Preparation method and application of Mn3O4 / graphene compound

Abstract

The invention relates to the technical field of electrochemical energy storage materials, in particular to a preparation method and application of a Mn3O4 / graphene compound, and the preparation method comprises the following steps: A, preparing a water-soluble divalent manganese salt solution for later use; b, adding a graphene oxide aqueous solution into the water-soluble bivalent manganese salt solution in the step A, and uniformly mixing to obtain a mixture; c, adding quaternary ammonium base and hydrogen peroxide into the mixture in the step B, stirring for reaction, then adding ammonia water and hydrazine hydrate for water bath heating reaction, and filtering, washing and drying precipitate obtained after the reaction to obtain a Mn3O4 / graphene compound; according to the method disclosed by the invention, graphene is introduced into Mn3O4, so that not only can the agglomeration of Mn3O4 be prevented, but also the structural stability of Mn3O4 can be improved, and the volume expansion and shrinkage of the material in the charge-discharge process can be inhibited, thereby prolonging the cycle life and reducing the capacity fading. In addition, graphene can form a conductive network among Mn3O4 particles, interface contact between the electrode material and electrolyte is improved, and transmission and diffusion of ions are promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage materials, and in particular to a preparation method and application of a Mn3O4 / graphene composite. Background Art

[0002] Manganese dioxide (Mn3O4) is widely used in electrode material systems for battery systems such as lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries due to its high specific capacity and good electrochemical stability. However, the inherent poor conductivity and insufficient structural stability of Mn3O4 lead to rapid capacity decay and unsatisfactory rate performance in practical applications. To address these problems, an effective strategy is to composite them with highly conductive carbon materials. This composite strategy can effectively improve the electrochemical performance of the material by constructing a conductive network and enhancing structural stability. Experiments have shown that Mn3O4 composited with highly conductive carbon materials can overcome the original shortcomings and significantly improve its energy storage performance.

[0003] As a new type of two-dimensional carbon-based material, graphene has become a highly sought-after material in energy storage devices due to its excellent electrical conductivity, superior electrochemical activity, and good mechanical strength. The composite formed by Mn3O4 and graphene synergistically utilizes their respective excellent properties, contributing to the high specific capacity of Mn3O4 while simultaneously improving its electrical conductivity. In Mn3O4 / graphene composite electrodes, the highly conductive graphene not only provides an efficient electron transport channel for Mn3O4, enhancing the material's conductivity, but also helps mitigate the volume expansion and contraction that may occur during the charge and discharge process, thereby enhancing the cycling stability of the composite electrode.

[0004] However, traditional Mn3O4 / graphene composites involve high temperature, high pressure conditions or complex steps, which limit their practical application value. Therefore, it is necessary to develop a simple, economical and effective method for preparing Mn3O4 / graphene composites. Summary of the Invention

[0005] In order to solve the above technical problems, embodiments of the present invention provide a preparation method and application of a Mn3O4 / graphene composite.

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: In one aspect, the present invention provides a method for preparing a Mn3O4 / graphene composite, comprising the following steps: A. Prepare a water-soluble divalent manganese salt solution and set aside; B. adding the graphene oxide aqueous solution to the water-soluble divalent manganese salt solution of step A and mixing to obtain a mixture; C. Add quaternary ammonium base and hydrogen peroxide to the mixture in step B, stir and react, then add ammonia water and hydrazine hydrate to carry out heating reaction in a water bath, filter, wash and dry the precipitate obtained after the reaction to obtain a Mn3O4 / graphene composite.

[0007] In some embodiments, in step A, the concentration of the water-soluble divalent manganese salt solution is 0.1-20 mol / L, wherein the water-soluble divalent manganese salt comprises at least one of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate.

[0008] In some embodiments, in step B, the concentration of the graphene oxide aqueous solution is 0.2-10 g / L.

[0009] In some embodiments, in step B, the ratio of the mass of the graphene oxide aqueous solution to the manganese ions in the water-soluble divalent manganese salt solution in step A is 2-100 g:1 mol.

[0010] In some embodiments, in step C, the molar ratio of the quaternary ammonium base to the manganese ions in the water-soluble divalent manganese salt solution in step B is 1 to 20:1.

[0011] In some embodiments, in step C, the molar ratio of the hydrogen peroxide to the manganese ions in the water-soluble divalent manganese salt solution in step B is 1-20:1.

[0012] In some embodiments, in step C, the quaternary ammonium base includes at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide, and the stirring time is 5 to 100 hours.

[0013] In some embodiments, in step C, the molar ratio of the ammonia water to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.5-10:1, and the molar ratio of the hydrazine hydrate to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.1-2:1.

[0014] In some embodiments, in step C, the water bath heating reaction is performed at a temperature of 50-100° C. for a time of 20-200 min.

[0015] On the other hand, the present invention provides an application of the Mn3O4 / graphene composite prepared by the above preparation method in an energy storage device.

[0016] The beneficial effects of the present invention are: The method of the present invention is based on the fact that Mn3O4 is a transition metal oxide with high specific capacity and good electrochemical performance. Due to its unique structural characteristics and physical and chemical properties, it has a wide range of applications in the energy storage field, especially the battery industry.

[0017] The method of the present invention introduces graphene into Mn3O4, which not only prevents Mn3O4 aggregation but also improves its structural stability, thereby increasing cycle life and reducing capacity decay. Furthermore, the highly conductive graphene forms a conductive network between the Mn3O4 particles, creating efficient electron transport pathways. This improves the interfacial contact between the electrode material and the electrolyte, promoting ion transport and diffusion. Due to these synergistic effects, the Mn3O4 / graphene composite exhibits excellent electrochemical properties, including high specific capacity, high energy density, and excellent rate and cycling performance.

[0018] The preparation method of the present invention is simple and economical, does not require high temperature, high pressure and complicated preparation process, and can be prepared by simply stirring at room temperature combined with water bath reaction, which is low in cost and suitable for large-scale production. It has the advantages of simplicity, economy and high efficiency.

[0019] The Mn3O4 / graphene composite prepared using the method of the present invention has broad application prospects in electrochemical energy storage devices such as zinc-ion batteries, lithium-ion batteries, sodium-ion batteries, and supercapacitors. This material exhibits significant advantages in high-performance energy storage, particularly in energy storage devices such as zinc-ion batteries, meeting the requirements of high energy density and long cycle life, and possesses significant application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the Mn3O4 / graphene composite prepared in Example 1; Figure 2 This is a graph showing the rate performance of a zinc ion battery using the Mn3O4 / graphene composite prepared in Example 1 as a cathode at different current densities in the range of 0.1 to 2 A / g; Figure 3 The Lagung plots of the Mn3O4 / graphene composites prepared in Examples 1-4 and Comparative Examples 1-4 as cathodes for zinc ion batteries; Figure 4 This is a test chart of the cycling performance of the Mn3O4 / graphene composite prepared in Example 1 as a cathode for zinc ion batteries at 1 A / g. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0022] Currently, traditional Mn3O4 / graphene composites involve high temperature, high pressure conditions or complex steps, which limits their practical application value, becoming a problem that needs to be solved urgently.

[0023] In order to solve the above technical problems, on the one hand, the present invention provides a method for preparing a Mn3O4 / graphene composite, comprising the following steps: A. Prepare a water-soluble divalent manganese salt solution and set aside; B. adding the graphene oxide aqueous solution to the water-soluble divalent manganese salt solution of step A and mixing to obtain a mixture; C. Add quaternary ammonium base and hydrogen peroxide to the mixture in step B, stir and react, then add ammonia water and hydrazine hydrate to carry out heating reaction in a water bath, filter, wash and dry the precipitate obtained after the reaction to obtain a Mn3O4 / graphene composite.

[0024] The purpose of introducing graphene oxide, quaternary ammonium base and hydrogen peroxide into the above-mentioned water-soluble divalent manganese salt solution is to generate MnO2 through reaction and attach it to the graphene surface, thereby forming a MnO2 / graphene oxide composite, and then reduce the MnO2 / graphene oxide to Mn3O4 / graphene by introducing ammonia water and hydrazine hydrate.

[0025] In some embodiments, in step A, the concentration of the water-soluble divalent manganese salt solution is 0.1-20 mol / L, wherein the water-soluble divalent manganese salt comprises at least one of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate.

[0026] Illustratively, the concentration of the water-soluble divalent manganese salt solution can be any one of 0.1mol / L, 0.6mol / L, 0.8mol / L, 1mol / L, 3mol / L, 5mol / L, 7mol / L, 8mol / L, 10mol / L, 11mol / L, 12mol / L, 13mol / L, 14mol / L, 15mol / L, 16mol / L, 17mol / L, 18mol / L, 19mol / L, and 20mol / L, or a range value between any two of them, which is not specifically limited in the embodiments of the present application.

[0027] In some embodiments, in step B, the concentration of the graphene oxide aqueous solution is 0.2-10 g / L.

[0028] For example, the concentration of the graphene oxide aqueous solution can be any one of 0.2 g / L, 0.3 g / L, 0.5 g / L, 0.8, 1 g / L, 2 g / L, 3 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, and 10 g / L, or a range value between any two of them, which is not specifically limited in the embodiments of the present application.

[0029] In some embodiments, in step B, the ratio of the mass of the graphene oxide aqueous solution to the manganese ions in the water-soluble divalent manganese salt solution is 2-100 g:1 mol. A ratio higher or lower than this ratio will result in a serious reduction in the performance of the Mn3O4 / graphene composite.

[0030] For example, the ratio of the mass of the graphene oxide aqueous solution to the manganese ions in the water-soluble divalent manganese salt solution can be 2g:1mol, 5g:1mol, 10g:1mol, 15g:1mol, 20g:1mol, 25g:1mol, 26g:1mol, 30g:1mol, 40g:1mol, 50g:1mol, 60g:1mol, 75g:1mol, 76g:1mol, 78g:1mol, 80g:1mol, 85g:1mol, 90g:1mol, 92g:1mol, g:1mol, 95g:1mol, 100g:1mol, and the stirring time can be 5h, 6h, 8h, 9h, 10h, 12h, 15h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 75h, 80h, 82h, 85h, 88h, 90h, 92h, 95h, 96h, 98h, 99h, and 100h, or any one of the point values ​​or the range value between any two of them, which is not specifically limited in the embodiments of the present application.

[0031] In some embodiments, in step C, the molar ratio of the quaternary ammonium base to the manganese ions in the water-soluble divalent manganese salt solution in step B is 1-20:1. A molar ratio higher or lower than this will result in the final failure to react and produce Mn3O4.

[0032] For example, the molar ratio of the quaternary ammonium base to the manganese ions in the water-soluble divalent manganese salt solution can be any one of 1:1, 3:1, 4:1, 5:1, 7:1, 10:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, and 20:1, or a range between any two of the above, which is not specifically limited in the embodiments of the present application.

[0033] In some embodiments, in step C, the molar ratio of hydrogen peroxide to manganese ions in the water-soluble divalent manganese salt solution in step B is 1-20:1. A molar ratio higher or lower than this will result in the final failure to react and produce Mn3O4.

[0034] For example, the molar ratio of hydrogen peroxide to manganese ions in the water-soluble divalent manganese salt solution can be any one of 1:1, 2:1, 3:1, 5:1, 6.5:1, 7:1, 8:1, 10:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, and 20:1, or a range between any two of the above, which is not specifically limited in the embodiments of the present application.

[0035] In some embodiments, in step C, the quaternary ammonium base includes at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide, and the stirring time is 5 to 100 hours.

[0036] In some embodiments, in step C, the molar ratio of the ammonia water to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.5-10:1, and the molar ratio of the hydrazine hydrate to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.1-2:1. If the ratios are higher or lower than the above ratios, the Mn3O4 / graphene composite cannot be formed.

[0037] Illustratively, the molar ratio of ammonia water to manganese ions in the water-soluble divalent manganese salt solution can be 0.5:1, 0.6:1, 0.8:1, 1:1, 1.73:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and the molar ratio of hydrazine hydrate to manganese ions in the water-soluble divalent manganese salt solution can be 0.1:1, 0.15:1, 0.2:1, 0.22:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, any one of the point values ​​or the range value between any two thereof, which is not specifically limited in the embodiments of the present application.

[0038] In some embodiments, in step C, the water bath heating reaction is performed at a temperature of 50-100° C. for a time of 20-200 min.

[0039] Illustratively, the temperature of the water bath heating reaction can be 50°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, or 100°C, and the time can be any one of 20 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 175 min, 180 min, 185 min, 190 min, or 200 min, and the embodiment of the present application is not specifically limited to this.

[0040] On the other hand, the present invention provides an application of the Mn3O4 / graphene composite prepared by the above preparation method in an energy storage device.

[0041] Illustratively, the energy storage device may be a zinc ion battery, a lithium ion battery, a sodium ion battery, or a supercapacitor, which is not specifically limited in the embodiments of the present application.

[0042] The method of the present invention is based on the fact that Mn3O4 is a transition metal oxide with high specific capacity and good electrochemical performance. Due to its unique structural characteristics and physical and chemical properties, it has a wide range of applications in the energy storage field, especially the battery industry.

[0043] The method of the present invention introduces graphene into Mn3O4, which not only prevents Mn3O4 from agglomerating but also improves its structural stability, helping to suppress the material's volume expansion and contraction during charge and discharge, thereby increasing cycle life and reducing capacity decay. Furthermore, the highly conductive graphene can form a conductive network between the Mn3O4 particles, creating efficient electron transport channels, improving the interfacial contact between the electrode material and the electrolyte, and promoting ion transport and diffusion. Due to these synergistic effects, the Mn3O4 / graphene composite exhibits excellent electrochemical properties, with high specific capacity, high energy density, and excellent rate and cycling performance.

[0044] The preparation method of the present invention is simple and economical, does not require high temperature, high pressure and complicated preparation process, and can be prepared by simply stirring at room temperature combined with water bath reaction, which is low in cost and suitable for large-scale production. It has the advantages of simplicity, economy and high efficiency.

[0045] The Mn3O4 / graphene composite prepared using the method of the present invention has broad application prospects in electrochemical energy storage devices such as zinc-ion batteries, lithium-ion batteries, sodium-ion batteries, and supercapacitors. This material exhibits significant advantages in high-performance energy storage, particularly in energy storage devices such as zinc-ion batteries, meeting the requirements of high energy density and long cycle life, and possesses significant application value.

[0046] In order to objectively evaluate the technical effects of the embodiments of the present disclosure, the technical solutions provided by the present disclosure will be described in detail and exemplarily through experimental examples below.

[0047] In order to make the present application easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are merely illustrative and do not limit the scope of application of the present invention.

[0048] Unless otherwise specified, the operations and processing methods involved in this application are conventional methods in the art.

[0049] Unless otherwise specified, the instruments used in this application are conventional instruments in this field.

[0050] Example 1

[0051] The graphene oxide aqueous solution used in this example was purchased from Suzhou Tanfeng Technology Co., Ltd. with a concentration of 5 g / L.

[0052] The preparation method of the Mn3O4 / graphene composite of this embodiment includes the following steps: ① Add MnCl2 to deionized water and stir until it is completely dissolved. The concentration of MnCl2 in the solution is 3 mol / L.

[0053] ② Add graphene oxide aqueous solution to the above solution and stir until uniform. The mass of graphene oxide is related to the Mn content in the solution. 2+ The ratio is 22g:1mol.

[0054] ③ Add tetramethylammonium hydroxide (TMA·OH) and hydrogen peroxide (H2O2) to the above solution and stir vigorously to generate a black precipitate. 2+ The molar ratios were 4:1 and 6.5:1, respectively, and stirred for 12 h.

[0055] ④ Add ammonia water and hydrazine hydrate to the above solution, where the molar ratio of ammonia water to manganese ions in the solution is 1.73:1; the molar ratio of hydrazine hydrate to manganese ions in the solution is 0.35:1. Then, heat in an 85°C water bath for 1 hour to form a brown precipitate.

[0056] ⑤ The obtained precipitate is filtered, washed, and dried to obtain a Mn3O4 / graphene composite.

[0057] pass Figure 1 It can be seen from the scanning electron microscope image of the Mn3O4 / graphene composite prepared in Example 1 that a large number of Mn3O4 nanoparticles are anchored on the surface of the wrinkled graphene nanosheets.

[0058] Example 2

[0059] The graphene oxide used in this embodiment was prepared by the commonly used Hummers method, and the graphene oxide was dispersed in water to prepare a graphene oxide aqueous solution with a concentration of 6 g / L.

[0060] The preparation method of the Mn3O4 / graphene composite of this embodiment includes the following steps: ① Add MnSO4 to deionized water and stir until completely dissolved. The concentration of MnSO4 in the solution is 3 mol / L.

[0061] ② Add graphene oxide aqueous solution to the above solution and stir until uniform. The mass of graphene oxide is related to the Mn content in the solution. 2+ The ratio is 6g:1mol.

[0062] ③ Add tetramethylammonium hydroxide (TMA·OH) and hydrogen peroxide (H2O2) to the above solution and stir vigorously to generate a black precipitate. 2+ The molar ratios were 3:1 and 5:1, respectively, and stirred for 15 h.

[0063] ④ Add ammonia water and hydrazine hydrate to the above solution, where the molar ratio of ammonia water to manganese ions in the solution is 3:1; the molar ratio of hydrazine hydrate to manganese ions in the solution is 1:1. Then, heat in an 85°C water bath for 1 hour to form a brown precipitate.

[0064] ⑤ The obtained precipitate is filtered, washed, and dried to obtain a Mn3O4 / graphene composite.

[0065] Example 3

[0066] The graphene oxide used in this embodiment was prepared by the commonly used Hummers method, and the graphene oxide was dispersed in water to prepare a graphene oxide aqueous solution with a concentration of 4 g / L.

[0067] The preparation method of the Mn3O4 / graphene composite of this embodiment includes the following steps: ① Add Mn(NO3)2 to deionized water and stir until completely dissolved. The concentration of Mn(NO3)2 in the solution is 2 mol / L.

[0068] ② Add graphene oxide aqueous solution to the above solution and stir until uniform. The mass of graphene oxide is related to the Mn content in the solution. 2+ The ratio is 44.5g:1mol.

[0069] ③ Add tetrabutylammonium hydroxide (TBA·OH) and hydrogen peroxide (H2O2) to the above solution and stir vigorously to generate a black precipitate. 2+ The molar ratios were 12:1 and 15:1, respectively, and stirred for 8 h.

[0070] ④ Add ammonia water and hydrazine hydrate to the above solution, where the molar ratio of ammonia water to manganese ions in the solution is 8:1, and the molar ratio of hydrazine hydrate to manganese ions in the solution is 1.8:1. Then, heat in a 90°C water bath for 0.8 h to form a brown precipitate.

[0071] ⑤ The obtained precipitate is filtered, washed, and dried to obtain a Mn3O4 / graphene composite.

[0072] Example 4

[0073] The graphene oxide used in this example was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The graphene oxide was ultrasonically dispersed in deionized water to obtain a graphene oxide aqueous solution. The mass concentration of the graphene oxide aqueous solution was 5 g / L.

[0074] The preparation method of the Mn3O4 / graphene composite of this embodiment includes the following steps: ① Add Mn(CH3COO)2 to deionized water and stir until completely dissolved. The concentration of Mn(CH3COO)2 in the solution is 5 mol / L.

[0075] ② Add graphene oxide aqueous solution to the above solution and stir until uniform. The mass of graphene oxide is related to the Mn content in the solution. 2+ The ratio is 22g:1mol.

[0076] ③ Add tetraethylammonium hydroxide (TEAH) and hydrogen peroxide (H2O2) to the above solution and stir vigorously to generate a black precipitate. 2+ The molar ratios were 8:1 and 9:1, and the mixture was stirred for 12 h.

[0077] ④ Add ammonia water and hydrazine hydrate to the above solution, where the molar ratio of ammonia water to manganese ions in the solution is 1:1; the molar ratio of hydrazine hydrate to manganese ions in the solution is 0.2:1. Then, heat in an 85°C water bath for 1 hour to form a brown precipitate.

[0078] ⑤ The obtained precipitate is filtered, washed, and dried to obtain a Mn3O4 / graphene composite.

[0079] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that in step ③, the amount of TMA·OH relative to the amount of Mn contained in the solution is 2+ The molar ratio is 25:1.

[0080] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that in step ③, the amount of H2O2 relative to the amount of Mn contained in the solution is 2+ The molar ratio is 0.5:1.

[0081] Comparative Example 3 The graphene oxide used in this comparative example 3 was prepared by the commonly used Hummers method, and the graphene oxide was dispersed in water to prepare a graphene oxide aqueous solution with a concentration of 10 g / L.

[0082] The preparation method of the Mn3O4 / graphene composite comprises the following steps: ① Under stirring conditions, KMnO4 is added to the graphene oxide aqueous solution, wherein the ratio of graphene oxide to KMnO4 is 32g:1mol.

[0083] ② Add hydrazine hydrate to the above solution and stir for 30 minutes. The molar ratio of hydrazine hydrate to KMnO4 in the solution is 8:1.

[0084] ③ Transfer the above solution to a polytetrafluoroethylene-lined stainless steel autoclave and heat it to 180°C in an oven for 6 hours.

[0085] ④ The product after the above reaction is filtered, washed, and dried to obtain a Mn3O4 / graphene composite.

[0086] Comparative Example 4 The graphene oxide powder used in this comparative example 4 was prepared by the commonly used Hummers method.

[0087] The preparation method of the Mn3O4 / graphene composite comprises the following steps: ① Grind KMnO4 into fine powder and mix it with graphene oxide powder.

[0088] ② The above mixture was dispersed in ethylene glycol by ultrasonication. The concentration of KMnO4 in the dispersion was 0.05 mol / L. After ultrasonic dispersion for 60 min, a brown-black solution was obtained.

[0089] ③ Transfer the brown-black solution to a round-bottom flask and heat it to 150°C in a constant temperature oil bath with vigorous stirring at a speed of 500 r / min.

[0090] ④ Then, ethylenediamine was rapidly injected into the above solution as a reducing agent, with the volume ratio of ethylenediamine to the above solution being 1:20. The solution was further heated to 200°C and stirred vigorously for 3 hours to produce a black precipitate. The stirring speed was 500 r / min.

[0091] ⑤ Cool the obtained black precipitate and filter it to obtain a manganese alkoxide / graphene composite slurry.

[0092] ⑥ Disperse the manganese alkoxide / graphene composite slurry in deionized water and stir for 30 minutes to convert the manganese alkoxide / graphene composite into a Mn3O4 / graphene composite by hydrolysis. The volume ratio of deionized water to ethylene glycol in ② is 5:1.

[0093] ⑦ The above product was washed alternately with anhydrous ethanol and deionized water for 5 times, and then dried to obtain a Mn3O4 / graphene composite.

[0094] Application Examples A zinc ion battery was assembled using the metal atom-doped Mn3O4 / graphene composite prepared in Example 1 as the cathode, zinc foil as the anode, and 1 mol / L ZnSO4+1 mol / L MnSO4 aqueous solution as the electrolyte, and the corresponding electrical performance tests were performed. Figure 2 It can be seen that at current densities of 0.1A / g, 0.2A / g, 0.5A / g, 1A / g, and 2A / g, the specific capacities are 522.3mAh / g, 439.2mAh / g, 340.9mAh / g, 255.2mAh / g, and 176.8mAh / g, respectively. When the current density is restored to 0.1A / g, the specific capacity reaches 528.3mAh / g, which is higher than the initial specific capacity at 0.1A / g, indicating that it has good rate performance and cycling reversibility.

[0095] Figure 3 The Lagung plots for the Mn3O4 / graphene composite cathodes prepared in Examples 1-4 and Comparative Examples 1-2 are shown. Example 1 exhibits a high energy density of 730.8 Wh / kg at 139.9 W / kg and a high energy density of 231.3 Wh / kg at a power density of 2615.2 W / kg, outperforming the other Examples and Comparative Examples. Furthermore, the reaction temperatures of Comparative Examples 3 and 4 were higher than those of Examples 1-4, and the energy densities of Comparative Examples 1-4 were lower than those of Examples 1-4.

[0096] Figure 4 The cycling performance test of the Mn3O4 / graphene composite cathode prepared in Example 1 at 1 A / g shows that after 800 cycles, the capacity retention rate is 90%, indicating excellent cycling stability.

[0097] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0098] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a Mn3O4 / graphene composite, characterized in that: The following steps are involved: A. Prepare a water-soluble divalent manganese salt solution and set aside; B. adding the graphene oxide aqueous solution to the water-soluble divalent manganese salt solution of step A and mixing to obtain a mixture; C. Add quaternary ammonium base and hydrogen peroxide to the mixture in step B, stir and react, then add ammonia water and hydrazine hydrate to carry out heating reaction in a water bath, filter, wash and dry the precipitate obtained after the reaction to obtain a Mn3O4 / graphene composite.

2. The preparation method according to claim 1, characterized in that In step A, the concentration of the water-soluble divalent manganese salt solution is 0.1-20 mol / L, wherein the water-soluble divalent manganese salt is at least one of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate.

3. The preparation method according to claim 1, characterized in that In step B, the concentration of the graphene oxide aqueous solution is 0.2-10 g / L.

4. The preparation method according to claim 1, characterized in that In step B, the ratio of the mass of the graphene oxide aqueous solution to the manganese ions in the water-soluble divalent manganese salt solution is 2-100 g:1 mol.

5. The preparation method according to claim 1, characterized in that In step C, the molar ratio of the quaternary ammonium base to the manganese ions in the water-soluble divalent manganese salt solution in step B is 1 to 20:

1.

6. The preparation method according to claim 1, characterized in that In step C, the molar ratio of the hydrogen peroxide to the manganese ions in the water-soluble divalent manganese salt solution in step B is 1 to 20:

1.

7. The preparation method according to claim 1, 5 or 6, characterized in that: The quaternary ammonium base includes at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide, and the stirring time is 5 to 100 hours.

8. The preparation method according to claim 1, characterized in that In step C, the molar ratio of the ammonia water to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.5-10:1, and the molar ratio of the hydrazine hydrate to the manganese ions in the water-soluble divalent manganese salt solution in step A is 0.1-2:

1.

9. The preparation method according to claim 1, characterized in that In step C, the water bath heating reaction temperature is 50-100° C., and the time is 20-200 min.

10. Use of a Mn3O4 / graphene composite prepared by the preparation method according to any one of claims 1 to 9 in an energy storage device.

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