Modelling the electrical conductivity of Lithium-ion battery electrodes via a bonded-particle approach

• Modelling electrical conductivity of battery cathodes. • Consideration of contact and instrinsic resistances. • Experimental validation of results generated by resistor network model. • Developed model is applicable for any discrete particle structure. An electrode’s electrical conductivity greatly affects battery performance, justifying the need to fully understand the relation between particle microstructure and resulting electrical conductivity. This work proposes a model to assess the specific electrical conductivity of DEM electrode structures by analysing a network of conductive paths. NMC622- and NCA-based cathode structures, with a bond network representing the additive-binder matrix, are created and calendered numerically before being evaluated for electronic conductivity. The direct and bond contacts and, unprecedentedly, the internal particle resistances are taken into account to build a resistor network. The results obtained by this model are in great agreement with experimental electrical conductivities for NMC622- and NCA-based cathodes. Both the experimental cathodes and the developed conductivity model show an initial increase and later decrease of electrical conductivity as a function of calendering load, which is explained by a loss in particle bonds. Variations in the active material size distribution lead to the same changes in the electronic conductivity of experimental and simulated cathodes. This is attributed to the coordination number of the active material particles and the different types of particle contacts. To conclude, this model allows for a DEM simulation-independent, accurate evaluation of the electrical conductivity of any discrete particulate structure.