EP2984038A2

EP2984038A2 - Low-chloride electrolyte

Info

Publication number: EP2984038A2
Application number: EP14716348.9A
Authority: EP
Inventors: Thomas Linder; Matthias Boll; Eberhard Kuckert
Original assignee: Lanxess Deutschland GmbH
Current assignee: Lanxess Deutschland GmbH
Priority date: 2013-04-12
Filing date: 2014-04-10
Publication date: 2016-02-17
Also published as: US20160090310A1; WO2014167055A2; EP2789583A1; CN105143106A; WO2014167055A3

Abstract

The present invention relates to a method for producing low-chloride lithium hexafluorophosphate starting from lithium fluoride and phosphorus pentafluoride and the use thereof in an electrolyte.

Description

Low chloride electrolyte

The present invention relates to a process for the preparation of low-lithium lithium hexafluorophosphate starting from lithium fluoride and phosphorus pentafluond and its use in an electrolyte.

The proliferation of portable electronic devices, e.g. Laptop and palmtop computers, mobile phones or video cameras and thus also the need for light and powerful batteries and accumulators has dramatically increased in recent years worldwide. In addition, there will be the equipment of electric vehicles with such accumulators and batteries in the future.

Lithium hexafluorophosphate (LiPF ₆ ) has attained great industrial importance, especially as conducting salt in the production of powerful batteries. In order to ensure the functionality and service life and thus the quality of such accumulators, it is of particular importance that the lithium compounds used contain as low as possible amounts of chloride. Chloride ions are blamed for cell shorts due to corrosion.

Numerous processes for the production of lithium hexafluorophosphate are known from the prior art. For example, the preparation according to the following reaction scheme offers:

Stage 1 PCI ₃ + 3 HF -> PF ₃ + 3 HCl

Level 2 PF ₃ + Cl ₂ -> PCI2F3

Stage 3 PCI2F ₃ + 2 HF -> PF ₅ + 2 HCl

Stage 4 PF ₅ + LiF -> LiPF ₆

DE19712988A1 describes a batchwise process starting from phosphorus trichloride (PCI ₃ ). In a test reactor lithium fluoride were initially charged and heated at 150 ° C under argon. In a laboratory autoclave phosphorus trichloride was submitted, then added hydrogen fluoride and then elemental chlorine. The resulting gaseous mixture of hydrogen chloride and phosphorus pentafluoride was passed over the lithium fluoride in the experimental reactor to obtain lithium hexafluorophosphate. JP1 1 171518A2 describes a process for the preparation of lithium hexafluorophosphate which proceeds from phosphorus trichloride and hydrogen fluoride via phosphorus trifluoride, the latter being reacted with elemental chlorine first to phosphorodichloride trifluoride, this in turn with hydrogen fluoride to phosphorus pentafluoride and the latter finally with lithium fluoride to lithium hexafluorophosphate in an organic solvent. The organic solvents used are diethyl ether and dimethyl carbonate. Although JP 1 1 171518 A2 indicates the formation of toxic HCl gas, there is no indication in the prior art of the chloride content in the resulting lithium hexafluorophosphate. The procedure, however, suggests a significant chloride content.

No. 3,594,402 describes the preparation of improved lithium hexafluorophosphate from tetraacetonitrile lithium hexafluorophosphate by reaction of lithium fluoride and phosphorus pentafluoride with excess acetonitrile. The removal of the excess acetonitrile is carried out under vacuum.

Further, for example, US5378445 discloses a process for preparing solutions of lithium hexafluorophosphate comprising reacting a lithium salt, under basic conditions, with a salt consisting of sodium, potassium, ammonium or an organo-ammonium hexafluorophosphate salt in a low-boiling one -protonic organic solvent. A solution containing lithium hexafluorophosphate and a precipitated sodium, potassium, ammonium or organoammonium salt containing the anion of the lithium salt reactant is thereby obtained.

In DE2026110 a process for the preparation of hexafluorophosphate salts of lithium tetraacetonitrile is described, characterized in that a stoichiometric excess of acetonitrile with hexafluorophosphate salts of lithium at a temperature of about -40 ° C to about 80 ° C is reacted. The removal of the acetonitrile takes place under reduced pressure.

J. Liu, X. Li, Z. Wang, H. Guo, W. Peng, Y. Zhang, Q. Hu, Trans. Nonferrous Met. Soc. China 2010, 20, 344-348, a production method for lithium hexafluorophosphate is described. First, phosphorus pentafluoride is prepared from calcium fluoride and phosphorus pentoxide. Lithium hexafluorophosphate was synthesized in an acetonitrile solution by the reaction of lithium fluoride with Phosphorus pentafluond at room temperature. The purity of the produced lithium hexafluorophosphate was 99.98%.

The prior art shows that it is technically very complicated to achieve high purities for lithium hexafluorophosphate and in particular to keep the content of chloride low. Consequently, not all purity requirements can be met with the hitherto known processes for the preparation of lithium hexafluorophosphate.

Accordingly, it was an object of the present invention to develop an efficient process for producing low chloride lithium hexafluorophosphate.

The object of and the subject of the present invention is now a process for preparing low-lithium lithium hexafluorophosphate comprising at least the steps of a) contacting lithium fluoride in a first organic solvent containing a nitrile with a gas containing phosphorus pentafluoride and hydrogen chloride, wherein a reaction mixture comprising lithium hexafluorophosphate, a first organic solvent containing a nitrile and hydrogen chloride is obtained, b) contacting the reaction mixture formed according to a) with further organic solvent which is different from the first organic solvent, lithium hexafluorophosphate precipitating and c) separating off precipitated lithium hexafluorophosphate,

It should be noted at this point that the scope of the invention includes all possible and possible combinations of the above-listed and listed below, general or preferred ranges mentioned components, value ranges or process parameters.

In step a), lithium fluoride in a first organic solvent is contacted with a gas containing phosphorus pentafluond and hydrogen chloride to obtain a reaction mixture containing lithium hexafluorophosphate, a first organic solvent and hydrogen chloride.

The lithium fluoride used in step a) has, for example, a purity of 98.0000 to 99.9999% by weight, preferably 99.0000 to 99.9999% by weight, more preferably 99.9000 to 99.9995% by weight. , more preferably 99.9500 to 99.9995 Wt .-% and most preferably 99.9700 to 99.9995 wt .-% based on anhydrous product.

The lithium fluoride used furthermore preferably has foreign ions:

1) a content of 0.1 to 250 ppm, preferably 0.1 to 75 ppm, more preferably 0.1 to 50 and particularly preferably 0.5 to 10 ppm and most preferably 0.5 to 5 ppm of sodium in ionic form .

2) a content of 0.01 to 200 ppm, preferably 0.01 to 10 ppm, more preferably 0.5 to 5 ppm and particularly preferably 0.1 to 1 ppm of potassium in ionic form,

3) a content of 0.05 to 500 ppm, preferably 0.05 to 300 ppm, more preferably 0, 1 to 250 ppm and particularly preferably 0.5 to 100 ppm of calcium in ionic form and / or

4) a content of 0.05 to 300 ppm, preferably 0.1 to 250 ppm and more preferably 0.5 to 50 ppm of magnesium in ionic form.

The lithium fluoride used further has, for example, at foreign ions i) a content of 0.1 to 1000 ppm, preferably from 0.1 to 100 ppm and more preferably 0.5 to 10 ppm of sulfate and / or ii) a content of 0.1 to 1000 ppm, preferably 0.5 to 500 ppm chloride, also based on the anhydrous product and it is true that the sum of lithium fluoride and the aforementioned foreign ions does not exceed 1, 000,000 ppm, based on the total weight of the technical lithium carbonate based on the anhydrous product.

In one embodiment, the lithium fluoride contains a total of foreign metal ion content of 1000 ppm or less, preferably 300 ppm or less, more preferably 20 ppm or less, and most preferably 10 ppm or less.

Unless otherwise stated, the ppm data reported herein are generally by weight, and the contents of said cations and anions are determined by ion chromatography as indicated in the experimental section unless otherwise specified. The lithium fluoride with the aforementioned specifications can be obtained, for example, by a process comprising at least the following steps: i) providing an aqueous medium containing dissolved lithium carbonate ii) reacting the aqueous medium provided according to a) with gaseous hydrogen fluoride to form an aqueous suspension of solid lithium fluoride iii) Separation of the solid lithium fluoride from the aqueous suspension. Iv) Drying of the separated lithium fluoride.

According to step i), an aqueous solution containing lithium carbonate is provided.

The term "aqueous medium containing dissolved lithium carbonate" is to be understood here as meaning a liquid medium which contains i) dissolved lithium carbonate, preferably in an amount of at least 2.0 g / l, more preferably 5.0 g / l to maximum solubility in the aqueous medium at the selected temperature, most preferably 7.0 g / l to the maximum solubility in the aqueous medium at the selected temperature, in particular the content of lithium carbonate is 7.2 to 15.4 g / l in that the solubility of lithium carbonate in pure water at 0 ° C is 15.4 g / l at 20 ° C 13.3 g / l, at 60 ° C 10.1 g / l and at 100 ° C 7.2 g / l l) and consequently certain concentrations can only be achieved at certain temperatures ii) contains at least 50% by weight of water, preferably 80% by weight, more preferably at least 90% by weight, based on the total weight of the liquid medium, and iii ) preferably also feststof f is free or has a solids content of more than 0.0 to 0.5 wt .-%, preferably solids-free or a solids content of more than 0.0 to 0.1 wt .-%, more preferably solids-free or a solids content from more than 0.0 to 0.005 wt., And particularly preferably solids-free, wherein the sum of components i), ii) and preferably iii) at most 100 wt .-%, preferably 98 to 100 wt .-% and particularly preferably 99 up to 100 wt .-% based to the total weight of the aqueous medium containing dissolved lithium carbonate.

In a further embodiment of the invention, the aqueous medium containing dissolved lithium carbonate may contain, as further component iv), at least one water-miscible organic solvent.

Suitable water-miscible organic solvents are, for example, monohydric or polyhydric alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, ethylene glycol monomethyl ether,

Ethylene glycol monoethyl ether, propylene glycol, 1,3-propanediol or glycerol, ketones such as acetone or ethyl methyl ketone.

If the aqueous medium containing dissolved lithium carbonate contains at least one water-miscible organic solvent, their proportion may be, for example, more than 0.0% by weight to 20% by weight, preferably 2 to 10% by weight, in which case in each case in that the sum of the components i), ii), iii) and iv) contains a maximum of 100% by weight, preferably 95 to 100% by weight and particularly preferably 98 to 100% by weight, based on the total weight of the aqueous medium dissolved lithium carbonate is.

Preferably, however, the aqueous medium containing dissolved lithium carbonate is free of water-miscible organic solvents. The aqueous medium containing dissolved lithium carbonate may contain as further component v) a complexing agent, preferably in an amount of 0.001 to 1 wt .-%, preferably 0.005 to 0.2% by weight based on the total weight of the aqueous medium containing dissolved lithium carbonate. Complexing agents are preferably those whose complexes with calcium ions and magnesium ions form complexes which have a solubility of more than 0.02 mol / l at a pH of 8 and 20 ° C. Examples of suitable complexing agents are ethylenediaminetetraacetic acid (EDTA) and its alkali metal or ammonium salts, with ethylenediaminetetraacetic acid being preferred. In one embodiment, however, the aqueous medium containing dissolved lithium carbonate is free of complexing agents. To provide the aqueous solution containing lithium carbonate, the procedure is preferably such that solid lithium carbonate is brought into contact with a lithium carbonate-free or lithium-carbonate-poor aqueous medium so that the solid lithium carbonate at least partially dissolves. A low-lithium carbonate aqueous medium is understood as meaning an aqueous medium which has a lithium carbonate content of up to 1.0 g / l, preferably up to 0.5 g / l, of lithium carbonate but is not free of lithium carbonate.

The aqueous medium used for the preparation fulfills the conditions mentioned above under ii) and iii) and optionally comprises the components iv) and v). In the simplest case, the aqueous medium is water, preferably water having a specific electric resistance of 5 MQ ^"cm at 25 ° C or more.

In a preferred embodiment, steps i) to iv) are repeated one or more times, repeated one or more times. In this case, in the repetition for providing the aqueous medium containing dissolved lithium carbonate used as lithium carbonate-free or lithium carbonate poor aqueous medium, the aqueous medium obtained in a previous step iii) in the separation of solid lithium fluoride from the aqueous suspension of lithium fluoride. In this case, the lithium carbonate-free or lithium carbonate-poor aqueous medium contains dissolved lithium fluoride, typically up to the saturation limit at the respective temperature. In one embodiment, contacting the lithium carbonate-free or aqueous medium with the solid lithium carbonate may be accomplished in a stirred reactor, flow-through reactor, or other apparatus known to those skilled in the art for contacting liquid with solids. Preferably, in the sense of a short residence time and the achievement of a concentration of lithium carbonate in the aqueous medium used which is as close as possible to the saturation point, an excess of lithium carbonate is used, i. so much that complete dissolution of the solid lithium carbonate can not occur. In order to limit the solids content according to (ii) in this case, filtration, sedimentation, centrifugation or any other method known to the person skilled in the art for the separation of solids from or from liquid is then carried out, filtration being preferred.

If the process steps i) to iii) are repeated and / or carried out continuously, filtration through a cross-flow filter is preferred. The temperature during contacting can be carried out, for example, from the freezing point to the boiling point of the aqueous medium used, preferably 0 to 100.degree. C., particularly preferably 10 to 60.degree. C. and particularly preferably 10 to 35.degree. C., in particular 16 to 24.degree.

The pressure when contacting can be, for example, 100 hPa to 2 MPa, 900 hPa to 1200 hPa, in particular ambient pressure is particularly preferred.

In the context of the invention, technical lithium carbonate is understood as meaning lithium carbonate which has a purity of 95.0 to 99.9% by weight, preferably 98.0 to 99.8% by weight and particularly preferably 98.5 to 99.8% by weight. -% based on anhydrous product possesses.

Preferably, the technical lithium carbonate further contains foreign ions, i. ions that are not lithium or carbonate ions

1) a content of 200 to 5000 ppm, preferably 300 to 2000 and more preferably 500 to 1200 ppm of sodium in ionic form and / or

2) a content of 5 to 1000 ppm, preferably 10 to 600 ppm of potassium in ionic form and / or

3) a content of 50 to 1000 ppm, preferably 100 to 500 and particularly preferably 100 to 400 ppm of calcium in ionic form and / or

4) a content of 20 to 500 ppm, preferably 20 to 200 and particularly preferably 50 to 100 ppm of magnesium in ionic form.

5) a content of 50 to 1000 ppm, preferably 100 to 800 ppm of sulfate and / or

6) a content of 10 to 1000 ppm, preferably 100 to 500 ppm chloride, also based on the anhydrous product.

In general, the sum of lithium carbonate and the abovementioned foreign ions 1) to 4) and optionally i) and ii) does not exceed 1, 000,000 ppm, based on the total weight of the technical lithium carbonate, based on the anhydrous product. In a further embodiment, the technical lithium carbonate has a purity of 98.5 to 99.5 wt .-% and a content of 500 to 2000 ppm of foreign metal ions ie sodium, potassium, magnesium and calcium.

In a further embodiment, the technical lithium carbonate preferably additionally has a content of 100 to 800 ppm of foreign anions, i. Sulphate or chloride based on the anhydrous product.

Unless otherwise stated, the ppm data given herein are based on parts by weight, the contents of said cations and anions are determined by ion chromatography, unless stated otherwise in the experimental section.

In one embodiment of the method according to the invention, the provision of the aqueous medium containing lithium carbonate or the contacting of a lithium carbonate-free or poor, aqueous medium with solid lithium carbonate batchwise or continuously, wherein the continuous implementation is preferred. The aqueous medium containing dissolved lithium carbonate prepared according to step i) typically has a pH of 8.5 to 12.0, preferably of 9.0 to 11.5, measured or calculated at 20 ° C. and 1013 hPa.

Before the aqueous medium containing dissolved lithium carbonate provided in step i) is used in step (ii), it can be passed through an ion exchanger, in order to at least partially remove calcium and magnesium ions in particular. For example, weakly or strongly acidic cation exchangers can be used for this purpose. For use in the process according to the invention, the ion exchangers can be used in devices, such as, for example, flow columns which are filled with the cation exchangers described above, for example in the form of powders, beads or granules.

Particularly suitable are ion exchangers containing copolymers of at least styrene and divinylbenzene, which also contain, for example, aminoalkylenephosphonic acid groups or iminodiacetic acid groups.

Such ion exchangers are, for example, those of the Lewatit ™ type such as Lewatit ™ OC 1060 (AMP type), Lewatit ™ TP 208 (IDA type), Lewatit ™ E 304/88, Lewatit ™ S 108, Lewatit TP 207, Lewatit ™ S 100; those of the type Amberlite ™ such as Amberlite ™ IR 120, Amberlite ™ IRA 743; those of the Dowex ™ type, such as Dowex ™ HCR; those of the Duolite type, such as Duolite ™ C 20, Duolite ™ C 467, Duolite ™ FS 346; and Imac ™ type such as Imac ™ TMR, with Lewatit ™ types being preferred.

Preferably, such ion exchangers are used, which are as low-sodium as possible. For this purpose, it is advantageous to rinse the ion exchanger before use with the solution of a lithium salt, preferably an aqueous solution of lithium carbonate.

In one embodiment of the method according to the invention, no treatment with ion exchangers takes place.

According to step ii), the reaction of the aqueous medium provided according to step i) comprising dissolved lithium carbonate with gaseous hydrogen fluoride is carried out to give an aqueous suspension of solid lithium fluoride.

The reaction can be carried out, for example, by introducing or passing a gaseous hydrogen fluoride-containing gas stream into or over the aqueous medium containing dissolved lithium carbonate, or by spraying, atomizing or flowing through the aqueous medium containing dissolved lithium carbonate in or through a gas containing gaseous hydrogen fluoride.

Due to the very high solubility of gaseous hydrogen fluoride in aqueous media, it is preferred to pass, spray, mist or flow through it, with pass-over being even more preferred.

Gaseous hydrogen fluoride contained as a gaseous hydrogen fluoride gas or gas containing gaseous hydrogen fluoride can be used as such or a gas containing gaseous hydrogen fluoride and an inert gas, an inert gas is to be understood as a gas that does not react with lithium fluoride under the usual reaction conditions. Examples are air, nitrogen, argon and other noble gases or carbon dioxide, with air and more nitrogen being preferred.

The proportion of inert gas can vary as desired and, for example, 0.01 to 99 vol .-%, preferably 1 to 20 vol .-%. In the reaction according to step ii), lithium fluoride is formed, which precipitates due to the fact that it is less soluble in the aqueous medium than lithium carbonate, and consequently forms an aqueous suspension of solid lithium fluoride. It is known to those skilled in the art that lithium fluoride has a solubility of about 2.7 g / l at 20 ° C. The reaction is preferably carried out in such a way that the resulting aqueous suspension of solid lithium fluoride reaches a pH of 3.5 to 8.0, preferably 4.0 to 7.5, and more preferably 5.0 to 7.2. Carbon dioxide is liberated at the stated pH values. In order to enable its release from the suspension, it is advantageous to pass the suspension to, for example, stirring or via static mixing elements.

The temperature in the reaction according to step ii) can be, for example, from the freezing point to the boiling point of the aqueous medium containing dissolved lithium carbonate, preferably 0 to 65 ° C, more preferably 15 to 45 ° C and particularly preferably 15 to 35 ° C, especially 16 up to 24 ° C. The pressure in the reaction according to step ii) can be, for example, 100 hPa to 2 MPa, 900 hPa to 1200 hPa, in particular ambient pressure is particularly preferred.

In step iii), the separation of the solid lithium fluoride from the aqueous suspension. Separation is accomplished, for example, by filtration, sedimentation, centrifugation, or any other method known to those skilled in the art for separating solids from or from liquids, with filtration being preferred.

If the filtrate for step i) is used again and the process steps a) to c) are carried out repeatedly, filtration through a cross-flow filter is preferred.

The solid lithium fluoride thus obtained typically still has a residual moisture of from 1 to 40% by weight, preferably from 5 to 30% by weight.

Before the lithium fluoride separated in step iii) is dried according to step iv), it can be washed once or several times with water or a medium containing water and water-miscible organic solvents. Water is preferred. Water having an electric resistance of 15 MQ ^"cm at 25 ° C or more particularly preferred. From step iii) adhering to the solid lithium fluoride water with foreign ions is thereby removed as far as possible.

In step iv), the lithium fluoride is dried. The drying can be carried out in any apparatus known to the person skilled in the art for drying. Preferably, the drying is carried out by heating the lithium fluoride, preferably at 100 to 800 ° C, more preferably 200 to 500 ° C.

As the first organic solvent, for example, a nitrile, a combination of nitriles or a combination of at least one nitrile with at least one non-nitrile organic solvent may be used.

Examples of suitable nitriles are acetonitrile, propanenitrile and benzonitrile. Particular preference is given to using acetonitrile.

For example, the molar ratio of nitriles used to the amount of lithium ions present in the reaction mixture from step a) is at least 1: 1, preferably at least 10: 1 and more preferably at least 50: 1 and most preferably at least 100: 1.

When used as the first organic solvent are those which are not nitrile, those organic solvents are preferably used which are liquid at room temperature and have a boiling point of 300 ° C or less at 1013 hPa and further at least one oxygen atom or a nitrogen atom or both contain.

Preferred organic solvents are those which have no protons which have a pKa value at 25 ° C., based on water or an aqueous comparison system of less than 20. Such organic solvents are also referred to in the literature as "aprotic" solvents.

Examples of such other organic solvents are liquid at room temperature esters, organic carbonates, ketones, ethers, acid amides or sulfones. Examples of ethers are diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethylene glycol dimethyl and diethyl ether, 1, 3-Propandioldimethyl and diethyl ether, dioxane and tetrahydrofuran.

Examples of esters are methyl and ethyl acetate and butyl acetate or organic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) or propylene carbonate (PC) or ethylene carbonate (EC).

An example of a sulphone is sulfolane.

Examples of ketones are acetone, methyl ethyl ketone and acetophenone.

Examples of acid amides are N, N-dimethylformamide, Ν, Ν-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone or hexamethylphosphoric triamide.

The first organic solvent according to the invention may also contain several of said organic solvents.

In an alternative embodiment, solid lithium fluoride is contacted with a first organic solvent.

In a further alternative embodiment, a first organic solvent is initially charged and solid lithium fluoride is added.

The resulting suspension containing lithium fluoride and a first organic solvent is contacted with gas containing phosphorus pentafluoride and hydrogen chloride.

In an alternative embodiment, the contacting of lithium fluoride and a first organic solvent takes place under inert gas, preferably under argon.

The gas used in step a) comprising phosphorus pentafluoride and hydrogen chloride can be prepared in a manner known per se by a process comprising at least the following steps.

1) Reaction of phosphorus trichloride with hydrogen fluoride to phosphorus trifluoride and hydrogen chloride

2) Reaction of phosphorus trifluoride with elemental chlorine to phosphorodichloride trifluoride 3) Reaction of phosphorodichloride trifluoride with hydrogen fluoride to give phosphorus pentafluond and hydrogen chloride

As the gas containing phosphorus pentafluoride and hydrogen chloride, therefore, there is typically used a gas mixture containing 5 to 41% by weight of phosphorus pentafluoride and 6 to 59% by weight of hydrogen chloride, preferably 20 to 41% by weight of phosphorus pentafluond and 40 to 59% by weight of hydrogen chloride preferably 33 to 41 wt .-% phosphorus pentafluond and 49 to 59 wt .-% hydrogen chloride are used, wherein the proportion of phosphorus pentafluoride and hydrogen chloride, for example, 1 1 to 100 wt .-%, preferably 90 to 100 wt .-% and particularly preferably 95 to 100 wt .-% is.

The difference to 100 wt .-%, if present at all, may be chlorine, hydrogen fluoride or inert gases, wherein an inert gas is to be understood here as a gas which does not react with phosphorus pentafluoride, fluorine or hydrogen chloride or lithium fluoride under the usual reaction conditions. Examples are nitrogen, argon and other noble gases or carbon dioxide, with nitrogen being preferred.

The difference to 100 wt .-%, if any, may alternatively or additionally continue to be hydrogen fluoride.

Based on the overall process via stages 1) to 3), hydrogen fluoride is used, for example, in an amount of 4.5 to 8 mol, preferably 4.8 to 7.5 mol and more preferably 4.8 to 6.0 mol of hydrogen fluoride per mole of phosphorus trichloride used.

The gas containing phosphorus pentafluond and hydrogen chloride is therefore typically a gas mixture containing 5 to 41% by weight of phosphorus pentafluond, 6 to 59% by weight of hydrogen chloride and 0 to 50% by weight of hydrogen fluoride, preferably 20 to 41% by weight of phosphorus pentafluond, 40 to 59 wt .-% of hydrogen chloride and 0 to 40 wt .-% of hydrogen fluoride, particularly preferably 33 to 41 wt .-% phosphorus pentafluond, 49 to 59 wt .-% hydrogen chloride and 0 to 18 wt .-% hydrogen fluoride, wherein the proportion of Phosphorus pentafluoride, hydrogen chloride and hydrogen fluoride, for example, 1 1 to 100 wt .-%, preferably 90 to 100 wt .-% and particularly preferably 95 to 100 wt .-% is. In an alternative embodiment, the term gas comprising phosphorus pentafluoride and hydrogen chloride in step a) is understood to mean that the suspension containing lithium fluoride and a first organic solvent is contacted first with hydrogen chloride gas and then with phosphorus pentafluoride gas.

In a further alternative embodiment, the term gas comprising phosphorus pentafluoride and hydrogen chloride in step a) is understood to mean that the suspension containing lithium fluoride and first organic solvent is first brought into contact with phosphorus pentafluoride gas and subsequently with hydrogen chloride gas.

The reaction pressure in step a) is, for example, 500 hPa to 5 MPa, preferably 900 hPa to 1 MPa, and more preferably 0, 1 MPa to 0.5 MPa.

The reaction temperature in step a) is for example -60 ° C to 150 ° C, preferably between 20 to 150 ° C and most preferably between -10 ° C and 20 ° C or between 50 and 120 ° C. At temperatures above 120 ° C., it is preferable to work under a pressure of at least 1500 hPa.

The reaction time in step a) is for example 10 seconds to 24 hours, preferably 5 minutes to 10 hours.

When using a gas containing phosphorus pentafluoride and hydrogen chloride, the gas leaving the reaction vessel in an aqueous solution of alkali hydroxide, preferably an aqueous solution of potassium hydroxide, more preferably in a 5 to 30 wt .-%, most preferably in a 10 to 20 wt .-%, in particular preferably in a 15 wt .-% solution of potassium hydroxide in water collected. Preferably, the preparation of the gas or gas mixture used in step a) takes place in the gas phase. The reactors to be used for this purpose, preferably tube reactors, in particular stainless steel tubes, and the reaction vessels to be used for the synthesis of the lithium hexafluorophosphate are known to the person skilled in the art and are described, for example, in the Textbook of Technical Chemistry - Volume 1, Chemical Reaction Engineering, M. Baerns, H. Hofmann, A. Renken , Georg Thieme Verlag Stuttgart (1987), pp. 249-256. The contacting according to step a) can be carried out, for example, by introducing the gas containing phosphorus pentafluoride and hydrogen chloride into the suspension.

In an alternative embodiment, the gas containing phosphorus pentafluoride and hydrogen chloride is passed over the suspension containing lithium fluoride and a first organic solvent.

The temperature during the contacting according to step a) can be carried out, for example, from the freezing point to the boiling point of the aqueous medium used, preferably 0 to 100 ° C, more preferably 10 to 60 ° C and particularly preferably 10 to 35 ° C, especially 16 to 24 ° C. ,

The pressure during the contacting according to step a) can be, for example, 100 hPa to 2 MPa, 900 hPa to 1200 hPa, in particular ambient pressure is particularly preferred.

The contacting according to step a) can be carried out, for example, continuously or batchwise in any reaction vessel known to the person skilled in the art for the reaction of liquids with gases, which is preferably resistant to hydrogen fluoride, such as those of Teflon.

For example, in an alternative embodiment, the resulting reaction mixture is stirred with lithium fluoride in a first organic solvent during contacting, alternatively during and after contacting, or, alternatively, after contacting the gas containing phosphorus pentafluoride and hydrogen chloride. The contacting can be facilitated by introducing mixing energy e.g. by static or non-static mixing elements.

The prepared reaction mixture containing lithium hexafluorophosphate, a first organic solvent and hydrogen chloride is stirred for example for a period of 10 seconds to 24 hours, preferably 5 minutes to 12 hours, more preferably 10 minutes to 4 hours and most preferably 30 minutes to 2 hours and then filtered, preferably through a filter having a pore size of 50 nm. The further organic solvent according to the invention is characterized in that in the other organic solvent lithium hexafluorophosphate a lower solubility than in the first organic solvent.

It is clear to the person skilled in the art that the dissolution behavior depends on the temperature, inasmuch as the aforementioned requirement for the selected temperature in step b) has to be met.

The temperature during the contacting can take place, for example, and preferably from the freezing point to the boiling point of the organic solvent or its low-boiling component used, for example from -45 to 80.degree. C., more preferably from 10 to 60.degree. C. and particularly preferably from 10 to 35.degree , in particular from 16 to 24 ° C.

The pressure when contacting can be, for example, from 100 hPa to 2 MPa, preferably from 900 hPa to 1200 hPa, ambient pressure is particularly preferred.

Preferred as another organic solvent is toluene. The solubility of lithium hexafluorophosphate in the first organic solvent and in the other organic solvent as such can be determined by a few preliminary experiments.

The first organic solvent according to the invention and the further organic solvent are preferably subjected to a drying process prior to their use, more preferably a drying process over a molecular sieve.

The content of impurities, in particular water, of the first organic solvent according to the invention and of the further organic solvent should be as low as possible. In one embodiment, it is from 0 to 500 ppm, preferably from 0 to 200 ppm, more preferably from 0 to 100 ppm, and most preferably 1 ppm or less.

The contacting of the further organic solvent with the reaction mixture from step a) can be carried out, for example, by adding the reaction mixture containing lithium hexafluorophosphate, a first organic solvent and hydrogen chloride to the initially introduced further organic solvent. Likewise, any other order of contacting further organic solvent with the reaction mixture of step a) is basically suitable.

In an alternative embodiment, the contacting can be carried out, for example, such that the reaction mixture from step a) is initially charged and further organic solvent is added.

The contacting of the further organic solvent with the reaction mixture from step a) can be carried out, for example, continuously, for example by introducing the further organic solvent or discontinuously, for example by adding in portions, preferably by dropwise addition. Any container known to those skilled in the art of contacting solutions is suitable for contacting. The contacting can be facilitated by introducing mixing energy, for example, by static or non-static mixing elements.

The temperature according to step b) can, for example, and preferably from the freezing point to the boiling point of the organic solvent or its low-boiling component used, for example from -45 to 80 ° C, more preferably from 10 to 60 ° C and particularly preferably from 10 to 35 ° C, in particular from 16 to 24 ° C.

The pressure during the contacting according to step b) can be, for example, from 100 hPa to 2 MPa, preferably from 900 hPa to 1200 hPa, ambient pressure is particularly preferred.

The contacting of the further organic solvent with the reaction mixture from step a) preferably takes place over a period of one second to 48 hours, preferably from 10 seconds to 2 hours, particularly preferably from 30 seconds to 45 minutes and very particularly preferably from 1 minute to 30 minutes.

In an alternative embodiment, after step b), mixing may be achieved by introducing mixing energy, e.g. take place by static or non-static mixing elements.

In an alternative embodiment, the mixture containing lithium hexafluorophosphate, a first organic solvent and another organic solvent, for example, for a period of 10 seconds to 24 Stirred hours, preferably 1 minutes to 12 hours, more preferably 5 minutes to 2 hours and most preferably 10 minutes to 1 hours.

The contacting according to step b) leads to a precipitation of the lithium hexafluorophosphate. In a further embodiment, further contacting with further organic solvent or other organic solvents may be carried out after step b). This has the purpose that in addition to the drying, a further solvent exchange can take place.

Separation of the precipitated lithium hexafluorophosphate can be accomplished by any method known to those skilled in the art of solids and liquid separation. For example, the separation can be effected by sedimentation, centrifugation or filtration, for example by pressure filtration or suction filtration. The separation can be carried out, for example, by using a paper filter, polymer filter, a glass frit or a ceramic frit, preferably by a Teflon filter, in particular by a filter with a defined pore size, for example a filter with a pore size of <5 μm, preferably <1 μm, more preferably < 200 nm.

In an alternative embodiment, the, for example, separated, solid lithium hexafluorophosphate under inert gas, preferably argon, dried. If the separation is carried out in an alternative embodiment, the setting of a specific content of lithium hexafluorophosphate is possible. If it is largely complete, highly pure lithium hexafluorophosphate can be obtained as a solid. Almost complete here means that the remaining content of organic solvent is 5000 ppm or less, preferably 2000 ppm or less.

In an alternative embodiment, for example, the lithium hexafluorophosphate prepared according to the invention is dissolved in a first organic solvent. The dissolution takes place for example at a temperature of -45 ° C to room temperature, preferably at a temperature of -10 to 10 ° C and more preferably at a temperature of -5 to 5 ° C. This solution is contacted with more organic solvent. This can be done, for example, that the solution of lithium hexafluorophosphate in a first organic Is submitted solvent and further organic solvent is added. In an alternative embodiment, the further organic solvent may be charged and the solution of lithium hexafluorophosphate added in a first organic solvent. As already described above, lithium hexafluorophosphate precipitates out as a solid. The precipitated solid can be separated from the first organic solvents and the other organic solvents by the above-described separation methods. Preferred is the use of a Teflon reverse frit to separate the solid lithium hexafluorophosphate. This process, referred to as recrystallization, can be repeated as often as desired one to three times.

The solid lithium hexafluorophosphate can be washed in an alternative embodiment with organic solvent, preferably the other organic solvent described above. Surprisingly, despite the high concentrations of hydrogen chloride in step a), the reaction product lithium hexafluorophosphate contains only small amounts of chloride after completion of step c). Without wishing to be bound by any theory, the Applicant conjectures that the chlorides remain in the first organic solvent. Lithium hexafluorophosphate is less soluble in the other organic solvent and therefore precipitates.

Lithium hexafluorophosphate produced according to the invention typically has a content of impurities of 0 to 10,000 ppm, preferably 0 to 5,000 ppm, more preferably 0 to 1, 000 and most preferably 0 to 100 ppm.

Examples of typical impurities are hydrolytic decomposition products, in particular lithium difluorophosphate, acids, and metal cations, in particular calcium, chromium, iron, magnesium, molybdenum, cobalt, nickel, cadmium, lead, potassium or sodium and foreign anions, in particular sulfate, hydroxide, bicarbonate and carbonate ,

In an alternative embodiment, impurities, for example acids, may be added by addition of basic substances, for example a base selected from the group consisting of alkaline earth hydroxides, alkaline earth hydrogen carbonates, Alkaline earth carbonates, lithium hydroxide, lithium bicarbonate and lithium carbonate are brought into contact and neutralized.

Lithium hexafluorophosphate prepared according to the invention typically has a chloride content of 0 to 100 ppm, preferably 0 to 50 ppm, more preferably 0 to 5 ppm and most preferably 0 to 1 ppm.

The chloride content is determined as indicated in the examples.

Due to the low chloride content, the lithium hexafluorophosphate prepared according to the invention can be further processed, for example, into electrolytes suitable for electrochemical storage devices. The invention further relates to the use of the lithium hexafluorophosphate according to the invention as or for the production of electrolytes for lithium batteries.

Electrolytes can be prepared by per se generally known methods by contacting lithium hexafluorophosphate with organic solvent and optionally additives.

The invention further relates to a process for preparing electrolytes for lithium batteries, characterized in that the lithium hexafluorophosphate used comprises, according to a process comprising at least the steps a) to c) and optionally d) of the process according to the invention. The electrolytes prepared by the process according to the invention may contain further conductive salts such as, for example, lithium fluorosulfonylimide.

The advantage of the invention lies in particular in the efficient procedure and in the small amount of chloride in the lithium hexafluorophosphate prepared according to the invention. Examples

In the following, the term "%" is always to be understood as meaning% by weight and "ppm" always as "ppm by weight".

"Under inert gas condition", or inert gas means that the water and oxygen content of the atmosphere is below 1 ppm.

Determination of chloride and hexafluorophosphate content:

For the ion chromatography used in the present work, see Publication L. Terborg, S. Nowak, S. Passerini, M. Winter, U. Karst, P.R. Haddad, P.N. Nesterenko, Ion Chromatography determination of hydrolysis products of hexafluorophosphate salts in aqueous solution. Analytica Chimica Acta 714 (2012) 121-126 and the literature cited therein.

The analysis for the presence of chloride and hexafluorophosphate ions was carried out by ion chromatography. The following devices and settings are used for this:

Device type: Dionex ICS 2100

Column: lonPac® AS20 2 ^* 250-mm "Analytical Column with guard"

Sample volume: 1 μΙ

Eluent: KOH gradient: 0 min / 15 mM, 10 min / 15 mM, 13 min / 80 mM,

27 min / 100 mM, 27.1 min / 15 mM, 34 min / 15 mM

Eluent flow rate: 0.25 ml / min

Temperature: 30 ° C

Self-Regenerating Suppressor: ASRS® 300 (2-mm)

The detection limit for chloride ions is 1 ppm.

Determination of total acid as hydrogen fluoride:

With regard to the determination of the total acid used in the present work, reference is made to the publication M. Schmidt, U. Heider, A. Kuehner, R. Oesten, M. Jungnitz, N. Ignat'ev, P. Sartori, Lithium fluoroalkylphosphates: a new class of conducting salts for electrolytes for high energy lithium-ion batteries. Journal of Power Sources 97-98 (2001) 557-560 and the literature cited therein. For the determination of the total acid were 1, 79 g of the electrolyte solid in 13.21 g of a mixture of ethylene carbonate and dimethyl carbonate (weight ratio 1: 1) under Cooling solved. Part of the solution was titrated according to the reference cited above for total acid determination. In a glass jar, 0.2 ml of indicator solution (50 mg of bromothymol blue in 50 ml of anhydrous isopropanol) was titrated under inert conditions with a 0.01 N tetrabutylammonium hydroxide solution (in anhydrous isopropanol) until the color changes to blue-green. Subsequently, about 1 000 mg of electrolyte solution was weighed to the nearest 0.1 mg. It was titrated again to a cyan color change with 0.01 N tetrabutylammonium hydroxide solution, and the consumption of tetrabutylammonium hydroxide solution was accurately weighed to 0.1 mg. Determination of the water content:

Water contents were, unless stated otherwise, determined by the method according to Karl Fischer, which is known to the person skilled in the art and described, for example, in P. Bruttel, R. Schlink, "Water Determination by Karl Fischer Titration", Metrohm Monograph 8.026.5001, 2003 -06., Photometric determination of metal contents (iron, nickel, lead, cadmium):

Metal contents were determined by means of a photometric rapid test from Merck (Spectroquant® cuvette test). The photometer used was a Spectroquant Pharo 100 M (Merck).

The detection limit for iron is 1.3 ppm. The detection limit for nickel is 2.6 ppm.

The detection limit for lead is 2.6 ppm.

The detection limit for cadmium is 0.6 ppm. Phosphorus pentafluoride:

Examples 1 to 4 were carried out with commercially available phosphorus pentafluoride (99%, but GmbH, CAS 7647-19-0).

The phosphorus pentafluoride of Examples 5 and 6 was prepared as follows:

Stage 1: PCI ₃ + 3 HF -> PF ₃ + 3 HCl

Reaction of phosphorus trichloride with hydrogen fluoride to phosphorus trifluoride and hydrogen chloride

Step 2: PF ₃ + Cl ₂ -> PCI ₂ F ₃

Reaction of phosphorus trifluoride with elemental chlorine to phosphorodichloride trifluoride

Step 3: PCI ₂ F ₃ + 2 HF -> PF ₅ + 2 HCl

Reaction of phosphorodichloride trifluoride with hydrogen fluoride to form phosphorus pentafluoride and hydrogen chloride

Total: PCI ₃ + 5 HF + CI ₂ -> PF ₅ + 5 HCl

Experimental PFs preparation:

Through a heated to 280 ° C, about 6 m long reactor tube, a mixture of 20 g / h of hydrogen fluoride and 1 1, 4 ml / h of phosphorus trichloride (both gaseous) was passed. This reaction mixture was cooled to room temperature, introduced 6.5 l / h of chlorine and passed through another, about 6 m long reactor tube at room temperature.

General production conditions:

Unless otherwise stated, all work was carried out under argon inert gas. Acetonitrile (Fluka, Trace Select> 99.9%), toluene (Azelis, grade, dried over P ₂ 0 ₅ and distilled) and lithium fluoride (Sigma-Aldrich, 99.995%) were purchased from Sigma-Aldrich. The water content of the organic solvents used was below 50 ppm. In some cases, work is carried out in a glove box (Mbraun unilab), with oxygen and water content in the atmosphere being below 0.1 ppm. Example 1: Preparation of lithium hexafluorophosphate in acetonitrile (saturated)

250 ml of acetonitrile and 25.61 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus. 180 g of hydrogen chloride gas and then 186.58 g of gaseous phosphorus pentafluoride were first introduced into the resulting suspension. The resulting reaction mixture was stirred for one hour. The reaction mixture was filtered and the resulting solid was blown dry in an argon stream. 153 g of solid (44% yield) were obtained. Example 2: Preparation of lithium hexafluorophosphate in acetonitrile and subsequent precipitation with toluene

250 ml of acetonitrile and 6.49 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus. In the resulting suspension were first 27.35 g of hydrogen chloride gas (chloride content of the suspension after initiation: 12, 1 wt .-%) and then introduced 47.24 g of gaseous phosphorus pentafluoride. The resulting reaction mixture was stirred for one hour. The reaction mixture was metered into 500 ml of toluene. The precipitated solid was filtered off and blown dry in an argon stream. There was obtained 34.7 g of solid (91% yield).

Example 3: Preparation of lithium hexafluorophosphate in acetonitrile and subsequent precipitation with toluene

250 ml of acetonitrile and 6.49 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus. In the resulting suspension were first 27.35 g of hydrogen chloride gas (chloride content in the suspension after initiation: 12, 1 wt .-%) and then 47.24 g of gaseous phosphorus pentafluoride initiated. The resulting reaction mixture was stirred for one hour. The reaction mixture was metered into 1000 ml of toluene and stirred for 15 minutes. The precipitated solid was filtered off and blown dry in an argon stream. There were obtained 29.1 g of solid (77% yield).

Example 4: Preparation of lithium hexafluorophosphate in acetonitrile and subsequent precipitation with toluene and recrystallization

250 ml of acetonitrile and 6.49 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus. In the resulting suspension were first 27.35 g of hydrogen chloride gas (chloride content of the suspension after initiation: 12.1%) and then introduced 47.24 g of gaseous phosphorus pentafluoride. The resulting reaction mixture was stirred for one hour. The reaction mixture was metered into 500 ml of toluene and stirred for 15 minutes. The precipitated solid was filtered off and blown dry in an argon stream. There was obtained 29.5 g of solid (79% yield).

To crystallize:

In the glove box, 20 g of the resulting solid were dissolved in 88 g of acetonitrile at 0 ° C. The resulting solution was treated with 352 g of toluene. The precipitated solid was filtered off immediately via a Teflon reverse frit, washed with 50 ml of toluene, dried by blowing with argon. There were obtained 14.75 g of solid.

Characterization of the solid:

Chloride content: Below the detection limit

Lithium hexafluorophosphate: 98.0% by weight EXAMPLE 5 Preparation of Lithium Hexafluorophosphate in Acetonitrile and Subsequent Precipitation with Toluene and Recrystallization 250 ml of acetonitrile and 6.49 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus without an upstream cooling trap. The gaseous phosphorus pentafluoride / hydrogen chloride mixture (PF ₅ / HCl) prepared according to the above procedure was introduced into the resulting suspension until nominally 1 equivalent of phosphorus pentafluoride (calculated from the consumption of PCI ₃ , 20 ml consumption) was contained. The resulting reaction mixture was stirred for one hour. The reaction mixture was metered into 500 ml of toluene and stirred for 15 minutes. The precipitated solid was filtered off and blown dry in an argon stream. There was obtained 30.3 g of solid (79% yield). From the solid, a solution (1 1, 8 wt .-% lithium hexafluorophosphate) in dimethyl carbonate / ethylene carbonate (DMC / EC) was prepared.

To crystallize:

In the glove box, 15 g of the solid obtained were dissolved in 66 g of acetonitrile at 0 ° C. The resulting solution was treated with 264 g of toluene. The precipitated solid was filtered off immediately via a Teflon reverse frit, washed with 50 g of toluene and blown dry in an argon stream. There were obtained 17, 15 g of solid.

Characterization of the solid: Chloride content: Below the detection limit

Lithium hexafluorophosphate: 80.0% by weight

Example 6: Preparation of lithium hexafluorophosphate in acetonitrile and subsequent precipitation with toluene and recrystallization

250 ml of acetonitrile and 6.49 g of lithium fluoride were initially charged at room temperature in an argon-filled 500 ml Teflon apparatus with an upstream cold trap. The gaseous phosphorus pentafluoride / hydrogen chloride mixture (PF ₅ / HCl) prepared according to the above procedure was introduced into the resulting suspension until nominally 1 equivalent of phosphorus pentafluoride (calculated from the consumption of PCI ₃ , 20 ml consumption) was contained. The resulting reaction mixture was stirred for one hour. The reaction mixture was metered into 500 ml of toluene and stirred for 15 minutes and allowed to stand overnight. The precipitated solid was filtered off and blown dry in an argon stream. There was obtained 48.0 g of solid (71% yield). recrystallization:

In the glove box, 40 g of the resulting solid were dissolved in 176 g of acetonitrile at 0 ° C. The resulting solution was treated with 704 g of toluene. The precipitated solid was immediately washed via Teflon reverse frit, washed with 50 g of toluene, and blown dry in an argon stream. There was obtained 16.9 g of solid.

Characterization of the solid:

Chloride content: Below the detection limit

Lithium hexafluorophosphate: 99.0% by weight

Claims

claims

1 . A process for preparing low-lithium lithium hexafluorophosphate comprising at least the steps of a) contacting lithium fluoride in a first organic solvent containing a nitrile with a gas containing phosphorus pentafluoride and hydrogen chloride to obtain a reaction mixture containing lithium hexafluorophosphate, a first organic solvent containing a nitrile and hydrogen chloride, b) contacting the reaction mixture formed according to a) with further organic solvent which is different from the first organic solvent, lithium hexafluorophosphate precipitating and c) separating off precipitated lithium hexafluorophosphate.

2. The method according to claim 1, characterized in that the lithium fluoride used in step a) has a purity of 98.0000 to 99.9999 wt .-%, preferably 99.0000 to 99.9999 wt .-%, more preferably 99, 9000 to 99.9995 wt .-%, particularly preferably 99.9500 to 99.9995 wt .-% and very particularly preferably 99.9700 to 99.9995 wt .-% based on anhydrous product.

3. The method according to claim 1 or 2, characterized in that the first organic solvent is a nitrile, a combination of nitriles or a combination of at least one nitrile with at least one organic solvent which is not nitrile, preferably acetonitrile is used.

4. The method according to any one of claims 1 to 3, characterized in that the contacting of lithium fluoride and a first organic solvent under inert gas, preferably under argon, takes place.

5. The method according to any one of claims 1 to 4, characterized in that the gas used in step a) containing phosphorus pentafluoride and hydrogen chloride can be prepared by a process comprising at least the following steps: 1) Reaction of phosphorus trichloride with hydrogen fluoride to phosphorus trifluoride and hydrogen chloride

2) Reaction of phosphorus trifluoride with elemental chlorine to phosphorodichloride trifluoride

3) Reaction of phosphorodichloride trifluoride with hydrogen fluoride to form phosphorus pentafluoride and hydrogen chloride

6. The method according to any one of claims 1 to 5, characterized in that the gas containing phosphorus pentafluoride and hydrogen chloride, a gas mixture containing 5 to 41 wt .-% phosphorus pentafluoride, 6 to 59 wt .-% hydrogen chloride and 0 to 50 wt .-% of hydrogen fluoride , preferably 20 to 41 wt .-% phosphorus pentafluoride, 40 to 59 wt .-% hydrogen chloride and 0 to 40 wt .-% of hydrogen fluoride, particularly preferably 33 to 41 wt .-% phosphorus pentafluoride, 49 to 59 wt .-% hydrogen chloride and 0 to 18 wt .-% of hydrogen fluoride, wherein the proportion of phosphorus pentafluoride, hydrogen chloride and hydrogen fluoride, for example, 1 1 to 100 wt .-%, preferably 90 to 100 wt .-% and particularly preferably 95 to 100 wt .-% is.

7. The method according to any one of claims 1 to 6, characterized in that the temperature when contacting in step a) from the freezing point to the boiling point of the aqueous medium used, preferably 0 to 100 ° C, more preferably 10 to 60 ° C and more preferably 10 to 35 ° C, in particular 16 to 24 ° C.

8. The method according to any one of claims 1 to 7, characterized in that in the inventive, different from the first organic solvent, further organic solvent, preferably toluene, lithium hexafluorophosphate having a lower solubility than in the first organic solvent.

9. The method according to any one of claims 1 to 8, characterized in that further organic solvent is preferably toluene.

10. The method according to any one of claims 1 to 9, characterized in that the contacting of the further organic solvent with the reaction mixture containing lithium hexafluorophosphate, a first organic Solvent and hydrogen chloride is such that the reaction mixture containing lithium hexafluorophosphate, a first organic solvent and hydrogen chloride is added to the submitted further organic solvent.

1 1. Method according to one of claims 1 to 10, characterized in that lithium hexafluorophosphate produced according to the invention in a further step d) at a temperature of -45 ° C to room temperature, preferably at a temperature of -10 to 10 ° C and more preferably at a temperature from -5 to 5 ° C dissolved in a first organic solvent and in a further step e) is brought into contact with further organic solvent, wherein lithium hexafluorophosphate precipitates and then in a step f) lithium hexafluorophosphate is separated.

12. The method according to any one of claims 1 to 1 1, characterized in that the lithium hexafluorophosphate according to the invention a chloride content of 0 to 100 ppm, preferably 0 to 50 ppm, more preferably 0 to 5 ppm and most preferably 0 to 1 ppm having.

13. Lithium hexafluorophosphate, characterized in that it has a chloride content of 0 to 28 ppm, preferably from 0 to 5 ppm and most preferably from 0 to 1 ppm.

14. A process for producing electrolytes for lithium batteries, characterized in that it comprises at least one process of claims 1 to 12.

15. The use of lithium hexafluorophosphate according to claim 14 and their solutions as or for the preparation of electrolytes in lithium batteries.