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Constructing Ultrahigh-Capacity Zinc–Nickel–Cobalt Oxide@Ni(OH)2 Core–Shell Nanowire Arrays for High-Performance Coaxial Fiber-Shaped Asymmetric Supercapacitors

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journal contribution
posted on 07.11.2017, 00:00 by Qichong Zhang, Weiwei Xu, Juan Sun, Zhenghui Pan, Jingxin Zhao, Xiaona Wang, Jun Zhang, Ping Man, Jiabin Guo, Zhenyu Zhou, Bing He, Zengxing Zhang, Qingwen Li, Yuegang Zhang, Lai Xu, Yagang Yao
Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc–nickel-cobalt oxide (ZNCO)@Ni­(OH)2 nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm3 (10.678 F/cm2) at a current density of 1 mA/cm2, These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm2) and four times higher than Ni­(OH)2/CNTF electrodes (2.55 F/cm2). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni­(OH)2 NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly­(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm3 (573.75 mF/cm2) and an exceptional energy density of 33.66 mWh/cm3 (204.02 μWh/cm2) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices.