Free-standing Supercapacitor Electrode Research Articles

A novel path towards synthesis of nitrogen-rich porous carbon nanofibers for high performance supercapacitors

A facile and efficient nitrogen doping strategy is proposed to improve the nitrogen content, increase surface area, and tune the configuration of nitrogen-related defects in the carbon nanostructures for application as supercapacitors. To this end, carbon nanofibers (CNFs) were fabricated via pyrolysis of polyacrylonitrile (PAN) nanofibers with sacrificial polymers (PMMA). By lowering the interfacial tension between PAN and PMMA in DMF with the aid of surfactants, the size of the sacrificial PMMA islands in the continuous PAN phase was significantly reduced, promoting the formation of pores and increase the specific surface area (SSA) of the host CNF during pyrolysis. The synthesis of N-doped CNF with a controlled N-bonding structure was achieved by pyrolysis of precursor on Ni surface in the presence of melamine as a nitrogen source. We showed that the concentration and configuration of N-related defects in CNFs can be respectively enhanced and controlled by absorption of the oxygen-containing sites onto a metallic substrate. Furthermore, the surface area was also increased by absorbing oxygen on the Ni surface. The synthesized porous nitrogen-rich CNFs as a binder-free and free-standing electrode for supercapacitors demonstrated remarkable electrochemical capacitance, superb rate capability, and possessed excellent long-term stability over 10,000 cycles (capacitance retention of 94%).

Electrodeposited NiSe on a forest of carbon nanotubes as a free-standing electrode for hybrid supercapacitors and overall water splitting

NiSe nanoparticles are electrodeposited over a forest of carbon nanotubes (CNTs) to form an intertwined and porous network. The assynthesized composite (denoted as CNT@NiSe/SS) is used as a free-standing and multifunctional electrode for bothsupercapacitorsand overallwater splitting applications. For a supercapacitor application, CNT@NiSe/SS exhibits higher specific capacity and improved rate capability compared with individual NiSe and CNTs. A hybrid supercapacitor device consisting of battery-like CNT@NiSe/SS and EDLC-like graphene delivers a maximum energy density of 32.1 Wh kg−1 at a power density of 823 W kg−1 and has excellent stability after a floating test of 50 h. On the other hand, CNT@NiSe/SS also serves as a bifunctional electrocatalyst with high activity for overall water splitting. The CNT@NiSe/SS electrode displays excellent hydrogen and oxygen evolution reaction performance with the lowest overpotential of 174 mV at 10 mA cm−2 and 267 mV at 50 mA cm−2, respectively. The symmetrical two-electrode system requires an operating potential of 1.71 V to achieve a current density of 10 mA cm−2. Furthermore, this electrolyzer shows a negligible increment in potential after 24 hof continuouswater splitting. The outstanding performances of CNT@NiSe/SS can be attributed to the synergistic effect of NiSe and CNTs.

Polypyrrole/Carbon Nanotube Freestanding Electrode with Excellent Electrochemical Properties for High-Performance All-Solid-State Supercapacitors.

In this study, a facile and environmentally friendly method was used to prepare a freestanding supercapacitor electrode displaying excellent areal capacitance and good cycle life performance. First, we prepared polypyrrole nanoparticles (PPyNP) through a simple in situ chemical polymerization using the plant-derived material curcumin as a bioavailable template. A PPyNP/f-CNT freestanding composite electrode of high mass loading (ca. 14 mg cm–2) was prepared after blending the mixtures of the prepared PPyNP and functionalized CNTs (f-CNTs). The performance of the as-prepared material as a supercapacitor electrode was evaluated in a three-electrode setup using aqueous 1 M H2SO4 as the electrolyte. The PPyNP/f-CNT freestanding composite electrode exhibited a high areal capacitance of 4585 mF cm–2 and a corresponding volumetric capacitance of 176.35 F cm–3 at a current density of 2 mA cm–2. A symmetric all-solid-state supercapacitor assembled using two identical pieces of PPyNP/f-CNT composite electrodes exhibited maximum areal energy and power density of 129.24 μW h cm–2 and 12.5 mW cm–2, respectively. Besides, this supercapacitor device exhibited good cycle life performance, with 79.03% capacitance retention after 10,000 charge/discharge cycles. These results suggest practical applications for these PPyNP/f-CNT freestanding composite electrode-based symmetric all-solid-state supercapacitors.

MXene/RGO composite aerogels with light and high-strength for supercapacitor electrode materials

Abstract The existence of inevitable hole defects in the hydrothermal process of graphene hydrogels makes the strength of the prepared aerogel to be further improved. We design a simple self-assembly method of standing at room tempreture for preparing MXene/RGO composite aerogel. The strong forces from different directions make this three-dimensional (3D) porous aerogel unique fusiform shape and stiffer wall of the pores to exhibit favorable strength of 16.18 MPa and excellent cyclic compression performance at a load capacity up to 10 kg (2 MPa). And as a freestanding supercapacitior electrode, it shows excellent electrochemical energy storage performance of 233 F g−1 at 1 A g−1 with an outstanding cycling performance of 91.01% after 10,000 cycles. Besides, this research lays a certain theoretical reference for free-standing supercapacitor electrode materials.

Graphene-quantum-dots-induced MnO2 with needle-like nanostructure grown on carbonized wood as advanced electrode for supercapacitors

Hydrothermal and electrochemical deposition methods have been employed to fabricate porous wood carbon (PWC)/pseudocapacitive hybrid materials for use as free-standing supercapacitor electrodes. However, their cycling stability is poor because of the inherent storage mechanism of pseudocapacitive materials, and their specific capacitance requires further improvement. In this study, PWC was directly produced as a conductive matrix by pyrolyzing natural balsa wood, and then manganese dioxide (MnO2) and graphene quantum dots (GQDs) were deposited to fabricate a PWC/MnO2/GQDs electrode by a hydrothermal method. GQDs significantly boosts the ions transport, and protects MnO2 from falling off both the external surface and inside the channel of PWC. Compared with a PWC/MnO2 electrode, the unique needle-like nanostructures formed by adding GQDs resulted in a better electrochemical performance for a supercapacitor electrode, including a moderate areal specific capacitance (2712 mF cm−2 at a current density of 1.0 mA cm−2), good rate capability, and excellent cycling stability (95.3% retention after 2000 cycles). This indicated that GQDs-decorated composites will promote the development of high-performance energy storage devices.

Graphene Quantum Dot Reinforced Electrospun Carbon Nanofiber Fabrics with High Surface Area for Ultrahigh Rate Supercapacitors.

High surface area, good conductivity, and high mechanical strength are important for carbon nanofiber fabrics (CNFs) as high-performance supercapacitor electrodes. However, it remains a big challenge because of the trade-off between the strong and continuous conductive network and a well-developed porous structure. Herein, we report a simple strategy to integrate these properties into the electrospun CNFs by adding graphene quantum dots (GQDs). The uniformly embedded GQDs play a crucial bifunctional role in constructing an entire reinforcing phase and conductive network. Compared with the pure CNF, the GQD-reinforced activated CNF exhibits a greatly enlarged surface area from 140 to 2032 m2 g-1 as well as a significantly improved conductivity and strength of 5.5 and 2.5 times, respectively. The mechanism of the robust reinforcing effect is deeply investigated. As a freestanding supercapacitor electrode, the fabric performs a high capacitance of 335 F g-1 at 1 A g-1 and extremely high capacitance retentions of 77% at 100 A g-1 and 45% at 500 A g-1. Importantly, the symmetric device can be charged to 80% capacitance within only 2.2 s, showing great potential for high-power startup supplies.

Hierarchical CoS@MoS2 core-shell nanowire arrays as free-standing electrodes for high-performance asymmetric supercapacitors

The freestanding hierarchical core-shell nanoarchitectures exemplify the substantial interest in the development of next-generation electrode materials for energy storage systems . Herein, the hierarchical 3D CoS@MoS2 nanowire arrays (NWAs) are synthesized through a cost-effective hydrothermal process and followed by an effective sulfurization. The structural and morphological investigations of hierarchical 3D CoS@MoS2 NWAs are carried out for each stage. The 3D CoS@MoS2 NWAs yields a high specific capacity of 374.75 mA h g−1 and an areal capacity of 1.39 mA h cm−2 at a current density of 4 mA cm−2, exceptional rate capability (∼70.1% retention of the capacity at 20 mA cm−2), and remarkable cycling performance (∼96.2% retention of the capacity after 10,000 consecutive charge-discharge cycles), which are superior to the corresponding CoS nanowires and MoS2 nanosheets counterparts. The assembled CoS@MoS2//Fe2O3@rGO asymmetric supercapacitor (ASC) exhibits a broader working potential window of 1.7 V, ultrahigh energy density of 95.7 W h Kg−1 at the power density of 711.2 W kg−1, and super-long cycling stability (∼95.5% retention of capacity after 10,000 cycles), demonstrating that the hierarchical 3D CoS@MoS2 NWAs are promising as potential candidates for hig-performance SCs.

Highly porous cobalt oxide-decorated carbon nanofibers fabricated from starch as free-standing electrodes for supercapacitors

Hybrid supercapacitor with improved energy density was prepared by electrospinning using biopolymer, and a simple dip-coating method. Through the optimization of the dip-coating time and post-heat treatment process, carbon nanofiber with highly porous structure and Co3O4 particles formed on the surface was successfully fabricated. It was found that Co3O4/C nanofibers dipped for one hour exhibited a highly porous microstructure with a specific surface area of 964 m2/g, and this was mainly composed of pores with an average diameter of 2.4 nm. These characteristics contributed to superior electrochemical properties of hybrid nanofibers, among which a 137 F/g specific capacitance was achieved with a very stable cycle life (91% retention after 5,000 cycles). The combination of porous carbon nanofiber derived by optimized calcination process of Co precursor and redox reaction from the Co3O4 provided a synergistic effect for enhanced specific capacitance of the hybrid supercapacitor.

In-situ construction of metal organic frameworks derived Co/Zn–S sandwiched graphene film as free-standing electrodes for ultra-high energy density supercapacitors

Metal organic frameworks (MOFs) with in situ porous nanostructures and high specific surface area have been widely used in supercapacitors, and the reduced graphene oxide (rGO) nanosheets is an excellent electronic conductor and support in loading other materials. Herein, for the first time, we report the unique Co/Zn-MOF derived Co/Zn–S polyhedron homogeneously embedded between the rGO sheets film as a binder-free electrode for high performance hybrid supercapacitor. Using a mild in situ synthesis method and vulcanization process, a 3D nano-electrode material Co/Zn–S@rGO is prepared by combining Zn0.76Co0.24S nanoparticles with rGO film. Among them, Co/Zn–S@rGO-7 samples with optimizing ratio deliver a high capacitance of 1640 F g−1 at the current density of 1 A g−1 in 6 M KOH alkaline aqueous electrolyte. The asymmetric supercapacitor (Co/Zn–S@rGO-7//AC) using Co/Zn–S@rGO as the positive electrode and activated carbon as the negative electrode shows an ultra-high energy density of 91.8 W h kg−1, when the power density is 800 W kg−1. Moreover, the device also shows a high cycle stability under high current density (90.3% capacity retention after 8000 cycles). It shows that the electrode materials prepared by this method has a good application prospect in electrochemical energy storage.

Highly flexible and mechanically strong polyaniline nanostructure @ aramid nanofiber films for free-standing supercapacitor electrodes

A key challenge for the fabrication of flexible electrochemical capacitors is to prepare robust electrode materials with excellent integration of high specific capacitances and superior mechanical properties. Aramid nanofibers (ANFs) are emerging candidates for constructing flexible electrode materials due to their superior mechanical properties. However, the present ANF based electrode materials are generally designed by mixing ANFs with electrochemically active components, which results in an unfavorable trade-off in mechanical and electrochemical properties. In this work, we reported flexible, mechanically strong, and free-standing supercapacitor electrodes based on polyaniline (PANI) nanostructure functionalized ANF films for the first time. The flexible PANI@ANF film electrodes achieved an efficient combination of mechanical and electrochemical performance in a single platform with a specific capacitance of 441.0 F g-1 at a current density of 1 A g-1 and a tensile strength of 233.3 MPa, respectively. This kind of free-standing electrode material may have great potential in the development of flexible energy-storage devices. Furthermore, we anticipate that this study may provide insight into the functionalization of aramid nanofiber-based materials for structural energy and power systems with high mechanical performance.

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

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

NiCoSe2/Ni3Se2 lamella arrays grown on N-doped graphene nanotubes with ultrahigh-rate capability and long-term cycling for asymmetric supercapacitor

In this paper, we report a one-step electrodeposited synthesis strategy for directly growing NiCoSe2/Ni3Se2 lamella arrays (LAs) on N-doped graphene nanotubes (N-GNTs) as advanced free-standing positive electrode for asymmetric supercapacitors. Benefiting from the synergetic contribution between the distinctive electroactive materials and the skeletons, the as-constructed N-GNTs@NiCoSe2/Ni3-Se2 LAs present a specific capacitance of ~1308 F g−1 at a current density of 1 A g−1. More importantly, the hybrid electrode also reveals excellent rate capability (~1000 F g−1 even at 100 A g−1) and appealing cycling performance (~103.2% of capacitance retention over 10,000 cycles). Furthermore, an asymmetric supercapacitor is fabricated by using the obtained N-GNTs@NiCoSe2/Ni3Se2 LAs and active carbon (AC) as the positive and negative electrodes respectively, which holds a high energy density of 42.8 W h kg−1 at 2.6 kW kg−1, and superior cycling stability of ~94.4% retention over 10,000 cycles. Accordingly, our fabrication technique and new insight herein can both widen design strategy of multicomponent composite electrode materials and promote the practical applications of the latest emerging transition metal selenides in next-generation high-performance supercapacitors.

A facile pre-assembly strategy toward grain boundary-induced-graphene based hybrid frameworks with high capacitance

Three-dimensional graphene based hybrid frameworks (GHFs) prepared by chemical vapor deposition (CVD) have shown extraordinary promise for energy-storage but are usually limited by the lack of facile and efficient preparation strategies. Herein, a facile and general strategy is developed to synthesize near-nanoporous GHFs via mechanically-assisted pre-assembly and CVD processes. Functional nanomaterials (FNMs) are pre-filled into copper-nanopowders (CuNPs) as semi-sacrificial templates of CVD-graphene. A grain boundary-induced-graphene growth mechanism is demonstrated: during CVD process, graphene preferentially nucleates/grows along the abundant grain-boundaries formed by the fusion of CuNPs. Meanwhile, these FNMs are firmly combined with graphene-frameworks by π-π interactions and/or van der Waals forces, thus GHFs are constructed. Furthermore, two typical GHFs containing single-wall carbon nanotubes and molybdenum disulfide (defined as G/SWNT and G/MoS2, respectively) are used as freestanding supercapacitor-electrodes: Both GHFs exhibit high capacitance (232.4 F g−1 for G/SWNT and 331.1 F g−1 for G/MoS2) and impressive stability (96.62% capacitance-retention after 10,000 cycles for G/SWNT; 92.18% retention after 5000 cycles for G/MoS2), which due to the firmly combination of active FNMs and near-nanoporous graphene-frameworks by our strategy. These results suggest that our pre-assembly strategy can prepare various GHFs with excellent energy-storage performance.

Functional molecules regulated and intercalated nickel-cobalt LDH nano-sheets on carbon fiber cloths as an advanced free-standing electrode for high-performance asymmetric supercapacitors

With the aim to enhance the performance of pseudo-capacitor electrode materials, a novel free-standing hybrid electrode through integrating vertically aligned sodium dodecyl benzene sulfonate (SDBS) intercalated NiCo LDH nanosheets and carbon fiber cloth (CFC) was synthesized via a one-step hydrothermal method. The SDBS could serve as NiCo LDH growth regulator and interlayer distance expander. Upon SDBS intercalation the LDH interlayer space increase from 0.79 nm to 1.52 nm, the enlarged interspace could significantly facilitate the ion transportation and boost the specific electrochemical performance. Moreover, the as-prepared NiCo-SDBS-LDH@CFC hybrid material delivers an excellent specific capacity of 748.2 C g−1 at 0.5 A g−1 and outstanding rate capacity of 78.9% at 10 A g−1. Contributed by the delicately engineered electrodes, a high performance of asymmetric supercapacitor (ASC) is constructed, which exhibited a high energy density of 70.94 Wh kg−1 at a power density of 400 W kg−1, the energy density can still remain as high as 59.11 Wh kg−1 at a high power density of 8000 W kg−1. Furthermore, the ACS cell manifests a long lifespan of 89.96% capacitance retention at 10 A g−1 even after 10000 cycles. This work not only demonstrates an attractive strategy for rational design and modification of LDH-based electrodes, but also provides superior nanostructured free-standing electrodes for high energy density supercapacitors.

All-carbon flexible supercapacitors based on electrophoretic deposition of graphene quantum dots on carbon cloth

In this work, a flexible, free-standing supercapacitor electrode fabricated using a combination of Graphene Quantum Dots (GQD) and carbon cloth. The GQD was synthesized using a simple peroxide-assisted hydrothermal method and was electrodeposited on carbon cloth to ensure intimate contact. The presence of GQD on the surface of the carbon cloth greatly enhanced its capacitance, resulting in a flexible EDLC electrode with an areal capacitance of 70 mF cm−2 at a scan rate of 50 mV s−1 even with a negligible mass loading. We have also demonstrated a fully-flexible symmetric full-cell fabricated using the GQD/carbon cloth composite with a high-rate capability, showing a rectangular CV curve even at a high scan rate of 1 V s−1 and capacitance of 24 mF cm−2 at a scan rate of 50 mV s−1 when flexed and un-flexed.

CuMnO2-reduced graphene oxide nanocomposite as a free-standing electrode for high-performance supercapacitors

Free-standing electrodes have attracted wide attention for advanced supercapacitors. Herein, direct deposition of CuMnO2 and CuMnO2-reduced graphene oxide (rGO) nanocomposite on nickel foam (NF) substrates was performed through a simple hydrothermal process. The simultaneous deposition makes full use of the synergistic effect formed by the large pseudocapacitance of CuMnO2 and excellent electrical conductivity of rGO, which results a greater performance improvement of the nanocomposite comparing with that of bare CuMnO2. Remarkably, the CuMnO2-rGO/NF electrode displays a large specific capacitance of 1727 F g−1 at 3 A g−1 and manifests exceptional cycling stability with a retention ratio of 125% of the initial capacitance over consecutive 5000 cycles. Furthermore, a rGO/NF//CuMnO2-rGO/NF asymmetric supercapacitor exhibits great electrochemical performance by delivering high energy density (37.5 Wh kg−1) and high power density (4250 W kg−1) as well as excellent cycling stability (3.3% decay after 4000 cycles). The presented results suggest that CuMnO2-rGO nanocomposite can be considered as a potential candidate for highly stable and high-rate supercapacitors.

Porous polyvinyl chloride films as substrate for polyaniline-based flexible and robust free-standing electrodes for high performance supercapacitors

Abstract Polymeric materials have been recognized as flexible substrate for free-standing electrodes in energy storage devices. Here, porous polyvinyl chloride (PVC) films with different porous diameters were designed via solution-coating method with ZnO powder and polyethylene glycol (PEG) as pore-forming agent, respectively. After in situ chemical oxidation polymerization of aniline, the polyvinyl chloride/polyaniline (PVC/PANI) composite films were obtained as flexible and robust free-standing electrode materials for high performance supercapacitors. Based on the optimization of the kind and addition amount of pore-forming agent, feeding amount of aniline, and polymerization strategy, the optimized microporous Z-PVC/PANI-2 composite film possessed the best comprehensive performance owing to its uniform microporous surface, including electrical conductivity of 18.2 S cm−1 at room temperature, high specific capacitance of 533.7 F g−1 (areal capacitance of 688 mF cm−2 of the composite film) at a current density of 1 A g−1, good rate capacitance properties retaining 63.3% at a high current density of 10 A g−1 and 58.2% at a scan rate of 100 mV s−1 and excellent long-term electrochemical stability retaining 95.0% after 2000 CV cycles, together with the excellent flexibility and tensile tolerance performance with capacitance retention of 92.0% after 100 cycles of 180°-bending, 76.8% at stress of 9.5 MPa for 5 min and 57.2% for 60 min.

Misfit-layered cobaltite Ca3Co4O9+δas a new electrode for supercapacitor with excellent cycling stability

One of the major challenges for transition metal used as supercapacitor electrode is their poor electrical conductivity. In this study, misfit-layered cobaltite Ca3Co4O9+δ (CCO) oxide is successfully synthesized using sol-gel method. The structure, morphology and surface composition of the obtained CCO powder are characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy measurement. Herein the CCO exhibits a high electrical conductivity of 62.0 S cm−1 at room temperature. The prepared CCO electrode was characterized by cyclic voltammetry and galvanostatic charge–discharge method to evaluate its electrochemical performances. The CCO electrode displays good capacitance features with a mass specific capacitance of 229.3 F g−1 at a scanning rate of 2 mV s−1, which are mainly due to its high electrical conductivity and unique layered structure. Furthermore, the CCO electrode shows outstanding cycling performance with 107% capacitance retention after 44 000 cycles. More importantly, the bulk CCO can be directly used as free-standing electrode for electrochemical supercapacitors with an area specific capacitance (340 mF cm−2) and excellent cycling stability.

Bi-metal organic framework nanosheets assembled on nickel wire films for volumetric-energy-dense supercapacitors

Metal organic frameworks are regarded as promising electrode material for supercapacitors, however, low conductivity and pulverization hinder their application as free-standing film electrodes for high-performance supercapacitors. Herein, we demonstrate a core-sheath structured film electrode based on bi-metal organic framework nanosheets assembled on Ni wire for energy-dense supercapacitors. Dual metal-based vertically oriented metal organic frameworks nanosheets assembled on Ni wires can offer high surface areas, structure stability, as well as high conductivity, capacity, and rate capability. The as-fabricated Ni@CoNi-MOF film electrode delivers a specific capacity of 813C cm−3 at 0.5 A cm−3 and a high rate performance of 325C cm−3 at 5 A cm−3. Moreover, the assembled hybrid supercapacitor based on Ni@CoNi-MOF film (positive electrode) and graphene/carbon nanotube hybrid film (negative electrode) exhibits a high volumetric capacitance of 100 F cm−3 at 0.5 A cm−3 and an high energy density of 31.3 mWh cm−3 with the power density of 3769.4 mW cm−3. Remarkably, capacitance of as-assembled hybrid supercapacitor device retains 100% after 10000 cycles at 3 A cm−3, indicating a long cycling stability. The concept design of this work can give an insight for engineering metal organic frameworks based or other similar electrode materials for volumetric-energy dense supercapacitors.

Fabrication of 3D hierarchically structured carbon electrode for supercapacitors by carbonization of polyaniline/carbon nanotube/graphene composites

Composite materials with carbon nanotubes (CNTs) and graphene oxide (GO) are considered to be superior for energy storage applications due to their intriguing structural and electrical properties. The electrochemical performance of CNT/GO-based electrodes can be improved by introducing porous carbon materials into them. Herein, we have carbonized the composite consisted of polyaniline (PANI), GO and CNTs on stainless steel plates and investigated their electrochemical performances as a free-standing and binder-free electrode for supercapacitors. The carbonized PANI with a coral-like nanostructure was formed over CNT and GO surface. Furthermore, the introduction of GO efficiently prevents the excessive agglomeration of PANI in the resultant composite materials. The carbonized composite electrode exhibited the high specific capacitance of 465 mF cm−2 at a current density of 1 mA cm−2. Moreover, the carbon electrode obtained by annealing at a higher temperature of 550 °C showed the excellent rate capability and cyclic stability. For example, the 78% of initial capacitance retention was observed when the current density changed from 1 mA cm−2 to 8 mA cm−2, and the capacitance retention of 84% was achieved after 1000 charge/ discharge cycles. This 3D hierarchically structured carbon electrode can be considered as a potential candidate for next-generation energy storage devices.