Silicon (Si) is considered to be one of the most promising anode materials for next-generation lithium-ion batteries primarily due to its high theoretical specific capacity of up to 4200 mAh g^-1 and its abundance in nature. However, the irreversible capacity loss and poor cycle life caused by the dramatic volumetric expansion of Si upon alloying with lithium (Li) (>300%) prevents practical implementation of anodes with high Si loading. A better understanding of the interactions between the electrochemistry and mechanical behavior of Si anodes during cycling is therefore needed to develop novel materials and electrode design that can efficiently accommodate the volumetric expansion. In addition, there are significant questions regarding the interactions of the Si with the surrounding carbon materials.

In this work, we use nano-resolution x-ray computed tomography (nano-CT) and an in-house micro-capillary sample cell to directly observe the cycling (lithiation/delithiation) process of Si particle-based electrodes as a function of time. We will show preliminary results on the effects of the electrode composition (Si particle size distribution, particle proximity, etc.) on the Li-Si alloy phase nucleation and propagation.

This material is based upon work supported by the National Science Foundation under Grant No. CBET-1705321. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.