Electrochemical extraction of lithium

Abstract

Disclosed herein is an apparatus for separating lithium ions from solution. The apparatus includes a first lithium selective reactor. The first lithium selective reactor includes a lithium selective electrode configured to absorb lithium ions from the solution, a separator, and a counter electrode. The apparatus further includes a lithium rejective reactor. The lithium rejective reactor includes a lithium rejective electrode, a separator, and a counter electrode.

Description

ELECTROCHEMICAL EXTRACTION OF LITHIUMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and any benefit of U.S. Provisional Application No. 63 / 548,614, filed February 1, 2024, the content of which is incorporated herein by reference in its entirety.FIELD OF DISCLOSURE

[0002] This disclosure relates to apparatuses, methods, and techniques for extracting ions (e.g., lithium (Li+) ions) from aqueous solutions or brine. One purpose for the extraction is to provide ions for battery applications. The present disclosure can, among other things, improve lithium-ion extraction efficiency and decrease the cost of the extraction process.BACKGROUND

[0003] Electrochemical [ion] extraction processes (EEPs) can extract ions valuable for a number of applications, such as lithium-ion battery applications, from brine or other aqueous solutions. While other techniques (e.g., membrane filtration or dialysis-based techniques) use pressure as the driving force for ion removal, EEPs use voltage and / or current. Doing so can substantially improve efficiency and require less energy. EEPs may also not require substantial chemical processes to regenerate their facilitating materials (e.g., electrodes and / or membranes) after long periods of use, as other techniques do. For these reasons, EEPs can improve cyclability and production lifetimes. By balancing the liquid / active material contact time, flow rate, and / or ion production rate, EEPs can decrease pressure drop across the ion extraction system. Such can further lower operational power requirements. Overall, EEPs can potentially increase the ion capture rate with traditional brines. They can even extend ion extraction to previously inaccessible liquids (e.g., seawater).

[0004] Because of these advantages, EEPs are highly promising in reducing the cost and environmental impact of ion extraction. However, substantial barriers to commercialization remain. For example, fabrication and operating costs of EEP systems need to be minimized (e.g., by minimizing operating pressure) at scale. To maintain EEP advantages, any scaled-up ion extraction system should sustain high fluid contact time with active materials to maintain high and uniform intercalation. Providing active EEP intercalating material with substantial thickness to operate at scale with low bulk resistivity and without cracking can be challenging. Currently, most active EEP materials run into materials limitations atthicknesses around 200 pm. It would be advantageous to reduce such cost and efficiency barriers and, therefore, overall lithium production cost.SUMMARY

[0005] To overcome these and other technical barriers, the following innovative solutions are described herein.

[0006] In one example an apparatus separates lithium ions from solution. The apparatus includes a first lithium selective reactor. The first lithium selective reactor includes a lithium selective electrode configured to absorb lithium ions from the solution, a separator, and a counter electrode. The apparatus further includes a lithium rejective reactor. The lithium rejective reactor includes a lithium rejective electrode, a separator, and a counter electrode.

[0007] The first lithium selective reactor may be configured to provide a first lithium selective reactor output having a lithium concentration greater than a lithium concentration of the solution. The lithium rejective reactor may be configured to input the first lithium selective reactor output and provide a lithium rejective reactor output having a lithium concentration greater than the lithium concentration of the first lithium selective reactor output. The first lithium selective reactor output may derive at least in part from recovering lithium ions that the lithium selective electrode of the first lithium selective reactor absorbed from the solution. Recovering lithium ions may include flowing a solution with a relatively low lithium concentration over the lithium selective electrode of the first lithium selective reactor.

[0008] The apparatus may further include a second lithium selective reactor. The second lithium selective reactor includes a lithium selective electrode that absorbs lithium ions, a separator, and a counter electrode. The first lithium selective reactor may be configured to provide a first lithium selective reactor output having a lithium concentration greater than a lithium concentration of the solution. The second lithium selective reactor may be configured to input the first lithium selective reactor output and provide a second lithium selective reactor output having a lithium concentration greater than the lithium concentration of the first lithium selective reactor output. The lithium rejective reactor may be configured to input the second lithium selective reactor output and provide a lithium rejective output having a lithium concentration greater than a lithium concentration of the second lithium selective reactor output.

[0009] The first lithium selective reactor output may derive at least in part from recovering lithium ions from the lithium selective electrode of the first lithium selective reactor that wereabsorbed from the solution. The second lithium selective reactor output may derive at least in part from recovering lithium ions from the lithium selective electrode of the second lithium selective reactor that were absorbed from the first lithium selective reactor output.

[0010] Recovering lithium ions may include flowing a solution with a relatively low lithium concentration over at least one of the lithium selective electrode of the first lithium selective reactor and the lithium selective electrode of the second lithium selective reactor. The lithium selective electrode of the first lithium selective reactor may include at least one of LiMn2O4 (LMO), MnCL, and lithium nickel cobalt manganese oxide. The lithium selective electrode of the first lithium selective reactor may include primarily LMO. The lithium selective electrode of the second lithium selective reactor may include at least one of LMO, MnO?, and lithium nickel cobalt manganese oxide. The lithium selective electrode of the second lithium selective reactor may include primarily LMO. At least one of the counter electrode of the first lithium selective reactor and the counter electrode of the lithium rejective reactor may include at least one of polypyrrole (PPy), platinum, graphite, graphene, gold, carbon paper, carbon nanotubes, iron and iron alloy, nickel and nickel alloys, cobalt and cobalt compounds, and a conductive polymer. The counter electrodes of the first lithium selective reactor, the second lithium selective reactor, and the lithium rejective reactor may include primarily PPy. The lithium rejective electrode of the lithium rejective reactor may include at least one of Ko.i- o.2FeFe(CN)e (Prussian Blue or “PB”), K2MnFe(CN)e, and K2NiFe(CN)e. The lithium rejective electrode of the lithium rejective reactor may include primarily PB.

[0011] The apparatus may include a second lithium rejective reactor. It may include at least one of a third lithium selective reactor and a third lithium rejective reactor. The solution may be a brine. A brine output by the apparatus may have a Li+fraction of more than 90%. A pressure applied to flow brine through the apparatus may be 70 psi or less.

[0012] This disclosure also includes a method for separating lithium ions from solution. The method includes absorbing lithium ions from the solution via a first lithium selective reactor. The first lithium selective reactor includes a lithium selective electrode that absorbs the lithium ions from the solution, a separator, and a counter electrode. The method also includes providing, to a lithium rejective reactor, an interim liquid. The interim liquid includes lithium ions extracted from the solution and a lithium concentration higher than a lithium concentration of the solution. The lithium rejective reactor includes a lithium rejective electrode that rejects lithium ions from the interim liquid, but absorbs other ions from the interim liquid, a separator, and a counter electrode. The method further includes outputting a liquid with a lithium concentration higher than the lithium concentration of the solution.

[0013] The providing the interim liquid to the lithium rejective reactor may include receiving, via a second lithium selective reactor, an output of the first lithium selective reactor. The second lithium selective reactor may include a lithium selective electrode that absorbs lithium ions from the output of the first lithium selective reactor to provide the interim liquid, a separator, and a counter electrode. The solution may be a brine. The output liquid may have a Li+fraction of more than 90%. A pressure applied to the brine during the method may be 70 psi or less.

[0014] These and other variations are described in more detail below.BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 A shows an exemplary corrugated electrochemical cell 100 and a flow pattern F through cell 100 that may be used in conjunction with the present disclosure.

[0016] FIG. IB shows an experimental setup with a model cell 100m for testing purposes.

[0017] FIG. 1C shows a cyclic voltammetry (CV) test using LMO electrode material with various ions that indicates a strong Li+affinity.

[0018] FIG. ID shows a CV test using LMO electrode material with a multicomponent solution also indicating a strong Li+affinity.

[0019] FIG. IE shows a CV test using PB electrode material with various ions that indicates a strong affinity for Na+, K+, and Ca2+ions over Li+.

[0020] FIG. IF shows a CV test using PB electrode material with a multicomponent solution also indicating a strong affinity for Na+, K+, and Ca2+ions over Li+.

[0021] FIG. 2 is a flowchart showing method 200 using the Li+Selective / Rejective (SR) configuration of Implementation 1 to extract Li+from brine flow F in conjunction with this disclosure.

[0022] FIG. 3 A shows components of channel Cl of cell 100 implementing Li+extraction from brine flow F according to method 200.

[0023] FIG. 3B shows components of channel Cl during recovery of Li+ions after extraction.

[0024] FIG. 3C shows components of channel C2 of cell 100 implementing a Li+rejective step of method 200.

[0025] FIG. 3D shows outflow of non-Li+ions from channel C2 of cell 100 after implementing method 200.

[0026] FIG. 4A is part of a flowchart showing method 400 using the Li+Selective / Selective / Rejective (SSR) configuration of Implementation 2 to extract Li+from brine flow F as presented in conjunction with this disclosure.

[0027] FIG. 4B is another part of a flowchart showing method 400.

[0028] FIG. 5 A shows components of channel Cl of cell 100 implementing Li+extraction from brine flow F according to method 400.

[0029] FIG. 5B shows components of channel Cl during recovery of Li+ions after extraction.

[0030] FIG. 5C shows components of channel C2 of cell 100 implementing a second Li+selective step of method 400.

[0031] FIG. 5D shows components of channel Cl an Li+rejective step of method 400.

[0032] FIG. 6A shows a first part of a method 600 that may implement multiple channels of cell 100 in S and R modes to increase Li+concentration in conjunction with this disclosure.

[0033] FIG. 6 A shows a second part of method 600.DETAILED DESCRIPTIONConventional Lithium Brine Extraction

[0034] Increasing demand for lithium in electric vehicle batteries, renewable energy, and portable electronics has led to the search for new extraction methods. Today, much of the lithium for these applications originates from natural liquid brine reservoirs. For example, lithium is extracted from brine reservoirs beneath salt flats in South America and China. Other lithium-rich brine resources include geothermal and oil field brines, such as those in and around the Salton Sea in Southern California.

[0035] Lithium recovery from brine by most conventional processes can take weeks or months. Drilling is typically required as a first step to access underground brine deposits. Brine is then pumped from those deposits to the surface and distributed to evaporation ponds. The ponds concentrate the ions in the brine through solar evaporation of excess water. In some cases, reverse osmosis (RO) can concentrate the brine and speed up the process. In any case, evaporation results in a concentrated brine that includes multiple unwanted elements / ions (e.g., potassium and sodium) in addition to the lithium sought for battery applications.

[0036] After evaporation, the remaining brine is pumped to a lithium recovery facility for lithium separation and extraction. The specific extraction technique required depends on various factors, most particularly brine composition (i.e., concentration of lithium, other ionicspecies, and impurities). For example, high concentration of Mg2+relative to Li+concentration in some Chinese and South American brines requires relatively high consumption of chemicals, loss of lithium, and substantial waste generation.

[0037] Regardless, extraction typically includes one or more of the following steps. The first step filters specific contaminants or unwanted constituents. In the second step, chemical solvents and reagents can isolate desirable products and byproducts through processes such as precipitation. Precipitated solids can subsequently be removed (e.g., by filtering). The brine is treated either electrochemically or chemically (e.g., with a reagent, such as sodium carbonate to form lithium carbonate). Either way, a high Li+concentrated material is removed, filtered, and dried for distribution. Different reagents may be applied to produce other commonly sold forms of lithium, such as lithium hydroxide, lithium chloride, lithium bromide, and butyl lithium. Leftover brine may be returned to the underground reservoir.Other Techniques - Electrochemical Extraction

[0038] Techniques other than solar evaporation can facilitate faster and more direct lithium extraction from brine. These include electrochemical extraction, solvent extraction, ionexchange resin extraction, inorganic absorbent extraction, nanofiltration, and phosphate precipitation followed by electrodialysis.

[0039] Electrochemical methods, in particular, use ionic charge in the brine, e.g., Li+, to entrap and / or extract ions. Such techniques are sustainable since they use electrons as reactants in electrolysis or electrodialysis. They are faster than evaporation technologies, use less chemicals and water, and produce less waste. They may expand productive capacity with relatively little environmental impact.

[0040] However, the relatively low lithium content of natural brines (e.g., 100-300 ppm) and their contamination from other ions pose challenges for electrochemical techniques. Many ions in the brine have the same or similar charge as Li+, complicating and slowing down lithium separation. Many processes require the brine to pass multiple times through the electrochemical extraction system to obtain suitable amounts of purified lithium compounds with a high fraction of Li+cations. They also require pressure to be applied, e.g., via a pump, to circulate brine through the system. All of this adds time and cost to the extraction process. Therefore, it would be advantageous to develop an electrochemical lithium extraction technique that can improve ion extraction efficacy. It would also be advantageous to develop a technique with an increased speed of extraction, decreased number of cycles to yieldconcentrated lithium, and that generated less waste water, brine, and other chemicals. The systems and techniques presented below are directed toward these and other advantages.Corrugated Electrochemical Cell 100

[0041] FIG. 1 A shows an exemplary corrugated electrochemical cell 100 and a brine flow pattern F through cell 100 that may be used in conjunction with the present disclosure. FIG. 1 A assumes that lithium (Li+) interacts with various components of cell 100 via both flow- through and flow-by interactions described in more detail below. Cell 100 can, among other things, lower the flow rate local to (and within) each electrode while maintaining a high total flow rate F. Cell 100 does this principally by directing flow F through multiple channels C in cell 100 in parallel, rather than implementing a more conventional series approach. Parallel flow of F can relatively evenly distribute pressure, current, and potential in cell 100’s electrodes and, thereby, increase the efficiency of the electrochemical reactions that extract the Li+with a relatively low-pressure drop. Since pressure must be externally applied (e.g., via pump) to cell 100 to overcome this pressure drop, lowering the pressure drop can lower both the cost and energy required for ion extraction. It can also increase ion yield and decrease the number of cycles to produce a given ion amount, where each "cycle” represents a single pass of flowing brine F through cell 100. In conventional ion extraction, several cycles (e.g., up to five or six) are typically necessary for suitable ion extraction.

[0042] Cell 100 includes an input 110 for flow F of brine. The brine F flows out of the cell at output 120. While it is in cell 100, the brine flow F encounters the aforementioned parallel electrochemical channels C. Although FIG. 1 A shows three channels C (i.e., channels Cl, C2, and C3) in cell 100, this is merely exemplary. It is to be understood that any suitable number of channels C may be used to implement the present disclosure. Each added channel appears to increase the operating efficiency of cell 100. Limits on the number of channels are practical and / or financial.

[0043] Each channel C may include, as shown in FIG. 1A, an electrode 130, a counter electrode 140, a porous separator 170, and a current collector 150. Electrical wiring 160 delivers potential and current to the components, particularly to electrodes 130 and 140. The porous separator 170 separates each channel C. These components will be discussed in more detail below, as will be the flow F of brine through cell 100. Each channel C’s components may be configured to remove Li+or to remove ions other than Li+depending on the application. As shown below, it can be advantageous to apply a scheme in which both Li+selection and rejection are used sequentially to enhance cell 100’s overall ability to remove Li+from brine.Electrodes 130 and 140

[0044] FIG. 1 A shows how brine F may flow at Fl from channel Cl to channel C2 through separator 170 to take advantage of differences in ion extraction in channels Cl and C2. As discussed in more detail below, each channel C may have different electrodes 130 and 140 that collect Li+in different ways. Using such different techniques in tandem or parallel can improve overall ion collection.

[0045] Electrodes 130 and 140 may comprise any suitable electrode material, including any number of metals and alloys. Electrodes 130 and 140 may also be formed by a novel electrode formation process that allows the fabrication of ultra-thick (e.g., 900-2000 pm) electrodes, potentially lowering the cost of Li+production by 75%. As an overview, the method uses a mixture of hydrophobic and hydrophilic materials, a stress-relief carbon material, and tuning the rate of drying (e.g., with water and organic solvents).Parallel, Channeled Li+-Selective and Li+-Rejective Reactors

[0046] Cell 100 may include different types of reactors for ion extraction. These reactors may be employed in parallel channels e.g., Cl, C2, and C3. The channels may include any electrode that would be included in either a Li+-Selective or Li+-Rejective Reactor setup, as discussed in more detail below and described more generally herein.

[0047] To select appropriate electrode materials, the Li+affinity of several candidates was explored via a model of cell 100. The model 100m appears in FIG. IB along with its control system. Model 100m included one channel C so that each candidate electrode material could be tested at a time. The cell assembly was approximately 1.5 inches x 1.5 inches in size. Testing showed that model 100m exhibited a linear relationship between pressure drop over the electrodes during brine flow. According to the results, a flow rate of 3.1 mL / (min cm2) (close to the minimum flow rate necessary to extract Li+) correlates to a pressure drop of around 3.9 psi. This pressure drop is considered to be very low. Since the concentration of lithium in brines is often very low (100-300 ppm), a lithium extraction plan of 100 kton / year assumes a flow rate of 109 m3 / min. With the conventional reactor design, the pressure drop will easily get above 50 psi, which will increase the pumping energy cost by 13 times and the total cost by 100%.

[0048] Testing for electrode materials was performed on the following Li+-Selective candidates: LMO, MnCE, and lithium nickel cobalt manganese oxide. Testing was performedon the following Li+-Rejective candidates: PB, K2MnFe(CN)e, and K2NiFe(CN)e. The counter electrode in these experiments was PPy-coated carbon cloth. Solutions with Li+, Na+, K+, and Ca2+ions were chosen because these ions are the major constituents in target brines. Testing results generally showed that the most cost-effective and Li+-Selective is LMO. The results also showed that the most cost-effective and Li+-Rejective material is PB.

[0049] More specifically, FIGs. 1C and ID show CV results confirming LMO’s role as a LG- Selective electrode material. FIG. 1C shows CV for LMO in LiCl, NaCl, KC1, and CaCh solutions. FIG. ID shows LMO results in mixed 3% LiCl, 3% NaCl, 3% KC1, and 3% CaCh. Each CV curve shows a negative half cycle when Li+intercalation into the LMO electrode material occurs. They also show a positive de-intercalation or ion recovery cycle. For LMO, these data show that a current density for LiCl at a cell voltage of 0.6 V is approximately 160 times that for NaCl and KC1. They show it is 7.3 times that for KC1. This indicates that LMO has an extremely high preference for Li+. FIG. ID confirms this by showing LMO’s preference for LiCl over other compounds in multicomponent systems.

[0050] CV results also confirm PB’s role as a Li+-Rejective electrode material. CV results are shown for PB in LiCl, NaCl, KC1, and CaCh solutions in FIG. IE. FIG. IF shows PB results in mixed 3% LiCl, 3% NaCl, 3% KC1, and 3% CaCh. These data show a substantially greater selectivity ofNa+, K+, and Ca2+ions against Li+ions (i.e., 7-20 times). Consistently, FIG. IF shows PB’s preference for KC1 over other compounds in multicomponent systems. In contrast to FIG. ID, FIG. IF shows no discernible LiCl signature.We note that the temperature of the brine in the above-discussed simulations and experiments was between 50-110°C. Pressure in cells 100 and 100m was kept between 14-70 psi to maintain the brine flow at the elevated temperature. Li+-Selective Reactor (S)

[0051] Channels C of cell 100 can be set up as Li+-Selective reactors, or electrochemical cells that remove and sequester Li+ions from brine flow F. Reactor type and function are determined by the type of electrodes 130 and 160 in each channel C.

[0052] Exemplary materials for electrode 130 in Li+- selective reactors include any number of Li+trapping or sensitive materials. Suitable materials include, for example, LMO, Mn02, and lithium nickel cobalt manganese oxide. Of these materials, as shown above, LMO may perform particularly well while also being relatively cost-effective. Examples include lithium cobalt oxide (LiCoO2), Lithium iron phosphate (LiFePO4 or LFP), Lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC).

[0053] Counter-electrode 140 can include any suitable electrode material that does not necessarily trap Li+. Exemplary materials include polypyrrole (PPy) (e.g., as PPy-coatedcarbon cloth). Other exemplary materials that may be included are: silver, copper, titanium, (graphite, graphene, still other carbon materials (e.g., carbon paper and / or carbon nanotubes), steel or other iron alloys, nickel and nickel alloys, cobalt and cobalt compounds, and other conductive polymers (e.g., polyaniline).Li+-Rejective Reactor (R)

[0054] Each channel C can alternatively be set up as an Li+- rejective reactor, or an electrochemical cell that rejects Li+ions from brine flow F, but that may take up or intercalate other ions. As discussed above, the reactor type is determined by the type of electrodes 130 and 160 in the channel C.

[0055] Electrodes 130 of Li+- rejective reactors include any suitable Li+rejecting materials. These include, for example, PB, K2MnFe(CN)e, and K2NiFe(CN)e. Of these materials, as shown above, PB performs particularly well and is cost-effective. In general, these materials fall into the following two categories: 1) transition metal PB analogues including PB with different valances, K2MnFe(CN)6, K2NiFe(CN)6, K2CuFe(CN)6, K2CoFe(CN)6, K2ZnFe(CN)e, and K2VFe(CN)e. and2) Rare-earth metal analogues including K2LaFe(CN)e, K2CeFe(CN)6, K2GdFe(CN)6, and K2PrFe(CN)6.

[0056] The counter-electrode 140 can be any suitable electrode material that does not necessarily trap Li+. These include any of the materials described above in the context of counter electrode 140 for Li+-Selective reactors. PPy, in particular, may be used.Current Collector 150

[0057] Cell 100 further includes porous current collectors 150. As shown in FIG. 1A, collectors 150 may be formed as material sheets to increase surface area (i.e., area of contact with brine flow F). For the same reason, they may include mesh-like structures having relatively large pores. Increasing surface area of collector 150 increases collected current and the overall efficiency of cell 100.

[0058] Collectors 150 can be made of conductive and corrosion-resistive material, e.g., metallic or metal-including material. Exemplary materials include nickel (Ni) and Ni alloys, aluminum (Al) alloys, copper (Cu) alloys, stainless steels, graphite, and titanium (Ti), as well as alloys including these components. Ti sheets, in particular, were found to exhibit relatively little pitting corrosion when used as current collector sheets 150 in cell 100 at applied voltages between -1.0 and 1.0 V under cyclic voltammetry (CV) measurements. The general corrosion rate of such sheets 150 evaluated using the maximum current density is < 1.5 pm per year, indicating relatively high corrosion resistance. Sheets 150 may include othermaterials that either lend conductivity or structural stability. Examples include various types of paper, including carbon or carbon paper, AvCarb EP40, Carb EP40T (commercial gas diffusion substrates provided by Fuel Cell Store), etc.

[0059] Sheets 150 separate flow F in different channels C in cell 100. They can also collect current from the brine F as it navigates from one channel to another. The porous nature of sheets 150 may facilitate movement of ions between the electrolyte solution F and the electrode surface. This aids the ion separation process. Sheet 150 conductivity allows collected electrons to flow to the rest of the cell 100. Such may drive electrochemical reactions taking place at electrodes 130 and 140. Sheets 150 can provide a large surface area that can enhance efficiency of the electrochemical reactions by allowing more active sites for ion adsorption or release. They can also provide structural support that maintains the structural integrity of cell 100 and its electrodes 130 and 140, preventing collapse or deformation during operation and under pressure from brine flow F.Porous Separator 170

[0060] The porous separator 170 separates electrode 130 from counter electrode 140. Ions from brine F traverse the porous separator 170 under the influence of an electric field created by biasing electrodes 130 and 170. Porous separator 170 is “porous” in the sense that it allows such flow of ions and the brine F that carries them. Porous separators 170 in cell 100 may include any suitable materials, particularly those commonly used as separators in electrochemical cells. Example materials for separator 170 include, but are not limited to: polymer separators (e.g., polyethylene (PE) and polypropylene (PP) membranes), cellulose- based separators, glass fiber separators, ceramic separators, polymer-ceramic separators, porous polyolefin separators, other membranes (), nonwoven fabrics, and composite polymer separators.Exemplary Implementation 1: SR Cell

[0061] In Exemplary Implementation 1, the channels C of cell 100 have the following configuration: channel Cl is an Li+-Selective Reactor and C2 is a Li+-Rejective Reactor. This configuration will be referred to as “SR,” short for Li+-Selective (Cl) and Li+-Rejective (C2). Channel C3 is not necessarily part of Implementation 1. Exemplary Implementation 1 uses rejective reactor C2 to process brine that has already been rendered Li+rich via S reactor Cl. Such reactors can potentially raise Li+purity or cation fraction in brine to 80% in 2-3 cycles. See, e.g., X. Zhao et al., Review on the electrochemical extraction of lithium, J. of Electroanalytical Chem 850 (2019) 113389. This improves performance by decreasing thenumber of cycles necessary to remove Lit It increases overall Li+selectivity and decreases operating cost / pressure.

[0062] FIG. 2 is a flowchart showing method 200 using the SR configuration of Implementation 1 to extract Li+from brine flow F. FIGs. 3A-3C show the components of cell 100 implementing method 200. Although FIG. 2 shows a sequence of steps, it is to be understood that this presentation is not limiting. When appropriate, steps shown in flowchart 200 may be taken in a different order in accordance with this disclosure.

[0063] Before the implementation of method 200, brine flow F may have been directly extracted from an underground brine reservoir, as described above. Brine flow F may be processed prior to lithium extraction via cell 100 using any of the techniques described or implied herein. For example, brine flow F may be subject to filtration and / or centrifuge to eliminate or decrease unwanted components in the brine (e.g., rocks, minerals, other debris).

[0064] In step 202 of method 200, brine flow F enters channel Cl of cell 100. Since the cell’s configuration is SR, Channel Cl is in a Li+-Selective configuration. This is shown in FIG.3A.

[0065] At step 204, as shown in FIG. 3A, Li+-Selective electrode 130a extracts ions from brine flow F. The exact identity of the ions extracted from brine flow F by channel Cl will depend on the material in electrode 130a as well as the ionic composition of the brine flow F. As shown in in FIG. 3 A merely for the purposes of illustration and example, electrode 130a has pulled Na+and Li+from the brine flow F. Although brine flow F is depicted as including Ca2+, a divalent positive ion, electrode 130a, as depicted in FIG. 3A, is such that it does not accommodate this ion to the extent it accommodates Li+and Na+. In other implementations, electrode 130a may accommodate and remove Ca2+.

[0066] Channel Cl depletes Li+relative to the ion’s concentration in original brine flow F. The Li+depleted flow, labeled in FIG. 3 A as “RF,” can be ejected or eliminated from cell 100 in this step.

[0067] In step 206 (FIG. 3B), Li+sequestered by channel Cl is recovered. More specifically, solution S flows through channel Cl to remove Li+ions from electrode 130a where they have been sequestered. Solution S can be brine, saline, or any other suitable solution for removing Li+ions from electrode 130a. Recovered Li+is dissolved into new brine solution Fl. As a result, brine Fl has an enhanced Li+concentration relative to original brine F. As discussed above, depending on the particulars, the relative concentration of Li+in Fl at this point can be upwards of 80%.

[0068] As shown in FIGs. 3B and 3C, Fl is fed to channel C2 for further Li+extraction. That is, in step 206, brine Fl transitions from channel Cl to channel C2. Since cell 100 is being operated as SR in method 200, Channel C2 is in a Li+-Rejective configuration. This is shown in FIG. 3C. Operating a Li+-Rejective step after the Li+ concentration of Fl has been increased above 80% will further enhance the lithium composition of the target brine. In some instances, step 206 can raise the Li+fraction (where “Li+fraction” means the proportion of cations that are Li+) to around 99%.

[0069] In step 208 (FIG. 3C), Li+-Rejective electrode 130b extracts certain ions from ion- depleted flow Fl. At the same time, electrode 130b rejects Li+ions. The specific reason electrode 130b rejects Li+and extracts other ions, as well as the exact identity of the ions extracted depend on the material in electrode 130b and the ionic composition of Fl. FIG. 3C shows, for example, electrode 130b pulling Na+from brine flow Fl. Electrode 130b may be made of Li+-Rejective material, unlike electrode 130a (FIG. 3A). Examples of such electrode materials include PB. As shown in FIG. 3C, in step 208 channel C2 provides a Li+-enhanced or “purified LiCl” brine F2, which may have a Li+cation fraction of up to 99%. Brine F2 retains CF that was not removed in previous steps. Brine F2 exits cell 100 at step 208 and is ready for further processing in step 210.

[0070] FIG. 3D shows an optional post-treatment step for channel C2 after the performance of method 200. In FIG. 3D, solution S is flowed over Li+rejective electrode 130b to remove ions adhered to electrode 130b. Once removed, the ions exit in a new brine containing the rejected flow RF. Flow RF may be recycled, disposed of, or returned to the brine source. Since RF is generally depleted of Li+ ions, it may not be useful for Li-ion battery applications. However, there may still be other ions (or other components) in RF that are useful for these and other applications.Exemplary Implementation 2: SSR Cell

[0071] In Exemplary Implementation 2, the channels C of cell 100 have the following configuration: channel Cl is an Li+-Selective Reactor, C2 is a Li+- Selective Reactor, and C3 is a Li+-Rejective Reactor. This configuration will be referred to as “SSR.” In this configuration, C2 is a second Li+-Selective reactor C2 processing brine that has already been rendered Li+rich via a selective reactor Cl. This can improve performance over the SSR reactor in Exemplary Implementation 1 by decreasing the number of cycles necessary to remove the Li+and by increasing overall Li+selectivity and decreasing operating cost / pressure.

[0072] FIGs. 4 A and 4B present a flowchart showing method 400 using the SSR configuration of Implementation 2 to extract Li+from brine flow F. Although FIGs. 4A and 4B show a sequence of steps, it is to be understood that this presentation is not limiting. When appropriate, steps shown in flowchart 400 may be taken in a different order in accordance with this disclosure. FIGs. 5A-5E show the components of cell 100 implementing method 400.

[0073] In step 402, brine flow F enters channel Cl of cell 100. Channel Cl is in a Li+- Selective configuration. Prior to flowing into Cl, brine F may have been directly extracted from an underground brine reservoir, as described above, and / or pre-processed.

[0074] At step 404, as shown in FIG. 5A, Li+-Selective electrode 130a extracts ions from brine flow F. The ions extracted from brine flow F by channel Cl depend on electrode 130a and brine F composition. For example, electrode 130a may extract Na+and Ca2+in addition to Li+. The Li+depleted flow, labeled in FIG. 5 A as “RF,” can be ejected or eliminated from cell 100 in this step, in the same or similar manner as described above in the context of step 204 of method 200.

[0075] In step 406, Li+sequestered by channel Cl is recovered (FIG. 5B). More specifically, as discussed above in the context of method 200, step 206 and FIG. 3B, solution S flows through channel Cl to remove Li+ions from electrode 130a where they have been sequestered. Solution S can be brine, saline, or any other suitable solution for removing Li+ ions from electrode 130a. Recovered Li+is dissolved into new brine solution Fl. Fl is fed to channel C2 for further Li+extraction. Since the cell’s configuration is SSR, Channel C2 is also in a Li+-Selective configuration.

[0076] In step 408 (FIG. 5C), Li+-Selective electrode 130b extracts Li+ and other ions (e.g., Na+and Ca2+to varying degrees) from Li+ion-enriched flow Fl. The exact identity of the ions extracted depends on the material in electrode 130b as well as the ionic composition of Fl. As discussed above, depending on the precise composition of the electrodes in C2, different ions may be extracted from brine Fl. In particular, electrode 130b of C2 may be selected to complement the extraction capabilities of electrode 130a of Cl. For example, electrode 130b may have an enhanced ability to extract Li+from a Li+-rich brine, i.e., Fl. Such would enhance the overall Li+extraction capabilities of cell 100 over its use in SR mode.

[0077] In step 410 (FIG. 5D), Li+sequestered by channel Cl is recovered (e.g., as discussed in the context of step 406 above). Recovered Li+is dissolved into new brine solution F2. F2 is fed to channel C3.

[0078] In step 412 (FIG. 5E), Li+-Rejective electrode 130c in channel C3 extracts ions from Li+ion-depleted flow F2, but rejects Li+ions. The exact identity of the ions extracted depends on the material in electrode 130c as well as the ionic composition of F2. In one example, electrode 130c includes PB. In step 412, channel C3 provides a purified LiCl brine F3. This purified brine F3 exits cell 100 and is ready for further processing in step 414.

[0079] The same optional post-treatment step shown in FIG. 3D for channel C2 may be performed for channel C3 at this stage. In other words, solution S may be flowed over Li+rejective electrode 130c to remove adhered ions. Once removed, the ions may exit cell 100 in a new brine containing the rejected flow RF.General Method for Operating Cell 100

[0080] Although exemplary SR and SSR configurations are shown above in methods 200 and 400, respectively, it should be noted that cell 100 has the capacity to operate in other modes. In particular, it may be advantageous to use multiple S or R steps beyond 1-2 in order to increase the Li+ratio of brine without requiring substantially high pressure, energy, or cycles through the electrochemical system. FIGs. 6A and 6B show a method 600 that may use any suitable number of channels in S and R mode to increase the overall concentration of Li+as much as possible. Although FIGs. 6A and 6B show a sequence of steps, it is to be understood that this presentation is not limiting. When appropriate, steps shown in flowchart 600 may be taken in a different order in accordance with this disclosure.

[0081] At step 602, brine F flows into cell 100. As discussed above, brine F may have been extracted, filtered, and otherwise pre-processed before entering cell 100. Pre-processing both ensures that brine F is relatively pure and that contaminants and debris do not substantially hinder functioning of cell 100. At step 604, method 600 determines whether any of the channels C in cell 100 are setup as Li+-Selective channels. If there are no Li+-Selective channels, method 600 moves directly to step 608.

[0082] On the other hand, if there are Li+-Selective channels, the method passes to step 606, which includes three sub-steps 606a-606c. Sub-steps 606a-606c allow each of the Li+- Selective channels Cn in cell 100 to increase the relative concentration of Li+in the brine. More specifically, step 606a allows channel Ci to remove Li+from the brine. Step 606b recovers the removed Li+and adds it to concentrated brine B. Step 606c provides the Li+concentrated brine to the next Li+-Selective channel Ci+i. When all Li+-Selective channels Cn have been utilized, step 606 terminates and method 600 moves to step 608.

[0083] At step 608, method 600 determines whether any of the channels C in cell 100 are set up as Li+-Rejective channels. If there are no Li+-Rejective channels, method 600 moves directly to step 612.

[0084] On the other hand, if there are Li+-Rejective channels, the method passes to step 610, which includes two sub-steps 610a and 610b. Sub-steps 610a and 610b allow each of the Li+- Rejective channels Cj in cell 100 to increase the relative concentration of Li+in the brine. More specifically, step 610a allows channel Ci to remove ions other than Li+from the brine. Step 610b recovers the Li+enhanced brine BE and provides it to the next of the Li+-Rejective channel Ci+i . When all Li+-Rejective channels Cj have been utilized, step 610 terminates and method 600 moves to step 612.

[0085] At step 612, method 600 terminates by providing Li+-enhanced brine BE for further processing outside of cell 100.

[0086] While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions— such as alternative materials, structures, configurations, methods, circuits, devices and components, software, hardware, control logic, alternatives as to form, fit and function, and so on— may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to becritical values or ranges only if so expressly stated. Parameters identified as “approximate” or “about” a specified value are intended to include both the specified value and values within 10% of the specified value, unless expressly stated otherwise. Further, it is to be understood that the drawings accompanying the present application may, but need not, be to scale, and therefore may be understood as teaching various ratios and proportions evident in the drawings. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.

Claims

We claim:

1. An apparatus for separating lithium ions from solution, the apparatus comprising: a first lithium selective reactor comprising: a lithium selective electrode configured to absorb lithium ions from the solution; a separator; and a counter electrode; and a lithium rejective reactor comprising: a lithium rejective electrode; a separator; and a counter electrode.

2. The apparatus of claim 1, wherein: the first lithium selective reactor is configured to provide a first lithium selective reactor output having a lithium concentration greater than a lithium concentration of the solution; and the lithium rejective reactor is configured to: input the first lithium selective reactor output; and provide a lithium rejective reactor output having a lithium concentration greater than the lithium concentration of the first lithium selective reactor output.

3. The apparatus of claim 2, wherein the first lithium selective reactor output derives at least in part from recovering lithium ions that the lithium selective electrode of the first lithium selective reactor absorbed from the solution.

4. The apparatus of claim 3, wherein the recovering lithium ions comprises flowing a solution with a relatively low lithium concentration over the lithium selective electrode of the first lithium selective reactor.

5. The apparatus of claim 1, further comprising: a second lithium selective reactor comprising: a lithium selective electrode that absorbs lithium ions;a separator; and a counter electrode.

6. The apparatus of claim 5, wherein: the first lithium selective reactor is configured to provide a first lithium selective reactor output having a lithium concentration greater than a lithium concentration of the solution; and the second lithium selective reactor is configured to: input the first lithium selective reactor output; and provide a second lithium selective reactor output having a lithium concentration greater than the lithium concentration of the first lithium selective reactor output; and the lithium rejective reactor is configured to: input the second lithium selective reactor output; and provide a lithium rejective output having a lithium concentration greater than a lithium concentration of the second lithium selective reactor output.

7. The apparatus of claim 6, wherein at least one of: the first lithium selective reactor output derives at least in part from recovering lithium ions from the lithium selective electrode of the first lithium selective reactor that were absorbed from the solution; and the second lithium selective reactor output derives at least in part from recovering lithium ions from the lithium selective electrode of the second lithium selective reactor that were absorbed from the first lithium selective reactor output.

8. The apparatus of claim 7, wherein the recovering lithium ions comprises flowing a solution with a relatively low lithium concentration over at least one of the lithium selective electrode of the first lithium selective reactor and the lithium selective electrode of the second lithium selective reactor.

9. The apparatus of claim 1, wherein the lithium selective electrode of the first lithium selective reactor comprises at least one of LiMn2O4 (LMO), MnCh, and lithium nickel cobalt manganese oxide.

10. The apparatus of claim 9, wherein the lithium selective electrode of the first lithium selective reactor comprises primarily LMO.

11. The apparatus of claim 5, wherein the lithium selective electrode of the second lithium selective reactor comprises at least one of LMO, MnO2, and lithium nickel cobalt manganese oxide.

12. The apparatus of claim 11, wherein the lithium selective electrode of the second lithium selective reactor comprises primarily LMO.

13. The apparatus of claim 1, wherein at least one of the counter electrode of the first lithium selective reactor and the counter electrode of the lithium rejective reactor comprises at least one of polypyrrole (PPy), platinum, graphite, graphene, gold, carbon paper, carbon nanotubes, iron and iron alloy, nickel and nickel alloys, cobalt and cobalt compounds, and a conductive polymer.

14. The apparatus of claim 5, wherein the counter electrodes of the first lithium selective reactor, the second lithium selective reactor, and the lithium rejective reactor comprise primarily PPy.

15. The apparatus of claim 1, wherein the lithium rejective electrode of the lithium rejective reactor comprises at least one of Ko.i-o.2FeFe(CN)e (Prussian Blue or “PB”), K2MnFe(CN)6, and K2NiFe(CN)6.

16. The apparatus of claim 15, wherein the lithium rejective electrode of the lithium rejective reactor comprises primarily PB and a number of PB analogues.

17. The apparatus of claim 1, further comprising a second lithium rejective reactor.

18. The apparatus of claim 17, further comprising at least one of: a third lithium selective reactor; and a third lithium rejective reactor.

19. The apparatus of claim 1, wherein the solution is a brine.

20. The apparatus of claim 1, wherein a brine output by the apparatus has a Li+fraction of more than 90%.

21. The apparatus of claim 1, wherein a pressure applied to flow brine through the apparatus is 70 psi or less.

22. A method for separating lithium ions from solution comprising: absorbing lithium ions from the solution via a first lithium selective reactor, the first lithium selective reactor comprising: a lithium selective electrode that absorbs the lithium ions from the solution; a separator; and a counter electrode; and providing, to a lithium rejective reactor, an interim liquid comprising: lithium ions extracted from the solution; and a lithium concentration higher than a lithium concentration of the solution, the lithium rejective reactor comprising: a lithium rejective electrode that rejects lithium ions from the interim liquid, but absorbs other ions from the interim liquid; a separator; and a counter electrode; and outputting a liquid with a lithium concentration higher than the lithium concentration of the solution.

23. The method of claim 22, wherein the providing the interim liquid to the lithium rejective reactor comprises: receiving, via a second lithium selective reactor, an output of the first lithium selective reactor, the second lithium selective reactor comprising: a lithium selective electrode that absorbs lithium ions from the output of the first lithium selective reactor to provide the interim liquid; a separator; and a counter electrode.

24. The method of claim 22, wherein the solution is a brine.

25. The method of claim 22, wherein the output liquid has a Li+fraction of more than 90%.

26. The method of claim 22, wherein a pressure applied to the brine during the method is 70 psi or less.

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