Design of Flexible Supercapacitors Using Metal Oxide-Decorated Carbon Nanotube Sheet
- PDF / 24,467,449 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 180 Views
Design of Flexible Supercapacitors Using Metal Oxide-Decorated Carbon Nanotube Sheet Meredith C.K. Sellers1, Niels P. Zussblatt1, Andrew P. Friedl1, and Charles P. Marsh1,2 1
US Army Engineer Research and Development Center, Construction Engineering Research Laboratory, 2902 Newmark Drive, Champaign, IL 61822, USA. 2 University of Illinois at Urbana-Champaign, Department of Nuclear Plasma and Radiological Engineering, 216 Talbot Laboratory, 104 South Wright Street, Urbana, IL 61801, USA. ABSTRACT The economical production of flexible, chemically-functionalized carbon nanotube (CNT) electrodes is appealing for the manufacture of electronic textiles with integrated charge storage capability. In this paper, a commercial CNT sheet is treated with 0.02 M potassium permanganate at room temperature to accomplish in-situ deposition of manganese dioxide. The morphology, elemental oxidation states, and crystallinity of the modified CNT sheet are studied using SEM, EDX, XPS, and XRD. Manganese loading is varied from 4 to 20 weight-percent by tuning solution treatment time, and metal oxide hydration state is influenced by thermal annealing at 200 °C. Electrochemical measurements reveal that charge is stored not only via CNT-induced electrical double-layer capacitance, but also through metal oxide-mediated Faradic reactions. The MnO2-decorated CNT sheet exhibits a specific capacitance of 89.6 F/g at 1 A/g, a tenfold enhancement compared to pristine CNT sheet. Overall, this simplified processing approach holds promise for cost-effective incorporation of electrochemical capacitors into functional fabrics for energy-generation applications. INTRODUCTION Electronic textiles—fabrics designed with integrated, active capabilities—offer innovative possibilities for power generation and storage, as well as human interface elements and environmental sensing [1, 2]. Their enhanced properties typically arise from conducting/semiconducting fibers or modification of conventional fibers with nanoelectronics and chemical treatments. In particular, electrochemical capacitors, or supercapacitors, are promising energy storage solutions for incorporation into textiles due to their high charging/discharging rates and small masses. They often contain composites of carbon nanotubes (CNTs), whose high specific surface area and electrical conductivity permit doublelayer capacitance. If a supercapacitor also contains metal oxide nanoparticles, pseudocapacitive behavior may lead to the storage of additional charge in reversible surface reactions [3]. Because the synthesis and assembly of CNT-based supercapacitors comprising binder-enriched slurries of active material, resistance-lowering interlayers, and current collectors is often time-consuming, a simple route to the manufacture of sub-micron thin film electrodes and easily scalable devices is appealing. Recent progress in fullerene processing has facilitated the fabrication of large-area conductive multi-walled CNT sheets [4]. Due to the mechanical integrity of such non-woven sheets, chemical function
