Preparation method of porous carbon material and application of carbon material prepared by the method

Abstract

The application discloses a preparation method of a porous carbon material and application of the carbon material prepared by the method. The porous carbon is synthesized by taking plastic powder as a precursor, adding transition metal salt and metal halide and performing high-temperature carbonization, and the obtained material has a porous structure suitable for ion / electron transmission of an electrolyte, is high in self stability, large in specific capacitance, and not lower than 155 F.g ‑1 -1 when a current density is 1 A.g ‑1 The mixed capacitor assembled by using the carbon material and commercial Ni(OH)2 has high specific capacitance, excellent coulomb efficiency and good cycle performance.

Description

Technical Field

[0001] This invention relates to a method for preparing porous carbon materials, and also to the application of the carbon materials prepared by this method in energy storage. Background Technology

[0002] Polymer resin materials, due to their excellent fatigue resistance, abrasion resistance, and aging resistance, are highly versatile in applications such as beverage bottles, textiles, and films. With the widespread use of resin materials, their efficient recycling and high-value utilization have become research hotspots. PET, as a carbon-rich thermoplastic polyester, can be used to prepare novel porous carbon materials through thermochemical conversion, showing great potential in energy storage fields such as supercapacitors and lithium / sodium-ion batteries. For example, CN108394889 A discloses a method and equipment for extracting carbon materials from plastics, which involves heating plastics and metal halides together, using molten salt and a high temperature of approximately 1300℃ to promote the graphitization of carbon materials, with a current density of 1 A·g. -1 The specific capacitance of the obtained carbon material is 73.0 F·g. -1 Based on this, CN 110538637 A discloses a method for converting plastics into carbonaceous nanostructured materials. This method employs specific salt and heating techniques to reduce the carbonaceous structure to nanoscale dimensions, thereby increasing the specific capacitance of the carbonaceous nanostructured materials. The current density is 1 A·g. -1 The specific capacitance of the carbon nanostructure material is 162 F·g. -1 .

[0003] Hybrid supercapacitors (HSCs) combine battery-type Faraday electrodes (such as metal-organic frameworks, oxides, hydroxides, etc.) with electric double-layer capacitor (EDLC) electrodes, such as activated carbon, within the same energy storage unit, forming a unique synergistic working mechanism. The battery-type electrode provides high energy density through redox reactions, while the EDLC electrode achieves high power density through surface physical charge adsorption, ultimately achieving synergistic optimization of both performance characteristics.

[0004] The problem that needs to be solved is how to prepare carbon materials suitable for hybrid supercapacitor electrodes in one step using polymer resin materials. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing porous carbon materials, which is a simple method for preparing materials suitable for hybrid supercapacitor electrodes; another purpose of this invention is to provide applications of this porous carbon material.

[0006] Technical solution: The present invention provides a method for preparing porous carbon materials, comprising the following steps: taking resin, mixing it with a transition metal salt and / or a first metal halide, covering the mixture with a second metal halide, heating it to a temperature not lower than 600°C, and then cooling it down to perform carbonization.

[0007] Preferably, the transition metal salt is at least one selected from vanadium salt, chromium salt, manganese salt, iron salt, cobalt salt, nickel salt, and copper salt. More preferably, the transition metal salt is at least one selected from sulfate, nitrate, hydrochloride, phosphate, and carbonate of vanadium, chromium, manganese, iron, cobalt, nickel, and copper.

[0008] Preferably, the first metal halide and the second metal halide are the same or different, and each is independently selected from at least one of lithium, sodium, potassium, magnesium, calcium and zinc halides.

[0009] Preferably, the resin is at least one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS).

[0010] Preferably, the weight ratio of the resin to the total weight of the transition metal salt and / or the first metal halide is 5:0.3~3. When the transition metal salt and the first metal halide salt are added simultaneously, their weight ratio is 1:0.5~3, and the weight ratio of the resin to the second metal halide is 1:4~6. More preferably, the weight ratio of the resin to the total weight of the transition metal salt and / or the first metal halide is 5:0.8~1.8, where the transition metal salt is a nickel salt or a cobalt salt, and the first metal halide is a magnesium halide. When the transition metal salt and the first metal halide salt are added simultaneously, their weight ratio is 1:0.8~2.5. When the transition metal salt is a cobalt salt, the weight ratio of the cobalt salt to the magnesium halide is 1:1.2~2.5.

[0011] Preferably, the final carbonization temperature is 600~900℃, and the heating rate is 3~6℃ / min. More preferably, the final carbonization temperature is 650~750℃.

[0012] Preferably, the method for preparing porous carbon materials includes: mixing carbonization products with an alkali, and activating them at a temperature not lower than 600°C under inert gas protection. More preferably, the final activation temperature is 650~800°C, the activation heating rate is 3~6°C / min, and the activation duration is not less than 1.5 hours.

[0013] Preferably, the alkali is potassium hydroxide, the weight ratio of carbonization product to alkali is 1:3~9, and the activation duration is 1.5~2.5 hours.

[0014] Preferably, the method for preparing porous carbon materials includes: washing the activated product with water and / or acid until the activated product is neutral, and then drying it.

[0015] The porous carbon material prepared by the aforementioned method can be used as the negative electrode of a hybrid supercapacitor.

[0016] Preferably, the positive electrode of the supercapacitor is Ni(OH)2, and the electrolyte is KOH.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention prepares carbon materials by a one-pot method, utilizes molten salt to promote carbonization and improve the electrochemical performance of carbon materials, simplifies the process route, and the carbon materials prepared as negative electrodes have high stability and large specific capacity, 1 A·g -1 At current density, the specific capacitance is not less than 155 F·g -1 (1) The porous structure is suitable for electrolyte ion / electron transport; (2) The PET-derived carbon anode material prepared by the present invention has a high yield of carbon material prepared by the molten salt method, which is higher than that of commercial activated carbon (105~120 F·g). -1 (3) The PET-derived carbon material prepared in this invention exhibits better electrochemical performance and demonstrates good commercial value for waste utilization; (4) When assembled into a hybrid capacitor, Ni(OH)2 / / PAC-Ni exhibits the best energy storage performance at 1 A·g -1 Its specific capacitance can reach 159.76 F·g at a given current density. -1 . Attached Figure Description

[0018] Figure 1 SEM image of PAC-700 / 800 / 900 porous carbon prepared in Example 1;

[0019] Figure 2 Charge-discharge curves of PAC-700 / 800 / 900 porous carbon prepared in Example 1 at different current densities;

[0020] Figure 3 SEM image of PAC-Ni / Mg / NiMg prepared in Example 2;

[0021] Figure 4 N2 adsorption-desorption test and pore size distribution of PAC-Ni / Mg / NiMg prepared in Example 2;

[0022] Figure 5 XPS spectra of PAC-Ni / Mg / NiMg prepared in Example 2;

[0023] Figure 6 The charge-discharge curves of PAC-Ni / Mg / NiMg prepared in Example 2 at different current densities;

[0024] Figure 7The CV diagram of Ni(OH)2 / / PAC-Ni / Mg / NiMg prepared in Example 2;

[0025] Figure 8 Charge-discharge curves of Ni(OH)2 / / PAC-Ni / Mg / NiMg prepared in Example 2;

[0026] Figure 9 SEM image of PAC-Co / CoMg / CoMg2 prepared in Example 3;

[0027] Figure 10 N2 adsorption-desorption test and pore size distribution of PAC-Co / CoMg / CoMg2 prepared in Example 3;

[0028] Figure 11 XPS spectrum of PAC-Co / CoMg / CoMg2 prepared in Example 3;

[0029] Figure 12 Charge-discharge curves of PAC-Co / CoMg / CoMg2 prepared in Example 3 at different current densities;

[0030] Figure 13 The CV diagram of Ni(OH)2 / / PAC-Co / CoMg / CoMg2 prepared in Example 3;

[0031] Figure 14 The charge-discharge curves of Ni(OH)2 / / PAC-Co / CoMg / CoMg2 prepared in Example 3 under different current densities are shown. Detailed Implementation

[0032] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] Example 1: Supercapacitor negative electrode material prepared by carbonization of PET plastic and assembly and testing of asymmetric supercapacitor, including the following steps:

[0034] (1) First, transfer 5 g of PET plastic powder into a crucible and cover it with excess NaCl (about 25 g). Make three copies in parallel. Place the crucible in a muffle furnace and heat at a rate of 5 °C / min. -1 The material was carbonized in air at three different temperatures: 700 ℃, 800 ℃, and 900 ℃ (the temperature was immediately lowered after reaching the highest temperature). After carbonization, the carbonized material collected from the crucible was washed and dried (this method is also applicable to other types of plastic products, such as PE, PS, PVC, etc.).

[0035] (2) The dried material was mixed with KOH in water at a mass ratio of 1:6, left to stand for 12 h, and then dried at 60 °C until it reached a viscous state. Subsequently, it was placed in a tube furnace and dried at 5 °C·min. -1 The material was activated at a heating rate of 700 °C for 2 h in a nitrogen atmosphere. Finally, the activated material was washed with hydrochloric acid and deionized water until neutral and then dried to obtain three different carbon materials, labeled as PAC-700, PAC-800, and PAC-900 (PAC-700 / 800 / 900).

[0036] (3) Prepare a single electrode by mixing the material prepared in step (1) with acetylene black and PTFE in a mass ratio of 30:6:4. Perform a three-electrode test in a 6 mol / L KOH solution, where the carbon material is used as the working electrode, the Hg / HgO electrode is used as the reference electrode, and the Pt wire is used as the counter electrode.

[0037] Scanning electron microscope (SEM) images of carbon materials obtained at different carbonization temperatures are shown below. Figure 1 ,Depend on Figure 1 It can be seen that the three carbon materials have obvious layered and porous structures, such as Figure 1 In parts a and b, there are obvious gaps between the PAC-700 material sheets, and in some areas the sheets overlap with a sense of layering; for example... Figure 1 In parts c and d, PAC-800 exhibits a sponge-like structure; such as Figure 1 In parts e and f, the PAC-900 material exhibits a rough surface formed by the accumulation of a large number of small particles.

[0038] Charge-discharge curves of carbon materials obtained at different carbonization temperatures are shown below. Figure 2 As shown, within a voltage window of -1 to 0 V, the specific capacitance of the three PAC-700 / 800 / 900 materials at a current density of 1 A·g -1 The time was 150 F·g -1 139F·g -1 102 F·g -1 The specific capacitance of PAC-700 material is significantly higher than that of PAC-800 / 900. Therefore, we can deduce that the specific capacitance of carbon materials decreases with increasing carbonization temperature, meaning that the energy storage capacity of carbon materials weakens. Thus, the optimal carbonization temperature is determined to be 700℃.

[0039] Example 2: Effect of replacing the metal salt with Ni and / or Mg on the negative electrode material of a supercapacitor

[0040] (1) Grind and mix 5 g of PET plastic powder with 0.5 g of magnesium sulfate heptahydrate MgSO4·7H2O and 0.5 g of nickel chloride hexahydrate NiCl2·6H2O. Then transfer the mixture to a crucible and cover it with excess NaCl (about 25 g). Then carbonize it in air at 700°C in a muffle furnace. The remaining steps are the same as steps (2) to (3) of Example 1 to obtain PAC-NiMg.

[0041] (2) Change the mass of the metal salt in step (1) to 1 g magnesium sulfate heptahydrate MgSO4·7H2O and 1 g nickel chloride hexahydrate NiCl2·6H2O respectively to obtain PAC-Ni and PAC-Mg.

[0042] The SEM images of the three materials PAC-Ni / Mg / NiMg are shown below. Figure 3 ,like Figure 3 In part a, PAC-Ni exhibits a large lamellar structure with obvious wrinkles or irregular textures, a rough surface with some pits, and some rough particles in front of these pits; such as Figure 3 In part b, PAC-Mg exhibits a more complex structure, with aggregation forming irregular blocks, and internal porous or layered characteristics; for example... Figure 3 In part c, PAC-NiMg contains a large number of particles with similar shapes and sizes, and these particles are finely distributed without obvious large plate-like structures.

[0043] from Figure 4 The N2 adsorption-desorption tests showed that the N2 adsorption-desorption isotherms of all three materials exhibited H1-type hysteresis loop characteristics, indicating that the materials are mainly composed of uniform mesopores (2-50 nm) with nearly cylindrical or tubular channel shapes and good inter-channel connectivity, which is conducive to the rapid transport of electrolyte ions. The adsorption capacity of PAC-NiMg was between that of PAC-Ni and PAC-Mg, and the isotherm trend showed that the development level of its pore structure was also between the two, indicating a certain nitrogen adsorption capacity.

[0044] XPS spectra of the three carbon material samples prepared are as follows: Figure 5 As shown in the C 1s fractional integral plot, the peaks at 283.71 eV, 282.59 eV, and 283.51 eV correspond to Ni-C, Mg-C, and Ni-C / Mg-C bonds, respectively. Similarly, in the O 1s fractional integral plot, the peaks at 529.84 eV, 530.44 eV, and 530.05 eV correspond to Ni-O, Mg-O, and Ni-O / Mg-O bonds, respectively, which together confirm that the material contains Ni and Mg elements.

[0045] Figure 6 The charge-discharge curves of three materials, PAC-Ni, PAC-Mg, and PAC-NiMg, are shown from left to right. Their charge and discharge curves are nearly linear and exhibit good symmetry, suggesting that their capacitance originates from double-layer capacitance energy storage. At 1.0 A g... -1 At the given current density, the specific capacitances of samples PAC-Ni, PAC-Mg, and PAC-NiMg were 247.17 F / g. -1 227.88 Fg -1 237.17 F g -1 PAC-Ni exhibits the best charge storage capacity, while PAC-NiMg shows an improvement over PAC-Mg alone due to the effect of Ni. Figure 7 The images show the cyclic voltammetry curves of three materials, PAC-Ni, PAC-Mg, and PAC-NiMg, at different scan rates, from left to right. The images show that the CV curves of the three materials are approximately rectangular, which can also be used to determine that their energy storage mode is double-layer capacitor energy storage.

[0046] A Ni(OH)₂ / / PAC-Ni / Mg / NiMg device was fabricated using a commercially available Ni(OH)₂ electrode as the positive electrode, PAC-Ni / Mg / NiMg as the negative electrode, and 6 mol / L KOH as the electrolyte. Figure 8 The figures, from left to right, show Ni(OH)2 / / PAC-Ni, Ni(OH)2 / / PAC-Mg, and Ni(OH)2 / / PAC-NiMg at 1 A·g -1 At a given current density, Ni(OH)₂ / / PAC-Ni exhibits the largest specific capacitance, reaching 159.76 F·g. -1 , possibly as Figure 3 As shown, PAC-Ni has a large average pore size and a high degree of graphitization. The larger pore size and better conductivity allow for a more complete internal reaction.

[0047] Example 3: Effect of replacing the metal salt with Mg and / or Co on the negative electrode material of a supercapacitor

[0048] (1) Grind and mix 5 g of PET plastic powder with 0.5 g of magnesium sulfate heptahydrate MgSO4·7H2O and 0.5 g of cobalt chloride hexahydrate CoCl2·6H2O. Then transfer the mixture to a crucible and cover it with excess NaCl (about 25 g). Then carbonize it in air at 700 °C in a muffle furnace. The remaining steps are the same as steps (2) to (3) to obtain PAC-CoMg.

[0049] (2) Change the mass of the metal salt in step (1) to 1 g cobalt chloride hexahydrate CoCl2·6H2O or 0.5 g cobalt chloride hexahydrate CoCl2·6H2O and 1.0 g magnesium sulfate heptahydrate MgSO4·7H2O to obtain PAC-Co and PAC-CoMg2.

[0050] The SEM images of the three materials PAC-Co / CoMg / CoMg2 are shown below. Figure 9 ,like Figure 9 In part a, PAC-Co is distributed in an interwoven, needle-like aggregate of varying sizes, such as... Figure 9 In part b, PAC-CoMg shows a change in material structure after magnesium salt doping, exhibiting a veil-like distribution. This is likely due to the alteration of the crystal growth environment by the addition of Mg. Fibrous structures are also visible, which can increase the specific surface area and improve the transport and storage of electrolyte ions. With increasing amounts of magnesium salt added, such as... Figure 9 In part c, PAC-CoMg2 exhibits a strip-like structure. Compared to PAC-Co, PAC-CoMg has a finer and denser structure, exhibiting both regularity and complexity.

[0051] from Figure 10 The pore size distribution diagram shows that the pore sizes of the three materials are mainly distributed in the mesopore range. The N2 adsorption-desorption isotherms are all Type I isotherms. The PAC-CoMg material shows an increased specific surface area, presumably related to a decrease in the degree of graphitization. The pore volume of the three materials increases sequentially, indicating a more porous internal structure that can improve the transport efficiency of electrolyte ions.

[0052] Figure 11 XPS spectra of C, Co, and Mg in three materials are shown. In the C 1s spectrum, the structures around 282.7 eV, 284.3 eV, and 286.7 eV are presumed to be C-Co / CC, C=C, and CO bonds. The shift in the carbon peak at 282.7 eV is presumably due to the influence of the doped metal on the electron cloud density distribution. In the Co 2p spectrum, absorption peaks around 780 eV and 795.3 eV correspond to Co 2p3 / 2 and Co 2p1 / 2 absorption peaks, respectively. Furthermore, since PAC-Co lacks Mg, there is no characteristic XPS peak for Mg 1s. Characteristic Mg peaks were found around 1302 eV in PAC-CoMg and PAC-CoMg2, corresponding to the Mg-O characteristic peak. In summary, the XPS results show that active metal components were detected in all three carbon materials.

[0053] Figure 12In the image, from left to right, the charge-discharge curves of PAC-Co, PAC-CoMg, and PAC-CoMg2 are shown. All images exhibit good linearity. PAC-Co shows better symmetry, indicating less polarization during charge-discharge, better reversibility of the electrode reaction, lower energy loss, and more stable and efficient characteristics. (The image shows a charge-discharge curve for PAC-Co, PAC-CoMg, and PAC-CoMg2 from 1 A g.) -1 At a current density of [value missing], the specific capacitances of the three samples PAC-Co, PAC-CoMg, and PAC-CoMg2 were 200 F·g [value missing]. -1 155 F·g -1 163 F·g -1 The PAC-Co material has the largest specific capacitance, indicating that it has the strongest charge storage capacity. Figure 13 In the middle, from left to right, the cyclic voltammetry (CV) curves of three materials, PAC-Co, PAC-CoMg, and PAC-CoMg2, at different scan rates are shown. By comparison, the CV curve area of ​​PAC-Co is the largest compared to the other two materials. The larger the area, the stronger its charge storage capacity and the larger its specific capacitance. The CV curves of the other three samples show rectangular characteristics, which proves their double-layer capacitance characteristics.

[0054] Figure 14 As can be seen, from left to right, the galvanostatic charge-discharge curves of three devices—Ni(OH)2 / / PAC-Co, Ni(OH)2 / / PAC-CoMg, and Ni(OH)2 / / PAC-CoMg2—are shown at different current densities. (The last part, "1 A·g," appears to be an incomplete sentence or fragment and doesn't translate directly. It can be omitted.) -1 At the given current density, the specific capacitance of Ni(OH)₂ / / PAC-Co reaches 121.77 F·g. -1 The peak energy density is 28.75 W h·kg. -1 The power density is 1700 W·kg -1 However, it is slightly lower than that of Ni(OH)2 / / PAC-Ni. This may be because Ni contributes more to the capacitance during energy storage. Although the co-doping of Mg increases its specific capacitance by a limited margin, its specific surface area is improved, indicating that the introduction of Mg can regulate its morphology and structure.

Claims

1. A method for preparing porous carbon materials, characterized in that, The process includes the following steps: taking resin, mixing it with a transition metal salt and / or a first metal halide, covering the mixture with a second metal halide, heating it to a temperature not lower than 600°C, and then cooling it down to perform carbonization.

2. The method for preparing porous carbon materials according to claim 1, characterized in that, The transition metal salt is at least one of vanadium salt, chromium salt, manganese salt, iron salt, cobalt salt, nickel salt, and copper salt.

3. The method for preparing porous carbon materials according to claim 1, characterized in that, The first metal halide and the second metal halide may be the same or different, and each is independently selected from at least one of lithium, sodium, potassium, magnesium, calcium and zinc halides.

4. The method for preparing porous carbon materials according to claim 1, characterized in that, The resin is at least one of polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polystyrene.

5. The method for preparing porous carbon materials according to claim 1, characterized in that, The weight ratio of the resin to the total weight of the transition metal salt and / or the first metal halide is 5:0.3~3. When the transition metal salt and the first metal halide salt are added simultaneously, their weight ratio is 1:0.5~2.

5. The weight ratio of the resin to the second metal halide is 1:4~6.

6. The method for preparing porous carbon materials according to claim 5, characterized in that, The weight ratio of the resin to the total weight of the transition metal salt and / or the first metal halide is 5:0.8~1.8, where the transition metal salt is a nickel salt or a cobalt salt, and the first metal halide is a magnesium halide.

7. The method for preparing porous carbon materials according to claim 1, characterized in that, The final carbonization temperature is 600~900℃, and the heating rate is 3~6℃ / min.

8. The method for preparing porous carbon materials according to claim 1, characterized in that, The preparation method further includes: mixing the carbonized product with an alkali, activating it under inert gas protection by heating to a temperature not lower than 600°C, and activating it for a duration of not less than 1.5 hours.

9. The method for preparing porous carbon materials according to claim 8, characterized in that, The alkali is potassium hydroxide, the weight ratio of carbonization product to alkali is 1:3~9, the final activation temperature is 650~800℃, and the activation duration is 1.5~2.5 hours.

10. The application of the porous carbon material prepared by any one of claims 1 to 9 in supercapacitors.

Images