MnBi2Te4O x Nanosheets and their preparation and application in cathode materials for aqueous zinc ion batteries

Abstract

The present invention provides an aqueous zinc ion battery positive electrode material oxidized MnBi2Te4 and its preparation method and application. The positive electrode is a typical two-dimensional layered structure material with a large interlayer spacing, which is convenient for Zn 2+ The insertion and extraction of ions can be effectively reduced, and the ion diffusion distance can be effectively reduced, providing sufficient active sites for zinc ion storage. Compared with other electrode materials, the MnBi2Te4 oxidized cathode material of the present invention has high reversible capacity, excellent rate performance and long cycle stability. ‑1 The discharge capacity can reach 393.1 mAh g ‑1 ; in 1A g ‑1 After 1000 cycles of charge and discharge at a current density of , the capacity retention rate is as high as 87.3%.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous zinc ion batteries, and in particular to an oxidized MnBi2Te4 cathode material for aqueous zinc ion batteries, a preparation method and an application thereof. Background Art

[0002] With the continuous development of society and economy, global demand for energy continues to grow, and the imbalance between energy supply and demand is becoming increasingly prominent. The development of efficient, clean, and renewable energy sources has become a focus of attention worldwide. As we all know, electrochemical energy storage, due to its high efficiency, stability, and convenience, is considered an ideal solution to the energy crisis. Among various electrochemical energy storage technologies, lithium-ion batteries (LIBs) offer numerous advantages, such as high operating voltage, high specific energy, and low self-discharge, and have been widely used in digital electronics, electric vehicles, and other fields. However, due to the inherent drawbacks of LIBs, such as the flammability, volatility, and toxicity of the organic electrolytes used, as well as the limited distribution of lithium metal resources, researchers are eager to develop new LIB alternatives. Zinc is abundant in nature and offers advantages such as low cost, easy access, safety, and non-toxicity. Aqueous Zn-ion batteries (AZBs) are expected to become a strong contender for future electrochemical energy storage systems due to their low cost, high safety, and environmental friendliness. Furthermore, Aqueous Zn-ion batteries offer significant advantages, such as high theoretical specific capacity and low redox potential, and hold great promise for development.

[0003] In the research on aqueous zinc ion batteries, due to the 2+ Many researchers have focused on developing suitable, reversible Zn 2+ This is because the positive electrode material, as the main material for storing zinc ions, largely determines the operating voltage and discharge specific capacity of the aqueous zinc ion battery. In the current technology for aqueous zinc ion batteries, commonly used positive electrode materials include manganese-based oxides, vanadium-based oxides, Prussian blue and its analogues. For aqueous zinc ion batteries with manganese-based materials as positive electrodes, due to the large volume of embedded and released zinc ions, multiple charge and discharge will cause the lattice collapse of the positive electrode material, thereby causing the dissolution of the manganese-based material. The poor cycle stability of vanadium-based materials and the low specific capacity of Prussian blue materials also hinder the practical application of aqueous zinc ion batteries.

[0004] In the prior art, the Chinese patent publication number is CN 113921805 A, which discloses a method for preparing anion-doped vanadium trioxide positive electrode materials for aqueous zinc-ion batteries. This method effectively improves the capacity and rate performance of vanadium-based oxides in aqueous zinc-ion batteries through a doping process. However, the preparation method requires a step-temperature calcination treatment, and the process is relatively complicated. At the same time, layered two-dimensional materials such as MoS2, TiS2, MXene, etc. are used in the storage of ion batteries due to their unique layered structure. However, the capacity and structural stability of these layered two-dimensional materials in aqueous zinc-ion batteries are still unsatisfactory. Changwei Li [Energy Storage Materials 2022 49 144] et al. introduced N-doped carbon elements between MoS2 layers by combining interlayer polymerization with template assistance to prepare MoS2 nanocages with enlarged interlayer spacing. However, at 0.1Ag -1 At a current density of 1.5 GHz, the battery capacity can only reach 247.8 mAh g -1 Another Chinese patent publication number is CN 110010862 B, which discloses a storage method in which TiS2 is loaded into MXene-Ti3C2 sheets to establish a supportive channel for ion embedding and extraction, thereby improving the charge-discharge capacity and cycle performance. However, the specific capacity of the battery is still less than 120 mAh g -1 , and the cycle stability life is short. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned prior art aqueous zinc ion battery positive electrode materials, such as low positive electrode material capacity, poor cycle performance, and complex preparation process, the present invention provides an aqueous zinc ion battery positive electrode material MnBi2Te4O x Nanosheets and their preparation method, the material has excellent electrochemical properties, and the preparation method is simple and low cost. Oxidized MnBi2Te4, namely MnBi2Te4O x Nanosheets are a two-dimensional layered material that exhibits a unique layered structure and large interlayer spacing. As a positive electrode for aqueous zinc ion batteries, the material has high energy density and excellent electrochemical performance, and has excellent application potential in aqueous zinc ion battery storage. The layered two-dimensional positive electrode material of the present invention is oxidized MnBi2Te4, namely MnBi2Te4O x Nanosheets have many advantages, such as simple preparation method, high energy density, good cycle stability, and environmental friendliness, and are expected to become ideal electrode materials for aqueous zinc ion batteries. Specifically, the present invention adopts the following technical solutions:

[0006] A manganese bismuth tellurium oxide MnBi2Te4O of the present invention xThe nanosheets are prepared by oxidizing manganese bismuth tellurium (MnBi2Te4) in a muffle furnace, grinding the oxidized material in N-methylpyrrolidone, dispersing the oxidized material in isopropyl alcohol, ultrasonically dispersing the oxidized material, washing the oxidized material, filtering the oxidized material, and drying the oxidized material. Preferably, the oxidation temperature in the muffle furnace is 180° C. to 300° C., and the oxidation time is 250 to 320 minutes.

[0007] As a preferred technical solution, the manganese bismuth tellurium oxide MnBi2Te4O of the present invention x The method for preparing the nanosheets comprises the following steps:

[0008] (1) Preparation of oxidized MnBi2Te4: The raw material manganese bismuth tellurium MnBi2Te4 is placed in a muffle furnace and oxidized at 200-280°C for 270-300 minutes to obtain MnBi2Te4 oxide;

[0009] (2) preparing an oxidized MnBi2Te4 nanosheet suspension: adding N-methylpyrrolidone (NMP) to the oxidized MnBi2Te4 prepared in step (1) and grinding the mixture thoroughly, then dispersing the mixture in isopropyl alcohol (IPA), and ultrasonically treating the mixture with ice water to obtain an oxidized MnBi2Te4 nanosheet suspension;

[0010] (3) Cleaning and drying of oxidized MnBi2Te4 nanosheets: The oxidized MnBi2Te4 nanosheet suspension obtained in step (2) was washed with anhydrous ethanol, vacuum filtered, and dried to obtain manganese bismuth tellurium oxide MnBi2Te4O x Nanosheets.

[0011] The present invention prepares oxidized MnBi2Te4 with different compositions by controlling the oxidation temperature to find the optimal temperature to achieve the best electrochemical performance. Therefore, the effects of oxidized MnBi2Te4 cathode at different oxidation temperatures on the electrochemical performance are explored. Figure 5 As can be seen from a and 5b, when MnBi2Te4 is not oxidized, it has the worst performance. After MnBi2Te4 is oxidized, its electrochemical performance is improved. In addition, MnBi2Te4 has the best electrochemical performance when the oxidation temperature is 240°C. Therefore, in step 1), the oxidation temperature of the raw material MnBi2Te4 in the muffle furnace is preferably 200-275°C and the oxidation process duration is 276-291 minutes, especially the oxidation temperature is 230-250°C and the oxidation process duration is 280-290 minutes. For example, the oxidation temperature can be 200°C and the oxidation process duration can be 276 minutes; the oxidation temperature can also be 240°C and the oxidation duration can be 284 minutes; the oxidation temperature can also be 275°C and the oxidation duration can be 291 minutes; but the oxidation temperature is particularly preferably 240°C and the oxidation duration is 282-288 minutes.

[0012] Preferably, in step 2), the ultrasonic treatment time is preferably 30 to 90 minutes, more preferably 40 to 80 minutes, and most preferably 50 to 60 minutes. In step 3), the vacuum drying temperature is 55 to 65°C, and the drying time is preferably 6 to 9 hours; for example, when the drying temperature is 55°C, the drying time is 9 hours; or when the drying temperature is 60°C, the drying time is 7.5 hours; or when the drying temperature is 65°C, the drying time is 6 hours.

[0013] Manganese bismuth tellurium oxide MnBi2Te4O prepared by the present invention x The nanosheets can be used in aqueous zinc ion battery cathode materials to obtain better electrochemical performance. Specifically, the application can be carried out by the following method steps: manganese bismuth tellurium oxide MnBi2Te4O x The nanosheets were uniformly mixed with acetylene black and polyvinylidene fluoride in NMP solution to obtain a mixed slurry. The slurry was then coated on an electrode and dried in a vacuum drying oven to prepare manganese bismuth tellurium oxide MnBi2Te4O x Nanosheet positive electrode.

[0014] Among them, preferably, manganese bismuth tellurium oxide MnBi2Te4O x The mass ratio of nanosheets, acetylene black and polyvinylidene fluoride is (6-8):(1-3):(0.5-1.5). For example, the mass ratio of oxidized MnBi2Te4 nanosheets:acetylene black:polyvinylidene fluoride is 6:1:0.5, 7:2:1 or 8:3:1.5.

[0015] Among them, preferably, the titanium sheet is a square sample with a specification of 1 cm×1 cm, and the drying temperature can be 55°C to 65°C, and the drying time is 6 to 9 hours; for example, when the drying temperature is 55°C, the drying time is 9 hours; or when the drying temperature is 60°C, the drying time is 7.5 hours; or when the drying temperature is 65°C, the drying time is 6 hours.

[0016] Beneficial effects

[0017] (1) In the preparation method of oxidized MnBi2Te4 as the positive electrode material of aqueous zinc ion batteries of the present invention, the oxidized MnBi2Te4 is a layered two-dimensional material, exhibiting a typical layer structure and excellent performance, and has excellent application potential in aqueous zinc ion battery storage.

[0018] (2) The oxidized MnBi2Te4 of the positive electrode material of the present invention has a lattice spacing of 0.327 nm. The larger interlayer spacing is conducive to the insertion and extraction of zinc ions, and the material has excellent electrochemical properties.

[0019] (3) The present invention provides an oxidized MnBi2Te4 cathode material for aqueous zinc ion batteries, a preparation method thereof, and an application thereof. Compared with Prussian blue analogs, some layered materials, etc., which have lower specific capacity when used as cathode materials, the oxidized MnBi2Te4 electrode of the present invention exhibits a specific capacity of 393.1 mAh g when used as a cathode. -1 (0.4Ag -1 )’s high reversible capacity, excellent rate performance and long cycle stability.

[0020] (4) Compared with traditional lithium and sodium ion batteries, the oxidized MnBi2Te4 as the positive electrode material of the aqueous zinc ion battery of the present invention has many advantages such as abundant resources, high safety, no pollution, simple preparation process, etc., and has great application potential in the field of energy storage devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 a, 1b are oxidized MnBi2Te4 nanosheets (manganese bismuth tellurium oxide MnBi2Te4O x Nanosheets) preparation steps and the structure of aqueous zinc ion batteries;

[0022] Figure 2 a is the SEM image of the raw material MnBi2Te4(pristine) of the present invention, Figure 2 b is an SEM image of the oxidized MnBi2Te4 of the present invention (oxidation temperature is 240°C);

[0023] Figure 3 TEM images and element mapping images of the oxidized MnBi2Te4 nanosheets (240°C) of the present invention; in the figure, the Mn element is shown in green, the Bi element is shown in purple, the Te element is shown in yellow, and the O element is shown in red.

[0024] Figure 4 XRD images of original and oxidized MnBi2Te4 at different oxidation temperatures of the present invention;

[0025] Figure 5 a, 5b are the CV curves of MnBi2Te4 oxidized at different oxidation temperatures of the present invention (0.2mv s -1 ) and GCD curve (0.4Ag -1 );

[0026] Figure 6 EIS images of original and oxidized MnBi2Te4 at different oxidation temperatures of the present invention;

[0027] Figure 7 For oxidized MnBi2Te4 (240℃) electrode in 0.2~2Ag -1GCD curve under current density;

[0028] Figure 8 The image shows the rate performance of the oxidized MnBi2Te4 (240℃) electrode.

[0029] Figure 9 a is the CV curve of the oxidized MnBi2Te4 electrode at different scan rates. Figure 9 b is a straight line graph of Log(i) and Log(v) based on the current response at the three peaks in 9a.

[0030] Figure 10 Cycling stability image of oxidized MnBi2Te4 (240℃) electrode; DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below. However, it should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] Example 1

[0034] A method for preparing MnBi2Te4 for oxidation of a positive electrode material for aqueous zinc ion batteries, comprising the following steps:

[0035] (1) Preparation of oxidized manganese bismuth telluride: 0.1 g of raw material manganese bismuth telluride (MnBi2Te4) was placed in a muffle furnace for oxidation at a temperature of 240°C and a duration of 284 min to obtain MnBi2Te4 oxide;

[0036] (2) Preparation of an oxidized MnBi2Te4 nanosheet suspension: An appropriate amount (100 μl) of NMP was added to the oxidized MnBi2Te4 prepared in step 1) for thorough grinding, and then the mixture was dispersed in 45 ml of isopropanol solution. After ultrasonic treatment with ice water for 1 h, the mixed solution was converted into a uniform suspension to obtain an oxidized MnBi2Te4 nanosheet suspension;

[0037] (3) Cleaning and drying of oxidized MnBi2Te4 nanosheets: The oxidized MnBi2Te4 nanosheet suspension obtained in step 2) was washed with anhydrous ethanol and vacuum filtered (using a circulating water multi-purpose vacuum pump for filtration, with the instrument displaying -0.1 MPa during the filtration process until the filtration was complete). The suspension was then placed in a vacuum drying oven and dried to obtain oxidized MnBi2Te4 nanosheets. The drying temperature was 60°C and the drying time was 7.5 hours.

[0038] (4) Preparation of an Oxidized MnBi2Te4 Positive Electrode: The oxidized MnBi2Te4 nanosheets obtained in step 3) were uniformly mixed with acetylene black and polyvinylidene fluoride in an NMP solution to obtain a mixed slurry. The slurry was then coated on a titanium sheet and dried in a vacuum drying oven to prepare an oxidized MnBi2Te4 positive electrode. The mass ratio of oxidized MnBi2Te4 nanosheets: acetylene black: polyvinylidene fluoride was 7:2:1; the titanium sheet was a 1 cm × 1 cm square sample; and the drying temperature was 60°C and the drying time was 7.5 hours.

[0039] The performance test of the oxidized MnBi2Te4 positive electrode prepared in this example is as follows:

[0040] The prepared oxidized MnBi2Te4 electrode was used as the positive electrode, and the zinc foil with a thickness of 100 μm was used as the negative electrode. The concentration of -1 The Zn(CF3SO3)2 aqueous solution was used as the electrolyte to test its electrochemical performance. Figure 1 A certain amount of MnBi2Te4 is oxidized at high temperature in a muffle furnace, mixed with N-methylpyrrolidone (NMP) and fully ground, and then the ground material is dispersed in isopropanol, ultrasonically treated in ice water, washed and dried to obtain oxidized MnBi2Te4 nanosheets. The structure of the aqueous zinc ion battery using oxidized MnBi2Te4 as the positive electrode in the embodiment is shown in FIG. Figure 1 As shown in b, its energy storage mechanism is based on the insertion and extraction of zinc ions in the cathode during the charge and discharge process. Figure 2 As shown in a, it can be clearly seen that MnBi2Te4 presents a two-dimensional layered structure. Figure 2 b is the SEM image of the oxidized MnBi2Te4 of the present invention (oxidation temperature is 240℃). The oxidized MnBi2Te4 still maintains the layered structure of MnBi2Te4, which can effectively reduce the ion diffusion distance and provide sufficient active sites for zinc ion storage. The TEM image and element mapping of the oxidized MnBi2Te4 nanosheets are shown in Figure 2. Figure 3 As shown, it can be clearly seen that Mn, Bi, Te and O elements are uniformly dispersed on the oxidized MnBi2Te4 nanosheets. Figure 4 The XRD patterns of original and oxidized MnBi2Te4 at different oxidation temperatures are shown. The strong and obvious diffraction peaks of the original material are strongly correlated with MnBi2Te4 (Simulation) and Bi2Te3 (PDF#15-0863). This is because during the synthesis of Mn-doped Bi2Te3, the raw material MnBi2Te4 material inevitably contains Bi2Te3. Compared with the unoxidized MnBi2Te4, the diffraction peaks of the oxidized MnBi2Te4 do not shift significantly, and no other impurity peaks appear, indicating that the appropriate oxidation process does not change the main structure of the unoxidized MnBi2Te4 material. CV curves of oxidized MnBi2Te4 at different oxidation temperatures (0.2mv s -1 ) and GCD curve (0.4Ag -1 )like Figure 5 As shown in Figure 2, it can be seen that the electrochemical performance of MnBi2Te4 is improved after oxidation, and the highest specific capacity is achieved when the oxidation temperature is 240 °C; Figure 5 As shown in b, at 0.4Ag -1 At a current density of 1.5 volts, the raw material manganese bismuth telluride (MnBi2Te4) was directly used as the positive electrode for performance testing, and its discharge capacity was 275.9 mAh g -1 Under the same conditions, MnBi2Te4 oxidized at 200℃, 240℃, and 275℃ was used as the positive electrode for performance testing, and its discharge capacity was 296.5, 393.1, and 291.6 mAh g, respectively. -1 It can be seen that the electrochemical performance of MnBi2Te4 as the positive electrode is improved after oxidation, and the highest specific capacity is achieved when the oxidation temperature is 240℃. Figure 6 Figure 3 is the EIS image of oxidized MnBi2Te4 at different oxidation temperatures of the present invention. The fitting results show that the oxidized MnBi2Te4 (240℃) has the lowest ESR (11.3Ω) and Rct (53.5Ω). Figure 7 The GCD curves of oxidized MnBi2Te4 (240℃) / / Zn battery are shown at 0.2, 0.4, 0.8, 1.2, 1.6, 2.0Ag -1 At the current density, the discharge capacity is 390.2, 393.1, 390.8, 384.1, 353.7, and 317.1 mAh g, respectively. -1 The rate performance of oxidized MnBi2Te4 (240℃) / / Zn battery is shown in Figure 2. Figure 8 As shown in Figure 2, the specific capacity can still be well recovered after multiple charge and discharge cycles, showing excellent rate performance. The CV curves of the oxidized MnBi2Te4 (240℃) electrode at different scan rates are shown in Figure 2. Figure 9As shown in a, based on Figure 9 The straight line graph of Log(i) and Log(v) made from the current response at the three peaks in a is as follows Figure 9 According to the power law, the measured current (i) and the scan rate (v) obey the empirical relationship: i = av b , where a and b are adjustable parameters. The value of b can be obtained from the slope of the log(i) relative to log(v) curve, which provides a deeper understanding of the energy storage mechanism. When the b value is close to 0.5, it indicates diffusion control, and when the b value is close to 1, it indicates surface capacitance control. The b value fitting results of peak 1, peak 2 and peak 3 are 0.67, 0.84 and 0.61 respectively, indicating that the process is controlled by both surface capacitance and diffusion. The cycle stability image of the oxidized MnBi2Te4 electrode is shown in Figure 2. Figure 10 As shown, at 1A g -1 At a current density of 1.5 GHz, the coulombic efficiency remains high throughout the entire cycle, with a capacity retention rate of up to 87.3% after 1,000 cycles. Furthermore, the oxidized MnBi2Te4 positive electrode for aqueous zinc ion batteries prepared by the present invention has many advantages, such as simple preparation and low cost.

[0041] In the technical solution of the present invention, in the embodiments, although some numerical values ​​with better effects are given, for example, when preparing the oxidized MnBi2Te4 nanosheet suspension, 100μl NMP is added to the oxidized MnBi2Te4 obtained in step 1) and fully ground, and dispersed in 45ml of isopropanol solution, the present invention is not limited to the volumes of NMP and isopropanol and the grinding time given in the above embodiments. The specific volumes of NMP and isopropanol and the grinding time should be determined according to actual needs; for example, the embodiments give a drying time with better effect for the preparation of the oxidized MnBi2Te4 positive electrode, but the present invention is not limited to the drying time given in the above embodiments. Since the drying time is 6 to 9h, 7.5h in the embodiment can be taken, and 6h, 9h, etc. can also be taken, but the time should not be too short, and the specific drying time needs to be determined according to actual needs; that is, the content claimed for protection of the present invention is based on the scope recorded and explained in the claims.

[0042] Example 2

[0043] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 1), the oxidation temperature of the raw material MnBi2Te4 is 200°C.

[0044] Example 3

[0045] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 1), the oxidation temperature of the raw material MnBi2Te4 is 275°C.

[0046] The present invention prepares oxidized MnBi2Te4 by controlling different oxidation temperatures, finds an optimal temperature to achieve optimal electrochemical performance, and explores the effects of oxidized MnBi2Te4 cathodes at multiple different oxidation temperatures from low to high on electrochemical performance. Figure 5 As can be seen from Figures 5a and 5b, when MnBi2Te4 is not oxidized, it has the worst performance. After MnBi2Te4 is oxidized, its electrochemical performance is improved. In addition, MnBi2Te4 has the best electrochemical performance when the oxidation temperature is 240℃.

[0047] Example 4

[0048] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 2), the ultrasonic treatment time is 30 minutes.

[0049] Example 5

[0050] A preparation method of MnBi2Te4 for oxidation of positive electrode materials for aqueous zinc ion batteries is similar to that of Example 1, except that in step 2), the ultrasonic treatment time is 90 minutes.

[0051] Example 6

[0052] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 3), the drying temperature is 55°C and the drying time is 9 hours.

[0053] Example 7

[0054] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 3), the drying temperature is 65°C and the drying time is 6 hours.

[0055] Example 8

[0056] A preparation method for oxidizing MnBi2Te4 for aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 4), the mass ratio of oxidized MnBi2Te4 nanosheets: acetylene black: polyvinylidene fluoride is 6:1:0.5.

[0057] Example 9

[0058] A preparation method for oxidizing MnBi2Te4 for aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 4), the mass ratio of oxidized MnBi2Te4 nanosheets: acetylene black: polyvinylidene fluoride is 8:2:1.5.

[0059] Example 10

[0060] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 4), when the drying temperature is 55°C, the drying time is 9 hours.

[0061] Example 11

[0062] A preparation method of MnBi2Te4 for oxidation of aqueous zinc ion battery positive electrode material is similar to Example 1, except that in step 4), when the drying temperature is 65°C, the drying time is 6 hours.

[0063] It should be noted that the above embodiments are only illustrative of the present invention and do not have any restrictive effect. Any non-substantial modifications made by those skilled in the art on the basis of the present invention should fall within the scope of protection of the present invention.

Claims

1. A manganese bismuth tellurium oxide MnBi2Te4O x The preparation method of the nanosheets comprises the following steps: oxidizing manganese bismuth tellurium MnBi2Te4 in a muffle furnace, grinding the MnBi2Te4 in N-methylpyrrolidone, dispersing the MnBi2Te4 in isopropyl alcohol for ultrasonic dispersion, washing, filtering and drying the MnBi2Te4.

2. The preparation method according to claim 1, wherein The oxidation temperature in the muffle furnace is 180° C. to 300° C., and the oxidation time is 250 to 320 minutes.

3. The preparation method according to claim 1 or 2, wherein The following steps are involved: (1) Preparation of oxidized MnBi2Te4: The raw material manganese bismuth tellurium MnBi2Te4 is placed in a muffle furnace and oxidized at 200-280°C for 270-300 minutes to obtain MnBi2Te4 oxide; (2) preparing an oxidized MnBi2Te4 nanosheet suspension: adding N-methylpyrrolidone to the MnBi2Te4 oxide prepared in step (1) and grinding the mixture thoroughly, then dispersing the mixture in isopropanol, and ultrasonically treating the mixture with ice water to obtain an oxidized MnBi2Te4 nanosheet suspension; (3) Cleaning and drying of oxidized MnBi2Te4 nanosheets: The oxidized MnBi2Te4 nanosheet suspension obtained in step (2) was washed with anhydrous ethanol, vacuum filtered, and dried to obtain manganese bismuth tellurium oxide MnBi2Te4O x Nanosheets.

4. The preparation method according to claim 3, wherein In the step (2), when the mass of the raw material MnBi2Te4 is 0.1 g, the volumes of N-methylpyrrolidone and isopropanol are 0.1-0.2 mL and 40-50 mL, respectively, and the ice water ultrasonic treatment time is 30-90 min.

5. The preparation method according to claim 3, wherein In the step (3), the oxidized MnBi2Te4 nanosheet suspension is first washed with anhydrous ethanol, vacuum filtered, and then placed in a vacuum drying oven for drying.

6. The preparation method according to claim 1, wherein In the step (3), when the drying temperature is 55 to 65° C., the drying time is 6 to 9 hours.

7. A manganese bismuth tellurium oxide MnBi2Te4O x Nanosheets are obtained by the preparation method according to any one of claims 1 to 6.

8. The manganese bismuth tellurium oxide MnBi2Te4O according to claim 7 x Application of nanosheets in cathode materials for aqueous zinc-ion batteries.

9. The use according to claim 8, wherein the following method steps are used: manganese bismuth telluride oxide MnBi2Te4O x The nanosheets were uniformly mixed with acetylene black and polyvinylidene fluoride in NMP solution to obtain a mixed slurry. The slurry was then coated on an electrode and dried in a vacuum drying oven to prepare manganese bismuth tellurium oxide MnBi2Te4O x Nanosheet positive electrode.

10. The use according to claim 9, characterized in that Manganese bismuth tellurium oxide MnBi2Te4O x The mass ratio of the nanosheets, acetylene black and polyvinylidene fluoride is (6-8):(1-3):(0.5-1.5).

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