Patent Application
20250236980
Overuse of fossil fuels as a major energy source has resulted in critical challenges such as limited resources, pollution, increasing carbon emissions, and the resulting climate crisis. Social concern has catalyzed a transition to, and heightened interest in, carbon-neutral energies in both transportation and grid sectors. The development of lithium-ion batteries (LIBs) for use in electric vehicles (EV) and stationary storage has raised an urgent need for an increase in lithium production. While spodumene minerals (LiAlSi2O6) are a major source for global commercial lithium production, brine resources account for 70% to 80% of the U.S. lithium deposits. (See, U.S. Department of Energy, “Battery Critical Materials Supply Chain Challenges and Opportunities,” DOE/EE-2535, December, 2021). Therefore, the domestic lithium obtention in the U.S. will necessarily look to rely heavily on lithium-rich brines in the immediate and near future. The estimated lithium resources found in California's Salton Sea region geothermal fluids alone exceeds the current U.S. demand for lithium. (See, Ventura et al., “Selective Recovery of Lithium from Geothermal Brines,” California Energy Commission, CEC-500-2020-020, March, 2020). Geothermal brines have great potential to be developed into a robust lithium supply but still remain a commercially untapped source due to technical challenges.
Lithium is a key constituent of lithium-ion batteries (LIBs) that are used in several applications, particularly in consumer electronics, electric vehicles (EVs), and energy storage systems (ESSs). The global drive for clean energy and transportation has initiated a jump in sales of EVs and ESSs and is expected to accelerate it further. This will cause an increase in demand for lithium (Li), mainly as two battery-grade Li-based chemicals: lithium carbonate (Li2CO3) and lithium hydroxide (LiOH·H2O). Lithium is also important for other sectors, including in ceramics, glass, pharmaceuticals, polymers, metallurgy, and aerospace. Given such significance, Li remains on a list of critical materials whose sustained, reliable supply over the next few decades is important for both the economy and security.
Globally, lithium is found in three types of deposits: brines, hard rock deposits (or pegmatite deposits), and sedimentary deposits (clay). The major commercial sources of these deposits are located outside the United States-Saline brines (such as those in Chile) that collectively account for 50 to 75% of global lithium production, and hard rock deposits in Australia and China. However, lithium production from these sources has been known to fluctuate over the years for a variety of reasons. This, along with the supply chain issues during the CoVID-19 crisis and the critical importance of lithium, has generated concern about the likelihood of lithium shortages in the future and its resultant negative effects on the economy. It has also sharpened the focus on exploring opportunities for production of lithium.
Compared to its extraction from saline (Salar) brines and hard rock deposits, lithium production from these brines has lower land and water demands, is less carbon-intensive via use of geothermal energy for plant operation, and involves less turnaround time for lithium supply. Also, after lithium extraction, the lithium-barren brine is returned back to the reservoir, thereby addressing environmental and social concerns associated with brine evaporation in case of saline (Salar) brines. Estimates suggest that geothermal brine-based lithium production lowers land requirement by a factor of about 10,000 over evaporation-based projects for the same amount of lithium produced. Lithium production from both geothermal and non-geothermal brines involves the use of reserves that are being used for other economic purposes, meaning that these are brownfield investments that may not incur high costs for investors.
Geothermal brines refer to hot, concentrated saline solutions that flow through hot rocks and are used to generate electricity via geothermal power plants. These brines mostly made of water, while also being rich in major elements and minerals such as potassium, arsenic, boron, silica, and most critically, lithium. The extraction of these elements and minerals from geothermal brines is useful as it provides alternative sources of their supply, as well as important in order to avoid their harmful impacts on geothermal power plant components. Examples of such harmful impacts are corrosion of power plant equipment and scaling inside pipes that can damage this equipment and reduce its heat transfer efficiency.
Conventionally, lithium is extracted from Salar brines through evaporative concentration, where brine water is evaporated using solar radiation, and the left-over concentrate is processed to obtain lithium. However, lithium extraction from both geothermal and non-geothermal brines utilizes a different group of technologies, collectively termed direct lithium extraction (DLE). Direct lithium extraction from brines, without the use of evaporative ponds, may result in less land disturbance and less water use if the brine is extracted from deep aquifers that are disconnected from fresh water aquifers, surface waters, and vegetation.
In the DLE process/technology, initially, fresh brine (or brine obtained after geothermal power generation) is withdrawn from the reservoir and processed chemically to selectively strip Li-containing material from it. The Li-containing material is subsequently processed further in multiple steps to produce the final Li-chemical (Li2CO3, LiCl, lithium metal, and/or LiOH). The residual spent brine (after recovering the Li-containing material from it) is reinjected back into the brine using injection wells. The use of DLE technology for brines is beneficial compared to evaporative concentration on multiple counts. Evaporative concentration requires the brines to contain extremely high amounts of lithium (>>2,000 mg/kg), limiting its applicability for most brines with much lower Li content (60-600 mg/kg) for which DLE can be used. Further, evaporative concentration can only be used in specific geographies and climatic regions that receive abundant sunshine and less rainfall over any time horizon, since a large amount of time is needed to extract the desired lithium (typically many months). In contrast, DLE processes can be used to extract lithium from brines in a matter of hours. Also, in case of Salar brines, almost all of the water from the brine is lost to evaporation, raising concerns. However, DLE technology offers the option to re-inject the spent brine back into the reservoir, thus reducing these concerns. DLE comprises a variety of technologies and techniques, including precipitation, sorption, ion-exchange, solvent separation/extraction, membranes (membrane separation), and electrochemical separation technologies.
Thus, technologies available for commercial lithium production from Salar brines and spodumene minerals require energy-intensive, costly, time- and resource-consuming procedures for lithium concentration, impurity removal, and product purification. (See, A. Chagnes & J. Swiatowska, (Eds.), “Lithium process chemistry: Resources, extraction, batteries, and recycling,” Elsevier Science Publishing, 2015). For instance, Direct Lithium Extraction (DLE), including adsorption, ion exchange, and solvent extraction, exploits selective adsorbents to separate out lithium and represents the latest trend for lithium obtention, potentially providing faster production and less environmental impact than legacy methods. However, DLE technologies have not been tested at large scales and over long periods of time. Thus, the practical techno-economic analyses (TEA) are still to be determined. This knowledge gap has left ample space for other DLE approaches to be developed. For instance, electrochemical methods are an emerging strategy for extraction of lithium, usually in a product form of LiCl. Electrodialysis (ED) and capacitive deionization (CDI) both use an electric field to separate Li+ and Cl− from other brine ions, but the product purity is largely impaired by limited ion selectivity. (See, Zavahir et al., Desalination, 500, ARTN 114883, doi:10.1016/j.desal.2020.114883, 2021). More recently, aqueous stable lithium ion battery cathodes such as olivine LiFePO4 and spinel LiMn2O4 have been explored for use in collecting Li+ via selective intercalation; however, such approaches appear to have substantial limitations in Li+ selectivity, extraction rate, extraction capacity, materials stability, and/or operational consistency. (See, Battistel et al., Adv. Mater, 32, ARTN 1905440, doi:10.1002/adma.201905440, 2020).
To overcome these technical drawbacks currently existing in the field of DLE, described hereinbelow are Redox Flow Lithium Extraction (RFLE) methods, systems, and technologies aiming at achieving energy-saving, fast-rate, high-purity lithium obtention. Because of its differentiated cell design, the disclosed RFLE methods are well poised to address the aforementioned technical issues of legacy DLE methods. The RFLE cells described herein are multi-component systems utilizing ion-selective and superconductive membranes of advanced materials within flow cells continually supplied with redox active reagents through a continuous circulating redox shuttle. The described systems and methods therefore provide a continuously flowing system for obtaining high-purity lithium from diverse raw materials sources such as geothermal brine or seawater. These described systems and methods achieve these results while utilizing a very low amount of energy. Relatively high lithium extraction rates are obtainable through these described systems and methods with relatively low cost and high longevity. Finally, the systems and methods described herein provide an environmentally low impact solution to the lithium extraction problem facing the economy.
The limited available lithium production and refining capacities have posed critical challenges for sustaining battery supply chains, deploying more clean energy technologies, and mitigating the climate crisis. Improved lithium production capacity from currently untapped geothermal brines will expand lithium supply from diversified sources and reduce the risk of supply chain disruption. The advantages of low energy input and high energy efficiency will lead to the use of less electricity, reduction in energy cost, and mitigation of carbon emission. Therefore, the technology described herein is expected to have potential to enhance energy resilience, sustainability, and security that will assist the establishment of a clean, decarbonized economy.
Provided are systems and methods for environmentally low-impact, low energy, continuous, and high purity extraction of lithium from diverse liquid sources such as geothermal brine and seawater. Lithium obtained by these systems and methods is in the form of one or more of LiCl, LiOH, Li2CO3, and solid lithium metal. The systems are multicomponent comprising several flow cells, one or more redox shuttle systems, optional fluid pumps and holding tanks, selective anion exchange membranes (AEMs), and lithium ion conducting solid-state electrolyte (LiCSSE) membranes, all fluidly connected together in a closed or open system that is liquid-tight to prevent leakage at any stage. The RFLE cells or stacks described herein utilize lithium ion-conducting solid state membranes within flow cells continually supplied with redox active reagents through a continuous circulating redox shuttle.
The redox flow lithium extraction systems described herein comprise LiCSSE membranes, anion exchange membranes (AEMs), and flow cells arranged in a system. The flow cells comprise in one embodiment at least a catholyte flow cell, an analyte flow cell, a lithium base flow cell, and a brine water flow cell. The lithium base flow cell and brine water flow cell are fluidly connected by the LiCSSE membrane that lies between these two flow cells in a water-tight manner, and the lithium base flow cell is fluidly connected to an anolyte flow cell by one of the AEMs in a similar manner.
In one embodiment of such systems, a brine water (geothermal brine, raw material lithium source water) flow cell is fluidly connected to a catholyte flow cell by another one of the AEMs, there being two AEMs in this embodiment of the system. In the described RFLE systems, the catholyte flow cell and the anolyte flow cell are fluidly connected to one another by one or more fluid channels such that a fluid is carried from one to the other in a circulating and continuous manner, optionally pushed along by one or more in-line pumps, and interconnected with one or more holding tanks.
In the described RFLE systems, the catholyte flow cell and the anolyte flow cell each comprise an electrode. In the described RFLE systems, the LiCSSE membrane is positioned between the two AEMs within the system, the lithium base flow cell comprises an first inlet allowing a flow of lithium base fluid into the lithium base flow cell and an first outlet allowing an outflow of lithium-rich product from the lithium base flow cell, and the brine water flow cell comprise an second inlet allowing a flow of sea water or brine into the flow cell and an second outlet allowing an outflow of the lithium-rich product. In some embodiments, the catholyte cell and/or the anolyte cell comprise an interdigitated flow field.
In the described RFLE systems, lithium ions pass through the LiCSSE membrane from the brine water flow cell and into the lithium base flow cell, chloride ions pass through a first one of the AEMs from the brine water flow cell into the catholyte flow cell, and chloride ions pass through a second one of the AEMs from the anolyte flow cell into the lithium base flow cell. In some embodiments, the LiCSSE membrane is a laser-etched membrane. In other embodiments, the LiCSSE membrane further comprises one or more dopants.
In such systems, the one or more fluid channels comprise a fluid comprising a redox shuttle molecule (RSM), where the RSM undergoes oxidation and reduction in the catholyte and anolyte flow cells. That is, the redox shuttle molecule yields a loss of electrons in the catholyte flow cell, and anions are conducted into catholyte through AEM to balance the loss of electrons as well; and the redox shuttle molecules yield a gain of electrons, and anions are conducted into lithium base flow cell through AEM in the redox shuttle molecule and chloride ions in the anolyte flow cell chemically react with the redox shuttle molecule to yield a gain of electrons in the redox shuttle molecule.
In certain embodiments, the redox shuttle molecule is an organometallic molecule, or a (ferrocenylmethyl) trimethylammonium chloride (FcNCl) molecule or any combination thereof. In other embodiments, the redox shuttle molecule comprises 1,1′-bis[3-(trimethylammonio)propyl]ferrocene dichloride (BTMAP-Fc). In certain embodiments, the LiCSSE membrane comprises one or more of: (i) Li1.3Al0.3Ti1.7(PO4)3 (LATP), Li1+yZr2(SiO4)y(PO4)3-y (LYTP), Li3Zr2-ySi2-4yP1+4yO12 (LZSP), Li1+xYxZr1-x(PO4)3 (LYZP), Li1+x+yYXZr2-x(SiO4)y(PO4)3-y (LYZSP), (Li1+xAlyGe2-y(PO4)3 (LAGP), Li1.5Al0.5Ge1.5(PO4)3, and Li3.1Zr1.95Mg0.05Si2PO12, (ii) Li3xA2/3-xBO3, wherein A is La, Na, K, Ca, Sr, or Ba, and wherein B is Ti, Sc, In, Al, Sm, Ga, Ti, Zr, Hf, Sn, Ge, Nb, or Ta, (iii) Li7-xMxLa3Zr2O12, wherein M is Al, Ga, Fe, or Ge, (iv) Li7La3-xExZr2O12 wherein E is Sr or Y, (v) Li7La3Zr2-xJxO12, wherein J is Ta, Te, Nb, Sb, W, Mo, Cr, or Ti, (vi) Li6P1-mWmS5X, wherein X is Br, Cl, or I; and wherein W is Si, Sb, or As, (vii) Li2QRy, wherein Q is In, Y, Er, Zn, or Zr, and wherein R is Cl, Br, or I, or (viii) Li3OV, wherein V is Br or Cl, and wherein x, y, and m each have a value of 0 to 1. In some embodiments, the LiCSSE membrane is an Li+-selective brine-stable lithium superionic conductor (LiSICON) and comprises one or more layers, optionally comprising one or more alternating porous/dens/porous trilayers in a sandwich structure. In said embodiments, the one or more layers are no more than about 15 microns to about 35 or more microns thick.
In some embodiments, the RFLE system described herein is considered to be as single cell stack, and embodiments are contemplated comprising multiple cell stacks, such as 2, 3, 4, 5, 10, 20, 50, or even 100 cells fluidly connected in serial or parallel, achieving substantial output of Li-rich product. Thus, in certain embodiments, the described RFLE systems further comprise one or more bipolar plates.
In another embodiment, directed to recovery and enrichment of lithium hydroxide, the system comprises an LiCSSE) membrane, an anion exchange membrane (AEM), and three flow cells, wherein the three flow cells comprise an anolyte flow cell, a catholyte flow cell, and a brine water flow cell, wherein the anolyte flow cell and brine water flow cell are fluidly connected to the LiCSSE membrane, wherein the brine water flow cell and the catholyte flow cell are fluidly connected to the AEM. In such embodiments, the anolyte flow cell and catholyte flow cell each comprise an electrode. Further, in such embodiments, the anolyte flow cell comprises an first inlet allowing a flow of lithium-lean base fluid into the anolyte flow cell and an first outlet allowing an outflow of a lithium-rich product from the anolyte flow cell, wherein the lithium-lean base fluid has a lower concentration of lithium as compared with the lithium-rich product. In such systems, the brine water flow cell comprises an second inlet allowing a flow of sea water or brine into the brine water flow cell and an second outlet allowing an outflow of waste water. In such systems, lithium ions are attracted by and pass through the LiCSSE membrane from the brine water flow cell and into the anolyte flow cell, and chloride ions are attracted by and pass through the AEM from the brine water flow cell into the catholyte flow cell. Further, one or more fluid channels continuously circulate fluid comprising a redox shuttle molecule (RSM) through the catholyte flow cell, and the RSM undergoes electrochemical oxidation in the catholyte flow cell while simultaneously the RSM is elsewhere oxidized in a further flow cell to regenerate the reduced RSM. Such systems optionally comprise one or more fluid pumps positioned in line with the one or more fluid channels.
In other embodiments of the described systems, lithium metal, is produced in purified form by the system. Such embodiment comprise an LiCSSE membrane, an anion exchange membrane (AEM), and three flow cells, wherein the three flow cells comprise an anolyte flow cell, a catholyte flow cell, and a brine water flow cell, wherein the anolyte flow cell and brine water flow cell are fluidly connected to the LiCSSE membrane, wherein the brine water flow cell and the catholyte flow cell are fluidly connected to the AEM. In such embodiments, the anolyte flow cell and the catholyte flow cell each comprise an electrode. Here, the anolyte flow cell comprises an first inlet allowing a flow of lithium organic electrolyte fluid into the anolyte flow cell and an first outlet allowing an outflow of a lithium organic electrolyte from the anolyte flow cell. In these embodiments, the electrode in the anolyte flow cell attracts deposits of lithium metal during operation of the system. In this embodiment, the brine water flow cell comprises an second inlet allowing a flow of sea water or brine into the brine water flow cell and an second outlet allowing an outflow of waste water.
In the lithium metal extraction embodiment, lithium ions are attracted by and pass through the LiCSSE membrane from the brine water flow cell and into the anolyte flow cell, and chloride ions are attracted by and pass through the AEM from the brine water flow cell into the catholyte flow cell. As in other embodiments, one or more fluid channels continuously circulate fluid comprising a redox shuttle molecule (RSM) through the catholyte flow cell, and the RSM undergoes electrochemical oxidation in the catholyte flow cell while simultaneously is elsewhere oxidized in a further flow cell to regenerate the reduced RSM. Likewise, such embodiments may optionally comprise one or more fluid pumps positioned in line with the one or more fluid channels.
In such embodiments directed to lithium metal (s) extraction, the anolyte flow cell comprises a lithiophobic anode. The lithium collects onto the lithiophobic anode in particles, as a precipitate thereon, which is later removed from the lithiophobic anode in flakes. In such embodiments directed to lithium hydroxide extraction and lithium metal extraction, the RSM is regenerated either chemically or electrochemically. In chemical regeneration, a reducing agent, such as a saccharide, such as, but not limited to, glucose or sucrose, is employed to assist in RSM regeneration. In electrochemical embodiments, further flow cells comprise a reducing agent such as, but not limited to, FeCl2.
Also described are methods of extracting lithium from various liquid lithium sources using the described systems, which comprise providing a system as described in, for instance,
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify critical or essential features of the claimed subject matter, nor is it intended to fully limit the scope of the claimed subject matter described more fully hereinbelow.
For a more precise understanding of the disclosed systems, compositions, and methods of use thereof, reference is made to specific embodiments thereof illustrated in the drawings. The drawings presented herein are not drawn to scale and any reference to dimensions in the drawings or the following description are with reference to specific embodiments. It will be clear to one of skill in the art that variations of these dimensions are possible while still maintaining full functionality for the intended purpose. Such variations are specifically contemplated and incorporated into this disclosure notwithstanding the specific embodiments set forth in the following drawings.
The term “a” or “an” entity as used herein refers to one or more of that entity; for example, “a flow cell,” is understood to represent one or more flow cells. As such, the terms “a” (or “an”), “one or more,” and “at least one” are herein used interchangeably herein.
Furthermore, “and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. Thus, the term “and/or” as used in a phrase such as “A and/or B” herein is intended to include “A and B,” “A or B,” “A” (alone), and “B” (alone). Likewise, the term “and/or” as used in a phrase such as “A, B, and/or C” is intended to encompass each of the following embodiments: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B (alone); and C (alone).
As used herein, the term “about” or “approximately” refers to a variation of 10% from the indicated values (e.g., 50%, 45%, 40%, etc.), or in case of a range of values, means a 10% variation from both the lower and upper limits of such ranges. For instance, “about 50%” refers to a range of between 45% and 55%.
Unless defined otherwise, scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is related.
Units, prefixes, and symbols are denoted in their Systeme International de Unites (SI) accepted form. Numeric ranges are inclusive of the numbers defining the range. The headings provided herein are not limitations of the various aspects or aspects of the disclosure, which can be had by reference to the specification as a whole. Accordingly, the terms defined immediately below are more fully defined by reference to the specification in its entirety.
The term “flow cell” as used herein means a container comprising an inlet and an outlet, wherein reactants or substrates for reaction flow fluidly into the container through the inlet and then flow out of the container through the outlet. The container is designed to hold liquid in a liquid-tight manner and allow a flow of fluid from one or more inlets through the container to one or more outlets.
The term “fluid channel” as used herein means a pipe, tube, or other conveyance means for carrying liquid fluidly connected to one or more flow cells. The fluid channel conveys the redox shuttle molecule from one part of the RFLE cell stack to another, and is connected to one or more inlets and outlets of the various flow cells.
The term “catholyte flow cell” as used herein means a flow cell in which electrons are gained by the redox shuttle molecule. In the catholyte flow cell, the redox shuttle molecule loses electrons and becomes oxidized. The catholyte flow cell may comprise one or more electrodes.
The term “anolyte flow cell” as used herein means a flow cell in which electrons are gained by the redox shuttle molecule, which is reduced, as a result. The anolyte flow cell may comprise one or more electrodes.
The term “lithium base flow cell” or “lithium ion flow cell” as used herein means a flow cell in which lithium ion is enriched. In the lithium base flow cell, lean lithium-lean liquid, i.e., liquid being low in lithium ion concentration, enters through one or more inlets, and lithium-rich liquid, i.e., liquid having a lithium ion concentration greater than the lithium-lean liquid, exits from the flow cell through one or more outlets.
The terms “water flow cell” and “brine water flow cell” are used interchangeably herein and means a flow cell into which flows a geothermal brine liquid, or seawater, through one or more inlets of the brine water flow cell. This flow cell is alternatively referred to herein as a brine water flow cell or geothermal brine flow cell, and the like. Into this flow cell flows the liquid raw seawater or Saline from which lithium is to be extracted by the RFLE.
The term “anion exchange membrane” (AEM) as used herein means a flat sheet-like polymeric material comprising ionic exchange groups. Such membranes are commercially available in different sizes and thicknesses and comprise different available polymers. (See, AMVN, DSVN, AAVN, ASVN, and AHO products (these are product names), for example, from SELEMION™, AGC Chemicals Americas, Inc., Exton, PA, US). Such membranes are in the form of a flat sheet with varying thickness and having an amorphous phase for ion transport. The AEM is highly selective for negative ions, such as chloride ions, hydroxide ions, carbon trioxide, and the like.
The term “redox shuttle molecule” (RSM) as used herein means a chemical molecule that carries or is capable of carrying one or more electrons. The RSM acts as a redox component carrying electrons from one flow cell, the catholyte flow cell, to another flow cell, i.e., the anolyte flow cell, such that within the catholyte flow cell, the RSM is oxidized, and within the anolyte flow cell, the RSM is reduced. The RSM aids in removal of ions from one flow cell to another to facilitate enrichment of lithium ion in the RFLE.
The term “lithium ion-selective brine-stable lithium superionic conductor” (LiSICON) as used herein means a material that possesses highly selective (ion-selective) high ionic conductivity over a broad range of temperatures and having the chemical formula Li2+2xZn1-xGeO4, and the like, but is thermally and electrochemically stable over long periods of time. Such conductors are commercially available in many different formats, shapes, sizes, and ion selectivity. The LiSICON, as implied by its name, is highly selective for lithium ion, meaning that it very efficiently conducts lithium ions. The LiSICON membrane is a type of lithium-ion conducting solid-state electrolyte (LICSSE). That is, LICSSE membranes, i.e., membranes made of LICSSE material, are a broader category of such membranes possessing the aforementioned functionality, while LiSICON membranes, i.e., membranes made of LiSICON materials, are a species of LICSSE membranes especially designed for this task and possessing additional stability in saltwater environments. LiSICON materials are synthesized as powders, tape-cast into thing films and then sintered into membranes. These membranes will be of varying thicknesses such that they provide greater than 1 mS/cm conductivity. An optimal thickness of the described membranes allows for a balanced tradeoff between low area specific resistance (ASR) and mechanical strength.
The RFLE technology described herein achieves energy-saving, fast-rate, high-purity lithium obtention and has many advantages over legacy technologies aimed at lithium production. Because of its cell design, the RFLE systems and methods described herein aid in addressing the technical issues facing the lithium field. Due to the high Li+ and counter ion selectivities enabled by the membranes employed in these described systems, a continuous mode of high-purity lithium collection directly from the geothermal brine is obtained. The symmetric redox shuttling operation achieved by RSMs gives rise to a near-zero cell voltage. Therefore, a dramatic drop in energy consumption is observed. The flow cell designs described herein allow for a theoretically infinite lithium extraction capacity ascribed to the uninterrupted redox shuttling reactions, and high lithium extraction rates enabled by the fast kinetics of solution-phase reactions.
Taking advantage of recent progress in flow batteries, counter ion-bearing organic redox molecules that have high chemical stability and crossover resistance are employed at only mM-scale concentrations, yielding operational longevity and low cost benefits. Importantly, the RFLE systems and methods described herein are highly and directly adaptable to diverse lithium sources with both ultra-dilute (seawater) to concentrated (Salar brines) lithium. Finally, the RFLE systems and methods described herein use electrons to drive pure lithium harvesting and thus eliminates the needs for chemical addition, pretreatment and purification procedures. Its operation does not require use of large volumes of land and water and generates only a negligible amount of wastes. With the other ions remaining, the delithiated geothermal brine can be pumped directly back to recharge the geothermal reservoirs. These features lead to an important advantage of environmental benignity.
Thus, the RFLE systems and methods described herein advances the state of the art of the lithium extraction field. Compared to the current commercial and near-mature lithium mining technologies, the RFLE systems and methods described herein offers the following advantageous performance characteristics: (i) low energy consumption, (ii) fast extraction rate, (iii) high product purity, (iv) unlimited extraction capacity, (v) continuous, uninterrupted extraction, (vi) environmental friendliness, and (vii) ready adaptability to diverse brine sources. It should be noted that the RFLE systems and methods described herein are in some embodiments able to be used for primary resource as well as secondary resource processing. The various elements, aspects, uses, features, and performance metrics of the RFLE systems are described hereinbelow.
As shown in
In the system of
In
In addition, in some embodiments, the produced LiCl is converted into LiOH by membrane electrodialysis. (See,
As an example of further downstream processing of the product stream created by the RFLE described herein, in some embodiments, the lithium-rich product stream is further concentrated to about 3000 ppm to about 5000 ppm lithium. In such embodiments, the lithium enriched solution is collected from lithium base flow cells and further manipulated by known means to concentrate the product to the desired ppm. Additionally, captured LiCl, in some embodiments, is converted into Li2CO3 by known means, such as by adding soda ash (Na2CO3), at a temperature ranging from about 25° C. to about 100° C. In such embodiments, high-purity crystalized Li2CO3 is recovered.
In other embodiments, compressed CO2 is added to convert LiCl into Li2CO3 owing to circular economy and environmental sustainability. The compressed CO2 may be supplied through a plastic hose or other gas channel into concentrated LiCl product stream at the temperature ranging from about 25° C. to about 100° C. The flow rate of CO2 is adjusted in the range of about 1 to about 10 bubbles per second, for instance, using a downstream bubble counter. In such embodiments, high-purity crystalized Li2CO3 is recovered.
End plates 1 are able to be affixed to one another thereby creating a sandwich. The end plates are in some embodiments made of metals or composite metals, such as stainless steel, aluminum, titanium. In other embodiments the end plates are comprised of one or more polymer materials, such as polyvinyl chloride (PVC), polypropylene (PP), and/or poly ethyl ether ketone (PEEK). Affixing endplates together is achieved by screws or clamps. When the end plates are comprised of metal materials, such embodiments optionally include within the assembly one or more insulating gaskets, made of rubber materials and/or poly tetra fluor ethylene (PTFE), and in some embodiments insulating washers are included to inhibit short circuits.
In the described RFLE system of
In the anolyte flow cell of
In the catholyte flow cell, the redox shuttle molecules are electrochemically oxidized. In one embodiment, the oxidized electrolyte is chemically reduced to an initial state of charge by added reducing agents, such as glucose, fructose, or other saccharide, for example. Glucose, fructose or other saccharide are inexpensive reducing agents that are readily available, and produce non-contaminating products of only CO2 and H2O. In another embodiment, the oxidized electrolyte (RSM) is reduced to an initial state of charge by electrochemical reaction, as depicted in
Thus, in the embodiment depicted in
It is to be understood that various other RSMs are substitutable within these schematics depicted in
The collected lithium metal products, collected in the forms of lithium metal flakes or particles, are washed using blank organic solvents and then dried under vacuum (about 10 psi to about 30 psi) at a temperature of from about 20° C. to about 100° C. In this embodiment, the blank organic solvents include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,3-dioxolane (DOL), and dimethoxy ethane (DME), for example.
In this embodiment raw geothermal brine is pushed via pump or other means into one or more inlets of the brine water flow cell in the middle of the diagram. In the brine water flow cell, as in other embodiments, lithium ion is separated from negative counter ion and each ion is conducted out of the brine water flow cell through one or more membranes, such as the LiCSSE and AEM membranes. The redox flow lithium extraction system for lithium metal products depicted in
In the described anolyte flow cell of
In the described RFLE system of
In the catholyte flow cell of
It is noteworthy that contemplated herein are embodiments of systems that are applicable not only to production, enrichment, or purification of LiCl, but also are capable of producing other lithium-counter ion pairs, such as, but not limited to, LiOH (LiOH·H2O), Li2CO3, and lithium metal. In some embodiments, the system produces an LiOH (LiOH·H2O) stream alone and no LiCl by conversion of LiCl into LiOH using, for instance, the membrane electrodialysis system depicted in
It is to be generally understood that the embodiments of
In some embodiments, the RFLE system is composed of sandwiched flow cells, creating a stack, such as that depicted in
For instance, in
Redox shuttle molecules are employed by the various embodiments of the RFLE systems described herein to continuously replenish needed electrons in the system that maintain the proper electrochemical balances across the various AEM and LiSICON membranes. In the embodiment depicted in
An exemplary embodiment of this chemical reaction scheme is depicted in
Furthermore, while FcNCl is depicted as the redox flow shuttle molecule in
Aside from ferrocene-based redox shuttle molecules, other shuttle molecules are employed in embodiments directed to LiCl, LiOH, Li2CO3, and lithium metal extraction as depicted in
The concentration of the redox shuttle molecule in the circulating fluid is not particularly limited but in some embodiments is between about 0.05 M to about 2 M depending on the identity of the RS molecule. In some embodiments, the concentration of the redox shuttle is between 0.05 M and 0.10 M, between 0.05 M and 0.25 M, between 0.05 M and 0.50 M, between 0.05 M and 0.75 M, between 0.05 M and 1.0 M, or between 0.05 M and 1.5 M. In some embodiments, the concentration of the redox shuttle is between 1 M and 2 M, between 0.5 M and 2.0 M, between 0.75 M and 1.0 M, between 0.25 M and 0.5 M, between 0.5 M and 0.75 M, between 1.5 M and 2.0 M, between 1.8 M and 2.0 M, or between 0.1 M and 0.2 M.
In the embodiments depicted in
The LiCSSE membranes are fabricated using different types of LiCSSE materials, including perovskite oxide LiCSSE material (Li3xLa2/3-xTiO3, where the La can be submitted by Na, K, Ca, Sr or Ba, and the Ti can be replaced by Sc, In, Al, Sm, Ga, Ti, Zr, Hf, Sn, Ge, Nb or Ta), or garnet-type LiCSSE material (Li7-xMxLa3Zr2O12, M=Al, Ga, Fe and Ge; Li7La3-xNxZr2O12, N═Sr and Y; Li7La3Zr2-xBxO12, B═Ta, Te, Nb, Sb, W, Mo, Cr and Ti), or sulfide LiCSSE material (Li6P1-mYmS5X, X═Br, Cl and I; and Y═Si, Sb and As), or halide LiCSSE material (Li2MXy, M=In, Y, Er, Zn and Zr, X═Cl, Br and I), or anti-perovskite oxide LiCSSE material (Li3OX, X═Br and Cl).
Polymer/inorganic composite LiCSSE membranes, in some embodiments, are made from cation conducting polymers which include but are not limit the following materials: sulfonated poly ether ether ketone, sulfonated poly styrene, sulfonated poly(p-phenylene oxide), and inorganic LiCSSE materials. Inorganic LiCSSE materials include, but are not limited to, perovskite-type oxide LiCSSE material (Li3xLa2/3-xTiO3, where the La can be submitted by Na, K, Ca, Sr or Ba, and the Ti can be replaced by Sc, In, Al, Sm, Ga, Ti, Zr, Hf, Sn, Ge, Nb or Ta), garnet-type LiCSSE material (Li7-xMxLa3Zr2O12, M=Al, Ga, Fe and Ge; Li7La3-xNxZr2O12, N═Sr and Y; Li7La3Zr2-xBxO12, B═Ta, Te, Nb, Sb, W, Mo, Cr and Ti), sulfide LiCSSE material (Li6P1-mYmS5X, X═Br, Cl and I; and Y═Si, Sb and As), halide LiCSSE material (Li2MXy, M=In, Y, Er, Zn and Zr, X═Cl, Br and I), and anti-perovskite oxide LiCSSE material (Li3OX, X═Br and Cl).
In addition, in some certain embodiments, different inorganic composite LiCSSE membranes are employed as a membrane in the described RFLE system. The inorganic composite LiCSSE membrane may comprise two or more, such as three or more, four or more, or even five to ten or more, of LiCSSE-type perovskite oxide LiCSSE membranes (Li3xLa2/3-xTiO3, where the La can be submitted by Na, K, Ca, Sr or Ba, and the Ti can be replaced by Sc, In, Al, Sm, Ga, Ti, Zr, Hf, Sn, Ge, Nb or Ta), garnet-type LiCSSE membranes (Li7-xMxLa3Zr2O12, M=Al, Ga, Fe and Ge; Li7La3-xNxZr2O12, N═Sr and Y; Li7La3Zr2-xBxO12, B═Ta, Te, Nb, Sb, W, Mo, Cr and Ti), sulfide LiCSSE membranes (Li6P1-mYmS5X, X═Br, Cl and I; and Y═Si, Sb and As), halide LiCSSE membranes (Li2MXy, M=In, Y, Er, Zn and Zr, X═Cl, Br and I), and anti-perovskite oxide LiCSSE membranes (Li3OX, X═Br and Cl).
In some embodiments, the LiCSSE membrane comprises LATP. For manufacturing, various LiCSSE materials are synthesized as powders, tape-cast into thing films and then sintered into membranes. These membranes will be of varying thicknesses such that they provide greater than 1 mS/cm conductivity. An optimal thickness of the described membranes allows for a balanced tradeoff between low ASR and mechanical strength.
The ASR of an RFLE cell, measured via electrochemical impedance spectroscopy (EIS), reflects its ion, charge, and mass transport resistances (RΩ, RCT, and RMT, respectively) and determines its overpotential and energy loss. Without wishing to be bound by theory, due to the low ionic conductivity, LiCSSE membranes are likely the major ohmic contributors in RFLE cells. This suggestion is supported by the Nyquist plots shown in
In various embodiments of the LiCSSE membranes incorporated into the systems described herein, the membranes are structurally stable for numerous days, for instance up to about 30, about 60, about 90, about 120, about 240, about 365 days or more, such as about 1, about 2, about 3, about 5, and even about 10 years or more while immersed in or otherwise continually being exposed to geothermal brine conditions.
The LiCSSE material is as much as about 90%, about 92%, about 94%, about 96%, about 98%, and even about 99% or more selective towards lithium ion conduction.
In some embodiments, the LiCSSE membrane is a phase-pure, dense LiCSSE separator membrane that is self-supported. In such embodiments, the LiCSSE membrane has a density of greater than 80%, 90%, 92%, 94%, 96% or even 98% and an ionic conductivity of greater than 1 mS/cm.
LiSICON membranes are generally manufactured using slurry, tape-casting, and sintering techniques to obtain dense membranes with greater than 95% density and greater than 1 mS/cm conductivity. (See, for instance, DeWees et al., ChemSusChem, 12(16):3713-3725, 2019, said methods described therein incorporated herein by reference for all purposes). In some embodiments the LiSICON membrane is self-supported. In some embodiments, the LiSICON membrane is protected by a thin film coating to prevent degradation due to continuous exposure to brine fluids.
LiSICON membranes have been synthesized from various methods known in the art, which are generally described as solid- and liquid-based approaches as generally described below.
The solid-based synthesis methods include solid-state synthesis, melt-quenching, and fast sintering techniques. In solid-state synthesis, the precursors (generally metal oxides) are mixed using ball milling, and complete solid-state reaction and densification through calcination and sintering heat treatment under the conditions of high temperatures (about 700° C. to about 1200° C.) and long dwell times, i.e., more than 12 hours. However, high temperature heat treatment results in lithium source loss and formation of a secondary phase, leading to low ionic conductivity.
In melt-quenching synthesis, the precursors are melted at higher temperatures, i.e., about 1500° C., followed by quenching at room temperature to form an amorphous glass, which is then further sintered to achieve crystallization. The properties of the formed solid electrolyte, including density, ionic conductivity, and phase purity, strongly depend on the chemical precursors, sintering methods, and temperature.
Fast-sintering techniques have been developed to reduce lithium source loss during heat-treatment at high temperatures. In principle, the high heating rates, e.g., more than 100° C. per min, are achieved by utilizing electrical currents, voltage, or electromagnetic energy methods, during solid-state sintering or densification. The high-grade solid electrolytes with high density, ionic conductivity, and phase purity are achieved by optimizing electrical currents, voltages, and electromagnetic energy.
The liquid-based synthesis methods include sol-gel, coprecipitation, and solution- or evaporation induced self-assembly. Compared to solid-based synthesis methods, the liquid-based synthesis methods require lower heat-treatment temperatures and can achieve better particle size and morphology of solid electrolytes. In such methods, a colloidal solution is formed using a solvent intermediate and then a gel network, followed by heat treatment for crystallization. The sol-gel method provides an effective pathway for high-purity crystalline solid electrolytes at lower heat-treatment temperature.
The coprecipitation method usually involves the dissolution of salt compounds of two desired precursors in the aqueous solution, followed by precipitation upon pH adjustment. The co-precipitate is freeze-dried and undergoes intermediate- to high-temperature calcination to achieve crystalline solid electrolytes. The sintering temperature and holding time play a very important role in the formation of high phase purity and ionic conductivity.
To reduce the cost of organic solvent and sintering temperature, solution-based synthesis is developed for LiCSSE and/or LiSICON solid electrolytes. The precursors are dissolved or suspended in water. The mixture is achieved by removing excess water, followed by heat treatment at relative low temperature (about 600° C. to about 800° C.). In addition, some venders, such as MTI corporation (Richmond, CA, US) and MSE Supplies LLC (Tucson, AZ, US), provide some small size LiSICON membranes. However, these commercial LiSICON membranes are high in price and lead to a high cost RFLE system.
In some embodiments, one or more dopants are added to the LiSICON membrane. The LiSICON dopants are not particularly limited but are in some embodiments selected from one or more dopants. Two doping approaches are known in the art and have been adopted: (1) doping at cation sites of hexahedron [TiO6], and (2) doping at cation (P) or anion (O) sites of tetrahedron [PO4]. The dopants at the cation sites of hexahedron [TiO6] are not particularly limited but are in some embodiments selected from one or more of Ga3+, Sc3+, Y3+ Te4+, Sn4+ and Zr4+. (See, for instance, Kothari et al., Physica B: Condensed Matter, 501:90-94, 2016; Wang et al, Electrochimica Acta, 399:139367, 2021, Xu et. al, Nanomaterials, 12(12):2082, 2022; and Gan et al., Electrochimica Acta, 423:140567, 2022, all of which are incorporated herein by reference specifically for the disclosure and description of dopants utilized in LiSICON assembly).
Dopant cations having bigger radii enlarges the lattice parameters of crystal structures, which improves ion conductivity of LiSICON membranes. The substitutions of cation (P) or anion (0) sites in tetrahedron [PO4] are not particularly limited but are in some embodiments selected from one or more of Si4+, V5+, Nb5+, S2− and Cl−. (See, Liu et al., Journal of Alloys and Compounds, 756:103-110, 2018; Vijayan et al., Journal of Physics and Chemistry of Solids, 72(6):613-619, 2011; Chang et al., Journal of the American Ceramic Society, 88(7):1803-1807, 2005; Cai et al., Solid State Ionics, 354:115399, 2020; Li et al., Materials Chemistry Frontiers, 5(14):5336-5343, 2021; and Kizilaslan et al., Physical Chemistry Chemical Physics, 22(30):17221-17228, 2020, all of which are incorporated herein by reference specifically for the disclosure and description of dopants utilized in LiSICON assembly). The substitution of cation site (P) in the [PO4] can increase the density during pellet or membranes sintering due to the formation of low melting oxides. In addition, the dopants in the anion site (0) of [PO4] enhances the Li-ion transport in the grain boundaries because weaker electronegativity of doping anions compared to oxygen reduced the attraction of lithium ions.
Particularly, it is noted that in some embodiments the anion exchange membranes (AEMs) comprise one or more of anion selective and commercially available materials, including, but not limited to, SELEMION™ AEMs (such as products named AMVN, DSVN and ASVN) developed by AGC Engineering (Chiba City, Chiba, Japan), NEOSEPTA AEMs (such as products named AFX, AHA, and AHO) fabricated by ASTOM Corporation (Ujitawara, Kyoto, Japan), Fumasep AEMs (such as products named FAA-3-20, FAP-330, FAPQ-330, FAB-PK-130, etc.) purchased from Fuel Cell Store (Bryan, Texas, USA). In some embodiments, the AEM material is as much as 90%, 92%, 94%, 96%, 98%, and even 99% or more selective towards chloride ion conduction. The Cl− selectivity is easily evaluated using H-type diffusion cells by known methods, with the AEM separating a simulated brine and a blank solution, for example.
AEMs are commercially available in various forms and formats, in planar sheets of varying thicknesses and as conventional resins. The AEM is designed to be highly selective for negative ions, i.e., they bind to and assist in transport of monovalent anions across or through the membrane material, e.g., from one flow cell into another.
Electrodes are, in some embodiments, comprised of commercial carbon cloth, (Hydro-LAT-1400 and Hydro-LAT-2400 purchased from Fuel Cell Store, or CCP10 carbon cloth, such as those commercially available from Fuel Cell Earth (Woburn, MA, US), carbon paper (AvCarb EP40, AvCarb MGL 190 and AvCarb MGL 280, such as those commercially available from Full Cell Store (Woburn, MA, US) and graphite felts (SIGRACELL carbon and graphite felts, commercially available from SGL Carbon LLC (Wiesbaden, DE). In other embodiments, electrodes are comprised of one or more of carbon paper and graphite felts.
It is known that the morphology and surface chemistry of porous carbon electrodes largely affect electron transfer kinetics through tuning accessible redox sites, wettability, or electrocatalysis. Such morphology and surface chemistry can be varied to obtain optimum ASR in the RFLE. Thus, the morphology and surface chemistry or porousness of the electrode material is not particularly limited. The surface of the electrodes is in some embodiments functionalized by addition of, for example, heteroatoms and/or nanomaterials.
The size and shape of the flow cell is not particularly limited, but may be round, square, or any other shape. The flow cell may be flat or spherical or cuboid, or any other shape desired for the intended use. The main purpose of the flow cell is to allow a fluid stream containing ions and/or redox shuttle components to enter into the container so that they may make contact with one or more of the membranes, electrodes, and the like positioned within each flow cell, as described in further detail hereinbelow. After reaction therewith, the fluid is then allowed to flow out of the container through the outlet. Each flow cell may have one or more inlets and outlets, but will always have at least one inlet and at least one outlet. The size and shape of the inlets and outlets are not particularly limited but may be round or pipe-shaped, or any shape that efficiently allows passage of fluid through the container at a desired flow rate. The flow cell may optionally also comprise one or more controllers for controlling fluid flow through the inlet or the outlet at a desired flow rate. The flow cell may be comprised of any known materials such as plastics, metals, or other polymers and mixtures thereof known to be able to hold fluid without leakage. Further, the term “flow cell” is a generic term intended to encompass several different species of flow cell including, but not limited to, catholyte flow cell, anolyte flow cell, lithium base flow cell, brine water flow cell, and the like. In some instances, the flow cell will further comprise one or more electrodes.
Flow cells are interconnected by one or more fluid channels. Fluid channels are comprised of any known material such as metal, polymer, plastic, carbon fiber, and mixtures thereof.
At least one or more walls of the flow cells are comprised solely of an AEM or other membrane, such as an LiCSSE membrane, etc. That is, the flow cell is built such that it is liquid-tight except for one or more sides comprised of porous or semi-porous membranes that allow ions to pass therethrough from one flow cell to an adjacent flow cell. (See,
In some embodiments, the electrolytes flow rate in different flow cells are in the range from about 20 ml/min to about 100 ml/min. In some embodiments, the flow rate is from about 20 ml/min to about 30 ml/min, from about 20 ml/min to about 40 ml/min, from about 20 ml/min to about 50 ml/min, about 20 ml/min, about 30 ml/min, about 40 ml/min, about 50 ml/min, about 50 to about 100 ml/min, about 50 ml/min to about 60 ml/min, about 50 ml/min to about 70 ml/min, about 50 ml/min to about 80 ml/min, about 50 ml/min to about 90 ml/min, or from about 90 ml/min to about 100 ml/min.
Catholyte and anolyte flow cells described herein as components of the described systems are generally comprised of a graphite current collector and an electrode, where the redox shuttle electrolytes flow through and complete electrochemical reactions.
Lithium base and brine flow cells described herein as components of the described system are generally comprised of a flow chamber, which clamps a piece of LiCSSE and is separated by AEMs on the other side.
An exemplary RFLE is depicted in
Methods using these described RFLE systems produce purified lithium ion fluid, or lithium-rich fluid, that is as much as about 95%, about 96%, about 98%, and about 99% or more pure LiCl, LiOH, or lithium metal. Purity is easily determined by known methodologies such as inductively-coupled plasma-mass spectroscopy (ICP-MS). In some embodiments, additional purification methods are employed to the lithium-rich fluid obtained from the outlets to further improve purity of chloride ion selection, such as size exclusion-based membrane engineering, e.g., incorporation of silica-based fillers to shrink the ion transport channel size. (See, for instance, Zhang et al., Energ. Environ. Sci., 5:6299-6303, doi:10.1039/c1ee02571f, 2012).
The lithium extraction rate (LER) and specific energy consumption (SEC) of the described RFLE systems mainly depend on the current density. The higher charging current density results in higher LER and more SEC. At the current density ranging from 1 mA/cm2 to 100 mA/cm2, the RFLE systems described herein achieve equal to or greater than about 1.5 to 150 mgLiCl/(cm2·h) and SEC of equal to or more than 0.06 to 5 kWh·kg−1LiCl, and greater than about 99% LiCl, LiOH, or Li metal product purity are achieved by the described RFLE systems.
Further modifications and alternative embodiments of various aspects of the methods and systems described herein will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the disclosed methods and systems. It is to be understood that the forms of the disclosed methods and systems shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the disclosed methods and systems are capable of being utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosed methods and systems. Changes may be made in the elements described herein without departing from the spirit and scope of the disclosed methods and systems as described in the following claims.
All of the references cited above, as well as all references cited herein, are incorporated herein by reference in their entireties. The following examples are offered by way of illustration and not by way of limitation. The experimental results obtained on the membrane and electrochemical cells provided below show the promising characteristics of RFLE systems for DLE. The high selectivity of the membrane and flow cell design have paved the way for substantial performance metrics for the RFLE, especially the extraction rate, energy consumption, and product purity.
Sandwiched porous/dense/porous trilayer structures were fabricated for Li1.3Al0.3Ti1.7(PO4)3 (LATP) membranes to provide enhanced conductivity while maintaining the mechanical strength of the LiSICON structures. The trilayer LATP membranes were fabricated via the following three steps.
The first step is the synthesis of LATP electrolyte. The LATP solid electrolyte (Li1.3Al0.3Ti1.7(PO4)3) was prepared by solid-state method. Stoichiometric amounts of Li2CO3, TiO2, (NH4)2H(PO4)3, and Al2O3 were mixed and ground for 1 hour in an agate mortar. The mixture was heated at 800° C. for 24 hours at 5° C./min. Then the heated mixture was ball-milled at 350 rpm for 3 hours.
The second step comprises fabrication of dense layers and porous layers by tape casting. The tape slurry for the dense layers was prepared by blending LATP powder (40 wt %), dispersant (Menhaden fish oil, 0.2 wt %), binder (polyvinyl butyral, 7.4 wt %) and plasticizer (Benzyl butyl phthalate, 7.4 wt %) in ethanol/toluene (5/1, vol), followed by mixing in a Thinky planetary centrifugal bubble free mixer (Thinky USA, Laguna Hills, CA, US) at 2000 rpm for 5 minutes. The slurry was cast onto a dust-free silicone-coated polyethylene terephthalate (SiPET) carrier film after degassing under vacuum for 10 minutes. The doctor blade gap was set to 150 m. The cast membrane was dried overnight at room temperature. The tape was removed from the carrier film (the thickness of dried tape is around 35 m, see
The third step is treatment by hot-pressure and sintering. In the hot-pressure process, the tapes were clamped between two pieces of mylar sheets. The porous tape was hot pressured at 70° C. under 1000 pounds for 30 seconds, followed by hot-pressing at 70° C. under 5 tons for 10 min. The hot-pressed porous tape was then cut in half. The dense tape with the same size as the cut porous tape was put onto the top of the hot-pressed porous tape. These two tapes were then hot-pressed at 70° C. under 1000 pounds for 30 seconds, followed by further hot-pressure treatment at 70° C. under 5 tons for 10 min. The other porous tape was put onto the surface of the pressed porous/dense tape. A similar hot-pressure process was completed at 70° C. under 1000 pounds for 30 seconds, followed by hot-pressing at 70° C. under 5 tons for 10 min. The trilayer tape was then sintered at 1000° C. for at least 24 hours. The porosity of porous layer is around 45% (vol). The porosity of porous layers is tunable by increasing the amount of pore inducing agent. The porosity of the porous layer is in the range from 15% to 65% (vol).
The different size membranes are cut using laser cuter at RT. Disc membranes were laser-cut, and are shown in
Additional sandwich structures were also made by laser etching as shown in
The LATP membrane was fabricated using a tape casting method. The tape slurry was prepared by blending LATP powder (70 wt %), dispersant (Menhaden fish oil, 0.5 wt %), binder (polyvinyl butyral, 14.75 wt %), and plasticizer (benzyl butyl phthalate, 14.75 wt %) in ethanol/toluene (5/1, vol), followed by mixing using a Thinky planetary centrifugal mixer (Thinky USA, Laguna Hills, CA, US) at 2000 rpm for 5 minutes. The slurry was cast onto a dust-free silicone-coated polyethylene terephthalate (SiPET) carrier film after degassing under vacuum for 10 minutes. The doctor blade gap was set to 1200 m. The cast membrane was dried overnight at room temperature. The tape was removed from the carrier film and cut into different shapes. The self-supported tape membrane was etched using laser-cuter (PLA 6.75 mode, Universal Laser Systems, Scottsdale, AZ, US). The maximum laser power was 15 W. The laser pulse per inch was 500, and the etching speed was about 0.1 mm/min to 1 mm/min. The etched self-supported tape membrane was then sintered at 450° C. for 3 hours, followed by sintering heat treatment at 950° C. for 3 hours.
The self-supported structures essentially start with a relatively thick, dense LiSICON green tape, and through various processes, portions of the membrane are removed through subtractive manufacturing techniques, leaving behind extremely thin regions of ceramic electrolyte material, supported by thicker veins of material. The etching feature of a laser cutting device allowed high precision in cut depth, providing membrane thicknesses down to 15 microns. Many geometries were tested, including honeycomb, triangular, and square grids as shown in
In this example, large-area LATP membranes were manufactured by a solid state method. The stoichiometric amounts of Li2CO3, TiO2, (NH4)2H(PO4)3 and Al2O3 were mixed and ground for 1 hour in an agate mortar. The mixture was heated at 800° C. for 24 hours at 5° C./min, then the heated mixture was ball-milled at 350 rpm for 3 hours. The LATP membrane was fabricated by the tape casting method. The tape slurry was prepared by blending LATP powder (70 wt %), dispersant (Menhaden fish oil, 0.5 wt %), binder (polyvinyl butyral, 14.75 wt %) and plasticizer (benzyl butyl phthalate, 14.75 wt %) in ethanol/toluene (5/1, vol.), followed by Thinky mixer (Thinky USA, Laguna Hills, CA, US) at 2000 rpm for 5 minutes. The slurry was cast onto a dust-free silicone-coated polyethylene terephthalate (SiPET) carrier film after degassing under vacuum for 10 minutes. The doctor blade gap was set to 800 m. The casted membrane was dried overnight at room temperature. The tape was removed from the carrier film and cut into cycle shape with 1 inch diameter. The cycle membranes were sintered at 450° C. for 3 hours, followed by sintering heat treatment at 950° C. for 3 hours. At last, the LATP membrane was polished down to a thickness of 300 m.
Provided in this example is proof-of-concept data showing successful validation of the feasibility of the RFLE design at a small scale with LZSP membranes.
The LZSP solid electrolyte (Li3Zr2Si2PO12) was prepared by a solid-state method. Stoichiometric amounts of Li2CO3, ZrO2, (NH4)2H(PO4)3 and SiO2 were mixed and ground for 1 hour in an agate mortar. The mixture was firstly heated to 500° C. at 5° C./min and maintained at that temperature for 3 hours, then the temperature was increased to 1100° C. at a rate of 5° C./min and maintained at that temperature for 3 hours. The heated mixture was ball-milled at 350 rpm for 3 hours.
The LZSP membrane was then fabricated by a tape casting method. The tape slurry was prepared by blending LZSP powder (70 wt %), dispersant (Menhaden fish oil, 0.5 wt %), binder (polyvinyl butyral, 14.75 wt %) and plasticizer (benzyl butyl phthalate, 14.75 wt %) in ethanol/toluene (5/1, vol), followed by ball-milling at 300 rpm for 30 minutes. The slurry was cast onto a dust-free silicone-coated polyethylene terephthalate (SiPET) carrier film after degassing under vacuum for 10 minutes. The doctor blade gap was set to 800 m. The casted membrane was dried overnight at room temperature. The tape was removed from the carrier film and cut into cycle shape with 1 inch diameter. The cycle membranes were sintered at 600° C. for 3 hours, followed by sintering heat treatment at 1200° C. for 3 hours. At last, the LZSP membrane was polished down to a thickness of 300 m.
Instead of the traditional compressive bolt fastening used for redox flow batteries, an epoxy adhesive was used to glue the cell parts together and provide leak-free sealing. This sealing method eliminates the need of high mechanical compression forces and allows for a reliable assembly of the brittle LiSICON separator in RFLE cells.
A large volume (4 L) of a simulated brine containing 30 mM LiCl, 2.2 M NaCl, and 0.36 M KCl was circulated through its channel. The LiCl influent was started with a base concentration of 0.05 M and a small volume of 20 mL. The RS electrolyte contained 0.05 M FcNCl/FcNCl+ at 50% SOC, and SGL graphite felt electrodes were used. An area specific ohmic resistance of 190 Ω·cm2 was measured by electrochemical impedance spectroscopy (EIS) before Li extraction. The RFLE cell was tested at a series of constant current densities from 1 to 5 mA/cm2 for a total of 10 hours (each current density for 2 hours). After the test, the LZSP remained structurally stable without any fracturing signs. (See,
The lithium single ion conduction membrane, such as LiSICON-type solid-state electrolyte membrane (Li1+xAlyGe2-y(PO4)3 (LAGP) is one of the most commonly employed technologies for lithium extraction from seawater or brine. However, the high cost of Germanium (Ge) increases the total cost of the extraction process. However, Li1+xAlxTi2-x(PO4)3 (0.3≤x≤0.5, LATP) exhibited instability in aqueous electrolytes, where the LATP membranes were pulverized into powder during lithium ion extraction. In the prior experiment, Example 3, the Li3Zr2-ySi2-4yP1+4yO12, (0≤y≤0.5, LZSP) showed outstanding stability in aqueous electrolyte, even though more electrolytes were permeated into the Li-lean tank. In this experiment, the composition of LZSP is further optimized and tested for performance in lithium extraction in a model flow battery. Here, the effect of redoxmer electrolyte concentration and flow rate on the lithium extraction flow battery performance was investigated.
As presented in
To simulate natural brine and reduce electrolyte impedance, an artificial brine with LiCl, NaCl, and KCl (see Table 1) and 0.2 LiCl electrolyte were used as brine and lithium-lean electrolyte in LEFBs, which was used to balance the concentration of different ions. One piece of LZSP was clamped with two flow chambers and sandwiched by two pieces of commercial ASV-N anion exchange membranes. The effective electrode area of 1.6 cm2 was used as electrode.
Optimal flow rate improves LEFB performance through accelerating mass transfer on the surface of electrodes, especially in the case of low concentration electrolyte. The LEFB performance was evaluated at different flow rates between 40 mL/min and 60 mL/min. As shown in
The cell voltage started to drastically increase at high current densities (more than 8 mA/cm2). Different from the initial color of redox shuttle electrolyte in LEFB, the color of redox shuttle electrolyte turned to light yellow from dark green after charging, which indicated the SOC of electrolyte differed from a pristine electrolyte of 50% SOC. Without wishing to be bound by any specific theory, it is postulated that perhaps the increase in cell voltage results from electrolyte SOC change. Additionally, the higher flow rate raises the possibility of the formation of interstices among different battery parts, which may result in some internal side reactions between the epoxy glue and redox shuttle solution.
These results may be ascribed to higher concentration polarization at high current density. To minimize the influence of concentration polarization on LEFB performance, higher concentration redox shuttle electrolyte was employed in flow battery test.
As shown in
Higher current density for the LEFB test is beneficial to increase lithium extraction rate. Therefore, based on the LEFBs performance of different electrolytes, the energy consumption and lithium extraction rate were further analyzed. The trade-off between energy consumption and lithium extraction rate was presented in
The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. That is, the above examples are included to demonstrate various exemplary embodiments of the described methods and systems. It will be appreciated by those of skill in the art that the techniques disclosed in the examples represent techniques discovered by the inventor to function well in the practice of the described methods and systems, and thus can be considered to constitute optional or exemplary modes for its practice. However, those of skill in the art will, in light of the present disclosure, appreciate that many changes can be made in these specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the described methods and systems.
