Targeted leaching operation for efficient separation of lithium battery materials

Abstract

The present invention relates to a method for separating graphite and metal from black mass, comprising the steps of: a) preparing black mass; b) performing a flotation treatment using the black mass, wherein the treatment yields a metal-rich precipitate and a graphite-containing phase, and the metal-rich precipitate and the graphite-containing phase are separated from each other; c) leaching the metal-rich precipitate using an acidic leaching agent to obtain a metal-containing liquid and a graphite-rich solid; d) separating the metal-containing liquid and the graphite-rich solid; e) leaching the graphite-containing phase from step b) using an acidic extractant containing the metal-containing liquid from step d) to obtain a metal-rich liquid and a graphite-rich solid; and f) separating the metal-rich liquid from step e) and the graphite-rich solid from step e).

Description

Technical Field

[0001] The present invention relates to a method for separating graphite and metals from black mass.

Background Art

[0002] Electromobility is becoming increasingly important. At the same time, the availability of the required raw materials is not sufficient. Against this background, the importance of recycling lithium-ion battery cells is increasing. Saving chemicals and reducing aqueous and solid waste are also becoming important.

[0003] During the recycling of lithium-ion battery cells, so-called black mass can be obtained by common treatment methods such as crushing and heat treatment. Black mass is referred to as "black mass" in English. Black mass can be obtained, for example, by crushing the cell and removing cell components such as electrolyte, binder, foil conductor, housing, etc. Black mass contains a large amount of active materials of the anode and cathode, particularly graphite and metals, and the above metals include one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper and aluminum.

[0004] In order to reuse the components of black mass, its separation is necessary. Furthermore, for graphite, in order to enable the reuse of the material in the high-tech industry, it is important that the separation is gentle.

Summary of the Invention

Problems to be Solved by the Invention

[0005] From such a background, the object of the present invention is to show an efficient, material-compatible and resource-saving separation of the components of black mass.

Means for Solving the Problems

[0006] As a result of efforts to achieve this objective, a method for separating graphite and metal from black mass was developed, comprising the following steps: a) A step of preparing black mass (the black mass is preferably derived from lithium-ion battery cells), b) A step of carrying out a flotation treatment using the black mass, wherein in the treatment a metal-rich precipitate and a graphite-containing phase are obtained, and the metal-rich precipitate and the graphite-containing phase are separated from each other. c) A step of leaching the metal-rich precipitate using an acidic leaching agent to obtain a metal-containing liquid and a graphite-rich solid. d) A step of separating the metal-containing liquid from the graphite-rich solid, e) A step of leaching the graphite-containing phase from step b) using an acidic extractant containing the metal-containing liquid from step d) to obtain a metal-rich liquid and a graphite-rich solid. f) A step of separating the metal-rich liquid from step e) and the graphite-rich solid from step e). A method including this was obtained.

[0007] This method is called the double leaching method and involves leaching of the metal-rich precipitate from step b) (first leaching) and leaching of the graphite-containing phase from step b) (second leaching). The leaching agent used to leach the metal-rich precipitate in step c) is used again for leaching in step e). In other words, the extractant is largely composed of the metal-containing liquid from step d), and the addition of, for example, oxidizing agents and auxiliary agents for the second leaching is not excluded. The extractant and, as a result, the metal-containing liquid from step d) are further enriched with metal by the leaching in step e) (second leaching). At the same time, the graphite in the graphite-containing phase is purified. During the second leaching, the pH value rises slightly, and as a result, after the completion of the second leaching, it is possible to obtain copper from the metal-rich liquid from step f) without further adjustment of the pH value. Slight adjustment of the pH value can yield more metal, saving resources and avoiding waste.

[0008] The graphite-rich solid is obtained from black mass by the method according to the present invention (in steps d) and f). The graphite-rich solid can also be called graphite due to its purity. The graphite-rich solid (graphite) is purified by the method according to the present invention to achieve a quality suitable for use in batteries or as a recycled material in general high-tech industries. That is, a pure graphite-rich solid is obtained by the method according to the present invention. The graphite-rich solid from steps d) and f) has a graphite content of 95% to 99.5% by weight, particularly 98.0% to 99.5% by weight, based on the total weight of the graphite-rich solid from steps d) and f), respectively. In other words, the graphite-rich solid from step d) has a graphite content of 95% to 99.5% by weight, particularly 98.0% to 99.5% by weight, based on the total weight of the graphite-rich solid from step d). In other words, the graphite-rich solid from process f) has a graphite content of 95% to 99.5% by weight, and especially 98.0% to 99.5% by weight, based on the total weight of the graphite-rich solid from process f).

[0009] The method according to the present invention is also gentle, so that graphite retains its morphology. As a result, graphite is suitable as a recycled material in battery cells or in high-tech industries in general. An advantage of the method according to the present invention is that the morphology of graphite remains substantially unchanged. In particular, graphite maintains its spherical shape, surface structure, and electrochemical properties for use as a negative electrode material and in other high-tech applications, such as in bipolar plates of electrolytic devices for hydrogen generation.

[0010] The metal portion of the black mass is further introduced into a solution by the method according to the present invention. The acid solution is enriched with metal, and this metal-rich liquid can be used for efficient metal recovery.

[0011] The term "metal" includes one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum. In particular, if the black mass contains LiFePO4, phosphorus, along with one or more metals, is also separated from the black mass using the method according to the present invention. In particular, if the black mass contains LiFePO4, phosphorus is also enriched in the metal-rich liquid from step e).

[0012] The acidic leaching agent is preferably aqueous. This means that the acidic leaching agent contains a significant proportion (>50% by weight) of water.

[0013] The acidic extractant is preferably aqueous. This means that the acidic extractant contains a significant proportion (>50% by weight) of water.

[0014] The method according to the present invention includes the step of preparing black mass. The black mass for this purpose can be obtained, for example, from a lithium-ion battery cell or can be obtained from the free market. Preferably, the black mass is derived from at least one lithium-ion battery cell. The black mass contains graphite and a positive electrode active material, preferably selected from NMC active material (lithium nickel manganese cobalt oxide active material) and LFP active material (LiFePO4 active material) and mixtures thereof. In other words, the black mass contains graphite and a metal, the metal being one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum. In particular, if the black mass contains LFP active material, the black mass may also contain phosphorus. In a preferred embodiment, the average particle size of the black mass is in the range of 125 μm to 1.5 mm.

[0015] The flotation process successfully yields metal-rich precipitates and graphite-containing phases from black mass, and the metal-rich precipitates and graphite-containing phases are separated without issue, both with excellent results. Flotation using black mass is well known to those skilled in the art, for example, as described in Anna Vanderbruggen et al., “Improving Separation Efficiency in End-of-Life Lithium-Ion Batteries Flotation Using Attrition Pre-Treatment” (January 2022, Minerals 12(1)), the entirety of which is incorporated herein by reference.

[0016] In the flotation process, a collector is preferably used. Kerosene is preferably used as the collector. The collector improves the separation of the graphite-containing phase. As a result, the yield of graphite increases, and the metal-rich precipitate has a lower graphite content, i.e., is purer. Certainly, the collector also takes up metals from the active material. Therefore, a gentle and effective purification of the graphite-containing phase and subsequent acquisition of the metals is important. The metals are obtained by purification through a second leaching.

[0017] In the flotation process, a foaming agent is preferably used. Methyl isobutylcarbinol is preferably used as the foaming agent. The foaming agent improves flotation and contributes to efficient separation.

[0018] The lithium-ion battery cell is preferably selected from NMC lithium-ion battery cells and / or LFP lithium-ion battery cells.

[0019] The metal-containing liquid and the graphite-rich solid are preferably separated by filtration in step d).

[0020] The metal-rich liquid from step e) and the graphite-rich solid from step e) are preferably separated by filtration in step f).

[0021] In a preferred embodiment, the metal-rich liquid from step f) has a pH value in the range of 0.0 to 1.5. In other words, the second leaching partially neutralizes the metal-containing liquid from step d) and the extremely acidic leaching agent derived from the first leaching contained in the liquid. The partial neutralization saves reagents for adjusting the pH value and reduces the amount of aqueous waste, thereby saving chemicals in further treatment.

[0022] When the pH value is increased by the second leaching, it becomes possible to obtain copper from the metal-rich liquid from step f) without further adjusting the pH value. Therefore, in a preferred embodiment, the method includes obtaining copper from the metal-rich liquid from step f) without further adjusting the pH value. By slightly adjusting the pH value, it is possible to obtain further metals (particularly selected from lithium, nickel, manganese, cobalt, iron, and aluminum). Since no adjustment or only slight adjustment of the pH value is required, reagents for adjusting the pH value are saved and the amount of aqueous waste is reduced.

[0023] In a preferred embodiment, the leaching agent and the extractant contain an oxidizing agent. The oxidizing agent helps dissolve the metal part of the black mass and improves the yield of the method. The oxidizing agent is preferably hydrogen peroxide. The concentration of hydrogen peroxide in the leaching agent in step c) and in the extractant in step e) is 0.1% to 10% by volume based on the total volume of each agent.

[0024] The leaching agent and the extractant are acidic. The leaching agent and the extractant preferably contain at least one inorganic acid. The at least one acid is preferably selected from hydrogen chloride and sulfuric acid.

[0025] The pH value of the leaching agent in step c) is preferably ≤ 0.0. A particularly preferred range for the pH value of the leaching agent in step c) is -1.5 to 0.0.

[0026] In one embodiment, the acid concentration in the leaching agent in step c) is 0.5 mol / L to 4 mol / L.

[0027] The metal-containing liquid from step d) and the extractant preferably have a pH value < 1.0. A particularly preferred range of the pH value of the metal-containing liquid from step d) and the extractant is -0.5 to 0.5.

[0028] The temperature in step c) is preferably 30°C to 80°C.

[0029] The reaction time in step c) is preferably 60 minutes to 120 minutes.

[0030] The temperature in step e) is preferably 30°C to 60°C.

[0031] The reaction time in step e) is preferably 30 minutes to 120 minutes.

[0032] [[ID=二十一]] [[ID=二十二]] During leaching the metal-rich precipitate in step c), the ratio of the metal-rich precipitate to the acidic leaching agent (mass to volume) is preferably 1:5 to 1:15. In other words, 5 L to 15 L of the acidic leaching agent is used per 1 kg of the metal-rich precipitate.

[0033] In one embodiment, the method includes, before step a), preparing a lithium-ion battery cell and obtaining black mass from the lithium-ion battery cell. Obtaining black mass includes crushing the lithium-ion battery cell. The crushing of the lithium-ion battery cell preferably results in an average particle size in the range of 125 μm to 1.5 mm.

[0034] To remove the organic binder and electrolyte components, the lithium-ion battery cell can be heat-treated at 480°C to 650°C, preferably 480°C to 600°C.

[0035] In one embodiment, the method includes, before step a), heat-treating the lithium-ion battery cell and then crushing the lithium-ion battery cell.

[0036] In one embodiment, the method includes crushing the lithium-ion battery cell under an inert gas before step a), and then heat-treating the lithium-ion battery cell.

[0037] In one embodiment, the method includes crushing lithium-ion battery cells with water before step a), and then heat-treating the lithium-ion battery cells. In other words, it utilizes water shredder technology.

[0038] In one embodiment, the method includes removing the foil conductor after heat treatment. Removal is carried out by a general mechanical process, such as sieving.

[0039] The embodiments described herein may be combined with each other as necessary, unless otherwise clearly indicated by the subject matter and the description of the embodiments.

[0040] The verbs "contain" and "comprise" and their conjugations also include the verb "consist of" and its conjugations.

[0041] Preferred embodiments are also presented in the claims. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 is a schematic diagram of the method according to the present invention. [Modes for carrying out the invention]

[0043] The present invention is further described below with reference to exemplary embodiments.

[0044] In this exemplary embodiment, black mass is obtained first. The starting point for this exemplary embodiment is an NMC lithium-ion battery. The lithium-ion battery is a waste lithium-ion battery (also known as end-of-life, EoL) and manufacturing waste from lithium-ion battery manufacturing. The lithium-ion battery is depleted and is broken down to the module or cell level.

[0045] Lithium-ion battery cells and modules are crushed under nitrogen (N2) conditions to an average particle size of approximately 150 μm. They are then heat-treated at 480-600°C to remove organic binders and electrolyte components. An alternative method involves directly heat-treating (also known as pyrolysis) the battery cells at 480-600°C before crushing. A further alternative involves crushing the battery cells using water, followed by heat-treating the crushed portion at 480-600°C.

[0046] After heat treatment, any remaining residue from the foil conductor and housing is removed by sieving.

[0047] What remains is black trout. The black trout is then processed by flotation, in which the black trout is placed in water and mixed with additives such as kerosene as a collection agent and methyl isobutylcarbinol as a foaming agent. A graphite-containing floss product is then produced using compressed air. In optimal operation, a graphite purity of 80-90% can already be achieved at this stage, and at least 75% quality is achieved. The metallic parts sink to the bottom during flotation, a process called tailing.

[0048] The graphite-containing floss product (graphite-containing phase) and tailing (metal-rich precipitate) are then leached separately from each other. Leaching agents containing hydrogen chloride (HCl) and / or sulfuric acid (H2SO4) can be used. H2O2 is additionally used as an oxidizing agent.

[0049] The Tailing fraction (metal-rich precipitate) is leached first. A leaching agent containing hydrochloric acid with a pH of -1.5 to 0.0 is selected here. Furthermore, 35% H2O2 is added to the suspension. Hydrogen peroxide accounts for 5% by volume of the total solution. The ratio (mass to volume) of metal-rich precipitate to acidic leaching agent is approximately 1:6.

[0050] In this exemplary embodiment, the leaching time is approximately 150 minutes. The temperature in this exemplary embodiment is 30°C to 80°C. The suspension is constantly stirred. Since the acid is consumed by this method, the pH value remains acidic after completion, at -0.5 to 0.5.

[0051] After the leaching time has elapsed, the suspension is filtered using common filtration techniques to separate the solid from the metal ion-enriched liquid (metal-containing liquid). The solid is a graphite-enriched product (a graphite-rich solid) suitable for further processing. The aforementioned liquid (containing metal ions and having an acidic pH value) is used as a leaching agent (extractant) for the graphite-containing floss product.

[0052] The graphite-containing floss product is mixed with the leaching agent from the first leaching (enriched with metal ions and having an acidic pH value) and leached. A reduced acid concentration is optimal for gently treating the enriched graphite fraction, which allows for the preservation of morphology. The leaching time is approximately 100 minutes at a temperature of 30°C to 60°C. Furthermore, 35% H2O2 is added to the suspension. Hydrogen peroxide accounts for approximately 5% by volume of the total solution. The suspension is stirred constantly.

[0053] After the leaching time has elapsed, the suspension is filtered by common filtration techniques to separate the solid from the liquid, which is further enriched with metal ions. The solid is a graphite product (graphite-rich solid) with a purity of ≥98.0%. The graphite retains its morphology and is therefore suitable as a recycled material for use in new battery technologies. Alternatively, other high-tech industries can be selected. The highly metal-enriched residual leaching solution (metal-rich liquid) has a pH of 0.0 to 1.5 after processing. This makes it possible to recover copper from, for example, the residue of foil conductors without further adjustment of the pH. After slight adjustment of the pH, it is possible to obtain further metals (in this exemplary embodiment, in particular Co, Ni, and Mn).

Claims

1. A method for separating graphite and metals from black mass, comprising the following steps: a) The process of preparing black mass, b) A step of performing a flotation treatment using the black mass, wherein in the treatment a metal-rich precipitate and a graphite-containing phase are obtained, and the metal-rich precipitate and the graphite-containing phase are separated from each other. c) A step of leaching the metal-rich precipitate using an acidic leaching agent to obtain a metal-containing liquid and a graphite-rich solid. d) A step of separating the metal-containing liquid from the graphite-rich solid, e) A step of leaching the graphite-containing phase from step b) using an acidic extractant containing the metal-containing liquid from step d) to obtain a metal-rich liquid and a graphite-rich solid. f) A step of separating the metal-rich liquid from step e) and the graphite-rich solid from step e). A method that includes this.

2. The method according to claim 1, wherein the metal-rich liquid from step f) has a pH value in the range of 0.0 to 1.

5.

3. The method according to claim 1 or 2, further comprising the step of obtaining copper from the metal-rich liquid from step f) without further adjustment of the pH value.

4. The method according to any one of claims 1 to 3, wherein the graphite-rich solid from step d) and step f) has a graphite content of 95% to 99.5% by weight, based on the total weight of the graphite-rich solid from step d) and step f), in each case.

5. The method according to any one of claims 1 to 4, wherein the morphology of the graphite remains substantially unchanged.

6. The method according to any one of claims 1 to 5, wherein the leaching agent and the extractant contain an oxidizing agent, preferably hydrogen peroxide.

7. The method according to any one of claims 1 to 6, wherein the leaching agent and the extractant contain at least one inorganic acid, preferably at least one acid selected from hydrogen chloride and sulfuric acid.

8. The method according to any one of claims 1 to 7, wherein the pH value of the leaching agent in step c) is ≤ 0.

0.

9. The method according to any one of claims 1 to 8, wherein the metal-containing liquid and the extractant from step d) have a pH value of < 1.0, preferably -0.5 to 0.

5.

10. The method according to any one of claims 1 to 9, wherein a collection agent is used in the flotation process.

11. The method according to any one of claims 1 to 10, wherein the concentration of hydrogen peroxide in the leaching agent and the extracting agent in step c) is 0.1% by volume to 10% by volume based on the total volume of each agent.

12. The method according to any one of claims 1 to 11, wherein the temperature in step c) is 30°C to 80°C.

13. The method according to any one of claims 1 to 12, wherein the temperature in step e) is 30°C to 60°C.

14. The method according to any one of claims 1 to 13, wherein the black mass contains graphite and a positive electrode active material selected from an NMC active material, an LFP active material, and a mixture thereof.

15. The method according to any one of claims 1 to 14, wherein the metal comprises one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum.

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