Electrodes for lithium ion extraction and method for manufacturing same

Abstract

Disclosed herein is an electrode for separating lithium ions from solution. The electrode includes a contact layer, a carbon layer disposed on the contact layer, and a lithium ion interactive layer disposed on the carbon layer. The lithium ion interactive layer includes a slurry cast material that has a thickness greater than 500 microns and is substantially free of cracks.

Description

ELECTRODES FOR LITHIUM ION EXTRACTION AND METHOD FOR MANUFACTURING SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and any benefit of U.S. Provisional Application No. 63 / 668,342, filed July 8, 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 fabricating electrodes for various applications including the extraction of ions (e.g., lithium (Li+) ions) from aqueous solutions or brine. One purpose is to fabricate electrodes that extract ions for battery applications. The present disclosure can, among other things, improve electrode performance, 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 avoid the need for substantial chemical processes to regenerate their facilitating materials (e.g., electrodes and / or membranes) after long periods of use, as required by other techniques. 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 substantialthickness to operate at scale with low bulk resistivity and without cracking can be challenging. Currently, most active EEP materials run into materials limitations at thicknesses around 200 pm (microns). 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] One example is an electrode for separating lithium ions from solution. The electrode includes a contact layer, a carbon layer disposed on the contact layer, and a lithium ion interactive layer disposed on the carbon layer. The lithium ion interactive layer includes a slurry cast material that has a thickness greater than 500 microns, and is substantially free of cracks.

[0007] The lithium ion interactive layer may have a thickness of at least 700 microns, at least 900 microns, at least 1,000 microns, at least 1,500 microns, or at least 2,000 microns. The lithium ion interactive layer may include a lithium ion selective material. The lithium ion selective material may include at least one of lithium manganese oxide (LMO), MnCE, and lithium nickel cobalt manganese oxide. The lithium ion selective material may include primarily LMO. The lithium ion interactive layer may include a lithium ion rejective material. The lithium ion rejective material 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 ion rejective material may include primarily PB.

[0008] The electrode may have a resistivity of 0.7 Q cm2or less. It may have a contact resistivity of 0.5 Q cm2or less, 0.3 Q cm2or less, or 0.2 Q cm2or less. The inventive electrode may have a porosity of 30%-70% or more.

[0009] Also disclosed herein is an apparatus for separating lithium ions from solution. The apparatus may include a first lithium selective reactor. The first lithium selective reactor may include a lithium selective electrode comprising an electrode as disclosed or claimed herein, and configured to absorb lithium ions from the solution, a separator, and a counter electrode. The apparatus may also include a lithium rejective reactor. The lithium rejective reactor may include a lithium rejective electrode, a separator, and a counter electrode.

[0010] 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 lithiumconcentration greater than the lithium concentration of the first lithium selective reactor output.

[0011] 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. The apparatus may further include a second lithium selective reactor. The second lithium selective reactor may include 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.

[0012] 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 were absorbed 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. 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. 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), silver, 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 solution may be a brine. A brine output by the apparatus may have a Li+fraction of more than 90%.

[0013] Also disclosed herein is a method for fabricating an electrode for separating lithium ions from solution. The method includes forming a slurry. The slurry includes a binder, an organic solvent, and an active material. The method includes applying the slurry to a surface while the slurry is wet, forming an electrode layer by drying the applied slurry at a substantially uniform rate. The formed electrode layer may have a thickness of 500 microns or more and a resistivity of 0.7 Q cm2or less.

[0014] Drying the applied slurry at a substantially uniform rate may include controlling a dampness in the slurry. Controlling a dampness in the slurry may include adjusting a composition of the binder. Adjusting the composition of the binder may include adjusting a hydrophobicity of the binder. Adjusting the hydrophobicity of the binder may include altering a ratio of hydrophobic components of the binder to hydrophilic components of the binder. The binder may include at least one of poly vinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyurethane (PU), polyethylene (PE), polyethylene oxide (PEO), an acrylic resin, an epoxy resin, and an alkyd resin. The binder may have the composition of PVDF:PVA:PEO = 100:5: 10. Drying the applied slurry at a substantially uniform rate may include controlling a humidity over an outer surface of the slurry. Controlling the humidity may include maintaining the humidity at a level consistent with a level of dampness throughout the slurry. Controlling the humidity may include using a humidifier or water sprayer. Controlling the humidity may include using an air conditioner.

[0015] Controlling the humidity may include applying liquid to an environment of the slurry. Applying liquid may include misting the liquid. The liquid may include at least one of water and the organic solvent. Controlling the humidity may include at least one of venting gas in an environment of the slurry and providing dry gas to the environment of the slurry.

[0016] Drying the applied slurry at a substantially uniform rate may include maintaining a temperature of the slurry. Maintaining the temperature may include at least one of heating the slurry and heating an environment of the slurry. Maintaining the temperature may include at least one of cooling the slurry and cooling an environment of the slurry. Maintaining the temperature may include venting an environment of the slurry. Maintaining the temperature may include at least one of resistive heating, oven heating, and providing heated gas to an environment of the slurry.

[0017] Drying the applied slurry at a substantially uniform rate may include drying the slurry at the rate of 2 hours or slower. The surface may include carbon. The carbon may include carbon cloth.

[0018] The formed electrode layer may have a thickness of at least one of 700 microns or more, 900 microns or more, 1000 microns or more, 1500 microns or more, and 2000 microns or more. The formed electrode layer may have a contact resistivity that is at least one of 0.5 Q cm2or less, 0.3 fi cm2or less, and 0.2 cm2or less. The organic solvent may include at least one of n-methyl-2-pyrrolidone (NMP), acetone, methyl ethyl ketone (MEK), acetonitrile, cyclohexanone, butyronitrile, ethanol, methanol, and dimethyl sulfoxide(DMSO). The active material may include at least one of lithium manganese oxide (LMO), MnO2, and lithium nickel cobalt manganese oxide, Ko.i-o.2FeFe(CN)e (Prussian Blue or “PB”), K2MnFe(CN)6, and K2NiFe(CN)6.

[0019] The formed electrode layer may have a porosity of 40-60% or more. These and other variations are described in more detail below.BRIEF DESCRIPTION OF DRAWINGS

[0020] 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.

[0021] FIG. IB shows an experimental setup with a model cell 100m for testing purposes.

[0022] FIG. 1C shows a cyclic voltammetry (CV) test using lithium manganese oxide (LMO) electrode material with various ions that indicates a strong Li+affinity.

[0023] FIG. ID shows a CV test using LMO electrode material with a multicomponent solution also indicating a strong Li+affinity.

[0024] 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+.

[0025] 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+.

[0026] FIG. 2A is a flowchart showing method 200 to fabricate electrode 230 according to aspects of this disclosure.

[0027] FIG. 2B is a diagram showing layers of electrode 230 fabricated by method 200.

[0028] FIG. 2C is a photograph of an actual electrode 230a fabricated by method 200.

[0029] FIG. 2D shows experimental results relating to the resistivity of electrode 230a.

[0030] FIG. 2E is a Scanning Electron Microscopy (SEM) image showing porosity in electrode 230a.

[0031] FIG. 2F is a schematic of part of the method 200 used to create electrode 230a.

[0032] FIG. 2G is a flowchart showing method 250 using the Li+Selective / Rejective (SR) configuration of Implementation 1 to extract Li+from brine flow F in conjunction with this disclosure.

[0033] FIG. 3 A shows components of channel Cl of cell 100 implementing Li+extraction from brine flow F according to method 200.

[0034] FIG. 3B shows components of channel Cl during recovery of Li+ions after extraction.

[0035] FIG. 3C shows components of channel C2 of cell 100 implementing a Li+rejective step of method 200.

[0036] FIG. 3D shows outflow of non-Li+ions from channel C2 of cell 100 after implementing method 200.

[0037] 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.

[0038] FIG. 4B is another part of a flowchart showing method 400.

[0039] FIG. 5 A shows components of channel Cl of cell 100 implementing Li+extraction from brine flow F according to method 400.

[0040] FIG. 5B shows components of channel Cl during recovery of Li+ions after extraction.

[0041] FIG. 5C shows components of channel C2 of cell 100 implementing a second Li+selective step of method 400.

[0042] FIG. 5D shows components of channel C2 during an Li+rejective step of method 400.

[0043] FIG. 5E shows components of channel C3 during an Li+rejective step of method 400.

[0044] 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.

[0045] FIG. 6B shows a second part of method 600.DETAILED DESCRIPTIONConventional Lithium Brine Extraction

[0046] 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.

[0047] 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.

[0048] 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 ionic species, 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.

[0049] 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

[0050] 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.

[0051] 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.

[0052] 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. Separation processes require 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 applying pressure, e.g., via a pump, to circulate brine through the system. All of this adds time and cost to the extraction process.

[0053] Such problems can be compounded by limitations in the electrodes used in many of these Li+ extraction cells. In particular, the amount of brine electrodes can process per unittime tends to depend on the volume of the electrode, corresponding to the amount of active ion extractor in the electrode. Electrode volume, in turn, is limited by the ability to fabricate the portion of the electrode including the lithium extractor material. These materials tend to be produced by solidifying from slurry, which can create a brittle structure prone to cracking both during and after the electrode fabrication process. Cracking and / or compositional inhomogeneities can render the electrodes inefficient and, in some cases, inoperable. Growing suitable electrode structures without such defects is an extremely slow process. It can generate only limited quantities of crack-free electrode material, usually measured in terms of electrode thickness. Typical processes can only generate defect-free electrodes with a thickness of 100 microns or less. This limits the amount of brine they can process, slowing down the entire operation of the cell and requiring additional passes of brine through the cell.

[0054] Therefore, it would be advantageous to develop an electrochemical cell that has electrodes able to process more brine per pass. Increasing the amount of volume or thickness of such electrodes, in particular, will improve ion extraction efficacy. It would also be advantageous to develop a technique with an increased speed of extraction, decreased number of cycles to yield concentrated 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

[0055] 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. This particular electrochemical cell 100 and its operation is explained in more detail in co-pending U.S. Provisional Patent Application No. 63 / 548,614 herein incorporated by reference in its entirety. As explained therein, cell 100 uses multiple extractors configured with lithium selective and rejective materials to increase extraction efficiency. These materials may be incorporated into thick electrodes made according to methods disclosed herein to further increase extraction efficiency.

[0056] 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 theelectrochemical 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.

[0057] 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.

[0058] 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

[0059] 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.

[0060] 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 (described below in the context of method 200 in FIG. 2A) that allows the fabrication of ultra-thick (e.g., 900-2000 micron) electrodes, potentially lowering the cost of Li+production by 75%. As an overview, the method uses a mixture ofhydrophobic and hydrophilic materials, a stress-relief carbon material, and tuning the rate of drying (e.g., with water and organic solvents).Electrode Materials Selection for Parallel, Channeled Li+-Selective and Li+-Rejective Reactors

[0061] 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.

[0062] 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%.

[0063] Testing for electrode materials was performed on the following Li+-Selective candidates: LMO, MnCh, and lithium nickel cobalt manganese oxide. Testing was performed on 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.

[0064] More specifically, FIGs. 1C and ID show CV results confirming LMO’s role as a Li+- 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 LMOhas an extremely high preference for Li+. FIG. ID confirms this by showing LMO’s preference for LiCl over other compounds in multicomponent systems.

[0065] 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)

[0066] 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.

[0067] Exemplary materials for electrode 130 in Li+- selective reactors include any number of Li+trapping or sensitive materials. Suitable materials include, for example, LMO, MnCL, 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 (LiNiMnCoO? or NMC).

[0068] Counter-electrode 140 can include any suitable electrode material that does not necessarily trap Li+. Exemplary materials include polypyrrole (PPy) (e.g., as PPy-coated carbon 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)

[0069] 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.

[0070] 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 materialsfall 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.

[0071] 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.Electrode Fabrication

[0072] As discussed above, electrodes for use in cell 100 may be made more efficient via the fabrication process disclosed herein. The following fabrication applies mainly to Li selective or rejective electrodes of type 130 described above, as well as electrodes 130a, 130b, 230, and 230a described below. They may include any of the above materials disclosed as “active materials,” or, in this context, electrode materials that interact with Li+ions in the brine 100. The processes disclosed below may also be used to fabricate any other electrode disclosed or suggested herein, including counter electrode 140. Moreover, the description of electrode fabrication techniques disclosed herein is not limited to use for fabricating electrodes for cell 100 or similar cells. It is to be understood that the electrodes fabricated as described may be used in any suitable cell for extraction of ions, including lithium. They may potentially be used for other electrochemical applications, including as electrode materials for various battery systems, including battery systems employing lithium ions.

[0073] FIG. 2A is a flowchart showing an exemplary method 200 for fabricating an electrode 230. FIG. 2B shows an exemplary layer structure for the electrode 230 fabricated by the method. Electrode 230 can be, for example, electrode 130, electrode 140, or any other electrode discussed or implied according to the present disclosure. Although FIG. 2A shows a sequence of steps, it is to be understood that this presentation is not limiting. When appropriate, steps shown for method 200 may be taken in a different order, or omitted entirely, in accordance with this disclosure.

[0074] At step 202, a frame or substrate 232 for electrode 230 can be chosen. One purpose for the frame or substrate 232 is to provide structural integrity to electrode 230 both during and after fabrication (see, e.g., placement of substrate 232 relative to the rest of electrode 230 in FIG. 2B). Suitable materials for frame 232 include any of those mentioned herein, particularly those materials that may impart more structural integrity than the materials used for other layers in electrode 230. These include carbon-based materials (e.g., graphite and graphene, carbon composites), carbon cloth, other cloth, felt, graphene, or other forms ofcarbon. Carbon (and other flexible materials) may be particularly advantageous for use in substrate 232 because it may absorb and / or dissipate stresses that accumulate during electrode 230 fabrication. Metals may also be used, including aluminum, copper, and other suitable materials.

[0075] Frame or substrate 232 may be placed, deposited, or layered on a contact 231, as shown in FIG. 2B. Contact 231 can provide a point of contact for wires or other currentcarrying conduits. That is, wires can be connected (e.g., soldered or welded) to contact 231 to direct electrical current between electrode 230 and other portions of a device connected by the wires. The device connected by the wires to contact 231 can include, for example, cell 100. Contact 231 can include any suitable material for a current conducting contact, including conductive composites, carbon, metals like aluminum, copper, steel, gold, silver, and mixtures or alloys thereof. Contact 231 can take on any suitable form, such as a layer of deposited material, a slab of material, or a foil, for example. Others include titanium alloys, nickel based alloys, stainless steels (AISI 304, 316, 321, 430, 410, duplex 2205 and duplex 2507.)

[0076] Next a slurry is prepared that includes “active material.” Active material is any suitable material that interacts with Li+ions in solution, either to selectively absorb or reject the ions. Slurry preparation, application, and electrode formation from the slurry can represent time-consuming aspects of electrode fabrication. This is particularly true since the final, deployed structure of the dried slurry in electrode 230 is important for its functioning. The slurry needs to be provided with the right components, applied at the correct rate via the right techniques, and dried at a suitably slow rate, to avoid substantial cracking and defect formation in the final structure of electrode 230, particularly in electrode layers 233 and 234. Cracks and other defects, once formed, are generally not easily eliminated from its structure. These defects can interrupt charge flow and / or serve as anomalous concentrators of charge and / or ions. Such defects can render portions of electrode 230 useless and / or degrade the overall capacity and functioning of electrode 230. In addition, the slurry should be prepared such that it imparts a suitable amount of porosity to electrode layers 233 and 234 of electrode 230 as it dries. Porosity allows electrode layers 233 and 234 to interact with brine or other liquid for ion extraction. At the same time, electrode layers 233 and 234 should retain a certain level of conductivity in the material between the pores. There is a tradeoff between this conductivity and the level of porosity which, as discussed in more detail below, can be manipulated in method 200.

[0077] In step 204, the solvent is prepared for the slurry. The solvent can be any suitable solvent for the electrode material, particularly organic solvents. Examples of suitable solvents include n-methyl-2-pyrrolidone (NMP), acetone, methyl ethyl ketone (MEK), acetonitrile, cyclohexanone, butyronitrile, ethanol, methanol, dimethyl sulfoxide (DMSO), and combinations thereof. Others include toluene, benzene, chloroform, tetrahydrofuran (THF), ethyl acetate, Xylene, decalin, trichlorobenzene, methylene chloride, pyridine, dichloromethane, dioxane, Phenol / l,l,2,2-tetrachloroethane, trifluoroacetic acid, and hexafluoroisopropanol (HFIP).

[0078] At step 206, binder is added to the solvent to create the slurry. Any suitable binder that may be dissolved in the solvent may be used. Examples of suitable binders include polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyurethane (PU), polyethylene (PE), acrylic resins, epoxy resins, alkyd resins, and other suitable binders. Others include Polyethylene Terephthalate (PET), Nylon (Polyamides), Polylactic Acid (PLA), Polycarbonate (PC), Polypropylene (PP), Polyethylene (PE), polyethylene oxide (PEO), styrene butadiene rubber (SBR), Acrylonitrile (AN), Polyimide (PI), Polyacrylonitrile (PAN), carboxymethyl cellulose (CMC), cyclodextrin (CD), sodium alginate (SA), polysaccharide, Perfluorosulfonate ionomer (Nafion), Lithiated perfluorosulfonate ionomer ((PTFE), Sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups (SPEEK- FSA-Li), poly(perfluoroalkylsulfonyl)imide (PFSILi) ionene, poly (1 -pyrenemethyl methacrylate), poly(l -pyrenemethyl methacrylate-co-tri ethylene oxide methyl ether methacrylate) (PPyE), 3, 6-poly (phenanthrenequinone) (PPQ), poly(4,4-bis(2-ethylhexyl)-4JT- cyclopenta[2,l-Z>;3,4-Z>']dithiophene-methylbenzoate)(PCPDT-MB), poly(3,4- ethylenedioxythiophene) / poly-(styrene-4-sulfonate) (PEDOT :PSS), SA-3, 4- propylenedioxythiophene-2,5-dicarboxylic acid (ProDOT), poly(2,7-9,9-dioctylfluorene) (PF-COONa).

[0079] These and other suitable binders differ widely in terms of their relative hydrophobicity and hydrophilicity, two properties that can be exploited to increase the stability of the slurry during deposition and drying in accordance with aspects of the present disclosure. More specifically, the binder components should be chosen to balance these properties and ensure the appropriate amount of moisture and / or humidity in the drying slurry so that the drying process occurs at a rate slow enough to prevent substantial cracking or defect formation. For example, the following can be used as hydrophilic binders that can, under the right circumstances, increase the water content of the slurry based on the ambienthumidity: PVA, acrylic resins, and epoxy resins. The following binders can be used as hydrophobic binders to, under the right circumstances, decrease the water content of the slurry based on the ambient humidity: PVDF, PMMA, PTFE, PU, PE, and alkyd resins. Still other binders may be used to balance the water content of the slurry based on their hydrophobicity / hydrophilicity. Any of these binders can be combined in suitable proportions to slow the drying rate and / or maintain structural stability of the slurry as it dries and forms electrode 230. It should be appreciated that any suitable binder and / or combination of binders, whether expressly disclosed herein or not, can be used for this purpose in accordance with the present disclosure. Exemplary binder combinations include: Polyvinylidene Fluoride (PVDF), Polyvinyl Alcohol (PVA), and Polyethylene Oxide (PEO) in a ratio of 100:5: 10; PVDF, Styrene-Butadiene Rubber (SBR), and PEO in a ratio of 100:5: 10; and PVDF, Carboxymethyl Cellulose (CMC), and PEO in a ratio of 100:5: 10.

[0080] Care should be taken in this step to select a binder combination that can facilitate relatively slow and uniform drying of the slurry. Generally, this involves selecting a binder combination that balances hydrophobicity and hydrophilicity. The balance can be adjusted depending on ambient conditions, and specifically humidity or moisture near the drying slurry. In cases where the environment is more humid, the binder can include a greater proportion of hydrophobic binders. In one example, a blend including a greater proportion of PVDF and PVA may be used to decrease water content of the slurry as it dries. In cases where the environment is less humid, the binder can include a greater proportion of hydrophilic binder species to increase water content of the slurry and slow drying. In this case, for example, the binder can include a blend of PVA, acrylic resins and more hydrophilic resins to increase the water content of the slurry as it dries. Any suitable combination of binders may be used to balance water content of the slurry within the context of the present disclosure.

[0081] In step 208, salts are added to the slurry. The added salts may include lithium salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) (LiN(CFs 802)2), Lithium Trifluoromethanesulfonate (LiOTf) (LiCFsSCE) and other similar salts. For example, other salts that may be used include lithium hexafluorophosphate (LiPFe), lithium perchlorate (LiCKL), lithium tetrafluorob orate (LiBF4), lithium difluoro(oxalato)borate (LiDFOB) (LiBF2C2O4), lithium bi s(oxalato)b orate (LiBOB) (LiB(C2O4)2), lithium trifluoromethanesulfonate (LiTf or LiOTf) (LiCFsSOs), and lithium nitrate (LiNOs). Exemplary salts include: Lithium 12-hydroxy stearate, Lithium acetate, Lithium amide, Lithium aspartate, Lithium azide, Lithium borohydride, Lithium bromide, Lithium carbonate,Lithium chlorate, Lithium citrate, Lithium cyanide, Lithium diphenylphosphide, Lithium hexafluorogermanate, Lithium hexafluorophosphate, Lithium hypochlorite, Lithium hypofluorite, Lithium metaborate, Lithium methoxide, Lithium naphthalene, Lithium niobate, Lithium nitrite, Lithium oxalate, Lithium stearate, Lithium succinate, Lithium sulfate, Lithium sulfide, Lithium tantalate, Lithium tetrachloroaluminate, Lithium tetrafluoroborate, Lithium tetrakis(pentafluorophenyl)borate, and Lithium tungstate.

[0082] At step 210, an active material is added to the slurry. The precise chemical identity of the active material added can depend on the particular use of electrode 230. For example, if the electrode is a Li+selective material, the active material will be Li+selective. Exemplary lithium selective active materials that may be used include: LMO, MnCL, and lithium nickel cobalt manganese oxide (NCM or NMC). On the other hand, if the electrode is to be Li+rejective, its active material will be predominantly Li+rejective. Exemplary lithium rejective active materials that may be used include: Prussian Blue or “PB,” K2MnFe(CN)e, and K2NiFe(CN)e. Others include: Potassium Manganese Iron Cyanide (K2MnFe(CN)e), Potassium Iron Iron Cyanide (KFeFe(CN)e), Potassium Cobalt Iron Cyanide (K2CoFe(CN)e), Potassium Nickel Iron Cyanide (IGNiFefCNf,), Potassium Copper Iron Cyanide (IGCuFefCNf,), Potassium Zinc Iron Cyanide (K2ZnFe(CN)e), Potassium Yttrium Iron Cyanide (KYFe(CN)e), Potassium Lanthanum Iron Cyanide (KLaFe(CN)e), Potassium Cerium Iron Cyanide (KCeFe(CN)e), Potassium Praseodymium Iron Cyanide (KPrFe(CN)e), Potassium Holmium Iron Cyanide (KHoFe(CN)e), Potassium Manganese Iron Cyanide (KMnFe(CN)e), Potassium Cobalt Iron Cyanide (KCoFe(CN)e), Potassium Nickel Iron Cyanide (KNiFe(CN)e), Potassium Copper Iron Cyanide (KCuFe(CN)e), and Potassium Zinc Iron Cyanide (KZnFe(CN)e).

[0083] At step 212, the slurry is mixed to disperse its solid particles in the liquid comprising the solvent and binder. This dispersion can be enhanced by mechanical stirring, milling, or ultrasonic agitation, among other suitable techniques. Suitable means for mixing and stirring the slurry in this step include mechanical agitation (e.g., using blades, paddles, or impellers), using turbine mixers, anchor mixers (e.g., mixers with a scraping function), high-shear mixing, rotor-stator mixers, inline high-shear mixers, ultrasonic mixers, planetary mixers, propeller mixers, and static mixing.

[0084] In this step, as well as in any other slurry preparation steps (i.e., steps 204, 206, 208, and 210), other materials may be added to the slurry. For example, materials may be added to the slurry to increase the overall conductivity of material in electrode layers 233 and 234.Suitable materials for increasing electrode material conductivity include carbon in various forms, such as carbon black.

[0085] At step 214, the slurry may be applied to the frame or substrate 232 chosen in step 202. The slurry may be applied in any suitable manner. For example, the slurry may be poured or spread onto the substrate 232 using a casting technique. Common methods include blade casting, tape casting, or slot die coating. The slurry may be painted on and / or applied by a suitable applicator. Depending on slurry viscosity, it may be advantageous to provide a container for the slurry as it dries. The slurry may be applied to substantially all of the frame or substrate 232. It may be applied to a mere portion of the frame or substrate 232. During this step, the thickness of the slurry layer may be controlled by adjusting various parameters (e.g., a position of a mixing blade, slurry pouring rate, movement of substrate 232 as the slurry is applied, or the flow rate of the slurry, etc.). During application, liquid (e.g., water and / or organic solvent) may be applied to the slurry to maintain a level of wetness in the slurry.

[0086] At step 216, the slurry is dried to form the electrode layer 233 (and optionally 234) of electrode 230. More specifically, in this step, the wet slurry is dried to evaporate the solvent to leave behind a solid film of dispersed particles bound together by binder. Drying can be carried out at room temperature or in a controlled environment such as an oven. Preferably, drying is performed under conditions in which the humidity is well-controlled. As shown in FIG. 2B, this step may include the formation of two or more electrode layers 233 and 234. Layers 233 and 234 may be chemically and / or physically distinct from one other. It is to be understood that using method 200 to fabricate any suitable number of electrode layers 233 is within the scope of the present disclosure.

[0087] In particular, growing relatively thick electrodes 230 (e.g., on order of 1000 microns) requires a relatively well-controlled slurry drying process. The drying should be as uniform across the slurry as possible. Uniform drying can prevent cracking or warping of the drying slurry in the electrode layers 233 and 234. As discussed above, uniform drying can be assisted by choosing a binder with hydrophobicity / hydrophilicity properties that compliment humidity in the ambient, drying environment. Uniform drying of slurry / electrode layers 233 and 234 can also be assisted in this step by applying liquid (e.g., water and / or organic solvent) to the slurry to maintain a level of uniform dampness / dryness in the slurry during the drying process. The environment may be kept humid, for example, by misting liquid in the environment.

[0088] More generally, the drying rate for the slurry may be 2-24 hours depending on the thickness. Preferably, the drying rate may be 2 to 3 hours. The drying rate for the slurry should be kept as slow as possible to retard or eliminate defect formation in layers 233 and 234. The drying time will depend on the thickness of the electrode being fabricated, among other things. In one example, a slurry may be dried for 2-3 hours to create a 500 micron electrode. In another, it may be dried for 5-6 hours to create a 900 micron electrode. In still another, it may be dried for 12 hours to create a 1500 micron electrode. In yet another, it may be dried for 24 hours to create a an electrode having a thickness of 2000 microns.

[0089] One exemplary way of controlling the drying rate within the scope of method 200 is to control the temperature of electrode 230 and its environment during drying. Temperature may be controlled by applying hot air or other heated gases, infrared drying, microwave drying, and vacuum drying. This can include monitoring the slurry drying rate and adjusting the temperature accordingly. For example, when the drying rate is too slow, the temperature of the electrode 230 and its environment can be increased to accelerate solvent evaporation. Alternatively, when the drying rate is too fast, it may be slowed by decreasing the temperature of the electrode 230 and / or its environment. Lowering the temperature may decrease the drying rate by decreasing the rate of solvent evaporation. Temperature control may include imposing a gradual heating or cooling profile over time to avoid sudden changes in temperature. Sudden changes may cause rapid solvent evaporation that might cause cracking or warping. Temperature may be controlled by any suitable method including using an oven or a controlled heating device (e.g., resistive heating) or cooling (e.g., air conditioning and / or refrigeration).

[0090] In addition, controlling the humidity of the drying environment can significantly affect the drying rate. Lower humidity levels increase the drying rate by enhancing solvent evaporation. Dehumidifiers can be placed in the drying area to maintain low humidity levels. Utilizing controlled humidity chambers to maintain a consistent humidity level can improve electrode 230 formation. Increasing airflow over the surface of the slurry can enhance solvent evaporation by continuously removing solvent-saturated air and replacing it with drier air. This can be done by installing fans or blowers to create controlled airflow and to remove exhaust gas. Drying may be performed in an inert atmosphere (e.g., filled with argon gas) to control the drying rate and prevent chemical reactions (e.g., oxidation).

[0091] Step 216 may include post-drying processing. Post-drying processing may include densifying or compressing (i.e., “calendaring”) the dried slurry. Densification in this way can decrease the porosity of the electrode material and increase its electrical conductivity. Post-drying processing may further include sintering or curing, to achieve desired mechanical and physical properties.FIG. 2C shows an electrode 230a fabricated using method 200. Specifically, electrode 230a has a thickness of nearly 900 microns. As shown in FIG. 2C, electrode 230a is substantially free of detectable cracks or defects. Electrode 230a was cast on an aluminum foil contact 231. Electrode 230a has LMO as its active material. Binders PVDF / PVA / PEO and conductive carbon black were used to create its electrode layer 233. This yielded a slurry drying rate of 5-6 hours in an environment having a temperature of 40° C and a relative humidity of 90%.

[0092] FIG. 2D shows the measured performance of electrode 230a measured via electrochemical impedance spectroscopy (EIS). FIG. 2F shows a schematic of the process to fabricate electrode 230a from slurry according to steps in method 200. More specifically, FIG. 2D shows the real and imaginary components of the resistance of electrode 230a when tested in a brine containing 6% LiCl. The plots show that electrode 230a has an equivalent series contact resistance of - 0.2 Q cm2. For reading the EIS curve, the most important point is the intercept at X-axis. This curve shows that the resistance or resistivity is 0.5 ohm / cm2. FIG. 2E shows porosity of the same sample measured via Scanning Electron Microscopy (SEM).

[0093] The results in FIGs. 2C and 2D imply and the image in FIG. 2E shows a suitable porosity for electrode 230a. More specifically, the conductivity implied by the results shown in FIG. 2D imply a porosity of electrode 230a between 30 and 70%. This is particularly important since there is a tradeoff between the porosity of electrode 230a and its conductivity. More specifically, for electrode 230a to function efficiently, it would be best for it to have a resistivity not greater than 1 ohm / cm2with an optimal porosity of 45-55%. These results show how achieving these thresholds leads to proper functioning of electrode 230a in cell 100. The porosity was measured using a porosimeter.Current Collector

[0094] Cell 100 further includes porous current collectors 150. As shown in FIG. 1 A, 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.

[0095] 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 other materials 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.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

[0096] 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

[0097] 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 the number of cycles necessary to remove Lit It increases overall Li+selectivity and decreases operating cost / pressure.

[0098] FIG. 2G is a flowchart showing method 250 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 250. Although FIG. 2G shows a sequence of steps, it is to be understood that this presentation is not limiting. When appropriate, steps shown in flowchart 250 may be taken in a different order in accordance with this disclosure.

[0099] Before the implementation of method 250, 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).

[0100] In step 252 of method 250, 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. 3 A.

[0101] At step 254, 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. 3 A, 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+.

[0102] 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.

[0103] In step 256 (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 suitablesolution 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%.

[0104] As shown in FIGs. 3B and 3C, Fl is fed to channel C2 for further Li+extraction. That is, in step 256, brine Fl transitions from channel Cl to channel C2. Since cell 100 is being operated as SR in method 250, 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 256 can raise the Li+fraction (where “Li+fraction” means the proportion of cations that are Li+) to around 99%.

[0105] In step 258 (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 258 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 258 and is ready for further processing in step 259.

[0106] FIG. 3D shows an optional post-treatment step for channel C2 after the performance of method 250. 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

[0107] 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 SSRreactor 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] In step 410 (FIG. 5D), Li+sequestered by channel C2 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.

[0114] 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.

[0115] 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

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] At step 612, method 600 terminates by providing Li+-enhanced brine BE for further processing outside of cell 100.

[0122] 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 representativevalues 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. 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 electrode for separating lithium ions from a solution, the electrode comprising: a contact layer; a carbon layer disposed on the contact layer; a lithium ion interactive layer disposed on the carbon layer, wherein the lithium ion interactive layer comprises a slurry cast material; wherein the lithium ion interactive layer has a thickness greater than 500 microns; and wherein the lithium ion interactive layer is substantially free of cracks.

2. The electrode of claim 1, wherein the lithium ion interactive layer has a thickness of at least 700 microns.

3. The electrode of claim 2, wherein the lithium ion interactive layer has a thickness of at least 1,000 microns.

4. The electrode of claim 3, wherein the lithium ion interactive layer has a thickness of at least 1,500 microns.

5. The electrode of claim 4, wherein the lithium ion interactive layer has a thickness of at least 2,000 microns.

6. The electrode of claim 1, wherein the lithium ion interactive layer comprises a lithium ion selective material.

7. The electrode of claim 6, wherein the lithium ion selective material comprises at least one of lithium manganese oxide (LMO), MnCh, and lithium nickel cobalt manganese oxide.

8. The electrode of claim 6, wherein the lithium ion selective material comprises primarily LMO.

9. The electrode of claim 1, wherein the lithium ion interactive layer comprises a lithium ion rejective material.

10. The electrode of claim 9, wherein the lithium ion rejective material comprises at least one of K2MnFe(CN)6, and K2NiFe(CN)6.

11. The electrode of claim 9, wherein the lithium ion rejective material comprises primarily Ko.i-o.2FeFe(CN)6.

12. The electrode of claim 1 having a contact resistivity of 0.7 Q cm2or less.

13. The electrode of claim 12 having a contact resistivity of 0.5 Q cm2or less.

14. The electrode of claim 13 having a contact resistivity of 0.3 Q cm2or less.

15. The electrode of claim 14 having a contact resistivity of 0.2 Q cm2or less.

16. An apparatus for separating lithium ions from a solution, the apparatus comprising: a first lithium selective reactor comprising: a lithium selective electrode comprising the electrode of claim 1 and 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.

17. The apparatus of claim 16, 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.

18. The apparatus of claim 17, 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.

19. The apparatus of claim 16, further comprising: a second lithium selective reactor comprising: a lithium selective electrode that absorbs lithium ions; a separator; and a counter electrode.

20. The apparatus of claim 19, 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.

21. The apparatus of claim 20, 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.

22. The apparatus of claim 21, wherein the recovering lithium ions comprises flowing a solution with a relatively low lithium concentration over at least one of the lithiumselective electrode of the first lithium selective reactor and the lithium selective electrode of the second lithium selective reactor.

23. The apparatus of claim 16, 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.

24. The apparatus of claim 16, wherein the solution is a brine.

25. The apparatus of claim 24, wherein a brine output by the apparatus has a Li+fraction of more than 90%.

26. A method of fabricating an electrode for separating lithium ions from a solution, the method comprising: forming a slurry comprising: a binder; an organic solvent; and an active material; applying the slurry to a surface while the slurry is wet; forming an electrode layer by drying the applied slurry at a substantially uniform rate, wherein the formed electrode layer: has a thickness of 500 microns or more; and has a contact resistivity of 0.7 cm2or less.

27. The method of claim 26, wherein drying the applied slurry at a substantially uniform rate comprises controlling a dampness in the slurry.

28. The method of claim 27, wherein controlling a dampness in the slurry comprises adjusting a composition of the binder.

29. The method of claim 28, wherein adjusting the composition of the binder comprises adjusting a hydrophobicity of the binder.

30. The method of claim 29, wherein adjusting the hydrophobicity of the binder comprises altering a ratio of hydrophobic components of the binder to hydrophilic components of the binder.

31. The method of claim 30, wherein the binder comprises at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyurethane (PU), polyethylene (PE), an acrylic resin, an epoxy resin, and an alkyd resin.

32. The method of claim 31, wherein the binder comprises a combination including acrylic resin and PMMA.

33. The method of claim 26, wherein drying the applied slurry at a substantially uniform rate comprises controlling a humidity over an outer surface of the slurry.

34. The method of claim 33, wherein controlling the humidity comprises maintaining the humidity at a level consistent with a level of dampness throughout the slurry.

35. The method of claim 33, wherein controlling the humidity comprises using a humidifier.

36. The method of claim 33, wherein controlling the humidity comprises using an air conditioner.

37. The method of claim 33, wherein controlling the humidity comprises applying liquid to an environment of the slurry.

38. The method of claim 37, wherein applying liquid comprises misting the liquid.

39. The method of claim 37, wherein the liquid comprises at least one of water and the organic solvent.

40. The method of claim 33, wherein controlling the humidity comprises at least one of venting gas in an environment of the slurry and providing dry gas to the environment of the slurry.

41. The method of claim 33, wherein drying the applied slurry at a substantially uniform rate comprises maintaining a temperature of the slurry.

42. The method of claim 41, wherein maintaining the temperature comprises at least one of heating the slurry and heating an environment of the slurry.

43. The method of claim 41, wherein maintaining the temperature comprises at least one of cooling the slurry and cooling an environment of the slurry.

44. The method of claim 41, wherein maintaining the temperature comprises venting an environment of the slurry.

45. The method of claim 41, wherein maintaining the temperature comprises at least one of resistive heating, oven heating, and providing heated gas to an environment of the slurry.

46. The method of claim 26, wherein drying the applied slurry at a substantially uniform rate comprises drying the slurry for 24 hours or more.

47. The method of claim 26, wherein drying the applied slurry at a substantially uniform rate comprises drying the slurry at the rate for 12 hours or more.

48. The method of claim 26, wherein drying the applied slurry at a substantially uniform rate comprises drying the slurry for 2 hours or more.

49. The method of claim 26, wherein the surface comprises carbon.

50. The method of claim 49, wherein the carbon comprises carbon cloth.

51. The method of claim 26, wherein the formed electrode layer has a thickness of at least one of 700 microns or more, 1,000 microns or more, 1,500 microns or more, 1,700 microns or more, and 2,000 microns or more.

52. The method of claim 26, wherein the formed electrode layer has a contact resistivity that is at least one of 0.5 fi cm2or less, 0.3 Q cm2or less, and 0.2 Q cm2or less.

53. The method of claim 26, wherein the organic solvent comprises at least one of n-methyl- 2-pyrrolidone (NMP), acetone, methyl ethyl ketone (MEK), acetonitrile, cyclohexanone, butyronitrile, ethanol, methanol, and dimethyl sulfoxide (DMSO).

54. The method of claim 26, wherein the active material comprises at least one of lithium manganese oxide (LMO), MnO2, and lithium nickel cobalt manganese oxide, Ko.i- o.2FeFe(CN)6K2MnFe(CN)6, and K2NiFe(CN)6.

55. The method of claim 33, wherein the formed electrode layer has a porosity of 45-55% or more.

56. The electrode of claim 1 having a porosity of 45-55% or more.

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