Melamine formaldehyde / MXene composite material and derivative carbon material thereof, and preparation method and application of melamine formaldehyde / MXene composite material and derivative carbon material

Abstract

The invention relates to the field of nano materials and electrochemical technology materials, in particular to a melamino-formaldehyde / MXene composite material, a derived carbon material thereof, a preparation method and application. According to the preparation method disclosed by the invention, MXene is taken as a substrate, and protonated melamine formaldehyde molecules are inserted into MXene layers through an electrostatic self-assembly effect, so that the melamine formaldehyde / MXene composite material is synthesized; and carrying out high-temperature calcination on the basis to prepare the melamine formaldehyde / MXene composite material derived carbon material. According to the invention, active sites for adsorption and catalytic conversion of iodine species are provided while self-stacking of MXene is solved, and the melamine formaldehyde / MXene composite material is used as the positive electrode material of the aqueous zinc-iodine battery, so that the iodine species can be effectively anchored, and the active sites for catalytic conversion of iodine are fully provided; the reversibility and the structural stability of the electrode reaction are enhanced, so that the electrochemical performance of the battery is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanomaterials and electrochemical technology materials, in particular to melamine formaldehyde / MXene composite material and its derived carbon material, and a preparation method and application thereof. BACKGROUND

[0002] As one of the emerging energy storage devices, aqueous zinc-ion batteries (AZIBs) have attracted extensive attention due to their low cost, low redox potential [−0.76 V (vs. SHE), SHE is the standard hydrogen electrode], high capacity (820 mAh⋅g −1 ), high safety, and other advantages. Iodine-based materials as the positive active material of aqueous zinc-iodine batteries have the advantages of low cost (rich in the ocean, 50−60 μg⋅L −1 ), relatively high specific capacity (211 m Ah⋅g −1 ), good cycle stability and environmental protection, attracting the attention of many researchers. However, aqueous zinc-iodine batteries also have the problems of poor conductivity, self-discharge, slow kinetics, low energy density, and stability of zinc negative electrode. Therefore, constructing iodine positive electrode carrier materials is a common and effective strategy to solve the problems of low conductivity of iodine and its polyiodide ions, easy dissolution of intermediate products in electrolyte, slow conversion rate of polyiodide ions, and shuttle effect. For these reasons, it is urgent to design a carrier material with good conductivity and strong adsorption to load iodine as the positive active material to significantly improve the conductivity and stability of the positive electrode host.

[0003] MXenes is a new type of two-dimensional material and a typical transition metal oxide. MXenes is very rich in types, with more than 30 types such as titanium carbide, vanadium carbide, titanium nitride, Nb4C3, Zr3C2, and TiNbC, Mo2TiC2, etc. Due to its high conductivity, open layered structure, rich active metal atoms and rich surface functional groups, it is considered to be an ideal carrier for I2. However, due to the presence of some functional groups (−F, −OH, etc.) on the surface of Ti3C2T x , the agglomeration of the layers is easily caused by the van der Waals force and hydrogen bond force between the functional groups, which reduces the affinity with electrolyte ions, reduces the charge transfer channel, and damages the charge storage capacity, thereby reducing the performance of zinc-iodine batteries. In addition, the exposed metal atoms on the surface of MXene are easily oxidized at the negative electrode oxidation potential, which causes the complete conversion of T−C bond to TiO2 particles and C, which seriously affects its energy storage capacity. SUMMARY

[0004] The application provides a melamine formaldehyde / MXene composite material and a derived carbon material thereof, and an iodine-based positive electrode material is obtained by anchoring an iodine positive electrode by using the melamine formaldehyde / MXene composite material and the derived carbon material thereof, the iodine-based positive electrode material has good conductivity, and excellent cycle stability and battery capacity are achieved.

[0005] To solve the above technical problems, the technical scheme adopted by the application is as follows: a melamine formaldehyde / MXene composite material, MXene layers uniformly wrap melamine formaldehyde microspheres, N elements are uniformly distributed in the melamine formaldehyde / MXene composite material, and the melamine formaldehyde / MXene composite material contains 25.8% pyridine N, 17.05% pyrrole N and 9.57% graphite N.

[0006] The application further provides a preparation method of the melamine formaldehyde / MXene composite material, and the preparation method comprises the following steps: (1) etching and stripping a MAX phase precursor material by a fluorine salt method to obtain a few-layer two-dimensional MXene powder; (2) adding formic acid to a mixed solution of melamine and formaldehyde to obtain protonated melamine formaldehyde microsphere powder; (3) dispersing the melamine formaldehyde microspheres obtained in the step (2) into a water solution of the two-dimensional MXene powder dissolved in the step (1), and adsorbing positively charged melamine formaldehyde molecules to the few-layer MXene by electrostatic attraction to obtain a mixed solution; (4) after the mixed solution is fully reacted, centrifugal cleaning is performed by using deionized water, and MF / MXene composite material is obtained after freeze-drying.

[0007] As a further limitation of the technical scheme of the application, in the step (1), the MAX phase precursor material is etched by an etching method, and the specific steps are as follows: A. At room temperature, 6 M HCl solution is added to a polytetrafluoroethylene beaker, and then LiF powder is added into a constant-temperature heating magnetic stirrer to obtain a clear and transparent LiF / HCl mixed solution; B. The Ti3AlC2 is evenly divided into four parts, and is added into the LiF / HCl mixed solution in four times in a fume hood; C. The mixed solution is heated in a water bath at 40-45 DEG C and continuously stirred, reacts for 40-48 h, and is centrifugally washed with water for 6-8 times until the pH is neutral, to obtain multi-layer Ti3C2T x precipitate; D. The Ti3C2T xAfter adding ultrapure water in the precipitate and shaking, under Ar gas condition, ice water bath ultrasonic for 1 h, after centrifugation, the upper dark solution was poured out, and freeze-drying was carried out to obtain a few layers of two-dimensional Ti3C2T x The powder is a MXene powder.

[0008] As a further limitation of the technical scheme of the application, the mass ratio of LiF in step A to Ti3AlC2 in step B is 1:1.

[0009] As a further limitation of the technical scheme of the application, the mass-volume ratio of melamine, formaldehyde, deionized water and formic acid in step (2) is 2.5g:10mL:220mL:0.3mL.

[0010] As a further limitation of the technical scheme of the application, the mass-volume ratio of two-dimensional MXene powder, protonated melamine formaldehyde microsphere powder and deionized water in step (3) is 100mg:300mg:100mL.

[0011] The preparation method of the melamine formaldehyde / MXene composite material derived carbon material adopts the above-mentioned melamine formaldehyde / MXene composite material, and comprises the following steps: calcining the melamine formaldehyde / MXene composite material in a tube furnace at 500°C for 2.5h, with an heating rate of 5°C / min, and passing argon gas, to prepare the melamine formaldehyde / MXene composite material derived carbon material.

[0012] The application also provides a preparation method of a zinc-iodine battery positive electrode, which adopts the above-mentioned melamine formaldehyde / MXene composite material or melamine formaldehyde / MXene composite material derived carbon material, and comprises the following steps: S1, mixing and stirring the melamine formaldehyde / MXene composite material or melamine formaldehyde / MXene composite material derived carbon material, conductive carbon powder and binder uniformly to obtain a positive electrode material mixture; S2, uniformly coating the positive electrode material mixture in step S1 on carbon cloth to obtain a zinc-iodine battery positive electrode.

[0013] Preferably, the mass ratio of the melamine formaldehyde / MXene composite material or melamine formaldehyde / MXene composite material derived carbon material, conductive carbon powder and binder in step S1 is 8:1:1.

[0014] The application also provides the application of the zinc-iodine battery positive electrode obtained by the above-mentioned preparation method in the field of energy storage.

[0015] Compared with the prior art, the application has the following beneficial effects: 1. The application first prepares a positive electrode material for aqueous zinc-iodine batteries by using melamine formaldehyde and two-dimensional MXene as raw materials; the introduction of melamine formaldehyde not only changes the two-dimensional MXene into a three-dimensional structure, but also effectively adsorbs and catalyzes the iodine component.

[0016] 2. In the application, the melamine formaldehyde / MXene composite material or the derived carbon material thereof is used as a positive electrode material for an aqueous zinc-iodine battery, which can effectively anchor iodine species and fully provide active sites for catalytic conversion of iodine, thereby enhancing the reversibility and structural stability of the electrode reaction, and greatly improving the electrochemical performance of the battery. The positive electrode material prepared from the melamine formaldehyde / MXene composite material has a specific capacity of 209.39 mA h g −1 ) at 1.0 C (1.0 C = 211 mA h g −1 ), and a specific capacity retention rate of 84.45% after 5000 cycles, and the melamine formaldehyde / MXene composite material also maintains good electrochemical performance under high current conditions and soft package battery structure.

[0017] 3. In the application, melamine is a commonly used industrial raw material, which is widely available and low in price, and the compounding method with MXene is green and simple. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the SEM diagram of the material obtained by reacting examples 3 and 4 of the application; wherein (a) is the SEM diagram of the melamine formaldehyde / MXene composite material prepared in example 3, and (b) is the SEM diagram of the melamine formaldehyde / MXene composite material derived carbon material prepared in example 4.

[0019] Figure 2 is the XRD diagram of the melamine formaldehyde / MXene composite material and the derived carbon material thereof obtained by reacting examples 3 and 4 of the application, and the raw material MAX (Ti3AlC2) and pure Ti3C2T x material.

[0020] Figure 3 is the aqueous zinc-iodine battery and the cycle performance curve prepared by examples 3 and 4 and comparative examples of the application. DETAILED DESCRIPTION

[0021] The application will be further described below in combination with specific examples.

[0022] Instruments and reagents: The drugs used in the examples are all of analytical purity and can be directly used without further purification.

[0023] MAX (Ti3AlC2) was purchased from Jilin Shiyi Technology Co., Ltd., lithium fluoride, zinc sulfate heptahydrate, potassium iodide, N-methyl-2-pyrrolidone, LA133 were purchased from Shanghai Aladdin Biochem Technology Co., Ltd., Ketjen black was purchased from Macklin Reagent.

[0024] The cycle performance test of all samples was carried out on a blue electric test system (Wuhan, China). The cycle performance was obtained at a current of 1.0 C. Example 1

[0025] A melamine formaldehyde / MXene composite material is prepared as a positive electrode of a water-based zinc-iodine battery, and the preparation method comprises the following steps: This example uses fluorine salt method etching to prepare few-layer MXene, and protonated melamine formaldehyde and few-layer MXene are compounded by electrostatic adsorption. The specific experimental scheme is as follows: (1) 80 mL of 6M HCl solution was added to a polytetrafluoroethylene beaker, 4 g of LiF powder was added into a constant temperature heating magnetic stirrer, heated to 40°C in a water bath, and stirred at 400 rpm / min for 30 min to obtain a clear and transparent LiF / HCl mixed solution.

[0026] (2) 4 g of Ti3AlC2 (400 mesh) was evenly divided into four portions, and was added to the above mixed solution in four times with a time interval of 10 minutes.

[0027] (3) The above mixed solution was stirred at 40°C in a water bath for 40 h (400 rpm / min).

[0028] (4) After the reaction was completed, the solution was divided into centrifuge tubes and centrifuged at 3500 rpm / min for 3 min. After centrifugation, the precipitate was taken and 30 mL of deionized water was added in each centrifuge tube, shaken and mixed, ultrasonicated for 10 min, and centrifuged at 3500 rpm / min for 5 min. The above steps were repeated 6-7 times until the pH value of the supernatant was close to 6 and neutral.

[0029] (5) 30 mL of deionized water was added to the above precipitate and shaken uniformly, and Ar gas was introduced for 1 h of stripping in an ice water bath at 750 W.

[0030] (6) The liquid after ultrasonic treatment was again divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min to obtain a dark green supernatant, which was a few-layer Ti3C2T x dispersion liquid, liquid nitrogen freezing, freeze-drying, to obtain few-layer Ti3C2T x powder.

[0031] (7) Take 10 mL of formaldehyde and 220 mL of ultrapure water in a 300 mL polytetrafluoroethylene beaker, stir to evenly disperse the formaldehyde into the ultrapure water, and place in a 80°C water bath.

[0032] (8) Take 2.5 g of melamine powder and add it to the above mixture to form a uniform solution.

[0033] (9) After the melamine is completely dissolved, add 0.3 mL of formic acid to the above solution to adjust the pH value.

[0034] (10) The resulting mixture is kept at 80°C, 400 rpm / min, and magnetically stirred for 1 h, so that the transparent solution becomes a milky white solution, and MF microspheres are obtained.

[0035] (11) The milky white solution is divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, and the precipitate is washed with deionized water and anhydrous ethanol twice respectively.

[0036] (12) Collect the white precipitate and vacuum dry at 60°C for 14 h to obtain the final MF microspheres.

[0037] (13) Pour 0.2 g of Ti3C2T x powder into 200 mL of deionized water, stir to dissolve, and form a (TC) water dispersion (1 mg / mL −1 ), and disperse 0.6 g of MF microspheres as a template into the TC water dispersion, and ultrasonic for 30 min.

[0038] (14) The mixed solution is divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, the precipitate is collected, frozen with liquid nitrogen, and freeze-dried for 24 h to obtain melamine formaldehyde / MXene composite material, marked as NC@TC composite material.

[0039] (15) Mix the melamine formaldehyde / MXene (NC@TC) composite material obtained in step (14) with conductive carbon powder (ketjen black, Super C), and binder (PVDF, LA133) according to the mass ratio of 8:1:1 to obtain an anode material mixture; (16) The anode material mixture in step (15) is evenly coated on carbon cloth (HCP330N) to obtain a zinc-iodine battery anode. Example 2

[0040] A melamine formaldehyde / MXene composite material is prepared as a water-based zinc-iodine battery anode, and the preparation method comprises the following steps: This example uses fluorosalt etching to prepare few-layer Ti3C2T x MXene, and protonated melamine formaldehyde and few-layer Ti3C2Tx MXene composite, the specific experimental procedure is as follows: (1) 80 mL of 6M HCl solution was added to a polytetrafluoroethylene beaker, 4 g of LiF powder was added into a constant temperature heating magnetic stirrer, heated to 40°C in a water bath, and stirred for 30 min at a speed of 400 rpm / min, to obtain a clear transparent LiF / HCl mixed solution.

[0041] (2) 4 g of Ti3AlC2 (400 mesh) was evenly divided into four portions, and was added to the above mixed solution in four times with an interval of 10 minutes.

[0042] (3) The above mixed solution was stirred at 40°C in a water bath for 48 h (400 rpm / min).

[0043] (4) After the reaction was completed, the solution was divided into centrifuge tubes and centrifuged at 3500 rpm / min for 3 min. After centrifugation, the precipitate was taken and 30 mL of deionized water was added in each centrifuge tube, shaken and mixed uniformly, ultrasonicated for 10 min, and centrifuged at 3500 rpm / min for 5 min, repeated 6-7 times until the pH value of the supernatant was close to 6, and stopped.

[0044] (5) 30 mL of deionized water was added to the above precipitate, shaken uniformly, and Ar gas was introduced, and ultrasonicated for 1 h in an ice water bath at 750 W for stripping.

[0045] (6) The liquid after ultrasonication was again divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min to obtain a dark green supernatant, which was a few-layer dispersion liquid, frozen in liquid nitrogen, and freeze-dried to obtain a few-layer Ti3C2T x MXene powder.

[0046] (7) 10 mL of formaldehyde and 220 mL of ultrapure water were taken in a 300 mL polytetrafluoroethylene beaker, and the formaldehyde was uniformly dispersed in the ultrapure water by stirring, and placed in an 80°C water bath.

[0047] (8) 2.5 g of melamine powder was added to the above mixture to form a uniform solution.

[0048] (9) After the melamine was completely dissolved, 0.3 mL of formic acid was added to the above solution to adjust the pH value.

[0049] (10) The obtained mixture was kept at 80°C, 400 rpm / min, and magnetically stirred for 1 h, so that the transparent solution became a milky white solution, and MF microspheres were obtained.

[0050] (11) The milky white solution was divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, and the precipitate was washed with deionized water and anhydrous ethanol respectively for two times.

[0051] (12) Collect the white precipitate, dry it under vacuum at 60°C for 14 h to obtain the final MF microspheres.

[0052] (13) Put 0.2 g Ti3C2T x powder into 200 mL deionized water, stir to dissolve it, and form a Ti3C2T x (TC) aqueous dispersion (1 mg / mL −1 ), and disperse 0.6 g of MF microspheres into the TC aqueous dispersion, and ultrasonicate for 30 min.

[0053] (14) Distribute the mixed solution into centrifuge tubes, centrifuge at 6000 rpm / min for 10 min, collect the precipitate, freeze it using liquid nitrogen, and freeze-dry it for 24 h to obtain melamine formaldehyde / MXene composite material, marked as NC@TC composite material.

[0054] (15) Mix and stir the melamine formaldehyde / MXene (NC@TC) composite material obtained in step (14) with conductive carbon powder (ketjen black, Super C), and binder (PVDF, LA133) according to a mass ratio of 8:1:1 to obtain an anode material mixture; (16) Uniformly coat the anode material mixture in step (15) on carbon cloth (HCP330N) to obtain a zinc-iodine battery anode. Example 3

[0055] A melamine formaldehyde / MXene composite material is prepared as a water-based zinc-iodine battery anode, and the preparation method comprises the following steps: This example uses fluorosalt etching to prepare few-layer Ti3C2T x MXene, and protonated melamine formaldehyde and few-layer Ti3C2T x MXene are compounded through electrostatic adsorption, and the specific experimental scheme is as follows: (1) Put 80 mL of 6M HCl solution into a polytetrafluoroethylene beaker, add 4 g of LiF powder into a constant-temperature heating magnetic stirrer, heat the water bath to 45°C, and stir for 30 min at a speed of 400 rpm / min to obtain a clear and transparent LiF / HCl mixed solution.

[0056] (2) Divide 4 g of Ti3AlC2 (400 mesh) into four equal parts, and add them into the above mixed solution in four times with a time interval of 10 min.

[0057] (3) Stir the above mixed solution in a water bath at 45°C for 40 h (400 rpm / min).

[0058] (4) After the reaction is completed, the solution is divided into centrifuge tubes and centrifuged at 3500 rpm / min for 3 min. After centrifugation, the precipitate is taken and 30 mL of deionized water is added to each centrifuge tube, shaken by hand to mix, ultrasonic for 10 min, centrifuged at 3500 rpm / min for 5 min, repeated 6-7 times, until the pH value of the supernatant is close to 6, and stop when it is neutral.

[0059] (5) 30 mL of deionized water is added to the above-mentioned precipitate, shaken uniformly, and Ar gas is introduced, ultrasonic for 1 h in an ice water bath at 750 W to perform stripping.

[0060] (6) The liquid after ultrasonic is again divided into centrifuge tubes, centrifuged at 6000 rpm / min for 10 min, and a dark green supernatant is obtained, which is a few-layer dispersion liquid, frozen in liquid nitrogen, and freeze-dried to obtain a few-layer Ti3C2T x MXene powder.

[0061] (7) 10 mL of formaldehyde and 220 mL of ultrapure water are taken in a 300 mL polytetrafluoroethylene beaker, and the formaldehyde is uniformly dispersed in the ultrapure water by stirring, and placed in a 80°C water bath.

[0062] (8) 2.5 g of melamine powder is added to the above mixture to form a uniform solution.

[0063] (9) After the melamine is completely dissolved, 0.3 mL of formic acid is added to the above solution to adjust the pH value.

[0064] (10) The obtained mixture is kept at 80°C, 400 rpm / min, and magnetically stirred for 1 h, so that the transparent solution becomes a milky white solution, and MF microspheres are obtained.

[0065] (11) The milky white solution is divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, and the precipitate is washed with deionized water and anhydrous ethanol respectively for two times.

[0066] (12) The white precipitate is collected and vacuum dried at 60°C for 14 h to obtain the final MF microspheres.

[0067] (13) 0.2 g of Ti3C2T x powder is poured into 200 mL of deionized water, stirred to dissolve, and a Ti3C2T x (TC) aqueous dispersion (1 mg / mL −1 ) is formed, and 0.6 g of MF microspheres is dispersed into the TC aqueous dispersion as a template and ultrasonic for 30 min.

[0068] (14) The mixed solution was divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, the precipitate was collected, frozen with liquid nitrogen, and freeze-dried for 24 h to obtain melamine formaldehyde / MXene composite material, marked as NC@TC composite material.

[0069] (15) The melamine formaldehyde / MXene (NC@TC) composite material obtained in step (14) was mixed with conductive carbon powder (ketjen black, Super C) and binder (PVDF, LA133) according to a mass ratio of 8:1:1 to obtain a positive electrode material mixture. (16) The positive electrode material mixture in step (15) was uniformly coated on carbon cloth (HCP330N) to obtain a zinc-iodine battery positive electrode. Example 4

[0070] A melamine formaldehyde / MXene composite material derived carbon material is prepared as a water-based zinc-iodine battery positive electrode A few-layer MXene is prepared by etching and peeling off using a fluorosalt method, protonated melamine formaldehyde and few-layer MXene are compounded by electrostatic adsorption, and then calcined at 500°C. The specific experimental scheme is as follows: (1) 80 mL of 6M HCl solution was added to a polytetrafluoroethylene beaker, 4 g of LiF powder was added into a constant temperature heating magnetic stirrer, heated to 45°C in a water bath, and stirred at 400 rpm / min for 30 min to obtain a clear and transparent LiF / HCl mixed solution.

[0071] (2) 4 g of Ti3AlC2 (400 mesh) was evenly divided into four portions and added to the above mixed solution in four times with an interval of 10 min.

[0072] (3) The above mixed solution was stirred at 45°C in a water bath for 40 h (400 rpm / min).

[0073] (4) After the reaction was completed, the solution was divided into centrifuge tubes and centrifuged at 3500 rpm / min for 3 min. After centrifugation, the precipitate was taken and 30 mL of deionized water was added in each centrifuge tube, shaken and mixed, ultrasonicated for 10 min, and centrifuged at 3500 rpm / min for 5 min. The operation was repeated 6-7 times until the pH value of the supernatant was close to 6 and neutral.

[0074] (5) 30 mL of deionized water was added to the above precipitate and shaken uniformly, Ar gas was introduced, and ultrasonication was performed in an ice water bath at 750 W for 1 h for peeling off.

[0075] (6) The liquid after ultrasonic is again divided into centrifuge tube, 6000 rpm / min centrifugation for 10 min, the ink green supernatant is a few layer dispersion, liquid nitrogen freezing, freeze-drying, can get a few layer Ti3C2T x MXene powder.

[0076] (7) Take 10 mL formaldehyde and 220 mL ultrapure water in a 300 mL polytetrafluoroethylene beaker, stir to make formaldehyde evenly dispersed in ultrapure water, and place in a 80°C water bath.

[0077] (8) Take 2.5 g of melamine powder and add it to the above mixture to form a uniform solution.

[0078] (9) After the melamine is completely dissolved, 0.3 mL of formic acid is added to the above solution to adjust the pH value.

[0079] (10) The obtained mixture is kept at 80°C, 400 rpm / min, magnetic stirring for 1 h, the transparent solution becomes milky white solution, and MF microspheres are obtained.

[0080] (11) The milky white solution is divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, and the precipitate is washed with deionized water and anhydrous ethanol respectively for two times.

[0081] (12) The white precipitate is collected and vacuum dried at 60°C for 14 h to obtain the final MF microspheres.

[0082] (13) 0.2 g Ti3C2T x powder is poured into 200 mL deionized water, stirred to dissolve, and a Ti3C2T x (TC) aqueous dispersion (1 mg / mL −1 ) is formed, 0.6 g of MF microspheres is dispersed into the TC aqueous dispersion as a template, and ultrasonic is performed for 30 min.

[0083] (14) The mixed solution is divided into centrifuge tubes and centrifuged at 6000 rpm / min for 10 min, the precipitate is collected, frozen with liquid nitrogen, and freeze-dried for 24 h to obtain NC@TC composite material.

[0084] (15) The melamine formaldehyde / MXene (NC@TC) composite material is calcined at 500°C for 2.5 h under argon protection (heating rate 5°C / min), and taken out at room temperature to obtain melamine formaldehyde / MXene composite material derived carbon material (NC@TC−P) product.

[0085] (16) The melamine formaldehyde / MXene composite material derived carbon material (NC@TC-P) is mixed and stirred with conductive carbon powder (ketjen black, Super C) and a binder (PVDF, LA133) at a mass ratio of 8:1:1 to obtain a positive electrode material mixture; (17) The positive electrode material mixture in step (16) is uniformly coated on carbon cloth (HCP330N) to obtain a zinc-iodine battery positive electrode.

[0086] I. Test: 1. Electrochemical performance test: The zinc-iodine battery positive electrodes in examples 1-4, glass fiber separators (GF / D), aqueous electrolyte, and zinc foil negative electrodes are assembled into aqueous zinc-iodine battery button cells. The aqueous electrolyte is an iodine ion-containing Zn 2+ salt solution, such as: ZnSO4+KI, Zn(CH3COO)2+KI, Zn(OTf)2+KI The button cells are subjected to constant current charge and discharge tests at a current density of 1.0C (1.0C=211mAhg −1 ).

[0087] 2. Performance result analysis: As can be seen from Figure 1 , the Ti3C2T x MXene flakes can uniformly wrap the MF microspheres, and the MF microspheres still retain the spherical morphology and good monodispersity. The melamine formaldehyde / MXene composite material derived carbon material has no obvious melamine formaldehyde microspheres, but only flakes with large and uniform spacing. As can be seen from Figure 2 , the XRD patterns of the raw material MAX(Ti3AlC2), pure Ti3C2T x , example 3 melamine formaldehyde / MXene composite material, and example 4 melamine formaldehyde / MXene composite material derived carbon material show that the (002) crystal plane moves to a lower angle, indicating that Ti3C2T x is successfully prepared, and the (110) crystal plane does not shift to a high angle, indicating that the melamine formaldehyde and MXene are successfully compounded.

[0088] As can be seen from Figure 3 , the positive electrode material prepared from the melamine formaldehyde / MXene composite material has a mass specific capacity of 209.39mAhg −1 after 100 charge and discharge cycles of the aqueous zinc-iodine battery button cell in the constant current charge and discharge test at a current density of 1.0C (1.0C=211mAhg −1, the coulombic efficiency remained at 89.5% after the first two cycles; the positive electrode material prepared by the melamine formaldehyde / MXene composite derived carbon material in the constant current charge-discharge test at a current density of 1.0C (1.0C=211mAhg −1 ) was subjected to 100 charge-discharge cycles, and the mass specific capacity of the water-based zinc-iodine battery button cell was 106.67mAhg −1 .

[0089] The above electrochemical performance test shows that the water-based zinc-iodine battery composed of the melamine formaldehyde / MXene (NC@TC) composite material as the positive electrode and the zinc foil as the negative electrode in Example 3 of the application has high mass specific capacity and excellent cycle stability during charging and discharging.

[0090] Comparative example A pure Ti3C2T x MXene material is prepared as a positive electrode of a water-based zinc-iodine battery A few-layer Ti3C2T x MXene is prepared by etching and stripping with a fluorine salt method, protonated melamine formaldehyde and a few-layer Ti3C2T x MXene are combined by electrostatic adsorption, and the specific experimental scheme is as follows: (1) 80mL of 6M HCl solution is added to a polytetrafluoroethylene beaker, 4g of LiF powder is added into a constant temperature heating magnetic stirrer, heated to 45℃ in a water bath, and stirred at 400rpm / min for 30min to obtain a clear and transparent LiF / HCl mixed solution.

[0091] (2) 4g of Ti3AlC2 (400 mesh) is evenly divided into four portions, and is added to the above mixed solution in four times with a time interval of 10min.

[0092] (3) The above mixed solution is stirred at 45℃ in a water bath for 40h (400rpm / min).

[0093] (4) After the reaction is completed, the solution is divided into centrifuge tubes and centrifuged at 3500rpm / min for 3min. After centrifugation, the precipitate is taken and 30mL of deionized water is added in each centrifuge tube, shaken and mixed, ultrasonicated for 10min, and centrifuged at 3500rpm / min for 5min, repeated for 6-7 times, until the pH value of the supernatant is close to 6, and neutralization is stopped.

[0094] (5) 30mL of deionized water is added to the above precipitate, shaken and mixed, Ar gas is introduced, and stripping is carried out in an ice water bath at 750W for 1h.

[0095] (6) The ultrasonicated liquid was evenly divided into centrifuge tubes again and centrifuged at 6000 rpm / min for 10 min to obtain a dark green supernatant, which is a few-layer Ti3C2T x The dispersion was frozen in liquid nitrogen and freeze-dried to obtain a few-layer Ti3C2T x MXene powder.

[0096] (7) The Ti3C2T x MXene was mixed with conductive carbon powder (Ketjen Black, SuperC) and binder (PVDF, LA133) in a mass ratio of 8:1:1 to obtain a cathode material mixture. (8) The positive electrode material mixture in step (7) is evenly coated on carbon cloth (HCP330N) to obtain a zinc-iodine battery positive electrode.

[0097] 2. Electrochemical performance test: The button cell was subjected to constant current charge and discharge test, and the current density was set to 1.0C (1.0C = 211mAhg −1 ).

[0098] 3. Analysis of electrochemical performance results: Depend on Figure 3 It can be seen that pure Ti3C2T is used in the existing technology. x Aqueous zinc-iodine batteries with MXene as the positive electrode have a current density of 1.0C (1.0C = 211mAhg −1 ) constant current charge and discharge test, after 100 cycles, the mass specific capacity is 105.60mAhg −1 .

[0099] By comparing the cycle performance diagram of the melamine formaldehyde / MXene composite material of Example 3, it can be seen that the cycle stability of the melamine formaldehyde / MXene composite material of the present invention is greatly improved.

[0100] In summary, the present invention provides a method for preparing a melamine formaldehyde / MXene composite material and its derived carbon material-anchored iodine cathode material, demonstrating excellent performance in aqueous zinc-iodine batteries. While addressing MXene self-stacking, the present invention also provides active sites for iodine adsorption and catalytic conversion, achieving excellent cycling stability and high battery capacity in aqueous zinc-iodine batteries through a green and simple synthesis method. Overall, the synthesis of a melamine formaldehyde / MXene composite-anchored iodine cathode via electrostatic self-assembly opens new possibilities for the research of high-capacity and long-life Zn−I₂ batteries, representing a promising method for preparing cathode materials.

[0101] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the patent protection scope of the present application.

Claims

1. A melamine formaldehyde / MXene composite material, characterized in that: The MXene sheets uniformly wrapped the melamine formaldehyde microspheres, and the nitrogen element was evenly distributed in the melamine formaldehyde / MXene composite material, containing 25.8% pyridinic nitrogen, 17.05% pyrrolic nitrogen and 9.57% graphitic nitrogen.

2. The method for preparing a melamine formaldehyde / MXene composite material according to claim 1, wherein: The following steps are involved: (1) Fluoride salt method is used to etch and peel off the MAX phase precursor material to produce a few-layer two-dimensional MXene powder; (2) adding formic acid to a mixed solution of melamine and formaldehyde to obtain protonated melamine formaldehyde microsphere powder; (3) dispersing the melamine formaldehyde microspheres obtained in step (2) into the aqueous solution of the dissolved two-dimensional MXene powder in step (1), so that the positively charged melamine formaldehyde molecules are adsorbed onto the few-layer MXene by electrostatic action to obtain a mixed solution; (4) After the mixed solution is fully reacted, it is centrifuged and washed with deionized water, and then freeze-dried to obtain a melamine formaldehyde / Mxene composite material.

3. The method for preparing a melamine formaldehyde / MXene composite material according to claim 2, wherein: In step (1), the MAX phase precursor material is etched by etching, and the specific steps are as follows: A. At room temperature, add 6 M HCl solution to a polytetrafluoroethylene beaker, then add LiF powder and place it in a constant temperature heated magnetic stirrer to obtain a clear and transparent LiF / HCl mixture; B. Divide Ti3AlC2 into four equal parts and add them into the LiF / HCl mixture in a fume hood in four portions; C. The mixed solution was placed in a water bath at 40-45°C and heated with constant stirring for 40-48 hours. The mixture was then centrifuged and washed with water 6-8 times until the pH was neutral to obtain multilayer Ti3C2T x precipitation; D. Ti3C2T x Ultrapure water was added to the precipitate and shaken, and then ultrasonicated in an ice-water bath for 1 h under Ar gas conditions. After centrifugation, the upper dark solution was poured out and freeze-dried to obtain a few-layer two-dimensional Ti3C2T x Powder, i.e. MXene powder.

4. The method for preparing a melamine formaldehyde / MXene composite material according to claim 3, wherein: The mass ratio of LiF in step A to Ti3AlC2 in step B is 1:

1.

5. The method for preparing a melamine formaldehyde / MXene composite material according to claim 3, wherein: The mass volume ratio of melamine, formaldehyde, deionized water and formic acid in step (2) is 2.5 g:10 mL:220 mL:0.3 mL.

6. The method for preparing a melamine formaldehyde / MXene composite material according to claim 3, wherein: In step (3), the mass volume ratio of the two-dimensional MXene powder, the protonated melamine formaldehyde microsphere powder and the deionized water is 100 mg:300 mg:100 mL.

7. A method for preparing a carbon material derived from a melamine formaldehyde / MXene composite material, comprising preparing the carbon material from the melamine formaldehyde / MXene composite material according to claim 1, wherein: The method comprises the following steps: calcining the melamine formaldehyde / MXene composite material in a tube furnace at 500° C. for 2.5 hours at a heating rate of 5° C. / min and passing argon gas to prepare a melamine formaldehyde / MXene composite material-derived carbon material.

8. A method for preparing a zinc-iodine battery positive electrode, comprising: using the melamine-formaldehyde / MXene composite material according to claim 1 or the melamine-formaldehyde / MXene composite material-derived carbon material according to claim 7, wherein: The following steps are involved: S1. Mixing the melamine formaldehyde / MXene composite material or the melamine formaldehyde / MXene composite material-derived carbon material with the conductive carbon powder and the binder to obtain a positive electrode material mixture; S2. Evenly coating the positive electrode material mixture in step S1 on carbon cloth to obtain a zinc-iodine battery positive electrode.

9. The method for preparing a zinc-iodine battery positive electrode according to claim 8, wherein: In step S1, the mass ratio of the melamine formaldehyde / MXene composite material or the melamine formaldehyde / MXene composite material, the conductive carbon powder and the binder is 8:1:

1.

10. Application of the zinc-iodine battery positive electrode obtained according to the preparation method of claim 8 or 9 in the field of energy storage.

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