Lithium hexafluorophosphate
Lithium hexafluorophosphate is an inorganic compound with the formula LiPF6. It is a white crystalline powder. It is used in commercial secondary batteries, an application that exploits its high solubility in non aqueous, polar solvents. Specifically, solutions of lithium hexafluorophosphate in carbonate blends of ethylene carbonate, dimethyl carbonate, diethyl carbonate and/or ethyl methyl carbonate, with a small amount of one or many additives such as fluoroethylene carbonate and vinylene carbonate, serve as state-of-the-art electrolytes in lithium-ion batteries. This application also exploits the inertness of the hexafluorophosphate anion toward strong reducing agents, such as lithium metal.
The salt is relatively stable thermally, but loses 50% weight at 200 °C. It hydrolyzes near 70 °C according to the following equation forming highly toxic HF gas:
Owing to the Lewis acidity of the Li+ ions, LiPF6 also catalyses the tetrahydropyranylation of tertiary alcohols.
In lithium-ion batteries, LiPF6 reacts with Li2CO3, which may be catalysed by small amounts of HF:
