PRODUCING LITHIUM DIRECTLY FROM LITHIUM FEED SOURCES

Abstract

A process is provided for producing lithium directly from a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, lithium hydroxide, and a combination thereof. The lithium feed solution is provided in an electrolysis cell comprising a cathode suitable for electrolysis of lithium, and an anode. An ionizing electric current is provided to the electrolysis cell, thereby providing lithium metal at the cathode. The present process can advantageously streamline the lithium production process, reduce operating costs, and/or improve energy efficiency in production of lithium.

Claims

1. A process for producing lithium directly from lithium containing brine or liquor, the process comprising: providing a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, and a combination thereof; providing the lithium feed solution to an electrolysis cell comprising a cathode suitable for electrolysis of lithium, and an anode; providing an ionizing electric current to the electrolysis cell, thereby providing lithium metal at the cathode.

2. The process of claim 1, wherein the lithium chloride brine contains 1.5-18% lithium.

3. The process of claim 1, wherein the lithium chloride brine contains 4-6% lithium.

4. The process of claim 3, wherein the lithium chloride brine is prepared by evaporation in an evaporation pond.

5. The process of claim 4, wherein the evaporation pond is selected from the group consisting of a solar evaporation pond and an electric evaporation pond.

6. The process of claim 4, wherein the lithium chloride brine is returned from the electrolysis cell to the evaporation pond.

7. The process of claim 1, wherein the lithium sulfate spodumene liquor contains 1-18% lithium.

8. The process of claim 1, wherein the lithium sulfate spodumene liquor contains 1.5-18% lithium.

9. The process of claim 1, wherein the lithium sulfate spodumene liquor contains 16-18% lithium.

10. The process of claim 1, wherein the lithium sulfate spodumene liquor is provided from a reservoir, and the lithium sulfate spodumene liquor is returned from the electrolysis cell to the reservoir.

11. The process of claim 1, wherein the lithium feed solution is prepared without removing boron or magnesium.

12. The process of claim 1, wherein the lithium feed solution is continuously provided to the electrolysis cell, and the lithium metal is continuously produced at the cathode.

13. The process of claim 1, wherein the temperature in the electrolysis cell for providing lithium metal is 15 to 40 C.

14. The process of claim 1, wherein the temperature in the electrolysis cell for providing lithium metal is approximately 23 C.

15. The process of claim 1, wherein the lithium feed solution has a pH of 3-9.

16. A process for producing lithium directly from lithium hydroxide or lithium hydroxide monohydrate, the process comprising: providing an aqueous lithium feed solution selected from the group consisting of a lithium hydroxide solution, a lithium hydroxide monohydrate solution, and a combination thereof; providing the lithium feed solution in an electrolysis cell comprising a cathode suitable for electrolysis of lithium, and an anode; providing an ionizing electric current to the electrolysis cell, thereby providing lithium metal at the cathode.

17. The process of claim 16, wherein the lithium hydroxide solution contains 1.5-18% lithium.

18. The process of claim 16, wherein the lithium hydroxide solution contains 1-18% lithium.

19. The process of claim 16, wherein the lithium feed solution is continuously provided to the electrolysis cell, and the lithium metal is continuously produced at the cathode.

20. The process of claim 16, wherein the temperature in the electrolysis cell for providing lithium metal is 15 to 40 C.

21. The process of claim 16, wherein the temperature in the electrolysis cell for providing lithium metal is approximately 23 C.

22. The process of claim 16, wherein the lithium feed solution has a pH of 7-14.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0030] FIG. 1 is a flow diagram showing the process for producing lithium according to an embodiment of the present disclosure.

[0031] FIG. 2 is a perspective view of a first embodiment of a lithium producing cell structure used to produce lithium in the process of FIG. 1.

[0032] FIG. 3 is an elevation view of the lithium producing cell of FIG. 2.

[0033] FIG. 4 is a section view taken along A-A of FIG. 3.

[0034] FIG. 5 is a perspective view of a lithium producing cell according to a second embodiment of the present disclosure.

[0035] FIG. 6 is an exploded view of the lithium producing cell of FIG. 5.

DETAILED DESCRIPTION

[0036] The present disclosure generally relates to producing lithium directly from a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, lithium hydroxide, and a combination thereof. Additionally the present disclosure also relates to continuous processes for obtaining lithium metal.

[0037] Lithium can be extracted from the earth by either pumping of brine from the ground or mining spodumene, petalite or lepidolite ore from the earth. Salar brines can be described as underground reservoirs that contain high concentrations of dissolved salts, such as lithium, potassium, and sodium. The lithium-rich water is pumped to the surface into a series of evaporation ponds where solar evaporation occurs over a number of months. In the first stage of evaporation, salts of sodium, potassium, magnesium, etc., can be harvested from the brine as byproducts. Lithium concentration reached in this first stage is raised to 1.5% lithium in the evaporation pond. The brine is then transported to a secondary evaporation pond where lithium concentration is raised further to approximately 4-6% lithium. Potassium is often first harvested from early ponds, while later ponds have increasingly high concentrations of lithium.

[0038] In conventional lithium producing processes, when the lithium chloride in the evaporation ponds reaches an optimum concentration, the solution is pumped to a recovery plant where extraction and filtering remove any unwanted boron or magnesium. The lithium chloride solution is then treated with sodium carbonate (soda ash), thereby precipitating lithium carbonate. The lithium carbonate is filtered, dried and ready for delivery. Excess residual brines are pumped back into the salar.

[0039] According to certain non-limiting embodiments, the process for producing lithium uses the lithium chloride solution before boron and magnesium extraction, filtering, or before it is treated with soda ash and converted into lithium carbonate. The lithium chloride solution according to an embodiment could be pumped directly from the evaporating pond or evaporation process, through the electrolysis cell, and returned back into the evaporating pond or process.

[0040] Conventional methods of extraction of lithium from spodumene and other minerals require a number of hydrometallurgical steps. For example, the ore is first crushed and heated in a rotary calcining kiln in order to convert the lithium crystal phase from alpha to beta (a process referred to as decrepitation). This allows the lithium present in the ore to be displaced by sodium. The resulting spodumene concentrate is cooled and milled into a fine powder before being mixed with sulfuric acid and roasted again. A thickener-filter system then separates waste from the concentrated liquor, while precipitation removes magnesium and calcium from this solution. Finally, soda ash is added and lithium carbonate is crystallized, heated, filtered and dried as 99 percent pure lithium carbonate.

[0041] Lithium can be extracted from spodumene concentrates after roasting and acid roasting operations. A concentrate with at least 6% Li.sub.2O (approximately 75% spodumene) is suitable for roasting. Roasting is performed at about 1050 C., during which spodumene will go through a phase transformation from -spodumene to -spodumene. The -spodumene is virtually refractory to hot acids. As a result of the phase transformation, the spodumene crystal structure expands by about 30% and becomes amenable to hot sulfuric acid attack. Due to this expansion, the specific gravity of the spodumene decreases from 3.1 g/cm.sup.3 (natural -spodumene) to around 2.4 g/cm.sup.3 (-spodumene). After roasting, the material is cooled and then mixed with sulfuric acid (95-97%). The mixture is roasted again at about 200 C. An exothermic reaction starts at 170 C. and lithium is extracted from -spodumene to form lithium sulfate, which is soluble in water.

[0042] According to certain non-limiting embodiments, this lithium sulfate solution after the roasting operations is used as feed stock for producing lithium. The lithium sulfate solution could be pumped directly from or provided from a reservoir, through the electrolysis cell, and then returned back into the reservoir.

[0043] In conventional lithium producing processes, the end product of both the brine and ore processes is typically lithium carbonate. Lithium carbonate is a stable white powder, which is a key intermediary in the lithium market because it can be converted into specific industrial salts and chemicals, or processed into lithium metal.

[0044] According to certain non-limiting embodiments, the present disclosure provides directly processing a lithium feed solution to the cell into lithium metal prior to processing into lithium carbonate. Suitable lithium feed solutions to the cell include but are not limited to concentrated lithium chloride brine from salar ponds, sulfuric acid liquor from ore operations, and a combination thereof. Lithium containing solutions obtained from spodumene or clay using alkaline, chlorination, or other leaching operations may also be acceptable feed stock. According to certain non-limiting embodiments, these lithium-containing solutions have a concentration of 1-18% lithium. According to certain non-limiting embodiments, these lithium-containing solutions have a concentration of 1.5-18% lithium. According to certain non-limiting embodiments, these lithium-containing solutions have a concentration of 16-18% lithium. According to certain non-limiting embodiments, lithium containing solutions obtained from concentrating seawater, seawater, or bitterns may also be acceptable and resulting feed have a concentration of 1-18% lithium. According to certain non-limiting embodiments, lithium containing solutions obtained by leaching of lithium from recycled lithium batteries would also make acceptable feed stock and have a lithium concentration of 1-18% lithium. In certain non-limiting embodiments, lithium carbonate may not be present in the lithium feed solution according to the present disclosure.

[0045] A lithium metal according to an embodiment may be produced using a cell as shown in FIGS. 2-4. In FIGS. 2-4, the electrolytic cell 9 includes a cathode 7, an anode 8, and the lithium feed solution, which is used as electrolyte in the electrolytic cell 9. The anode 8 is in contact with the lithium feed solution. A lithium ion conducting membrane 2 separates the anode and cathode compartments. The cathode 7 is immersed in non-aqueous catholyte 5, providing a path for lithium ion flow from the membrane 2 to the cathode 7. When a potential is applied across the electrolytic cell 9, electrolysis proceeds and lithium metal builds up on the cathode 7.

[0046] In a non-limiting embodiment, the cathode 7 is suitable for electrolysis of lithium, and comprises a suitable material that is non-reactive with lithium metal or the catholyte 5. In an embodiment, the cathode 7 can be made from copper. In an embodiment, the anode 8 can be made from titanium or niobium coated with platinum, gold, or ruthenium. In certain other non-limiting embodiments, the anode 8 can be made from any material that is compatible with the anolyte, such as concentrated lithium chloride brine from salar ponds, sulfuric acid liquor from ore operations, and a combination thereof. As illustrated in FIG. 2, an anionic selective membrane 2 is inserted between the cathode 7 and the anode 8, and only lithium flows through the membrane 2.

[0047] In a non-limiting embodiment, a lithium chloride brine containing 1.5-18% lithium or a lithium sulfate spodumene liquor containing 1.5-18% lithium can be utilized as the lithium feed solution 6 to directly produce lithium metal in an electrolysis cell using electrolysis as shown in the reactions below:

Li.sup.++e.sup..fwdarw.Li metalCathode:

O.fwdarw.O.sub.2+e.sup. or Cl.sup..fwdarw.Cl.sub.2+e.sup.Anode:

2Li+2O.fwdarw.2Li+O.sub.2 or 2LiCl.fwdarw.2Li+Cl.sub.2Total:

In an embodiment, the lithium chloride brine contains 4-6% lithium.

[0048] In certain other non-limiting embodiments, a lithium hydroxide solution containing 1.5-18% lithium can be utilized as the lithium feed solution to directly produce lithium metal in an electrolysis cell using electrolysis as shown in the reactions below:

Li.sup.++e.sup..fwdarw.Li metalCathode:

O.fwdarw..sub.2+e.sup.Anode:

2Li+2O.fwdarw.2Li+O.sub.2Total:

[0049] According to certain non-limiting embodiments, electrolysis is performed at approximately 23 C. to produce lithium (and oxygen or chlorine gas as a byproduct).

[0050] In a non-limiting embodiment, the lithium feed solution is continuously fed or provided into the electrolytic cell 9, and the lithium metal is continuously produced at the cathode. Specifically, the lithium feed solution is circulated through the electrolytic cell 9 via an inlet of the cell body, spent electrolyte is discharged via an outlet of the cell body, and the oxygen or chlorine gas released by the anode is vented off. In an embodiment, lithium chloride brine is prepared by solar or electric evaporation in an evaporation pond, and the lithium chloride brine is returned from the electrolysis cell to the evaporation pond. In another embodiment, lithium sulfate spodumene liquor is provided from a reservoir or feed tank, and the lithium sulfate spodumene liquor is returned from the electrolysis cell to the reservoir or feed tank. In another embodiment, the lithium feed solution is selected from the group consisting of a lithium hydroxide solution, a lithium hydroxide monohydrate solution, and a combination thereof, and the lithium feed solution is circulated via a pump. In certain other non-limiting embodiments, the lithium producing process is conducted as a batch process.

[0051] In a non-limiting embodiment, the cell body can be made of a suitably rigid material such as polypropylene. The lithium producing processes described herein are not limited in this regard. The membrane holder 1 shall be electrically insulating to prevent electron flow between the anode and cathode compartments, preventing electrolysis of the water based lithium feed solution when applying voltage above 2.5 vdc. The membrane 2 is an electrical insulator which only allows lithium ion flow, not electron flow.

[0052] The advantages of producing lithium on-site directly from spodumene, brine, or other liquid concentrate or leaching agent without transportation or delivery over a substantial distance are streamlining the lithium production process, reducing operating costs, and/or improving energy efficiency in production of lithium. While the process according to an embodiment could be used for production of bulk lithium metal, according to other non-limiting embodiments it is more suited for applications requiring the electrodeposition of thin layers of pure lithium metal (such as for lithiated anodes or cathodes in secondary batteries) and the production of very high purity lithium products and related compounds.

[0053] By way of example and not limitation, the following examples are illustrative of various methods of the present disclosure for producing lithium directly from a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, lithium hydroxide, and a combination thereof. The processes below are provided for exemplification only, and they can be modified by the skilled artisan to the necessary extent, depending on the special features that are desired.

EXAMPLES

Example 1

[0054] The cell used in Example 1 is shown schematically in FIGS. 5-6. 75 mm50 mm25 micron pieces of copper were washed in a concentrated sulfuric acid solution. The samples were then rinsed with deionized water three times, and dried with a wipe. The samples were then loaded into an argon atmosphere glove box, exchanging the atmosphere of the antechamber three times. The bench flow cell show in FIGS. 5-6 was set up with an 8M aqueous lithium chloride solution circulating through the anode side of the cell, and a 1M LiPF6 (lithium hexafluorophosphate) EC (ethylene carbonate)-DMC (dimethyl carbonate) organic electrolyte circulating through the cathode (plating) side of the cell. As illustrated in FIG. 6, an anionic selective membrane 14 is inserted between the cathode 18 (copper film) and the anode 12, and only lithium flows through the membrane 14. The samples were then loaded into a sample holder where the copper was masked, allowing 16 square centimeters of copper to be exposed to the electrolyte on one side. The sample holder with substrate was then loaded in the bench flow cell.

[0055] Flow was initiated on the bench cell for both the aqueous and non-aqueous electrolytes, and the flow rate was controlled for each. The pH of the aqueous electrolyte was monitored during the deposition. The initial pH was 6.13, and the final pH was 5.94. A potentiostat was used to perform the deposition at 3.75 volts for 7200 seconds using a chronoamperometry mode. The ionizing electric current spiked at 71.57 mA, with a follow on current at approximately 41 mA. At the end of deposition, the sample was removed from the sample holder, washed three times with dimethyl carbonate, and dried. The lithium plating on the samples demonstrated that pure lithium can be plated directly from a lithium chloride brine feed. Specifically, the resultant lithium film exhibited a blue color, which is indicative of a nano-rod morphology within the lithium metal film. Without wishing to be bound by any particular theory, it is believed that the blue appearance might be due to a structural coloration effect, whereby the fine microscopic surface produces a structural color by interference among light waves scattered by two or surfaces of the film.

Example 2

[0056] The cell used in Example 2 is shown schematically in FIGS. 5-6. 75 mm50 mm25 micron pieces of copper were washed in a concentrated sulfuric acid solution. The samples were then rinsed with deionized water three times, and dried with a wipe. The samples were then loaded into an argon atmosphere glove box, exchanging the atmosphere of the antechamber three times. The bench flow cell show in FIGS. 5-6 was set up with an 8M aqueous lithium chloride solution circulating through the anode side of the cell, and a 1M LiPF6 EC-DMC organic electrolyte circulating through the cathode (plating) side of the cell. As illustrated in FIG. 6, an anionic selective membrane 14 is inserted between the cathode 18 (copper film) and the anode 12, and only lithium flows through the membrane 14. The samples were then loaded into a sample holder where the copper was masked, allowing 16 square centimeters of copper to be exposed to the electrolyte on one side. The sample holder with substrate was then loaded in the bench flow cell.

[0057] Flow was initiated on the bench cell for both the aqueous and non-aqueous electrolytes, and the flow rate was controlled for each. The pH of the aqueous electrolyte was monitored during the deposition. The initial pH was 5.94, and the final pH was 5.75. A potentiostat was used to perform the deposition at 3.75 volts for 2500 seconds using a chronoamperometry mode. The ionizing electric current spiked at 72.9 mA, with a follow on current at approximately 44 mA. The resultant lithium film exhibited a grey color, which is indicative of a dense spherical morphology within the lithium metal film.

[0058] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.