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

An operando bimodal atomic force microscopy system was constructed to perform nanomechanical mapping of an amorphous Si thin film electrode deposited on a Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 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 x in lithium silicide (Li x Si) simultaneously with real-time surface topography observation. At the initial stage of lithiation, the average modulus steeply decreased due to the generation of Li x Si from intrinsic Si, followed by a moderate modulus reduction until the electrode capacity reached 3300 mAh g -1 (Li content x = 3.46). In the following delithiation, the gradual recovery of the average modulus of Li x Si was observed up to 1467 mAh g -1 (Li content x = 1.54) at which delithiation stopped due to the significant volume change induced by phase transformation of Li x Si.