Heavy Water Enables New Analyses of Aqueously Processed Cathodes
Aqueously processed cathodes for lithium ion batteries have the potential to increase the sustainability of the production process and to simplify the recycling. They do not contain critical materials such as the organic solvent N-methyl-2-pyrrolidone (NMP) and the fluorine-containing binder polyvinylidene difluoride (PVDF). These are replaced by water and a natural, fluorine-free binder such as carboxymethyl cellulose (CMC). However, the water interacts with the cathode material and modifies its structure. This reduces the lifetime of the battery cells. A team from MEET Battery Research Center at the University of Münster has now investigated where exactly the water molecules and protons settle in the material.
Heavy Water Used in the Production of Electrode Paste
For the first time, the research team used heavy water (D2O) for this purpose. “This enabled us to precisely track where protons accumulate in the material. Previous analyses had not completely clarified this process,” explains MEET scientist Joshua Engler. “By using heavy water for the electrode paste, we ensured that the detected water was definitely introduced during the production process and not, for example, by ambient air during storage.” The results help to understand the reactions within the cell in detail. This is the first step that will allow the researchers to develop approaches to avoid the structural weaknesses caused by water.
New methods such as the aqueous processing of electrodes are designed to make batteries more environmentally friendly and cost-effective. “If we could eliminate environmentally harmful materials such as NMP and PVDF in the cathodes, we could also reduce the production and recycling costs of lithium ion batteries,” Engler concludes.
Detailed Results Online Available
The entire study has been published by the authors Joshua Engler, Alexandros Tsoufios, Dr Markus Börner, Dr Simon Wiemers-Meyer and Dr Sascha Nowak, MEET Battery Research Center, as well as Prof. Dr Martin Winter, MEET Battery Research Center and Helmholtz Institute Münster of Forschungszentrum Jülich, in the journal “Advanced Energy and Sustainability Research”.