WO2025106968A1

WO2025106968A1 - Selective recovery of li from brine solutions & coversion to lioh in a single electrochemical cell

Info

Publication number: WO2025106968A1
Application number: PCT/US2024/056377
Authority: WO
Inventors: Christopher ARGES; Feifei SHI; Tanmay Dinesh KULKARNI; Hanrui ZHANG; Aliya Muhammad I AL DHAMEN
Original assignee: Penn State Research Foundation
Current assignee: Penn State Research Foundation
Priority date: 2023-11-17
Filing date: 2024-11-18
Publication date: 2025-05-22
Anticipated expiration: 2026-05-17

Abstract

Described herein is a device and method for capacitive deionization including a bipolar membrane. The bipolar membrane capacitive deionization is an electrochemical separation device for the removal and recovery of critical elements like lithium. In particular, the device removes lithium ions selectively from briny fluid. After capturing the lithium ions from a fluid, the lithium ions are recovered in the form of lithium hydroxide. The bipolar membrane capacitive deionization unit utilizing selective lithium electrodes includes a bipolar membrane, a carbon electrode, a lithium iron phosphate (LFP) coated carbon electrode, and current collectors operating in alternate charging and discharging cycle.

Description

Attorney Docket No.11196-113WO1 SELECTIVE RECOVERY OF LI FROM BRINE SOLUTIONS & COVERSION TO LIOH IN A SINGLE ELECTROCHEMICAL CELL STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH [0001] This invention was made with government support under Grant No. DE-SC0022304 awarded by the Department of Energy. The government has certain rights in the invention CROSS-REFERENCE TO RELATED APPLICATIONS [0002] This application is a continuation of U.S. Provisional Patent Application No. 63/600,167, filed November 17, 2023, which is incorporated herein by reference in its entirety. BACKGROUND [0003] High-purity lithium carbonate (Li2CO3) and lithium hydroxide (LiOH) are cornerstone precursors in the production of lithium-ion batteries (LiBs). The lithium cation (Li⁺) for these LiBs is primarily sourced from salt-lake brines and geothermal brines where the Li⁺ from these solutions is extracted as lithium chloride (LiCl) and then converted to either Li2CO3 or LiOH.^1-3 In recent years, LiB producers, especially those using nickel- cobalt-manganese (NCM) cathodes that provide greater energy density,^4-7 favor LiOH as a precursor over Li2CO3 because LiOH has a higher solubility in water, greater lithium content in the anhydride form, and enables CO₂-free oxidizing conditions and lower decomposition temperatures during calcination/ sintering processes.^8-10 [0004] Solar evaporation is a widely deployed method for lithium extraction. However, it suffers from major drawbacks such as lengthy processing times (1 to 2 years) and high water demand (100-800 m³/ton of lithium carbonate equivalent).^1,11 However, the landscape of lithium extraction has evolved with recent strides in Direct Lithium Extraction (DLE) technologies to mitigate the negative externalities of conventional processes. Innovations in DLE span diverse platforms, encompassing electrochemical, adsorptive, absorptive, and pressure-driven methods, expediting lithium removal and recovery processes.^1,3,12-14 Notably, electrochemical platforms have received significant attention in recent years over non- electrochemical techniques, leveraging their precision in targeting specific ionic species, even at low concentrations (a few ppm).^1,3 Within the realm of electrochemical DLE, two Attorney Docket No.11196-113WO1 prominent separation platforms have emerged: i) a capacitive deionization (CDI)-focused route employing intercalating electrodes and ii) a membrane-driven electrodialysis (ED) route utilizing monovalent selective cation-exchange membranes (CEMs). Each philosophy has its inherent advantages and drawbacks. Regarding CDI, its ion-selective intercalating electrodes excel at isolating Li⁺ from a spectrum of competing ions – e.g., sodium (Na⁺), magnesium (Mg²⁺), potassium (K⁺), and calcium (Ca²⁺).^1,15-17 However, it cannot convert the separated lithium salt to LiOH and needs to be coupled with a bipolar membrane electrodialysis (BPM- ED), electrolysis, or ion-exchange to alkalize the lithium salt product (i.e., Li₂CO₃ and/or LiCl) to LiOH.¹⁸ In the membrane-driven pathway, an ED or BPM-ED platform incorporating monovalent selective cation exchange membranes (CEMs) can separate Li+ from the divalent competing ions (Mg²⁺ and Ca²⁺) while also converting lithium salts to LiOH in the case of BPM-ED.^2,19-21 The selective membranes (CEMs) typically consist of positively charged polyethyleneimine (PEI) layers covalently tethered to the membrane (CEM) that repeal divalent ions while allowing for the passage of monovalent ions like Li⁺. However, the surface-modified CEMs are unable to differentiate between Li⁺ and other monovalent ions (Na⁺ and K⁺).^1,19,22 An ED-based separation platform is therefore paired with an ion-exchange (IX) adsorption column downstream for the removal of monovalent cations (Na⁺ and K⁺) and further enrichment of lithium salts.^1,23 SUMMARY [0005] Described herein is a device and method for capacitive deionization including a bipolar membrane. The bipolar membrane capacitive deionization is an electrochemical separation device for the removal and recovery of critical elements like lithium. In particular, this technology removes lithium ions selectively from sodium chloride and lithium chloride salt mixtures in water. After capturing the lithium ions from a processing fluid, the lithium ions are recovered in the form of lithium hydroxide – which is the preferable lithium salt type for making lithium-ion battery electrodes. The bipolar membrane capacitive deionization unit utilizing selective lithium electrodes consists of a bipolar membrane, a carbon electrode, a lithium iron phosphate (LFP) coated carbon electrode, and current collectors. This device operates in alternate charging and discharging cycle. [0006] In some aspects, described herein is a device for selective ion separation, the device including: a first electrode including an intercalation material layer configured to reversibly captures and releases a cation through cyclic intercalation/deintercalation, wherein the Attorney Docket No.11196-113WO1 intercalation material layer is disposed on a surface of the first electrode; a second electrode; and a bipolar membrane, wherein the bipolar membrane is disposed on a surface of the second electrode. [0007] In some aspects, the bipolar membrane includes a cation exchange layer, an anion exchange layer, and a catalyst disposed between the anion exchange layer and the cation exchange layer, wherein the catalyst includes water dissociation catalyst and/or a hydroxide ion-proton recombination catalyst. [0008] In some aspects, the catalyst includes tin oxide, titanium oxide, silica, platinum group metals, graphitic carbon, activated carbon, or combinations thereof. [0009] In some aspects, the anion exchange layer is disposed on the surface of the second electrode. [0010] In some aspects, the device further includes a cation exchange membrane, wherein the cation exchange membrane is disposed on the surface of the first electrode. [0011] In some aspects, the cation exchange membrane is a selective cation exchange membrane. [0012] In some aspects, the cation includes one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. In some aspects, the cation includes lithium. [0013] In some aspects, the intercalation material layer includes one of LixFePO4 (0<x<1), Li_xMnPO₄ (0≤x<1), Li_xFe_yMn_1-yPO₄, λ-MnO₂, Li_xMnO₂, Li_xNi_0.6Co_0.2Mn_0.2O₂(0≤x<1), LixNi0.8Co0.1Mn0.1O2(0≤x<1), LixNi0.5Co0.2Mn0.3O2(0≤x<1), LixNi0.33Co0.33Mn0.33O2(0≤x<1), Li_xNi_0.6Co_0.2Al_0.2O₂(0≤x<1), Li_xNi_0.8Co_0.1Al_0.1O₂(0≤x<1), Li_xNi_0.5Co_0.2Al_0.3O₂(0≤x<1), LixNi0.33Co0.33Al0.33O2(0≤x<1), LixNiO2(0≤x<1), LixCoO2, LiNixMn2-xO4 (0 < x < 0.5), LiNixCoyMnzO2 (x+y+z=1), LiNixCoyAlzO2(0≤x<1), Li3V2(PO4)3, V2O5, H2TiO3, Li2TiO3, TiO2, Lithium titanate (Li4Ti5O12), Prussian blue analogues, NaxFePO4, Na3V2(PO4)3, NaNixCoyMnzO2, NaNixCoyAlzO2, NaxNiO2(0≤x<1), NaxCoO2(0≤x<1), NaV2O5, K_xFePO₄(0≤x<1), K₃V₂(PO₄)₃, KNi_xCo_yMn_zO₂ (x+y+z=1), KNi_xCo_yAl_zO₂, K_xNiO₂(0≤x<1), KxCoO2(0≤x<1), or other layered metal oxides and polyanionic compounds. In some aspects, the intercalation material includes a modified intercalation material, wherein the modification includes one or more of carbon/N-doped carbon/graphene/graphene oxide/reduced-graphene oxide coating, AlPO₄/Al₂O₃/CeO₂ coating, metal elemental Al, Fe, Cr, Ti, Ni doped. In some aspects, the intercalation material layer includes LixFePO4 (0<x<1). Attorney Docket No.11196-113WO1 [0014] In some aspects, the intercalation material layer further includes a polymer material, wherein the polymer material forms a composite membrane-electrode structure. In some aspects, the intercalation material layer includes an open lattice structure. [0015] In some aspects, the intercalation material layer exhibits an intercalation capacity of at least 30 mg g^-1 of the intercalation material. [0016] In some aspects, the bipolar membrane is configured to operate under reverse bias and forward bias in alternating cycles. [0017] In some aspects, the first electrode further includes a current collector. [0018] In some aspects, the second electrode includes carbon and a current collector. [0019] In some aspects, the device is configured to receive an aqueous processing fluid. [0020] In some aspects, the aqueous processing fluid includes one or more of the cation and one or more salts. In some aspects, the aqueous processing fluid includes deionized water or a hydroxide salt including the cation. [0021] In some aspects, a pH of the aqueous processing fluid is lowered relative to the received aqueous processing fluid in situ upon a reverse voltage bias. In some aspects, a pH of the aqueous processing fluid is raised relative to the received aqueous processing fluid in situ upon a forward voltage bias. [0022] In some aspects, the cation from the aqueous processing fluid is selectively intercalated by the intercalation material layer upon a reverse voltage bias. In some aspects, the cation is released by deintercalation and forms a hydroxide salt upon a forward voltage bias. [0023] In some aspects, the device is a membrane capacitive deionization device or a capacitive deionization device. [0024] In some aspects, described herein is a system including the device. In some aspects, the system further includes a voltage source. In some aspects, the system further includes a pH monitor, a thermometer, a conductivity monitor, a pressure monitor, a flow monitor, and any other monitoring device. In some aspects, the system further includes a control system. [0025] In some aspects, described herein is a method for using the device. The method includes applying a reverse voltage bias to the device, wherein a first electrode of the device selectively intercalates the cation; applying a forward voltage bias to the device, wherein the Attorney Docket No.11196-113WO1 cation deintercalates from the first electrode and forms a hydroxide salt; collecting an effluent including the hydroxide salt. [0026] In some aspects, the method is repeated using any proportion of the aqueous processing fluid and the effluent. [0027] In some aspects, providing the aqueous processing fluid includes flowing the aqueous processing fluid continuously through a spacer channel. [0028] In some aspects, the cation includes one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. In some aspects, the cation includes lithium. [0029] Additional advantages will be set forth in part in the description which follows or may be learned by practice. The advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS [0030] Figs.1A and 1B show schematics of the device of a first embodiment (Fig.1A) and a second embodiment (Fig.1B). [0031] Figs.2A-2D show (Fig.2A) bipolar membrane capacitive deionization (BPM-CDI) cell configuration A (acidic pH in the spacer channel during the charge cycle); (Fig.2B) configuration B (alkaline/basic pH in the spacer channel during the charge cycle); (Fig.2C) the BPM-CDI cell (configuration A) with delithiated LFP coated electrode (negative electrode) for the targeted removal of Li⁺ ions from brine mixtures in the charge cycle; and (Fig.2D) discharge cycle in the BPM-CDI cell (configuration A) for the release of Li⁺ ions in the LiOH form and concentration through recirculation setup across multiple discharge cycles. [0032] Figs.3A-3D show (Fig.3A) steady-state pH of the effluent stream as a function of different cell voltage values in BPM-CDI configurations A and B (refer to the schematics shown in Fig.2A and Fig.2B, respectively); (Fig.3B) process stream pH effluent as a function of time in configuration A across eight alternating charge cycles to 2 V and discharge cycles to -0.5 V; (Fig.23C) process stream pH effluent as a function of time with configuration B across eight alternating charge to 2 V and discharge cycles to -0.5 V; and Attorney Docket No.11196-113WO1 (Fig.3D) comparison of the process stream pH effluent as a function of time in configuration A with a FUMASEP BPM (black curve) and a NEOSEPTA BPM (red curve) across eight charge cycles to 2 V and discharge cycles to -0.5 V. These experiments were performed with a 1000 ppm NaCl feed processed through the cell in a continuous flow mode (20 ml/min). [0033] Figs.4A-4F show (Fig.4A) H-cell setup to probe ion crossover/leakage across the BPM where the two chambers are separated by a FUMASEP BPM; (Fig.4B) Predicted ion movement during the discharge cycle in config. A of the BPM-CDI device; (Fig.4C) pH variation in the anode and cathode chambers of the H-cell after applying 0.5 V across intervals of 2 minutes; (Fig.4D) H-cell set up to probe the electroneutrality in the chambers and its subsequent effect on the pH of the chamber; (Fig.5E) a simplified illustration of the type of ions present at the start of the discharge cycle in configuration A of the BPM-CDI device; (Fig.4F) pH of the supporting electrolyte in the anode chamber (1000 ppm NaCl) and cathode chamber (100 ppm NaCl) in the H-cell versus time after applying 1 V across the BPM. [0034] Figs.5A-5D show Li⁺ separation results with BPM-CDI featuring a delithiated LFP electrode: (Fig.5A) pH profile during Li⁺ capture from brine solution (25 ppm each of Li⁺ and Na⁺), (Fig.5B) the removal of Li⁺ ions from mixtures with Na⁺ during the charge cycle, (Fig.5C) the removal of Li⁺ ions from mixtures with Mg²⁺ during the charge cycle (negative electrode), and (Fig.5D) Li⁺ concentration in the recirculated capture solution during discharge cycles. [0035] Figs.6A-6B show (Fig.6A) recirculated capture solution concentration across multiple discharge cycles, and (Fig.6B) SEM image of the negative electrode used in the synthetic brine experiments. [0036] Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. DETAILED DESCRIPTION [0037] The present invention can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following Attorney Docket No.11196-113WO1 description. However, before the present articles, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific or exemplary aspects of articles, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. [0038] The following description of the invention is provided as an enabling teaching of the invention in its best, currently known aspect. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those of ordinary skill in the pertinent art will recognize that many modifications and adaptations to the present invention are possible and may even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is again provided as illustrative of the principles of the present invention and not in limitation thereof. DEFINITIONS [0039] As used herein, the terms "optional" or "optionally" mean that the subsequently described event or circumstance can or cannot occur and that the description includes instances where said event or circumstance occurs and instances where it does not. [0040] It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate aspects, can also be provided in combination in a single aspect. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single aspect, can also be provided separately or in any suitable sub-combination. [0041] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a “device” includes aspects having two or more such devices unless the context clearly indicates otherwise. [0042] It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. As used in the specification and in the claims, the term “comprising” can include the aspects “consisting of” and “consisting essentially of.” Unless defined otherwise, all technical and scientific terms Attorney Docket No.11196-113WO1 used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In this specification and in the claims which follow, reference will be made to a number of terms that shall be defined herein. [0043] For the terms "for example" and "such as," and grammatical equivalences thereof, the phrase "and without limitation" is understood to follow unless explicitly stated otherwise. It is further understood that these phrases are used for explanatory purposes only. It is further understood that the term “exemplary,” as used herein, means “an example of” and is not intended to convey an indication of a preferred or ideal aspect. [0044] The expressions "ambient temperature" and "room temperature" as used herein are understood in the art and refer generally to a temperature from about 20 °C to about 35 °C. [0045] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values, inclusive of the recited values, may be used. Further, ranges can be expressed herein as from “about” one particular value and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. [0046] Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint. Unless stated otherwise, the term “about” means within 5% (e.g., within 2% or 1%) of the particular value modified by the term “about.” [0047] All disclosed values also include values that fall within ±10% variation from the disclosed value unless otherwise indicated or inferred. In other words, if a range of 1 to 10 is disclosed, then a range of about 1 to about 10 is disclosed. In such aspects, it is understood that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, amounts, sizes, formulations, parameters, and other quantities and characteristics include both exact values but also approximate, larger or smaller values as desired, reflecting tolerances, conversion Attorney Docket No.11196-113WO1 factors, rounding, measurement error, and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstances, the value that provides equivalent results or effects cannot be reasonably determined. In general, an amount, size, formulation, parameter, or other quantity or characteristic is "about," "approximate," or "at or about," whether or not expressly stated to be such. Where "about," "approximate," or "at or about" is used before a quantitative value, the parameter also includes the specific quantitative value itself unless expressly stated otherwise. [0048] As used herein, the term or phrase “effective,” “effective amount,” or “conditions effective to” refers to such amount or condition that is capable of performing the function or property for which an effective amount or condition is expressed. As will be pointed out below, the exact amount or particular condition required will vary from one aspect to another, depending on recognized variables such as the materials employed and the processing conditions observed. Thus, it is not always possible to specify an exact “effective amount” or “condition effective to.” However, it should be understood that an appropriate, effective amount will be readily determined by one of ordinary skill in the art. [0049] When a range is expressed, a further aspect includes from the one particular value and to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g., the phrase "x to y" includes the range from 'x' to 'y' as well as the range greater than 'x' and less than 'y'. The range can also be expressed as an upper limit, e.g., 'x, y, z, or less' and should be interpreted to include the specific ranges of ‘x,’ ‘y,’ ‘z,’ 'about x,' 'about y,' and 'about z' as well as the ranges of 'less than x,' 'less than y, or 'less than z,' or 'less than about x,' 'less than about y, and 'less than about z.' Likewise, the phrase ' x, y, z, or greater' should be interpreted to include the specific ranges of ‘x,’ ‘y,’ ‘z,’ 'about x,' 'about y,' and 'about z' as well as the ranges of 'greater than x,' greater than y,' 'greater than z,' or 'greater than about x,' greater than about y,' 'greater than about z.' In addition, the phrase " 'x' to 'y'," where 'x' and 'y' are numerical values, also includes "about 'x' to about 'y'." [0050] Such a range format is used for convenience and brevity and, thus, should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of " 0.1% to 5%" should be interpreted to include not only the explicitly recited values of 0.1% to 5% but also include individual values (e.g., 1%, 2%, 3%, and 4%) Attorney Docket No.11196-113WO1 and the sub-ranges (e.g., 0.5% to 1.1%; 5% to 2.4%; 0.5% to 3.2%, and 0.5% to 4.4%, and other possible sub-ranges) within the indicated range. [0051] Throughout this disclosure, various aspects of the invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, a description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, 6 and any whole and partial increments therebetween. This applies regardless of the breadth of the range. [0052] In still further aspects, when the specific values are disclosed between two end values, it is understood that these end values can also be included. [0053] In still further aspects, when the range is given, and exemplary values are provided, it is understood that any ranges can be formed between any exemplary values within the broadest range. For example, if individual numbers 1, 2, 3, 4, 5, 6, 7, etc. are disclosed, then the ranges 1-7, 2-7, 3-7, 4-7, 5-7, 6-7, 1-6, 1-5, 1-4, 1-3, 1-2, 2-6, 2-5, etc. are also disclosed. [0054] References in the specification and concluding claims to parts by weight of a particular element or component in a composition denote the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed. Thus, in a mixture containing 2 parts by weight of component X and 5 parts by weight, components Y, X, and Y are present at a weight ratio of 2:5 and are present in such a ratio regardless of whether additional components are contained in the mixture. [0055] A weight percent (wt.%) of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. A mol percent (mol%) of a component, unless specifically stated to the contrary, is based on the total moles of the components present in the formulation or composition in which the recited component is included. [0056] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or Attorney Docket No.11196-113WO1 intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements or layers should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," "on" versus "directly on"). [0057] As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. [0058] It will be understood that the terms "first," "second," etc., may be used herein to describe various elements, components, regions, layers, and/or sections. These elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. [0059] As used herein, the term "substantially" means that the subsequently described event or circumstance completely occurs or that the subsequently described event or circumstance generally, typically, or approximately occurs. [0060] Still further, the term “substantially” can, in some aspects, refer to at least about 80 %, at least about 85 %, at least about 90 %, at least about 91 %, at least about 92 %, at least about 93 %, at least about 94 %, at least about 95 %, at least about 96 %, at least about 97 %, at least about 98 %, at least about 99 %, or about 100 % of the stated property, component, composition, or other condition for which substantially is used to characterize or otherwise quantify an amount. [0061] In other aspects, as used herein, the term “substantially free,” when used in the context of a composition or component of a composition that is substantially absent, is intended to refer to an amount that is then about 1 % by weight, e.g., less than about 0.5 % by weight, less than about 0.1 % by weight, less than about 0.05 % by weight, or less than about 0.01 % by weight of the stated material, based on the total weight of the composition. [0062] As used herein, the term “intercalation material” is intended to encompass a material having a regular structure that, when an ion is adsorbed, substantially retains the structure. As used herein, a regular structure is intended to include crystalline structures, lattice structures, and other regular structures having vacancies therein. It should also be Attorney Docket No.11196-113WO1 understood that an intercalation material is intended to encompass materials capable of intercalation and de-intercalation that retain, substantially, the starting structure. [0063] As used herein, the term “active surface” is intended to encompass a surface of an electrode participating in an electrochemical reaction with the working ion(s). [0064] As used herein, the term “forward bias” in intended to mean an applied bias that allows current to flow easily in one direction, which is well known in the art. Forward bias may be accomplished when the positive terminal of the voltage supply is connected to the anode, and the negative terminal is connected to the cathode. [0065] As used herein, the term “reverse bias” is intended to mean an applied bias that blocks current flow or causes it to flow in the opposite direction, which is well known in the art. Reverse bias may be accomplished when the positive terminal of the voltage supply is connected to the cathode, and the negative terminal is connected to the anode. [0066] While aspects of the present invention can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of ordinary skill in the art will understand that each aspect of the present invention can be described and claimed in any statutory class. Unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that an order be inferred in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to the arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification. [0067] The present invention may be understood more readily by reference to the following detailed description of various aspects of the invention and the examples included therein and to the Figures and their previous and following description. DEVICE [0068] Referring generally to the figures, a device for selective ion separation is shown, according to various implementations. [0069] Referring now to Fig.1A, a first embodiment of the device is shown. In some aspects, the device 100a includes a first electrode 110, a second electrode 120, and a bipolar Attorney Docket No.11196-113WO1 membrane 130. The first electrode 110 includes a current collector 112 and an intercalation material layer 114. The second electrode 120 includes a current collector and a carbon layer. In some aspects, the carbon layer includes a conductive carbon. The bipolar membrane 130 includes a cation exchange layer 132 and an anion exchange layer 134. In some aspects, the second electrode 120 is in contact with the bipolar membrane 130. In still further aspects, the second electrode 120 is in contact with the anode exchange layer 132 of the bipolar membrane 130. In some aspects, the current collector 112 is in contact with the intercalation material layer 114. In some aspects, the first electrode 110 is separated by a spacer channel 142 from the bipolar membrane 130. In some aspects, the bipolar membrane 130 further comprises a catalyst, wherein the catalyst is a water dissociation catalyst and/or a hydroxide ion-proton recombination catalyst. In some aspects, the catalyst is disposed between the cation exchange layer 132 and the anion exchange layer 134. [0070] Referring now to Fig.1B, a second embodiment of the device is shown. In some aspects, the device 100b includes a first electrode 110, a second electrode 120, a bipolar membrane 130, and a cation exchange membrane 150. The first electrode 110 includes a current collector 112 and an intercalation material layer 114. In some aspects, the cation exchange membrane 150 is a selective cation exchange membrane. The second electrode 120 includes a current collector and a carbon layer. In some aspects, the carbon layer includes a conductive carbon. The bipolar membrane 130 includes a cation exchange layer 132 and an anion exchange layer 134. In some aspects, the second electrode 120 is in contact with the bipolar membrane 130. In still further aspects, the second electrode 120 is in contact with the anode exchange layer 132 of the bipolar membrane 130. In some aspects, the first electrode 110 is in contact with the cation exchange membrane 150. In further aspects, the current collector 112 is in contact with the intercalation material layer 114. In still further aspects, the intercalation material layer 114 is in contact with the cation exchange membrane 150. In some aspects, the cation exchange membrane 150 is separated by a distance 142 from the bipolar membrane 130. In some aspects, the device 100a (100b) is configured to receive a processing fluid at a first end 140, to allow the processing fluid to flow within the spacer channel 142 between the first electrode 110 (cation exchange membrane 150) and the bipolar membrane 130, and to output an effluent at a second end 144. [0071] In some aspects, processing fluid is an aqueous processing fluid. In some aspects, the aqueous processing fluid includes a cation and one or more salts. In some aspects, the Attorney Docket No.11196-113WO1 aqueous processing fluid includes deionized water, a hydroxide salt, the effluent, or combinations thereof. [0072] In some aspects, the cation includes one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. In some aspects, the cation includes lithium. [0073] In some aspects, the intercalation material layer intercalates the cation, preferably, the intercalation material layer selectively intercalates the cation. For example, when the aqueous processing fluid includes the cation and one or more salts, the intercalation material layer selectively intercalates the cation. [0074] In some aspects, the intercalation material layer includes a material having an open lattice structure. In some aspects the intercalation material layer includes one of LixFePO4 (0<x<1), LixMnPO4 (0≤x<1), LixFeyMn1-yPO4, λ-MnO2, LixMnO2, Li_xNi_0.6Co_0.2Mn_0.2O₂(0≤x<1), Li_xNi_0.8Co_0.1Mn_0.1O₂(0≤x<1), Li_xNi_0.5Co_0.2Mn_0.3O₂(0≤x<1), LixNi0.33Co0.33Mn0.33O2(0≤x<1), LixNi0.6Co0.2Al0.2O2(0≤x<1), LixNi0.8Co0.1Al0.1O2(0≤x<1), Li_xNi_0.5Co_0.2Al_0.3O₂(0≤x<1), Li_xNi_0.33Co_0.33Al_0.33O₂(0≤x<1), Li_xNiO₂(0≤x<1), Li_xCoO₂, LiNixMn2-xO4 (0 < x < 0.5), LiNixCoyMnzO2 (x+y+z=1), LiNixCoyAlzO2(0≤x<1), Li₃V₂(PO₄)₃, V₂O₅, H₂TiO₃, Li₂TiO₃, TiO₂, Lithium titanate (Li₄Ti₅O₁₂), Prussian blue analogues, NaxFePO4, Na3V2(PO4)3, NaNixCoyMnzO2, NaNixCoyAlzO2, NaxNiO2(0≤x<1), Na_xCoO₂(0≤x<1), NaV₂O₅, K_xFePO₄(0≤x<1), K₃V₂(PO₄)₃, KNi_xCo_yMn_zO₂ (x+y+z=1), KNixCoyAlzO2, KxNiO2(0≤x<1), KxCoO2(0≤x<1), or other layered metal oxides and polyanionic compounds. [0075] In further aspects, the intercalation material is modified, wherein modifications include one or more of carbon/N-doped carbon/graphene/graphene oxide/reduced-graphene oxide coating, AlPO₄/Al₂O₃/CeO₂ coating, metal elemental Al, Fe, Cr, Ti, Ni doped. In still further aspects, the intercalation material further includes a polymer material, wherein the polymer material forms a hybrid thereof. In exemplary aspects, the intercalation material layer includes LixFePO4 (0<x<1). [0076] In some aspects, the cation intercalates into the intercalation material and forms, for example LiFe_xMn_yPO₄/FePO₄ (x+y=1), LiMn₂O₄/λ-MnO₂, LiNi_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂ (x+y+z =1), LiNixCoyAlzO2/NixCoyAlzO2 (x+y+z =1)/NixCoyAlzO2/NixCoyAlzO2, LiNixMn2-xO4/NixMn2- _xO₄, H₂TiO₃, Li₂TiO₃, Li_xTiO₂(0≤x<1)/TiO₂, Lithium titanate (Li₄Ti₅O₁₂), Attorney Docket No.11196-113WO1 NaFe_xMn_yPO₄/FePO₄ (x+y=1), NaMn₂O₄/λ-MnO₂, NaNi_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂/Ni_xCo_yMn_zO₂(x+y+z =1), NaNixCoyAlzO2/NixCoyAlzO2 (x+y+z =1)/NixCoyAlzO2/NixCoyAlzO2, NaNixMn2-xO4/NixMn2- _xO₄,Na_xTiO₂/TiO₂, KFe_xMn_yPO₄/FePO₄ (x+y=1), KMn₂O₄/λ-MnO₂, KNixCoyMnzO2/NixCoyMnzO2/NixCoyMnzO2/NixCoyMnzO2(x+y+z =1), KNi_xCo_yAl_zO₂/Ni_xCo_yAl_zO₂ (x+y+z =1)/Ni_xCo_yAl_zO₂/Ni_xCo_yAl_zO₂, KNi_xMn_2-xO₄/Ni_xMn_2- xO4, KxTiO2(0≤x<1)/TiO2. [0077] In some aspects, the intercalation material has an intercalation capacity of 5 mg g^-1 to 500 mg g^-1 of the intercalation material. For example, the intercalation material has an intercalation capacity of 5 mg g^-1 to 450 mg g^-1, 5 mg g^-1 to 400 mg g^-1, 5 mg g^-1 to 350 mg g- ¹, 5 mg g^-1 to 300 mg g^-1, 5 mg g^-1 to 250 mg g^-1, 5 mg g^-1 to 200 mg g^-1, 5 mg g^-1 to 250 mg 1 to 200 mg g^-1, 5 mg g^-1 to 150 mg g^-1, 5 mg g^-1 to 100 mg g^-1, 5 mg g^-1 to 50 mg 1 to 500 mg g^-1, 50 mg g^-1 to 450 mg g^-1, 50 mg g^-1 to 400 mg g^-1, 50 mg g^-1 to mg g^-1 to 300 mg g^-1, 50 mg g^-1 to 250 mg g^-1, 50 mg g^-1 to 200 mg g^-1, 50 mg

g^-1 to 150 mg g^-1, 50 mg g^-1 to 100 mg g^-1, 100 mg g^-1 to 500 mg g^-1, 100 mg g^-1 to 450 mg g- ¹, 100 mg g^-1 to 400 mg g^-1, 100 mg g^-1 to 350 mg g^-1, 100 mg g^-1 to 300 mg g^-1, 100 mg g^-1 to 250 mg g^-1, 100 mg g^-1 to 200 mg g^-1, 100 mg g^-1 to 150 mg g^-1, 150 mg g^-1 to 500 mg g^-1, 150 mg g^-1 to 450 mg g^-1, 150 mg g^-1 to 400 mg g^-1, 150 mg g^-1 to 350 mg g^-1, 150 mg g^-1 to 300 mg g^-1, 150 mg g^-1 to 250 mg g^-1, 150 mg g^-1 to 200 mg g^-1, 200 mg g^-1 to 500 mg g^-1, 200 mg g^-1 to 450 mg g^-1, 200 mg g^-1 to 400 mg g^-1, 200 mg g^-1 to 350 mg g^-1, 200 mg g^-1 to 300 mg g^-1, 200 mg g^-1 to 250 mg g^-1, 250 mg g^-1 to 500 mg g^-1, 250 mg g^-1 to 450 mg g^-1, 250 mg g^-1 to 400 mg g^-1, 250 mg g^-1 to 350 mg g^-1, 250 mg g^-1 to 300 mg g^-1, 300 mg g^-1 to 500 mg g^-1, 300 mg g^-1 to 450 mg g^-1, 300 mg g^-1 to 400 mg g^-1, 300 mg g^-1 to 350 mg g^-1, 350 mg g^-1 to 500 mg g^-1, 350 mg g^-1 to 450 mg g^-1, 350 mg g^-1 to 400 mg g^-1, 400 mg g^-1 to 500 mg g^-1, 400 mg g^-1 to 450 mg g^-1, or 450 mg g^-1 to 500 mg g^-1, including exemplary capacities of 25 mg g^-1, 75 mg g^-1, 125 mg g^-1, 175 mg g^-1, 225 mg g^-1, 275 mg g^-1, 325 mg g- ¹, 375 mg g^-1, 425 mg g^-1, and 475 mg g^-1. [0078] In some aspects, the intercalation material intercalates the cation at a voltage of 4.5 V or less. For example, the cation intercalates at a voltage of 4.5 V, 4 V, 3.5 V, 3 V, 2.5 V, 2.0V, 1.5V, 1.0 V, 0.5 V, 0.0 V, -0.5 V, -1.0 V, -1.5 V, -2.0V, -2.V, or -3.0 V. [0079] In some aspects, the bipolar membrane is configured to operate with a forward voltage bias and a reverse voltage bias in alternating cycles. In some aspects, the catalyst Attorney Docket No.11196-113WO1 includes tin oxide, titania (i.e., titanium oxide), silica, platinum group metals, graphitic carbon, activated carbon, or mixtures or layers thereof. [0080] In some aspects, a pH of the aqueous processing fluid is lowered relative to the received aqueous processing fluid in situ upon a reverse voltage bias. For example, the pH of the aqueous processing fluid is lowered from about 7 to about 6, from about 7 to about 5, from about 7 to about 4, from about 7 to about 3, from about 7 to about 2, from about 7 to about 1, from about 6 to about 5, from about 6 to about 4, from about 6 to about 3, from about 6 to about 2, and from about 6 to about 1. Exemplary pH values attained in the aqueous processing fluid include about 6.5, about 5.5, about 4.5, about 3.5, about 2.5, and about 1.5. [0081] In some aspects, the pH of the aqueous processing fluid is raised relative to the received aqueous processing fluid in situ upon a forward voltage bias. For example, the pH of the aqueous processing fluid is raised from about 6 to about 7, from about 6 to about 8, from about 6 to about 9, from about 6 to about 10, from about 6 to about 11, from about 6 to about 12, from about 7 to about 8, from about 7 to about 9, from about 7 to about 10, from about 7 to about 11, from about 7 to about 12. Exemplary pH values attained in the aqueous processing fluid include about 6.5, about 7.5, about 8.5, about 9.5, about 10.5, and about 11.5. [0082] In some aspects, the intercalation material layer intercalates the cation upon a reverse voltage bias. For example, the intercalation material layer intercalates lithium ion upon a reverse voltage bias. In some aspects, the intercalation material layer deintercalates the cation and forms a hydroxide salt thereof upon a forward voltage bias. For example, the intercalation material layer deintercalates lithium ion and forms lithium hydroxide upon a forward voltage bias. [0083] In some aspects, the device is a capacitive deionization device or a membrane capacitive deionization device. [0084] In some aspects, a system is disclosed including the device, a voltage source, a control system, a pH monitor, a thermometer, a conductivity monitor, a pressure monitor, a flow monitor, and any other monitoring device. It is contemplated that the system and device can be used for single-system of ion capture and purification. METHOD [0085] In some aspects, a method of selective cation separation is disclosed. The method includes providing a processing fluid comprising the cation to the device as disclosed, Attorney Docket No.11196-113WO1 applying a reverse voltage bias to the device, wherein a first electrode of the device selectively intercalates the cation, applying a forward voltage bias to the device, wherein the cation deintercalates from the first electrode and forms a hydroxide salt, and collecting an effluent comprising the hydroxide salt. In some aspects, the method is repeated using any proportion of the aqueous processing fluid and the effluent. [0086] In some aspects, providing the aqueous processing fluid includes flowing the aqueous processing fluid continuously through a spacer channel. In some aspects, the forward voltage bias and the reverse voltage bias comprises a voltage of 3.0V or less. [0087] In some aspects, the aqueous processing fluid comprises the cation and one or more salts during the steps of applying a reverse voltage bias and intercalating the cation. In some aspects, the aqueous processing fluid comprises deionized water, a hydroxide salt, the effluent, or combinations thereof. [0088] In some aspects, the cation includes one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. In some aspects, the cation includes lithium. EXAMPLE [0089] In this study, a capacitive deionization platform was demonstrated. The platform integrates delithiated lithium iron phosphate (LFP) intercalation electrodes with a bipolar membrane (BPM), amalgamating the strengths of both capacitive deionization (CDI) and BPM electrode-deposition (ED)-based routes. The bipolar membrane capacitive deionization (BPM-CDI) device, depicted in Figs.2A-2D, not only selectively captures lithium ions (Li⁺) from brine solutions but also facilitates the in situ conversion to lithium hydroxide (LiOH) upon Li⁺ release. Both processes occur within a unitized electrochemical cell—a notable example of process intensification. Working in tandem, the LFP electrode demonstrates improved capabilities by selectively removing lithium ions (Li⁺) over all competing ions. Concurrently, the BPM plays a crucial role in modulating pH, contributing to both the removal (charging) and recovery (discharge) phases of the process. Notably, in the recovery (discharge) phase, the release of captured Li⁺ ions from the intercalated LFP electrode triggers the spontaneous dissociation of water in the process stream, resulting in LiOH, while free protons from the dissociation of water flow through the cation exchange membrane in the BPM for proton-hydroxide ion recombination. Utilizing molecular dynamics (MD) simulations and external half-cell (H-cell) electrochemical experiments, it was shown that the Attorney Docket No.11196-113WO1 mechanism for water dissociation is water redistribution of protons and hydroxide ions in the presence of lithium ions released into the process stream during the discharge phase of the BPM-CDI unit. Overall, the BPM-CDI platform demonstrates efficacy in selectively removing Li⁺ from synthetic geothermal brine, achieving concentrations of up to 124 ppm LiOH (36 ppm Li) after eight cycles. Through rigorous analysis of discharge characteristics and LFP electrode stability, a BPM-CDI is presented for potential deployment as a direct lithium extraction (DLE) platform, showcasing its promise for efficient lithium removal and conversion, thus contributing to sustainable resource extraction through advanced electrochemical technologies. [0090] Results [0091] Investigating the pH inversion effect in BPM-CDI. The use of a BPM in a capacitive deionization setup has been shown previously for selective recovery of metallic Cu from model wastewater solutions through electrodeposition at the carbon electrode surface in the metallic form facilitated by the creation of an acidic environment at the BPM.²⁴ In the publication, the effect of cell operating parameters on the modulation of pH in the spacer channel during the charge cycle was delineated. However, the BPM-CDI device operated in alternating charging and discharging cycles, akin to traditional CDI or membrane CDI cells. The inclusion of a BPM enables pH control in the spacer channel depending on the location of the BPM, cell voltage, residence time, and dilute feed concentration.²⁴ During the charge cycle in both configurations A and B, the BPM operates under reverse bias, i.e., it dissociates water at the bipolar junction (interface between the ion-exchange layers of the BPM where the water dissociation catalyst exists) to produce protons and hydroxide ions. In BPM-CDI configuration A (see Fig.2A), the cation-exchange layer (CEL) side of the BPM faces the process stream and protons generated through water dissociation migrate through the CEL of the BPM to create an acidic pH in the process stream. Conversely, in configuration B (see Fig.2B), where the BPM is located at the negative electrode, the BPM releases hydroxide ions into the process stream when operating under reverse bias. The variation of steady-state pH with the operating cell voltage across both configurations is depicted in Fig.3A. These experiments utilized a commercial FUMASEP BPM with a supporting electrolyte of aqueous NaCl (1000 ppm) fed into a continuous flow mode (20 ml/min). As the applied voltage across the BPM increases, the extent of water dissociation increases,²⁵ releasing more hydroxide ions and protons into the process stream, thereby altering its acidity (configuration A) or alkalinity (configuration B). During the discharge cycle, it was initially expected that the Attorney Docket No.11196-113WO1 dissociated hydroxide ions and protons would recombine under forward bias at the bipolar junction, and the process stream effluent would return to its feed pH value (i.e., neutral pH of 6 to 7). However, in the operation of the BPM-CDI cell, configuration A exhibited an alkaline pH upon discharge, while configuration B showed an acidic pH upon discharge. These observations were made over multiple alternating charge-discharge cycles (Figs.3B- 3C). This behavior was also demonstrated by another commercial BPM, Neosepta BPM (Fig. 3D), indicating this phenomenon was related to the process and not the properties of the BPM. To comprehend the "pH-inversion" effect in BPM-CDI upon discharging, MD simulations and external H-cell experiments were performed. [0092] To investigate the origin and mechanism of the pH inversion phenomenon observed during the discharge cycle, the ion-concentration gradients in the spacer channel of the bipolar membrane (BPM) were replicated using a half-cell (H-cell) setup (Figs.3A and 3D). During the charge cycle sodium ions (Na⁺) adsorbed (electrosorption) at the negative electrode (Fig.2A) are desorbed in the discharge cycle, entering the spacer channel. The concentration of the desorbed cations (Na⁺) in configuration A must be balanced with negative counterions for maintaining electroneutrality. However, the negative counterions such as Cl- ions exited the spacer channel with the process stream during the charging cycle. It is important to note that chloride ions (Cl-) cannot migrate to and adsorb into the positive electrode (charge cycle) because of Donnan exclusion (i.e., the cation exchange layer of the BPM in configuration A mitigates its inclusion into the membrane). Similarly, the hydroxide ions (OH-) stored at the positive electrode during the charge cycle cannot conduct through the CEL of the BPM during the discharge cycle due to Donnan exclusion. Therefore, the excess of positively charged ions (Na⁺) lacks sufficient negative counterions in the spacer channel during the initial period of the discharge cycle. [0093] To understand the shift in solution pH when introducing cations into the spacer (between the boundary layers of the CEL of the BPM and the positive electrode during the discharge cycle, Fig.4E), an H-cell setup was deployed to mirror the conditions of the BPM- CDI process. In the H-cell setup, the anode chamber was populated with a higher concentration (1000 ppm) aqueous NaCl solution while the cathode chamber was filled with a lower concentration (100 ppm) aqueous NaCl solution. The two chambers were separated using a sulfonated polysulfone CEM. Using the Pt-Ir mesh, a voltage of 1 V was applied to drive the cation (Na⁺) transport from the anode chamber to the cathode chamber conducting through the CEM (Fig.4D). In this H-cell setup, a CEM was utilized for separating the Attorney Docket No.11196-113WO1 chambers instead of a BPM as the CEM facilitated the transport of Na⁺ from the anode chamber to the cathode chamber. It is to be noted that a BPM separator (between the two chambers in the H-cell) would not be permissive of Na⁺ ion conduction through its anion exchange layer (AEL) due to Donnan exclusion. As Na⁺ ions migrate to the cathode chamber after the application of voltage, the concentration of ions in the cathode chamber starts to represent the conditions in the spacer channel of the BPM-CDI cell (configuration A) during the discharge cycle consisting of an excess of positively charged ions (Na⁺) and lacking sufficient negative Cl- counterions. It was observed that the concentration of the positive ions without a balancing counterion enables redistribution of the water equilibrium with hydroxide ions and hydronium leading to a larger fraction of hydroxide ions. This dissociation balances the number of cations to anions in the process stream to satisfy electroneutrality leading to a pH increase (Fig.4F). [0094] The observed dissociation of water creating hydroxide ions that contribute to the increase in the pH of the spacer solution (in configuration A) during the discharge cycle should also create protons based on electroneutrality principles. In the BPM-CDI cell (configuration A), it is hypothesized that the CEL of the BPM serves as a proton sink taking up these protons from the process stream. Meanwhile, the hydroxide ions (OH-) stored at the electrode adjacent to the BPM during the charging cycle (i.e. the positive electrode) are repelled from the electrode towards the AEL of the BPM as the polarity of the electrode becomes negative during the discharge cycle. These hydroxide ions conducting from the AEL of the BPM recombine with the protons from the CEL of the BPM to produce water at the bipolar junction under forward bias. This observed behavior accounts for the pH increase (i.e., pH inversion) upon discharging in configuration A. [0095] Lithium recovery from brine solutions and conversion to LiOH. The efficacy of the delithiated LFP for the selective capture of Li⁺ ions was evaluated by employing a porous activated carbon electrode infiltrated with a paste containing 80% LFP, 10% PVDF, and 10% conductive carbon.¹⁵ The affinity of the LFP-coated electrode deployed in the BPM-CDI cell for Li⁺ separation was first evaluated separately against Mg²⁺ and Na⁺ ions, which represent the most challenging ions for selective Li⁺ capture.^1,13 An idealized binary brine solution containing lithium chloride and competing sodium/magnesium chloride was fed into a BPM- CDI device to assess the selectivity as prescribed by Sholl et. al.²⁹ The BPM plays an important role in modulating the pH during both the charging and discharging cycle (Figs.5A and 5B). During the charge cycle, the BPM acidifies the process stream in the spacer channel Attorney Docket No.11196-113WO1 which is crucial for preventing carbonate or phosphate scaling in geothermal and salt lake brines.^12,13,30 Unlike other DLE platforms requiring external acid pretreatment¹⁹, in situ water dissociation by the BPM releases protons in the spacer channel, eliminating the need for external acid, reducing waste streams, and avoiding downstream processes to remove additional introduced anions. This is a significant feature of the BPM-CDI device and is relevant for the scale-up considerations. Moreover, industrial processes producing mineral acids such as hydrochloric acid and sulfuric acid are energy-intensive and environmentally detrimental. Hydrochloric acid is derived from chlorine and hydrogen, which are produced through the chlor-alkali process and steam methane reforming respectively. Sulfuric acid is derived from sulfur dioxide generated during fossil fuel mining. Hence, in situ pH adjustment using a BPM has advantages over using mineral acids or bases. The LFP-coated electrode serves as the negative electrode in the charging process (Fig.2C). It captures Li⁺ ions via intercalation owing to the ion-sieving effect.¹ During the discharge step, the polarity in the BPM-CDI unit is flipped, and the LFP-coated electrode has a positive bias releasing (i.e., deintercalation) Li⁺ ions into the spacer channel. As the Li⁺ ions are discharged, the BPM acts as a proton sink, catalyzing spontaneous water dissociation in the presence of lithium ions and the acceptance of protons by the cation exchange layer, leading to LiOH formation and a rise in solution pH. This is identical to the mechanism described in the previous section on H- cell experiments and MD simulations. For the discharge process, the feed is switched to a separate solution of pure DI water just before the first discharge cycle begins. LiOH is collected and concentrated in the DI water solution by recirculating this solution during consecutive discharge cycles (Fig.2D). [0096] A typical geothermal brine has a concentration of Li⁺ ions between 10-50 ppm (1.5- 7 mM).³¹ To adhere to guidelines for investigating new separation platforms and materials, a synthetic binary solution containing 25 ppm each of Li⁺ and X⁺ ions (Na⁺ and Mg²⁺) was processed through the BPM-CDI device.²⁹ Before deploying the LFP electrode for Li⁺ capture, the electrode was electrochemically delithiated in a traditional CDI configuration.^15,31 As previously discussed, the BPM played a crucial role in tuning the pH of the spacer channel during this process. Consistent with the trend observed in earlier pH control experiments with aqueous NaCl solutions (Fig.3A; configuration A of BPM-CDI), the pH of the spacer channel consisting of 25 ppm (3.6 mM) Li⁺ from 153.6 ppm LiCl and 25 ppm (1.1 mM) Na⁺ from 63.5 ppm aqueous NaCl solution remained acidic across the eight charge cycles with an average steady-state pH of 3.2 (Fig.5A). During the discharge cycle, Attorney Docket No.11196-113WO1 the pH of the solution became alkaline as the recovered ions (predominantly Li⁺) were released and concentrated in the smaller volume of recovery solution in the hydroxide form due to the pH inversion effect. The Li⁺ removal across the eight charging cycles was 11.7% while the Na⁺ removal was only 0.3% with several cycles exhibiting 0% of Na⁺ ions (Fig. 5B). Further exploration of ion removal from a binary solution of Li⁺ and Mg²⁺ salts (25 ppm concentration each for Li⁺ and Mg²⁺ ions) suggested similarly high selectivity for lithium ions. The average removal of Li⁺ across eight consecutive charge cycles was 13.0% while that of Mg²⁺ was only 1.1% (Fig.5C). By recirculating a limited volume of discharge solution across consecutive cycles, the LiOH was steadily concentrated from 0 ppm (pure DI water) before the start of the experiment to 7.1 ppm (1 mM) after eight consecutive cycles (Fig.5D) with negligible (< 1 ppm) concentrations of Na⁺ and Mg²⁺ ions. Increasing the LiOH concentration was achieved by limiting the volumetric flow rate of the discharge solution in addition to increasing the number of cycles and the geometric area size of the cell (e.g., from 25 cm² to 250 cm²). [0097] After assessing the selectivity of Li⁺ removal in binary solutions, a synthetic geothermal brine solution was processed through the BPM-CDI. The concentrations of the major competing cations in this solution were 25 ppm (3.6 mM) Li⁺, 682 ppm (29.7 mM) Na⁺, 137 ppm (3.5 mM) K⁺, 200 ppm (8.2 mM) Mg²⁺, and 211 ppm (5.3 mM) Ca²⁺.^11,31 The results from experiments using synthetic brine are presented in Figs.6A-6B. The percent removal of Li⁺ from the brine solution was 10.3%, consistent with the results of binary experiments. The removal of Na⁺ and Mg²⁺ was less than 0.5% (0.4% for Na⁺ and 0.3% Mg²⁺) while the removal of Ca²⁺ and K⁺ was below the limit of detection (~0% each). During the discharge cycles, the flow rate of the process stream was physically constrained to the lowest possible value (2 mL/min) to increase the solution’s residence time in the BPM-CDI unit and to enhance the concentration of LiOH in the capture solution. Li⁺ was the largest concentration in the capture solution after eight discharge cycles corresponding to a 124 ppm (5.2 mM) LiOH concentration, while the concentrations of the competing ions were 32 ppm (1.4 mM) Na⁺ and 27 ppm (1.1 mM) Mg²⁺. The concentration of Ca²⁺ and K⁺ was undetected in the recirculated capture solution after eight discharge cycles. Although the concentrations of the Na⁺ and Mg²⁺ competing ions were larger than what was observed in the experiments with binary mixtures (Fig.6A), it is important to note that the concentration values of these ions in the feed were 26x and 8x larger for Na⁺ and Mg²⁺, respectively, when compared to Li⁺. The previous experiments were at a 1:1 feed ratio of Li⁺ with the other competing ions. Attorney Docket No.11196-113WO1 The synthetic brine feed solution was 2 % Li⁺ of all the cations in the solution. The recirculated capture solution composition was 37% Li⁺ of all the cations in the solution. Overall, the BPM-CDI with a delithiated LFP electrode demonstrated high selectivity toward Li⁺ removal relative to the feed concentrations. The average Li⁺ adsorption capacity demonstrated by the LFP electrode over eight cycles in this study was 7.1 mg g^-1, which is comparable to other reports in the literature.^1,31 Finally, the specific energy consumption in the BPM-CDI device was 6.4 Wh molLi^-1, which is slightly higher than traditional electrosorption-based (CDI/MCDI) platforms that use LFP intercalation electrodes for selective lithium recovery due to the inclusion of the BPM in the BPM-CDI cell.¹ However, the specific energy consumption of the BPM-CDI was still lower than other traditional platforms that use MnO2-based intercalation electrodes. It is noted that the traditional CDI/MCDI platforms cannot convert Li⁺ salts to LiOH, unlike the BPM-CDI platform. The conversion to LiOH increases the energy intensity as both chloro-alkali and BPM electrodialysis are energy intensive. [0098] A rigorous post-mortem surface analysis (SEM, EDS, and XPS) was performed to assess if significant ionic impurities (Na⁺, Mg²⁺, K⁺, Ca²⁺) were present in the delithiated LFP electrode after use in BPM-CDI and to determine if any degradation occurred on the electrode surface. The BPM-CDI cell with the negative electrode treated with the synthetic brine was subjected to another charge cycle with the brine solution and then dismantled to analyze the ions on the negative electrode surface (i.e. before performing a discharge cycle). The EDX spectrum indicated no significant presence of the competing ions with only a minimal amount of calcium (0.21 wt%) and magnesium (0.06 wt%) detected. Due to the weak energy of lithium's X-ray signals, its presence was challenging to detect using SEM- EDX. Hence, post-mortem XPS analysis was performed to confirm lithium presence in the LFP crystal structure. Deconvoluting the high-resolution spectrum of the 3p2 Fe peak reveals the presence of a 1s shoulder peak of the lithium, which is embedded in the octahedral 4a site of the crystal structure.³² The 3p2 peak of the pristine electrode at the binding energy of 55.9 eV was a much sharper peak indicating the initial absence of Li. The XPS spectrum also underscores the absence of other competing ions, aligning with SEM-EDX analysis of the electrode. Surface analysis confirms the LFP electrode's selectivity for targeted Li⁺ capture without any signs of structural degradation after multiple cycles of Li⁺ capture and release. [0099] Methods Attorney Docket No.11196-113WO1 [0100] pH variation experiments in the BPM-CDI cell. A commercial CDI cell (ECSCell) was used to conduct the BPM-CDI experiments. As illustrated in Figs.2A-2D, the BPM-CDI cell comprised a commercial BPM (Fumasep BPM (Fumatech) or Neosepta BPM (Astom Corp)) for pH modulation and porous carbon electrodes (Kuraray, Japan). The dimensions of the BPM and electrodes used in this work are 5×5 cm². The electrodes were functionalized through treatment with 1 M nitric acid (Millipore Sigma) at 95^o C.^33,34 Aqueous 1000 ppm sodium chloride (NaCl, Millipore Sigma) was used as the supporting electrolyte during the pH measurement studies. Deionized water (18.2 Mohm) was used as a solvent to prepare all aqueous solutions used in this work. An external cell voltage was applied using a Gamry AE 3000 potentiostat. A peristaltic pump (ANKO) was used to deliver the aqueous NaCl solution through the cell while the process stream pH (Fig.3A-3D) was measured through an in-line pH and reference probes (Microelectrodes, Inc.). In configuration A during the charge cycle, the BPM was placed at the positive electrode with the cation exchange layer of the BPM interfaced with the spacer channel as illustrated in Fig.2A. Conversely, in configuration B, the BPM was positioned at the negative electrode during the charge cycle with the anion exchange layer of the BPM facing the process stream. During the discharge cycle, the polarity of the electrodes was flipped to release the ions electrosorbed during the charge cycle (cations in configuration A and anions in configuration B) in the spacer channel into the process stream. [0101] H-cell experiments for probing co-ion leakage/crossover in commercial BPMs. To investigate any possible ion leakage/crossover across the BPM that may lead to the pH inversion effect in the discharge cycle, the BPM was studied externally in the H-cell (Fig. 4B). The BPM was placed at the junction between the two compartments (anode and cathode) in the H-cell with the cation exchange layer of the BPM facing the anode (Pt-Ir mesh, ThermoFisher) and the anion exchange layer oriented towards the cathode (Pt-Ir mesh). Two Ag/AgCl electrodes (Pine Research) were used as the reference electrodes, suspended in each chamber using Luggin capillaries (Fig.4A). The anode and the cathode chambers were filled with equal volumes (75 mL) of 1000 ppm NaCl solution and 1000 ppm NaOH (Millipore Sigma) solutions respectively. A small potential (0.5 V) was applied across the BPM using a GAMRY potentiostat for intervals of two minutes and the pH of each chamber was analyzed using a Mettler Toledo pH probe by collecting a 5 ml sample after each interval. The pH variation of the chambers is presented in Fig.4C. Attorney Docket No.11196-113WO1 [0102] Using a half-cell (H-cell) setup, the ion-concentration gradients across the BPM and electrodes were replicated to mirror the conditions of the process stream in the spacer channel. By subjecting the BPMs to a forward bias (0.5 V, similar to the discharge cycle conditions) in the H-cell, the variation of the pH across both chambers was monitored to probe ion leakage across the BPM. However, the analysis of the pH showed no leakage of co- ions through the BPM's ion-exchange layers (Fig.4C). This experiment confirmed that the pH inversion effect did not originate from the ion crossover or leakage through the ion- exchange layers of the BPM. [0103] H-cell experiments for replicating spacer channel ionic conditions. The conditions in the spacer channel were mimicked using the H-cell setup (Fig.4E) to assess the electroneutrality in the spacer. The anode chamber consists of a high concentration (1000 ppm) of NaCl while the cathode chamber was populated with a low concentration (100 ppm) of NaCl. The two chambers were separated with a lab-synthesized sulfonated polysulfone (SPSf) cation exchange membrane (CEM). The membrane was synthesized as described in previous work.³⁵ A small voltage (1 V) was applied for intervals of 2 minutes to spur the electro-migration of Na⁺ ions from the anode chamber (high concentration) to the cathode chamber (low concentration). After each interval, a 5 ml sample was collected from both chambers to measure the pH (Mettler Toledo pH probe) presented in Fig.4F. These experiments were repeated thrice to obtain the standard error for the pH measurements. [0104] Fabrication of lithium iron phosphate (LFP) coated carbon electrodes. The LiFePO₄ (LFP) coated carbon electrodes were fabricated by coating an ink of LFP (TMAX), polyvinylidene fluoride (PVDF, TMAX), and conductive carbon (TMAX) on activated carbon cloth electrodes (25 cm²). The composition (weight ratio) of the ink was 8:1:1 LFP: PVDF: carbon dissolved in anhydrous N-Methyl-2-pyrrolidone (NMP, Sigma-Aldrich). The LFP-coated carbon electrodes were electrochemically delithiated in a traditional CDI cell configuration in the presence of 100 ppm CaCl2 electrolyte before their application for lithium capture experiments. [0105] Lithium removal experiments from brine solutions. The BPM-CDI cell was assembled with the delithiated LFP electrode, FUMASEP BPM, and activated carbon electrode as represented in Fig.2C. Binary separation experiments were first conducted with a feed solution containing 25 ppm Li⁺ (153.6 ppm LiCl, Millipore Sigma) and 25 ppm Na⁺ (63.5 ppm NaCl, Millipore Sigma) feed solution and later with a feed solution containing 25 ppm Li⁺ (153.62 ppm LiCl) and 25 ppm Mg²⁺ (97.95 ppm MgCl2) during the charge cycle. Attorney Docket No.11196-113WO1 The solution was fed through the cell using the peristaltic pumps at a flow rate of 20 mL/min. During the discharge cycle, a feed of DI water was fed through the first discharge cycle and later recirculated during consecutive discharge cycles. A voltage of 1.5 V was applied during each charge cycle for a period of 120 seconds while a voltage of -0.5 V was applied during the discharge cycle. The pH of the effluent stream was recorded using a Microelectrodes pH probe. During the charge cycle, a sample was collected every 30 seconds to measure the concentration using ion chromatography (ThermoFisher Dionex IC 6000). The percent removal was calculated using Equation 1 using the final concentration at the end of the charge cycle. After the completion of binary experiments, a synthetic geothermal brine solution was processed through the cell at a flow rate of 20 mL/min. The concentration of cations in the synthetic brine represents the concentrations of Tibet geothermal brine.³¹ %_{^^^^^^^ = ^1 − ^^} _{^^^ ^100% (1)} where Ce = final concentration

ion [0106] Similar to binary feed solution experiments, a voltage of 1.5 V was applied during each charge cycle for a period of 120 seconds while a voltage of -0.5 V was applied during the discharge cycle. During the first discharge cycle, a DI water feed was fed through the cell at a slower flow rate (2 mL/min) to collect the LiOH solution and this capture solution was recirculated during consecutive discharge cycles for the concentration of LiOH. The specific energy consumption (energy consumption per mol of lithium captured) and the electrode adsorption capacity for lithium were calculated by analyzing the moles of lithium recovered in the discharge solution using Equations 2 and 3, respectively. ^_{^^^^^^^ ^^^^^^ ^^^^^^^^^^^ ^ ℎ ^^^"# $^% = & ' ()*} _{+,-./ ,0 - (2)} ₍₃₎

[0107] Post-mortem surface analysis of the LFP-coated electrode using SEM and XPS. The LFP electrode used in the brine experiments was analyzed to assess the effect of the ion intercalation and degradation of the electrode. The BPM-CDI cell containing the LFP electrode was first subjected to a charge cycle with the synthetic brine solution to enable ion Attorney Docket No.11196-113WO1 removal at the LFP electrode surface. Without running a discharge cycle, the BPM-CDI cell was dissembled and the LFP electrode was dried under vacuum for SEM and XPS analysis. A non-destructive field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS) was carried out using a Karl Zeiss Merlin field-emission scanning electron microscope with EDS elemental analysis capability. The working distance was set to about 8.5-9.0 mm, and the accelerating voltage was fixed at 15 kV for acquiring SEM images. Note that this high 15 kV accelerating voltage was used to have sufficient X-ray excitation from samples when conducting EDS analysis and SEM measurement simultaneously. Normal SEM measurement do not require this high accelerating voltage. The EDS elemental maps were collected by the Smart-EDS system coupled with Karl Zeiss Merlin FESEM. The energy resolution was around 130 eV, and the probe current was maintained above 1.6 nA to secure enough X-ray count rate. X-ray photoelectron spectroscopy (XPS) was performed using the Physical Electronics VersaProbe III with a monochromatic Al K source (E = 1486.6 eV) and a concentric hemispherical analyzer. Charges were neutralized using argon ions and low-energy electrons (5 eV). All survey spectra and high-resolution spectra are calibrated with the C1s spectral line (284.8 eV). The Li 1s-Fe3p peaks were deconvoluted based on the binding energies reported in the literature.³² [0108] Discussion [0109] Direct lithium extraction (DLE) platforms are crucial for mitigating the substantial water demands (100-800 m³ per ton of lithium carbonate) and prolonged processing durations (12-18 months) associated with solar evaporation methods.¹¹ The majority of DLE methods necessitate some form of chemical pre-processing (e.g., acid treatment to prevent carbonate and phosphate scaling) and post-processing (e.g., base addition for LiOH product synthesis). The chemical burden of DLE methods becomes non-trivial as processing sites are expected to handle up to 21,000 m³ of brine volume per day.¹¹ BPM-based electrochemical platforms, particularly BPM-CDI, offer advantages over other DLE methods by utilizing in situ pH adjustment to obviate external acid-base requirements. A recent study by Liu et al. utilized a combination of a traditional CDI cell with LFP electrodes for selective Li⁺ capture, followed by a BPM-ED device for pH adjustments, resulting in the synthesis of high-purity (>99%) LiOH at $4.1/kg LiOH.H2O, six times cheaper than the current market price.¹⁸ A singular BPM-based CDI platform, as demonstrated in this article, can further optimize LiOH production costs with advancements in LFP electrode selectivity to eliminate minor impurities (specifically Na⁺ and Mg²⁺) from the product stream. Attorney Docket No.11196-113WO1 [0110] While the results show promising selective Li⁺ capture, the amount of Li⁺ removal is constrained by the adsorption capacity of the delithiated LFP electrode. To surpass the demonstrated 15% Li⁺ ion removal in this report, further improvements can be achieved by tuning the LFP electrode's capacity, which is contingent upon the number of vacant sites in the LFP crystal skeleton. The theoretical capacity is significantly lower (44 mg Li g^-1 FePO4) by several orders of magnitude compared to porous carbon electrodes where the actual capacity exhibited in recent studies has been limited to 10-20 mg g^-1.³¹ Enhancing electrode capacity without sacrificing selectivity, which porous carbon electrodes cannot provide, is a critical research area for scaling up and proliferating electrosorption-based DLE technologies such as the BPM-CDI cell. Sun et al. demonstrated a 57% increase in electrode capacity by incorporating porogens like polyethylene glycol (PEG) and ammonium bicarbonate (NH4HCO3) in an H-cell setup.³¹ It is contemplated that adapting the electrode synthesis advancements to improve the actual capacity of LFP-coated electrodes in BPM-CDI cells while assessing selectivity and electrode stability in a flow-by-cell setup is another avenue to improve performance. This will also enable expanding the BPM-CDI device's brine-treating capabilities to salt-lake brines with higher concentrations (>100 ppm or 14.4 mM) of Li⁺ ions. [0111] In summary, this study investigated bipolar membrane capacitive deionization (BPM-CDI) with delithiated LFP-coated electrodes as a standalone platform for direct lithium extraction (DLE) while also producing lithium hydroxide (LiOH). The BPM plays a critical role in eliminating the pre-processing and post-processing acid-base requirements paired with other DLE technologies. Through rigorous experimental analysis, the selectivity and removal of Li⁺ in idealized binary Li/Na and Li/Mg solutions were examined. Furthermore, H-cell experiments and MD simulations were leveraged for the comprehension of the ‘pH inversion’ effect in the discharge cycle leading to the formation of hydroxide ions during the Li⁺ recovery phase. Using a synthetic geothermal brine solution, the BPM-CDI with the delithiated LFP-coated electrodes demonstrated a highly selective removal of 10.3% for Li⁺ ions compared to 0.4% for Na⁺ and 0.3% for Mg²⁺ ions. Through the tuning of the discharge stream parameters, the concentration of LiOH was 124 ppm (36 ppm Li) after eight consecutive recirculation cycles. Scaling up the geometric area of the BPM-CDI unit and using multiple units in series, as well as materials and systems optimization, can further Li⁺ recovery and LiOH enrichment. Finally, post-mortem analysis of LFP electrodes using SEM and XPS demonstrated electrode stability over multiple cycles of lithium recovery and release with model geothermal brine solutions. Overall, this research contributes to the ongoing Attorney Docket No.11196-113WO1 efforts towards sustainable and efficient lithium capture – which is essential for supporting the rapidly growing demand for lithium-ion batteries (LiBs) in various industries, including electric vehicles and grid-scale energy storage systems paired with intermittent renewable energy sources. EXEMPLARY ASPECTS [0112] Exemplary aspect 1. A device for selective ion separation, the device comprising: a first electrode comprising an intercalation material layer configured to reversibly captures and releases a cation through cyclic intercalation/deintercalation, wherein the intercalation material layer is disposed on a surface of the first electrode; a second electrode; and a bipolar membrane, wherein the bipolar membrane is disposed on a surface of the second electrode. [0113] Exemplary aspect 2. The device of exemplary aspect 1, wherein the bipolar membrane comprises a cation exchange layer, an anion exchange layer, and a catalyst disposed between the anion exchange layer and the cation exchange layer, wherein the catalyst comprises water dissociation catalyst and/or a hydroxide ion-proton recombination catalyst. [0114] Exemplary aspect 3. The device of exemplary aspect 2, wherein the catalyst comprises tin oxide, titanium oxide, silica, platinum group metals, graphitic carbon, activated carbon, or combinations thereof. [0115] Exemplary aspect 4. The device of exemplary aspect 2, wherein the anion exchange layer is disposed on the surface of the second electrode. [0116] Exemplary aspect 5. The device of any one of exemplary aspects 1-4, the device further comprising a cation exchange membrane, wherein the cation exchange membrane is disposed on the surface of the first electrode. [0117] Exemplary aspect 6. The device of exemplary aspect 5, wherein the cation exchange membrane is a selective cation exchange membrane. [0118] Exemplary aspect 7. The device of any one of exemplary aspects 1-6, wherein the cation comprises one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. Attorney Docket No.11196-113WO1 [0119] Exemplary aspect 8. The device of exemplary aspect 7, wherein the cation comprises lithium. [0120] Exemplary aspect 9. The device of any one of exemplary aspects 1-8, wherein the intercalation material layer comprises one of LixFePO4 (0<x<1), LixMnPO4 (0≤x<1), LixFeyMn1-yPO4, λ-MnO2, LixMnO2, LixNi0.6Co0.2Mn0.2O2(0≤x<1), LixNi0.8Co0.1Mn0.1O2(0≤x<1), LixNi0.5Co0.2Mn0.3O2(0≤x<1), LixNi0.33Co0.33Mn0.33O2(0≤x<1), Li_xNi_0.6Co_0.2Al_0.2O₂(0≤x<1), Li_xNi_0.8Co_0.1Al_0.1O₂(0≤x<1), Li_xNi_0.5Co_0.2Al_0.3O₂(0≤x<1), LixNi0.33Co0.33Al0.33O2(0≤x<1), LixNiO2(0≤x<1), LixCoO2, LiNixMn2-xO4 (0 < x < 0.5), LiNi_xCo_yMn_zO₂ (x+y+z=1), LiNi_xCo_yAl_zO₂(0≤x<1), Li₃V₂(PO₄)₃, V₂O₅, H₂TiO₃, Li₂TiO₃, TiO2, Lithium titanate (Li4Ti5O12), Prussian blue analogues, NaxFePO4, Na3V2(PO4)3, NaNi_xCo_yMn_zO₂, NaNi_xCo_yAl_zO₂, Na_xNiO₂(0≤x<1), Na_xCoO₂(0≤x<1), NaV₂O₅, KxFePO4(0≤x<1), K3V2(PO4)3, KNixCoyMnzO2 (x+y+z=1), KNixCoyAlzO2, KxNiO2(0≤x<1), K_xCoO₂(0≤x<1), or other layered metal oxides and polyanionic compounds. [0121] Exemplary aspect 10. The device of exemplary aspect 9, wherein the intercalation material comprises a modified intercalation material, wherein the modification comprises one or more of carbon/N-doped carbon/graphene/graphene oxide/reduced-graphene oxide coating, AlPO4/Al2O3/CeO2 coating, metal elemental Al, Fe, Cr, Ti, Ni doped. [0122] Exemplary aspect 11. The device of exemplary aspect 9, wherein the intercalation material layer comprises Li_xFePO₄ (0<x<1). [0123] Exemplary aspect 12. The device of exemplary aspect 9, wherein the intercalation material layer further comprises a polymer material, wherein the polymer material forms a composite membrane-electrode structure. [0124] Exemplary aspect 13. The device of any one of exemplary aspects 1-12, wherein the intercalation material layer comprises an open lattice structure. [0125] Exemplary aspect 14. The device of any one of exemplary aspects 1-13, wherein the intercalation material layer exhibits an intercalation capacity of at least 30 mg g^-1 of the intercalation material. [0126] Exemplary aspect 15. The device of any one of exemplary aspects 1-14, wherein the bipolar membrane is configured to operate under reverse bias and forward bias in alternating cycles. Attorney Docket No.11196-113WO1 [0127] Exemplary aspect 16. The device of any one of exemplary aspects 1-15, wherein the first electrode further comprises a current collector. [0128] Exemplary aspect 17. The device of any one of exemplary aspects 1-16, wherein the second electrode comprises carbon and a current collector. [0129] Exemplary aspect 18. The device of any one of exemplary aspects 1-17, wherein the device is configured to receive an aqueous processing fluid. [0130] Exemplary aspect 19. The device of exemplary aspect 18, wherein the aqueous processing fluid comprises one or more of the cation and one or more salts. [0131] Exemplary aspect 20. The device of exemplary aspect 18, wherein the aqueous processing fluid comprises deionized water or a hydroxide salt comprising the cation. [0132] Exemplary aspect 21. The device of any one of exemplary aspects 18-20, wherein a pH of the aqueous processing fluid is lowered relative to the received aqueous processing fluid in situ upon a reverse voltage bias. [0133] Exemplary aspect 22. The device of any one of exemplary aspects 18-21, wherein a pH of the aqueous processing fluid is raised relative to the received aqueous processing fluid in situ upon a forward voltage bias. [0134] Exemplary aspect 23. The device of any one of exemplary aspects 18-22, wherein the cation from the aqueous processing fluid is selectively intercalated by the intercalation material layer upon a reverse voltage bias. [0135] Exemplary aspect 24. The device of any one of exemplary aspects 18-23, wherein the cation is released by deintercalation and forms a hydroxide salt upon a forward voltage bias. [0136] Exemplary aspect 25. The device of any one of exemplary aspects 1-24, wherein the device is a membrane capacitive deionization device or a capacitive deionization device. [0137] Exemplary aspect 26. A system comprising the device of any one of exemplary aspects 1-25. [0138] Exemplary aspect 27. The system of exemplary aspect 26, further comprising a voltage source. Attorney Docket No.11196-113WO1 [0139] Exemplary aspect 28. The system of any one of exemplary aspects 26-27, further comprising a pH monitor, a thermometer, a conductivity monitor, a pressure monitor, a flow monitor, and any other monitoring device. [0140] Exemplary aspect 29. The system of any one of exemplary aspects 26-28, further comprising a control system. [0141] Exemplary aspect 30. A method of selective cation separation, the method comprising: providing an aqueous processing fluid comprising the cation to a device, wherein the device comprises the device of any one of exemplary aspects 1-29; applying a reverse voltage bias to the device, wherein a first electrode of the device selectively intercalates the cation; applying a forward voltage bias to the device, wherein the cation deintercalates from the first electrode and forms a hydroxide salt; collecting an effluent comprising the hydroxide salt. [0142] Exemplary aspect 31. The method of exemplary aspect 30, wherein the method is repeated using any proportion of the aqueous processing fluid and the effluent. [0143] Exemplary aspect 32. The method of exemplary aspect 30 or 31, wherein providing the aqueous processing fluid comprises flowing the aqueous processing fluid continuously through a spacer channel. [0144] Exemplary aspect 33. The method of any one of exemplary aspects 30-32, wherein the cation comprises one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. REFERENCES 1. Wu, L. et al. Lithium recovery using electrochemical technologies: Advances and challenges. Water Research 221, 118822 (2022). 2. Chen, Q.-B. et al. Development of recovering lithium from brines by selective- electrodialysis: Effect of coexisting cations on the migration of lithium. Journal of Membrane Science 548, 408-420 (2018). 3. Gmar, S. & Chagnes, A. Recent advances on electrodialysis for the recovery of lithium from primary and secondary resources. Hydrometallurgy 189, 105124 (2019). 4. Li, W., Erickson, E. M. & Manthiram, A. High-nickel layered oxide cathodes for lithium-based automotive batteries. Nature Energy 5, 26-34 (2020). Attorney Docket No.11196-113WO1 Manthiram, A. A reflection on lithium-ion battery cathode chemistry. Nature Communications 11, 1550 (2020). Li, W., Lee, S. & Manthiram, A. High-Nickel NMA: A Cobalt-Free Alternative to NMC and NCA Cathodes for Lithium-Ion Batteries. Advanced Materials 32, 2002718 (2020). Kim, Y., Seong, W. M. & Manthiram, A. Cobalt-free, high-nickel layered oxide cathodes for lithium-ion batteries: Progress, challenges, and perspectives. Energy Storage Materials 34, 250-259 (2021). Mohamed, N. & Allam, N. K. Recent advances in the design of cathode materials for Li-ion batteries. RSC Advances 10, 21662-21685 (2020). Jianming Zheng and Pengfei Yan and Luis Estevez and Chongmin Wang and Ji- Guang, Z. Effect of calcination temperature on the electrochemical properties of nickel-rich LiNi0.76Mn0.14Co0.10O2 cathodes for lithium-ion batteries. Nano Energy 49, 538-548 (2018). Yanbin Chen and Shunlin Song and Xuequan Zhang and Yafei, L. The challenges, solutions and development of high energy Ni-rich NCM/NCA LiB cathode materials. Journal of Physics: Conference Series 1347, 012012 (2019). Vera, M. L., Torres, W. R., Galli, C. I., Chagnes, A. & Flexer, V. Environmental impact of direct lithium extraction from brines. Nature Reviews Earth & Environment 4, 149-165 (2023). https://doi.org/10.1038/s43017-022-00387-5 Meshram, P., Pandey, B. D. & Mankhand, T. R. Extraction of lithium from primary and secondary sources by pre-treatment, leaching and separation: A comprehensive review. Hydrometallurgy 150, 192-208 (2014). Khalil, A., Mohammed, S., Hashaikeh, R. & Hilal, N. Lithium recovery from brine: Recent developments and challenges. Desalination 528, 115611 (2022). Liu, G., Zhao, Z. & Ghahreman, A. Novel approaches for lithium extraction from salt- lake brines: A review. Hydrometallurgy 187, 81-100 (2019). Liu, C. et al. Lithium Extraction from Seawater through Pulsed Electrochemical Intercalation. Joule 4, 1459-1469 (2020). Du, X. et al. A novel electroactive λ-MnO2/PPy/PSS core–shell nanorod coated electrode for selective recovery of lithium ions at low concentration. Journal of Materials Chemistry A 4, 13989-13996 (2016). Attorney Docket No.11196-113WO1 Srimuk, P., Su, X., Yoon, J., Aurbach, D. & Presser, V. Charge-transfer materials for electrochemical water desalination, ion separation and the recovery of elements. Nature Reviews Materials 5, 517-538 (2020). Liu, X. et al. (Pre-Print, Research Square, 2023). Foo, Z. H., Thomas, J. B., Heath, S. M., Garcia, J. A. & Lienhard, J. H. Sustainable Lithium Recovery from Hypersaline Salt-Lakes by Selective Electrodialysis: Transport and Thermodynamics. Environmental Science & Technology 57, 14747- 14759 (2023). Chen, X. et al. Production of lithium hydroxide by electrodialysis with bipolar membranes. Separation and Purification Technology 274, 119026 (2021). Ji, Z.-y. et al. Preliminary study on recovering lithium from high Mg2+/Li+ ratio brines by electrodialysis. Separation and Purification Technology 172, 168-177 (2017). Nie, X.-Y., Sun, S.-Y., Sun, Z., Song, X. & Yu, J.-G. Ion-fractionation of lithium ions from magnesium ions by electrodialysis using monovalent selective ion-exchange membranes. Desalination 403, 128-135 (2017). Swain, B. Recovery and recycling of lithium: A review. Separation and Purification Technology 172, 388-403 (2017). Kulkarni, T., Al Dhamen, A. M. I., Bhattacharya, D. & Arges, C. G. Bipolar Membrane Capacitive Deionization for pH-Assisted Ionic Separations. ACS ES&T Engineering (2023). Kole, S. et al. Bipolar membrane polarization behavior with systematically varied interfacial areas in the junction region. Journal of Materials Chemistry A 9, 2223- 2238 (2021). Martinez, R. J. & Farrell, J. Quantifying Electric Field Enhancement of Water Dissociation Rates in Bipolar Membranes. Industrial & Engineering Chemistry Research 58, 782-789 (2019). Strathmann, H., Krol, J. J., Rapp, H. J. & Eigenberger, G. Limiting current density and water dissociation in bipolar membranes. Journal of Membrane Science 125, 123- 142 (1997). Onsager, L. Deviations from Ohm's Law in Weak Electrolytes. The Journal of Chemical Physics 2, 599-615 (2004). https://doi.org/10.1063/1.1749541 Sholl, D. S. & Lively, R. P. Exemplar Mixtures for Studying Complex Mixture Effects in Practical Chemical Separations. JACS Au 2, 322-327 (2022). Attorney Docket No.11196-113WO1 Alkhadra, M. A. et al. Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion. Chemical Reviews 122, 13547-13635 (2022). Sun, S. et al. Green recovery of lithium from geothermal water based on a novel lithium iron phosphate electrochemical technique. Journal of Cleaner Production 247, 119178 (2020). Xiong, W., Hu, Q. & Liu, S. A novel and accurate analytical method based on X-ray photoelectron spectroscopy for the quantitative detection of the lithium content in LiFePO4. Analytical Methods 6, 5708-5711 (2014). Palakkal, V. M., Rubio, J. E., Lin, Y. J. & Arges, C. G. Low-Resistant Ion-Exchange Membranes for Energy Efficient Membrane Capacitive Deionization. ACS Sustainable Chemistry & Engineering 6, 13778-13786 (2018). Ahn, H.-J. et al. Nanostructured carbon cloth electrode for desalination from aqueous solutions. Materials Science and Engineering: A 449-451, 841-845 (2007). Jordan, M. L. et al. Integrated Ion-Exchange Membrane Resin Wafer Assemblies for Aromatic Organic Acid Separations Using Electrodeionization. ACS Sustainable Chemistry & Engineering (2023). Plimpton, S. Fast parallel algorithms for short-range molecular dynamics. Journal of computational physics 117, 1-19 (1995). Wang, J., Wolf, R. M., Caldwell, J. W., Kollman, P. A. & Case, D. A. Development and testing of a general amber force field. Journal of computational chemistry 25, 1157-1174 (2004). Wang, J., Wolf, R. M., Caldwell, J. W., Kollman, P. A. & Case, D. A. Erratum: Development and testing of a general amber force field (Journal of Computational Chemistry (2004) 25 (1157)). Journal of Computational Chemistry 26, 114 (2005). Li, P., Song, L. F. & Merz, K. M., Jr. Systematic Parameterization of Monovalent Ions Employing the Nonbonded Model. Journal of Chemical Theory and Computation 11, 1645-1657 (2015). Sengupta, A., Li, Z., Song, L. F., Li, P. & Merz, K. M., Jr. Parameterization of Monovalent Ions for the OPC3, OPC, TIP3P-FB, and TIP4P-FB Water Models. Journal of Chemical Information and Modeling 61, 869-880 (2021). Berendsen, H. J. C., Grigera, J. R. & Straatsma, T. P. The missing term in effective pair potentials. The Journal of Physical Chemistry 91, 6269-6271 (1987). Essmann, U. et al. A smooth particle mesh Ewald method. The Journal of chemical physics 103, 8577-8593 (1995). Attorney Docket No.11196-113WO1 Lorentz, H. A. Ueber die Anwendung des Satzes vom Virial in der kinetischen Theorie der Gase. Annalen der Physik 248, 127-136 (1881). Nosé, S. A molecular dynamics method for simulations in the canonical ensemble. Molecular Physics 52, 255-268 (1984). Hoover, W. G. Canonical dynamics: Equilibrium phase-space distributions. Physical Review A 31, 1695-1697 (1985). Berendsen, H. J. C., Postma, J. P. M., van Gunsteren, W. F., DiNola, A. & Haak, J. R. Molecular dynamics with coupling to an external bath. The Journal of Chemical Physics 81, 3684-3690 (1984). Kühne, T. D. et al. CP2K: An electronic structure and molecular dynamics software package - Quickstep: Efficient and accurate electronic structure calculations. The Journal of Chemical Physics 152 (2020). Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized Gradient Approximation Made Simple. Physical Review Letters 77, 3865-3868 (1996). VandeVondele, J. & Hutter, J. Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases. The Journal of Chemical Physics 127 (2007). Goedecker, S., Teter, M. & Hutter, J. Separable dual-space Gaussian pseudopotentials. Physical Review B 54, 1703-1710 (1996). https://doi.org/10.1103/PhysRevB.54.1703 Zhang, Y. & Yang, W. Comment on ``Generalized Gradient Approximation Made Simple''. Physical Review Letters 80, 890-890 (1998). Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics 132 (2010). Bussi, G., Donadio, D. & Parrinello, M. Canonical sampling through velocity rescaling. The Journal of Chemical Physics 126 (2007). Gaussian 16 Rev. C.01 (Wallingford, CT, 2016). Becke, A. D. Density‐functional thermochemistry. III. The role of exact exchange. The Journal of Chemical Physics 98, 5648-5652 (1993). Petersson, G. A. et al. A complete basis set model chemistry. I. The total energies of closed‐shell atoms and hydrides of the first‐row elements. The Journal of Chemical Physics 89, 2193-2218 (1988). Attorney Docket No.11196-113WO1 Scalmani, G. & Frisch, M. J. Continuous surface charge polarizable continuum models of solvation. I. General formalism. J Chem Phys 132, 114110 (2010).

Claims

Attorney Docket No.11196-113WO1 WHAT IS CLAIMED IS: Claims 1. A device for selective ion separation, the device comprising: a first electrode comprising an intercalation material layer configured to reversibly captures and releases a cation through cyclic intercalation/deintercalation, wherein the intercalation material layer is disposed on a surface of the first electrode; a second electrode; and a bipolar membrane, wherein the bipolar membrane is disposed on a surface of the second electrode. 2. The device of claim 1, wherein the bipolar membrane comprises a cation exchange layer, an anion exchange layer, and a catalyst disposed between the anion exchange layer and the cation exchange layer, wherein the catalyst comprises water dissociation catalyst and/or a hydroxide ion-proton recombination catalyst. 3. The device of claim 2, wherein the catalyst comprises tin oxide, titanium oxide, silica, platinum group metals, graphitic carbon, activated carbon, or combinations thereof. 4. The device of claim 2, wherein the anion exchange layer is disposed on the surface of the second electrode. 5. The device of any one of claims 1-4, the device further comprising a cation exchange membrane, wherein the cation exchange membrane is disposed on the surface of the first electrode. 6. The device of claim 5, wherein the cation exchange membrane is a selective cation exchange membrane. 7. The device of any one of claims 1-6, wherein the cation comprises one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium. 8. The device of claim 7, wherein the cation comprises lithium. Attorney Docket No.11196-113WO1 9. The device of any one of claims 1-8, wherein the intercalation material layer comprises one of Li_xFePO₄ (0<x<1), Li_xMnPO₄ (0≤x<1), Li_xFe_yMn_1-yPO₄, λ-MnO₂, LixMnO2, LixNi0.6Co0.2Mn0.2O2(0≤x<1), LixNi0.8Co0.1Mn0.1O2(0≤x<1), Li_xNi_0.5Co_0.2Mn_0.3O₂(0≤x<1), Li_xNi_0.33Co_0.33Mn_0.33O₂(0≤x<1), Li_xNi_0.6Co_0.2Al_0.2O₂(0≤x<1), LixNi0.8Co0.1Al0.1O2(0≤x<1), LixNi0.5Co0.2Al0.3O2(0≤x<1), LixNi0.33Co0.33Al0.33O2(0≤x<1), Li_xNiO₂(0≤x<1), Li_xCoO₂, LiNi_xMn_2-xO₄ (0 < x < 0.5), LiNi_xCo_yMn_zO₂ (x+y+z=1), LiNixCoyAlzO2(0≤x<1), Li3V2(PO4)3, V2O5, H2TiO3, Li2TiO3, TiO2, Lithium titanate (Li₄Ti₅O₁₂), Prussian blue analogues, Na_xFePO₄, Na₃V₂(PO₄)₃, NaNi_xCo_yMn_zO₂, NaNixCoyAlzO2, NaxNiO2(0≤x<1), NaxCoO2(0≤x<1), NaV2O5, KxFePO4(0≤x<1), K₃V₂(PO₄)₃, KNi_xCo_yMn_zO₂ (x+y+z=1), KNi_xCo_yAl_zO₂, K_xNiO₂(0≤x<1), K_xCoO₂(0≤x<1), or other layered metal oxides and polyanionic compounds. 10. The device of claim 9, wherein the intercalation material comprises a modified intercalation material, wherein the modification comprises one or more of carbon/N-doped carbon/graphene/graphene oxide/reduced-graphene oxide coating, AlPO₄/Al₂O₃/CeO₂ coating, metal elemental Al, Fe, Cr, Ti, Ni doped. 11. The device of claim 9, wherein the intercalation material layer comprises Li_xFePO₄ (0<x<1). 12. The device of claim 9, wherein the intercalation material layer further comprises a polymer material, wherein the polymer material forms a composite membrane-electrode structure. 13. The device of any one of claims 1-12, wherein the intercalation material layer comprises an open lattice structure. 14. The device of any one of claims 1-13, wherein the intercalation material layer exhibits an intercalation capacity of at least 30 mg g^-1 of the intercalation material. 15. The device of any one of claims 1-14, wherein the bipolar membrane is configured to operate under reverse bias and forward bias in alternating cycles. 16. The device of any one of claims 1-15, wherein the first electrode further comprises a current collector. Attorney Docket No.11196-113WO1 17. The device of any one of claims 1-16, wherein the second electrode comprises carbon and a current collector. 18. The device of any one of claims 1-17, wherein the device is configured to receive an aqueous processing fluid. 19. The device of claim 18, wherein the aqueous processing fluid comprises one or more of the cation and one or more salts. 20. The device of claim 18, wherein the aqueous processing fluid comprises deionized water or a hydroxide salt comprising the cation. 21. The device of any one of claims 18-20, wherein a pH of the aqueous processing fluid is lowered relative to the received aqueous processing fluid in situ upon a reverse voltage bias. 22. The device of any one of claims 18-21, wherein a pH of the aqueous processing fluid is raised relative to the received aqueous processing fluid in situ upon a forward voltage bias. 23. The device of any one of claims 18-22, wherein the cation from the aqueous processing fluid is selectively intercalated by the intercalation material layer upon a reverse voltage bias. 24. The device of any one of claims 18-23, wherein the cation is released by deintercalation and forms a hydroxide salt upon a forward voltage bias. 25. The device of any one of claims 1-24, wherein the device is a membrane capacitive deionization device or a capacitive deionization device. 26. A system comprising the device of any one of claims 1-25. 27. The system of claim 26, further comprising a voltage source. 28. The system of any one of claims 26-27, further comprising a pH monitor, a thermometer, a conductivity monitor, a pressure monitor, a flow monitor, and any other monitoring device. 29. The system of any one of claims 26-28, further comprising a control system. Attorney Docket No.11196-113WO1 30. A method of selective cation separation, the method comprising: providing an aqueous processing fluid comprising the cation to a device, wherein the device comprises the device of any one of claims 1-29; applying a reverse voltage bias to the device, wherein a first electrode of the device selectively intercalates the cation; applying a forward voltage bias to the device, wherein the cation deintercalates from the first electrode and forms a hydroxide salt; collecting an effluent comprising the hydroxide salt. 31. The method of claim 30, wherein the method is repeated using any proportion of the aqueous processing fluid and the effluent. 32. The method of claim 30 or 31, wherein providing the aqueous processing fluid comprises flowing the aqueous processing fluid continuously through a spacer channel. 33. The method of any one of claims 30-32, wherein the cation comprises one of lithium, sodium, potassium, rubidium, cesium, francium, copper, nickel, cobalt, rhodium, palladium, silver, iridium, platinum, gold, lanthanum, cerium, and neodymium.