Modeling the dimension changes under external pressure of unit cell with a system level approach

Summary:

Dimensional changes in the electrodes can affect the electrochemical response of the battery and generates stresses which leads to its premature failure. Thus, understanding the volume expansion of Lithium-ion cell during cycling under external pressure is essential to improve cell design and predict aging phenomena. In this work, the volume change response of a unit cell has been investigated, based on previous studies, through an electrochemical pseudo-2D model coupled with a 1D mechanical model. A system level model has been implemented in Modelica language. The electrochemical domain has been experimentally validated using a unit cell with NCM 811/ graphite chemistry.
Physics related model parameters have been experimentally characterized including the influence of the external pressure up to 5 MPa. The simulation model considers the particle volume changes in the positive and the negative electrodes and scales it to the cell level, the unit cell expansion has been numerically calculated and qualitatively verified with published work. The validation of the volume change is planned for complete cell configuration under external pressures in upcoming work.