Transition-metal nitrides exhibit wide potential windows and good electrochemical performance, but usually experience imbalanced practical applications in the energy storage field due to aggregation, poor circulation stability, and complicated syntheses. In this study, a novel and simple multiphase polymeric strategy was developed to fabricate hybrid vanadium nitride/carbon(VN/C) membranes for supercapacitor negative electrodes, in which VN nanoparticles were uniformly distributed in the hierarchical porous carbon 3D networks. The supercapacitor negative electrode based on VN/C membranes exhibited a high specific capacitance of 392.0 F g^(-1) at 0.5 A g^(-1) and an excellent rate capability with capacitance retention of 50.5% at 30 A g^(-1). For the asymmetric device fabricated using Ni(OH)_2//VN/C membranes, a high energy density of 43.0 Wh kg^(-1) at a power density of800 W kg^(-1) was observed. Moreover, the device also showed good cycling stability of 82.9% at a current density of 1.0 A g^(-1) after 8000 cycles. This work may throw a light on simply the fabrication of other high-performance transition-metal nitridebased supercapacitor or other energy storage devices.
Yage WuYunlong YangXiaoning ZhaoYongtao TanYing LiuZhen WangFen Ran
This article reported the electrochemical performance of a novel cabon microsphere/MnO2nanosheets(CMS/MnO2) composite prepared by a in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy(SEM) and transmission electron microscopy(TEM) revealed that MnO2nanosheets homogeneously grew onto the surface of CMS to form a loose-packed and dandelion-like core/shell microstructure. The unique microstructure plays a basic role in electrochemical accessibility of electrolyte to MnO2active material and a fast diffusion rate within the redox phase. The results of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry indicated that the prepared CMS/MnO2composite presented high capacitance of 181 F g-1and long cycle life of 61% capacity retention after 2000 charge/discharge cycles in 1 mol/L Na2SO4solution, which show strong promise for high-rate electrochemical capacitive energy storage applications.
Xuanxuan ZhangFen RanHuili FanYongtao TanLei ZhaoXiaoming LiLingbin KongLong Kang
A novel bird nest-like nanostructured MnO2(BNNS-MnO2) was prepared by a facile and cost-effective strategy. Their structures and morphologies were characterized by field emission scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction. Capacitive behaviors were investigated by cyclic voltammetry and galvanostatic charge-discharge. The obtained nano-MnO2 possesses a well designed loose-assembled hierarchical nanoarchitecture with an appropriate crystallinity which gives rise to excellent performances as an electrode material for supercapacitors. A maximum specific capacitance of 917 F/g has been obtained at a current density of 5 mA/cm2 in 6 mol/L KOH aqueous solution, and a specific capacitance of 210 F/g has been maintained for 500 cycles. As the low cost of MnSO4 and KCr2O7 and the low reaction temperature, the present method avoids the requirements for complicated operations, time/energy-consuming and expensive reagents, and perhaps is ready for the industrialization of nano-MnO2 production.
Fen RanHuili FanLingren WangLei ZhaoYongtao TanXuanxuan ZhangLingbin KongLong Kang
Microporous carbon nanofibers(MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone(PVP).PVP together with a mixed solvent of N,N-Dimethylformamide and dimethyl sulfoxide was used as poreforming agent.The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated.The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g.The good performance was owing to the high specific surface area and the large amount of micro-pores,which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process.This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance.
Chang LiuYongtao TanYing LiuKuiwen ShenBowu PengXiaoqin NiuFen Ran
In this study,nano-polyanline and manganese oxide nanometer tubular composites(nano-PANI@MnO2)were prepared by a surface initiated polymerization method and used as electrochemical capacitor electrode materials; and the effect of aniline amount on the microstructure and electrochemical performance was investigated. The microstructures and surface morphologies of nano-PANI@MnO2 were characterized by X-ray diffraction,scanning electron microscopy and fourier transformation infrared spectroscope. The electrochemical performance of these composite materials was performed with cyclic voltammetry,charge–discharge test and electrochemical impedance spectroscopy,respectively. The results demonstrate that the feed ratio of aniline to MnO2 played a very important role in constructing the hierarchically nano-structure,which would,hence,determine the electrochemical performance of the materials. Using the templateassisted strategy and controlling the feed ratio of aniline to MnO2,the nanometer tubular structure of nanoPANI@MnO2 was obtained. A maximum specific capacitance of 386 F/g was achieved in aqueous 1 mol/L Na NO3 electrolyte with the potential range from 0 to 0.6 V(vs. SCE).
Fen RanYunlong YangLei ZhaoXiaoqin NiuDingjun ZhangLingbin KongYongchun LuoLong Kang
This article reported the electrochemical behaviors of a novel hollow carbon microspheres/manganese dioxide nanosheets(micro-HC/nano-MnO2) composite prepared by an in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy reveal that MnO2 nanosheets homogeneously grow onto the surface of micro-HC to form a loose-packed microstructure. The quantity of MnO2 required in the electrode layer has thereby been reduced significantly, and higher specific capacitances have been achieved. The micro-HC/nano-MnO2 electrode presents a high capacitance of 239.0 F g-1 at a current density of 5 m A cm-2, which is a strong promise for high-rate electrochemical capacitive energy storage applications.
Hui-li FanFen RanXuan-xuan ZhangHai-ming SongXiao-qin NiuLing-bin KongLong Kang
