Systems and methods for metals production from brine solutions

Abstract

A method and system are disclosed for the direct room temperature production of lithium and other metals from brine solutions containing salts of various metal cations via a combination of sorbent extraction and electrochemical extraction / plating processes. The process uses a framework material that can reversibly insert / extract desired metal cations to absorb the desired metal ions from the brine solution. The metal-loaded framework material is then transferred to an electrochemical cell where the metal ions are extracted from the structure and plated in metallic form onto a conductive substrate. This process is a combination of methods to take metal ions directly from a brine solution to produce the end product metal, and is a significant improvement over current industrial processes in reducing the energy required for metal production.

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 327,231, filed April 4, 2022, the entire contents of which are incorporated herein by reference.

[0002] background 1. Technical Field The present disclosure relates generally to methods for producing metals at or near room temperature. More specifically, the present disclosure relates to methods for producing metals from brine solutions at or near room temperature. [Background technology]

[0003] 2. Description of Related Art For lithium, the typical products are lithium hydroxide monohydrate (also loosely referred to as lithium hydroxide or LiOH) and lithium carbonate (Li2CO3). Both chemicals are industrially important as precursor compounds to the cathode materials in lithium-ion batteries. With the growth in demand and production of electric vehicles, not only is the demand for these products growing, but a market for lithium in metallic form is also emerging. This sudden demand is resulting from the emergence of next-generation battery chemistries that allow lithium metal to be used as the anode in secondary lithium batteries with higher energy and power density than current lithium-ion technology. However, to meet the production targets of the commercialization of these battery chemistries, the expected future demand for lithium metal will require improvements in current production methods of lithium metal.

[0004] Currently, the production of lithium metal and many of its alloys uses a molten salt electrolytic process. The electrolytic cell in which this process takes place consists of a stainless steel cathode, a graphite anode, and a eutectic KCl-LiCl electrolyte. The process is carried out at approximately 400-500 °C and results in lithium metal with a purity of over 97%. The high temperatures required to carry out the electrolytic process consume a lot of energy and release chlorine gas (Cl2) as a highly toxic and undesirable by-product in the reverse reaction to the formation of lithium metal at the cathode. Other alkali or alkaline earth metals require high temperature processes such as molten salt electrolysis for potassium, carbothermic reduction for sodium, or the silicothermic process for magnesium. Summary of the Invention

[0005] overview The present disclosure provides a method and system for producing metals directly from a brine solution consisting of solvated salts with various cations and anions. A scaffold or framework material is inserted into the brine solution where it accepts metal ions, such as lithium ions, and then placed in a compatible electrolyte solution; where the metal ions can be removed and plated onto a substrate as a metal, such as lithium metal on copper. The process may use any scaffold or framework structure that can reversibly intercalate / deintercalate with the metal ion of interest and is stable in both the brine solution and in a suitable electrolyte solution. Additionally, the present invention includes an apparatus for selectively taking metal ions from a brine solution containing salts of a single or many different cations and plating them as the metal of interest, where the only input of the apparatus is a brine solution containing the metal ions with any type of counter anion, and the product output of the apparatus is the metal. The process, and the apparatus for performing the process, may operate as a batch or continuous process.

[0006] For the case of lithium metal, further improvements to this system could result in battery grade lithium metal, potentially in a roll-to-roll fashion and potentially in a form acceptable for use as a lithium battery anode. For now, the initial idea is to produce crude (>90% purity) lithium metal from a lithium brine solution. These further improvements to result in battery grade lithium metal may also be applied to produce other high purity metals of interest for secondary battery applications, such as sodium, potassium, or magnesium metal.

[0007] Other objects, features and advantages of the present disclosure will be apparent from the following detailed description. However, since various changes and modifications within the spirit and scope of the present disclosure will be apparent to those skilled in the art from this detailed description, it should be understood that the following detailed description and specific examples, although indicating specific aspects of the present disclosure, are given by way of illustration only. It should be noted that simply because a particular compound is ascribed to one particular general formula, it does not mean that the compound cannot belong to another general formula. [Brief description of the drawings]

[0008] So that the features, advantages, and objects of the present disclosure, as well as others which may become apparent, may be accomplished and more fully understood, a more particular description of the present disclosure as outlined above will be made by reference to embodiments thereof, which are illustrated in the accompanying drawings, which form a part hereof. It should be noted, however, that the drawings merely illustrate exemplary embodiments of the invention and are not therefore to be considered as limiting its scope; the disclosure may be susceptible of other embodiments which are equally effective.

[0009] [Figure 1] FIG. 1 is a general schematic diagram of the disclosed method for going from brine to lithium metal with a reusable sorbent framework material. [Diagram 2]FIG. 1 is a schematic diagram of one embodiment of the disclosed method for going from brine to lithium metal with a reusable sorbent framework material. [Diagram 3] FIG. 1 is a schematic diagram of one embodiment of the disclosed method for going from brine to lithium metal with a reusable sorbent framework material. [Figure 4] FIG. 1 is a detailed schematic diagram of the overall process of taking lithium ions from a brine solution to the end product of lithium metal. [Diagram 5] FIG. 1 is a schematic diagram of an apparatus for continuous direct lithium metal production from a brine solution. [Figure 6] FIG. 1 is a schematic diagram of an apparatus for batch production of lithium metal directly from a brine solution - this apparatus can be outfitted to allow for continuous processing if multiple cells are chained together. [Figure 7] FIG. 1 is a schematic diagram of a composite electrode matrix for embedding absorbent material and transitioning between extraction and metal plating stages. [Figure 8] FIG. 1 is an isometric view of the test cell setup for the proof-of-concept experiments performed in Example 2. [Figure 9] FIG. 1 is a top view of the test cell setup for the proof-of-concept experiments performed in Example 2. [Figure 10] FIG. 1 is a front view of the test cell setup for the proof-of-concept experiments performed in Example 2. [Figure 11] FIG. 1 is the overall experimental setup for the proof-of-concept run performed in Example 2. [Figure 12] The starting conductive substrate, in this case copper foil, prior to the lithium metal plating process. [Figure 13] It is a plated metal on a conductive substrate, in this case lithium metal on copper foil. [Figure 14] 1 is a scanning electron microscope image of as-received lithium metal produced via conventional manufacturing methods and rolled into all-metal foil. [Figure 15]1 is a scanning electron microscope image of a lithium metal anode plated on copper produced via the methods disclosed herein. [Figure 16] 1 is an X-ray photoelectron spectrum of as-received lithium metal (T sample) produced via conventional manufacturing methods and rolled in all-metal foil, and a lithium metal anode deposited on copper produced via the methods disclosed herein. [Figure 17] 1 is a plot of cycle number vs. specific capacity for a battery comprised of a LiFePO4-based cathode and a lithium metal anode produced via the methods disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Detailed Description of Aspects The present disclosure provides a method for producing metals directly from a brine solution, which is an aqueous solution of salts of many different cations. The overall process, and variations that serve as different aspects of the disclosed method, are shown in Figures 1-3. In the case of lithium, current industrial methods for lithium metal production must be carried out at temperatures ranging from 400°C to 500°C and involve the use of toxic chlorine gas (Cl2 (g) ) as a by-product, in contrast to the disclosed methods, all of which can be performed at room temperature and produce no toxic by-products. Additionally, the disclosed methods require equipment to perform the sorbent extraction process in tandem with the metal electrodeposition in a continuous manner. This process can be performed to provide any metal of interest, provided the starting brine solution contains the metal cation of the particular metal of interest. Metals to which this process can be extended include, but are not limited to, sodium, potassium, or magnesium.

[0011] Combining sorbent extraction with electrodeposition of metals in non-aqueous media requires a framework material capable of reversibly inserting / extracting ions of the final desired metal. For the purpose of producing metals from a brine solution, the sorbent framework must be capable of reversibly inserting / extracting metal ions. The sorbent framework must be stable in aqueous brine solutions and capable of inserting metal ions. In addition, due to the reactivity of some possible final metal products, such as lithium metal, the metal-loaded sorbent framework must be stable in non-aqueous electrolyte media and capable of electrochemically extracting metal ions therefrom. For illustrative purposes, the case of lithium metal production is discussed for the remainder of this disclosure, but it is understood that any metal of interest whose cation is present in the starting brine solution can be substituted.

[0012] The mechanism of sorbent extraction whereby lithium ions are inserted into the framework material in the brine solution may consist of, but is not limited to, concentration-driven insertion, chemical reduction / oxidation reactions, electrochemical reduction / oxidation reactions, or combinations thereof. The sorbent framework refers to a crystalline material with the ability to selectively insert / extract lithium ions over other ions present in the brine solution, such as sodium, potassium, magnesium, and calcium. These materials may further include transition metal complexes that form a framework with coordination complexes that allow for selective binding of lithium ions. In some embodiments, these complexes may preferentially bind lithium ions over other ions, such as calcium, magnesium, potassium, or sodium ions. In other embodiments, these sorbent frameworks may start with lithium coordinated to the sorbent framework and then the lithium is removed through a process of delithiation; the delithiation process provides an sorbent structure that can readily incorporate new lithium ions from the brine solution. Organic or inorganic materials that may be useful for this purpose include, but are not limited to, organosulfur compounds, carbonyl compounds, imine compounds, anatase TiO2, rutile TiO2, Li4Ti5O 12 , LiFePO4, and TiNb2O7. In addition, the absorbent framework may be comprised of a material in which lithium has already been synthesized to the capacity of the crystal structure, in which case a delithiation step is required before the material can be used as an absorbent framework. The absorbent framework is used in the absorbent extraction step and is then washed and dried to prevent contamination of the non-aqueous electrolyte medium required for the final step in the process. After washing and drying, the lithiated framework material is placed in a non-aqueous electrolyte solution where lithium ions are extracted from the framework absorbent material and plated onto a conductive substrate. Methods of lithium extraction in this non-aqueous electrolyte medium include, but are not limited to, concentration-driven reactions, pressure-driven reactions, chemical reduction / oxidation reactions, electrochemical reduction / oxidation reactions, or combinations thereof.

[0013] The final lithium metal product of the disclosed method may be further processed to produce battery grade lithium metal. This battery grade lithium metal may be further processed to produce a lithium metal anode for a primary or secondary lithium battery. The disclosed process may also be tailored to directly produce battery grade lithium metal and / or a lithium metal anode that may be used directly in a primary or secondary lithium battery. Such primary or secondary lithium battery chemistries that may use the lithium metal anode made directly by the disclosed process include, but are not limited to, Li-MnO2 batteries; Li-O2 batteries; Li-S batteries; Li[Ni x Mn y Co z ]O2(x + y + z = 1), Li[Ni x Co y Al z ]O2(x + y + z = 1), Li[Ni x Mn y ]O2(x + y = 1), Li[Li x Ni y Mn z ]O2(x + y + z = 1), or LiFePO4 cathodes; hybrid lithium metal batteries; or all-solid-state lithium metal batteries. The process may be tailored to produce high grade lithium metal or directly produce lithium metal anodes through the formulation of non-aqueous solvents with solvated lithium conductive salts that are used to extract lithium ions from the absorbent framework and plate them onto a conductive substrate.

[0014] Due to the unique nature of the combinatorial process of the present disclosure, new equipment must be constructed to perform the process from start to finish, either in a continuous or batch process. Figure 5 shows a schematic diagram of an apparatus that allows for a continuous process to produce lithium metal from a brine solution, possibly in a roll-to-roll manner. In this apparatus, the absorbent framework material is transferred between the brine solution and the non-aqueous solvent with lithium conductivity salt. A washing bath and a drying step are placed between each of the two main tanks - the brine tank and the non-aqueous solvent tank - to prevent either system from being contaminated by the other. In this design, the brine solution is the only aspect that must be replenished during use, since the lithium source should be continuously available. However, even this brine replenishment can be made into a continuous process with a suitable pumping system. Figure 6 shows an apparatus that allows for batch processing of the method described herein. In this apparatus, the absorbent framework remains in place while the required liquids - either the brine solution, the washing solution, or the non-aqueous solvent with conductivity salt - are passed through the apparatus depending on which process step is occurring. Optionally, a counter electrode is passed through the cell when lithium metal deposition is occurring. The non-aqueous solvent may be recycled in this device design.

[0015] The manner in which the absorbent scaffold structure is transferred or placed into the device will vary depending on the desired throughput for the process. In one embodiment of the method and device, a conductive additive, such as carbon black, graphene, or reduced graphene oxide, and a polymer binder, such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), may be embedded into the absorbent scaffold material. Some non-limiting examples of conductive additives include 0-50 wt%. Similarly, non-limiting examples of polymer binders include 0-30 wt%. Additionally, the composite may be cast onto a substrate. The substrate may be either a two-dimensional substrate, such as a metal foil, or a three-dimensional substrate, such as a metal foam. A schematic diagram of one embodiment in which a composite of absorbent scaffold material, conductive additive, and polymer binder is cast onto a two-dimensional metal foil substrate for use in any of the devices shown in Figures 5 and 6 is shown in Figure 7.

[0016] This specification, including the summary, brief description of the drawings, and detailed description, as well as the appended claims, refer to specific features of the present disclosure, including process or method steps. Those skilled in the art will understand that the present invention includes all possible combinations and uses of the specific features described herein. Those skilled in the art will understand that the present disclosure is not limited to or by the description of the embodiments provided herein.

[0017] It is also understood by those skilled in the art that the technical terms used to describe specific embodiments do not limit the scope or breadth of the present disclosure.When interpreting this specification and the appended claims, all terms should be interpreted in the broadest possible manner consistent with the context of each term.All technical and scientific terms used in this specification and the appended claims have the same meaning as commonly understood by those skilled in the art to which this invention belongs, unless otherwise defined.

[0018] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise. The verb "includes" and its conjugations should be construed as referring to elements, components, or steps in a non-exclusive manner. A referenced element, component, or step may be present, utilized, or combined with other elements, components, or steps not expressly referenced. The verb "operatively connecting" and its conjugations means completing any type of joint required to form a connection between two or more objects that were not previously joined, including electrical, mechanical, or fluid joints. If a first component is operatively connected to a second component, the connection may be either direct or through a common connector. "Optionally" and its various forms mean that the subsequently described event or circumstance may or may not occur. The description includes cases where the event or circumstance occurs and cases where it does not occur.

[0019] Conditional language, particularly "can," "could," "might," or "may," is generally intended to convey that some embodiments may include certain features, elements, and / or operations, but other embodiments do not, unless specifically stated otherwise or understood otherwise within the context in which it is used. Thus, such conditional language is generally not intended to imply that the features, elements, and / or operations are required for one or more embodiments; or that one or more embodiments necessarily include logic for determining, with or without user input or prompting, whether those features, elements, and / or operations are included or performed in a particular embodiment.

[0020] Thus, the systems and methods described herein are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While illustrative embodiments of the present systems and methods have been set forth for purposes of disclosure, there are numerous changes in procedural details for achieving the desired results. These and other similar modifications may readily suggest themselves to those skilled in the art and are intended to be encompassed within the spirit of the systems and methods disclosed herein and the appended claims. EXAMPLES

[0021] Example 1: Olivine-type FePO4 as an absorbent framework material for lithium metal production from aqueous brine solutions In one embodiment of the present invention, LiFePO4 may be chemically delithiated to form an FePO4 framework structure that serves as a vehicle to obtain lithium ions from the brine solution and make them lithium metal. In order to form the correct crystal structure to reversibly insert / extract lithium ions into it, FePO4 must be synthesized as LiFePO4 with lithium already present therein. Thus, for this proof-of-concept experiment, 31.56 g (0.2 moles) of LiFePO4 was chemically delithiated to FePO4 by mixing the starting LiFePO4 in aqueous solution with 27.032 g (.01 moles) of potassium persulfate (K2S2O8). The solution was mixed for 24 hours to ensure the structure was fully delithiated. The chemically delithiated FePO4 was allowed to settle to the bottom of the solution for 30 minutes, and the powder was collected to test for lithiation in real brine solution. Then, the chemically delithiated FePO4 was placed in the actual brine solution, and Na2S2O3 was added as a reagent to obtain lithium ions from the brine solution and insert them into the FePO4 structure to reform LiFePO4. The proof that the lithiation of the FePO4 absorbent framework material absorbed lithium from the brine solution was tested by inductively coupled plasma optical emission spectroscopy (ICP-OES) to observe the lithium concentration in the brine solution before and after the brine lithiation process of FePO4.

[0022] The results from the ICP-OES test are presented in Table 1; the results provide empirical proof that the chemically delithiated FePO4 reabsorbed lithium ions when placed in a brine solution. The dramatic reduction in lithium concentration after the brine lithiation procedure indicates that the majority of the lithium ions in the brine solution were intercalated into the FePO4 framework sorbent material to reform LiFePO4. One major concern in lithium extraction from a brine solution is the uptake of magnesium ions. For comparison, the magnesium content of the brine solution before and after the FePO4 lithiation procedure is also included in Table 1. The change in magnesium content in the brine before and after the FePO4 sorbent extraction was much less than the change in lithium content, indicating that the chemically delithiated LiFePO4 sorbent is highly lithium selective. Other ions of less interest in lithium extraction from brine are sodium, calcium, and potassium, and the concentrations of these ions did not show any significant change after the brine lithiation procedure. Thus, the chemically delithiated FePO4 was shown to be highly lithium selective in the uptake of cations from the brine solution.

[0023] Table 1. Lithium insertion from brine solution into FePO4 chemically delithiated from synthetic LiFePO4. TIFF2025513203000001.tif23161

[0024] After the brine lithiation procedure, the chemically delithiated FePO4 (now LiFePO4 via brine lithiation) may be washed and dried to remove residual salts from soaking in the brine solution, and then transferred to an electrochemical cell to extract lithium ions from the LiFePO4 and plate them as lithium metal onto a conductive substrate. Example 1 provided embodies the system outlined in FIG.

[0025] Example 2: A fully electrochemical process for producing lithium metal from a brine solution with a suitable sorbent framework materialIn one embodiment, as depicted in FIG. 3, the method of the present disclosure may include a process of absorbent extraction and lithium metal deposition performed electrochemically. In addition, if the absorbent framework material is synthesized as a lithium-containing material, the initial delithiation may also be performed electrochemically. For demonstration purposes, LiFePO4 is the starting material for this proof-of-concept experiment. LiFePO4 is integrated into an electrode composite consisting of conductive additives and a polymer binder material. The composite LiFePO4 electrode is then placed in an electrochemical cell as shown in FIGS. 8-10 with a non-aqueous solvent containing solvated lithium conductive salts. The LiFePO4 electrode is then electrochemically delithiated to obtain a FePO4 electrode. The FePO4 electrode may then be placed in a brine solution and electrochemically lithiated. The relithiated LiFePO4 electrode may then be placed again in a non-aqueous electrolyte solution to electrochemically extract lithium ions from the LiFePO4 structure and plate it onto a conductive substrate. Indeed, for this demonstration, the electrochemical cell was filled with a non-aqueous solvent with solvated lithium conductivity salt for the initial electrochemical delithiation step, with brine for the absorbent framework extraction step, and then washed with a cleaning solvent to avoid contaminating the cell for the final extraction and plating step; the final extraction and plating step was performed in a fresh solvent bath of non-aqueous solvent with solvated lithium conductivity salt. The complete experimental setup for this series of tests is provided in FIG. 11. A power supply was used to provide a constant voltage across the cell for all electrochemically driven steps. The starting conductive substrate, in this case copper foil, before the lithium metal plating step is shown in FIG. 12. The plated metal on the conductive substrate, in this case lithium metal on copper foil, is shown in FIG. 13. Table 2 shows the analytical results of several cycles performed with the method and system described herein. The concentration of lithium in the brine decreased with each cycle of absorbent extraction followed by lithium metal plating from the lithiated absorbent material in a separate non-aqueous solvent bath with lithium conductivity salt.The weight and thickness of the lithium metal plated after each cycle are also provided in Table 2, demonstrating that extremely thin lithium metal can be produced. The thickness and weight of the final metal product produced during each cycle can be further tuned through the amount of sorbent framework material used in the production run.

[0026] Table 2. Proof-of-concept results of chemically delithiated LiFePO4-olivine FePO4 framework for lithium metal production directly from brine solutions. TIFF2025513203000002.tif51161

[0027] FIG. 14 shows the morphology of lithium metal produced by conventional molten salt electrolysis calendered into a free-standing foil. Even with existing processes, the surface is not completely smooth, and the inhomogeneity provides nucleation sites for dendritic lithium when cycled in a battery. The lithium metal produced by the disclosed method (FIG. 15) shows extremely large grains, which is an indication of a dense lithium metal plating, beneficial for use in secondary lithium metal batteries. Further spectroscopic evidence that the plated metal is indeed lithium metal and not another metal with similar optical properties is provided in FIG. 16. FIG. 16 shows the X-ray photoelectron spectroscopy (XPS) spectra for the as-purchased lithium metal sample shown in FIG. 14 (Sample T) and the lithium metal anode produced by the disclosed method (Sample AK). The similarity of the large peak around 55 eV demonstrates the presence of metallic lithium in both samples, and the other peaks present are likely due to surface contamination or alternative lithium products resulting when the lithium metal is exposed to various conditions. These additional peaks are common because XPS is a surface-sensitive technique that probes the bonding state of chemical species within the first 5-10 nanometers of a sample.

[0028] To demonstrate the viability of the lithium metal anode product produced by the disclosed method, a coin cell was prepared with the lithium metal and a commercially available LiFePO4 composite cathode. The cycling of the coin cell is shown in FIG. 17 - starting at a low current rate of C / 20 and then cycling iteratively to a final rate of C / 3 for extended cycling. The cell exhibited stable cycling and high coulombic efficiency over the duration of the galvanostatic cycling experiment. Thus, it was shown that the lithium metal anode produced by the present method can serve as a viable anode in secondary lithium cells and, if optimized, could enhance the performance matrix of secondary lithium metal batteries, as expected for cells incorporating lithium metal anodes in place of conventional graphite anodes.

Claims

1. A method for preparing high-purity metals, including the following steps: (A) A step of exposing an absorbent material that absorbs metal ions to a brine solution in order to form a metal-filled absorbent material; and (B) A step of exposing the metal-filled absorbent material to an electric current in order to obtain the high-purity metal and the metal-consumed absorbent material.

2. The method according to claim 1, wherein the brine solution contains at least 0.3 ppm of lithium.

3. The method according to claim 2, wherein the brine contains one or more impurity metal salts, and the impurity metal salts are different from the metal ions.

4. The method according to claim 3, wherein the brine solution contains an impurity metal salt selected from lithium salts, calcium salts, magnesium salts, sodium salts, potassium salts, cesium salts, boron salts, barium salts, strontium salts, or combinations thereof.

5. The method according to claim 1, wherein the absorbent material is a solid material.

6. The method according to claim 1, wherein the absorbent material is a lithium intercalation material.

7. The method according to claim 1, wherein the absorbent material is fixed to the surface.

8. The method according to claim 1, wherein the absorbent material is generated after exposure to a monovalent or divalent metal-consuming solution.

9. The method according to claim 1, wherein the metal-filled absorbent material is incorporated into a composite containing a conductive material.

10. The method according to claim 1, wherein the metal-filled absorbent material is incorporated into a composite containing a polymer binder.

11. The method according to claim 1, wherein the metal-filled absorbent material is prepared to serve as an electrode.

12. The method according to claim 1, wherein an electric current is passed between the metal-filled absorbent material and the second electrode.

13. The method according to claim 12, wherein the second electrode enables the deposition of metal.

14. The method according to claim 1, comprising the step of washing the monovalent or divalent metal-consumed absorbent material with a washing solution in order to obtain a purified consumable absorbent material.

15. The method according to claim 1, further comprising the step of drying the purified consumed absorbent material in order to obtain a dried, purified consumed absorbent material.

16. (A) Absorbent material; (B) A first chamber containing one or more sealable openings for introducing fluid; (C) Electrodes for depositing metal; and (D) Power supply An apparatus for preparing metals, comprising the following:

17. The apparatus according to claim 16, wherein the absorbent material is deposited on a second electrode.

18. The apparatus according to claim 16, wherein the electrode, the second electrode, and the energy source are configured to allow energy to flow from the energy source to the electrode and the second electrode.

19. The apparatus according to claim 16, further comprising a second chamber.

20. The apparatus according to claim 19, wherein the second electrode is configured to rotate between the chamber and the second chamber.

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