A MOF-pitch-based porous carbon composite material, a preparation method and applications thereof

Abstract

This invention relates to the field of carbon composite materials, specifically providing a MOF-pitch-based porous carbon composite material, its preparation method, and its applications. The preparation method includes the following steps: doping a transition metal oxide and a nitrogen source into a MOF material to obtain a MOF precursor; mixing the MOF precursor with an amine crosslinking agent and oxidized pitch, followed by pre-carbonization and activation to obtain pitch-based porous carbon; and fluorinating the pitch-based porous carbon to obtain the MOF-pitch-based porous carbon composite material. The MOF-pitch-based porous carbon composite material prepared by this method possesses high pore volume, high crush strength, and high initial efficiency, exhibiting excellent electrochemical and electrical properties when used as a negative electrode material for lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of carbon composite material preparation, specifically to a MOF-pitch-based porous carbon composite material, its preparation method, and its application. Background Technology

[0002] Currently, porous carbon materials on the market are mainly made from biomass, resin, or pitch through carbonization and activation. They suffer from the shortcomings of individual material properties. For example, the pore size and pore volume of biomass materials cannot be controlled, affecting the carrying capacity of active substances and resulting in low specific capacity. Resin-based materials have defects such as high self-impedance and poor power performance. Although pitch-based materials have good power performance, they are difficult to pore-create, have small pore size and pore volume, and poor storage performance. The above-mentioned traditional porous carbon materials also suffer from low initial efficiency due to numerous surface defects, non-uniform pore structure, and poor compatibility with electrolytes, further limiting their applications. MOF materials (metal-organic framework materials) are a class of crystalline porous materials formed by the self-assembly of metal ions or metal clusters and organic ligands through coordination bonds. They combine the advantages of inorganic and organic materials, giving them the properties of porosity and large specific surface area, as well as advantages such as low impedance and high power performance. However, they have low crush strength. Therefore, there is an urgent need to develop a porous carbon material that combines high pore volume, high crush strength, and high initial efficiency. Summary of the Invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a MOF-pitch-based porous carbon composite material, its preparation method and application, so as to solve the above-mentioned technical problems.

[0004] One objective of this invention is to provide a method for preparing MOF-pitch-based porous carbon composite materials, the method comprising the following steps: MOF precursors are obtained by doping transition metal oxides with nitrogen sources into MOF materials. The MOF precursor was mixed with an amine crosslinking agent and oxidized asphalt, and then pre-carbonized and activated to obtain the asphalt-based porous carbon. The asphalt-based porous carbon was fluorinated to obtain the MOF-asphalt-based porous carbon composite material.

[0005] Preferably, the mass ratio of the MOF precursor, amine crosslinking agent, and oxidized asphalt is 100:(10~30):(50~100).

[0006] Preferably, the amine crosslinking agent includes any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, m-phenylenediamine, or propylenediamine.

[0007] Preferably, the pre-carbonization is carried out in an inert gas atmosphere, the pre-carbonization temperature is 300~500℃, and the pre-carbonization time is 1~3h; the activation is carried out in a carbon dioxide atmosphere, the activation temperature is 1100~1300℃, and the activation time is 1~3h.

[0008] Preferably, the process of doping the MOF material with a transition metal oxide and a nitrogen source to obtain the MOF precursor includes: The MOF material was immersed in a mixed solution of transition metal oxide and nitrogen source, dispersed evenly, and then spray-dried to obtain the MOF precursor.

[0009] Preferably, the fluorination modification of the pitch-based porous carbon includes: Under pressure of 0.01~100Pa and temperature of 100~200℃, fluorocarbon gas is introduced at a flow rate of 0.01~1L / min, and an electric field is applied to ionize the fluorocarbon gas to generate fluorine free radicals, thereby fluorinating the asphalt-based porous carbon; the fluorination treatment time is 10~120min.

[0010] Preferably, the mass ratio of the MOF material, transition metal oxide, and nitrogen source is 100:(1~5):(1~5); The MOF material includes any one or more of ZIF-8, UiO-66, MIL-101 or MOF-74; The transition metal oxides include CeO2, La2O3, Y2O3, and Pr6O. 11 Any one or more of LaCoO3 or LaMnO3; The nitrogen source includes any one or more of melamine, urea, pyrrole, thiophene, or dopamine.

[0011] Preferably, the fluorocarbon gas includes any one or more of CF4, CCl3F, CCl2F2, or C2F6.

[0012] The second objective of this invention is to provide a MOF-asphalt-based porous carbon composite material, which is prepared by the preparation method described above.

[0013] The third objective of this invention is to provide an application of the MOF-pitch-based porous carbon composite material as described above, which is used to prepare lithium-ion battery anode materials.

[0014] The beneficial effects of this invention include: This invention involves doping MOF materials with transition metal oxides and nitrogen sources. The catalytic effect of transition metal oxides can regulate the orientation and arrangement of the carbon skeleton during subsequent pre-carbonization and activation processes, thereby reducing structural defects in the carbon skeleton. At the same time, nitrogen doping of the composite porous carbon skeleton with nitrogen sources can reduce the impedance and resistivity of MOF-pitch-based porous carbon composite materials, thereby improving the conductivity of porous carbon composite materials and improving rate performance. By combining oxidized bitumen with MOF precursor, the two work synergistically. The MOF precursor has the characteristics of high specific surface area and uniform pore structure, which provides a template for the subsequent formation of nano-micro multi-level pore structure of composite porous carbon skeleton. Oxidized bitumen has the properties of high anisotropy and high compaction density, which can improve the overall compactness of MOF precursor, thereby enhancing the crushing strength of MOF precursor. Amine crosslinking agents can be used to combine MOF precursors with oxidized asphalt to form a three-dimensional network structure. During the pre-carbonization process, the carbon orientation arrangement of the composite porous carbon skeleton can be optimized. During the activation process, the composite porous carbon skeleton can be stably pore-forming, inhibiting the collapse and structural expansion of the composite porous carbon skeleton pores, forming a nano-micro multi-level pore structure, thereby increasing the pore volume of asphalt-based porous carbon and ensuring that asphalt-based porous carbon has high compressive strength. Fluorination modification of pitch-based porous carbon can introduce fluorine elements onto the surface of pitch-based porous carbon, which can improve the compatibility of MOF-pitch-based porous carbon composite material with lithium hexafluorophosphate in electrolyte, thereby improving the first-pass efficiency of MOF-pitch-based porous carbon composite material. The synergistic effect of MOF precursor, oxidized asphalt, amine crosslinking agent and fluorine element in this invention enables MOF-asphalt-based porous carbon composite material to have high pore volume, high crush strength and high first-pass efficiency. Attached Figure Description

[0015] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a SEM image of the MOF-asphalt-based porous carbon composite material prepared in Example 1 of the present invention. Detailed Implementation

[0016] The following description includes certain specific details to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that the embodiments can be implemented without employing one or more of these specific details, but using other methods, components, materials, etc.

[0017] Unless otherwise required by the present invention, throughout the specification and the following claims, the words “comprising” and “including” shall be interpreted in an open-ended, inclusive sense, meaning “including but not limited to”.

[0018] Throughout this specification, the terms "an embodiment," "an embodiment," "a preferred embodiment," or "some embodiments" refer to including, in at least one embodiment, a specific reference element, structure, or feature associated with that embodiment. Therefore, the phrases "in an embodiment," "in a preferred embodiment," or "in some embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. Furthermore, specific elements, structures, or features may be combined in one or more embodiments in any suitable manner.

[0019] One objective of this invention is to provide a method for preparing MOF-pitch-based porous carbon composite materials, the method comprising the following steps: MOF precursors are obtained by doping transition metal oxides with nitrogen sources into MOF materials. The MOF precursor was mixed with an amine crosslinking agent and oxidized asphalt, and then pre-carbonized and activated to obtain the asphalt-based porous carbon. The asphalt-based porous carbon was fluorinated to obtain the MOF-asphalt-based porous carbon composite material.

[0020] Specifically, by doping MOF materials with transition metal oxides and nitrogen sources, the catalytic effect of transition metal oxides can be used to regulate the orientation and arrangement of the carbon skeleton during the subsequent pre-carbonization and activation process, thereby reducing structural defects in the carbon skeleton. At the same time, nitrogen source doping can reduce the impedance and resistivity of MOF-pitch-based porous carbon composite materials, thereby improving the conductivity of porous carbon composite materials and improving rate performance. Specifically, by combining oxidized asphalt with MOF precursor, the two work synergistically. The MOF precursor has the characteristics of high specific surface area and uniform pore structure, which provides a template for the subsequent formation of nano-micro multi-level pore structure of composite porous carbon skeleton. Oxidized asphalt has the properties of high anisotropy and high compaction density, which can improve the overall compactness of MOF precursor, thereby enhancing the crushing strength of MOF precursor. Furthermore, amine crosslinking agents are not only binders in physical mixing, but more importantly, through multiple amino groups in their molecular structure, they form hydrogen bonds with oxygen-containing functional groups on the surface of oxidized asphalt, and simultaneously coordinate with metal clusters in the MOF precursor, thereby connecting the MOF precursor and oxidized asphalt at the molecular level into a three-dimensional network structure. This chemical crosslinking structure is retained and further transformed into an integrated composite porous carbon skeleton during subsequent pre-carbonization and activation processes. Amine crosslinking agents enable the MOF precursor and oxidized asphalt to combine to form a three-dimensional network structure. During pre-carbonization, they can optimize the carbon orientation arrangement of the composite porous carbon skeleton, and during activation, they can stably create pores in the composite porous carbon skeleton, inhibiting pore collapse and structural expansion, forming a nano- to micro-level multi-level pore structure, thereby increasing the pore volume of asphalt-based porous carbon and ensuring that the asphalt-based porous carbon has high compressive strength. Furthermore, by fluorinating the pitch-based porous carbon, the surface defects of the pitch-based porous carbon can be reduced. Introducing fluorine into the surface of the pitch-based porous carbon can improve the compatibility of the MOF-pitch-based porous carbon composite material with lithium hexafluorophosphate in the electrolyte, thereby improving the first-pass efficiency of the MOF-pitch-based porous carbon composite material.

[0021] The synergistic effect of MOF precursor, oxidized asphalt, amine crosslinking agent and fluorine element in this invention enables MOF-asphalt-based porous carbon composite material to have high pore volume, high crush strength and high first-pass efficiency.

[0022] In this invention, the mass ratio of the MOF precursor, amine crosslinking agent, and oxidized asphalt is 100:(10~30):(50~100). When the mass fraction of the MOF precursor is 100, the mass fraction of the amine crosslinking agent ranges from 10 to 30, for example: 10, 15, 20, 25, or 30, etc., and the mass fraction of the oxidized asphalt ranges from 50 to 100, for example: 50, 60, 70, 80, 90, or 100, etc.

[0023] Specifically, when the mass fraction of the amine crosslinking agent is less than 10 parts, it will lead to insufficient crosslinking between the MOF precursor and the oxidized asphalt, resulting in weak three-dimensional network strength. At high temperatures, the pores of the composite porous carbon skeleton are prone to collapse, and the structural stability is poor. When the mass fraction of the amine crosslinking agent is greater than 30 parts, it will lead to excessive crosslinking between the MOF precursor and the oxidized asphalt, resulting in excessive rigidity of the composite porous carbon skeleton. This will easily lead to local stress concentration, cracking, and pulverization, affecting the pore volume and compressive strength of the composite porous carbon skeleton. When the mass fraction is between 10 and 30 parts, the crosslinking density of the three-dimensional network is moderate, which ensures the structural stability of the composite porous carbon skeleton without excessive crosslinking.

[0024] Specifically, when the mass fraction of the oxidized asphalt is less than 50 parts, the coating effect on the MOF precursor is weak, the overall composite porous carbon skeleton is discontinuous, and the structural strength is low. When it is more than 100 parts, the excessive amount of oxidized asphalt causes the pores of the MOF precursor to be blocked, resulting in a decrease in the specific surface area and pore volume of the composite porous carbon skeleton. When it is between 50 and 100 parts, the oxidized asphalt can continuously coat the composite porous carbon skeleton while fully preserving the pore structure of the MOF precursor.

[0025] In this invention, the amine crosslinking agent includes any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, hexanediamine, m-phenylenediamine, or propylenediamine, for example: ethylenediamine, diethylenetriamine, triethylenetetramine, hexanediamine, m-phenylenediamine, propylenediamine, ethylenediamine and diethylenetriamine, ethylenediamine and triethylenetetramine, ethylenediamine and hexanediamine, ethylenediamine and m-phenylenediamine, ethylenediamine and propylenediamine, diethylenetriamine and triethylenetetramine, diethylenetriamine and hexanediamine, diethylenetriamine and m-phenylenediamine, diethylenetriamine and propylenediamine, triethylenetetramine and hexanediamine, triethylenetetramine and m-phenylenediamine, triethylenetetramine and propylenediamine, hexanediamine and m-phenylenediamine, hexanediamine and propylenediamine, or m-phenylenediamine and propylenediamine, without limitation herein.

[0026] Specifically, the ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, m-phenylenediamine, and propylenediamine undergo cross-linking reactions with the MOF precursor and oxidized pitch through amino groups to construct a stable three-dimensional network structure. Simultaneously, nitrogen doping of the composite porous carbon skeleton can be achieved during the activation process, synergistically improving the electrochemical performance of the MOF-pitch-based porous carbon composite material. The amine cross-linking agents can be used alone or in combination; different amine cross-linking agents can synergistically cross-link, increasing the three-dimensional network density and enhancing the structural stability of the composite porous carbon skeleton.

[0027] In this invention, the pre-carbonization is carried out in an inert gas atmosphere, and the pre-carbonization temperature is 300~500℃, for example: 300℃, 400℃ or 500℃; the inert gas includes any one or more of nitrogen, helium and argon, for example: nitrogen, helium, argon, nitrogen and helium, nitrogen and argon, helium and argon, or nitrogen and helium and argon.

[0028] Specifically, when the pre-carbonization temperature is below 300°C, the volatiles in the MOF precursor, amine crosslinking agent, and oxidized asphalt are not completely removed, resulting in insufficient structural strength of the pre-carbonized product. This makes the carbon skeleton prone to collapse and deformation during subsequent activation. When the temperature is above 500°C, the organic components in the MOF precursor, amine crosslinking agent, and oxidized asphalt undergo excessive pyrolysis, causing small molecules to escape rapidly and in large quantities, impacting the composite porous carbon skeleton and causing it to crack. This is not conducive to subsequent activation and pore formation. When the pre-carbonization temperature is controlled at 300~500°C, the composite porous carbon skeleton can be initially solidified, and the carbon orientation arrangement of the composite porous carbon skeleton can be standardized.

[0029] In this invention, the pre-carbonization time is 1 to 3 hours, for example: 1 hour, 2 hours or 3 hours.

[0030] Specifically, by controlling the pre-carbonization time to 1-3 hours, the MOF precursor, amine crosslinking agent, and organic components in oxidized asphalt can be fully pyrolyzed at 300-500°C, and small molecule volatiles in the system can be completely removed, thus initially solidifying the composite porous carbon skeleton.

[0031] In this invention, the activation is carried out under a carbon dioxide atmosphere, and the activation temperature is 1100~1300℃, for example: 1100℃, 1200℃ or 1300℃, etc. Specifically, the activation temperature is controlled at 1100~1300℃, and carbon dioxide is introduced as an activation gas. The carbon dioxide etches and creates pores on the composite porous carbon skeleton, opening up the closed pores to form a nano-micro multi-level pore structure. This increases the specific surface area and pore richness of the pitch-based porous carbon, thereby increasing the pore volume. This ensures that the pore structure is fully formed and avoids excessive ablation and collapse of the carbon skeleton.

[0032] In this invention, the activation time is 1 to 3 hours, for example: 1 hour, 2 hours or 3 hours, etc. Specifically, by controlling the activation time to 1-3 hours, the pre-carbonized product can be fully activated at 1100-1300°C to form pitch-based porous carbon with a nano-micron hierarchical pore structure.

[0033] In this invention, the process of doping a transition metal oxide and a nitrogen source into a MOF material to obtain a MOF precursor includes: The MOF material was immersed in a mixed solution of transition metal oxide and nitrogen source, dispersed evenly, and then spray-dried to obtain the MOF precursor.

[0034] Specifically, MOF materials are soaked and adsorbed with transition metal oxides and nitrogen sources, which allow the metal oxides and nitrogen sources to be uniformly attached to the pores and surface of the MOF materials. The transition metal oxides play a catalytic role in the pre-carbonization and activation process, which can regulate the carbon orientation arrangement of the composite porous carbon skeleton and reduce the internal structural defects of the composite porous carbon skeleton, thereby synergistically improving the conductivity of the porous carbon composite material. During the high-temperature treatment, the nitrogen source allows nitrogen atoms to be embedded in the composite porous carbon skeleton, providing more conductive sites for the composite porous carbon skeleton, improving the conductivity of the MOF-pitch-based porous carbon composite material, and thus improving the rate performance.

[0035] In this invention, the fluorination modification of the pitch-based porous carbon includes: Under pressure of 0.01~100Pa and temperature of 100~200℃, fluorocarbon gas is introduced at a flow rate of 0.01~1L / min, and an electric field is applied to ionize the fluorocarbon gas to generate fluorine free radicals, thereby fluorinating the asphalt-based porous carbon; the fluorination treatment time is 10~120min.

[0036] Specifically, by fluorinating pitch-based porous carbon with fluorine radicals generated from the ionization of fluorocarbon gas, fluorine functional groups can be introduced onto the surface of pitch-based porous carbon to form carbon-fluorine bonds, reducing surface defects. On the one hand, fluorine has good compatibility with lithium hexafluorophosphate in the electrolyte. On the other hand, carbon-fluorine bonds can reduce the surface energy of pitch-based porous carbon, improve hydrophobicity, reduce side reactions between MOF-pitch-based porous carbon composite materials and electrolytes, and promote the formation of a solid electrolyte interface film on the surface of MOF-pitch-based porous carbon composite materials to reduce lithium ion consumption. This can improve the initial efficiency and storage performance of MOF-pitch-based porous carbon composite materials.

[0037] In this invention, the pressure of the fluorination modification is 0.01~100 Pa, for example: 0.01 Pa, 1 Pa, 5 Pa, 50 Pa or 100 Pa, etc., and is not limited here; Specifically, when the pressure is below 0.01 Pa, the gas density is too low, and the electric field cannot ionize the fluorocarbon gas to produce sufficient fluorine radicals, resulting in insufficient fluorination modification. When the pressure is above 100 Pa, the gas density is too high, and the particles collide frequently, making it impossible to ionize stable and uniform fluorine radicals. This can also damage the structure of the composite porous carbon skeleton and lead to uneven surface modification. When the pressure is between 0.01 and 100 Pa, the fluorine radical activity is moderate, the modification is uniform, and it is not easy to damage the composite porous carbon skeleton, thus balancing the modification effect and structural integrity.

[0038] In this invention, the fluorination modification temperature is 100~200℃, for example: 100℃, 150℃ or 200℃, etc., and is not limited here; Specifically, when the fluorination modification temperature is below 100°C, the fluorine radical reactivity is insufficient, and carbon-fluorine bonds cannot be formed on the surface of the composite porous carbon skeleton, resulting in poor modification effect. When the temperature is above 200°C, the composite porous carbon skeleton is prone to thermal decomposition, which destroys the structure of the composite porous carbon skeleton. When the fluorination modification temperature is controlled at 100~200°C, the fluorination modification of the composite porous carbon skeleton can be sufficient and the structure can be stable.

[0039] In this invention, the flow rate of the fluorinated modified fluorocarbon gas is 0.01~1L / min, for example: 0.01L / min, 0.05L / min, 0.1L / min, 0.5L / min or 1L / min, etc., and is not limited here; Specifically, when the flow rate of the fluorinated modified fluorocarbon gas is below 0.01 L / min, the flow rate of the fluorocarbon gas is too small, the supply of active fluorine radicals is insufficient, the fluorination modification is incomplete, and the fluorocarbon gas in the low-temperature plasma reactor is slowly renewed, and reaction byproducts are easy to accumulate, affecting the uniformity of modification. When the flow rate is above 1 L / min, the flow rate of the fluorocarbon gas is too fast, the residence time is short, and the fluorocarbon gas does not have enough time to fully dissociate into active fluorine radicals, resulting in a decrease in modification efficiency. When the flow rate of the fluorinated modified fluorocarbon gas is 0.01~1 L / min, the supply and discharge of fluorocarbon gas reach a balance, and the modification is uniform, sufficient, and efficient.

[0040] In this invention, the fluorination modification time is 10~120 min, for example: 10 min, 30 min, 60 min, 90 min or 120 min, etc., and is not limited here.

[0041] Specifically, when the fluorination modification time is less than 10 min, the reaction between fluorine radicals and the surface of the composite porous carbon skeleton is insufficient, resulting in a low degree of fluorination modification. When the time is greater than 120 min, the electric field can easily cause excessive etching of the composite porous carbon skeleton, destroying the hierarchical pore structure. When the fluorination modification time is controlled to be between 10 and 120 min, the fluorination modification of the composite porous carbon skeleton can be sufficient, while protecting the composite porous carbon skeleton structure from excessive etching.

[0042] In this invention, the mass ratio of the MOF material, transition metal oxide, and nitrogen source is 100:(1~5):(1~5). When the mass fraction of the MOF material is 100, the mass fraction of the transition metal oxide ranges from 1 to 5, for example: 1, 2, 3, 4, or 5, etc., which is not limited here. The mass fraction of the nitrogen source also ranges from 1 to 5, for example: 1, 2, 3, 4, or 5, etc., which is not limited here.

[0043] Specifically, when the mass fraction of transition metal oxide is less than 1 part, it cannot provide enough catalytic sites for the MOF precursor, and cannot fully catalyze the carbon orientation arrangement of the composite porous carbon framework in the subsequent pre-carbonization and activation, resulting in many internal structural defects in the composite porous carbon framework; when the mass fraction of transition metal oxide is more than 5 parts, the excess transition metal oxide will cause particle agglomeration, and the agglomerated particles will cover the pore openings and channels of the MOF precursor, which will reduce the pore volume of the MOF-asphalt-based porous carbon composite material. When the mass fraction of nitrogen source is less than 1 part, the number of active groups provided is insufficient, making it impossible to fully achieve nitrogen doping of the composite porous carbon skeleton during subsequent pre-carbonization and activation processes. This results in insufficient formation of active sites and inadequate improvement of the material's conductivity. When the mass fraction of nitrogen source is greater than 5 parts, excess nitrogen source will remain on the surface of the composite porous carbon skeleton. Its chemical activity will trigger side reactions, increase surface defects, and cause the composite porous carbon skeleton to collapse easily. At the same time, it will affect ion transport efficiency and reduce the cycle stability and electrochemical performance of MOF-pitch-based porous carbon composite materials.

[0044] In this invention, the MOF material includes any one or more of ZIF-8, UiO-66, MIL-101, and MOF-74, for example: ZIF-8, UiO-66, MIL-101, MOF-74, ZIF-8 and UiO-66, ZIF-8 and MIL-101, ZIF-8 and MOF-74, UiO-66 and MIL-101, UiO-66 and MOF-74, MIL-101 and MOF-74, ZIF-8 and UiO-66 and MIL-101, ZIF-8 and UiO-66 and MOF-74, or ZIF-8 and MIL-101 and MOF-74, etc., and is not limited herein.

[0045] Specifically, ZIF-8, UiO-66, MIL-101, and MOF-74 all have the characteristics of large specific surface area and rich pore structure, which can provide excellent porous carbon skeleton templates for the preparation of MOF-asphalt-based porous carbon composite materials, achieve stable loading of transition metal oxides and nitrogen sources, and synergistically construct high-strength, high-pore-volume, and high-conductivity composite porous carbon skeletons with oxidized asphalt and amine crosslinking agents. Different MOF materials can be mixed to complement each other's advantages and further improve specific surface area, pore volume, and structural stability.

[0046] In this invention, the transition metal oxides include CeO2, La2O3, Y2O3, and Pr6O. 11 Any one or more of LaCoO3, LaMnO3, for example: CeO2, La2O3, Y2O3, Pr6O 11LaCoO3, LaMnO3, CeO2 and La2O3, CeO2 and Y2O3, CeO2 and Pr6O 11 CeO2 with LaCoO3, CeO2 with LaMnO3, La2O3 with Y2O3, La2O3 with Pr6O 11 La2O3 and LaCoO3, La2O3 and LaMnO3, Y2O3 and Pr6O 11 Y₂O₃ with LaCoO₃, Y₂O₃ with LaMnO₃, Pr₆O 11 With LaCoO3, Pr6O 11 With LaMnO3, LaCoO3 with LaMnO3, CeO2 with La2O3 with Y2O3, La2O3 with Y2O3 with Pr6O 11 Or Y2O3 and Pr6O 11 Similar to LaCoO3, etc., without limitation.

[0047] Specifically, CeO2, La2O3, Y2O3, and Pr6O 11 LaCoO3 and LaMnO3 both exhibit high-temperature stability and can effectively regulate the carbon orientation arrangement of the composite porous carbon skeleton during pre-carbonization and activation processes, reducing structural defects and improving the mechanical strength and electrical conductivity of the composite porous carbon skeleton. The transition metal oxides can be used alone or in combination, and different transition metal oxides can exert a synergistic catalytic effect to comprehensively improve the electrical conductivity and mechanical strength of the porous carbon composite material.

[0048] In this invention, the nitrogen source includes any one or more of melamine, urea, pyrrole, thiophene, and dopamine, such as: melamine and urea, melamine and pyrrole, melamine and thiophene, melamine and dopamine, urea and pyrrole, urea and thiophene, urea and dopamine, pyrrole and thiophene, pyrrole and dopamine, or thiophene and dopamine, melamine and urea and pyrrole, urea and pyrrole and thiophene, or pyrrole and thiophene and dopamine, etc., without limitation.

[0049] Specifically, melamine, urea, pyrrole, thiophene, and dopamine can all introduce nitrogen atoms into the composite porous carbon framework during the pre-carbonization and activation process, thereby improving the conductivity of the porous composite material. Different nitrogen sources can be used individually or in combination to achieve synergistic regulation of doping mode and active sites, thereby optimizing the conductivity of the porous carbon composite material.

[0050] In this invention, the fluorocarbon gas includes any one or more of CF4, CCl3F, CCl2F2, and C2F6, for example: CF4, CCl3F, CCl2F2, C2F6, CF4 and CCl3F, CF4 and CCl2F2, CF4 and C2F6, CCl3F and CCl2F2, CCl3F and C2F6, or CCl2F2 and C2F6, which are not limited herein.

[0051] Specifically, CF4, CCl3F, CCl2F2, and C2F6 can be excited to form highly active fluorine radicals and / or chlorine radicals under the action of low-temperature plasma, which can fluorinate or modify the surface of pitch-based porous carbon, improve the compatibility with lithium hexafluorophosphate in the electrolyte, and thus improve the first-pass efficiency and storage performance of MOF-pitch-based porous carbon composite materials.

[0052] The second objective of this invention is to provide a MOF-asphalt-based porous carbon composite material, which is prepared by the preparation method described above.

[0053] The third objective of this invention is to provide an application of MOF-asphalt-based porous carbon composite material, which is used to prepare lithium-ion battery anode materials.

[0054] Example 1 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Soak 100g of MOF-74 material in 100g of Y2O3 aqueous solution with a mass concentration of 5wt%, then add 100g of dopamine aqueous solution with a mass concentration of 5wt% and disperse evenly, then spray dry to obtain MOF precursor.

[0055] The mass ratio of MOF-74, Y2O3, and dopamine is 100:5:5.

[0056] S2: Mix 100g of MOF precursor with 30g of triethylenetetramine and 100g of oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air in the tube and heat to 500℃ for pre-carbonization for 1 hour. Then, heat to 1300℃ and introduce carbon dioxide gas for activation for 1 hour to obtain asphalt-based porous carbon.

[0057] The mass ratio of the MOF precursor, triethylenetetramine, and oxidized asphalt is 100:30:100.

[0058] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 100 Pa, heat to 200 °C, and introduce CF4 gas into the low-temperature plasma reactor at a flow rate of 1 L / min to fluorinate the pitch-based porous carbon for 10 min to obtain MOF-pitch-based porous carbon composite material.

[0059] Figure 1 This is a SEM image of the MOF-pitch-based porous carbon composite material prepared in this embodiment. Figure 1 It can be seen that the MOF-asphalt-based porous carbon composite material exhibits a granular structure with a uniform size distribution and a particle size between 5 and 10 μm.

[0060] Example 2 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Soak 100g of MIL-101 material in 100g of 1wt% La2O3 aqueous solution, then add 100g of 1wt% melamine aqueous solution and disperse evenly, then spray dry to obtain MOF precursor.

[0061] The mass ratio of MIL-101, La2O3, and melamine is 100:1:1.

[0062] S2: Mix 100g of MOF precursor with 10g of diethylenetriamine and 50g of oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air from the tube and heat to 300℃ for pre-carbonization for 3h. Then, heat to 1100℃ and introduce carbon dioxide gas for activation for 3h to obtain asphalt-based porous carbon.

[0063] The mass ratio of the MOF precursor, diethylenetriamine, and oxidized asphalt is 100:10:50.

[0064] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 0.01 Pa, heat to 100 °C, and introduce CF4 gas into the low-temperature plasma reactor at a flow rate of 0.01 L / min to fluorinate the pitch-based porous carbon for 120 min to obtain MOF-pitch-based porous carbon composite material.

[0065] Example 3 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Soak 100g of ZIF-8 material in 100g of CeO2 aqueous solution with a mass concentration of 3wt%, then add 100g of urea aqueous solution with a mass concentration of 3wt% and disperse evenly, then spray dry to obtain MOF precursor.

[0066] The mass ratio of ZIF-8, CeO2, and urea is 100:3:3.

[0067] S2: Mix 100g MOF precursor with 20g ethylenediamine and 80g oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air from the tube and heat to 400℃ for pre-carbonization for 2 hours. Then, heat to 1200℃ and introduce carbon dioxide gas for activation for 2 hours to obtain asphalt-based porous carbon.

[0068] The mass ratio of the MOF precursor, ethylenediamine, and oxidized asphalt is 100:20:80.

[0069] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 10 Pa, heat to 150 °C, and introduce CF4 gas into the low-temperature plasma reactor at a flow rate of 0.05 L / min to fluorinate and modify the pitch-based porous carbon. After fluorination modification for 60 min, MOF-pitch-based porous carbon composite material is obtained.

[0070] Example 4 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Immerse 100g of UiO-66 material in 100g of Pr6O with a mass concentration of 2wt%. 11 The solution was then mixed with 100g of a 2wt% pyrrole aqueous solution and dispersed evenly. The mixture was then spray-dried to obtain the MOF precursor.

[0071] Among them, UiO-66 and Pr6O 11 The mass ratio of pyrrole is 100:2:2.

[0072] S2: Mix 100g MOF precursor with 15g hexamethylenediamine and 60g oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air in the tube and heat to 500℃ for pre-carbonization for 1 hour. Then, heat to 1200℃ and introduce carbon dioxide gas for activation for 2 hours to obtain asphalt-based porous carbon.

[0073] The mass ratio of the MOF precursor, hexamethylenediamine, and oxidized asphalt is 100:15:60.

[0074] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 50 Pa, heat to 200 °C, and introduce CCl3F gas into the low-temperature plasma reactor at a flow rate of 0.1 L / min to fluorinate the pitch-based porous carbon for 100 min to obtain MOF-pitch-based porous carbon composite material.

[0075] Example 5 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Soak 100g of MOF-74 material in 100g of 4wt% LaCoO3 aqueous solution, then add 100g of 4wt% thiophene aqueous solution and disperse evenly, then spray dry to obtain MOF precursor.

[0076] The mass ratio of MOF-74, LaCoO3, and thiophene is 100:4:4.

[0077] S2: Mix 100g MOF precursor with 25g m-phenylenediamine and 70g oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air in the tube and heat to 500℃ for pre-carbonization for 1 hour. Then, heat to 1300℃ and introduce carbon dioxide gas for activation for 1 hour to obtain asphalt-based porous carbon.

[0078] The mass ratio of the MOF precursor, m-phenylenediamine, and oxidized asphalt is 100:25:70.

[0079] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 1 Pa, heat to 100 °C, and introduce CCl2F2 gas into the low-temperature plasma reactor at a flow rate of 0.01 L / min to fluorinate the pitch-based porous carbon for 120 min to obtain MOF-pitch-based porous carbon composite material.

[0080] Example 6 This embodiment provides a method for preparing MOF-pitch-based porous carbon composite material, the preparation method including the following steps: S1: Soak 100g of MOF-74 material in 100g of 5wt% LaMnO3 aqueous solution, then add 100g of 5wt% dopamine aqueous solution and disperse evenly, then spray dry to obtain MOF precursor.

[0081] The mass ratio of MOF-74, LaMnO3, and dopamine is 100:5:5.

[0082] S2: Mix 100g MOF precursor with 30g propylenediamine and 90g oxidized asphalt evenly and transfer to a tube furnace. First, introduce nitrogen inert gas to purge the air from the tube and heat to 400℃ for pre-carbonization for 2 hours. Then, heat to 1200℃ and introduce carbon dioxide gas for activation for 2 hours to obtain asphalt-based porous carbon.

[0083] The mass ratio of the MOF precursor, propylenediamine, and oxidized asphalt is 100:30:90.

[0084] S3: Transfer the pitch-based porous carbon to a low-temperature plasma reactor, evacuate to 5 Pa, heat to 100 °C, and introduce C2F6 gas into the low-temperature plasma reactor at a flow rate of 0.05 L / min to fluorinate and modify the pitch-based porous carbon. After fluorination modification for 50 min, MOF-pitch-based porous carbon composite material is obtained.

[0085] Example 7 The difference between this embodiment and Embodiment 1 is that the MOF material is changed to ZIF-8, while the rest of the preparation methods and parameters remain the same as in Embodiment 1.

[0086] Example 8 The difference between this embodiment and Embodiment 1 is that the MOF material is changed to MIL-101, while the rest of the preparation methods and parameters remain the same as in Embodiment 1.

[0087] Example 9 The difference between this embodiment and Example 1 is that the transition metal oxide is changed to CeO2, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0088] Example 10 The difference between this embodiment and Example 1 is that the nitrogen source is changed to melamine, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0089] Example 11 The difference between this embodiment and Example 1 is that the amount of amine crosslinking agent is adjusted to 10g and the amount of oxidized asphalt is 50g, so that the mass ratio of MOF precursor, triethylenetetramine, and oxidized asphalt in step 2 is 100:10:50. The rest of the preparation methods and parameters are the same as in Example 1.

[0090] Comparative Example 1 The difference between this comparative example and Example 1 is that no transition metal oxide is added in step 1, while the rest of the preparation methods and parameters are the same as in Example 1.

[0091] Comparative Example 2 The difference between this comparative example and Example 1 is that no MOF material is added in step 1, while the rest of the preparation methods and parameters are the same as in Example 1.

[0092] Comparative Example 3 The difference between this comparative example and Example 1 is that no oxidized asphalt is added in step 2, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0093] Comparative Example 4 The difference between this comparative example and Example 1 is that step S3 is omitted, while the remaining preparation methods and parameters remain the same as in Example 1.

[0094] Comparative Example 5 The difference between this comparative example and Example 1 is that no amine crosslinking agent is added in step 2, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0095] Performance testing 1. Physicochemical performance testing: The pore volume and pore size of the porous carbon composite materials obtained in Examples 1-11 and Comparative Examples 1-4 were tested in accordance with the national standard GB / T 21650.2-2022 "Determination of Pore Volume and Pore Size Distribution of Activated Carbon". The specific surface area was tested according to the national standard GB / T 19587-2022 "Determination of Specific Surface Area of ​​Solid Materials by Gas Adsorption BET Method"; The resistivity of each porous carbon composite material was measured using a four-probe tester. The compressive strength of porous carbon composite material was tested using a compressive strength tester. The material was compressed at a speed of 5 mm / min until it broke. The pressure changed instantaneously, and the critical maximum stress at which the material was destroyed was recorded as the compressive strength. The test results are shown in Table 1 below.

[0096] Table 1

[0097] 2. Button cell battery performance test: Using the porous carbon composite materials corresponding to Examples 1-11 and Comparative Examples 1-4 as negative electrode materials for lithium-ion batteries, coin cells were prepared 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 then dried and rolled to obtain the negative electrode sheet. The binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The ratio of porous carbon composite material, SP, LA132, and NMP was 70g:15g:15g:300mL. The electrolyte was a LiPF6 solution with a concentration of 1mol / L, wherein the solvent was a mixture of EC and DEC with a volume ratio of 1:1. A lithium metal sheet was used as the counter electrode, and a polypropylene (PP) membrane was used as the separator. Each coin cell was assembled in an argon-filled glove box, and then the following performance tests were performed: Electrochemical performance testing: Electrochemical performance was specifically tested using the Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 1.5V, and the charge / discharge rate was 0.1C. The specific capacity and initial efficiency of the corresponding coin cell were tested. At the same time, the rate performance (1C / 0.1C) and storage performance of the corresponding coin cell were tested (the specific capacity of the coin cell under full charge was A1, and after being placed at 45℃ for 24 hours and cycling once, the specific capacity A2 was tested. The storage performance was calculated as A2 / A1×100%).

[0098] The test results are shown in Table 2 below.

[0099] Table 2

[0100] As can be seen from Tables 1 and 2, the MOF-pitch-based porous carbon composite materials prepared in Examples 1-11 of this invention possess a reasonable pore size distribution, large pore volume, high specific surface area, high crush strength, and low resistivity. When used as a negative electrode material for lithium-ion batteries, they exhibit high specific capacity, high initial efficiency, excellent rate performance, and high storage performance. This is because: the MOF material serves as the structural template for the MOF-pitch-based porous carbon composite material, providing a uniform initial pore structure and framework support; the transition metal oxides are uniformly dispersed in the matrix, catalyzing the carbon orientation arrangement of the composite porous carbon framework during pre-carbonization and activation, thus increasing the material's specific surface area and pore structure richness; the nitrogen source doping of the composite porous carbon framework during pre-carbonization and activation improves the electrochemical performance of the MOF-pitch-based porous carbon composite material; and the amine crosslinking agent achieves crosslinking and curing with the MOF precursor and oxidized pitch during pre-carbonization. During the activation process, the composite porous carbon skeleton is stably pore-forming, inhibiting pore collapse and structural expansion, and improving the crushing strength of the composite porous carbon skeleton. On the other hand, nitrogen doping is introduced into the composite porous carbon skeleton, which improves the conductivity and electrochemical performance of MOF-pitch-based porous carbon composite materials. Oxidized pitch enhances the compactness of MOF precursors by coating them, thereby increasing the compaction density and crushing strength of MOF-pitch-based porous carbon composite materials. Fluorination modification of pitch-based porous carbon introduces fluorine functional groups on the surface of pitch-based porous carbon, forming carbon-fluorine bonds, which improves the compatibility of MOF-pitch-based porous carbon composite materials with lithium hexafluorophosphate in the electrolyte, thereby improving the first-pass efficiency and storage performance. The complementary advantages and synergistic effects of each component ensure that MOF-pitch-based porous carbon composite materials have high pore volume and high crushing strength, while also exhibiting excellent conductivity and electrochemical performance.

[0101] As can be seen from Tables 1 and 2, in Example 1 of this invention, MOF-74 was used as the MOF material. A MOF precursor was prepared by mixing MOF-74, Y2O3, and dopamine in a mass ratio of 100:5:5. The MOF precursor, triethylenetetramine, and oxidized asphalt were mixed in a mass ratio of 100:30:100. The pre-carbonization temperature was 500℃ and the pre-carbonization time was 1h. The activation temperature was 1300℃ and the activation time was 1h. At the same time, the asphalt-based porous carbon was fluorinated and modified in a low-temperature plasma reactor under the conditions of 100Pa pressure, 200℃ temperature, CF4 gas flow rate of 1L / min and treatment time of 10min. The components and process conditions were well matched, and the prepared MOF-asphalt-based porous carbon composite material showed the best crush strength and first-time efficiency.

[0102] Comparing Examples 1 with Examples 4, 7, and 8, it can be seen that after replacing MOF-74 with UiO-66, ZIF-8, and MIL-101 respectively, the crushing strength of the materials decreased from 242 MPa in Example 1 to 221 MPa, 205 MPa, and 208 MPa. Except for a slight increase in Example 8, the specific surface area in Examples 4 and 7 decreased to varying degrees from 1929 m² / g. This is because the thermal stability and pore regularity of the framework of ZIF-8 and UiO-66 are not as good as those of MOF-74, and they are more prone to structural collapse during pre-carbonization and activation, resulting in insufficient formation of nano- to micro-level multi-level pore structures, which in turn affects the specific surface area and crushing strength. On the other hand, MIL-101 has a rich original pore structure and high porosity retention after activation, but its own framework crushing strength is low, resulting in an increase in specific surface area but a lower crushing strength.

[0103] A comparison of Example 1 with Examples 3, 4, 5, 6, and 9 shows that CeO2 and Pr6O2 were used respectively. 11 After replacing Y₂O₃ with LaCoO₃ and LaMnO₃, the specific surface area of ​​the material decreased from 1929 m² / g in Example 1 to 1867 m² / g, 1804 m² / g, 1911 m² / g, 1898 m² / g, and 1703 m² / g, respectively, and the compressive strength decreased from 242 MPa to 230 MPa, 221 MPa, 237 MPa, 231 MPa, and 207 MPa, respectively. This is due to the substitution of Y₂O₃ with CeO₂ and Pr₆O₃. 11 The catalytic pore-forming ability of LaCoO3 is weaker than that of Y2O3. During the pre-carbonization and activation process, it is difficult to fully catalyze the carbon orientation arrangement of the composite porous carbon framework, and it is impossible to fully construct the nano-micro multi-level pore structure, resulting in a limited increase in specific surface area. Although LaCoO3 and LaMnO3 have high catalytic activity, their atomic compatibility with MOF precursors is not as good as that of Y2O3. Moreover, LaMnO3 has insufficient high-temperature stability, and its catalytic effect decreases during the activation process, making it difficult to fully catalyze the carbon orientation arrangement of the composite porous carbon framework.

[0104] A comparison of Examples 1 with Examples 2, 3, 4, 5, and 10 shows that after replacing dopamine with melamine, urea, pyrrole, thiophene, and melamine respectively as the nitrogen source, the crushing strength decreased from 242 MPa to 212 MPa, 230 MPa, 221 MPa, 237 MPa, and 211 MPa, respectively. Except for Example 10, which showed an increased specific surface area, the specific surface area of ​​the other examples was lower than that of Example 1. The corresponding specific capacity, initial efficiency, rate performance, and storage performance were all lower than those of Example 1. This is because melamine undergoes significant degradation at high temperatures. During the decomposition process, a large amount of gas is released rapidly. Although the number of pores and the specific surface area increase, the carbon skeleton pore walls become thinner and the overall structure becomes looser. The mechanical stability of the composite porous carbon skeleton decreases, resulting in a reduction in crush strength and electrochemical performance. The nitrogen doping uniformity of urea, pyrrole, and thiophene and their interface modification effect on the carbon skeleton are not as good as those of dopamine, making it difficult to construct a stable and efficient conductive network structure. This leads to an increase in irreversible capacity and a decrease in ion transport efficiency, making the mechanical stability and electrochemical performance of the composite porous carbon skeleton inferior to that of Example 1.

[0105] A comparison of Example 1 and Example 11 shows that after reducing the amount of triethylenetetramine and oxidized asphalt, the crushing strength of the material decreased from 242 MPa to 204 MPa. The corresponding specific capacity, initial efficiency, rate performance, and storage performance were all lower than those of Example 1. This is because the reduced amount of triethylenetetramine leads to insufficient cross-linking between the MOF precursor and the oxidized asphalt, making it impossible to form a stable three-dimensional cross-linked network structure. During the activation process, the composite porous carbon skeleton is prone to pore collapse, resulting in a decrease in pore volume. The reduced amount of oxidized asphalt weakens its coating and densification support for the MOF precursor, making it impossible to form a dense and continuous composite porous carbon skeleton. The mechanical support capacity is insufficient, and the conductive network is discontinuous, leading to a simultaneous decrease in the crushing strength and conductivity of the material.

[0106] As can be seen from the comparison between Example 1 and Examples 2, 4, 5, and 6, when fluorinating the pitch-based porous carbon, the compressive strength of the material deteriorated to varying degrees and the resistivity increased after using different pressures, reaction temperatures, gas flow rates, processing times, and types of fluorocarbon gases. The specific capacity, initial efficiency, rate performance, and storage performance were all lower than those of Example 1. This is because when the fluorination modification parameters deviate from the optimal conditions, either the fluorination modification is insufficient or the composite porous carbon skeleton structure collapses, resulting in uneven distribution of fluorine groups on the material surface. This leads to an increase in side reactions between the MOF-pitch-based porous carbon composite material and the electrolyte, and a decrease in initial efficiency.

[0107] A comparison of Example 1 and Comparative Example 1 shows that without the introduction of transition metal oxides, the pore volume of the material is reduced from 0.99 cm³ in Example 1. 3 / g decreased to 0.87cm 3The specific surface area decreased from 1929 m² / g to 1518 m² / g, the crushing strength decreased from 242 MPa to 167 MPa, and the resistivity decreased from 3.48 Ω. cm increased to 6.89Ω The specific capacity decreased from 354.3 mAh / g to 256.1 mAh / g, and the initial efficiency decreased from 56.3% to 44.1%, with significant reductions in both rate performance and storage performance. This is due to the lack of catalytic action from transition metal oxides, which fails to fully catalyze the carbon orientation arrangement of the composite porous carbon framework during pre-carbonization and activation, resulting in insufficient activation and pore formation, and a decrease in pore volume. Simultaneously, the internal structural defects of the composite porous carbon framework increase, interfacial impedance increases, mechanical stability weakens, and crush strength decreases, leading to a significant deterioration in the material's conductivity and electrochemical performance.

[0108] A comparison of Example 1 and Comparative Example 2 shows that when MOF material is not used as the matrix, the pore volume of the material is reduced from 0.99 cm³ in Example 1. 3 / g decreased to 0.75cm 3 The specific surface area decreased from 1929 m² / g to 1419 m² / g, the compressive strength decreased from 242 MPa to 188 MPa, and the resistivity decreased from 3.48 Ω. cm increased to 5.78Ω The specific capacity decreased from 354.3 mAh / g to 269.2 mAh / g, and the initial efficiency decreased from 56.3% to 46.4%, with rate performance and storage performance significantly lower than in Example 1. This is because the lack of MOF material as a template prevents the material from constructing a nano- to micro-level porous structure, resulting in insufficient ion transport channels and decreased pore volume. At the same time, without MOF material to provide stable framework support, the carbon framework structure is loose, with poor mechanical stability and a significant reduction in crush strength, which in turn leads to a significant deterioration in the material's conductivity and electrochemical performance.

[0109] As can be seen from the comparison between Example 1 and Comparative Example 3, without the addition of oxidized asphalt, the pore volume of the material decreased from 0.99 cm³ / g in Example 1 to 0.92 cm³ / g; the crushing strength decreased from 242 MPa to 143 MPa; the resistivity increased from 3.48 Ω·cm to 8.34 Ω·cm; the specific capacity decreased from 354.3 mAh / g to 287.9 ​​mAh / g; the initial efficiency decreased from 56.3% to 42.1%; the rate performance decreased from 84.6% to 65.3%; and the storage performance decreased from 94.9% to 86.2%. This is because oxidized asphalt has high anisotropy and high compaction density, which improves the compactness of MOF precursors and thus enhances their crush strength. Its absence will cause MOF precursors to lack effective coating and reinforcement, making them prone to pore collapse and skeleton loosening during precarbonization and activation, resulting in a decrease in pore volume. At the same time, it is impossible to form a continuous and dense composite carbon skeleton, resulting in insufficient mechanical support, a significant reduction in crush strength, and further a decrease in electrical conductivity and electrochemical performance.

[0110] A comparison of Example 1 and Comparative Example 4 shows that without plasma fluorination modification, the resistivity decreased from 3.48 Ω. cm increased to 4.81Ω The discharge specific capacity decreased from 354.3 mAh / g to 292.7 mAh / g, and the initial efficiency decreased from 56.3% to 40.2%, with significant declines in both rate performance and high-temperature storage performance. This is because the asphalt-based porous carbon was not plasma-fluorinated, making it impossible to introduce fluorine functional groups onto the material surface. This resulted in decreased compatibility between the electrolyte and the material surface, increased electrolyte side reactions, increased interfacial impedance, and reduced lithium-ion transport efficiency.

[0111] As can be seen from the comparison between Example 1 and Comparative Example 5, without the addition of amine crosslinking agents, the pore volume and crush strength of the material deteriorated significantly. The pore volume decreased from 0.99 cm³ / g in Example 1 to 0.71 cm³ / g in Comparative Example 5; the crush strength decreased from 242 MPa in Example 1 to 128 MPa in Comparative Example 5; the resistivity increased from 3.48 Ω·cm to 7.92 Ω·cm; the specific capacity decreased from 354.3 mAh / g to 241.5 mAh / g; the initial efficiency decreased from 56.3% to 41.8%; the rate performance decreased from 84.6% to 63.7%; and the storage performance decreased from 94.9% to 81.5%. This is because amine crosslinking agents are the key to the stable combination of MOF precursor and oxidized asphalt to form a three-dimensional network structure. Their absence prevents the two from forming a chemically crosslinked three-dimensional network, resulting in only a simple physical mixing. During the pre-carbonization and activation process, interface separation easily occurs, leading to pore collapse and a decrease in pore volume. The oxidized asphalt cannot exert its high compaction density advantage, and the crush strength decreases sharply.

[0112] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing MOF-pitch-based porous carbon composite material, characterized in that, The preparation method Includes the following steps: MOF precursors are obtained by doping transition metal oxides with nitrogen sources into MOF materials. The MOF precursor was mixed with an amine crosslinking agent and oxidized asphalt, and then pre-carbonized and activated to obtain the asphalt-based porous carbon. The asphalt-based porous carbon was fluorinated to obtain the MOF-asphalt-based porous carbon composite material.

2. The method for preparing MOF-pitch-based porous carbon composite material according to claim 1, characterized in that, The mass ratio of the MOF precursor, amine crosslinking agent, and oxidized asphalt is 100:(10~30):(50~100).

3. The method for preparing MOF-pitch-based porous carbon composite material according to claim 1, characterized in that, The amine crosslinking agent includes any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, m-phenylenediamine, or propylenediamine.

4. The method for preparing MOF-pitch-based porous carbon composite material according to claim 1, characterized in that, The pre-carbonization is carried out in an inert gas atmosphere at a temperature of 300-500°C for 1-3 hours. The activation is carried out in a carbon dioxide atmosphere at a temperature of 1100-1300°C for 1-3 hours.

5. The method for preparing MOF-pitch-based porous carbon composite material according to claim 1, characterized in that, The method of doping MOF materials with transition metal oxides and nitrogen sources to obtain MOF precursors includes: The MOF material was immersed in a mixed solution of transition metal oxide and nitrogen source, dispersed evenly, and then spray-dried to obtain the MOF precursor.

6. The method for preparing MOF-pitch-based porous carbon composite material according to claim 1, characterized in that, The fluorination modification of the asphalt-based porous carbon includes: Under pressure of 0.01~100Pa and temperature of 100~200℃, fluorocarbon gas is introduced at a flow rate of 0.01~1L / min, and an electric field is applied to ionize the fluorocarbon gas to generate fluorine free radicals, thereby fluorinating the asphalt-based porous carbon; the fluorination treatment time is 10~120min.

7. The method for preparing MOF-pitch-based porous carbon composite material according to claim 5, characterized in that, The mass ratio of the MOF material, transition metal oxide, and nitrogen source is 100:(1~5):(1~5). The MOF material includes any one or more of ZIF-8, UiO-66, MIL-101 or MOF-74; The transition metal oxides include CeO2, La2O3, Y2O3, and Pr6O. 11 Any one or more of LaCoO3 or LaMnO3; The nitrogen source includes any one or more of melamine, urea, pyrrole, thiophene, or dopamine.

8. The method for preparing MOF-pitch-based porous carbon composite material according to claim 6, characterized in that, The fluorocarbon gas includes any one or more of CF4, CCl3F, CCl2F2, or C2F6.

9. A MOF-pitch-based porous carbon composite material, characterized in that, The MOF-asphalt-based porous carbon composite material was prepared using the preparation method described in any one of claims 1 to 8.

10. The application of the MOF-pitch-based porous carbon composite material as described in claim 9, characterized in that, The MOF-asphalt-based porous carbon composite material is used to prepare lithium-ion battery anode materials.

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