DE102023111177A1 - Process for treating a wastewater stream from the production of cathode active material - Google Patents

Abstract

The invention relates to a method for producing lithium-containing cathode active materials. The invention also relates to a treatment of a lithium-containing wastewater stream which originates from the production of the cathode material, and wherein recovered lithium is returned to the production process of the lithium-containing cathode active material in a cyclic process.

Description

The invention relates to a method for producing lithium-containing cathode active materials. The invention also relates to a treatment of a lithium-containing wastewater stream which originates from the production of the cathode material, and wherein recovered lithium is returned to the production process of the lithium-containing cathode active material in a cyclic process.

background

Electromobility is under great criticism due to the lack of sustainability in the production of electric batteries, especially the cathode active material containing lithium ions. Both the extraction of lithium, the lack of closed-loop recycling and the limited quantities of lithium available represent a major challenge for the production processes. The production of the cathode active material cannot be considered a "green technology" according to the current state of technology. Not only the high energy requirements, but also the high demand for lithium and other metal oxides, such as nickel, cobalt and manganese, make the future of electromobility very questionable. This invention is therefore of particular importance for the future technology of electromobility. Electromobility with lithium-ion batteries only has a future by closing the loop and preventing waste water and waste from the production process. This invention enables (almost) 100% waste- and wastewater-free production of cathode active material.

Often, the discharge conditions of the production facilities and the limit values to be observed for lithium, nickel, cobalt, manganese, sulfate, etc. cannot be implemented with the current state of technology. This is why evaporation systems are often used to concentrate the wastewater. The high energy consumption required for this is not in line with the idea of sustainability. Further processing and recovery of lithium from the concentrate (bottom product) is also significantly more complex and costly than the lithium-rich solution produced in this invention through optimized material flows.

The object of the present invention was therefore to provide a waste and wastewater-free process for producing a lithium-containing cathode active material, in which the raw materials end up exclusively in the product through closed-loop processing and impurities (such as sulfate) are separated and converted into a usable product. The losses of raw materials, in particular lithium and other metals contained in the preliminary product, should be reduced to a minimum and the generation of waste should be excluded. A further aim of the present invention was that the entire production process can be carried out without additional water, in particular demineralized or deionized water.

subject matter of the invention

The object is achieved by a method comprising the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

1. a) Bereitstellen eines oder mehrerer Metallverbindungen 3;
2. b) Bereitstellen einer Lithiumverbindung 1;
3. c) Entwässern 11 der Metallverbindung und Entwässern 9 der Lithiumverbindung und Abtrennen des entstehenden Kondensats 15, 19 zur Weiterführung in die Waschwasser-Vorlage 47 und Verwendung als Waschwasser;
4. d) Herstellen eines Metall-Oxidgitters und Li-Einlagerung 24
5. e) Waschen 28 der aus Schritt d) erhaltenen Lithium-Metalloxidverbindung 26 mit der Waschwasser-Vorlage 34 aus Schritt c), Filtern der Lithium-Metalloxidverbindung über eine Filtereinrichtung 32 und Abtrennen eines Filtrats 42 und eines Feststoffes 44;
6. f) Reinigen der Filtereinrichtung mit der Waschwasservorlage 38 und Rückführen des Spülwassers 40 zur Waschwasser-Vorlage 47 und Aufbereiten der Waschwasser-Vorlage 47 zum Erhalt eines Li-reichen Stoffstroms 48;
7. g) Aufbereiten des Li-haltigen Stoffstroms 60 aus Schritt f) um eine Lithiumverbindung 62 zu erhalten und Rückführung der nach Aufbereitung erhaltenen Lithiumverbindung in das Verfahren.

The invention provides a method for this purpose, comprising the steps:

1. a) providing one or more metal compounds 3;
2. b) providing a lithium compound 1;
3. c) dewatering 11 the metal compound and dewatering 9 the lithium compound and separating the resulting condensate 15, 19 for further conveyance into the wash water receiver 47 and use as wash water;
4. d) Preparation of a metal oxide lattice and Li incorporation 24
5. e) washing 28 the lithium metal oxide compound 26 obtained from step d) with the wash water receiver 34 from step c), filtering the lithium metal oxide compound through a filter device 32 and separating a filtrate 42 and a solid 44;
6. f) cleaning the filter device with the wash water reservoir 38 and returning the rinse water 40 to the wash water reservoir 47 and processing the wash water reservoir 47 to obtain a Li-rich material stream 48;
7. g) processing the Li-containing material stream 60 from step f) to obtain a lithium compound 62 and returning the lithium compound obtained after processing to the process.

In the process according to the invention, it is preferred that the wash water reservoir 47 from step f) is subjected to an ultra-filtration 49 and the resulting filtrate/clear phase 50 is transferred to a filtrate collecting container 51.

According to an advantageous embodiment of the invention, the filtrate/clear phase 50 is subjected to nanofiltration 53 and/or diffusion dialysis, wherein the resulting filtrate 54 is fed to the wash water receiver 47 and wherein a Li-enriched solution 56 is separated.

According to the invention, the Li-rich solution 56 is subjected to a membrane separation process 61, whereby a Li-rich and sulfate-poor material stream 60 is obtained, whereby the Li-rich material stream is dewatered and the dewatered Li product is fed to the lithium compound 1 and the condensate 64 is fed to the wash water receiver 47.

According to an advantageous embodiment of the invention, the filtering in step e) is carried out by means of a chamber filter press 32 and the return flow from the cleaning of the chamber filter press 32 is fed to the washing water reservoir 47.

The Li concentration in the wash water reservoir 47 is kept constant during the process.

It is also preferred in the sense of the method according to the invention that the respective material streams from the respective filtration and washing processes are cascaded into the washing water reservoir 47. In 3 the cascading is visible. The material streams with the lowest Li concentration 15, 19 and 64 are at the rear end of the cascade, followed by material stream 46, then 54 and finally the material streams 40 and 42 follow in the storage tank 47.

The process does not require any externally supplied water, distilled water or deionized water. Therefore, according to a further advantageous embodiment of the invention, no external deionized water is supplied.

The metal oxides used in the process according to the invention are preferably metal hydroxides comprising the metals Ni, Mn, Co, Al or mixtures thereof, with combinations of Co, Ni and Mn with Li being most preferred.

The lithium compound is preferably lithium hydroxide or lithium carbonate, which usually contain water of hydration. Most preferred is LiOH*1H ₂ O.

The additives for the preparation of the Li metal oxide compounds are preferably boric acid, aluminum sulfate, zirconium oxide and aluminum hydroxide. However, other additives, for example sulfuric acid, caustic soda, titanium dioxide and the like, can also be used according to the invention.

The use of LiOH*1H ₂ O as a starting material advantageously leads to the formation of a condensate during the dewatering step, which is collected and reused for later washing steps. This completely eliminates the need for deionized water. According to the state of the art, approximately 2.5 m ³ of deionized water is required per ton of cathode active material produced. At a current market price of deionized water of €0.80/m ^3, this already corresponds to a saving of €2 per ton of cathode active material. The dewatering of the precursor intermediate product (metal hydroxide mixture) also produces a condensate, which, however, only makes up a small proportion due to the significantly lower water content (depending on product quality), and which is also added to the washing water for the sake of completeness. This enables the use of other qualities with a higher water content, among other things.

Detailed description of the invention

The positive electrode in the battery is often referred to as the "cathode." Most conventional lithium-ion batteries use lithium cobalt oxide as the cathode. However, in recent years, many alternative material systems have been developed and used.

In most cases, however, lithium and oxygen are still an essential component of the system. Only the metallic element cobalt is often completely or partially replaced by other metallic elements such as nickel and manganese. For this reason, most lithium-ion batteries can be referred to as a so-called lithium metal oxide cathode. However, systems are also known that use lithium iron phosphate as a material, for example.

Lithium metal oxides are manufactured as solid powders. When selecting the powder as a suitable material for use as a cathode in a lithium-ion battery (LiB), the microstructure, morphology, particle size and the degree and type of possible impurities in the powder play a crucial role. These influence the electrochemical properties of the battery that is subsequently manufactured from it.

In particular, the energy density, which is of great importance for the range of electric vehicles, for example, is influenced by the structural parameters mentioned above.

The microstructure of the cathode must therefore be precisely adjusted. This can be achieved by the correct selection of raw materials and by a controlled manufacturing process for cathode powders. As the term suggests, a lithium metal oxide is a mixed crystal of lithium oxide and oxides of other metals. These mixed crystals are created by thermally treating a mixture of the individual oxides at high temperatures, typically between 800-1000 °C under certain atmospheric conditions. The individual oxides are in turn provided by adding different raw materials to the mixture. The starting materials are often hydroxides or carbonates of lithium and the other metallic elements.

By heat treatment of these starting materials, water (H2O) or carbon dioxide (CO2) is released at temperatures of 600-800 °C; the remaining oxides later participate in a solid solution through further treatments.

Basically, in the production of the cathode, in a first step, various oxides are obtained from the respective hydroxides or carbonates of the same elements and then in a second step the desired mixed crystal is produced from these oxides.

The first step, in which two solids react with each other to form a third solid and gases are released, is called calcination. The second step is called sintering or solid diffusion. Calcination takes place almost independently of time as soon as the temperatures and starting materials required to start the reaction are available. Consequently, the first steps of the thermal treatment in the manufacture of the cathode are relatively quick. The diffusion processes to form the solid solutions, on the other hand, are very time-dependent and take significantly longer. In the state of the art, the two steps are usually carried out one after the other in one process, but in others the calcination products are first cooled and later sintered in a separate thermal process.

In addition to costs and production capacity in a small space, product quality is also one of the success factors for cathode powder manufacturers. Because, for the same price, battery manufacturers naturally prefer materials with, for example, higher energy density. This can be achieved by making the best possible use of the thermodynamic influences on the calcination and sintering processes.

1 shows a simplified version of a typical manufacturing process for such cathode materials. Intermediate steps such as sieving/magnetic separation and deagglomeration are not listed in full because the resulting small losses are negligible for the representation of the material flows.

The material flows shown in the block diagram, the closed loop, and in particular the use of condensates instead of pure demineralized water, eliminate the need for additional demineralized water. Instead of many wastewater flows with different concentrations, there is only one wastewater flow, which is reduced from 2.5-4 liters per kg of product (CAM) to 0 liters per kg. For example, the cost savings compared to the water requirement typical for the industry are around 3 liters per kg of product.

The big advantage over the conventional process is the high concentration of lithium, which makes recovery possible and economical.

Only through the recycling and reuse of the washing water, which is part of the invention, can a consistent product quality be achieved.

Part of the invention is that the concentration of lithium or lithium sulfate in the wash water is kept constant. This is what enables the process to be controlled. The resulting constant process conditions result in a consistent product quality. This is possible for the first time thanks to this invention.

By circulating the washing water and having already dissolved lithium in a defined concentration in the washing water, the undesirable re-dissolution of lithium from the metal oxide lattice is avoided. The washing process is only intended to wash out excess lithium that is not stored in the lattice. The problems are known in existing systems. A solution to this problem has not yet been found in the state of the art.

Re-dissolution of heavy metals (Ni, Co, Mn, etc.) is not expected due to the pH range of pH 10-12.

Therefore, these are not taken into account in the quality of the wash water supply.

The concentration in the wash water reservoir is limited by the solubility, in particular the solubility of lithium or lithium salts. Li ₂ SO ₄ has a good solubility of 342 g/l at 25°C in water. This results in a maximum concentration of 43.18 g/l dissolved lithium. The concentration of lithium is also determined depending on product quality, recipes, precursors used, additives and other process parameters. In the example shown (material flows in the block diagram) and the corresponding precursors used, the concentration is defined as 15 g/l lithium.

The defined concentration of lithium in the wash water reservoir is also determined taking into account the technical and economic operation of the subsequent processes for the recovery of lithium. processing of the solution and recovery of the raw materials, in particular lithium (sulfate).

One of the features of the invention is that a subsequent ultrafiltration is used to separate any solid particles and the concentrate is returned to the container in which the washing process takes place. This guarantees that no losses of product, lithium, etc. occur even when concentrate is discharged and thus no additional waste streams are generated. Other methods of solid/liquid separation can also be used, such as sedimentation, use of inclined or lamella clarifiers, filter presses or other deep and surface filtration methods. A combination of different methods for solid/liquid separation is also possible.

The invention relates mainly to the material flow and the return of the concentrate to the process. The solids-rich solution can be returned either to the container in which the washing process takes place, or to the storage container or directly to the feed line of the solid/liquid separation, in the example shown a chamber filter press 32.

Depending on which lithium concentration in the wash water reservoir is considered sensible or necessary, a subsequent concentration can be carried out, e.g. by means of nanofiltration. The low-lithium solution (filtrate) generated from the nanofiltration is returned to the wash water reservoir. The concentration of lithium (sulfate) in the wash water reservoir is kept constant by discharging the solution enriched with lithium (sulfate) (concentrate).

The material flows “return filter cloth cleaning”, “filtrate chamber filter press” 32, “filtrate nanofiltration”, “condensate from lithium hydroxide monohydrate drying”, “condensate from precursor drying”, “condensate from filter cake drying” can also be collected separately.

One variant of the invention provides for a cascaded merging of the individual material streams. The individual material streams are fed to the respective cascade stage depending on their purity and volume. With this variant of the wash water reservoir (47), concentration fluctuations in the water inlet (34) are avoided, which makes it possible to run the washing process within a very narrow tolerance range. The "condensate from the precursor drying" (19) is so small that it can actually be ignored. However, for the sake of completeness, this is included in the invention because there are many different precursor products with different components, different purity and also different water content.

Part of the invention is that the lithium (sulfate)-rich solution (concentrate) from the nanofiltration is fed to a diffusion dialysis, whereby the lithium-containing solution in the wash water reservoir can also be removed directly and fed to the diffusion dialysis without prior concentration or without prior nanofiltration.

A semi-permeable anion exchange membrane is preferably used (acid diffusion dialysis). This membrane allows the H ⁺ and SO ₄ ^2- ions to diffuse and the lithium ions are retained. This means that sulfuric acid is recovered in the diffusate, which is used as a raw material elsewhere. We recover LiOH*xH2O in the dialysate. This LiOH*xH2O can be mixed directly with the purchased LiOH*1H ₂ O and used in the production process. The higher water content should not be a problem because a drying process takes place afterwards anyway. However, if the higher water content causes problems during blending, dewatering (63) can also be provided upstream.

A further component of the invention is that the demineralized water required for diffusion dialysis is replaced by the condensate water (“condensate from lithium hydroxide monohydrate drying” and/or “condensate from precursor drying”) from production and thus no further need for demineralized water is required. The (demineralized) water required for diffusion dialysis can also be replaced or mixed with condensate water only in part.

• 1: Ein Blockfließbild der Stoffströme in einem CAM-Prozess gemäß der Erfindung;
• 2: Ein Blockfließbild der Stoffströme in einem CAM-Prozess gemäß Stand der Technik;
• 3: die Kaskadierung, wobei diestoffströme mit der niedrigsten Li-Konzentration 15, 19 und 64 sind am hintersten Ende der Kaskade, gefolgt von Stoffstrom 46, dann 54 und zuletzt folgen die Stoffströme 40 und 42 in den Vorlagebehälter 47;

Referring to the 1 The invention will now be explained in more detail. The figures show:

• 1 : A block flow diagram of the material flows in a CAM process according to the invention;
• 2 : A block flow diagram of the material flows in a CAM process according to the state of the art;
• 3 : the cascading, where the streams with the lowest Li concentration 15, 19 and 64 are at the rear end of the cascade, followed by stream 46, then 54 and finally streams 40 and 42 follow in the feed tank 47;

list of reference symbols

1

template lithium-containing precursor

3

Template Precursor Metal Oxide Mixture

5

addition of Li precursor

7

addition precursor

9

Dewatering/drying Li precursor

11

Dewatering/Drying Precursor

13

Anhydrous lithium oxide

15

Condensate from drying Li-containing precursor

17

Anhydrous metal oxide mixture

19

condensate from precursor drying

21

mixing container

22

template additives

24

Generation of Me oxide lattice and Li intercalation

26

supply of CAM product in washing process

28

washing container CAM product

30

Feed chamber filter press from washing process

32

device for solid/liquid separation (e.g. chamber filter press)

34

water inlet in washing process

36

Inflow concentrate from UF into collection tank concentrate

37

Concentrate collection container38 - Filter cloth cleaning inlet (Clothwash)

39

inflow concentrate in washing process

40

return filter cloth cleaning (Clothwash)

42

filtrate chamber filter press

43

Inlet condensate water in wash water reservoir

44

CAM product (e.g. filter cake) for drying

45

drying of solids (e.g. filter cake)

46

Condensate from drying filter cake

47

wash water storage tank (e.g. 5-way cascade)

48

feed solids filter (e.g. ultrafiltration)

49

solid filter (e.g. ultrafiltration)

50

solid-free solution

51

filtrate collection tank

52

feed (e.g. nanofiltration)

53

concentration unit (e.g. nanofiltration)

54

Lithium (sulfate)-poor solution from concentration unit (e.g. NF filtrate)

55

condensate collection tank

56

Lithium (sulfate)-rich solution from concentration unit (e.g. NF concentrate)

57

water inlet (e.g. diffusion dialysis)

58

sulfate-rich material flow

59

sulfuric acid

60

lithium-rich material flow

61

membrane separation processes (e.g. diffusion dialysis)

62

feed recovered LiOH*xH2O

63

Drain

64

Condensate drain from drying recovered LiOH*xH2O

66

inflow sedimentation

68

Sedimentation process, low in solids

70

Sedimentation process, rich in solids

72

Solid-free or low-solids solution from solid filter

74

Solid-rich solution from solid filter

Description of the procedure:

Condensates 15, 19 from the drying processes of the Li precursor 1 and the metal oxide mixture 3 are collected in a container 47 and (re)used as a template for the washing process. The majority of the condensate comes from the drying of the lithium hydroxide monohydrate. A small proportion comes from the drying of the preferably metal hydroxides.

After the Li metal oxides or the mixed Li metal oxides have been produced, the reaction product is washed and filtered. Filtration is preferably carried out in a chamber filter press 32 through a filter cloth, although all other filtering methods known to those skilled in the art can also be used. The filtrate from the chamber filter press is used for cleaning the filter cloth (so-called cloth wash). This prevents or reduces the redissolution of lithium at the filter cloth/CAM product interface.

The water flows of the condensates, the filtrate from the chamber filter press and the return rinse water from the cloth wash are collected in a storage tank.

The filtrate from the chamber filter press is initially circulated to prevent filtrate contaminated with solids from entering the wash water reservoir at the beginning (build-up of the filter cake, turbidity run). The switchover to the wash water reservoir can also be carried out using Sensor technology (turbidity) can be monitored and controlled.

The concentration of lithium, sulfate, etc. in the wash water is kept almost constant. The lithium concentration is expected to be 20-25 g/l. This lithium concentration range has a positive effect on the washing process because it significantly reduces the undesirable re-dissolution of lithium. Ideally, the value should be around 23 g/l.

Subsequent processing and recovery of lithium are facilitated by the high concentration of lithium in the template 47.

The further concentration of the resulting lithium sulfate can preferably be carried out by means of nanofiltration or diffusion dialysis. A combination of nanofiltration and diffusion dialysis is also possible.

To avoid loading the nanofiltration or diffusion dialysis with solid particles, a filter is installed upstream to separate the solids. This solids separation can include micro- and/or ultrafiltration as well as other solids separation processes.

Further processing of lithium sulfate to obtain lithium oxide monohydrate can be carried out, for example, as in EP 2 762 611 described.

The concentrate from micro- or ultrafiltration can preferably be further concentrated in subsequent steps, e.g. using a lamella clarifier or simply in a thickener and subsequent chamber filter press or decanter. The filter cake can be delivered as a product according to customer specifications by blending (mixing off-spec with product). Preferably, the concentrate from ultrafiltration can also be added directly to the container in which the washing process takes place.

The process can also be carried out in stages. Since the remaining amount in volume is very small, the recovery of lithium or lithium hydroxide monohydrate can also be carried out externally.

The process, in particular the material flows, is the actual invention, which enables a closed loop and practically no losses occur. There is no need for additional resources such as deionized water, raw materials and chemicals for pH correction.

The recipe and precursors used may differ from the variant shown. The additives and precursors vary depending on customer requirements.

• • Konstante Produktqualität
• • Beherrschter Prozess (Sensibilität des Waschprozesses nach aktuellem Stand der Technik ist nicht mehr gegeben).
• • Gemäß den Preisen aus dem Jahr 2022 für Rohstoffe, etc. wird gegenüber dem Stand der Technik eine Einsparung von etwa 2.000 € pro Tonne CAM-Produkt erzielt.

The invention brings the following advantages:

• • Consistent product quality
• • Controlled process (sensitivity of the washing process according to the current state of the art is no longer given).
• • Based on 2022 prices for raw materials, etc., savings of around €2,000 per ton of CAM product will be achieved compared to the state of the art.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2762611 [0054]

Claims (10)

Method for producing a Li-containing cathode material comprising the steps: a) providing one or more metal compounds (3); b) providing a lithium compound (1); c) dewatering (11) the metal compound and dewatering (9) the lithium compound and separating the resulting condensate (15, 19) for further conveyance into the wash water receiver (47) and use as wash water; d) producing a metal oxide lattice and Li incorporation (24) e) washing (28) the lithium metal oxide compound (26) obtained from step d) with the wash water receiver (34) from step c), filtering the lithium metal oxide compound via a filter device (32) and separating a filtrate (42) and a solid (44); f) cleaning the filter device with the wash water reservoir (38) and returning the rinse water (40) to the wash water reservoir (47) and processing the wash water reservoir (47) to obtain a Li-rich material stream (48); g) processing the Li-containing material stream (60) from step f) to obtain a lithium compound (62) and returning the lithium compound obtained after processing to the process. Method according to one of the preceding claims, wherein the wash water reservoir (47) from step f) is subjected to an ultrafiltration (49) and the resulting filtrate/clear phase (50) is transferred to a filtrate collecting container (51). procedure according to claim 2 , wherein the filtrate/clear phase (50) is subjected to nanofiltration (53) and/or diffusion dialysis, wherein the resulting filtrate (54) is fed to the wash water receiver (47) and wherein a Li-enriched solution (56) is separated. procedure according to claim 3 , wherein the Li-rich solution (56) is subjected to a membrane separation process (61) to obtain a Li-rich stream (60) and a sulfate-poor stream, wherein the Li-rich stream is dewatered and the dewatered Li product is fed to the lithium compound (1) and the condensate (63) is fed to the wash water receiver (47). Method according to one of the preceding claims, wherein the filtering (32) in step e) is carried out by means of a chamber filter press and wherein the return flow from the cleaning of the chamber filter press with the filtrate (42) is fed to the washing water reservoir (47). Method according to one of the preceding claims, wherein the Li concentration in the wash water reservoir (47) is kept constant. Method according to one of the preceding claims, wherein no external demineralized water is supplied. A process according to any one of the preceding claims, wherein the lithium compound is LiOH*1H ₂ O. A method according to any one of the preceding claims, wherein the metal compound comprises metals selected from Ni, Mn, Co, Al, Zn, Fe, or mixtures thereof. Method according to one of the preceding claims, wherein the respective material streams from the respective filtration and washing processes are cascadedly fed to the washing water reservoir 47.

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