Preparation method of mn-metal organic framework material, product and application thereof

Abstract

The application discloses a preparation method of Mn-metal organic framework material and application of the product, and belongs to the technical field of electrochemistry. The specific method is as follows: a MOF-74(Mn) precursor is prepared by a solvothermal reaction of a manganese source and 2,5-dihydroxyterephthalic acid in a solvent; a sodium source and a nickel source are mixed with the MOF-74(Mn) precursor according to a stoichiometric ratio, and high-temperature calcination treatment is carried out to obtain the Mn-metal organic framework material. The MOF-74(Mn) with a unique skeleton structure is used as a key precursor in the preparation of a sodium ion battery electrode material. Through the process design of in-situ high-temperature calcination of the MOF-74(Mn), the structure stability of the electrode material is strengthened while the electrode material is constructed, and the specific capacity of the battery is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, and in particular relates to a method for preparing Mn-metal-organic framework materials, as well as their products and applications. Background Technology

[0002] Sodium-ion batteries, with their outstanding advantages such as low cost and excellent performance at high and low temperatures, have gradually achieved large-scale application and become an important candidate system for large-scale energy storage devices. Currently, the electrode materials for sodium-ion batteries mainly cover layered materials, polyanionic materials, and organic materials. Among them, layered materials have become the mainstream choice in research and application due to their simple preparation process and high theoretical specific capacity. However, traditional layered electrode materials have inherent defects such as slow ion diffusion rate and poor cycle stability, making it difficult to meet the higher requirements of battery energy density, safety performance, and cycle life in large-scale energy storage scenarios. Therefore, developing novel layered electrode materials that combine high energy density, high safety, and excellent cycle performance has become an important research direction that urgently needs breakthroughs in the field of sodium-ion batteries. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for preparing Mn-metal-organic framework materials, along with their products and applications.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing Mn-metal-organic framework materials includes the following steps: MOF-74(Mn) precursor was prepared by solvothermal reaction of manganese source and 2,5-dihydroxyterephthalic acid (DHTA) in solvent; Sodium source, nickel source and MOF-74(Mn) precursor are mixed in stoichiometric ratio and subjected to high-temperature calcination to obtain Mn-metal-organic framework material.

[0005] This invention first employs a solvothermal method to successfully synthesize a manganese-based metal-organic framework material, MOF-74(Mn), using 2,5-dihydroxyterephthalic acid as an organic framework ligand to bridge manganese metal ions. This MOF-74(Mn), with its unique framework structure, is then used as a key precursor in the preparation of electrode materials for sodium-ion batteries. Through a process design involving in-situ high-temperature calcination of MOF-74(Mn), the structural stability of the electrode material is enhanced while simultaneously constructing it, significantly improving the battery's specific capacity. This invention fundamentally solves the structural collapse problem of traditional layered electrode materials during charge-discharge cycling, significantly enhancing the structural stability and overall electrochemical performance of the electrode material.

[0006] Furthermore, the specific preparation method of the MOF-74(Mn) precursor is as follows: A manganese source was added to N,N-dimethylformamide and anhydrous ethanol to obtain a manganese-containing solution; 2,5-Dihydroxyterephthalic acid was added to N,N-dimethylformamide (DMF) to obtain a 2,5-dihydroxyterephthalic acid solution; The 2,5-dihydroxyterephthalic acid solution was poured into a manganese-containing solution and stirred to obtain a mixed solution. A solvothermal reaction was carried out, and the reaction product was cooled to room temperature, centrifuged, washed, and dried to obtain the MOF-74(Mn) precursor.

[0007] Furthermore, the ratio of manganese source, N,N-dimethylformamide, and anhydrous ethanol is 1.187 g: 40 mL: 5 mL; the manganese source is MnCl2·4H2O.

[0008] Furthermore, the ratio of 2,5-dihydroxyterephthalic acid to N,N-dimethylformamide is 0.594 g: 20 mL.

[0009] Furthermore, the solvothermal reaction is carried out at a temperature of 120°C for 24 hours.

[0010] Furthermore, the sodium source is selected from sodium carbonate (Na2CO3); the nickel source is selected from nickel oxide (NiO).

[0011] Furthermore, the specific operation steps of the high-temperature calcination treatment are as follows: heat up to 500°C at a heating rate of 5°C / min, and hold at this temperature for 2 hours; continue to heat up to 900°C at a heating rate of 5°C / min, and hold at this temperature for 15 hours; after the reaction is completed, cool to room temperature.

[0012] The present invention also provides a Mn-metal-organic framework material, which is prepared by the above preparation method.

[0013] The present invention also provides a sodium-ion battery positive electrode sheet comprising the above-mentioned Mn-metal-organic framework material.

[0014] The present invention also provides a sodium-ion battery comprising the above-described sodium-ion battery positive electrode.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention introduces a high specific surface area manganese-based metal-organic framework (MOF) material as a precursor into the electrode material preparation system to improve the discharge performance of sodium-ion batteries. MOF materials possess the structural advantages of large specific surface area and high porosity; the ample pore space provides a convenient channel for the migration and shuttle of metal ions within the crystal transition layer. Their stable three-dimensional framework structure not only maintains the stability of the material's porosity but also effectively alleviates the volume expansion problem during sodium ion insertion / extraction. This manganese-based MOF material is applied to NaNi… 0.5 Mn 0.5 The preparation of O2 electrode materials can also effectively suppress Mn 3+ The Ginger-Taylor effect fundamentally improves the structural collapse problem of materials during charge-discharge cycles, enhancing the cycle stability of electrode materials while significantly improving their conductivity and specific capacity. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The image shows the microstructure of the MOF-74(Mn) precursor prepared in Example 1. Figure 2 The image shows the microstructure of the novel NNMO prepared in Example 1. Figure 3 The image shows the microstructure of the NNMO prepared in Comparative Example 1. Figure 4 The XRD patterns are of the MOF-74(Mn) precursor prepared in Example 1, the novel NNMO, and the NNMO prepared in Comparative Example 1. Figure 5 The specific surface area and pore size distribution of the NNMO prepared in Comparative Example 1 are shown in the diagram. Figure 6 The specific surface area and pore size distribution of the novel NNMO prepared in Example 1 are shown in the diagram. Figure 7 The cycling specific capacity of the materials prepared in Example 1 and Comparative Example 1 at a rate of 0.1C; Figure 8 The rate performance of the materials prepared in Example 1 and Comparative Example 1; Figure 9 Nyquist plots of the materials prepared in Example 1 and Comparative Example 1; Figure 10 Cyclic voltammetry (CV) curves of the material prepared in Comparative Example 1 at a scan rate of 0.1 mV / s; Figure 11The image shows the cyclic voltammetry curve of the material prepared in Example 1 at a scan rate of 0.1 mV / s. Detailed Implementation

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0018] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0020] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0022] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0023] All raw materials used in this invention were purchased from the market.

[0024] The technical solution of the present invention will be further illustrated by the following embodiments.

[0025] Example 1 A method for preparing a novel Mn-metal-organic framework material includes the following steps: (1) Preparation of MOF-74(Mn) precursor: 1) Add 1.187 g of MnCl2·4H2O to 40 mL of N,N-dimethylformamide and 5 mL of anhydrous ethanol, stir for 10 min to dissolve completely, and obtain a manganese-containing solution. 2) Add 0.594 g of 2,5-dihydroxyterephthalic acid to 20 mL of N,N-dimethylformamide and stir for 10 min to dissolve it completely to obtain a 2,5-dihydroxyterephthalic acid solution. 3) Pour the 2,5-dihydroxyterephthalic acid solution prepared in step 2) into the manganese-containing solution prepared in step 1), and stir continuously at 600 rpm for 15 min until the solution turns transparent brownish-red to obtain a mixed solution; pour the mixed solution into the liner of the reaction vessel and react at 120℃ for 24 h. After the temperature cools to room temperature, centrifuge the solution at 6000 rpm for 3 min, washing it three times alternately with anhydrous ethanol and DHTA during the process, and then place it in a 60℃ forced-air drying oven to dry for 8 h to obtain the MOF-74(Mn) precursor; (2) Mn-metal-organic framework materials (NaNi) 0.5 Mn 0.5 Preparation of O2): Weigh 0.529g of Na2CO3 (10% excess to compensate for the lack of sodium during high-temperature calcination), 0.374g of NiO, and 0.5346g of the MOF-74(Mn) precursor prepared in step (1). Grind thoroughly in an agate mortar for 1 hour. Disperse the gray powder into a porcelain boat and place the porcelain boat in a tube furnace. Heat to 500℃ at a heating rate of 5℃ / min and hold at this temperature for 2 hours. Continue heating to 900℃ at a heating rate of 5℃ / min and hold at this temperature for 15 hours. After the reaction is complete, cool to room temperature to obtain the novel NaNi. 0.5 Mn 0.5 O2 material (referred to as novel NNMO).

[0026] Comparative Example 1 Traditional NaNi 0.5 Mn 0.5 The method for preparing O2 includes the following steps: Weigh 0.529g of Na2CO3 (10% excess to compensate for sodium loss during high-temperature calcination), 0.374g of NiO, and 0.435g of MnO2 according to the stoichiometric ratio. Grind the above raw materials thoroughly in an agate mortar for 1 hour. Then, disperse the gray powder into a porcelain boat and place the porcelain boat in a tube furnace. Heat the furnace to 500℃ at a heating rate of 5℃ / min and hold at this temperature for 2 hours. Continue heating the furnace to 900℃ at a heating rate of 5℃ / min and hold at this temperature for 15 hours. After the reaction is complete, cool to room temperature to obtain conventional NaNi. 0.5 Mn 0.5 O2 material (NNMO for short).

[0027] Application Example 1 Assembly of button batteries 1. Preparation of electrode sheets Raw materials: polyvinylidene fluoride (PVDF), N-methylpyrrolidone (NMP), carbon black (Ketjen black), active materials; The method is as follows: Weigh out the active materials (NaNi prepared in Example 1 or Comparative Example 1) according to a mass ratio of 7:2:1. 0.5 Mn 0.5 0.07g of O2 material, 0.02g of carbon black and 0.01g of PVDF were ground evenly in a mortar and pestle. Then, 200 μL of NMP was slowly added and stirred into a paste. The paste was then evenly coated onto copper foil using a coating tool. The copper foil was vacuum dried at 90°C for 8 hours and then cut into 14×14mm circular positive electrode sheets using a cutting tool.

[0028] 2. Battery assembly Raw materials: positive electrode sheet with active material, sodium electrolyte (NaClO4), nickel foam (14×14mm), lithium sheet (14×14mm), separator (GF / D, 18×18mm), argon gas, button cell positive and negative electrode shell (CR2025). The method is as follows: Place the positive electrode sheet with active material into the battery case, then place the GF / D separator, slowly add 100µL of electrolyte to completely wet the electrode sheet, then place the lithium sheet, nickel foam and battery case in sequence, and then press the sheet with a tablet press at 55MPa for 10 seconds.

[0029] Figure 1 The image shows the microstructure of the MOF-74(Mn) precursor prepared in Example 1. As can be seen from the image, the precursor material exhibits a perfect umbrella-like structure, indicating that it has a larger specific surface area.

[0030] Figure 2 The image shows the microstructure of the novel NNMO prepared in Example 1. As can be seen from the image, the novel NNMO exhibits a distinct blocky structure composed of small nanoparticles, with numerous pores and a high density of nanoparticles. This increases the porosity of the novel material, which is beneficial for the deintercalation / intercalation of sodium ions between the positive and negative electrode materials, thus ensuring its excellent electrochemical performance.

[0031] Figure 3 The image shows the microstructure of NNMO prepared in Comparative Example 1. As can be seen from the image, the NNMO material is formed by stacking of bulk layers with irregular shapes.

[0032] Figure 4The XRD patterns of the MOF-74(Mn) precursor prepared in Example 1, the novel NNMO, and the NNMO prepared in Comparative Example 1 are shown. As can be seen from the figures, the novel NNMO prepared using the MOF-74(Mn) precursor exhibits a (003) characteristic peak near 16.5° and a (104) characteristic peak near 42°, respectively. This indicates that the novel NNMO material was successfully prepared. The intensity of the nickel oxide impurity peak near 42° in the novel NNMO is weaker than that in the NNMO, further demonstrating the better crystallinity of the novel NNMO material, which provides a guarantee for subsequent discharge specific capacity.

[0033] Figure 5 The figure shows the specific surface area and pore size distribution of NNMO prepared in Comparative Example 1. It can be seen from the figure that the adsorption-desorption isotherm of NNMO belongs to Type III in the IUPAC classification. The specific surface area of ​​NNMO is 0.84 m². 2 / g. The pore size distribution (PSDs) of the NNMO material was calculated using the BJH model. The PSDs were mainly concentrated in the 1-50 nm range, with most being mesoporous and a pore volume of 0.000314 cm³. 3 / g, with an average adsorption pore size of 10.2942nm.

[0034] Figure 6 The figure shows the specific surface area and pore size distribution of the novel NNMO prepared in Example 1. As can be seen from the figure, the adsorption-desorption isotherm of the novel NNMO belongs to Type III in the IUPAC classification. The specific surface area of ​​the novel NNMO is 3.8710 m² / g, which is much larger than that of NNMO (0.84 m² / g). 2 The pore size distribution (PSDs) of the novel NNMO material, with a volume of 0.002809 cm³, can be attributed to the introduction of MOF-74(Mn) into the material structure. The PSDs were calculated using the BJH model, showing a concentration mainly in the 1-50 nm range, falling between micropores and mesopores. 3 / g, with an average adsorption pore size of 18.5834nm. The pore volume and average pore size of the novel NNMO electrode material are much larger than those of NNMO material, which is beneficial for sodium ions to shuttle back and forth in the transition metal layer channel and improve its discharge specific capacity.

[0035] Performance testing: 1. The performance of the novel NNMO prepared in Example 1 and the NNMO material prepared in Comparative Example 1 were tested in the Newway Battery Testing System.

[0036] Figure 7The figure shows the cycle capacity of the materials prepared in Example 1 and Comparative Example 1 at a rate of 0.1C. As can be seen from the figure, the discharge capacity of the novel NNMO is significantly higher than that of NNMO, and then gradually decreases, indicating that the discharge capacity decay of the novel NNMO prepared using the MOF-74(Mn) precursor is relatively stable. This is because the robust porous network structure of MOF-74(Mn) suppresses the collapse of the internal crystal structure of NNMO.

[0037] 2. The performance of the novel NNMO prepared in Example 1 and the NNMO material prepared in Comparative Example 1 were tested.

[0038] Figure 8 The figure shows the rate performance of the materials prepared in Example 1 and Comparative Example 1. As can be seen from the figure, when the discharge rate increases from low to high and then decreases again, the specific capacity of the novel NNMO material prepared from the MOF-74(Mn) precursor is relatively well preserved, and it exhibits good reversibility after five charge-discharge cycles at a high rate of 5C back to a low rate of 0.1C. Furthermore, by comparison, the novel NNMO exhibits a higher discharge specific capacity than NNMO at all discharge rates.

[0039] 3. The performance of the novel NNMO prepared in Example 1 and the NNMO material prepared in Comparative Example 1 were tested.

[0040] Figure 9 The Nyquist plots of the materials prepared in Example 1 and Comparative Example 1 show that the slope of the straight line of the novel NNMO material is larger than that of the NNMO material. At the same time, the charge transfer resistance (Rct) corresponds to the semicircle in the high-frequency region, indicating that the novel NNMO electrode material has a smaller internal resistance and better electrolyte contact performance.

[0041] 4. The NNMO material prepared in Comparative Example 1 was subjected to performance testing.

[0042] Figure 10 The figure shows the cyclic voltammetry (CV) curves of the material prepared in Comparative Example 1 at a scan rate of 0.1 mV / s. As can be seen from the figure, in the CV of the NNMO cathode material, the four redox reaction pairs are located at 3.25 / 2.41 V, 3.36 / 3.01 V, 3.59 / 3.35 V and 3.79 / 3.52 V, respectively.

[0043] 5. The novel NNMO prepared in Example 1 was subjected to performance testing.

[0044] Figure 11The cyclic voltammetry (CV) curves of the material prepared in Example 1 at a scan rate of 0.1 mV / s are shown, revealing four reduction peaks at 2.41, 3.21, 3.45, and 3.60 V during the cathode scan. The peak intensities are significantly higher than those of NNMO. ΔV can, to some extent, represent the polarization of the material. In the CV of the novel cathode material, the redox pairs of the novel NNMO electrode material are located at 2.88 / 2.45 V, 3.28 / 3.18 V, 3.51 / 3.48 V, and 3.73 / 3.65 V, with ΔV values ​​of 0.43, 0.1, 0.03, and 0.08 V, respectively. The results indicate that the polarization of the novel NNMO electrode material is significantly reduced, and the charge-discharge reversibility is improved. Due to the high porosity of the MOF-74(Mn) precursor, the increase in internal resistance can be effectively suppressed, and the novel NNMO material can be effectively protected from side reactions with the electrolyte and structural damage.

[0045] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a Mn-metal-organic framework material, characterized in that, Includes the following steps: MOF-74(Mn) precursor was prepared by solvothermal reaction of manganese source and 2,5-dihydroxyterephthalic acid in solvent; Sodium source, nickel source and MOF-74(Mn) precursor are mixed in stoichiometric ratio and subjected to high-temperature calcination to obtain Mn-metal-organic framework material.

2. The preparation method according to claim 1, characterized in that, The specific preparation method of the MOF-74(Mn) precursor is as follows: A manganese source was added to a mixed solvent of N,N-dimethylformamide and anhydrous ethanol to obtain a manganese-containing solution. 2,5-Dihydroxyterephthalic acid was added to N,N-dimethylformamide to obtain a 2,5-dihydroxyterephthalic acid solution; The 2,5-dihydroxyterephthalic acid solution was poured into a manganese-containing solution and stirred to obtain a mixed solution. A solvothermal reaction was carried out, and the reaction product was cooled to room temperature, centrifuged, washed, and dried to obtain the MOF-74(Mn) precursor.

3. The preparation method according to claim 2, characterized in that, The ratio of manganese source, N,N-dimethylformamide and anhydrous ethanol is 1.187 g: 40 mL: 5 mL; the manganese source is MnCl2·4H2O.

4. The preparation method according to claim 2, characterized in that, The ratio of 2,5-dihydroxyterephthalic acid to N,N-dimethylformamide is 0.594 g: 20 mL.

5. The preparation method according to claim 2, characterized in that, The solvothermal reaction was carried out at a temperature of 120°C for 24 hours.

6. The preparation method according to claim 1, characterized in that, The sodium source is selected from sodium carbonate; the nickel source is selected from nickel oxide.

7. The preparation method according to claim 1, characterized in that, The specific operating steps of the high-temperature calcination treatment are as follows: heat up to 500°C at a heating rate of 5°C / min, and hold at this temperature for 2 hours; continue to heat up to 900°C at a heating rate of 5°C / min, and hold at this temperature for 15 hours. After the reaction is completed, cool to room temperature.

8. A Mn-metal-organic framework material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A positive electrode sheet for a sodium-ion battery, characterized in that, It comprises the Mn-metal-organic framework material as described in claim 8.

10. A sodium-ion battery, characterized in that, It comprises the sodium-ion battery positive electrode as described in claim 9.

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