Investigating the role of crystallographic orientation of single crystalline silicon on their electrochemical lithiation behavior: Surface chemistry of Si determines the bulk lithiation

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The role of substrate orientation on the electrochemical lithiation of single crystalline Si has been investigated using Si single crystal having two orientations. It has been demonstrated that the lithiation process in Si (100) occurs via amorphization while that in Si (111) occurs through the intermediacy of various Li-Si alloying phases ranging from LixSi to Li15Si4. Three phase lithiation process has been observed in Si (111). Post electrochemical cycling analysis by ex-situ XRD, XPS and AFM studies reveals that the lithiation in two differently oriented Si facets {i.e. Si (100) and Si (111)} indeed occurs differently. The model developed on the basis of insights gained from the AFM studies also supports the hypothesis built on the basis of initial CV measurements.