3D nanostructured CuxO modified copper foam as a binder-free electrode for all-solid-state supercapacitor

Copper oxides (Cu_xO) play an active role in the field of binder-free electrodes for supercapacitors due to their own advantages, including high theoretical capacity, non-toxicity, low cost, etc. Developing mild and cheap process to prepare Cu_xO nanomaterials would broad its application in supercapacitors. In this paper, copper oxide is used as an active material and copper foam (CF) is chosen as a substrate to synthesize metal oxide-based electrodes by an in-situ oxidation method. Ingeniously, the availability of copper foam has a dual nature encompassing as a collector as well as a copper source. The as-obtained Cu_xO/CF-60 electrode possesses an area capacitance of 354.6 mF cm⁻² under 2 mA cm⁻². It also has superior cycle stability with 93.8 % of initial capacitance undergo 5000 charge-discharge cycles. Moreover, the all-solid-state asymmetric supercapacitor, combining Cu_xO/CF-60 and activated carbon (AC) pasted on nickel foam (NF) as the respective positive and negative electrodes, exhibits an energy density of 25 μWh cm⁻² when power density reaches 3 mW cm⁻². The Cu_xO/CF-60//AC/NF device displays better cycling stability as 80.2 % of initial capacitance after 5000 cycles. This work provides a simple way for designing Cu_xO based electrodes and lays the foundation for subsequent improvements in electrochemical performance.     

Synthesis of cross-linked graphene aerogel/Fe2O3 nanocomposite with enhanced supercapacitive performance

In this work, cross-linked graphene aerogel (CL-GA) and its composite with Fe₂O₃ nanoparticles (NPs) were synthesized through a one-step hydrothermal procedure by using p-phenylenediamine (PPD). Structural characterizations revealed that in the preparation of the composite PPD acts as a cross-liker and provides high surface area by decreasing restacking of graphene sheets and functions as nitrogen source simultaneously. The electrochemical characteristics of the nanocomposite were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS) and Fast Fourier transform continues cyclic voltammetry (FFTCCV). The results show that cross-linked graphene aerogel/Fe₂O₃ (CL-GA/Fe₂O₃) nanocomposite displays enhanced supercapacitive performance, where it has capacitance of 445 at 1 A g⁻¹, high energy density of 63 W h Kg⁻¹, and 89% capacitance retention after 5000 cycles in 3 M KOH. Presence of PPD considerably improved supercapacitive performance of nanocomposite as a result it could be promising material in synthesis of efficient graphene/metal oxide-based electrode material for high performance supercapacitors.     

Enhanced electrochemical performance of hybrid composite microstructure of CuCo2O4 microflowers-NiO nanosheets on 3D Ni foam as positive electrode for stable hybrid supercapacitors

Self-assembled composite porous structures comprising CuCo₂O₄ microflowers and NiO hexagonal nanosheets were synthesized on a conducting 3D Ni foam surface [CCO/NO] using a simple hydrothermal method. This unique composite assembly was further characterized and electrochemically evaluated as a binder-free positive electrode for hybrid supercapacitor application. The study showed that the CCO/NO exhibited a maximum areal capacitance of 1444 mF cm^?2, significantly higher than the parent CuCo₂O₄ and NiO electrodes, with remarkable stability of 88.5% for 10,000 galvanostatic charge-discharge cycles. Key features for the enhanced electrochemical performance of CCO/NO can be related to a lowered diffusion resistance because the hybrid nanocomposite porous assembly generates short diffusion paths for electrolyte ions and more active sites for reversible faradaic transition for charge storage. The hybrid supercapacitor was assembled using activated carbon as a negative electrode and CCO/NO as a positive electrode in alkaline electrolyte, performed at an improved potential of 1.6 V. Device showed a maximum areal capacitance of 122 mF cm^?2, a maximum areal energy density of 43 μWh cm^?2, and a maximum areal power density of 5.1 mW cm^?2. This hybrid supercapacitor showed remarkable cyclic stability up to 98% for 10,000 cycles. This study encourages the development of low-cost, high-performance, durable electrode designs using hybrid composite for next-generation energy storage systems.     

Improvement of electrochemical performance of titania nanowires for supercapacitor electrodes by in-situ growth of polyaniline nanoparticles

Supercapacitors with excellent electrochemical performance are considered the most promising candidates to meet the increasing energy demand. Herein, we developed a novel electrode material for supercapacitors, polyaniline (PANI)-3-aminopropyl triethoxysilane (APTEs)-titania nanowires (TNW), which was synthesized on potassium doped titanium foil via a simple two-step procedure. In the composite, the nano-mesh structure formed by APTEs-coated TNW serves as the framework for the growth of PANI nanoparticles, and PANI nanoparticles act as the electrochemically active part. The specific capacitance of PANI-APTEs-TNW of up to 315.16 mF cm^?2 at 0.2 mA cm^?2 in 1.0 M H₂SO₄ solution is achieved, while that of PANI-TNW is 271.67 mF cm^?2. Meanwhile, the capacitance retention rate of PANI-APTEs-TNW is 86.8% after 1000 cycles under 1.5 mA cm^?2. Compared to PANI-TNW, the better capacitive behavior of PANI-APTEs-TNW is attributed to the anchoring effect of APTEs, which is highly interactive and exhibits compact structures between the TNW and PANI nanoparticles, resulting in a stable structure during the rapid charge-discharge process. This strategy is characterized by its good electrochemical properties, simple equipment, low cost of raw materials, and large-area preparation. Thus, our findings provide an effective method for the design of high-performance supercapacitors and promote their practical applications.     

Electrochemical behavior of CuO/rGO nanopellets for flexible supercapacitor,non-enzymatic glucose,and H2O2 sensing application

In the present article, graphene oxide (GO) sheets and monoclinic copper oxide (CuO) nanocrystals are connected with each other and result in the formation of CuO/rGO nanopellets, and these nanopellets synthesized using coprecipitation method. The nanopellet structured CuO/rGO composite on carbon cloth, which act as current collector exhibits specific capacitance of 188 F g^?1 at a current density of 0.2 A g^?1 and up to 96.3% capacity retention after 2000 charge-discharge cycles. It shows a maximum energy density of 7.32 Wh kg^?1 and power density of 53 W kg^?1. The glucose sensing characteristics of CuO/rGO nanopellet is investigated on carbon cloth and ITO substrate. It shows glucose sensitivity of 0.805 mA mM^?1 cm^?2 and 0.2982 mA mM^?1 cm^?2 for a bundle like structured CuO/rGO composite on carbon cloth and ITO substrate, respectively. Further H₂O₂ sensing is studied on ITO substrate, which manifests H₂O₂ sensitivity of 84.39 μA mM^?1 cm^?2. The results indicate that nanopellet structured CuO/rGO composite could be a promising electrode material for supercapacitor, glucose, and H₂O₂ sensor.     

Microwave assisted synthesis of rGO/ZnO composites for non-enzymatic glucose sensing and supercapacitor applications

Zinc oxide (ZnO) and Graphene Oxide (GO) are known to show good electrochemical properties. In this paper, rGO/ZnO nanocomposites have been synthesised using a simple microwave assisted method. The nanocomposites are characterized using XRD, Raman, SEM and TEM. XRD reveals the wurtzite structure of ZnO and TEM shows the heterogeneous nucleation of ZnO nanocrystals anchored onto graphene sheets. The electrochemical properties of the rGO/ZnO nanocomposite enhanced significantly for applications in glucose sensors and supercapacitors. The non-enzymatic glucose sensor of this nanocomposite tested using cyclic voltammetry (CV) and chronoamperometry, exhibits high sensitivity (39.78 mA cm⁻² mM⁻¹) and a lower detection limit of 0.2 nM. The supercapacitor electrode of rGO/ZnO nanocomposite exhibits a significant increase in specific capacitance.     

Tailoring carboxyl tubular carbon nanofibers/MnO2 composites for high-performance lithium-ion battery anodes

Three kinds of novel carboxyl modification tubular carbon nanofibers (CMTCFs) and MnO₂ composites materials (CMTCFs/MnO₂) are prepared by combining hyper-crosslinking, liquid phase oxidation and hydrothermal technology. The complex morphology and crystal phase of MnO₂ in CMTCFs/MnO₂ are effectively regulated by adjusting the hydrothermal reaction time. The δ-MnO₂ nanosheet-wrapped CMTCFs (CMTCFs@MNS) are used as anode and compared with the other two CMTCFs/MnO₂. Electrochemical analysis shows that CMTCFs@MNS electrode exhibits a large reversible capacity of 1497.1 mAh g⁻¹ after 300 cycles at 1000 mA g⁻¹ and a long cycling reversible capacity of 400.8 mAh g⁻¹ can be maintained after 1000 cycles at 10 000 mA g⁻¹. CMTCFs@MNS manifests an average reversible capacity of 256.32 mAh g⁻¹ at 10 000 mA g⁻¹ after twelve changes in current density. In addition, the structural superiority of CMTCFs@MNS electrode is clarified by characterizing the microscopic morphology and crystal phase of the electrode after electrochemical performance test.     

A novel high power symmetric ZnO/carbon aerogel composite electrode for electrochemical supercapacitor

We present, for the first time, a new material of symmetric electrochemical supercapacitor in which zinc oxide (ZnO) with carbon aerogel (CA) was used as active material. Physical properties of ZnO/CA composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that ZnO has single hexagonal structure and the grain size increases with increase of ZnO compository. The result of cyclic voltammetry indicates that the specific capacitance of ZnO/CA composite in 6 M KOH electrolyte was approximately 25 F/g at 10 mV/s for 2:1 composition. AC impedance analysis reveals that ZnO with carbon aerogel powder enhanced the conductivity by reducing the internal resistance. Galvanostatic charge/discharge measurements were done at various current densities, namely 25, 50, 75, and 100 mA/cm². It was found that the cells have excellent electrochemical reversibility and capacitive characteristics in KOH electrolyte. The maximum capacitance of the ZnO/CA supercapacitor was 500 F/g at 100 mA/cm². It has been observed that the specific capacitance is constant up to 500 cycles at all current densities, which implies that the dendrite formation was controlled.     

Enhanced rate capability of nanostructured three-dimensional graphene/Ni3S2 composite for supercapacitor electrode

Three-dimensional graphene/Ni₃S₂ (3DG/Ni₃S₂) composite electrodes were produced by a facile two-step synthesis route involving chemical vapor deposition (CVD) growth of graphene foam and in situ hydrothermal synthesis of Ni₃S₂. The porous structure of the prepared 3DG is ideal for use as a scaffold for fabricating monolithic composite electrodes. The relative content of Ni₃S₂ initially increased and then decreased with increasing hydrothermal reaction time. The basal surface of the electrode was completely covered after 6 h of hydrothermal reaction. The size of the Ni₃S₂ microspheres also increased with increasing hydrothermal reaction time. The composite electrodes exhibited good specific capacitance (11.529 F cm⁻² at 2 mA cm⁻², i.e., 2611.9 F g⁻¹ at 5 mV s⁻¹) and cyclability (retention of 88.97% capacitance after 1000 charge/discharge cycles at 20 mA cm⁻²). These results are attributed to the fact that the uniform distribution of the Ni₃S₂ microspheres increased the specific surface area of the electrode and facilitated electron transfer and ion diffusion. The 3D multiplexed and highly conductive pathways provided by the defect-free graphene foam also ensured rapid charge transfer and conduction to improve the rate capability of the supercapacitors.     

SiBCN ceramic aerogel/graphene composites prepared via sol-gel infiltration process and polymer-derived ceramics (PDCs) route

The SiBCN ceramic aerogel/graphene composites were synthesized by combining a simple sol-gel infiltration process with CO₂ supercritical drying technology and polymer-derived ceramics route. In order to select the best preceramic sample for sintering, the micromorphology of PSNB aerogel/graphene composites fabricated with different graphene oxide solution concentrations were investigated. The microstructure evolution of the prepared SiBCN ceramic aerogel/graphene composites and phase composition were studied by SEM, TEM and XRD, the pore structure of the preceramic composites pyrolyzed at 1200 °C was tested by specific surface area and pore size analyzer. Furthermore, the compressive strain-stress curve and toughening mechanisms of composites were also investigated in detail. The results showed that all the preceramic composites and obtained ceramic aerogel composites possessed the mesoporous structure. The basic structure of SiBCN aerogel network changed from the initial spherical particles accumulation to the nanowires lapping with the sintering temperature increased from 800 °C to 1200 °C. After pyrolyzing at 1200 °C, the specific surface area and pore volume for the sample were 101.61 m² g⁻¹ and 1.43 cm³ g⁻¹, respectively, and a small amount of β-SiC crystalline phases were formed in amorphous ceramic matrix and had an relatively uniform distribution. Moreover, the paepared ceramic aerogel composites possessed a certain degree of toughness, the toughening mechanisms of composite samples mainly included the crack deflection, graphene pull-out, graphene bridging and graphene crumpling.     

Manganese oxide nanoflakes grown around cobalt oxide nanobundles with improved charge-storage performance for supercapacitors

Cobalt oxide nanobundle arrays (denoted as CoO) consisting of nanorods were homogeneously grown around the stainless steel wire mesh (SSWM) through a simple hydrothermal synthesis and subsequent heat treatment. The highly dispersed CoO can act as a supporting platform for the deposition of manganese oxide (MnO₂) nanoflakes to engineer a CoO@MnO₂ core-shell array structure. Without the CoO supports, the MnO₂ was found to be prone to form aggregated nanoflakes on the SSWM substrate. CoO arrays with a one-dimensional nanorod skeleton can mitigate the aggregation of two-dimensional MnO₂ nanoflakes. The CoO@MnO₂ core-shell arrays integrate the advantages of abundant active edge sites, conductive networks for charge transfer, and pore channels for easy transport of electrolyte. The CoO@MnO₂ electrode realizes a larger charge-storage capacity than the pristine MnO₂ electrode in an aqueous sodium sulfate solution (1 M). The specific capacitances of CoO@MnO₂ under 0.15 mA cm^-2 and 7.50 mA cm^-2 reach 79 mF cm^-2 and 53 mF cm^-2, respectively, much more than that of MnO₂ (31 mF cm^-2 and 20 mF cm^-2). The CoO@MnO₂ core-shell electrode shows a definite improvement in supercapacitive behavior compared to the pristine MnO₂ electrode, resulting from reduced charge- and mass-transfer resistance during charge-storage process.     

Preparation and characterization of manganese oxide/CNT composites as supercapacitive materials

Manganese oxide was synthesized and dispersed on carbon nanotube (CNT) matrix by thermally decomposing manganese nitrates. CNTs used in this paper were grown directly on graphite disk by chemical vapor deposition technique. The capacitive behavior of manganese oxide/CNT composites was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1 M Na₂SO₄ aqueous solutions. When the loading mass of MnO₂ is 36.9 μg cm^− 2, the specific capacitance of manganese oxide/CNT composite (based on MnO₂) at the charge–discharge current density of 1 mA cm^− 2 equals 568 F g^− 1. Additionally, excellent charge–discharge cycle stability (ca. 88% value of specific capacitance remained after 2500 charge–discharge cycles) and power characteristics of the manganese oxide/CNT composite electrode can be observed. The effect of loading mass of MnO₂ on specific capacitance of the electrode has also been investigated.     

Hydrothermal synthesis and activation of graphene-incorporated nitrogen-rich carbon composite for high-performance supercapacitors

Graphene-incorporated nitrogen-rich carbon composite with nitrogen content of ca. 10 wt.% has been synthesized by an effective yet simple hydrothermal reaction of glucosamine in the presence of graphene oxide (GO). The nitrogen content of carbon composite is nearly twice as high as that of hydrothermal carbon without graphene. GO is favorable for the high nitrogen doping in the carbon composite by the reaction between the glucosamine-released ammonia and GO. The hydrothermal carbon composite is further activated by KOH, and graphene in the activated carbon composite demonstrates a positive effect of increasing specific surface area, pore volume and electrical conductivity, resulting in superior electrochemical performance. The activated carbon composite with higher specific surface area and micropore volume possesses higher specific capacitance with a value of 300 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH aqueous solution in the two electrode cell. Larger mesopore volume and higher conductivity of the activated carbon composite will provide fast ion and electron transfer, thus leading to higher rate capacity with a capacitance retention of 76% at 8 A g⁻¹ in comparison to the activated hydrothermal carbon without graphene.     

Enhancing electrochemical performance of Fe3O4/graphene hybrid aerogel with hydrophilic polymer

Graphene hybrid aerogels have attracted attention as electrode materials because of their unique porous architectures. However, their electrochemical performance is limited by the intrinsic hydrophobicity and the ease of aggregation of graphene nanosheets. We demonstrate a unique methodology to produce graphene hybrid aerogels through assembly of graphene nanosheets, nanometer‐scale ferroferric oxide (Fe₃O₄), and hydrophilic poly(vinyl alcohol) (PVA) into three‐dimensional hierarchical macrostructures. Electrochemical performance measurements exhibit a significant improvement in the specific capacitance of this ternary hybrid aerogel with remarkable cycling stability. Specifically, the specific capacitance is nearly 6.6 times higher than that of the neat graphene aerogel, and a cycling capacitance retention rate of 99% was achieved after 2000 cycles at a high current density of 0.5 A g^?1. Electrochemical impedance spectroscopy measurements demonstrate a lower resistance in the Fe₃O₄/graphene/PVA aerogel electrode compared with that of both neat graphene and Fe₃O₄/graphene aerogel electrodes. The obtained graphene hybrid aerogels with outstanding cycling performance and high energy density are very promising as electrode materials for supercapacitors. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45566.     

Graphene/Polyaniline Aerogel with Superelasticity and High Capacitance as Highly Compression-Tolerant Supercapacitor Electrode

Superelastic graphene aerogel with ultra-high compressibility shows promising potential for compression-tolerant supercapacitor electrode. However, its specific capacitance is too low to meet the practical application. Herein, we deposited polyaniline (PANI) into the superelastic graphene aerogel to improve the capacitance while maintaining the superelasticity. Graphene/PANI aerogel with optimized PANI mass content of 63 wt% shows the improved specific capacitance of 713 F g^?1 in the three-electrode system. And the graphene/PANI aerogel presents a high recoverable compressive strain of 90% due to the strong interaction between PANI and graphene. The all-solid-state supercapacitors were assembled to demonstrate the compression-tolerant ability of graphene/PANI electrodes. The gravimetric capacitance of graphene/PANI electrodes reaches 424 F g^?1 and retains 96% even at 90% compressive strain. And a volumetric capacitance of 65.5 F cm^?3 is achieved, which is much higher than that of other compressible composite electrodes. Furthermore, several compressible supercapacitors can be integrated and connected in series to enhance the overall output voltage, suggesting the potential to meet the practical application.     

Effects of specific surface area of electrode and different electrolyte on capacitance properties in nano porous-structure CrN thin film electrode for supercapacitor

Thickness and specific surface area of the film electrode are critical parameters for supercapacitors. The relationship between the thickness and the specific surface area of the film directly affects the capacitance and electrochemical stability performance of super supercapacitors, which virtually affects the contact chance of ion in the electrolyte on the surface of electrode and the ion transport path of electrode. In this paper, the CrN thin films with a thickness of 200–3500 nm are prepared using direct current magnetron sputtering. Atomic force microscopy (AFM) technique is introduced to investigate the relationship between thickness and the specific surface area of the CrN films. The electrochemical performances of CrN electrode with the nanoporousper structure is analyzed in different electrolytes H₂SO₄, Na₂SO₄ and NaCl aquous solutions. The specific surface area of the film increases linearly with the film thickness increases. The areal capacitance is also linearly related to the specific surface area. The spurtted CrN film with a thickness of 3370 nm has a specific surface of up to 43.59 cm² per cm² footprint area. Its areal and volume capacitances reache to 53.92 mF cm^?2 and 650 F cm^?3 at 5 mV s^?1, respectively. In addition, the areal capacitance of CrN film electrode with 655 nm possesses reaches to 40.53 mF cm^?2 for 0.5 M H₂SO₄ solution, 32.69 mF cm^?2 for 0.5 M Na₂SO₄ solution and 9.17 mF cm^?2 for NaCl solution at a scan rate of 5 mV s^?1. Furthermore, the CrN film electrode exhibits excellent capacitance retention of 95.3%, 93.8% and 89.9% in H₂SO₄, Na₂SO₄ and NaCl electrolytes, respectively, after 2000 cycles. Therefore, the sputtered CrN thin film is an potential electrode material for electrochemical supercapacitors.     

Hollow ZnSnO3 cubes@carbon/reduced graphene oxide ternary composite as anode of lithium ion batteries with enhanced electrochemical performance

The ternary composite, carbon coated hollow ZnSnO₃ (ZS@C) cubes encapsulated in reduced graphene oxide sheets (ZS@C/rGO), was synthesized via low-temperature coprecipitation and colloid electrostatic self-assembly. The uniform carbon-coating layer not only plays a role in buffering the volume change of ZnSnO₃ cubes in the charging/discharging processes, but also forms three-dimensional network with the cooperation of graphene to maintain the structural integrity and improve the electrical conductivity. The results show that the reduced graphene oxide sheets encapsulated ZS@C microcubes with a typical core-shell structure of ~700 nm in size exhibit an improved electrochemical performance compared with bare ZS@C microcubes. The ZS@C/rGO electrode delivered an initial discharge capacity of 1984 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and maintained a capacity of 1040 mA h g⁻¹ after 45 cycles. High specific capacity and superior cycle stability indicate that the ZS@C/rGO composite has a great potential for the application of lithium-ion anode material.     

Electrospinning-derived ZnCo2O4@carbon nanofiber composite for high-performance lithium ion storage

The degradation of the cobalt-zinc oxide structure and its poor conductivity during the charge and discharge limit their further applications for lithium ion storage. Herein, ZnCo₂O₄@carbon nanofiber composite with nano-fibrous structure is obtained by electrospinning, annealing in argon and low-temperature oxidation to effectively overcome the above issue. The active sites of ZnCo₂O₄ are evenly dispersed inside the carbon nanofibers, which can effectively avoid its aggregation and improve electrical conductivity. Additionally, the stable nanofibrous structure can maintain structural stability. The composite exhibits superior lithium ion storage capacity when being served as anode electrode. The ZnCo₂O₄@carbon nanofiber electrode possesses a high capacity of 1071 mA h g⁻¹ at 0.1 A g⁻¹. Besides, the electrode shows an outstanding rate capability of 505 mA h g⁻¹ at 3 A g⁻¹ and maintain 714 mA h g⁻¹ after 250 cycles when current density is adjusted to 0.2 A g⁻¹ again. Additionally, the electrode has an outstanding long-cycle performance, which remains a capacity of 447.165 mA h g⁻¹ at 0.5 A g⁻¹ after 500 cycles and 421.477 mA h g⁻¹ at 1 A g⁻¹ after 518 cycles. This result demonstrates that ZnCo₂O₄@carbon nanofiber composite has potential application prospects in the fields of advanced energy storage.     

Facile synthesis of sandwich-like polyaniline/boron-doped graphene nano hybrid for supercapacitors

The physicochemical property of chemically prepared graphene can be significantly changed due to the incorporating of heteroatoms into graphene. In this article, boron-doped graphene sheets are used as carbon substrates instead of graphene for loading polyaniline by in situ polymerization. Compared with the individual component and polyaniline/non-doped graphene, the sandwich-like polyaniline/boron-doped graphene exhibits remarkably enhanced electrochemical specific capacitance in both acid and alkaline electrolytes. In a three-electrode configuration, the hybrid has a specific capacitance about 406 F g⁻¹ in 1 M H₂SO₄ and 318 F g⁻¹ in 6 M KOH at 1 mV s⁻¹. In the two-electrode system of a symmetric supercapacitor, this hybrid achieves a specific capacitance about 241 and 189 F g⁻¹ at 0.5 A g⁻¹ with a specific energy density around 19.9 and 30.1 Wh kg⁻¹, in the acid and alkaline electrolytes, respectively. The as-obtained polyaniline/boron-doped graphene hybrid shows good rate performance. Notably, the obtained electrode materials exhibit long cycle stability in both acid and alkaline electrolytes (∼100% and 83% after 5000 cycles, respectively). The improved electrochemical performance of the hybrid is mainly attributed to the introduction of additional p-type carriers in carbon systems by boron-doping and the well combination of pseudocapacitive conducting polyaniline.     

Preparation and capacitive properties of cobalt-nickel oxides/carbon nanotube composites

In this paper, nickel-cobalt oxides/carbon nanotube (CNT) composites were prepared by adding and thermally decomposing nickel and cobalt nitrates directly onto the surface of carbon nanotube/graphite electrode to form nickel and cobalt oxides. Carbon nanotubes used in this paper were grown directly on graphite substrate by chemical vapor deposition technique. The capacitive behavior of nickel-cobalt oxides/CNT electrode was investigated by cyclic voltammetry and galvanostatic charge-discharge method in 1 M KOH aqueous solutions. The results show that nickel-cobalt oxides/CNT composite electrode has excellent charge-discharge cycle stability (0.2% and 3.6% losses of the specific capacitance are found at the 1000th and 2000th charge-discharge cycles, respectively) and good charge-discharge properties at high currrent density. Additionally, the effect of Ni/Co molar ratio on specific capacitance of the composite electrode was investigated and the highest specific capacitance (569 F g⁻¹ at 10 mA cm⁻²) is obtained at Ni/Co molar ratio = 1:1.