Magnetic lithium-rich electrode, and preparation method therefor and use thereof

Abstract

The present disclosure provides a magnetic lithium-rich electrode, and a preparation method therefor and a use thereof. The magnetic lithium-rich electrode comprises a current collector and an active material layer provided on a surface of the current collector; the active material layer comprises an electrode active material, a magnetic material, a conductive agent, and a binder; the porosity of the magnetic lithium-rich electrode is 10-60%. In the present disclosure, by means of a magnetic field-assisted lithium extraction method in which a magnetic field is applied in an electrode preparation process, electrode porosity and the lithium ion conduction rate can be improved, thus the electrode internal mass transfer rate is increased and the electrochemical lithium extraction efficiency is markedly improved.

Description

A magnetic lithium-rich electrode and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of lithium extraction from salt lakes and relates to a magnetic lithium-rich electrode and a preparation method and application thereof. Background Art

[0002] Lithium is a key strategic resource widely used in lithium batteries. The rapid development of the new energy sector has driven a rapid increase in market demand for lithium resources, making low-cost, efficient lithium resource development a crucial factor for companies to compete in this market. Discovered lithium resources are primarily found in salt lake brines, seawater, and ores, with salt lake lithium accounting for approximately 70%. Due to the high cost and difficulty of mining lithium ore, and its increasing depletion and depletion with continued mining, extracting lithium from salt lake brines has become a trend in lithium resource development.

[0003] There are many salt lakes in western my country, but their development level is low due to their high magnesium-to-lithium ratio. Currently, the main methods for extracting lithium from brine at home and abroad include precipitation, solvent extraction, evaporation crystallization, electrodialysis, ion exchange adsorption, etc. Precipitation, as a mature lithium extraction technology, has the disadvantages of high energy consumption, complex process flow, high cost, and low lithium recovery rate. The extraction method has a fast lithium extraction rate, but the dissolution of the extractant in the brine can easily cause environmental pollution; the adsorption method has problems such as low adsorption capacity, adsorbent dissolution, and high water consumption. In recent years, many researchers at home and abroad have conducted extensive exploration and research on new lithium extraction processes. Electrochemical lithium extraction technology has good use value and application prospects.

[0004] The principle of electrochemical lithium extraction is to charge the working electrode to release lithium ions to form a lithium ion sieve, discharge it in brine to allow lithium ions to selectively enter the lithium ion sieve, and achieve lithium enrichment through cyclic operation of the charge and discharge process.

[0005] CN105600807A discloses a method for electrochemically extracting lithium salts from brine with a high magnesium-to-lithium ratio. Spinel-type LiMn2O4 is uniformly coated on a titanium mesh current collector as a working electrode. The titanium mesh is placed in a LiCl solution as a counter electrode. The electrode is charged at a constant voltage to release lithium ions from the LiMn2O4 to form a lithium ion sieve. Discharging the electrode system in brine with a high magnesium-to-lithium ratio can selectively embed lithium ions into the lithium ion sieve. The charge and discharge cycle operation realizes the electrochemical extraction of lithium salts. However, due to the presence of a large amount of impurity elements (such as magnesium, sodium, etc.) in the salt lake brine, the brine has a high viscosity, resulting in a problem of slow mass transfer of the solution inside the electrode in this method, which further leads to low efficiency of electrochemical lithium extraction.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The purpose of the present disclosure is to provide a magnetic lithium-rich electrode and its preparation method and application. The present disclosure uses a magnetic field-assisted method to apply a magnetic field during the electrode preparation process, which can increase the porosity of the electrode and the lithium ion conduction rate, thereby increasing the mass transfer rate inside the electrode and significantly improving the electrochemical lithium extraction efficiency.

[0009] To achieve this disclosure purpose, the present disclosure adopts the following technical solutions:

[0010] In the first aspect, an embodiment of the present disclosure provides a magnetic lithium-rich electrode, which includes a current collector and an active material layer arranged on the surface of the current collector, wherein the active material layer includes an electrode active material, a magnetic material, a conductive agent and a binder, and the porosity of the magnetic lithium-rich electrode is 10 to 60%, for example: 10%, 20%, 30%, 40% or 60%, etc.

[0011] The magnetic lithium-rich electrode described in the embodiment of the present disclosure contains magnetic material. During the preparation of the electrode, a magnetic field is applied, and the movement direction of the magnetic particles is controlled by changing the direction of the magnetic field, so that the magnetic particles rotate repeatedly under the action of the changing magnetic field, thereby improving the electrode porosity and lithium ion conductivity.

[0012] In one embodiment, the current collector comprises carbon fiber or titanium mesh.

[0013] In one embodiment, the electrode active material includes any one of lithium manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate, or a combination of at least two thereof.

[0014] In one embodiment, the magnetic substance includes ferrosoferric oxide.

[0015] In one embodiment, the particle size of the magnetic material is 10-200 nm, for example, 10 nm, 50 nm, 80 nm, 100 nm or 200 nm.

[0016] In one embodiment, the conductive agent includes acetylene black and / or conductive carbon black.

[0017] In one embodiment, the binder includes polyvinylidene fluoride.

[0018] In one embodiment, the mass ratio of the electrode active material, magnetic substance, conductive agent and binder is 1:(0.01-0.2):(0.1-0.2):(0.1-0.15), for example: 1:0.01:0.1:0.1, 1:0.05:0.12:0.11, 1:0.1:0.15:0.12, 1:0.15:0.18:0.14 or 1:0.2:0.2:0.15, etc.

[0019] In one embodiment, the lithium ion conductivity of the magnetic lithium-rich electrode is 10 -5 ~10 -2 S / cm, for example: 10 -5 S / cm, 2×10 -4 S / cm, 5×10 -3 S / cm, 8×10 -3 S / cm or 10 -2 S / cm, etc.

[0020] In one embodiment, the porosity of the magnetic lithium-rich electrode is 20-50%.

[0021] The porosity of the magnetic lithium-rich electrode described in the embodiment of the present disclosure is preferably controlled at 20-50%. If the pores are too large, the mechanical strength of the electrode is poor, which reduces the cycle performance. If the porosity is too small, the mass transfer effect of the brine solution is poor.

[0022] In a second aspect, an embodiment of the present disclosure provides a method for preparing a magnetic lithium-rich electrode as described in the first aspect, the preparation method comprising the following steps:

[0023] The electrode active material, magnetic substance, conductive agent, binder and solvent are mixed to obtain slurry, a reverse magnetic field is applied to the current collector, and the slurry is coated on the surface of the current collector to obtain a lithium-rich electrode.

[0024] In the embodiment of the present disclosure, a small amount of magnetic material is added when preparing the electrode slurry, and a changing magnetic field is applied during the coating process to cause the magnetic material to move in different directions within the electrode. The movement trajectory can form a pore structure within the electrode, that is, the path for lithium ions to move within the active material layer, thereby improving lithium ion conductivity.

[0025] In one embodiment, the solvent comprises N-methylpyrrolidone.

[0026] In one embodiment, the viscosity of the slurry is 1-10 Pa·s, for example, 1 Pa·s, 2 Pa·s, 5 Pa·s, 8 Pa·s or 10 Pa·s.

[0027] In one embodiment, the intensity of the variable direction magnetic field is 0.5-5 T, for example, 0.5 T, 1 T, 2 T, 3 T, 4 T or 5 T.

[0028] In one embodiment, the coating density is 150-200 mg / cm 2 , for example: 150mg / cm 2 、160mg / cm 2 、170mg / cm 2 、180mg / cm 2 or 200mg / cm 2 wait.

[0029] In one embodiment, the coating is followed by drying.

[0030] In one embodiment, the drying temperature is 50-80°C, for example, 50°C, 55°C, 60°C, 70°C or 80°C.

[0031] In one embodiment, the drying time is 4 to 8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0032] In a third aspect, the present disclosure provides a method for extracting lithium from a salt lake by means of a magnetic field-assisted electrochemical deintercalation method, the method comprising the following steps:

[0033] (1) Using the magnetic lithium-rich electrode described in the first aspect as the positive electrode and the AgCl electrode as the negative electrode, injecting electrolyte and performing constant voltage reaction to obtain a magnetic lithium-poor electrode;

[0034] (3) The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane. A magnetic lithium-rich electrode is placed in the anode chamber, and a magnetic lithium-poor electrode is placed in the cathode chamber. Salt lake brine is injected into the cathode chamber, and a salt solution is injected into the anode chamber. A magnetic field is applied to the electrodes while applying constant voltage. The current is as low as 150 mA to terminate the reaction.

[0035] In the embodiment of the present disclosure, adding a magnetic field during the lithium extraction process can promote the flow of brine, increase the contact rate between brine and active substances, and improve the efficiency of lithium extraction.

[0036] In one embodiment, the electrolyte in step (1) includes sodium chloride solution and / or potassium chloride solution.

[0037] In one embodiment, the concentration of the electrolyte is 0.05-0.1 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L or 0.1 mol / L.

[0038] In one embodiment, the voltage of the constant voltage reaction is 0.8V to 1.2V, for example, 0.8V, 0.9V, 1V, 1.1V, or 1.2V.

[0039] In one embodiment, the salt solution in step (2) includes sodium chloride solution and / or potassium chloride solution.

[0040] In one embodiment, the concentration of the salt solution is 0.05 to 0.1 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L or 0.1 mol / L.

[0041] In one embodiment, the constant voltage power supply in step (2) is 0.3-1.2V, for example, 0.3V, 0.5V, 0.8V, 1V or 1.2V.

[0042] In one embodiment, the intensity of the magnetic field is 0.1-1 T, for example, 0.1 T, 0.2 T, 0.5 T, 0.8 T or 1 T.

[0043] Compared with the related art, the present disclosure has the following beneficial effects:

[0044] (1) The present invention adds a small amount of magnetic material when preparing the electrode slurry, and applies a changing magnetic field during the coating process, so that the magnetic material moves in different directions in the electrode. The movement trajectory can form a pore structure in the electrode, that is, the path for lithium ions to move in the active material layer, thereby improving the lithium ion conductivity.

[0045] (2) During the lithium extraction process, the present invention applies a magnetic field with controllable magnitude and direction to the electrodes, which can regulate the motion of the magnetic material within the electrodes. The motion of the magnetic material within the mass transfer channel can disturb the brine, promote the flow of the brine, accelerate the contact between the brine and the active material, and improve the efficiency of lithium extraction.

[0046] (3) The electrode prepared in the present invention has a good mass transfer effect on brine. After lithium extraction, the lithium concentration in the lithium-rich anode liquid can reach more than 3.04 g / L, and has excellent electrochemical salt lake lithium extraction performance.

[0047] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0049] FIG1 is a schematic structural diagram of the magnetic lithium-rich electrode described in Example 1 of the present disclosure, wherein 1 is electrode active material, 2 is magnetic substance, and 3 is magnetic flux lines.

[0050] Figure 2 is a schematic diagram of the apparatus for magnetic field-assisted electrochemical deintercalation of lithium from salt lakes as described in Example 1 of the present disclosure. In particular, 1 is a coil, 2 is an iron core, 3 is lithium ions, 4 is a KCl solution, 5 is an anion exchange membrane, and 6 is brine. DETAILED DESCRIPTION

[0051] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0052] Example 1

[0053] This embodiment provides a method for extracting lithium from a salt lake by means of a magnetic field-assisted electrochemical deintercalation method, the method comprising the following steps:

[0054] (1) 100g of lithium iron phosphate and 10g of ferroferric oxide (D 50 =50nm), 20g acetylene black and 15g PVDF were mixed and added to NMP to form a slurry with a viscosity of 10Pa·s. The slurry was heated at 150mg / cm 2 The density of the magnetic particles was coated on the titanium mesh current collector, and a magnetic field with a strength of 2T was applied to the current collector at a frequency of 2 times / min. The magnetic particles were repeatedly rotated under the action of the magnetic field. The particles were then dried at 80 ° C for 4 h to obtain a porosity of 30% and a lithium ion conductivity of 5.83×10 -3 S / cm magnetic lithium-rich electrode;

[0055] (2) Using a magnetic lithium-rich electrode as the positive electrode, an AgCl electrode as the negative electrode, and a 0.05 mol / L KCl solution as the electrolyte, the lithium-rich electrode was delithiated at a constant voltage of 1.0 V to obtain a magnetic lithium-poor electrode;

[0056] (3) The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane, and a magnetic lithium-rich electrode and a magnetic lithium-poor electrode are placed in the anode chamber and the cathode chamber respectively. Brine is injected into the cathode chamber and a 0.05KCl solution is injected into the anode chamber. Lithium is extracted at a constant voltage of 0.3V. At the same time, a 1T reversing magnetic field is applied to the electrode by a magnetic field regulating device with a reversing frequency of 3 times / min to regulate the motion state of the magnetic material in the electrode. When the current is as low as 150mA, the reaction is terminated.

[0057] The structural schematic diagram of the magnetic lithium-rich electrode in a magnetic field is shown in Figure 1, and the schematic diagram of the device for magnetic field-assisted electrochemical deintercalation and lithium extraction from salt lakes is shown in Figure 2. It can be seen from Figures 1-2 that the present invention applies a reverse magnetic field during the process of lithium extraction from salt lakes. Due to the magnetic material present in the electrode, the motion state of the magnetic material changes under the action of the reverse magnetic field, which can promote the flow of brine, accelerate the contact between brine and active materials, and improve the efficiency of lithium extraction.

[0058] Example 2

[0059] This embodiment provides a method for extracting lithium from a salt lake by means of a magnetic field-assisted electrochemical deintercalation method, the method comprising the following steps:

[0060] (1) 100g of lithium iron phosphate and 1g of ferroferric oxide (D 50 =100nm), 10g acetylene black and 10g PVDF were mixed and added to NMP to form a slurry with a viscosity of 1Pa·s. The slurry was heated at 150mg / cm 2 The density of the magnetic particles was coated on the titanium mesh current collector, and a magnetic field with a strength of 0.5 T was applied to the current collector at the same time. The frequency of the direction change was 2 times / min, so that the magnetic particles rotated repeatedly under the action of the direction-changing magnetic field. Then, the magnetic particles were dried at 50 ° C for 8 h to obtain a porosity of 20% and a lithium ion conductivity of 4.67×10 -3 S / cm magnetic lithium-rich electrode;

[0061] (2) Using a magnetic lithium-rich electrode as the positive electrode, an AgCl electrode as the negative electrode, and a 0.05 mol / L KCl solution as the electrolyte, the lithium-rich electrode was delithiated at a constant voltage of 1.0 V to obtain a magnetic lithium-poor electrode;

[0062] (3) The electrolysis device was separated into an anode chamber and a cathode chamber using an anion exchange membrane. A magnetic lithium-rich electrode and a magnetic lithium-poor electrode were placed in the anode chamber and the cathode chamber, respectively. Brine was injected into the cathode chamber and a 0.05KCl solution was injected into the anode chamber. Lithium was extracted at a constant voltage of 0.5V. Simultaneously, a 0.1T reversing magnetic field was applied to the electrodes using a magnetic field regulating device at a frequency of 3 times / min to regulate the motion of the magnetic material within the electrodes. The reaction was terminated when the current dropped to 150mA.

[0063] Example 3

[0064] This embodiment provides a method for extracting lithium from a salt lake by means of a magnetic field-assisted electrochemical deintercalation method, the method comprising the following steps:

[0065] (1) 100g lithium iron phosphate and 15g ferroferric oxide (D 50=20nm), 15g acetylene black and 15g PVDF were mixed and added to NMP to form a slurry with a viscosity of 5Pa·s. The slurry was stirred at 200mg / cm 2 The density of the magnetic particles was coated on the titanium mesh current collector, and a magnetic field with a strength of 1 T was applied to the current collector at a frequency of 2 times / min. The magnetic particles were repeatedly rotated under the action of the magnetic field. The particles were then dried at 60 ° C for 5 h to obtain a porosity of 40% and a lithium ion conductivity of 6.35×10 -3 S / cm magnetic lithium-rich electrode;

[0066] (2) Using a magnetic lithium-rich electrode as the positive electrode, an AgCl electrode as the negative electrode, and a 0.05 mol / L KCl solution as the electrolyte, the lithium-rich electrode was delithiated at a constant voltage of 1.0 V to obtain a magnetic lithium-poor electrode;

[0067] (3) The electrolysis device was separated into an anode chamber and a cathode chamber using an anion exchange membrane. A magnetic lithium-rich electrode and a magnetic lithium-poor electrode were placed in the anode chamber and the cathode chamber, respectively. Brine was injected into the cathode chamber and a 0.05KCl solution was injected into the anode chamber. Lithium was extracted at a constant voltage of 0.5V. Simultaneously, a 0.5T reversing magnetic field was applied to the electrodes using a magnetic field regulating device at a frequency of 3 times / min to regulate the motion of the magnetic material within the electrodes. The reaction was terminated when the current dropped to 150mA.

[0068] Example 4

[0069] The only difference between this embodiment and embodiment 1 is that the magnetic field strength in step (1) is 0.3 T, the porosity is 10%, and the lithium ion conductivity is 2.39×10 -3 S / cm magnetic lithium-rich electrode, and other conditions and parameters are exactly the same as those in Example 1.

[0070] Example 5

[0071] The only difference between this embodiment and embodiment 1 is that the magnetic field strength in step (1) is 6 T, the porosity is 60%, and the lithium ion conductivity is 6.61×10 -3 S / cm magnetic lithium-rich electrode, and other conditions and parameters are exactly the same as those in Example 1.

[0072] Example 6

[0073] The only difference between this embodiment and embodiment 1 is that the magnetic field strength in step (3) is 0.05 T, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0074] Example 7

[0075] The only difference between this embodiment and embodiment 1 is that the magnetic field strength in step (3) is 1.2 T, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0076] Comparative Example 1

[0077] The only difference between this comparative example and Example 1 is that no magnetic field is applied to the current collector during the coating process in step (1). Other conditions and parameters are exactly the same as those in Example 1.

[0078] Comparative Example 2

[0079] The only difference between this comparative example and Example 1 is that no magnetic field is applied to the electrodes during the lithium extraction process in step (3), and the other conditions and parameters are exactly the same as those in Example 1.

[0080] Comparative Example 3

[0081] A method for extracting lithium from salt lakes by electrochemical deintercalation assisted by a magnetic field is provided, the method comprising the following steps:

[0082] (1) 100g of lithium iron phosphate was mixed with 10g of sodium bicarbonate, 20g of acetylene black and 15g of PVDF, added to NMP, and mixed evenly to obtain an electrode slurry. The mixture was heated to 150mg / cm 2 The density of the coating was coated on the titanium mesh current collector and then dried at 80 ° C for 4 h to obtain the lithium-rich electrode;

[0083] (2) Using a lithium-rich electrode as the positive electrode, an AgCl electrode as the negative electrode, and a 0.05 mol / L KCl solution as the electrolyte, the lithium-rich electrode was delithiated at a constant voltage of 1.0 V to obtain a lithium-poor electrode;

[0084] (3) The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane. 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 and 0.05KCl solution is injected into the anode chamber. Lithium is extracted at a constant voltage of 0.3V. The reaction is terminated when the current drops to 150mA.

[0085] Performance testing:

[0086] The lithium concentration of the lithium-rich solutions obtained in the examples and comparative examples was tested, and the test results are shown in Table 1:

[0087] Table 1

[0088] As can be seen from Table 1, from Examples 1-3, the lithium concentration of the lithium-rich solution prepared by the magnetic field-assisted electrochemical deintercalation method for lithium extraction from salt lakes disclosed in the present invention can reach above 3.04 g / L.

[0089] By comparing Example 1 with Examples 4-5, it can be seen that in the lithium extraction process described in the present disclosure, the magnetic field strength applied to the current collector when preparing the lithium-rich electrode will affect the subsequent lithium extraction effect. The first magnetic field strength is controlled at 0.5~5T, and the lithium extraction effect is better. If the strength is too large, the movement range of the magnetic particles is too large and the movement speed is too fast, resulting in excessively large pores, poor mechanical strength of the electrode, and reduced cycle performance. If the strength is too small, the magnetic particles cannot rotate, resulting in low porosity and poor mass transfer of the brine solution.

[0090] By comparing Example 1 with Examples 6-7, it can be seen that in the lithium extraction process described in the present disclosure, the magnetic field strength applied to the electrode will affect the subsequent lithium extraction effect. The second magnetic field strength is controlled at 0.1~1T, and the lithium extraction effect is better. If the strength is too large, the magnetic particles move out of a certain range, resulting in uneven distribution, which leads to uneven disturbance of the brine and uneven mass transfer of the solution. If the strength is too small, the movement amplitude of the magnetic particles is small, and the disturbance effect on the brine is small.

[0091] By comparing Example 1 and Comparative Example 1, it can be seen that when preparing the electrode slurry, the present invention adds a small amount of magnetic material and applies a changing magnetic field during the coating process to make the magnetic material move in different directions in the electrode. The movement trajectory can form a pore structure in the electrode, that is, the path for lithium ions to move in the active material layer, thereby improving lithium ion conductivity.

[0092] A comparison between Example 1 and Comparative Example 2 demonstrates that, during the lithium extraction process, the present disclosure applies a controllable magnetic field to the electrodes, thereby regulating the motion of the magnetic material within the electrodes. The motion of the magnetic material within the mass transfer channel can disturb the brine, promoting its flow and accelerating its contact with the active material, thereby improving lithium extraction efficiency.

[0093] By comparing Example 1 and Comparative Example 1, it can be seen that the present invention applies a magnetic field during the preparation of the electrode, and controls the movement direction of the magnetic particles by changing the direction of the magnetic field, so that the magnetic particles rotate repeatedly under the action of the changing magnetic field, thereby improving the electrode porosity and lithium ion conductivity. The addition of a magnetic field during the lithium extraction process can promote the flow of brine, increase the contact rate between brine and active materials, and improve the lithium extraction efficiency.

Claims

1. A magnetic lithium-rich electrode, comprising a current collector and an active material layer arranged on the surface of the current collector, wherein the active material layer comprises an electrode active material, a magnetic substance, a conductive agent and a binder, and the porosity of the magnetic lithium-rich electrode is 10 to 60%.

2. The magnetic lithium-rich electrode according to claim 1, wherein: The current collector includes carbon fiber or titanium mesh.

3. The magnetic lithium-rich electrode according to claim 1, wherein: The electrode active material includes any one of lithium manganese oxide, lithium iron phosphate or lithium manganese iron phosphate, or a combination of at least two thereof.

4. The magnetic lithium-rich electrode according to claim 1, wherein: The magnetic material includes ferroferric oxide; Optionally, the particle size of the magnetic substance is 10 to 200 nm.

5. The magnetic lithium-rich electrode according to claim 1, wherein: The conductive agent includes acetylene black and / or conductive carbon black.

6. The magnetic lithium-rich electrode according to claim 1, wherein: The binder includes polyvinylidene fluoride.

7. The magnetic lithium-rich electrode according to any one of claims 1 to 6, wherein: The mass ratio of the electrode active material, the magnetic substance, the conductive agent and the binder is 1:(0.01-0.2):(0.1-0.2):(0.1-0.15).

8. The magnetic lithium-rich electrode according to any one of claims 1 to 7, wherein: The lithium ion conductivity of the magnetic lithium-rich electrode is 10 -5 ~10 -2 S / cm; Optionally, the porosity of the magnetic lithium-rich electrode is 20-50%.

9. A method for preparing the magnetic lithium-rich electrode according to any one of claims 1 to 8, the method comprising the following steps: The electrode active material, magnetic substance, conductive agent, binder and solvent are mixed to obtain slurry, a reversing magnetic field is applied to the current collector, and the slurry is coated on the surface of the current collector to obtain a lithium-rich electrode.

10. The preparation method according to claim 9, wherein The solvent includes N-methylpyrrolidone; Optionally, the viscosity of the slurry is 1 to 10 Pa·s; Optionally, the intensity of the directional magnetic field is 0.5 to 5 T; Optionally, the coating density is 150-200 mg / cm 2 ; Optionally, drying is performed after the coating; Optionally, the drying temperature is 50-80°C; Optionally, the drying time is 4 to 8 hours.

11. A method for extracting lithium from salt lakes by electrochemical deintercalation assisted by a magnetic field, the method comprising the following steps: (1) Using the magnetic lithium-rich electrode as claimed in any one of claims 1 to 8 as the positive electrode and the AgCl electrode as the negative electrode, injecting electrolyte and reacting at a constant voltage to obtain a magnetic lithium-poor electrode; (3) The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane, a magnetic lithium-rich electrode is placed in the anode chamber, and a magnetic lithium-poor electrode is placed in the cathode chamber. Salt lake brine is injected into the cathode chamber, and a salt solution is injected into the anode chamber. A magnetic field is applied to the electrodes while power is supplied at a constant voltage. The current is as low as 150 mA to terminate the reaction.

12. The method of claim 11, wherein: The electrolyte in step (1) comprises sodium chloride solution and / or potassium chloride solution; Optionally, the concentration of the electrolyte is 0.05-0.1 mol / L; Optionally, the voltage of the constant voltage reaction is 0.8-1.2V.

13. The method according to claim 11 or 12, wherein: The salt solution in step (2) includes sodium chloride solution and / or potassium chloride solution; Optionally, the concentration of the salt solution is 0.05-0.1 mol / L.

14. The method according to any one of claims 11 to 13, wherein: The voltage of the constant voltage power supply in step (2) is 0.3 to 1.2 V; Optionally, the intensity of the magnetic field is 0.1-1T.

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