skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Thursday, June 13 until 2:00 AM ET on Friday, June 14 due to maintenance. We apologize for the inconvenience.


Title: Facile Fabrication of Multivalent VO x /Graphene Nanocomposite Electrodes for High‐Energy‐Density Symmetric Supercapacitors
Abstract

Supercapacitors have emerged as one of the leading energy‐storage technologies due to their short charge/discharge time and exceptional cycling stability; however, the state‐of‐the‐art energy density is relatively low. Hybrid electrodes based on transition metal oxides and carbon‐based materials are considered to be promising candidates to overcome this limitation. Herein, a rational design of graphene/VOxelectrodes is proposed that incorporates vanadium oxides with multiple oxidation states onto highly conductive graphene scaffolds synthesized via a facile laser‐scribing process. The graphene/VOxelectrodes exhibit a large potential window with a high three‐electrode specific capacitance of 1110 F g–1. The aqueous graphene/VOxsymmetric supercapacitors (SSCs) can reach a high energy density of 54 Wh kg–1with virtually no capacitance loss after 20 000 cycles. Moreover, the flexible quasi‐solid‐state graphene/VOxSSCs can reach a very high energy density of 72 Wh kg–1, or 7.7 mWh cm–3, outperforming many commercial devices. WithRct < 0.02 Ω and Coulombic efficiency close to 100%, these gel graphene/VOxSSCs can retain 92% of their capacitance after 20 000 cycles. The process enables the direct fabrication of redox‐active electrodes that can be integrated with essentially any substrate including silicon wafers and flexible substrates, showing great promise for next‐generation large‐area flexible displays and wearable electronic devices.

 
more » « less
NSF-PAR ID:
10388389
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Energy Materials
Volume:
11
Issue:
26
ISSN:
1614-6832
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    For the sustainable growth of future generations, energy storage technologies like supercapacitors and batteries are becoming more and more common. However, reliable and high‐performance materials’ design and development is the key for the widespread adoption of batteries and supercapacitors. Quantum dots with fascinating and unusual properties are expected to revolutionize future technologies. However, while the recent discovery of quantum dots honored with a Nobel prize in Chemistry, their benefits for the tenacious problem of energy are not realized yet. In this context, herein, chemical‐composition tuning enabled exceptional performance of NiCo2O4(NCO)/graphene quantum dots (GQDs) is reported, which outperform the existing similar materials, in supercapacitors. A comprehensive study is performed on the synthesis, characterization, and electrochemical performance evaluation of highly functional NCO/GQDs in supercapacitors delivering enhanced energy efficiency. The high‐performance, functional NCO/GQDs electrode materials are synthesized by the incorporation of GQDs into NCO. The effect of variable amount of GQDs on the energy performance characteristics of NCO/GQDs in supercapacitors is studied systematically. In‐depth structural and chemical bonding analyses using X‐ray diffraction (XRD) and Raman spectroscopic studies indicate that all the NCO/GQDs composites crystallize in the spinel cubic phase of NiCo2O4while graphene integration evident in all the NCO/GQDs. The scanning electron microscopy imaging analysis reveals homogeneously distributed spherical particles with a size distribution of 5–9 nm validating the formation of QDs. The high‐resolution transmission electron microscopy analyses reveal that the NCOQDs are anchored on graphene sheets, which provide a high surface area of 42.27 m2g−1and high mesoporosity for the composition of NCO/GQDs‐10%. In addition to establishing reliable electrical connection to graphene sheets, the NCOQDs provide reliable 3D‐conductive channels for rapid transport throughout the electrode as well as synergistic effects. Chemical‐composition tuning, and optimization yields NCO/GQDs‐10% to deliver the best specific capacitance of 3940 Fg−1at 0.5 Ag−1, where the electrodes retain ≈98% capacitance after 5000 cycles. The NCO/GQD‐10%//AC asymmetric supercapacitor device demonstrates outstanding energy density and power density values of 118.04 Wh kg−1and 798.76 W kg−1, respectively. The NCO/GQDs‐10%//NCO/GQDs‐10% symmetric supercapacitor device delivers excellent energy and power density of 24.30 Wh kg−1and 500 W kg−1, respectively. These results demonstrate and conclude that NCO/GQDs are exceptional and prospective candidates for developing next‐generation high‐performance and sustainable energy storage devices.

     
    more » « less
  2. Abstract

    All‐solid‐state flexible asymmetric supercapacitors (ASCs) are developed by utilization of graphene nanoribbon (GNR)/Co0.85Se composites as the positive electrode, GNR/Bi2Se3composites as the negative electrode, and polymer‐grafted‐graphene oxide membranes as solid‐state electrolytes. Both GNR/Co0.85Se and GNR/Bi2Se3composite electrodes are developed by a facile one‐step hydrothermal growth method from graphene oxide nanoribbons as the nucleation framework. The GNR/Co0.85Se composite electrode exhibits a specific capacity of 76.4 mAh g−1at a current density of 1 A g−1and the GNR/Bi2Se3composite electrode exhibits a specific capacity of 100.2 mAh g−1at a current density of 0.5 A g−1. Moreover, the stretchable membrane solid‐state electrolytes exhibit superior ionic conductivity of 108.7 mS cm−1. As a result, the flexible ASCs demonstrate an operating voltage of 1.6 V, an energy density of 30.9 Wh kg−1at the power density of 559 W kg−1, and excellent cycling stability with 89% capacitance retention after 5000 cycles. All these results demonstrate that this study provides a simple, scalable, and efficient approach to fabricate high performance flexible all‐solid‐state ASCs for energy storage.

     
    more » « less
  3. Abstract

    Supercapacitors have attracted enormous attention for energy storage in both academic and industrial sectors in the past years. In this study, all‐solid‐state flexible asymmetric supercapacitors (ASCs) without any binder, incorporated with the hydrophilic carbon cloth (HCC) with MnO2nanocomposite (HCC@MnO2) as the positive electrode, the HCC with polypyrrole (PPy) (HCC@PPy) as the negative electrode, and polyvinyl alcohol (PVA)–LiCl gel as both gel electrolyte and separator, are reported. The HCC@MnO2and HCC@PPy electrodes are prepared by direct deposition of either MnO2nanoparticles or PPy nanofilms on the HCC through a simple, facile, and controllable electrochemical deposition method, respectively. The HCC@MnO2and HCC@PPy electrodes provide rich contact area for gel electrolyte, facilitating the rapid delivery of electrolyte ions, and also minimize the resistance of ASCs. As a result, all‐solid‐state flexible binder‐free HCC@MnO2//HCC@PPy ASCs exhibit a large operating voltage of 1.8 V, high energy density of 28.2 Wh kg−1at the power density of 420.5 W kg−1, and excellent cycling stability (91.2% capacitance retention after 5000 cycles). The present study provides a facile, scalable, and efficient approach to fabricate all‐solid‐state ASCs with high electrochemical storage performance for flexible electronics.

     
    more » « less
  4. Abstract

    Light‐weight graphite foam decorated with carbon nanotubes (dia. 20–50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g−1, 22.85 and 12.58 Wh kg−1, 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4–0.45 g cm−3) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices.

     
    more » « less
  5. Nitrogen-doped, 3-dimensional graphene (N3DG), synthesized as a one-step thermal CVD process, was further functionalized with atmospheric pressure oxygen plasma. Electrodes were fabricated and tested based on the functionalized N3DG. Their characterization included scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmet–Teller (BET), and electrochemical measurements. The tested electrodes revealed a 208% increase in the specific capacitance compared to pristine 3D graphene electrodes in a three-electrode configuration. The performed doping and plasma treatment enabled an increase in the electrode‘s surface area by 4 times compared to pristine samples. Furthermore, the XPS results revealed the presence of nitrogen and oxygen functional groups in the doped and functionalized material. Symmetric supercapacitors assembled from the functionalized 3D graphene using aqueous and organic electrolytes were compared for electrochemical performance. The device with ionic electrolyte EMIMB4 electrolyte exhibited a superior energy density of 54 Wh/kg and power density of 1224 W/kg. It also demonstrated a high-cyclic stability of 15,000 cycles with a capacitance retention of 107%. 
    more » « less