Method for direct lithium metal production from lithium brine solutions

Abstract

A method and apparatus is disclosed for direct lithium extraction from brine solutions via a combined solvent extraction and electrowinning process that involves solvent extraction integrated with the electrodeposition of lithium metal from a non-aqueous solution, with the additional feature of solvent regeneration. Direct lithium metal collection from brine via a compatible solvent significantly reduces the operational and capital costs associated with current molten salt electrolysis methods for lithium metal production.

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 319,210, filed March 11, 2022, and U.S. Provisional Patent Application No. 63 / 339,479, filed May 8, 2022, both of which are incorporated by reference in their entireties.

[0002] background 1. Technical Field The present disclosure relates generally to a method for producing lithium metal, and more specifically, to a method for producing lithium metal by electrochemical deposition directly onto a substrate from a brine solution. [Background technology]

[0003] 2. Description of Related Art Lithium metal and many of its alloys are currently produced via molten salt electrolysis. The molten salt electrolysis process is carried out with a eutectic mixture of lithium chloride and potassium chloride as the electrolyte, a graphite anode, and a stainless steel cathode. KCl is added to the electrolyte mixture to lower the melting point of the KCl-LiCl mixture to about 400-420°C, compared to the melting point of pure LiCl, which is >600°C. The electrolysis process produces molten lithium metal at the cathode with a purity of >97%, due to the lower decomposition voltage of LiCl compared to KCl. Although the process produces high purity lithium metal, it is energy intensive due to the operating temperatures above 400°C, and the chlorine gas (Cl) produced at the anode is very volatile. 2 ) is also an undesirable by-product due to its high toxicity. Therefore, there remains a need to develop new methods for preparing high purity lithium metal. Summary of the Invention

[0004] overview This disclosure discloses a method and apparatus for direct lithium plating from aqueous brine solutions having lithium concentrations ranging from 100 ppm to 20,000 ppm at normal ambient temperatures via a solvent extraction-electrowinning process. The process involves selective lithium solvent extraction with a water-immiscible solvent and electrowinning lithium from the lithium impregnated solvent before being recycled for additional lithium extraction. The process is unique in that it utilizes the electrowinning of lithium metal in a water-immiscible solvent instead of stripping the lithium ions back into the aqueous phase. It should be noted that unlike base metals, lithium metal cannot be electrowinning from the aqueous phase due to its high reactivity with water. This approach also simplifies the solvent extraction process by eliminating half the process involving stripping, as the stripping role is performed by electrowinning. Another advantage of this process is that it does not require fresh water, which is important in remote and extremely arid lithium mining regions, such as desert environments and areas in the "lithium triangle" of South America (Argentina, Bolivia, and Chile). Electroplating or electrowinning of lithium metal directly from brine via a lithium salt-compatible solvent greatly reduces the operational and capital costs associated with current lithium metal production methods and greatly simplifies the process. Electrowinning can also be used to selectively extract metals from multi-component solutions of suitable solvents. The lithium metal deposited on the working electrode substrate in this process may be further purified for use in making lithium metal electrodes for primary or secondary lithium metal batteries. This process requires less energy and cost than the current state-of-the-art commercial lithium metal production method, which requires a molten salt electrolysis process followed by casting and extrusion of lithium metal ingots.

[0005] In one embodiment, the present disclosure discloses a process that requires combining the brine with an additional water-immiscible solvent; the additional water-immiscible solvent has a greater affinity for the lithium salt in the solution compared to the main salt impurities such as sodium, potassium, magnesium, and calcium chloride, as well as boric acid. In addition, the solvent has the advantage of having a wide electrochemical stability window. The added solvent must be highly soluble in the lithium salt, such as LiCl, immiscible with the brine solution, and have a wide electrochemical stability window. The brine solution and the added solvent are mixed to allow for the transfer of the lithium salt from the brine to the added solvent. The mixture is then allowed to settle and separate, separating the added solvent, which is saturated with the lithium salt, from the immiscible aqueous brine, which is depleted of the lithium salt. The lithium salt-loaded solution is continuously overflowed or underflowed into the electrochemical cell to electroplate lithium metal onto the cathode substrate. The lithium-depleted water-immiscible solvent phase is recycled and contacted with incoming fresh lithium salt-containing brine for continuous extraction.

[0006] In another aspect, the present disclosure provides a process for the solvent extraction of lithium chloride by combining one solvent having lithium salt selectivity for hydrometallurgical separation with a lithium brine solution. The brine solution and additive solvent are mixed to allow for the transfer of the lithium salt from the brine to the additive solvent, which is then contacted with a second solvent having desirable properties for the electroplating of lithium, and lithium is transferred to the second solvent. The second solvent with the solvated lithium salt may be extracted and used in an electrochemical cell to plate lithium metal onto a cathode substrate. Both the exhausted first and second solvents are recycled.

[0007] In another aspect, the present disclosure provides a process in which a cation exchange membrane may be used to assist in the transfer of lithium ions from a concentrated lithium brine solution to an alternative solvent for plating as lithium metal onto a conductive substrate. [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 invention as outlined above will be made by reference to embodiments thereof, which are illustrated in the accompanying drawings, which form a part hereof, but it should be noted that the drawings merely illustrate exemplary embodiments of the invention and therefore should not be considered as limiting its scope; the invention may be susceptible of other embodiments which are equally effective.

[0009] [Figure 1] FIG. 1 shows a schematic illustration of one embodiment of the method of the present disclosure for obtaining lithium metal directly from a lithium brine solution through a combined solvent extraction and electrowinning approach. [Diagram 2] FIG. 1 is a schematic diagram of an electrochemical cell used in an electrowinning process to plate lithium metal directly onto a cathode substrate from a solution of a lithium salt in a solvent. [Diagram 3] Figure 2 depicts an optical photograph of a schematic prototype three-electrode cell. [Figure 4] An optical photograph of the inside of the three-electrode cell shown in FIG. [Diagram 5] Optical photograph of the complete proof-of-concept prototype setup is shown, consisting of a 3-electrode cell connected to a potentiostat to control the electrochemical parameters during the lithium electrowinning process. [Figure 6] Voltammograms (or current-voltage curves) obtained during the electrodeposition of lithium metal onto a copper cathode in an electrochemical cell containing a 1 M LiPF6-DEC solution as the electrolyte, where DEC is a poorly water-miscible (< 4 wt%) solvent that dissolves the LiPF6 lithium salt. [Figure 7] 1 shows a voltammogram of the electrodeposition of lithium metal at a fixed potential in an electrochemical cell and the resulting lithium metal deposited on a copper-plated platinum cathode. [Figure 8] 4 depicts the electrochemical cell of FIG. 3 after electrodeposition of lithium metal onto the lithium copper substrate. [Figure 9] Voltammograms (current vs. voltage curves) obtained during the electrodeposition of lithium onto a copper substrate are shown. The lithium salt used during this measurement was LiPF6 and the solvent was diethylene carbonate. The concentration of the salt in the solvent was 1M LiPF6 in DEC. This salt in solvent solution was used for demonstration purposes. [Figure 10] 9 shows the current versus time plot for another run of lithium deposition from solution where a constant potential of 4 V was applied versus an Ag / AgCl reference electrode. This voltage was chosen after observing the plating voltages observed in the voltammogram of FIG. [Figure 11] 1 shows optical photographs of the results of an electrodeposition experiment carried out to obtain the current versus time plot of FIG 10. The left strip shows the copper cathode substrate before the experiment, and the right strip shows the lithium metal deposited on the copper cathode substrate after the electrodeposition process has been carried out. [Figure 12] FIG. 1 shows a schematic of one embodiment for enabling lithium metal deposition directly from brine with the aid of a cation exchange membrane that allows only lithium ions to pass from the lithium brine phase to the lithium salt in the solvent phase for electrodeposition onto a cathode substrate. [Figure 13] FIG. 12 shows cyclic voltammograms for lithium metal plating experiments carried out in the schematic prototype cell. [Figure 14] A process for simultaneous lithium extraction and electroplating is shown. [Figure 15] 15A and 15B show a demonstration apparatus for simultaneous lithium extraction and preparation for electroplating, including the cell layout. [Figure 16] 1 shows a cell process involving a sandwich liquid membrane. [Figure 17] A schematic diagram of a processing cell for sustainable, continuous R2R production of lithium from aqueous brine is shown. [Figure 18]FIG. 1 shows a schematic diagram of a processing cell for the deposition of lithium metal films onto moving Cu foils from an organic solution medium. [Figure 19] 1 shows the design architecture of an electroplating cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Detailed Description of Aspects The method and system of the present disclosure are described in more detail below with reference to the accompanying drawings in which various embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be considered limited to the illustrative embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

[0011] Direct lithium extraction (DLE) from brines is a challenging problem. The most abundant lithium brine resources on Earth, such as those in the South American "lithium triangle" (Argentina-Bolivia-Chile), are concentrated brines with high levels of total dissolved solids. These lithium brines are extracted by ion extraction, primarily Li + , Na + , K + , Mg 2+ , Ca 2+ , B + , and H + ), as well as anions (mainly Cl - , S.O. 4 2- , and O.H. - ) salts. Most direct lithium extraction techniques use fresh water to either elute lithium from the sorbent or to strip it from the lithium-selective solvent. However, the regions where direct lithium extraction is practiced are extremely dry, making their application even more difficult.

[0012] There is a high demand for lithium metal as future high capacity batteries will use lithium metal anodes. Currently, the world production of lithium metal is very low, and a large supply-demand gap is expected. This disclosure presents a new, significantly lower cost approach to achieve freshwater-free lithium metal production. This is achieved by an integrated solvent extraction (SE) with a novel electrodeposition (ED) approach as shown in Figure 1.

[0013] In the disclosed method of producing lithium metal directly from lithium brine, the lithium ions in the brine are selectively extracted into an added solvent medium by solvent extraction or membrane assisted solvent extraction. The lithium ions are then electrochemically deposited onto a conductive substrate from the final lithium-loaded organic or inorganic solvent medium in a process known as electrowinning. This process may also involve a series of solvent extraction steps prior to electrowinning lithium metal from the organic or inorganic solvent medium onto a conductive substrate. Lithium salts that may be used to electrodeposit lithium include, but are not limited to, LiCl, LiClO 4 , Li 2 SO 4 , or LiPF 6 The final purity of lithium deposited from the entire process starting with lithium brine can range from 80-99.99%. The final thickness of lithium metal plated from the initial concentrated brine solution can range from 1 nm to 5 mm. The solvent must have several key characteristics to enable integration into the process of the present disclosure: (1) the solvent must be able to highly solubilize or selectively extract dissolved Li ions / salts from the aqueous brine; (2) the solvent must enable cathodic deposition of Li metal; (3) the solvent must have long-term stability to resist reactive degradation of the anode in the electrochemical cell during the process; and (4) the solvent must be water immiscible. In the case of membrane-assisted solvent extraction, the membrane provides selective permeation of lithium from the brine into the additive solvent.

[0014] The lithium metal product resulting from the above process may be further refined to serve as an anode material in a primary or secondary battery in which the metallic lithium serves as at least one of the electrodes. Such battery chemistries for which viable metallic lithium metal electrodes may be produced by this process include, but are not limited to, lithium oxygen batteries; lithium sulfur batteries; rechargeable lithium metal batteries with lithium ion intercalation cathodes; lithium-MnO 2 primary batteries; and solid-state lithium metal batteries, which contain a solid-state lithium-ion conductor as the electrolyte rather than a liquid electrolyte with a solvated lithium-ion conductive salt.

[0015] Battery grade lithium metal requires additional purification after lithium metal ingots are produced from molten salt electrolysis to obtain the >99.8% purity of lithium metal required for secondary battery operation, and also requires additional steps for electrode fabrication in order to use the lithium metal in secondary batteries. The disclosed techniques can bypass the purification and electrode fabrication steps to directly produce battery grade lithium metal in the form of electrodes. Lithium metal electrodes produced by the disclosed methods can be 1 nm to 5 mm. This process may be done roll-to-roll to produce full commercial scale rolls of lithium metal plated on copper electrodes for use in the commercial fabrication of lithium metal secondary batteries; it limits the number of processing steps and further reduces the production cost of lithium metal electrodes for the relevant battery chemistry.

[0016] A. The device that actually performs the separation 14 illustrates a solvo-electro deposition process 100 for producing a lithium film. In one embodiment, the solvo-electro deposition process 100 may include step 102 of providing an aqueous brine, step 104A of producing a pure Li-containing aqueous solution (e.g., LiCl (lithium chloride)), step 104B of electrodepositing (e.g., membrane-assisted) lithium from an organic solution medium, and step 106 of resulting in Li metal film deposition (e.g., for a battery anode). In a related alternative embodiment, the solvo-electro deposition process 100 may include step 102 of providing an aqueous brine, step 104C of directly electrodepositing (e.g., membrane-assisted) lithium from an organic solution medium, and step 106 of resulting in dark gray Li metal film deposition (e.g., for a battery anode).

[0017] In connection with Fig. 14, Figs. 15A and 15B show a batch cell system 120 for use in connection with one embodiment illustrated in Fig. 14. Fig. 15A is a photographic representation of a laboratory demonstration version of a process cell (e.g., batch cell) system 120 and associated solvoelectrodeposition process 100 for simultaneously extracting and electrodepositing lithium in connection with the embodiment associated with Fig. 14. Fig. 15B is a graphical representation of the batch cell system separately shown in Fig. 15A. The batch cell system 120 may include a cell containment unit 122 (e.g., a vessel that can contain a liquid electrolyte and can house, e.g., electrodes and / or membranes), a working electrode 124 (e.g., a cathode, e.g., made of copper or another metal), a counter electrode 126 (e.g., an anode, e.g., made of mixed metal oxide (MMO) or platinum (Pt), a reference electrode 128 (e.g., to aid in measuring baseline conductivity), and a metal foil 130 (e.g., made of copper). Upon electrodeposition, the resulting composite metal foil 130A may include a base metal foil 130 and a lithium layer 132. As further seen in FIG. 15B, the processing cell (e.g., batch cell) system 120 includes a membrane 134 (e.g., a CEM or selective cation exchange membrane (sCEM)); +The process cell 120 may further include an anodic chamber 136 containing a lithium-containing aqueous brine, and a cathodic chamber 138 containing an organic solution medium of Li-X (salt) solvent. In one embodiment, the boundaries of the anodic chamber 136 and the cathodic chamber 138 may be at least partially defined by the cell containment unit 122 and the membrane 134. In one embodiment, the membrane 134 may be positioned between the working electrode 124 and the counter electrode 126. The counter electrode 326 and the working electrode 324 may be configured to be charged in a manner to drive the electrodeposition of lithium onto a metal foil 330 / 330A extending through / into the lithium-containing organic solution (e.g., in the cathodic chamber 138). In one embodiment, the process cell 120 may define a galvanic cell. In one embodiment, the counter electrode 126 is charged with Li in the anodic chamber 136. + The working electrode 124 may be in contact with a lithium-carrying organic solution in the cathodic chamber 138. In one embodiment, the cell containment unit 122 may be defined as a housing and / or container.

[0018] FIG. 15B illustrates an example laboratory demonstration of the batch cell process of FIG. 14 that allows for the electrodeposition of a Li metal layer 132 (from an organic solvent Li-X solution) onto a plate or foil cathode 130 (e.g., copper) while an organic solution medium (e.g., a lithium-containing organic electrolyte solution) in the cathode chamber 138 simultaneously extracts lithium from the aqueous solution or brine in the anode chamber 136. (As seen in FIG. 15B) + Conductive or Li +A selective membrane 134 may be placed between the organic and aqueous solutions. The extractive electrodeposition cell 120 may be configured with two chambers 136, 138 defined by the cell containment unit 122 and the intermediate membrane 134. One chamber 136 may contain an aqueous brine solution and the other chamber 138 may contain an organic solution. Each solution may also be replenished as needed from an external reservoir tank and / or natural source (e.g., lake, pond, aquifer, and / or well), with the lake 102 shown in FIG. 14 as an example of such a replenishment source. The process 100 of FIGS. 15A and 15B may be considered a solvo-electroextractive electrodeposition process in a single unit process cell 120. Depending on the cell dimensions, configuration, and solutions selected (brine and organic solutions), the current density for two-electrodeposition may be 100 / cm2 of membrane or cathode surface area. 2 During electrodeposition with a fixed current, the operating voltage can be 0 to 10 volts (including the Li reduction potential of about 3.2 V vs. the Ag / AgCl(KCl) reference electrode, plus the IR drop).

[0019] 16 illustrates a derivative cell configuration according to one embodiment of the present disclosure. The derivative cell configuration, generally labeled as a processing cell 220, includes a cell containment unit 222, a working electrode 224 (e.g., a cathode, e.g., made of copper or another metal), a counter electrode 226 (e.g., an anode, e.g., made of mixed metal oxide (MMO) or platinum (Pt)), a reference electrode 228, a composite metal foil 230A (e.g., made of copper and coated with a lithium layer), a Li-X solvent liquid membrane 234 (e.g., including a pair of CEMs and an intermediate solvent zone (not individually labeled)), a Li +The electrochemical cell may include an anode chamber 236 containing an aqueous brine, and a cathode chamber 238 containing an organic solution medium of Li-X solvent. It should be understood that throughout this disclosure, similarly numbered components (e.g., 120, 220, 320, and 420; 124, 224, 324, and 424; etc.) can be expected to be similar in function and / or design, unless specifically stated to the contrary for a given embodiment.

[0020] In comparison between FIG. 15B and FIG. 16, the intermediate membrane 134 (CEM or alternative CEM) in the two-chamber cell 120 of FIG. 15B may be replaced with a sandwiched liquid membrane or liquid chamber 234 as shown in FIG. 16. The sandwiched liquid membrane 234 may include a Li-X solvent sandwiched between two solid Li conductive membranes or CEMs (components not individually labeled). The liquid membrane 234 provides a Li-X solvent for permeation from the aqueous solution in the anode chamber 236 to the organic solution in the cathode chamber 238. + As such, FIG. 16 illustrates a process cell 220 for solvoelectroextraction-deposition process in a single unit batch that utilizes a sandwiched liquid membrane 234 to enable selective transport of Li ions from the aqueous brine in the anode chamber 236 into the organic solution medium in the cathode chamber 238. In the case of recirculating the liquid membrane 234 of the liquid in the intermediate chamber through the outer loop of the dehydration column, the liquid membrane (or chamber) serves as a barrier to block the transport of water molecules from the aqueous brine chamber to the organic solution chamber (while allowing Li transfer). This aids in sustained operation for hours with simultaneous extraction and deposition.

[0021] 17 illustrates one embodiment of a process cell 320 conducive to industrial large-scale continuous production using a roll-to-roll (R2R) arrangement to deposit a Li metal film onto a substrate foil (e.g., copper foil, or other metal film or web) while extracting lithium, for example, from an aqueous brine. The process cell 320, as illustrated in FIG. 17, includes a cell containment unit 322 (e.g., a vessel that can contain a liquid electrolyte and can house, for example, an electrode and / or a membrane), a working electrode 324 (e.g., a cathode, e.g., made of copper or another metal), a counter electrode 326 (e.g., an anode, e.g., made of mixed metal oxide (MMO) or platinum (Pt), a reference electrode 328 (e.g., typically positioned near (within a few millimeters) the cathode surface), a metal foil 330 (e.g., copper foil), a composite metal foil 330A (e.g., made of copper when coated with a lithium layer), a membrane 334 (e.g., a CEM or sCEM), a Li + The apparatus may include an anode chamber 336 containing an aqueous brine, a brine source 336A (e.g., a lake, well, aquifer, and / or storage container) for use in the anode chamber 336, a cathode chamber 338 containing an organic solution medium of Li-X solvent, an input / feed foil roll 340A, a product foil roll 340B (e.g., lithium-coated copper foil), a hold tank 342 (e.g., in which the product foil roll 340B is held) filled with an inert gas (e.g., argon (Ar)), and a dehydration column 344 (e.g., a dehydration column bed of zeolite). In one embodiment, the membrane 334 may be positioned between the working electrode 324 and the counter electrode 326. The counter electrode 326 and the working electrode 324 may be configured to be charged in a manner to drive the electrodeposition of lithium onto the metal foil 330 / 330A extending through the lithium-containing organic solution. The processing cell 320 may further include connecting conduits and / or one or more additional intermediate rollers (such as those shown but not labeled) as needed to facilitate fluid movement / replenishment and / or foil movement.

[0022] The roll-to-roll processing cell 320 of FIG. 17 can facilitate a continuous multi-step deposition process. In the first step, Li is introduced from an external source or reservoir 336A. + In a second step, the aqueous brine solution in the anode chamber 336 is replenished as needed to continuously provide Li + may be continuously transferred from the aqueous phase into the organic phase. In a third step, electrodeposition of Li metal may occur on a moving copper cathode 324 (e.g., in the form of copper foil 330 fed from a feed foil roll 340A) in a cathode (e.g., organic solution) chamber 338 while the Cu foil web 330, 330A is continuously moving through the electrodeposition zone. The moisture level of the organic phase may be controlled by a dehydration column 344 and associated recirculation loop. By a fourth step, the product roll 340B of Li metal-Cu foil web 330A may be stored and / or stored in an inert gas chamber 342; an argon (Ar) gas atmosphere or another suitable inert gas is provided in the chamber along with any necessary hardware to facilitate recovery of the product roll 340B.

[0023] 18 illustrates a roll-to-roll (R2R) cathodic deposition process for depositing a lithium (Li) metal film via an organic solution onto a moving metal (e.g., copper) according to one embodiment of the present disclosure. The R2R cathodic deposition process may be accomplished using a roll-to-roll (R2R) processing cell 420. The R2R processing cell 420 may include a cell containment unit 422, a working electrode 424 (e.g., a cathode, e.g., made of copper or another metal), a counter electrode 426 (e.g., an anode, e.g., made of mixed metal oxide (MMO) or platinum (Pt), a metal foil 430 (e.g., copper foil), a composite metal foil 430A (e.g., made of copper upon coating with a lithium layer), a cathode chamber 438 containing an organic solution medium of Li-X solvent, an input / feed foil roll 440A, a product foil roll 440B (e.g., lithium coated copper foil), an argon (Ar) gas filled hold tank 442 (e.g., in which the product foil roll 440B is held), and a dehydration column 444. The counter electrode 426 (e.g., anode) and the working electrode 424 (e.g., cathode) may be configured to be charged in a manner to drive the electrodeposition of lithium onto the metal foil 430 / 430A extending through the lithium-containing organic solution. It is noted that unlike the system 320 shown in FIG. 17, the R2R processing cell 420 may not incorporate a separate anode chamber and / or membrane, for example, since the Li-carrying organic solution serves as the Li source instead of the brine. Instead, both the anode 426 and the cathode 428 may be contained within the same chamber (e.g., 438), thereby simplifying the construction relative to the system 320 of FIG. 16.

[0024] Further, with reference to FIG. 18, if one or more lithium-containing organic solutions serve as the Li source, a R2R cathode deposition process using a roll-to-roll (R2R) processing cell 420 may be utilized, thereby simplifying the R2R arrangement as described above. In this case, the water content of the organic solution for the electrodeposition zone (e.g., 438) for the moving cathode 424 (e.g., metal (e.g., Cu) foil web 430; and composite (e.g., Li-Cu) foil web 430A) may be controlled to minimize the dissolution rate of the deposited Li metal (not individually labeled). Also, more Li-containing organic solution may be continuously fed into the electrodeposition tank / chamber 438 during continuous / sustained production. A stationary anode 426 may be placed outside the organic solution and / or modified with one or more coating materials (e.g., LFP (lithium iron phosphate)) to minimize anode degradation for longer organic media life. Also, other additives (such as ionic liquids) may be added or otherwise utilized in the organic phase to increase the solubility of the Li-X salt and refine the electrodeposition performance. For example, the ionic liquid (organic phase) may be heated to just above 180° C. (i.e., the melting point of Li metal) to allow electrodeposition and collection of liquid Li metal around the cathode.

[0025] In one embodiment, the linear speed of the driven copper web (v), the applied electrodeposition current (i), the width of the deposited lithium layer (w), and the current efficiency of lithium deposition (η) are related by the following equation: Q = iη / vw Equation 1 where Q is the total charge passed. Q is related to the amount of lithium metal deposited on the cathode surface. For example, for lithium with a single positive charge, each charge corresponds to a single lithium atom.

[0026] The electrodeposition time is defined by the following formula: t = η / vw Equation 2

[0027] To deposit useful lithium metal for battery anodes, it can be important to control the plating current density and thickness. In one embodiment, the lithium deposition rate is less than 0.2 mA / cm 2 ~0.8 mA / cm 2 and 1 mAh / cm 2 ~100 mAh / cm 2 where mA = milliamperes; cm = centimeters; and h = hours. From the above, the thickness range equivalent can be considered to be proportional to the resulting thickness since each charge corresponds to a single lithium atom. Using the two ranges, the electrodeposition time can be calculated using Equations 1 and 2. For example, for a total of 100 mAh / cm 2 An equal amount of Li was plated and it was then cooled to 0.2 mA / cm 2 If one were to perform this at a rate of 0.1% then the total deposition time would be 500 hours. Based on these conditions for Li electroplating, deposition times could range, for example, from 1.25 to 500 hours, based on the parameters selected and the thickness / thickness equivalent desired.

[0028] In one embodiment, a design with increased overlap of the cathode and anode may allow for extended electroplating times while still providing reasonable linear production rates. It should be understood that various design architectures may be utilized to achieve electroplating conditions. One such design for electroplating is shown in FIG. 19; this design features an extended overlap surface area for the two electrodes. The R2R processing cell 520 may include a cell containment unit 522, a working electrode 524 (e.g., made of copper or another metal, e.g., a cathode), a counter electrode 526 (e.g., made of mixed metal oxide (MMO) or platinum (Pt), e.g., an anode), and a metal foil 530 (e.g., copper foil), similar to the R2R processing cell 420. Unlike the R2R processing cell 420, the R2R processing cell 520 may further include a series of intermediate transport rolls 540C that carry the metal foil 530. The intermediate transport rolls 540C may be configured to facilitate defining multiple foil sections (e.g., two of which are labeled 530A and 530B), and a given foil section may be defined between the nearest pair of intermediate transport rolls 540C. The foil sections may together define multiple adjacent foil sections, e.g., 530A and 530B. In addition, a given counter electrode 526 may be considered an anode and may include / define multiple anode extensions (i.e., define a multi-prong anode 526); one of which is labeled as 526A. Each anode extension may extend between an associated pair of adjacent foil sections (e.g., anode extension 526A extends between foil sections 530A and 530B) to together define a given electroplating zone Z; multiple such electroplating zones Z may be defined by the R2R processing cell 520. The electrode surface overlap area A may facilitate increased plating volume and / or increased linear velocity v in Equation 2.In one embodiment, the R2R electroplating process facilitated by the R2R processing cell 520 may enable lithium electroplating reactions over a range of, for example, 0.5-1000 hours, 5-400 hours, or 20-300 hours, etc. In one embodiment, the large surface area overlap A associated with the R2R processing cell 520 may extend the mass transport window, where ion transport in the electrolyte is driven by the multi-prong anode 526.

[0029] It should be noted that the configuration of the processing cell is not necessarily limited to the exemplary design shown in the above figures. Besides variations in organic solution engineering, electrode designs and material types can be easily modified for improved performance, and such modifications are considered to be within the scope of the present disclosure. Furthermore, unless expressly excluded otherwise, it should be understood that the components described with respect to the various embodiments may be mixed and / or matched with respect to each other. In addition, although copper is discussed as a candidate material onto which lithium may be electrodeposited, it should be understood that other conductive metals or metal alloys may also serve as suitable substrates onto which lithium may be deposited.

[0030] In summary, one or more embodiments of the present disclosure may result in (1) a roll-to-roll Li metal film (battery anode) production technique; and / or a technique for lithium metal production and lithium ion extraction from either aqueous or organic solutions. Integrated hybrid solvo-electroprocessing allows for simultaneous lithium extraction and metal production in a single stage batch or continuous operation. "Solvo-processing" is the process for preparing Li metal films suitable for electrodeposition. + Organic solutions can be used as a transport medium or as a solvent to selectively extract lithium from aqueous brines. In the former case, the Li + Selective membranes (solid CEM or liquid) are used to extract Li for DLE (direct lithium extraction) from source brine. +The "electro-processing" of the present disclosure can utilize electrically enhanced rates of electrodialysis (for lithium extraction and transport mobility) and / or electrodeposition (for Li metal film production). Aqueous-organic biphasic electrodialysis can be uniquely implemented for the extraction / transport of lithium from aqueous brine / solution into organic solution media. Relative to competing electrowinning processes for Li metal production, the present technology can provide: (1) a lower cost option for producing Li metal films as battery anodes (thickness < 20 μm); and / or (2) simultaneous DLE and Li metal film electrodeposition from aqueous brine in a single integrated process.

[0031] The technology may manifest itself as one or more features. The technology allows for the combination of Li extraction (from aqueous brine) and Li metal (battery anode) production simultaneously in a continuous process that does not require process water. The process may be operated in either roll-to-roll (R2R) or batch mode for Li metal production (via electrodeposition of Li from the organic phase) and / or continuous lithium extraction from the aqueous brine. The technology may be implemented with an organic phase as the electrodeposition medium that may be either lithium salt soluble or lithium ion selective (as in the organic solution obtained from solvent extraction). The system may feature a dehydration method that can control the water content of the organic phase, thereby allowing for sustained electrodeposition of Li metal with better current efficiency and / or better Li metal film deposition. The method associated with the present disclosure provides for the transfer of Li between the aqueous and organic phases driven by an electrodeposition phenomenon. +The greater concentration gradient can result in faster direct lithium extraction (DLE) rates from aqueous brines. The integrated process can exploit phenomena such as electrodialysis to achieve faster ion mobility and / or transport from the aqueous phase into the organic phase. The system allows for lower temperature (e.g., room and / or ambient temperature), lower cost processing than molten salt electrowinning. The R2R version of the system and method can be used to directly produce film deposition of Li metal onto copper foil webs, which can be used, for example, as a suitable platform for Li battery anodes. EXAMPLES

[0032] Below are proof-of-principle exemplary cases that provide methods and specific conditions to enable lithium metal electrodeposition from a solvent extracted solution. The invention is in no way limited to these examples.

[0033] Example 1: LiPF as an ionic conductivity salt 6 Lithium deposition from organic solvents accompanied by A schematic diagram of the three-electrode electrochemical cell used to electrodeposit lithium metal, consisting of a working electrode (a cathode such as copper, copper-plated platinum, or another conductive substrate), a reference electrode (such as Ag / AgCl), and a counter electrode (anode) is shown in Figure 2. The experimental cell used to demonstrate lithium metal electrowinning directly from a solvent medium with a solvated lithium salt is shown in Figure 3.

[0034] Specifically, in one embodiment, the electrochemical cell comprises a well-defined circular flat surface (0.5 cm 2A cathodic copper rod is used as the working electrode with the sides electrically insulated so that only the cathode (Ag / AgCl (1M KCl)) face (gap of < 1 mm) is exposed to the electrolyte solution. A glass-encapsulated reference electrode (Ag / AgCl (1M KCl)) face (gap of < 1 mm) was used as the reference electrode. A platinum foil ring anode is placed concentrically at the bottom of the electrodeposition cell to serve as the counter electrode. The above-mentioned components are shown in FIG. 4 for clarity. It should be noted that the design of the electrochemical cell and the selection of electrodes (in shape, material type, and dimensions) are not limited to this example in terms of geometry, physical dimensions, or material composition. The overall experimental setup for the electrochemical cell and lithium metal electrowinning process is shown in FIG. 5.

[0035] FIG. 6 shows the voltammogram obtained during an initial linear sweep voltammetry experiment to determine the plating voltage of lithium metal onto a copper current collector in the experimental setup depicted in FIG. 5 with the experimental cell shown in FIG. 3. The electrolyte solution for this demonstration was 1M LiPF 6 in diethyl carbonate (DEC). The reduction-oxidation (redox) reaction was observed to occur near -2.8 V vs. Ag / AgCl reference electrode, as indicated by a dramatic increase in the absolute value of the measured current of the electrochemical cell. The onset of this initial current increase is due to breakdown of the DEC solvent, which is known to have a finite electrochemical stability window. A secondary redox reaction begins at approximately 3.2 V vs. Ag / AgCl, as indicated by the onset of electrochemical plating of lithium. This observed potential for lithium deposition is consistent with the thermodynamically predicted potential for this reaction based on a table of standard reduction potentials, i.e., the difference in the standard reduction potentials of lithium metal and the Ag / AgCl reference electrode (-3.045 V - 0.2223 V = -3.2673 V). This agreement between the experimentally observed potential and the thermodynamically predicted potential provides a preliminary indication that lithium metal can be electrowinning from solution. For reference, relevant standard reduction reactions and their corresponding potentials versus the standard hydrogen electrode (SHE) are provided. Li+ + e - → Li -3.045 V (cathode reduction reaction for Li metal deposition) AgCl + e - → Ag + + Cl - 0.2223 V (reference electrode, Ag / AgCl (1M KCl)) 2H + + 2e - → H 2 0.00 V (Standard Hydrogen Electrode, SHE)

[0036] In order to produce meaningful amounts of metallic lithium, a chronoamperometric experiment was performed in which the electrochemical cell voltage was held constant and the current was recorded as a function of time. The results from this experiment are presented in Figure 7. During this measurement, the cell voltage was held constant at -3.5 V versus the Ag / AgCl reference electrode. An optical photograph of the electrochemical cell showing the formation of a large grey solid deposit on the copper working electrode is shown in Figure 8. The grey deposit was collected for analysis and washed with N-methylpyrrolidine (NMP). One quick test to determine if the grey deposit contains metallic lithium is to submerge the solid in water. Metallic lithium can be produced by the reaction Li(s) + H 2 O(l) → LiOH(l) + H 2 (g) reacts violently with water. When the solid deposit collected from the chronoamperometry experiment was submerged in deionized water, gas bubbles immediately formed, which was believed to be due to hydrogen outgassing. In addition, the grey solid gradually dissolved, exposing the underlying copper substrate. The submerged water was analyzed using ICP to determine the amount and confirm the presence of Li. Based on the amount of lithium recorded, it was estimated that a layer of lithium between 2 and 7 microns was deposited in different experiments. The current efficiency was calculated to be in the range of 60-80%.

[0037] In the later stages of electrodeposition, dendritic lithium metal is formed (Figure 5). The faradaic efficiency of this lithium metal electrodeposition process was calculated to be 61%. In principle, the deposition rate (mg / s) of lithium metal onto the cathode surface can be controlled by varying the voltage and current applied in the electrochemical cell. Faraday's law, in one form, is: m / MW = [I t] / [n F]

[0038] where m = mass of deposited species (g), MW = molecular weight of deposited species, I = current (A), t = time (s), n = electron equivalents / mole, and F = Faraday's constant (96,485.3 C / eq or As / eq). For the lithium metal deposition process described herein, the MW is 6.941 g / mole and n = 1 electron / mole. The other values ​​in the above equation are either experimentally determined, experimentally applied, or are physical constants.

[0039] The above equation can be rewritten to determine the rate of lithium plating or lithium deposition: m / t = [I MW] / [n F]

[0040] If I is unknown but m / t is known, the equation can be rewritten again to solve for the required current to be applied to obtain the desired deposition rate: I = [m / tn F] / MW

[0041] This last equation can be used to adjust the deposition rate during processing in the methods described in this invention to obtain a lithium metal electrode of a desired thickness for use in a primary or secondary lithium metal battery.

[0042] Example 2: Scalability demonstration of lithium metal electrowinning for commercial production of lithium metal electrodes The copper rod cathode surface in the previous examples provided limited surface area for lithium deposition (0.5 cm 2 ). To increase the surface area for cathodic electrodeposition of Li metal, a long strip of copper was used as the working electrode, rather than a single end face of a copper rod. This copper strip had an electrochemically active surface area more than 10 times larger than the face of the copper rod used in the original lithium electrowinning experiments. This expansion of the working electrode demonstrates the scalability of this approach towards commercial applications, which require roll-to-roll deposition of lithium onto copper substrates up to 3 meters wide.

[0043] A proof-of-concept experiment similar to that of the previous example was performed on this larger copper-based working electrode. A linear sweep voltammogram showing a similar onset potential for lithium metal deposition as the small-scale electrowinning experiment is presented in FIG. 9. FIG. 10 shows the current versus time plot for a chronoamperometric experiment performed on the larger copper working electrode in the electrowinning cell. For this measurement, the cell voltage was held at −4 V versus the Ag / AgCl reference electrode. In this case, the voltage for this example was increased from that of Example 1 to overcome a possible kinetic barrier caused by the larger electrochemically active cathode surface area. As in Example 1, the electrochemical cell for lithium metal electrowinning from a solvent medium contained an Ag / AgCl reference electrode, a platinum counter electrode, and 1M LiPF as the electrolyte. 6 A visual confirmation of lithium metal deposition onto the larger copper working electrode is provided in FIG. 11, which shows the copper substrate before and after the electrowinning process.

[0044] The disclosed method for producing lithium metal from brine can be easily modified to utilize existing equipment or components for commercial electroplating or electrowinning. The electrowinning cell can utilize roll-to-roll cathodic deposition to provide scalable, large surface area deposition of lithium metal onto a substrate surface that is submerged in and pulled through a plating electrolyte medium. An example of this embodiment includes rolling copper foil through a liquid lithium electrolyte medium to plate lithium metal onto the copper foil substrate. Several existing commercial electrodeposition cells, such as industrial electrowinning or electroplating cells, may be modified and adapted for this room temperature hybrid solvent extraction and electrowinning process.

[0045] Example 3: Membrane-assisted lithium metal production from concentrated lithium brine One embodiment of the enclosed method allows for the use of a cation exchange membrane to aid in the separation of lithium ions from the concentrated lithium brine into an alternative solvent medium from which lithium metal may be plated. An electrochemical cell that may be used in this process is schematic in FIG. 12. In this cell, lithium ions are electrochemically driven from the concentrated lithium brine, through a lithium ion selective cation exchange membrane, into a solvent medium, and finally plated onto a metallic substrate used as the cathode in the cell. A cyclic voltammogram for such an electrochemical cell is provided in FIG. 13. The electrochemical cell used in this experiment consisted of a copper substrate cathode, a platinum anode, concentrated lithium brine as the anolyte, a lithium conductive salt solvated in a solvent as the catholyte, and a cation exchange membrane as a separator between compartments containing two different electrolyte media. Although this experiment shows the reversibility of the process, in practice, it is believed that the concentrated lithium brine would be continuously replenished to provide a constant source of lithium ions to drive the operation of the cell. As with Example 2, this process may also be modified to be a continuous roll-to-roll process.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

Claims

1. (A) extracting the lithium brine with a solvent to obtain a lithium solution; and (B) exposing the lithium solution to a voltage or current to obtain lithium metal.

1. A method for preparing lithium metal, comprising:

2. 10. The method of claim 1, wherein the lithium metal comprises at least 80% purity.

3. 10. The method of claim 1, wherein the lithium brine contains greater than 0.3 ppm lithium.

4. 4. The method of claim 3, wherein the brine comprises from about 50 ppm to about 75,000 ppm of lithium.

5. 10. The method of claim 1, wherein the solvent is water-immiscible.

6. 10. The method of claim 1, wherein the solvent is a polar aprotic solvent.

7. 10. The method of claim 1, further comprising a second solvent.

8. 10. The method of claim 1, further comprising extracting the lithium solution with the second solvent to obtain a purified lithium solution.

9. 10. The method of claim 8, further comprising exposing the purified lithium solution to a voltage or current in place of the lithium solution.

10. The method of claim 1 , comprising using at least two electrodes to apply the voltage or current.

11. 10. The method of claim 1, comprising applying a voltage of about -6 V to about 6 V.

12. 10. The method of claim 1, wherein the method is performed continuously.

13. 10. The method of claim 1, further comprising returning the lithium solution to the extraction step after the lithium solution has been exposed to the voltage or current.

14. 10. The method of claim 1, further comprising exposing the lithium-containing solution or lithium brine, with or without other soluble impurity ions, to a lithium-selective membrane.

15. 10. The method of claim 1, wherein the lithium is deposited on a cathode.

16. 10. The method of claim 1, wherein the lithium is deposited in a roll-to-roll process.

17. (A) Extraction chamber; (B) Plating chamber Equipped with the extraction chamber is in fluid communication with the plating chamber; the plating chamber comprises a cathode and the extraction chamber comprises an anode; Apparatus for obtaining lithium metal.

18. further comprising a lithium-selective membrane; the lithium-selective membrane is positioned between the extraction chamber and the plating chamber; further comprising a power source connected to the anode and cathode and capable of delivering a voltage or current; 18. The device of claim 17.

19. (A) a containment cell containing at least a lithium-containing solution; (B) a counter electrode extending into the containment cell; and (C) a working electrode extending into the containment cell; Equipped with the working electrode comprises a metal foil configured to be continuously moved through the lithium-containing solution via a roll-to-roll conveying system; and the counter electrode and the working electrode are configured to be charged in a manner to drive electrodeposition of lithium onto the metal foil extending through the lithium-containing solution. A system for cathodic electrodeposition of lithium (Li) onto a moving metal foil.

20. (A) Containment cell; (B) a counter electrode extending into the containment cell; (C) a working electrode comprising a metal foil extending into the containment cell; and a cation exchange membrane contained within the containment cell and positioned between the counter electrode and the working electrode; the cation exchange membrane and the containment cell together define a first chamber and a second chamber; the first chamber contains the working electrode and is configured to contain a lithium-containing organic solution; the second chamber contains the counter electrode and is configured to hold at least one of a lithium-containing aqueous solution or a lithium-containing brine; and the counter electrode and the working electrode are configured to be charged in a manner to drive both the movement of lithium ions through the cation exchange membrane and the electrodeposition of lithium onto the metal foil in contact with the lithium-containing organic solution. A system for the cathodic electrodeposition of lithium (Li) onto metal foils.

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