The development of new materials for efficient and durable systems used for energy storage and conversion is crucial for current and future energy technologies. Performance and lifetime of batteries strongly depend on the 3D morphology of advanced structured cathode materials and on morphology changes during operation. A profound understanding of degradation mechanisms that affect the performance and limit the lifetime of systems for energy storage and conversation is mandatory for the development of more stable and robust solutions. The potential of X-ray microscopy and nano-XCT studies of kinetic processes in 3D-structured systems has been demonstrated mainly at synchrotron radiation beamlines. In this talk, we are presenting customized solutions for laboratory nano-XCT tools with integrated operando cell, and we are demonstrating their applicability for the study of kinetic processes in materials that cause degradation of batteries [1].

In a battery degradation study, we demonstrate the capabilities of laboratory X-ray microscopy and nano X-ray computed tomography (nano-XCT) for the non-destructive imaging of the electrode material’s 3D morphology and defects, such as microcracks, at sub-micron resolution. We investigate the morphology of Na0.9Fe0.45Ti1.55O4 sodium iron titanate (NFTO) cathode material for Li- ion and Na- ion battery systems using laboratory-based in situ and operando X-ray microscopy.

During the operando study, microcrack growth is already visible in all spatial dimensions during the first charge/discharge cycle and leads to the separation of the large solid particles into smaller ones after 38 cycles. The rapid occurrence and development of microcracks during the very first cycles are supposed to be the reason for the previously observed capacity deterioration and decrease in the Fe2+/Fe3+ redox conversion ratio. Chemo-mechanical stress caused by the supposed electrochemical substitution of Na by Li ions might accelerate the processes of microcrack formation and propagation. The demonstrated approach allows tracking of the formation and propagation of microcracks in the active phase down to a single particle semi-quantitatively. The data obtained provide morphological insights on material performance and degradation, as well as the size and density-dependence of the fracture behaviour.

[1] V. Shapovalov, K. Kutukova, et al., Crystals, 2022, 12, 3.