Thermal characteristics study and optimization of air-cooling structures for dual-system battery packs

doi:10.19799/j.cnki.2095-4239.2025.0122

Abstract

Abstract:

The widespread application of lithium-ion batteries in electric vehicles is limited by performance constraints. To address the shortcomings of single-material systems, this study proposes a dual-system battery pack design integrating ternary lithium (NCM) and lithium iron phosphate (LFP) batteries, which has been successfully applied in practical vehicle systems. To ensure thermal safety, we investigate the thermal characteristics of a dual-system battery pack composed of 18650 NCM and LFP cells. A three-dimensional electrochemical–thermal coupling model is developed for the dual-system battery pack. Three air-cooling configurations (Z-type, U-type, and T-type) are designed, and experiments are conducted to analyze heat generation differences between the two cell types and to validate the model. Thermal dissipation performance under natural and forced air cooling is compared at different cell positions, leading to an optimized cell arrangement. The results show that the optimized layout effectively reduces the maximum temperature difference in the battery pack, improving temperature uniformity. At an inlet wind speed of 8 m/s, the U-type configuration reduces maximum temperature, average temperature, and maximum temperature difference by 7.68%, 6.86%, and 21.2%, respectively, compared to the Z-type configuration. Despite exhibiting a higher inlet-outlet pressure differential (78.21 Pa vs. 50.59 Pa for the Z-type), the U-type configuration achieves enhanced thermal uniformity through improved airflow distribution, effectively balancing cooling efficiency and pressure drop. Orthogonal experiments further examine the impact of intra-group spacing in the U-type configuration. Kruskal-Wallis test results indicate that within the range of 1.5—4.5 mm, intra-group spacing has minimal influence on temperature, while the cooling configuration and inlet air velocity predominantly determine thermal management performance. This research provides critical insights into optimizing thermal safety in hybrid battery systems.

Key words: lithium-ion batteries, dual-system battery packs, air-cooling thermal management system, numerical simulation, structural optimization

CLC Number:

TM 912

Zheng CHEN, Jingyuan HU, Zhigang ZHAO, Jiangwei SHEN, Xuelei XIA, Fuxing WEI. Thermal characteristics study and optimization of air-cooling structures for dual-system battery packs[J]. Energy Storage Science and Technology, 2025, 14(9): 3463-3475.

Figures/Tables 17

Fig. 1

Fig. 2

Fig. 3

Table 1

Physical parameters of the two types of batteries"

电池参数	数值	电池参数	数值
$ρ b a t t, N C M$ /(kg/m³)	2082.2	$ρ b a t t, L F P$ /(kg/m³)	2500.7
$k a, N C M$ /[W/(m·K)]	29.541	$k a, L F P$ /[W/(m·K)]	29.52
$k r, N C M$ /[W/(m·K)]	0.773	$k r, L F P$ /[W/(m·K)]	0.873
$c p, N C M$ /[J/(kg·K)]	1345.9	$c p, L F P$ /[J/(kg·K)]	1374.8

Table 1

Fig. 4

Table 2

Fig. 5

Fig. 6

Table 3

Fig. 7

Fig. 8

Fig. 9

Table 4

Fig. 10

Fig. 11

Fig. 12

Table 5

Orthogonal table and simulation results"

组合	x₁/mm	x₂/mm	y₁/mm	y₂/mm	$T m a x$ /℃	$T a v e$ /℃	$Δ T m a x$ /℃
1	1.5	1.5	1.5	1.5	43.57	40.66	7.15
2	1.5	2.5	2.5	2.5	43.41	40.75	6.41
3	1.5	3.5	3.5	3.5	43.14	40.61	6.02
4	1.5	4.5	4.5	4.5	43.17	40.57	5.92
5	2.5	1.5	2.5	3.5	43.62	40.86	6.32
6	2.5	2.5	1.5	4.5	43.21	40.63	6.09
7	2.5	3.5	4.5	1.5	43.58	40.74	7.02
8	2.5	4.5	3.5	2.5	43.41	40.73	6.26
9	3.5	1.5	3.5	4.5	43.56	40.71	6.39
10	3.5	2.5	4.5	3.5	43.40	40.67	6.55
11	3.5	3.5	1.5	2.5	43.25	40.66	6.47
12	3.5	4.5	2.5	1.5	43.33	40.62	6.72
13	4.5	1.5	4.5	2.5	44.19	41.08	7.24
14	4.5	2.5	3.5	1.5	44.03	40.81	7.74
15	4.5	3.5	2.5	4.5	43.26	40.56	6.39
16	4.5	4.5	1.5	3.5	43.06	40.51	6.22

Table 5

References 29

[1]	唐康, 刘振祥, 唐丹, 等. 分布式电池系统热平衡控制设计[J]. 电池, 2024, 54(1): 41-46. DOI:10.19535/j.1001-1579.2024.01.009.
	TANG K, LIU Z X, TANG D, et al. Design of thermal balancing control for distributed battery system[J]. Dianchi(Battery Bimonthly), 2024, 54(1): 41-46. DOI:10.19535/j.1001-1579.2024.01.009.
[2]	孙涛, 郑侠, 郑岳久, 等. 基于电化学热耦合模型的锂离子电池快充控制[J]. 汽车工程, 2022, 44(4): 495-504. DOI: 10.19562/j.chinasae. qcgc.2022.04.005.
	SUN T, ZHENG X, ZHENG Y J, et al. Fast charging control of lithium-ion batteries based on electrochemical-thermal coupling model[J]. Automotive Engineering, 2022, 44(4): 495-504. DOI: 10.19562/j.chinasae.qcgc.2022.04.005.
[3]	PATEL J, PATEL R, SAXENA R, et al. Thermal analysis of high specific energy NCM-21700 Li-ion battery cell under hybrid battery thermal management system for EV applications[J]. Journal of Energy Storage, 2024, 88: 111567. DOI: 10.1016/j.est. 2024.111567.
[4]	SCHÖBERL J, ANK M, SCHREIBER M, et al. Thermal runaway propagation in automotive lithium-ion batteries with NMC-811 and LFP cathodes: Safety requirements and impact on system integration[J]. eTransportation, 2024, 19: 100305. DOI: 10.1016/j.etran.2023.100305.
[5]	WANG G, JIN B, WANG M Z, et al. State of charge estimation for "LiFePO₄-LiCoxNi_yMn_1- x_- yO₂" hybrid battery pack[J]. Journal of Energy Storage, 2023, 65: 107345. DOI: 10.1016/j.est.2023. 107345.
[6]	YAO S, WANG G, ZHU H, et al. Equalization method of 'LiCoxNiyMn_1- x_- yO₂-LiFePO₄' hybrid battery pack based on charging electric quantity estimation[J]. Journal of Energy Storage, 2023, 69: 107959. DOI: 10.1016/j.est.2023.107959.
[7]	WANG M Z, WANG G, LUO Q, et al. Study on the configuration of LiCoxNiyMn_1- x_- yO₂-LiFePO₄ hybrid battery pack[J]. Applied Energy, 2024, 372: 123744. DOI: 10.1016/j.apenergy.2024. 123744.
[8]	EBBS-PICKEN T, DA SILVA C M, AMON C H. Design optimization methodologies applied to battery thermal management systems: A review[J]. Journal of Energy Storage, 2023, 67: 107460. DOI: 10.1016/j.est.2023.107460.
[9]	宋梦琼, 彭宇, 廖自强. 基于电化学热耦合模型的电池热管理研究[J]. 储能科学与技术, 2024, 13(2): 578-585. DOI: 10.19799/j.cnki. 2095-4239.2023.0620.
	SONG M Q, PENG Y, LIAO Z Q. Research on battery thermal management based on electrochemical model[J]. Energy Storage Science and Technology, 2024, 13(2): 578-585. DOI: 10.19799/j.cnki.2095-4239.2023.0620.
[10]	LI W, XIE Y, HU X S, et al. An internal heating strategy for lithium-ion batteries without lithium plating based on self-adaptive alternating current pulse[J]. IEEE Transactions on Vehicular Technology, 2023, 72(5): 5809-5823. DOI: 10.1109/TVT.2022. 3229187.
[11]	LI K J, WANG H B, XU C S, et al. Multi-objective optimization of side plates in a large format battery module to mitigate thermal runaway propagation[J]. International Journal of Heat and Mass Transfer, 2022, 186: 122395. DOI: 10.1016/j.ijheatmasstransfer. 2021.122395.
[12]	刘书琴, 王小燕, 张振东, 等. 锂离子电池组液冷式热管理系统的设计及优化[J]. 储能科学与技术, 2023, 12(7): 2155-2165. DOI: 10. 19799/j.cnki.2095-4239.2023.0152.
	LIU S Q, WANG X Y, ZHANG Z D, et al. Experimental and simulation research on liquid-cooling system of lithium-ion battery packs[J]. Energy Storage Science and Technology, 2023, 12(7): 2155-2165. DOI: 10.19799/j.cnki.2095-4239.2023.0152.
[13]	VERMA S P, SARASWATI S. Numerical and experimental analysis of air-cooled lithium-ion battery pack for the evaluation of the thermal performance enhancement[J]. Journal of Energy Storage, 2023, 73: 108983. DOI: 10.1016/j.est.2023.108983.
[14]	SHI Y, AHMAD S, LIU H Q, et al. Optimization of air-cooling technology for LiFePO₄ battery pack based on deep learning[J]. Journal of Power Sources, 2021, 497: 229894. DOI: 10.1016/j.jpowsour.2021.229894.
[15]	FAN Y Q, BAO Y, LING C, et al. Experimental study on the thermal management performance of air cooling for high energy density cylindrical lithium-ion batteries[J]. Applied Thermal Engineering, 2019, 155: 96-109. DOI: 10.1016/j.applthermaleng. 2019.03.157.
[16]	KANG D, LEE P Y, YOO K, et al. Internal thermal network model-based inner temperature distribution of high-power lithium-ion battery packs with different shapes for thermal management[J]. Journal of Energy Storage, 2020, 27: 101017. DOI: 10.1016/j.est. 2019.101017.
[17]	ZHANG Y, SONG X D, MA C Y, et al. Effects of the structure arrangement and spacing on the thermal characteristics of Li-ion battery pack at various discharge rates[J]. Applied Thermal Engineering, . DOI: 10.1016/j.applthermaleng.2019.114610.
[18]	刘剑, 于立博, 吴振兴, 等. 基于风冷的锂离子电池充放电设备热特性影响研究[J]. 储能科学与技术, 2024, 13(3): 914-923. DOI: 10. 19799/j.cnki.2095-4239.2023.0688.
	LIU J, YU L B, WU Z X, et al. Effect of thermal characteristics of lithium-ion battery charging and discharging equipment on air cooling[J]. Energy Storage Science and Technology, 2024, 13(3): 914-923. DOI: 10.19799/j.cnki.2095-4239.2023.0688.
[19]	徐晓斌, 徐业飞, 张恒运, 等. 风冷电池模组热性能及成组效率的多目标优化[J]. 储能科学与技术, 2022, 11(2): 553-562. DOI: 10. 19799/j.cnki.2095-4239.2021.0407.
	XU X B, XU Y F, ZHANG H Y, et al. Multiobjective optimization of thermal performance and grouping efficiency for air cooling battery module[J]. Energy Storage Science and Technology, 2022, 11(2): 553-562. DOI: 10.19799/j.cnki.2095-4239.2021. 0407.
[20]	SARMADIAN A, WIDANAGE W D, SHOLLOCK B, et al. Experimentally-verified thermal-electrochemical simulations of a cylindrical battery using physics-based, simplified and generalised lumped models[J]. Journal of Energy Storage, 2023, 70: 107910. DOI: 10.1016/j.est.2023.107910.
[21]	LI A, YUEN A C Y, WANG W, et al. Numerical investigation on the thermal management of lithium-ion battery system and cooling effect optimization[J]. Applied Thermal Engineering, 2022, 215: 118966. DOI: 10.1016/j.applthermaleng.2022.118966.
[22]	BERNARDI D, PAWLIKOWSKI E, NEWMAN J. A general energy balance for battery systems[J]. Journal of the Electrochemical Society, 1985, 132(1): 5-12. DOI: 10.1149/1.2113792.
[23]	HE H S, CHEN X J, FLY A, et al. A Fast Activation Energy Derivation (FAED) approach for Lumped Single Particle model in lithium-ion battery module-level heat generation prediction[J]. Journal of Power Sources, 2023, 580: 233431. DOI: 10.1016/j.jpowsour.2023.233431.
[24]	LEMPERT J, KOLLMEYER P, MALYSZ P, et al. Battery entropic heating coefficient testing and use in cell-level loss modeling for extreme fast charging[J]. SAE International Journal of Advances and Current Practices in Mobility, 2020, 2(5): 2712-2720. DOI: 10.4271/2020-01-0862.
[25]	XIE Y Q, SHI S, TANG J C, et al. Experimental and analytical study on heat generation characteristics of a lithium-ion power battery[J]. International Journal of Heat and Mass Transfer, 2018, 122: 884-894. DOI: 10.1016/j.ijheatmasstransfer.2018.02.038.
[26]	GOMADAM P M, WHITE R E, WEIDNER J W. Modeling heat conduction in spiral geometries[J]. Journal of the Electrochemical Society, 2003, 150(10): A1339. DOI: 10.1149/1.1605743.
[27]	ZHANG S B, NIE F, CHENG J P, et al. Optimizing the air flow pattern to improve the performance of the air-cooling lithium-ion battery pack[J]. Applied Thermal Engineering, 2024, 236: 121486. DOI: 10.1016/j.applthermaleng.2023.121486.
[28]	Introduction to computational fluid dynamics: Development, Application and analysis \| SpringerLink [EB].
[29]	MONIRUL I M, QIU L, RUBY R. Accurate SOC estimation of ternary lithium-ion batteries by HPPC test-based extended Kalman filter[J]. Journal of Energy Storage, 2024, 92: 112304. DOI: 10.1016/j.est.2024.112304.

三元锂电池参数	数值	磷酸铁锂电池参数	数值
额定容量/Ah	2	额定容量/Ah	2
额定电压/V	3.6	额定电压/V	3.2
充电截止电压/V	4.2	充电截止电压/V	3.65
放电截止电压/V	2.5	放电截止电压/V	2.0

电池	参数	SOC
电池	参数	0.9	0.8	0.7	0.6	0.5	0.4	0.3	0.2	0.1	0
LFP	欧姆内阻/mΩ	58.0	57.6	58.0	57.1	58.6	55.2	58.9	58.3	55.5	63.8
	极化内阻/mΩ	27.6	32.0	34.4	35.0	33.2	39.0	39.4	45.9	58.9	91.5
	总内阻/mΩ	85.6	89.6	92.4	92.1	91.8	94.2	98.3	104.2	114.4	155.3

NCM	欧姆内阻/mΩ	36.6	36.6	36.6	36.9	37.2	37.2	37.9	38.7	38.7	36.6
	极化内阻/mΩ	9.9	11.2	12.1	11.7	8.4	8.0	7.7	9.0	10.1	9.9
	总内阻/mΩ	46.5	47.8	48.7	48.6	45.6	45.2	45.6	47.7	48.8	46.5

电池布局方式	散热结构	最高温度/℃	平均温度/℃	最大温差/℃
交替布局	Z形散热结构	51.30	45.76	13.48
	U形散热结构	47.72	43.05	8.92
	T形散热结构	48.65	44.27	10.75

优化布局	Z形散热结构	48.57	45.57	7.04
	U形散热结构	44.87	42.26	6.48
	T形散热结构	47.20	44.30	6.68