Electrode material for lithium extraction from salt lake, preparation method therefor and use thereof

Abstract

Disclosed are an electrode material for lithium extraction from salt lake, and a preparation method and a use thereof. The preparation method comprises the following steps: (1) heating an electrode active material, and mixing the heated electrode active material with an organic solvent to obtain a dispersion liquid; (2) mixing the dispersion liquid with an organic positive electrode coating agent, and implementing a heating reflux reaction; and (3) cooling a material obtained by the heating reflux reaction, and removing a supernatant after centrifugation to obtain an electrode material for lithium extraction from salt lake. In the present application, an organic positive electrode material coating layer is coated on the surface of an electrode material, so that the mechanical strength of an electrode can be improved, and the electrode has high lithium ion conductivity in the lithium extraction process while the electrode capacity is not reduced.

Description

Electrode material for lithium extraction from salt lakes, preparation method and application thereof Technical Field

[0001] The embodiments of the present application relate to the technical field of lithium extraction from salt lakes, for example, an electrode material for lithium extraction from salt lakes, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium is a key strategic resource widely used in lithium batteries. The rapid development of the new energy sector has driven a rapid increase in market demand for lithium resources, making low-cost, efficient lithium resource development a crucial factor for companies to compete in this market. Discovered lithium resources are primarily found in salt lake brines, seawater, and ores, with salt lake lithium accounting for approximately 70%. Due to the high cost and difficulty of mining lithium ore, and its increasing depletion and depletion with continued mining, extracting lithium from salt lake brines has become a trend in lithium resource development.

[0003] There are many salt lakes in western my country, but their development level is low due to their high magnesium-to-lithium ratio. Currently, the main methods for extracting lithium from brine at home and abroad include precipitation, solvent extraction, evaporation crystallization, electrodialysis, ion exchange adsorption, etc. Precipitation is a relatively mature technology, but it has the disadvantages of high energy consumption, complex process flow, high cost, and low lithium recovery rate. The extraction method has a fast lithium extraction rate, but the dissolution of the extractant in the brine can easily cause environmental pollution; the adsorption method has problems such as low adsorption capacity, adsorbent dissolution, and high water consumption. In recent years, many researchers at home and abroad have conducted extensive exploration and research on new lithium extraction processes. Electrochemical lithium extraction technology has good use value and application prospects.

[0004] CN107201452A discloses a method for extracting lithium from a lithium-containing solution based on LiMn2O4 electrode material, which uses lithium-intercalated LiMn2O4 and lithium-deintercalated Li 1-x Mn2O4 is used as an electrode pair, which is placed in a recovery liquid and an extraction liquid separated by an anion exchange membrane. After constant voltage power is applied, lithium ions are embedded in the cathode electrode material and extracted. At the same time, the lithium in the anode electrode is released into a clean solution to achieve lithium recovery and enrichment. However, since the electrode preparation requires a binder to bond the electrode active material to the current collector, the electrode has problems with poor lithium ion conductivity and hydrophilicity when extracting lithium.

[0005] CN113265538A discloses a method for preparing a highly conductive porous electrode for lithium extraction from salt lakes, which includes modifying the binder used in the electrode preparation process by blending inorganic nanoparticles and polar hydrophilic polymer organic matter to improve the hydrophilicity of the binder. The method solves the above-mentioned problem by modifying the binder or forming a conductive coating on the surface of the electrode active material. However, since the coating has no electrical deintercalation activity, it will lead to a problem of reduced lithium extraction capacity of the electrode.

[0006] The above solutions have the problems of poor lithium ion conductivity and hydrophilicity or low lithium extraction capacity of the electrode, which limits their application in practice.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The embodiment of the present application provides an electrode material for lithium extraction from salt lakes, a preparation method thereof, and an application thereof. The present application coats an organic positive electrode material coating layer on the surface of the electrode material, which not only improves the mechanical strength of the electrode, but also enables the electrode to have higher lithium ion conductivity during the lithium extraction process without reducing the electrode capacity.

[0010] In a first aspect, an embodiment of the present application provides a method for preparing an electrode material for lithium extraction from a salt lake, the preparation method comprising the following steps:

[0011] (1) heating the electrode active material and mixing it with an organic solvent to obtain a dispersion;

[0012] (2) mixing the dispersion and the organic positive electrode coating agent, and heating and refluxing the mixture;

[0013] (3) Cooling and centrifuging the material obtained by the heating reflux reaction, and removing the supernatant to obtain the electrode material for lithium extraction from the salt lake.

[0014] In the preparation process of the electrode material for lithium extraction from salt lakes described in this application, a high-temperature electrode active material is added to an organic solvent, and the organic matter is carbonized on the surface of the active material, increasing the active sites on the surface of the electrode material and improving the surface energy, thereby making it easy for the organic positive electrode coating agent to adhere to the surface of the electrode material and react to form a uniform organic positive electrode material coating layer. The organic positive electrode material coating layer not only has a good lithium ion transmission rate, but also can form a lithium ion diffusion channel between the surface of the electrode active material and the binder, providing a transmission path for lithium ions, thereby accelerating the migration of lithium ions and improving the lithium extraction efficiency of the electrode. And because the organic matter is sticky, it can replace part of the role of PVDF, which can improve the mechanical strength of the electrode, prevent the electrode active particles from falling off, and make the electrode have higher cycle stability.

[0015] Preferably, the electrode active material in step (1) includes any one of lithium iron phosphate, lithium manganese iron phosphate or lithium manganate, or a combination of at least two thereof.

[0016] Preferably, the heating temperature is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C.

[0017] Preferably, the organic solvent in step (1) comprises any one or a combination of at least two of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, methanol or ethanol.

[0018] Preferably, the volume ratio of the mass of the electrode active material to the organic solvent is 0.05 to 0.1 g / mL, for example, 0.05 g / mL, 0.06 g / mL, 0.07 g / mL, 0.08 g / mL or 0.1 g / mL.

[0019] Preferably, the organic positive electrode coating agent in step (2) includes any one of the precursors or monomers of anthraquinone, acid anhydride, and imide compounds, or a combination of at least two of them.

[0020] Preferably, the mass ratio of the organic positive electrode coating agent to the electrode active material is (12-68):100, for example: 12:100, 20:100, 25:100, 40:100 or 68:100, etc., preferably (25-38):100.

[0021] Preferably, the temperature of the heating reflux reaction in step (2) is 140-160°C, for example, 140°C, 145°C, 150°C, 155°C or 160°C.

[0022] Preferably, the heating reflux reaction time is 6 to 48 hours, for example: 6 hours, 8 hours, 20 hours, 30 hours or 48 hours.

[0023] Preferably, the cooling method in step (3) comprises ice bath cooling.

[0024] Preferably, after removing the supernatant, the precipitate is washed and dried.

[0025] In a second aspect, an embodiment of the present application provides an electrode material for lithium extraction from salt lakes, wherein the electrode material for lithium extraction from salt lakes is prepared by the method described in the first aspect.

[0026] Preferably, the electrode material for lithium extraction from salt lakes comprises an electrode active material core and a carbon layer and an organic positive electrode material coating layer sequentially stacked on the surface of the electrode active material core;

[0027] Preferably, the material of the organic positive electrode material coating layer includes oxygen-containing conjugated carbonyl organic matter.

[0028] The present application coats the surface of the electrode active material with an oxygen-containing conjugated carbonyl organic coating layer (i.e., an organic positive electrode material coating layer), which enables the electrode to have high lithium ion conductivity during the lithium extraction process without reducing the electrode capacity. The oxygen-containing conjugated carbonyl organic coating layer can provide lithium ion embedding sites during the discharge process, thereby being able to accept the embedding of lithium ions during the electrochemical deintercalation and lithium extraction process, allowing the electrode to accommodate more lithium ions, thereby improving lithium ion conductivity and adhesion while effectively avoiding a decrease in electrode capacity.

[0029] Preferably, based on the mass of the electrode material for lithium extraction from salt lakes as 100%, the mass fraction of the organic positive electrode material coating layer is 10-40%, for example: 10%, 15%, 20%, 30% or 40%, etc., preferably 20-30%.

[0030] In a third aspect, an embodiment of the present application provides a salt lake lithium extraction electrode, which comprises the electrode material for salt lake lithium extraction as described in the second aspect.

[0031] In a fourth aspect, an embodiment of the present application provides a method for extracting lithium from a salt lake, wherein the method uses the salt lake lithium extraction electrode described in the third aspect as an anode, and uses a lithium-poor electrode made from the salt lake lithium extraction electrode described in the third aspect as a cathode.

[0032] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0033] (1) In the embodiment of the present application, a layer of organic positive electrode material coating is coated on the surface of the electrode material, which can not only improve the mechanical strength of the electrode and prevent the active particles of the electrode from falling off, but also increase the adsorption capacity and cycle stability of the electrode.

[0034] (2) When the electrode material for lithium extraction from salt lakes described in the embodiments of the present application is used in the process of lithium extraction from salt lakes, the lithium concentration in the brine after lithium extraction can reach below 0.15 g / L, the lithium concentration in the anolyte can reach above 3.1 g / L, the adsorption capacity mg(Li) / g(LiFePO4) can reach above 27.87, and the capacity retention rate can reach above 95% after 100 cycles, showing good adsorption performance and cycle performance. That is, the electrode material described in the present application can increase the adsorption capacity and cycle stability of the electrode.

[0035] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0036] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0037] Example 1

[0038] This embodiment provides an electrode material for lithium extraction from salt lakes. The preparation method of the electrode material for lithium extraction from salt lakes is as follows:

[0039] (1) 10 g of lithium iron phosphate calcined at high temperature and air flow milled at 600° C. was dispersed in 200 mL of N,N′-dimethylformamide (DMF) to obtain a dispersion;

[0040] (2) Under nitrogen atmosphere, pyromellitic anhydride (10 mmol, 2.18 g) and 2-aminoimidazole (15 mmol, 1.245 g) were added to the dispersion at a mass ratio of 34.25:100 to lithium iron phosphate, and the mixture was heated to 140°C, stirred continuously, and refluxed for 40 h.

[0041] (3) After the reaction is completed, the temperature is lowered, and the solution is cooled in an ice bath to precipitate. After centrifugation, the supernatant is removed, and the precipitate is washed and dried to obtain an electrode active material coated with a polycarbonyl nitrogen heterocyclic organic compound, with a coating layer having a mass fraction of 26%.

[0042] Example 2

[0043] This embodiment provides an electrode material for lithium extraction from salt lakes. The preparation method of the electrode material for lithium extraction from salt lakes is as follows:

[0044] (1) 10 g of lithium iron phosphate calcined and airflow-pulverized at 700°C was dispersed in 100 mL of N'N-dimethylacetamide (DMFAC);

[0045] (2) Under nitrogen atmosphere, 1,4,5,8-naphthalenetetracarboxylic anhydride (5 mmol, 1.34 g) and 2-aminobenzimidazole (15 mmol, 2.0 g) were added to the dispersion at a mass ratio of 33.4:100 to lithium iron phosphate, and the mixture was heated to 160° C., stirred continuously, and refluxed for 8 h.

[0046] (3) After the reaction is completed, the temperature is lowered, and the solution is cooled in an ice bath to precipitate. After centrifugation, the supernatant is removed, and the precipitate is washed and dried to obtain an electrode active material coated with a polycarbonyl nitrogen heterocyclic organic compound, wherein the mass fraction of the coating layer is 25%.

[0047] Example 3

[0048] This embodiment provides an electrode material for lithium extraction from salt lakes. The preparation method of the electrode material for lithium extraction from salt lakes is as follows:

[0049] (1) 10 g of lithium iron phosphate calcined at high temperature and air flow milled at 800° C. was dispersed in 100 mL of dimethyl sulfoxide (DMSO) to obtain a dispersion;

[0050] (2) Under nitrogen atmosphere, 1,4,5,8-naphthalenetetracarboxylic anhydride (5 mmol, 1.34 g) and 3-amino-1,2,4-triazole (10 mmol, 0.84 g) were added to the dispersion at a mass ratio of 21.8:100 to lithium iron phosphate. The mixture was heated to 150°C and refluxed for 15 h with continuous stirring.

[0051] (3) After the reaction is completed, the temperature is lowered, and the solution is cooled in an ice bath to precipitate. After centrifugation, the supernatant is removed, and the precipitate is washed and dried to obtain an electrode active material coated with a polycarbonyl nitrogen heterocyclic organic compound. The mass fraction of the coating layer is 17.8%.

[0052] Example 4

[0053] This embodiment provides an electrode material for lithium extraction from salt lakes. The preparation method of the electrode material for lithium extraction from salt lakes is as follows:

[0054] (1) 10 g of lithium iron phosphate electrode active material, which had been calcined and airflow-pulverized at 700° C., was dispersed in 100 mL of N-methylpyrrolidone to obtain a dispersion;

[0055] (2) Under nitrogen atmosphere, 2,3,3,4-biphenyltetracarboxylic anhydride monomer and diaminodiamine monomer were added to the dispersion at a molar ratio of 1:1.05 to carry out polymerization reaction. The total mass of the two monomers was 4 g, and the mass ratio of the two monomers to lithium iron phosphate was 40:100. The reaction was carried out at 150°C for 8 hours.

[0056] (3) After the reaction is completed, the supernatant is removed by centrifugation, and the precipitate is washed, dried, ground, and sieved to obtain a dry powder, which is then subjected to a high-temperature thermal imidization treatment at 330°C for 60 minutes to obtain polyimide-coated lithium iron phosphate, with a coating layer mass fraction of 39.5%.

[0057] Example 5

[0058] The only difference between this embodiment and embodiment 1 is that the volume of DMF is 250 mL, and other conditions and parameters are exactly the same as those in embodiment 1.

[0059] Example 6

[0060] The only difference between this embodiment and embodiment 1 is that the volume of DMF is 50 mL, and other conditions and parameters are exactly the same as those in embodiment 1.

[0061] Comparative Example 1

[0062] In this comparative example, lithium iron phosphate is directly used as the electrode active material.

[0063] Comparative Example 2

[0064] The only difference between this comparative example and Example 1 is that the lithium iron phosphate is not subjected to heat treatment in step (1), and the other conditions and parameters are exactly the same as those in Example 1.

[0065] Comparative Example 3

[0066] This comparative example provides an electrode material for lithium extraction from salt lakes. The preparation method of the electrode material for lithium extraction from salt lakes is as follows:

[0067] (1) The lithium iron phosphate active material was placed in a 5 g / L dopamine salt solution at a solid-liquid mass ratio of 1:5, the pH was adjusted to 8.5, and the mixture was stirred at 20°C for 15 hours;

[0068] (2) After the reaction is completed, the mixture is filtered and washed, and the filter residue is dried at 100° C. to obtain polydopamine-coated lithium iron phosphate.

[0069] Performance testing:

[0070] The electrode active materials obtained in the examples and comparative examples, the conductive agent acetylene black, and the binder PVDF were mixed in a mass ratio of 8:1:1 and added to NMP to form an electrode slurry. The slurry was coated on the titanium mesh current collector at a coating density of 200 mg / cm 2 , and then dried at 50 ° C for 6 hours to obtain an electrode. The prepared electrode was used as the positive electrode, the AgCl electrode was used as the negative electrode, and the 0.05 mol / L KCl solution was used as the electrolyte. The lithium-rich electrode was delithiated at a constant voltage of 1.0 V to obtain a lithium-poor electrode. The electrolysis device was separated into an anode chamber and a cathode chamber by an anion exchange membrane. The lithium-rich electrode and the lithium-poor electrode were placed in the anode chamber and the cathode chamber respectively. Brine was injected into the cathode chamber, and NaCl solution was injected into the anode chamber. A voltage of 0.3 V was applied to the anode and cathode to extract lithium. The lithium concentrations of the brine and the anode solution after lithium extraction, as well as the adsorption capacity and capacity retention rate of the electrode are shown in Table 1:

[0071] Table 1

[0072] As can be seen from Table 1, it can be obtained from Examples 1-2 that the electrode material for lithium extraction from salt lakes described in the present application is made into an electrode and used in the process of lithium extraction from salt lakes. After lithium extraction, the lithium concentration in the brine can reach below 0.15 g / L, the lithium concentration in the anolyte can reach above 3.1 g / L, the adsorption capacity mg(Li) / g(LiFePO4) can reach above 27.87, and the capacity retention rate can reach above 95% after 100 cycles, showing good adsorption performance and cycle performance. That is, the electrode material described in the present application can increase the adsorption capacity and cycle stability of the electrode.

[0073] By comparing Example 1 with Examples 3-4, it can be seen that in the preparation process of the electrode material for lithium extraction from salt lakes described in the present application, the amount of organic positive electrode coating agent added will affect the proportion of the coating layer in the material, and thus affect the performance of the material. The mass ratio of the organic positive electrode coating agent and the electrode active material is controlled at (25-38):100 (the mass fraction of the organic positive electrode material coating layer in the electrode material for lithium extraction from salt lakes is controlled at 20-30%). The performance of the electrode material for lithium extraction from salt lakes is good. If the proportion of the coating layer is too high, the stability of the electrode will be reduced due to unstable chemical reactions of the organic matter. If the proportion of the coating layer is too low, there is no obvious improvement effect on the lithium ion transfer rate and electrode capacity of the electrode.

[0074] By comparing Example 1 and Examples 5-6, it can be seen that in the preparation process of the electrode material for lithium extraction from salt lakes described in the present application, the mass of the active material and the volume ratio of the organic solvent will affect its performance. The mass of the active material and the volume ratio of the organic solvent are controlled at 0.05-0.1 g / mL, and the electrode material for lithium extraction from salt lakes has better performance. If there is too much organic solvent, the amount of active material is relatively small, and the concentration of the subsequently added organic positive electrode coating agent is too low, it is difficult to form a uniform coating layer on the surface of the active material. If there is too little organic solvent, a carbonized layer with active sites cannot be formed on the surface of the active material.

[0075] By comparing Example 1 and Comparative Example 1, it can be seen that the present application coats the surface of the electrode active material with an organic positive electrode material coating layer, which not only improves the mechanical strength of the electrode, but also enables the electrode to have higher lithium ion conductivity during the lithium extraction process without reducing the electrode capacity.

[0076] By comparing Example 1 and Comparative Example 2, it can be seen that in the present application, a high-temperature electrode active material is added to an organic solvent, and the organic matter is carbonized on the surface of the active material, increasing the active sites on the surface of the electrode material and improving the surface energy, thereby making it easy for the organic positive electrode coating agent to adhere to the surface of the electrode material and react to form a uniform organic positive electrode material coating layer.

[0077] From the comparison between Example 1 and Comparative Example 3, it can be seen that the type of the organic positive electrode coating agent described in the present application is relatively important. Although the use of polydopamine for coating can enhance the hydrophilicity and lithium ion conductivity of the electrode, it cannot increase the electrode capacity.

[0078] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing an electrode material for lithium extraction from a salt lake, comprising the following steps: (1) heating the electrode active material and mixing it with an organic solvent to obtain a dispersion; (2) mixing the dispersion and the organic positive electrode coating agent, and heating and refluxing the mixture; (3) Cooling and centrifuging the material obtained by the heating reflux reaction, and removing the supernatant to obtain the electrode material for lithium extraction from the salt lake.

2. The preparation method according to claim 1, wherein The electrode active material in step (1) includes any one of lithium iron phosphate, lithium manganese iron phosphate or lithium manganate, or a combination of at least two of them.

3. The preparation method according to claim 1 or 2, wherein: The heating temperature is 600-800°C.

4. The preparation method according to any one of claims 1 to 3, wherein The organic solvent in step (1) includes any one of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, methanol or ethanol, or a combination of at least two thereof.

5. The preparation method according to any one of claims 1 to 4, wherein: The mass ratio of the electrode active material to the volume ratio of the organic solvent is 0.05 to 0.1 g / mL.

6. The preparation method according to any one of claims 1 to 5, wherein: The organic positive electrode coating agent in step (2) includes any one of anthraquinone, acid anhydride, and a precursor or monomer of an imide compound, or a combination of at least two thereof; Preferably, the mass ratio of the organic positive electrode coating agent to the electrode active material is (12-68):100, preferably (25-38):

100.

7. The preparation method according to any one of claims 1 to 6, wherein: The temperature of the heating reflux reaction in step (2) is 140-160° C. Preferably, the heating reflux reaction time is 6 to 48 hours.

8. The preparation method according to any one of claims 1 to 7, wherein: The cooling method in step (3) comprises ice bath cooling; Preferably, after removing the supernatant, the precipitate is washed and dried.

9. An electrode material for extracting lithium from a salt lake, wherein: The electrode material for lithium extraction from salt lakes is prepared by the method as described in any one of claims 1 to 8.

10. The electrode material for lithium extraction from salt lakes as claimed in claim 9, wherein: The electrode material for extracting lithium from salt lakes comprises an electrode active material core and a carbon layer and an organic positive electrode material coating layer which are sequentially stacked on the surface of the electrode active material core.

11. The electrode material for lithium extraction from salt lakes according to claim 10, wherein: The material of the organic positive electrode material coating layer includes oxygen-containing conjugated carbonyl organic matter.

12. The electrode material for lithium extraction from salt lakes according to claim 10 or 11, wherein: Taking the mass of the electrode material for lithium extraction from salt lakes as 100%, the mass fraction of the organic positive electrode material coating layer is 10-40%, preferably 20-30%.

13. A salt lake lithium extraction electrode, wherein: The salt lake lithium extraction electrode comprises the electrode material for salt lake lithium extraction as described in any one of claims 9 to 12.

14. A method for extracting lithium from a salt lake, characterized in that: The salt lake lithium extraction method uses the salt lake lithium extraction electrode as claimed in claim 13 as an anode, and uses the lithium-poor electrode made from the salt lake lithium extraction electrode as claimed in claim 13 as a cathode.

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