Resins vs. Metals: Which is Better for Preventing Thermal Runaway?

By Samudrapom DamReviewed by Lexie CornerNov 19 2024

Thermal runaway is a critical issue in electronics, particularly in battery technology, where overheating can lead to catastrophic failures. In lithium-ion batteries, this phenomenon occurs when the cell enters an uncontrollable, self-heating state.¹

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To address this challenge, researchers and companies are focusing on advanced materials, such as resins and metals, that can mitigate thermal runaway effects.

Understanding Thermal Runaway

Thermal runaway is a rapid self-heating process in a cell, driven by exothermic reactions within its materials, resulting in the release of stored chemical energy. While it can be triggered by factors such as mechanical deformation, overcharging, or short circuits, overheating is the primary cause of thermal runaway.^2,3

Overheating occurs due to cooling system failure, exposure to high external temperatures, or excessive Joule heating caused by aging-related increases in internal resistance. Lithium-ion batteries are particularly susceptible to thermal runaway.^2,3

In these batteries, the solid electrolyte interphase layer decomposes and breaks down in an exothermic reaction when the cell temperature reaches about 80 °C. As the temperature rises to 120 °C–130 °C, the separator melts, causing internal short circuits and generating more heat. At 130 °C–150 °C, the cathode breaks down due to another exothermic chemical reaction with the electrolyte, generating additional oxygen.^2,3

At 150 °C–180 °C, oxygen generation can cause a self-sustaining fire, resulting in thermal runaway. This process may produce smoke, fire, explosions, and the release of gas, particulates, and shrapnel.^1,3 Thus, recent studies have investigated prevention strategies, including the use of resins and metals, to enhance the safety and reliability of battery-powered devices.²

Properties of Resins

Resins are valued for their excellent insulating properties, making them effective in preventing the transfer of heat and protecting sensitive components in electronic devices and batteries. Many resins, like epoxy, exhibit high heat resistance, allowing them to maintain structural integrity at elevated temperatures. Epoxy resins can withstand temperatures up to 150–200 °C.^4,5

These materials are used in coatings or encapsulation to shield electronics from thermal damage. Their ability to resist thermal degradation makes resins ideal for managing heat buildup in critical applications. Additionally, certain resins can be designed to undergo minimal expansion or breakdown under heat, enhancing their durability in high-temperature environments.^4,5

For instance, SABIC has developed the Stamax 30YH570 resin, a 30 % glass fiber-reinforced copolymer designed for thermal runaway protection in electric vehicle batteries. During thermal runaway box testing conducted according to UL 2596 standards, the resin demonstrated durability by withstanding internal box temperatures of 420 °C.⁶

Similarly, Polyplastics Co. Ltd. has introduced Durafide polyphenylene sulfide (PPS) 6150T73, a material with exceptional heat resistance and high electric and thermal insulation properties designed to prevent thermal runaway lithium-ion battery-powered electric vehicles. The resin retains its insulation properties even after exposure to temperatures as high as 1,000 °C (1,832 °F) for 30 minutes.⁷

Companies like Amco Polymers are developing advanced resin formulations to enhance fire resistance and thermal stability. Products offered by Amco Polymers, including liquid crystal polymer, polyphenylene sulfide, and polysulfone/polyethersulfone, possess excellent heat resistance, high heat deflection temperature of 260 °C-270 °C, good thermal stability, and very low coefficient of thermal expansion.⁸

A key limitation of resins is their susceptibility to degradation at high temperatures, which can reduce their effectiveness in critical applications. To address this issue, research efforts are underway to develop heat-resistant resins with improved thermal stability.^4,5

Properties of Metals

Metals are widely used for heat management due to their high thermal conductivity, enabling efficient heat transfer and dissipation from sensitive components. This property makes metals, such as aluminum, copper, and various alloys, suitable for preventing heat accumulation, hotspots, and the risk of thermal runaway in batteries and electronic devices.^9,10

The rapid heat dissipation properties of metals help maintain stable operating conditions, enhancing the longevity and safety of electronic devices. Different metal alloys provide varying levels of thermal performance to suit specific applications.^9,10

For instance, a study published in Crystals described the development and manufacturing of high-performance hypereutectic aluminum-silicon (Al-Si) alloys using a powder metallurgy method.¹¹

The Al-Si system combines a favorable coefficient of thermal expansion (CTE) with high thermal conductivity, making it well-suited for industries prioritizing thermal management, such as electronics and electric vehicles.¹¹ These alloys are particularly useful for structural heat sink applications requiring reliability under thermal cycling, as well as reflective optics and instrument assemblies demanding mechanical and thermal stability.¹¹

While metals are effective for thermal management, they pose challenges such as corrosion and thermal expansion. Corrosion can degrade metal surfaces over time, reducing their heat dissipation efficiency.^12,13

Additionally, temperature-induced expansion and contraction can cause structural stresses. Addressing these issues requires the development of strategies to enhance the durability and reliability of metals in heat management applications.^12,13

Comparative Analysis

A comparative analysis of resins and metals highlights their respective advantages in managing heat and preventing thermal runaway. Factors such as temperature resistance, weight, and ease of application are key considerations in selecting the most suitable material for specific use cases.^14,15

Organic carbonate solvents are the most flammable components of electrolytes. Incorporating flame-retardant chemicals into organic electrolytes can help mitigate this risk. For instance, a poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) shell with a triphenyl phosphate (TPP) core can be used for enhanced safety.^14,15

When the battery temperature rises excessively, the PVDF-HFP shell melts, allowing the TPP core to mix with the electrolyte and prevent combustion. Solid electrolytes, which are non-flammable, have minimal leakage, and offer extended lifespan, further enhance the safety of lithium-ion batteries compared to liquid electrolytes.^14,15

Poly(methyl methacrylate) (PMMA) and PVDF-HFP could be utilized as solid electrolytes in batteries. Additionally, T_i3C₂Tz MXene, tailored with a customized surface end base, can enhance battery safety by supporting anodes with higher capacity and lower working potential, making it a promising material for advanced energy storage applications.^14,15

A study published in Cell Reports Physical Science explored a metal-coated polymer current collector designed to disconnect internal short circuits by withdrawing from the heating region. The collector was tested in 18650 cells, where it demonstrated a reduced thermal runaway risk during nail penetration, as well as lower manufacturing costs and mass.¹⁶

Specifically, cells with aluminum-coated polymer current collectors showed 100 % success in preventing thermal runaway during nail penetration, retaining more than 4 V cell voltage, while standard cells with aluminum current collectors consistently experienced thermal runaway.¹⁶

Resins are well-suited for applications requiring high thermal stability and corrosion resistance, while metals are suitable for scenarios that demand high thermal conductivity and excellent heat dissipation.^4-16

In weight-sensitive applications, such as electric vehicles, resins offer advantages due to their lighter weight compared to metals like aluminum. Additionally, resins benefit from simpler processing methods, unlike metals, which often require more complex manufacturing techniques.^4-16

Choosing the Right Material for Thermal Runaway Prevention

The choice between resins and metals for preventing thermal runaway depends on specific requirements, such as thermal conductivity, weight, and ease of processing. Resins are ideal for lightweight, corrosion-resistant applications, while metals are preferred for high thermal conductivity and heat dissipation.

In many cases, hybrid solutions that combine the advantages of both materials can provide the most effective approach, enhancing safety and performance by utilizing the unique strengths of each material.

More from AZoM: Li-Ion Batteries and SEI Analysis

References and Further Reading

1. UL Research Institutes. (2021). What Is Thermal Runaway? [Online] UL Research Institutes. Available at https://ul.org/research/electrochemical-safety/getting-started-electrochemical-safety/what-thermal-runaway (Accessed on 18 November 2024)
2. Pfrang, A., Kriston, A., Ruiz, V., Lebedeva, N., Di Persio, F. (2017). Safety of Rechargeable Energy Storage Systems with a focus on Li-ion Technology. Emerging Nanotechnologies in Rechargeable Energy Storage Systems. DOI: 10.1016/B978-0-323-42977-1.00008-X, https://www.sciencedirect.com/science/article/abs/pii/B978032342977100008X
3. Warner, JT. (2019). Lithium-ion battery operation. Lithium-Ion Battery Chemistries. DOI: 10.1016/B978-0-12-814778-8.00003-X, https://www.sciencedirect.com/science/article/abs/pii/B978012814778800003X
4. West Virginia University. (2008). Introduction To Polymers (Resins). [Online] West Virginia University. Available at https://web.statler.wvu.edu/~rliang/2008.pdf (Accessed on 18 November 2024)
5. Dallaev, R., Pisarenko, T., Papež, N., Sadovský, P., Holcman, V. (2023). A Brief Overview on Epoxies in Electronics: Properties, Applications, and Modifications. Polymers. DOI: 10.3390/polym15193964, https://www.mdpi.com/2073-4360/15/19/3964
6. Sabic. (n.d.). STAMAX™. [Online] Sabic. Available at: https://www.sabic.com/en/products/polymers/polypropylene-pp/stamax  (Accessed on 18 November 2024)
7. Plastics Engineering. (n.d.). Polyplastics’ New PPS Resin Withstands Thermal Runaway in EVs [Online] Plastics Engineering. Available at https://www.plasticsengineering.org/2023/09/polyplastics-new-pps-resin-withstands-thermal-runaway-in-evs-001893/ (Accessed on 18 November 2024)
8. AmcoPolymers. (n.d.). Resin Types. [Online] AmcoPolymers. Available at https://www.amcopolymers.com/products/resin-types (Accessed on 18 November 2024)
9. Kailas, SV. (n.d.). Thermal properties. [Online] Indian Institute of Science. Available at https://archive.nptel.ac.in/content/storage2/courses/112108150/pdf/Web_Pages/WEBP_M15.pdf (Accessed on 18 November 2024)
10.  Brigham Young University. (n.d.). Thermal Properties of Pure Metals. [Online]  Brigham Young University. Available at https://cleanroom.byu.edu/thermal_properties (Accessed on 18 November 2024)
11.  Lewis, P., et al. (2024). Aluminium-Silicon Lightweight Thermal Management Alloys with Controlled Thermal Expansion. Crystals. DOI: 10.3390/cryst14050455, https://www.mdpi.com/2073-4352/14/5/455
12.  Balangao, JK. (2024). Corrosion of Metals: Factors, Types and Prevention Strategies. Journal of Chemical Health Risks. https://www.researchgate.net/publication/377534338_Corrosion_of_Metals_Factors_Types_and_Prevention_Strategies
13.  How Heating Metal Affects Its Properties [Online] Available at http://sites.isdschools.org/hselectives_ind_tech/useruploads/index/5-18_Diman_Machine_Technology_2.pdf  (Accessed on 18 November 2024)
14.  McKerracher, RD., Guzman-Guemez, J., Wills, RG., Sharkh, SM., Kramer, D. (2021). Advances in Prevention of Thermal Runaway in Lithium-Ion Batteries. Advanced Energy and Sustainability Research. DOI: 10.1002/aesr.202000059, https://onlinelibrary.wiley.com/doi/full/10.1002/aesr.202000059
15.  Zhi, M., et al. (2024). Review of prevention and mitigation technologies for thermal runaway in lithium-ion batteries. Aerospace Traffic and Safety. DOI: 10.1016/j.aets.2024.06.002, https://www.sciencedirect.com/science/article/pii/S2950338824000044
16.  Pham, MT., et al. (2021). Prevention of lithium-ion battery thermal runaway using polymer-substrate current collectors. Cell Reports Physical Science. DOI: 10.1016/j.xcrp.2021.100360, https://www.sciencedirect.com/science/article/pii/S266638642100045X

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