A MOF doped porous carbon and a preparation method and application thereof

Abstract

The application discloses MOF doped porous carbon and a preparation method and application thereof, and belongs to the field of material preparation.The method comprises the following steps: mixing MOF material, a polymer, a metal salt and a pore-forming agent, performing oxidation polymerization, carbonization and water vapor activation to obtain a porous carbon precursor; and then performing non-metallic alkali gas doping, carbon source gas amorphous carbon coating and reducing gas surface modification in sequence to obtain the MOF doped porous carbon.The closed pore structure of the MOF is utilized to reduce expansion, the pore-forming agent is carbonized to form large pores for storing active materials, and the doped metal and non-metal elements improve the conductivity and improve the rate performance of the material.The obtained porous carbon has low resistivity, high specific capacity, high initial efficiency and excellent cycle performance as a negative electrode material of a lithium ion battery, and solves the technical problems of high expansion of existing porous carbon without closed pores and deviation of power performance.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials technology, and in particular to a MOF-doped porous carbon, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as a new generation of energy storage devices, have been widely used in consumer electronics, power batteries, and large-scale energy storage. The anode material is one of the core components determining the energy density, power density, and cycle life of lithium-ion batteries. Porous carbon, due to its high specific surface area, controllable pore structure, and good conductivity, is a key matrix material for preparing high-performance silicon-carbon anodes and other high-capacity anodes.

[0003] Existing porous carbon precursors mainly fall into three categories: biomass, resin-based, and pitch-based. While biomass raw materials are low-cost, they suffer from low compaction density and difficulty in controlling pore volume. Resin-based raw materials have higher compaction density, but their cost remains high and they exhibit significant impedance. Pitch-based raw materials offer good fast-charging performance, but their low pore volume limits the specific capacity of the anode material. Porous carbon prepared from these three types of raw materials struggles to simultaneously achieve a balance between fast-charging performance, capacity, cost, and compaction density, thus hindering the further development of high-energy-density lithium-ion batteries.

[0004] Therefore, it is necessary to improve the overall electrochemical performance of porous carbon and its silicon-carbon materials by selecting an improved carbon-based precursor material and a new process method. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing MOF-doped porous carbon, a composite material obtained by the method, and the application of the composite material as a negative electrode material for lithium-ion batteries, aiming to solve the problems of high expansion, power performance deviation and low initial efficiency of existing porous carbon.

[0006] A method for preparing MOF-doped porous carbon, the method comprising: MOF material, polymer solution, metal salt and pore-forming agent are mixed and then subjected to oxidative polymerization, carbonization and steam activation in sequence to obtain porous carbon precursor; The porous carbon precursor is sequentially reacted with a non-metallic alkaline gas, a carbon source gas, and a reducing gas. The reactions are non-metallic alkaline gas doping, carbon source gas coating, and reducing gas surface modification on the porous carbon precursor, respectively, to obtain MOF-doped porous carbon.

[0007] Preferably, the mass ratio of MOF:polymer solution:metal salt:pore-forming agent is 10-30:1000:1-5:1-5; The oxidative polymerization is carried out at a temperature of 50-100℃ for 1-3 hours. The carbonization temperature is 1100-1300℃, and the time is 1-3 hours; The steam activation temperature is 900-1000℃, the flow rate is 100-500 SCCM, and the time is 60-600 min.

[0008] Preferably, the temperature at which the porous carbon precursor reacts with the non-metallic alkaline gas is 1200-1500℃, the flow rate of the non-metallic alkaline gas is 10-100 SCCM, and the time is 30-300 min. The porous carbon precursor reacts with the carbon source gas at a temperature of 700-900℃, a flow rate of 100-500 SCCM, and a time of 30-300 min. The porous carbon precursor reacts with the reducing gas at a temperature of 500-700℃, a flow rate of 10-100 SCCM, and a time of 30-300 min.

[0009] Preferably, the MOF material is selected from one of ZIF-8, MOF-808, ZIF-67, MOF-818, MOF-74, MOF-545 or MIL-101(Cr); The polymer is selected from epoxy resin, acrylic resin, polyurethane or phenolic resin, and the solvent is selected from dibutyl phthalate, ethyl acetate, acetone or cyclohexanone. The polymer solution has a mass concentration of 5-20 wt%. The pore-forming agent is selected from one of polystyrene microspheres, polymethyl methacrylate, or carbamoyl hydrazide. The metal salt is selected from one of the chlorides or nitrates of magnesium, lithium, copper, nickel, or cobalt.

[0010] Preferably, the non-metallic alkaline gas is selected from one of dinitrogen tetrahydride, phosphine, and ammonia; The carbon source gas is selected from one of methane, ethane, acetylene, and ethylene; The reducing gas is carbon monoxide and / or hydrogen.

[0011] Another object of the present invention is to provide a MOF-doped porous carbon, which is prepared by the preparation method described above.

[0012] Preferably, the MOF-doped porous carbon has a pore size of 2.05-2.25 nm and a pore volume of 1.0-1.15 m³. 3 / g, specific surface area is 1750-2000m² 2 / g, tap density is 0.4-0.5g / cm³ 3 The powder resistivity is 1.15-1.5 Ω·cm.

[0013] Another objective of this invention is to provide the application of the above-mentioned MOF-doped porous carbon as a negative electrode material for lithium-ion batteries.

[0014] The embodiments of the present invention have the following beneficial effects: Introducing MOF materials, metal salts, and pore-forming agents into polymer-based porous carbon precursors can effectively reduce volume expansion during charging and discharging by utilizing the macroporous structure of MOF materials themselves; metal doping can improve the electronic conductivity of the material; and organic pore-forming agents form spherical pores after carbonization, giving the resulting porous carbon high pore size, large pore volume, high conductivity, and high compaction density.

[0015] In porous carbon precursors, non-metallic alkaline gases are used for activation and pore formation, carbon source gases are used for carbon coating, and reducing gases are used for surface modification. The activation and pore formation by non-metallic alkaline gases further enhances the richness of the material's pore structure. Amorphous carbon coating and the removal of oxygen-containing functional groups such as hydroxyl and carboxyl groups from the material surface by reducing gases significantly reduce side reactions between the material and the electrolyte and improve the first coulombic efficiency. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] in: Figure 1 The image shows a SEM image of the MOF-doped porous carbon prepared in Example 1. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0021] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0022] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0023] In this application, if the unit of a data range is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0024] In this application, terms such as "multiple," "various," and "repeatedly" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "multiple" means two or more. This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0025] The "scope" disclosed in this application is defined by a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way may include end values ​​or not.

[0026] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] Example 1 A method for preparing porous carbon from MOF materials includes the following steps: Step S1: 20g ZIF-8 was added to 1000g of 10wt% epoxy resin in an ethyl acetate solution, along with 3g magnesium chloride and 3g polystyrene microspheres. The mixture was then oxidatively polymerized at 80℃ for 2h, filtered, and the resulting material was carbonized at 1200℃ for 2h. After cooling to 950℃, steam was introduced and activated at a flow rate of 300 SCCM for 300min to obtain a porous carbon precursor. Step S2: The porous carbon precursor was transferred to a rotary kiln and heated to 1300°C. Nitrogen tetrahydrogen gas was introduced at a flow rate of 50 SCCM for 150 min. Then, the temperature was lowered to 800°C and ethylene gas was introduced at a flow rate of 300 SCCM for 150 min to coat the precursor with amorphous carbon. Finally, the temperature was lowered to 600°C and carbon monoxide gas was introduced at a flow rate of 50 SCCM for 150 min to obtain the porous carbon composite material.

[0031] Example 2 A method for preparing porous carbon from MOF materials includes the following steps: Step S1: 10g of MOF-808 was added to 1000g of 10wt% acrylic resin in acetone solution, along with 1g of lithium chloride and 1g of polymethyl methacrylate, and mixed thoroughly. The mixture was then oxidatively polymerized at 50℃ for 3h, filtered, and the resulting material was carbonized at 1100℃ for 3h. After that, the temperature was lowered to 900℃, and steam was introduced at a flow rate of 100SCCM for 600min to obtain a porous carbon precursor. Step S2: The porous carbon precursor was transferred to a rotary kiln and heated to 1200°C. Phosphine gas was introduced at a flow rate of 10 SCCM for 300 min. Then, the temperature was lowered to 700°C and methane gas was introduced at a flow rate of 100 SCCM for 300 min to coat the precursor with amorphous carbon. Finally, the temperature was lowered to 500°C and hydrogen gas was introduced at a flow rate of 10 SCCM for 300 min to obtain the porous carbon composite material.

[0032] Example 3 A method for preparing porous carbon from MOF materials includes the following steps: Step S1: 30g ZIF-67 was added to 1000g of a 5wt% polyurethane cyclohexanone solution, along with 5g copper chloride and 5g carbamoyl hydrazine, and mixed thoroughly. The mixture was then oxidatively polymerized at 100℃ for 1h, filtered, and the resulting filter residue was carbonized at 1300℃ for 1h. After cooling to 1000℃, steam was introduced and activated at a flow rate of 500 SCCM for 60min to obtain a porous carbon precursor. Step S2: The porous carbon precursor was transferred to a rotary kiln and heated to 1500°C. Ammonia gas was introduced at a flow rate of 100 SCCM for 30 min. Then, the temperature was lowered to 900°C and methane gas was introduced at a flow rate of 500 SCCM for 30 min to coat the amorphous carbon. Finally, the temperature was lowered to 700°C and carbon monoxide gas was introduced at a flow rate of 100 SCCM for 30 min to obtain the porous carbon composite material.

[0033] Comparative Example 1 Unlike Example 1, ZIF-8 material is not added in step S1, but everything else is the same as in Example 1.

[0034] Comparative Example 2 Unlike Example 1, magnesium chloride and polystyrene microspheres are not added in step S1, but everything else is the same as in Example 1.

[0035] Comparative Example 3 Unlike Example 1, nitrogen tetrahydrogen gas is not introduced in step S2; otherwise, it is the same as Example 1.

[0036] Comparative Example 4 Unlike Example 1, ethylene gas is not introduced in step S2; otherwise, it is the same as Example 1.

[0037] Comparative Example 5 Foamed carbon (pore size 1-5μm, porosity 70-90%, compressive strength 1-10Mpa) was used to replace ZIF-8MOF material.

[0038] Experimental example: 1. Scanning electron microscopy (SEM) test: Depend on Figure 1 As can be seen from the examples, the porous carbon composite material prepared in the examples exhibits a porous structure with a uniform size distribution and a particle size between 5 and 10 μm.

[0039] 2. Physicochemical and button cell tests: 2.1 Physicochemical property testing: The pore volume and pore size of the porous carbon obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to the national standard GB / T 38949-2020 "Determination of Pore Size of Porous Membranes - Standard Particle Method". The specific surface area and tap density were tested according to the national standard GB / T 38823-2020 "Silicon Carbon". The powder resistivity of each porous carbon composite material was tested using a four-probe tester. The test results are shown in Table 1 below.

[0040] 2.2 Button Cell Battery Performance Test: The porous carbon composite materials corresponding to Examples 1-3 and Comparative Examples 1-5 were used as negative electrode materials for lithium-ion batteries to prepare coin cells according to the following method: A binder, conductive agent, and solvent were added to the corresponding porous carbon composite materials, stirred to form a slurry, coated onto copper foil, and dried and rolled to obtain a negative electrode sheet. The binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The ratio of composite material, SP, LA132, and NMP was 80g:15g:15g:300mL. The electrolyte was a solution with LiPF6 as the electrolyte and a concentration of 1.1mol / L. The solvent was a mixture of EC and DEC with a volume ratio of 1:1. The lithium metal sheet was used as the counter electrode, and the separator was a polypropylene (PP) membrane.

[0041] Each button cell was assembled in an argon-filled glove box, and then the following performance tests were performed: Electrochemical performance testing: Electrochemical performance was specifically performed using the Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 2.0V, and the charge / discharge rate was 0.1C. The discharge specific capacity and initial efficiency of the corresponding coin cells were tested. At the same time, the rate performance (1C / 0.1C) and cycle performance (0.1C / 0.1C, 100 cycles) of the corresponding coin cells were also tested. The test results are shown in Table 1. Table 1 As shown in Table 1, the comparative tests of the examples and comparative examples reveal that Examples 1-3 exhibit low powder resistivity, high specific capacity, and superior initial efficiency and rate performance. When the MOF-doped porous carbon prepared in this invention is used as a negative electrode material for lithium-ion batteries, its powder resistivity can be reduced to 1.18-1.49 Ω·cm, its specific capacity can reach 302-340 mAh / g, its initial efficiency can reach 42.1%-47.3%, and its capacity retention after 100 cycles can reach 86.3%-88.9%. Its overall electrochemical performance is significantly better than that of Comparative Example 1 (without MOF), Comparative Example 2 (without metal salt and pore-forming agent), Comparative Example 3 (without non-metallic alkaline gas doping), Comparative Example 4 (without amorphous carbon coating), and Comparative Example 5 (without MOF material), demonstrating a synergistic gain effect. This is because the MOF doping in the examples increases the electronic conductivity and reduces polarization, thus improving rate performance; simultaneously, the high pore size and volume of the MOF material reduces expansion and improves cycle performance.

[0042] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing MOF-doped porous carbon, the method comprising: MOF material, polymer, metal salt and pore-forming agent are mixed and then subjected to oxidative polymerization, carbonization and steam activation in sequence to obtain porous carbon precursor; The porous carbon precursor is sequentially reacted with a non-metallic alkaline gas, a carbon source gas, and a reducing gas to obtain MOF-doped porous carbon.

2. The preparation method according to claim 1, characterized in that, The mass ratio of MOF:polymer solution:metal salt:pore-forming agent is 10-30:1000:1-5:1-5.

3. The preparation method according to claim 1, characterized in that, The oxidative polymerization is carried out at a temperature of 50-100℃ for 1-3 hours. The carbonization temperature is 1100-1300℃, and the time is 1-3 hours; The steam activation temperature is 900-1000℃, the flow rate is 100-500 SCCM, and the time is 60-600 min.

4. The preparation method according to claim 1, characterized in that, The porous carbon precursor reacts with the non-metallic alkaline gas at a temperature of 1200-1500℃, a flow rate of 10-100 SCCM, and a time of 30-300 min. The porous carbon precursor reacts with the carbon source gas at a temperature of 700-900℃, a flow rate of 100-500 SCCM, and a time of 30-300 min. The porous carbon precursor reacts with the reducing gas at a temperature of 500-700℃, a flow rate of 10-100 SCCM, and a time of 30-300 min.

5. The preparation method according to claim 1, characterized in that, The MOF material is selected from one of ZIF-8, MOF-808, ZIF-67, MOF-818, MOF-74, MOF-545 or MIL-101(Cr); The polymer is selected from epoxy resin, acrylic resin, polyurethane or phenolic resin, and the solvent is selected from dibutyl phthalate, ethyl acetate, acetone or cyclohexanone, with a mass concentration of 5-20 wt%. The pore-forming agent is selected from one of polystyrene microspheres, polymethyl methacrylate, or carbamoyl hydrazide. The metal salt is selected from one of the chlorides or nitrates of magnesium, lithium, copper, nickel, or cobalt.

6. The preparation method according to claim 1, characterized in that, The non-metallic alkaline gas is selected from one of dinitrogen tetrahydrogen, phosphine, and ammonia. The carbon source gas is selected from one of methane, ethane, acetylene, and ethylene; The reducing gas is carbon monoxide and / or hydrogen.

7. A MOF-doped porous carbon, prepared by the preparation method according to any one of claims 1-5.

8. The application of MOF-doped porous carbon as described in claim 6 or 7 as a negative electrode material for lithium-ion batteries.

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