Tracking Li-ion Diffusion Changes in Electrochemically Aged Ni-rich Li-ion Battery Cathodes

Ni-rich Li-ion battery cathodes like LiNi0.8Mn0.1Co0.1O2 (NMC811) are the most industry-ready candidates for next-generation high-energy-density batteries. The biggest roadblock preventing their commercialisation is their electrochemical performance degradation over long-term (>100s of cycles) cycling. Thus, it is important to study the material properties of such electrochemically aged cathodes if we are to devise strategies to mitigate their performance fade. A key material property, which is hard to probe via conventional methods, is the Li-ion diffusion coefficient. In this study, we want to use positive muon spin relaxation experiments to track how the Li-ion diffusion properties change in aged NMC811 cathodes. To ensure that most representative results are obtained, measurements will be made directly on industry-like single-layer pouch cells without any modifications, which, to the best of our knowledge, will be a first of its kind experiment. Two sets of experiments will be performed in this study. Firstly, two cells—fresh and after 100 cycles—will be studied in their open-circuit-voltage, charged and discharged states. Secondly, on the discharged cells, we will perform variable temperature experiments on the discharged cells. An Xpress access proposal has already been submitted to optimise the signal and experimental setup for the pouch cells.