(Invited) Fabricating High Performance Fiber-Shaped Supercapacitor from the State-of-the-Art Carbon Nanotube Fiber

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Fiber shaped supercapacitors are being actively developed as one of the most robust power supplies available for wearable and portable applications [1,2]. The development of fiber shaped current collector with excellent flexibility, light weight, chemical stability and good conductivity has become very important. CNT fibers (CNTF) has been highlighted as a superior core component, with highly densified and aligned structure [3]. Newly developed state-of-the-art CNTF exhibits unprecedentedly high performance, such as high strength (100 cN tex-1), electrical conductivity (2 MS m-1) and excellent flexibility (50% knot efficiency), which could not be realized in the previous version of CNTF [4]. Therefore, novel strategy must be developed to be applied for this utmost CNTF with low surface area and very smooth surface with few functional groups.In this talk, we introduce a simple and efficient strategy to construct a hybrid 3D structure on a fiber-shaped support material for a high-performance FSSC [5]. A state-of-the-art liquid crystal spun CNTF with a highly densified structure and high electrical conductivity was utilized as the basic core component of FSSC. To fabricate a stereoscopic hybrid 3D structure, GO and/or Mxene, which are the most representative 2D materials, were vertically attached to CNTF by electrophoretic deposition as a hierarchical scaffold for further hybridization. It was very important to further deposit pseudocapacitive active materials immediately after the deposition of GO to solidify and maintain the 3D structure of GO, which is simple but highly efficient. The prepared Ni-Co oxide/VG@CNTF (NC/VG@CNTF) hybrid electrode exhibits prominent specific capacitance (1724 F g-1 at 1 A g-1, total electrode weight) and mechanical durability (93.1% capacitance retention at 5,000 bending cycles). Remarkably, FCCSs fabricated with asymmetric configurations show unprecedentedly high energy and power densities, demonstrating the superiority of our proposed strategy (energy density of 65 Wh kg-1 at a power density of 100 kW kg-1). This demonstrates that state-of-the-art CNTF can be an excellent candidate suitable for various wearable and flexible applications. Acknowledgements This research was supported by Korea Institute of Science and Technology (KIST) Institutional Program and Open Research Program (ORP), and grants from the National Research Foundation of Korea government (NRF, 2019R1A5A8080326).