WO2025000290A1 - Electrode active material coated with solid-state electrolyte layer, and preparation method therefor and use thereof - Google Patents

Abstract

The invention relates to the technical field of extraction of lithium from a salt lake. Disclosed are an electrode active material (1) coated with a solid-state electrolyte layer (2), and a preparation method therefor and the use thereof. The structure of the electrode active material (1) coated with the solid-state electrolyte layer (2) is a core-shell structure, wherein a core structure is composed of the electrode active material (1), and a shell structure is composed of the solid-state electrolyte layer (2); and the solid-state electrolyte layer (2) is formed by complexing polyethylene oxide, which is doped with inorganic nanoparticles, with a lithium salt, and has good lithium ion conductivity. The electrode active material (1) coated with the solid-state electrolyte layer (2) is used for preparing an electrode for extraction of lithium from a salt lake, and the obtained electrode for extraction of lithium from a salt lake has better lithium extraction efficiency, cycling stability and lithium extraction capacity.

Description

A solid electrolyte layer coated electrode active material and its preparation method and application Technical Field

The present disclosure relates to the technical field of lithium extraction from salt lakes, and in particular to an electrode active material coated with a solid electrolyte layer, and a preparation method and application thereof.

Background Art

In recent years, with the rapid development of new energy vehicles and chemical energy storage, the global demand for lithium resources has continued to increase, and lithium has become an important strategic resource. Lithium resources in nature mainly exist in salt lake brine, seawater and ores, of which salt lake lithium resources account for about 70%. Therefore, the extraction of lithium from salt lake brine has attracted more and more attention.

Salt lake brine contains lithium, sodium, potassium, magnesium and other elements. The main methods for extracting lithium from it include precipitation, solvent extraction, evaporation crystallization, electrodialysis, ion exchange adsorption, etc. However, these methods have certain disadvantages, such as the high cost of electrodialysis and membrane separation, and the solvent extraction agent is easy to cause environmental pollution. In recent years, domestic and foreign researchers have conducted extensive exploration and research on new lithium extraction processes, and electrochemical lithium extraction technology has good use value and application prospects.

The principle of electrochemical lithium extraction is to charge the working electrode in the electrolyte solution to release lithium ions to form a lithium-depleted electrode. The lithium-rich electrode and the lithium-depleted electrode are used as the anode and cathode respectively. Lithium salt solution is added to the anode and salt lake brine is added to the cathode. Driven by the external potential, Li in the brine is selectively embedded in the lithium-depleted electrode. At the same time, the lithium-rich electrode releases Li into the solution to form a lithium-depleted electrode. The selective enrichment of lithium is achieved through electrode exchange and cyclic operation.

Although the electrochemical deintercalation method has good application prospects in lithium extraction from salt lakes, there are still problems such as low lithium exchange capacity and poor electrode cycle stability. The binder PVDF used in the preparation of electrode slurry is not conductive. When the electrode active material combines with the binder, the lithium ion transmission is blocked, thereby limiting the lithium extraction capacity of the electrode.

Patent CN113265538B provides a method for preparing highly conductive porous electrodes for lithium extraction from salt lakes. Inorganic nanoparticles and polar hydrophilic macromolecular organic matter are used to blend and modify the binder in the electrode preparation process to improve the hydrophilicity of the binder. Finally, the prepared electrode material is subjected to surface chemical modification in a conductive polymer monomer solution to improve the overall conductivity of the electrode. The increase in hydrophilicity can promote The electrode is wetted with brine, but it cannot improve the transmission of lithium ions and increase the electrode exchange capacity. The conductive polymer coating modification mainly increases the electronic conductivity of the electrode surface, but cannot increase the ionic conductivity of the interface between the active material and the binder inside the electrode.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide an electrode active material coated with a solid electrolyte layer and a preparation method and application thereof. The electrode active material coated with a solid electrolyte layer of the present invention is used to prepare a salt lake lithium extraction electrode, which can promote the migration of lithium ions during lithium extraction and increase the lithium extraction capacity and efficiency of the electrode.

To achieve the above objectives, the technical solution adopted by the present disclosure is:

In a first aspect, a method for preparing an electrode active material coated with a solid electrolyte layer is provided, comprising the following steps:

After the electrode active material, ethylene oxide, catalyst, inorganic nanoparticles, lithium source and solvent are uniformly mixed, a cross-linking agent is added to carry out polymerization reaction at 50-80° C. for 18-30 hours, and after the reaction is completed, an electrode active material coated with a solid electrolyte layer is obtained;

The mass of ethylene oxide is 5-20% of the mass of the electrode active material;

The mass of the catalyst is 0.1-1% of the mass of ethylene oxide, the mass of the inorganic nanoparticles is 5-25% of the mass of ethylene oxide, the mass of the lithium source is 5-15% of the mass of ethylene oxide, and the mass of the crosslinking agent is 0.1-1% of the mass of ethylene oxide.

The structural schematic diagram of the electrode active material coated with the solid electrolyte layer of the present disclosure is shown in Figure 1. The structure of the electrode active material coated with the solid electrolyte layer is a core-shell structure, wherein the core structure is composed of the electrode active material and the shell structure is composed of the solid electrolyte layer. In the preparation process of the electrode active material coated with the solid electrolyte layer, a solid electrolyte layer is coated on the surface of the electrode active material by in-situ polymerization. The solid electrolyte layer is formed by complexing polyethylene oxide doped with inorganic nanoparticles and lithium salts, and has good lithium ion conductivity. The present disclosure adjusts the preparation parameters of the electrode active material coated with the solid electrolyte layer to obtain solid electrolyte layers of different thicknesses; for example, when other preparation parameters remain unchanged, the thickness of the solid electrolyte layer can be increased by increasing the content of ethylene oxide. The content of the lithium source will affect the lithium ion conductivity of the electrode active material coated with the solid electrolyte layer. If the lithium source content is too little or too much, the lithium ion conductivity will decrease; the present disclosure selects the mass of the lithium source to be 8-12% of the mass of ethylene oxide to obtain a solid electrolyte layer coated electrode active material with better lithium ion conductivity.

Specifically, the temperature and time of the polymerization reaction will affect the mechanical properties and lithium ion conductivity of the electrode active material coated with the solid electrolyte layer. If the temperature of the polymerization reaction is too low or the time is too short, ethylene oxide cannot fully undergo the polymerization reaction, resulting in a loose structure of the solid electrolyte layer, thereby causing the mechanical properties and lithium ion conductivity of the electrode active material coated with the solid electrolyte layer to decrease; if the polymerization reaction time is too long or the temperature is too high, the thickness of the solid electrolyte layer is too thick, and the mechanical properties and lithium ion conductivity of the electrode active material coated with the solid electrolyte layer will not be significantly improved.

In one embodiment, the mass of the inorganic nanoparticles is 10-20% of the mass of ethylene oxide.

In the present disclosure, the mass of the inorganic nanoparticles can be 5%, 8%, 10%, 12%, 15%, 17%, 20%, 23%, 25% of the mass of ethylene oxide, or a range consisting of any two of the above values; specifically, the inorganic nanoparticles can reduce the erosion of the solution on the electrode active material coated with the solid electrolyte layer, and increase the mechanical strength of the electrode active material coated with the solid electrolyte layer; on the other hand, the hydroxyl groups on the surface of the inorganic nanoparticles can increase the activity of the solid electrolyte layer, thereby increasing the lithium ion conductivity of the electrode active material coated with the solid electrolyte layer. The present disclosure selects the mass of the inorganic nanoparticles to be 10-20% of the mass of ethylene oxide, thereby making the performance of the electrode active material coated with the solid electrolyte layer better.

In one embodiment, the electrode active material is at least one of lithium iron phosphate and lithium manganese iron phosphate;

and/or, the average particle size of the electrode active material is 0.5-5 μm;

And/or, the catalyst is a quaternary ammonium base; specifically one or more of tetramethylammonium hydroxide, tetraethoxyammonium hydroxide, methyltriethylammonium hydroxide and tetrapropylammonium hydroxide;

and/or, the inorganic nanoparticles are at least one of SiO ₂ nanoparticles, ZnO nanoparticles, Al ₂ O ₃ nanoparticles, HBO ₂ nanoparticles, and TiO ₂ nanoparticles;

And/or, the average particle size of the inorganic nanoparticles is 1-50 nm;

And/or, the cross-linking agent is ethylene glycol dimethacrylate;

And/or, the lithium source is at least one of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium bis(trifluoromethylsulfonyl)imide.

In one embodiment, the electrode active material is first added to the solvent, and then ethylene oxide is added, and after stirring evenly, the catalyst, inorganic nanoparticles and lithium source are added and ultrasonically mixed; the ultrasonic mixing time is 15-30 minutes.

It is understood that those skilled in the art can select a suitable mixing method according to actual needs, such as stirring, ball milling, sand milling, ultrasound, etc. The specific mixing time is as long as the components can be mixed evenly. The present invention selects ultrasound for 15-30 minutes to obtain a mixed solution with better mixing effect.

In one embodiment, after the reaction is completed, the obtained reaction product needs to be centrifuged, washed, and dried to obtain an electrode active material coated with a solid electrolyte layer.

It is understandable that after the polymerization reaction is completed, the resulting reactant is a mixed liquid, which contains a solvent and some components that have not reacted completely. In order to obtain a higher purity solid electrolyte layer-coated electrode active material, after the polymerization reaction is completed, the resulting reactant needs to be post-treated, such as centrifugation, washing and drying.

In one embodiment, the drying temperature is 80-100° C.; and/or the drying time is 10-15 h.

It is understandable that those skilled in the art can select appropriate temperature and time for drying to obtain the electrode active material coated with the solid electrolyte layer. In the present disclosure, the drying is performed at a temperature of 80-100° C. for 10-15 hours.

In a second aspect, a solid electrolyte layer-coated electrode active material is provided, wherein the solid electrolyte layer-coated electrode active material is prepared by the above-mentioned method for preparing the solid electrolyte layer-coated electrode active material.

In one embodiment, the solid electrolyte layer has a thickness of 10-100 nm.

In the present disclosure, the thickness of the solid electrolyte layer can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm; it can also be a range composed of any two of the above values. It can be understood that the thickness of the solid electrolyte layer has an impact on the performance of the electrode for lithium extraction from salt lakes. On the one hand, the lithium ion diffusion channel formed by the solid electrolyte layer with a thickness of less than 10nm is small, and it cannot effectively serve as a solution mass transfer channel; on the other hand, when the thickness of the solid electrolyte layer is greater than 100nm, the performance of the electrode for lithium extraction from salt lakes does not increase significantly. The present disclosure selects a solid electrolyte layer with a thickness of 30-70nm to obtain an electrode for lithium extraction from salt lakes with better performance.

In a third aspect, the invention provides the use of the electrode active material coated with the solid electrolyte layer in the preparation of electrodes for lithium extraction from salt lakes.

In a fourth aspect, an electrode for lithium extraction from salt lakes is provided, characterized in that the electrode for lithium extraction from salt lakes comprises an electrode active material coated with the above-mentioned solid electrolyte layer.

In one embodiment, the porosity of the electrode for extracting lithium from salt lakes is 20-40%; the electrode for extracting lithium from salt lakes comprises the following components: an electrode active material coated with a solid electrolyte layer, a binder, and a conductive agent; Taking the mass of the electrode active material coated by the solid electrolyte layer as 100 parts by weight, the mass content of each component is: 15-25 parts of the binder and 5-15 parts of the conductive agent.

The schematic diagram of the structure of the electrode for lithium extraction from salt lakes obtained in the present invention is shown in FIG1 , wherein the surface of the electrode active material is coated with a dense solid electrolyte layer; the electrode for lithium extraction from salt lakes having a porosity of 20-40% is prepared by using the electrode active material, the binder, and the conductive agent coated with the solid electrolyte layer in the present invention. On the one hand, the solid electrolyte layer can form a lithium ion diffusion channel between the electrode active material and the binder, providing a transmission path for lithium ions. During the process of lithium extraction from salt lakes, lithium ions enter and exit the diffusion channel formed by the solid electrolyte layer, promoting the migration of lithium ions, and increasing the lithium extraction capacity and lithium extraction efficiency of the electrode for lithium extraction from salt lakes. efficiency; on the other hand, brine serves as a lithium ion transmission medium, and the solid electrolyte layer can reduce the erosion of brine on the electrode active material, increase the mechanical strength of the electrode active material, and improve the cycle stability of the electrode; at the same time, the solid electrolyte has excellent lithium ion conductivity, and increasing the thickness of the solid electrolyte layer will not reduce the conductivity of the electrode; in addition, the present invention uses 15-25 parts by weight of a binder to improve the bonding strength of the electrode for lithium extraction from salt lakes. While improving the mechanical strength of the electrode, the binder cooperates with other components, and the lithium extraction efficiency of the electrode for lithium extraction from salt lakes will not be reduced due to the use of the binder.

In one embodiment, the porosity of the electrode for lithium extraction from salt lakes is 25-35%.

In the present disclosure, the porosity of the electrode for lithium extraction from salt lakes can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%; the porosity of the electrode for lithium extraction from salt lakes can also be a range composed of any two of the above values. Specifically, when the porosity of the electrode for lithium extraction from salt lakes is 20-40%, on the one hand, it can ensure the mechanical strength of the electrode, and on the other hand, it can provide a good channel for the diffusion and mass transfer of brine inside the electrode, effectively improving the mass transfer of the solution inside the electrode; on the basis of the above porosity, when the porosity of the electrode for lithium extraction from salt lakes is 25-35%, the lithium extraction effect and cycle stability of the electrode for lithium extraction from salt lakes are better.

In one embodiment, the mass of the binder is 18-22 parts by weight.

In the electrode for lithium extraction from salt lakes, the binder is not conductive. When the binder is combined with the electrode active material, the transmission of lithium ions is hindered, thereby limiting the lithium extraction capacity of the electrode for lithium extraction from salt lakes. It is understandable that when the content of the binder is less than 15 parts, the lithium extraction capacity of the electrode for lithium extraction from salt lakes increases, but the mechanical strength and cycle stability of the electrode for lithium extraction from salt lakes are low; the present disclosure selects 18-22 parts by weight of the binder to obtain an electrode for lithium extraction from salt lakes with better mechanical strength, cycle stability and lithium extraction effect.

In one embodiment, the binder is polyvinylidene fluoride; and/or the conductive agent is at least one of acetylene black and Ketjen black.

In the present disclosure, polyvinylidene fluoride is abbreviated as PVDF.

In a fifth aspect, the present disclosure also provides a method for preparing a lithium extraction electrode for a salt lake, comprising the following steps:

The binder is dissolved in an organic solvent to obtain a binder solution; the electrode active material coated with a solid electrolyte layer, a pore former, and a conductive agent are added to the binder solution and stirred evenly; the obtained slurry is coated on a current collector and dried to obtain a lithium extraction electrode for salt lakes.

In one embodiment, the organic solvent is N-methylpyrrolidone; and/or the mass of the organic solvent is 120-150% of the mass of the electrode active material coated by the solid electrolyte layer; the pore former is at least one of (NH ₄ ) ₂ CO ₃ , NH ₄ HCO ₃ , NaCl, and KCl; and/or the mass of the pore former is 10-20% of the mass of the electrode active material coated by the solid electrolyte layer.

In the present disclosure, during the preparation of the electrode slurry, a certain proportion of easily pyrolyzed solid salts is added. These solid salts will be evenly dispersed on the surface and inside of the electrode. During the drying process, the solid salts are thermally decomposed, so that the original position of the solid salt can be retained inside the salt lake lithium extraction electrode to present a porous shape. The present disclosure obtains electrodes for salt lake lithium extraction with different porosities by adjusting the amount of solid salt added.

In one embodiment, the stirring is vacuum stirring; and or, the stirring time is 0.5-2h.

In one embodiment, the drying temperature is 100-200° C.; and/or the drying time is 10-20 h.

In a sixth aspect, the present disclosure provides application of the electrode for lithium extraction from salt lakes in lithium extraction from salt lakes.

Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses a solid electrolyte layer-coated electrode active material, a binder, and a conductive agent to prepare an electrode for lithium extraction from a salt lake with a porosity of 20-40%. On the one hand, the solid electrolyte layer can form a lithium ion diffusion channel between the electrode active material and the binder, providing a transmission path for lithium ions. During the process of lithium extraction from a salt lake, lithium ions enter and exit the diffusion channel formed by the solid electrolyte layer, promoting the migration of lithium ions and increasing the lithium extraction capacity and efficiency of the electrode for lithium extraction from a salt lake; on the other hand, brine acts as a lithium ion transmission medium, and the solid electrolyte layer can reduce the erosion of the brine on the electrode active material, increase the mechanical strength of the electrode active material, and improve the cycle stability of the electrode; at the same time, the solid electrolyte has excellent lithium ion conductivity, and increasing the thickness of the solid electrolyte layer will not reduce the conductivity of the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the electrode structure for lithium extraction from salt lakes disclosed in the present invention, wherein 1 is an electrode active material, 2 is a solid electrolyte layer, and 3 is a current collector.

DETAILED DESCRIPTION

In order to better illustrate the purpose, technical scheme and advantages of the present disclosure, the present disclosure will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present disclosure in detail, rather than to limit the present disclosure. All other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure. The experimental reagents and instruments involved in the implementation of the present disclosure are all commonly used ordinary reagents and instruments unless otherwise specified.

In the embodiments and comparative examples disclosed herein, the average particle size of lithium iron phosphate is 3 μm; the average particle size of SiO ₂ nanospheres is 25 nm.

Example 1

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment includes the following steps:

(1) Weigh 50 g of lithium iron phosphate and place it in a three-necked flask, add 500 mL of acetonitrile, dissolve 5 g of ethylene oxide in the acetonitrile, stir evenly to obtain a mixed solution, then add 50 mg of catalyst tetramethylammonium hydroxide, 250 mg _{of SiO2} nanospheres and 250 mg of lithium perchlorate, ultrasonicate for 15 min, then add 50 mg of cross-linking agent ethylene glycol dimethacrylate, and stir at 80°C for 18 h for polymerization;

(2) The product obtained by the polymerization reaction was centrifuged, washed, and dried at 80° C. for 15 h to obtain lithium iron phosphate coated with a solid electrolyte layer, wherein the thickness of the solid electrolyte layer was 50 nm.

Example 2

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment includes the following steps:

(1) Weigh 50 g of lithium iron phosphate and place it in a three-necked flask, add 500 mL of acetonitrile, dissolve 10 g of ethylene oxide in the acetonitrile, stir evenly to obtain a mixed solution, then add 100 mg of catalyst tetramethylammonium hydroxide, 1 g _{of SiO2} nanospheres and 1.5 g of lithium perchlorate, ultrasonicate for 20 min, then add 75 mg of cross-linking agent ethylene glycol dimethacrylate, and stir at 65°C for 24 h for polymerization;

(2) The product obtained by the polymerization reaction was centrifuged, washed, and dried at 100° C. for 10 h to obtain lithium iron phosphate coated with a solid electrolyte layer, wherein the thickness of the solid electrolyte layer was 100 nm.

Example 3

(1) Weigh 50 g of lithium iron phosphate and place it in a three-necked flask, add 500 mL of acetonitrile, dissolve 2.5 g of ethylene oxide in acetonitrile, stir evenly to obtain a mixed solution, then add 25 mg of catalyst tetramethylammonium hydroxide, 250 mg _{of SiO2} nanospheres and 200 mg of lithium perchlorate, ultrasonicate for 30 min, and then add 25 mg of crosslinking agent dimethyl Ethylene glycol acrylate was polymerized at 50°C with stirring for 30h;

(2) The product obtained by the polymerization reaction was centrifuged, washed, and dried at 90° C. for 12 h to obtain lithium iron phosphate coated with a solid electrolyte layer, wherein the thickness of the solid electrolyte layer was 15 nm.

Example 4

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment is different from that in Embodiment 1 only in that the mass of silicon dioxide in step (1) is 0.5 g.

Example 5

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment is different from that in Embodiment 1 only in that the mass of silicon dioxide in step (1) is 0.75 g.

Example 6

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment is different from that in Embodiment 1 only in that the mass of silicon dioxide in step (1) is 1 g.

Example 7

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment is different from that in Embodiment 1 only in that the mass of lithium perchlorate in step (1) is 0.4 g.

Example 8

The preparation of the electrode active material coated with the solid electrolyte layer in this embodiment is different from that in Embodiment 1 only in that the mass of lithium perchlorate in step (1) is 0.6 g.

Example 9

The preparation of the solid electrolyte layer-coated electrode active material in this embodiment is different from that in Embodiment 1 only in that the mass of ethylene oxide in step (1) is 4 g, and the thickness of the solid electrolyte layer in the obtained solid electrolyte layer-coated electrode active material is 30 nm.

Example 10

The preparation of the solid electrolyte layer-coated electrode active material in this embodiment is different from that in Embodiment 1 only in that the mass of ethylene oxide in step (1) is 7.5 g, and the thickness of the solid electrolyte layer in the obtained solid electrolyte layer-coated electrode active material is 70 nm.

Embodiment 11

The preparation of the electrode for lithium extraction from salt lakes in this embodiment includes the following steps:

Add PVDF into N-methylpyrrolidone and stir until completely dissolved to obtain a mixed glue solution;

The lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1, NH ₄ HCO ₃ and acetylene black were added to the mixed glue solution, and vacuum stirred for 0.5 h to obtain a mixed slurry; wherein the added amounts of PVDF, NH ₄ HCO ₃ , acetylene black and N-methylpyrrolidone were 20%, 15%, 5% and 120% of the mass of the lithium iron phosphate coated with the solid electrolyte layer, respectively;

The obtained mixed slurry was coated on a titanium mesh with a coating density of 150 mg lithium iron phosphate/cm ² , and then dried at 120° C. for 10 h to obtain an electrode for lithium extraction from salt lakes with a porosity of 30%.

Example 12

The preparation of the electrode for lithium extraction from salt lakes in this embodiment includes the following steps:

Add PVDF into N-methylpyrrolidone and stir until completely dissolved to obtain a mixed glue solution;

The lithium iron phosphate coated with the solid electrolyte layer obtained in Example 2, NH ₄ HCO ₃ and Ketjen black were added to the mixed glue solution, and the mixture was stirred under vacuum for 1 hour to obtain a mixed slurry; the added amounts of PVDF, NH ₄ HCO ₃ , Ketjen black and N-methylpyrrolidone were 15%, 20%, 15% and 150% of the mass of the lithium iron phosphate coated with the solid electrolyte layer, respectively;

The obtained mixed slurry was coated on a titanium mesh with a coating density of 200 mg lithium iron phosphate/cm ² , and then dried at 120° C. for 14 hours to obtain an electrode for extracting lithium from a salt lake with a porosity of 40%.

Embodiment 13

The preparation of the electrode for lithium extraction from salt lakes in this embodiment includes the following steps:

Add PVDF into N-methylpyrrolidone and stir until completely dissolved to obtain a mixed glue solution;

The solid electrolyte layer-coated lithium iron phosphate, NH ₄ HCO ₃ , and Ketjen black obtained in Example 3 are added to the mixed glue solution of step (3), and stirred under vacuum for 2 hours to obtain a mixed slurry; the added amounts of PVDF, NH ₄ HCO ₃ , Ketjen black, and N-methylpyrrolidone are 25%, 10%, 12%, and 135% of the mass of the solid electrolyte layer-coated lithium iron phosphate, respectively;

The obtained mixed slurry was coated on a titanium mesh with a coating density of 200 mg lithium iron phosphate/cm ² , and then dried at 100° C. for 20 hours to obtain an electrode for lithium extraction from a salt lake with a porosity of 20%.

Embodiment 14

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 4 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 15

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 5 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Example 16

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 6 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 17

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 7 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 18

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 8 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 19

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 9 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 20

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 10 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Embodiment 21

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of PVDF added is 18% of the mass of the lithium iron phosphate coated by the solid electrolyte layer.

Embodiment 22

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of PVDF added is 22% of the mass of the lithium iron phosphate coated with the solid electrolyte layer.

Embodiment 23

The difference between the preparation of the electrode for lithium extraction from salt lakes in this embodiment and the preparation of the electrode for lithium extraction from salt lakes in embodiment 11 is that the amount of NH ₄ HCO ₃ added is 12% of the mass of the lithium iron phosphate coated with the solid electrolyte layer; the porosity of the obtained electrode for lithium extraction from salt lakes is 25%.

Embodiment 24

The preparation of the electrode for lithium extraction from salt lakes in this embodiment differs from that in Example 11 only in that the amount of NH ₄ HCO ₃ added is 18% of the mass of the lithium iron phosphate coated with the solid electrolyte layer; and the porosity of the obtained electrode for lithium extraction from salt lakes is 35%.

Comparative Example 1

The preparation of the electrode active material coated with the solid electrolyte layer in this comparative example is different from that in Example 1 only in that the mass of silicon dioxide in step (1) is 0.2 g.

Comparative Example 2

The preparation of the electrode active material coated with the solid electrolyte layer in this comparative example is different from that in Example 1 only in that the mass of silicon dioxide in step (1) is 1.4 g.

Comparative Example 3

The preparation of the electrode active material coated with the solid electrolyte layer in this comparative example is different from that in Example 1 only in that the mass of lithium perchlorate in step (1) is 0.2 g.

Comparative Example 4

The preparation of the electrode active material coated with the solid electrolyte layer in this comparative example is different from that in Example 1 only in that the mass of lithium perchlorate in step (1) is 0.8 g.

Comparative Example 5

The preparation of the electrode for lithium extraction from salt lake in this comparative example comprises the following steps:

(1) Add PVDF to N-methylpyrrolidone and stir until completely dissolved to obtain a mixed glue solution;

(2) adding lithium iron phosphate, NH ₄ HCO ₃ , and acetylene black to the mixed glue solution, and stirring for 5 hours to obtain a mixed slurry; the added amounts of PVDF, NH ₄ HCO ₃ , acetylene black, and N-methylpyrrolidone are 8%, 15%, 5%, and 120% of the mass of lithium iron phosphate, respectively;

(3) The mixed slurry was coated on a titanium mesh with a coating density of 150 mg lithium iron phosphate/cm ² , and then dried at 120° C. for 10 h to obtain an electrode for lithium extraction from a salt lake.

Comparative Example 6

The difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of PVDF added is 10% of the mass of the lithium iron phosphate coated with the solid electrolyte layer.

Comparative Example 7

The difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of PVDF added is 30% of the mass of the lithium iron phosphate coated with the solid electrolyte layer.

Comparative Example 8

The difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of NH ₄ HCO ₃ added is 8% of the mass of the lithium iron phosphate coated with the solid electrolyte layer; the porosity of the obtained electrode for lithium extraction from salt lakes is 18%.

Comparative Example 9

The difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the amount of NH ₄ HCO ₃ added is 22% of the mass of the lithium iron phosphate coated with the solid electrolyte layer; and the porosity of the obtained electrode for lithium extraction from salt lakes is 43%.

Comparative Example 10

The only difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Comparative Example 1 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Comparative Example 11

The only difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Comparative Example 2 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Comparative Example 12

The only difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is that the lithium iron phosphate coated with the solid electrolyte layer obtained in Comparative Example 3 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Comparative Example 13

The difference between the preparation of the electrode for lithium extraction from salt lakes in this comparative example and the preparation of the electrode for lithium extraction from salt lakes in Example 11 is only that the lithium iron phosphate coated with the solid electrolyte layer obtained in Comparative Example 4 replaces the lithium iron phosphate coated with the solid electrolyte layer obtained in Example 1.

Lithium extraction test:

The lithium-extracting electrode obtained from each embodiment and comparative example is used as the anode, nickel foam is used as the cathode, and 20g/L NaCl solution is used as the electrolyte. A voltage of 1.0V is applied to both ends of the electrode until the current density is less than 0.5A/m2 to produce a delithiation electrode.

The electrolysis device is separated into an anode chamber and a cathode chamber by an anion exchange membrane. The electrode for lithium extraction from salt lake obtained in each embodiment and comparative example is used as an anode, and the electrode for delithiation state obtained in each embodiment and comparative example is used as a cathode, which are placed in the anode chamber and the cathode chamber respectively. The electrode for lithium extraction from salt lake obtained in each embodiment and the electrode for delithiation state are made corresponding to each other. For example, the electrode for lithium extraction from salt lake obtained in Example 1 is used as an anode, and the electrode for delithiation state obtained in Example 1 is used as a cathode. Brine is injected into the cathode chamber, and NaCl solution is injected into the anode chamber. A voltage of 0.3 V is applied to the cathode and the cathode for constant voltage electrolysis for 8 hours.

The changes in lithium ion concentration of the brine before and after the lithium extraction reaction in the embodiment and the comparative example, the lithium concentration of the anode liquid after the lithium extraction, and the capacity retention rate of the electrode after 100 lithium extractions are shown in Table 1.

Table 1

It can be seen from Table 1 that the electrode for lithium extraction from salt lakes obtained in the present invention has a high lithium extraction efficiency and a capacity retention rate of more than 88% after 100 cycles, indicating that the electrode active material coated with the solid electrolyte layer of the present invention can produce an electrode for lithium extraction from salt lakes with high lithium extraction efficiency and high capacity retention rate.

Finally, it should be noted that the above embodiments are used to illustrate the technical solution of the present disclosure rather than to limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present disclosure can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present disclosure.

Claims (19)

A method for preparing an electrode active material coated with a solid electrolyte layer, characterized in that it comprises the following steps: After the electrode active material, ethylene oxide, catalyst, inorganic nanoparticles, lithium source and solvent are uniformly mixed, a cross-linking agent is added to carry out polymerization reaction at 50-80° C. for 18-30 hours, and after the reaction is completed, an electrode active material coated with a solid electrolyte layer is obtained; The mass of ethylene oxide is 5-20% of the mass of the electrode active material; The mass of the catalyst is 0.1-1% of the mass of ethylene oxide, the mass of the inorganic nanoparticles is 5-25% of the mass of ethylene oxide, the mass of the lithium source is 5-15% of the mass of ethylene oxide, and the mass of the crosslinking agent is 0.1-1% of the mass of ethylene oxide. The preparation method according to claim 1, characterized in that the mass of the inorganic nanoparticles is 10-20% of the mass of ethylene oxide. The preparation method according to claim 1, characterized in that the electrode active material is at least one of lithium iron phosphate and lithium manganese iron phosphate; and/or, the average particle size of the electrode active material is 0.5-5 μm; And/or, the catalyst is a quaternary ammonium base; and/or, the inorganic nanoparticles are at least one of SiO ₂ nanoparticles, ZnO nanoparticles, Al ₂ O ₃ nanoparticles, HBO ₂ nanoparticles, and TiO ₂ nanoparticles; And/or, the average particle size of the inorganic nanoparticles is 1-50 nm; And/or, the cross-linking agent is ethylene glycol dimethacrylate; And/or, the lithium source is at least one of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium bis(trifluoromethylsulfonyl)imide. The preparation method according to claim 1 is characterized in that the electrode active material is first added to the solvent, and then ethylene oxide is added, and after stirring evenly, the catalyst, inorganic nanoparticles and lithium source are added, and ultrasonic mixing is performed; the ultrasonic mixing time is 15-30min. The preparation method according to claim 1 is characterized in that after the reaction is completed, the obtained reaction product is centrifuged, washed and dried to obtain an electrode active material coated with a solid electrolyte layer. The electrode for lithium extraction from salt lakes according to claim 5, characterized in that the drying temperature is 80-100° C.; and/or the drying time is 10-15 h. A solid electrolyte layer-coated electrode active material, characterized in that the solid electrolyte layer-coated electrode active material is prepared by the preparation method of the solid electrolyte layer-coated electrode active material according to any one of claims 1 to 6. The electrode active material coated with a solid electrolyte layer as described in claim 7 is characterized in that the thickness of the solid electrolyte layer is 10-100 nm. Use of the electrode active material coated with the solid electrolyte layer as claimed in claim 7 or 8 in the preparation of electrodes for lithium extraction from salt lakes. An electrode for lithium extraction from salt lakes, characterized in that the electrode for lithium extraction from salt lakes comprises an electrode active material coated with a solid electrolyte layer as described in claim 7 or 8. The electrode for lithium extraction from salt lakes as described in claim 10 is characterized in that the porosity of the electrode for lithium extraction from salt lakes is 20-40%; the electrode for lithium extraction from salt lakes comprises the following components: an electrode active material coated with a solid electrolyte layer, a binder, and a conductive agent; based on the mass of the electrode active material coated with the solid electrolyte layer as 100 parts by weight, the mass content of each component is: 15-25 parts of the binder and 5-15 parts of the conductive agent. The electrode for extracting lithium from salt lakes as described in claim 11 is characterized in that the porosity of the electrode for extracting lithium from salt lakes is 25-35%. The electrode for lithium extraction from salt lakes as described in claim 11, characterized in that the mass of the binder is 18-22 parts by weight. The electrode for lithium extraction from salt lakes according to claim 11, characterized in that the binder is polyvinylidene fluoride; and/or the conductive agent is at least one of acetylene black and Ketjen black. The method for preparing an electrode for lithium extraction from a salt lake as described in any one of claims 11 to 14 is characterized in that it comprises the following steps: dissolving a binder in an organic solvent to obtain a binder solution; adding an electrode active material coated with a solid electrolyte layer, a pore-forming agent, and a conductive agent to the binder solution, stirring evenly, coating the resulting slurry on a current collector, and drying to obtain a lithium extraction electrode for a salt lake. The preparation method according to claim 15, characterized in that the organic solvent is N-methylpyrrolidone; and/or the mass of the organic solvent is 120-150% of the mass of the electrode active material coated with the solid electrolyte layer; the pore former is at least one of _{( NH4} ) _2CO3 , _NH4HCO3 , _NaCl , and KCl; and/or the mass of the pore former is 10-20% of the mass of the electrode active material coated with the solid electrolyte layer. The preparation method according to claim 15, characterized in that the stirring is vacuum stirring; and or the stirring time is 0.5-2h. The preparation method according to claim 15, characterized in that the drying temperature is 100-200°C; and/or the drying time is 10-20h. Use of the electrode for lithium extraction from salt lakes as described in any one of claims 11 to 14 in extracting lithium from salt lakes.