Broad ion beam cross-sectioning, microscopy, and image analysis of battery electrode morphology

Abstract: Lithium-ion batteries (LiB) are witnessing an increasing demand for electric vehicles. It provides a sustainable energy storage solution that is more efficient and ecofriendly than the fossil fuels. However, LiB are prone to ageing, which changes the dynamics of the electrochemical reactions over time and usage, and consequently affects its life and performance.. Ageing can manifest through multiple mechanisms that are also intertwined. Therefore, the understanding of these mechanisms is vital to designing more efficient and longer lasting batteries. Physical characterization of the electrodes and other battery materials provides insights into the ageing mechanism, it helps visualize the effects or causes of the mechanism and can provide an aid to the electrochemical measurements. This project develops the technique of BIB-SEM and image analysis to study the electrode morphology and quantify the ageing mechanisms. Results from the method development show that there is an increase in the electrode dimensions with a ageing, there is also increase in particle cracking that is location based. The extent of particle cracking is higher, closer to the separator and gradually reduces closer to the current collector. This is also followed by an expected increase in porosity and reduction in tortuosity. The Li plating was also observed between the separator and graphite, the region consisted of filiform dendrites which extended into the separator. However, better imaging needs to be used to study the separator and the Li inclusions. The results also need to be compared against electrochemical measurements to correlate with the physical quantification