Author: Variant Energy
Summary: Upgrading to a Variant Energy pouch cell vacuum sealer significantly improved the cell-to-cell repeatability for a lithium-ion battery materials startup.
A lithium-ion battery materials startup developing a new component to help make EV battery cells lighter and cheaper had spent significant effort refining the "front end" of their prototype pouch cell build process - slurry mixing, coating, calendering, etc. using Variant Energy equipment.
While the "front end" process was optimized, they were performing the final pouch seal with a VacMaster food sealer, a common tool in energy storage research labs for its ubiquity and price point. The electrochemical testing data using the VacMaster showed a large and undesirable spread in the performance of otherwise identical cells.
Understanding the Critical Role of Vacuum Sealing
Figure 1. A completed vacuum-sealed pouch cell.
As the last step in the cell build process, vacuum sealing can be overlooked, especially when there are so many other critical steps in making a lithium-ion battery cell. The important process parameters (and possible failure modes) in pouch cell vacuum sealing include:
- Ultimate Vacuum Pressure: Adequate vacuum is necessary to enable proper electrolyte wetting and ensure a gas-free cell interior. Insufficient vacuum can leave parts of the cell electrochemically inaccessible, while excessive vacuum may cause critical electrolyte additives to evaporate, leading to mass loss.
- Vacuum Pumpdown Rate: Evacuating gas too quickly can cause the electrolyte to bubble, leading to spillage and mass loss.
- Final Heat Seal Temperature and Pressure: If the seal temperature is too high, it can irreversibly damage cell components. Conversely, a temperature that’s too low will result in an incomplete seal, leading to electrolyte leakage and moisture ingress.
- Heat Seal Location: Even with optimal pressure and temperature, incorrect seal placement can cause heat damage or allow leakage.
How Variant Energy’s Pouch Cell Vacuum Sealer Addresses These Issues
The Variant Energy pouch cell vacuum sealer offers GWh-scale process control for laboratory-scale cell prototyping:
- Vacuum Control: PLC control of all vacuum parameters, including pumpdown rate, ultimate pressure, dwell time, vent rate, and pump-purge cycles.
- Sealing Accuracy: Sealing parameters are managed with PLC control, including electronic regulation of sealing pressure, dwell time, and PID temperature control of sealing jaws.
- Reliability: Designed for repeatable and reliable operation, with recipe storage and a fixture design that ensures consistent seal location.
- Compact Design: Suitable for use in standard-depth gloveboxes.
Customer Success Story: A Transformative Upgrade
After upgrading from the VacMaster food sealer to the Variant Energy vacuum sealer, the customer repeated the cell build using identical input materials and upstream processes - only the vacuum sealer was changed.
The results were clear: the Variant Energy sealer delivered a significant improvement in capacity retention and reduced cell-to-cell variability, as demonstrated in the discharge capacity retention graph above.
Building Confidence in Battery Testing Platforms
When researching and developing novel battery components, having a stable and reliable testing platform is critical to detecting small signals in performance and making confident conclusions from your data. Significant time and money can be wasted trying to make decisions from noisy and inconsistent electrochemical data.
Contact Variant Energy today to discuss how our advanced equipment can enhance your lab-scale battery cell production.
Email: sales@variantenergy.co