Negative Electrode Material For Supercapacitors Research Articles

Ultrathin manganese dioxide nanosheets grown on partially unzipped nitrogen-doped carbon nanotubes for high-performance asymmetric supercapacitors

In this work, N-doped carbon nanotubes (NCNTS) have been easily unzipped using a chemical oxidation method to obtain porous and multi-defective partially unzipped N-doped carbon nanotubes (PU-NCNTs), which are promising as negative electrode materials for supercapacitors and are also suitable substrate materials for the efficient loading of ultrathin manganese dioxide (MnO2) nanosheets. Herein, the PU-NCNT/MnO2 composite was synthesized through a simple microwave irradiation method. Moreover, we have fabricated an asymmetric supercapacitor (ASC) using PU-NCNT/MnO2 composite as cathode, PU-NCNTs as anode and neutral aqueous Na2SO4 as electrolyte. Because of the synergistic effects of the PU-NCNTs electrode and the high capacitance as well as good rate performance of PU-NCNT/MnO2 composite, the asymmetric cell exhibited good electrochemical performance. The optimized ASC can be worked stably in the voltage window of 0–1.8 V and exhibited a maximum energy density of 14.76 Wh kg−1 at the current density of 1 A g−1. Additionally, the PU-NCNT/MnO2//PU-NCNT ASC exhibited long cycling stability with 80.5% specific capacitance retained after 1000 cycles at a current density of 1 A g−1. These encouraging results show that PU-NCNT/MnO2 could be promising materials for commercial use of supercapacitors.

Design and preparation of MoO2/MoS2 as negative electrode materials for supercapacitors

In this work, the MoO2/MoS2 composite material with unique flower-like microsphere structure is prepared via a facile hydrothermal synthesis. Furthermore, the composite material is served as negative electrode for supercapacitors. Ascribe to the synergistic effect, including the improved electron conductivity, the coexistence of two energy storage mechanisms, and a stable flower-like microsphere structure, the as-fabricated MoO2/MoS2 exhibits a high specific capacitance of 433.3Fg−1 at a scan rate of 5mVs−1 and a superior cycling stability of 84.41% retention after 5000cycles compared to that of pure MoO2 (33.33% retention after 2000cycles) and pure MoS2 (58.33% retention after 2000cycles) at a current density of 1Ag−1 in 1M Na2SO4 electrolyte. Moreover, we also synthesize a series of MoO2/MoS2 electrode materials, which are used to further illustrate the synergistic effect in MoO2/MoS2 composite materials. This work signifies such materials as negative electrodes exhibit bright application prospects for supercapacitors.

Synthesis of Ag Anchored Ag3VO4 Stacked Nanosheets: Toward a Negative Electrode Material for High-Performance Asymmetric Supercapacitor Devices

Ag/α-Ag3VO4 stacked nanosheets were prepared through a low-temperature hydrothermal route. Cetyltrimethylammonium bromide has been used as a surfactant in the preparation of Ag/α-Ag3VO4 stacked nanosheets. X-ray diffraction revealed mixed metallic silver with Ag/α-Ag3VO4 nanosheets, which was further confirmed by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). FESEM and HRTEM images clearly showed that the silver anchored with silver vanadium oxide stacked nanosheets. The electrochemical performance of the Ag/α-Ag3VO4 stacked nanosheets was examined by cyclic voltammetry and galvanostatic charge–discharge techniques. Both studies indicated that Ag/α-Ag3VO4 is a suitable negative electrode material for supercapacitors and delivers a maximum specific capacitance of 461 F g–1 at a specific current of 2 A g–1. The asymmetric supercapacitor device yielded a specific cell capacitance of 97 F g–1 at a specific current of 1 A g–1. The device delive...

Molybdenum dioxide-anchored graphene foam as a negative electrode material for supercapacitors

Molybdenum dioxide nanoparticles of diameter 100 nm were anchored uniformly to a three-dimensional (3D) graphene foam using an ultrasonication-assisted deposition method. X-ray diffraction and Raman spectroscopy indicated that the molybdenum dioxide nanoparticles had a monoclinic crystal structure. The 3D graphene/MoO2 nanoparticle composite showed excellent pseudocapacitive ability as its specific capacitance reached 404 F g−1 at a scan rate of 2 mV s−1 in the negative potential range, −1.0 to −0.2 V, in a neutral solution. Overall, the 3D graphene/MoO2 nanoparticle composite has great potential as an anode material for the next generation of high-performance supercapacitors.

Synthesis and Pseudocapacitve Properties of Tungsten Oxide Nanorods

Tungsten oxide (WO3) nanorods were fabricated and evaluated as negative electrode materials for supercapacitors. The influence of the concentration of sodium chloride and pH value of the synthesis solution were investigated. The pH value of solution and sodium chloride play important roles in the formation of uniform dispersed nanorods of WO3. Cyclic voltammetry and chronopotentiometry results show that nanorods WO3 film exhibit advanced pseudocapacitive performance over a negative potential range of − 0.6 V to 0.2 V vs. SCE in 1M H2SO4 with the high specific capacitance of 114 F g-1, compared to that of the bulk WO3 electrode materials.

Mesoporous carbon–manganese oxide composite as negative electrode material for supercapacitors

3D-assembles of silica spheres were used as hard template to synthesize porous carbon materials with large mesopores to be included as current collectors in supercapacitors and developing large surface areas reaching up to 900 m 2/g. Birnessite-type MnO 2 was deposited by a co-precipitation method in the porous network. Electrochemical performances of resulting MnO 2/C nanocomposites were evaluated by cyclic voltammetry and showed an initial capacitance and a retained capacitance after 500 cycles for the nanocomposite at 6 wt% MnO 2 in C of about 660 and 490 F/g, respectively.

Characterization of the Electrochemical and Ion-Transport Properties of a Nanoporous Carbon at Negative Polarization by the Single-Particle Method

In this work, the electrochemical processes occurring in a nanoporous carbon, obtained from silicon carbide and used as negative electrode material for supercapacitors, have been investigated by means of the single-particle microelectrode method. The processes studied deal with hydrogen adsorption, evolution, and oxidation using KOH as electrolyte. It was found that adsorption of hydrogen started at , hydrogen evolution at vs Hg∣HgO, and that hydrogen oxidation occurs in two steps. The first oxidation process takes place between 0 and , shown by a well-defined current peak on the voltammograms. The second oxidation stage occurs between 0.1 and , indicated by a successive increase in current with the number of cycles. It was also found that after the first oxidation process, subsequent cycling between and leads to a larger accumulation of hydrogen inside the nanopores and to a decrease of the effective diffusion coefficient of potassium ions. Subsequent oxidation, in a second process, leads to a total consumption of hydrogen and to an increase of .