Validation of a Thermal-Electric Li-Ion Battery Model

Journal of Power Sources

2016

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

mentioning

confidence: 99%

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

Journal of Power Sources

2016

“…The value of Note that the stiffness coefficients and the coefficient of the 1 st order viscoelastic relaxation in Eqs. (9)) and (10)) depend on the SOC. Hence, we use Eqs.…”

Section: S T K K S T K S T K K S T K S Tmentioning

confidence: 99%

“…Thus, there have been considerable efforts to develop battery models to depict the dynamics of Li-ion batteries. These include electrical equivalent circuit models [5,6], electro-chemical models [7], and the heat transfer models [8][9][10][11]. Moreover, the exploitation of various control methods and strategies for battery management system (BMS) is increasing [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Phenomenological force and swelling models for rechargeable lithium-ion battery cells

Journal of Power Sources

Siegel

et al. 2016

Three phenomenological force and swelling models are developed to predict mechanical phenomena caused by Li-ion intercalation: a 1-D force model, a 1 st order relaxation model, and a 3-D swelling model. The 1-D force model can estimate the Li-ion intercalation induced force for actual pack conditions with preloads. The model incorporates a nonlinear elastic stiffness to capture the mechanical consequences of Li-ion intercalation swelling. The model also separates the entire state of charge range into three regions considering phase transitions. The 1 st order relaxation model predicts dynamic swelling during relaxation periods. A coefficient of relaxation is estimated from dynamic and quasi-static swelling at operational conditions. The 3-D swelling model predicts the swelling shape on the battery surface for all states of charge. This model introduces an equivalent modulus of elasticity, which is dependent on the state of charge, to

“…Numerical simulations based on computational fluid dynamics and finite element methods have been conducted to predict the thermodynamics of LIB cells and packs [67][68][69][70][71]. A variety of heat transfer models have been created and validated through experiments [72][73][74][75]. Moreover, lumped parameter thermal models with novel thermal management schemes have been proposed for next-generation battery management systems [76][77][78][79][80][81].…”

Section: Introductionmentioning

confidence: 99%

Characterization and modeling of the thermal mechanics of lithium-ion battery cells

2016

Applied Energy

h i g h l i g h t sThermal swelling shape is different than Li-ion intercalation swelling shape. Nonuniform temperature and gap creation leads to a convex shape at free conditions. Important parameters of thermal mechanics are estimated through experiments. A coupled thermal-structural analysis accurately predicts thermal swelling shape. Nonuniform temperature still plays a critical role at pack conditions. Keywords:Lithium-ion battery Battery swelling shape Thermal expansion The coefficient of thermal expansion The coupled thermal-structural analysis a b s t r a c tThe thermal mechanics of Lithium-ion (Li-ion) batteries is explored with a focus on thermal swelling. Experiments show for the first time that the swelling shape of prismatic battery cells due to temperature variations is significantly different from that due to Li-ion intercalation in unconstrained conditions. In contrast to uniform and orthotropic Li-ion intercalation swelling in a direction perpendicular to electrodes, the nonuniform temperature distribution in the jellyroll and the gaps/voids between electrodes result in distinguishable different swelling shapes. A unique coupled thermal-structural analysis with a simple, but efficient 3-D finite numerical model is proposed to investigate the impact of temperature variations on the thermal behaviors of battery cells. Anisotropic heat conduction and temperature dependency of the coefficient of thermal expansion are taken into account and found to have an impact on temperature distribution and thermal expansion. Experimental validation of the proposed model clearly demonstrates that the coupled thermal-structural analysis with the proposed model can predict accurately the thermal swelling at unconstrained conditions. The solution at pack (constrained) conditions shows that the nonuniform temperature distribution of the jellyroll still plays a critical role for the thermal swelling shape, although the gaps/voids do not occur because of the constraints from spacers in the pack, suggesting that the estimation of core temperature is important. Such an accurate model, able to estimate cell thermal behavior, is beneficial to the design of Li-ion batteries, development of stress or strain sensors, optimum sensor placement, and thermal management of not only single battery cells but also battery packs.