Simulation of Macro Scale Mechanical Behavior of Pouch Cell Lithium-Ion Batteries

Electrochemical energy storage devices suffer from capacity fade due to mechanical, thermal and electrochemical interaction. This study focuses on mechanical phenomena in lithium ion pouch cell batteries. A finite element model is developed to predict swelling/shrinking in cathode/anodes due to thermal expansion and lithium intercalation, as well as in-plane and out-of-plane deformation. Transport of lithium, transport of heat and generation of heat are obtained through measurement or numerical simulations.

Pouch cell batteries are composed of a large number of individual thin layers which are stacked together. To correctly capture the plate-like behavior of individual layers while limiting the in-plane discretization, a computational mesh with large aspect ratio elements is needed. As such elements may suffer from spurious stiffening effects a high performance finite element formulation is developed. This small-strain, solid-shell finite element formulation accurately captures both the in-plane and out-of-plane behavior of individual layers.

Figure 1  below shows a cross section of the pouch cell mesh resolving indivdual layers and folder separator construction.