Electromobility is transforming industry. Millions of battery cells are produced. Each and every one must be sealed. Absolutely sealed. Electrolyte leakage can destroy the cell. Or worse: cause a fire. Sealing coating for batteries is therefore a critical element of cell production.

And it is not only about sealing. Coatings in modern battery cells fulfill several functions at the same time. They seal. They electrically insulate. They improve assembly. They protect against corrosion. All of this in a very confined space and under extreme requirements.

Why batteries impose special requirements

A lithium-ion battery is a chemical reactor. Inside are highly reactive substances. The electrolyte is flammable. The electrodes operate under voltage. All of this in a hermetically sealed housing. Seals must function under these conditions.

• Chemical resistance. The electrolyte attacks many materials. The coating must be resistant to it. Over the entire service life of the battery.
• Temperature resistance. Batteries get hot. During charging. During discharging. Especially during fast charging. The coating must withstand temperatures from minus 40 to plus 80 degrees and beyond.
• Electrical insulation. Short circuits are dangerous. The coating must electrically insulate where required. Reliably. Even at high humidity.
• Long-term stability. A vehicle battery is expected to last ten years or longer. The coating must not fail during this period. No aging. No embrittlement. No cracking.
• Hermetic sealing. No electrolyte may leak. No moisture may enter. The sealing requirements are extremely high.

Which functions the coating fulfills

Coating for battery components is multifunctional. Depending on the component and its position, it performs different tasks.

• The primary function for sealing components. Electrolyte stays in, moisture stays out.
• Electrical insulation. Between housing and terminal, between positive and negative. Wherever short circuits must be prevented.
• Seals must be assembled. A low-friction coating facilitates press-fitting and prevents damage.
• Metal parts are susceptible to corrosion. The coating protects against oxidation and contact corrosion.
• Elastomer seals tend to stick. A coating prevents this and enables automated feeding.

Which components are coated

In a battery cell and in the battery pack, numerous components benefit from a functional coating.

• The feedthrough of the terminals through the housing must be absolutely sealed. Highly precise seals are used here.
• Safety valves release gas in the event of overpressure. The seal must close reliably, but open safely in an emergency.
• Housing seals. The lid must seal tightly on the housing. For prismatic cells, often a circumferential seal.
• Insulating rings and insulating washers. Separate conductive parts from each other. Prevent short circuits within the cell.
• Cell connector seals. In the battery pack, busbars connect the individual cells. The feedthroughs must be sealed.
• Cooling system seals. Liquid cooling requires leak-tight connections. Coolant must not come into contact with electronics.

Most of these components are mass small parts. They are manufactured in very large quantities. An electric vehicle contains thousands of such components. Efficient coating is therefore essential.

Which materials are used in batteries

Sealing components are made of different materials. Each imposes its own requirements on the coating.

EPDM. The standard for many sealing applications. Good temperature resistance, but limited resistance to certain electrolytes. Coats well.

FKM/Viton. Fluoroelastomer for maximum chemical resistance. More expensive than EPDM, but indispensable in critical applications. Coating requires specialized adhesion promotion.

Silicone. High temperature resistance and good electrical insulation properties. Soft and flexible. Challenging to coat.

PTFE. Nearly chemically inert. Excellent low-friction properties. Often used as a coating material itself.

Plastics such as PA, PBT, or PPS. For insulating parts and structural components. Coatable with suitable adhesion promoters.

Metals such as aluminum and steel. For housings, terminals, and structural parts. Coating for corrosion protection or electrical insulation.

Coating battery components in the drum process

Drum coating is ideal for mass production of battery components. Sealing coating for batteries is carried out efficiently and reproducibly.

In the SC-Coater®, the seals are processed as bulk material. They are gently heated and sprayed with the functional coating. Rotation ensures uniform distribution. Each part is fully coated. Process parameters are precisely controlled.

• High volumes. Millions of parts per year are feasible. Capacities grow with the electromobility market.
• Consistent quality. Automated processes ensure reproducible results. Batch after batch.
• Defined coating thicknesses. Coating thickness affects function and dimensions. It is precisely set and controlled.
• Gentle processing. Elastomers are sensitive. Low process temperatures protect the material.
• 95 percent coating efficiency means minimal material loss. This reduces costs and conserves resources.

All details about the process can be found on our page about contract coating.

Quality requirements of the automotive industry

The automotive industry places the highest demands on quality and traceability. This is especially true for safety-relevant components such as battery seals.

Process capability. Coating processes must be statistically controlled. Cpk values of 1.33 or higher are required.

Traceability. Each batch must be documented. Material, process parameters, test results. Complete.

Incoming goods inspection. Sampling inspections according to AQL or zero-defect strategies. Requirements are defined in the specification.

Cleanliness. Technical cleanliness is critical in battery production. Particles can cause short circuits. The coating must not introduce contamination.

Our processes in the area of functional surfaces are designed to meet these requirements.

From prototype to series production

Developing a new battery generation takes years. The coating must be considered from the outset. We support our customers through all phases.

In the concept phase, we clarify requirements. What function should the coating perform? Which materials are used? What volumes are planned? On this basis, we develop a proposal for the coating system.

In the sampling phase, we coat prototypes and pre-series parts. They are tested, assembled into cells, and evaluated under real conditions. Feedback is incorporated into optimization.

After approval, we start series production. The approved samples define the standard. Each batch is tested and documented. This ensures consistent quality over the entire production period.

Special Coatings can, upon request, handle the complete project planning. From material selection to sampling to series delivery.

Coatings for the mobility of tomorrow

Sealing coating for batteries is an invisible but indispensable element of electromobility. It ensures that batteries operate safely. For years. Under extreme conditions. Without compromise.

Electromobility is growing rapidly. Demand for coated battery components is increasing. With our experience in functional coating and our capacity for large volumes, we are prepared for this growth. As a partner to the automotive industry. As a specialist for mass small parts.

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Frequently asked questions

Which functions does a sealing coating fulfill in batteries?

The coating can perform multiple functions: sealing against electrolyte leakage, electrical insulation, friction reduction for easier assembly, corrosion protection, and prevention of sticking during automated feeding.

Which components in batteries are coated?

Typical components include terminal seals, valve seals, housing seals, insulating rings and washers, cell connector seals, and cooling system seals. Most of these are mass small parts.

Which materials can be coated?

All common sealing materials: EPDM, FKM/Viton, silicone, as well as plastics such as PA, PBT, or PPS. Metal parts made of aluminum or steel can also be functionally coated. The coating system is tailored to the respective material.

How are automotive industry quality requirements met?

Through statistically controlled processes, complete documentation and traceability, defined test plans, and compliance with technical cleanliness requirements. Specific requirements are agreed in the specification.

Can large volumes be processed?

Yes. Drum coating is designed for mass production. Millions of parts per year are feasible. Capacities are expanded in line with the market growth of electromobility.

How long does it take from inquiry to series production?

That depends on complexity. Simple applications can be brought to series production within a few weeks. For new developments with extensive sampling and approval processes, it takes correspondingly longer. A realistic timeline is created after the initial project discussion.