Lithiation mechanisms of amorphous silicon electrodes in Li-ion batteries probed by in-operando neutron reflectometry

可充电锂离子电池被广泛用作储能设备，将是未来需求的关键。朝着这个方向迈出的重要一步是实现具有高比容量的负极材料，如硅(4ah/g)。充放电循环中的电极过程对于从根本上理解和优化这些电池起着关键作用。本研究的目的是用工作中中子反射仪对电化学驱动的锂在非晶硅电极中(均相/非均相)的掺锂/脱锂机理进行实验研究。在恒流充电和恒电位充电过程中，对薄膜电极和体积电极的电化学电池进行恒电位控制实验。在特殊模拟的基础上，结果将给出锂化机理(均相Li掺入、移动相界等)的信息。此外，还将利用二次离子质谱仪(SIMS)、X射线光电子能谱(XPS)和X射线衍射仪(GIXRD)进行异地实验，以获得更多的系统参数，用于电极表征和可靠的反射率模式模拟。这些实验将有助于进一步发展中子反射法，作为一种有前景的电池系统运行中表征方法。

Rechargeable lithium-ion batteries are widely used as energy storage devices and will be essential for future demands. An important step towards this direction is the implementation of negative electrode materials with a high specific capacity like silicon (4 Ah/g). Electrode processes during charging and discharging cycles play a key role for a fundamental understanding and an optimization of these batteries. Objective of the present proposal is the experimental determination of the mechanisms of electrochemically driven lithium incorporation/extraction (homogeneous/heterogeneous) in amorphous silicon electrodes by in-operando neutron reflectometry.Potentiostat controlled experiments on electrochemical cells with thin film and volume electrodes will be done during galvanostatic charging and additionally potentiostatic charging. Based on special modelling, the results will give information on the lithiation mechanism (homogenous Li incorporation, moving phase boundary etc.) as a function of current density, electrode potential and cycle number.In addition, ex-situ experiments with secondary ion mass spectrometry (SIMS), X-ray photo electron spectroscopy (XPS), and X-ray diffractometry (GIXRD) will be applied in order to obtain additional system parameters for electrode characterization and for a reliable modelling of reflectivity patterns.The experiments should contribute to a further development of neutron reflectometry as a promising method for in-operando characterization of battery systems.