A method for preparing porous carbon for supercapacitors from biomass and plastics

Abstract

The application belongs to the technical field of resource comprehensive utilization and capacitor material, and provides a method for preparing porous carbon for supercapacitors from biomass and plastic. The method comprises the following steps: crushing, screening and drying the biomass and plastic, gradually heating the mixed raw materials to a first temperature under an inert atmosphere and keeping the temperature for a period of time to obtain pre-carbonized materials, mixing the pre-carbonized materials and an activating agent, activating and forming pores at a second temperature under an inert atmosphere to obtain carbon materials, and acid washing, water washing and drying the carbon materials to obtain porous carbon; the second temperature is higher than the first temperature. The application promotes the generation of carbon through the synergistic effect between biomass and plastic, selectively regulates the pore structure and defect degree, forms porous carbon material with high specific surface area and high pore volume, and the defect degree can be controlled between 0.50 and 1.00, which exhibits excellent energy storage performance.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive resource utilization and capacitor materials technology, specifically relating to a method for preparing porous carbon materials from biomass and plastics and their application in porous carbon supercapacitor electrode materials. Background Technology

[0002] With the rapid development of various electronic devices, electrical installations, and new energy vehicles, there is an urgent need for advanced energy storage equipment. Meanwhile, clean energy sources such as solar, wind, and tidal power, due to their significant fluctuations, often cannot be directly connected to the power grid. This necessitates the full integration of high-performance, high-capacity energy storage devices with the power grid system. Among existing energy storage technologies, supercapacitors, due to their rapid charge-discharge characteristics and long cycle life, demonstrate enormous potential and value in future energy systems.

[0003] Currently, supercapacitors employ two energy storage mechanisms. One is the double-layer capacitor, represented by carbon-based materials, which relies on the physical attraction between ions and the electrode surface; therefore, its capacitance primarily depends on the surface properties accessible to ions and the pore size distribution. The other is the pseudocapacitive principle based on metal oxides, where energy storage occurs through a reversible Faraday charge reaction process. In fact, regardless of the mechanism, electrode materials in supercapacitors play a crucial role in electrochemical performance, prompting researchers to actively develop novel high-performance electrode materials to meet the growing demands of emerging technologies. However, current supercapacitors exhibit relatively low energy densities, creating a bottleneck in their application and development. Obtaining high-capacitance and superior high-power supercapacitor carbon materials through simple, low-cost, and multi-faceted methods presents a significant challenge.

[0004] Among the electrode materials used, porous carbon materials, characterized by short ion transport distance, low resistance, and high charge storage density, have proven to be an ideal electrode material for supercapacitors. Biomass-derived carbon materials, due to their ability to inherit the unique structure, renewability, and environmental friendliness of their precursors, are currently the main raw materials for porous carbon preparation. The preparation of biomass porous carbon often requires activation with substances such as alkalis, acids, water vapor, and CO2, or is obtained through a template method. Patent CN102431993A discloses a method for preparing porous carbon materials using rice husks as a carbon source. This invention uses zinc chloride as an activator and employs microwave-assisted heating to obtain mesoporous carbon materials, which exhibit excellent rate performance in supercapacitors. Patent CN112794324A discloses a porous carbon material with high mesoporosity, which first undergoes hydrothermal treatment of lignin and alkali carbonates, followed by carbonization and activation processes. Patent CN109485029A discloses a method for preparing a layer-by-layer self-assembled lignin / oxalate composite through the layer-by-layer self-assembly of lignin and oxalate, followed by carbonization and acid washing to obtain a porous carbon material. The porous carbon material of this invention has a porous size of 200-1500 μm. 2 ·g -1 The pore volume is 0.5-1.5 cm³. 3 / g, its application in supercapacitors exhibits 320 Fg -1 It exhibits high specific capacitance and excellent rate performance. Although numerous studies and patents have reported on this technology, it often faces drawbacks such as complex processes, high costs, and low specific surface area and mesoporous ratio of carbon materials. Summary of the Invention

[0005] To address the problems existing in current technologies, this invention provides a method for preparing porous carbon for supercapacitors from biomass and plastics. By adding waste plastics to waste biomass raw materials, the synergistic carbon-promoting effect between the two substances and the strong interaction during the carbonization process allows for in-situ control of pore structure, defect level, and microstructure. Furthermore, using waste biomass and waste plastics as raw materials achieves the goal of preparing high-performance porous capacitor carbon with a simple and low-cost technology, while also fulfilling an environmentally friendly measure of resource recycling.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing porous carbon for supercapacitors from biomass and plastics includes the following steps:

[0008] Biomass and plastics are crushed, sieved, and dried. The uniformly mixed raw materials are gradually heated to a first temperature under an inert atmosphere and maintained for a period of time to obtain a pre-carbonized material. The pre-carbonized material is mixed with an activator and activated to form pores under an inert atmosphere at a second temperature to obtain a carbon material. The carbon material is acid-washed, water-washed, and dried to obtain porous carbon. The second temperature is higher than the first temperature.

[0009] Furthermore, the biomass is one or more of corn stalks, rice stalks, wheat stalks, poplar wood, pine wood, chemical lignin, organic solvent lignin, sulfate lignin, and alkali lignin, and the plastic is one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyethylene terephthalate; the mass ratio of biomass to plastic is 1~9:0~9.

[0010] Furthermore, the activator is one or more of ZnCl2, H3PO4, Na2CO3, NaHCO3, NaOH, K2CO3, KHCO3, and KOH; the acid used for pickling is one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0011] Furthermore, the inert atmosphere is one of high-purity nitrogen, high-purity argon, and high-purity helium.

[0012] Furthermore, the first temperature is 400~600℃, the holding time of the first temperature is 0.5~5h, and the rate of rising to the first temperature is 0.5~20℃ / min; the second temperature is 700~900℃, the holding time of the second temperature is 0.5~5h, and the rate of rising to the second temperature is 0.5~20℃ / min.

[0013] Furthermore, the mass ratio of pre-carbonized material to activator is 1:0~3.

[0014] Furthermore, the mixing methods for biomass and plastics include one or more of the following: wet mixing with stirring, dry ball milling mixing, and dry roller mixing.

[0015] The present invention also provides a porous carbon prepared by the above method.

[0016] The present invention also provides the application of the above-mentioned porous carbon in the preparation of electrode sheets, wherein the electrode sheets are prepared by coating the porous carbon, conductive agent and binder as described in claim 8 onto nickel foam.

[0017] Furthermore, the mass ratio of porous carbon, conductive agent, and binder is 8:1:1.

[0018] A method for preparing porous carbon for supercapacitors from biomass and plastics includes the following steps:

[0019] (1) Crush, sieve and dry all kinds of raw materials;

[0020] (2) Mix the two or more different types of materials processed in step (1) above in a certain proportion;

[0021] (3) The material obtained in step (2) above is heated to 400-600℃ in an inert atmosphere at a heating rate of 0.5-20℃ / min and held for 0.5-5h to promote the pre-carbonization of the material;

[0022] (4) Further activate and create pores in the pre-carbonized material of step (3) above, wherein the activation and pore-forming is performed in any of the following ways:

[0023] 1) The pre-carbonized material is activated to create pores in an inert environment at a temperature of 700~900℃;

[0024] 2) Mix the pre-carbonized material with the activator and activate it in an inert environment at a temperature of 700~900℃ to create pores;

[0025] (5) The carbon material obtained in step (4) above is acid-washed, water-washed and dried to finally obtain porous carbon material;

[0026] In step (1) of this invention, the particle size of the raw material screened is 80~200 mesh;

[0027] In step (1) of this invention, the drying temperature is 60~120℃ and the drying time is 12~48 h;

[0028] In step (1) of this invention, the raw materials are one or more of biomass and plastics. The biomass materials are one or more of corn stalks, rice stalks, wheat stalks, poplar wood, pine wood, chemical lignin, organic solvent lignin, sulfate lignin, and alkali lignin. The plastic materials are one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyethylene terephthalate.

[0029] Furthermore, the mixed substances in step (2) of the present invention are two or more of the above-mentioned materials, preferably alkali lignin and polyethylene terephthalate. The mixing method in step (3) of the present invention is one or more of stirring wet mixing, dry material ball milling mixing, and dry material roller mixing, preferably dry material roller mixing.

[0030] Furthermore, in step (3) of the present invention, the mixing time is 0.5~8h.

[0031] In step (3) of this invention, the inert atmosphere is one of high-purity nitrogen, high-purity argon, or high-purity helium.

[0032] In step (4) of this invention, the heating rate for further heating is 10℃ / min.

[0033] The activation time in step (4) of this invention is 0.5~4 h.

[0034] In step (4) of the present invention, the mixing method with the activator is one or more of the following: dry material ball milling, dry material roller mixing, and stirring wet mixing. The solvent for wet mixing is an aqueous solution, and the preferred mixing method is stirring wet mixing.

[0035] Furthermore, the activator is one or more of ZnCl2, H3PO4, Na2CO3, NaHCO3, NaOH, K2CO3, KHCO3, and KOH, preferably KOH.

[0036] Furthermore, the mixing time is 0.5 to 8 hours, preferably 6 hours.

[0037] The acid used in step (5) of this invention is one or more of sulfuric acid, nitric acid, and hydrochloric acid, preferably hydrochloric acid.

[0038] Furthermore, the water washing in step (5) of the present invention specifically involves repeatedly rinsing with deionized water until the deionized water after rinsing is neutral.

[0039] Furthermore, the drying in step (5) of the present invention is carried out at a temperature of 80~160℃ and for a time of 12~24h.

[0040] Beneficial effects

[0041] This invention promotes carbon generation through the synergistic effect between biomass and plastics, selectively modulates the pore structure and defect level, forming porous carbon materials with high specific surface area and high pore volume, while the defect level can be controlled between 0.50 and 1.00 (as measured by Raman spectroscopy). G / I D (Indicating the degree of defect) demonstrates excellent energy storage performance.

[0042] The preparation method of this invention includes physically mixing dried biomass raw materials, such as alkaline lignin, and waste plastics, such as PET, in a certain mass ratio to obtain a powder mixture, pre-carbonizing it under an inert atmosphere, and then performing a secondary activation treatment on the obtained material to obtain a porous carbon material. This invention provides a simple, low-cost, versatile, and efficient high-quality porous carbon material for supercapacitor applications, achieving a specific surface area of ​​1059.55 m² without the addition of an additional activator. 2 ·g -1 The hierarchical porous carbon material has a specific capacitance of 197.7 F·g. -1 (0.1 A·g-1 ) and 153.9 F·g -1 (0.1 A·g -1 By adjusting the appropriate activator, a specific surface area of ​​2857.70 m² was obtained. 2 ·g -1 The hierarchical porous carbon material has a specific capacitance of 310.5 F·g. -1 (0.1 A·g -1 ) and 237.8 F·g -1 (1 A·g -1 ).

[0043] This invention utilizes biomass resources and waste plastics as raw materials, focusing on the carbon-promoting mechanism between biomass and plastics. Through simple carbonization and activation processes, the pore structure and specific surface area of ​​the carbon material can be selectively controlled to obtain porous carbon materials with high specific surface area. Compared to traditional activated carbon materials, this is beneficial for further improving the capacity and rate performance of supercapacitors. Furthermore, this invention transforms waste into energy storage materials, offering significant environmental advantages, further reducing pollution emissions and enhancing resource utilization, and is a promising technology for achieving energy conservation and emission reduction. Attached Figure Description

[0044] Figure 1 This is a scanning electron microscope image of the hierarchical porous carbon material prepared in Example 2;

[0045] Figure 2 The Raman spectra of the hierarchical porous carbon materials in Examples 2 and 7 and Comparative Examples 1 and 2 are shown.

[0046] Figure 3 This is a nitrogen adsorption-desorption curve diagram for Example 2;

[0047] Figure 4 This is a nitrogen adsorption-desorption curve diagram for Example 7;

[0048] Figure 5 The graphs show constant current charge and discharge at different current densities in Example 2.

[0049] Figure 6 The graphs show constant current charge and discharge at different current densities in Example 7.

[0050] Figure 7 Cyclic voltammetry at different scan rates in Example 2;

[0051] Figure 8 The images show cyclic voltammetry at different scan rates in Example 7. Detailed Implementation

[0052] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below; obviously, the following description is only a part of the embodiments, and for those skilled in the art, the technical solution of the present invention can be applied to other similar scenarios without creative effort; to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention will be further described in detail below.

[0053] Example 1

[0054] Step 1: Crush PET (polyethylene terephthalate) and alkaline lignin separately, then sieve to obtain particles with a size of 80-100 mesh, and dry the particles in an oven at 80℃ for 24 hours.

[0055] Step 2: Weigh 7 g of treated alkaline lignin and 3 g of PET and mix them using a roller mixer. Add a certain mass of spherical zirconia beads during mixing to ensure thorough tumbling and mixing of the raw materials.

[0056] Step 3: Place the mixed raw materials in the constant temperature zone of a tube furnace, introduce high-purity nitrogen at a flow rate of 50 mL / min, and raise the temperature from room temperature to 600℃ at a heating rate of 2℃ / min. Hold the mixture at 600℃ for 2 hours for pre-carbonization.

[0057] Step 4: The pre-carbonized material is heated to 900℃ at a heating rate of 10℃ / min and held for 2 hours to promote further carbonization and pore formation. Then it is naturally cooled to room temperature to obtain carbon material.

[0058] Step 5: The carbon material obtained in Step 4 is acid-washed with 2 M hydrochloric acid, filtered, and then washed with distilled water until neutral. It is then dried in an oven at 105℃ to obtain porous carbon material.

[0059] Step 6: The above porous carbon material is mixed in a ratio of active material (porous carbon material): conductive agent (acetylene black): binder (polyvinylidene fluoride) = 8:1:1 and coated onto nickel foam to prepare an electrode sheet, which is then tested in 6 MKOH electrolyte.

[0060] This embodiment yielded a specific surface area of ​​949.29 m². 2 ·g -1 The micropore volume is 1.17 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 69.2% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D With a value of 0.77, the material's specific capacitance reaches 177.8 F·g. -1 (0.1 A·g-1 ) and 143.0 F·g -1 (1 A·g -1 ).

[0061] The high specific surface area and abundant porous structure are due, on the one hand, to the release of small molecule products during the high-temperature process. On the other hand, at an even higher secondary temperature, the alkaline substances in alkaline lignin act as activators, reacting with carbon and promoting further pore formation.

[0062] Example 2

[0063] Except that the mass ratio of alkaline lignin to PET in step two of Example 1 is 5g: 5g, the hierarchical porous carbon material was prepared using the same method as in Example 1.

[0064] This embodiment yielded a specific surface area of ​​1059.55 m². 2 ·g -1 The micropore volume is 1.44 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 74.3% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D With a value of 0.82, the material's specific capacitance reaches 197.7 F·g. -1 (0.1 A·g -1 ) and 153.9 F·g -1 (1 A·g -1 ).

[0065] The appropriate ratio of biomass to plastic is crucial, as it determines the strength of their respective effects on carbon reconstruction and synergistic carbon formation during pyrolysis. In this patent embodiment, a 5:5 ratio is optimal when no additional activator is used. Figure 1 The microstructure of carbon materials is shown, and the presence of pore structures can be clearly observed on their surface. Figure 2 The degree of defect in carbon materials was demonstrated. With the addition of PET plastic, its primary pyrolysis products condense and crosslink with the primary pyrolysis products of lignin, reconstructing the carbon and adjusting its degree of defect. Figure 3 These are the N2 physical adsorption-desorption curves of carbon materials. The large amount of nitrogen adsorption at low pressure indicates the existence of a microporous structure, and the appearance of hysteresis loops indicates that the carbon material surface has a mesoporous structure. Higher specific surface area and more micro and mesopores further enhance its energy storage performance. Figure 5The charge-discharge curves of the carbon material at different current densities, exhibiting highly linear behavior and nearly symmetrical shape, demonstrate that the anode material possesses ideal capacitive behavior and high energy storage performance. Analysis of the charge-discharge curves shows that the material's specific capacitance reaches 197.7 F·g⁻¹ (0.1 A·g⁻¹) and 153.9 F·g⁻¹ (1 A·g⁻¹). The CV curves were obtained at incremental scan rates from 5 to 100 mV / s. Figure 7 The carbon material exhibits a near-ideal rectangular shape, further demonstrating its capacitive properties and ultrafast response.

[0066] Example 3

[0067] Except that the mass ratio of alkaline lignin to PET in step two of Example 1 is 3g:7g, the hierarchical porous carbon material was prepared using the same method as in Example 1.

[0068] This embodiment yielded a specific surface area of ​​550.20 m². 2 ·g -1 The micropore volume is 0.46 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 54.3% of the micropores. The material's I... G / I D With a value of 0.87, the material's specific capacitance reaches 101.2 F·g. -1 (0.1 A·g -1 ) and 86.9 F·g - (1 A·g -1 ).

[0069] Compared to Examples 1, 2, and Comparative Example 1, the carbon material obtained in Example 3 does not have an advantage in specific surface area and pore volume, but it exhibits excellent energy storage performance. On the one hand, this material has relatively more micropores; on the other hand, its relatively more carbon defects provide sites for adsorbing ions.

[0070] Example 4

[0071] Except for replacing the initial heating rate of 20°C / min in step three of Example 1, the hierarchical porous carbon material was prepared using the same method as in Example 1.

[0072] This embodiment yielded a specific surface area of ​​723.52 m². 2 ·g -1 The micropore volume is 1.14 cm³. 3 ·g -1 Hierarchical porous carbon materials in which mesopores account for 92.3% of micropores.

[0073] Compared to the carbon material obtained in Example 1, the carbon material obtained in Example 4 has a higher proportion of mesopores. At a higher heating rate, the substances volatilized from the pyrolysis of biomass and plastics rapidly impact the carbon material, and there is less secondary reaction between biomass and plastics within a shorter timeframe. Ultimately, this results in a carbon material with fewer micropores and more mesopores.

[0074] Example 5

[0075] Except for replacing the initial heating rate of 10°C / min in step three of Example 1, porous carbon materials were prepared using the same method as in Example 1.

[0076] This embodiment yielded a specific surface area of ​​754.34 m². 2 ·g -1 The micropore volume is 1.20 cm³. 3 ·g -1 Hierarchical porous carbon materials in which mesopores account for 90.8% of micropores.

[0077] Compared to the carbon material obtained in Example 1, the carbon material obtained in Example 5 has a higher proportion of mesopores. At a higher heating rate, the substances volatilized from the pyrolysis of biomass and plastics rapidly impact the carbon material, and there is less secondary reaction between biomass and plastics within a shorter time. Ultimately, this results in a carbon material with fewer micropores and more mesopores. In this patent, a heating rate of 2°C / min is more conducive to the formation of porous carbon.

[0078] Comparative Example 1

[0079] Except that all raw materials in step two of Example 1 are replaced with alkaline lignin, porous carbon materials are prepared using the same method as in Example 1.

[0080] This comparative example yielded a specific surface area of ​​814.87 m². 2 ·g -1 The micropore volume is 0.55 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 83.6% of the micropores. The material's I... G / I D The value is 0.17, and the material's specific capacitance reaches 77.3 F·g. -1 (0.1 A·g -1 ) and 90.3 F·g -1 (1 A·g -1 ).

[0081] The carbon material obtained in Comparative Example 1 had a lower specific surface area and pore volume than the carbon material obtained in Example 1, indicating that the addition of PET can effectively adjust the specific surface area and improve the pore structure of the carbon material.

[0082] Comparative Example 2

[0083] Except that all raw materials in step two of Example 1 are replaced with PET, porous carbon materials are prepared using the same method as in Example 1.

[0084] This comparative example yielded a specific surface area of ​​6.47 m². 2 ·g -1 The micropore volume is 0.03 cm³. 3 ·g -1 A carbon material in which mesopores account for 95.7% of the micropores; this material's I... G / I D The value is 1.09, and the specific capacitance of this material is 11.8 F·g. -1 (0.1 A·g -1 ) and 2.6 F·g -1 (1 A·g -1 ).

[0085] Compared to the examples with added alkaline lignin, the carbon materials obtained when only PET is used as raw material have smaller specific surface areas and pore volumes, and their energy storage performance is lower than that of carbon materials prepared by mixing the two. Because PET does not contain alkaline substances or non-network structures that can act as activators, its activation and pore-forming effects are poor under high-temperature conditions.

[0086] Example 6

[0087] In the original Example 3, the carbon material obtained in step 3 was mixed with the activator. Specifically, the carbon material and potassium hydroxide were weighed at a mass ratio of 1:1. First, the potassium hydroxide was dissolved in distilled water. The carbon material was then added to the potassium hydroxide solution and stirred for 6 hours. Subsequently, the mixture was heated to 80°C to evaporate the water. After evaporation, it was transferred to a 105°C oven for further drying and dehydration for 24 hours. The dehydrated mixture was then placed in a tube furnace and heated to 850°C at a rate of 10°C / min and held for 2 hours. It was then allowed to cool naturally to room temperature. The remaining steps were the same as in Example 3.

[0088] This embodiment yielded a specific surface area of ​​1,240.45 m². 2 ·g -1 The micropore volume is 0.76 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 37.4% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D The value is 0.86, and the specific capacitance of this material is 185.3 F·g. -1 (0.1 A·g -1 ) and 164.9 F·g -1 (1 A·g-1 ).

[0089] Compared to Example 3, the carbon material obtained in Example 6 has a higher specific surface area and better energy storage performance. By adding an activator during the second temperature treatment, the reaction between the activator and carbon activates and creates pores in the carbon material, further resulting in a carbon material with a high specific surface area.

[0090] Example 7

[0091] The porous carbon material was prepared using the same method as in Example 7, except that the mass ratio of carbon material to potassium hydroxide was changed to 1:3 instead of 1 in Example 6.

[0092] This embodiment yielded a specific surface area of ​​2,857.70 m². 2 ·g -1 The micropore volume is 2.22 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 40.6% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D The value is 0.94, and the specific capacitance of this material is 310.5 F·g. -1 (0.1 A·g -1 ) and 237.8 F·g -1 (1 A·g -1 ).

[0093] Compared to other embodiments, Example 7 exhibits the best energy storage performance. An activator was added during the second temperature treatment process, with a carbon material to potassium hydroxide mass ratio of 1:3. This resulted in a porous carbon material with ultra-high specific surface area and certain defects, which is beneficial for ion energy storage.

[0094] Figure 4 The curves show the physical adsorption-desorption of nitrogen on carbon materials. The large amount of nitrogen adsorption at low pressure indicates the existence of a microporous structure, and the appearance of the hysteresis loop indicates that the carbon material surface has a mesoporous structure. Figure 6 The charge-discharge curves of the carbon material at different current densities, along with its highly linear behavior and nearly symmetrical shape, demonstrate that the anode material exhibits ideal capacitive behavior and high energy storage performance. Analysis of the charge-discharge curves shows that the material's specific capacitance reaches 1310.5 F·g. -1 (0.1 A·g -1 ) and 237.8 F·g -1 (1 A·g -1 CV curves were obtained at scan rates increasing from 5 to 100 mV / s. Figure 8The carbon material exhibits a near-ideal rectangular shape with a larger internal area, further demonstrating its capacitive properties and ultrafast response.

[0095] Example 8

[0096] The porous carbon material was prepared using the same method as in Example 7, except that the activation temperature was changed to 900°C instead of Example 7.

[0097] This embodiment yielded a specific surface area of ​​1920.73 m². 2 ·g -1 The micropore volume is 1.77 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 48.3% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D The value is 1.10, and the specific capacitance of this material is 232.2 F·g. -1 (0.1 A·g -1 ) and 183.6 F·g -1 (1 A·g -1 ).

[0098] Compared to Example 7, the carbon material obtained in Example 8 has a lower specific surface area and a decreased specific capacitance. The second activation temperature significantly affects the pore structure of the carbon material. Higher temperatures favor the reaction between potassium hydroxide and the carbon material, leading to a greater conversion of micropores to mesopores. However, this results in a relative reduction in micropores and specific surface area, as well as the collapse of some macropores and mesopores.

[0099] Example 9

[0100] The porous carbon material was prepared using the same method as in Example 7, except that the activation temperature was changed to 800°C instead of 800°C in Example 9.

[0101] This embodiment yielded a specific surface area of ​​2,539.96 m². 2 ·g -1 The micropore volume is 1.67 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 36.0% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D The value is 1.00, and the specific capacitance of this material is 252.9 F·g. -1 (0.1 A·g -1 ) and 219.2 F·g -1 (1 A·g -1 ).

[0102] Compared to Example 7, the carbon material obtained in Example 9 has a lower specific surface area and a lower specific capacitance. Different second activation temperatures significantly affect the pore structure of the carbon material; a temperature of 800°C produces an activation pore-forming effect. Selecting a suitable activation pore-forming temperature is crucial. In this patent, in the additional method of adding an activator at a second temperature, a temperature of 850°C is more conducive to forming porous carbon materials for supercapacitors.

[0103] Comparative Example 3

[0104] Except that the raw material in step two of Example 6 is replaced with alkaline lignin, porous carbon materials are prepared using the same method as in Example 6.

[0105] This comparative example yielded a specific surface area of ​​1403.71 m². 2 ·g -1 The micropore volume is 1.87 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 66.8% of the micropores. (The last part, "I," appears to be a typo and is left untranslated.) G / I D The value is 0.91, and the material's specific capacitance reaches 117.1 F·g. -1 (0.1 A·g -1 ) and 103.6 F·g -1 (1 A·g -1 ).

[0106] Compared to Example 7, the carbon material obtained in Comparative Example 3 has a lower specific surface area and a smaller specific capacitance. When the raw material is only alkaline lignin, even the addition of a small amount of activator during the second temperature activation process promotes pore expansion, as can be seen from the pore volume compared to Comparative Example 1. However, this is accompanied by the loss of carbon material, and the further expansion of pores is not conducive to ion adsorption.

[0107] Comparative Example 4

[0108] Except that the raw material in step two of Example 7 is replaced with PET, porous carbon materials are prepared using the same method as in Example 7.

[0109] This comparative example yielded a specific surface area of ​​3263.60 m². 2 ·g -1 The micropore volume is 1.70 cm³. 3 ·g -1 This is a hierarchical porous carbon material in which mesopores account for 16.3% of the micropores. The material's I... G / I D The value is 1.12, and the material's specific capacitance reaches 292.6 F·g. -1 (0.1 A·g-1 ) and 232.2 F·g -1 (1 A·g -1 ).

[0110] Compared to Example 7, Comparative Example 4 yielded a carbon material with the highest specific surface area. However, the carbon material had a lower specific capacitance, resulting in inferior energy storage performance compared to Example 7. The carbon material obtained in Comparative Example 4 had a lower mesoporous content, making it more difficult for ions to enter the micropores, thus reducing the number of accessible micropores. An appropriate micro-mesoporous ratio is necessary for excellent supercapacitor electrode materials. Furthermore, and crucially, a completely amorphous carbon structure does not promote charge localization at defect sites, leading to weakened interactions between ions and carbon and impaired ion adsorption.

[0111] Comparative Example 5

[0112] Except for step four in Example 3, carbon materials were prepared using the same method as in Example 3.

[0113] This comparative example yielded a specific surface area of ​​27.14 m². 2 ·g -1 The micropore volume is 0.13 cm³. 3 ·g -1 A carbon material in which mesopores account for 99.1% of the micropores; this material's I... G / I D The value is 0.88, and the material's specific capacitance reaches 13.1 F·g. -1 (0.1 A·g -1 ) and 5.6 F·g -1 (1 A·g -1 ).

[0114] The above results indicate that activation at the second temperature is necessary. Carbon materials that have not undergone the second temperature process do not undergo complete carbonization at 600°C alone, resulting in only partial pore formation.

[0115] Comparative Example 6

[0116] Except for replacing step three in Example 3 with a heating rate of 20°C / min and a temperature of 900°C, and omitting step four, carbon materials were prepared using the same method as in Example 3.

[0117] This comparative example yielded a specific surface area of ​​525.60 m². 2 ·g -1 The micropore volume is 0.61 cm³. 3 ·g -1 A carbon material in which mesopores account for 73.1% of the micropores; this material's I... G / I DWith a value of 0.95, the material's specific capacitance reaches 83.7 F·g. -1 (0.1 A·g -1 ) and 65.3 F·g -1 (1 A·g -1 ).

[0118] The above results indicate that the initial temperature hold primarily serves for pre-carbonization and to facilitate the secondary reaction between biomass and plastics to reconstruct new carbon materials. The initial temperature hold also promotes the formation of more micropores. Direct treatment at 900℃ leads to the rapid volatilization of volatile substances during pyrolysis, impacting the surface structure of the carbon material and thus forming more mesopores. It should be noted that shorter treatment times and higher temperatures retain some of the original biomass structure, which is also a contributing factor to the formation of more mesopores.

[0119] Comparative Example 7

[0120] The carbon material obtained in Example 3 was further mixed with an activator and activated to create pores at high temperature. Specifically, the carbon material and potassium hydroxide obtained in Example 3 were weighed at a mass ratio of 1:3. First, the potassium hydroxide was dissolved in distilled water, and the carbon material was added to the potassium hydroxide aqueous solution and stirred for 6 hours. Then, the mixture was heated to 80°C to evaporate the water. After evaporation, it was transferred to a 105°C oven for further drying and dehydration for 24 hours. The dehydrated mixture was then placed in a tube furnace and heated to 850°C at a heating rate of 10°C / min and held for 2 hours, followed by natural cooling to room temperature. Subsequently, it was acid-washed with 2M hydrochloric acid, filtered, and then washed with distilled water until neutral. Finally, it was dried in a 105°C oven to obtain the porous carbon material.

[0121] This comparative example yielded a specific surface area of ​​1102.73 m². 2 ·g -1 The micropore volume is 1.50 cm³. 3 ·g -1 A carbon material in which mesopores account for 70.0% of the micropores; the I of this material G / I D With a value of 0.90, the material's specific capacitance reaches 186.9 F·g. -1 (0.1 A·g -1 ) and 156.0 F·g -1 (1 A·g -1When carbon materials that have undergone a second temperature treatment are activated to create pores using an activator, the carbon materials are difficult to activate to obtain a high specific surface area, even with the addition of a high proportion of activator. Combined with Comparative Examples 4, 6, and 7, the technical advantages of the first temperature pre-carbonization and the higher second temperature activation in this patent are further demonstrated, enabling the easy preparation of porous carbon materials for use in supercapacitors.

[0122] This invention utilizes the re-condensation and cross-linking of the pyrolysis products of biomass and plastics at high temperatures to form carbon materials with a certain degree of defects. By adjusting the raw material ratio, the degree of defects in the material is improved, promoting ion adsorption at the defect sites. Furthermore, using a mixture of biomass and plastics as raw materials, pre-carbonization at a first temperature and activation pore formation at a second temperature achieves control over the specific surface area and pore structure. The presence of the plastic component effectively increases the microporous structure for ion adsorption, and adjusting the micro-mesopore ratio of the carbon material, with an appropriate amount of mesopores, promotes faster ion transport and transfer into the micropores. In Example 2, without adding additional activators, under the conditions of a biomass to plastic ratio of 5:5, a first temperature (pre-carbonization temperature) of 600°C, a heating rate of 2°C / min, and a second temperature of 900°C, the prepared carbon material exhibits the best energy storage performance under the same conditions. Its specific surface area, micro-mesopore ratio, and degree of defects are more suitable for supercapacitors. In Example 7, using an activator, with a biomass to plastic ratio of 3:7, a first temperature (pre-carbonization temperature) of 600°C, a heating rate of 2°C / min, a second temperature of 850°C, potassium hydroxide as the activator, and a pre-carbonized material to activator ratio of 1:3, the prepared carbon material exhibited the best energy storage performance according to this patent. This is due to the higher specific surface area, suitable micro-mesopore ratio, and a certain degree of defect in the carbon material.

Claims

1. The application of porous carbon in the preparation of electrode sheets, characterized in that, The electrode sheet is prepared by coating porous carbon, a conductive agent, and a binder onto nickel foam; the method for preparing the porous carbon includes the following steps: Biomass and plastics are crushed, sieved, and dried, then mixed using a roller mixer. The mixed raw materials are placed in the constant temperature zone of a tube furnace, and high-purity nitrogen is introduced at a flow rate of 50 mL / min. The temperature is increased from room temperature to 600℃ at a rate of 2℃ / min, and held at 600℃ for 2 hours for pre-carbonization to obtain pre-carbonized material. The pre-carbonized material is mixed with an activator, heated to 900℃ at a rate of 10℃ / min, and held for 2 hours, then naturally cooled to room temperature to obtain carbon material. The carbon material is acid-washed with hydrochloric acid, filtered, and then washed with distilled water until neutral. Finally, it is dried in a 105℃ oven to obtain porous carbon material. The biomass is alkaline lignin; the plastic is polyethylene terephthalate; the mass ratio of biomass to plastic is 1~9:1~9; the mass ratio of pre-carbonized material to activator is 1:1~3.

2. The application according to claim 1, characterized in that, The mass ratio of porous carbon, conductive agent and binder is 8:1:

1.

3. The application according to claim 1, characterized in that, The mass ratio of biomass to plastic is 3:

7.

4. The application according to claim 1, characterized in that, The concentration of the hydrochloric acid is 2M.

5. The application according to claim 1, characterized in that, Biomass and plastics are crushed and then sieved to obtain particles of 80-100 mesh size. The particles are then dried in an oven at 80°C for 24 hours and then mixed.

6. The application according to claim 1, characterized in that, Spherical zirconia beads are added when biomass and plastics are mixed.

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