A porous electrode plate for electro-deintercalation and extraction of lithium, its preparation method, and its electro-deintercalation and extraction apparatus.

Abstract

This invention belongs to the field of electrochemical lithium extraction technology, and relates to a porous electrode plate for electrochemical lithium extraction and its preparation method and device. The porous electrode plate for electrochemical lithium extraction includes a current collector and slurry coatings on both sides of the current collector. The slurry coating has a channel structure formed by interconnected macropores and internal micropores. The preparation method of the porous electrode plate for electrochemical lithium extraction includes the following steps: (1) preparing an electrode slurry; (2) coating the electrode slurry on both sides of the current collector, and drying it after coating to obtain a coated electrode plate; (3) placing the dried coated electrode plate in a hot press for flat pressing, then immersing it in water, and finally rinsing it with water to obtain the porous electrode plate for electrochemical lithium extraction. This invention improves the ion and electron conduction during electrode plate operation and enhances the lithium extraction performance of the electrode plate by adding polyvinyl alcohol fiber and soluble salt as pore-forming agents to the electrode slurry and introducing a flat pressing process to manufacture the electrode plate.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical lithium extraction technology, specifically relating to a porous electrode plate for electro-deintercalation and extraction of lithium, its preparation method, and an electro-deintercalation and extraction device. Background Technology

[0002] Lithium, a key element in the modern electric vehicle revolution, is hailed as the energy metal of the 21st century and is commonly used in the manufacture of electric vehicles, portable computers, power tools, and power supplies. With the continuous development of new energy vehicles, the influence of lithium resources in the energy sector is further increasing.

[0003] Lithium extraction processes from brine mainly include evaporation crystallization, solvent extraction, adsorbent methods, and membrane separation. Compared to these methods, electro-extraction lithium extraction technology, as an emerging lithium extraction method, has the advantages of being green and environmentally friendly, having low energy consumption, and minimal electrode material loss. Its principle is based on the electrochemical differences between lithium ions and other coexisting ions, allowing the electrode to selectively insert / extract lithium ions by controlling the potential. For example, CN 116964233A discloses a high-efficiency lithium extraction electrode material and electrode from salt lakes. Using LiFePO4 / FePO4 coated with lithium titanium oxide as the electrode pair, lithium ions are extracted by inserting into the cathode electrode after energization, while lithium ions in the anode electrode are released into a clean solution, achieving lithium recovery and enrichment. This lithium extraction method has advantages such as high selectivity and environmental friendliness. Currently, electro-extraction lithium extraction technology suffers from low extraction efficiency and poor stability due to the influence of ion and electron conduction during the lithium extraction process, which greatly limits its application and development. Therefore, it is necessary to develop a simple and reliable method to prepare high-performance electro-deintercalation lithium extraction plates in order to improve the problem of poor ion and electron conduction during the lithium extraction process of the plates, thereby enhancing the lithium extraction performance of the plates.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the problems of low lithium extraction efficiency and poor stability in existing electro-extraction lithium extraction technologies, the present invention aims to provide a porous electrode plate for electro-extraction lithium extraction, its preparation method, and an electro-extraction lithium extraction device, which optimizes the electronic and ion conduction during the lithium extraction process of the electrode plate, thereby improving the lithium extraction performance of the electrode plate.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a porous electrode plate for electrolytic lithium extraction, the porous electrode plate for electrolytic lithium extraction comprising a current collector and a slurry coating on both sides of the current collector, the slurry coating having a channel structure formed by interconnected macropores and internal micropores;

[0008] In an optional embodiment, the thickness of the slurry coating on one side of the porous electrode plate for electro-deintercalation of lithium is 1-3 mm, preferably 2 mm.

[0009] In an optional embodiment, the water adsorption capacity of the porous electrode plate used for electro-deintercalation and extraction of lithium is 0.40 g / g to 0.95 g / g;

[0010] In an optional embodiment, the resistance of the porous electrode plate used for electro-deintercalation of lithium is 60mΩ-300mΩ;

[0011] In an optional embodiment, the lithium extraction capacity of the porous electrode plate used for electro-deintercalation and extraction of lithium is 7.0 mg / g to 17.6 mg / g.

[0012] The porous electrode plate prepared by this invention for electro-deintercalation and lithium extraction has a slurry coating on both sides of the current collector with a channel structure formed by interconnected macropores and internal micropores. This three-dimensional channel structure can provide channels for lithium ion transport, enhance the ion conduction capacity of the electrode plate, reduce concentration polarization, and thus improve the lithium extraction capacity of the electrode plate.

[0013] Secondly, the present invention provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0014] S1. Preparation of electrode paste;

[0015] S2. Coat the electrode paste on both sides of the current collector, and dry it after coating to obtain the coated electrode plate;

[0016] S3. The dried coated electrode plate is first placed on a hot press for flat pressing, then soaked in water, and then rinsed with water to obtain a porous electrode plate for electro-deintercalation and lithium extraction.

[0017] The present invention employs a flat pressing process to compress the coating, increase the contact between the coatings, enhance conductivity, greatly shorten the electron conduction path during the electrode insertion / extraction process, improve the electron transport rate, thereby improving electron conduction and increasing the energy density of the electrode.

[0018] In an optional embodiment, the electrode slurry in step S1 is composed of a solvent, an active material composition, and a pore-forming agent, wherein the active material composition is composed of an active material, a hydrophilic agent, a conductive agent, a binder, and a structural agent.

[0019] In an optional embodiment, the process of preparing the electrode paste in step S1 is to first mix the hydrophilic agent and binder with the solvent to obtain a colloid, and then add the conductive agent, active material, structural agent and pore-forming agent to the colloid for mixing.

[0020] In an optional embodiment, the active material includes at least one of lithium iron phosphate, lithium manganese oxide, and lithium manganese iron phosphate.

[0021] In an optional embodiment, the hydrophilic agent includes at least one of polyethylene glycol (PEG), polydopamine, chitosan, or polyvinyl alcohol;

[0022] In an optional embodiment, the conductive agent includes at least one of conductive carbon (SP), conductive graphite (KS-6), Ketjen black, or carbon nanotubes.

[0023] In an optional embodiment, the adhesive includes at least one of polyvinylidene fluoride (PVDF) or polyvinylidene fluoride (HSV900);

[0024] In an optional embodiment, the structural agent is carbon fiber (CF);

[0025] In an optional embodiment, the pore-forming agent is composed of polyvinyl alcohol fibers and a soluble salt;

[0026] In an optional embodiment, the contents of each component in the active material composition, calculated by weight percentage, are as follows: active material 67wt%-85wt%, hydrophilic agent 2wt%-10wt%, conductive agent 4wt%-10wt%, binder 4wt%-10wt%, and structural agent 1wt%-3wt%.

[0027] In an optional embodiment, the solvent content is 90wt%-130wt% of the weight of the active material composition;

[0028] In an optional embodiment, the content of the pore-forming agent is 11wt%-40wt% of the weight of the active material composition;

[0029] In an optional embodiment, the weight ratio of polyvinyl alcohol fiber to soluble salt in the pore-forming agent is (0.1-1.2):1;

[0030] In an optional embodiment, the chopped length of the polyvinyl alcohol fiber is 2-6 mm, preferably 3 mm, and the fiber diameter is less than 20 μm, preferably less than 10 μm;

[0031] In an optional embodiment, the soluble salt includes at least one of NaCl, KCl, K2SO4, Na2SO4, or KNO3;

[0032] In an optional embodiment, the particle size of the soluble salt is 50-300 mesh, preferably 150 mesh.

[0033] The pore-forming agent of this invention contains not only soluble salts but also water-soluble polyvinyl alcohol fibers. When used in combination with soluble salts, the interconnected pore structure formed after the linear polyvinyl alcohol fibers dissolve can effectively avoid the problem of uneven cracking in the electrode plate, solve the difficulty of poor ion channel connectivity, and effectively control the degree of cracking inside the electrode plate. This allows lithium ions to have a good path during transport, and ion conduction is smoother during electro-deintercalation, accelerating brine circulation, reducing concentration polarization, improving ion conduction during electrode operation, and improving the lithium extraction performance of the electrode plate.

[0034] In an optional embodiment, the current collector of the porous electro-deintercalation lithium electrode plate in step S2 includes at least one of titanium mesh, ruthenium-iridium plated titanium mesh, graphite plate, or carbon fiber cloth.

[0035] In an optional embodiment, the coating in step S2 is performed using a coating mold, and the drying includes first holding at 40-55°C for 7-9 hours, and then holding at 75-90°C for 10-14 hours.

[0036] In an optional implementation, the hot press in step S3 is set to a temperature of 65-80°C, a pressure of 0.2-0.8 MPa, and a plate compression ratio of 20%-50%.

[0037] In an optional embodiment, the soaking time in step S3 is 22-26 hours to dissolve the pore-forming agent in the electrode plate.

[0038] In an optional embodiment, the rinsing time in step S3 is 15-30 minutes to remove soluble residues remaining on the electrode surface.

[0039] Thirdly, the present invention provides an electro-deintercalation lithium extraction device, the electro-deintercalation lithium extraction device comprising the porous electro-deintercalation lithium extraction electrode plate as described in the first aspect.

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

[0041] (1) The present invention adds water-soluble polyvinyl alcohol fiber as a pore-forming agent to the electrode slurry. The resulting pore structure can effectively avoid the problem of uneven cracking of the electrode plate and solve the problem of poor ion channel connectivity. This makes the degree of cracking inside the electrode plate controllable, allowing lithium ions to have a good path during transport, making ion conduction smoother during the electro-deintercalation process, accelerating brine circulation, reducing concentration polarization, enhancing ion conduction during electrode operation, and improving the lithium extraction performance of the electrode plate.

[0042] (2) The present invention adds a flat pressing process in the electrode preparation process. This process can not only increase the compaction density of the electrode, but also increase the contact area between the slurry coatings, enhance conductivity, make the internal connection of the coating more compact, greatly shorten the electron conduction path of the electrode during the electro-deintercalation process, improve the electron transmission rate, effectively improve the electron conduction of the electrode, and thus improve the energy density and lithium extraction efficiency of the electrode.

[0043] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0044] The accompanying drawings are provided to further understand the technical solutions herein and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions herein and do not constitute a limitation on the technical solutions herein.

[0045] Figure 1 SEM images of (a) a porous electrode plate for electro-deintercalation and extraction of lithium prepared in Example 1 of the present invention and (b) an electro-deintercalation and extraction of lithium without the addition of a pore-forming agent prepared in Comparative Example 1.

[0046] Figure 2 This is a schematic diagram of the flat pressing process of the porous electrode plate for electro-deintercalation and lithium extraction prepared in Example 1 of the present invention;

[0047] Figure 3 EIS images of porous electrode plates for electro-deintercalation and extraction of lithium prepared in Examples 1-4 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as limiting the scope of the invention.

[0049] It should be noted that, unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0050] This invention provides a porous electrode plate for electrode extraction and insertion of lithium, comprising a current collector and slurry coatings on both sides of the current collector. The slurry coatings have a channel structure formed by interconnected macropores and internal micropores. The slurry coatings are formed by drying an electrode slurry.

[0051] This invention provides a method for preparing a porous electrode plate for lithium extraction and intercalation, the method comprising the following steps:

[0052] S1. Preparation of electrode paste;

[0053] S2. Coat the electrode paste on both sides of the current collector, and dry it after coating to obtain the coated electrode plate;

[0054] S3. The dried coated electrode plate is first placed on a hot press for flat pressing, then soaked in water, and then rinsed with water to obtain a porous electrode plate for lithium extraction and intercalation.

[0055] Specifically, the present invention will describe each of the above steps one by one.

[0056] S1. First, add the hydrophilic agent and binder to the solvent and stir to dissolve to make a glue solution. Then, dry mix the conductive agent, delithiated active material and structural agent. After mixing evenly, add them to the glue solution and stir evenly. Finally, add the pore-forming agent and stir evenly to make the electrode slurry.

[0057] In some embodiments, the active material composition comprises, by weight percentage, the following components: an active material of 67wt%-85wt%, for example, 67wt%, 75wt%, 80wt%, or 85wt%; a hydrophilic agent of 2wt%-10wt%, for example, 2wt%, 5wt%, 8wt%, or 10wt%; a conductive agent of 4wt%-10wt%, for example, 4wt%, 6wt%, 8wt%, or 10wt%; a binder of 4wt%-10wt%, for example, 4wt%, 5wt%, 7wt%, or 10wt%; and a structural agent of 1wt%-3wt%, for example, 1wt%, 1.5wt%, 2.5wt%, or 3wt%, but not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0058] In some embodiments, the solvent content is 90wt%-130wt% of the mass of the active material composition, for example, it can be 90wt%, 100wt%, 110wt%, 120wt% or 130wt%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable;

[0059] In some embodiments, the content of the pore-forming agent is 11wt%-40wt% of the mass of the active material composition; for example, it can be 11wt%, 20wt%, 30wt% or 40wt%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0060] In some embodiments, the mass ratio of the water-soluble polyvinyl alcohol fiber to the soluble salt is (0.1-1.2):1, for example, it can be 0.1:1, 0.5:1, 0.8:1 or 1.2:1, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0061] The content of pore-forming agent in the electrode slurry of this invention affects the physical strength and electrochemical performance of the electrode plate. If the content is too low, it cannot provide a good ion transport channel for the electrode plate, resulting in poor ion conduction and poor electrochemical performance. If the content is too high, there will be too many cavities inside the electrode plate, and the coatings cannot be tightly connected. On the one hand, the electron conduction ability will also be poor, and on the other hand, the physical strength of the electrode plate will be low, and the coating will be easy to fall off.

[0062] In this invention, the electrode slurry uses a combination of water-soluble polyvinyl alcohol (PVA) fibers and soluble salts as pore-forming agents. This combination enhances electrode performance. If the mass ratio of PVA fibers to soluble salts is too high or too low, the electrochemical performance of the electrode will be poor. The macropores created by the PVA fibers provide excellent pathways for ion transport, making ion conduction more efficient. The coating interior, where macropores are not formed, also requires ion conduction; the addition of soluble salts effectively fills this gap in transport channels. The two complement each other, achieving a better overall effect.

[0063] S2. The electrode paste is coated on both sides of the current collector titanium mesh using a coating mold. The coating thickness is the same as that of the coating mold. After coating, the electrode is dried to obtain the coated electrode plate.

[0064] In some embodiments, the drying process includes first holding the product at 40-55°C for 7-9 hours, for example, at 40°C, 45°C, 50°C, or 55°C for 7, 8, or 9 hours, and then holding it at 75-90°C for 10-14 hours, for example, at 75°C, 80°C, 85°C, or 90°C for 10, 12, or 14 hours, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0065] S3. The dried coated electrode plate is first placed on a hot press for flat pressing, and the temperature, pressure and compression ratio are set. Then the electrode plate is immersed in water and rinsed with water to obtain a porous electrode plate for electro-deintercalation and extraction of lithium.

[0066] In some embodiments, the hot press is set at a temperature of 65-80°C, for example, 65°C, 70°C, 75°C or 80°C, and a pressure of 0.2-0.8 MPa, for example, 0.2 MPa, 0.4 MPa, 0.6 MPa or 0.8 MPa. The plate compression ratio is 20%-50%, for example, 20%, 30%, 40% or 50%, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0067] In some embodiments, the soaking time is 22-26 hours, for example, 22 hours, 24 hours or 26 hours, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0068] In some embodiments, the rinsing time is 15-30 minutes, for example, 15 minutes, 20 minutes, 25 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0069] In the flat pressing process used in this invention, the compression ratio of the electrode plate affects the performance of the electrode plate. If the compression ratio of the electrode plate is too high, a large number of ion channels will be lost, resulting in poor ion conduction of the electrode plate and a risk of coating crushing, which will lead to poor electrochemical performance of the electrode plate. If the compression ratio of the electrode plate is too low, the contact between the coatings will not be well enhanced, and the effect of enhancing the electron conduction of the electrode plate will not be achieved.

[0070] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0071] Example 1

[0072] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0073] S1. According to the formula, first add PEG and PVDF to the solvent N-methylpyrrolidone (NMP) and stir to dissolve to prepare a gel solution. Then, dry mix SP, LFP, and CF, and add them to the prepared gel solution and stir evenly. Finally, add NaCl (150 mesh) and polyvinyl alcohol fibers (short fiber length of 3 mm, fiber diameter less than 10 μm) and stir evenly to prepare the electrode slurry. The active material composition, calculated by mass percentage, consists of 4.7 wt% PEG, 5.3 wt% PVDF, 78.6 wt% LFP (20% delithiation rate), 9.6 wt% SP, and 1.8 wt% CF; the NMP content is 100 wt% of the active material composition; the total content of the pore-forming agent is 30 wt% of the active material composition, and the mass ratio of polyvinyl alcohol fibers to NaCl in the pore-forming agent is 0.5:1, i.e., the content of both is 20 wt% NaCl and 10 wt% polyvinyl alcohol fibers.

[0074] S2. Using a 2mm coating mold, the electrode paste prepared in S1 is coated on both sides of the current collector titanium mesh. The coating thickness is the same as that of the coating mold. After coating, the electrode is first baked at 50℃ for 8 hours, and then baked at 85℃ for 12 hours to obtain the coated electrode plate.

[0075] S3. Place the dried coated electrode plate in a hot press and compress it at a temperature of 70℃ and a pressure of 0.5MPa with a compression ratio of 35%. Then, place the electrode plate in 200mL of water and stir and soak for 24h to dissolve the NaCl and polyvinyl alcohol fibers in the electrode plate. After that, rinse the electrode plate under running water for 20min to clean the residual soluble substances on the surface of the electrode plate, and obtain a porous electrode plate for electro-deintercalation and extraction of lithium.

[0076] SEM images of the porous electrode plate for lithium electro-extraction and intercalation prepared in this embodiment and the lithium electro-extraction and intercalation electrode plate without pore-forming agent prepared in Comparative Example 1 are shown below. Figure 1 As shown in the figure, the coating has a channel structure formed by interconnected macropores and internal micropores. A schematic diagram of the flat-pressing process for the porous electrode plate used for electro-deintercalation and lithium extraction obtained in this embodiment is shown below. Figure 2 As shown in the figure, the internal contact of the electrode coating is tighter after flat pressing.

[0077] Example 2

[0078] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0079] S1 is the same as step S1 in Example 1, except that the total content of the pore-forming agent is 27 wt% of the mass of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.8:1, that is, the contents of the two are: 15 wt% NaCl and 12 wt% polyvinyl alcohol fiber.

[0080] S2. Using a 2mm coating mold, the electrode paste prepared in S1 is coated on both sides of the current collector titanium mesh. The coating thickness is the same as that of the coating mold. After coating, it is first baked at 40℃ for 9 hours, and then baked at 75℃ for 14 hours to obtain the coated electrode plate.

[0081] S3. Place the dried coated electrode plate in a hot press and compress it at a temperature of 70℃ and a pressure of 0.5MPa with a compression ratio of 35%. Then, place the electrode plate in 200mL of water and stir and soak for 22h to dissolve the NaCl and polyvinyl alcohol fibers in the electrode plate. After that, rinse the electrode plate under running water for 15min to clean the residual soluble substances on the surface of the electrode plate, and obtain a porous electrode plate for electro-deintercalation and extraction of lithium.

[0082] Example 3

[0083] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0084] S1. The steps are the same as in Example 1, except that the content of NMP is 90 wt% of the mass of the active material composition; the total content of the pore-forming agent is 11 wt% of the mass of the active material composition; and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.1:1, that is, the contents of the two are: 10 wt% NaCl and 1 wt% polyvinyl alcohol fiber.

[0085] The ratio of the active material composition was changed to: 8 wt% PEG, 4 wt% PVDF, 83 wt% LFP (delithiation rate 20%), 4 wt% SP, and 1 wt% CF.

[0086] S2. Using a 2mm coating mold, the electrode paste prepared in S1 is coated on both sides of the current collector titanium mesh. The coating thickness is the same as that of the coating mold. After coating, it is first baked at 55℃ for 7 hours, and then baked at 90℃ for 10 hours to obtain the coated electrode plate.

[0087] S3. Place the dried coated electrode plate in a hot press at a temperature of 70℃ and a pressure of 0.5MPa, with a compression ratio of 35%. Then, place the electrode plate in 200mL of water and stir and soak for 26h to dissolve the NaCl and polyvinyl alcohol fibers in the electrode plate. After that, rinse the electrode plate under running water for 30min to clean the residual soluble substances on the surface of the electrode plate, and obtain a porous electrode plate for electro-deintercalation and extraction of lithium.

[0088] Example 4

[0089] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0090] S1 is the same as step S1 in Example 1, except that the total content of the pore-forming agent is 33 wt% of the mass of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 1.2:1, that is, the contents of the two are: 15 wt% NaCl and 18 wt% polyvinyl alcohol fiber.

[0091] The ratio of the active material composition was changed to: 2wt% PEG, 6wt% PVDF, 85wt% LFP (delithiation rate 20%), 5wt% SP, and 2wt% CF.

[0092] S2-S3 are the same as the steps in Example 1.

[0093] Example 5

[0094] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0095] S1. According to the formula, first add PEG and PVDF to the solvent NMP and stir to dissolve to prepare a gel solution. Then, dry mix SP, LFP, and CF, and add them to the prepared gel solution and stir evenly. Finally, add NaCl and polyvinyl alcohol fiber and stir evenly to prepare the electrode slurry. The active material composition, calculated by mass percentage, comprises 10wt% PEG, 10wt% PVDF, 67wt% LFP (20% delithiated), 10wt% SP, and 3wt% CF; the NMP content is 130wt% of the active material composition; the total content of the pore-forming agent is 40wt% of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 1:1, i.e., the content of both is 20wt% NaCl and 20wt% polyvinyl alcohol fiber.

[0096] S2-S3 are the same as the steps in Example 1.

[0097] Example 6

[0098] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium. The specific steps of the method are the same as those in Embodiment 1, except that the compression ratio is set to 20% in step S3.

[0099] Example 7

[0100] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium. The specific steps of the method are the same as those in Embodiment 1, except that the compression ratio is set to 50% in step S3.

[0101] Example 8

[0102] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0103] S1 is the same as step S1 in Example 1, except that the total content of the pore-forming agent is 30 wt% of the mass of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.2:1, that is, the contents of the two are: 25 wt% NaCl and 5 wt% polyvinyl alcohol fiber.

[0104] S2-S3 are the same as the steps in Example 1.

[0105] Example 9

[0106] This embodiment provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0107] S1 is the same as step S1 in Example 1, except that the total content of the pore-forming agent is 30 wt% of the mass of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 1:1, that is, the contents of the two are: 15 wt% NaCl and 15 wt% polyvinyl alcohol fiber.

[0108] S2-S3 are the same as the steps in Example 1.

[0109] Comparative Example 1

[0110] This comparative example provides a method for preparing an electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0111] No pore-forming agent is added during the preparation of the electrode paste:

[0112] S1. According to the formula, first add PEG and PVDF to the solvent NMP and stir to dissolve them to prepare a gel solution. Then, dry mix SP, LFP, and CF, and add them to the prepared gel solution and stir evenly to prepare an electrode slurry. The active material composition, calculated by mass percentage, comprises 4.7 wt% PEG, 5.3 wt% PVDF, 78.6 wt% LFP (20% delithiation rate), 9.6 wt% SP, and 1.8 wt% CF; the NMP content is 100 wt% of the active material composition.

[0113] S2-S3 are the same as the steps in Example 1.

[0114] Comparative Example 2

[0115] This comparative example provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0116] The flat pressing process is not used when preparing the electrode plates:

[0117] S1-S2 are the same as the steps in Example 1.

[0118] S3. Place the dried coated plates in 200ml of water and stir and soak for 24 hours to dissolve the NaCl and polyvinyl alcohol fibers in the plates. Rinse under running water for 20 minutes to clean the residual soluble substances on the surface of the plates.

[0119] Comparative Example 3

[0120] This comparative example provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0121] Polyvinyl alcohol fiber without pore-forming agent is not added when preparing electrode paste:

[0122] S1. According to the formula, first add PEG and PVDF to the solvent NMP and stir to dissolve to prepare a gel solution. Then, dry mix SP, LFP, and CF, and add them to the prepared gel solution and stir evenly. Finally, add NaCl and stir evenly to prepare the electrode slurry. The active material composition, calculated by mass percentage, contains 4.7 wt% PEG, 5.3 wt% PVDF, 78.6 wt% LFP (20% delithiated), 9.6 wt% SP, and 1.8 wt% CF; the NMP content is 100 wt% of the active material composition; and 30 wt% NaCl (the pore-forming agent content is 30 wt% of the active material composition).

[0123] S2-S3 are the same as the steps in Example 1.

[0124] Comparative Example 4

[0125] This comparative example provides a method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium, the method comprising the following steps:

[0126] No pore-forming agent NaCl is added during the preparation of the electrode paste.

[0127] S1. According to the formula, first add PEG and PVDF to the solvent NMP and stir to dissolve to prepare a gel solution. Then, dry mix SP, LFP, and CF, and add them to the prepared gel solution and stir evenly. Finally, add polyvinyl alcohol fiber and stir evenly to prepare the electrode slurry. The active material composition, calculated by mass percentage, contains 4.7 wt% PEG, 5.3 wt% PVDF, 78.6 wt% LFP (20% delithiated), 9.6 wt% SP, and 1.8 wt% CF; the NMP content is 100 wt% of the active material composition; and 30 wt% polyvinyl alcohol fiber (the pore-forming agent content is 30 wt% of the active material composition).

[0128] S2-S3 are the same as the steps in Example 1.

[0129] Performance testing:

[0130] The water absorption, resistance, electrochemical performance, and lithium extraction performance of the electrode plates prepared in Examples 1-9 and Comparative Examples 1-4 were evaluated, specifically including the following steps:

[0131] (1) Water absorption test

[0132] The electrode plate is immersed in a certain volume of pure water for 2 hours, and the aqueous solution is required to completely submerge the electrode plate. The mass difference M (g) before and after the electrode plate absorbs water is measured, and the mass of the electrode plate coating is m (g). Then the water absorption is M / m (g / g).

[0133] (2) Resistance test

[0134] The resistance of the plate was measured using a RM3544 resistance meter from HIOKI Electric Co., Ltd. The positive terminal of the resistance meter was clamped to the current collector titanium mesh, and the negative terminal was clamped to the coating. The average value of the resistance data at 6 points was taken as the resistance of the plate.

[0135] (3) Electrochemical performance testing

[0136] The electrochemical performance of the plates was measured using the Wuhan Landian Battery Testing System CT3002K. The positive and negative electrode clips of Landian were clamped onto the plate tabs for testing. The rate test steps were 3 times each at 0.1C, 0.2C, and 0.5C, and the cycle test step was a long cycle test at 0.2C.

[0137] (4) Lithium extraction performance test

[0138] The specific capacity of the plates at 0.1C was measured using the Wuhan Landian Battery Testing System CT3002K. The theoretical lithium extraction capacity of the plates was calculated based on the average specific capacity. During testing, the plates were first clamped with glass plate electrode clips to ensure good contact. The glass plate electrode clips were then assembled into the brine solution of the lithium extraction device, ensuring the brine completely submerged the plate coating and that the plates were on the same horizontal plane. Finally, the positive and negative electrodes of the Landian testing system were clamped to the glass plate electrode clips, respectively. The rate and cycle test program were set in the Landian testing software, and the test process was initiated.

[0139] The test results are shown in Table 1-2:

[0140] Table 1

[0141] Experiment number Resistance (mΩ) Water absorption (g / g) Example 1 92 0.88 Example 2 89 0.84 Example 3 85 0.62 Example 4 97 0.87 Example 5 126 0.83 Example 6 114 0.90 Example 7 80 0.71 Example 8 87 0.77 Example 9 103 0.85 Comparative Example 1 100 0.45 Comparative Example 2 145 0.90 Comparative Example 3 94 0.72 Comparative Example 4 105 0.94

[0142] Table 2

[0143]

[0144] As can be seen from Tables 1-2, and from Examples 1-9, when the content of the pore-forming agent and the compression ratio of the electrode plate are within the specified range, the porous electrode plate prepared by the method of the present invention for electro-deintercalation and lithium extraction can effectively improve its electronic and ionic conduction capabilities, reduce the electrode plate impedance and resistance, and enhance the electrode plate electrochemical performance.

[0145] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention creates pores by adding soluble substances, namely water-soluble polyvinyl alcohol fiber and soluble salt, to the electrode plate. This results in a channel structure formed by interconnected macropores and internal micropores inside the electrode plate, which reduces electrode impedance and enhances ion diffusion capability. Therefore, the electrode plate has excellent rate performance and cycle performance, and enhances lithium extraction capability.

[0146] As can be seen from the comparison between Example 1 and Comparative Example 2, the porous electrode plate for electro-deintercalation and extraction of lithium prepared by the present invention adopts a flat pressing process. Compared with Comparative Example 2, the internal contact of the electrode plate coating after flat pressing is more compact, which effectively reduces the resistance and impedance of the electrode plate, thereby improving the conductivity of the electrode plate and enhancing the electrochemical performance of the electrode plate.

[0147] As can be seen from the comparison between Example 1 and Comparative Examples 3-4, the electrode plate of Example 1 has better electrical performance and lithium extraction performance. The present invention uses water-soluble polyvinyl alcohol fiber and soluble salt in combination to create pores in the slurry coating, forming a channel structure with interconnected macropores and internal micropores, which is conducive to the full utilization of the electrode plate's electrochemical performance and lithium extraction performance.

[0148] In summary, this invention incorporates water-soluble fibers and soluble salts into the preparation of a porous electrode slurry for lithium extraction and intercalation. These fibers are then dissolved through water immersion to create pores. This effectively addresses the challenge of poor ion channel connectivity, improves ion conduction during electrode operation, and enhances the lithium extraction performance of the electrode. Furthermore, the addition of a flat-pressing process during electrode preparation significantly increases the electrode's energy density and the contact area between the slurry coatings, resulting in tighter internal connections and improved electron conduction, thus enhancing the lithium extraction efficiency of the electrode.

[0149] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A porous electrode plate for electro-deintercalation and extraction of lithium, characterized in that, The porous electrode plate for electrolytic lithium extraction includes a current collector and a slurry coating on both sides of the current collector. The slurry coating has a channel structure formed by interconnected macropores and internal micropores. The slurry coating is composed of a solvent, an active material composition, and a pore-forming agent. The active material composition is composed of an active material, a hydrophilic agent, a conductive agent, a binder, and a structural agent. The pore-forming agent is composed of polyvinyl alcohol fibers and soluble salts.

2. The porous electrode plate for electro-deintercalation and extraction of lithium according to claim 1, characterized in that, The porous electrode plate used for electro-deintercalation and lithium extraction satisfies one or more of the following characteristics:

1. The thickness of the single-sided slurry coating of the porous electrode plate used for electro-deintercalation and lithium extraction is 1-3 mm; 2. The water adsorption capacity of the porous electrode plate used for electro-deintercalation and extraction of lithium is 0.40 g / g-0.95 g / g; 3. The resistance of the porous electrode plate used for electro-deintercalation and lithium extraction is 60mΩ-300mΩ; IV. The lithium extraction capacity of the porous electrode plate used for electro-deintercalation and lithium extraction is 7.0 mg / g-17.6 mg / g.

3. A method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to any one of claims 1 to 2, characterized in that, Includes the following steps: Step S1: Prepare electrode paste; Step S2: Coat the electrode paste on both sides of the current collector, and dry it after coating to obtain the coated electrode plate; Step S3: Place the dried coated electrode plate on a hot press for flat pressing, then soak it in water, and then rinse it with water to obtain a porous electrode plate for electro-deintercalation and lithium extraction. In step S1, the electrode slurry is composed of a solvent, an active material composition, and a pore-forming agent. The active material composition is composed of an active material, a hydrophilic agent, a conductive agent, a binder, and a structural agent. Or / and, the process of preparing the electrode paste is to first mix the hydrophilic agent and binder with the solvent to obtain a colloid, and then add the conductive agent, active material, structural agent and pore-forming agent to the colloid for mixing; The pore-forming agent is composed of polyvinyl alcohol fibers and soluble salts.

4. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 3, characterized in that, The active material includes at least one of lithium iron phosphate, lithium manganese oxide, and lithium manganese iron phosphate. Or / and, the hydrophilic agent includes at least one of polyethylene glycol, polydopamine, chitosan or polyvinyl alcohol; Or / and, the conductive agent includes at least one of conductive carbon, conductive graphite, Ketjen black, or carbon nanotubes; Or / and, the adhesive comprises at least one of polyvinylidene fluoride or polyvinylidene fluoride; Or / and, the structural agent is carbon fiber.

5. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 3, characterized in that, The active material composition comprises, by weight percentage, 67wt%-85wt% of active material, 2wt%-10wt% of hydrophilic agent, 4wt%-10wt% of conductive agent, 4wt%-10wt% of binder, and 1wt%-3wt% of structural agent; Or / and, the content of the solvent is 90wt%-130wt% of the weight of the active material composition.

6. The method for preparing a porous electrode plate for electro-extraction and extraction of lithium according to any one of claims 3 to 4, characterized in that, The content of the pore-forming agent is 11wt%-40wt% of the weight of the active material composition; Or / and, the weight ratio of polyvinyl alcohol fiber to soluble salt in the pore-forming agent is (0.1-1.2):1; Or / and, the chopped length of the polyvinyl alcohol fiber is 2-6 mm and the fiber diameter is less than 20 μm; Or / and, the soluble salt includes at least one of NaCl, KCl, K2SO4, Na2SO4 or KNO3; Or / and, the particle size of the soluble salt is 50-300 mesh.

7. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 3, characterized in that, In step S2, the current collector of the porous electro-deintercalation lithium electrode plate includes at least one of titanium mesh, ruthenium-iridium plated titanium mesh, graphite plate or carbon fiber cloth. Or / and, the drying process includes first holding at 40-55°C for 7-9 hours, and then holding at 75-90°C for 10-14 hours.

8. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 3, characterized in that, In step S3, the hot press is set to a temperature of 65-80℃, a pressure of 0.2-0.8MPa, and a plate compression ratio of 20%-50%. Or / and, the soaking time is 22-26 hours; Or / and, the rinsing time is 15-30 minutes.

9. An electro-deintercalation and extraction device for lithium, characterized in that, The electro-deintercalation lithium extraction device includes a porous electrode plate for electro-deintercalation lithium extraction as described in any one of claims 1 to 2.

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