Researchers at the MEET Battery Research Center at the University of Münster have reported that the additive lithium difluorophosphate, or DFP, can improve new electrolyte formulations for high-voltage battery applications. The team studied how different concentrations of fluoroethylene carbonate, or FEC, combined with DFP performed during long-term cycling tests, with a focus on reducing degradation inside battery cells and limiting capacity loss.
The study builds on earlier work from the same group. In that research, the scientists found that electrolytes containing similar amounts of ethylene carbonate, or EC, and FEC performed worse in high-voltage cells than the conventional electrolyte blend of EC and ethyl methyl carbonate. They also observed that replacing EC entirely with FEC led to much better performance, regardless of voltage. The new study asked whether EC and FEC could still be used together as cosolvents if DFP was added.
According to the researchers, DFP is typically used to prevent the dissolution of transition metals. In this work, the additive showed a synergistic effect with FEC and also helped reduce electrolyte decomposition. As a result, the EC and FEC combination became viable again, and in their tests it even outperformed the standard EC- and ethyl methyl carbonate-based electrolyte.
To better understand the aging process, the researchers used instrumental analysis to identify the products formed during cycling. Their analysis showed that decomposition products from FEC and DFP helped offset the negative effects seen in the EC-FEC-only formulation. The team said this provides a clearer picture of how the two electrolyte components interact and why the combination works more effectively with the additive.
The authors said these mechanistic insights are important for designing targeted electrolyte formulations and improving the long-term performance of battery cells in high-voltage applications. The study was published by Nick Fehlings, Alexandros Tsoufios, Tim Messink, Dr. Simon Wiemers-Meyer, Dr. Sascha Nowak, and Prof. Dr. Martin Winter in the journal Small Methods.
Source: Small Methods
