Heat Generation in Lithium Iron Phosphate/Graphite Batteries: Simulation with Validation through Isothermal and Adiabatic Calorimetric Measurements

Abstract

This work evaluates the heat generation characteristics of a cylindrical lithium iron phosphate/graphite battery. Two experimental approaches are used: Heat flow measurements in an isothermal calorimeter and temperature measurement-based heat generation rate measurements in a quasi-adiabatic Accelerating Rate Calorimeter (ARC).The experimental results are compared to simulation results of an equivalent circuit model featuring a single resistance, voltage hysteresis representation, and reversible heat generation through entropy representation. The thermal model parameters are adapted to the respective experimental setups.Results visualize the specific use-cases of the experimental approaches. Isothermal calorimeter measurements enable a strict control of temperature for the battery, however, smooth the higher dynamics of the battery heat transfer due to the thermal mass of the setup. The high rate of heat transfer to ambient enables an evaluation of specific operating temperatures as well as long-duration tests, e.g., full cycles or dynamic current profiles.Instead, quasi-adiabatic measurements vary strongly in temperature during the operation but provide highly-dynamic information about heat generation rates. The rapid rise in temperature approaches safety limits and thus only low current, charge or discharge tests are possible, with a following rest period required.Simulation results are discussed with a focus on the heat generation rate and the heat transfer to ambient rate. While in general good agreements between simulation and experiment is achieved, specific differences reveal improvement potential for the model as well as for its parametrization. References M. Keyser, A. Pesaran, Q. Li, S. Santhanagopalan, K. Smith, E. Wood, S. Ahmed, I. Bloom, E. Dufek and M. Shirk, Journal of Power Sources, 367, 228 (2017).A. Pesaran, M. Keyser, G. Kim, S. Santhanagopalan and K. Smith, Tools for designing thermal management of batteries in electric drive vehicles (presentation), in, National Renewable Energy Lab.(NREL), Golden, CO (United States) (2013).M. Schimpe, M. Naumann, N. Truong, H. C. Hesse, S. Santhanagopalan, A. Saxon and A. Jossen, Applied Energy, 210, 211 (2018).A. R. Saxon, Battery Extreme Fast Charge: A Thermal Prospective, in, National Renewable Energy Lab.(NREL), Golden, CO (United States) (2019).J. Geder, R. Arunachala, S. Jairam and A. Jossen, in 2015 IEEE Green Energy and Systems Conference (IGESC), p. 24 (2015).