Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D15/00—Lithium compounds
  • C01D15/005—Lithium hexafluorophosphate

Definitions

• the present invention relates to a process for manufacturing lithium hexafluorophosphate (LiPF ⁇ ) • Lithium hexafluorophosphate is mainly used as an electrolyte in rechargeable batteries.
• Hydrogen fluoride (HF) ⁇ 200 p.p.m.
• Lithium fluoride (LiF) ⁇ 1000 p.p.m.
• H are detrimental to the electrochemical behavior of the battery, in particular to the formation of the passivation layer at the interface of the lithium / electrolyte or Li x C6 / electrolyte electrode, which has the consequence of impairing the capacity of the battery and its lifespan (number of charge and discharge cycles).
• LiPF ⁇ involve a step in which the crystallized LiPF ⁇ is either dissolved or in contact with a large excess of liquid HF.
• the strategy then consists in obtaining large crystals of LiPF 6 by crystallization. dimensions (1 to 3 mm) and tending towards the most perfect possible (quasi-single crystals) in order to minimize the quantities of HF which are dissolved and / or occluded therein.
• Japanese patent application 4-175216 teaches the production of gaseous PF 5 by the reaction of PCI 5 with anhydrous HF in large excess at -30 ° C to give first white crystals of HPFg in HF and the concomitant volatilization of hydrogen chloride (HCl) produced in the reaction. The temperature then rose to -10 ° C to give PF 5 gas according to the reaction:
• the gaseous PF 5 thus obtained is introduced continuously into a solution of LiF, HF in HF in order to obtain LiPF ⁇ crystals with a uniform diameter of 2 to 3 mm. These crystals are separated from the filtrate by an ordinary technique which is not specified. The yield is 70% and the purity indicated is 99.98%.
• the analytical methods indicated for lithium and phosphorus are atomic absorption spectrometry and 1 absorptiometry. On the other hand, there is no indication of an HF assay method.
• Japanese patent application 5-279003 describes a process for the synthesis of LiPF ⁇ which can be used as an electrolyte in rechargeable batteries and which does not contain phosphorus oxyfluoride (O ⁇ PF ⁇ ).
• the HF is distilled under nitrogen to concentrate the solution then the latter is cooled to between 0 ° C and -20 ° C to give LiPF ⁇ crystals.
• Examples 1, 2 and 3 indicate respective yields of 65.6%, 62.3% and 64.9% of crystallized LiPF ⁇ having respective residual contents of acid compounds, assayed by titrimetry in aqueous media, of 11, 12 and 12 ppm of H, which corresponds for the skilled person to 220, 240, and 240 ppm of HF.
• Japanese patent application 6-56413 describes a process comprising the following steps:
• a gas mixture PF 5 + 5HC1 is generated by reaction of
• the gas mixture thus obtained is introduced into a crystallizing reactor containing LiF dissolved in liquid HF.
• the crystals obtained are dissolved by raising the temperature to room temperature then the solution obtained is crystallized by lowering the temperature at -20 ° C to give crystals having a particle size of 1 to 3 mm.
• the crystals are collected and then dried under reduced pressure.
• Example 1 indicates a yield of 35% for a purity of at least 99%.
• the mother liquors of Example 1 which still contain 113 g of LiPF ⁇ are recycled in Example 2 with a new quantity of LiF to give LiPF 6 with a yield of 95% calculated relative to the new quantity of LiF and a indicated purity of at least 99%.
• the methods of analysis establishing purity are not mentioned.
• Japanese patent application 6-298506 describes a recrystallization process for LiPF ⁇ in HF comprising a final stage of drying under vacuum or under dry nitrogen sweeping between 60 ° C and 130 ° C.
• the residual content of acid impurities indicated in Examples 1, 2 and 3 is respectively 150, 100 and 60 p.p.m., which is interpreted by a person skilled in the art as being an HF content. The method for determining these contents is not indicated.
• Japanese patent application 9-268005 describes a process for crystallizing LiPFç in HF comprising a final drying step.
• Examples 1 and 3 indicate respective free acid contents of 100 and 99%. .m. for yields which are not indicated.
• the free acid is HF.
• the contents of insoluble residues in these same examples are respectively 0.08% and 0.07% by weight. Furthermore, the method for determining these contents is not explained.
• patent application WO 98/06666 discloses a process in which LiF is reacted with PCI 5 or POCI3 at a reaction temperature of -20 ° C to 300 ° C for 0.1 to 10 h to give LiPFç according to: a) PCI 5 + 6LiF -> 5LiCl + LiPFô b) 4P0C1 3 + 18LiF ⁇ 12LiCl + Li 3 P0 + 3 LiPF 6 and the LiPF ⁇ from the mixture is isolated as a solution: ethers, nitriles, esters, sulfones are used as solvent , carbonates, halogenated hydrocarbons and / or tertiary amines.
• Example 1 The purity obtained (Example 1) is only 99.8% because 0.2% of chloride remains in the LiPF ⁇ . In addition, the methods of analysis are not described.
• the object of the present invention is to provide a process for manufacturing LiPFg having a residual HF content of less than 20 pp. (lower limit of detection of the analytical method) by reaction of LiF and PF 5 with a yield relative to the LiF reacted, greater than 99%.
• the proposed process must also be industrial to allow the production of large quantities of LiPFg having an HF content of less than 20 ppm.
• These objectives are achieved by the LiPF 6 production process, according to the invention, by reaction of LiF with PF5. in a liquid, characterized in that this liquid is sulfur dioxide (SO 2 ).
• SO 2 sulfur dioxide
• the liquid (SO 2 ) replaces the liquid HF as reaction medium and thus makes it possible to avoid all the technical problems linked to the elimination of HF from the solid LiPFc.
• the liquid containing the LiF and the PF 5 is at a temperature below 40 ° C.
• this temperature ranges from -10 ° C to + 10 ° C.
• the PFs / LiF molar ratio is greater than or equal to 1.05. This excess of PF 5 avoids the reverse reaction of decomposition of LiPF 6 into PF 5 and LiF.
• SO 2 liquid comes from a gas mixture containing hydrogen chloride (HC1).
• HC1 behaves like an inert compound, without causing a reduction in the purity of the LiPF ⁇ obtained.
• HCl is present in the reaction in an HCI / PF 5 molar ratio substantially equal to 5.
• the PF 5 used in the industrial synthesis of LiPF ⁇ is often produced by reaction PCI 5 with anhydrous HF which leads to a gas mixture PF 5 + 5HC1.
• the process of the present invention also makes it possible to greatly minimize the other usual impurities of
• Solid LiPF ⁇ has a residual HF content of less than
• the solid LiPF 6 also has a content of residue insoluble in 1,2-dimethoxyethane of less than 100 ppm (detection limit of the analytical method used).
• the present invention will be better understood using the following experimental part.
• LiPF ⁇ powder A known quantity of LiPF ⁇ powder is taken, to which is added deuterated acetonitrile (CD 3 CN, 0.5 ml) previously dried on a 3A molecular sieve. The powder dissolves, forming a solution. This is introduced into a screw tube for NMR and we then proceed to
• the doublet centered on 6 ppm corresponds to the PF ⁇ species with a coupling constant J PF of 707 Hz.
• the doublet centered on -104 pp. corresponds to the HF species with a coupling constant J HF of 480 Hz.
• the detection limit in HF is 150 pp. molar compared to the total sum of fluorinated species present in the solution analyzed. This limit value expressed in pp. mass is approximately 20.
• the insoluble content is calculated as follows:
• the solid to be analyzed is transferred to a dry glove box whose water content in its atmosphere is less than 10 p.p.m. volume.
• the LiF used below as a reference sample, comes from the company Aldrich under the commercial reference 20,364-5 and is of a purity of 99.99% by weight.
• PF 5 comes from the company Ozark-Mahoning (lot DF-
• EXAMPLE 1 26.4 g of previously dried LiF is introduced into a dry glove box (H 2 O ⁇ 10 ppm by volume) into a metallic stainless steel reactor of grade 316 L, equipped with four valves and fitted with a magnetic bar. under dry nitrogen. After the reactor was closed in a glove box, it was connected by two of its valves on the one hand to a source of liquid SO 2 and on the other hand to a source of PF 5 by separate pipes. These pipes were previously passive with PF 5 , then degassed under reduced pressure less than 1 mm Hg, for one hour. Then transferred 516 g of SO 2 and the reaction medium SO 2 + LiF is stirred by a magnetic stirrer. The reaction medium of the reactor is cooled to 3 ° C. The pressure inside the reactor is 0.08 MPa. PF 5 gases are then gradually added at a rate of 150 g / hour for
• the third valve is open to let SO 2 and excess PF 5 escape in gaseous form.
• the temperature of the reaction medium is less than 30 ° C.
• the gaseous effluent is trapped in a washing system. This gaseous effluent can also be recovered by condensation for a new use.
• Insoluble residue not detected because less than 100 p.p.m. mass.
• This product has an indicated purity of 99.99 +%.
• the third valve is then gradually opened in order to let the gaseous mixture (SO2 + PF5 in excess + HCl) escape in gaseous form.
• the temperature is less than 25 ° C.
• the gaseous effluent is partly recycled in another LiPFg synthesis operation and for another part trapped in a washing system.
• S elemental sulfur
• Insoluble residue not detected because less than 100 p.p.m. mass.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Secondary Cells (AREA)

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• 1998
  • 1998-08-21 FR FR9810634A patent/FR2782517B1/fr not_active Expired - Fee Related
• 1999
  • 1999-06-25 WO PCT/FR1999/001531 patent/WO2000010917A1/fr not_active Application Discontinuation
  • 1999-06-25 EP EP99967830A patent/EP1119520A1/fr not_active Withdrawn
  • 1999-06-25 AU AU42720/99A patent/AU4272099A/en not_active Abandoned
  • 1999-06-25 JP JP2000566196A patent/JP2002539059A/ja not_active Withdrawn
  • 1999-06-25 US US09/763,188 patent/US6500399B1/en not_active Expired - Fee Related

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