Method for purifying a leaching filtrate from the black mass of lithium-ion batteries

Abstract

The present invention relates to a method for purifying a leaching filtrate from the black mass of lithium-ion batteries, the filtrate containing lithium and at least one solubilised organic compound, the method comprising the step of adding an oxidizing agent, a Fenton catalyst and optionally a phosphate salt to the filtrate so as to obtain a solution containing lithium and depleted of the at least one solubilised organic compound.

Description

Process for purifying a filtrate from the leaching of black mass from lithium-ion batteries Technical Field

[0001] La présente invention concerne le domaine général du recyclage des batteries used lithium-ion batteries or lithium-ion battery production scrap and in particular the recovery of lithium and possibly other valuable metals present in these batteries or scrap, such as cobalt, nickel, manganese and their mixtures.

[0002] Elle concerne plus particulièrement la purification du filtrat de lixiviation de la black mass of lithium-ion batteries in order to remove organic impurities and recover lithium and possibly other valuable metals.

[0003] When recycling used lithium-ion batteries, after separating the plastics, the parts containing the electrodes such as the battery cells are crushed or shredded to produce a powdery metallic fraction called "black mass".

[0004] Similarly, during the lithium-ion battery manufacturing process, semi-finished products such as active material powders or non-compliant batteries considered as production scrap may be produced and should be recycled. These products can be treated in the same way as used lithium-ion batteries and will contribute to the production of the metallic powder fraction called "black mass".

[0005] It is generally known to dissolve the black mass in sulfuric acid in the presence of an oxidation-reduction reagent in order to maximize the dissolution yield and thus obtain a leachate, the liquid part of which after the implementation of a solid / liquid separation step is called leaching filtrate.

[0006] This leaching filtrate of the black mass contains lithium and possibly other valuable metals such as nickel, cobalt and / or manganese which are of interest to recover but also solubilized organic compounds which should be eliminated, the most common being ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dimethoxyethane (DME), N-methyl-2-pyrrolidone (NMP), etc.

[0007] These organic compounds, and their degradation products, are in fact considered impurities in the process and must be removed from the leaching filtrate. For convenience, the indicator for monitoring the presence of these compounds is the concentration of total organic carbon (TOC), which groups together all the organic compounds that can coexist within a solution.

[0008] It would therefore be interesting to have a process that would eliminate these organic compounds and thus reduce the total organic carbon concentration of the leaching filtrate while avoiding the production of new polluting products.

[0009] The inventors realized that it was possible to use a "Fenton" type reaction, that is to say, the chemical degradation of these compounds in order to produce water and CO2 in the presence of a Fenton catalyst.

[0010] En particulier le catalyseur de Fenton peut consister en des matériaux from the lithium ion batteries themselves when the latter are Lithium-Iron-Phosphate batteries, which is particularly interesting because it also contributes to the recycling of said batteries and makes it possible to recover the lithium present in these batteries.

[0011] Par ailleurs cette réaction peut être mise en œuvre à tout endroit du procédépurification but is particularly advantageous when implemented after the Al / Fe lime precipitation leaching filtrate purification step because the pH range and temperature are favorable.

[0012] Finally, the inventors surprisingly discovered that this reaction is improved when carried out in the presence of a phosphate salt because this makes it possible to reduce the TOC more significantly and therefore to promote the depletion of the solution in solubilized organic compound. Presentation of the invention

[0013] The present invention therefore relates to a method for purifying a leaching filtrate from the black mass of lithium-ion batteries, said filtrate containing lithium and at least one solubilized organic compound, said method comprising the step of adding an oxidizing agent, a Fenton catalyst, and optionally a phosphate salt to said filtrate so as to obtain a solution containing lithium and depleted in said at least one solubilized organic compound.

[0014] In this application, the expressions “between ... and ...”, “from ... to ...” and “in the range ...- ...”, must be understood to include limits unless explicitly stated otherwise.

[0015] According to the present invention, the term "solution depleted in said at least one solubilized organic compound" means that the solution contains a lower quantity of said at least one solubilized organic compound than the quantity initially present before the implementation of the step, advantageously a TOC concentration lower than that initially present before the implementation of the step. The TOC concentration can be measured by a TOC meter according to standard NF 1484. In particular, the TOC concentration eliminated by the process according to the invention can be between 5% and 90%, advantageously between 10% and 90%, more advantageously between 18% and 88%.

[0016] The lithium-ion batteries according to the invention may comprise, and advantageously consist of, Lithium-Iron-Phosphate (LFP) type batteries in which the electrodes are made of mixed lithium and iron phosphate (LiFePO4) and graphite, or LFP / LTO (Lithium-Iron-Phosphate / Lithium-Titanium-Oxide) type batteries, in which the electrodes are made of mixed lithium and iron phosphate and mixed lithium and titanium oxide (Li4Ti5O12), or Nickel Cobalt-Aluminium (NCA) batteries or Nickel Manganese Cobalt (NMC) batteries or even batteries comprising at least one of the three elements nickel, cobalt or manganese.

[0017] For the purposes of the present invention, the term "black mass" or "black mass" means the powdery fraction containing fine metal particles obtained after separation of the plastic materials and grinding / treatment of the parts containing electrodes such as battery cells, used lithium-ion batteries or lithium-ion battery scrap (non-compliant lithium-ion batteries or semi-finished products manufactured during the lithium-ion battery manufacturing process). Typically the black mass is produced by sieving to 500 µm or less. There are two main processing routes used for the production of the black mass: - heat treatment processes at temperatures > 400°C. A black mass called "thermal black mass" or "thermal black mass" is obtained and - high-intensity mechanical treatments. A black mass called "mechanical black mass" or "mechanical black mass" is obtained. The black mass according to the invention can therefore consist of a thermal black mass, a mechanical black mass, or a mixture of thermal black mass and mechanical black mass in any proportion.

[0018] La masse noire contient du lithium mais elle peut également contenir d’autresvaluable metals such as nickel, cobalt and / or manganese. It also contains, despite the separation of plastics, organic compounds, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, N-methyl-2-pyrrolidone, carboxy methyl cellulose and mixtures thereof. It may also include many other impurities such as aluminum, calcium, iron, fluorine, phosphorus and / or copper. It may also contain magnesium. It also contains graphite. The typical composition of a black mass (thermal or mechanical) apart from the carbon content is shown in Table 1 below:

[0019] [Table 1] Elements % by mass [TOC] ≤ 2 Li 2-6 Ni 10-30 Co 3-9 Mn 3-9 Al 1-3 Ca 0-2 Mg 0-2 Cu 2-6 Fe 0-3 F 1-8 PO4 3- 0-2

[0020] For the purposes of the present invention, the term "black mass leaching filtrate" means the liquid part resulting from the leaching of the black mass. In general, the leaching is carried out with sulfuric acid in the presence of an oxidizing-reducing compound and the leaching step is followed by a solid / liquid separation step (advantageously by filtration) in order to recover the liquid part, thus called the black mass leaching filtrate.

[0021] In the context of the present invention, this leaching filtrate may be the liquid part directly resulting from the solid / liquid separation after leaching of the black mass, but it may also be the liquid part obtained after one or more purification steps which follow / follow this solid / liquid separation. Thus, advantageously, this leaching filtrate corresponds to the liquid part obtained after a purification step by precipitation of Al / Fe, in particular with lime.

[0022] Ainsi le procédé selon la présente invention peut comprendre une étape preliminary purification by precipitation of Al / Fe, in particular with lime, and recovery of the liquid part. The recovery of the liquid part can be carried out by all solid / liquid separation methods known to those skilled in the art such as filtration, decantation, centrifugation, etc. tc…

[0023] The method according to the present invention may also comprise, before this purification step or before the addition step according to the present invention if this preliminary purification step is not present, a step of leaching the black mass of lithium-ion batteries followed by a solid / liquid separation step in order to recover the liquid part. The recovery of the liquid part may be carried out by any solid / liquid separation methods known to those skilled in the art such as filtration, decantation, centrifugation, etc. In particular, the black mass may be a mixture of thermal black mass and mechanical black mass, in particular in a mass ratio of 50 / 50. Advantageously, this leaching step is carried out by a method well known to those skilled in the art, more advantageously using an acid, such as sulfuric acid H2SO4. Advantageously, the quantity in moles of acid is calculated to correspond to a molar ratio H+ / (Li+Co+Ni+Mn) necessary for the dissolution of lithium and possibly cobalt, manganese and / or nickel present in the black mass, in particular between 90 and 150%, preferably between 110 and 130%. In particular the pH is less than 2. More particularly the temperature is greater than 50°C, in particular greater than 70°C, more particularly it is 90°C. Advantageously the leaching step lasts 4 hours. Advantageously, the leaching step is carried out in the presence of an oxido-reducing compound, in particular a reducing compound, more advantageously chosen from hydrogen peroxide, SO2 in gas form and their mixtures, in particular, it is SO2 in gas form.In particular, the content of redox compound used is that necessary to adjust the redox potential in a range between 200 and 800 mV vs Ag / AgCl, more advantageously between 200 and 700 mV vs Ag / AgCl, more particularly between 200 and 600 mV vs Ag / AgCl. In an advantageous embodiment, the acid is added to a first reactor and the redox compound to a second reactor. The mass yield of lithium and optionally nickel and / or cobalt and / or manganese leaching (calculated according to the following formula: 1 - mass of the element (in g) in solid form obtained at the end of the leaching step / initial mass of element (in g) in the filtrate before the leaching step) is advantageously. greater than 90%, more advantageously greater than 95%, even more advantageously greater than 99%.

[0024] The leaching filtrate of the black mass according to the invention, more simply called “leaching filtrate” in the remainder of the application, contains lithium. It may contain at least one other valuable metal, advantageously chosen from nickel, cobalt and their mixtures. Advantageously, it is a mixture of lithium (Li), nickel (Ni), manganese (Mn) and cobalt (Co). The lithium, and possibly nickel, cobalt and / or manganese, contents of the leaching filtrate according to the invention depend on the contents present in the black mass and the contents which may have been lost during any previous purification steps.

[0025] The lithium content of the leaching filtrate according to the invention can thus be ≤ 15g / l, more advantageously between 5g / l and 14g / l, in particular between 9g / l and 11g / l.

[0026] La teneur en nickel du filtrat de lixiviation selon l’invention, si le nickel estpresent, can thus be included in the range 10-60 g / l, more advantageously between 30 g / l and 55 g / l, in particular between 44 g / l and 48 g / l.

[0027] The cobalt content of the leaching filtrate according to the invention, if cobalt is present, can thus be in the range 1-40 g / l, more advantageously between 5 g / l and 20 g / l, in particular between 12 g / l and 15 g / l.

[0028] The manganese content of the leaching filtrate according to the invention, if manganese is present, may be ≤ 50 g / l, more advantageously between 5 g / l and 30 g / l, in particular between 12 g / l and 15 g / l.

[0029] Le filtrat de lixiviation selon l’invention contient au moins un composésolubilized organic compound, compound that one seeks to eliminate. Advantageously, the at least one organic compound is chosen from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, N-methyl-2-pyrrolidone, carboxy methyl cellulose and mixtures thereof.

[0030] The concentration of total organic carbon (TOC), in particular measured by a TOC meter according to standard NF 1484, of the leaching filtrate according to the invention is advantageously between 10 mg / l and 5000 mg / l, advantageously between 600 mg / l and 3000 mg / l.

[0031] Le filtrat de lixiviation selon l’invention peut contenir d'autres impuretés tellesthan aluminum (Al), calcium (Ca), fluorine (F), magnesium (Mg), iron (Fe), phosphorus (P) and / or copper (Cu). The contents of aluminum (Al), calcium (Ca), fluorine (F), magnesium (Mg), iron (Fe), phosphorus (P) and / or copper (Cu) in the leaching filtrate according to the invention depend on the contents present in the black mass and the quantities eliminated during any prior purification steps.

[0032] The aluminum content of the leaching filtrate according to the invention, if aluminum is present, can thus be ≤ 20 g / l, more advantageously between 1 g / l and 10 g / l, in particular between 2 g / l and 4 g / l. Advantageously, if the filtrate is obtained after a purification step by precipitation of Al / Fe, the aluminum content will be < 100 mg / l.

[0033] The calcium content of the leaching filtrate according to the invention, if calcium is present, can thus be ≤ 0.7 g / lg / l, more advantageously between 0.2 g / l and 0.6 g / l, in particular between 0.3 g / l and 0.5 g / l.

[0034] La teneur en fluor du filtrat de lixiviation selon l’invention, si le fluor est present, can thus be ≤ 20 g / l, more advantageously between 4 g / l and 10 g / l in particular between 6 g / l and 8 g / l.

[0035] The magnesium content of the leaching filtrate according to the invention, if magnesium is present, can thus be ≤ 5 g / l, more advantageously between 3 g / l and 4 g / l.

[0036] The iron content of the leaching filtrate according to the invention, if iron is present, can thus be ≤ 10 g / l, more advantageously between 0.5 g / l and 5 g / l, in particular between 1 g / l and 2 g / l. Advantageously, if the filtrate is obtained after a purification step by precipitation of Al / Fe, the iron content will be < 2 mg / l.

[0037] Phosphorus content in the form of PO4 3-of the leaching filtrate according to the invention, if phosphorus is present, can thus be ≤ 10 g / l, more advantageously between 0.1 g / l and 5 g / l, in particular between 0.5 g / l and 4 g / l.

[0038] La teneur en cuivre du filtrat de lixiviation selon l’invention, si le cuivre est present, can thus be ≤ 30 g / l, more advantageously between 2 g / l and 20 g / l, in particular between 9 g / l and 11 g / l.

[0039] The process according to the invention is carried out by adding an oxidizing agent, a Fenton catalyst, and optionally a phosphate salt to the leaching filtrate according to the invention. The reactants may be added in any order. Preferably, if present, the phosphate salt is added first, then the Fenton catalyst and finally the oxidizing agent.

[0040] Advantageously, the oxidizing agent according to the invention is the usual one for Fenton reactions, in particular chosen from the group consisting of sodium persulfate, ozone, air, O2, hydrogen peroxide and their mixtures, advantageously it is hydrogen peroxide, in particular at between 30 and 35%.

[0041] The amount of oxidizing agent added depends on the TOC concentration of the filtrate according to the invention and advantageously the oxidizing agent / TOC molar ratio is between 1 and 50, preferably between 1 and 25, more advantageously between 2 and 10.

[0042] For the purposes of the present invention, the term “Fenton catalyst” means all catalysts that can be used to catalyze Fenton-type reactions.

[0043] Advantageously, the Fenton catalyst according to the invention is chosen from the group consisting of a source of iron, UV radiation, ozone and their mixtures, advantageously it is a source of iron, alone or mixed with UV radiation or ozone, more advantageously it is a source of iron alone.

[0044] Advantageously, the iron source is selected from the group consisting of iron II sulfate (FeSO4), iron II phosphate, lithium iron phosphate, in the form of the compound LiFePO4 as such or in the form of materials for or derived from lithium-iron-phosphate batteries, iron metal (Fe(0)) and their mixtures. Advantageously, these are iron II sulfate (FeSO4), iron metal (Fe(0)) or LiFePO4.

[0045] In an advantageous embodiment, the iron source is lithium iron phosphate, in the form of the compound LiFePO4 as such or in the form of materials for or derived from lithium-iron-phosphate batteries.

[0046] Indeed, the use of materials for batteries or from LFP (Lithium-Iron-Phosphate) type batteries, in their cathodic form, pieces (scraps), or shredded used batteries is particularly interesting in the context of the present invention because it contributes to the recycling of said batteries.

[0047] The amount of Fenton catalyst added takes into account the elements already present in solution that can contribute positively or negatively to the reaction, called reactive elements. In particular, it is known that too large an excess of metallic elements such as iron or copper can have a negative impact on the reaction. Advantageously, the amount of Fenton catalyst added makes it possible to obtain a catalyst concentration (in g / l of reactive elements) in the filtrate according to the invention corresponding to between 0.1 and 10 g / L of reactive element, preferably between 0.1 and 1.5 g / l of reactive elements.

[0048] Dans un mode de réalisation particulièrement avantageux, un sel de phosphate is added to said filtrate in combination with the oxidizing agent and Fenton catalyst.

[0049] Advantageously, it is sodium phosphate or lithium phosphate, in particular sodium phosphate. More particularly sodium phosphate dodecahydrate (Na3PO4.12H2O).

[0050] The amount of phosphate salt added depends on the molar amount of aluminum and iron in the filtrate according to the invention.

[0051] The inventors surprisingly noticed that the addition of phosphate salt made it possible to further improve the elimination of solubilized organic compounds present in the filtrate according to the invention and therefore the depletion of this filtrate in solubilized organic compounds, that is to say the reduction of the TOC concentration.

[0052] In an advantageous embodiment, the addition step of the process according to the invention is carried out at a temperature between 10°C and 95°C, advantageously between 30°C and 90°C, more advantageously between 40°C and 80°C, even more advantageously between 50°C and 75°C, in particular it is 60°C. This temperature is advantageously maintained throughout the duration of the reaction between the reactants (oxidizing agent, Fenton catalyst and / or phosphate salt) and the leaching filtrate.

[0053] In another advantageous embodiment, the Fenton catalyst is a source of iron and the addition step of the process according to the invention is carried out on a filtrate having an initial pH of between 2 and 5, advantageously between 2.5 and 4.

[0054] On entend au sens de la présente invention par « pH initial du filtrat de leaching » the pH of the leaching filtrate before carrying out the addition step according to the invention.

[0055] Advantageously, the pH is adjusted at the start of the reaction (i.e. during the addition step) and / or throughout the duration of the reaction between the reactants (oxidizing agent, Fenton catalyst and / or phosphate salt) and the leaching filtrate, advantageously by adding a base, in order to obtain the desired pH, in particular a pH between 2.5 and 4. Advantageously, the base is chosen from the group consisting of sodium hydroxide (NaOH) and lime (CaO), more advantageously it is lime.

[0056] Dans encore un autre mode de réalisation avantageux, le procédé selon the invention comprises an additional step of solid / liquid separation in order to recover said solution containing lithium depleted in said at least one solubilized organic compound. This step can be implemented by any solid / liquid separation methods known to those skilled in the art such as such as filtration, decantation, centrifugation, etc. Advantageously, it involves filtration, particularly under pressure.

[0057] Advantageously, the reaction between the oxidizing agent, the Fenton catalyst and the optional phosphate salt with the at least one solubilized organic compound lasts between 10 minutes and 5 hours, in particular between 30 minutes and 3 hours, more advantageously between 1 hour and 2 hours.

[0058] In an advantageous embodiment, the method according to the present invention may comprise one or more steps intended to reduce the TOC concentration which may be prior to the addition step according to the invention, such as upstream drying of the black mass and / or filtration of the filtrates on suitable media known to those skilled in the art and / or treatment with compounds such as activated carbon, or even subsequent steps such as filtration of the filtrates on suitable media and / or treatment with compounds such as activated carbon.

[0059] Le lithium et les éventuels autres métaux de valeur présents dans la partieliquid obtained with the process according to the invention can be recovered and separated by methods well known to those skilled in the art, in particular by neutralization and / or solvent extraction.

[0060] The present invention will be better understood from reading the description of the examples which follow. The examples are given for informational purposes only and are not limiting. Unless otherwise stated in the examples, the pressure is atmospheric pressure and the temperatures are indicated in °C. EXAMPLE

[0061] Table 2 below brings together the reaction conditions and the results obtained by implementing the process according to the invention on a leaching filtrate according to the invention obtained after purification by Al / Fe precipitation. It contains a lithium content between 3 and 5g / L.

[0062] The TOC concentration is measured by a TOC meter according to standard NF 1484.

[0063] Examples 1 to 18 are carried out using hydrogen peroxide as the oxidizing agent: H2O2 at 30% in Examples 1 to 13 and H2O2 at 35% in Examples 14 to 18.

[0064] Examples 1-7 and 14-18 are implemented using FeSO4 as the iron source.

[0065] Examples 8 to 10 are implemented using Fe(0) as the iron source.

[0066] Examples 11 to 13 are implemented using LiFePO4 as the iron source.

[0067] L'exemple 14 est mis en œuvre avec en outre ajout de 1,96 g de phosphate sodium dodecahydrate (Na3PO4.12H2O).

[0068] Examples 1 to 4 are carried out without pH adjustment, Examples 5 to 18 are carried out with pH adjustment.

[0069] Examples 16 to 18 are carried out in the presence of a base (CaO at 10% by mass in the case of examples 16 and 17 and NaOH at 25% by mass in the case of example 18) in order to neutralize the pH.

[0070] Example 9 is implemented by simultaneous addition of the Fenton catalyst (Fe(0)) and the oxidizing agent (hydrogen peroxide).

[0071] [Table 2] Ex Quantity Quantity Quantity T Duration Initial pH Final pH % [TOC] filtrate H2O2in g Fe in g reaction reaction eliminated (ml) in °C in h after reaction (%) 1 30 0.5 1.5 50-75 2 0 < pH < 4 2 < pH < 5 57% 2 30 1 1.5 50-75 2 0 < pH < 4 2 < pH < 5 71% 3 30 0.5 0.75 50-75 2 0 < pH < 4 2 < pH < 5 44% 4 30 2 5 50-75 2 0 < pH < 4 2 < pH < 5 19% 5 50 4.8 1.5 50-75 2 0 < pH < 4 2 < pH < 5 71% 6 50 2.4 1.5 50-75 2 0 < pH < 4 2 < pH < 5 64% 7 50 2.4 1.5 50-75 2 0 < pH < 4 2 < pH < 5 74% 8 50 4.8 5.5 50-75 2 0 < pH < 4 2 < pH < 5 76% 9 50 4.8 5.5 50-75 2 0 < pH < 4 2 < pH < 5 83% 10 50 4.8 2 50-75 2 0 < pH < 4 2 < pH < 5 77% 11 50 4.8 5.5 50-75 2 0 < pH < 4 2 < pH < 5 69% 12 50 4.8 5.5 50-75 2 0 < pH < 4 2 < pH < 5 82%13 50 2.4 1.5 50-75 2 0 < pH < 4 2 < pH < 5 42% 14 50 4.7 0.5 50-75 1.5 0 < pH < 4 2 < pH < 5 88% 15 50 4.7 0.5 50-75 1.5 0 < pH < 4 2 < pH < 5 44% 16 50 4.7 5.5 50-75 1.5 0 < pH < 4 2 < pH < 5 86% 17 50 4.7 5.5 50-75 1.5 0 < pH < 4 2 < pH < 5 85% 18 50 4.7 5.5 50-75 1.5 0 < pH < 4 2 < pH < 5 87%

[0072] It should be noted that the presence of a phosphate salt such as sodium phosphate makes it possible to improve the process according to the invention since the TOC elimination increases from 44% (example 15) when it is not present to 88% (example 14) when it is present. There is therefore a very significant reduction in this concentration in the presence of this agent.

[0073] The method according to the present invention is therefore particularly effective in depleting the leaching filtrate of solubilized organic compound and therefore reducing the TOC concentration.

Claims

Claims

1. A method for purifying a leaching filtrate from the black mass of lithium-ion batteries, said filtrate containing lithium and at least one solubilized organic compound, said method comprising the step of adding an oxidizing agent, a Fenton catalyst, and optionally a phosphate salt to said filtrate so as to obtain a solution containing lithium and depleted in said at least one solubilized organic compound.

2. A method according to claim 1, characterized in that the phosphate salt, advantageously sodium phosphate, is added to said filtrate in combination with the oxidizing agent and the Fenton catalyst.

3. A method according to any one of claims 1 or 2, characterized in that the filtrate contains at least one other valuable metal, advantageously chosen from nickel, cobalt and mixtures thereof.

4. Process according to any one of claims 1 to 3, characterized in that the at least one organic compound is chosen from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, N-methyl-2-pyrrolidone, carboxy methyl cellulose and mixtures thereof.

5. Process according to any one of claims 1 to 4, characterized in that the oxidizing agent is chosen from the group consisting of sodium persulfate, ozone, air, O2, hydrogen peroxide and mixtures thereof, advantageously it is hydrogen peroxide.

6. Process according to any one of claims 1 to 5, characterized in that the Fenton catalyst is chosen from the group consisting of an iron source, UV radiation, ozone and mixtures thereof, advantageously it is hydrogen peroxide. It is a source of iron alone.

7. Method according to claim 6, characterized in that the source of iron is chosen from the group consisting of iron II sulfate, iron II phosphate, lithium iron phosphate, in the form of the compound. LiFePO4 as such or in the form of materials for or derived from lithium-iron-phosphate batteries, iron metal and mixtures thereof.

8. Process according to any one of claims 1 to 7, characterized in that the addition step is carried out at a temperature between 10°C and 95°C, advantageously between 50°C and 75°C.

9. Process according to any one of claims 1 to 8, characterized in that the Fenton catalyst is a source of iron and in that the addition step is carried out on a filtrate having an initial pH between 2 and 5, advantageously between 2.5 and 4.

10. Process according to any one of claims 1 to 9, characterized in that the filtrate is obtained after a purification step by precipitation of Al / Fe, in particular with lime.

11. A method according to any one of claims 1 to 10, characterized in that the lithium-ion batteries comprise Lithium-Iron-Phosphate type batteries or Lithium-Iron-Phosphate / Lithium-Titanium-Oxide type batteries.

12. A method according to any one of claims 1 to 11, characterized in that the black mass comes from used lithium-ion batteries and / or lithium-ion battery production scrap.