Facile synthesis of sulfurized polyacrylonitrile composite as cathode for high-rate lithium-sulfur batteries

Sulfurized polyacrylonitrile(SPAN)as a promising cathode material for lithium sulfur(Li-S)batteries has drawn increasing attention for its improved electrochemical performance in carbonate-based electrolyte.However,the relatively poor electronic and ionic conductivities of SPAN limit its high-rate and lowtemperature performances.In this work,a novel one-dimensional nanofiber SPAN(SFPAN)composite is developed as the cathode material for Li-S batteries.Benefitting from its one-dimensional nanostructure,the SFPAN composite cathode provides fast channels for the migration of ions and electronics,thus effectively improving its electrochemical performance at high rates and low temperature.As a result,the SFPAN maintains a high reversible specific capacity^1200 mAh g−1 after 400 cycles at 0.3 A g−1 and can deliver a high capacity of^850 mAh g−1 even at a high current density of 12.5 A g−1.What is more,the SFPAN can achieve a capacity of^800 mAh g−1 at 0℃and^1550 mAh g−1 at 60℃,thus providing a wider temperature range of applications.This work provides new perspectives on the cathode design for high-rate lithium-sulfur batteries.

Green and efficient cycloaddition of CO2 toward epoxides over thiamine derivatives/GO aerogels under mild and solvent-free conditions

Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.