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Zusammenfassung:
In situ nanoindentation is used to measure the modulus and hardness of amorphous LixSi during its formation by electrochemical lithiation of (111) silicon surfaces. Due to the large volume changes experienced during lithiation, accurate knowledge of an electrode's mechanical properties is essential for predicting reliability and developing design guidelines for battery electrodes. We observe a clear decrease in modulus and hardness during lithiation. By accounting for the growing thickness of the amorphous layer, we obtain reliable in operando values for the modulus (45 GPa) and hardness (1 GPa) of the amorphous LixSi, which are in reasonable agreement with literature values obtained under less well-defined electrochemical conditions. Furthermore, a small increase in modulus just prior to amorphization and the formation of amorphous islands at the early stages lend credence to the idea of the formation of precursor defects in the crystalline silicon prior to amorphization.
