Recovery of iron phosphate from a multi-metal mixture

Abstract

The invention relates to a method for separating iron phosphate from a black mass, wherein the method comprises the following steps: - providing the black mass, wherein the black mass comprises a lithium iron phosphate cathode material thermally treated at 400°C to 900°C; - leaching the black mass with a leaching agent to form a solution, wherein the solution contains lithium, iron and phosphate, and wherein the leaching agent contains sulfuric acid; and - precipitating iron phosphate from the solution.

Description

[0001] Recovery of iron phosphate from a multimetal mixture

[0002] Description

[0003] The invention relates to a method for separating materials from a black mass, and in particular to a method for separating iron phosphate from a black mass. The invention further relates to a method for obtaining iron phosphate from a lithium iron phosphate cathode material.

[0004] Electromobility continues to gain importance. At the same time, the availability of the required raw materials is insufficient and not always guaranteed. Against this backdrop, the recycling of lithium-ion battery cells is becoming increasingly important. Saving chemicals and reducing aqueous and solid waste are also becoming increasingly important for ecological reasons.

[0005] When recycling lithium-ion battery cells, so-called "black mass" can be obtained from lithium-ion batteries using common treatment methods such as mechanical processing, thermal treatment, and / or similar processes. Black mass can be obtained, for example, by crushing the cell and removing cell components such as electrolyte, binder, conductive foils, and casing. Black mass contains large quantities of anode and / or cathode material, for example, graphite and metals selected from lithium, iron, nickel, manganese, cobalt, copper, and aluminum. Recently, cathode material based on lithium iron phosphate (also called LFP) has gained importance in the field of electromobility. Lithium iron phosphate cathode material contains large quantities of lithium, iron, and phosphate.

[0006] Reusing the components of the black mass may require their efficient and clean separation. For example, phosphate is not only a recoverable material, but also a substance that can interfere with purification processes and contaminate other recoverable materials. Thus, one goal is to recover technologically relevant raw materials and remove impurities for further raw material extraction. For the anode material, gentle separation is also essential to enable its reuse, especially in high-tech industries. Current state-of-the-art solutions still have room for improvement.

[0007] For example, DE 11 2021 005 338 T5 relates to the field of battery material recovery and discloses a method for recovering iron phosphate from an LFP cathode material. Among other things, it does not disclose how the anode material is recovered and that the LFP cathode material is subjected to a thermal treatment at 400°C to 900°C.

[0008] Rujuan Zheng et al. describe experiments to optimize the leaching of LFP cathode material by varying the leaching parameters ("Optimized Li and Fe recovery from spent lithium-ion batteries via a solution-precipitation method"; RSC Adv., 2016, 6, 43613-43625). The anode material is separated before the thermal treatment of the cathode material. Crushed LFP cathode material, thermally pretreated at 350-650 °C, is leached in sulfuric acid. According to this publication, the optimal concentration of sulfuric acid for leaching the cathode material is 2.5 mol / L.

[0009] Against this background, one object of the present invention is to provide an efficient, material- and resource-saving separation of the components of black mass obtained from battery cells with cathode material based on lithium iron phosphate. The generation of waste should be reduced wherever possible.

[0010] The efforts to solve this problem resulted in a process for separating iron phosphate from a black mass, which process comprises the following steps:

[0011] - Providing the black mass, wherein the black mass comprises a lithium iron phosphate cathode material thermally treated at 400 °C to 900 °C,

[0012] - leaching the black mass with a leaching agent to form a solution, the solution containing lithium, iron and phosphate and the leaching agent containing sulphuric acid, - precipitating iron phosphate from the solution.

[0013] The process may be part of a more comprehensive process for separating components from black mass and / or lithium-ion battery cells.

[0014] The black mass can be obtained from the recycling of lithium-ion battery cells using common treatment methods. The black mass can be obtained, for example, by crushing lithium-ion battery cells and removing cell components such as electrolyte, binder, conductive foils, and casings. The black mass used in the process according to the invention can contain large amounts of anode material and cathode material, with the cathode material comprising lithium iron phosphate cathode material containing at least lithium, iron, and phosphate. In other words, at least part of the black mass is obtained from battery cells with cathode material based on lithium iron phosphate.

[0015] Important for the present process is that the black mass comprises a lithium iron phosphate cathode material thermally treated at 400 °C to 900 °C. In other words, the lithium iron phosphate cathode material has been subjected to a heat treatment at 400 °C to 900 °C. The thermal treatment subsequently enables efficient separation and recovery of the components.

[0016] The process comprises leaching the black mass with a leaching agent to form a solution containing lithium, iron, and phosphate. The solution may also contain other elements, for example, selected from aluminum, cobalt, copper, manganese, nickel, sodium, silicon, carbon, and fluorine.

[0017] In other words, the invention also relates to the use of a black mass comprising a lithium iron phosphate cathode material thermally treated at 400 °C to 900 °C in a process for separating iron phosphate from a black mass, the process comprising the following steps:

[0018] - Providing the black mass, - Leaching the black mass with a leaching agent to form a solution, wherein the solution contains lithium, iron and phosphate and wherein the leaching agent contains sulphuric acid,

[0019] - Precipitation of iron phosphate from solution.

[0020] The thermal treatment subsequently enables efficient separation and recovery of the components. The thermal treatment (= heat treatment) is preferably pyrolysis. The oxygen content during the heat treatment is preferably no more than 21 vol.%. In a preferred embodiment, the thermal treatment is carried out in a reducing atmosphere. Before or after the thermal treatment of the lithium iron phosphate cathode material at 400°C to 900°C, comminution can take place to provide the black mass for the process according to the invention. Preferably, no solid carbon is added during the thermal treatment. In particular, coal, activated carbon, anthracite, or the like is preferably not added to the thermal pretreatment and / or pyrolysis.Preferably, the black mass provided also contains thermally treated anode material, for example > 20 wt.% and up to 70 wt.% anode material, based on the total weight of the black mass provided.

[0021] The leaching agent contains sulfuric acid and is preferably aqueous.

[0022] The inventors have found that the process can be most efficiently replicated using sulfuric acid.

[0023] The concentration of sulfuric acid in the leaching agent is preferably <2.0 M, more preferably <1.5 M, even more preferably <1.0 M. This includes, among others, concentrations such as about 0.1 M, about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M, about 0.7 M, about 0.8 M, about 0.9 M, and ranges comprising several of these or all of these concentrations. For example, the concentration of sulfuric acid in the leaching agent can be between 0.1 M and 0.8 M, more preferably between 0.2 M and 0.5 M, particularly preferably about 0.5 M. In one embodiment, the concentration of sulfuric acid in the leaching agent is between 0.1 M and 0.4 M.

[0024] In other words, the concentration of sulfuric acid in the leaching agent is preferably <2.0 mol / L, more preferably <1.5 mol / L, even more preferably <1.0 mol / L. This includes, among other concentrations, for example, about 0.1 mol / L, about 0.2 mol / L, about 0.3 mol / L, about 0.4 mol / L, about 0.5 mol / L, about 0.6 mol / L, about 0.7 mol / L, about 0.8 mol / L, about 0.9 mol / L, and ranges comprising several of these or all of these concentrations. For example, the concentration of sulfuric acid in the leaching agent can be between 0.1 mol / L and 0.8 mol / L, more preferably between 0.2 mol / L and 0.5 mol / L, particularly preferably about 0.5 mol / L. In one embodiment, the concentration of sulfuric acid in the leaching agent is between 0.1 mol / L and 0.4 mol / L.

[0025] The inventors have determined that the process can be implemented most efficiently using dilute sulfuric acid. Higher concentrations lead to the dissolution of undesirable components during leaching of the black mass, resulting in less pure products subsequently separated from the solution. Furthermore, higher concentrations can lead to a deterioration in the properties of the anode material if it has not been separated prior to leaching. Therefore, the process design allows for the separation of the anode material before or after leaching, making the process easier to integrate into existing processes. A further advantage is that using more concentrated acid requires a larger amount of lye for neutralization. Using less concentrated solutions can reduce the amount required. This conserves resources and makes the process more sustainable. Furthermore, less concentrated leaching agents are safer.

[0026] The ratio (w / v) of black mass to leaching agent when leaching the black mass is preferably 1:8 to 1:25, more preferably 1:9 to 1:15. The range 1:8 to 1:25 includes, among other things, ratios such as about 1:8, about 1:9, about 1:10, about 1:11, about 1:12, about 1:13, about 1:14, about 1:15, about 1:16, about 1:17, about 1:18, about 1:19, about 1:20, about 1:21, about 1:22, about 1:23, about 1:24, about 1:25 and ranges comprising several of these or all of these ratios. This figure refers to the ratio of black mass in grams to leaching agent in milliliters, i.e., g / mL or m / v (mass / volume). In other words, 8-25 mL, more preferably 9 mL to 15 mL, of leaching agent is used per gram of black mass when leaching the black mass.

[0027] The inventors have determined that the process can be carried out most efficiently under these conditions. The combination of sulfuric acid at the specified concentration, the ratio (w / v) of black mass to leaching agent, and the other process parameters leads to very high yields and purities with low resource consumption.

[0028] The temperature during leaching of the black mass is preferably 40°C to 80°C, preferably 50°C to 70°C. This includes, among others, temperatures such as about 40°C, about 50°C, about 60°C, about 70°C, as well as ranges comprising several of these or all of these temperatures.

[0029] The inventors have determined that the process can be carried out most efficiently under these conditions. Combining this temperature with the other process parameters leads to very high yields and purities with low resource and energy consumption.

[0030] There are no particular restrictions on the time required to leach the black mass with a leaching agent. The time required to leach the black mass with a leaching agent can range from 30 minutes to 240 minutes, for example, but preferably between 60 minutes and 120 minutes.

[0031] In a preferred embodiment, no oxidizing agent is added during leaching, in particular no oxidizing agent selected from peroxide, persulfate, ozone, hypochlorite, chlorate, perchlorate, nitrate, N2O, NO2, oxygen, halogen and mixtures thereof.

[0032] The process according to the invention does not require an oxidizing agent during leaching. This saves resources and reduces costs. Furthermore, eliminating oxidizing agents can prevent metallic contaminants from entering the solution, thus facilitating process control.

[0033] Another advantage of the gentle process control of the method according to the invention is that physical separation of anode material can take place before or after leaching the black mass. In other words, physical separation of anode material can take place after the black mass has been prepared and before iron phosphate is precipitated from the solution, whereby the separation of anode material can take place before or after leaching the black mass. In a preferred embodiment, the separation of anode material takes place before leaching the black mass. In a further preferred embodiment, the separation of anode material takes place after leaching the black mass.

[0034] The advantageous process control opens up further possibilities for integrating the process according to the invention into existing recycling processes and thus further optimizing yields and purities.

[0035] The physical separation of anode material is preferably carried out by filtration or flotation.

[0036] In the process according to the invention, the prepared black mass preferably contains anode material, for example, graphite-containing anode material or graphite. The anode material has preferably been thermally treated together with the lithium iron phosphate cathode material, preferably at 400°C to 900°C.

[0037] As described above, the anode material can be separated before or after leaching, particularly by physical means.

[0038] As described above, separation of the anode material prior to leaching is not necessary due to the gentle process. Even when the anode material is exposed to the leaching agent, the conditions are so mild that the morphology of the anode material, such as graphite, remains essentially unchanged. In other words, the anode material, such as graphite, retains its spherical shape, surface structure, and electrochemical properties for use as an anode material.

[0039] Accordingly, in a preferred embodiment, leaching the black mass comprises leaching lithium iron phosphate cathode material and anode material. The anode material may form an insoluble residue in the leaching agent, which can be separated, particularly by filtration or flotation.

[0040] When the black mass is leached with a leaching agent, a solution is formed that contains lithium, iron and phosphate from the thermally treated lithium iron phosphate cathode material that has been processed into black mass.

[0041] Preferably, leaching the black mass produces a residue that is insoluble in the leaching agent, and the insoluble residue is substantially free of iron phosphate. Preferably, the residue contains less than 5% by weight, more preferably less than 1% by weight, of iron phosphate. In other words, during leaching, at least a large portion of the iron and phosphate (as well as the lithium) dissolves.

[0042] When the black mass is leached with a leaching agent, a solution is formed containing lithium, iron, and phosphate. Furthermore, a residue insoluble in the leaching agent may be obtained. If a residue insoluble in the leaching agent is obtained, the invention involves separating the residue and the solution containing lithium, iron, and phosphate to precipitate iron phosphate from the solution.

[0043] This process allows purer products to be obtained in higher yields.

[0044] Preferably, the precipitation of iron phosphate takes place with the addition of a base, preferably a nitrogen-containing base. The nitrogen-containing base can, for example, be selected from ammonia, pyridine, piperidine, EDTA (ethylenediaminetetraacetate), basic tertiary nitrogen compounds such as triethylamine, basic amino acids such as lysine, arginine and histidine, and mixtures thereof. In a preferred embodiment, the base or the mixture of bases is added in the form of a basic buffer system, wherein the buffer system contains the corresponding base(s) and the corresponding acid(s), e.g. ammonia and ammonium hydroxide. In a preferred embodiment, ammonia is added to precipitate iron phosphate. Preferably, <5 vol.%, e.g. between 1 vol.% and <5 vol.%, of a base, preferably ammonia, is added to precipitate iron phosphate, based on the total volume of the solution.

[0045] Because of the acidic leaching agent, the solution has an acidic pH during and after leaching. By adjusting the pH (increasing the pH) with a base, iron phosphate can be selectively precipitated. The inventors have discovered that using a nitrogenous base and a buffer system allows for more precise pH adjustment and, in addition, particularly pure products can be obtained in high yields. Furthermore, the relatively low concentration of sulfuric acid during leaching requires a relatively small amount of base, which conserves raw materials and makes the entire process more sustainable.

[0046] Preferably, the precipitation of iron phosphate takes place with the addition of an oxidizing agent. The oxidizing agent can be selected, for example, from peroxide, persulfate, ozone, hypochlorite, chlorate, perchlorate, nitrate, N2O, NO2, oxygen, halogen, and mixtures thereof. In a preferred embodiment, a peroxide, preferably hydrogen peroxide, is added to precipitate iron phosphate. Preferably, <5 vol.%, e.g., between 1 vol.% and <5 vol.%, of an oxidizing agent, preferably hydrogen peroxide, is added to precipitate iron phosphate, based on the total volume of the solution.

[0047] The inventors have found that using an oxidizing agent can improve yield and purity.

[0048] In a preferred embodiment, to precipitate iron phosphate, <5 vol.%, e.g., between 1 vol.% and <5 vol.%, of an oxidizing agent, preferably hydrogen peroxide, and <5 vol.%, e.g., between 1 vol.% and <5 vol.%, of a base, preferably ammonia, are added, based on the total volume of the solution. The inventors have found that using an oxidizing agent in combination with a base can improve yield and purity.

[0049] In a preferred embodiment, the thermal treatment of the lithium iron phosphate cathode material takes place at 400°C to 900°C in an oxygen-containing atmosphere. In other words, the atmosphere contains 5 vol% to 21 vol% oxygen.

[0050] The inventors have discovered that this allows less oxidizing agent to be used when precipitating iron phosphate.

[0051] Preferably, the precipitation of iron phosphate takes place at a temperature between 20 °C and 60 °C, preferably between 35 °C and 60 °C.

[0052] The inventors have found that particularly good yields and purities can be obtained using the chemicals and process parameters described herein.

[0053] When iron phosphate is precipitated from a solution containing lithium, iron, and phosphate, a solution low in iron phosphate is obtained. The solution low in iron phosphate is preferably separated from the iron phosphate precipitate and subjected to lithium extraction.

[0054] The low-iron phosphate solution contains only very small amounts of the elements iron, cobalt, copper, manganese, nickel, sodium, and fluorine and is therefore suitable for extracting lithium in pure form and with high yield. In a preferred embodiment, lithium extraction involves extracting lithium as lithium carbonate or LiOH.

[0055] Optionally, the low-iron phosphate solution can be further purified for lithium extraction, e.g. if particularly pure lithium is to be obtained or if strong impurities are expected.

[0056] In a preferred embodiment, the lithium extraction comprises raising the pH of the iron phosphate-poor solution by adding a base to precipitate at least one hydroxide selected from Al, Cu, and Mn hydroxides, and separating the precipitate to obtain a purified solution. The base for raising the pH of the iron phosphate-poor solution can be selected from sodium carbonate, sodium hydroxide, or a combination thereof.

[0057] The use of sodium carbonate can promote the formation of lithium carbonate, which is why sodium carbonate may be preferred. In another embodiment, sodium hydroxide is preferred.

[0058] In a preferred embodiment, the lithium extraction comprises separating the Ü2SO4, preferably by solvent extraction or an ion exchanger. The separation of Li?SO4 can be carried out from the purified solution or from the iron phosphate-poor solution.

[0059] The lithium extraction preferably comprises the formation of lithium carbonate. In a preferred embodiment, the lithium extraction comprises the formation of lithium carbonate, preferably by adding carbon dioxide or sodium carbonate, and the crystallization of lithium carbonate. The formation of lithium carbonate can occur in the purified solution or in the iron phosphate-poor solution.

[0060] According to this preferred embodiment, the process according to the invention can therefore also be described as a process for separating iron phosphate and / or lithium from a black mass. The lithium or lithium carbonate obtained by the process according to the invention has a high purity.

[0061] As mentioned at the beginning, the process can be part of a more comprehensive process for separating components from black mass and / or lithium-ion battery cells.

[0062] In one embodiment of the invention, the provision of the black mass comprises a thermal treatment of lithium iron phosphate cathode material at 400 °C to 900 °C. Accordingly, in a preferred embodiment, the method according to the invention represents a method for obtaining iron phosphate from a lithium iron phosphate cathode material, the method comprising the following steps:

[0063] - Providing a black mass comprising a thermal treatment of lithium iron phosphate cathode material at 400 °C to 900 °C,

[0064] - leaching the black mass with a leaching agent to form a solution, the solution containing lithium, iron and phosphate and the leaching agent containing sulphuric acid,

[0065] - Precipitation of iron phosphate from solution.

[0066] The same described advantages, explanations, preferred embodiments, etc. apply to this embodiment of the invention as to the method according to claim 1, which starts from a black mass that has already been thermally treated, i.e., a black mass comprising a lithium iron phosphate cathode material thermally treated at 400°C to 900°C. For example, the method according to the invention preferably comprises the thermal treatment of anode material, for example, graphite-containing anode material or graphite, together with the lithium iron phosphate cathode material at 400°C to 900°C.

[0067] Preferably, before or after the thermal treatment of the lithium iron phosphate cathode material at 400 °C to 900 °C, comminution takes place in order to provide the black mass for the process according to the invention.

[0068] In a preferred embodiment of the method according to the invention, the provision of the black mass prior to the thermal treatment of the lithium iron phosphate cathode material at 400 °C to 900 °C comprises a further thermal pretreatment of a lithium ion battery cell at not more than 350 °C to decompose the conductive salt and to volatilize solvent and a subsequent comminution of the battery material to provide the lithium iron phosphate cathode material.

[0069] This process for extracting iron phosphate from a lithium iron phosphate cathode material achieves a high yield and purity of lithium and iron phosphate.

[0070] The invention also relates to a recycling product containing lithium, preferably lithium carbonate, and / or a recycling product containing iron phosphate, wherein the recycling product is obtainable by a process according to the invention.

[0071] The process control of the method according to the invention enables the provision of recycling products that are particularly pure and are ideally suited for reuse in battery materials.

[0072] The invention is explained below by way of example with reference to the attached drawing, wherein the features shown below can represent an aspect of the invention both individually and in combination, and wherein the invention is not limited to the following drawing, the following description and the following embodiment.

[0073] Fig. 1 shows a schematic flow diagram of an exemplary embodiment of a method according to the present invention.

[0074] First, black mass 11 is provided 10. The black mass 11 originates from battery cells with cathode material based on lithium iron phosphate. The lithium-ion battery cells were crushed, and the lithium iron phosphate cathode material, together with the anode material, was subjected to a heat treatment 13 at approximately 600°C. The provided black mass 11 therefore also contains anode material 12, since this was not separated either before or after the heat treatment 13.

[0075] The next step is leaching 14. During this step, the black mass 11 is leached with a leaching agent 15 at approximately 60 °C. The leaching agent 15 is aqueous and contains 0.5 M sulfuric acid. The ratio (w / v) of black mass 11 to leaching agent 15 during leaching 14 of the black mass 11 is approximately 1:12. This produces a solution 16 containing lithium, iron, and phosphate. A residue 17 remains that is insoluble in the leaching agent 15.

[0076] The solution 16 is separated by filtration from the residue 17, which is insoluble in the leaching agent. This also separates the anode material 12, graphite. Alternatively, the anode material 12 can be removed before leaching 14, for example by flotation. Overall, the anode material 12 is exposed to only mild conditions and can thus be easily reused. The next step involves the precipitation 18 of iron phosphate 19 from the solution 16. This process selectively precipitates iron phosphate 19 from the solution 16. In this example, the pH is adjusted to approximately 2 by adding hydrogen peroxide 20 and ammonia 21. During the exothermic reaction, a temperature between 20 °C and 60 °C is established. The resulting iron phosphate 19 is very pure (> 95%), and the yield is 99%.Through further purification steps, i.e., redissolution with solution purification, washing of the filter cake, and recrystallization, battery-grade iron phosphate can be achieved.

[0077] When iron phosphate 19 is precipitated 18 from solution 16, which contains lithium, iron, and phosphate, a solution 22 low in iron phosphate is obtained and separated from the iron phosphate precipitate. The low-iron phosphate solution 22 is very pure and rich in lithium. The low-iron phosphate solution 22 contains less than 100 ppm of each of the elements iron, cobalt, copper, manganese, nickel, and sodium, and less than 250 ppm of fluorine. Pure lithium 23, in particular pure lithium carbonate, can be formed from the low-iron phosphate solution 22.

[0078] To form particularly pure lithium 23 in the form of lithium carbonate, the pH of the iron phosphate-poor solution 22 is first raised by adding NaOH. This causes Al, Cu, and Mn to precipitate as hydroxides and separate them to obtain a further purified solution. O2SO4 can be removed from the purified solution by solvent extraction or an ion exchanger. Then, by adding carbon dioxide, lithium carbonate can be formed, which can be obtained by crystallization.

[0079] List of reference symbols

[0080] 10 Providing black mass

[0081] 11 Black mass

[0082] 12 Anode material

[0083] 13 Heat treatment of lithium iron phosphate cathode material and anode material

[0084] 14 Alkalis 15 Leaching agents

[0085] 16 Solution containing lithium, iron and phosphate

[0086] 17 insoluble residue

[0087] 18 cases of iron phosphate 19 iron phosphate

[0088] 20 hydrogen peroxide

[0089] 21 Ammonia

[0090] 22 low-iron phosphate solution

[0091] 23 Lithium

Claims

Claims 1. A process for separating iron phosphate from a black mass, the process comprising the following steps: - Providing the black mass, wherein the black mass comprises a lithium iron phosphate cathode material thermally treated at 400 °C to 900 °C, - leaching the black mass with a leaching agent to form a solution, the solution containing lithium, iron and phosphate and the leaching agent containing sulphuric acid, - Precipitation of iron phosphate from solution.

2. Process at least according to claim 1, characterized in that the concentration of sulfuric acid in the leaching agent is < 2.0 M.

3. A method according to at least one of the preceding claims, characterized in that the concentration of sulfuric acid in the leaching agent is between 0.1 M and 0.8 M, preferably 0.2 M and 0.5 M, particularly preferably about 0.5 M.

4. Method according to at least one of the preceding claims, characterized in that the black mass contains anode material.

5. A process according to at least one of the preceding claims, characterized in that before the precipitation of iron phosphate and after the leaching of the black mass, a physical separation of anode material takes place, preferably by filtration or flotation.

6. Method according to at least one of the preceding claims, characterized in that the provided black mass contains anode material, wherein the anode material has been thermally treated together with the lithium iron phosphate cathode material at 400 °C to 900 °C, and before the precipitation of iron phosphate and after the leaching of the black mass, a physical separation of anode material takes place, preferably by filtration or flotation, wherein the concentration of sulfuric acid in the leaching agent is < 1.0 M.

7. A method according to at least one of the preceding claims, characterized in that the morphology of the anode material remains substantially unchanged and the anode material retains its electrochemical properties for use as anode material.

8. A process according to at least one of the preceding claims, characterized in that the ratio (w / v) of black mass to leaching agent when leaching the black mass is 1:8 to 1:25, preferably 1:9 to 1:

15.

9. Process according to at least one of the preceding claims, characterized in that the temperature during leaching of the black mass is 40 °C to 80 °C, preferably 50 °C to 70 °C.

10. A process according to at least one of the preceding claims, characterized in that the precipitation of iron phosphate takes place with the addition of a base, preferably a nitrogen-containing base.

11. A process according to at least one of the preceding claims, characterized in that between 1 vol.% and <5 vol.% of ammonia is added to precipitate iron phosphate, based on the total volume of the solution.

12. A process according to at least one of the preceding claims, characterized in that the precipitation of iron phosphate takes place with the addition of an oxidizing agent.

13. A process according to at least one of the preceding claims, characterized in that, for the precipitation of iron phosphate, between 1 vol.% and <5 vol.% of an oxidizing agent, preferably hydrogen peroxide, is added, based on the total volume of the solution.

14. A process according to at least one of the preceding claims, characterized in that the precipitation of iron phosphate takes place at a temperature between 20 °C and 60 °C, preferably between 35 °C and 60 °C.

15. A process according to at least one of the preceding claims, characterized in that the process is a process for separating iron phosphate and lithium from a black mass, wherein a solution low in iron phosphate is obtained upon precipitation of iron phosphate from the solution, wherein the solution low in iron phosphate is separated from the iron phosphate precipitate and subjected to lithium extraction, wherein the lithium extraction comprises at least one of the following steps: - raising the pH of the iron phosphate-poor solution by adding a base to precipitate at least one hydroxide selected from Al, Cu and Mn hydroxide and separating the precipitate to obtain a purified solution; - separation of Ü2SO4 by solvent extraction or ion exchange; - extraction of lithium as lithium carbonate or LiOH; - forming lithium carbonate, for example by adding sodium carbonate, and crystallizing lithium carbonate.