A preparation method for lithium extraction electrode and its application

Abstract

A method for preparing a lithium-extraction electrode and its application. This method first blocks part of the electrode surface, then uses conductive glue to electrostatically spray the unblocked areas of the electrode surface. By blocking the surface where carbon fiber filaments are not required to be implanted, the conductive glue is prevented from adhering to the surface where carbon fiber filaments are not required to be implanted. The carbon fiber filaments are implanted on the electrode surface by electrostatic flocking, and finally heat-cured to firmly bond the carbon fiber filaments to the electrode surface, thereby obtaining a lithium-extraction electrode. The lithium-extraction electrode prepared by the above preparation method is used in the extraction of lithium from salt lakes. By implanting carbon fiber filaments on the electrode surface, this method reduces the thickness of the diffusion layer, increases the unit production capacity of the deintercalation tank for electrochemical lithium extraction, and improves the efficiency of lithium extraction.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of lithium extraction from salt lakes, and particularly relates to a preparation method of a lithium extraction electrode and its application. Background Art

[0002] There are also various alkaline earth metal ions coexisting with lithium ions in salt lake brine. Among them, magnesium ions have similar physical properties to lithium ions, which greatly increases the difficulty of lithium extraction. Current research focuses on the effect of Mg on Li extraction, and a series of methods are used to achieve ion separation and then obtain lithium products. The processes and methods of lithium extraction from salt lakes have become increasingly mature, such as ion exchange and adsorption, nanofiltration, electrochemical lithium extraction, electrodialysis, etc. Among them, the electrochemical lithium extraction method utilizes the working principle of aqueous lithium batteries, with ion sieves that have a "memory effect" on lithium ions as electrode materials, salt lake brine as cathode electrolyte, and a supporting electrolyte that does not contain magnesium as anolyte, thus forming an electrochemical deintercalation system. However, when electrochemical lithium extraction is carried out on lithium-containing solutions with low lithium ion concentrations, especially brine with low lithium content in salt lakes, the problem of low current density will arise during the electrochemical reduction reaction. Low current density means that fewer lithium ions reach the surface of the electrode plate per unit time, the mass transfer of the solution is poor, the solution disturbance is insufficient, and more fresh solution cannot be brought sufficiently close to the surface of the cathode electrode plate. This also means that the coating material on the cathode electrode plate has less contact with the fresh solution, and the concentration of lithium ions reaching its surface is low, which reduces the efficiency of lithium ion embedding into the coating material per unit time.

[0003] There are three ways for reactive particles to transfer mass in the liquid phase: electromigration, convection, and diffusion. For lithium solutions with different lithium concentrations, under certain externally applied conditions, the amount of electromigration is proportional to the mobility of the ions, the electric field strength, and the lithium ion concentration. Therefore, increasing the amount of electromigration is not easy. Convection refers to the relative flow between one part of the solution and another, and is divided into natural convection and forced convection. Natural convection is caused by density and temperature differences between different parts of the solution. Forced convection is caused by external stirring of the solution, such as the introduction of compressed gas or mechanical stirring, or ultrasonic stirring. Diffusion refers to the spontaneous movement of a reactive particle from a high-concentration area to a low-concentration area when there is a concentration difference in the solution, that is, when the concentration of a reactive particle is different in different regions. The surface of the lithium extraction electrode plate and the liquid layer near it can be roughly divided into a double electric layer, a diffusion layer and a convection layer. When the lithium solution to be extracted is saturated salt lake brine, its double electric layer is usually very thin and can be ignored. The main mass transfer modes in the diffusion layer are electromigration and diffusion. The thickness of this layer is generally 10 -3 ~10 -2Centimeters. According to fluid mechanics, in a diffusion layer area so close to the electrode surface, the convection velocity of the liquid in the diffusion layer area will be very small. The closer to the electrode surface, the smaller the convection velocity. Therefore, the convective mass transfer effect generated in the diffusion layer area is very small, which makes the mass transfer mode of the lithium solution to be extracted in the diffusion layer area mainly diffusion. The transmission rate of lithium ions is slow. When the diffusion of lithium ions from the solution to the electrode surface cannot replenish the number of consumed lithium ions in time, then even if the steps of the electrochemical reaction can keep up with the speed of electron movement, the electrochemical reaction speed is reduced due to the decrease in lithium ion concentration near the electrode surface. At the cathode, there will still be accumulation of electrons, making the electrode negative, forming concentration polarization, reducing the current density of the reaction, and reducing the efficiency of lithium ion insertion into the electrode. Summary of the Invention

[0004] The present disclosure aims to at least solve the technical problems existing in the above-mentioned prior art. To this end, the present disclosure proposes a method for preparing a lithium extraction electrode and its application, which can improve the mass transfer of the lithium solution to be extracted, thereby improving the lithium extraction efficiency.

[0005] According to one aspect of the present disclosure, a method for preparing a lithium extraction electrode is proposed, comprising the following steps:

[0006] S1: shielding a portion of the electrode surface, and electrostatically spraying the unshielded area of ​​the electrode surface with conductive glue to obtain a pretreated electrode with multiple areas of conductive glue distributed on the surface;

[0007] S2: hydrophilic carbon fiber fibers are implanted on the surface of the pretreated electrode by electrostatic flocking, and heated and cured to obtain the lithium extraction electrode.

[0008] In some embodiments of the present disclosure, in step S1, the electrode is prepared by the following method: mixing the electrode active material with a conductive agent, a pore-forming agent, PVDF, and N-methylpyrrolidone to prepare a slurry, coating the obtained slurry on a current collector, and drying and soaking the mixture in water to obtain the electrode.

[0009] In some embodiments of the present disclosure, in step S1, the electrode active material is at least one of lithium manganese oxide, lithium iron phosphate, or lithium nickel cobalt manganese oxide.

[0010] In some embodiments of the present disclosure, in step S1, the pore-forming agent is at least one of NaCl, KCl, Na2SO4 or K2SO4. The pore-forming agent is a soluble inorganic salt solid that can be removed by soaking in water, thereby achieving pore formation.

[0011] In some embodiments of the present disclosure, in step S1, the conductive agent is at least one of carbon black, graphene, or carbon nanotubes. Optionally, the carbon black is acetylene black or Ketjen black.

[0012] In some embodiments of the present disclosure, in step S1, the added amounts of the conductive agent, pore-forming agent, PVDF, and N-methylpyrrolidone are 10%-15%, 5%-15%, 8%-15%, and 150%-200% of the mass of the electrode active material, respectively.

[0013] In some embodiments of the present disclosure, in step S2, the hydrophilic carbon fiber filaments are prepared by the following method: separating carbon fiber bundles to obtain single carbon fiber filaments, and treating the carbon fiber filaments with a strong acid to obtain the hydrophilic carbon fiber filaments.

[0014] In some embodiments of the present disclosure, in step S2, the carbon fiber tows are separated by calcining the carbon fiber tows at 200-500°C for 1-3 hours in an oxygen atmosphere, and then calcining them at 600-900°C for 1-3 hours in a protective atmosphere, to obtain single carbon fiber filaments. Using low-temperature oxygen calcination followed by high-temperature calcination can enhance the stability of the resulting single carbon fibers.

[0015] In some embodiments of the present disclosure, in step S2, the length of the hydrophilic carbon fiber is 0.1-1.5 mm and the diameter is 5-20 μm. -3 ~10 -2 Centimeters, so the length of carbon fiber selected is 0.1-1.5mm.

[0016] In some embodiments of the present disclosure, in step S2, the strong acid is at least one of nitric acid, sulfuric acid or hydrochloric acid, and the concentration of the strong acid is 1-4 mol / L.

[0017] In some embodiments of the present disclosure, in step S2, the process of treating the carbon fiber filaments with the strong acid is to place the carbon fiber filaments in the strong acid for reflux treatment, the reflux temperature is 70-100° C., and the reflux time is 2-5 hours.

[0018] In some embodiments of the present disclosure, the process of step S1 is as follows: covering the electrode surface with a two-dimensional planar shield having multiple through-holes distributed on the shield, thereby forming multiple exposed areas on the electrode surface; then electrostatically spraying the exposed areas with the conductive adhesive; and removing the shield to obtain the pretreated electrode having multiple areas of conductive adhesive distributed at intervals on the surface. The through-holes distributed on the shield can maximize the uniform distribution of the conductive adhesive across the entire electrode surface. Optionally, the through-holes are circular or quasi-circular in shape.

[0019] In some embodiments of the present disclosure, in step S1, the area of ​​a single exposed area is 0.1-1 cm 2 .

[0020] In some embodiments of the present disclosure, in step S1, after the electrostatic spraying, the total area of ​​the conductive adhesive on the electrode surface accounts for 5%-25% of the electrode surface area. If the spraying area is too large, the transmission rate of lithium ions into the electrode will be affected. If the spraying area is too small, the range of disturbance of the solution diffusion layer by the fibers on the electrode surface is too small, and the convection effect of the solution in the diffusion layer cannot be enhanced.

[0021] In some embodiments of the present disclosure, in step S1, the conductive adhesive is at least one of graphene conductive adhesive, acrylate conductive adhesive, hydroxymethyl cellulose conductive adhesive, polyurethane conductive adhesive, epoxy resin conductive adhesive, silicone resin conductive adhesive or polyimide conductive adhesive.

[0022] In some embodiments of the present disclosure, in step S1, after the electrostatic spraying, the thickness of the conductive glue on the surface of the electrode is 100-200 μm.

[0023] In some embodiments of the present disclosure, in step S1, the time for electrostatic spraying is 10-60 seconds.

[0024] In some embodiments of the present disclosure, in step S2, the density of the hydrophilic carbon fiber on the surface of the lithium extraction electrode is 0.05-0.2 g / cm 2 .

[0025] In some embodiments of the present disclosure, in step S2, the voltage of the high-voltage electrostatic field generated by the electrostatic flocking is 20-50 kV, and the electrostatic flocking time is 5-20 s.

[0026] In some embodiments of the present disclosure, in step S2, the heating and curing temperature is 70-90° C. and the time is 20-80 min.

[0027] The present invention also provides the use of the lithium extraction electrode prepared by the preparation method in extracting lithium from salt lakes.

[0028] According to the embodiments of the present disclosure, there are at least the following beneficial effects:

[0029] 1. This method first blocks part of the electrode surface, and then uses conductive glue to electrostatically spray the unblocked areas of the electrode surface. By blocking the surface where the carbon fiber filaments do not need to be implanted, the conductive glue is prevented from sticking to the surface where the carbon fiber filaments do not need to be implanted. During the electrostatic spraying process, the conductive glue sprayed by the nozzle is atomized and negatively charged. The electrode is placed at zero potential or grounded. The atomized conductive glue is attracted by the electrode with different potential and deposited on the electrode surface, completing the electrostatic spraying process. The carbon fiber filaments are implanted on the electrode surface through electrostatic flocking. The electrostatic flocking process will generate a high-voltage electrostatic field in the flocking room. The carbon fiber filaments rise to the electrode surface under the action of the high-voltage electrostatic field and are evenly distributed vertically on the electrode surface coated with the conductive glue. Finally, heat curing is used to firmly compound the carbon fiber filaments with the electrode surface.

[0030] 2. When electrochemical deintercalation and lithium extraction is carried out, the mass transfer effect is usually enhanced by enhancing the convection of the solution. In the deintercalation tank used for electrochemical lithium extraction, the liquid close to the electrode surface can be divided into a double layer, a diffusion layer and a convection layer. When the lithium solution to be extracted is saturated salt lake brine, its double layer is usually very thin and can be ignored; and the diffusion layer is very close to the electrode surface. According to fluid mechanics, the closer to the electrode surface, the smaller the convection speed; therefore, the effect of convection mass transfer generated in the diffusion layer is very small, which makes the mass transfer mode of the lithium solution to be extracted in the diffusion layer area mainly diffusion. When the lithium ion transport on the electrode surface is controlled by diffusion, concentration polarization is likely to occur. The thicker the diffusion layer, the more severe the concentration polarization, which leads to intensified cathode polarization of the electrode and reduced efficiency of lithium ion insertion into the electrode. This method implants carbon fiber filaments on the surface of the electrode. The carbon fiber filaments can disturb the solution near the electrode, reduce the thickness of the diffusion layer, and enhance the convection mass transfer effect near the electrode. This can effectively improve the concentration polarization problem of the lithium liquid to be extracted near the electrode surface. The activity of lithium ions near the electrode surface is increased, and the electrochemical reaction conditions of lithium ions in the lithium solution to be extracted are optimized, so that lithium ions near the electrode surface can be more smoothly and quickly embedded in the electrode, thereby increasing the working current density of the deintercalation tank for electrochemical lithium extraction, increasing the unit production capacity of the deintercalation tank for electrochemical lithium extraction, and improving the lithium extraction efficiency. In addition, the carbon fiber filaments formed by the surface composite of this method are hydrophilic and conductive, which can also further improve the lithium extraction efficiency of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present disclosure is further described below with reference to the accompanying drawings and embodiments, wherein:

[0032] Figure 1 This is a process flow chart of Example 1 of the present disclosure. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the concept and technical effects of the present disclosure in conjunction with embodiments to fully understand the purpose, features and effects of the present disclosure.

[0034] Example 1

[0035] This example prepares a salt lake lithium extraction electrode, referring to Figure 1 The specific process is:

[0036] (1) Preparation of lithium extraction electrode: LiFePO4, acetylene black, NaCl, PVDF and N-methylpyrrolidone were mixed to prepare electrode slurry, and the electrode slurry was coated on the titanium mesh. After drying at 80℃ for 4h, it was repeatedly soaked in deionized water for 3 times, each time for 1h to obtain the lithium extraction electrode.

[0037] The added amounts of acetylene black, NaCl, PVDF and N-methylpyrrolidone are 12%, 8%, 10% and 200% of the mass of the active material LiFePO4, respectively.

[0038] (2) Preparation of hydrophilic carbon fiber monofilaments: A flexible carbon fiber bundle with a length of 1 mm was passed through a tubular furnace and heated to 400°C at 5°C / min in air and calcined for 2 h. Subsequently, nitrogen was introduced and heated to 800°C at 5°C / min and calcined for 2 h to remove surface colloids. A stable single carbon fiber monofilament with a diameter of 15 μm was obtained. Subsequently, 2 mol / L nitric acid was used to reflux at 80°C for 3 h, and then separated and dried to obtain a hydrophilic flexible carbon fiber monofilament.

[0039] (3) Electrostatic spraying: Cover the electrode surface with a shielding cloth, and evenly distribute multiple shielding cloths with an area of ​​0.3 cm 2 The circular through holes form a uniform distribution of 0.3cm on the electrode surface. 2 For a single exposed area, an electrostatic spraying device is used to spray acrylic conductive glue on the surface of the electrode where carbon fiber needs to be implanted. The spraying time is 30 seconds and the spraying thickness is 130 μm. After removing the masking cloth, a pretreated electrode with multiple conductive glues evenly distributed on the surface is obtained. The total area covered by the conductive glue on the electrode surface accounts for 10% of the electrode surface area.

[0040] (4) Implanting carbon fiber: Use an electrostatic flocking device to implant carbon fiber monofilaments on the surface of the pretreated electrode. After the electrostatic flocking device is connected to the power supply, under the 30KV high-voltage electrostatic field formed in the flocking room, the carbon fiber is evenly distributed vertically on the electrode surface coated with acrylic conductive glue. The density of the implanted carbon fiber monofilaments is 0.1g / cm 2 , time is 10s.

[0041] (5) Curing: The electrode after flocking in step (4) is heated and cured at 80° C. for 40 min to ensure that the carbon fiber is firmly bonded to the electrode surface, thereby obtaining a salt lake lithium extraction electrode.

[0042] Example 2

[0043] This embodiment prepares a salt lake lithium extraction electrode, and the specific process is as follows:

[0044] (1) Preparation of lithium extraction electrode: LiFePO4, acetylene black, NaCl, PVDF and N-methylpyrrolidone were mixed to prepare electrode slurry, and the electrode slurry was coated on the titanium mesh. After drying at 80℃ for 4h, it was repeatedly soaked in deionized water for 3 times, each time for 1h to obtain the lithium extraction electrode.

[0045] The added amounts of acetylene black, NaCl, PVDF and N-methylpyrrolidone are 12%, 8%, 10% and 200% of the mass of the active material LiFePO4, respectively.

[0046] (2) Preparation of hydrophilic carbon fiber monofilaments: A flexible carbon fiber bundle with a length of 0.5 mm was passed through a tubular furnace and heated to 300°C at 5°C / min in air and calcined for 3 h. Subsequently, nitrogen was introduced and heated to 700°C at 5°C / min and calcined for 1 h to remove surface colloids and obtain a stable single carbon fiber monofilament with a diameter of 10 μm. Subsequently, 3 mol / L nitric acid was used to reflux at 90°C for 4 h, and then separated and dried to obtain a hydrophilic flexible carbon fiber monofilament.

[0047] (3) Electrostatic spraying: Cover the electrode surface with a shielding cloth, and evenly distribute multiple shielding cloths with an area of ​​0.6 cm 2 The circular through holes form a uniform distribution of 0.6cm on the electrode surface. 2 For a single exposed area, graphene conductive glue was sprayed on the surface of the electrode where carbon fiber was to be implanted using an electrostatic spraying device. The spraying time was 40 seconds and the spraying thickness was 160 μm. After removing the masking cloth, a pretreated electrode with multiple conductive glues evenly distributed on the surface was obtained. The total area covered by the conductive glue on the electrode surface accounted for 15% of the electrode surface area.

[0048] (4) Implanting carbon fiber: Use an electrostatic flocking device to implant carbon fiber monofilaments on the surface of the pretreated electrode. After the electrostatic flocking device is connected to the power supply, under the 40KV high-voltage electrostatic field formed in the flocking room, the carbon fiber is evenly distributed vertically on the electrode surface coated with graphene conductive glue. The density of the implanted carbon fiber monofilaments is 0.15g / cm 2 , time is 15s.

[0049] (5) Curing: The electrode after flocking in step (4) is heated and cured at 90° C. for 60 min to ensure that the carbon fiber is firmly bonded to the electrode surface, thereby obtaining a salt lake lithium extraction electrode.

[0050] Example 3

[0051] This embodiment prepares a salt lake lithium extraction electrode, and the specific process is as follows:

[0052] (1) Preparation of lithium extraction electrode: LiFePO4, acetylene black, NaCl, PVDF and N-methylpyrrolidone were mixed to prepare electrode slurry, and the electrode slurry was coated on the titanium mesh. After drying at 80℃ for 4h, it was repeatedly soaked in deionized water for 3 times, each time for 1h to obtain the lithium extraction electrode.

[0053] The added amounts of acetylene black, NaCl, PVDF and N-methylpyrrolidone are 12%, 8%, 10% and 200% of the mass of the active material LiFePO4, respectively.

[0054] (2) Preparation of hydrophilic carbon fiber monofilaments: A flexible carbon fiber bundle with a length of 1.5 mm was passed through a tubular furnace and heated to 500°C at 5°C / min in air and calcined for 1 hour. Subsequently, nitrogen was introduced and heated to 900°C at 5°C / min and calcined for 1 hour to remove surface colloids. A stable single carbon fiber monofilament with a diameter of 20 μm was obtained. Subsequently, 4 mol / L nitric acid was used to reflux at 100°C for 3 hours, and then separated and dried to obtain a hydrophilic flexible carbon fiber monofilament.

[0055] (3) Electrostatic spraying: Cover the electrode surface with a shielding cloth, and evenly distribute multiple shielding cloths with an area of ​​1 cm 2 The circular through holes form a uniform distribution of 1cm on the electrode surface. 2 For a single exposed area, an electrostatic spraying device is used to spray hydroxymethyl cellulose conductive adhesive on the surface of the electrode where carbon fibers need to be implanted. The spraying time is 60 seconds and the spraying thickness is 200 μm. After removing the masking cloth, a pretreated electrode with multiple conductive adhesives evenly distributed on the surface is obtained. The total area covered by the conductive adhesive on the electrode surface accounts for 25% of the electrode surface area.

[0056] (4) Implanting carbon fibers: Use an electrostatic flocking device to implant carbon fiber monofilaments on the surface of the pretreated electrode. After the electrostatic flocking device is connected to a power source, under the 50KV high-voltage electrostatic field formed in the flocking room, the carbon fibers are evenly distributed vertically on the electrode surface coated with hydroxymethyl cellulose conductive glue. The density of the implanted carbon fiber monofilaments is 0.2g / cm 2 , time is 20s.

[0057] (5) Curing: The electrode after flocking in step (4) is heated and cured at 100° C. for 80 min to ensure that the carbon fiber is firmly bonded to the electrode surface, thereby obtaining a salt lake lithium extraction electrode.

[0058] Example 4

[0059] This embodiment prepares a salt lake lithium extraction electrode, and the specific process is as follows:

[0060] (1) Preparation of lithium extraction electrode: LiFePO4, acetylene black, NaCl, PVDF and N-methylpyrrolidone were mixed to prepare electrode slurry, and the electrode slurry was coated on the titanium mesh. After drying at 80℃ for 4h, it was repeatedly soaked in deionized water for 3 times, each time for 1h to obtain the lithium extraction electrode.

[0061] The added amounts of acetylene black, NaCl, PVDF and N-methylpyrrolidone are 12%, 8%, 10% and 200% of the mass of the active material LiFePO4, respectively.

[0062] (3) Preparation of hydrophilic carbon fiber monofilaments: A flexible carbon fiber bundle with a length of 0.1 mm was placed in a tubular furnace and heated to 200°C at 5°C / min in air and calcined for 3 h. Subsequently, nitrogen was introduced and heated to 600°C at 5°C / min and calcined for 3 h to remove surface colloids. A stable single carbon fiber monofilament with a diameter of 5 μm was obtained. Subsequently, 1 mol / L nitric acid was used to reflux at 70°C for 2 h, and then separated and dried to obtain a hydrophilic flexible carbon fiber monofilament.

[0063] (3) Electrostatic spraying: Cover the electrode surface with a shielding cloth, and evenly distribute multiple shielding cloths with an area of ​​0.1 cm 2 The circular through holes form a uniform distribution of 0.1cm on the electrode surface. 2 For a single exposed area, an electrostatic spraying device is used to spray epoxy resin conductive glue on the surface of the electrode where carbon fiber needs to be implanted. The spraying time is 10 seconds and the spraying thickness is 100 μm. After removing the masking cloth, a pretreated electrode with multiple conductive glues evenly distributed on the surface is obtained. The total area covered by the conductive glue on the electrode surface accounts for 5% of the electrode surface area.

[0064] (4) Implanting carbon fiber: Use an electrostatic flocking device to implant carbon fiber monofilaments on the surface of the pretreated electrode. After the electrostatic flocking device is connected to the power supply, under the 20KV high-voltage electrostatic field formed in the flocking room, the carbon fiber is evenly distributed vertically on the electrode surface coated with epoxy resin conductive glue. The density of the implanted carbon fiber monofilaments is 0.05g / cm 2 , time is 5s.

[0065] (5) Curing: The electrode after flocking in step (4) is heated and cured at 70° C. for 20 min to ensure that the carbon fiber is firmly bonded to the electrode surface, thereby obtaining a salt lake lithium extraction electrode.

[0066] Comparative Example

[0067] In this comparative example, a lithium extraction electrode was prepared, and its preparation method was consistent with step (1) of Example 1.

[0068] Test example

[0069] Lithium extraction experiment: The prepared lithium extraction electrode was used as the anode and nickel foam was used as the cathode. They were placed in a 20 g / L NaCl solution and a voltage of 1 V was applied across the electrodes until the current density was lower than 0.5 A / m 2 , obtaining a lithium-deficient electrode. The electrolysis device was separated into a cathode chamber and an anode chamber using an anion membrane. The prepared lithium-rich electrode and lithium-deficient electrode were placed in the anode chamber and cathode chamber respectively. Brine was injected into the cathode chamber respectively. The composition of the brine was 0.68g / L Li, 60.2g / L Na, 75.4g / LMg, 6.1g / L K, 3.87g / L Ca, and 7.97g / L SO4. 2- , 50 mmol / L lithium chloride solution was injected into the anode chamber as the supporting electrolyte, a voltage of 0.9 V was applied to the cathode and anode, and electrolysis was carried out at 10°C for 5 hours.

[0070] The main indicators of lithium extraction obtained after lithium extraction experiments on the electrodes obtained in the examples and comparative examples are shown in Table 1.

[0071] Table 1

[0072]

[0073] It can be seen from Table 1 that the lithium extraction electrode prepared in the embodiment has a significantly increased flow density when used for lithium extraction from salt lakes compared with the unmodified electrode in the comparative example, and the cell voltage is lower. The lithium concentration of the obtained lithium-rich liquid is higher, and the lithium recovery rate is significantly increased, indicating that the salt lake lithium extraction electrode prepared in the embodiment can achieve efficient extraction of lithium from salt lakes.

Claims

1. A method for preparing a lithium extraction electrode for lithium extraction from a salt lake, characterized in that: The following steps are involved: S1: shielding a portion of the electrode surface, and electrostatically spraying the unshielded area of ​​the electrode surface with conductive glue to obtain a pretreated electrode with multiple areas of conductive glue distributed on the surface; S2: electrostatically flocking hydrophilic carbon fiber fibers onto the surface of the pretreated electrode, and heating and curing the pretreated electrode to obtain the lithium extraction electrode; In step S1, the electrode is prepared by the following method: an electrode active material is mixed with a conductive agent, a pore-forming agent, PVDF, and N-methylpyrrolidone to prepare a slurry, the obtained slurry is coated on a current collector, and the slurry is dried and soaked in water to obtain the electrode; the electrode active material is at least one of lithium manganese oxide, lithium iron phosphate, or lithium nickel cobalt manganese oxide; after the electrostatic spraying, the thickness of the conductive glue on the surface of the electrode is 100-200 μm; In step S2, the hydrophilic carbon fiber filaments are prepared by the following method: separating carbon fiber tows to obtain single carbon fiber filaments, and treating the carbon fiber filaments with a strong acid to obtain the hydrophilic carbon fiber filaments.

2. The preparation method according to claim 1, characterized in that In step S1, the pore-forming agent is at least one of NaCl, KCl, Na2SO4 or K2SO4.

3. The preparation method according to claim 1, characterized in that In step S1, the conductive agent is at least one of carbon black, graphene or carbon nanotubes.

4. The preparation method according to claim 1, characterized in that In step S1, the added amounts of the conductive agent, pore-forming agent, PVDF, and N-methylpyrrolidone are 10%-15%, 5%-15%, 8%-15%, and 150%-200% of the mass of the electrode active material, respectively.

5. The preparation method according to claim 1, characterized in that In step S2, the carbon fiber bundles are separated by calcining the carbon fiber bundles at 200-500° C. for 1-3 hours in an oxygen atmosphere, and then calcining them at 600-900° C. for 1-3 hours in a protective atmosphere to obtain single carbon fiber filaments.

6. The preparation method according to claim 1, characterized in that In step S2, the hydrophilic carbon fiber filaments have a length of 0.1-1.5 mm and a diameter of 5-20 μm.

7. The preparation method according to claim 1, characterized in that In step S2, the strong acid is at least one of nitric acid, sulfuric acid or hydrochloric acid, and the concentration of the strong acid is 1-4 mol / L.

8. The preparation method according to claim 1, characterized in that In step S2, the process of treating the carbon fiber filaments with the strong acid is to place the carbon fiber filaments in the strong acid for reflux treatment, the reflux temperature is 70-100° C., and the reflux time is 2-5 hours.

9. The preparation method according to claim 1, characterized in that The process of step S1 is: covering the surface of the electrode with a two-dimensional planar covering, and a plurality of through holes are distributed on the covering, thereby forming a plurality of exposed areas on the surface of the electrode, and then electrostatically spraying the exposed areas with the conductive glue, and after removing the covering, the pretreated electrode with a plurality of conductive glues distributed at intervals on the surface is obtained.

10. The preparation method according to claim 9, characterized in that In step S1, the area of ​​a single exposed area is 0.1-1 cm 2 .

11. The preparation method according to claim 1, characterized in that In step S1, after the electrostatic spraying, the total area covered by the conductive glue on the electrode surface accounts for 5%-25% of the electrode surface area.

12. The preparation method according to claim 1, characterized in that In step S1, the conductive adhesive is at least one of graphene conductive adhesive, acrylate conductive adhesive, hydroxymethyl cellulose conductive adhesive, polyurethane conductive adhesive, epoxy resin conductive adhesive, silicone resin conductive adhesive or polyimide conductive adhesive.

13. The preparation method according to claim 1, characterized in that In step S1, the electrostatic spraying time is 10-60s.

14. The preparation method according to claim 1, characterized in that In step S2, the density of the hydrophilic carbon fiber on the surface of the lithium extraction electrode is 0.05-0.2 g / cm 2 .

15. The preparation method according to claim 1, characterized in that In step S2, the voltage of the high-voltage electrostatic field generated by the electrostatic flocking is 20-50 kV, and the electrostatic flocking time is 5-20 seconds.

16. The preparation method according to claim 1, characterized in that In step S2, the temperature of the heating and curing is 70-90° C., and the time is 20-80 minutes.

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