Highly loaded MXene/carbon nanotube yarn electrodes for improved asymmetric supercapacitor performance
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Research Letter
Highly loaded MXene/carbon nanotube yarn electrodes for improved asymmetric supercapacitor performance Jong Woo Park, Dong Yeop Lee, Hyunsoo Kim, and Jae Sang Hyeon, Center for Self-Powered Actuation, Department of Biomedical Engineering, Hanyang University, Seoul 04763, Korea Monica Jung de Andrade, and Ray H. Baughman, The Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX 75083, USA Seon Jeong Kim, Center for Self-Powered Actuation, Department of Biomedical Engineering, Hanyang University, Seoul 04763, Korea Address all correspondence to Seon Jeong Kim at [email protected] (Received 19 November 2018; accepted 9 January 2019)
Abstract Yarn-type supercapacitors should have high energy density in small given spaces, and the one attempt among many is to comprise the electrodes asymmetrically. However, the low capacitance of conventional materials causes the widened operating voltage useless. In this study, we have utilized a novel material MXene with carbon nanotubes (CNTs) to make highly loaded MXene/CNT yarn electrodes, which exhibited a remarkable areal capacitance. With MnO2/CNT biscrolled cathode and PVA/LiCl gel electrolyte, the plied asymmetric yarn supercapacitor had energy density of 100 µWh/cm2. The yarn supercapacitor could operate under mechanical deformations without performance degradation.
Yarn-type one-dimensional electrochemical energy storage devices which are lightweight, flexible, and even stretchable are gaining much interest due to the development of wearable electronics and flexible energy harvesters.[1–3] Among the various yarn-type energy storage systems, an asymmetric yarn supercapacitor is worth paying attention to. It normally utilizes an aqueous electrolyte which is less harmful and still can operate at a high voltage of up to 2 V due to its asymmetry in electrodes. The high operating potential gives much higher energy density to the device, which is especially important in yarn-type energy storage media because of its limited footprint. However, there is a limiting factor for applying an asymmetric configuration to yarn supercapacitors, the low capacitance negative electrode materials. Materials which store electrical energy by electrochemical double layer capacitance, such as carbon materials [carbon nanotubes (CNTs), ordered mesoporous carbon, reduced graphene oxide, etc.][4–6] have often been utilized as negative electrode materials, resulting in a low energy density of the supercapacitor. Recently, other materials (PPy, Fe3O4, VN, MoS2, etc.) that have a higher capacitance than conventional carbon materials have been used to enhance the performance of yarn-type asymmetric supercapacitors.[7–13] MXene, especially Ti3C2Tx in which Tx denotes surface functional groups (–O, –H, –F), is an emerging material for its graphene-like two-dimensional shape and special properties, and a high volumetric capacitance (1500 F/cm3). MXene is
a promising material for yarn-type energy storage systems, to reduce their overall sizes.[14–19] It has a nega
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