Lithium extraction

Abstract

A system comprising a first cell 20 comprising a source of lithium, a molten metal 30 and an anode 40; and a second cell (Fig. 3, 60) comprising a molten salt electrolyte (Fig. 3, 70) and a conductive substrate; wherein the molten metal receives lithium from the source to form a lithium-rich molten metal alloy when the system applies a voltage between the anode and the molten metal; and wherein the system is configured such that the lithium is transferred from the alloy to the conductive substrate. The system may be configured to allow the alloy to be moved from the first cell to the second after it is formed. The molten metal may have a higher density than the lithium source, which may comprise a borate melt 10. The molten metal may comprise Al, Sn, Pb, Bi, Sb, Zn and alloys thereof. The electrolyte may comprise chloride and fluoride salts.

Description

CROSS-REFERENCE

[0001] This application claims priority to U.S. Provisional Application No. 63 / 428,546 filed November 29, 2022, which is entirely incorporated herein by reference. BACKGROUND

[0002] Conventional lithium extraction methods from ores, such as spodumene, involve chemical and pyro-metallurgical processes. These methods are generally inefficient and generate significant waste. Meanwhile, aluminum extraction from bauxite relies on slightly more efficient processes, such as the Bayer process to produce alumina and the Hall-Heroult electrolytic process to obtain aluminum metal.

[0003] There is a growing need for improved electrolytic methods for lithium extraction and purification that are more economically productive, less wasteful, and environmentally friendly. Such methods for lithium extraction should ideally be comparable to the Hall-Heroult and Hoopes processes used in aluminum production, which allows for improved lithium extraction from lithium-containing ores and recycled batteries. SUMMARY

[0004] Provided herein is a method comprising: (a) contacting a source of lithium with a molten metal; (b) extracting lithium from the source of lithium and transferring the lithium to the molten metal, thereby forming a lithium-rich molten metal alloy; and (c) transferring the lithium from the lithium-rich molten metal alloy to a conductive substrate. The source of lithium may comprise a borate melt. The method may further comprise, before (a), dissolving material comprising lithium ions in the borate melt. The material comprising lithium ions may comprise a lithium ore. The lithium ore may comprise spodumene. The borate melt may comprise a fluoride salt. The fluoride salt may be selected from the group consisting of NaF, KF, CaF2, and combinations thereof. Preferably, the molten metal has a higher density than the borate melt.

[0005] Step (b) may comprise applying a voltage across an anode and the molten metal. The method may further comprise, before (c), contacting the lithium-rich molten metal alloy with a molten salt electrolyte. Step (c) may comprise applying a voltage across a cathode and the lithium-rich molten metal alloy, causing lithium ions to be released from the lithium-rich molten metal alloy and reduced to lithium metal at the cathode.

[0006] The borate melt may be maintained at a temperature between 600°C and 1000°C.

[0007] Step (c) may be performed at a temperature between 300°C and 800°C.

[0008] The cathode may comprise an inert material. The cathode may comprise a material selected from the group consisting of nickel, copper, titanium, and carbon (graphite).

[0009] The molten salt electrolyte may comprise a salt selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof. Accordingly, the molten salt electrolyte may comprise a salt selected from the group consisting of LiCl, KC1, RbCl, CsCl, SrCk, BaCh, and combinations thereof. The molten salt electrolyte may comprise fluoride salts. The fluoride salts may be selected from the group consisting of LiF, CaF2, and combinations thereof.

[0010] Preferably, steps (a) and (b) are carried out in a first cell, and (c) is carried out in a second cell that is different from the first cell. The method may be used for a scale-up production.

[0011] In a certain aspect, this disclosure provides a system comprising a first cell comprising: a source of lithium and a molten metal, and a second cell comprising: a molten salt electrolyte and a conductive substrate. The molten metal may be configured to receive lithium from the source of lithium to form a lithium-rich molten metal alloy. The lithium-rich molten metal alloy may be moved from the first cell to the second cell after it is formed. The lithium may be transferred from the lithium-rich molten metal alloy to the conductive substrate to form a lithium metal layer.

[0012] The source of lithium may comprise a borate melt that material comprising lithium ions is dissolved in. The material comprising lithium ions may comprise lithium ore, such as spodumene. The borate melt may comprise a fluoride salt. The fluoride salt may be selected from the group consisting of NaF, KF, CaF2, and combinations thereof.

[0013] Preferably, the molten metal is denser than the borate melt. The first cell may further comprise an anode, wherein a voltage is applied between the anode and the molten metal to form the lithium-rich molten metal alloy. The anode is generally immersed in the borate melt.

[0014] The anode in the first cell preferably comprises carbon.

[0015] The conductive substrate is preferably a cathode. The cathode may be an inert material. The cathode may comprise a material selected from the group consisting of nickel, copper, titanium, and carbon (graphite). The cathode may be immersed in the molten salt electrolyte in the second cell.

[0016] A voltage may be applied across the cathode and the lithium-rich molten metal alloy to extract lithium ions from the lithium-rich molten metal alloy and to form a lithium metal layer.

[0017] The borate melt may comprise a fluoride salt. The fluoride salt may be NaF, KF, CaF2, and combinations thereof.

[0018] The first cell may be kept at a temperature between 600 and 1000°C. The second cell may be kept at a temperature between 300 and 800 °C.

[0019] The molten salt electrolyte may comprise salts selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof. Accordingly, the molten salt electrolyte may comprise salts selected from the group consisting of LiCl, KC1, RbCl, CsCl, SrCh, BaCh, and combinations thereof. The molten salt electrolyte may comprise fluoride salts. The fluoride salts may be selected from the group consisting of LiF, CaF2, and combinations thereof.

[0020] In accordance with one embodiment of the disclosure, lithium is extracted from a lithium ion containing material by a process that includes the steps of: dissolving the lithium ion containing material in a borate melt; disposing the borate melt and a molten metal in a first cell, the molten metal being denser than the borate melt and forming a layer of molten metal below the borate melt; immersing an anode in the first cell; applying voltage across the anode and the layer of molten metal so that lithium ion is reduced to lithium metal at the layer of molten metal, thereby forming an alloy of the molten metal with the lithium metal at the bottom of the first cell; disposing the alloy of the molten metal at the bottom of a second cell; disposing a molten salt electrolyte on top of the alloy of molten metal, the molten salt electrolyte being free of oxides; immersing a cathode in the molten salt electrolyte; applying a voltage across the cathode and the alloy of molten metal, so that lithium ion is released from the alloy of molten metal and is reduced to lithium metal at the cathode. Although the molten salt electrolyte is preferably free of oxides, the molten salt electrolyte may have small (trace) amounts of oxides present without adversely affecting the method.

[0021] The lithium ion containing material is preferably a lithium ore, such as spodumene.

[0022] The anode in the first cell preferably includes carbon.

[0023] The borate melt may include a fluoride. The fluoride may be selected from the group consisting of NaF, KF, CaF2, and combinations thereof.

[0024] The first cell may be kept at a temperature between 600 and 1000°C. The second cell may be kept at a temperature between 300 and 800°C.

[0025] The cathode immersed in the molten salt electrolyte may be an inert material. The cathode may include a material selected from the group consisting of nickel, copper, titanium, and carbon (graphite). The molten salt electrolyte may include salts selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof. The molten salt electrolyte may include salts selected from the group consisting of LiCl, KC1, RbCl, CsCl, SrCh, BaCh, and combinations thereof. The molten salt electrolyte may include fluoride salts. The fluoride salts may include LiF, CaF2, and combinations thereof.

[0026] Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. INCORPORATION BY REFERENCE

[0027] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0029] Fig. 1 provides the steps associated with an embodiment of the disclosed method.

[0030] Fig. 2 illustrates a first stage in which lithium ions dissolved in a borate melt are electrolytically reduced at a layer of molten metal functioning as a cathode to form a lithium alloy with the molten metal, in accordance with some embodiments.

[0031] Fig. 3 illustrates a second stage in which the lithium alloy with the molten metal serves as an anode in an electrolytic cell, releasing lithium ions into a molten salt electrolyte. At the cathode of the cell, the lithium ions are reduced to lithium metal, thereby providing a layer of high purity lithium that floats to the top of the molten salt electrolyte. DETAILED DESCRIPTION

[0032] Unless defined otherwise, all terms of art, notations and other technical and scientific terms or terminology used herein are intended to have the same meaning as is commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art.

[0033] Throughout this application, various embodiments may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0034] As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a sample” includes a plurality of samples, including mixtures thereof.

[0035] Whenever the term “at least,” “greater than,” or “greater than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “at least,” “greater than” or “greater than or equal to” applies to each of the numerical values in that series of numerical values. For example, greater than or equal to 1, 2, or 3 is equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0036] The expressions “at least about A, B, and C” and “at least about A, B, or C” may be construed to mean at least about A, at least about B, or at least about C. The expressions “at most about A, B, and C” and “at most about A, B, or C” may be construed to mean at most about A, at most about B, or at most about C.

[0037] The expression “between about A and B, C and D, and E and F” may be construed to mean between about A and about B, between about C and about D, and between about E and about F. The expression “between about A and B, C and D, or E and F” may be construed to mean between about A and about B, between about C and about D, or between about E and about F.

[0038] As used herein, the term “about” a number refers to that number plus or minus 10% of that number. The term “about” a range refers to that range minus 10% of its lowest value and plus 10% of its greatest value.

[0039] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0040] A “cathode” is an electrode where reduction occurs.

[0041] An “anode” is an electrode where oxidation occurs.

[0042] The term “spodumene” refers to a lithium aluminum silicate mineral with the chemical formula LiAl(SiO3)2 and is the dominant lithium ore and one of the primary sources 6 of lithium. Spodumene is typically found in granitic pegmatites, a type of rock that forms from slowly cooling magma deep within the Earth's crust. There are two main crystalline forms of spodumene: alpha-spodumene and beta-spodumene. Alpha-spodumene is the more common, naturally occurring form, while beta-spodumene forms when alpha-spodumene is heated to high temperatures (above 900°C). Beta-spodumene is more reactive and easier to process for lithium extraction than the alpha form.

[0043] A “fluoroborate melt” is a molten mixture of borate salts and fluoride salts. It refers to a mixture of fluoroborate compounds in their liquid or molten state. Fluoroborates are compounds that contain boron, fluorine, and other elements. They are a subclass of the larger borate family but have a distinct chemical composition featuring the BFF anionic group.

[0044] ‘‘Borate salts” are salts with oxyborate anions.

[0045] The term “borate melt” refers to borate compounds or a mixture thereof in their liquid / molten state. Borates are compounds that contain boron and oxygen, typically in the form of the BO3 or BO4 structural units that are joined together to form various anionic groups. Examples of common borates include borax (Na2B4O?-lOFEO), boric acid (H3BO3), and lithium borate ^264()7).

[0046] “Oxyborate anions” are anions with chemical formula of BxOyn‘. , where x, y, and n are positive integers not equal to zero. Common oxyborate anions include BOs3', B4O?2', and B2O42;

[0047] The term “molten salt electrolyte” refers to a type of electrolyte that consists of salt compounds in a liquid or molten state. They are essential components in electrochemical processes, including batteries, fuel cells, and various other applications. Molten salt electrolytes are formed by heating solid salts to high temperatures until they melt, turning into a liquid form. These high temperatures allow ions in the salt to move more freely, facilitating ionic conductivity. The molten salt electrolyte may include at least one ionic species having a higher reduction potential than Li+. The molten salt electrolyte may comprise one or more salts selected from the group consisting of aluminum salts, titanium salts, alkali metal salts, alkaline earth metal salts, ammonium salts, and combinations thereof. The molten salt electrolyte may comprise aluminum salts, such as aluminum chloride. The molten salt electrolyte may comprise anions chosen from the group consisting of halides, nitrates, nitrites, sulfates, sulfites, carbonates, hydroxides and combinations thereof.

[0048] The molten salts may comprise solutions of A1CF, and may include LiCl, NaCl, and KC1. The molten salts may include chloroaluminate salts. Some such embodied chloroaluminate molten salt electrolytes can operate at temperatures at or near the boiling point of water.

[0049] The molten salt electrolytes disclosed herein are non-flammable. Because these inorganic molten salt electrolytes operate at temperatures well below the melting point of lithium, they are not significantly corrosive, and there is no danger from the leakage of molten lithium.

[0050] An example of the disclosed method involves two electrochemical stages, as summarized in Fig. 1, and according to the embodiments of Fig. 2 (Stage 1) and Fig. 3 (Stage 2).

[0051] Stage 1: a. Dissolve lithium ore or other lithium ion containing material in a borate melt 10, the borate melt 10 including a fluoride salt in a first cell 20 (step 1 of Fig. 1); b. position the borate melt 10 on top of a layer of molten metal 30, the molten metal 30 being denser than the borate melt 10 (step 3 of Fig. 1); c. immerse a carbon anode 40 in the borate melt 10 (step 5 of Fig. 1); and d. apply a current 50 between the anode 40 and the layer of molten metal 30, thereby forming an alloy of lithium and other reduced metals from the lithium ore (step 7 of Fig. 1), and releasing gas 55 as CO / CO2 at the anode 40.

[0052] Stage 2: a. Dispose the layer of molten metal 30, now comprising an alloy of molten metal and lithium from Stage 1 in the bottom of a second cell 60 and cover with a molten salt electrolyte 70 (step 9 of Fig. 1); b. immerse a cathode 80 in the molten salt electrolyte 70 (step 11 of Fig. 1), wherein the cathode is a conductive substrate; and c. apply a current 90 across the cathode 80 and the alloy of molten metal and lithium, releasing Li+ from the alloy and reducing the Li+ to form a layer of lithium metal 100 at the cathode 80 (step 13 of Fig. 1).

[0053] The lithium ore or other lithium ion containing material of stage one may include, but is not limited to, spodumene (LiAlSi2Oe), lepidolite (K(Li,Al,Rb)2( ALSi)40io(F,OH)2), petalite (LiAlSi40io), lithium brines, hectorite clay (Nao.3(Mg,Li)3Si40io(OH)2), geothermal brines, or recycled lithium-ion batteries.

[0054] The borate melt 10 may include borate salts chosen from the group consisting of sodium salts, potassium salts, calcium salts, magnesium salts, and combinations thereof. The borate melt may include fluoride salts. The fluoride salts may be chosen from the group consisting of NaF, KF, CaF2, MgF2, and combinations thereof. The borate melt 10 may be capable of breaking down the lithium ore structure by dissolving metal oxides, including lithium oxide (Li2O) present in the ore. The metal fluoride components may improve the solubility of the lithium compounds in the borate melt. The temperature of the borate melt 10 may be between 850 and 950 degrees centigrade. The temperature of the borate melt 10 may be higher than about 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C. The temperature of the borate melt 10 may be lower than about 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C. The temperature of the borate melt 10 may be between about 700°C and 1000°C, between about 750°C and 950°C, between about 800°C and 900°C, or between about 850°C and 1000°C. After the lithium ore is dissolved in the borate melt containing the metal fluoride, the melt may be cooled and solidified.

[0055] The layer of molten metal 30 of stage one may include a metal selected from the group consisting of Al, Sn, Pb, Bi, Sb, Zn, and alloys of the same. The layer of molten metal may include Sn. The layer of molten metal may include an alloy of Pb and Sb.

[0056] The anode 40 of stage one may include carbon, so that as lithium ion is reduced at the layer of molten metal 30, forming a lithium-containing alloy, carbon at the anode 40 is oxidized to CO2 or CO, which is released as a gas. The anode electrode 40 may comprise graphite, platinum (Pt), titanium (Ti), or a combination thereof.

[0057] When a current 50 is applied across the anode 40 and the layer of molten metal 30, the molten metal may selectively extract lithium from a lithium-containing source, such as a borate melt with lithium salts. Lithium may be soluble in the molten metals, resulting in the formation of a lithium-rich molten metal alloy. The lithium-rich molten metal alloy may comprise lithium of at least about 0.1 weight% (wt%), 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, or 60 wt% relative to a total weight of the lithium-rich molten metal alloy. The lithium-rich molten metal alloy may comprise lithium of at most about 0.1 weight% (wt%), 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, or 70 wt% relative to a total weight of the lithium-rich molten metal alloy.

[0058] The potential applied across the anode 40 and the layer of molten metal 30 may be at least about 3 V, 4 V, 5 V, 6 V, 7 V, 8 V, 9V, 10V, 11V, or 12V. The potential applied across the anode 40 and the layer of molten metal 30 may be at most about 3 V, 4V, 6V, 7V, 8V, 9V, 10V, 1IV, or 12V. The potential applied across the anode 40 and the layer of molten metal 30 may be about 3V to 12V, 4V to 9V, 5V to 8V, or 6 V to 7V.

[0059] An amount of the lithium transferred from the borate melt to the molten metal may comprise at least about 0.1 mg / hr, 0.5 mg / hr, 1 mg / hr, 5 mg / hr, 10 mg / hr, 50 mg / hr, 100 mg / hr, 150 mg / hr, 200 mg / hr, 250 mg / hr, 300 mg / hr, 350 mg / hr, 400 mg / hr, 450 mg / hr, 500 mg / hr, 550 mg / hr, 600 mg / hr, 650 mg / hr, 700 mg / hr, 750 mg / hr, 800 mg / hr, 850 mg / hr, 900 mg / hr, 950 mg / hr, 1,000 mg / hr, 1,200 mg / hr, 1,400 mg / hr, 1,600 mg / hr, 1,800 mg / hr, 2,000 mg / hr, 2,500 mg / hr, 3,000 mg / hr, 3,500 mg / hr, 4,000 mg / hr, 4,500 mg / hr, 5,000 mg / hr, 5,500 mg / hr, 6,000 mg / hr, 6,500 mg / hr, 7,000 mg / hr, 7,500 mg / hr, 8,000 mg / hr, 8,500 mg / hr, 9,000 mg / hr, 9,500 mg / hr, 10,000 mg / hr, 20,000 mg / hr, 30,000 mg / hr, 40,000 mg / hr, 50,000 mg / hr, 60,000 mg / hr, 70,000 mg / hr, 80,000 mg / hr, 90,000 mg / hr, 100,000 mg / hr, 110,000 mg / hr, or 120,000 mg / hr. An amount of the lithium transferred from the borate melt to the molten metal may comprise at most about 0.1 mg / hr, 0.5 mg / hr, 1 mg / hr, 5 mg / hr, 10 mg / hr, 50 mg / hr, 100 mg / hr, 150 mg / hr, 200 mg / hr, 250 mg / hr, 300 mg / hr, 350 mg / hr, 400 mg / hr, 450 mg / hr, 500 mg / hr, 550 mg / hr, 600 mg / hr, 650 mg / hr, 700 mg / hr, 750 mg / hr, 800 mg / hr, 850 mg / hr, 900 mg / hr, 950 mg / hr, 1,000 mg / hr, 1,200 mg / hr, 1,400 mg / hr, 1,600 mg / hr, 1,800 mg / hr, 2,000 mg / hr, 2,500 mg / hr, 3,000 mg / hr, 3,500 mg / hr, 4,000 mg / hr, 4,500 mg / hr, 5,000 mg / hr, 5,500 mg / hr, 6,000 mg / hr, 6,500 mg / hr, 7,000 mg / hr, 7,500 mg / hr, 8,000 mg / hr, 8,500 mg / hr, 9,000 mg / hr, 9,500 mg / hr, 10,000 mg / hr, 20,000 mg / hr, 30,000 mg / hr, 40,000 mg / hr, 50,000 mg / hr, 60,000 mg / hr, 70,000 mg / hr, 80,000 mg / hr, 90,000 mg / hr, 100,000 mg / hr, 110,000 mg / hr, or 120,000 mg / hr.

[0060] The molten salt of the second stage is formulated to be liquid at the operating temperature of the cell. The temperature of the molten salt of the second stage may be between about 300°C and about 800°C. The temperature of the molten salt of the second stage may be higher than about 200 °C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C. The temperature of the molten salt of the second stage may be lower than about 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C. The temperature of the molten salt of the second stage may be between about 200°C and 900°C, between about 250°C and 850°C, between about 300°C and 800°C, between about 350°C and 750°C, between about 400°C and 700°C, between about 450°C and 650°C, between about 500°C and 600°C, or between about 550°C and 750°C.

[0061] The molten salt may include, but is not limited to, LiCl, KC1, RbCl, CsCl, SrCh, BaCh, and combinations thereof. The molten salt formulation may comprise fluoride salts. The molten salt formulation may comprise fluoride salts with highly cathodic decomposition potentials, such fluoride salts including, but not limited to LiF, CaF2, and combinations thereof. The molten salt electrolyte is generally free of oxides, but the molten salt electrolyte may have small (trace) amounts of oxides present. The method disclosed herein may work with small (trace) amounts of oxides present. The molten salt electrolyte may comprise oxides of at least about 0.01 wt % to about 5 wt%. The molten salt electrolyte may comprise oxides of at most about 0.01 wt % to about 5 wt%. Preferably, the molten salt electrolyte may comprise oxides of at most about 5 wt%, more preferably at most about 1 wt%, even more preferably at most about 0.01 wt% relative to the total weight of the molten salt electrolyte.

[0062] In preferred embodiments, the molten salt is formulated to be a liquid at the desired operating temperature. The melting temperature of the molten salt electrolyte may be higher than about 100°C, 95°C, 90°C, 85°C, 80°C, 75°C, 70°C, 65°C, 60°C, 55°C, 50°C, 45°C, 40°C, 3 5 °C or 30°C. The melting temperature of the molten salt electrolyte may be higher than about 100°C or higher than about 75°C or higher than about 50°C or higher than about 30°C. The melting temperature of the molten salt electrolyte may be lower than about 100°C, 95°C, 90°C, 85°C, 80°C, 75°C, 70°C, 65°C, 60°C, 55°C, 50°C, 45°C, 40°C, 35°C or 30°C. The melting temperature of the molten salt electrolyte may be lower than about 100°C or lower than about 75°C or lower than about 50°C or lower than about 30°C.

[0063] For the second stage, the cathode is a preferably a conductive substrate. The cathode may comprise a current collector. The current collector may comprise carbonaceous material, Ti, Al, Cu, Ni, stainless steel, or combinations thereof. The cathode may comprise a metal current collector or a carbon current collector. The cathode may comprise a lithium absorption electrode comprising graphite or metals that alloy with lithium. The cathode may comprise an electrically conductive slurry comprising an electrically conductive additive.

[0064] The potential applied across the cathode 80 and the alloy of molten metal and lithium may be at least about 3 V, 4V, 5 V, 6V, 7 V, 8 V, 9V, 10V, 1IV, or 12V. The potential applied across the cathode 80 and the alloy of molten metal and lithium may be at most about 3 V, 4V, 6V, 7V, 8V, 9V, 10V, 1IV, or 12V. The potential applied across the cathode 80 and the alloy of molten metal and lithium may be about 3 V to 12V, 4V to 9 V, 5 V to 8 V, or 6V to 7V.

[0065] An amount of the lithium transferred from the alloy of molten metal and lithium to the cathode may comprise at least about 0.1 mg / hr, 0.5 mg / hr, 1 mg / hr, 5 mg / hr, 10 mg / hr, 50 mg / hr, 100 mg / hr, 150 mg / hr, 200 mg / hr, 250 mg / hr, 300 mg / hr, 350 mg / hr, 400 mg / hr, 450 mg / hr, 500 mg / hr, 550 mg / hr, 600 mg / hr, 650 mg / hr, 700 mg / hr, 750 mg / hr, 800 mg / hr, 850 mg / hr, 900 mg / hr, 950 mg / hr, 1,000 mg / hr, 1,200 mg / hr, 1,400 mg / hr, 1,600 mg / hr, 1,800 mg / hr, 2,000 mg / hr, 2,500 mg / hr, 3,000 mg / hr, 3,500 mg / hr, 4,000 mg / hr, 4,500 mg / hr, 5,000 mg / hr, 5,500 mg / hr, 6,000 mg / hr, 6,500 mg / hr, 7,000 mg / hr, 7,500 mg / hr, 8,000 mg / hr, 8,500 mg / hr, 9,000 mg / hr, 9,500 mg / hr, 10,000 mg / hr, 20,000 mg / hr, 30,000 mg / hr, 40,000 mg / hr, 50,000 mg / hr, 60,000 mg / hr, 70,000 mg / hr, 80,000 mg / hr, 90,000 mg / hr, 100,000 mg / hr, 110,000 mg / hr, or 120,000 mg / hr. An amount of the lithium transferred from the alloy of molten metal and lithium to the cathode may comprise at most about 0.1 mg / hr, 0.5 mg / hr, 1 mg / hr, 5 mg / hr, 10 mg / hr, 50 mg / hr, 100 mg / hr, 150 mg / hr, 200 mg / hr, 250 mg / hr, 300 mg / hr, 350 mg / hr, 400 mg / hr, 450 mg / hr, 500 mg / hr, 550 mg / hr, 600 mg / hr, 650 mg / hr, 700 mg / hr, 750 mg / hr, 800 mg / hr, 850 mg / hr, 900 mg / hr, 950 mg / hr, 1,000 mg / hr, 1,200 mg / hr, 1,400 mg / hr, 1,600 mg / hr, 1,800 mg / hr, 2,000 mg / hr, 2,500 mg / hr, 3,000 mg / hr, 3,500 mg / hr, 4,000 mg / hr, 4,500 mg / hr, 5,000 mg / hr, 5,500 mg / hr, 6,000 mg / hr, 6,500 mg / hr, 7,000 mg / hr, 7,500 mg / hr, 8,000 mg / hr, 8,500 mg / hr, 9,000 mg / hr, 9,500 mg / hr, 10,000 mg / hr, 20,000 mg / hr, 30,000 mg / hr, 40,000 mg / hr, 50,000 mg / hr, 60,000 mg / hr, 70,000 mg / hr, 80,000 mg / hr, 90,000 mg / hr, 100,000 mg / hr, 110,000 mg / hr, or 120,000 mg / hr.

[0066] When a current 90 is applied across the cathode 80 and the alloy of molten metal and lithium, Li+ may be released from the alloy and reduced to form a layer of lithium metal 100 at the cathode 80. The thickness of the lithium metal layer on the cathode may be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 pm. The thickness of the lithium metal layer on the cathode may be at least about 1, 5, 10, 20, 30, 40, 50, 100, 200, 300, 400, or 500 pm. The thickness of the lithium metal layer on the cathode may be at most about 1, 5, 10, 20, 30, 40, 50, 100, 200, 300, 400, or 500 pm. The thickness of the lithium metal layer on the cathode may be about between 1 and 380 pm, between 1 and 370 pm, between 1 and 360 pm, between 1 and 350 pm, between 1 and 340 pm, between 1 and 330 pm, between 1 and 320 pm, between 1 and 310 pm, between 1 and 300 pm, between 1 and 250 pm, between 1 and 200 pm, between 1 and 150 pm, between 1 and 100 pm, between 1 and 90 pm, between 1 and 80 pm, between 1 and 70 pm, between 1 and 60 pm, between 1 and 50 pm, between 1 and 45 pm, between 1 and 40 pm, between 1 and 35 pm, between 1 and 30 pm, between 1 and 25 pm, between 1 and 20 pm, between 1 and 15 pm, between 1 and 10 pm, or between 1 and 5 pm.

[0067] The density of the lithium metal deposited may range from about 0.2 g / cm3 to 0.534 g / cm3. The density of the lithium metal deposited may be at least about 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, or 0.534 g / cm3. The density of the lithium metal deposited may be at most about 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, or 0.534 g / cm3.

[0068] As embodied in Fig. 3, as the lithium metal is reduced at the cathode, it remains in a molten state and floats to the top of the cell, forming a layer of liquid lithium metal 100. The liquid layer of lithium metal 100 can be recovered from the top of the molten salt electrolyte 70 by siphoning off, by dipping onto a colder substrate, or by allowing the layer of lithium metal to cool around the cathode. The cathode 80 may include a material selected from the group consisting of nickel, copper, carbon, titanium, and combinations thereof. The cathode 80 may be a nickel mesh. The lithium metal layer may form around the cathode 80, so that upon cooling it provides a lithium metal electrode. The lithium metal layer may be treated by refining or post processes.

[0069] The method disclosed herein may be used for a scale-up production.

[0070] The embodiments of the disclosure described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present disclosure as defined in any appended claims. LIST OF EMBODIMENTS

[0071] The following list of embodiments of the invention are to be considered as disclosing various features of the invention, which features can be considered to be specific to the particular embodiment under which they are discussed, or which are combinable with the various other features as listed in other embodiments. Thus, simply because a feature is discussed under one particular embodiment does not necessarily limit the use of that feature to that embodiment. Embodiment 1. A process for extracting lithium from a lithium ion containing material comprising the steps of: dissolving the lithium ion containing material in a borate melt; disposing the borate melt and a molten metal in a first cell, the molten metal being denser than the borate melt and forming a layer of molten metal below the borate melt; immersing an anode in the first cell; applying voltage across the anode and the layer of molten metal so that lithium ion is reduced to lithium metal at the layer of molten metal, thereby forming an alloy of the molten metal with the lithium metal at the bottom of the first cell; disposing the alloy of the molten metal at the bottom of a second cell; disposing a molten salt electrolyte on top of the alloy of molten metal, the molten salt electrolyte being free of oxides; immersing a cathode in the molten salt electrolyte; applying a voltage across the cathode and the alloy of molten metal, so that lithium ion is released from the alloy of molten metal and is reduced to lithium metal at the cathode. Embodiment 2. The process of Embodiment 1 wherein the lithium ion containing material comprises a lithium ore. Embodiment 3. The process of Embodiment 2 wherein the lithium ore includes spodumene. Embodiment 4. The process of Embodiment 1 wherein the anode in the first cell comprises carbon. Embodiment 5. The process of Embodiment 1 wherein the borate melt includes a fluoride. Embodiment 6. The process of Embodiment 5 wherein the fluoride is selected from the group consisting of NaF, KF, CaF2, and combinations thereof. Embodiment 7. The process of Embodiment 1 wherein the first cell is kept at a temperature between 600 and 1000°C. Embodiment 8. The process of Embodiment 1 wherein the second cell is kept at a temperature between 300 and 800 °C. Embodiment 9. The process of Embodiment 1 wherein the cathode is an inert material. Embodiment 10. The process of Embodiment 9, wherein the cathode comprises a material selected from the group consisting of nickel, copper, titanium, and carbon (graphite). Embodiment 11. The process of Embodiment 1 wherein the molten salt electrolyte includes salts selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof. Embodiment 12. The process of Embodiment 1 wherein the molten salt electrolyte includes salts selected from the group consisting of LiCl, KC1, RbCl, CsCl, SrCk, BaCh, and combinations thereof. Embodiment 13. The process of Embodiment 1 wherein the molten salt electrolyte includes fluoride salts. Embodiment 14. The process of Embodiment 13 wherein the fluoride salts are selected from the group consisting of LiF, CaF2, and combinations thereof. NUMBERED CLAUSES 1. A method comprising: (a) contacting a source of lithium with a molten metal; (b) extracting lithium from the source of lithium and transferring the lithium to the molten metal, thereby forming a lithium-rich molten metal alloy; and (c) transferring the lithium from the lithium-rich molten metal alloy to a conductive substrate. 2. The method of clause 1, wherein the source of lithium comprises a borate melt. 3. The method of clause 2, further comprising, before (a), dissolving a material comprising lithium ions in the borate melt. 4. The method of clause 3, wherein the material comprising lithium ions comprises a lithium ore. 5. The method of clause 4, wherein the lithium ore comprises spodumene. 6. The method of any one of clauses 2 to 5, wherein the borate melt comprises a fluoride salt. 7. The method of clause 6, wherein the fluoride salt is selected from the group consisting of NaF, KF, CaF2, and combinations thereof. 8. The method of any one of clauses 2 to 7, wherein the molten metal has a higher density than the borate melt. 9. The method of any one of clauses 1 to 8, wherein (b) comprises applying a voltage across an anode and the molten metal. 10. The method of any one of clauses 1 to 9, further comprising, before (c), contacting the lithium-rich molten metal alloy with a molten salt electrolyte. 11. The method of any one of clauses 1 to 10, wherein (c) comprises applying a voltage across a cathode and the lithium-rich molten metal alloy, causing lithium ions to be released from the lithium-rich molten metal alloy and reduced to lithium metal at the cathode. 12. The method of any one of clauses 2 to 11, wherein the borate melt is maintained at a temperature between 600 °C and 1000°C. 13. The method of any one of clauses 1 to 11, wherein (c) is performed at a temperature between 300 °C and 800 °C. 14. The method of any one of clauses 11 to 13, wherein the cathode comprises an inert material. 15. The method of any one of clauses 11 to 14, wherein the cathode comprises a material selected from the group consisting of nickel, copper, titanium, and carbon. 16. The method of any one of clauses 10 to 15, wherein the molten salt electrolyte comprises a salt selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof. 17. The method of clause 17, wherein the molten salt electrolyte comprises a salt selected from the group consisting of LiCl, KC1, RbCl, CsCl, SrCh, BaCh, and combinations thereof. 18. The method of any one of clauses 16 to 17, wherein the molten salt electrolyte comprises fluoride salts. 19. The method of clause 18, wherein the fluoride salts are selected from the group consisting of LiF, CaF2, and combinations thereof. 20. The method of any one of clauses 1 to 19, wherein (a) and (b) are carried out in a first cell, and (c) is carried out in a second cell that is different from the first cell. 21. The method of any one of clauses 1 to 20, wherein the molten metal includes tin or an alloy of Pb and Sb, optionally wherein the molten metal consists of tin. 22. The method of any one of clauses 9 to 21, wherein the anode is a carbon anode. 23. The method of clause 1, wherein (a) and (b) are carried out in a first cell, and (c) is carried out in a second cell that is different from the first cell; wherein (b) comprises applying a voltage across an anode and the molten metal and wherein (c) comprises applying a voltage across a cathode and the lithium-rich molten metal alloy, causing lithium ions to be released from the lithium-rich molten metal alloy and reduced to lithium metal at the cathode; wherein the source of lithium comprises a borate melt, wherein the borate melt optionally comprises a fluoride salt such as NaF, KF, CaF2, and combinations thereof. 24. The method of clause 23, wherein the method comprises before (c), contacting the lithium-rich molten metal alloy with a molten salt electrolyte, wherein the molten salt electrolyte optionally comprises a salt selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof; wherein a cathode is immersed 17 in the molten salt electrolyte. 25. The method of clause 23 or 24, wherein the anode in the first cell includes carbon and the cathode in the second cell comprises a material selected from the group consisting of nickel, copper, titanium, and carbon.

Claims

1. A system comprising:a first cell comprising:a source of lithium;a molten metal; andan anode; anda second cell comprising:a molten salt electrolyte; anda conductive substrate;wherein the molten metal is configured to receive lithium from the source of lithium to form a lithium-rich molten metal alloy;wherein the system is configured to apply a voltage between the anode and the molten metal to form the lithium-rich molten metal alloy; andwherein the system is configured such that the lithium may be transferred from the lithium-rich molten metal alloy to the conductive substrate to form a lithium metal layer.

2. The system of claim 1, wherein the system is configured such that the lithium-rich molten metal alloy may be moved from the first cell to the second cell after it is formed.

3. The system of claim 1 or 2, wherein the molten metal has a higher density than the source of lithium.

4. The system of any one of claims 1 to 3, wherein the source of lithium comprises a borate melt.

5. The system of any one of claims 1 to 4, wherein the conductive substrate is a cathode.

6. The system of claim 5, which is configured such that as lithium ions are reduced to lithium metal at the cathode, it remains in a molten state and floats to the top of the cell, forming a layer of liquid lithium metal.

7. The system of any one of claims 1 to 6, wherein the anode comprises carbon, platinum, titanium, or a combination thereof.

8. The system of any one of claims 5 to 7, wherein the cathode comprises an inert material.

9. The system of any one of claims 5 to 7, wherein the cathode comprises a current collector, and wherein the current collector comprises carbonaceous material, titanium, aluminum, copper, nickel, stainless steel, or a combination thereof.

10. The system of any one of claims 5 to 9, which is configured such that a voltage may be applied across the cathode and the lithium-rich molten metal alloy to extract lithium ions from the lithium-rich molten metal alloy and to form a lithium metal layer.

11. The system of any one of claims 1 to 10, wherein the molten metal comprises a metal selected from the group consisting of Al, Sn, Pb, Bi, Sb, Zn, and alloys of the same.

12. The system of any one of claims 1 to 11, wherein the molten metal comprises Sn or an alloy of Pb and Sb.

13. The system of any one of claims 1 to 12, wherein the lithium-rich molten metal alloy comprises lithium of at least 0.1 wt % relative to a total weight of the lithium-rich molten metal alloy.

14. The system of any one of claims 1 to 13, wherein the lithium-rich molten metal alloy comprises lithium of at most 70 wt % relative to a total weight of the lithium-rich molten metal alloy.

15. The system of any one of claims 1 to 14, wherein the molten salt electrolyte comprises a salt selected from the group consisting of lithium halides, sodium halides, potassium halides, and combinations thereof.

16. The system of any one of claims 1 to 15, wherein the molten salt electrolyte comprises a salt selected from the group consisting of LiCl, KC1, RbCL CsCl, SrCh, BaCh, and combinations thereof.

17. The system of any one of claims 1 to 16, wherein the molten salt electrolyte comprises fluoride salts.

18. The system of claim 17, wherein the fluoride salts are selected from the group consisting of LiF, CaF2, and combinations thereof.

19. The system of any one of claims 4 to 18, wherein the borate melt comprises a fluoride salt, wherein the fluoride salt is selected from the group consisting of NaF, KF, CaF2, and combinations thereof.

20. The system of any one of claims 1 to 19, wherein the first cell is maintained at a temperature between 600 °C and 1000°C.

21. The system of any one of claims 1 to 20, wherein the second cell is maintained at a temperature between 300 °C and 800 °C.

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