Cho Jung Sang, Kang Yun Chan
Department of Materials Science and Engineering, Korea University , Anam-Dong, Seongbuk-Gu, Seoul 136-713, Republic of Korea.
ACS Appl Mater Interfaces. 2016 Feb 17;8(6):3800-9. doi: 10.1021/acsami.5b10278. Epub 2016 Feb 4.
A simple and easily scalable process for the formation of metal oxide hollow nanospheres using nanoscale Kirkendall diffusion called the "all-in-one beaker method" is introduced. The Fe2O3, SnO2, NiO, and Co3O4 hollow nanospheres are successfully prepared by the all-in-one beaker method. The detailed formation mechanism of aggregate-free hematite hollow nanospheres is studied. Dimethylformamide solution containing Fe acetate, polyacrylonitrile (PAN), and polystyrene (PS) transforms into aggregate-free Fe2O3 hollow nanospheres. The porous structure formed by the combustion of PS provides a good pathway for the reducing gas. The carbon matrix formed from PAN acts as a barrier, which can prevent the aggregation of metallic Fe nanopowders by surrounding each particle. The Fe-C bulk material formed as an intermediate product transforms into aggregate-free Fe2O3 hollow nanospheres by the nanoscale Kirkendall diffusion process. The mean size and shell thickness of the hollow Fe2O3 nanospheres measured from the TEM images are 52 and 9 nm, respectively. The discharge capacities of the Fe2O3 nanopowders with hollow and dense structures and the bulk material for the 200th cycle at a current density of 0.5 A g(-1) are 1012, 498, and 637 mA h g(-1), respectively, and their capacity retentions calculated compared to those in the second cycles are 92, 45, and 59%, respectively. Additionally, Fe2O3 hollow nanospheres cycled at 1 A g(-1) after 1000 cycles showed a high discharge capacity of 871 mA h g(-1) (capacity retention was 80% from the second cycle). The Fe2O3, SnO2, NiO, and Co3O4 hollow nanospheres show excellent cycling performances for lithium-ion storage because they have a high contact area with the liquid electrolyte and space for accommodating a huge volume change during cycling.
介绍了一种使用纳米级柯肯达尔扩散形成金属氧化物空心纳米球的简单且易于扩展的方法，即“一体化烧杯法”。通过一体化烧杯法成功制备了Fe2O3、SnO2、NiO和Co3O4空心纳米球。研究了无团聚赤铁矿空心纳米球的详细形成机理。含有醋酸铁、聚丙烯腈（PAN）和聚苯乙烯（PS）的二甲基甲酰胺溶液转变为无团聚的Fe2O3空心纳米球。PS燃烧形成的多孔结构为还原气体提供了良好的通道。由PAN形成的碳基质起到屏障作用，通过包围每个颗粒可以防止金属Fe纳米粉末的团聚。作为中间产物形成的Fe-C块状材料通过纳米级柯肯达尔扩散过程转变为无团聚的Fe2O3空心纳米球。从TEM图像测量的空心Fe2O3纳米球的平均尺寸和壳厚度分别为52和9nm。在0.5A g(-1)的电流密度下，空心和致密结构的Fe2O3纳米粉末以及块状材料在第200次循环时的放电容量分别为1012、498和637mA h g(-1)，与第二次循环相比计算得到的容量保持率分别为92%、45%和59%。此外，在1A g(-1)下循环1000次后的Fe2O3空心纳米球显示出871mA h g(-1)的高放电容量（从第二次循环起容量保持率为80%）。Fe2O3、SnO2、NiO和Co3O4空心纳米球对锂离子存储表现出优异的循环性能，因为它们与液体电解质具有高接触面积以及在循环过程中容纳巨大体积变化的空间。
