EP4400616A2 - Multi-stage recycling process - Google Patents

Abstract

The present invention relates to a method for treating components. More specifically, it is a recycling process which is particularly suitable for recovering raw materials from batteries and accumulators, but also from strong magnets and fuel cells. In particular, it is a method for recovering raw materials from components which contain at least cobalt and nickel, the method comprising the following steps: - mechanical treatment of the components - chemical treatment of the components in a solution, whereby the components are at least partially decomposed - treatment of the cobalt ions with chloride ions to form complexes - electrochemical extraction of cobalt from the solution - electrochemical extraction of nickel from the solution

Description

Field of the invention

The present invention relates to a method for treating components. More specifically, it is a recycling process that is particularly suitable for recovering raw materials from batteries and accumulators, but also from strong magnets and fuel cells.

Background of the invention

In view of rising raw material prices and also ecological advantages, the recycling of used components is becoming increasingly relevant.

The US Patent Application 2013/0206607 A1 discloses a process for recovering lithium from lithium-ion batteries. The battery material is placed in an acid bath at 50 °C.

The European Patent 3 279 343 B1 discloses a method for recovering copper from lithium-ion batteries. The process involves recovering copper by leaching with an acidic solution and then separating it from the solution.

The two processes described are very specific. They do not reveal a complete closed recycling process in which several raw materials can be systematically recovered. The processes also do not give rise to the expectation that raw materials can be recovered in high purity.

The recycling process according to the invention aims to achieve complete recycling, both in terms of the number of recovered raw materials and in terms of their quality. The process should be suitable for batteries but also for other components which contain significant amounts of rare earths in particular.

More detailed description

The recycling process according to the invention comprises a large number of individual process steps. The process stands out from other processes in that a particularly high raw material recovery rate can be achieved. For example, a rate of more than 97% (wt. %) of the material supplied can be recovered as raw material that can be further processed. In addition, it is relevant that a very high degree of purity can be achieved, in individual cases also a degree of purity of more than 97%, more than 98%, more than 99%, more than 99.5%, more than 99.7 or even more than 99.9 or 99.95% or 99.98 or 99.99%.

This particular efficiency of the process depends on the consistent combination of all process steps described in more detail below. This also results in synergies between the various process steps. These synergies are usually obvious to the person skilled in the art, but are also addressed in many cases below.

Physical process steps

The first steps of the process can be summarized as physical process steps. These physical process steps include in particular the physical raw material preparation, the discharge of charged cells and physical separation processes, in particular the comminution of the raw materials.

The present process is particularly suitable for components that contain metal salts from which metals can be recovered in the course of this process. In particular, lithium (Li), cobalt (Co), nickel (Ni) and manganese can be recovered from the corresponding metal salts. (Mn). The components can have various compounds with the mentioned and other metals or metal salts, whereby the term metal compound herein also includes the metal itself.

The materials to be recycled can be, for example, components from fuel cells or rechargeable batteries or magnets. The recycling of magnets is particularly interesting with regard to their use in electric car engines or wind turbine generators. Strong magnets - and in particular strong magnets that contain rare earths - are a focus here. Rechargeable batteries are often referred to as accumulators, but the word battery and accumulator are used interchangeably here.

Larger batteries, such as automotive batteries, comprise a large number (more than 100 or typically more than 1,000) of individual battery cells, for example in the form of lithium-ion cells. The individual cells typically have a voltage of 1-5 V and are combined into modules, which in turn have a voltage of 5 V-80 V. These modules in turn form systems, which can have a voltage of 80 V-800 V. Such a system can represent the essential element of an automotive battery.

If batteries are recycled in this process, it can be assumed that they have a residual charge. In preparation for the next steps in the process, the batteries must be discharged as completely as possible. Devices with an AC/DC inverter are usually used for this purpose. Discharge protocols are usually also created during the discharge. It is useful if the residual energy that was stored in the batteries is recovered and fed back into the grid.

Alternatively or in addition, a saline solution discharge can also be used. The saline solution creates a short circuit between the battery poles. This can involve using saline solutions that have such low conductivity that a sudden short-circuit discharge is impossible. As a rule, a solution, preferably a 6% by weight solution, of NaHCOs and Na ₂ CO ₃ is used.

For an automotive battery, an early step is disassembly (usually the first step after discharge). This disassembly can be done manually and destructively, for example with angle grinders or chisels. This also separates easily distinguishable components, such as lithium-ion cells and housings and wiring elements or electronic components.

The mechanical treatment may also include dismantling the components with a water jet.

The physical separation process includes a crushing step as an essential step. In this process, the components, which are usually pre-crushed manually, are further crushed under high mechanical pressure. In addition to the pressure forces, shear and tear forces can also act, for example if a working surface (e.g. a roller surface) is provided with corresponding structures (e.g. with teeth).

The mechanical separation process is also called shredding. Known shredding devices can be used.

A four-shaft shredding machine is useful. Screening devices can be arranged under this machine. This means that the components are not only shredded into particle sizes of less than 10 mm, but different particle sizes can also be sorted. For example, sorting can be carried out for particle sizes from 5 mm to 0.5 mm. The mechanical separation process should in any case be suitable for producing particles with diameters of less than 10 mm, but also individual particles with diameters of less than 1 mm.

Mechanical shredding should generally be carried out under protective gas, such as nitrogen or argon. The residual energy possibly contained in batteries can pose a fire or explosion hazard.

It is also advisable to cool the batteries down considerably before applying the physical separation process, for example by deactivating the batteries in liquid nitrogen for one hour. This leads to an even more complete discharge and also allows the battery to be crushed more easily.

During physical separation, electrolyte is usually released from the batteries. For example, anhydrous aprotic solvents are used in lithium-ion batteries. These solvents are purified by distillation.

In another physical separation process, a magnetic separation into ferrous and non-ferrous metals is carried out. A magnetic separator is used for this. The separator works with gravity. Powdery material can fall downwards due to gravity, for example through a grid. In the falling particle stream, however, iron particles are deflected and separated by a strong magnetic field. Such a strong magnetic field can be effectively generated with neodymium magnets. The magnets can also be used to collect the ferrous metals.

In the next step of the physical separation, air flow separation can be used. Gravity also acts in this separation process. Against the direction of gravity - i.e. from below -air is blown in. Heavy parts fall downwards against the air flow, light parts are carried upwards by the air flow. This makes it possible to separate the particles into a light and a heavy fraction. The separation depends on the particle size and the material density. For example, copper and aluminum are easy to separate because of their very different material densities (copper 8.96 g/cm ³ , whereas aluminum 2.7 g/cm ³ ). Metals with similar material densities can often be separated easily because they are in different forms, for example copper is typically present as a metal foil and cobalt is present as a cobalt oxide salt.

Chemical treatment and separation Chemical digestion:

After the raw materials have been mechanically crushed and converted into particles, these particles are further broken down chemically. An acid, especially diluted sulfuric acid, is used for this purpose. The particles are then converted into (sulfuric acid) solution. This solution, including the particles, is subsequently referred to as the solution. The particles are often referred to as "black mass" when they essentially comprise the cathode material of lithium-ion batteries. The chemical treatment is preferably carried out in a temperature range of 60 to 80°C, particularly conveniently at around 70°C.

This decomposition process can be controlled by adding potassium permanganate. Potassium permanganate is used as an oxidizing agent to decompose the metal ions and transfers them into solution. There, further chemical and electrochemical treatment is easily possible.

In the digestion step, metal sulfates are formed from salts, especially Li, Ni, Mn and Co.

Chemical separation of metal sulfates:

Different metal sulfates can be separated from the solution in specific reactions, usually this is done by precipitation. The individual reactions can run in parallel or one after the other. In addition to the reactions listed here for specific metals, other reactions can be used depending on the raw material used.

Precipitation of cobalt: The precipitation of cobalt from the sulfate solution can be conveniently carried out using sodium hydroxide solution. The reaction sequence is as follows:

2NaOH + CoSO ₄ = Co(OH) ₂ + Na ₂ SO ₄

This produces cobalt(II) hydroxide.

Precipitation of nickel: The precipitation of nickel from the sulfate solution can conveniently be carried out with multidentate ligands, for example with diacetyldioxime or with butanedione dioxime.

Separation of cobalt from nickel-containing sulfate solution: Separation of cobalt with Cyanex 272 (trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate) is particularly useful when a nickel-containing sulfate solution is present. Simultaneous electrolysis of cobalt and nickel is practically impossible, since their standard potentials hardly differ (-0.226 volts for nickel and -0.280 volts for cobalt).

However, pretreatment with Cyanex 272 makes it possible for practically only cobalt to be extracted from the sulfate solution and the extraction of nickel to remain negligible. Nickel can then be extracted electrochemically in a separate step.

As described below, it is also possible to electrochemically deposit several metal ions, in particular Ni-Co and Mn ions, simultaneously.

Separation of manganese: Manganese can be separated from the (sulfate) solution better through a synproportionation reaction than through precipitation. This takes advantage of the fact that manganese can exist in many different oxidation states. It is useful if a simultaneous reduction and oxidation of manganese from a higher and a lower oxidation state takes place. In this process, manganese dioxide (MnO ₂ ) is formed starting from the intermediate tetravalent oxidation state.

In summary, the reaction looks like this:

2MnO ₄ ^- + 3Mn ²⁺ + 4OH ^- = 5MnO ₂ + 2H ₂ O

Electrochemical separation processes

At the end of the chemical treatment, the raw materials are typically in the form of a metal salt containing the metal to be deposited. As described, this is particularly true for Co, Ni and Mn.

The metal can be extracted from the corresponding metal salts by electrolysis, usually by reducing the metal cation to the elemental metal at the cathode.

The corresponding electrolysis reactions for Co and Ni are as follows:

Ni ²⁺ + 2e ^- = Ni E°= - 0.226 V

Co ²⁺ + 2e ^- = Co E ⁰ = - 0.28 V

Anode reaction:

2H ₂ O =O ₂ +4H ⁺ + 4e- E°= - 1.23 V

In addition to the reactions, the standard potential for each reaction is also given. As can be seen, the standard potential for nickel and cobalt is very similar. It is therefore not possible to separate nickel and cobalt from a mixed sulfate solution at the same time. With such a mixed sulfate solution, it is advisable to carry out electrolysis only after chemical pretreatment. This pretreatment can be carried out using Cyanex 272. After this pretreatment, cobalt can be extracted from the sulfate solution. Nickel can then be extracted electrochemically in a further separate step.

Simultaneous electrolysis of nickel and manganese dioxide: It has proven to be particularly advantageous if nickel and manganese dioxide are deposited simultaneously.

In such a double reaction, nickel is deposited reductively on the cathode (as described above). However, manganese dioxide can be deposited simultaneously by oxidation on the anode. This happens when divalent manganese ions are oxidized to trivalent manganese ions. These in turn decompose into divalent and tetravalent manganese ions. From these, manganese dioxide is formed, which is then deposited on the anode.

With the following electrochemical parameters, both the anode reaction and the cathode reaction can proceed optimally: 3 volts voltage, 250 amperes/m ² current density. Temperature of approximately 50°C.

It is also possible to electrochemically deposit Ni, Co and Mn ions simultaneously. A chemical post-treatment is then required to separate the metals. The cobalt and nickel deposited on the cathode are dissolved in hydrochloric acid. The divalent ions can be chemically deposited from this hydrochloric acid solution by complex formation with Cyanex 272 for cobalt and diacetyldioxime for nickel.

Treatment and precipitation of lithium ions: After the reactions described, lithium ions typically still remain in the (sulfate) solution. These lithium ions can first be chemically precipitated from the solution with sodium carbonate (Na ₂ CO ₃ ) as lithium carbonate (Li ₂ CO ₃ ):

Na ₂ CO ₃ + Li ₂ SO ₄ = Li ₂ CO ₃ + Na ₂ SO ₄

The lithium carbonate can then be purified by recrystallization. Lithium carbonate can then be dissolved in an aprotic solvent (an ionic liquid) and electrochemically deposited as lithium metal.

In further reaction steps, rare earth metals can be separated. This is particularly relevant for the recycling of neodymium, for example from neodymium magnets (such magnets are also often used in wind turbines).

Precipitation of rare earth elements: In addition to metal sulfates, the solution usually contains rare earth elements, and neodymium is used in particular in components to be recycled. For example, the recycling of neodymium-iron-boron magnets is considered. In a first step, two components are added to the sulfate solution with a mixture of metal, semi-metal and rare earth ions: sulfuric acid and sodium hydroxide. It is advisable to use 200 ml of sulfuric acid (concentration 150 g/l) and 665 ml of sodium hydroxide solution (concentration 200 g/l) for 1,000 ml of original solution (sulfate solution). The chemical precipitation takes place thus in a ratio of 2:1:1 milliliter of original solution to milliliter of sulfuric acid to milliliter of NaOH.

In order to achieve precipitation of the rare earths, the pH value must be increased to 2. The addition of sodium sulfate before increasing the pH value is necessary in order to be able to precipitate the rare earths as double sulfate despite leaching with sodium hydroxide solution.

An organic phase is added to this aqueous solution for extraction; this organic phase consists of a solvent and an organic complexing agent. Kerosene is a suitable solvent. Tri-n-butyl phosphate (TBA) can be used as a complexing agent, particularly for the separation of light rare earth metals, and various ethylhexyl phosphoric acid esters (HDEHP, EHEHPA) can be used for heavier rare earths.

The solution obtained in this way is mixed in a mixing system (shaken funnel) by vigorous stirring. The subsequent demixing of the aqueous and organic phases allows these phases to be separated. In a next step, the organic phase is washed out with an aqueous solution. In this way, an aqueous solution with a single rare earth element, e.g. neodymium, is obtained.

This solution with a rare earth element can be subjected to a precipitation reaction, for example by adding oxalic acid. This produces a rare earth oxalate. The rare earth oxalate can in turn easily be converted into a rare earth oxide. Rare earth oxides are common commercial products. The conversion takes place by calcination at approx. 800°C in air with the release of CO ₂ .

Electrochemical separation processes in ionic liquid

Ionic liquids allow the application of separation processes for a range of valuable substances that are typically dissolved in the (sulfate) solution. For example, it is also possible to obtain neodymium through an electrochemical separation process instead of through precipitation reactions.

An ionic liquid is understood here to be an ionically structured aprotic compound with a melting point of less than 100°C. Preferably, the melting point is even below 25°C, so that the ionic liquid is generally in liquid form at room temperature. Such ionic liquids are also referred to as RTIL (or Room Temperature Ionic Liquids ). Depending on the substance to be dissolved, a different ionic liquid is appropriate. In the context of this invention, the metal deposition is generally carried out on an aluminum/titanium cathode and a platinum anode.

Electrochemical deposition of neodymium: Neodymium deposition is conveniently carried out in a phosphonium-based ionic liquid at a potential of Nd ^{3+ /} ND of -2.431 volts vs. platinum. A suitable ionic liquid is trihexyltetradecylphosphonium chloride.

Electrochemical lithium deposition: This is carried out with a piperidinium-based ionic liquid at a potential of -2.3 volts relative to the platinum anode.

Electrochemical dysprosium deposition: This deposition is conveniently carried out using a guanidinium-based ionic liquid on an aluminum sheet. A potential of -0.7 volts (or less than -0.8 volts...) is applied to the platinum anode. Reduction of Dy(III) to Dy(0) occurs here via a single reaction step.

Electrochemical deposition of gold, platinum and ruthenium: The metals are dissolved in an ionic liquid, with iron sulfate and/or zinc sulfate added as a reducing agent. This is best done at a temperature of 70°C.

The preferred procedure is as follows: platinum, gold and/or ruthenium are dissolved in an ionic liquid (preferably: 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide) in the presence of FeSO ₄ or ZnSO ₄ solution as a reducing agent at a temperature of 70°C. The dissolved divalent noble metal ions are electrochemically reduced to the elemental metal at reduction potentials of platinum, gold and ruthenium at 1.20 V, 1.40 V or 0.45 V on a carrier electrode (aluminum/titanium sheet).

Electrochemical cleaning of graphite:

The solution can also contain graphite. The process according to the invention can also comprise the chemical and/or electrochemical cleaning of graphite. In particular, aluminum and copper contamination can be removed.

The chemical reactions (precipitations) and electrochemical reactions described leave small amounts of metal ions (Li, Co, Mn, Ni, Al) in the solution. These can be electrochemically dialyzed in a neutralization system with a heavy metal separator.

In Fig.1 A diagram shows an example of a process for extracting raw materials. The process begins with a few, essentially physical steps for raw material preparation, shown in field 10. In a first step 12, the raw materials are shredded. In addition to manual preparation, a shredder is mainly used. This delivers a raw material powder, which is collected in a container 14. Before shredding, the charged components are usually unloaded.

When batteries, such as lithium-ion batteries, are shredded, the electrolyte fluid they contain is collected. The electrolyte fluid of lithium-ion batteries typically consists of anhydrous, aprotic solvents and a conductive salt, usually lithium hexafluorophosphate.

The conductive salt adheres to the raw material powder, so that the addition of an organic solvent (e.g. acetonitrile) can be provided to wash out the conductive salt.

For this purpose, a mixing container for powder and solvent 16 is provided. It is supplemented by a solvent storage container 16A. Extracted electrolyte can be collected in a container 18.

The powdered raw materials prepared in this way are physically separated in further process steps. This takes place in the process units in frame 20.

In particular, a magnetic separation 22 takes place first, in which iron powder is separated from the powder and collected in the container 24. The material is then subjected to an air flow separation 26. In this process, aluminum and copper components are separated. These can then be collected in suitable containers, such as a Container 28A for aluminum powder and a container 28B for copper powder. After this process step 26, the black mass 30 is obtained from the starting material for the further process steps.

This black mass 30 is mixed with other substances in the mixing system 42, especially with sulphuric acid. In addition to sulphuric acid, oxidizing agents can also be added, such as hydrogen peroxide and potassium permanganate. The corresponding substances are provided in suitable containers, for example container 42.

After the black powder has been prepared in the mixing plant, it is transferred to an electrolysis unit 50. Nickel and manganese dioxide electrolysis in particular can take place here.

Hydrogen is usually produced during this electrolysis. This hydrogen can be discharged via a pipe and reused in a suitable manner. A cost-effective reuse can take place in a combined heat and power plant 52. In this way, the plant can be operated completely or at least partially in an energy-self-sufficient manner.

In area 60, suitable wet chemical process steps are carried out. It is advisable to extract cobalt or a cobalt compound, then extract manganese or a manganese compound and then extract lithium or a lithium compound.

In particular, a substance can be added to the remaining mass from the storage container 62, which allows the recovery of cobalt (II) hydroxide in the container 64. A suitable substance is sodium hydroxide.

In particular, a substance can be added to the remaining mass from the storage container 66, which allows the extraction of manganese dioxide in the container 68. A suitable substance is potassium permanganate.

In particular, a substance can be added to the remaining mass from the storage container 70, which allows the extraction of lithium carbonate in the container 72. A suitable substance is sodium carbonate.

At the end of these process steps, the added raw materials are almost completely recovered. In a final process step, the residual material is transferred to a neutralization system 80 in which acids and alkalis are neutralized. Advantageously, this also rejects a heavy metal separator.

Pure process water can be obtained from the neutralization system 80 and collected in the container 82. The collected process water can also be used in the process itself. For this purpose, it is advantageously led to the mixing system 40, where it can be used to prepare the black mass 30.

Overall, a very efficient process can be set up for an unusually complete recovery of raw materials. The raw materials are kept at a high level of purity. By recovering the process water and using the hydrogen produced during electrolysis to generate energy, the process can be operated largely autonomously.

List of reference symbols

10

Physical preparation

12

Shredding

14

powder

16

Mixing container

16A

Solvent storage tank

18

Electrolyte collection container

20

Physical separation

22

magnetic separation

24

Iron powder container

26

Airflow separation

28A

Aluminium powder container

28B

Copper powder container

30

black mass

40

Mixing plant

42

Feed tank

50

Electrolysis unit

52

Hydrogen derivation

54

Combined heat and power plant

60

electrochemical units

62

Reagent for cobalt deposition

64

Cobalt/cobalt compound deposition

66

Reagent for manganese deposition

68

Manganese/manganese compound deposition

70

Reagent for lithium deposition

72

Lithium/lithium compound deposition

80

Neutralization system

82

Process water container

Claims (12)

Process for the recovery of raw materials from components which contain at least cobalt compounds and nickel compounds, the process comprising the following steps: - mechanical treatment of components - chemical treatment of the components in a solution, whereby the components are at least partially decomposed - Treatment of cobalt ions with chloride ions to form complexes - electrochemical extraction of cobalt from solution - electrochemical extraction of nickel from solution Method according to claim 1, wherein the mechanical treatment comprises dismantling the components with a shredder and/or a water jet. A method according to any one of the preceding claims, wherein the solution is a sulfate solution. Process according to one of the preceding claims, in which metal salts are dissolved in the sulfate solution. Process according to the preceding claim, in which dissolved metal salts are chemically masked. Method according to one of the preceding claims, in which the components contain manganese compounds and manganese dioxide is present in the solution and a reduction of manganese dioxide to manganese (II) oxide takes place. Process according to one of the preceding claims, in which nickel ions and manganese ions are present in the solution and a redox reaction takes place to reduce nickel with simultaneous oxidation of the manganese ions. Method according to one of the preceding claims, in which the components contain lithium compounds and lithium ions are present in the solution, which are precipitated as lithium carbonate with the aid of sodium carbonate. Process according to the preceding claim, in which lithium carbonate is dissolved with an ionic liquid and is electrochemically deposited as lithium metal. A process according to any preceding claim, wherein hydrogen is produced during the electrochemical extraction of nickel and said hydrogen is collected. Process according to the preceding claim, in which the hydrogen is used in a combined heat and power plant. Process according to one of the preceding claims, in which water is recovered in a neutralization plant.

Images