A method for preparing graphitized mesoporous carbon spheres using rapid Joule heating and its application

Abstract

The present invention discloses a method and application for preparing graphitized mesoporous carbon spheres using rapid Joule heat, belonging to the field of novel carbon materials and electrochemical technology. Specifically, it involves using a mixture of polycyclic aromatic hydrocarbon compounds and expanded graphite as a precursor, subjecting the solid precursor to instantaneous high temperature through the Joule heat generated by pulse discharge, and then rapidly cooling the polycyclic aromatic hydrocarbon compounds to highly ordered mesoporous carbon spheres in a very short period of time. By changing conditions such as the pretreatment process and Joule heat discharge parameters, the particle size and graphitization degree of the mesoporous carbon are regulated to achieve the preparation of highly graphitized carbon nanomaterials of expanded graphite-loaded mesoporous carbon. This method does not involve solvents and special gas atmospheres, and the preparation process is green, environmentally friendly, simple and easy. The prepared graphitized mesoporous carbon sphere / expanded graphite composite material is applied to potassium ion batteries, showing enhanced electrochemical energy storage properties, and provides ideas for the efficient preparation and performance optimization of graphitized mesoporous carbon.

Description

Technical Field

[0001] The present invention belongs to the field of novel carbon materials and electrochemical technology, and specifically relates to a method and application of preparing hollow graphitized mesoporous carbon spheres by using polycyclic aromatic hydrocarbon compounds and expanded graphite as raw materials through rapid Joule heat. Background Art

[0002] The development of high-performance lithium-ion batteries is crucial for regulating the energy output of intermittent renewable energy sources such as solar and wind power. In the foreseeable future, the high cost and limited availability of lithium resources will hinder the further application of lithium in this field. Potassium-ion batteries, as an ideal alternative to lithium-ion batteries for large-scale energy storage, have attracted widespread attention due to their abundant resources and low prices, and have gradually become a research hotspot in the field of new energy materials. Graphite-based materials exhibit amazing electrochemical activity as potassium-ion battery anodes because their layered structure can be used for potassium ion intercalation, and their low platform potential is not only suitable for electrode materials with high operating voltage and high energy density, but also avoids the formation of potassium dendrites and related safety issues.

[0003] Expanded graphite is a low-cost derivative of graphite, consisting of abundant nanosheets, and has the advantages of multi-scale pore structure, moderate specific surface area, and excellent thermal / electrical conductivity. However, due to the strong π-π interaction between the nanosheets, the product is very easy to form sheet stacking and agglomeration, resulting in the actual specific surface area being much smaller than the theoretical specific surface area, and the capacitance performance is not high. Using expanded graphite as a carbon carrier to insert nanomaterials between the layers, such as micro-nano carbon materials with high conductivity, high specific surface area and high stability, is expected to obtain composite electrode materials with improved comprehensive electrochemical performance. Graphitized mesoporous carbon spheres, also known as graphene spheres, are a kind of sp 3 Three-dimensional nanomaterials combined with hybrid orbitals can provide a spatial barrier to inhibit the accumulation of graphene nanosheets while maintaining the superior electrochemical properties of graphene itself. Common preparation methods for graphene spheres include chemical vapor deposition (CVD), template method, carbonization coating method, etc. Unfortunately, although the above methods give the materials excellent physical and chemical properties, defects such as cumbersome processing, high cost and strict condition control hinder their widespread application in industrial production. Therefore, designing graphitized mesoporous carbon spheres with a simple preparation process and achieving their macro-control has important practical significance and application value for obtaining carbon electrode materials with high energy storage properties. Summary of the Invention

[0004] To address the current challenges of complex, costly, and stringent control conditions for preparing graphene spheres, the present invention provides a method for preparing high-purity graphitized mesoporous carbon spheres using a rapid Joule heating technique. The method is simple, easy to operate, and readily commercializable. The composite carbon material produced by this method exhibits a high degree of graphitization, high electrical conductivity, and high specific capacitance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing graphitized mesoporous carbon spheres using rapid Joule heating comprises the following steps:

[0007] Step 1, using expanded graphite as a carrier and a conductive additive and a polycyclic aromatic hydrocarbon compound as a carbon source, the two raw materials are mixed in a mass ratio of 1:5 to 30 to obtain a mixture;

[0008] Step 2: placing the mixture in an autoclave, heating the temperature to 40-500° C. at a heating rate of 1-10° C. / min, maintaining the temperature for 2-10 hours, and taking out the polycyclic aromatic hydrocarbon compound / expanded graphite precursor wrapped by the crystals on the surface of the expanded graphite after cooling;

[0009] Step 3: Take the polycyclic aromatic hydrocarbon compound / expanded graphite precursor prepared in step 2 and use the high voltage, high heat and high pressure of rapid Joule heat to convert the polycyclic aromatic hydrocarbon compound into turbine-shaped graphitized mesoporous carbon spheres, which are loaded on the surface of expanded graphite to obtain graphitized mesoporous carbon spheres.

[0010] Furthermore, the mass ratio of the expanded graphite to the polycyclic aromatic hydrocarbon compound is 1:8-15.

[0011] Furthermore, the polycyclic aromatic hydrocarbon compound is any one of naphthalene, anthracene, phenanthrene, pyrene and their derivatives.

[0012] Furthermore, the treatment temperature in step 2 is 100-350°C.

[0013] Furthermore, the constant temperature time in step 2 is 6 to 10 hours.

[0014] Furthermore, the discharge time of the rapid Joule heat in step 3 is 0.5 to 5 seconds.

[0015] Furthermore, the pre-treatment capacitor voltage for rapid Joule heating in step 3 is 20 to 80V.

[0016] Furthermore, the number of times of the rapid Joule heating pretreatment in step 3 is 1 to 10 times.

[0017] Furthermore, the capacitor voltage of the rapid Joule heating in step 3 is 90 to 220V.

[0018] Furthermore, the number of rapid Joule heat discharges in step 3 is 1 to 5 times.

[0019] The present invention relates to a low-cost, environmentally friendly, recyclable, scalable, and sustainable fast Joule heating (FJH) technology that utilizes high-current discharge from a capacitor to convert polycyclic aromatic hydrocarbon compounds into a stable, naturally occurring carbon form, namely graphene, on a large scale. This process, which does not utilize furnaces, solvents, or reactive gases, produces so-called derivative graphitized mesoporous carbon spheres in less than one second, with a turbine structure between stacked graphene layers. Compared to currently used methods for preparing graphene-based carbon materials, the FJH synthesis method is environmentally friendly, efficient, and convenient, and the resulting graphene product has the advantages of high quality and few structural defects. In the composite material prepared by the present invention, (i) expanded graphite has high conductivity, acting as a conductive additive while facilitating the formation of a conductive network, thereby improving the electronic conductivity of the graphitized mesoporous carbon spheres; (ii) expanded graphite, as a carrier material with a unique structure, can disperse the aggregation of graphene spheres; and (iii) the graphitized mesoporous carbon spheres, in turn, provide a spatial barrier to prevent the re-accumulation of expanded graphite nanosheets. The graphitized mesoporous carbon sphere / expanded graphite composite electrode prepared by the present invention exhibits excellent rate performance when used in potassium ion batteries. In addition, graphitized mesoporous carbon has potential application in other aspects such as supercapacitor electrodes, catalysis, and functional materials.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. An environmentally friendly, green, simple and efficient method for preparing graphitized mesoporous carbon spheres was established.

[0022] 2. In the rapid Joule heating process, polycyclic aromatic hydrocarbons are used as carbon sources, and highly conductive and low-cost expanded graphite is used as a conductive additive and loading matrix. The Joule heat generated raises the temperature of the polycyclic aromatic hydrocarbons with poor conductivity to a high temperature and then rapidly drops it, avoiding the volatilization of the polycyclic aromatic hydrocarbon compounds, thereby achieving the conversion into high-purity, low-defect, high-quality graphitized mesoporous carbon spheres.

[0023] 3. The rapid Joule heating process simultaneously achieves the loading of graphitized mesoporous carbon spheres onto the multi-scale pore structure of expanded graphite. The expanded graphite disperses the aggregation of graphene spheres, which in turn provide a spatial barrier to prevent the re-accumulation of expanded graphite nanosheets.

[0024] 4. Compared with traditional synthesis methods, the FJH process does not contain any solvents, catalysts and reaction gases. The prepared graphitized mesoporous carbon spheres / expanded graphite exhibit significantly enhanced electrochemical performance when used as potassium ion battery anodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope photograph of the anthracene / expanded graphite precursor in Example 1;

[0026] Figure 2This is a scanning electron microscope photograph of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared in Example 1;

[0027] Figure 3 This is a transmission electron micrograph of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared in Example 1;

[0028] Figure 4 This is a high-magnification transmission electron microscopy photograph of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared in Example 1;

[0029] Figure 5 is the X-ray diffraction spectrum of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared in Example 1;

[0030] Figure 6 The rate performance test of a potassium ion battery half-cell assembled with the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared in Example 1 was conducted. DETAILED DESCRIPTION

[0031] The present invention is further described below with reference to several examples for a better understanding of the protection content of the present invention. However, it should be noted that the content to be protected by this application is not limited to the following embodiments.

[0032] Example 1

[0033] Example 1 provides an anthracene-derived graphitized mesoporous carbon sphere / expanded graphite and a preparation method thereof, the steps of which are as follows:

[0034] Expanded graphite and 98% pure naphthalene were mixed in a mass ratio of 1:8. The mixture was then sealed in a custom-made stainless steel reactor filled with argon and pretreated in a muffle furnace. The temperature was raised to 150°C at a rate of 2°C / min and held at that temperature for 8 hours to prepare the anthracene / expanded graphite precursor. 120 mg of the anthracene / expanded graphite precursor powder was transferred to a custom-made quartz tube. The loaded powder was compressed using copper gaskets as electrodes, which contacted the sample. A tungsten carbide cylindrical rod was connected to the circuit. The initial resistance was controlled to within 2Ω. Before the reaction, the FJH reaction chamber was evacuated to a pressure of 0.02 atm. A capacitor bank was then charged using a DC power supply. The parameters were: pretreatment capacitor voltage of 50V, five pretreatment cycles, applied capacitor voltage of 90V, and two discharge cycles. After the reaction, the apparatus was rapidly cooled to room temperature, ensuring that the capacitor bank was fully discharged. The product was then collected.

[0035] Example 2

[0036] Expanded graphite and 98% pure anthracene were mixed in a mass ratio of 1:8. The mixture was then sealed in a custom stainless steel reactor filled with argon and pretreated in a muffle furnace. The process described in Example 1 was used, with the capacitor voltage set at 90 V, 110 V, 130 V, 150 V, 180 V, 200 V, and 220 V, with each discharge repeated twice. The product was then collected. This yielded composite materials of anthracene-derived graphitized mesoporous carbon spheres / expanded graphite corresponding to different rapid Joule heating voltages.

[0037] Example 3

[0038] Example 3 provides a naphthalene-derived graphitized mesoporous carbon sphere / expanded graphite and a preparation method thereof, the steps are as follows:

[0039] Expanded graphite and 98% pure naphthalene were mixed in a mass ratio of 1:10. The mixture was then sealed in a custom-made stainless steel reactor filled with argon and pretreated in a muffle furnace. The temperature was raised to 100°C at a rate of 2°C / min and held constant for 10 hours to prepare the naphthalene / expanded graphite precursor. 120 mg of the precursor naphthalene / expanded graphite powder was transferred to a custom-made quartz tube. The loaded powder was compressed using copper gaskets as electrodes, contacting the sample. A tungsten carbide cylindrical rod was connected to the circuit. The initial resistance was controlled to within 2Ω. Before the reaction, the FJH reaction chamber was evacuated to a pressure of 0.02 atm. A capacitor bank was then charged using a DC power supply with the following parameters: a pretreatment capacitor voltage of 50V, five pretreatment cycles, an applied capacitor voltage of 90V, and two discharge cycles. After the reaction, the apparatus was rapidly cooled to room temperature, ensuring that the capacitor bank was fully discharged. The product was then collected. That is, a naphthalene-derived graphitized mesoporous carbon sphere / expanded graphite composite material is obtained.

[0040] Implementation Case 4

[0041] Expanded graphite and purity are 98% naphthalene in a mass ratio of 1:10 mixed.Then sealed in a special stainless steel reactor full of argon, placed in a muffle furnace and pre-treated, adopting the processing method of embodiment 3, capacitor voltage is arranged on 90V, 110V, 130V, 150V, 180V, 200V, 220V and each discharges 2 times.Subsequently, product is collected.That is, corresponding naphthalene-derived graphitized mesoporous carbon spheres / expanded graphite composite materials are obtained under different Joule thermal voltages.

[0042] Example 5

[0043] Example 5 provides a phenanthrene-derived graphitized mesoporous carbon sphere / expanded graphite and a preparation method thereof, the steps being as follows:

[0044] Expanded graphite and 98% pure phenanthrene were mixed in a mass ratio of 1:10. The mixture was then sealed in a custom stainless steel reactor filled with argon and pretreated in a muffle furnace, preferably at a heating rate of 3°C / min to 200°C and held there for 5 hours. The phenanthrene / expanded graphite precursor product was prepared. 120 mg of the precursor phenanthrene / expanded graphite powder was transferred to a custom quartz tube. The loaded powder was compressed using copper gaskets as electrodes, contacting the sample. A tungsten carbide cylindrical rod was connected to the circuit. The initial resistance was controlled to within 2Ω. Before the reaction, the FJH reaction chamber was evacuated to a pressure of 0.02 atm. A capacitor bank was then charged using a DC power supply with the following parameters: a pretreatment capacitor voltage of 20V, three pretreatment cycles, an applied capacitor voltage of 110V, and two discharge cycles. After the reaction, the apparatus was rapidly cooled to room temperature, ensuring that the capacitor bank was fully discharged. The product was then collected.

[0045] Example 6

[0046] Expanded graphite and 98% phenanthrene with a purity of 98% are mixed in a mass ratio of 1:10. The mixture is then sealed in a special stainless steel reactor filled with argon and placed in a muffle furnace for pretreatment. The process of Example 5 is adopted, and the capacitor voltage is arranged on 90V, 110V, 130V, 150V, 180V, 200V, and 220V, and each discharges 2 times. Subsequently, the product is collected. The corresponding naphthalene-derived graphitized mesoporous carbon spheres / expanded graphite composite materials are obtained under different Joule thermal voltages.

[0047] Example 7

[0048] Comparative Examples 1-6, Example 7 The expanded graphite is directly mixed with naphthalene, anthracene, and phenanthrene in a mass ratio of 1:10, respectively, without pretreatment. 120 mg of the three mixture powders are taken respectively and transferred to a customized quartz tube, and the loaded powder is compressed using a copper gasket as an electrode. The copper gasket is in contact with the sample, and the tungsten carbide cylindrical rod is connected to the circuit. The initial resistance is controlled within 2 Ω. Before the reaction, the FJH reaction box is vacuumed to reduce the air pressure in the box to 0.02 atmospheres. The capacitor bank is then charged with a DC power supply, and the parameters are set: pretreatment capacitor voltage 20 V, pretreatment number 5 times, applied capacitor voltage 120 V, and discharge number 1 time. After the reaction is completed, the device is rapidly cooled to room temperature to ensure that the capacitor bank is fully discharged. Subsequently, the product is collected.

[0049] Result analysis:

[0050] Figure 1 This is a scanning electron microscope image of the anthracene / expanded graphite precursor prepared according to Example 1. It can be clearly seen from the image that anthracene is wrapped around the surface of the expanded graphite in the form of crystals. Figure 2The anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material was prepared after rapid Joule heating according to Example 1. The mesoporous carbon spheres were uniform in size, with a particle size of about 30-40 nm. Figure 3 The transmission electron microscopy photograph of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared according to Example 1 under the condition of a diameter of 200 nm shows that the graphene spheres have the appearance of a grape bunch with an interconnected structure in three-dimensional space. Figure 4 This is a high-magnification transmission electron microscopy photograph of the anthracene-derived graphitized mesoporous carbon sphere / expanded graphite composite material prepared according to Example 1 at 20 nm. The material has a typical hollow nanocage morphology, which can effectively reduce the diffusion length of ions in the solid phase, thereby obtaining better electrochemical kinetics to ensure excellent rate performance. Figure 5 The X-ray diffraction spectrum shows that after rapid Joule thermal discharge, there is a very sharp and strong diffraction peak at 2θ of 25° without other impurities, corresponding to the C002 characteristic peak, indicating that anthracene is completely converted into highly graphitized mesoporous carbon spheres. When used as a negative electrode material for potassium ion batteries, the rate performance of this material is as follows Figure 6 As shown, at 0.1Ag -1 The charge capacity at a current density of 1000 mAh g -1 , at 2.0A g -1 It can still maintain 175.1mAh g -1 reversible capacity.

[0051] Any matters not described in detail in this specification are prior art known to those skilled in the art. Although the above description of the present invention is based on specific illustrative embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating, characterized in that: The steps include: Step 1, using expanded graphite as a carrier and a conductive additive and a polycyclic aromatic hydrocarbon compound as a carbon source, the two raw materials are mixed in a mass ratio of 1:5 to 30 to obtain a mixture; Step 2: placing the mixture of step 1 in an autoclave, heating the temperature to 40-500° C. at a heating rate of 1-10° C. / min, maintaining the temperature for 2-10 hours, and taking out the polycyclic aromatic hydrocarbon compound / expanded graphite precursor wrapped by the crystals on the surface of the expanded graphite after cooling; Step 3: Taking the polycyclic aromatic hydrocarbon compound / expanded graphite precursor prepared in step 2, using high voltage, high heat and high pressure of rapid Joule heating to convert the polycyclic aromatic hydrocarbon compound into turbine-shaped graphitized mesoporous carbon spheres, which are loaded on the surface of expanded graphite to obtain a graphitized mesoporous carbon sphere / expanded graphite composite material; The rapid Joule heating in step 3 requires pretreatment, and the pretreated capacitor voltage is 20 to 80V; the number of pretreatments is 1 to 10 times; the discharge time of the rapid Joule heating in step 3 is 0.5 to 5 s; the capacitor voltage of the rapid Joule heating in step 3 is 90 to 220V.

2. The method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating according to claim 1, wherein: The mass ratio of the expanded graphite to the polycyclic aromatic hydrocarbon compound is 1:8-15.

3. The method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating according to claim 1, wherein: The polycyclic aromatic hydrocarbon compound is any one of naphthalene, anthracene, phenanthrene, pyrene and their derivatives.

4. The method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating according to claim 1, wherein: The treatment temperature in step 2 is 100-350°C.

5. The method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating according to claim 1, wherein: The constant temperature time in step 2 is 6 to 10 hours.

6. The method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating according to claim 1, wherein: The number of rapid Joule heat discharges in step 3 is 1 to 5 times.

7. Use of a graphitized mesoporous carbon sphere / expanded graphite composite material prepared by the method for preparing a graphitized mesoporous carbon sphere / expanded graphite composite material using rapid Joule heating as claimed in any one of claims 1 to 6 as an electrode in a potassium ion battery.

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