Numerical Simulation of a Li-Ion Cell Using a Thermoelectrochemical Model Including Degradation

A thermoelectrochemical model for the simulation of Li-ion cells is presented and numerically solved herein. The model, based on Newman’s (Newman and Thomas-Alyea, Electrochemical Systems, Wiley, New York, 2004) concentrated solution theory, covers electrochemical, thermal and aging effects. The degradation mechanism considered is the growth, due to a solvent decomposition reaction, of the Solid Electrolyte Interface layer (SEI) in the graphite electrode. Model homogenization is phenomenological but detailed particle-scale models are considered for the diffusion of species within active particles and SEI. The one dimensional thermal model incorporates reversible, irreversible, and ohmic heat generation, as well as the temperature dependence of the various transport, kinetic and mass transfer parameters. The governing equations are semi-discretized in space using finite elements (with FEniCS software package (Alnaes et al., Arch Numer Softw 3(100), 2015)) and integrated in time with implicit Euler method. For each time step, this leads to a set of nonlinear equations that is solved fully coupled through Newton’s iterations. This implementation is used to numerically simulate several charge-discharge cycles of a cell at 1C regime with an execution time around 50 times faster than real-time in a standard PC.