Just a few more years and electric cars might bridge what is now the main competitive gap separating them from internal combustion vehicles: the length of time needed for charging them. The announcement was made by Antonio Bertei and Marco Lagnoni, respectively associate professor and researcher in Chemical Engineering at the Department of Civil and Industrial Engineering at the University of Pisa, who, together with colleagues from eight other prestigious international institutions, authored a study recently published in Nature Communications.
“Fast charge capability, driving range and safety of lithium-ion batteries are the main concerns that influence the broader market uptake of electric vehicles, but thanks to the results of our study, these limits might be overcome within the next few years,” explains Professor Antonio Bertei. “Our investigations allowed us to quantify the mechanisms that aggravate battery ageing during fast charging of lithium-ion batteries that use graphite electrodes.”
The graphite electrode during charging, as seen under the optical microscope. In the image, graphite particles are visible, while the various colors, ranging from golden to red, indicate different phases of graphite. The red arrows point to lithium plating, a degradation phenomenon whose dynamics were analyzed in the study.
Specifically, the research group – of which Bertei and Lagnoni are the only Italian partners – has shown that the fast-charging process, as it is conceived today, can cause metallic lithium deposition on the surface of the graphite anode (the negative electrode). This phenomenon, if not properly considered, can lead to irreversible loss of lithium, limiting energy performance and impairing battery safety. But, most importantly, the researchers confirmed that this ‘lithium plating’ phenomenon is partly reversible and they were able to precisely outline the dynamics of its reabsorption and how to integrate it into the battery’s overall operation. This result was obtained thanks to the contribution of the University of Pisa, where advanced physical-mathematical models were developed to support and complement cutting-edge experimental analyses.
Marco Lagnoni and Antonio Bertei
“The computational model we developed for this study allowed us to observe ‘lithium plating’ in graphite anodes and to show that it can be reabsorbed by the electrode, thus slowing down battery ageing,” adds Marco Lagnoni. “You just need to have rest periods at different states of charging. We even coined the motto ‘resting for being faster’ to describe the approach that will need to inform the future development of advanced fast-charging protocols designed for next-generation automotive batteries.”
The result achieved by the study published in Nature Communications under the title Multiscale dynamics of charging and plating in graphite electrodes coupling operando microscopy and phase-field modelling is set to mark the future of electric mobility. In addition to the University of Pisa, eight other prestigious international organisations were involved: University College London (UK), Queen Mary University (UK), Massachusetts Institute of Technology (USA), University of Oxford (UK), Harwell Science and Innovation Campus (UK), University of Birmingham (UK), National Renewable Energy Laboratory in Denver (USA) and Beijing University of Technology (CN).