Project reference: Pressure-stable lid for cylindrical cell with liquefied gas electrolyte

New electrolyte chemistry from South 8 Technologies

South 8 Technologies was founded in 2016 as a spin-out from the University of UC San Diego in California. South 8 is developing the patented Liquefied Gas (LiGas®) Electrolyte technology for lithium ion batteries. This technology is now to be commercialized with the help of funding from the investment firm Anzu Partners and a group of well-known co-investors in the amount of 12 million US dollars.

Cell housing: Customized lid for standard cell can

South 8 intends to use its gaseous electrolyte in cylindrical cells, initially in the 18650 format. While conventional cell cans are robust enough to handle the pressure requirements, the special challenge is to develop a fitting lid for the prefabricated cell can that can withstand the particularly high pressure of a gaseous electrolyte. A classic lid with a crimp connection is unsuitable for this purpose. The specially designed lid was appropriate for the production of first prototypes, but proved to be too heavy for mass production and therefore not applicable. The concrete task for EAS Batteries in this service project is now to develop a lid with a maximum height of 5 millimeters that is as light as possible.

Cylindrical cell design - fast and reliable

The application of the LiGas® electrolyte in a cylindrical cell requires in particular the EAS core competence of developing round cells. South 8 entrusted EAS with the conception, design and implementation of the customized lid in the form of a prototype, as the EAS cell development team is able to implement the desired solution very quickly and reliably due to its know-how and expertise. The second top competence on the behalf of EAS, which is essential for the development of the South-8 cell lid, is the good networking with suppliers of cell components. Despite the worldwide supply bottlenecks, EAS has the desired raw material from Germany and Europe available in time for lid production.

Design, process adaptation, prototype production and testing

After fine-tuning the targets with South 8, EAS started to design the cell lid with regard to the special requirement for pressure stability and under consideration of the demanding material selection with regard to compatibility with the electrolyte LiGas®. First, the cell developers determined all the necessary parameters of the future application, adapted the thickness of the lid to the wall thickness of the standardized cell can, and calculated a modified shape that ensures that the lid can be welded in easily and in a space-saving manner - without the heat generated by this process step damaging the separator. From the CAD models and the drawings derived from them, EAS had all the necessary parts manufactured, assembled and tested in various stages.

Logo South 8 Technologies

Further added value: precondition for higher energy density created

EAS Batteries successfully developed the cell lid for South-8-Technologies. EAS has not only met but exceeded the target specifications of the cell lid. The lid weighs only 2.35 grams, it is 4.2 millimeters high and the weld seam withstands internal pressures of more than 120 bar, well above the desired venting pressure of the lid. The reduced weight, in particular, brings crucial added value to the future South 8 cell: the energy density of the planned South 8 cell in 18650 format increases significantly. In addition, the design concept of the cell lid is transferable to other cell formats planned by South 8, such as a 21700 cell or a 46XXX format.


"The result of our collaboration with EAS Batteries has far exceeded our expectations. Thanks to EAS, our first cell even starts with a significantly better energy density than originally targeted. And this added value continues for us in every upcoming cell format. In addition, EAS has proven to be an extremely reliable partner and service provider. Despite the worldwide supply bottlenecks, EAS delivered on time and on budget with a high degree of initiative. Excellent!" Cyrus Rustomji, CEO South 8 Technologies