Motion-enhancement assisted digital image correlation of lithium-ion batteries during lithiation
By Jnawali, Anmol; Radhakrishnan, Anand N. P.; Kok, Matt D. R.; Iacoviello, Francesco; Brett, Daniel J. L.; Shearing, Paul R.
Published in Journal of Power Sources
2022
Abstract
For the first time, a motion enhancement and registration technique (MERt) – an advanced phase based motion enhancement method combined with an optical flow based digital image correlation process is used to investigate batteries. This, in combination with the non-invasive investigative nature of X-ray computed tomography, makes for a powerful tool to examine the mechanism behind (de)lithiation of Li-ion cells. Through MERt, which magnifies the displacement of electrodes and tracks any internal changes, it is generally observed that the electrode expands outwards, but once encountering the solid barrier that is the cell casing, the electrode has nowhere to expand but inwards, which is why the electrode deformations initiate at the cell core. The technique clearly affirms that the greatest movement of electrodes during lithiation occurs at pre-existing inflection points in the jelly roll, which are a result of the manufacturing process, and eventually leads to the large deformations observed in this and previous works. MERt also indicates a contortion of the cell casings during lithiation which may be caused by the uneven expansion of the electrodes, but requires further studies to confirm.