Computer simulation of the influence of thermal conditions on the performance of conventional and unconventional lithium-ion battery geometries

doi:10.1016/j.energy.2018.02.026

Energy

Volume 149, 15 April 2018, Pages 262-278

https://doi.org/10.1016/j.energy.2018.02.026 Get rights and content

Highlights

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The influence of the thermal conditions in different battery geometries is analyzed.
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The geometries include conventional and unconventional geometries.
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The thermal conditions include isothermal, adiabatic and different temperatures.
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The best overall performance is obtained for interdigitated and gear geometries.
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The dissipated heat depends on the geometrical parameters.

Abstract

Thermal analysis is a fundamental issue for the proper evaluation of the performance of lithium ion batteries. Thus, this work reports on the theoretical simulation of the effect of different thermal conditions on the performance of batteries with conventional and non-conventional geometries.

The investigated geometries include conventional geometries (layer by layer), interdigitated, horseshoe, spiral, ring, antenna and gear that can be fabricated by printed technologies for flexible/wearable electronic device applications. The thermal conditions are isothermal, adiabatic and environmental conditions and the computational simulations are based on the electrochemical (Newman/Doyle/Fuller) model.

Generally, the best battery performance is obtained for interdigitated and gear geometries, regardless of thermal conditions. The dissipated ohmic heat is mainly influenced by the maximum distance that the ions move until their intercalation and the thickness of the separator. The present work allows the proper design of the batteries in order to optimize performance for specific applications.

Introduction

Electrical energy is increasingly being obtained through renewable sources, such as, solar, wind, waves, bioenergy and geothermal, leading to the need for efficient energy storage systems [1,2].

These energy storage systems are essential for portable electronic devices such as mobile phone and computers but also for transportation systems, i.e, hybrid electric vehicles (HEVs) [3] and pure electric vehicles (PEVs) [4], in which lithium-ion batteries are the most commonly used energy storage systems [5].

Lithium-ion batteries are light weight, show high energy density (210 Wh.kg⁻¹), low charge loss, no memory effect, large service-life and high number of charge/discharge cycles [6].

The main constituents of a lithium-ion battery are the anode (negative electrode), the cathode (positive electrode) and the separator/electrolyte and the main issues to improve its performance are specific energy, power, safety and reliability [7].

Lithium-ion batteries are extremely sensitive to certain temperature ranges, typically being functional between −20 °C and ∼50 to 60 °C [8]. During the cycling of a battery, its temperature increases and, if the temperature exceeds certain limits, exothermic reactions can occur, resulting in increased internal pressure, rupture or even explosion of the battery [9,10].

For certain applications, in which high discharge rates are required, the thermal management of the batteries is critical in order to optimize performance and to avoid structural damage and consequently loss battery performance during operation [2,10,11].

Thermal management systems (TMS) are implemented with the objective to avoid overheating of battery packs [12]. Most TMS make use of cooling mediated by air [13], liquid [14], heat pipe [15], or phase change materials (PCM) [8]. Recently, the cooling efficiency of the parallel air-cooled battery thermal management system (BTMS) was optimized with U-type flow. For the process at 5C discharge rate, the temperature difference among the battery cells is reduced by 70% after optimization, leading to a power consumption reduction of 32% [16]. Further, the thermal behavior of batteries was analyzed in thermal/climate chambers which the use forced air convection to distribute heat, introducing a novel thermal management system which maintains cell temperature reliably whilst minimizing also the thermal gradients. The proposed method reduces external temperature deviations of the cell to within 1.5 °C, providing reliable data for parameterizing a thermally discretized model [17].

The thermal performance of a Li-ion battery for a phase change material (PCM) loaded with carbon fibers was studied, showing that the carbon fibers have a significant influence in the thermo-physical properties of the PCM through the improvement of the effective thermal conductivity [18]. Further, the thermal conductivity of the PCM with double copper mesh increases by 36% compared with that of the PCM composed of paraffin (PA) and expanded graphite (EG) [19].

The analysis of the thermal conditions is very important in order to optimize those systems and for batteries applied into microgrids structures [[20], [21], [22], [23]].

The thermal performance of battery modules under different cell arrangement structures was investigated by three-dimensional computational fluid dynamics (CFD) method and it was verified that when the fan is located on top of the module, the best cooling performance is achieved and the most desired structure with forced air cooling is the cubic arrangement [24].

Finally, the thermal behavior of high-power lithium-ion cells was investigated using an accelerating rate calorimeter. It is shown that heat generation is less marked at higher C-rates, resulting in a larger irreversible heat component during charging and discharging at high current rates [25].

The influence of the thermal conditions on the performance of lithium ion battery should be analyzed for each battery component [26]. In particular, the thickness of the electrodes strongly affects the overall heat generation [27], as the generated ohmic heat is larger for thicker electrodes [27].

The size of each active material also affects the generation of heat [11] and the effect of particle size for the LiMn₂O₄ active material was studied by using a thermal model [28], demonstrating the higher generation of heat for larger particles size [28]. Further, the geometry of the battery also influences its thermal behavior [10,29]. The thermal model for the behavior of LiNi_xCo_yMn_zO₂ (NCM) lithium-ion batteries for high charge/discharge processes (up to 8C) compares well with experimental, allowing to assess the influence of the external heat release conditions and charge/discharge rate on the thermal behavior of the batteries. It is concluded that favorable heat release conditions or effective and active thermal management are the key for the thermal control of lithium-ion batteries [30].

The thermal behavior of batteries with cylindrical, prismatic and pouch cell geometries was analyzed under different electrical loads and cooling conditions [31].

In relation to cylindrical cell geometries, it is observed a decreasing heat transfer resistance with increasing radius due to adiabatic condition at the cell core. On the other hand, differential temperature across the cell thickness must be considered for prismatic cells [31].

The thermal behavior of a lithium ion battery during galvanostatic discharge was analyzed by computer simulation showing that higher cell temperatures raise the risk of thermal runaway (TR) and more rapid degradation of the cell [32].

A thermal runaway (TR) propagation model was applied to a large format lithium ion battery module and it was concluded that TR propagation can be prevented by increasing the TR triggering temperature by modifying the separator, reducing the total electric energy released during TR by discharging the battery and enhancing the heat dissipation by increasing the convection coefficient [33]. The effect of heat sources in the thermal runaway processes of lithium-ion batteries composed of different chemistries using accelerating rate calorimetry (ARC) and differential scanning calorimetry (DSC) was analyzed, showing that internal short circuit is not the only way to thermal runaway, but can also lead to extra electrical heat, which is comparable with the heat released by the chemical reactions [34].

New lithium-ion unconventional battery geometries, such as ring, spiral, horseshoe, antenna and gear have been reported in Ref. [29], as they can be fabricated by 3D printing technologies and provide more adequate geometries for specific applications.

Considering the relevance of the thermal issues in lithium-ion batteries, the novelty of this work is to evaluate and analyze the effect of different thermal conditions on those new unconventional geometries (interdigitated, horseshoe, spiral, ring, antenna and gear) as well as in conventional geometries, for comparison. The applied scan rates are correlated to the area of each component and the battery geometries used are based on graphite and lithium iron phosphate (LiFePO₄) as active material for the anode and cathode electrode, respectively.

These geometries are proposed as an alternative for portable and wearable devices considering their better integration into devices and can be produced by 3D printing techniques with industrial scalability. These geometries were recently reported [29], but their thermal characteristics have not been evaluated yet. In this work, the thermal properties were analyzed as a function of the maximum distance for the ions to move to the current collector, d_max, distance between current collectors, d_cc, and the thickness of the separator and electrodes. Thus, this work will allow the proper dimensional design and thermal condition optimization of those batteries.

Section snippets

Materials and preparation of the electrodes

For the validation of the theoretical thermal model, a full-cell was developed.

For the preparation of the electrodes (anode and cathode), carbon coated lithium iron phosphate, C-LiFePO₄ (LFP, Particle size: D10 = 0.2 μm, D50 = 0.5 μm and D90 = 1.9 μm), poly(vinylidene fluoride) (PVDF, Solef 5130) and N,N′-dimethyl propylene urea (DMPU) were acquired from Phostech Lithium, Solvay and LaborSpirit, respectively. Timrex SLG3 graphite particles and carbon black (Super P-C45) were obtained from

Theoretical simulation model

Simulations were performed by applying the electrochemical model based on the Newman/Doyle/Fuller equations coupled with the thermal behavior.

This electrochemical model describes the electrochemical processes that occurs in battery components, electrodes, separator and current collectors, including the thermal behavior.

The flowchart of the coupling of both models is present in Fig. 1.

Thus, the initial temperature is defined and the battery operates in the discharge process, allowing to

Results and discussion

Theoretical model simulations were thus applied in all different lithium-ion battery geometries in different thermal conditions: isothermal, adiabatic and environmental conditions (cold, regular and hot temperatures) keeping constant the area of the components.

The theoretical model was first validated with the experimental results obtained for the developed full cell.

The main objective is to evaluate how the performance of the batteries with different geometries are affected by the thermal

Conclusions

Thermal properties are a critical issue in lithium-ion batteries as they strongly influence battery performance and safety. Thus, for maximizing battery performance it is essential to properly analyze the effect of the thermal behavior of different battery geometries through computer simulations. This work shows the effect of the thermal conditions (isothermal, adiabatic, cold, regular and hot conditions) in different battery geometries, including conventional (layer by layer) and

Acknowledgments

This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014 and UID/CTM/50025/2013 and grant SFRH/BPD/112547/2015 (C.M.C.). Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged.

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Computer simulation of the influence of thermal conditions on the performance of conventional and unconventional lithium-ion battery geometries

Highlights

Abstract

Introduction

Section snippets

Materials and preparation of the electrodes

Theoretical simulation model

Results and discussion

Conclusions

Acknowledgments

Mech Syst Signal Process

J Power Sources

J Power Sources

J Power Sources

J Power Sources

J Power Sources

J Power Sources

J Power Sources

J Power Sources

Energy Convers Manag

Energy

Energy

Energy

Energy

Elec Power Syst Res

Int J Electr Power Energy Syst

Appl Energy

Appl Energy

Appl Energy

Energy

J Power Sources

Appl Energy

IntJ Heat Mass Transf