Porous carbon composite material and preparation method thereof

Abstract

The invention discloses porous carbon and a preparation method thereof, and the preparation method comprises the following steps: adding a high polymer material, a magnesium-based coupling agent, a cellulose derivative, a heteroatom compound and a carbon nanotube conductive liquid thereof into an alkali solution, mixing, filtering, curing, and activating to obtain a porous carbon precursor; and then raising the temperature to 1500-2000 DEG C, sintering at high temperature, and introducing metal steam for doping to obtain the porous carbon composite material. According to the obtained material, the electronic conductivity and strength of the material are improved through the carbon nanotubes and the metal, the compressive strength is improved, the electronic conductivity of the material is improved through heteroatoms, and the conductivity of the material is improved through the high crystallization strength of cellulose.

Description

Technical Field

[0001] The present invention belongs to the field of functional composite material preparation, in particular to a porous carbon composite material and a preparation method thereof. Background Art

[0002] The porous carbon currently on the market is mainly prepared by carbonization and activation of biomass materials or resin bases. Although its porous structure brings high specific surface area, the characteristics of many defects lead to low initial efficiency and large impedance of the material, and the porous structure itself reduces the compressive ability of the material and reduces the compaction density. Although some researchers have tried to improve electronic conductivity by doping heteroatoms and improve compaction density by morphology control, the improvement in electronic conductivity is limited due to the low doping ratio, and the problem of improving the compressive strength of the material is not touched upon. For example, the sulfur-doped porous carbon disclosed in patent application number CN202010778597.8 has improved electronic conductivity to a certain extent, but the improvement effect is not significant, and there is no improvement in the compressive strength of the material.

[0003] These defects have caused significant restrictions in industrial applications: in the field of lithium-ion batteries, as the core negative electrode material, low electronic conductivity leads to high internal resistance of the battery and large energy loss. The initial efficiency is only 32%-35%, which is difficult to meet the high energy conversion efficiency requirements of new energy vehicle power batteries. The weak compressive resistance makes the material compaction density only 1.1-1.14g / cm 3 , which limits the improvement of the energy density per unit volume of the electrode and restricts the breakthrough in the endurance of power batteries. In the field of supercapacitors, insufficient conductivity limits the improvement of power density and cannot adapt to high-frequency, high-power energy storage scenarios such as rail transit braking energy recovery; at the same time, the material's easy deformation under pressure shortens the cycle life of supercapacitors and increases the maintenance cost of emergency power supplies for industrial equipment. In the field of industrial adsorption and separation, porous carbon is prone to structural collapse in equipment such as high-pressure adsorption towers due to its weak compressive resistance. Its specific surface area increases sharply to 3000m2 under a pressure of 20T. 2 / g or more, resulting in a sharp decline in adsorption performance, making it difficult to stably apply to high-pressure adsorption scenarios such as chemical VOCs recovery and environmental wastewater treatment. In addition, in the industrial production of electrode materials, existing porous carbon is easily broken during the compaction process, resulting in uneven electrode structure and low product yield, which increases the cost of large-scale manufacturing and hinders its efficient application in industrial fields such as energy storage and environmental protection. These problems together constitute the key obstacles to the advancement of porous carbon materials to high-performance, industrial applications. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] In order to improve the electronic conductivity and mechanical strength of porous carbon composite materials, the present invention improves the electronic conductivity and mechanical strength of the material by doping carbon nanotubes and metals into spherical porous carbon; at the same time, a method for preparing the porous carbon composite material is provided.

[0006] The purpose of the present invention is to provide a porous carbon composite material, characterized by being composed of 1-5wt% carbon nanotubes, 1-5wt% metal, and 90-98wt% porous carbon matrix.

[0007] Furthermore, the metal is one or more of metal magnesium, metal lithium, and metal zinc.

[0008] Furthermore, the porous carbon matrix has a spherical pore structure and a specific surface area of ​​≥1600m 2 / g, pore size 2-10nm.

[0009] The present invention also aims to provide a method for preparing a porous carbon composite material, which is characterized by:

[0010] Step S1:

[0011] According to the mass ratio of polymer: magnesium-based coupling agent: cellulose derivative: heteroatom compound: carbon nanotube conductive liquid: alkaline solution = 100:10-30:1-5:1-5:100-300:1000-2000, the polymer, magnesium-based coupling agent, cellulose derivative, heteroatom compound and carbon nanotube conductive liquid are added to the alkaline solution and mixed, and reacted at a temperature of 50-120° C. for 1-6 hours, filtered, and the obtained material was cured at 500-700° C. for 1-6 hours, then heated to 1000-1300° C., and water vapor was introduced and activated at a flow rate of 100-500 ml / min for 30-300 minutes to obtain a porous carbon precursor;

[0012] Step S2:

[0013] The porous carbon precursor is added to a vacuum furnace, heated to 1500-2000°C, evacuated to 0.01-0.1 Pa, and then metal vapor is introduced at a flow rate of 10-50 ml / min for 30-300 minutes, and then cooled to room temperature to obtain a porous carbon composite material.

[0014] Furthermore, the high molecular polymer in step S1 is one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polypropylene chloride or polybutadiene;

[0015] Furthermore, in step S1, the magnesium-based coupling agent is one of distearoyloxyisopropoxy magnesium ester, isopropyl dioleyl acyloxy magnesium ester, bis(dioctyloxypyrophosphate)ethylene magnesium ester or isopropyl distearoyloxy magnesium ester;

[0016] Furthermore, in step S1, the cellulose derivative is one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose phthalate;

[0017] Furthermore, the heteroatom compound is one of ammonia, urea, melamine, dopamine, and pyrrole; the concentration of the carbon nanotube conductive liquid is 1-5 wt%;

[0018] Furthermore, the alkali solution is ethanolamine, N,N-dimethylethanolamine, dimethylamine, 1,6-hexanediamine, and the concentration is 5-20 wt%.

[0019] Furthermore, the metal in step S2 is one of metal magnesium, metal lithium and metal zinc.

[0020] Furthermore, step S2 may also include immersing the porous carbon precursor in molten metal, keeping the temperature at 200-700° C. under inert atmosphere for 30-180 minutes, then taking it out for cooling, acid washing, and drying to obtain the porous carbon composite material.

[0021] Among them, step S1 converts high molecular polymers, cellulose derivatives, etc. into porous carbon skeletons containing heteroatoms and carbon nanotubes through low-temperature mixing reaction, medium-temperature curing carbonization, and high-temperature water vapor activation. Alkali solution (organic amine, such as ethanolamine) provides an alkaline environment to promote mild swelling or degradation of high molecular polymers (such as polyethylene); at the same time, the organic amine itself contains N elements, which can be used as a heteroatom source to initially participate in the system combination. The magnesium-based coupling agent (such as distearoyloxyisopropoxy magnesium ester) plays a "bridge role" by combining one end with the non-polar high molecular polymer through a hydrophobic group (stearoyl), and the other end with a polar group (magnesium ester group) to solve the compatibility problem between the polymer and cellulose, making the system more evenly dispersed. The solubility / dispersibility of cellulose derivatives (such as carboxymethyl cellulose) is improved under alkaline conditions, and their chain structure forms a "template skeleton", providing initial spatial support for the subsequent porous structure; at the same time, their hydroxyl groups can combine with the hydroxyl groups on the surface of carbon nanotubes (or active sites generated after alkali treatment) through hydrogen bonds, assisting the dispersion of carbon nanotubes. Under the synergistic action of coupling agents and cellulose derivatives, carbon nanotubes (1-5wt%) are evenly dispersed in the system, avoiding agglomeration and initially constructing a conductive network. Heteroatom compounds (such as urea and pyrrole) are anchored in the system through hydrogen bonds or chemical reactions (such as the combination of pyrrole's amino group and cellulose's hydroxyl group), reserving the "source" for subsequent heteroatom (N) doping. A uniform multi-component mixed system is formed (polymer, cellulose, carbon nanotubes, and heteroatom compounds are tightly combined through the action of coupling agents and alkali solutions), laying a uniform foundation for the subsequent carbonization and formation of porous structures.

[0022] At temperatures of 500-700°C, polymers (such as polyethylene, melting point approximately 130°C) and cellulose derivatives undergo pyrolysis and carbonization: polymer chains break and dehydrogenate, transforming into amorphous carbon; cellulose derivatives dehydrate and decarboxylate, forming a hydroxyl-rich carbonaceous skeleton. Together, these two components form a preliminary carbon matrix. A magnesium-based coupling agent decomposes at high temperatures, leaving residual magnesium evenly dispersed within the carbon matrix, acting as a catalyst for subsequent activation (promoting pore formation). Heteroatom compounds (such as urea) decompose, releasing nitrogen atoms that replace carbon atoms in the carbon skeleton (or form C-N bonds), creating a preliminary heteroatom doping process. This introduces electron-deficient sites and enhances the conductivity of the carbon matrix. At these temperatures, carbon nanotubes (CNTs) exhibit high chemical stability and are firmly embedded within the carbon matrix, forming a preliminary "CNT-carbon matrix" conductive network. This results in a structurally stable preliminary carbon skeleton, anchoring the CNTs and heteroatoms while removing volatile small molecules (such as water and carbon dioxide) from the system, providing a solid carbonaceous foundation for subsequent high-temperature activation.

[0023] At high temperatures of 1000-1300°C, water vapor acts as an activator to react with the carbon skeleton to produce an oxidative etching reaction. By selectively removing some carbon atoms, a large number of micropores (2-10nm) and mesopores are formed in the carbon matrix, significantly increasing the specific surface area (≥1600m 2 / g). At high temperatures, heteroatoms (N) are further stably doped into the carbon lattice (forming pyridinic N, pyrrolic N, etc.), enhancing the electron conductivity of the carbon matrix (N has a higher electronegativity than C and can introduce free electrons). At high temperatures, the carbon nanotubes and the carbon matrix partially fuse (enhanced interfacial bonding), creating a more continuous conductive network and reducing electron transport resistance. The result is a porous carbon precursor with a spherical pore structure (2-10nm), an ultra-high specific surface area, and containing N heteroatoms and carbon nanotubes, providing abundant pore channels and active sites for subsequent metal doping.

[0024] In step S2, metals (Mg, Li, Zn) are introduced into the porous carbon precursor through metal vapor doping or molten metal impregnation, forming a "carbon-carbon nanotube-metal" composite structure, improving conductivity and mechanical strength. A vacuum environment (0.01-0.1 Pa) lowers the metal evaporation threshold. At high temperatures of 1500-2000°C, metals (such as Li, melting point 180°C; Mg, melting point 650°C) evaporate into atomic-level vapor, which rapidly diffuses through the pores of the porous carbon precursor into the carbon skeleton.

[0025] The metal vapor combines with the defect sites on the carbon skeleton surface (active sites containing N heteroatoms), partially forming metal carbides (such as MgC2) or forming intercalation structures between carbon layers (such as Li embedded in carbon layers); high temperature also promotes the graphitization of the carbon matrix (improving the degree of order), further reducing the resistance to electron transport. The metal is evenly dispersed in the carbon skeleton in the form of atomic or nanoparticles, and cooperates with carbon nanotubes to build a "three-dimensional conductive network", significantly improving the electronic conductivity (the metal itself has excellent conductivity, such as the conductivity of Li is ≈1.1×10 7 S / m).

[0026] Alternatively, a molten metal impregnation method can be used, where the metal (such as Zn, melting point 420°C; Mg, melting point 650°C) melts into a liquid at 200-700°C, and penetrates into the pores with the help of the capillary action of the high porosity of the porous carbon precursor. The temperature is kept high (30-180 minutes) to allow the metal to fully fill the pores. After cooling, the molten metal solidifies into nanoparticles or thin layers, adhering to the pore walls or carbon surface; subsequent pickling (such as dilute hydrochloric acid) can remove excess metal on the surface, retaining only the metal components that are stably bound in the pores. The metal fills the pores in the form of particles / thin layers, which not only avoids clogging the micropores (maintaining a high specific surface area), but also reduces the interface resistance through the "conductive path in the pores" and improves the conductivity. After the molten metal is filled, the "pore support effect" of the carbon skeleton is combined with the "structural reinforcement effect" of the metal, significantly improving the mechanical strength (such as compression resistance) of the composite material.

[0027] A "carbon-carbon nanotube-metal" composite structure is formed through step S2, and the strong interaction between metal and carbon (such as chemical bonding) enhances the connection strength of the carbon skeleton and improves the mechanical properties (flexural and compressive strength) of the composite material.

[0028] Beneficial effects:

[0029] 1. By adding a magnesium-based coupling agent to the polymer material, the carbon nanotubes and metal are coupled to form a network structure during the carbonization process, thereby enhancing the bonding force of the material and improving the strength. The high mechanical strength of the carbon nanotubes and the high electronic conductivity of the metal are utilized to reduce the impedance and improve the compressive strength.

[0030] 2. The formed "carbon-carbon nanotube-metal" composite structure has high mechanical properties. Its heteroatoms improve the electronic conductivity of the material and the strong crystalline strength of cellulose itself further improves the conductivity of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is the SEM image of the porous carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] For numerical ranges herein, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in that stated range is also encompassed within the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0035] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0038] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0039] Example 1

[0040] A method for preparing a porous carbon composite material comprises the following steps:

[0041] Step S1:

[0042] 100 g of polyethylene, 20 g of distearoyloxyisopropoxy magnesium ester, 3 g of carboxymethyl cellulose, 3 g of ammonia water and 300 g of a 1 wt% carbon nanotube conductive liquid were added to 1500 g of a 10 wt% ethanolamine solution, mixed, and reacted at 80° C. for 3 h. The mixture was filtered and cured at 600° C. for 3 h. The temperature was then raised to 1200° C., water vapor was introduced, and activated at a flow rate of 300 ml / min for 150 min to obtain a porous carbon precursor.

[0043] Step S2:

[0044] The porous carbon precursor was added to a vacuum furnace, heated to 1800°C, and evacuated to 0.01 Pa. Then, metal magnesium vapor was introduced at a flow rate of 30 ml / min for 150 minutes to obtain a porous carbon composite material.

[0045] Example 2

[0046] A method for preparing a porous carbon composite material comprises the following steps:

[0047] Step S1:

[0048] 100 g of polypropylene, 10 g of bis(dioctyloxypyrophosphate)ethylene magnesium ester, 1 g of cellulose derivative, 1 g of urea and 100 g of a 1 wt% carbon nanotube conductive liquid were added to 1000 g of N,N-dimethylethanolamine solution, mixed, and reacted at 50° C. for 6 h. The mixture was filtered and cured at 500° C. for 6 h. The temperature was then raised to 1000° C., water vapor was introduced, and activated at a flow rate of 100 ml / min for 300 min to obtain a porous carbon precursor.

[0049] Step S2:

[0050] The porous carbon precursor was added to a vacuum furnace, heated to 1500°C, and evacuated to 0.01 Pa. Metal lithium vapor was then introduced at a flow rate of 10 ml / min for 300 minutes to obtain a porous carbon composite material.

[0051] Example 3

[0052] A method for preparing a porous carbon composite material comprises the following steps:

[0053] Step S1:

[0054] 100 g of polystyrene, 30 g of isopropyl distearoyl magnesium ester, 5 g of hydroxypropyl methylcellulose, 5 g of melamine and 100 g of a 5 wt% carbon nanotube conductive liquid were added to 2000 g of a 10 wt% dimethylamine solution, mixed, and reacted at 120° C. for 1 h. The mixture was filtered and cured at 700° C. for 1 h. The temperature was then raised to 1300° C., steam was introduced, and activated at a flow rate of 100 ml / min for 30 min to obtain a porous carbon precursor.

[0055] Step S2:

[0056] The porous carbon precursor was added to a vacuum furnace, heated to 2000°C, and evacuated to 0.01 Pa. Metal zinc vapor was then introduced at a flow rate of 50 ml / min for 30 minutes to obtain a porous carbon composite material.

[0057] Example 4

[0058] A method for preparing a porous carbon composite material comprises the following steps:

[0059] Step S1: Add 100g of polyethylene, 20g of distearoyloxyisopropoxy magnesium ester, 3g of carboxymethyl cellulose, 3g of ammonia water and 300g of 1wt% carbon nanotube conductive liquid to 1500g of 10wt% ethanolamine solution, react at 80°C for 3h, filter and cure at 600°C for 3h, heat to 1200°C, introduce water vapor (flow rate 300ml / min) and activate for 150min to obtain a porous carbon precursor.

[0060] Step S2: Immerse the porous carbon precursor in molten metal zinc (melting point 420°C), keep it warm at 500°C under argon protection for 60 minutes, take it out and cool it, then pickle it with 5wt% dilute hydrochloric acid for 2 hours, wash it with distilled water until it is neutral, and vacuum dry it at 80°C for 12 hours to obtain a porous carbon composite material.

[0061] Comparative Example 1:

[0062] The difference from Example 1 is that no metallic magnesium vapor is introduced, that is, the porous carbon precursor in step S1 is used as the negative electrode.

[0063] Comparative Example 2:

[0064] The difference from Example 1 is that no carbon nanotube conductive liquid is added in step S1 , and the rest is the same as Example 1.

[0065] Comparative Example 3:

[0066] The difference from Example 4 is that: in step S2, no molten metal infiltration is performed, and the porous carbon precursor in step S1 is directly used as the sample.

[0067] Performance Testing

[0068] 1. Scanning electron microscope (SEM) test:

[0069] The SEM photo of the porous carbon composite material prepared in Example 1 is as follows: Figure 1 As shown by Figure 1 It can be seen that the material has a granular structure with uniform size distribution and the particle size is between 5-10μm.

[0070] 2. Physical and chemical testing and button battery testing:

[0071] 2.1 Physical and chemical performance test:

[0072] The pore volume and pore size of the porous carbons obtained in Examples 1-3 and Comparative Examples 1-3 were tested with reference to the national standard GB / T-38949-2020 “Standard particle method for determination of pore size of porous membranes”;

[0073] The particle size powder compaction density (2T), specific surface area and tap density were tested in accordance with the national standard GB / T-24533-2019 "Graphite for Lithium-ion Battery Graphite Anode Materials";

[0074] The powder conductivity of each porous carbon material was tested using a four-probe tester;

[0075] The above test results are shown in Table 1;

[0076] The pressure-specific surface area method is used to test the compressive resistance of the material, that is, the compressive resistance of the material is determined by applying a certain pressure to cause a change in the specific surface area of ​​the material.

[0077] The test results are shown in Table 3.

[0078] 2.2 Button battery performance test:

[0079] The porous carbon corresponding to Examples 1-3 and Comparative Examples 1-3 was used as the negative electrode material for lithium-ion batteries to prepare button batteries according to the following method:

[0080] A binder, a conductive agent and a solvent were added to each corresponding porous carbon, stirred to make a slurry, coated on a 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), the solvent was NMP, and the usage ratio of metal-doped porous carbon: SP: LA132: NMP was 80g:15g:15g:300mL; the electrolyte was a solution with LiPF6 as the electrolyte with a concentration of 1 mol / L, wherein the solvent was a mixture of EC and DEC with a volume ratio of 1:1; the metal lithium sheet was the counter electrode, and the diaphragm was a polypropylene (PP) film.

[0081] Each button cell was assembled in an argon-filled glove box, and then the following performance tests were performed: Electrochemical performance test: Specifically, the electrochemical performance was performed on a Wuhan Blue Power CT2001A battery tester, with a charge and discharge voltage range of 0.005V to 2.0V and a charge and discharge rate of 0.1C. The discharge specific capacity and initial efficiency of the corresponding button cell were tested. At the same time, the room temperature charging DCR (50% SOC) and cycle performance test (0.1C / 0.1C, 100 weeks) of the corresponding button cell were tested; and the diffusion coefficient of its material was tested by GITT; the test results are shown in Table 2.

[0082] Table 1

[0083]

[0084]

[0085] It can be seen from the data in Table 1 above that the specific capacity and the first efficiency of the porous carbon composite materials prepared in Examples 1-3 of the present application are significantly better than those in Comparative Examples 1-3; it can be seen from the experimental results that: the embodiments improve the electronic and ionic conductivity of the material, reduce polarization, reduce DCR, and improve the specific capacity of the material and its first efficiency; at the same time, the doping of magnesium to form a structurally stable magnesium silicate improves the structural stability of the material and improves the cycle performance.

[0086] Table 2

[0087]

[0088] As can be seen from Table 2, Examples 1-3 have low powder resistivity and high first efficiency. This is because the metal in the examples improves the electronic conductivity of the material, and the pore volume and pore diameter of the material are increased by adding a pore-forming agent to the resin, thereby increasing the specific surface area, improving the liquid absorption capacity of the material, and improving the diffusion coefficient of the material.

[0089] Table 3

[0090]

[0091] It can be seen from Table 3 that after the step pressure is applied, the specific surface area of ​​the embodiment material increases slightly, indicating that the material has strong compressive resistance under high pressure. The reason is that the embodiment material is doped with metal elements to enhance the compressive resistance of the material.

[0092] (4) Soft pack performance test:

[0093] The porous carbon composite materials corresponding to Examples 1-3 and Comparative Examples 1-3 were doped with 90% artificial graphite as negative electrode materials (i.e., negative electrode sheets) and the positive electrode ternary materials (LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2), electrolyte and diaphragm are assembled into a 5Ah soft-pack battery; wherein, the diaphragm is celegard2400, the electrolyte is LiPF6 solution (the solvent is a mixed solution of EC and DEC with a volume ratio of 1:1, and the concentration of LiPF6 is 1.1 mol / L) to prepare the soft-pack battery.

[0094] The following performance tests are performed on each soft pack battery:

[0095] The test conditions for the cycle performance test are: charge and discharge voltage range of 2.5~4.2V, temperature of 25±3.0℃, charge and discharge rate of 1.0C / 1.0C, and cycle number of 500 times; at the same time, the initial DCR of the battery is tested.

[0096] The test conditions for the rate test are:

[0097] The constant current ratio of each soft-pack battery under the 2C condition is tested as follows: 2C constant current capacity / (2C constant current capacity+0.1C constant voltage capacity); the test results are shown in Table 4 below.

[0098] Table 4

[0099] Example Cycle performance retention rate DCR(Ω) Rate performance (constant current ratio) Example 1 285.7 2.34 92.1％ Example 2 279.2 3.26 91.6％ Example 3 292.3 1.78 92.9％ Example 4 281.5 3.78 91.0％ Comparative Example 1 234.5 6.73 88.3％ Comparative Example 2 219.5 5.71 89.3％ Comparative Example 3 232.1 6.12 88.9％

[0100] As can be seen from Table 4, Examples 1-3 have excellent cycle and rate performance. The reason is that the example materials have low impedance and excellent diffusion coefficient, which increases the transmission rate of lithium ions during the charge and discharge process and improves the rate performance.

[0101] By analyzing the results of the examples and comparative examples, it can be concluded that the synergistic effect of metal doping and carbon nanotubes can significantly improve the material properties: the powder compaction density of Examples 1-4 (1.21-1.34 g / cm 3 ), tap density (0.50-0.54g / cm 3 ) are higher than the comparative example (compacted density 1.10-1.14g / cm 3 , tap density 0.33-0.37g / cm 3 ), the powder resistivity (0.77-0.85Ω·cm) is much lower than that of the control example (1.95-2.05Ω·cm), indicating that the conductive network and structural support jointly constructed by the two can enhance the mechanical properties and conductivity.

[0102] The introduction of metal can significantly optimize battery performance. The first-time efficiency (48.3%-53.9%) and discharge specific capacity (279.2-292.3 mAh / g) of Examples 1-4 are significantly higher than those of the comparative example (first-time efficiency 32.5%-35.6%, specific capacity 219.5-234.5 mAh / g). Furthermore, the DCR is lower and the diffusion coefficient is larger, because the metal improves the electron conduction and ion diffusion capabilities, thereby reducing energy loss.

[0103] The material's compressive strength is significantly enhanced: at a pressure of 20T, the specific surface area of ​​the embodiment (2031-2213m 2 / g) is much lower than that of the comparative example (3002-3121m 2 / g), indicating that the metal-filled pores and the carbon nanotube skeleton synergistically inhibit structural collapse and improve high-pressure stability.

[0104] Both metal introduction methods are effective, and the performance of Example 4 (molten metal infiltration) is close to that of Examples 1-3 (metal vapor doping) (e.g., compacted density 1.25 vs 1.28 g / cm 3 , resistivity 0.85vs0.82Ω·cm), indicating that both steam doping and melt infiltration can achieve uniform metal doping and meet performance requirements.

[0105] The present invention optimizes the performance of porous carbon by synergizing carbon nanotubes with metals (magnesium, lithium, zinc, etc., introduced by steam doping or melt infiltration), combined with the effects of magnesium-based coupling agents and cellulose derivatives: reducing resistivity, improving compaction and tap density; enhancing the battery's initial efficiency, specific capacity and cyclability; and improving compressive resistance. Both metal introduction methods are effective and are suitable for batteries, supercapacitors and other fields.

[0106] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0107] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0108] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A porous carbon composite material, characterized in that: The porous carbon consists of 1-5 wt% of carbon nanotubes, 1-5 wt% of metal and 90-98 wt% of porous carbon matrix.

2. The porous carbon composite material according to claim 1, wherein: The metal is one or more of metal magnesium, metal lithium and metal zinc.

3. The porous carbon composite material according to claim 1, wherein: The porous carbon matrix has a spherical pore structure with a specific surface area of ​​≥1600m 2 / g, pore size 2-10nm.

4. A method for preparing a porous carbon composite material, characterized in that: Step S1: According to the mass ratio of polymer: magnesium-based coupling agent: cellulose derivative: heteroatom compound: carbon nanotube conductive liquid: alkaline solution = 100:10-30:1-5:1-5:100-300:1000-2000, the polymer, magnesium-based coupling agent, cellulose derivative, heteroatom compound and carbon nanotube conductive liquid are added to the alkaline solution and mixed, and reacted at a temperature of 50-120° C. for 1-6 hours, filtered, and the obtained material was cured at 500-700° C. for 1-6 hours, then heated to 1000-1300° C., and water vapor was introduced and activated at a flow rate of 100-500 ml / min for 30-300 minutes to obtain a porous carbon precursor; Step S2: The porous carbon precursor is added to a vacuum furnace, heated to 1500-2000°C, evacuated to 0.01-0.1 Pa, and then metal vapor is introduced at a flow rate of 10-50 ml / min for 30-300 minutes, and then cooled to room temperature to obtain a porous carbon composite material.

5. The method for preparing a porous carbon composite material according to claim 4, wherein: The high molecular weight polymer in step S1 is one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polypropylene chloride or polybutadiene.

6. The method for preparing a porous carbon composite material according to claim 4, wherein: In step S1, the magnesium-based coupling agent is one of distearoyloxyisopropoxy magnesium ester, isopropyl dioleyl acyloxy magnesium ester, bis(dioctyloxypyrophosphate)ethylene magnesium ester or isopropyl distearoyloxy magnesium ester.

7. The method for preparing a porous carbon composite material according to claim 4, wherein: In step S1, the cellulose derivative is one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose phthalate; the heteroatom compound is one of ammonia, urea, melamine, dopamine, and pyrrole; and the concentration of the carbon nanotube conductive liquid is 1-5 wt%.

8. The method for preparing a porous carbon composite material according to claim 4, wherein: In step S2, the metal is one of metal magnesium, metal lithium and metal zinc.

9. The method for preparing a porous carbon composite material according to claim 4, wherein: The step S2 may also be to immerse the porous carbon precursor in molten metal, keep it warm at 200-700° C. under inert atmosphere for 30-180 minutes, then take it out, cool it, pickle it, and dry it to obtain the porous carbon composite material.

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