(Invited) Exact and Approximate Methods for Analytical Modeling of Thermal and Electrochemical Transport in Li-Ion Batteries

Abstract

This talk will summarize ongoing research on analytical modeling of thermal and electrochemical transport in Li-ion cells. These transport processes govern the performance and safety of Li-ion cells, and therefore are important to understand and optimize for a variety of electrochemical energy conversion and storage applications, such as grid energy storage, electric vehicles, aerospace, etc. Analytical models for steady-state and transient thermal behavior of a single cell will be presented. These models utilize well-known analytical techniques for solving the partial differential equations arising from the principle of conservation of energy. An iterative analytical model for thermal performance during cyclic operation will be presented. This model solves for the temperature distribution in a stepwise fashion, utilizing the temperature distribution at the end of each cyclic process as the initial condition for the next cyclic process. Approximate models for thermal runaway behavior will be introduced, highlighting the key role of thermal properties of the cell towards preventing thermal runaway. Important considerations related to the linearization of non-linear heat generation terms during thermal runaway will be discussed. Finally, modeling of phase change thermal management of Li-ion cells by integrating perturbation method based techniques with an iterative technique to solve coupled heat transfer problems will be discussed. These analytical methods help better understand the fundamental transport processes in a Li-ion cell, and are also often useful for correct experimental design and data analysis.