Preparation method and application of nitrogen-carbon porous material based on bimetallic ZIFs

Abstract

The present invention belongs to the technical field of synthesis and preparation of negative electrode materials for lithium-ion batteries, and specifically discloses a preparation method and application of a nitrogen-carbon porous material based on bimetallic ZIFs, comprising the following steps: S1, dissolving zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and an organic ligand in a DMF solution in molar ratio, stirring evenly to obtain a reaction solution, generating a solid product by a solvent thermal synthesis method, and obtaining a bimetallic zeolite imidazolate framework powder material through centrifugation, washing, and drying; S2, pyrolysis and carbonization treatment of the bimetallic zeolite imidazolate framework powder material obtained in S1 under an inert atmosphere, cooling, soaking in a dilute hydrochloric acid solution, filtering, washing with water until neutral, and drying to obtain a nitrogen-carbon porous material. The present invention uses the prepared nitrogen-carbon porous material based on bimetallic ZIFs as a negative electrode material for lithium-ion batteries. The negative electrode material has high specific capacity, excellent cycle stability, and good rate performance, and shows good application prospects in the field of lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis and preparation of lithium ion battery negative electrode materials, and in particular to a preparation method and application of a nitrogen-carbon porous material based on bimetallic ZIFs. Background Art

[0002] With the rapid development of portable electronic devices, electric vehicles, and other fields, the requirements for lithium-ion battery performance are increasing. As a key component of lithium-ion batteries, the performance of anode materials directly affects important battery indicators such as energy density, charge-discharge efficiency, and cycle life. Traditional graphite anode materials have a relatively low theoretical specific capacity (approximately 372 mAh / g), which is difficult to meet the requirements of high-performance lithium-ion batteries. Therefore, the development of new anode materials with high capacity, long cycle life, and good rate performance has become a current research hotspot.

[0003] Prior art nitrogen-carbon porous materials have shown great potential for lithium-ion battery applications due to their unique porous structure, high conductivity, and good chemical stability. Zeolitic imidazolate framework (ZIFs) materials, with their highly ordered crystal structure, rich pore structure, and adjustable metal centers, are ideal precursors for preparing nitrogen-doped porous carbon. By introducing bimetallic centers into the ZIFs structure, the electronic structure and pore properties of the material can be further manipulated, thereby optimizing its performance as anode materials for lithium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a nitrogen-carbon porous material based on bimetallic ZIFs. The prepared negative electrode material has high specific capacity, excellent cycle stability and good rate performance, and shows good application prospects in the field of lithium-ion batteries.

[0005] To achieve the above objectives, the present invention provides a method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs, comprising the following steps:

[0006] S1. Dissolving zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and an organic ligand in a DMF solution in a molar ratio, stirring uniformly to obtain a reaction solution, generating a solid product by a solvothermal synthesis method, and obtaining a bimetallic zeolite imidazolate framework powder material by centrifugation, washing, and drying.

[0007] S2. Under an inert atmosphere, the bimetallic zeolite imidazolate framework powder material obtained in S1 is subjected to pyrolysis and carbonization treatment, cooled to form a block product, soaked in a dilute hydrochloric acid solution, filtered, washed with water until neutral, and dried to obtain a nitrogen-carbon porous material.

[0008] Preferably, in S1, the molar ratio of the zinc nitrate hexahydrate to the cobalt nitrate hexahydrate is 1-9:1-9, and the specific molar ratio is one of 9:1, 3:1, 1:1, 1:3, and 1:9.

[0009] Preferably, in S1, the organic ligands are imidazole and benzimidazole, and the molar ratio thereof is 13.5:1.5.

[0010] Preferably, in S1, the solvent thermal synthesis method is specifically:

[0011] The reaction solution is placed in a stainless steel reactor lined with polytetrafluoroethylene and moved into a drying oven. The temperature is 110-130°C and the reaction time is 24-96h. After the reactor is cooled to room temperature in the drying oven, the upper layer of solvent is poured out, washed, and dried to obtain a solid product.

[0012] Preferably, in S2, the pyrolysis carbonization treatment is specifically:

[0013] The bimetallic zeolite imidazolate framework material is placed in a covered quartz porcelain boat, transferred to a tube furnace protected by an inert atmosphere, and heated to 600-900°C at a heating rate of 2-5°C / min, and kept at this temperature for 2-4 hours, and naturally cooled to room temperature to obtain a solid product.

[0014] Preferably, in S2, the dilute hydrochloric acid solution immersion treatment time is 3 to 16 hours.

[0015] To achieve the above objectives, the present invention also provides an application of a nitrogen-carbon porous material in a negative electrode material for a lithium-ion battery.

[0016] Preferably, the preparation method is as follows:

[0017] The nitrogen-carbon porous material, conductive agent and binder are mixed evenly in a certain proportion, and then N-methylpyrrolidone solvent is added to make a slurry. The slurry is evenly coated on a copper foil current collector, and after drying and punching, a lithium-ion battery negative electrode material is obtained.

[0018] Preferably, the conductive agent is acetylene black, the binder is polyvinylidene fluoride, and the mass ratio of the nitrogen-carbon porous material, acetylene black and polyvinylidene fluoride is 8:1:1 or 7:2:1.

[0019] Preferably, the slurry is prepared by ball milling, and the coating thickness of the slurry is 200-400 μm.

[0020] Therefore, the present invention adopts the above-mentioned preparation method of the nitrogen-carbon porous material based on bimetallic ZIFs and its application, and the beneficial effects are as follows:

[0021] (1) The nitrogen-carbon porous material prepared by the present invention uses a bimetallic zeolite imidazolate skeleton as a precursor and utilizes the synergistic effect of the bimetallic to effectively regulate the pore structure and electronic structure of the material. The prepared nitrogen-doped porous carbon has a rich and uniformly distributed multi-level pore structure.

[0022] (2) The negative electrode material prepared by the present invention has a high specific capacity. By doping nitrogen atoms, the material is given an additional pseudocapacitive effect, which significantly improves the specific capacity of the material. Compared with traditional graphite negative electrode materials, the specific capacity is greatly improved and can reach 750mAh / g.

[0023] (3) The nitrogen-carbon porous negative electrode material prepared by the present invention has good rate performance and excellent cycle stability. Its rich and evenly distributed multi-level pore structure is conducive to the rapid transmission and storage of lithium ions. It can still maintain a high capacity retention rate after multiple charge and discharge cycles. After 100 cycles, the capacity retention rate can reach 98.7%, showing good application prospects in the field of lithium-ion batteries.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an SEM image of the nitrogen-carbon porous material of Example 1 of the preparation method of a nitrogen-carbon porous material based on bimetallic ZIFs of the present invention;

[0026] Figure 2 The powder XRD patterns of the nitrogen-carbon porous materials of Examples 1 to 5 of the preparation method of the bimetallic ZIFs-based nitrogen-carbon porous material of the present invention are as follows;

[0027] Figure 3 1. The charge-discharge cycle diagrams of the sixth and seventh application examples of the nitrogen-carbon porous material based on bimetallic ZIFs of the present invention;

[0028] Figure 4 These are rate diagrams of application examples 6 and 7 of a nitrogen-carbon porous material based on bimetallic ZIFs of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0030] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0031] Example 1

[0032] A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs comprises the following steps:

[0033] (1) Zinc nitrate hexahydrate and cobalt nitrate hexahydrate were weighed in a molar ratio of 9:1. Imidazole and benzimidazole were selected as organic ligands and dissolved in a DMF solution. The three solvents were mixed and stirred for about 30 minutes and then transferred to a 100 ml stainless steel reactor lined with polytetrafluoroethylene. The reactor was placed in an electric forced air drying oven and kept at a constant temperature of 130°C for 96 hours. After the reactor was cooled to room temperature in the drying oven, the upper layer of solvent was poured off, the product was removed with a spatula, and the precipitate was collected by centrifugation. The product was washed with DMF three times, and then the sample was dried in a vacuum drying oven at 110°C for 12 hours. Bimetallic zeolite imidazolate framework (ZIFs) powder was obtained.

[0034] (2) The obtained bimetallic zeolite imidazolate framework (ZIFs) powder was placed in a covered quartz boat, then transferred to a tube furnace and heated to 600°C at a heating rate of 5°C / min under inert gas protection, and kept at this temperature for 2 hours for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was naturally cooled to room temperature, and the obtained block product was taken out and soaked in a dilute hydrochloric acid solution for 6 hours to remove any possible residual metal impurities. The mixture was then filtered and washed with water until neutral, and then placed in a vacuum drying oven again and dried at 100°C for 24 hours to obtain a nitrogen-carbon porous material.

[0035] Example 2

[0036] A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs comprises the following steps:

[0037] (1) Zinc nitrate hexahydrate and cobalt nitrate hexahydrate were weighed in a molar ratio of 3:1. Imidazole and benzimidazole were selected as organic ligands and dissolved in a DMF solution. The four solvents were mixed and stirred for about 30 minutes and then transferred to a 100 ml stainless steel reactor lined with polytetrafluoroethylene. The reactor was placed in an electric forced air drying oven (120°C) and kept warm for 96 hours. After the reactor was cooled to room temperature in the drying oven, the upper layer of solvent was poured off, the product was removed with a spatula, and the precipitate was collected by centrifugation. The product was washed with DMF three times, and then the sample was dried in a vacuum drying oven at 110°C for 12 hours. Bimetallic zeolite imidazolate framework (ZIFs) powder was obtained.

[0038] (2) The obtained bimetallic zeolite imidazolate framework (ZIFs) powder was placed in a covered quartz boat, then transferred to a tube furnace under inert gas protection, heated to 700°C at a heating rate of 5°C / min, and kept at this temperature for 2 hours for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was naturally cooled to room temperature. The obtained block product was taken out and soaked in a dilute hydrochloric acid solution for 16 hours to remove any possible residual metal impurities. The mixture was then filtered and washed with water until neutral, and then placed in a vacuum drying oven again and dried at 100°C for 24 hours to obtain a nitrogen-carbon porous material.

[0039] Example 3

[0040] A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs comprises the following steps:

[0041] (1) Zinc nitrate hexahydrate and cobalt nitrate hexahydrate were weighed in a molar ratio of 1:1. Imidazole and benzimidazole were selected as organic ligands and dissolved in DMF solution. The four solvents were mixed and stirred for about 30 minutes and then transferred to a 100 ml stainless steel reactor lined with polytetrafluoroethylene. The reactor was placed in an electric forced air drying oven and kept at a constant temperature of 130°C for 48 hours. After the reactor was cooled to room temperature in the drying oven, the upper layer of solvent was poured out, the product was removed with a spatula, and the precipitate was collected by centrifugation. The product was washed with DMF three times, and then the sample was dried in a vacuum drying oven at 110°C for 12 hours. Bimetallic zeolite imidazolate framework (ZIFs) powder was obtained.

[0042] (2) The obtained bimetallic zeolite imidazolate framework (ZIFs) powder was placed in a covered quartz porcelain boat, transferred to a tube furnace, and heated to 800°C at a heating rate of 5°C / min under inert gas protection. The mixture was then kept at this temperature for 3 hours for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was naturally cooled to room temperature. The obtained block product was taken out and soaked in a dilute hydrochloric acid solution for 10 hours to remove any possible residual metal impurities. The mixture was then filtered and washed with water until neutral. The mixture was then placed in a vacuum drying oven and dried at 100°C for 24 hours to obtain a nitrogen-carbon porous material.

[0043] Example 4

[0044] A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs comprises the following steps:

[0045] (1) Zinc nitrate hexahydrate and cobalt nitrate hexahydrate were weighed in a molar ratio of 1:3. Imidazole and benzimidazole were selected as organic ligands and dissolved in DMF solution. The four solvents were mixed and stirred for about 30 minutes and then transferred to a 100 ml stainless steel reactor lined with polytetrafluoroethylene. The reactor was placed in an electric forced air drying oven and kept at 130°C for 96 hours. After the reactor was cooled to room temperature in the drying oven, the upper layer of solvent was poured out, the product was removed with a spatula, and the precipitate was collected by centrifugation. The product was washed with DMF three times, and then the sample was dried in a vacuum drying oven at 110°C for 12 hours. Bimetallic zeolite imidazolate framework (ZIFs) powder was obtained.

[0046] (2) The obtained bimetallic zeolite imidazolate framework (ZIFs) powder was placed in a covered quartz boat, transferred to a tube furnace, and heated to 900°C at a heating rate of 5°C / min under inert gas protection. The mixture was then kept at this temperature for 2 hours for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was naturally cooled to room temperature. The obtained block product was taken out and soaked in a dilute hydrochloric acid solution for 3 hours to remove any possible residual metal impurities. The mixture was then filtered and washed with water until neutral. The mixture was then placed in a vacuum drying oven and dried at 100°C for 24 hours to obtain a nitrogen-carbon porous material.

[0047] Example 5

[0048] A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs comprises the following steps:

[0049] (1) Zinc nitrate hexahydrate and cobalt nitrate hexahydrate were weighed in a molar ratio of 1:9. Imidazole and benzimidazole were selected as organic ligands and dissolved in a DMF solution. The four solvents were mixed and stirred for about 30 minutes and then transferred to a 100 ml stainless steel reactor lined with polytetrafluoroethylene. The reactor was placed in an electric forced air drying oven and kept at a constant temperature of 110°C for 96 hours. After the reactor was cooled to room temperature in the drying oven, the upper layer of solvent was poured off, the product was removed with a spatula, and the precipitate was collected by centrifugation. The product was washed with DMF three times, and then the sample was dried in a vacuum drying oven at 110°C for 12 hours. Bimetallic zeolite imidazolate framework (ZIFs) powder was obtained.

[0050] (2) The obtained bimetallic zeolite imidazolate framework (ZIFs) powder was placed in a covered quartz porcelain boat, transferred to a tube furnace, and heated to 800°C at a heating rate of 5°C / min under inert gas protection. The mixture was then kept at this temperature for 2 hours for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was naturally cooled to room temperature. The obtained block product was taken out and soaked in a dilute hydrochloric acid solution for 10 hours to remove any possible residual metal impurities. The mixture was then filtered and washed with water until neutral. The mixture was then placed in a vacuum drying oven and dried at 100°C for 24 hours to obtain a nitrogen-carbon porous material.

[0051] Example 6

[0052] The nitrogen-carbon porous material prepared in Example 1 was mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride, PVDF) in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added, and the mixture was ball-milled for 4 hours to form a uniform slurry. The slurry was evenly coated on a copper foil current collector to a thickness of 200 μm. The coated copper foil was then dried in a vacuum drying oven at 100°C for 24 hours. After drying, the foil was punched into circular shapes using a sheet puncher to serve as the negative electrode material for lithium-ion batteries.

[0053] Example 7

[0054] The nitrogen-carbon porous material prepared in Example 3 was mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride, PVDF) in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added, and the mixture was ball-milled for 4 hours to form a uniform slurry. The slurry was evenly coated on a copper foil current collector to a thickness of 200 μm. The coated copper foil was then placed in a vacuum drying oven and dried at 100°C for 24 hours. After drying, it was punched into circular shapes using a sheet puncher to serve as the negative electrode material for lithium-ion batteries.

[0055] Experimental testing

[0056] The nitrogen-carbon porous materials prepared in Examples 1 to 5 were subjected to SEM structural analysis. The SEM results of the sample obtained in Example 1 are as follows: Figure 1 As shown in Figure 2, it can be clearly seen that the material has a porous structure and contains a small amount of carbon nanotubes.

[0057] The bimetallic zeolite imidazolate frameworks (ZIFs) prepared in Examples 1 to 5 were subjected to XRD analysis. The results are as follows: Figure 2 As shown. You can see the spectrum of the synthetic material and the standard ZIF-62 spectrum Figure 1 The results show that the bimetallic ZIF crystal structure was successfully synthesized in Examples 1 to 5. The lithium-ion battery negative electrode materials prepared in Examples 6 and 7 were assembled into battery performance analysis. The charge and discharge cycle results are shown in Figure 2. Figure 3 As shown, the magnification results are as follows Figure 4 shown.

[0058] The charge and discharge voltage is 0.01-3.0V and 0.1A·g -1 The cycle performance test was carried out at a current density of 1.5, and the first cycle discharge capacity was 763.5 mA·h·g -1 After 100 cycles, the specific capacity is 753.8 mA·h·g -1 , with a high capacity and a capacity retention rate of up to 98.7%, which can still maintain a high capacity retention rate after multiple charge and discharge cycles. At current densities of 0.1, 0.2, 0.5, 1, 2, and 5A·g-1, the reversible capacities are 887.2, 676.2, 534.8, 570.7, 454.5, and 380.2 mA·h·g-1, respectively. -1 When the current density returns to 0.1A·g -1 When 62-(Zn:Co=1:1) obtained 700.3mA·h·g -1Therefore, the present invention adopts the above-mentioned preparation method of the nitrogen-carbon porous material based on bimetallic ZIFs and its application to prepare a negative electrode material with high specific capacity, excellent cycle stability and good rate performance, showing good application prospects in the field of lithium-ion batteries.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs and application of the prepared nitrogen-carbon porous material in anode materials for lithium-ion batteries, characterized in that: The preparation method is as follows: A nitrogen-carbon porous material, a conductive agent, and a binder are uniformly mixed in a certain proportion, and then N-methylpyrrolidone solvent is added to form a slurry. The slurry is evenly coated on a copper foil current collector, and then dried and punched to obtain a lithium-ion battery negative electrode material. The lithium-ion battery negative electrode material has a specific capacity of 750 mAh / g and a capacity retention rate of 98.7% after 100 cycles. The preparation method of the bimetallic ZIFs-based nitrogen-carbon porous material comprises the following steps: S1. Dissolving zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and an organic ligand in a DMF solution in a molar ratio, stirring uniformly to obtain a reaction solution, generating a solid product by a solvothermal synthesis method, and obtaining a bimetallic zeolite imidazolate framework powder material by centrifugation, washing, and drying. S2. Under an inert atmosphere, the bimetallic zeolite imidazolate framework powder material obtained in S1 is subjected to pyrolysis and carbonization treatment, cooled to form a block product, soaked in a dilute hydrochloric acid solution, filtered, washed with water until neutral, and dried to obtain a nitrogen-carbon porous material; In S1, the organic ligands are imidazole and benzimidazole, and the molar ratio of imidazole to benzimidazole is 13.5:1.

5.

2. The use of the nitrogen-carbon porous material prepared by the preparation method of the bimetallic ZIFs-based nitrogen-carbon porous material according to claim 1 in a negative electrode material for a lithium-ion battery, characterized in that: In S1, the molar ratio of the zinc nitrate hexahydrate to the cobalt nitrate hexahydrate is 1-9:1-9.

3. Application of the nitrogen-carbon porous material prepared by the method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs according to claim 1 in a negative electrode material for a lithium ion battery, characterized in that: In S1, the solvent thermal synthesis method is specifically: The reaction solution is placed in a stainless steel reactor lined with polytetrafluoroethylene and moved into a drying oven. The temperature is 110-130°C and the reaction time is 24-96h. After the reactor is cooled to room temperature in the drying oven, the upper layer of solvent is poured out, washed, and dried to obtain a solid product.

4. Application of the nitrogen-carbon porous material prepared by the method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs according to claim 1 in a negative electrode material for a lithium ion battery, characterized in that: In S2, the pyrolysis carbonization treatment is specifically as follows: The bimetallic zeolite imidazolate framework powder material is placed in a covered quartz porcelain boat, transferred to a tube furnace protected by an inert atmosphere, and heated to 600-900°C at a heating rate of 2-5°C / min, and kept at this temperature for 2-4 hours, and naturally cooled to room temperature to obtain a solid product.

5. Application of the nitrogen-carbon porous material prepared by the method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs according to claim 1 in a negative electrode material for a lithium ion battery, characterized in that: In S2, the dilute hydrochloric acid solution immersion treatment time is 3 to 16 hours.

6. Application of the nitrogen-carbon porous material prepared by the method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs according to claim 1 in a negative electrode material for a lithium-ion battery, characterized in that: The conductive agent is acetylene black, the binder is polyvinylidene fluoride, and the mass ratio of the nitrogen-carbon porous material, acetylene black and polyvinylidene fluoride is 8:1:1 or 7:2:

1.

7. Application of the nitrogen-carbon porous material prepared by the method for preparing a nitrogen-carbon porous material based on bimetallic ZIFs according to claim 1 in a negative electrode material for lithium-ion batteries, characterized in that: The slurry is prepared by ball milling, and the coating thickness of the slurry is 200-400 μm.

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