MXene / C electrode material based on PAN carbonization and preparation method thereof

Abstract

According to the prepared MXene / C electrode material based on PAN carbonization, a nitrogen-doped carbon layer generated through polyacrylonitrile (PAN) in-situ carbonization serves as a supporting spacer to be inserted between MXene nanosheet layers, the MXene nanosheet layers are tightly bridged, the interlayer spacing of MXene is effectively enlarged, re-stacking of nanosheets is inhibited, and in the carbonization process, the MXene / C electrode material can be used for preparing the MXene / C electrode material based on PAN carbonization. Abundant mesopores and fissure holes are generated in the composite material by introducing and decomposing a sacrificial template (PMMA nanosphere), and a three-dimensional through ion transmission channel is constructed; the nitrogen-doped carbon layer not only serves as a supporting spacer to be inserted between MXene nanosheet layers, but also coats the surfaces of the MXene nanosheets,-F end groups on the surfaces of the MXene nanosheets are weakened, and C-O (H) and C-N functional groups are enriched, so that the interface wettability, the conductivity and the anti-oxidation stability of the material are improved, and the material can be widely applied to the technical field of electrochemical energy storage materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical energy storage materials, in particular to a composite electrode material for modifying two-dimensional layered materials by in-situ carbonization of polymers, and especially to a MXene / C electrode material based on PAN carbonization and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for sustainable energy and efficient energy storage systems worldwide, it is particularly important to develop electrochemical energy storage devices with high power density, long cycle life and fast charging and discharging capacity. As an electrochemical element between traditional batteries and ordinary capacitors, supercapacitors have a highly reversible energy storage process and mainly rely on physical mechanisms. Therefore, supercapacitors can be repeatedly charged and discharged without any effect on their specific capacitance. However, the energy density of supercapacitors is usually lower than that of batteries, which to some extent limits their wide application.

[0003] In order to obtain a device with high power and high energy density, the ideal electrode material should have high conductivity, large specific surface area and abundant electrochemical active sites. Two-dimensional transition metal carbides and nitrides (MXene), especially Ti3C2Tx, have been considered as a potential supercapacitor electrode material since its advent. Its unique layered structure, extremely high intrinsic conductivity (about 20000 S cm-1), hydrophilic surface and adjustable surface chemistry (end group T is -O, -OH, -F, etc.), can provide considerable double-layer capacitance and significant pseudo-capacitance.

[0004] However, there are two major technical obstacles on the way to push the actual performance of MXene to the theoretical limit: First, the uncontrollable stacking of nanosheet layers. Strong interlayer van der Waals forces make MXene nanosheets easily restack during film formation or electrode preparation, forming a dense microstructure. This stacking seriously blocks the ion transport channel, greatly reduces the effective specific surface area accessible to electrolyte ions, and significantly prolongs the ion diffusion path. As a direct result, the rate performance of the electrode is severely deteriorated. It performs well at low scan rates or small current densities, but as soon as it is subjected to fast charging and discharging, its available specific capacity will be sharply reduced. Second, the structural instability under electrochemical cycling. Especially in aqueous electrolytes (such as commonly used sulfuric acid and alkali), the active end groups on the surface (such as -OH) are not stable during long-term electrochemical cycling and are easily and irreversibly oxidized to form electrochemically inert titanium dioxide (TiO2). This process not only consumes the active sites that provide pseudo-capacitance, but also destroys the conductive network of the material, resulting in a continuous decrease in the specific capacitance of the electrode with the increase in the number of cycles, which seriously restricts the service life of the device.

[0005] To address these challenges, the prior art has proposed various improvements. For example, some studies have introduced one-dimensional carbon nanotubes or two-dimensional graphene as spacers to separate the MXene layers, which can alleviate the stacking to some extent. However, the foreign spacers often have poor interface contact with MXene, and may introduce additional costs and complex processes, even at the expense of the volumetric energy density of the electrode. Another strategy is to construct a three-dimensional porous aerogel structure to create more ion transport channels, but this method usually focuses on the regulation of physical structure and does not provide an effective solution to the intrinsic instability of MXene. Moreover, the preparation process is often cumbersome.

[0006] Therefore, there is an urgent need in the art for a simple, efficient and controllable electrode material that can simultaneously address the stacking problem of MXene and the intrinsic instability, as well as a preparation method thereof. SUMMARY

[0007] The present application aims to solve the above technical problems and provides a MXene / C electrode material based on polyacrylonitrile (PAN) carbonization with optimized structure and stable performance, as well as a preparation method thereof.

[0008] To this end, the present application provides a preparation method of a MXene / C electrode material based on PAN carbonization, comprising the following steps:

[0009] (1) Preparation of slurry:

[0010] Mix the MXene dispersion liquid with a solvent (such as anhydrous ethanol) and stir until uniform,

[0011] Add sacrificial template PMMA nanospheres to the above uniformly stirred dispersion liquid and continue stirring to disperse uniformly,

[0012] Add the polymer precursor polyacrylonitrile (PAN) and stir until completely dissolved to form a uniform mixed slurry;

[0013] (2) Shaping and pretreatment:

[0014] Form the mixed slurry obtained in step (1) into a thin film shape by vacuum filtration, and dry the shaped material at room temperature for 24 hours to obtain a self-supporting MXene / PMMA / PAN precursor thin film;

[0015] (3) Heat treatment:

[0016] Place the precursor thin film obtained in step (2) in a tube furnace and perform programmed temperature heat treatment under inert gas protection:

[0017] First, heat at a rate of 3℃ / min to 300℃ and hold for 1 hour to complete the pretreatment of PAN in an argon atmosphere,

[0018] Then, the temperature is increased to the target carbonization temperature at a rate of 5℃ / min, and the temperature is kept for 2 hours,

[0019] Finally, the temperature is naturally cooled to room temperature under the protection of argon, and a MXene / C electrode material is obtained by carbonization of polyacrylonitrile (PAN).

[0020] Specifically, during the heat treatment, the PAN undergoes cyclization, dehydrogenation and aromatization reactions, and is converted into nitrogen-doped amorphous carbon; at the same time, the PMMA nanospheres are decomposed and escape under heat, leaving pores in the material; and finally, the MXene / C composite electrode material with the characteristics of spacing, bridging and porosity is obtained. The MXene / C composite electrode material not only can realize effective spacing, conductive bridging and pore construction between the MXene layers at the same time, but also can form a protective layer on its surface to inhibit oxidation, thereby simultaneously improving its specific capacity, rate performance and cycle stability.

[0021] Preferably, the MXene is Ti3C2T x , which is etched from MAX Ti3AlC2 using HCL and LiF.

[0022] Preferably, the average Mw of the polyacrylonitrile (PAN) is 149000-151000.

[0023] The polymer precursor used in the application can be polyacrylonitrile (PAN) or quinone amine polymer (PAQ), and is preferably polyacrylonitrile (PAN).

[0024] Preferably, the mass ratio of the MXene to the PAN is 10:1-10:5, and is preferably 10:4.

[0025] Preferably, the diameter of the PMMA nanospheres is 1-3 microns, and is preferably 2 microns.

[0026] Preferably, the addition amount of the PMMA nanospheres is 20%-40% of the total mass of the MXene, the PAN and the PMMA, and is preferably 30%.

[0027] Preferably, the target carbonization temperature is 400℃-800℃, and is preferably 600℃.

[0028] A MXene / C electrode material based on carbonization of PAN is prepared by the above method.

[0029] Preferably, the MXene / C electrode material has a three-dimensional porous structure, and the nitrogen-doped carbon layer generated by carbonization of PAN is not only intercalated between the MXene layers, but also coated on the surface of the layers, forming a three-dimensional continuous conductive network to inhibit the restacking of the MXene layers; the porous structure provides a fast transmission channel for ions, and the nitrogen doping in the carbon layer enhances the electrochemical activity of the material.

[0030] The application provides a MXene / C electrode material based on PAN carbonization and a preparation method thereof, and has the following beneficial effects:

[0031] The MXene / C electrode material prepared by the application is a three-dimensional composite structure obtained by in-situ carbonization of PAN between and on the surface of MXene layers, and has the following characteristics:

[0032] 1. Spacing and bridging structure: the nitrogen-doped amorphous carbon layer formed after carbonization of PAN is inserted between the MXene nanosheet layers as a supporting spacer and tightly bridges the layers, effectively expanding the interlayer spacing of MXene and inhibiting the restacking of the nanosheets;

[0033] 2. Porous structure: during the carbonization process, the introduced and decomposed sacrificial template (PMMA nanospheres) generates abundant mesopores and crack pores in the composite material, constructing a three-dimensional ion transmission channel;

[0034] 3. Surface coating and modification: the nitrogen-doped carbon layer is not only inserted between the MXene nanosheet layers as a supporting spacer, but also coated on the surface of the MXene nanosheets, weakening the -F end groups on the surface, enriching C-O (H) and C-N functional groups, and thus improving the interface wettability, conductivity and oxidation resistance stability of the material.

[0035] In summary, the MXene / C electrode material prepared by the application realizes four synergistic regulations of “spacing” (expanding the interlayer spacing), “bridging” (constructing a conductive network), “poration” (creating an ion channel) and “protection” (forming an oxidation-resistant carbon layer) of the MXene material in one step through in-situ carbonization of PAN, essentially improving the microstructure and interface chemistry of the MXene and laying a material foundation for improving the electrochemical performance thereof.

[0036] Meanwhile, the preparation process is simple and controllable, common PAN and a template agent are used, and the complex structure can be constructed through one-step carbonization, so that the process is simple, highly reproducible and easy to scale up, and the shortcomings of the prior art, such as complicated process and poor interface contact, are overcome. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 SEM and TEM images of the sample in Example 1;

[0038] Figure 2 XRD and XPS images of the sample of Example 1;

[0039] Figure 3 Nitrogen adsorption-desorption isotherms and pore size distribution of MXene / C composites obtained at different target carbonization temperatures;

[0040] Figure 4 CV, GCD, EIS and specific capacitance curves of MXene / C composites obtained at different target carbonization temperatures in 3M H2SO4 electrolyte;

[0041] Figure 5 CV, GCD, EIS and specific capacitance curves of MXene / C composites obtained at different PAN contents in 3M H2SO4 electrolyte. DETAILED DESCRIPTION

[0042] The present application will be further described below in conjunction with the accompanying drawings and specific examples, so as to help understand the content of the present application. The methods used in the present application are conventional methods unless otherwise specified; the raw materials and devices used are conventional commercially available products unless otherwise specified.

[0043] Example 1

[0044] The present application adopts a PMMA template assisted confined carbonization process to synthesize MXene / C composites. First, 10 mL MXene dispersion liquid (5 mg·mL -1 ) is mixed with 5 mL anhydrous ethanol and stirred for 10 min to obtain a uniform dispersion. Then 30 mg of PMMA nanospheres is added and continue to stir for 30 min. Then 20 mg of PAN is added and stirred for another 30 min to form a uniform slurry. The obtained slurry is vacuum filtered through a hydrophilic polytetrafluoroethylene filter membrane (pore size 0.22 μm) to form a self-supporting MXene / PMMA / PAN hybrid film. The film is peeled off and naturally dried at room temperature overnight.

[0045] The obtained MXene / PMMA / PAN film is placed in a tube furnace and heat treated under argon atmosphere: first, heated to 300℃ at a rate of 3℃·min -1 and kept for 1 h to achieve inert atmosphere pretreatment; then heated to 600℃ at a rate of 5℃·min 1 and kept for 2 h to completely carbonize PAN and fully decompose PMMA. The final sample is naturally cooled to room temperature under argon protection to obtain a porous black film, which is denoted as MXene / C.

[0046] Ti3C2T xComparison of SEM, XRD, XPS, and TEM images of Mxene before and after carbonization:

[0047] As shown in Figure 1, Figure 1(a) shows Ti3C2T x Figure 1(b) shows the SEM image of the cross-section of MXene; Figure 1(c) shows the SEM image of the cross-section of MXene / C; x SEM images of MXene surfaces; Figure 1(d) shows the SEM image of the MXene / C surface; Figure 1(e) shows the SEM image of Ti3C2T. x HR-TEM image of MXene; Figure 1(f) shows HR-TEM image of MXene / C. In this invention, MXene material was successfully modified by in-situ carbonization of PAN to prepare MXene / C composite electrode material. Figure 1 (a) and Figure 1 (c) shows the structure of unmodified MXene material, exhibiting a distinct layered stacking characteristic, which limits its ion transport performance. Figure 1 (b) and Figure 1 (d) illustrates the properties of the MXene / C composite material, showing a distinct porous structure and spacing on the surface. This structural change originates from the nitrogen-doped carbon layer formed during PAN carbonization, which not only effectively suppresses the layer stacking of MXene but also creates a more permeable three-dimensional porous structure, thereby significantly improving the material's electrical conductivity and electrochemical performance. This modification scheme solves the stacking problem of traditional MXene materials and enhances their overall performance in electrochemical energy storage applications. Figure 1 (e) is a high-resolution TEM image of pure MXene with a lattice spacing of approximately 1.12 nm. Figure 1 (f) is a high-resolution TEM image of the MXene / C composite material of the present invention. It can be seen that the layered stripes are clearer and the interlayer spacing is increased to about 1.34 nm, indicating that the nitrogen-doped carbon layer obtained by PAN carbonization has been inserted into and partially covered between the MXene sheets. While suppressing the tight stacking of the sheets, it has constructed a wider and more continuous interlayer channel, which structurally verifies the effective control of the interlayer spacing and pore structure of MXene by the composite design of the present invention.

[0048] like Figure 2 As shown, the MXene / C electrode material prepared in Example 1 of this invention and unmodified MXene were subjected to XRD and XPS spectra tests. Figure 2 (a) is Ti3C2T x XRD patterns of MXene and MXene / C; Figure 2 (b)Ti3C2T x Full spectrum of MXene and MXene / C;Figure 2 (c) is Ti3C2T x High-resolution Ti 2p XPS spectra of MXene; Figure 2 (d) is Ti3C2T x High-resolution C1S XPS spectra of MXene; Figure 2 (e) is Ti3C2T x High-resolution O 1S XPS spectra of MXene; Figure 2 (f) shows the high-resolution Ti 2p XPS spectrum of MXene / C; Figure 2 (g) is the high-resolution C1S XPS spectrum of MXene / C; Figure 2 (h) shows the high-resolution O 1S XPS spectrum of MXene / C. In the MXene / C composite material prepared in this invention, Figure 2 XRD phase analysis of (a) shows that the (002) diffraction peak of pure MXene is located at 2θ = 6.92°, while the (002) peak of MXene / C shifts to 2θ = 6.4°. This low-angle shift phenomenon indicates that Ti3C2T x The interlayer spacing of MXene is increased due to carbon intercalation. MXene / C exhibits broad diffuse peaks at 2θ = 24-26° and 43°, corresponding to the (002) and (100) diffraction patterns of amorphous carbon, respectively. This indicates that the nitrogen-rich amorphous carbon generated after PAN heat treatment at 600℃ has intercalated or coated the MXene layers, effectively increasing the interlayer spacing, reducing the order of layers, and suppressing recombination, providing a structural basis for hierarchical porous structures and ion accessibility. Figure 3 (b) XPS full spectrum showed that both MXene / C and MXene contain C, Ti, O, and F elements; MXene / C showed a significant new N 1s peak, with enhanced C 1s signal and weakened F 1s signal, consistent with the pattern of -F end groups transforming to -O / -OH and forming a nitrogen-doped carbon capping layer after carbonization. In the high-resolution C 1s spectrum, MXene mainly exhibited C-Ti (=281.8 eV) and sp 2 The MXene / C spectrum is dominated by CC (=284.8 eV), with small amounts of CO (=286.4 eV) and C=O (=288.6 eV); while the CC and CN (=284.8 eV) components are significantly enhanced, and the C-Ti content is relatively weakened, indicating that the nitrogen-doped amorphous carbon generated by PAN carbonization has been successfully coated or intercalated between the MXene sheets. In the O 1s spectrum, Ti3C2T xMXene is dominated by Ti-O (=529.28 eV) and CO(H) (=532.22 eV); the proportion of CO(H) in the composite material increases significantly, while Ti-O is still observable, indicating an increase in -O / -OH functional groups and the retention of some Ti-O end groups. In the Ti 2p spectrum, both are dominated by Ti-C (2p... 3 / 2 The main component is 455.21 eV, with a small amount of Ti. 3+ / Ti 2+ The surface TiO2 content is 458.58 eV; the Ti-C backbone in the composite material remains intact, with only slight surface oxidation and defect state modulation. Through this nitrogen-doping modification method, the conductivity, stability, and electrochemical performance of the MXene / C composite material are significantly improved, providing an excellent material basis for the application of electrochemical energy storage devices such as supercapacitors.

[0049] Example 2 Control Group

[0050] Effect of different carbonization final temperatures on the structure of MXene / C composite materials

[0051] In this control group, the MXene / C composite material was prepared under the same MXene to PAN mass ratio (e.g., approximately 10:4). The effect of the final carbonization temperature on the pore structure and interlayer structure was investigated by varying the final carbonization temperature. The preparation method of the intermediate MXene / PMMA / PAN precursor film for the MXene / C composite material in this control group was the same as in Example 1. During the heat treatment process, several precursor films were carbonized at different target carbonization temperatures, as follows:

[0052] MXene Sample A: Untreated Ti3C2T x MXene

[0053] MXene / C sample B: Target carbonization temperature 400 ℃, denoted as 400 ℃-MXene / C;

[0054] MXene / C sample C: Target carbonization temperature 600 ℃, denoted as 600 ℃-MXene / C;

[0055] MXene / C sample D: Target carbonization temperature 800 ℃, denoted as 800 ℃-MXene / C.

[0056] The heating rate, holding time, and argon flow rate are the same as in Example 1, i.e., 3 °C·min. -1 Heat to 300 °C and hold for 1 hour, then reduce temperature by 5 °C / min. -1 They were heated to their respective target carbonization temperatures and held at those temperatures for 2 hours, then naturally cooled to room temperature under argon protection.

[0057] like Figure 3 As shown, nitrogen adsorption-desorption and pore size distribution tests were performed on MXene / C composites obtained by treatment at different target carbonization temperatures and untreated MXene. Figure 3 (a) is Ti3C2T x Nitrogen adsorption and desorption isotherms of MXene and MXene / C at different carbonization temperatures; Figure 4 (b) is Ti3C2T x Pore ​​size distributions of MXene and MXene / C at different carbonization temperatures. The spectra show that sample A has a BET specific surface area of ​​approximately 9 m². 2 ·g -1 Sample B has a specific surface area only slightly higher than sample A, and its pore size distribution is biased towards micro / small pores, indicating that the PAN carbonization is insufficient and the carbon skeleton has a limited effect on the expansion of the lamellar structure; Sample C has the highest specific surface area, increasing to about 25 μm. 2 ·g -1 The surface area increased by nearly three times, and the isotherm showed a typical type IV pattern. Mesopores of 2-50 nm were dominant, indicating that the degree of PAN carbonization was moderate at this temperature, forming a stable carbon framework while retaining abundant mesopores, exhibiting a typical layered fractured pore structure. The specific surface area of ​​sample D decreased significantly, to only 4.68 m². 2 ·g -1 It is speculated that this is due to the high graphitization of the carbon skeleton at high temperatures, accompanied by pore collapse.

[0058] Comparison of electrochemical test results using MXene / C films obtained at different target carbonization temperatures and uncarbonized MXene as working electrodes under the same test conditions (3 M H2SO4 electrolyte, three-electrode system):

[0059] like Figure 4 As shown, different electrode samples at 3 mol·L -1 The cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) results in the H2SO4 electrolyte fully demonstrate the superiority of the material design of this invention. Figure 4 (a) shows that, compared with the unmodified MXene electrode, the MXene / C composite current collector obtained by PAN carbonization has a significantly larger CV curve integral area under the same voltage window and scan rate, indicating that its charge storage capacity and capacitance contribution are significantly improved. Figure 4 In (b), under the same current density, the discharge time of GCD is significantly prolonged; such as Figure 4 (c) In the EIS Nyquist curve, the radius of the semicircle in the high-frequency region is significantly reduced, and the oblique line in the low-frequency region is closer to vertical, indicating that the solution resistance and charge transfer resistance are reduced, the ion diffusion resistance is reduced, and the interfacial electrochemical kinetics are significantly improved. Figure 5(d) Further comparison of different carbonization conditions shows that the MXene / C electrode obtained at a carbonization temperature of 600 °C has the highest specific capacitance and the best rate performance across the entire current density range. This fully demonstrates that the strategy of constructing a nitrogen-doped carbon framework in the MXene layers through in-situ carbonization of PAN can significantly improve the specific capacitance and cycle stability of the material while reducing internal resistance and optimizing pore structure, thereby achieving comprehensive optimization of the overall electrochemical performance of the electrode.

[0060] The control group experiment shows that in the system of this invention, when the target carbonization temperature is about 600 °C, the interlayer structure, pore structure and framework stability reach a better balance.

[0061] Example 3 Control Group

[0062] Different PAN contents MXene / C PAN Comparison of preparation and experimental properties of composite materials

[0063] In this control group, the effect of PAN mass fraction on the structure and properties of MXene / C composite materials was systematically investigated by changing the amount of PAN added, under the condition that the carbonization final temperature was fixed at 600 ℃.

[0064] Precursor preparation: The MXene dispersion was prepared in the same manner as in Example 1, with a concentration of 5 mg·mL⁻¹. -1 The volume used per application is 10 mL; the mass percentage of PMMA nanospheres is kept constant, and they are added to the MXene dispersion according to the method in Example 1; different masses of PAN are weighed to make the mass ratio of MXene to PAN 10:1, 10:2, 10:3, 10:4, and 10:5, and MXene / PAN slurries with different ratios are prepared in sequence. The corresponding precursor films are obtained by filtration, drying, and heat treatment as in Example 1 to obtain MXene / C composite materials with different PAN addition amounts.

[0065] like ​ As shown, under the same test conditions (3 M H2SO4 electrolyte, three-electrode system), electrochemical tests were conducted using MXene / C films with different PAN contents as working electrodes, and the following observations were made:

[0066] As the mass ratio of MXene to PAN increases from 10:1 to 10:4, the integral area of ​​the cyclic voltammetry (CV) curve gradually increases, the discharge time of the galvanostatic charge-discharge (GCD) is prolonged, and the charge transfer resistance in the electrochemical impedance spectroscopy (EIS) gradually decreases. This indicates that the nitrogen-doped carbon framework formed by appropriate PAN carbonization is beneficial to improving the specific surface area, optimizing the pore structure, and improving the interfacial charge transport.

[0067] When the mass ratio of MXene to PAN is 10:4, the sample is subjected to a moderate current density (e.g., 1 A·g).-1 It exhibits the longest discharge time and the lowest charge transfer resistance, and has the best overall electrochemical performance.

[0068] When the mass ratio of MXene to PAN is further increased to 10:5, the CV area and discharge time decrease slightly, and the radius of the high-frequency semicircle of EIS increases, indicating that the excess carbon phase causes partial pore blockage and restricts ion diffusion, thereby weakening the performance.

[0069] As can be seen from the above experiments, in the MXene / C system of the present invention, by controlling the mass ratio of MXene to PAN at about 10:4 and performing carbonization treatment at about 600 °C, an MXene / C composite electrode material with optimized interlayer structure, pore structure and electrochemical performance can be obtained.

[0070] Applications of the MXene / C composite electrode material prepared by this invention:

[0071] High-performance supercapacitors: can be directly used as electrodes in supercapacitors, especially suitable for applications requiring high power density, fast charge and discharge, and long cycle life.

[0072] Other electrochemical energy storage systems: The material's good conductivity and stable structure also make it a promising candidate as a conductive additive or composite electrode matrix material for lithium-ion batteries, sodium-ion batteries, or metal-air batteries, thereby improving the rate performance of the batteries.

[0073] In summary, this invention, through the synergistic effect of PMMA nanospheres, forms nitrogen-doped amorphous carbon layers by in-situ carbonization of polyacrylonitrile (PAN) between and on the surface of MXene layers. This not only acts as a supporting spacer inserted between MXene nanosheet layers, tightly bridging them and effectively expanding the interlayer spacing of MXene and inhibiting nanosheet recombination, but also simultaneously coats the surface of the MXene nanosheets, weakening their -F end groups and enriching CO(H) and CN functional groups, effectively improving the material's interfacial wettability, conductivity, and oxidation stability. Furthermore, the raw materials used in this invention are readily available, the process is simple and easy to control, possessing good potential for large-scale production and commercial application, and can effectively promote the development of high-performance, low-cost energy storage devices.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included in the protection of the present invention.

Claims

1. A method for preparing MXene / C electrode material based on PAN carbonization, characterized in that, Includes the following steps: (1) Slurry preparation: Mix the MXene dispersion with the solvent and stir until homogeneous. Add sacrificial template agent PMMA nanospheres to the above well-stirred dispersion, and continue stirring to ensure uniform dispersion. Add the polymer precursor PAN and stir until completely dissolved to form a homogeneous slurry; (2) Molding and pretreatment: The mixed slurry obtained in step (1) was vacuum filtered and shaped into a thin film. The shaped material was dried at room temperature to obtain a self-supporting MXene / PMMA / PAN precursor film. (3) Heat treatment: The precursor film obtained in step (2) was placed in a tube furnace and subjected to programmed temperature rise heat treatment under inert gas protection: First, the temperature was increased to 300℃ at a rate of 3℃ / min and held for 1 hour to complete the pretreatment of PAN under an argon atmosphere. Then, the temperature is increased to the target carbonization temperature at a rate of 5℃ / min, and held at this temperature for 2 hours. Finally, the material was naturally cooled to room temperature under argon protection to obtain PAN-carbonized MXene / C electrode material.

2. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The MXene is Ti3C2T x It is formed by etching MAX Ti3AlC2 with HCl and LiF.

3. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The average Mw of the PAN is 149,000~151,000.

4. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The mass ratio of MXene to PAN is 10:1 to 10:5, preferably 10:

4.

5. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The diameter of the PMMA nanospheres is 1-3 micrometers, preferably 2 micrometers.

6. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The amount of PMMA nanospheres added is 20%-40% of the total mass of MXene, PAN, and PMMA, preferably 30%.

7. The method for preparing an MXene / C electrode material based on PAN carbonization according to claim 1, characterized in that, The target carbonization temperature is 400℃-800℃, preferably 600℃.

8. An MXene / C electrode material based on PAN carbonization, characterized in that, The MXene / C electrode material is prepared by the method described in any one of claims 1-7.

9. The MXene / C electrode material based on PAN carbonization according to claim 8, characterized in that, The MXene / C electrode material has a three-dimensional porous structure. The nitrogen-doped carbon layer generated by PAN carbonization is not only intercalated between MXene sheets, but also coated on the surface of the sheets, forming a three-dimensional continuous conductive network and inhibiting the re-stacking of MXene sheets. The porous structure provides a fast transport channel for ions, and the nitrogen doping in the carbon layer enhances the electrochemical activity of the material.

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