Designing Knitted Architectures for Applications in Electrochemical Capacitors

In recent years, numerous reports on yarn and fiber capacitors have appeared in the literature. These capacitors have demonstrated excellent electrochemical performance under mechanical stress, making them viable for applications in wearable and flexible electronics [1-3]. However, few of these yarns have been constructed into full size textiles, or tested in lengths longer than a few centimeters. The goal of this study is to explain how the electrochemical performance is effected when capacitive and conductive yarns are fabricated into different knitted structures. We also identify how researchers can design the capacitance and resistance of a textile capacitor to achieve desired device properties. The capacitance and equivalent series resistance for each geometry is determined from galvanostatic cycling, cyclic voltammetry and impedance spectroscopy. Classic sandwiched, interdigitated (Fig. 1) and modified electrode configurations in fabrics will be discussed. All devices are fabricated on a Shima Seiki industrial knitting machine making these geometries viable solutions for any researcher to scale up their capacitive yarns. References: 1. K. Jost, G. Dion, Y. Gogotsi, “Textile Energy Storage in Perspective,” Review Article in Issue on Flexible Energy Storage and Conversion , Journal of Materials Chemistry A , Feb. 2014, DOI: 10.1039/C4TA00203B 2. K. Jost, D. Stenger, C.R. Perez, J.K. McDonough, K. Lian, Y. Gogotsi, G. Dion, “Knitted and screen printed carbon fiber textile-supercapacitors for applications in wearable electronics,” Energy and Environmental Science , 6 (2013) 2698-2705 3. K. Jost, C.R. Perez, J.K. McDonough, V. Presser, M. Heon, G. Dion, Y. Gogotsi, “Carbon Coated Textiles for Flexible Energy Storage in Smart Garments.” Energy and Environmental Science . 4 (2011) 5060-5067 Fig. 1. Front and back photographs of stainless steel yarn knitted into a symmetric interdigitated supercapacitor, where each electrode is physically separated by a non-conductive yarn knitted between the fingers.