Targeted leaching operation for efficient separation of the lithium-battery substances

Abstract

The invention relates to a method for separating graphite and metal from a black mass, the method comprising the following steps: a) providing the black mass; b) carrying out a flotation process using the black mass, in which process a metal-rich precipitate and a graphite-containing phase are obtained, and the metal-rich precipitate and the graphite-containing phase are separated from one another; c) leaching the metal-rich precipitate using an acidic leaching agent, with a metal-containing liquid and a graphite-rich solid being obtained; d) separating the metal-containing liquid and the graphite-rich solid; e) leaching the graphite-containing phase from step b) using an acidic extraction agent, the extraction agent containing the metal-containing liquid from step d), with a metal-rich liquid and a graphite-rich solid being obtained; f) separating the metal-rich liquid from step e) and the graphite-rich solid from step e).

Description

[0001] Targeted leaching for efficient separation of lithium battery materials

[0002] Description

[0003] The invention relates to a method for separating graphite and metal from a black mass.

[0004] Electromobility is becoming increasingly important. At the same time, the availability of the required raw materials is insufficient. Against this backdrop, the recycling of lithium-ion battery cells is becoming increasingly important. Saving chemicals and reducing aqueous and solid waste are also becoming increasingly important.

[0005] When recycling lithium-ion battery cells, so-called black mass can be obtained from lithium-ion batteries using common treatment methods such as crushing, thermal treatment, or similar. Black mass can be obtained, for example, by crushing the cell and removing cell components such as electrolyte, binder, conductive foils, and casing. The black mass contains large quantities of the active material of the anode and cathode, particularly graphite and metal, where the metal comprises one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum.

[0006] Reusing the components of the black mass requires their separation. For graphite, the separation process should also be gentle to enable reuse of the material, especially in high-tech industries.

[0007] Against this background, one object of the present invention is to provide an efficient, material- and resource-saving separation of the components of the black mass.

[0008] The efforts to solve this problem result in a process for separating graphite and metal from a black mass, comprising g) providing the black mass, wherein the black mass preferably originates from a lithium-ion battery cell,

[0009] 3

[0010] SUBSTITUTE SHEET (RULE 26) h) subjecting the black mass to a flotation process to obtain a metal-rich precipitate and a graphite-containing phase, and separating the metal-rich precipitate and the graphite-containing phase from each other, i) leaching the metal-rich precipitate with an acidic leaching agent to obtain a metal-containing liquid and a graphite-rich solid, j) separating the metal-containing liquid and the graphite-rich solid, k) leaching the graphite-containing phase from b) with an acidic extractant, the extractant containing the metal-containing liquid from d), to obtain a metal-rich liquid and a graphite-rich solid, l) separating the metal-rich liquid from e) and the graphite-rich solid from e).

[0011] The process can be described as a double leaching process, whereby the metal-rich precipitate from b) (first leaching) and the graphite-containing phase from b) (second leaching) are leached. The leaching agent used to leach the metal-rich precipitate in c) is reused for leaching in e). In other words, the extractant consists largely of the metal-containing liquid from d), although the addition of, for example, oxidizing agents, auxiliary materials, etc. for the second leaching should not be excluded. By leaching in e) (the second leaching), the extractant and thus also the metal-containing liquid from d) are further enriched with metal. At the same time, the graphite in the graphite-containing phase is purified.During the second leaching, the pH increases slightly, so that after the second leaching is complete, copper can be extracted from the metal-rich liquid from step f) without further pH adjustment. Extracting other metals is possible after a slight pH adjustment. This saves resources and avoids waste.

[0012] By means of the process according to the invention, a graphite-rich solid is obtained from the black mass (in d) and f)). Due to its purity, the graphite-rich solid can also be referred to as graphite. The graphite-rich solid (graphite) is purified by the process according to the invention, whereby a quality is achieved which is suitable for use as a recyclate in batteries or generally in the high-tech industry. By means of the process according to the invention, a pure graphite-rich solid is obtained. The graphite-rich solid from d) and f) each has a graphite content of between 95 wt.% and 99.5 wt.%, in particular between 98.0 wt.% and 99.5 wt.%, based on the total weight of the graphite-rich solid from d) and f). In other words, the graphite-rich solid from d) has a graphite content of between 95 wt.% and 99.5 wt.%, based on the total weight of the graphite-rich solid from d).- %, in particular between 98.0 wt.% and 99.5 wt.%. In other words, the graphite-rich solid from f) has a graphite content of between 95 wt.% and 99.5 wt.%, in particular between 98.0 wt.% and 99.5 wt.%, based on the total weight of the graphite-rich solid from f).

[0013] The process according to the invention is also gentle, so the graphite retains its morphology. This makes the graphite suitable as a recyclate in battery cells or generally in the high-tech industry. The process according to the invention has the advantage that the morphology of the graphite remains essentially unchanged. In particular, the graphite retains its spherical shape, surface structure, and electrochemical properties for use as anode material and for other high-tech applications, e.g., in bipolar plates in electrolysis devices for hydrogen production.

[0014] Furthermore, the process according to the invention dissolves the metallic components from the black mass. The acid solution is enriched with metal, and the metal-rich liquid can be used for efficient metal recovery.

[0015] The term "metal" encompasses one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum. Along with the one or more metals, the process according to the invention also separates phosphorus from the black mass, particularly when the black mass contains LiFePO4. Phosphorus is also enriched in the metal-rich liquid from e), particularly when the black mass contains LiFePO4.

[0016] The acidic leaching agent is preferably aqueous. This means that the acidic leaching agent contains a large proportion (> 50 wt%) of water.

[0017] The acidic extractant is preferably aqueous. This means that the acidic extractant contains a large proportion (> 50 wt%) of water.

[0018] The method according to the invention comprises providing a black mass. For this purpose, black mass can be obtained, for example, from lithium-ion battery cells or purchased on the open market. The black mass preferably originates from at least one lithium-ion battery cell. The black mass contains graphite and a cathode active material, preferably selected from NMC active material (lithium nickel manganese cobalt oxide active material) and LFP active material (LiFePC^ active material), as well as mixtures thereof. In other words, the black mass contains graphite and metal, wherein the metal comprises one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper, and aluminum. The black mass can also contain phosphorus, particularly if the black mass contains LFP active material. In a preferred embodiment, the average particle size of the black mass is in the range from 125 pm to 1.5 mm.

[0019] The flotation process is particularly effective in extracting and separating the metal-rich precipitate and the graphite-containing phase from the black mass. Flotation processes using black mass are known to those skilled in the art and are described, for example, by Anna Vanderbruggen et al. in "Improving Separation Efficiency in End-of-Life Lithium-Ion Batteries Flotation Using Attrition Pre-Treatment" (January 2022, Minerals 12 (1)), which is hereby incorporated in its entirety.

[0020] A collector is preferably used in the flotation process. Kerosene is preferably used as the collector. The collector leads to improved separation of the graphite-containing phase. This increases the yield of recovered graphite, and the metal-rich precipitate contains less graphite and is therefore purer. However, the collector also entrains metal from the active material, which is why gentle and effective subsequent purification of the graphite-containing phase and metal recovery is important. This purification and metal recovery is achieved through the secondary leaching process.

[0021] A frother is preferably used in the flotation process. Methylisobutylcarbinol is preferably used as the frother. The frother improves flotation and contributes to efficient separation.

[0022] The lithium-ion battery cell is preferably selected from an NMC lithium-ion battery cell and / or an LFP lithium-ion battery cell.

[0023] Preferably, the separation of the metal-containing liquid and the graphite-rich solid in d) is carried out by filtration.

[0024] Preferably, the metal-rich liquid from e) and the graphite-rich solid from e) in f) are separated by filtration. In a preferred embodiment, the metal-rich liquid from f) has a pH in the range of 0.0 to 1.5. In other words, the second leaching partially neutralizes the metal-containing liquid from d) and the extremely acidic leaching agent from the first leaching contained therein. This partial neutralization saves chemicals in the subsequent process by eliminating the need for pH-adjusting reagents, and the amount of aqueous waste is reduced.

[0025] The increased pH value due to the second leaching enables the recovery of copper from the metal-rich liquid from f) without further pH adjustment. In a preferred embodiment, the process therefore comprises the recovery of copper from the metal-rich liquid from f) without further pH adjustment. The recovery of other metals (in particular selected from lithium, nickel, manganese, cobalt, iron, and aluminum) is possible after slight further pH adjustment. Since no or only slight further pH adjustment is necessary, chemicals are saved by saving on pH-adjusting reagents and the amount of aqueous waste is reduced.

[0026] In a preferred embodiment, the leaching agent and the extraction agent contain an oxidizing agent. The oxidizing agent supports the dissolution of the metallic components of the black mass and improves the yield of the process. The oxidizing agent is preferably hydrogen peroxide. The concentration of hydrogen peroxide in the leaching agent in c) and in the extraction agent in e) is preferably 0.1 vol.% to 10 vol.%, based on the total volume of the respective agent.

[0027] The leaching agent and the extraction agent are acidic. Preferably, the leaching agent and the extraction agent contain at least one inorganic acid. Preferably, the at least one acid is selected from hydrogen chloride and sulfuric acid.

[0028] Preferably, the pH value in the leaching agent in c) is <0.0. A particularly suitable range for the pH value in the leaching agent in c) is between -1.5 and 0.0.

[0029] In one embodiment, the acid concentration in the leaching agent in c) is 0.5 mol / L to 4 mol / L. Preferably, the metal-containing liquid from d) and the extraction agent have a pH <1.0. A particularly suitable range for the pH of the metal-containing liquid from d) and the extraction agent is -0.5 to 0.5.

[0030] Preferably, the temperature in c) is between 30 °C and 80 °C.

[0031] Preferably, the reaction time in c) is 60 minutes to 180 minutes.

[0032] Preferably, the temperature in e) is between 30 °C and 60 °C.

[0033] Preferably, reaction time in e) is 30 minutes to 120 minutes.

[0034] Preferably, the ratio (mass to volume) of metal-rich precipitate to acidic leaching agent when leaching the metal-rich precipitate in c) is 1:5 to 1:15. In other words, 5 liters to 15 liters of acidic leaching agent are used per kilogram of metal-rich precipitate.

[0035] In one embodiment, the method comprises, before a), providing a lithium-ion battery cell and obtaining black mass from the lithium-ion battery cell. Obtaining the black mass comprises comminuting the lithium-ion battery cell. Comminuting the lithium-ion battery cell preferably results in an average particle size in the range of 125 pm to 1.5 mm.

[0036] To remove organic binder and electrolyte components, the lithium-ion battery cell can be thermally treated at 480 °C - 650 °C, preferably 480 °C - 600 °C.

[0037] In one embodiment, the method comprises a) thermally treating the lithium-ion battery cell and subsequently comminuting the lithium-ion battery cell.

[0038] In one embodiment, the method comprises a) comminuting the lithium-ion battery cell under protective gas and subsequently thermally treating the lithium-ion battery cell.

[0039] In one embodiment, the method comprises, prior to a), comminuting the lithium-ion battery cell using water, followed by thermal treatment of the lithium-ion battery cell. In other words, water shredding technology is used. In one embodiment, the method comprises removing the conductive foils after the thermal treatment. Removal is carried out using standard mechanical processing steps, such as screening.

[0040] Embodiments within this document may be combined with one another as desired, unless the subject matter and the description of the embodiments clearly indicate otherwise.

[0041] The verbs "to contain" and "to encompass" and their conjugations also include the verb "to consist of" and its conjugations.

[0042] Preferred embodiments are also set out in the patent claims.

[0043] Fig. 1 gives an overview of a method according to the invention.

[0044] The invention is further illustrated below using an embodiment.

[0045] In this example, black mass is first obtained. The starting point in this example is NMC lithium-ion batteries. The lithium-ion batteries are used lithium-ion batteries that have reached the end of their life (also known as end-of-life, EoL) and production waste from lithium-ion battery production. The lithium-ion batteries are deeply discharged and disassembled down to the module or cell level.

[0046] The lithium-ion battery cells and lithium-ion battery modules are crushed under nitrogen (N2) to an average particle size of approximately 150 pm. This is followed by a thermal treatment at 480–600 °C to remove organic binder and electrolyte components. An alternative would be direct thermal pretreatment (also known as pyrolysis) of the battery cells at a temperature between 480–600 °C followed by crushing. Another alternative would be to crush the battery cells using water, followed by thermal treatment of the crushed fraction at 480–600 °C.

[0047] After thermal treatment, the conductive foils and any remaining casing residue are removed by sieving. What remains is the black mass. The black mass is then treated by flotation, in which the black mass is added to water and mixed with additives such as kerosene as a collector and methylisobutylcarbinol as a foaming agent. A foam product containing graphite is then created using compressed air. With optimized processing, a graphite purity of 80% to 90% can be achieved, with a minimum quality of 75% being achieved. The metallic components fall to the bottom during flotation and are called tailings.

[0048] The graphite-containing foam product (graphite-containing phase) and the tailings (metal-rich precipitate) are then leached separately. Leaching agents containing hydrogen chloride (HCl) and / or sulfuric acid (H2SO4) can be used. Additionally, H2O2 is used as an oxidizing agent.

[0049] First, the tailings fraction (metal-rich precipitate) is leached. A leaching agent containing hydrochloric acid and a pH value of -1.5 to 0.0 is selected. 35% H2O2 is also added to the suspension. The hydrogen peroxide makes up 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] The leaching time in this example is approximately 150 minutes. The temperature in this example is between 30°C and 80°C. The suspension is continuously stirred. Acid is consumed during the process, so the pH remains acidic after completion, between -0.5 and 0.5.

[0051] After the leaching period, the suspension is filtered using standard filtration technology and separated into solids and a liquid enriched with metal ions (metal-containing liquid). The solid is an enriched graphite product (graphite-rich solid) suitable for further processing. The liquid, which contains metal ions and has an acidic pH, is used as a leaching agent (extraction agent) for the graphite-containing foam product.

[0052] The graphite-containing foam product is mixed with the leaching agent from the first leaching (enriched with metal ions and with an acidic pH) and leached. The reduced acid concentration is optimal for gentle treatment of the enriched graphite fraction, allowing for the preservation of its morphology. The leaching time is approximately 100 minutes at a temperature of 30°C to 60°C. Additionally, 35% H2O2 is added to the suspension. The hydrogen peroxide makes up approximately 5% by volume of the total solution. The suspension is kept under constant stirring.

[0053] After the leaching time, the suspension is filtered using standard filter technology and separated into solid and liquid, which is even more highly enriched with metal ions. The solid is a graphite product with a purity of > 98.0% (graphite-rich solid). The graphite has retained its morphology and is therefore suitable as a recyclate for use in new battery technology. Alternatively, another high-tech industry can be selected. The highly metal-enriched residual leaching solution (metal-rich liquid) has a pH value between 0.0 and 1.5 after treatment. This enables the recovery of copper, for example, from residues of the electrical conductor foils, without further pH adjustment. The recovery of the other metals (in this example, in particular Co, Ni, and Mn) is possible after slight adjustment of the pH value.

Claims

Targeted leaching for efficient separation of lithium battery materials Claims 1. A process for separating graphite and metal from a black mass, comprising a) providing the black mass; b) carrying out a flotation process on the black mass, whereby 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) leaching the metal-rich precipitate with an acidic leaching agent, whereby a metal-containing liquid and a graphite-rich solid are obtained; d) separating the metal-containing liquid and the graphite-rich solid; e) leaching the graphite-containing phase from b) with an acidic extractant, wherein the extractant contains the metal-containing liquid from d), whereby a metal-rich liquid and a graphite-rich solid are obtained; f) separating the metal-rich liquid from e) and the graphite-rich solid from e).

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

5.

3. A process according to any one of the preceding claims, comprising recovering copper from the metal-rich liquid of f) without further adjustment of the pH.

4. A process according to any one of the preceding claims, wherein the graphite-rich solid from d) and f) has a graphite content of between 95 wt.% and 99.5 wt.%, based on the total weight of the graphite-rich solid from d) and f).

5. A process according to any one of the preceding claims, wherein the morphology of the graphite remains substantially unchanged.

6. A process according to any one of the preceding claims, wherein the leaching agent and the extracting agent contain an oxidizing agent, preferably hydrogen peroxide.

7. A process according to any one of the preceding claims, wherein the leaching agent and the extracting agent contain at least one inorganic acid, preferably at least one acid selected from hydrogen chloride and sulfuric acid.

8. A process according to any one of the preceding claims, wherein the pH in the leaching agent in c) is < 0.

0.

9. Process according to any one of the preceding claims, wherein the metal-containing liquid from d) and the extractant have a pH < 1.0, preferably from -0.5 to 0.

5.

10. A process according to any one of the preceding claims, wherein a collector is used in the flotation process.

11. A process according to any one of the preceding claims, wherein the concentration of hydrogen peroxide in the leaching agent in c) and in the extraction agent is from 0.1 vol% to 10 vol%, based on the total volume of the respective agent.

12. A process according to any one of the preceding claims, wherein the temperature in c) is between 30°C and 80°C.

13. A process according to any one of the preceding claims, wherein the temperature in e) is between 30°C and 60°C.

14. A method according to any one of the preceding claims, wherein the black mass contains graphite and a cathode active material selected from NMC active material, LFP active material and mixtures thereof.

15. A process according to any one of the preceding claims, wherein the metal comprises one or more metals selected from lithium, nickel, manganese, cobalt, iron, copper and aluminum.

Images