Lithium extraction from alpha-spodumene

Abstract

This disclosure provides systems, methods, and apparatus related to lithium extraction. In one aspect, a method includes providing spodumene ore. The spodumene ore comprises particles. Spodumene (LiAlSi 2 O 6 ) in the spodumene ore comprises α-spodumene. The spodumene ore is mixed with a sodium-containing compound and second compound to form a mixture. The second compound comprises an aluminum-containing compound, a magnesium- containing compound, or mixtures thereof. The mixture is heat treated generating lithium carbonate (Li 2 CC 3 ).

Description

Attorney Docket No.: 2024-019-02 LITHIUM EXTRACTION FROM ALPHA-SPODUMENE Inventors: Gerbrand Ceder, Michael Whittaker, Shilong Wang, Nathan Szymanski, Yan Zeng RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 550,902, filed 7 February 2024, which is hereby incorporated by reference. STATEMENT OF GOVERNMENT SUPPORT

[0002] This invention was made with government support under Contract No. DE-AC02- 05CH11231 awarded by the U.S. Department of Energy. The government has certain rights in this invention. BACKGROUND

[0003] The demand for Li is experiencing a rapid surge, showing a 27% increase in 2023 alone. As much as 80% of this demand originates from the battery market, which has been stimulated by the widespread adoption of electric vehicles and portable electronics. As a result, predictions forecast that annual Li demand (as Li2CO3equivalent) may exceed 2 Mtons by the year 2030. To meet the growing demand, an ample and reliable supply of Li is needed.

[0004] Currently, most Li-ion cathodes are synthesized from Li2CO3 or LiOH, which can each be obtained by processing brines or solid minerals. Of these two sources, solid Li minerals are more uniformly distributed across the globe while Li-rich brine deposits are heavily concentrated in Argentina, Chile, and Bolivia. More and more deposits of spodumene (LiAlSi2O6), the most prevalent and Li-rich mineral, have become available around the world. Its abundance, coupled with the fact that spodumene has a higher Li content than brines, creates the potential for a rich source of Li at low cost. SUMMARY

[0005] One innovative aspect of the subject matter described in this disclosure can be implemented in method including providing spodumene ore. The spodumene ore comprises particles. Spodumene (LiAlSi2O6) in the spodumene ore comprises α-spodumene. The spodumene ore is mixed with a sodium-containing compound and second compound to form aAttorney Docket No.: 2024-019-02 mixture. The second compound comprises an aluminum-containing compound, a magnesium- containing compound, or mixtures thereof. The mixture is heat treated generating lithium carbonate (Li2CO3).

[0006] Another innovative aspect of the subject matter described in this disclosure can be implemented in a method including providing spodumene ore. The spodumene ore comprises particles. Spodumene (LiAlSi2O6) in the spodumene ore comprises α-spodumene. The spodumene ore is mixed with sodium carbonate (Na2CO3) and aluminum oxide (Al2O3) to form a mixture. A molar ratio of the sodium carbonate to the spodumene is about 1:1. A molar ratio of the aluminum oxide to the spodumene is about 1:2. The mixture is heat treated, generating lithium carbonate (Li2CO3). After heat treating the mixture, the mixture is mixed with water to dissolve the lithium carbonate and to generate a solution. The solution is filtered to remove impurities from the solution. The water is removed from the solution by heating the solution.

[0007] Another innovative aspect of the subject matter described in this disclosure can be implemented in a method including providing spodumene ore. The spodumene ore comprises particles. Spodumene (LiAlSi2O6) in the spodumene ore comprises α-spodumene. The spodumene ore is mixed with sodium carbonate (Na2CO3) and magnesium oxide (MgO) to form a mixture. The mixture is heat treated, generating lithium carbonate (Li2CO3). After heat treating the mixture, the mixture is mixed with water to dissolve the lithium carbonate and to generate a solution. The solution is filtered to remove impurities from the solution. The water is removed from the solution by heating the solution. In some implementations, a molar ratio of the sodium carbonate to the spodumene is about 1:2 in the mixture, and a molar ratio of the magnesium oxide to the spodumene is about 2:1 in the mixture.

[0008] Details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A shows an example of an XRD pattern (Cu Kα) of raw spodumene concentrate. Figure 1B shows reference patterns for the two most predominant phases α- spodumene (ICSD #9668) and α-SiO2(ICSD #100341).Attorney Docket No.: 2024-019-02

[0010] Figures 2A and 2B shows the results of in situ XRD studies of the solid-state reaction between α-spodumene and Na2CO3. Figure 2A shows a heatmap representing intensities obtained from synchrotron XRD measurements applied in situ while heating. The values of 2θ shown on the x-axis of the heatmap were obtained by converting the synchrotron wavelength (λ = 0.4959 A°) into Cu Kα (λ = 1.5406 A°) for ease of analysis. Figure 2B shows a plot of the weight fraction of each phase as a function of temperature.

[0011] Figure 3A shows XRD patterns (Cu Kα) of the products that were obtained by reacting α-spodumene with Na2CO3. The data is shown for the sample before and after leaching with water. The washing procedure results in a solid residue (not dissolved) and a leachate which is dried and characterized. The pattern of this leachate confirms the presence of Li2CO3(ICSD #66941), whose reference peaks are shown in Figure 3B.

[0012] Figure 4A shows XRD patterns (Cu Kα) of the products that were obtained by reacting α-spodumene with Na2CO3 and Al2O3. The data is shown for the sample before and after leaching with water. The washing procedure results in a solid residue (not dissolved) and a leachate which is dried and characterized. The pattern of this leachate confirms the presence of Li2CO3 (ICSD #66941), whose reference peaks are shown Figure 4B.

[0013] Figure 5 shows the percentage of Li extracted from spodumene in the form of Li2CO3plotted as a function of hold time at 750 °C for two different reactions (R1 and R2). These yields are determined from ICP-MS measurements performed on the leachate after washing. The circles and triangles represent experimentally measured data whereas the dashed lines are linear interpolations.

[0014] Figure 6 shows an example of a flow diagram illustrating a process generating lithium carbonate. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to some specific examples of the invention including the best modes contemplated by the inventors for carrying out the invention. Examples of these specific embodiments are illustrated in the accompanying drawings. While the invention is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended toAttorney Docket No.: 2024-019-02 cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0016] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. Particular example embodiments of the present invention may be implemented without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.

[0017] Various techniques and mechanisms of the present invention will sometimes be described in singular form for clarity. However, it should be noted that some embodiments include multiple iterations of a technique or multiple instantiations of a mechanism unless noted otherwise.

[0018] The terms “about” or “approximate” and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range can be ± 20%, ± 15%, ± 10%, ± 5%, or ± 1%. The terms “substantially” and the like are used to indicate that a value is close to a targeted value, where close can mean, for example, the value is within 80% of the targeted value, within 85% of the targeted value, within 90% of the targeted value, within 95% of the targeted value, or within 99% of the targeted value.

[0019] Spodumene is typically found in a dense monoclinic structure of the clinopyroxene type, often referred to as α-spodumene. To extract Li from this structure and produce a compound (often Li2CO3or LiOH) that is useful for Li-ion cathode synthesis, most traditional methods first transform α-spodumene into its high-temperature tetragonal polymorph (denoted as β-spodumene) at temperatures exceeding 1000 °C. This energy-intensive heating step is generally considered to be necessary since β-spodumene has lower density and is therefore more amenable to chemical attack. Acid digestion can then be performed using concentrated sulfuric acid at temperatures of around 250 °C, resulting in the formation of Li2SO4. Soda ash (Na2CO3) is typically added to the solution after acid leaching to precipitate Li2CO3, which can be separated from the remaining byproducts by washing the entire sample with water. Recently, some progress has been made in improving upon the traditional approach to Li extraction from spodumene.

[0020] As described herein, Li2CO3can be formed with a high yield by directly reacting α- spodumene with a sodium-containing compound (e.g., Na2CO3) and an aluminum-containingAttorney Docket No.: 2024-019-02 compound (e.g., Al2O3) or a magnesium-containing compound (e.g., MgO). This solid-state reaction can be performed at a relatively low temperature compared to the α- to β-spodumene transformation (e.g., about 750 °C) and with a short hold time (e.g., about 4 hours).

[0021] Figure 6 shows an example of a flow diagram illustrating a process generating lithium carbonate (Li2CO3). Starting at block 605 of the process 600, spodumene ore is provided. The spodumene ore comprises particles. In some embodiments, the spodumene ore consists of particles. In some embodiments, the spodumene ore has particle sizes of less than about 100 microns, less than about 75 microns, about 5 microns to 100 microns, or about 5 microns to 75 microns.

[0022] The spodumene (LiAlSi2O6) in the spodumene ore comprises α-spodumene. In some embodiments, the spodumene in the spodumene ore consists essentially of α-spodumene. In some embodiments, the spodumene in the spodumene ore is greater than or equal to about 75%, about 80%, about 85%, about 90%, about 95%, or about 99% α-spodumene. In some embodiments, the spodumene in the spodumene ore does not consist of β-spodumene or essentially does not consist of β-spodumene. In some embodiments, the spodumene in the spodumene ore is less than equal to about 5%, about 2% or about 1% β-spodumene.

[0023] In some embodiments, petalite ore is provided. The petalite ore includes petalite (LiAlSi4O10). In some embodiments, lepidolite ore is provided. The lepidolite ore includes lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2).

[0024] Returning to Figure 6, at block 610, the spodumene ore is mixed with a sodium- containing compound and a second compound to form a mixture. The second compound comprises an aluminum-containing, a magnesium-containing compound, or mixtures thereof. In some embodiments, the mixing the spodumene ore with the sodium-containing compound and the second compound is performed using a ball mill.

[0025] In some embodiments, the sodium-containing compound comprises a sodium salt. In some embodiments, the sodium-containing compound is a sodium-containing compound from a group Na2CO3, NaHCO3, NaOH, NaCl, and Na2O2. In some embodiments, the sodium- containing compound comprises Na2CO3. In some embodiments, the sodium-containing compound consists essentially of Na2CO3. In some embodiments, the sodium containing compound comprises a sodium aluminate or a hydrated sodium aluminate.

[0026] In some embodiments, the second compound comprises an aluminum salt. In someAttorney Docket No.: 2024-019-02 embodiments, the second compound is an aluminum-containing compound from a group Al2O3, Al(OH)3, and AlO(OH). In some embodiments, the second compound comprises Al2O3. In some embodiments, the second compound consists essentially of Al2O3. In some embodiments, the second compound comprises an aluminum-containing compound that is contained in bauxite ore or refined bauxite ore. In some embodiments, the second compound comprises a sodium aluminate or a hydrated sodium aluminate. In some embodiments, an amount of the sodium- containing compound is mixed with the spodumene ore such that there are about 2 sodium atoms of the sodium-containing compound for 1 lithium atom in the spodumene ore. In some embodiments, an amount of the second compound is mixed with the spodumene ore such that there is about 1 aluminum atom of the second compound for 1 lithium atom in the spodumene ore. In some embodiments, a molar ratio of sodium carbonate to the spodumene in the spodumene ore is about 1:1. In some embodiments, a molar ratio of aluminum oxide to the spodumene in the spodumene ore is about 1:2.

[0027] In some embodiments, the second compound comprises MgO. In some embodiments, the second compound consists essentially of MgO. In some embodiments, second compound is a magnesium-containing compound that decomposes to MgO at elevated temperatures. Such compounds include MgCO3and Mg(OH)2, for example. In some embodiments, an amount of the sodium-containing compound is mixed with the spodumene ore such that there is about 1 sodium atom of the sodium-containing compound for 1 lithium atom in the spodumene ore (i.e., a 1:1 Na:Li ratio). In some embodiments, an amount of the second compound is mixed with the spodumene ore such that there are about 2 magnesium atoms of the second compound for 1 lithium atom in the spodumene ore (i.e., a 2:1 Mg:Li ratio).

[0028] Returning to the process 600, at block 615 the mixture is heat treated, generating lithium carbonate (Li2CO3). In some embodiments, the heat treatment is at about 500 °C to 800 °C, about 600 °C to 800 °C, about 500 °C to 750 °C, or about 550 °C to 750 °C. In some embodiments, the heat treatment is performed for a time period of about 10 minutes to 4 hours, about 10 minutes to 1 hour, or about 10 minutes to 30 minutes.

[0029] In some embodiments, the process 600 includes the operation at block 620. At block 620, after heat treating the mixture, the mixture is mixed with water to dissolve the lithium carbonate and to generate a solution. In some embodiments, the solution is heated to dissolve the lithium carbonate in the water. This helps to ensure that the lithium carbonate is dissolved in theAttorney Docket No.: 2024-019-02 water.

[0030] In some embodiments, the process 600 includes the operation at block 625. At block 625, after mixing the mixture with water, the solution is filtered to remove impurities from the solution. In some embodiments, filtering the solution is performed with an inorganic membrane. In some embodiments, the inorganic membrane comprises a silicon dioxide membrane having a pore size of about 50 nanometers to 500 nanometers, or about 100 nanometers.

[0031] In some embodiments, the process 600 includes the operation at block 630 (e.g., either after block 620 or block 625). At block 630, the water is removed from the solution. In some embodiments, the water is removed by evaporation. In some embodiments, the water is removed by evaporation by heating the solution to about 50 °C to 150 °C, about 50 °C to 95 °C, or about 70 °C.

[0032] The spodumene ore may need to be ground or otherwise processed after it is mined. In some embodiments, the process 600 includes crushing and grinding the spodumene ore. In some embodiments, the spodumene ore is crushed with a jaw crusher or gyratory crusher and ground in a semi-autonomous grinding mill, ball mill, or attritor mill.

[0033] In some embodiments, the process 600 is performed using spodumene concentrate or a mixture of spodumene concentrate and spodumene ore. Spodumene concentrate, also referred to as spodumene concentrate 6 or SC6, is a high-purity lithium ore. Spodumene concentrate generally has about 5.0 to 7.2 weight percent (e.g., about 6 weight percent) lithium oxide (Li2O) content.

[0034] As described in the Examples below, to clarify the role of each reactant in extracting Li from α-spodumene, in situ XRD was applied to characterize its reaction with Na2CO3 (excluding Al2O3). The resulting data shows the formation of nepheline (NaAlSiO4) and Li2SiO3 above 600 °C, consistent with previous reports. Washing the product with water reveals a third product, Li2CO3, but in quantities that suggest only 76% of Li is extracted from spodumene when Na2CO3 is used as the sole reactant. The limited yield of Li in the form of Li2CO3 is attributed to the competing formation of Li2SiO3. To avoid this byproduct and improve the purity of Li2CO3, Al2O3 was identified as an effective additive which traps the silicate anions from spodumene and provides increased thermodynamic driving force to form Li2CO3. The reaction with Na2CO3and Al2O3was tested experimentally, and its products were characterized using XRD and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). These measurementsAttorney Docket No.: 2024-019-02 reveal that > 90% (specifically 90.4%) of Li is successfully extracted from spodumene in the form of Li2CO3, which can be isolated using a low-cost washing procedure without acid. This approach can become an environmentally friendly method of using domestically sourced α- spodumene to create Li-salts for the battery industry.

[0035] The following examples are intended to be examples of the embodiments disclosed herein, and are not intended to be limiting. EXAMPLE – General Material Preparation and Synthesis

[0036] The lithium-based ore used in the Examples was α-spodumene (LiAlSi2O6), obtained from deposits located in North Carolina, United States. The spodumene concentrate was ground and sieved to a particle size less than 75 μm. The processed spodumene samples were combined with Na2CO3and Al2O3as precursors for Li extraction. These precursors were stoichiometrically mixed, with 33% excess spodumene added to compensate for the impurities that accompany it, using a planetary ball mill at 250 rpm for 12 hours. The precursors were then dried in a 70 °C oven overnight and pelletized. The precursors were sintered at 750 °C in air for different times (10 minutes, 30 minutes, 2 hours, 4 hours, and 8 hours) before letting them cool naturally to room temperature. EXAMPLE – Characterization of Spodumene Concentrate

[0037] Previous studies have reported that the ore mined from the Carolina Tin-Spodumene Belt (TSB) area in North Carolina generally contains 20% spodumene, 30% quartz, 43% feldspar, and 5% mica. There also tends to be trace amounts of biotite, calcite, pyrite, chlorite, apatite, and other silicates present.

[0038] The ore was purified using a combination of physical separation, size reduction, floatation, and magnetic separation. The resulting concentrate was then ground and filtered to obtain particles <75 μm in diameter by passing the sample through a 200 mesh. Scanning Electron Microscopy (SEM) confirmed that the sieved concentrate contained particles with size ranging from 5 μm to 75 μm.

[0039] The XRD pattern obtained from this sample is shown in Figure 1A, and Rietveld refinement indicates that α-spodumene is the majority phase, comprising 69.6 ± 0.14% of the sample’s weight. Three impurities were also identified: quartz (SiO2, 18.8 ± 0.06%), feldspar (NaAlSi3O8, 9.4 ± 0.09%), and lepidolite mica (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2, 2.1 ± 0.01%). These results are consistent with previous work, in which quartz and feldspar are reported toAttorney Docket No.: 2024-019-02 accompany spodumene. Related studies have also shown the prevalence of lepidolite distributed in pegmatite minerals, from which spodumene is sourced. A spodumene weight fraction of 69.6% corresponds to a Li2O content of 5.59% in the sample, which aligns well with previous reports on the Li2O content in spodumene, generally ranging from 5.0% to 7.2%. The ICP-MS measurements produced a similar value of 6.18% Li2O in the spodumene concentrate (Table 1), and this value is used to determine the Li yield reported in later Examples. Li2O Al2O3 SiO2 Na2O K2O Fe2O3 CaOa e . e g rac on o ac emen a x e roup That Exists in Spodumene Concentrate, as Determined by ICP-MS Measurements EXAMPLE – Reaction of α-Spodumene with Na2CO3

[0040] The reaction that occurs between α-spodumene and Na2CO3was first studied without introducing any other additives. These reactants were mixed in a 2:1 molar ratio to match the stoichiometry needed to form Li2CO3 and nepheline, according to the chemical equation below: 2LiAlSi2O6+ Na2CO3→ Li2CO3+ 2NaAlSiO4+ 2SiO2(R1) (ΔG = −24meV / atom or −2.3kJ / mol)

[0041] The reaction energy (ΔG) was determined using ab initio calculations and normalized by the total number of atoms (or moles of atoms) in the products formed. The reactant mixture was packed in a sapphire capillary and heated to 800 °C in air at a rate of 10 °C / min. The heating process was monitored separately using in situ XRD measurements at the Advanced Light Source (ALS) powder diffraction Beamline 12.2.2, where the sample was scanned four times each minute.

[0042] The heatmap shown in Figure 2A shows XRD intensities that were collected from the sample containing α-spodumene and Na2CO3as it was heated to 800 °C. Reaction products were identified and their weight fractions were determined using Rietveld refinement. Only crystalline phases were accounted for, neglecting the possible formation of amorphous byproducts that areAttorney Docket No.: 2024-019-02 often prevalent in Si-containing systems but difficult to identify using XRD alone. The weight fraction of each crystalline phase is plotted as a function of temperature in Figure 2B. These results show that α-spodumene and Na2CO3 begin to react at 600 °C, forming nepheline (NaAlSiO4) as the majority product. It is anticipated that Li2CO3forms in addition to nepheline; however, Li2CO3 is difficult to detect in multiphase XRD patterns owing to its weak scattering of X-rays, and therefore an attempt was not made to quantify its weight fraction without first isolating it from the other compounds. In contrast, a minority Li2SiO3phase is clearly detected shortly after the formation of nepheline. The weight fractions of both phases continue to grow until 750 °C, at which point spodumene is mostly consumed. No further changes are observed upon heating the sample above 750 °C. Throughout all the temperatures that were sampled, there is little change to the amount of SiO2that exists in the starting material. Though, it does exhibit a well-established phase transition from its α to β polymorph in the range of 550 °C – 600 °C.

[0043] The observed formation of Li2SiO3 suggests that not all Li was successfully extracted from spodumene in the form of Li2CO3, which itself is difficult to detect from XRD alone. The origin of Li2SiO3 can be found by inspecting the proposed reaction (R1), which shows that any Li2CO3 formed by reacting Na2CO3 with spodumene must also be accompanied by the formation of SiO2to balance the chemical equation – i.e., the silicate anions from spodumene cannot be accommodated by nepheline alone. DFT computations indicate that a reaction between Li2CO3 and SiO2 becomes thermodynamically favorable at temperatures above 400 °C, and this finding is consistent with the fact that Li2SiO3does indeed form shortly after the appearance of nepheline at 600 °C (Figure 2B). These results are also in agreement with previous findings of the simultaneous formation of NaAlSiO4 and Li2SiO3 at 560 °C when β-spodumene reacts with Na2CO3. Despite the presence of Li2SiO3 in the sample, its low weight fraction (∼6.0%) relative to that of NaAlSiO4 (∼79.1%) suggests that Li2SiO3 contains only about 24.1% of the Li that was extracted from spodumene. In the next Example it is shown that much of the remaining (unaccounted for) Li is present in the form of Li2CO3. EXAMPLE – Separation of Li2CO3from NaAlSiO4

[0044] The reaction of α-spodumene with Na2CO3 produces a mixture of NaAlSiO4 and Li2SiO3, with Li2CO3anticipated as a potential byproduct. Detecting Li2CO3directly is made difficult by the fact that it scatters X-rays weakly, exhibits strong peak overlap with NaAlSiO4, and likely has a low weight fraction in the sample compared to the heavier NaAlSiO4 phase. ToAttorney Docket No.: 2024-019-02 validate that Li2CO3is present, it was separated from the other phases by leveraging their solubility differences in water. Li2CO3 is reported to have a solubility of 1.30 g per 100 g of water (pH = 7) at 25 °C, whereas NaAlSiO4, Li2SiO3, and SiO2 are poorly soluble under the same conditions. The separation process used here follows a similar procedure to the methods outlined in previous studies, where Li2CO3 was isolated from several aluminosilicate phases using water. In the current work, the products were added to DI water, with the assistance of sonication to reduce particle agglomeration. The solution was then stirred thoroughly for 1.5 hours to ensure complete dissolution of Li2CO3, followed by filtering of the sample through an inorganic membrane with a pore size of 0.1 μm. The filtered liquid was placed in an oven and kept at 70 °C overnight to evaporate water and isolate the solid. This solid was characterized using XRD measurements, and its Li concentration was determined using ICP-MS measurements.

[0045] The XRD patterns collected from the sample before and after the washing procedure are shown in Figure 3A. Before washing, the XRD pattern contains peaks from both NaAlSiO4and Li2SiO3, while the suspected peaks from Li2CO3 are difficult to detect. After washing, the XRD pattern from the solid residue (that was not dissolved in water) appears similar to the original pattern, suggesting that NaAlSiO4and Li2SiO3remain inert in this treatment. The XRD pattern obtained from the leachate (that was dissolved in water and then dried) matches well with the reference pattern for Li2CO3, as shown in Figure 3B. Rietveld refinement also confirms Li2CO3as a majority phase (90 ± 0.2%) in the sample. The rest of the sample appears to be comprised of SiO2(10 ± 0.3%). This indicates that the washing procedure is effective in isolating Li2CO3 from the other solid byproducts that formed from the solid-state reaction between α- spodumene and Na2CO3. Despite its success, ICP-MS measurements performed on the leachate reveal that only 69% of Li was successfully extracted from spodumene and recovered in the form of Li2CO3. This finding is consistent with the earlier observation that some of the Li from spodumene instead formed Li2SiO3, which has a low solubility in water and is less useful for battery manufacturing. EXAMPLE – Introducing Al2O3 as an Additive

[0046] It was shown in the previous Examples that Na2CO3 can extract Li from α-spodumene through a solid-state reaction which forms Li2CO3, Li2SiO3, NaAlSiO4, and SiO2. Isolation of Li2CO3can then be achieved through a washing process, but only with a moderate (69%) yieldAttorney Docket No.: 2024-019-02 of Li as determined by ICP-MS. Avoiding the formation of Li2SiO3is important to increasing this yield further. For this task, Al2O3 was introduced as an additive that participates in the solid- state reaction between α-spodumene and Na2CO3. The choice of Al2O3 is motivated by two anticipated benefits. First, its addition compensates for the excess silicate anions in spodumene and reduces the likelihood of Li2SiO3 formation. This means that Li2CO3 can now form as the sole byproduct of NaAlSiO4 based on the following reaction stoichiometry: 2LiAlSi2O6 + 2Na2CO3 + Al2O3 → Li2CO3 + 4NaAlSiO4 + CO2 (R2) (ΔG = −95meV / atom or −9.2kJ / mol)

[0047] Second, this reaction has a much larger thermodynamic driving force than the reaction between Na2CO3 and spodumene (without Al2O3). The change in the free energy (ΔG) associated with forming Li2CO3 increases from −24 meV / atom (R1) to −95 meV / atom (R2) after Al2O3is introduced as an additive.

[0048] To validate the effectiveness of the newly proposed reaction (R2), α-spodumene was mixed with Na2CO3 and Al2O3 in a 2:2:1 molar ratio and heated the sample to 750 °C for 30 minutes. After letting the sample cool to room temperature, it was manually ground and washed with water using the same procedure outlined in the previous Example. The XRD patterns obtained from the sample before and after washing with water are shown in Figure 4A. These results show that the sample obtained directly after synthesis contains a predominant NaAlSiO4phase. XRD performed on the solid residue (after removing Li2CO3) also reveals a Li2SiO3byproduct, but Rietveld refinement suggests that its weight fraction is nearly cut in half (decreasing from 6.0% to 3.1%) relative to the sample prepared using Na2CO3 alone. What little Li2SiO3does form likely originates from reactions with the SiO2phase that coexists with spodumene. As shown in Figure 1A, the spodumene concentrate used in this study contains a prominent SiO2 impurity with a weight fraction of 18.8%. Therefore, although Al2O3 circumvents the formation of additional SiO2during the extraction of Li from spodumene, it does not prevent any reactions that may occur between Li2CO3 (extracted from spodumene) and SiO2 (that is already present in the sample).

[0049] Despite the presence of Li2SiO3in the sample, its reduced weight fraction points to the success of the proposed reaction (R2) and suggests that more Li from spodumeneAttorney Docket No.: 2024-019-02 successfully contributed to the formation of Li2CO3instead of becoming trapped in Li2SiO3. Enhanced Li2CO3 formation is further evidenced by the results from ICP-MS measurements performed on the leachate, which reveals that 85% of all Li from spodumene is present in the form of Li2CO3. This represents a 16% increase in yield compared to the sample prepared without Al2O3. Although both samples (made with and without Al2O3) display a strong diffuse background in XRD, which may be caused by the presence of amorphous impurities that likely contain Si, confirmation of the high Li yield with ICP-MS suggests that such impurities have little effect on Li2CO3 formation. Further improvements can also be achieved with longer hold time at 750 °C, as demonstrated in the next Example. EXAMPLE – Maximizing the Yield of Li2CO3

[0050] To adjust the heating profile so that Li2CO3is maximized, various hold times at 750 °C for reactions with (R2) and without Al2O3 (R1) were tested. Five hold times were tested: 10 minutes, 30 minutes, 2 hours, 4 hours, and 8 hours. After each hold, the sample was allowed to cool and Li2CO3was separated from the reaction byproducts by washing the sample with water as described in previous Examples. XRD patterns of the solid products were obtained for samples before and after washing. XRD was also performed on the leachate after evaporating water from it. The yield of Li in the form of Li2CO3was determined by ICP-MS as a percentage of the total Li available in spodumene. These values are plotted as a function of hold time for each set of reactants in Figure 5. Both reactions exhibit a similar trend in the Li yield, though adding Al2O3(R2) consistently leads to higher yields (+15% on average). At a very short hold time of only 10 minutes, the Li yield ranges from 15% to 20% as the reaction with α-spodumene is likely incomplete. This reaction appears to progress quickly as a large increase in the Li yield is observed from 10 minutes to 30 minutes, resulting in yields of 85% and 69% with and without Al2O3, respectively. At longer hold times, only small changes in the Li yield occur. Reactions involving Al2O3 reach a maximum yield of 90.4% at 4 hours of hold time while those without Al2O3 reach a maximum yield of 76.4% at a shorter hold time of 2 hours.

[0051] At hold times greater than 4 hours, ICP-MS measurements indicate the Li yield tends to decrease for both reactions tested here. It is possible that this decrease can be attributed to the reaction that slowly occurs between Li2CO3 and SiO2; however, this seems unlikely as there is no clear change in the amount of Li2SiO3formed at different hold times. Instead, it is suspected that the observed decrease in Li yield is caused by the volatility of Li2CO3at high temperature.Attorney Docket No.: 2024-019-02 Considering that Li2CO3has a melting point of 732 °C, prolonged exposure at 750 °C is likely to result in some degree of volatility. This effect is well reported in previous studies, and as such, excess amounts of Li2CO3 are often used when synthesizing Li-ion cathodes at high temperature. For the extraction of Li from spodumene, lower temperatures (≤ 750 °C) or relatively short hold times (≤ 4 hours) may be used to avoid this volatility and maximize the yield of Li2CO3. CONCLUSION

[0052] Further details regarding the embodiments described herein can be found in S. Wang et al., “Direct Lithium Extraction from α-Spodumene through Solid-State Reactions for Sustainable Li2CO3 Production,” Inorg. Chem. 2024, 63, 29, 13576–13584, which is hereby incorporated by reference.

[0053] In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

Claims

Attorney Docket No.: 2024-019-02 CLAIMS What is claimed is:

1. A method comprising: providing spodumene ore, the spodumene ore comprising particles, spodumene (LiAlSi2O6) in the spodumene ore comprising α-spodumene; mixing the spodumene ore with a sodium-containing compound and second compound to form a mixture, the second compound comprising an aluminum-containing compound, a magnesium-containing compound, or mixtures thereof; and heat treating the mixture, the heat treating generating lithium carbonate (Li2CO3).

2. The method of claim 1, further comprising after heat treating the mixture, mixing the mixture with water to dissolve the lithium carbonate and to generate a solution; and removing the water from the solution.

3. The method of claim 2, wherein the water is removed by evaporation.

4. The method of claim 2, wherein the water is removed by evaporation by heating the solution to about 50 °C to 150 °C.

4. The method of claim 2, further comprising: heating the solution after mixing the mixture with water to dissolve the lithium carbonate in the water.

5. The method of claim 2, further comprising: after mixing the mixture with water, filtering the solution to remove impurities from the solution.

6. The method of claim 5, wherein filtering the solution is performed with an inorganic membrane.Attorney Docket No.: 2024-019-02 7. The method of claim 5, wherein filtering the solution is performed with an inorganic membrane, and wherein the inorganic membrane comprises a silicon dioxide membrane having a pore size of about 50 nanometers to 500 nanometers.

8. The method of claim 1, wherein the spodumene ore consists of particles.

9. The method of claim 1, wherein the spodumene ore has particle sizes of less than about 100 microns.

10. The method of claim 1, wherein the sodium-containing compound comprises a sodium salt.

11. The method of claim 1, wherein the sodium-containing compound is a sodium-containing compound from a group Na2CO3, NaHCO3, NaOH, NaCl, and Na2O2.

12. The method of claim 1, wherein the sodium-containing compound comprises Na2CO3.

13. The method of claim 1, wherein the sodium-containing compound consists essentially of Na2CO3.

14. The method of claim 1, wherein the second compound comprises an aluminum salt.

15. The method of claim 1, wherein the second compound is an aluminum-containing compound from a group Al2O3, Al(OH)3, and AlO(OH).

16. The method of claim 1, wherein the second compound comprises Al2O3.

17. The method of claim 1, wherein the second compound consists essentially of Al2O3.

18. The method of claim 1, wherein the second compound comprises an aluminum-containing compound that is contained in bauxite ore or refined bauxite ore.Attorney Docket No.: 2024-019-02 18. The method of claim 1, wherein the second compound comprises MgO.

18. The method of claim 1, wherein the second compound consists essentially of MgO.

19. The method of claim 1, wherein an amount of the sodium-containing compound is mixed with the spodumene ore such that there are about 2 sodium atoms of the sodium-containing compound for 1 lithium atom in the spodumene ore, and wherein an amount of the second compound is mixed with the spodumene ore such that there is about 1 aluminum atom of the aluminum-containing compound for 1 lithium atom in the spodumene ore.

19. The method of claim 1, wherein an amount of the sodium-containing compound is mixed with the spodumene ore such that there are about 1 sodium atoms of the sodium-containing compound for 1 lithium atom in the spodumene ore, and wherein an amount of the second compound is mixed with the spodumene ore such that there is about 2 magnesium atoms of the magnesium-containing compound for 1 lithium atom in the spodumene ore.

20. The method of claim 1, wherein the mixing the spodumene ore with the sodium-containing compound and the second compound is performed using a ball mill.

21. The method of claim 1, wherein the heat treating is at about 500 °C to 800 °C.

22. The method of claim 1, wherein the heat treating is for a time period of about 10 minutes to 4 hours.

23. The method of claim 1, further comprising: crushing and grinding the spodumene ore.

24. The method of claim 23, wherein the spodumene ore is crushed with a jaw crusher or gyratory crusher and ground in a semi-autonomous grinding mill, ball mill, or attritor mill.Attorney Docket No.: 2024-019-02 26. A method comprising: providing spodumene ore, the spodumene ore comprising particles, spodumene (LiAlSi2O6) in the spodumene ore comprising α-spodumene; mixing the spodumene ore with sodium carbonate (Na2CO3) and aluminum oxide (Al2O3) to form a mixture, a molar ratio of the sodium carbonate to the spodumene being about 1:1, and a molar ratio of the aluminum oxide to the spodumene being about 1:2; heat treating the mixture, the heat treating generating lithium carbonate (Li2CO3); after heat treating the mixture, mixing the mixture with water to dissolve the lithium carbonate and to generate a solution; filtering the solution to remove impurities from the solution; and removing the water from the solution by heating the solution.

27. A method comprising: providing spodumene ore, the spodumene ore comprising particles, spodumene (LiAlSi2O6) in the spodumene ore comprising α-spodumene; mixing the spodumene ore with sodium carbonate (Na2CO3) and magnesium oxide (MgO) to form a mixture; heat treating the mixture, the heat treating generating lithium carbonate (Li2CO3); after heat treating the mixture, mixing the mixture with water to dissolve the lithium carbonate and to generate a solution; filtering the solution to remove impurities from the solution; and removing the water from the solution by heating the solution.

28. The method of claim 27, wherein a molar ratio of the sodium carbonate to the spodumene is about 1:2 in the mixture, and a molar ratio of the magnesium oxide to the spodumene is about 2:1 in the mixture.