Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
1] Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK [2].
Nat Commun. 2014;5:3217. doi: 10.1038/ncomms4217.
Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.
纳米结构硅阳极在可充电锂离子电池中是石墨碳的极具吸引力的替代品，因为它们具有极高的容量。尽管具有这些优势，但仍有许多问题需要解决，最基本的问题是要了解控制反应和结构重排的复杂动力学和热力学。要阐明这一点，需要实时原位计量学，如果要在真实的循环条件下对整个电极结构进行原子级的多个循环进行研究，则这是极具挑战性的。在这里，我们报告了在导电碳纤维支撑体上生长的硅纳米线提供了一个稳健的模型电池系统，可以通过（7）Li 原位 NMR 光谱进行研究。该方法可以在第 2 个循环及以后跟踪非晶态硅化物的（脱）合金化反应。与密度泛函理论计算相结合，结果深入了解了非晶态和非晶态到晶态的锂硅化物转化，特别是在低电压下的转化，这与实际的循环策略高度相关。
