A method for preparing highly conductive carbon black by directional pyrolysis of biomass and its applications.

Abstract

This disclosure presents a method and application for preparing highly conductive carbon black by directed pyrolysis of biomass. The method includes selecting biomass raw materials and extracting aromatic components from them; dissolving the extracted aromatic components in a polar solvent, forming ordered aggregates through metal ion crosslinking and self-assembly, and spray-drying to obtain precursor microspheres; mixing the precursor microspheres with a confining medium, placing them in a protective atmosphere furnace, and subjecting them to high-temperature pyrolysis to limit carbon particle growth and inhibit ash migration, obtaining a pyrolysis product; washing the pyrolysis product with water to remove the confining medium, then treating it with an inorganic acid, and repeatedly washing until neutral to obtain an acid-washed product; and treating the acid-washed product at high temperature in a protective atmosphere to obtain highly conductive carbon black. This disclosure uses the extraction of endogenous aromatic structures from biomass (lignin, fused-ring extracts) as a "molecular template" and a "liquid-phase pre-assembly-confined pyrolysis-purification graphitization" process to prepare highly conductive carbon black with an acetylene-like structure.

Description

Technical Field

[0001] This disclosure belongs to the field of advanced carbon material preparation and new energy device technology, specifically relating to a method and application of preparing highly conductive carbon black by biomass directional pyrolysis. Background Technology

[0002] The new energy industry is experiencing explosive growth, with global lithium battery shipments projected to exceed 1.5 TWh by 2025, and the conductive agent market reaching 8 billion yuan. Currently, the import dependence of conductive carbon black (such as Super P and acetylene black) exceeds 60%, highlighting the urgent need for domestic substitution. Although carbon nanotube (CNT) conductive agents exhibit superior performance, their high cost (200-400 yuan / kg) means that carbon black-based conductive agents still hold a 70% market share.

[0003] The technological trend of conductive carbon black requires high specific surface area (>200 m²). 2 It combines high density (DBP > 120 mL / 100g) with low metal impurity content (<50 ppm, battery grade), and ash content affects cycle life. EU battery regulations require disclosure of carbon footprint, giving biomass-based materials a green premium advantage. However, natural biomass has a low degree of graphitization, resulting in intrinsic conductivity <10 S / m; alkali metals (Na, K) in the ash cause side reactions at the battery interface; and poor batch stability makes it difficult to meet the consistency requirements of high-end batteries.

[0004] Therefore, developing a method for directionally constructing highly conductive carbon black using the aromatic components of biomass is of great strategic significance for achieving domestic substitution of new energy conductive agents and the "dual carbon" goal. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method and application for preparing highly conductive carbon black by directional pyrolysis of biomass.

[0006] One aspect of this disclosure provides a method for preparing highly conductive carbon black by directional pyrolysis of biomass, the method comprising: Select biomass raw materials rich in lignin, tannin, or polyphenolic aromatic structures, and extract aromatic components from the biomass raw materials; The extracted aromatic components were dissolved in a polar solvent and formed into ordered aggregates through metal ion crosslinking and self-assembly. The precursor microspheres were obtained by spray drying. Precursor microspheres are mixed with a confining medium and placed in a protective atmosphere furnace. The mixture is then subjected to high-temperature pyrolysis to limit the growth size of carbon particles and inhibit ash migration, thereby obtaining the pyrolysis product. The pyrolysis product is washed with water to remove the confining medium, then treated with inorganic acid, and repeatedly washed until neutral to obtain the acid-washed product. The pickling product was treated at high temperature in a protective atmosphere to obtain highly conductive carbon black.

[0007] Optionally, the biomass raw material is selected from at least one or a combination of several of the following: papermaking black liquor lignin, coconut shell carbonized material, seaweed extract, waste circuit board pyrolysis oil, and sludge organic matter.

[0008] Optionally, the metal salt used for the metal ion crosslinking is selected from FeCl3, AlCl3 or ZrOCl2, and the metal loading is 0.5-2.0 wt%.

[0009] Optionally, the confinement medium is a NaCl-KCl molten salt mixture or MgO and CaO nanoparticles; The amount of the confining medium used is 2-5 times the mass of the biomass raw material; The heating rate of the high-temperature pyrolysis treatment is 5-10℃ / min, the holding temperature is 600-1000℃, and the time is 2-4h.

[0010] Optionally, the inorganic acid treatment is carried out at a temperature of 60-90℃ for 4-12 hours, and the concentration of the inorganic acid is 1-3 mol / L.

[0011] Optionally, the pickling product is subjected to high-temperature treatment in a protective atmosphere at a temperature of 800-1000℃ for 2-4 hours.

[0012] Optionally, after mixing the precursor microspheres with a confining medium and placing them in a protective atmosphere furnace for high-temperature pyrolysis to limit the growth size of carbon particles and inhibit ash migration, and obtaining the pyrolysis product, the method further includes: The biomass raw material is activated by KOH or CO2, with an activation temperature of 700-900℃ and a time of 1-2 hours. The mass ratio of the biomass raw material to KOH is 1:(2-4).

[0013] Optionally, after treating the pickling product at high temperature in a protective atmosphere to obtain highly conductive carbon black, the method further includes: The highly conductive carbon black is subjected to surface oxidation regulation or coating treatment.

[0014] In another aspect of this disclosure, a highly conductive carbon black prepared by directed pyrolysis of biomass is provided, wherein the highly conductive carbon black is prepared by the method described above; wherein, The highly conductive carbon black has an acetylene black-like chain-like dendritic aggregate structure and a specific surface area of ​​200-3000 m². 2 / g, ash content <0.1 wt%, powder conductivity >10 S / cm, metal impurity content <100 ppm, and surface oxygen functional group content of 5-15 at.

[0015] In another aspect of this disclosure, an application of highly conductive carbon black is proposed, wherein the highly conductive carbon black described above is used in lithium battery conductive agents, conductive plastics, supercapacitor electrodes, or environmental remediation electrodes.

[0016] This disclosure presents a method and application for preparing highly conductive carbon black by directed pyrolysis of biomass. The method includes: selecting biomass raw materials rich in lignin, tannin, or polyphenolic aromatic structures, and extracting aromatic components from the biomass raw materials; dissolving the extracted aromatic components in a polar solvent, forming ordered aggregates through metal ion crosslinking and self-assembly, and spray-drying to obtain precursor microspheres; mixing the precursor microspheres with a confining medium, placing them in a protective atmosphere furnace, and subjecting them to high-temperature pyrolysis to limit the growth size of carbon particles and inhibit ash migration, obtaining a pyrolysis product; washing the pyrolysis product with water to remove the confining medium, then treating it with an inorganic acid, and repeatedly washing until neutral to obtain an acid-washed product; and treating the acid-washed product at high temperature in a protective atmosphere to obtain highly conductive carbon black. This disclosure uses the extraction of endogenous aromatic structures from biomass (lignin, fused-ring extracts) as a "molecular template" and a "liquid-phase pre-assembly-confined pyrolysis-purification graphitization" process to prepare highly conductive carbon black with an acetylene-like structure. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for preparing highly conductive carbon black by directional pyrolysis of biomass, as described in a specific embodiment of this disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0019] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing highly conductive carbon black by directional pyrolysis of biomass, specifically including the following steps S110~S150: S110. Aromatic component extraction: Select biomass raw materials rich in lignin, tannin or polyphenolic aromatic structures, and extract the aromatic components from the biomass raw materials through solvent extraction or hydrothermal liquefaction.

[0020] In step S110, the biomass raw material is selected from at least one or a combination of several of the following: papermaking black liquor lignin, coconut shell carbonized material, seaweed extract, waste circuit board pyrolysis oil, and sludge organic matter.

[0021] In step S110, solvent extraction may be performed using a polar solvent, such as a mixture of ethanol and water.

[0022] S120, Liquid-phase pre-assembly: The extracted aromatic components are dissolved in a polar solvent, and ordered aggregates are formed through metal ion cross-linking and self-assembly. The precursor microspheres are obtained by spray drying.

[0023] In step S120, the metal salt used for metal ion crosslinking is selected from FeCl3, AlCl3 or ZrOCl2, the metal loading is 0.5-2.0 wt%, the crosslinking treatment temperature is 55-65℃, and the time is 1.5-2.5h, which is used to catalyze the formation of carbon microspheres but avoid excessive graphitization.

[0024] In step S120, the precursor microspheres have a particle size of 10-30 μm.

[0025] This embodiment involves dissolving aromatic components in a polar solvent, obtaining ordered aggregates through self-assembly / metal ion crosslinking, and then obtaining precursor microspheres through spray drying. On one hand, this allows the aromatic components to pre-form a regular aggregate structure, aiding in the formation of a more ordered carbon framework during pyrolysis. This ordered carbon structure improves the conductivity of the final carbon black. On the other hand, spray drying directly yields microspherical precursors with uniform morphology and controllable particle size, resulting in a more regular morphology for the final carbon black. Metal ion crosslinking also assists in the graphitization of the carbon structure during subsequent pyrolysis, while simultaneously helping to regulate the degree of order in the aggregates.

[0026] S130, confined pyrolysis: The precursor microspheres are mixed with the confining medium and placed in a protective atmosphere furnace. The mixture is then subjected to high-temperature pyrolysis to limit the growth size of carbon particles and inhibit ash migration, thereby obtaining the pyrolysis product.

[0027] In step S130, the amount of confining medium is 2-5 times the mass of the biomass raw material. This mass ratio ensures that each precursor microsphere is fully separated during pyrolysis into carbon, effectively preventing the carbon particles from sintering, agglomerating, and overgrowing at high temperatures, thereby obtaining uniform and fine primary carbon particles. At the same time, it avoids the uneven enrichment and confinement of ash on the surface or inside of the carbon black particles. If the amount of medium is too small, an effective isolation layer cannot be formed, resulting in severe sintering and agglomeration of the particles and uneven size.

[0028] In step S130, the confinement medium is molten salt or metal oxide. For example, the molten salt can be a NaCl-KCl molten salt mixture (NaCl to KCl mass ratio of 1:1, melting point approximately 660℃). The molten salt provides an ion-conducting environment, which can promote the directional condensation and aromatization of biomass aromatic components during pyrolysis, contributing to the formation of a more ordered graphite microcrystalline structure. Alternatively, the metal oxide can be MgO or CaO nanoparticles, which can effectively restrict the migration, sintering, and excessive growth of carbon particles at high temperatures, thereby obtaining more uniform and finer primary carbon particles. Simultaneously, they can act as templates, guiding carbon atoms to arrange themselves in an orderly manner on their surface, promoting the formation of local graphite microcrystals.

[0029] In step S130, the protective atmosphere is selected from high-purity nitrogen (N2) or high-purity argon (Ar). The heating rate of the high-temperature pyrolysis treatment is 5-10℃ / min, which allows the precursor to pyrolyze slowly and the volatiles to gradually precipitate, avoiding structural collapse. The holding temperature is 600-1000℃ and the time is 2-4h, which can ensure sufficient carbonization and allow the carbon structure to gradually aromatize, without causing excessive particle growth due to excessive temperature / time.

[0030] This embodiment restricts the growth size of carbon particles by using a confined medium, avoiding excessive agglomeration and growth of carbon particles at high temperatures, resulting in carbon black particles with more uniform and finer particle sizes. At the same time, it can inhibit the outward migration of ash and fix ash impurities within the confined space, facilitating subsequent purification and removal.

[0031] In other preferred embodiments, for applications requiring ultra-high specific surface area, step S130 further includes a KOH activation or CO2 activation process. The activation temperature is 700-900℃ and the time is 1-2 hours. KOH, as a chemical activator, reacts with the carbon skeleton at high temperature to create a hierarchical pore structure from micropores to mesopores inside the carbon black particles. CO2 activation is a physical activation. At high temperature, CO2 reacts with carbon to etch the carbon matrix, forming a rich and uniformly sized microporous structure. Both methods can enable the carbon black to obtain a specific surface area much higher than that of the unactivated product, making it easy to obtain an ultra-high specific surface area.

[0032] S140. Purification treatment: The pyrolysis product is washed with water to remove the confining medium, and then treated with inorganic acid. After repeated washing until neutral, the acid-washed product is obtained.

[0033] In step S140, the inorganic acid treatment is carried out at a temperature of 60-90°C for 4-12 hours. The inorganic acid is preferably HCl or HNO3, and its concentration is 1-3 mol / L.

[0034] This embodiment uses a step-by-step purification process: first, water washing removes easily soluble impurities and reduces acid consumption; then, acid washing deeply removes metallic impurities. At this stage, most impurities have been removed, avoiding the impact of residual impurities on the conductivity of the final carbon black. This process has low cost and high impurity removal efficiency.

[0035] S150, High-temperature purification: The acid-washed product is treated at high temperature in a protective atmosphere to further reduce metal impurities and oxygen-containing functional groups on the surface, resulting in highly conductive carbon black.

[0036] In step S150, the pickling product is subjected to high-temperature treatment in a protective atmosphere at a temperature of 800-1000℃ for 2-4 hours.

[0037] In step S150, the protective atmosphere is a hydrogen / argon mixture (H2 volume percentage is 5-10 vol%). Hydrogen acts as a reducing agent, which can further reduce the residual metal oxide impurities and convert the impurities into easily removable metallic states. Argon acts as an inert protective gas to prevent high-temperature oxidation of carbon materials. Low-concentration hydrogen can complete the reduction and purification while avoiding the safety risks of high-concentration hydrogen. The final carbon black obtained after treatment has extremely low metal impurities, few oxygen-containing functional groups, and the graphitization degree of the carbon structure will be further improved, ultimately achieving high conductivity.

[0038] In other preferred embodiments, step S150 is followed by: surface oxidation regulation or coating treatment of the highly conductive carbon black to optimize its dispersibility in battery slurry or polymer matrix.

[0039] It should be noted that oxidation control treatment introduces polar oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups onto the surface of carbon black. On the one hand, this enhances the electrostatic repulsion between particles, and on the other hand, it improves the interfacial compatibility between carbon black and polar slurry media / matrix, thus preventing particle agglomeration and sedimentation.

[0040] It should be further noted that in the coating process, by using coating dispersants, conductive polymers, coupling agents and other modified layers, the agglomeration of carbon black particles is prevented by the steric hindrance effect. For non-polar polymer matrices, coating layers that are compatible with the matrix structure can also be selected to further improve interfacial compatibility and allow carbon black to be uniformly dispersed in the matrix.

[0041] This disclosure utilizes biomass rich in aromatic structures as raw material, with the endogenous aromatic structures of the biomass serving as "molecular templates." Using molten salt or metal oxides as confinement media, a liquid-phase pre-assembly-confined pyrolysis-purification graphitization process is employed. By controlling the growth of graphite crystallites through directional pyrolysis, a highly conductive carbon black with an acetylene-like structure and a specific surface area of ​​200-3000 m² is prepared. 2 With an ash content of <0.1 wt% and a powder conductivity of >10 S / cm, it can replace imported conductive carbon black in the fields of power batteries and high-end conductive materials.

[0042] In another aspect, this disclosure provides a highly conductive carbon black prepared by directed pyrolysis of biomass, which is obtained by the method described above; wherein the highly conductive carbon black has an acetylene black-like chain-like dendritic aggregate structure and a specific surface area of ​​200-3000 m². 2 / g, ash content <0.1 wt%, powder conductivity >10 S / cm, metal impurity (Na, K, Fe, Ni, etc.) content <100 ppm, and surface oxygen functional group content of 5-15 at.

[0043] In another aspect of this disclosure, an application of highly conductive carbon black is proposed, which is used in lithium battery conductive agents, conductive plastics, supercapacitor electrodes, or environmental remediation electrodes.

[0044] The preparation method and specific applications of highly conductive carbon black will be further explained below with reference to specific embodiments: Example 1 This embodiment provides a method for preparing highly conductive carbon black by directed pyrolysis of biomass: Lignin from papermaking black liquor was selected as the biomass raw material, and its aromatic components were extracted. The extracted aromatic components were dissolved in a polar solvent (ethanol / water mixture), and FeCl3 was added for metal ion crosslinking. The metal loading was 1.0 wt%, and ordered aggregates were formed through self-assembly. Precursor microspheres were obtained by spray drying. The precursor microspheres were mixed with a confinement medium (NaCl-KCl molten salt mixture) at a mass ratio of 1:3 and placed in a protective atmosphere furnace. The mixture was heated to 800℃ at a heating rate of 8℃ / min and held at this temperature for 3 hours for high-temperature pyrolysis treatment to obtain the pyrolysis product. The pyrolysis product was washed with water to remove the confinement medium, and then treated with 2 mol / L hydrochloric acid at 75℃ for 8 hours. After repeated washing until neutral, an acid-washed product was obtained. The acid-washed product was treated at 900℃ for 3 hours in a protective atmosphere to obtain highly conductive carbon black.

[0045] Testing revealed that the highly conductive carbon black obtained in this embodiment possesses an acetylene black-like chain-like dendritic aggregate structure with a specific surface area of ​​856 m². 2 The material has an ash content of 0.06 wt.%, a powder conductivity of 18.5 S / cm, a metal impurity content of 68 ppm, and a surface oxygen functional group content of 8.2 at.%. When used as a conductive agent in lithium batteries, the resistivity of the electrode sheet is 0.85 Ω·cm at an addition amount of 2%.

[0046] Example 2 The difference between this embodiment and Example 1 is that the metal ion crosslinking type is changed from FeCl3 to AlCl3, while the metal loading remains at 1.0 wt%. The remaining steps and parameters are exactly the same as in Example 1. Specifically, using lignin from papermaking black liquor as raw material, aromatic components are extracted and dissolved in a polar solvent. AlCl3 is added for metal ion crosslinking, with a metal loading of 1.0 wt%. Precursor microspheres are obtained through self-assembly and spray drying. These microspheres are then mixed with NaCl-KCl molten salt at a mass ratio of 1:3 and pyrolyzed at 8℃ / min to 800℃ for 3 hours. After washing with water, treatment with 2 mol / L hydrochloric acid at 75℃ for 8 hours, and washing until neutral, the microspheres are treated at 900℃ in a protective atmosphere for 3 hours to obtain highly conductive carbon black.

[0047] The specific surface area of ​​the highly conductive carbon black obtained in this embodiment was measured to be 792 m². 2 / g, ash content is 0.05wt.%, powder conductivity is 15.2 S / cm, metal impurity content is 52 ppm, and surface oxygen functional group content is 7.5 at.%. When used as a conductive agent for lithium batteries, the electrode resistivity is 1.02 Ω·cm at an addition amount of 2%. Compared with Example 1, Al 3+ The degree of order in the aggregates formed by cross-linking is slightly lower than that of Fe. 3+ This results in slightly poorer connectivity of the carbon black conductive network and a decrease in conductivity.

[0048] Example 3 The difference between this embodiment and Example 1 is that the metal loading is adjusted from 1.0 wt% to 2.0 wt%, while the remaining steps and parameters are exactly the same as in Example 1. Specifically, using lignin from papermaking black liquor as raw material, aromatic components are extracted and then FeCl3 is added for metal ion crosslinking. The metal loading is 2.0 wt%. After self-assembly and spray drying, precursor microspheres are obtained. Subsequent pyrolysis, acid washing, and high-temperature treatment steps are the same as in Example 1.

[0049] Testing showed that the specific surface area of ​​the highly conductive carbon black obtained in this embodiment was 923 m². 2 The powder has an ash content of 0.07 wt.%, a powder conductivity of 22.3 S / cm, a metal impurity content of 85 ppm, and a surface oxygen functional group content of 9.1 at.%. When used as a conductive agent in lithium batteries, the electrode resistivity is 0.71 Ω·cm at an addition of 2%. Compared with Example 1, appropriately increasing the metal loading is beneficial for forming more ordered aromatic aggregates, resulting in a more complete conductive network of carbon black after pyrolysis and an increase in conductivity of approximately 20%.

[0050] Example 4 The difference between this embodiment and Example 1 is that the confinement medium is replaced with MgO nanoparticles instead of a NaCl-KCl molten salt mixture; the remaining steps and parameters are exactly the same as in Example 1. Specifically, using lignin from papermaking black liquor as raw material, aromatic components are extracted and FeCl3 (metal loading 1.0 wt%) is added. The mixture undergoes self-assembly and spray drying to obtain precursor microspheres. The precursor microspheres are mixed with MgO nanoparticles at a mass ratio of 1:3, and pyrolyzed at 8℃ / min to 800℃ for 3 hours. After washing with water, treatment with 2 mol / L hydrochloric acid at 75℃ for 8 hours, and washing until neutral, the mixture is then subjected to high-temperature treatment at 900℃ in a protective atmosphere for 3 hours to obtain highly conductive carbon black.

[0051] Testing showed that the specific surface area of ​​the highly conductive carbon black obtained in this embodiment was 738 m². 2 The ash content was 0.09 wt.%, the powder conductivity was 14.6 S / cm, the metal impurity content was 76 ppm, and the surface oxygen functional group content was 7.8 at.%. When used as a conductive agent in lithium batteries, the electrode resistivity was 1.08 Ω·cm at an addition of 2%. Compared with Example 1, the limiting effect of MgO nanoparticles on carbon particle growth as a confinement medium was slightly weaker than that of the molten salt system, resulting in a slightly wider carbon black particle size distribution and a slight decrease in conductivity.

[0052] Example 5 The difference between this embodiment and Example 1 is that the high-temperature pyrolysis temperature is adjusted from 800℃ to 1000℃, while the remaining steps and parameters are exactly the same as in Example 1. Specifically, using lignin from papermaking black liquor as raw material, aromatic components are extracted and FeCl3 (metal loading 1.0 wt%) is added. Precursor microspheres are obtained through self-assembly and spray drying. These microspheres are mixed with NaCl-KCl molten salt at a mass ratio of 1:3 and pyrolyzed at 1000℃ for 3 hours at a rate of 8℃ / min. After washing with water, treatment with 2 mol / L hydrochloric acid at 75℃ for 8 hours, and washing until neutral, the microspheres are then treated at 900℃ in a protective atmosphere for 3 hours to obtain highly conductive carbon black.

[0053] The specific surface area of ​​the highly conductive carbon black obtained in this embodiment was measured to be 712 m². 2 The powder has an ash content of 0.04 wt.%, a powder conductivity of 24.1 S / cm, a metal impurity content of 61 ppm, and a surface oxygen functional group content of 6.3 at.%. When used as a conductive agent in lithium batteries, the electrode resistivity is 0.65 Ω·cm at an addition amount of 2%. Compared with Example 1, increasing the pyrolysis temperature is beneficial to improving the graphitization degree of the carbon material, and the conductivity is significantly increased by about 30%, but the specific surface area is reduced.

[0054] Comparative Example 1 This comparative example provides a method for preparing highly conductive carbon black by directional pyrolysis of biomass. Compared with Example 1, this comparative example does not use the preferred range of the present invention for several key process parameters, in order to illustrate the technical advantages of the present invention. Specifically, as follows: Ordinary corn stalks (non-aromatic biomass raw material, without aromatic component extraction) were selected as raw material, directly crushed and dissolved in a polar solvent without metal ion cross-linking (no self-assembled ordered structure), and directly spray-dried to obtain precursor microspheres. The precursor microspheres were mixed with a confinement medium (NaCl-KCl molten salt mixture) at a mass ratio of 1:1 (insufficient confinement medium), placed in a protective atmosphere furnace, and directly heated to 500℃ at a heating rate of 15℃ / min (too fast heating rate, too low pyrolysis temperature), and held at this temperature for 1 hour (insufficient time) to obtain the pyrolysis product. The pyrolysis product was washed with water to remove the confinement medium, and then soaked in 0.5 mol / L hydrochloric acid at room temperature for 2 hours (insufficient acid concentration, too low temperature, insufficient time). After washing, an acid-washed product was obtained. The acid-washed product was treated at 600℃ for 1 hour in a protective atmosphere (insufficient treatment temperature, insufficient time) to obtain the carbon black product.

[0055] Testing revealed that the carbon black product obtained in this comparative example was amorphous granular with no chain-like aggregate structure, a specific surface area of ​​156 m² / g, an ash content of 0.85 wt.%, a powder conductivity of only 2.3 S / cm, a metallic impurity content of 342 ppm, and a surface oxygen-containing functional group content of 12.5 at.%. When used as a conductive agent in lithium batteries, the electrode resistivity was 4.52 Ω·cm at an addition of 2%. Compared to Example 1 (conductivity 18.5 S / cm, electrode resistivity 0.85 Ω·cm), the conductivity of this comparative example decreased by approximately 88%, while the electrode resistivity increased by approximately 4.3 times. The results show that when key parameters such as lack of aromatic structure, lack of aromatic component extraction, lack of metal ion cross-linking, insufficient amount of confinement medium, improper pyrolysis process (excessive heating rate, low temperature, insufficient time), insufficient acid washing and purification, and unsuitable subsequent high-temperature treatment conditions all deviate from the preferred range of this invention, an ordered aggregate structure and acetylene-like black chain dendritic morphology cannot be formed, resulting in low graphitization degree, high impurity content, and severely degraded electrical conductivity of the carbon material.

[0056] This disclosure presents a method for preparing highly conductive carbon black by directional pyrolysis of biomass, and its application, which has the following advantages compared to existing technologies: 1. Liquid-phase pre-assembly technology: Extract aromatic components (lignin, tannin, humic acid) from biomass and form ordered aggregates through self-assembly, serving as precursors for primary carbon black particles. Metal ion chelation controls the crosslinking density, avoiding excessive graphitization at high temperatures that could lead to surface area loss.

[0057] 2. Advantages of confined pyrolysis mechanism: Using molten salt (NaCl-KCl) or metal oxide (MgO) as the pyrolysis medium, the molten salt or metal oxide confined medium not only inhibits particle sintering and limits the growth size of carbon particles (20-50 nm), and inhibits ash migration to achieve in-situ separation, but also provides an ion conduction environment to promote the directional condensation of aromatic rings to form graphite microcrystals, achieving "low-temperature and high-efficiency graphitization", with energy consumption reduced by 40% compared with traditional graphitization.

[0058] 3. Purity control advantages: The three-stage purification process (water washing and desalting - acid washing to remove metals - high-temperature hydrogen treatment and reduction) controls metal impurities to <100 ppm. Surface oxidation regulates the carboxyl / hydroxyl ratio, or amorphous carbon / polymer coating improves dispersibility in battery slurry or plastic matrix, meeting the stringent requirements of power batteries and avoiding side reactions at the battery interface.

[0059] 4. Structural controllability: By adjusting the pre-assembly conditions, the amount of confining medium, and the activation process, the specific surface area (200-3000 m² / g) and pore size distribution can be controlled within a wide range to adapt to different application scenarios (conductive agents, supercapacitors, environmental remediation).

[0060] 5. Resource recycling advantages: Fully utilize waste materials such as black liquor from papermaking, waste circuit boards, and sludge to achieve "waste treatment with waste", which is in line with the goals of circular economy and carbon neutrality, and has significant environmental and social benefits.

[0061] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing highly conductive carbon black by directional pyrolysis of biomass, characterized in that, The method includes: Select biomass raw materials rich in lignin, tannin, or polyphenolic aromatic structures, and extract aromatic components from the biomass raw materials; The extracted aromatic components were dissolved in a polar solvent and formed into ordered aggregates through metal ion crosslinking and self-assembly. The precursor microspheres were obtained by spray drying. The precursor microspheres were mixed with a confined medium and placed in a protective atmosphere furnace for high-temperature pyrolysis to obtain the pyrolysis product. The pyrolysis product is washed with water to remove the confining medium, then treated with inorganic acid, and repeatedly washed until neutral to obtain the acid-washed product. The pickling product was subjected to high-temperature treatment in a protective atmosphere to obtain highly conductive carbon black.

2. The method according to claim 1, characterized in that, The biomass raw materials are selected from at least one or a combination of several of the following: papermaking black liquor lignin, coconut shell carbonized material, seaweed extract, waste circuit board pyrolysis oil, and sludge organic matter.

3. The method according to claim 1, characterized in that, The metal salt used for the metal ion crosslinking is selected from FeCl3, AlCl3 or ZrOCl2, and the metal loading is 0.5-2.0 wt%.

4. The method according to claim 1, characterized in that, The confinement medium is a NaCl-KCl molten salt mixture or MgO and CaO nanoparticles; The amount of the confining medium used is 2-5 times the mass of the biomass raw material; The heating rate of the high-temperature pyrolysis treatment is 5-10℃ / min, the holding temperature is 600-1000℃, and the time is 2-4h.

5. The method according to claim 1, characterized in that, The inorganic acid treatment is carried out at a temperature of 60-90℃ for 4-12 hours, and the concentration of the inorganic acid is 1-3 mol / L.

6. The method according to claim 1, characterized in that, The pickling products are treated at high temperature in a protective atmosphere at 800-1000℃ for 2-4 hours.

7. The method according to any one of claims 1-6, characterized in that, The method further includes mixing precursor microspheres with a confining medium, placing them in a protective atmosphere furnace, and subjecting them to high-temperature pyrolysis to limit carbon particle growth and inhibit ash migration, thereby obtaining the pyrolysis product. The biomass raw material is activated by KOH or CO2, with an activation temperature of 700-900℃ and a time of 1-2 hours. The mass ratio of the biomass raw material to KOH is 1:(2-4).

8. The method according to any one of claims 1-6, characterized in that, After treating the acid-washed product at high temperature in a protective atmosphere to obtain highly conductive carbon black, the method further includes: The highly conductive carbon black is subjected to surface oxidation regulation or coating treatment.

9. A highly conductive carbon black prepared by directional pyrolysis of biomass, characterized in that, The highly conductive carbon black is prepared by the method described in any one of claims 1 to 8; wherein... The highly conductive carbon black has an acetylene black-like chain-like dendritic aggregate structure and a specific surface area of ​​200-3000 m². 2 / g, ash content <0.1 wt%, powder conductivity >10 S / cm, metal impurity content <100 ppm, and surface oxygen functional group content of 5-15 at.

10. An application of highly conductive carbon black, characterized in that, The highly conductive carbon black described in claim 9 can be used in lithium battery conductive agents, conductive plastics, supercapacitor electrodes, or environmental remediation electrodes.

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