Synthesis of porous C/Fe3O4 microspheres by spray pyrolysis with NaNO3 additive for lithium-ion battery applications

In this work, we successfully synthesized porous C/Fe₃O₄ microspheres by spray pyrolysis at 700ºC with a sodium nitrate (NaNO₃) additive in the precursor solution. Furthermore, we studied their electrochemical properties as anode material for Li-ion batteries. The systematic studies by various characterization techniques show that NaNO₃ catalyzes the carbonization of sucrose and enhances the crystallization of Fe₃O₄. Moreover, an aqueous etching can easily remove sodium compounds to produce porous C/Fe₃O₄ microspheres with large surface areas and pore volumes. The porous C/Fe₃O₄ microspheres exhibit a reversible capacity of ~780 mAh g^–1 in the initial cycles and ~520 mAh g^–1 after 30 cycles at a current density of 50 mA g^–1. Moreover, a reversible capacity of ~400 mAh g^–1 is attainable after 200 cycles, even at a high current density of 500 mA g^–1. The wide range of pores produced from the removal of sodium compounds might enable easy electrolyte penetration and facilitate fast Li-ion diffusion, while the N-doping can promote the electronic conductivity of the carbon. These features of porous C/Fe₃O₄ microspheres led to the improved electrochemical properties of this sample.

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Changes in the Hydration State of a Block Copolymer of Poly(N‐isopropylacrylamide) and Poly(ethylene oxide) on Thermosensitive Micellization in Water

A diblock copolymer of poly(N‐isopropylacrylamide) and poly(ethylene oxide) (PiPA‐b‐PEO) has been prepared by radical polymerization with a ceric ion initiation system. Its thermosensitive micellization has been investigated by means of IR and fluorescence spectroscopy. The PiPA segments are critically dehydrated above 33.5°C (5 wt.‐%) and associate through hydrophobic interaction to form the hydrophobic core of the micelle. In contrast, the change in the hydration state of the PEO segments upon micellization is small.