Glass separators for Li-ion batteries

Safe high-tech batteries for electric cars

3. März 2021, 14:26 Uhr | Irina Hübner
Ultradünner Glas-Separator für Li-Ionen-Batterien.
The glass separator for lithium-ion batteries developed at the University of Bayreuth. For large-scale use, the thickness must be significantly reduced again.
© UBT/Uli Schadeck

The operational reliability of lithium-ion batteries depends crucially on separators that ensure spatial separation of the electrodes. In a joint project, the University of Bayreuth will develop novel separators made of glass together with several industrial partners.

The joint project »Glass separators for lithium-ion batteries (GlasSeLIB)« aims to further increase the safety of high-tech batteries and at the same time extend their service life. It starts on March 1 and will be funded by the Bavarian Research Foundation with more than 375,000 euros over the next three years.

The new separators envisaged are filigree glass membranes. In contrast to previous separators, they are expected to have excellent temperature resistance up to at least 500 °C. With their help, it will be possible to produce a new type of separator. With their help, it will be possible to further increase the operational reliability of batteries in electric vehicles, laptops, smartphones and numerous other high-tech applications. At the same time, the new separators are expected to slow down the aging of battery cells.

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Glass composition with high chemical activity

For this purpose, a special glass composition must be developed that is characterized by high chemical activity. However, these advantages can only be achieved if it is possible to manufacture particularly thin membranes of less than 20 µm. This is a manufacturing challenge, but one that is imperative to ensure that the operational reliability of batteries increases or at least is maintained if battery performance - for example, storage capacity - becomes significantly higher in the future.

To ensure that the glass membranes developed in Bayreuth actually meet the requirements placed on them, they are tested in the laboratories of the industrial partners Varta and Tesla. »The close cooperation in the joint project is aimed at ensuring that in three years we will have novel separators that guarantee the operationally reliable use of lithium-ion batteries in high-tech electronics,« says project leader Prof Dr.-Ing. Thorsten Gerdes from Keylab Glastechnologie.

Until now, microporous polymer films have generally been used as separators in lithium-ion batteries. They quickly become unstable when the cell overheats. In addition, their ionic conductivity in the electrolyte is low. In order to further extend the useful life of portable terminals or increase the ranges of electric vehicles, battery cell manufacturers are now forced to increase the proportion of chemically active materials and reduce the proportion of chemically passive materials. This is problematic, however, if - as in the case of the polymer films - safety-relevant materials are involved. However, the resulting risks can be avoided from the outset if thin glass membranes replace the polymer films.

The coordinator of the joint project is the KeyLab Glass Technology at the University of Bayreuth, which is based at the Chair of Ceramic Materials. Research partners are the Chair of Materials Process Engineering at the University of Bayreuth and four companies: Füller Glastechnologie, Vitrulan Glass Textile, Varta Microbattery and Tesla Germany at the Munich site. The research work is carried out in close cooperation with the Bavarian Center for Battery Technology (BayBatt), a central scientific institution of the University of Bayreuth.

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