Crystallization method for separating metals

Abstract

The present disclosure relates to a crystallization method for recovering metals from starting materials containing Ni and Li. The starting materials, in aqueous solution or solid form, are reacted with an aqueous solution at a temperature of at least 45° C., preferably reaching an acidity of at least 500 g / L sulfuric acid. After solid / liquid separation of the reaction products, a solid residue is obtained containing most of the Ni as hydrated sulfates, and an effluent solution containing most of the Li. The method is particularly suitable for the recycling of lithium-ion rechargeable batteries.

Description

Technical Field

[0001] The present disclosure relates to a crystallization method for separating metals from starting materials in aqueous solution or solid form, which contain metals Ni and Li.

Background Art

[0002] Ni and Li are currently often present together in several materials, especially those related to the manufacture or recycling of rechargeable lithium-ion batteries. Currently common battery chemistries include cathode powders (NMC) containing metals Li, Ni, Mn, and Co. Other commonly used chemistries utilize cathode powders (NCA) containing Li, Ni, Co, and Al, or cathode powders (NMCA) containing Li, Ni, Co, Mn, and Al. In potentially future chemistries, Na could replace Li.

[0003] The recycling of lithium-ion batteries, including both manufacturing waste and end-of-life batteries, is becoming increasingly necessary. This results in the treatment of a complex waste stream mainly including lithium-ion batteries and all their components, such as electrode foils, electrolytes, separators, packaging materials, and electronic components, and possibly also certain amounts of non-lithium batteries, such as nickel-cadmium batteries, nickel-metal hydride batteries, and zinc-based batteries. These manufacturing waste and end-of-life battery derivatives can also be used for recycling in the form of powder fractions, such as black masses, which are the result of mechanical pretreatment and / or thermal pretreatment.

[0004] As the number of components added to products increases, the chemical complexity of the materials involved increases towards the end of the manufacturing cycle. Thus, battery cells and modules may contain a vast number of different elements, such as Ni, Co, Mn, Li, Na, Fe, Al, V, P, F, C, Ti, and Mg in the cathode, Li, Ti, Si, C, Al, and Cu in the anode, Li, F, P, and volatile organic compounds in the electrolyte, and plastics containing Al, Fe, Cu, Ni, Cr, Sb, and Cl and Br in the casing.

[0005] The amount of used batteries is expected to exceed 100,000 metric tons per year in the next decade, mainly due to the ongoing electrification of the automotive industry worldwide. The battery recycling business is expected to grow accordingly. Common to the recycling process is the need to separate Li from Ni, and optionally Mn and Co, if they are present. Separating Ni, Mn, and Co from each other is not always necessary, on the other hand, as compounds containing these three metals together can form a suitable starting point for manufacturing cathode materials for new batteries.

[0006] One conventional battery scrap recycling method, described in US2019152797, uses solvent extraction to extract Co and Ni from a purified leachate containing Ni, Co, Li, etc., yielding a Ni and Co product with reduced Li. In this operation, a base such as NaOH or NH4OH is consumed stoichiometrically in proportion to the amount of Ni recovered. As a result, considerable operating costs and substantial salt emissions follow.

[0007] Other methods are based on crystallizing nickel sulfate from the leaching solution while leaving lithium in the solution. However, due to the relatively high lithium content in the battery and therefore in the leaching solution, 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 illustrated in CN108439438: calcined lithium-containing battery waste is acid-leached to produce a solution containing lithium, co, nickel, magnesium, aluminum, feces, and copper. From this, copper, feces, and aluminum are first removed, then lithium is removed using an extractant, and then the mixed nickel sulfate, co, and magnesium sulfate are crystallized. A similar method is known in CN107768763: battery waste is leached in acid, and then copper, feces, and aluminum are removed from the resulting solution by precipitation. Lithium is then removed as lithium (LiF) using hydrogen fluoride, and the mixed nickel sulfate, co, and magnesium sulfate are crystallized.

[0008] US10995014 teaches a method for crystallizing metal sulfates from acidic solutions. It specifically deals with the crystallization of NMC (Ni, Mn, Co) from a solution also containing Li. Crystallization is carried out by water removal at an endpoint pH of approximately 1. While achieving some selectivity for Li, the crystallized solution still contains high levels of dissolved NMC.

[0009] These known methods require an additional Li removal step before recovering Ni sulfate, and optionally Co sulfate and Mn sulfate as well. This has several drawbacks. Firstly, in both methods, the reagent is still stoichiometrically consumed with respect to the extracted Li. Secondly, the extraction step is costly, as it typically requires expensive extractants and additional process steps, such as loading the (one or more) metals to be removed onto the extractant and removing the extractant. Furthermore, hydrogen fluoride is a highly toxic reagent, resulting in additional safety investments and operating costs. Additionally, the introduction of fluoride into the system complicates wastewater treatment later on. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent Application Publication 2019 / 152797 Specification [Patent Document 2] Chinese Patent Application Publication No. 108439438 Specification [Patent Document 3] Chinese Patent Application Publication No. 107768763 Specification [Patent Document 4] U.S. Patent No. 10995014 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Therefore, an 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. [Means for solving the problem]

[0012] According to the first embodiment, a method for selectively recovering a transition metal M containing Ni from an aqueous solution of starting materials, wherein the solution also contains Li, - A step of crystallizing Ni by adjusting the solution to reach an acidity A expressed in g / L of sulfuric acid at a temperature T expressed in degrees Celsius, according to formula A≧1100-6.7*T, where T is between 45°C and the boiling point of the solution, thereby obtaining a mixture of solid and liquid reaction products; and - A step in which the reaction product is separated into solid and liquid, thereby obtaining a solid residue containing most of the Ni to be added to the method as hydrated nickel sulfate, and an effluent solution containing most of the Li to be added to the method. Methods including this will be revealed.

[0013] "Majority" means at least 50% by mass. "Effluent solution" means the sum of filtrate and wash water.

[0014] A typical source flow is leachate from acidic leaching methods that handle lithium-ion batteries or their derivatives. Another example is purging or bleeding in standard Ni or NMC sulfate crystallization methods. A further example is purging or bleeding in a Cu electrolytic extraction plant. Such bleed flows can indeed contain Ni and Li if lithium-ion batteries are supplied upstream in certain process steps.

[0015] According to the second embodiment, a method for selectively recovering a transition metal M containing Ni from a solid starting material, wherein the solid also contains Li, - A process of crystallizing Ni by contacting a solid with an aqueous medium adjusted to reach an acidity A expressed in g / L of sulfuric acid at a temperature T expressed in degrees Celsius according to formula A≧1100-6.7*T, where T is between 45°C and the boiling point of the aqueous medium, thereby obtaining a mixture of solid and liquid reaction products; and - A step in which the reaction product is separated into solid and liquid, thereby obtaining a solid residue containing most of the Ni to be added to the method as hydrated nickel sulfate, and an effluent solution containing most of the Li to be added to the method. Methods including this will be revealed.

[0016] Typical sources of solid-form starting materials containing Ni and Li include scrap or waste, such as cathode materials containing black lumps, which is a well-known waste stream in the recycling of lithium-ion batteries.

[0017] In this second embodiment, the hydrated nickel sulfate precipitate is formed starting from a solid rather than a solution. The general progressive concept of this method is the same whether starting from an aqueous solution or a solid. Although not bound by a specific reaction mechanism, it can be assumed that the solid dissolves and then readily crystallizes from the liquid phase.

[0018] Both embodiments rely on the abrupt changes 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. This allows for the selective crystallization of Ni, i.e., without coprecipitation of Li, even in solutions containing considerable concentrations of Li. The preliminary Li removal step is therefore not necessary in most practical cases.

[0019] "Preparing" an aqueous medium or solution means obtaining the required temperature by heating using external means or by dilution enthalpy when high-concentration sulfuric acid is added. The required acid concentration can be obtained by adding high-concentration sulfuric acid or by evaporation of water. Evaporation is advantageous when carried out under partial vacuum. The addition of acid and evaporation of water may be combined. Obviously, evaporation of water beyond the solubility limit of Li must be avoided. Strongly acidic Ni and Li-containing solutions from upstream of the process steps can be used directly with little or no further acidification. This may be the case when processing solutions from acid leaching or electrolytic extraction.

[0020] The above formula defines the relationship between the acidity and temperature necessary to ensure sufficient selectivity. It has been found that when the acidity actually decreases, it is advantageous for the crystallization temperature to be higher. These conditions actually promote the formation of lower Ni hydrates, such as nickel sulfate monohydrate, and suppress the formation of higher Ni hydrates, such as nickel sulfate hexahydrate. In combination with the acidity and temperature conditions defined above, a low Ni residual solubility is achieved and the Ni loss in the mother liquor is reduced.

[0021] A solution temperature below 45 °C is not sufficient. A temperature of at least 50 °C is preferred, and a temperature of at least 60 °C is even more preferred. When the required acidity level is reached by adding concentrated acid, the dilution enthalpy will typically heat the solution above the minimum value required. The minimum temperature is also useful when the acidity is reached by evaporation of water: at lower temperatures, evaporation is too slow unless expensive high-vacuum techniques are applied. Regardless of the temperature, a solution containing at least 500 g / L, or even at least 600 g / L, of sulfuric acid is preferred.

[0022] When starting from a solid containing Ni, Mn or Co in a higher oxidation state, it may be chosen to add a reducing agent in order to more easily reduce the oxidation states of Ni, Mn and Co to 2. Cations with a higher valence are only slightly soluble, while divalent cations are certainly soluble. This enables the dissolution-crystallization mechanism proposed above to occur. In the absence of a reducing agent, Mn is particularly likely to form insoluble oxides. Nevertheless, this can become an advantage if one wishes to separate Mn from Ni and Co: Ni and Co will form water-soluble hydrate sulfates, while Mn will remain as an insoluble oxide.

[0023] The solid / liquid separation step can be advantageously carried out at a temperature below 60°C, even when crystallization is carried out at a higher temperature. Once formed, there does not appear to be significant redissolution of the crystallized seeds. The lower operating temperature results in less corrosion of the separation device. Relevant solid / liquid separation devices are decanters, centrifuges and all kinds of filters. This solid / liquid separation step usually includes a washing step. The washing can be carried out using water.

[0024] The Li-containing effluent is very acidic and, by the following exemplary experimental examples: - As a recycling stream for the acid leaching of lithium-ion batteries or their derivatives; - As a leaching agent or neutralizing agent in the operation of processing lithium ores such as spodumene; - As a sulfuric acid source after separating the acid using, for example, a sulfuric acid solvent extraction unit or an acid purification system; and - For example, for recovering Li using solvent replacement can be advantageously used.

[0025] In a further embodiment according to any of the above embodiments, for T between 50°C and the boiling point of the solution, the acidity A of the solution expressed in g / L of sulfuric acid and the temperature T of the solution expressed in degrees Celsius are selected according to the formula A ≧ 1250 - 6.7*T. Thereby, while further increasing the solubility of Li, the residual solubility of Ni can be surely made lower. A person skilled in the art will easily optimize the operating conditions by maximizing the Ni yield with respect to nickel sulfate hydrate while not exceeding the dissolution limit of Li.

[0026] Note that the above processing conditions are also suitable for the separation of Ni and Na. Na has a tendency to actually precipitate as a double salt with Ni and is a problem that can be reduced or avoided when working under the conditions defined in this disclosure.

[0027] In a further embodiment according to any of the above embodiments, most of the Li reaches at least 80% by mass, or preferably at least 90% by mass of the Li input to the method.

[0028] In further embodiments according to any of the embodiments described above, the majority of the Ni is at least 60% by mass, or preferably at least 80% by mass, of the Ni introduced into the method.

[0029] In further embodiments according to any of the embodiments described above, the solid residue obtained in the solid / liquid separation step contains a hydrated sulfate according to the formula NiSO4.xH2O, (wherein x is the average hydration coefficient, x < 5, preferably x < 2).

[0030] These characteristics reflect a limitation or reduction in the hydration coefficient in the residue. It is preferable that only compounds with low solubility are formed. This result is obtained by applying the acidity level and temperature constraints characterized in any of the embodiments described above. Higher acidity and temperature result in lower hydration coefficients. A drying step of 24 hours at 50°C removes most of the free water (moisture) from the residue. As illustrated in the experimental example, a further heating step at 250°C forms nickel sulfate monohydrate (x=1), but heating to 400°C removes most of the hydration water (x=0). The mass loss at 250°C can thus be used to calculate the hydration coefficient of the NiSO4 salt. Dehydration of other metal salts in the residue may also contribute to the mass loss measured at 250°C and should be taken into consideration when calculating the hydration coefficient of NiSO4.

[0031] In further embodiments according to any of the embodiments described above, the starting material has a Ni:Li mass ratio of at least 0.15. This ratio allows for crystallization with a yield of at least 60% even at low Ni concentrations, while avoiding undesirable Li precipitation.

[0032] Later embodiments indicate a preference for obtaining a Ni-rich concentrate. This result is achieved thanks to the formation of lower hydrates, such as Ni sulfate monohydrate. This contrasts with the prior art crystallization schemes, which typically result in the formation of Ni sulfate hexahydrate.

[0033] Pure nickel sulfate hexahydrate has a nickel content of 22% by mass, while pure nickel sulfate monohydrate has a nickel content of 34% by mass. Depending on the reaction conditions, different nickel hydrate species may exist adjacent to each other. This makes it more difficult to determine the exact amount of nickel sulfate monohydrate. A retrospectively calculated value would be the average of all different hydrate species. However, the formation of nickel sulfate monohydrate remains beneficial even if it does not reach the theoretical maximum of 34% mentioned above.

[0034] In further embodiments according to any of the embodiments described above, the starting material further contains Co. Co can precipitate together with Ni, which is advantageous. In such embodiments, the Ni:Co molar ratio is preferably at least 1. This ratio ensures a reduced solubility of Co compared to the same solution containing little to no Ni. Since Co is the most valuable metal, it is important to ensure a good yield of Co in the solid residue. Experimental examples demonstrate a remarkable synergistic effect between Ni and Co.

[0035] In further embodiments according to any of the embodiments described above, the sum of Ni and Co forms the majority of the transition metal M.

[0036] In further embodiments according to any of the embodiments described above, the starting material further comprises Mn.

[0037] In further embodiments according to any of the embodiments described above, the starting materials are derived from rechargeable batteries, particularly lithium-ion batteries. “Derived from rechargeable batteries” means liquid or solid products associated with the manufacture or recycling of secondary lithium-ion batteries or their derivatives, such as original or used rechargeable batteries, manufacturing waste, scrap, leachates, and black lumps. Current rechargeable lithium-ion batteries typically contain Li, Ni, Mn, and Co as a homogeneous mixture. In future rechargeable batteries, Li may be replaced by Na. Batteries may contain many other elements, which are considered unavoidable impurities in recycling processes. Because Li is separated from Ni, Mn, and Co, the disclosed method is suitable for processing such batteries or their scrap. The characteristic of these three metals crystallizing together is advantageous, as many methods for preparing rechargeable battery precursors involve starting compounds containing just these three metals. The ratio of the three metals may be adjusted before and after precipitation to achieve the desired composition.

[0038] In further embodiments according to any of the embodiments described above, Ni forms the majority of the transition metal M.

[0039] The present invention is illustrated in Experimental Examples 1 to 7.

[0040] The solubility limits of Li and Ni were investigated in Experimental Examples 1 to 3. The results are shown in Figures 1 to 4. [Brief explanation of the drawing]

[0041] [Figure 1] This figure shows the solubility of Li and Ni as a function of acidity at 90°C. [Figure 2] This figure shows the solubility of Li and Ni as a function of acidity at 50°C. [Figure 3] This figure shows the solubility of Li and Co in the presence of Ni as a function of acidity at 80°C. [Figure 4]This figure shows the solubility of Li and Co as a function of acidity at 80°C in the absence of Ni (for comparison). [Figure 5] This figure shows the TGA of relevant metal hydrates, illustrating partial dehydration at 250°C and complete dehydration at 400°C. [Modes for carrying out the invention]

[0042] Experimental Example 1: Ni-Li system as a function of H2SO4 concentration at 90°C Crystallization tests will be performed on different solutions prepared according to Table 1.

[0043] [Table 1]

[0044] Each solution is stirred and heated to 90°C. The water is evaporated until the total volume is halved. During this evaporation, Ni and Li become saturated and crystallize as hydrated NiSO4 and Li2SO4. The slurry is then filtered through a Buchner funnel. The solutions are analyzed for Ni and Li, and the H2SO4 concentration is measured by titration. The results are shown in Figure 1.

[0045] These crystallization experiments show that while the concentration of NiSO4 decreases sharply from over 500 g / L at 90°C, the solubility of Li2SO4 increases. This supports the possibility of obtaining high yield and selectivity for Ni crystallization.

[0046] Experimental Example 2: Ni-Li behavior as a function of H2SO4 concentration at 50°C Crystallization tests will be performed on different solutions prepared according to Table 2.

[0047] [Table 2]

[0048] These solutions were treated in the same manner as in Experimental Example 1, except that a temperature of 50°C was chosen instead of 90°C. The results are shown in Figure 2.

[0049] These crystallization experiments indicate that a higher acid concentration is required to completely suppress Ni solubility at 50°C compared to 90°C. To ensure excellent Ni yield and selectivity relative to Li, an acid concentration of at least 750 g / L at 50°C is preferred.

[0050] Experimental Example 3: Effect of Ni on Co crystallization Crystallization tests will be performed on different solutions prepared according to Table 3 and Table 4.

[0051] [Table 3]

[0052] [Table 4]

[0053] These solutions were treated in the same manner as in Experimental Example 1, except that a temperature of 80°C was chosen instead of 90°C. The results are shown in Figures 3 and 4.

[0054] These results support the idea that the presence of Ni promotes the crystallization of Co. When NiSO4 is absent from the system, nearly twice the amount of Co remains in the crystallization effluent.

[0055] Selective separation methods are further illustrated in Experimental Examples 4 through 7.

[0056] Experimental Example 4: A method starting from a Ni-Li solution Add 1 L of a solution containing 110 g / L Ni, 11.4 g / L Li as sulfates, and 250 g / L H2SO4 to a 2 L beaker. Stir this solution and heat it to a temperature of 95°C. Evaporate the water until a total slurry volume of 500 mL is obtained. Continue evaporation at atmospheric pressure for 3 hours.

[0057] The slurry is filtered through a preheated Buchner funnel. 300 mL of filtrate containing 11.8 g / L Ni and 32 g / L Li is collected. The H2SO4 concentration of the final filtrate is determined to be 710 g / L H2SO4 by titration. The residue is washed with 430 mL of water. In industrial implementations, the wash water is recycled and not considered a loss. Therefore, in this and subsequent experimental examples, the contents of the wash water are added to the yield. 392 g of crystals containing 25% Ni and only 0.3% Li are obtained. The residue further contains sulfates and water of hydration. After washing, the residue is dried at 50°C for 24 hours to remove all impregnated water. After drying in a vacuum furnace, the mass loss after drying at 250°C for 1 hour under an N2 atmosphere is 26%. If nickel sulfate is converted to a monohydrate salt, this mass loss corresponds to the removal of H2O. A 26% mass loss corresponds to 3.4 moles of H2O per mole of Ni. Therefore, the average hydration coefficient x of the crystallized nickel sulfate salt is 4.4, which is significantly lower than the usual hydration coefficient of 6.

[0058] [Table 5]

[0059] This experiment demonstrates a high direct NiSO4 crystallization yield: 89% of the Ni crystallized. The Ni yield can be further increased by reusing the wash water and returning it to the crystallization method. The crystals are contaminated with only a small amount of Li. Li is recovered via the effluent (total of filtrate and wash water) with a yield of 95%.

[0060] Experimental Example 5: Method starting from NMC-Li solution Add 1 L of a solution containing 68 g / L of Ni, 23 g / L of Mn, 24 g / L of Co, 14 g / L of Li, 11 g / L of Na, and 10 g / L of Al as sulfates to a 2 L beaker.

[0061] The solution is stirred while 400 mL of concentrated H2SO4 with a concentration of 1740 g / L is added. The mixture is heated on a heating plate to 95°C. The water is evaporated until a total slurry volume of 950 mL is obtained. The slurry is filtered through a heated Buchner funnel. 810 mL of 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 is collected. The H2SO4 concentration determined by titration is 830 g / L. The residue is washed with 670 mL of water. 320 g of dry residue containing 18.8% Ni, 7% Mn, 7.1% Co, 0.2% Li, and 0.01% Na is obtained. The residue further contains sulfates, water of hydration, and trace impurities. After washing, the residue is dried at 50°C for 24 hours to remove all impregnated water. After drying, thermogravimetric analysis (TGA) is performed on the dried crystals under N2. The results of this TGA are shown in Figure 5. The mass loss due to drying at 250°C under an N2 atmosphere in the TGA (Step A in Figure 5) is 2.6%. This corresponds to a mass loss of 0.3 moles of H2O per mole of total Ni and Co, which corresponds to an average hydration coefficient x of 1.3. MnSO4 is assumed to exist as its monohydrate salt after crystallization and does not undergo further dehydration at 250°C. After dehydration at 250°C, the salt is further heated to 400°C to remove all hydration water (x=0). A mass loss of 10% is measured by heating from 250°C to 400°C (Step B in Figure 5). This mass loss confirms that Ni, Co, and Mn existed as monohydrate sulfates (x=1) at 250°C.

[0062] [Table 6]

[0063] This experimental example illustrates the high recovery yields of Ni, Mn, and Co in the crystals. A high NMC crystallization yield of 91% is achieved, with only 0.2% Li contamination in the crystals. Li is recovered via the effluent (total of filtrate and wash water), with a recovery yield of 96%. Most impurities such as Na and Al remain in the solution. The Ni, Mn, and Co yields can be further increased by recycling the wash water and returning it to the crystallization method.

[0064] Experimental Example 6: A method starting from NMC-Li solid Mix 300 g of NMC cathode powder with the composition 25% Ni, 15% Mn, 15% Co, and 5.2% Li with 200 mL of water and add to a 2 L beaker. Place the beaker on a heating plate and stir to maintain the cathode powder in a suspended state. While raising the temperature to 95°C, add 1 L of concentrated H2SO4 with a concentration of 1740 g / L. To ensure that Ni, Mn, and Co are divalent, add 775 mL of 30% H2O2 solution as a reducing agent to the mixture over 9.5 hours. Filter the mixture through a heated Buchner funnel. Collect 1.6 L of filtrate. The filtrate contains 3.8 g / L Ni, 6.5 g / L Mn, 2.2 g / L Co, and 8.4 g / L Li. Determine the H2SO4 concentration as 775 g / L by titration.

[0065] The residue is washed with 850 mL of water. 567 g of dry residue containing 12% Ni, 6.3% Mn, 7.4% Co, and 0.3% Li is obtained. The residue further contains sulfates and water of hydration.

[0066] [Table 7]

[0067] This experimental example demonstrates the in-situ reaction of solids containing Ni and Li treated with high acidity. Ni oxides in the solid raw materials are converted to sulfates, while most of the Li dissolves. Mn and Co behave similarly to Ni. An overall yield of 83% for Ni, Mn, and Co is achieved. The yields of Ni, Mn, and Co can be further increased by reusing the wash water and returning it to the crystallization process. 90% of the Li is recovered in the effluent (total of filtrate and wash water).

Claims

1. A method for selectively recovering a transition metal M containing Ni from an aqueous solution of starting materials, wherein the solution also contains Li. - A step of crystallizing Ni by adjusting the solution to reach an acidity A expressed in g / L of sulfuric acid at a temperature T expressed in degrees Celsius, according to the formula A ≥ 1100 - 6.7 * T, where T is between 45°C and the boiling point of the solution, thereby obtaining a mixture of solid and liquid reaction products; and - A step in which the reaction product is separated into solid and liquid, thereby obtaining a solid residue containing at least 50% by mass of Ni to be added to the method as hydrated nickel sulfate, and an effluent solution containing at least 50% by mass of Li to be added to the method. Includes, The aforementioned starting material has a mass ratio of Li to Ni of 0.33 or less. A method in which Ni forms at least 45.4% by mass of the transition metal M.

2. A method for selectively recovering a transition metal M containing Ni from a solid starting material, wherein the solid also contains Li. - A step of crystallizing Ni by contacting the solid with the aqueous medium, which has been adjusted to reach an acidity A expressed in g / L of sulfuric acid at a temperature T expressed in degrees Celsius according to formula A ≥ 1100 - 6.7 * T, where T is between 45°C and the boiling point of the aqueous medium, thereby obtaining a mixture of solid and liquid reaction products; and - A step in which the reaction product is separated into solid and liquid, thereby obtaining a solid residue containing at least 50% by mass of Ni to be added to the method as hydrated nickel sulfate, and an effluent solution containing at least 50% by mass of Li to be added to the method. Includes, The aforementioned starting material has a mass ratio of Li to Ni of 0.33 or less. A method in which Ni forms at least 45.4% by mass of the transition metal M.

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

4. The method according to claim 1 or 2, wherein the effluent solution contains at least 80% by mass of the Li introduced into the method.

5. The method according to claim 1 or 2, wherein the solid residue contains at least 60% by mass of the Ni added to the method.

6. The solid residue obtained in the solid / liquid separation process is given by formula NiSO ４ . xH ２ The method according to claim 1 or 2, comprising a hydrated sulfate according to formula O, (wherein x is the mean hydration coefficient and x < 5).

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

15.

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

9. The method according to claim 8, wherein the Ni:Co molar ratio is at least 1.

10. The method according to claim 9, wherein the sum of Ni and Co forms at least 50% by mass of the transition metal M.

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

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

13. The method according to claim 1 or 2, wherein Ni forms at least 50% by mass of the transition metal M.

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