Coal liquefaction residue-based composite carbon fiber, method for preparing the same, and carbon fiber negative electrode

Abstract

The present application relates to the technical field of chemical engineering and material cross, and especially relates to a coal liquefaction residue-based composite carbon fiber, a preparation method thereof and a carbon fiber negative electrode; the method comprises the following steps: obtaining an extract by extracting coal liquefaction residue, and obtaining the composite carbon fiber by carbonizing the extract after spinning. The preparation method solves the problem of difficult spinning of the coal liquefaction residue extract, and the extract and the spinning aid are added to each other to synergistically prepare the fiber raw yarn with uniform diameter distribution and stable framework, while realizing the resource utilization of the coal liquefaction residue and reducing the post-treatment and discharge of the coal liquefaction residue.

Description

A coal liquefaction residue-based composite carbon fiber, its preparation method, and carbon fiber anode. Technical Field

[0001] This invention relates to the field of interdisciplinary technology of chemical engineering and materials science, and in particular to a coal liquefaction residue-based composite carbon fiber, its preparation method, and a carbon fiber anode. Background Technology

[0002] Carbon fiber, as a widely used inorganic fiber, has excellent properties, low density, and high strength. It is a functional fiber material that is widely used in various fields of military and civilian industries, such as aircraft, shipbuilding, automobile manufacturing, wind power generation, and fuel cells.

[0003] On the one hand, the biggest bottleneck facing my country's carbon fiber industry is the excessively high production cost. Finding low-cost, high-quality carbon sources has significant research value and application prospects. On the other hand, direct coal liquefaction is one of the important ways to efficiently and cleanly convert coal into clean fuels and high-value chemicals. However, the direct coal liquefaction process generates coal liquefaction residue, which accounts for about 30 wt% of the total raw coal. As the main coal liquefaction waste, it has high carbon, ash, and sulfur content, making it difficult to achieve efficient and clean utilization and thus preventing its large-scale application to date. At the same time, the coal liquefaction process involves high-temperature catalytic cracking and other reactions, resulting in coal residue containing more cracking products than coal, which are more toxic to the environment. There is an urgent need in the market for a method to utilize coal liquefaction residue as a resource. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a coal liquefaction residue-based composite carbon fiber, its preparation method, and a carbon fiber anode, in order to solve at least one of the problems in the prior art, namely, the difficulty in utilizing coal liquefaction residue as a resource and the high difficulty in utilizing carbon fiber as a resource.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] A method for preparing a composite carbon fiber anode material based on coal liquefaction residue includes: extracting coal liquefaction residue to obtain an extract, spinning the extract, and then carbonizing the extract to obtain composite carbon fiber.

[0007] Preferably, the preparation method includes:

[0008] Step 1: Extract the coal liquefaction residue to obtain the extract;

[0009] Step 2: Prepare a spinning solution by mixing the coal liquefaction residue extract with a polymer spinning aid;

[0010] Step 3: Spin the spinning solution to obtain fiber precursors;

[0011] Step 4: The fiber precursor is pre-oxidized and carbonized to obtain composite carbon fiber.

[0012] Preferably, the polymeric spinning aid includes any one of polyacrylonitrile, polyvinylpyrrolidone, and polystyrene.

[0013] Preferably, the preparation of the spinning solution in step 2 includes: dissolving coal liquefaction residue extract and polymeric spinning aid in a strongly polar solvent to prepare the spinning solution.

[0014] Preferably, the mass-to-volume ratio of the mixture of coal liquefaction residue extract, polymeric spinning aid, and strong polar solvent is 1:2.5-4 g / ml.

[0015] Preferably, the mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 10wt% to 75wt%, and more preferably, 65wt% to 75wt%.

[0016] Preferably, the polymeric spinning aid is selected from polyacrylonitrile or polyvinylpyrrolidone, and the pre-oxidation in step 4 includes: heating to 260°C to 290°C in air or oxygen atmosphere at a heating rate of 4°C / min to 6°C / min, and holding at that temperature for 1.5h to 3h.

[0017] Preferably, the polymeric spinning aid is polystyrene, and the pre-oxidation in step 4 includes: heating to 145°C to 155°C at a heating rate of 4°C / min to 6°C / min in an air or oxygen atmosphere, and holding at that temperature for 1.5h to 3h.

[0018] A coal liquefaction residue-based composite carbon fiber, prepared using the above method, has a diameter of 259 nm-539 nm.

[0019] A coal liquefaction residue-based composite carbon fiber anode, prepared using the above-described method, exhibits an electrode specific capacitance of 157.3 F·g. -1 ~246.7 F·g -1 .

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] (1) By setting the mass ratio of coal liquefaction residue extract and polymer spinning aid in the fiber raw material, the present invention can prepare carbon fiber raw material yarn with an addition amount of 10wt% to 75wt% of coal liquefaction residue extract, which has good spinnability. The carbon fiber prepared therefrom is used as electrode material and is superior to or close to the sample prepared without adding residue extract. At the same time, it realizes the resource utilization of coal liquefaction residue and reduces the post-treatment and discharge of coal liquefaction residue.

[0022] (2) In this invention, the extract adheres to the surface of the polymer spinning aid through interaction, which solves the problem that the extract is not spun due to insufficient molecular weight. At the same time, it improves the surface properties of the polymer spinning aid and reduces the occurrence of agglomeration. The two work together to produce fiber filaments with uniform diameter distribution and stable framework.

[0023] (3) Although the carbon fibers prepared by this invention exhibit mutual fusion at the nanoscale, they are still complete carbon fiber sheets at the macroscale. On this basis, KOH activation is carried out to create pores, improve the fiber surface structure and pore size distribution, and increase the rate of charged particles entering and exiting the fiber, thus exhibiting its double-layer capacitance characteristics.

[0024] (4) The specific capacitance of the carbon fiber prepared by this invention is 157.3 F·g. -1 ~246.7 F·g -1 change.

[0025] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0026] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0027] Figure 1 is a schematic diagram of the coal liquefaction principle in one embodiment of the present invention;

[0028] Figure 2 is a flowchart of a method for preparing raw material yarn by spinning in one embodiment of the present invention;

[0029] Figure 3a is a SEM image of the fiber precursor prepared in Example 1 of the present invention;

[0030] Figure 3b is a magnified SEM image of the fiber precursor prepared in Example 1 of the present invention;

[0031] Figure 4a is a SEM image of the fiber precursor prepared in Example 2 of the present invention;

[0032] Figure 4b is a magnified SEM image of the fiber precursor prepared in Example 2 of the present invention;

[0033] Figure 5a is a SEM image of the fiber precursor prepared in Example 3 of the present invention;

[0034] Figure 5b is a magnified SEM image of the fiber precursor prepared in Example 3 of the present invention;

[0035] Figure 6 shows the FTIR analysis results of the coal liquefaction residue and coal liquefaction residue extract of the present invention;

[0036] Figure 7 shows the FTIR analysis of the fiber precursors prepared in Examples 1-3 of this invention;

[0037] Figure 8a is a SEM image of the carbon fibers prepared in Example 1 of the present invention;

[0038] Figure 8b is a magnified SEM image of the carbon fibers prepared in Example 1 of the present invention;

[0039] Figure 8c is a SEM image of the carbon fibers prepared in Example 2 of the present invention;

[0040] Figure 8d is a magnified SEM image of the carbon fibers prepared in Example 2 of the present invention;

[0041] Figure 8e is a SEM image of the carbon fibers prepared in Example 3 of the present invention;

[0042] Figure 8f is a magnified SEM image of the carbon fibers prepared in Example 3 of the present invention;

[0043] Figure 9 is a SEM image of the carbonized fiber in Example 9 of the present invention;

[0044] Figure 10 is a SEM image of the fiber precursor of Comparative Example 2 of the present invention;

[0045] Figure 11 is a SEM image of the fiber precursor of Comparative Example 5 of the present invention;

[0046] Figure 12 is a SEM image of the fiber precursor of Comparative Example 6 of the present invention;

[0047] Figure 13 is a SEM image of the carbonized fiber of Comparative Example 13 of the present invention.

[0048] Figure 14 is a SEM image of the fiber precursor prepared in Comparative Example 14 of the present invention.

[0049] Figure Labels

[0050] Metering pump 1; syringe 2; spinning solution zone 3; nozzle 4; receiving screen 5; high voltage power supply 6; capillary tube 401. Detailed Implementation

[0051] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0052] The coal liquefaction process involves a series of complex physical and chemical changes, which can remove more than 85% of sulfur and the vast majority of nitrogen. The liquefaction products, comprising 50% of the raw material mass, can replace petroleum products as a high-calorific-value, low-pollution fuel or, after separation, as an important chemical raw material. However, most pollutants and impurities remain in the coal liquefaction residue, which comprises 20%–30% of the raw material mass. These pollutants and impurities undergo complex physical and chemical changes to generate substances with even more complex physicochemical properties, increasing the difficulty of separating and utilizing the coal liquefaction residue, as shown in Figure 1.

[0053] The high-boiling-point organic matter in coal (molecular weight greater than 5000) is catalytically cracked to produce liquefied oil, gas, coal char, and asphaltene; among them, coal char and some asphaltene enter the coal liquefaction residue; the low-boiling-point organic matter in coal directly constitutes liquefied oil and gas; and the inert ash in coal enters the coal liquefaction residue.

[0054] C1 is the main body of high-boiling-point organic matter, C2 is the main body of low-boiling-point organic matter, and C3 is inert ash.

[0055] The inventors discovered that coal liquefaction residue mainly consists of asphaltene containing aromatic structures, heavy oil without aromatic structures, and inert ash. The aromatic asphaltene and the non-aromatic heavy oil can be separated by solvent extraction and inert ash, and the average molecular weight of the two components is between 1000 and 2000. This indicates that coal liquefaction residue contains more aromatic compounds, and its composition differs significantly from that of coal. Furthermore, due to its smaller molecular weight and more stable structure, it is difficult to undergo catalytic cracking treatment like coal. Simultaneously, the similar physical properties of the main components in coal liquefaction residue make physical separation difficult. Additionally, the enrichment of impurity elements in coal liquefaction residue places higher demands on the toxicity resistance and service life of catalysts for further catalytic decomposition. Moreover, the presence of impurities and toxic elements as organic compounds makes the separation and harmless treatment of the components of coal liquefaction residue particularly challenging.

[0056] To address the difficulties in processing and utilizing coal liquefaction residues in existing technologies, this invention proposes a method for preparing coal liquefaction residue-based composite carbon fiber materials:

[0057] The coal liquefaction residue is extracted to obtain an extract, which is then spun and carbonized to obtain composite carbon fibers.

[0058] On the one hand, the inventors discovered that the average molecular weight of coal liquefaction residue extract is between 1,000 and 2,000, which does not meet the molecular weight range required for conventional spinning raw materials. As a result, the spun products have poor mechanical properties and are difficult to form and use for making carbon fibers. By setting the mass ratio of coal liquefaction residue extract and polymeric spinning aid in the fiber raw material, it is possible to prepare carbon fiber raw material yarn with an addition amount of 10wt% to 75wt% of coal liquefaction residue extract, thereby realizing the resource utilization of coal liquefaction residue and reducing the post-treatment and discharge of coal liquefaction residue.

[0059] On the other hand, the inventors discovered that coal liquefaction residue extracts with an average molecular weight between 1,000 and 2,000 can effectively improve the morphology of carbon fibers prepared using a single polymeric spinning aid as a spinning raw material, and improve the problems of agglomeration and uneven fiber diameter distribution.

[0060] This invention discloses a method for preparing composite carbon fiber based on coal liquefaction residue, comprising: extracting coal liquefaction residue to obtain an extract, spinning the extract and then carbonizing it to obtain composite carbon fiber.

[0061] Specifically, it includes the following steps:

[0062] Step 1: Extract the coal liquefaction residue to obtain the extract;

[0063] Step 2: Prepare a spinning solution by mixing the coal liquefaction residue extract with a polymer spinning aid;

[0064] Step 3: Spin the spinning solution to obtain fiber precursors;

[0065] Step 4: The fiber precursor is pre-oxidized and carbonized to obtain composite carbon fiber.

[0066] Specifically, in order to improve the extraction effect, step 1 includes crushing and sieving the coal liquefaction residue before extraction.

[0067] Specifically, the coal liquefaction residue is screened through a 200-mesh sieve.

[0068] Specifically, in order to remove moisture, the coal liquefaction residue after crushing and screening is vacuum dried.

[0069] Specifically, in order to retain heavy oil and asphaltene in the coal liquefaction residue and reduce the risk of spontaneous combustion of some volatile components in the coal liquefaction residue, it is vacuum dried at 60℃~80℃ for 4h~24h.

[0070] Understandably, the lack of oxygen in a vacuum environment greatly reduces the risk of spontaneous combustion of volatile components.

[0071] Specifically, a mixture of acetone and carbon disulfide is used as the extraction solvent.

[0072] It should be noted that the coal liquefaction residue extract after extraction has had its ash residue removed and is mainly composed of asphaltene containing aromatic structures and heavy oil without aromatic structures.

[0073] Preferably, a volume ratio of acetone to carbon disulfide of 1:1 can achieve good selectivity and high extraction rate for coal liquefaction residue extracts with an average molecular weight of less than 2000.

[0074] Specifically, a Soxhlet extractor is used to extract coal liquefaction residue, and the residue is allowed to stand for 5–120 minutes.

[0075] Specifically, during the extraction of coal liquefaction residue, the mass-to-volume ratio of coal liquefaction residue to extraction solvent is 1:5 to 60 g / ml.

[0076] Specifically, step 1 also includes: removing the solvent from the extract of coal liquefaction residue using a rotary evaporator to obtain coal liquefaction residue extract.

[0077] Specifically, in step 2, the coal liquefaction residue extract and the polymeric spinning aid are dissolved in a strongly polar solvent to prepare the spinning solution.

[0078] Specifically, the highly polar solvent is N,N-dimethylformamide.

[0079] Specifically, the mass-to-volume ratio of the mixture of coal liquefaction residue extract, polymeric spinning aid, and strongly polar solvent is 1:2.5–4 g / ml. If the mass-to-volume ratio of the mixture to the strongly polar solvent is lower than 1:2.5 g / ml, the fibers become too dispersed and difficult to collect during spinning due to the decrease in solute and increase in solvent. If the mass-to-volume ratio of the mixture to the strongly polar solvent is higher than 1:4 g / ml, the fibers hardly disperse during spinning due to the increase in solute and decrease in solvent, and there is a risk of tube blockage after a period of time.

[0080] Specifically, the mass-to-volume ratio of the mixture of coal liquefaction residue extract, polymeric spinning aid, and strongly polar solvent is: 1:2.5 g / ml, 1:2.6 g / ml, 1:2.7 g / ml, 1:2.8 g / ml, 1:2.9 g / ml, 1:3.0 g / ml, 1:3.1 g / ml, 1:3.2 g / ml, 1:3.3 g / ml, 1:3.4 g / ml, 1:3.5 g / ml, 1:3.6 g / ml, 1:3.7 g / ml, 1:3.8 g / ml, 1:3.9 g / ml, and 1:4.0 g / ml.

[0081] The mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymer spinning aid is 10wt% to 75wt%. Carbon fiber raw material yarn with an addition amount of 10wt% to 75wt% of coal liquefaction residue extract is prepared, realizing the resource utilization of coal liquefaction residue and reducing the post-treatment and emission of coal liquefaction residue.

[0082] It should be noted that the coal liquefaction residue extract adheres to the surface of the polymer spinning aid through interaction, which solves the problem that the extract itself is too small to be spun. When the coal liquefaction residue extract is co-soluble with the polymer spinning aid, hydrogen bonding and benzene ring conjugation effects will occur. This allows the coal liquefaction residue extract to interact with the polymer spinning aid molecules in the spinning solution stage and be drawn into one-dimensional nanofibers under a high voltage electric field.

[0083] Preferably, the mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 65wt% to 75wt%. Carbon fibers prepared from spinning raw materials within this range can effectively improve the capacitance performance of supercapacitors.

[0084] Specifically, in step 2, the mass percentages of the coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid are: 65wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, and 75wt%.

[0085] Specifically, the polymeric spinning aid in step 2 includes any one of polyacrylonitrile, polyvinylpyrrolidone, and polystyrene. Compared to using polyacrylonitrile, polyvinylpyrrolidone, or polystyrene as the sole spinning raw material to prepare carbon fibers, using polyacrylonitrile, polyvinylpyrrolidone, or polystyrene as polymeric spinning aids, along with coal liquefaction residue extract, to prepare carbon fibers effectively improves the problems of uneven fiber diameter distribution and ellipsoidal fiber structure, resulting in a more uniform fiber arrangement.

[0086] It should be noted that the coal liquefaction residue extract improved the surface properties of the polymer spinning aid and reduced the occurrence of agglomeration. The two worked synergistically to produce fiber precursors with uniform diameter distribution and stable framework.

[0087] Preferably, the polymeric spinning aid in step 2 is polyacrylonitrile; using polyacrylonitrile as the polymeric spinning aid and spinning carbon fiber with coal liquefaction residue extract, and then using the carbon fiber as an electrode, its specific capacitance is close to that of the carbon fiber electrode prepared by spinning with polyacrylonitrile as the only spinning raw material.

[0088] It should be noted that the carbon fibers prepared by spinning polyacrylonitrile and coal liquefaction residue extract can still maintain a uniform long nanofiber structure (length range given) under high-temperature carbonization treatment. During electrode use: the micropore structure generated during KOH activation is more uniformly distributed, and the optimal pore structure distribution is ensured, resulting in more active sites per unit area of ​​electrode surface, which improves the exchange rate of electrolyte particles at the electrode-electrolyte interface, thus having the largest specific capacitance.

[0089] Specifically, when preparing the spinning solution, the dissolution temperature of the polymeric spinning aid and the coal liquefaction residue extract is 60℃~80℃.

[0090] Preferably, water bath heating is used in the preparation of the spinning solution.

[0091] Specifically, the process of preparing the spinning solution includes ultrasonic-assisted dispersion, which ensures that the polymer spinning aid and the coal liquefaction residue extract are completely dissolved.

[0092] Preferably, the solute is dispersed for 1 to 8 hours under ultrasonic assistance at 25 kHz to 130 kHz to ensure complete dissolution.

[0093] Specifically, the spinning method in step 3 includes electrospinning, which involves transferring the spinning solution into a syringe and spinning on a high-voltage electrospinning machine. A relatively stable jet is obtained by adjusting the positive and negative voltage and the injection speed, as shown in Figure 2.

[0094] The high-voltage electrostatic spinning machine consists of a metering pump 1, a syringe 2 controlled by the metering pump 1, a spinning solution zone 3 at the bottom of the syringe 2, a nozzle 4 connected to the spinning solution zone 3, a receiving screen 5 for receiving the spun yarn, and a high-voltage power supply 6. A high-voltage power supply 6 applies a high-voltage electric field between the nozzle 4 and the receiving screen 5. The electric field force applied between the nozzle nozzle and the receiving screen 5 acts in the opposite direction to the surface tension of the spinning solution, thus generating an outward force on the surface of the hemispherical droplet. As the electric field gradually increases, the same charges in the solution are forced to accumulate on the surface of the droplet. The electric field generated by the surface charge of the droplet causes the droplet at the nozzle to gradually change from a hemispherical shape to a cone shape (Taylor cone). At the same time, a capillary tube 401 is provided inside the nozzle 4. When the electric field is large enough, the jet is ejected from the surface of the droplet through the capillary tube 401. The jet is then accelerated and elongated by the electric field force. Meanwhile, the volatile solvent begins to evaporate, creating a jet stream. The diameter of the jet stream decreases as the solvent evaporates, and the viscosity of the jet increases.

[0095] As the jet leaves the substrate region near the droplet surface and enters the next region, it disperses due to the repulsive force of the charges on the jet surface, forming many tiny fibers of similar diameter that fall onto the receiving screen, resulting in a thin film material with a nanofiber structure. The final fiber diameter depends on the charge per unit length and the amount of fibers formed by the jet dispersion.

[0096] It should be noted that the spinning process is mainly affected by the molecular weight of the solute, the concentration of the spinning solution, the injection speed of the syringe, and the strength of the high-voltage electric field: the molecular weight of the solute affects the viscosity and surface tension of the spinning solution; the concentration of the spinning solution affects the shrinkage rate of the fiber after forming; the injection speed of the syringe affects the fiber diameter and the spray distance, which in turn affects the dispersibility; the strength of the high-voltage electric field affects the formation of the Taylor cone, which affects the fiber dispersion and forming.

[0097] The inventors discovered that because the average molecular weight of coal liquefaction residue extract is between 1000 and 2000, its structure is relatively regular and its crystallinity is high, making it impossible to spin and form fibers, thus hindering the preparation of carbon fibers. Therefore, they introduced 25wt%–90wt% of polymeric spinning aid and 10wt%–75wt% of coal liquefaction residue extract as a mixed solute in the spinning solution, which improved the difficulty of spinning and forming coal liquefaction residue extract alone. At the same time, the amount of polymeric spinning aid used was reduced, lowering the cost of carbon fiber preparation. This also enabled the resource utilization of coal liquefaction residue.

[0098] Specifically, when polyacrylonitrile is selected as the polymer spinning aid, in order to meet the spinning requirements, the parameters of the high-voltage electrospinning machine are set as follows: negative pressure range of -3.5 to -3kV; positive pressure range of 12kV to 12.5kV; and ejection speed of 0.12mm / min to 0.13mm / min.

[0099] Specifically, when polyvinylpyrrolidone is selected as the polymer spinning aid, in order to meet the spinning requirements, the parameters of the high-voltage electrospinning machine are set as follows: negative pressure range of -4.5 to -4kV; positive pressure range of 13kV to 13.5kV; and ejection speed of 0.12mm / min to 0.13mm / min.

[0100] Specifically, when polystyrene is selected as the polymer spinning aid, in order to meet the spinning requirements, the parameters of the high-voltage electrospinning machine are set as follows: negative pressure range of -4.5 to -4kV; positive pressure range of 13kV to 13.5kV; and ejection speed of 0.17mm / min to 0.18mm / min.

[0101] It should be noted that the syringe injection speed affects the fiber diameter and spray distance of the spun yarn, which in turn affects the spinning dispersion: if the syringe injection speed is too low, the injection distance will be too short, resulting in uneven fiber dispersion; if the syringe injection speed is too high, the jet dispersion time will be too short and the density will be too high, which will also lead to uneven fiber dispersion; if the positive and negative pressure difference is too small, the high voltage electric field strength will be too weak, affecting the formation of Taylor cone and affecting fiber dispersion and shaping; if the positive and negative pressure difference is too large, the high voltage electric field strength will be too strong, causing excessive fiber dispersion and reducing the yarn take-up rate.

[0102] Specifically, the polymeric spinning aid is selected from polyacrylonitrile or polyvinylpyrrolidone. The pre-oxidation in step 4 includes: heating to 260℃~290℃ in an air or oxygen atmosphere at a heating rate of 4℃ / min~6℃ / min, and holding at that temperature for 1.5h~3h.

[0103] Specifically, polystyrene is selected as the polymeric spinning aid, and the pre-oxidation in step 4 includes: heating to 145℃~155℃ in an air or oxygen atmosphere at a heating rate of 4℃ / min~6℃ / min, and holding at that temperature for 1.5h~3h.

[0104] It should be noted that pre-oxidation is a dehydrogenation stabilization process under the action of oxygen. The fibers obtained through spinning will lose hydrogen and undergo molecular bonding. If the pre-oxidation rate is too fast or the temperature is too high, the carbon fiber morphology will collapse, while if the pre-oxidation is too slow, the ineffective reaction time will be prolonged. Therefore, it is necessary to control the pre-oxidation heating rate and reaction temperature within a reasonable range. If the isothermal time is too short, the pre-oxidation reaction time will be insufficient, affecting stability; if the isothermal time is too long, the pre-oxidation reaction time will be too long, prolonging the ineffective reaction time.

[0105] Specifically, step 4 also includes: further carbonizing the pre-oxidized fiber filaments in an inert atmosphere to prepare composite carbon fibers.

[0106] Specifically, the inert atmosphere can be any one of N2, helium, or argon.

[0107] Specifically, the carbonization temperature is 600℃~800℃, and the temperature is increased to the specified temperature at a heating rate of 2℃ / min~4℃ / min, and held for 1h~3h.

[0108] Carbonization temperatures of 600℃ to 800℃ produce carbon fibers with better uniformity of carbonization morphology than those prepared by carbonization below 600℃. However, as the carbonization temperature increases, at 900℃, the fibers may even completely decompose, making it impossible to obtain complete carbonized fibers. Composite carbon fibers prepared at carbonization temperatures of 600℃ to 800℃ exhibit better morphology.

[0109] A slower heating rate helps to form carbon uniformly, resulting in carbon fibers with a more uniform morphology and better electrical properties; if the heating rate is too slow, the carbonization reaction time will be too long, prolonging the ineffective reaction time.

[0110] If the heat preservation time is too short, the carbonization reaction time will be insufficient, affecting stability and electrical performance; if the constant temperature time is too long, the carbonization reaction time will be too long, prolonging the ineffective reaction time.

[0111] On the other hand, the present invention provides a coal liquefaction residue-based composite carbon fiber, which is prepared by the above method.

[0112] Specifically, the diameter of the coal liquefaction residue-based composite carbon fiber is 259nm to 539nm.

[0113] On the other hand, this invention discloses a coal liquefaction residue-based composite carbon fiber anode, comprising an outer foamed nickel electrode plate and a carbon fiber layer between the foamed nickel electrode plate, wherein the carbon fiber layer comprises coal liquefaction residue-based composite carbon fiber prepared by the above method, and the carbon fiber specific capacitance is 157.3 F·g.-1 ~246.7 F·g -1 .

[0114] This invention discloses a method for preparing a composite carbon fiber negative electrode based on coal liquefaction residue, comprising: pressing the above-mentioned composite carbon fiber and foamed nickel plate to prepare a carbon fiber negative electrode for use as a capacitor negative electrode.

[0115] Specifically, the pressing pressure is 8MPa to 12MPa, and the pressing time is 1min to 5min.

[0116] To further illustrate the advancements of the present invention, the following embodiments and comparative examples are provided:

[0117] Example 1

[0118] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, including:

[0119] Step 1: Crush 5g of Shenmu-Fugu sub-bituminous coal liquefaction residue, sieve it through a 200-mesh screen, vacuum dry it at 80℃ for 24h, and then use 300mL of an equal volume of acetone / carbon disulfide mixed solvent as the extraction solvent to extract the coal liquefaction residue using the Soxhlet extraction method to obtain the extract. Remove the solvent from the extract by rotary evaporation to obtain the coal liquefaction residue extract.

[0120] Step 2: The coal liquefaction residue extract and polyacrylonitrile with an average molecular weight of 150,000 were heated in an 80°C water bath and dispersed under ultrasonic assistance at 25 kHz for 5 hours to completely dissolve the solute in N,N-dimethylformamide to prepare the spinning solution; the mass-to-volume ratio of the total amount of coal liquefaction residue extract and polyacrylonitrile to the strongly polar solvent was 1:2.5 g / mL; different masses of coal liquefaction residue extract were added to polyacrylonitrile and dissolved in 10 mL of N,N-dimethylformamide solvent, so that the coal liquefaction residue extract accounted for 75 wt% of the total amount of extract and polyacrylonitrile in the spinning solution (total mass of solute was 1 g), and ultrasonically dispersed for 5 hours to completely dissolve the solute;

[0121] Step 3: Electrospin the spinning solution, with the distance between the injection device and the receiving device 15cm, the negative electrode voltage -3kV, and the positive electrode voltage 12kV; the injection speed is 0.12mm / min, to obtain fiber filaments;

[0122] Step 4: Pre-oxidize the fiber precursor; heat to 280℃ in air at a heating rate of 5℃ / min and hold at that temperature for 2 hours; heat to 800℃ in N2 atmosphere at a heating rate of 3℃ / min to prepare composite carbon fibers with different carbonization temperatures.

[0123] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0124] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, wherein the composite carbon fiber is cut into 1×1cm pieces. 2 The sheet-like active material was pressed with a nickel foam electrode plate at 10 MPa for 1 min to obtain a carbon fiber electrode, which was used as the negative electrode of the capacitor.

[0125] Example 2

[0126] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, including:

[0127] Step 1: Crush 5g of Shenmu-Fugu sub-bituminous coal liquefaction residue, sieve it through a 200-mesh screen, vacuum dry it at 80℃ for 24h, and then use 300mL of an equal volume of acetone / carbon disulfide mixed solvent as the extraction solvent to extract the coal liquefaction residue using the Soxhlet extraction method to obtain the extract. Remove the solvent from the extract by rotary evaporation to obtain the coal liquefaction residue extract.

[0128] Step 2: The coal liquefaction residue extract and polyvinylpyrrolidone (PVP) with an average molecular weight of 220,000 were heated in an 80°C water bath and dispersed under ultrasonic assistance at 25 kHz for 5 hours to completely dissolve the solute in N,N-dimethylformamide to prepare the spinning solution. The mass-to-volume ratio of the total amount of coal liquefaction residue extract and PPVP to the strongly polar solvent was 1:3 g / mL. Different masses of coal liquefaction residue extract were added to PPVP and dissolved in 10 mL of N,N-dimethylformamide solvent. The spinning solution (total mass of solute 1 g) with the coal liquefaction residue extract accounting for 75 wt% of the total extract and PPVP was ultrasonically dispersed for 5 hours to completely dissolve the solute.

[0129] Step 3: Electrospin the spinning solution, with the distance between the injection device and the receiving device 15cm, the negative electrode voltage -4.5kV, and the positive electrode voltage 13.5kV; the injection speed is 0.12mm / min, to obtain the fiber filament;

[0130] Step 4: Pre-oxidize the fiber precursor; heat to 280℃ in air at a heating rate of 5℃ / min and hold at that temperature for 2 hours; heat to 800℃ in N2 atmosphere at a heating rate of 3℃ / min to prepare composite carbon fibers with different carbonization temperatures.

[0131] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0132] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, wherein the composite carbon fiber is cut into 1×1cm pieces. 2 The sheet-like active material was pressed with a nickel foam electrode plate at 11 MPa for 1 min to obtain a carbon fiber electrode, which was used as the negative electrode of the capacitor.

[0133] Example 3

[0134] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, including:

[0135] Step 1: Crush 5g of Shenmu-Fugu sub-bituminous coal liquefaction residue, sieve it through 200 mesh, vacuum dry it at 75℃ for 24h, and then use 25mL of an equal volume of acetone / carbon disulfide mixed solvent as the extraction solvent to extract the coal liquefaction residue by Soxhlet extraction to obtain the extract. Remove the solvent from the extract by rotary evaporation to obtain the coal liquefaction residue extract.

[0136] Step 2: The coal liquefaction residue extract and polystyrene with an average molecular weight of 192,000 were heated in a water bath at 80°C and dispersed under ultrasonic assistance at 130 kHz for 5 hours to completely dissolve the solute in N,N-dimethylformamide to prepare a spinning solution. The mass-to-volume ratio of the total amount of coal liquefaction residue extract to polystyrene to the strongly polar solvent was 1:4 g / mL. Different masses of coal liquefaction residue extract were added to polystyrene and dissolved in 10 mL of N,N-dimethylformamide solvent. The spinning solution (total mass of solute 1 g) with the coal liquefaction residue extract accounting for 75 wt% of the total amount of extract and polystyrene was ultrasonically dispersed for 5 hours to completely dissolve the solute.

[0137] Step 3: Electrospin the spinning solution, with the distance between the injection device and the receiving device 15cm, the negative electrode voltage -4.5kV, and the positive electrode voltage 13.5kV; the injection speed is 0.18mm / min, to obtain the fiber filament;

[0138] Step 4: Pre-oxidize the fiber precursor; heat to 150℃ in air at a heating rate of 5℃ / min and hold at that temperature for 2 hours; heat to 600℃ in N2 atmosphere at a heating rate of 3℃ / min to prepare composite carbon fibers with different carbonization temperatures.

[0139] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0140] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, wherein the composite carbon fiber is cut into 1×1cm pieces. 2 The sheet-like active material was pressed with a nickel foam electrode plate at 8 MPa for 1 min to obtain a carbon fiber electrode, which was used as the negative electrode of the capacitor.

[0141] Example 4

[0142] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the coal liquefaction residue extract accounts for 65 wt% of the total extract and polyacrylonitrile, while the other conditions are the same as in Embodiment 1.

[0143] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0144] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0145] Example 5

[0146] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the pre-oxidation adopts a heating rate of 6℃ / min, while the other conditions are the same as in Embodiment 1.

[0147] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0148] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0149] Example 6

[0150] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the carbonization adopts a heating rate of 4℃ / min, while the other conditions are the same as in Embodiment 1.

[0151] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0152] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0153] Example 7

[0154] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the pre-oxidation constant temperature is 260℃, while the other conditions are the same as in Embodiment 1.

[0155] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0156] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0157] Example 8

[0158] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 3 in that the pre-oxidation constant temperature is 145℃, while the other conditions are the same as in Embodiment 3.

[0159] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0160] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0161] Example 9

[0162] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the carbonization constant temperature is 600℃, while the other conditions are the same as in Embodiment 1.

[0163] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0164] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0165] Comparative Example 1

[0166] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the polyacrylonitrile in the spinning solution is replaced by an equal amount of coal liquefaction residue extract, and no polyacrylonitrile is added. The other conditions are the same as in Embodiment 1.

[0167] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0168] Comparative Example 2

[0169] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the coal liquefaction residue extract accounts for 10 wt% of the total extract and polyacrylonitrile, and the other conditions are the same as in Embodiment 1.

[0170] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0171] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0172] Comparative Example 3

[0173] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the coal liquefaction residue extract accounts for 80 wt% of the total extract and polyacrylonitrile, while the other conditions are the same as in Embodiment 1.

[0174] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0175] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0176] Comparative Example 4

[0177] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the coal liquefaction residue extract accounts for 5 wt% of the total extract and polyacrylonitrile, while the other conditions are the same as in Embodiment 1.

[0178] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0179] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0180] Comparative Example 5

[0181] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Example 1 is that the mass-volume ratio of the total amount of coal liquefaction residue extract and polyacrylonitrile to the strongly polar solvent is 1:1.5 g / mL, and the other conditions are the same as in Example 1.

[0182] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0183] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0184] Comparative Example 6

[0185] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Example 1 is that the mass-volume ratio of the total amount of coal liquefaction residue extract and polyacrylonitrile to the strongly polar solvent is 1:5 g / mL, and the other conditions are the same as in Example 1.

[0186] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0187] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0188] Comparative Example 7

[0189] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the pre-oxidation heating rate is 8℃ / min, while the other conditions are the same as in Embodiment 1.

[0190] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0191] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0192] Comparative Example 8

[0193] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the pre-oxidation constant temperature is 300℃, while the other conditions are the same as in Embodiment 1.

[0194] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0195] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0196] Comparative Example 9

[0197] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the pre-oxidation constant temperature is 250℃, while the other conditions are the same as in Embodiment 1.

[0198] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0199] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0200] Comparative Example 10

[0201] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 3 in that the pre-oxidation constant temperature is 160℃, and the other conditions are the same as in Embodiment 3.

[0202] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0203] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0204] Comparative Example 11

[0205] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 3 in that the pre-oxidation constant temperature is 130℃, and the other conditions are the same as in Embodiment 3.

[0206] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0207] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0208] Comparative Example 12

[0209] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the carbonization constant temperature is 900℃, while the other conditions are the same as in Embodiment 1.

[0210] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0211] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0212] Comparative Example 13

[0213] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber, which differs from Embodiment 1 in that the carbonization constant temperature is 400℃, while the other conditions are the same as in Embodiment 1.

[0214] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0215] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber electrode, which is prepared using the above-mentioned composite carbon fiber according to the method of Example 1.

[0216] Comparative Example 14

[0217] This embodiment discloses a method for preparing coal liquefaction residue-based composite carbon fiber. The difference from Embodiment 1 is that the coal liquefaction residue extract in the spinning solution is replaced by an equal amount of polyacrylonitrile, and no coal liquefaction residue extract is added. The other conditions are the same as in Embodiment 1.

[0218] This embodiment also discloses a coal liquefaction residue-based composite carbon fiber, which is prepared according to the above method.

[0219] Experimental Example

[0220] The fiber precursors, carbon fibers, and electrodes prepared by the methods of the examples and comparative examples were tested. Due to space limitations, only the results of the characterization data are shown in this section. The results are as follows:

[0221]

[0222]

[0223] Comparing Examples 1 and 4 with Comparative Examples 2 and 3, it can be seen that when the mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 65wt% to 75wt%, carbon fibers prepared from spinning raw materials within this range, when used as electrodes, can effectively improve the specific capacitance performance of supercapacitors compared to samples without residue extract. When the mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 10wt% to 75wt%, carbon fibers prepared from spinning raw materials within this range, when used as electrodes, are superior to or close to samples prepared without residue extract.

[0224] The mass percentage of coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 65wt%–75wt%. Carbon fibers prepared from this range of spinning raw materials possess a microporous structure (pore size less than 2nm, not shown), which contributes more to the specific capacitance of the electrode material than mesoporous structures (pore size between 2nm and 50nm), effectively improving the capacitance performance of supercapacitors.

[0225] SEM analysis of fiber precursor

[0226] As shown in Figures 3a, 3b, 4a, 4b, 5a, and 5b, the three types of fiber precursors prepared in Examples 1-3 all exhibit a long cylindrical structure with a uniform diameter distribution. Compared to the carbon fibers prepared in Examples 2 and 3, the carbon fibers prepared by spinning polyacrylonitrile and coal liquefaction residue extract in Example 1 can still maintain a uniform long nanofiber structure under high-temperature carbonization treatment. During electrode use, the micropore structure generated during KOH activation is more uniformly distributed, ensuring optimal pore structure distribution, resulting in more active sites per unit area of ​​electrode surface, increasing the exchange rate of electrolyte particles at the electrode-electrolyte interface, and thus exhibiting the largest specific capacitance.

[0227] FTIR analysis of coal liquefaction residue and coal liquefaction residue extract

[0228] As shown in Figure 6, due to the different vibrational modes between atoms in each molecule, even simple compounds have complex and characteristic infrared spectra. Therefore, by analyzing the infrared spectra of compounds, the molecular structure of unknown compounds can be determined. Figure 6 shows the infrared spectra of coal liquefaction residue and coal liquefaction residue extract. The functional group assignments are analyzed based on the wavenumber and intensity of the absorption peaks, and the infrared spectra of coal-based pitch and its extracts are compared and analyzed. It can be seen from the figure that at 3041 cm⁻¹... -1 and 1593cm -1 The absorption peak at 1434 cm⁻¹ is the stretching vibration absorption peak of the CH bond and C=C skeleton on the aromatic ring. -1The peak at 1238 cm⁻¹ is a vibrational peak in the aromatic ring skeleton, indicating the presence of aromatic ring structures in all four samples. -1 and 1032cm -1 The two absorption peaks are attributed to the stretching vibrations of hydroxyl groups and ether bonds, respectively, indicating that the oxygen element in the organic components of the sample exists in two forms: hydroxyl groups and oxygen-bridged bonds. At 2918 cm⁻¹ -1 2856cm -1 and 1377cm -1 Multiple absorption peaks are observed at 910–650 cm⁻¹, representing in-plane symmetric and asymmetric vibrational absorption peaks of CH, indicating the presence of -CH₂- and -CH₃ structural units in the sample. These absorption peaks are located between 910 and 650 cm⁻¹. -1 There are multiple absorption peaks within the range, which represent out-of-plane bending vibrations of the aromatic ring, indicating that the aromatic ring has a large number of substituents.

[0229] Therefore, we can determine that the coal liquefaction residue extract adheres to the surface of the polymer spinning aid through interaction, which solves the problem of insufficient molecular weight that prevents spinning. At the same time, it improves the surface properties of the polymer spinning aid and reduces the occurrence of agglomeration. The two work together to produce fiber precursors with uniform diameter distribution and stable framework.

[0230] FTIR analysis of fiber precursors

[0231] Figure 7 shows the FTIR spectra of the fiber precursors from Examples 1-3. The characteristic peak position of the C=C double bond in the benzene ring in the coal liquefaction residue extract is 1593 cm⁻¹. -1 The characteristic peaks of this bond in the three fiber precursors prepared in Examples 1-3 were shifted to 1452 cm⁻¹, respectively. -1 1438cm -1 1542cm -1 This indicates that the benzene ring in the coal liquefaction residue extract and the characteristic functional groups in the spinning aid have a conjugation effect, causing the characteristic peak of the C=C double bond of the benzene ring to shift to the low frequency region. From the degree of shift, it can be seen that the conjugation effect of the three fiber precursors prepared in Examples 1-3 decreases sequentially.

[0232] In addition, the infrared spectra of coal liquefaction residue extract and polymeric spinning aid are located at 3650 cm⁻¹. -1 ~3600cm -1 The stretching vibration absorption peak of the free hydroxyl group and 3400 cm⁻¹ -1 -3200cm -1 The stretching vibration peaks of intermolecular hydrogen bonds were not obvious; however, the infrared spectra of the fiber precursors prepared in Example 1 at 3402 cm⁻¹ were different. -1 Infrared spectra of fiber precursors prepared in Example 2 (3434 cm⁻¹) -1Broad absorption peaks were found at all locations, which is a typical spectral characteristic of intermolecular hydrogen bonding. Combining the peak intensity and peak position, it can be concluded that the intermolecular hydrogen bonding of the fiber precursor in Example 1 is stronger than that of the fiber precursor prepared in Example 2.

[0233] In summary, when the coal liquefaction residue extract is co-dissolved with the three polymeric spinning aids, hydrogen bonding and benzene ring conjugation occur. This allows the coal liquefaction residue extract to interact with the polymeric spinning aid molecules during the spinning solution stage and be drawn into one-dimensional nanofibers under a high-voltage electric field. This is consistent with the hypothesis of the spinning process. Therefore, we can confirm that the extract adheres to the surface of the polymeric spinning aid through interaction, solving the problem of insufficient molecular weight preventing spinning, while also improving the surface properties of the polymeric spinning aid and reducing agglomeration. These two factors synergistically produce fiber precursors with uniform diameter distribution and a stable framework.

[0234] SEM analysis of carbon fiber

[0235] As shown in Figures 8a-8f, nanoscale observation reveals that heat treatment significantly altered the morphology of the three fiber precursors in Examples 1-3, with diameters ranging from 259-539 nm. The carbon fiber prepared in Example 1 largely retained the elongated cylindrical shape of the corresponding precursor fiber, with its diameter reduced to half that of the original spun fiber. The surface became smoother, with only slight melting observed on a small number of fiber surfaces. The carbon fiber prepared in Example 2 had a diameter reduced to approximately 259 nm, and fiber breakage was very pronounced. It is speculated that molecular chain breakage occurred during the heat treatment stage of PVP. The melting phenomenon was even more pronounced in the carbon fiber prepared in Example 3, with multiple fibers swelling into a planar structure. A possible reason is that the PS molecular chains were completely vaporized during the carbonization process, and the single fibers were eventually swelled and bonded together during this process. Although the three fibers exhibited fusion at the nanoscale, they remained intact carbon fiber sheets at the macroscale. KOH activation and pore-forming on this basis improved the fiber surface structure and pore size distribution, increasing the rate of charged particle entry and exit within the fiber and demonstrating its double-layer capacitance characteristics.

[0236] Electrochemical performance of composite carbon fiber electrodes prepared with different spinning aids

[0237] The composite carbon fiber electrodes prepared in Examples 1-3 at 0.5 A·g -1At a current density of 0.5 A·g, the overall trend of specific capacitance is: Example 1 > Example 2 > Example 3. This is mainly because the carbon fibers prepared in Example 1 can still maintain a uniform long nanofiber structure under high-temperature carbonization treatment, which ensures a more uniform distribution of micropore structure generated during KOH activation and also ensures an optimal pore structure distribution, resulting in more active sites per unit area of ​​electrode surface and improving the exchange rate of electrolyte particles at the electrode-electrolyte interface. -1 The specific capacitance of the composite carbon fiber electrodes prepared in Examples 1, 2, and 3 was 246.7 F·g. -1 201.6F·g -1 157.3 F·g -1 The specific capacitance of the prepared carbon fiber electrode is 157.3 F·g. -1 ~246.7 F·g -1 The variation is that the specific capacitance of the carbon fiber electrode prepared from polyacrylonitrile carbon fiber is 235.0 F·g. -1 ~246.7 F·g -1 The capacitance performance of the composite carbon fiber electrode in Example 1, while ensuring a blending content of 75 wt% of coal liquefaction residue extract, is close to or even exceeds the specific capacitance performance of the activated carbon fiber electrode in Comparative Example 14, which uses polyacrylonitrile as the sole precursor.

[0238] Comparing Figures 3a and 14, it can be seen that, compared with Comparative Example 14, Example 1 significantly improves the problems of uneven fiber diameter distribution and ellipsoidal fiber structure, and the fiber arrangement structure is more uniform. The surface properties of the polymer spinning aid are improved, reducing the occurrence of agglomeration. The polymer spinning aid and the extract work together to produce fiber filaments with uniform diameter distribution and stable framework.

[0239] Comparing Examples 1 and 9 with Comparative Examples 12 and 13, it can be seen that using a carbonization isothermal temperature of 600℃ to 800℃ is more conducive to obtaining better specific capacitance performance than using a carbonization isothermal temperature outside the above range.

[0240] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A coal liquefaction residue-based composite carbon fiber anode, characterized in that, The preparation method includes: Step 1: Extracting coal liquefaction residue with a mixed solvent of acetone and carbon disulfide in a volume ratio of 1:1 to achieve extraction of coal liquefaction residue extract with an average molecular weight of less than 2000; Step 2: Preparing a spinning solution by mixing the coal liquefaction residue extract with a polymeric spinning aid; the mass percentage of the coal liquefaction residue extract in the mixture of coal liquefaction residue extract and polymeric spinning aid is 65wt%~75wt%; the polymeric spinning aid includes any one of polyacrylonitrile, polyvinylpyrrolidone, and polystyrene; Step 3: Spinning the spinning solution to obtain fiber precursors; Step 4: Pre-oxidizing and carbonizing the fiber precursors to obtain composite carbon fibers; the diameter of the coal liquefaction residue-based composite carbon fibers is 366nm~539nm, and the carbon fibers have a microporous structure with a pore size of less than 2nm; Step 5: Pressing the composite carbon fibers and foamed nickel plates to prepare carbon fiber negative electrodes, which are used as negative electrodes for capacitors.

2. The coal liquefaction residue-based composite carbon fiber anode according to claim 1, characterized in that, Step 2 involves preparing the spinning solution by dissolving coal liquefaction residue extract and a high-molecular-weight spinning aid in a strongly polar solvent.

3. The coal liquefaction residue-based composite carbon fiber anode according to claim 2, characterized in that, The mass-to-volume ratio of the mixture of coal liquefaction residue extract, polymeric spinning aid, and strongly polar solvent is 1:2.5~4 g / ml.

4. The coal liquefaction residue-based composite carbon fiber anode according to claim 1, characterized in that, The polymeric spinning aid is selected from polyacrylonitrile or polyvinylpyrrolidone. The pre-oxidation in step 4 includes: heating to 260℃~290℃ in an air or oxygen atmosphere at a heating rate of 4℃ / min~6℃ / min, and holding at that temperature for 1.5h~3h.

5. The coal liquefaction residue-based composite carbon fiber anode according to claim 1, characterized in that, Polystyrene is selected as the polymeric spinning aid. The pre-oxidation in step 4 includes: heating to 145℃~155℃ in an air or oxygen atmosphere at a heating rate of 4℃ / min~6℃ / min, and holding at that temperature for 1.5h~3h.

6. The coal liquefaction residue-based composite carbon fiber anode according to claim 1, characterized in that, The specific capacitance of the carbon fiber anode is 157.3 F·g. -1 ~246.7 F·g -1 .

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