Microstructural evolution induced by micro-cracking during fast lithiation of single-crystalline silicon

作者：Choi Yong Seok; Pharr Matt; Kang Chan Soon; Son Seoung Bum; Kim Seul Cham; Kim Kee Bum; Roh Hyunchul; Lee Se Hee; Oh Kyu Hwan; Vlassak Joost J^*

来源：Journal of Power Sources, 2014, 265: 160-165.

DOI：10.1016/j.jpowsour.2014.04.124

• Lithium-ion batteries
• Silicon
• Microstructure
• Non-uniform lithiation
• Micro-crack

We report observations of microstructural changes in {100} and {110} oriented silicon wafers during initial lithiation under relatively high current densities. Evolution of the microstructure during lithiation was found to depend on the crystallographic orientation of the silicon wafers. In {110} silicon wafers, the phase boundary between silicon and LixSi remained flat and parallel to the surface. In contrast, lithiation of the {100} oriented substrate resulted in a complex vein-like microstructure of LixSi in a crystalline silicon matrix. A simple calculation demonstrates that the formation of such structures is energetically unfavorable in the absence of defects due to the large hydrostatic stresses that develop. However, TEM observations revealed micro-cracks in the {100} silicon wafer, which can create fast diffusion paths for lithium and contribute to the formation of a complex vein-like LixSi network. This defect-induced microstructure can significantly affect the subsequent delithiation and following cycles, resulting in degradation of the electrode.

• 出版日期2014-11-1