Quantitative analysis of the structural evolution in Si anode via multi-scale image reconstruction.

Despite the high theoretical capacity, silicon (Si) anode suffers from dramatical capacity loss, due to its massive volume swings (up to 300%) during cycling. Hence, thorough understanding of the structural evolution mechanism is necessary and essential for performance optimization of Si anode. Herein, a multi-scale three-dimensional (3D) image reconstruction technique is firstly applied to visualize the structural evolution process of Si anodes. Three key components (Si particles, inactive components, and voids) in the electrode are quantitatively analyzed by the focused ion beam and scanning electron microscope (FIB-SEM) technology. Furthermore, the average sizes of Si particles were run statistics during the cycling. By combining the componential observation within the electrode (macroscopic information) and the 3D models of the particle with solid electrolyte interphase (SEI) layer (microscopic information), the failure mechanism of Si anode is vividly demonstrated. This work establishes a new methodology to quantitatively analyze the structural and compositional evolution of Si anode, which could be further applied for the studies of many other electrode materials with similar issues.