Gas-Tight Foil As a Low-Cost Alternative to Metal Membranes for Immersion-Cooled Batteries

Immersion-cooled batteries are gaining more importance when it comes to fast charging, high performance and modular battery design. This is also a challenge for emergency degassing. Which materials and designs are suitable for asymmetric pressures? Negative pressure during filling, high working pressure, even higher burst pressure. At the same time, the component should have a very low overall height. Ideally suitable for modular applications. Particular importance is attached to accelerations in the X, Y and Z directions. A good solution are gas-tight membranes.

Gas-tight membranes are made of different materials. In the case of membranes made of metal or plastic, predetermined breaking points are required for opening at a defined overpressure. This requires additional processing steps and here the diaphragm thicknesses are most often weakened to the previously calculated material thickness by means of a laser. The media resistance can be impaired especially at these tapers, and the tolerances are also subject to large fluctuations. This effect is more pronounced with plastics than with metals. Especially if the IPx7 test (1 metre water column) is to be passed. If this type of diaphragm is to be used in liquid-cooled batteries, this “predetermined breaking point” is heavily stressed, since the filling vacuum of over 1 bar is usually far above the bursting pressure. End-of-line testing during the production process is also difficult. A gas-tight PET membrane provides a remedy here. Konzelmann’s engineers have developed alternative gas-tight bursting rings made of plastic. A simple component? Not at all. In contrast to common membranes, e.g. made of PTFE, a PET membrane has no fibre or sponge structure. Thanks to the back-injection technology in combination with a special embossing, the injected plastic binds the membrane securely in the hybrid composite. An innovative rupture sensor can be designed in such a way that the membrane can withstand the high filling vacuum on the one hand and allow a low bursting pressure on the other. Ultimately, a plastic ring is married with a diaphragm in a single process step. Another advantage is the simple 100% end-of-line testing by means of air pressure and optics. Due to the simple design and the low cycle rate, very large quantities can therefore be produced.