HK1236585A1 - Producing lithium - Google Patents

Description

Production of lithium

Technical Field

The present disclosure relates generally to an improved method for obtaining lithium metal and an electrolytic cell for performing the method.

Background

Lithium is a soft silvery-white metal belonging to the alkali metal chemical group. 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 in free form in nature, but rather only in compositions, usually ionic in nature. Like other alkali metals, lithium has a single valence electron, which is easily discarded to form a cation. Therefore, it is a good conductor of heat and electricity, and is a highly reactive element. Due to its reactivity, lithium is usually stored under a blanket of hydrocarbons, usually mineral oil. In humid air, lithium darkens rapidly to form lithium hydroxide (LiOH and LiOH₂O) black coating.

The use of lithium compounds includes lithium oxide as a flux for processing silicon dioxide into glazes with a low coefficient of thermal expansion, lithium carbonate (Li)₂CO₃) As a component in ovenware, and lithium hydroxide as a strong base, which can be heated with fat to produce lithium stearate soap. Lithium soaps are useful for oil thickening and grease manufacturing. Metallic lithium can be used as a flux for welding or soldering, promoting the melting of the metal to eliminate oxide formation by gettering impurities. Its melting quality is important for use as a flux for the production of ceramics, enamels and glasses. Metallic lithium is used to manufacture primary lithium batteries.

Lithium carbonate is a common form of lithium produced from spodumene or lithium-containing brines. Lithium metal may be extracted from lithium carbonate in the following stages:

conversion of lithium carbonate to lithium chloride;

and (4) electrolyzing lithium chloride.

To convert lithium carbonate to lithium chloride, lithium carbonate is heated and mixed with hydrochloric acid (typically 31% HCl) in a stirred reactor:

Li₂CO₃(s)+2HCl(aq)→’2LiCl(aq)+H₂O(aq)+CO₂(g) (Eq-2)

the carbon dioxide formed is vented from the reactant solution. A small amount of barium chloride may be added to precipitate any sulfate. After filtration, the solution was evaporated to a marketable 40% LiCl liquid product. Potassium chloride can be added to provide anhydrous lithium-potassium chloride (45% LiCl; 55% KCl) with a reduced melting point (614 ℃ down to about 420 ℃). The lithium chloride-potassium chloride (45% LiCl; 55% KCl) in a molten pure and anhydrous state can then be used to produce lithium metal in a steel reaction cell.

A steel electrolytic cell has an outer ceramic separator and a steel bar on the bottom as the cathode. The anode is constructed of graphite, which slowly sloughs off during processing. The cell may be heated by gas combustion between the ceramic separator and the steel wall inside the cell. Lithium metal accumulates at the surface of the cell walls and is then cast into ingots. The chlorine produced by the reaction is carried away. Typically, the electrolysis process is run using cell voltages of 6.7-7.5V, and typical cell currents may be in the range of 30-60 kA. The process consumes 30-35kWh of electric energy and 6.2-6.4kg of LiCl for 1 kg of lithium metal produced with an energy efficiency of 20-40%.

Li⁺+e^-→ Li metal cathode

Cl^-→1/2Cl₂+e^-Anode

2LiCl→2Li+Cl₂Total of

One cryogenic technique involves electrolysis of brine to form chlorine at the anode and sodium or potassium hydroxide through a series of cathodic reactions. The formation of any of these hydroxides may involve an alkali cation such as Li⁺Reduction to metal at the liquid mercury cathode, followed by reaction of the amalgam formed with water. The process operates at near room temperature using lower voltages than required for molten salt systems.

U.S. patent No. 8,715,482 to amandola et al provides a system and method for avoiding mercury electrodes. The liquid metal alloy electrode system of U.S. patent No. 8,715,482 includes: an electrolytic cell comprising a liquid metal cathode and an aqueous solution, wherein the aqueous solution contains lithium ions and at least one anion selected from the group consisting of sulfuric acid, trifluoromethanesulfonic acid, fluorosulfonic acid, trifluoroboric acid, trifluoroacetic acid, trifluorosilicic acid, and kinetic-hindered acids, and wherein the lithium ions are generated from lithium carbonate. A heating system maintains the temperature of the electrolytic cell and liquid metal circulation system above the melting point of the liquid metal cathode but below the boiling point of the aqueous solution. The lithium reduced from the electrolytic cell is extracted from the liquid metal cathode using an extraction solution suitable for separating lithium metal and a distillation system. Such systems are solid at room temperature and less toxic than previous systems.

U.S. patent No. 6,770,187 to Putter et al discloses another approach that overcomes some of the high energy consumption and high temperature requirements of prior art approaches. The method of Putter et al enables the recovery of alkali metals, in particular lithium, from aqueous lithium waste. The cell provided by Putter et al comprises an anode compartment containing an aqueous solution of at least one alkali metal salt, a cathode compartment and an ion-conducting solid composite separating the anode and cathode compartments from each other, wherein the part of the surface of the solid electrolyte composite in contact with the anode compartment and/or the part of the surface of the solid electrolyte in contact with the cathode compartment is provided with at least one further ion-conducting layer. The electrolyte used in us patent No. 6,770,187 is water or water and an organic solvent.

Previous systems for producing lithium involve significant capital and operating costs. There is a need for a direct and improved electrolysis process that requires lower capital and operating costs in a system that efficiently provides for the direct generation of lithium metal. Furthermore, Putter et al indicate that "alkali metal ion conductors of this type are often not resistant to water and/or alkali metals, and therefore experiments have resulted in the alkali metal ion conductors being damaged after only a short time. Such damage may include mechanical failure of the ion conductor or loss of its conductivity. "accordingly, it is another object of the present disclosure to keep the ion conductor stable for a longer operating life.

There is a need for a process that does not suffer from the above-mentioned drawbacks (high energy consumption, high temperatures, etc.). Another object is to provide an electrolytic cell suitable for carrying out the method.

Disclosure of Invention

The present disclosure provides an electrolytic cell and method featuring a selectively permeable barrier composite that provides direct recovery of lithium metal. The electrolytic cell and method have reasonable energy consumption, and the lithium ion conductive composite layer is stable even in highly corrosive anode compartment acid environments.

In one embodiment, the present disclosure provides an electrolytic cell for producing lithium comprising: a cathode; a sulfuric acid solution containing lithium ions, and a composite material layer between the cathode and the sulfuric acid solution. The composite layer comprises a lithium ion-conductive glass-ceramic material and a lithium ion-conductive barrier membrane. In such an embodiment, the composite layer may have at least 10^-7An ion conductivity of S/cm and is non-reactive to both lithium metal and the lithium ion conducting glass-ceramic material.

In one embodiment, the lithium ion-conducting barrier membrane comprises a physical organogel electrolyte.

In one embodiment, the lithium ion-conductive barrier membrane comprises an organogel product of in-situ thermally irreversible gelation and single-ion dominant conductivity.

In one embodiment, the lithium ion conducting glass-ceramic material comprises a glass-ceramic active metal ion conductor.

In one embodiment, the lithium ion conductive glass-ceramicThe material comprises an ionically conductive glass-ceramic comprising: 26 to 55 mol% of P₂O₅0 to 15 mol% SiO₂25 to 50 mol% GeO₂+TiO₂(wherein GeO)₂Is in the range of 0 to 50% and TiO₂In the range of 0 to 50%), 0 to 10 mol% of ZrO₂0 to 10 mol% of M₂O₃0 to 15 mol% of Al₂O₃0 to 15 mol% of Ga₂O₃And 3 to 25 mol% Li₂And O. In such embodiments, the ion-conducting glass-ceramic contains a predominant crystalline phase comprising at least one of: li_1+x(M,Al,Ga)_x(Ge_1-yTi_y)_2-x(PO₄)₃Wherein X is not more than 0.8, Y is not less than 0 but not more than 1.0, and M is an element selected from Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb; and Li_1+x+yQ_xTi_2-xSi₃P_3-yO₁₂Wherein 0 is<X≤0.4，0<Y is 0.6 or less, and Q is Al or Ga.

In one embodiment, the composite layer has at least 10^-4Ion conductivity of S/cm.

In one embodiment, the cathode comprises a non-aqueous catholyte. In such embodiments, the catholyte may comprise an ionic liquid.

In one embodiment, the cathode comprises an active material selected from the group consisting of: solid oxidants, liquid oxidants and gaseous oxidants.

In one embodiment, the lithium ion-conducting glass-ceramic material comprises a protective ceramic composite that is substantially impermeable to water (ions).

In one embodiment, the cathode is movable along the axis of the cell for producing lithium.

In one embodiment, the sulfuric acid solution is selected from a sulfuric acid electrolyte and a sulfuric acid leach solution.

In another embodiment, the present disclosure provides a method of producing lithium, the method comprising: providing an electrolytic cell comprising: a solution, an anode in contact with the solution, a cathode, and a layer of composite material between the cathode and the solution; and providing an ionization current to the electrolytic cell to produce lithium metal at the cathode. The solution comprises a sulfuric acid solvent and a source of lithium ions. The composite layer comprises a lithium ion glass ceramic material and a lithium ion conductive barrier membrane. The composite layer isolates lithium metal produced at the cathode from the solution as the lithium metal is formed.

In one embodiment, the composite layer has at least 10^-7An ion conductivity of S/cm and is non-reactive to both lithium metal and the lithium ion conducting glass-ceramic material.

In one embodiment, the cathode may move away from the anode along the axis of the electrolytic cell as the lithium metal is produced at the cathode.

In one embodiment, the electrolytic cell comprises an upper portion containing the cathode and a lower portion containing the solution. The electrolytic cell is configured to drive the cathode away from the composite layer when the lithium metal is formed on the cathode.

In one embodiment, the lithium ion-conducting barrier membrane comprises a physical organogel electrolyte. In this regard, the lithium ion conductive barrier film may comprise an in situ thermally irreversible gelation and single ion dominant conductivity organogel product.

In one embodiment, the source of lithium ions comprises at least one selected from the group consisting of: lithium carbonate, lithium chloride and spodumene.

In one embodiment, the source of lithium ions comprises a lithium salt that dissociates in the sulfuric acid solvent. The non-lithium portion of the salt is released from the solution as a gas.

In one embodiment, the solution is selected from a sulfuric acid electrolyte and a sulfuric acid leach solution.

In one embodiment, the lithium metal produced at the cathode is extracted as a pure metal phase.

In yet another embodiment, a method of producing lithium is provided. The method comprises the following steps: providing a solution; providing a layer of composite material between a cathode and the solution; and generating an electric current across the solution to produce lithium metal at the cathode. The solution includes a hydrated acid solvent and lithium ions dissolved in the hydrated acid solvent. The composite layer comprises a lithium ion-containing glass-ceramic material. The composite layer isolates lithium metal produced at the cathode from the solution as the lithium metal is formed.

In one embodiment, the composite layer comprises a lithium ion-conductive barrier membrane.

In one embodiment, the hydrated acid is sulfuric acid. In such an embodiment, the solution may be selected from a sulfuric acid electrolyte and a sulfuric acid leach solution.

In one embodiment, the lithium metal produced at the cathode is extracted as a pure metal phase.

In another embodiment, the present disclosure provides a lithium metal product. The lithium metal product comprises lithium metal produced by the process of: providing a layer of composite material between the cathode and the solution; and generating an electric current across the solution to produce the lithium metal at the cathode. The solution contains lithium ions dissolved in sulfuric acid. The composite layer comprises a lithium ion-containing glass-ceramic material.

In one embodiment, the composite layer comprises a lithium ion-conductive barrier membrane.

In one embodiment, the composite layer isolates lithium metal produced at the cathode from the solution as the lithium metal is formed.

In one embodiment, the lithium metal produced at the cathode is extracted as a pure metal phase.

In one embodiment, the solution is selected from a sulfuric acid electrolyte and a sulfuric acid leach solution.

It is an advantage of the present disclosure to provide an improved method for producing lithium and an improved lithium producing electrolytic cell for producing lithium. The improved process and improved electrolytic cell for producing lithium allow for the production of lithium metal at lower cost and with reasonable energy consumption.

Another advantage of the present disclosure is to provide a lithium metal product formed by the improved method of producing lithium.

Other features and advantages will be described herein and will become apparent from the following detailed description and the accompanying drawings.

Drawings

The foregoing summary, as well as the following detailed description of the present disclosure, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the disclosure is not limited to the particular arrangements, examples, and instrument devices shown.

FIG. 1 shows a schematic view of aA schematic elevation view illustrating a structure of an electrolytic cell for producing lithium used in an embodiment of the present disclosure;

FIG. 2Showing schematic details of the construction of the cell for the production of lithium of figure 1; and is

FIG. 3Schematic component decomposition details of the lithium producing cell of example 1 are shown.

Detailed Description

The present disclosure relates to an electrolytic cell and method for producing lithium metal using a selectively permeable barrier composite.

Lithium is an important component of the electrolyte and electrodes in batteries due to its high electrochemical potential. A typical lithium ion battery can produce about 3 volts, compared to 2.1 volts for a lead-acid battery and 1.5 volts for a zinc-carbon battery. It also has a high charge and power to weight ratio due to its low atomic mass. Lithium ion batteries are high energy density rechargeable batteries. Other rechargeable battery types include lithium ion polymer batteries, lithium iron phosphate batteries, and nanowire batteries.

The present disclosure relates to a process for producing lithium metal from a lithium carbonate feedstock (or other lithium salts such as lithium chloride, which dissociates in an acid electrolyte and liberates the non-lithium portion of the feedstock (i.e., carbonate or chloride) as a gas). The method can continuously process lithium carbonate into lithium metal. The method includes dissociating lithium carbonate using a sulfuric acid electrolyte, placing the lithium ions in a processing solution, and discharging a carbonate fraction without bringing it into solution.

The use of sulfuric acid for the lithium carbonate process is important for reasons described below. Lithium carbonate is substantially insoluble in water and organic solvents. Lithium cannot be efficiently extracted from lithium carbonate salts using aqueous electrolytes with or without organic solvents. The use of a sulfuric acid solution provides a much higher solubility of lithium carbonate in the solution, allowing for efficient production of lithium metal from lithium carbonate. By dissociating lithium carbonate and placing only lithium ions in solution, the electrolyte solution remains stable and does not increase the concentration of the non-lithium ion portion of the feedstock. Lithium carbonate may be continuously fed to a tank outside the electrolytic cell, discharging CO released from the sulfuric acid electrolyte₂A gas. The acid electrolyte does not have to be disposed of or replenished and lithium carbonate can be continuously added to the feed tank, with CO vented₂And harvesting lithium metal from the cathode. This can be done continuously or as a batch process.

The present disclosure provides a cathode separated from a lithium ion rich solution by a selectively permeable barrier composite (LIC-GC-BF). The composite material comprises a lithium ion-conducting glass-ceramic layer (LI-GC) and a lithium ion-conducting barrier film (LI-BF). The LIC-GC-BF composite allows for the direct production of lithium metal from solution and deposition of lithium metal directly on a clean cathode without the need for additional extraction processes. The system for producing lithium metal may include: an electrolyte feed system that provides a lithium ion rich electrolyte to the electrolytic cell; an electrolytic cell that moves lithium metal from a water-based lithium ion solution through a LIC-GC-BF composite; and a method of packaging lithium metal. The system may be used in a lithium metal continuous production process or a batch process.

Features of the present invention will become apparent from the accompanying drawings and the following detailed discussion, which illustrate by way of example, and not by way of limitation, preferred embodiments of the invention.

Figures 1 and 2 illustrate the production process of the present invention wherein a lithium rich electrolyte is passed through an extraction cell. When an electrical potential is applied to the system, lithium metal accumulates on the moving cathode beneath the intercalated composite layer. Fig. 1 is a schematic elevation view of an electrolytic cell structure for producing lithium, and fig. 2 is schematic detail of the electrolytic cell structure of fig. 1. In fig. 1 and 2, an electrolytic cell 10 according to one embodiment includes an upper section 12 and a lower section 14. The cell 10 features a movable cathode 16 across the cross-section of the cell. Cathode 16 is displaced along the axis of cell 10, advancing as an electrolytic reaction occurs in electrolyte 18 above cathode 16 by the LIC-GC-BF composite layer. An anode 20 is provided in the upper cell section 12. The cell segment 12 above the cathode 10 is charged with electrolyte 18 through an inlet 22, electrolysis proceeds, and spent electrolyte is discharged through an outlet 24. Cathode 16 is in contact with electrolyte 18 through a composite layer 28 sandwiched between cathode 16 and electrolyte 18. The composite layer 28 includes a lithium ion-conductive glass ceramic layer (LI-GC)30 adjacent to the electrolyte 18 and a lithium ion-conductive barrier film (LI-BF)32 interposed between the ceramic layer 30 and the cathode 18. The barrier layer 32 and the glass-ceramic layer 30 composite 28 separate the lithium formed at the cathode 16 from the electrolyte 18. As lithium metal is formed and deposited on the advancing cathode 16 through the composite layer 28, the shaft 26 urges the cathode 16 and the composite 28 to advance. The lithium metal produced at the solid cathode 16 can be extracted as a pure metal phase.

Suitable feeds to the electrolytic cell include water-soluble lithium salts, including but not limited to Li₂CO₃And LiCl. To improve solubility, lithium salts are dissolved in hydrated acids and used as electrolytes in electrolytic cells. Lithium carbonate (Li)₂CO₃) Was used as the starting material for the initial experiments.

Some suitable electrolytic cell components in the construction of electrolytic cells for the production of lithium are described in US20130004852, which is incorporated by reference in its entirety into the present disclosure.

Suitable electrolyte 18 components include water-soluble lithium salts, including but not limited to Li₂CO₃And LiCl. In order to improve the solubility, a lithium salt may be dissolved in a hydrated acid to be used as an electrolyte. Lithium carbonate (Li)₂CO₃) Is the most readily available lithium salt, is relatively inexpensive, and is the preferred source of lithium. Cathode 16 is characterized by an embedded composite material (Li-GC/Li-BF)28, meaning that composite material 28 is interposed or intercalated between cathode 16 and electrolyte 18. Cathode 16 may be characterized as "displaced," meaning that the cathode travels along the axis of cell 10, expelling the lithium produced through composite material 28 and isolating the cathode-deposited lithium. The cathode comprises a suitable material that is non-reactive with the lithium metal and the composite layer. The Li-GC/Li-BF composite layer is a static barrier between the anode compartment and the lithium metal formed on the cathode. The cathode is moved to accommodate the successively thickened lithium metal layer on the cathode.

The composite material layer (Li-GC/Li-BF)28 includes a lithium ion conductive glass ceramic layer (LI-GC)30 and a lithium ion conductive barrier film (LI-BF) 32. The substantially water impermeable layer (LI-GC)30 may be an active metal ion conductive glass or glass-ceramic (e.g., a lithium ion conductive glass-ceramic having high active metal ion conductivity and high stability to aggressive acidic electrolytes). Suitable materials are substantially impermeable to water, ionically conductive, andand is compatible with aqueous or other electrolytes (catholyte) and/or cathode materials that would otherwise adversely react with lithium metal. These glass or glass-ceramic materials are substantially gapless, non-swellable, and inherently ion-conductive. That is, their ion conducting properties are not dependent on the presence of liquid electrolytes or other agents. They also have a high ionic conductivity of at least 10^-7S/cm, usually at least 10^-6S/cm, e.g. at least 10^-5S/cm to 10^-4S/cm and up to 10^-3S/cm or higher such that the multilayer protective structure has a total ionic conductivity of at least 10^-7S/cm and up to 10^-3S/cm or higher. The layer preferably has a thickness of about 0.1 to 1000 microns, or an ionic conductivity of about 10 in the layer^-7About 0.25 to 1 micron in the case of S/cm, or an ionic conductivity in said layer of about 10^-4To about 10^-3In the case of S/cm, it is between about 10 and 1000 microns, preferably between 1 and 500 microns, 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 phosphorus-based glasses, oxide-based glasses, phosphorus-oxynitride-based glasses, sulfur-based glasses, oxide/sulfide-based glasses, selenide-based glasses, gallium-based glasses, germanium-based glasses or boracite glasses (e.g., as described in D.P. Button et al, Solid State Ionics, Vols.9-10, Part 1,585-592 (12 months 1983)), ceramic active metal ion conductors such as lithium β -alumina, sodium β -alumina, Li super ion conductor (LISICON), Na super Ion Conductor (ICNASON), etc., or glass ceramic active metal conductors₃PO₄.Li₂S.SiS₂、Li₂S.GeS₂.Ga₂S₃And Li₂O。

Suitable glass-ceramic materials (LI-GC) include lithium ion-conductive glass-ceramics having the following composition in mole percent: p₂O₅26-55％；SiO₂0-15％；GeO₂+TiO₂25-50% of GeO₂0-50％，TiO₂0-50％；ZrO₂0-10％；M₂O₃0-10％；Al₂O₃0-15％；Ga₂O3 0-15％；Li₂O3-25% and contains a predominant crystalline phase comprising: li_1+x(M,Al,Ga)_x(Ge_1-yTi_y)_2-x(PO₄)₃Wherein X is not more than 0.8 and Y is not less than 0 not more than 1.0, and wherein M is an element selected from Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb; and/or Li_1+x+yQ_xTi_2-xSi₃P_3-yO₁₂Wherein 0 is<X≤0.4，0<Y ≦ 0.6, and wherein Q is Al or Ga. Other examples include 11Al₂O₃、Na₂O.11Al₂O₃、(Na,Li)_{i+ x}Ti_2-xAl_x(PO₄)₃(x is more than or equal to 0.6 and less than or equal to 0.9) and a crystallography-related structure, Na₃Zr₂Si₂PO₁₂、Li₃Zr₂Si₂PO₄、Na₅ZrP₃O₁₂、Na₅TiP₃O₁₂、Na₃Fe₂P₃O₁₂、Na₄NbP₃O₁₂、Li₅ZrP₃O₁₂、Li₅TiP₃O₁₂、Li₅Fe₂P₃O₁₂And Li₄NbP₃O₁₂And combinations thereof, which are optionally sintered or melted. Suitable ceramic ion-active metal ion conductors are described, for example, in U.S. patent No. 4,985,317 to Adachi et al, which is incorporated by reference herein in its entirety.

Suitable LI-GC materials include those available from Ohara, Inc. (Kanagawa, JP) under the trademark LIC-GC^TM、LISICON、Li₂O--Al₂O₃--SiO₂--P₂O₅--TiO₂(LATP) products. Suitable materials with similar high lithium metal ion conductivity and environmental/chemical resistance are manufactured by Ohara and other companiesAnd (4) manufacturing. See, e.g., Inda, DN20100113243, now U.S. patent No. 8,476,174, which is incorporated herein by reference in its entirety. U.S. Pat. No. 8,476,174 discloses a glass-ceramic comprising at least LiTi₂P₃O₁₂A crystal of the structure satisfying 1<I_A113/I_A1042 or less, wherein I_A104Is the peak intensity, I, assigned to the crystal plane index 104(2 theta 20 to 21 deg.)_A113Is the peak intensity assigned to the crystal plane index 113(2 θ ═ 24 to 25 °), as determined by X-ray diffraction.

The lithium ion conductive barrier film 32(Li-BF) is typically a lithium metal ion conductive film or coating having high lithium metal ion conductivity. The lithium ion conductive barrier film 32(Li-BF) is a lithium metal ion conductive film or coating having a high lithium metal ion conductivity, typically from 1.0mS/cm to 100 mS/cm. High transference number (t) of lithium ions₊) Is preferred. Low t₊Li⁺The electrolyte will hinder performance by allowing an ion concentration gradient to occur within the cell, causing high internal resistance that may limit cell life and limit the rate of reduction. t is t₊0.70 to t₊A migration number between 1.0 is preferred. The lithium ion conductive barrier film is non-reactive to both lithium metal and the LiC-GC material.

The LI-BF film 32 comprises an active metal composite, wherein the "active metals" are lithium, sodium, magnesium, calcium and aluminum, which are used as active materials for the battery. Suitable LI-BF materials include reactive metals and Cu₃N, reactive metal nitrides, reactive metal phosphides, reactive metal halides, reactive metal phosphosulfide glasses, and reactive metal phosphorus oxynitride glasses (Cu)₃N、L₃N、Li₃P, LiI, LiF, LiBr, LiCl, and LiPON). The LI-BF material must also provide protection against dendrite formation on the cathode due to contact with the LI-GC material. This may be achieved by creating a physical distance between the cathode and the LI-GC and/or providing a physical barrier that the dendrites cannot easily penetrate. A preferred LI-BF film is formed by in situ thermally irreversible gelation and gelation as described in the following documentsPhysical organogel electrolyte produced by single ion dominant conduction: kim et al, "physical organogel electrolyte: characterization by in situ thermal irreversible gelation and single-ion dominant conduction "(A physicalogenated by in situ thermal-reversible gelation and single-ion-precursor con-duction), Scientific Reports 3, article number: 1917(doi:10.1038/srep01917) (5/29/2013). The electrolyte has a t at room temperature₊Conductivity of 0.84 and 8.63 mS/cm. Such organogel electrolytes can be built into porous membranes to provide additional structure and resistance to dendrite penetration. Typical porous membranes have a thickness of 1 μm to 500. mu.m, for example 20 μm. Acceptable porous films include the HIPORE polyolefin flat film manufactured by Asahi Kasei E-materials Corporation.

The lithium metal produced by the production method can be used as part of a continuous lithium metal production process. In particular, the process of the invention may utilize inexpensive lithium carbonate or an equivalent source of lithium ions.

The process can be used to directly produce lithium metal from an acid solution used to leach lithium metal from spodumene ore or other natural sources of lithium. For example, a process for converting spodumene ore to lithium carbonate includes leaching minerals from the ore using sulfuric acid. Lithium is then precipitated from the sulfuric acid solution using sodium carbonate to form lithium carbonate. The process of the present invention may be used to process lithium directly from the sulphuric acid leach liquor before it is precipitated into lithium carbonate. In this case, electrolyte 18 in fig. 1 and 2 would be replaced with a sulfuric acid solution used to leach minerals from spodumene.

The following examples illustrate, by way of example and not by way of limitation, lithium production processes consistent with the present disclosure.

Examples

An electrolytic cell for the production of lithium is schematically shown in figure 3. The cell 110 includes a cell cover 116, a seat 118, a Pt anode 112, a cathode 124, and a porous polyolefin with a binderLI-GC conductive glass 114 of the lithium ion conductive barrier film 120 in the hydrocarbon planarization film 122. The supported LI-GC-BF multilayer is interposed between the cathode 124 and the lithium ion rich electrolyte 18 (in fig. 1 and 2). The cell also includes a load bearing capacity with gaskets 128A sleeve structure 126. A gasket seals between the LI-GC and the housing to prevent electrolyte leakage from the anode compartment into the cathode compartment. Another gasket allows the LI-GC to be sealedThe sleeve was uniformly compressed to prevent the LI-GC panel from cracking.

The cell 110 includes an anode 112 which is a platinized titanium anode, 1 "× 4", rhodium and palladium jewelry plating, a cathode which is an internally fabricated 1.4 inch circular palladium cathode disk LI-GC 114 materialG71-3N33 DIA 2IN × 150 μm, tape casting, 150 μm thick, 2 inches, round, available from Ohara Corporation,23141 Arroyo Vista, Ranchosanta Margarta, California 92688.

The lithium ion conductive gel electrolyte 120 is made from the following materials: PVA-CN polymers supplied by Dr.Hyun-Kon Song of Ulsan National Institute of Science and Technology, by Ulsan south Korea, purchased from Alfa Aesar, stock number H61502; LiPF₆(lithium hexafluorophosphate), 98%; EMC (ethyl methyl carbonate), 99% from Sigma Aldrich, product No. 754935; EC (ethylene carbonate), anhydrous, from sigma aldrich, product No. 676802; and porous membrane ND420, polyolefin flat film, from Asahi Corp.

LI-BF barrier 120 was fabricated in an argon purged glove box. The glove box contains all the materials, precision scales, syringes and other cell components and is then inflated and emptied 4 times before starting the electrolyte manufacturing process.

The organogel electrolyte was mixed as follows: 4.0ml of EMC was liquefied by heating to about 140 ℉ and placed in a vial. Then 2.0ml of EMC was added to the vial, 0.133g (2% wt) of PVA-CN polymer was added to the vial, and the mixture was stirred for 1 hour to dissolve the PVA-CN. Then 0.133g (2% wt) FEC is added as SEI forming additive, followed by 0.972g (1M) LiPF₆And mixed to complete the organogel electrolyte mixture. The cell was then assembled in a glove box. The LI-GC and gasket were held in place, sealing the anode and cathode compartments from each other. The cathode side of the LI-GC was wetted with the organogel electrolyte mixture, and the HIPORE membrane was placed on the cathode side of the LI-GC and wetted again with the organogel electrolyte mixture. The cathode disk was then placed on top of the organogel mixture. Placing the electrolytic cell inBag and sealed while still under argon purge. Then sealing with assembled electrolytic cellThe bag was placed in an oven at 60 ℃ for 24 hours to gel the electrolyte.

The cell 110 was removed from the oven and placed in an argon purged glove box, which was allowed to cool to room temperature. The empty space above the cathode disk is sealed with a transparent polypro tape and the electrode wires are fastened. The electrolytic cell 110 is now ready, removed from the glove box, and connected to an electrolyte circulation system.

The electrolyte 18 was prepared using 120g of lithium carbonate in 200ml of deionized water and 500ml of 20% wt sulfuric acid. Sulfuric acid was slowly added to the lithium carbonate suspension and mixed well. The undissolved lithium carbonate was allowed to settle. The supernatant was collected from the stock solution to give a 18% wt lithium stock solution. The 18% wt lithium solution has a measured pH of 9. The pH of the solution was lowered by adding 20% wt sulfuric acid. Likewise, sulfuric acid is added slowly to minimize foaming. The 18% wt lithium stock solution was adjusted to a pH of 4.5. The preferred pH is between 3.0 and 4.5, most preferably between a pH of 3.0 and a pH of 4.0, but the process can be run at a pH of 7.0 or lower. A pH above 7.0 will result in dissolution of the carbonate.

The electrolyte mixture is then poured into the circulation system. The circulation pump was started and the solution was circulated for 30 minutes to check for leaks.

Lithium ion rich electrolyte 18 flows through the upper half of cell 110 over LI-GC-BF multilayer 114/120 and through anode 112. When a potential is applied to the system, lithium metal accumulates on the moving cathode below the LI-GC-BF multilayer 114/120 system.

A Gamry Reference3000 potentiostat/galvanostat/ZRA was attached to the electrolytic cell 110. There was no significant activity at voltages of 3-6 volts. When the voltage rises to 10V, the system responds. As the voltage rises to 11vdc, the current draw (amplitude draw) increases. No gassing was observed on the anode side of the cell at 11 vdc. The GamryReference3000 does not rise above 11 vdc. Since no gassing occurs at 11vdc, the reduction rate is most likely much higher if the voltage is increased. Even higher voltages and reduction rates are preferred if negligible oxygen is generated at the anode. The pH of the electrolyte at zero time was 4.46. After 35 minutes, the pH of the solution decreased to 4.29 and was 4.05 at the end of the experiment. The decreased pH indicates the removal of lithium ions from the electrolyte solution.

A current draw of 20mA was observed at the beginning of the experiment. After 30 minutes, the current draw was slowly increased to 60 mA. The current remained fairly constant at this value for the next 30 minutes. The experiment timer and graph were paused for 30 minutes to extend the experiment (voltage was held at 11 vdc). After a running time of approximately 65 minutes, large current spikes and sudden severe gassing were observed on the anode side of the electrolysis cell. This indicates a failure of the LI-GC-BF 114/120 film.

When the cell 110 was turned on and the cathode 124 side was exposed to electrolyte leaking through LI-GC-BF 114/120, a rapid gassing and a bright white flame were observed, demonstrating that the cell produced lithium metal through the LI-GC-BF 114/120 membrane system by electrolysis of lithium ions in aqueous sulfuric acid.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

Claims (33)

1. An electrolytic cell for producing lithium comprising:

a cathode;

a sulfuric acid solution containing lithium ions; and

a composite layer between the cathode and the sulfuric acid solution,

wherein the composite layer comprises a lithium ion-conducting glass-ceramic material and a lithium ion-conducting barrier membrane.

2. The lithium producing cell of claim 1, whereinThe composite layer has at least 10^-7An ion conductivity of S/cm and is non-reactive to both lithium metal and the lithium ion conducting glass-ceramic material.

3. The lithium producing electrolytic cell of claim 1, wherein the lithium ion conducting barrier membrane of the composite layer comprises a physical organogel electrolyte.

4. The lithium producing electrolytic cell of claim 1, wherein the lithium ion conducting barrier membrane comprises an in situ thermally irreversible gelation and uniionic dominant conductivity organogel product.

5. The lithium-producing electrolytic cell of claim 1, wherein the lithium ion conducting glass-ceramic material comprises a glass-ceramic active metal ion conductor.

6. The lithium-producing electrolytic cell of claim 1, wherein the lithium ion-conducting glass-ceramic material comprises an ion-conducting glass-ceramic comprising: 26 to 55 mol% of P₂O₅(ii) a 0 to 15 mol% SiO₂(ii) a 25 to 50 mole% GeO₂+TiO₂Wherein GeO₂Is in the range of 0 to 50% and TiO₂In the range of 0 to 50 mol%; 0 to 10 mol% of ZrO₂(ii) a 0 to 10 mol% of M₂O₃(ii) a 0 to 15 mol% of Al₂O₃(ii) a 0 to 15 mol% Ga₂O₃And 3 to 25 mol% Li₂O, and

wherein the ion-conducting glass-ceramic contains a predominant crystalline phase comprising at least one of: li_1+x(M,Al,Ga)_x(Ge_1-yTi_y)_2-x(PO₄)₃Wherein X is not more than 0.8, Y is not less than 0 but not more than 1.0, and M is an element selected from Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb; and Li_1+x+yQ_xTi_2-xSi₃P_3-yO₁₂Wherein 0 is<X≤0.4，0<Y is 0.6 or less, and Q is Al or Ga.

7. The lithium producing cell of claim 1, wherein the composite layer has at least 10^-4Ion conductivity of S/cm.

8. The lithium-producing cell of claim 1, wherein the cathode comprises a non-aqueous catholyte.

9. The lithium-producing electrolytic cell of claim 8, wherein the catholyte comprises an ionic liquid.

10. The lithium-producing electrolytic cell of claim 1, wherein the cathode comprises an active material selected from the group consisting of: solid oxidants, liquid oxidants and gaseous oxidants.

11. The lithium-producing electrolytic cell of claim 1, wherein the lithium ion conducting glass-ceramic material comprises a protective ceramic composite that is substantially impervious to water.

12. The lithium producing cell of claim 1, wherein the cathode is movable along an axis of the lithium producing cell.

13. The lithium producing cell of claim 1, wherein the sulfuric acid solution is selected from the group consisting of sulfuric acid electrolyte and sulfuric acid leach liquor.

14. A method of producing lithium, the method comprising:

providing an electrolytic cell comprising:

a solution comprising a sulfuric acid solvent and a source of lithium ions;

an anode in contact with the solution;

a cathode; and

a composite layer between the cathode and the solution, the composite layer comprising a lithium ion glass ceramic material and a lithium ion-conductive barrier membrane; and is

Providing an ionization current to the electrolytic cell to produce lithium metal at the cathode,

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

15. The method of producing lithium of claim 14, wherein the composite layer has at least 10^-7An ion conductivity of S/cm and is non-reactive to both lithium metal and the lithium ion conducting glass-ceramic material.

16. The method of producing lithium of claim 14, wherein the cathode is movable along an axis of the electrolytic cell away from the anode as the lithium metal is produced at the cathode.

17. The method of producing lithium of claim 14, wherein:

the electrolytic cell comprises an upper part containing the cathode and a lower part containing the solution, and

the electrolytic cell is configured to drive the cathode away from the composite layer when the lithium metal is formed on the cathode.

18. The method of producing lithium of claim 14 wherein the lithium ion-conducting barrier membrane comprises a physical organogel electrolyte.

19. The method of producing lithium of claim 14, wherein the lithium ion-conductive barrier membrane comprises an in-situ thermally irreversible gelation and single-ion dominant conductivity organogel product.

20. The method of producing lithium of claim 14, wherein the source of lithium ions comprises at least one selected from the group consisting of: lithium carbonate, lithium chloride and spodumene.

21. The method of producing lithium of claim 14, wherein:

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

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

22. A method of producing lithium according to claim 14, wherein the lithium metal produced at the cathode is extracted as a pure metal phase.

23. The method of producing lithium of claim 14, wherein the solution is selected from the group consisting of sulfuric acid electrolyte and sulfuric acid leach liquor.

24. A method of producing lithium, the method comprising:

providing a solution comprising a hydrated acid solvent and lithium ions dissolved in the hydrated acid solvent;

providing a composite layer between a cathode and the solution, the composite layer comprising a lithium ion glass-ceramic material; and

generating an electrical current across the solution to produce lithium metal at the cathode,

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

25. The method of producing lithium of claim 24, wherein the composite layer comprises a lithium ion-conductive barrier membrane.

26. The method for producing lithium of claim 24, wherein the hydrated acid is sulfuric acid.

27. The method of producing lithium of claim 26, wherein the solution is selected from the group consisting of a sulfuric acid electrolyte and a sulfuric acid leach solution.

28. A method of producing lithium according to claim 24, wherein the lithium metal produced at the cathode is extracted as a pure metal phase.

29. A lithium metal product, comprising:

lithium metal produced by the steps of:

providing a composite layer between a cathode and a solution comprising lithium ions dissolved in sulfuric acid; and is

Generating an electrical current across the solution to produce the lithium metal at the cathode,

wherein the composite layer comprises a lithium ion glass-ceramic material.

30. The lithium metal product of claim 29, wherein the composite layer comprises a lithium ion-conductive barrier film.

31. The lithium metal product of claim 29, wherein the composite layer isolates lithium metal produced at the cathode from the solution as the lithium metal is formed.

32. The lithium metal product of claim 29, wherein the lithium metal produced at the cathode is extracted as a pure metal phase.

33. The lithium metal product of claim 29, wherein the solution is selected from the group consisting of sulfuric acid electrolyte and sulfuric acid leach liquor.