Electrochemical-mechanical multi-scale model and validation with thickness change measurements in prismatic lithium-ion batteries

A multi-scale model able to evaluate volume changes from atomic level of active material up to battery level of prismatic lithium iron phosphate-graphite batteries is presented in this work. The model goes through the scales according to the following steps: changes of lattice parameters as a function of lithium intercalation and consequent lattice volume deformation; active material particles deformation; electrode volume changes and porosity reduction; evaluation of the effects of the hard case on the overall battery thickness change through finite element modelling. From the experimental side, the thickness change of prismatic LFP-graphite batteries is measured during operation at different current rates with high-precision optical sensors and the statistical analysis of the results is carried out. Scanning electron microscope analyses are carried out on electrode samples for measuring model parameters and to give a visual proof of the existence of different scales in lithium ion batteries. Finally, the results of the multi-scale model are validated with the experiments.