E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

where researchers can compare battery electrode samples that have or have not artificially generated conductive carbon in the binder material. Researchers can use this databank to access realistic architectures for modelling or analysis. High-energy X-rays from large synchrotrons are used to quantify gradients in lithiation and degradation throughout the depth of electrodes during fast charging and within individual electrode particles while they degrade. This can be used to understand the failure mechanisms of lithium-ion batteries in a range of mechanical and thermal abuse scenarios. This has led to an open-source battery failure databank containing hundreds of high-speed radiography videos of catastrophic battery failure alongside their thermal responses. The databank gives researchers and engineers an insight into designing safer battery systems. MRI for sodium cells Magnetic resonance imaging (MRI) can be effective in developing rechargeable sodium-ion batteries. A key challenge in the development of these batteries is understanding how the sodium behaves inside the battery as it goes through its charge-discharge cycle, enabling the points of failure and degradation mechanisms to be identified. In medical imaging, MRI scanning uses the body’s natural sodium content to provide a more detailed picture of tissue health and disease. The same technique is used to monitor how the sodium performs in different anode and cathode materials. It can also monitor the growth of dendrites that grow inside the battery over time and cause it to fail or even catch fire. MRI gives information about the changes in a sodium-ion battery’s components during its operation, something that is currently not available using other techniques. It will enable the identification of methods for detecting failure mechanisms as they happen, giving insights into how to manufacture longer-life and higher performing batteries. A major challenge for the characterisation of sodium batteries is that certain states of sodium within the electrodes are metastable, and the materials in the cell can be highly sensitive to changes in environmental conditions when a battery is dismantled for analysis. Another technique, nuclear magnetic resonance spectroscopy (NMR), which is similar to MRI, has previously been used to quantify the deposition of microstructural sodium on metallic anodes and determine the chemical environment in hard-carbon anodes. This provides peaks of data that are attributed to the sodium adsorbed at defect sites in the carbon, which subsequently pools between graphene layers. However, NMR is extremely sensitive to trace air/moisture, and the peak associated with sodium in the carbon has been found to disappear over a few hours. So while MRI has lower spatial resolution than X-ray or electron microscopes, it can probe both electrode and electrolyte environments, providing a more holistic view than NMR with visualisation of the 3D microstructure of the metallic electrodes in the cell. Lithiummetal cell analysis Lithium metal is an ideal anode material thanks to its extremely high theoretical specific capacity (3860 mAh/g), low density (0.59 g/cm3 ) and the lowest negative electrochemical potential (-3.05 V versus standard hydrogen electrode). However, the use of lithium-metal batteries (LMBs) is still limited owing to dendrite growth in the cell during cycling. This growth is responsible for early cell failure and even short-circuits and fires. But specific detection techniques can be applied to verify the internal condition of new LMB chemistries through cycling tests and examine the dendrite growth. Six non-invasive techniques have been investigated to anticipate LMB failures and to lay the basis for innovative self-healing mechanisms. The methodology governing these Focus | Battery testing MRI image of a sodium battery cell (Courtesy of University of Nottingham) 36 January/February 2023 | E-Mobility Engineering