Modeling the steady state response of the solid phase diffusion process in Lithium-ion cells

Accurate battery models are crucial for the evaluation of Lithium-ion batteries states and performance. Physics based models can represent the battery’s non-linear behavior but may not take into account the whole battery’s phenomena given the high complexity of the equations. Despite their simplicity, traditional equivalent circuit models (ECM) may not represent non- linear behaviour especially in low state of charge (SoC) area. To take the best of the above modeling approaches, a physics-based ECM is presented. This model is built on separating solid and liquid diffusion effects in Li-ion cells whose diffusion is strongly non-linear with SoC. A detailed identification methodology of the solid diffusion’s steady-state response was proposed. Thanks to this model, diffusion parameters present less non-linearities and are easier to be identified, while reducing the dimensions of lookup tables and characterization tests time.