LiMn2O4/CNT cathode. Chemical bonding is confirmed between the active materials and CNT scaffolds for the first time, which is the most important characteristic of the stretchable electrodes in a lithium-ion battery system. ☐ With the unique mechanical and electrochemical properties, a variety of new technologies, such as smart textiles, soft robotics, active medical implants, and stretchable consumer electronics will benefit from the CNT film-based stretchable energy storage devices.
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Keywords
Applied sciences, Carbon, Energy, Film, Nanocomposites, Nanotube, Storage, Stretchable