Negative Capacitance for Electrostatic Supercapacitors

The increasing demand for efficient storage of electrical energy is one of the main challenges in the transformation toward a carbon neutral society. While electrostatic capacitors can achieve much higher power densities compared to other storage technologies like batteries, their energy densities are comparatively low. Here, it is proposed and demonstrated that negative capacitance, which is present in ferroelectric materials, can be used to improve the energy storage of capacitors beyond fundamental limits. While negative capacitance was previously mainly considered for low power electronics, it is shown that ferroelectric/dielectric capacitors using negative capacitance are promising for energy storage applications. Compared to earlier results using (anti)ferroelectric materials for electrostatic energy storage, much higher efficiencies of more than 95% even for ultrahigh energy densities beyond 100 J cm^?3 are demonstrated using nonepitaxial thin films suitable for integration on 3D substrates. Stable operation up to 150 °C and 10⁸ charging/discharging cycles is further demonstrated.     

Flexible Lead‐Free Perovskite Oxide Multilayer Film Capacitor Based on (Na0.8K0.2)0.5Bi0.5TiO3/Ba0.5Sr0.5(Ti0.97Mn0.03)O3 for High‐Performance Dielectric Energy Storage

Flexible thin film dielectric capacitors with high energy storage density and a fast charging–discharging rate have attracted increasing attention as the development of microelectronics progresses toward flexibility and miniaturization. In this work, an all‐inorganic thin film dielectric capacitor with a multilayer structure based on (Na_0.8K_0.2)_0.5Bi_0.5TiO₃ and Ba_0.5Sr_0.5(Ti_0.97Mn_0.03)O₃ is designed and synthesized on a mica substrate. By optimizing the periodic number (N), concomitantly enhanced breakdown strength and large polarization difference are achieved in the film with N = 6, which contributes to the large energy density (W_rec) of 91 J cm^?3, high efficiency (η) of 68%, and fast discharging rate of 47.6 µs. The obtained energy density is the highest value up to now in flexible dielectric capacitors, including lead‐free and lead‐based inorganic films as well as organic dielectric films. Moreover, no obvious deterioration of the energy storage performance is observed in the wide ranges of working temperature (?50–200 °C), operating frequency (500 Hz to 30 kHz), and fatigue cycles (1–10⁸). Besides, the W_rec and η are ultra‐stable under various bending radii (R = 12–2 mm) and even after 10⁴ bending cycles at R = 4 mm, demonstrating an outstanding mechanical bending endurance. This excellent performance will allow the capacitor thrive in flexible microenergy storage systems.     

Fatigue‐Free and Bending‐Endurable Flexible Mn‐Doped Na0.5Bi0.5TiO3‐BaTiO3‐BiFeO3 Film Capacitor with an Ultrahigh Energy Storage Performance

As the rapid development of intelligent systems moves toward flexible electronics, capacitors with extraordinary flexibility and an outstanding energy storage performance will open up broad prospects for powering portable/wearable electronics and pulsed power applications. This work presents a simple one‐step process to fabricate a flexible Mn‐doped 0.97(0.93Na_0.5Bi_0.5TiO₃‐0.07BaTiO₃)‐0.03BiFeO₃ (Mn:NBT‐BT‐BFO) inorganic thin film capacitor with the assistance of a 2D fluorophlogopite mica substrate. The film element, which has a high breakdown strength, great relaxor dispersion, and the coexistence of ferroelectric and antiferroelectric phases, has a high recoverable energy storage density (W_rec ≈81.9 J cm^?3), high efficiency (η ≈64.4%), superior frequency stability (500 Hz–20 kHz), excellent antifatigue property (1 × 10⁹ cycles), and a broad operating temperature window (25–200 °C). The all‐inorganic Mn:NBT‐BT‐BFO/Pt/mica capacitor has a prominent mechanical‐bending resistance without obvious deterioration in its corresponding energy storage capability when it is subjected to a bending radius of 2 mm or repeated bending for 10³ cycles. This work is the first demonstration of an all‐inorganic flexible film capacitor and sheds light on dielectric energy storage devices for portable/wearable applications.     

Superior Energy‐Storage Capacitors with Simultaneously Giant Energy Density and Efficiency Using Nanodomain Engineered BiFeO3‐BaTiO3‐NaNbO3 Lead‐Free Bulk Ferroelectrics

Dielectric capacitors are receiving a great deal of attention for advanced pulsed power owing to their high power density and quick charge/discharge rate. However, the energy density is limited and the efficiency and the thermal stability are also not ideal, which has been a longstanding obstacle to developing desirable dielectric materials. These concerns have are addressed herein by fabricating nanodomain‐engineered BiFeO₃‐BaTiO₃‐NaNbO₃ bulk ferroelectrics, integrating a high‐spontaneous‐polarization gene, wide band gaps, and a heterogeneous nanodomain structure, generating record‐excellent comprehensive performance of giant energy‐storage density W_rec ≈8.12 J cm^?3, high efficiency η ≈90% and excellent thermal stability (±10%, ?50 to 250 °C) and ultrafast discharge rate (t_0.9 < 100 ns). Significantly enhanced dielectric breakdown strength of BiFeO₃‐based solid solutions is mainly attributed to the substitution of NaNbO₃, which provides an increased band gap, refined grain size, and increased resistivity. The formation of nanoscale domains as evidenced by piezoresponse force microscopy and transmission electron microscopy enables nearly hysteresis‐free polarization‐field response and temperature‐insensitive dielectric response. In comparison with antiferroelectric capacitors, the current work provides a new solution to successfully design next‐generation pulsed power capacitors by fully utilizing relaxor ferroelectrics in energy‐storage efficiency and thermal stability.     

Polarization Orientation,Piezoelectricity, and Energy Harvesting Performance of Ferroelectric PVDF‐TrFE Nanotubes Synthesized by Nanoconfinement

1D nanostructures of soft ferroelectric materials exert promising potential in the fields of energy harvesting and flexible and printed nanoelectronics. Here, improved piezoelectric properties, energy‐harvesting performance, lower coercive fields, and the polarization orientation of poly(vinylidene fluoride–trifluoroethylene) (PVDF‐TrFE) nanotubes synthesized with nanoconfinement effect are reported. X‐ray diffraction (XRD) patterns of the nanotubes show the peak corresponding to the planes of (110)/(200), which is a signature of ferroelectric beta phase formation. Piezoforce spectroscopy measurements on the free‐standing horizontal nanotubes bundles reveal that the effective polarization direction is oriented at an inclination to the long axis of the nanotubes. The nanotubes exhibit a coercive field of 18.6 MV m^?1 along the long axis and 40 MV m^?1 (13.2 MV m^?1 considering the air gap) in a direction perpendicular to the long axis, which is lower than the film counterpart of 50 MV m^?1. The poled 200 nm nanotubes, with 40% reduction in poling field, give larger piezoelectric d₃₃ coefficient values of 44 pm V^?1, compared to poled films (≈20 pm V^?1). The ferroelectric nanotubes deliver superior energy harvesting performance with an output voltage of ≈4.8 V and power of 2.2 μW cm^?2, under a dynamic compression pressure of 0.075 MPa at 1 Hz.     

High‐Performance Relaxor Ferroelectric Materials for Energy Storage Applications

Relaxor ferroelectrics usually possess low remnant polarizations and slim hystereses, which can provide high saturated polarizations and superior energy conversion efficiencies, thus receiving increasing interest as energy storage materials with high discharge energy densities and fast discharge ability. In this study, a relaxor ferroelectric multilayer energy storage ceramic capacitor (MLESCC) based on 0.87BaTiO₃‐0.13Bi(Zn_2/3(Nb_0.85Ta_0.15)_1/3)O₃ (BT‐BZNT) with inexpensive Ag/Pd inner electrodes is prepared by the tape casting method. The MLESCC with two dielectric layers (layer thicknesses of 5 µm) sintered by a two‐step sintering method exhibits excellent energy storage properties with a record‐high discharge energy density of 10.12 J cm^?3, a high energy efficiency of 89.4% achieved at an electric field of 104.7 MV m^?1, a high temperature stability of the energy storage density (with minimal variation of <±5%), and energy efficiency (>90%) over a range of ?75 to 150 °C at 40 MV m^?1. These results suggest that the BT‐BZNT relaxor ferroelectric ceramic material can provide realistic solutions for high‐power energy storage capacitors.     

Tuning Nanofillers in In Situ Prepared Polyimide Nanocomposites for High‐Temperature Capacitive Energy Storage

Modern electronics and electrical systems demand efficient operation of dielectric polymer‐based capacitors at high electric fields and elevated temperatures. Here, polyimide (PI) dielectric composites prepared from in situ polymerization in the presence of inorganic nanofillers are reported. The systematic manipulation of the dielectric constant and bandgap of the inorganic fillers, including Al₂O₃, HfO₂, TiO₂, and boron nitride nanosheets, reveals the dominant role of the bandgap of the fillers in determining and improving the high‐temperature capacitive performance of the polymer composites, which is very different from the design principle of the dielectric polymer composites operating at ambient temperature. The Al₂O₃‐ and HfO₂‐based PI composites with concomitantly large bandgap and moderate dielectric constants exhibit substantial improvement in the breakdown strength, discharged energy density, and charge–discharge efficiency when compared to the state‐of‐the‐art dielectric polymers. The work provides a design paradigm for high‐performance dielectric polymer nanocomposites for electrical energy storage at elevated temperatures.     

High Energy Density Aqueous Li‐Ion Flow Capacitor

High energy density Li‐ion hybrid flow capacitors are demonstrated by employing LiMn₂O₄ and activated carbon slurry electrodes. Compared to the existing aqueous flow electrochemical capacitors, the hybrid one exhibits much higher energy densities due to the introduction of high capacity Li‐insertion materials (e.g., LiMn₂O₄ in the present work) as the flowable electrode with asymmetrical cell configuration. A record energy density, i.e., 23.4 W h kg^?1 at a power of 50.0 W kg^?1 has been achieved for aqueous flow capacitors tested at static condition reported to date. A full operational Li‐ion flow capacitor tested in an intermittent‐flow mode has also been demonstrated. The Li‐ion hybrid flow capacitor shows great promise for high‐rate grid applications.     

CuSbSe2 as a Potential Photovoltaic Absorber Material: Studies from Theory to Experiment

CuSbSe₂ appears to be a promising absorber material for thin‐film solar cells due to its attractive optical and electrical properties, as well as earth‐abundant, low‐cost, and low‐toxic constituent elements. However, no systematic study on the fundamental properties of CuSbSe₂ has been reported, such as defect physics, material, optical, and electrical properties, which are highly relevant for photovoltaic application. First, using density functional theory calculations, CuSbSe₂ is shown to have benign defect properties, i.e., free of recombination‐center defects, and flexible defect and carrier concentration which can be tuned through the control of growth condition. Next, systematic material, optical, and electrical characterizations uncover many unexplored fundamental properties of CuSbSe₂ including band position, temperature‐dependent band gap energy, Raman spectrum, and so on, thus providing a solid foundation for further photovoltaic research. Finally, a prototype CuSbSe₂‐based thin film solar cell is fabricated by a hydrazine solution process. The systematic theoretical and experimental investigation, combined with the preliminary efficiency, confirms the great potential of CuSbSe₂ for thin‐film solar cell applications.     

Thermally Durable Lithium‐Ion Capacitors with High Energy Density from All Hydroxyapatite Nanowire‐Enabled Fire‐Resistant Electrodes and Separators

The reliability and durability of lithium‐ion capacitors (LICs) are severely hindered by the kinetic imbalance between capacitive and Faradaic electrodes. Efficient charge storage in LICs is still a huge challenge, particularly for thick electrodes with high mass loading, fast charge delivery, and harsh working conditions. Here, a unique thermally durable, stable LIC with high energy density from all‐inorganic hydroxyapatite nanowire (HAP NW)‐enabled electrodes and separators is reported. Namely, the LIC device is designed and constructed with the electron/ion dual highly conductive and fire‐resistant composite Li₄Ti₅O₁₂‐based anode and activated carbon‐based cathode, together with a thermal‐tolerant HAP NW separator. Despite the thick‐electrode configuration, the as‐fabricated all HAP NW‐enabled LIC exhibits much enhanced electrochemical kinetics and performance, especially at high current rates and temperatures. Long cycling lifetime and state‐of‐the‐art areal energy density (1.58 mWh cm^?2) at a high mass loading of 30 mg cm^?2 are achieved. Benefiting from the excellent fire resistance of HAP NWs, such an unusual LIC exhibits high thermal durability and can work over a wide range of temperatures from room temperature to 150 °C. Taking full advantage of synergistic configuration design, this work sets the stage for designing advanced LICs beyond the research of active materials.     

Fast Sodium Storage in TiO2@CNT@C Nanorods for High‐Performance Na‐Ion Capacitors

Na‐ion capacitors have attracted extensive interest due to the combination of the merits of high energy density of batteries and high power density as well as long cycle life of capacitors. Here, a novel Na‐ion capacitor, utilizing TiO₂@CNT@C nanorods as an intercalation‐type anode and biomass‐derived carbon with high surface area as an ion adsorption cathode in an organic electrolyte, is reported. The advanced architecture of TiO₂@CNT@C nanorods, prepared by electrospinning method, demonstrates excellent cyclic stability and outstanding rate capability in half cells. The contribution of extrinsic pseudocapacitance affects the rate capability to a large extent, which is identified by kinetics analysis. A key finding is that ion/electron transfer dynamics of TiO₂@CNT@C could be effectively enhanced due to the addition of multiwalled carbon nanotubes. Also, the biomass‐derived carbon with high surface area displays high specific capacity and excellent rate capability. Owing to the merits of structures and excellent performances of both anode and cathode materials, the assembled Na‐ion capacitors provide an exceptionally high energy density (81.2 W h kg^?1) and high power density (12 400 W kg^?1) within 1.0–4.0 V. Meanwhile, the Na‐ion capacitors achieve 85.3% capacity retention after 5000 cycles tested at 1 A g^?1.     

High‐Energy Density Li‐Ion Capacitor with Layered SnS2/Reduced Graphene Oxide Anode and BCN Nanosheet Cathode

Lithium‐ion capacitors (LICs) with capacitor‐type cathodes and battery‐type anodes are considered a promising next‐generation advanced energy storages system that meet the requirements of high energy density and power density. However, the mismatch of charge‐storage capacity and electrode kinetics between positive and negative electrodes remains a challenge. Herein, layered SnS₂/reduced graphene oxide (RGO) nanocomposites are developed for negative electrodes and a 2D B/N codoped carbon (BCN) nanosheet is designed for the positive electrode. The SnS₂/RGO derived from SnS₂‐bonded RGO of high conductivity exhibits a capacity of 1198 mA h g^?1 at 100 mA g^?1. Boron and nitrogen atoms in BCN are found to promote adsorption of anions, which enhance the pseudocapacitive contribution as well as expanding the voltage of LICs. A quantitative kinetics analysis indicates that the SnS₂/RGO electrodes with a dominating capacitive mechanism and a diminished intercalation process, benefit the kinetic balance between the two electrodes. With this particular structure, the LIC is able to operate at the highest operating voltage for these devices recorded to date (4.5 V), exhibiting an energy density of 149.5 W h kg^?1, a power density of 35 kW kg^?1, and a capacity retention ratio of 90% after 10 000 cycles.     

Aqueous Solution‐Processable Small Molecular Metal‐Chelate Complex Electrolyte for Flexible All‐Solid State Energy Storage Devices

A small molecular metal‐chelate complex, tris(8‐hydroxyquinoline‐5‐sulfonic acid) aluminum (AlQSA₃), that has three sulfonic acid groups per molecule leading to an excellent solubility in water is reported as a liquid‐free perfect solid‐state electrolyte for flexible film‐type all‐solid‐state energy storage devices. The AlQSA₃ material is synthesized by one‐step reaction of aluminum triisopropoxide and 8‐hydroxyquinoline‐5‐sulfonic acid. The aqueous solutions of AlQSA₃ are applied to fabricate flexible film‐type all‐solid state electric double layer capacitors with indium‐tin oxide thin film electrodes. The ion conductivity of the AlQSA₃ film reaches 0.116 mS cm^?1, while a pronounced hysteresis are obtained in the cyclic voltammetry measurement. The AlQSA₃ film capacitors exhibit an output voltage of 1.5 V at 20 μA cm^?2, which is considerably stable by the repeated operation. In particular, the peak output voltage is well kept even after 180° bending for 500 times in the case of the flexible AlQSA₃ film capacitors.     

Conductive,Solution‐Processed Dioxythiophene Copolymers for Thermoelectric and Transparent Electrode Applications

Conjugated polymers with high electrical conductivities are attractive for applications in capacitors, biosensors, organic thermoelectrics, and transparent electrodes. Here, a series of solution processable dioxythiophene copolymers based on 3,4‐propylenedioxythiophene (ProDOT) and 3,4‐ethylenedioxythiophene (EDOT) is investigated as thermoelectric and transparent electrode materials. Through structural manipulation of the polymer repeat unit, the conductivity of the polymers upon oxidative solution doping is tuned from 1 × 10^?3 to 3 S cm^?1, with a polymer consisting of a solubilizing alkylated ProDOT unit and an electron‐rich biEDOT unit (referred to as PE₂) showing the highest electrical conductivity. Optimization of the film casting method and screening of dopants result in AgPF₆‐doped PE₂ achieving a high electrical conductivity of over 250 S cm^?1 and a thermoelectric power factor of 7 μW m^?1 K^?2. Oxidized spray cast films of PE₂ are also assessed as a transparent electrode material for use with another electrochromic polymer. This bilayer shows reversible electrochemical switching from a colored charge‐neutral state to a highly transmissive color‐neutral, oxidized state. These results demonstrate that dioxythiophene‐based copolymers are a promising class of materials, with ProDOT–biEDOT serving as a soluble analog to the well‐studied PEDOT as a p‐type thermoelectric and electrode material.     

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.     

Nature of FeSe2/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Potassium ion hybrid capacitors have great potential for large‐scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro‐sulfonyl)imide‐based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N‐doping carbon‐coated FeSe₂ clusters are demonstrated as the anode material for a hybrid capacitor, delivering a reversible capacity of 295 mAh g^?1 at 100 mA g^?1 over 100 cycles and a high rate capability of 158 mAh g^?1 at 2000 mA g^?1 over 2000 cycles. Meanwhile, through density functional theory calculations, in situ X‐ray diffraction, and ex situ transmission electron microscopy, the evolution of FeSe₂ to Fe₃Se₄ for the electrochemical reaction mechanism is successfully revealed. The battery‐supercapacitor hybrid using commercial activated carbon as the cathode and FeSe₂/N‐C as the anode is obtained. It delivers a high energy density of 230 Wh kg^?1 and a power density of 920 W kg^?1 (the energy density and power density are calculated based on the total mass of active materials in the anode and cathode).     

Atmospheric‐Pressure Chemical Vapor Deposition of Iron Pyrite Thin Films

Iron pyrite (cubic FeS₂) is a promising candidate absorber material for earth‐abundant thin‐film solar cells. In this report, single‐phase, large‐grain, and uniform polycrystalline pyrite thin films are fabricated on glass and molybdenum‐coated glass substrates by atmospheric‐pressure chemical vapor deposition (AP‐CVD) using the reaction of iron(III) acetylacetonate and tert‐butyl disulfide in argon at 300 °C, followed by sulfur annealing at 500–550 °C to convert marcasite impurities to pyrite. The pyrite‐marcasite phase composition depends strongly on the concentration of sodium in the growth substrate and the sulfur partial pressure during annealing. Phase and elemental composition of the films are characterized by X‐ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, and X‐ray photoelectron spectroscopy. The in‐plane electrical properties are surprisingly insensitive to phase and elemental impurities, with all films showing p‐type, thermally activated transport with a small activation energy (≈30 meV), a room‐ temperature resistivity of ≈1 Ω cm, and low mobility. These ubiquitous electrical properties may result from robust surface effects. These CVD pyrite thin films are well suited to fundamental electrical studies and the fabrication of pyrite photovoltaic device stacks.     

A Flexible Quasi‐Solid‐State Asymmetric Electrochemical Capacitor Based on Hierarchical Porous V2O5 Nanosheets on Carbon Nanofibers

The development of 3D nanoarchitectures on flexible current collectors has emerged as an effective strategy for preparing advanced portable and wearable power sources. Herein, a flexible and efficient electrode is demonstrated based on electrospun carbon fibers (ECF) substrate with elaborately designed hierarchical porous V₂O₅ nanosheets (V₂O₅–ECF). The unique configuration of V₂O₅–ECF composite film fully enables utilization of the synergistic effects from both high electrochemical performance of V₂O₅ and excellent conductivity of ECF, endowing the films to be an excellent electrode for flexible and lightweight electrochemical capacitors (ECs). Benefiting from their intriguing structural features, V₂O₅–ECF and ECF films, directly used as electrodes for flexible asymmetric quasi‐solid‐state electrochemical capacitors, achieve superior flexibility and reliability, enhanced energy/power density, and outstanding cycling stability. Moreover, the ability to power light‐emitting diodes (LED) also indicates the feasibility for practical use. Therefore, it is believed that this novel design may find promising application in flexible devices in future.     

Engineering Mixed Ionic Electronic Conduction in La0.8Sr0.2MnO3+δ Nanostructures through Fast Grain Boundary Oxygen Diffusivity

Nanoionics has become an increasingly promising field for the future development of advanced energy conversion and storage devices, such as batteries, fuel cells, and supercapacitors. Particularly, nanostructured materials offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. However, the enhancement of the mass transport properties at the nanoscale has often been found to be difficult to implement in nanostructures. Here, an artificial mixed ionic electronic conducting oxide is fabricated by grain boundary (GB) engineering thin films of La_0.8Sr_0.2MnO_3+δ. This electronic conductor is converted into a good mixed ionic electronic conductor by synthesizing a nanostructure with high density of vertically aligned GBs with high concentration of strain‐induced defects. Since this type of GBs present a remarkable enhancement of their oxide‐ion mass transport properties (of up to six orders of magnitude at 773 K), it is possible to tailor the electrical nature of the whole material by nanoengineering, especially at low temperatures. The presented results lead to fundamental insights into oxygen diffusion along GBs and to the application of these engineered nanomaterials in new advanced solid state ionics devices such are micro‐solid oxide fuel cells or resistive switching memories.     

Large‐Area,Ultrathin Inorganic Network Coverages–Graphene Hierarchical Electrodes for Flexible,Heat‐Resistant Energy Storage Application

Graphene and quasi‐2D graphene‐like materials with an ultrathin thickness have been investigated as a new class of nanoscale materials due to their distinctive properties. A novel “molecular tools‐assistances” strategy is developed to fabricate two kinds of graphene‐based electrodes, ultrathin Fe‐doped MnO₂ network coverage–graphene composites (G‐MFO) and ultrathin MoS₂ network coverage–graphene composites (G‐MoS₂) with special hierarchical structures. Such structures enable a large contact interface between the active materials and graphene and thus fully exploit the synergistic effect from both the high specific capacitance of MFO or MoS₂ and the superb conductivity of graphene. Benefiting from their unique structural features, G‐MFO and G‐MoS₂ films directly use as free‐standing electrodes for flexible asymmetric supercapacitors with a nonaqueous gel electrolyte. The device achieves a high energy/power density, superior flexibility, good rate capability as well as outstanding performance stability even at a high temperature. This work represents a promising prototype to design new generation of hybrid supercapacitors for future energy storage devices.