A General Energy Balance for Battery Systems

TLDR

Accurate prediction of battery cell temperature and heat generation, driven by electrochemical reactions, phase changes, mixing, and joule heating, is essential for design and thermal management. The authors present a comprehensive energy balance equation that integrates these effects, discuss simplifications, and demonstrate its application to specific systems. The developed energy balance accurately estimates cell thermal characteristics, and its use in models of cells discharged via two reaction mechanisms highlights the complexity of heat generation and the advantage of a general equation.

Abstract

A general energy balance for battery systems has been developed. This equation is useful for estimating cell thermal characteristics. Reliable predictions of cell temperature and heat‐generation rate are required for the design and thermal management of battery systems. The temperature of a cell changes as a result of electrochemical reactions, phase changes, mixing effects, and joule heating. The equation developed incorporates these effects in a complete and general manner. Simplifications and special cases are discussed. The results of applying the energy balance to a mathematical model of the cell discharged through two different reaction mechanisms are given as examples. The examples illustrate how the energy equation may be applied to a specific system to examine the relative contributions corresponding to the terms in the equation. The examples show that the processes involved in cell heat generation may be complex and that the application of a sufficiently general energy equation is advantageous.