12 Oct 2020
Direct observation of Li-ion battery degradation paves the road to a more reliable future
León Romano Brandt and colleagues in Prof Alexander Korsunsky’s team at MBLEM lab in Oxford Engineering Science use Diamond synchrotron light to reveal how batteries degrade during charging.
Electric vehicles, grid storage and other power systems rely progressively on energy storage using lithium ion batteries. Increasing demand requires more reliable battery systems that maintain capacity for longer, but the problem turns out to be rooted in complex interactions that involve chemistry, crystallography, and mechanics.
León Romano Brandt, DPhil student in Professor Alexander Korsunsky’s team (Multi-Beam Laboratory for Engineering Microscopy, MBLEM) spearheaded a new study into how battery cathodes evolve during charging that was published in RSC’s Energy and Environmental Science.
DPhil student and lead author León Romano Brandt (left) and Professor Alexander Korsunsky (right)
Prof. Korsunsky clarifies, “The principal impact of our results are unprecedented direct insights into the degradation processes in Li-ion battery cathodes that pose a key limitation to their wider use. Whilst new cathode materials are being developed to increase power and energy density, chemo-mechanical coupling phenomena convert a proportion of stored energy into stresses and strains that eventually get released by cracking, leading to the loss of connectivity and capacity fading.“
León Romano Brandt explains: “The principal challenge in understanding and quantifying these processes is their transient nature: they need to be observed as they unfold, i.e. operando. Furthermore, comparing nominally similar samples is not enough, as they are never identical at the micro- to nano-scale level of our interrogation.”
“Therefore, we had to develop a whole raft of approaches to enable the study of single electrode particles as they are being charged in situ. We used two different synchrotron beamlines at Diamond, B16 Test Beamline for microbeam diffraction (and stress evaluation) and I13 for ptychographic tomography nanoscale imaging of cracking.”
Research was carried out in collaboration with Oxford’s Department of Materials and Department of Chemistry, as well as the Polytechnic Department of Engineering and Architecture (DPIA), University of Udine, The Henry Royce Institute and The Faraday Institution. Korsunsky adds, “We made extensive use of the Multi-Beam Laboratory for Engineering Microscopy (MBLEM) that provided crucial support for sample preparation and offline characterisation. “
“These results pave the way to designing better, more reliable, longer lasting batteries for future applications in grid energy storage, automotive industry, and more.”
Key funding for this research came from EPSRC awards and Diamond joint studentships.