A manganese-based adsorbent for relieving qi stagnation, its preparation method and integrated application in a chain

Abstract

The present disclosure provides an air-repellent manganese-based adsorbent and a preparation method and chain-integrated application thereof, wherein the preparation method comprises the following steps: (1) mixing a manganese source and a lithium source with water to obtain a mixed solution; (2) mixing the mixed solution with a trimellitic acid solution for a hydrothermal reaction; (3) sintering the material obtained by the hydrothermal reaction to obtain the air-repellent manganese-based adsorbent. The present disclosure prepares an air-repellent manganese-based adsorbent by modification, and the adsorbent can avoid the accumulation and rupture of bubbles to produce a cavitation effect that damages its microstructure, thereby improving the stability of the adsorbent, and can also be directly used to synthesize MOF-coated lithium manganate positive electrode materials after lithium extraction fails.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of lithium extraction from salt lakes, and relates to a gas-venting manganese-based adsorbent, a preparation method thereof, and an integrated chain application. Background Art

[0002] Lithium is known as the "oil of the future" and is the solid element with the highest redox potential, the largest specific heat capacity, the smallest density, the lightest weight, and the highest energy density at room temperature. It is widely used in the fields of energy, electronics, chemical engineering, aerospace, etc. Currently, about three-quarters of the world's lithium resources are used to manufacture lithium-ion batteries. With the growth of the new energy vehicle industry and the energy storage industry, the demand for lithium-ion batteries and lithium resources is also increasing day by day. There are huge amounts of lithium resources in salt lake brines, accounting for about 60% of the world's lithium resources. How to efficiently extract lithium from salt lake brines has become an urgent problem to be solved.

[0003] Currently, the technologies applicable to lithium extraction from salt lakes mainly include precipitation method, adsorption method, extraction method, and membrane separation method. Among them, the adsorption method is considered to be one of the most promising methods for efficient lithium extraction in liquid environments. The adsorbent materials used in the adsorption method include aluminum-based adsorbents, manganese-based adsorbents, and titanium-based adsorbents. Although aluminum-based adsorbents are currently widely used in industrial applications, their adsorption capacity is low and they are prone to introducing other impurities, resulting in a high content of miscellaneous salts in the desorbed solution. The adsorption capacity of manganese-based adsorbents is 4 times that of aluminum-based adsorbents.

[0004] CN117101596A discloses a multi-metal doped hybrid manganese-based lithium ion sieve adsorbent and a preparation method thereof. The preparation method is to uniformly mix a lithium source, a manganese source, and a multi-metal source as raw materials, calcine to obtain a multi-metal doped hybrid manganese-based lithium ion sieve precursor powder, then add it to a solvent, stir and mix it with a polymer binder and a pore-forming agent to obtain a slurry, and use wet granulation to obtain particulate matter, and finally obtain the multi-metal doped hybrid manganese-based lithium ion sieve adsorbent through lithium elution.

[0005] CN113617327A discloses a synthesis method of a nano single crystal manganese-based lithium adsorbent, belonging to the technical field of lithium extraction, including the following steps: S1. uniformly mix a manganese source and a lithium source to obtain a raw material mixture, and then dry it; S2. perform two-stage calcination on the dried raw material mixture, and cool it after the calcination is completed to obtain the manganese-based lithium adsorbent.

[0006] When the manganese-based adsorbent prepared by the above scheme is used for lithium extraction, oxygen will be generated, which will damage the microstructure of the adsorbent, affect the stability, and further affect its lithium extraction effect. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail in this article. This overview is not intended to limit the scope of protection of the claims.

[0008] The purpose of the present disclosure is to provide a gas-removing manganese-based adsorbent, its preparation method, and an integrated application in a chain. The present disclosure prepares a gas-removing manganese-based adsorbent through modification. The adsorbent can avoid the cavitation effect caused by the accumulation and rupture of bubbles, which damages its microstructure, improve the stability of the adsorbent, and can be directly used to synthesize a lithium manganese oxide cathode material coated with MOF after lithium extraction fails.

[0009] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0010] In the first aspect, the present disclosure provides a preparation method of a gas-removing manganese-based adsorbent, and the preparation method includes the following steps:

[0011] (1) Mix a manganese source and a lithium source with water to obtain a mixed solution;

[0012] (2) Mix the mixed solution with a trimellitic acid solution for hydrothermal reaction;

[0013] (3) Sinter the material obtained from the hydrothermal reaction to obtain the gas-removing manganese-based adsorbent.

[0014] The manganese-based adsorbent (LMO) is mainly composed of lithium manganese oxide. After pickling, fast lithium ions can be replaced by hydrogen ions to form lithium vacancies. When encountering lithium-containing brine, the lithium vacancies in the manganese-based adsorbent will quickly and selectively extract lithium ions to achieve high-selectivity extraction of lithium, thereby avoiding the interference of other ions. However, oxygen will be generated during lithium extraction by the manganese-based adsorbent, and cavitation effects will occur when bubbles rupture, which will damage the microstructure of the adsorbent and affect its stability.

[0015] The present disclosure adds a modifier (trimellitic acid) during the preparation of the lithium ion sieve, so that the lithium ion sieve forms a flower-like structure during the hydrothermal synthesis process, with a high specific surface area and high porosity, which is conducive to the rapid escape of gas, avoids the cavitation effect caused by the accumulation and rupture of bubbles, damages the microstructure of the adsorbent, and improves the stability of the ion sieve. And the -COOH ligand present on the surface of the ion sieve can improve the hydrophilicity of the adsorbent and the wetting effect of the brine, thereby improving the adsorption efficiency.

[0016] In one embodiment, the manganese source in step (1) includes any one or a combination of at least two of manganese chloride, manganese nitrate, or manganese sulfate.

[0017] In one embodiment, the lithium source includes lithium hydroxide, lithium chloride, lithium nitrate, or lithium sulfate.

[0018] In one embodiment, the molar ratio of manganese element to lithium element in the mixed solution is 1:(1 - 3), for example: 1:1, 1:1.5, 1:2, 1:2.5, or 1:3, etc.

[0019] In one embodiment, the total concentration of metal ions in the mixed solution is 0.1 - 0.5 mol / L, for example: 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0020] In one embodiment, the concentration of the trimellitic acid solution in step (2) is 0.01 - 0.05 mol / L, for example: 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L or 0.05 mol / L, etc.

[0021] In one embodiment, the solvent of the trimellitic acid solution includes any one or a combination of at least two of ethanol, N-methylpyrrolidone or dimethylformamide.

[0022] In one embodiment, the temperature of the hydrothermal reaction in step (2) is 150 - 180 °C, for example: 150 °C, 155 °C, 160 °C, 170 °C or 180 °C, etc.

[0023] In one embodiment, the time of the hydrothermal reaction is 10 - 20 h, for example: 10 h, 12 h, 15 h, 18 h or 20 h, etc.

[0024] In one embodiment, the temperature of the sintering treatment in step (3) is 400 - 500 °C, for example: 400 °C, 420 °C, 450 °C, 480 °C or 500 °C, etc.

[0025] In one embodiment, the time of the sintering treatment is 3 - 5 h, for example: 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc.

[0026] In a second aspect, the present disclosure provides a gas-permeable manganese-based adsorbent, which is prepared by the method as described in the first aspect.

[0027] In a third aspect, the present disclosure provides an application of the gas-permeable manganese-based adsorbent as described in the second aspect, and the gas-permeable manganese-based adsorbent is used for lithium extraction from salt lakes.

[0028] Optionally, the gas-permeable manganese-based adsorbent is acidified before lithium extraction.

[0029] Optionally, the acidifying agent for the acidification includes a hydrochloric acid solution.

[0030] Optionally, the concentration of the hydrochloric acid solution is 0.2 - 1 mol / L, for example: 0.2 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, etc.

[0031] Optionally, after acidification, washing and drying treatments are carried out.

[0032] Optionally, the gas-venting manganese-based adsorbent is used to obtain a spent lithium ion sieve after lithium extraction from a salt lake.

[0033] Fourthly, the present disclosure provides a method for preparing a modified lithium manganese oxide cathode material, comprising the following steps: (A) mixing the above-mentioned spent lithium ion sieve, a lithium source, a doped metal source and a solvent to obtain a mixed solution;

[0034] (B) heating and reacting the mixed solution to obtain a modified lithium manganese oxide cathode material.

[0035] Trimellitic acid on the surface layer of the gas-venting manganese-based adsorbent in the present disclosure can be directly used to synthesize a MOF material after the lithium ion sieve fails, obtaining lithium manganese oxide coated with MOF. The obtained lithium manganese oxide has excellent electrochemical performance. And the outer layer of MOF can inhibit the dissolution of manganese in the lithium manganese oxide electrode during use, improving the cycle stability of the material. The chain integration application of the gas-venting manganese-based adsorbent is realized, and the application efficiency of the gas-venting manganese-based adsorbent is improved.

[0036] In one embodiment, the lithium source in step (A) includes any one or a combination of at least two of lithium hydroxide, lithium chloride, lithium nitrate, lithium sulfate or lithium acetate.

[0037] In one embodiment, the doped metal source includes any one or a combination of at least two of a titanium source, a zirconium source or a cobalt source.

[0038] In one embodiment, the solvent includes any one or a combination of at least two of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone or water.

[0039] In one embodiment, the solid-liquid ratio of the spent lithium ion sieve to the solvent is 0.1-0.5 g / mL, for example: 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL or 0.5 g / mL, etc.

[0040] In one embodiment, the concentrations of lithium element and doped metal element in the mixed solution are independently 0.01-0.05 mol / L, for example: 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L or 0.05 mol / L, etc.

[0041] In one embodiment, the temperature of the heating reaction in step (B) is 120-180 °C, for example: 120 °C, 140 °C, 150 °C, 170 °C or 180 °C, etc.

[0042] In one embodiment, the time of the heating reaction is 3-8 h, for example: 3 h, 4 h, 5 h, 6 h or 8 h, etc.

[0043] Fifthly, the present disclosure provides a modified lithium manganese oxide cathode material, which is prepared by the method as described in the fourth aspect.

[0044] Compared with the prior art, the present disclosure has the following beneficial effects:

[0045] (1) The present disclosure prepares a gas-venting manganese-based adsorbent through modification. The adsorbent can avoid the problem that the manganese-based adsorbent generates oxygen during lithium extraction, and the cavitation effect caused by the accumulation and rupture of bubbles damages its microstructure, thereby improving the stability of the adsorbent. After the lithium extraction fails, the adsorbent can be directly used to synthesize the lithium manganese oxide cathode material coated with MOF. The lithium manganese oxide cathode material has excellent electrochemical performance, and the outer layer of MOF can inhibit the dissolution of manganese during the use of the lithium manganese oxide electrode, improving the cycle stability of the material.

[0046] (2) The adsorption capacity of the gas-venting manganese-based adsorbent described in the present disclosure can reach more than 34.85 mg / g, and the capacity retention rate can reach more than 85.73% after 100 cycles. After the lithium extraction fails, it can be directly used to prepare the lithium manganese oxide cathode material. The 0.5C gram capacity of the battery made can reach more than 127.29 mAh / g, and the capacity retention rate can reach more than 90.12% after 100 cycles. It shows good effects compared with the commercially available lithium manganese oxide cathode material, realizing the integrated effect of the preparation, lithium extraction and recycling of the gas-venting manganese-based adsorbent for the preparation of the lithium manganese oxide cathode material.

[0047] Other aspects can be understood after reading and understanding the drawings and the detailed description. Description of the Drawings

[0048] The drawings are used to provide a further understanding of the technical solutions herein, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solutions herein, and do not constitute a limitation to the technical solutions herein.

[0049] Figure 1 It is the SEM image of the gas-venting manganese-based adsorbent prepared in Example 1 of the present disclosure.

[0050] Figure 2 It is the infrared test image of the gas-venting manganese-based adsorbent prepared in Example 1 of the present disclosure after hydrochloric acid modification (modified HMO) and after failure to prepare the modified lithium manganese oxide cathode material. Detailed Embodiments

[0051] The technical solutions of the present disclosure will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present disclosure and should not be regarded as specific limitations to the present disclosure.

[0052] Example 1

[0053] This embodiment provides a gas-permeable manganese-based adsorbent, and the preparation method of the gas-permeable manganese-based adsorbent is as follows:

[0054] (1) Dissolve manganese chloride and lithium chloride in water according to the molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, and the total concentration of metal ions in the mixed solution is 0.3 mol / L;

[0055] (2) Dissolve trimellitic acid in ethanol to obtain a trimellitic acid solution with a concentration of 0.02 mol / L. Mix the mixed solution with the trimellitic acid solution to form a homogeneous solution, pour it into a reaction kettle, and carry out hydrothermal reaction at 160 °C for 12 h. After the reaction, filter, wash, and dry;

[0056] (3) Place the dried powder in a sintering furnace at 450 °C for 4 h to obtain the gas-permeable manganese-based adsorbent.

[0057] The SEM diagram of the gas-permeable manganese-based adsorbent is as Figure 1 shown, and it can be seen from Figure 1 that the lithium ion sieve described in the present disclosure forms a flower-like structure during the hydrothermal synthesis process.

[0058] Example 2

[0059] This embodiment provides a gas-permeable manganese-based adsorbent, and the preparation method of the gas-permeable manganese-based adsorbent is as follows:

[0060] (1) Dissolve manganese nitrate and lithium nitrate in water according to the molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, and the total concentration of metal ions in the mixed solution is 0.1 mol / L;

[0061] (2) Dissolve trimellitic acid in ethanol to obtain a trimellitic acid solution with a concentration of 0.01 mol / L. Mix the mixed solution with the trimellitic acid solution to form a homogeneous solution, pour it into a reaction kettle, and carry out hydrothermal reaction at 150 °C for 20 h. After the reaction, filter, wash, and dry;

[0062] (3) Place the dried powder in a sintering furnace at 400 °C for 5 h to obtain the gas-permeable manganese-based adsorbent.

[0063] Example 3

[0064] This embodiment provides a gas-permeable manganese-based adsorbent, and the preparation method of the gas-permeable manganese-based adsorbent is as follows:

[0065] (1) Dissolve manganese nitrate and lithium nitrate in water according to the molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, and the total concentration of metal ions in the mixed solution is 0.5 mol / L;

[0066] (2) Dissolve trimellitic acid in ethanol to obtain a trimellitic acid solution with a concentration of 0.05 mol / L. Mix the mixed solution with the trimellitic acid solution to form a homogeneous solution, pour it into a reaction kettle, and carry out hydrothermal reaction at 180 °C for 10 h. After the reaction, filter, wash, and dry;

[0067] (3) Sinter the dried powder at 500 °C for 3 h to obtain the gas-venting manganese-based adsorbent.

[0068] Example 4

[0069] The difference between this example and Example 1 is only that the concentration of the trimellitic acid solution is 0.005 mol / L, and other conditions and parameters are exactly the same as those in Example 1.

[0070] Example 5

[0071] The difference between this example and Example 1 is only that the concentration of the trimellitic acid solution is 0.1 mol / L, and other conditions and parameters are exactly the same as those in Example 1.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is only that the trimellitic acid solution is not used, and other conditions and parameters are exactly the same as those in Example 1.

[0074] Comparative Example 2

[0075] This comparative example uses a commercially available manganese-based lithium ion sieve adsorbent.

[0076] Performance test:

[0077] Immerse the manganese-based adsorbents of the examples and comparative examples in a 0.5 mol / L hydrochloric acid solution, shake at a constant temperature of 25 °C for 24 h. After the product is vacuum filtered, wash it with deionized water until neutral, and dry to obtain the modified manganese-based lithium ion sieve (modified HMO, infrared test diagram as Figure 2 shown);

[0078] Immerse the modified HMO in a solution containing Li + solution, the concentration of Li + is 100 - 300 mg / L, shake at a constant temperature of 25 °C for 24 h, and use ICP to test the content of Li + in the solution. Calculate the adsorption capacity through the following formula:

[0079]

[0080] Q: Adsorption capacity mg / g, C o : Brine concentration before adsorption mg / L, C e : Brine concentration after adsorption mg / L, V: Solution volume L, m: Lithium ion sieve mass g.

[0081] The ratio of the adsorption capacity after 100 test cycles to the initial adsorption capacity was used to obtain the capacity retention rate after 100 cycles. The test results are shown in Table 1 as follows:

[0082] Table 1

[0083] Adsorption capacity (mg / g) Capacity retention rate after 100 cycles (%) Example 1 35.43 85.91 Example 2 34.85 85.87 Example 3 35.01 85.73 Example 4 32.13 84.36 Example 5 33.57 82.88 Comparative Example 1 30.58 82.67 Comparative Example 2 30.67 82.14

[0084] It can be seen from Table 1 that, as obtained from Examples 1-3, the adsorption capacity of the gas-venting manganese-based adsorbent described in the present disclosure can reach more than 34.85 mg / g, and the capacity retention rate after 100 cycles can reach more than 85.73%.

[0085] By comparing Example 1 with Examples 4-5, it can be obtained that in the preparation process of the gas-venting manganese-based adsorbent described in the present disclosure, the concentration of the trimellitic acid solution will affect its performance. Controlling the concentration of the trimellitic acid solution at 0.01-0.05 mol / L results in a better adsorbent. If the concentration of the trimellitic acid solution is too high, it will affect the formation of the adsorbent morphology. In addition, it will affect the formation of MOF in the subsequent synthesis process and reduce the capacity of lithium manganate. If the concentration of the trimellitic acid solution is too low, it will affect the formation of the adsorbent morphology. In addition, it is difficult to form an MOF coating in the subsequent synthesis process, affecting the electrochemical performance of lithium manganate.

[0086] By comparing Example 1 with Comparative Example 1, it can be obtained that the present disclosure adds a modifier (trimellitic acid) during the preparation of the lithium ion sieve, enabling the lithium ion sieve to form a flower-like structure during the hydrothermal synthesis process, having a high specific surface area and high porosity, which is conducive to the rapid dissipation of gas, avoiding the cavitation effect caused by the accumulation and rupture of bubbles and damaging the microstructure of the adsorbent, and improving the stability of the ion sieve. And the -COOH ligand present on the surface of the ion sieve can improve the hydrophilicity of the adsorbent and the wetting effect of the brine, thereby improving the adsorption efficiency.

[0087] By comparing Example 1 with Comparative Example 2, it can be obtained that oxygen is generated during the lithium extraction of the manganese-based adsorbent, and the cavitation effect occurs when the bubbles burst, which will damage the microstructure of the adsorbent and affect the stability. The present disclosure prepared a gas-venting manganese-based adsorbent through a simple modification method. The adsorbent can avoid the cavitation effect caused by the accumulation and rupture of bubbles and damage its microstructure, improving the stability of the adsorbent.

[0088] Application Example 1

[0089] This application example provides a modified lithium manganate cathode material, and the preparation method of the modified lithium manganate cathode material is as follows:

[0090] In Example 1, the adsorption capacity decreased by 30% after lithium extraction from the salt lake, obtaining a spent adsorbent. The spent adsorbent, lithium hydroxide, and titanium tetrachloride salt were added to acetonitrile and stirred evenly. The solid-liquid ratio of the spent adsorbent to acetonitrile was 0.2 g / ml, and the lithium and titanium ion concentrations in the mixed solution were 0.02 mol / L and 0.01 mol / L respectively. The mixed solution was placed in an autoclave and reacted at 150 °C for 5 h to obtain the modified lithium manganese oxide cathode material. The infrared test pattern is as shown in Figure 2 shown.

[0091] Application Example 2

[0092] This application example provides a modified lithium manganese oxide cathode material, and the preparation method of the modified lithium manganese oxide cathode material is as follows:

[0093] In Example 1, the adsorption capacity decreased by 30% after lithium extraction from the salt lake, obtaining a spent adsorbent. The spent adsorbent, lithium hydroxide, and zirconium nitrate were added to acetonitrile and stirred evenly. The solid-liquid ratio of the spent adsorbent to N,N-dimethylformamide was 0.5 g / ml, and the lithium and zirconium ion concentrations in the mixed solution were 0.03 mol / L and 0.05 mol / L respectively. The mixed solution was placed in an autoclave and reacted at 180 °C for 3 h to obtain the modified lithium manganese oxide cathode material.

[0094] Application Example 3

[0095] This application example provides a modified lithium manganese oxide cathode material, and the preparation method of the modified lithium manganese oxide cathode material is as follows:

[0096] In Example 1, the adsorption capacity decreased by 30% after lithium extraction from the salt lake, obtaining a spent adsorbent. The spent adsorbent, lithium hydroxide, and cobalt chloride were added to acetonitrile and stirred evenly. The solid-liquid ratio of the spent adsorbent to N,N-dimethylformamide was 0.1 g / ml, and the lithium and cobalt ion concentrations in the mixed solution were 0.03 mol / L and 0.02 mol / L respectively. The mixed solution was placed in an autoclave and reacted at 120 °C for 8 h to obtain the modified lithium manganese oxide cathode material.

[0097] Comparative Application Example 1

[0098] This comparative application example uses a commercially available lithium manganese oxide cathode material.

[0099] Performance test:

[0100] According to the lithium-ion battery test requirements specified in GB / T 36276-2018 "Lithium-ion Batteries for Electric Energy Storage", the modified lithium manganese oxide materials prepared in Application Examples 1-3 were made into 1200 mAh soft-pack batteries, and the specific capacity (0.5C) and cycle retention rate (100 cycles, 0.5C) of the materials were respectively tested in the voltage range of 3.0 - 4.3 V. The test results are shown in Table 2:

[0101] Table 2

[0102] 0.5C gram capacity (mAh / g) Cycle retention rate (%) Application Example 1 128.91 90.12 Application Example 2 127.29 90.24 Application Example 3 128.17 90.18 Comparative Application Example 1 110.64 88.24

[0103] As can be seen from Table 2, by comparing Application Examples 1-3 with Comparative Application Example 1, it can be obtained that after the lithium-extracting manganese-based adsorbent described in the present disclosure fails, it can be directly used to prepare the lithium manganese oxide cathode material. The 0.5C specific capacity of the battery made therefrom can reach more than 127.29 mAh / g, and the capacity retention rate can reach more than 90.12% after 100 cycles. Compared with the commercially available lithium manganese oxide cathode material, it shows good effects, realizing the integrated effect of the preparation, lithium extraction and recycling of the air-permeable manganese-based adsorbent.

[0104] The infrared test diagram of the air-permeable manganese-based adsorbent after hydrochloric acid modification (modified HMO) and the modified lithium manganese oxide cathode material (Application Example 1) prepared after failure in Example 1 is as Figure 2 shown. From Figure 2 it can be seen that trimellitic acid exists in the modified HMO and is consumed when the modified lithium manganese oxide cathode material is prepared after failure.

Claims

1. A method for preparing an air-repellent manganese-based adsorbent, comprising the following steps: (1) mixing a manganese source and a lithium source with water to obtain a mixed solution; (2) mixing the mixed solution with a trimellitic acid solution to carry out a hydrothermal reaction; (3) sintering the material obtained by the hydrothermal reaction to obtain the gas-repellent manganese-based adsorbent; The concentration of the trimellitic acid solution in step (2) is 0.01-0.05 mol / L.

2. The preparation method according to claim 1, wherein The manganese source in step (1) includes any one of manganese chloride, manganese nitrate or manganese sulfate, or a combination of at least two of them.

3. The preparation method according to claim 1, wherein The lithium source includes lithium hydroxide, lithium chloride, lithium nitrate or lithium sulfate.

4. The preparation method according to claim 1, wherein The molar ratio of manganese element to lithium element in the mixed solution is 1:(1-3).

5. The preparation method according to claim 1, wherein The total concentration of metal ions in the mixed solution is 0.1-0.5 mol / L.

6. The preparation method according to claim 1, wherein The solvent of the trimellitic acid solution includes any one of ethanol, N-methylpyrrolidone or dimethylformamide, or a combination of at least two of them.

7. The preparation method according to claim 1, wherein The temperature of the hydrothermal reaction in step (2) is 150-180°C.

8. The preparation method according to claim 7, wherein The hydrothermal reaction time is 10 to 20 hours.

9. The preparation method according to claim 1, wherein The sintering temperature in step (3) is 400-500°C.

10. The preparation method according to claim 9, wherein The sintering time is 3 to 5 hours.

11. An air-repellent manganese-based adsorbent prepared by the method according to any one of claims 1 to 10.

12. A use of the gas-repellent manganese-based adsorbent as claimed in claim 11, wherein: The air-repellent manganese-based adsorbent is used for extracting lithium from salt lakes.

13. Use of the gas-repellent manganese-based adsorbent as claimed in claim 12, wherein: The air-repellent manganese-based adsorbent is acidified before lithium extraction.

14. The use of the gas-repellent manganese-based adsorbent according to claim 13, wherein: The acidifying agent for acidification includes hydrochloric acid solution.

15. Use of the gas-repellent manganese-based adsorbent as claimed in claim 14, wherein: The concentration of the hydrochloric acid solution is 0.2-1 mol / L.

16. The use of the gas-repellent manganese-based adsorbent according to claim 13, wherein: After the acidification, water washing and drying are performed.

17. The use of the gas-repellent manganese-based adsorbent according to claim 12, wherein: The air-repellent manganese-based adsorbent is used to extract lithium from a salt lake to obtain a spent lithium ion sieve.

18. A method for preparing a modified lithium manganese oxide positive electrode material, comprising the following steps: (A) mixing the spent lithium ion sieve as claimed in claim 17, a lithium source, a doping metal source and a solvent to obtain a mixed solution; (B) heating the mixed solution to react and obtain the modified lithium manganese oxide positive electrode material.

19. The preparation method according to claim 18, wherein: The lithium source in step (A) includes any one of lithium hydroxide, lithium chloride, lithium nitrate, lithium sulfate or lithium acetate, or a combination of at least two thereof.

20. The preparation method according to claim 18, wherein: The doping metal source includes any one of a titanium source, a zirconium source or a cobalt source, or a combination of at least two of them.

21. The preparation method according to claim 18, wherein The solvent includes any one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone or water, or a combination of at least two thereof.

22. The preparation method according to claim 18, wherein The solid-to-liquid ratio of the failed lithium ion sieve and the solvent is 0.1-0.5 g / mL.

23. The preparation method according to claim 18, wherein The concentrations of lithium element and doping metal element in the mixed solution are independently 0.01-0.05 mol / L.

24. The preparation method according to claim 18, wherein The temperature of the heating reaction in step (B) is 120-180°C.

25. The preparation method according to claim 24, wherein The heating reaction time is 3 to 8 hours.

26. A modified lithium manganate positive electrode material, wherein: The modified lithium manganate positive electrode material is prepared by the method as described in any one of claims 18 to 25.

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