High-performance Flexible Solid-state Supercapacitors Research Articles

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.

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.

Dodecahedral NC-doped CoSe2 nanoparticles with excellent stability for high-performance flexible solid-state supercapacitors

In this study, CoSe2/NC composites with stable dodecahedral structures were prepared by a simple one-step carbonization-selenization method using ZIF-67 as the precursor, and the effect of annealing time on their morphology and properties was investigated. SEM and TEM characterization results showed that the material with an annealing time of 1 h had the most stable framework structure and complete selenization. Under a three-electrode system with 2.0 M KOH as the electrolyte, CoSe2/NC-1 possesses a high capacity of 554.4F/g at 1 A/g and excellent cycling stability (92% capacity retention after 21,000 cycles). In addition, a flexible solid-state supercapacitor was assembled with CoSe2/NC-1 as the positive electrode and AC as the negative electrode. The power density was 800 W/Kg at 1 A/g, and the cycling stability was tested at 91.53% after 6000 cycles at 2 A/g. The flexible solid-state supercapacitors were tested for suppleness, and their voltage could still reach 1.6 V with stable specific capacity and light up LED bulbs when measured at 0°, 90° and 180°. Undoubtedly, the CoSe2/NC-1 material prepared in this study exhibits promising electrochemical characteristics, making it a viable candidate for implementation in flexible solid-state supercapacitors.

High ionic conductivity and toughness hydrogel electrolyte for high-performance flexible solid-state zinc-ion hybrid supercapacitors enabled by cellulose-bentonite coordination interactions

The lamellar structure of BT and coordination interaction with cellulose make cellulose hydrogel electrolytes have both high ionic conductivity and mechanical strength, and assembled ZHSCs can be applied in the field of wearable electronic devices.

Controlled synthesis of Fe3O4 microparticles with interconnected 3D network structures for high-performance flexible solid-state asymmetric supercapacitors

The eco-friendly Fe-based oxides have attracted broad attention in supercapacitors on account of large theoretical capacities and cost-effective technologies associated with production and recycling. However, inferior conductivity and bad structural stability are still the main obstacles for its promoted application than the competition. In this work, well-designed Fe 3 O 4 microparticles with homogeneous size distribution, high crystallinity, and amorphous carbon shell have been synthesized and deposited on carbon fabric as an anode electrode via a series of feasible techniques, including anodic electrodeposition, polymerization, and annealing. The interconnected 3D network structures of electroactive materials are featured by high specific surface area and fast diffusion rate of ions. The sufacial carbon layer of Fe 3 O 4 particles, serves as the armor, which not only boosts electrical conductivity, but also maintains structural stability of the electrode during electrochemical processes. The electrochemical results show that the binder-free anode exhibits a remarkable areal capacitance of 0.95 F·cm −2 , a wide potential window of 1.2 V, and an outstanding cycling stability in 1 M KOH electrolyte (capacitance retention of 93.39 % over 8000 charge-discharge cycles). After combining with a NiCo-based cathode, 4.93 F·cm −3 volumetric capacitance, 1.8 mWh·cm −3 energy density, and 198 mW·cm −3 power density are achieved for the flexible solid-state asymmetric supercapacitor, which displays impressive cycling stability, excellent mechanical flexibility, and obvious performance advantages as compared with previously reported flexible energy storage devices. This work provides a feasible strategy to design a flexible Fe-based anode with superior conductivity and long-term stability for high-performing flexible solid-state asymmetric supercapacitor towards practical applications. • High crystallinity Fe 3 O 4 microparticles were deposited on CF via stepwise strategy. • Polypyrrole was served as carbon source and barrier material during annealing. • The 3D network structures embrace good conductivity and fast diffusion rate. • The anode exhibits large capacitance, wide potential window and good stability. • Bending test and 8000 GCD cycles demonstrate the flexibility and cycling stability.

One-step preparation of flexible nanocellulose-based composite hydrogel supercapacitors with high specific capacitance

Supercapacitors (SCs) have ultra-high specific capacitance far exceeding traditional capacitors, and have become an important direction in the field of capacitor research. However, SCs devices based on carbon materials usually require a high temperature environment for N-doping or compounding of pseudocapacitive materials, which greatly increases the manufacturing cost and the difficulty of industrialized production. Herein, we fabricated cellulose-based flexible hydrogel supercapacitors by Fe3+ facilitated one-step ternary composite of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN)/sulfonated carbon nanotubes (SCNT)/polyaniline (PANI). The combination of these three substances could form a porous and flexible three-dimensional conductive hydrogel just at room temperature. By comparing the performance of supercapacitors prepared with different ratios of three substances, it was found that the best supercapacitors exhibited a high area specific capacitance of 1786 mF/cm2 at a current density of 1 mA/cm2 and excellent flexibility. Therefore, these composite hydrogels are promising for high-performance flexible solid-state supercapacitors.

High-Performance Flexible Solid-State Supercapacitors Based on MnO2-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

High-Performance Flexible Solid-State Supercapacitors Based on MnO₂-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

High performance flexible carbon cloth-based solid-state supercapacitors with redox-mediated gel electrolytes

The electrochemical performance of supercapacitors is mainly determined by both the electrodes and electrolytes. By integration of the flexible electrodes with redox-mediated gel electrolytes, high performance solid state supercapacitors were designed in the present work. The flexible carbon cloth (CC)-based electrodes were prepared by covalent immobilization of tetraaniline (TA) onto the oxidized carbon cloth (OCC). Hydroquinone (HQ) and p-phenylenediamine (PPD) were used as redox additive respectively to enhance the electrochemical property of the PVA-H2SO4 gel electrolyte. After optimization, high performance flexible solid-state symmetric supercapacitors (SSSCs) were obtained with specific capacitance of 834.0 mF/cm2, retention of 93.69% after 10,000 CV cycles and 108.5% after 500 cycles of 180°-bending, and energy density of 74.2 mWh/cm2 at power density of 405.3 mW/cm2. Such outstanding comprehensive performance makes them promising potential for practical application.

Facile preparation of graphene@polyaniline nanofiber network/oxidized carbon cloth composites for high-performance flexible solid-state supercapacitors.

The complicated preparation process and low energy density of polyaniline (PANI)-based electrodes limit their wide applications in flexible energy storage devices. In this work, a reduced graphene (rGO)-wrapped polyaniline nanofiber network (PANI-NFN)/oxidized carbon cloth (OCC) (rGO@PANI-NFN/OCC) composite was prepared by a facile impregnation method using reactive templates of MnO2 on the surface of OCC. The as-prepared rGO@PANI-NFN/OCC composite exhibited a high area specific capacitance of 4438 mF cm-2 and maintained an initial capacitance of 88.2% after 3000 GCD cycles. It can be used as an independent electrode to construct flexible solid-state supercapacitors (FSSCs), and the FSSCs based on rGO@PANI-NFN/OCC also exhibit a high energy density of 117.9 μW h cm-2 and 88.39% retention after 500 bending cycles, which shows a great prospect for flexible energy storage device applications. The enhanced performance of rGO@PANI-NFN/OCC composites is mainly attributed to the synergistic effect of PANI-NFN structures with a large specific surface area and a rGO wrap layer to reduce the swelling and shrinking of PANI.

Partially nitrogenized mesoporous Co3O4 nanoflakes as a binder-free positive electrode for high-performance flexible solid-state asymmetric supercapacitors

Flexible energy storage and conversion devices have drawn intensive attention in wearable electronics. Herein, partially nitrogenized mesoporous Co3O4 nanoflakes were deposited on hydrophilic conductive carbon fabric (N-Co3O4@CF) through a simple two-step preparation method, involving the electrodeposition of the precursor and subsequent thermal annealing under controlled conditions. The binder-free N-Co3O4@CF material was designed to be and innovative positive electrode with a greatly enhanced capacity of 473.3 C g−1 owing to the changes in the electrical conductivity and electrochemical active sites caused by nitrogen introduction. Moreover, a flexible solid-state asymmetric supercapacitor (FSASC) combined with N-Co3O4@CF as the positive electrode and 3D interconnected Fe2O3 nanosheet networks (Fe2O3@CF) materials as the negative electrode was assembled. The fabricated FSASC achieved a high specific capacitance of 111.6 F g−1 and excellent cycling stability (93.8% capacitance retention after 10,000 cycles). In addition, the device exhibited exceptional flexibility and excellent mechanical stability after flexibility tests, including bending the FSASC at various bending angles (no significant change of the CV and GCD curves after bending 180°) and a 100-bending-cycle durability test (only 5% loss in capacitance after continuous bending). Finally, the FSASC device delivered a competitive energy density of 39.7 Wh kg−1 with the low-cost, lightweight and easy fabrication features, which may open up a promising opportunity for wearable energy storage device.

A high performance flexible solid-state asymmetric supercapacitor based on composite of reduced graphene oxide@dysprosium sulfide nanosheets and manganese oxide nanospheres

The reduced graphene oxide@dysprosium sulfide (rGO@Dy2S3) composite and MnO2 films are synthesized using successive ionic layer adsorption and reaction and from chemical bath deposition methods, respectively. Addition of rGO in Dy2S3 film enhances specific surface area from 40 to 78 m2g-1. Using these films flexible solid-state symmetric; rGO@Dy2S3//Dy2S3@rGO and asymmetric; MnO2//Dy2S3@rGO supercapacitor devices are fabricated. The solid-state asymmetric supercapacitor device exhibits specific energy of 41 Wh kg−1 at specific power 1330 W kg−1. The stability of asymmetric supercapacitor is 86% after 5000 cycles and flexibility of 82% at the bending angle 165°. This work highlights the first time use of rGO@Dy2S3 composite thin film material to fabricate symmetric and asymmetric supercapacitor devices and also demonstrates the superior performance of asymmetric device than symmetric one.

Wool textile-derived nitrogen-doped porous carbon cloth for a binder-free electrode material for high-performance flexible solid-state supercapacitors

With the rapid development of portable electronics and wearable devices, flexible solid-state supercapacitor (SC) has recently stimulated wide research interest. Herein, we one-step prepared a nitrogen-doped porous carbon cloth material by directly carbonizing a biomass wool textile without any chemical or physical activation. The obtained wool-derived nitrogen-doped porous carbon cloth (WNPCC) has a microporous structure with a high specific surface area of ~ 500 m2 g−1, as well as superior mechanical property that can be arbitrarily folded. As an electrode material without adding conductive agent and binder, greatly improved electrochemical performance is achieved by the WNPCC in comparison with the commercial carbon cloth and reported flexible SC electrodes. The area specific capacitance of the optimized WNPCC in three-electrode tests is 1012 mF cm−2 (1 mA cm−2), and meanwhile, an excellent durability at 90° bent state is proved. The PVA/H2SO4-based SC shows energy density of 76.6 µWh cm−2 at a power density of 0.60 mW cm−2 and retains 55 µWh cm−2 even at a high power density of 6.73 mW cm−2 with a wide voltage window of 1.4 V. More importantly, the specific capacitance value does not evidently decline when bending the SC device to various degrees in 2000 runs. This work provides a facile route to prepare flexible electrode material using sustainable biomass precursor, which not only is directly used as electrode for all-solid-state SCs, but also can act as the flexible conductive supporter for battery or electrocatalysis applications.

The construction of sea urchin spines-like polypyrrole arrays on cotton-based fabric electrode via a facile electropolymerization for high performance flexible solid-state supercapacitors

The most explored flexible supercapacitors based on PPy electrodes face a huge challenge of poor cycle performance. Here, we demonstrate successful construction of sea urchin spines-like PPy arrays on cotton-based fabric electrode via a facile electropolymerization and employ it in enhancing the cyclic stability of the supercapacitors without recombination of PPy with other capacitive materials. This novel fabric electrode (called EPPy-PPy/NF/CF) consists of a cotton fabric (CF) coated with PVA-co-PE nanofibers (NF) as a flexible substrate (NF/CF). The formation mechanism of the spiny PPy with nanocavities is explored, and the effects of surface wettability of the support electrode (PPy/NF/CF), micellar size, and bubble generation on the nucleation and growth of the PPy during electropolymerization are elucidated. Significantly, the flexible solid-state symmetrical EPPy-PPy/NF/CF supercapacitor exhibits striking cycling stability with 100% retention after 10,000 cycles at a current density of 4 mA cm−2. The superior cyclic stability can be attributed to the spiny PPy arrays, which can shorten the transmission paths of counter ions and charges, thereby weakening stress-induced damages to the PPy skeleton. Additionally, this flexible supercapacitor also shows a great potential for application in portable and wearable electronic devices.

Hierarchical core-shell structure of NiCo2O4 nanosheets@HfC nanowires networks for high performance flexible solid-state hybrid supercapacitor

• The hierarchical free-standing core-shell NiCo 2 O 4NSs @HfC NWs /CC was obtained. • HfC NWs network was used as the superhighway for electron transport. • NiCo 2 O 4NSs @HfC NWs /CC exhibits excellent electrochemical properties. • The hybrid supercapacitor shows good performance stability and flexibility. Rationally constructing the electrode with the hierarchical structure, different components, and the flexibility is a promising approach to further improve the electrochemical properties and meet the demand for flexible electronic devices. In this paper, for the first time, hafnium carbide nanowires (HfC NWs ) networks, with the metrics of large specific surface area, excellent conductivity, and chemical/physical stability, are served as nanoscale conductive skeletons on carbon cloth (CC) for supporting the porous NiCo 2 O 4 nanosheets (NSs). Benefiting from the structural advantages, the as-formed free-standing core-shell NiCo 2 O 4NSs @HfC NWs /CC exhibits a high specific capacitance of 2102 F g −1 at a current density of 1 A g −1 , good rate capability (85% capacitance retention at 20 A g −1 ) and outstanding cycling stability (98% capacitance retention after 5000 cycles at 10 A g −1 ). Additionally, assembled with the NiCo 2 O 4NSs @HfC NWs /CC and activated carbon (AC)/CC, the flexible solid-state hybrid supercapacitor displays a high energy density of 53 Wh kg −1 at a power density of 800 W kg −1 and excellent performance stability with good flexibility. More impressively, our work could not only further widen the application of HfC NWs , but also put forward the new thinking of rational construction of high-performance flexible supercapacitors.

Boosting the electrochemical properties of polyaniline by one-step co-doped electrodeposition for high performance flexible supercapacitor applications

A facile one-step co-doped electrodeposition method is proposed to prepare polyaniline (PANI) electrodes with improved supercapacitive properties. During electrodeposition of PANI films, sulfuric acid and perchloric acid simultaneously act as dopants to obtain sulfuric acid and perchloric acid co-doped PANI (SP-PANI) electrode. For comparison, single-doped PANI (i.e., sulfuric acid-doped PANI (S-PANI) and perchloric acid-doped PANI (P-PANI)) electrodes are prepared with the same electrodeposition parameters. Electrochemical measurements indicate that the SP-PANI electrodes exhibit substantially improved electrochemical capacitive properties with respect to single-doped PANI electrodes. This improvement can be attributed to the fact that the co-doping changes the morphology, electrical conductivity, and roughness of the PANI films electrodeposited, thus leading to easy pathway for electron transport and increased electroactive surface area. Moreover, we have demonstrated the feasibility of SP-PANI electrodes for use in high performance flexible solid-state supercapacitors. The assembled supercapacitor with SP-PANI electrodes shows high areal capacitance of 149.3 mF cm−2 at 0.5 mA cm−2. It also features high mechanical flexibility, good electrochemical capacitive properties, and superior deformation and electrochemical stability, making it have high application potential in flexible electrochemical energy storage.

Exceptional interfacial electrochemistry of few-layered 2D MoS2 quantum sheets for high performance flexible solid-state supercapacitors

Extracting the hidden knowledge behind the exception charge storage mechanism involved in the MoS2 quantum sheets electrode material.

Superior cycle stability carbon layer encapsulated polyaniline nanowire core-shell nanoarray free-standing electrode for high performance flexible solid-state supercapacitors

Polyaniline (PANI) materials possess extremely high theoretical capacitance and easy strategies to modify free-standing electrode for high performance flexible solid-state supercapacitors (FSSCs). However, low cycle stability of PANI limits its application. So how to improve cycle stability of PANI materials becomes particularly important. Herein, carbon layer is introduced to encapsulate PANI nanoarray grown on functional carbon cloth (fCC-PANI array-C) through hydrothermal method to improve cycle stability of this free-standing electrode. When reaction time is extended to 2 h, the fCC-PANI array-C exhibits high areal capacitance of 1695 mF/cm2 at 0.5 mA/cm2 and maintains extremely excellent cycle stability about 102% of its original value after 10 000 cycles at 100 mV/s. Furthermore, fCC-PANI array-C is employed to assemble FSSCs. The as-prepared FSSCs also exhibit high areal capacitance (819.62 mF/cm2) and keep 89% cycle stability after 5000 cycles at 50 mA/cm2. More importantly, the FSSCs show superior mechanical properties and flexibility, and still maintains 98% of its original value when bent at 180° after 1000 cycles. Moreover, the FSSCs are further employed as energy-storage device to light up a red LED. Therefore, FSSCs based on fCC-PANI array-C exhibit possibility that can be applied as high property flexible energy-storage devices.

Cu(I)/Cu(II) partially substituting the Co(II) of spinel Co3O4 nanowires with 3D interconnected architecture on carbon cloth for high-performance flexible solid-state supercapacitors

The 3D interconnected architecture nanowires of Co3O4 partially substituted by Cu(I)/Cu(II) coated on the carbon cloth ([email protected]) with high specific surface area were fabricated by a facile and low-cost hydrothermal approach and consequent thermal annealing. The prepared binder-free [email protected] electrode exhibits high specific capacitance (1947.2 F g−1 or 973.6 C g−1 at 1 A g−1) and superior cyclic stability (93.76% retention of initial value up to 10,000 cycles). In addition, the [email protected] and synthesized Fe2O3@CC are used as positive and negative electrodes in the presence of PVA-KOH as a gel electrolyte to assemble a flexible solid-state asymmetric supercapacitor. The as-assembled flexible device shows a high specific capacitance of 182.7 F g−1, high energy density of 57.1 W h kg−1 at the power density of 749.75 W kg−1, remarkable cyclic stability with 93.25% retention after 10,000 cycles and almost no capacity loss under different bending angles. Therefore, this material has potential application for wearable electronics with the excellent mechanical flexibility.

Facile synthesis of freestanding cellulose/RGO/silver/Fe2O3 hybrid film for ultrahigh-areal-energy-density flexible solid-state supercapacitor

We report the design of a freestanding cellulose/RGO/silver/Fe2O3 hybrid film for direct use as electrodes for construction of high-performance flexible solid-state supercapacitor (FSS). It is well characterized and found to feature noticeable capacitive properties due to the unique structure, high conductivity and dual electroactive species (i.e., RGO and Fe2O3) for charge storage. As demonstrated in a three-electrode system, such film electrode achieves the maximum areal and volumetric capacitance of 2044 mF cm−2 and 75.7 F cm−3, respectively, with prominent rate performance and long-term cyclic durability. Later, a symmetric FSS device is constructed by employing this film as both anode and cathode electrodes. The as-assembled device offers the highest areal and volumetric capacitance of 1132 mF cm−2 and 18.2 F cm−3, respectively, displays inconspicuous performance degradation under different curved states, and possesses the largest areal energy density of 226.4 μWh cm−2, which is far better than that of many advanced symmetric and asymmetric flexible supercapacitors. The attractive capacitive behaviors and easy fabrication processes could render cellulose/RGO/silver/Fe2O3 hybrid film a promising material for the applications in next-generation flexible and wearable electronics in the future.

A dual-doped strategy to enhance the electrochemical performances of electropolymerized polyaniline electrodes for flexible energy storage

We have designed a simple dual-doped strategy to boost the supercapacitive properties of polyaniline (PANi) electrodes. Specifically, dual-doped PANi (DD-PANi) electrodes are prepared via electrochemical polymerization, during which phosphoric acid and hydrochloric acid serve as dopants simultaneously. Electrochemical measurements indicate that the DD-PANi electrodes exhibit substantially improved electrochemical properties with respect to single-doped PANi electrodes (i.e., phosphoric acid-doped PANi and hydrochloric acid-doped PANi electrodes). This improvement can be attributed to the fact that dual-doped strategy changes the morphology and roughness of electropolymerized PANi films, thus leading to increased electroactive surface area and short pathway for electron/ion transport. The resultant DD-PANi electrodes exhibit high areal capacitance of 382.1 mF cm−2 at 0.5 mA cm−2, as well as ideal cycling performance (retaining 91.2% of initial capacitance after 5000 cycles). Furthermore, we have explored the feasibility of DD-PANi electrodes for high performance flexible solid-state supercapacitors. The assembled supercapacitor using DD-PANi electrodes features high mechanical flexibility, good electrochemical capacitive properties, and superior long-term stability (including deformation stability and electrochemical stability), which ensure its potential for applications in flexible energy storage devices.