US20200149174A1

US20200149174A1 - Producing lithium

Info

Publication number: US20200149174A1
Application number: US16/743,602
Authority: US
Inventors: Lawrence Ralph Swonger
Original assignee: Alpha EN Corp
Current assignee: Alpha EN Corp
Priority date: 2013-07-10
Filing date: 2020-01-15
Publication date: 2020-05-14
Also published as: AU2015287769B2; JP6866289B2; US20150014184A1; JP2017528603A; WO2016007761A1; CA2954639A1; CN106574386A; EP3167099A1; AU2015287769A1; JP2021063301A; EP3167099A4; KR20170028424A

Abstract

A electrolytic process for continuous production of lithium metal from lithium carbonate or other lithium salts by use of an aqueous acid electrolyte and a lithium producing cell structure which includes: a cell body with a cathode within the cell body; an electrolyte aqueous solution within the cell body, the solution containing lithium ion and an anion; and a composite layer intercalated between the cathode and the electrolyte aqueous solution, the composite layer comprising a lithium ion conductive glass ceramic (LI-GC) and a lithium ion conductive barrier film (LI-BF) that isolates cathode-forming lithium from the electrolyte aqueous solution.

Description

This application claims the benefit of provisional application Ser. No. 61/844,482, filed Jul. 10, 2013, the disclosure of which is incorporated into this specification by reference in its entirety.

BACKGROUND OF THE INVENTION

The invention is a continuous process for obtaining lithium metal and a cell for carrying out the process.
Lithium is a soft, silver-white metal belonging to the alkali metal group of chemical elements. It is the lightest metal and the least dense solid element. Lithium is highly reactive and flammable. Because of its high reactivity, it does not occur freely in nature, and instead, only appears in compositions, usually ionic in nature. Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation. Because of this, it is a good conductor of heat and electricity as well as a highly reactive element. Because of its reactivity, lithium is usually stored under cover of a hydrocarbon, often mineral oil. In moist air, lithium rapidly tarnishes to form a black coating of lithium hydroxide (LiOH and LiOH.H₂O).
Uses of lithium compounds include lithium oxide as a flux for processing silica to glazes of low coefficients of thermal expansion, lithium carbonate (Li₂CO₃), as a component in ovenware and with lithium hydroxide, which is a strong base that can be heated with a fat to produce a lithium stearate soap. Lithium soap can be used to thicken oils and in the manufacture of lubricating greases. Metallic lithium can be used as a flux for welding or soldering to promote fusing of metals to eliminate oxide formation by absorbing impurities. Its fusing quality is important as a flux for producing ceramics, enamels and glass. Metallic lithium is used to manufacture primary lithium batteries.
Lithium carbonate is a common form of lithium produced from spodumene or lithium containing brine. Lithium metal can be can be extracted from lithium carbonate in phases:
Conversion of lithium carbonate into lithium chloride.
Electrolysis of lithium chloride.
To convert lithium carbonate to lithium chloride the lithium carbonate is heated and mixed with hydrochloric acid (typically 31% HCL) in an agitated reactor:
Li2CO3 (s)+2HCl (aq)->2LiCl (aq)+H₂O (aq)+CO2 (g) (Eq-2)
The formed carbon dioxide is vented from the reactant solution. A small amount of barium chloride can be added to precipitate any sulfate. After filtering, the solution is evaporated to a saleable 40% LiCl liquid product. Potassium chloride can be added to provide a dry lithium chloride-potassium chloride (45% LiCl; 55% KCl) of decreased melting point (614° C. to approximate 420° C.). Then the lithium chloride-potassium chloride (45% LiCl; 55% KCl) in a molten pure and dry state can be utilized to produce lithium metal in a steel reaction cell.
One steel cell has exterior ceramic insulation and a steel rod on the bottom as a cathode. The anode is constructed of graphite, which slowly sloughs-off during processing. The cell can be heated by gas firing between ceramic insulation and a cell's interior steel wall. Lithium metal accumulates at the surface of the cell wall and is then poured into ingots. Chloride gas generated by reaction is routed away. Typically, the electrolysis process is u operated with a cell voltage of 6.7˜7.5V, the typical cell current can be in the range of 30˜60 kA. The processing consumes 30˜35 kWh of electricity energy and 6.2˜6.4 kg LiCl to produce one kilogram lithium metal with 20˜40% energy efficiency.
Cathode: Li⁺ +e ⁻→Li metal
Anode: Cl⁻→½Cl₂ +e ⁻
Total: 2LiCl→2Li+Cl₂
A low temperature technology involves electrolysis of brine to form chlorine at an anode and sodium hydroxide or potassium hydroxide via a series of cathode reactions. The formation of either of these hydroxides can involve the reduction of an alkali cation, e.g. Li⁺ to metal at a liquid mercury cathode, followed by reaction of the formed mercury amalgam with water. The process operates near room temperature with a lower voltage than required for the molten salt system.
Amendola et al. U.S. Pat. No. 8,715,482 provides a system and process that obviates a mercury electrode. The liquid metal alloy electrode system of U.S. Pat. No. 8,715,482 includes: an electrolytic cell comprising a liquid metal cathode and an aqueous solution wherein the aqueous solution containing lithium ion and at least an anion selected from sulfate, trifluoromethane sulfonate, fluorosulfonate, trifluoroborane, trifluoroacetate, trifluorosilicate and kinetically hindered acid anions and wherein the lithium ion is produced from lithium carbonate. A heating system maintains temperature of the cell and liquid metal circulating systems higher than the melting point of the liquid metal cathode but lower than the boiling point of the aqueous solution. The reduced lithium from the electrolytic cell is extracted from the liquid metal cathode using a suitable extraction solution and a distillation system for isolating the lithium metal. This system is solid at room temperature and is less toxic than previous systems.
Putter at al. U.S. Pat. No. 6,770,187 discloses another process that overcomes some of the high energy consumption and high temperature requirement of prior art processes. The Putter et al process enables recycling of alkali metals from aqueous alkali metal waste, in particular lithium from aqueous lithium waste. Putter et al provides an electrolysis cell comprising an anode compartment which comprises an aqueous solution of at least one alkali metal salt, a cathode compartment and an ion conducting solid composite that separates the anode compartment and the cathode compartment from one another, wherein that part of the surface of the solid electrolyte composite that is in contact with the anode compartment and/or that part of the surface of the solid electrolyte that is in contact with the cathode compartment has/have at least one further ion-conducting layer. The electrolyte used in U.S. Pat. No. 6,770,187 is water or water with organic solvent.
Previous lithium producing system have involved substantial capital and operating costs. There is a need for a direct and improved electrolysis process that requires reduced capital and operating costs in a system that effectively provides direct production of lithium metal. Additionally, Potter et al. points out that “[a]lkali metal ion conductors of this type are frequently not resistant to water and/or to alkali metals, and the experiment therefore leads to damage of the alkali metal ion conductors after only a short period. This damage can comprise either mechanical failure of the ion conductor or loss of its conductivity. A further aim of the current invention therefore is to keep the ion conductors stable over a prolonged working life.
There is a need for a process that does not have the disadvantages described above (high energy consumption, high temperature, etc.). A further object is to provide an electrolysis cell suitable for carrying out this process.

BRIEF DESCRIPTION OF THE INVENTION

The invention provides an electrolysis cell and process characterized by a selective permeable barrier composite that provides for direct recovery of lithium metal. The cell and process are reasonably energy consuming and the lithium ion conducting composite layer is stable even in a highly corrosive anode compartment acid environment. In an embodiment, the invention is a lithium producing cell structure, comprising: a cell body with an anode and cathode within the cell body; an electrolyte aqueous solution within the cell body, the solution containing lithium ion; and a composite layer intercalated between the cathode and the electrolyte aqueous solution, the composite layer comprising a substantially impervious, lithium ion conductive composite layer (Li-GC) such as a glass ceramic and an active lithium ion conducting separation layer (Li-BF) that isolates cathode-forming lithium from the Li-GC.
In an embodiment, the invention is a process for producing lithium, comprising: providing a lithium ion source (lithium carbonate) and at least an acid in an aqueous solvent wherein lithium anion is dissolved in the solvent to form a lithium feed solution; providing an anode in contact with the solution; providing a cathode suitable for electrolysis of lithium; providing an ionizing electric current to the electrolysis cell thereby producing lithium metal at the cathode; and providing a composite layer transecting an axis of the cell body, the composite layer, comprising a lithium ion glass ceramic and lithium ion conductive barrier film that isolates cathode-forming lithium from the anion-containing solution as lithium metal is formed.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 of the drawings is a schematic elevation view of a lithium producing cell structure;

FIG. 2 is a schematic detail of the cell structure of FIG. 1; and

FIG. 3 is a schematic exploded detail of a cell of this application.

DETAILED DESCRIPTION OF THE INVENTION

Because of lithium's high electrochemical potential, it is an important component of electrolyte and electrodes in batteries. A typical lithium-ion battery can generate approximately 3 volts, compared with 2.1 volts for lead-acid or 1.5 volts for zinc-carbon cells. Because of its low atomic mass, it also has a high charge- and power-to-weight ratio. Lithium-ion batteries are high energy-density rechargeable batteries. Other rechargeable battery types include the lithium-ion polymer battery, lithium iron phosphate battery, and the nanowire battery.
This invention is for the production of lithium metal from lithium carbonate feed stock (or other lithium salt such as lithium chloride which dissociates in an acid electrolyte and releases the non-lithium portion of the feed stock as gas). My process can continuously process lithium carbonate into lithium metal. This is done by using a sulfuric acid electrolyte to disassociate lithium carbonate, placing the lithium ions into solution for processing and venting off the carbonate portion without it entering into solution.
The use of sulfuric acid for lithium carbonate processing is important: Lithium carbonate is essentially insoluble in water and organic solvents. Lithium cannot be efficiently extracted from lithium carbonate salt using an aqueous electrolyte with or without organic solvent. Use of a sulfuric acid solution provides much higher solubility of lithium carbonate into solution allowing efficient production of lithium metal from lithium carbonate. By disassociating the lithium carbonate and only placing the lithium ions into solution, the electrolyte solution remains stable and does not build up a concentration of the non-lithium ion portion of the feed stock. Lithium carbonate can be continuously fed into a tank outside of the electrolysis cell, venting off the CO₂gas released by the sulfuric acid electrolyte. The acid electrolyte does not need to be disposed of or replenished, lithium carbonate can be continuously added to a feed tank, venting off CO2 and harvesting lithium metal from a cathode. This can be continuously operated or conducted as a batch process.
The invention provides a cathode separated from lithium ion rich solution by a selectively permeable barrier composite (LIC-GC-BF). The composite comprises a lithium Ion conductive glass ceramic layer (LI-GC) and a lithium ion conductive barrier film (LI-BF). The LIC-GC-BF composite allows for direct production of lithium metal from solution and direct deposition of lithium metal onto a clean cathode, without need for an additional extraction process. The inventive system can include: an electrolyte feed system that provides a lithium ion rich electrolyte to the electrolysis cell; an electrolytic cell to move lithium metal from a water-based lithium ion solution through the LIC-GC-BF composite; and a method to package lithium metal. The invention can be part of a continuous lithium metal production process or as a batch process.
Features of the invention will become apparent from the drawings and following detailed discussion, which by way of example without limitation describe preferred embodiments of the invention.
The FIGS. 1 and 2 illustrate a production process of the invention wherein lithium-rich electrolyte flows through an extraction cell. When potential is applied to the system, lithium metal builds up on a moving cathode below an intercalated composite layer. FIG. 1 of the drawings is a schematic elevation view of lithium producing cell structure and FIG. 2 is a schematic detail of the cell structure of FIG. 1. In FIG. 1, and FIG. 2, the electrolytic cell 10 according to an embodiment of the invention, includes an upper section 12 and lower section 14. The cell 10 is characterized by a movable cathode 16 that transects a cross-section of the cell. The cathode 16 transposes an axis of cell 10, advancing as an electrolysis reaction takes place in electrolyte 18 above the cathode 16, through the LIC-GC-BF composite layer. Anode 20 is provided to the cell upper section 12. The cell section 12 above the cathode 10 is loaded with electrolyte 18 via inlet 22, electrolysis proceeds and spent electrolyte is discharged via outlet 24. The cathode 16 is in contact with the electrolyte 18 through a composite layer 28 intercalated between the cathode 16 and electrolyte 18. The composite layer 28 comprises a lithium ion conductive glass ceramic layer (LI-GC) 30 adjacent the electrolyte 18 and a lithium ion conductive barrier film (LI-BF) 32 interposed between the ceramic layer 30 and cathode 18. The barrier layer 32 and glass ceramic layer 30 composite 28 isolates forming lithium at cathode 16 from electrolyte 18. Shaft 26 advances the cathode 16 and composite 28 as lithium metal is formed and deposited through the composite layer 28 onto the advancing cathode 16. The Lithium metal produced at the solid cathode 16 can be drawn off as a pure metallic phase.
Suitable feed to the cell includes water-soluble lithium salts including but not limited to Li₂CO₃and LiCl. To improve solubility, the lithium salt is dissolved in hydrated acid and used as electrolyte in the electrolytic cell. Lithium Carbonate (Li2CO3) was used as feed stock for initial trials.
Some suitable cell components in the present invention are described in US20130004852, which is incorporated into this disclosure in its entirety by reference.
Suitable electrolyte 18 components include water-soluble lithium salts including but not limited to Li₂CO₃and LiCl. To improve solubility the lithium salt can be dissolved in hydrated acid to be used as electrolyte. Lithium carbonate (Li₂CO₃) is the most readily available lithium salt, being relatively inexpensive and is a preferred lithium source. Cathode 16 is characterized by the intercalated composite (Li-GC/Li-BF) 28 meaning the composite 28 is inserted or interposed between the cathode 16 and electrolyte 18. The cathode 16 can be characterized as “transpositioning” meaning the cathode advances along an axis of the cell 10 to transpire produced lithium through the composite 28 and to isolate cathode-deposited lithium. The cathode comprises a suitable material that is non-reactive with lithium metal and the composite layer. The Li-GC/Li-BF composite layer is a stationary barrier between the anode compartment and the lithium metal forming on the cathode. The cathode moves to accommodate the continuously thickening layer of lithium metal on the cathode.
Composite layer (Li-GC/Li-BF) 28 includes lithium ion conductive glass ceramic layer (LI-GC) 30 and lithium ion conductive barrier film (LI-BF) 32. The substantially impervious layer (LI-GC) 30 can be an active metal ion conducting glass or glass-ceramic (e.g., a lithium ion conductive glass-ceramic that has high active metal ion conductivity and stability to aggressive electrolytes that vigorously react with lithium metal. Suitable materials are substantially impervious, ionically conductive and chemically compatible with aqueous electrolytes or other electrolyte (catholyte) and/or cathode materials that would otherwise adversely react with lithium metal. Such glass or glass-ceramic materials are substantially gap-free, non-swellable and are inherently ionically conductive. That is, they do not depend on the presence of a liquid electrolyte or other agent for their ionically conductive properties. They also have high ionic conductivity, at least 10⁻⁷S/cm, generally at least 103 S/cm, for example at least 10⁻⁵S/cm to 10⁻⁴S/cm, and as high as 10⁻³S/cm or higher so that the overall ionic conductivity of the multi-layer protective structure is at least 10⁻⁷S/cm and as high as 10⁻³S/cm or higher. The thickness of the layer is preferably about 0.1 to 1000 microns, or, where the ionic conductivity of the layer is about 10⁻⁷S/cm, about 0.25 to 1 micron, or, where the ionic conductivity of the layer is between about 10⁻⁴about 10⁻³S/cm, about 10 to 1000 microns, preferably between 1 and 500 microns, and more preferably between 50 and 250 microns, for example, about 150 microns.
Examples of glass ceramic layer (LI-GC) 30 include glassy or amorphous metal ion conductors, such as a phosphorus-based glass, oxide-based glass, phosphorus-oxynitride-based glass, sulpher-based glass, oxide/sulfide based glass, selenide based glass, gallium based glass, germanium-based glass or boracite glass (such as are described D. P. Button et al., Solid State Ionics, Vols. 9-10, Part 1, 585-592 (December 1983); ceramic active metal ion conductors, such as lithium beta-alumina, sodium beta-alumina, Li superionic conductor (LISICON), Na superionic conductor (NASICON), and the like; or glass ceramic active metal ion conductors. Specific examples include LiPON, Li₃PO₄Li₂S.SiS₂, Li₂S.GeS₂.Ga₂S₃, Li₂O.
Suitable glass-ceramic materials (LI-GC) include a lithium ion conductive glass-ceramic having the following composition in mol percent: P₂O₅26-55%; SiO₂0-15%; GeO₂+TiO₂25-50%; in which GeO₂0-50%; TiO₂0-50%; ZrO₂0-10%; M₂O₃0-10%; Al₂O₃0-15%; Ga₂O₃0-15%; Li₂O 3-25% and containing a predominant crystalline phase comprising Li_1+x(M, Al, Ga)_x(GeO_1−yTi_y)_2−x(PO₄)₃where X≤0.8 and 0≤Y≤1.0 and where M is an element selected from the group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and/or Li_1+x+yQ_xTi₂₋Si₃P3−yO₁₂where 0<≤0.4 and 0<Y≤0.6, and where Q is Al or Ga. Other examples include 11Al₂O₃, Na₂O.11Al₂O₃, (Na, Li)_i+XTi_2−xAl_x(PO₄)₃(0.6≤x≤0.9) and crystallographically related structures, Na₃Zr₂Si₂PO₁₂, Li₃Zr₂Si₂PO₄, Na₅ZrP₃O₁₂, Na₅TiP₃O₁₂, Na₃Fe₂P₃O₁₂, Na₄NbP₃O₁₂, Li₅ZrP₃O₁₂, Li₅TiP₃O₁₂, Li₅Fe₂P₃O₁₂and Li₄NbP₃O₁₂and combinations thereof; optionally sintered or melted. Suitable ceramic ion active metal ion conductors are described, for example, in U.S. Pat. No. 4,985,317 to Adachi et al., incorporated by reference herein in its entirety.
Suitable LI-GC material includes a product from Ohara, Inc. (Kanagawa, JP), trademarked LIC-GC™, LISICON, LiO—Al₂S—SiO—P₂O₅—TiO₂(LATP). Suitable material with similarly high lithium metal ion conductivity and environmental/chemical resistance are manufactured by Ohara and others. See for example, Inda, DN20100113243, now U.S. Pat. No. 8,476,174, incorporated herein in their entirety by reference. U.S. Pat. No. 8,476,174 discloses a glass-ceramic comprising at least crystallines having a having a LiTi₂P₃O₁₂structure, the crystallines satisfying 1<I_A113/I_A104≤2, wherein I_A104is the peak intensity assigned to the plane index 104 (2Θ=20 to 21°), and I_A113is the peak intensity assigned to the plane index 113 (2Θ=24 to 25°) as determined by X-ray diffractometry.
The lithium ion conductive barrier film 32 (Li-BF) is a lithium metal ion conductive film or coating with high lithium metal ion conductivity, typically The lithium ion conductive barrier film 32 (LI-BF) is a lithium metal ion conductive film or coating with high lithium metal ion conductivity, typically 1.0 mS/cm to 100 mS/cm. A high lithium ion transference number (t₊) is preferred. Low t₊ Li+ electrolytes will hinder performance by allowing ion concentration gradients within the cell, leading to high internal resistances that may limit cell lifetime and limit reduction rates. Transference numbers between t₊=0.70 and t₊=1.0 are preferred. The lithium ion conductive barrier film is non-reactive to both lithium metal and the LI-GC material.
The LI-BF film 32 includes an active metal composite, where “active metals” are lithium, sodium, magnesium, calcium, and aluminum used as the active material of batteries. Suitable LI-BF material includes a composite reaction product of active metal with Cu₃N, active metal nitrides, active metal phosphides, active metal halides, active metal phosphorus sulfide glass and active metal phosphorous oxynitride glass (Cu₃N, L₃N, Li₃P, LiI, LiF, LiBr, LiCl and LiPON). The LI-BF material must also protect against dendrites forming on the cathode from coming in contact with the LI-GC material. This may be accomplished by creating physical distance between the cathode and LI-OC and/or providing a physical barrier that the dendrites do not penetrate easily. One preferred LI-BF film is a physical organogel electrolyte produced by in situ thermo-irreversible gelation and single ion-predominant conduction as described by Kim et al. in Scientific Reports at http//www.nature.com/srep/2013/130529/srcp01917/fig_tab/srep01917_F1.html. (article number: 1917 doi:10.1038/srep01917). This electrolyte has t=0.84 and conductivity of 8.63 mS/cm at room temperature. This organogel electrolyte can be set up in a porous membrane to provide additional structure and resistance to dendrite penetration. Typical porous membrane thickness is 1 um to 500 um, for example 20 um. Acceptable porous membrane includes HIPORE polyolefin flat-film membrane by Asahi Kasci E-materials Corporation.
The invention produces lithium metal that can be used as part of a continuous lithium metal production process. In particular, the present process can utilize inexpensive lithium carbonate or an equivalent source of lithium ions. The process can be used to produce lithium metal directly from the acid solution used to leech lithium metal out of spodumene ore or other natural lithium sources.
Features of the invention are apparent from the drawings and following detailed discussion, which by way of example without limitation describe one preferred embodiments of the invention.

Example

The cell used is shown schematically in FIG. 3. The cell 110 includes cell cover 116, retainer 118, Pt anode 112, cathode 124 and a LI-GC conductive glass 114 with lithium ion conductive barrier film 120 incorporated into a porous polyolefin flat-film membrane 122. The supported LI-GC-BF multilayer is intercalated between cathode 124 and a lithium ion-rich electrolyte 18 (in FIGS. 1 and 2). The cell further comprises supporting Teflon® sleeve structure 126 with gaskets 128. One gasket seals between the LI-GC and the housing to prevent leakage of the electrolyte from the anode compartment into the cathode compartment. The other gasket allows for even compression of the LI-GC by the Teflon Sleeve to prevent breakage of the LI-GC plate.
The cell 110 includes anode 112 that is a platinized titanium anode, 1″×4″ rhodium and palladium jewelry plating). The cathode is a palladium cathode disk fabricated in-house, 1.4 inch round. The LI-GC 114 material is LICGC® G71-3 N33: DIA 2 IN×150 um Tape cast, 150 um thick, 2 inch round from Ohara Corporation, 23141 Arroyo Vista, Rancho Santa Margarita, Calif. 92688.
The lithium ion conducting gel electrolyte 120 is fabricated from: a PVA-CN polymer supplied by the Ulsan National Institute of Science and Technology in Ulsan South Korea, Dr. Hyun-Kon Song, UNIST/82.52.217.2512/echem.kr., procured from Alfa Aesar, stock number H61502; LiPF6 (Lithium hexaflourophosphate), 98%; EMC (ethyl methyl carbonate), 99%, from Sigma Aldrich, product Number 754935; EC (ethylene carbonate), anhydrous, from Sigma Aldrich, product number 676802 and a porous membrane, ND420 polyolefin flat-film membrane from Asahi Corp.
The LI-BF barrier layer 120 is fabricated in an argon purged glove bag. The glove bag is loaded with all materials, precision scale, syringes, and other cell components then filled and evacuated 4 times before the start of the electrolyte fabrication process.
The organogel electrolyte is mixed up as follows: 4.0 ml of EMC is liquified by heating to about 140° F., and placed in a vial 2.0 ml of the EMC is then added-to the vial 0.133 g (2% wt) PVA-CN polymer is added to the vial and the is agitated for 1 hour to dissolve the PVA-CN. Then 0.133 g (2% wt) FEC is added as SEI-forming additive 0.972 g (1M) LiPF6 is then added and mixed to complete the organogel electrolyte mixture. The electrolysis cell is then assembled inside the glove bag. With the LI-GC and gaskets in place, the anode and cathode compartments are sealed from each other. The organogel electrolyte mixture is used to wet the cathode side of the LI-GC, the HIPORE membrane is placed on the cathode side of the LI-GC and wetted again with organogel electrolyte mixture. The cathode disk is then placed on top of the organogel mixture. The cell is placed in a Mylar® bag and sealed while still under argon purge. The sealed Mylar® bag with assembled cell is then placed in an oven at 60 C for 24 hours to gel the electrolyte.
The electrolysis cell 10 is removed from the oven and placed in the argon purged glove bag, and allowed to cool to room temperature. Clear polypro tape is used to seal the empty space above the cathode disc and secure the electrode wire. The electrolysis cell 10 is now ready for use, is removed from the glove bag, and is connected to the electrolyte circulating system.
An electrolyte 18 is prepared with 120 g of lithium carbonated in 200 ml of deionized water and 500 ml of 20% wt sulfuric acid. The sulfuric acid is slowly added to the lithium carbonate suspension and mixed well. Undissolved lithium carbonate is allowed to settle. A supernatant is collected from the stock solution, an 18% wt lithium stock solution. The 18% wt lithium solution has a measured pH of 9. Solution pH is lowered by addition of 20% wt sulfuric acid. Again, the sulfuric acid is added slowly to minimize foaming. The 18% wt lithium stock solution is adjusted to pH 4.5. Preferred PH is between PH3.0 and PH4.5, most preferred is between PH3.0 and PH4.0, but process can be run at PH7.0 or below. PH above 7.0 will result in carbonate in solution.
The electrolyte mixture is then poured into the circulating system. The circulating pump is primed and solution circulated for 30 minutes to check for leaks.
The lithium ion-rich electrolyte 18 flows through the top half of cell 110 over the LI-GC-BF multilayer 114/120 and past anode 112. When potential is applied to the system, lithium metal builds up on the moving cathode below the LI-GC-BF multilayer 114/120 system.
A Gamry Reference 3000 Potentiostat/Galvanostat/ZRA is attached to the cell 10. At voltages of 3-6 volts there is no significant activity. When voltage is raised to 10V the system responds. Amperage draw increases when voltage is raised to 11 vdc. No gassing on the anode side of the cell was noted at 11 vdc. The Gamry Reference 3000 would not go above 11 vdc. Since no gassing occurred at 11 vdc the reduction rate could most likely be much higher if voltage were increased. An even higher voltage and reduction rate are preferable if achieved with negligible oxygen production at the anode. PH of the electrolyte at time zero is 4.46. PH of the solution decreases to 4.29 after 35 minutes, and is 4.05 at the end of the experiment. The lowering PH indicates lithium ion removal from the electrolyte solution.
An amperage draw of 20 mA is noted at the start of the experiment. The amperage draw slowly increased to 60 mA after 30 minutes. Amperage holds fairly steady at this value for another 30 minutes. Experiment timer and graph are paused for 30 minutes to extend experiment (voltage held at 11 vdc). After approximately 65 minutes of run time a large amperage spike and sudden vigorous gassing is noted on the anode side of the cell This is indicative of LiCOC 114/12 membrane failure.
Rapid gassing and bright white flame is observed when the cell 10 is opened and cathode 16 side is exposed to electrolyte leaking through the LI-GC 114/120, evidencing that the cell produces lithium metal by electrolysis of lithium ions in a sulfuric acid aqueous solution, through a LI-GC-BF 114/120 membrane system.
While preferred embodiments of the invention have been described, the present invention is capable of variation and modification and therefore should not be limited to the precise details of the Examples. The invention includes changes and alterations that fall within the purview of the following claims.

Claims

What is claimed is:

1: A process for continuously producing lithium on a cathode comprising:

providing an electrolytic cell comprising:

a lithium feed solution comprising a sulfuric acid solvent and a lithium ion source selected from the group consisting of lithium carbonate, lithium chloride, spodumene, and combinations thereof;

an anode in contact with the lithium feed solution;

the cathode; and

a composite layer between the cathode and the lithium feed solution, the composite layer comprising a lithium ion conductive glass ceramic material and a lithium ion conducting electrolyte between the lithium ion conductive glass ceramic material and the cathode; and

providing an ionizing electric current to the electrolytic cell to continuously produce lithium metal at the cathode,

wherein the composite layer isolates the lithium metal produced at the cathode from the lithium feed solution as the lithium metal is formed, and the lithium feed solution is continuously provided.

2: The process for producing lithium of claim 1, wherein the lithium ion conducting electrolyte is an ionic liquid.

3: The process for producing lithium of claim 1, wherein the lithium ion conducting electrolyte is a non-aqueous electrolyte.

4: The process for producing lithium of claim 1, wherein the composite layer has an ion conductivity of at least 10⁻⁷S/cm and is nonreactive to both lithium metal and the cathode.

5: The process for producing lithium of claim 1, wherein the cathode is moveable along an axis of the electrolytic cell away from the anode as the lithium metal is produced at the cathode.

6: The process for producing lithium of claim 1, wherein a physical distance is present between the cathode and the lithium ion conductive glass ceramic material.

7: The process for producing lithium of claim 1, wherein:

the electrolytic cell comprises a first portion containing the cathode and a second portion containing the lithium feed solution, and

the electrolytic cell is configured to drive the cathode away from the lithium ion conductive glass ceramic as the lithium metal is formed on the cathode.

8: The process for producing lithium of claim 1, wherein:

the lithium ion source consists of a lithium salt that dissociates in the sulfuric acid solvent, and

a non-lithium portion of the salt is released from the solution as a gas.

9: The process for producing lithium of claim 1, wherein the lithium metal produced at the cathode is drawn off as a pure metallic phase.

10: The process for producing lithium of claim 1 comprising drawing off the lithium metal produced at the cathode, without any additional extraction processes.

11: A process for continuously producing lithium on a cathode comprising:

providing a lithium feed solution comprising a hydrated acid solvent and a lithium ion source selected from the group consisting of lithium carbonate, lithium chloride, spodumene, and combinations thereof dissolved in the hydrated acid solvent;

providing a composite layer between a cathode and the lithium feed solution, the composite layer comprising a lithium ion conductive glass ceramic material and a lithium ion conducting electrolyte between the lithium ion conductive glass ceramic material and the cathode; and

generating a current across the lithium feed solution to continuously produce lithium metal at the cathode,

12: The process for producing lithium of claim 11, wherein the hydrated acid is sulfuric acid.

13: The process for producing lithium of claim 11, wherein the lithium feed solution is selected from the group consisting of: a sulfuric acid electrolyte and a sulfuric acid leaching solution.

14: The process for producing lithium of claim 11, wherein the lithium ion conducting electrolyte is an ionic liquid.

15: The process for producing lithium of claim 11, wherein the lithium ion conducting electrolyte is a non-aqueous electrolyte.

16: The process for producing lithium of claim 11, wherein a physical distance is present between the cathode and the lithium ion conductive glass ceramic material.

17: The process for producing lithium of claim 11, wherein the lithium metal produced at the cathode is drawn off as a pure metallic phase.

18: The process for producing lithium of claim 11, comprising drawing off the lithium metal produced at the cathode, without any additional extraction processes.

19: A continuous lithium-producing cell for producing lithium on a cathode, comprising:

a continuously-provided lithium feed solution comprising a sulfuric acid solvent and a lithium ion source selected from the group consisting of lithium carbonate, lithium chloride, spodumene, and combinations thereof;

an anode in contact with the lithium feed solution;

a cathode; and

a composite layer between the cathode and the lithium feed solution, the composite layer comprising a lithium ion conductive glass ceramic material and a lithium ion conducting electrolyte between the lithium ion conductive glass ceramic material and the cathode;

wherein the composite layer isolates the lithium metal produced at the cathode from the lithium feed solution as the lithium metal is formed.

20: A lithium metal product comprising lithium metal produced by the process of claim 1.