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Lithium hexafluorophosphate
Names
	IUPAC name lithium hexafluorophosphate
Identifiers
CAS Number	21324-40-3 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:172376;
ChemSpider	146939 ;
ECHA InfoCard	100.040.289
PubChem CID	23688915;
UNII	T9T8DY51J3 ;
CompTox Dashboard (EPA)	DTXSID2066698 ;
	InChI InChI=1S/F6P.Li/c1-7(2,3,4,5)6;/q-1;+1 Key: AXPLOJNSKRXQPA-UHFFFAOYSA-N ; InChI=1/F6P.Li/c1-7(2,3,4,5)6;/q-1;+1 Key: AXPLOJNSKRXQPA-UHFFFAOYAJ;
	SMILES [Li+].F[P-](F)(F)(F)(F)F;
Properties
Chemical formula	LiPF6
Molar mass	151.905 g/mol
Appearance	white powder
Density	2.84 g/cm3
Melting point	200 °C (392 °F; 473 K)
Solubility in water	soluble
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P280, P305+P351+P338, P310
Flash point	Non-flammable
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Lithium tetrafluoroborate
Other cations	Sodium hexafluorophosphate; Potassium hexafluorophosphate; Ammonium hexafluorophosphate
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Lithium hexafluorophosphate is an inorganic compound with the formula Li PF₆. It is a white crystalline powder.

Production

LiPF₆ is manufactured by reacting phosphorus pentachloride with hydrogen fluoride and lithium fluoride^[1] ^[2]

PCl₅ + LiF + 5 HF → LiPF₆ + 5 HCl

Suppliers include Targray and Morita Chemical Industries Co., Ltd.

Chemistry

The salt is relatively stable thermally, but loses 50% weight at 200 °C (392 °F). It hydrolyzes near 70 °C (158 °F)^[3] according to the following equation forming highly toxic HF gas:

LiPF₆ + 4 H₂O → LiF + 5 HF + H₃PO₄

Owing to the Lewis acidity of the Li⁺ ions, LiPF₆ also catalyses the tetrahydropyranylation of tertiary alcohols.^[4]

In lithium-ion batteries, LiPF₆ reacts with Li₂CO₃, which may be catalysed by small amounts of HF:^[5]

LiPF₆ + Li₂CO₃ → POF₃ + CO₂ + 3 LiF

Application

The main use of LiPF₆ 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.^[6]^[7]^[8] 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.^[9]

References

^ Dunn, JB; Gaines, L; Barnes, M; Sullivan, J; Wang M (Sep 2014). "Material and Energy Flows in the Materials Production, Assembly, and End-of-Life Stages of the Automotive Lithium-Ion Battery Life Cycle". p. 28. Retrieved 5 December 2020.
^ O'Leary, Brian (11 May 2011). "High-Volume Manufacturing of LiPF6, A Critical Lithium-ion Battery Material" (PDF). p. 5. Retrieved 5 December 2020.
^ Xu, Kang (October 2004). "Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries". Chemical Reviews. 104 (10): 4303–4418. doi:10.1021/cr030203g. PMID 15669157. S2CID 33074301.
^ Nao Hamada; Sato Tsuneo (2004). "Lithium Hexafluorophosphate-Catalyzed Efficient Tetrahydropyranylation of Tertiary Alcohols under Mild Reaction Conditions". Synlett (10): 1802–1804. doi:10.1055/s-2004-829550.
^ Bi, Yujing; Wang, Tao; Liu, Meng; Du, Rui; Yang, Wenchao; Liu, Zixuan; Peng, Zhe; Liu, Yang; Wang, Deyu; Sun, Xueliang (2016). "Stability of Li2CO3 in cathode of lithium ion battery and its influence on electrochemical performance". RSC Advances. 6 (23): 19233–19237. Bibcode:2016RSCAd...619233B. doi:10.1039/C6RA00648E. ISSN 2046-2069.
^ Goodenough, John B.; Kim, Youngsik (9 February 2010). "Challenges for Rechargeable Li Batteries". Chemistry of Materials. 22 (3): 587–603. doi:10.1021/cm901452z.
^ Qian, Yunxian; Hu, Shiguang; Zou, Xianshuai; Deng, Zhaohui; Xu, Yuqun; Cao, Zongze; Kang, Yuanyuan; Deng, Yuanfu; Shi, Qiao; Xu, Kang; Deng, Yonghong (2019). "How electrolyte additives work in Li-ion batteries". Energy Storage Materials. 20: 208–215. doi:10.1016/j.ensm.2018.11.015. ISSN 2405-8297. S2CID 139865927.
^ Jow, T. Richard; Borodin, Oleg; Ue, Makoto; Xu, Kang (2014). Electrolytes for Lithium and Lithium-Ion Batteries. Springer: New York. ISBN 9781493903023.
^ Corrosion inhibition of aluminum current collector with molybdate conversion coating in commercial LiPF6-esters electrolytes. 2021. Corrosion Sci. 190/11. S.L. Yang, S.M. Li, Y.B. Meng, M. Yu, J.H. Liu, B. Li. doi: 10.1016/j.corsci.2021.109632.