A novel thermal swelling model for a rechargeable lithium-ion battery cell

Abstract

The thermal swelling of rechargeable lithium-ion battery cells is investigated as a function of the charge state and the charge/discharge rate. The thermal swelling shows significant dependency on the state of charge and the charge rate. The thermal swelling follows a quadratic form at low temperatures, and shows linear characteristics with respect to temperature at high temperatures in free-swelling conditions. Moreover, the equivalent coefficient of thermal expansion is much larger than that of each electrode and host materials, suggesting that the separator and the complex shape of the cell play a critical role in thermal expansion. Based on the experimental characterization, a novel thermal swelling model is proposed. The model introduces an equivalent coefficient of thermal expansion for the cell and also considers the temperature distribution throughout the battery by using heat transfer theory. The comparison between the proposed model and experiments demonstrates that the model accurately predicts thermal swelling at a variety of charge/discharge rates during operation and relaxation periods. The © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ model is relatively simple yet very accurate. Hence, it can be useful for battery management applied to prolong the cycle life of cells and packs. Keywords Lithium-ion battery; phase transition; swelling; thermal expansion; the coefficient of thermal expansion 1. Introduction Concerns for energy security, instability in world oil markets, and limitations of carbon emissions have accelerated the development of eco-friendly, high-efficiency automobiles. This drives automobile industries toward the development of vehicle electrification technology.Electrified vehicles currently use lithium-ion (Li-ion) batteries as the reversible power source.Li-ion batteries have advantages such as high power/energy density, high potential, and low selfdischarge rate. They are also environmentally friendly and have a long life cycle [1][2][3].While vehicle electrification with the advent of the Li-ion batteries [4] enhances fuel efficiency and reduces CO 2 emissions, many challenges still exist when using Li-ion batteries such as their limited performance at low temperatures [5] and their thermal runaway [6]. Especially, extensive research on vehicle electrification has been driven by stringent safety standards for air and ground applications. Therefore, recent research focuses on the thermal distribution and the heat dissipation of Li-ion battery packs [7,8] as elevated temperatures not only can cause thermal runaway but can also degrade battery life. A variety of heat transfer models have been created

Battery Capacity Fading Estimation Using a Force-Based Incremental Capacity Analysis

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“…Contacts are nonlinear phenomena that affect the stiffness of the system, making it dependent on the contact status (areas of closed contact or gap). Therefore, these complex contacts create complex mechanical constraints which affect the overall swelling shape of battery cells [91].…”

“…1, see also [91]) ranging from 25°C to 45°C was used to calibrate the equivalent coefficient of thermal expansion of the jellyroll for the through-plane direction (a thro ) in the model. Uniform temperature elevation, which was the same conditions for experiments, was imposed in the static structural analysis to the jellyroll and case from 25°C to 45°C with 5°C increments.…”

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