Preparation method and application of surface villus modified composite carbon material

Abstract

The invention discloses a surface villus modified composite carbon material preparation method, which comprises: S1, carrying out cleaning, drying and crushing treatment on a carbon source having a multi-dimensional skeleton structure to obtain multi-dimensional skeleton solid powder; s2, mixing the multi-dimensional skeleton solid powder obtained in the step S1 with one-dimensional cellulose nanofibers according to a certain mass ratio to form mixed solid powder, adding deionized water, stirring to form a uniform viscous material, and drying to obtain a fluff composite precursor; and S3, carrying out carbonization treatment on the fluff composite precursor obtained in the step S2 to obtain the surface fluff modified composite carbon material. According to the invention, the carbon composite material with fluff modification on the surface is directionally constructed by utilizing the idea of multidimensional carbon skeleton compounding, and the directional regulation and control of the physical morphology of the traditional carbon material are realized.

Description

Technical Field

[0001] This invention relates to the technical field of carbon composite materials, and in particular to the technical field of composite carbon materials with surface fluffing modification. Background Technology

[0002] With the rapid development of wearable and foldable electronic devices and IoT technology, the demand for high-performance flexible energy storage devices is becoming increasingly urgent. Flexible supercapacitors are considered an excellent alternative to traditional flexible batteries due to their high power density, fast charge and discharge capabilities, and long cycle life. However, traditional flexible supercapacitor electrode materials (such as activated carbon, carbon nanotubes, and graphene) still face severe challenges in terms of flexibility, cost, and sustainability. Against this backdrop, developing new carbon-based electrode materials that are low-cost and possess both excellent flexibility and high energy density has become an important research direction in the field of energy storage materials.

[0003] Among the many electrode materials, carbon materials have been widely used in the preparation of flexible supercapacitor electrodes due to their wide availability, low cost, excellent conductivity, and high chemical stability. The specific surface area, porosity, and conductivity of carbon materials are closely related to their morphology.

[0004] Carbon materials widely used in supercapacitor electrodes can be classified into three types based on their physical structure: three-dimensional porous carbon materials (such as biomass-derived carbon), two-dimensional layered structures (such as graphene), and one-dimensional carbon nanofibers.

[0005] Different physical structures have a crucial impact on the electrochemical energy storage performance of carbon materials; biomass-derived porous carbon materials have received widespread attention in recent years due to their advantages such as wide availability, low cost, and environmental friendliness; agricultural waste (such as rice husks, coconut shells, and corn stalks) can be converted into porous carbon materials after high-temperature carbonization because they are rich in cellulose, hemicellulose, and lignin; these carbon materials have a large specific surface area and better structural stability in recycling, but their conductivity is limited, and the rigid carbon skeleton is difficult to withstand repeated bending deformation; graphene has a layered structure, excellent flexibility, and high conductivity. However, this layered structure makes it prone to stacking after multiple cycles, limiting its long-term recycling. Cellulose nanofibers have a one-dimensional fibrous structure, are usually extracted from biomass, have no obvious melting point, and can maintain their physical morphology to form carbon fibers (CNF) after successful carbonization. This carbon fiber structure has excellent flexibility and conductivity. Based on the characteristics of carbon materials of different dimensions, the key scientific problem in this field is to simultaneously improve the conductivity, specific surface area, flexibility and cycle stability of multidimensional carbon materials through structural design, and to achieve the directional construction of the physical morphology of high-performance carbon materials.

[0006] Combining carbon materials of different dimensions can construct multidimensional conductive networks, potentially enabling the directional construction of unique physical morphologies of carbon materials to address the aforementioned issues. Currently explored carbon materials with unique morphologies include honeycomb structures, flower-like layered structures, and sea urchin-like structures. These materials possess unique physical morphologies and are expected to acquire numerous electrochemically active sites, thereby enhancing their electrochemical performance. However, morphology design typically employs metal / metal oxide surface growth, which is costly and environmentally unfriendly. Inspired by the "fluffy" structures found in nature (such as plant root hairs and animal hair), such multi-level fiber networks can endow materials with high specific surface area, excellent mechanical flexibility, and rapid ion transport capabilities, providing new ideas for the functional design of carbon materials. However, achieving the directional construction of "fluffy" carbon structures through green and low-cost processes remains a significant technical challenge. Summary of the Invention

[0007] To address the problems of poor flexibility, unstable cyclic structure, and lack of methods for the directional construction of physical morphology in traditional multidimensional carbon materials, this invention combines a precursor material with a multidimensional framework structure with cellulose nanofibers with a one-dimensional framework structure. Through a controllable pyrolysis process, the directional construction of "fluffy" flexible carbon materials is achieved, efficiently combining multidimensional framework carbon materials and one-dimensional carbon nanofibers, providing a new approach for the preparation of "fluffy" morphological carbon materials.

[0008] To achieve the above objectives, this invention proposes a method for preparing a composite carbon material with a surface textured surface, comprising the following steps: S1. The carbon source with a multidimensional framework structure is cleaned, dried and crushed to obtain a multidimensional framework solid powder.

[0009] S2. The multidimensional skeleton solid powder obtained in step S1 is mixed with one-dimensional cellulose nanofibers at a certain mass ratio to form a mixed solid powder. Deionized water is added and stirred to form a uniform viscous substance, which is then dried to obtain a villous composite precursor.

[0010] S3. The fluffy composite precursor obtained in step S2 is subjected to carbonization treatment to obtain a surface-fluffy modified composite carbon material.

[0011] Preferably, in step S1, the carbon source of the multidimensional framework structure has a three-dimensional framework structure or a two-dimensional layered structure.

[0012] Preferably, the three-dimensional skeleton structure is porous, tubular, or spiral.

[0013] Preferably, in step S1, the carbon source of the multidimensional framework structure is selected from one or more of biomass materials, asphalt, and graphene.

[0014] Preferably, the biomass material is selected from one or more of broad bean pod peels and soybean meal, lychee peel, and orange peel.

[0015] Preferably, in step S2, the one-dimensional cellulose nanofibers are derived from plant cellulose or bacterial cellulose.

[0016] As a preferred method, the preparation method of the plant cellulose nanofibers is as follows: Alkali treatment step: First, cellulose-rich biomass is mixed with an alkaline solution of 2-5% by mass, and magnetically stirred at 60-120℃ for at least 2 hours, then filtered and washed several times with deionized water to obtain solid residue; the solid residue is then subjected to acid treatment; the purpose of the above pretreatment process is to dissolve lignin and hemicellulose and extract cellulose; finally, the extracted cellulose is crushed to nanoscale size using a high-pressure homogenizer or ball mill to obtain cellulose nanofibers.

[0017] Preferably, the prepared cellulose nanofibers have a diameter range of 1-100 nm and a length range of 0.1-1 μm.

[0018] Preferably, the mass ratio of the multidimensional skeleton solid powder to the cellulose nanofibers is not less than 10:3.

[0019] The addition of an appropriate amount of cellulose nanofibers can prevent clogging of the pores or layered structures of carbon sources with multidimensional framework structures.

[0020] Preferably, in step S2, deionized water is added to the mixed solid powder in small amounts several times, and stirred at 200-500 rpm for 10-30 minutes using a magnetic stirrer until a uniform viscous substance is formed; then the uniform viscous substance is dried until completely dry to obtain the fluff composite precursor.

[0021] During this process, dynamic hydrogen bonds are formed between the hydroxyl groups on the surface of cellulose nanofibers through water molecules, and they are uniformly attached to the carbon source surface with a multidimensional structure, which is conducive to the formation of villous structures on the multidimensional framework carbon surface.

[0022] Preferably, in step S3, the specific steps of the carbonization treatment are as follows: the fluff composite precursor obtained in step S2 is subjected to high-temperature carbonization treatment, the carbonization heating rate is 2-10℃ / min, the atmosphere is CO2 gas, and the temperature is 600-800℃.

[0023] A CO2-active atmosphere is beneficial for increasing the surface porosity of composite carbon materials, forming an excellent surface porous structure.

[0024] The present invention also proposes a composite carbon material with surface villous modification, which is prepared by the above preparation method. The composite carbon material has villous fibers with a diameter of 40-80 nm and a length of 0.2-1 μm grown on its surface or in its pores.

[0025] Preferably, the composite carbon material has a specific surface area of ​​500~1000m² / g and a graphite interlayer spacing greater than 0.35nm.

[0026] The present invention also proposes the application of the above-mentioned surface-textured composite carbon material in the field of energy storage.

[0027] Preferably, the composite carbon material is used as the electrode of the flexible supercapacitor.

[0028] The beneficial effects of this invention are: 1. This invention utilizes the concept of multidimensional carbon skeleton composite to directionally construct carbon composite materials with a fluffy surface, thereby achieving directional control of the physical morphology of traditional carbon materials; 2. This invention can realize the directional construction of villous carbon materials using bibimbap-based carbon materials, and the carbon source used is low-cost and has green sustainability; 3. This invention uses dual-carbon-based materials and does not use any polluting chemical reagents. It employs a method of hydrolyzed cellulose hydrogen bonding crosslinking and cellulose nanofiber physical winding to successfully composite fluffy carbon fibers onto the surface and pores of multidimensional carbon materials through a simple mixed pyrolysis carbonization method. The preparation conditions and process are simple.

[0029] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0030] Figure 1 These are SEM images of the original three-dimensional biomass and one-dimensional cellulose nanofibers; Figure 2 This describes the skeleton structure and surface morphology of the comparative example BBHS and the embodiment BBHS@CNF of the present invention; Figure 3 These are TEM images and element mappings of the comparative BBHS and the embodiment BBHS@CNF of this invention; Figure 4 These are the N2 adsorption / desorption curves of the comparative example BBHS and the example BBHS@CNF of this invention; Figure 5 These are the XRD and Raman spectra of the comparative example BBHS and the example BBHS@CNF of this invention; Figure 6 These are the XPS spectra of the comparative BBHS and the example BBHS@CNF of this invention; Figure 7 This is an electrochemical performance curve of the comparative example BBHS and the example BBHS@CNF of the present invention; Figure 8This is an electrochemical performance curve of the flexible supercapacitor composed of BBHS@CNF in the embodiments of the present invention at different bending angles; Figure 9 This is an electrochemical performance curve of the symmetrical flexible supercapacitor assembled by BBHS@CNF according to an embodiment of the present invention; Figure 10 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0031] Example 1 Reference Figure 1 to Figure 10 A method for preparing a composite carbon material with a surface textured surface includes the following steps: Step 1: Rinse the broad bean skins with deionized water to remove surface impurities. Dry the washed broad bean skins at 110℃ until all moisture is removed. Crush the dried broad bean skins with a pulverizer and pass them through a 60-mesh sieve. Step 2: Use plant-based cellulose nanofibers as the source of one-dimensional carbon fibers.

[0032] The preparation method of plant cellulose nanofibers is as follows: Alkali treatment: First, mix the cellulose-rich biomass (such as straw, bamboo, and wood) with an alkaline solution (such as KOH or NaOH) with a mass concentration of 2-5%. Stir magnetically at a temperature of 60-120℃ for at least 2 hours, then filter and wash several times with deionized water to obtain solid residue. The solid residue was then treated with an acid solution following the steps described above. Finally, the extracted cellulose is broken down to nanoscale size using a high-pressure homogenizer or ball mill to obtain cellulose nanofibers.

[0033] The prepared cellulose nanofibers have diameters ranging from 1 to 100 nm and lengths ranging from 0.1 to 1 μm.

[0034] Broad bean peel powder and cellulose nanofibers were placed in a beaker at a mass ratio of 10:1. A small amount of deionized water was added to the beaker to dissolve the cellulose nanofibers. The mixture was then magnetically stirred for 30 minutes to ensure that the broad bean peel powder and cellulose nanofibers were mixed evenly. The stirred viscous mixture was then dried at 90°C to obtain a mixed solid product.

[0035] Step 3: Transfer the mixed solid product into a ceramic boat and place it in a tube furnace. Heat it to 750°C at a heating rate of 10°C min⁻¹ under a CO₂ atmosphere and hold for 30 min.

[0036] After cooling, a composite carbon material with a "fluffy" surface is obtained, denoted as BBHS@CNF.

[0037] Step 4: The BBHS@CNF carbon material prepared above is mixed with acetylene black and polytetrafluoroethylene at a mass ratio of 7:2:1. Isopropanol is used to assist in grinding into an electrode film. The electrode film is cut into 1cm×1cm electrode sheets and placed in a drying oven at 115℃ for 8 hours along with 1cm×2cm nickel foam. Then, the electrode sheets are pressed onto one end of the nickel foam at a pressure of 6MPa for 25 seconds to obtain a composite carbon material BBHS@CNF electrode with a surface "fluff" modified by broad bean pod peel and cellulose nanofiber.

[0038] Step 5: The compacted electrode with nickel foam as the current collector prepared in Step 4 is used as the working electrode, counter electrode, and reference electrode, respectively, along with a platinum electrode and a saturated calomel electrode. Using 6M KOH solution as the electrolyte, the specific capacitance of the BBHS@CNF electrode was measured to be 204 F / g (current density = 1A / g) on ​​an electrochemical workstation; the charge transfer internal resistance was 1.1 Ω; and the working voltage window was 1.05V.

[0039] Step 6: The flexible BBHS@CNF electrode obtained in Step 5 is used to prepare a symmetrical flexible supercapacitor using polyvinyl alcohol (PVA)-KOH gel electrolyte.

[0040] The PVA-KOH gel electrolyte was prepared as follows: 3g of PVA was added to 30ml of deionized water; the solution was stirred in a water bath at 90℃ until it became clear; then 10ml of 6 M / L KOH was slowly added dropwise to the stirred PVA aqueous solution, and stirring was continued for 30min; after the mixed solution was cooled, the PVA-KOH gel electrolyte was obtained; the symmetrical flexible BBHS@CNF electrode was immersed in the PVA-KOH gel electrolyte (the active material parts were placed opposite each other), and dried at room temperature overnight to obtain FASSC.

[0041] Step 7: The voltage window of the flexible symmetrical supercapacitor was measured to be 2V under the two-electrode system, and it had a specific energy density of 100.6Wh / kg at a high power density of 2001W / kg.

[0042] Example 2 In this embodiment, the precursor biomass of the multidimensional framework carbon material is soybean meal.

[0043] The other specific operating steps are the same as in Example 1, as follows: Step 1: Rinse the soybean meal with deionized water to remove surface impurities. Dry the washed broad bean skins at 110℃ until all moisture is removed. Crush the dried soybean meal with a grinder and pass it through a 60-mesh sieve.

[0044] Step 2: Replace the broad bean pod powder with soybean meal powder.

[0045] Step 3 yields a composite carbon material with a surface "fluff" modified from soybean meal, denoted as BMC@CNF.

[0046] Step 4 yields the BMC@CNF electrode.

[0047] Step 5: The specific capacitance of the BMC@CNF electrode was measured to be 190 F / g (current density = 1 A / g) on ​​the electrochemical workstation; the charge transfer internal resistance was 1.2Ω; and the operating voltage window was 1.05V.

[0048] The symmetrical flexible supercapacitor obtained in step 6 is designated as FASSC-1.

[0049] Step 7 ultimately yields a voltage window of 2V for FASSC-1, with a specific energy density of 94.4Wh / kg at a high power density of 1999.1 W / kg.

[0050] This embodiment shows that the capacitance performance of soybean meal-derived carbon materials is slightly worse than that of broad bean pod-derived carbon materials, and the specific power density and energy density of the symmetrical flexible supercapacitors composed of them are slightly reduced.

[0051] Example 3 In this embodiment, the carbon source for the multidimensional framework structure is reduced graphene oxide.

[0052] Everything else is the same as in Example 1.

[0053] Step 1: Rinse the graphene oxide powder with deionized water to remove surface impurities; dry the washed graphene oxide powder at 110°C until all moisture is removed.

[0054] Step 2: Replace the broad bean pod powder with redox graphene powder.

[0055] Step 3 yields a composite carbon material with a surface "fluff" modified by redox graphene, denoted as RGO@CNF.

[0056] Step 4 yields the RGO@CNF electrode.

[0057] Step 5: The specific capacitance of the RGO@CNF electrode was measured to be 170 F / g (current density = 1 A / g) on ​​an electrochemical workstation, the charge transfer internal resistance was 0.9 Ω, and the working voltage window was 1.05 V.

[0058] The symmetrical flexible supercapacitor obtained in step 6 is designated as FASSC-2.

[0059] Step 7 ultimately yields a voltage window of 2V for FASSC-2, with a specific energy density of 83.3Wh / kg at a high power density of 1999W / kg.

[0060] This embodiment shows that the specific capacitance of the "fluffy" carbon material composed of reduced graphene oxide and cellulose nanofibers remains almost unchanged, but the charge transfer resistance decreases, resulting in better conductivity. The specific power density and energy density of the symmetrical flexible supercapacitor formed by this material decrease slightly.

[0061] Example 4 In this embodiment, the one-dimensional cellulose nanofibers are bacterial cellulose nanofibers.

[0062] Everything else is the same as in Example 1.

[0063] Step 2: Using bacterial cellulose nanofibers as the source of one-dimensional carbon fibers, broad bean pod powder and bacterial cellulose nanofibers were placed in a beaker at a mass ratio of 10:1. A small amount of deionized water was added to the beaker to dissolve the bacterial cellulose nanofibers, and the mixture was magnetically stirred for 30 minutes to ensure that the broad bean pod powder and bacterial cellulose nanofibers were mixed evenly. The stirred viscous mixture was then dried at 90°C to obtain a mixed solid product.

[0064] Step 3 yields the composite carbon material, denoted as BBHS@CNF-1.

[0065] Step 4 yields the BBHS@CNF-1 electrode.

[0066] Step 5: The specific capacitance of the BBHS@CNF-1 electrode was measured to be 195 F / g (current density = 1 A / g) on ​​the electrochemical workstation, the charge transfer internal resistance was 1Ω, and the working voltage window was 1.05V.

[0067] The symmetrical flexible supercapacitor obtained in step 6 is designated as FASSC-3.

[0068] Step 7 ultimately yields a voltage window of 2V for FASSC-3, with a specific energy density of 97.2Wh / kg at a high power density of 1999.5 W / kg.

[0069] This embodiment shows that the specific capacitance and charge transfer resistance of the "fluffy" carbon material composed of bacterial cellulose nanofibers are slightly reduced, and the specific power density and energy density of the symmetrical flexible supercapacitor composed of it are slightly decreased.

[0070] Example 5 In this embodiment, the mass ratio of broad bean peel powder to cellulose nanofibers is 10:2.

[0071] Everything else is the same as in Example 1.

[0072] Step 3 yields a composite carbon material with a surface "fluff" modified from soybean meal, denoted as BBHS@CNF-2.

[0073] Step 4 yields the BBHS@CNF-2 electrode.

[0074] Step 5 uses the same testing setup as in Example 1. The specific capacitance of the BBBHS@CNF-2 electrode was measured to be 220 F / g (current density = 1 A / g) on ​​an electrochemical workstation, the charge transfer internal resistance was 0.8Ω, and the operating voltage window was 1.05V.

[0075] The symmetrical flexible supercapacitor obtained in step 6 is designated as FASSC-5.

[0076] Step 7 ultimately yields a voltage window of 2V for FASSC-5, with a specific energy density of 111.1Wh / kg at a high power density of 1999.8 W / kg.

[0077] This embodiment demonstrates that composite carbon materials with increased cellulose nanofiber incorporation ratio exhibit higher specific capacity and lower charge transfer resistance, and the resulting symmetrical flexible supercapacitor shows a slight increase in specific power density and energy density.

[0078] Example 6 In this embodiment, the magnetic stirring time after adding biomass powder and cellulose nanofibers to deionized water is 10 minutes.

[0079] Everything else is the same as in Example 1.

[0080] Step 3 yields a composite carbon material with a surface "fluff" modified from soybean meal, denoted as BBHS@CNF-3.

[0081] Step 4 yields the BBHS@CNF-3 electrode.

[0082] Step 5: The specific capacitance of the BBBHS@CNF-3 electrode was measured to be 197 F / g (current density = 1 A / g) on ​​the electrochemical workstation, the charge transfer internal resistance was 1.1Ω, and the working voltage window was 1.05V.

[0083] The symmetrical flexible supercapacitor obtained in step 6 is designated as FASSC-5.

[0084] Step 7 ultimately yields a voltage window of 2V for FASSC-5, with a specific energy density of 98.3Wh / kg at a high power density of 1999.3W / kg.

[0085] This embodiment shows that the specific capacitance and charge transfer resistance of the "fluffy" composite carbon material electrode obtained by magnetic stirring for 10 min remain almost unchanged, while the specific energy density of the symmetrical flexible supercapacitor is slightly reduced.

[0086] Example 7 In this embodiment, step 3 involves transferring the mixed solid product into a ceramic boat and placing it in a tube furnace. Under a CO2 atmosphere, the furnace is heated to 700°C at a heating rate of 10°C min⁻¹ and held for 30 min. After cooling, a composite carbon material with a "fluffy" surface is obtained, denoted as BBHS@CNF-4.

[0087] Everything else is the same as in Example 1.

[0088] Step 4 yields the BBHS@CNF-4 electrode.

[0089] Step 5: The specific capacitance of the BBBHS@CNF-4 electrode was measured to be 187 F / g (current density = 1 A / g) on ​​the electrochemical workstation; the charge transfer internal resistance was 1.3 Ω; and the operating voltage window was 1.05 V.

[0090] The symmetrical flexible supercapacitor obtained in step 6 is denoted as FASSC-6.

[0091] Step 7 ultimately yields a voltage window of 2V for FASSC-6, with a specific energy density of 92.7Wh / kg at a high power density of 1999.8W / kg.

[0092] This embodiment shows that the specific capacitance of the fluffy composite carbon material electrode prepared by raising the carbonization temperature to 750°C is slightly reduced, the charge transfer resistance is increased, and the specific energy density of the symmetrical flexible supercapacitor is reduced.

[0093] Comparative Example 1: The operation was the same as in Example 1, except that the cellulose nanofibers in this comparative example were not hydrolyzed and cross-linked, but were directly mixed with biomass powder in powder form and pyrolyzed.

[0094] The composite carbon material obtained in this comparative example did not show obvious "fluff" morphology on its surface, and severe agglomeration occurred.

[0095] Comparative Example 2: The operation is the same as in Example 1, except that one-dimensional cellulose nanofibers are not introduced in this comparative example, but two-dimensional graphene is introduced. Three-dimensional biomass and two-dimensional graphene are mixed and pyrolyzed to obtain composite carbon materials.

[0096] The composite carbon material obtained in this comparative example did not exhibit a "fluffy" surface modification structure.

[0097] Comparative Example 3: This comparative example did not introduce cellulose nanofibers; instead, biomass-derived carbon materials were directly prepared by pyrolysis. The specific steps are as follows: Step 1: Rinse the broad bean skins with deionized water to remove surface impurities. Dry the washed broad bean skins at 110℃ until all moisture is removed. Crush the dried broad bean skins with a pulverizer and pass them through a 60-mesh sieve.

[0098] Step 2: Transfer the broad bean pod powder into a ceramic boat and place it in a tube furnace. Under a CO2 atmosphere, heat it to 750°C at a heating rate of 10°C / min and hold for 30 min. After cooling, the carbon material is obtained and is denoted as BBHS.

[0099] Step 3: Prepare the BBHS electrode, a carbon material derived from broad bean pod peel.

[0100] Step 4: The specific capacitance of the BBHS electrode was measured to be 144 F / g (current density = 1 A / g) using an electrochemical workstation.

[0101] The charge transfer internal resistance is 5.4Ω, and the operating voltage window is 1.05V.

[0102] The symmetrical flexible supercapacitor obtained in step 5 is designated as FASSC-7.

[0103] Step 6 ultimately yields a voltage window of 2V for FASSC-7, with a specific energy density of 68.8Wh / kg at a high power density of 2000W / kg.

[0104] in, Figure 1 (a) is a SEM image of broad bean pod skin before carbonization; Figure 1 (b) is a SEM image of cellulose nanofibers before carbonization.

[0105] from Figure 1 It can be seen that the broad bean pod skin has a three-dimensional spiral tubular skeleton structure and a regular, rough layered structure on the surface. This structure is expected to form an excellent three-dimensional skeleton structure after carbonization.

[0106] Cellulose nanofibers exhibit a distinct one-dimensional fibrous aggregate structure, and after carbonization, they are expected to form carbon nanofiber structures. Both materials are excellent "fluffy" composite carbon precursors.

[0107] Figure 2 (a) is a SEM image of BBHS; Figure 2 (b) is the SEM image of BBHS@CNF.

[0108] It can be seen that, compared with BBHS, BBHS@CNF has grown a "fluffy" structure on its surface and in its pores, indicating the successful composite of cellulose nanofibers.

[0109] The prepared composite carbon materials with surface-fiber modification have villous fibers with a diameter of 40-80 nm and a length of 0.2-1 μm growing on the surface or in the pores.

[0110] The composite carbon material has a specific surface area of ​​500~1000 m² / g and a graphite interlayer spacing greater than 0.35 nm.

[0111] Figure 3 (a) is a TEM image of BBHS; Figure 3 (b) is the TEM image of BBHS@CNF; Figure 3 (c) is the element mapping diagram of BBHS@CNF.

[0112] It can be seen that BBHS carbon materials exhibit a distinct disordered carbon structure, with the carbon crystal faces exhibiting a short-range ordered hard carbon morphology.

[0113] Compared to BBHS, BBHS@CNF exhibits a more ordered carbon crystal plane structure. The carbon crystal plane has a more long-range ordered structure, indicating that BBHS@CNF may have a higher degree of graphitization, which is more conducive to electron transfer. The elemental mapping diagram shows that there are a large number of C elements on the surface of BBHS@CNF, and self-doping of N and O atoms has been achieved.

[0114] Figure 4 (a) is the N2 adsorption-desorption curve of the BBHS sample; Figure 4 (b) is the N2 adsorption-desorption curve of the BBHS@CNF sample.

[0115] It can be seen that both materials have type I adsorption-desorption curves and H4 type hysteresis loops. These curve characteristics indicate that micropores and mesopores exist simultaneously in carbon materials. The pore size distribution results show that both BBHS and BBHS@CNF samples are dominated by a large number of mesoporous structures. The average pore size of the two carbon materials was calculated using the BJH method. The average pore sizes of BBHS and BBHS@CNF are 3.8 nm and 3.6 nm, respectively.

[0116] This invention relates to a composite carbon material with a surface "fluff" modification, which has excellent specific capacitance and rate performance as an electrode material for flexible symmetrical supercapacitors. The specific capacitance can reach 204 F / g, and the capacity retention rate can reach 81% at a high current density of 10 A / g. In aqueous electrolytes, it has a high voltage window of 1.05 V and extremely small charge transfer resistance (1.1 Ω).

[0117] The symmetrical flexible supercapacitor made from the composite carbon material modified by this "fluff" has a voltage window of up to 2V and can still have a high specific energy density of 100.6Wh / kg at a high power density of 2001W / kg.

[0118] Furthermore, the composite carbon material electrode modified with this "fluff" exhibits excellent mechanical flexibility, and the electrochemical performance of the flexible supercapacitor is almost unaffected by different bending angles.

[0119] Compared with existing carbon materials with unique physical morphology, this invention prepares composite carbon materials with unique "fluffy" physical morphology using inexpensive bibliophilic precursor materials. Compared with previous methods of preparing carbon materials by growing metal / metal compounds on the surface of carbon materials to directionally construct unique morphologies, this invention greatly reduces experimental costs and avoids pollution caused by chemical reagents, providing a new approach for the green and low-cost directional construction of carbon material physical morphology.

[0120] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite carbon material with a surface textured surface, characterized in that, Includes the following steps: S1. The carbon source with a multidimensional framework structure is cleaned, dried and crushed to obtain a multidimensional framework solid powder; S2. The multidimensional skeleton solid powder obtained in step S1 is mixed with one-dimensional cellulose nanofibers in a certain mass ratio to form a mixed solid powder. Deionized water is added and stirred to form a uniform viscous substance. After drying, a villous composite precursor is obtained. S3. The fluffy composite precursor obtained in step S2 is subjected to carbonization treatment to obtain a surface-fluffy modified composite carbon material.

2. The method for preparing the composite carbon material with surface textured fluff as described in claim 1, characterized in that: In step S1, the carbon source of the multidimensional framework structure has a three-dimensional framework structure or a two-dimensional layered structure.

3. The method for preparing the composite carbon material with surface textured fluff as described in claim 1, characterized in that: The carbon source of the multidimensional framework structure is selected from one or more of biomass materials, asphalt, and graphene; the one-dimensional cellulose nanofibers are derived from plant cellulose or bacterial cellulose.

4. The method for preparing the composite carbon material with surface textured fluff as described in claim 3, characterized in that, The preparation method of the plant cellulose nanofibers is as follows: First, the cellulose-rich biomass is treated with alkali and then with acid; finally, the extracted cellulose is crushed to nanoscale size using a high-pressure homogenizer or ball mill to obtain cellulose nanofibers.

5. The method for preparing the composite carbon material with surface textured fluff as described in claim 4, characterized in that: The prepared cellulose nanofibers have diameters ranging from 1 to 100 nm and lengths ranging from 0.1 to 1 μm.

6. The method for preparing the composite carbon material with surface textured fluff as described in claim 1, characterized in that: In step S2, the mass ratio of the multidimensional framework solid powder to the cellulose nanofibers is not less than 10:

3.

7. The method for preparing the composite carbon material with surface textured fluff as described in claim 1, characterized in that: In step S3, the specific steps of carbonization are as follows: the fluff composite precursor obtained in step S2 is subjected to high-temperature carbonization treatment, the carbonization heating rate is 2-10℃ / min, the atmosphere is CO2 gas, and the temperature is 600-800℃.

8. A composite carbon material with a surface textured surface, characterized in that: The composite carbon material is prepared by any one of the preparation methods described in claims 1-7, wherein villous fibers with a diameter of 40-80 nm and a length of 0.2-1 μm are grown on the surface or in the pores.

9. The composite carbon material with surface textured fluff as described in claim 8, characterized in that: The composite carbon material has a specific surface area of ​​500~1000 m² / g and a graphite interlayer spacing greater than 0.35 nm.

10. The composite carbon material with surface textured surface as described in claim 8 is used in the field of energy storage.

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