Method for producing cathode material from spent batteries

Abstract

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

Description

[0001] Process for producing cathode material from battery waste

[0002] The present invention relates to a process for producing cathode material from battery waste and to a cathode material obtained according to the process according to the invention.

[0003] The transport or mobility transition refers to the social, technological, and political process of converting transport and mobility to sustainable energy sources, low-carbon mobility, and the interconnection of various forms of private and local public transport. One pillar of the mobility transition is the so-called drive transition, which involves the gradual replacement of combustion engines with those powered by hydrogen, fuel cells, or battery-electric vehicles.

[0004] The declared and most important goal of the mobility transition is climate and environmental protection. To achieve this, not only reducing CO2 emissions is essential, but also an efficient recycling system to avoid environmental pollution and the impending shortage of raw materials in the production of battery-electric drive alternatives.

[0005] In the field of battery-electric drives, lithium-ion batteries (LIBs) in particular have proven to be a promising storage system for the required electrical energy. However, without a parallel and sensible global recycling strategy for such batteries, the stated goal of the mobility transition cannot be achieved. A holistic recovery of the valuable metals contained in used battery materials, such as cobalt, nickel, and manganese, but especially lithium, is therefore essential. While the primary production of lithium from brines harnesses solar power, which initially appears ecologically sound, current extraction entails major interventions in the water resources of the regions concerned. Studies indicate a specific freshwater consumption of approximately 44 liters per kilogram of extracted lithium.Even though global lithium reserves are estimated to be relatively high, they are finite, and the described primary production process is lengthy. Quantitative and rapid recovery through sustainable recycling of lithium together with the other valuable metals cobalt, nickel, and manganese to produce new cathode active materials (CAM) is preferable in any case. Initial efforts toward a sustainable materials cycle are described in the state of the art.

[0006] For example, US 2013 / 0302226 describes a method for recycling batteries, comprising: producing a solution of battery materials from spent cells; precipitating impurities from the produced solution; adjusting the solution to achieve a predetermined ratio of desired materials; and precipitating the desired material in the predetermined ratio to form cathode material for a new battery having the predetermined ratio of the desired transition metals.

[0007] US 2017 / 0077564 relates to a method for recycling lithium-ion batteries, comprising: identifying a molar ratio for cathode materials for a new battery; forming a leach solution by combining crushed battery material from a lithium battery recycling stream with an acidic leaching agent and hydrogen peroxide (H2O2) to separate cathode materials from undissolved materials; filtering the undissolved materials from the formed leach solution so that the dissolved salts of the cathode materials remain in the leach solution; determining a composition of the leach solution by identifying a molar ratio of the salts of the cathode material dissolved therein; adding Ni, Co, Mn, or Al salts in sulfate (xSCU) or hydroxide (xOH) form based on the determined composition to adjust the molar ratio of the dissolved cathode material salts in the leach solution.that it corresponds to the identified molar ratio for the recycled battery, including the addition of a solution of aluminum sulfates and a chelating agent; and increasing the pH of the leaching solution to at least 10 to precipitate and filter metal ions of the cathode materials to form a charge material precursor by leaching the Ni, Co, Mn, and Al salts remaining in the leach solution as a combined hydroxide (OH)2 or carbonate (CO3) with a molar ratio corresponding to the identified molar ratio for the recycled battery, wherein the charge precursor material reacts upon sintering to form active cathode materials in an oxide form after sintering with lithium carbonate (U2CO3). It should be emphasized that all pH adjustments, and in particular the precipitation of the precursor, are carried out by adding NaOH. While the methods proposed in the prior art endeavor toto avoid the separation and energy-intensive conversion of the transition metals into their solid sulfates as much as possible, and to use the resulting mixed solution with Ni / Co / Mn sulfate and U2SO4 directly to precipitate the cathode precursor after adjusting the transition metal stoichiometry. However, in conventional processes, lithium is recovered as sparingly soluble U2CO3 by adding Na2CCh. However, this approach is complex due to the solubility ratios of lithium carbonate and lithium sulfate, making a truly quantitative recovery of the lithium virtually impossible or only possible at considerable expense. However, non-quantitative recovery of lithium not only has cost disadvantages, but the release of lithium-salt-containing solutions into nature (inland waters) is generally not possible for environmental reasons. Furthermore, the recovery of lithium as carbonate represents a salt translocation.This is associated with a further neutral salt load, in addition to the neutral salt load generated during the precipitation of the precursor. Overall, it can be assumed that at least 1.5 moles of Na2SO4 are produced per mole of UMO2. Therefore, there is still a need for a process that allows the efficient and quantitative recovery of cathode materials from decommissioned lithium-ion batteries.

[0008] This need is addressed by the present invention, which surprisingly found that the production of cathode materials from battery waste can be based entirely on lithium hydroxide (LiOH) instead of sodium hydroxide (NaOH), thereby avoiding the usual neutral salt waste and allowing the production of low-sodium or sodium-free products without increasing the actual demand for LiOH.

[0009] Therefore, a first object of the present invention is a process for producing cathode material from battery waste, comprising the steps of: a) dissolving the cathode material from comminuted battery waste by treatment with a leaching agent to obtain a

[0010] 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 splitting the filtrate into LiOH and leaching agent by electrolysis; d) converting the cathode material precursor mixed hydroxide to active cathode material using at least part of the LiOH recovered in step c).

[0011] In the context of the present invention, it was surprisingly found that by using LiOH, the use of which is usually not preferred due to its high cost, not only the amount of neutral salt waste could be reduced, but even an improvement in the CO2 footprint could be achieved.

[0012] In the process according to the invention, the transition metals contained in the cathode material of used lithium-ion batteries, in particular Ni, Co, and Mn, are converted into the soluble form of their salts in a cathode material precursor solution by treatment with a leaching agent. From this solution, the transition metals are then precipitated, optionally after pre-purification and / or partial separation, by adding LiOH in the form of a solid mixed hydroxide, which forms the precursor for the subsequent active cathode material. The lithium salt of the leaching agent is obtained as the filtrate, which is converted back into LiOH and the leaching agent by electrolysis. The active cathode material is obtained from the mixed hydroxide of the transition metals obtained in the process according to the invention by further reaction. This active cathode material can then be used to produce lithium-ion batteries, thus closing the material cycle.

[0013] Within the scope of the process according to the invention, used lithium-ion batteries, and in particular their cathode material, are used as battery waste. The cathode material is in particular selected from the group consisting of LiMOz layer structures with preferably M = Ni, Co and / or Mn and / or Al, in particular LiCo oxides (LCO), Li(Ni / Co) oxides (LNCO), Li(Ni / Co / Mn) oxides (LNCMO), Li(Ni / Co / Al) oxides (LNCAO), Li(Ni / Al) oxides (LNAO), Li(Ni / Mn) oxides (LNMO), or UMzCU spinel structures with preferably M = Ni, Co and / or Mn, optionally with Al doping or any desired mixtures.

[0014] In a preferred embodiment, the cathode material used contains Ni and Co and preferably Mn and / or Al.

[0015] The cathode material can be subjected to a purification step before use in the process according to the invention to remove organic solvents and electrolyte residues such as LiPFe. Therefore, in a preferred embodiment, the process according to the invention comprises a purification step for the cathode material to be used. This purification step preferably consists of washing the cathode material with water.

[0016] 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, wherein the reducing agent is preferably H2O2 or SO2.

[0017] The cathode material obtained from the battery waste may contain other components such as iron, copper, or aluminum, which are also converted into the form of their soluble salts by treating the cathode material with the leaching agent and are accordingly found in the cathode material precursor solution. In these cases, it is advantageous to carry out pre-purification. Therefore, an embodiment is preferred in which the process according to the invention further comprises a pH-dependent precipitation of at least one of the salts of Fe, Cu, and Al from the cathode material precursor solution. In contrast to the conventional procedure of precipitating the metals by adding NaOH, precipitation in the process according to the invention is preferably carried out by adding LiOH. Alternatively, the impurities can also be separated by solvent extraction.In this case, any activation of the extraction agent used or pH adjustment is also preferably carried out with LiOH. Regardless of the pre-treatment method chosen, this prevents the introduction of sodium into the process circuit.

[0018] From the cathode material precursor solution, if necessary after separation of Fe, Cu and / or Al, the cathode material precursor mixed hydroxide NixCo y Mn z (OH)2 is precipitated, which serves as the basis for the production of the active cathode material. This procedure has the advantage of eliminating the need for a complex, complete separation and separate crystallization of the individual transition metal salts. Unlike some prior art processes, in the process according to the invention, the lithium is not precipitated together with the transition metal salts, but remains in solution.

[0019] The transition metals in the active cathode materials (CAM) are present in a specific ratio to each other, which, among other things, determines the battery's performance. This ratio of transition metals is usually achieved by adjusting the cathode material precursor accordingly.

[0020] Therefore, an embodiment is preferred in which the process according to the invention further comprises a step of controlling and optionally adjusting, preferably the cathode material precursor solution, with respect to the metal stoichiometry depending on the desired composition of the active cathode material to be produced.

[0021] Adjusting the metal stoichiometry is traditionally achieved by adding the appropriate component or components. This has the disadvantage that sometimes significant amounts of "new" material, usually in the form of solid sulfates, must be applied, as described, for example, in US 2017 / 0077564. During the crystallization of the sulfates, significant amounts of energy are consumed through the evaporation of water, which, in the case of nickel, results in a carbon footprint of approximately 1.5 kilograms of CO2 per kilogram of nickel. However, to protect the climate, any unnecessary CO2 generation should be avoided.

[0022] Within the scope of the present invention, it was surprisingly found that the adjustment can be achieved by targeted separation, thereby avoiding the use of additional material and the associated disadvantages. Therefore, an embodiment is preferred in which the adjustment is achieved by at least partially separating one or more of the constituents of the cathode material precursor solution, preferably by solvent extraction. In this case, any activation of the extraction agent used or pH adjustment is preferably carried out with LiOH.This approach is particularly advantageous in that the current cathode material, in which Ni, Co and Mn are present in a ratio of 1 : 1 : 1, is currently being converted to nickel-rich materials in which the transition metals are present, for example, in a ratio of Ni : Co : Mn of 8 : 1 : 1, a ratio which would otherwise require the addition of large amounts of nickel.

[0023] The process according to the invention provides that a solid cathode material precursor mixed hydroxide and a filtrate containing at least the Li salt of the leaching agent are obtained from the cathode material precursor solution by treatment with LiOH. In a preferred embodiment, the treatment is carried out such 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 stated refers in each case to the operating temperature. In order to carry out the precipitation in a controlled manner and to obtain spherical particles, NH3 can be added during the precipitation process, wherein the NH3 concentration is preferably 1-17 g / l, more preferably 5-15 g / l, particularly preferably 8-12 g / l. The precipitation can be carried out at room temperature, but preferably between a temperature of 20 and 80 °C, particularly preferably between 40 and 65 °C.

[0024] In step c) of the process according to the invention, the filtrate obtained in step b) is split into LiOH and the corresponding leaching agent by electrolysis, allowing the leaching agent used in step a) to be recovered. In a preferred embodiment, electrodialysis technology is used for the electrolysis. In a particularly preferred embodiment, bipolar membranes are additionally used for the electrolysis, which allows a significant increase in the space / time yield to be achieved.

[0025] As explained above, the filtrate obtained in step b) of the process according to the invention may contain NH3 under certain circumstances. Therefore, for purification, the filtrate can be subjected to distillation before electrolysis.

[0026] The process according to the invention aims to provide a closed cycle. Therefore, an embodiment is preferred in which the leaching agent obtained in step c) is used at least partially for the treatment of the cathode material in step a) of the process according to the invention. In a particularly preferred embodiment, the LiOH obtained in step c) of the process according to the invention is used at least partially for the treatment of 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 U2CO3. This can advantageously be used in the subsequent process run. The conversion to U2CO3 is advantageously carried out by treating the LiOH with CO2.

[0028] Step d) of the process according to the invention involves converting the obtained cathode material precursor mixed hydroxide into the active cathode material, at least partially using the LiOH recovered in step c). In a preferred embodiment, the conversion is carried out by reaction with solid LiOH*H2O or U2CO3.

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

[0030] In contrast to conventional prior art processes, the process according to the invention relies on LiOH. Therefore, an embodiment in which no NaOH is used in the process is preferred. This avoids the otherwise generated neutral salt waste and, in addition, the electrical energy required to recover LiOH by electrolysis is somewhat lower than for the production of NaOH by conventional chlor-alkali electrolysis, which in turn has a positive effect on the CO2 footprint. The energetic advantage of the overall process is even greater when using NaOH, the resulting neutral salt Na2SO4 must be crystallized by water evaporation because, depending on the location, it cannot be released directly into the environment. The present process not only does not have this energetic disadvantage but is also completely flexible with regard to location.Furthermore, the produced amounts of LiOH are reused to produce the cathode precursor material, so that only very small amounts of LiOH actually need to be present in the recycling company's cycle. The process according to the invention makes it possible for the cathode material to be recycled to be the sole source of Na. The introduced amounts of Na can be removed from the cycle, for example, via solvent extraction or ion exchange, or by means of electrochemical processes. This can be done continuously or at longer or shorter intervals, as needed. In this context, the process according to the invention allows the Na to disappear from the global battery cycle over time.

[0031] A further aspect of the present invention is a cathode material, in particular for lithium-ion batteries, obtained according to the process of the invention, wherein the cathode material is substantially free of sodium, wherein the sodium content is preferably less than 500 ppm, more preferably less than 50 ppm, particularly preferably less than 10 ppm, in each case based on the total weight of the cathode material. Preferably, the cathode material has a transition metal stoichiometry of Nis / ioCoi / ioMni / io or Nii / sCoi / sMni / s.

[0032] The advantages of the present invention will be described in more detail with reference to the following examples and figures, which, however, are not to be understood as a limitation of the inventive concept.

[0033] Figure 1 schematically shows a preferred sequence of the process according to the invention. The spent lithium-ion batteries (LIBs) are first crushed and then mixed with a leaching agent and, if appropriate, a reducing agent to dissolve the valuable metals contained in the cathode material of the spent LIBs (cathode material precursor solution). Undesirable components such as Fe, Cu, or Al can be separated from this solution in the form of their hydroxides by adding LiOH and adjusting the appropriate pH. The separated hydroxides can then be fed into an adjacent recycling cycle. In the purified solution, the ratio of Ni, Co, and Mn to one another is monitored and, if necessary, adjusted depending on the desired stoichiometry in the subsequent active cathode material.Subsequently, the metals Ni, Co, and Mn are precipitated by adding LiOH as a precursor (cathode material precursor mixed hydroxide) and subjected to further conversion to the desired active cathode material. The filtrate obtained during precipitation (mother liquor) is separated into LiOH and leaching agent, such as sulfuric acid, using electrodialysis. The leaching agent is returned to the process, and the LiOH is partially converted to solid LiOH*H2O and partially fed back into the process cycle. The solid LiOH*H2O can, for example, be used to produce the active cathode material from the cathode material precursor mixed hydroxide, thus closing the cycle.

[0034] The present invention offers the advantage of allowing the efficient conversion of the common Nii / sCoi / sMni / s cathode material to the Ni-richer material Nis / ioCoi / ioMni / io. Tables 1 and 2 compare the inventive solution of adjustment by separation and the conventional addition method in the prior art. Table 1 illustrates the amounts of Ni, Co, and Mn that accrue from 1000 kg of common Nii / sCoi / sMni / s ("third mix") as feedstock and the amounts of Co and Mn that must be separated to achieve the new Ni-rich stoichiometry. The "excess" Co thus obtained can, for example, be processed into Co metal powder, and "excess" Mn can be passed on directly to the steel industry as Mn hydroxide or Mn oxyhydroxide.

[0035] Table 1 :

[0036] Alternatively, NiSO4 can be added to adjust the desired stoichiometry, as described in the prior art. This results in the scenario shown in Table 2, with an apparently high proportion of purchased material. Table 2:

[0037] As can be seen from Table 2, the stoichiometry adjustment is achieved by massively purchasing "virgin material" - in this case the Ni component. According to the upper estimate, the purchase of Ni thus leaves a CO2 footprint of approximately 1.5 kg CO2 per kg Ni, which is avoided by the inventive procedure.

[0038] The following illustrates the advantages achieved by using LiOH instead of NaOH.

[0039] Chlor-alkali electrolysis , ei 2 0.623 kg CO2 / kg Ni(OH)2

[0040] Chlor-alkali electrolysis currently produces approximately 60 million tons of NaOH per year worldwide, which, according to state-of-the-art technology, is also used in the production of precursors for active materials in lithium-ion batteries. This corresponds to a minimum emission of approximately 18 million tons of CO2 per year.

[0041] Li2SO4 electrodialysis A R G = 397 kJ 199 kJ / mol OH (aq) -► 1.19 kWh el / kg Ni(OH)20.584 kg CO2 / kg Ni(OH)2

[0042] Alternatively, the process according to the invention advantageously utilizes LiSCU electrodialysis. The free enthalpies indicate the minimum electrical work required. Due to overvoltages and ohmic resistances, the actual electrical work required for chlor-alkali electrolysis, for example, is approximately 50% higher. This means that the use of NaOH as a precipitant has a CO2 footprint of approximately 1 kg of CO2 per 1 kg of precursor.

[0043] Lithium sulfate electrolysis actually requires slightly less energy than chlor-alkali electrolysis. Furthermore, it is possible to further reduce the energy requirements of the electrochemical process by significantly increasing efficiency by using lithium sulfate electrodialysis via stacking of bipolar membranes.

Claims

Patent claims 1. A process for producing cathode material from battery waste, comprising the steps: a) dissolving the cathode material from comminuted battery waste by treatment 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 splitting the filtrate into LiOH and leaching agent by electrolysis; d) converting the cathode material precursor mixed hydroxide to active cathode material using at least part of the LiOH recovered in step c).

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

3. Process according to one of the preceding claims, characterized in that the cathode material used in step a) is subjected to a cleaning step before treatment with the leaching agent, said cleaning step preferably consisting of washing with water.

4. Process according to at least one of the preceding claims, characterized in that the leaching agent is a mineral acid, preferably sulfuric acid, wherein the leaching agent further comprises a reducing agent, preferably H2O2 or SO2.

5. The method according to at least one of the preceding claims, characterized in that the method further comprises a pH-dependent precipitation of the salts of Fe, Cu and / or Al from the cathode material precursor solution, wherein the pH is preferably adjusted by adding LiOH. Process according to at least one of the preceding claims, characterized in that the process further comprises a step of monitoring and, if appropriate, adjusting the cathode material precursor solution with respect to the metal stoichiometry depending on the desired composition of the cathode material to be produced. Process according to claim 6, characterized in that the adjustment is carried out by at least partially separating one or more of the constituents of the cathode material precursor solution. Process according to at least one of the preceding claims, characterized in that the cathode material precursor solution has a pH of 9 to 14, preferably 10 to 13. Process according to at least one of the preceding claims, characterized in that the filtrate is subjected to distillation before the electrolysis.Process according to at least one of the preceding claims, characterized in that electrodialysis technology is used for the electrolysis. Process according to at least one of the preceding claims, characterized in that the leaching agent recovered in step c) is at least partially used for the treatment in step a). Process according to at least one of the preceding claims, characterized in that the LiOH recovered in step c) is at least partially converted into a solid state, preferably in the form of solid LiOH *xH O and / or U CO . Process according to claim 12, characterized in that at least a portion of the LiOH converted into its solid state is used to convert the cathode material precursor mixed hydroxide to active cathode material.Process according to at least one of the preceding claims, characterized in that the LiOH used in step b) is at least partly the LiOH recovered in step c). Process according to at least one of the preceding claims, characterized in that no NaOH is used in the process. Cathode material obtained by a process according to at least one of the preceding claims, characterized in that the cathode material is essentially free of sodium, wherein the content of sodium or one of its compounds is preferably less than 500 ppm, more preferably less than 50 ppm, particularly preferably less than 10 ppm, in each case based on the total weight of the cathode material.

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