Method for producing cathode material from spent batteries

Abstract

The present invention relates to a method for producing a cathode material from spent batteries and to the cathode material obtained according to the method of the invention.

Description

[Technical Field]

[0001] The present invention relates to a process for producing cathode material from spent batteries and to the cathode material obtainable by the process according to the invention. [Background technology]

[0002] The transport or mobility transition defines the social, technological and political process by which transport and mobility are converted to sustainable energy sources, the moderate use of mobility and the networking of various forms of individual transport and local public transport. One pillar of the mobility transition is the so-called drive transition, which involves the gradual replacement of internal combustion engines with those powered by hydrogen, fuel cells or by battery power. The most important declared goal of the mobility transition is climate and environmental protection. To achieve this, not only is it necessary to reduce CO2 emissions, but also efficient closed-loop systems to avoid the pollution of the environment and the threat of raw material shortages in the production of battery-electric drive alternatives.

[0003] In the field of battery-electric drives, lithium-ion batteries (LIBs), in particular, have proven to be a promising storage system for the necessary electrical energy. However, without a parallel and sensible global recycling strategy for such batteries, the declared goals of the mobility transition cannot be achieved. Therefore, the comprehensive recovery of valuable metals contained in used battery materials, especially lithium, such as cobalt, nickel, and manganese, is essential. While primary production of lithium from saltwater uses solar power, which initially appears ecologically compatible, current production is associated with a significant intervention in the water balance of the relevant regions. Studies have shown that a specific freshwater consumption of approximately 44 liters per kilogram of extracted lithium can be expected. Even if global lithium reserves are estimated to be relatively high, they are finite, and the described primary production processes are long. A quantitative and rapid recovery by sustainable recycling of lithium together with other valuable metals, cobalt, nickel, and manganese, for the production of new cathode active materials (CAMs) is preferable in both cases. Initial efforts in sustainable reuse cycles are described in the prior art.

[0004] Specifically, U.S. Patent Application Publication No. 2013 / 0302226 describes a method for recycling batteries that includes producing a solution of battery materials from used cells, precipitating impurities from the produced solution, adjusting the solution to achieve a predetermined ratio of desired materials, and precipitating the desired materials in the predetermined ratio to form a cathode material for a new battery having the predetermined ratio of desired transition metals.

[0005] U.S. Patent Application Publication No. 2017 / 0077564 describes a process for recycling lithium ion batteries, comprising: identifying a molar ratio of cathode material for a new battery; forming a leach solution by combining pulverized battery material from a lithium battery recycle stream with an acidic leachant and hydrogen peroxide (H2O2) to separate the cathode material from undissolved material; filtering the undissolved material from the formed leach solution such that dissolved salts of the cathode material remain in the leach solution; determining the composition of the leach solution by identifying a molar ratio of salts of the cathode material dissolved in the leach solution; and adding a solution of aluminum sulfate and a chelating agent based on the determined composition. The process involves adding Ni, Co, Mn, or Al salts as sulfates (xSO4) of oxides (xOH) to adjust the molar ratio of the dissolved cathode material salts in the leach solution to correspond to the specified molar ratio in the recycled battery; raising the pH of the leach solution to at least 10 to precipitate and filter out the metal ions of the cathode material; and forming a charged material precursor by converting the Ni, Co, Mn, and Al salts remaining in the caustic solution as complex hydroxides (OH)2 or carbonates (CO3) in a molar ratio equal to the specified molar ratio in the recycled battery, where the charged precursor material responds to sintering to form the active cathode material in oxide form after sintering with lithium carbonate (Li2CO3). It should be emphasized that all pH adjustments, especially precursor precipitation, are performed by adding NaOH.

[0006] Methods proposed in the prior art attempt to avoid, as much as possible, the separation and energy-consuming conversion of transition metals to their solid sulfates and directly use the resulting mixed solution of Ni / Co / Mn sulfates and Li2SO4 for the precipitation of cathode precursors after adjusting the stoichiometric composition of the transition metals. However, in conventional processes, lithium is recovered as sparingly soluble Li2CO3 by adding Na2CO3. However, due to the solubility ratio of lithium carbonate and lithium sulfate, this approach is complicated and makes practical quantitative recovery of lithium virtually impossible or only possible at considerable cost. Not only does non-quantitative recovery of lithium have cost disadvantages, but for environmental reasons, the release of solutions containing lithium salts into natural (inland) waters is generally not possible. Furthermore, the recovery of lithium as carbonate corresponds to a resalination process, which involves the further generation of neutral salts in addition to the neutral salt load resulting from the precipitation of the precursor. Therefore, overall, it is believed that at least 1.5 moles of Na2SO4 are formed per mole of LiMO2. Therefore, there remains a need for a process that allows for the efficient and quantitative recovery of cathode material from lithium-ion batteries that are no longer in use. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2013 / 0302226 [Patent Document 2] US Patent Application Publication No. 2017 / 0077564 Summary of the Invention [Problem to be solved by the invention]

[0008] This need is addressed by the present invention, which has surprisingly found that the production of cathode materials from battery waste can be based entirely on lithium hydroxide (LiOH) rather than sodium hydroxide (NaOH), thereby avoiding the normally occurring neutral salt waste and producing a low-sodium or sodium-free product without increasing the actual need for LiOH. [Means for solving the problem]

[0009] Accordingly, the present invention first provides a process for producing a cathode material from spent batteries, comprising: a) dissolving cathode material from shredded battery waste by treating it with a leaching agent to obtain a cathode material precursor solution; b) treating the cathode material precursor solution with LiOH to obtain a solid cathode material precursor mixed hydroxide and a filtrate containing at least the Li salt of the leaching agent; c) separating the filtrate obtained in step b) and partitioning the filtrate into LiOH and a leaching agent using electrolysis; and d) converting the cathode material precursor mixed hydroxide into an active cathode material that at least partially utilizes the LiOH recovered in step c).

[0010] Within the scope of the present invention, it has surprisingly been found that by using LiOH, which is usually not preferred due to its high cost, not only can the amount of neutral salt waste be reduced, but also an improved CO footprint can be achieved.

[0011] Within the scope of the process according to the present invention, the transition metals, in particular Ni, Co, and Mn, contained in the cathode material of used lithium-ion batteries are converted into soluble forms of their salts in a cathode material precursor solution by treatment with a leaching agent. Subsequently, optionally after pre-washing and / or partial separation, the transition metals are precipitated from this solution by adding LiOH in the form of a solid mixed hydroxide, thereby forming a precursor in the subsequent active cathode material. The lithium salt of the leaching agent is obtained as a filtrate, which is converted back into LiOH and the leaching agent by electrolysis. The mixed hydroxide of the transition metals obtained in the process according to the present invention is further converted into an active cathode material, which can then be used to manufacture lithium-ion batteries, thereby closing the recycling loop.

[0012] As part of the process according to the invention, used lithium-ion batteries are used in particular as battery waste and in particular as their cathode material, which is selected in particular from the group consisting of LiMO bilayer structures, preferably with M=Ni, Co and / or Mn and / or Al, in particular LiCoOxide (LCO), Li(Ni / Co)Oxide (LNCO), Li(Ni / Co / Mn)Oxide (LNCMO), Li(Ni / Co / Al)Oxide (LNCAO), Li(Ni / Al)Oxide (LNAO), Li(Ni / Mn)Oxide (LNMO), or LiMO spinel structures, preferably with M=Ni, Co and / or Mn, optionally with Al doping or any mixture.

[0013] In a preferred embodiment, the cathode material used contains Ni and Co, preferably Mn and / or Al.

[0014] Prior to use in the process according to the invention, the cathode material may be subjected to a washing step to remove organic solvents, such as LiPF, and electrolyte residues. Thus, in a preferred embodiment, the process according to the invention includes a step of washing the cathode material to be used. Preferably, this washing step consists of washing the cathode material with water.

[0015] In a preferred embodiment, the leaching agent is a mineral acid, preferably sulfuric acid. In a further preferred embodiment, a reducing agent is added to the leaching agent, preferably H2O2 or SO2.

[0016] The cathode material obtained from battery waste may also contain other components, such as iron, copper, or aluminum, which are also converted into their soluble salt form by treating the cathode material with a leaching agent and thus found in the cathode material precursor solution. In these cases, pre-cleaning is advantageous. Therefore, preferred embodiments involve the process of the present invention further comprising pH-dependent precipitation of at least one salt of Fe, Cu, or Al from the cathode material precursor solution. In contrast to the common procedure of precipitating metals by adding NaOH, precipitation in the process of the present invention is preferably carried out by adding LiOH. Alternatively, impurities can be separated by solvent extraction. In this case, any activation or pH adjustment of the extractant used is also preferably carried out with LiOH. Regardless of the pre-cleaning method selected, sodium entry into the process cycle is avoided.

[0017] Cathode material precursor mixed hydroxide Ni x Co y Mn z (OH)2 is precipitated from the cathode material precursor solution, optionally after removal of Fe, Cu, and / or Al, which serves as the basis for the production of the active cathode material. This procedure has the advantage that complex complete separation and separate crystallization of the individual transition metal salts is not required. In contrast to what is described in some prior art processes, in the process of the present invention, lithium is not precipitated with the transition metal salt but rather remains in solution.

[0018] The transition metals are present in the active cathode material (CAM) in a certain ratio to each other that determines, among other things, the performance of the battery. This ratio of transition metals is usually achieved by appropriate adjustments in the cathode material precursors.

[0019] Therefore, preferred are embodiments in which the process according to the present invention further comprises the step of preferably controlling and optionally adjusting the cathode material precursor solution with respect to metal stoichiometry depending on the desired composition of the active cathode material to be produced.

[0020] The metal stoichiometric composition is conventionally adjusted by adding one or more corresponding components, which has the disadvantage that a significant amount of "new" material, usually in the form of a solid sulfate, may have to be applied, as described, for example, in U.S. Patent Application Publication No. 2017 / 0077564. During the crystallization of the sulfate, a significant amount of energy is consumed by evaporating water, which, in the case of nickel, results in a CO2 footprint of approximately 1.5 kilograms of CO2 per kilogram of Ni. However, in order to protect the climate, unnecessary production of CO2 should be avoided.

[0021] In the context of the present invention, it has surprisingly been found that the preparation can be carried out by targeted separation, thereby avoiding the use of additional materials and the associated drawbacks. Therefore, preferred embodiments involve the preparation being carried out by at least partially separating one or more of the components of the cathode material precursor solution, preferably by solvent extraction. In this case, any activation or pH adjustment of the extractant used is preferably carried out with LiOH. This procedure is particularly advantageous insofar as current cathode materials, which are present in a 1:1:1 ratio of Ni, Co, and Mn, are converted into materials rich in transition metals, e.g., nickel, where the Ni:Co:Mn ratio is 8:1:1, which requires the addition of large amounts of nickel to achieve this ratio.

[0022] The process according to the present invention provides that a filtrate containing a solid cathode material precursor mixed hydroxide and at least a Li salt of the leaching agent is obtained from the cathode material precursor solution by treatment with LiOH. In a preferred embodiment, the treatment is carried out so that the precipitation of the cathode material precursor is carried out at a pH of 9 to 14, preferably 10 to 13. The pH value indicates the temperature used. To carry out the precipitation in a controlled manner and obtain spherical particles, NH3 can be added during the precipitation process, with the NH3 concentration preferably being in the range of 1 to 17 g / L, more preferably 5 to 15 g / L, and particularly preferably 8 to 12 g / L. The precipitation can be carried out at room temperature, but preferably at a temperature of 20 to 80°C, and particularly preferably 40 to 65°C.

[0023] In step c) of the process according to the invention, the filtrate obtained in step b) is separated by electrolysis into LiOH and the corresponding leaching agent, thereby making it possible to recover the leaching agent used in step a). In a preferred embodiment, electrodialysis technology is used for the electrolysis. In a particularly preferred embodiment, a bipolar membrane is additionally used for the electrolysis, which means that a significant increase in space / time yield can be achieved.

[0024] As mentioned above, the filtrate obtained in step b) of the process according to the invention may contain NH3, therefore, for purification, the filtrate may be subjected to distillation before electrolysis.

[0025] The process according to the invention aims to provide a closed circuit, therefore an embodiment is preferred in which the leaching agent obtained in step c) is at least partly used for the treatment of the cathode material in step a) of the process according to the invention.

[0026] In a particularly preferred embodiment, the LiOH obtained in step c) of the process according to the invention is at least partly used to treat the cathode material precursor solution in step b).

[0027] In a preferred embodiment, the LiOH obtained in step c) of the process according to the invention is at least partially converted into a solid state, preferably in the form of solid LiOH·H2O and / or Li2CO3, which can be advantageously used in the further course of the process. The conversion to Li2CO3 is preferably carried out by treating LiOH with CO2.

[0028] Step d) of the process according to the invention results in the conversion of the resulting cathode material precursor mixed hydroxide into the active cathode material, at least in part using the LiOH recovered in step c). In a preferred embodiment, the reaction is carried out by reacting with solid LiOH·H2O or Li2CO3.

[0029] In a preferred embodiment, the LiOH converted to its solid state from step c) of the process according to the invention is at least partially used for the conversion of the cathode material precursor mixed hydroxide into active cathode material, thereby closing a further gap in the circuit.

[0030] In contrast to prior art processes, the process of the present invention relies on LiOH. Therefore, an embodiment in which NaOH is not used in the process is preferred. On the one hand, this avoids the neutral salt waste that would otherwise be generated, and on the other hand, the electrical energy required to recover LiOH by electrolysis is slightly lower compared to the production of NaOH by conventional chloralkali electrolysis, which has a positive effect on the CO₂ footprint. If the neutral salt Na₂SO₄ obtained when using NaOH had to be crystallized by water evaporation, the energy advantage of the entire process would be even higher, since in some locations the neutral salt cannot be directly released into the environment. Not only does the present process not have this energy disadvantage, but it is also completely flexible in terms of location. Furthermore, the amount of LiOH produced is reused to produce cathode precursor material, so that only a small amount of LiOH actually needs to be present in the recycling company's cycle.

[0031] The process according to the invention allows the only source of Na input to be the cathode material to be recycled. The amount of Na introduced can be removed from the circulation process, for example, via solvent extraction or ion exchangers, or using electrochemical processes. If desired, this can be done continuously or at more or less long intervals. In this regard, the process according to the invention allows Na to disappear from the global battery circuit over time.

[0032] A further aspect of the present invention is a cathode material, particularly for lithium-ion batteries, obtainable by the process according to the present invention, which is essentially free of sodium, the sodium content being preferably less than 500 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, respectively, based on the total weight of the cathode material. 8 / 10 Co 1 / 10 Mn 1 / 10 or Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The transition metal stoichiometry is:

[0033] The advantages of the present invention are illustrated by the following examples and figures, which should not be understood as limiting the scope of the present invention. [Brief explanation of the drawings]

[0034] [Figure 1] 1 shows a schematic representation of a preferred course of the process according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Used lithium-ion batteries (LIBs) are first crushed to bring the valuable metals contained in the cathode material of the used LIBs into solution (cathode material precursor solution), which is then mixed with a leaching agent and, if necessary, a reducing agent. Undesirable components such as Fe, Cu, or Al can be separated from this solution in the form of hydroxides by adding LiOH and adjusting the appropriate pH value. The separated hydroxides can then be fed to an adjacent recycling cycle. In the purified solution, the ratios of Ni, Co, and Mn to each other are controlled and, if necessary, adjusted according to the desired stoichiometric composition of the resulting active cathode material. The metals Ni, Co, and Mn are then precipitated by adding LiOH as a precursor (cathode material precursor mixed hydroxide) and further converted into the desired active cathode material. The filtrate (mother liquor) obtained during precipitation is separated into LiOH and a leaching agent, such as sulfuric acid, using electrodialysis and returned. The leaching agent is fed back to the process, and LiOH is partially converted to solid LiOH·HO and partially fed back to the process cycle. Solid LiOH·H2O can be used, for example, to produce active cathode material from cathode material precursor mixed hydroxides, thereby completing the cycle.

[0036] The present invention is a general Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The cathode material is a Ni-rich material. 8 / 10 Co 1 / 10 Mn 1 / 10 Tables 1 and 2 compare the present solution of preparation by separation with the conventional addition method in the prior art. Table 1 shows the results of the conventional Ni 1 / 3 Co 1 / 3 Mn 1 / 3The amounts of Ni, Co, and Mn occurring as raw materials in the "one-third mixture" are shown, as well as the amounts of Co and Mn that need to be separated to achieve the new Ni-rich stoichiometric composition. The "excess" Co thus obtained can be processed, for example, into Co metal powder, and the "excess" Mn can be delivered directly to the steel industry as Mn hydroxide or Mn oxyhydroxide.

[0037] [Table 1]

[0038] Alternatively, NiSO4 can be added to adjust the desired stoichiometry as described in the prior art, which leads to the scenario shown in Table 2, where the proportion of purchased commodity is clearly higher.

[0039] [Table 2]

[0040] As can be seen from Table 2, the stoichiometry is achieved by purchasing "virgin material," in this case the Ni component, in bulk. According to the above estimates, purchasing Ni leaves a CO footprint of approximately 1.5 kg CO per kg Ni, which is avoided by the procedure according to the present invention.

[0041] The advantages achieved by using LiOH instead of NaOH are explained below. Chlor-alkali electrolysis 2 Na + (aq) +2 Cl - (ag) +2 H2O → 2 Na + (aq) +2 OH - (aq) +Cl2+H2

[0042] [ka]

[0043] Chloralkali electrolysis currently produces around 60 million tonnes of NaOH per year worldwide, which is also used to produce precursors for the active material in state-of-the-art lithium-ion batteries, corresponding to a minimal emission of around 18 million tonnes of CO2 per year. Li2SO4 electrodialysis 2Li + (aq) +2 SO4 2- (aq) +3 H2O → 2 Li + (aq) +2 OH - (aq) +SO4 2- (aq) +H2+1 / 2 O2

[0044] [ka]

[0045] Alternatively, LiSO electrodialysis is advantageously provided as part of the process of the present invention. Gibbs free energy refers to the minimum electrical work that must be done. Due to overpotential and ohmic resistance, the actual electrical work required for, for example, chloralkali electrolysis is about 50% higher. This means that the use of NaOH as a precipitant has a CO footprint of about 1 kg CO per kg of precursor.

[0046] Lithium sulfate electrolysis requires slightly less energy than chloralkali electrolysis. There is also the potential to further reduce the energy requirements of the electrochemical process by significantly increasing the efficiency of lithium sulfate electrodialysis through stacking of bipolar membranes.

Claims

1. A process for manufacturing cathode material from used batteries, a) Dissolving the cathode material from shredded battery waste by treating it with a leachate to obtain a cathode material precursor solution, b) The step of treating the cathode material precursor solution with LiOH to obtain a solid cathode material precursor mixed hydroxide and a filtrate containing at least the Li salt of the leaching agent, c) Separating the filtrate obtained in step b) and dividing the filtrate into LiOH and leaching agent using electrolysis, d) A step of converting the cathode material precursor mixed hydroxide into an active cathode material that uses at least partially the LiOH recovered in step c), A process that includes this.

2. The process according to claim 1, characterized in that the cathode material contains Ni and Co, preferably Mn and / or Al.

3. The process according to claim 1, characterized in that the cathode material used in step a) is subjected to a washing step before treatment with the leaching agent, wherein the washing step preferably consists of washing with water.

4. The leaching agent is a mineral acid, preferably sulfuric acid, and the leaching agent is a reducing agent, preferably H ２ O ２ or SO ２ The process according to claim 1, further comprising:

5. The process according to claim 1, further comprising a pH-dependent precipitate of a salt of Fe, Cu and / or Al from the cathode material precursor solution, wherein the pH value is preferably adjusted by adding LiOH.

6. The process according to claim 1, further comprising the step of controlling and optionally adjusting the cathode material precursor solution with respect to the metal stoichiometric composition according to a desired composition of the cathode material to be manufactured.

7. The process according to claim 6, characterized in that the adjustment is carried out by separating at least one or more components of the cathode material precursor solution.

8. The process according to claim 1, characterized in that the cathode material precursor solution has a pH of 9 to 14, preferably 10 to 13.

9. The process according to claim 1, characterized in that the filtrate is subjected to distillation before electrolysis.

10. The process according to claim 1, characterized in that electrodialysis technology is used for electrolysis.

11. The process according to claim 1, characterized in that the leachate recovered in step c) is used at least partially for the treatment in step a).

12. The LiOH obtained in step c) is preferably solid LiOH·H ２ O and / or Li ２ CO ３ The process according to claim 1, characterized in that it is converted to a solid state in a form that is at least partially solid.

13. The process according to claim 12, characterized in that at least a portion of the LiOH converted to a solid state is used to convert the cathode material precursor mixed hydroxide into an active cathode material.

14. The process according to claim 1, characterized in that the LiOH used in step b) is at least partially the LiOH recovered in step c).

15. The process according to claim 1, characterized in that NaOH is not used in the process.

16. A cathode material obtained by a process according to at least one of claims 1 to 15, wherein the cathode material is essentially sodium-free, and the content of sodium or one of its compounds is preferably less than 500 ppm, preferably less than 50 ppm, and more preferably less than 10 ppm, based on the total weight of the cathode material.

Images