Joint non-invasive identification of an electrochemical and thermal model for an ultra high-power Li-ion pouch cell

Abstract

Accurate physical models of battery cells are required to design safe and reliable Battery Management Systems (BMSs). Due to the safety-critical nature of cell voltage and temperature, both the electrical and thermal behavior of the cell need to be precisely predicted. In this work, an electrochemical – the Single Particle Model (SPM) – and a lumped thermal model are experimentally identified and validated for an ultra high-power pouch cell. To ease its application, the proposed identification procedure is based exclusively on non-invasive tests, i.e., requiring only voltage, current, and temperature measurements. Specifically, the identification protocol is based on two steps: (1) the equilibrium potentials are identified from quasi-static tests; (2) the kinetics and thermal parameters are jointly optimized from a highly dynamic current profile. Due to the high power requirements, the considered pouch cell is always kept pressed by an external fixture, which is properly considered in the modeling and identification. The SPM is compared with a first-order Equivalent Circuit Model (ECM) and the validation is finally performed on two different dynamic tests, showing the good capability of the identified electrochemical and thermal model to match the measured outputs (voltage and temperature) while giving an insight on the internal cell states.