High-performance Flexible Supercapacitors Research Articles

CNT@SrTiO3 Nanocomposites Synthesized by In Situ Reaction for a High-Performance Flexible Supercapacitor.

This study presents the in situ synthesis of CNT@SrTiO3 nanocomposite films for the development of high-performance flexible supercapacitors. The synthesis process involved the use of organic-inorganic hybrid polymers containing metal elements as precursors for thermal decomposition reaction under a reducing atmosphere. Due to the formation of chemical bonding between Ti elements and the CNTs, the interface between STO and CNT surface could provide additional active sites for ion transport and storage. Thereby, the incorporation of SrTiO3 nanoparticles into CNTs enhanced the electrochemical performance of the resulting nanocomposite membranes. To further investigate the influence of STO content and synthesis temperature, we conducted a detailed analysis. The findings indicated that the CNT@STO film with 25% STO content, synthesized at 700 °C, and possessed optimal performance with an areal capacitance of 6682 mF·cm-2 at 5 mV·s-1. Furthermore, a symmetrical flexible supercapacitor assembled by two CNT@STO-25 electrodes demonstrated strong application potential in wearable devices, owing to its long cycle life, excellent flexibility, and high energy density of 430.2 μWh·cm-2 (corresponding power density of 4.5 mW·cm-2). Based on these results, we believe that this study provides a fresh idea for the development of novel flexible energy storage materials.

Construction of novel coaxial electrospun polyetherimide@polyaniline core-shell fibrous membranes as free-standing flexible electrodes for supercapacitors

Designing porous and flexible electrodes with excellent electrochemical properties is crucial to fabricate high-performance flexible supercapacitors. Conductive polymer-based electrospun fibers are expected to be an ideal material for constructing flexible electrodes due to the enormous specific surface area, unique pore structure and inherent flexibility. However, the exploration of such electrospun fibers with facile preparation methods and high areal capacitance remains challenging. Herein, a novel polyetherimide@polyaniline core-shell fibrous membranes (PEI@PANI CFMs) is fabricated via simply coaxial electrospinning and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) secondary doping. With the aid of polyetherimide, highly concentrated emeraldine base polyaniline (EB-PANI) can be perfectly wrapped on the surface of fibers without any spinning assistants, ensuring the well-developed pore structures, superior hydrophilicity, good electrical conductivity and outstanding mechanical flexibility. Benefiting from the synergistic effect of structure and constituents, such flexible PEI@PANI CFMs as electrode materials can provide more accessible electrochemical active sites and decrease the ion diffusion resistance. Therefore, the PEI@PANI CFMs present outstanding areal capacitance of 1159.9 mF cm−2 and remarkable energy density of 46.91 μW h cm−2 in the electrodes and symmetric supercapacitors, demonstrating great potential for applications in flexible energy storage field. This fabrication strategy provides a simple and practicable way to manufacture polyaniline-based fibrous membranes for high-performance flexible electrode materials.

Graphene nanoribbons on three-dimensional carbon nanomaterials for high-performance flexible zinc-ion hybrid supercapacitors

The rational design of electrodes is crucial for the performance and practical applications of flexible zinc-ion hybrid supercapacitors (ZIHS). In this paper, we have developed an easy strategy to design electrodes based on current collectors with vertically aligned nanohole arrays on their surfaces. Zinc nanosheet arrays were deposited on a porous aluminum oxide/aluminum (AAO) film to form a Zn@AAO anode. Graphene nanoribbons (GR) unzipped for carbon nanotubes were coated on a unique three-dimensional carbon pre-coated AAO (CAAO) film to form a GR@CAAO composite cathode. After assembling with ZnSO4/gelatin gel electrolyte, a quasi-solid Zn@AAO//GR@CAAO ZIHS with a potential of 1.6 V was obtained. The as-prepared ZIHS exhibits an areal capacitance of 156 mF cm−2 at 0.25 mA cm−2 and a high energy density of 56 μW h cm−2 at 0.202 mW cm−2, an excellent flexibility as well as long cycle life.

Xylan derived carbon sphere/graphene composite film with low resistance for supercapacitor electrode

Reduced graphene oxide (rGO) films suffer from low capacitance for inner unreduced oxygen functional groups, restacking of sheets and high contact resistance. Herein, carbon spheres derived from renewable xylan were added to graphene oxide with large sheet area to fabricate film by gelation and filtration, followed by in situ reduction for high-performance flexible supercapacitor. rGO film with transverse size about 13 μm showed a good specific capacitance of 967 mF/cm2 at a scanning rate of 5 mV/s and increased to 1786 mF/cm2 by in situ reducing its inner part, which generally remained oxidized due to outer hindering from hydrophobic graphene. Then, by hydrothermal carbonization of xylan and activation with KOH, activated carbon sphere (aXCS) was prepared, which had a diameter of 150–200 nm and a specific capacitance of 270 F/g. The aXCS acted as spacer and connector to avoid restacking of graphene sheets and decrease interlayer contact resistance, resulting 94% increase in capacitance performance from rGO film to aXCS/rGO film. Therefore, combined in situ reduction and enhancement through compositing aXCS, the final film (aXCS/rGO-AA) showed a boosted specific capacitance of 755 mF/cm2 at 1 mA/cm2 in double electrode system, power density of 22.5–2250 mW/cm2, and energy density of 11.88–25.2 mWh/cm2. Meanwhile, aXCS/rGO-AA had outstanding cycling stability that its specific capacitance maintained 108.7% after 10,000 cycles of charge–discharge, showing promising potential in wearable and portable electronics.Graphical abstract

High-performance stretchable flexible supercapacitor based on lignosulfonate/Prussian blue analogous nanohybrids reinforced rubber by direct laser writing

With the advent of the Internet-of-Things (IoT) era, flexible supercapacitors (F-SC) have emerged as one of the most promising power sources for wearable devices. However, the rapid fabrication of F-SC with high energy density and stretchability remains a challenge. In this study, an intrinsically stretchable rubber-based supercapacitor, for the first time, was fabricated from Co-Fe Prussian blue analogous (Co-Fe PBA)/sodium lignosulfonate (LS) nanohybrids (PBA-LS) reinforced carboxylated nitrile rubber (XNBR) by direct laser writing (DLW) technology. Under the transient photothermal action of programable high-energy laser irradiation, biomass-derived LS among PBA-LS nanohybrids was directly transformed into patterned porous graphitized carbon on the surface of PBA-LS/XNBR substrates (PLX), while Co-Fe PBA was pyrolyzed into bimetallic compound nanoparticles as pseudocapacitive materials embedded into the carbon framework. Benefiting from the in-situ doping of the bimetallic compounds within the LS-derived carbon framework on flexible PLX substrates, the rubber-based electrode showed an excellent electrochemical activity, reversibility and stability. Accordingly, symmetric interdigitated F-SCs could be rapidly fabricated by DLW, showing high areal capacitance of 479.08 mF cm−2 and energy density of up to 80.07 μWh cm−2. To achieve their stretchability, “island-bridge” structured stretchable F-SCs (SF-SC) were fabricated through Kirigami technology and liquid metal linkage. The rubber-based SF-SC demonstrated high voltage window and energy density as well as excellent electromechanical stability for powering small devices. This work provided new insights into the scalable fabrication of flexible energy storage devices by DLW, and it was of significant importance for the development of rubber-based flexible electronics and the valorization of biomass LS.

Rational design of integrated high-performance flexible zinc-ion hybrid supercapacitors based on electroactive biomass regulated graphene oxide

Rational design of integrated high-performance flexible zinc-ion hybrid supercapacitors based on electroactive biomass regulated graphene oxide

Evolving non-aggregated ZIF-8 nanoparticles into hierarchically porous hollow carbon nanofibers for high-performance flexible zinc-ion hybrid supercapacitor

Zinc-ion hybrid supercapacitors are garnering widespread interest in wearable energy storage devices due to their high power density, intrinsic safety and cost-effectiveness. However, the primary obstacle to their progress lies in the scarcity of cathode materials that concurrently demonstrate excellent flexibility and high energy density. Herein, we deliberately design a coaxial electrospinning ZIF-8 derived hollow carbon nanofiber film electrode (C-PAN(ZIF-8)@PVP) to achieve high-performance flexible ZHSCs. The distinctive configuration of C-PAN(ZIF-8)@PVP electrode comprises a shell of homogeneously distributed ZIF-8 derived porous carbon nanoparticles, which are bound together by N-doped carbon fibers derived from polyacrylonitrile (PAN), and a channel through the fiber created by the decomposition of polyvinylpyrrolidone (PVP). This unique architecture coupled with N, O co-doping bestows ample electrolyte infiltration, complete exposure of active sites, and a rapid pathway for electron conduction, resulting in facilitated ion diffusion kinetics, abundant active sites and enhanced electronic conductivity of the C-PAN(ZIF-8)@PVP electrode. As a result, the assembled ZHSC delivers a high reversible capacity of 116 mAh g−1 at 0.1 A g−1 and remarkable capacity retention of 100% over 4000 cycles at 5 A g−1. Moreover, it exhibits exceptional mechanical flexibility, capable of delivering stable output under arbitrary deformation. The intricate structural design strategy offers valuable insights for the development of high-performance electrode materials.

Polyaniline with manganese based mixed chalcogenides (MnSSe-HT-PANI) heterostructure for the development of high-performance flexible supercapacitor

Mixed ligand systems in transition metal based dichalcogenides (TMDs) are seems to be the most interesting electroactive materials towards a renewable energy storage perspective. Chemical substitution of sulphur-based TMDs with selenium atoms via a one-step solvothermal technique has demonstrated the facile way to develop manganese sulfoselenide (MnS1-xSex) microclusters in an aqueous solution. The stoichiometric variation of S vs Se can be controlled via Se concentration in an aqueous Na2S solution. The optimized Se concentration results in the formation of high crystalline MnS0.1MSe0.025M at which the secondary growth of polyaniline nanorods has been decorated (MnSSe-HT-PANI) to protect and enhance the electrochemical performance of the as-designed electroactive material. The as-prepared heterostructure with good crystallinity and homogeneous particle size distribution allows the significant improvement of the migration of charge carriers from electrode to electrolyte during electrochemical reactions. The maximum specific capacity of MnSSe-HT-PANI is calculated to be 1250 C g−1@0.1 A g−1 which is 1.7 times improved as compared to bare MnSSe-HT (701 C g−1@0.1 A g−1) in an aqueous electrolyte. The corresponding device on a flexible carbon cloth template delivers the maximum specific capacitance/capacity of 148.4 F g−1/222.6 C g−1@ 1.5 A g−1 current density from GCD analysis having maximum energy and power density of 46.37 Wh kg−1 and 15.04 kW kg−1, respectively. The device shows a capacitance retention of 88.32 % after 10K cycles with a coulombic efficiency of 90.12 %. The device's performance remains unaltered under rigorous mechanical stress with a bending angle of 0° to 135°. The high performance and stability of the cell are mainly due to the coating of electroactive materials with high molecular weight polyaniline (PANI) based conducting polymer matrix. This strategy to improve the electrochemical performance of the as-designed heterostructure can drag the industrial attention to develop flexible portable energy storage systems.

Screen-printed MXene-based all-solid-state textile supercapacitors

Textile-based supercapacitors (TSCs) have drawn increasing attention in recent years owing to their potential applications in wearable electronics. However, it remains a critical challenge to increase the energy density of TSCs. Herein, we develop a screen-printing strategy to scalable construct high-performance MXene-based all-solid-state textile supercapacitors, which exhibit excellent electrochemical performance, including high specific capacitance (4979.2 mF cm−2) and energy density (62.2 µWh cm−2). The electrochemical performance of assembled MXene-based TSCs is superior to the-state-of-the-art TSCs. This work provides a new strategy for fabricating high-performance flexible supercapacitors and paves the way for the development of wearable energy storage devices.

High-performance flexible asymmetric supercapacitors based on Hy-NiCoS/CNTs composites on porous graphene films

This research focused on the synthesized NiCoS/CNT composites by a hydrothermal method using thiourea and then drop-cast on laser-induced graphene (LIG) with porous structures for an active electrode of flexible asymmetric supercapacitors. Surface topography, cross-sectional outline, chemical structure and properties, and electrical properties of LIG, NiCoS, and Hy-NiCoS materials were measured and analyzed. In the two-electrode device, the Hy-NiCoS electrode has a high areal capacitance of 817 mF/cm2 under 0.5 mA/cm2 current density and a low internal resistance of 5.19 Ω. Furthermore, the prepared flexible asymmetric supercapacitors (Hy-NiCoS/AC) demonstrated excellent energy density of 0.017 mWh/cm2, power density of 3.2 mW/cm2, and areal capacitance of 85 mF/cm2 under 0.5 mA/cm2 current density. When the bending angles were 0°, 45°, and 90°, the areal capacitances of the prepared flexible asymmetric supercapacitors were 77.7, 75.0, and 70.8 mF/cm2, respectively. There is no obvious capacitance decay even at a large bending angle of 90°, which means that the asymmetric supercapacitor has excellent flexibility and stability. Based on the flexible asymmetric supercapacitors with excellent electrochemical performance, the proposed supercapacitors can be widely used in wearable electronic devices and healthcare products.

Preparation of NiMoO4 porous nanosheets by freezing method as adhesive-free electrodes for high-performance flexible supercapacitors

Preparation of NiMoO4 porous nanosheets by freezing method as adhesive-free electrodes for high-performance flexible supercapacitors

High-performance flexible solid-state asymmetric supercapacitor with NiCo2S4 as a cathode and a MXene-reduced graphene oxide sponge as an anode

Ti3C2 MXenes have revealed immense potential in energy storage systems.

Lead-free halide perovskites for high-performance thin-film flexible supercapacitor applications

The growing interest in smart portable electronic devices demands a flexible and lightweight power supply.

In situ growth of binder-free CoNi0.5-MOF/CC electrode for high-performance flexible solid-state supercapacitor application.

Metal organic frameworks (MOFs) with binder-free electrodes have shown promise for portable electrochemical energy storage applications. However, their low specific capacitance and challenges associated with the attachment of active materials to the substrate constrain their practical utility. In this research, we prepared a CoNi0.5-MOF/CC electrode by in situ growth of CoNi0.5-MOF on an H2O2-pretreated carbon cloth (CC) without using any binder. It exhibits a higher specific capacitance of 1337.5 F g-1 than that of CoNi0.5-MOF (∼578 F g-1) at a current density of 1 A g-1 and an excellent rate ability of 88% specific capacitance retention at a current density of 10 A g-1 after 6000 cycles. The as-assembled flexible asymmetric solid-state supercapacitor based on the CoNi0.5-MOF/CC positive electrode and a nitrogen-doped graphene (N-Gr) negative electrode exhibits an energy density of 61.46 W h kg-1 at a power density of 1244.56 W kg-1 and holds a stable capacitance of ∼125 F g-1 at 1 A g-1 when the flexible supercapacitor is bent, showing great potential for flexible electronics application. The H2O2 is indicated to play an important role, enhancing the adhesion of CoNi0.5-MOF on CC and reducing its charge transfer resistance by functionalizing the carbon fiber during the pretreatment of the CC matrix. The results provide a great way to prepare a flexible asymmetric solid-state supercapacitor with both high power density and high energy density for practical application.

Ultrathin redox active hydrogel electrolytes for high performance flexible supercapacitors

Flexible supercapacitors (FSCs) based on hydrogel electrolytes have the advantages of high ionic conductivity, no liquid leakage, flexibility and versatility, making them the most promising power source for wearable devices....

Advanced MnOx/MnWO4 hetero-nanoflakes with abundant oxygen vacancies for high-performance flexible asymmetric supercapacitors with high energy density

High-performance flexible supercapacitors assembled with MnOx/MnWO4@C-3 hetero-nanoflake anodes, exhibiting a maximum areal energy density of 48.49 mW h cm−2.

3D printed MXene-based films and cellulose nanofiber reinforced hydrogel electrolyte to enable high-performance flexible supercapacitors

A flexible supercapacitor with favorable and stable electrochemical performance was prepared by using 3D printed CNF/MWCNT/MXene films and CNF/PAM hydrogel electrolyte.

In Situ Construction of NiCoMn-LDH Derived from Zeolitic Imidazolate Framework on Eggshell-Like Carbon Skeleton for High-Performance Flexible Supercapacitors.

Active compounds based on LDH (ternary layered double hydroxide) are considered the perfect supercapacitor electrode materials on account of their superior electrochemical qualities and distinct structural characteristics, and flexible supercapacitors are an ideal option as an energy source for wearable electronics. However, the prevalent aggregation effect of LDH materials results in significantly compromised actual specific capacitance, which limits its broad practical applications. In this research, a 3D eggshell-like interconnected porous carbon (IPC) framework with confinement and isolation capability is designed and synthesized by using glucose as the carbon source to disperse the LDH active material and enhance the conductivity of the composite material. Second, by constructing NiCoMn-LDH nanocage structure based on ZIF-67 (zeolitic imidazolate framework-67) at the nanometer scale the obtained IPC/NiCoMn-LDH electrode material can expose more active sites, which allows to achieve excellent specific capacitance (2236 F g-1 / 310.6 mAh g-1 at 1 A g-1 ), good rate as well as the desired cycle stability (85.9% of the initial capacitance upon 5000 cycles test). The constructed IPC/NiCoMn-LDH//IPC ASC (asymmetric supercapacitor) exhibits superior capacitive property (135 F g-1 /60.1 mAh g-1 at 0.5 A g-1 ) as well as desired energy density (40Wh kg-1 at 800W kg-1 ).

Protective hydrothermal treatment to improve ion pathway in Ti3C2Tx MXene for high-performance flexible supercapacitors

The strong re-stacking of Ti3C2Tx MXene nanosheets severely blocks ion transport pathway and sacrifices electrochemical performance. Here, a protective hydrothermal treatment is used to improve ion pathway in Ti3C2Tx MXene. The protective hydrothermal treatment is simply conducted in the hydrothermal kettle (filled with N2 atmosphere) placed in vacuum oven. The optimal Ti3C2Tx is achieved by the hydrothermal treatment of 150 °C for 12h, and recorded as h-Ti3C2Tx@150 °C/12h. The h-Ti3C2Tx@150 °C/12h film electrode achieves significantly improved ion transport pathways and enhanced ion accessibility with more pseudocapacitive active sites due to the increased interlayer spacing and pores as well as decreased flake size. According to DFT calculations, a small number of oxides (TiO2 nanoparticles) produced during the hydrothermal treatment also facilitate to increase the capacitive performance of h-Ti3C2Tx@150 °C/12h. Therefore, the h-Ti3C2Tx@150 °C/12h film electrode achieves significantly increased capacitance and rate performance. The h-Ti3C2Tx@150 °C/12h film electrode exhibits excellent capacitance (498.3 F g−1 and 1911 F cm−3 at 1 A g−1) and rate performance (63 % retention from 1 to 20 A g−1) with high cycling stability (98.2 % retention after 20 000 cycles), which are among the best electrochemical performances of undoped Ti3C2Tx based film electrodes reported so far. Thick h-Ti3C2Tx@150 °C/12h film electrode of 33.1 μm thickness exhibits an ultra-high areal capacitance of 3.23 F cm−2 at 1 A g−1. Moreover, the h-Ti3C2Tx@150 °C/12h-based flexible symmetric supercapacitor device exhibits excellent energy storage performance (117 F g−1 at 0.5 A g−1 and 23.4 Wh kg−1 at 299.8 W kg−1) with high cycling stability (84 % retention after 3000 cycles) and bending stability, outperforming most of previously reported Ti3C2Tx-based flexible supercapacitors. The impressive results indicate the great application potential of the h-Ti3C2Tx@150 °C/12h film in flexible energy storage devices.

Fabrication of Porous Reduced Graphene Oxide Encapsulated Cu(OH)2 Core-shell Structured Carbon Fiber-Based Electrodes for High-Performance Flexible Supercapacitors.

To explore next-generation flexible supercapacitors, lightweight, superior conductivity, low cost, and excellent capacitance are the preconditions for practical use. However, subjected to unsatisfactory conductivity, limited surface areas, and poor porosity leading to long ion transport channels, carbon fiber (CF)-based flexible supercapacitors need to further boost the electrochemical properties. Hence, a porous reduced graphene oxide encapsulated Cu(OH)2 core-shell structured CF-based electrode was fabricated through a scalable approach. The inexpensive Cu(OH)2 nanoarrays were controllably grown in situ on a CF substrate, with residual Cu promoting conductivity. Porous graphene oxide (PrGO), which served as the shell, was realized by Ni nanoparticle etching, which not only provided more active sites for capacitance as well as shortened accessible pathways for the ion transport but also effectively alleviated the exfoliation of the internal active materials. Moreover, thanks to this distinctive core-shell architecture, the extra space between the outer PrGO layer and the internal ordered Cu(OH)2 nanoarrays provided increased space for capacitance storage. The assembled PrGO/Cu(OH)2/Cu@CF electrode exhibited an excellent areal capacitance, reaching up to 722 mF cm-2 at a current density of 0.5 mA cm-2, attributed to its superior structure and materials advantages. The resulting PrGO/Cu(OH)2/Cu@CF//AC//CF asymmetric flexible all-solid-state supercapacitor achieved a high energy density of 0.052 mWh cm-2 and exhibited long-term durability. This work proposes a low-cost and effective way to fabricate hierarchically structured electrodes for wearable CF-based supercapacitors.