Electrode material for extracting lithium from salt lake, electrode and preparation and application thereof

Abstract

The invention discloses an electrode material for extracting lithium from a salt lake. The electrode material comprises an electrode active material and an additive, the electrode active material is an ion sieve, and the additive is tourmaline powder. The invention further discloses an electrode containing the electrode material for extracting lithium from the salt lake and used for extracting lithium from the salt lake as well as a preparation method and application of the electrode. According to the electrode material for salt lake lithium extraction, tourmaline powder is added into an electrode active material, the tourmaline powder and an ion sieve are ground and activated in an organic dispersing agent, and an electrode for salt lake lithium extraction is prepared on a current collector together with a conductive agent and a binder. In the lithium extraction process, the tourmaline powder forms a micro electric field near the ion sieve, so that the potential difference between an electrode active material and a double-electrode-layer interface of the brine is reduced, the migration and diffusion speed of double-electrode-layer interface ions is regulated and controlled, the Li < + > flux of the double-electrode-layer interface is increased, and the lithium extraction efficiency and the lithium extraction capacity of the salt lake brine with the high magnesium-lithium ratio are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from salt lakes, and particularly relates to electrode materials, electrodes, their preparation and application for lithium extraction from salt lakes. Background Technology

[0002] With the explosive growth of lithium-ion batteries used in electrochemical energy storage, electric vehicles, and portable electronic products, the market demand for lithium resources is expected to grow at a rate of 20% annually. By 2030, electric vehicles and lithium energy storage systems will require 2700 GWh of lithium-ion batteries annually, necessitating approximately 2.43 million tons of lithium per year. Lithium resources in salt lake brines account for over 60% of global reserves, and my country has proven lithium reserves of 5.1 million tons, with 70-80% of these reserves located in salt lake brines. Therefore, developing efficient lithium extraction technologies from salt lakes is urgently needed. Compared to the traditional energy-intensive and time-consuming concentration-precipitation method, electrochemical lithium extraction methods are greener, more efficient, and more selective. However, the extremely low lithium concentration and excessively high magnesium-to-lithium ratio in current salt lake brines pose significant challenges to electrochemical lithium extraction technologies. Due to the high lithium content of Li... + Mg 2+ The properties are quite similar, and Li + The ionic mobility in dilute solutions is less than that of Mg. 2 + Na + and K + Mg coexists in large quantities in high-viscosity brine 2+ Na + and K + Further reduced Li + The low ion mobility, low lithium-ion concentration, and low ion mobility significantly reduce the lithium-ion Li+ at the electrode-brine double layer interface. + The high magnesium-to-lithium ratio in brine leads to severe concentration polarization and reduced selectivity, making the electrochemical separation of magnesium and lithium more difficult. Overcoming the challenges of magnesium-to-lithium separation in brine with a high magnesium-to-lithium ratio and achieving efficient lithium extraction is a key technical problem in lithium extraction from salt lakes. Summary of the Invention

[0003] The purpose of this invention is to provide an electrode material for lithium extraction from salt lakes, which enables the electrode to efficiently extract lithium from salt lake brine with a high magnesium-to-lithium ratio.

[0004] The technical solution of this invention is as follows: An electrode material for lithium extraction from salt lakes includes an electrode active material and an additive; the electrode active material is an ion sieve, and the additive is tourmaline powder.

[0005] Preferably, the ion sieve is lithium manganese oxide or lithium iron phosphate, and the tourmaline powder is at least one of nano-sized magnesium tourmaline powder, lithium tourmaline powder, and calcium tourmaline powder.

[0006] The electrode material for lithium extraction from salt lakes of this invention incorporates tourmaline powder into the electrode active material. The tourmaline powder particles, carrying a positive charge at one end and a negative charge at the other, generate a statically polarized electric field, creating a micro-electric field around the mixed electrode active material. This reduces the potential difference at the electric double layer interface between the electrode active material and the salt lake brine, effectively controlling the ion migration and diffusion rates in the electrolyte and at the electric double layer interface. This reduces the resistance to lithium ion insertion during electrochemical lithium extraction and increases the Li-ion potential at the electrode-brine electric double layer interface. + The increased flux improves the selectivity and capacity of electrochemical lithium extraction, making it particularly suitable for lithium extraction from salt lake brines with high magnesium-to-lithium ratios.

[0007] Preferably, the tourmaline powder has a particle size of 8000-20000 mesh, and the particle size ratio of the tourmaline powder to the ion sieve is 1:5-15. This particle size distribution ensures that the tourmaline powder dispersed around the electrode active material forms a micro-electric field within the effective range of the double layer formed by the electrode active material particles and the liquid. The synergistic effect of the tourmaline powder particles and the electrode active material particles not only effectively reduces the lithium ion migration resistance on the electrode surface and in the liquid, but also further reduces the lithium ion migration resistance between the solid and liquid layers on the surface of the electrode active material particles inside the electrode. This comprehensively improves the lithium ion intercalation rate around the electrode active material particles throughout the entire electrode, thereby increasing the overall electrode reaction rate and the utilization rate of the electrode active material.

[0008] Preferably, the mass ratio of tourmaline powder to the ion sieve is 1~3:9. Electrodes made from electrode materials incorporating tourmaline powder in this ratio exhibit the highest lithium-ion selectivity and lithium extraction capacity when extracting lithium from salt lake water with a high magnesium-to-lithium ratio.

[0009] The present invention also provides an electrode for lithium extraction from salt lakes, comprising the aforementioned electrode material for lithium extraction from salt lakes. The current collector used in the electrode for lithium extraction from salt lakes can be a titanium-based current collector, such as a titanium plate or titanium mesh.

[0010] The present invention also provides a method for preparing the above-mentioned electrode for lithium extraction from salt lakes, comprising the following steps: Step 1: Mix the ion sieve and tourmaline powder evenly in a certain proportion to prepare electrode material for lithium extraction from salt lakes; Step 2: After adding conductive agent, binder and organic dispersant, grind for 20-30 minutes to prepare slurry; Step 3: Apply the slurry to the current collector, vacuum dry at 50-80°C for 10-12 hours, and roll press to obtain the electrode for lithium extraction from salt lake.

[0011] Conductive agents can include conductive carbon black, activated carbon, acetylene black, carbon nanotubes, graphene, carbon fibers, and conductive graphite. Binders can be selected from polyvinylidene fluoride, polytetrafluoroethylene, carboxymethyl cellulose, epoxy resin, vinyl acetate, chlorinated rubber, styrene-butadiene rubber, etc. Organic dispersants can be selected from N-methylpyrrolidone, ethanol, dimethylacetamide, N,N-dimethylformamide, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylformamide, or dimethyl sulfoxide, etc. The mass ratio of electrode material, binder, conductive agent, and organic dispersant for lithium extraction from salt lakes is 6–9.5:0.5–2:0–2:20–40. In step two, the ion sieve and tourmaline powder are ground in the presence of the organic dispersant, ensuring uniform mixing of the ion sieve and tourmaline powder with the conductive agent and binder, while also making the crystal structure of the tourmaline powder more consistent. The obtained slurry is coated onto the current collector in step three, dried, and then rolled. The resulting lithium extraction electrode from the salt lake has a compact macroscopic structure and good durability and conductivity in the salt lake brine. It is best to pre-treat the current collector. The pre-treatment method is as follows: clean the surface of the current collector with ethanol, deionized water, and then wipe the surface with dilute acids such as hydrochloric acid, sulfuric acid, and acetic acid at 0.001~0.003 mol / L, followed by rinsing with deionized water and drying at approximately 80°C.

[0012] Preferably, the organic dispersant contains a grinding activator, which is at least one selected from 1,4-bis(trifluoromethyl)benzene, 1,2-bis(trifluoromethyl)benzene, and 1,3-bis(trifluoromethyl)benzene. Adding the grinding activator allows the tourmaline powder particles to be arranged and aligned according to polarity during the grinding process, fully activating and enhancing the micro-electric field, which is beneficial for the rapid embedding of lithium ions in the manufactured electrode during use. The amount of grinding activator added is 0.1 to 0.5 times the mass of the tourmaline powder.

[0013] More preferably, the organic dispersant is N-methylpyrrolidone; the coating thickness is 50-100 micrometers; the rolling speed is 10-200 cm / s, and the rolling pressure is 10-20 MPa. This results in a compact and stable electrode structure, less prone to electrode material detachment.

[0014] The present invention also provides a method for applying the above-mentioned electrode for lithium extraction from salt lakes, comprising the following steps: Step 1: Charging and Lithium De-lithiation Assemble a charging lithium recovery tank; vertically divide the electrodialysis tank into left and right chambers using anion exchange membranes, and fill each chamber with charging electrolyte; place an inert electrode in the left chamber and place the lithium extraction electrode for salt lakes prepared according to this invention in the right chamber; connect the negative terminal of the power supply to the inert electrode and the positive terminal of the power supply to the lithium extraction electrode for salt lakes; the charging electrolyte is a NaCl, KCl, or CsCl solution with a concentration of 10~20 g / L; Lithium removal during charging: Use a charge / discharge device for constant current and constant voltage charging: first charge at 0.1~1C to 0.5~1.2V, then charge at constant voltage until the current density is less than 0.03mA / cm². 2 The reaction is then terminated to obtain a lithium-poor state electrode for lithium extraction from salt lakes. Step 2, Lithium extraction by discharge Assemble the discharge lithium extraction cell; use an anion exchange membrane to vertically divide the electrodialysis cell into left and right chambers, and fill them with salt lake brine; set an inert electrode in the left chamber and set the lithium-poor state salt lake lithium extraction electrode obtained in step one in the right chamber; connect the positive terminal of the power supply to the inert electrode and the negative terminal of the power supply to the salt lake lithium extraction electrode. Lithium extraction by discharge: Turn on the charge / discharge device to perform constant current and constant voltage discharge: first discharge at 0.1~1C to -0.2~-0.6V, then discharge at constant voltage until the current density is less than 0.01mA / cm. 2 The reaction was terminated, and a lithium-rich electrode for lithium extraction from salt lakes was obtained. Step 3: Assemble the lithium-rich salt lake lithium extraction electrode obtained in Step 2 into the right chamber of the charging lithium recovery tank used in Step 1; repeat Step 1 and Step 2, and after the last Step 1 is completed, collect the liquid in the charging lithium recovery tank to obtain a lithium-rich solution.

[0015] Preferably, the inert electrode is a disordered porous carbon electrode or a titanium mesh electrode. Using a disordered porous carbon electrode can adsorb the chlorine gas produced in the reaction, which is environmentally friendly.

[0016] The beneficial effects of this invention are as follows: The electrode material for lithium extraction from salt lakes of the present invention incorporates tourmaline powder into the electrode active material. During the lithium extraction process, the tourmaline powder generates a micro-electric field near the ion sieve, reducing the potential difference at the double-layer interface between the electrode active material and the salt lake brine. This regulates the migration and diffusion rates of ions at the double-layer interface, increasing the Li-potential at the double-layer interface. + The flux was increased, improving the efficiency and capacity of lithium extraction from salt lake brines with a high magnesium-to-lithium ratio. Attached Figure Description

[0017] Figure 1 A schematic diagram of the charging and lithium removal recycling tank.

[0018] Figure 2 This is a schematic diagram of the discharge lithium extraction cell.

[0019] In the figure: 1. Inert electrode; 21. Electrode for lithium extraction from lithium-rich salt lakes; 22. Electrode for lithium extraction from lithium-poor salt lakes; 3. Anion exchange membrane; 4. Charging electrolyte; 5. Simulated salt lake brine. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the embodiments.

[0021] The simulated West Taigir salt lake water used below is Li + Mg 2+ Na + K + The chloride aqueous solutions had concentrations of 320.4 mg / L, 17333.6 mg / L, 93877.5 mg / L, and 10010.6 mg / L, respectively.

[0022] The following is about Li in solution + Mg 2+ Concentration was detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). Example 1

[0023] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: Step 1: Mix lithium manganese oxide with a particle size of 3~10 μm and magnesium tourmaline powder with a particle size of 8000 mesh at a mass ratio of 3:1 to prepare electrode material for lithium extraction from salt lakes. Step 2: Add conductive carbon black, binder polyvinylidene fluoride, and organic dispersant N-methylpyrrolidone. The mass ratio of electrode material for lithium extraction from salt lakes: polyvinylidene fluoride: conductive carbon black: N-methylpyrrolidone is 8:2:1:20. Grind in a ball mill for 20 minutes to make a slurry. Step 3: The slurry is coated onto a 20 cm × 20 cm titanium plate with a coating thickness of 50 micrometers, vacuum dried at 80°C for 10 hours, and then rolled at a speed of 10 cm / s and a pressure of 10 MPa to obtain an electrode for lithium extraction from salt lakes.

[0024] II. Lithium Extraction from Simulated Salt Lake Water Step 1: Charging and Lithium De-lithiation Assemble the charging lithium stripping and recovery tank; the structure of the charging lithium stripping and recovery tank is as follows: Figure 1 As shown.

[0025] A 4-liter electrodialysis tank was vertically and evenly divided into left and right chambers using an ASE anion exchange membrane 3 from ASTOM Corporation of Japan, and each chamber was filled with a 10 g / L NaCl solution as the charging electrolyte 4. A disordered porous carbon electrode was placed in the left chamber as an inert electrode 1, and the electrode for lithium extraction from the salt lake prepared above was placed in the right chamber. The negative terminal of the power supply was connected to the disordered porous carbon electrode, and the positive terminal of the power supply was connected to the electrode for lithium extraction from the salt lake.

[0026] Lithium removal during charging: The charge / discharge device is turned on for constant current and constant voltage charging: first, charge at a constant current of 0.5C to 1.2V, then charge at a constant voltage of 1.2V until the current density reaches 0.02mA / cm². 2The reaction was terminated, and a lithium-poor state electrode for lithium extraction from salt lakes was obtained in the right chamber. The electrode was then removed and rinsed with deionized water.

[0027] Step 2, Lithium extraction by discharge Assemble the discharge lithium extraction cell; the structure of the discharge lithium extraction cell is as follows: Figure 2 As shown.

[0028] A 4-liter electrodialysis tank is vertically and evenly divided into left and right chambers using a polybenzimidazole anion exchange membrane 3, and each chamber is filled with 1.5L of simulated salt lake brine 5 (simulated Xitaijir Salt Lake water is used in this embodiment). A disordered porous carbon electrode 1 is placed in the left chamber as an inert electrode, and a lithium-poor state salt lake lithium extraction electrode 22 obtained in step one of this embodiment is placed in the right chamber. The positive terminal of the power supply is connected to the disordered porous carbon electrode, and the negative terminal of the power supply is connected to the lithium-poor state salt lake lithium extraction electrode.

[0029] Lithium extraction by discharge: Turn on the charge / discharge device for constant current and constant voltage discharge: first discharge at a constant current of 0.5C to -0.2V, then discharge at... -0.2V constant voltage discharge to a current density of 0.005mA / cm² 2 The reaction was then terminated. A lithium-rich electrode for lithium extraction from the brine lake was obtained in the right chamber. This electrode was removed and rinsed with deionized water.

[0030] Step 3: Assemble the lithium-rich brine extract electrode 21 obtained in Step 2 into the right chamber of the charging and delithiation recovery tank used in Step 1, and perform charging and delithiation again. Repeat Step 1 and Step 2 for a total of 5 cycles, and finally perform Step 1 again to collect the liquid in the charging and delithiation recovery tank to obtain a lithium-rich solution. Example 2

[0031] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: Step 1: Mix lithium iron phosphate with a particle size of 3~10μm and lithium tourmaline powder with a particle size of 8000 mesh at a mass ratio of 6:1 to prepare electrode material for lithium extraction from salt lakes. Step 2: Add conductive carbon black, binder polyvinylidene fluoride, and organic dispersant N-methylpyrrolidone. The mass ratio of electrode material for lithium extraction from salt lakes: polyvinylidene fluoride: N-methylpyrrolidone is 6:2:40. Grind in a ball mill for 30 minutes to make a slurry. Step 3: The slurry is coated onto a 20 cm × 20 cm titanium plate with a coating thickness of 100 micrometers, vacuum dried at 50°C for 12 hours, and then rolled at a speed of 200 cm / s and a pressure of 20 MPa to obtain an electrode for lithium extraction from salt lakes.

[0032] II. Lithium Extraction from Simulated Salt Lake Water Step 1: Charging and Lithium De-lithiation Assemble the charging delithiation and recovery tank; using the electrode for lithium extraction from salt lakes prepared in this embodiment, assemble the charging delithiation and recovery tank in the same way as in Example 1.

[0033] Lithium removal during charging: The charge / discharge device is turned on for constant current and constant voltage charging: first, charge at a constant current of 1.0C to 1.0V, then charge at a constant voltage of 1.0V until the current density reaches 0.02mA / cm². 2 The reaction was terminated, and a lithium-poor state electrode for lithium extraction from salt lakes was obtained in the right chamber. The electrode was then removed and rinsed with deionized water.

[0034] Step 2, Lithium extraction by discharge Assemble the discharge lithium extraction cell; assemble the discharge lithium extraction cell using the same method as in Example 1. Fill each of the left and right chambers with 1.5L of simulated Xitaijier Salt Lake water. Place the lithium-poor state salt lake lithium extraction electrode obtained in step one in the right chamber; connect the positive terminal of the power supply to the disordered porous carbon electrode, and connect the negative terminal of the power supply to the salt lake lithium extraction electrode.

[0035] Lithium extraction by discharge: The charge-discharge apparatus is turned on for constant current and constant voltage discharge: first, a constant current of 0.1C is applied to discharge to -0.6V, then a constant voltage of -0.6V is applied to discharge to a current density of 0.005mA / cm², at which point the reaction is terminated. A lithium-rich electrode for lithium extraction from the salt lake is obtained in the right chamber. This electrode is then removed and rinsed with deionized water.

[0036] Step 3: Assemble the lithium-rich salt lake lithium extraction electrode obtained in Step 2 into the right chamber of the charging and lithium stripping recovery tank used in Step 1, and perform charging and lithium stripping again. Repeat Step 1 and Step 2 for a total of 5 cycles, and finally perform Step 1 again to collect the liquid in the charging and lithium stripping recovery tank to obtain a lithium-rich solution. Example 3

[0037] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: Step 1: Mix lithium manganese oxide with a particle size of 3~10 μm and magnesium tourmaline powder with a particle size of 8000 mesh at a mass ratio of 3:1 to prepare electrode material for lithium extraction from salt lakes. Step two: Add conductive carbon black, polyvinylidene fluoride (PVDF) binder, and organic dispersant. The mass ratio of the electrode material for lithium extraction from salt lakes to PVDF to conductive carbon black to organic dispersant is 8:2:1:20, where the organic dispersant is N-methylpyrrolidone. Before mixing, add 1,4-bis(trifluoromethyl)benzene to the weighed N-methylpyrrolidone. The amount of 1,4-bis(trifluoromethyl)benzene added is 0.1 times the mass of the magnesium tourmaline powder. Mix well and then add it to the electrode material for lithium extraction from salt lakes. Then grind in a ball mill for 20 minutes to prepare a slurry.

[0038] Step 3: This step uses the exact same method as in Example 1 to obtain the electrode for lithium extraction from salt lakes.

[0039] II. Lithium Extraction from Simulated Salt Lake Water Step 1: Charging and Lithium De-lithiation Assemble the charging lithium recovery tank; using the electrode for lithium extraction from salt lakes prepared in this embodiment, assemble the charging lithium recovery tank in the same way as in Example 1, except that the left and right chambers are filled with 20g / L CsCl solution as the charging electrolyte.

[0040] Lithium removal during charging: The charge / discharge system is turned on for constant current and constant voltage charging: first, charge at a constant current of 0.1C to 1.2V, then charge at a constant voltage of 1.2V until the current density reaches 0.02mA / cm². 2 The reaction was terminated, and a lithium-poor state electrode for lithium extraction from salt lakes was obtained in the right chamber. The electrode was then removed and rinsed with deionized water.

[0041] Step 2, Lithium extraction by discharge Assemble the discharge lithium extraction cell; assemble the discharge lithium extraction cell using the same method as in Example 1. Fill each of the left and right chambers with 1.5L of simulated Xitaijier Salt Lake water. Place the lithium-poor state salt lake lithium extraction electrode obtained in step one of this example in the right chamber; connect the positive terminal of the power supply to the disordered porous carbon electrode, and connect the negative terminal of the power supply to the salt lake lithium extraction electrode.

[0042] Lithium extraction by discharge: Turn on the charge / discharge device to perform constant current and constant voltage discharge: first, discharge at a constant current of 0.1C to -0.6V, then discharge at a constant voltage of -0.6V until the current density reaches 0.005mA / cm². 2 The reaction was then terminated. A lithium-rich electrode for lithium extraction from the brine lake was obtained in the right chamber. This electrode was removed and rinsed with deionized water.

[0043] Step 3: Assemble the lithium-rich salt lake lithium extraction electrode obtained in Step 2 into the right chamber of the charging and lithium stripping recovery tank used in Step 1, and perform charging and lithium stripping again. Repeat Step 1 and Step 2 for a total of 5 cycles, and finally perform Step 1 again to collect the liquid in the charging and lithium stripping recovery tank to obtain a lithium-rich solution. Example 4

[0044] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: Step 1: Lithium manganese oxide with a particle size of 3~10 μm and calcium tourmaline powder with a particle size of 20000 mesh are mixed evenly at a mass ratio of 9:1 to prepare electrode material for lithium extraction from salt lakes. Step two: Add conductive carbon black, polyvinylidene fluoride (PVDF) binder, and organic dispersant. The mass ratio of the electrode material for lithium extraction from salt lakes to PVDF to conductive carbon black to organic dispersant is 8:2:1:20, where the organic dispersant is N-methylpyrrolidone. Before mixing, add 1,3-bis(trifluoromethyl)benzene to the weighed N-methylpyrrolidone. The amount of 1,3-bis(trifluoromethyl)benzene added is 0.5 times the mass of the calcium tourmaline powder. Mix well and then add it to the electrode material for lithium extraction from salt lakes. Then grind in a ball mill for 20 minutes to prepare a slurry.

[0045] Step 3: This step uses the exact same method as in Example 1 to obtain the electrode for lithium extraction from salt lakes.

[0046] II. Lithium Extraction from Simulated Salt Lake Water Step 1: Charging and Lithium De-lithiation Assemble the charging lithium recovery tank; using the electrode for lithium extraction from salt lakes prepared in this embodiment, assemble the charging lithium recovery tank in the same way as in Example 1, except that the left and right chambers are filled with 20g / L KCl solution as the charging electrolyte.

[0047] Lithium removal during charging: The charge / discharge system is turned on for constant current and constant voltage charging: first, charge at a constant current of 0.1C to 1.2V, then charge at a constant voltage of 1.2V until the current density reaches 0.02mA / cm². 2 The reaction was terminated, and a lithium-poor state electrode for lithium extraction from salt lakes was obtained in the right chamber. The electrode was then removed and rinsed with deionized water.

[0048] Step 2, Lithium extraction by discharge The discharge lithium extraction cell was assembled using the same method as in Example 1, and the lithium-poor state electrodes for lithium extraction from salt lakes obtained in step one were used to assemble the discharge lithium extraction cell.

[0049] Lithium extraction was performed using the same method as in Example 1, and a lithium-rich electrode for lithium extraction from salt lakes was obtained after rinsing.

[0050] Step 3: Assemble the lithium-rich salt lake lithium extraction electrode obtained in Step 2 into the right chamber of the charging and lithium stripping recovery tank used in Step 1, and perform charging and lithium stripping again. Repeat Step 1 and Step 2 for a total of 5 cycles, and finally perform Step 1 again to collect the liquid in the charging and lithium stripping recovery tank to obtain a lithium-rich solution. Example 5

[0051] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: Step 1: Lithium manganese oxide with a particle size of 3~10 μm and calcium tourmaline powder with a particle size of 20000 mesh are mixed evenly at a mass ratio of 9:1 to prepare electrode material for lithium extraction from salt lakes. Step two: Add conductive carbon black, polyvinylidene fluoride (PVDF) binder, and organic dispersant. The mass ratio of the electrode material for lithium extraction from salt lakes to PVDF to conductive carbon black to organic dispersant is 8:2:1:20, where the organic dispersant is N-methylpyrrolidone. Before mixing, add 1,2-bis(trifluoromethyl)benzene to the weighed N-methylpyrrolidone. The amount of 1,2-bis(trifluoromethyl)benzene added is 0.3 times the mass of the calcium tourmaline powder. Mix well and then add it to the electrode material for lithium extraction from salt lakes. Then grind in a ball mill for 20 minutes to prepare a slurry.

[0052] Step 3: This step uses the exact same method as in Example 1 to obtain the electrode for lithium extraction from salt lakes.

[0053] II. Lithium Extraction from Simulated Salt Lake Water The electrode assembly for lithium extraction from salt lakes prepared in this embodiment is used to assemble a charging delithiation and recovery tank. Lithium is extracted from simulated Xitaijier Salt Lake water using the same method as in Example 4. The liquid in the charging delithiation and recovery tank is collected to obtain a lithium-rich solution. Example 6

[0054] I. Preparation of electrodes for lithium extraction from salt lakes, the method is as follows: The only difference between this embodiment and Example 2 is that grinding was not performed in step two. After lithium iron phosphate with a particle size of 3-10 μm and lithium tourmaline powder with a particle size of 8000 mesh were mixed evenly at a mass ratio of 6:1, conductive carbon black, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (N-methylpyrrolidone) organic dispersant were directly added. The mass ratio of electrode material for lithium extraction from salt lakes: PVDF: N-methylpyrrolidone was 6:2:40. The mixture was then stirred and stirred evenly. The lithium extraction electrode was prepared using the same step three as in Example 2.

[0055] II. Lithium Extraction from Simulated Salt Lake Water Using the same method and equipment as in Example 2, lithium extraction was performed on simulated salt lake water using the lithium extraction electrode prepared in this example. This process was repeated 5 times, and finally step one was performed again. The liquid in the charging and delithiation recovery tank was collected to obtain a lithium-rich solution. Example 7

[0056] The only difference between this embodiment and Embodiment 2 is that large-particle lithium tourmaline powder with a particle size of 500 mesh is used in step one. A lithium extraction electrode is prepared using the same method and remaining raw materials as in Embodiment 2, and this electrode is used to extract lithium from simulated saline water. The lithium extraction method and equipment are exactly the same as in Embodiment 2. Finally, the liquid in the charging and delithiation recovery tank is collected to obtain a lithium-rich solution. Example 8

[0057] The only difference between this embodiment and Embodiment 2 is that larger-particle lithium tourmaline powder with a particle size of 3-10 μm is used in step one. A lithium extraction electrode is prepared using the same method and remaining raw materials as in Embodiment 2, and lithium extraction is performed on simulated saline water using this electrode. The lithium extraction method and equipment are exactly the same as in Embodiment 2. Finally, the liquid in the charging and delithiation recovery tank is collected to obtain a lithium-rich solution.

[0058] Comparative Example 1 I. Preparation of electrodes for lithium extraction The only difference between this comparative example and Example 2 is that lithium tourmaline powder was not added during the preparation of the lithium extraction electrode.

[0059] II. Lithium Extraction from Simulated Salt Lake Water Using the same method and equipment as in Example 2, lithium extraction was performed on simulated salt lake water using the lithium extraction electrode prepared in this comparative example. This process was repeated 5 times, and finally step one was performed again. The liquid in the charging and delithiation recovery tank was collected to obtain a lithium-rich solution.

[0060] Detection: The Li in the lithium-rich solutions obtained in each embodiment and comparative example + Mg 2+ The concentration of the lithium was detected, and the lithium-magnesium selectivity coefficient and lithium extraction capacity were calculated. The results are recorded in Table 1.

[0061] Formula for calculating lithium-magnesium selectivity coefficient: Lithium-magnesium selectivity coefficient = ×

[0062] It is a simulation of Li in salt lake brine + The concentration is expressed in mg / L. -1 ; After step one of the first cycles in the lithium extraction process from the salt lake is completed, the Li in the solution in the charging and lithium stripping recovery tank is... + Concentration, unit is mg / L -1 ; Li is a lithium-rich solution + Concentration, unit is mg / L -1 ; It simulates the Mg in salt lake brine. 2+ The concentration is expressed in mg / L. -1 ; It is Mg in lithium-rich solution 2+ Concentration, unit is mg / L -1 ; Lithium extraction capacity calculation formula:

[0063] in, ; This refers to the volume of electrolyte in the lithium recovery tank during charging, expressed in liters (L). m It is the mass of the electrode active material in the electrode, in grams, and n is the number of charge-discharge cycles.

[0064] Table 1

[0065] The data in Table 1 shows that: The electrode material for lithium extraction from salt lakes of the present invention, due to the addition of tourmaline powder, exhibits excellent magnesium-lithium separation and high lithium extraction capacity when used to extract lithium from simulated Xitaijir Salt Lake water with a high magnesium-to-lithium ratio. For example, in Examples 1 to 8, the lithium-magnesium selectivity coefficients all reached over 1027, and the lithium extraction capacity all reached over 20.4 mg / g. In particular, in Example 3, a conductive agent, binder, and organic dispersant were added to the electrode material for lithium extraction from salt lakes, followed by activation with a grinding activator. This resulted in a high lithium-magnesium selectivity coefficient of 1570.7 and a lithium extraction capacity of 24.2 mg / g when extracting lithium from simulated Xitaijir Salt Lake water with a high magnesium-to-lithium ratio. In contrast, in Comparative Example 1, the electrode material for lithium extraction from the same simulated salt lake water did not contain tourmaline powder, resulting in poor magnesium-lithium separation, a lithium-magnesium selectivity coefficient of only 443.4, and a low lithium extraction capacity of only 16.1 mg / g.

[0066] It should be noted that the descriptions of these embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. In addition, the above are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

Claims

1. An electrode material for lithium extraction from salt lakes, comprising an electrode active material and additives; characterized in that, The electrode active material is an ion sieve, and the additive is tourmaline powder.

2. The electrode material for lithium extraction from salt lakes as described in claim 1, characterized in that, The ion sieve is lithium manganese oxide or lithium iron phosphate, and the tourmaline powder is at least one of nano-sized magnesium tourmaline powder, lithium tourmaline powder, and calcium tourmaline powder.

3. The electrode material for lithium extraction from salt lakes as described in claim 1, characterized in that, The tourmaline powder has a particle size of 8000~20000 mesh, and the particle size ratio of the tourmaline powder to the ion sieve is 1:5~15.

4. The electrode material for lithium extraction from salt lakes as described in any one of claims 1 to 3, characterized in that, The mass ratio of the tourmaline powder to the ion sieve is 1~3:

9.

5. An electrode for lithium extraction from salt lakes, characterized in that, It includes the electrode material for lithium extraction from salt lakes as described in any one of claims 1 to 4.

6. A method for preparing the electrode for lithium extraction from salt lakes as described in claim 5, characterized in that, Includes the following steps: Step 1: Mix the ion sieve and tourmaline powder evenly in a certain proportion to prepare electrode material for lithium extraction from salt lakes; Step 2: After adding conductive agent, binder and organic dispersant, grind for 20-30 minutes to prepare slurry; Step 3: Apply the slurry to the current collector, vacuum dry at 50-80°C for 10-12 hours, and roll press to obtain the electrode for lithium extraction from salt lake.

7. The method for preparing the electrode for lithium extraction from salt lakes as described in claim 6, characterized in that, The organic dispersant contains a grinding activator, which is at least one of 1,4-bis(trifluoromethyl)benzene, 1,2-bis(trifluoromethyl)benzene, and 1,3-bis(trifluoromethyl)benzene.

8. The method for preparing the electrode for lithium extraction from salt lakes as described in claim 7, characterized in that, The organic dispersant is N-methylpyrrolidone; the coating thickness is 50-100 micrometers; the rolling speed is 10-200 cm / s, and the rolling pressure is 10-20 MPa.

9. The application method of the electrode for lithium extraction from salt lakes as described in claim 5, characterized in that, Includes the following steps: Step 1: Charging and Lithium De-lithiation Assemble a charging lithium extraction and recovery tank; vertically divide the electrodialysis tank into left and right chambers using anion exchange membranes, and fill each chamber with charging electrolyte; place an inert electrode in the left chamber and place the electrode for lithium extraction from salt lakes as described in claim 5 in the right chamber; connect the negative terminal of the power supply to the inert electrode and the positive terminal of the power supply to the electrode for lithium extraction from salt lakes; the charging electrolyte is a NaCl, KCl, or CsCl solution with a concentration of 10~20 g / L; Lithium removal during charging: Use a charge / discharge device for constant current and constant voltage charging: first charge at 0.1~1C to 0.5~1.2V, then charge at constant voltage until the current density is less than 0.03mA / cm². 2 The reaction is then terminated to obtain a lithium-poor state electrode for lithium extraction from salt lakes. Step 2, Lithium extraction by discharge Assemble the discharge lithium extraction cell; use an anion exchange membrane to vertically divide the electrodialysis cell into left and right chambers, and fill them with salt lake brine; set an inert electrode in the left chamber and set the lithium-poor state salt lake lithium extraction electrode obtained in step one in the right chamber; connect the positive terminal of the power supply to the inert electrode and the negative terminal of the power supply to the salt lake lithium extraction electrode. Lithium extraction by discharge: Turn on the charge / discharge device to perform constant current and constant voltage discharge: first discharge at 0.1~1C to -0.2~-0.6V, then discharge at constant voltage until the current density is less than 0.01mA / cm. 2 The reaction was terminated, and a lithium-rich electrode for lithium extraction from salt lakes was obtained. Step 3: Assemble the lithium-rich salt lake lithium extraction electrode obtained in Step 2 into the right chamber of the charging delithiation and recovery tank used in Step 1. Repeat steps one and two. After the last step one is completed, collect the liquid in the charging and delithiation recovery tank to obtain a lithium-rich solution.

10. The method of applying the electrode for lithium extraction from salt lakes as described in claim 9, characterized in that, The inert electrode is a disordered porous carbon electrode or a titanium mesh electrode.

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