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.

Description

PRIORITY CLAIM

This application claims the benefit of U.S. Provisional Patent Application No. 62/542,413, filed Aug. 8, 2017, and U.S. Provisional Patent Application No. 62/581,140, filed Nov. 3, 2017, the disclosures of each of which are incorporated into this specification by reference in its entirety.

FIELD OF TECHNOLOGY

The present disclosure generally relates to producing lithium directly from feed sources. More specifically, for example, the present disclosure relates to producing lithium using 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.

BACKGROUND

Lithium is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Lithium is highly reactive and flammable, though it is the least reactive of the alkali metals. Because of its high reactivity, lithium does not occur freely in nature. Instead, lithium only appears naturally in compositions, usually ionic in nature. Therefore, lithium metal can be obtained only by extraction of lithium from such compounds containing lithium.

Currently, common ways of obtaining lithium are through extraction of lithium present in either spodumene or brine, producing lithium carbonate first. Lithium is then obtained from the lithium carbonate in two phases: (1) conversion of lithium carbonate into lithium chloride, and (2) electrolysis of lithium chloride using a high-temperature molten salt such as LiCl.

SUMMARY

Previous production of lithium metal from spodumene or brine typically has been at locations remote from the lithium production facilities, involving first the production of lithium chloride (directly, or from lithium carbonate as an intermediary), followed by high temperature electrolysis of molten lithium chloride salt at a location remote from the feed stock production. There is a need for a process that produces lithium on-site directly from the spodumene or brine, without transportation or delivery of the spodumene or brine over a substantial distance, which could involve substantial operating costs and/or is less efficient.

In an embodiment, the present disclosure relates to a process for producing lithium directly from lithium containing brine or liquor. The process includes providing a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, and a combination thereof. The lithium feed solution is provided to 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.

In an embodiment, the lithium chloride brine contains 1.5-18% lithium.

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

In an embodiment, the lithium chloride brine is prepared by evaporation in an evaporation pond.

In an embodiment, the evaporation pond is selected from the group consisting of a solar evaporation pond and an electric evaporation pond.

In an embodiment, the lithium chloride brine is returned from the electrolysis cell to the evaporation pond.

In an embodiment, the lithium sulfate spodumene liquor contains 1-18% lithium.

In an embodiment, the lithium sulfate spodumene liquor contains 1.5-18% lithium.

In an embodiment, the lithium sulfate spodumene liquor contains 16-18% lithium.

In an embodiment, 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.

In an embodiment, the lithium feed solution is prepared without removing boron or magnesium.

In an embodiment, the lithium feed solution is continuously provided to the electrolysis cell, and the lithium metal is continuously produced at the cathode.

In an embodiment, the temperature in the electrolysis cell for providing lithium metal is 15 to 40° C.

In an embodiment, the temperature in the electrolysis cell for providing lithium metal is approximately 23° C.

In an embodiment, the lithium feed solution has a pH of 3-9.

An advantage of the present disclosure is to produce lithium on-site directly from the spodumene or brine. By using a lithium feed solution selected from the group consisting of lithium chloride brine, lithium sulfate spodumene liquor, and a combination thereof, the spodumene or brine can be directly used without converting to lithium carbonate or lithium chloride, and without transportation or delivery over a substantial distance as in conventional lithium producing processes, therefore desirably streamlining the lithium production process, reducing operating costs, and/or improving energy efficiency in production of lithium. As shown in Table 1, the process for producing lithium according to certain non-limiting embodiments eliminates all of the large scale production processes required to turn lithium containing brine or spodumene into lithium metal, instead depositing pure lithium metal directly from lithium containing brine or spodumene liquor.

TABLE 1
Cost savings by elimination of process steps
			Spodumene ore
Lithium brine	Lithium brine	Spodumene ore	(conventional
Embodiment	(conventional process)	Embodiment	process)
Multi-stage	Multi-stage	Processing ore into	Processing ore into
Solar	Solar	spodumene liquor	spodumene liquor
Evaporation	Evaporation
Electrolysis of	Purification with organic	Electrolysis of	Calcination
lithium brine directly	solvents, filtration, and	spodumene liquor
to pure lithium metal,	precipitation	directly to pure
deposited onto desire		lithium metal,
substrate (such as		deposited onto desire
copper anode		substrate (such as
material)		copper anode
		material)
	Addition of soda ash and		Thermal leaching with
	carbonation to produce		soda ash
	lithium carbonate
	Drying		Bicarbonization
	Screening and processing		Filtration and impurity
	into lithium carbonate		removal
	powder
	Shipment of lithium		Lithium carbonate
	carbonate to lithium		crystallization
	metal producer
	Convert lithium		Screening and
	carbonate to lithium		processing into
	chloride		lithium carbonate
			powder
	Add potassium chloride		Shipment of lithium
	to reduce melt temp of		carbonate to lithium
	lithium chloride		metal producer
	High temperature		Convert lithium
	electrolysis of LiCl/KCl		carbonate to lithium
	mix to produce lithium		chloride
	metal.
	Shipment of lithium		Add potassium
	ingots to roll processing		chloride to reduce
	facility		melt temp of lithium
			chloride
	Rolling of lithium metal		High temperature
	into thin film		electrolysis of
			LiCl/KCl mix to
			produce lithium metal.
	Shipment of lithium film		Shipment of lithium
	to facility to process onto		ingots to roll
	substrate		processing facility
	Rolling of thin lithium		Rolling of lithium
	film onto desired		metal into thin film
	substrate.
			Shipment of lithium
			film to facility to
			process onto substrate
			Rolling of thin lithium
			film onto desired
			substrate.

In an embodiment, the present disclosure relates to a process for producing lithium directly from an aqueous lithium feed solution selected from the group consisting of a lithium hydroxide solution, a lithium hydroxide monohydrate solution, 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.

In an embodiment, the lithium hydroxide solution contains 1.5-18% lithium.

In an embodiment, the lithium feed solution is continuously provided to the electrolysis cell, and the lithium metal is continuously produced at the cathode.

In an embodiment, the temperature in the electrolysis cell for providing lithium metal is 15 to 40° C.

In an embodiment, the temperature in the electrolysis cell for providing lithium metal is approximately 23° C.

In an embodiment, the lithium feed solution has a pH of 7-14.

An advantage of the present disclosure is to produce lithium metal directly from lithium hydroxide in a basic pH aqueous solution resulting in extended selective membrane life, and simplification of handling over the previously proposed acid solutions.

Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

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

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.

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

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

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

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

DETAILED DESCRIPTION

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.

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.

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.

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.

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.

Lithium can be extracted from spodumene concentrates after roasting and acid roasting operations. A concentrate with at least 6% Li₂O (approximately 75% spodumene) is suitable for roasting. Roasting is performed at about 1050° C., during which spodumene will go through a phase transformation from α-spodumene to β-spodumene. The α-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/cm³ (natural α-spodumene) to around 2.4 g/cm³ (β-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 β-spodumene to form lithium sulfate, which is soluble in water.

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.

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.

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.

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.

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.

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⁺+e⁻→Li metal  Cathode:

O→½O₂+e⁻ or Cl⁻→½Cl₂+e⁻  Anode:

2Li+2O→2Li+O₂ or 2LiCl→2Li+Cl₂  Total:

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

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⁺+e⁻→Li metal  Cathode:

O→½Ò₂+e⁻  Anode:

2Li+2O→2Li+O₂  Total:

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

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.

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.

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.

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

The cell used in Example 1 is shown schematically in FIGS. 5-6. 75 mm×50 mm×25 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.

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

The cell used in Example 2 is shown schematically in FIGS. 5-6. 75 mm×50 mm×25 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.

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.

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.

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.