High-bonding-strength low-resistance electrode for electrochemical lithium extraction

Abstract

The utility model relates to a high-bonding-strength low-resistance electrode for electrochemical lithium extraction, which belongs to the technical field of lithium resource development and utilization and is used for solving the problems that the bonding strength of a base body and an active material of an existing electrode for electrochemical lithium extraction is low, and the active material of the electrode is easy to fall off; electrode surface potential distribution is not uniform, and polarization is serious. The electron transmission path is far, and the current density is low. The utility model relates to a high-bonding-strength low-resistance electrode for electrochemical lithium extraction. The high-bonding-strength low-resistance electrode comprises a titanium mesh, the titanium mesh is formed by arranging a plurality of unit mesh holes, the unit mesh holes are one or more of square, rhombus, triangle, hexagon or circle, adjacent unit mesh holes share one common mesh hole edge, and the unit mesh holes are communicated with one another through the common mesh hole edges. The bonding strength of the electrode active material and the surface of the electrode is high, and the electrode active material is not easy to fall off; the surface potentials of the electrodes are approximately equal, and the electrodes are difficult to polarize; and a current transmission path is short.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium resource development and utilization, in particular to a high-binding-strength and low-resistance electrode for electrochemical lithium extraction. Background Art

[0002] With the rapid development of new energy vehicles, the demand for power batteries has grown rapidly, which in turn has led to a surge in the consumption of lithium products. Lithium products are mainly extracted and prepared from salt lake brine, lithium-containing ores, and waste lithium-ion batteries, and lithium products extracted and prepared from salt lake brine account for more than 60% of lithium production. Therefore, how to extract lithium resources from salt lake brine efficiently, greenly, and at low cost is of great significance to promoting the sustainable development of the new energy industry.

[0003] At present, the main methods for extracting lithium from salt lake brine include precipitation, electrodialysis, membrane, extraction, adsorption, etc. Among them, precipitation is only suitable for treating salt lake brine with a low magnesium-to-lithium ratio, and it must go through a long evaporation and concentration process; although electrodialysis and membrane separation are environmentally friendly, they are prone to membrane contamination due to the complex composition of brine, and ion exchange membranes cannot efficiently separate monovalent ions such as lithium, sodium, and potassium; although the extraction method has good selectivity, the extractant also has a certain solubility in brine, which brings about problems such as extractant dissolution and environmental pollution; the lithium ion sieve adsorption method has the advantages of high selectivity, but it requires acid for desorption, which consumes a lot of acid and has high energy consumption. In addition, the adsorption capacity and cycle stability of the adsorbent need to be improved.

[0004] In response to the problem of the difficulty in efficiently developing and utilizing lithium resources in salt lakes, researchers have developed a series of new lithium extraction technologies. Among them, the electrochemical deintercalation method (Chinese patents 201010555927.3, 202110555821.1 and US Patent US9062385B2, etc.) uses electrode materials with excellent selectivity for lithium (LiFePO4 / FePO4 or LiMn2O4 / λ-MnO2) to selectively extract lithium from brine. While extracting lithium, a lithium-rich solution with a lithium concentration greater than 5g / L can be obtained simultaneously, which greatly reduces the energy consumption of the lithium extraction process. It only needs electricity to be produced, which is green and environmentally friendly.

[0005] However, the electrodes used in electrochemical salt lake lithium extraction technology have problems such as low bonding strength between the conductive matrix and the active material, uneven potential distribution on the electrode surface, and long electron transmission paths, which lead to problems such as easy detachment of the electrode active material, severe polarization, and low current density. Utility Model Content

[0006] In view of the above analysis, the embodiments of the utility model aim to provide a high bonding strength and low resistance electrode for electrochemical lithium extraction, which is used to solve at least one of the following problems of existing electrodes for electrochemical lithium extraction: 1. The bonding strength between the matrix and the active material is low, which makes the electrode active material easy to fall off; 2. The potential distribution on the electrode surface is uneven and the electrode polarization is serious; 3. The electron transmission path is long and the current density of the electrode is low.

[0007] The purpose of this utility model is mainly achieved through the following technical solutions:

[0008] The utility model provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, comprising a titanium mesh;

[0009] The titanium mesh is composed of a plurality of unit meshes arranged in an arrangement;

[0010] The unit mesh is one or more of a square, a rhombus, a triangle, a hexagon or a circle, and adjacent unit meshes share a common mesh edge, and the unit meshes are interconnected through the common mesh edge.

[0011] Furthermore, the area of ​​the titanium mesh holes accounts for 30-60% of the total geometric area of ​​the titanium mesh.

[0012] Furthermore, the side length or diameter of the unit mesh is proportional to the 1.5-2.2 power of the thickness of the titanium mesh.

[0013] Furthermore, the side length or diameter of the unit mesh is 0.22-11.2 mm.

[0014] Furthermore, the width of the unit mesh edge is 0.2-3 mm.

[0015] Furthermore, the surface of the titanium mesh includes a metal coating, and the coating thickness is 0.2-20 μm.

[0016] Furthermore, titanium plate conductive strips are arranged on the titanium mesh, and the titanium plate conductive strips are evenly distributed on the titanium mesh with equal intervals.

[0017] Furthermore, the width of the titanium plate conductive strip is 10-15 mm, and the conductive strip interval is 50-500 mm.

[0018] Furthermore, the unit mesh structure of the titanium mesh is uniformly coated with lithium extraction slurry.

[0019] Furthermore, the electrode also includes a current lead-out terminal, which is arranged on one side of the long side of the titanium mesh, and the current lead-out terminal is connected to the titanium mesh by any one of welding, bolt connection or rivet connection.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The utility model processes titanium plates or titanium wires into titanium meshes with special mesh structures uniformly distributed in square, rhombus, triangle, hexagon, circle and the like, wherein the side length of the meshes is proportional to the 1.5-2.2 power of the thickness of the titanium mesh, the area of ​​the meshes accounts for 30-60% of the total geometric area of ​​the titanium mesh, and a current lead-out terminal is provided at one end of the long side of the titanium mesh; the electrode active materials on both sides of the titanium mesh can form a "ring envelope" through the meshes of the titanium mesh, thereby enhancing the bonding strength between the active materials and the electrode surface, thereby effectively solving the problem of the active materials falling off and slagging due to long-term circulation; at the same time, the mesh design can reduce the mass of the titanium mesh and reduce the manufacturing cost of the electrode.

[0022] 2. The uniform distribution of the titanium mesh pores and the optimization of the mesh specifications of the utility model can greatly make the electrode potential at various locations on the electrode surface approximately equal, thereby reducing the electrode polarization of the electrode during the lithium extraction process and improving the electrochemical performance of the electrode.

[0023] 3. The current lead-out terminal of the utility model is arranged on one side of the long side of the titanium mesh, which greatly shortens the electron transmission path and reduces the resistance of the lithium extraction process. The processed titanium mesh can be further electroplated to attach a layer of metal coating to the surface of the titanium mesh, so that the conductivity of the titanium mesh is effectively improved, thereby realizing high current density lithium extraction and extending the service life of the electrode.

[0024] 4. The electrode preparation process provided by the utility model is simple, the manufacturing cost is low, and it is easy to realize large-scale application.

[0025] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by implementing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components.

[0027] Figure 1 This is a schematic diagram of a titanium mesh with square meshes in Example 1 of the utility model;

[0028] Figure 2 This is a schematic diagram of a titanium mesh with diamond-shaped meshes in Example 2 of the present utility model;

[0029] Figure 3 This is a schematic diagram of a titanium mesh with triangular mesh holes in Example 3 of the present utility model;

[0030] Figure 4 This is a schematic diagram of a titanium mesh with hexagonal meshes in Example 4 of the utility model;

[0031] Figure 5 This is a schematic diagram of a titanium mesh with hexagonal and diamond-shaped composite meshes in Example 5 of the utility model;

[0032] Figure 6 This is a schematic diagram of a titanium mesh with circular mesh holes in Example 6 of the present utility model;

[0033] Figure 7 This is a relationship diagram between the electrode capacity retention rate and the number of cycles of the electrodes provided in Example 1, Example 4, Comparative Example 1 and Comparative Example 2 of the present invention during the lithium extraction process.

[0034] Reference numerals:

[0035] 1-titanium mesh, 2-current lead-out terminal, 3-titanium plate conductive strip. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0037] The utility model provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, comprising a titanium mesh and a lithium extraction slurry;

[0038] The titanium mesh is processed into a mesh structure by titanium plate or titanium wire, and is composed of a plurality of unit meshes arranged in an arrangement, and the unit meshes are one or more of square, rhombus, triangle, hexagon or circle, and adjacent unit meshes share a common mesh edge, and the unit meshes are interconnected through the common mesh edge;

[0039] The lithium extraction slurry is evenly coated on the double-sided mesh structure of the titanium mesh;

[0040] A current lead-out terminal is provided on one side of the long side of the titanium mesh, and the current lead-out terminal is a titanium plate with a thickness of 1-3 mm;

[0041] Titanium metal has strong corrosion resistance and high electrical conductivity (3.1×10 6 S / m) and other characteristics, is a good electrode matrix, the utility model in order to improve the strength of the electrode and reduce the internal resistance of the electrode matrix, the high strength, easy processing, small internal resistance of the titanium plate or titanium wire as the electrode matrix;

[0042] The titanium plate or titanium wire is one of titanium materials such as pure titanium and titanium alloy, and the titanium alloy can be one of titanium aluminum alloy, titanium nickel alloy, titanium copper alloy, titanium molybdenum alloy, and TC4 titanium alloy;

[0043] In order to ensure that the titanium mesh has good physical strength during use and that a large area of ​​the titanium mesh is not easily bent or deformed, and because the resistance of a conductor is inversely proportional to its cross-sectional area (R = ρL / S), the titanium plate or titanium wire needs to have a certain thickness; specifically, the thickness / wire diameter of the titanium plate / titanium wire is 0.5-3 mm;

[0044] Specifically, the processing method of titanium plate into titanium mesh can be one of punching forming and stamping stretching; the processing method of titanium wire into titanium mesh can be one of plain weave, twill weave, and dense weave; the specifications of the titanium mesh holes (such as the density of the mesh holes, the size of the mesh holes, and the thickness of the mesh hole edges) affect the processing difficulty, cost, and electrochemical performance of the electrode. If the titanium mesh holes are too dense or the mesh holes are too small, the processing is difficult; and if the mesh holes are too large, it is easy to cause insufficient contact between the electrode active material and the substrate, and increase the difficulty of coating. Therefore, the area of ​​the titanium mesh holes is designed to account for 30-60% of the total geometric area of ​​the titanium mesh, which can ensure that the electrode has good processing performance and cost advantages.

[0045] Specifically, the side length of the titanium mesh unit mesh is proportional to the 1.5-2.2 power of the titanium mesh thickness; the side length of the titanium mesh unit mesh ranges from 0.22 to 11.2 mm; this ensures that the electrode with a mesh with a larger side length has a lower resistance.

[0046] Specifically, the width of the unit mesh edge is 0.2-3mm; the thickness of the mesh edge is closely related to the resistance of the electrode. The thinner the mesh edge, the greater the electrode resistance, the greater the voltage drop at each part of the electrode, and the more uneven the potential distribution at each part of the electrode, which leads to worse electrochemical performance of the electrode; the width of the unit mesh edge is 0.2-3mm, which can ensure that the electrode has lower resistance and voltage drop.

[0047] Specifically, in order to efficiently lead out the current during the lithium extraction process and realize large-current lithium extraction, a current lead-out terminal is provided on one side of the long side of the titanium mesh; and in order to reduce the heat problem caused by the current flowing into the current lead-out terminal, the thickness of the current lead-out terminal is greater than the thickness / wire diameter of the titanium plate or titanium wire; the current lead-out terminal is a titanium plate with a thickness of 1-3 mm; the current lead-out terminal can be connected to the titanium mesh by welding, bolt connection, rivet connection, etc.

[0048] Specifically, the lithium extraction slurry is evenly coated on the double-sided mesh structure of the titanium mesh, and the lithium extraction slurry includes an electrode active material, a conductive agent, a binder and a solvent; the electrode active material is Li 1-x FePO4(0≤x≤1), Li 1-x Mn2O4(0≤x≤1), Li 1+xThe invention discloses a method for preparing a lithium-ion battery comprising: preparing a lithium-ion battery comprising at least one of FePO4(OH)(0≤x≤1); the conductive agent is at least one of acetylene black and Ketjen black, the binder is polyvinylidene fluoride (PVDF), and the solvent is N-methylpyrrolidone (NMP); the electrode active material is uniformly mixed with the conductive agent and the binder in a mass ratio of (85-90):(5-10):(5-10), and then the solvent is added for slurrying to obtain a lithium extraction slurry having a viscosity of 500-1200 Pa·s.

[0049] The coating density of the lithium extraction slurry is 60-150 mg / cm 2 (based on electrode active material), which is much better than the coating density of lithium slurry on titanium plate in the prior art (generally 40-60 mg / cm 2 , the coating density is too high and it is easy to fall off); this is because the current density in the lithium extraction process is proportional to the mass of the lithium extraction slurry. Applying more lithium extraction slurry can effectively increase the current per unit area of ​​the electrode. The mesh structure of the titanium mesh makes the lithium extraction slurry and the substrate form a "ring envelope", which can effectively improve the bonding strength between the slurry and the substrate, thereby making the lithium extraction slurry coating density reach 60-150 mg / cm 2 .

[0050] Under the condition of ensuring that the electrode has high bonding strength, the resistance and corrosion resistance of the electrode are also important factors affecting the efficiency of electrochemical lithium extraction; in order to further reduce the resistance of the electrode for electrochemical lithium extraction and improve the corrosion resistance of the electrode, the utility model can also electroplate the processed titanium mesh. By electroplating, a layer of metal coating is attached to both sides of the titanium mesh, which can not only enhance the conductivity of the titanium mesh, but also effectively avoid the corrosion of the electrode by the high-salt environment of salt lake brine; specifically, the metal electroplated on both sides of the titanium mesh is preferably one of ruthenium, iridium, platinum, tantalum and other metals, that is, a layer of ruthenium, iridium, platinum, tantalum and other metal coating is formed on the surface of the titanium mesh; the coating thickness is 0.2-20μm.

[0051] In order to further shorten the transmission path of electrons during lithium extraction, titanium plate conductive strips with the same thickness as the titanium mesh can be added during the weaving of the titanium mesh to minimize the electron transfer resistance; specifically, the width of the conductive strips is 10-15mm, and the conductive strip spacing is 50-500mm; the titanium plate conductive strips are evenly distributed on the titanium mesh at equal intervals, then the number of titanium plate conductive strips N = L / (W+L1), where N is the number of titanium plate conductive strips; L is the length of the titanium mesh; W is the width of the conductive strip, and L1 is the conductive strip spacing, all in mm.

[0052] Example 1

[0053] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0054] A 0.5 mm thick pure titanium plate is punched into a titanium mesh with uniformly distributed square meshes, and a current lead-out terminal is provided on one side of the long side of the titanium mesh, as shown in the schematic diagram. Figure 1 As shown;

[0055] Among them, the mesh area accounts for about 30% of the total geometric area of ​​the titanium mesh, the side length of the square unit mesh is 0.22mm (the side length of the mesh is the 2.2th power of the thickness of the titanium mesh), and the width of the unit mesh side is 1mm; the current lead-out terminal is a 2mm thick titanium plate, the titanium plate and the titanium mesh can be connected by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh;

[0056] The square mesh titanium mesh after punching is trimmed, polished, cleaned and dried, and then a lithium extraction slurry with a viscosity of 1200 Pa·s is coated on both sides of the titanium mesh, and a high bonding strength and low resistance electrode for electrochemical lithium extraction is obtained after drying; wherein LiFePO4 in the lithium extraction slurry is an electrode active material, the conductive agent is acetylene black, the adhesive is PVDF, the solvent in the pulping process is NMP, the mass ratio of LiFePO4, acetylene black and PVDF is 85:10:5, and the coating density of the lithium extraction slurry is 80 mg / cm 2 .

[0057] Weigh the square mesh titanium mesh without lithium extraction slurry coating, the size is 100cm 2 The weight of the titanium mesh is 15.79g, which is significantly less than the 0.5mm thick and 100cm 2 The pure titanium plate (22.55 g) shows that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing the cost;

[0058] In this embodiment, the square mesh structure titanium mesh electrode coated with lithium extraction slurry is electrochemically delithiated to prepare lithium-deficient Li 1-x FePO4 (0≤x<1) square mesh structure titanium mesh electrode, with the Li 1-x The square mesh structure titanium mesh electrode of FePO4 (0≤x<1) was used as the working electrode, and the square mesh structure titanium mesh electrode of another embodiment which was not de-lithiated was used as the counter electrode to construct an electrochemical lithium extraction system, and lithium was selectively extracted from salt lake brine (the composition of brine is shown in Table 1). The lithium extraction results showed that the average current density of the square mesh structure titanium mesh electrode of this embodiment reached 26A / m 2 .

[0059] Table 1 Main components of salt lake brine

[0060] Element <![CDATA[Li + ]]> <![CDATA[Na + ]]> <![CDATA[K + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> Concentration, g / L 0.51 31.02 11.23 13.58 50.43 68.19

[0061] Example 2

[0062] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0063] Titanium wire with a wire diameter of 0.8 mm is processed into a titanium mesh with uniformly distributed diamond meshes through plain weaving, and a current lead-out terminal is provided at one end of the titanium mesh, as shown in the schematic diagram. Figure 2 As shown;

[0064] Among them, the mesh area accounts for about 50% of the total geometric area of ​​the titanium mesh, the side length of the rhombus unit mesh is 0.72mm (the side length of the mesh is 1.5 times the thickness of the titanium mesh), and the width of the unit mesh side is 0.2mm; the current lead-out terminal is a 1mm thick titanium plate, the titanium plate and the titanium mesh can be connected by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh;

[0065] The square mesh titanium mesh after punching is trimmed, polished, cleaned and dried, and then a lithium extraction slurry with a viscosity of 500Pa·s is coated on both sides of the titanium mesh. After drying, a high-bonding-strength and low-resistance electrode for electrochemical lithium extraction is obtained; wherein, LiMn2O4 in the lithium extraction slurry is the electrode active material, the conductive agent is Ketjen black, the adhesive is PVDF, and the solvent in the slurry making process is NMP; the mass ratio of LiMn2O4, Ketjen black and PVDF is 90:5:5. The coating density of the lithium extraction slurry is 150mg / cm 2 .

[0066] Weigh the diamond-shaped titanium mesh without coating the lithium extraction slurry, the size is 500cm 2 The weight of the titanium mesh is 11.25g, which is significantly less than the 0.1mm thick and 500cm 2 The pure titanium plate (22.50 g) shows that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing the cost;

[0067] In this embodiment, the diamond mesh structure titanium mesh electrode coated with lithium extraction slurry is electrochemically delithiated to prepare lithium-deficient Li 1-x Mn2O4 (0≤x<1) diamond mesh structure titanium mesh electrode, with the Li 1-x The Mn2O4 (0≤x<1) diamond mesh structure titanium mesh electrode was used as the working electrode, and another diamond mesh structure titanium mesh electrode of this embodiment that was not de-lithiated was used as the counter electrode to construct an electrochemical lithium extraction system to selectively extract lithium from salt lake brine (the brine composition is shown in Table 1). The lithium extraction results showed that the average current density of the square mesh structure titanium mesh electrode of this embodiment reached 30A / m 2 .

[0068] Example 3

[0069] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0070] A 3 mm thick titanium-nickel alloy plate is processed by stamping and stretching into a titanium mesh with uniformly distributed triangular meshes, and a current lead-out terminal is provided at one end of the titanium mesh, as shown in the schematic diagram. Figure 3 As shown;

[0071] Among them, the mesh area accounts for about 60% of the total geometric area of ​​the titanium mesh, the side length of the triangular unit mesh is 9mm (the side length of the mesh is the square of the thickness of the titanium mesh), and the width of the unit mesh side is 3mm; the current lead-out terminal is a 3mm thick titanium plate, the titanium plate and the titanium mesh can be connected by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh;

[0072] The triangular mesh titanium mesh after stamping and stretching is trimmed, polished, cleaned and dried, and then a lithium extraction slurry with a viscosity of 800Pa·s is coated on both sides of the titanium mesh. After drying, a high-bonding strength and low-resistance electrode for electrochemical lithium extraction is obtained; wherein, LiFePO4(OH) in the lithium extraction slurry is the electrode active material, the conductive agent is Ketjen black, the adhesive is PVDF, and the solvent in the slurry making process is NMP; the mass ratio of LiFePO4(OH), Ketjen black and PVDF is 85:10:5. The coating density of the lithium extraction slurry is 60mg / cm 2 .

[0073] Weigh the triangular structure titanium mesh without lithium extraction slurry coating, the size is 100cm 2 The weight of the titanium mesh is 52g, which is significantly less than the 2mm thick and 100cm 2 The pure titanium plate (130g) shows that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing the cost;

[0074] In this embodiment, the triangular mesh structure titanium mesh electrode coated with the lithium extraction slurry is electrochemically delithiated to prepare the lithium-deficient Li 1+x FePO4(OH)(0≤x<1) triangular mesh structure titanium mesh electrode, with the Li 1+x The triangular mesh structure titanium mesh electrode of FePO4(OH)(0≤x<1) was used as the working electrode, and the triangular mesh structure titanium mesh electrode of another embodiment which was not de-lithiated was used as the counter electrode to construct an electrochemical lithium extraction system to selectively extract lithium from salt lake brine (the composition of the brine is shown in Table 1). The lithium extraction results showed that the average current density of the square mesh structure titanium mesh electrode of this embodiment reached 24A / m 2 .

[0075] Example 4

[0076] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0077] The 2mm thick titanium-molybdenum alloy wire is processed into a titanium mesh with uniformly distributed hexagonal meshes through dense weaving, and a current lead-out terminal is provided at one end of the titanium mesh, and a titanium plate conductive strip with the same thickness as the titanium mesh is provided. The schematic diagram is shown in FIG. Figure 4 As shown;

[0078] Among them, the mesh area accounts for about 40% of the total geometric area of ​​the titanium mesh, the side length of the hexagonal unit mesh is 3.48mm (the side length of the mesh is 1.8 times the thickness of the titanium mesh), and the width of the unit mesh side is 1.5mm; the current lead-out terminal is a 2.5mm thick titanium plate, the titanium plate and the titanium mesh can be connected by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh; the width of the titanium plate conductive strip is 10mm, the conductive strip interval is 500mm, the length of the titanium mesh is 1600mm, and the number of conductive strips = 1600 / (500+10) = 3.1, that is, the number of conductive strips is 3;

[0079] The densely woven hexagonal mesh titanium mesh is trimmed, polished, cleaned, and dried, and then a lithium extraction slurry with a viscosity of 1000 Pa·s is coated on both sides of the titanium mesh, and after drying, a high-bonding-strength, low-resistance electrode for electrochemical lithium extraction is obtained; wherein, Li in the lithium extraction slurry is 0.5 FePO4 is the electrode active material, the conductive agent is Ketjen black, the binder is PVDF, and the solvent in the pulping process is NMP; Li 0.5 The mass ratio of FePO4, Ketjen black and PVDF is 90:5:5. The coating density of lithium extraction slurry is 100mg / cm 2 .

[0080] Weigh the hexagonal titanium mesh without lithium slurry coating, the size is 200cm 2 The weight of the titanium mesh is 50.40g, which is significantly less than the 1mm thick and 200cm 2 The pure titanium plate (84g) shows that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing the cost;

[0081] The triangular mesh structure titanium mesh electrode coated with lithium extraction slurry in this embodiment is subjected to electrochemical lithium removal to prepare a lithium-deficient FePO4 hexagonal mesh structure titanium mesh electrode. The FePO4 hexagonal mesh structure titanium mesh electrode is used as a working electrode and another hexagonal mesh structure titanium mesh electrode of this embodiment that has not been de-lithiated is used as a counter electrode to construct an electrochemical lithium extraction system to selectively extract lithium from salt lake brine (the composition of the brine is shown in Table 1). The lithium extraction results show that the average current density of the hexagonal mesh structure titanium mesh electrode of this embodiment reaches 29A / m 2 .

[0082] Example 5

[0083] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0084] The titanium copper alloy wire with a thickness of 0.9 mm is processed into a titanium mesh with a uniformly distributed hexagonal and rhombus composite shape through twill weaving, and a current lead-out terminal is provided at one end of the titanium mesh, as shown in the schematic diagram. Figure 5 As shown;

[0085] Among them, the mesh area accounts for about 55% of the total geometric area of ​​the titanium mesh. The side lengths of the hexagonal and rhombus unit meshes are both 0.85 mm (the side length of the mesh is the 1.6th power of the thickness of the titanium mesh), and the width of the unit mesh side is 1 mm. The current lead-out terminal is a 1 mm thick titanium plate, which can be connected to the titanium mesh by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh.

[0086] The above-mentioned twill-woven hexagonal and diamond-shaped titanium meshes were trimmed, polished, cleaned, and dried, and then a lithium extraction slurry with a viscosity of 700Pa·s was coated on both sides of the titanium mesh. After drying, a high-bonding-strength, low-resistance electrode for electrochemical lithium extraction was obtained; wherein, FePO4 in the lithium extraction slurry is the electrode active material, the conductive agent is acetylene black, the adhesive is PVDF, and the solvent in the slurry making process is NMP; the mass ratio of FePO4, acetylene black and PVDF is 85:10:5. The coating density of the lithium extraction slurry is 75mg / cm 2 .

[0087] Weigh the titanium mesh with hexagonal and diamond composite structures without coating the lithium extraction slurry, with a size of 100 cm 2 The weight of the titanium mesh is 31.32g, which is significantly less than the 0.8mm thick and 100cm 2 The pure titanium plate (69.6g) shows that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing the cost;

[0088] In this embodiment, the hexagonal and diamond mesh structure titanium mesh electrodes coated with lithium extraction slurry are electrochemically delithiated to prepare lithium-deficient Li 1-x FePO4 (0<x≤1) hexagonal and rhombus composite mesh structure titanium mesh electrode, with the Li 1- x The FePO4 (0<x≤1) hexagonal and diamond mesh structure titanium mesh electrode was used as the working electrode, and the other hexagonal and diamond mesh structure titanium mesh electrode of this embodiment that was not de-lithiated was used as the counter electrode to construct an electrochemical lithium extraction system to selectively extract lithium from salt lake brine (the brine composition is shown in Table 1). The lithium extraction results showed that the average current density of the hexagonal and diamond composite mesh structure titanium mesh electrode of this embodiment reached 25A / m2 .

[0089] Example 6

[0090] This embodiment provides a high-binding-strength and low-resistance electrode for electrochemical lithium extraction, including a titanium mesh and a lithium extraction slurry;

[0091] A 1.2 mm thick TC4 titanium alloy plate is punched into a titanium mesh with uniformly distributed circular meshes, and a current lead-out terminal is provided at one end of the titanium mesh, as shown in the schematic diagram. Figure 6 As shown;

[0092] Among them, the mesh area accounts for about 45% of the total geometric area of ​​the titanium mesh, the diameter of the circular unit mesh is 1.50mm (the mesh side length is the 2.2th power of the titanium mesh thickness), and the width of the unit mesh side is 2mm; the current lead-out terminal is a 2mm thick titanium plate, the titanium plate and the titanium mesh can be connected by welding, and the current lead-out terminal is set on one side of the long side of the titanium mesh;

[0093] The punched circular mesh titanium mesh is trimmed, polished, cleaned and dried, and then a lithium extraction slurry with a viscosity of 1000Pa·s is coated on both sides of the titanium mesh. After drying, a high-bonding-strength and low-resistance electrode for electrochemical lithium extraction is obtained; wherein, LiMn2O4 in the lithium extraction slurry is the electrode active material, the conductive agent is acetylene black, the adhesive is PVDF, and the solvent in the slurry making process is NMP; the mass ratio of LiMn2O4, acetylene black and PVDF is 85:10:5. The coating density of the lithium extraction slurry is 120mg / cm 2 .

[0094] Weigh the titanium mesh with circular structure without coating the lithium extraction slurry, the size is 100cm 2 The weight of the titanium mesh is 29.77g, which is significantly less than the 1.2mm thick and 100cm 2 TC4 titanium alloy plate (54.12g), indicating that the electrode provided by the utility model can effectively save the amount of titanium material, thereby reducing costs;

[0095] In this embodiment, the circular mesh structure titanium mesh electrode coated with the lithium extraction slurry is electrochemically delithiated to prepare the lithium-deficient Li 1-x Mn2O4 (0≤x<1) circular mesh structure titanium mesh electrode, with the Li 1-x The Mn2O4 (0≤x<1) circular mesh structure titanium mesh electrode was used as the working electrode, and another circular mesh structure titanium mesh electrode of this embodiment that was not de-lithiated was used as the counter electrode to construct an electrochemical lithium extraction system to selectively extract lithium from salt lake brine (the brine composition is shown in Table 1). The lithium extraction results showed that the average current density of the square mesh structure titanium mesh electrode of this embodiment reached 29A / m 2 .

[0096] Example 7

[0097] This embodiment provides a high-bonding-strength and low-resistance electrode for electrochemical lithium extraction, and the structure is similar to that of Embodiment 1. The difference is that in this embodiment, the square mesh titanium mesh is polished and cleaned, and then iridium-plated, so that the surface thereof has a layer of iridium metal coating, and the coating thickness is 0.2 μm;

[0098] The electrochemical lithium extraction system was constructed in the same manner as described in Example 1. The results showed that the current density of the lithium extraction electrode of the square structure titanium mesh after ruthenium plating reached 29A / m 2 ; Due to the electroplating treatment, the resistance of the electrode is further reduced, thereby further improving the current density during the lithium extraction process.

[0099] Example 8

[0100] This embodiment provides a high-bonding-strength and low-resistance electrode for electrochemical lithium extraction, and the structure is similar to that of Embodiment 1. The difference is that in this embodiment, the square mesh titanium mesh is polished and cleaned, and then iridium-plated, so that the surface thereof has a layer of iridium metal coating, and the coating thickness is 1 μm;

[0101] The electrochemical lithium extraction system was constructed in the same manner as described in Example 1. The results showed that the current density of the square structure titanium mesh lithium extraction electrode after ruthenium plating reached 30A / m 2 ; Due to the electroplating treatment, the resistance of the electrode is further reduced, thereby further improving the current density during the lithium extraction process.

[0102] Example 9

[0103] This embodiment provides a high-bonding-strength and low-resistance electrode for electrochemical lithium extraction, and the structure is similar to that of Embodiment 2. The difference is that in this embodiment, the diamond mesh titanium mesh is polished and cleaned, and then iridium-plated, so that the surface thereof has a layer of iridium metal coating, and the coating thickness is 20 μm;

[0104] The electrochemical lithium extraction system was constructed in the same manner as described in Example 2. The results showed that the current density of the square structure titanium mesh lithium extraction electrode after ruthenium plating reached 35A / m 2 ; Due to the electroplating treatment, the resistance of the electrode is further reduced, thereby further improving the current density during the lithium extraction process.

[0105] By comparing Example 1 with Example 7 and Example 8, and Example 2 with Example 9, it can be found that by electroplating the titanium mesh after stamping so that a metal coating is attached to both sides of the titanium mesh, the resistance of the current collector (titanium mesh) can be reduced, thereby achieving an increase in the current density of the lithium extraction process.

[0106] Comparative Example 1

[0107] This comparative example provides an electrode for electrochemical lithium extraction. The difference from Example 1 is that the pure titanium plate is not punched and formed, but the lithium extraction slurry is directly coated on the titanium plate as the current collector. The coating density of the electrode slurry is 50 mg / cm 2 , the rest is the same as Example 1.

[0108] The obtained electrode was pretreated and lithium was extracted from salt lake brine using the same steps as in Example 1. The results showed that the average current density during the lithium extraction process was 20 A / m 2 ; The current density of this electrode is significantly lower than the high binding strength electrode provided in Example 1, indicating that stamping and forming the titanium plate into a titanium mesh can increase the coating density of the electrode slurry, thereby increasing the current density of the lithium extraction process; at the same time, it can save materials and reduce costs.

[0109] Comparative Example 2

[0110] This comparative example provides an electrode for electrochemical lithium extraction. The difference from Example 4 is that the titanium-molybdenum alloy plate is not subjected to dense weaving treatment, but the titanium-molybdenum alloy plate is directly used as the current collector for lithium extraction slurry coating. The coating density of the slurry is 60 mg / cm 2 , the rest is the same as Example 4.

[0111] The obtained electrode was pretreated and lithium was extracted from salt lake brine using the same steps as in Example 4. The results showed that the average current density during the lithium extraction process was 23 A / m 2 .

[0112] Comparative Example 3

[0113] This comparative example provides an electrode for electrochemical lithium extraction, which is different from Example 1 in that the mesh area accounts for 80% of the geometric area of ​​the titanium mesh, and the rest is the same as Example 1.

[0114] The obtained electrode was pretreated and lithium was extracted from salt lake brine using the same steps as in Example 1. The results showed that the average current density during the lithium extraction process was 18 A / m 2 Compared with the current density of Example 1, the current density of this comparative example is significantly reduced, indicating that after the proportion of the mesh area to the geometric area of ​​the titanium mesh increases, the electrode active material cannot form a good annular envelope with the electrode group, which easily leads to poor contact, thereby reducing the current density and failing to achieve high current density lithium extraction.

[0115] Comparative Example 4

[0116] This comparative example provides an electrode for electrochemical lithium extraction, which is different from Example 1 in that the mesh area accounts for 10% of the geometric area of ​​the titanium mesh, and the rest is the same as Example 1.

[0117] The obtained electrode was pretreated and lithium was extracted from salt lake brine using the same steps as in Example 1. The results showed that the average current density during the lithium extraction process was 27 A / m 2 , which is equivalent to the current density of Example 1. However, the titanium mesh not coated with lithium extraction slurry was weighed, and the size was 100 cm 2 The weight of the titanium mesh is 20.35 g, which is nearly 29% higher than that of the titanium mesh in Example 1. This indicates that the reduction in the proportion of mesh area to the geometric area of ​​the titanium mesh will increase the amount of titanium material and the cost; in addition, the increase in the weight of the titanium mesh will also increase the weight of the entire lithium extraction equipment, thereby increasing the difficulty of equipment manufacturing.

[0118] Comparative Example 5

[0119] This comparative example provides an electrode for electrochemical lithium extraction, which is different from Example 4 in that the side length of the hexagonal mesh is 8 mm (the side length of the mesh is the cube of the thickness of the titanium mesh), and the rest is the same as Example 4.

[0120] The obtained electrode was pretreated and lithium was extracted from salt lake brine using the same steps as in Example 4. The results showed that the average current density during the lithium extraction process was 16 A / m 2 , which is significantly lower than the current density of Example 4. This indicates that the increase in the ratio of the side length of the titanium mesh to the thickness of the titanium mesh will increase the resistance of the titanium mesh electrode, resulting in a large voltage drop at various locations of the electrode, leading to a decrease in the current density, and thus failing to achieve high current density lithium extraction.

[0121] Comparative Example 6

[0122] This comparative example provides a high bonding strength and low resistance electrode for electrochemical lithium extraction, and its structure is similar to that of Example 4. The difference is that in this example, during the titanium mesh weaving process, no titanium plate conductive strip with the same thickness as the titanium mesh is added.

[0123] The electrochemical lithium extraction system was constructed in the same manner as described in Example 4. The results showed that the current density of the titanium mesh lithium extraction electrode after removing the conductive strip was only 27 A / m 2 , which is less than the current density of Example 4, indicating that the provision of the conductive strips can further shorten the electron transmission path, improve the overall conductivity of the electrode, and thus increase the current density during the lithium extraction process.

[0124] The electrodes obtained in Example 1, Example 4 and Comparative Example 1 and Comparative Example 2 were subjected to cyclic lithium extraction experiments, and the capacity retention rate of the electrodes during the cycle was monitored; the capacity retention rate of the electrodes during the cyclic lithium extraction process varied with the number of cycles as shown in FIG. Figure 7 As shown. Figure 7It can be seen that for the titanium mesh electrode, the electrode capacity retention rate is still above 93% after 500 cycles, which is much higher than the capacity retention rate (74%) of the titanium plate or titanium alloy plate electrode after 500 cycles. Therefore, stamping the titanium plate or titanium alloy plate into a titanium mesh with a special shape structure is conducive to enhancing the cycle stability of the electrode, so that the electrode still has a high capacity retention rate after long-term cycling. The reason is that the special shape structure of the titanium mesh allows the active materials on both sides of the electrode to be tightly combined with the titanium mesh with high bonding strength; in addition, the active materials on both sides of the titanium mesh can be directly bonded through the mesh holes, and are not easy to fall off during long-term cycling.

[0125] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A high bonding strength and low resistance electrode for electrochemical lithium extraction, characterized in that: Includes titanium mesh; The titanium mesh is composed of a plurality of unit meshes arranged in an arrangement; The unit mesh is one or more of a square, a rhombus, a triangle, a hexagon or a circle, and adjacent unit meshes share a common mesh edge, and the unit meshes are interconnected through the common mesh edge.

2. The electrode according to claim 1, characterized in that The area of ​​the titanium mesh holes accounts for 30-60% of the total geometric area of ​​the titanium mesh.

3. The electrode according to claim 1, characterized in that The side length or diameter of the unit mesh is proportional to the 1.5-2.2 power of the thickness of the titanium mesh.

4. The electrode according to claim 1, characterized in that The side length or diameter of the unit mesh is 0.22-11.2 mm.

5. The electrode according to claim 1, characterized in that The width of the unit mesh edge is 0.2-3 mm.

6. The electrode according to claim 1, characterized in that The surface of the titanium mesh includes a metal coating, and the coating thickness is 0.2-20 μm.

7. The electrode according to claim 1, characterized in that Titanium plate conductive strips are arranged on the titanium mesh, and the titanium plate conductive strips are evenly distributed on the titanium mesh with equal intervals.

8. The electrode according to claim 7, characterized in that The width of the titanium plate conductive strip is 10-15 mm, and the conductive strip interval is 50-500 mm.

9. The electrode according to any one of claims 1 to 8, characterized in that: The unit mesh structure of the titanium mesh is evenly coated with lithium extraction slurry.

10. The electrode according to any one of claims 1 to 8, characterized in that: The electrode further comprises a current lead-out terminal, which is arranged on one side of the long side of the titanium mesh and is connected to the titanium mesh by any one of welding, bolt connection or rivet connection.

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