All‐Printed MnHCF‐MnOx‐Based High‐Performance Flexible Supercapacitors

Here, a simple active materials synthesis method is presented that boosts electrode performance and utilizes a facile screen‐printing technique to prepare scalable patterned flexible supercapacitors based on manganese hexacyanoferrate‐manganese oxide and electrochemically reduced graphene oxide electrode materials (MnHCF‐MnO_x/ErGO). A very simple in situ self‐reaction method is developed to introduce MnO_x pseudocapacitor material into the MnHCF system by using NH₄F. This MnHCF‐MnO_x electrode materials can deliver excellent capacitance of 467 F g^?1 at a current density of 1 A g^?1, which is a 2.4 times capacitance increase compared to MnHCF. In addition a printed, patterned, flexible MnHCF‐MnO_x/ErGO supercapacitor is fabricated, showing a remarkable areal capacitance of 16.8 mF cm^?2 and considerable energy and power density of 0.5 mWh cm^?2 and 0.0023 mW cm^?2, respectively. Furthermore, the printed patterned flexible supercapacitors also exhibit exceptional flexibility, and the capacitance remains stable, even while bending to various angles (60°, 90°, and 180°) and for 100 cycles. The flexible supercapacitor arrays integrated by multiple prepared single supercapacitors can power various LEDs even in the bent states. This approach offers promising opportunities for the development of printable energy storage materials and devices with high energy density, large scalability, and excellent flexibility.     

High Performance,Flexible, Solid‐State Supercapacitors Based on a Renewable and Biodegradable Mesoporous Cellulose Membrane

A flexible, transparent, and renewable mesoporous cellulose membrane (mCel‐membrane) featuring uniform mesopores of ≈24.7 nm and high porosity of 71.78% is prepared via a facile and scalable solution‐phase inversion process. KOH‐saturated mCel‐membrane as a polymer electrolyte demonstrates a high electrolyte retention of 451.2 wt%, a high ionic conductivity of 0.325 S cm^?1, and excellent mechanical flexibility and robustness. A solid‐state electric double layer capacitor (EDLC) using activated carbon as electrodes, the KOH‐saturated mCel‐membrane as a polymer electrolyte exhibits a high capacitance of 110 F g^?1 at 1.0 A g^?1, and long cycling life of 10 000 cycles with 84.7% capacitance retention. Moreover, a highly integrated planar‐type micro‐supercapacitor (MSC) can be facilely fabricated by directly depositing the electrode materials on the mCel‐membrane‐based polymer electrolyte without using complicated devices. The resulting MSC exhibits a high areal capacitance of 153.34 mF cm^?2 and volumetric capacitance of 191.66 F cm^?3 at 10 mV s^?1, representing one of the highest values among all carbon‐based MSC devices. These findings suggest that the developed renewable, flexible, mesoporous cellulose membrane holds great promise in the practical applications of flexible, solid‐state, portable energy storage devices that are not limited to supercapacitors.     

Nanostructured Ternary Electrodes for Energy‐Storage Applications

A three‐component, flexible electrode is developed for supercapacitors over graphitized carbon fabric, utilizing γ‐MnO₂ nanoflowers anchored onto carbon nanotubes (γ‐MnO₂/CNT) as spacers for graphene nanosheets (GNs). The three‐component, composite electrode doubles the specific capacitance with respect to GN‐only electrodes, giving the highest‐reported specific capacitance (308 F g^?1) for symmetric supercapacitors containing MnO₂ and GNs using a two‐electrode configuration, at a scan rate of 20 mV s^?1. A maximum energy density of 43 W h kg^?1 is obtained for our symmetric supercapacitors at a constant discharge‐current density of 2.5 A g^?1 using GN–(γ‐MnO₂/CNT)‐nanocomposite electrodes. The fabricated supercapacitor device exhibits an excellent cycle life by retaining ≈90% of the initial specific capacitance after 5000 cycles.     

Graphene–Cellulose Paper Flexible Supercapacitors

A simple and scalable method to fabricate graphene‐cellulose paper (GCP) membranes is reported; these membranes exhibit great advantages as freestanding and binder‐free electrodes for flexible supercapacitors. The GCP electrode consists of a unique three‐dimensional interwoven structure of graphene nanosheets and cellulose fibers and has excellent mechanical flexibility, good specific capacitance and power performance, and excellent cyclic stability. The electrical conductivity of the GCP membrane shows high stability with a decrease of only 6% after being bent 1000 times. This flexible GCP electrode has a high capacitance per geometric area of 81 mF cm^?2, which is equivalent to a gravimetric capacitance of 120 F g^?1 of graphene, and retains >99% capacitance over 5000 cycles. Several types of flexible GCP‐based polymer supercapacitors with various architectures are assembled to meet the power‐energy requirements of typical flexible or printable electronics. Under highly flexible conditions, the supercapacitors show a high capacitance per geometric area of 46 mF cm^?2 for the complete devices. All the results demonstrate that polymer supercapacitors made using GCP membranes are versatile and may be used for flexible and portable micropower devices.     

Battery‐like Supercapacitors from Vertically Aligned Carbon Nanofiber Coated Diamond: Design and Demonstrator

To fabricate battery‐like supercapacitors with high power and energy densities, big capacitances, as well as long‐term capacitance retention, vertically aligned carbon nanofibers (CNFs) grown on boron doped diamond (BDD) films are employed as the capacitor electrodes. They possess large surface areas, high conductivity, high stability, and importantly are free of binder. The large surface areas result from their porous structures. The containment of graphene layers and copper metal catalysts inside CNFs leads to their high conductivity. Both electrical double layer capacitors (EDLCs) in inert solutions and pseudocapacitors (PCs) using Fe(CN)₆^3?/4? redox‐active electrolytes are constructed with three‐ and two‐electrode systems. The assembled two‐electrode symmetrical supercapacitor devices exhibit capacitances of 30 and 48 mF cm^?2 at 10 mV s^?1 for EDLC and PC devices, respectively. They remain constant even after 10 000 charging/discharging cycles. The power densities are 27.3 and 25.3 kW kg^?1 for EDLC and PC devices, together with their energy densities of 22.9 and 44.1 W h kg^?1, respectively. The performance of these devices is superior to most of the reported supercapacitors and batteries. Vertically aligned CNF/BDD hybrid films are thus useful to construct high‐performance battery‐like and industry‐orientated supercapacitors for future power devices.     

High‐Performance Fiber‐Shaped All‐Solid‐State Asymmetric Supercapacitors Based on Ultrathin MnO2 Nanosheet/Carbon Fiber Cathodes for Wearable Electronics

Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO₂ nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g^?1 at a current density of 2.5 A g^?1 and possess superior cycle stability. When MnO₂ nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g^?1 and an exceptional energy density of 27.2 Wh kg^?1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.     

High Volumetric Capacitance,Ultralong Life Supercapacitors Enabled by Waxberry‐Derived Hierarchical Porous Carbon Materials

Supercapacitors with fast charge/discharge rate and long cycling stability (>50 000 cycles) are attractive for energy storage and mobile power supply. In this paper, a facile strategy is developed to fabricate an Fe₂O₃/FeS‐decorated N, S‐codoped hierarchical porous carbon hybrid. Its microstructure and compositions can be readily controlled through adjusting the hydrothermal reaction between waxberry and iron sulfate. The constructed supercapacitors with the as‐prepared carbon materials from this reaction are able to exhibit outstanding capacitive performance with a superfast charge/discharge rate (<1 s), ultralong cycle life (>50 000 cycles, 80 A g⁻¹), ultrahigh volumetric capacitance (1320.4 F cm⁻³, 0.1 A g⁻¹), and high energy density (100.9 W h kg⁻¹, 221.9 W h L⁻¹). The outstanding performance makes it one of the best biomass‐derived supercapacitors. The superior capacitive behavior is likely to arise from the N and S codoping on the surface/edge/skeleton of the carbon microspheres and nanosheet composites coupled with the fast redox reaction of Fe₂O₃/FeS. Overall, this research presents a new avenue for developing the next generation of sustainable high‐performance energy storage device.     

Ionogel Electrolytes for High‐Performance Lithium Batteries: A Review

Ionic liquids (ILs) are important electrolytes for applications in electrochemical devices. An emerging trend in ILs research is their hybridization with solid matrices, named ionogels. These ionogels can not only overcome the fluidity of ILs but also exhibit high mechanical strength of the solid matrix. Therefore, they show promise for applications in building lithium batteries. In this review, various types of solid matrices for confining ILs are summarized, including nonmetallic oxides, metal oxides, IL‐tethered nanoparticles, functionalized SiO₂, metal–organic frameworks, and other structural materials. The synthetic strategies for ionogels are first documented, focusing on physical confinement and covalent grafting. Then, the structure, ionic conductivity, thermal stability, and electrochemical stability of ionogels are addressed in detail. Furthermore, the authors highlight the potential applications of state‐of‐art ionogels in lithium batteries. The authors conclude this review by outlining the remaining challenges as well as personal perspectives on this hot area of research.     

Superior Multifunctional Activity of Nanoporous Carbons with Widely Tunable Porosity: Enhanced Storage Capacities for Carbon‐Dioxide,Hydrogen, Water,and Electric Charge

Nanoporous carbons (NPCs) with engineered specific pore sizes and sufficiently high porosities (both specific surface area and pore volume) are necessary for storing energy in the form of electric charges and molecules. Herein, NPCs, derived from biomass pine‐cones, coffee‐grounds, graphene‐oxide and metal‐organic frameworks, with systematically increased pore width (<1.0 nm to a few nm), micropore volume (0.2–0.9 cm³ g^?1) and specific surface area (800–2800 m² g^?1) are presented. Superior CO₂, H_2, and H₂O uptakes of 35.0 wt% (≈7.9 mmol g^?1 at 273 K), 3.0 wt% (at 77 K) and 85.0 wt% (at 298 K), respectively at 1 bar, are achieved. At controlled microporosity, supercapacitors deliver impressive performance with a capacity of 320 and 230 F g^?1 at 500 mA g^?1, in aqueous and organic electrolytes, respectively. Excellent areal capacitance and energy density (>50 Wh kg^?1 at high power density, 1000 W kg^?1) are achieved to form the highest reported values among the range of carbons in the literature. The noteworthy energy storage performance of the NPCs for all five cases (CO₂, H₂, H₂O, and capacitance in aqueous and organic electrolytes) is highlighted by direct comparison to numerous existing porous solids. A further analysis on the specific pore type governed physisorption capacities is presented.     

Partial Nitridation‐Induced Electrochemistry Enhancement of Ternary Oxide Nanosheets for Fiber Energy Storage Device

Fiber‐based power sources are receiving interest in terms of application in wearable electronic devices. Herein, fiber‐shaped all‐solid‐state asymmetric energy storage devices are fabricated based on a partially nitridized NiCo₂O₄ hybrid nanostructures on graphite fibers (GFs). The surface nitridation leads to a 3D “pearled‐veil” network structure, in which Ni–Co–N nanospheres are mounted on NiCo₂O₄ nanosheets' electrode. It is demonstrated that the hybrid materials are more potent than the pure NiCo₂O₄ in energy storage applications due to a cooperative effect between the constituents. The Ni–Co–N segments augment the pristine oxide nanosheets by enhancing both capacity and rate performance (a specific capacity of 384.75 mAh g⁻¹ at 4 A g⁻¹, and a capacity retention of 86.5% as the current is increased to 20 A g⁻¹). The whole material system has a metallic conductivity that renders high‐rate charge and discharge, and an extremely soft feature, so that it can wrap around arbitrary‐shaped holders. All‐solid‐state asymmetric device is fabricated using Ni–Co–N/NiCo₂O₄/GFs and carbon nanotubes/GFs as the electrodes. The flexible device delivers outstanding performance compared to most oxide‐based full devices. These structured hybrid materials may find applications in miniaturized foldable energy devices.     

Novel Metal@Carbon Spheres Core–Shell Arrays by Controlled Self‐Assembly of Carbon Nanospheres: A Stable and Flexible Supercapacitor Electrode

The high performance of electrochemical energy‐storage devices relies largely on scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. Carbon nanopsheres (CNSs) are widely used for energy storage and conversion devices. Here, the directional assembly of CNSs on a vertical‐standing metal scaffold into a core/shell array structure is reported. The method uses a three‐step all‐solution synthesis strategy (chemical bath deposition, electrodeposition, and hydrothermal) and begins from ZnO microrod arrays as a sacrificial template. The self‐assembly of CNSs can be correlated to a simultaneous etching effect to the ZnO accompanying the polymerization of glucose precursor. The Ni microtube/CNSs arrays are selected as an example for structural and electrochemical characterizations. The novel type of metal/CNSs arrays is demonstrated to be a highly stable electrode for supercapacitors. The electrodes of metal/CNSs arrays are assembled into symmetric supercapacitors and exhibit high capacitances of 227 F g^?1 (at 2.5 A g^?1) and an outstanding cycling stability with capacitance retention of 97% after 40 000 cycles.     

Graphene‐Indanthrone Donor–π–Acceptor Heterojunctions for High‐Performance Flexible Supercapacitors

To overcome the low energy density bottleneck of graphene‐based supercapacitors and to organically endow them with high‐power density, ultralong‐life cycles, etc., one rational strategy that couple graphene sheets with multielectron, redox‐reversible, and structurally‐stable organic compounds. Herein, a graphene‐indanthrone (IDT) donor–π–acceptor heterojunction is conceptualized for efficient and smooth 6H⁺/6e^? transfers from pseudocapacitive IDT molecules to electrochemical double‐layer capacitive graphene scaffolds. To construct this, water‐processable graphene oxide (GO) is employed as a graphene precursor, and to in situ exfoliate IDT industrial dyestuff, followed by a hydrothermally‐induced reduction toward GO and self‐assembly between reduced GO (rGO) donors (D) and IDT acceptors (A), affording rGO‐π‐IDT D–A heterojunctions. Electrochemical tests indicate that rGO‐π‐IDT heterojunctions deliver a gravimetric capacitance of 535.5 F g^?1 and an amplified volumetric capacitance of 685.4 F cm^?3. The assembled flexible all‐solid‐state supercapacitor yields impressive volumetric energy densities of 31.3 and 25.1 W h L^?1, respectively, at low and high power densities of 767 and 38 554 W L^?1, while exhibiting an exceptional rate capability, cycling stability, and enduring mechanically‐challenging bending and distortions. The concept and methodology may open up opportunities for other two‐dimensional materials and other energy‐related devices.     

Formation of Yolk‐Shelled Ni–Co Mixed Oxide Nanoprisms with Enhanced Electrochemical Performance for Hybrid Supercapacitors and Lithium Ion Batteries

Yolk‐shelled particles with tailored physical and chemical properties are attractive for electrochemical energy storage. Starting with metal acetate hydroxide with tetragonal prism‐like shapes, yolk‐shelled Ni–Co mixed oxide nanoprisms with tunable composition have been prepared by simple thermal annealing in air. It is found that the yolk‐shelled structure is formed due to the fast thermally driven contraction process. With the favorable porous structure and composition, these yolk‐shelled Ni–Co oxide particles manifest greatly enhanced electrochemical properties when evaluated as electrodes for both hybrid supercapacitors and lithium ion batteries. In particular, the resultant Ni_0.37Co oxide sample delivers very high specific capacitance of over 1000 F g^?1 at a current density of 10 A g^?1 with remarkably high capacitance retention of 98% after 15 000 cycles.     

Graphitic Petal Electrodes for All‐Solid‐State Flexible Supercapacitors

The charge storage characteristics of a composite nanoarchitecture with a highly functional 3D morphology are reported. The electrodes are formed by the electropolymerization of aniline monomers into a nanometer‐thick polyaniline (PANI) film that conformally coats graphitic petals (GPs) grown by microwave plasma chemical vapor deposition (MPCVD) on conductive carbon cloth (CC). The hybrid CC/GPs/PANI electrodes yield results near the theoretical maximum capacitance for PANI of 2000 F g^?1 (based on PANI mass) and a large area‐normalized specific capacitance of ≈2.6 F cm^?2 (equivalent to a volumetric capacitance of ≈230 F cm^?3) at a low current density of 1 A g^?1 (based on PANI mass). The specific capacitances remain above 1200 F g^?1 (based on PANI mass) for currents up to 100 A g^?1 with correspondingly high area‐normalized values. The hybrid electrodes also exhibit a high rate capability with an energy density of 110 Wh kg^?1 and a maximum power density of 265 kW kg^?1 at a current density of 100 A g^?1. Long‐term cyclic stability is good (≈7% loss of initial capacitance after 2000 cycles), with coulombic efficiencies >99%. Moreover, prototype all‐solid‐state flexible supercapacitors fabricated from these hybrid electrodes exhibit excellent energy storage performance.     

Hierarchical Fabric Decorated with Carbon Nanowire/Metal Oxide Nanocomposites for 1.6 V Wearable Aqueous Supercapacitors

Aqueous asymmetric supercapacitors (ASCs) may offer comparable or higher energy density than electric double‐layer capacitors (EDLCs) based on organic electrolytes. As such, ASCs may be more suitable for integration into smart textiles, where the use of flammable organic solvents is not acceptable. However, reported ASC devices typically suffer from poor rate capability and low areal loadings. This study demonstrates the development of nitrogen‐doped carbon (N‐C) nanowire/metal oxide (Fe₂O₃ and MnO₂) nanocomposite electrodes directly produced on the internal surface of a conductive fabric for use as high‐rate electrodes for solid‐state ASCs. The N‐C nanowires provide fast and efficient pathways for electrons, while short diffusion paths within nanosized metal oxides enable fast ion transport, leading to greatly enhanced performance at high rates. The porous structure of the fabric enables high areal capacitance loading in each electrode (≈150 mF cm^?2). Both electrodes show high specific capacitance of ≈180 F g^?1 (Fe₂O₃) and ≈250 F g^?1 (MnO₂) and excellent rate capability. Solid‐state ASCs assembled by using an aqueous gel electrolyte operate at 1.6 V and deliver over 60 mF cm^?2 during ≈50 s charging/discharging time and over 30 mF cm^?2 for ≈5 s discharge.     

Large‐Scale Conductive Yarns Based on Twistable Korean Traditional Paper (Hanji) for Supercapacitor Applications: Toward High‐Performance Paper Supercapacitors

A simple and scalable method to fabricate a yarn‐type supercapacitor with a large specific capacitance without the aid of traditional pseudocapacitive electrode materials such as conducting polymers and metal oxides is reported. The yarn‐type supercapacitors are made from twisting reduced graphene oxide (rGO) or/and single‐walled carbon nanotubes (SWNTs)‐coated Korean traditional paper (KTP). The yarn‐type paper supercapacitor displays surprisingly enhanced electrochemical capacitance values, showing synergistic effect between rGO and SWNTs (500 times larger than performance of yarn‐type rGO‐coated paper supercapacitors). Coating rGO or/and SWNTs on KTP gives good morphology to the composite film, in which porosity increases and mean pore diameter decreases. The yarn‐type rGO/SWNT paper supercapacitor shows good mechanical strength, high flexibility, excellent electrochemical performance, and long‐life operation. The yarn‐type supercapacitor has an excellent electrochemical performance with a specific capacitance of 366 F g^?1 at scan rate of 25 mV s^?1 and high stability without any degradation in electrical performance up to 10 000 charge–discharge cycles. The average capacitance of rGO/SWNT@KTP yarn‐type supercapacitors is seven times higher than that of sheet‐type supercapacitors at scan rate of 500 mV s^?1. The lighting of a red light‐emitting diode (LED) is demonstrated by the yarn‐type paper supercapacitor without connecting supercapacitors in series.     

A Three‐Dimensionally Interconnected Carbon Nanotube–Conducting Polymer Hydrogel Network for High‐Performance Flexible Battery Electrodes

High‐performance flexible energy‐storage devices have great potential as power sources for wearable electronics. One major limitation to the realization of these applications is the lack of flexible electrodes with excellent mechanical and electrochemical properties. Currently employed batteries and supercapacitors are mainly based on electrodes that are not flexible enough for these purposes. Here, a three‐dimensionally interconnected hybrid hydrogel system based on carbon nanotube (CNT)‐conductive polymer network architecture is reported for high‐performance flexible lithium ion battery electrodes. Unlike previously reported conducting polymers (e.g., polyaniline, polypyrrole, polythiophene), which are mechanically fragile and incompatible with aqueous solution processing, this interpenetrating network of the CNT‐conducting polymer hydrogel exibits good mechanical properties, high conductivity, and facile ion transport, leading to facile electrode kinetics and high strain tolerance during electrode volume change. A high‐rate capability for TiO₂ and high cycling stability for SiNP electrodes are reported. Typically, the flexible TiO₂ electrodes achieved a capacity of 76 mAh g^–1 in 40 s of charge/discharge and a high areal capacity of 2.2 mAh cm^–2 can be obtained for flexible SiNP‐based electrodes at 0.1C rate. This simple yet efficient solution process is promising for the fabrication of a variety of high performance flexible electrodes.     

Highly Defective Layered Double Perovskite Oxide for Efficient Energy Storage via Reversible Pseudocapacitive Oxygen‐Anion Intercalation

The use of perovskite materials as anion‐based intercalation pseudocapacitor electrodes has received significant attention in recent years. Notably, these materials, characterized by high oxygen vacancy concentrations, do not require high surface areas to achieve a high energy storage capacity as a result of the bulk intercalation mechanism. This study reports that reduced PrBaMn₂O_6–δ (r‐PBM), possessing a layered double perovskite structure, exhibits ultrahigh capacitance and functions as an excellent oxygen anion‐intercalation‐type electrode material for supercapacitors. Formation of the layered double perovskite structure, as facilitated by hydrogen treatment, is shown to significantly enhance the capacitance, with the resulting r‐PBM material demonstrating a very high gravimetric capacitance of 1034.8 F g^?1 and an excellent volumetric capacitance of ≈2535.3 F cm^?3 at a current density of 1 A g^?1. The resultant formation of a double perovskite crystal oxide with a specific layered structure leads to the r‐PBM with a substantially higher oxygen diffusion rate and oxygen vacancy concentration. These superior characteristics show immense promise for their application as oxygen anion‐intercalation‐type electrodes in pseudocapacitors.     

Flash Converted Graphene for Ultra‐High Power Supercapacitors

Supercapacitors are known for their rapid energy charge–discharge properties, often ten to a hundred times faster than batteries. However, there is still a demand for supercapacitors with even faster charge–discharge characteristics to fulfill the requirements of emerging technologies. The power and rate capabilities of supercapacitors are highly dependent on the morphology of their electrode materials. An electrically conductive 3D porous structure possessing a high surface area for ions to access is ideal. Using a flash of light, a method to produce highly interconnected 3D graphene architectures with high surface area and good conductivity is developed. The flash converted graphene is synthesized by reducing freeze‐dried graphene oxide using an ordinary camera flash as a photothermal source. The flash converted graphene is used in coin cell supercapacitors to investigate its electrode materials properties. The electrodes are fabricated using either a precoating flash conversion or a postcoating flash conversion of graphene oxide. Both techniques produce supercapacitors possessing ultra‐high power (5–7 × 10⁵ W kg^?1). Furthermore, optimized supercapacitors retain >50% of their capacitance when operated at an ultrahigh current density up to 220 A g^?1.     

Boron Element Nanowires Electrode for Supercapacitors

The pursuit of new categories of active materials as electrodes of supercapacitors remains a great challenge. Herein, for the first time, elemental boron as a superior electrode material of supercapacitors is reported, which exhibits significantly high capacitances and excellent rate performance in all alkaline, neutral, and acidic electrolytes. Notably, boron nanowire‐carbon fiber cloth (BNWs‐CFC) electrodes achieve a capacitance up to 42.8 mF cm^?2 at a scan rate of 5 mV s^?1 and 60.2 mF cm^?2 at a current density of 0.2 mA cm^?2 in the acidic electrolyte. Moreover, in all these three kinds of electrolytes, BNWs‐CFC electrodes demonstrate a decent cycling stability with >80% capacitance retention after 8000 charging/discharging cycles. The Dominating energy storage mechanism of BNWs in the different electrolytes is analyzed by looking into the kinetics of the electrochemical process. Subsequently, the BNWs‐CFC electrode is used to fabricate a flexible solid‐state supercapacitor, which reveals a specific capacitance up to 22.73 mF cm^?2 and good mechanical performance after 1000 bending cycles. This study opens a new avenue to explore elemental boron‐based new nanomaterials for the application of energy storage with superior electrochemical performance.