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Abstract: Porous graphitic carbons (PGC) are synthesized to be used in internal parallel hybrid devices. The hybrid devices are assembled with a LiFePO4 cathode, and an anode based on a mixture of PGC and Li4Ti5O12. Then the hybrid devices are characterized by galvanostatic charge/discharge, rate charge/discharge and cycle performance testing. The results show that PGC hybrid devices possess better performance than the commercial activated carbon hybrid device. Moreover, the internal parallel hybrid device with 25% PGC, denoted as T3P1F, exhibits an optimal performance with high energy density, high power density and stable cycling performance. [Copyright &y& Elsevier]

Abstract: A novel MnO2/polypyrrole (PPy) heterogeneous composite with nanotubular structure is reported by a facile preparation of in situ chemical polymerization via a reactive template of MnO2. MnO2 nanotubes are found to be served as both appropriate oxidants and scaffolds to polymerize conducting PPy nanocoatings on the surface, thus constructing a unique coaxial configuration. The electrochemical measurements show that both components in the hybrid nanocomposites exhibit highly pseudocapacitive behavior in neutral KCl aqueous electrolyte. MnO2/PPy nanocomposites prepared from an initial MnO2/pyrrole ratio (3:1) deliver a maximum specific capacitance of 337 F g−1 at 0.5 A g−1 with good rate capability and long-term cycling stability, demonstrating their promising applications in high-performance supercapacitors. Moreover, the synthetic methodology may provide a generic guideline in developing different nanostructured MnO2/PPy electrode materials for electrochemical energy storage. [Copyright &y& Elsevier]

Abstract: MnO2/carbon nanotubes (CNTs)–embedded carbon nanofibers (CNFs) nanocomposites (MnO2/CNTs–CNFs) have been prepared using electrospinning and in situ redox deposition technique. The as-prepared nanocomposites were directly employed as freestanding electrodes to evaluate the electrochemical properties. Results showed that the nanoscopic MnO2 deposits were incorporated uniformly into the CNTs–embedded CNFs network structure, which hold a great promise for high-performance supercapacitor applications. Compared to the pure CNFs substrate, the improved electric conductivity of CNTs–embedded CNFs substrate enabled a better utilization of MnO2 coating, thus resulting in higher specific capacitance (374F/g) and better rate capability (53.4%). Excellent capacitance retention of 94% of the initial capacitance after 1000cycles was achieved on the freestanding MnO2/CNTs–CNFs nanocomposites electrode. The specific capacitance was found to increase significantly with the increase in the electrolyte temperature, which offered an insight into the practical supercapacitor applications. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers (CNFs)/MnO2 nanocomposites were prepared as freestanding electrodes using in situ redox deposition and electrospinning. The electrospun CNFs substrates with porosity and interconnectivity enabled the uniform incorporation of birnessite-type MnO2 deposits on each fiber, thus showing unique and conformal coaxial nanostructure. CNFs not only provided considerable specific surface area for high mass loading of MnO2 but also offered reliable electrical conductivity to ensure the full utilization of MnO2 coatings. The effect of MnO2 loading on the electrochemical performances was investigated by cyclic voltammetry (CV), impedance measurements and Galvonostatic charging/discharging technique. The results showed that an ultrathin MnO2 deposits were indispensable to achieve better electrochemical performance. The maximum specific capacitance (based on pristine MnO2) attained to 557F/g at a current density of 1A/g in 0.1M Na2SO4 electrolyte when the mass loading reached 0.33mg/cm2. This freestanding electrode also exhibited good rate capability (power density of 13.5kW/kg and energy density of 20.9Wh/kg at 30A/g) and long-term cycling stability (retaining 94% of its initial capacitance after 1500 cycles). These characteristics suggested that such freestanding CNFs/MnO2 nanocomposites are promising for high-performance supercapacitors. [Copyright &y& Elsevier]