Ex-situ depth-sensing indentation measurements of electrochemically produced Si–Li alloy films

We report for the first time ex-situ measurements of the Young's modulus and hardness of Si and Si–Li alloy thin film electrodes at various stages of lithium insertion via depth-sensing indentation experiments. Lithium is electrochemically inserted into the Si electrode, after which its mechanical properties are investigated in an anoxic environment. The Young's modulus was found to decrease from an initial value of 92 GPa for pure Si to 12 GPa at full lithium insertion (Li15Si4). The hardness changes from an initial value of 5 GPa for Si to 1.5 GPa for Li15Si4.

► Mechanical properties of silicon thin films with differing concentrations of inserted lithium were determined.
► Lithium was inserted electrochemically at room temperature.
► Nanoindentation was used to determine elastic modulus and hardness.