skip to main content

Title: Stretchable All‐Gel‐State Fiber‐Shaped Supercapacitors Enabled by Macromolecularly Interconnected 3D Graphene/Nanostructured Conductive Polymer Hydrogels

Nanostructured conductive polymer hydrogels (CPHs) have been extensively applied in energy storage owing to their advantageous features, such as excellent electrochemical activity and relatively high electrical conductivity, yet the fabrication of self‐standing and flexible electrode‐based CPHs is still hampered by their limited mechanical properties. Herein, macromolecularly interconnected 3D graphene/nanostructured CPH is synthesized via self‐assembly of CPHs and graphene oxide macrostructures. The 3D hybrid hydrogel shows uniform interconnectivity and enhanced mechanical properties due to the strong macromolecular interaction between the CPHs and graphene, thus greatly reducing aggregation in the fiber‐shaping process. A proof‐of‐concept all‐gel‐state fibrous supercapacitor based on the 3D polyaniline/graphene hydrogel is fabricated to demonstrate the outstanding flexibility and mouldability, as well as superior electrochemical properties enabled by this 3D hybrid hydrogel design. The proposed device can achieve a large strain (up to ≈40%), and deliver a remarkable volumetric energy density of 8.80 mWh cm−3(at power density of 30.77 mW cm−3), outperforming many fiber‐shaped supercapacitors reported previously. The all‐hydrogel design opens up opportunities in the fabrication of next‐generation wearable and portable electronics.

more » « less
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Materials
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. 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
  2. Carbon fiber-based structural lithium-ion batteries are attracting significant attention in the automotive and aerospace industries due to their dual capability of energy storage and mechanical load-bearing, leading to weight reduction. These batteries utilize lightweight carbon fiber (CF) composites, which offer excellent stiffness, strength-to-weight ratios, and electrical conductivity. Polyacrylonitrile-based CFs, comprising graphitic and amorphous carbon, are particularly suitable for Li-ion battery applications as they allow the storage of lithium ions. However, integrating lithium iron phosphate (LFP) into CFs poses challenges due to complex lab-scale processes and the use of toxic dispersants, hindering large-scale industrial compatibility. To address this, we investigate the development of water-based LFP-integrated CF structural Li-ion batteries. Homogeneous suspensions are created using cellulose nanocrystals (CNCs) to form hybrid structures. The battery system employs LFP-modified CF as the cathode, unsized CF as the anode, and a water-based electrolyte. The LFP-CNC-graphene nanoplatelet (GNP) hybrids are coated onto CFs through immersion coating. Scanning electron microscopy (SEM) images confirm the well-dispersed and well-adhered LFP-CNC-GNP structures on the CF surface, contributing to their mechanical interlocking and electrochemical performance. The batteries demonstrate a specific energy density of 62.67 Wh/kg and a specific capacity of 72.7 mAh/g. Furthermore, the cyclic voltammetry experiments reveal the stability of the LFP-CNC-GNP-coated CF batteries over 200 cycles without degradation. This research enables the engineering of hybrid nanostructured battery laminates using novel LFP-CNC-GNP-coated CFs, opening avenues for the development of innovative Li-ion structural batteries. 
    more » « less
  3. Recently, graphene fibers derived from wet-spinning of graphene oxide (GO) dispersions have emerged as viable electrodes for fiber-shaped supercapacitors (FSCs) and/or batteries, wherein large surface area, high electrical conductivity, and sufficient mechanical strength/toughness are desired. However, for most fiber electrodes reported so far, compromises have to be made between energy-storage capacity and mechanical/electrical performance, whereas a graphene fiber with high capacity and sufficient toughness for direct machine weaving or knitting is yet to be developed. Inspired by the alum mordant used for natural dyes in the traditional textile dyeing industry, our research group has synthesized wet-spun GO fibers and coagulated them with different multivalent cations ( e.g. Ca 2+ , Fe 3+ , and Al 3+ ), where dramatically different fiber morphologies and properties have been observed. The first principles density functional theory has been further employed to explain the observed disparities via cation–GO binding energy calculation. When assembled into solid-state FSCs, Al 3+ -based reduced GO (rGO) fibers offer excellent stability against bending, and a specific capacitance of 148.5 mF cm −2 at 40 mV s −1 , 1.4, 4.8, and 6.8 times higher than that of the rGO fibers based on other three coagulation systems (Fe 3+ , Ca 2+ and acetic acid), respectively. The volumetric energy density of the Al 3+ -based FSC is up to 13.26 mW h cm −3 , while a high power density of 250.87 mW cm −3 is maintained. 
    more » « less
  4. Abstract

    Stretchable supercapacitors (SCs) have attracted significant attention in developing power‐independent stretchable electronic systems due to their intrinsic energy storage function and unique mechanical properties. Most current SCs are generally limited by their low stretchability, complicated fabrication process, and insufficient performance and robustness. This study presents a facile method to fabricate arbitrary‐shaped stretchable electrodes via 4D printing of conductive composite from reduced graphene oxide, carbon nanotube, and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate. The electrode patterns of an arbitrary shape can be deposited onto prestretched substrates by aerosol‐jet printing, then self‐organized origami (ridge) patterns are generated after releasing the substrates from holding stretchers due to the mismatched strains. The stretchable electrodes demonstrate superior mechanical robustness and stretchability without sacrificing its outstanding electrochemical performance. The symmetric SC prototype possesses a gravimetric capacitance of ≈21.7 F g−1at a current density of 0.5 A g−1and a capacitance retention of ≈85.8% from 0.5 to 5 A g−1. A SC array with arbitrary‐shaped electrodes is also fabricated and connected in series to power light‐emitting diode patterns for large‐scale applications. The proposed method paves avenues for scalable manufacturing of future energy‐storage devices with controlled extensibility and high electrochemical performance.

    more » « less
  5. Abstract

    Along with the quick development of flexible and wearable electronic devices, there is an ever‐growing demand for light‐weight, flexible, and wearable power sources. Because of the high power density, excellent cycling stability and easy fabrication, flexible supercapacitors are widely studied for this purpose. Graphene‐based nanomaterials are attractive electrode materials for flexible and wearable supercapacitors owing to their high surface area, good mechanical and electrical properties, and excellent electrochemical stability. The 2D structure and high aspect ratio of graphene nanosheets make them easy to assemble into films or fibers with good mechanical properties. In recent years, enormous progress has been made in developing flexible and wearable graphene‐based supercapacitors. Here, the material and structure design strategies for developing film‐shaped and emerging fiber‐shaped flexible supercapacitors based on graphene nanomaterials are summarized.

    more » « less