MXene modified polyaniline hydrogel as well as preparation method and application thereof

Abstract

The invention discloses MXene modified polyaniline hydrogel and a preparation method and application thereof.The preparation method of the MXene modified polyaniline hydrogel comprises the following steps that MXene dispersion liquid and polyaniline dispersion liquid are mixed, and MXene / polyaniline mixed liquid is formed; the MXene / polyaniline mixed solution is subjected to a hydrothermal reaction, and the MXene modified polyaniline hydrogel is formed. The preparation method is simple and convenient in process flow, and has relatively high practical value and market prospect. The prepared MXene modified polyaniline hydrogel not only shows excellent electrochemical performance, but also has high energy density and cycling stability when being used as a cathode and assembled with an MXene anode to form a flexible asymmetric supercapacitor, and shows good application prospects in the fields of flexible wearable electronic equipment and the like. The application scene of the MXene modified polyaniline hydrogel electrode material is effectively widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy storage, and particularly relates to an MXene-modified polyaniline hydrogel, a preparation method thereof, and an application thereof. Background Art

[0002] Although polyaniline has become a research hotspot due to its good conductivity and ultra-high pseudocapacitance behavior, when a single polyaniline component is used as a pseudocapacitor electrode material, due to its frequent structural deterioration (such as volume expansion and contraction, etc.) during the charge-discharge redox reaction process, its chain-like structure is gradually damaged, resulting in a decrease in the electrochemical properties such as specific capacitance, rate performance, and cycle stability of the polyaniline electrode. This defect severely limits its practical application as a supercapacitor electrode. Summary of the Invention

[0003] In order to solve the problems proposed in the above background art, the purpose of the present invention is to provide an MXene-modified polyaniline hydrogel, a preparation method thereof, and an application thereof. MXene has excellent electrical conductivity and provides good electrochemical properties for the charge-discharge process. In addition, due to the strong attraction between the positive charges (such as -N + groups) on the polyaniline chain and the negative charges (such as -F, -OH, etc. groups) on the surface of the MXene nanosheets, they are tightly combined. Moreover, there are a large number of hydrogen bonds between MXene and polyaniline, which is beneficial to the formation of a uniform mixture during the mixing process of MXene and polyaniline. The MXene nanosheets may decompose into some small nanosheets, forming more hydrogen bonds, making the interaction with the polyaniline chain stronger and improving the electrochemical properties. After hydrothermal treatment, MXene is partially oxidized to form titanium dioxide, and the formation of titanium dioxide can further enhance the hydrogen bond interaction. Secondly, titanium dioxide usually exhibits high pseudocapacitance, thus enhancing the electrochemical properties. In addition, since polyaniline is the main component, after hydrothermal treatment, polyaniline molecules can be interconnected to form a cross-linked structure, and the oxidative decomposition of the MXene nanosheets has almost negligible influence on the mechanical strength, ensuring the formation of the hydrogel. Therefore, the introduction of a small amount of MXene can modify polyaniline molecules and enhance the interaction, which helps to provide good electrochemical properties.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a preparation method of an MXene-modified polyaniline hydrogel, comprising the following steps:

[0005] (1) Mix an MXene dispersion liquid with a polyaniline dispersion liquid to form an MXene / polyaniline mixed liquid;

[0006] (2) Perform hydrothermal reaction on the MXene / polyaniline mixed liquid in step (1) to form an MXene-modified polyaniline hydrogel.

[0007] Further, the MXene includes Ti2CT x , Ti3C2T x , Ti4C3T x , and at least one of them, where Tx is selected from -OH, -O, -F or -Cl.

[0008] Further, in step (1), the mass ratio of the MXene contained in the MXene dispersion to the polyaniline contained in the polyaniline dispersion is 0.05:7 to 0.6:7;

[0009] In step (2), the temperature of the hydrothermal reaction is 120 - 200 °C, and the time of the hydrothermal reaction is 3 - 7 h.

[0010] Further, in step (1), the mass ratio of the MXene contained in the MXene dispersion to the polyaniline contained in the polyaniline dispersion is 0.3:7;

[0011] In step (2), the temperature of the hydrothermal reaction is 180 °C, and the time of the hydrothermal reaction is 5 h.

[0012] When the proportion of MXene is too high, the amount of titanium dioxide produced during the hydrothermal process is too high, which will affect the formation and strength of the hydrogel. When the hydrothermal reaction temperature is lower than 120 °C, it is difficult to form the hydrogel; when the hydrothermal reaction temperature is higher than 200 °C, too much titanium dioxide is produced by MXene, affecting the performance of the hydrogel. When the reaction time is lower than 3 h, it is difficult to form the hydrogel; when the reaction time is higher than 7 h, the amount of titanium dioxide generated is too high, affecting the performance of the hydrogel.

[0013] Further, the MXene dispersion is prepared by the following method: etching the Ti source (Ti2AlC, Ti3AlC2, Ti4AlC3) using a lithium fluoride / hydrochloric acid system to prepare the MXene dispersion;

[0014] The polyaniline dispersion is prepared by the following method: using ammonium persulfate to initiate the polymerization of aniline to prepare the polyaniline dispersion.

[0015] On the other hand, the present invention provides an MXene - modified polyaniline hydrogel prepared by the preparation method of the MXene - modified polyaniline hydrogel described in any one of the above.

[0016] On the other hand, the present invention provides an application of the MXene - modified polyaniline hydrogel as a flexible electrode material.

[0017] On yet another hand, the present invention provides an application of the MXene - modified polyaniline hydrogel as a flexible supercapacitor electrode material.

[0018] On the other hand, the present invention provides an application of MXene-modified polyaniline hydrogel in flexible energy storage devices.

[0019] Furthermore, the flexible energy storage device includes a flexible supercapacitor and a battery.

[0020] On the other hand, the present invention provides an MXene-modified polyaniline hydrogel electrode, which is prepared by the following method: the above-mentioned MXene-modified polyaniline hydrogel is coated in a conductive current collector to obtain the MXene-modified polyaniline hydrogel electrode.

[0021] Furthermore, the present invention provides an MXene-modified polyaniline hydrogel electrode, which is prepared by the following method:

[0022] (1) Cut the above-mentioned MXene-modified polyaniline hydrogel into thin slices;

[0023] (2) Wrap the thin slices with a conductive current collector and apply pressure to make the MXene-modified polyaniline hydrogel electrode. The conductive current collector includes a stainless steel mesh, a carbon cloth, and a nickel mesh.

[0024] Furthermore, in step (1), the thickness of the thin slices is 0.5 - 2 mm.

[0025] On the other hand, the present invention provides a flexible asymmetric supercapacitor, including the above-mentioned MXene-modified polyaniline hydrogel electrode.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention proposes an innovative strategy of hydrothermally assembling and modifying polyaniline with a highly conductive MXene functional material, and prepares an MXene-modified polyaniline hydrogel. This modification strategy effectively utilizes the high conductivity of MXene nanosheets and the characteristic of generating titanium dioxide during the hydrothermal process, effectively improving the electrochemical performance of the polyaniline electrode material (MXene has excellent conductivity, and the negative charges on the surface of MXene nanosheets (such as -F, -OH and other groups) and the positive charges on the polyaniline chain (such as -N + groups) form strong interactions, improving the conductivity of the MXene-modified polyaniline hydrogel, which is beneficial to the rapid diffusion of ions and the transmission of electrons during the electrochemical test process, thereby improving the electrochemical performance; after hydrothermal treatment, MXene is partially oxidized to form titanium dioxide, and titanium dioxide can further enhance the interaction between components by increasing hydrogen bond connection, and titanium dioxide usually exhibits high pseudocapacitance, thereby further enhancing the electrochemical performance of the MXene-modified polyaniline hydrogel), effectively realizing the overall optimization of the performance of the electrode material;

[0028] 2) The MXene-modified polyaniline hydrogel of the present invention not only exhibits excellent electrochemical performance by itself (the specific capacitance can reach 483.1 F g -1 , 1 - 20 Ag -1 When it is, the rate performance reaches 79.8%. After 6000 cycles of charge and discharge tests at a current density of 30 A g -1 , the specific capacitance retention rate is still 80%, and the Coulomb efficiency is 98%), but also when it is used as the cathode and assembled with the MXene anode into a flexible asymmetric supercapacitor, it has high energy density and cycle stability performance (the energy density reaches 23.6 Wh kg -1 , after 9000 cycles of tests, the specific capacitance can be retained at 89.4%). It shows good application prospects in the fields of flexible wearable electronic devices, etc., effectively broadening the application scenarios of MXene-modified polyaniline hydrogel electrode materials;

[0029] 3) The preparation method process flow of the MXene-modified polyaniline hydrogel of the present invention is simple, and it has high practical value and market prospects. Brief Description of the Drawings

[0030] Figure 1 The SEM diagrams of MXene, single polyaniline hydrogel, and the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention are shown, where Figure 1 a in is the SEM diagram of MXene, Figure 1 b in is the SEM diagram of single polyaniline hydrogel, Figure 1 c in is the SEM diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention at 5K magnification, Figure 1 d in is the SEM diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention at 20K magnification;

[0031] Figure 2 The TEM diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention is shown, where Figure 2 a in is the low-magnification morphology TEM diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention, Figure 2 b in is the HRTEM diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention;

[0032] Figure 3 The TEM-EDX diagram of the MXene-modified polyaniline hydrogel prepared in Example 1 of the present invention;

[0033] Figure 4 The Ti2p XPS diagrams of MXene and the MXene-modified polyaniline hydrogel (M-PANI) prepared in Example 1 of the present invention are shown, whereFigure 4 In which, a is the Ti 2p XPS diagram of MXene, Figure 4 and b is the Ti 2p XPS diagram of the MXene-modified polyaniline hydrogel (M-PANI) prepared in Example 1 of the present invention;

[0034] Figure 5 is the electrochemical performance diagram of the MXene-modified polyaniline hydrogel electrode prepared in Example 2 of the present invention, in which Figure 5 a is the CV curve diagram of the MXene electrode, the single polyaniline hydrogel (PANI) electrode, and the MXene-modified polyaniline hydrogel (M-PANI) electrode prepared in Example 2 of the present invention at a scanning rate of 5 mV s -1 ; Figure 5 b is the GCD curve diagram of the MXene electrode, the single polyaniline hydrogel (PANI) electrode, and the MXene-modified polyaniline hydrogel (M-PANI) electrode prepared in Example 2 of the present invention at a current density of 1 A g -1 ; Figure 5 c is the specific capacitance curve diagram of the MXene electrode, the single polyaniline hydrogel (PANI), and the MXene-modified polyaniline hydrogel (M-PANI) electrode prepared in Example 2 of the present invention at different current densities, Figure 5 and d is the specific capacitance retention rate and Coulomb efficiency result diagram of the MXene-modified polyaniline hydrogel electrode prepared in Example 2 of the present invention after 6000 cycles of charge-discharge tests at a current density of 30 A g -1 ;

[0035] Figure 6 is the structural schematic diagram of the flexible asymmetric supercapacitor prepared in Example 3 of the present invention;

[0036] Figure 7 is the electrochemical performance diagram of the flexible asymmetric supercapacitor prepared in Example 3 of the present invention, in which Figure 7 a is the CV curve diagram of the flexible asymmetric supercapacitor prepared in Example 3 of the present invention at different bending angles, Figure 7 b is the GCD curve diagram of the flexible asymmetric supercapacitor prepared in Example 3 of the present invention at current densities of 1 Ag -1 , 2 Ag -1 , 5 Ag -1 , 8 Ag -1 , 10 Ag -1 , 20 Ag -1 ; Figure 7 c is the EIS diagram of the flexible asymmetric supercapacitor prepared in Example 3 of the present invention, Figure 7The picture in shows two series-connected asymmetric supercapacitor devices prepared in Example 3 of the present invention powering an LED lamp. Detailed implementation manners

[0037] To better understand the content of the present invention, the following further explains the content of the present invention in combination with specific implementation methods. However, the protected content of the present invention is not limited to the following examples.

[0038] The morphology of the samples was studied by scanning electron microscopy SEM (Hitachi Su-8010FE) and transmission electron microscopy TEM (Thermo Scientific Talos F200i S), and the chemical structure was studied by X-ray photoelectron spectroscopy XPS (Thermo Fisher Scientific K-Alpha).

[0039] All electrochemical performance tests were carried out using a Chenhua CHI760E electrochemical workstation.

[0040] Example 1

[0041] Preparation of MXene-modified polyaniline hydrogel: (1) Stir and mix the MXene dispersion and the polyaniline dispersion to form an MXene / polyaniline mixture. The mass ratio of MXene contained in the MXene dispersion to polyaniline contained in the polyaniline dispersion is 0.3:7.

[0042] The MXene dispersion was prepared by the following method: The MXene dispersion was prepared by etching Ti3AlC2 using a lithium fluoride / hydrochloric acid system. The specific steps are as follows. Dissolve 1.32 g of lithium fluoride in 20 mL of 9 mol L -1 hydrochloric acid aqueous solution, then add 1 g of Ti3AlC2 and stir at 37 °C for 24 h. Then, adjust the pH to neutral by centrifugal washing, then sonicate for 1 h, and then centrifuge at 3000 r / min to take the supernatant as the MXene dispersion.

[0043] The polyaniline dispersion was prepared by the following method: The polyaniline dispersion was prepared by using ammonium persulfate to initiate the polymerization of aniline. The specific preparation process is as follows. At room temperature and gentle stirring, dissolve 2 g of sodium dodecyl sulfate in 250 mL of 1 mol L -1 sulfuric acid aqueous solution, then add 0.5 mL of aniline monomer and stir for 2 hours; then, add 15 mL of ammonium persulfate aqueous solution containing 1.25 g of ammonium persulfate and continue to stir for 24 hours. Purify by dialysis and adjust the pH to 2.6 to obtain the polyaniline dispersion.

[0044] (2) The MXene / polyaniline mixture obtained in step (1) is placed in a hydrothermal reactor for hydrothermal reaction to form MXene-modified polyaniline hydrogel (M-PANI). The temperature of the hydrothermal reaction is 180 °C, and the time of the hydrothermal reaction is 5 h.

[0045] The MXene, single polyaniline hydrogel, and MXene-modified polyaniline hydrogel prepared in Example 1 are respectively subjected to electron microscopy scanning, and their SEM images are as Figure 1 shown. As can be seen from Figure 1 a in Figure 1 , MXene mainly shows a structure of nanosheet stacking; as can be seen from Figure 1 b in Figure 1 , polyaniline nanoparticles are crosslinked into a three-dimensional network structure. As can be seen from Figure 1 c in Figure 1 and Figure 2 d in Figure 2 , the MXene-modified polyaniline hydrogel shows a three-dimensional porous crosslinked network structure similar to that of the single polyaniline hydrogel. However, the presence of MXene nanosheets is difficult to observe. This result may be attributed to the low content of MXene introduced in the MXene-modified polyaniline hydrogel and the strong interaction between polyaniline molecules and MXene nanosheets, such as π-π stacking, hydrogen bonding, van der Waals forces, etc. Further TEM characterization is used to verify the presence of MXene in the MXene-modified polyaniline hydrogel, and the results are as Figure 2 shown. As can be seen from Figure 2 , the HRTEM image shows obvious lattice fringes, indicating the presence of MXene. In addition, the chemical composition distribution of the MXene-modified polyaniline hydrogel is characterized by TEM-EDX, and the results are as Figure 3 shown. The high consistency of the distribution of Ti and O elements indicates that part of MXene has been converted into titanium dioxide. These results show that there is a close surface contact and strong interaction force between MXene nanosheets and polyaniline nanoparticles, which is beneficial to improving the electrochemical performance of the MXene-modified polyaniline hydrogel.

[0046] The MXene and the MXene-modified polyaniline hydrogel prepared in Example 1 are respectively subjected to XPS testing, and the Ti 2p XPS image is as Figure 4 shown. As can be seen from Figure 4 a in 2+ , the Ti 2p of MXene shows three doublets, corresponding to Ti-C (454.9 eV), Ti 2+ 2p 1 / 2 (455.5 eV), Ti 3+ 2p 1 / 2 (456.4 eV), Ti-O (458.8 eV), Ti-C (461.1 eV) and Ti 2 + / Ti 3+ 2p3 / 2 (462.2 eV) bond; From Figure 4 As can be seen from b in 2+ / Ti 3+ 2p 1 / 2 (459.2 eV), Ti - O(459.7 eV), Ti 2+ / Ti 3+ 2p 3 / 2 (461.3 eV) and Ti - O(465.0 eV) bonds. Compared with the spectrum of MXene, the peak intensity of the Ti - C bond in the MXene - modified polyaniline hydrogel becomes weaker (from ~23.11% to 8.25%), and the Ti - O bond becomes stronger (from ~9.81% to 53.82%). This indicates that part of the MXene is transformed into titanium dioxide during the hydrothermal treatment process, and this result is consistent with the SEM and TEM analyses. Since titanium dioxide has a high pseudocapacitance contribution, it can provide a good specific capacitance for the MXene - modified polyaniline hydrogel electrode.

[0047] Example 2

[0048] Preparation of MXene electrode, single polyaniline hydrogel (PANI) electrode, and MXene - modified polyaniline hydrogel (M - PANI) electrode: (1) Cut the single polyaniline hydrogel (PANI) and the MXene - modified polyaniline hydrogel (M - PANI) prepared in Example 1 into thin slices (~10×10×1 mm); Cut the MXene into small pieces of size ~10×10 mm;

[0049] (2) Wrap the thin slices and small pieces with a stainless - steel mesh current collector and apply a pressure of 10 MPa to make MXene electrode, single polyaniline hydrogel (PANI) electrode, and MXene - modified polyaniline hydrogel (M - PANI) electrode.

[0050] Perform electrochemical performance tests on the MXene electrode, single polyaniline hydrogel (PANI) electrode, and MXene - modified polyaniline hydrogel (M - PANI) electrode prepared in Example 2: Use a platinum electrode and a silver chloride electrode as the counter electrode and reference electrode respectively, and the MXene electrode, single polyaniline hydrogel electrode, and MXene - modified polyaniline hydrogel electrode as the working electrodes respectively. Test the electrochemical performance in 2 mol L -1 H2SO4 electrolyte. The results are as Figure 5 shown. From Figure 5As can be seen from a in, compared with the MXene electrode and the single polyaniline hydrogel electrode, the MXene-modified polyaniline hydrogel electrode shows obvious redox peaks and has the largest integral area, indicating the highest specific capacitance. This obvious redox peak is attributed to the ion doping behavior and redox reaction in the polyaniline molecules. From Figure 5 As can be seen from b in, the MXene-modified polyaniline hydrogel electrode shows a broad shoulder peak and a low voltage drop, and has the longest discharge time, indicating the highest specific capacitance. This result is consistent with the CV analysis. From Figure 5 As can be seen from c in, at 1 A g -1 , the specific capacitance value of the MXene-modified polyaniline hydrogel is 483.1 F g -1 , which is much higher than that of the single polyaniline hydrogel (271.6 F g -1 ) and MXene (244.1 F g -l ). This is mainly attributed to the strong interaction between the MXene and polyaniline components, which significantly improves the specific capacitance of the MXene-modified polyaniline hydrogel. In addition, titanium dioxide has a high pseudocapacitance contribution, which can further improve the specific capacitance of the MXene-modified polyaniline hydrogel. At the same time, the high conductivity of MXene can promote ion diffusion and charge transfer, thus improving the electrochemical performance. From Figure 5 As can be seen from c in, in the range of current density from 1 to 20 A g -1 , the specific capacitance retention rate of the MXene-modified polyaniline hydrogel electrode is 79.8%, and when the current density increases to 30 A g -1 , it still remains 73.0%, indicating excellent rate performance. From Figure 5 As can be seen from d in, after 6000 cycles of charge-discharge tests at a current density of 30 A g -1 , the specific capacitance retention rate of the MXene-modified polyaniline hydrogel electrode is still 80%, and the Coulomb efficiency is 98%, indicating excellent cycle stability.

[0051] Example 3

[0052] Preparation of flexible asymmetric supercapacitor: Using the aramid nanofiber-based hydrogel electrolyte (soaked in 2 M H2SO4) as the electrolyte diaphragm, the MXene-modified polyaniline hydrogel (M-PANI) electrode prepared in Example 2 as the cathode and the MXene electrode as the anode to assemble a flexible asymmetric supercapacitor, as Figure 6 shown.

[0053] Perform electrochemical performance tests on the flexible asymmetric supercapacitor prepared in Example 3, and the results are as Figure 7 shown. From Figure 7As can be seen from a in the figure, the CV curves of the flexible asymmetric supercapacitor prepared in Example 3 at different bending angles (initially 0°, 90°, 120°, and restored to 0° after testing up to 120°) at 5 mV s -1 show a high degree of coincidence, indicating good mechanical flexibility; this good flexibility and electrochemical stability enable the capacitor device to exhibit an approximately 77 F g -1 specific capacitance at 5 mV s -1 . As can be seen from Figure 7 b in the figure, the GCD curve shows obvious linear deviation, and the charge / discharge process exhibits good symmetry, indicating fast charge transfer, reversible redox kinetics, and high Coulomb efficiency. As can be seen from Figure 7 c in the figure, the flexible asymmetric supercapacitor prepared in Example 3 has a low resistance value, corresponding to the above results. As can be seen from Figure 7 d in the figure, connecting the flexible asymmetric supercapacitors prepared in Example 3 in series can light up a 2.2 V LED lamp, highlighting the practical application prospects of this flexible asymmetric supercapacitor in the energy storage field.

[0054] Example 4

[0055] The preparation method of the MXene-modified polyaniline hydrogel in Example 1 and the preparation method of the MXene-modified polyaniline hydrogel electrode in Example 2 were the same. Only the mass ratio of MXene contained in the MXene dispersion to polyaniline contained in the polyaniline dispersion was changed, and MXene-modified polyaniline hydrogel electrodes with mass ratios of 0.2:7 and 0.4:7 were prepared respectively.

[0056] Electrochemical performance tests were carried out on the two MXene-modified polyaniline hydrogel electrodes prepared in Example 4: platinum electrodes and silver chloride electrodes were used as the counter electrode and reference electrode, and the two MXene-modified polyaniline hydrogel electrodes prepared in Example 4 were used as the working electrodes respectively. Their specific capacitances at different current densities were tested in a 2 mol L -1 H2SO4 electrolyte. The results are shown in the following table. As can be seen from the table, as the proportion of MXene increases, the specific capacitance value of the electrode first increases significantly and then decreases. When the mass ratio of MXene contained in the MXene dispersion to polyaniline contained in the polyaniline dispersion is 0.3:7, the maximum specific capacitance is 483.1 F g -1 , and when the proportion of MXene is further increased, the specific capacitance of the electrode begins to decline. And when the current density is in the range of 1 - 20 A g -1When in the range, the rate performance of the electrodes prepared with the mass ratios of MXene to polyaniline being 0.2:7, 0.3:7, and 0.4:7 are 68.7%, 79.8%, and 69.3% respectively. When the mass ratio of MXene to polyaniline is 0.3:7, the rate performance of the electrode is the best.

[0057]

[0058] In summary, using highly conductive MXene as a modifier, MXene-modified polyaniline hydrogel was obtained through a hydrothermal assembly reaction, showing excellent electrochemical performance. For example, the specific capacitance can reach 483.1 F g -1 , 1 - 20 A g -1 When, the rate performance reaches 79.8%; assembling it as the cathode with the MXene anode into an asymmetric supercapacitor, showing an energy density of 23.6 Wh kg -1 , after 9000 cycle tests, the specific capacitance can be retained at 89.4%. The present invention proposes a strategy for preparing MXene-modified polyaniline hydrogel, and applying it to the energy storage field can improve the electrochemical performance of flexible electrode materials.

[0059] The above are only specific embodiments of the present invention, not all embodiments. Any equivalent transformation of the technical solution of the present invention made by those of ordinary skill in the art by reading the specification of the present invention is covered by the claims of the present invention.

Claims

1. A preparation method of MXene-modified polyaniline hydrogel, characterized in that, It includes the following steps: (1) Mix the MXene dispersion liquid with the polyaniline dispersion liquid to form a MXene / polyaniline mixed liquid; (2) Carry out a hydrothermal reaction on the MXene / polyaniline mixed liquid in step (1) to form a MXene-modified polyaniline hydrogel.

2. The preparation method of the MXene-modified polyaniline hydrogel according to claim 1, characterized in that, The MXene includes Ti2CT x , Ti3C2T x , Ti4C3T x and at least one of them, where T x is selected from -OH, -O, -F or -Cl.

3. The preparation method of the MXene-modified polyaniline hydrogel according to claim 1, wherein In step (1), the mass ratio of MXene contained in the MXene dispersion liquid to polyaniline contained in the polyaniline dispersion liquid is 0.05:7 to 0.6:7; In step (2), the temperature of the hydrothermal reaction is 120 to 200 °C, and the time of the hydrothermal reaction is 3 to 7 h.

4. The preparation method of the MXene-modified polyaniline hydrogel according to claim 3, wherein, In step (1), the mass ratio of MXene contained in the MXene dispersion liquid to polyaniline contained in the polyaniline dispersion liquid is 0.3:7; In step (2), the temperature of the hydrothermal reaction is 180 °C, and the time of the hydrothermal reaction is 5 h.

5. A MXene-modified polyaniline hydrogel, characterized in that, It is prepared by the preparation method of the MXene-modified polyaniline hydrogel according to any one of claims 1-4.

6. Application of the MXene-modified polyaniline hydrogel according to claim 5 as a flexible electrode material.

7. Application of the MXene-modified polyaniline hydrogel according to claim 5 as a flexible supercapacitor electrode material.

8. Application of the MXene-modified polyaniline hydrogel according to claim 5 in a flexible energy storage device, and the flexible energy storage device includes a flexible supercapacitor and a battery.

9. A MXene-modified polyaniline hydrogel electrode, characterized in that, It is prepared by the following method: the MXene-modified polyaniline hydrogel according to claim 5 is coated on a conductive current collector to prepare a MXene-modified polyaniline hydrogel electrode.

10. A flexible asymmetric supercapacitor, characterized in that, It includes the MXene-modified polyaniline hydrogel electrode according to claim 9.

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