DE19805356C1 - Lithium hexafluorophosphate is produced by reacting phosphorus pentachloride with an acidified lithium fluoride-diethylether suspension - Google Patents

Abstract

Pure lithium hexafluorophosphate (LiPF6) is produced by reacting phosphorus pentachloride with a slightly acidified suspension of lithium fluoride in diethylether. Pure LiPF6 is produced by reacting PCl5 with a suspension of LiF, diethylether and an anhydrous protic acid HX (X = halogen, sulfate or carboxylic acid group), followed by neutralizing the acid with a base, filtering and isolating the pure LiPF6.

Description

The invention relates to a process for the production of pure lithium hexafluorophosphate, LiPF ₆ , from LiF and PCl ₅ in diethyl ether.

Lithium hexafluorophosphate, LiPF ₆ , is currently used as a conductive salt in all commercial lithium ion batteries. LiPF ₆ is a moderately hydrolysis-sensitive substance that is extremely hygroscopic and releases hydrogen fluoride (HF) in contact with moist air. HF has an extremely damaging effect on the cycle stability of lithium ion batteries, since it can detach metals from the cathodes consisting of transition metal oxides and thus cause the electrodes to decay.

The battery manufacturers therefore prefer the LiPF ₆ in a form which is as little sensitive to hydrolysis as possible, ie which has the smallest possible specific surface area. Furthermore, the LiPF ₆ should be free-flowing so that it can be processed in automated systems. Finally, it should be ensured that the not inconsiderable heat of solution is released in a controlled manner in the production of electrolyte solutions.

All of these requirements are met by a coarse LiPF ₆ crystal or granulate with an even grain size distribution. This product must be available in as pure a form as possible, because it is known that, in addition to the lowest possible HF contents, e.g. B. also a low chloride content is necessary to ensure good cycle stability with rechargeable batteries.

Lithium hexafluorophosphate is usually prepared from purified PF ₅ and lithium fluoride in a solvent (HF or organic solvents such as diethyl ether or acetonitrile). Since the PF ₅ gas is contaminated on the one hand with impurities from the synthesis (e.g. POF ₃ , HCl and the like) and on the other hand during the reaction with LiF in a liquid medium with traces of moisture with the release of HF, POF ₃ , Li [PO ₂ F ₂ ] and other products, the raw product obtained generally has to be cleaned due to the high purity requirements of the battery industry.

For cleaning, the raw product z. B. from anhydrous HF be recrystallized. This method has the disadvantage that last traces of acid and lithium fluoride are very difficult can be separated. It also requires because of  Corrosive and toxic properties of HF are complex Reaction technology.

Therefore, synthetic processes that avoid the use of HF are easier to implement on an industrial scale. For example, US Pat. No. 3,607,020 proposes a process for the preparation of LiPF ₆ in which LiF is reacted with PF ₅ in an inert organic solvent, lower saturated alkyl ethers and lower alkyl esters of aliphatic saturated monocarboxylic acids being particularly suitable as solvents. This process has the disadvantage that PF ₅ gas must be synthesized immediately before the process is carried out, since this raw material is not available on the market.

US Pat. No. 378,445 describes a process for the preparation of LiPF ₆ solutions in which a lithium salt is reacted with a salt containing the hexafluorophosphate ion in a low-boiling, aprotic, organic solvent in a basic medium. However, the LiPF ₆ solution obtained is relatively heavily contaminated and must first be cleaned before being used as an electrolyte.

JP 09245807 A and CA-A 2,193,119 describe processes for the production of LiPF ₆ in which LiF is reacted with expensive PF ₅ gas which is not available in large quantities in a non-aqueous organic solvent. The production of crystalline, solvent-free LiPF ₆ is not intended using these processes.

Another process (EP 643 433 B1) is based on ammonium hexafluorophosphate, which is carried out with LiH in aprotic solvents according to the equation

to LiPF _{6 is} implemented. This process has the disadvantage that NH ₄ PF ₆ and LiH are relatively expensive raw materials.

In a further process (US Pat. No. 5,378,445), starting from MPF ₆ (M = Na, K, NH ₄ , NR ₄ ), the lithium compound is produced according to the equation

M = Na, K, NH ₄ NR ₄ X = halogen etc.
prepared as a solution in organic solvents. The process has the disadvantages that the metal hexafluorophosphates (MPF ₆ ) are not available or are only available at high prices and the solutions are contaminated by the anion X (for example 0.1% KCl or 3% KBr).

German patent application 196 32 543 describes, among other things, a process for the production of LiPF ₆ from the cheap raw materials LiF and PCl ₅ under autogenous pressure or optionally in organic solvents, in particular in diethyl ether, according to the equation

6LiF + PCl ₅ → LiPF ₆ + 5LiCl (3)

suggested.

This method has the disadvantage that finely powdered, chloride-containing end products are formed (e.g., 0.2% Cl ^-. - content in the printing industry). It was also found that during the direct synthesis in diethyl ether there is a discoloration of the initially colorless reaction mixture. The bluish-black impurities remain in the raw LiPF ₆ product after removal of the solvent and are extremely difficult to separate.

When LiPF ₆ crystallizes from organic donor solvents such as diethyl ether or acetonitrile, complexes usually form between LiPF ₆ and solvency (LiPF _6. D _x ; D = donor solvency, x = 1 ... 4). The solvate complexes, most of which are in the form of well-formed crystals, decompose to a surface-rich, difficult-to-handle powder when they dry at temperatures below the solvate decomposition point.

The decomposition of the well-defined acetonitrile complex LiPF ₆ . (CH ₃ CN) ₄ under reduced pressure at temperatures up to 30 ° C is a pure, but surface-active, and therefore difficult to handle solvent-free product (US Pat. No. 3,594,402).

When LiPF ₆ is crystallized from diethyl ether, a solvate complex is also obtained, the solvate decomposition point of which is approximately 40 ° C. (own experiments).

The production of a solvate-free LiPF ₆ from an ethereal solution has been known for a long time. Thus, according to US Pat. No. 3,607,020, LiPF _{6 is produced} from LiF and PF ₅ in ether at 0 to 50 ° C. and the LiPF ₆ crystals obtained are dried at 30 to 35 ° C. under reduced pressure (0.2 mm).

Similarly, according to DE 196 14 503 A1, the drying of LiPF ₆ , which is produced by reacting LiF with PF ₅ and dissolved in diethyl ether, at max. 40 ° C under vacuum. Temperatures of about 40 ° C are generally not exceeded because product decomposition according to the equation

is feared. So z. B. in US Pat. No. 3,594,402 claims that the dissociation according to reaction (4) begins at approximately 20 ° C. and LiPF ₆ decomposes at 30 to 40 ° C.

Depending on the production conditions, the LiPF ₆ isolated from ethereal solutions at temperatures of 40 ° C. contains a certain amount of "crystal ether" (approx. 1 to 2 mol), which can be removed relatively quickly and completely during vacuum drying, but this inevitably results in a dusty, surface-rich product is obtained.

The object of the invention is to avoid the disadvantages known from the prior art and to create a process which, starting from cheap raw materials, provides a technically simple, manageable process, an easy-to-handle, pure LiPF ₆ , which has a purity of <99, Has 8%.

The object is achieved by the method specified in claim 1. Subclaims 2 to 11 disclose features that further develop the method according to the invention. When the method according to the invention is carried out according to subclaims 12 to 14, a pure LiPF ₆ obtained by total evaporation is obtained. Alternatively, 15 to 24 process features are specified in the subclaims which lead to a highly pure LiPF ₆ obtained by crystallization.

In the process according to the invention, a diethyl ether-containing LiF suspension is reacted with PCl ₅ , the LiF suspension being weakly acidified before the PCl _{5 is} metered in. It was surprisingly found that acidification, for example with HCl gas, accelerates the LiPF ₆ formation reaction and, at the same time, suppresses side reactions. Also particularly striking is the phenomenon that the discoloration of the reaction mixture is absent or is greatly delayed.

Before starting the reaction with PCl ₅ , the LiF suspension containing diethyl ether is acidified. It is also possible to acidify the diethyl ether before adding LiF and use it for slurrying the lithium fluoride.

Anhydrous protic acids HX are used for acidification, where X can be: a halogen, sulfate or a carboxylic acid residue. Preferred acids are their corresponding ones Lithium salts in ether or ether / hydrocarbon mixtures are as poorly soluble as possible. HCl- and HF gas, the former because of the easier handling is particularly advantageous.

The acid concentration can be between 0.01 and 0.5 mmol / g Suspension. The range is particularly preferred between 0.02 and 0.2 mmol / g.

The reaction temperature is 0 to 35 ° C, the preferred range is between 15 and 30 ° C.

The response time is u. a. of the reaction temperature and Stirring intensity influenced. In the preferred temperature range between 15 and 30 ° C are typically 2 to 8 hours for one practically quantitative sales needed. Depending on the chosen one Reaction conditions (acid concentration, metering time, Mixing intensity, stoichiometry and temperatures) that remains Reaction mixture colorless throughout the reaction time, or it only becomes yellowish or slightly bluish towards the end.

The PCl _{5 is} metered into the acidified, well-stirred LiF suspension at temperatures between 0 and 35 ° C. The amount of PCl ₅ metered in is chosen so that 6.06 to 12 mol LiF are present per mol PCl ₅ . Since the theoretical stoichiometric ratio PCl ₅ to LiF is 1: 6, LiF is present in a defined excess. A ratio PCl ₅ to LiF of 1: 6.3 to 1: 7.2 is preferred. In principle, higher LiF surpluses lead to faster and more complete utilization of the PCl _{5 used} , but the economy of the process is adversely affected.

After the end of the reaction, the reaction mixture is neutralized with a base, the amount of base to be used corresponding at least to the amount of acid used. Ammonia, LiOH, Li ₂ CO ₃ , LiH or organolithium compounds such as methyl lithium or butyllithium can be used as bases. Preferred are methyl lithium, which is available on the market in the form of an ethereal solution, and lithium hydride, which does not leave any troublesome by-products in the neutralization.

Because of the insolubility of lithium hydride, it is (based on the amount of acid used) up to 10 times, preferably 3 to 6 times molar excess is used. Excess Lithium hydride can be used together with the ether-insoluble ones Lithium halides can be conveniently separated by filtration.

The concentration of the as a suspension in diethyl ether submitted lithium fluoride is preferably 10 to 40%.

Either pure, dry diethyl ether or a mixture of diethyl ether and a solvent consisting of one or more hydrocarbons is used as the reaction medium. Possible hydrocarbons are alkanes, such as. B. preferably pentane, hexane, heptane or cyclohexane and aromatics, such as. B. preferably toluene, xylene or ethylbenzene. The amount of the additional solvent optionally used can vary within wide limits and can be, for example, 0.3 to 3 parts by weight of the amount of LiF. A further dilution is possible, but makes no sense for technical and economic reasons. The solvent can either be introduced as a whole before the acidification and metering in of PCl ₅ or be added during the PCl ₅ metering or in the post-reaction phase. It improves the stirrability of the reaction suspension and makes it possible to replace part of the more expensive diethyl ether. Furthermore, it can be used as a crystallization aid in the crystallization cleaning step (see below) to be carried out optionally.

The neutralized reaction mixture is then filtered, decanted or centrifuged to remove the insoluble by-products and the excess lithium fluoride. An ethereal LiPF ₆ crude product solution is obtained in this way. The raw solution is contaminated, among other things, with chlorine-containing compounds, especially PCl ₃ .

In the production of LiPF ₆ according to a state-of-the-art process (see also Comparative Example 1), in which non-acidified diethyl ether is used, approx. 0.5 to 1.5 mol% PCl ₃ (determined from the integration ratio PCl ₃ : PF ₆ ^- observed in the ³¹ P-NMR spectrum) as an impurity. It has surprisingly been found that the acidification of the diethyl ether by the method according to the invention leads to a significant decrease in the PCl ₃ contamination: it is only in the range of the ³¹ P-NMR detection sensitivity (approx. 0.02%) or less.

Insoluble constituents (LiCl, LiF, LiH, LiOH) of the ethereal crude LiPF ₆ product solution are filtered off, and the slightly yellowish or colorless LiPF ₆ solution is either dried by evaporation or further purified by crystallization in the manner described below.

By total evaporation, a moderately clean LiPF ₆ quality (content approx. 99.8%) can be obtained from the filtrate. In order to achieve a product which is easy to handle, ie one with a low specific surface area, the diethyl ether and the solvent which may be present are distilled off at normal or only moderately reduced pressure (600 to 1000 mbar). After removal of the majority of ether, the bottom temperature is increased to 40 to 100 ° C., preferably 50 to 75 ° C., by external heating. To remove the last diethyl ether or further solvent residues, the pressure can (at the same time) be reduced (expediently) (to, for example, 0.1 to 10 mbar). Surprisingly, no product decomposition according to reaction equation (4) was observed at the relatively high temperatures. On the other hand, the bottom temperatures are above the decomposition point of the LiPF ₆ etherate, which is why an ether-free, dust-free solid product forms directly. Depending on the drying conditions chosen, either a lumpy product or a granulate is obtained.

A crystallization process can be selected for higher purity requirements. For this purpose, an aprotic crystallization aid is added to the ethereal crude product solution, which does not or only poorly dissolves LiPF ₆ in pure form and has a higher boiling point than diethyl ether.

Alternatively, the crude product solution, which has been pre-evaporated to a LiPF ₆ concentration of 20 to 50%, preferably 30 to 45%, in pure diethyl ether can be mixed with the crystallization aid and then filtered.

This crystallization aid is e.g. B. another ether (Methyl tert-butyl ether (MTBE), dibutyl ether, Diisopropyl ether), an alkane (e.g. heptane, methylcyclohexane, Octane) or an aromatic hydrocarbon (e.g. benzene, Toluene, ethylbenzene) or a mixture of the above Fabrics. Heptane, methylcyclohexane, Toluene and methyl tert-butyl ether.

The amount of the crystallization aid is 0.2 to 5 parts by weight of the amount of LiPF _{6 present} in diethyl ether solution. 0.3 to 1.5 parts by weight, based on the dissolved LiPF ₆ , are particularly preferred.

The LiPF ₆ solution in the solvent mixture defined above is concentrated at normal or slightly reduced pressure. The jacket temperature of the still is initially 40 to 70 ° C. According to the different boiling points, practically pure diethyl ether initially distills, which continuously worsens the solvent capacity of the remaining solvent for the impurities and also LiPF ₆ . When an Et ₂ O: LiPF ₆ ratio of approx. 1.2 to 2.3 is reached, the distillation is interrupted and the distillation residue is freed of any precipitated impurities by filtration.

The clear filtrate is then reduced to a residual ether amount of 0 evaporated further up to 30%. The bottom temperature rises up to approx. 40 to 90 ° C. Lithium hexafluorophosphate exits turns out as a colorless, coarsely crystalline solid. Of the  Solid is removed by filtration or centrifugation from the Free mother liquor. This solid / liquid is preferably Separation step carried out at temperatures ≧ 40%.

The crystals are treated with an aliphatic and / or aromatic hydrocarbon washed, preferably Pentane, hexane or toluene are used, and then dried. Drying is preferably carried out at elevated Temperatures (30 to 50%) under reduced pressure.

In this way, a solvent-free, coarse crystalline Obtain product with a purity of <99.9%.

The object of the invention is described below with reference to Comparative and exemplary embodiments explained in more detail.

Examples 1 and 5 were compared for comparison purposes State of the art, the remaining examples were carried out by the method according to the invention.

Example 1: (Comparative example): reaction of LiF with PCl ₅ in neutral diethyl ether at 25 ° C. (according to German patent application 196 32 543)

170.0 g (8.3 mol, 38% excess) of dried lithium fluoride were suspended in 920 g of diethyl ether in a 2-1 double jacket vessel. At an internal temperature of 25%, 207 g (1.0 mol) of PCl ₅ from a metering bulb were added over the course of 18 minutes. The internal temperature was kept below 28% by counter-cooling. After 2 hours the reaction mixture began to turn purple; after 32 g (1.23 mol) of LiF had been added again, the reaction suspension discolored briefly, but the violet color was observed again after 15 minutes.

After a reaction time of 3.5 hours, the reaction mixture was mixed with 2.6 g of LiH were added and the mixture was stirred for a further 1.5 hours. The suspension was filtered and the residue with 3 portions of ether washed.

963 g of a blue-gray solution were obtained. The solution was concentrated in vacuo at 25 ° C. (weight 518 g) and a sample was hydrolyzed and analyzed by elemental analysis:

Li = 1.12%; P = 5.25%; F = 18.5%; Cl = 0.48%

The raw LiPF ₆ yield was therefore approx. 128 g (84%), the solution had a LiPF ₆ content of approx. 24.7%. PCl ₃ (δ ³¹ P = -220 ppm) was detected in the ³¹ P NMR spectrum; the molar ratio PCl ₃ : LiPF ₆ was approximately 1.2: 100.

Example 2: Reaction of LiF with PCl ₅ in acidic diethyl ether at 25 ° C

256.8 g (9.90 mol, 10% excess) of LiF in 1184 g of hydrochloric diethyl ether (H ⁺ = 0.08 mmol / g, total 95 mmol) were introduced into a 3-1 double-jacket reactor with a Teflon dispersing disc, reflux condenser and solids metering device ) submitted. At an internal temperature between 24 and 27 ° C, 312 g (1.50 mol) of PCl _{5 were} metered in in portions within 1 hour.

After a total reaction time of 5 hours, it started discolor the solution slightly yellowish. There were 3.15 g (0.40 mol) lithium hydride carefully added (initially strong  Gas evolution) and then was refluxed for about 20 minutes cooked.

After filtration, 1288 g of a clear, almost colorless solution were obtained (Li = 0.65%, F = 11.4%, P = 3.1%), the content of LiPF _{6 was} approximately 15.2% (corresponding to one LiPF ₆ - crude product yield of approx. 86%). According to the ³¹ P-NMR spectrum, the molar ratio PCl ₃ : LiPF _{6 was} 0.02: 100.

Examples 1 and 2 show that much less undesired PCl _{3 is} formed by acidification and product discoloration can be largely avoided.

Example 3: Reaction of LiF with PCl ₅ in 007 mmol H ⁺ / g Et ₂ O at 20 to 37 ° C

18.8 g of dried LiF (726 mmol, 10% excess) in 103 g of hydrochloric acid diethyl ether (0.07 mmol of H ⁺ / g) were placed in a 250 ml Schienk flask with reflux condenser and 22.8 g (110 mmol) PCl ₅ added. As a result of the heat of reaction released, the reaction mixture heated to boiling (36 ° C.) within 13 minutes. After 50 minutes the temperature dropped back below 35 ° C. A slight reddish discoloration was noticed after 80 minutes.

Example 4: Reaction of LiF with PCl ₅ in 0.14 mmol H ⁺ / g Et ₂ O at 20 to 37 ° C

As in Example 3, 20.6 g of LiF (793 mmol, 10% excess) were suspended in 100 g of hydrochloric acid diethyl ether (0.14 mmol of H ⁺ / g, total amount of 14 mmol) and with 25.0 g (120 mmol) of PCl ₅ transferred. The mixture heated to boiling within about 7 minutes. After about 1.5 hours there was a very weak yellowing, which did not increase in the following 1.5 hours. 0.2 g (25 mmol) of LiH were added and the mixture was refluxed for 15 minutes. After filtration, a practically colorless ethereal LiPF ₆ solution was obtained.

Examples 3 and 4 (different variants of the inventive method) show that the different Discoloration behavior is dependent on the acid concentration. At an acid concentration of 0.14 mmol / g was also at relatively high reaction temperatures a colorless product solution receive.

Example 5: (comparative example): total evaporation to powder (according to German patent application 196 32 543)

380 g of the filtered solution from Example 1 (LiPF ₆ content approx. 15.2%, corresponding to 57.8 g content) were in a rotary evaporator (bath temperature 30 to 40 ° C) in vacuo (last 1 mbar) to dryness and constant weight evaporated. 53 g (yield: 92%) of a yellowish, dust-fine powder were obtained.

Example 6: Total evaporation to the granulate

88 kg of a LiPF ₆ solution prepared as in Example 2 were first concentrated to a concentration of 31% LiPF ₆ . This concentrated solution was evaporated to dryness in a heatable planetary mixer (jacket temperature 45 to 55 ° C.) first at normal pressure, then in vacuo (about 50 mbar) in about 5 hours. 14.2 kg of yellowish granules (grain size 1 to 3 mm) were obtained.

Yield: 88%, Cl content: 0.08%.

Examples 5 and 6 demonstrate that when the bottom temperature is increased above 40 ° C., granules can be obtained, while below 40 ° C. a yellowish, dust-fine powder is obtained, and that pure LiPF _{6 is} produced by the process according to the invention.

Example 7: Crystallization from Et ₂ O / hexane at RT

364 g of a 38% ethereal LiPF ₆ solution (prepared analogously to Example 2) were mixed with 450 g of hexane at about 15 ° C. with stirring in about 30 minutes. That in the form of z. LiPF ₆ etherate which precipitated T. well-formed crystal needles was isolated in a glass frit and washed with a little pentane. The filter-moist product (278 g) was dried in vacuo (0.1 mbar) at room temperature. 122 g (88%) of pure LiPF _{6 were obtained} in the form of a white, very finely crystalline powder (purity <99.9%).

Example 8: Crystallization from Et ₂ O / toluene at 50 to 70 ° C

91.4 g of crude LiPF ₆ (Cl content 1.2%) were dissolved in 144 g of ether in a 500 ml Schlenk flask, and 95 g of toluene were added. The cloudy solution was stirred for 30 minutes and then filtered.

The clear, yellow filtrate was concentrated at a pressure of 700 mbar and an oil bath temperature of 70 ° C until the distillate temperature rose to about 55 ° C. Colorless, coarse crystals precipitated out. The residue (213 g) was filtered while warm, the crystals were washed with toluene and hexane and then dried in vacuo. 79.7 g (87%) of pure LiPF _{6 were} obtained (Cl content 50 ppm).

Examples 7 and 8 according to the invention demonstrate the different crystallization behavior of LiPF ₆ from diethyl ether / hydrocarbon mixtures below and above about 40 ° C.

Example 9: Crystallization from Et ₂ O / toluene at 40 to 75 ° C

197 g of crude LiPF ₆ (Cl content 0.06%) were dissolved in 460 g of ether and 195 g of toluene were added. The slightly cloudy solution was stirred at RT for 2 hours and then filtered. The clear solution was concentrated at normal pressure and a bath temperature of initially 40 ° C., then increasing to 75 ° C. After 474 g of distillate had been separated off, the LiPF _{6 which} precipitated out in the form of large, colorless crystals was filtered off, washed and dried. The yield was 194 g (98%), the chloride content was <20 ppm.

This example shows that from a relatively pure LiPF ₆ raw product quality, a chloride-free LiPF ₆ can be obtained practically without losses.

Example 10: Crystallization from Et ₂ O / toluene at approx. 60 ° C without polishing filtration

178 g of a yellow 20.1% crude ethereal LiPF ₆ solution (containing 0.4% chloride) were mixed with 36 g of toluene at RT. A yellow, clear solution was formed. Ether was distilled off on a rotary evaporator at a bath temperature of initially 50 ° C., later 60 ° C. and slightly reduced pressure (first 1000, then 700 mbar). After approximately 110 ml of distillate (= 55% of the ether) had been separated off, a precipitate began to separate. A further 60 ml of ether were distilled off. The suspension was filtered and the solid filtered off was washed with a little toluene and hexane.

There were 31.3 g (88%) of a dust-free, coarse crystalline and obtained pure white crystals. The chloride content was still <20 ppm.

In this example, a dilute LiPF ₆ solution was mixed with a hydrocarbon and evaporated until solvate-free, pure LiPF ₆ failed. In the present case, the ether was not removed completely, so that the impurities remained in the solution and polishing filtration was not necessary.

Example 11: Crystallization from Et ₂ O / methylcyclohexane at 70 ° C

86.0 g of crude LiPF ₆ (Cl content 0.5%) were dissolved in 201 g of diethyl ether and 88 g of methylcyclohexane were added. The slightly cloudy solution was filtered; the clear filtrate was concentrated at a bath temperature of 70 ° C and a pressure of 800 mbar. 190 g of distillate were separated off and the residue was filtered. In this way, 84 g (98%) of a coarse crystallizate with a chloride content of 70 ppm could be obtained.

From this example it is clear that instead of the aromatic Toluene saturated hydrocarbons can be used.

Claims (24)

1. A process for the production of pure LiPF ₆ from LiF and PCl ₅ in diethyl ether, characterized in that
that a suspension of LiF, diethyl ether and an anhydrous protic acid HX, where X is a halogen, sulfate or carboxylic acid residue, is reacted with PCl ₅ ,
that the acid HX is neutralized with a base after the reaction has ended,
that the neutralized mixture is filtered and
that the pure LiPF _{6 is} isolated from the filtrate. 2. The method according to claim 1, characterized in that the acidic suspension of LiF in either diethyl ether Add LiF in acidified diethyl ether or by Acidify a suspension of LiF in diethyl ether will be produced. 3. The method according to claim 1 or 2, characterized in that as acid HX gaseous HCl or gaseous HF is used. 4. The method according to one or more of claims 1 to 3, characterized in that the acid concentration is 0.01 to 0.5 mmol / g suspension, preferably 0.02 to 0.2 mmol / g Suspension. 5. The method according to one or more of claims 1 to 4, characterized in that the reaction temperature 0 to 35 ° C, preferably 15 to 30 ° C.   6. The method according to one or more of claims 1 to 5, characterized in that the reaction time 2 to 8 Hours. 7. The method according to one or more of claims 1 to 6, characterized in that PCl ₅ to LiF in a molar ratio of 1: 6.06 to 1:12, preferably 1: 6.3 to 1: 7.2, is used. 8. The method according to one or more of claims 1 to 7, characterized in that the base NW, LiOH, Li ₂ CO ₃ , LiH or an organolithium compound, preferably LiH or methyl lithium, is used. 9. The method according to claim 8, characterized in that the Base LiH up to 10 times, preferably 3 to 6 times, molar excess added to the amount of acid used becomes. 10. The method according to one or more of claims 1 to 9, characterized in that LiF in so much diethyl ether is suspended that a suspension with a LiF Concentration of 10 to 40% arises. 11. The method according to one or more of claims 1 to 10, characterized in that before or during the implementation 0.3 to 3 parts by weight of an aliphatic and / or aromatic solvent per part by weight of LiF added become.   12. The method according to one or more of claims 1 to 11, characterized in that after the implementation of the Diethyl ether and the solvent removed by distillation become. 13. The method according to claim 12, characterized in that the bottom temperature in the distillative diethyl ether and solvent removal towards the end of the Distillation process 40 to 100 ° C, preferably 50 to 75 ° C. 14. The method according to claim 12 or 13, characterized characterized in that the distillative diethyl ether and Solvent removal started at 1000 to 600 mbar and the pressure after separation of the bulk of the Diethyl ether and the solvent gradually reduced and that it is finally dried under full vacuum. 15. The method according to one or more of claims 1 to 10, characterized in that an aprotic crystallization aid, which has a higher boiling point than diethyl ether and hardly or does not dissolve LiPF ₆ in pure form, is added after the reaction of the solution of LiPF ₆ in diethyl ether has taken place becomes. 16. The method according to one or more of claims 1 to 10, characterized in that the LiPF ₆ solution in diethyl ether is evaporated to a LiPF ₆ concentration of 20 to 50%, preferably 30 to 45% and then an aprotic crystallization aid, which in turn has a higher boiling point than diethyl ether and in its pure form hardly or does not dissolve LiPF ₆ , is added. 17. The method according to claim 15 and / or 16, characterized characterized in that the crystallization aid Alkane or an aromatic or an ether, preferably heptane or methylcyclohexane or toluene or methyl tert. Butyl ether. 18. The method according to one or more of claims 15 to 17, characterized in that the crystallization aid in an amount of 0.2 to 5 parts by weight, preferably 0.3 to 1.5 parts by weight, based on the LiPF ₆ amount of the solution, is added. 19. The method according to one or more of claims 15 to 18, characterized in that the diethyl ether is distilled off to an Et ₂ O: LiPF ₆ weight ratio of 1.2: 1 to 2.3: 1 and the solution is filtered. 20. The method according to one or more of claims 15 to 19, characterized in that the LiPF ₆ -containing solution is evaporated, the diethyl ether being distilled off to a residual amount of 0 to 30% of the amount initially introduced, the bottom temperature being 40 increases to 90 ° C and where LiPF _{6 separates} as a crystalline, solvate-free solid. 21. The method according to claim 20, characterized in that the deposited, crystalline LiPF _{6 is} separated from the mother liquor by filtration or centrifugation. 22. The method according to claim 21, characterized in that the separation from the mother liquor at temperatures of above 40 ° C. 23. The method according to claim 21 or 22, characterized in that the crystalline LiPF ₆ with an aliphatic and / or aromatic hydrocarbon, preferably pentane or hexane or toluene, washed and then dried. 24. The method according to claim 23, characterized in that drying at temperatures of 20 to 70 ° C, preferred 30 to 50 ° C, and preferably under reduced pressure is made.