Benefits of Using Thermally Conductive Adhesives and Encapsulants in Li-Ion Batteries | Adhesives manufacturing company

Benefits of Using Thermally Conductive Adhesives and Encapsulants in Li-Ion Batteries

Thermally Conductive Adhesives Provide Structural Strength While Eliminating Heat

Thermal interface materials (TIMs) dissipate heat naturally generated by the Li-ion battery cells within EV battery systems. TIMs provide a thermally conductive layer between two materials, such as a cylindrical Li-ion battery cell and a cooling plate. These materials should not touch but need a way to transfer heat effectively. Using TIMs in gaps between heat sources and heat sinks enables a higher and more efficient heat flow (Figure 1).

Figure 1: Thermal interface materials improve heat flow

Most thermal interface materials (TIMs) have additional uses beyond transferring heat from cells to heat sinks. Thermally conductive structural adhesives (TCSAs), for example, not only help with heat transfer but also possess dielectric properties, which prevent electrical charges from passing between surfaces. In addition, TCSAs bond materials together and provide structural support. Given that electric vehicle (EV) batteries need both structural integrity and strong bonds to withstand the rigors of being on the road, using TCSAs as TIMs is a natural choice.

Thermally conductive adhesives adhere to a wide range of substrates, including metals, thermosets, and thermoplastics. They facilitate heat transfer from cells to cooling plates or other cooling mechanisms within the battery pack. TCSAs bond various components within a battery assembly including:

• Prismatic cells to other prismatic cells
• Pouch cells to cold plates
• Cylindrical cells to cell carriers
• Cooling grievances running between cells
• Cells to side walls
• Cold plates to the bottom of subsequent modules
• Cylindrical cells to cold plates

Figure 2: Example of thermally conductive adhesives bonding cylindrical cells to a cold plate

Encapsulants Isolate Heat Events & Provide Structure

Fires in Li-ion battery packs are rare but possible. When the battery short-circuits, overheats, or gets damaged in a collision, thermal runaway can spiral into electrolyte combustion and fires or explosions. Unlike other types of fires, Li-ion battery fires cannot be suffocated or put out by water and burn for a long period. Encapsulants play an important part in thermal management by stopping fires before they spread to other Li-ion cells and keeping battery components in place upon impact.

H.B. Fuller's patented, UL 94 V-0-rated polyurethane (PU) foam encapsulant is the first of its kind. When an individual battery cell is exposed to an open flame, the encapsulant keeps the fire from spreading to other cells. Figure 3 shows a cluster of cylindrical Li-ion battery cells encased in foam encapsulant before and after inducing thermal runaway in the center-most cell. Removing the encapsulant material reveals how well the fire in the central cell was isolated from the surrounding cells.

Figure 3: H.B. Fuller's patented foam encapsulant prevents fires from spreading between battery cells

Fires may also break out during extreme impacts, like crashes. Damage to the battery system can threaten the assembly's thermal stability. For example, if two metal components typically separated by a TIM pad shake free from their protective layer and make close contact, the heat could build quickly and start a fire. Encapsulants' semi-structural and impact-resistant properties hold battery components in place during a collision, lessening the possibility of thermal runaway initiated by undesired interactions between loose components.

Encapsulants may also play an important role in unitizing the battery assembly and protecting cells from corrosion by creating an effective barrier to the coolant solution or moisture that could be present inside a battery pack.

The encapsulant is dispensed around battery cells during assembly (Figure 4). Once it has cured, its unitizing properties also work towards maintaining a more homogeneous temperature range environment, dissipating the energy generated by the cells and ensuring a consistent internal temperature. The encapsulant also protects battery components from external environmental hazards like road salt or moisture that might penetrate the outer layers of the pack.

Figure 4: Foam encapsulant is used to pot cells which helps unitize battery packs and provides structure

Product Spotlight: EV Protect™ 5006

H.B. Fuller EV Protect 5006 can optimize the life and use of EV battery systems. The encapsulant is lightweight compared with alternative materials (1.33 pounds/gallon compared to 12.51 pounds/gallon). Less weight from the battery pack increases an EV's range. The encapsulant also has a fast dispense, cure, and cycle time. Because it expands five times its liquid state, EV Protect 5006 encapsulant requires less material than alternatives, reducing shipping and material handling costs.

Features:

• Low density makes it ultra-light-weight
• Structural properties allow manufacturers to eliminate components
• Meets UL 94 V-0
• Helps protect against NVH

Partnering for a Sustainable Future

Our team is committed to providing innovative solutions for your energy storage and battery needs. By working together, we can drive advancements in battery technologies that ensure the performance and safety of your products. For more information, download H.B. Fuller's newest e-book or email [email protected].

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