Measuring Mechanical Properties during the Electrochemical Lithiation of Silicon

Abstract

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.

Nanosilicon anodes for high performance rechargeable batteries

“…GPa after full lithiation [248]. (ii) The hardness of c-Si, a-Li3.5Si and c-Li3.75Si measured by in-situ indentation were 14.8, 1.0 and 0.8 GPa, respectively [249]. (iii) A charge-coupled device optical measurement system was developed to in-situ monitor the deformation and elastic modulus evolution, presenting a 90 % decrease in elastic modulus of Si composite after lithiation [250].…”

In situ and operando characterisation of Li metal – Solid electrolyte interfaces

“…[49] With intelligent cell design, it seems possible to probe mechanical responses at the lithiumsolid electrolyte interface in situ akin to the work done on the lithium-silicon system by Epler and coworkers. [50] There are significant opportunities to pursue this approach, allowing the mechanical properties of chemical reaction products at the interface to be measured, as dynamic changes in stress/strain during cycling are quantified for a more comprehensive understanding of the chemo-mechanical degradation of these interfaces.…”

Avoiding Fracture in a Conversion Battery Material through Reaction with Larger Ions

“…In addition to the effect of reaction front shape on fracture processes, the mechanical properties of the lithiated, sodiated, and potassiated materials may be different, which could also influence fracture characteristics. While the mechanical properties (e.g., yield strength, elastic modulus) of a number of different lithium alloy materials have been measured, 20,40,[47][48][49] the mechanical properties of conversion materials, as well as Na and K electrode materials, have been less studied.…”