Comparing Seal Materials: When should I use aluminum or PE seals?
The battery test cells in the PAT series are characterized by their high impermeability to the outside atmosphere. This increases the long-term stability of the cell chemistry and enables long-term measurements over several thousand hours. (See example here.) When designing the PAT-Cell, the number of seals was reduced as much as possible to limit potential leaks. The lid seal is, therefore, crucial for the cell’s tightness. Lid seals are available in different materials. In addition to the standard seals made of PE, we also offer an aluminum version.
But when should you use which seal?
To answer this question, we tested several PAT-Cells with PE and aluminum sealing rings for approximately 400 hours and compared their results. We paid particular attention to capacity retention and coulomb efficiency.
Test setup:
- 6 PAT-Cells ( Three cells each are built with PE or Al seals.)
- Electrodes: NCM111 vs graphite
- Electrolyte: LP32
- Temperature: 25°C
- Measurement procedure used: cc-cv cycles at 0.1C
- Potentiostat: PAT-Tester-i-16
Test results:
The evaluation of the measurement results shows that the standard PE sealing performs very well up to approx. 100 hours. Only when the test duration is extended does the impact of improved sealing with the aluminum version become evident in the results. After 400 hours, we measured an excellent Coulomb Efficiency of over 99.8% with aluminum seals compared to the 99.6% of the PE seals.
A look at the capacity retention also shows the advantages of the aluminum seal with a longer test duration. After 400 hours, it is still over 98%, while the cells with PE seals range between 97-98%.
Our recommendation and final thoughts
The test results show excellent performance of PAT-Cells with aluminum lid seals. Therefore, we strongly recommend using metal seals, especially for long-term and all experiments in which the gas pressure is measured. For all other applications, however, the standard lid seal made of PE is still a very good choice, performing very similarly in experiments with shorter durations.
What must be considered with aluminum seals?
- Compatible cell lids: Special insulated metal seal lids are required for aluminum seals. Many cells are equipped with these ex-works; an overview can be found below.
- Care during installation: Metal seals are very sensitive. During installation, damage to the sealing rings and impurities must be avoided at all costs. Even a single human hair can severely impair the seal.
- Special installation tool: A torque wrench is required to close a PAT-Cell with an installed aluminum seal.
Which PAT-Cells are compatible?
The following PAT-Cells are factory-fitted with a cell lid that is suitable for aluminum seals:
The corresponding metal seal lids can be retrofitted for all other PAT-Cell models or older cells. Of course, the required tools are also available here.
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