Abstract
AbstractFlexible capacitors are a promising power source for foldable and biological electronic devices. Although various materials and device structures have been explored, they are still limited by low energy densities and slow rate capabilities compared to their rigid counterparts. Here, asymmetric carbon nanohorns are proposed as an active material to fabricate flexible solid‐state carbon wire (CW)‐based electrochemical supercapacitors (ss‐CWECs) which exhibit high power density and ultra‐low cutoff frequency. By controlling the electric arc reaction at low temperature (77 K), asymmetric single‐wall carbon nanohorns (SWCNHs) are synthesized with high yield. Based on microscopy and electrochemical characterization, the fundamental reaction mechanism in polyvinyl‐based electrolyte system is elucidated, as being associated with deprotonation reaction at acid, base, and elevated temperature conditions. Additionally, by using activated carbon, multi‐walled carbon nanotubes, and SWCNHs as hybrid electrode materials (5:1:1), remarkable specific length capacitance of 48.76 mF cm−1 and charge–discharge stability (over 2000 times cycles) of ss‐CWECs are demonstrated, which are the highest reported to date. Furthermore, a high‐pass filter for eliminating ultra‐low electronic noise is demonstrated, which enables an optical Morse Code communication system to be operated. Current results confirm the SWCNHs as promising materials for high‐performance soft electronics and energy storage applications.
Highlights
Introduction electronic devices various materials and device structures have been explored, they are still limited by low energy densities and slow rate capabilities compared to their rigid counterparts
By employing Activated carbon (AC), multi-walled carbon nanotubes (CNTs), and single-walled carbon nanohorns (AC/MWCNTs/single-wall carbon nanohorns (SWCNHs)) as hybrid electrode material in ss-CWECs, we demonstrate remarkable specific length capacitance and excellent cycling reliability going beyond results reported to date
Poly(vinyl alcohol) (PA)/KOH as a solid-state electrolyte and hybrid AC/MWCNT/SWCNHs coated on a carbon fiber backbone as the electrodes are used to demonstrate soft ss-CWECs, which
Summary
SWCNHs were produced by an arc discharge method via immersed carbon in liquid nitrogen.[19]. This peak can be seen in the case of PA/KOH, while none appears on PA and PA/H3PO4 room temperature samples This demonstrates that PA treated with KOH exhibits more crystallized morphology, which is consistent with x-ray powder diffraction results (Figure S4, Supporting Information). The processing and operating temperature of an electrolyte can influence the performance of ESCs, as many electrochemical or chemical reactions are closely related to temperature.[31] It should be noted that the intensity of the O H stretching peak at 3350 cm−1 decreased after the pure PA film was annealed. As seen in the Scheme 2, within PA/H3PO4 medium, olefin moieties will be generated in PA deprotonation reactions, but radicals will be the main product in its reactions with KOH, which result in different wettability properties and impacts on physical electrolyte contact with electrodes. We select PA/KOH as the electrolyte for fabricating ss-CWECs which can provide better electrochemical performance than PA/H3PO4
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