Preparation method and application of melamine modified MXene material

Abstract

The invention discloses a preparation method and application of a melamine modified MXene material, and belongs to the field of nano materials. The preparation method comprises the following steps: firstly, selectively etching in a LiF / HCl mixed solution, and preparing a Ti3C2Tx nanosheet in a layering manner; secondly, adding melamine, mixing with the Ti3C2Tx suspension, and stirring to promote the formation of hydrogen bonds between end groups; after stirring is finished, standing is kept for 12 h, and the formed hydrogen-bond interaction is further stabilized. And finally, the final product Ti < 3 > C < 2 > T < x > / MA is obtained through the processes of washing, freeze drying and the like. In the Ti < 3 > C < 2 > T < x > / MA material, the optimal content of melamine is 2.1 wt%, and the transmission of lithium ions is optimized by a triazine ring structure. The melamine modified MXene material disclosed by the invention has the characteristics of large specific surface area, high lithium storage capacity, excellent lithium ion diffusivity, multiple lithium storage sites, good rate capability and the like.

Description

Technical Field

[0001] The invention belongs to the field of nanomaterials, and specifically relates to a preparation method and application of melamine-modified MXene materials. Background Art

[0002] With the surge in global energy demand and the increasing constraints on fossil fuel resources, the scale of renewable energy installations, primarily solar and wind power, continues to expand. However, their geographical dependence and intermittent nature place an urgent demand on efficient energy storage systems. In this context, lithium-ion batteries, due to their high energy density, long cycle life, and environmentally friendly properties, have become the core technology for energy storage in electric vehicles and smart electronic products. In lithium-ion batteries, the anode material, as a key component, directly impacts battery performance. Therefore, the research and development of new lithium-ion battery anode materials with excellent performance is crucial.

[0003] Since the discovery of new graphene-like two-dimensional transition metal carbon / nitride materials (MXene) in 2001, more than 70 different MAX phases have been reported, and Ti3C2T x Because of its good electrical conductivity and hydrophilicity, rich active sites and excellent mechanical properties, it has gradually developed into the most widely used MXene material, such as alkali metal batteries, metal air batteries and capacitors. The main step of its preparation method is to selectively etch the Al layer in the Ti3AlC2 phase, and the etching process inevitably introduces a variety of functional groups. The stacking of nanosheets and the introduction of unfavorable functional groups (F, OH) will reduce the Ti3C2T x The lithium storage sites are blocked, the diffusion rate of lithium ions is reduced, and the actual capacity is low. This technical problem needs to be solved urgently. Summary of the Invention

[0004] The present invention aims to overcome the existing Ti3C2T x In order to solve the technical deficiencies existing in lithium-ion batteries, a method for preparing melamine (MA) modified MXene materials with large specific surface area, high lithium storage capacity, excellent rate performance and strong lithium ion diffusion ability is provided.

[0005] The present invention also provides a MA-modified two-dimensional nano-Ti3C2T x Materials (Ti3C2T x / MA) in electrochemistry.

[0006] To solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] Ti3C2T x The preparation method of the MA material comprises the following steps in sequence:

[0008] 1. Ti3C2Tx Preparation of nanosheet suspension

[0009] 1.1 Add LiF to HCl and stir until it is completely dissolved; then, add Ti3AlC2 powder to the solution;

[0010] 1.2 Transfer the mixed solution obtained in step 1.1 to a constant temperature oil bath for reaction. After the reaction is completed, centrifuge and wash the solid residue until the pH of the supernatant is close to neutral;

[0011] 1.3 The bottom reaction product obtained in step 1.2 was ultrasonicated in an ice bath under the protection of inert gas; the ultrasonicated solution was centrifuged and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension;

[0012] Ti3C2T x Preparation of MA

[0013] 2.1 Add MA powder to deionized water with ultrasonic stirring to dissolve it completely; slowly add it dropwise to the Ti3C2T x Nanosheet suspension; the MA and Ti3C2T x The mass ratio is 1 to 12:10;

[0014] 2.2 After stirring, the solution obtained in step 2.1 was allowed to stand, and then centrifuged and washed until the pH of the filtrate was close to neutral;

[0015] 2.3 The centrifugal product obtained in step 2.2 was freeze-dried to obtain the target product Ti3C2T x / MA material.

[0016] Furthermore, the MA binds to Ti3C2T through hydrogen bonds. x The -OH, -F and other functional groups on the surface are connected and self-assembled to obtain a higher specific surface area.

[0017] Furthermore, in step 1.1, 0.998 g of LiF was added to 10 mL of concentrated HCl and stirred until completely dissolved; then, 1 g of Ti3AlC2 powder was added to the solution.

[0018] Furthermore, in step 1.2, the mixed solution obtained in step 1.1 is transferred to a constant temperature oil bath at 36° C. for reaction for 24 hours to etch away the Al layer. After the reaction is completed, the solid residue is washed by centrifugation with deionized water until the pH of the supernatant is close to neutral;

[0019] Furthermore, in step 2.1, MA powder was added to 25 mL of deionized water and ultrasonically stirred for 5 min to completely dissolve it; it was slowly added dropwise to the Ti3C2T xNanosheet suspension; the MA and Ti3C2T x The mass ratio of MA is 1 to 12:10, preferably 2:10; in step 2.2, the solution obtained in step 2.1 is allowed to stand for 12 hours after stirring, and then centrifuged and washed with deionized water for multiple times to wash away excess MA in the solution until the pH of the filtrate is close to neutral.

[0020] Furthermore, in step 2.3, the optimal content of MA in the Ti3C2Tx / MA material is 2.1 wt %, and its BET specific surface area is 76.4 m 2 g -1 ;

[0021] The electrochemical application of the product obtained by the preparation method of the hydrogen bond network Ti3C2Tx / MA material is to use 1-methyl-2-pyrrolidone as solvent to x / MA material, conductive agent and binder are mixed, ground and coated on copper foil, and then vacuum dried; the electrode sheets are assembled into button half-cells in a glove box filled with argon; lithium foil is used as the counter electrode, Celgard 2400 is used as the diaphragm, and the electrolyte is LiPF6 dissolved in a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate.

[0022] Furthermore, the conductive agent is acetylene black; the binder is polyvinylidene fluoride; the conductive agent is acetylene black; the binder is polyvinylidene fluoride; the mass ratio of the MA-modified MXene material, the conductive agent and the binder is 8:1:1 respectively.

[0023] Furthermore, the volume ratio of ethylene carbonate, dimethyl carbonate and diethyl carbonate is 1:1:1.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the present invention prepares Ti3C2T x In the / MA material, MA and Ti3C2T x There is a hydrogen bond network connection on the surface functional groups, which avoids the x The self-stacking of nanosheets increases the specific surface area of the material.

[0025] The present invention prepares Ti3C2T x MA and Ti3C2T among MA materials xThe hydrogen bonding of surface functional groups not only prevents the self-stacking of nanosheets, but more importantly, MA also shields the -OH end groups from hindering lithium-ion transport. During lithium storage, the high electron cloud density of the triazine ring in MA pulls lithium ions near the -OH end groups toward the unsaturated nitrogen and away from the -OH, thus preventing the -OH end groups from hindering lithium-ion transport. This invention leverages the synergistic effect of MA's hydrogen-bonding network to optimize the specific surface area of MXene and shield the -OH end groups, significantly improving lithium-ion transport and diffusion capabilities.

[0026] MA is an organic negative electrode material, and the triazine ring can serve as a lithium storage site. When the content of MA is very low, there is spatial interface modification, and the adsorption of lithium by the triazine ring has the effect of changing the lithium ion transmission path. When pure MA is used or the MA content exceeds a certain threshold, it itself becomes an ordinary lithium storage material. See Example 2-4 to verify that excessive MA leads to performance degradation ( Figure 10 ). Example 2 shows that excessive MA (5.1wt%) will lead to performance degradation. Example 4 is a case of exploring the upper limit of the feed ratio. Only when a specific content of MA is used, it can form an interface modification function in space, thereby improving the lithium storage properties of titanium carbide. In the solution of the present invention, Ti3C2T x After MA modification, the specific surface area (76.4m 2 g-1) was significantly higher than that of the comparative example (27.6m 2 g -1 ), and the cycle capacity (387.7 mAh g -1 ) exceeds the theoretical capacity of commercial graphite anode (372mAh g -1 ). The significant improvement in the lithium ion diffusion coefficient was verified by testing (see Figure 13 ), thus demonstrating the improving effect of the hydrogen bond network on dynamics.

[0027] MA modified Ti3C2T prepared by the present invention x MA has a unique triazine ring structure, which not only "shields" the -OH end group, but also provides a better lithium storage site for lithium ion storage. The MA of the present invention forms a stable structure through physical adsorption (non-chemical bonding), avoids the stacking of MXene sheets, and shields the -OH end group from Li + Obstacles (see Figures 7-8 redshift comparison).

[0028] The present invention prepares MA-modified Ti3C2T x The process is simple, and the target product can be obtained only by stirring, without complicated processes such as annealing, which can save costs and facilitate large-scale production.

[0029] Ti3C2T prepared by the present inventionx The optimal content of MA in / MA is 2.1wt%, and its triazine ring structure optimizes the transmission of lithium ions. Based on the unique triazine ring structure of MA, it provides better lithium storage sites and reduces the ion diffusion energy barrier, effectively improving the lithium storage capacity. The MA of the present invention is grafted onto Ti3C2T by hydrogen bonding. x It is a strategy to balance functionalization and intrinsic performance, which expands its application potential in the fields of composite materials, energy storage, etc. x / MA material has large specific surface area, fast lithium ion diffusion, high lithium storage capacity and good rate performance. x The preparation method of / MA material is simple, the MA modification amount is controllable, and it is suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described in detail below through specific examples. These examples are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. As mentioned throughout the specification and claims, "including" or "comprising" is an open-ended term and is interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims. Unless otherwise specified, the various reagents and materials used in the present invention can be purchased from the market.

[0031] Figure 1 Ti3C2T in Example 1 x and MA to form Ti3C2T x / Optical image of MA;

[0032] Figure 2 Ti3C2T in Example 1 x / MA、Ti3C2T x and Zeta potential diagram of MA;

[0033] Figure 3 XRD spectra of Example 1, Comparative Example 1 and MA;

[0034] Figure 4 Infrared spectra of Example 1 and Comparative Example 1;

[0035] Figure 5 XPS O1s patterns of Example 1 and Comparative Example 1;

[0036] Figure 6 MA modified Ti3C2T prepared in Example 1 xSEM images of the material and mapping of Ti, C, O, F and N elements;

[0037] Figure 7 In Example 1, Ti3C2T x / MA XPS Nls chart;

[0038] Figure 8 Infrared spectra of Comparative Example 1 at 0.01V and 3V;

[0039] Figure 9 Infrared spectra of Example 1 at 0.01V and 3V;

[0040] Figure 10 Comparison of cycle performance between examples and comparative examples;

[0041] Figure 11 Comparison of cycles between Example 1 and Comparative Example 1 at different temperatures;

[0042] Figure 12 Constant current intermittent titration curves of Example 1 and Comparative Example 1;

[0043] Figure 13 Comparison of lithium ion diffusion coefficients of Example 1 and Comparative Example 1;

[0044] Figure 14 Electrochemical impedance spectroscopy of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is illustrated by the following examples, but the protection scope of the present invention is not limited thereto. Any equivalent replacement or parameter adjustment based on the technical features of the present invention falls within the scope of protection of this patent.

[0046] Example 1:

[0047] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. Finally, the ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension.

[0048] Weigh 10 mg of MA powder, add 25 mL of deionized water, and sonicate for 5 min to completely dissolve it. Then, slowly add it dropwise to 25 mL of the 2 mg mL prepared above under magnetic stirring. -1 Ti3C2T x After the addition is complete, inert gas protection is introduced and stirring is continued for 24 hours. The stirred solution is allowed to stand for 12 hours, and then centrifuged and washed three times with deionized water (3500 rpm, 5 minutes) to wash away the excess MA in the solution until the pH of the filtrate is close to neutral. Finally, the centrifuged product is freeze-dried to obtain the final Ti3C2T x / MA materials. MA in Ti3C2T x The content in the / MA material is 2.1 wt%.

[0049] 1. Electrochemical performance test

[0050] The active material, conductive agent acetylene black, and binder polyvinylidene fluoride were mixed in a mass ratio of 8:1:1 using 1-methyl-2-pyrrolidone as the solvent. After thorough grinding, the mixture was coated onto copper foil and then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 0.8 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cells in an argon-filled glove box. The cells used lithium foil as the counter electrode, Celgard 2400 as the separator, and 1 M LiPF₆ dissolved in a 1:1:1 (volume) mixture of ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) as the electrolyte. All galvanostatic charge-discharge tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V. The electrochemical impedance spectra were collected on a CHI-760E electrochemical workstation with a measurement frequency range of 100 kHz to 10 mHz. The constant current intermittent titration technique was performed by applying 0.05Ag on the LAND test system. -1 The pulse current is applied for 20 minutes, and then the test is performed under open circuit state for 2 hours.

[0051] See also Figure 1 As shown, Figure 1 Intuitively gives Ti3C2T x Optical image of the interaction between Ti3C2T and MA. Before MA was added, x The electrostatic repulsion between the nanosheets themselves caused the solution to disperse evenly and form a colloidal dispersion. When MA was added, obvious stratification occurred, with the upper layer being a transparent solution and the lower layer being a precipitate after self-assembly. This can be attributed to the fact that after the addition of MA, the Ti3C2T x The nanosheets generate hydrogen bonding forces, Ti3C2T xThe terminal functional groups of the MA molecules will react with the nitrogen on the MA molecules, inducing the two-dimensional sheets to self-assemble and then settle.

[0052] See also Figure 2 As shown, Figure 2 Due to the presence of highly electronegative functional groups on the surface, Ti3C2T x The Zeta potential value of MA is -39.6mV. x Nanosheet surface, which will lead to Ti3C2T x The electrostatic repulsion between the nanosheets is weakened (from -39.6 mV to -23.6 mV). When the weakened electrostatic repulsion is not enough to resist its high surface energy, Ti3C2T x The nanosheets spontaneously assemble to lower the overall surface energy of the material, resulting in a large amount of sediment being observed at the bottom of the sample bottle.

[0053] See also Figure 3 As shown, Figure 3 The XRD spectra of Example 1, Comparative Example 1 and MA are shown. Compared with Comparative Example 1, the position of the (002) characteristic diffraction peak of Example 1 is slightly forward. The increase in interlayer spacing after MA modification can improve the performance of Ti3C2T x The electrolyte accessibility of nanosheets promotes Li + migration, thereby achieving good lithium storage performance.

[0054] See also Figure 4 As shown, Figure 4 As shown, the -OH and C=O absorption peaks of Example 1 are significantly red-shifted compared to Comparative Example 1, which is caused by the formation of hydrogen bonds. O1s XPS spectrum ( Figure 5 )-OH and C=O, further proving that MA and Ti3C2T x There are hydrogen bonds. In addition, Figure 6 The element distribution in the sample of Example 1 is provided. The N element is evenly distributed with the Ti, C, O, and F elements, further indicating that MA is successfully modified in the Ti3C2T x The XPS spectrum of nitrogen element in Example 1 ( Figure 7 ) also confirmed this phenomenon.

[0055] Figure 8 and Figure 9 The infrared spectra of Example 1 and Comparative Example 1 at 0.01V (lithium ion insertion) and 3V (lithium ion extraction) are shown. In Comparative Example 1, the insertion of lithium ions causes a red shift of -OH, while in Example 1, no obvious shift of -OH occurs, which confirms that MA "shields" the -OH and Li + The interaction between them.

[0056] Afterwards, we conducted a constant current charge and discharge test on the battery with a current density of 0.1Ag -1 .like Figure 10 As shown, MA and Ti3C2T x The optimal ratio of MA to Ti3C2T is 2:10 (MA content is 2.1wt%, Example 1). x The feed ratio of 12:10 (Example 4) is a case of exploring the upper limit of the feed ratio, verifying that excessive MA leads to performance degradation. At the same time, the lithium storage capacity of Example 1 is significantly increased compared with Comparative Example 1, and its cycle performance is excellent. After 100 cycles, the discharge capacity of Example 1 can reach 387.7 mAh g -1 , while comparative example 1 only has 198.5 mAh g -1 .

[0057] In order to verify the Ti3C2T x To investigate the potential of MA electrode materials in practical applications, we conducted constant current charge and discharge tests at temperatures ranging from 50 to -20°C. Figure 11 ). The results show that 0.1Ag -1 The discharge capacities of Example 1 at current densities of 50, 40, 30, 20, 10, 0, -10, and -20 °C were 417.7, 388.6, 338.3, 310.8, 287.2, 245.0, 194.1, and 136.5 mAh g -1 , and the discharge capacity values in each temperature gradient are higher than those in Comparative Example 1. The excellent capacity retention in a wide temperature range shows that the modified invention has good electrochemical stability and reversibility, and is more suitable for applications under extreme conditions.

[0058] Then, we conducted an in-depth study on its lithium storage dynamics. Figure 12 As shown in Figure 1, the titration curve was obtained by applying a 20-min pulse current to the electrode and then maintaining a relaxation time of 2 h. The diffusion coefficient extracted from the GITT curve is shown in Figure 1. Figure 13 Ti3C2T at different voltages x / MA have a relatively larger ion diffusion coefficient, indicating that Ti3C2T x / MA has better Li + Diffusion kinetics ability, which is caused by the modification of MA. Figure 14 The Nyquist curve in the frequency range of 100kHz to 10mHz is shown, wherein the impedance value of the embodiment is lower than that of the comparative example 1. In summary, the MA modification strategy improves the electrochemical process of Ti3C2T x charge transfer capability.

[0059] Example 2:

[0060] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. Finally, the ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension.

[0061] Weigh 30 mg of MA powder, add 25 mL of deionized water, and sonicate for 5 min to completely dissolve it. Then, slowly add it dropwise to 25 mL of the 2 mg mL prepared above under magnetic stirring. -1 Ti3C2T x After the addition is complete, inert gas protection is introduced and stirring is continued for 24 hours. The stirred solution is allowed to stand for 12 hours, and then centrifuged and washed three times with deionized water (3500 rpm, 5 minutes) to wash away the excess MA in the solution until the pH of the filtrate is close to neutral. Finally, the centrifuged product is freeze-dried to obtain the final Ti3C2T x / MA materials. Among them, MA in Ti3C2T x The content in the / MA material is 5.1wt%.

[0062] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The mixture was then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 1 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cell half-cells in an argon-filled glove box. The cells used lithium foil as the counter electrode, Celgard 2400 as the separator, and 1 M LiPF₆ dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) in a 1:1:1 volume ratio. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0063] Example 3:

[0064] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. Finally, the ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension.

[0065] Weigh 15 mg of MA powder, add 25 mL of deionized water, and sonicate for 5 minutes to completely dissolve it. Then, slowly add it dropwise to 25 mL of the 2 mg mL prepared above under magnetic stirring. -1 Ti3C2T x After the addition is complete, inert gas protection is introduced and stirring is continued for 24 hours. The stirred solution is allowed to stand for 12 hours, and then centrifuged and washed three times with deionized water (3500 rpm, 5 minutes) to wash away the excess MA in the solution until the pH of the filtrate is close to neutral. Finally, the centrifuged product is freeze-dried to obtain the final Ti3C2T x / MA material.

[0066] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The mixture was then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 1 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cells in an argon-filled glove box. The cells used lithium foil as the counter electrode, Celgard 2400 as the separator, and 1 M LiPF₆ dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) in a 1:1:1 volume ratio as the electrolyte. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0067] Example 4:

[0068] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. Finally, the ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension.

[0069] Weigh 60 mg of MA powder, add 25 mL of deionized water, and sonicate for 5 minutes to completely dissolve it. Then, slowly add it dropwise to 25 mL of the 2 mg mL prepared above under magnetic stirring. -1 Ti3C2T x After the addition is complete, inert gas protection is introduced and stirring is continued for 24 hours. The stirred solution is allowed to stand for 12 hours, and then centrifuged and washed three times with deionized water (3500 rpm, 5 minutes) to wash away the excess MA in the solution until the pH of the filtrate is close to neutral. Finally, the centrifuged product is freeze-dried to obtain the final Ti3C2T x / MA material.

[0070] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The mixture was then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 1 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cells in an argon-filled glove box. The cells used lithium foil as the counter electrode, Celgard 2400 as the separator, and 1 M LiPF₆ dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) in a 1:1:1 volume ratio as the electrolyte. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0071] Example 5:

[0072] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. Finally, the ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension.

[0073] Weigh 5 mg of MA powder, add 25 mL of deionized water, and sonicate for 5 min to completely dissolve it. Then, slowly add it dropwise to 25 mL of the 2 mg mL prepared above under magnetic stirring. -1 Ti3C2T x After the addition is complete, inert gas protection is introduced and stirring is continued for 24 hours. The stirred solution is allowed to stand for 12 hours, and then centrifuged and washed three times with deionized water (3500 rpm, 5 minutes) to wash away the excess MA in the solution until the pH of the filtrate is close to neutral. Finally, the centrifuged product is freeze-dried to obtain the final Ti3C2T x / MA material.

[0074] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The mixture was then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 1 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cells in an argon-filled glove box. Lithium foil served as the counter electrode, Celgard 2400 was used as the separator, and the electrolyte was 1 M LiPF₆ dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) in a 1:1:1 volume ratio. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0075] Comparative Example 1:

[0076] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. The ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension. Finally, the supernatant product was freeze-dried to obtain the final Ti3C2T x Material.

[0077] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The mixture was then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrode sheet was approximately 1 to 1.2 mg. The cut electrode sheets were assembled into CR-2025 coin cell half-cells in an argon-filled glove box. Lithium foil served as the counter electrode, Celgard 2400 was used as the separator, and the electrolyte was 1 M LiPF₆ dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) in a 1:1:1 volume ratio. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0078] Comparative Example 2:

[0079] First, 0.998g LiF was added to 10mL concentrated HCl (12M) and stirred until completely dissolved. Then, 1g of Ti3AlC2 powder was slowly added to the solution, and the mixed solution was transferred to a 36°C constant temperature oil bath for 24h to etch away the Al layer. After the reaction was completed, the solid residue was repeatedly centrifuged and washed with deionized water (3500rpm, 5min) until the pH of the supernatant was close to neutral. Afterwards, the bottom reaction product was redispersed in 20mL deionized water and ultrasonicated in an ice bath for 1h under inert gas protection. The ultrasonicated solution was centrifuged for 1h (3500rpm), and the supernatant was collected to obtain Ti3C2T x The supernatant product was then freeze-dried to obtain Ti3C2T x Finally, Ti3C2T xThe material was calcined in a tube furnace with Ar as protective gas at 300°C for 3 h to obtain the final product.

[0080] The obtained Ti3C2T x The active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 8:1:1, thoroughly ground, and coated onto copper foil. The electrodes were then dried in a vacuum oven at 60°C and 120°C for 12 hours, respectively. The final active material loading on the electrodes was approximately 1 to 1.2 mg. The cut electrodes were assembled into CR-2025 coin cells in an argon-filled glove box. The cells used lithium foil as the counter electrode, Celgard 2400 as the separator, and 1 M LiPF₆ dissolved in a 1:1:1 (volume) mixture of ethylene carbonate / dimethyl carbonate / diethyl carbonate (EC / EMC / DEC) as the electrolyte. All galvanostatic charge-discharge (GCD) tests were recorded using a LANDCT2001A test system over a voltage range of 0.01 to 3.00 V.

[0081] The above description is only a specific embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformation made using the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a melamine-modified MXene material, comprising the following steps in sequence:

1. Ti3C2T x Preparation of nanosheet suspension 1.1 Add LiF to HCl and stir until it is completely dissolved; then, add Ti3AlC2 powder to the solution; 1.2 Transfer the mixed solution obtained in step 1.1 to a constant temperature oil bath for reaction. After the reaction is completed, centrifuge and wash the solid residue until the pH of the supernatant is close to neutral; 1.3 The bottom reaction product obtained in step 1.2 was ultrasonicated in an ice bath under the protection of inert gas; the ultrasonicated solution was centrifuged and the supernatant was collected to obtain Ti3C2T x Nanosheet suspension; Ti3C2T x Preparation of MA 2.1 Add melamine powder to deionized water with ultrasonic stirring to dissolve it completely; slowly add it dropwise to the Ti3C2T x Nanosheet suspension; the melamine and Ti3C2T x The mass ratio is 1 to 12:10; 2.2 After stirring, the solution obtained in step 2.1 was allowed to stand, and then centrifuged and washed until the pH of the filtrate was close to neutral; 2.3 The centrifuged product obtained in step 2.2 is freeze-dried to obtain the target product, melamine-modified MXene material.

2. The method for preparing melamine-modified MXene materials according to claim 1, characterized in that: Melamine binds to Ti3C2T through hydrogen bonds x The -OH and -F functional groups on the surface connect and self-assemble to form a three-dimensional structure.

3. The method for preparing melamine-modified MXene materials according to claim 2, characterized in that: In step 1.1, 0.998 g of LiF was added to 10 mL of concentrated HCl and stirred until completely dissolved; then, 1 g of Ti3AlC2 powder was added to the solution.

4. The method for preparing melamine-modified MXene materials according to claim 3, characterized in that: In step 1.2, the mixed solution obtained in step 1.1 was transferred to a constant temperature oil bath at 36°C for 24 h to etch away the Al layer. After the reaction was completed, the solid residue was washed by centrifugation with deionized water until the pH of the supernatant was close to neutral.

5. The method for preparing melamine-modified MXene materials according to claim 4, characterized in that: In step 2.1, melamine powder was added to 25 mL of deionized water with ultrasonic stirring for 5 min to completely dissolve it; and it was slowly added dropwise to the Ti3C2T x In the nanosheet suspension; in step 2.2, after stirring, the solution obtained in step 2.1 was allowed to stand for 12 h, and then centrifuged and washed several times with deionized water to wash away excess melamine in the solution until the pH of the filtrate was close to neutral.

6. The method for preparing melamine-modified MXene materials according to claim 5, characterized in that: In step 2.3, the content of melamine in the melamine-modified MXene material is 2.1 wt%.

7. An electrochemical application of a product obtained by the method for preparing a melamine-modified MXene material according to any one of claims 1 to 6, characterized in that: Using 1-methyl-2-pyrrolidone as a solvent, melamine-modified MXene material, a conductive agent, and a binder were mixed, ground, and then coated on a copper foil and vacuum-dried. The electrode sheets were assembled into a button half-cell in an argon-filled glove box. Lithium foil was used as the counter electrode, Celgard 2400 was used as the diaphragm, and the electrolyte was LiPF6 dissolved in a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate.

8. Application of the product obtained by the preparation method of melamine-modified MXene material according to claim 7 in electrochemistry, characterized in that: The conductive agent is acetylene black; the binder is polyvinylidene fluoride; the mass ratio of the melamine-modified MXene material, the conductive agent and the binder is 8:1:1 respectively.

9. Application of the product obtained by the preparation method of melamine-modified MXene material according to claim 8 in electrochemistry, characterized in that: The volume ratio of the ethylene carbonate, dimethyl carbonate and diethyl carbonate is 1:1:1.

Images