A method for combining aluminum-air battery discharge and in-situ adsorption of discharge products to extract lithium.

Abstract

This invention relates to the field of lithium extraction technology from salt lakes, specifically to a method combining aluminum-air battery discharge and in-situ adsorption of discharge products for lithium extraction. A high magnesium-to-lithium ratio solution is used as the electrolyte in the aluminum-air battery, aluminum or aluminum alloy is used as the anode, and a catalyst layer composed of MnO2 catalyst, activated carbon, and polytetrafluoroethylene serves as the cathode. The resulting aluminum-air battery is then discharged. Lithium is adsorbed in situ using the colloid formed by the discharge products, achieving magnesium-lithium separation. Continuous operation is achieved through internal electrolyte circulation and centrifugal separation. The method provided by this invention has a short process flow, simple operation, low production cost, continuous operation, and is easy to industrialize, achieving both electrical energy generation from discharge and lithium ion enrichment in a high magnesium-to-lithium ratio solution.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from salt lakes, specifically to a method for lithium extraction that combines aluminum-air battery discharge with in-situ adsorption of discharge products. Background Technology

[0002] Compared to lithium-ion batteries, aluminum-air batteries have the advantages of abundant resources, high energy density, good safety performance, and high added value of by-products, making them a type of battery with great development potential.

[0003] With the rapid development of the new energy vehicle sector, the demand for lithium has surged, and the development of lithium extraction technology has received increasing attention. Extracting lithium from salt lake brine offers advantages such as low extraction cost, environmental friendliness, and low energy consumption. However, because magnesium and lithium ions are located diagonally on the periodic table and have very similar chemical properties, they are difficult to separate. Traditional methods for magnesium removal not only require large amounts of reagents but also result in incomplete magnesium-lithium separation, significantly increasing process costs and making it difficult to obtain lithium products that meet quality requirements. Currently, methods developed for lithium extraction from salt lake brine include precipitation, solvent extraction, calcination leaching, electrodialysis, carbonization, adsorption, and electrochemical deintercalation / intercalation. Common adsorbents used in adsorption methods include ion sieves and aluminum salt adsorption, but these currently suffer from drawbacks such as low adsorption efficiency, high solubility, and susceptibility to contamination.

[0004] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that magnesium ions and lithium ions are located on opposite sides of the periodic table and have very similar chemical properties, making them difficult to separate. Traditional methods for removing magnesium not only require large amounts of reagents but also result in incomplete magnesium-lithium separation, significantly increasing process costs and making it difficult for the obtained lithium products to meet quality requirements. This invention provides a method for lithium extraction that combines aluminum-air battery discharge with in-situ adsorption of discharge products. It utilizes the layered structure of aluminum salts in the colloidal material of aluminum-air batteries to specifically adsorb lithium ions, thereby achieving the separation of magnesium and lithium.

[0006] To achieve the above objectives, this invention discloses a method for lithium extraction from aluminum-air batteries through discharge and in-situ adsorption of discharge products, comprising the following steps:

[0007] S1, using a high magnesium-to-lithium ratio solution as the electrolyte for an aluminum-air battery, aluminum or aluminum alloy as the anode, and an air electrode containing MnO2 catalyst as the cathode.

[0008] S2, Discharge the aluminum-air battery assembled in step S1;

[0009] S3, the electrolyte of the aluminum-air battery is internally circulated, the colloid in the storage tank is collected, and it is separated by centrifugation and washed with water 2-3 times to obtain a lithium-rich solution.

[0010] In step S1, the magnesium ion / lithium ion ratio in the high magnesium-lithium ratio solution is ≥6, and the solution pH is ≤7.

[0011] The battery cathode material in step S1 includes MnO2 catalyst, activated carbon, and polytetrafluoroethylene.

[0012] In step S2, the discharge is a constant current discharge with a discharge current density of 5~20 mA / cm². 2 The discharge time is 2~48h.

[0013] In step S3, a peristaltic pump is used to maintain the internal circulation of the electrolyte during the discharge process.

[0014] In step S3, the centrifugation speed is 1000-5000 r / min, and the centrifugation time is 10-30 min.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. This invention utilizes a high magnesium-to-lithium ratio solution as the electrolyte, and aluminum and air as the positive and negative electrodes of the battery, respectively. While obtaining electrical energy, it utilizes the adsorption properties of the anode products to achieve selective adsorption of lithium ions, ultimately enriching lithium ions in the brine. It combines the functions of aluminum-air battery discharge and in-situ adsorption and lithium extraction of discharge products.

[0017] 2. The colloidal aluminum salt layered structure obtained by the method of the present invention has excellent selectivity for lithium ions, and is particularly suitable for solutions with high magnesium-to-lithium ratios, especially for solving the problem of magnesium-to-lithium separation in salt lake brines.

[0018] 3. The in-situ generated colloidal aluminum salt layered structure has high reactivity with lithium in magnesium and lithium solutions, and the adsorption capacity of lithium ions in magnesium and lithium solutions can reach 52 mg / g.

[0019] 4. It is easy to operate, can realize continuous production on site, and is easy to apply in industrial applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the apparatus used in this invention;

[0021] Figure 2 XRD phase analysis of the layered structure of aluminum salt adsorbed lithium ions obtained in Example 1;

[0022] Figure 3 The constant current discharge curve of the aluminum-air battery in Example 1 is shown. Detailed Implementation

[0023] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] An aluminum-air battery was assembled using high-purity aluminum (99.99%) as the anode and an air electrode material composed of MnO2 catalyst, activated carbon, and polytetrafluoroethylene as the cathode. An aqueous solution containing 10 g / L magnesium ions and 0.5 g / L lithium ions was added as the electrolyte (MgO). 2+ / Li + =20:1), constant current discharge, with a controlled current density of 5 mA / cm². 2 The discharge time was 2 hours; a peristaltic pump was used to ensure the internal circulation of the electrolyte during the discharge process; after discharge, the reaction colloid was collected by centrifugation at 1000 r / min for 10 min; the colloid was washed two to three times with water, and the relevant filtrate was collected to obtain a lithium-rich solution; the magnesium and lithium ion concentrations in the solution before and after the discharge reaction were analyzed using an ICP-GDS instrument; the aluminum-containing colloid was dried, weighed, and its adsorption capacity was calculated; the colloidal phase XRD analysis is as follows. Figure 1 As shown in Table 1, the changes in ion concentration before and after the reaction are shown in the table; the lithium content in the precipitate is 25 mg / g.

[0026] Table 1. Changes in ion concentration before and after the reaction in Example 1

[0027]

[0028] Example 2

[0029] The difference between this embodiment and Example 1 is the addition of an aqueous solution containing 20 g / L magnesium ions and 0.5 g / L lithium ions as the aluminum-air battery electrolyte (Mg). 2+ / Li + =40:1), and everything else was the same as in Example 1. The changes in ion concentration before and after the reaction are shown in Table 2; the lithium content in the precipitate was 20 mg / g.

[0030] Table 2 Changes in ion concentration before and after the reaction in Example 2

[0031]

[0032] Example 3

[0033] The difference between this embodiment and Example 1 is that the anode material is changed to an Al-Ga alloy with a Ga element mass fraction of 0.1%. Everything else is the same as in Example 1. The changes in ion concentration before and after the reaction are shown in Table 3. The lithium content in the precipitate is 30 mg / g.

[0034] Table 3 Changes in ion concentration before and after the reaction in Example 3

[0035]

[0036] Example 4

[0037] The difference between this embodiment and Embodiment 1 is that the constant current discharge density is set to 20 mA / cm². 2 The centrifugation parameters were changed to a centrifugation speed of 5000 r / min and a centrifugation time of 30 min. All other parameters were the same as in Example 1. The results of the changes in ion concentration before and after the reaction are shown in Table 4. The lithium content in the precipitate was 47 mg / g.

[0038] Table 4. Changes in ion concentration before and after the reaction in Example 4

[0039]

[0040] Example 5

[0041] The difference between this embodiment and Example 1 is that the constant current discharge time is set to 48 h, while all other aspects are the same as in Example 1. The changes in ion concentration before and after the reaction are shown in Table 5; the lithium content in the precipitate is 52 mg / g.

[0042] Table 5. Changes in ion concentration before and after the reaction in Example 5

[0043]

[0044] Example 6

[0045] The difference between this embodiment and Embodiment 1 is that the constant current discharge density is set to 2 mA / cm². 2 The discharge time was 24 hours, and everything else was the same as in Example 1. The changes in ion concentration before and after the reaction are shown in Table 6. The lithium content in the precipitate was 10 mg / g.

[0046] Table 6. Changes in ion concentration before and after the reaction in Example 6

[0047]

[0048] Example 7

[0049] The difference between this embodiment and Embodiment 1 is that the constant current discharge density is set to 30 mA / cm². 2 The discharge time was 24 hours, and everything else was the same as in Example 1. The changes in ion concentration before and after the reaction are shown in Table 7. The lithium content in the precipitate was 14 mg / g.

[0050] Table 7 Changes in ion concentration before and after the reaction in Example 7

[0051]

[0052] Example 8

[0053] The difference between this embodiment and Example 1 is that the pH value of the solution is controlled to reach 10 by adding NaOH dropwise. Everything else is the same as in Example 1. The results of the changes in ion concentration before and after the reaction are shown in Table 8. The lithium content in the precipitate is 40 mg / g.

[0054] Table 8 Changes in ion concentration before and after the reaction in Example 8

[0055]

[0056] The analysis results of Examples 1-5 show that the magnesium ion concentration in the solution did not change significantly before and after discharge, while the lithium ion concentration decreased significantly. The calculated colloidal lithium ion adsorption capacity was between 20-52 mg / g, indicating a significant adsorption effect and clearly achieving the purpose of magnesium-lithium ion separation (see Tables 1-5). Comparison with Example 6 shows that when the current density is set to 2 mA / cm², [the following data is missing from the original text]. 2 At this time, the formation of colloidal substances is slow, and the adsorption effect on lithium ions is not obvious, only 10 mg / g. Comparatively, in Example 7, it can be seen that when the current density is set to 30 mA / cm², the adsorption effect is significantly reduced. 2 At the same time, the adsorption effect on lithium ions was not significant (14 mg / g), which may be related to the structure of the colloidal phase formed. Comparatively, in Example 8, setting the electrolyte to an alkaline solution (pH=10) resulted in better lithium ion adsorption (40 mg / g), but poor magnesium ion separation, meaning magnesium ions were co-precipitated with the colloidal substances. The above analysis shows that only when the current density is set between 5-20 mA / cm²... 2 Within the specified range, and ensuring that the electrolyte solution pH is ≤7, the present invention exhibits good adsorption and separation of lithium ions.

[0057] Figure 2 The XRD phase analysis of the dried colloid in Example 1 is shown, which conforms to the diffraction peaks of the layered structure of LiAl2(OH)6Cl phase. The above characterization results explain the single adsorption effect of the aluminum salt colloid of the present invention on lithium ions.

[0058] Figure 3 The figure shows the discharge behavior of the aluminum-air battery in Example 1. It can be seen that the aluminum-air battery obtained in Example 1 can discharge normally according to the set current density and obtain electrical energy.

[0059] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for combining aluminum-air battery discharge and in-situ adsorption of discharge products for lithium extraction, characterized in that, Includes the following steps: S1, using a high magnesium-to-lithium ratio solution as the electrolyte for an aluminum-air battery, pure aluminum or aluminum alloy as the battery anode, and air electrode as the battery cathode. S2, Discharge the aluminum-air battery assembled in step S1; S3, the electrolyte of the aluminum-air battery is internally circulated, the colloid in the storage tank is collected, and it is separated by centrifugation and washed with water 2-3 times to obtain a lithium-rich solution; In step S1, the mass concentration ratio of magnesium ions to lithium ions in the high magnesium-to-lithium ratio solution is ≥6, and the solution pH is ≤7. In step S3, a peristaltic pump is used to maintain the internal circulation of the electrolyte during the discharge process.

2. The method for combining aluminum-air battery discharge and in-situ adsorption of discharge products for lithium extraction as described in claim 1, characterized in that, The cathode material in step S1 is an air electrode material containing a MnO2 catalyst.

3. The method for combining aluminum-air battery discharge and in-situ adsorption of discharge products for lithium extraction as described in claim 1, characterized in that, In step S2, the discharge is a constant current discharge with a discharge current density of 5~20 mA / cm². 2 The discharge time is 2~48h.

4. The method for combining aluminum-air battery discharge and in-situ adsorption of discharge products for lithium extraction as described in claim 1, characterized in that, In step S3, the centrifugation speed is 1000-5000 r / min, and the centrifugation time is 10-30 min.

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