Papers by Keyword: Electrochemical Performance

Abstract: A microwave irradiation involved process was applied to fabrication of graphene/polyaniline nanocomposite via in-situ polymerization of aniline monomers on graphene sheets. Structure and morphology of composites were characterized through scanning electron microscopy, Raman spectra, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectra. Electrochemical performances for energy storage applications were examined by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. Owing to the homogeneous coating of polyanilline on the large surface of graphene, graphene/polyaniline composite-based electrode exhibits remarkably enhanced capacitive behavior with a specific capacitance of 429 F/g at 0.2 A g^-1, a good cyclic stability and an excellent conducting behavior, which are much superior to those of individual components of composites. The improved electrochemical behavior of the composite resulting from the irradiation of microwave suggests the promising potentials for supercapacitors.

Abstract: Wet recycling method was utilized for recycling manganese from waste Zn-Mn batteries to obtain MnCO₃. It was indicated that soaking time, the concentration and volume of acid all have great effects on the yield of MnCO₃. The productivity of MnCO₃ can reach 64.65%, when the concentration of HCl acid is 5mol/L, and with a volume of 40ml, under 180min soaking time. The productivity of MnCO₃ can also reach 63.36%, when the concentration of HNO₃ is 6mol/L, with 60ml volume by soaking for 80min. Furthermore, LiMn₂O₄ was synthesized in air atmosphere with the recycled MnCO₃ and Li₂CO₃ under different calcination temperatures. The electrochemical performances of prepared LiMn₂O₄ were studied and the results present preferable electrochemical properties.

Abstract: The Co-Ni mixed oxides/graphene composite has been prepared using the solution based oxidation route. The structures of bare Co-Ni mixed oxides and Co-Ni mixed oxides/graphene composite is clearly studied by X-ray diffraction. The electrochemical properties of Co-Ni mixed oxides/graphene composite are investigated by Cyclic Voltammetry (CV) and galvanostatic charge discharge test. The result shows that, the NiO phase has not been detected in the composite, and the graphene composite delivers a discharge capacity of 353.6 F/g at a current density of 0.32 A g^-1.

Abstract: In order to enhance the electrochemical properties of Co-B alloys used as negative electrode materials of alkaline rechargeable batteries, Co-B alloy was successfully prepared by a chemical reduction method with the assistance of the sonication. The phase structure and the surface morphology of the as-prepared Co-B alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen physisorption. Moreover, the electrochemical performance was characterized by galvonostatic charge-discharge tests, electrochemical impedance spectroscopy (EIS) and anodic polarization (AP). Co-B alloy prepared with the assistance of the sonication consists of small particles with a uniform distribution. The electrochemical measurements showed that at a discharge current density of 100 mA/g, the initial discharge capacity was 858.1 mAh/g and the discharge capacity was 322.6 mA/g even at the 100th cycle with the capacity retention of 37.6%.

Abstract: A proton exchange membrane (PEM) fuel cell is an electrochemical device that directly converts chemical energy of hydrogen into electric energy.The structure of the flow channel is critical to the PEM fuel cell performance. In this paper, the effect of the cathode flow channel baffles on PEM fuel cell performance was investigated numerically. A three-dimensional model was established for the PEM fuel cell which consisted of bipolar plates with three serpentine flow channels, gas diffusion layers, catalyst layers and PEM. Baffles were added in the cathode flow channels to study the effect of the cathode flow channel baffle on the PEM fuel cell performance. And then, numerical simulation for the PEM fuel cell with various cathode channel baffle heights ranging from 0.2 mm to 0.6 mm was conducted.The simulated results show that there existed an optimal cathode flow channel baffle height in terms of the electrochemical performance as all other parameters of the PEM fuel cell were kept constant. It is found that the PEM fuel cell had the good electrochemical performance as the flow channel baffle heights was 0.4mm in this work.

Abstract: To improve electrochemical performance of Li ion battery , we synthesis flower-like V₆O₁₃ in oxalic acid solvent with HCl. The composition and morphology of the V₆O₁₃ were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements, respectively. The synthesized flowers-like V₆O₁₃ are less than 600nm in the width of the ribbon and have purity phase of the V₆O₁₃.The electrochemical performance of the flowers-like V₆O₁₃ were characterized by charge and discharge performance, EIS and CV. The flowers-like V₆O₁₃ exhibited high electrochemical performance.

Abstract: Si/C composites were prepared by spray dying and carbonization process using silica powder, artificial graphite and glucose as raw materials. The physicochemical property and electrochemical performance of composite materials were characterized by XRD, SEM, constant current charge-discharge and cyclic voltammeter (CA) test, respectively. The results show that composite anode materials have pure phase structure with particle size of 5~20μm, and its special structure that silicon and graphite particles are constructed can exhibit good electrochemical performance. The initial discharge specific capacity of Si/C composites is 1033.2mAhg^-1 at a current density of 100mAg^-1.While the current density is as high as 600mAg^-1, the discharge specific capacity is 584.2mAhg^-1, and the first cycle coulombic efficiency is 77.3% at 100mAg^-1.The mechanism of capacity fading of Si/C composites is discussed by different morphology characterization after 100 cycles.

Abstract: Si/C composite was prepared using different procedures and different C sources in this work. According to the electrochemical performances, it was found that the discharge capacity for Si/C composite (SC1) by the electrostatic spinning procedure using polyvinylpyrrolidone as the C source was 2200mAh/g. In contrast, the cell with the pure Si particle exhibited an initial discharge capacity of only 13mAh/g. Moreover, after 30 cycles, SC1 sample had the higher capacities and the better capacity retention performances than other samples because of its lower charge transfer resistance. The inclusion of carbon not only worked as a stable electric conductive pathway but also buffer the volume expansion of the silicon during the process of charging and discharging.

Abstract: Theoretical capacity of silicon is 4200mAhg^-1, but pure silicon had huge volume change during lithium insertion, which reduces the cycle life of silicon. In this paper, pure silicon was replaced of metallic silicon to relieve volume effect. Metallic silicon contains some alloying elements which improve the conductivity of the electrode material. The elements in metallic silicon will relief the volume change of silicon substrate during lithium insertion/ de-lithiation process. Metallic silicon was treated by mechanical alloying (MA) which is an effective method to reduce particle sizes of metallic silicon. The results show that MA can improve cycle performance of metallic silicon. Metallic silicon treated by MA performs a better cycling performance compared with the unsettled materials and a higher discharge capacity in the first cycle.

Abstract: ZnO quantum dots (QDs) are anchored on graphene oxide (GO) by a wet chemical self-assembling technique. Firstly, GO are functionalized with thiol (f-GO) by a series of chemical reactions and the ZnO alcogel are prepared by a sol–gel process. Secondly, the f-GO/ZnO composite is obtained by a self-assembling technique. Typically, X-ray diffraction (XRD), scanning electron microscopy (SEM) and EDS spectrum are employed to characterize the structure, morphology and composition of the obtained samples, moreover, the electrochemical performance of the as-prepared electrode is also detected by cyclic voltammetry and galvanostatic charge–discharge experiments. It is found that the f-GO/ZnO-1 possesses the highest specific values of 149.4F/g and good long-term cycle stability. The results show that the f-GO/ZnO nanocomposite could be used as electrode material for high performance supercapacitors.