Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713, Republic of Korea.
ACS Nano. 2015 Apr 28;9(4):4026-35. doi: 10.1021/acsnano.5b00088. Epub 2015 Mar 17.
A structure denoted as a "bubble-nanorod composite" is synthesized by introducing the Kirkendall effect into the electrospinning method. Bubble-nanorod-structured Fe2O3-C composite nanofibers, which are composed of nanosized hollow Fe2O3 spheres uniformly dispersed in an amorphous carbon matrix, are synthesized as the target material. Post-treatment of the electrospun precursor nanofibers at 500 °C under 10% H2/Ar mixture gas atmosphere produces amorphous FeOx-carbon composite nanofibers. Post-treatment of the FeOx-carbon composite nanofibers at 300 °C under air atmosphere produces the bubble-nanorod-structured Fe2O3-C composite nanofibers. The solid Fe nanocrystals formed by the reduction of FeOx are converted into hollow Fe2O3 nanospheres during the further heating process by the well-known Kirkendall diffusion process. The discharge capacities of the bubble-nanorod-structured Fe2O3-C composite nanofibers and hollow bare Fe2O3 nanofibers for the 300th cycles at a current density of 1.0 A g(-1) are 812 and 285 mA h g(-1), respectively, and their capacity retentions measured from the second cycle are 84 and 24%, respectively. The hollow nanospheres accommodate the volume change that occurs during cycling. The unique structure of the bubble-nanorod-structured Fe2O3-C composite nanofibers results in their superior electrochemical properties by improving the structural stability during long-term cycling.
通过引入柯肯达尔效应到静电纺丝方法中，合成了一种被称为“气泡-纳米棒复合材料”的结构。作为目标材料，合成了由纳米尺寸的空心 Fe2O3 球体均匀分散在非晶态碳基体中的气泡-纳米棒结构的 Fe2O3-C 复合纳米纤维。在 500°C 下，将电纺前体纳米纤维在 10% H2/Ar 混合气体气氛中进行后处理，生成非晶态 FeOx-碳复合纳米纤维。在空气气氛下，将 FeOx-碳复合纳米纤维在 300°C 下进行后处理，生成气泡-纳米棒结构的 Fe2O3-C 复合纳米纤维。在进一步的加热过程中，通过众所周知的柯肯达尔扩散过程，FeOx 还原形成的固态 Fe 纳米晶转化为空心 Fe2O3 纳米球。在电流密度为 1.0 A g(-1)时，经过 300 次循环后，气泡-纳米棒结构的 Fe2O3-C 复合纳米纤维和空心 bare Fe2O3 纳米纤维的放电容量分别为 812 和 285 mA h g(-1)，从第二次循环开始的容量保持率分别为 84%和 24%。空心纳米球容纳了在循环过程中发生的体积变化。气泡-纳米棒结构的 Fe2O3-C 复合纳米纤维的独特结构通过提高长期循环过程中的结构稳定性，改善了其电化学性能。
