Lee Hyojin, Kim Min Gyu, Choi Cheol Ho, Sun Yang-Kook, Yoon Chong Seung, Cho Jaephil
Department of Applied Chemistry, Kumoh National Institute of Technology, Gumi, Korea.
J Phys Chem B. 2005 Nov 10;109(44):20719-23. doi: 10.1021/jp052620y.
Amorphous Ge nanoparticles with the particle size of approximately 10 nm were prepared by capping butyl groups and were characterized using XAS, TEM, FT-IR reflectance, and electrochemical cycling. The XAS results for the first-cycle Ge nanoparticles exhibited either a little particle aggregation after reformation of the Ge-Ge metallic bond or reformation of Ge-Ge metallic bond followed by a little particle aggregation. More interestingly, butyl groups, being electrochemically stable, remained after cycling, and the quantum mechanical calculation of the thermodynamic energy of the reaction using the GAMESS (General Atomic and Molecular Electronic Structure System) program suggested the formation of a very stable surface Ge-C bond that cannot be easily subjected to the subsequent chemical reactions. Initial charge capacity is 1470 mAh/g with an irreversible capacity ratio of 12%; no capacity fading was observed out to 30 cycles. Even at 5 C rate discharging, capacity retention was 98%, compared to that at 0.2 C rate discharging. In addition, the capacity was fully recovered at 0.2 C rate cycling.
通过封端丁基制备了粒径约为10 nm的非晶态锗纳米颗粒，并使用X射线吸收光谱（XAS）、透射电子显微镜（TEM）、傅里叶变换红外反射光谱（FT-IR）和电化学循环对其进行了表征。首次循环的锗纳米颗粒的XAS结果显示，在锗-锗金属键重新形成后出现了少量颗粒聚集，或者是锗-锗金属键重新形成后接着出现了少量颗粒聚集。更有趣的是，电化学稳定的丁基在循环后仍然存在，使用GAMESS（通用原子和分子电子结构系统）程序对反应的热力学能量进行的量子力学计算表明形成了非常稳定的表面锗-碳键，该键不易发生后续化学反应。初始充电容量为1470 mAh/g，不可逆容量比为12%；在30次循环内未观察到容量衰减。即使在5 C倍率放电时，与0.2 C倍率放电相比，容量保持率仍为98%。此外，在0.2 C倍率循环时容量完全恢复。
