Electronic Vehicles (EVs) have been at the center of attention in recent years. With the automotive industry becoming more aligned with sustainable development goals, the focus has shifted toward EVs and improving their performance.
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Maintaining the temperature and heat level of electronic components, batteries, and packaging materials in electric cars is a complex process. The focus for improved thermal performance initially involved researching battery cells that are safer, more durable, and capable of withstanding thermal exposure.
Subsequently, the design of battery packing has gained significance in preventing thermal events that could lead to explosions or, at the very least, mitigate potential severe consequences if an explosion occurs. An effective battery packing design aims to keep the temperature of the battery cells within the optimal range.
The Complexities of EV Electronics Packaging
Packaging companies encounter distinctive challenges when handling EVs—the delicate nature of electronic components utilized in EVs demands specialized packaging solutions. The distinct shape and size of EV parts necessitate tailor-made packaging designs to securely accommodate them.
The battery packs are generally much larger than the ones present in conventional vehicles, requiring adequate packaging to protect them from damage during travel. The rising demand for EVs also poses challenges concerning volume and scalability in the packaging industry.
The packaging material and design adopted by the companies are finalized, with considerations for the size, weight, and unique shape of the electric car’s battery. Instead of using conventional materials and simple designs, modern manufacturers use specialized types of packaging for the electronics of these novel automobiles. The packaging consists of thermally insulated foam, specialized custom containers, and additional supplementary cushioning for protection against excessive force.
To reduce the carbon footprint and emission of harmful gases, packaging companies are focusing on developing strategies that minimize waste products and reduce carbon dioxide (CO2) production. This is evident by the use of biodegradable packaging material and the optimization of conventional manufacturing processes.
How Does Battery Thermal Management System Improve Thermal Performance?
Lithium-ion batteries (LIBs) are extensively used to power modern electric cars. When an EV operates, the temperatures of the electronic components and batteries increase, requiring careful monitoring and maintenance. This is facilitated by a specialized system called the Battery Thermal Management System (BTMS).
An article published in Batteries highlights that BTMS designs and strategies can be classified based on their working principles and the coolant material employed for heat transport. The working principle of BTMS can involve either direct transfer between the coolant and batteries or an indirect cooling system incorporated within the BTMS.
Indirect cooling is achieved by using a pipe through which heat is released. EVs also use different types of coolant materials to ensure optimum operational temperature. BTMSs may be air-cooled systems, liquid-cooled, or use phase-change materials (PCMs) as a cooling material.
Compared to other thermal management systems, a BTMS using air as a coolant is relatively simple in design and cost-effective. However, the low heat capacity of air becomes a major limitation of these systems. In contrast, a liquid-cooled BTMS utilizes a liquid with higher heat capacity than air. As an alternative, PCMs, particularly those based on paraffin, have been developed to enhance heat capacity and are widely recommended for cooling electric vehicle batteries.
BTMS based on PCMs exhibits high efficiency and stable performance, especially under extreme conditions. This is attributed to the PCM's capacity to store heat during the phase change process. However, it is important to note that PCM materials typically have low heat conductivity. The PCM must also undergo a regeneration process after being fully melted to maintain its effectiveness.
Thermal Control of EV Power Electronics: Impact of Additive Manufacturing
The thermal management solution's design influences the reliability and power density of power electronics (PEs). In the evolving landscape of the EV industry, which strives for increased efficiency and output power, the cooling system must efficiently handle the excess heat generated in PEs.
According to an article published in IEEE Transactions on Transportation Electrification, indirect, direct, and double-sided cooling methods are prevalent in EVs, constituting 14 % to 33 % of the total volume of traction inverters. However, as the packaging sizes of PEs are anticipated to decrease, the challenge of dissipating increasing heat persists. Ongoing research is therefore focused on exploring advanced cooling technologies.
Power semiconductor devices serve as pivotal components in the PE systems of EVs. Elevated temperatures can induce undesirable alterations in material properties, and the mechanical stresses arising from high transient temperatures or thermal cycling may lead to mechanical failures or fatigue. Selecting suitable packaging materials plays a crucial role in preventing these failures.
Breakthroughs in the domain of additive manufacturing have enabled the companies to redesign the heat sinks, leading to significant improvements in the thermal performance of EVs. The automobile manufacturer Toyota has used additive manufacturing to develop fins made using 3D printing, resulting in improved outward heat flow.
Advanced cooling techniques, like air jet impingement, have additionally been incorporated. Additive manufacturing has also been applied to produce microchannel heat sinks to achieve superior thermal performance.
Polyurethane (PU) Foam Packaging: Enhancing EV Electronics
Polyurethane (PU) foam has recently been used in packaging electronic components of EVs. The lightweight nature of the foam packaging is a significant advantage, as the EV batteries are already heavy. Thus, using PU foam leads to considerable weight savings compared to traditional packaging materials.
PU foam has been used in various studies, demonstrating superior thermal attributes. It enables an efficient heat flow from the source to the sink, ensuring an optimum temperature is maintained when the vehicle operates. When a stable and optimum operational temperature is sustained, it minimizes the damage caused to the batteries and improves the durability of electronic components. Moisture cannot pass through this packaging, ensuring the components are safe and working correctly.
Novel Material Barriers and Packaging for Thermal Runaway Management
LIB thermal runaways can arise from mechanical and thermal stresses, potentially leading to severe collateral damage, fires, or explosions. To address this issue, a novel approach (published in the International Journal of Heat and Mass Transfer) involves using a "smart" nonwoven electrospun separator packaging with thermal-triggered flame-retardant properties for LIBs.
Triphenyl phosphate (TPP) is added to the separator, and during a thermal runaway event, the protective polymer shell melts due to increased temperatures. This melting triggers the release of the flame-retardant TPP, effectively suppressing the combustion of highly flammable electrolytes.
Another innovative solution involves incorporating a fast and reversible thermo-responsive polymer switching material inside batteries to prevent thermal runaway. This material comprises electrochemically stable graphene-coated spiky nickel nanoparticles mixed in a polymer matrix with a high thermal expansion coefficient. Batteries equipped with this self-regulating material within the electrode can swiftly shut down under abnormal conditions, such as overheating and short circuits. Importantly, these batteries can resume their normal function once the abnormal conditions are addressed, without compromising performance.
The packaging of electronic components and batteries in EVs plays a crucial role in ensuring the safety and durability of the components. Advances in materials science and the use of interdisciplinary technologies, such as artificial intelligence, are ensuring improved thermal management systems and better packaging designs.
More from AZoM: How can We Characterize a Lithium-Ion Battery with FIB-SIMS?
References and Further Reading
Anchor Bay Packaging Corporation. (2023). EV Parts & Battery Packaging. [Online] Anchor Bay Packaging Corporation. Available at: https://www.anchorbaypackaging.com/ev-battery-packaging/ [Accessed 17 February 2024].
Thanalertkultorn, P. (2023). Polyurethane (PU) foam for battery packaging in electric vehicles (EVs). [Online] LinkedIn. Available at: https://www.linkedin.com/pulse/polyurethane-pu-foam-battery-packaging-electric-evs-thanalertkultorn-xfhvc/ [Accessed 18 February 2024].
Widyantara, RD., et al. (2022). Review on Battery Packing Design Strategies for Superior Thermal Management in Electric Vehicles. Batteries. doi.org/10.3390/batteries8120287
Jones-Jackson, S. et al. (2022). Overview of current thermal management of automotive power electronics for traction purposes and future directions. IEEE Transactions on Transportation Electrification. doi.org/10.1109/TTE.2022.3147976
Lin, J. et al. (2021). A review on recent progress, challenges and perspective of battery thermal management system. International Journal of Heat and Mass Transfer. doi.org/10.1016/j.ijheatmasstransfer.2020.120834
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