Powder Technology, Vol.349, 1-11, 2019
Numerical simulation of the behavior of lithium-ion battery electrodes during the calendaring process via the discrete element method
Calendering is a key process step in the production chain of lithium ion battery electrodes since it strongly affects the microstructure and micromechanics of the electrodes and hence, the performance and life of the battery. A comprehensive understanding is therefore necessary to find optimal levels of calendering which can help to enhance conductive and mechanical properties. Within this context, this study proposes a novel discrete element method (DEM) approach which can capture the mechanical properties of single Li [Ni-1/3 Mn-1/3 Co-1/3]O-2 (NMC) particles with an appropriate elasto-plastic contact model, as well as the mechanical behavior of the additive binder matrix via an additional bond model . With the support of real produced cathodes, the simulations were able to reproduce the calendering process while providing detailed information about the changes in electrode structural and mechanical parameters. In particular, the investigated features comprise the electrode porosity and thickness along with the specific free surface area, the contact area between NMC particles and current collector, the coordination number of NMC particles, the number of broken bonds and the directionality of the contacts together with the generated stress within the electrode. Moreover, the simulations are able to capture the viscoelastic response of the electrode, showing that the relative elastic recovery can be almost up to 17%, an important piece of information that cannot be obtained experimentally to date. Having established the fundamentals and simulation feedback, an upcoming publication is meant to complete this research by providing a numerical overview of the relations between the electrode structure and its properties affected by the calendering process and during the first electrochemical cycles. (C) 2019 Elsevier B.V. All rights reserved.