Operando X-Ray Imaging of Battery Electrodes

Licentiate thesis, 2024

Batteries are now part of our daily life as they enable easy usage of portable devices and are now essential for us to travel, communicate, work, read, or listen to music. The diversity of battery applications continuously increases and new demands of for instance capacity, charge time and sustainability have emerged. There is thus a need to either increase the understanding of existing technologies or develop new chemistries. At the core of a battery complex reactions are taking place at the electrodes, covering multiple length and time scales. This poses a great challenge to understand mechanisms and based on this develop new solutions. One way to tackle this challenge is to carry out operando experiments where properties or processes are investigated while the battery is being cycled.

This work focuses on operando analysis of three different battery systems, comprising both current lithium-ion batteries (LIBs) and next generation battery concepts, using X-ray imaging techniques. The key processes addressed are lithium plating, a classic degradation mechanism in LIBs batteries, the dissolution and reprecipitation of active material in lithium-sulfur batteries and the sodiation of hard carbon anodes for sodium- ion batteries. X-ray imaging allows to follow the processes in real time as well as image an extended volume of the electrode to correlate changes in morphology to the electrochemical processes taking place during cycling. From XTM experiments, we found that electrolyte composition affects the morphology of lithium plating at the graphite/separator interface and observed a change in the size distribution of sulfur particles after their redeposition at the end of the charge. Through S/WAXS tomography, we show that the sodiation of a hard carbon anode spatial inhomogeneities.