Metallic manganese composite asphalt carbon material and preparation method and application thereof

Abstract

The invention discloses a manganese metal composite asphalt carbon material as well as a preparation method and application thereof, and relates to the technical field of carbon materials. The preparation method comprises the following steps: mixing a potassium permanganate solution, asphalt and a pore-forming agent, and carrying out solvothermal reaction to obtain an asphalt carbon precursor; and sequentially carrying out calcination, non-reducing acid leaching and solid-liquid separation on the asphalt carbon precursor to obtain the metal manganese composite asphalt carbon material. By using potassium permanganate and the pore-forming agent, the interlayer spacing and disorder degree of the carbon material are increased, the pore structure is rich, more interfaces are provided for rapid embedding and separation of sodium ions in carbon layer gaps, the sodium storage performance of the obtained carbon material is remarkably improved, the preparation method does not need expensive reagents and equipment, and the cost is low. The process is simple, the complexity and cost of the process are reduced, large-scale application is facilitated, and the method is suitable for producing electrode materials and being applied to sodium ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon materials, and particularly relates to a metal manganese composite asphalt carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its rich surface defects and functional groups, as well as the randomly arranged graphene sheet structure, hard carbon exhibits excellent and balanced performance in terms of reversible capacity, working potential, cycle life, and resource abundance. Therefore, it is regarded as one of the most promising candidate anode materials for sodium-ion batteries. Sodium-ion batteries have become an ideal choice with great potential in the field of large-scale energy storage due to their significant advantages such as abundant and widely distributed sodium resources, high safety and stability, and excellent low-temperature performance. However, in the development of anode materials for sodium-ion batteries, limited by the relatively large radius of Na+ ions (about 1.34 times that of lithium ions), traditional commercial graphite anodes for lithium ions perform poorly in sodium-ion batteries, which has become a key factor restricting the rapid development of the sodium-ion battery industry. Therefore, the development of hard carbon materials is of great significance for developing low-cost anode materials for sodium-ion batteries with simple manufacturing processes, safety, environmental friendliness, and excellent performance, and realizing their commercial applications.

[0003] The precursors of hard carbon mainly come from biomass, resins, polymers, and heavy organic substances, etc. Among them, coal tar pitch, as an important by-product of the coal chemical industry, is an important coal-based heavy organic substance. The asphalt carbon with wide sources, low price, and high carbon yield has become an ideal precursor for preparing carbon-based anode materials. However, due to the strong π-π interaction during the heating process, the polycyclic aromatic hydrocarbons in coal tar pitch easily cause the asphalt carbon material to form carbon sheets with nearly parallel stacking, resulting in less defects and higher graphitization degree of the obtained carbon material, which is not conducive to the intercalation of Na + with a large ionic radius, and the sodium storage performance is poor.

[0004] In addition, the current preparation methods of asphalt-based hard carbon materials are mainly limited to chemical activation and template addition, and generally have the disadvantage of cumbersome process flows. For example, the chemical activation method usually requires multiple impregnations, high-temperature treatments, and complex post-treatment processes. Each step requires precise control of reaction conditions and time, otherwise it is easy to cause a significant decline in material performance. In the template addition method, the selection range of soft / hard templates is narrow, and the removal process of the template may cause the collapse and damage of the target material shell, resulting in changes in the target structure and unstable performance. At the same time, these methods usually require the use of various chemical reagents and complex equipment, which have high requirements for the professionalism of operators and the production environment, further increasing the complexity and cost of the process, thus seriously affecting the large-scale production and practical application of asphalt-based hard carbon materials. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems in the prior art. To this end, the object of the present invention is to provide a method for preparing a metal manganese composite asphalt carbon material, which uses potassium permanganate having both cross-linking and oxidizing effects, combines with a pore-forming agent, regulates the structure and chemical evolution of asphalt, improves the sodium storage performance of the obtained carbon material, and has a simple process.

[0006] The second aspect of the present invention lies in providing a metal manganese composite asphalt carbon material.

[0007] The third aspect of the present invention lies in providing an electrode material.

[0008] The fourth aspect of the present invention lies in providing a sodium-ion battery.

[0009] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0010] The first aspect of the present invention provides a method for preparing a metal manganese composite asphalt carbon material, comprising the following steps:

[0011] Mix a solution of potassium permanganate, asphalt and a pore-forming agent, and carry out a solvothermal reaction to obtain an asphalt carbon precursor; successively calcine and acid-leach the asphalt carbon precursor with a non-reducing acid, and obtain the metal manganese composite asphalt carbon material after solid-liquid separation.

[0012] The present invention uses potassium permanganate as a cross-linking agent, which has both cross-linking and oxidizing functions. Combining with the use of a pore-forming agent, it can effectively regulate the structure and chemical evolution of asphalt during the solvothermal reaction and calcination processes.

[0013] Starting from the molecular structure level of asphalt, the strong oxidizing property of potassium permanganate is used to fully oxidize asphalt, significantly increasing the content of its surface oxygen-containing functional groups (such as carboxyl and hydroxyl groups). Then, during the calcination process, the introduced oxygen-containing functional groups are used to weaken the strong π-π bond interaction between aromatics in asphalt, inhibit the graphitization orientation of asphalt at high temperatures, and at the same time, the multivalent Mn enriched in asphalt reacts with the carbon atoms obtained by carbonization of asphalt during the calcination process to form a C-Mn-C three-dimensional structure, thereby reducing the graphitization degree of the carbon material and avoiding the formation of carbon sheets that are close to parallel stacking. The addition of the pore-forming agent successfully induces the formation of a rich hierarchical porous structure on the surface of the carbon material, increasing the active sites of the carbon material.

[0014] Therefore, through the use of potassium permanganate and the pore-forming agent, not only the interlayer spacing and disorder degree of the carbon material are increased, but also the pore structure is rich, and more interfaces are provided for the rapid insertion and extraction of sodium ions in the carbon layer gaps, significantly improving the sodium storage performance of the obtained carbon material.

[0015] In addition, the preparation method provided by the present invention does not require the use of expensive reagents and equipment, the process is simple, reducing the complexity and cost of the process, and is conducive to large-scale application.

[0016] Specifically, the solution of potassium permanganate is an aqueous solution of potassium permanganate.

[0017] Preferably, the mass ratio of the asphalt to the potassium permanganate is 1:(3-10).

[0018] More preferably, the mass ratio of the asphalt to the potassium permanganate is 1:(5-7).

[0019] Preferably, the mass ratio of the asphalt to the pore former is 1:(0.5-2).

[0020] More preferably, the mass ratio of the asphalt to the pore former is 1:(0.5-1.5).

[0021] Even more preferably, the mass ratio of the asphalt to the pore former is 1:(0.8-1.2).

[0022] Preferably, the asphalt is waste asphalt, such as waste coal asphalt.

[0023] More preferably, the softening point of the waste asphalt > 200 °C.

[0024] Preferably, the temperature of the solvothermal reaction is 150-250 °C, for example, it can be 160 °C, 180 °C, 200 °C, 230 °C or 250 °C.

[0025] More preferably, the temperature of the solvothermal reaction is 180-220 °C.

[0026] Even more preferably, the temperature of the solvothermal reaction is 200-210 °C.

[0027] Preferably, the time of the solvothermal reaction is 19-28 h.

[0028] Preferably, after the solvothermal reaction, it further includes the steps of washing and drying; the washing is centrifugal washing, and the precipitate obtained by washing is dried at 50-70 °C for 10-15 h.

[0029] Preferably, the temperature of the calcination is 800-1200 °C.

[0030] More preferably, the temperature of the calcination is 900-1100 °C.

[0031] Preferably, the time of the calcination is 1-5 h.

[0032] More preferably, the time of the calcination is 2-4 h.

[0033] Preferably, the non-reducing acid includes hydrochloric acid; the concentration of the non-reducing acid is 0.5 to 2 mol / L.

[0034] More preferably, the concentration of the non-reducing acid is 0.5 to 1.5 mol / L.

[0035] Even more preferably, the concentration of the non-reducing acid is 0.8 to 1.2 mol / L.

[0036] Preferably, the acid leaching step includes: immersing the product obtained by calcination in an acid solution, dispersing it, and then standing at room temperature overnight.

[0037] More preferably, the dispersion includes ultrasonic dispersion, stirring dispersion, and it is sufficient to achieve uniform dispersion.

[0038] Acid leaching can dissolve the residual magnesium component of the pore former and promote the formation of the carbon skeleton structure. During the acid leaching process, the amount of acid used can be such that it can submerge the product obtained by calcination.

[0039] Preferably, after the solid-liquid separation, it includes the steps of washing and drying; the drying temperature is 50 to 70 °C, and the drying time is 10 to 15 h.

[0040] Preferably, the pore former includes magnesium gluconate.

[0041] Using magnesium gluconate as the pore former is beneficial to maintaining the stability of the pore structure of the material and having good performance after washing with a non-reducing acid.

[0042] Preferably, the pitch is pretreated pitch; the pretreatment includes the following steps: crushing the pitch, mixing it with an alcohol solvent, and the solid obtained after solid-liquid separation is the pretreated pitch.

[0043] More preferably, the alcohol solvent includes ethanol. Ethanol, as a dispersant and extractant, can separate polycyclic aromatic hydrocarbon components and part of the oil phase from the pitch. Subsequently, after solid-liquid separation, the solid is obtained, and after washing with ethanol, it is dried at 50 to 70 °C for 10 to 15 h to complete the pretreatment.

[0044] Even more preferably, the mass ratio of the pitch to the ethanol is (40 to 60):1.

[0045] The second aspect of the present invention provides a metal manganese composite pitch carbon material prepared by the preparation method described in the first aspect of the present invention, and the metal manganese composite pitch carbon material is mainly composed of a composite phase of manganese tetroxide and graphite carbon.

[0046] More preferably, the metal manganese composite pitch carbon material contains a C-Mn-C crosslinked structure.

[0047] Preferably, the manganese metal composite asphalt carbon material contains mesopores and micropores structures.

[0048] Preferably, the interlayer spacing of the manganese metal composite asphalt carbon material is 0.34 - 0.4 nm.

[0049] More preferably, the interlayer spacing of the manganese metal composite asphalt carbon material is 0.36 - 0.4 nm. For example, the interlayer spacing can be 0.36 nm, 0.38 nm, 0.39 nm or 0.4 nm, and more preferably it is 0.37 - 0.39 nm.

[0050] The third aspect of the present invention provides an electrode material, and the electrode material includes the manganese metal composite asphalt carbon material described in the second aspect of the present invention.

[0051] Preferably, the electrode material is a positive electrode material or a negative electrode material.

[0052] More preferably, the negative electrode material further includes a conductive agent and a polymer matrix; the conductive agent is conductive carbon black, and the polymer matrix is polyvinylidene fluoride (PVDF).

[0053] More preferably, the mass ratio of the manganese metal composite asphalt carbon material, the conductive agent and the polymer matrix is (6 - 8):(1 - 3):1.

[0054] The manganese metal composite asphalt carbon material of the present invention contains a manganese tetraoxide phase, and the multivalence of Mn in the manganese tetraoxide can be used to generate a crosslinking effect with carbon atoms, expanding the interlayer spacing of the manganese metal composite asphalt carbon material, providing a place for the insertion and extraction of Li+ / Na+, thereby providing more lithium / sodium storage sites and improving the sodium storage performance. Therefore, it is very suitable for preparing electrode materials, especially negative electrode materials, to solve the problem that traditional commercial graphite negative electrodes perform poorly in sodium ion batteries.

[0055] The fourth aspect of the present invention provides a sodium ion battery, and the sodium ion battery includes the manganese metal composite asphalt carbon material described in the second aspect of the present invention, or the electrode material described in the third aspect of the present invention.

[0056] Compared with the prior art, the beneficial effects of the present invention are:

[0057] 1) The preparation method of the manganese composite asphalt carbon material provided by the present invention improves the content of oxygen-containing functional groups on the asphalt surface through potassium permanganate, weakens the strong π-π bond interaction between aromatic hydrocarbons during calcination to inhibit the graphitization orientation of the asphalt, and at the same time, Mn cross-links with carbon atoms to form a C-Mn-C three-dimensional structure, thereby reducing the graphitization degree of the carbon material and avoiding the formation of carbon sheets with nearly parallel stacking. The addition of the pore-forming agent enriches the hierarchical porous structure on the surface of the carbon material and increases the defects of the carbon material. Therefore, the preparation method of the present invention not only increases the interlayer spacing and disorder degree of the carbon material, but also enriches the pore structure, provides more interfaces for the rapid insertion and extraction of sodium ions in the carbon layer gap, significantly improves the sodium storage performance of the carbon material, and the preparation method has a simple process, does not require the use of expensive reagents or equipment, and is suitable for large-scale production.

[0058] 2) The manganese composite asphalt carbon material obtained by the preparation method of the present invention is mainly composed of a composite phase of manganese tetroxide and graphite carbon, and has a three-dimensional structure formed by C-Mn-C cross-linking, with a relatively low graphitization degree, and at the same time contains a rich mesoporous structure, increasing the surface defects of the carbon material and providing more sodium storage active sites. Therefore, the manganese composite asphalt carbon material obtained by the present invention can provide more interfaces for the rapid insertion and extraction of sodium ions in the carbon layer gap, has excellent sodium storage performance, and is suitable for preparing electrode materials, such as anode materials. When the anode material is used to prepare a sodium-ion battery, it is beneficial to improve the adsorption and desorption kinetics characteristics of the sodium-ion battery and enhance the electrochemical performance of the battery, especially the rate performance and cycle performance. Brief Description of the Drawings

[0059] Figure 1 It is a schematic diagram of the preparation process of the manganese composite asphalt carbon material in Example 1.

[0060] Figure 2 It is the SEM image of the manganese composite asphalt carbon material obtained in Example 1; among them, Figure 2 Figures a and b in it are SEM images at a scale of 500 nm, Figure 2 Figures c and d in it are SEM images at a scale of 200 nm.

[0061] Figure 3 It is the SEM image of the manganese composite asphalt carbon material obtained in Example 1 at a scale of 100 nm; among them, Figure 3 Figures a and b in it are SEM images at different positions.

[0062] Figure 4 It is the nitrogen adsorption-desorption isotherm curve and the corresponding pore size distribution diagram of the manganese composite asphalt carbon material obtained in Example 1.

[0063] Figure 5 It is the XRD pattern of the manganese composite asphalt carbon material obtained in Example 1.

[0064] Figure 6 The rate performance graph of the battery prepared with the manganese metal composite asphalt carbon material obtained in Example 1.

[0065] Figure 7 The first charge-discharge curve graph of the battery prepared with the manganese metal composite asphalt carbon material obtained in Example 1.

[0066] Figure 8 The cycle performance graph of the battery prepared with the manganese metal composite asphalt carbon material obtained in Example 1.

[0067] Figure 9 The cycle performance graph of the batteries prepared with the manganese metal composite asphalt carbon materials obtained in Example 1 and Example 2.

[0068] Figure 10 The rate performance graph of the batteries prepared with the manganese metal composite asphalt carbon materials obtained in Example 1 and Examples 3 - 4.

[0069] Figure 11 The rate performance graph of the battery prepared with the materials obtained in Example 1 and Comparative Example 1.

[0070] Figure 12 The XRD graph of the manganese metal composite asphalt carbon material after acid leaching in Comparative Example 1. Detailed implementation manners

[0071] The content of the present invention will be further described in detail through specific embodiments below. Unless otherwise specified, the raw materials, reagents or devices used in the embodiments and comparative examples can be obtained from conventional commercial channels or can be obtained by existing technical methods. Unless otherwise specified, the test or measurement methods are conventional methods in the art.

[0072] The following will be described in detail with specific embodiments.

[0073] Example 1

[0074] A preparation method of a manganese metal composite asphalt carbon material, the process is as Figure 1 shown, and specifically includes the following steps:

[0075] S1. Grind the needle-like waste coal tar pitch into fine particles, mix it with ethanol at a mass ratio of 50:1, and magnetically stir at room temperature for 3 h. During this process, ethanol serves as a dispersant and an extractant to separate the polycyclic aromatic hydrocarbon components and part of the oil phase in the pitch; then collect the precipitate by suction filtration and wash it with ethanol multiple times to remove the surface oil stains; place the washed pitch powder in an oven at 60 °C and dry it for 12 hours to obtain the pretreated waste coal tar pitch;

[0076] S2. Weigh the waste coal tar, potassium permanganate and magnesium gluconate solids obtained in step S1 in a mass ratio of 1:6:1, dissolve potassium permanganate in 150 mL of deionized water, stir until completely dissolved, and prepare a potassium permanganate solution; then, use a mortar to fully mix the waste coal tar and magnesium gluconate solids, and after mixing evenly, slowly add the mixture to the potassium permanganate solution, magnetically stir for 3 hours until the mixture is evenly mixed to form a mixed dispersion, and then transfer the mixed dispersion to a 200 mL polytetrafluoroethylene liner, seal it in a hydrothermal reactor, and perform a solvent thermal reaction at 200°C for 24 hours; after the reaction is completed, naturally cool to room temperature, use ultrapure water as a detergent, and centrifuge and wash the obtained precipitate three times; finally, place the product in a vacuum drying oven and vacuum dry it at 60°C for 12 hours to obtain an oxidatively cross-linked asphalt carbon precursor (cross-linked asphalt);

[0077] S3. The asphalt carbon precursor obtained in step S2 is spread on a corundum porcelain boat and placed in the center of the constant temperature zone of a tubular furnace, and nitrogen is introduced for atmosphere protection, and then the temperature is raised to 1000°C at a rate of 5°C / min, and calcined at this temperature for 3h; after the calcination, the furnace body is naturally cooled and annealed to obtain a gray hard block intermediate;

[0078] S4. The intermediate obtained in step S3 is immersed in a 1.0 mol / L hydrochloric acid solution and ultrasonically treated for 30 minutes until the system is fully dispersed. The main purpose of acid leaching is to dissolve the residual magnesium component and promote the formation of the carbon skeleton structure. After the ultrasonic treatment, it is allowed to stand overnight to achieve solid-liquid separation. Subsequently, the precipitate is collected by filtration and washed with ultrapure water for multiple times to remove residual acid and ion components. Finally, the obtained product is placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a metal manganese composite asphalt carbon material.

[0079] Example 2

[0080] A method for preparing a metal manganese composite pitch carbon material is different from that of Example 1 in that the solvent thermal reaction temperature in step S2 is 180° C.; the rest is the same as Example 1.

[0081] Example 3

[0082] A method for preparing a metal manganese composite pitch carbon material is different from that of Example 1 in that the mass ratio of waste coal tar and potassium permanganate in step S2 is 1:1; the rest is the same as Example 1.

[0083] Example 4

[0084] A method for preparing a metal manganese composite asphalt carbon material is different from that of Example 1 in that the mass ratio of waste coal tar and potassium permanganate in step S2 is 1:3; the rest is the same as Example 1.

[0085] Comparative Example 1

[0086] A preparation method of an asphalt carbon material, which is different from Example 1 in that: in step S3, the acid leaching is carried out with a mixed solution of oxalic acid and sulfuric acid instead of 1.0 mol / L hydrochloric acid solution; the rest is the same as Example 1. Among them, the preparation method of the mixed solution of oxalic acid and sulfuric acid is as follows:

[0087] Weigh 0.90 g of oxalic acid and dissolve it in 10 mL of distilled water to prepare a 1 mol / L oxalic acid solution; measure 14 mL of concentrated sulfuric acid, dilute it with 250 mL of distilled water and make up the volume to prepare a 1 mol / L sulfuric acid solution; mix 10 mL of the oxalic acid solution with 40 mL of the sulfuric acid solution to obtain a mixed solution of oxalic acid and sulfuric acid.

[0088] Result detection

[0089] Electrochemical performance test: Mix the metal manganese composite asphalt carbon materials prepared in each example with conductive carbon black (SuperP) and polyvinylidene fluoride (PVDF) evenly according to the mass ratio of 7:2:1, then add N-methylpyrrolidone (NMP) to make an electrode slurry, uniformly load it on the copper foil electrode, and coat it with a 150 μm thick coater to obtain an electrode; transfer the prepared electrode to a 60 °C vacuum oven for drying for 12 hours, and use it for assembling a half-cell after drying. The assembly of the half-cell is carried out in a glove box filled with argon, and the oxygen concentration and water concentration in the glove box are strictly controlled within 1 ppm. The electrolyte is a 1 mol / L sodium hexafluorophosphate solution, the separator is glass fiber GF / D, and the commercial sodium sheet is used as the reference electrode of the battery. In the electrochemical performance test, the voltage window is set to 0.01 - 3 V, and the current density is set to 0.1 A·g-1, 0.2 A·g-1, 0.5 A·g-1, 1 A·g-1, 2 A·g-1, 5 A·g-1, 10 A·g-1 for the rate performance test; the cycle performance test is carried out at a current density of 1 A·g-1.

[0090] Characterization of structural features: Carry out SEM and XRD characterizations on the metal manganese composite asphalt carbon material of Example 1.

[0091] The analysis of the test results is as follows:

[0092] 1. Characterization of the structural properties of the metal manganese composite asphalt carbon material of Example 1

[0093] Figure 2SEM image of the manganese metal composite asphalt carbon material of Example 1. Figures a and b therein are SEM images of the manganese metal composite asphalt carbon material of Example 1 at a scale of 500 nm. This SEM image shows that in the manganese metal composite asphalt carbon material, manganese tetroxide and the asphalt carbon matrix form a tight cross-linked network, and this cross-linked structure exhibits significant disorder characteristics, providing a convenient channel for the diffusion of sodium ions. Figure 2 Figures c and d therein are the material morphologies of the manganese metal composite asphalt carbon material at a scale of 200 nm. It can be observed that a rich hierarchical pore structure is distributed on its surface. This three-dimensional through-porous architecture can promote the sodium ion insertion / extraction kinetics and significantly improve the rate performance of the battery formed by the manganese metal composite asphalt carbon material.

[0094] Figure 3 Figures a and b therein both show the SEM images of the manganese metal composite asphalt carbon material at a scale of 100 nm. From Figure 3 it can be seen that the pore size distribution of the manganese metal composite asphalt carbon material of the present invention is mainly concentrated in the micropore (<2 nm) and mesopore (2 - 50 nm) ranges, presenting a stepped distribution state. The rich pore structure can shorten the ion transport path, promote the sodium ion insertion / extraction kinetics, and thus improve the rate performance of the battery.

[0095] Figure 4 Nitrogen adsorption / desorption isotherm curve of the manganese metal composite asphalt carbon material of Example 1. The attached figure therein is the corresponding pore size distribution diagram. From Figure 4 it can be seen that the adsorption / desorption isotherm curve of the manganese metal composite asphalt carbon material of the present invention presents typical type-IV characteristics and has an obvious hysteresis loop, indicating that there is a rich mesopore structure inside the material. Further combined with the pore size distribution diagram, it can be found that there are a large number of mesopore pores in the manganese metal composite asphalt carbon material, which is consistent with the fitting result of the adsorption / desorption isotherm.

[0096] Figure 5 Shows the spectrum of the manganese metal composite asphalt carbon material (Pitch-1000) obtained in Example 1 in the wide-angle XRD test. The test angle range is from 5° to 80°. By comparing the XRD results with the standard PDF card of manganese tetroxide (No. 80-0382), it can be determined that the product after calcination at 1000 °C is mainly composed of a composite phase of manganese tetroxide and graphite carbon, and no other impurity phases are detected, and the material has good homogeneity. In addition, by calculating the crystal plane spacing of the material (002) peak using Bragg's formula, it is obtained that the interlayer spacing of the manganese metal composite asphalt carbon material of the present invention is 0.381 nm, which is much larger than the interlayer spacing of graphite of 0.335 nm, indicating that the graphitization degree of this material is relatively low. At the same time, the interlayer spacing range is between 0.34 and 0.40 nm, indicating that the interlayer spacing obtained by the present invention is moderate and can provide a suitable sodium storage site.

[0097] 2. Electrochemical Performance Test of Sodium-Ion Batteries Prepared with the Manganese Composite Asphalt Carbon Material of Example 1

[0098] Figure 6 Fig. shows the rate performance of the battery prepared with the manganese composite asphalt carbon material of Example 1 in the current density range of 0.1 - 10 A / g. As Figure 6 can be seen, the specific capacity of the battery prepared with this manganese composite asphalt carbon material is 324.5 mAh / g at a current density of 0.1 A / g, which is significantly higher than that of the conventional asphalt carbon material without manganese tetroxide composite (generally about 90 mAh / g). At a high current density of 1.0 A / g, the battery using this manganese composite asphalt carbon material still maintains a capacity of 228 mAh / g, and the capacity retention ability is as high as 75.49%. In the present invention, the improvement of the performance of the manganese composite asphalt carbon material is mainly attributed to two important factors. One is that the cross-linked structure formed by the participation of multivalent manganese can provide an efficient channel for the migration of sodium ions in the electrolyte, thus significantly improving the rate performance of the material; the other is that the developed pore structure enhances the kinetic behavior during the sodium ion insertion and extraction process, further improving the capacity index of the material.

[0099] Figure 7 Fig. is the first charge-discharge curve of the battery prepared with the manganese composite asphalt carbon material of Example 1. It can be seen that the specific capacity of the battery prepared with this manganese composite asphalt carbon material is 389.5 mAh / g during the first discharge, and the charge specific capacity is 324.5 mAh / g. The corresponding first charge-discharge efficiency (ICE) is 83.3%. The relatively high first charge-discharge efficiency indicates that the battery prepared with the manganese composite asphalt carbon material of the present invention as the negative electrode material has a large reversible capacity, and the irreversible capacity consumed by the solid electrolyte interface (SEI) is relatively low, which reflects the good performance of the manganese composite asphalt carbon material. In addition, there is no obvious plateau in the charge-discharge curve, indicating that the capacity mainly comes from the insertion and extraction process of sodium ions.

[0100] Figure 8 Fig. is the performance of the manganese composite asphalt carbon material of Example 1 at a current density of 1 A / g after 150 cycles. The results show that the battery prepared with this material still maintains a capacity retention rate of 91.2% after 150 cycles, indicating that the structure of the material is stable during the cycling process, showing good cycle stability and excellent sodium storage performance.

[0101] 3. Comparison of Electrochemical Performance of Batteries Prepared with the Manganese Composite Asphalt Carbon Materials of Example 1 and Example 2

[0102] Figure 9Figure showing the effect of different solvothermal temperatures in Examples 1 and 2 on the cycling performance of batteries prepared with metal manganese composite asphalt carbon materials, where PHC-1000(200) corresponds to Example 1 and PHC-1000(180) corresponds to Example 2. The results show that at a current density of 1 A / g, when the solvothermal temperature is 180 °C, the specific capacity of the battery is 155.1 mAh / g; while when the temperature rises to 200 °C, the specific capacity of the battery at the same current density increases to 214.1 mAh / g, a year-on-year increase of 27.5%. The main source of this difference is the softening point temperature of the asphalt. The waste coal asphalt used as the raw material in the present invention has a relatively high softening point (>200 °C). When the solvothermal reaction temperature is low, the asphalt and potassium permanganate mainly undergo solid-phase reactions. Limited by the insufficient mass transfer driving force between the materials, the cross-linking and oxidation effects of potassium permanganate are not fully exerted. As the solvothermal temperature increases, the reaction gradually changes from a solid-phase reaction to a liquid-phase or emulsion-phase reaction, and the materials are more fully contacted, achieving uniform mixing at the microscale, thus significantly improving the modification effect of potassium permanganate and ultimately enhancing the performance of the material.

[0103] 4. Comparison of the electrochemical performance of batteries prepared with metal manganese composite materials in Example 1 and Examples 3 - 4

[0104] Figure 10 Figure showing the effect of different potassium permanganate addition amounts in Examples 1 and Examples 3 - 4 on the rate performance of batteries prepared with metal manganese composite materials, where PHC-1000(1:6) corresponds to Example 1, PHC-1000(1:1) corresponds to Example 3, and PHC-1000(1:3) corresponds to Example 4. The experimental results show that when the addition amount of potassium permanganate is 6 times that of the asphalt, the rate performance of the battery prepared with this material is optimal, and the specific capacity at a current density of 0.1 A / g reaches 324.5 mAh / g. As the addition amount of potassium permanganate decreases, the specific capacities of the prepared batteries decrease to 213 mAh / g (1:3) and 156.2 mAh / g (1:1) respectively, indicating that the addition amount of potassium permanganate has a significant impact on the cross-linking and oxidation effects of metal manganese composite asphalt carbon materials. When the addition amount of potassium permanganate is 6 times that of the asphalt, the interface between the metal manganese phase and the graphite carbon phase of the obtained metal manganese composite asphalt carbon material is more tightly combined, and the rate performance is better.

[0105] 5. Comparison of the electrochemical performance of batteries prepared with metal manganese composite asphalt carbon materials in Example 1 and Comparative Example 1

[0106] Pickling with conventional acids (such as hydrochloric acid / sulfuric acid, etc.) cannot thoroughly clean the manganese tetroxide in the metal manganese composite asphalt carbon material. Therefore, in the present invention, an acid with reducing properties is used to treat it. Manganese tetroxide is reduced by oxalic acid to lower its oxidation state, forming solid manganese oxalate. Then, sulfuric acid is used to dissolve the solid manganese oxalate, and finally, Mn is removed by centrifugation.

[0107] Figure 11 It shows the influence of the retention of the manganese tetroxide phase in the carbon structure on the electrochemical performance. It can be seen that when the metal manganese is removed, the electrochemical performance of the battery prepared from this material is significantly reduced. The specific capacity at a current density of 0.1 A / g is only 233.9 mAh / g, and when cycled to 10 A / g, the capacity is only 62.9 mAh / g, and the capacity retention rate is only 26.8%. In contrast, the capacity retention rate of the battery prepared from the metal manganese composite asphalt carbon material of Example 1 under the same conditions is 75.49%, which indicates that the rate performance of the carbon material after removing the manganese tetroxide phase has decreased significantly. This is because when the material is etched with a reducing acid, the cross-linked structure in the metal manganese composite asphalt carbon material is damaged, resulting in the deterioration of the electrochemical performance of the material. The manganese tetroxide phase plays a key role in the material structure, and its retention helps to maintain the stability of the cross-linked structure.

[0108] Figure 12 Shown is the XRD pattern of the asphalt carbon material obtained after treatment with the reducing acid in Comparative Example 1. It can be observed that after treatment, the characteristic diffraction peaks of manganese tetroxide have disappeared, which indicates that the reducing acid has successfully removed the manganese tetroxide phase in the material. What remains are mainly the characteristic peaks of the carbon material, including the standard diffraction peaks of the (002) crystal plane and the (100) crystal plane, which correspond to the layered structure and the planar structure of the graphite material respectively. The presence of these peaks indicates that the material still maintains a certain degree of graphitization after acid treatment.

[0109] In summary, in the present invention, by utilizing the strong oxidation ability of potassium permanganate, oxygen-containing functional groups are introduced into the asphalt during the preparation process, and at the same time, a C-Mn-C cross-linked structure is formed, significantly inhibiting the planar orientation problem of the asphalt carbon layer at high temperatures, increasing the micro disorder degree of the metal manganese composite asphalt carbon material, and improving the sodium storage performance of the material. At the same time, the pore-forming agent magnesium gluconate can induce the formation of a rich pore structure on the surface of the carbon material, thereby providing more sodium storage active sites. Therefore, the metal manganese composite asphalt carbon material prepared in the present invention is suitable for preparing the negative electrode material for sodium-ion batteries. The sodium-ion battery equipped with the metal manganese composite asphalt carbon material of the present invention has a specific capacity of 324 mAh / g at 0.1 A / g, a capacity retention rate of 91.2% after 150 cycles, and an initial Coulomb efficiency of 82.69%, with excellent electrochemical performance, good rate performance and cycle performance.

[0110] In addition, the preparation method of the present invention belongs to the solvothermal one-pot synthesis method, which integrates the steps of oxidation, crosslinking, and pore formation in one process section, can significantly simplify the process flow, improve production efficiency and atomic utilization rate, and is suitable for large-scale production.

[0111] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a metal manganese composite asphalt carbon material, characterized in that, It includes the following steps: Mix a solution of potassium permanganate, pitch, and a pore-forming agent, and conduct a solvothermal reaction to obtain a pitch carbon precursor; subject the pitch carbon precursor to calcination and non-reducing acid leaching in sequence, and obtain the metal manganese composite pitch carbon material after solid-liquid separation.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the pitch to the potassium permanganate is 1:(3-10); And / or, the mass ratio of the pitch to the pore-forming agent is 1:(0.5-2).

3. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction is 150-250 °C.

4. The preparation method according to claim 1, wherein The temperature of the calcination is 800-1200 °C.

5. The preparation method according to claim 1, characterized in that, The non-reducing acid includes hydrochloric acid; the concentration of the non-reducing acid is 0.5-2 mol / L.

6. The preparation method according to claim 1, characterized in that, The pore-forming agent includes magnesium gluconate.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The pitch is a pretreated pitch; the pretreatment includes the following steps: Crush the pitch, mix it with an alcohol solution, and the solid obtained after solid-liquid separation is the pretreated pitch.

8. A metal manganese composite asphalt carbon material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The metal manganese composite pitch carbon material is mainly composed of a composite phase of manganese tetroxide and graphite carbon.

9. An electrode material, characterized in that, The electrode material includes the metal manganese composite pitch carbon material described in claim 8.

10. A sodium-ion battery, characterized in that, The sodium ion battery includes the metal manganese composite pitch carbon material described in claim 8, or the electrode material described in claim 9.

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