Preparation method of electrode for electrochemical lithium extraction

Abstract

The invention relates to a preparation method of an electrode for electrochemical lithium extraction, belongs to the technical field of lithium resource development and utilization, and solves the problems of low interface bonding strength, large resistance change, poor electrode cycling stability and low current efficiency in a lithium extraction process of an electrode current collector prepared by an existing method and a lithium extraction active material. The method comprises the following steps: carrying out physical treatment or chemical treatment on a flat current collector to obtain a current collector with concave-convex morphology on the surface; uniformly coating the lithium extraction slurry on the surface of a current collector with concave-convex morphology, and drying to obtain the electrode for electrochemical lithium extraction; the tabulate current collector can be used as an anode current collector and also can be used as a cathode current collector, and the thickness of the tabulate current collector is 200-10000 [mu] m; and the specific surface area of the current collector with the concave-convex morphology is 1-10m < 2 > / g. The interface bonding strength of the electrode current collector prepared by the method and the lithium extraction active material is high, and the current efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of lithium resource development and utilization technology, and in particular to a method for preparing an electrode for electrochemical lithium extraction. Background Technology

[0002] With the rise of strategic industries such as new energy, the demand for power batteries in the new energy sector has surged, leading to a rapid increase in lithium salt consumption. In nature, lithium resources are mainly found in salt lake brines, lithium-bearing ores, and seawater, with salt lake brines accounting for over 60% of global lithium resources. Therefore, the clean and efficient extraction of lithium from salt lake brines is of great significance for promoting the sustainable development of the new energy industry.

[0003] Currently, the development and utilization of lithium resources in salt lake brine mainly relies on technologies such as precipitation, electrodialysis, membrane separation, solvent extraction, and ion sieve adsorption. However, all of these methods have significant limitations: precipitation requires a magnesium-to-lithium ratio in the brine to be below 8 and depends on natural evaporation for concentration, with a cycle of 12-18 months and low production efficiency; while electrodialysis / membrane separation methods have environmental advantages, the calcium content in the brine... 2+ Mg 2+ High-valence ions are prone to causing membrane fouling, and existing monovalent ion exchange membranes are susceptible to Li... + / Na + The separation coefficient is only 2-3, resulting in insufficient lithium extraction efficiency; although solvent extraction method for Li + The selectivity coefficient can reach over 50, but the extractant (such as the TBP-kerosene system) has a solubility of 0.5-1.2 g / L in brine, resulting in significant extractant loss and a risk of organic pollution. While lithium-ion sieve adsorption method... + The adsorption capacity reaches 20-30 mg / g, but desorption requires strong acid, and the capacity decays severely after the adsorbent is cycled, resulting in high industrialization costs.

[0004] To overcome the aforementioned technical bottlenecks, researchers developed an electrochemical lithium extraction technology from brine lakes. This technology extracts Li directly from brine under an electric field by constructing a selective lithium extraction system. + Simultaneously enriching lithium to over 5 g / L significantly shortens the lithium extraction cycle and reduces energy consumption. However, the core electrode components of the electrochemical deintercalation method still face the following key issues: active materials are prone to detachment; the interaction between the active material and the metal current collector relies solely on physical mixing or simple coating, resulting in low interfacial bonding strength; due to varying bonding strengths, the contact resistance between the coating and the current collector varies greatly, leading to uneven potential distribution on the electrode surface, large local overpotentials, and consequently, decreased current efficiency.

[0005] The aforementioned problems severely restrict the cycle life of electrodes and lithium extraction efficiency, and breakthroughs in salt lake lithium extraction technology are urgently needed through electrode structure innovation. Summary of the Invention

[0006] In view of the above analysis, the embodiment of the present application aims to provide a preparation method of an electrode for electrochemical lithium extraction, at least to solve one of the following problems existing in the prior art electrode for electrochemical lithium extraction: 1. The interface bonding strength between the current collector and the lithium extraction active material is low, the lithium extraction active material is easy to fall off due to long-term cycling, and the electrode has poor cycling stability; 2. The interface resistance between the current collector and the lithium extraction active material changes greatly, the electrode surface potential distribution is uneven, the local overpotential of the electrode is large, it is easy to be polarized, and the current efficiency of the lithium extraction process is low.

[0007] The purpose of the present application is mainly realized by the following technical solutions:

[0008] The present application provides a preparation method of an electrode for electrochemical lithium extraction, comprising the following steps:

[0009] S1: Physically or chemically treating a flat plate-shaped current collector to obtain a current collector with a concave-convex surface morphology;

[0010] S2: Uniformly coating lithium extraction slurry on the surface of the current collector with a concave-convex surface morphology, and obtaining an electrode for electrochemical lithium extraction after drying;

[0011] The flat plate-shaped current collector is a current collector that can act as both an anode current collector and a cathode current collector, and is one or more of a titanium plate, a titanium alloy plate, a graphite plate, and a conductive polymer plate, with a thickness of 200 μm-10000 μm;

[0012] The specific surface area of the current collector with a concave-convex surface morphology is 1-10 m 2 / g.

[0013] Further, the surface of the current collector with a concave-convex surface morphology has two morphologies, the largest peak height or valley depth of which is a primary morphology, and the rest is a secondary morphology;

[0014] Taking the horizontal plane of the surface of the flat plate-shaped current collector as the reference, the peak height or valley depth H1 of the primary morphology is 50 μm-500 μm, and the peak height or valley depth H2 and the peak width W of any secondary morphology are 0.05-1 power of the peak height or valley depth of the primary morphology.

[0015] Further, the physical treatment is one or more of turning, sandblasting, sanding, laser ablation, laser engraving, and laser texturing;

[0016] The chemical treatment is one or more of chemical corrosion, chemical oxidation, and chemical deposition.

[0017] Further, the turning adopts a negative rake large radius of curvature tool, and the cutting depth is 50-300 μm, the rotation speed is 500-800 r / min, the feed rate is 0.1-3 mm / r, the negative rake angle of the negative rake large radius of curvature tool is-5° to-10°, and the large radius of curvature is 0.3-0.6 mm.

[0018] Further, in the sandblasting process, the air pressure is 0.4-0.7 MPa, the spraying distance is 100-300 mm, the vertical angle is 75-85°, and the processing time is 10-60 s.

[0019] Further, in the sanding process, the mesh number of the sandpaper or sand belt is 60-120 mesh, the grinding pressure is 0.2-0.5 MPa, the feed speed is 500-1500 μm / s, and the grinding time is 1-5 min.

[0020] Further, in the laser ablation process, a nanosecond to femtosecond pulsed laser is used, the laser wavelength is 532 nm or 1064 nm, the single pulse energy is 5-50 mJ, the energy density is 1-10 J / cm2, the repetition frequency is 1000-2000 Hz, and the scanning speed is 50-200 mm / s.

[0021] In the laser engraving process, a continuous or long-pulse fiber laser is used in an argon atmosphere, the wavelength is 1064 nm, the peak power is 1-3 kW, the spot size is 200-500 μm, and the scanning speed is 100-300 mm / s.

[0022] In the laser texturing process, a short-pulse ultraviolet laser is used under nitrogen auxiliary blowing, the wavelength is 355 nm, the pulse energy is 0.1-1 mJ, the spot size is 50-300 μm, the repetition frequency is 10-50 kHz, and the scanning speed is 200-800 mm / s.

[0023] Further, in the chemical etching process, the reaction temperature is 30-50℃, and the reaction time is 20-40 min.

[0024] The chemical etching solution is one of a hydrofluoric acid-nitric acid mixed solution and an alkaline hydrogen peroxide solution.

[0025] Further, in the chemical oxidation process, the reaction temperature is 50-90℃, and the reaction time is 15-30 min.

[0026] The chemical oxidation solution is one of an alkaline hydrogen peroxide solution and an ammonium persulfate-sulfuric acid mixed solution.

[0027] In the chemical deposition process, the deposition temperature is 30-90 DEG C, the deposition time is 60-120 min, the pulse current is 30-60 mA / cm2, and the pH value of the plating solution is 3-10; the chemical deposition solution is one of a nickel-molybdenum alloy plating solution and a metal ruthenium composite plating solution.

[0028] The application also provides the current collector with the concave-convex morphology and the application thereof in preparing the electrode for electrochemical lithium extraction.

[0029] Compared with the prior art, the application can realize at least one of the following beneficial effects:

[0030] 1. The method optimizes the electrode structure, enhances the adhesion strength of the current collector and the lithium extraction active material, prevents the lithium extraction active material from falling off and slagging due to long-term lithium extraction and solution scouring, and improves the cycle performance of the electrode by selecting the flat plate-shaped current collector and performing surface physical or chemical treatment.

[0031] 2. The method optimizes the electrode structure by selecting the flat plate-shaped current collector and performing surface physical or chemical treatment, so that the concave-convex morphology with micron / nanometer level protrusions is formed on the surface of the current collector, the contact points with the active material are increased, the electron transmission path is shortened, the interfacial resistance of the current collector and the lithium extraction active material is reduced, the overall conductivity of the electrode is improved, and large current density lithium extraction is realized.

[0032] 3. The current collector of the lithium extraction electrode has the concave-convex morphology, and the surface microstructure of the concave-convex morphology can make the current distribution of the electrode uniform, inhibit the local polarization of the electrode, and be beneficial to improving the current efficiency of the lithium extraction process.

[0033] 4. The current collector and the electrode preparation process are simple and easy to realize industrial application.

[0034] The above technical solutions can be combined with each other in the application to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent description, and some advantages will become apparent from the description, or will be understood by implementing the application. The purposes and other advantages of the application can be realized and obtained from the contents specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0036] Figure 1 FIG. 1 is a schematic diagram of the surface morphology of the current collector with the concave-convex morphology according to the application;

[0037] Figure 2A schematic diagram of the current collector with concave-convex morphology of embodiment 1 of the present application;

[0038] Figure 3 A schematic diagram of the current collector with concave-convex morphology of embodiment 2 of the present application;

[0039] Figure 4 A schematic diagram of the current collector with concave-convex morphology of embodiment 3 of the present application;

[0040] Figure 5 A schematic diagram of the current collector with concave-convex morphology of embodiment 4 of the present application;

[0041] Figure 6 A schematic diagram of the current collector with concave-convex morphology of embodiment 5 of the present application;

[0042] Figure 7 A schematic diagram of the current collector with concave-convex morphology of embodiment 6 of the present application;

[0043] Figure 8 A schematic diagram of the current collector with concave-convex morphology of embodiment 7 of the present application;

[0044] Figure 9 A super-depth-of-field photo of the current collector with concave-convex morphology of embodiment 7 of the present application;

[0045] Figure 10 A schematic diagram of the current collector with concave-convex morphology of embodiment 8 of the present application;

[0046] Figure 11 A schematic diagram of the current collector with concave-convex morphology of embodiment 9 of the present application.

[0047] Reference signs:

[0048] 1-primary morphology peak height, 2-secondary morphology peak height, 3-secondary morphology peak width.

[0049] DETAILED DESCRIPTION

[0050] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which form a part of this application. The accompanying drawings and the embodiments together illustrate the principles of the present application, but are not intended to limit the scope of the present application.

[0051] The present application provides a preparation method of an electrode for electrochemical lithium extraction, comprising the following steps:

[0052] S1: physically or chemically treating a flat plate-shaped current collector to obtain a current collector with concave-convex morphology on the surface;

[0053] S2: uniformly coating lithium extraction slurry on the surface of the current collector with concave-convex morphology, and obtaining an electrode for electrochemical lithium extraction after drying.

[0054] Specifically, in step S1, the flat plate-shaped current collector is a current collector capable of serving as both an anode current collector and a cathode current collector, and is preferably one or more of a titanium plate, a titanium alloy plate, a graphite plate, and a conductive polymer plate; and the thickness is 200 μm to 10,000 μm.

[0055] The flat plate-shaped current collector has high electrical conductivity. For example, the electrical conductivity of the titanium plate is 2.3 x 10 6 S / m, the electrical conductivity of the titanium alloy plate is 2.5 x 10 6 S / m, the electrical conductivity of the graphite plate is 1.0 x 10 6 S / m, and the electrical conductivity of the conductive polymer plate is 1.0 x 10 2 S / m.

[0056] It should be noted that, in the process of electrochemical lithium extraction, the lithium-rich lithium extraction active material obtained by delithiation of the anode lithium extraction active material, and the lithium-rich lithium extraction active material obtained by lithiation of the cathode lithium extraction active material. After the lithium extraction is completed, the positive and negative directions of the power supply are exchanged and the brine is re-injected to perform lithium extraction again. At this time, the anode of the previous cycle serves as the cathode of the current lithium extraction, and the cathode of the previous cycle serves as the anode of the current lithium extraction, thereby realizing the simultaneous extraction and enrichment of lithium in the brine. In addition, the current collector should have good chemical stability in aqueous solution and should not be chemically corroded under the condition of power supply. Therefore, the flat plate-shaped current collector used in the present application needs to satisfy the condition of being capable of serving as both an anode current collector and a cathode current collector.

[0057] Industrialized electrochemical lithium extraction electrodes often require a large working area, and at the same time, the loading capacity (i.e., coating density) of the lithium extraction active material is increased as much as possible while ensuring good wettability. Therefore, the flat plate-shaped current collector of the present application needs to have good rigidity, and the thickness is preferably 200 μm to 10,000 μm.

[0058] In an electrochemical lithium extraction device, liquid flow is generally used to enhance the mass transfer process and reduce concentration polarization. Therefore, in order to avoid the problem of lithium extraction active material falling off caused by the scouring effect during the solution flow process, the current collector needs to have a high specific surface area to increase the contact sites between the lithium extraction active material and the current collector, so that the current collector and the lithium extraction active material are tightly combined. That is, the surface of the current collector needs to be processed to increase the specific surface area. The specific surface area of the flat plate-shaped current collector of the present application is 0.01 to 0.1 m 2 / g, and the specific surface area of the current collector with a concave-convex morphology is 1 to 10 m 2 / g.

[0059] Specifically, in step S1, the current collector surface with the concave-convex morphology has two kinds of morphologies, wherein the morphology with the largest peak height or valley depth is a primary morphology, and the rest is a secondary morphology; taking the horizontal plane of the flat plate-shaped current collector surface as a reference, the peak height or valley depth H1 of the primary morphology is 50-500 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.05-1 power of the peak height (or valley depth) of the primary morphology.

[0060] Specifically, in step S1, the physical treatment is one or more of turning, sand blasting, sanding, laser ablation, laser engraving, and laser texturing; and the chemical treatment is one or more of chemical etching, chemical oxidation, and chemical deposition.

[0061] Specifically, when the flat plate-shaped current collector surface is subjected to the turning treatment, by controlling the cutting depth, the rotation speed, and the feed rate, and using a negative rake angle / large blunt radius cutter, the surface layer material of the current collector is subjected to significant plastic flow, accumulation, and bulging instead of being cut off; finally, a surface structure composed of continuous / semi-continuous bulging ridges parallel to the feed direction, accompanied by grooves, and significant flanging edges is formed, and is superimposed with scale-like structures, micro-creases, etc.; such a complex, three-dimensional morphology surface with a large number of "anchor points" greatly increases the contact area and mechanical embedding capacity between the current collector and the electrode active material; wherein the cutting depth is 50-300 μm, the rotation speed is 500-800 r / min, the feed rate is 0.1-3 mm / r, the negative rake angle of the negative rake angle / large blunt radius cutter used is -5° to -10°, and the large blunt radius is 0.3-0.6 mm.

[0062] Specifically, when the flat plate-shaped current collector surface is subjected to the sand blasting treatment, by controlling the air pressure, the blasting distance, the vertical angle, and the treatment time in the sand blasting process, and using compressed air to drive the abrasive to impact the current collector surface at a high speed, a random distribution of three-dimensional concave-convex structures without directionality is formed on the current collector surface; this process significantly increases the specific surface area and the mechanical anchor points of the current collector, and finally improves the adhesion of the electrode material. Wherein, the air pressure in the sand blasting process is 0.4-0.7 MPa, the blasting distance is 100-300 mm, the vertical angle is 75-85°, and the treatment time is 10-60 s; preferably, the abrasive is one of silicon carbide abrasive, alumina abrasive, or glass bead abrasive, and the particle size of the abrasive is 300-500 μm.

[0063] Specifically, when sanding the surface of the flat plate-shaped current collector, by controlling the mesh number of sandpaper / sand belt, grinding pressure, feed speed, grinding time, unidirectional grinding and assisted cooling liquid, the surface of the current collector forms a composite concave-convex structure of directional grooves and random topography; this process significantly increases the specific surface area of the current collector through sanding, enhances the mechanical interlocking force and interface conductivity of the electrode material, and has the advantages of low cost and easy scale-up. Among them, the mesh number of sandpaper / sand belt is 60-120 mesh, the grinding pressure is 0.2-0.5 MPa, the feed speed is 500-1500 μm / s, and the grinding time is 1-5 min; preferably, the abrasive is one of diamond, silicon carbide or natural corundum, and the particle size of the abrasive is 120-300 μm.

[0064] Specifically, the surface of the flat plate-shaped current collector is subjected to laser ablation, laser engraving or laser texturing surface treatment, by adjusting the laser pulse, energy density, frequency, scanning speed, power, spot size, etc., the surface of the current collector forms random pits, particle deposition layer and other concave-convex surface structures; this process forms a multi-level concave-convex structure on the surface of the current collector through laser ablation, laser engraving or laser texturing treatment, the directional microstructure can provide mechanical locking effect, optimize the ion diffusion path, and balance the conductivity and active material load stability. In the laser ablation process, nanosecond to femtosecond pulsed laser is used, the laser wavelength is 532 nm or 1064 nm, the single pulse energy is 5-50 mJ, the energy density is 1-10 J / cm 2 , the repetition frequency is 1000-2000 Hz, and the scanning speed is 50-200 mm / s; in the laser engraving process, continuous or long pulse fiber laser is used in argon atmosphere, the wavelength is 1064 nm, the peak power is 1-3 kW, the spot size is 200-500 μm, and the scanning speed is 100-300 mm / s; in the laser texturing process, short pulse ultraviolet laser is used under the assistance of nitrogen blowing, the wavelength is 355 nm, the pulse energy is 0.1-1 mJ, the spot size is 50-300 μm, the repetition frequency is 10-50 kHz, and the scanning speed is 200-800 mm / s.

[0065] Specifically, when the flat plate-shaped current collector is subjected to chemical etching, chemical oxidation and / or chemical deposition surface treatment, chemical etching liquid, chemical oxidation electrolyte and chemical deposition solution are configured respectively, by adjusting the composition, reaction temperature and reaction time of the chemical etching liquid, chemical oxidation electrolyte and / or chemical deposition solution, the surface of the current collector forms honeycomb-like micro-pits, coral-like protrusions, spherical deposition particles and other concave-convex surface structures; through chemical etching, chemical oxidation and / or chemical deposition treatment, the surface of the current collector is concave-convex, which significantly increases the specific surface area of the current collector, improves the conductivity and strengthens the mechanical interlocking, thereby improving the cycle stability of the electrode material in the lithium extraction process.

[0066] In the chemical etching process, the reaction temperature is 30-50 DEG C, and the reaction time is 20-40 min; preferably, the chemical etching solution is one of a hydrofluoric acid-nitric acid mixed solution, an alkaline hydrogen peroxide solution, wherein in the hydrofluoric acid-nitric acid mixed solution, the volume concentration of HF is 5-10 vol%, and the volume concentration of HNO3 is 15-30 vol%; in the alkaline hydrogen peroxide solution, the molar concentration of NaOH is 2-5 mol / L, and the volume concentration of H2O2 is 5-15 vol%

[0067] In the chemical oxidation process, the reaction temperature is 50-90 DEG C, and the reaction time is 15-30 min; preferably, the chemical oxidation solution is one of an alkaline hydrogen peroxide solution, an ammonium persulfate-sulfuric acid mixed solution, wherein in the alkaline hydrogen peroxide solution, the molar concentration of NaOH is 2-5 mol / L, and the volume concentration of H2O2 is 5-20 vol%; in the ammonium persulfate-sulfuric acid mixed solution, the molar concentration of ammonium persulfate is 0.5-1.5 mol / L, and the volume concentration of sulfuric acid is 10-20 vol%.

[0068] In the chemical deposition process, the deposition temperature is 30-90 DEG C, the deposition time is 60-120 min, and the pulse current is 30-60 mA / cm 2 ; the pH value of the plating solution is 3-10; the chemical deposition solution is one of a nickel-molybdenum alloy plating solution and a metal ruthenium composite plating solution; preferably, in the nickel-molybdenum alloy plating solution, the concentration of Ni 2+ is 1.0-1.5 M, the concentration of MoO4 2- is 0.1-0.3 M, and the concentration of the complexing agent sodium citrate is 0.2-0.5 M; in the metal ruthenium plating solution, the concentration of ruthenium is 0.02-0.1 mol / L, and the concentration of boric acid is 30-50 g / L.

[0069] It should be noted that the chemical etching and the chemical oxidation are suitable for flat plate-shaped current collectors of titanium plates and titanium alloy plates; the turning, sandblasting, sanding, laser ablation, laser engraving, laser texturing, and chemical deposition are suitable for flat plate-shaped current collectors of all materials mentioned in the application.

[0070] Specifically, in step S2, the lithium extraction slurry comprises lithium extraction active material, conductive agent and binder, wherein the mass fraction of lithium extraction active material is 70-90%, the mass fraction of conductive agent is 5-20%, and the mass fraction of binder is 5-10%. In order to extract lithium from brine environment, not only is it required that the lithium extraction active material has good selectivity, but also is it required that the reaction potential of lithium extraction active material is in the stable region of water, so the lithium extraction active material is one of lithium ion battery cathode materials stable in aqueous solution; preferably, the lithium extraction active material is at least one of lithium iron phosphate, lithium manganate, lithium titanium phosphate, lithium manganese silicate, lithium iron silicate, etc. Lithium extraction active material generally has poor conductivity, and additional conductive agent is required to be added during preparation of lithium extraction slurry to enhance the electron conduction ability between lithium extraction active materials and the overall conductivity of the electrode; preferably, the conductive agent is at least one of acetylene black, carbon nanotube, ketchen black and graphene. In order to effectively bond the lithium extraction active material, the conductive agent and the current collector, a binder needs to be added during the preparation of the lithium extraction slurry to obtain a lithium extraction electrode with high bonding strength; preferably, the binder is polyvinylidene fluoride (PVDF).

[0071] Here, the lithium extraction slurry further comprises a solvent, preferably N-methyl pyrrolidone (NMP), and the amount of solvent is 2-3 times the mass of solid (i.e. lithium extraction active material, conductive agent and binder). In order to make the solvent volatilize and form a microporous structure on the surface of the electrode coating layer, a suitable drying temperature and drying time are required, the drying temperature is 70-120°C, and the drying time is 6-24h.

[0072] In the process of electrochemical lithium extraction, the electrode is required to have a high current density, and the current density is closely related to the active material coated on the surface of the current collector. Therefore, the electrode obtained after drying needs to have a high coating density; low coating density results in low current density, and too high coating density increases the tortuosity of the electrode, which is not conducive to the mass transfer of the solution inside the electrode; specifically, the coating density of the lithium extraction electrode after drying is 25-120mg / cm 2 The coating method is preferably one or more of doctor blade coating, roller coating or spraying, etc.

[0073] The method optimizes the electrode structure, enhances the adhesion strength of the current collector and the lithium extraction active material, prevents the active material from falling off due to long-term circulation, and further improves the cycle stability of the electrode; meanwhile, the micron / nanometer level protrusions formed by the concave-convex morphology of the current collector increase the contact points with the active material, effectively shorten the electron transmission path, and reduce the interface resistance between the current collector and the lithium extraction active material, thereby improving the current density; meanwhile, the current distribution is more uniform, the overpotential of the electrode is reduced, the local polarization of the electrode is inhibited, and the current efficiency of the lithium extraction process is improved; the current collector processing and electrode preparation provided by the method are simple and easy to realize industrial application.

[0074] The electrode for electrochemical lithium extraction prepared by the method is practically applied to the salt lake lithium extraction by the electrochemical deintercalation method, and includes the following steps:

[0075] S1: preparing a ferric phosphate electrode: an electrolytic cell is divided into an anode chamber and a cathode chamber by an anion membrane, an electrode for electrochemical lithium extraction prepared by the method is used as an anode, foamed nickel is used as a cathode, 2-4 L of a sodium chloride solution with a concentration of 18-22 g / L is filled into the anode chamber and the cathode chamber, the cathode liquid adopts an acid-adjusted solution with a pH of 3-4, constant current electrolysis is performed by applying a voltage of 1.0-2.0 V between the concave-convex morphology current collector and the foamed nickel, and the electrolysis is ended when the current is lower than 0.5 A / m 2 , that is, the ferric phosphate electrode is prepared.

[0076] S2: lithium extraction process: an electrolytic cell is divided into an anode chamber and a cathode chamber by an anion membrane, 1.5-2 L of a sodium chloride solution with a concentration of 8-12 g / L is filled into the anode chamber as a supporting electrolyte, 6-8 L of brine to be tested is filled into the cathode chamber, an electrode for electrochemical lithium extraction prepared by the method is used as an anode, and a ferric phosphate electrode prepared in step S1 is used as a cathode. Constant voltage electrolysis is performed at 10-45 DEG C by applying a voltage of 0.3-0.5 V, and the electrolysis is ended when the current is lower than 150 mA.

[0077] After the lithium extraction process is completed, the positive and negative directions of the power supply are exchanged and the brine is refilled to perform lithium extraction again, at this time, the anode in the last cycle is used as the cathode in this cycle, and the cathode in the last cycle is used as the anode in this cycle, so that the lithium in the brine is extracted and enriched synchronously.

[0078] The electrode for electrochemical lithium extraction prepared by the method has an adhesion strength of greater than or equal to 11 N / m (such as 11.83-15.59 N / m), and a current density of greater than or equal to 20 A / m 2 (such as 20.88-32.33 A / m 2), current efficiency ≥ 90% (such as 90.35-94.32%), electrode capacity ≥ 27 mg / g (such as 27.56-34.55 mg / g), capacity retention rate ≥ 95% (such as 95.36-98.68%) after 300 cycles of lithium extraction.

[0079] Embodiment 1

[0080] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, comprising the following steps:

[0081] S1: performing physical treatment or chemical treatment on the flat plate-shaped current collector to obtain a current collector with a concave-convex surface topography;

[0082] The flat plate-shaped titanium plate current collector has a thickness of 5000 μm and an electrical conductivity of 2.3×10 6 S / m.

[0083] The surface is physically treated by turning, wherein the cutting depth is 200 μm, the rotation speed is 800 r / min, the feed rate is 3 mm / r, a sharp hard alloy turning tool is used for turning, wherein the negative rake angle is -10°, and the blunt circle radius is 0.6 mm.

[0084] After turning, the current collector with the concave-convex surface topography is obtained, and the specific surface area is 3 m 2 / g. The primary topography and the secondary topography of the current collector with the concave-convex surface topography obtained after turning are the same, so the peak height H1 of the primary topography is 200 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary topography are the first power of the peak height (or valley depth) of the primary topography.

[0085] The current collector with the concave-convex surface topography is as shown in the accompanying drawings. Figure 2

[0086] S2: uniformly coating lithium extraction slurry on the surface of the current collector with the concave-convex surface topography to obtain an electrode for electrochemical lithium extraction after drying.

[0087] The lithium extraction slurry comprises lithium extraction active material (lithium iron phosphate), conductive agent (acetylene black) and binder (PVDF), the mass fraction of the lithium extraction active material (lithium iron phosphate) is 80%, the mass fraction of the conductive agent (acetylene black) is 10%, and the mass fraction of the binder (PVDF) is 10%; and the lithium extraction slurry further comprises solvent (NMP), and the mass of the solvent (NMP) is 2.5 times the mass of all the solids (namely the lithium extraction active material, the conductive agent and the binder).

[0088] The lithium extraction slurry is uniformly coated on the surface of the current collector with the concave-convex surface by using a doctor blade, the drying temperature is 90°C, the drying time is 16 h, and the electrode for electrochemical lithium extraction with a coating density of 80 mg / cm 2 is obtained after drying.​

[0089] Embodiment 2

[0090] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, and the method comprises the following steps:

[0091] S1: performing physical treatment or chemical treatment on a flat plate-shaped current collector to obtain a current collector with a concave-convex surface;

[0092] The thickness of the flat plate-shaped graphite current collector is 10000 μm, and the conductivity of the graphite plate is 1.0*10 6 S / m.

[0093] The surface is physically treated by sand blasting, the silicon carbide abrasive with a particle size of 300 μm-500 μm is selected, the air pressure in the sand blasting process is 0.5 MPa, the spraying distance is 200 mm, the vertical angle is 85°, and the treatment time is 60 s.

[0094] The impact kinetic energy in the sand blasting process is controlled to obtain the current collector with the concave-convex surface after sand blasting, and the specific surface area is 10 m 2 / g, wherein the peak height H1 of the primary morphology is 500 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.5-0.8 times the peak height (or valley depth) of the primary morphology.

[0095] The current collector with the concave-convex surface is as shown in the accompanying drawings. Figure 3

[0096] S2: uniformly coating lithium extraction slurry on the surface of the current collector with the concave-convex surface to obtain an electrode for electrochemical lithium extraction after drying.

[0097] The lithium extraction slurry comprises lithium extraction active material (lithium manganate), conductive agent (carbon nanotube) and binder (PVDF), the mass fraction of the lithium extraction active material (lithium manganate) is 90%, the mass fraction of the conductive agent (carbon nanotube) is 5%, and the mass fraction of the binder (PVDF) is 5%; and the lithium extraction slurry further comprises solvent (NMP), and the mass of the solvent (NMP) is twice the mass of all the solids (namely the lithium extraction active material, the conductive agent and the binder).

[0098] The lithium extraction slurry is uniformly coated on the surface of the current collector with the concave-convex surface by means of a doctor blade, the drying temperature is 120 ℃, the drying time is 6 h, and the electrode for electrochemical lithium extraction with a coating density of 120 mg / cm 2 is obtained after drying.

[0099] Embodiment 3

[0100] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, and the method comprises the following steps:

[0101] ​S1: physically or chemically treating the flat plate-shaped current collector to obtain a current collector with a concave-convex surface topography;

[0102] The thickness of the flat plate-shaped titanium alloy plate current collector is 3000 pm, the electrical conductivity of the titanium alloy plate is 2.5 x 10 6 S / m.

[0103] The surface is physically treated by sanding, and diamond abrasives with a particle size of 120 pm-300 pm are selected, wherein the mesh number of the sandpaper / sand belt is 120 mesh, the grinding pressure is controlled to be 0.3 MPa, the feeding speed is 1200 pm / s, and the cold liquid is supplemented for single-direction grinding for 3 min, and the fine particles generated by the abrasives are used for secondary grinding on the groove surface, so that the current collector with the concave-convex surface topography is obtained, and the specific surface area is 2 m 2 / g, the peak height H1 of the primary topography is 300 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary topography are 0.4-0.6 times the peak height (or valley depth) of the primary topography.

[0104] The current collector with the concave-convex surface topography is as shown in the accompanying Figure 4 ;

[0105] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with the concave-convex surface topography, and obtaining an electrode for electrochemical lithium extraction after drying.

[0106] The lithium extraction slurry includes lithium extraction active material (lithium titanium phosphate), conductive agent (ketjen black), and binder (PVDF), the mass fraction of the lithium extraction active material (lithium titanium phosphate) is 70%, the mass fraction of the conductive agent (ketjen black) is 20%, and the mass fraction of the binder (PVDF) is 10%; and the lithium extraction slurry further includes solvent (NMP), and the mass of the solvent (NMP) is 3 times the mass of all the solids (i.e., the lithium extraction active material, the conductive agent, and the binder);

[0107] The lithium extraction slurry is uniformly coated on the surface of the current collector with the concave-convex surface by roll coating, the drying temperature is 70 DEG C, the drying time is 24 h, and the electrode for electrochemical lithium extraction with a coating density of 90 mg / cm 2 is obtained after drying.

[0108] Embodiment 4

[0109] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, including the following steps:

[0110] S1: physically or chemically treating the flat plate-shaped current collector to obtain a current collector with a concave-convex surface topography;

[0111] The thickness of the flat plate-shaped titanium plate current collector is 200 pm, and the electrical conductivity of the titanium plate is 2.3 x 10 6 S / m.

[0112] The surface is physically treated by laser ablation, nanosecond to femtosecond pulse laser, wavelength is 1064 or 532 nm, by adjusting the single pulse energy 30 mJ and the energy density 8 J / cm 2 The ablation depth is controlled, the heat affected zone and the pulse overlap rate are adjusted by combining the 1500 Hz repetition frequency and the scanning speed 150 mm / s, the secondary micro-nano structure is generated by using the melt recondensation and the micro-explosion effect, so that the current collector with the concave-convex topography is obtained, and the specific surface area is 6 m 2 / g; wherein the peak height H1 of the primary topography is 35 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary topography are 0.2-0.8 times of the peak height (or valley depth) of the primary topography.

[0113] The current collector with the concave-convex topography is as shown in the accompanying drawings. Figure 5

[0114] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with the concave-convex topography, and obtaining the electrode for electrochemical lithium extraction after drying.

[0115] The lithium extraction slurry includes lithium extraction active material (lithium manganese silicate), conductive agent (graphene), and binder (PVDF), the mass fraction of the lithium extraction active material (lithium manganese silicate) is 90%, the mass fraction of the conductive agent (graphene) is 5%, and the mass fraction of the binder (PVDF) is 5%; and further includes solvent (NMP), and the mass of the solvent (NMP) is 2.5 times of the mass of all solid substances (i.e. the lithium extraction active material, the conductive agent, and the binder);

[0116] The lithium extraction slurry is uniformly coated on the surface of the current collector with the concave-convex topography by roller coating, the drying temperature is 100 ℃, the drying time is 12 h, and the electrode for electrochemical lithium extraction with the coating density of 80 mg / cm 2 is obtained after drying.

[0117] Embodiment 5

[0118] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, including the following steps:

[0119] S1: physically or chemically treating a flat plate-shaped current collector to obtain a current collector with a concave-convex topography on the surface;

[0120] The thickness of the flat plate-shaped titanium alloy plate current collector is 1000 μm, and the conductivity of the titanium alloy is 2.5×10 6 S / m.

[0121] ​The surface is physically treated by laser engraving. In an argon atmosphere, a continuous or long-pulse fiber laser (wavelength 1064 nm) is used to form a primary morphology by synergistically regulating the melting depth with a peak power of 2 kW and a spot size of 300 μm. By controlling the heat input distribution with a scanning speed of 250 mm / s and a multi-pass overlapping strategy, the secondary morphology is generated by using the molten pool fluctuation effect and micro-area vaporization, thereby obtaining a current collector with a concave-convex surface having a specific surface area of 5 m 2 / g; wherein the peak height H1 of the primary morphology is 400 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.05-0.2 times the peak height (or valley depth) of the primary morphology.

[0122] The current collector with a concave-convex surface is as shown in FIG. 1. Figure 6

[0123] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with a concave-convex surface, and obtaining an electrode for electrochemical lithium extraction after drying.

[0124] The lithium extraction slurry includes lithium extraction active material (lithium iron silicate), conductive agent (ketjen black), and binder (PVDE). The mass fraction of the lithium extraction active material (lithium iron silicate) is 80%, the mass fraction of the conductive agent (ketjen black) is 10%, and the mass fraction of the binder (PVDE) is 10%. The lithium extraction slurry also includes solvent (NMP), and the mass of the solvent (NMP) is 2.5 times the mass of all the solids (lithium extraction active material, conductive agent, and binder).

[0125] The lithium extraction slurry is uniformly coated on the surface of the current collector with a concave-convex surface by roller coating. The drying temperature is 90°C, and the drying time is 18 h. An electrode for electrochemical lithium extraction with a coating density of 70 mg / cm 2 is obtained after drying.

[0126] Embodiment 6

[0127] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, including the following steps:

[0128] S1: physically or chemically treating a flat plate-shaped current collector to obtain a current collector with a concave-convex surface;

[0129] The thickness of the flat plate-shaped conductive polymer plate current collector is 2000 μm, and the electrical conductivity is 1.0×10 2 S / m.

[0130] ​The surface is physically treated by laser texturing. A short pulse ultraviolet laser (wavelength 355 nm) is used under nitrogen auxiliary blowing. The ablation intensity is regulated by pulse energy 0.6 mJ and spot size 200 μm to form a primary morphology. Then, the thermal accumulation effect is adjusted by 40 kHz repetition frequency and scanning speed 600 mm / s. The photochemical decomposition and thermal stress peeling are used to generate a secondary morphology, so that the current collector with concave-convex morphology is obtained, and the specific surface area is 3 m 2 / g; wherein the peak height H1 of the primary morphology is 400 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.5-0.9 times the peak height (or valley depth) of the primary morphology.

[0131] The current collector with concave-convex morphology is as shown in FIG. 1. Figure 7

[0132] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with concave-convex morphology, and obtaining the electrode for electrochemical lithium extraction after drying.

[0133] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (ketjen black) and binder (PVDE). The mass fraction of the lithium extraction active material (lithium iron silicate) is 80%, the mass fraction of the conductive agent (ketjen black) is 10%, and the mass fraction of the binder (PVDE) is 10%. The lithium extraction slurry also includes solvent (NMP) whose mass is 3 times the mass of all the solids (i.e. lithium extraction active material, conductive agent and binder).

[0134] The lithium extraction slurry is uniformly coated on the surface of the current collector with concave-convex morphology by spraying. The drying temperature is 100°C, and the drying time is 16 h. The electrode for electrochemical lithium extraction with a coating density of 80 mg / cm 2 is obtained after drying.

[0135] Example 7

[0136] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, including the following steps:

[0137] S1: physically or chemically treating the flat plate-shaped current collector to obtain a current collector with concave-convex morphology on the surface;

[0138] The thickness of the flat plate-shaped titanium plate current collector is 1000 μm, and the conductivity of the titanium plate is 2.3×10 6 S / m.

[0139] ​The surface of the current collector is chemically treated by chemical etching. A mixed solution of hydrofluoric acid and nitric acid (HF concentration 10 vol%, HNO3 concentration 30 vol%) is used as the etching medium. The reaction rate is controlled by a reaction temperature of 40°C and an etching time of 30 min, so that the current collector with a concave-convex surface is obtained. The specific surface area of the current collector is 1 m 2 / g; wherein the peak height H1 of the primary morphology is 250 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.1-0.3 times the peak height (or valley depth) of the primary morphology.

[0140] The current collector with a concave-convex surface is as shown in FIGS. 1-2. Figure 8 and FIGS. 3-4. Figure 9

[0141] S2: The lithium extraction slurry is uniformly coated on the surface of the current collector with a concave-convex surface. After drying, an electrode for electrochemical lithium extraction is obtained.

[0142] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (acetylene black), and binder (PVDE). The mass fraction of the lithium extraction active material (lithium iron phosphate) is 80%, the mass fraction of the conductive agent (ketjen black) is 10%, and the mass fraction of the binder (PVDE) is 10%. The lithium extraction slurry also includes solvent (NMP), and the mass of the solvent (NMP) is 3 times the mass of all the solids (i.e., the lithium extraction active material, the conductive agent, and the binder).

[0143] The lithium extraction slurry is uniformly coated on the surface of the current collector with a concave-convex surface by spraying. The drying temperature is 95°C, and the drying time is 14 h. After drying, an electrode for electrochemical lithium extraction with a coating density of 90 mg / cm 2 is obtained.

[0144] Example 8

[0145] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, including the following steps.

[0146] S1: A flat plate-shaped current collector is physically or chemically treated to obtain a current collector with a concave-convex surface.

[0147] The thickness of the flat plate-shaped titanium plate current collector is 500 μm, and the conductivity of the titanium plate is 2.3 x 10 6 S / m.

[0148] The surface of the current collector is chemically treated by chemical oxidation. An alkaline hydrogen peroxide solution (NaOH concentration 4 mol / L, H2O2 concentration 20 vol%) is used as the oxidation medium. The growth rate of the oxidation layer is controlled by reacting at a constant temperature of 60°C for 20 min, so that the current collector with a concave-convex surface is obtained. The specific surface area of the current collector is 2.5 m 2 ​H2 / W=0.25-0.5; wherein the peak height H1 of the primary morphology is 100 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.25-0.5 power of the peak height (or valley depth) of the primary morphology.

[0149] The current collector with the concave-convex morphology is as shown in FIG. 1. Figure 10 The current collector with the concave-convex morphology is as shown in FIG. 1.

[0150] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with the concave-convex morphology, and obtaining the electrode for electrochemical lithium extraction after drying.

[0151] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (ketjen black), and binder (PVDE), the mass fraction of the lithium extraction active material (lithium iron phosphate) is 80%, the mass fraction of the conductive agent (ketjen black) is 10%, and the mass fraction of the binder (PVDE) is 10%; and the lithium extraction slurry further includes solvent (NMP), and the mass of the solvent (NMP) is 3 times the mass of all the solids (i.e., the lithium extraction active material, the conductive agent, and the binder).

[0152] The lithium extraction slurry is uniformly coated on the surface of the current collector with the concave-convex morphology by spraying, the drying temperature is 80°C, the drying time is 20 h, and the electrode for electrochemical lithium extraction with a coating density of 25 mg / cm 2 is obtained after drying.

[0153] Embodiment 9

[0154] The embodiment provides a preparation method of an electrode for electrochemical lithium extraction, and the method comprises the following steps:

[0155] S1: physically or chemically treating a flat plate-shaped current collector to obtain a current collector with a concave-convex morphology on the surface;

[0156] The thickness of the flat plate-shaped titanium plate current collector is 3000 pm, and the conductivity of the titanium plate is 2.3 x 10 6 S / m.

[0157] Chemical deposition is used to chemically treat the surface, a nickel-molybdenum alloy plating solution (Ni 2+ is 1.0 M, MoO4 2- is 0.3 M, and the complexing agent sodium citrate is 0.2 M), and the deposition is performed under an 80°C high-temperature environment and an alkaline condition with a pH value of 8, and under a 30 mA / cm 2 pulse current for 120 min, so as to obtain the current collector with the concave-convex morphology, and the specific surface area is 3 m 2 / g; wherein the peak height H1 of the primary morphology is 200 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.5-0.8 power of the peak height (or valley depth) of the primary morphology.

[0158] The current collector with the concave-convex morphology is as shown in FIG. 1.Figure 11 as shown;

[0159] S2: uniformly coating the lithium extraction slurry on the surface of the current collector with a concave-convex topography, and obtaining an electrode for electrochemical lithium extraction after drying.

[0160] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (ketjen black), and binder (PVDE), the mass fraction of the lithium extraction active material (lithium iron phosphate) is 80%, the mass fraction of the conductive agent (ketjen black) is 10%, and the mass fraction of the binder (PVDE) is 10%; and further includes solvent (NMP), the mass of the solvent (NMP) is 3 times the mass of all solids (i.e., the lithium extraction active material, the conductive agent, and the binder).

[0161] The lithium extraction slurry is uniformly coated on the surface of the current collector with a concave-convex topography by spraying, the drying temperature is 80°C, the drying time is 20h, and an electrode for electrochemical lithium extraction with a coating density of 100mg / cm 2 is obtained after drying.

[0162] Comparative Example 1

[0163] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction, the flat titanium plate current collector used is the same as that in Example 1, the lithium extraction slurry and the coating method are the same as those in Example 1, and the difference lies in that the surface of the current collector is not subjected to physical or chemical treatment to have a concave-convex topography.

[0164] Specific preparation steps are as follows:

[0165] The lithium extraction slurry is uniformly coated on the smooth surface of the current collector by a doctor blade, and an electrode for electrochemical lithium extraction is obtained after drying.

[0166] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (acetylene black), and binder (PVDF), the mass fraction of the lithium extraction active material (lithium iron phosphate) is 80%, the mass fraction of the conductive agent (acetylene black) is 10%, and the mass fraction of the binder (PVDF) is 10%; and further includes solvent (NMP), the mass of the solvent (NMP) is 2.5 times the mass of all solids (i.e., the lithium extraction active material, the conductive agent, and the binder).

[0167] The lithium extraction slurry is uniformly coated on the surface of the current collector with a smooth surface by a doctor blade, the drying temperature is 90°C, the drying time is 16h, and an electrode for electrochemical lithium extraction with a coating density of 80mg / cm 2 is obtained after drying.

[0168] Comparative Example 2

[0169] This comparative example provides a method for preparing an electrode for electrochemical lithium extraction. The preparation method is similar to that of Example 9, except that the surface of the flat titanium plate current collector is treated by chemical deposition, and the electrode is prepared under alkaline conditions at 20°C and pH 8, with a current of 10 mA / cm². 2 Deposition under pulsed current for 10 min yields a current collector with an uneven surface morphology, wherein the peak height H1 of the primary morphology is 3 μm, and the peak height (or valley depth) H2 and peak width W of any secondary morphology are 0.01-0.03 powers of the peak height (or valley depth) of the primary morphology.

[0170] Comparative Example 3

[0171] This comparative example provides a method for preparing an electrode for electrochemical lithium extraction, which is similar to that in Example 9, except that the coating density of the electrode for electrochemical lithium extraction is 150 mg / cm³. 2 .

[0172] Comparative Example 4

[0173] This comparative example provides a method for preparing an electrode for electrochemical lithium extraction, which is similar to that in Example 9, except that the coating density of the electrode for electrochemical lithium extraction is 10 mg / cm³. 2 .

[0174] Comparative Example 5

[0175] This comparative example provides a method for preparing an electrode for electrochemical lithium extraction. The preparation method is similar to that in Example 1, except that:

[0176] The surface was physically treated by turning, with a cutting depth of 200 μm, a rotation speed of 300 r / min, a feed rate of 0.05 mm / r, and a carbide turning tool with a sharp angle, a negative rake angle of -2°, and a rounding radius of 0.02 mm.

[0177] After turning, a current collector with an uneven surface is obtained, wherein the peak height H1 of the primary morphology is 20 μm, and the peak height (or valley depth) H2 and peak width W of any secondary morphology are the first power of the peak height (or valley depth) of the primary morphology.

[0178] Comparative Example 6

[0179] This comparative example provides a method for preparing an electrode for electrochemical lithium extraction. The preparation method is similar to that in Example 2, except that:

[0180] The surface was physically treated by sandblasting, using silicon carbide abrasive with a particle size of 20μm-50μm. The air pressure during the sandblasting process was 0.3MPa, the spray distance was 200mm, the vertical angle was 60°, and the treatment time was 5s.

[0181] The impact kinetic energy is controlled by controlling the parameters in the sandblasting process, so that after sandblasting, the current collector with a concave-convex surface is obtained, wherein the peak height H1 of the primary morphology is 30 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.05-0.1 power of the peak height (or valley depth) of the primary morphology.

[0182] Comparative Example 7

[0183] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction, which is similar to that of Example 3, except that:

[0184] The surface is physically treated by sanding, and diamond abrasive with a particle size of 20-30 pm is selected, wherein the mesh number of the sandpaper / sand belt is 300 meshes, the grinding pressure is controlled to be 0.1 MPa, the feed speed is 400 pm / s, and cooling liquid is supplemented for single-direction grinding for 30 s, and at the same time, the fine particles generated by the abrasive crushing are used for secondary grinding on the groove surface, so that the current collector with a concave-convex surface is obtained, wherein the peak height H1 of the primary morphology is 30 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.1-0.2 power of the peak height (or valley depth) of the primary morphology.

[0185] Comparative Example 8

[0186] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction, which is similar to that of Example 4, except that:

[0187] The surface is physically treated by laser ablation, and nanosecond to femtosecond pulsed laser with a wavelength of 1064 or 532 nm is used, and the single-pulse energy is controlled to be 4 mJ and the energy density is controlled to be 0.5 J / cm 2 The ablation depth is controlled, the heat-affected zone and the pulse overlap rate are adjusted by combining the repetition frequency of 1500 Hz and the scanning speed of 100 mm / s, the secondary micro-nano structure is generated by using the recondensation of the melt and the micro-explosion effect, so that the current collector with a concave-convex surface is obtained, wherein the peak height H1 of the primary morphology is 20 pm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.1-0.2 power of the peak height (or valley depth) of the primary morphology.

[0188] Comparative Example 9

[0189] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction, which is similar to that of Example 5, except that:

[0190] The surface is physically treated by laser engraving. In an argon atmosphere, a continuous or long-pulse fiber laser (wavelength 1064 nm) is used to form a primary morphology by synergistically regulating the melting depth with a peak power of 2 kW and a spot size of 50 μm. The heat input distribution is controlled by a scanning speed of 80 mm / s and a multi-pass overlapping strategy. The secondary morphology is generated by using the molten pool fluctuation effect and micro-area vaporization, thereby obtaining a current collector with a concave-convex surface, wherein the peak height H1 of the primary morphology is 40 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.05-0.2 powers of the peak height (or valley depth) of the primary morphology.

[0191] Comparative Example 10

[0192] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction. The preparation method is similar to that of Example 6, except that:

[0193] The surface is physically treated by laser texturing. In a nitrogen auxiliary purge, a short-pulse ultraviolet laser (wavelength 355 nm) is used to form a primary morphology by regulating the ablation intensity with a pulse energy of 0.6 mJ and a spot size of 30 μm. The heat accumulation effect is adjusted by a repetition frequency of 40 kHz and a scanning speed of 1000 mm / s. The secondary morphology is generated by using photochemical decomposition and thermal stress peeling, thereby obtaining a current collector with a concave-convex surface, wherein the peak height H1 of the primary morphology is 30 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.1-0.15 powers of the peak height (or valley depth) of the primary morphology.

[0194] Comparative Example 11

[0195] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction. The preparation method is similar to that of Example 7, except that:

[0196] The surface is chemically treated by chemical etching. A hydrofluoric acid-nitric acid mixed solution (HF concentration 10 vol%, HNO3 concentration 30 vol%) is used as the etching medium. The reaction rate is regulated by a reaction temperature of 20°C and an etching time of 5 min, thereby obtaining a current collector with a concave-convex surface, wherein the peak height H1 of the primary morphology is 20 μm, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.1-0.15 powers of the peak height (or valley depth) of the primary morphology.

[0197] Comparative Example 12

[0198] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction. The preparation method is similar to that of Example 8, except that:

[0199] The surface of the current collector is chemically treated by chemical oxidation. An alkaline hydrogen peroxide solution (NaOH concentration of 4 mol / L and H2O2 concentration of 20 vol%) is used as an oxidation medium. The current collector with a concave-convex surface is obtained by reacting at a constant temperature of 30 DEG C for 10 min to control the growth rate of the oxidation layer, so that the peak height H1 of the primary morphology is 20 microns, and the peak height (or valley depth) H2 and the peak width W of any secondary morphology are 0.05-0.15 power of the peak height (or valley depth) of the primary morphology.

[0200] Comparative Example 13

[0201] The present comparative example provides a preparation method of an electrode for electrochemical lithium extraction. The preparation method is similar to that of Example 9, except that the slurry ratio is different during the preparation of the slurry.

[0202] The lithium extraction slurry includes lithium extraction active material (lithium iron phosphate), conductive agent (ketjen black) and binder (PVDE). The mass fraction of the lithium extraction active material (lithium iron phosphate) is 50%, the mass fraction of the conductive agent (ketjen black) is 30%, and the mass fraction of the binder (PVDE) is 20%. The lithium extraction slurry also includes a solvent (NMP), and the mass of the solvent (NMP) is 3 times the mass of all the solids (i.e., the lithium extraction active material, the conductive agent and the binder).

[0203] The lithium extraction slurry is uniformly coated on the surface of the current collector with a concave-convex surface by spraying. The drying temperature is 80 DEG C, and the drying time is 20 h. The electrode for electrochemical lithium extraction with a coating density of 100 mg / cm 2 is obtained after drying.

[0204] Experimental Example 1

[0205] Based on the principle of electrochemical deintercalation, the electrodes prepared in Examples 1-9 and Comparative Examples 1-13 are used to extract lithium directly from salt lake brine. The composition of the brine is shown in Table 1. The relevant parameters of the electrode for lithium extraction and the current density, current efficiency, electrode lithium ion intercalation capacity and other data of the lithium extraction process are shown in Table 2.

[0206] Table 1 Main components (g / L) of the salt lake brine used in Experimental Example 1

[0207] Element Li + ]]> Na + ]] K + ]]> Ca 2+ ]]> Mg 2+ ]]> Cl - ]]> SO4 2- ]]> B2O3 Concentration 0.42 22.72 2.86 0.31 2.83 34.65 16.75 1.57

[0208] Table 2 Electrode parameters and current density, current efficiency and electrode capacity in the lithium extraction process of Experimental Example 1

[0209]

[0210] According to the results in Table 2, the electrode provided by this invention can comprehensively improve the current density, current efficiency, and electrode capacity during the lithium extraction process. Comparing the data from Example 1 and Comparative Example 1, it can be seen that the electrode with an uneven surface on the current collector provided by this invention has an adhesion strength, current density, current efficiency, and electrode capacity of 14.25 N / m, 25.83 A / m², 90.22%, and 30.33 mg / g, respectively, all of which are higher than the adhesion strength (3.59 N / m) and current density (15.23 A / m²) of the electrode with a smooth surface (Comparative Example 1). 2 The current density, current efficiency (50.55%), and electrode capacity (15.18 mg / g) were compared with those of Example 9 and Comparative Example 2. It is evident that although the current collector surface was made uneven through chemical deposition, the peak height of the primary morphology and the peak width and peak height (or valley depth) of the secondary morphology were not within the range required by this invention. Therefore, its adhesion strength, current density, current efficiency, and electrode capacity were still significantly lower than those prepared with current collectors having larger surface morphologies. Comparing the data of Example 9 with Comparative Examples 3 and 4, it is evident that excessively thick electrode coating or too low coating density is detrimental to the overall improvement of current density, current efficiency, and electrode capacity. Combining the data of Examples 1-8 and Comparative Examples 5-12, it is evident that although the current collector formed an uneven morphology after processing, the peak height (or valley depth) of its primary morphology was low, resulting in low electrode adhesion strength and poor lithium extraction performance. Therefore, the improvement in electrode lithium extraction performance is the combined result of optimizing the electrode surface unevenness and coating density.

[0211] Experimental Example 2

[0212] Based on the electrochemical intercalation / deintercalation method, the lithium extraction performance of the electrodes prepared in Examples 1-9 and Comparative Examples 1-13 was tested in the brine of a salt lake. The brine composition is shown in Table 3. The number of cycles and capacity retention of the electrodes used for lithium extraction are shown in Table 4.

[0213] Lithium extraction methods:

[0214] 1. Preparation of the iron phosphate electrode: The electrolytic cell was divided into an anode chamber and a cathode chamber using an anion exchange membrane. Electrochemical lithium extraction electrodes prepared in Examples 1-9 and Comparative Examples 1-13 were used as anodes, and nickel foam was used as the cathode. Both the anode and cathode chambers were filled with 2L of a 20g / L sodium chloride solution. The pH of the cathode solution was adjusted to 3-4 using acid. Constant current electrolysis was performed by applying a voltage of 1.0V across the uneven current collector and the nickel foam. When the current was below 0.5A / m... 2 Electrolysis is completed at the specified time, thus obtaining the iron phosphate electrode.

[0215] 2. Lithium extraction process: The electrolytic cell is divided into anode and cathode compartments by anion membrane. The anode compartment is filled with 1.5 L of sodium chloride with a concentration of 10 g / L as supporting electrolyte, and the cathode compartment is filled with 7 L of brine (the composition of the brine is shown in Table 3). The electrodes prepared in Examples 1-9 and Comparative Examples 1-13 are used as anodes, and the iron phosphate electrode prepared is used as a cathode. Constant voltage electrolysis is carried out at 30°C and a voltage of 0.3 V, and the electrolysis is stopped when the current is lower than 150 mA.

[0216] Table 3 Main components of the brine used in Experimental Example 2 (g / L)

[0217] Element Li + ]]> Na + ]] K + ]]> Mg 2+ ]]> Ca 2 ]]> SO4 2- ]]> B HCO3 - ]]> Cl - ]]> Concentration 0.54 105.51 11.17 10.08 0.46 13.17 0.20 0.33 196.15

[0218] Table 4 Cycle number and capacity retention rate of the lithium extraction electrode in the cycle process of Experimental Example 2

[0219]

[0220]

[0221] From the cycle data of the electrodes in Table 4, it can be seen that the capacity retention rates of the electrodes prepared using the current collector with a concave-convex surface are all above 95% after 300 cycles of lithium extraction, while the capacity retention rate of the electrode prepared using the current collector with a flat surface in Comparative Example 1 is only 31.56% after 100 cycles of lithium extraction due to the partial shedding of the lithium extraction active material and electrode polarization. The peak height of the primary and secondary surface topographies of the current collector in Comparative Example 2 is low, and there is still a problem of partial shedding during the cycle lithium extraction process, and the capacity retention rate after 100 cycles is also low (42.19%). In summary, the capacity retention rates of the electrodes in Examples 1-8 and Comparative Examples 5-12 are lower than those in Examples. Therefore, the electrode prepared using the current collector with a concave-convex surface according to the present application can greatly improve the cycle stability of the electrode material.

[0222] The above description is only a preferred embodiment of the present application, and the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A method for producing an electrode for electrochemically extracting lithium, characterized by, The method comprises the following steps: S1: physically or chemically treating a flat plate-shaped current collector to obtain a current collector with a surface having a concave-convex morphology; S2: uniformly coating a lithium extraction slurry on the surface of the current collector with the concave-convex morphology to obtain an electrode for electrochemical lithium extraction after drying; The flat plate-shaped current collector is a current collector capable of serving as an anode current collector and a cathode current collector, and is one or more of a titanium plate, a titanium alloy plate, a graphite plate, and a conductive polymer plate, with a thickness of 200 μm-10000 μm; The specific surface area of the current collector with the concave-convex morphology is 1-10 m 2 / g.

2. The production method according to claim 1, characterized by, The surface of the current collector with the concave-convex morphology has two morphologies, and the morphology with the largest peak height or valley depth is a primary morphology, and the rest are secondary morphologies; Taking the horizontal plane of the surface of the flat plate-shaped current collector as a reference, the peak height or valley depth H1 of the primary morphology is 50 μm-500 μm, and the peak height or valley depth H2 and the peak width W of any secondary morphology are 0.05-1 power of the peak height or valley depth of the primary morphology.

3. The preparation method according to claim 2, characterized in that, The physical treatment is one or more of turning, sand blasting, sand grinding, laser ablation, laser engraving, and laser texturing. The chemical treatment is one or more of chemical corrosion, chemical oxidation, and chemical deposition.

4. The production method according to claim 3, characterized by, In the turning, the cutting depth is 50-300 μm, the rotation speed is 500-800 r / min, the feed rate is 0.1-3 mm / r, the negative rake angle of the large blunt radius tool used is -5° to -10°, and the large blunt radius is 0.3-0.6 mm.

5. The preparation method according to claim 3, characterized in that, In the sand blasting, the air pressure is 0.4-0.7 MPa, the spraying distance is 100-300 mm, the vertical angle is 75-85°, and the treatment time is 10-60 s.

6. The preparation method according to claim 3, characterized in that, In the sand grinding, the mesh number of the sandpaper or sand belt is 60-120 mesh, the grinding pressure is 0.2-0.5 MPa, the feed speed is 500-1500 μm / s, and the grinding time is 1-5 min.

7. The preparation method according to claim 3, characterized in that, In the laser ablation, a nanosecond to femtosecond pulsed laser is used, the laser wavelength is 532 nm or 1064 nm, the single pulse energy is 5-50 mJ, the energy density is 1-10 J / cm2, the repetition frequency is 1000-2000 Hz, and the scanning speed is 50-200 mm / s. In the laser engraving, a continuous or long pulse fiber laser is used in an argon atmosphere, the wavelength is 1064 nm, the peak power is 1-3 kW, the spot size is 200-500 μm, and the scanning speed is 100-300 mm / s. In the laser texturing, a short pulse ultraviolet laser is used under nitrogen auxiliary blowing, the wavelength is 355 nm, the pulse energy is 0.1-1 mJ, the spot size is 50-300 μm, the repetition frequency is 10-50 kHz, and the scanning speed is 200-800 mm / s.

8. The preparation method according to claim 3, characterized in that, In the chemical corrosion, the reaction temperature is 30-50℃, and the reaction time is 20-40 min. The chemical corrosion liquid is one of a hydrofluoric acid-nitric acid mixed solution and an alkaline hydrogen peroxide solution.

9. The preparation method according to claim 3, characterized in that, In the chemical oxidation, the reaction temperature is 50-90℃, and the reaction time is 15-30 min. The chemical oxidation solution is one of alkaline hydrogen peroxide solution and ammonium persulfate-sulfuric acid mixed solution; In the chemical deposition process, the deposition temperature is 30-90℃, the deposition time is 60-120min, the pulse current is 30-60mA / cm 2 , and the pH value of the plating solution is 3-10. The chemical deposition solution is one of nickel-molybdenum alloy plating solution and metal ruthenium composite plating solution.

10. A current collector with a concave-convex surface topography and its application in preparing an electrode for electrochemical lithium extraction.

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