The Chemistry Department’s Dr Zhenjiang Yu has collaborated with academics in Beijing and Berlin to produce a review of the current methods of imaging all-solid-state batteries, with the aim to help shed light on how these batteries work and how we can improve them.

All-solid-state batteries (or ASSBs) are the next generation of battery technology. Unlike their more common lithium-ion counterparts, SSBs use solid-state electrolytes instead of highly flammable liquid electrolytes to store energy. This substitution makes them significantly safer than liquid-based batteries, which can be prone to leaking and subsequently catching fire or even exploding. ASSBs also have the potential to hold a greater level of charge than conventional lithium-ion equivalents, meaning that they would be well-positioned to replace lithium-ion batteries where frequent recharging is an issue – such as in electric vehicles.

That said, today’s ASSBs are not without their issues. Structural flaws within the batteries’ materials – such as cracks within the electrodes, loose contacts, and the growth of microscopic lithium structures known as “dendrites” – can cause problems with short circuiting and recharging, as well as lead to the overall capacity of the ASSB declining rapidly. However, studying and detecting these issues has long proved a problem due to the fact that disassembling a battery cell can in turn cause it further damage, making it difficult to identify the original issues.

Dr Yu of Lancaster University, alongside fellow academics based at the Chinese Academy of Sciences, Technische Universität Berlin, and Helmholtz-Zentrum Berlin, have therefore been working on a range of different approaches to imaging ASSBs, including the use of X-ray tomography, neutron imaging, and electron-based imaging such as focused ion beam scanning electron microscopy (FIB-SEM), and cryogenic electron microscopy (cryo-TEM). Imaging batteries in these ways is crucial to bolstering scientists’ understanding of the complex electro-chemo-mechanical interactions that take place within them without compromising the batteries’ structural integrity.

The culmination of their work is recorded in the review paper: Visualizing the Future: Recent Progress and Challenges on Advanced Imaging Characterization for All-Solid-State Batteries, which was recently published in ASC Energy Letters. It catalogues the research outcomes of both their own and their contemporaries’ numerous experiments into the imaging of ASSBs in order to suggest future directions for further research.

The paper examines the relative benefits of using each different type of imaging, and how they can be utilised to shed light on the inner workings and processes of ASSBs. X-ray imaging, for example, can provide excellent insight into the mechanical components of batteries, producing high resolution 3D images of their internal structures and revealing any changes or potential causes of failure, such as the appearance of cracks or the formation of dendrites. Neutron imaging, meanwhile, is highly sensitive to certain light elements such as hydrogen and lithium. This makes it extremely valuable for examining any problems with the distribution or structure of the lithium ions within ASSBs, which is the root cause of many of the recharging and lifespan issues they face. On the other hand, electron-based imaging excels at capturing the nanoscale, so has applications in examining the atomic-level microstructures of ASSBs.

The team also outline the limitations of the various imaging approaches. Neutron and X-ray imaging both have relatively low image resolutions, restricting the level of detail they are able to produce, with the former also having the potential to inflict radiation damage onto the ASSBs as well. Electron-based methods also have their issues, with their high costs for sample preparation and the potential for damage to be inflicted to the sample whilst conducting the imaging. Despite these drawbacks, the authors maintain the need to use a combination of imaging techniques in order to promote a holistic understanding of ASSBs.

On the publication of the article, Dr Yu commented: “Advanced imaging techniques, such as neutron imaging, X-ray tomography, FIB-SEM, and cryo-TEM, offer ways to uncover these failure mechanisms. This comprehensive review underscores the transformative potential of imaging technologies in diagnosing and optimizing the performance of ASSBs, paving the way for safer and more efficient energy storage solutions. It also emphasizes the need for multidisciplinary approaches to integrate imaging with electrochemistry and materials science.”