Electrochemical and Thermal Analysis of Lithium-Ion Batteries Based on Variable Solid-State Diffusion Coefficient Concept

Abstract

Accurate battery models are of great significance for the optimization design and management of lithium-ion batteries. This study uses a pseudo-two-dimensional electrochemical model combined with a three-dimensional thermal model to describe the electrodynamics and thermodynamics of commercial LIBs and adopts the concept of variable solid-state diffusion in the electrochemical model to improve the fitting ability of the model. Compared with the discharge curve without the VSSD concept, the progressiveness of the model is verified. On the other hand, by comparing the temperature distribution of batteries with different negative electrode thicknesses, it is found that the battery temperature decreases with the increase in battery thickness. At the same time, with the increase in active material volume fraction, the gradient of electrochemical performance is greater, and the heat generation rate is higher. This model can be used for online management of batteries, such as estimating charging status and internal temperature, and further constructing a lithium battery electrochemical capacity degradation model based on the VSSD concept to study the aging behavior of lithium batteries.

Keywords

• lithium-ion battery
• electrochemical model
• thermal model
• VSSD
• sine approximation