US20150252485A1

US20150252485A1 - Method and electrochemical device for low environmental impact lithium recovery from aqueous solutions

Info

Publication number: US20150252485A1
Application number: US14/429,326
Authority: US
Inventors: Ernesto Julio CALVO; Florencia MARCHINI
Original assignee: Consejo Nacional de Investigaciones Cientificas y Tecnicas CONICET
Current assignee: Consejo Nacional de Investigaciones Cientificas y Tecnicas CONICET
Priority date: 2012-09-19
Filing date: 2013-09-19
Publication date: 2015-09-10
Also published as: AR092617A1; CN106170340A; CN106170340B; AU2013317990A1; WO2014047347A1; CL2015000568A1; US20140076734A1

Abstract

An efficient and low environmental impact method is disclosed for the recovery of lithium from aqueous solution, for example, brines from high altitude salt lakes. The method comprises the use of an electrochemical reactor with electrodes which are highly selective for lithium, where lithium ions are inserted in the crystal structure of manganese oxide in the cathode, and extracted from the crystal structure of manganese oxide in the anode. Also disclosed are three-dimensional carbon electrodes embedded in manganese oxides formed by impregnating a porous support, for example a carbon felt, with a manganese oxide/carbon black slurry.

Description

BACKGROUND OF THE INVENTION

The industrial importance of lithium either in the metallic form or as a chemical compound is rapidly increasing due to its multiple application in diverse fields such as batteries, pharmacological preparations (e.g., to treat manic depression), coolants, aluminum smelting, ceramics, enamels and glasses, nuclear fuels, or the production of electronic grade crystals of lithium niobate, tantalite and fluoride. Lithium compounds are required for the fabrication of several components in lithium-air and lithium-ion batteries for electric and hybrid electric vehicles, such as the cathode materials and electrolyte salts. Some batteries require highly pure lithium metal.
In the case of lithium-ion batteries, lithium compounds can be required for the fabrication of the cathode. Lithium compounds such as lithium manganese oxide, lithium iron phosphate, or mixed metal oxides such as lithium cobalt nickel manganese oxide can be used as active materials for cathodes.
Lithium compounds, e.g., lithium chloride or lithium carbonate, are typically produced by extraction from lithium-containing minerals such as spodumene (lithium aluminum silicate) through traditional mining or by extraction from lithium-containing brines, such as those found in high altitude salt lakes such as the Salar de Atacama in Chile, Salar de Uyuni in Bolivia, Salar de Ollaroz, or Salar del Hombre Muerto in Argentina. Alternative brine sources, such as, geothermal, oilfield, and relict hydrothermal brines are also promising sources for lithium extraction.
The current commercial method for extraction and purification of lithium from high altitude lakes relies on an evaporitic process of fractional recrystallization of chlorides of lithium, sodium, potassium, magnesium, etc. In this process, deposits containing lithium are dissolved in water or recovered as brines, evaporated in open ponds to concentrate the salts, and lithium is precipitated as lithium carbonate by the addition of soda ash. Subsequently, the lithium-depleted brine is discarded. The chemical process is relatively simple, however, it has a high environmental impact since it takes place in high altitude salt lakes (over 4,000 meters above sea level), were water is scarce and ecosystems are fragile. This extraction process profoundly alters the water balance in the high altitude salt lake, introduces chemicals in the environment, and generates large volumes of chemical waste. For example, the evaporation and concentration of brines under the effect of solar energy in a very slow process in which for every metric ton of lithium carbonate produced, at least a million liters (220,000 US gallons) of water are lost by evaporation at high altitude in desert regions.
The lithium reserves on land, mainly from brines, are about 14 million tons. There is interest in developing alternative reserves to meet growing demand. In seawater, lithium reserves are estimated at about 230 million tons, although lithium is present in much lower concentrations than in the brines from salt flats (0.1-0.2 ppm) and therefore it is much more expensive to extract. See, e.g., Abe & Chitrakar, Hydrometallurgy 19:117-128 (1987); Chitrakar et al., Ind. Eng. Chem. Res. 40:2054-2058, (2001); Kaneko & Takahashi, Colloids and Surfaces 47:69-79 (1990); Kitajou, Ars Separatoria Acta 2:97-106 (2003); Kunugita et al., Kagaku Kogaku Ronbunshu 16:1045-1052 (1990); Miyai et al., Separation Science and Technology 23:179-191 (1988); Ooi et al., Separation Science and Technology 4:270-281 (1986); Dang and Steinberg, Energy 3:325-336 (1978); Ryabtsev et al., Russian Journal of Applied Chemistry 75:1069-1074 (2002).
Therefore, there is a need for methods and devices to extract lithium efficiently and economically from brines and from low concentration sources while having a reduced impact on the environment.

BRIEF SUMMARY

The present disclosure provides an efficient and low environmental impact method for the recovery of lithium from aqueous solutions, for example, brines from high altitude salt lakes. More particularly, the disclosed method comprises the use of an electrochemical device with electrodes which are highly selective for lithium. Lithium ions are inserted in the crystal structure of a battery-type lithium insertion electrode (e.g., a manganese oxide) functioning as cathode in an extraction step in which the electrolyte is a brine or other aqueous solution containing lithium. The insertion lithium is then extracted from the crystal structure of manganese oxide in an extraction or concentration step it which the battery-type lithium insertion electrode functions as the anode and the electrolyte is a diluted aqueous solution.
Also disclosed are electrochemical devices comprising three-dimensional electrodes composed of a porous substrate (e.g., a carbon felt) embedded in a lithium insertion compound (e.g., a manganese oxide), and the assembly of multiple electrochemical devices to form an electrochemical reactor. In some aspects, the disclosed battery-type electrodes are formed by impregnating a porous support, for example a carbon felt or calcined coke carbon particles, with a lithium-manganese oxide/carbon black slurry, and subsequently delithiating the lithium-manganese oxide electrolytically.
The present disclosure provides a packed bed electrochemical cell for extracting lithium from an aqueous solution containing lithium ions comprising:

- (a) a first electrode comprising a compartment packed with a high surface carbon substrate coated with a lithium insertion compound comprising LiMn₂O₄,
- (b) a second electrode comprising a compartment packed with a high surface carbon substrate coated with a chloride reversible electrode material; and
- (c) a non-membranous porous material interposed between the first and second electrode,
- wherein the high surface carbon substrate comprises calcined coke carbon particles.

In some aspects, the calcined coke carbon particles are calcined petroleum coke carbon particles. In some aspects, the chloride reversible electrode material comprises polypyrrole. In some aspects, the non-membranous porous material separating the first and second electrode comprises a porous fritted glass separator. In some aspects, packed bed electrochemical cell further comprises current collection contacts which are in contact with the electrodes. In some aspects, the current collection contacts are titanium mesh current collectors.
The present disclosure also provides a packed bed electrochemical cell reactor comprising at least two packed bed electrochemical cells.
The present disclosure also provides an electrochemical method for extracting lithium from an aqueous solution containing lithium ions comprising:

- (a) contacting two electrodes with an aqueous solution containing lithium ions, wherein the electrodes are a battery-type electrode, and a chloride or polypyrrole reversible electrode;
- (b) applying a voltage or circulating a current between the two electrodes, wherein the lithium ions are captured by the battery-type electrode; and,
- (c) exchanging the aqueous solution containing lithium ions with a dilute solution of lithium chloride (or a dilute solution of potassium chloride) and reversing the electrical polarity,
- wherein the reversal of polarity releases lithium ions from the battery-type electrode into the dilute solution.

In some aspects, the above disclosed method further comprises repeating steps (a)-(c) at least twice using the aqueous solution containing lithium ions resulting from the previous step (c) as the aqueous solution containing lithium ions of the subsequent step (a) wherein the aqueous solution from each successive step (c) is used as the aqueous solution containing lithium ions of the next step (a). In some aspects, steps (a)-(c) are repeated at least three times, wherein the aqueous solution from each successive step (c) is used as the aqueous solution containing lithium ions of the next step (a).
In some aspects, the aqueous solution is selected from the group consisting of sea water, lake water, underground water, hot-springs water, geothermal brine, oilfield brine, relict hydrothermal brine, or high altitude salt lake brine. In specific aspects, the aqueous solution is sea water. In other specific aspects, the aqueous solution is a high-altitude salt lake brine. In some aspects, the aqueous solution comprises lithium ions and contaminant non-lithium metal ions. In some aspects, the battery-type electrode is a lithium insertion battery-type electrode comprising a porous or high surface substrate and a lithium insertion compound. In some aspects, the substrate is a carbon substrate. In other aspects, the carbon substrate is a conductive substrate. In some aspects, the battery-type electrode comprises a conductive additive material. In certain aspects, the conductive additive material is carbon black. In some aspects, the lithium insertion compound comprises a manganese oxide. In some aspects, the manganese oxide comprises γ-MnO₂and/or λ-MnO₂. In some aspects, the manganese oxide has a spinel crystal structure. In certain aspects, the manganese oxide comprises LiMn₂O₄. In other aspects, the lithium insertion compound comprises lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, or combinations thereof. In some aspects, the lithium cobalt oxide comprises LiCoO₂. In other aspects, the lithium iron phosphate comprises LiFePO₄. In some aspects, the battery-type electrode is prepared by electrolytical delithiation of a porous or high surface substrate coated with lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), lithium manganese oxide (LiMn₂O₄), or combinations thereof. In some aspects, the carbon substrate is selected from the group consisting of carbon felt, carbon cloth, carbon paper, graphite granules, granite foam, high surface area graphite fiber, and combinations thereof. In some aspects, the carbon substrate is a carbon felt. In some aspects, the carbon substrate is a calcined coke carbon substrate. In some aspects, the chloride reversible electrode comprises a porous or high surface carbon substrate and silver metal particles. In other aspects, the silver metal particles are nanoparticles. In some aspects, the chloride reversible electrode comprises an electrically conductive polymer. In other aspects, the electrically conductive polymer is a polypyrrole. In some aspects, the lithium ions in the aqueous solution are captured by insertion in the crystal structure of the battery-type electrode.
The present disclosure also provides an electrochemical device for extracting lithium from an aqueous solution containing lithium ions comprising at least one battery-type electrode comprising a porous or high surface substrate coated with a lithium insertion compound, wherein said device does not comprise a counter-electrode. In some aspects, the device further comprises a chloride reversible electrode or a polypyrrole reversible electrode. In some aspects, the substrate is a carbon substrate. In other aspects, the carbon substrate is a conductive substrate. In some aspects, the battery-type electrode comprises a conductive additive material. In some aspects, the conductive additive material is carbon black. In other aspects, the lithium insertion compound comprises a manganese oxide. In some aspects, the manganese oxide comprises γ-MnO₂and/or λ- MnO₂. In some aspects, the manganese oxide has a spinel crystal structure. In some aspects, the manganese oxide comprises LiMn₂O₄. In other aspects, the lithium insertion compound comprises lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, or combinations thereof. In some aspects, the lithium cobalt oxide comprises LiCoO₂. In other aspects, the lithium iron phosphate comprises LiFePO₄. In some aspects, the battery-type electrode is prepared by electrolytical delithiation of a porous or high surface substrate coated with lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), lithium manganese oxide (LiMn₂O₄), or combinations thereof. In some aspects, the carbon substrate is selected from the group consisting of carbon felt, carbon cloth, carbon paper, graphite granules, granite foam, high surface area graphite fiber, and combinations thereof. In some aspects, the carbon substrate is a carbon felt. In some aspects, the carbon substrate is a calcined coke carbon substrate. In some aspects, the chloride reversible electrode comprises a porous or high surface carbon substrate and silver metal particles. In some aspects, the silver metal particles are nanoparticles. In some aspects, the chloride reversible electrode comprises an electrically conductive polymer. In some aspects, the electrically conductive polymer is a polypyrrole. In other aspects, the lithium ions in the aqueous solution are captured by insertion in the crystal structure of the battery-type electrode. In some aspects, the battery-type electrode and chloride reversible electrode are positioned in separate half-cells. In some aspects, the half-cell comprising the battery-type electrode and the half-cell comprising the chloride reversible electrode or the polypyrrole reversible electrode are separated by a semi-permeable electrolysis membrane. In some aspects, the electrolysis membrane is an ionomer membrane. In some aspects, the ionomer membrane is a NAFION® membrane. In some aspects, the NAFION® membrane is NAFION® 324. In some aspects, the half-cell comprising the battery-type electrode and the half-cell comprising the chloride reversible electrode or the polypyrrole reversible electrode are not separated by a semi-permeable electrolysis membrane. In some aspects, the half-cell comprising the battery-type electrode and the half-cell comprising the chloride reversible electrode or the polypyrrole reversible electrode are separated by a porous material. In some aspects, the porous material is a gauze. In some aspects, the gauze is a polyester gauze. In some aspect, the porous material is porous fritted glass.
The instant disclosure also provides a lithium extraction plant for extracting lithium from an aqueous solution containing lithium ions comprising at least one electrochemical device as disclosed herein. In some aspects, the aqueous solution containing lithium ions is a brine. In other aspects, the brine is obtained from a high-altitude salt lake. In some aspects, the lithium extraction plant is controlled by a clean energy voltage source. In other aspects, the clean energy voltage source is a solar power source.
The present disclosure also provides a method to manufacture high purity lithium comprising using the methods, electrochemical devices, or the lithium extraction plants disclosed herein.
The present disclosure also provides an electrochemical process for extracting lithium from an aqueous solution containing lithium ions comprising using (a) the packed bed electrochemical cells disclosed herein, (b) the packed bed electrochemical reactors disclosed herein, (c) the lithium extraction methods disclosed herein, (d) the electrochemical devices disclosed herein, (e) the lithium extraction plants disclosed herein, or (e) any combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a graph showing an X-ray diffraction pattern of a LiMn₂O₄standard.

FIG. 2 is a graph showing an X-ray diffraction pattern of a sample of lithium and manganese oxide (LiMn₂O₄) prepared in the laboratory and used in the assays to extract lithium from brine using electrochemical ion exchange.

FIG. 3 is an electron microscopy image of LiMn₂O₄nanocrystals used to extract lithium from brine using electrochemical ion exchange.

FIG. 4 is an electron microscopy image of a conductive carbon felt electrode.

FIG. 5 shows an electrochemical cell for the extraction of lithium from brines. The cathode is inserted in the “S” half-cell, which contains the brine. The anode is inserted in the “HCl” half-cell which contains a 0.1 M HCl solution. A NAFION® ionomer membrane is interposed between both half cells.

FIG. 6 shows a cyclic voltammogram of carbon felt electrodes embedded with LiMn₂O₄at 50 mVs⁻¹in 50 mM LiClO₄aqueous solution. The chemical intercalation of lithium ions in manganese oxides proceeds according to the equation: LiMn₂O₄(LiMn^IIIMn^IVO₄)→2α−MnO₂+Li⁺+e⁻.

FIG. 7(A) is a schematic representation of the FM100 type electrochemical reactor for the electrochemical extraction of lithium from brines and concentration of lithium chloride solutions.

FIG. 7(B) shows the components of a disassembled FM100 type electrochemical reactor.

FIG. 8 is a photograph of a electrochemical reactor for the extraction of lithium ions from brines with brine circulation through the half-cell containing the cathode and lithium extraction solution in the anode connected to a titanium pump (Cole Parmer 75211 flow pump).

FIG. 9 shows current transients of lithium ion insertion into a LiMn₂O₄carbon loaded electrode at 0.2 V vs. Ag/AgCl, and lithium release at 1.2 V vs. Ag/AgCl in a lithium perchlorate 50 mM aqueous solution.

FIG. 10 is a schematic representation of the oxidized/reduced states of polypyrroles, which on oxidation uptakes anions in order to maintain neutrality of charges and conversely on reduction releases the anions into solution.

FIG. 11A, B, and C show different view of the experimental setup used in the polypyrrole/carbon Electrode and a LiMn₂O₄/carbon electrode system presented in Example 7.

FIG. 12 shows an SEM micrograph of carbon fibers in a carbon felt covered by LiMn₂O₄crystals corresponding to the experimental setup presented in Example 7.

FIG. 13 shows an SEM micrograph depicting the polypyrrole deposit on carbon felts corresponding to the experimental setup presented in Example 7.

FIG. 14 shows transients corresponding to four lithium chloride capture steps in the LiMn₂O₄/carbon felt cathode corresponding to the experimental setup presented in Example 7.

FIG. 15 shows current transients for a sequence of lithium recovery steps during which lithium was released from a LiMn₂O₄electrode according to the experimental conditions presented in Example 7.

FIG. 16 shows the evolution of the electrical charge during the release of lithium ions from the LiMn₂O₄/carbon electrode into the electrolyte according to the experimental conditions presented in Example 7.

FIG. 17 shows an SEM micrograph of coke particles loaded with LiMn₂O₄crystals corresponding to the experimental setup presented in Example 8.

FIG. 18 shows a Press Filter reactor (type FM100)with axial flux of electrolyte and perpendicular current flow. The reactor consists of (i) titanium current collectors, (ii) carbon felt support and petroleum calcined coke carbon support of LiMn₂O₄at one electrode, (iii) carbon felt support and polypyrrole at the other electrode, (iv) a Teflon framework, and (v) a polyester gauze in undivided cells.

FIG. 19 shows charge and discharge transients corresponding to the capture and release of lithium ions by a LiMn₂O₄electrode according to experimental conditions presented in Example 8.

FIG. 20 shows discharge and charge curves at constant current (±0.5 mA/cm²) during 2 hours by a LiMn₂O₄electrode according to experimental conditions presented in Example 8.

FIG. 21 shows a potential-charge curve for a LiMn₂O₄electrode according to experimental conditions presented in Example 8.

FIG. 22 shows a three dimensional reactor at the laboratory scale with coke compact bed electrodes loaded respectively with LiMn₂O₄and polypyrrole corresponding to the experimental packed bed setup presented in Example 8.

FIG. 23 shows a longitudinally packed bed cylindrical reactor prototype that includes a glass cylinder with two compartments separated by porous fritted glass, titanium mesh current collectors with titanium rod electrical connectors, two packed beds containing 20 g of coke loaded with electrode materials, rubber stoppers, and tubing to connect to a piston flow pump.

FIG. 24 shows the pressure drop in the reactor shown in FIG. 23 measured at different flow rates (0-30 mL per second) using a mercury pressure meter.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses an efficient and environmentally benign method for the extraction of lithium value from aqueous electrolytic solutions containing lithium ions together with other metal ions such as sodium, potassium, magnesium, and chloride ions (e.g., chloride rich brines, sea water, etc.).
The method and the devices described herein selectively extract lithium from solutions containing other ions, even when these other ions are present in relatively high concentrations. The present disclosure also provides a clean technology for the rapid extraction of lithium with low energy consumption. In this respect, the methods and devices disclosed herein can be used to extract lithium from brines or salt deposits in high altitude lakes without altering the balance of water, unlike the evaporation methods used at present to recover lithium from salt lakes in South America and other locations. It should be noted that the methods disclosed herein can be applied, for example, to (i) artificial brines containing only lithium or lithium and other salts, and (ii) to natural brines. A person skilled in the art would appreciate that methods suitable for lithium extraction from artificial brines containing only lithium, lithium and low concentrations of other salts, or artificial brines with defined compositions, may be unable to successfully extract lithium from natural brines containing not only lithium but also high sodium concentrations and high concentrations of many other salts.
In particular, the present disclosure provides an electrochemical process for the extraction of lithium from an aqueous solution containing lithium ions comprising the insertion of lithium ions into the crystal structure of a lithium insertion material, e.g., a manganese oxide, embedded on a porous substrate, e.g., a carbon felt, in the cathode and the subsequent deinsertion (extraction) of lithium ions from the crystal structure of lithium saturated oxides in the anode. In some aspects, the lithium insertion material is supported by calcined coke carbon particles.
Lithium recovery from sea water, which contains approximately 0.17 mg/L lithium, has been described in U.S. Patent Publ. No. 2011/0174739 using an adsorption/desorption process with manganese oxide as adsorbent in a polymer membrane. Unlike the present invention, the adsorbed lithium in the membrane is then released by treating with a hydrochloric acid solution, resulting in the generation of large volume of chemical waste. The method disclosed herein avoids this drawback by using an electrochemical approach in which a low valence metal cation is oxidized in a battery-type lithium insertion electrode and chloride is released at the chloride reversible electrode by electro-reduction.
In one aspect, the electrochemical method disclosed herein comprises the reduction of Mn^IVions of the cubic spinel manganese oxide MnO₂to Mn^III, which then undergoes the spontaneous insertion of lithium ions present in the solution (e.g., a salt lake brine or sea water) into the crystal structure of a LiMn₂O₄oxide (or another suitable lithium ion insertion material such as LiCoO₂, LiFePO₄, etc.). In the subsequent lithium concentration step of the method disclosed herein, Mn^IIIis oxidized to Mn^IVby reverting the electrochemical cell polarity, thus releasing the inserted lithium ions present in the crystal structure of the ion insertion material to the aqueous solution. This results in an increase in the lithium chloride concentration in the aqueous solution.
Likewise, the method can be generalized by using other lithium insertion materials, such as lithium compounds containing iron or cobalt. In these cases, for example, oxidation of Co^IIto Co^IIIor Fe^IIto Fe^III, respectively in the LiFePO₄and LiCoO₂containing electrodes releases lithium ions contained in their respective crystal structures to the aqueous solution.
In both steps (lithium extraction and lithium release/concentration) the second electrode is a reversible electrode, for example, an Ag/AgCl reversible electrode or a polypyrrole reversible electrode. For example, in the lithium extraction step an Ag/AgCl reversible electrode can uptake chloride ions from the solution to form insoluble silver chloride. Then, in the lithium release/concentration step, the Ag/AgCl reversible electrode can release chloride to the solution by formation of metallic silver. Similarly, when a polypyrrole reversible electrode is used in the lithium release/concentration step, the polypyrrole releases chloride ions into the solution. Accordingly, the balance of charge in the electrochemical cell is maintained by chloride and lithium ions, and no hydrogen ion imbalance modifies the solution pH (this is a critical difference with respect to methods that use an inert counter electrode, e.g., the process described in U.S. Pat. No. 5,198,081).

Definitions

The term, “lithium” as used herein refers to lithium metal, lithium ions, lithium atoms, or lithium compounds depending on the context. The term “lithium compounds” in reference to lithium products extracted from an aqueous solution containing lithium ions comprises, for example, lithium chloride, lithium hydroxide, lithium phosphate, lithium carbonate, etc.
The term “battery-type electrode” as used herein refers to an electrode comprising components commonly found in lithium-battery cathodes, such as lithium manganese oxides with a spinel structure. Normal spinel structures are usually cubic closed-packed oxides with one octahedral and two tetrahedral sites per oxide. The tetrahedral points are smaller than the octahedral points. Trivalent cations (B³⁺) occupy the octahedral holes because of a charge factor, but can only occupy half of the octahedral holes. Divalent cations (A2⁺) occupy ⅛ of the tetrahedral holes. A normal spinel is LiMn₂O₄.
In addition, there are intermediate cases where the cation distribution can be described as (A_1-xB_x)[A_x/2B_1-x/2]₂O₄, where parenthesis ( ) and brackets [ ] are used to denote tetrahedral and octahedral sites, respectively, and A and B represent cations. The so-called inversion degree x adopts values between 0 (normal) and 1 (inverse), and it is x=⅔ for a fully random cation distribution.
The term “lithium insertion compound” as used herein refers to a compound that can host and release lithium reversibly. In the insertion process, lithium ions are intercalated in the crystal structure of the hosting compound. The term intercalation as used herein refers to a property of a material that allows ions to readily move in and out of the crystal structure of the material without the material changing its crystal structure.
The term “conductive substrate” as used herein refers to a substrate functioning as an electrode. Therefore, the electrically conductive substrate used herein encompass those made from electrically conductive material and those obtained by coating, deposition or lamination of an electrically conductive layer of a “conductive additive material” on the surface of a non-electrically conductive substrate.
The term “conductive additive material” refers to an electrically conductive composition that can be applied to an otherwise non-conductive substrate to confer conductive properties to it. The electrically conductive additive material can include electrically conductive particulate or non-particulate materials. For example, the conductive additive material can include electrically conductive materials such as carbon black or carbon nanofibers. Other suitable electrically conductive particulate materials include, but are not limited to, metallic particulates (e.g., electrically conductive metals such as aluminum, silver, nickel, etc. in the form of a granule, flake, sphere of varying size and size distributions), non-electrically conductive grade carbon black, particles or fibers coated with electrically conductive materials, carbon fibers, inherently conductive polymers (i.e., a class of polymeric materials having conjugated chain configurations giving them the intrinsic ability to transfer electrons like a semiconductor, such as polyacetylene or polyaniline).
The conductive additive material can also include a liquid component in which the electrically conductive material is dispersed. The liquid component used in the conductive additive material can be selected from a variety of liquid components. Suitable liquid components include, but are not limited to, polyester vehicles, polyol vehicles, epoxies, plasticizers, monomers (e.g., styrene, divinyl benzene, vinyl toluene, etc.).
The term “substrate” as used herein refers to structures used during the manufacture of electrodes upon which other layers are fabricated, e.g., a carbon felt upon which a manganese oxide is deposited. In some aspects, the substrate comprises calcined coke carbon particles. In some aspects, the coke carbon particles are generated by petroleum calcination.
The term “nanoparticle” as used herein refers to a particle with at least two dimensions of 100 nanometers (nm) or less. The term nanoparticle includes, for example, nanospheres, nanorods, nanofibers, including nanowires, nanobelts, nanosheets, nanocards, and nanoprisms.
The term “carbon black” as used herein refers to any of various finely divided forms of carbon made by the incomplete combustion or thermal decomposition of a carbonaceous fuel.
The term “carbon felt” as used herein refers to a textile material that predominantly comprises randomly oriented and intertwined carbon fibers, which are typically fabricated by carbonization of organic felts (see, e.g., IUPAC Compendium of Chemical Terminology 2^ndEdition (1997)). Most typically, organic textile fibrous felts are subject to pyrolysis at a temperature of at least 1200° K., more typically 1400° K., and most typically 1600° K. in an inert atmosphere, resulting in a carbon content of the residue 99 wt %, more typically 95 wt %, and most typically 99 wt %. Carbon felts have a surface of at least about 0.01-100 m²/g, and more typically 0.1-5 m²/g, most typically 0.3-3 m²/g. When carbon felt is activated, it will typically have a surface area of more than 100-500 m²/g, more typically at least about 500-1200 m²/g, and most typically at least about 1200-1500 m²/g or even more. Depending on the organic textile material and carbonization conditions, the carbon felt can be graphitic, amorphous, have partial diamond structure (added or formed by carbonization), or a mixture thereof.
It must be noted that, as used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. The terms “a” (or “an”), as well as the terms “one or more,” and “at least one” can be 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).
Units, prefixes, and symbols are denoted in their Système 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 embodiments of the invention, which can be had by reference to the specification as a whole. It is understood that wherever embodiments are described herein with the language “comprising,” otherwise analogous embodiments described in terms of “consisting of” and/or “consisting essentially of” are also provided.

Electrochemical Method for Lithium Extracting

The present disclosure provides an electrochemical method for extracting lithium from an aqueous solution containing lithium ions comprising:

- i. contacting two electrodes with an aqueous solution containing lithium ions wherein the electrodes (an anode and a cathode) are a battery type electrode, and a chloride reversible electrode (“lithium extraction step”);
- ii. applying a voltage or circulating a current between the two electrodes (being the cathode negative and the anode positive during lithium extraction step), wherein the lithium ions are captured by the battery-type electrode; and,
- iii. exchanging the aqueous solution containing lithium ions with a dilute solution of lithium chloride and reversing the electrical polarity, thus releasing lithium ions into the dilute solution (“lithium release/concentration step”).

In some aspects, steps (ii) and (iii) are repeated several times. In some aspects, steps (ii) and (iii) are repeated 2 times. In some aspects, steps (ii) and (iii) are repeated 3 times. In some aspects, steps (ii) and (iii) are repeated 4 times. In some aspects, steps (ii) and (iii) are repeated more than four times.
In some aspects, the repetition of steps (ii) and (iii) can enrich the Li:Na concentration ratio in dilute solution with respect to the brine by at least 2-fold, at least 4-fold, at least 6-fold, at least 8-fold, at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, at least 100-fold, at least 200-fold, at least 300-fold, at least 400-fold, at least 500-fold, at least 600-fold, at least 800-fold, at least 900-fold, at least 1000-fold, at least 1100-fold, at least 1200-fold, at least 1300-fold, at least 1400-fold, at least 1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold, 1900-fold, or at least 2000-fold.
In some aspects, the enrichment in the Li:Na concentration resulting from the repetition of steps (ii) and (iii) can be used to increase the purify of the resulting lithium produced using the methods disclosed herein.
In some aspects, step (iii) is repeated several times. In some aspects, step (iii) is repeated 2 times. In some aspects, step (iii) is repeated 3 times. In some aspects, step (iii) is repeated 4 times. In some aspects, step (iii) is repeated more than four times.
In some aspects, the repetition of steps (iii) can enrich the Li:Na concentration ratio in dilute solution with respect to the brine by at least 2-fold, at least 4-fold, at least 6-fold, at least 8-fold, at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, at least 100-fold, at least 200-fold, at least 300-fold, at least 400-fold, at least 500-fold, at least 600-fold, at least 800-fold, at least 900-fold, at least 1000-fold, at least 1100-fold, at least 1200-fold, at least 1300-fold, at least 1400-fold, at least 1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold, 1900-fold, or at least 2000-fold. In some aspects, the repetition of step (iii) can enrich the Li:Na concentration in the brine more than 2000-fold.
In some aspects, the repetition of step (iii) can enrich the Li:Na concentration in the brine more than 2000-fold. In some aspects, the enrichment in the Li:Na concentration resulting from the repetition of step (iii) can be used to increase the purify of the resulting lithium produced using the methods disclosed herein.
In some aspects, the aqueous solution obtained in step (iii) can be used as the aqueous solution containing lithium ions of step (i), and steps (i) to (iii) can be performed recursively using the aqueous solution from each successive step (iii) as the aqueous solution containing lithium ions of the next step (i). In some aspects, the step sequence (i)-(iii) is repeated 2 times, wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i). In some aspects, the step sequence (i)-(iii) is repeated 3 times, wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i). In some aspects, the step sequence (i)-(iii) is repeated 4 times, wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i). In some aspects, the step sequence (i)-(iii) is repeated more than 4 times, wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i).
In some aspects, the repetition of step sequence (i)-(iii), wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i), can enrich the Li:Na concentration ratio in dilute solution with respect to the brine by at least 2-fold, at least 4-fold, at least 6-fold, at least 8-fold, at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, at least 100-fold, at least 200-fold, at least 300-fold, at least 400-fold, at least 500-fold, at least 600-fold, at least 800-fold, at least 900-fold, at least 1000-fold, at least 1100-fold, at least 1200-fold, at least 1300-fold, at least 1400-fold, at least 1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold, 1900-fold, or at least 2000-fold. In some aspects, the repetition of step sequence (i) and (iii), wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i), can enrich the Li:Na concentration in the brine more than 2000-fold.
In some aspects, the repetition of step sequence (i)-(iii), wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i), can enrich the Li:Na concentration in the brine more than 2000-fold. In some aspects, the enrichment in the Li:Na concentration resulting from the repetition of step sequence (i)-(iii), wherein the aqueous solution from each successive step (iii) is used as the aqueous solution containing lithium ions of the next step (i), can be used to increase the purify of the resulting lithium produced using the methods disclosed herein.
In some aspects, the disclosed process can be applied to diverse aqueous solutions containing lithium, for example, sea water, lake water, underground water, hot-springs water, geothermal brines, oilfield brines, relict hydrothermal brines, etc. Thus, in some aspects, the aqueous solution can contain low concentrations of lithium (e.g., about 0.17 ppm for sea water), whereas in other aspects the aqueous electrolytic solution can contain high concentrations of lithium (e.g., about 700 ppm brines from high altitude lakes).
In spine aspects, the lithium concentration in the aqueous electrolytic solution is at least about 0.10 ppm, or at least about 0.12 ppm, or at least about 0.14 ppm, or at least about 0.16 ppm, or at least about 0.18 ppm, or at least about 0.20 ppm, or at least about 0.22 ppm, or at least about 0.24 ppm, or at least about 0.26 ppm, or at least about 0.28 ppm, or at least about 0.30 ppm. In some aspects, the lithium concentration in the aqueous electrolytic solution is at least about 0.4 ppm, or at least about 0.5 ppm, or at least about 0.6 ppm, or at least about 0.7 ppm, or at least about 0.8 ppm, or at least about 0.9 ppm, or at least about 1 ppm. In other aspects, the lithium concentration in the aqueous electrolytic solution is at least about 2 ppm, or at least about 3 ppm, or at least about 4 ppm, or at least about 5 ppm, or at least about 6 ppm, or at least about 7 ppm, or at least about 8 ppm, or at least about 9 ppm, or at least about 10 ppm. In other aspects, the lithium concentration in the aqueous electrolytic solution is at least about 20 ppm, or at least about 30 ppm, or at least about 40 ppm, or at least about 50 ppm, or at least about 60 ppm, or at least about 70 ppm, or at least about 80 ppm, or at least about 90 ppm, or at least about 100 ppm. In other aspects, the lithium concentration in the aqueous electrolytic solution is at least about 150 ppm, or at least about 200 ppm, or at least about 250 ppm, or at least about 300 ppm, or at least about 350 ppm, or at least about 400 ppm, or at least about 450 ppm, or at least about 500 ppm, or at least about 550 ppm, or at least about 600 ppm, or at least about 650 ppm, or at least about 700 ppm, or at least about 750 ppm, or at least about 800 ppm, or at least about 850 ppm, or at least about 900 ppm, or at least about 950 ppm, or at least about 1000 ppm. The method disclosed herein is applicable to any lithium containing aqueous electrolytic solution, e.g., a solution containing lithium chloride, lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, lithium phosphate, etc.
In some aspects, the disclosed methods can be applied to aqueous solutions comprising lithium ions and contaminant non-lithium metal ions (e.g., sodium, potassium, etc.) and/or non-metal ions (e.g., chloride, sulfate, carbonate, nitrate, etc.). Conversely, the disclosed methods can be applied to solutions containing a purified or partially purified single lithium compound such as lithium carbonate in order to produce lithium chloride.
The disclosed methods can also be applied by maintaining the electrical polarity, and reversing the half-cells in which each electrode is located, instead of maintaining the location of the electrodes and reversing the electrical polarity.
In some aspects, the dilute lithium chloride solution in the “lithium release/concentration step” can be replaced with a dilute lithium perchlorate solution. Lithium perchlorate is generally used as an inert electrolyte in lithium batteries.
Lithium containing ore (e.g., spodumene, petalite, amblygonite, lithia micas such as zinnwaldite or lepidolite) can also be used as a source provided that a lithium-containing aqueous electrolytic solution is produced therefrom. In some aspects, an aqueous electrolytic solution suitable to use in the methods disclosed herein can be prepared by dissolving natural deposits (e.g., salt deposits from high altitude salt lakes or subsurface evaporitic salt deposits) or artificial deposits (e.g., salt deposits from salt works).
In some aspects, prior to purification according to the electrochemical methods disclosed herein, impurities (e.g., ions other than lithium, such as metal or non-metal ions) present in the aqueous electrolytic solution can be reduced or removed via suitable processes known in the art for removing or reducing the respective impurities (e.g., precipitation or ion exchange).
In some aspects, the voltage or circulating current can be provided by a conventional (e.g., electricity generated from conventional fossil-fuel sources such as coal or gas, or nuclear power) or a clean energy source, for example solar energy (e.g., from thermal or photovoltaic generators). Other clean energy sources can be used, for example, energy obtained from hydroelectric generators, biomass, geothermal sources, wind energy, wave/tidal energy, landfill gas, or gas powered fuel cells.
In some aspects, a small DC voltage is applied between the two electrodes, being the battery-type electrode negative and the chloride reversible electrode positive during the lithium extraction step. In some aspects, the DC voltage is between about 0.1 and about 0.5 V. In some aspects, the DC voltage is lower than 0.1 V. In other aspects, the DC voltage is higher than 0.5 V. In some aspects, the DC voltage is at least about 0.1 V, or at least about 0.2 V, or at least about 0.3 V, or at least about 0.4 V, or at least about 0.5 V. Alternatively a DC current can circulated with the same electrode polarity. In some aspects, the DC current is between 0.5 and about 1.0 mA.cm⁻². In some aspects, the DC current is lower than 0.5 mA.cm⁻². In other aspects, the DC current is higher than 1.0 mA.cm⁻². In some aspects, the DC current is at least about 0.5 mA.cm⁻², or at least about 0.6 mA.cm⁻², or at least about 0.7 mA.cm⁻², or at least about 0.8 mA.cm⁻², or at least about 0.9 mA.cm⁻², or at least about 1.0 mA.cm⁻².
In some aspects,, the extractive electrochemical processes disclosed herein can be operated under constant potential. In other aspects, the extractive electrochemical processes disclosed herein can be operated under current control.
In some aspects, after contacting the aqueous solution with the electrodes and applying the DC voltage between the electrodes, the aqueous electrolytic solution can be exchanged by a dilute aqueous solution (e.g., a dilute lithium chloride solution) in order to provide ohmic conductivity to the electrochemical cell, and the electrical polarity can then be reversed. In this step, the battery-type lithium insertion electrode (e.g., carbon felt loaded with manganese dioxide) is the positive electrode, and manganese ions (or cobalt, iron, etc. depending on the lithium insertion compound used) can be oxidized to release lithium ions into the dilute solution. As a result, the concentration of lithium ions increases in the dilute aqueous solution. Conversely, the chloride reversible electrode (e.g., a silver/silver chloride electrode or a polypyrrole electrode) is the negative electrode. When the material in the negative electrode is reduced, for example, the polypyrrole or the silver chloride are reduced (e.g., to silver) releasing chloride ions to form a lithium chloride concentrated solution.
In some aspects, the concentration of lithium chloride in the dilute solution prior to reversing the electrolytic polarity is about 50 millimolar. In some aspects, the concentration of lithium chloride in the dilute solution prior to reversing the electrolytic polarity is at least about 10 millimolar, or at least about 15 millimolar, or at least about 20 millimolar, or at least about 25 millimolar, or at least about 30 millimolar, or at least about 35 millimolar, or at least about 40 millimolar, or at least about 45 millimolar, or at least about 50 millimolar, or at least about 55 millimolar, or at least about 60 millimolar, or at least about 65 millimolar, or at least about 70 millimolar, or at least about 75 millimolar, or at least about 80 millimolar, or at least about 85 millimolar, or at least about 90 millimolar, or at least about 95 millimolar, or at least about 100 millimolar.
The battery-type lithium insertion electrode disclosed herein can comprise a porous or high surface substrate and a lithium insertion compound. The porous or high surface substrate can be, for example, a conductive porous carbon felt, reticulated vitreous carbon, calcined coke carbon, or any other large area conductive carbon electrode material in which a lithium insertion material can be embedded.
Any high surface or porous carbon structure, or combinations thereof, can be used to make the electrodes disclosed herein. For example, the electrodes can be made using carbon cloth, carbon paper, graphite granules, graphite foam, high surface area graphite fiber, calcined coke carbon, etc. Non-carbon based conductive porous substrates can also be used. In some aspects, the substrate is a high surface composite material comprising a carbon component, e.g., carbon powder or carbon fibers and/or calcined coke carbon, and a non-carbon binder. In some aspects, the electrodes can be made using combinations of carbon materials (e.g., a carbon cloth sleeve containing a carbon-based foam or carbon granules, or calcined coke carbon).
In some aspects, the lithium insertion electrode comprises a high surface or porous substrate comprising calcined coke carbon particles. In some aspects, the calcined coke carbon particles are obtained by petroleum calcination. In some aspects, the calcined coke carbon particles have a diameter of about 200 to about 800 micrometers. In some aspects, the calcined coke carbon particles have a diameter of at least about 100, at least about 200, at least about 300, at least about 400, at least about 500, at least about 600, at least about 700, at least about 800, at least about 900, or at least about 1000 micrometers. In some specific aspects, the calcined coke carbon particles have a diameter of about 500 micrometers.
In some aspects, the carbon felt substrate has a surface area of about 500 to about 3000 m²g⁻¹. To some aspects, the carbon felt substrate has a surface area of at least about 500, at least about 600, at least about 700, at least about 800, at least about 900, at least about 1000, at least about 1100, at least about 1200, at least about 1300, at least about 1400, at least about 1500, at least about 1600, at least about 1700, at least about 1800, at least about 1900, at least about 2000, at least about 2100, at least about 2200, at least about 2300, at least about 2400, at least about 2500, at least about 2600, at least about 2700, at least about 2800, at least about 2900, or at least about 3000 m²g⁻¹.
These porous substrates can be used to prepare the battery-type lithium insertion electrode, the chloride reversible electrode, or both.
In some aspects, the carbon substrate is a conductive carbon substrate (e.g., a carbon nanotube substrate or a graphite-based substrate). However, in cases where the substrate is non-conductive the battery-type lithium insertion electrode can include a conductive additive material. In some aspects, the conductive additive material is carbon black, for example, SHAWINIGAN BLACK® or VULCAN® carbon black. Accordingly, the battery-type lithium insertion electrodes can be prepared by applying a slurry composed of a lithium insertion compound (e.g., a lithium manganese oxide) and a conductive additive material (for example, carbon black) suspended in a suitable solvent to a porous conductive substrate, for example, a carbon felt and/or calcined coke carbon particles (e.g., petroleum calcined coke carbon particles).
The lithium insertion compound is typically a lithium insertion oxide such as a lithium manganese oxide. The lithium manganese oxide is a precursor for producing a manganese oxide that can be used as an ion-sieve type lithium adsorbent. Thus, in some aspects, the battery-type lithium insertion electrode can comprise a carbon felt and/or petroleum calcined coke carbon (e.g., petroleum calcined coke carbon particles) embedded with an lithium insertion material comprising, but not limited to, γ-MnO₂and/or λ-MnO₂. In some aspects, the lithium insertion manganese oxide is γ-MnO₂. In some aspects, the lithium insertion manganese oxide is λ-MnO₂.
Once the battery-type lithium insertion compound has been incorporated into the battery-type lithium insertion electrode, the battery-type lithium insertion compound can be electrochemically delithiated. The electrochemical removal of lithium ions from the crystal structure of the battery-type lithium insertion compound leaves voids in the crystal structure, therefore producing an ion-sieve type manganese oxide than can be used as a high selectivity lithium adsorbent. Accordingly, when the ion-sieve type manganese oxide is exposed to the aqueous solution containing lithium ions during the lithium extraction step, the voids in the crystal structure of the manganese oxide can be filled with lithium from the aqueous solution containing lithium ions.
In some aspects, the lithium insertion oxide comprises an oxide of manganese having a structure of spinel, particularly a spinel structure with a 3D tunnel structure. As an example, the manganese oxide can be Li_nMn_2-xO₄, where 1≦n≦1.33, 0≦x≦0.33, and n≦1+x, for example Li_1.33Mn_1.67O₄or Li_1.6Mn_1.6O₄.
In some aspects, the manganese oxide is LiMn₂O₄however, other battery-type lithium insertion compounds can be used, such as lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), etc. Other lithium insertion materials known in the art include, e.g., lithium nickel manganese oxides (see, e.g., Ohzuku et al., Journal of Materials Chemistry 21:10179-10188 (2011)); lithium nickel oxides (see, e.g., Ohzuku et al., Journal of Materials Chemistry 21:10179-10188 (2011)); cobalt vanadium oxides (see, e.g., Hibino et al., Electrochem. Solid-State Lett 8:A500-A503 (2005)); molybdenum oxides (see, e.g., Lee et al., Advanced Materials 20:3627-3632 (2008); vanadium oxides (see, e.g., Liu et al., Advanced Materials 14:27-30 (2002)); inverse spinel vanadates like LiNiVO₄(see, e.g., Broussely et al., Electrochimica Acta 43:3-22 (1999)); or lithium manganese oxides further comprising trivalent metals such as aluminum, chromium, gallium, indium or scandium (see, e.g., PCT Publ. No. WO 01/24293). In some aspects, the battery-type lithium insertion electrode comprises a single battery-type lithium insertion compound. In other aspects, the battery-type lithium insertion electrode can comprise more than one battery-type lithium insertion compound.
The reversible chloride electrode can also comprise a porous or high surface carbon substrate (e.g., a carbon felt or calcined coke carbon, as disclosed above) and metal particles, for example, silver metal particles. In some aspects, the silver particles can be nanoparticles. Methods to deposit metal particles or a metal coating on a substrate are well known in the art, for example, using layer-by-layer deposition. Thus, in some aspects, the reversible chloride electrode can comprise silver nanoparticles supported in a conductive carbon felt on which they have deposited by layer-by-layer deposition of silver ions. These silver ions are entrapped in a polyelectrolyte multilayer on the carbon felt fibers, which by chemical or electrochemical reduction can yield silver nanoparticles of large surface area. In turn, these silver nanoparticles can react with chloride ions to form silver chloride.
In some aspects, the reversible chloride electrode comprises a high surface or porous substrate comprising calcined coke carbon particles. In some aspects, the calcined coke carbon particles can be obtained by petroleum calcination. In some aspects, the calcined coke carbon particles have a diameter of about 200 to about 800 micrometers. In some aspects, the calcined coke carbon particles have a diameter of at least about 100, at least about 200, at least about 300, at least about 400, at least about 500, at least about 600, at least about 700, at least about 800, at least about 900, or at least about 1000 micrometers. In some specific aspects, the calcined coke carbon particles have a diameter of about 500 micrometers.
Non-silver metal containing electrodes can be employed to make reversible chloride electrodes. For example, alternative chloride reversible electrodes comprising electrically conductive polymers (e.g., polypyrrole/chloride, polyanilines, polyphenols, etc.) can be used. Thus, in some aspects, the chloride reversible electrode can comprise a conductive polymer such as polypyrrole which can uptake and release chloride ions.
Other conducting polymers having good electrochemical activity, such as polyaniline, polythiophene, polyimide, polyacetylene, polyphenylene vinylene, polyphenylene sulfate, or combinations of conducting polymers can be used to make reversible chloride electrodes. See, for example, Imisides et al., Electroanalysis 3: 879-889 (2005); Bidan, Sensor and Actuators b: Chemical 6:45-56 (1992); Walram & Bargon, Canadian Journal of Chemistry 64:76-95 (1986); Mermilliod et al. Journal of the Electrochemical Society 133:1073-1079 (1986); Roth & Graupner, Synthetic Metals 57:3623-3631 (1993), all of which are herein incorporated by reference in their entireties.
In some aspects, the polypyrrole reversible chloride electrode can also comprise a porous or high surface carbon substrate (e.g., a carbon felt and/or calcined coke carbon particles, as disclosed above). Methods to produce a polypyrrole coating on a substrate are well known in the art, for example, using chemical polymerization on the substrate. Thus, in some aspects, the reversible chloride electrode can comprise polypyrrole formed by chemical polymerization onto a conductive carbon felt and/or calcined coke carbon particles. Then, the polypyrrole can react with chloride. In some aspects, the polypyrrole reversible chloride electrode can include other components such a dopants. In some aspects, the polypyrrole reversible chloride electrode can contain silver, for example silver particles (e.g., nanoparticles) entrapped in polymerized polypyrrole films or coatings. See, e.g., Song & Shiu. Journal of Electroanalytical Chemistry 498:161-170 (2001).

Electrochemical Device for Lithium Extraction

The present disclosure also provides an electrochemical device for extracting lithium from an aqueous solution containing lithium ions comprising at least one battery-type lithium insertion electrode comprising a porous or high surface substrate coated with a lithium insertion compound, wherein the device does not comprise a counter-electrode. In some aspects, the electrochemical device further comprises a chloride reversible Electrode, e.g., an Ag/AgCl or polypyrrole chloride reversible electrode. Battery-type lithium insertion electrodes and chloride reversible electrodes suitable for use in the electrochemical device of the present disclosure have been described in detail above.
The electrochemical device disclosed herein can comprise two compartments or half-cells, each composed of an electrode immersed in a solution of electrolyte. These half-cells are designed to contain the oxidation half-reaction and reduction half-reaction separately. In some aspects, the battery-type lithium insertion electrode and the chloride reversible electrode are positioned in separate half-cells. In some aspects, the half-cell comprising the battery-type lithium insertion electrode and the half-cell comprising the chloride reversible electrode are separated by a semi-permeable electrolysis membrane, such as an ionomer membrane (e.g., a NAFION® membrane). In some aspects, the NAFION® membrane is NAFION® 324. Any available semi-permeable electrolysis membrane which selectively passes cations and inhibits the passage of anions can be employed in the present device. Such membranes are well known to those skilled in the art. In some aspects, no membrane is used. In some aspects, as porous material separates the half cells. In some aspects, the porous material can be a gauze. In some aspects, the gauze can be a polyester gauze. In some aspects, the porous material can be porous fritted glass.
In some aspects, the electrochemical device is a packed bed reactor. In this reactor configuration, the battery-type lithium insertion electrode materials and the chloride reversible electrode materials (e.g., porous particles such as calcined coke carbon particles loaded, for example, with either LiMn₂O₄or polypyrrol) are placed between a current collector (e.g., a titanium collectors) and a separating porous barrier (e.g., a polyester gauze). In some aspects, the packed bed reactor does not comprise a semi-permeable electrolysis membrane separating the cathodic and anodic compartments.
In some aspects, the lithium extracting particles in the packed bed reactor comprise about 13 g of LiMn₂O₄per 60 g of calcined coke particles. In some aspects, the lithium extracting particles contain at least about 1 g, at least about 2 g, at least about 3 g, at least about 4 g, at least about 5 g, at least about 6 g, at least about 7 g, at least about 8 g, at least about 9 g, at least about 10 g, at least about 11 g, at least about 12 g, at least about 13 g, at least about 14, or at least about 15 g of LiMn₂O₄per 60 g of calcined coke particles.
In some aspects, the aqueous solution is directly fed to an electrochemical device for lithium extraction. In other aspects, the aqueous electrolytic solution can be concentrated with respect to lithium content. In yet other aspects, impurities are removed from the aqueous electrolytic solution, which is subsequently concentrated with respect to the lithium content.
In some aspects, the electrochemical device can be constructed, for example, using a FM100 press filter electrochemical reactor format as disclosed in Example 4. In one aspect, the electrochemical device comprises two current collector contacts (e.g., stainless steel metal plates) which are in contact with the carbon felt electrodes (e.g., battery-type lithium insertion electrode and chloride reversible electrode, respectively). The battery-type lithium insertion electrode and reversible electrodes are mounted on insulating supports (e.g., TEFLON® frames), and flow field channels allow the solutions to circulate. Insulators allowing solutions to circulate (e.g., TEFLON® net separators) are intercalated between each electrode to prevent short circuit of the electrodes. The reactor is held together by insulated screws that go through all the component plates. The system is expandable to several electrodes in a stack (see FIG. 7A and 7B).
In some aspects, the FM100 electrochemical reactor can be assembled according to the FM100 electrochemical cell format disclosed in Example 8. Accordingly, in some aspects, the reactor comprises current collector contacts (e.g., titanium metal plates) that are in contact with carbon felt electrodes comprising a functionalized porous substrate. For example, one electrode comprises a carbon felt comprising calcined petroleum coke carbon particles supporting a battery-type lithium insertion electrode material (e.g., LiMn₂O₄), whereas the other electrode comprises a carbon felt comprising calcined petroleum coke carbon particles supporting a chloride reversible electrode material (e.g., polypyrrole). The electrodes are separated by a non-membranous porous material (for example, a polyester gauze or porous fritted glass) which can optionally be mounted on a suitable support (e.g., a TEFLON® frame). In order to increase the production of lithium, several undivided electrochemical cells can be stacked and connected in series. The same current can circulated through all the electrochemical cells in series. See FIG. 18.
In some aspects, the electrochemical reactor is a packed bed reactor assembled according to the packed bed electrochemical cell format disclosed in Example 8. Accordingly, in some aspects the electrodes comprise a functionalized porous substrate (e.g., calcined petroleum coke carbon) without a carbon felt substrate. In this configuration, one electrode comprises a compartment packed with calcined petroleum coke carbon particles supporting a battery-type lithium insertion electrode material (e.g., LiMn₂O₄), whereas the other electrode comprises a compartment packed with calcined petroleum coke carbon particles supporting a chloride reversible electrode material (e.g., polypyrrole). Both compartments can be separated by a non-membranous porous material, for example porous fritted glass. The reactor also comprises current collection contacts which are in contact with the electrodes. In some aspects, titanium mesh current collectors with titanium rod electrical connectors can be used. See FIG. 22 and FIG. 23.
In some cases, the packed bed reactor can comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 of the packed bed electrochemical cells disclosed above. A person skilled in the art would appreciate that the electrochemical cells disclosed herein can be assembled in various configurations, e.g., in series or in parallel, and also that the cells disclosed herein could be combined in series or in parallel with other electrochemical cells designed to extract other commercially valuable ions from brines.
The term “non-membranous porous material” refers to materials such as woven and nonwoven fabrics (e.g., gauzes), glass fiber mats, melt blown mats, felts, fritted glass, and the like. These porous non-membranous materials are used extensively as filtration media or as prefilters for filtrations. Accordingly, the term non-membranous porous material encompasses any materials known in the art that are suitable for filtration or prefiltration, and in general to prevent the migration of macroscopic particles (e.g., carbon particles such as carbon black particles) between two or more separated compartments.
One skilled in the art would appreciate that other cell configurations and materials can be used to (i) construct an electrochemical device comprising the battery-type lithium insertion electrode and the chloride reversible electrode disclosed in the instant application and (ii) to operate such electrochemical device according to the methods disclosed herein. For example, instead of stainless steel or titanium plates or meshes the electrochemical device can use any other corrosion-resistant metal, alloy, or conductive synthetic material or composite. In addition, insulators (if used) can be built using TEFLON®, KAPTON®, MYLAR®, polyurethane, PVC, silicone rubber, glass, etc. See, for example, M. I. Ismail, Ed, “Electrochemical reactors their science and technology—Part A: Fundamentals, electrolysers, batteries and fuel cells”. Elsevier, Amsterdam, The Netherlands, 1989. ISBN 0-444-87139-X;
Stainless steel, plastic tubing or other suitable tubing allows the brine and clean electrolyte, respectively, to circulate through the three-dimension expanded carbon felt electrodes containing the active materials (e.g., manganese oxide, silver deposit, silver nanoparticles, polypyrrole).
The electrochemical device can connected through the current collector contacts to an external power supply which uses power obtained, e.g., from a clean energy source such as solar energy, wind energy, geothermal energy, etc. The aqueous solution containing lithium ions (e.g., a brine from a high altitude salt lake) and the dilute solution of lithium chloride can be circulated through the device at a constant flow. In some aspects, the solutions can be circulated at a variable flow. In some aspects, solutions are circulated at about 20 to about 50 mL/minute. In some cases, solutions are circulated at flow rates lower that about 20 mL/minute. In other cases, solutions are circulated at flow rates higher than about 50 mL/minute. In some cases solutions are circulated at flow rates of about 5 mL/minute, or about 10 mL/minute, or about 15 mL/minute, or about 20 mL/minute, or about 25 mL/minute, or about 30 mL/minute, or about 35 mL/minute, or about 40 mL/minute, or about 45 mL/minutes, or about 50 mL/minute, or about 55 mL/minute, or about 60 mL/minute, or about 65 mL/minute, or about 70 mL/minute, or about 75 mL/minute.
In some aspects, more than one electrochemical device can be operated simultaneously via the some voltage or current source. In this case, the electrochemical devices can be operated either in series or in parallel. In other aspects, each electrochemical device is operated with a separate voltage or current source.

Electrochemically Purified Lithium

In some aspects, the methods and devices disclosed herein can be used to produce a very high purity lithium chloride solution that can be crystallized and used to produce lithium metal with extremely low levels of impurities (e.g., for battery components). Accordingly, in some aspects, the disclosed method and devices can produce lithium chloride at a purity level of least about 99.9%. In other aspects, the lithium chloride produced according to the disclosed methods and devices has a purity of at least about 99.99%. In other aspects, the lithium chloride produced according to the disclosed methods and devices has a purity of at least about 99.999%. The high purity lithium can be electrolyzed into lithium metal.

Electrochemical Plant for Lithium Extraction

The present disclosure also provides an electrochemical plant to extract lithium and other valuable metals by using as feeding material brines extracted from high altitude salt lakes. The electrochemical plant comprises a plurality of electrochemical devices according to the present invention in which brines extracted from a high altitude salt lake are processed, and lithium is extracted according to the methods disclosed herein. The electrochemical plant can be operated using low environmental impact energy sources such as solar energy, wind energy, or geothermal energy. The use of this type of energy source obviates the need to construct high footprint power generation equipment or power transmission lines. Furthermore, the use of clean energy sources reduces the probability of environmental damage caused by fossil fuel spills or fume emissions in the high altitude ecosystem. The brines used as feedstock for the plant can be obtained by drilling under the lake surface, and the processed lithium-depleted brines can be reinjected under the lake surface, further reducing the environmental and visual impact of the plant. This production process is highly advantageous over existing technologies in that (i) the lithium-containing salt deposits do not need to be dissolved in water, thus reducing loss of water from the high altitude ecosystem through evaporation, (ii) the process does not require added chemicals such as soda ash, and (iii) the process does not release by-products (e.g., sodium chloride) that can accumulate in the high altitude salt lake.
A similar approach can be used to implement an electrochemical plant to extract lithium from sea water, in which the electrochemical plant can be operated using low environmental impact energy sources such as solar energy, wind energy, tidal energy, or geothermal energy and the processed lithium-depleted sea water is returned to the ocean.
In some aspects, the methods and devices disclosed herein can be used to recycle lithium. According to this approach, metallic lithium extracted from, e.g., lithium batteries, is dissolved to yield a lithium salt that can be processed by using the methods and devices disclosed herein to produce highly pure lithium. In other aspects, the methods and devices disclosed herein can be used to refine lithium. According to this approach, lithium obtained at low purity levels using the methods and devices disclosed herein or obtained using traditional methods can be further refined using the methods and devices disclosed herein in order to generate high purity lithium.

Equivalents

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
All publications, patents, and patent applications referred to herein are expressly incorporated by reference in their entireties.

EXAMPLES

Example 1

LiMnO₄Preparation

LiMn₂O₄was synthesized using solid state chemistry, 0.377 g of Li₂CO₃(Aldrich) and 1.74 g of MnO₂(Aldrich) were thoroughly mixed at a molar 0.51:2 ratio in a mortar, and heated at 350° C. for 12 hours. Samples were subsequently heated at 800° C. for 24 hours with 3 cycles of grinding and firing. The resulting powder was characterized by scanning electron microscopy (SEM) and X-ray Diffraction (XRD).
An X-ray diffractogram of a LiMn₂O₄sample obtained according to the method described above is shown in FIG. 2. The comparison of such diffractogram with an X-ray diffractogram of a LiMn₂O₄standard (FIG. 1) indicated that a single phase mixed oxide was obtained. SEM examination of the resulting LiMn₂O₄samples showed very well formed crystals with average size of several nanometers to a micrometer (see FIG. 3).

Example 2

Preparation of Carbon Felt Embedded with LiMn₂O₄

Conductive carbon felt electrodes (National Electric Carbon Products, a division of Morgan Specialty Graphite; Greenville, S.C., US) were cut into 20×10×3 mm pieces, thoroughly washed with 1:1 isopropanol:Milli-Q water and finally rinsed with Milli-Q water (FIG. 4).
The synthesized LiMn₂O₄powder was loaded onto the carbon felt electrode as a slurry prepared with 80% Li—Mn oxide, 10% carbon black (Chevron Phillips SHAWINIGAN BLACK®) and 10% PVC (polyvinyl chloride) in dichloromethane. Subsequently, the carbon felts were dried at 60° C. under vacuum during 24 hours.
The LiMn₂O₄loaded carbon felt electrodes were subsequently subjected to electrolysis to de-lithiate the oxide while keeping the highly selective crystal structure to allow the intercalation of lithium ions. The oxide loaded carbon electrode was placed in one of the compartments in a two compartment TEFLON® cell, and a platinum counterelectrode was placed in the second compartment. Both compartments were separated by a NAFION® 324 membrane (E.I. du Pont de Nemours and Company). A silver/silver chloride 3 M KCl reference electrode was used and 0.1 M sodium chloride or 0.1 M hydrochloric acid was used as electrolyte.
The intercalation-deintercalation of lithium ions was characterized by cyclic voltammetry in a 6 mL two-compartment TEFLON® cell separated by a NAFION® 324 membrane. Cyclic voltammetry measurements were conducted using an Autolab PG30 potentiostat (Eco Chemie, Netherlands) (see FIG. 5).
The resulting voltammograms are shown in FIG. 6. The cyclic voltammetry data (50 mVs⁻¹) was consistent with the insertion lithium in the crystal structure of the manganese dioxide during the reduction cycle and the release of lithium ions from the crystal structure of the manganese dioxide during the oxidation cycle as described by Cairns et al. (Journal of The Electrochemical Society 146:4339-4347 (1999)). The observed reaction was LiMn₂O₄(LiMn^IIIMn^IVO₄)→2α−MnO₂+Li⁺+e⁻, which corresponds to the oxidation of Mn(III) ions in the mixed oxide lattice and expulsion of lithium ions into solution during the anodic cycle.

Example 3

Preparation of Silver Chloride Reversible Electrodes

Several approaches were used to prepare chloride reversible electrodes.
In one chloride reversible electrode preparation, silver was directly deposited from a commercial silver cyanide bath (Argex, Laring S.A., Argentina) by holding the potential of the carbon felt at −0.1 V. The silver cyanide bath had been previously sonicated in isopropanol for 30 minutes and rinsed with Milli-Q water. Silver crystals of 100 nanometers to 1 micrometer were obtained on the conductive carbon fibers.
In another chloride reversible electrode preparation, a layer-by-layer polyelectrolyte multilayer was deposited on the carbon fibers as described, for example, in Rubner et al., Langmuir 18:3370-75 (2002), and Vago et al., Chem. Commun. 5746-48 (2008). The polyelectrolyte multilayer functioned as a nanoreactor to confine the silver ions. The silver ions were further reduced chemically with 5 mM sodium borohydride or reduced electro-chemically to yield large surface area nanoparticles on the carbon fibers.
In another preparation, ten millimolar poly(acrylyc acid) and poly (allylamine) were self-assembled layer by layer by sequential dipping the carbon felt in the respective polyelectrolyte solution with rinsing between dipping steps. Then, the modified carbon felt was subject to silver ion exchange by dipping it in a 10 to 50 millimolar silver nitrate solution in water, rinsing in distilled water, and reducing chemically or electrochemically. The resulting nanoparticles deposited onto the carbon fibers of the felt were examined by SEM and further characterized by cyclic voltammetry in 50 millimolar lithium chloride.

Example 4

Construction of Electrochemical Reactor

A FM100 press filter electrochemical reactor for the extraction of lithium from chloride containing brines, salt water, hot-spring water, etc., was built in stainless steel with a plastic separator between the two carbon felts electrodes (reversible to lithium, and reversible to chloride ions, respectively), as depicted in FIG. 7.
The electrochemical cell shown schematically in FIG. 7A was constructed using 5 mm stainless steel plates (B), and thin TEFLON® plates (G). Two 2 mm stainless steel plates (FP) acted as current collectors and were in contact with the carbon felt electrodes in TEFLON® frames (S), with flow field channels to circulate the liquid. A TEFLON® net separator was intercalated between each carbon felt electrode (46×156×3 mm, approx. 60 cm²cross section), i.e., lithium insertion electrode, and chloride reversible electrode, to prevent short circuit of the conducting carbon electrodes. The sandwich cell was held together by insulated screws that went through all the component plates. The system is expandable to several electrodes in a stack.
Stainless steel or plastic tubing allowed the brine and clean electrolyte, respectively, to circulate through the three-dimension expanded carbon felt electrodes containing the active materials (manganese oxide and silver deposit or nanoparticles respectively).
The electrochemical cell was connected through the current collector contacts to an external power supply. The brine and clean recovery electrolyte were circulated at variable flow, typically 20 to 50 mL/min with a Cole-Parmer 75211 flow pump (Cole-Parmer, Vernon Hills, Ill.). The cell potential was controlled with a potentiostat/galvanostat (Radiometer DEA 332 (Radiometer, Denmark) or Autolab PG30 (EcoChemie, Netherlands) with a 20 Ampere current booster). The selectivity for Li⁺/Na⁺depended on the relative concentrations of the cations, with larger selectivity for lithium concentrated solutions (large Li⁺/Na⁺) (FIG. 8).

Example 5

Lithium Extraction-Release Transient Experiments

FIG. 9 depicts transients of (i) lithium ion insertion into a LiMn₂O₄carbon loaded electrode at 0.2 V vs. Ag/AgCl (“lithium extraction step”), and lithium release at 1.2 V vs. Ag/AgCl in a 50 mM lithium perchlorate aqueous solution (“lithium release/concentration step”). This experiment showed the capacity of the system to extract lithium from an aqueous solution by insertion in the crystal structure of a manganese oxide lithium insertion compound deposited on a carbon felt, while release of lithium occurs in the dilute recovery solution.

Example 6

Electrochemical Plant to Extract Lithium from High Altitude Salt Lakes

The battery-type lithium insertion electrode and chlorine reversible electrodes, “lithium extraction”/“lithium release/concentration” method, and electrochemical device design disclosed in the present application can be applied to the large scale processing of brines from high altitude lakes (e.g., salares from the Argentinian puna).
A clean energy source (e.g., solar, wind, geothermal or a combination thereof) is used to power pumps that extract lithium-rich brine from below the lake surface. The electrochemical plant uses a plurality of electrochemical devices powered by the clean energy source to process the brine and extract its lithium content. The lithium depleted brine is subsequently pumped below the lake surface. The resulting lithium chloride can be further refined using the electrochemical devices disclosed in the instant application to yield high purity lithium chloride, in a form with a purity greater than 99%. The purified lithium chloride can in turn be electrolyzed directly by conventional methods using the electric power from the clean energy source to produce lithium metal for a variety of purposes.
This extraction system is sustainable since it does not consume water by evaporation as in the present process used to extract lithium from salt lakes. Furthermore, the extraction system is faster that the presently used evaporation method (minutes-hours in the system and methods disclosed in the instant patent application versus months in the evaporation method). In addition, the disclosed system has a low energy impact since the insertion (extraction) of lithium from the brine is a spontaneous process in a battery-type electrode, and the release of lithium and pumping of brine and electrolyte are low consuming energy processes that can be powers by renewable energy sources such as solar energy.

Example 7

Use of a Polypyrrole/Carbon Chloride Reversible Electrode to Capture (or Release)

Chloride Ions and a LiMn₂O₄/Carbon Insertion Electrode to Capture (or Release) Lithium

Polypyrrole is a conducting polymer that can be deposited onto the carbon felt fibers either by chemical or electrochemical polymerization of pyrrole from acid solutions. Upon oxidation polypyrrole uptake anions in order to maintain neutrality of charges and conversely on reduction polypyrrole releases the anion into solution. Thus, polypyrrole can be employed as anode/cathode to capture/release selectively anions such as chloride from the electrolyte, in our case a brine, according to the reactions shown in FIG. 10. Accordingly, an extraction process was designed in which the lithium intercalation cathode was a carbon-supported LiMn₂O₄electrode, and the reversible chloride electrode capturing chloride ions simultaneously to the cathodic insertion of lithium ions was a composite electrode comprising polypyrrole supported on carbon felt.
Polypyrrole electrodes offer several advantages over Ag/AgCl electrodes. Their cost is lower, they are easy to manufacture using chemical oxidation of a pyrrole solution in contact with the carbon substrate (for example, a carbon felt), they do not release silver ions into the environment, and they have a large surface area.

General Description of the Lithium Extraction Process

A lithium extraction process was implement in which lithium chloride was extracted from a sodium rich lithium brine (Li:Na 1:100) by enrichment of a lithium chloride (LiCl) solution by successive electrochemical insertion in LiMn₂O₄supported on carbon felt cathode in contact with the brine, followed by release of LiCl from the electrode in a lithium free KCl electrolyte solution. Carbon felt-based electrodes were used. Carbon felt is conductive and presents a very high surface area to support the catalyst oxide for lithium insertion, LiMn₂O₄.
Since the lithium extraction selectivity with respect to sodium depended on the Li to Na concentration ratio, successive electrochemical steps of insertion and release were need to selectively extract lithium.
The lithium insertion electrode (positive cathode) comprised a mixed lithium manganese oxide which in its reduced state had tri and tetravalent manganese ions in the crystal lattice, i.e., Mn^IIIand Mn^IVand Li⁺inserted in the crystal compensates the lower electrical charge of Mn^III. The insertion process occurred spontaneously as in a battery.
The second electrode (negative anode) captured chloride ions to compensate the charge of polypyrrole in its reduced neutral state PP^o, which underwent simultaneous oxidation to the [PP⁺Cl⁻] state.
During the release of LiCl in the lithium free electrolyte, the reverse process occurred at the electrodes with the opposite polarity, i.e., the manganese oxide was the negative electrode (anode) and the polypyrrole electrode was the positive electrode (cathode). This process was not spontaneous and required the supply of energy to the electrochemical cell.
During the lithium chloride recovery step, lithium ions were selectively inserted at the cathode and chloride ions at the anode, while during the release of lithium chloride into the lithium free electrolyte, the opposite reaction occurred:
At each electrode the electrochemical processes were, at the cathode:
and at the reduced neutral polypyrrole anode:
It was possible to calculate the capacity of LiMn₂O₄since 181 grams of the compound contain 7 grams of lithium. Therefore, a full insertion can produce a theoretical maximum of 39 mg of lithium per gram of manganese oxide. In the case of LiFePO₄158 grams of the compound can insert 7 grams of lithium, and therefore can produce a theoretical maximum of 44.3 mg of lithium per gram of iron phosphate.
The previously shown FIG. 6 a cyclic voltammetry of lithium insertion/release at a carbon supported LiMn₂O₄electrode. The electrode potential was indicated with respect to a Ag/AgCl reference electrode and also in the Li/Li+ scale. In the cathodic extreme lithium was inserted into the manganese oxide lattice, while at positive potentials release of lithium ions from the oxide to the solution occurred. See Cairns et al. Journal of The Electrochemical Society 146: 4339-4347 (1999). Since the electrode potential is a measure of the degree of lithium insertion in the oxide (see, Tarascon & Guyomard, J. Electrochem. Soc. 138: 2864 (1991)), the electrode potential was monitored during insertion and release of lithium from brines.

Electrodes

Conductive carbon felt electrodes (National Electric Carbon Products, a division of Morgan Specialty Graphite, Greenville, S.C., USA) were cut in 50×50 mm pieces, supported in TEFLON® holders, and immersed in 180 mL of electrolyte (brine or recovery solution). The photographs in FIG. 11 depict the experimental setup.
A TEFLON® frame held the carbon felt electrodes separated by a TEFLON® net to avoid short circuit. Each electrode was connected via a gold plate to the leads of the potentiostat. No membrane such as NAFION™ was employed in this experimental setup.
Carbon felt samples (50×50 mm) were cleaned with isopropanol during 5 minutes and then pre-treated with dilute sulfuric acid for 10 minutes with sonication. LiMn₂O₄electrodes were prepared by impregnating the carbon felt pieces with a slurry made of 2.4 g LiMn₂O₄. 0.3 g SHAWINIGAN BLACK® carbon, and 0.3 g PVC binder suspended in 5 mL of N-methylpyrrolidone, and dried at 70° C. for 12 hours. FIG. 12 shows SEM micrographs of the resulting carbon fibers in the felt covered by LiMn₂O₄crystals. Good coverage of the carbon fibers by the LiMn₂O₄crystals was observed.
Polypyrrole electrodes were obtained by chemical polymerization of pyrrole as follows: Carbon felt samples were sequentially immersed in 0.5 M pyrrole in 0.02 M hydrochloric acid (solution A) and 0.5 M ammonium persulfate (solution B), for 5 minutes in each solution. After rinsing with distilled water, the felts were dried at 105° C. for 24 hours. FIG. 13 is an SEM micrograph depicting the polypyrrole deposit on the carbon felts.
Two electrochemical treatments were employed for the capture of lithium chloride from the brine and for the release of the captured lithium into a lithium free solution as follows:

- a. For capturing lithium at the cathode and chloride at the anode, a galvanostatic method was used. −25 mA of constant DC current was applied to a 25 cm²geometric area of the three-dimensional porous carbon felt electrodes, following the electrode potential as a function of time. The electrolysis charge was given by the current times the elapsed time, typically 7200 seconds (2 hours) or 180 coulombs.
- b. For the release of LiCl into a lithium free solution containing dilute potassium chloride, or eventually containing dilute lithium chloride, a potentiostatic treatment under stirring was employed as follows. The LiMn₂O₄/carbon electrode was polarized at 1.4 V vs. Ag/AgCl; 3 M NaCl reference electrode, and oxidation of Mn^IIIreleased the inserted lithium. The current transient was followed. On the other electrode (negative) the release of chloride occurred as oxidized polypyrrole was reduced.
  Extraction of Lithium from Natural Brines

The capacity of the disclosed method and device to extract selectively lithium from a natural brine was tested using brine samples of the Ollaroz salt lake in the province of Jujuy (Argentina), with contained a Li:Na concentration ratio of 1:100. In addition to lithium, the brine samples contained sodium, potassium, magnesium, boron, etc. The chemical analysis by atomic emission of the brine showed, among other components, Li: 1.3 g/L; Na: 62.6 g/L; Ca: 3.6 g/L; Mg: 3.3 g/L; K: 8.1 g/L.
1. Insertion of LiCl from Natural Brine
Lithium ions were inserted in the LiMn₂O₄/carbon felt cathode and chloride ions where inserted in the polypyrrole/carbon felt anode from a brine solution (180 mL) with a 1:100 lithium to sodium initial concentration ratio using galvanostatic electrochemical insertion. The electrode Geometric Area was 25 cm²and the load was 0.6 g of LiMn₂O₄. When a constant current of −25 mA was applied to the electrochemical reactor, the cathode potential with respect to a Ag/AgCl; 3 M NaCl reference electrode (approx. 3 V vs. Li/Li⁺) evolved with time during lithium insertion. Total charge was 180 coulomb.
FIG. 14 shows four transients corresponding to four lithium chloride capture steps. The electrode potential depended on the lithium concentration in solution according to the Nernst equation. In the first extraction the brine solution was highly concentrated in lithium, while the subsequent lithium recovery solutions were very dilute (in the millimolar range). The total electrical charge passed was −180 coulombs (−25 mA×7200 seconds). If all the charge was due to lithium insertion, then 13 mg of lithium should have been extracted.

2. Rinsing the Felts

Electrodes were rinsed with distilled water by immersion in a series of water baths under stirring until the sodium concentration in the washing liquid was less than 1 ppm.

3. Lithium Release

The release of lithium can be achieved by passing a constant current (galvanostatic pulse) or by applying a constant potential in the region where Mn^IIIis oxidized to Mn^IVas shown in the cyclic voltammetry above. The potentiostatic transient is preferred to avoid reaching excessive oxidant potential when lithium is depleted in the brine or recovery electrolyte.
In the lithium release process, the polarity of the electrodes was reversed in an electrolyte solution containing no lithium but containing dilute KCl as a background electrolyte to provide enough conductivity. The potentiostatic electrochemical release of lithium ions from the LiMn₂O₄/carbon felt anode and the release of chloride from the polypyrrole/carbon felt cathode took place in a lithium free 0.05 M KCl solution under potential control at 1.4 V during 7200 seconds with a total charge of 22.18 Coulombs. The electrolyte was stirred to avoid concentration polarization of lithium ions at the electrode surface. FIG. 15 shows the current transients for a sequence of lithium recovery steps during which lithium was released from the LiMn₂O₄electrode. Alternatively, in some experiments (not shown) a dilute lithium chloride solution was used, which was then enriched in lithium during the process.
The electrolyte was analyzed for lithium and sodium yield. The enrichments process yielded 1.9 mg (1.5 mM) of lithium and 3.9 mg (0.94 mM) of sodium. Therefore the first electrochemical insertion extraction step achieved a Li:Na atomic ratio of 1.59 from 0.01 in the initial brine. The sodium retained at the electrode could have been electrostatically adsorbed onto the large area of oxide and carbon felt and also co-inserted into the LiMn₂O₄nanoparticles. Since the crystallographic ionic radius of the sodium ion (9.8 nm) or potassium (13.6 nm), is larger that of lithium ion (6.8 nm), less sodium or potassium can insert into the spinel oxide lattice.
The resulting liquid from the first extraction (with a Li:Na atomic ratio of 1.59) was subjected to a second extraction process with a LiMn₂O₄/carbon felt cathode and a reduced polypyrrole anode after thoroughly rinsing the electrodes employed in the first step. The galvanostatic potential-time transient showed a similar shape as the one obtained in the first electrochemical extraction step. The release of LiCl in a lithium free KCl dilute solution took place under potentio-static control at 1.4 V (reversing the electrodes polarity) during the same time, 7200 seconds. FIG. 16 shows the evolution of the electrical charge during the release of lithium ions from the LiMn2O4/carbon electrode into the electrolyte.
As shown in TABLE 1, increasing the number of extraction/release steps increased the selectivity of lithium with respect to sodium from an initial Li:Na concentration ratio of 1:100 to a final Li:Na concentration ratio of 12.4:1 after three cycles.

TABLE 1

Results from increasing the number of extraction and
release steps to increase lithium selectivity.

Extraction	[Li ]	ppm Li	[Na ]	Ppm Na	[Li]/[Na]

					0.01
1st.	1.5	1.9	0.94	3.9	1.59
2nd.	2.3	2.9	1.08	4.5	2.30
3rd.	3.5	4.9	0.31	1.3	12.4

indicates data missing or illegible when filed

Example 8

Alternative Electrodes and Electrochemical Device

In this alternative method, particles of carbon (calcined coke from petroleum) with a diameter in the 200-800 micrometer range were loaded with either LiMn₂O₄or polypyrrol and placed in a thin packed bed between a titanium current collector and a polyester gauze. This arrangement allowed the electrolyte to flow axially at a considerable flow rate (i.e., 2 to 30 mL per second) while keeping good electrical contact among the coke particles, and among the coke particles and the current collector. The reactor assembly had no separating membrane between the cathodic and anodic compartments.
Achieving high electrolyte flow with low pressure drop, good particle to particle electrical contact, and low ohmic drop at the lowest electrolyte concentrations is important in electrochemical reactor design. The use of coke particles several hundred micrometers in size gave (i) a larger surface area of contact between the electrode material supported on carbon particles and the electrolyte and (ii) a good flowbed as compared to the use of only carbon felts as described in the previous Example.
In a typical preparation of the lithium extracting electrode material, 60 g of 500 micrometer size coke particles were mixed with 13 g of LiMn₂O₄, 2.75 g of polyvinylidene fluoride (PVDF), and 2.75 g of VULCAN® carbon black. This mixture was dispersed in pyrrolydone, thoroughly stirred during 24 hours, and dried in a vacuum oven at 70° C. for 24 hours. The resulting powder was compressed between the carbon felt and the polyester gauze.
For the chloride extracting electrode material, 60 g of 500 micrometer size coke particles were dispersed in a solution containing 0.5 M pyrrole. 0.02 hydrochloric acid and a solution of 0.5 M ammonium persulfate. After evaporation at 110° C. for 24 hours, the coke particles loaded with polypyrrole were washed with distilled water, dried, and compressed between the carbon felt and the polyester gauze of the second electrode. A typical SEM micrograph of coke particles loaded with LiMn₂O₄crystals is shown in FIG. 17.
The functionalized coke electrode particles were used to assemble a Press Filter reactor (type FM100) with axial flux of electrolyte and perpendicular current flow as shown in FIG. 18. The reactor consisted of (i) titanium current collectors, (ii) carbon felt support and petroleum calcined coke carbon support of LiMn₂O₄at one electrode, (iii) carbon felt support and polypyrrole at the other electrode, (iv) a TEFLON® framework, and (v) a polyester gauze in undivided cells. In order to increase the production of lithium, several undivided cells were stacked and connected in series in a FM100 type reactor. The same current was circulated through all the cells in series, while a potential difference between the anode and cathode of each cell (typically 1.2 v) was applied.
The charge and discharge transients showed that the capture and release of lithium ions by LiMn₂O₄was reversible (see FIG. 19).
Theoretically, each 7 g of lithium extracted from brine would require an electrical charge of 26.8 A.h (96,500 coulombs/3600 s.h⁻¹). To extract 7 g of Li⁺, 126 g of LiMn₂O₄or 174 g of MnO₂would be needed. Since the concentration of lithium in brines of the Argentinian Puna (for example, brines from the Ollaroz Saltpan) is approximately 1 g per liter, 7 liters of brine would yield a theoretical maximum of 7 g of lithium.
In the first cycle, the LiMn₂O₄electrode was delithiated to produce the lithium ion insertion oxide electrode material, which spontaneously extracted lithium ions when contacted with lithium containing brines. The discharge and charge curves at constant current (±0.5 mA/cm²) during 2 hours are shown in FIG. 20. FIG. 21 shows a plot of potential-charge. Integration of the potential-charge curve indicated that the energy balance per ton of lithium extracted was 200 kWh.
The functionalized coke electrode particles were also used to assemble an alternative type of reactor. A packed bed reactor with both LiMn₂O₄and polypyrrol supported on coke carbon was assembled according to the configuration showed in FIG. 22. This configuration provided proof of concept for a practical three dimensional reactor at the laboratory scale with coke compact bed electrodes loaded respectively with LiMn₂O₄and polypyrrole. The electrolyte flow and current flow were longitudinal. The system presented large ohmic drops at the packed bed flooded with electrolyte but very small pressure drops.
The longitudinally packed bed cylindrical reactor prototype consisted of a glass cylinder with two compartments separated by porous fritted glass, titanium mesh current collectors with titanium rod electrical connectors, two packed beds containing 20 g of coke loaded with electrode materials, rubber stoppers, and tubing connecting to a piston flow pump (see FIG. 23 and TABLE 2). By connecting a mercury pressure meter, the pressure drop in the reactor was measured at different flow rates (0-30 mL per second) as shown in FIG. 24.

TABLE 2

Characteristics of packed bed cylindrical reactor prototype.

Mass of coke particles	20	g
Packed Bed Height	4	cm
Reactor diameter	4	cm
Reactor cross section	12.57	cm²
Pack bed volume	50.27	cm³
Coke density	2,0075	g/cm³

	Pososity	80.85%

Considering (i) solar panels having a cost of $2,000 per kW, (ii) a power consumption of 200 kWh per ton of lithium extracted, and (iii) a solar energy production of 50 kW in one day, one ton of lithium could be recovered per day with a capital investment of $100,000 dollars (800 square meters of solar panels, which have a life time of 30 years). During the 30 year lifetime of the solar panels, this solar-powered electrochemical production system could yield 11,000 tons of lithium. Accordingly, the cost of the production using the electrochemical extraction method disclosed herein would be approximately $10 per ton of lithium (plus the cost of energy for pumping brine and other engineering operations as well as energy losses due to kinetics, etc.). This system could be used to recover lithium from aqueous solutions, including salt lake brines, sea water, geothermal water, and oil salt water. In addition to its low monetary cost, the process is highly advantageous since (i) it is clean, not consuming water, lime or Solvay, (ii) it has a low energy cost, c.a. 200 kWh/ton, (iii) it is selective for lithium with respect to sodium if applied in repeated cycles, and (iv) it produces high purity lithium chloride suitable for battery use.
It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.
The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
The breadth and scope of the present invention 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.

Claims

1. A packed bed electrochemical cell for extracting lithium from an aqueous solution containing lithium ions comprising:

(a) a first electrode comprising a compartment packed with a high surface carbon substrate coated with a lithium insertion compound comprising LiMn₂O₄,

(b) a second electrode comprising a compartment packed with a high surface carbon substrate coated with a chloride reversible electrode material; and

(c) a non-membranous porous material interposed between the first and second electrode,

wherein the high surface carbon substrate comprises calcined coke carbon particles.

2. The packed bed electrochemical cell according to claim 1, wherein the calcined coke carbon particles are calcined petroleum coke carbon particles.

3. The packed bed electrochemical cell according to claim 1, wherein the chloride reversible electrode material comprises polypyrrole.

4. The packed bed electrochemical cell according to claim 1, wherein the non-membranous porous material separating the first and second electrode comprises a porous fritted glass separator.

5. The packed bed electrochemical cell according to claim 1, further comprising current collection contacts which are in contact with the electrodes.

6. The packed bed electrochemical cell according to claim 5, where the current collection contacts are titanium mesh current collectors.

7-32. (canceled)

33. An electrochemical device for extracting lithium from an aqueous solution containing lithium ions comprising at least one battery-type electrode comprising a porous or high surface substrate coated with a lithium insertion compound, wherein said device does not comprise a counter-electrode.

34. The electrochemical device according to claim 33, wherein the device further comprises a chloride or polypyrrole reversible electrode.

35. The electrochemical device according to claim 33, wherein the substrate is a carbon substrate.

36. The electrochemical device according to claim 35, wherein the carbon substrate is a conductive substrate.

37. The electrochemical device according to claim 33, wherein the battery-type electrode comprises a conductive additive material.

38. The electrochemical device according to claim 37, wherein the conductive additive material is carbon black.

39. The electrochemical device according to claim 33, wherein the lithium insertion compound comprises a manganese oxide.

40. The electrochemical device according to claim 39, wherein the manganese oxide comprises γ-MnO₂and/or λ-MnO₂.

41. The electrochemical device according to claim 39, wherein the manganese oxide has a spinel crystal structure.

42. The electrochemical device according to claim 39, wherein the manganese oxide comprises LiMn₂O₄.

43. The electrochemical device according to claim 33, wherein the lithium insertion compound comprises lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, or combinations thereof.

44. The electrochemical device according to claim 43, wherein the lithium cobalt oxide comprises LiCoO₂.

45. The electrochemical device according to claim 43, wherein the lithium iron phosphate comprises LiFePO₄.

46. The electrochemical device according to claim 33, wherein the battery-type electrode is prepared by electrolytical delithiation of a porous or high surface substrate coated with lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), lithium manganese oxide (LiMn₂O₄), or combinations thereof.

47. The electrochemical device according to claim 33, wherein the carbon substrate is selected from the group consisting of carbon felt, carbon cloth, carbon paper, graphite granules, granite foam, high surface area graphite fiber, and combinations thereof.

48. The electrochemical device according to claim 33, wherein the carbon substrate is a carbon felt.

49. The electrochemical device according to claim 34, wherein the chloride reversible electrode comprises a porous or high surface carbon substrate and silver metal particles.

50. The electrochemical device according to claim 49, wherein the silver metal particles are nanoparticles.

51. The electrochemical device according to claim 34, wherein the chloride reversible electrode further comprises an electrically conductive polymer.

52. The electrochemical device according to claim 51, wherein the electrically conductive polymer is a polypyrrole.

53. The electrochemical device according to claim 33, wherein the lithium ions in the aqueous solution are captured by insertion in the crystal structure of the battery-type electrode.

54. The electrochemical device according to claim 34, wherein the battery-type electrode and chloride reversible electrode are positioned in separate half-cells.

55. The electrochemical device according to claim 54, wherein the half-cell comprising the battery-type electrode and the half-cell comprising the chloride reversible electrode are separated by a semi-permeable electrolysis membrane.

56. The electrochemical device according to claim 55, wherein the electrolysis membrane is an ionomer membrane.

57. The electrochemical device according to claim 56, wherein the ionomer membrane is a NAFION® membrane.

58. The electrochemical device according to claim 57, wherein the NAFION® membrane is NAFION® 324.

59-67. (canceled)