FIELD OF THE INVENTION

The present invention relates to a method and apparatus for producing solutions of pure concentrated lithium chloride and lithium metal from aqueous solutions containing dilute lithium chloride and other salts.

BACKGROUND

Demand for lithium has increased in recent years due to the acceleration of the global transition to electric vehicles and the use of lithium in the batteries of these vehicles. Currently, the most prevalent method for lithium production is natural evaporation of underground brine reservoirs containing lithium chloride. The underground brine reservoirs at the high-altitude salt flats or salars of Chile, Bolivia, and Argentina contain some of the highest concentrations of lithium chloride in the world, typically in the range of 1 ,000 - 7,000 ppm, and most of the world’s lithium production via evaporation is based there. However, the evaporation method is slow, expensive, and has a large environmental impact, including loss of important water resources.

In this evaporation method, large quantities of brine are pumped up to expansive evaporation ponds and concentrated by natural evaporation over a period of approximately 18 months. The other salts in the brine, such as sodium chloride and potassium chloride are present in much higher concentrations than lithium chloride, typically 100x higher. As the water evaporates, these other salts become saturated and eventually precipitate out of the brine. Thus, progressively the concentration of lithium chloride increases relative to these other salts. When this concentration has reached a suitably high level, the lithium chloride is precipitated out of the brine as lithium carbonate by the addition of sodium carbonate. Lithium carbonate is stable and therefore the predominant commercial intermediate of lithium. However, it must be processed further to obtain pure lithium metal usable for battery fabrication. This is achieved by first converting the lithium carbonate back to lithium chloride and performing electrolysis. The lithium chloride is mixed with potassium chloride to lower the melting point and the mixture is melted in an electrochemical cell where it is separated into pure lithium and chlorine gas. However, this process is laborious and energy-intensive.

Many underground brine reservoirs exist in other locations such as North America, Europe, and Asia. However, their lithium chloride concentrations are lower than in the salars, typically on the order of several hundred ppm. At these concentrations, it is uneconomic to extract lithium from them via the evaporation process and they remain largely unexploited. In recent years, various attempts have been made to improve the lithium extraction process.

U.S. Pat. No. 10,648,090 to Snydacker et al. (the US090 patent) discloses an ion exchange process whereby a particle of a lithium binding compound such as lithium manganese oxide or lithium iron phosphate is coated with a protective layer of ceramic such as zirconia or silicon carbide. These coated particles are then embedded in a porous polymer bead to form a stable ion exchange bead that is selective for lithium and can withstand repetitive cycling with hydrochloric acid solution which is used to release the bound lithium. The main limitations to this approach are the large quantities of freshwater that are required for the hydrochloric acid recovery solution and fact that the final product is lithium chloride solution which must still be processed further to produce pure lithium metal.

EnergyX Corporation utilizes a membrane filtration process whereby metal organic frameworks are integrated into polymer membranes to form mixed matrix membranes that have a very precise pore size for separating lithium chloride from other salts. Again, the product is lithium chloride solution which must be still be processed further to produce pure lithium metal.

U.S. Pat. No. 20140076734 to Calvo et al. (the US734 patent) discloses an electrochemical process for recovery of lithium chloride from aqueous solutions. Fig. 1 shows the electrochemical cell 15 of the US734 patent which is made up of two symmetric assemblies. One assembly consists of a stainless steel housing 16, PTFE gasket 17, stainless steel current collector 18, PTFE electrode frame 19, and carbon felt working electrode 20 as indicated in Figur 7 of US734. The other assembly is identical with the exception that it contains a carbon felt counter electrode 22. The two assemblies are bolted together with a PTFE separation mesh 21 in between to prevent the two electrodes from contacting each other. The three dimensional carbon felt working electrode 20 is coated with a lithium binding compound such as manganese oxide and the three dimensional carbon felt counter electrode 22 is coated with a chlorine binding compound such as silver or polypyrrole. Fig. 2 shows the flow path 23 that the brine solution takes as it is pumped through the cell 15. As the mesh 21 provides less of an obstacle than the felt electrodes, the majority of the brine flow is through the net rather than through the electrodes. A voltage is applied to the electrodes and the lithium chloride in the solution separates into lithium ions, which diffuse into and bind to the working electrode 20, and chlorine ions, which diffuse into and bind to the counter electrode 22. When the electrodes become fully loaded, a conductive dilute lithium chloride or potassium chloride solution is recycled through the cell 15 and the polarity of the electrodes is reversed. Lithium and chlorine ions are released from their respective electrodes and recombine to form a concentrated lithium chloride solution. Once again, all subsequent processing steps are required to produce pure lithium metal.

OBJECT OF THE DISCLOSURE

Therefore, it is an object of the present disclosure to provide an improved apparatus and method which are capable of producing solutions of preferably pure concentrated lithium chloride and lithium metal in an efficient manner.

SUMMARY OF THE INVENTION

The object has been solved with the subject matter defined in the independent claims.

The present invention is a method and apparatus for producing solutions of preferably pure concentrated lithium chloride and lithium metal directly from aqueous solutions of dilute lithium chloride and other salts in a single apparatus. It consists of an electrochemical cell with a working electrode incorporating a lithium binding compound and a counter electrode incorporating a chlorine binding compound. A brine solution containing lithium chloride and other salts is pumped through the cell while a voltage is applied to the electrodes. Lithium chloride molecules separate into lithium ions which selectively bind to the working electrode and chlorine ions which bind to the counter electrode while the most of the other salts pass through the cell. When the electrodes become fully loaded, the brine solution is replaced with a polar organic solvent and the voltage is increased, driving the chlorine ions off the counter electrode as chlorine gas. When the chlorine has been driven off, the polarity of the electrodes is reversed, and the lithium is released from the working electrode into the solvent as an insoluble precipitate. The solvent with lithium precipitate is collected in an inert atmosphere recovery tank where the less dense lithium floats on the solvent. The solvent is drained off and the lithium precipitate is dried by heating and evaporation of any remaining solvent. Upon further heating, the lithium precipitate is melted and drained into an inert atmosphere canister and solidifies upon cooling as pure lithium metal.

In another embodiment, once the lithium and chlorine ions have been bound to the working electrode and counter electrode respectively, and the electrodes are fully loaded, the brine solution is replaced with a solvent such as water and the polarity of the electrodes is reversed. The lithium ions and chlorine ions are repelled off their respective electrodes and recombine in the solvent, producing in a pure concentrated solution of lithium chloride. In effect, a dilute solution of lithium chloride combined with other salts (brine) is transformed into a concentrated solution of pure lithium chloride which then facilitates the more economic further processing of the lithium chloride into commercial intermediate products such as lithium carbonate and lithium hydroxide.

According to a first aspect of the invention, a method for producing lithium metal from aqueous solutions containing lithium chloride is disclosed, comprising: a. Providing a working electrode coated with a lithium binding compound b. Providing a counter electrode coated with a chlorine binding compound c. Placing the electrodes in an enclosure d. Filling the enclosure with an aqueous solution containing lithium chloride e. Applying a voltage between the electrodes and causing the lithium chloride molecules to disassociate into lithium ions and chlorine ions f. Allowing the lithium ions to bind to the lithium binding compound on the working electrode, and allowing the chlorine ions to bind to the chlorine binding compound on the counter electrode g. Rinsing and drying the electrodes to remove water and unbound salts h. Filling the enclosure with an electrically conductive recovery liquid that does not disassociate at the voltages required to release the chlorine ions from the counter electrode i. Increasing the voltage and allowing the bound chlorine ions to be released from the counter electrode into the recovery liquid as chlorine gas

Emptying the recovery liquid with chlorine gas from the enclosure. According to an embodiment of the invention, the method according to the first aspect of the invention further comprises: a. Refilling the enclosure with a polar organic solvent as the electrically conductive recovery liquid b. Reversing the polarity of the electrodes and allowing the bound lithium ions to be released from the working electrode into the solvent as insoluble lithium precipitate c. Transferring the solvent and lithium precipitate from the enclosure to an inert atmosphere tank d. Draining out the solvent and drying the lithium precipitate e. Melting the lithium precipitate and solidifying it as pure lithium metal.

According to a further embodiment of the invention, the method according to the first aspect of the invention further comprises: a. Providing a third recovery electrode and placing it in the enclosure such that the capture electrode is between the recovery electrode and the counter electrode b. Refilling the enclosure with a polar organic solvent as the electrically conductive recovery liquid c. Applying a positive charge or no charge to the counter electrode d. Applying a negative charge to the recovery electrode and a positive charge to the capture electrode and allowing the bound lithium ions to be released from the working electrode into the solvent as insoluble lithium precipitate e. Transferring the solvent and lithium precipitate from the enclosure to an inert atmosphere tank f. Draining the solvent out of the tank and drying the lithium precipitate g. Melting the lithium precipitate and solidifying it as pure lithium metal.

According to an embodiment of the invention, the method according to the first aspect of the invention further comprising applying the negative charge to the recovery electrode and the positive charge to the capture electrode in short pulses rather than continuously to maximize the amount of lithium ions being transferred in the solvent to the recovery tank compared to the amount of lithium ions becoming bound to the recovery electrode.

According to a further embodiment of the invention, the method according to the first aspect of the invention further comprises: a. Flowing solvent through the enclosure while reversing the polarity between the recovery electrode and the capture electrode in short pulses to release any lithium ions bound to the recovery electrode into the solvent b. Transferring the solvent and lithium precipitate from the enclosure to the inert atmosphere tank.

According to a second aspect of the invention, an electrochemical filter cell for extracting lithium from aqueous solutions containing lithium chloride comprises: a. A porous tubular counter electrode filter positioned concentrically inside of a porous tubular working electrode filter with a gap in between to prevent the two electrodes from short circuiting b. A lithium binding compound coating the internal surfaces of the porous working electrode filter c. A chlorine binding compound coating the internal surfaces of the porous counter electrode d. A permeable current collector covering the outer tubular surface of the working electrode filter e. A permeable current collector covering the inner tubular surface of the counter electrode filter f. A non-conductive tubular housing outside of the working electrode with a gap in between for flow of process fluids g. A conductive working endcap with inlet that attaches to the housing and that is in electrical contact with the working current collector h. A conductive counter endcap with outlet that attaches to the housing and that is in electrical contact with the counter current collector.

According to a third aspect of the invention, an electrochemical filter cell for extracting lithium from aqueous solutions containing lithium chloride comprises: a. A porous tubular counter electrode filter positioned concentrically inside of a porous tubular working electrode filter with a gap in between to prevent the two electrodes from short circuiting b. A lithium binding compound coating the internal surfaces of the porous working electrode filter c. A chlorine binding compound coating the internal surfaces of the porous counter electrode d. A permeable cathode current collector covering the outer tubular surface of the working electrode filter e. A permeable anode current collector covering the inner tubular surface of the working electrode filter f. A permeable anode current collector covering the inner tubular surface of the counter electrode filter g. A non-conductive tubular housing outside of the working electrode with a gap in between for flow of process fluids h. A non-porous tubular recovery electrode lining the inner surface of the tubular housing i. An access point in the non-conductive tubular housing that allows an electrical connection to the recovery electrode j. A working endcap which seals against one end of the housing and the electrode filters and which provides access for process liquids to the annular space between the recovery electrode and the working electrode, while also allowing for electrical connections to the current collectors k. A counter endcap which seals against the other end of the housing and the electrode filters and which provides access for process liquids to the tubular space inside the counter electrode, while also allowing for electrical connections to the current collectors.

According to an embodiment of the invention, the filter cell according to the second or third aspect of the invention further comprises: a. Gaskets for sealing the housing and the ends of the electrode filters to the working endcap. b. Gaskets for sealing the housing and the ends of the electrode filters to the counter endcap.

According to an embodiment of the invention, the filter cell according to the second or third aspect of the invention further comprises: a flow path for the aqueous solution and any recovery liquid wherein the direction of flow takes either the forward or reverse sequence of the following steps: a. In the inlet and through the working endcap b. Over the outer surface of the cathode working current collector c. Through the permeable cathode working current collector d. Through the porous working electrode filter e. Through the permeable anode working current collector f. Through the gap g. Through the porous counter electrode filter h. Through the permeable anode counter current collector i. Over the inner surface of the anode counter current collector j. Out the outlet.

According to a fourth aspect of the invention, a method using an electrochemical filter cell for extracting lithium from aqueous solutions containing lithium chloride is disclosed, comprising: a. Providing a stack of porous sheet materials stacked in the following sequence: i. Counter electrode coated with chlorine binding compound ii. Counter electrode current collector iii. Counter electrode coated with chlorine binding compound iv. Flow spacer v. Recovery electrode vi. Flow spacer vii. Capture electrode coated with lithium binding compound viii. Capture electrode current collector ix. Capture electrode coated with lithium binding compound x. Flow spacer xi. Recovery electrode xii. Flow spacer b. Attaching connector tabs to the current collectors and recovery electrodes and winding the stack around a central mandrel to create a spiral filter element and c. Fitting the filter element with anti-telescoping element endcaps, inserting the filter element inside of a housing, attaching the connector tabs to current connectors, and sealing the housing with two housing endcap assemblies d. Applying a positive charge to the counter electrode current collector and a negative charge to the working electrode current collector e. Providing a flow of an aqueous solution containing lithium chloride through the filter cell and allowing the lithium chloride to disassociate into lithium ions and chlorine ions f. Allowing the chlorine ions to bind to the working electrode and the chlorine ions to bind to the counter electrode g. Replacing the flow of aqueous solution with a flow of a polar organic solvent h. Increasing the voltage between the working electrode and the counter electrode and allowing the chlorine to be released from the counter electrode and removed from the filter cell in the flow of solvent i. Once all the chlorine has been removed, applying no charge or a positive charge to the counter electrode current collector, applying a positive charge to the working electrode current collector, and applying a negative charge to the recovery electrodes j. Allowing the lithium to be released from the working electrodes and removed from the filter cell to an inert atmosphere tank as insoluble precipitate in the flow of solvent k. Draining out the solvent from the tank and drying the lithium precipitate l. Melting the lithium precipitate and solidifying it as pure lithium metal.

According to a further embodiment of the invention, the method according to the fourth aspect of the invention further comprises: applying the negative charge to the recovery electrodes and the positive charge to the capture electrode current collector in short pulses rather than continuously to maximize the amount of lithium being removed from the filter cell to the tank in the solvent compared to the amount of lithium becoming bound to the recovery electrode.

According to another embodiment of the invention, the method according to the fourth aspect of the invention further comprises: a. Flowing solvent through the filter cell while reversing the polarity between the recovery electrodes and the capture electrode current collector in short pulses to release any lithium bound to the recovery electrodes into the solvent b. Transferring the solvent and lithium precipitate from the filter cell to the tank.

According to a fifth aspect of the invention, a method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts is disclosed, comprising: a. Providing a stack of porous sheet materials stacked in the following sequence: i. Counter electrode comprising a chlorine binding compound ii. Counter electrode current collector iii. Counter electrode comprising a chlorine binding compound iv. Flow spacer v. Capture electrode comprising a lithium binding compound vi. Capture electrode current collector vii. Capture electrode comprising a lithium binding compound viii. Flow spacer b. Attaching connector tabs to the current collectors and winding the stack around a central mandrel to create a spiral filter element and c. Fitting the filter element with anti-telescoping element endcaps, inserting the filter element inside of a housing, attaching the connector tabs to current connectors, and sealing the housing with two housing endcap assemblies d. Applying a positive charge to the counter electrode current collector and a negative charge to the working electrode current collector e. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts axially through the filter cell and allowing the lithium chloride to disassociate into lithium ions and chlorine ions f. Allowing the chlorine ions to bind to the working electrode and the chlorine ions to bind to the counter electrode while the majority of other salts pass through the cell g. Flushing the filter cell with air to remove the dilute mixed salt solution h. Providing a flow of a recovery solvent such as water into the filter cell i. Reversing the polarity of the electrodes such that the working electrode is now positively charged and the counter electrode is negatively charged j. Allowing the lithium ions and the chlorine ions to be repelled from their respective electrodes and recombine in the solvent to form a high purity concentrated lithium chloride solution k. Recycling the solution through the filter cell as necessary to bring all of the lithium chloride into solution l. Flushing out the filter cell with air to recover all of the solution.

According to a sixth aspect of the invention, a method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts is disclosed, comprising: a. Providing a first stack of porous sheet materials stacked in the following sequence: i. Capture electrode comprising a lithium binding compound ii. Capture electrode current collector iii. Capture electrode comprising a lithium binding compound b. Providing a second stack of porous sheet materials stacking in the following sequence: i. Counter electrode comprising a chlorine binding compound ii. Counter electrode current collector iii. Counter electrode comprising a chlorine binding compound c. Providing a flow spacer d. Spirally wrapping either the first stack or second stack around a porous or perforated inner fluid flow pipe to form an inner electrode section of the filter element e. Attaching a current connector to the inner electrode current collector f. Wrapping the flow spacer around the inner electrode section g. Wrapping the other stack around the flow spacer for form an outer electrode section of the filter element h. Attaching a current connect to the outer electrode current collector i. Fitting the filter element with anti-telescoping element endcaps, inserting the filter element inside of a housing, attaching the connector tabs to current connectors, and sealing the housing with two housing endcap assemblies j. Providing an outer fluid flow channel between the inner surface of the housing wall and the outer surface of the outer electrode section k. Providing gaps in the endcap on the filter cell inlet side such that fluid can flow into the filter cell and to the outer flow channel l. Providing gaps in the endcap on the filter cell outlet side such that fluid can flow from the inner flow pipe and out of the filter cell m. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts such that solution enters the filter cell, flows axially through the outer flow channel, flows radially inward through the filter element, flows axially through the inner flow channel, and exits the filter cell n. Providing a negative charge to the working electrode current collector and a positive charge to the counter electrode current collector o. Allowing the lithium chloride molecules to disassociate into lithium ions and chlorine ions and selectively bind to the working electrode and counter electrode respectively while the other salts pass through the filter element p. When the electrodes are fully loaded with ions, flushing the filter cell with air to remove the dilute mixed salt solution q. Providing a flow of a recovery solvent such as water into the filter cell r. Reversing the polarity of the electrodes such that the working electrode is now positively charged and the counter electrode is negatively charged s. Allowing the lithium ions and the chlorine ions to be repelled from their respective electrodes and recombine in the solvent to form a high purity concentrated lithium chloride solution t. Recycling the solution through the filter cell as necessary to bring all of the lithium chloride into solution u. Flushing out the filter cell with air to recover all of the solution.

According to a seventh aspect of the invention, a method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts is disclosed, comprising: a. Providing a stack of porous sheet materials stacked in the following sequence: i. Capture electrode comprising a lithium binding compound ii. Capture electrode current collector iii. Capture electrode comprising a lithium binding compound iv. Flow spacer v. Counter electrode comprising a chlorine binding compound vi. Counter electrode current collector vii. Counter electrode comprising a chlorine binding compound viii. Flow spacer b. Spirally wrapping the stack around a porous or perforated inner fluid flow pipe c. Attaching current connectors to the current collectors d. Fitting the filter element with anti-telescoping element endcaps, inserting the filter element inside of a housing, attaching the connector tabs to current connectors, and sealing the housing with two housing endcap assemblies e. Providing an outer fluid flow channel between the inner surface of the housing wall and the outer surface of the stack f. Providing gaps in the endcap on the filter cell inlet side such that fluid can flow into the filter cell and to the outer flow channel g. Providing gaps in the endcap on the filter cell outlet side such that fluid can flow from the inner flow pipe and out of the filter cell h. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts such that solution enters the filter cell, flows axially through the outer flow channel, flows radially inward through the filter element, flows axially through the inner flow channel, and exits the filter cell i. Providing a negative charge to the working electrode current collector and a positive charge to the counter electrode current collector j. Allowing the lithium chloride molecules to disassociate into lithium ions and chlorine ions and selectively bind to the working electrode and counter electrode respectively while the other salts pass through the filter element k. When the electrodes are fully loaded with ions, flushing the filter cell with air to remove the dilute mixed salt solution l. Providing a flow of a recovery solvent such as water into the filter cell m. Reversing the polarity of the electrodes such that the working electrode is now positively charged and the counter electrode is negatively charged n. Allowing the lithium ions and the chlorine ions to be repelled from their respective electrodes and recombine in the solvent to form a high purity concentrated lithium chloride solution o. Recycling the solution through the filter cell as necessary to bring all of the lithium chloride into solution p. Flushing out the filter cell with air to recover all of the solution.

According to an eight aspect of the invention, a method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts is disclosed, comprising: a. Providing a first electrochemical filter unit with one or more filter cells each with one or more filter elements that have a working electrode with a lithium binding compound b. Providing a second electrochemical filter unit with one or more filter cells each with one or more filter elements that have a working electrode with a non-lithium binding compound such as various Prussian blue analogs that bind sodium, calcium, potassium, and magnesium ions c. Applying a negative electrical charge to the working electrodes and a positive electrical charge to the counter electrodes in the first electrochemical filter unit d. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts through the first electrochemical filter unit such that lithium ions are selectively intercalated into the working electrodes along with some amount of other ions such as sodium, calcium, potassium, and magnesium, while the majority of these other ions pass through e. Reversing the polarity of the electrodes in the first electrochemical filter unit and recovering the released lithium and other ions as a concentrated solution in a recovery solvent such as water. f. Returning the polarity of the electrodes in the first electrochemical filter unit to their original state g. Passing the recovery solvent with salts from the first pass through the first filter unit for a second pass such that lithium ions are once again selectively intercalated into the working electrodes while most of the other ions pass through h. Reversing the polarity of the electrodes in the first electrochemical filter unit again and recovering the release lithium ions and much lower concentration of other ions as a concentrated solution in a second recovery solvent such as water i. Applying a negative electrical charge to the working electrodes and a positive electrical charge to the counter electrodes in the first electrochemical filter unit j. Passing the second recovery solvent with salts through the second electrochemical filter unit such that most of the lithium chloride passes through but most of the other salts such as sodium, calcium, potassium, and magnesium are selectively intercalated into the working electrodes. k. Taking the concentrated solution on now highly pure lithium chloride for further processing l. Reversing the polarity of the electrodes in the second electrochemical filter unit m. Passing a recovery solvent such as water through the second electrochemical filter to flush out the other intercalated ions and prepare the filter for the next run.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter which should be considered as examples of the invention without limiting the scope of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a top sectional view of the electrochemical cell in the U.S. Pat. No. 20140076734 patent;

Fig. 2 is a top sectional view of the electrochemical cell in the U.S. Pat. No. 20140076734 patent showing the flow path of the aqueous solution containing lithium chloride;

Fig. 3 is a side sectional view of one embodiment of the present invention;

Fig. 4 is a side sectional view of one embodiment of the present invention showing the flow path of the aqueous solution containing lithium chloride. Fig. 5 is a side sectional view of another embodiment of the present invention incorporating a third recovery electrode.

Fig. 6 is a top sectional view of the embodiment in Fig. 5.

Fig. 7 is a side sectional view of the embodiment in Fig. 5 showing the fluid flow path during capture of the lithium from the brine and also during release of the chlorine gas.

Fig. 8 is a side sectional view of the embodiment in Fig. 5 showing the fluid flow path during recovery of the lithium from the capture electrode.

Fig. 9 is a top sectional view of another embodiment of the present invention comprising a sheet stack of electrode materials rolled into a spiral element. This spiral element is designed for recovery of lithium metal and the fluid flow is in the flow-by configuration.

Fig. 10 is a top sectional view of another embodiment of the present invention comprising a sheet stack of electrode materials rolled into a spiral element. This spiral element is designed for recovery of lithium chloride and the fluid flow is in the flow-by configuration.

Fig. 11 is a side sectional view of the spiral element from either Fig. 9 or Fig. 10 in a housing.

Fig. 12 is a top sectional view of another embodiment of the present invention comprising a sheet stack of electrode materials rolled into a spiral element. This spiral element has an inner capture electrode section and an outer counter electrode section separated by a flow spacer. This spiral element is designed for recovery of lithium chloride and the fluid flow direction is in the flow-through configuration.

Fig. 13 is a side sectional view of the spiral element from either Fig. 12 or Fig. 14 in a housing.

Fig. 14 is a top sectional view of another embodiment of the present invention comprising a sheet stack of electrode materials rolled into a spiral element. This spiral element has alternating capture electrode and counter electrode layers separated by flow spacer layers. This spiral element is designed for recovery of lithium chloride and the fluid flow direction is in the flow-through configuration.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 3 shows one embodiment of an electrochemical cell in accordance with the principles of this invention which is part of an apparatus for producing lithium metal from aqueous solutions containing lithium chloride. The cell produces lithium precipitate in a liquid, ideally a liquid in which the lithium precipitate is not soluble. The apparatus also includes a recovery tank where the lithium precipitate and liquid from the cell are transferred. The precipitate is separated from the liquid and then melted and solidified to yield lithium metal.

The tubular electrochemical filter cell 1 employs the principles of both filtration and electrochemistry to optimize the extraction of lithium from an aqueous solution. The filter cell 1 consists of a tubular counter electrode filter 8 positioned inside of a tubular working electrode filter 7 with a narrow gap 24 between the two. The counter electrode filter 8 has a counter current collector 9 applied to its inner tubular surface, including in the form of a metallic mesh or paint, and the working electrode filter has a working current collector 6 applied to its outer tubular surface, also including in the form of metallic mesh or paint. In one embodiment the metallic mesh or paint is made from stainless steel, copper, aluminum, or silver.

At one end there is a metallic working endcap 3 in electrical contact with the working current collector 6 and at the other end there is a metallic counter endcap 12 in electrical contact with the counter current collector 9. In one embodiment, the metallic working endcap 3 and counter endcap 12 are made from stainless steel, copper, or aluminum. The entire assembly is held together by an electrically non-conductive tubular housing 10 into which both the working endcap 3 and the counter endcap 12 screw, thus compressing the assembly. Gaskets are provided to prevent leakage of process liquids around the working electrode filter 7 and counter electrode filter 8, as well as out of the housing 10. A working endcap outer gasket 4 is provided to seal the counter endcap 3 against the housing 10 and a working endcap inner gasket 5 is provided to seal the counter endcap 3 against the working electrode filter 7 and the counter electrode filter 8. A counter endcap gasket 11 is provided to seal the housing 10, working electrode filter 7 and counter electrode filter 8 against the counter endcap 12.

The working electrode filter 7 is a porous material with high internal surface area and good electrical conductivity which is impregnated with a lithium binding compound. In one embodiment of the invention the working electrode filter 7 is made from a mixture of activated carbon powder, conductive carbon powder, and a suitable binder. Preferably the binder is also conductive. The mixture is then molded into shape, either by extrusion or compression molding, and heat cured. After curing, a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, and a suitable binder such as PVC in a suitable solvent such as N-methylpyrrolidone, is pumped through the working electrode 7 to coat the internal surfaces. The counter electrode filter 8 is made in a similar fashion with the exception that the internal surfaces are coated with a chlorine binding compound such as polypyrrole.

The filter cell 1 is operated by applying a voltage across the electrodes and pumping an aqueous solution containing lithium chloride and other salts, such as an underground brine, into the inlet 2. Fig.4 shows the flow path 14 of the aqueous solution as it passes through the working endcap 3, in between the housing 10 and the outer surface of the working current collector 6, through the working current collector 6, through the working electrode filter 7, through the gap 24, through the counter electrode filter 8, through the counter current collector 9, and out the outlet 13. The tubular shape of the electrode filters provides inward compressive strength and can accommodate high inward flowrates and pressure drops, thus increasing the rate at which the working electrode can be loaded with lithium ions.

As the lithium chloride molecules pass into the region between the working current collector 6 and the counter current collector 9, they disassociate into lithium ions and chlorine ions. The lithium ions are bound into the binding compound on the working electrode filter 7 and the chlorine ions are bound to the chlorine binding compound on the counter electrode filter 8. In this embodiment of the invention, the solution flow is through the electrodes as opposed to over the electrodes, as in the prior art. This allows for rapid transport of ions to available binding sites on the electrodes and loading of the electrodes. In the prior art, transport of ions to available binding sites in the electrodes is primarily through the slower process of diffusion.

Once the working electrode filter 7 and counter electrode filter 8 are fully loaded with lithium and chlorine ions respectively, the filter cell 1 is purged with air, rinsed with pure water, and purged with air again to provide a dry environment free of any residual salts. The voltage across the electrodes is then increased and a polar organic solvent such as acetonitrile is recycled through the filter cell 1 . The higher voltage causes the chlorine ions to be released from the counter electrode filter 8 as chlorine gas, which is entrained in the solvent and removed downstream of the filter cell 1 . When all the chlorine has been removed, the polarity of the working electrode filter 7 and the counter electrode filter 8 is reversed and lithium ions are released into the flowing solvent. In one embodiment, the flow path 14 of the solvent is reversed to facilitate the flushing of the released lithium ions from the working electrode filter 7.

The flushed lithium and solvent are collected in an inert atmosphere tank to prevent oxidation of the sensitive lithium. The lithium is not soluble in the solvent and floats on the surface due to its lower density. The majority of the solvent is drained from a bottom outlet and any solvent remaining in the lithium is evaporated by heating, leaving behind dry pure lithium precipitate in the bottom of the tank. The tank is heated to melt the lithium precipitate and liquid lithium is drained from the bottom outlet into an inert atmosphere canister where it is cooled and solidifies into pure lithium metal ready for use.

In some cases, the concentration of other salts in the aqueous solution are considerably higher than that of lithium chloride. For example, underground brines may have sodium chloride concentrations which are a hundred times higher than the lithium chloride concentrations. In such cases, a significant ratio of sodium ions may be bound along with the lithium ions. Repetitive binding and recovery steps into aqueous solutions of dilute lithium chloride may be employed to successively increase the lithium ratio to desired levels.

In summary, a novel electrochemical cell for extraction of lithium chloride from brines and release of pure lithium metal is disclosed. The cell is composed of two porous electrodes positioned inside a housing with a narrow gap between them. The working electrode is impregnated with a compound that selectively binds lithium ions such as various manganese oxide and Prussian Blue analogs. The counter electrode is impregnated with a compound that binds chlorine ions such as silver and polypyrrole. The brine is pumped through the charged electrodes and lithium ions selectively bind to the working electrode and chlorine ions bind to the counter electrode while the majority of other salts pass through. When the working electrode is fully loaded, the brine is replaced with a polar organic solvent and the voltage increased to release the chlorine ions from the counter electrode as chlorine gas. Then the polarity of the electrodes is reversed, and the lithium ions are released into the solvent. The solvent with the insoluble lithium ions is collected in an inert tank and the solvent is drained and evaporated, leaving dry pure lithium metal precipitate. This precipitate is melted, drained into an inert canister, and solidified as pure lithium metal ready for use.

Fig. 5 shows another embodiment of an electrochemical cell in accordance with the principles of this invention in a side sectional view. Tubular electrochemical filter cell 61 employs three electrodes compared to the two electrodes employed in filter cell 1 as shown in Fig. 3 wherein a third recovery electrode is added. A tubular counter electrode 40 has a counter electrode anode current collector 41 on its inner surface which is connected to a counter electrode anode current connector 26. A tubular capture electrode 34 fits around the counter electrode 40 with a small gap in between such that the two electrodes do not touch and short circuit each other. The capture electrode 34 has a capture electrode cathode current collector 35 on its outer surface which is connected to a capture electrode cathode current connector 25. The capture electrode 34 also has a capture electrode anode current collector 36 on its inner surface which is connected to a capture electrode anode current connector 39. The filter cell 61 has an outer housing 31 integrated with a recovery electrode 32 which in turn is connected to a recovery electrode cathode current connector 33.

The filter cell 61 has a bottom endcap 37 which seats an electrode holder 38. The filter cell 61 also has a top endcap 28. Both top endcap 28 and bottom endcap 37 seal against the housing 31 via o-rings 30 and flange clamps 29. Gaskets 27 seal the counter electrode 40 and the capture electrode 34 against the top endcap 28 and the electrode holder 38. Arrow 42 shows the current flow when filter cell 61 is in the lithium capture mode of operation and arrow 43 shows the current flow then the filter cell 61 is in the lithium recovery mode of operation.

Electrode connectors 25, 26, 33, and 39 are made from one or more materials from a group of materials including metals such as steel, aluminum, copper, and nickel. Gaskets 27 and o-rings 30 are made from one or more materials from a group of materials including synthetic polymers such as EPDM rubber, neoprene, and PTFE. Endcaps 28 and 37, electrode holder 38, and housing 31 are made from one or more materials from a group of materials including thermoplastics and FRP. Recovery electrode 32 is made from one or more materials from a group of materials including steel, aluminum, copper, and nickel.

The capture electrode 34 is a porous material with high internal surface area and good electrical conductivity which is impregnated with a lithium binding compound. In one embodiment of the invention the capture electrode 34 is made at least from a mixture of activated carbon powder, conductive carbon powder, and a suitable binder. Preferably the binder is also conductive. The mixture is then molded into shape, either by extrusion or compression molding, and heat cured. After curing, a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, and a suitable binder such as PVC in a suitable solvent such as N-methylpyrrolidone, is pumped through the working electrode 7 to coat the internal surfaces. The counter electrode 40 is made in a similar fashion with the exception that the internal surfaces are coated with a chlorine binding compound such as polypyrrole.

Fig. 6 shows a top sectional view of the filter cell 61 with arrows indicating the direction of fluid flow during various modes of operation. When the filter cell 61 is in lithium capture mode, the brine solution flows in the forward fluid flow direction 44 from the outer flow area 62 through the gap 63 and into the inner flow area 64. When the filter cell 61 is in chlorine release mode, the solvent flows also in the forward fluid flow direction 44. When the filter cell 61 is in lithium recovery mode, the solvent flows in the reverse fluid flow direction 45 from inner flow area 64 through the gap 63 into the outer flow area 62. The forward fluid flow direction 44 can also be seen in the side sectional view of the filter cell 61 in Fig. 7 and the reverse fluid flow direction 45 can be seen in the side sectional view of the filter cell 61 in Fig. 8.

To operate the filter cell 61 , the brine solution containing lithium chloride is first pumped through the filter cell 61 in the forward fluid flow direction 44 while an electrical capture current 42 is created between the counter electrode anode current collector 41 and the capture electrode cathode current collector 35. Lithium chloride disassociates into lithium ions which bind to the capture electrode 34 and chlorine ions which bind to the counter electrode 40. The brine is replaced with a polar organic solvent such as acetonitrile flowing in the forward fluid flow direction 44 and the applied voltage is increased resulting in chlorine being released from the counter electrode 40 as chlorine gas and carried out of the filter cell 61 with the solvent.

To recover the lithium, power to the counter electrode 40 is switched off and instead an electrical recovery current 43 is created between the capture electrode anode current collector 36 and the recovery electrode 32. Lithium is dislodged from the capture electrode 34 and carried out of the filter cell 61 as insoluble precipitate in the solvent now flowing in the reverse fluid flow direction 45. Once all the lithium has been dislodged from capture electrode 34, any lithium that adheres to recovery electrode 32 is dislodged by pulsed charging until all the lithium is carried out of the filter cell 61 in the solvent. Pulsed charging means applying a positive charge to the recovery electrode 32 and a negative charge to the capture electrode 34 for only a short period of time so that lithium is dislodged into the solvent flow but does not have enough time to migrate and rebind to the capture electrode 34. Intervals between the pulses are adjusted so that the dislodged lithium has enough time to be carried out of the filter cell 61 with the solvent before the next charge is applied.

Fig. 9 shows still another embodiment of an electrochemical filter element in accordance with the principles of this invention in top sectional view and closeup. A spiral electrochemical filter element 54 employs a sheet stack 46 of different sheets of material each on the order of several tens of microns to several millimeters thick stacked on top of each other and spirally wound around a mandrel 53. The sheet stack 46 consists of the following 12 sheets stacked in order: a. Counter electrode sheet 47 b. Counter electrode current collector sheet 48 c. Counter electrode sheet 47 d. Flow spacer sheet 49 e. Recovery electrode sheet 50 f. Flow spacer sheet 49 g. Capture electrode sheet 51 h. Capture electrode current collector sheet 52 i. Capture electrode sheet 51 j. Flow spacer sheet 49 k. Recovery electrode sheet 50 l. Flow spacer sheet 49

At the outermost spiral, current collector tabs 55 are attached to each of the 2 current collector sheets and the 2 recovery electrode sheets so that they can be connected to electrical power.

The capture electrode sheet 51 is a porous material with high internal surface area and good electrical conductivity which is impregnated with a lithium binding compound. In one embodiment of the invention the capture electrode sheet 51 is made from activated carbon felt incorporating a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, conductive carbon powder, and a suitable binder. The counter electrode sheet 47 is made in a similar fashion with the exception that the internal surfaces are coated with a chlorine binding compound such as polypyrrole. The current collector sheets 48 and 52 and the recovery electrode sheet 50 are made from one or more materials from the group of materials including steel, aluminum, copper, and nickel meshes. The flow spacer sheet 49 is made from one or more materials from the group of materials including solvent resistant plastic meshes such as PTFE mesh.

Fig. 10 shows another embodiment of an electrochemical filter element in accordance with the principles of this invention in top sectional view and closeup. This electrochemical filter element is designed to produce a concentrated solution of lithium chloride rather than lithium metal. A spiral electrochemical filter element 68 employs a sheet stack 67 of different sheets of material each on the order of several tens of microns to several millimeters thick stacked on top of each other and spirally wound around a mandrel 53. The sheet stack 67 consists of the following 8 sheets stacked in order: a. Counter electrode sheet 47 b. Counter electrode current collector sheet 48 c. Counter electrode sheet 47 d. Flow spacer sheet 49 e. Capture electrode sheet 51 f. Capture electrode current collector sheet 52 g. Capture electrode sheet 51 h. Flow spacer sheet 49

At the outermost spiral, current collector tabs 55 are attached to each of the 2 current collector sheets so that they can be connected to electrical power.

The capture electrode sheet 51 is a porous material with high internal surface area and good electrical conductivity which is impregnated with a lithium binding compound. In one embodiment of the invention the capture electrode sheet 51 is made from a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, conductive carbon powder, and a suitable binder. The counter electrode sheet 47 is made in a similar fashion from a chlorine binding compound such as polypyrrole, conductive carbon powder, a suitable binder.

The current collector sheets 48 and 52 are made from one or more materials from the group of materials including steel, aluminum, copper, and nickel meshes. The flow spacer sheet 49 is made from one or more materials from the group of materials including plastic meshes such as PTFE mesh.

Fig. 11 shows a side sectional view of filter cell 66 incorporating filter element 54 or 68 fitted with an anti-telescoping element endcap 56 on either end to hold the spiral-wound sheet stack 46 or 67 in place. The filter element 54 or 68 is placed inside a housing 57 fitted with two endcap assemblies 58. Current collector tabs 55 are attached to current connectors 59 that are secured through the housing 57 so that they can be connected to electrical power. During capture mode, brine enters the housing 57 through one end, flows axially through the flow spacer sheets 49 in forward fluid flow direction 60, and exits through the other end. During this time, the capture electrode sheet 51 is negatively charged and the counter electrode sheet 47 is positively charged. The LiCI molecules disassociate and Li ⁺ binds to capture electrode sheet 51 and Cl- binds to the counter electrode sheet 47.

In the case of filter element 54, during release mode, the brine is replaced with a polar organic solvent such as acetonitrile and the voltage is increased causing Ch to bubble off the counter electrode sheet 47 and be carried out of the filter element 54 through the flow spacer sheets 49 with the solvent. During recovery mode, power to the counter electrode sheet 47 is turned off and instead a positive charge is applied to the capture electrode sheet 51 and a negative charge is applied to the recovery electrode sheet 50. Lithium is dislodged from the capture electrode sheet 51 and carried out of the filter element 54 through the flow spacer sheets 49 as insoluble precipitate in the solvent now flowing in the reverse fluid flow direction 65. Once all the lithium has been dislodged from capture electrode sheet 51 , any lithium that adheres to recovery electrode sheet 50 is dislodged by pulsed charging until all the lithium is carried out of the filter element 54 in the solvent.

In the case of filter element 68, during release mode, the brine is replaced with a solvent such as water, and the polarity of the electrodes is reversed such that the capture electrode sheet 51 is positively charged and the counter electrode sheet 47 is negatively charged. Lithium ions are chlorine ions are repelled from their respective electrodes and combine in the water to form a concentrated solution of lithium chloride. This solution may be recycled through the filter cell 66 a number of times to ensure that all the ions have combined and been dissolved into the solution. To prevent mixing of the brine and the water, the filter cell 66 can first be flushed out with air prior to introduction of the water. Similarly, to ensure all the water with lithium chloride has been recovered from filter cell 66, the filter cell 66 can again be flushed with air. Fig. 12 shows another embodiment of an electrochemical filter element in accordance with the principles of this invention in top sectional view and closeup. This electrochemical filter element is designed to produce a concentrated solution of lithium chloride rather than lithium metal and the fluid flow direction is radially through the electrode sheets rather than axially over them. A spiral electrochemical filter element 69 employs sheet stacks of different sheets of material each on the order of several tens of microns to several millimeters thick stacked on top of each other and spirally wound around an inner flow channel 71 formed around a central mandrel 53. The inner section of the filter element 69 consists of a spirally wound stack made up of a capture electrode current collector sheet 52 with a capture electrode sheet 51 on either side. The outer section of the filter element 69 consists of a spirally wound stack made up of a counter electrode current collector sheet 48 with a counter electrode sheet 47 on either side. The inner and outer sections are separated by a flow spacer sheet 49.

At the outermost spiral of both the inner section and the outer section, current collector tabs 55 are attached to each of the current collector sheets so that they can be connected to electrical power.

The capture electrode sheet 51 is a porous material with high internal surface area and good electrical conductivity which is impregnated with a lithium binding compound. In one embodiment of the invention the capture electrode sheet 51 is made from a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, conductive carbon powder, and a suitable binder. The counter electrode sheet 47 is made in a similar fashion from a chlorine binding compound such as polypyrrole, conductive carbon powder, a suitable binder.

The current collector sheets 48 and 52 are made from one or more materials from the group of materials including steel, aluminum, copper, and nickel meshes. The flow spacer sheet 49 is made from one or more materials from the group of materials including plastic meshes such as PTFE mesh.

Whereas Fig. 12 shows one embodiment of the present invention which is a spiral electrochemical filter element with an inner capture electrode section and an outer counter electrode section separated by a flow spacer, Fig. 14 shows another embodiment of the present invention which is a spiral electrochemical filter element with alternating capture electrode and counter electrode layers separated by flow spacer layers. This flow through alternating filter element 76 employs a flow thorough sheet stack for lithium chloride 75 of different sheets of material each on the order of several tens of microns to several millimeters thick stacked on top of each other and spirally wound around an inner flow channel 71 formed around a central mandrel 53. The flow through sheet stack for lithium chloride 75 is made up of the following sequence of material sheets: a. Counter electrode sheet 47 b. Counter electrode current collector sheet 48 c. Counter electrode sheet 47 d. Flow spacer sheet 49 e. Capture electrode sheet 51 f. Capture electrode current collector sheet 52 g. Capture electrode sheet 51 h. Flow spacer sheet 49

At the outermost spiral, current collector tabs 55 are attached to each of the current collector sheets so that they can be connected to electrical power.

In one embodiment of the invention the capture electrode sheet 51 is made from a lithium binding compound such as lithium manganese oxide or a Prussian Blue analog, conductive carbon powder, and a suitable binder. The counter electrode sheet 47 is made in a similar fashion from a chlorine binding compound such as polypyrrole, conductive carbon powder, a suitable binder.

The counter electrode current collector sheets 48 and capture electrode current collector sheets 52 are made from one or more materials from the group of materials including steel, aluminum, copper, and nickel meshes. The flow spacer sheet 49 is made from one or more materials from the group of materials including plastic meshes such as PTFE mesh.

Fig. 13 shows a side sectional view of filter cell 66 incorporating filter element 69 or 76 fitted with an anti-telescoping outer channel endcap 72 on the inlet end and an inner channel endcap 74 on the outlet end to hold the spiral wound sheet stacks in place. The filter element 69 or 76 is placed inside a housing 57 fitted with two endcap assemblies 58.

Current collector tabs 55 are attached to current connectors 59 that are secured through the housing 57 so that they can be connected to electrical power. During capture mode, brine enters the housing 57 through one end, flows axially through the outer flow channel 73, radially through the filter element 69 or 71 , axially through the inner flow channel 71 in forward fluid flow direction 60, and exits through the other end. During this time, the capture electrode sheet 51 is negatively charged and the counter electrode sheet 47 is positively charged. The LiCI molecules disassociate and Li ⁺ binds to capture electrode sheet 51 and Cl- binds to the counter electrode sheet 47.

During release mode, the brine is replaced with a solvent such as water, and the polarity of the electrodes is reversed such that the capture electrode sheet 51 is positively charged and the counter electrode sheet 47 is negatively charged. Lithium ions and chlorine ions are repelled from their respective electrodes and combine in the water to form a concentrated solution of lithium chloride. This solution may be recycled through the filter cell 66 a number of times to ensure that all the ions have combined and been dissolved into the solution. To prevent mixing of the brine and the water, the filter cell 66 can first be flushed out with air prior to introduction of the water. Similarly, to ensure all the water with lithium chloride has been recovered from filter cell 66, the filter cell 66 can again be flushed with air.

When large quantities of lithium need to be extracted in a commercial application of the invention, then multiple filter elements 69 or 76 can be fitted end to end in an elongated housing 57. For example, 8 filter elements can be fitted in a single housing. Similarly, multiple filter cells with such elongated housings can be manifolded together and serviced by single pumping and process control system to form an electrochemical filter unit. For example, 12, 36, 72 or 144 or more of such filter cells can be manifolded together.

To minimize the volume of solvent such as water used to recover the lithium chloride from the filter element, the solvent can be used multiple times. For example, fresh water can be used to recovery the lithium chloride a first time and sent to a storage tank. Fresh brine can then be passed through the filter element to capture new lithium chloride. Then the water solution with lithium chloride dissolved in it from the first recovery step can be used again to recovery the new lithium chloride. This process can be repeated until the concentration of lithium chloride in the solvent approaches saturation.

Although the lithium binding compound in the capture electrode 51 has high selectivity for lithium ions, some other ions such as sodium, calcium, potassium, and magnesium ions, may also be captured along with the lithium ion. The ratio of other ions captured relative to lithium ions depends on the relative concentration of their salts in the original brine. For example, the ratio of lithium chloride concentration to the concentration of other salts in the brine might be on the order of 1 :100. In such a case, the ratio of lithium ions to other ions captured in the filter element might on the order of 1 :1 . Once these salts are recovered from the filter element in the recovery solvent, which is typically water, they can be passed through the filter element to be captured again. Due to the selectivity of the lithium binding compound and the lower relative concentration of the other salts in the recovery solution, the capture ratio of lithium ions to other ions may now be on the order of 10:1 .

When these ions are recovered as their respective salts in fresh solvent, typically water, it may be necessary to increase the purity of the lithium chloride still further. Rather than take this solution for another lithium capture cycle through the filter element, where the larger quantity of lithium will be bound and the lesser quantity of other salts will pass through, it is more efficient to pass the solution through a second filter element that has a capture electrode made with a binding compound that is selective for these other salts and allows the lithium chloride to pass through. A first capture and recovery cycle through such a second filter element can increase the ratio of lithium chloride to other salts such that it is on the order of 100:1 . A second cycle through this second filter element can further increase the ratio of lithium chloride to other salts such that it is on the order of 1 ,000:1 . At this point the lithium chloride will be 99.9% pure and a suitable precursor for manufacturer of battery grade lithium carbonate and lithium hydroxide.

A novel electrochemical cell for extraction of lithium chloride from brines and release of pure lithium metal is disclosed, wherein the cell is composed of two porous electrodes positioned inside a housing with a narrow gap between them and preferably a third recovery electrode. The working electrode is impregnated with a compound that selectively binds lithium ions such as various manganese oxide and Prussian Blue analogs. The counter electrode is impregnated with a compound that binds chlorine ions such as silver and polypyrrole. Brine is pumped through the charged electrodes and lithium ions selectively bind to the working electrode and chlorine ions bind to the counter electrode while the majority of other salts pass through. When the working electrode is fully loaded, the brine is replaced with a polar organic solvent and the voltage increased to release the chlorine ions from the counter electrode as chlorine gas. Then the polarity of the electrodes is reversed between the capture electrode and the recovery electrode, and the lithium ions are released into the solvent. The solvent with the insoluble lithium ions is collected in an inert tank and the solvent is drained and evaporated, leaving dry pure lithium metal precipitate. This precipitate is melted, drained into an inert canister, and solidified as pure lithium metal ready for use.

Reference Signs

1. Filter cell

2. Inlet

3. Working endcap

4. Working endcap outer gasket

5. Working endcap inner gasket

6. Working current collector

7. Working electrode filter

8. Counter electrode filter

9. Counter current collector

10. Housing

11 . Counter endcap gasket

12. Counter endcap

13. Outlet

14. Flow path

15. Cell

16. Housing

17. Gasket

18. Current collector

19. Electrode frame

20. Working electrode

21. Mesh

22. Counter electrode

23. Flow path

24. Gap

25. Capture electrode cathode current connector

26. Counter electrode anode current connector

27. Gasket

28. Top endcap

29. Flange clamp

30. O-ring

31. Housing

32. Recovery electrode

33. Recovery electrode cathode current connector