WO2024259612A1 - Electrochemical deintercalation-based lithium extraction method - Google Patents

Abstract

The present disclosure provides an electrochemical deintercalation-based lithium extraction method. The method comprises the following steps: (1) injecting a salt solution into an anode chamber of an electrochemical deintercalation-based lithium extraction device, injecting salt-lake brine into a cathode chamber thereof, using a lithium-rich electrode as an anode, using a lithium-poor electrode as a cathode, applying a first voltage to carry out primary lithium extraction, and suspending the reaction when the current is lower than 0.2 mA; (2) removing the lithium-poor electrode, using the lithium-rich electrode as the cathode, using an auxiliary electrode as the anode, applying a second voltage to carry out secondary lithium extraction, and suspending the reaction when the current is lower than 0.2 mA; and (3) removing the auxiliary electrode, using the lithium-poor electrode as the cathode, repeating the steps of primary lithium extraction and secondary lithium extraction to carry out multi-stage lithium extraction until the relation is satisfied: a-b < 1%, ending the first multi-stage lithium extraction, carrying out the multi-stage lithium extraction after switching the anode and the cathode, and repeating the multi-stage lithium extraction for n times to obtain a lithium-rich solution. The method disclosed by the present disclosure can fully exert the adsorption performance of materials, reduces capacity attenuation of thereof, and avoids the problem of mismatch between capacities.

Description

A method for electrochemical deintercalation and extraction of lithium Technical Field

The present invention belongs to the technical field of lithium extraction from salt lakes, for example, a method for extracting lithium through electrochemical deintercalation.

Background Art

Lithium is the lightest metal in nature and has many special chemical properties. Therefore, lithium metal and its compounds have a wide range of uses, such as in glass, metallurgy, lubricants, refrigerants, and ceramics. With the rise of the electric vehicle industry, the demand for lithium resources has increased dramatically. Metallic lithium and its compounds are mainly found in lithium ores and salt lakes. In the early days, lithium resources were mainly extracted from lithium ores, but with the decline in the grade of lithium ores and the increase in mining costs, lithium extraction from salt lakes has gradually attracted people's attention.

The main methods of extracting lithium from salt lakes include solvent extraction, precipitation, adsorption and electrochemical methods. As an important research direction for extracting lithium from salt lakes, electrochemical deintercalation is green and pollution-free.

CN102382984A discloses a method and device for separating magnesium and lithium from salt lake brine and enriching lithium. The electrodialysis device is separated into two areas, a lithium salt chamber and a brine chamber, by an anion exchange membrane. The brine chamber is filled with salt lake brine, and the lithium salt chamber is filled with a supporting electrolyte solution that does not contain Mg ²⁺ ; a conductive substrate coated with an ion sieve is placed in the brine chamber as a cathode; a conductive substrate coated with a lithium-intercalated ion sieve is placed in the lithium salt chamber as an anode; under the drive of an external potential, the Li ⁺ in the brine in the brine chamber is embedded in the ion sieve to form a lithium-intercalated ion sieve, and the lithium-intercalated ion sieve in the lithium salt chamber releases Li ⁺ into the conductive solution and then returns to an ion sieve; the post-lithium-intercalated liquid in the brine chamber is discharged, and salt lake brine is added again, and the electrodes of the two chambers are exchanged and placed, and the cycle operation is repeated. The separation of lithium and other ions is achieved efficiently, and a lithium-rich solution is obtained at the same time. Although in the theoretical lithium extraction process, the rates of the cathode lithium intercalation reaction and the anode lithium delithiation reaction are the same, the capacities of the anode and cathode are matched. However, in actual application, the brine has high viscosity and low lithium ion concentration but high impurity ion concentration, which affects the lithium insertion reaction of the cathode and leads to mismatch in the capacity of the anode and cathode. Swapping the anodes will further increase the capacity mismatch.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

The purpose of the present disclosure is to provide a method for electrochemical deintercalation and extraction of lithium, which can give full play to the adsorption performance of the material, reduce its capacity decay, and avoid the problem of capacity mismatch.

In order to achieve the purpose of this disclosure, the present disclosure adopts the following technical solutions:

In a first aspect, the present disclosure provides a method for electrochemical deintercalation and extraction of lithium, the method comprising the following steps:

(1) injecting a salt solution into the anode chamber of the electrochemical deintercalation and lithium extraction device, injecting salt lake brine into the cathode chamber, using the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, applying a first voltage to perform one-step lithium extraction, and suspending the reaction when the current of the one-step lithium extraction reaction is lower than 0.2 mA;

(2) removing the lithium-poor electrode, using the lithium-rich electrode of step (1) as the cathode and the auxiliary electrode as the anode, applying a second voltage to perform a two-step lithium extraction, and suspending the reaction when the current of the two-step lithium extraction reaction is lower than 0.2 mA;

(3) removing the auxiliary electrode, using the lithium-poor electrode described in step (2) as the cathode, repeating the steps of one-step lithium extraction and two-step lithium extraction to perform multi-stage lithium extraction until |a-b|<1%, ending the first multi-stage lithium extraction, switching the anode and cathode and performing multi-stage lithium extraction again, repeating the multi-stage lithium extraction n times, and obtaining a lithium-rich solution, wherein a is the endpoint current value of the one-step lithium extraction, and b is the initial current value of the next stage of one-step lithium extraction.

The disclosed embodiment divides the lithium extraction process into multiple stages. After the first stage of the lithium extraction process, the anode that has been completely de-lithiated is processed to convert the anode into a cathode, and an auxiliary electrode is connected to the anode, so that the anode in the first stage of the lithium extraction process is used as a cathode in the lithium-rich solution to perform a second-step lithium extraction reaction, so that it is converted from a lithium-rich state to a lithium-poor state again, and then the second stage of the lithium extraction reaction is performed, which can ensure that the anode and cathode capacities of the multi-stage lithium extraction process are matched. The lithium-rich electrode adsorbs again after de-intercalation, and after the adsorption is completed, the solution can be replaced with pure Deintercalation of the lithium-rich solution can improve the purity and concentration of the lithium-rich solution and reduce the subsequent impurity removal and concentration steps.

In one embodiment, the cathode chamber and the anode chamber in step (1) are vertically divided by an anion exchange membrane.

In one embodiment, the lithium-rich electrode includes a conductive substrate coated with a lithium-rich active material.

In one embodiment, the lithium-deficient electrode includes a conductive substrate coated with a lithium-deficient active material.

The lithium-poor electrode is prepared by the following method:

The lithium-rich electrode is connected to the positive electrode, the AgCl electrode is connected to the negative electrode, and placed in a salt solution for constant voltage reaction. The reaction is stopped when the current decreases to 0.1 mA, and the lithium-rich active material is converted into lithium-poor active material to obtain the lithium-poor electrode.

In one embodiment, the lithium-rich active material includes any one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium titanate or lithium manganate, or a combination of at least two thereof.

In one embodiment, the conductive substrate includes any one of aluminum foil, titanium sheet, carbon paper, carbon cloth or titanium mesh, or a combination of at least two thereof.

In one embodiment, the salt solution in step (1) includes any one of sodium sulfate, potassium sulfate, lithium sulfate, sodium chloride, potassium chloride or lithium chloride, or a combination of at least two thereof.

In one embodiment, the concentration of the salt solution in step (1) is 0.2-1 mol/L, for example, 0.2 mol/L, 0.4 mol/L, 0.6 mol/L, 0.8 mol/L or 1 mol/L.

In one embodiment, in step (1), the first voltage is 0.2-1.5V, for example, 0.2V, 0.5V, 1V, 1.2V or 1.5V.

In one embodiment, the auxiliary electrode in step (2) comprises any one of graphite rod, platinum sheet, titanium sheet, titanium mesh, carbon cloth or carbon paper, or a combination of at least two thereof.

In one embodiment, the auxiliary electrode is placed in the anode chamber or the cathode chamber.

In one embodiment, in step (2), the second voltage is 0.2-2V, for example, 0.2V, 0.8V, 1V or 2V.

In one embodiment, in step (2), n is 2 to 5, for example, 2, 3, 4 or 5.

As an optional solution of the embodiment of the present disclosure, the method includes the following steps:

(1) A lithium-rich electrode is used as an anode and a lithium-poor electrode is used as a cathode. An anion exchange membrane is used to vertically divide the electrolytic cell into a cathode chamber and an anode chamber. A 0.2-1 mol/L salt solution is injected into the anode chamber, and salt lake brine is injected into the cathode chamber. A voltage of 0.2-1.5 V is applied to perform a one-step lithium extraction reaction. The reaction is stopped when the current of the one-step lithium extraction reaction is lower than 0.2 mA.

(2) removing the lithium-poor electrode that has not completely absorbed lithium, using the lithium-rich electrode described in step (1) as the cathode and the auxiliary electrode as the anode, applying a voltage of 0.2 to 2 V to perform a two-step lithium extraction reaction, and pausing the reaction when the current of the two-step lithium extraction reaction is lower than 0.2 mA;

(3) removing the auxiliary electrode, using the lithium-poor electrode described in step (2) as the cathode, repeating the steps of one-step lithium extraction and two-step lithium extraction to perform multi-stage lithium extraction until |a-b|<1%, ending the first multi-stage lithium extraction, switching the anode and cathode and performing multi-stage lithium extraction again, repeating the multi-stage lithium extraction 2 to 5 times to obtain a lithium-rich solution, wherein a is the endpoint current value of the one-step lithium extraction, and b is the initial current value of the next stage of one-step lithium extraction.

Compared with the related art, the present disclosure has the following beneficial effects:

(1) The present invention uses an auxiliary electrode to assist the lithium-rich electrode in re-adsorbing after deintercalation. If the auxiliary electrode is placed on the brine side, a higher voltage can be applied to quickly extract lithium due to the low impurities in the lithium-rich solution, thereby accelerating the recovery of the lithium-deintercalated electrode's delithiation capacity.

(2) The lithium-rich electrode disclosed in the present invention adsorbs again after deintercalation. After the adsorption is completed, the solution can be replaced with a pure lithium-rich solution for deintercalation, which can improve the purity and concentration of the lithium-rich solution and reduce the subsequent impurity removal and concentration steps.

(3) The concentration of lithium ions in the lithium-rich solution obtained by the lithium extraction method disclosed in the present invention can reach 11.26 mol/L above.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

Figure 1 is a schematic diagram of the process flow of the electrochemical deintercalation and lithium extraction scheme described in Example 1 of the present disclosure, 1-lithium-poor electrode (cathode), 2-lithium-rich electrode (anode), 3-auxiliary electrode (anode), 4-lithium-rich electrode (cathode) in the previous lithium extraction process.

Figure 2 is a schematic diagram of the process flow of the electrochemical deintercalation and lithium extraction scheme described in Example 2 of the present disclosure, 1-lithium-poor electrode (cathode), 2-lithium-rich electrode (anode), 3-auxiliary electrode (anode), 4-lithium-rich electrode (cathode) in the previous lithium extraction process.

FIG3 is a schematic diagram of the process flow of the electrochemical deintercalation and extraction of lithium described in the present disclosure.

DETAILED DESCRIPTION

The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

Example 1

This embodiment provides a method for electrochemical deintercalation and extraction of lithium, the flow diagram of the method is shown in FIG1 , and the method comprises the following steps:

(1) An electrochemical deintercalation and lithium extraction device is used, and an anion exchange membrane is used to vertically divide the electrolytic cell into a cathode chamber and an anode chamber. A sodium chloride salt solution with a cation concentration of 0.2 mol/L is added to the anode chamber, and salt lake brine is added to the cathode chamber. Aluminum foil coated with lithium-rich lithium iron phosphate is used as the anode, and aluminum foil coated with The aluminum foil of lithium-poor lithium iron phosphate is used as the cathode, and a constant voltage power supply of 0.7V is connected to carry out the lithium extraction reaction. The reaction is stopped when the current is lower than 0.2mA.

(2) removing the lithium-poor electrode that has not completely absorbed lithium, using the graphite rod auxiliary electrode as the anode and the lithium-rich electrode in step (1) as the cathode to perform electrochemical lithium extraction, wherein the lithium-rich electrode in step (1) is converted into a lithium-poor electrode in step (1), and thus can re-absorb lithium when used as a cathode to be converted into a lithium-rich electrode, the auxiliary electrode can be placed in the anode chamber, connected to a constant voltage power supply of 0.7 V, and perform a lithium extraction reaction, and the reaction is suspended when the current is lower than 0.2 mA;

(3) Remove the auxiliary electrode, use the lithium-poor electrode that has not completely absorbed lithium in step (2) as the cathode, repeat the steps of the one-step lithium extraction reaction and the two-step lithium extraction reaction, until the difference between the initial current value after the two-step lithium extraction treatment and the end current value before the treatment is less than 0.5% of the end current value before the treatment, do not repeat the auxiliary electrode treatment step, end the first multi-stage lithium extraction process, switch the cathode and cathode and perform multi-stage lithium extraction again, repeat the multi-stage lithium extraction 3 times, and obtain a lithium-rich solution. The schematic diagram of the electrochemical deintercalation and lithium extraction process is shown in Figure 3.

Example 2

This embodiment provides a method for electrochemical lithium extraction, the flow diagram of which is shown in FIG2 , and the method comprises the following steps:

(1) using an electrochemical deintercalation and lithium extraction device, using an anion exchange membrane to vertically divide the electrolytic cell into a cathode chamber and an anode chamber, adding a sodium chloride salt solution in the anode chamber, the cation concentration of the solution is 0.2 mol/L, adding salt lake brine in the cathode chamber, using an aluminum foil coated with lithium-rich lithium iron phosphate as the anode, and using an aluminum foil coated with lithium-poor lithium iron phosphate as the cathode, connecting a 0.7V constant voltage power supply, and performing a lithium extraction reaction, and suspending the reaction when the current is lower than 0.2 mA;

(2) removing the lithium-poor electrode that has not completely absorbed lithium, using the graphite rod auxiliary electrode as the anode and the lithium-rich electrode in step (1) as the cathode to perform electrochemical lithium extraction, wherein the lithium-rich electrode in step (1) is The cathode chamber is transformed into a lithium-poor electrode, so it can re-adsorb lithium and transform into a lithium-rich electrode when used as a cathode. The auxiliary electrode can be placed in the cathode chamber and connected to a 2V constant voltage power supply to perform a lithium extraction reaction. The reaction is suspended when the current is lower than 0.2mA.

(3) removing the auxiliary electrode, using the lithium-poor electrode that has not completely absorbed lithium in step (2) as the cathode, repeating the one-step lithium extraction reaction and the two-step lithium extraction reaction until the difference between the initial current value after the two-step lithium extraction treatment and the end-point current value before the treatment is less than 0.5% of the end-point current value before the treatment, and not repeating the auxiliary electrode treatment step, terminating the first multi-stage lithium extraction process, switching the anode and cathode and performing multi-stage lithium extraction again, repeating the multi-stage lithium extraction three times, and obtaining a lithium-rich solution.

Example 3

The only difference between this embodiment and embodiment 1 is that the voltage of the one-step lithium extraction reaction is 1.8 V, and the other conditions and parameters are exactly the same as those in embodiment 1.

Example 4

The only difference between this embodiment and embodiment 1 is that the voltage of the two-step lithium extraction reaction is 2.5V, and the other conditions and parameters are exactly the same as those in embodiment 1.

Comparative Example 1

The only difference between this comparative example and Example 1 is that no auxiliary electrode is provided, and only a simple exchange of the positive and negative electrodes is performed. Other conditions and parameters are exactly the same as those in Example 1.

Performance Testing:

The test results of lithium ion concentration in the lithium-rich solution obtained in the embodiment and the comparative example are shown in Table 1:

Table 1

As can be seen from Table 1, from Examples 1-2, the concentration of lithium ions in the lithium-rich solution obtained by the lithium extraction method disclosed in the present invention can reach more than 11.26 mol/L. An auxiliary electrode is used to assist the lithium-rich electrode in re-adsorbing after deintercalation. If the auxiliary electrode is placed on the brine side, since the lithium-rich solution has fewer impurities, a higher voltage can be applied to quickly extract lithium, thereby accelerating the recovery of the lithium-depleted electrode's delithiation capacity. At the same time, a side reaction of chlorine gas generation will occur on the auxiliary electrode side. Chlorine gas can oxidize organic matter in the brine, reduce the viscosity of the brine, and the bubbles generated when chlorine gas is generated can stir the brine, making the solution components more evenly dispersed, thereby ultimately improving the lithium extraction efficiency of the next stage.

By comparing Example 1 and Example 3, it can be seen that in the process of electrochemical deintercalation and lithium extraction described in the present invention, the voltage of the one-step lithium extraction will affect the lithium extraction effect. The voltage of the one-step lithium extraction is controlled at 0.2-1.5V, and the lithium extraction effect is better. If the voltage of the one-step lithium extraction is too high, side reactions are likely to occur to produce chlorine gas, which reduces the lithium extraction efficiency. In addition, too high a voltage will also cause impurity ions to enter the lithium ion sieve, affecting the purity of the lithium-rich solution.

By comparing Example 1 and Example 4, it can be seen that in the process of electrochemical deintercalation and lithium extraction described in the present invention, the voltage of the two-step lithium extraction will affect the lithium extraction effect. The voltage of the two-step lithium extraction is controlled at 0.2-2V, and the lithium extraction effect is better. Properly increasing the voltage can increase the lithium extraction speed. If the voltage of the two-step lithium extraction is too high, it may cause the cycle life of the lithium ion sieve to be reduced.

By comparing Example 1 with Comparative Example 1, it can be seen that the present disclosure treats the anode that has been completely de-lithiated after a process is completed, converts the anode into a cathode, and connects an auxiliary electrode to the anode, so that the anode is completely de-lithiated after a process is completed. The anode in the process acts as a cathode in the lithium-rich solution to extract lithium, so that it changes from a lithium-rich state to a lithium-poor state again. At the same time, a side reaction of chlorine generation occurs on the auxiliary electrode side. Chlorine can oxidize organic matter in the brine, reduce the viscosity of the brine, and the bubbles generated when chlorine is generated can stir the brine, making the solution components more evenly dispersed, and ultimately improving the efficiency of lithium extraction in the next stage. Then, the second lithium extraction reaction is carried out, which can ensure the matching of the cathode and anode capacity in the multi-stage lithium extraction process. Give full play to the adsorption performance of the material and reduce the problem of capacity decay.

Claims (13)

A method for electrochemical deintercalation and extraction of lithium, the method comprising the following steps: (1) injecting a salt solution into the anode chamber of the electrochemical lithium extraction device, injecting salt lake brine into the cathode chamber, using the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode to apply a first voltage to perform one-step lithium extraction, and suspending the reaction when the current of the one-step lithium extraction is lower than 0.2 mA; (2) removing the lithium-poor electrode, using the lithium-rich electrode of step (1) as a cathode and the auxiliary electrode as an anode, applying a second voltage to perform a two-step lithium extraction reaction, and suspending the reaction when the current of the two-step lithium extraction reaction is lower than 0.2 mA; (3) removing the auxiliary electrode, using the lithium-poor electrode described in step (2) as the cathode, repeating the steps of one-step lithium extraction and two-step lithium extraction to perform multi-stage lithium extraction until |a-b|<1%, ending the first multi-stage lithium extraction, switching the anode and cathode and performing multi-stage lithium extraction again, repeating the multi-stage lithium extraction n times, and obtaining a lithium-rich solution, wherein a is the endpoint current value of the one-step lithium extraction, and b is the initial current value of the next stage of one-step lithium extraction. The method according to claim 1, wherein the cathode chamber and the anode chamber in step (1) are vertically divided by an anion exchange membrane. The method according to claim 1 or 2, wherein the lithium-rich electrode comprises a conductive substrate coated with a lithium-rich active material, and the lithium-poor electrode comprises a conductive substrate coated with a lithium-poor active material. The method according to claim 2 or 3, wherein the lithium-rich active material comprises any one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium titanate or lithium manganate, or a combination of at least two thereof. The method according to claim 3, wherein the conductive substrate comprises any one of aluminum foil, titanium sheet, carbon paper, carbon cloth or titanium mesh, or a combination of at least two thereof. The method according to any one of claims 1 to 5, wherein the salt solution in step (1) comprises any one of sodium sulfate, potassium sulfate, lithium sulfate, sodium chloride, potassium chloride or lithium chloride, or a combination of at least two thereof. The method according to any one of claims 1 to 6, wherein the concentration of the salt solution in step (1) is 0.2 to 1 mol/L. The method according to any one of claims 1 to 7, wherein in step (1), the first voltage is 0.2 to 1.5 V. The method according to any one of claims 1 to 8, wherein the auxiliary electrode in step (2) comprises any one of a graphite rod, a platinum sheet, a titanium sheet, a titanium mesh, a carbon cloth or a carbon paper, or a combination of at least two thereof. The method according to any one of claims 1 to 9, wherein the auxiliary electrode is placed in the anode chamber or the cathode chamber. The method according to any one of claims 1 to 10, wherein in step (2), the second voltage is 0.2 to 2V. The method according to any one of claims 1 to 11, wherein in step (2), n is 2 to 5. The method according to any one of claims 1 to 12, wherein the method comprises the following steps: (1) A lithium-rich electrode is used as an anode and a lithium-poor electrode is used as a cathode. An anion exchange membrane is used to vertically divide the electrolytic cell into a cathode chamber and an anode chamber. A 0.2-1 mol/L salt solution is injected into the anode chamber, and salt lake brine is injected into the cathode chamber. A voltage of 0.2-1.5 V is applied to carry out a lithium extraction reaction. The reaction is stopped when the current of the lithium extraction reaction is lower than 0.2 mA. (2) removing the lithium-poor electrode that has not completely absorbed lithium, using the lithium-rich electrode described in step (1) as the cathode and the auxiliary electrode as the anode, applying a voltage of 0.2 to 2 V to perform two-step lithium extraction, and pausing the reaction when the current of the two-step lithium extraction reaction is lower than 0.2 mA; (3) removing the auxiliary electrode, using the lithium-poor electrode described in step (2) as the cathode, repeating the steps of one-step lithium extraction and two-step lithium extraction to perform multi-stage lithium extraction until |ab|<1%, ending the first multi-stage lithium extraction, switching the anode and cathode and performing multi-stage lithium extraction again, repeating the multi-stage lithium extraction 2 to 5 times to obtain a lithium-rich solution, wherein a is the endpoint current value of the one-step lithium extraction, and b is the initial current value of the next stage of one-step lithium extraction.