Methods for recovering lithium as a secondary raw material from electrochemical energy storage systems

Abstract

Described is a process for recovering lithium as a secondary raw material from energy storage material, provided by discarded and pretreated electrochemical energy storage devices and / or by production waste from the manufacture of electrochemical energy storage devices, comprising the following process steps: a) Provision of lithium-containing energy storage material obtained from decommissioned energy storage systems through pretreatment and / or energy storage material from waste from the production of electrochemical energy storage systems, which energy storage material is the starting material for the subsequent process steps, b) chemical extraction of Li compounds from the energy storage material to obtain a Li-containing solution c) Concentrating the Li-containing solution, d) cases of at least one Li compound from the concentrated solution and e) Separation of at least one precipitated Li compound from the remaining solution.

Description

[0001] The invention relates to a method for recovering lithium as a secondary raw material from energy storage material provided by discarded and pretreated electrochemical energy storage devices and / or by production waste from the manufacture of electrochemical energy storage devices.

[0002] Electrochemical energy storage devices are rechargeable batteries, particularly lithium-ion batteries, nickel-metal hydride batteries, and electrolytic capacitors. Such energy storage devices, especially lithium-ion batteries, are used as so-called stand-alone batteries and, more extensively, in the form of battery modules to power electrical devices such as laptops, mobile phones, power tools, and increasingly in connection with electromobility, particularly as energy storage in motor vehicles. The electrochemical energy storage devices used in motor vehicles must have a high energy density and be able to store the required power. These energy storage devices are often high-voltage batteries.

[0003] The increasing global use of electrochemical energy storage devices, particularly in connection with the rise of electromobility, is leading to a growing volume of end-of-life batteries and battery modules. The higher production rates required to meet increased demand mean that the quantity of production rejects is also rising. Furthermore, the natural resources from which the elements needed to manufacture these energy storage devices are extracted are limited. Against this backdrop, various approaches have been proposed to recover the raw materials contained in these unusable electrochemical energy storage devices—both end-of-life batteries and battery modules, as well as production rejects—as secondary raw materials.For such a process to become established on the market, it must be manageable, cost-effective, and environmentally friendly. When recovering secondary raw materials from electrochemical energy storage systems, a particular focus is also placed on lithium recovery.

[0004] To recover valuable materials as secondary raw materials from such electrochemical energy storage devices, these devices are first deconstructed to gain access to the substances located inside the energy storage device, particularly the electrode material. Such deconstruction of electrochemical energy storage devices can be carried out in various ways. Pyrolytic deconstruction processes are known, including those in which the electrochemical energy storage devices do not need to be discharged beforehand. During pyrolytic deconstruction of electrochemical energy storage devices, not only are the energy cells opened, but the organic components present in such an energy storage device are also decomposed through pyrolysis and removed from the pyrolysis reactor. A pyrolysis residue (pyrolysis slag) remains.During pyrolysis, some of the lithium present in such electrochemical energy storage devices can be recovered. The pyrolysis slag, also known as black mass due to its high graphite content, contains not only graphite and lithium but also other recoverable elements such as copper, iron, aluminum, cobalt, nickel, and manganese. Mechanical digestion processes are also known. In these processes, the electrochemical energy storage devices must first be discharged before being crushed, with or without their casings. Combined digestion processes, which combine mechanical and pyrolytic digestion, are also known.

[0005] To recover the aforementioned and other valuable materials contained in the processed material as secondary raw materials, various recovery routes are employed. The valuable materials contained in the energy storage material can be recovered hydrometallurgically, specifically through solvent extraction, electrolysis, and chemical precipitation reactions. Alternatively, valuable materials can be recovered via a pyrometallurgical recovery route, in which a metal alloy of Cu, Co, Ni, and Fe is produced from the processed material. In this process, Li remains bound in the slag.To make the recycling of electrochemical energy storage devices economically viable even when the proportions of particularly valuable elements, such as cobalt and nickel, are lower and the proportion of less valuable elements, such as copper, iron, and aluminum, is higher, a pyrometallurgical recycling process using an inductively heated reduction reactor is proposed in WINDISCH-KERN, Stefan [et al.]: Recycling of Lithium-Ion Batteries: Challenges and Current Research Results. In: Berg- und Hüttenmännische Monatshefte, Vol. 166, 2021, No. 3, pp. 150-156. In this reactor, the oxide compounds are reduced, which should also enable the recovery of lithium with a higher recovery rate.

[0006] German patent DE10 2018 117 237 A1 discloses a process for the hydrometallurgical recycling of lithium-ion traction batteries. Following thermal treatment with the addition of oxygen and the removal of organic components from the shredded battery material – the energy storage material – a Li-Co-Ni-Mn solution is prepared using an aqueous acid. The transition metals are then separated from this solution as sulfides by adding hydrogen sulfide. After separating the precipitate, lithium is precipitated from the remaining liquid phase by adding potassium or sodium carbonate at temperatures between 85 and 100°C.

[0007] Another process for processing lithium-containing energy storage devices is known from WO 2024 / 046889 A1. In this process, following pyrolysis to provide the energy storage material, the black mass is subjected to neutral leaching with water. Primarily, the lithium carbonate formed during pyrolysis is dissolved from the black mass. During the leaching process, it is advantageous to introduce carbon dioxide into the leaching solution to maintain the pH value in the neutral to slightly acidic range, as this facilitates the selective separation of lithium from the black mass. The leaching residue is then carbonated to recover any remaining lithium compounds. In this process step, other elements to be recovered, such as aluminum, iron, cobalt, nickel, and manganese, are also dissolved from the black mass. The dissolved lithium carbonate is subsequently precipitated by evaporating the lithium-containing solution.

[0008] DE 10 2018 102 026 A1 discloses a process for recycling lithium batteries. This process uses sulfuric acid for the chemical digestion. The digestion itself is preferably carried out at a temperature of at least 140°C. This process differs from pyrometallurgical processes for pretreating energy storage materials.

[0009] The subsequently published EP 4 556 585 A1 describes a lithium recovery system from black mass. The black mass is first subjected to heat treatment to convert it into soluble and insoluble substances. This heat-treated material is then leached in water. After removal of impurities, the leaching solution is concentrated. Subsequently, the lithium contained in the concentrated leaching solution is precipitated as a Li compound by the application of heat.

[0010] WO 2022 / 268792 A1 discloses a process for recycling battery materials by means of reductive pyrometallurgical treatment. This prior art process is intended to recover the active cathode material and, in particular, the lithium used. It is designed so that the lithium is separated at the beginning of the processing and thus does not have to be carried through the entire process chain. In this prior art, the reductive treatment is carried out using a lithium-containing solution with a reducing agent. This mixture is heated. Subsequently, a suspension step takes place in an aqueous or organic suspension medium, in which a solid reducing agent and a lithium-containing solution are obtained. The reducing agent is then separated from the lithium-containing solution. This prior art also differs from pyrometallurgical treatment processes for energy storage materials.

[0011] WO 2024 / 246339 A1 discloses a process for extracting lithium from a lithium-containing solid. This process, like DE 10 2018 102 026 A1, also uses sulfuric acid to dissolve lithium or lithium compounds from the black mass.

[0012] Based on this discussed state of the art, the invention aims to propose a method for recovering lithium as a secondary raw material from energy storage material resulting from electrochemical energy storage devices opened up by pretreatment and / or from production waste, with which relatively pure lithium carbonate can be recovered with low energy and solvent input and at the same time with a relatively high recovery rate, particularly also in a sustainable manner.

[0013] According to the invention, this problem is solved by a method having the features of claim 1.

[0014] Advantageous further developments are the subject of the subclaims and also result from the description.

[0015] A special feature of the process according to the invention is that, to increase efficiency compared to conventional methods, the lithium-containing solution obtained by lye treatment (chemical extraction) is concentrated before the precipitation step of at least one lithium compound. This process step is remarkable in several respects. Firstly, the inclusion of this process step in the recovery route allows the chemical extraction step – the lye treatment – ​​to be carried out with a relatively high liquid content in the solid / liquid ratio (ratio between energy storage material and lye solution) without compromising precipitation. This cleverly utilizes the solubility behavior of lithium compounds in the energy storage material, namely that the lower the lithium content of the lye solution, the more rapidly these compounds can be dissolved from the energy storage material.During the process step of concentrating the lithium-containing solution, the leaching agent is removed, so that the subsequent and independently carried out step of precipitation of at least one lithium compound is performed based on a lithium solution enriched with respect to its lithium content. Therefore, in this process, it is generally not necessary to evaporate the leaching liquid during the precipitation step, as is the case with previously known processes.

[0016] In a preferred embodiment, the step of concentrating the lithium-containing solution is carried out by reverse osmosis. This is not only energy-efficient, but also avoids introducing any additional substances into the lithium-containing solution that could potentially lead to impurities in the lithium compound(s) to be recovered. Furthermore, the permeate obtained during reverse osmosis (the leaching liquid removed from the lithium-containing solution) can be reused in the chemical extraction step. The same applies to the residual solution remaining after separating the at least one precipitated lithium compound. This process is therefore particularly resource-efficient, especially with regard to the use of the leaching liquid.

[0017] If the energy storage material is sourced from decommissioned electrochemical energy storage devices, these devices undergo pretreatment. Such pretreatment typically involves mechanical, metallurgical, and / or pyrolytic processes. This pretreatment primarily serves to make the material contained within the energy storage device accessible. Mechanical treatment can be achieved, for example, by shredding. When combining mechanical and pyrolytic treatments, the mechanical treatment is preferably performed after the pyrolytic treatment, but it can also be performed before the pyrolytic treatment. A pyrolytic treatment has the advantage that, after this treatment, the recovered lithium in the pyrolytically treated energy storage material is typically present predominantly as lithium carbonate.Lithium carbonate can be chemically extracted from the black mass provided by mechanical and / or pyrolytic treatment as a starting material using a neutral leaching liquid.

[0018] The process step of concentrating the lithium-containing solution is made more efficient with respect to the lithium content of the concentrated solution by converting at least one lithium compound dissolved in the solution into a compound with a higher solubility than the lithium compound extracted from the energy storage material during chemical extraction. This allows the lithium-containing solution to be concentrated significantly further, enabling the removal of a larger portion of the leaching liquid without the risk of lithium precipitation and subsequent losses in the recovered product.

[0019] This process is further optimized by converting the more soluble lithium compound into a less soluble one after the concentration step of the lithium-containing solution and before the precipitation step. The less soluble lithium compound may well be the one that has been dissolved from the energy storage material. The precipitation step can then be carried out with correspondingly low energy input and, importantly for the industrial application of this process, a relatively short process time.

[0020] The advantages and implementation of this process are illustrated below using the chemical extraction of lithium carbonate (Li2CO3) from the energy storage material as an example: The chemical extraction is carried out with water as a neutral leaching solution at room temperature. During this step, the pH of the leaching solution increases. This is desirable, so no measures are taken to prevent the pH increase. While in the leaching solution of step b) the lithium is initially present in a first Li compound with lower solubility – in this case, lithium carbonate – this Li compound dissolved by the leaching process is converted in a subsequent process step into a Li compound with higher solubility, namely lithium bicarbonate (LiHCO3) – also known as lithium hydrogen carbonate. At room temperature (20°C), the solubility of lithium bicarbonate (LiHCO3) in water is about four times higher than that of lithium carbonate (Li2CO3). The Li content in the Li-containing solution is then more than twice as high.The conversion of lithium carbonate to lithium bicarbonate is carried out through carbonation by adding CO2 to the Li-containing solution. This also lowers the pH value, typically to the neutral range (pH 7-8).

[0021] Converting lithium carbonate to a more soluble lithium compound such as lithium bicarbonate (LiHCO3) allows for an increase in the lithium concentration in the solution without causing bound lithium to precipitate. Typically, the leached lithium-containing solution contains between 1.5 and 2.3 g / L Li. During concentration, preferably by reverse osmosis, the lithium content can be increased to 3 to 5 g / L Li, and sometimes even higher, depending on the initial lithium content of the energy storage material. Concentration of the lithium-containing solution is stopped before there is a risk of lithium compound precipitation. The lithium concentration in the lithium-containing solution naturally depends on the lithium content of the energy storage material being leached.

[0022] In a subsequent process step, the more soluble lithium compound, typically lithium bicarbonate, is converted back to lithium carbonate by raising the pH of the concentrated lithium-containing solution to achieve the desired precipitation of lithium carbonate. The pH of this solution is preferably raised to a value between 9.5 and 10.5, particularly to about 10. A hydroxide is typically added to the solution to increase the pH. Calcium hydroxide (Ca(OH)₂) in the form of lime milk is preferably used for this purpose. An advantage of this is that the calcium phases have very low solubility, thus preventing any accumulation in the process. Furthermore, the use of calcium hydroxide has the advantage that other elements, especially fluorine and phosphorus, are at least partially removed from the lithium-containing solution by the precipitation of fluorine and phosphorus compounds.This also has a positive effect on the desired purity of the lithium carbonate to be recovered from the energy storage material.

[0023] In principle, other hydroxides can also be used instead of calcium hydroxide for this purpose, for example sodium hydroxide (NaOH). If sodium hydroxide is used, the pH increase and precipitation steps can be carried out simultaneously.

[0024] When calcium hydroxide is used for pH adjustment in a precipitation step following concentration, a solid / liquid separation is performed to separate the solid phases formed upon addition of the calcium hydroxide before the lithium carbonate precipitation. Due to the concentration of the dissolved lithium and the conversion of the dissolved Li compound to a less soluble form, namely lithium carbonate, this solution can be precipitated simply by adding heat, i.e., by heating the concentrated Li-containing solution. It is sufficient to heat the concentrated Li-containing solution to a temperature between 60°C and 90°C. The temperature to which this solution is heated depends on the intended energy input and the process duration required for the lithium carbonate precipitation.To ensure that the precipitation process is both energy-efficient and rapid, in a preferred embodiment the concentrated lithium-containing solution is heated to 80°C. This utilizes not only the lower solubility of lithium carbonate as the lithium compound to be precipitated compared to the more solubilizing lithium compound, typically lithium bicarbonate, but also the decreasing solubility of lithium carbonate with increasing temperature. The precipitated lithium carbonate is then separated from the remaining mother liquor – the residual liquor – in a manner known per se.

[0025] The lithium carbonate obtained in this way not only has a high degree of purity, but the energy input required to extract the lithium carbonate from the black mass is also significantly lower than in previously known processes where lithium carbonate is precipitated from a Li-containing solution by evaporation.

[0026] Except for the precipitation step (step f)), the individual process steps, particularly in the case of the lithium carbonate system described above, can be carried out at room temperature. This also has a positive effect on energy consumption. Due to the solubility of lithium carbonate, if the recovery yield is to be improved, the leaching process can also be carried out at a temperature below room temperature.

[0027] Using this method - illustrated by the example of the Li-carbonate system - 50% to 70% of the lithium present in the energy storage material, especially when present as black mass, can be recovered using economically viable process times.

[0028] The foregoing explanation of the process according to the invention using the carbonate system as an example also applies, with appropriate adjustment of process parameters, to the recovery of lithium in the chloride and sulfate systems.

[0029] The residual lye and, if concentration is carried out by reverse osmosis, the permeate can be recycled in a single-stage recovery process as described above. According to another embodiment, the residual lye and, if available, the permeate are fed to a second recovery stage. This second recovery stage is carried out using the same process steps as described above. In this embodiment, the residue from the leaching process in step b) – the solid fraction – forms the starting material for recovering any lithium not yet extracted during the first recovery stage. Typically, this chemical extraction step is carried out in the second downstream recovery stage to extract a second lithium compound from the energy storage material.For example, if the chemical extraction step in the first recovery stage primarily dissolves lithium carbonate, the subsequent recovery stage typically dissolves lithium fluoride. The leaching parameters are adjusted accordingly. This includes, for instance, the temperature at which the leaching step is carried out. While leaching to dissolve lithium carbonate in the first recovery stage is typically performed at room temperature, the leaching step to dissolve lithium fluoride is preferably carried out at an elevated temperature, typically between 70°C and 90°C. Performing this process step at 80°C is advantageous to ensure that the chemical extraction process for dissolving this additional lithium compound is carried out efficiently at a sufficiently high temperature.In this configuration, the residue from the solid / liquid separation following the leaching step (step b)) can be leached using the residual lye from the first recovery stage. Preferably, the residual lye is diluted with fresh leaching liquid, typically water, to ensure sufficient solubility for the further lithium compound, for example, lithium fluoride, to be extracted from the filter cake of the solid / liquid separation after the leaching step of the first recovery stage. The dilution is preferably carried out in a ratio of 1:1 to 1:3. The solid / liquid ratio in this leaching step should be between 1:30 and 1:50 to obtain a sufficient lithium concentration in the lithium-containing solution at the end of this second leaching step. A ratio of 1:40 is typical, especially if the temperature of the leaching liquid is elevated.

[0030] The subsequent process steps of the second recovery stage can be carried out in a separate process line within the same recovery plant. However, it is also possible to feed the lithium-containing leaching liquid obtained in the second recovery stage into the subsequent process steps of the first recovery stage. In this case, the lithium-containing leaching liquid is introduced into the lithium-containing liquid obtained from the chemical extraction step of the first recovery stage after the solid fraction (leached energy storage material) has been separated.

[0031] In the course of such a two-stage leaching of the energy storage material, typically the black mass, for example in the Li-carbonate system 80% or more of the lithium present in the energy storage material can be recovered.

[0032] The process for recovering lithium as a secondary raw material from energy storage materials of decommissioned electrochemical energy storage devices and / or from production waste during the manufacture of electrochemical energy storage devices has been described above in both one- and two-stage versions. The process can also be carried out in three or more stages, with these additional recovery stages corresponding to and being carried out in accordance with the second stage described above. This is particularly advantageous when a further lithium compound is to be extracted from the energy storage material.

[0033] The invention is explained below using exemplary embodiments. The figures shown are: Fig. 1: A flowchart illustrating the inventive process for recovering lithium in the form of lithium carbonate as a secondary raw material from discarded electrochemical energy storage devices and Fig. 2: a design of the procedure of Fig. 1 with a further recovery stage.

[0034] To recover lithium as a secondary raw material from the electrochemical energy storage devices used up in the illustrated embodiment, these devices are first decongested so that the lithium-containing energy storage material is available as the starting material for the recovery process. In the illustrated embodiment, the energy storage devices are decongested pyrolytically, as this can be carried out without having to discharge or open the electrochemical energy storage devices beforehand. Such pyrolytic decongestion is performed in the illustrated embodiment according to the method described in EP 3 836 289 A1 of the applicant. It is understood that pyrolytic decongestion can also be carried out in other ways. The black mass produced in this way as energy storage material is then hydrometallurgically processed to recover the lithium it contains.Due to the pyrolytic breakdown of the electrochemical energy storage devices, the lithium is primarily bound as lithium carbonate.

[0035] In the first step (step b)) of the recovery process, the black mass is leached with a pH-neutral alkaline solution, whereby water is used as the leaching solution in the illustrated embodiment. In addition to lithium carbonate, the black mass also contains lithium fluoride (LiF). Due to the significantly lower solubility of lithium fluoride compared to lithium carbonate, correspondingly less lithium is dissolved from this compound during the leaching process. The leaching process is carried out in such a way that the pH value rises to 9 or higher during the leaching process. Depending on the amount of dissolved lithium carbonate, the pH value can be allowed to rise to as high as 12. The pH increase during leaching is desirable because neither cobalt nor nickel are dissolved at an elevated pH of the leaching solution. Any previously dissolved cobalt or nickel would then precipitate out again.This contributes to the purity of the recovered lithium carbonate. Therefore, the leaching step already ensures that lithium is extracted from the energy material as selectively as possible.

[0036] Following the leaching of the black mass, a solid / liquid separation process is carried out to separate the leaching residue (leached black mass) as a solid component from the leaching liquid. A filter press is typically used for this purpose.

[0037] In a subsequent process step, the pH value of the lithium-containing solution, which increased during leaching, is lowered again. In the illustrated embodiment, this is achieved by adding CO₂. This carbonation lowers the pH value to a neutral medium, specifically to a neutral pH of 7 to 8. The pH reduction is carried out so that the lithium carbonate in solution is converted into lithium bicarbonate (LiHCO₃). The solubility of lithium bicarbonate is significantly higher than that of lithium carbonate. Therefore, this lithium-containing solution can be concentrated to a much greater extent with dissolved lithium bicarbonate than with dissolved lithium carbonate. Carbonation also has the advantage that aluminum dissolved during leaching precipitates as aluminum hydroxide and, to some extent, also as aluminum-ferrous compounds.

[0038] In a subsequent solid / liquid separation, the solids precipitated by carbonation are removed from the lithium-containing solution. This is done, for example, in a specially designed filter section. The resulting lithium carbonate recovered through this process has a correspondingly higher purity level.

[0039] In the next step, the lithium-containing solution is concentrated by reverse osmosis, typically resulting in a lithium content of 2.5 to 5 g / L. The achievable lithium content depends on the lithium content of the incoming stream. Generally, the lithium-containing solution is concentrated to 3 to 4 g / L. Concentrating the lithium content in the solution by reverse osmosis proves to be particularly energy-efficient, primarily because energy-intensive evaporation processes are not required. Furthermore, no chemicals are needed for the concentration process, which would compromise the purity of the recovered product—lithium carbonate—unless these chemicals are removed by one or more additional process steps prior to lithium carbonate precipitation. If desired, an antiscalant can be used to prevent the deposition of sparingly soluble compounds on or within the membrane.This extends the service life of a membrane and improves process stability.

[0040] The pH of the concentrated lithium-containing solution is then raised to convert the dissolved lithium bicarbonate back to lithium carbonate. In the illustrated embodiment, this is achieved by adding calcium hydroxide (Ca(OH₂)), preferably in the form of lime milk. Raising the pH in this step by adding calcium hydroxide not only achieves the desired increase for the aforementioned purposes but also causes at least some fluorine and phosphorus to precipitate. This step thus also improves the purity of the recovered lithium carbonate.

[0041] In this step of the pH adjustment, the pH is raised to between 9.5 and 11. A preferred pH increase is to 10 in order to keep the amount of calcium hydroxide added as low as possible.

[0042] Before the lithium carbonate in the concentrated lithium-containing solution is precipitated, the solids precipitated by the pH increase are removed from the solution by solid / liquid separation. Preferably, a filter press is used for this solid / liquid separation.

[0043] The lithium carbonate is precipitated from the concentrated lithium-containing solution, with a pH of, for example, 10, simply by heating the solution. This cleverly utilizes the fact that the solubility of lithium carbonate decreases with increasing temperature. At 100°C, the solubility is 7.2 g / l, while at room temperature, and thus also during the leaching step of the black mass, it is approximately 13.3 g / l. The lithium-containing solution is typically heated to 60 to 90°C, preferably to 80°C, but in any case, to a temperature below the boiling point of the concentrated lithium-containing solution. This ensures a sufficiently rapid precipitation process with low energy consumption. Due to the prior concentration, the energy-intensive evaporation process used for this purpose in the prior art can be omitted for the precipitation of lithium carbonate.

[0044] The precipitated lithium carbonate is removed from the residual lye by a solid / liquid separation.

[0045] Typically, this process can recover 50 to 70% of the lithium contained in the black mass as a starting material.

[0046] The above process has been described using a lithium carbonate system as an example. The chemical extraction step primarily dissolves lithium carbonate from the energy storage material. The solid fraction separated from the Li-containing solution after the leaching step typically contains other Li compounds, particularly lithium fluoride. The lithium from these Li compounds is also suitable for recovery.

[0047] At the in Fig. In the embodiment shown in Figure 2, the leaching residue (solid fraction) is fed into a further recovery stage for this purpose. The process steps of the second recovery stage are essentially identical to those of the first recovery stage described above. This second recovery stage also begins with a leaching step. The chemical extraction process by leaching in this second recovery stage is carried out with leaching parameters that are favorable for dissolving lithium fluoride. This leaching step is therefore carried out at an elevated temperature, typically between 75°C and 85°C, and in particular around 80°C. The solid / liquid ratio is significantly higher than in the chemical extraction step for dissolving lithium carbonate and is typically between 1:30 and 1:45, and in particular around 1:40.The solid / liquid ratio can be changed by reducing the liquid content to as low as 1:8 to 1:20 when Ca(OH)2 is added to the leaching solution. This increases the Li concentration in the leaching solution.

[0048] For the leaching step in the second recovery stage, both the residual solution and the permeate from the first recovery stage can be used. The same applies to the residual solution and the permeate from the second recovery stage if this stage, along with all process steps, is carried out in a separate process line within the same plant.

[0049] The lithium-containing solution obtained after solid / liquid separation in the second recovery stage during leaching can be fed into the first recovery stage for the purpose of carrying out further process steps. This solution is combined with the lithium-containing liquid from the chemical extraction process of the first recovery stage for the purpose of carbonation. In the Fig. In the embodiment shown in Figure 2, the second recovery stage is, however, independent of the first recovery stage with regard to the process steps carried out and is carried out with the subsequent steps of carbonation, concentration, pH increase and precipitation as described in Figure 2. Fig. The first recovery stage is described in section 1.

[0050] Parallel to the process, in Fig.1 The change in pH value (dashed line) and temperature (solid line) for each process step is shown.

[0051] If the two recovery stages described above are carried out, approximately 80% or more of the lithium present as a reactant in the black mass can be recovered. It is understood that, to further increase the lithium recovery rate, the process can also be carried out with additional recovery stages following the second stage.

[0052] The invention has been described with reference to exemplary embodiments. Without departing from the scope of protection described by the applicable claims, numerous further embodiments of the inventive concept would be apparent to a person skilled in the art, without these needing to be explained in more detail within the scope of these explanations.

Claims

[1] Method for recovering lithium as a secondary raw material from energy storage material provided by spent and pretreated electrochemical energy storage devices and / or by production waste from the manufacture of electrochemical energy storage devices, comprising the following process steps: a) Provision of lithium-containing energy storage material obtained from decommissioned energy storage systems through pretreatment and / or energy storage material from waste from the production of electrochemical energy storage systems, which energy storage material is the starting material for the subsequent process steps, b) chemical extraction of Li compounds from the energy storage material to obtain a Li-containing solution, wherein the chemical extraction step is carried out with a neutral leaching liquid, in particular with water, and the pH of the leaching liquid is increased during the chemical extraction, c) Converting the Li compound dissolved from the energy storage material into a Li compound of higher solubility, wherein, in order to carry out the step of converting the Li compound dissolved by chemical extraction into such a higher solubility, the pH value of the Li-containing solution is lowered by adding CO2, d) Concentrating the Li-containing solution, e) Converting the Li compounds of higher solubility dissolved in the concentrated Li-containing solution into Li compounds of lower solubility, f) cases of at least one Li compound from the concentrated solution and g) Separation of at least one precipitated Li compound from the remaining solution. [2] Method according to claim 1, characterized by , that decommissioned electrochemical energy storage devices are broken down by mechanical and / or pyrolytic treatment to provide energy storage material as black mass. [3] Method according to claim 1 or 2, characterized by that the leaching process is carried out at room temperature and with a solid / liquid ratio of 1:3 to 1:20, preferably 1:10 or about 1:

10. [4] Method according to any one of claims 1 to 3, characterized by that the pH value is increased to 10-12 during the chemical extraction process. [5] Method according to any one of claims 1 to 4, characterized by that the pH value of the Li-containing solution is lowered into the neutral pH range to a pH value of 6 to 9, preferably 7 to 8. [6] Method according to any one of claims 1 to 5, characterized by , that in order to convert Li compounds of higher solubility in the concentrated Li-containing solution into Li compounds of lower solubility, the pH value of the concentrated Li-containing solution is raised. [7] Method according to claim 6, characterized bythat the pH value is raised to 9.5 to 11, especially to about 10. [8] Method according to claim 6 or 7, characterized by that the pH increase is achieved by adding Ca(OH)2 to the concentrated Li-containing solution. [9] Method according to claim 8, characterized by , that after raising the pH of the concentrated Li-containing solution and before precipitating at least one Li compound, a solid / liquid separation is carried out. [10] Method according to any one of claims 1 to 9, characterized by that the concentration of the Li-containing solution is carried out by means of reverse osmosis. [11] Method according to any one of claims 1 to 10, characterized by, that the at least one Li compound is precipitated from the concentrated Li-containing solution by the supply of heat, wherein the concentrated Li-containing solution is heated at most only to a temperature below its boiling point, in particular to a temperature between 60 °C and 90 °C, in particular to about 80 °C. [12] Method according to any one of claims 1 to 11, characterized by , that a solid / liquid separation is carried out between the chemical extraction step and the step of concentrating the Li-containing solution. [13] Method according to any one of claims 1 to 12, characterized by, that the process is carried out in at least two recovery stages and that, in order to recover Li compounds remaining in the solid fraction after chemical extraction in a first recovery stage, this solid fraction or part thereof is used as a starting material for carrying out the process according to one or more claims 1 to 12 in a second recovery stage. [14] Procedure Claim 13, characterized by , that the liquid content in a second recovery stage during chemical extraction is many times greater in a solid / liquid ratio than in the preceding recovery stage. [15] Method according to claim 13 or 14, characterized by that the second recovery stage is carried out in a process line separate from the first recovery stage. [16] Method according to any one of claims 1 to 15, characterized by, that the residual solution remaining after the step of separating the at least one precipitated Li compound is used as the leaching liquid or as part thereof for carrying out the chemical extraction. [17] The method of claim 16 as referring back to claim 13, characterized by , that the chemical extraction in a second recovery stage to dissolve one or more different Li compounds than in the chemical extraction step of the preceding recovery stage is carried out at an elevated temperature, to a temperature of 70 °C to 90 °C, in particular at about 80 °C. [18] Method according to claim 10, characterized by that the water removed from the Li-containing solution during concentration by reverse osmosis is used as a leaching liquid or as part of it for the chemical extraction process step.

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