Application of an in-situ grown three-dimensional ZIF-8 / MXene composite material in the preparation of zinc-iodine batteries

Abstract

The present invention belongs to the technical field of functional coatings, and specifically relates to the application of an in-situ grown three-dimensional ZIF-8 / MXene composite material in the preparation of zinc-iodine batteries. The protective coating prepared by the present invention comprises a composite material and a binder, and the protective coating is attached to the surface of a zinc electrode. The composite material is composed of MXene two-dimensional nanosheets and ZIF-8 nanoparticles, and the ZIF-8 nanoparticles are uniformly distributed on the MXene two-dimensional nanosheets. The present invention also discloses a specific preparation method for the above-mentioned coating, and the obtained coating can effectively avoid the aggregation of MXene nanosheets and make the electric field uniform by charge redistribution, and the electric field is uniform at 1mA cm ‑2 Under current conditions, the Z@M‑Zn anode exhibited a cycle life exceeding 1050 h, excellent corrosion resistance, and full battery performance exceeding 2400 cycles. This study provides a facile approach for designing reversible zinc anodes and is expected to be more widely used in other metal-based anode systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional coatings, and specifically relates to an application of an in-situ grown three-dimensional ZIF-8 / MXene composite material in the preparation of a zinc-iodine battery. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Aqueous rechargeable batteries have significant advantages in large-scale energy storage, such as ease of assembly, high safety, and low cost, and therefore have broad application prospects. Among various types of aqueous batteries, zinc-based batteries stand out due to their high theoretical capacity, low redox potential, and abundant natural resources. However, the zinc negative electrode will produce dendrites due to uneven electric field distribution, and may even pierce the battery separator, causing a short circuit. In addition, the zinc negative electrode is prone to hydrogen evolution reaction in aqueous electrolytes, resulting in a local increase in pH and subsequent corrosion of the zinc negative electrode surface.

[0004] To address these issues, researchers have explored various strategies, including three-dimensional structural engineering, surface modification, electrolyte optimization, and membrane modification. Among these methods, surface modification has become one of the most effective methods due to its simplicity of operation, excellent scalability, and potential to improve the performance of zinc anodes. In particular, MXenes, as a class of two-dimensional transition metal carbides and / or nitrides, have attracted widespread attention. MXenes have M n+1 X n T x The general formula, wherein M represents a transition metal, X represents carbon and / or nitrogen, T x Indicates the surface terminal groups (such as -F, -O, -OH). 2+ The uniform deposition of ions has significant advantages, which is crucial for reducing dendrite formation and improving the overall performance of zinc batteries (corrosion resistance, conductivity, cycling stability, etc.). Therefore, the rational design of composite materials to avoid MXene aggregation is crucial for the synthesis of stable coatings and is an urgent problem to be solved by those skilled in the art. Iodine is abundant in seawater, and aqueous zinc-iodine batteries have become a new type of energy storage device. The application of modified zinc anodes to zinc-iodine batteries is of great strategic significance. Summary of the Invention

[0005] In response to the needs of the existing technology, the purpose of the present invention is to provide an in situ grown three-dimensional ZIF-8 / MXene composite material for the preparation of zinc-iodine batteries. By utilizing the synergistic properties of MXenes and metal organic framework compounds (MOFs) to improve the zinc negative electrode, the in situ growth of ZIF-8 nanoparticles on the MXene surface can not only prevent aggregation but also improve the electrochemical performance, providing a promising strategy for the development of reversible zinc negative electrodes with corrosion resistance, long cycle life and high capacity.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides an application of an in-situ grown three-dimensional ZIF-8 / MXene composite material in the preparation of a zinc-iodine battery, wherein a slurry prepared from the composite material and a binder is attached to the surface of a zinc electrode as a protective coating;

[0008] The composite material consists of MXene two-dimensional nanosheets and ZIF-8 nanoparticles, and the ZIF-8 nanoparticles are uniformly distributed on the MXene two-dimensional nanosheets.

[0009] Preferably, the binder is selected from one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide; further preferably, the binder is polyvinylidene fluoride (PVDF).

[0010] Preferably, the method for preparing the in situ grown three-dimensional ZIF-8 / MXene composite material comprises the following steps:

[0011] S1. Add MAX powder to etching solution to perform etching reaction to obtain MXene dispersion;

[0012] S2, adding ZIF-8 nanoparticles to the MXene dispersion to obtain a composite material (ZIF-8 skeleton-modified MXene two-dimensional nanosheets ZIF-8@MXene);

[0013] S3. Mix the composite material and the binder, and apply the obtained slurry on the electrode sheet and dry it.

[0014] Preferably, in step S1, the MAX powder is selected from one or more of Ti3AlC2, V2AlC and Nb2AlC; and the etching solution is selected from one or more of HF, HCl and LiF.

[0015] Preferably, in step S1, the temperature of the etching reaction is 30-50° C., and the time is 12-36 hours; further preferably, the temperature of the etching reaction is 40° C., and the time is 24 hours.

[0016] Preferably, in step S1, the mixture obtained after the etching reaction is washed with ultrapure water and subjected to ultrasonic stripping in sequence to obtain a MXene suspension, and then centrifuged to obtain a MXene dispersion;

[0017] The pH value of the mixture after washing with ultrapure water is neutral;

[0018] The ultrasonic stripping operation is specifically as follows: under nitrogen protection, the neutral mixture after washing with ultrapure water is placed in an ice water bath and ultrasonicated for 0.8 to 1.2 hours; preferably, the ultrasonication time is 1 hour;

[0019] The centrifugal speed is set to 3000-5000 rpm; preferably, the centrifugal speed is set to 4200 rpm.

[0020] Further preferably, the MXene dispersion is freeze-dried to obtain solid MXene two-dimensional nanosheets; the freeze-drying temperature is -50 to -70°C, and the time is 20 to 50 hours; preferably, the freeze-drying temperature is -60°C, and the time is 30 hours.

[0021] Preferably, in step S2, the ZIF-8 nanoparticles are prepared by mixing a 2-methylimidazole aqueous solution with a Zn(NO3)2·6H2O aqueous solution, followed by washing, centrifugation, and freeze-drying;

[0022] Wherein, the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:30 to 1:80; preferably, the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:50;

[0023] The mixing reaction time is 2 to 5 hours; preferably, the mixing reaction time is 4 hours;

[0024] The freeze-drying temperature is -50 to -70°C, and the time is 20 to 50 hours; preferably, the freeze-drying temperature is -60°C, and the time is 30 hours.

[0025] Preferably, in step S2, the composite material is prepared by first adding 2-methylimidazole to a MXene dispersion, then mixing and reacting with a Zn(NO3)2·6H2O aqueous solution, and then washing, centrifuging, and freeze-drying in sequence;

[0026] The mass ratio of the MXene dispersion to 2-methylimidazole is 20:1 to 50:1; more preferably, the mass ratio of the MXene dispersion to 2-methylimidazole is 35:1;

[0027] The mixing reaction time is 2 to 5 hours; preferably, the mixing reaction time is 4 hours;

[0028] The freeze-drying temperature is -50 to -70°C, and the time is 20 to 50 hours; preferably, the freeze-drying temperature is -60°C, and the time is 30 hours.

[0029] Preferably, in step S3, the mixed composite material and binder are added to an organic solvent to form a slurry, which is then coated on the electrode sheet; further preferably, the organic solvent is N-methyl-2-pyrrolidone.

[0030] Preferably, in step S3, the mass ratio of the composite material to the binder is 10:1 to 8:1, preferably 9:1.

[0031] Preferably, in step S3, the coating thickness is 10 μm, and a drying treatment is performed after coating, specifically: under vacuum conditions, the coated electrode is dried at 55-65° C. for 15-30 hours; further preferably, the coated electrode is dried at 60° C. for 24 hours.

[0032] Preferably, in step S3, the diameter of the electrode sheet is 8 to 10 mm, more preferably 10 mm.

[0033] In a second aspect of the present invention, a battery negative electrode is provided, which includes an in-situ grown three-dimensional ZIF-8 / MXene composite material and a binder.

[0034] Preferably, the slurry prepared by the in situ grown three-dimensional ZIF-8 / MXene composite material and the binder is coated on the zinc foil as a protective coating; the mass ratio of the composite material to the binder is 10:1 to 8:1, preferably 9:1.

[0035] The third aspect of the present invention provides a zinc-iodine battery, comprising the battery negative electrode described in the second aspect, and also comprising a positive electrode sheet, a separator and an electrolyte.

[0036] Preferably, the preparation method of the positive electrode sheet is specifically as follows: adding aniline to a phytic acid aqueous solution, adding an oxidant aqueous solution to the obtained aniline phytic acid aqueous solution to cause a polymerization reaction to obtain a black porous carbon material PCM-NP co-doped with N and P; then mixing with iodine and heating to react to obtain iodine-loaded PCM-NP, mixing the PCM-NP with a conductive agent and a binder, and rolling it into an electrode sheet.

[0037] Wherein, the volume ratio of the phytic acid aqueous solution to the aniline is 4:1; the volume ratio of the aniline phytic acid aqueous solution to the oxidant aqueous solution is 5:1;

[0038] The polymerization reaction temperature is 3-5°C and the reaction time is 12-36h;

[0039] The product after the polymerization reaction is washed and then subjected to high-temperature pyrolysis, wherein the pyrolysis temperature is 800-1200° C. and the time is 1-5 hours;

[0040] The mass ratio of the black porous carbon material PCM-NP to iodine is 1:1 to 4:1, preferably 2:1;

[0041] The heating reaction temperature is 100-150°C and the time is 4-8 hours;

[0042] The mass ratio of the iodine-loaded PCM-NP, the conductive agent, and the binder is 7-8:1-2:0.8-1.2; preferably 7.5:1.5:1;

[0043] Further preferably, the oxidant is any one of persulfate or peroxide; the persulfate is any one of ammonium persulfate, sodium persulfate, potassium persulfate, manganese persulfate, potassium hydrogen persulfate or potassium peroxymonosulfonate; and the peroxide is hydrogen peroxide or peracetic acid.

[0044] The beneficial effects achieved by one or more of the above technical solutions of the present invention are as follows:

[0045] (1) The present invention proposes to in situ grow ZIF-8 nanoparticles on the MXene surface, which not only prevents the occurrence of MXene aggregation but also improves the electrochemical performance, providing a promising strategy for the development of reversible zinc anodes with long cycle life and high capacity.

[0046] (2) The zinc anode sheet coated with ZIF-8@MXene prepared in the present invention has excellent performance in symmetrical batteries. -2 The cycle life exceeds 1050h; when assembled into a full battery with iodine-loaded polyaniline positive electrode sheets, an ultra-long life of 2400 cycles is achieved.

[0047] (3) The ZIF-8@MXene coating prepared in the present invention has excellent corrosion resistance. The corrosion potential of Z@M-Zn (-0.972 V vs Ag / AgCl) is significantly higher than that of bare zinc (-0.983 V vs Ag / AgCl), MXene-Zn (-0.980 V vs Ag / AgCl), ZIF-8-Zn (-0.975 V vs Ag / AgCl) and ZIF-8 / Ti3C2T x -Zn (-0.978V vs Ag / AgCl), and the corrosion current of Z@M-Zn (0.25mA cm -2 ) is significantly lower than the other four electrodes (bare zinc is 2.1 mA cm -2 MXene-Zn is 1.58 mA cm -2, ZIF-8-Zn is 0.65 mA cm -2 ,ZIF-8 / Ti3C2T x -Zn is 1.37 mA cm -2 ).

[0048] (4) The contact angle test of the coating was conducted in the present invention. The results showed that there was no significant difference between MXene-Zn (75.8°) and ZIF-8-Zn (69.8°) and bare zinc. However, after the two were composited, the contact angle changed significantly (95.6°), which increased significantly. This shows that the hydrophobicity of Z@M-Zn in the electrolyte was significantly enhanced, thereby improving the corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0050] Figure 1 (a) SEM image of Ti3AlC2 of the present invention; (b) TEM image of MXene;

[0051] Figure 2 XRD patterns of MXene before and after etching of the present invention;

[0052] Figure 3 The SEM and TEM images of Z@M of the present invention are shown;

[0053] Figure 4 Element distribution diagram of Z@M of the present invention;

[0054] Figure 5 Tafel test and the corresponding corrosion current density bar graph;

[0055] Figure 6 Contact angle test of the coatings prepared in Example 1 and Comparative Examples 1 to 3 of the present invention;

[0056] Figure 7 It is a linear sweep voltammetry test;

[0057] Figure 8 Coulombic efficiency test of asymmetric battery (3mA cm -2 ,1.5mAh cm -2 );

[0058] Figure 9 For long cycle test of symmetrical battery (1mA cm -2 ,1mAh cm -2 );

[0059] Figure 10Long-term cycle testing was carried out on a full battery assembled with Z@M-Zn anode and iodine-loaded polyaniline. DETAILED DESCRIPTION

[0060] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0061] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0062] Example 1 :This embodiment provides a protective coating for zinc-iodine batteries and a preparation method thereof

[0063] (1) Synthesis of Ti3C2T x MXene dispersion: 30 mL of 9 M hydrochloric acid solution and 2 g of LiF powder were added to a polytetrafluoroethylene reaction vessel and mixed thoroughly to form a uniform solution. 1.5 g of Ti3AlC2 powder was slowly added to the solution and kept at 40 ° C for 24 h. After etching, it was washed with ultrapure water until neutral and ultrasonicated in an ice water bath under nitrogen protection for 1 h to obtain a MXene suspension, which was then centrifuged (4200 rpm, 60 min) to obtain Ti3C2T x MXene dispersion;

[0064] (2) Synthesis of ZIF-8@MXene: 6.8 g of 2-methylimidazole (2-MIM) was added to 100 mL of Ti3C2T x In the MXene dispersion, 15 mL of an aqueous solution containing 445 mg of Zn(NO3)2·6H2O was added to the above solution, stirred for 4 h, then washed with water and centrifuged (8000 rpm, 5 min), and freeze-dried at -60 °C for 30 h.

[0065] (3) Preparation of a coated zinc anode: 120 mg of ZIF-8@MXene and polyvinylidene fluoride (PVDF) prepared in step (2) were added to 300 μL of N-methyl-2-pyrrolidone (NMP) solvent in a mass ratio of 9:1, and then coated on a zinc foil with a scraper and vacuum dried at 60 °C for 12 h to obtain a zinc electrode with a Z@M coating (Z@M-Zn), which was then cut into electrode sheets with a diameter of 10 mm using a microtome.

[0066] Comparative Example 1 :This comparative example provides a protective coating for zinc-iodine batteries and its preparation method

[0067] The difference from Example 1 is that no ZIF-8 nanoparticles were added to this comparative example; the specific operation was as follows:

[0068] (1) The Ti3C2T ... x The MXene dispersion was freeze-dried at -60 °C for 30 h to obtain solid MXene two-dimensional nanosheets;

[0069] (2) Preparation of coated zinc negative electrode: 120 mg of the prepared MXene two-dimensional nanosheets and polyvinylidene fluoride (PVDF) were added to 300 μL of N-methyl-2-pyrrolidone (NMP) solvent in a mass ratio of 9:1, and then coated on zinc foil with a scraper and vacuum dried at 60 °C for 12 h to obtain a zinc electrode with a MXene coating (MXene-Zn), which was then cut into electrode sheets with a diameter of 10 mm using a slicer.

[0070] Comparative Example 2 :This comparative example provides a protective coating for zinc-iodine batteries and its preparation method

[0071] The difference from Example 1 is that Ti3C2T is not added in this comparative example. x MXene dispersion; the specific operation is:

[0072] (1) Synthesis of ZIF-8: 6.8 g of 2-MIM was dissolved in 100 mL of water. 15 mL of an aqueous solution containing 445 mg of Zn(NO3)2·6H2O was added to the solution and stirred for 4 h. The mixture was then washed with water and centrifuged (8000 rpm, 5 min). The product was freeze-dried at -60 °C for 30 h.

[0073] (2) Preparation of coated zinc anode: 120 mg of the prepared ZIF-8 and polyvinylidene fluoride (PVDF) were added to 300 μL of N-methyl-2-pyrrolidone (NMP) solvent at a mass ratio of 9:1, and then coated on zinc foil with a scraper and vacuum dried at 60 °C for 12 h to obtain a zinc electrode with a ZIF-8 coating (ZIF-8-Zn), which was then cut into electrode sheets with a diameter of 10 mm using a microtome.

[0074] Comparative Example 3 :This comparative example provides a protective coating for zinc-iodine batteries and its preparation method

[0075] (1) Synthesis of Ti3C2T xMXene dispersion: 30 mL of 9 M hydrochloric acid solution and 2 g of LiF powder were added to a polytetrafluoroethylene reaction vessel and mixed thoroughly to form a uniform solution. 1.5 g of Ti3AlC2 powder was slowly added to the solution and kept at 40 ° C for 24 h. After etching, it was washed with ultrapure water until neutral and ultrasonicated in an ice water bath under nitrogen protection for 1 h to obtain a MXene suspension, which was then centrifuged (4200 rpm, 60 min) to obtain Ti3C2T x MXene dispersion;

[0076] (2) Ti3C2T obtained in step (1) x The MXene dispersion was filtered using a 3501 diaphragm with a liquid volume of 50 ml, and then naturally dried at room temperature.

[0077] (3) Synthesis of mixed solution: 6.8 g of 2-MIM was added to 100 mL of water to dissolve, and 15 mL of aqueous solution containing 445 mg of Zn(NO3)2·6H2O was added to the above solution and mixed well;

[0078] (4) Synthesis of ZIF-8 / Ti3C2T x : Immerse the film obtained in step (2) in the mixed solution obtained in step (3) and stir for 4 hours, then rinse with water and dry at room temperature;

[0079] (5) Preparation of coated zinc anode: 120 mg ZIF-8@MXene and polyvinylidene fluoride (PVDF) prepared in step (4) were added to 300 μL N-methyl-2-pyrrolidone (NMP) solvent at a mass ratio of 9:1, and then coated on zinc foil with a scraper and dried in vacuum at 60 °C for 12 h to obtain ZIF-8 / Ti3C2T x Coating (ZIF-8 / Ti3C2T x -Zn) and then cut it into electrode sheets with a diameter of 10 mm using a microtome.

[0080] Material characterization:

[0081] like Figure 1 As shown, the Ti3AlC2 MAX precursor can be seen as a three-dimensional block through scanning electron microscopy (SEM), with layers tightly stacked to form obvious textures ( Figure 1 a); Two-dimensional nanosheets were obtained after etching and ultrasonic exfoliation ( Figure 1 b).

[0082] like Figure 2As shown, X-ray diffraction (XRD) analysis shows that the characteristic Al peak (104) disappears and the (002) crystal plane shifts significantly to the left, from 9.6° to 7.2°, thus confirming the successful synthesis of MXene.

[0083] like Figure 3 As shown, SEM and TEM images reveal that ZIF-8 nanoparticles are uniformly distributed on the MXene two-dimensional nanosheets in the Z@M composite.

[0084] like Figure 4 As shown, the element distribution map shows that Ti, C, N and Zn elements are evenly distributed, further verifying the uniform distribution of ZIF-8 on MXene.

[0085] Corrosion resistance test:

[0086] like Figure 5 As shown in Figure 2, the corrosion potential of Z@M-Zn (-0.972 V vs Ag / AgCl) is significantly higher than that of bare zinc (-0.983 V vs Ag / AgCl), MXene-Zn (-0.980 V vs Ag / AgCl), ZIF-8-Zn (-0.975 V vs Ag / AgCl), and ZIF-8 / Ti3C2T x -Zn (-0.978V vs Ag / AgCl), and the corrosion current of Z@M-Zn (0.25mA cm -2 ) is significantly lower than the other four electrodes (bare zinc is 2.1 mA cm -2 , MXene-Zn is 1.58 mA cm -2 , ZIF-8-Zn is 0.65 mA cm -2 ,ZIF-8 / Ti3C2T x -Zn is 1.37 mA cm -2 ), therefore, the Z@M-Zn electrode prepared in this application has the highest corrosion resistance.

[0087] The inventors have found that the change in the corrosion resistance of the coating is closely related to the structure, such as Figure 6 As shown in the figure, the contact angle test results show that MXene-Zn (75.8°), ZIF-8-Zn (69.8°) and ZIF-8 / Ti3C2T x -Zn (63.3°) is not much different from bare zinc (72.3°), but the contact angle changes significantly after the two are composited (95.6°), which increases significantly. This shows that the hydrophobicity of Z@M-Zn in the electrolyte is significantly enhanced, thereby improving the corrosion resistance.

[0088] Electrochemical performance test:

[0089] The cycle life of zinc anodes is related to discharge depth, current intensity, area capacity, electrolyte dosage, electrolyte additives, and surface modification strategies. Among surface modification strategies, coating is a highly effective method. Its conductivity, zinc affinity, hydrophobicity, corrosion resistance, and stability are all related to the cycle life of zinc anodes. Extending the cycle life and improving the performance of zinc anodes are the result of the combined effects of multiple properties.

[0090] (1) Figure 7 As shown, the hydrogen evolution reaction characteristics were determined by linear sweep voltammetry (LSV). A three-electrode test was performed in 1 M Na2SO4 solution with zinc foil as the working electrode, Ag / AgCl as the reference electrode, and a graphite rod as the counter electrode.

[0091] The results show that compared with bare zinc (-1.651V vs Ag / AgCl), MXene-Zn (-1.742V vs Ag / AgCl), ZIF-8-Zn (-1.783V vs Ag / AgCl), ZIF-8 / Ti3C2T x -Zn (-1.687 V vs Ag / AgCl), at a current density of 5 mA cm -2 When the temperature is 0.5000 W / min, the hydrogen evolution potential of Z@M-Zn is more negative (-1.860 V vs Ag / AgCl), which proves that it has a better hydrogen evolution inhibition effect.

[0092] (2) The zinc negative electrode sheet, iodine-doped polyaniline positive electrode sheet, electrolyte and diaphragm prepared in Example 1 and Comparative Examples 1-2 were respectively assembled to obtain a symmetrical battery, an asymmetric battery and a zinc-iodine full battery, wherein the symmetrical battery and the full battery used 2M ZnSO4 solution as the electrolyte, and the asymmetric battery used 1M Na2SO4 solution as the electrolyte, and all used glass fiber GD as the diaphragm.

[0093] like Figure 8 As shown, Cu foil is used as positive electrode, bare zinc or modified zinc foil is used as negative electrode, and the electrolyte is 1M Na2SO4. -2 , 1.5mAh cm -2 The coulombic efficiency of the asymmetric battery was tested under 400 nm saturation. Z@M-Zn showed high coulombic efficiency (99.93%) and good reversibility, with a cycle life of more than 1200 h.

[0094] like Figure 10 As shown, a symmetrical cell was assembled with two identical bare zinc or modified zinc foils as electrodes, and the electrolyte was 2M ZnSO4. -2 , 1mAh cm -2Long-term cycling tests were conducted under 400 nm CMOS conditions. Z@M-Zn exhibited a long cycle life exceeding 1000 h and optimal stability. In contrast, bare zinc shorted after only 100 hours of cycling due to continuous dendrite growth.

[0095] like Figure 9 As shown, the Z@M anode was assembled with an iodine-loaded PCM-NP cathode to form a zinc-iodine battery. Electrochemical testing was performed in a 2M ZnSO₄ electrolyte. Compared to the 72.9% capacity retention of bare zinc, the Z@M-Zn anode retained a high capacity of 86.1% after 2400 cycles, demonstrating enhanced reversibility and cycling stability.

[0096] To synthesize the iodine-doped polyaniline cathode, 8 mL of phytic acid solution and 12 mL of water were mixed, followed by the addition of 5 mL of aniline at 4°C. Subsequently, 0.96 g of ammonium persulfate was added to 5 mL of water and the mixture was allowed to react at 4°C for 15 hours. The resulting product was washed and pyrolyzed at 1000°C for 2 hours to obtain a black porous carbon material co-doped with nitrogen and phosphorus (PCM-NP). 80 mg of PCM-NP was then mixed with iodine at a mass ratio of 2:1 and heated at 120°C for 6 hours to obtain the iodine-loaded PCM-NP.

[0097] Preparation of positive electrode sheets with iodine-loaded PCM-NPs: 120 mg PCM-NPs, acetylene black and polytetrafluoroethylene (PTFE) were mixed evenly in a mass ratio of 7.5:1.5:1, then rolled into electrode sheets, and finally cut into electrode sheets with a diameter of 10 mm using a slicer.

[0098] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An application of an in-situ grown three-dimensional ZIF-8 / MXene composite material in the preparation of a zinc-iodine battery. A slurry prepared from the composite material and a binder is attached to the surface of a zinc electrode as a protective coating. The composite material consists of MXene two-dimensional nanosheets and ZIF-8 nanoparticles, and the ZIF-8 nanoparticles are evenly distributed on the MXene two-dimensional nanosheets; The method for preparing the in-situ grown three-dimensional ZIF-8 / MXene composite material comprises the following steps: S1. Add MAX powder to the etching solution to perform etching reaction to obtain MXene dispersion; S2, the composite material is prepared by first adding 2-methylimidazole to a MXene dispersion, then mixing and reacting with a Zn(NO3)2·6H2O aqueous solution, and then washing, centrifuging, and freeze-drying in sequence; S3. Mix the composite material and the binder, and apply the obtained slurry on the electrode sheet and dry it.

2. The use according to claim 1, characterized in that The binder is selected from one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide.

3. The use according to claim 2, characterized in that The binder is polyvinylidene fluoride.

4. The use according to claim 1, wherein In step S1, the MAX powder is selected from one or more of Ti3AlC2, V2AlC and Nb2AlC; the etching solution is selected from one or more of HF, HCl and LiF; the temperature of the etching reaction is 30-50°C, and the time is 12-36 hours.

5. The use according to claim 4, characterized in that The temperature of the etching reaction is 40° C. and the time is 24 h.

6. The use according to claim 1, wherein In step S2, the mass ratio of the MXene dispersion to 2-methylimidazole is 20:1 to 50:1, the mixing reaction time is 2 to 5 hours, and the freeze-drying temperature is -50 to -70°C, and the time is 20 to 50 hours.

7. The use according to claim 6, characterized in that The mass ratio of the MXene dispersion to 2-methylimidazole was 35:1; the mixing reaction time was 4 h; and the freeze-drying temperature was -60°C and the time was 30 h.

8. The use according to claim 1, wherein In step S3, the mixed composite material and binder are added to an organic solvent to form a slurry, which is then coated on the electrode sheet.

9. The use according to claim 8, characterized in that The organic solvent is N-methyl-2-pyrrolidone; the mass ratio of the composite material to the binder is 10:1~8:1; the coating thickness is 10 μm, and a drying process is performed after coating, specifically: under vacuum conditions, the coated electrode is dried at 55~65°C for 15~30 hours.

10. The use according to claim 9, characterized in that The mass ratio of the composite material to the binder is 9:1; and the coated electrode is dried at 60° C. for 24 h.

11. The use according to claim 8, wherein The diameter of the electrode sheet is 8-10 mm.

12. The use according to claim 11, characterized in that The diameter of the electrode sheet is 10 mm.

13. A battery negative electrode, characterized in that: The battery negative electrode includes the in-situ grown three-dimensional ZIF-8 / MXene composite material according to claim 1, and also includes a binder.

14. The battery negative electrode according to claim 13, wherein: The slurry prepared by the in-situ grown three-dimensional ZIF-8 / MXene composite material and the binder is coated on the zinc foil as a protective coating; the mass ratio of the composite material to the binder is 10:1 to 8:

1.

15. The battery negative electrode according to claim 14, wherein: The mass ratio of the composite material to the binder is 9:

1.

16. A zinc-iodine battery, characterized in that: The battery negative electrode according to any one of claims 13 to 15 further comprises a positive electrode sheet, a separator and an electrolyte.

17. The zinc-iodine battery according to claim 16, wherein: The method for preparing the positive electrode sheet specifically comprises: adding aniline to a phytic acid aqueous solution, adding an oxidant aqueous solution to the obtained aniline phytic acid aqueous solution to cause a polymerization reaction to obtain a black porous carbon material PCM-NP co-doped with nitrogen and phosphorus; then mixing with iodine and heating the PCM-NP to obtain iodine-loaded PCM-NP, mixing the PCM-NP with a conductive agent and a binder, and rolling the PCM-NP into an electrode sheet. Wherein, the volume ratio of the phytic acid aqueous solution to aniline is 4:1; The polymerization reaction temperature is 3-5°C and the reaction time is 12-36 hours; The product after the polymerization reaction is washed and then subjected to high-temperature pyrolysis, the pyrolysis temperature is 800-1200° C., and the time is 1-5 h; The mass ratio of the black porous carbon material PCM-NP to iodine is 1:1 to 4:1; The heating reaction temperature is 100-150°C and the time is 4-8 hours; The mass ratio of the iodine-loaded PCM-NP, the conductive agent, and the binder is 7-8:1-2:0.8-1.

2.

18. The zinc-iodine battery according to claim 17, characterized in that: The mass ratio of the black porous carbon material PCM-NP to iodine is 2:1; the mass ratio of the iodine-loaded PCM-NP, the conductive agent, and the binder is 7.5:1.5:

1.

19. The zinc-iodine battery according to claim 17, wherein: The oxidant is any one of persulfate or peroxide; the persulfate is any one of ammonium persulfate, sodium persulfate, potassium persulfate, manganese persulfate, potassium hydrogen persulfate or potassium peroxymonosulfonate; the peroxide is hydrogen peroxide or peracetic acid.

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