Flexible Films Derived from Electrospun Carbon Nanofibers Incorporated with Co3O4 Hollow Nanoparticles as Self‐Supported Electrodes for Electrochemical Capacitors

Flexible porous films are prepared from electrospun carbon nanofibers (CNFs) embedded with Co₃O₄ hollow nanoparticles (NPs) and are directly applied as self‐supported electrodes for high‐performance electrochemical capacitors. Uniform Co₃O₄ hollow NPs are well dispersed and/or embedded into each CNF with desirable electrical conductivity. These Co₃O₄‐CNFs intercross each other and form 3D hierarchical porous hybrid films. Benefiting from intriguing structural features, the unique binder‐free Co₃O₄ hollow NPs/CNF hybrid film electrodes exhibit high specific capacitance (SC), excellent rate capability and cycling stability. As an example, the flexible hybrid film with loading of 35.9 wt% Co₃O₄ delivers a SC of 556 F g^?1 at a current density of 1 A g^?1, and 403 F g^?1 even at a very high current density of 12 A g^?1. Remarkably, almost no decay in SC is found after continuous charge/discharge cycling for 2000 cycles at 4 A g^?1. This exceptional electrochemical performance makes such novel self‐supported Co₃O₄‐CNFs hybrid films attractive for high‐performance electrochemical capacitors.     

Flexible Asymmetric Supercapacitor Based on Structure‐Optimized Mn3O4/Reduced Graphene Oxide Nanohybrid Paper with High Energy and Power Density

A highly flexible Mn₃O₄/reduced graphene oxide (rGO) nanohybrid paper with high electrical conductivity and high mass loading of Mn₃O₄ nanofibers (0.71 g cm^?3) is developed via a facile gel formation and electrochemical reduction process, which is low‐cost, environmental friendly, and easy to scale up. Confined Mn₃O₄ nanofibers are well dispersed within the rGO sheets, which demonstrate to be a promising cathode material for flexible asymmetric supercapacitors (ASCs). When coupled with an electrochemically reduced rGO paper as the anode, a flexible ASC device, based on the Mn₃O₄/rGO nanohybrid paper as the cathode, is assembled; and it demonstrates remarkable electrochemical performance: a high volumetric capacitance of 54.6 F cm^?3 (546.05 mF cm^?2), and remarkable volumetric energy and power density (0.0055 Wh cm^?3 and 10.95 W cm^?3) being achieved with excellent cycling ability. The nanohybrid paper shows great improvement for flexible energy devices in terms of electrochemical properties.     

Carbon‐Stabilized High‐Capacity Ferroferric Oxide Nanorod Array for Flexible Solid‐State Alkaline Battery–Supercapacitor Hybrid Device with High Environmental Suitability

Iron oxides are promising to be utilized in rechargeable alkaline battery with high capacity upon complete redox reaction (Fe³⁺ Fe⁰). However, their practical application has been hampered by the poor structural stability during cycling, presenting a challenge that is particularly huge when binder‐free electrode is employed. This paper proposes a “carbon shell‐protection” solution and reports on a ferroferric oxide–carbon (Fe₃O₄–C) binder‐free nanorod array anode exhibiting much improved cyclic stability (from only hundreds of times to >5000 times), excellent rate performance, and a high capacity of ≈7776.36 C cm^?3 (≈0.4278 C cm^?2; 247.5 mAh g^?1, 71.4% of the theoretical value) in alkaline electrolyte. Furthermore, by pairing with a capacitive carbon nanotubes (CNTs) film cathode, a unique flexible solid‐state rechargeable alkaline battery‐supercapacitor hybrid device (≈360 μm thickness) is assembled. It delivers high energy and power densities (1.56 mWh cm^?3; 0.48 W cm^?3/≈4.8 s charging), surpassing many recently reported flexible supercapacitors. The highest energy density value even approaches that of Li thin‐film batteries and is about several times that of the commercial 5.5 V/100 mF supercapacitor. In particular, the hybrid device still maintains good electrochemical attributes in cases of substantially bending, high mechanical pressure, and elevated temperature (up to 80 °C), demonstrating high environmental suitability.     

Self‐Standing Porous LiCoO2 Nanosheet Arrays as 3D Cathodes for Flexible Li‐Ion Batteries

Self‐standing electrodes are the key to realize flexible Li‐ion batteries. However, fabrication of self‐standing cathodes is still a major challenge. In this work, porous LiCoO₂ nanosheet arrays are grown on Au‐coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co₃O₄ nanosheet arrays as the template followed by quick annealing in air. The binder‐free and self‐standing LiCoO₂ nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO₂ nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g^?1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li₄Ti₅O₁₂ nanosheet arrays as anode, an all‐nanosheet array based LiCoO₂//Li₄Ti₅O₁₂ flexible Li‐ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO₂//Li₄Ti₅O₁₂ battery can deliver large specific reversible capacities of 130.7 mA h g^?1 at 0.1 C rate and 85.3 mA h g^?1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li‐ion batteries.     

Flexible Sodium‐Ion Pseudocapacitors Based on 3D Na2Ti3O7 Nanosheet Arrays/Carbon Textiles Anodes

Flexible energy storage devices are critical components for emerging flexible and wearable electronics. Improving the electrochemical performance of flexible energy storage devices depends largely on development of novel electrode architectures and new systems. Here, a new class of flexible energy storage device called flexible sodium‐ion pseudocapacitors is developed based on 3D‐flexible Na₂Ti₃O₇ nanosheet arrays/carbon textiles (NTO/CT) as anode and flexible reduced graphene oxide film (GFs) as cathode without metal current collectors or conducting additives. The NTO/CT anode with advanced electrode architectures is fabricated by directly growing Na₂Ti₃O₇ nanosheet arrays on carbon textiles with robust adhesion through a simple hydrothermal process. The flexible GF//NTO/CT configuration achieves a high energy density of 55 Wh kg^?1 and high power density of 3000 W kg^?1. Taking the fully packaged flexible sodium‐ion pseudocapacitors into consideration, the maximum practical volumetric energy density and power density reach up to 1.3 mWh cm^?3 and 70 mW cm^?3, respectively. In addition, the flexible GF//NTO/CT device demonstrates a stable electrochemical performances with almost 100% capacitance retention under harsh mechanical deformation.     

Rambutan‐Like Hybrid Hollow Spheres of Carbon Confined Co3O4 Nanoparticles as Advanced Anode Materials for Sodium‐Ion Batteries

Transition metal oxides, possessing high theoretical specific capacities, are promising anode materials for sodium‐ion batteries. However, the sluggish sodiation/desodiation kinetics and poor structural stability restrict their electrochemical performance. To achieve high and fast Na storage capability, in this work, rambutan‐like hybrid hollow spheres of carbon confined Co₃O₄ nanoparticles are synthesized by a facile one‐pot hydrothermal treatment with postannealing. The hierarchy hollow structure with ultrafine Co₃O₄ nanoparticles embedded in the continuous carbon matrix enables greatly enhanced structural stability and fast electrode kinetics. When tested in sodium‐ion batteries, the hollow structured composite electrode exhibits an outstandingly high reversible specific capacity of 712 mAh g^?1 at a current density of 0.1 A g^?1, and retains a capacity of 223 mAh g^?1 even at a large current density of 5 A g^?1. Besides the superior Na storage capability, good cycle performance is demonstrated for the composite electrode with 74.5% capacity retention after 500 cycles, suggesting promising application in advanced sodium‐ion batteries.     

Mesoporous NiCo2O4 Nanowire Arrays Grown on Carbon Textiles as Binder‐Free Flexible Electrodes for Energy Storage

Binary metal oxides has been regarded as a promising class of electrode materials for high‐performance energy storage devices since it offers higher electrochemical activity and higher capacity than mono‐metal oxide. Besides, rational design of electrode architectures is an effective solution to further enhance electrochemical performance of energy storage devices. Here, the advanced electrode architectures consisting of carbon textiles uniformally covered by mesoporous NiCo₂O₄ nanowire arrays (NWAs) are successfully fabricated by a simple surfactant‐assisted hydrothermal method combined with a short post annealing treatment, which can be directly applied as self‐supported electrodes for energy storage devices, such as Li‐ion batteries, supercapacitors. The as‐prepared mesoporous NiCo₂O₄ nanowires consist of numerous highly crystalline nanoparticles, leaving a large number of mesopores to alleviate the volume change during the charge/discharge process. Electrode architectures presented here promise fast electron transport by direct connection to the growth substrate and facile ion diffusion path provided by both the abundant mesoporous structure in nanowires and large open spaces between neighboring nanowires, which ensures every nanowire participates in the ultrafast electrochemical reaction. Benefiting from the intrinsic materials and architectures features, the unique binder‐free NiCo₂O₄/carbon textiles exhibit high specific capacity/capacitance, excellent rate capability, and cycling stability.     

Oxygen‐Deficient Bismuth Oxide/Graphene of Ultrahigh Capacitance as Advanced Flexible Anode for Asymmetric Supercapacitors

Oxygen‐deficient bismuth oxide (r‐Bi₂O₃)/graphene (GN) is designed, fabricated, and demonstrated via a facile solvothermal and subsequent solution reduction method. The ultrafine network bacterial cellulose (BC) as substrate for r‐Bi₂O₃/GN exhibits high flexibility, remarkable tensile strength (55.1 MPa), and large mass loading of 9.8 mg cm^?2. The flexible r‐Bi₂O₃/GN/BC anode delivers appreciable areal capacitance (6675 mF cm^?2 at 1 mA cm^?2) coupled with good rate capability (3750 mF cm^?2 at 50 mA cm^?2). In addition, oxygen vacancies have great influence on the capacitive performance of Bi₂O₃, delivering significantly improved capacitive values than the untreated Bi₂O₃ flexible electrode, and ultrahigh gravimetric capacitance of 1137 F g^?1 (based on the mass of r‐Bi₂O₃) can be obtained, achieving 83% of the theoretical value (1370 F g^?1). Flexible asymmetric supercapacitor is fabricated with r‐Bi₂O₃/GN/BC and Co₃O₄/GN/BC paper as the negative and positive electrodes, respectively. The operation voltage is expanded to 1.6 V, revealing a maximum areal energy density of 0.449 mWh cm^?2 (7.74 mWh cm^?3) and an areal power density of 40 mW cm^?2 (690 mW cm^?3). Therefore, this flexible anode with excellent electrochemical performance and high mechanical properties shows great potential in the field of flexible energy storage devices.     

General Synthesis of N‐Doped Macroporous Graphene‐Encapsulated Mesoporous Metal Oxides and Their Application as New Anode Materials for Sodium‐Ion Hybrid Supercapacitors

A general method to synthesize mesoporous metal oxide@N‐doped macroporous graphene composite by heat‐treatment of electrostatically co‐assembled amine‐functionalized mesoporous silica/metal oxide composite and graphene oxide, and subsequent silica removal to produce mesoporous metal oxide and N‐doped macroporous graphene simultaneously is reported. Four mesoporous metal oxides (WO_{3? x} , Co₃O₄, Mn₂O₃, and Fe₃O₄) are encapsulated in N‐doped macroporous graphene. Used as an anode material for sodium‐ion hybrid supercapacitors (Na‐HSCs), mesoporous reduced tungsten oxide@N‐doped macroporous graphene (m‐WO_{3? x} @NM‐rGO) gives outstanding rate capability and stable cycle life. Ex situ analyses suggest that the electrochemical reaction mechanism of m‐WO_{3? x} @NM‐rGO is based on Na⁺ intercalation/de‐intercalation. To the best of knowledge, this is the first report on Na⁺ intercalation/de‐intercalation properties of WO_{3? x} and its application to Na‐HSCs.     

In‐Plane Assembled Orthorhombic Nb2O5 Nanorod Films with High‐Rate Li+ Intercalation for High‐Performance Flexible Li‐Ion Capacitors

Organic hybrid supercapacitors that consist of a battery electrode and a capacitive electrode show greatly improved energy density, but their power density is generally limited by the poor rate capability of battery‐type electrodes. In addition, flexible organic hybrid supercapacitors are rarely reported. To address the above issues, herein an in‐plane assembled orthorhombic Nb₂O₅ nanorod film anode with high‐rate Li⁺ intercalation to develop a flexible Li‐ion hybrid capacitor (LIC) is reported. The binder‐/additive‐free film exhibits excellent rate capability (≈73% capacity retention with the rate increased from 0.5 to 20 C) and good cycling stability (>2500 times). Kinetic analyses reveal that the high rate performance is mainly attributed to the excellent in‐plane assembly of interconnected single‐crystalline Nb₂O₅ nanorods on the current collector, ensuring fast electron transport, facile Li‐ion migration in the porous film, and greatly reduced ion‐diffusion length. Using such a Nb₂O₅ film as anode and commercial activated carbon as cathode, a flexible LIC is designed. It delivers both high gravimetric and high volumetric energy/power densities (≈95.55 Wh kg^?1/5350.9 W kg^?1; 6.7 mW h cm^?3/374.63 mW cm^?3), surpassing previous typical Li‐intercalation electrode‐based LICs. Furthermore, this LIC device still keeps good electrochemical attributes even under serious bending states (30°–180°).     

A Scalable Free‐Standing V2O5/CNT Film Electrode for Supercapacitors with a Wide Operation Voltage (1.6 V) in an Aqueous Electrolyte

While vanadium oxides have many attractive pseudocapacitive features for energy storage, their applications are severely limited by the poor electronic conductivity and low specific surface area. To overcome these limitations, a scalable, free‐standing film electrode composed of intertwined V₂O₅ nanowires and carbon nanotubes (CNTs) using a blade coating process has been prepared. The unique architecture of this hybrid electrode greatly facilitates electronic transport along CNTs while maintaining rapid ion diffusion within V₂O₅ nanowires and fast electron transfer across the V₂O₅/CNTs interfaces. When tested in a neutral aqueous electrolyte, this hybrid film electrode demonstrates a volumetric capacitance of ≈460 F cm^?3. Moreover, a symmetric capacitor based on two identical film electrodes displays a wide operation voltage window of 1.6 V, delivering a volumetric energy density as high as 41 Wh L^?1.     

Three‐Dimensional Co3O4@MnO2 Hierarchical Nanoneedle Arrays: Morphology Control and Electrochemical Energy Storage

In this paper, a highly ordered three‐dimensional Co₃O₄@MnO₂ hierarchical porous nanoneedle array on nickel foam is fabricated by a facile, stepwise hydrothermal approach. The morphologies evolution of Co₃O₄ and Co₃O₄@MnO₂ nanostructures upon reaction times and growth temperature are investigated in detail. Moreover, the as‐prepared Co₃O₄@MnO₂ hierarchical structures are investigated as anodes for both supercapacitors and Li‐ion batteries. When used for supercapacitors, excellent electrochemical performances such as high specific capacitances of 932.8 F g^?1 at a scan rate of 10 mV s^?1 and 1693.2 F g^?1 at a current density of 1 A g^?1 as well as long‐term cycling stability and high energy density (66.2 W h kg^?1 at a power density of 0.25 kW kg^?1), which are better than that of the individual component of Co₃O₄ nanoneedles and MnO₂ nanosheets, are obtained. The Co₃O₄@MnO₂ NAs are also tested as anode material for LIBs for the first time, which presents an improved performance with high reversible capacity of 1060 mA h g^?1 at a rate of 120 mA g^?1, good cycling stability, and rate capability.     

Atomic Layer Deposited Non‐Noble Metal Oxide Catalyst for Sodium–Air Batteries: Tuning the Morphologies and Compositions of Discharge Product

Catalysts can play a critical role in the development of sodium–air batteries (SABs). Atomic layer deposition (ALD) technology enables rational design and atomic utilization of catalyst by homogenously distributing catalytically active material on a variety of substrates. Here, a novel hierarchical nanostructured Co₃O₄ is decorated on carbon nanotubes by ALD (CNT@Co₃O₄) and used as a catalyst for SABs. CNT@Co₃O₄ demonstrates better performance and longer cycle life than a mechanically mixed CNT/Co₃O₄ nanocomposite. Well‐dispersed ALD Co₃O₄ catalyst on CNTs, which serves as functionalized active sites, enables rapid electron exchange and high oxygen reduction/evolution activities. Synchrotron‐based X‐ray analysis including X‐ray absorption near edge structure, extended X‐ray absorption fine structure, and scanning transmission X‐ray microscopy characterization techniques have been employed to elucidate the activity of Co₃O₄ and to investigate the nanoscale discharge product distribution found in SABs. This analysis reveals that Co₃O₄ catalyst can promote the electrochemical decomposition of sodium peroxide, superoxide, and carbonates. The role of the catalyst in SABs is clarified and discussed in detail.     

Understanding Origin of Voltage Hysteresis in Conversion Reaction for Na Rechargeable Batteries: The Case of Cobalt Oxides

Conversion reaction electrodes offer a high specific capacity in rechargeable batteries by utilizing wider valence states of transition metals than conventional intercalation‐based electrodes and have thus been intensively studied in recent years as potential electrode materials for high‐energy‐density rechargeable batteries. However, several issues related to conversion reactions remain poorly understood, including the polarization or hysteresis during charge/discharge processes. Herein, Co₃O₄ in Na cells is taken as an example to understand the aforementioned properties. The large hysteresis in charge/discharge profiles is revealed to be due to different electrochemical reaction paths associated with respective charge and discharge processes, which is attributed to the mobility gap among inter‐diffusing species in a metal oxide compound during de/sodiation. Furthermore, a Co₃O₄–graphene nanoplatelet hybrid material is demonstrated to be a promising anode for Na rechargeable batteries, delivering a capacity of 756 mAh g^?1 with a good reversibility and an energy density of 96 Wh kg^?1 (based on the total electrode weight) when combined with a recently reported Na₄Fe₃(PO₄)₂(P₂O₇) cathode.     

Superior Rate Mesoporous Carbon Sphere Array Composite via Intercalation and Conversion Coupling Mechanisms for Potassium-Ion Capacitors

Carbonaceous materials have been usually adopted as the anode for high energy density potassium-ion hybrid capacitors (KICs) owing to their low voltage plateau, high conductivity, and excellent electrochemical compatibility. The improvements of their specific capacity and sluggish intercalation mechanism are still challenges to further boost the energy density of KICs while maintaining high power density and long cycle life. Herein, a N-doped mesoporous carbon sphere array composite is developed by a dual-templates method. The N-doped carbon sphere array with interpenetrated macro- and meso-pores facilitates the fast electron transport and rapid K⁺ diffusion. The uniformly introduced Co₃O₄ nanoparticles (NPs) confined in the array enable a kinetically boosted conversion reaction for excess and fast K⁺ storage. The partially oxidized Co NPs can efficiently enhance the conductivity of the entire composite. By introducing this optimized conversion capacity from encapsulated Co₃O₄ NPs, the composite with intercalation and conversion coupling mechanisms displays superior capacity and cycle life. The assembled KICs exhibit high energy/power densities (148 Wh kg⁻¹/124 W kg⁻¹) and great cycling performance (94% after 5000 cycles, 0.5 A g⁻¹). This promising strategy demonstrates an example for carbonaceous composite anode with synergistic K⁺ storage hybrid mechanism toward high performance KICs.     

Lithiation‐Induced Vacancy Engineering of Co3O4 with Improved Faradic Reactivity for High‐Performance Supercapacitor

Transition metal oxides are promising electrode candidates for supercapacitor because of their low cost, high theoretical capacity, and good reversibility. However, intrinsically poor electrical conductivity and sluggish reaction kinetics of these oxides normally lead to low specific capacity and slow rate capability of the devices. Herein, a commonly used cobalt oxide is used as an example to demonstrate that lithiation process as a new strategy to enhance its electrochemical performance for supercapacitor application. Detailed characterization reveals that electrochemical lithiation of Co₃O₄ crystal reduces the coordination of the Co? O band, leading to substantially increased oxygen vacancies (octahedral Co²⁺ sites). These vacancies further trigger the formation of a new electronic state in the bandgap, resulting in remarkably improved electrical conductivity and accelerated faradic reactions. The lithiated Co₃O₄ exhibits a noticeably enhanced specific capacity of 260 mAh g^?1 at 1 A g^?1, approximately fourfold enhancement compared to that of pristine Co₃O₄ (66 mAh g^?1). The hybrid supercapacitor assembled with lithiated Co₃O₄//N‐doped activated carbon achieves high energy densities in a broad range of power densities, e.g., 76.7 Wh kg^?1 at 0.29 kW kg^?1, 46.9 Wh kg^?1 at a high power density of 18.7 kW kg^?1, outperforming most of the reported hybrid supercapacitors.     

Regulating Oxygen Substituents with Optimized Redox Activity in Chemically Reduced Graphene Oxide for Aqueous Zn-Ion Hybrid Capacitor

Functionalizing carbon cathode surfaces with oxygen functional groups is an effective way to simultaneously tailor the fundamental properties and customize the electrochemical properties of aqueous Zn-ion hybrid capacitors. In this work, the oxygen functional groups of chemically reduced graphene oxide (rGO) are systematically regulated via a series of reductants and varied experimental conductions. Carboxyl and carbonyl have been proven to significantly enhance the aqueous electrolyte wettability, Zn-ion chemical adsorption, and pseudocapacitive redox activity by experimental study and computational analysis. The rGO cathode produced through hydrogen peroxide assisted hydrothermal reduction exhibits a specific capacitance of 277 F g⁻¹ in 1 m ZnSO₄ after optimization of surface oxygen functional groups. In addition, a quasi-solid-state flexible Zn-ion hybrid capacitor (ZHC) with a polyacrylamide gel electrolyte and a high loading mass of 5.1 mg cm⁻² are assembled. The as-prepared quasi-solid state ZHC can offer a superior areal capacitance of 1257 mF cm⁻² and distinguished areal energy density of 342 µW h cm⁻². The significant enhancement of redox activity and Zn-ion storage capability by regulating the oxygen functional groups can shed light on the promotion of electrochemical charge storage properties even beyond protic electrolyte systems.     

Ultrathin Mesoporous NiCo2O4 Nanosheets Supported on Ni Foam as Advanced Electrodes for Supercapacitors

A facile two‐step method is developed for large‐scale growth of ultrathin mesoporous nickel cobaltite (NiCo₂O₄) nanosheets on conductive nickel foam with robust adhesion as a high‐performance electrode for electrochemical capacitors. The synthesis involves the co‐electrodeposition of a bimetallic (Ni, Co) hydroxide precursor on a Ni foam support and subsequent thermal transformation to spinel mesoporous NiCo₂O₄. The as‐prepared ultrathin NiCo₂O₄ nanosheets with the thickness of a few nanometers possess many interparticle mesopores with a size range from 2 to 5 nm. The nickel foam supported ultrathin mesoporous NiCo₂O₄ nanosheets promise fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with an ultrahigh specific capacitance of 1450 F g^?1, even at a very high current density of 20 A g^?1, and excellent cycling performance at high rates, suggesting its promising application as an efficient electrode for electrochemical capacitors.     

Growth of Metal–Metal Oxide Nanostructures on Freestanding Graphene Paper for Flexible Biosensors

Flexible biosensors are of considerable current interest for the development of portable point‐of‐care medical products, minimally invasive implantable devices, and compact diagnostic platforms. A new type of flexible electrochemical sensor fabricated by depositing high‐density Pt nanoparticles on freestanding reduced graphene oxide paper (rGOP) carrying MnO₂ nanowire networks is reported. The triple‐component design offers new possibilities to integrate the mechanical and electrical properties of rGOP, the large surface area of MnO₂ networks, and the catalytic activity of well‐dispersed and small‐sized Pt nanoparticles prepared via ultrasonic‐electrodeposition. The sensitivity and selectivity that the flexible electrode demonstrates for nonenzymatic detection of H₂O₂ enables its use for monitoring H₂O₂ secretion by live cells. The strategy of structurally integrating metal, metal oxide, and graphene paper will provide new insight into the design of flexible electrodes for a wide range of applications in biosensing, bioelectronics, and lab‐on‐a‐chip devices.     

All‐Solid‐State Asymmetric Supercapacitors with Metal Selenides Electrodes and Ionic Conductive Composites Electrolytes

All‐solid‐state flexible asymmetric supercapacitors (ASCs) are developed by utilization of graphene nanoribbon (GNR)/Co_0.85Se composites as the positive electrode, GNR/Bi₂Se₃ composites as the negative electrode, and polymer‐grafted‐graphene oxide membranes as solid‐state electrolytes. Both GNR/Co_0.85Se and GNR/Bi₂Se₃ composite electrodes are developed by a facile one‐step hydrothermal growth method from graphene oxide nanoribbons as the nucleation framework. The GNR/Co_0.85Se composite electrode exhibits a specific capacity of 76.4 mAh g^?1 at a current density of 1 A g^?1 and the GNR/Bi₂Se₃ composite electrode exhibits a specific capacity of 100.2 mAh g^?1 at a current density of 0.5 A g^?1. Moreover, the stretchable membrane solid‐state electrolytes exhibit superior ionic conductivity of 108.7 mS cm^?1. As a result, the flexible ASCs demonstrate an operating voltage of 1.6 V, an energy density of 30.9 Wh kg^?1 at the power density of 559 W kg^?1, and excellent cycling stability with 89% capacitance retention after 5000 cycles. All these results demonstrate that this study provides a simple, scalable, and efficient approach to fabricate high performance flexible all‐solid‐state ASCs for energy storage.