Electrode and preparation method therefor, device for extracting lithium from salt lake, and method for extracting lithium from salt lake

Abstract

The present disclosure belongs to the technical field of extraction of lithium from a salt lake, and particularly relates to an electrode and a preparation method therefor, a device for extracting lithium from a salt lake, and a method for extracting lithium from a salt lake. The surface of an electrode matrix is modified by using an amphoteric diblock copolymer, so as to form a diblock copolymer coating layer; and the amphoteric diblock copolymer contains both a hydrophilic block and a hydrophobic block, wherein the hydrophobic block is easily adsorbed on the surface of the electrode matrix to form a stable coating, and the hydrophilic block can improve the hydrophilicity of the electrode and can also complex lithium ions on the surface of the electrode, thereby improving the lithium extraction efficiency.

Description

Electrode and preparation method thereof, salt lake lithium extraction device and salt lake lithium extraction method Technical Field

[0001] The present disclosure belongs to the technical field of lithium extraction from salt lakes, and specifically relates to an electrode and a preparation method thereof, a salt lake lithium extraction device, and a salt lake lithium extraction method. Background Art

[0002] In recent years, with the rapid development of new energy vehicles and chemical energy storage, global demand for lithium resources has continued to increase. Natural lithium resources are primarily found in salt lake brine, seawater, and ores, with salt lake lithium accounting for approximately 70%. Consequently, salt lake lithium extraction technology has attracted increasing attention. In recent years, researchers have conducted extensive research and development on new lithium extraction processes, and the resulting electrochemical lithium extraction technology has shown promising application value and prospects.

[0003] The principle of electrochemical lithium extraction is to charge the working electrode in the electrolyte solution to release lithium ions to form a lithium-depleted electrode. The lithium-rich electrode and the lithium-depleted electrode are used as the anode and cathode respectively. An electrolyte solution free of impurities is added to the anode, and salt lake brine is added to the cathode. Driven by the external potential, the Li in the brine is selectively embedded in the lithium-depleted electrode, and at the same time, the lithium-rich electrode releases Li into the solution to form a lithium-depleted electrode. Through electrode exchange and cyclic operation, selective enrichment of lithium is achieved.

[0004] While electrochemical lithium extraction holds promise for applications in salt lakes, the high concentration of impurities and lithium concentration in the brine make electrochemical deintercalation a relatively low-efficiency method. Furthermore, the highly hydrophobic PVDF binder used in electrode slurry preparation reduces the wettability of the brine, hindering mass transfer and thus impacting lithium extraction efficiency.

[0005] In view of this, the present disclosure is proposed.

[0006] Summary of the Invention

[0007] The purpose of the present disclosure includes providing an electrode and a preparation method thereof, a salt lake lithium extraction device and a salt lake lithium extraction method, aiming to significantly improve the lithium extraction efficiency of salt lake lithium extraction.

[0008] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

[0009] In a first aspect, the present disclosure provides a solution comprising an electrode, comprising an electrode substrate and an amphiphilic diblock copolymer coating layer coated on the surface of the electrode substrate, wherein the electrode substrate comprises a current collector and a positive electrode active coating attached to the current collector;

[0010] The amphiphilic diblock copolymer coating layer contains a hydrophilic segment and a hydrophobic segment.

[0011] In some embodiments of the present disclosure, the hydrophilic segment is selected from at least one of polyoxyethylene, polyethylene glycol, and polyacrylic acid.

[0012] In some embodiments of the present disclosure, the hydrophobic segment is selected from at least one of polystyrene, polybutadiene, and polyoxypropylene.

[0013] In some embodiments of the present disclosure, the hydrophilic segment is polyethylene oxide and the hydrophobic segment is polystyrene.

[0014] In some embodiments of the present disclosure, in the electrode, the mass proportion of the amphiphilic diblock copolymer coating layer is 0.1%-5%.

[0015] In some embodiments of the present disclosure, the molecular weight of the amphiphilic diblock copolymer used to form the amphiphilic diblock copolymer coating layer is 5000-50000 Da, and the mass ratio of the hydrophilic segment to the hydrophobic segment is 1:(1.6-4).

[0016] In some embodiments of the present disclosure, the positive electrode active coating contains a positive electrode active material, and the positive electrode active material is selected from at least one of lithium iron phosphate, lithium manganese oxide, and lithium nickel cobalt manganese oxide.

[0017] In some embodiments of the present disclosure, the positive electrode active coating further contains a conductive agent and a binder, and the mass ratio of the positive electrode active material, the conductive agent and the binder is 100:(10-20):(10-15).

[0018] In some embodiments of the present disclosure, the current collector is selected from at least one of aluminum foil, titanium mesh, and carbon fiber cloth.

[0019] In some embodiments of the present disclosure, the conductive agent is selected from at least one of acetylene black and conductive carbon black.

[0020] In some embodiments of the present disclosure, the binder is selected from at least one of polyvinylidene fluoride and polypropylene.

[0021] In some embodiments of the present disclosure, the thickness of the current collector is 10 μm-15 μm, and the thickness of the positive electrode active coating is 100 μm-300 μm.

[0022] In a second aspect, the solution provided by the present disclosure also includes a method for preparing an electrode, comprising: forming an amphiphilic diblock copolymer coating layer on an electrode substrate.

[0023] In some embodiments of the present disclosure, the preparation method includes: dispersing the amphiphilic diblock copolymer to obtain a copolymer dispersion, and using the copolymer dispersion to form an amphiphilic diblock copolymer coating layer on the surface of the electrode substrate.

[0024] In some embodiments of the present disclosure, the process of forming the amphiphilic diblock copolymer coating layer includes: immersing the electrode substrate in a copolymer dispersion, and then taking it out and drying it after immersion.

[0025] In some embodiments of the present disclosure, the mass fraction of the amphiphilic diblock copolymer in the copolymer dispersion is 2%-5%.

[0026] In some embodiments of the present disclosure, the soaking time is 4 hours to 12 hours, and the soaking temperature is 15°C to 30°C.

[0027] In some embodiments of the present disclosure, the drying temperature is 60° C.-80° C., and the drying time is 4 h-6 h.

[0028] In some embodiments of the present disclosure, the preparation process of the electrode substrate includes: applying a positive electrode active slurry on a current collector, and drying to form a positive electrode active coating;

[0029] The preparation process of the positive electrode active slurry includes: mixing the positive electrode active material, the conductive agent and the binder, and homogenizing the slurry using a dispersant.

[0030] In some embodiments of the present disclosure, during the process of forming the positive electrode active coating, the drying temperature is controlled to be 100° C.-120° C., and the drying time is controlled to be 10 h-20 h.

[0031] In a third aspect, the solution provided by the present disclosure also includes a salt lake lithium extraction device, comprising a lithium-rich electrode and a lithium-poor electrode;

[0032] The lithium-rich electrode is an electrode in any of the above embodiments or an electrode prepared by the preparation method in any of the above embodiments.

[0033] In some embodiments of the present disclosure, the lithium-poor electrode is prepared by delithiation of the lithium-rich electrode in the above embodiments.

[0034] In some embodiments of the present disclosure, an electrolysis device is further included, wherein an anion exchange membrane is provided in the electrolysis device to separate the electrolysis device into an anode chamber and a cathode chamber.

[0035] In some embodiments of the present disclosure, the material of the anion exchange membrane is selected from at least one of polystyrene, polypropylene and polyamide.

[0036] In a fourth aspect, the solution provided by the present disclosure also includes a method for extracting lithium from a salt lake, comprising: extracting lithium using the salt lake lithium extraction device in any of the above embodiments.

[0037] In some embodiments of the present disclosure, the process includes placing a lithium-rich electrode and a lithium-poor electrode in an anode chamber and a cathode chamber, respectively, injecting brine into the cathode chamber, injecting an electrolyte into the anode chamber, and then applying power.

[0038] In some embodiments of the present disclosure, the electrolyte injected into the anode chamber is selected from at least one of a potassium chloride solution and a sodium chloride solution, and the concentration of the electrolyte is 0.05 mol / L-0.10 mol / L.

[0039] In some embodiments of the present disclosure, the power-on voltage is 0.3V-1.2V.

[0040] The surface of the electrode substrate is modified by using an amphiphilic diblock copolymer to form a diblock copolymer coating layer. The amphiphilic diblock copolymer contains both hydrophilic and hydrophobic segments. The hydrophobic segment is easily adsorbed on the surface of the electrode substrate to form a stable coating. The role of the hydrophilic segment is mainly manifested in two aspects: on the one hand, the hydrophilic segment can increase the wettability of the brine to the electrode, and the hydrophilic segment and the solution can form a stable solvation layer, thereby hindering the aggregation of colloids and particles in the solution, preventing them from entering the interior of the electrode and causing blockage of the mass transfer channel; on the other hand, the hydrophilic segment also has an excellent ability to complex lithium ions. In the cationic aggregation layer on the electrode surface, it can specifically complex lithium ions, making the lithium ion flow distribution on the interface more uniform, promoting the entry of lithium ions into the interior of the electrode, and improving the lithium extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0042] FIG1 is a diagram showing a process for preparing an electrode according to the present disclosure;

[0043] FIG2 is a diagram of the overall preparation process of the electrode for lithium extraction from salt lakes provided by the present disclosure;

[0044] Figure 3 shows the trend of anode lithium concentration over time. DETAILED DESCRIPTION

[0045] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0046] The endpoints of the ranges and any values ​​disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0047] The solution provided by the embodiment of the present disclosure includes a method for preparing an electrode. Referring to FIG. 1 , an amphiphilic diblock copolymer coating layer is formed on an electrode substrate, and the electrode substrate is modified using the amphiphilic diblock copolymer.

[0048] It should be noted that since the amphiphilic diblock copolymer contains both hydrophilic and hydrophobic segments, the hydrophobic segment is easily adsorbed on the surface of the electrode substrate to form a stable coating; the role of the hydrophilic segment is mainly manifested in two aspects: on the one hand, the hydrophilic segment can increase the wettability of the brine to the electrode, and the hydrophilic segment and the solution can form a stable solvation layer, thereby hindering the aggregation of colloids and particles in the solution, preventing them from entering the interior of the electrode and causing blockage of the mass transfer channel; on the other hand, the hydrophilic segment also has an excellent ability to complex lithium ions. In the cationic aggregation layer on the electrode surface, it can specifically complex lithium ions, making the lithium ion flow distribution on the interface more uniform, promoting the entry of lithium ions into the interior of the electrode, and improving the lithium extraction efficiency.

[0049] Specifically, referring to FIG. 2 , an embodiment of the present disclosure provides a method for preparing an electrode, comprising the following steps:

[0050] S1. Preparation of positive electrode active slurry

[0051] The preparation process of the positive electrode active slurry includes: mixing the positive electrode active material, the conductive agent and the binder, and homogenizing the slurry with a dispersant, stirring and mixing them thoroughly to form an electrode slurry.

[0052] In some embodiments, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium manganese oxide, and lithium nickel cobalt manganese oxide, and may be any one or more of the above. Commonly used positive electrode active materials are suitable for the embodiments of the present disclosure. Specifically, the ratio of nickel, cobalt, and manganese in the lithium nickel cobalt manganese oxide is not limited and may be commercially available materials such as NCM811 and NCM622.

[0053] In some embodiments, the conductive agent is selected from at least one of acetylene black and conductive carbon black, and can be any one or more of the above; the binder is selected from at least one of polyvinylidene fluoride (PVDF) and polypropylene (PP), and can be any one or more of the above, preferably PVDF.

[0054] In some embodiments, the mass ratio of the positive electrode active material, the conductive agent and the binder is 100:(10-20):(10-15), such as 100:10:10, 100:12:11, 100:15:13, 100:17:14, 100:20:15, etc.

[0055] The type and amount of the dispersant are not limited, and may be, but not limited to, N-methylpyrrolidone (NMP), as long as it can form a uniform slurry, and will be evaporated and removed during subsequent drying.

[0056] S2. Preparation of electrode substrate

[0057] The positive electrode active slurry is coated on the current collector and dried to form a positive electrode active coating, thus obtaining an electrode matrix.

[0058] In some embodiments, the current collector is selected from at least one of aluminum foil, titanium mesh, and carbon fiber cloth. Any one or more of these materials may be selected based on the application scenario. The thickness of the current collector is 10 μm to 15 μm, and the thickness can be adjusted as needed, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0059] In some embodiments, the coating thickness is controlled so that the thickness of the positive electrode active coating after drying is 100 μm-300 μm to ensure the electrochemical performance of the electrode substrate.

[0060] In some embodiments, during the formation of the positive electrode active coating, the drying temperature is controlled to be 100° C. to 120° C. and the drying time is controlled to be 10 hours to 20 hours to form a tightly bonded coating. Specifically, the drying temperature can be 100° C., 110° C., 120° C., etc., and the drying time can be 10 hours, 15 hours, 20 hours, etc.

[0061] S3, forming an amphiphilic diblock copolymer coating layer

[0062] An amphiphilic diblock copolymer coating layer is formed on the electrode substrate. The method for preparing the coating layer is not limited and various existing methods can be used, which are not listed here one by one.

[0063] In some embodiments, the coating process includes dispersing the amphiphilic diblock copolymer to obtain a copolymer dispersion, and using the copolymer dispersion to form an amphiphilic diblock copolymer coating layer on the surface of the electrode substrate. In actual operation, the electrode substrate can be immersed in the copolymer dispersion, removed after immersion, and dried to form a uniform coating.

[0064] The amphiphilic diblock copolymer is a commercially available material containing a hydrophilic segment and a hydrophobic segment. The hydrophilic segment is selected from at least one of polyoxyethylene (PEO), polyethylene glycol (PEG), or polyacrylic acid (PAA), and the hydrophobic segment is selected from at least one of polystyrene (PS), polybutadiene (PBD), and polyoxypropylene (PPO). The hydrophilic segment and the hydrophobic segment can be selected from any one or more of the above. The amphiphilic diblock copolymer is prepared by copolymerization. Preferably, the hydrophilic segment is polyoxyethylene and the hydrophobic segment is polystyrene, that is, the amphiphilic diblock copolymer is a polyoxyethylene-polystyrene copolymer (PEO-PS), which is a commercially available material. After modification with PEO-PS, the lithium extraction efficiency can be further improved.

[0065] In some embodiments, the molecular weight of the amphiphilic diblock copolymer used to form the amphiphilic diblock copolymer coating is 5000-50000 Da, and the mass ratio of the hydrophilic segment to the hydrophobic segment is 1:(1.6-4). By controlling the specific parameters of the amphiphilic diblock copolymer, the lithium extraction efficiency can be further improved. Specifically, the mass ratio of the hydrophilic segment to the hydrophobic segment can be 1:1.6, 1:2.0, 1:3.0, 1:4.0, etc.

[0066] In some embodiments, the preparation process of the copolymer dispersion includes: mixing the amphiphilic diblock copolymer and a solvent, the solvent can be but is not limited to water, and the mass fraction of the amphiphilic diblock copolymer in the copolymer dispersion is 2%-5%, such as 2%, 3%, 4%, 5%, etc.

[0067] In some embodiments, the soaking time is 4 hours to 12 hours, and the soaking temperature is 15°C to 30°C, that is, the soaking can be carried out at room temperature, which is convenient to operate. Specifically, the soaking time can be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, etc.; the soaking temperature can be 15°C, 20°C, 25°C, 30°C, etc.

[0068] In some embodiments, after immersion, the electrode substrate is taken out for drying at a temperature of 60°C to 80°C and a drying time of 4 to 6 hours to remove water and uniformly disperse the amphiphilic diblock copolymer on the surface of the electrode substrate. Specifically, the drying temperature may be 60°C, 70°C, 80°C, etc., and the drying time may be 4 hours, 5 hours, 6 hours, etc.

[0069] An embodiment of the present disclosure also provides an electrode, comprising an electrode substrate and an amphiphilic diblock copolymer coating layer coated on the surface of the electrode substrate, wherein the electrode substrate comprises a current collector and a positive electrode active coating attached to the current collector; wherein the amphiphilic diblock copolymer coating layer contains a hydrophilic segment and a hydrophobic segment.

[0070] It should be noted that the electrode matrix is ​​modified using an amphiphilic diblock copolymer containing both hydrophilic and hydrophobic segments. The hydrophilic segment can not only increase the hydrophilicity of the electrode, but also complex the lithium ions on the electrode surface, thereby improving the lithium extraction efficiency.

[0071] In some embodiments, in the electrode, the mass proportion of the amphiphilic diblock copolymer coating layer is 0.1%-5% (such as 0.1%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, etc.), and the mass of the introduced amphiphilic diblock copolymer coating layer is preferably controlled within the above range to further improve the lithium extraction efficiency of the lithium-rich electrode.

[0072] In some embodiments, the lithium-rich electrode can be delithiated to obtain a lithium-poor electrode. The specific delithiation operation process is not limited, and existing delithiation methods can be used.

[0073] In some embodiments, the delithiation process includes: using a lithium-rich electrode as the positive electrode, placing the positive electrode and the negative electrode in an electrolyte, applying power to the positive electrode and the negative electrode, and delithiating the lithium-rich electrode at a constant voltage to obtain a lithium-poor electrode. The power supply voltage can be 0.5V-2V, such as 0.5V, 1.0V, 1.5V, 2.0V, etc.

[0074] In some embodiments, the negative electrode is selected from at least one of a silver chloride electrode and nickel foam. Any of the above electrodes can be used as the negative electrode to complete the delithiation process.

[0075] In some embodiments, the electrolyte is selected from at least one of potassium chloride solution and sodium chloride solution, and can be any one or more of the above. The concentration of the electrolyte is 0.05mol / L-0.10mol / L, such as 0.05mol / L, 0.06mol / L, 0.07mol / L, 0.08mol / L, 0.09mol / L, 0.10mol / L, etc.

[0076] The disclosed embodiment also provides a salt lake lithium extraction device, comprising the above-mentioned lithium-rich electrode and the above-mentioned lithium-poor electrode, and may also include an electrolysis device, on which an anion exchange membrane is provided to separate the electrolysis device into an anode chamber and a cathode chamber.

[0077] In some embodiments, the material of the anion exchange membrane is selected from at least one of polystyrene, polypropylene, and polyamide, and may be any one or more of the above.

[0078] The embodiment of the present disclosure also provides a method for extracting lithium from a salt lake, comprising: extracting lithium using the above-mentioned salt lake lithium extraction device, which has the advantage of high lithium extraction efficiency.

[0079] In actual operation, a lithium-rich electrode and a lithium-poor electrode are placed in the anode chamber and cathode chamber, respectively. Brine is injected into the cathode chamber, and an electrolyte is injected into the anode chamber. Then, power is applied to the electrodes to extract lithium at a constant voltage, causing lithium to be selectively enriched in the lithium-poor electrode. The voltage applied can be 0.3V to 1.2V, such as 0.3V, 0.5V, 0.8V, 1.0V, 1.2V, etc.

[0080] In some embodiments, the electrolyte injected into the anode chamber is selected from at least one of potassium chloride solution and sodium chloride solution, and can be any one or more of the above. The concentration of the electrolyte is 0.05mol / L-0.10mol / L, such as 0.05mol / L, 0.06mol / L, 0.07mol / L, 0.08mol / L, 0.09mol / L, 0.10mol / L, etc.

[0081] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0082] It should be noted that the components of the brine used in the following examples and comparative examples are shown in Table 1.

[0083] Table 1 Composition of brine

[0084] Example 1

[0085] This embodiment provides a method for extracting lithium from a salt lake, and the specific steps are as follows:

[0086] Preparation of lithium-rich electrodes:

[0087] (1) Add 100g of lithium iron phosphate (LiFePO4), 10g of acetylene black, and 10g of binder PVDF to 180g of NMP and stir thoroughly to form a positive electrode active slurry.

[0088] (2) The positive electrode active slurry was coated on a current collector (aluminum foil with a thickness of 10 μm) and dried at 100° C. for 15 h to obtain an electrode substrate. The thickness of the positive electrode active coating formed after drying was 100 μm.

[0089] (3) Dissolve polyoxypropylene-polyoxyethylene copolymer (PPO-PEO, purchased from Ruixi Biotechnology, with a molecular weight of 12,000 Da) in water and stir to prepare a copolymer dispersion with a mass fraction of 2%.

[0090] (4) The electrode substrate prepared in step (2) was immersed in the copolymer dispersion prepared in step (3) for 8 h, taken out and dried at 60° C. for 6 h to obtain a lithium-rich electrode having an amphiphilic diblock copolymer coating layer.

[0091] Preparation of lithium-deficient electrodes:

[0092] The lithium-rich electrode prepared in step (4) was used as the positive electrode, the AgCl electrode was used as the negative electrode, and the 0.05 mol / L NaCl solution was used as the electrolyte. The lithium-rich electrode was delithiated at a constant voltage of 1.0 V. When the current was lower than 0.5 A / m 2 When the power is stopped, a lithium-poor electrode is obtained.

[0093] Lithium extraction from salt lakes:

[0094] The electrolysis device was separated into an anode chamber and a cathode chamber by an anion exchange membrane (polystyrene). The lithium-rich electrode and the lithium-poor electrode were placed in the anode chamber and the cathode chamber, respectively. Brine was injected into the cathode chamber and 0.05 mol / L KCl solution was injected into the anode chamber. A constant voltage of 0.3 V was applied to the anode and cathode, and lithium was extracted by electrolysis at 25°C for 8 hours.

[0095] Example 2

[0096] This embodiment provides a method for extracting lithium from a salt lake, and the specific steps are as follows:

[0097] Preparation of lithium-rich electrodes:

[0098] (1) Add 100g of lithium iron phosphate (LiFePO4), 20g of acetylene black, and 15g of binder PVDF to 150g of NMP and stir thoroughly to form a positive electrode active slurry.

[0099] (2) The positive electrode active slurry obtained in step (1) was coated on a current collector (aluminum foil with a thickness of 15 μm) and dried at 120° C. for 10 h to obtain an electrode substrate. The thickness of the positive electrode active coating formed after drying was 200 μm.

[0100] (3) Dissolve polyoxyethylene-polystyrene copolymer (PEO-PS, purchased from Xi'an Qiyue Biological, with a molecular weight of 25500Da) in water and stir to prepare a copolymer dispersion with a mass fraction of 3%.

[0101] (4) The electrode substrate prepared in step (2) was immersed in the copolymer dispersion prepared in step (3) for 6 hours, taken out and dried at 80° C. for 4 hours to obtain a lithium-rich electrode having an amphiphilic diblock copolymer coating layer.

[0102] Preparation of lithium-deficient electrodes:

[0103] The lithium-rich electrode prepared in step (4) was used as the positive electrode, the AgCl electrode was used as the negative electrode, and the 0.05 mol / L NaCl solution was used as the electrolyte. The lithium-rich electrode was delithiated at a constant voltage of 1.0 V. When the current was lower than 0.5 A / m 2 When the power is stopped, a lithium-poor electrode is obtained.

[0104] Lithium extraction from salt lakes:

[0105] The electrolysis device was separated into an anode chamber and a cathode chamber by an anion exchange membrane (polypropylene). The lithium-rich electrode and the lithium-poor electrode were placed in the anode chamber and the cathode chamber, respectively. Brine was injected into the cathode chamber and 0.05 mol / L KCl solution was injected into the anode chamber. A constant voltage of 0.3 V was applied to the anode and cathode, and lithium was extracted by electrolysis at 25°C for 8 hours.

[0106] Example 3

[0107] This embodiment provides a method for extracting lithium from a salt lake, and the specific steps are as follows:

[0108] Preparation of lithium-rich electrodes:

[0109] (1) Add 100g of lithium iron phosphate (LiFePO4), 15g of acetylene black, and 12g of binder PVDF to 200g of NMP and stir thoroughly to form a positive electrode active slurry.

[0110] (2) The positive electrode active slurry obtained in step (1) was coated on a current collector (aluminum foil with a thickness of 12 μm) to obtain an electrode, and then dried at 100° C. for 15 h to obtain an electrode substrate. The thickness of the positive electrode active coating formed after drying was 250 μm.

[0111] (3) Dissolve polyoxyethylene-polyoxypropylene copolymer (PEO-PPO, purchased from Ruixi Biotechnology, with a molecular weight of 12,000 Da) in water and stir to prepare a copolymer dispersion with a mass fraction of 2%.

[0112] (4) The electrode substrate prepared in step (2) was immersed in the copolymer dispersion prepared in step (3) for 10 hours, taken out and dried at 80° C. for 4 hours to obtain a lithium-rich electrode having an amphiphilic diblock copolymer coating layer.

[0113] Preparation of lithium-deficient electrodes:

[0114] The lithium-rich electrode prepared in step (4) was used as the positive electrode, the AgCl electrode was used as the negative electrode, and the 0.05 mol / L NaCl solution was used as the electrolyte. The lithium-rich electrode was delithiated at a constant voltage of 1.0 V. When the current was lower than 0.5 A / m 2 When the power is stopped, a lithium-poor electrode is obtained.

[0115] Lithium extraction from salt lakes:

[0116] The electrolysis device was separated into an anode chamber and a cathode chamber by an anion exchange membrane (polyamide). The lithium-rich electrode and the lithium-poor electrode were placed in the anode chamber and the cathode chamber respectively. Brine was injected into the cathode chamber and 0.05 mol / L KCl solution was injected into the anode chamber. A constant voltage of 0.3 V was applied to the anode and cathode, and lithium was extracted by electrolysis at 25°C for 8 hours.

[0117] Example 4

[0118] The only difference from Example 1 is that the polyoxypropylene-polyoxyethylene copolymer (PPO-PEO) in step (3) is replaced by polystyrene-polyacrylic acid (PS-PAA) (Ruixi Biotechnology, molecular weight 6000 Da).

[0119] Example 5

[0120] The only difference from Example 1 is that the polyoxypropylene-polyoxyethylene copolymer (PPO-PEO) in step (3) is replaced by polystyrene-polyethylene glycol (PS-PEG) (Hangzhou Xinqiao Biological, molecular weight 10000Da.

[0121] Example 6

[0122] The only difference from Example 1 is that the polyoxypropylene-polyoxyethylene copolymer (PPO-PEO) in step (3) is replaced by polybutadiene-polyoxyethylene (PBD-PEO) (Ruixi Biotechnology, molecular weight 9000Da).

[0123] Example 7

[0124] The only difference from Example 1 is that the mass fraction of the copolymer dispersion in step (3) is 1%.

[0125] Example 8

[0126] The only difference from Example 1 is that the mass fraction of the copolymer dispersion in step (3) is 0.2%.

[0127] Example 9

[0128] The only difference from Example 1 is that the mass fraction of the copolymer dispersion in step (3) is set to 6%.

[0129] Example 10

[0130] The only difference from Example 1 is that the electrode substrate in step (4) is immersed in the copolymer dispersion for 1 hour.

[0131] Comparative Example 1

[0132] This comparative example provides a method for extracting lithium from salt lakes. The only difference from Example 1 is that no amphiphilic diblock copolymer coating layer is formed on the electrode substrate. The specific steps are as follows:

[0133] (1) Add 100g of lithium iron phosphate (LiFePO4), 10g of acetylene black, and 10g of binder PVDF to 180g of NMP and stir thoroughly to form a positive electrode active slurry.

[0134] (2) The positive electrode active slurry obtained in step (1) was coated on a current collector (aluminum foil with a thickness of 10 μm), and dried at 100° C. for 15 h to obtain a finished electrode. The thickness of the positive electrode active coating formed after drying was 100 μm.

[0135] (3) With the electrode of step (2) as the positive electrode, the AgCl electrode as the negative electrode, and 0.05 mol / L NaCl solution as the electrolyte, the lithium-rich electrode was delithiated at a constant voltage of 1.0 V. When the current was lower than 0.5 A / m 2 When the power is stopped, a lithium-poor electrode is obtained.

[0136] (4) The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane (polystyrene), and the electrode obtained in step (2) and the lithium-deficient electrode obtained in step (3) are placed in the anode chamber and the cathode chamber, respectively. Brine is injected into the cathode chamber, and a 0.05 mol / L KCl solution is injected into the anode chamber. A constant voltage of 0.3 V is applied to the anode and cathode, and lithium is extracted by electrolysis at 25°C for 8 h.

[0137] Comparative Example 2

[0138] This comparative example provides a method for extracting lithium from a salt lake. The only difference from comparative example 1 is that nano-silica is introduced in step (1). Since nano-silica has a large specific surface area and hydroxyl groups on its surface, it can be blended and modified with PVDF to enhance the hydrophilic properties of PVDF.

[0139] The specific steps are as follows:

[0140] (1) Add 100g of lithium iron phosphate (LiFePO4), 10g of acetylene black, 5g of nano-silicon dioxide (particle size of 50nm), and 10g of binder PVDF to 180g of NMP, and stir and mix thoroughly to form a positive electrode active slurry.

[0141] (2) The positive electrode active slurry obtained in step (1) was coated on a current collector (aluminum foil with a thickness of 10 μm), and dried at 100° C. for 15 h to obtain a finished electrode.

[0142] (3) With the electrode of step (2) as the positive electrode, the AgCl electrode as the negative electrode, and 0.05 mol / L NaCl solution as the electrolyte, the lithium-rich electrode is delithiated at a constant voltage of 1.0 V. The power-on time is when the current is less than 0.5 A / m 2When the power is stopped, a lithium-poor electrode is obtained.

[0143] (4) The electrolysis device was separated into an anode chamber and a cathode chamber by an anion exchange membrane (polyamide). The lithium-rich electrode and the lithium-poor electrode were placed in the anode chamber and the cathode chamber, respectively. Brine was injected into the cathode chamber and 0.05 mol / L KCl solution was injected into the anode chamber. A constant voltage of 0.3 V was applied to the anode and cathode, and lithium was extracted by electrolysis at 25°C for 8 h.

[0144] Comparative Example 3

[0145] This comparative example provides a method for extracting lithium from a salt lake, which differs from Example 1 only in that no hydrophobic group is introduced in step (3), that is, the polyoxypropylene-polyoxyethylene copolymer (PPO-PEO) in step (3) is replaced by polyoxyethylene (PEO) with a molecular weight of 10,000 Da.

[0146] Comparative Example 4

[0147] This comparative example provides a method for extracting lithium from a salt lake, which differs from Example 1 only in that no hydrophilic group is introduced in step (3), that is, the polyoxypropylene-polyoxyethylene copolymer (PPO-PEO) in step (3) is replaced by polyoxypropylene (PPO) with a molecular weight of 20,000 Da.

[0148] Test Example 1

[0149] The changes in lithium ion concentration of the brine before and after the lithium extraction reaction in the embodiment and the comparative example, the lithium concentration of the anolyte after the completion of lithium extraction, and the capacity retention rate of the electrode after 100 lithium extractions were detected. The results are shown in Table 2 and Figure 3.

[0150] Table 2 Lithium extraction effect test results of the salt lake lithium extraction method provided by the embodiment and comparative example

[0151] It can be seen that the lithium-rich electrode and the lithium-poor electrode prepared in the embodiment have a higher lithium extraction efficiency after being used for lithium extraction from salt lakes, and still maintain a good capacity after 100 cycles. Industrial Applicability

[0152] The present invention utilizes an amphiphilic diblock copolymer to modify the surface of an electrode substrate to form a diblock copolymer coating. Because the amphiphilic diblock copolymer contains both hydrophilic and hydrophobic segments, it can form a stable coating on the electrode substrate surface while also improving lithium extraction efficiency. The process for forming the diblock copolymer coating is easy to operate and has excellent industrial applicability.

Claims

1. An electrode, characterized in that: It comprises an electrode substrate and an amphiphilic diblock copolymer coating layer coated on the surface of the electrode substrate, wherein the electrode substrate comprises a current collector and a positive electrode active coating attached to the current collector; Wherein, the amphiphilic diblock copolymer coating layer contains a hydrophilic segment and a hydrophobic segment.

2. The electrode according to claim 1, characterized in that The hydrophilic segment is selected from at least one of polyoxyethylene, polyethylene glycol and polyacrylic acid.

3. The electrode according to claim 1 or 2, characterized in that The hydrophobic segment is selected from at least one of polystyrene, polybutadiene and polyoxypropylene.

4. The electrode according to any one of claims 1 to 3, characterized in that The hydrophilic segment is polyethylene oxide, and the hydrophobic segment is polystyrene.

5. The electrode according to any one of claims 1 to 4, characterized in that In the electrode, the mass proportion of the amphiphilic diblock copolymer coating layer is 0.1%-5%.

6. The electrode according to any one of claims 1 to 5, characterized in that The molecular weight of the amphiphilic diblock copolymer used to form the amphiphilic diblock copolymer coating layer is 5000-50000 Da, and the mass ratio of the hydrophilic segment to the hydrophobic segment is 1:(1.6-4).

7. The electrode according to any one of claims 1 to 6, characterized in that The positive electrode active coating contains a positive electrode active material, and the positive electrode active material is selected from at least one of lithium iron phosphate, lithium manganese oxide and nickel cobalt lithium manganese oxide.

8. The electrode according to claim 7, characterized in that The positive electrode active coating layer also contains a conductive agent and a binder, and the mass ratio of the positive electrode active material, the conductive agent and the binder is 100:(10-20):(10-15).

9. The electrode according to claim 8, characterized in that The current collector is selected from at least one of aluminum foil, titanium mesh and carbon fiber cloth.

10. The electrode according to claim 8 or 9, characterized in that: The conductive agent is selected from at least one of acetylene black and conductive carbon black.

11. The electrode according to any one of claims 8 to 10, characterized in that The binder is selected from at least one of polyvinylidene fluoride and polypropylene.

12. The electrode according to any one of claims 9 to 11, characterized in that The thickness of the current collector is 10 μm-15 μm, and the thickness of the positive electrode active coating is 100 μm-300 μm.

13. A method for preparing the electrode according to any one of claims 1 to 12, characterized in that: include: The amphiphilic diblock copolymer coating layer is formed on the electrode substrate.

14. The preparation method according to claim 13, characterized in that: include: The amphiphilic diblock copolymer is dispersed to obtain a copolymer dispersion, and the copolymer dispersion is used to form the amphiphilic diblock copolymer coating layer on the surface of the electrode substrate.

15. The preparation method according to claim 14, characterized in that: The process of forming the amphiphilic diblock copolymer coating layer comprises: immersing the electrode substrate in the copolymer dispersion, taking it out after immersion, and drying it.

16. The preparation method according to claim 15, characterized in that: The mass fraction of the amphiphilic diblock copolymer in the copolymer dispersion is 2%-5%.

17. The preparation method according to claim 15 or 16, characterized in that: The soaking time is 4h-12h, and the soaking temperature is 15℃-30℃.

18. The preparation method according to any one of claims 15 to 17, characterized in that: The drying temperature is 60℃-80℃, and the drying time is 4h-6h.

19. The preparation method according to any one of claims 13 to 18, characterized in that: The preparation process of the electrode substrate comprises: coating the positive electrode active slurry on the current collector, and forming the positive electrode active coating after drying; The preparation process of the positive electrode active slurry includes: mixing the positive electrode active material, the conductive agent and the binder, and homogenizing the mixture with a dispersant.

20. The preparation method according to claim 19, characterized in that: During the process of forming the positive electrode active coating, the drying temperature is controlled to be 100° C.-120° C., and the drying time is controlled to be 10 h-20 h.

21. A device for extracting lithium from a salt lake, characterized in that: Including lithium-rich electrodes and lithium-poor electrodes; Wherein, the lithium-rich electrode is the electrode described in any one of claims 1-12 or the electrode prepared by the preparation method described in any one of claims 13-20.

22. The salt lake lithium extraction device according to claim 21, characterized in that: The lithium-poor electrode is prepared by delithiating the lithium-rich electrode.

23. The salt lake lithium extraction device according to claim 21, characterized in that: The invention also comprises an electrolysis device, wherein an anion exchange membrane is arranged in the electrolysis device to separate the electrolysis device into an anode chamber and a cathode chamber.

24. The salt lake lithium extraction device according to claim 23, characterized in that: The material of the anion exchange membrane is selected from at least one of polystyrene, polypropylene and polyamide.

25. A method for extracting lithium from a salt lake, characterized in that: include: Lithium is extracted using the salt lake lithium extraction device described in any one of claims 21-24.

26. The method for extracting lithium from salt lake according to claim 25, characterized in that: include: The lithium-rich electrode and the lithium-poor electrode are placed in the anode chamber and the cathode chamber respectively, brine is injected into the cathode chamber, electrolyte is injected into the anode chamber, and then electricity is applied.

27. The method for extracting lithium from salt lake according to claim 26, characterized in that: The electrolyte injected into the anode chamber is selected from at least one of a potassium chloride solution and a sodium chloride solution, and the concentration of the electrolyte is 0.05 mol / L-0.10 mol / L.

28. The method for extracting lithium from salt lake according to claim 26 or 27, characterized in that: The power-on voltage is 0.3V-1.2V.

Images