WO2025040555A1

WO2025040555A1 - Method for extracting lithium from lithium-containing batteries

Info

Publication number: WO2025040555A1
Application number: PCT/EP2024/072992
Authority: WO
Inventors: Sebastian LEAPER; Ahmed ABDELKARIM; Adel ABDELKADER
Original assignee: Watercycle Technologies Ltd
Current assignee: Watercycle Technologies Ltd
Priority date: 2023-08-21
Filing date: 2024-08-15
Publication date: 2025-02-27
Anticipated expiration: 2026-02-21
Also published as: GB202312756D0; AR133594A1

Abstract

The present invention relates to a method for extracting lithium from one or more lithium-containing batteries, the method comprising a dissolution step, the dissolution step comprising exposing a lithium-containing battery to an acidic leaching solution.

Description

METHOD FOR EXTRACTING LITHIUM FROM LITHIUM-CONTAINING BATTERIES

Field of the Invention

The present invention relates to a method of recovering lithium and other valuable components (such as graphite, plastics, copper, and battery minerals) from one or more lithium-containing batteries.

Background

There is increasing demand in the world for batteries, in particular lithium-ion batteries, perhaps due to the increasing use of, and demand for, electric vehicles. Lithium is therefore a valuable resource, obtained from the environment either through mining lithium ore or extraction of mineral-rich salt lake brine. Both methods have environmental impact, with brine extraction thought to risk soil salinization and damage to the local eco-structure and landscape, while mining operations occupy large areas of land and often permanently scars the landscape. Lithium mining and processing also involves significant water consumption, with considerable risk of affecting local water supplies and aquaculture through leaching of by-products.

Waste materials containing lithium, such as lithium batteries, represent a valuable source of lithium. Lithium battery recycling is key to realising a circular lithium economy and assisting progress towards Net-Zero. However, current commercial applications of battery recycling technology are immature and are limited by high cost and low product recovery.

There are three typical methods of recycling lithium-containing batteries: (a) direct physical recycling; (b) hydrometallurgical processing; and (c) pyrometallurgical processing.

Direct physical recycling involves discharging and dismantling batteries into separate cells, the cells are then further dismantled and separated into electrodes, current collectors, casings and the like. Optionally, the components are cleaned to remove electrolytes. The electrodes are then further processed to physically remove valuable lithium-containing anode/cathode material. This lithium-containing anode/cathode material can then be purified and re-lithiated for direct re-use in new batteries.

Direct physical recycling involves many steps that require complicated and careful disassembly so as to avoid contamination of the lithium-containing anode/cathode material. This is often done by hand (that is, using manual labour) and is therefore expensive and cannot be scaled up easily. However, the recovered product of direct physical recycling needs little further chemical processing before use in batteries.

Hydrometallurgical processing involves discharging batteries, then a comminution process (typically shredding). This allows for mechanical separation of the produced particles using, for example, magnets to remove ferrous and non-ferrous metals, flotation tanks to remove plastics, and so on. This allows for the separation of the electrode materials (so called black mass) from other components. A detailed review of the many mechanical processing steps can be found in Sommerville et al. [1], Typically, the electrode material is then leached, for example by dissolution in acid, to provide a mixed-metal solution containing, for example, iron, cobalt, manganese, and lithium ions. Through precipitation with, for example, barium hydroxide, a solution of lithium hydroxide can be obtained, allowing for the production of solid lithium hydroxide which can be used to generate virgin electrode material.

Hydrometallurgical processing involves multiple separation steps to isolate the electrode material before purification. This represents a significant cost at large scales and can entail significant safety considerations. Furthermore, lithium containing materials are lost during each separation step. Typically, hydrometallurgical processing is used to recover transition metal products and not lithium due to high cost.

Pyrometallurgical processing involves exposing batteries to multiple heating steps, first to remove liquid electrolytes, then a second step at a higher temperature for the pyrolysis of plastics, then a third step at yet higher temperatures to smelt metallic elements. After cooling, the metallic product (containing copper, cobalt, manganese and iron) can be separated from the slag (containing lithium and other non-metallic elements). The metallic product can then be further processed to recover the cobalt. The lithium- containing slag is typically not processed to recover lithium due to high recovery costs; however, the slag might in theory be processed by a similar route to the hydrometallurgical process detailed above.

As can be seen above, each of the three typical processes have steps in their methods that result in high costs for recovering lithium from lithium batteries.

There is therefore considerable interest in improved methods for recovering and reusing lithium.

The present invention has been devised in light of the above considerations.

Summary of the Invention

The present inventors sought to provide an improved method for recycling one or more lithium-containing batteries that has fewer steps, lower costs, less waste of lithium and fewer safety considerations.

In doing so, the inventors propose a method for recycling a lithium-containing battery (or batteries) that involves the direct dissolution of at least one lithium-containing battery or cell. In other words, the inventors propose a method of extracting lithium from a battery that does not involve the isolation of electrode materials before the leaching step.

Accordingly, in a first aspect, the invention may provide a method of extracting lithium from a lithium- containing battery, the method comprising a dissolution step, the dissolution step comprising exposing the lithium-containing battery to an acidic leaching solution.

A battery in the context of the invention is one wherein the individual battery cells have not been physically dismantled into component parts, for example, into electrodes, current collectors, casings and the like, as in the direct physical recycling process, or broken up into pieces (comminuted), for example by shredding. In some embodiments, the battery is one capable of holding an electrical charge. The battery may be processed to, for example, remove wiring and casings that are external to the lithium- containing cells before application of the present invention.

The inventors observe the process of the first aspect may have the following advantages: (1) the method is simpler as no disassembly, comminution or mechanical separation steps are needed and therefore the cost of extracting lithium from the lithium-containing battery (or batteries) would be reduced; (2) higher recovery of lithium from the lithium-containing battery (or batteries) can be reached as no electrode material is lost during separation; (3) all components of the battery (or batteries) are exposed to the leach solution, including lithium-containing electrolytes, increasing yield when compared to a process that uses black mass alone, (4) the plastic, binder and graphite of the battery (or batteries) can be recovered in intact forms, reducing the amount of processing; and (5) the method can minimize both upstream and downstream wastewater treatment and can also reduce the downstream processing of the produced materials.

In some embodiments, the method comprises a discharge step wherein the lithium-containing battery is discharged in an acidic discharge solution.

If a battery contains a substantial electric charge, then the battery may overheat during discharge and cause the electrode materials to become exposed to the discharge solution. If the discharge solution is separate to the leach solution, for example if a brine solution is used as a discharge solution, then the brine becomes contaminated with lithium. This decreases the yield of lithium in the subsequent dissolution step and produces a large amount of lithiated brine that can be difficult to recover and purify the lithium from. By using an acidic discharge solution, lithium can be recovered from the discharge solution without contamination from other salts.

In some embodiments, the acidic discharge solution is used to form the acidic leaching solution. This can be done by adding additional acid to the acidic discharge solution. Optionally, the acidic discharge solution is added to the acidic leaching solution.

This allows for fewer steps to be taken, as additional acid can be added to the acidic discharge solution to provide the acidic leaching solution. This is also beneficial if lithium is present in the acidic discharge solution after discharge, as it can be extracted as part of the discharge solution.

In some embodiments, the acidic discharge solution is the acidic leaching solution. That is, the lithium- containing battery is discharged in the acidic leaching solution in the same step as dissolution, the discharge and dissolution steps occur together, that is, concurrently. In other words, the process does not comprise a step of discharging the battery before the dissolution step. In some embodiments, the battery used in the dissolution step is not in a discharged state (that is, it contains electrical charge).

By using the leaching solution as the discharge solution, there are fewer steps and waste is avoided by ensuring that all of the lithium contained in the battery (or batteries) is extracted in the dissolution step.

The temperature at which the discharge step occurs is not particularly limited. In some embodiments the discharge step occurs at ambient temperature or at reduced temperature. By performing the discharge step at ambient or reduced temperature, charged batteries can be discharged more safely.

In some embodiments, the method of the invention comprises:

(i) a discharge step comprising exposing a lithium-containing battery to an acidic discharge solution to discharge the battery; followed by

(ii) a dissolution step comprising exposing the lithium-containing battery to an acidic leaching solution.

In some embodiments, the method of the invention is a hydrometallurgical process and/or a direct lithium extraction process that comprises a dissolution step, the dissolution step comprising exposing a lithium- containing battery to an acidic leaching solution.

In some embodiments, the method of the invention comprises:

(i) a dissolution step comprising exposing a lithium-containing battery to an acidic leaching solution to obtain a dissolution step liquor;

(ii) a processing step comprising a hydrometallurgical process whereby one or more nonlithium components are removed from the dissolution step liquor, and/or a direct lithium extraction process whereby lithium is extracted from the dissolution step liquor, to provide a purified lithium containing liquor; and

(iii) an isolation step comprising producing a solid lithium compound from the purified lithium containing liquor. In some embodiments, the method of the invention comprises:

(ii) a dissolution step comprising exposing the lithium-containing battery to an acidic leaching solution to obtain a dissolution step liquor;

(iii) a processing step comprising a hydrometallurgical process whereby one or more nonlithium components are removed from the dissolution step liquor, and/or a direct lithium extraction process whereby lithium is extracted from the dissolution step liquor, to provide a purified lithium containing liquor; and

(iv) an isolation step comprising producing a solid lithium compound from the purified lithium containing liquor.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Figure 1 shows a flow chart of a process according to the state of the art.

Figure 2 shows a flow chart of a process according to the invention.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

Batteries

The invention relates to a method of extracting lithium from at least one lithium-containing battery. In the context of this invention, a battery can comprise a single cell or multiple cells. The term ‘battery’ is intended to include both a battery and an individual cell. In the context of this invention, ‘at least one lithium-containing battery’ can be a lithium-containing battery or multiple lithium-containing batteries, or a lithium-containing cell or multiple lithium-containing cells, or a combination of one or more lithium containing batteries and one or more lithium containing cells. The type of battery (or batteries) used in the process of the invention is not particularly limit, provided the battery contains lithium (as for example, lithium ions or lithium metal). For example, the at least one battery could be, or comprise, a lithium metal battery (that is, a non-rechargeable lithium battery), such as a lithium air battery, a lithium iron disulfide battery, and/or a lithium manganese dioxide battery; and/or the at least one battery could be, or comprise, a lithium ion battery (that is, a rechargeable lithium battery) such as a lithium nickel manganese cobalt oxide (NMC) battery, a lithium nickel cobalt aluminium oxide (NCA) battery, a lithium iron phosphate (LFP) battery, a lithium manganese oxide (LMO) battery, a lithium cobalt oxide (LCO) battery, and/or a lithium polymer battery (LiPo).

In some embodiments, the at least one battery is, or comprises, an NMC and/or LFP battery. In some embodiments, the at least one battery is, or comprises, an NMC battery.

The battery (or batteries) used in the method of the invention can be waste (that is, used), such as those recovered from the recycling process, or the battery (or batteries) can be unused.

The at least one battery used in the process is suitably substantially whole, that is, the battery has not been shredded, granulated, milled, or otherwise comminuted, or dismantled into electrodes, current collectors, casings and the like.

In some embodiments, the battery used in the process is, or comprises, a substantially whole cell. In some embodiments, the at least one battery is a substantially whole cell. It has not be subjected to shredding.

In some embodiments, the battery is capable of storing an electrical charge. In some embodiments, the battery contains electrical charge.

A substantially whole battery comprises an anode, a cathode and an electrolyte between them, all contained in a sealed envelope or enclosure. In some embodiments, the battery comprises additional components such as one or more of current collectors, electrical terminals, wiring, structural casings, labels, and the like. In some embodiments, the battery is hermetically sealed.

In some embodiments, the sealed enclosure of the battery comprises a metal, for example steel, stainless steel or aluminium. In some embodiments, the sealed enclosure of the battery comprises a plastic, for example polypropylene, polyvinylchloride, polyethylene terephthalate and the like. In some embodiments, the sealed enclosure is aluminised plastic. In some embodiments, the sealed enclosure of the battery is aluminium foil or nickel-coated steel.

Process according to the invention

A process according to the prior art is shown schematically in Figure 1.

Figure 1 includes the following:

The first step is to discharge the battery or cell. This is required to make further handling and processing of the battery safer as there is less danger of fires when working with a discharged battery. The discharge of the battery can be done in many ways. Typically, this has been done through attaching a resistive load to the battery or by submerging the battery in a salt solution (for example, a sodium chloride solution). The next step is shredding, where the cell (or cell(s) within a battery) are mechanically cut into smaller pieces. There may be an optional step of dismantling the battery as part of the shredding step to remove, for example, large pieces of plastic packaging, large current collectors or busbars.

The next steps all relate to the separation of black mass from the shredded battery; these separation steps can be performed in any order as it does not impact the processing of the battery.

One separation step is electrolyte extraction, where solvent, such as acetonitrile or supercritical CO2, is used to remove the electrolyte solution from the shredded battery.

Another separation step is magnetic separation, where strong magnets are used to attract ferrous metals from the shredded battery, which can be collected for further recycling.

Another separation step is eddy current separation, where strong magnets are used to repel non-ferrous metals by inducing eddy currents within the metal; these non-ferrous metals can also be collected for further recycling.

Another separation step is air sieving, where different density materials are separated using air currents. This separates low density materials such as plastics and films from denser materials such as electrode materials.

After the separation steps, the electrode materials are typically thermally treated at a raised temperature to dry the material and to decompose any polymer binders in the electrode material.

The product, after the thermal treatment, is substantially pure electrode material, the so-called “black mass”.

The next step is to dissolve the black mass in an acid solution. This produces a strongly acidic solution containing various metal salts (such as those of Li, Cu, Mn, Fe, Co) and a residual solid formed of materials within the black mass that are resistant to dissolution by acid (gold, plastics, and carbon/graphite).

Once the metallic elements are in solution, typical hydrometallurgical steps can be performed to separate the desired components from one another, thereby producing a substantially pure solution of lithium ions.

This solution of lithium ions can be dried (or the salt crystallised or otherwise precipitated) to provide a solid lithium salt, such as lithium hydroxide monohydrate or lithium carbonate.

In contrast, a process according to the invention is shown schematically in Figure 2.

Figure 2 includes the following:

The first step is dissolution. This may optionally also be effective as the discharge step if the battery or cell contains electrical charge. As the acidic leaching solution is conductive, any electrical charge within the battery or cell is discharged through the solution. The acidic leaching solution also acts to break down the sealed envelope of the cell (or cell(s) within the battery), thereby exposing the anode, cathode, electrolyte and the like to the leaching solution without mechanical separation or comminution. The acidic solution then acts on the anode and cathode materials to dissolve the lithium contained therein, bringing it into solution.

The product of this dissolution step is a solution that is substantially the same as that produced by the dissolution step of the prior art, in that it contains various metal salts including Li, Cu, Mn, Fe and Co.

The next step is filtration, where all non-soluble components of the battery is removed, such as the battery envelope, wiring, current collectors, plastics, graphite, and the like. This leaves the lithium- containing solution produced in the dissolution step.

The lithium-containing solution can be processed in the same way as is typical in the art so as to produce solid lithium hydroxide monohydrate or lithium carbonate.

The lithium-containing solution can also be processed using DLEC™ (Direct Lithium Extraction and Crystallisation); this can produce a wider range of lithium salts including but not limited to lithium chloride, lithium sulphate, lithium hydroxide, lithium carbonate.

Dissolution step

This step may be referred to as ‘leaching’ in the methods of the prior art as a first step in the chemical processing of black mass, after the mechanical processing of a battery (or batteries).

In the method of the invention, the dissolution step is the first step in the chemical processing of the at least one lithium-ion battery, without any mechanical processing of the battery.

In the dissolution step, the battery (or batteries) are exposed to an acid or acidic solution (also called the “leaching solution”). The acid is capable of breaking down the protective enclosure of the lithium- containing battery (or lithium-containing cell(s)) thereby exposing and penetrating the anode and cathode layers. The acid then reacts with metals, metal oxides, electrolytes and other metal compounds in the cell (or cell(s) of a battery or batteries), converting them to salts which are soluble in the acidic solution, including the lithium present in the cell (or cell(s) of a battery or batteries). The resultant solution is the so- called “dissolution step liquor”.

The acid of the leaching solution is not particularly limited. For example, the leaching solution may comprise one or more acids selected from sulfuric acid, phosphoric acid, hydrochloric acid, citric acid and oxalic acid. In some embodiments it is sulfuric acid. In some embodiments it is hydrochloric acid.

Concentrated (for example 98 wt%, 18 M) sulfuric acid can be used. Other acids that can be used include mineral acids such as concentrated (for example 85 wt%, 15 M) phosphoric acid, and concentrated (for example 37 wt%, 12.3 M) hydrochloric acid as well as organic acids such as citric acid, and oxalic acid.

When using acids which are solid at room temperature, for instance citric acid and oxalic acid, concentrated solutions of the acids can be employed. For instance at room temperature 55-65 wt% (for example 59.2 wt%) citric acid solution or 9 wt% oxalic acid solution can be used. More concentrated acid solutions can be formed using heating, for example 76.2 wt% citric acid solution can be used at 70 °C. The processes of the present invention may also be conducted under milder conditions, that is, the leaching solution is not a concentrated acid, for example from 0.1 to 10 M solutions. Optionally, the acid has a concentration from 2 M to 8 M. Optionally, the concentration is around 2 M. Optionally, the concentration is around 3 M. Optionally, the concentration is around 4 M. Optionally, the concentration is around 5 M. Optionally, the concentration is around 6 M. Optionally, the concentration is around 7 M. Optionally, the concentration is around 8 M.

In one embodiment the leaching solution comprises hydrochloric acid. The concentration of hydrochloric acid in the leaching solution may be 12 M or more (that is, concentrated hydrochloric acid), optionally 12.3 M, optionally from about 2 to 12 M, optionally about 12 M, optionally about 10 M, optionally about 8 M, optionally about 6 M, optionally about 4 M, optionally about 2 M. The concentration of hydrochloric acid in the leaching solution may be 37 wt%, optionally about 20 wt%, optionally about 15 wt%, optionally about 10 wt%.

In one embodiment the leaching solution comprises sulfuric acid. The sulfuric acid may be substantially pure (that is, anhydrous). The sulfuric acid may be used as a solution in water, for example as a 96 wt% solution (that is, a concentrated solution), optionally from about 5 to 100 wt%, optionally about 80 wt%, optionally about 60 wt%, optionally about 40 wt%, optionally about 20 wt%.

In other embodiments, the leaching solution comprises phosphoric acid. Phosphoric acid may be used as a 75-100% concentrated solution (by mass, in water). In other embodiments, the leaching solution comprises citric acid. Citric acid may be used as a 40-85% solution (by mass, in water). In other embodiments, the leaching solution comprises oxalic acid. Oxalic acid may be used as a 5-15% solution (by mass, in water).

The ratio of the amount of acid to the battery (or batteries) being used is not particularly limited as it will depend on the type of battery (or batteries) and the acid being used. For instance, a larger number of moles of a monoprotic acid, such as hydrochloric acid, will be required in comparison to a diprotic acid, such as sulphuric acid.

The ratio of acid to the mass of the battery (or batteries) may be from 1-100 moles of acid to 1 kg of battery (or batteries).

In embodiments where the leaching solution comprises hydrochloric acid, the ratio of hydrochloric acid to the battery (or batteries) may be, for example, 1-100 moles of hydrochloric acid to 1 kg of battery (or batteries), optionally 20-80 moles, optionally 30-60, or 40-50 moles . A suitable example is about 46 moles of hydrochloric acid to 1 kg of battery (or batteries).

In embodiments where the leaching solution comprises sulfuric acid, the ratio of sulfuric acid to the battery (or batteries) may be, for example, 1-50 moles of sulfuric acid is used to 1 kg of battery (or batteries), optionally 10-40 moles, optionally 20-30 moles, optionally 15-30 moles, optionally 20-25 moles, optionally 22-24 moles, optionally 23 moles.

The ratio of solid (that is, the battery or batteries) to liquid (that is, the leaching solution) is from 10 to 10000 g/L, optionally from 50 to 500 g/L. In some embodiments where the leaching solution comprises concentrated hydrochloric acid, the ratio of the battery (or batteries) to hydrochloric acid is from 100-10,000 g/L, optionally 100-5,000 g/L, optionally 200-2000 g/L, optionally 100-1000 g/L, optionally 150-500 g/L, optionally about 200 g/L.

In embodiments where the leaching solution comprises concentrated sulfuric acid, the ratio of the battery (or batteries) to sulfuric acid is 100-10,000 g/L, optionally 200-5,000 g/L, optionally 400-2000 g/L, optionally 600-1200 g/L, optionally 700-900 g/L, optionally about 800 g/L.

The above solid to liquid ratios are given for concentrated acids, the ratios can be adapted depending on the concentration of the acid used. For example, for 6 M hydrochloric acid, the weight ratios can be halved when compared to the concentrated (12 M) hydrochloric acid. Similarly, the amount of acid used in the ratios above can be diluted in water to provide a greater volume of leaching solution to that of acid used.

In some embodiments the dissolution step is performed at room temperature. In some embodiments the dissolution step is performed at above room temperature, for example 50-100°C, optionally, 40-90°C optionally 60-80°C, optionally 70-80°C, optionally 60-65°C, optionally 70 °C.

The length of time the battery (or batteries) is exposed to the leaching solution in the dissolution step will vary depending on the concentration of the acid, the temperature and the type of battery used. In some embodiments, the dissolution step is performed for 1 day or more. Optionally, 2 days or more. Optionally, 3 days or more. Optionally, 5 days or more. Optionally, 7 days or more. Optionally, 10 days or more.

In some embodiments the dissolution step is performed using mechanical agitation, for example with stirring, jet agitation or ball milling. In some embodiments, the at least one battery is stirred in the leaching solution. In some embodiments, during the dissolution step, the at least one battery is removed from the leaching solution and agitated, or manually separated or otherwise broken up into smaller pieces, and then returned to the leaching solution.

Discharge step

In some embodiments, the dissolution step is also effective as a discharge step. In some embodiments, the discharge step is performed concurrently with dissolution, that is, the discharge step occurs in the leaching solution. In some embodiments, the discharge is performed in an acidic discharging solution with a lower concentration than the leaching solution, then once the battery (or batteries) is discharged, the concentration of the acid is increased by the addition of more acid to reach the desired concentration of the leaching solution.

In some embodiments, the acidic discharging solution is less concentrated than the acidic leaching solution. That is, the concentration of acid present in the leaching solution is higher than the concentration of acid present in the discharging solution. In some embodiments, the discharging solution has a concentration of acid that is about 90% of the concentration of acid present in the leaching solution, optionally about 80%, optionally about 70%, optionally about 60%, optionally about 50%, optionally about 40%, optionally about 30%, optionally about 20%, optionally about 10%, optionally about 5%. In some embodiments, the discharging solution has a concentration of acid that is from 10 to 90% of the concentration of acid present in the leaching solution, optionally from 20 to 80%, optionally from 30 to 70%.

In some embodiments, the discharging solution has a concentration of acid that is at least 5% of the concentration of acid present in the leaching solution, optionally at least 10%, optionally at least 20%. In some embodiments, the discharging solution has a concentration of acid that is less than 90% of the concentration of acid present in the leaching solution, optionally less than 80%.

The time that the at least one battery takes to discharge will vary with the charge remaining in the battery, the concentration of acid in the discharge solution and the type of battery. In embodiments where the discharge solution is different to that of the leaching solution, the at least one battery can be added to the discharge solution for, for example, from 1-100 hours, optionally about 20 hours, before the discharge solution is changed to the leaching solution.

In some embodiments the discharge step occurs at ambient temperature. Optionally from 0 to 40 °C, optionally about 20°C.

In some embodiments, the method does not include a step wherein a battery is discharged in a salt solution before the dissolution step. Optionally, the method does not include a step wherein a battery is discharged in a sodium chloride solution (that is, brine) before the dissolution step.

Additional dissolution steps

In some embodiments, an additional step of removing solids from the dissolution step liquor is performed after the dissolution step. For example, the mixture may be separated by gravity separation, filtration, centrifugation, hydrocyclonic separation or the like. In some embodiments, multiple filtrations can be used to first separate large pieces of the battery (or batteries), such as plastic materials, and then to remove particulate matter such as graphite.

In embodiments where additional filtering step(s) are present after the dissolution step, optionally the solid components are washed with a washing liquid (such as water), and the washing liquid then re-added to the dissolution step liquor.

Processing Step

Once the dissolution step liquor is acquired, the dissolution step liquor may by purified by any suitable means to provide a purified lithium product. For example, by using hydrometallurgical processing as known in the art, or through the use of DLEC™ (Direct Lithium Extraction and Crystallisation), optionally in combination with hydrometallurgical processes. The result of the processing step is a purified lithium containing liquor. In some embodiments, this contains lithium as substantially the only metallic component in the solution.

In some embodiments, the purified lithium containing liquor comprises one or more of lithium chloride, lithium bromide, lithium acetate, lithium hydroxide, lithium carbonate, lithium sulfate, and lithium citrate. Preferably, the extraction step liquor comprises lithium chloride or lithium hydroxide, optionally the purified lithium containing liquor is a substantially pure aqueous lithium hydroxide solution. Optionally the purified lithium containing liquor is a substantially pure aqueous lithium chloride solution.

Direct Lithium Extraction

In some embodiments, the dissolution step liquor is treated using a Direct Lithium Extraction (DLE) process. That is, the processing step comprises a DLE process.

This selectively separates the lithium ions from the other ionic species in the dissolution step liquor. The product of this step is a solution enriched in lithium ions, the so-called purified lithium containing liquor. Optionally, the purified lithium containing liquor is substantially free of metallic impurities.

Direct lithium extraction is a process where lithium is selectively extracted from impure solutions containing large amounts of multiple ionic species, wherein the majority of other components are left in solution. There are a number of DLE techniques known in the art, including electrodialysis, nanofiltration, adsorption and ion-exchange. The latter two approaches hold the most promise in terms of lithium selectivity, energy consumption and cost.

DLE processes enrich a solution in lithium ions, that is, the product of the DLE process is a solution that has a higher concentration of lithium ions than the solution fed into the DLE process.

The DLE process used is not particularly limited. Any suitable DLE process can be used. General DLE methods are well known in the art and will not be discussed in great detail here.

In one embodiment, the DLE process is an adsorptive process or an ion-exchange process. These processes use materials that selectively uptake lithium from solution. The lithium can then be ‘released’ from the enriched selective material to provide substantially pure lithium containing solutions.

For example, the selective material may be provided as beads in a column, with the dissolution step liquor poured into/through the column; or it may be provided in the form of hollow fibers, with the dissolution step liquor fed through or over the fibers. This facilitates the uptake of the lithium and replaces protons in the material. This initial contact, removing the lithium from the dissolution step liquor and ‘storing’ it in the selective material, can be termed an ‘adsorption step’ of the DLE process.

In order to conserve charge, clearly, in order to desorb (release) the lithium ions they must be replaced with a suitable cation; this is often a proton as suitable protic acidic solutions are readily available. Similarly, using basic solutions encourages the adsorption (take up) of lithium from solution, by removing protons from the lithium-ion sieve material. By varying pH, the selective ‘adsorption’ (take up) and ‘desorption’ (release) of lithium can be carefully controlled. A more basic lithium-containing solution provides the fastest lithium extraction rate; a more acidic release solution provides the fastest lithium release rate. However, rate must also be balanced against other factors such as acid/base safety and toxicity, additional cost and so on.

As the dissolution step liquor is acidic, the pH of the solution can be raised by, for example, the addition of sodium hydroxide or the like. Lithium selective materials

A lithium selective material (Lithium-Ion Sieve, LIS) is needed for the desired ion exchanges to occur in the processing step.

It may be for example a metal organic framework, a zeolite, a layered double hydroxide or a metal oxide. Lithium metal oxides and their hydrogen precursors are particularly suitable for use as a lithium selective material held in the matrix material. Lithium manganese oxide (LMO) and its corresponding hydrogen manganese oxide (HMO) derived from LMO, and lithium titanium oxide (LTO) and its corresponding hydrogen titanium oxide (HTO) derived from LTO are suitable.

[It will be recognised that, of course, during the ion exchange reaction a compound such as lithium manganese oxide (LMO) will be converted, to at least some degree, to hydrogen manganese oxide (HMO) on contact with the release solution; it will convert back when it leaches lithium ions from a suitable feedstock. Accordingly, the ion selective material may be accurately described as both LMO and HMO derived from LMO depending on its state of lithium ion loading. The applies equally to LTO and HTO derived from LTO, of course.]

Typically, the lithium selective material is not used in the pure form, but it is rather contained within or embedded in a matrix.

The matrix used here is not particularly limited beyond that it has good chemical and thermal stability. Suitable matrix materials include ceramics and polymers. Suitable ceramics include oxides such as alumina, zirconia and titania. Suitable polymers include both thermoplastics and thermosetting plastics. In some preferred embodiments the matrix material comprises one or more selected from: polysulfone (PSU), polyethersulfone (PES), polyketone (PK), polyetherketone (PEK), poly etheretherketone (PEEK), polyetherketoneketone (PEKK), polyimide. In some embodiments it consists of one of those. PES is particularly preferred. Therefore preferably the matrix material comprises or consists of PES.

The matrix is suitably porous; this increases the flow of the feedstock to the selective material (which may not necessarily be present on the outer surface of the matrix material) and facilitates transfer of lithium ions. The pores effectively increase the active surface area of the material. Accordingly larger pores, for example of an average pore size 0.1-2 pm, for example 0.5-1 pm, are preferable.

For the present lithium-ion-exchange material, a porosity of > 60% may be suitable, in particular s 80%. The pores may have a size (D50) of < 2 pm, for example < 1 pm.

The selective material may suitably be provided in the form of particles.

In some embodiments, the particle size of the selective material is < 50 pm, suitably < 25 pm, or < 10 pm. Most suitable is a particle size of < 5 pm, or < 3 pm.

On the other hand, the particles may suitably have a size of > 200 nm, for example > 400 nm, > 1 pm, or > 2 pm.

Lithium ion-exchange material As explained above, the lithium-ion-exchange material includes a selective material and a matrix material. It may be provided in various morphologies; for example, it may be formed into beads (for example, substantially spherical beads of average diameter 0.01-10 mm) or, more suitably, into a membrane form.

Such a membrane might be a simple flat (e.g., cast) membrane, or have a more complex structure such as that of a hollow fiber. Hollow fiber (HF) membranes have been found by the inventors to have several advantages in DLE processes; in particular, a high useful surface area especially where the dissolution step liquor is flown in contact with the lithium-ion-exchange material.

Such hollow fibers are known in the art of water treatment; they are elongate, generally extruded members with a bore (hollow part) inside the substantially circular cross-section fiber.

A hollow fiber morphology of the material may be preferable as a solution brought into contact with the fiber has surface contact with a large active area. Hollow fibers can also be packed into a housing to form a membrane module; flow of solution through the module again allows high surface contact and hence efficient lithium extraction and release.

Suitable hollow fiber dimensions will be apparent to those skilled in the art. For example, a hollow fiber length of 0.2-2 m, an outer diameter of 0.4-5 mm, and a wall thickness of 10-200 pm may be used.

The hollow fibers themselves may have, for example, a length of about 1 m, an outer diameter of about 1 mm, and an inner (bore) diameter of about 0.9 mm.

Methods of making suitable beads or membranes will be apparent to those of skill in the art. Hollow fiber membranes are used often in water treatment technologies; general methods for their fabrication are also well know.

Adsorption

The adsorption step, as well as suitably being conducted at raised pH, may also or instead suitably be conducted at raised temperature (that is, above room temperature; for example 30°C or higher, 40°C or higher, 50°C or higher, 60°C or higher, or 70°C or higher).

A temperature of 25-70°C, and particularly 50-70°C, may be preferred,

The length of time for which there is contact between the dissolution step liquor and the selective material depends on several factors, for example how the selective material is provided. If it is provided in fibers, or a column, through which a solution is flown, the rate of flow is important. If the selective material is simply placed in contact with a stationary solution for some length of time, the time it is left is the relevant feature.

In some embodiments, the adsorption step may be conducted for 10-150 minutes.

After a given time, the de-lithiated dissolution step liquor is suitably removed from contact with the selective material, and the selective material may be rinsed with fresh water. This can remove any impurities loosely bound to the lithium-ion-exchange material before the release step is carried out.

Desorption In order to release the lithium from the selective material, a protic acidic solution (release solution) is introduced; this replaces the lithium ions with protons. This can be termed a ‘release step’ of the DLE process. The lithium is released from the selective material, forming a lithium-rich solution which can be removed for further processing, this lithium-rich solution is the so-called purified lithium containing liquor.

Typically, HCI is used in the release step due to the low cost. In other embodiments, the release solution comprises one or more acids selected from the group of HCI, HBr, HI, HNO3, H2SO4, H3PO4, H3BO3, HCIO4, HBF4, HPFe. In some embodiments, the release solution comprises one or more organic acids. The organic acid may be one which comprises a carboxylic acid group. Optionally, the organic acid comprises two or more carboxylic acid groups. Suitable organic acids include acetic acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, citric acid, malic acid, and tartaric acid.

The pH of the release solution (which is generally aqueous) depends of course on the acid included in it and how much is included; generally, it has a pH <7, for example <6, <5, <4, or <3.

In the release step, the lithium-ion exchange material is exposed to a release solution. Suitably this can be done batch-wise or using a continual flow of organic acid solution.

The release step may suitably be conducted at raised temperature (that is, above room temperature; for example, 30°C or higher, 40°C or higher, 50°C or higher, 60°C or higher, or 70°C or higher).

The release step may suitably be conducted at up to 70°C. A temperature above room temperature, for example around 25-70°C, suitably 50-70°C, may be preferred.

Purified Lithium Containing Liquor

The purified lithium containing liquor produced by a DLE process substantially only contains water, lithium cations and the conjugate base anion of the acid used in the DLE desorption step.

For example, if HCI is used in the release solution of a selective adsorption DLE process, the purified lithium containing liquor is substantially pure LiCI in water.

As the DLE process also increases the concentration of lithium in a given solution, it is possible to produce concentrated solutions of lithium (that is, the concentration of lithium in the extraction step liquor produced by the DLE extraction is higher than the concentration of lithium in the dissolution step liquor).

In some embodiments, an optional concentration step is performed after the DLE processing step, that is the purified lithium containing liquor is concentrated. Suitable means of concentrating the purified lithium containing liquor includes distillation processes such as solar evaporation, vacuum distillation, flash distillation and membrane distillation; reverse osmosis and electrodialysis

Hydrometallurgical Process

In some embodiments, the dissolution step liquor is treated using a hydrometallurgical process. That is, the processing step comprises a hydrometallurgical process. The hydrometallurgical process removes non-lithium ions from the dissolution step liquor. The product of this step is a solution enriched in lithium ions, the so-called purified lithium containing liquor. Optionally, the purified lithium containing liquor is substantially free of metallic impurities.

Hydrometallurgical processes are well known in the art and will not be discussed in detail here.

Typically, hydrometallurgical processing exploits the varying solubility of metal salts. Notably, that lithium hydroxide is highly soluble whereas transition metal hydroxides are insoluble.

In some embodiments, the dissolution step liquor is diluted at the start of the hydrometallurgical process; however, more conveniently it is not diluted.

Transition metal precipitation step

One typical step in the hydrometallurgical process is a transition metal precipitation step. A base is added to the dissolution step liquor to raise the pH. The base can be provided as a solid, liquid or aqueous solution. Preferably, the base is water soluble (an alkali) as homogeneous solutions react more rapidly than heterogeneous mixtures.

The pH of the solution is increased to precipitate the so-called insoluble metals from the dissolution step liquor as a precipitate. The term ‘insoluble metals’ is understood in the art and refers to those metals whose relevant salt(s) (for example, hydroxides if the first base is a source of hydroxide ions; sulfides if the first base is a source of sulfide ions) are not soluble (<1 mg/mL, suitably <0.5 mg/mL, more suitably <0.1 mg/mL) in the liquor generated by addition of the base to the dissolution step liquor. The composition of the precipitate will depend on what was present in the original lithium-containing battery (or batteries) used and in the base used in the precipitation step. Typically, the precipitate will comprise hydroxides of the insoluble metals (in particular where the first base is a source of hydroxide ions). The precipitate may also comprise sulfides, oxides, or carbonates of the insoluble metals. The first precipitate may also comprise the base used in the first precipitation step. Typically the precipitate will comprise insoluble compounds of nickel, cobalt and manganese. Suitable bases for use in the first precipitation step may include ammonium persulfate, ammonium carbonate, aqueous ammonia, barium hydroxide and calcium hydroxide.

In some embodiments, the base is not an alkali metal (Li, Na, K, Rb, Cs, Fr)-containing base; the use of alkali metal containing bases may be undesirable as the introduction of alkali metal anions can contaminate the lithium hydroxide product.

In some embodiments where sulfuric acid is used in the dissolution step, the base is barium hydroxide. The use of barium hydroxide is preferable as both insoluble metal hydroxides and insoluble barium sulfate will precipitate. This leaves substantially pure lithium hydroxide in solution.

In some preferred embodiments, the base is ammonium persulfate, ammonium carbonate or aqueous ammonia, and particularly is suitably ammonium persulfate. The use of an ammonium base is advantageous because the ammonium cations can be readily removed from the first precipitate (for example, reprecipitated black mass) by heating. In general, fewer impurities in the precipitate (reprecipitated black mass) mean that it may be more suitable for reuse and/or have higher resale value, requiring less processing.

The amount of the base required to precipitate the transition metals depends on the amount of acid used and the composition of the lithium-containing battery (or batteries). Preferably, at least an equimolar amount of base to acid is used. For diprotic acids, such as sulphuric acid, at least two moles of base is used per mole of acid. For triprotic acids, such as phosphoric acid, at least three moles of base is used per mole of acid.

The solubility of transition metal hydroxides varies dependent on the metallic species and the pH of the solution. Typically, metal hydroxides are soluble at low pH (around pH 0) and at high pH (around pH 14), with low solubilities at intermediate pH. For example, the lowest solubility for aluminium is around pH 6-7; for iron, pH 7-9; for nickel, pH 10 10.5; for cobalt, pH 10-12; and for manganese, pH 11-12. However, some metals will start precipitating around pH 3, for example iron.

Therefore, the optimum pH for the transition metal precipitation step varies depending on the composition of the lithium-containing battery (or batteries). In the precipitation step a quantity of the base sufficient to raise the pH of the dissolution liquor to pH 3-12 may preferably be added.

After addition of the base in the transition metal precipitation step, the precipitated metal products may be isolated by any suitable means. This includes, but is not limited to, gravity settling, filtration, centrifugation, and hydrocyclonic separation.

Sulfate removal step

As an acid is used in the dissolution step, the dissolution step liquor comprises conjugate base ions of the dissolution step acid, for example sulfate ions if sulfuric acid is used. These can contaminate the lithium when a solid lithium salt is isolated from the purified lithium containing liquor.

In some embodiments, for example where sulfuric acid is used in the dissolution step, there may be an optional step to remove sulphate ions from the dissolution step liquor or from the purified lithium containing liquor.

Alkali metal sulfate salts have very low aqueous solubilities. Therefore, the removal of sulfate anions can be performed by adding an alkaline earth (Be, Mg, Ca, Sr, Ba, Ra) salt to the dissolution step liquor or the purified lithium containing liquor. The source of alkaline earth ions is suitably an alkaline earth metal hydroxide such as Mg(OH)2, Ca(OH)2, Sr(OH)2 or Ba(OH)2, or an alkaline earth metal oxide (which hydrate to provide corresponding alkaline earth metal hydroxides) such as MgO, CaO, SrO or BaO. Preferably the second base is soluble in water therefore Ca(OH)2 or Ba(OH)2 is preferred.

For example, when calcium hydroxide is used, a precipitate of calcium sulfate is formed, which can be removed from the supernatant liquor, thereby reducing impurities that may contaminate the purified lithium containing liquor produced in the processing step. Analogously, when a different acid such as phosphoric acid or hydrochloric acid is used in the dissolution step, a step can be performed to remove phosphate anions or chloride anions, respectively, similarly for organic acids such as oxalic acid and citric acid.

This has the advantage that, the purity of lithium produced by the method of the invention is improved. Furthermore, recovered salts, such as calcium sulfate or barium sulfate, can be sold or used in other processes. This can improve the economic viability of the present process.

Purified Lithium Containing Liquor

In some embodiments, the purified lithium containing liquor produced by the hydrometallurgical processing step substantially only contains water, lithium cations and the conjugate base anion of the dissolution step acid.

In some embodiments, the purified lithium containing liquor produced by the hydrometallurgical processing step is a substantially pure solution of lithium hydroxide.

In some embodiments, the purified lithium containing liquor produced by the hydrometallurgical process may also contain sodium ions, magnesium ions, and/or calcium ions.

As the hydrometallurgical processing step requires the addition of various solutions to the dissolution step liquor, in some embodiments the concentration of lithium in the purified lithium containing solution is reduced when compared to the dissolution step liquor

In some embodiments, an optional concentration step is performed after the hydrometallurgical processing step, that is the purified lithium containing liquor is concentrated. Suitable means of concentrating the purified lithium containing liquor includes distillation processes such as solar evaporation, vacuum distillation, flash distillation and membrane distillation; reverse osmosis and electrodialysis.

Alkali Earth Metal Removal Step

In some embodiments, an optional alkali earth metal removal step may be performed on the dissolution step liquor or the purified lithium containing liquor.

Optionally, this can be achieved by flowing the dissolution step liquor or the purified lithium containing liquor through a commercial water softening ion-exchange resin. Such resins include sodium salts of strongly acidic resins and sodium salts of weakly acidic resins, for example sodium polystyrene sulfonate and the like.

Optionally this can be achieved by performing nanofiltration on the dissolution step liquor or the purified lithium containing liquor.

Alkali earth metal cations, such as magnesium and calcium cations, form insoluble carbonates.

Therefore, any alkali earth metal cations present in the purified lithium containing solution will be coprecipitated with lithium carbonate if lithium carbonate is desired Removing alkali earth metal ions from the purified lithium containing solution allows for a precipitative isolation step, where sodium carbonate is added to the purified lithium containing solution to produce lithium carbonate.

Therefore, it is preferable to remove any alkali earth metals before the isolation step as this increases the purity of the lithium carbonate.

Isolation Step

Once a purified lithium containing liquor is obtained, the next step is to isolate the solid salt from the purified lithium containing liquor.

The lithium salt may be isolated by evaporation of the liquid or by crystallisation. Suitable techniques are known to the art and will not be discussed here. An example crystallisation technique is antisolvent crystallisation wherein the lithium salt precipitates from solution upon addition of a suitable organic solvent such as acetone. The antisolvent may then be recovered after separation of the solid lithium salt by, for example, distillation.

The lithium salt may be isolated through precipitation of lithium carbonate. In this embodiment, sodium carbonate is added to the purified lithium containing solution to precipitate lithium carbonate, which can be separated by any usual means.

The lithium salt isolated in the isolation step may be, or comprise, lithium chloride, lithium hydroxide (optionally as lithium hydroxide monohydrate), lithium carbonate, lithium citrate, and lithium oxalate.

***

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/- 10%.

References

A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein.

[1] R. Sommerville et al., A review of physical processes used in the safe recycling of lithium ion batteries, Sustainable Materials and Technologies, Volume 25, 2020.

Claims

Claims:

1 . A method for extracting lithium from one or more lithium-containing batteries, the method comprising a dissolution step, the dissolution step comprising exposing a lithium-containing battery to an acidic leaching solution.

2. The method of claim 1 , wherein the method does not comprise a comminution step such as shredding before the dissolution step.

3. The method of claim 1 or claim 2, wherein the method comprises a discharge step, before the dissolution step, wherein the lithium-containing battery is discharged in an acidic discharge solution.

4. The method of claim 3, wherein the discharge solution is the leaching solution.

5. The method of any one of the preceding claims, wherein the method comprises an insolation step, after the dissolution step, the isolation step comprising producing a solid lithium salt.

6. The method of claim 5, wherein the method of the invention comprises:

(iii) an isolation step comprising producing a solid lithium compound from the purified lithium containing liquor.

7. The method of claim 5 or 6, wherein the solid lithium salt is or comprises a salt selected from the group of lithium chloride, lithium hydroxide, and lithium carbonate.

8. The method of any one of the preceding claims, wherein the lithium containing battery is a lithium nickel manganese cobalt oxide (NMC) battery and/or a lithium iron phosphate (LFP) battery.

9. The method of any one of the preceding claims, wherein the leaching solution is or comprises an acid selected from the group of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and citric acid

10. The method of claim 9, wherein the leaching solution is hydrochloric acid, optionally 6M hydrochloric acid.

11 . The method of any one of claims 2 to 10, wherein the discharge solution is or comprises an acid selected from the group of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and citric acid

12. The method of claim 11 , wherein the discharge solution is hydrochloric acid, optionally 6M hydrochloric acid.

13. The method of any one of the preceding claims, wherein the dissolution step is performed at a raised temperature, optionally from 50 to 100°C.

14. The method of any one of the preceding claims, wherein the discharge step is performed at ambient or reduced temperature, optionally from 0 to 40°C.