Nanomechanical Mapping of Amorphous Silicon Thin Film Electrodes in All-Solid-State Lithium-Ion Battery Configuration during Electrochemical Lithiation and Delithiation.

An bimodal atomic force microscopy system was constructed to perform nanomechanical mapping of an amorphous Si thin film electrode deposited on a LiLaZrTaO solid electrolyte sheet during electrochemical lithiation/delithiation. The evolution of Young's modulus maps of the Si electrode was successfully tracked as a function of apparent Li content in lithium silicide (LiSi) simultaneously with real-time surface topography observation. At the initial stage of lithiation, the average modulus steeply decreased due to the generation of LiSi from intrinsic Si, followed by a moderate modulus reduction until the electrode capacity reached 3300 mAh g (Li content = 3.46). In the following delithiation, the gradual recovery of the average modulus of LiSi was observed up to 1467 mAh g (Li content = 1.54) at which delithiation stopped due to the significant volume change induced by phase transformation of LiSi.