Lithium hexafluorophosphate is an inorganic compound with the formula LiPF<sub>6</sub>. It is a white crystalline powder.
LiPF<sub>6</sub> is manufactured by reacting phosphorus pentachloride with hydrogen fluoride and lithium fluoride
The salt is relatively stable thermally, but loses 50% weight at 200 ðC (392 ðF). It hydrolyzes near 70 ðC (158 ðF) according to the following equation forming highly toxic HF gas:
Owing to the Lewis acidity of the Li<sup>+</sup> ions, LiPF<sub>6</sub> also catalyses the tetrahydropyranylation of tertiary alcohols.
In lithium-ion batteries, LiPF<sub>6</sub> reacts with Li<sub>2</sub>CO<sub>3</sub>, which may be catalysed by small amounts of HF:
The main use of LiPF<sub>6</sub> is in commercial secondary batteries, an application that exploits its high solubility in polar aprotic 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 takes advantage of the inertness of the hexafluorophosphate anion toward strong reducing agents, such as lithium metal, as well as of the ability of [PF6-] to passivate the positive aluminium current collector.