Application of Three Types of Sealants in New Energy Vehicle Batteries

　　Currently, the use of automobiles is increasing day by day. New energy electric vehicles represent a mainstream trend in addressing issues related to energy, the environment, and urban transportation, and they also constitute a primary direction for the future development of the automotive industry. However, the safety of new energy vehicles is increasingly attracting widespread attention from everyone.
　　With the rapid development of new energy vehicles, reports of fires involving these vehicles have become increasingly common. The safety of new energy vehicles is attracting growing public attention.
　　As the power source of new energy vehicles, power battery failures are a major cause of safety concerns; approximately 80% of all faults in new energy vehicles originate from the power battery.

　　The investigation found that there are several factors contributing to battery failures:
　　Battery leakage;
　　Local short circuit;
　　Insulation damaged.

　　When a battery is subjected to external impact or experiences excessive charge/discharge that leads to heat buildup, the aforementioned issues may arise, potentially causing fire and explosion accidents.

　　 Solution:
　　Sealants possess excellent performance; to address safety concerns in power batteries, it is necessary to take a comprehensive approach that considers collision and vibration resistance, flame retardancy, thermal conductivity, and waterproofing.
　　Impact and Shock Resistance: Since the cells and other internal components of the battery are not securely fixed, they can easily deform or shift upon impact, leading to short circuits and electrolyte leakage.
　　Flame Retardancy: The battery contains multiple cells; if one cell catches fire, it can ignite the others. Flame‑retardant treatment can effectively reduce the likelihood of fires.
　　Thermal Conductivity: The internal structure of power batteries is highly concentrated, with high power and significant heat generation. However, air has a low thermal conductivity, making it easy for heat to accumulate and leading to reduced battery life.
　　Waterproofing: Once moisture enters the interior of a power battery, it can lead to electrolyte degradation and even cause short circuits.

　　 Three Types of Sealants Used in Batteries

　　There are three types of sealing adhesives for power batteries:
　　Acrylic sealant;
　　Epoxy sealant;
　　Organosilicon sealant.

　 　Acrylic sealant

　　Advantages of acrylic sealant:
　　High bonding strength, up to 20 MPa.
　　Wide range of applicable substrates: metals and nonmetals
　　Fast room-temperature curing: 315 min
　　Resistant to a certain degree of impact.
　　The operating temperature should not exceed 120°C.

　　Acrylic sealant applications in batteries:

　　The cylindrical battery is bonded and secured to the base.
　　Adhesive sealing of the terminal posts.

　　 Epoxy sealant
　　Advantages of epoxy sealant:
　　High bonding strength, 5–20 MPa.
　　Wide range of applicable substrates: ceramics, metals, glass, plastics, rubber, paper, fabric, and more.
　　Cures quickly at room temperature.
　　Resistant to a certain degree of impact.
　　Operating temperature: -30–120°C.
　　Epoxy sealant in battery applications: Used for bonding and securing the cells together.

　　 Organosilicone sealant
　　Advantages of silicone sealants: Silicone is a polymer material whose main chain consists of Si–O linkages.
　　It exhibits excellent resistance to high and low temperatures (60–260°C).
　　Good weather resistance.
　　Electrical insulation (volume resistivity up to 1 × 10¹⁴ Ω·cm).
　　After curing, it becomes an elastomer with excellent shock absorption and impact resistance.
　　The thermal conductivity reaches 0.203 W/m·K (compared to 0.023 W/m·K for air), and the thermal conductivity can be significantly increased after adding thermal conductive fillers.
　　It exhibits excellent flame retardancy. The combustion temperature is approximately 430°C, while the flame temperature reaches 750°C. After burning, it forms SiO₂ with no corrosive gases produced. When flame‑retardant fillers are added, it can achieve a V-0 flame‑retardant rating. Testing method: The sample undergoes two 10‑second burn tests; the flame must be extinguished within 30 seconds, and no burning materials should fall off. Once a single cell catches fire, it can effectively prevent adjacent cells from igniting.
　　It exhibits excellent water vapor permeability resistance. After being sealed with organic silicone sealant, the PAcK can pass the IP67 waterproof test. Test method: Completely immerse the sealed PAcK in a water tank, ensuring the top is 0.15–1 meter below the water surface, and maintain continuous immersion for 30 minutes. No changes in performance are observed, and no water enters the interior of the PAcK. This effectively prevents water vapor from penetrating the battery.
　　It exhibits excellent thermal conductivity, with a thermal conductivity coefficient reaching 0.2–0.3 W/m·K (compared to air’s 0.023 W/m·K). After adding thermally conductive fillers, the thermal conductivity can be significantly enhanced. It can effectively transfer the heat generated inside the battery to the surface, reducing heat buildup and extending battery life. Organic silicone sealants possess outstanding performance, meeting the requirements for shock resistance, waterproofing, flame retardancy, and thermal conductivity in power batteries, while also ensuring reliable operation under various climatic conditions—thereby effectively enhancing the safety of power batteries.

　　Application of Organic Silicone Sealants in Batteries:
　　Battery PACK frame sealing.
　　Battery bonding and fixing.
　　Sealed and fixed internal components.
　　Encapsulation inside power batteries.