Pressure Sensitive Adhesives in EV Batteries

Commonly used in end-of-line packaging, pressure sensitive adhesives (PSAs) are quickly moving into electric vehicle (EV) battery production. The hot melt materials offer the adhesion and flexibility needed for cell to pack and pouch cell lamination applications.

In order to be dispensed, PSAs need to be melted down. Traditional hot melt systems work like slow cookers, melting material from the outside in. When melted adhesive sits for extended periods of time, charring occurs. Charring causes adhesive degradation, inconsistent application, plugged lines, bad thermal conductivity and safety concerns.  

Simply put, equipment used to glue cartons shut does not work well for sealing battery packs. EV production requires much more precision and data control than end-of-line packaging.

Equipment used to apply pressure sensitive and other hot melt adhesives in EV batteries needs to:

• melt material on demand, preventing charring
• come equipped with closed loop control and data tracking
• integrate with programmable logic control (PLC) and robotic applicators

Use these five questions to identify the right hot melt equipment for your EV battery line:

1. Can it track system performance?
2. How does it save money?
3. Can you depend on it for consistent quality?
4. How much maintenance is required?
5. How safe is the system for equipment operators?

The ability to monitor critical metrics, such as temperature, production levels and adhesive usage,  creates repeatability and raises overall efficiency.

To further boost system performance, ask for remote monitoring. Getting real-time updates on a smart phone, tablet, or computer can help you make quick adjustments now before something becomes a problem later.

It is critical your equipment can integrate into either a robotic or gantry style production process. The availability of a communications gateway module (CGM) that connects to Ethernet IP or Profinet (for example) is also integral to process control.

A good hot melt system can provide operational savings in these areas:

• Time savings: Heating adhesives before dispense, takes time. The time needed to get your system up and running depends on the size of the reservoir and its melting surface. Hot melt tank systems with high material volume start up much more slowly than an on-demand hot melt system that heats only what your production throughput requires.
• Maintenance savings: Adhesive charred inside a hot melt tank, hose, or applicator causes unplanned maintenance – and downtime. Choosing a system that melts enough pressure sensitive adhesive (PSA) only when you need it, almost eliminates charring and related maintenance costs.
• Material savings and quality control: Changes in material viscosity can change the flow rate and lead to over application, wasting adhesive and damaging quality. Bead sizes that are slightly off affect an EV battery’s thermal conductivity and weight. 

Consistent quality relies on how pressure sensitive adhesive (PSA) is handled from the melter to the applicator or nozzle. Hot melt equipment with closed loop control can assure that the material stays at the desired temperature and viscosity for ideal dispense.

Closed loop control can also prevent the two top causes of inconsistent PSA quality: char and thermal shock.

• When char forms, it blocks the melting system, hose, or nozzle, resulting in unpredictable bead dispense. 
• Thermal shock happens when unmelted pellets are added to molten material. This changes viscosity, causing poor adhesive performance and inconsistent dispense. 

Charring typically happens when a system is keeping pressure sensitive adhesive (PSA) heated for a long time. Charred material sticks to the sides of the tank, hoses, applicators and nozzles, causing blockages that need to be cleaned.

Cleaning out char can shut down EV battery production for anywhere from 30 minutes to hours (if full system shut-down, plus reheating the system to temperature, is needed).

Melt-on-demand equipment eliminates charring by heating only the amount of adhesive needed when it’s needed. This also speeds warm-up time; you could be up and running in as little as 15 minutes.

Working with manual hot melt systems is dangerous. While refilling the tanks, operators come in close proximity to the melted adhesive, putting them at risk of severe burns and inhaling toxic fumes.

Automatic adhesive feeds transfer new material as needed, eliminating the need for an operator to ever come in contact with hot adhesive hazards.