Process

Abstract

A process for the at least partial conversion of a metal compound (M(Y)x) to a metal fluoride (MFz), such as lithium fluoride, which comprises the addition of a solution of a metal compound (M(Y)x) to

Description

Field of the invention The present invention relates to a process for the fluorination of a metal compound. This process is particularly useful in the production of lithium fluoride. Background of the invention Lithium salts (such as LiF I LiPFe) are used in batteries, such as commercial secondary batteries, an application that exploits their high solubility in non-aqueous solvents. Lithium salts (such as LiF I LiPFe) are prepared from precursor lithium compounds. One such precursor lithium compound is lithium bicarbonate (LiHCOa), which finds use because of its comparatively high solubility in water when compared to other compounds such as lithium carbonate (U2CO3), which requires larger vessels for making and storing. Currently lithium bicarbonate production occurs by carbonation of lithium carbonate with CO2 generally in an aqueous environment in a reactor: U2CO3 + CO2 + H2O #2 UHCO3 generating an aqueous solution of lithium bicarbonate, which is metastable, and so can be stored and / or further processed as necessary. The process can be batch. These batch processes are often operated at low CO2 pressure, which is inefficient. There are also continuous production processes. In the currently used continuous production processes typically an admixture of water and lithium carbonate is charged into a reactor with a source of carbon dioxide (often bubbled through the lithium carbonate solution). This can be challenging as the initial solubility of lithium carbonate in water is low relative to other lithium compounds. Lithium carbonate has a higher solubility in water at lower temperatures. As the solubility of lithium carbonate is higher at lower temperatures the reactors are generally cooled. The carbon dioxide may be recycled. In the currently used continuous production processes, rapid CO2 dissolution is not attained. This has a negative impact in that the slow dissolution of CO2 limits the conversion of lithium carbonate to lithium bicarbonate. The carbon dioxide utilization efficiency can be low at about 30-40%. To address the poor conversion rate large batch reactors are required for industrial scale production. However, even so these large reactors (and the associated equipment) are typically complex, expensive to operate systems. An alternate route would be to prepare LiF out of lithium sulfate (Li2SO4); U2SO4 being itself a precursor to lithium carbonate and therefore lower in cost. However, using lithium sulfate for the production of LiF has a number of key drawbacks which to date have prevented its use. For example, Lithium sulfate obtained from lithium sources such as rocks, clays, brines, recycled batteries and others typically contains several percent of other sulfate species such as sodium sulfate. Furthermore, the direct fluorination of lithium sulfate to produce LiF generate yields as low as 75%, making this route uneconomical and unpractical. Also, this process often requires the use of hydrogen fluoride or hydrofluoric acid as the fluoride source, which are both extremely hazardous materials. Thus, there is a need for an improved method of producing lithium fluoride from precursor compounds such as lithium sulphate. Summary of the invention According to a first aspect of the present invention there is provided a process for the at least partial conversion of a metal compound (M(Y)X) to a metal fluoride (MFZ), comprising the addition of a solution of a metal compound(M(Y)x) to a solution of fluoride; followed by extraction of the metal fluoride (MFZ) from the solution wherein the metal fluoride produced has a particle size range having one or more of the following properties:- i) a Dv10, Dn10 and I or Dsa10 (pm) in the range of about 1 to about 40; ii) a Dv50, Dn50 and I or Dsa50 (pm) in the range of 5 to 70; and iii) a Dv80, Dn80 and / or Dsa80 (pm) in the range of 10-130. The present invention has been found to be highly beneficial. The invention has been found to be highly advantageous in that a metal fluoride with a highly controllable particle size has been found to be able to be produced. Particles with sizes in these ranges have been found to possess a number of advantages. For example, they can be made to high purity. Without wishing to be bound by theory this is postulated to occur because impurity inclusions and occlusions (which accommodate one or more impurities, such as one or more of the stating materials) can be reduced. Additionally the particles have been found to be easy to convey between vessels, without clogging and causing blockages. As such, the particles are highly suited for further processing, such as for feeding to a reactor or a vessel for onward conversion, without caking and causing blockages. It will be understood that a Dx particle size is defined as the point on the distribution curve below which x% of the particles fall. Here the suffix “v” means particles when measured by volume. Here the suffix “n” means particles when measured by number. Here the suffix “sa” means particles when measured by surface area. As a further illustration: Dv10 is the 10th percentile of the cumulative volume distribution. It is the size below which there is 10% of the volume of the sample. Dn10 the diameter below which 10% of the total count of all particles analyzed is represented. Dsa10 is the 10th percentile of the cumulative surface area distribution. It is the size below which there is 10% of the surface area of the sample. Preferably particle size distribution (PSD) (to establish the Dx particle size) was measured using laser diffraction on a Malvern Mastersizer 3000 instrument with an Aero S dry powder dispersion unit attachment to facilitate handling and measurement of dry powders otherwise operated in a standard manner according to the manufacturer’s guidelines. Preferably the D10 (p.m) is less than about 35 p.m, more preferably less than about 30 p.m, more preferably less than about than 30 p.m, more preferably less than about 25 p.m, more preferably less than about 20 p.m, more preferably less than about 18 p.m, more preferably less than about 16 p.m, more preferably less than about 14 p.m, more preferably less than about 12 p.m, more preferably less than about 10 p.m, more preferably less than about 8 p.m, more preferably less than about 6 p.m, more preferably less than about 5 p.m. Preferably the D10 (p.m) is more than about 2 p.m, more preferably more than about 4 p.m, more preferably more than about than 6 p.m, more preferably more than about 8 p.m, more preferably more than about 10 p.m, more preferably more than about 12 p.m, more preferably more than about 15 p.m, more preferably more than about 20 p.m, more preferably more than about 20 p.m, more preferably more than about 30 p.m, more preferably more than about 35 p.m. Additionally and I or alternatively the D10 (p.m) is preferably in the range of about 1 to about 35; more preferably in the range of about 1 to about 30, more preferably in the range of about 1 to about 25; more preferably in the range of about 2 to about 25; more preferably in the range of about 3 to about 25; more preferably in the range of about 5 to about 25; more preferably in the range of about 5 to about 20; more preferably in the range of about 5 to about 15; more preferably in the range of about 7 to about 13; for example about 10. Preferably the D50 (p.m) is less than about 65 p.m, more preferably less than about 60 p.m, more preferably less than about than 55 p.m, more preferably less than about 50 p.m, more preferably less than about 45 p.m, more preferably less than about 40 p.m, more preferably less than about 35 p.m, more preferably less than about 30 p.m, more preferably less than about 25 p.m, more preferably less than about 20 p.m, more preferably less than about 15 p.m, more preferably less than about 10 p.m. Preferably the D50 (p.m) is more than about 7 p.m, more preferably more than about 9 p.m, more preferably more than about than 10 p.m, more preferably more than about 15 p.m, more preferably more than about 20 p.m, more preferably more than about 25 p.m, more preferably more than about 30 p.m, more preferably more than about 35 p.m, more preferably more than about 40 p.m, more preferably more than about 45 p.m, more preferably more than about 50 p.m, more preferably more than about 55 p.m, more preferably more than about 60 p.m, more preferably more than about 65 p.m. Additionally and I or alternatively the D50 (p.m) is preferably in the range of about 5 to about 65; more preferably in the range of about 5 to about 55, more preferably in the range of about 10 to about 50; more preferably in the range of about 15 to about 45; more preferably in the range of about 20 to about 40; more preferably in the range of about 25 to about 35; more preferably in the range of about 27 to about 33; for example about 30. Preferably the D80 (p.m) is less than about 125 p.m, more preferably less than about 115 p.m, more preferably less than about than 105 p.m, more preferably less than about 95 p.m, more preferably less than about 85 p.m, more preferably less than about 75 p.m, more preferably less than about 65 p.m, more preferably less than about 55 p.m, more preferably less than about 45 p.m, more preferably less than about 35 p.m, more preferably less than about 25 p.m, more preferably less than about 15 p.m. Preferably the D80 (p.m) is more than about 11 p.m, more preferably more than about 13 p.m, more preferably more than about than 15 p.m, more preferably more than about 25p.m, more preferably more than about 35 p.m, more preferably more than about 45 p.m, more preferably more than about 55 p.m, more preferably more than about 65 p.m, more preferably more than about 75 p.m, more preferably more than about 85 p.m, more preferably more than about 95 p.m, more preferably more than about 105 p.m, more preferably more than about 115 p.m. Additionally and I or alternatively the D80 (p.m) is preferably in the range of about 15 to about 125; more preferably in the range of about 20 to about 120, more preferably in the range of about 30 to about 90; more preferably in the range of about 35 to about 85; more preferably in the range of about 40 to about 80; more preferably in the range of about 50 to about 70; more preferably in the range of about 55 to about 65; for example about 60. It will be appreciated that any of the preferred ranges for the D10 (p.m), D50 (p.m) and D80 (p.m) are combinable. Preferred combinations of ranges for the D10 (p.m), D50 (p.m) and D80 (p.m) are as follows: ranges for the D10 (p.m) from about 5 to about 15, D50 (p.m) from about 20 to about 40 and D80 (p.m) from about 40 to about 80. Most preferably the D10 (p.m) is about 10, D50 (p.m) is about 30 and D80 (p.m) is about 60. It will be understood that any or all of the preferred particle sizes described above may refer to Dv, Dn and / or Dsa. Most preferably any or all of the preferred particle sizes described above refer to Dv. This invention avoids the use of high hazard sources of fluoride such as hydrogen fluoride whilst with the additional benefits of generating minimal aqueous waste and improving the volumetric efficiency of the process. As a result, metal fluorides such as LiF can be prepared from low cost metal compounds such as Li2SO4. It has also been found that the process may be scaled up without significant increases in wastage. We have found that particles with desirable size properties can be produced by careful control of process conditions. Preferably the relative amounts of salt (M(Y)X) and solution of fluoride are approximately equivalent. Namely the ratio of salt (M(Y)X) to solution of fluoride is about 1:1. This is preferably on a molar basis; with about one mole of salt (M(Y)X) to about one mole of solution of fluoride. The reaction (with these preferred ratios) has been found to proceed largely to completion; namely practically all of the metal salt (M(Y)X) is converted to a metal fluoride (MFZ). Other ratios are contemplated. M in M(Y)X and MFZ may be the same or different. Preferably the admixture of the solution of a metal compound (M(Y)X) and the solution of fluoride are mixed. Preferably the reaction time is between 1 and 1000 minutes, such as from 1 to 500 minutes, more preferably from 10 to 300 minutes, more preferably from 10 to 120 minutes, more preferably from 10 to 90 minutes, more preferably from 20 to 90 minutes, more preferably from 30 to 90 minutes, for example about 30 minutes or about 60 minutes. Preferably the admixture is mixed during the reaction time. Here, it has been found that an excessive mixing time can (where solid I particulate metal fluoride (MFZ) is formed) detrimentally lower the particle size of the metal fluoride (MFZ). This is postulated to occur by attrition between metal fluoride (MFZ) particles. Hence, the preferred (short) reaction times above. The process can be performed over a wide temperature range, which is only limited by the freezing and boiling points of the metal compound (M(Y)X) and metal fluoride (MFZ) solutions but is conveniently performed around room temperature and pressure for example between 20 and 25°C. Preferably the metal compound (M(Y)X) is a salt that comprises lithium and more preferably is a lithium salt. Preferably the metal compound (M(Y)X) comprises lithium sulphate and more preferably is lithium sulphate. Generally, the solution of fluoride comprises an alkali metal or alkaline earth metal fluoride. Preferably it is an alkali metal fluoride and more preferably is sodium and I or potassium fluoride. Preferably the solution of the metal compound (M(Y)X) and the solution of fluoride comprise aqueous solutions. Preferred concentrations are: metal salt (M(Y)X), between 1 to 2 mol / l, more preferably between 1.25 to 1,75mol / l, most preferably about 1.5 mol / l; solution of fluoride between 0.4 to 1.4 mol / l, more preferably between 0.65 to 1.15mol / l, most preferably about 0.9 mol / l. Generally, the extraction step comprises crystallization of the metal fluoride (MFZ) from the solution. It has been observed that the order of addition (of the metal compound (M(Y)x)and the fluoride solution can influence the nature of the product material. It has been observed that addition of the metal compound (M(Y)X) to the fluoride solution is more preferable. This mode of addition has been found to result in metal fluoride (MFZ) having lower content of the metal compound (M(Y)X). Without wishing to be bound by theory it is presumed that this mode of addition results in a smaller portion of the anion Y of the metal compound becoming occluded within the structure of the resultant metal fluoride (MFZ). Thus, most preferably the metal compound (M(Y)X) is added to the fluoride solution. (Addition of the fluoride solution (generally based on a metal fluoride salt) to the metal compound (M(Y)X) generally means that a portion of the cation of the metal compound becomes occluded within the structure of the resultant metal fluoride (MFZ).) Optionally the metal compound (M(Y)X) is purified prior to use. In one preferred embodiment where the product metal fluoride is LiF and metal compound (M(Y)X) is Li2SO4the purification comprises ion exchange which has been found to be highly beneficial in greatly reducing the presence of other metal compounds such as residual alkalis, alkaline earth and transition metals in the product metal fluoride. The extraction may comprise addition of a metal fluoride (MFZ) to induce crystallisation (and hence separation from reactant solution) of the resultant metal fluoride (MFZ). This process may be repeated multiple times. Hence, it is preferred that the metal fluoride (MFZ) is in crystalline form. The metal fluoride (MFZ) may be purified after extraction. The purification may include one or more of water recycling and filtering process of the impure solid metal fluoride (MFZ). The purification may include solvation and re-crystallization of the impure solid metal fluoride (MFZ). This process may be repeated multiple times. Preferably the pH of the process is from about 5 to about 12. This is the pH at the start and I or end of the process. Preferably further processing steps are avoided I reduced. It has been found that any additional processing steps can detrimentally affect particle size; lead to growth or reduction in particle size. The metal fluoride (MFZ) may be used to make other metal I lithium salts (such as M(PFe) w I LiPFe). Thus, according to a second aspect of the present invention there is provided a process for making a metal hexafluorophosphate (M(PFe)w) by reacting a metal fluoride (MFZ) produced by a process according to the first aspect of the present invention. According to a third aspect of the present invention there is provided metal fluoride (MFZ) I metal hexafluorophosphate (M(PFe)w) produced by a process according to the first and I or second aspect of the present invention. It will be appreciated that aspects of the first aspect of the present invention shall be taken to apply mutatis mutandis to the second and third aspect of the present invention. The invention will now be described with reference to the following non-limiting Examples. Examples Example 1 Preparation of Lithium fluoride (LiF) - Laboratory Scale Examples A 10 or 20 litre vessel was arranged with an overhead mixer. A solution was prepared and added to the vessel. A separate feed solution for addition to the vessel was also prepared. One of these solutions comprises sodium fluoride (NaF) and one comprised lithium sulphate (U2SO4). The density and weight of each solution was measured. The feed solution was added to the vessel solution over a specified period of addition. The combined solutions were also mixed for a specified period of time, after the feed solution had all been added. Any observations such as foaming, spike of temperature were observed. The reactors contents were filtered, washed and dried. This procedure was followed according to the Examples below. Reaction Order of Addition Addition Time (minutes) Stir Time (minutes) Desired Quantity LiF(g) Mixing Vessel Volume (litres) Volume (ml) / Concentration (g / i)* U2SO4 used Volume / Concentration (g / i) NaF used Start PH End PH Displacement Wash 01 NaF into Li2SO4 10 30 125 20 3247 (10.3) 6100 (40.4) 11.4 11.7 1 02 NaF into Li2SO4 20 30 200 20 5196 (10.3) 10100 (40.4) 11.4 11.8 2 03 Li2SO4 into NaF 26 30 125 20 3247 (10.3) 6010 (40.4) 10.1 12.2 2 04 NaF into Li2SO4 29 30 98 10 2250 (11.7) 4021 (40.4) 12.0 12.1 2 05 NaF into Li2SO4 26 30 98 10 2250 (11.7) 4021 (40.4) 9.7 10.10 2 06 NaF into Li2SO4 31 30 98 10 2250 (11.7) 4021 (40.4) 7.0 7.8 2 07 Li2SO4 into NaF 62 30 80 10 2184 (9.8) 3957 (36) 9.57 12.15 4 08 Li2SO4 into NaF 64 30 80 10 2184 (9.8) 3669 (36) 9.73 12.19 4 09 Li2SO4 into NaF 10 30 80 10 2184 (9.8) 3957 (36) 9.88 12.15 4 10 Li2SO4 into NaF 10 30 80 10 2184 (9.8) 3669 (36) 9.67 12.17 4 11 Li2SO4 into NaF 62 30 80 10 2184 (9.8) 3957 (36) 9.83 12.25 4 12 Li2SO4 into NaF 61 30 80 10 2184 (9.8) 3669 (36) 9.78 12.23 4 13 Li2SO4 into NaF 10 30 80 10 2184 (9.8) 3957 (36) 9.70 12.20 4 14 Li2SO4 into NaF 10 30 80 10 2184 (9.8) 3669 (36) 9.61 12.23 4 15 Li2SO4 into NaF 180 30 80 10 2282 (9.4) 3669 (36) 6.82 10.29 2 16 Li2SO4 into NaF 180 30 80 10 2282 (9.4) 3669 (36) 6.75 10.27 2 17 Li2SO4 into NaF 600 30 80 10 2282 (9.4) 3669 (36) 6.63 10.12 2 18 Li2SO4 into NaF 180 1048 80 10 2282 (9.4) 3669 (36) 6.69 10.12 2 19 NaF into Li2SO4 600 30 80 10 2438 (8.8) 3669 (36) 9.79 9.98 2 22 Li2SO4 into NaF 180 30 88 10 1996 (11.8) 4037 (36.0) 6.87 10.22 2 23 Li2SO4 into NaF 180 30 80 10 2438 (8.78) 3655 (50) 8.22 10.29 2 24 Li2SO4 into NaF 600 30 80 10 901 (23.8) 3669 (36.0) 7.27 8.75 2 25 Li2SO4 into NaF 600 30 60 10 676 (23.76) 2752 (36.0) 5.19 7.07 2 26 Li2SO4 into NaF 600 30 80 10 901 (23.8) 3669 (36.0) 10.7 8.91 2 - as grams of Li per litre. Reaction LiF yield (%) Na in Solids (ppm) SO4 in solids (ppm) D1O (pm) D50 (pm) D80 (pm) 01 94 5260 16777 4.9 9.2 13.6 02 89 4590 21570 03 91 19362 1797 13.1 25.3 36.3 04 93 3858 14380 05 90 11128 14380 06 94 2226 20371 07 88 12537 2397 13.0 27.0 39.7 08 87 13000 1498 17.1 33.6 48.9 09 89 21100 2996 6.5 13.1 19.3 10 86 20920 4494 6.8 13.7 20.3 11 87 12908 1797 11.8 25.8 38.7 12 84 12463 1797 11.6 25.2 38.0 13 86 21600 2996 6.7 13.6 30.3 14 84 20800 3595 8.9 18.1 36.6 15 87 10534 1498 17.0 44.0 72.6 16 89 4674 1198 17.7 38.4 59.6 17 88 4748 899 33.7 68.7 106.0 18 88 8680 899 23.4 47.4 69.7 19 87 2671 11384 12.3 33.0 59.0 22 90 7567 1498 10.4 24.0 36.1 23 87 8457 4194 - - - 24 81 6520 3295 11.0 14.3 13.7 25 80 7780 5392 14.3 36.9 44.5 26 80 7060 5093 13.7 63.9 123 Two comparative Examples using HF instead of NaF as the fluorinating agent, were performed.. Comparative Reaction Examples - Protocol Reaction Order of Addition Addition Time (minutes) Stir Time (minutes) Desired Quantity LiF(g) Mixing Vessel Volume (litres) Volume (ml) / Concentration (g / l)*Li2SO4 used Volume / Concentration (g / l) NaF used Start PH End PH Displacement Wash 20 Li2S04 into HF** 180 30 120 10 3423 (9.4) 1888 (5%) 2.57 7.07 2 21 Li2S04 into HF** 240 30 120 10 3657 (8.8) 1888 (5%) 2.58 7.00 2 Reaction Examples - Results Reaction LiF yield (%) Na in Solids (ppm) SO4 in solids (ppm) D10 (pm) D50 (pm) D80 (pm) 20 39 / 54 2374 / 8235 11983 / 15279 75.3 / 7.3 448 / 17.1 979 / 31.1 21 52 / 41 964 / 9051 7190 / 14979 18.5 / 5.7 65.8 / 11.8 287.0 / 17.7 For examples 20 and 21 the results (yield and particle size) (with the use of HF) are considerably worse than the remainder of the results. These examples aid in illustrating the use of problematic fluorinating agents such as a HF. It can be seen that adding the lithium sulphate solution to the sodium fluoride solution results in lithium fluoride being produced that has a lower sulphate content than when sodium fluoride is added to lithium sulphate. Thus, the present invention provides a method of making high purity LiF from alternative low-cost sources of lithium, such as lithium sulphate. The present invention also allows a high degree of control over the particle size or adjusting the particle size. Example 2 -Crystal growth and Purification The lithium fluoride produced (about 10 g) was placed into a glass Soxhlet extraction vessel, comprising a Pyrex glass thimble with a fritted disc. The minimum volume of water (about 100 ml) required to fill the extraction vessel was boiled below in a boiling flask above a hot plate. The vapour then condenses inside a condenser, filling the thimble directly below and gradually solubilising a portion of the LiF each time the Soxhlet extraction vessel filled and emptied thereby breaking open the crystal structure in the process. Each time the Soxhlet vessel filled it emptied and was filtered through the fritted disc taking with it a portion of the initial LiF charge. The re-boiling process was repeated numerous times until all LiF in the thimble had gone into solution in the extraction vessel and had drained into the boiling flask. It was noted that as the concentration of LiF increases in the fixed volume of water, it slowly recrystallised, leaving soluble impurities in solution. This created larger, high purity crystals of grade >99.95%, with yields >80%. This process avoided the use of high hazard HF and generate minimal aqueous waste due to the volumetrically efficient procedure. It has shown that low purity LiF from low cost U2SO4 feed can be purified safely to a high spec material and can be scaled up without significant increases in wastage. In this Example crystals of LiF provided from U2SO4 feed (sample name: LiFP-03) Initially contained 19362 ppm Na and 1797 ppm SO42; and had a D(50) of 25.3 p.m After purification, analysis of the crystals showed a reduction in Na and SO42' content to 50 and 120 ppm, respectively. Additionally, the average particle size of the new crystals had increased from a D(50) of 25.3 to 38.2 microns. Further samples of material produced in the reaction examples above were subjected to this treatment and analysed by ICP-OES after treatment: LiF (ca. 10 g) was suspended in a Pyrex thimble above a fritted disc within a condensing collection chamber. The condenser was connected to a Huber chiller with a set point of 10 °C. DI water (200 mL) was added to a boiling flask with a magnetic stirrer bar beneath the chamber atop a heating plate. The flask and vapour siphon arm of the chamber were wrapped in aluminium foil. The cycle of boiling, dissolution and reprecipitation is repeated until no more solid remains in the thimble. After, the flask was cooled to room temperature, the solid suspension filtered under vacuum and the solid washed with 2x 50 mL cold DI water. The solids were then dried at 105 °C overnight and analysed. Reaction example Mass LiF used(g) Sodium (ppm) Sulphate (ppm) Potassium (ppm) Before After Before After Before After 15 10.1646 10534 44 1498 45 11 <2 17 10.0153 4748 13 899 45 83 <2 22 10.0463 7567 58 7567 45 43 <8 24 10.1707 6520 81 3295 117 65 <3 Thus, there are provided methods whereby high purity lithium fluoride can be produced from low cost lithium salts like lithium sulphate with desirable particle sizes as defined by D(10), D(50) and D(80).

Claims

1. A process for the at least partial conversion of a metal compound (M(Y)X) to a metal fluoride (MFZ),comprising the addition of a solution of a metal compound (M(Y)X) to a solution of fluoride;followed by extraction of the metal fluoride (MFZ) from the solution;wherein the metal fluoride produced has a particle size range having one or more of the following properties:-i. a Dv10, Dn10 and I or Dsa10 (pm) in the range of about 1 to about 40;ii. a Dv50, Dn50 and I or Dsa50 (pm) in the range of about 5 to about 70; andiii. a Dv80, Dn80 and I or Dsa80 (pm) in the range of about 10 to about 130.

2. A process according to claim 1, wherein the metal fluoride produced has a particle sizerange having one or more of the following properties:-i. a Dv10 (pm) in the range of about 1 to about 40;ii. a Dv50 (pm) in the range of about 5 to about 70; andiii. a Dv80 (pm) in the range of about 10 to about 130.

3. A process according to claim 1 or 2, wherein the metal compound (M(Y)X) is a lithium salt or comprises lithium.

4. A process according to claim 1, 2 or 3, wherein the metal compound (M(Y)X) is or comprises lithium sulphate.

5. A process according to any one of the preceding claims, wherein the solution of fluoride is or comprises sodium and I or potassium fluoride.

6. A process according to any one of the preceding claims, where the solution of the metal compound (M(Y)X) and the solution of fluoride comprise aqueous solutions.

7. A process according to any one of the preceding claims, wherein the extraction step comprises crystallization of the metal fluoride (MFZ) from the solution.

8. A process according to any one of the preceding claims, wherein the metal compound (M(Y)X) is purified prior to use.

9. A process according to claim 8, wherein the process comprises ion exchange.

10. A process according to any one of the preceding claims, wherein the extraction comprises addition of a metal fluoride (MFZ).

11. A process according to claim 10, wherein the metal fluoride (MFZ) is in crystalline form.

12. A process according to any one of the preceding claims, wherein the metal fluoride (MFZ) is purified after extraction.

13. A process according to claim 12, wherein the purification includes one or more of water recycling and filtering process of the impure solid metal fluoride (MFZ).

14. A process according to claim 12 or 13, wherein the purification includes solvation and recrystallization of the impure solid metal fluoride (MFZ).

15. A process for making a metal hexafluorophosphate (M(PFe)w) by reacting a metal fluoride (MFZ) produced by a process according to any one of claims 1 to 14.

15. A process according to any of the preceding claims wherein particle size was measured using a Malvern Mastersizer 3000 instrument with an Aero S dry powder dispersion unit attachment.

17. A metal fluoride (MFZ) I metal hexafluorophosphate (M(PFe)w) produced by a process according to any one of claims 1 to 16.

18. A process for the at least partial conversion of lithium sulphate to lithium fluoride, comprising the addition of an aqueous solution of lithium sulphate to a solution of sodium and I or potassium fluoride; followed by extraction of the lithium fluoride from the solution, wherein the lithium sulphate is purified prior to use, wherein the metal fluoride produced has a particle size range having one or more of the following properties:-i) a Dv10, Dn10 and I or Dsa10 (p.m) in the range of about 1 to about 40;ii) a Dv50, Dn50 and I or Dsa50 (p.m) in the range of about 5 to about 70; andiii) a Dv80, Dn80 and / or Dsa80 (p.m), in the range of about 10 to about 130.

19. A process according to claim 18, wherein the metal fluoride produced has a particle size range having one or more of the following properties:-i. a Dv10 (p.m) in the range of about 1 to about 40;ii. a Dv50 (p,m) in the range of about 5 to about 70; andiii. a Dv80 (p,m) in the range of about 10 to about 130.