A granular electrode for lithium extraction, its preparation method and application

Abstract

This invention belongs to the field of lithium extraction technology, and relates to a granular electrode for lithium extraction, its preparation method, and its application. The electrode preparation method involves first mixing electrode active materials, auxiliary materials, and a dispersant to obtain an active material slurry, then granulating and drying it into electrode active particles, and finally stacking these particles on the surface of a current collector to form the electrode. In this method, the granulated active material, due to its uniform geometric distribution, results in small deviations in current density during electrolysis and stable electrode quality. Furthermore, the granulation process is simple, eliminating the need for complex slurry preparation and precise viscosity control, saving the solvent drying and recovery step, reducing process complexity and energy consumption, and improving efficiency. The stable granulated stacking structure enhances the bonding strength between the active material and the current collector, solving the problem of easy coating detachment. Moreover, the granular active material filler is easy to replace, and can be directly removed if it fails. The unit amount of lithium extraction current collector used is small, and standardized granular production enables large-scale, quality-controlled production, effectively reducing costs.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology, specifically relating to a granular electrode for lithium extraction, its preparation method, and its application. Background Technology

[0002] In existing electrochemical lithium extraction processes, the coating of active materials is a crucial step. Currently, the common method is to uniformly coat the active material onto the surface of a metal current collector. A similar scenario, such as the manufacturing of positive and negative electrodes for lithium-ion batteries, involves uniformly coating the electrode active material onto the surface of a metal current collector, such as copper or aluminum foil, using specialized equipment like transfer coating machines or extrusion coating machines to form the positive and negative electrode sheets. This traditional active material coating method has several drawbacks. The preparation of the slurry during the coating process is extremely demanding. Active materials, conductive agents, binders, and solvents must be mixed using high-speed stirring, planetary stirring, or twin-screw extruders to ensure a uniform, particle-free slurry with precise viscosity control. Even so, in practice, the viscosity of the slurry is still easily affected by various factors, such as changes in the properties of conductive carbon, binders, and solvents, leading to unstable coating quality. Furthermore, the drying and recovery of solvents during the coating process is not only an energy-intensive and costly process, but also requires extremely precise process parameters. Drying too quickly can lead to skinning or cracking of the coating surface, reducing the adhesion of the active material to the carrier material; drying too slowly will severely impact production efficiency. Additionally, numerous problems exist in the subsequent calendering process. During calendering, uneven stretching between coated and uncoated areas can easily cause wrinkling; high compression can lead to lithium plating in the anode, while low compression can cause a loss of cathode conductivity. Moreover, during dry mixing, strong mixing stress can cause conductive carbon black to clump, reducing slurry viscosity and affecting coating quality. Coatings formed through electrostatic aerosol discharge have low adhesion and are prone to delamination during winding. During coating and calendering with rollers, the carrier material can also wrinkle, and heating the calendering rollers to ensure calendering results further increases energy consumption.

[0003] Patent documents with application numbers 202110555919.7, patent number 202110555785.9, and patent number 202410189686.7 all propose electrode preparation methods for electrochemical / electrochemical lithium extraction. However, these patents focus on solving problems related to the hydrophilicity, conductivity, and adhesion of active materials, essentially still involving coating onto rigid titanium mesh, titanium plates, or graphite current collectors. Problems remain, including high current collector costs and difficulties in recycling, low effective area leading to current collector waste, difficulty in controlling coating precision and automation, poor consistency, and the inherent difference in surface properties between the current collector and organic binders resulting in poor adhesion and easy powder shedding or even detachment during operation. Summary of the Invention

[0004] To overcome the technical problems of large coating quality fluctuations, cumbersome preparation processes, easy coating peeling, and high production costs in existing technologies, the purpose of this invention is to provide a granular electrode for lithium extraction, its preparation method, and its application. This preparation method employs an electrochemical intercalation-deintercalation method for lithium extraction. By abandoning the traditional active material coating process, it uses a method of granulating active materials and then stacking them around the current collector, achieving a significant improvement in lithium extraction efficiency, a substantial reduction in production costs, and enhanced process stability and environmental adaptability. This method uses a conductive adsorption particle design to replace the traditional current collector coating process, achieving highly efficient lithium extraction and recovery.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0007] S1: After mixing the electrode active material, auxiliary materials and dispersant, an active material slurry is obtained;

[0008] The electrode active material is a lithium-ion battery cathode material;

[0009] The auxiliary material consists of a binder, a conductive agent, a pore-forming agent, and a hydrophilic agent;

[0010] S2: Granulate the active material mud and then dry it to obtain electrode active particles;

[0011] S3: The electrode active particles are deposited on the surface of the current collector to obtain the granular electrode for lithium extraction.

[0012] Preferably, the solid content of the active material mud is 30% to 85%.

[0013] Preferably, the auxiliary material is composed of a binder, a conductive agent, a pore-forming agent, and a hydrophilic agent; based on the total mass of the electrode active material and the auxiliary material being 100%, the electrode active material accounts for 70% to 90%, the binder accounts for 2% to 8%, the conductive agent accounts for 3% to 15%, the pore-forming agent accounts for 3% to 15%, and the hydrophilic agent accounts for 1% to 6%; the dispersant accounts for 90% to 130% of the total mass of the electrode active material and the auxiliary material.

[0014] Preferably, the particle size of the electrode active particles is 0.5~3mm.

[0015] Preferably, during the stacking process, the stacking thickness is controlled to be 3.0~10.0 mm, and the porosity after stacking is 20%~50%.

[0016] Preferably, the porosity after stacking is controlled by particle gradation or layered stacking method when the electrode active particles are stacked on the surface of the current collector.

[0017] Preferably, the particle size distribution method is as follows: by mass percentage, the proportion of electrode active particles with a particle size of 0.5~1mm is 20%~30%, the proportion of electrode active particles with a particle size of 1~2mm is 40%~50%, and the proportion of electrode active particles with a particle size of 2~3mm is 20%~30%.

[0018] Preferably, the layered stacking method specifically includes bottom layer particles, middle layer particles, and top layer particles;

[0019] By mass percentage, the bottom layer particles comprise 60% to 70% electrode active particles with a diameter of 2 to 3 mm and 30% to 40% electrode active particles with a diameter of 1 to 2 mm.

[0020] Of the intermediate layer particles, 30% are electrode active particles with a particle size of 2-3 mm, 50% are electrode active particles with a particle size of 1-2 mm, and 20% are electrode active particles with a particle size of 0.5-1 mm.

[0021] In the top layer of particles, electrode active particles with a particle size of 1-2 mm account for 50%-60%, and electrode active particles with a particle size of 0.5-1 mm account for 40%-50%.

[0022] A particulate electrode for lithium extraction is prepared by the method described above.

[0023] The above-mentioned application of a particulate electrode for lithium extraction in electrochemical lithium extraction.

[0024] Compared with the prior art, the method of the present invention has at least the following beneficial effects:

[0025] This invention discloses a method for preparing granular electrodes for lithium extraction. Firstly, the method involves granulating and stacking active materials. The particles achieve a uniform distribution due to their geometric morphology, resulting in minimal deviation in current density distribution during electrolysis and ensuring the stability of electrode quality. The binder in the auxiliary materials helps enhance the bonding force within the particles and between the particles and the current collector; the conductive agent improves the electrode's conductivity; the pore-forming agent creates a porous structure, facilitating lithium-ion transport; and the hydrophilic agent improves the electrode's hydrophilicity, thus optimizing the performance of the active particles. Secondly, regarding the preparation process, traditional coating methods require stringent slurry preparation, precise viscosity control, and costly solvent drying and recovery, with stringent parameter requirements. This method, however, simplifies the active material granulation process, eliminating the need for complex slurry preparation and precise viscosity control. It also eliminates the solvent drying and recovery steps, reducing production steps, lowering process complexity and energy consumption, and improving production efficiency. Furthermore, regarding the issue of coating peeling, compared to coating methods which are prone to cracking and poor adhesion during drying and calendering, this method results in a more stable structure after granulation, with tighter bonding between particles. This enhances the bonding strength between the active material and the current collector, solving the problems of poor adhesion and easy powder shedding in coated electrodes. Moreover, traditional coated electrodes are complex to replace and recycle, and the current collector is costly and difficult to recycle. This method uses granular active material fillers, simplifies the replacement process, and allows for direct replacement after failure without complex disassembly. It uses less current collector per unit lithium extraction, and standardized particle production enables large-scale, quality-controlled production, reducing production costs.

[0026] Furthermore, the solid content of the active material slurry is 30% to 85%. A suitable solid content facilitates the smooth progress of subsequent granulation operations. If the solid content is too low, the material will be too thin during granulation, making it difficult to form stable particles; if the solid content is too high, the material will be too dry and hard, which is detrimental to granulation and the uniformity of particle quality. This range ensures that the active material slurry has good formability and uniformity during the granulation process, thereby obtaining electrode active particles of stable quality.

[0027] Furthermore, the auxiliary materials are composed of binders, conductive agents, pore-forming agents, and hydrophilic agents. Based on the total mass of the electrode active material and auxiliary materials as 100%, the electrode active material accounts for 70%–90%, the binder for 2%–8%, the conductive agent for 3%–15%, the pore-forming agent for 3%–15%, and the hydrophilic agent for 1%–6%. The dispersant accounts for 90%–130% of the total mass of the electrode active material and auxiliary materials. The binder in the auxiliary materials helps enhance the bonding force between the particles and between the particles and the current collector; the conductive agent improves the conductivity of the electrode; the pore-forming agent forms a porous structure, which is beneficial for lithium ion transport; and the hydrophilic agent improves the hydrophilicity of the electrode. The reasonable setting of the proportions of each component can optimize the performance of the electrode active particles, such as conductivity, structural stability, and ion transport performance. At the same time, a reasonable range of dispersant proportions helps to ensure uniform mixing of the active material slurry.

[0028] Furthermore, the particle size of the electrode active particles is 0.5~3mm, which is conducive to particle accumulation on the current collector surface. If the particle size is too small, the particles may easily clog pores during accumulation, affecting ion transport; if the particle size is too large, the accumulation structure will not be dense enough, reducing the electrochemical performance of the electrode. A suitable particle size range can ensure the structural stability and electrochemical performance after particle accumulation.

[0029] Furthermore, during the stacking process, the stacking thickness is controlled to be 3.0~10.0 mm, and the porosity after stacking is 20%~50%. A suitable stacking thickness ensures that the electrode has sufficient active material to participate in the lithium extraction reaction, while avoiding excessive thickness that would lead to overly long ion transport paths and affect reaction efficiency. A suitable porosity facilitates electrolyte penetration within the electrode and lithium ion transport, thereby improving the electrode's electrochemical performance.

[0030] Furthermore, the electrode active particles are stacked on the surface of the current collector. The porosity after stacking is controlled by either particle gradation or layered stacking. These two methods allow for more precise control of the internal structure of the electrode to meet different electrochemical performance requirements. By rationally controlling the porosity, the distribution of the electrolyte and the lithium-ion transport path can be optimized, thereby improving the lithium extraction efficiency and stability of the electrode.

[0031] Furthermore, the particle gradation method is specifically as follows: by mass percentage, the proportion of electrode active particles with a particle size of 0.5~1mm is 20%~30%, the proportion of electrode active particles with a particle size of 1~2mm is 40%~50%, and the proportion of electrode active particles with a particle size of 2~3mm is 20%~30%. This gradation method allows particles of different sizes to fill each other, reducing the gaps between particles, increasing the compactness of the packing, and forming a reasonable pore structure, which is conducive to the penetration of electrolyte and the transport of lithium ions, thereby improving the electrochemical performance of the electrode.

[0032] Furthermore, the layered stacking method specifically includes bottom-layer particles, middle-layer particles, and top-layer particles; by mass percentage, in the bottom-layer particles, electrode active particles with a particle size of 2-3 mm account for 60%-70%, and electrode active particles with a particle size of 1-2 mm account for 30%-40%; in the middle-layer particles, electrode active particles with a particle size of 2-3 mm account for 30%, electrode active particles with a particle size of 1-2 mm account for 50%, and electrode active particles with a particle size of 0.5-1 mm account for 20%; in the top-layer particles... In the particles, electrode active particles with a particle size of 1~2mm account for 50%~60%, and electrode active particles with a particle size of 0.5~1mm account for 40%~50%. This layered stacking method can optimize the internal structure of the electrode according to the characteristics of particles with different sizes. The bottom layer of particles uses larger particles to provide a good support structure. The middle layer of particles is reasonably matched with particles of different sizes to ensure the uniformity of ion transport and reaction. The top layer of particles uses smaller particles to help improve the contact performance with the current collector, thereby improving the overall electrochemical performance and stability of the electrode. Attached Figure Description

[0033] To more clearly illustrate the present invention, the accompanying drawings used in the embodiments or technical description will be briefly described below. Obviously, the drawings described below are only embodiments of the present invention. Those skilled in the art can obtain other drawings from the following drawings without creative effort.

[0034] Figure 1 This is a SEM image of the electrode active particles prepared in Example 1 of the present invention;

[0035] Figure 2 This is a schematic diagram of the electrode system assembly structure in the lithium extraction experiment of the present invention, wherein 1 is an anion exchange membrane, 2 is a first active particle stacking layer, 3 is a current collector, 4 is a second active particle stacking layer, and 5 is a shell.

[0036] Figure 3 This is the lithium extraction cycle data of the particulate lithium iron phosphate active material in Example 3 of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether right or wrong, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0039] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

[0040] In this article, unless otherwise specified, terms such as "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0041] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0042] The present invention discloses a preparation method of a granular electrode for lithium extraction, comprising the following steps:

[0043] S1: After mixing the electrode active material, auxiliary materials, and dispersant, an active material mud, i.e., soft material, is obtained.

[0044] Among them, the electrode active material is a positive electrode material for a lithium-ion battery, specifically one or a mixture of several of LiFePO4 (lithium iron phosphate), LiMn2O4 (lithium manganate), LiNi x Co y Mn (1 x y) O2 (lithium nickel cobalt manganese oxide) ternary materials and their derivatives (where x > 0, y < 1, 0 < x + y < 1).

[0045] The electrode active material needs to be delithiated. The delithiation operation can be carried out before mixing or after granulation, that is, the electrode active material is delithiated before step S1 or after step S2 is completed to form a lithium-deficient active material. The delithiation amount is controlled at 10% - 50%.

[0046] The delithiation process here is a crucial step for the electrode active material and can be performed before mixing or after granulation. Its purpose is to induce a lithium-deficient state in the electrode active material, thereby improving its performance during lithium extraction. Specifically, delithiation before mixing involves directly processing the original electrode active material, while delithiation after granulation processes the granulated active material.

[0047] Common delithiation methods include electrochemical delithiation, which involves applying specific current and voltage to remove lithium ions from the electrode active material, and chemical delithiation, which uses suitable chemical reagents to react with the electrode active material to remove lithium ions, thereby forming a suitable low-lithiation active material.

[0048] The auxiliary materials consist of binders, conductive agents, pore-forming agents, and hydrophilic agents.

[0049] Preferably, the adhesive comprises at least one of polyester resin, epoxy resin, phenolic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylpyrrolidone, sodium carboxymethyl cellulose (CMC), polyaniline, styrene-butadiene rubber latex (SBR), polypropylene, and derivatives thereof, wherein the derivatives include hydrophilic derivatives or conductive derivatives.

[0050] The conductive agent includes at least one of graphite, graphene, super-P, Ketjen black, acetylene black, 3,4-ethylenedioxythiophene polymer (PEDOT), conductive metal nanoparticles, and carbon nanotubes.

[0051] The conductive metal nanopowder includes at least one of silver powder, titanium powder, and platinum powder.

[0052] The pore-forming agent is a solid soluble inorganic salt, preferably at least one of sodium chloride, potassium chloride, lithium chloride, ammonium bicarbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate.

[0053] The hydrophilic agent is at least one of a polymeric polyol and a polymeric alcohol amine.

[0054] The dispersant (i.e., solvent) includes at least one of ethanol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, isopropanol, propylene glycol, glycerol and their derivatives.

[0055] Dispersants are used to adjust the solid content of soft materials within the range of 30% to 85% to prevent molding difficulties caused by excessively low or high solid content.

[0056] Based on the total mass of electrode active material and auxiliary materials as 100%, the proportions of electrode active material are 70%~90%, binder is 2%~8%, conductive agent is 3%~15%, pore-forming agent is 3%~15%, and hydrophilic agent is 1%~6%; the mass of dispersant accounts for 90%~130% of the total mass of electrode active material and auxiliary materials. During the granulation process, the above raw material proportions can be finely adjusted as needed to enhance the binding force between particles and improve granulation stability, but the amount of each raw material must be strictly controlled to avoid negatively affecting the electrochemical performance of the active material.

[0057] S2: Granulate the active material mud and then dry it to obtain electrode active particles;

[0058] This invention forms the electrode active material into granules, eliminating the need for designing and preparing coating molds, thus solving the problem of uneven coating and enabling easy recycling and reuse of the current collector. Simultaneously, it allows for a larger effective amount of electrode active material, more thorough contact between the electrolyte and the active material, and highly controllable consistency in the electrochemical lithium extraction system.

[0059] The granulation principle of this invention involves using a granulation device to prepare particles of a certain shape and size from the soft material obtained in step S1. These particles are then dried at a specific temperature, resulting in the electrode active material product. Long-term storage of the electrode active particle product under certain conditions, with materials available as needed, facilitates the continuous and rapid replacement of electrochemical lithium extraction active materials.

[0060] The granulation method is generally wet granulation. This invention preferably uses rotary extrusion granulation and spray granulation, but equipment such as a spherical pelletizer can also be used to convert the obtained non-spherical particles into spherical particles.

[0061] Further preferably, the granules after wet granulation need to be dried by stepped heating to remove moisture. The stepped heating drying process is preferably to first dry at 30~60℃ for 2~8 hours, and then raise the temperature to 85~95℃ for 2~8 hours.

[0062] The granular active material prepared by this invention has a specific shape, including spherical, columnar, hollow columnar, teardrop, or other shapes. More preferably, it is spherical, columnar, or hollow columnar. Spherical particles have optimal packing density and flowability, ensuring uniform distribution within the electrolytic cell and reducing mass transfer dead zones; columnar particles have higher compressive strength, making them suitable for high-flow-rate electrolyte systems; hollow columnar particles increase specific surface area through their internal hollow structure, enhancing the electrolyte wetting effect.

[0063] Specifically, the prepared particulate active material has a certain size, preferably 0.5~3mm. The lower limit of the particle size is set at 0.5mm to avoid the migration and loss of excessively small particles during electrolyte circulation, and the upper limit is controlled at 3mm to ensure that the internal diffusion distance of the particles is ≤1.5mm, thereby reducing the loss of active material utilization.

[0064] The granular active material product prepared by this invention can be stored for a long time. In practical applications, it can be "taken out as needed" through a granule metering and feeding device. When replacing it, there is no need to disassemble the main structure of the electrochemical lithium extraction system, thus meeting the needs of uninterrupted production.

[0065] S3: The active electrode particles obtained by the present invention are stacked on the surface of a conductive current collector to form an electrochemical lithium extraction electrode, namely a granular electrode for lithium extraction, which can be used to perform electrochemical lithium extraction in a lithium extraction device.

[0066] The active electrode particles prepared according to this invention are stacked on the surface of a conductive current collector to form an electrochemical lithium extraction electrode. During the stacking process, the stacking thickness and density are controlled. The stacking thickness can be adjusted according to the specific design of the lithium extraction device and the actual lithium extraction requirements, and is maintained between 3.0 and 10.0 mm. By optimizing the stacking density, a structure that is both compact and has a certain porosity is formed between the active material particles, with the porosity controlled between 20% and 50%. Here, porosity is used to represent the stacking density. Such a structure is conducive to the rapid transport and intercalation / deintercalation of lithium ions in the active material, while ensuring effective electron conduction.

[0067] Further preferred methods include using particle size distribution or layered packing to optimize packing density, i.e., using particle size distribution or layered packing to control porosity after packing.

[0068] A further preferred embodiment of the particle size distribution is as follows: small particles: 0.5~1mm, accounting for 20%~30% (mass percentage, the same below); medium particles: 1~2mm, accounting for 40%~50%; large particles: 2~3mm, accounting for 20%~30%. That is, by mass percentage, electrode active particles with a particle size of 0.5~1mm account for 20%~30%, electrode active particles with a particle size of 1~2mm account for 40%~50%, and electrode active particles with a particle size of 2~3mm account for 20%~30%.

[0069] The layered stacking method is as follows: the bottom layer serves as a support layer, which can consist of 60% to 70% large particles (2-3 mm) and 30% to 40% medium particles (1-2 mm), excluding small particles; the middle layer serves as the main reaction layer, which can consist of 30% large particles (2-3 mm) + 50% medium particles (1-2 mm) + 20% small particles (0.5-1 mm); the top layer can consist of smaller particles, with 50% to 60% medium particles (1-2 mm) and 40% to 50% small particles (0.5-1 mm), excluding large particles.

[0070] That is, when the layered stacking method is adopted, it includes bottom layer particles, middle layer particles and top layer particles;

[0071] In the bottom layer of particles, electrode active particles with a particle size of 2-3 mm account for 60%-70%, and electrode active particles with a particle size of 1-2 mm account for 30%-40%.

[0072] Of the intermediate layer particles, 30% are electrode active particles with a particle size of 2-3 mm, 50% are electrode active particles with a particle size of 1-2 mm, and 20% are electrode active particles with a particle size of 0.5-1 mm.

[0073] In the top layer of particles, electrode active particles with a particle size of 1-2 mm account for 50%-60%, and electrode active particles with a particle size of 0.5-1 mm account for 40%-50%.

[0074] Furthermore, to enhance the conductivity between particles and between particles and the current collector, an appropriate amount of conductive material can be mixed with the active particle material before filling. The conductive material includes conductive carbon. Additionally, to prevent problems such as loose stacking during the stacking process, a method of simultaneous stacking and vibration can be employed.

[0075] In addition, such as Figure 2 As shown, this invention also discloses a granular electrode system for lithium extraction, including an anion exchange membrane 1, and cathode plates symmetrically arranged on both sides of the anion exchange membrane 1 and a housing 5; the cathode plate includes a current collector 3 and a first active particle stack layer 2 and a second active particle stack layer 4 stacked on both sides of the current collector 3. That is, the current collector stacked with lithium iron phosphate particles serves as the cathode plate, paired with a suitable anode (such as a titanium electrode), and the anion exchange membrane 1 is embedded between the cathode plates. For a specific assembly configuration, please refer to... Figure 2 ,like Figure 2As shown, the electrode system in this lithium extraction experiment includes an anion exchange membrane 1, and a first active particle stack 2, a current collector 3, a second active particle stack 4, and a shell 5 symmetrically arranged on both sides of the anion exchange membrane 1. The shell 5 is located on the outermost side and serves to protect and house the internal components. Next to the inner side of the shell is the second active particle stack 4, which is a lithium iron phosphate particle stack. The particles are stacked in a graded manner, with small particles (0.5~1mm) accounting for 25%, medium particles (1~2mm) accounting for 50%, and large particles (2~3mm) accounting for 25%. The horizontal thickness is 5mm and the porosity is 35%. Next is the current collector 3, which is a 70×70mm graphite plate current collector, used as a conductive electrode to collect current. After that is the first active particle stack 2, which is a lithium iron phosphate particle stack (the second active particle stack 4 has the same structural parameters). Further inside is the anion exchange membrane 1, which is embedded between the plates to selectively allow ions to pass through. All components are arranged in an orderly manner to achieve the function of extracting lithium from brine.

[0076] Compared to coating methods, this invention results in a more stable structure formed by the granulation and stacking of active materials. The particles are tightly bonded together through physical stacking and the synergistic effect of the components in the raw material, avoiding problems such as cracks, wrinkles, and poor adhesion caused by coating drying and calendering processes. This significantly improves the bonding strength between the active material and the current collector, ensuring the structural integrity and performance stability of the active material during long-term lithium extraction. It fundamentally solves the problems of poor adhesion and easy powder shedding in coated electrodes. Furthermore, coating processes are prone to coating thickness fluctuations due to differences in scraper precision or slurry flowability, while granular materials achieve a uniform distribution through their own geometric shape, resulting in smaller deviations in current density distribution during electrolysis. Moreover, the active material granulation process in this method is relatively independent and simple, eliminating the need for complex slurry preparation and precise viscosity control required by traditional coating methods. It also avoids the energy-intensive and costly process of solvent drying and recovery, reducing production steps, lowering process complexity and energy consumption, and improving production efficiency.

[0077] In addition, the filling and replacement process of the present invention is more simplified. The granular active material does not need to be attached to the metal current collector. The filling process can be directly filled into the corresponding chamber without the need for the traditional coating-drying-tightening-sealing filling. After failure, it can also be directly removed and replaced without complicated disassembly of the device. In contrast, the replacement and recycling of traditional coating electrodes and the disassembly of the device are complicated. The coating and current collector need to be separated. After separation, the coating is difficult to reuse. The current collector also needs additional processing before it can be reused. The overall replacement cycle is longer and the cost is higher.

[0078] In addition, the electrochemical performance of this invention is effectively improved, mainly due to the larger capacity per unit area, longer device life at the same current density, and less current collector required per unit lithium extraction, resulting in lower cost. Furthermore, through standardized production of particle size and shape, the capacity deviation of different batches of active materials is ≤3%, and the difference in lithium extraction efficiency between individual electrolytic cells is ≤5%, achieving quality control in large-scale production.

[0079] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0080] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art, unless otherwise stated. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0081] Example 1

[0082] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0083] S1. Preparation of Active Materials: Lithium iron phosphate with 30% delithiation is selected as the main active material for lithium intercalation. It is combined with appropriate binders, conductive agents, pore-forming agents, and hydrophilic agents. By mass percentage, the electrode active materials are mixed evenly in the following proportions: LiFePO4 80%, PVC 5%, acetylene black 5%, ammonium bicarbonate 7%, and polyethylene glycol 3%. An appropriate amount of N-methylpyrrolidone (NMP) is added to the mixture to adjust the humidity to a suitable range, and the mixture is thoroughly stirred to form a soft material (55% solid content).

[0084] S2. The soft material is granulated using a rotary granulator (1.5mm mesh size), dried at 30℃ for 4 hours, and then heated to 90℃ for 6 hours to obtain the dried active material. The dried product is then spherical using a spheroidizer and sieved to obtain 0.5~3mm spherical particles, which are lithium iron phosphate electrode active particles.

[0085] Figure 1The image shows an SEM image of the electrode active particles prepared in Example 1 of this invention. As can be seen from the image, the electrode active particles exhibit a relatively regular spherical morphology, with a relatively concentrated particle size distribution. This indicates that the granulation, drying, spherical rolling, and sieving operations in the previous active material preparation process resulted in spherical particles with a certain particle size range and relatively uniform morphology. A certain amount of porosity exists between the particles, which corresponds to the 35% porosity achieved during the packing operation. This porous structure facilitates electrolyte penetration and ion transport, positively impacting the insertion and extraction of lithium ions during lithium extraction and contributing to improved electrochemical performance of the electrode.

[0086] S3. After stacking the lithium iron phosphate electrode active particles, an electrochemical lithium extraction electrode is obtained. Specifically, the stacking process involves using a 70×70mm graphite plate (current collector) as the conductive electrode. The particles are stacked in a graded manner (25% small particles 0.5~1mm, 50% medium particles 1~2mm, and 25% large particles 2~3mm). The hopper is vibrated during stacking. The horizontal stacking thickness is 5mm, and the porosity is 35%, resulting in a current collector stacked with lithium iron phosphate particles.

[0087] This embodiment further uses the prepared current collector packed with lithium iron phosphate particles to conduct a lithium extraction experiment, specifically:

[0088] The current collector 3, which is stacked with lithium iron phosphate particles, is used as the cathode, and a suitable anode (such as a titanium electrode) is paired with it. An anion exchange membrane 1 is embedded between the plates. For specific assembly details, please refer to [reference needed]. Figure 2 ,like Figure 2 As shown, the electrode system in this lithium extraction experiment includes an anion exchange membrane 1, and a first active particle stack 2, a current collector 3, a second active particle stack 4, and a shell 5 symmetrically arranged on both sides of the anion exchange membrane 1. The shell 5 is located on the outermost side and serves to protect and house the internal components. Next to the inner side of the shell 5 is the second active particle stack 4, which is a lithium iron phosphate particle stack. The particles are stacked in a graded manner, with small particles (0.5~1mm) accounting for 25%, medium particles (1~2mm) accounting for 50%, and large particles (2~3mm) accounting for 25%. The horizontal thickness is 5mm and the porosity is 35%. Next is the current collector 3, which is a 70×70mm graphite plate current collector, used as a conductive electrode to collect current. After that is the first active particle stack 2, which is a lithium iron phosphate particle stack (the second active particle stack 4 has the same structural parameters). Further inside is the anion exchange membrane 1, which is embedded between the plates to selectively allow ions to pass through. All components are arranged in an orderly manner to achieve the function of extracting lithium from brine.

[0089] After assembling the electrode system, the current density was set to 35 A / m. 2The voltage was 0.5V. Lithium extraction experiments were conducted on the simulated brine in Table 1-1 using the two pairs of electrodes described above. Due to the relatively small size of the electrodes, the amount of lithium extracted in a single pass was limited. Therefore, a certain amount of electrolyte was added to the anode side to enhance the conductivity of the solution. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution. Simultaneously, to increase the lithium concentration in the lithium-rich solution, the cathode / anode chambers were continuously circulated and reversed, while the current mode was switched to achieve an increase in lithium concentration. The lithium extraction effect in this embodiment is shown in Table 1-2.

[0090] Table 1-1 Composition of Simulated Brine

[0091]

[0092] Table 1-2 Cyclic Test Data of Particulate Active Materials

[0093]

[0094] As shown in Table 1-2, after 10 cycles of lithium extraction, the capacity retention rate is greater than 97% and the powder removal rate is less than 0.1%.

[0095] Comparative Example 1

[0096] An electrochemical lithium extraction electrode prepared using a method disclosed in Chinese patent application CN118389852 A was used in a lithium extraction experiment. Specifically:

[0097] S1 uses a 1.5mm thick, square-mesh titanium mesh (0.22mm side length) as the coating substrate, which is cleaned, polished, and dried before use.

[0098] S2, prepare an active material slurry using the same material ratio as in Example 1;

[0099] S3, the above-mentioned uniformly mixed slurry is uniformly coated onto the prepared titanium mesh current collector. The current collector size is 70mm×70mm, the coating thickness is 5mm, and the coating area is 70mm×70mm. It is dried under the same drying process as in Example 1.

[0100] S4, the prepared electrode was subjected to brine lithium extraction under the same conditions as in Example 1, and the lithium extraction effect is shown in Tables 1-3:

[0101] Table 1-3 Coating method cyclic test data

[0102]

[0103] As shown in Table 1-3, after 10 cycles of lithium extraction, the capacity retention rate was less than 90%, and the powder removal rate reached 0.15%.

[0104] The comparative test results of Example 1 and Comparative Example 1 show that the present invention, by making the active material into granules, effectively improves the effective filling capacity and lithium adsorption capacity of the equipment, reduces the powder removal rate, and greatly improves the lithium extraction efficiency and structural stability.

[0105] Example 2

[0106] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0107] S1. Preparation of Active Materials: Lithium manganese oxide with 10% delithiation is selected as the main active ingredient for lithium intercalation. It is combined with appropriate binders, conductive agents, pore-forming agents, and hydrophilic agents. Based on the total mass of the electrode active material and auxiliary materials as 100%, the following mixtures are prepared: 70% LiMn₂O₄ (electrode active material), 8% PVDF (hydrophilic agent), 3% acetylene black, 7% carbon nanotubes, 8% sodium bicarbonate, and 4% polyethylene glycol. An appropriate amount of N-methylpyrrolidone is added to the mixture to adjust the humidity to a suitable range. The mixture is then thoroughly stirred to form a soft material (40% solid content), or active material slurry.

[0108] S2. The material is extruded into strips (1.5 mm in diameter) by a twin-screw extruder (screw speed 50 rpm), immersed in water, and then the columnar particles with a shear length of 0.5~3 mm are taken out, dried at 45℃ for 8 hours, and then heated to 80℃ for 6 hours to obtain lithium iron phosphate electrode active particles.

[0109] S3. The active particles of the lithium iron phosphate electrode are deposited on the surface of the current collector to obtain an electrochemical lithium extraction electrode. The specific deposition process is as follows: a roughened titanium mesh of 70×70mm is selected as the conductive electrode (current collector). The particle size distribution ratio is 70% medium particles (1~2mm) and 30% small particles (0.5~1mm). The horizontal deposition thickness is 3mm, and the deposition porosity is 20%, thus obtaining a current collector with deposited lithium iron phosphate particles, i.e., a granular electrode for lithium extraction.

[0110] This embodiment further uses the prepared current collector packed with lithium iron phosphate particles to conduct a lithium extraction experiment, specifically:

[0111] A current collector with stacked lithium iron phosphate particles is used as the cathode, paired with a suitable anode (such as a titanium electrode), and an anion exchange membrane is embedded between the plates. After assembling the electrode system, the current density is set to 35 A / m. 2 The voltage was 0.5V. Lithium extraction experiments were conducted on a brine using the two pairs of electrodes described above. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution. Simultaneously, to increase the lithium concentration in the lithium-rich solution, the cathode / anode chambers were continuously circulated and reversed, while the current mode was switched to achieve the desired lithium concentration. The specific lithium extraction results are shown in Table 2-1.

[0112] Table 2-1 Cyclic Test Data of Particulate Active Materials

[0113]

[0114] Comparative Example 2

[0115] This comparative example uses a method for preparing an electrode plate for electro-intercalation / deintercalation disclosed in Chinese patent application CN117865292 A, and lithium extraction experiments are conducted. Specifically:

[0116] S1 uses a titanium mesh current collector of the same size as in Example 2.

[0117] S2, coating is performed using the same proportion of slurry as in Example 2;

[0118] S3, the preparation of the lithium extraction coating is the same as in Comparative Example 1;

[0119] S4, dry under the same drying process as in Example 2;

[0120] S5, the prepared electrode was subjected to brine lithium extraction under the same conditions as in Example 2, and the lithium extraction effect is shown in Table 2-2:

[0121] Table 2-2 Coating Method Cyclic Test Data

[0122]

[0123] The comparative test results of Example 2 and Comparative Example 2 show that the present invention effectively improves the capacity cycling stability, effectively reduces the powder removal rate, and greatly improves the lithium extraction efficiency and structural stability by making the active material into granules.

[0124] Example 3

[0125] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0126] S1. Preparation of electrode active material: Select ternary lithium nickel cobalt manganese oxide (LiNiO) with 50% delithiation. 0.5 Co 0.4 Mn 0.1 O2) is used as the active ingredient for lithium intercalation, combined with appropriate binders, conductive agents, pore-forming agents, and hydrophilic agents, according to the active ingredient LiNi 0.5 Co 0.4 Mn 0.1 The ingredients are mixed evenly in the following proportions: 90% O2, 2% CMC, 3% graphene, and 5% PEG-2000.

[0127] S2. Using a method of freezing intervention granulation combined with sintering: the raw material is mixed with a 50% ethanol aqueous solution (soft material solid content 85%) and injected into a columnar mold. It is frozen at -20℃ for 12h to form a gel. After vacuum drying, it is calcined at 130℃ for 4h (the pore-forming agent decomposes to form a hollow structure) to obtain hollow columnar particles (particle size 0.5~3mm) and lithium nickel cobalt manganese oxide electrode active particles are obtained.

[0128] S3. The lithium nickel cobalt manganese oxide electrode active particles are deposited on the surface of the current collector to obtain an electrochemical lithium extraction electrode. The specific deposition process is as follows: a roughened 70×70mm titanium mesh is used as the conductive electrode (current collector). A layered deposition method is adopted, specifically: bottom layer thickness 14mm: 65% 2~3mm particles + 35% 1~2mm particles; middle layer thickness 42mm: 30% 2~3mm particles + 50% 1~2mm particles + 20% 0.5~1mm particles; top layer thickness 14mm: 55% 1~2mm particles + 45% 0.5~1mm particles. The horizontal deposition thickness is 10mm, and the deposition porosity is 50%, resulting in a current collector with deposited lithium nickel cobalt manganese oxide electrode active particles. After assembly, a granular electrode for lithium extraction is obtained.

[0129] This embodiment further employs a current collector with stacked lithium nickel cobalt manganese oxide electrode active particles for lithium extraction experiments, specifically:

[0130] A current collector with stacked lithium nickel cobalt manganese oxide electrode active particles is used as the electrode, and an anion exchange membrane is embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V. Meanwhile, to increase the lithium concentration in the lithium-rich solution, the lithium concentration is increased by continuously circulating and reversing the cathode / anode chambers while simultaneously switching the current mode.

[0131] See Figure 3 As can be seen, after 50 cycles, the capacity retention rate was 104.58%, with no obvious powder shedding, demonstrating good cycling stability.

[0132] Example 4

[0133] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0134] 1. Preparation of Active Materials: Lithium iron phosphate and lithium manganese oxide with 25% delithiation were mixed in a 1:1 ratio as the main active material for lithium intercalation, along with appropriate binders, conductive agents, pore-forming agents, and hydrophilic agents. The active material was prepared by mixing 85% active material, 4% binder (PVDF and SBR mixed in a 3:2 ratio), 5% conductive agent (conductive carbon black and carbon nanotubes mixed in a 1:1 ratio), 4% pore-forming agent (ammonium bicarbonate and sodium chloride mixed in a 2:1 ratio), and 2% sodium dodecyl sulfate. A twin-screw extruder was used for segmented granulation: the first stage (300 rpm) produced spherical particles (LiFePO4-based, 0.5~3 mm in diameter) using a spherical mill; the second stage (200 rpm) produced columnar particles (LiMn2O4-based, 0.5~3 mm in diameter). The particles were mixed at the end to maintain their shape, dried at 50℃ for 6 hours, and then heated to 95℃ for 4 hours.

[0135] 2. Stacking process: A roughened 70×70mm titanium mesh was selected as the conductive electrode. A layered stacking method was used, with columnar particles stacked on top and spherical particles stacked on the bottom. The horizontal stacking thickness was 7.5mm, and the stacking porosity was 40%, resulting in a granular electrode for lithium extraction.

[0136] This embodiment further employs the prepared granular electrode for lithium extraction to conduct lithium extraction experiments, specifically:

[0137] A current collector with stacked lithium iron phosphate particles is used as an electrode, and an anion exchange membrane is embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V. Meanwhile, to increase the lithium concentration in the lithium-rich solution, the lithium concentration is increased by continuously circulating and reversing the cathode / anode chambers while simultaneously switching the current mode.

[0138] The adsorption capacity retention rate is ≥96% after 10 cycles, the powder removal rate is ≤0.03%, and it is suitable for high magnesium brine (Mg 20g / L) systems.

[0139] Example 5

[0140] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0141] 1. Preparation of active materials: Lithium nickel cobalt manganese oxide (LiNiO) is selected as a ternary material with 40% delithiation. 0.3 Co 0.4 Mn 0.3O2), combined with appropriate binders, conductive agents, pore-forming agents, and hydrophilic agents. The active ingredient (75%), PVDF (6%), conductive agent (graphite, Ketjen black, and carbon nanotubes mixed in a 3:1:1 ratio), pore-forming agent (ammonium bicarbonate and sodium bicarbonate mixed in a 2:1 ratio), and PEG (2%) are mixed evenly. Ultrasonic-assisted spray granulation is used: the raw material and NMP (soft material solid content 45%) are ultrasonically dispersed (300W, 10min), and granulated using a pressure spray dryer (atomization pressure 0.3MPa, inlet temperature 160℃) to form hollow columnar particles with a wall thickness of 150μm. After crushing and sieving, particles of 0.5~2mm are obtained.

[0142] 2. Stacking process: A roughened 70×70mm titanium mesh is selected as the conductive electrode. A graded stacking method is used, with small particles (0.5~1mm) accounting for 40% and medium particles (1~2mm) accounting for 60%. The horizontal stacking thickness is 3mm, and the stacking porosity is 25%, thus creating a granular electrode for lithium extraction.

[0143] This embodiment further employs the prepared granular electrode for lithium extraction to conduct lithium extraction experiments, specifically:

[0144] The prepared lithium-extraction particulate electrode is used as the electrode, with an anion exchange membrane embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V. Meanwhile, to increase the lithium concentration in the lithium-rich solution, the lithium concentration is increased by continuously circulating and reversing the cathode / anode chambers while simultaneously switching the current mode.

[0145] Current density 35A / m 2 Under these conditions, the capacity retention rate is ≥95% after 10 cycles, and the powder removal rate is ≤0.02%.

[0146] Example 6

[0147] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0148] S1: After mixing the electrode active material LiFePO4, binder PVC, conductive agent Ketjen black, pore-forming agent sodium bicarbonate, hydrophilic agent polymeric polyol and dispersant NMP, an active material mud (i.e. soft material) is obtained; the LiFePO4 is delithiated before mixing to form a lithium-deficient active material, and the amount of delithiation is controlled at 10%.

[0149] Based on the total mass of electrode active material and auxiliary materials as 100%, the electrode active material accounts for 70%, the binder accounts for 5%, the conductive agent accounts for 15%, the pore-forming agent accounts for 8%, the hydrophilic agent accounts for 2%, and the dispersant accounts for 130% of the total mass of electrode active material and auxiliary materials.

[0150] S2: The active material is granulated using an extrusion-water immersion-granulation process and then dried to obtain spherical electrode active particles with a particle size of 0.5 mm;

[0151] S3: The active electrode particles obtained in this invention are deposited on the surface of a conductive current collector to form an electrochemical lithium extraction electrode. During the deposition process, the deposition thickness is controlled and maintained at 3.0 mm.

[0152] This embodiment optimizes the packing density using a particle size distribution method, that is, controlling the porosity after packing by using a particle size distribution method or a layered packing method. Specifically, by mass percentage, electrode active particles with a particle size of 0.5~1mm account for 25%, electrode active particles with a particle size of 1~2mm account for 45%, and electrode active particles with a particle size of 2~3mm account for 30%.

[0153] This embodiment further employs the prepared granular electrode for lithium extraction to conduct lithium extraction experiments, specifically:

[0154] The prepared lithium-extraction particulate electrode is used as the electrode, with an anion exchange membrane embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V.

[0155] This embodiment operates at a current density of 35 A / m 2 After 10 cycles, the capacity retention rate was 98.44%, and the powder removal rate was 0.017%.

[0156] Example 7

[0157] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0158] S1: After mixing the electrode active material LiMn2O4, binder PTFE, conductive agent acetylene black, pore-forming agent ammonium bicarbonate, hydrophilic agent polyolamine and NMP, an active material mud (i.e. soft material) is obtained.

[0159] The electrode active material undergoes a delithiation process after granulation to form a lithium-deficient active material, with the delithiation rate controlled at 50%.

[0160] Based on the total mass of electrode active material and auxiliary materials as 100%, the electrode active material accounts for 90%, the binder accounts for 3%, the conductive agent accounts for 3%, the pore-forming agent accounts for 3%, the hydrophilic agent accounts for 1%, and the dispersant accounts for 90% of the total mass of electrode active material and auxiliary materials.

[0161] S2: The active material is granulated by extrusion-water immersion-granulation process and then dried to obtain spherical electrode active particles with a particle size of 3mm.

[0162] S3: The active electrode particles obtained in this invention are deposited on the surface of a conductive current collector to form an electrochemical lithium extraction electrode. During the deposition process, the deposition thickness is controlled and maintained at 10.0 mm.

[0163] In this embodiment, particle size distribution is used to optimize the packing density. Specifically, by mass percentage, electrode active particles with a particle size of 0.5~1mm account for 30%, electrode active particles with a particle size of 1~2mm account for 50%, and electrode active particles with a particle size of 2~3mm account for 20%.

[0164] This embodiment further employs the prepared granular electrode for lithium extraction to conduct lithium extraction experiments, specifically:

[0165] The prepared lithium-extraction particulate electrode is used as the electrode, with an anion exchange membrane embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V.

[0166] This embodiment operates at a current density of 35 A / m 2 After 10 cycles, the capacity retention rate was 98.45%, and the powder removal rate was 0.016%.

[0167] Example 8

[0168] A method for preparing a particulate electrode for lithium extraction includes the following steps:

[0169] S1: After mixing the electrode active material LiFePO4, binder PVDF, conductive agent Super-P, pore-forming agent sodium chloride, hydrophilic agent polyethylene glycol and NMP, an active material mud (i.e. soft material) is obtained.

[0170] The electrode active material undergoes a delithiation process before mixing to form a low-lithiation active material, with the delithiation amount controlled at 30%.

[0171] Based on the total mass of electrode active material and auxiliary materials as 100%, the electrode active material accounts for 80%, the binder accounts for 3%, the conductive agent accounts for 4%, the pore-forming agent accounts for 8%, the hydrophilic agent accounts for 5%, and the dispersant accounts for 110% of the total mass of electrode active material and auxiliary materials.

[0172] S2: The active material mud is granulated by extrusion-water immersion-granulation process and then dried to obtain electrode active particles with a particle size of 2mm.

[0173] S3: The active electrode particles obtained in this invention are deposited on the surface of a conductive current collector to form an electrochemical lithium extraction electrode. During the deposition process, the deposition thickness is controlled and maintained at 5.0 mm.

[0174] This embodiment employs a layered stacking method to optimize packing density. Specifically, the layered stacking method includes a bottom layer of particles, a middle layer of particles, and a top layer of particles. In the bottom layer of particles, 65% of the electrode active particles have a diameter of 2-3 mm, and 35% have a diameter of 1-2 mm. In the middle layer of particles, 30% of the electrode active particles have a diameter of 2-3 mm, 50% have a diameter of 1-2 mm, and 20% have a diameter of 0.5-1 mm. In the top layer of particles, 55% of the electrode active particles have a diameter of 1-2 mm, and 45% have a diameter of 0.5-1 mm.

[0175] This embodiment further employs the prepared granular electrode for lithium extraction to conduct lithium extraction experiments, specifically:

[0176] The prepared lithium-extraction particulate electrode is used as the electrode, with an anion exchange membrane embedded between the electrode plates. For specific details, please refer to [reference needed]. Figure 2 The two pairs of electrodes described above were used to conduct a lithium extraction experiment on a certain brine. A magnesium chloride solution with a magnesium content of 20 g / L was used as the initial anode solution, and the current density was controlled at 35 A / m. 2 The cutoff voltage is 0.5V.

[0177] This embodiment operates at a current density of 35 A / m 2 After 10 cycles, the capacity retention rate was 96.88%, and the powder removal rate was 0.017%.

[0178] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing a granular electrode for lithium extraction, characterized in that, Includes the following steps: S1: After mixing the electrode active material, auxiliary materials and dispersant, an active material slurry is obtained; The electrode active material is a lithium-ion battery cathode material; The auxiliary material consists of a binder, a conductive agent, a pore-forming agent, and a hydrophilic agent; S2: The active material mud is granulated and dried to obtain electrode active particles; the electrode active material is subjected to delithiation treatment before step S1 or after step S2 to form a lithium-deficient active material. The particle size of the electrode active particles is 0.5~3mm; During the deposition process, the deposition thickness is controlled at 3.0~10.0 mm, and the porosity after deposition is 20%~50%. S3: The electrode active particles are deposited on the surface of the current collector to obtain the granular electrode for lithium extraction. The electrode active particles are stacked on the surface of the current collector, and the porosity after stacking is controlled by particle gradation or layered stacking. The particle size distribution is as follows: by mass percentage, electrode active particles with a particle size of 0.5~1mm account for 20%~30%, electrode active particles with a particle size of 1~2mm account for 40%~50%, and electrode active particles with a particle size of 2~3mm account for 20%~30%. The layered stacking method specifically includes bottom layer particles, middle layer particles, and top layer particles; By mass percentage, the bottom layer particles comprise 60% to 70% electrode active particles with a diameter of 2 to 3 mm and 30% to 40% electrode active particles with a diameter of 1 to 2 mm. Of the intermediate layer particles, 30% are electrode active particles with a particle size of 2-3 mm, 50% are electrode active particles with a particle size of 1-2 mm, and 20% are electrode active particles with a particle size of 0.5-1 mm. In the top layer of particles, electrode active particles with a particle size of 1-2 mm account for 50%-60%, and electrode active particles with a particle size of 0.5-1 mm account for 40%-50%.

2. The method for preparing a particulate electrode for lithium extraction according to claim 1, characterized in that, The solid content of the active material mud is 30%~85%.

3. The method for preparing a particulate electrode for lithium extraction according to claim 1, characterized in that, Based on the total mass of electrode active material and auxiliary materials as 100%, the proportion of electrode active material is 70%~90%, the proportion of binder is 2%~8%, the proportion of conductive agent is 3%~15%, the proportion of pore-forming agent is 3%~15%, and the proportion of hydrophilic agent is 1%~6%; the mass of dispersant accounts for 90%~130% of the total mass of electrode active material and auxiliary materials.

4. A granular electrode for lithium extraction, characterized in that, It is prepared by the method described in any one of claims 1 to 3.

5. The application of the granular electrode for lithium extraction as described in claim 4 in electrochemical lithium extraction.

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