lithium difluorophosphate is a compound used in lithium-ion batteries. This product is a high-purity, nontoxic chemical that has a low melting point, making it easy to handle. It can also be used as a chemical intermediate and is widely used in electronics, medical devices, and electric vehicles. The growing demand for electric vehicles is expected to drive market growth over the forecast period.

The synthesis of lithium difluorophosphate can be done by reacting hexafluorophosphate with ammonium fluoride or sodium chloride. Both reactions are thermodynamically driven by the evolution of carbon dioxide gas, and produce water as a by-product. Reaction (7) is best performed in a sealed pressure tube with a high-temperature oven. However, this reaction is not feasible for lab scale applications because of the large number of equipment required to perform this operation.

A simpler, safer method for the synthesis of lithium difluorophosphate was developed that uses a low-pressure high energy ball mill and does not require an oven. The hexafluorophosphate and sodium chloride were added to a milling vial, and the mixture was milled for 2, 6, or 13 h. Unlike the sealed-tube synthesis, this method did not produce any hydrolysis of hexafluorophosphate to form difluorophosphate and produced only a small amount of unwanted monofluorophosphate salt (PO3F2) by-product.

The resulting NaFO was tested in lithium-ion cells and displayed excellent performance as an additive to inhibit dendrite formation. The long-term cycling data exhibited that cells cycled with NaFO had similar cell performance to those of cells with LFO or MAFO, and were only slightly less efficient than the control cells. This performance was maintained after exposing the cells to a higher upper cut-off voltage (4 V).