A device for extracting lithium from salt lakes and a manufacturing process thereof

Abstract

The application provides a device for extracting lithium from salt lakes, which is formed by winding a hard cylindrical material around a core, wherein the core comprises an anode sheet, a cathode sheet and a diaphragm arranged between the anode sheet and the cathode sheet, the anode sheet and the cathode sheet are wound around the core, anode tabs and cathode tabs are respectively led out from the anode sheet and the cathode sheet along the width direction, the anode tabs and the cathode tabs are located on the same end surface and at least one tab is led out in each layer of the winding structure, wherein the anode sheet is a current collector coated with a lithium adsorbent, a binder, a conductive agent and aluminum powder, the particle size of the aluminum powder is 1-20 microns, and the diaphragm is a hydrophobic porous flexible plastic. The device is formed by porous treatment of the anode sheet and winding of the anode sheet, the cathode sheet and the diaphragm to form a winding structure, which not only increases the adsorption area of the electrode, but also effectively reduces the diffusion resistance of lithium ions in the anode, and further improves the adsorption efficiency of the electric control lithium extraction device.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium extraction from salt lakes, specifically relating to an apparatus for lithium extraction from salt lakes using an electronically controlled method. Background Technology

[0002] Lithium is a silvery-white metal with advantages such as light weight, high reactivity, high hardness, and high melting point. It is widely used in high-energy batteries, organic synthesis, high-end equipment, clean production, and biomedicine, and holds significant strategic importance for the national economy and national defense. Lithium has been listed as a strategic mineral by countries and regions such as the EU and the US, and China also included it in its strategic mineral catalog in 2016. The main sources of lithium are salt lake brine and ore, with approximately 80% of my country's lithium resources distributed in salt lake brine in regions such as Qinghai and Tibet. Therefore, developing cost-effective and efficient salt lake lithium extraction technologies is urgently needed.

[0003] Electro-controlled lithium extraction technology, based on the working principle of lithium-ion batteries, uses a material with lithium-ion adsorption properties as the anode and a material with high adsorption capacity as the cathode, utilizing potential control of Li... + By embedding / de-embedding ions in the anode material and utilizing the rapid diffusion and enrichment of ions under the action of the electrode electric field, the goal of efficiently extracting lithium ions from brine can be achieved.

[0004] Electro-controlled lithium extraction technology, due to the high lithium-ion selectivity of its cathode material, can specifically address the problem of high magnesium-to-lithium ratios in my country's salt lakes. Secondly, its method of controlling lithium-ion diffusion and embedding to the anode using electrical energy effectively meets environmental requirements. However, due to the low temperatures, complex composition, high viscosity, and low lithium-ion concentration in western salt lake regions, current electro-controlled lithium extraction can only operate at low current densities. Furthermore, current electro-controlled lithium extraction technologies typically use titanium coated with precious metals as electrode plates, resulting in high electrode processing costs, complex processes, and generally flat-plate coating, leading to low equipment space utilization.

[0005] Currently, the technical problems mentioned above result in the disadvantages of low production efficiency, short electrode life, and high equipment investment and operating costs in actual production of the electronically controlled lithium extraction process. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention provides a novel structure for an electronically controlled lithium extraction device, which significantly improves the production efficiency of electronically controlled lithium extraction by improving the electrode structure.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] The present invention provides an apparatus for lithium extraction from salt lakes in a first aspect. The apparatus uses a rigid cylindrical material as a core and is formed by winding an anode sheet, a cathode sheet, and a diaphragm stacked between the anode sheet and the cathode sheet around the core as an axis. Anode tabs and cathode tabs are respectively led out along the width direction on the anode sheet and the cathode sheet. The anode tabs and cathode tabs are located on the same end face and at least one tab is led out in each layer of the winding structure.

[0009] The anode sheet is a current collector coated with lithium adsorbent, binder, conductive agent and aluminum powder, wherein the particle size of the aluminum powder is 1 to 20 μm; the diaphragm is a hydrophobic porous flexible plastic.

[0010] The lithium extraction device of the present invention improves the adsorption efficiency of lithium ions by adopting a winding structure for the anode plate, cathode plate and diaphragm, and leading out a multi-tab structure on the cathode and anode plates. At the same time, after the device is immersed in salt lake brine, the aluminum powder dissolves and forms a porous structure, which increases the contact area between the anode and the brine, reduces the resistance of lithium ion transfer inside the electrode and further improves the lithium extraction efficiency.

[0011] In some specific embodiments of the device of the present invention, the material coated on the anode sheet contains 75-90% lithium adsorbent by mass, for example, 80%, 85%, or 88%; 4-12% binder by mass, for example, 5%, 8%, or 10%; 4-12% conductive agent by mass, for example, 5%, 8%, or 10%; and 0.5-2% aluminum powder by mass, for example, 1%, 1.2%, or 1.5%.

[0012] In some preferred embodiments, the lithium adsorbent has a mass percentage of 80-85%, for example, 82% or 84%; the binder has a mass percentage of 6-12%, for example, 8% or 10%; the conductive agent has a mass percentage of 6-12%, for example, 8% or 10%; and the aluminum powder has a mass percentage of 1-1.5%, for example, 1.2% or 1.4%.

[0013] In the lithium extraction device from salt lakes provided by this invention, the pore size of the diaphragm is 1–1000 mm. 2 For example, 100mm 2 200mm 2 Preferably 500-900mm 2 For example, 600mm 2 700mm 2 800mm 2 More preferably, the diaphragm is selected from one or more of modified polyurethane, polytetrafluoroethylene or polypropylene.

[0014] In some specific embodiments, anode tabs and cathode tabs are led out along the width direction on the anode sheet and cathode sheet respectively. During the winding process, at least one tab is led out on the cathode sheet and anode sheet in each winding layer. During the specific winding process, the diameter of the winding center gradually increases, so that the distance between adjacent tabs gradually increases. In the device after winding, the tabs can overlap in a certain direction. Specifically, the distance between adjacent tabs on each electrode sheet is ≤50cm, for example, 20cm, 30cm, 40cm.

[0015] In the lithium extraction device from salt lakes provided by this invention, the cathode sheet is selected from activated carbon fiber cloth, the thickness of which is 1-5 mm, for example, 2 mm or 4 mm; the specific surface area is 500-1500 m². 2 / g, for example, 800m 2 / g, 1000m 2 / g, 1200m 2 / g. The material used for the core in the device can be one of polyethylene, acrylonitrile, or PVC.

[0016] In the lithium extraction device from salt lakes provided by this invention, the lithium adsorbent is LiMn2O4, LiFePO4, LiFePO4, or LiNi. 0.5 Mn 1.5 O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 One or more of O2 or LiV2O5; the conductive agent is one or more of carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube, conductive graphite or graphene; the binder is one or more of PVDF (polyvinylidene fluoride), PA (polyacrylic acid) or PAI (polyamide imide).

[0017] In some specific embodiments, the current collector is one or more of titanium foil, titanium plate, or ruthenium-coated titanium plate.

[0018] In a second aspect, the present invention provides a manufacturing process for the above-mentioned device, comprising the following steps:

[0019] Step 1: Mix and dissolve lithium adsorbent, binder, conductive agent and aluminum powder in an organic solvent to form an anode slurry, and coat the positive electrode slurry onto the current collector, and dry it to obtain the anode sheet;

[0020] Step 2: The anode sheet, the cathode sheet, and the diaphragm stacked between the anode sheet and the cathode sheet are wound into shape using a core as the axis;

[0021] Step 3: After forming, cut out anode tabs and cathode tabs from the same end face of each anode and cathode sheet.

[0022] In some specific embodiments, the organic solvent in step one is selected from N-methylpyrrolidone (NMP) or dimethyl carbonate (DMC).

[0023] The above technical solution achieves the following technical effects:

[0024] The device of this invention increases the contact area between the adsorption electrode and the brine during application by making the anode plate porous, thereby reducing the transfer resistance of lithium ions inside the adsorption electrode and improving the adsorption efficiency.

[0025] The lithium extraction device from salt lakes provided by this invention uses a winding structure and a multi-tab structure with at least one tab led out in each layer of the winding structure. This not only increases the adsorption area of ​​the electrode, but also effectively reduces the diffusion resistance of lithium ions inside the anode, thereby further improving the adsorption efficiency of the electronically controlled lithium extraction device.

[0026] The device of the present invention replaces the traditional ion exchange resin membrane by setting a flexible porous hydrophobic material as a diaphragm between the anode plate and the cathode plate, which greatly reduces the lithium ion diffusion resistance and improves the current efficiency; at the same time, the hydrophobic material can quickly achieve dehydration, thereby improving production efficiency. Attached Figure Description

[0027] Figure 1 : A schematic diagram of the cross-sectional structure of the lithium extraction device from salt lakes in Embodiment 1 of the present invention;

[0028] Figure 2 : Figure 1 Longitudinal sectional view of the device;

[0029] Figure 3 : Figure 1 A schematic diagram of the unfolded anode plates in the device;

[0030] Figure 4 : Figure 1 A schematic diagram of the unfolded cathode plate in the device;

[0031] Figure 5 : A schematic diagram of the cross-sectional structure of the lithium extraction device from salt lakes in Embodiment 2 of the present invention;

[0032] Figure 6 : A schematic diagram of the cross-sectional structure of the lithium extraction device from the salt lake in Comparative Example 3 of this invention. Detailed Implementation

[0033] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0034] 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.

[0035] The formed lithium extraction device from the salt lake was placed in an adsorption tank containing the brine to be tested (specific components are shown in Table 1 below). The device's tabs were connected to an external power supply, causing the deintercalated anode to undergo a lithium intercalation reaction. Before powering on, the lithium ion concentration was C1, and the total volume of the adsorption tank was V. After powering on for a hours, the connection between the tabs and the external circuit was disconnected, and the lithium ion concentration was measured to be C2.

[0036] Table 1

[0037] Content (g / L) 1.85 1.52 85.4 0.71

[0038] In the following examples of this invention, the performance of the lithium extraction device is tested using the following methods:

[0039] The adsorption capacity is calculated as: (C1-C2)×V;

[0040] Method for determining adsorption efficiency: (C1-C2)×V / a.

[0041] Example 1

[0042] Step 1: Mix LiMn2O4, PVDF, carbon black, and aluminum powder (particle size 10μm) in a mass ratio of 8:1:1:0.1, and dissolve them in NMP solvent to form an anode slurry with a solid content of 70%. Coat both sides of this slurry onto a titanium foil with a thickness of 0.02mm, a length of 13200mm, and a width of 320mm, controlling the coating density on one side to be 0.065mg / mm. 2 Then, it is dried to obtain the anode plate;

[0043] Step 2: A hydrophobic flexible mesh is fabricated using modified polyurethane material with a mesh size of 30mm × 30mm, a thickness of 2mm, and a width of 320mm as a diaphragm; a membrane is constructed using a material with a thickness of 1mm, a width of 320mm, and a specific surface area of ​​1000m². 2 / g of activated carbon fiber cloth is used as the cathode sheet; and a cylindrical material made of polyethylene plastic with a diameter of 50mm and a height of 300mm is used as the core.

[0044] Step 3: The anode sheet, diaphragm, and cathode sheet are sequentially wound into shape using polyethylene material as the core; then, a tab with a width of 30mm and a height of 20mm is cut from the same end face of each layer of anode and cathode sheet (e.g., ...). Figure 3 , 4 (As shown); and NMP was used as a solvent to clean off the coating on the anode tab, resulting in the following: Figure 1 The lithium extraction device shown.

[0045] Example 2

[0046] This embodiment uses the same manufacturing process as Embodiment 1, the only difference being step three, where two tabs, each 30mm wide and 20mm high, are cut from the same end face of each anode and cathode sheet, resulting in the following... Figure 5 The lithium extraction device shown.

[0047] Example 3

[0048] This embodiment uses the same manufacturing process as Embodiment 1, the only difference being that in step one, the aluminum powder particle size is 20μm.

[0049] Example 4

[0050] This embodiment uses the same manufacturing process as Embodiment 1, the only difference being in step two, where the separator mesh is 10×10mm.

[0051] Comparative Example 1

[0052] Step 1: Same as Example 1;

[0053] Step 2: Using a 50μm thick cation exchange membrane as raw material, cut it into 320mm wide pieces to serve as separators; using a membrane with a thickness of 0.1mm, a width of 320mm, and a specific surface area of ​​1000m²... 2 / g of activated carbon fiber cloth is used as the cathode sheet; and a cylindrical material made of polyethylene plastic with a diameter of 50mm and a height of 300mm is used as the core.

[0054] Step 3: The anode sheet, diaphragm, and cathode sheet are wound sequentially with polyethylene material as the core; then, a tab with a width of 30mm and a height of 20mm is cut from the same end face of each layer of anode sheet and cathode sheet; and the coating on the anode tab is cleaned off using NMP as a solvent to obtain the lithium extraction device.

[0055] Comparative Example 2

[0056] Step 1: Mix LiMn2O4, PVDF, carbon black, and aluminum powder (particle size D50 of 12μm) in a mass ratio of 8:1:1:0.1, and dissolve them in NMP solvent to form an anode slurry with a solid content of 70%. Coat both sides of this slurry onto a titanium foil with a thickness of 0.02mm, a length of 300mm, and a width of 320mm, controlling the coating density on one side to be 0.065mg / mm. 2 Then, it is dried to obtain the anode plate;

[0057] Step 2: A hydrophobic flexible mesh is fabricated using modified polyurethane material with a mesh size of 30mm × 30mm, a thickness of 2mm, and a width of 320mm as a diaphragm; a membrane is constructed using a material with a thickness of 0.1mm, a width of 320mm, and a specific surface area of ​​1000m². 2 / g of activated carbon fiber cloth was used as the cathode sheet;

[0058] Step 3: Stack the anode sheet, diaphragm, and cathode sheet sequentially, with the anode sheet consisting of 4 layers; then, cut a tab with a width of 30mm and a height of 20mm from the same end face of each anode sheet and cathode sheet; and use NMP as a solvent to clean off the coating on the anode tab to obtain the lithium extraction device.

[0059] Comparative Example 3

[0060] Step 1: Mix LiMn2O4, PVDF, and carbon black in a mass ratio of 8:1:1, and dissolve them in NMP solvent to form an anode slurry with a solid content of 70%. Coat both sides of this slurry onto a titanium foil 0.02 mm thick, 300 mm long, and 320 mm wide, controlling the coating density on one side to be 0.065 mg / mm². 2 Then, it is dried to obtain the anode plate;

[0061] Step 2: Using a 50μm thick cation exchange membrane as raw material, cut it into 320mm wide pieces to serve as separators; using a membrane with a thickness of 0.1mm, a width of 320mm, and a specific surface area of ​​1000m²... 2 / g of activated carbon fiber cloth was used as the cathode sheet;

[0062] Step 3: Stack the anode sheet, diaphragm, and cathode sheet sequentially, with the anode sheet consisting of 4 layers. Then, cut a tab 30mm wide and 20mm high from the same end face of each anode and cathode sheet layer; use NMP as a solvent to clean off the coating on the anode tab, obtaining the desired result. Figure 6 The lithium extraction device shown.

[0063] The lithium extraction device obtained above was placed in the brine of the salt lake where lithium was to be extracted, and the electrode tabs were connected to an external power source. Before first use, the device should be allowed to stand in the brine for 3 hours before being powered on. The adsorption capacity and efficiency of lithium ions after powering the device with a 1.5V external power source for 3 hours are shown in the table below:

[0064]

[0065]

[0066] As can be seen from the data in the table above, the lithium extraction device from salt lakes of the present invention adopts a structure with at least one tab, which effectively reduces the diffusion resistance of lithium ions inside the electrode and improves the adsorption efficiency. At the same time, controlling the particle size of the aluminum powder coated on the anode plate further increases the adsorption capacity of lithium ions. As can be seen from the comparative data, the hydrophobic porous flexible material as the diaphragm of the device and the setting of the winding structure can significantly improve the lithium extraction efficiency.

Claims

1. A device for lithium extraction from salt lakes, characterized in that, The device uses a rigid cylindrical material as the core, and is formed by winding an anode sheet, a cathode sheet, and a diaphragm around the core. The diaphragm is stacked between the anode sheet and the cathode sheet. Anode tabs and cathode tabs are respectively led out along the width direction on the anode sheet and the cathode sheet. The anode tabs and cathode tabs are located on the same end face, and at least one tab is led out in each layer of the winding structure. The anode sheet is a current collector coated with lithium adsorbent, binder, conductive agent and aluminum powder, wherein the particle size of the aluminum powder is 1~20 μm; the diaphragm is a hydrophobic porous flexible plastic. In the material coated on the anode sheet, the lithium adsorbent has a mass percentage of 75-90%, the binder has a mass percentage of 4-12%, the conductive agent has a mass percentage of 4-12%, and the aluminum powder has a mass percentage of 0.5-2%. The lithium adsorbent is LiMn2O4, LiFePO4, or LiNi. 0.5 Mn 1.5 O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 One or more of O2 or LiV2O5.

2. The apparatus according to claim 1, characterized in that, In the material coated on the anode sheet, the lithium adsorbent has a mass percentage content of 80-85%, the binder has a mass percentage content of 6-12%, the conductive agent has a mass percentage content of 6-12%, and the aluminum powder has a mass percentage content of 1-1.5%.

3. The apparatus according to claim 2, characterized in that, The diaphragm is selected from one or more of modified polyurethane, polytetrafluoroethylene, or polypropylene.

4. The apparatus according to claim 3, characterized in that, On the anode and cathode plates, the distance between adjacent tabs is ≤50 cm.

5. The apparatus according to claim 4, characterized in that, The cathode sheet is selected from activated carbon fiber cloth, which has a thickness of 1~5 mm and a specific surface area of ​​500~1500 m² / g.

6. The apparatus according to any one of claims 1 to 5, characterized in that, The core material is polyethylene or PVC.

7. The apparatus according to any one of claims 1 to 5, characterized in that, The conductive agent is one or more of carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, conductive graphite or graphene. The adhesive is one or more of PVDF, PA, or PAI.

8. The apparatus according to claim 7, characterized in that, The current collector is one or more of titanium foil, titanium plate, or ruthenium-coated titanium plate.

9. A manufacturing process for the device according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Mix and dissolve lithium adsorbent, binder, conductive agent and aluminum powder in an organic solvent to form an anode slurry, coat the anode slurry onto the current collector, and dry it to obtain the anode sheet; Step 2: The anode sheet, the cathode sheet, and the diaphragm stacked between the anode sheet and the cathode sheet are wound into shape using a core as the axis; Step 3: After forming, cut out anode tabs and cathode tabs from the same end face of each anode and cathode sheet.

10. The manufacturing process according to claim 9, characterized in that, The organic solvent mentioned in step one is selected from N-methylpyrrolidone or dimethyl carbonate.

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