Oxalate fluoride

An oxalate fluoride is a mixed anion compound contains both oxalate and fluoride anions. Many of these compounds have high birefringence.
With nonmetals, some are related to the oxalatophosphates and oxalatoborates with the addition of fluoride.

Formation

For some metal oxalate complexes, fluoride can displace some oxalate. This happens with aluminium.
With gallium the reverse happens, and oxalate displaces fluoride ligands.

Use

Difluorooxalaotoborates are under investigation as electrolytes, or electrolyte additives in lithium ion batteries or supercapacitors. Their advantage is greater thermal stability, up to 200 or 300 °C, ability to form ionic liquids, and for supercapacitors, support for higher voltages.