硅是一种具有应用前景的负极材料。为了解决在电化学循环过程中由于硅电极体积变化较大、导电性比较差而造成负极材料比容量迅速衰减及其循环性能不稳定的问题,本研究利用溶胶-凝胶法,经过镁热反应制得具有三明治结构的负极材料石墨烯-...硅是一种具有应用前景的负极材料。为了解决在电化学循环过程中由于硅电极体积变化较大、导电性比较差而造成负极材料比容量迅速衰减及其循环性能不稳定的问题,本研究利用溶胶-凝胶法,经过镁热反应制得具有三明治结构的负极材料石墨烯-硅-石墨烯;通过实验研究发现负极材料G-Si-1:1具有较好的电化学性能,在电流密度为0.1 A/g时首次放电比容量为1150 m A·h·g^(-1),循环100周时放电比容量为534.2 m A·h·g^(-1)。负极材料石墨烯纳米片负载硅纳米颗粒的合成路线较为简单,并且具有较高的放电比容量和较好的循环性能,在未来具有较好的应用前景。展开更多
High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reac...High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reaction to get the mixture of V and MgO,and then the products were further nitrided at 1473 K in N2 atmosphere.Finally,the as-prepared samples were acid-leached to obtain pure VN powders.X-ray diffractometry and field-emission scanning electron microscopy were used to analyze the phase transition and morphological evolution of the samples.The results reveal that the overall morphology of the obtained VN powder retains the morphology of the initial V2 O3 powders.After removing MgO by acidic leaching,the porous VN particles can be obtained,with the oxygen content of 0.178 wt.%.Compared with the traditional methods,high purity VN powders with a small amount of oxygen and no carbon can be obtained.展开更多
Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage. It is, therefore, important to under- stand the underlying dehydrogenation mecha...Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage. It is, therefore, important to under- stand the underlying dehydrogenation mechanisms for further development of these ma- terials. We present a systematic theoretical investigation on the dehydrogenation mecha- nisms of the Mg2(BH4)2(NH2)2 compounds. We found that dehydrogenation takes place most likely via the intermolecular process, which is favorable both kinetically and thermo- dynamically in comparison with that of the intramolecular process. The dehydrogenation of Mg2(BH4)2(NH2)2 initially takes place via the direct combination of the hydridie H in BH4 and the protie H in NH2-, followed by the formation of Mg-H and subsequent ionic recombination of Mg-Hδ-…Hδ+-N.展开更多
文摘硅是一种具有应用前景的负极材料。为了解决在电化学循环过程中由于硅电极体积变化较大、导电性比较差而造成负极材料比容量迅速衰减及其循环性能不稳定的问题,本研究利用溶胶-凝胶法,经过镁热反应制得具有三明治结构的负极材料石墨烯-硅-石墨烯;通过实验研究发现负极材料G-Si-1:1具有较好的电化学性能,在电流密度为0.1 A/g时首次放电比容量为1150 m A·h·g^(-1),循环100周时放电比容量为534.2 m A·h·g^(-1)。负极材料石墨烯纳米片负载硅纳米颗粒的合成路线较为简单,并且具有较高的放电比容量和较好的循环性能,在未来具有较好的应用前景。
基金Project(51725401) supported by the National Natural Science Foundation of China
文摘High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reaction to get the mixture of V and MgO,and then the products were further nitrided at 1473 K in N2 atmosphere.Finally,the as-prepared samples were acid-leached to obtain pure VN powders.X-ray diffractometry and field-emission scanning electron microscopy were used to analyze the phase transition and morphological evolution of the samples.The results reveal that the overall morphology of the obtained VN powder retains the morphology of the initial V2 O3 powders.After removing MgO by acidic leaching,the porous VN particles can be obtained,with the oxygen content of 0.178 wt.%.Compared with the traditional methods,high purity VN powders with a small amount of oxygen and no carbon can be obtained.
文摘Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage. It is, therefore, important to under- stand the underlying dehydrogenation mechanisms for further development of these ma- terials. We present a systematic theoretical investigation on the dehydrogenation mecha- nisms of the Mg2(BH4)2(NH2)2 compounds. We found that dehydrogenation takes place most likely via the intermolecular process, which is favorable both kinetically and thermo- dynamically in comparison with that of the intramolecular process. The dehydrogenation of Mg2(BH4)2(NH2)2 initially takes place via the direct combination of the hydridie H in BH4 and the protie H in NH2-, followed by the formation of Mg-H and subsequent ionic recombination of Mg-Hδ-…Hδ+-N.