Method for directly producing lithium metal from aqueous solution of lithium salt

Abstract

The invention relates to a method and a device for directly extracting lithium from a saline solution through a solvent extraction and electrolytic deposition combined process. According to the process, solvent extraction and electrodeposition of metal lithium in a non-aqueous solution are combined, and a solvent regeneration function is added. The lithium metal is directly extracted from the saline water through the compatible solvent, and compared with a current molten salt electrolysis method for producing the lithium metal, the related operation and capital cost is remarkably reduced.

Description

[0001] This application claims priority to U.S. Provisional Application No. 63 / 319,210, filed on March 11, 2022, and priority to U.S. Provisional Application No. 63 / 339,479, filed on May 8, 2022, the entire contents of both of which are incorporated herein by reference. Technical Field

[0002] The present disclosure generally relates to a method for producing lithium metal. More specifically, the present disclosure relates to a method for producing lithium metal by electrochemical deposition directly from a brine solution onto a substrate. Background Art

[0003] Lithium metal and many of its alloys are currently produced by molten salt electrolysis. The molten salt electrolysis process is carried out with a eutectic mixture of lithium chloride and potassium chloride (which serves as an electrolyte), a graphite anode, and a stainless steel cathode. KCl is added to the electrolyte mixture to reduce the melting point of the KCl-LiCl mixture to about 400-420°C, while the melting point of pure LiCl is >600°C. Since LiCl has a lower decomposition voltage than KCl, the electrolysis process can produce molten lithium metal with a purity greater than 97% at the cathode. Although the process produces high-purity lithium metal, its operating temperature of more than 400°C makes the process very energy-intensive, and the chlorine gas (Cl2) produced at the anode is not a desired byproduct due to its high toxicity. Therefore, there is still a need to develop new methods for preparing high-purity lithium metal. Summary of the invention

[0004] The present disclosure discloses a method and apparatus for direct lithium plating from an aqueous brine solution by a solvent extraction-electrolytic deposition process, the brine solution having a lithium concentration of 100 ppm to 20,000 ppm at normal ambient temperature. The method involves the use of a water-immiscible solvent for lithium-selective solvent extraction and the electrolytic deposition of lithium from the lithium-impregnated solvent, which is then recycled for additional lithium extraction. Instead of stripping lithium ions back to the aqueous phase, the electrolytic deposition of lithium metal in a water-immiscible solvent is used, and the above method is unique in view of this fact. It should be noted that, unlike the base metal, it is impossible to electrolytically deposit lithium from the aqueous phase due to the high reactivity of lithium metal with water. This method also simplifies the solvent extraction process, and the stripping process involved in half of the process is no longer necessary because the stripping task is performed by electrolytic deposition. Another advantage of the method is that no fresh water is required, which is very important for remote and extremely arid areas where lithium is mined, such as desert environments and the South American "lithium triangle" (Argentina, Bolivia and Chile). Extracting lithium metal by direct electroplating or electrolytic deposition from brine with lithium salt compatible solvents will significantly reduce the operating and capital costs associated with current lithium metal production methods and greatly simplify the process. Electrolytic deposition 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 method can be further purified for lithium metal electrode manufacturing for primary or secondary lithium metal batteries. The process requires less energy and cost intensiveness than the current advanced commercial lithium metal production method, which requires a molten salt electrolysis process followed by lithium metal ingot casting and extrusion.

[0005] In one embodiment, the present disclosure discloses a method that requires combining brine with an additional water-insoluble solvent that has a greater affinity for lithium salts in solution than major salt impurities such as sodium chloride, potassium chloride, magnesium chloride and calcium chloride, as well as boric acid. In addition, this solvent also has a wide electrochemical stability window. The added solvent must have a high solubility for lithium salts (e.g., LiCl), be immiscible with the brine solution, and have a wide electrochemical stability window. The brine solution and the additional solvent are mixed to transfer the lithium salts from the brine to the added solvent. The mixture is then separated, and during the separation process, the lithium salt-saturated added solvent and the lithium salt-depleted (lithium-poor) immiscible aqueous brine are separated. The lithium salt-loaded solvent continuously overflows or underflows into the electrochemical cell to electroplate lithium metal onto the cathode substrate. The water-insoluble solvent phase, now depleted of lithium, is recycled and contacted with the newly entered lithium salt-containing brine for continuous extraction.

[0006] In another embodiment, the present disclosure provides a method wherein solvent extraction of lithium chloride can be combined with a lithium salt selective solvent for hydrometallurgical separation with an aqueous solution of a lithium brine. The aqueous brine solution is mixed with an additional solvent to transfer the lithium salt from the brine to the additional solvent. The solvent is now contacted with a second solvent having the desired properties for electroplating lithium and the lithium is transferred to the second solvent. The second solvent in which the lithium salt is dissolved can be extracted and used in an electrochemical cell to plate lithium metal onto a cathode substrate. Both the first and second depleted solvents can be recycled.

[0007] In another embodiment, the present disclosure provides a method in which a cation exchange membrane can be used to assist in the transfer of lithium ions from a concentrated aqueous lithium salt solution to an alternative solvent medium for plating as lithium metal on an electronically conductive substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to understand in more detail the features, advantages and purposes of the present invention and how other features, advantages and purposes that may be apparent are achieved, the invention briefly summarized above may be described in more detail with reference to the embodiments of the invention shown in the accompanying drawings, which form a part of this specification. It should be noted, however, that the drawings illustrate only exemplary embodiments of the present invention and are therefore not to be considered as limiting the scope of the present invention, as the present invention may have other equally effective embodiments.

[0009] Figure 1 A schematic diagram of one embodiment of the disclosed method for directly obtaining lithium metal from an aqueous lithium salt solution by a combined solvent extraction and electrowinning process is shown.

[0010] Figure 2 Depicted 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 consisting of a lithium salt in a solvent.

[0011] Figure 3 Shown Figure 2 Optical photograph of the three-electrode battery prototype shown.

[0012] Figure 4 Shown Figure 3 Optical photograph of the interior of the three-electrode battery shown.

[0013] Figure 5 An optical photograph of a complete prototype setup used for proof of concept is shown. The setup consists of a three-electrode cell connected to a potentiostat to control the electrochemical parameters during lithium electrodeposition.

[0014] Figure 6The voltammogram (or current-voltage curve) obtained when lithium metal is electrodeposited onto a copper cathode in an electrochemical cell containing a 1M LiPF6-DEC solution as the electrolyte is shown. DEC is a solvent that dissolves LiPF6 lithium salt, which has low water miscibility (<4 wt%).

[0015] Figure 7 A voltammogram is shown for lithium metal electrodeposition at a fixed voltage, with the resulting lithium metal deposited onto a copper-plated platinum cathode in an electrochemical cell.

[0016] Figure 8 Describes the process of electrodepositing lithium metal onto a copper substrate. Figure 3 electrochemical cell.

[0017] Fig. 9 The voltammogram (current versus voltage curve) obtained when lithium was electrodeposited onto a copper substrate is shown. The lithium salt used in the measurements was LiPF6 and the solvent was diethylene carbonate. The concentrate of the salt in the solvent was a 1M solution of LiPF6 in DEC. The salt solution in the solvent is used for illustration purposes.

[0018] Fig.10 Another current versus time plot for lithium deposition from solution is shown, where a constant potential of 4 V relative to a Ag / AgCl reference electrode was applied. This voltage was observed after Fig. 9 The voltammogram was observed after the plating voltage was selected.

[0019] Fig.11 It is shown that to obtain Fig.10 Optical photograph of the results of an electrodeposition experiment performed with a current vs. time plot. The left strip shows the copper cathode substrate before the experiment. The right strip shows the lithium metal deposited on the copper cathode substrate after the electrodeposition process.

[0020] Fig.12 A schematic diagram of one of the embodiments for direct deposition of lithium metal from brine by means of a cation exchange membrane that allows only lithium ions to transfer from the lithium brine phase to the lithium salt in the solvent phase for electrodeposition onto the cathode substrate is shown.

[0021] Fig.13 Shown in Fig.12 Cyclic voltammograms of lithium metal plating experiments performed in the prototype cell shown in .

[0022] Fig.14 A process for simultaneous lithium extraction and electroplating is shown.

[0023] Figures 15A and 15B A demonstration apparatus for preparing simultaneous lithium extraction and electroplating including a cell layout is shown.

[0024] Fig.16A cell process including an interlayer liquid membrane is shown.

[0025] Fig.17 A schematic diagram of a process cell for sustained continuous R2R production of lithium from aqueous brines is shown.

[0026] Fig.18 A schematic diagram of a processing cell for depositing lithium metal films from an organic solution medium onto a moving copper foil is shown.

[0027] Fig.19 The design structure of the electroplating cell is shown. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] The methods and systems of the present disclosure will be described more fully below with reference to the accompanying drawings, in which embodiments of the present disclosure are shown. The methods and systems of the present disclosure may take many different forms and should not be construed as being limited to the illustrated embodiments set forth herein; rather, these embodiments are provided to make the present disclosure thorough and complete and to fully convey its scope to those skilled in the art. Like reference numerals denote like elements throughout.

[0030] Direct extraction of lithium from brines (DLE) is a challenging problem. The richest brine lithium 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 nearly saturated mixed salt solutions containing cations (primarily Li+, Na+, K+, Mg2+, Ca2+, B+, and H+) and anions (primarily Cl-, SO42-, and OH-). Most direct lithium extraction technologies use fresh water to elute lithium from an adsorbent or strip it from a lithium-selective solvent. However, the areas where direct lithium extraction can be performed are extremely arid, making its application more challenging.

[0031] As future high-capacity batteries are expected to use lithium metal anodes, the demand for lithium metal is expected to be high. Currently, the production of lithium metal worldwide is very small, and the gap between supply and demand is expected to be large. The present disclosure provides a new method for producing lithium metal without using fresh water and with significantly reduced costs. Figure 1 As shown, the method is achieved by integrating solvent extraction (SE) and a new electrodeposition (ED) method.

[0032] In the disclosed method of producing lithium metal directly from lithium brines, lithium ions in the brine are selectively extracted into an added solvent medium by solvent extraction or membrane-assisted solvent extraction. Then, in a process called electrolytic deposition, the lithium ions are electrochemically deposited from the final lithium-impregnated organic or inorganic solvent medium onto an electronically conductive substrate. Before the lithium metal is electrolytically deposited from the organic or inorganic solvent medium onto the electronically conductive substrate, a series of solvent extraction steps may also be used. Lithium salts that can be used to electrodeposit lithium include, but are not limited to, LiCl, LiClO4, Li2SO4, or LiPF6. Throughout the process starting from the lithium brine, the final purity of the deposited lithium can be 80 to 99.99%. The final thickness of the lithium metal plated from the starting concentrated brine solution can be in the range of 1 nm to 5 mm in thickness. The solvent must possess several key features to be integrated into the disclosed methods: (1) the solvent can be highly soluble or selectively extract dissolved lithium ions / salts from the aqueous brine; (2) the solvent allows for cathode deposition of lithium metal; (3) the solvent has long-term stability to resist degradation by anode reactivity in the electrochemical cell during processing; and (4) the solvent must be immiscible with water. In the case of membrane-assisted solvent extraction, the membrane can selectively permeate lithium from the brine into the added solvent.

[0033] The lithium metal product obtained by the above method can be further purified and used as an anode material in a primary or secondary battery, wherein the metallic lithium is used as at least one electrode. The feasible metallic lithium electrodes that can be produced by this process include, but are not limited to, lithium-oxygen batteries, lithium-sulfur batteries, rechargeable lithium metal batteries with lithium ion insertion cathodes, lithium-manganese dioxide primary batteries, and solid-state lithium metal batteries, which contain a solid lithium ion conductor as an electrolyte instead of a liquid electrolyte with a solvated lithium ion conducting salt.

[0034] After the production of lithium metal ingots by molten salt electrolysis, battery-grade lithium metal requires additional purification to obtain lithium metal with a purity greater than 99.8% required for the operation of secondary batteries, and additional electrode manufacturing steps are also required to obtain lithium metal for secondary batteries. The disclosed technology can bypass the purification step and the electrode manufacturing step to directly produce battery-grade lithium metal in the form of electrodes. The lithium metal electrodes made by the disclosed method can be between 1nm and 5mm. The process can produce full commercial-scale lithium metal rolls plated on copper electrodes in a roll-to-roll manner for commercial manufacture of lithium metal secondary batteries, thereby limiting the number of process steps and further reducing the production cost of lithium metal electrodes of related battery chemistry.

[0035] A. Device for carrying out separation

[0036] Fig.14A solvation electrodeposition process 100 for producing a lithium film is shown. In one embodiment, the solvent electrodeposition process 100 may include the steps of providing an aqueous brine 102, generating a pure lithium-containing aqueous solution (e.g., LiCl (lithium chloride)) 104A, electrodepositing lithium from an organic solution medium 104B (e.g., membrane-assisted), and generating a lithium metal film deposit 106 (e.g., for a battery anode). In another optional related embodiment, the solvation electrodeposition process 100 may include the steps of providing an aqueous brine 102, electrodepositing lithium directly from an organic solution medium 104C (e.g., membrane-assisted), and generating a dark gray lithium metal film deposit 106 (e.g., for a battery anode).

[0037] about Fig.14 , Figures 15A and 15B Shows about Fig.14 FIG. 15A is a block diagram of a battery system 120 related to an embodiment of the present invention. Fig.14A photographic representation of a laboratory demonstration version of a process cell (e.g., a batch cell) system 120 and a related solvation electrodeposition process 100 for simultaneous extraction and electrodeposition of lithium related to an embodiment. FIG. 15B is a graphical representation of the batch cell system additionally shown in FIG. 15A. The batch cell system 120 may include a cell housing unit 122 (e.g., a container capable of holding a liquid electrolyte and carrying, for example, electrodes and / or membranes), a working electrode 124 (e.g., a cathode made of, for example, copper or another metal), a counter electrode 126 (e.g., an anode made of, for example, a mixed metal oxide (MMO) or platinum (Pt)), a reference electrode 128 (e.g., to help measure 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 from FIG. 15B , the process cell (e.g., batch cell) system 120 may also include a membrane 134 (e.g., a CEM or a selective cation exchange membrane (sCEM)); and an anode chamber 136 carrying an aqueous brine containing Li+ (e.g., from a storage tank / container, a lake, a pond, and / or a well) and a cathode chamber 138 carrying a Li-X (salt) solvent organic solution medium. In one embodiment, the respective boundaries of the anode chamber 136 and the cathode chamber 138 may be at least partially defined by the battery housing unit 122 and the membrane 134. In one embodiment, the membrane 134 may be located between the working electrode 124 and the counter electrode 126. The counter electrode 326 and the working electrode 324 may be configured in a charging manner to drive lithium electrodeposition onto a metal foil 330 / 330A extending through / into the lithium-containing organic solution (e.g., in the cathode chamber 138). In one embodiment, the process cell 120 may define a galvanic cell. In one embodiment, the counter electrode 126 may contact the aqueous brine containing Li+ in the anode chamber 136, and the working electrode 124 may contact the lithium-loaded organic solution in the cathode chamber 138. In one embodiment, the battery housing unit 122 may be defined as a housing and / or container.

[0038] FIG. 15B shows Fig.14A laboratory demonstration example of a batch battery process that enables 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 the organic solution medium (e.g., an organic electrolyte solution containing lithium) in the cathode chamber 138 can simultaneously extract lithium from an aqueous solution or brine in the anode chamber 136. A Li+ conductive or Li+ selective membrane 134 can be placed in the middle between the organic solution and the aqueous solution (as shown in Figure 15B). This extraction-electrodeposition cell 120 can be configured with two chambers 136, 138, defined by a battery housing unit 122 and an intermediate membrane 134. One chamber 136 can contain one or more aqueous brine solutions, and the other chamber 138 can contain an organic solution. In addition, the corresponding solutions can be replenished from external storage tanks and / or natural sources (e.g., lakes, ponds, aquifers and / or wells) as needed, respectively, wherein Fig.14 Lake 102 shown in FIG. 1 is an example of a replenishment source. Figures 15A and 15B The process 100 can be considered as a solvent-electroextraction-electrodeposition process in a single process cell 120. Depending on the size, configuration and selected solution (saline and organic solution) of the cell, the current density of the two-electrode electrodeposition can be in the range of 0.1-100 mA per cm2 of membrane or cathode surface area. During the fixed current electrodeposition process, the operating voltage can be 0 to 10 volts (which includes the lithium reduction potential and IR voltage drop of about 3.2 V relative to the Ag / AgCl (KCl) reference electrode).

[0039] Fig.16 A derivative cell configuration according to an embodiment of the present disclosure is shown. The derivative cell configuration (generally labeled as process cell 220) may include a cell housing unit 222, a working electrode 224 (e.g., a cathode made of, for example, copper or another metal), a counter electrode 226 (e.g., an anode made of, for example, a 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 region (not separately labeled)). An anode chamber 236 carrying an aqueous brine containing Li+ and a cathode chamber 238 carrying a Li-X solvent organic solution medium. In the present disclosure, it should be understood that unless there is a specific description to the contrary for a given embodiment, similarly numbered components (e.g., 120, 220, 320 and 420; 124, 224, 324 and 424, etc.) should be similar in function and / or design.

[0040] In comparison of Figure 15B and Fig.16 When Fig.16As shown, the intermediate membrane 134 (CEM or selective CEM) in the dual chamber battery 120 of FIG. 15B can be replaced by an interlayer liquid membrane or liquid chamber 234. The interlayer liquid membrane 234 may include a Li-X solvent sandwiched between two solid lithium conductive membranes or CEMs (components not individually labeled). The liquid membrane 234 can provide Li+ selectivity for the organic solution that permeates from the aqueous solution in the anode chamber 236 to the cathode chamber 238. Therefore, Fig.16 A process cell 220 for a solvent-electroextraction-electrodeposition process in a single batch is shown, using an interlayer liquid membrane 234 to selectively transfer Li ions from the aqueous brine in the anode chamber 236 to the organic solution medium in the cathode chamber 238. With the liquid membrane 234 of the liquid in the intermediate chamber recirculated through an external loop of the dehydration column, the liquid membrane (or chamber) can act as a barrier to prevent the transfer of water molecules from the brine chamber to the organic solution chamber (while allowing lithium transfer). This will help maintain several hours of operation in simultaneous extraction and deposition.

[0041] Fig.17 One embodiment of a process cell 320 is shown that facilitates industrial-scale continuous production of lithium metal film deposition on a substrate foil (e.g., copper foil or other metal film or mesh) while simultaneously extracting lithium from an aqueous brine using, for example, a roll-to-roll (R2R) arrangement. Fig.17As shown, the process cell 320 may include a cell housing unit 322 (e.g., a container capable of containing a liquid electrolyte and carrying, for example, electrodes and / or membranes), a working electrode 324 (e.g., a cathode made of, for example, copper or another metal), a counter electrode 326 (e.g., an anode made of, for example, a mixed metal oxide (MMO) or platinum (Pt)), a reference electrode 328 (e.g., typically located close to the cathode surface (within a few millimeters)), a metal foil 330 (e.g., a copper foil), a composite metal foil 330A (e.g., made of copper when coated with a lithium layer), a membrane 334 (e.g., CEM or SCEM), an anode chamber 336 carrying an aqueous brine containing Li+, a brine source 336A for the anode chamber 336 (e.g., a lake, a well, an aquifer, and / or a storage container), a cathode chamber 338 carrying a Li-X solvent organic solution medium, an input / feed foil roll 340A, a product foil roll 340B (e.g., a lithium-coated copper foil), an inert gas (e.g., argon (Ar)), a gas-filled holding tank 342 (e.g., in which the product foil roll 340B can be retained), and a dehydration column 344 (e.g., a zeolite dehydration column bed). In one embodiment, the membrane 334 can be disposed between the working electrode 324 and the counter electrode 326. The counter electrode 326 and the working electrode 324 can be configured to charge in a manner that drives lithium electrodeposition onto the metal foil 330 / 330A extending through the lithium-containing organic solution. The process cell 320 may also include connecting conduits and / or one or more additional intermediate rollers (as shown but not labeled) to facilitate fluid movement / replenishment and / or metal foil movement, as desired.

[0042] Fig.17 The roll-to-roll process battery 320 can facilitate a continuous multi-step deposition process. In the first step, the aqueous brine solution in the anode chamber 336 can be supplemented as needed to continuously provide Li+ from an external source or reservoir 336A. In the second step, Li+ can be continuously transferred from the aqueous phase to the organic phase via the membrane 334. In the third step, in the cathode (e.g., organic solution) chamber 338, Li metal can be electrodeposited onto a moving copper cathode 324 (e.g., in the form of a copper foil 330 supplied from a feed foil roll 340A), and the Cu foil mesh 330, 330A can be continuously moved through the electrodeposition zone. The water content level of the organic phase can be controlled by a dehydration column 344 and an associated recycling loop. According to the fourth step, the product roll 340B of the lithium metal-copper foil mesh 330A can be preserved and / or stored in an inert gas chamber 342, which is provided with argon (Ar) gas or another suitable inert gas and any hardware required to facilitate the collection of the product roll 340B.

[0043] Fig.18A roll-to-roll (R2R) cathode deposition process for depositing a lithium (Li) metal film onto a moving metal (e.g., copper) foil web from an organic solution is shown according to one embodiment of the present disclosure. The R2R cathode deposition process can be implemented using a roll-to-roll (R2R) process cell 420. The R2R process cell 420 can include a cell housing unit 422, a working electrode 424 (e.g., a cathode made of, for example, copper or another metal), a counter electrode 426 (e.g., an anode made of, for example, a mixed metal oxide (MMO) or platinum (Pt)), a metal foil 430 (e.g., a copper foil), a composite metal foil 430A (e.g., made of copper when coated with a lithium layer), a cathode chamber 438 carrying a Li-X solvent organic solution medium, an input / feed foil roll 440A, a product foil roll 440B (e.g., a lithium-coated copper foil), an argon (Ar) gas-filled holding tank 442 (e.g., in which the product foil roll 440B can be retained), and a dehydration column 444. The counter electrode 426 (eg, anode) and the working electrode 424 (eg, cathode) may be configured to be charged in a manner that drives lithium electrodeposition onto the metal foil 430 / 430A extending through the lithium-containing organic solution. Fig.17 Unlike the system 320 shown, the R2R process cell 420 may, for example, not include a separate anode chamber and / or membrane because an organic lithium-carrying solution is used as a lithium source instead of brine. Instead, both the anode 426 and cathode 428 may be included in the same chamber (e.g., 438), thereby reducing the number of anode chambers and / or membranes relative to the R2R process cell 420. Fig.16 The system 320 in the embodiment simplifies the structure.

[0044] In addition, regarding Fig.18 , if one or more lithium-containing organic solutions are used as a lithium source, an R2R cathode deposition process using a roll-to-roll (R2R) process battery 420 can be used, allowing for a simplified R2R arrangement, as described above. In this case, the water content of the organic solution in the electrodeposition zone (e.g., 438) for the mobile cathode 424 (e.g., metal (e.g., Cu) foil mesh 430; and composite (e.g., Li-Cu)) foil mesh 430A) can be controlled to minimize the dissolution rate of the deposited lithium metal (not separately labeled). In addition, in a continuous, ongoing production process, more Li-containing organic solution can be continuously supplied to the electrodeposition tank / chamber 438. In order to minimize anode degradation and extend the service life of the organic medium, the fixed anode 426 can be placed outside the organic solution, and / or the anode 426 can be modified with one or more coating materials (e.g., LFP (lithium iron phosphate)). In addition, other additives (e.g., ionic liquids) that can be added or otherwise used in the organic phase can be used to enhance the solubility of the Li-X salt and improve the electrodeposition performance. For example, the ionic liquid (organic phase) can be heated to slightly above 180 °C (i.e., the melting point of Li metal) to achieve electrodeposition of liquid Li metal and harvesting around the cathode.

[0045] In one embodiment, the line speed (v) of the copper mesh drive, the applied deposition current (i), the deposited lithium layer width (w), and the current efficiency (η) of lithium deposition can be related by:

[0046] Q = iη / vw Equation 1

[0047] Where Q is the total amount of 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. For example, for lithium with a single positive charge, each charge corresponds to a single lithium atom.

[0048] The electrodeposition time can be defined by the following equation:

[0049] t = η / vw Equation 2

[0050] In order to deposit useful lithium metal for battery anodes, it is important to control the plating current density and thickness. In one embodiment, the lithium deposition rate can be controlled within a current density in the range of 0.2mA / cm2 to 0.8mA / cm2 and a thickness range equivalent to 1mAh / cm2 to 100mAh / cm2, where mA = milliamperes; cm = centimeters; h = hours. As described above, considering that each charge corresponds to a single lithium atom, the thickness range equivalent can be considered to be proportional to the thickness produced. Using these two ranges, the electrodeposition time can be calculated using equations 1 and 2. For example, if a total of 100mAh / cm2 of Li equivalent is plated at a rate of 0.2mA / cm2, the total deposition time is converted to 500 hours. Based on these conditions for Li electroplating, the deposition time can be in the range of 1.25 to 500 hours based on the selected parameters and the desired thickness / thickness equivalent.

[0051] In one embodiment, a design that increases the overlap of the cathode and anode can achieve longer plating times while still allowing for reasonable linear production speeds. It should be understood that various design architectures can be used to achieve the plating conditions. Fig.19A design for electroplating is shown, which is characterized by expanding the overlapping surface area of ​​the two electrodes. Similar to the R2R process cell 420, the R2R process cell 520 may include a battery housing unit 522, a working electrode 524 (e.g., a cathode made of copper or another metal), a counter electrode 526 (e.g., an anode made of mixed metal oxides (MMO) or platinum (Pt)) and a metal foil 530 (e.g., copper foil). Unlike the R2R processing tank 420, the R2R processing tank 520 may also include a series of intermediate conveyor rolls 540C carrying the metal foil 530. The intermediate conveyor roll 540C may be configured to facilitate defining multiple foil portions (e.g., two of which 530A and 530B are marked), and a given foil portion may be defined between a pair of adjacent intermediate conveyor rolls 540C. The foil portions may define multiple adjacent foil portions together, such as 530A and 530B. In addition, a given counter electrode 526 can be considered as an anode and can include / define multiple anode extensions, one of which is marked as 526A (i.e., defining a multi-forked anode 526). Each anode extension can extend between a pair of adjacent foil portions (e.g., anode extension 526A between foil portions 530A and 530B) accompanying, jointly defining a given electroplating zone Z, wherein multiple such electroplating zones Z can be defined by the R2R processing tank 520. The electrode surface overlap area A can promote an increase in the amount of plating, and / or can make the linear velocity V in equation 2 faster. In one embodiment, the R2R electroplating process promoted by the R2R process cell 520 can achieve, for example, a lithium plating reaction time in the range of 0.5 to 1000 hours, 5-400 hours, or 20-300 hours. In one embodiment, the large surface area overlap A associated with the R2R process cell 520 can extend to a mass transport window, wherein the ion transport in the electrolyte is driven by the multi-forked anode 526.

[0052] Note that the process cell configuration is not necessarily limited to the illustrative designs shown in the above-mentioned figures. In addition to changes in the organic solution engineering, the electrode design and material type can be easily modified to obtain better performance, and these modifications are considered to be within the scope of the present disclosure. In addition, unless otherwise expressly excluded, it should be understood that the components described with respect to the various embodiments can be mixed and / or matched with each other. In addition, although copper has been discussed as a candidate material for electrodepositing lithium, it should be understood that other conductive metals or metal alloys can also be used as suitable substrates on which lithium is deposited.

[0053] In summary, one or more embodiments of the present disclosure may produce (1) roll-to-roll Li metal film (battery anode) production technology; and / or technology for producing lithium metal and extracting lithium ions from aqueous solutions or from organic solutions. Integrated mixed solvent-electroprocessing can simultaneously perform lithium extraction and metal production in a single-stage batch or continuous operation. "Solvent processing" can utilize organic solutions as Li+ transport media suitable for electrodeposition, or as solvents for selective extraction of lithium from aqueous brines. In the former case, a Li+ selective membrane (solid CEM or liquid) between the aqueous and organic phases can increase the Li+ transport selectivity for DLE (direct lithium extraction) from the source brine. The "electroprocessing" of the present disclosure can utilize the electrically enhanced rate of electrodialysis (for lithium extraction and transport mobility) and / or electrodeposition (for Li metal film production). The aqueous-organic dual-phase electrodialysis technology can uniquely extract / transport lithium from aqueous brines / solutions into organic solution media. Relative to competing electrolytic deposition processes for producing lithium metal, the present technology can provide (1) a lower cost option for producing lithium metal films as battery anodes (less than 20 μm thick); and / or (2) simultaneous DLE and lithium metal film electrodeposition from aqueous brine in a single integrated process.

[0054] The technology may be characterized in one or more of the following ways. The technology may allow for simultaneous lithium extraction (from aqueous brine) and lithium metal (battery anode) production in a continuous process flow without the need for water treatment. The method may be operated in roll-to-roll (R2R) or batch mode for Li metal production (by electrodeposition of lithium from an organic phase) and / or continuous extraction of lithium from an aqueous brine. The technology may employ an organic phase as an electrodeposition medium, which may be lithium salt soluble or lithium ion selective (e.g., an organic solution obtained from solvent extraction). The system may be characterized by a dehydration method to control the water content of the organic phase to achieve continuous electrodeposition of lithium metal with better current efficiency and / or better Li metal filled deposit quality. Methods associated therewith may achieve faster direct lithium extraction (DLE) rates from aqueous brines due to the larger Li+ concentration gradient between the aqueous and organic phases driven by the electrodeposition phenomenon. Integrated methods may utilize phenomena similar to electrodialysis to accelerate the rate of ion movement and / or transport from the aqueous phase to the organic phase. Compared to molten salt electrolytic deposition, the present system can achieve low temperature (e.g., room temperature and / or ambient temperature), low cost processing. R2R versions of the present system and method can be used to produce thin film deposits of Li metal directly on copper foil meshes, which can be used as a suitable platform for Li battery anodes, for example.

[0055] The following are some proof-of-principle examples that provide methods and specific conditions for metallic lithium electrodeposition from solvent extraction solutions. The present invention is by no means limited to these examples.

[0056] Example 1: Lithium deposition from organic solvents using LiPF6 as an ion-conducting salt.

[0057] Figure 2 A schematic diagram of a three-electrode electrochemical cell for lithium metal electrodeposition is shown, consisting of a working electrode (cathode, such as copper, platinum plated with copper, or other conductive substrate), a reference electrode (such as Ag / AgCl), and a counter electrode (anode). Figure 3 The exact experimental cell used to demonstrate the electrolytic deposition of lithium metal directly from a solvent medium in which a lithium salt is dissolved is shown.

[0058] Specifically, in one embodiment, the electrochemical cell uses a cathode copper rod as the working electrode, which is electrically insulated on one side so that only the well-defined circular flat surface (0.5 cm2) at the bottom is exposed to the electrolyte solution. A glass-encapsulated reference electrode (Ag / AgCl (1M KCl)) surface (<1 mm gap) is used as the reference electrode. A platinum foil annular anode is concentrically placed at the bottom of the electrodeposition tank to serve as the counter electrode. For clarity, Figure 4 The components specified above are shown in FIG. 1 . Note that the design of the electrochemical cell and the selection of electrodes (shape, material type and size) are not limited to this example in terms of geometry, physical dimensions or material composition. The complete experimental setup of the electrochemical cell and lithium metal electrolytic deposition process is shown in FIG. Figure 5 shown.

[0059] Figure 6 The voltammogram obtained during the initial linear sweep voltammetry experiment for Figure 5 The plating voltage of lithium metal on a copper current collector was determined in the experimental setup depicted in FIG. 1 , where the experimental cell was Figure 3 . The electrolyte solution used for this demonstration was 1M LiPF6 in diethyl carbonate (DEC). A reduction-oxidation (redox) reaction was observed to occur at around -2.8V relative to an Ag / AgCl reference electrode, as indicated by a sharp increase in the absolute value of the measured current of the electrochemical cell. The initial cause of the current increase was the decomposition of the DEC solvent, which is known to have a limited electrochemical stability window. The secondary redox reaction began at approximately 3.2V relative to Ag / AgCl, which is attributed to the onset of lithium electrochemical plating. The observed lithium deposition potential is consistent with the thermodynamic potential predicted for the reaction based on the standard reduction potential table, i.e., the difference between the standard reduction potentials of lithium metal and the Ag / AgCl reference electrode (-3.045V-0.2223V=-3.2673V). This consistency between the experimentally observed potential and the thermodynamically predicted potential preliminarily suggests that metallic lithium can be electroextracted from the solution. For reference, the relevant standard reduction reactions and the corresponding potentials relative to the standard hydrogen electrode (SHE) are provided herein.

[0060] Li++e-→Li -3.045V (cathodic reduction reaction for Li metal deposition)

[0061] AgCl+e-→Ag++Cl- 0.2223V (reference electrode, Ag / AgCl (1M KCl))

[0062] 2H++2e-→H2 0.00V (standard hydrogen electrode, SHE)

[0063] To generate a certain amount of metallic lithium, a chronoamperometric experiment was performed, in which the voltage of the electrochemical cell was kept constant and the current was recorded as a function of time. The results of this experiment are shown in Figure 7 During the measurement, the voltage of the cell was kept constant at -3.5 V relative to the Ag / AgCl reference electrode. Figure 8 An optical photograph of an electrochemical cell is shown in which a large gray solid deposit has formed on the copper working electrode. For analysis, the gray deposit was collected and washed with N-methylpyrrolidine (NMP). A quick test to determine whether the gray deposit contains metallic lithium is to immerse the solid in water. Metallic lithium reacts violently with water with the reaction formula Li(s)+H2O(l)LiOH(l)+H2(g). When the solid deposit harvested from the chronoamperometry experiment was immersed in deionized water, bubbles formed immediately, which can be attributed to hydrogen evolution. In addition, the gray solid gradually dissolved away, exposing the copper substrate underneath. The immersed water was analyzed using ICP to determine the lithium content and confirm the presence of lithium. Based on the amount of lithium recorded, it is estimated that a 2-7 micron lithium layer was deposited in different experiments. The current efficiency was calculated to be in the range of 60-80%.

[0064] In the later stage of electrodeposition, dendritic lithium metal ( Figure 5 ). The Faraday efficiency of this lithium metal electrodeposition process is calculated to be 61%. In principle, the deposition rate (mg / s) of lithium metal on the cathode surface can be controlled by varying the voltage and current applied in the electrochemical cell. One form of Faraday's law is:

[0065] m / MW=[I t] / [n F]

[0066] Wherein, m = mass of deposited material (g), MW = molecular weight of deposited material, I = current (A), t = time (s), n = electron equivalent / mole, F = Faraday constant (96,485.3C / eq or As / eq). For the lithium metal deposition process described herein, MW is 6.941 g / mole, and n = 1 electron / mole. The other values ​​of the equation are experimentally measured, experimentally applied values, or physical constants.

[0067] The equation can be rewritten to determine the rate of lithium plating or lithium deposition:

[0068] m / t=[I MW] / [n F]

[0069] 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:

[0070] I=[m / tn F] / MW

[0071] This final equation can be used to adjust the deposition rate during the method described in the present invention to obtain a lithium metal electrode of a desired thickness for use in primary or secondary lithium metal batteries.

[0072] Example 2: Demonstration of scalability of lithium metal electrowinning for commercial lithium metal electrode production.

[0073] The copper rod cathode surface in the previous example has a limited surface area for lithium deposition (0.5 cm2). In order to expand the surface of the cathode electrodeposition of Li metal, a long copper strip is used as the working electrode instead of a single end face of the copper rod. The copper strip has an electrochemically active surface area more than 10 times larger than the surface of the copper rod used in the original lithium electrolytic deposition experiment. The expansion of this working electrode demonstrates the scalability of this method for commercial applications, which requires lithium deposition on copper substrates up to three meters wide in a roll-to-roll manner.

[0074] A proof-of-concept experiment similar to the previous example was performed for this larger copper-based working electrode. The linear sweep voltammogram is presented in Fig. 9 , which shows a similar lithium metal deposition onset potential to that of the smaller electrowinning experiments. Fig.10 A current versus time graph is shown for a chronoamperometric experiment conducted in an electrowinning cell with a larger copper working electrode. During this measurement, the cell voltage was maintained at -4 V relative to an Ag / AgCl reference electrode. The voltage for this example was greater than that for Example 1 to overcome kinetic barriers that may occur due to the larger electrochemically active surface area of ​​the cathode. As with Example 1, the electrochemical cell for the electrowinning of lithium metal from a solvent medium consisted of an Ag / AgCl reference electrode, a platinum counter electrode, and 1 M LiPF6 in DEC as the electrolyte. Fig.11 Direct confirmation of lithium metal deposition onto a larger copper working electrode is provided, showing the copper substrate before and after the electrowinning process.

[0075] The disclosed method of producing lithium metal from brine can be readily modified to utilize existing commercial electroplating or electrowinning equipment or components. The electrowinning cell can utilize roll-to-roll cathodic deposition to scalably and large-surface-area deposit lithium metal onto a substrate surface that is immersed and pulled through a plating electrolyte medium. An example of this embodiment is passing a copper foil roll through a liquid lithium electrolyte medium to plate lithium metal onto a copper foil substrate. Some existing commercial electrodeposition cells, such as industrial electrowinning cells or plating cells, can be modified and adapted for this room temperature mixed solvent extraction and electrowinning process.

[0076] Example 3: Membrane-assisted preparation of lithium metal from concentrated lithium brine.

[0077] One embodiment of the accompanying method allows for the use of a cation exchange membrane to help separate lithium ions from a concentrated lithium brine into an alternative solvent medium from which lithium metal can then be plated. Fig.12 An electrochemical cell that can be used for this process is demonstrated, in which lithium ions are electrochemically driven from a concentrated lithium brine, through a lithium-ion selective cation exchange membrane, into a solvent medium, and ultimately plated onto a metal substrate that serves as the battery's cathode. Fig.13 A cyclic voltammogram of such an electrochemical cell is provided. The electrochemical cell of this experiment includes a copper substrate cathode, a platinum anode, a concentrated lithium brine as an anolyte, a lithium conductive salt dissolved in a solvent as a catholyte, and a cation exchange membrane as a separator between compartments containing two different electrolyte media. Although this experiment demonstrates the reversibility of the process, in practice, the concentrated lithium brine needs to be continuously replenished to provide a constant source of lithium ions to drive the operation of the cell. As with Example 2, the method can be modified to a continuous roll-to-roll process.

[0078] The specification, including the summary of the invention, the accompanying drawings and the detailed description, and the appended claims are directed to specific features (including process or method steps) of the present disclosure. It is understood by those skilled in the art that the present invention includes all possible combinations and uses of the specific features described in the specification. It is understood by those skilled in the art that the present invention is not limited to or by the description of the embodiments given in the specification.

[0079] It is also understood by those skilled in the art that the terms used to describe a particular embodiment do not limit the scope or breadth of the present disclosure. In interpreting the specification and the appended claims, all terms should be interpreted in the broadest possible manner consistent with the context of each term. Unless otherwise defined, all technical and scientific terms used in the specification and the appended claims have the same meaning as those commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0080] As used in the specification and the appended claims, the singular forms "one", "an" and "the" include plural references unless the context clearly indicates otherwise. The verb "comprise" and its conjugated forms should be interpreted as referring to an element, part or step in a non-exclusive manner. The quoted element, part or step can exist, use or combine with other elements, parts or steps that are not clearly quoted. The verb "operably connectable" and its conjugated forms mean to complete the required engagement of any type, including electricity, machinery or fluid, to form a connection between two or more previously unengaged objects. If the first component is operably connected to the second component, the connection can occur directly or through a common connector. "Optionally" and its various forms mean that the event or situation described subsequently may or may not occur. The description includes an instance where an event or situation occurs and an instance where the event or situation does not occur.

[0081] Unless specifically stated otherwise, or otherwise understood in the context of use, conditional language such as "can," "may," "might," or "could" is generally intended to convey that some embodiments may include, while other embodiments do not, certain features, elements, and / or operations. Thus, such conditional language is generally not intended to imply that one or more embodiments require features, elements, and / or operations in any way, or that one or more embodiments must include logic for deciding, with or without user input or prompting, whether such features, elements, and / or operations are included in or will be performed in any particular embodiment.

[0082] Therefore, the systems and methods described herein are well adapted to carry out the objects and obtain the results and advantages mentioned, as well as other objects and advantages inherent therein. Although example embodiments of the systems and methods have been given for purposes of disclosure, there are many changes in the details of the processes for achieving the desired results. These and other similar modifications may be readily appreciated by those skilled in the art, and these and other similar modifications are intended to be included within the spirit of the systems and methods disclosed herein and within the scope of the appended claims.

Claims

1. A method for preparing lithium metal, comprising: (A) extracting 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.

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

3. The method of claim 2, wherein the lithium metal comprises at least 90% purity.

4. The method of claim 3, wherein the lithium metal comprises at least 95% purity.

5. The method of any one of claims 1-4, wherein the lithium brine comprises greater than 0.3 ppm lithium.

6. The method of claim 5, wherein the lithium brine comprises from about 50 ppm to about 75,000 ppm lithium.

7. The method of claim 6, wherein the lithium brine comprises from about 100 ppm to about 40,000 ppm lithium.

8. The method of any one of claims 1-7, wherein the solvent is immiscible with water.

9. The method according to any one of claims 1 to 8, wherein the solvent has a greater solubility for lithium than water.

10. The method according to any one of claims 1 to 9, wherein the solvent is an organic solvent.

11. The method according to any one of claims 1 to 10, wherein the solvent is a polar aprotic solvent.

12. The method according to claim 11, wherein the solvent is a C1-C6 dialkyl carbonate.

13. The method of claim 12, wherein the solvent is diethyl carbonate.

14. The method of any one of claims 1-13, wherein the method further comprises a second solvent.

15. The method according to any one of claims 1 to 14, wherein the method further comprises extracting the lithium solution with the second solvent to obtain a purified lithium solution.

16. The method of claim 15, wherein the method further comprises exposing the purified lithium solution to a voltage or current instead of the lithium solution.

17. The method of any one of claims 14-17, wherein the second solvent has a higher stability than the solvent at the voltage.

18. The method of any one of claims 1-17, wherein the method comprises applying the voltage or current using at least two electrodes.

19. The method of claim 18, wherein the method comprises using three electrodes.

20. A method according to claim 18 or claim 19, wherein the method comprises the use of a working electrode, a counter electrode and a reference electrode.

21. The method of any one of claims 1-20, wherein the method comprises applying a voltage of about -6V to about 6V.

22. The method of claim 21, wherein the voltage is about -5V to about 5V.

23. The method of claim 22, wherein the voltage is about -4V to about 4V.

24. The method according to any one of claims 1 to 23, wherein the method is performed continuously.

25. The method of any one of claims 1-24, wherein the method further comprises returning the lithium solution to the extraction step after the lithium solution has been exposed to the voltage or current.

26. The method of any one of claims 1-25, wherein the method further comprises exposing a lithium-containing solution or a lithium brine, with or without other soluble impurity ions, to a lithium selective membrane.

27. The method of claim 26, wherein the lithium-containing solution or lithium brine with or without other soluble impurity ions is exposed to the lithium selective membrane while applying the voltage.

28. The method of claim 26, wherein the lithium-containing solution or lithium brine, with or without other soluble impurity ions, is exposed to the lithium selective membrane prior to applying the voltage.

29. The method of any one of claims 1-28, wherein the lithium is deposited on the cathode.

30. The method of claim 29, wherein the lithium is deposited on a metal cathode.

31. The method of claim 30, wherein the lithium is deposited on a copper cathode.

32. The method of any one of claims 1-31, wherein the lithium is deposited in a roll-to-roll process.

33. A device for obtaining lithium metal, comprising: (A) Extraction chamber; (B) electroplating chamber; wherein the extraction chamber is in fluid communication with the electroplating chamber; The electroplating chamber includes a cathode and the extraction chamber includes an anode.

34. The device of claim 33, wherein the device further comprises a lithium selective membrane.

35. Apparatus according to claim 33 or 34, wherein the lithium selective membrane is located between the extraction chamber and the electroplating chamber.

36. The device of any one of claims 33-35, wherein the device further comprises a power source connected to the anode and the cathode and capable of delivering a voltage or current.

37. The apparatus of any one of claims 33 to 36, wherein the electroplating chamber further comprises a second reference electrode.

38. The apparatus of any one of claims 33-37, wherein the cathode is configured to allow roll-to-roll deposition.

39. The device of any one of claims 33-38, wherein the extraction chamber is configured to allow mixing of liquids within the chamber.

40. The apparatus of any one of claims 33 to 39, wherein the extraction chamber is configured to allow only a portion of liquid from the extraction chamber to flow into the electroplating chamber.

41. The apparatus of any one of claims 33 to 40, wherein the extraction chamber is configured to allow only a portion of liquid from the extraction chamber to flow into the electroplating chamber after passing through a drying chamber.

42. A system for electrodepositing a lithium (Li) cathode onto a moving metal foil, the system comprising: (A) a battery containing unit containing at least one lithium-containing solution; (B) a counter electrode extending within the battery housing unit; as well as (C) a working electrode extending within the battery housing unit, The working electrode comprises a metal foil configured to be continuously moved through a lithium-containing solution via a roll-to-roll conveyor system, and the counter electrode and the working electrode are configured to be charged in a manner to drive lithium electrodeposition onto the metal foil extending through the lithium-containing solution.

43. The system according to claim 42 further includes a cation exchange membrane, which is arranged in the battery holding unit and is located between the counter electrode and the working electrode, and the cation exchange membrane and the battery holding unit jointly define a first chamber and a second chamber, the first chamber is provided with the working electrode and is configured to accommodate a lithium-containing organic solution, and the second chamber is provided with the counter electrode and is configured to accommodate a lithium-containing aqueous solution.

44. A system according to claim 43, wherein the cation exchange membrane defines a first cation exchange membrane, and the system also includes a second cation exchange membrane in the battery housing unit, the first cation exchange membrane and the second cation exchange membrane define an interlayer liquid membrane therebetween, and the interlayer liquid membrane contains a lithium solvent.

45. The system of claim 42, further comprising: A series of intermediate transport rolls for carrying the metal foil, the intermediate transport rolls being configured to facilitate defining a plurality of foil portions, a given foil portion being defined between a pair of adjacent intermediate transport rolls, the pair of electrodes being in the form of anodes defining a plurality of anode extensions, at least one anode extension being configured to extend between an associated pair of adjacent foil portions.

46. ​​A system for electrodepositing a lithium (Li) cathode onto a metal foil, the system comprising: (A) a battery housing unit; (B) a counter electrode extending within the battery housing unit; (C) a working electrode extending in the battery housing unit, the working electrode comprising a metal foil; The cation exchange membrane is carried in the battery containing unit and is located between the counter electrode and the working electrode. The cation exchange membrane and the battery containing unit together define a first chamber and a second chamber. The first chamber carries the working electrode and is configured to contain a lithium-containing organic solution. The second chamber carries the counter electrode and is configured to retain at least one of a lithium-containing aqueous solution or a lithium-containing brine. The counter electrode and the working electrode are configured to be in a charged state to drive lithium ions to move through the cation exchange membrane and deposit lithium onto a metal foil in contact with the lithium-containing organic solution.

Images