Sandwich composite material and preparation method and application thereof, and preparation method of water-based zinc ion battery negative electrode

Abstract

The application relates to the technical field of aqueous zinc ion batteries, in particular to a sandwich composite material and a preparation method and application thereof and a preparation method of an aqueous zinc ion battery negative electrode. The application provides a preparation method of a sandwich composite material, which comprises the following steps: mixing MAX, sodium chloride and copper chloride, performing heat treatment to obtain an intermediate product; sequentially performing cleaning, solid-liquid separation and drying on the intermediate product to obtain the sandwich composite material. The sandwich composite material can make the aqueous zinc ion battery negative electrode have excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, and in particular to a sandwich composite material, its preparation method and application, and a method for preparing the negative electrode of an aqueous zinc-ion battery. Background Technology

[0002] Currently, novel rechargeable batteries are gaining popularity as energy storage devices. With increasingly stringent requirements for safe and sustainable energy storage, low-cost, high-capacity, safe, and non-toxic aqueous zinc-ion batteries are poised to become the next generation of energy storage devices, replacing lithium-ion batteries, particularly for large-scale energy storage. Compared to traditional commercial batteries, aqueous zinc-ion batteries utilize neutral or weakly acidic electrolytes, which effectively improve ionic conductivity and mitigate reactions between alkaline electrolytes and the zinc anode. However, significant issues remain, including dendrite growth, chemical corrosion, and hydrogen evolution reaction. Dendrite growth, in particular, not only punctures the battery separator but also accelerates the degradation of the zinc anode, drastically shortening battery life and reducing zinc utilization and coulombic efficiency, severely hindering the commercialization of aqueous zinc-ion batteries. Therefore, the development of stable zinc anodes with long cycle life is crucial.

[0003] It has been reported that homogenizing the local current density (or electric field distribution) on the zinc anode surface can fundamentally optimize zinc nucleation on the surface and suppress dendrite formation. Two-dimensional transition metal carbides / nitrides (MXenes) can uniformly distribute the electric field on the zinc anode surface, guiding Zn... 2+ The deposition of MXene lowers the nucleation energy barrier of zinc and effectively inhibits the growth of zinc dendrites. Furthermore, MXene possesses good hydrophilicity, high conductivity, and excellent structural stability, making it an ideal material for modifying zinc anodes. Optimizing the terminating groups of MXene can further enhance the uniformity of zinc deposition. However, simply coating with MXene to suppress the effects of chemical corrosion and hydrogen evolution on zinc anodes is far from satisfactory. Summary of the Invention

[0004] The purpose of this invention is to provide a sandwich composite material, its preparation method and application, and a method for preparing an aqueous zinc-ion battery anode. The sandwich composite material of this invention can give the aqueous zinc-ion battery anode excellent cycle stability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a sandwich composite material, comprising the following steps:

[0007] MAX, sodium chloride and copper chloride are mixed and heat-treated to obtain an intermediate product;

[0008] The intermediate product is sequentially washed, separated into solid and liquid components, and dried to obtain the sandwich composite material.

[0009] Preferably, the mass ratio of MAX, sodium chloride, and copper chloride is (1-3):(1.052-3.156):(2.046-6.138).

[0010] Preferably, the heat treatment is performed in a protective atmosphere.

[0011] Preferably, the heat treatment temperature is 450–850°C, the time is 3–8 hours, and the heating rate to the heat treatment temperature is 0.5–5°C / min.

[0012] Preferably, the cleaning agent used for cleaning is a (NH4)2S2O8 solution with a concentration of 0.1 to 0.5 mol / L.

[0013] The present invention also provides a sandwich composite material prepared by the preparation method described above, comprising MXene and Cu nanoparticles loaded between two-dimensional sheets of the MXene.

[0014] Preferably, the thickness of the MXene is 10–20 μm;

[0015] The Cu nanoparticles have a particle size of 500–900 nm.

[0016] The present invention also provides the application of the sandwich composite material described in the above technical solution in aqueous zinc-ion batteries.

[0017] This invention provides a method for preparing an aqueous zinc-ion battery negative electrode, comprising the following steps:

[0018] The sandwich composite material described in the above technical solution is mixed with polyvinylidene fluoride to obtain a slurry;

[0019] After coating the slurry onto the surface of zinc foil and drying it, the negative electrode of the aqueous zinc-ion battery is obtained.

[0020] Preferably, the mass ratio of the sandwich composite material to polyvinylidene fluoride is (7-9):(3-1).

[0021] This invention provides a method for preparing a sandwich composite material, comprising the following steps: mixing MAX, sodium chloride, and copper chloride, and heat-treating to obtain an intermediate product; sequentially cleaning, separating solid and liquid components, and drying the intermediate product to obtain the sandwich composite material. In this invention, copper chloride primarily serves to etch MAX. Copper chloride undergoes redox reactions with the "A" in MAX, extracting the "A" and causing MAX to layer and generate MXene. Simultaneously, the MXene undergoes Cl-termination. During this process, the generated "A" chloride will volatilize at high temperatures, and copper will appear between the MXene layers. The high-temperature molten salt has a certain fluidity, allowing some of the copper between the MXene layers to flow out. Sodium chloride acts as a confinement agent, trapping some copper within the MXene layers. Cleaning removes the copper outside the layers. This method differs from adding a copper source to MXene etched with HCl or HF. It not only allows control over the position of Cu on the MXene but also is more environmentally friendly and suitable for experimental conditions because it does not use concentrated acid. The sandwich composite material prepared by the method described in this invention not only inherits the excellent physicochemical properties of zinc-loving MXene, but also confines corrosion-resistant Cu nanoparticles within the layered structure of MXene, effectively preventing the redeposition of MXene nanosheets. Furthermore, the strong interfacial contact between MXene and Cu nanoparticles in the sandwich composite material prepared by this method provides better interfacial coupling, further improving the reversible transport of ions and electrons. Through the synergistic effect of these two components, zinc preferentially grows along the (002) plane, forming a smooth and uniform deposition surface, inhibiting zinc corrosion caused by the hydrogen evolution reaction, and achieving excellent cycle stability of the zinc anode. Simultaneously, the preparation method is simple and easy to implement. Attached Figure Description

[0022] Figure 1 The image shows a SEM image of the sandwich composite material described in Example 1.

[0023] Figure 2 The image shows a SEM image of the zinc foil described in Example 1.

[0024] Figure 3 This is a SEM image of the negative electrode of the aqueous zinc-ion battery described in Example 1;

[0025] Figure 4 The image shows the XRD pattern of the sandwich composite material described in Example 1.

[0026] Figure 5 The XRD patterns are of the zinc foil and the negative electrode of the aqueous zinc-ion battery described in Example 1.

[0027] Figure 6The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 10 mA·cm⁻¹. -2 Long-cycle performance curves at current densities;

[0028] Figure 7 Zinc-ion symmetric cells prepared from pure zinc foil at 1 mA·cm -2 SEM images after 100 cycles at a current density;

[0029] Figure 8 The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 1 mA·cm⁻¹. -2 SEM images after 100 cycles at a current density;

[0030] Figure 9 The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 1 mA·cm⁻¹. -2 XRD pattern after 100 cycles at current density;

[0031] Figure 10 The zinc-ion full cell prepared using the aqueous zinc-ion battery negative electrode and pure zinc foil described in Example 1 was tested at 3 A·g. -1 The long-cycle performance curve at the current density. Detailed Implementation

[0032] This invention provides a method for preparing a sandwich composite material, comprising the following steps:

[0033] MAX, sodium chloride and copper chloride are mixed and heat-treated to obtain an intermediate product;

[0034] The intermediate product is sequentially washed, separated into solid and liquid components, and dried to obtain the sandwich composite material.

[0035] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0036] This invention involves mixing MAX, sodium chloride, and copper chloride, followed by heat treatment to obtain an intermediate product.

[0037] This invention does not impose any special limitation on the type of MAX; any type well-known to those skilled in the art can be used. In an embodiment of this invention, the MAX is specifically Ti3AlC2.

[0038] In this invention, the copper chloride is preferably CuCl2·2H2O.

[0039] In this invention, the preferred mass ratio of MAX, sodium chloride and copper chloride is (1-3):(1.052-3.156):(2.046-6.138), and more preferably 1:1.052:2.046.

[0040] In this invention, the preferred method of mixing is grinding. The grinding process is not specifically limited and can be performed using methods well-known to those skilled in the art. Preferably, the mixing process involves grinding MAX, sodium chloride, and copper chloride in a corundum boat.

[0041] In this invention, the heat treatment is preferably carried out in a protective atmosphere, preferably an argon atmosphere. The temperature of the heat treatment is preferably 450–850°C, more preferably 500–800°C, and most preferably 600–700°C; the time is preferably 3–8 hours, more preferably 4–7 hours, and most preferably 5–6 hours; the heating rate to the heat treatment temperature is preferably 0.5–5°C / min, more preferably 1–5°C / min, and most preferably 4–5°C / min. In this invention, the heat treatment is preferably carried out in a tube furnace.

[0042] In this invention, the heat treatment process is a redox reaction. Copper chloride extracts the A-site metal from MAX to generate ACl3, which then volatilizes at high temperature. MAX separates into layers and transforms into Cl-terminated MXene. The addition of sodium chloride enhances the fluidity of the melt, increases the contact area of ​​the reaction, and accelerates the reaction. It also has a certain confinement effect, fixing the generated Cu nanoparticles between the MXene layers. In addition, some copper nanoparticles are also present at the edges of the MXene layers.

[0043] After the heat treatment is completed, the present invention preferably includes cooling; the present invention does not have any special limitations on the cooling process, and any process known to those skilled in the art can be used.

[0044] After obtaining the intermediate product, the present invention sequentially washes, separates solids and liquids and dries the intermediate product to obtain the sandwich composite material.

[0045] In this invention, the cleaning agent used for cleaning is a (NH4)2S2O8 solution with a concentration preferably of 0.1 to 0.5 mol / L, more preferably 0.3 to 0.5 mol / L, and most preferably 0.4 to 0.5 mol / L.

[0046] After the cleaning is completed, the present invention preferably includes transferring the obtained solution to a beaker for stirring; in the present invention, the stirring speed is preferably 100-500 rpm, more preferably 200-400 rpm, and most preferably 200-300 rpm; the stirring time is preferably 4-20 h, more preferably 6-16 h, and most preferably 13-16 h.

[0047] After the stirring is completed, the present invention preferably includes repeated centrifugal washing with deionized water until neutral.

[0048] The present invention does not impose any special limitations on the solid-liquid separation process. Any process known to those skilled in the art can be used as long as the collection of precipitates is achieved.

[0049] In this invention, the drying method is preferably vacuum drying; the temperature of the vacuum drying is preferably 50-120°C, more preferably 60-110°C, and most preferably 80-100°C; the time is preferably 4-16 hours, more preferably 6-15 hours, and most preferably 8-12 hours.

[0050] The present invention also provides a sandwich composite material prepared by the preparation method described above, comprising MXene and Cu nanoparticles loaded between two-dimensional sheets of the MXene.

[0051] This invention does not impose any special limitation on the type of MXene; any type well-known to those skilled in the art can be used. In the embodiments of this invention, the MXene is specifically Ti3C2Cl2.

[0052] In this invention, the thickness of the MXene is preferably 10 to 20 μm.

[0053] In this invention, the particle size of the Cu nanoparticles is preferably 500-900 nm.

[0054] In this invention, the preferred mass ratio of MXene to Cu nanoparticles is (8-9.5):(2-0.5), more preferably (8.5-9.5):(1.5-0.5), and most preferably (9-9.5):(1-0.5).

[0055] In this invention, the copper nanoparticles possess strong corrosion resistance and hydrogen evolution inhibition properties; simultaneously, the copper nanoparticles can also guide Zn... 2+ Oriented deposition along the (002) plane weakens dendrites, making it a multifunctional zinc anode protection material.

[0056] The present invention also provides the application of the sandwich composite material described in the above technical solution in aqueous zinc-ion batteries.

[0057] This invention provides a method for preparing an aqueous zinc-ion battery negative electrode, comprising the following steps:

[0058] The sandwich composite material described in the above technical solution is mixed with polyvinylidene fluoride to obtain a slurry;

[0059] After coating the slurry onto the surface of zinc foil and drying it, the negative electrode of the aqueous zinc-ion battery is obtained.

[0060] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0061] The present invention mixes the sandwich composite material described in the above technical solution with polyvinylidene fluoride to obtain a slurry.

[0062] In this invention, the mass ratio of the sandwich composite material to polyvinylidene fluoride is preferably (7-9):(3-1), more preferably (8-9):(1.5-1), and most preferably (8.8-9):(1.2-1).

[0063] The present invention does not impose any special limitations on the mixing process; any process known to those skilled in the art can be used.

[0064] After obtaining the slurry, the present invention further coats the slurry onto the surface of zinc foil and dries it to obtain the negative electrode of the aqueous zinc-ion battery.

[0065] In this invention, the coating method is preferably spin coating; the spin coating speed is preferably 500-2500 rpm, more preferably 800-2000 rpm, and most preferably 1200-1600 rpm; the time is preferably 30-90 s, more preferably 40-80 s, and most preferably 50-60 s.

[0066] In this invention, the drying method is preferably vacuum drying; the temperature of the vacuum drying is preferably 70-120°C, more preferably 80-110°C, and most preferably 80-90°C; the time is preferably 4-12 hours, more preferably 6-10 hours, and most preferably 6-8 hours.

[0067] After drying, the thickness of the film layer prepared on the zinc foil surface is preferably 20–40 μm.

[0068] In this invention, the negative electrode of the aqueous zinc-ion battery is at 10 mA·cm⁻¹. -2 It can operate stably for 700 hours under ultra-high current density, with an overpotential of less than 65mV.

[0069] The following detailed descriptions, in conjunction with embodiments, illustrate the sandwich composite material, its preparation method, its application, and the preparation method of the aqueous zinc-ion battery anode provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] Take 1g Ti3AlC2, 1.052g NaCl and 2.046g CuCl2·2H2O and place them in a corundum boat. After thorough grinding and mixing, place the boat in a tube furnace and heat treat it at 650℃ in an argon atmosphere for 5h with a heating rate of 5℃ / min. After the reaction is completed, cool it to room temperature and take the boat out for later use.

[0072] The obtained ark was washed with a 0.5 mol / L (NH4)2S2O8 solution, the resulting solution was transferred to a beaker, and the beaker was placed on a magnetic stirrer and stirred vigorously for 16 h (stirring speed of 300 rps). Then it was repeatedly centrifuged with deionized water until neutral and the bottom precipitate was collected.

[0073] The obtained precipitate was dried in a vacuum drying oven at 80℃ for 12 hours to obtain a sandwich composite material (denoted as Cu / Ti3C2Cl2 MXene); the thickness of MXene was 10μm, the particle size of copper nanoparticles was 500nm, and the mass ratio of MXene to copper nanoparticles was 9.5:0.5.

[0074] The Cu / Ti3C2Cl2 MXene and polyvinylidene fluoride were mixed at a mass ratio of 9:1 to obtain a slurry;

[0075] The slurry was spin-coated onto the surface of zinc foil (spin-coating speed 1500 rpm, time 60 s), and then dried in a vacuum drying oven at 80°C for 6 hours to obtain an aqueous zinc-ion battery negative electrode with a film thickness of approximately 30 μm. At 10 mA·cm⁻¹ -2 It can operate stably for 700 hours under ultra-high current density with an overpotential of less than 65mV;

[0076] Figure 1 Here is a SEM image of the sandwich composite material, from... Figure 1 It can be seen that the sandwich composite material has a sandwich layered morphology; Figure 4 The XRD pattern of the sandwich composite material is shown below. Figure 4 It can be seen that the sandwich composite material contains characteristic peaks of copper and Ti3C2Cl2MXene, which confirms the successful preparation of the sandwich composite material;

[0077] Figure 2 The SEM image of the zinc foil is shown below. Figure 2It can be seen that the surface of the pure zinc foil is flat and smooth, without obvious graininess;

[0078] Figure 3 This is a SEM image of the negative electrode of the aqueous zinc-ion battery. Figure 3 It can be seen that the sandwich composite material is uniformly distributed on the zinc foil; Figure 5 The XRD patterns of the zinc foil and the negative electrode of the aqueous zinc-ion battery are shown below. Figure 5 It can be seen that characteristic peaks of the sandwich composite material were detected on the negative electrode of the aqueous zinc-ion battery, confirming that the sandwich composite material was successfully anchored on the zinc foil surface by spin coating.

[0079] Example 2

[0080] Take 2g Ti3AlC2, 2.104g NaCl and 4.092g CuCl2·2H2O and place them in a corundum boat. After thorough grinding and mixing, place it in a tube furnace and heat treat it at 450℃ in an argon atmosphere for 7h with a heating rate of 0.5℃ / min. After the reaction is completed, cool it to room temperature and take out the boat for later use.

[0081] The obtained ark was washed with a 0.3 mol / L (NH4)2S2O8 solution. The resulting solution was transferred to a beaker and placed on a magnetic stirrer and stirred vigorously for 20 h (stirring speed of 200 rpm). Then, it was repeatedly centrifuged with deionized water until neutral and the bottom precipitate was collected.

[0082] The obtained precipitate was dried in a vacuum drying oven at 50℃ for 16 hours to obtain a sandwich composite material (denoted as Cu / Ti3C2Cl2 MXene); the thickness of MXene was 15μm, the particle size of copper nanoparticles was 700nm, and the mass ratio of MXene to copper nanoparticles was 9:1.

[0083] The Cu / Ti3C2Cl2 MXene and polyvinylidene fluoride were mixed at a mass ratio of 8:2 to obtain a slurry;

[0084] The slurry was spin-coated onto the surface of zinc foil (at a spin speed of 2500 rpm for 30 s), and then dried in a vacuum drying oven at 70°C for 10 h to obtain an aqueous zinc-ion battery negative electrode. The film thickness on the negative electrode was approximately 20 μm. (The last sentence appears to be incomplete and possibly refers to a specific process: "At 10 mA·cm..."). -2 It can operate stably for 650 hours under ultra-high current density with an overpotential of less than 75mV.

[0085] Example 3

[0086] Take 3g Ti3AlC2, 3.156g NaCl and 6.138g CuCl2·2H2O and place them in a corundum boat. After thorough grinding and mixing, place it in a tube furnace and heat treat it at 850℃ in an argon atmosphere for 3h with a heating rate of 5℃ / min. After the reaction is completed, cool it to room temperature and take out the boat for later use.

[0087] The obtained ark was washed with a 0.1 mol / L (NH4)2S2O8 solution. The resulting solution was transferred to a beaker and stirred vigorously on a magnetic stirrer for 4 hours (stirring speed of 500 rpm). Then, it was repeatedly centrifuged with deionized water until neutral and the bottom precipitate was collected.

[0088] The obtained precipitate was dried in a vacuum drying oven at 120℃ for 4 hours to obtain a sandwich composite material (denoted as Cu / Ti3C2Cl2 MXene); the thickness of MXene was 20μm, the particle size of copper nanoparticles was 900nm, and the mass ratio of MXene to copper nanoparticles was 8.5:1.5.

[0089] The Cu / Ti3C2Cl2 MXene and polyvinylidene fluoride were mixed at a mass ratio of 7:3 to obtain a slurry;

[0090] The slurry was spin-coated onto the surface of zinc foil (spin-coating speed 500 rpm, time 90 s), and then dried in a vacuum drying oven at 120°C for 4 hours to obtain an aqueous zinc-ion battery negative electrode with a film thickness of approximately 40 μm. At 10 mA·cm⁻¹ -2 It can operate stably for 600 hours under ultra-high current density with an overpotential of less than 85mV.

[0091] Test case

[0092] The aqueous zinc-ion battery anodes prepared in Examples 1-3 were tested:

[0093] Using the aqueous zinc-ion battery anode or pure zinc foil prepared in Examples 1-3 as the anode, a 2 mol / L zinc sulfate solution (deionized water as the electrolyte) as the electrolyte, and glass fiber as the battery separator, a zinc-ion symmetric battery was assembled and its electrochemical performance was tested.

[0094] Figure 6 The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 10 mA·cm⁻¹. -2 The long-cycle performance curve at current density is obtained from Figure 6 It can be seen that the zinc-ion symmetric battery prepared by the aqueous zinc-ion battery negative electrode described in Example 1 has a performance of 10 mA·cm⁻¹. -2 It can operate stably for 700 hours at a current density with an overpotential of less than 65mV;

[0095] Figure 7 Zinc-ion symmetric cells prepared from pure zinc foil at 1 mA·cm -2 SEM images after 100 cycles at a current density, from Figure 7 It can be seen that the zinc-ion symmetric battery prepared from pure zinc foil exhibits a canine-toothed dendritic crystal morphology after 100 cycles.

[0096] Figure 8 The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 1 mA·cm⁻¹. -2 SEM images after 100 cycles at a current density, from Figure 8 It can be seen that after 100 cycles, the zinc-ion symmetric battery prepared by the aqueous zinc-ion battery anode in Example 1 exhibits a smooth and dense zinc plating morphology on the surface of the aqueous zinc-ion battery anode.

[0097] Figure 9 The zinc-ion symmetric battery prepared using the aqueous zinc-ion battery negative electrode described in Example 1 operates at 1 mA·cm⁻¹. -2 XRD patterns after 100 cycles at a current density, from Figure 9 It can be seen that zinc foil is deposited along the (100) plane, while the sandwich composite material can guide Zn to preferentially deposit along the (002) plane, weaken dendrites and thus inhibit zinc corrosion caused by hydrogen evolution reaction, achieving excellent cycle stability of zinc anode.

[0098] ZnCoMnO / C, Ketjen black, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1 to obtain a slurry. The slurry was uniformly coated on a stainless steel mesh and dried in a vacuum drying oven at 80°C for 12 hours to obtain a positive electrode sheet with ZnCoMnO / C as the active material. Using the positive electrode sheet as the positive electrode, the aqueous zinc-ion battery negative electrode or pure zinc foil prepared in Examples 1-3 was used as the negative electrode, a mixture of zinc sulfate and manganese sulfate (zinc sulfate concentration of 2 mol / L and manganese sulfate concentration of 0.1 mol / L) was used as the electrolyte, and glass fiber was used as the battery separator to assemble a zinc-ion full cell, and electrochemical performance was tested.

[0099] Figure 10 The zinc-ion full cell prepared using the aqueous zinc-ion battery negative electrode and pure zinc foil described in Example 1 was tested at 3 A·g. -1 The long-cycle performance curve at current density is obtained from Figure 10 It can be seen that the zinc-ion full cell at 3A·g -1 It also exhibits higher capacity and cycle stability than full cells assembled with bare zinc anodes at current densities;

[0100] As can be seen from the above, the sandwich composite material is a highly efficient zinc anode protection material. It can effectively suppress side reactions such as dendrite formation, corrosion, and hydrogen evolution, improve zinc utilization, and thus enhance the overall performance of zinc-ion full batteries, showing great application prospects.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a sandwich composite material, characterized in that, The steps are as follows: MAX, sodium chloride and copper chloride are mixed and heat-treated to obtain an intermediate product; The intermediate product is sequentially washed, separated into solid and liquid components, and dried to obtain the sandwich composite material; The mass ratio of MAX, sodium chloride, and copper chloride is 1:1.052:2.046; The cleaning agent used is a (NH4)2S2O8 solution with a concentration of 0.1~0.5 mol / L; The heat treatment temperature is 650℃, the time is 5h, and the heating rate to the heat treatment temperature is 5℃ / min. The sandwich composite material comprises MXene and Cu nanoparticles loaded between two-dimensional sheets of the MXene.

2. The preparation method according to claim 1, characterized in that, The heat treatment is carried out in a protective atmosphere.

3. The sandwich composite material prepared by the preparation method according to claim 1 or 2, characterized in that, It includes MXene and Cu nanoparticles loaded between the two-dimensional sheets of the MXene.

4. The sandwich composite material as described in claim 3, characterized in that, The thickness of the MXene is 10~20μm; The Cu nanoparticles have a particle size of 500~900 nm.

5. The application of the sandwich composite material according to claim 3 or 4 in an aqueous zinc-ion battery.

6. A method for preparing an aqueous zinc-ion battery negative electrode, characterized in that, Includes the following steps: The sandwich composite material described in claim 3 or 4 is mixed with polyvinylidene fluoride to obtain a slurry; After coating the slurry onto the surface of zinc foil and drying it, the negative electrode of the aqueous zinc-ion battery is obtained.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the sandwich composite material to polyvinylidene fluoride is (7~9):(3~1).

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