Linzers free lithium batteries from toxins

The basic building block of the new cathode binder is a substance made from castor oil from the tropical castor oil, as Klaus Bretterbauer and Felix Leibetseder from the Institute for Chemical Technology of Organic Substances at the Johannes Kepler University Linz explain in the journal “Advanced Energy Materials”. It is called “11-aminoundecanoic acid” and is linked in long polymer chains.

“The binder acts as a glue that holds the materials to the current collector,” says Leibetseder: “This prevents literally everything in the battery from falling apart during charging and discharging. The new binder adheres approximately ten times better to the aluminum foils that act as a current collector in such batteries than conventional polyvinylidene fluoride (PVDF, note),” explains Bretterbauer.

This significantly reduces the chance of a battery failing due to the electrode becoming detached from the current collector.

Free from toxic chemicals and water soluble
The common material PVDF and the processing aids contained therein also belong to the per- and polyfluoroalkyl compounds, or PFAS for short, which are increasingly being banned in the European Union due to their many harmful effects on health. To use PVDF to produce electrons, a solvent called N-methyl-2-pyrrolidone (NMP) is also used, which is known to reduce fertility.

“Our binder is fluorine-free and water-soluble,” says Bretterbauer. “This has the advantage that you can use water instead of NMP during production.” So there would be no health risk to production staff and no toxic waste would be generated. Water as a solvent can also be removed at lower temperatures than NMP, meaning less energy is required to produce the electrode.

More recyclable
Finally, the material can also be easily recovered when the battery life is at the end because it is water soluble. “This is why the rare, critical raw materials such as lithium, manganese and cobalt from the batteries are more easily accessible for recovery,” Bretterbauer explains. “Batteries containing PFAS, on the other hand, are difficult to recycle and pose a major risk to the environment, mainly due to their toxicity.”

“All in all, our approach is a lot more environmentally friendly,” says the researcher. On the other side of the battery, near the anode, replacements for harmful substances were found some time ago. “On the positive side, we have now been able to develop a material that is harmless, comes from a renewable raw material that does not compete with food production and that also has better adhesion than the material currently used.”

Can be used in different ways
The researchers see no restrictions on the use of the new binder. The material, developed from basic research to prototypes at the University of Linz, could hold together the components in the batteries of mobile phones and even electric cars.

Leibetseder reported that together with Karl-Heinz Pettinger from the Landshut University of Applied Sciences (Germany), button cells with the new material and larger battery prototypes manufactured by a “chamber filling machine” are being tested. These have proven themselves so well that we are now in discussions with industrial partners.

“We hope that we can soon use them to test our prototypes to see how they behave under high demands, for example in the automotive sector,” says Bretterbauer. He is optimistic that “the new batteries can be expected in the near future.”