Crystallization process for separating metals

Abstract

The present disclosure relates to a crystallization process for the recovery of metals from a starting material comprising Ni and Li. The starting material, in aqueous solution or in solid form, is reacted with an aqueous solution reaching an acidity of preferably at least 500 g / L of sulfuric acid, at a temperature of at least 45°C. Upon solid / liquid separation of the reaction product, a solid residue comprising a major fraction of Ni as a hydrated sulfate and an effluent solution comprising a major fraction of Li are obtained. The process is particularly suitable for the recovery of lithium-ion rechargeable batteries.

Description

Technical Field

[0001] This disclosure relates to a crystallization method for separating Ni and Li from starting materials in aqueous or solid form. Background Technology

[0002] Ni and Li are currently found together in a variety of materials, particularly those related to the production or recycling of rechargeable lithium-ion batteries. Popular battery chemistry includes cathode powders containing metallic Li, Ni, Mn, and Co (NMC). Other widely used chemistry utilizes cathode powders containing Li, Ni, Co, and Al (NCA) or Li, Ni, Co, Mn, and Al (NMCA). In future chemistry possibilities, Na could potentially replace Li.

[0003] The demand for lithium-ion battery recycling is increasing, encompassing both production waste and end-of-life batteries. This has led to the treatment of complex waste streams, which primarily consist of lithium-ion batteries and all their components, such as electrode foils, electrolytes, separators, casing materials, and electronic components, but may also include a certain amount of non-lithium batteries, such as nickel-cadmium, nickel-metal hydride, and zinc-based batteries. Derivatives from these production wastes and end-of-life batteries can also be recycled in the form of powder fractions, such as black lumps resulting from mechanical and / or thermal pretreatment.

[0004] As more and more components are added to the product, the chemical complexity of the materials involved increases near the end of the manufacturing cycle. Therefore, battery cells and modules can contain a wide variety of elements, such as Ni, Co, Mn, Li, Na, Fe, Al, V, P, F, C, Ti, and Mg in the positive electrode; Li, Ti, Si, C, Al, and Cu in the negative electrode; Li, F, P, and volatile organic compounds in the electrolyte; and Al, Fe, Cu, Ni, Cr, Sb, and plastics, as well as Cl and Br, in the casing.

[0005] A common feature of recycling processes is the need to separate Li from Ni, and optionally from Mn and Co (if present). On the other hand, the separation of Ni, Mn, and Co from each other is not always necessary, as compounds containing these three metals together can form a suitable starting point for producing cathode materials for new batteries.

[0006] In a conventional battery waste recycling process described in US2019152797, solvent extraction is used to extract Co and Ni from a purified leachate containing Ni, Co, Li, and other substances, resulting in Li-depleted Ni and Co products. This operation consumes alkali, such as NaOH or NH4OH, stoichiometrically with the amount of Ni recovered. Therefore, significant operating costs and substantial salt emissions are consistently present.

[0007] Other processes are based on crystallizing nickel sulfate from the leaching solution, thus leaving lithium in the solution. However, due to the relatively high lithium content in the battery, the lithium content in the leaching solution is also relatively high, and lithium tends to co-crystallize with nickel. To minimize subsequent lithium loss and nickel sulfate contamination, lithium is extracted from the solution before crystallization. This is described in CN108439438: calcined lithium-containing battery waste is acid-leached to produce a solution containing Li, Co, Ni, Mn, Al, Fe, and Cu. First, Cu, Fe, and Al are removed from the solution, then Li is removed with an extractant, and then the mixed Ni, Co, and Mn sulfates are crystallized. A similar process is also known from CN107768763: battery waste is leached in acid, followed by the removal of Cu, Fe, and Al from the resulting solution by precipitation. Li is then removed as LiF using hydrogen fluoride, and the mixed Ni, Co, and Mn sulfates are crystallized.

[0008] US10995014 teaches a method involving the crystallization of metal sulfates from acidic solutions. It specifically relates to the crystallization of NMC (Ni, Mn, Co) from solutions also containing Li. Crystallization is carried out by removing water at a final pH of approximately 1. Although some selectivity for Li is achieved, the crystallization solution still contains a high concentration of dissolved NMC.

[0009] These known processes require an additional lithium removal step before recovering nickel sulfate and, optionally, Co and Mn sulfates. This introduces several disadvantages. First and foremost, in both processes, reagents are still consumed stoichiometrically relative to the extracted Li. Furthermore, the extraction steps are expensive, as they typically require costly extraction reagents and additional process steps, such as loading one or more metals to be removed into the extractant and stripping the extractant. Additionally, hydrogen fluoride is a highly toxic reagent, leading to additional safety investments and operating costs. Moreover, introducing fluorides into the system complicates subsequent wastewater treatment. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide a crystallization method for recovering Ni from a starting solution or solid containing Ni and Li, while avoiding the need for a preliminary Li removal step.

[0011] According to a first embodiment, a method for selectively recovering a transition metal M containing Ni from a starting material in aqueous solution form, the solution also containing Li, the method comprising the following steps:

[0012] - According to formula A≥1100–6.7 Ni is crystallized by adjusting the solution at a temperature T (expressed in degrees Celsius) to an acidity A (expressed in g / L sulfuric acid), thereby obtaining a mixture of solid and liquid reaction products, wherein T is between 45°C and the boiling point of the solution; and

[0013] - The reaction product is subjected to solid / liquid separation to obtain a solid residue and an effluent solution, the solid residue containing a major portion of Ni as hydrated nickel sulfate entering the method, and the effluent solution containing a major portion of Li entering the method.

[0014] "Main component" means at least 50% by weight. "Effluent" means the sum of filtrate and wash water.

[0015] A typical source stream is the leachate from an acidic leaching process of lithium-ion batteries or their derivatives. Another example is purge or effluent from standard nickel sulfate or NMC sulfate crystallization processes. Yet another example is purge or effluent from copper electrolytic deposition stages. Such effluent streams can indeed contain Ni and Li when lithium-ion batteries are supplied to some upstream process steps.

[0016] According to a second embodiment, a method for selectively recovering a transition metal M comprising Ni from a starting material in solid form, the solid also comprising Li, is disclosed, the method comprising the following steps:

[0017] - According to formula A≥1100–6.7 Ni is crystallized by contacting the solid with an aqueous medium adjusted to an acidity A (expressed as g / L sulfuric acid) at a temperature T in degrees Celsius, thereby obtaining a mixture of solid and liquid reaction products, wherein T is between 45°C and the boiling point of the aqueous medium; and

[0018] - The reaction product is subjected to solid / liquid separation to obtain a solid residue and an effluent solution, the solid residue containing a major portion of Ni as hydrated nickel sulfate entering the method, and the effluent solution containing a major portion of Li entering the method.

[0019] A typical source of starting materials containing Ni and Li in solid form is cathode materials carrying waste or scrap, such as black lumps, which are well-known waste streams in lithium-ion battery recycling.

[0020] In this second embodiment, the formation of hydrated nickel sulfate precipitate begins with a solid rather than a solution. However, the overall inventive concept of the method remains the same regardless of whether it begins with an aqueous solution or a solid. Without being constrained by a specific reaction mechanism, it can be assumed that the solid dissolves and subsequently crystallizes readily from the liquid phase.

[0021] Both implementations rely on the abrupt shift in the solubility of Ni and Li when high sulfuric acid concentrations and high temperatures are reached: the solubility of Ni decreases sharply, while the solubility of Li increases. Even in solutions containing a considerable concentration of Li, this allows for selective crystallization of Ni (i.e., no co-precipitation with Li). Therefore, in most practical cases, a preliminary Li removal step is unnecessary.

[0022] "Adjustment" of the aqueous medium or solution means achieving the desired temperature by heating it using external means, or by utilizing the dilution enthalpy when adding highly concentrated sulfuric acid. The desired acid concentration can be obtained by adding highly concentrated sulfuric acid or by evaporating water. Evaporation can advantageously be carried out under partial vacuum. The addition of acid and the evaporation of water can be combined. Obviously, evaporation of water exceeding the solubility limit of Li must be avoided. Highly acidic Ni and Li-containing solutions from upstream process steps can be used directly, with almost no additional acidification. This may occur when processing solutions from acidic leaching solutions or from electrolytic deposition.

[0023] The above equation defines the relationship between acidity and temperature required to ensure sufficient selectivity. It has indeed been found that higher crystallization temperatures are advantageous when acidity decreases. These conditions effectively promote the formation of lower Ni hydrates, such as nickel sulfate monohydrate, and inhibit the formation of higher Ni hydrates, such as nickel sulfate hexahydrate. The combination of these acidity and temperature conditions results in low residual Ni solubility, leading to low Ni loss in the mother liquor.

[0024] A solution temperature below 45°C is undesirable. A temperature of at least 50°C is preferred, and at least 60°C is even more preferred. If the desired acidity level is achieved by adding concentrated acid, the dilution enthalpy will typically heat the solution above the required minimum. If the acidity is achieved by water evaporation, a minimum temperature is also useful: evaporation is too slow at lower temperatures unless expensive high-vacuum techniques are used. Regardless of temperature, a solution with at least 500 g / L, or even at least 600 g / L, of sulfuric acid is preferred.

[0025] When starting with a solid carrying Ni, Mn, or Co in a higher oxidation state, a reducing agent can be added to more easily lower the oxidation state of Ni, Mn, and Co to 2. The divalent cations are practically soluble, while the higher-valent cations are only slightly soluble. This allows the proposed dissolution-crystallization mechanism described above to occur. In the absence of a reducing agent, Mn will particularly readily form insoluble oxides. However, this can become an advantage if the goal is to separate Mn from Ni and Co: Ni and Co will form water-soluble hydrated sulfates, while Mn will remain as an insoluble oxide.

[0026] The solid / liquid separation step can advantageously be carried out at temperatures below 60°C, even if crystallization occurs at higher temperatures. In fact, once formed, significant redissolution of the crystals does not occur. Lower operating temperatures result in reduced corrosion of the separation equipment. Relevant solid / liquid separation equipment includes decanters, centrifuges, and all types of filters. The solid / liquid separation step typically also includes a washing step. Washing can be performed with water.

[0027] The following illustrative example demonstrates the advantageous use of highly acidic effluents carrying Li:

[0028] - As a recycle stream for acidic impregnation of lithium-ion batteries or their derivatives;

[0029] - As a leaching or neutralizing agent in the processing of lithium ores such as spodumene;

[0030] - As a source of sulfuric acid after the acid has been separated, for example, using a sulfuric acid solvent extraction unit or an acid purification system; and

[0031] - For example, Li recovery using solvent displacement.

[0032] In another embodiment according to any of the foregoing claims, according to formula A≥1250–6.7 T is selected as the acidity A of the solution, expressed in g / L sulfuric acid, and the temperature T of the solution, expressed in degrees Celsius, where T is between 50°C and the boiling point of the solution. This ensures a low residual Ni solubility while further increasing the Li solubility. Those skilled in the art will readily optimize the operating conditions by maximizing the Ni yield as hydrated nickel sulfate, while avoiding exceeding the Li solubility limit.

[0033] It should be noted that the above process conditions also apply to the separation of Ni and Na. Na tends to precipitate with Ni as a double salt, and this problem can be mitigated or avoided when operating under the conditions defined in this disclosure.

[0034] In another embodiment according to any of the foregoing, the main portion of the Li accounts for at least 80% by weight, or preferably at least 90% by weight, of the Li entering the method.

[0035] In another embodiment according to any of the foregoing, the main portion of the Ni accounts for at least 60% by weight, or preferably at least 80% by weight, of the Ni entering the method.

[0036] In another embodiment according to any of the preceding claims, the solid residue obtained in the solid / liquid separation step comprises hydrated sulfate according to the formula NiSO4·xH2O, where x is the average hydration factor, and x < 5, preferably x < 2.

[0037] These characteristics reflect a limited or reduced hydration factor in the residue. Preferably, only compounds with low solubility are formed. This result is obtained by applying the characteristics of acidity level and temperature constraints present in any of the above embodiments. Higher acidity and temperature result in a lower hydration factor. Drying at 50°C for 24 hours eliminates most of the free water (moisture) in the residue. As shown in the examples, a further heating step at 250°C results in the formation of nickel sulfate monohydrate (x=1), while heating to 400°C eliminates most of the hydrated water (x=0). Therefore, the weight loss at 250°C can be used to calculate the hydration factor of the NiSO4 salt. Dehydration of other metal salts in the residue also causes weight loss measured at 250°C, which should be taken into account when calculating the hydration factor of NiSO4.

[0038] In another embodiment according to any of the foregoing claims, the starting material has a Ni:Li weight ratio of at least 0.15. This ratio allows for the crystallization of even low concentrations of Ni in a yield of at least 60%, while avoiding undesirable Li precipitation.

[0039] The latter embodiment expresses a preferred method for obtaining Ni-rich concentrates. This result is achieved through the formation of lower hydrates such as nickel sulfate monohydrate. This contrasts with prior art crystallization schemes, which typically result in the formation of nickel sulfate hexahydrate.

[0040] Pure nickel sulfate hexahydrate has a Ni content of 22% by weight, while pure nickel sulfate monohydrate has a Ni content of 34% by weight. Depending on the reaction conditions, different Ni hydrate species can exist adjacent to each other. This makes it more difficult to determine the exact amount of nickel sulfate monohydrate in practice. The value calculated retrospectively will be the average of all different hydrate species. However, even if the theoretical maximum of 34% is not reached, the formation of nickel sulfate monohydrate is still beneficial.

[0041] In another embodiment according to any of the foregoing, the starting material further comprises Co. Co can precipitate together with Ni, which is advantageous.

[0042] Preferably, in such embodiments, the Ni:Co molar ratio is at least 1. This ratio ensures reduced Co solubility compared to the same solution containing less or no Ni. Since Co is the most valuable metal, it is important to ensure excellent yields of Co in the solid residue. The significant synergistic effect between Ni and Co has been demonstrated in the examples.

[0043] In another embodiment according to any of the foregoing, the total amount of Ni and Co forms the main component of the transition metal M.

[0044] In another embodiment according to any of the foregoing, the starting material further comprises Mn.

[0045] In another embodiment according to any of the foregoing claims, the starting material is derived from a rechargeable battery, particularly a lithium-ion battery. "Derived from a rechargeable battery" means liquid or solid products related to the production or recycling of secondary lithium-ion batteries or their derivatives, such as original or spent rechargeable batteries, production waste, scrap, leachate, and black lumps. Current rechargeable lithium-ion batteries typically contain Li, Ni, Mn, and Co as a close mixture. Future rechargeable batteries may replace Li with Na. Batteries may contain many other elements that are considered unavoidable impurities in recycling processes. The method of separating Li from Ni, Mn, and Co is itself suitable for handling such batteries or their waste. The characteristic of these three metals crystallizing together is advantageous because many processes for preparing rechargeable battery precursors involve starting compounds containing precisely these three metals. The proportions of these three metals can be adjusted before or after precipitation to achieve the desired composition.

[0046] In another embodiment according to any of the foregoing, Ni forms the main part of the transition metal M.

[0047] The present invention is illustrated in Examples 1 to 7. Attached Figure Description

[0048] The solubility limits of Li and Ni were investigated in Examples 1 to 3. The results are shown in... Figures 1 to 4 middle:

[0049] - Figure 1 The solubility of Li and Ni as a function of acidity is shown at 90 °C;

[0050] - Figure 2 The solubility of Li and Ni as a function of acidity is shown at 50 °C;

[0051] - Figure 3 The solubility of Li and Co as a function of acidity at 80 °C in the presence of Ni is shown.

[0052] - Figure 4 The solubility of Li and Co as a function of acidity at 80 °C is shown (compare); and

[0053] - Figure 5 The TGA of the relevant metal hydrate is shown, illustrating partial dehydration at 250°C and complete dehydration at 400°C. Detailed Implementation

[0054] Example 1: Ni-Li system as a function of H2SO4 concentration at 90℃

[0055] Crystallization tests were conducted on the different solutions prepared according to Table 1.

[0056] Table 1: Solutions containing Li and Ni

[0057]

[0058] Undissolved metal salts may exist.

[0059] Each solution was stirred and heated to 90°C. Water was evaporated until the total volume was halved. During this evaporation, Ni and Li became saturated and crystallized into hydrated NiSO4 and Li2SO4. The slurry was then filtered through a Büchner funnel. The Ni and Li content of the solutions was analyzed, and the H2SO4 concentration was measured by titration. The results are presented in… Figure 1 middle.

[0060] These crystallization experiments show that at 90 °C, the concentration of NiSO4 decreases sharply from above 500 g / L, while the solubility of Li2SO4 increases. This confirms that high Ni crystallization yields and selectivity can be obtained.

[0061] Example 2: Ni-Li characteristics as a function of H2SO4 concentration at 50℃

[0062] Crystallization tests were conducted on the different solutions prepared according to Table 2.

[0063] Table 2: Solutions containing Li and Ni

[0064]

[0065] Undissolved metal salts may be present.

[0066] These solutions were treated similarly to those in Example 1. However, a temperature of 50°C was chosen instead of 90°C. The results are presented as follows: Figure 2 middle.

[0067] These crystallization experiments show that a higher acid concentration is required at 50°C compared to 90°C to completely suppress Ni solubility. At 50°C, an acid concentration of at least 750 g / L is preferred to ensure excellent Ni yield and selectivity for Li.

[0068] Example 3: The effect of Ni on the crystallization of Co

[0069] Crystallization tests were conducted on the different solutions prepared according to Tables 3 and 4.

[0070] Table 3: Solutions containing Li, Ni, and Co

[0071]

[0072] Undissolved metals may be present.

[0073] Table 4: Ni-free solutions containing Li and Co (comparison)

[0074]

[0075] Undissolved metals may be present.

[0076] These solutions were treated similarly to those in Example 1. However, a temperature of 80°C was chosen instead of 90°C. The results are presented as follows: Figure 3 and Figure 4 middle.

[0077] These results confirm that the presence of Ni promotes the crystallization of Co. Even in the absence of NiSO4 in the system, the crystallized effluent still contained almost twice the amount of Co.

[0078] Selective separation processes are further illustrated in Examples 4 to 7.

[0079] Example 4: Process starting from Ni-Li solution

[0080] A 1 L solution containing 110 g / L Ni, 11.4 g / L Li as sulfates, and 250 g / L H₂SO₄ was added to a 2 L beaker. The solution was stirred and heated to 95 °C. Water was evaporated until a total slurry volume of 500 mL was obtained. Evaporation was carried out at atmospheric pressure for 3 hours.

[0081] The slurry was filtered through a preheated Büchner funnel. A 300 mL filtrate containing 11.8 g / L Ni and 32 g / L Li was recovered. The final filtrate's H₂SO₄ concentration was determined to be 710 g / L by titration. The residue was washed with 430 mL of water. In industrial practice, the wash water is recovered and not considered a loss. In this example and the following examples, the amount of wash water is therefore added to the yield. 392 g of crystals containing 25% Ni and only 0.3% Li were obtained. The residue also contained sulfate and hydrated water. After washing, the residue was dried at 50°C for 24 hours to remove all impregnated water. After drying in a vacuum furnace, the weight loss after drying at 250°C under a N₂ atmosphere for 1 hour was 26%. This weight loss corresponds to the removal of H₂O when the nickel sulfate is converted to a monohydrate salt. The 26% weight loss corresponds to 3.4 mol of H₂O per mole of Ni. Therefore, the average hydration factor x of the crystalline nickel sulfate is 4.4, which is significantly lower than the usual hydration factor of 6.

[0082] Table 5: Material balance of the separation process starting from Ni-Li solution

[0083]

[0084] This experiment demonstrates a high yield of direct NiSO4 crystallization: 89% of Ni was crystallized. The Ni yield can be further improved by recycling the wash water back into the crystallization process. Only a small amount of lithium contamination was observed in the crystals. Li was recovered from the effluent (the sum of filtrate and wash water) with a yield of 95%.

[0085] Example 5: Process starting from NMC-Li solution

[0086] Add a 1 L solution containing 68 g / L Ni, 23 g / L Mn, 24 g / L Co, 14 g / L Li, 11 g / L Na and 10 g / L Al as sulfates to a 2 L beaker.

[0087] The solution was stirred while 400 mL of concentrated H₂SO₄ with a concentration of 1740 g / L was added. The mixture was heated to 95°C on a hot plate. Water was evaporated until a total slurry volume of 950 mL was obtained. The slurry was filtered through a heated Büchner funnel. An 810 mL filtrate containing 6.2 g / L Ni, 0.02 g / L Mn, 0.01 g / L Co, 16 g / L Li, 13 g / L Na, and 11 g / L Al was recovered. The H₂SO₄ concentration was determined to be 830 g / L by titration. The residue was washed with 670 mL of water. A 320 g dry residue containing 18.8% Ni, 7% Mn, 7.1% Co, 0.2% Li, and 0.01% Na was obtained. The residue also contained sulfate, hydrated water, and trace impurities. After washing, the residue was dried at 50°C for 24 hours to remove all impregnated water. Following drying, the dried crystals were subjected to thermogravimetric analysis (TGA) under nitrogen. The results of this TGA are presented in... Figure 5 In TGA ( Figure 5 During step A), the weight loss during drying at 250°C under a N2 atmosphere was 2.6%. This corresponds to a loss of 0.3 mol H2O per mole of the sum of Ni and Co, corresponding to an average hydration factor x of 1.3. It is assumed that MnSO4 exists as a monohydrate salt after crystallization and will not undergo further dehydration at 250°C. After dehydration at 250°C, the salt is further heated to 400°C to remove all hydrated water (x=0). A weight loss of 10% was measured by heating from 250°C to 400°C. Figure 5 (Step B in the text). This weight loss confirms that Ni, Co, and Mn exist as sulfate monohydrate at 250°C (x=1).

[0088] Table 6: Material balance of the separation process starting from NMC-Li solution

[0089]

[0090]

[0091] This embodiment demonstrates high recovery rates of Ni, Mn, and Co in crystals. A high NMC crystallization yield of 91% was achieved, with only 0.2% Li contamination in the crystals. Li was recovered from the effluent (the sum of filtrate and wash water) at a recovery rate of 96%. Major impurities such as Na and Al remained in solution. The yields of Ni, Mn, and Co can be further improved by recycling the wash water back into the crystallization process.

[0092] Example 6: Processes starting from NMC-Li solid

[0093] 300 g of NMC cathode powder with a composition of 25% Ni, 15% Mn, 15% Co, and 5.2% Li was mixed with 200 mL of water and added to a 2 L beaker. The beaker was placed on a heating plate and stirred to keep the cathode powder suspended. When the temperature reached 95 °C, 1 L of concentrated H₂SO₄ with a concentration of 1740 g / L was added. Over a period of 9.5 hours, 775 mL of 30% H₂O₂ solution was added to the mixture as a reducing agent to ensure that Ni, Mn, and Co were divalent. The mixture was filtered through a heated Büchner funnel. 1.6 L of the filtrate was recovered. The filtrate contained 3.8 g / L Ni, 6.5 g / L Mn, 2.2 g / L Co, and 8.4 g / L Li. The concentration of H₂SO₄ was determined to be 775 g / L by titration.

[0094] The residue was washed with 850 ml of water. 567 g of dry residue containing 12% Ni, 6.3% Mn, 7.4% Co, and 0.3% Li was obtained. The residue also contained sulfate and hydrated water.

[0095] Table 7: Material balance of the separation process starting from NMC-Li solid

[0096]

[0097] This example demonstrates the in-situ reaction of Ni and Li-containing solids treated under high acidity. Ni oxides in the solid material are converted to sulfates, while most of the Li dissolves. Mn and Co behave similarly to Ni. A total yield of 83% for Ni, Mn, and Co was achieved. The yields of Ni, Mn, and Co can be further improved by recycling the wash water back into the crystallization process. 90% of the Li was recovered from the effluent (the sum of filtrate and wash water).

Claims

1. A method for selectively recovering a transition metal M containing Ni from a starting material in aqueous solution, the solution also containing Li, the method comprising the following steps: - According to formula A≥1100–6.7 Ni is crystallized by adjusting the solution at a temperature T in degrees Celsius to an acidity A in g / L sulfuric acid, thereby obtaining a mixture of solid and liquid reaction products, wherein T is between 45°C and the boiling point of the solution. and - The reaction product is subjected to solid / liquid separation to obtain a solid residue and an effluent solution, the solid residue containing a major portion of Ni as hydrated nickel sulfate entering the method, and the effluent solution containing a major portion of Li entering the method.

2. A method for selectively recovering a transition metal M comprising Ni from a starting material in solid form, said solid also comprising Li, the method comprising the following steps: - According to formula A≥1100–6.7 Ni is crystallized by contacting the solid with an aqueous medium adjusted to an acidity A in g / L sulfuric acid at a temperature T in degrees Celsius, thereby obtaining a mixture of solid and liquid reaction products, wherein T is between 45°C and the boiling point of the aqueous medium. and - The reaction product is subjected to solid / liquid separation to obtain a solid residue and an effluent solution, the solid residue containing a major portion of Ni as hydrated nickel sulfate entering the method, and the effluent solution containing a major portion of Li entering the method.

3. The method according to claim 1 or 2, wherein A ≥ 1250 - 6.7 T is selected as the acidity A of the solution, expressed in g / L sulfuric acid, and the temperature T of the solution, expressed in degrees Celsius, wherein T is between 50°C and the boiling point of the solution.

4. The method according to claim 1 or 2, wherein the main component of the Li is at least 80% by weight of the Li entering the method.

5. The method of claim 4, wherein the majority portion of the Li is at least 90% by weight of the Li entering the method.

6. The method according to claim 1 or 2, wherein the main portion of the Ni is at least 60% by weight of the Ni entering the method.

7. The method of claim 6, wherein the majority portion of the Ni is at least 80% by weight of the Ni entering the method.

8. The method according to claim 1 or 2, wherein the solid residue obtained in the solid / liquid separation step comprises hydrated sulfate according to the formula NiSO4·xH2O, where x is the average hydration factor and x < 5.

9. The method of claim 8, wherein x < 2.

10. The method according to claim 1 or 2, wherein the starting material has a Ni:Li weight ratio of at least 0.

15.

11. The method according to claim 1 or 2, wherein the starting material further comprises Co.

12. The method of claim 11, wherein the Ni:Co molar ratio is at least 1.

13. The method of claim 12, wherein the total amount of Ni and Co forms the major portion of the transition metal M.

14. The method according to claim 1 or 2, wherein the starting material further comprises Mn.

15. The method according to claim 1 or 2, wherein the starting material is derived from a rechargeable battery.

16. The method of claim 15, wherein the starting material is derived from a lithium-ion battery.

17. The method according to claim 1 or 2, wherein Ni forms the main portion of the transition metal M.

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