WO2023091087A2

WO2023091087A2 - A recycling method for active materials in lithium or sodium batteries

Info

Publication number: WO2023091087A2
Application number: PCT/SG2022/050836
Authority: WO
Inventors: Qing Wang; Feifei Zhang
Original assignee: National University Of Singapore
Priority date: 2021-11-18
Filing date: 2022-11-18
Publication date: 2023-05-25
Also published as: WO2023091087A3

Abstract

Disclosed herein is a method of method of recovering a valuable element from an active material of a lithium or sodium ion battery. The method requiring an active material comprising lithium or sodium ions, where the active material is added to a redox solution that is formed from a solvent and a redox mediator to form a redox solution in a first tank and then moving the redox solution from the first tank to a redox flow cell having a cathode compartment, which compartment has a cathode electrode, and an anode compartment, having an anode electrode, separated by an ion selective membrane, where the cathode electrode and anode electrode are attached to a power supply and the redox solution is subjected to an electrochemical reaction on the anode electrode, where the electrochemical reaction on the anode: regenerates the redox mediator, which is then returned to the first tank and reacts with the active material; and enables transport of the lithium or sodium ions through the ion selective membrane into the cathode compartment, which comprises an aqueous catholyte solution that is obtained from a second tank, and then capturing the lithium or sodium ions and producing hydrogen in the cathode compartment through an electrochemical reaction on the cathode electrode that produces LiOH or NaOH and hydrogen gas and transferring the resulting aqueous LiOH or NaOH and hydrogen gas in the resulting catholyte solution to a second tank, where: the aqueous catholyte solution comprises a hydrogen evolution catalyst to facilitate the production of LiOH or NaOH and hydrogen gas; and the valuable element is selected from one or more of the group consisting of Al, Cu, Co, Ni, Fe, Mn, V, and, more particularly, Na and Li.

Description

A RECYCLING METHOD FOR ACTIVE MATERIALS IN LITHIUM OR SODIUM BATTERIES

Field of Invention

The invention relates to a method recovering valuable elements from an active material of a lithium- and/or sodium-ion battery.

Background

The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

Lithium ion batteries (LIBs) are the undisputed choice of power source for portable devices and they are increasingly in demand for applications such as electrical energy storage (EEs) and electric vehicle (EV). LIBs may also be used in the electrical grid for power storage of renewable energy. After 30 years of commercialization and mass production, a myriad of LIBs have been produced. As will be appreciated, this has generated a massive amount of battery waste due to each battery having a limited lifespan. For example, over 1.2 billion smartphones were shipped in 2014 alone. Given that the general lifetime of a battery in such a device is around three years, then this implies that around 24,000 tonnes of lithium-ion battery cathode materials would have needed to be recycled in 2017 -with the recycled lithium material having a market value of roughly $1 billion USD. However, these end-of-life batteries, without proper treatment, may cause critical environmental damage.

Lithium and cobalt have been recognised as strategic resources as these elements are relatively rare in the earth’s crust. Moreover, spent LIBs comprise valuable metals such as Al, Cu, Co, Li, and the concentration of these elements is much higher than that in natural ores. Therefore, without recycling, these batteries would represent a big waste of valuable and scarce materials, such as Li, Co, Ni, etc. As will be appreciated, this problem will only be made worse by the expansion of LIBs into other applications with widespread use, such as their use in automotive (EVs) and stationary (power grid) energy storage. For sustainable development, it has never been so pressing to recycle the spent batteries and reuse the useful components.

Components of the spent end-of-life LIBs include casing, electrolyte, separator and electrode materials. The commonly used cathode materials are oxides compounds such as LiCoO2, LiNixMn_yCOzO2, LiMr^C and polyanionic LiFePC . Currently, the industrially-implemented recycling technologies are mainly pyrometallurgy and hydrometallurgy.

Pyrometallurgy involves using extremely high temperatures to smelt the metals and burn away the remaining components like carbon and the separator material. The formed metal alloy is then treated by hydrometallurgy to obtain various salts. Despite being simple and requiring no extra-sorting and pre-processing, the pyrometallurgical process uses a huge amount of energy and generates a large amount of toxic gases, as well as CO2.

The typical hydrometallurgical extraction process consists of the following steps: (1) releasing residual electricity of spent batteries by discharge pre-treatment; (2) removing plastic packaging and casings from the batteries, and separating out the cathode and anode electrodes; (3) scraping cathodic and anodic active materials from the electrodes; (4) dissolving the cathodic active material (such as LiCoO₂) using a strong acid (e.g. HCI or H2SO4) and H₂O₂ to form a solution containing Co²⁺, Li⁺, SO₄ ²' ions (leaching process); (5) adding NaOH to the resulting solution to precipitate Co(OH)₂, leaving Li⁺, Na⁺, OH; SO4²' ions in the solution; and then (6) adding Na₂CO3 to the solution to precipitate I 2CO3 (metal separation process).

The above hydrometallurgical extraction process recovers a high proportion of the battery elements and does not require a huge amount of energy. However, it suffers from the following issues. Firstly, the process is complicated and involves many steps. In addition, it requires addition of a large amount of chemicals such as HCI, H₂SO₄, H₂O₂, NaOH and Na₂CO₃. In connection to this addition, it generates a large amount of waste material after I 2CO3 has been precipitated, resulting in secondary pollution. Furthermore, traditional hydrometallurgical extraction processes are unable to effectively extract or leach LiFePO₄ because this material does not dissolve in acid. This is problematic because LiFePO₄ is a widely-used cathode material for electrical energy storage (EEs) and electric vehicle (EV).

One strategy that has been attempted to overcome some of the above problems is set out in PCT Patent Publication No. WO 2020/086000. Nevertheless, this method makes use of a sophisticated depolarised cathode and requires a complex flow cell construction, leading to a large footprint for the cell stack, mediocre productivity, as well as increased operating costs. There is therefore a need for a high-throughput, simpler and low-cost process for recycling LIBs that avoids using strong acids and mitigates generation of secondary waste material, which solves one or more problems identified above.

Summary of Invention

Aspects and embodiments of the invention will now be discussed by reference to the following numbered clauses.

1. A method of recovering a valuable element from an active material of a lithium- or sodium-ion battery, respectively, the method comprising:

(a) providing an active material comprising lithium or sodium ions;

(b) adding the active material to a redox solution that comprises a solvent and a redox mediator to form a redox solution comprising lithium or sodium ions in a first tank;

(c) moving the redox solution from the first tank to a redox flow cell comprising a cathode compartment, having a cathode electrode, and an anode compartment, having an anode electrode, separated by an ion selective membrane, where the cathode electrode and anode electrode are attached to a power supply and the redox solution is subjected to an electrochemical reaction on the anode electrode, where the electrochemical reaction on the anode: regenerates the redox mediator, which is then returned to the first tank and reacts with the active material; and enables transport of the lithium or sodium ions through the ion selective membrane into the cathode compartment, which comprises an aqueous catholyte solution that is obtained from a second tank comprising said aqueous catholyte solution;

(d) capturing the lithium or sodium ions and producing hydrogen in the cathode compartment through an electrochemical reaction on the cathode electrode that produces LiOH or NaOH and hydrogen gas and transferring the resulting aqueous LiOH or NaOH and hydrogen gas in the resulting catholyte solution to a second tank, wherein: steps (c) and (d) can be repeated until the active material is consumed; the aqueous catholyte solution comprises a hydrogen evolution catalyst to facilitate the production of LiOH or NaOH and hydrogen gas; and the valuable element is selected from one or more of the group consisting of Al, Cu, Co, Ni, Fe, Mn, V, and, more particularly, Na and Li.

2. The method according to Clause 1 , wherein the active material is a cathodic and/or anodic active material. 3. The method according to Clause 2, wherein the cathodic active material is still attached to a cathode electrode of a dismantled lithium- or sodium-ion battery or is provided free from the cathode electrode.

4. The method according to Clause 2 or Clause 3, wherein the cathodic active material is selected from one or more of NaFePCU, NaCoCh, Na 2(PO4)s, more particularly, Li_xFePC>4, LixNiaCodAlcOz, LixNi_uCo_vMn_wO2, Li_xCoO2, Li_xMn2O4, and LixNio 5Mn1.5O4, where 0 <x< 1 , a + b + c = 1 , and u + v + w = 1 , optionally wherein the cathodic active material is Li_xFePO4.

5. The method according to any one of the preceding clauses, wherein the hydrogen evolution catalyst is selected from one or more of the group consisting of Pt, Pd, Ir, Ru, C3N4, a metal alloy (e.g. Pt-Ni-Co and/or Pt-Fe), a metal oxide, a metal sulfide, a metal carbide, a metal nitride, a metal phosphide, and a metal selenide, where the metal in each of the oxide, sulfide, carbide, nitride, phosphide and selenide is selected from one or more of the group selected from Cu, Mn, and more particularly Co, Ni, Mo and W.

6. The method according to any one of the preceding clauses, wherein the redox mediator is selected from one or more of the group consisting of hydroquinonesulfonic acid and, more particularly, ferricyanide (M₃Fe(CN)₆), ferrocyanide (M₄Fe(CN)₆), ferrocene (C HioFe) and derivatives thereof, iodide (Ml) and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH₄.

7. The method according to Clause 6, wherein the redox mediator is selected from one or more of the group consisting of hydroquinonesulfonic acid and, more particularly, ferricyanide (M₃Fe(CN)₆), ferrocyanide (M₄Fe(CN)₆), iodide (Ml), and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH₄, optionally wherein the derivative of ferrocene is di(ethylsulfonic lithium) ferrocene (Ci4Hi6FeS20eLi2)

8. The method according to Clause 6 or Clause 7, wherein the total concentration of the redox mediator present in the solvent is from 0.05 M to 3 M, such as from 0.2 M to 0.5 M, such as about 0.4 M.

9. The method according to any one of the preceding clauses, wherein the second tank is fluidly connected to a hydrogen storage tank, which collects the hydrogen gas from the second tank. 10. The method according to any one of the preceding clauses, wherein the solvent is pure water.

11. The method according to any one of the preceding clauses, wherein the aqueous catholyte solution is initially selected from one of water or water comprising CO2.

12. The method according to any one of the preceding clauses, wherein after steps (b) and (c) have been completed, and:

(i) the active material is a lithium-ion battery material, then the aqueous catholyte solution is an aqueous LiOH solution, or an aqueous LiOH solution comprising CO2 with U2CO3 precipitate, optionally wherein the aqueous catholyte solution is an aqueous LiOH solution; or

(ii) the active material is a sodium-ion battery material, then the aqueous catholyte solution is an aqueous NaOH solution.

13. The method according to any one of Clauses 2 to 12, wherein the anodic active material is still attached to an anode electrode of a dismantled lithium-ion battery or is provided free from the anode electrode.

14. The method according to any one of Clauses 2 to 13, wherein the anodic active material is selected from one or more of Li₄Ti₅0i₂, graphite, silicon, hard carbon.

15. The method according to any one of the preceding clauses, wherein the active material is a cathodic active material of a dismantled lithium- or sodium-ion battery.

Drawings

FIG. 1 depicts the schematic of the oxidative redox targeting-based strategy for spent lithium ferrophosphate (LFP) material recycling coupled with hydrogen evolution reaction (HER).

FIG. 2 depicts (a) voltage profile of the oxidative leaching process at a current density of 100 mA/cm²; and (b) X-ray diffraction (XRD) patterns show the conversion of LFP to FP after oxidative leaching with [Fe(CN)6]^3-. Description

Disclosed herein is an effective approach for lithium- (or sodium-) ion battery material recycling. This may be accomplished by employing a high-throughput electrolytic flow cell to continuously break down the spent battery materials into valuable chemicals under ambient conditions, without consuming additional chemicals. The reacted redox species may be instantaneously regenerated on the anode for subsequent rounds of reactions while Li⁺ (or Na⁺) is separated in the form of LiOH (or NaOH) from the cathode compartment. Surprisingly, the cathodic process can effectively be carried out with the hydrogen evolution reaction (HER) using an electrocatalyst-modified cathode. With the assistance of an HER electrocatalyst, the HER reaction not only produces OH' for the formation of LiOH at a high-rate, but also generates H₂ as a valuable by-product. More importantly, even with low-cost HER electrocatalysts, such as metal alloys, metal oxides, metal sulfides, metal phosphides, or metal selenides, the current density could be readily increased by one order of magnitude at relatively low operating voltage, which considerably promotes the processing productivity and brings down the size of cell stack and the consequent cost.

Thus, in a first aspect of the invention, there is provided a method of recovering a valuable element from an active material of a lithium- or sodium-ion battery, respectively, the method comprising:

(a) providing an active material comprising lithium or sodium ions;

As will be appreciated, steps (c) and (d) will occur simultaneously once the process have been set in motion. In addition, it will be appreciated that one of Na and Li will be recovered. However, depending on the active material used, further valuable elements, such as Al, Cu, Co, Ni, Fe, Mn, V, and combinations thereof may also be recovered.

Advantages associated with this method include, but are not limited to the following.

• An increased current density and production of the desired products. In comparison with a recycling method that uses oxygen reduction reaction (ORR), the present invention may be carried out at a high current density, which produces OH’ for the formation of LiOH at a high-rate.

• Simplification of the flow cell construction, as well as a smaller cell stack. In comparison with the recycling paired with oxygen reduction reaction, the present invention operates with redox flow cells of simple construction and with a smaller size.

• In comparison with the recycling method that uses ORR, the present invention avoids using a sophisticated oxygen depolarized cathode to feed O2 and avoids the consumption of O2.

• Generation of the valuable by-product hydrogen

• This results in a reduced capital and processing costs, and therefore increased profit.

In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components/features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of’ or “consists essentially of”). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of’ or the phrase “consists essentially of’ or synonyms thereof and vice versa.

The phrase, “consists essentially of” and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

As will be appreciated, the process above is agnostic to whether the active material is obtained from a cathode and/or an anode. This is because the process can work for active materials of both types, though there may be a preference for cathode active materials.

As will be appreciated, the process described above relate to the recovery of lithium from spent (retired) batteries or from waste materials produced during the manufacturing process. As such, the active materials referred to above may not be capable of functioning in a battery in their current form and so there is a need to recover the lithium and other valuable elements for reuse.

The separator divides the cathode compartment from the anode compartment. It can be an electro-active ion conducting membrane (e.g., a lithium or sodium ion conducting membrane). The separator prevents cross-diffusion of the redox mediator and allows for movement of the electro-active ions (e.g., potassium ions, or, more particularly, lithium ions, sodium ions, magnesium ions, aluminum ions, silver ions, copper ions, protons, or a combination thereof; more particularly, the electro-active ions may be potassium ions, or, more particularly, lithium ions, sodium ions, magnesium ions, aluminum ions, copper ions, protons, or a combination thereof). For example, the separator may be a lithium phosphorus oxynitride glass, a lithium thiophosphate glass, sodium phosphorus oxynitride glass, a sodium thiophosphate glass, a NASICON-type lithium conducting glass ceramic, a NASICON-type sodium conducting glass ceramic, a Garnet-type lithium or sodium conducting glass ceramic, a ceramic nanofiltration membrane, a lithium or sodium ion-exchange membrane, or suitable combinations thereof.

Both electrodes in the apparatus, i.e. , the cathode and the anode, can be a carbon, a metal, or a combination thereof. Preferably, these two electrodes have high surface area, with or without one or more catalysts, to facilitate the charge collection process. They can be made of a carbon, a metal, or a combination thereof. Examples of an electrode can be found in Skyllas-Kazacos, et. al., Journal of The Electrochemical Society, 158, R55-79 (2011) and Weber, et. al., Journal of Applied Electrochemistry, 41 , 1137-64 (2011).

The cathodic active material may come from a depleted (retired) battery or from the manufacturing processes to manufacture such batteries. Any form of the cathodic active material may be used. For example, the cathodic active material may still be attached to a cathode electrode of a dismantled lithium- or sodium-ion battery or is provided free from the cathode electrode.

Examples of cathodic active materials include, but are not limited to, NaFePCU, NaCoCh, Na 2(PC>4)3, more particularly, LLFePC , LixNiaCofcAlcOa, Li_xNi_uCo_vMn_wO2, Li_xCoO2, Li_xMn2O4, and LixNio.5Mn1.5O4, where 0 <x< 1 , a + b + c = 1 , and u + v + w - 1 , and combinations thereof. In a particular embodiment of the invention that may be mentioned herein, the cathodic active material may be Li_xFePO4.

A redox mediator refers to a compound present (e.g., dissolved) in the solvent placed in the same tank (i.e. first tank) as the active material that acts as a molecular shuttle to transport the lithium to the electrode in the flow cell to which the tank is connected.

Any suitable redox mediator mentioned herein may be used in the method for recovering sodium or, more particularly, lithium ions from a cathodic active material. Particular examples that may be mentioned herein include, but are not limited to, hydroquinonesulfonic acid and, more particularly, ferricyanide (M₃Fe(CN)₆), ferrocyanide (M₄Fe(CN)₆), ferrocene (CioH Fe) and derivatives thereof (e.g. di(ethylsulfonic lithium) ferrocene (Ci4Hi₆FeS2O6Li₂)), iodide (Ml) and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH4. More particularly, the redox mediator may be selected from one or more of the group consisting of ferricyanide (M₃Fe(CN)_s), ferrocyanide (M₄Fe(CN)₆), iodide (Ml), and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH₄. As will be appreciated when seeking to recover sodium from a cathodic active material, M in the redox mediator may preferably be sodium and when seeking to recover lithium from a cathodic active material, M in the redox mediator may preferably be lithium.

Any suitable redox mediator that is compatible with the active material and the solvent used in the tank (i.e. first tank) may be used. Suitable redox mediators that may be mentioned herein include, but are not limited to ferricyanide (M₃Fe(CN)₆), ferrocyanide (M₄Fe(CN)₆), ferrocene (C HioFe) and derivatives thereof, iodide (Ml) and combinations thereof, where in each case M is independently selected from the group consisting of Li, Na, K and NH₄. As will be understood, when the active material contains lithium, M may preferably be Li and when the active material contains sodium, M may be Na. Any suitable concentration of the redox mediators may be used. For example, the total concentration of the redox mediator present in the solvent may be from 0.05 M to 2 M, such as from 0.05 M to 1.5 M, such as from 0.1 M to 1 M, such as from 0.3 M to 0.5 M, such as 0.2 M. Derivatives of ferrocene that may be mentioned herein include ferrocene derivatives having the structure:

In the above formulae, X is selected from H, F, Cl, Br, I, NO2, COOR, C1.20 alkyl, CF3, and COR, in which R is H or C1.20 alkyl; n is from 0 to 20.

Specific derivatives of ferrocene that may be mentioned herein include but are not limited to bromoferrocene, ferrocenylmethyl dimethyl ethyl ammonium bis(trifluoromethanesulfonyl)imide (Fc1 N112-TFSI), /V-(pyridin-2-ylmethylene)-1-(2- (diphenylphosphino) ferrocenyl) ethanamine (FeCp2PPh₂RCN), 1 ,1-dimethylferrocene (DMFc), tetraferrocene, di(ethylsulfonic sodium) ferrocene (Ci4Hi6FeS20eNa₂), and di(trimethanesulfonic sodium) ferrocene (Ci6H₂2FeS2O6Na₂).

In particular embodiments of the invention that may be mentioned herein, the derivatives of ferrocene may be di(trimethanesulfonic sodium) ferrocene (Ci6H₂2FeS2O6Na₂) or di(ethylsulfonic sodium) ferrocene (Ci4Hi₆FeS₂O6Na₂).

Further redox mediators that may be used in the current invention are described below with reference to WO 2013/012391.

Examples of redox mediators are discussed in depth in international application publication number WO 2013/012391, which is hereby incorporated by reference. For example, redox mediators disclosed in WO 2013/012391 include a metallocene derivative, a triarylamine derivative, a phenothiazine derivative, a phenoxazine derivative, a carbazole derivative, a transition metal complex, an aromatic derivative, a nitroxide radical, a disulfide, or a combination thereof.

The metallocene derivative used as a redox mediator may have the following structure:

In the above formula, M can be Fe, Co, Ni, Cr, or V; each of the cyclopentadienyl rings, independently, can be substituted with one or more of the following groups: F, Cl, Br, I, NO2, COOR, C1.20 alkyl, CF₃, and COR, in which R can be H or C1.20 alkyl.

The triarylamine derivative used as a redox mediator may have the following structure:

In the above formula, each of the phenyl rings, independently, can be substituted with one or more of the following groups: SO₃ and, more particularly, F, Cl, Br, I, NO2, COOR, C1-20 alkyl, CF₃, and COR, in which R can be H or C1.20 alkyl.

The phenothiazine derivative and the phenoxazine derivative used as a redox mediator may have the following structure:

R_a can be H or C1.20 alkyl, X can be O or S, each of the aromatic moieties is optionally substituted with one or more of the following groups: F, Cl, Br, I, NO2, COOR, R, CF₃, and COR, in which R can be H or C1.20 alkyl.

The aromatic derivative used as a redox mediator may have the following structure:

In these formulas, each of Ri, R2, R3, R4, Rs, and Rs, can be C1-20 alkyl, F, Cl, Br, I, NO2, COOR', CF3, COR', OR', OP(OR')(OR"), or NR'R", in which each of R' and R", independently, can be H, C1.20 alkyl.

The nitroxide radical used as a redox mediator may have the following structure:

In these formulas, each of R1 and R₂, independently, can be C1.20 alkyl or aryl. R1, R₂, and N together can form a heteroaryl, heteroaraalkyl, or heterocycloalkyl ring.

The disulfide used as a redox mediator may the following structure:

In these formulas, each of 1 and 2, independently, can be C1.20 alkyl, COOR', CF3, COR', OR', or NR'R", in which each of R' and R", independently, can be H or C1.20 alkyl.

Any suitable concentration of the redox mediator may be used in the solvent present in the first tank. Examples of suitable concentrations include, but are not limited to a total concentration of the redox mediator present in the solvent is from 0.05 M to 3 M, such as from 0.2 M to 0.5 M, such as about 0.4 M. When used herein, the term “total concentration” is intended to mean that the sum of concentrations of redox mediators (when more than one redox mediator is present) fall within the cited range.

Any suitable solvent may be used in the first tank. For example, any of the solvents (and combinations of solvents) referred to herein. In particular examples that may be mentioned herein, the solvent in the first tank may be water.

Any suitable solvent may be used in the first tank. As will be appreciated, the method above also requires a solvent to be present in both the tank containing the active material and the tank that collects the metal ion to be recycled from said active material. A suitable solvent is water, which may be used alone or in combination with an organic solvent suitable for use in a battery. Suitable organic solvents that may be mentioned herein include, but are not limited to a glyme solvent, a cyclic carbonate (such as propylene carbonate, ethylene carbonate, diethyl carbonate butylene carbonate, fluoroethylene carbonate, chloroethylene carbonate, vinylene carbonate, and/or the like), a linear carbonate (such as dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, and the like), a cyclic ester (such as y-butyrolactone, y- valerolactone, and the like), a linear ester (such as methyl formate, methyl acetate, methyl butyrate, and the like), a cyclic or linear ether other than a glyme (such as tetrahydrofuran (and derivatives thereof), 1 ,3-dioxane, 1 ,4-dioxane, 1 ,2-dimethoxy ethane, 1,4- dibutoxyethane, and the like), a nitrile (such as acetonitrile, benzonitrile, and/or the like), dioxolane or a derivative thereof, ethylene sulfide, sulfolane, and sultone or a derivative thereof. These solvents may be used in any suitable weight ratio with respect to the glyme solvent (e.g. tetraglyme). For example, the additional solvents may be selected from one or more of the group selected from propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, sulfolane, and acetonitrile.

The glyme solvent may be selected from one or more of the group consisting of ethylene glycol dimetheyl ether (monoglyme), diglyme, triglyme, tetraglyme, methyl nonafluorobutyl ether (MFE) and analogues thereof. Analogues of tetraglyme (CH₃(O(CH₂)₂)₄OCH₃) that may be mentioned include, but are not limited to, compounds where one or both of its CH₃ end members may be modified to either -C₂H₅ or to -CH₂CH₂CI, or other similar substitutions. In certain embodiments of the invention that may be mentioned herein, the glyme solvent is tetraglyme.

In particular embodiments that may be mentioned herein the solvent used in first or second tanks may be water alone or water in combination with a glyme solvent (e.g. water and tetraglyme). For example, the solvent in both tanks may simply be pure water.

In particular examples that may be mentioned herein, the solvent in the first tank may be water. Initially, the aqueous catholyte solution may be water, or water comprising CO₂. When used herein, when water is referred to, it is intended to refer to pure water, that is deionized water. Subsequently, as the method is conducted with a LIB active material, the aqueous catholyte solution starts to include LiOH and so, after steps (b) and (c) of the method above have been completed, the aqueous catholyte solution may be an aqueous LiOH solution, or an aqueous LiOH solution comprising air and CO₂ with Li₂CO₃ precipitate. Alternatively, if the method is conducted with a sodium active material (NIB), the aqueous catholyte solution starts to include NaOH and so, after steps (b) and (c) of the method above have been completed, the aqueous catholyte solution may be an aqueous NaOH solution, or an aqueous NaOH solution comprising air and CO₂ with Na₂CO₃ precipitate. Preferably, the initial solvent used in the method is water and so the LIB and NIB active materials would be expected to result in an aqueous LiOH or NaOH solution, respectively.

As will be appreciated, an important part of the current method is the ability to generate hydrogen, and thereby produce a useful by-product, while also reducing chemical consumption. This is achieved by ensuring that a hydrogen evolution catalyst is present in the catholyte. Any suitable hydrogen evolution catalyst may be used in the catholyte. For example, the hydrogen evolution catalyst may be selected from one or more of the group consisting of Pt, a metal alloy, a metal oxide, a metal sulfide, a metal carbide, a metal nitride, a metal phosphide, and a metal selenide. Any suitable metal alloy may be used in the current invention as the hydrogen evolution catalyst. For example, the metal alloy may be Pt-Ni-Co and/or Pt- Fe. Any suitable metal may be used in the metal oxide, a metal sulfide, a metal carbide, a metal nitride, a metal phosphide, and a metal selenide. For example, the metal may be one or more of the group selected from Cu and, more particularly, Co, Ni, Mo and W.

As will be appreciated, the generation of and accumulation of hydrogen in the cathode compartment and in the second tank is not desirable. To reduce issues (e.g. safety and pressure issues), the second tank may be fluidly connected to a hydrogen storage tank, which may collect the hydrogen gas from the second tank (e.g. by the hydrogen rising to the top of the second tank and being pumped or otherwise fed into the storage tank).

The method disclosed herein is agnostic to the type of active material used - in that it may come from a cathodic active material or an anodic active material. The anodic active material may come from a depleted (retired) battery. Any form of the anodic active material may be used. For example, the anodic active material may still be attached to an anode electrode of a dismantled sodium- or lithium-ion battery or is provided free from the anode electrode. Any suitable material may be used as the anodic active material. For example, the anodic active material may be selected from one or more of Li4Ti₅0i2, graphite, silicon, hard carbon. It will be appreciated that the graphite, silicon, and hard carbon active materials may be impregnated with sodium or, more particularly, lithium following use in a battery.

The process for recovering anodic active material is analogous to the process described hereinbefore for the recovery of cathodic active materials. While the process described herein make use of only a cathodic or anodic active materials separately, it will be appreciated that the same process as described above may be run for a combination of the cathodic and anodic active materials.

In particular embodiments mentioned herein, the active material may be a cathodic active material of a dismantled lithium- or sodium-ion battery.

The general process described above makes use of a flow cell-type arrangement, one embodiment of which is depicted in FIG. 1. It will be appreciated that the general design depicted in this figure is applicable to both cathode and anode active material recovery processes. While the illustration uses a lithium active material, it will be appreciated that a sodium active material may be used instead.

The recycling apparatus 100 comprises a redox targeting-based electrolytic flow cell 101 integrated with a H₂ storage tank 115. The redox targeting-based electrolytic flow cell 101 includes a cathodic cell compartment 102 comprising a catholyte tank 110, having a cathode 111, and a cathodic tank 112 comprising water (initially and then aqueous LiOH as the reaction proceeds) 113 and a HER catalyst, where the catholyte tank and the cathodic tank are fluidly connected to one another by a fluid pathway 114. The cathodic tank 112 may also be connected to a hydrogen gas storage tank 115 by a suitable fluid pathway 116. The anodic cell compartment 103 includes an anolyte tank 120, having an anode 121 , and an anodic tank 122 comprising an active material (e.g. LixFePCU) 123 and a redox mediator (e.g. [Fe(CN)₆]³7 Fe(CN)₆]⁴ ) in aqueous media, where the anolyte tank and the anodic tank are fluidly connected to one another by a fluid pathway 124. A cation-exchange membrane 130 is disposed between the catholyte 110 and anolyte 120 tanks, which allows cations to move from the anolyte tank to the catholyte tank 110. A current collector is also attached to the catholyte and anolyte tanks. It will be appreciated that the aqueous media in the respective cathodic and anodic sides can circulate through the respective fluid pathways to allow the reaction to occur.

Upon operation, for instance, the redox mediator (e.g. [Fe(CN)6]³ ) oxidizes the spent cathode material 123, in this example LixFePC , 0<x<1, and extracts lithium ions from the LixFePC to form FePO4 as a solid and the salt [Fe(CN)e]⁴7Li⁺, which is soluble in water. Simultaneously, the electrolyte containing [Fe(CN)6]⁴’ and Li⁺ circulates back to the anodic cell compartment 120 for the electrochemical reactions. [Fe(CN)e]⁴’ is oxidized on the anode 121 coupled with a H2O reduction process (HER) to produce H2 and OH’ on the cathode 111. Meanwhile, lithium ions migrate through the cation-exchange membrane 130 to the cathodic compartment 110 and forms LiOH solution. During the electrochemical process, the redox mediator [Fe(CN)e]³' is regenerated on the anode 121 for a second leaching round, while H2 is continuously produced on the cathode 111 with the assistance of HER electrocatalyst. The hydrogen is then passed into the cathodic tank 112, where it is allowed to bubble to the top of said tank for collection and transfer to the hydrogen storage tank.

An analogous process may be used for any active material derived from a cathode or anode active material, which may be lithium- or sodium-ion based.

Further aspects and embodiments of the invention are provided in the following non-limiting examples.

Examples

Example 1

High-throughput electrolytic flow cell

Based on the “redox-targeting concept”, a novel high-throughput electrolytic flow cell to continuously break down the spent battery materials into valuable chemicals at ambient conditions, without consuming additional chemicals, was developed.

The working principle of the oxidative redox targeting-based strategy for spent LFP material recycling coupled with HER process is illustrated in FIG. 1. The recycling setup 100 comprises a redox targeting-based electrolytic flow cell 101 integrated with a H₂ storage tank 115. As shown in FIG. 1 , there is a recycling setup 100 that includes a cathodic cell compartment 102 comprising a catholyte tank 110, having a cathode 111, and a cathodic tank 112 comprising LiOH 113, where the catholyte tank and the cathodic tank are fluidly connected to one another by a fluid pathway 114. The cathodic tank 112 may also include a hydrogen gas storage tank 115 that is connected by a suitable fluid pathway 116 to the cathodic tank 112. The recycling setup 100 also includes an anodic cell compartment 103 comprising an anolyte tank 120, having an anode 121, and an anodic tank 122 comprising Li_xFePO4 123, where the anolyte tank and the anodic tank are fluidly connected to one another by a fluid pathway 124. A cationexchange membrane 130 is disposed between the catholyte 110 and anolyte 120 tanks, which allows cations to move from the anolyte tank to the catholyte tank. A current collector is also attached to the catholyte and anolyte tank. Upon operation, for instance, the redox mediator [Fe(CN)₆]³’ oxidizes the spent cathode material LixFePC , 0<x<1 , and extract Li⁺ from Li_xFePC>4 to form FePC solid and [Fe(CN)e]⁴' /Li⁺ solution. Simultaneously, the electrolyte containing [Fe(CN)6]^4- and Li⁺ circulates back to the anodic cell compartment for the electrochemical reactions. [Fe(CN)s]⁴' is oxidized on the anode coupled with a H2O reduction process (HER) to produce H2 and OH' on the cathode. Meanwhile, Li⁺ migrates through a cation-exchange membrane to the cathodic cell compartment and forms LiOH solution. During the electrochemical process, the redox mediator [Fe(CN)e]³' is regenerated on the anode for a second leaching round, while H2 is continuously produced on the cathode with the assistance of HER electrocatalyst.

The spent LixFePC powder (black mass) consists of conductive agent and binder. 2 g of black mass was immersed into 50 mL of 0.4 M Li₄Fe(CN)₆ solution in the anodic tank. 50 mL of 0.1 M LiOH was used as the catholyte and HER electrocatalyst (such as Pt, metal alloys, metal oxides, metal sulfides, metal phosphides, or metal selenides) modified carbon felt was used as cathode. Both catholyte and anolyte were pumped flowing through the cell and tanks. The generated H₂ was collected from the cathodic tank and stored into a H₂ storage tank. The electric current density was kept at 100 mA/cm², and voltage changes on the cell were monitored by an Arbin battery testing system.

Example 2

Oxidative leaching

The oxidative leaching process was investigated in the system described in Example 1.

Results and discussion

As shown in FIG. 2a, the voltage was maintained at around 1.8 V and stopped at a cut-off voltage of 2.3 V at the end of the electrolytic process. A leaching efficiency of around 97% based on the charge capacity was calculated. After reaction, the black mass was extracted from anolyte and dried. The XRD patterns (FIG. 2b) indicate that all the indexed peaks of pristine olivine LiFePCU vanished after leaching process, instead of the new pattern consistent with that of FePO4. Meanwhile, the catholyte was collected and dried in an oven. White powder of LiOH was obtained after drying overnight. The quantity was nearly consistent with the charge capacity of the cell. With suitable redox mediators, similar process can be implemented to recycle batteries with LiCoO2, LiNii/sMni/3Coi/3O2 and other cathode materials.

Claims

(a) providing an active material comprising lithium or sodium ions;

(d) capturing the lithium or sodium ions and producing hydrogen in the cathode compartment through an electrochemical reaction on the cathode electrode that produces LiOH or NaOH and hydrogen gas and transferring the resulting aqueous LiOH or NaOH and hydrogen gas in the resulting catholyte solution to a second tank, wherein: steps (c) and (d) can be repeated until the active material is consumed; the aqueous catholyte solution comprises a hydrogen evolution catalyst to facilitate the production of LiOH or NaOH and hydrogen gas; and the valuable element is selected from one or more of the group consisting of Al, Cu, Co, Ni, Fe, Mn, V, Na and Li.

2. The method according to Claim 1 , wherein the active material is a cathodic and/or anodic active material.

3. The method according to Claim 2, wherein the cathodic active material is still attached to a cathode electrode of a dismantled lithium- or sodium-ion battery or is provided free from the cathode electrode.

4. The method according to Claim 2 or Claim 3, wherein the cathodic active material is selected from one or more of NaFePCU, NaCoCh, NaV2(PC>4)3, more particularly, LixFePCU, LLNiaCofcAIcC , Li_xNi_uCo_vMn_wO2, l_i_xCoO2, Li_xMn₂O4, and LixNio 5Mn1.5O4, where 0 <x< 1 , a + b + c = 1 , and u + v + w - 1 , optionally wherein the cathodic active material is Li_xFePO4.

5. The method according to any one of the preceding claims, wherein the hydrogen evolution catalyst is selected from one or more of the group consisting of Pt, a metal alloy, a metal oxide, a metal sulfide, a metal carbide, a metal nitride, a metal phosphide, and a metal selenide, where the metal in each of the oxide, sulfide, carbide, nitride, phosphide and selenide is selected from one or more of the group is selected from Ni, Co, Cu, Mo and W.

6. The method according to any one of the preceding claims, wherein the redox mediator is selected from one or more of the group consisting of ferricyanide (M₃Fe(CN)₆), ferrocyanide (M₄Fe(CN)₆), ferrocene (CioH Fe), hydroquinonesulfonic acid and derivatives thereof, iodide (Ml) and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH₄.

7. The method according to Claim 6, wherein the redox mediator is selected from one or more of the group consisting of ferricyanide (M₃Fe(CN)e), ferrocyanide (M4Fe(CN)6), iodide (Ml), and bromide (MBr), where in each case M is independently selected from the group consisting of Li, Na, K and NH₄, optionally wherein the derivative of ferrocene is di(ethylsulfonic lithium) ferrocene (Ci4Hi_SFeS2O6Li₂)

8. The method according to Claim 6 or Claim 7, wherein the total concentration of the redox mediator present in the solvent is from 0.05 M to 3 M, such as from 0.2 M to 0.5 M, such as about 0.4 M.

9. The method according to any one of the preceding claims, wherein the second tank is fluidly connected to a hydrogen storage tank, which collects the hydrogen gas from the second tank.

10. The method according to any one of the preceding claims, wherein the solvent is pure water.

11. The method according to any one of the preceding claims, wherein the aqueous catholyte solution is initially selected from one of water or water comprising CO2.

12. The method according to any one of the preceding claims, wherein after steps (b) and (c) have been completed, and: (i) the active material is a lithium-ion battery material, then the aqueous catholyte solution is an aqueous LiOH solution, or an aqueous LiOH solution comprising CO2 with U2CO3 precipitate, optionally wherein the aqueous catholyte solution is an aqueous LiOH solution; or

13. The method according to any one of Claims 2 to 12, wherein the anodic active material is still attached to an anode electrode of a dismantled lithium-ion battery or is provided free from the anode electrode.

14. The method according to any one of Claims 2 to 13, wherein the anodic active material is selected from one or more of Li₄Ti₅0i2, graphite, silicon, hard carbon.

15. The method according to any one of the preceding claims, wherein the active material is a cathodic active material of a dismantled lithium- or sodium-ion battery.