Porous pole plate for electrically de-intercalating and extracting lithium, preparation method of porous pole plate and device for electrically de-intercalating and extracting lithium

Abstract

The invention belongs to the technical field of electrochemical lithium extraction, and relates to a porous pole plate for electric de-intercalation lithium extraction, a preparation method of the porous pole plate and an electric de-intercalation lithium extraction device. The porous pole plate for electric de-intercalation lithium extraction comprises a current collector and slurry coatings on two sides of the current collector, wherein the slurry coatings have pore structures formed by connectivity macropores and internal micropores. The preparation method of the porous pole plate for electrically de-intercalating and extracting lithium comprises the following steps: (1) preparing electrode slurry; (2) coating two sides of a current collector with the electrode slurry, and drying after coating to obtain a coated pole plate; and (3) flatly pressing the dried coated polar plate in a hot press, soaking in water, and washing with water flow to obtain the porous polar plate for electrically de-intercalating and extracting lithium. According to the invention, the polyvinyl alcohol fiber and the soluble salt are added into the electrode slurry as the pore-forming agent, and a flat pressing process is introduced to manufacture the polar plate, so that ion conduction and electron conduction in the running process of the polar plate are improved, and the lithium extraction performance of the polar plate is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical lithium extraction, and specifically relates to a porous electrode plate for electrochemical lithium extraction, a preparation method thereof, and an electrochemical lithium extraction device. Background Art

[0002] As a key element of the modern electric vehicle revolution, lithium is called the energy metal of the 21st century and is often used in the manufacture of electric vehicles, portable computers, power tools and power supplies. With the continuous development of new energy vehicles, the impact of lithium resources in the energy field has further increased.

[0003] The main processes for lithium extraction from brine include evaporation crystallization, solvent extraction, adsorbent and membrane separation. Compared with these methods, electro-deintercalation lithium extraction technology, as an emerging lithium extraction method, has the characteristics of green environmental protection, low energy consumption and low electrode material loss; its principle is to use the difference in electrochemical properties between lithium ions and other coexisting ions, and to control the potential so that the electrode can selectively insert / extract lithium ions. For example, CN 116964233A discloses a high-efficiency salt lake lithium extraction electrode material and lithium extraction electrode, which uses lithium titanium oxide-coated LiFePO4 / FePO4 as an electrode pair, and after power is applied, lithium ions are embedded in the cathode electrode and extracted, while the lithium ions in the anode electrode are released into a clean solution to achieve lithium recovery and enrichment. This lithium extraction method has the advantages of high selectivity and environmental friendliness. At present, due to the influence of ion conduction and electron conduction in the lithium extraction process, the electro-deintercalation lithium extraction technology has problems such as low lithium extraction efficiency and poor stability, which greatly limits the application and development of the electro-deintercalation lithium extraction technology. Therefore, it is necessary to develop a simple and reliable method to produce an electrode with excellent performance for electro-deintercalation and lithium extraction, so as to improve the problem of poor ion conduction and electron conduction in the process of lithium extraction from the electrode, and thus improve the lithium extraction performance of the electrode.

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

[0005] In view of the problems of low lithium extraction efficiency and poor stability in the existing electro-deintercalation and lithium extraction technology, the purpose of the present invention is to provide a porous electrode plate for electro-deintercalation and lithium extraction, a preparation method thereof and an electro-deintercalation and lithium extraction device, aiming to optimize the electronic conduction and ion conduction in the process of lithium extraction from the electrode plate, thereby improving the lithium extraction performance of the electrode plate.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

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

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

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

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

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

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

[0014] S1. preparing electrode slurry;

[0015] S2, coating the electrode slurry on both sides of the current collector, and drying after coating to obtain a coated electrode plate;

[0016] S3, placing the dried coated electrode plate on a hot press for flat pressing, then soaking it in water, and finally rinsing it with water to obtain a porous electrode plate for electrical deintercalation and extraction of lithium.

[0017] The flat pressing process adopted in the present invention can compress the coating, increase the contact between the coatings, enhance the conductivity, greatly shorten the path of electron conduction in the electrode during the electrical deintercalation process, increase the electron transmission 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, and 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 slurry in step S1 is to first mix the hydrophilic agent and the binder with the solvent to obtain a glue solution, and then add the conductive agent, the active material, the structural agent and the pore-forming agent into the glue solution for mixing;

[0020] In an optional embodiment, the active material includes at least one of lithium iron phosphate, lithium manganese oxide, and lithium iron manganese 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 binder 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 consists of polyvinyl alcohol fibers and soluble salts;

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

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

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

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

[0030] In an optional embodiment, the short cut 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 the present invention contains not only soluble salts but also water-soluble polyvinyl alcohol fibers. When used in combination with the soluble salts, the interconnected pore structure formed after the linear polyvinyl alcohol fibers are dissolved can effectively avoid the problem of uneven cracks in the electrode plate, solve the difficulty of poor connectivity of the ion flow channel, and effectively control the degree of cracks inside the electrode plate, so that lithium ions have a good path during the transmission process, the ion conduction is smoother during the electrical deintercalation process, the brine circulation is accelerated, the concentration polarization is reduced, the ion conduction during the operation of the electrode plate is improved, and the lithium extraction performance of the electrode plate is improved.

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

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

[0036] In an optional embodiment, the setting temperature of the hot press in step S3 is 65-80° C., the pressure is 0.2-0.8 MPa, and the compression ratio of the plate is 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 flushing time in step S3 is 15-30 minutes to remove the soluble substances remaining on the surface of the electrode plate.

[0039] In a third aspect, the present invention provides an electro-deintercalation and lithium extraction device, which comprises the porous electro-deintercalation and lithium extraction 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 a pore-forming agent, water-soluble polyvinyl alcohol fiber, to the electrode slurry, and the formed pore structure can effectively avoid the problem of uneven cracks in the electrode plate and solve the difficulty of poor connectivity of the ion flow channel. This makes the degree of cracks inside the electrode plate controllable, allowing lithium ions to have a good path during the transmission process, and ion conduction is smoother during the electrical deintercalation process, which accelerates the brine circulation, reduces concentration polarization, enhances ion conduction during the operation of the electrode plate, and improves the lithium extraction performance of the electrode plate.

[0042] (2) The present invention adds a flat pressing process during the preparation of the electrode plate, which not only improves the compaction density of the electrode plate, but also increases the contact area between the slurry coating and enhances the conductivity, making the internal connection of the coating tighter, greatly shortening the electron conduction path of the electrode plate during the electrical deintercalation process, increasing the electron transmission rate, and effectively improving the electron conduction of the electrode plate, thereby improving the energy density and lithium extraction efficiency of the electrode plate.

[0043] Other aspects will be apparent upon reading and understanding the drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0045] Figure 1 The SEM images of (a) the porous electrode plate for lithium electrolysis and extraction prepared in Example 1 of the present invention and (b) the electrode plate for lithium electrolysis and extraction prepared in Comparative Example 1 without adding a pore-forming agent;

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

[0047] Figure 3 The EIS graphs of the porous plates for lithium electrolysis and extraction prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present disclosure and should not be regarded as specific limitations of the present invention.

[0049] It should be noted that, if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturers are not specified, are all conventional products that can be purchased commercially.

[0050] The present invention provides a porous lithium-extraction electrode plate, which includes a current collector and a slurry coating on both sides of the current collector, wherein the slurry coating has a pore structure formed by interconnected macropores and internal micropores, wherein the slurry coating is formed by drying an electrode slurry.

[0051] The present invention provides a method for preparing a porous lithium-extraction electrode, which comprises the following steps:

[0052] S1. preparing electrode slurry;

[0053] S2, coating the electrode slurry on both sides of the current collector, and drying after coating to obtain a coated electrode plate;

[0054] S3, placing the dried coated electrode plate on a hot press for flat pressing, then soaking it in water, and finally rinsing it with water to obtain a porous electrode plate for lithium extraction by electric deintercalation.

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

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

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

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

[0059] In some embodiments, the content of the pore former 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 values ​​not listed within the above numerical 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, and other values ​​not listed within the above numerical range are also applicable;

[0061] The content of the pore former in the electrode slurry of the present invention will affect the physical strength and electrochemical performance of the electrode plate. If the content is too low, the electrode plate cannot provide a good ion transmission channel path, the ion conduction of the electrode plate deteriorates, and the electrochemical performance of the electrode plate is poor. If the content is too high, there are too many cavities inside the electrode plate, and the coatings cannot be tightly connected. On the one hand, the electronic conduction ability is also deteriorated. On the other hand, the physical strength of the electrode plate is low and the coating is easy to fall off.

[0062] The pore-forming agent water-soluble polyvinyl alcohol fiber and soluble salt are used together in the electrode slurry of the present invention, and the two can improve the performance of the electrode plate. If the mass ratio of polyvinyl alcohol fiber to soluble salt is too high or too low, the electrochemical performance of the electrode plate will be poor. The macropores formed by polyvinyl alcohol fiber can provide a good path for ion transmission, making ion conduction smoother, and the inside of the coating without macropores also needs to conduct ions. The addition of soluble salt just makes up for this part of the transmission channel. The two complement each other and can achieve better results.

[0063] S2. Use a coating mold to coat the electrode slurry on both sides of the current collector titanium mesh. The coating thickness is consistent with the coating mold. After the coating is completed, it is dried to obtain a coated electrode plate.

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

[0065] S3, placing the dried coated electrode plate on a hot press for flat pressing, and setting the temperature, pressure and compression ratio, and then soaking the electrode plate in water, and then rinsing with water to obtain a porous electrode plate for lithium electro-deintercalation.

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

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

[0069] In the flat pressing process adopted by the present invention, the compression ratio of the electrode plate will affect 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, causing the ion conduction of the electrode plate to deteriorate, and there is a risk of coating crushing, which will lead to deterioration of the electrochemical performance of the electrode plate; if the compression ratio of the electrode plate is too low, the contact between the coatings is not well enhanced, and the effect of enhancing the electronic conduction of the electrode plate will not be achieved.

[0070] The features and performance of the present invention are further described in detail below in conjunction with the 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, PEG and PVDF are first added to the solvent N-methylpyrrolidone (NMP) and stirred to dissolve to form a glue solution, and then SP, LFP and CF are dry-mixed, mixed evenly, and added to the prepared glue solution and stirred evenly, and finally NaCl (150 mesh) and polyvinyl alcohol fiber (short fiber length is 3mm, fiber diameter is less than 10μm) are added and stirred evenly to form an electrode slurry. Among them, in the active material composition, the proportion of each component is 4.7wt% PEG, 5.3wt% PVDF, 78.6wt% LFP (lithium removal rate 20%), 9.6wt% SP, 1.8wt% CF by mass percentage; the content of NMP is 100wt% of the mass of the active material composition; the total content of the pore-forming agent is 30wt% of the mass of the active material composition, and the mass ratio of polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.5:1, that is, the content of the two is: 20wt% NaCl, 10wt% polyvinyl alcohol fiber.

[0074] S2. Use a 2mm coating mold to coat the electrode slurry prepared in S1 on both sides of the current collector titanium mesh. The coating thickness is consistent with the coating mold. After coating, bake at 50°C for 8h and then bake at 85°C for 12h to obtain a coated electrode plate.

[0075] S3. Place the dried coated plate in a hot press at a temperature of 70°C and a pressure of 0.5 MPa with a compression ratio of 35%; then place the plate in 200 mL of water and stir and soak for 24 hours to dissolve the NaCl and polyvinyl alcohol fibers in the plate; then rinse the plate under water for 20 minutes to rinse off the residual soluble substances on the surface of the plate to obtain a porous plate for electro-deintercalation and lithium extraction.

[0076] The SEM images of the porous electrode plate for lithium electrolysis and extraction prepared in this embodiment and the electrode plate for lithium electrolysis and extraction prepared in comparative example 1 without adding pore-forming agent are shown in FIG. Figure 1 As shown in the figure, it can be seen that the coating has a pore structure formed by interconnected macropores and internal micropores. The schematic diagram of the flat pressing process of the porous electrode plate for lithium extraction prepared in this embodiment is as follows Figure 2 As shown in the figure, it can be seen that the internal contact of the plate coating is closer 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. The same as step S1 of Example 1, except that the total content of the pore-forming agent is 27wt% of the mass of the active material composition, and the mass ratio of the polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.8:1, that is, the content of the two is: 15wt% NaCl, 12wt% polyvinyl alcohol fiber.

[0080] S2. Use a 2mm coating mold to coat the electrode slurry prepared in S1 on both sides of the current collector titanium mesh. The coating thickness is consistent with the coating mold. After coating, bake at 40°C for 9 hours and then bake at 75°C for 14 hours to obtain a coated electrode plate.

[0081] S3. Place the dried coated plate in a hot press at a temperature of 70°C and a pressure of 0.5 MPa with a compression ratio of 35%; then place the plate in 200 mL of water and stir and soak for 22 hours to dissolve the NaCl and polyvinyl alcohol fibers in the plate; then rinse the plate under water for 15 minutes to rinse off the residual soluble substances on the surface of the plate to obtain a porous plate for electro-deintercalation and lithium extraction.

[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 those 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 the 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, 1 wt% polyvinyl alcohol fiber.

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

[0086] S2. Use a 2mm coating mold to coat the electrode slurry prepared in S1 on both sides of the current collector titanium mesh. The coating thickness is consistent with the coating mold. After coating, bake at 55°C for 7h and then bake at 90°C for 10h to obtain a coated electrode plate.

[0087] S3. Place the dried coated plate in a hot press at a temperature of 70°C, a pressure of 0.5 MPa, and a compression ratio of 35%; then place the plate in 200 mL of water and stir and soak for 26 hours to dissolve the NaCl and polyvinyl alcohol fibers in the plate; then rinse the plate under water for 30 minutes to rinse off the residual soluble substances on the surface of the plate to obtain a porous plate for electro-deintercalation and lithium extraction.

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

[0091] The ratio of the active material composition was changed: 2wt% PEG, 6wt% PVDF, 85wt% LFP (lithium removal 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, PEG and PVDF are first added to the solvent NMP and stirred to dissolve to form a glue solution, and then SP, LFP and CF are dry-mixed, mixed evenly, added to the prepared glue solution and stirred evenly, and finally NaCl and polyvinyl alcohol fiber are added and stirred evenly to form an electrode slurry. Among them, in the active material composition, the proportion of each component is 10wt% PEG, 10wt% PVDF, 67wt% LFP (20% lithium removal), 10wt% SP, 3wt% CF, calculated by mass percentage; the content of NMP is 130wt% of the mass of the active material composition; the total content of the pore-forming agent is 40wt% 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 content of the two is: 20wt% NaCl, 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 lithium electrolysis and extraction. The specific steps of the method are the same as those of 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 lithium electrolysis and extraction. The specific steps of the method are the same as those of 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. The same as step S1 of Example 1, except that the total content of the pore-forming agent is 30wt% of the mass of the active material composition, and the mass ratio of the polyvinyl alcohol fiber to NaCl in the pore-forming agent is 0.2:1, that is, the content of the two is: 25wt% NaCl, 5wt% 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. The same as step S1 of Example 1, except that the total content of the pore-forming agent is 30wt% of the mass of the active material composition, and the mass ratio of the polyvinyl alcohol fiber to NaCl in the pore-forming agent is 1:1, that is, the contents of the two are: 15wt% NaCl, 15wt% 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 a lithium-extraction electrode plate, the method comprising the following steps:

[0111] No pore former is added when preparing electrode slurry:

[0112] S1. According to the formula, PEG and PVDF are first added to the solvent NMP and stirred to dissolve to form a glue solution, and then SP, LFP and CF are dry-mixed, mixed evenly, added to the prepared glue solution and stirred evenly to form an electrode slurry. Among them, in the active material composition, the proportion of each component is 4.7wt% PEG, 5.3wt% PVDF, 78.6wt% LFP (lithium removal rate 20%), 9.6wt% SP, 1.8wt% CF by mass percentage; the content of NMP is 100wt% of the mass 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] Flat pressing process is not used when preparing the plate:

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

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

[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] When preparing electrode slurry, no pore-forming agent polyvinyl alcohol fiber is added:

[0122] S1. According to the formula, PEG and PVDF are first added to the solvent NMP and stirred to dissolve to form a glue solution, and then SP, LFP and CF are dry-mixed, mixed evenly, added to the prepared glue solution and stirred evenly, and finally NaCl is added and stirred evenly to form an electrode slurry. Among them, in the active material composition, the proportion of each component is 4.7wt% PEG, 5.3wt% PVDF, 78.6wt% LFP (20% lithium removal), 9.6wt% SP, 1.8wt% CF, calculated by mass percentage; the content of NMP is 100wt% of the mass of the active material composition; 30wt% NaCl (the content of the pore-forming agent is 30wt% of the mass 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 when preparing electrode slurry:

[0127] S1. According to the formula, PEG and PVDF are first added to the solvent NMP and stirred to dissolve to form a glue solution, and then SP, LFP and CF are dry-mixed, mixed evenly, added to the prepared glue solution and stirred evenly, and finally polyvinyl alcohol fiber is added and stirred evenly to form an electrode slurry. Among them, in the active material composition, the proportion of each component is 4.7wt% PEG, 5.3wt% PVDF, 78.6wt% LFP (20% lithium removal), 9.6wt% SP, 1.8wt% CF, calculated by mass percentage; the content of NMP is 100wt% of the mass of the active material composition; 30wt% polyvinyl alcohol fiber (the content of the pore-forming agent is 30wt% of the mass 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 electric deintercalation and lithium extraction plates prepared in Examples 1-9 and Comparative Examples 1-4 were evaluated, specifically comprising the following steps:

[0131] (1) Water absorption test

[0132] Place the plate in a certain volume of pure water and soak it for 2 hours. The aqueous solution is required to completely immerse the plate. Measure the mass difference M (g) before and after the plate absorbs water. The mass of the plate coating is m (g), and the water absorption is M / m (g / g).

[0133] (2) Resistance test

[0134] The plate resistance was measured using a resistance meter RM3544 manufactured by Hioki Electric Co., Ltd. The positive electrode of the resistance meter was clamped between the current collector titanium mesh, and the negative electrode was clamped between the coating. The average value of the resistance data at the six points was taken as the plate resistance.

[0135] (3) Electrochemical performance test

[0136] Wuhan Blue Electric Battery Testing System CT3002K was used to measure the electrochemical performance of the plate. The Blue Electric positive and negative electrode clips were clamped on the plate ears for testing. The rate test step was 0.1C / 0.2C / 0.5C 3 times each, and the cycle step was 0.2C long cycle test.

[0137] (4) Lithium extraction performance test

[0138] The Wuhan Blue Electric Battery Test System CT3002K is used to measure the specific capacity of the plate at 0.1C, and the theoretical lithium extraction amount of the plate is calculated based on the average specific capacity of the plate. During the test, first clamp the pole ear of the plate with a glass electrode clamp to ensure good contact. Then assemble the glass electrode clamp into the brine solution of the electric deintercalation and lithium extraction device to ensure that the brine covers the entire coating of the plate and that the plates are on the same horizontal line. Finally, clamp the positive and negative poles of the Blue Electric electrode clamp of the Blue Electric test system with the pole ears of the glass electrode clamp, set the rate and cycle test program in the Blue Electric test software, and start the test process.

[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 Examples 1-9, when the pore former content and the plate compression ratio are within a limited range, the porous plate for lithium electrolysis prepared by the method of the present invention can effectively improve its electronic and ion conduction capabilities, reduce the plate impedance and resistance, and enhance the electrochemical performance of the plate.

[0145] From the comparison between Example 1 and Comparative Example 1, it can be seen that the present invention forms pores by adding soluble substances, namely water-soluble polyvinyl alcohol fibers and soluble salts, into the electrode plate, which forms a pore structure formed by interconnected macropores and internal micropores inside the electrode plate, thereby reducing the electrode impedance and enhancing the ion diffusion capacity, thereby making the electrode plate have excellent rate performance and cycle performance, and enhancing the lithium extraction capacity.

[0146] By comparing Example 1 and Comparative Example 2, it can be seen that the porous electrode plate for lithium electro-deintercalation prepared by the present invention adopts a flat pressing process. Compared with Comparative Example 2, the internal contact of the electrode coating after the electrode plate is flat pressed is tighter, 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] By comparing Example 1 with Comparative Examples 3-4, it can be seen that the electrical properties and lithium extraction performance of the electrode plate of Example 1 are more excellent. The present invention uses water-soluble polyvinyl alcohol fibers and soluble salts to form pores in the slurry coating, forming a pore structure of interconnected macropores and internal micropores, which is conducive to fully exerting the electrochemical properties and lithium extraction performance of the electrode plate.

[0148] In summary, the present invention adds water-soluble fibers and soluble salts in the process of preparing porous electro-deintercalation and lithium extraction plate electrode slurry, and then dissolves them by water immersion to form pores, which effectively solves the difficulty of poor connectivity of ion channels, improves ion conduction during the operation of the plate, and improves the lithium extraction performance of the plate. In addition, the flat pressing process is added in the process of plate preparation, which greatly increases the energy density of the plate on the one hand, and increases the contact area between the slurry coating on the other hand, making the internal connection of the coating more compact, effectively improving the electronic conduction of the plate, and improving the lithium extraction efficiency of the plate.

[0149] The applicant declares that the above is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A porous plate for lithium electrolysis, characterized in that: The porous electrode plate for electric deintercalation and extraction of lithium comprises a current collector and a slurry coating on both sides of the current collector, wherein the slurry coating has a pore structure formed by interconnected macropores and internal micropores.

2. The porous electrode plate for electro-deintercalation and extraction of lithium according to claim 1, characterized in that: The porous plate for lithium electrolysis and extraction satisfies one or more of the following characteristics ① to ④: ① The thickness of the slurry coating on one side of the porous plate for lithium electrolysis is 1-3 mm; ② The water adsorption capacity of the porous plate used for electro-deintercalation and extraction of lithium is 0.40g / g-0.95g / g; ③ The resistance of the porous plate used for electro-deintercalation and extraction of lithium is 60mΩ-300mΩ; ④ The lithium extraction amount of the porous plate used for electrical deintercalation and extraction of lithium is 7.0 mg / g-17.6 mg / g.

3. A method for preparing a porous electrode plate for lithium electrolysis according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step S1, preparing electrode slurry; Step S2, coating the electrode slurry on both sides of the current collector, and drying after coating to obtain a coated electrode plate; Step S3, placing the dried coated electrode plate on a hot press for flat pressing, then soaking it in water, and finally rinsing it with water to obtain a porous electrode plate for electrical deintercalation and extraction of lithium.

4. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 3, characterized in that: In step S1, the electrode slurry is composed of a solvent, an active material composition and a pore-forming agent, and 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 slurry is to first mix the hydrophilic agent and the binder with the solvent to obtain a glue solution, and then add the conductive agent, the active material, the structural agent and the pore-forming agent into the glue solution for mixing.

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

6. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to claim 4, characterized in that: Calculated by weight percentage, the content of each component in the active material composition is: 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.

7. The method for preparing a porous electrode plate for electro-deintercalation and extraction of lithium according to any one of claims 4 to 5, characterized in that: The content of the pore former 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 short cut length of the polyvinyl alcohol fiber is 2-6 mm, and the fiber diameter is less than 20 μm; Or / and, the soluble salt comprises at least one of NaCl, KCl, K2SO4, Na2SO4 or KNO3; Or / and, the particle size of the soluble salt is 50-300 mesh.

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 S2, the current collector of the porous lithium electrode comprises at least one of a titanium mesh, a ruthenium-iridium-plated titanium mesh, a graphite plate or a carbon fiber cloth; Or / and, the drying includes first keeping warm at 40-55°C for 7-9 hours, and then keeping warm at 75-90°C for 10-14 hours.

9. 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 setting temperature of the hot press is 65-80°C, the pressure is 0.2-0.8MPa, and the plate compression ratio is 20%-50%; Or / and, the soaking time is 22-26h; Or / and, the flushing time is 15-30min.

10. An electro-deintercalation lithium extraction device, characterized in that: The electro-deintercalation and lithium extraction device comprises the porous electrode plate for electro-deintercalation and lithium extraction as described in any one of claims 1 to 2.

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