Salt lake lithium extraction electrode, preparation method therefor and use thereof

Abstract

A salt lake lithium extraction electrode, a preparation method therefor and the use thereof. The preparation method comprises the following steps: (1) mixing an active substance, a conductive agent, a non-aqueous binder and a water-soluble polymer having a molecular weight of 100-800 with a solvent to obtain a paste; (2) coating a current collector with the paste to obtain an electrode, and immersing the electrode in water for soaking treatment; and (3) immersing the electrode subjected to the soaking treatment into an oxidizing agent solution, carrying out an oxidation reaction, and then immersing the electrode in water to terminate the oxidation reaction, so as to obtain the salt lake lithium extraction electrode. Adding the water-soluble polymer into the paste of the salt lake lithium extraction electrode and removing the water-soluble polymer by means of soaking enable nanoscale pores to be formed in the electrode; the removal of the water-soluble polymer can increase the specific surface area of the electrode, and in addition, the nanoscale pores also increase the structural stability of the electrode.

Description

A salt lake lithium extraction electrode and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of lithium extraction from salt lakes, and relates to a salt lake lithium extraction electrode and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of 3C (consumer electronics), power batteries, and energy storage devices has significantly increased demand for lithium resources, and the price of battery-grade lithium salts has also skyrocketed. Faced with rising prices and consumer demand, the development, storage, and recycling of lithium resources have become crucial support for the development of the new energy industry. Lithium ore, the primary source of lithium resources, is typically obtained through ore smelting. However, lithium extraction from salt lakes offers significant cost advantages over ore extraction and is gradually becoming the mainstream development direction. The technical solution for lithium extraction from salt lakes is a coupled multi-process design, including extraction, evaporation and crystallization, chemical precipitation, and adsorption. By integrating process design with traditional processes to develop more efficient salt lake lithium extraction processes, companies can reduce costs and increase efficiency, achieve green resource development, and reduce energy consumption and environmental pollution.

[0003] The electrochemical deintercalation and lithium extraction process can realize multi-scenario, low-energy, and pollution-free lithium resource mining. Coupling it with the lithium extraction process can effectively improve efficiency and reduce material consumption in subsequent processes. Driven by electric current, the electrochemical deintercalation plate selectively extracts lithium ions from the brine through the internal active substance. However, the traditional plate preparation method results in a low specific surface area of ​​the plate, making it difficult for brine to penetrate the interior of the plate. The deintercalation of lithium ions mainly relies on the surface of the plate, which greatly reduces the deintercalation efficiency and service life of the plate. In order to achieve efficient deintercalation of active substances and lithium ions, plates with high specific surface areas can be designed and prepared to increase the reaction sites between the active substances and lithium ions in the plate, thereby promoting efficient adsorption of lithium ions by the plate.

[0004] CN116745449A discloses a method for preparing a composite electrode for lithium extraction from salt lakes. The method comprises the following steps: first preparing nitrogen-doped carbon nanotubes; then mixing nitrogen-doped carbon nanotubes of different masses with electrode active materials of the same mass to obtain electrode active materials coated with nitrogen-doped carbon nanotube layers; then modifying the nitrogen-doped carbon nanotube layers with dopamine to prepare electrode slurries, which are then applied to current collectors so that the mass of the pore-forming agent in each active coating layer away from the current collector decreases in a gradient manner, and the thickness of the modified nitrogen-doped carbon coating layer in the electrode active material of the modified nitrogen-doped carbon coating layer decreases in a gradient manner.

[0005] CN113265538A discloses a method for preparing highly conductive porous electrodes for lithium extraction from salt lakes. The method involves modifying the binder used in the electrode preparation process by blending inorganic nanoparticles with polar hydrophilic polymers to improve the binder's hydrophilicity. During the electrode slurry preparation process, an inorganic salt pore-forming agent is added to form pores of varying sizes during drying, improving mass transfer within the electrode plate.

[0006] The above scheme uses pore-forming agents to control the specific surface area of ​​the plates, creating pores within the plates through gas generation or immersion desalination. However, the gases produced by salt decomposition gradually coalesce into larger gas cavities, causing bulging or cracking of the plates. Immersion desalination also creates pores with the same diameter as the salt particles. The uneven dispersion of salts results in larger pores within the plates and poor internal pore connectivity, leading to poor structural stability.

[0007] Summary of the Invention

[0008] 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.

[0009] The present invention aims to provide a salt lake lithium extraction electrode, its preparation method, and its application. A water-soluble polymer is added to the slurry of the salt lake lithium extraction electrode. After the electrode plate is formed, the water-soluble polymer is removed by soaking. Nanoscale pores are formed in situ within the polymer within the electrode plate. The removal of a large amount of water-soluble polymer increases the specific surface area within the electrode plate, increasing the contact area between the solution and the electrode plate. The presence of a large number of nanoscale pores also enhances the structural stability of the electrode plate.

[0010] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for preparing a lithium-extracted electrode from a salt lake, the method comprising the following steps:

[0012] (1) mixing an active material, a conductive agent, a non-aqueous binder, and a water-soluble polymer with a solvent to obtain a slurry;

[0013] (2) coating the slurry on a current collector to obtain an electrode, and immersing the electrode in water for immersion treatment;

[0014] (3) immersing the soaked electrode in an oxidant solution to carry out an oxidation reaction, and then immersing the electrode in water to terminate the oxidation reaction, thereby obtaining the salt lake lithium extraction electrode;

[0015] The molecular weight of the water-soluble polymer is 100-800.

[0016] The present invention discloses a method of adding a water-soluble polymer of suitable molecular weight to the slurry for preparing lithium electrodes extracted from salt lakes, and then removing the water-soluble polymer by soaking. The water-soluble polymer is easier to dissolve and disperse in the slurry during the preparation of the slurry, and can more evenly form pores inside the electrode plate. When the water-soluble polymer is dispersed inside the electrode plate, local microscopic regions agglomerate, but some of the micropores formed by the agglomeration are still nanoscale pores, which is conducive to ensuring the structural stability of the electrode plate. Some of the undissolved polymer inside the electrode plate can improve the hydrophilicity of the electrode plate and promote the penetration of brine into the electrode plate.

[0017] In one embodiment, the active material in step (1) includes lithium iron phosphate and / or lithium manganate.

[0018] The active material disclosed herein may include waste lithium iron phosphate, and the waste lithium iron phosphate should maintain a good olivine structure to facilitate stable insertion and extraction of lithium ions.

[0019] In one embodiment, the conductive agent includes any one of carbon black, KS-6, Ketjen black, carbon nanotubes, or acetylene black, or a combination of at least two thereof.

[0020] In one embodiment, the non-aqueous binder includes any one of polyvinylidene fluoride, polyvinyl chloride, polystyrene-butadiene rubber, polynitrile-butadiene rubber, or polydimethylsiloxane, or a combination of at least two thereof.

[0021] The non-water-washable binder disclosed in the present invention has good electrochemical stability and can adhere to active substances well.

[0022] In one embodiment, in the slurry, the mass of the non-aqueous binder accounts for 5-15% of the total solid mass, for example, 5%, 8%, 10%, 12% or 15%.

[0023] In one embodiment, the solvent includes but is not limited to any one or a combination of at least two of N-methylpyrrolidone (NMP), DMSO, DMF, dimethylacetamide and isopropyl alcohol.

[0024] In one embodiment, the water-soluble polymer in step (1) includes but is not limited to any one of polyvinyl alcohol, ethylene glycol polymer, polyvinyl pyrrolidone or polyacrylamide, or a combination of at least two thereof.

[0025] In one embodiment, in the slurry, the mass of the water-soluble polymer accounts for 5-30% of the total solid mass, for example, 5%, 10%, 15%, 20% or 30%, etc., and can be optionally 8-20%.

[0026] The water-soluble polymers disclosed herein should be soluble in NMP and can be removed by soaking in water.

[0027] In one embodiment, the material of the current collector in step (2) includes any one or a combination of at least two of titanium, titanium alloy, graphene, conductive carbon fiber cloth, nickel alloy or stainless steel.

[0028] In one embodiment, the thickness of the current collector is 1 to 5 mm, for example, 1 mm, 2 mm, 3 mm, 4 mm or 5 mm.

[0029] In one embodiment, the coating in step (2) is followed by drying.

[0030] In one embodiment, the drying process is performed by increasing the temperature using a gradient temperature increase method.

[0031] In one embodiment, the gradient temperature increase is to increase the temperature at a rate of 20°C / 6h from an initial temperature of 55°C until the electrode is completely dried.

[0032] The drying process disclosed herein uses a gradient temperature rise mode to remove the solvent, and the plate solvent is removed in a gradient manner through temperature control to reduce cracking of the plate.

[0033] In one embodiment, the soaking treatment time in step (2) is 8 to 96 hours, for example: 8 hours, 10 hours, 50 hours, 84 hours or 96 hours.

[0034] In one embodiment, the oxidant solution in step (3) comprises any one of hydrogen peroxide, potassium persulfate solution, sodium hypochlorite solution or sodium chlorate solution, or a combination of at least two thereof.

[0035] In one embodiment, the mass concentration of the oxidant solution is 0.1-5%, for example, 0.1%, 1%, 2%, 4% or 5%, etc., and can be optionally 0.25-2%.

[0036] In one embodiment, the temperature of the oxidation reaction is 20-60°C, for example, 20°C, 30°C, 40°C, 50°C or 60°C.

[0037] In one embodiment, the oxidation reaction time is 0.5 to 6 hours, for example, 0.5 hours, 0.8 hours, 1 hour, 2 hours or 6 hours.

[0038] In a second aspect, the present disclosure provides a salt lake lithium extraction electrode, which is prepared by the method described in the first aspect.

[0039] In a third aspect, the present disclosure provides a method for extracting lithium from a salt lake, wherein the method uses the salt lake lithium extraction electrode polarity as described in the second aspect to extract lithium.

[0040] Compared with the prior art, the present disclosure has the following beneficial effects:

[0041] (1) The method disclosed herein utilizes the space occupancy effect and water solubility of water-soluble polymers to prepare nano-scale pores in situ in the water-soluble polymers in the electrode plate. On the one hand, the size effect of polymer chain segment clusters is utilized to prepare cluster-sized pores inside the electrode plate, thereby ensuring structural stability while increasing the specific surface area of ​​the electrode plate. On the other hand, the unleached water-soluble polymer inside the electrode plate will also enhance the water solubility of the electrode plate and promote the infiltration of brine into the electrode plate. In addition, the polymer is easier to disperse in the slurry, making the pore distribution inside the electrode plate more uniform and improving the pore connectivity.

[0042] (2) The initial specific capacity of the salt lake lithium extraction electrode prepared by the method disclosed in the present invention can reach more than 67.34 mAh / g, and the specific capacity can reach more than 66.28 mAh / g after 60 cycles, and the capacity retention rate can reach more than 98.42%, which proves that the method disclosed in the present invention can effectively improve the performance and stability of the electrode plate.

[0043] Still other aspects will become apparent upon reading and understanding the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this 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.

[0045] FIG1 is a SEM image of the salt lake lithium extraction electrode prepared in Example 1. DETAILED DESCRIPTION

[0046] 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 used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0047] Example 1

[0048] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0049] (1) Polyvinylidene fluoride (PVDF) and PVA600 were fully dissolved in NMP to prepare a polymer solution, and lithium iron phosphate and carbon black were added to the polymer solution and stirred thoroughly to prepare a slurry. Lithium iron phosphate, polyvinylidene fluoride, PVA600 and carbon black were weighed in a mass ratio of 74:10:8:8;

[0050] (2) The slurry is scraped onto a porous titanium mesh to form a 1 mm electrode. The electrode is then heated in a gradient oven, first drying at 65°C for 6 h, and then the temperature is increased by 20°C every 6 h until the electrode is completely dried. The electrode is then immersed in water and allowed to stand for 60 h to leach out the residual salts, water-soluble polymers, and NMP inside the electrode, thereby obtaining an electrode with high porosity.

[0051] (3) Soaking the electrode in a 1% potassium persulfate aqueous solution at 40° C. for 2 h to obtain the salt lake lithium extraction electrode.

[0052] The SEM image of the salt lake lithium extraction electrode is shown in Figure 1.

[0053] Example 2

[0054] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0055] (1) Polydimethylsiloxane and PVP600 were fully dissolved in isopropyl alcohol to prepare a polymer solution, and lithium iron phosphate and carbon black were added to the polymer solution and stirred thoroughly to prepare a slurry. Lithium iron phosphate, polydimethylsiloxane, PVP600 and carbon black were weighed in a mass ratio of 74:5:10:11;

[0056] (2) The slurry was scraped onto a porous titanium mesh to form a 1 mm electrode. The electrode was then heated in a gradient oven, first at 65 °C for 6 h, and then the temperature was increased by 20 °C every 6 h until the electrode was completely dried. The electrode was then immersed in water and allowed to stand for 60 h to leach out the water-soluble polymer and isopropyl alcohol inside the electrode, thereby obtaining an electrode with high porosity.

[0057] (3) Soaking the electrode in a 0.25% hydrogen peroxide aqueous solution at 50° C. for 1 hour to obtain the salt lake lithium extraction electrode.

[0058] Example 3

[0059] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0060] (1) Polydimethylsiloxane and PAM800 were fully dissolved in isopropyl alcohol to prepare a polymer solution, and lithium iron phosphate and carbon nanotubes were added to the polymer solution and stirred thoroughly to prepare a slurry. Lithium iron phosphate, polydimethylsiloxane, PAM800 and carbon nanotubes were weighed in a mass ratio of 70:5:20:5;

[0061] (2) The slurry is scraped onto a porous titanium mesh to form a 1 mm electrode. The electrode is then heated in a gradient oven, first drying at 65°C for 6 h, and then the temperature is increased by 20°C every 6 h until the electrode is completely dried. The electrode is then immersed in water and allowed to stand for 72 h to leach out the residual salts, water-soluble polymers, and isopropyl alcohol inside the electrode, thereby obtaining an electrode with high porosity.

[0062] (3) Soaking the electrode in a 2% sodium hypochlorite aqueous solution at 40° C. for 2 h to obtain the salt lake lithium extraction electrode.

[0063] Example 4

[0064] The only difference between this embodiment and embodiment 1 is that the mass ratio of lithium iron phosphate to PVA600 is 79:3, and other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 5

[0066] The only difference between this embodiment and embodiment 1 is that the mass ratio of lithium iron phosphate to PVA600 is 52:30, and other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Example 6

[0068] The only difference between this embodiment and embodiment 1 is that the concentration of the potassium persulfate solution is 0.1%, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0069] Example 7

[0070] The only difference between this embodiment and embodiment 1 is that the concentration of the potassium persulfate solution is 3%, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Comparative Example 1

[0072] This comparative example provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0073] (1) Polyvinylidene fluoride (PVDF) was fully dissolved in NMP to prepare a binder solution, and lithium iron phosphate, carbon black, and ammonium bicarbonate were added to the binder solution and stirred thoroughly to prepare a slurry. Lithium iron phosphate, polyvinylidene fluoride, and carbon black were weighed in a mass ratio of 74:10:16;

[0074] (2) The slurry is scraped onto a porous titanium mesh to form a 1 mm electrode, which is then heated gradually in an oven. The electrode is first dried at 65° C. for 6 h, and the temperature is increased by 20° C. every 6 h until the electrode is completely dried, thereby obtaining the salt lake lithium extraction electrode.

[0075] Comparative Example 2

[0076] The only difference between this comparative example and Example 1 is that PVA600 is replaced with PVA6000, and the other conditions and parameters are exactly the same as those in Example 1.

[0077] Performance testing:

[0078] Electrochemical deintercalation tests were performed on the salt lake lithium extraction electrodes obtained in Examples 1-7 and Comparative Examples 1-2. The test results are shown in Table 1:

[0079] Table 1

[0080] As can be seen from Table 1, from Examples 1-3, the initial specific capacity of the salt lake lithium extraction electrode prepared by the method described in the present disclosure can reach more than 67.34 mAh / g, the specific capacity can reach more than 66.28 mAh / g after 60 cycles, and the capacity retention rate can reach more than 98.42%.

[0081] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the salt lake lithium extraction electrode described in the present disclosure, the proportion of the water-soluble polymer in the slurry solid will affect its performance. When the proportion of the water-soluble polymer in the solid is controlled at 5-20%, the performance of the salt lake lithium extraction electrode obtained is better. If the proportion of the water-soluble polymer is too high, the porosity is too high, which affects the physical stability of the electrode plate, and the overall structure of the electrode plate is easily broken under water erosion. If the proportion of the water-soluble polymer is too low, the porosity of the electrode plate is low, which affects the electrochemical performance of the electrode plate.

[0082] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the salt lake lithium extraction electrode described in the present disclosure, the mass concentration of the oxidant solution affects its performance. When the mass concentration of the oxidant solution is controlled at 0.25-2%, the performance of the salt lake lithium extraction electrode is better. If the mass concentration of the oxidant solution is too high or too low, the optimal charge and discharge capacity cannot be obtained. If the mass concentration of the oxidant solution is too low, the charge and discharge capacity is low.

[0083] By comparing Example 1 and Comparative Example 1, it can be seen that the present disclosure adds a water-soluble polymer of appropriate molecular weight to the preparation slurry of the lithium electrode extracted from the salt lake, and then removes the water-soluble polymer by soaking. The water-soluble polymer is easier to dissolve and disperse in the slurry when preparing the slurry, and can form pores more evenly inside the electrode plate; when the water-soluble polymer is dispersed inside the electrode plate, considering the polarity difference with the binder, some agglomeration will occur, but the slurry viscosity is relatively large and is limited to aggregation in local microscopic areas. Even if the polymer partially agglomerates, the micropores formed are still nanoscale pores, which is beneficial to ensuring the structural stability of the electrode plate; some undissolved polymer inside the electrode plate can improve the water solubility of the electrode plate and promote the penetration of brine into the electrode plate.

[0084] From the comparison between Example 1 and Comparative Example 2, it can be seen that in the preparation process of the salt lake lithium extraction electrode described in the present disclosure, the molecular weight of the polymer used cannot be too large. If the molecular weight of the polymer is too large, the lithium extraction performance is poor and the initial lithium extraction capacity is low.

Claims

1. A method for preparing a lithium electrode from a salt lake. The following steps are involved: (1) mixing an active material, a conductive agent, a non-aqueous binder, and a water-soluble polymer with a solvent to obtain a slurry; (2) coating the slurry on a current collector to obtain an electrode, immersing the electrode in water for immersion treatment to obtain a salt lake lithium extraction electrode plate with a high specific surface area; (3) immersing the soaked electrode in an oxidant solution to carry out an oxidation reaction, and then immersing the electrode in water to terminate the oxidation reaction, thereby obtaining the salt lake lithium extraction electrode; The molecular weight of the water-soluble polymer is 100-800.

2. The preparation method according to claim 1, in, The active material in step (1) includes lithium iron phosphate and / or lithium manganese oxide.

3. The preparation method according to claim 1 or 2, in, The conductive agent includes any one of carbon black, KS-6, Ketjen black, carbon nanotubes or acetylene black, or a combination of at least two thereof.

4. The preparation method according to any one of claims 1 to 3, in, The non-aqueous binder includes any one of polyvinylidene fluoride, polyvinyl chloride, polystyrene-butadiene rubber, polynitrile-butadiene rubber or polydimethylsiloxane, or a combination of at least two thereof.

5. The preparation method according to any one of claims 1 to 4, in, In the slurry, the mass of the non-aqueous binder accounts for 5-15% of the total solid mass.

6. The preparation method according to any one of claims 1 to 5, in, The solvent includes any one of N-methylpyrrolidone, DMSO, DMF or dimethylacetamide, or a combination of at least two thereof.

7. The preparation method according to any one of claims 1 to 6, in, The water-soluble polymer in step (1) includes any one of polyvinyl alcohol, ethylene glycol polymer, polyvinyl pyrrolidone or polyacrylamide, or a combination of at least two thereof.

8. The preparation method according to any one of claims 1 to 7, in, In the slurry, the mass of the water-soluble polymer accounts for 5-30% of the total solid mass.

9. The preparation method according to claim 8, in, In the slurry, the mass of the water-soluble polymer accounts for 5-20% of the total solid mass.

10. The preparation method according to any one of claims 1 to 9, in, The material of the current collector in step (2) includes any one of titanium, titanium alloy, graphene, conductive carbon fiber cloth, nickel alloy or stainless steel, or a combination of at least two of them.

11. The preparation method according to any one of claims 1 to 10, in, The thickness of the current collector in step (2) is 1 to 5 mm.

12. The preparation method according to any one of claims 1 to 11, in, After the coating in step (2), a drying process is performed.

13. The preparation method according to claim 12, in, The drying process is performed by heating the temperature by a gradient heating method.

14. The preparation method according to claim 13, in, The gradient temperature increase is to increase the temperature at a rate of 20°C / 6h at an initial temperature of 55°C until the electrode is completely dried.

15. The preparation method according to any one of claims 1 to 14, in, The soaking time in step (2) is 8 to 96 hours.

16. The preparation method according to any one of claims 1 to 15, in, The oxidant solution in step (3) comprises any one of hydrogen peroxide, sodium persulfate solution, potassium persulfate, ammonium persulfate, sodium hypochlorite solution or sodium chlorate solution, or a combination of at least two thereof; Optionally, the mass concentration of the oxidant solution is 0.1-5%.

17. The preparation method according to claim 16, in, The mass concentration of the oxidant solution in step (3) is 0.25-2%.

18. The preparation method according to any one of claims 1 to 17, in, The temperature of the oxidation reaction in step (3) is 20 to 60° C. Optionally, the oxidation reaction time is 0.5 to 6 hours.

19. A salt lake lithium extraction electrode prepared by the method according to any one of claims 1 to 18.

20. A method for extracting lithium using the salt lake lithium extraction electrode polarity as claimed in claim 19.

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