Lithium hexafluorophosphate

Lithium hexafluorophosphate
Names

IUPAC name lithium hexafluorophosphate
Identifiers
CAS Number	21324-40-3^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:172376
ChemSpider	146939^Y
ECHA InfoCard	100.040.289
PubChem CID	23688915
UNII	T9T8DY51J3^Y
CompTox Dashboard (EPA)	DTXSID2066698
InChI InChI=1S/F6P.Li/c1-7(2,3,4,5)6;/q-1;+1^Y Key: AXPLOJNSKRXQPA-UHFFFAOYSA-N^Y 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). N verify (what is ^YN ?) Infobox references

Chemical compound

Lithium hexafluorophosphate is an inorganic compound with the formula LiPF₆. 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.