[0001] This application claims the benefit of priority to United States Provisional Application No. 63/327,231, filed on April 4, 2022 the entire content of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

[0002] The present disclosure generally relates to a method for producing metal at or near room- temperature. More specifically, the present disclosure relates to a method for producing metal from a brine solution at or near room-temperature.

2. Description of Related Art

[0003] For lithium, typical commodities are lithium hydroxide monohydrate (also loosely referred to as lithium hydroxide or LiOH) and lithium carbonate (LiiCCh). Both chemicals are industrially important as precursor chemicals to lithium-ion battery cathode materials. With the growing demand and production of electric vehicles, not only is the demand for these commodities growing, but a market for lithium in its metallic form has emerged. This sudden demand stems from the emergence of next-generation battery chemistries that enable lithium metal to be used as an anode in secondary lithium batteries with energy and power densities that are higher than current lithium-ion technology. However, the current production methods for lithium metal must be improved to meet the upcoming demand for lithium metal to meet production targets of these battery chemistries as they become commercialized.

[0004] Currently, a molten salt electrolytic process is used to produce lithium metal and many of its alloys. The electrolytic cell that this process is performed in consists of a stainless-steel cathode, a graphite anode, and a eutectic KCl-LiCl electrolyte. This process is performed at -400- 500°C and yields a lithium metal of greater than 97% purity. The high temperature required to perform the electrolytic process is energy intensive and the counter reaction to the formation of lithium metal at the cathode is the evolution of an undesirable highly toxic chlorine gas (Ch) as a byproduct. Other alkali or alkaline earth metals require high temperature processing, such as molten salt electrolysis for potassium, carbothermal reduction for sodium, or a silicothermic process for magnesium.

SUMMARY

[0005] The present disclosure provides methods and systems to directly produce a metal from a brine solution consisting of solvated salts with various cations and anions. A skeleton or framework material is inserted into a brine solution, where it accepts metal-ions, such as lithium- ions, and then it is placed into a compatible electrolyte solution where the metal-ions can be removed and plated as a metal onto a substrate, such as lithium metal on copper. This process can use any skeleton or framework structure that can reversibly intercalate/deintercalate the metal-ions of interest and is stable in brine solutions as well as suitable electrolyte solutions. Additionally, this invention includes an apparatus for this process to take metal-ions selectively from a brine solution containing salts of a single or many different cations and plate it as a metal of interest such that the only input of the apparatus is a brine solution that contains metal-ions with any type of counter anions and the product output of the apparatus is metal. This process and the apparatus for performing this process can work in a batch or a continuous process.

[0006] For the case of lithium metal, further improvement to this system may yield battery grade lithium metal - possibly in a roll-to-roll fashion, and possibly in an acceptable form for use as a lithium battery anode. For now, the initial idea is to produce a crude (>90% purity) lithium metal from a lithium brine solution. These further improvements to yield 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 become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. Note that simply because a particular compound is ascribed to one particular generic formula doesn’t mean that it cannot also belong to another generic formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the features, advantages and objects of the disclosure, as well as others which may become apparent, are attained and can be understood in more detail, more particular description of the disclosure briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only example embodiments of the invention and is therefore not to be considered limiting of its scope as the disclosure may admit to other equally effective embodiments.

[0009] Figure 1. Overall schematic of the disclosed methods to go from brine to lithium metal with a reusable sorbent skeleton structure material.

[0010] Figure 2. Schematic of one embodiment of the disclosed methods to go from brine to lithium metal with a reusable sorbent skeleton structure material.

[0011] Figure 3. Schematic of one embodiment of the disclosed methods to go from brine to lithium metal with a reusable sorbent skeleton structure material.

[0012] Figure 4. Detailed schematic of overall process taking lithium ions from a brine solution to the final product of lithium metal.

[0013] Figure 5. Schematic of apparatus for continuous direct lithium metal production from brine solution.

[0014] Figure 6. Schematic of apparatus for batch production of lithium metal directly from brine solution - this apparatus can be outfitted to enable a continuous process if many cells are strung together.

[0015] Figure 7. Schematic of composite electrode matrix for embedding sorbent material and transferring between stages of extraction and metal plating processes.

[0016] Figure 8. Isometric view of test cell setup for proof-of-concept experiments conducted in Example 2.

[0017] Figure 9. Top view of test cell setup for proof-of-concept experiments conducted in Example 2.

[0018] Figure 10. Front view of test cell setup for proof-of-concept experiment conducted in Example 2.

[0019] Figure 11. Full experimental setup for proof-of-concept run performed in Example 2. [0020] Figure 12. The starting electronically conducting substrate - in this case copper foil - before the lithium metal plating step.

[0021] Figure 13. The plated metal on the electronically conducting substrate - in this case lithium metal on copper foil.

[0022] Figure 14. Scanning electron microscopy image of as purchased lithium metal produced via traditional manufacturing methods and rolled into an all-metal foil.

[0023] Figure 15. Scanning electron microscopy image of a lithium metal anode plated on copped produced via the methods disclosed herein.

[0024] Figure 16. X-Ray Photoelectron Spectra of an as purchased lithium metal produced via traditional manufacturing methods and rolled into an all-metal foil (T sample), and of the lithium metal anode deposited on copper produced via the methods disclosed herein.

[0025] Figure 17. Cycle number versus specific capacity plot of a battery consisting of an LiFcPC based cathode, and a lithium metal anode produced via the methods disclosed herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present disclosure provides methods to produce metal directly from a brine solution, which is an aqueous solution consisting of salts of many different cations. The overall process and variations that serve as different embodiments to the methods disclosed are shown in Figures 1-3. For lithium, in contrast to the current industrial methods of lithium metal production, which must be performed at temperatures ranging from 400°C to 500°C and produce toxic chlorine gas (Ch(g)) as a byproduct, the disclosed method can be performed entirely at room temperature and does not produce any toxic byproducts. Additionally, the disclosed method requires an apparatus to perform the processes of sorbent extract in tandem with metallic electrodeposition in a continuous fashion. This process can be performed to yield any metal of interest if the starting brine solution contains metal cations of the particular metal of interest. Metals that this process can be extended to include, but are not limited to sodium, potassium, or magnesium.

[0027] The combination of sorbent extraction into the electrodeposition of metals in a nonaqueous media requires a skeleton structure material that can reversibly insert/extract ions of the final desired metal. For the purpose of producing metal from a brine solution, the sorbent skeleton material must be able to reversibly insert/extract metal ions. The sorbent skeleton material must be stable in and be able to insert metal ions in an aqueous brine solution. Additionally, owing to the reactivity of some potential final metal products, such as lithium metal, the metal- imprcgnatcd sorbent skeleton material must be stable in a nonaqueous electrolyte media and have the ability for the metal-ions to be electrochemically extracted from it. For the purposes of description, the case of lithium metal production will be discussed for the remainder of this disclosure with the understanding that it can be substituted for any metal of interest with cations present in the starting brine solution.

[0028] The mechanism of sorbent extraction where lithium ions are inserted into a skeleton material in a brine solution can consist of, but is not limited to, a concentration driven insertion, a chemical reduction/oxidation reaction, an electrochemical reduction/oxidation reaction, or a combination thereof. Sorbent skeleton structures refers to a crystalline material with the ability to insert/extract lithium ions selectively over other ions present in brine solutions such as sodium, potassium, magnesium, and calcium. These materials may further comprise a transitional metal complex that forms a framework using a coordinate complex that allows for the selective binding of a lithium ion. In some embodiments, these complexes may preferentially bind lithium ions over other ions such as calcium ions, magnesium ions, potassium ions, or sodium ions. In other embodiments, these sorbent skeleton structures may be one started with lithium complexed to the sorbent skeleton structure and then have the lithium removed through a delithiating methods that provide a sorbent structure that can then readily uptake new lithium ions from a brine solution. Organic or inorganic materials that may serve this purpose include but are not limited to organosulfur compounds, carbonyl compounds, imine compounds, anatase TiOi, rutile TiOi, Li4TFOi2, LiFePO4 and TiNbjO?. Additionally, the sorbent skeleton material can consist of a material that is synthesized with lithium already in it to the fullest capacity of the crystalline structure, but in this case a delithiation step is required prior to use of the material as a sorbent skeleton material. The sorbent skeleton material is used in the sorbent extraction step, then it is washed and dried to prevent contamination of the nonaqueous electrolyte media that is required for the final step in the process. After washing and drying, the lithiated skeleton structured material is placed in a nonaqueous electrolyte solution where the lithium ions are extracted from the skeleton sorbent material and plated onto an electronically conductive substrate. The method of lithium extraction in this nonaqueous electrolyte media can include, but is not limited to, a concentration driven reaction, a pressure driven reaction, a chemical reduction/oxidation reaction, an electrochemical reduction/oxidation reaction, or a combination thereof. [0029] 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 be able to use a lithium metal anode made directly with the disclosed process include, but are not limited to Li-MnO batteries, Li-02 batteries, Li-S batteries, rechargeable lithium metal batteries with an Li[Ni _x Mn _y Co _z ]O2 (x+y+z=l), Li[Ni _x Co _y Al _z ]O2 (x + y + z = 1), Li[Ni _x Mn _y ]02 (x + y = 1), Li[Li _x Ni _y Mn _z ]02 (x + y + z = 1), or LiFePO4 cathode, hybrid lithium metal batteries, or all- solid- state lithium metal batteries. The process can be tailored to produce high grade lithium metal or directly produce lithium metal anodes through the formulation of the nonaqueous solvent with a solvated lithium conducting salt used for extracting lithium ions from the sorbent skeleton structure and plating them onto an electronically conductive substrate. [0030] Owing to the unique nature of the combined methods disclosed, new apparatuses must be constructed to perform the process from start to finish in either a continuous or batch process. Figure 5 shows a schematic of an apparatus that can enable a continuous process to produce lithium metal from a brine solution, possibly in a roll-to-roll fashion. In this apparatus, the sorbent skeleton material is transferred between a brine solution and a nonaqueous solvent with a lithium conducting salt. A wash bath and a drying step is placed between each of the two primary tanks - the brine tank and the nonaqueous solvent tank - to prevent contamination of either system with each other. In this design, the brine solution is the only aspect that must be replenished during use as a lithium source must continuously be available. However, even this brine replenishment can be made to be a continuous process with a suitable pump system. Figure 6 shows an apparatus that would enable a batch process of the methods described herein. In this apparatus, the sorbent skeleton structure remains stagnant while the necessary liquid - either brine solution, wash solution, or a nonaqueous solvent with a conducting salt - is passed into the apparatus depending on which process step is occurring. A counter electrode is passed into the cell as needed when deposition of lithium metal is occurring. The nonaqueous solvent can be recycled in this apparatus design.

[0031] The manner in which the sorbent skeleton structure is transferred or placed into the apparatus is dependent on the desired throughput for the process. In one embodiment of the methods and apparatuses, the sorbent skeleton material may be embedded with an electronically conductive additive - such as carbon black, graphene, or reduced graphene oxide - and a polymer binding agent - such as poly vinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). Some non-limiting examples of the electronically conductive additive include 0-50 wt%. Similarly, nonlimiting examples of the polymer binding agent include 0-30 wt%. Additionally, this composite may be cast onto a substrate. This substrate may either be a two-dimensional substrate, such as a metallic foil, or a three-dimensional substrate, such as a metallic foam. Figure 7 demonstrates a schematic of one embodiment where a composite of the sorbent skeleton material, an electronically conductive additive, and a polymer binder are casted onto a two-dimensional metallic foil substrate for use in either of the apparatuses shown in Figure 5 and Figure 6.

[0032] The Specification, which includes the Summary, Brief Description of the Drawings and the Detailed Description, and the appended Claims refer to particular features (including process or method steps) of the disclosure. Those of skill in the art understand that the invention includes all possible combinations and uses of particular features described in the Specification. Those of skill in the art understand that the disclosure is not limited to or by the description of embodiments given in the Specification.

[0033] Those of skill in the art also understand that the terminology used for describing particular embodiments does not limit the scope or breadth of the disclosure. In interpreting the Specification and 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 the Specification and appended Claims have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless defined otherwise.

[0034] As used in the Specification and appended Claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. The verb “includes” and its conjugated forms should be interpreted as referring to elements, components or steps in a non-exclusive manner. The referenced elements, components or steps may be present, utilized or combined with other elements, components or steps not expressly referenced. The verb “operatively connecting” and its conjugated forms means to complete any type of required junction, including electrical, mechanical or fluid, to form a connection between two or more previously non-joined objects. If a first component is operatively connected to a second component, the connection can occur either directly or through a common connector. “Optionally” and its various forms means that the subsequently described event or circumstance may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0035] Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that some implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language generally is not intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.

[0036] The systems and methods described herein, therefore, are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While example embodiments of the system and method have been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing 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 system and method disclosed herein and the scope of the appended claims.

[0037] Example 1: Olivine FePO4 as a sorbent skeleton material for lithium metal production from an aqueous brine solution.

[0038] In one embodiment of the present invention, LiFePO4 can be chemically delithiated to from an FePO4 skeleton structure that can serve as a vehicle to take lithium ions from a brine solution and turn them into lithium metal. To form the correct crystalline structure to reversibly insert/extract lithium ions into it, FePO4 must be synthesized with lithium pre-existing in it as LiFcPCU- Thus, for this proof-of-concept experiment, 31.56 g (0.2 mols) of LiFcPCU was chemically delithiated to FePC by mixing the starting LiFcPCU in an aqueous solution with 27.032 g (.01 mol) potassium persulfate (K2S2O8). The solution was mixed for 24 hours to ensure that structure was fully delithiated. The now chemically delithiated FePCU was allowed to settle to the bottom of the solution for 30 minutes and the powder was collected to be tested for lithiation in a real brine solution. The chemically delithiated FePO4 was then put into a real brine solution and NaiSiCh was added as a reagent to get lithium ions from the brine solution to insert into the FePC structure, reforming LiFePCU- Proof of lithiation of the FePC sorbent skeleton material absorbed lithium from the brine solution was tested with inductively coupled plasma- optical emission spectroscopy (ICP-OES) to observe the lithium concentration in the brine solution before and after the FcPOi brine lithiation process.

[0039] The results from the ICP-OES tests are presented in Table 1 and provide empirical proof that the chemically delithiated FePO4 reabsorbed lithium ions when placed into a brine solution. The drastic decrease in lithium concentration after the brine lithiation procedure indicates that most of the lithium ions in the brine solution inserted into the FePO4 skeleton sorbent material, reforming LiFePO4. A primary concern in the extraction of lithium from brine solutions is the uptake of magnesium ions. For comparison, the magnesium content of the brine solution before and after the FePCL lithiation procedure are included in Table 1. The change in magnesium content in the brine before and after the FePO4 sorbent extraction is considerably less than the change in lithium content, indicating that the chemically delithiated LiFePO4 sorbent is extremely lithium selective. Other ions of lesser interest in lithium extraction of brine are sodium, calcium, and potassium - the concentration of these ions did not show any change of significance after the brine lithiation procedure. Therefore, the chemically delithiated FePO4 is shown to be extremely lithium selective in its uptake of cations from the brine solution.

Table 1. Lithium insertion from brine solution into FcPCL that was chemically delithiated from as- synthesized LiFePCU.

[0040] After the brine lithiation procedure, the chemically delithiated FcPCk (now LiFcPCL after the brine lithiation) can be washed and dried to remove any residual salts leftover from being submerged in the brine solution and transferred to an electrochemical cell to extract the lithium ions from the LiFcPCL and plate them onto an electronically conductive substrate as lithium metal. The Example 1 provided embodies the system outlined in Figure 2.

[0041] Example 2: A fully electrochemical process for producing lithium metal from brine solutions with a compatible sorbent skeleton material. [0042] Tn one embodiment, as expressed in Figure 3, the current disclosed methods can include sorbent extraction and lithium metal deposition processes that arc performed electrochemically. Additionally, if the sorbent skeleton material is synthesized with as a lithium containing material, the initial delithiation can also be performed electrochemically. For the purposes of demonstration, LiFcPCU is the starting material for this proof-of-concept experiment. The LiFcPCU is integrated into an electrode composite consisting of an electronically conductive additive and a polymer binder material. Then the composite LiFcPCU electrode is placed into an electrochemical cell as shown in Figure 8-10 with a nonaqueous solvent containing a solvated lithium conducting salt. The LiFcPCU electrode is then electrochemically delithitated to obtain an FcPCU electrode. This FePO4 electrode can then be placed into a brine solution and electrochemically lithiated. This re- lithiated LiFcPCU electrode can then be placed again into a nonaqueous electrolyte solution to electrochemically extract the lithium ions from the LiFePCU structure and plate them onto an electronically conductive substrate. Practically, for this demonstration, the electrochemical cell was filled with nonaqueous solvent with a solvated lithium conducting salt for the initial electrochemical delithiation step, filled with brine for the sorbent skeleton extraction step, then the cell was washed with a cleaning solvent as to not contaminate the cell for the final extraction and plating step that was performed in a fresh bath of nonaqueous solvent with a solvated lithium conducting salt. The full experimental set up for this series of tests is provided in Figure 11. A power supply was used to supply constant voltage across the cell for all electrochemically driven steps. The starting electronically conducting substrate - in this case copper foil - before the lithium metal plating step is shown in Figure 12. The plated metal on the electronically conducting substrate - in this case lithium metal on copper foil - is shown in Figure 13. Table 2 shows the analytical results of a few cycles performed with the method(s) and system(s) described herein. The concentration of lithium in the brine lowered upon each cycle of performing the sorbent extraction and subsequently plating lithium metal from the lithiated sorbent material in a separate nonaqueous solvent bath with a lithium conductive salt. The weight and thickness of the lithium metal plated after each cycle is also provided in Table 2 and shows that extremely thin lithium metal can be produced. The thickness and weight of the final metal product produced during each cycle can be further tailored through the amount of sorbent skeleton material used in the production run. Table 2. Results from proof-of-concept experiment with a chemically delithiated LiFcPCL - olivine FCPO4- skeleton structure to produce lithium metal directly from brine solution.

[0043] Figure 14 shows the morphology of the lithium metal produced with conventional molten salt electrolysis methods that has been calendared into a free-standing foil. Even with extensive processing, the surface still is not completely smooth and the inhomogeneities provide nucleation sites for dendritic lithium when cycled in a battery . The lithium metal produced with the disclosed method (Figure 15) shows extremely large grains which is indicative of dense lithium metal platting and beneficial for use in a secondary lithium metal battery. Further spectroscopic evidence of that the metal platted is indeed lithium metal, rather than another metal with similar optical qualities, is provided in Figure 16. Figure 16 shows X-ray photoelectron spectroscopy (XPS) spectra for the as purchased lithium metal sample shown in Figure 14 (sample T) and for the lithium metal anode produced with the disclosed method (sample AK). The similarity of the major peaks around -55 eV demonstrate the presence of metallic lithium in both samples with other peaks present likely owing to surface contamination or alternative lithium products produced when the lithium metal has been exposed to various conditions. These additional peaks are prevalent since XPS is a surface sensitive technique that probes the binding states of chemical species within the first 5-10 nanometers of the sample.

[0044] To demonstrate the viability of the viability of the lithium metal anode product produced with the disclosed methods, a coin cell was prepared with this lithium metal and a commercial LiFePCL composite cathode. The cycling of this coin cell is shown in Figure 17 - the cell was started with a low current rate of C/20 and then iteratively take to a terminal rate of C/3 for extended cycling. The cell showed stable cycling and a high coulombic efficiency for the duration of the constant current cycling experiment. Therefore, it is shown that the lithium metal anode product produced with the current method can serve as a viable anode in a secondary lithium cell, and if optimized can enhance the performance metrics of secondary lithium metal batteries as expected for cells that incorporate a lithium metal anode instead of a traditional graphite anode.