A transition metal oxide positive electrode material with amorphous / nanocrystalline and its preparation method and application

Abstract

The present invention discloses a transition metal oxide cathode material with amorphous / nanocrystalline, its preparation method and application. In this material, an amorphous region and a nanocrystalline region coexist, and the nanocrystalline regions are connected by the amorphous. The nanocrystalline regions of this material can be used for ion storage. The amorphous region has high reactivity and can provide more active sites and ion diffusion channels, reducing the embedding energy barrier of zinc ions and the diffusion energy barrier inside the electrode material, thereby improving the rate performance and stability of the material. When applying a current density of 5 A / g, the theoretical specific capacity of the current mainstream crystalline material α-MnO2 is about 30 mAh / g, while the battery using the amorphous / nanocrystalline MnO2 material can maintain about 150 mAh / g, and its theoretical specific capacity is increased by 4 times compared with the traditional crystalline α-MnO2 material. This method has low cost, simple operation, novel strategy and obvious effect.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of aqueous zinc ion battery materials, and in particular to a method for preparing an amorphous / nanocrystalline transition metal oxide (Mn, V, Mo and other elements) positive electrode material. Technical Background

[0002] In recent years, the emergence of energy crisis and the vigorous development of new energy have put forward new requirements for the stability and continuity of the storage and release of electric energy. These demands have greatly stimulated the emergence and development of emerging energy storage systems. Among the many alternative energy storage systems, batteries have been deeply studied due to their wide applicability and popularity. At present, the shortage and uneven distribution of lithium resources have led to high prices for commercial lithium-ion batteries, which limits their further application in the field of large-scale energy storage in the future. However, compared with commercial lithium-ion batteries, aqueous zinc-ion batteries are expected to become one of the candidate battery systems for large-scale energy storage in the future due to their higher safety, low cost and good environmental compatibility.

[0003] Aqueous zinc ions have a low redox potential (-0.76V Zn Vs.Zn 2+ ) and a high theoretical specific capacity (820mAh / g). The classic aqueous zinc-ion battery consists of positive and negative electrode materials, a separator and an aqueous electrolyte. The aqueous electrolyte has a high ion migration number (two orders of magnitude higher than that of organic electrolytes) and is expected to achieve a higher rate performance. However, the lack of suitable cathode materials has become one of the problems faced in its development. Recently, many materials have been applied to aqueous zinc-ion batteries, which are generally divided into four categories: manganese-based, vanadium-based, Prussian blue analogs (PBAs) and organics. Transition cathode materials have received more attention due to their rich redox states, high operating voltage and moderate capacity.

[0004] Crystalline transition materials have been widely studied due to their good structural stability and large ion diffusion channels that are conducive to ion storage. However, due to their inherent low electronic conductivity, limited active sites and diffusion paths, they are not conducive to improving their rate performance. Researchers have proposed many modification strategies to improve their electrochemical performance. The strategies mainly include the following four aspects: carbon material composite, defect modulation and vacancy engineering. Many wonderful works have greatly improved the electrochemical performance of crystalline materials, but there is little research on amorphous materials with rich active sites and diffusion paths. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing amorphous / nanocrystalline transition metal oxide positive electrode materials and their applications in view of the above problems. The present invention prepares amorphous / nanocrystalline transition oxide positive electrode materials by heat treatment to achieve high current charge and discharge performance of aqueous zinc ion batteries. The amorphous and nanocrystalline parts coexist in the material, and the nanocrystalline regions are connected by amorphous. The synthesized amorphous / nanocrystalline transition metal oxide positive electrode materials have high reaction activity, low reaction energy barrier, and more active sites and diffusion paths. Thanks to the structural advantages of amorphous / nanocrystalline oxide positive electrode materials, aqueous zinc ion batteries based on amorphous / nanocrystalline oxide positive electrode materials show excellent electrochemical performance. The method has the characteristics of low cost, simple operation, obvious effect, and can be mass-produced.

[0006] When the current density is 5A / g, the theoretical specific capacity of α-MnO2 is about 30mAh / g, while the battery using amorphous / nanocrystalline MnO2 materials can maintain about 150mAh / g, and its theoretical specific capacity is 4 times higher than that of traditional crystalline α-MnO2 materials. At a higher current density of 10A / g, the traditional crystalline α-MnO2 material can no longer provide capacity, while the capacity of amorphous nanocrystalline materials remains at 100mAh / g, showing a strong high-current fast charge and discharge capability.

[0007] In order to solve the technical problem of the present invention, the proposed technical solution is: the preparation method of the amorphous / nanocrystalline transition metal oxide positive electrode material comprises the following steps:

[0008] (1) preparing an aqueous solution of a reducing precursor or an oxidizing precursor containing a certain proportion of a target element and a corresponding oxidizing agent or a reducing agent and stirring the aqueous solution to obtain a mixed solution I;

[0009] (2) placing the mixed solution I at a certain temperature for a period of time, washing it repeatedly with deionized water and centrifuging it to obtain a solid sample, and then freeze-drying the solid sample to obtain an amorphous oxide, which is recorded as powder sample I;

[0010] (3) The above-mentioned amorphous oxide is ground in advance, and then placed in a heating device and calcined for a period of time at a certain temperature in a specific gas atmosphere, which may be air, oxygen, argon, nitrogen, etc., to obtain a powder sample II; the powder sample II is the final product, amorphous / nanocrystalline transition metal oxide positive electrode material, denoted as AC-M x O y (AC is the abbreviation of amorphous / crystalline, which refers to amorphous / nanocrystalline structure; M is one of the transition metal elements Mn, V, and Mo, and the specific values ​​of x and y are based on the chemical formula (0<x, y<5).

[0011] Preferably, the reducing precursor or oxidizing precursor has the metal element in the target oxide, and the corresponding oxidizing substance or reducing substance may or may not contain the metal element, and can undergo a redox reaction to generate the target oxide. The feed ratio of the two is based on the number of electron transfers in the reaction.

[0012] Preferably, the mixed solution I is placed at room temperature (20-40° C.) and reacted for 0-24 hours to obtain an amorphous oxide intermediate.

[0013] Preferably, the amorphous oxide intermediate needs to be calcined for a certain period of time under a certain atmosphere to obtain the final target product, i.e., the amorphous / nanocrystalline transition metal oxide positive electrode material, and the heating equipment muffle furnace and tubular furnace are selected according to the calcination atmosphere.

[0014] Preferably, in step 1, the molar ratio of the reducing precursor or oxidizing precursor to its corresponding oxidizing agent or reducing agent is based on the number of electron transfers in its chemical reaction;

[0015] The reducing precursor is H2C2O4 and the corresponding oxidant is KMnO4 (molar ratio 5:2), the reducing precursor is CH3COOMn and the corresponding oxidant is KMnO4 (molar ratio 2:5), the oxidizing precursor is NH4VO3 and the corresponding reducing agent is H2C2O4 (molar ratio 1:1);

[0016] In step 2, the mixed solution I is placed at a certain temperature of 25°C for a period of time of 0 to 9 hours;

[0017] In step 3, the mixture is placed in a heating device and calcined in an air atmosphere at a certain temperature of 300 to 500° C. for a period of 0 to 24 hours to obtain powder sample II.

[0018] Preferably, the method comprises the following steps:

[0019] (1) preparing aqueous solutions of a reducing substance H2C2O4 and a Mn-containing oxidizing precursor KMnO4 in a certain molar ratio of 5:2 and stirring them uniformly, and adding the KMnO4 solution into the reducing agent solution to obtain a mixed solution I;

[0020] (2) placing the mixed solution I at room temperature of 20-40°C to react for a period of time, repeatedly washing and filtering with distilled water, and freeze-drying the solid sample to obtain an amorphous MnO2 intermediate, which is recorded as powder sample I;

[0021] (3) The above-mentioned amorphous MnO2 is ground in advance, placed in a porcelain boat, and placed in a muffle furnace of a heating device in an air atmosphere, and calcined at 300°C for 9 hours to obtain powder sample II; powder sample II is the final product, amorphous / nanocrystalline MnO2 positive electrode material, denoted as AC-MnO2.

[0022] In order to solve the technical problem of the present invention, another technical solution is proposed: an amorphous / nanocrystalline oxide positive electrode material prepared by any method.

[0023] In order to solve the technical problem of the present invention, another technical solution is proposed: the application of the amorphous / nanocrystalline oxide positive electrode material can be applied to battery positive electrode materials.

[0024] Preferably, it can be applied to aqueous zinc-ion batteries. The performance of amorphous / nanocrystalline oxide positive electrodes is greatly improved compared with mainstream α-MnO2, especially during high current charging and discharging, indicating that amorphous / nanocrystalline oxide positive electrode materials are materials with fast charging and discharging potential.

[0025] The invention provides a method for preparing a positive electrode material having an amorphous / nanocrystalline transition metal oxide, which comprises the following steps.

[0026] In some embodiments, the reducing and oxidizing materials may contain the target element at the same time or a certain reaction material may contain the target element, and the feed ratio thereof is based on the number of electron transfers in the chemical reaction.

[0027] In some embodiments, the temperature condition depends on the temperature condition at which the redox reaction can occur, and the reaction time of the mixed solution I depends on the reaction state and whether the reaction is sufficient.

[0028] In some embodiments, the material may be ground before calcination to obtain fine particles.

[0029] In some embodiments, the calcination atmosphere may be an inert atmosphere or air, depending on the desired final target product.

[0030] In some embodiments, the specific values ​​of the calcination temperature (200-1500° C.) and time depend on the temperature required to nucleate the material without growth and the degree of crystallization.

[0031] In some embodiments, the heating device (muffle furnace, tube furnace or other) is selected according to the calcination atmosphere.

[0032] The present invention has the following beneficial effects:

[0033] The invention discloses an amorphous / nanocrystalline transition metal oxide positive electrode material, in which amorphous regions and nanocrystalline regions coexist, and the nanocrystalline regions are connected by amorphous regions. The nanocrystalline region of the material can be used for ion storage, and the amorphous region has high reactivity and can provide more active sites and ion diffusion channels, thereby reducing the embedding energy barrier of zinc ions and the diffusion energy barrier inside the electrode material, thereby improving the rate performance and stability of the material. The method has the characteristics of low cost, simple operation, obvious effect, and mass production.

[0034] The amorphous / nanocrystalline MnO2 prepared by the method of the present invention has the characteristics of long-range disorder and short-range order. Figure 1 The broad peaks of the XRD pattern show that the prepared amorphous / nanocrystalline MnO2 has amorphous characteristics. Figure 2 HRTEM and Figure 3 The diffraction pattern shows that there are both nanocrystalline and amorphous regions inside the material, and the nanocrystalline regions are connected by amorphous regions. The size of the nanocrystalline region is 10 to 40 nm and there are crystal plane distortion and lattice distortion.

[0035] In the battery test, we compared the crystalline material α-MnO2, which is widely used in the current aqueous zinc-ion battery system. Under the same test conditions, when a current density of 5A / g is applied, the theoretical specific capacity of α-MnO2 is about 30mAh / g, while the battery using amorphous / nanocrystalline MnO2 materials can maintain about 150mAh / g, and its theoretical specific capacity is 4 times higher than that of traditional crystalline α-MnO2 materials. At a higher current density of 10A / g, the traditional crystalline α-MnO2 material can no longer provide capacity, while the capacity of our amorphous nanocrystalline material remains at 100mAh / g, showing a strong high-current rapid charge and discharge capability.

[0036] The present invention prepares an amorphous / nanocrystalline transition oxide positive electrode material by heat treatment, and realizes the high current charge and discharge performance of an aqueous zinc ion battery, wherein the amorphous and nanocrystalline parts coexist in the material, and the nanocrystalline regions are connected by the amorphous. The synthesized amorphous / nanocrystalline transition metal oxide positive electrode material has high reaction activity, low reaction energy barrier, and more active sites and diffusion paths. Thanks to the structural advantages of the amorphous / nanocrystalline oxide positive electrode material, the aqueous zinc ion battery based on the amorphous / nanocrystalline oxide positive electrode material exhibits excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The XRD pattern of amorphous / nanocrystalline MnO2 obtained in Example 1 of the present invention is

[0038] Figure 2 HRTEM image of amorphous / nanocrystalline MnO2 obtained in Example 1 of the present invention

[0039] Figure 3 The diffraction pattern of amorphous / nanocrystalline MnO2 obtained in Example 1 of the present invention is

[0040] Figure 4 This is the SEM image of amorphous / nanocrystalline MnO2 obtained in Example 1 of the present invention.

[0041] Figure 5This is a SEM image of α-MnO2, which is widely studied in aqueous zinc-ion batteries.

[0042] Figure 6 This is a graph showing the electrochemical performance of amorphous / nanocrystalline MnO2 obtained at different calcination temperatures in Example 1 of the present invention.

[0043] Figure 7 This is a graph of the electrochemical performance of amorphous / nanocrystalline MnO2 obtained at 300°C for different calcination times in Example 1 of the present invention.

[0044] Figure 8 The electrochemical performance diagram of amorphous / nanocrystalline MnO2 obtained in Example 3 of the present invention is compared with the performance of α-MnO2 nanorods after optimizing the slurry ratio.

[0045] Fig. 9 This is the electrochemical performance diagram of amorphous / nanocrystalline Mn3O4 obtained in Example 2 of the present invention.

[0046] Fig.10 This is the electrochemical performance diagram of amorphous / nanocrystalline MnO2 obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the performance of the present invention, and are not limited to the following examples.

[0048] Example 1: The oxidizing precursor contains the target element, and the reducing substance does not contain the target element.

[0049] A positive electrode material having amorphous / nanocrystalline MnO2, and a preparation method thereof is as follows:

[0050] (1) The reducing substance H2C2O4 and the Mn-containing oxidizing precursor KMnO4 were dissolved in 500 ml of deionized water at a molar ratio of 5:2 to prepare an aqueous solution and stirred evenly. The KMnO4 solution was added to the reducing agent solution to obtain a mixed solution I.

[0051] (2) The mixed solution I was placed at room temperature (25°C) to react for 9 hours, and then washed and filtered repeatedly with distilled water and the solid sample was freeze-dried to obtain an amorphous MnO2 intermediate, which was recorded as powder sample I; (3) The above-mentioned amorphous MnO2 was ground in advance, placed in a porcelain boat and placed in a heating device (muffle furnace) and calcined at 200°C, 300°C, and 400°C for 3 hours in an air atmosphere to obtain powder sample II; powder sample II is the final product amorphous / nanocrystalline MnO2 positive electrode material, recorded as AC-MnO2. Through testing, the above materials showed specific capacities of 40, 70, and 30 mAh / g at a current density of 4 A / g, respectively. The optimal calcination temperature was finally obtained to be 300°C through characterization of the performance. After that, the materials were calcined at 300°C for 3, 6, 9, and 24 hours, respectively. The obtained material showed the best specific capacity (110 mAh / g) at a current density of 5 A / g after calcination for 9 hours, and the optimal calcination time was obtained to be 9 hours.

[0052] Battery assembly and testing:

[0053] The amorphous / nanocrystalline manganese dioxide electrode was prepared by mixing MnO2 (70wt%), superconducting carbon black (Super-P) (10wt%), carbon nanotubes (10wt%) and polyvinylidene fluoride (PVDF) (10wt%) prepared by the above method in 1-methyl-2-pyrrolidone (NMP) to form a uniform slurry (no carbon nanotubes were added in the temperature and time screening stage and the above material ratio was based on a mass fraction of 7:2:1, which was later changed to 7:1:1:1 for the purpose of enhancing conductivity). It was then coated on titanium foil and dried in a conventional furnace at 60°C for 12h, and then vacuum dried for 12h. After drying, it was cut into circular pole pieces with a diameter of 14mm. The total load mass of the slurry was between 0.8 and 1.2mg. Zinc foil and glass fiber separator were used as negative electrode and separator, respectively, and 2M ZnSO4 and 0.25M MnSO4 additive solutions were used as electrolytes. The CR2025 button batteries were assembled in an indoor environment, left to stand for 8 hours, and their electrochemical properties were tested using a battery testing system.

[0054] The amorphous / nanocrystalline MnO2 prepared by the above method has the characteristics of long-range disorder and short-range order. Figure 1 The broad peaks of the XRD pattern show that the prepared amorphous / nanocrystalline MnO2 has amorphous characteristics. Figure 2 HRTEM and Figure 3 The diffraction pattern shows that there are both nanocrystalline and amorphous regions inside the material, and the nanocrystalline regions are connected by amorphous regions. The size of the nanocrystalline region is 10 to 40 nm and there are crystal plane distortion and lattice distortion.

[0055] Compared with the traditional crystalline material α-MnO2, under the same test conditions, when the current density of 5A / g is applied, the theoretical specific capacity of α-MnO2 is about 30mAh / g, while the battery using amorphous / nanocrystalline MnO2 material can maintain about 150mAh / g; at a higher current density of 10A / g, the traditional crystalline α-MnO2 material can no longer provide capacity, while the capacity of amorphous nanocrystalline material remains at 100mAh / g, showing a strong high-current fast charge and discharge capability. The test results show that the performance of amorphous / nanocrystalline MnO2 has been greatly improved compared to the current mainstream α-MnO2 nanorods (crystalline materials).

[0056] Example 2: Using different calcination atmospheres can change the precipitated crystal form.

[0057] A positive electrode material having amorphous / nanocrystalline Mn3O4, and a preparation method thereof is as follows:

[0058] (1) A reducing substance H2C2O4 and a Mn-containing oxidizing precursor KMnO4 are prepared into an aqueous solution in a certain molar ratio of 5:2 and stirred evenly, and the KMnO4 solution is added into the reducing agent solution to obtain a mixed solution I.

[0059] (2) The mixed solution I was placed at room temperature (25°C) to react for 9 hours, and then washed and filtered repeatedly with distilled water and the solid sample was freeze-dried to obtain an amorphous MnO2 intermediate, which was recorded as powder sample I.

[0060] (3) The above-mentioned amorphous MnO2 was ground in advance, placed in a porcelain boat and placed in a heating device (muffle furnace) and calcined for 3 hours at 300°C in an argon atmosphere to obtain powder sample II. Powder sample II is the final product amorphous / nanocrystalline Mn3O4 positive electrode material, denoted as AC-Mn3O4.

[0061] Battery assembly and testing:

[0062] Amorphous / nanocrystalline manganese dioxide electrode was prepared by mixing Mn3O4 (70wt%), superconducting carbon black (Super-P) (20wt%) and polyvinylidene fluoride (PVDF) (10wt%) prepared by the above method in 1-methyl-2-pyrrolidone (NMP) to form a uniform slurry. It was then coated on titanium foil and dried in a common furnace at 60°C for 12h, and then vacuum dried for 12h. After drying, it was cut into circular pole pieces with a diameter of 14mm. The total loading mass of the slurry was between 0.8 and 1.2mg. Zinc foil and glass fiber diaphragm were used as negative electrode and diaphragm, respectively, and 2M ZnSO4 and 0.25M MnSO4 additive solutions were used as electrolytes. CR2025 button cells were assembled under indoor conditions, then left to stand for 8h, and their electrochemical properties were tested by a battery test system.

[0063] When the conductivity of the slurry is not optimized, the battery using amorphous / nanocrystalline Mn3O4 material can maintain about 40mAh / g when a current density of 5A / g is applied. The test results show that the amorphous / nanocrystalline Mn3O4 synthesized by this scheme still maintains a certain capacity under high current density and is higher than traditional α-MnO2.

[0064] Example 3: Both the oxidizing and reducing precursors contain the target element, and the final products obtained by using different reaction raw materials have different performances in aqueous zinc ion batteries.

[0065] A positive electrode material having amorphous / nanocrystalline MnO2, and a preparation method thereof is as follows:

[0066] (1) A Mn-containing reducing substance CH3COOMn and an oxidizing substance KMnO4 are prepared into an aqueous solution in a molar ratio of 3:2 and stirred evenly, and the KMnO4 solution is added to the CH3COOMn solution to obtain a mixed solution I.

[0067] (2) The mixed solution I was placed at room temperature to react for a period of time, washed and filtered repeatedly with distilled water, and the solid sample was freeze-dried to obtain amorphous MnO2, which was recorded as powder sample I.

[0068] (3) The above-mentioned amorphous MnO2 was ground in advance, placed in a porcelain boat and placed in a heating device (tube furnace) and calcined at 300°C in an air atmosphere for 6 hours to obtain powder sample II. Powder sample II is the final product amorphous / nanocrystalline MnO2 positive electrode material, denoted as AC-MnO2.

[0069] Battery assembly and testing:

[0070] Amorphous / nanocrystalline manganese dioxide electrodes were prepared by mixing amorphous / nanocrystalline AC–MnO2 (80wt%), superconducting carbon black (Super-P) (10wt%) and polyvinylidene fluoride (PVDF) (10wt%) in 1-methyl-2-pyrrolidone (NMP) to form a uniform slurry. It was then coated on titanium foil and dried in a conventional furnace at 60°C for 12h, followed by vacuum drying for 12h. After drying, it was cut into circular pole pieces with a diameter of 14mm. The total loading mass of the slurry was between 0.8 and 1.2mg. Zinc foil and glass fiber separator were used as negative electrode and separator, respectively, and 2M ZnSO4 and 0.25M MnSO4 additive solutions were used as electrolytes. CR2025 button cells were assembled under indoor conditions, and then left to stand for 8h, and their electrochemical performance was tested by a battery test system.

[0071] When the conductivity of the slurry is not optimized, when a current density of 1A / g is applied, the battery using amorphous / nanocrystalline MnO2 material can maintain about 120mAh / g, while the material obtained in Example 1 can maintain about 280mAh / g. The test results show that the amorphous / nanocrystalline MnO2 synthesized by this scheme still maintains a certain capacity test result under a current density of 1A / g. This shows that the amorphous / nanocrystalline MnO2 synthesized by this scheme is lower than the material obtained in Implementation Plan 1, indicating that the use of different precursors has a certain influence on the material in the aqueous zinc ion battery system.

[0072] Embodiment 4:

[0073] A kind of amorphous / nanocrystalline VO2 positive electrode material, the preparation method thereof is as follows:

[0074] (1) The reducing substances H2C2O4 and NH4VO3 are prepared into an aqueous solution in a molar ratio of 1:1 and stirred evenly, and the NH4VO3 solution is added into the H2C2O4 solution to obtain a mixed solution I.

[0075] (2) The mixed solution I is placed at 100°C for a period of time, washed and filtered repeatedly with distilled water, and the solid sample is freeze-dried to obtain an amorphous VO2 intermediate, which is recorded as powder sample I.

[0076] (3) The above-mentioned amorphous VO2 was ground in advance, placed in a porcelain boat and placed in a heating device for calcining at 300°C for 3 hours to obtain powder sample II. Powder sample II is the final product amorphous / nanocrystalline VO2 positive electrode material, denoted as AC-VO2.

[0077] Battery assembly and testing:

[0078] The amorphous / nanocrystalline manganese dioxide electrode was prepared by mixing amorphous / nanocrystalline VO2 (70wt%), superconducting carbon black (Super-P) (10wt%), carbon nanotubes (10wt%) and polyvinylidene fluoride (PVDF) (10wt%) in 1-methyl-2-pyrrolidone (NMP) to form a uniform slurry. It was then coated on a titanium foil and dried in a conventional furnace at 60°C for 12h, and then vacuum dried for 12h. After drying, it was cut into circular pole pieces with a diameter of 14mm. The total loading mass of the slurry was between 0.8 and 1.2mg. Zinc foil and glass fiber separator were used as negative electrode and separator, respectively, and 2M ZnSO4 solution was used as electrolyte. CR2025 button cells were assembled under indoor environment, then left to stand for 8h, and their electrochemical performance was tested by a battery test system. The test results show that the amorphous / nanocrystalline VO2 synthesized by this scheme still maintains a certain capacity under high current density.

Claims

1. An application of amorphous / nanocrystalline oxide positive electrode material, characterized in that: (1) preparing aqueous solutions of a reducing substance H2C2O4 and a Mn-containing oxidizing precursor KMnO4 in a certain molar ratio of 5:2 and stirring them uniformly, and adding the KMnO4 solution to the reducing agent solution to obtain a mixed solution I; (2) The mixed solution I was placed at room temperature (25°C) to react for 9 hours, and then washed and filtered repeatedly with distilled water and the solid sample was freeze-dried to obtain an amorphous MnO2 intermediate, which was recorded as powder sample I; (3) The above-mentioned amorphous MnO2 was ground in advance, placed in a porcelain boat, and placed in a muffle furnace of a heating device in an air atmosphere, and calcined at 300°C for 9 h to obtain powder sample II; powder sample II is the final product amorphous / nanocrystalline MnO2 positive electrode material, denoted as AC-MnO2; (4) AC-MnO2 is used as battery positive electrode material.

2. The use of amorphous / nanocrystalline oxide positive electrode material according to claim 1, characterized in that: The prepared AC-MnO2 70wt%, superconducting carbon black Super-P 10wt%, carbon nanotubes 10wt% and polyvinylidene fluoride PVDF 10wt% were mixed in 1-methyl-2-pyrrolidone to form a uniform slurry, which was then coated on a titanium foil and dried in an ordinary furnace at 60°C for 12 h, and then vacuum dried for 12 h. After drying, it was cut into circular pole pieces with a diameter of 14 mm. The total loading mass of the slurry was between 0.8 and 1.2 mg. Zinc foil and glass fiber diaphragm were used as negative electrode and diaphragm, respectively, and 2 M ZnSO4 and 0.25 M MnSO4 additive solutions were used as electrolytes. CR2025 button batteries were assembled under indoor conditions, then left to stand for 8 h, and their electrochemical properties were tested by a battery testing system.

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