Porous manganese-based adsorbent, preparation method therefor and integrated chain use thereof

Abstract

A porous manganese-based adsorbent, a preparation method therefor and an integrated chain use thereof. 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 to implement a hydrothermal reaction; and (3) sintering a material obtained by the hydrothermal reaction to obtain the porous manganese-based adsorbent. The adsorbent can prevent bubble accumulation and rupture, avoiding the cavitation effect that may damage its microstructure, thereby improving the stability of the adsorbent. When lithium extraction fails, the adsorbent can also be directly used for synthesizing an MOF-coated lithium manganate positive electrode material.

Description

A gas-repellent manganese-based adsorbent, its preparation method, and chain-integrated application Technical Field

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

[0002] Lithium, known as the "oil of the future," is a solid element with the highest redox potential, largest specific heat capacity, smallest density, lightest weight, and highest energy density at room temperature. It is widely used in energy, electronics, chemicals, aerospace, and other fields. Currently, approximately three-quarters of the world's lithium resources are used to manufacture lithium-ion batteries. With the growth of the new energy vehicle and energy storage industries, the demand for lithium-ion batteries and lithium resources is also increasing. Salt lake brines contain vast lithium resources, accounting for approximately 60% of the world's lithium resources. Efficiently extracting lithium from these brines has become a pressing issue.

[0003] Currently, the main technologies applicable to lithium extraction from salt lakes include precipitation, adsorption, extraction, and membrane separation. Adsorption is considered one of the most promising methods for efficient lithium extraction in liquid environments. Adsorbent materials used in adsorption include aluminum-based, manganese-based, and titanium-based adsorbents. Although aluminum-based adsorbents are currently the most widely used in industrial applications, they have low adsorption capacity and are prone to introducing other impurities, resulting in high levels of foreign salts in the solution. Manganese-based adsorbents have an adsorption capacity four 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 comprises the following steps: uniformly mixing a lithium source, a manganese source and a multi-metal source as raw materials, calcining to obtain a multi-metal doped hybrid manganese-based lithium ion sieve precursor powder; then adding the precursor powder to a solvent, stirring and mixing it with a polymer binder and a porogen to obtain a slurry, wet granulating the granules, and finally eluting the granules with lithium to obtain the multi-metal doped hybrid manganese-based lithium ion sieve adsorbent.

[0005] CN113617327A discloses a method for synthesizing a nano single crystal manganese-based lithium adsorbent, which belongs to the field of lithium extraction technology and comprises the following steps: S1. uniformly mixing a manganese source and a lithium source to obtain a raw material mixture, and then drying the mixture; S2. roasting the dried raw material mixture in two stages, and cooling the mixture after roasting to obtain the manganese-based lithium adsorbent.

[0006] The manganese-based adsorbent prepared by the above scheme will produce oxygen when extracting lithium, which will damage the microstructure of the adsorbent, affect its stability, and thus affect its lithium extraction effect.

[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 purpose of the present disclosure is to provide an air-repellent manganese-based adsorbent, a preparation method thereof, and a chain-integrated application. The present disclosure prepares an air-repellent manganese-based adsorbent through modification. The adsorbent can avoid the accumulation and rupture of bubbles to produce cavitation effects that damage its microstructure, thereby improving the stability of the adsorbent. After the lithium extraction fails, it can also be directly used to synthesize MOF-coated lithium manganate positive electrode materials.

[0010] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for preparing an air-repellent manganese-based adsorbent, the preparation method comprising the following steps:

[0012] (1) mixing a manganese source and a lithium source with water to obtain a mixed solution;

[0013] (2) mixing the mixed solution with a trimellitic acid solution to carry out a hydrothermal reaction;

[0014] (3) Sintering the material obtained by the hydrothermal reaction to obtain the gas-repellent manganese-based adsorbent.

[0015] Manganese-based adsorbents (LMO) are primarily based on lithium manganese oxide compounds. After acid washing, they can replace lithium ions with hydrogen ions, forming lithium vacancies. When exposed to lithium-containing brine, the lithium vacancies in the manganese-based adsorbent rapidly and selectively extract lithium ions, achieving highly selective lithium extraction and avoiding interference from other ions. However, when extracting lithium with a manganese-based adsorbent, oxygen is generated, causing bubbles to burst and cavitation, which can damage the adsorbent's microstructure and affect its stability.

[0016] The present invention incorporates a modifier (trimellitic acid) during the preparation of a lithium ion sieve, resulting in a flower-like structure during the hydrothermal synthesis process. This structure, characterized by a high specific surface area and porosity, facilitates the rapid escape of gas, prevents cavitation damage to the adsorbent microstructure caused by bubble accumulation and rupture, and improves the stability of the ion sieve. Furthermore, the -COOH ligands present on the ion sieve surface enhance the adsorbent's hydrophilicity and improve brine wetting, thereby increasing adsorption efficiency.

[0017] In one embodiment, the manganese source in step (1) includes any one of manganese chloride, manganese nitrate or manganese sulfate, or a combination of at least two thereof.

[0018] In one embodiment, the lithium source comprises lithium hydroxide, lithium chloride, lithium nitrate, or lithium sulfate.

[0019] 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.

[0020] In one embodiment, the total concentration of metal ions in the mixed solution is 0.1 to 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.

[0021] In one embodiment, the concentration of the trimellitic acid solution in step (2) is 0.01 to 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.

[0022] In one embodiment, the solvent of the trimellitic acid solution includes any one of ethanol, N-methylpyrrolidone or dimethylformamide, or a combination of at least two thereof.

[0023] 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.

[0024] In one embodiment, the hydrothermal reaction time is 10 to 20 hours, for example, 10 hours, 12 hours, 15 hours, 18 hours or 20 hours.

[0025] 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.

[0026] In one embodiment, the sintering treatment time is 3 to 5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0027] In a second aspect, the present disclosure provides an air-phobic manganese-based adsorbent, which is prepared by the method described in the first aspect.

[0028] In a third aspect, the present disclosure provides an application of the air-repellent manganese-based adsorbent as described in the second aspect, wherein the air-repellent manganese-based adsorbent is used for extracting lithium from salt lakes.

[0029] Optionally, the air-repellent manganese-based adsorbent is acidified before lithium extraction.

[0030] Optionally, the acidifying agent comprises a hydrochloric acid solution.

[0031] Optionally, the concentration of the hydrochloric acid solution is 0.2 to 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.

[0032] Optionally, the acidification is followed by water washing and drying.

[0033] Optionally, the air-repellent manganese-based adsorbent is used to extract lithium from a salt lake to obtain a spent lithium ion sieve.

[0034] In a fourth aspect, the present disclosure provides a method for preparing a modified lithium manganate positive electrode material, comprising the following steps: (A) mixing the above-mentioned spent lithium ion sieve, a lithium source, a doping metal source, and a solvent to obtain a mixed solution;

[0035] (B) heating the mixed solution to react and obtain a modified lithium manganate positive electrode material.

[0036] The trimellitic acid on the surface of the aeroponic manganese-based adsorbent disclosed herein can be directly used to synthesize MOF materials after the lithium ion screen fails, resulting in MOF-coated lithium manganate with excellent electrochemical properties. Furthermore, the MOF on the outer layer can inhibit manganese dissolution during use of the lithium manganate electrode, improving the material's cyclic stability. This achieves chain-integrated application of the aeroponic manganese-based adsorbent, improving its application efficiency.

[0037] In one embodiment, the lithium source in step (A) comprises any one of lithium hydroxide, lithium chloride, lithium nitrate, lithium sulfate or lithium acetate, or a combination of at least two thereof.

[0038] In one embodiment, 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 thereof.

[0039] In one embodiment, the solvent includes any one or a combination of at least two of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone or water.

[0040] In one embodiment, the solid-to-liquid ratio of the spent lithium ion sieve and the solvent is 0.1 to 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.

[0041] In one embodiment, the concentrations of lithium and doping metal elements in the mixed solution are independently 0.01 to 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.

[0042] 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.

[0043] In one embodiment, the heating reaction time is 3 to 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours or 8 hours.

[0044] In a fifth aspect, the present disclosure provides a modified lithium manganate positive electrode material, which is prepared by the method described in the fourth aspect.

[0045] Compared with the prior art, the present disclosure has the following beneficial effects:

[0046] (1) The present invention discloses a modified gas-repellent manganese-based adsorbent, which can avoid the problem of oxygen generation during lithium extraction by manganese-based adsorbents, the accumulation and rupture of bubbles, and the cavitation effect that damages their microstructure, thereby improving the stability of the adsorbent. After the lithium extraction fails, the adsorbent can also be directly used to synthesize MOF-coated lithium manganese oxide positive electrode materials. The lithium manganese oxide positive electrode material has excellent electrochemical properties, and the outer layer MOF can inhibit the dissolution of manganese in the lithium manganese oxide electrode during use, thereby improving the material's cycle stability.

[0047] (2) The adsorption capacity of the air-repellent manganese-based adsorbent disclosed in the present invention 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 lithium manganese oxide positive electrode materials. The 0.5C gram capacity of the battery 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 positive electrode materials, it shows good results and realizes the chain integration effect of preparation, lithium extraction and recovery of the air-repellent manganese-based adsorbent for the preparation of lithium manganese oxide positive electrode materials.

[0048] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0050] FIG1 is a SEM image of the air-repellent manganese-based adsorbent prepared in Example 1 of the present disclosure.

[0051] FIG2 is an infrared test graph of the modified lithium manganese oxide positive electrode material made from the air-repellent manganese-based adsorbent obtained in Example 1 of the present disclosure after hydrochloric acid modification (modified HMO) and after failure. DETAILED DESCRIPTION

[0052] The technical solution of the present disclosure 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 disclosure and should not be regarded as specific limitations of the present disclosure.

[0053] Example 1

[0054] This embodiment provides an air-repellent manganese-based adsorbent, and the preparation method of the air-repellent manganese-based adsorbent is as follows:

[0055] (1) dissolving manganese chloride and lithium chloride in water at a molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, wherein the total concentration of metal ions in the mixed solution is 0.3 mol / L;

[0056] (2) dissolving trimellitic acid in ethanol to obtain a 0.02 mol / L trimellitic acid solution, mixing the mixed solution with the trimellitic acid solution to form a homogeneous solution, pouring the solution into a reactor for hydrothermal reaction at 160° C. for 12 h, and filtering, washing, and drying after the reaction is completed;

[0057] (3) The dried powder was sintered at 450° C. for 4 h to obtain the gas-repellent manganese-based adsorbent.

[0058] The SEM image of the aerophobic manganese-based adsorbent is shown in FIG1 . As can be seen from FIG1 , the lithium ion sieve disclosed herein forms a flower-like structure during the hydrothermal synthesis process.

[0059] Example 2

[0060] This embodiment provides an air-repellent manganese-based adsorbent, and the preparation method of the air-repellent manganese-based adsorbent is as follows:

[0061] (1) dissolving manganese nitrate and lithium nitrate in water at a molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, wherein the total concentration of metal ions in the mixed solution is 0.1 mol / L;

[0062] (2) dissolving trimellitic acid in ethanol to obtain a 0.01 mol / L trimellitic acid solution, mixing the mixed solution with the trimellitic acid solution to form a homogeneous solution, pouring the solution into a reactor for hydrothermal reaction at 150° C. for 20 h, and filtering, washing, and drying after the reaction is completed;

[0063] (3) The dried powder was sintered at 400° C. for 5 h to obtain the gas-repellent manganese-based adsorbent.

[0064] Example 3

[0065] This embodiment provides an air-repellent manganese-based adsorbent, and the preparation method of the air-repellent manganese-based adsorbent is as follows:

[0066] (1) dissolving manganese nitrate and lithium nitrate in water at a molar ratio of manganese element to lithium element of 1:3 to obtain a mixed solution, wherein the total concentration of metal ions in the mixed solution is 0.5 mol / L;

[0067] (2) dissolving trimellitic acid in ethanol to obtain a 0.05 mol / L trimellitic acid solution, mixing the mixed solution with the trimellitic acid solution to form a homogeneous solution, pouring the solution into a reactor for hydrothermal reaction at 180° C. for 10 h, and filtering, washing, and drying after the reaction is completed;

[0068] (3) The dried powder was sintered at 500° C. for 3 h to obtain the gas-repellent manganese-based adsorbent.

[0069] Example 4

[0070] The only difference between this embodiment and embodiment 1 is that the concentration of the trimellitic acid solution is 0.005 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Example 5

[0072] The only difference between this embodiment and embodiment 1 is that the concentration of the trimellitic acid solution is 0.1 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0073] Comparative Example 1

[0074] The only difference between this comparative example and Example 1 is that trimellitic acid solution is not used, and other conditions and parameters are exactly the same as those in Example 1.

[0075] Comparative Example 2

[0076] This comparative example uses a commercially available manganese-based lithium ion sieve adsorbent.

[0077] Performance testing:

[0078] The manganese-based adsorbents of the examples and comparative examples were immersed in a 0.5 mol / L hydrochloric acid solution and shaken at a constant temperature of 25°C for 24 hours. The products were vacuum filtered and washed with deionized water until neutral, and dried to obtain a modified manganese-based lithium ion sieve (modified HMO, the infrared test image of which is shown in FIG2 );

[0079] The modified HMO was immersed in Li + In solution, Li + The concentration was 100-300 mg / L, constant temperature and oscillation were performed at 25℃ for 24 hours, and the Li content in the solution was tested by ICP. + Content. The adsorption capacity is calculated by the following formula:

[0080] Q: adsorption capacity mg / g, C o : Brine concentration before adsorption mg / L, Ce : 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 cycles to the initial adsorption capacity is the capacity retention rate after 100 cycles. The test results are shown in Table 1:

[0082] Table 1

[0083] As can be seen from Table 1, from Examples 1-3, the adsorption capacity of the air-repellent manganese-based adsorbent disclosed in the present disclosure can reach above 34.85 mg / g, and the capacity retention rate can reach above 85.73% after 100 cycles.

[0084] By comparing Example 1 with Examples 4-5, it can be seen that during the preparation process of the air-repellent manganese-based adsorbent described in the present disclosure, the concentration of the trimellitic acid solution will affect its performance. The concentration of the trimellitic acid solution is controlled at 0.01 to 0.05 mol / L to obtain a better adsorbent effect. 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 MOF coating in the subsequent synthesis process, affecting the electrochemical performance of lithium manganate.

[0085] Comparison of Example 1 and Comparative Example 1 reveals that the present disclosure incorporates a modifier (trimellitic acid) during the preparation of the lithium ion sieve, resulting in the formation of a flower-like structure during the hydrothermal synthesis process. This structure possesses a high specific surface area and porosity, facilitating rapid gas escape, preventing cavitation damage to the adsorbent microstructure caused by bubble accumulation and rupture, and improving the stability of the ion sieve. Furthermore, the -COOH ligands present on the ion sieve surface enhance the adsorbent's hydrophilicity and improve brine wetting, thereby increasing adsorption efficiency.

[0086] By comparing Example 1 and Comparative Example 2, it can be seen that oxygen is generated when lithium is extracted from a manganese-based adsorbent, and the bubbles burst to cause a cavitation effect, which damages the microstructure of the adsorbent and affects its stability. The present invention prepares an air-repellent manganese-based adsorbent through a simple modification method. The adsorbent can avoid the accumulation and bursting of bubbles to cause a cavitation effect that damages its microstructure, thereby improving the stability of the adsorbent.

[0087] Application Example 1

[0088] This application example provides a modified lithium manganate positive electrode material. The preparation method of the modified lithium manganate positive electrode material is as follows:

[0089] Example 1: After lithium extraction from a salt lake, the adsorption capacity decreased by 30%, resulting in a spent adsorbent. The spent adsorbent, lithium hydroxide, and titanium tetrachloride were added to acetonitrile and stirred evenly. The solid-to-liquid ratio of the spent adsorbent to acetonitrile was 0.2 g / ml, and the concentrations of lithium and titanium ions 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 hours to obtain the modified lithium manganese oxide positive electrode material. The infrared test image is shown in Figure 2.

[0090] Application Example 2

[0091] This application example provides a modified lithium manganate positive electrode material. The preparation method of the modified lithium manganate positive electrode material is as follows:

[0092] In Example 1, after lithium extraction from a salt lake, the adsorption capacity decreased by 30%, resulting in a spent adsorbent. The spent adsorbent, lithium hydroxide, and zirconium nitrate were added to acetonitrile and stirred evenly. The solid-to-liquid ratio of the spent adsorbent to N,N-dimethylformamide was 0.5 g / ml, and the concentrations of lithium and zirconium ions 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 hours to obtain the modified lithium manganate positive electrode material.

[0093] Application Example 3

[0094] This application example provides a modified lithium manganate positive electrode material. The preparation method of the modified lithium manganate positive electrode material is as follows:

[0095] In Example 1, after lithium extraction from a salt lake, the adsorption capacity decreased by 30%, resulting in a spent adsorbent. The spent adsorbent, lithium hydroxide, and cobalt chloride were added to acetonitrile and stirred evenly. The solid-to-liquid ratio of the spent adsorbent to N,N-dimethylformamide was 0.1 g / ml, and the concentrations of lithium and cobalt ions 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 hours to obtain the modified lithium manganate positive electrode material.

[0096] Comparative Application Example 1

[0097] This comparative application example uses commercially available lithium manganese oxide positive electrode material.

[0098] Performance testing:

[0099] According to the lithium-ion battery testing requirements specified in GB / T 36276-2018 "Lithium-ion Batteries for Power Energy Storage", the modified lithium manganese oxide materials prepared in Application Examples 1-3 were made into 1200mAh soft-pack batteries. The gram capacity (0.5C) and cycle retention rate (100 cycles, 0.5C) of the materials were tested in the voltage range of 3.0 to 4.3V. The test results are shown in Table 2:

[0100] Table 2

[0101] As can be seen from Table 2, by comparing Application Examples 1-3 with Comparative Application Example 1, the air-repellent manganese-based adsorbent disclosed in the present invention can be directly used to prepare lithium manganate positive electrode materials after lithium extraction fails. The 0.5C gram capacity of the prepared battery can reach more than 127.29 mAh / g, and the capacity retention rate can reach more than 90.12% after 100 cycles. Compared with commercially available lithium manganate positive electrode materials, it shows good results and realizes the integrated chain effect of preparation, lithium extraction and recycling of air-repellent manganese-based adsorbents.

[0102] FIG2 shows infrared images of the modified lithium manganese oxide positive electrode material (Application Example 1) prepared after hydrochloric acid modification of the air-repellent manganese-based adsorbent prepared in Example 1 (modified HMO) and after failure. FIG2 shows that trimellitic acid is present in the modified HMO and is consumed during the preparation of the modified lithium manganese oxide positive electrode material after failure.

Claims

1. A preparation method of a gas-permeable manganese-based adsorbent, comprising the following steps: (1) Mix a manganese source and a lithium source with water to obtain a mixed solution; (2) Mix the mixed solution with a trimellitic acid solution for a hydrothermal reaction; (3) Sinter the material obtained from the hydrothermal reaction to obtain the gas-permeable manganese-based adsorbent.

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

3. The preparation method according to claim 1 or 2, wherein The lithium source includes lithium hydroxide, lithium chloride, lithium nitrate, or lithium sulfate.

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

5. The preparation method according to any one of claims 1-4, wherein, The total concentration of metal ions in the mixed solution is 0.1 - 0.5 mol / L.

6. The preparation method according to any one of claims 1-5, wherein, The concentration of the trimellitic acid solution in step (2) is 0.01 - 0.05 mol / L.

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

8. The preparation method according to any one of claims 1-7, wherein The temperature of the hydrothermal reaction in step (2) is 150 - 180 °C; Optionally, the time of the hydrothermal reaction is 10 - 20 h.

9. The preparation method according to any one of claims 1-8, wherein, The temperature of the sintering treatment in step (3) is 400 - 500 °C; Optionally, the time of the sintering treatment is 3 - 5 h.

10. A gas-permeable manganese-based adsorbent prepared by the method according to any one of claims 1 - 9.

11. An application of the gas-permeable manganese-based adsorbent according to claim 10, wherein the gas-permeable manganese-based adsorbent is used for lithium extraction from salt lakes; Optionally, the gas-permeable manganese-based adsorbent is acidified before lithium extraction; Optionally, the acidifying agent for acidification includes a hydrochloric acid solution; Optionally, the concentration of the hydrochloric acid solution is 0.2 - 1 mol / L; Optionally, after acidification, it is washed with water and dried; Optionally, a spent lithium ion sieve is obtained after lithium extraction from the salt lake using the gas-permeable manganese-based adsorbent.

12. A preparation method of a modified lithium manganese oxide cathode material, comprising the following steps: (A) Mix the spent lithium ion sieve according to claim 11, a lithium source, a doped metal source, and a solvent to obtain a mixed solution; (B) Heat-react the mixed solution to obtain the modified lithium manganese oxide cathode material.

13. The preparation method according to claim 12, wherein, 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; Optionally, 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; Optionally, the solvent includes any one or a combination of at least two of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, or water; Optionally, the solid-liquid ratio of the spent lithium ion sieve to the solvent is 0.1 - 0.5 g / mL; Optionally, the concentrations of lithium element and doped metal element in the mixed solution are independently 0.01 - 0.05 mol / L.

14. The preparation method according to claim 12 or 13, wherein, The temperature of the heat reaction in step (B) is 120 - 180 °C; Optionally, the time of the heat reaction is 3 - 8 h.

15. A modified lithium manganese oxide cathode material prepared by the method according to any one of claims 12 - 14.

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