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Hollow urchin-like iron-doped manganese dioxide (Fe-MnO) architectures were successfully prepared without any template or surfactant via a facile one-step hydrothermal route. Hollow urchin-like Fe-MnO architectures were made up of interleaving nanosheets, resulting in porous structures and high specific surface area. The formation mechanism of hollow urchin-like Fe-MnO architectures was proposed based on the Ostwald ripening process. When employed as supercapacitor electrode material, hollow urchin-like Fe-MnO delivered a specific capacitance of 203.3 F g at 250 mA g as well as a good capacity retention of 88.1% after 1000 cycles at 5 A g. Coupled with activated carbon (AC) negative electrode, Fe-MnO//AC asymmetric supercapacitor (Fe-MnO//AC ASC) achieved an energy density of 20.2 Wh kg at a power density of 225 W kg and 83.8% capacity retention after 1000 cycles at 3 A g, suggesting its potential applications for energy storage. [ABSTRACT FROM AUTHOR]

Abstract In this study, silicon (Si) nanoparticles have been prepared by a chemical reaction of calcium silicide (CaSi 2), sulfur and metallic sodium in an autoclave at 250 °C. X-ray powder diffraction pattern indicates that the obtained sample is cubic phase Si with the calculated lattice constant a = 5.436 Å. Electron microscopy images show the obtained Si sample is composed of nanoparticles with an average size of 50 nm. As an anode for lithium ion batteries, the as-prepared Si nanoparticles exhibit a reversible capacity of 1409 mA h g−1 at a current density of 2 A g−1 over 300 cycles. Highlights • Si nanoparticles are synthesized at a low temperature. • The obtained Si nanoparticles exhibit high capacity and excellent rate capacity. • Si nanoparticles exhibit a reversible capacity of 1409 mAh g−1 over 300 cycles. [ABSTRACT FROM AUTHOR]