High‐Performance Fiber‐Shaped All‐Solid‐State Asymmetric Supercapacitors Based on Ultrathin MnO₂ Nanosheet/Carbon Fiber Cathodes for Wearable Electronics

Abstract

Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO2 nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g−1 at a current density of 2.5 A g−1 and possess superior cycle stability. When MnO2 nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g−1 and an exceptional energy density of 27.2 Wh kg−1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.

Design and synthesis of hierarchical mesoporous WO3-MnO2 composite nanostructures on carbon cloth for high-performance supercapacitors

“…The Mn 2p core level spectrum reveals two major peaks at binding energies of 654.3 and 642.6 eV related to Mn 2p 1/2 and Mn 2p 3/2 levels, respectively ( Figure 5(c)). The spin-orbit separation of 11.7 eV is in good agreement with previous reports for MnO 2 [24,25]. In addition to this, the fitted O 1s spectrum is characterized by three peaks as shown in Figure 5(d).…”

Recent progress in carbon-based nanoarchitectures for advanced supercapacitors

“…Recently, Yu et al [79] prepared a novel composite structure via directly growing the MnO 2 ultrathin nanosheet arrays on conductive CFs. Then, a fiber-shaped all-solid-state highperformance asymmetric supercapacitor (ASC) was fabricated by adopting it as positive electrodes and the dip-coating graphene on CFs as negative electrodes, respectively.…”

“…On the other hand, the incorporation of nanostructured porous temples or precursor could both increase specific surface area and porosity and further enhance ion adsorption and ion diffusion. Due to their characteristics of light weight and flexibility, CFs are generally appreciated as a promising alternative for assembling flexible, wearable, and portable energy storage devices [79].…”

Carbon nanotubes and manganese oxide hybrid nanostructures as high performance fiber supercapacitors

“…Their wearable nature, low weight, and high flexibility make them suitable for powering portable microelectromechanical devices [4][5][6] or other wearable electronic systems [7][8][9][10][11] . Similar to conventional planar-and cylindrical-shaped supercapacitors, FSCs store energy via either the electrical double layer (EDL) principle or the pseudocapacitance mechanism 1 .…”

“…For the EDL-based FSCs 7,10,[12][13][14][15][16][17] , energy density is governed by the overall capability of the absorbing electrolytes (cations and anions), by having active materials embedded within electrodes. For the pseudo-capacitive FSCs [4][5][6]8,9,[18][19][20][21] , on the other hand, the overall amount of the redox-active materials of the electrodes is key for determining the energy density. Purely EDL-based FSCs with carbon materials arranged as fibers and/or yarns have resulted in high power densities and enhanced cycling stabilities; their energy densities however are often limited to a few mF cm −1 [22][23][24][25] .…”