Preparation method of covalently coupled MXene@antimonene heterostructure, product and application thereof

Abstract

The application discloses a preparation method of covalent bond coupled MXene@antimonene heterostructure, and the preparation method comprises the following steps: S1, performing surface modification treatment on a MXene material through a cationic surfactant solution, then adding an antimonene solution to perform two-phase self-assembly; S2, performing freeze-drying on the solution after the self-assembly is completed, and performing annealing treatment to obtain a covalent bond coupled MXene@antimonene heterostructure composite material. The application further discloses the covalent bond coupled MXene@antimonene heterostructure obtained through the above preparation method and application of the covalent bond coupled MXene@antimonene heterostructure in a lithium ion battery negative electrode. The covalent bond coupled MXene@antimonene heterostructure synthesized by the application has the advantages of enhanced structural stability, effective volume expansion relief, improved charge transfer kinetics through Ti-O-Sb covalent bond and reduced lithium ion migration energy barrier in a hetero-interface, so that the lithium ion can be rapidly transported in the electrode, and thus the electrode charge and discharge ion kinetics are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium battery energy storage, and particularly relates to a preparation method of a covalently coupled MXene@antimonene heterostructure, a product thereof and application. BACKGROUND

[0002] Under the background of the current global environmental concept turning to low carbon emission, the market of electric vehicles and portable electronic products is rapidly rising. Lithium ion batteries (LIBs) as the current leading electrochemical energy storage device are increasingly attracting people's attention. However, the current widely used negative electrode-graphite in commercial lithium ion batteries still faces a series of major problems, such as insufficient theoretical capacity, low lithium ion insertion potential, and slow lithium ion diffusion dynamics. Due to these inherent defects of graphite, it is difficult to meet the requirements of the next generation of lithium ion batteries for higher energy density, faster charging and discharging speed, and better safety and reliability. Therefore, researchers have been seeking new materials to replace the commercial graphite negative electrode. In recent years, with the demand for materials with higher theoretical capacity and higher safety during lithium insertion and extraction, alloy-type materials have attracted widespread attention as lithium battery negative electrodes.

[0003] Among various alloy-type materials, antimony (Sb) has attracted the attention of researchers due to its superior capacity of 660 mAh g -1 and a relatively high lithium insertion potential (0.8-0.9 V vs. Li + / Li), which greatly reduces the safety problems caused by lithium dendrites at a lower potential. In addition, compared with the close layer structure of graphite, antimony has an inherently unique two-dimensional wrinkled layer structure, which has a low packing density (only 39%), which helps to enhance the ion accessibility inside the electrode. However, similar to other alloy-type materials, antimony negative electrodes will exhibit a huge volume change (up to ~135%) during lithiation and delithiation, and have problems such as poor electronic conductivity and slow ion dynamics. Such a large volume change will cause the antimony electrode to crack and pulverize significantly, seriously damaging the mechanical stability and structural stability of the solid electrolyte interface film, which is the main reason for the unsatisfactory rate performance, capacity decline and poor cycle stability of the antimony negative electrode. In theory, constructing an antimony-based heterostructure with strong interfacial covalent bonds is expected to simultaneously solve the key challenges faced by the above-mentioned antimony-based negative electrode. However, due to the difficulty of forming stable chemical bond crosslinking between two phases, it is still challenging to synthesize covalently linked antimony-based heterostructures, and the formation process of covalent bonds usually involves complex means of adjusting the surface chemical properties of materials on a nanoscale.

[0004] To solve the intrinsic obstacles that hinder the industrial application of Sb alloys, researchers have proposed a strategy of combining antimony nanostructures with carbon materials to address the above challenges. Carbon structures can act as conductive matrices and stress buffers to inhibit the large volume change of antimony-based materials. However, the assembly between antimony nano-materials and carbon materials is usually through weak van der Waals interactions, and the stability of the composite structure still needs to be improved, so this strategy can only achieve limited improvement in the rate performance and cycle stability of the negative electrode. In addition, it is still quite difficult to design strong interactions or coupling between alloy nanostructures and conductive carbon substrates.

[0005] MXene is a new type of two-dimensional transition metal carbide, nitride or carbonitride. Due to its excellent electrical conductivity, super-hydrophilic surface, unique layered structure, adjustable surface chemical properties and rich functional groups, it has received extensive attention in the field of energy storage in recent years. More importantly, Ti3C2T x MXene (wherein T x The rich surface functional groups and the changeable surface charge distribution of MXene, represented by surface functional groups such as -OH, -O, -F, provide a promising way for synergistic integration with other nanomaterials through interfacial chemical bonds. However, the rich surface functional groups make the MXene nanosheet carry a large amount of negative charge, thereby showing strong electrostatic repulsion to the surface-charged antimonene peeled from antimony. This may be the main disadvantage of forming a strong heterostructure between MXene and antimony.

[0006] Therefore, there is an urgent need for a strategy to realize the synthesis of covalently bonded MXene and antimony-based heterostructures, thereby developing them as a highly potential negative electrode material for lithium ion batteries. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a covalently coupled MXene@antimonene heterostructure composite material. The synthesized covalently coupled MXene@antimonene heterostructure has the advantages of enhanced structural stability, effective relief of volume expansion, and improved charge transfer dynamics through Ti-O-Sb covalent bonds, and reduction of lithium ion migration energy barrier at the heterojunction interface, thereby facilitating the rapid transport of lithium ions within the electrode, thereby improving the electrode charge-discharge ion dynamics.

[0008] The present application provides the following technical solutions:

[0009] A preparation method of a covalently coupled MXene@antimonene heterostructure, the preparation method comprising the following steps:

[0010] S1, surface modification treatment of MXene material by cationic surfactant solution, then adding antimonene solution for two-phase self-assembly;

[0011] S2, freeze-drying the solution after self-assembly is completed, and performing annealing treatment to obtain the covalently coupled MXene@antimonene heterostructure composite material.

[0012] The technical concept of the preparation method provided by the application is that after the MXene material is grafted with a cationic group on the surface, an antimonene solution is added, an MXene@antimonene heterostructure is generated through electrostatic self-assembly, and then the antimonene nanosheet is combined onto the conductive MXene matrix through Ti-O-Sb covalent bonds through annealing.

[0013] In step S1, the MAX phase material Ti3AlC2 is etched by a hydrochloric acid solution containing fluoride ions to obtain Ti3C2T x MXene material.

[0014] In step S1, the method for etching the MAX phase material Ti3AlC2 to obtain the MXene material is:

[0015] S1-1, dissolving LiF powder and hydrochloric acid to form a mixed solution;

[0016] S1-2, adding Ti3AlC2 powder to the mixed solution to obtain an MXene phase material.

[0017] Specifically, 2g of LiF powder, 40ml of 9-12mol / L hydrochloric acid, and 2g of Ti3AlC2 powder are selected to ensure that Ti3AlC2 can be etched sufficiently and achieve a high MXene yield.

[0018] In step S1, the cationic surfactant solution is selected from a tetradecyltrimethylammonium bromide solution, a hexadecyltrimethylammonium bromide solution, and an octadecyltrimethylammonium bromide solution.

[0019] In step S1, the MAX phase material Ti3AlC2 is etched by a hydrochloric acid solution containing fluoride ions to obtain Ti3C2T x The method for etching the MAX phase material Ti3AlC2 to obtain the MXene material is:

[0020] S1-1, 30mL of 12M concentrated hydrochloric acid is added to 10mL of deionized water to configure a 9M hydrochloric acid solution, 2g of LiF powder is slowly added to the 9M hydrochloric acid solution to form a mixed solution, and the mixed solution is stirred in a constant-temperature water bath at 35℃ for 30 minutes;

[0021] S1-2, the Ti3AlC2 powder is slowly added to the above mixed solution within 10 minutes, and the mixed solution is stirred in a constant-temperature water bath at 35℃ for 24 hours to obtain an MXene phase material.

[0022] In step S1, the antimony block is crushed into powder and added to a mixed solution of isopropyl alcohol and deionized water for ball milling treatment, and the obtained material after ball milling is subjected to probe ultrasonic treatment to obtain an antimonene solution.

[0023] In step S2, the annealing temperature is 400-500 DEG C.

[0024] The application also provides a covalently coupled MXene@antimonene heterostructure obtained by the above preparation method.

[0025] In the covalently coupled MXene@antimonene heterostructure, the layered structure is well maintained, the antimonene nanosheet is coupled and anchored on the surface of the MXene nanosheet, and the size of the antimonene nanosheet is smaller than that of the MXene nanosheet.

[0026] The thickness of the antimonene nanosheet is 2.5-4.5 nm, and the thickness of about 5-9 antimony atom layers.

[0027] The application also provides an application of the above covalently coupled MXene@antimonene heterostructure composite material to a lithium ion battery negative electrode.

[0028] Compared with the prior art, the covalently coupled MXene@antimonene heterostructure composite material prepared by the application has the following advantages: the covalently coupled MXene@antimonene heterostructure composite material enhances the overall structural stability due to the existence of Ti-O-Sb covalent bonds, greatly relieves the volume expansion of the antimonene during the electrochemical lithium intercalation and deintercalation process of the electrode, improves the charge transfer dynamics between the two phases of MXene and antimonene, and greatly reduces the lithium ion diffusion energy barrier along the heterojunction interface. These characteristics make the covalently coupled MXene@antimonene heterostructure composite material have fast ion kinetics, excellent rate performance and cycle stability as a lithium ion battery negative electrode. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 (a-c) in the figure are HRTEM images of MXene@AME; (d) is a STEM-HAADF image of MXene@AME; (e) is an electron energy loss spectrum of titanium characteristic peaks extracted in a line scanning mode from region 1 (MXene nanosheet) and region 2 (MXene@AME interface); and (f) is an electron energy loss spectrum of oxygen characteristic peaks extracted in a line scanning mode from region 1 (MXene nanosheet) and region 2 (MXene@AME interface).

[0030] Figure 2 The figure is a Raman spectrum of MXene@AME, MXene and AME in different Raman shift regions.

[0031] Figure 3Sb 3d X-ray photoelectron spectrograms of MXene@AME and AME.

[0032] Figure 4 X-ray diffraction spectrograms of MXene@AME, MXene, AME and bulk antimony.

[0033] Figure 5 (a) and (b) in FIG. 11 are high-resolution transmission electron microscopy images and corresponding selected area electron diffraction patterns of MXene, respectively.

[0034] Figure 6 (a) and (b) in FIG. 12 are high-resolution transmission electron microscopy images of AME samples.

[0035] Figure 7 (a) is the normalized contribution rate of the surface control process of MXene@AME at different scanning rates; (b) is the normalized contribution rate of the surface control process of MXene at different scanning rates; (c) is the normalized contribution rate of the surface control process of AME at different scanning rates.

[0036] Figure 8 R f +R ct values (left Y-axis) and lithium ion diffusion coefficients in the lithiation / delithiation process (right Y-axis).

[0037] Figure 9 FIG. 13 is a comparison diagram of the specific capacity rate performance of MXene@AME, MXene, AME materials at different current densities. DETAILED DESCRIPTION

[0038] In order to make the present application more apparent and easy to understand, the technical solutions of the present application are further described below in combination with the drawings and specific examples. The examples described below are only used to explain the present application, and are not any form of and substantial limitation on the present application.

[0039] Example 1

[0040] This example prepared the MXene@antimonene (MXene@AME) heterostructure composite material according to the following steps.

[0041] Material preparation steps:

[0042] S1, etch the MAX phase material of Ti3AlC2 through a hydrochloric acid solution containing fluoride ions to obtain Ti3C2T x MXene material:

[0043] (1) Take 30 mL of 12M concentrated hydrochloric acid, add 10 mL of deionized water to prepare 40 mL of 9M hydrochloric acid solution, slowly add 2 g of LiF powder into the above 9M hydrochloric acid solution to form a mixed solution, and stir in a constant temperature water bath at 35°C for 30 minutes;

[0044] (2) Slowly add 2 g of Ti3AlC2 powder into the above mixed solution within 10 minutes, stir in a constant temperature water bath at 35°C for 24 hours to obtain a black mixed solution.

[0045] (3) After the black solution obtained in step (2) is cooled to room temperature, centrifugation, deionized water washing 5-6 times, until the supernatant pH value after centrifugation is about 6, finally the solution is centrifuged at 3500 rpm for 30 minutes, and the supernatant is collected, the concentration is controlled to be about 3 mg / mL.

[0046] S2, crush the antimony block into powder and add it to a mixed solution of isopropyl alcohol and deionized water for ball milling treatment, then the obtained material is subjected to probe ultrasonic treatment to obtain an antimony ene solution:

[0047] (1) Crush the large antimony block with a hammer to obtain antimony powder.

[0048] (2) Take 12 mL of isopropyl alcohol and add it to 3 mL of deionized water to form a mixed solution, then slowly add 2 g of antimony powder into the mixed solution of isopropyl alcohol / deionized water.

[0049] (3) Transfer the above mixture into a 50 mL ball mill tank, and take out the mixed solution after ball milling for 10 hours.

[0050] (4) Subject the above mixed solution to probe ultrasonic treatment in an ice bath environment for 1 hour, and continuously stir during the ultrasonic treatment.

[0051] (5) Centrifuge the supernatant obtained in step (4) at a speed of 3000 revolutions per minute for 3 minutes, and collect a small layer of antimony ene supernatant.

[0052] (6) Add 12 mL of isopropyl alcohol and 3 mL of deionized water mixed solution to the remaining precipitate again, repeat step S2 to obtain sufficient antimony ene solution, and the concentration of the antimony ene solution is controlled to be about 0.8 mg / mL.

[0053] S3, mix the Ti3C2T x MXene material prepared in S1 with the antimony ene solution to perform two-phase self-assembly:

[0054] (1) Take 8 mL of Ti3C2T xAdd MXene solution (approximately 3 mg / mL) to 3 mL of cetyltrimethylammonium bromide solution (2.5 mg / mL) and stir continuously for 1 hour.

[0055] (2) Add 30 mL of antimonene solution (0.8 mg / mL) prepared by S2 to the solution. Stir the solution for 1 hour to allow it to fully undergo interfacial self-assembly reaction, and then sonicate it in an ice bath for 20 minutes.

[0056] S4. Freeze-dry the self-assembled mixed solution from S3 and then perform high-temperature annealing to obtain a covalently coupled MXene@antimonene heterostructure composite material:

[0057] The mixture obtained in step S3 was freeze-dried for 24 hours, then annealed at 500°C for 3 hours at a heating rate of 4°C / min. Finally, the annealed composite material was taken out, which is the covalently coupled MXene@AME heterostructure composite material.

[0058] The MXene@AME heterostructure composite material prepared in this embodiment was characterized and tested. Figure 1 As shown in (a)-(d) of the figure, aberration-corrected transmission electron microscopy reveals that antimonyene nanosheets are loaded onto MXene nanosheets, with the size of the antimonyene nanosheets ranging from tens to hundreds of nanometers. Figure 1 As shown in (e) and (f), based on the electron energy loss spectrum, the spectral changes from region 1 (containing only MXene nanosheets) to region 2 (where MXene and antimonene form a heterostructure surface via covalent bonds) reveal a significant positive chemical shift in the characteristic peak of titanium, approximately 0.6 eV. This is likely due to charge transfer from titanium to oxygen via the Ti-O-Sb covalent bonds present at the interface. A chemical shift also occurs in the characteristic peak of oxygen (approximately 0.4 eV), indicating that oxygen plays a bridging role in promoting the covalent coupling between MXene and antimonene nanosheets.

[0059] In addition, such as Figure 2 As shown in the Raman spectrum, MXene@AME also exhibits a peak that is not present in either MXene or AME, which is a Ti-O-Sb covalent bond peak, confirming the existence of the covalent interface.

[0060] like Figure 3 As shown, in the XPS spectrum of antimony 3d, MXene@AME exhibits a new peak compared to AME nanosheets. This peak belongs to the Ti-O-Sb covalent bond peak, which further confirms the existence of covalent bonds between the two phases.

[0061] like Figure 4As shown, the X-ray diffraction spectrum results show that MXene@AME contains characteristic peaks of both MXene and AME, also confirming the successful assembly of the two phases.

[0062] Coating and electrochemical test of the negative electrode:

[0063] First, 80wt% of active material, 10wt% of carbon black and 10wt% of PVDF were mixed in N-methyl pyrrolidone solution to obtain a mixed electrode slurry. Then, the slurry was evenly coated on the cut copper foil using a doctor blade, and then the coated electrode was placed in a vacuum oven at a temperature of 80°C for drying for 24 hours. After the drying process was completed, the copper foil loaded with electrode material was punched to form a disc with a diameter of 11 millimeters, and the area mass of active substance loaded on each copper foil was controlled to be about 1 to 2 milligrams per square centimeter. In the assembly process of the electrode, CR2032 button cell was selected for assembly, lithium foil with a diameter of 14 millimeters was used as the counter electrode, the electrolyte was a solution containing 1 mol / L lithium hexafluorophosphate in ethylene carbonate / diethyl carbonate (volume ratio 1:1) and containing 5wt% fluoroethylene carbonate, and the separator was whatman glass fiber separator. All the assembly process was completed in an argon-filled glove box to ensure that the water and oxygen concentrations therein were less than 0.1 ppm.

[0064] The counter electrode was subjected to constant current charge and discharge rate test, and the voltage range was 0.01V~3V. The capacity retention rate of Example 1 at 0.1Ag -1 ~10A g -1 at a current density of 1 Ag -1 ~2mV s -1 was 64.6%. The cyclic voltammetry test was carried out on the electrochemical workstation at a scan rate of 0.2mV s -1 ~2mV s 5 , the voltage range was 0.01V~3V, and the surface control process accounted for 87.8%, 92.3%, 93.3%, 93.5%, 94.9%, and 96.1% at scan rates of 0.2, 0.5, 0.8, 1.0, 1.5, and 2mV s

[0065] The electrochemical impedance spectrum test was carried out at a frequency range of 0.1Hz-10 5 Hz, and the results showed that the charge transfer resistance was significantly smaller than that of MXene and AME at 1.5V, 1V, 0.4V, 0.01V, 0.65V, 0.85V, 1.85V, and 3V. The diffusion coefficient of lithium ions at the above voltages calculated from the electrochemical impedance spectrum was significantly increased compared with AME and slightly increased compared with MXene.

[0066] Comparative Example 1

[0067] The MXene material was prepared according to the following steps.

[0068] Material preparation steps:

[0069] The MAX phase material of Ti3AlC2 was etched by a hydrochloric acid solution containing fluoride ions to obtain Ti3C2T x MXene material:

[0070] (1) 30 mL of 12M concentrated hydrochloric acid was taken, 10 mL of deionized water was added to prepare 40 mL of 9M hydrochloric acid solution, 2g of LiF powder was slowly added into the above 9M hydrochloric acid solution to form a mixed solution, and stirred in a constant temperature water bath at 35℃ for 30 minutes.

[0071] (2) 2g of Ti3AlC2 powder was slowly added into the above mixed solution within 10 minutes, and stirred in a constant temperature water bath at 35℃ for 24 hours to obtain a black mixed solution.

[0072] (3) The black solution obtained in step (2) was cooled to room temperature, centrifuged, and washed with deionized water for 5-6 times until the supernatant pH value after centrifugation was about 6. Finally, the solution was centrifuged at 3500 rpm for 30 minutes, and the supernatant was collected, and the concentration was controlled to about 3mg / mL.

[0073] (4) The supernatant was freeze-dried for 24 hours to obtain MXene dry powder.

[0074] The MXene material prepared in Comparative Example 1 was subjected to characterization test.

[0075] As shown in (a) and (b) of FIG. 1, the characterization by transmission electron microscope showed that the MXene presented obvious sheet structure, and the electron diffraction appeared hexagonal ring diffraction pattern, which also confirmed that the crystallinity of the MXene was good. Figure 5 As shown in FIG. 2, the Raman spectrum exhibited obvious MXene characteristic peaks, which confirmed the integrity of the structure of the MXene material.

[0076] Figure 2 As shown in FIG. 3, the X-ray diffraction spectrum showed obvious (002) crystal face peak of the MXene, which confirmed the good peeling of the MAX phase and obtained Ti3C2T x MXene material.

[0077] Coating of the negative electrode and electrochemical test: Figure 4

[0078] Coating of the negative electrode and electrochemical test:

[0079] ​​First, 80wt% of active material, 10wt% of carbon black and 10wt% of PVDF were mixed in N-methyl pyrrolidone solution to obtain a mixed electrode slurry. Then, the slurry was uniformly coated on a cut copper foil using a doctor blade, and then the coated electrode was placed in a vacuum oven at a temperature of 80°C for drying for 24 hours. After the drying process was completed, the copper foil loaded with electrode material was punched to form a disc with a diameter of 11 mm, and the area mass of active substance loaded on each copper foil was controlled to be about 1 to 2 mg per square centimeter. In the assembly process of the electrode, a CR2032 button cell was selected for assembly, a lithium foil with a diameter of 14 mm was used as the counter electrode, the electrolyte was a solution containing 1 mol / L lithium hexafluorophosphate in ethylene carbonate / diethyl carbonate (volume ratio 1:1) and containing 5wt% fluoroethylene carbonate, and the separator was a whatman glass fiber separator. All the assembly process was completed in an argon-filled glove box to ensure that the water and oxygen concentrations therein were less than 0.1 ppm.

[0080] The counter electrode was subjected to constant current charge and discharge rate test, and the voltage range was 0.01V-3V. The capacity retention rate of Comparative Example 1 at 0.1Ag -1 -10A g -1 at a current density of 0.1 Ag -1 -2mV s -1 was 38.9%. The cyclic voltammetry test was carried out on an electrochemical workstation at a scan rate of 0.2mV s -1 -2mV s , and the voltage range was 0.01V-3V. By fitting, the proportion of surface control process at a scan rate of 0.2, 0.5, 0.8, 1.0, 1.5, 2mV s -1 was 62.6%, 72.7%, 75.6%, 77.8%, 81.6%, 84.3%, respectively.

[0081] The electrochemical impedance spectroscopy test was carried out at a frequency range of 0.1Hz-10 5 Hz, and the results showed that the charge transfer resistance at 1.5V, 1V, 0.4V, 0.01V, 0.65V, 0.85V, 1.85V, 3V was significantly larger than that of MXene@AME. The diffusion coefficient of lithium ions at the above voltages calculated from the electrochemical impedance spectroscopy was slightly smaller than that of MXene@AME.

[0082] Comparative Example 2

[0083] The AME (antimonene) material of the present comparative example was prepared according to the following steps.

[0084] Material preparation steps:

[0085] S2, the antimony bulk is crushed into powder and added into a mixed solution of isopropyl alcohol and deionized water for ball milling treatment. The obtained material after ball milling is further treated by probe sonication to obtain an antimonene solution:

[0086] (1) The bulk antimony bulk is crushed into powder by hammer.

[0087] (2) 12 mL of isopropyl alcohol is added into 3 mL of deionized water to form a mixed solution, and then 2 g of antimony powder is slowly added into the mixed solution of isopropyl alcohol / deionized water.

[0088] (3) The above mixture is transferred into a 50 mL ball mill tank, and the mixed solution is taken out after 10 hours of ball milling.

[0089] (4) The above mixed solution is treated by probe sonication for 1 hour in an ice bath environment, and the sonication power is 400 W. Stirring is continuously performed during the sonication process.

[0090] (5) The supernatant obtained in step (4) is centrifuged at a speed of 3000 rpm for 3 minutes, and the supernatant of a few layers of antimonene is collected.

[0091] (6) The mixed solution of 12 mL of isopropyl alcohol and 3 mL of deionized water is added again into the remaining precipitate, and step S2 is repeated to obtain a sufficient amount of antimonene solution. The concentration of the antimonene solution is controlled to be about 0.8 mg / mL.

[0092] (7) The collected antimonene solution is freeze-dried for 24 hours to obtain an AME (antimonene) powder material.

[0093] The AME material prepared in Comparative Example 2 is subjected to characterization tests.

[0094] As shown in (a) and (b) of FIG. 1, it can be observed from the transmission electron microscope image that the antimonene has a relatively thin layer structure, and the interlayer spacing of the (012) crystal plane is 0.31 nm. Figure 6 As shown in FIG. 2, the Raman spectrum result exhibits a clear characteristic peak of antimony, which confirms the stability of the antimonene structural properties after exfoliation.

[0095] Figure 2 As shown in FIG. 3, the X-ray photoelectron spectroscopy also exhibits the characteristic peak of the AME antimonene, which again confirms the existence of the AME.

[0096] As shown in FIG. 4, the X-ray diffraction spectrum result shows that the intensity of the (003) and (006) crystal plane peaks is greatly reduced compared to the bulk antimony, which indicates that the thickness along the c crystal axis direction is greatly reduced, and the antimony is exfoliated into a very thin antimonene layer structure. Figure 3 As shown in FIG. 5, the Raman spectrum result exhibits a clear characteristic peak of antimony, which confirms the stability of the antimonene structural properties after exfoliation.

[0097] Figure 4 As shown in FIG. 6, the X-ray photoelectron spectroscopy also exhibits the characteristic peak of the AME antimonene, which again confirms the existence of the AME. ​​

[0098] Negative electrode coating and electrochemical testing:

[0099] First, 80 wt% of active material, 10 wt% of carbon black, and 10 wt% of PVDF were mixed in an N-methylpyrrolidone solution to obtain a mixed electrode slurry. Next, the slurry was evenly coated onto pre-cut copper foil using a spatula, and then the coated electrode was dried in a vacuum oven at 80°C for 24 hours. After drying, the copper foil loaded with electrode material was perforated to form 11 mm diameter discs, with the area mass of active material loaded on each copper foil controlled to approximately 1 to 2 mg / cm². During electrode assembly, a CR2032 button cell was used, with a 14 mm diameter lithium foil as the counter electrode. The electrolyte consisted of a solution containing 1 mol / L lithium hexafluorophosphate in ethylene carbonate / diethyl carbonate (volume ratio 1:1) and 5 wt% fluoroethylene carbonate. A Whatman glass fiber membrane was used as the separator. The entire assembly process was completed in an argon-filled glove box to ensure that the water and oxygen concentrations were below 0.1 ppm.

[0100] A constant current charge-discharge rate test was conducted on the electrodes, with a voltage range of 0.01V to 3V. Comparative Example 2 was performed at 0.1Ag. -1 ~10A g -1 The capacity retention at current density is 6.3%. Using an electrochemical workstation, at 0.2 mV s... -1 ~2mV s -1 Cyclic voltammetry tests were performed on the voltage at a sweep rate of 0.01V to 3V, and the results were obtained by fitting at voltages of 0.2, 0.5, 0.8, 1.0, 1.5, and 2mV s. -1 The percentages of surface control processes at different scanning speeds were 5.6%, 10.0%, 11.9%, 13.2%, 15.0%, and 16.2%, respectively.

[0101] Electrochemical impedance spectroscopy (EIS) measurements, frequency range 0.1 Hz-10 Hz. 5 The results showed that its charge transfer resistance was significantly higher than that of MXene@AME at 1.5V, 1V, 0.4V, 0.01V, 0.65V, 0.85V, 1.85V, and 3V. The diffusion coefficient of lithium ions at the above voltages, calculated by electrochemical impedance spectroscopy, was significantly lower than that of MXene@AME.

[0102] For details regarding the coating and electrochemical testing results of the MXene@AME prepared in Example 1, the MXene prepared in Comparative Example 1, and the AME prepared in Comparative Example 2 as negative electrodes, please refer to [link / reference needed]. Figures 7-9 :

[0103] Figure 7The normalized contribution rates of the surface control processes of (a)-(c) in FIG. 1 are respectively the normalized contribution rates of the surface control processes of Example 1 and Comparative Examples 1-2 at different scanning rates, from Figure 7 It can be seen that the surface control process of MXene@AME (Example 1) is significantly higher than that of MXene (Comparative Example 1) and AME (Comparative Example 2), which indicates that the fast ion transfer reaction dominates in Example 1, while the slow ion diffusion limits the reaction kinetics in Comparative Example 2.

[0104] The charge transfer resistance of MXene@AME (Example 1) is significantly lower than that of MXene (Comparative Example 1) and AME (Comparative Example 2), and the lithium ion diffusion coefficient is significantly higher than that of AME (Comparative Example 2) and slightly higher than that of MXene (Comparative Example 1). This indicates that the covalently coupled heterostructure plays an important role in enhancing the ion kinetics. Figure 8

[0105] The charge transfer resistance of MXene@AME (Example 1) is significantly lower than that of MXene (Comparative Example 1) and AME (Comparative Example 2), and the lithium ion diffusion coefficient is significantly higher than that of AME (Comparative Example 2) and slightly higher than that of MXene (Comparative Example 1). This indicates that the covalently coupled heterostructure plays an important role in enhancing the ion kinetics. Figure 9 It can be seen from the specific capacity rate performance comparison chart of MXene@AME (Example 1), MXene (Comparative Example 1) and AME (Comparative Example 2) at different current densities that the capacity retention rate of MXene@AME (Example 1) is 64.6% at 0.1A g -1 ~ 10A g -1 The capacity retention rate of MXene (Comparative Example 1) is 38.9% at 0.1A g -1 ~ 10A g -1 The capacity retention rate of AME (Comparative Example 2) is 6.3% at 0.1A g -1 ~ 10A g -1 This is because MXene@AME has the smallest charge transfer resistance and higher lithium ion diffusion coefficient, showing excellent ion kinetics. This indicates that the covalently coupled MXene@antimonene heterostructure composite material prepared by the preparation method of the present application has excellent rate performance as the negative electrode of lithium ion battery.

[0106] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.​

Claims

1. A method for preparing a covalently coupled MXene@antimonene heterostructure, characterized in that, The preparation method includes the following steps: S1. After surface modification of MXene material with cationic surfactant solution, antimonyene solution is added for two-phase self-assembly. S2. After the self-assembled solution is freeze-dried and annealed, a covalently coupled MXene@antimonene heterostructure composite material is obtained.

2. The method for preparing the covalently coupled MXene@antimonene heterostructure according to claim 1, characterized in that, In step S1, the MAX phase material of Ti3AlC2 is etched by a hydrochloric acid solution containing fluoride ions to obtain Ti3C2T. x MXene material.

3. The method for preparing the covalently coupled MXene@antimonene heterostructure according to claim 1, characterized in that, In step S1, the cationic surfactant solution is selected from tetradecyltrimethylammonium bromide solution, hexadecyltrimethylammonium bromide solution, or octadecyltrimethylammonium bromide solution.

4. The method for preparing the covalently coupled MXene@antimonene heterostructure according to claim 1, characterized in that, In step S1, the antimony block is crushed into powder and added to a mixed solution of isopropanol and deionized water for ball milling. The material obtained after ball milling is then subjected to probe ultrasonic treatment to obtain an antimonyene solution.

5. The method for preparing the covalently coupled MXene@antimonene heterostructure according to claim 1, characterized in that, In step S2, the annealing temperature is 400–500°C.

6. A covalently coupled MXene@antimonene heterostructure obtained by the preparation method according to any one of claims 1-5.

7. The covalently coupled MXene@antimonene heterostructure according to claim 6, characterized in that, In the covalently coupled MXene@antimonene heterostructure, antimonene nanosheets are coupled and anchored to the surface of MXene nanosheets, and the size of the antimonene nanosheets is smaller than that of the MXene nanosheets.

8. The application of the covalently bonded MXene@antimonene heterostructure composite material of claim 6 in the negative electrode of a lithium-ion battery.

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