Efficient electrochemical model for lithium-ion cells

TL;DR

This paper introduces a simplified, computationally efficient electrochemical model for lithium-ion batteries that accurately captures key dynamics, suitable for real-time applications, especially with variable diffusivity in lithium iron phosphate cells.

Contribution

A novel low-order electrochemical model that simplifies complex PDEs with variable diffusivity, maintaining accuracy and enabling real-time simulation.

Findings

Model shows good agreement with experimental data

Simulations are computationally efficient

Model is well-posed and can be approximated by low-order models

Abstract

Lithium-ion batteries are used to store energy in electric vehicles. Physical models based on electro-chemistry accurately predict the cell dynamics, in particular the state of charge. However, these models are nonlinear partial differential equations coupled to algebraic equations, and they are computationally intensive. Furthermore, a variable solid-state diffusivity model is recommended for cells with a lithium ion phosphate positive electrode to provide more accuracy. This variable structure adds more complexities to the model. However, a low-order model is required to represent the lithium-ion cells' dynamics for real-time applications. In this paper, a simplification of the electrochemical equations with variable solid-state diffusivity that preserves the key cells' dynamics is derived. The simplified model is transformed into a numerically efficient fully dynamical form. It is proved that the simplified model is well-posed and can be approximated by a low-order finite-dimensional model. Simulations are very quick and show good agreement with experimental data.