M. Tyrrell, F.A. Mier
New Mexico Institute of Mining and Technology,
United States
Keywords: lithium-ion batteries, energy storage, modeling and simulation
Summary:
An alternative method of modeling and simulating lithium-ion batteries (LIBs) has been developed using a simplified equivalent power model which focuses on battery thermal behavior. The modeling and simulation of LIB thermal performance is an essential aspect towards designing grid energy storage systems. Existing battery models like the Newman, Tiedman, Gu, and Kim model, the Equivalent Circuit Model, and the Psuedo-2D model require multi-physics simulations which are fundamentally founded upon electrochemical processes. Electrochemical parameter identification and selection are required to build the full battery model. These battery parameters are nontrivial to obtain and often assume idealized properties which may not account for the lifetime fatigue of repeated battery loading. An alternative method of modeling and simulating LIBs is proposed which simplifies the multi-physics challenge to a purely electrical and thermal problem. The Equivalent Energy Method is a proposed semi-empirical LIB model which applies heat generation directly drawn from the electrical power output of the LIB. The spatial distribution of the heat generation applied to the battery is determined from the aspect ratio of the cell along with the anode and cathode tab locations. As a result, this LIB model relies on geometric parameters of the battery cell and simplified analytical evaluations prior to numerical simulation to reduce the required computation load. To account for the chemical processes which produces both power and heat, a thermal efficiency coefficient is used. This efficiency coefficient provides an avenue to study non-idealized thermal behavior due to cyclical thermal loading during charging and discharging. The model formulation achieves transient thermal profiles which are in congruence with established electrochemical models and existing experimental results. The Equivalent Energy Model produces a scalable model which can contribute to the modeling of larger battery arrays and allows for parameters changes including tab location and cell aspect ratios for further battery design optimization.