High-performance yarn electrode materials enhanced by surface modifications of cotton fibers with graphene sheets and polyaniline nanowire arrays for all-solid-state supercapacitors

Highly Ionic Conductive, Stretchable, and Tough Ionogel for Flexible Solid-State Supercapacitor

The increasing demand for wearable electronics calls for advanced energy storage solutions that integrate high  electrochemical performances and mechanical robustness. Ionogel is a promising candidate due to its stretchability combined with high ionic conductivity. However, simultaneously optimizing both the electrochemical and mechanical performance of ionogels remains a challenge. This paper reports a tough and highly ion-conductive ionogel through ion impregnation and solvent exchange. The fabricated ionogel consists of double interpenetrating networks of long polymer chains that provide high stretchability. The polymer chains are crosslinked by hydrogen bonds that induce large energy dissipation for enhanced toughness. The resultant ionogel possesses mechanical stretchability of 26, tensile strength of 1.34 MPa, and fracture toughness of 4175 J m-2. Meanwhile, due to the high ion concentrations and ion mobility in the gel, a high ionic conductivity of 3.18 S m-1 at room temperature is achieved. A supercapacitor of this ionogel sandwiched with porous fiber electrodes provides remarkable areal capacitance (615 mF cm-2 at 1 mA cm-2), energy density (341.7 µWh cm-2 at 1 mA cm-2), and power density (20 mW cm-2 at 10 mA cm-2), offering significant advantages in applications where high efficiency, compact size, and rapid energy delivery are crucial, such as flexible and wearable electronics.

Robust double-network polyvinyl alcohol-polypyrrole hydrogels as high-performance electrodes for flexible supercapacitors

The growing demands of flexible and wearable electronic devices boost the rapid development of flexible supercapacitors (FSCs). Conductive hydrogels are considered to be one type of promising electrode materials for FSCs due to their good processability and electrochemical properties. However, the poor mechanical properties of conductive hydrogels hinder their practical applications. Building robust cross-linked network structures is a feasible way to enhance their mechanical properties. Herein, the double-network polyvinyl alcohol (PVA)-polypyrrole (PPy) conductive hydrogels are synthesized by the freeze-thaw and in-situ polymerization method. The double-network structure not only enhances mechanical properties of the hydrogels, but also promotes their electrolyte ion transport. The maximum elongation at break of the optimized PVA-PPy hydrogels can reach 156.4%, and the specific capacitance is 1718.7 mF cm-2 at 0.5 mA cm-2. Furthermore, the energy densities of the symmetrical PVA-PPy FSCs are 46.7 and 13.3 μWh cm-2 at power densities of 200.0 and 2000.0 μW cm-2. Such excellent electrochemical performances and mechanical properties make the synthesized PVA-PPy hydrogels a promising candidate for FSCs.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Interfacial engineered PANI/carbon nanotube electrode for 1.8 V ultrahigh voltage aqueous supercapacitors

Flexible three-dimensional interconnected carbon nanotubes on the carbon cloth (3D-CNTs/CC) were obtained through simple magnesium reduction reactions. According to the Nernst equation, the cell voltage based on these pure carbon electrodes without any additives could reach 1.5 V due to the higher di-hydrogen evolution over potential in neutral 3.5 M LiCl electrolytes. In order to improve the electrochemical performance of the electrodes, 3D-CNTs/CC electrodes covered with polyaniline barrier layer (3D-PANI/CNTs/CC) were prepared byin situelectropolymerization using interfacial engineering method. The assembled symmetric supercapacitors display a broadened voltage of 1.8 V, high areal capacitance of 380 mF cm^-2, outstanding areal energy density of 85.5μWh cm^-2and 84% of its initial capacitance after 20 000 charge-discharge cycles. This work demonstrated that the interface engineering strategy provides a promising way to improve the energy density of carbon-based aqueous supercapacitors by widening the voltage and boosting the capacitance simultaneously.

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.

Flexible and Conductive Polymer Threads for Efficient Fiber-Shaped Supercapacitors via Vapor Copolymerization

Flexible fiber electrodes are critical for high-performance fiber and wearable electronics. In this work, we presented a highly conductive all-polymer fiber electrode by vapor copolymerization of 2,5-dibromo-3,4-vinyldioxythiophene (DBEDOT) and 2,5-diiodo-3,4-vinyldioxythiophene (DIEDOT) monomers on commonly used polyester threads (PETs) at a temperature as low as 80 °C. The poly(3,4-ethylenedioxythiophene) (PEDOT)-coated PET threads maintain excellent flexibility and show conductivity of 7.93 S cm^-1, nearly four times higher than that reported previously via homopolymerization of DBEDOT monomer. A MnO₂ active layer was embedded into the PEDOT double layers, and the flexible fiber composite electrode showed a high linear specific capacitance of 157 mF cm^-1 and improved stability, retaining 86.5% capacitance after 5000 cycles. Fiber-shaped solid-state supercapacitors (FSSCs) based on the composite electrodes were assembled, and they displayed superior electrochemical performance. This work provides a new approach to realize high-performance and stable wearable electronics.

Well-designed sophisticated structure of sandwich-like CC@NiAl-LDH@GO@NiCo-LDH material with unique advantages for high performance and practicality hybrid quasi-solid-state supercapacitors

A sandwich-like flexible architecture electrode material composed of NiAl-LDH nanoplates grown on carbon cloths (CC), coupled with GO interlayer and NiCo-LDH nanowire on the interlayer was successfully assembled via hydrothermal and chemical bath deposition (denoted as CC@NiAl-LDH@GO@NiCo-LDH). The promising combination of NiAl-LDH, graphene and NiCo-LDH forming a multilayer structure through electrostatic absorption and in-situ growth process which endow a high mass loading superiority and synergistic effect for supercapacitors. In addition, the interspace inside the sandwich-like architecture constructed by the graphene and the NiAl-LDH/ NiCo-LDH nano-flakes contribute to alleviate of the volume expansion during the cycling process and promote the diffusion rate of ions. The CC@NiAl-LDH@GO@NiCo-LDH material demonstrates excellent electrochemical performance which exhibit remarkable specific capacitance of 2359.8F·g^-1 (14.2F·cm^-2) at 1 A·g^-1 (6 mA·cm^-2) and outstanding capacitance retentions of 93.1% after 1500 cycles. Subsequently, the CC@NiAl-LDH@GO@NiCo-LDH material was used as cathode material to fabricate a hybrid quasi-solid-state supercapacitor that exhibits a high energy density of 52.0 Wh·kg^-1 at 796.7 W·kg^-1 and 38.4 Wh·kg^-1 at 12015 W·kg^-1, revealing its potential and viability for commercial applications. Furthermore, the hybrid quasi-solid-state supercapacitor can be applied under different extreme operating conditions such as bending, twisting, sour/alkali soaking, ice bathing, warm bathing, hammering and cutting conditions. It is predictable that the unique sandwich-like structure will be an extremely promising electrode material for high-performance supercapacitors.

Flexible core/shelled PPy@PANI nanotube porous films for hybrid supercapacitors

Flexibility of the films and the limited ion transport in the vertical direction of film highly restrict the development of flexible supercapacitors. Herein, we have developed hybrid porous films consisting of N-doped holey graphene nanosheets (NHGR) with abundant in-plane nanopores and the vertically aligned polyaniline nanowires arrays on polypyrrole nanotubes (PPy@PANI) via a two-step oxidative polymerization strategy and vacuum filtration. The rational design can efficiently shorten the diffusion path of electrons/ions, alleviate volume variation of electrodes during cycling, enhance electric conductivity of the hybrids, and while offer abundant active interfacial sites for electrochemical reaction. Benefiting from the distinctive structural and compositional merits, the obtained PPy@PANI/NHGR film electrode manifests an excellent electrochemical properties in terms of specific capacity (1348 mF cm^-2at a current density of 1 mA cm^-2), rate capability (81.2% capacitance retention from 1 to 30 mA cm^-2), and cycling stability (capacitance retention of 73.7% at 20 mA cm^-2after 7000 cycles). Matched with NHGR negative electrode, the assembled flexible all-solid-state asymmetric supercapacitor displays a remarkable areal capacitance of 359 mF cm^-2at 5 mA cm^-2, maximum areal energy density of 112.2μWh cm^-2at 3.747 mW cm^-2, and good flexibility at various bending angles while preserving stable cycling performance. The result shows the PPy@PANI/NHGR film with high flexibility and 3D ions transport channels is highly attractive for flexible energy storage devices.

A Review on the Production Methods and Applications of Graphene-Based Materials

Graphene-based materials in the form of fibres, fabrics, films, and composite materials are the most widely investigated research domains because of their remarkable physicochemical and thermomechanical properties. In this era of scientific advancement, graphene has built the foundation of a new horizon of possibilities and received tremendous research focus in several application areas such as aerospace, energy, transportation, healthcare, agriculture, wastewater management, and wearable technology. Although graphene has been found to provide exceptional results in every application field, a massive proportion of research is still underway to configure required parameters to ensure the best possible outcomes from graphene-based materials. Until now, several review articles have been published to summarise the excellence of graphene and its derivatives, which focused mainly on a single application area of graphene. However, no single review is found to comprehensively study most used fabrication processes of graphene-based materials including their diversified and potential application areas. To address this genuine gap and ensure wider support for the upcoming research and investigations of this excellent material, this review aims to provide a snapshot of most used fabrication methods of graphene-based materials in the form of pure and composite fibres, graphene-based composite materials conjugated with polymers, and fibres. This study also provides a clear perspective of large-scale production feasibility and application areas of graphene-based materials in all forms.

Surface Modification of Commercial Cotton Yarn as Electrode for Construction of Flexible Fiber-Shaped Supercapacitor

In this study, we report on the rational design and facile preparation of a cotton-reduced graphene oxide-silver nanoparticle (cotton-RGO-AgNP) hybrid fiber as an electrode for the building of a flexible fiber-shaped supercapacitor (FSSC). It was adequately characterized and found to possess a well-defined core−shell structure with cotton yarn as a core and a porous RGO-AgNP coating as a shell. Thanks to the unique morphological features and low electrical resistance (only 2.3 Ω·cm−1), it displayed attractive supercapacitive properties. When evaluated in a three-electrode setup, this FSSC electrode delivered the highest linear and volumetric specific capacitance of up to ca. 12.09 mF·cm−1 and ca. 9.67 F·cm−3 with a satisfactory rate capability as well as a decent cycling stability. On the other hand, an individual parallel symmetric FSSC cell constructed by this composite fiber fulfilled the largest linear and volumetric specific capacitance of ca. 1.67 mF·cm−1 and ca. 0.67 F·cm−3 and offered the maximum energy density, as high as ca. 93.1 μWh·cm−3, which outperformed a great number of graphene- and textile yarn-based FSSCs. Impressively, bending deformation brought about quite a limited effect on its electrochemical behaviors and almost no capacitance degradation took place during the consecutive charge/discharge test for over 10,000 cycles. Consequently, these remarkable performances suggest that the currently developed cotton-RGO-AgNP fiber has considerable application potential in flexible, portable and wearable electronics.

Solid-State Double-Network Hydrogel Redox Electrolytes for High-Performance Flexible Supercapacitors

Flexible supercapacitors have great potential applications in wearable and portable electronics, but their practical applications were limited due to the low energy density and mechanical flexibility of solid-state electrolytes used for the construction of flexible supercapacitors. In this study, we first report the solid-state double-network (DN) hydrogel electrolytes (HEs) incorporated with Na₂MoO₄ redox additives. It is found that the solid-state DN HEs with Na₂MoO₄ redox additives exhibit high electrochemical performance, excellent mechanical properties, and fast self-recovery features. We then demonstrate novel symmetric supercapacitors (SSCs) incorporated with the solid-state Na₂MoO₄ DN HEs and the active carbon cloths as the electrodes. The SSCs exhibit a specific capacitance of 84 mF/cm² at a current density of 1 mA/cm² and an energy density of 70 μWh/cm² at a power density of 3800 μWh/cm². Moreover, the SSCs retain approximately 80% capacitance retention after 7000 charge/discharge cycles, which indicates that the SSCs possess excellent flexibility and stability. All of these results demonstrate that the SSCs incorporated with the solid-state Na₂MoO₄ DN HEs as energy-storage devices have great practical applications in wearable and portable electronics.

High specific capacitance cotton fiber electrode enhanced with PPy and MXene by in situ hybrid polymerization

Fiber electrodes are the main functional elements of flexible and textile-based storage devices. This study proposes a Polypyrrole (PPy) and MXene composite, grown on cotton fiber, as a high capacitance electrode. Pyrrole (Py) and MXene are processed and deposited along with an in-situ polymerization. The mass and areal capacitance of the assembled (PPy/MXene)@Cotton electrode respectively reach to 506.6 F g^-1, at current density of 1 A g^-1 and 455.9 mF cm^-2 at scan rate of 0.9 mA cm^-2. These values outperform the PPy@Cotton fiber electrode, around 45.8% and 119% respectively. As-prepared fiber electrodes with mechanical strength of 107.3 MPa and conductivity of 60.8 S/m, offer intriguing application prospects in the field of weaving and flexible fibrous supercapacitors.

Iron oxides nanobelt arrays rooted in nanoporous surface of carbon tube textile as stretchable and robust electrodes for flexible supercapacitors with ultrahigh areal energy density and remarkable cycling-stability

We report a significant advance toward the rational design and fabrication of stretchable and robust flexible electrodes with favorable hierarchical architectures constructed by homogeneously distributed α-Fe₂O₃ nanobelt arrays rooted in the surface layer of nanoporous carbon tube textile (NPCTT). New insight into alkali activation assisted surface etching of carbon and in-situ catalytic anisotropic growth is proposed, and is experimentally demonstrated by the synthesis of the Fe₂O₃ nanobelt arrays/NPCTT. The Fe₂O₃/NPCTT electrode shows excellent flexibility and great stretchability, especially has a high specific areal capacitance of 1846 mF cm⁻² at 1 mA cm⁻² and cycling stability with only 4.8% capacitance loss over 10,000 cycles at a high current density of 20 mA cm⁻². A symmetric solid-state supercapacitor with the Fe₂O₃/NPCTT achieves an operating voltage of 1.75 V and a ultrahigh areal energy density of 176 µWh cm⁻² (at power density of 748 µW cm⁻²), remarkable cycling stability, and outstanding reliability with no capacity degradation under repeated large-angle twisting. Such unique architecture improves both mechanical robustness and electrical conductivity, and allows a strong synergistic attribution of Fe₂O₃ and NPCTT. The synthetic method can be extended to other composites such as MnO nanosheet arrays/NPCTT and Co₃O₄ nanowire arrays/NPCTT. This work opens up a new pathway to the design of high-performance devices for wearable electronics.

Microstructure Design of Carbonaceous Fibers: A Promising Strategy toward High-Performance Weaveable/Wearable Supercapacitors

Fiber-based supercapacitors (FSCs) possess great potential as an ideal type of power source for future weaveable/wearable electronics and electronic-textiles. The performance of FSCs is, without doubt, primarily determined by the properties of fibrous electrodes. Carbonaceous fibers, e.g., commercial carbon fibers, newly developed graphene fibers, and carbon nanotube fibers, are deemed as promising materials for weaveable/wearable supercapacitors owing to their exotic properties including high tensile strength and robustness, excellent electrical conductivity, good flexibility, and environmental stability. Nevertheless, bare carbonaceous fiber normally exhibits low capacitance originating from electric double-layer capacitance, which remains unsatisfactory for efficiently powering wearable and portable devices. Numerous efforts have been devoted to tailoring fiber properties by hybridizing pseudocapacitive materials, and impressive progress has been achieved thus far. Herein, the microstructures of pristine carbonaceous fibers are introduced in detail, and the recent advances in rational nano/microstructure design of their hybrids, which provides the feasibility to achieve the synergistic interaction between conductive agents and pseudocapacitive nanomaterials but are normally overlooked, are comprehensively reviewed. Besides, the challenges in developing high-performance fibrous electrodes are also elaborately discussed.

High-performance supercapacitors based on polyaniline nanowire arrays grown on three-dimensional graphene with small pore sizes

Three-dimensional graphene (3D GR)-based hybrids have received significant attention due to their unique structures and promising applications in supercapacitors. In this paper, 3D GR with small pore sizes has been prepared by chemical vapor deposition using commercial nickel nanowires as the template. After nitric acid treatment, the hydrophilicity of 3D GR improved. Polyaniline nanowire arrays (PANI NWAs) have been successfully grown on its surface by in situ polymerization to obtain hybrid PANI NWA/3D GR. The results show that PANI NWAs with a length of ∼300 nm vertically grow on 3D GR with a pore diameter of ∼2 μm. The small pore size of 3D GR not only improves the mechanical properties of 3D GR, but also provides numerous sites for the growth of PANI NWAs. Meanwhile, PANI NWAs provide a shorter ion diffusion path and larger contact area with the electrolyte. Due to the unique structure, the hybrid exhibits a high specific capacitance of 789.9 F g^-1 at 10 mV s^-1. When it is assembled into a symmetric supercapacitor, it exhibits an energy density of 32.2 W h kg^-1 at a power density of 793.3 W kg^-1 and maintains a good cycle stability of 90% after 5000 cycles at 1.0 A g^-1.

Effects of three fabric weave textures on the electrochemical and electrical properties of reduced graphene/textile flexible electrodes

Textile textures formed through woven, knitted or nonwoven weaving technology have critical effects on the electrical and electrochemical properties of flexible electrodes. Therefore, the effects of textile structures, including porosity and pore configuration, on the loading amount of reduction graphene (RGO), the electrical and electrochemical properties were systematically studied. The results show that knitted fabric had the highest mass loading of RGO sheets and lowest sheet resistance among these three fabrics. However, the specific capacitance of woven fabric was optimum 40.5 F g-1 at a scan rate of 5 mV s-1 within the voltage window of 0-0.8 V, which was ascribed to its suitable porosity and pore size firmly anchoring the RGO sheets. Also, the RGO/woven cotton electrodes exhibited good cycling stability and excellent electrochemical stability without an obvious loss in the capacitive performance. The above results provide a theoretical basis for the selection of textile substrates for high-performance flexible electrodes.

Multidimensional Hierarchical Fabric-Based Supercapacitor with Bionic Fiber Microarrays for Smart Wearable Electronic Textiles

Flexible textile-based supercapacitors (SCs) have attracted a lot of attention, with the artificial intelligence technology and smart wearable electronic textiles developing rapidly. However, energy-storage performance of common textile-based SCs is always restricted with the low-dimensional substrates (i.e., one-dimensional fibers or two-dimensional fabrics), and hence flexible textile-based SCs with multifarious hierarchical substrates are highly desired. Herein, a multidimensional hierarchical fabric electrode model with a bionic fiber microarray structure has been designed, inspired by the "grasp effect" of the sophisticated arrangement structures of hedgehog spines, and the bionic assembled SCs exhibit an enhanced specific areal capacitance (245.5 mF/cm² at 1 mV/cm²), compared with the planar fabric-based SCs (41.6 mF/cm²), and a high energy density (21.82 μWh/cm² at 0.4 mW/cm²). Besides, the SCs also show a stable capacitance ratio of 83.9% after 10 000 cycles and a mere capacitance loss under different bending states. As a proof of concept, an all-fabric smart electronic switch is fabricated with self-power and wearable properties, along with some other trial applications. Such a hierarchical fabric with a bionic fiber microarray structure is believed to enhance the performance of the assembled SCs. We foresee that the multidimensional hierarchical fabric would bring more promising prospects for flexible textile-based energy-storage systems and be used in smart wearable textile applications.

Building Carbon-Based Versatile Scaffolds on the Electrode Surface to Boost Capacitive Performance for Fiber Pseudocapacitors

In order to fabricate high performance fiber pseudocapacitors, the trade-off between high mass loading and high utilization efficiency of pseudocapacitive materials should be carefully addressed. Here, a solution that is to construct a carbon-based versatile scaffold is reported for loading pseudocapacitive materials on carbonaceous fibers. The scaffold can be easily built by conformally coating commercial pen ink on the fibers without any destruction to the fiber skeleton. Due to the high electrical conductivity and abundant macropore structure, it can provide sufficient loading room and a high ion/electron conductive network for pseudocapacitive materials. Therefore, their loading mass and utilization efficiency can be increased simultaneously, and thus the as-designed fibrous electrode displays a high areal capacitance of 649 mF cm^-2 (or 122 mF cm^-1 based on length), which is higher than most of the reported fiber pseudocapacitors. The simple and low-cost strategy opens up a new way to prepare high performance portable/wearable energy storage devices.

Hierarchical NiCo2S4@Nickel-Cobalt Layered Double Hydroxide Nanotube Arrays on Metallic Cotton Yarns for Flexible Supercapacitors

Constructing high capacitance active materials and three-dimensional (3D) conductive networks inside textile yarn frames is a promising strategy to synthesize yarn supercapacitor electrodes. In this study, growing NiCo₂S₄@Ni-Co layered double hydroxide (LDH) nanotube arrays on Au-metalized cotton yarns yields a novel yarn supercapacitor electrode material. The resulting yarn electrode possesses numerous merits, including high electrical conductivity from NiCo₂S₄ and Au-metalized cotton yarns, high capacitance of Ni-Co LDH nanosheets, and the 3D hierarchical electrode structure. The unique electrode structure leads to excellent electrochemical properties including high capacitance (5680 mF cm^-2), excellent rate performance, and stable cycling performance. A two-ply symmetric yarn supercapacitor assembled from the NiCo₂S₄/Ni-Co LDH/Au/cotton yarn electrode reaches an areal energy density of 3.5 μW h cm^-2.

Hydrothermal synthesis of PANI nanowires for high-performance supercapacitor

Polyaniline nanowires (PANI NWs) were synthesized under different temperatures through a facile hydrothermal method and used as electrodes for high-performance pseudocapacitor. The resulting samples were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron micrographs, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Electrochemical properties of these PANI electrodes are studied by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5M H2SO4 aqueous solution. The highest specific capacitance is obtained on the PANI NWs synthesized under 80°C (PANI-80) with 540.0 F g−1 at current density of 0.5 A g−1 accompanied with 82% specific capacitance retention after 1000 charge discharge cycles at 5 A g−1 current density.

Stretchable and Self-Healing Integrated All-Gel-State Supercapacitors Enabled by a Notch-Insensitive Supramolecular Hydrogel Electrolyte

Next-generation wearable electronics are expected to endure significant deformations and mechanical damage. Therefore, self-healing stretchable electrolytes with high ionic conductivity and robust mechanical strength, which have high tolerance of deformations and spontaneously recover electrochemical properties after external damage, are necessary conditions for the realization of flexible supercapacitors. Here, a new type of zwitterionic supramolecular hydrogel cross-linked through rationally designed ionic associations and hydrogen bonds is reported (PAD/H₂SO₄). The resultant supramolecular network realizes a high ionic conductivity of 57 mS cm^-1 and unprecedented mechanical properties such as a high toughness of 35 000 J m^-2, a notch-insensitive of up to 2200% strain, and efficient instantaneous self-healing within 5 min. Acting as an electrolyte, a novel flexible supercapacitor design strategy is proposed by integrating capacitive materials directly onto the PAD/H₂SO₄ hydrogel to achieve exceptional electrochemical performance, which can be repeatable for at least 50 cutting/healing cycles. The facile and versatile strategy for the construction of the integrated all-gel-state supercapacitors with self-healing stretchable electrolytes will provide new directions for future long-life flexible devices.