Salt lake lithium extraction electrode and preparation method and application thereof

Abstract

The invention provides a salt lake lithium extraction electrode and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing an active substance, a conductive agent, a binder and a solvent to obtain slurry, and coating a current collector with the slurry to obtain an electrode; (2) immersing the electrode into a non-solvent, curing, and then carrying out soaking treatment; and (3) carrying out oxidation treatment on the soaked electrode to obtain the salt lake lithium extraction electrode. The solvent and the non-solvent are mutually soluble in any proportion, and the interaction parameter of the non-solvent and the binder is gt; and 0.5. Uniform pores can be formed in the polar plate by adopting non-solvent pore forming, the connectivity between the pores is higher, the specific surface area of the polar plate is larger, a drying step is not needed, the technological process can be simplified, the workload can be reduced, meanwhile, cracks on the surface of the polar plate can be reduced, and the strength and the use durability of the polar plate can be improved.

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] As a key component of high-energy batteries, efficient acquisition and a stable supply of lithium resources are paramount to the development of the new energy industry. Currently, extracting lithium from salt lakes offers inherent cost advantages. However, significant variations in operating conditions across salt lakes globally limit their efficient development. Researchers are developing lithium extraction technologies tailored to the complex and changing conditions of these lakes.

[0003] Electrochemical deintercalation is a direct lithium extraction method. It utilizes active materials to selectively intercalate lithium ions under current-driven conditions. However, active materials typically cannot exist independently and must be attached to a binder to form a deintercalated plate. The preparation of deintercalated plates makes this method more promising for industrial application. However, compared to powders, the plates have significantly fewer reaction sites for lithium deintercalation, necessitating the design of a more porous plate structure to achieve efficient lithium ion deintercalation.

[0004] The prior art 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 mixture with dopamine to prepare electrode slurries, which are then applied to a current collector so that the mass of the pore-forming agent in each active coating layer away from the current collector decreases gradually, 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 gradually.

[0005] Prior art discloses a method for preparing highly conductive porous electrodes for lithium extraction from salt lakes. This involves modifying the binder used in the electrode preparation process by blending inorganic nanoparticles with polar hydrophilic polymers to increase 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, enhancing mass transfer within the electrode plate.

[0006] The electrode plates produced by the above scheme have uneven porosity and severe surface cracking. This not only fails to effectively improve the efficient mass transfer of brine, but also damages the structural strength of the plates, affecting long-term industrial application. Therefore, it is urgent to develop a plate structure with high porosity, uniform pores, and sufficient strength. A high-porosity plate structure can effectively break down concentration polarization, establish efficient mass transfer channels for brine, promote efficient mass transfer of brine within the plate, and achieve rapid lithium ion insertion and extraction.

[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 purpose of the present disclosure is to provide a salt lake lithium extraction electrode and its preparation method and application. The present disclosure adopts non-solvent pore formation to form uniform pores inside the electrode plate, the connectivity between the pores is stronger, the specific surface area of ​​the electrode plate is larger, and there is no need to introduce a drying step, which can simplify the process flow and reduce the workload. At the same time, it can reduce cracks on the surface of the electrode plate and improve the strength and durability 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 binder, and a solvent to obtain a slurry, and coating the slurry on a current collector to obtain an electrode;

[0013] (2) immersing the electrode in a non-solvent and performing an immersion treatment after solidification;

[0014] (3) performing oxidation treatment on the electrode that has been soaked to obtain the salt lake lithium extraction electrode;

[0015] The solvent and the non-solvent are miscible in any proportion, and the interaction parameter between the non-solvent and the binder is greater than 0.5.

[0016] The interaction parameter of the non-solvent and binder disclosed herein is a parameter that represents the change in interaction energy when the binder and non-solvent are mixed. It is represented by X, where the larger X is, the worse the solubility of the binder in the non-solvent is.

[0017] The present invention immerses the electrode coated with slurry into a non-solvent, and constructs a porous structure inside the electrode plate by exchanging the solvent and the non-solvent. Utilizing the uniform mass transfer of the non-solvent, a large number of continuous microscopic pores are constructed inside the electrode, effectively increasing the specific surface area of ​​the electrode plate and increasing the reaction sites between the active substance and the brine. During the preparation of the salt lake lithium extraction electrode, when the solvent and the non-solvent are exchanged, the solvent diffuses and dissolves into the non-solvent, and the non-solvent replaces the solvent to form pores. The interaction parameter between the binder and the non-solvent is large, and the solubility is poor. The electrode plate will not collapse due to the loss of solvent, which is more conducive to structural stability.

[0018] In one embodiment, the active material in step (1) includes lithium iron phosphate.

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

[0020] In one embodiment, the binder includes any one of polyamide, polyimide, polyvinylidene fluoride, or polydimethylsiloxane, or a combination of at least two thereof.

[0021] The present invention selects a suitable binder to prepare the electrode slurry, which is then immersed in a non-solvent after coating. The solvent and the binder have good compatibility. When the non-solvent is replaced, the formed structure is good, the structural porosity is high, and the overall strength of the plate is high.

[0022] In one embodiment, in the slurry, the mass of the 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 any one or a combination of at least two of N-methylpyrrolidone, isooctane dimethyl sulfoxide, or tetrahydrofuran.

[0024] The present invention selects a suitable solvent that can be replaced by a non-solvent, and the mass of the binder is controlled at 5-15% of the total solid mass. The appropriate amount of binder can maintain the structural stability of the electrode and avoid collapse during the process of solvent replacement without affecting the performance of the electrode.

[0025] In one embodiment, the coating thickness in step (1) is 1 to 9 mm, for example, 1 mm, 2 mm, 4 mm, 6 mm or 9 mm.

[0026] The present disclosure can ensure the structural stability of the pole piece by controlling the thickness of the coating, thereby preventing the collapse of the pole piece during the process of the solvent being replaced by the non-solvent.

[0027] In one embodiment, the material of the current collector in step (1) includes any one of titanium, titanium alloy, nickel alloy or stainless steel, or a combination of at least two thereof.

[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 non-solvent in step (2) is a liquid that is miscible with the solvent in any proportion and cannot dissolve the binder.

[0030] In one embodiment, the non-solvent includes any one of water, methanol or ethanol, or a combination of at least two thereof.

[0031] The present disclosure selects a suitable non-solvent to ensure that the binder is not replaced during the process of replacing the solvent, thereby ensuring the structural stability of the electrode and achieving the purpose of pore formation.

[0032] In one embodiment, the immersion time in the non-solvent in step (2) is 6 to 12 hours, for example, 6 hours, 7 hours, 8 hours, 10 hours or 12 hours.

[0033] During the preparation process of the salt lake lithium extraction electrode disclosed in the present invention, the soaking time in the non-solvent before solidification will affect its performance. By controlling the soaking time in the non-solvent before solidification to 6 to 12 hours, the performance of the salt lake lithium extraction electrode is better. If the soaking time is too short, the performance of the electrode will not be significantly improved. If the soaking time is too long, the stability of the electrode structure is poor.

[0034] In one embodiment, the oxidation treatment in step (3) comprises immersing the electrode in an oxidant solution.

[0035] In one embodiment, the oxidant solution includes any one of hydrogen peroxide, sodium persulfate solution, sodium hypochlorite solution or sodium chlorate solution, or a combination of at least two thereof.

[0036] The present invention discloses that the charge and discharge capacity of a salt lake lithium extraction electrode can be increased through oxidation treatment.

[0037] 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.

[0038] 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.

[0039] Compared with the prior art, the present disclosure has the following beneficial effects:

[0040] (1) The method disclosed in the present invention does not require a drying step after using a non-solvent to create pores, which can simplify the process flow and reduce the workload. At the same time, it can reduce cracks on the surface of the plate and improve the strength and durability of the plate.

[0041] (2) In the method disclosed herein, when the solvent and non-solvent are exchanged, a porous continuous surface is formed at the exchange interface, thereby ensuring the structural stability of the electrode plate while improving the mass transfer efficiency of the solution within the electrode plate. No pore-forming agent is required during pore formation, greatly reducing the number of operating steps and optimizing the process.

[0042] (3) The salt lake lithium extraction electrode prepared by the method disclosed in the present invention has an initial specific capacity of more than 83.68 mAh / g, a specific capacity of more than 84.36 mAh / g after 60 cycles, and a capacity retention rate of more than 99.33%. The salt lake lithium extraction electrode can effectively extract lithium from brine and can be stably circulated.

[0043] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0044] 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.

[0045] Example 1

[0046] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0047] (1) Polyvinylidene fluoride (PVDF) was 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. The ratio of lithium iron phosphate, polyvinylidene fluoride, and carbon black was 77:15:8. The slurry was scraped onto a porous titanium mesh using a template to form a 5 mm thick electrode;

[0048] (2) The electrode was slowly immersed in water (the interaction parameter between water and PVDF was > 0.5), allowed to stand for 6 h, solidified at 25 °C, and then immersed in water for 48 h to allow the NMP in the plate to fully exchange with water, solidify the slurry into pores, and obtain an electrode with higher porosity;

[0049] (3) The electrode was immersed in a 5% sodium persulfate aqueous solution at 50° C. for 1 hour, rinsed under running water, and immersed in water for 3 hours to terminate the oxidation reaction, thereby obtaining the salt lake lithium extraction electrode.

[0050] Example 2

[0051] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0052] (1) Polyvinylidene fluoride (PVDF) was 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. The ratio of lithium iron phosphate, polyvinylidene fluoride, and carbon black was 84:10:6. The slurry was scraped onto a porous titanium mesh using a template to form a 1 mm thick electrode;

[0053] (2) The electrode was slowly immersed in ethanol (the interaction parameter between ethanol and PVDF was > 0.5), allowed to stand for 10 h, solidified at 20 °C, and then immersed in ethanol for 15 h to allow the NMP in the electrode to fully exchange with the ethanol, solidify the slurry into pores, and obtain an electrode with higher porosity;

[0054] (3) The electrode was immersed in a 1% hydrogen peroxide aqueous solution at 50° C. for 1.5 hours, rinsed under running water, and immersed in water for 2 hours to terminate the oxidation reaction, thereby obtaining the salt lake lithium extraction electrode.

[0055] Example 3

[0056] This embodiment provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0057] (1) Polyvinylidene fluoride (PVDF) was fully dissolved in NMP 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. The lithium iron phosphate, polyvinylidene fluoride, and carbon nanotubes were in a ratio of 92:5:3. The slurry was scraped onto a porous titanium mesh using a template to form a 9 mm thick electrode;

[0058] (2) The electrode was slowly immersed in water (the interaction parameter between water and PVDF was > 0.5), allowed to stand for 12 h, solidified at 40 °C, and then immersed in water for 40 h to allow the NMP in the plate to fully exchange with water, solidify the slurry into pores, and obtain an electrode with higher porosity;

[0059] (3) The electrode was immersed in a 2% sodium hypochlorite aqueous solution at 40° C. for 2 h, rinsed under running water, and immersed in water for 5 h to terminate the oxidation reaction, thereby obtaining the salt lake lithium extraction electrode.

[0060] Example 4

[0061] The only difference between this embodiment and embodiment 1 is that the soaking time in water before curing in step (2) is 1 hour, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0062] Example 5

[0063] The only difference between this embodiment and embodiment 1 is that the soaking time in water before curing in step (2) is 15 hours, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0064] Comparative Example 1

[0065] The only difference between this comparative example and Example 1 is that no soaking is performed after curing, and other conditions and parameters are exactly the same as those in Example 1.

[0066] Comparative Example 2

[0067] The only difference between this comparative example and Example 1 is that water is replaced with isooctane (interaction parameter with the binder <0.5), and other conditions and parameters are exactly the same as those in Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides a salt lake lithium extraction electrode, and the preparation method of the salt lake lithium extraction electrode is as follows:

[0070] (1) Fully dissolving polyvinylidene fluoride (PVDF) in NMP to prepare a slurry, then adding lithium iron phosphate, carbon black and ammonium bicarbonate to the binder solution and stirring thoroughly to prepare a slurry, wherein the ratio of lithium iron phosphate, polyvinylidene fluoride and carbon nanotubes is 74:10:16;

[0071] (2) The slurry is scraped onto a porous titanium mesh to form a 1 mm electrode, which is then subjected to a gradient temperature increase in an oven. The electrode is first dried at 65°C for 6 hours, and the temperature is increased by 20°C every 6 hours until the electrode is completely dried. The electrode is then sintered at 300°C for 3 hours to obtain the salt lake lithium extraction electrode.

[0072] Performance testing:

[0073] Electrochemical deintercalation tests were performed on the salt lake lithium extraction electrodes obtained in Examples 1-5 and Comparative Examples 1-3. The test results are shown in Table 1:

[0074] Table 1

[0075] 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 83.68 mAh / g, the specific capacity can reach more than 84.36 mAh / g after 60 cycles, and the capacity retention rate can reach more than 99.33%.

[0076] 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 immersion time in the non-solvent before solidification will affect its performance. When the immersion time in the non-solvent before solidification is controlled to 6 to 12 hours, the performance of the salt lake lithium extraction electrode is better. If the time is too short, the performance of the electrode will not be significantly improved. If the time is too long, the stability of the plate structure is poor.

[0077] From the comparison between Example 1 and Comparative Example 1, it can be seen that in the preparation process of the salt lake lithium extraction electrode disclosed in the present invention, NMP cannot be completely leached out when it is continuously immersed in a non-solvent after solidification, which will damage the structure of the electrode plate.

[0078] By 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, a non-solvent replacement solvent with an interaction parameter with the binder greater than 0.5 is selected. When the solvent and the non-solvent are exchanged, the solvent diffuses and dissolves into the non-solvent, and the non-solvent replaces the solvent to form pores. The interaction parameter between the binder and the non-solvent is large and the solubility is poor. The electrode plate will not collapse due to the loss of solvent, which is more conducive to structural stability.

[0079] A comparison of Example 1 and Comparative Example 3 demonstrates that, in the method disclosed herein, when the solvent and non-solvent are exchanged, a porous, continuous surface is formed at the exchange interface, ensuring the structural stability of the electrode plate while improving the mass transfer efficiency of the solution within the electrode plate. No pore-forming agent is required during pore formation, significantly reducing the number of steps and optimizing the process. No drying step is required after pore formation, simplifying the process and reducing workload. This also reduces surface cracking on the electrode plate, improving its strength and durability.

Claims

1. A method for preparing a lithium extraction electrode from a salt lake, comprising the following steps: (1) Mix an active material, a conductive agent, a binder and a solvent to obtain a slurry, and coat the slurry on a current collector to obtain an electrode; (2) Immerse the electrode in a non-solvent for plate curing; (3) After subjecting the soaked electrode to an oxidation treatment, the lithium extraction electrode from the salt lake is obtained; The solvent and the non-solvent are miscible in any proportion, and the interaction parameter between the non-solvent and the binder > 0.

5.

2. The preparation method according to claim 1, wherein, the active material in step (1) includes lithium iron phosphate.

3. The preparation method according to claim 1 or 2, wherein, the binder includes any one or a combination of at least two of polyamide, polyimide, polyvinylidene fluoride or polydimethylsiloxane.

4. The preparation method according to any one of claims 1-3, wherein, in the slurry in step (1), the mass of the binder accounts for 5-15% of the total solid mass.

5. The preparation method according to any one of claims 1-4, wherein, the solvent includes any one or a combination of at least two of N-methylpyrrolidone, isooctane, dimethyl sulfoxide or tetrahydrofuran.

6. The preparation method according to any one of claims 1-5, wherein, the thickness of the coating in step (1) is 1-9 mm.

7. The preparation method according to any one of claims 1-6, wherein, the non-solvent in step (2) is a liquid that is miscible with the solvent in any proportion and cannot dissolve the binder.

8. The preparation method according to any one of claims 1-7, wherein, the non-solvent includes any one or a combination of at least two of water, methanol or ethanol.

9. The preparation method according to any one of claims 1-8, wherein, the time for immersing in the non-solvent in step (2) is 6-12 h.

10. The preparation method according to any one of claims 1-9, wherein, the oxidation treatment in step (3) includes immersing the electrode in an oxidant solution.

11. The preparation method according to claim 10, wherein, the oxidant solution in step (3) includes any one or a combination of at least two of hydrogen peroxide, sodium persulfate solution, sodium hypochlorite solution or sodium chlorate solution.

12. A lithium extraction electrode from a salt lake prepared by the method according to any one of claims 1-11.

13. A method for extracting lithium from a salt lake using the polarity of the lithium extraction electrode from a salt lake according to claim 12.