Method for producing cathode material from waste batteries

Abstract

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

Description

[0001] The present invention relates to a method for producing cathode material from spent batteries, and to a cathode material obtained by the method according to the invention.

[0002] The transport transition or mobility transition refers to the social, technological and political process of changing transport and mobility towards sustainable energy sources, gentle mobility and networks of different forms of personal mobility and local public transport. A core of the mobility transition is the so-called drive transition, which involves the gradual replacement of internal combustion engines with hydrogen-driven, fuel cell-driven or battery-electric engines.

[0003] The stated and most important goal of the mobility transition is to protect the climate and the environment. To achieve this goal, it is necessary not only to reduce CO 2 Emissions, and efficient closed-loop systems are also needed to avoid the threat of environmental pollution and raw material shortages in the production of battery-electric drive alternatives.

[0004] In the field of battery electric drives, lithium-ion batteries (LIBs) have proven in particular to be a promising storage system for the required electrical energy. However, the declared goals of the motor vehicle transition cannot be achieved without a parallel and rational global recycling strategy for such batteries. Therefore, comprehensive recovery of valuable metals such as cobalt, nickel and manganese, especially lithium, contained in spent battery materials is of vital importance. The primary production of lithium from brine using solar energy initially seemed ecologically compatible, but current production is associated with a significant intervention in the water balance of the regions concerned. According to studies, the specific amount of fresh water consumed per kilogram of lithium extracted is estimated to be about 44 liters. Even if the global lithium reserves are estimated to be relatively high, they are also limited and the primary production process described is also lengthy. A quantitative and rapid recovery of lithium and other precious metals cobalt, nickel and manganese to produce new cathode active materials (CAM) is in any case preferred through sustainable recovery. Initial efforts at sustainable recycling cycles are described in the prior art.

[0005] Therefore, US 2013 / 0302226 describes a method for recycling batteries, which comprises: producing a solution of battery materials from spent batteries; precipitating impurities from the produced solution; adjusting the solution to achieve a predetermined proportion of desired materials; and precipitating the desired materials in the predetermined proportion to form a cathode material for a new battery having the predetermined proportion of the desired transition metal.

[0006] US 2017 / 0077564 relates to a method for recycling lithium-ion batteries, comprising: determining a molar ratio of cathode material for a new battery; mixing pulverized battery material from a lithium battery recycling stream with an acidic leaching agent and hydrogen peroxide (H 2 O 2) to form a leachate, thereby separating the cathode material from the undissolved material; filtering the undissolved material from the formed leachate so that the dissolved salt of the cathode material remains in the leachate; determining the composition of the leachate by determining the molar ratio of the salt of the cathode material dissolved therein; adding sulfate (xSO) as hydroxide (xOH) based on the determined composition. 4 ) of the Ni salt, Co salt, Mn salt or Al salt to adjust the molar ratio of the salt of the cathode material dissolved in the leachate to correspond to the molar ratio of the determined recovery battery, including adding aluminum sulfate solution and chelating agent; and raising the pH of the leachate to at least 10 by converting the remaining Ni salt, Co salt, Mn salt and Al salt in the alkali solution into composite hydroxide (OH) at a molar ratio equal to the determined recovery battery 2 or complex carbonate (CO 3 ) to precipitate and filter out the metal ions of the cathode material to form a charging material precursor, wherein the charging precursor material is used in the reaction mixture with lithium carbonate (Li 2 CO 3 ) after sintering, an active cathode material in the form of an oxide is formed in response to sintering. It should be emphasized that all pH adjustments, and in particular the precipitation of the precursors, are performed by adding NaOH.

[0007] The methods proposed in the prior art attempt to avoid the separation and energy-consuming conversion of transition metals into their solid sulfates as much as possible, and to convert the resulting solid sulfates into Ni sulfate / Co sulfate / Mn sulfate and Li sulfate after adjusting the transition metal stoichiometry. 2 SO 4 The mixed solution is directly used to precipitate the cathode precursor. However, in the conventional method, by adding Na 2 CO 3 Insoluble Li 2 CO 3 The recovery of lithium in the form of carbonates is a process which involves the further production of neutral salts in addition to the neutral salt load resulting from the precipitation of the precursors. In summary, therefore, it can be considered that the amount of lithium recovered per mole of LiMO is 200 tantalum, which is 1 tantalum. The recovery of lithium in the form of carbonates is a process which involves the further production of neutral salts in addition to the neutral salt load resulting from the precipitation of the precursors. 2 At least 1.5 mol of Na 2 SO 4 Therefore, there remains a need for methods that can efficiently and quantitatively recover cathode materials from lithium-ion batteries that are no longer in use.

[0008] The present invention addresses this need by unexpectedly discovering that cathode materials can be produced from battery waste entirely based on lithium hydroxide (LiOH) rather than sodium hydroxide (NaOH), which avoids the neutral salt waste that is typically present and allows the production of a low-sodium product or a sodium-free product without increasing the actual demand for LiOH.

[0009] Therefore, the present invention firstly relates to a method for producing cathode material from spent batteries, comprising the following steps:

[0010] a) dissolving cathode material from pulverized battery waste by treating it with a leaching agent to obtain a cathode material precursor solution;

[0011] b) treating the cathode material precursor solution with LiOH to obtain a filtrate of a solid cathode material precursor mixed hydroxide and at least a Li salt containing the leaching agent;

[0012] c) separating the filtrate obtained in step b) by electrolysis to separate the filtrate into LiOH and a leaching agent;

[0013] d) converting the cathode material precursor mixed hydroxide into an active cathode material using at least part of the LiOH recovered in step c).

[0014] In the context of the present invention, it was unexpectedly found that by using LiOH, not only can the amount of neutral salt waste be reduced, but also the CO 2 footprint, although LiOH is generally not preferred for use due to its high cost.

[0015] In the process according to the invention, transition metals contained in the cathode material of the waste lithium-ion battery, in particular Ni, Co and Mn, are converted into salts in soluble form in a cathode material precursor solution by treatment with a leaching agent. Then, by adding LiOH, the transition metals are precipitated from the solution in the form of a solid mixed hydroxide, optionally after pre-cleaning and / or partial separation, which forms the precursor of the subsequent active cathode material. The lithium salt of the leaching agent is obtained in the form of a filtrate, which is converted back to LiOH and a leaching agent by electrolysis. The transition metal mixed hydroxide obtained in the process according to the invention is further converted into an active cathode material, which can then be used to produce lithium-ion batteries, thereby closing the recycling cycle.

[0016] As part of the method according to the invention, spent lithium-ion batteries are used in particular as battery waste, in particular as cathode material thereof. The cathode material is in particular selected from the group consisting of LiMO 2Layered structure, wherein preferably M=Ni, Co and / or Mn and / or Al, in particular LiCo oxide (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 LiM 2 O 4 Spinel structure, where preferably M = Ni, Co and / or Mn, optionally doped with Al or any mixture.

[0017] In a preferred embodiment, the cathode material used contains Ni and Co, preferably Mn and / or Al.

[0018] Before using the method according to the invention, the cathode material may be subjected to a cleaning step to remove organic solvents and electrolyte residues, such as LiPF 6 Therefore, in a preferred embodiment, the method according to the invention comprises a step of cleaning the cathode material to be used. Preferably, this cleaning step consists of washing the cathode material with water.

[0019] In a preferred embodiment, the leaching agent is an inorganic acid, preferably sulfuric acid. In a further preferred embodiment, a reducing agent is added to the leaching agent, and the reducing agent is preferably H 2 O 2 or SO 2 .

[0020] The cathode material obtained from 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 a leaching agent and are therefore present in the cathode material precursor solution. In this case, it is beneficial to perform a pre-cleaning. Therefore, in a preferred embodiment, the method according to the present invention also includes pH-dependent precipitation of at least one of Fe salts, Cu salts and Al salts from the cathode material precursor solution. Compared with the conventional method of precipitating metals by adding NaOH, the precipitation in the method according to the present invention is preferably carried out by adding LiOH. Alternatively, impurities can also 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 which pre-cleaning method is selected, sodium should be avoided from entering the method cycle.

[0021] Precipitating a cathode material precursor mixed hydroxide Ni from a cathode material precursor solution x Co y Mn z (OH) 2, optionally after removing Fe, Cu and / or Al, the precipitation is carried out, the cathode material precursor is mixed with hydroxide Ni x Co y Mn z (OH) 2 As a basis for the preparation of active cathode materials. The advantage of this method is that there is no need for complex complete separation and separate crystallization of individual transition metal salts. Contrary to what is described in some prior art methods, in the method according to the invention, lithium is not precipitated together with the transition metal salt, but remains in solution.

[0022] The transition metals are present in the active cathode material (CAM) in a certain ratio relative to each other, which, together with other factors, determines the performance of the battery. This ratio of transition metals is usually achieved by appropriate adjustment of the cathode material precursors.

[0023] Therefore, in a preferred embodiment, the method according to the present invention also includes a step of controlling and optionally adjusting the metal stoichiometry, preferably a step of controlling and optionally adjusting the metal stoichiometry of the cathode material precursor solution, according to the desired composition of the active cathode material to be produced.

[0024] The metal stoichiometry is usually adjusted by adding the corresponding one or more components, with the disadvantage that sometimes large amounts of "new" material, usually in the form of solid sulfates, must be used, as described, for example, in US 2017 / 0077564. During the crystallization of the sulfates, evaporation of water consumes a lot of energy, which in the case of nickel results in 10000 CO2 / kg of nickel. 2 The footprint is about 1.5 kg CO 2 However, to protect the climate, any unnecessary CO 2 produce.

[0025] In the context of the present invention, it was unexpectedly found that adjustments can be made by targeted separation, thereby avoiding the use of additional materials and the associated disadvantages. Therefore, in a preferred embodiment, the adjustment is made by at least partially separating out one or more 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. Current cathode materials, in which Ni, Co and Mn are present in the cathode material in a ratio of 1:1:1, are being transformed into nickel-rich materials in which transition metals are present, for example in which the ratio of Ni:Co:Mn is 8:1:1, and this method is particularly advantageous in this regard, otherwise a large amount of nickel needs to be added to achieve this ratio.

[0026] The method according to the invention provides for obtaining a solid cathode material precursor mixed hydroxide and a filtrate containing at least a Li salt of a leaching agent from a cathode material precursor solution by treating with LiOH. In a preferred embodiment, the treatment is carried out in such a way that the cathode material precursor precipitates at a pH of 9 to 14, preferably at a pH of 10 to 13. The pH information refers to the operating temperature. In order to carry out the precipitation in a controlled manner and obtain spherical particles, NH 3 , the NH 3 The concentration of is preferably 1 g / L to 17 g / L, preferably 5 g / L to 15 g / L, and particularly preferably 8 g / L to 12 g / L. The precipitation can be carried out at room temperature, but is preferably carried out at a temperature of 20°C to 80°C, particularly preferably at a temperature of 40°C to 65°C.

[0027] In step c) of the process according to the invention, the filtrate obtained in step b) is separated into LiOH and the corresponding leaching agent by means of electrolysis, so that the leaching agent used in step a) can be recovered. In a preferred embodiment, electrodialysis technology is used for the electrolysis. In a particularly preferred embodiment, bipolar membranes are also used for the electrolysis, which means that a significant increase in the space / time yield can be achieved.

[0028] As mentioned above, the filtrate obtained in step b) of the process according to the invention may contain NH 3 Therefore, for purification purposes, the filtrate may be distilled before electrolysis.

[0029] The method according to the invention aims at providing a closed circuit.Thus, in a preferred embodiment, the leaching agent obtained in step c) is at least partly used for the treatment of the cathode material in step a) of the method according to the invention.

[0030] In a particularly preferred embodiment, the LiOH obtained in step c) of the process according to the invention is at least partly used for treating the cathode material precursor solution in step b).

[0031] 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 into solid LiOH*H 2 O and / or Li 2 CO 3 This can be advantageously used in other processes of the method. 2 Treatment of LiOH advantageously proceeds to Li 2 CO 3 conversion.

[0032] Step d) of the process according to the invention provides for converting the obtained cathode material precursor mixed hydroxide into an active cathode material, at least partly using the LiOH recovered in step c). In a preferred embodiment, by reacting with solid LiOH*H 2 O or Li 2 CO 3 React to react.

[0033] In a preferred embodiment, the LiOH converted into its solid state from step c) of the process according to the invention is at least partly used for the conversion of the cathode material precursor mixed hydroxide into active cathode material, thus closing a further gap in the circuit.

[0034] In contrast to conventional prior art processes, the process according to the invention relies on LiOH. Therefore, in a preferred embodiment, no NaOH is used in the process. On the one hand, this avoids the neutral salt waste that would otherwise be generated, and on the other hand, the electrical energy required for recovering LiOH by electrolysis is slightly lower than for producing NaOH by conventional chlor-alkali electrolysis, which in turn has a positive effect on CO 2 If NaOH is used, the neutral salt Na 2 SO 4 If the LiOH has to be crystallized out by evaporation of water, the energy advantage of the entire method will be higher, because it cannot be released directly into the environment, depending on the location. The present method not only does not have this energy disadvantage, but is also very flexible in terms of location. In addition, the amount of LiOH produced is used again to produce cathode precursor materials, so only very small amounts of LiOH actually need to be present in the recycling company's cycle.

[0035] The method according to the invention makes it possible to use the cathode material to be recovered as the sole source of Na input. The amount of sodium introduced can be removed from the circulation process, for example by solvent extraction or ion exchangers, or an electrochemical process can also be used. Depending on the needs, this can be done continuously, or can be done at intervals of varying lengths. In this case, the method according to the invention allows Na to disappear from the entire battery circuit over time.

[0036] A further aspect of the present invention is a cathode material obtained by the process according to the invention, in particular a cathode material for a lithium ion battery, wherein the cathode material is substantially free of sodium, wherein the sodium content is preferably less than 500 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, each based on the total weight of the cathode material. The cathode material preferably has Ni 8 / 10 Co 1 / 10 Mn 1 / 10 or Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The stoichiometry of the transition metals.

[0037] The advantages of the present invention should be explained by the following embodiments and drawings, however, these embodiments and drawings should not be understood as limiting the idea of ​​the present invention.

[0038] Figure 1 The preferred process of the method according to the present invention is schematically shown. The spent lithium-ion battery (LIB) is first crushed and then mixed with a leaching agent and, if necessary, a reducing agent to convert the valuable metals contained in the cathode material of the spent LIB into a solution (cathode material precursor solution). By adding LiOH and adjusting the appropriate pH value, undesirable components such as Fe, Cu or Al can be separated from the solution in the form of their hydroxides. The separated hydroxide can then be sent to an adjacent recovery cycle. In the purified solution, the ratio of Ni, Co and Mn to each other is controlled and, if necessary, adjusted according to the stoichiometry in the desired subsequent active cathode material. The metals Ni, Co and Mn are then precipitated by adding LiOH as a precursor (cathode material precursor composite hydroxide) and further converted into the desired active cathode material. The filtrate (mother liquor) obtained during the precipitation process is separated back into LiOH and a leaching agent, such as sulfuric acid, by electrodialysis. The leaching agent is returned to the method, and the LiOH portion is converted into solid LiOH*H 2 O, part of which is returned to the process cycle. For example, solid LiOH*H 2 O can be used to produce active cathode materials from cathode material precursor mixed hydroxides, thus completing the cycle.

[0039] The advantage of the present invention is that it allows the common Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The cathode material is effectively converted into a more Ni-rich material Ni 8 / 10 Co 1 / 10 Mn 1 / 10 Tables 1 and 2 compare the scheme of adjusting by separation of the present invention and the common addition method in the prior art. Table 1 shows that as 1000 kg of common Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The amount of Ni, Co and Mn produced from the raw materials ("mix of thirds") and the amount of Co and Mn that needs to be separated off to reach the new nickel-rich stoichiometry. For example, the "excess" Co obtained in this way can be processed into Co metal powder, while the "excess" Mn can be directly transferred to the steel industry as manganese hydroxide or manganese hydroxyhydroxide.

[0040] Table 1:

[0041]

[0042] Alternatively, NiSO 4 To adjust the desired stoichiometry, as described in the prior art. This leads to the situation shown in Table 2, where the proportion of purchased goods is significantly higher.

[0043] Table 2:

[0044]

[0045] As can be seen in Table 2, the stoichiometric setting is achieved by purchasing large quantities of “raw materials”, in this case the Ni component. According to an upper limit estimate, the purchase of Ni leaves about 1.5 kg CO per kg Ni. 2 CO 2 footprint, which can be avoided by the method according to the invention.

[0046] The advantages gained by using LiOH instead of NaOH are explained below.

[0047] Chlor-alkali electrolysis

[0048]

[0049]

[0050] Currently, chlor-alkali electrolysis produces around 60 million tons of NaOH per year worldwide, which is also used to produce precursors for active materials in lithium-ion batteries according to existing technology. This corresponds to a minimum of around 18 million tons of CO per year. 2 emissions.

[0051] Li 2 SO 4 Electrodialysis

[0052]

[0053]

[0054] Alternatively, it is advantageous to provide Li 2 SO 4 Electrodialysis is used as part of the process according to the invention. The Gibbs free energy refers to the minimum electrical work that must be done. Due to the overvoltage and the ohmic resistance, the actual electrical work required, for example for chlor-alkali electrolysis, is about 50% higher. This means that for 1 kg of precursor, using NaOH as a precipitant, approximately 1 kg of CO 2 CO 2 Footprints.

[0055] Lithium sulfate electrolysis requires even slightly less energy than chlor-alkali electrolysis. When using lithium sulfate electrodialysis, the energy requirements of the electrochemical process can be further reduced by stacking bipolar membranes to significantly increase efficiency.

Claims

1. A method for producing cathode material from waste batteries, comprising the following steps: a) dissolving cathode material from pulverized 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 filtrate of a solid cathode material precursor mixed hydroxide and at least a Li salt of a leaching agent; c) separating the filtrate obtained in step b) and separating the filtrate into LiOH and a leaching agent using electrolysis; d) converting the cathode material precursor mixed hydroxide into an active cathode material using at least part of the LiOH recovered in step c).

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

3. The method according to any one of the preceding claims, characterized in that Before the treatment with the leaching agent, the cathode material used in step a) is subjected to a cleaning step which preferably consists of washing with water.

4. The method according to at least one of the preceding claims, characterized in that The leaching agent is an inorganic acid, preferably sulfuric acid, wherein the leaching agent further comprises a reducing agent, preferably the reducing agent is 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 Fe, Cu and / or Al salts from the cathode material precursor solution, wherein the pH is preferably adjusted by adding LiOH.

6. The method according to at least one of the preceding claims, characterized in that The method further comprises the step of controlling and optionally adjusting the cathode material precursor solution with respect to the metal stoichiometry, depending on the desired composition of the cathode material to be produced.

7. The method according to claim 6, characterized in that The adjustment is performed by at least partially separating one or more than one components of the cathode material precursor solution.

8. The method according to at least one of the preceding claims, characterized in that The pH value of the cathode material precursor solution is 9 to 14, preferably 10 to 13.

9. The method according to at least one of the preceding claims, characterized in that The filtrate was distilled prior to electrolysis.

10. The method according to at least one of the preceding claims, characterized in that The electrolysis is carried out using electrodialysis technology.

11. The method according to at least one of the preceding claims, characterized in that The leaching agent recovered in step c) is at least partly used for the treatment in step a).

12. The method according to at least one of the preceding claims, characterized in that The LiOH obtained in step c) is at least partially converted into a solid state, preferably in the form of solid LiOH*H2O and / or Li2CO3.

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

14. The method 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).

15. The method according to at least one of the preceding claims, characterized in that No NaOH was used in the process.

16. A cathode material obtained by the method according to at least one of the preceding claims, characterized in that The cathode material is substantially free of sodium, wherein the content of sodium or one of its compounds is preferably less than 500 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, each based on the total weight of the cathode material.

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