Evolution and mechanism of contact resistance of copper–aluminum electrical connectors in lithium-ion power batteries

Junlian Ge¹ , Jialin Zhu², Biao Ge¹ , Leon Sandforth³ , Junying Min⁴ *

¹School of Mechanical Engineering, Tongji University, Shanghai 201804, China.

²Hefei Gotion High-Tech Power Energy Co. Ltd., Hefei 230041, China.

³Chair for Electrical Energy Storage Systems, Institute for Photovoltaics (IPV), University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany.

⁴College of Automotive and Energy Engineering, Tongji University, Shanghai 201804, China.

DOI:

https://doi.org/10.7494/cmms.2026.2.1041

Abstract:

This study investigates the sensitivity of factors influencing the contact resistance and reliability assessment of bolted copper–aluminum electrical connectors. Through continuous energized dynamic testing, the temporal evolution of the contact resistance and temperature of the contact area were monitored throughout the experiment. In conjunction with observations of contact surface morphology and microstructural composition analysis, the intrinsic mechanisms underlying anomalous changes in contact resistance were explored in depth. The results indicated that, during continuous current flow, the contact resistance of aluminum busbar assemblies without plating exhibited an “initially low → rapid increase → gradual stabilization” pattern, whereas nickel-plated aluminum assemblies maintained stable resistance. Quantitatively, the contact resistance of the nickel-plated group remained at approximately 15 μΩ, while that of the bare aluminum group rose to 400–750 μΩ. The evolution of the contact interface was asymmetric, with the dynamic growth of the oxide layer on the aluminum surface being the dominant mechanism increasing resistance. Moreover, the aluminum coating significantly reduced contact resistance and enhanced connection reliability.

Cite as:

Ge, J., Zhu, J., Ge, B., Sandforth, L., & Min, J. (2026). Evolution and mechanism of contact resistance of copper-aluminum electrical connectors in lithium-ion power batteries. Computer Methods in Materials Science, 26(2), 5-22. https://doi.org/10.7494/cmms.2026.2.1041

Article (PDF):

Keywords:

Lithium-ion power batteries, Electrical connection, Contact resistance, Contact mechanism

Publication dates:

Received: 15.04.2026, accepted: 17.05.2026, published: 26.06.2026

Publication type:

Original scientific paper

References:

Alderete, B., Nayak, U. P., Mücklich, F., & Suarez, S. (2023). Influence of topography on electrical contact resistance of copper-based materials. Surface Topography: Metrology and Properties, 11(2), 025027. https://doi.org/10.1088/2051-672X/acdfea

Aronstein, J. (2004). An updated view of the aluminum contact interface. In Proceedings of the 50th IEEE Holm Conference on Electrical Contacts and the 22nd International Conference on Electrical Contacts. Electrical Contacts – 2004 (pp. 98–103). IEEE. https://doi.org/10.1109/HOLM.2004.1353101

Bao, Y.-f., Ren, L., Yu, Z.-t., Jiang, Y.-f., & Yang, K. (2018). An experimental study on contact resistance of coated galvanized steel sheet. Welding in the World, 62(3), 511–516. https://doi.org/10.1007/s40194-018-0583-9

Braunovic, M. (2003). Effect of connection design on the contact resistance of high power overlapping bolted joints. IEEE Transactions on Components and Packaging Technologies, 25(4), 642–650. https://doi.org/10.1109/TCAPT.2003.809108

Elkjaer, A., Ringen, G., Bjørge, R., Hagen, C. H. M., Lædre, S., & Magnusson, N. (2022). Reliability of bolted aluminum busbars for battery systems: effect of nickel coating and corrosive environment. IEEE Transactions on Transportation Electrification, 9(1), 1060–1071. https://doi.org/10.1109/TTE.2022.3196309

Feng, Y., Ding, Y., Mao, Z., Hu, X., Wang, Z., Huang, C.& Ye, C. (2021) Research on the Protective Performance of Tinning Layer on Electrical Copper Bars. Materials Protection, 54(06), 112–116. https://doi.org/10.16577/j.cnki.42-1215/tb.2021.06.020 [in Chinese].

Hu, M., Ye, Z., Liu, Q., Lv, Q., & Wang, L. (2019). Cause analysis and solution of quality problems of Tin plating layer on copper wiring head. Electric Locomotives & Mass Transit Vehicles, 54(06). https://doi.org/10.16212/j.cnki.1672-1187.2019.06.018 [in Chinese].

Huang, W., Xia, N., & Tian, S. (2022). Study on reliability of deep sea lithium battery connection mode. Marine Electric & Electronic Engineering, 42(04), 28–30+33. https://doi.org/10.13632/j.meee.2022.04.011 [in Chinese].

Kalich, J., Matzke, M., Pfeiffer, W., Schlegel, S., Kornhuber, L., & Füssel, U. (2022). Long-term behavior of clinched electrical contacts. Metals, 12(10), 1651. https://doi.org/10.3390/met12101651

Khayam, U., Sutrisno, B., Risdiyanto, A., & Suwarno (2014). Design of battery connection using copper conductor with tin and silver coating. In 2014 International Conference on Electrical Engineering and Computer Science (ICEECS) (pp. 326–330). IEEE. https://doi.org/10.1109/ICEECS.2014.7045271

Khayam, U., Hadisoeseno, N. P. Y., Suwarno, & Risdiyanto, A. (2017). Reducing contact resistance of high current connectors on electric vehicle by controlling contact pressure and addition of plating material. In 2017 4th International Conference on Electric Vehicular Technology (ICEVT) (pp. 61–64). IEEE. https://doi.org/10.1109/ICEVT.2017.8323534

Kolmer, P., Shukla, A., & Song, J. (2022). Methods of material and surface analysis for the evaluation of failure modes for electrical connectors. Technologies, 10(6), 124. https://doi.org/10.3390/technologies10060124

Oberst, M., Schlegel, S., & Gromann, S. (2018). Influence of oxygen on the aging of electrical joints with one bare and one coated aluminum contact member. In 2018 IEEE Holm Conference on Electrical Contacts (pp. 262–269). IEEE. https://doi.org/10.1109/HOLM.2018.8611688

Oberst, M., Hildmann, C., & Schlegel, S. (2021). Deterioration and Breakdown Mechanisms in force-fitted current-carrying Connections between Aluminum and Tin. In 2021 IEEE 66th Holm Conference on Electrical Contacts (HLM) (pp. 1–7). IEEE. https://doi.org/10.1109/HLM51431.2021.9671165

Runde, M. (2019). Inside the aluminum contact spot. In 2019 IEEE Holm Conference on Electrical Contacts (pp. 1–8). IEEE. https://doi.org/10.1109/HOLM.2019.8923842

Slade, P. G. (Ed.). (2017). Electrical Contacts: Principles and Applications (2nd ed.). CRC Press.

Song, J., Yuan, H., Shukla, A., Koch, Ch., & Hilmert, D. (2019). Correlation of connector contact failures in accelerated testing and in long-term use field vehicles. In 2019 IEEE Holm Conference on Electrical Contacts (pp. 296–302). IEEE. https://doi.org/10.1109/HOLM.2019.8923844

Song, J., Hilmert, D., & Kiel, F. (2025). Mechanisms of failure and state analysis of electrical connectors in automobiles. Engineering Failure Analysis, 173, 109427. https://doi.org/10.1016/j.engfailanal.2025.109427

Taheri, P., Hsieh, S., & Bahrami, M. (2011). Investigating electrical contact resistance losses in lithium-ion battery assemblies for hybrid and electric vehicles. Journal of Power Sources, 196(15), 6525–6533. https://doi.org/10.1016/j.jpowsour.2011.03.056

Tian, N. (2019). Sliding Contact Characteristics and Reliability Analysis of Different Contact Materials of Connector [Master’s thesis, Beijing University of Posts and Telecommunications] [in Chinese].

Wu, Q. (2017). Fretting Contact Characteristics and Reliability Analysis of Contact Pairs of Different Coating Materials [Master’s thesis, Beijing University of Posts and Telecommunications] [in Chinese].

Zhang, C., Ren, W., & Liao, X. (2022). On the relationship between contact resistance and load force for electrode materials with rough surfaces. Materials, 15(16), 5667. https://doi.org/10.3390/ma15165667

Zhang, S., Zhao, X., Ye, M., & He, Y. (2019). Theoretical and experimental study on electrical contact resistance of metal bolt joints. IEEE Transactions on Components, Packaging and Manufacturing Technology, 9(7), 1301–1309. https://doi.org/10.1109/TCPMT.2019.2920854

Zhi, H. (2016). Experimental Study if Electrical Contact Characteristics for Aviation Electrical Connector under Combined Environmental Stress [Master’s thesis, Harbin Institute of Technology] [in Chinese].

Zhu, Z. (2023). Study on Low Cost and High Performance Precious Metal Composite Electrical Contact Coating [Doctoral dissertation, University of Science and Technology Beijing]. https://doi.org/10.26945/d.cnki.gbjku.2023.000100 [in Chinese].