Selenium-doped Mn3O4 nanoflower as well as preparation method and application thereof

Abstract

The invention discloses a selenium-doped Mn3O4 nanoflower as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing a solution; (2) precipitation reaction; (3) vacuum drying; and (4) low-temperature selenylation induction reaction. The preparation method comprises the following steps: firstly, preparing MnO2 nanoflowers by adopting a precipitation reaction, and then carrying out a low-temperature selenylation induction reaction on the MnO2 nanoflowers, so as to successfully synthesize the selenium-doped Mn3O4 nanoflower positive electrode material. Selenium doping not only can improve the conductivity of Mn3O4 and increase the active sites of the material, but also can improve the structural stability of the electrode in the charging and discharging process, and shows more excellent zinc storage performance. In addition, the synthesis method is low in cost, simple to operate and suitable for large-scale production, and has application potential.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc ion battery materials, and in particular relates to a preparation method and application of selenium-doped Mn3O4 nanoflowers. Background Art

[0002] In recent years, aqueous zinc-ion batteries have stood out in the field of electrochemical energy storage due to their high energy density, suitable redox potential, low cost, high safety and abundant resources, and are ideal green energy storage systems. Manganese-based oxides have unique advantages such as low cost, abundant reserves, environmental friendliness, low toxicity and multiple valence states, and are suitable for use as positive electrode materials for aqueous zinc-ion batteries. As a type of manganese-based oxide, manganese tetraoxide (Mn3O4) has a stable structure and mixed valence states that are prone to defects, and exhibits excellent electrochemical activity in the fields of catalysis and batteries.

[0003] The hydrothermal method is a common method for synthesizing manganese tetraoxide, which has been reported in multiple patents. Application No. 202211497656.X (a micron flower ball-shaped manganese tetraoxide and its preparation and application) synthesized micron flower ball-shaped manganese tetraoxide by hydrothermal reaction at 270°C, and strong acid and strong base were used in its synthesis process. Invention patent CN201910013948.3 (a micron flower ball-shaped manganese tetraoxide and its preparation and application) synthesized micron flower ball-shaped manganese tetraoxide by hydrothermal method. In the zinc ion battery test, the capacity was 102mAh / g after 100 cycles. Invention patent CN201711080427.7 (a positive electrode material for aqueous zinc ion batteries) obtained a nano-flower ball-shaped manganese tetraoxide material grown on a stainless steel mesh through a high-pressure hydrothermal reaction, and a zinc storage capacity of 296mAh / g can be obtained after 50 cycles at a current density of 0.1A / g. However, the hydrothermal method has high equipment requirements, poor safety, and high production costs, which are not conducive to large-scale synthesis. At the same time, the low capacity is not conducive to commercial application. Therefore, how to develop a simple synthesis of high-performance Mn3O4 aqueous zinc-ion battery positive electrode material is a difficult point. Summary of the invention

[0004] In view of the above technical problems and the shortcomings in the art, the present invention provides a selenium-doped Mn3O4 nanoflower and a preparation method thereof, and uses it as a positive electrode material for zinc ion batteries. The selenium-doped Mn3O4 nanoflower exhibits good stability and high specific capacity. The synthesis method is simple and can be used for large-scale industrial production.

[0005] In a first aspect, the present invention provides a method for preparing selenium-doped Mn3O4 nanoflowers, comprising the following steps:

[0006] a. Add potassium permanganate solution dropwise into manganese salt solution under stirring and let stand for a while;

[0007] b. Centrifugally filtering the solid-liquid mixture and vacuum drying to obtain MnO2 nanoflower powder;

[0008] c. Grind a certain mass of MnO2 nanoflower powder and selenium powder thoroughly, and calcine them in an inert gas to obtain selenium-doped Mn3O4 nanoflowers.

[0009] Preferably, in step a, the manganese salt is one or more of manganese chloride, manganese sulfate, manganese acetate and manganese nitrate.

[0010] Preferably, in step a, the molar ratio of potassium permanganate to manganese salt is 2:3.

[0011] Preferably, in step a, the dropping speed is 5-20 ml / min.

[0012] Preferably, in step a, the standing time is 3-9 hours.

[0013] Preferably, in step b, the vacuum drying temperature is 70° C. and the drying time is 12 h.

[0014] Preferably, in step c, the mass ratio of MnO2 nanoflower powder to selenium powder is 200:10-40.

[0015] Preferably, in step c, the protective atmosphere is any one of nitrogen, argon, argon-hydrogen mixed gas, etc.

[0016] Preferably, in step c, the calcination temperature is 300-400° C., more preferably 350±20° C.; and the calcination time is 1 to 3 hours.

[0017] In a second aspect, the present invention provides selenium-doped Mn3O4 nanoflowers prepared by the method described in the first aspect.

[0018] In a third aspect, the present invention provides the use of selenium-doped Mn3O4 nanoflowers prepared by the method described in the first aspect as positive electrode materials for zinc ion batteries.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention first adopts the coprecipitation method to synthesize MnO2 nanoflower powder, and then performs selenization treatment at low temperature to obtain selenium-doped Mn3O4 nanoflowers. The introduction of selenium can not only induce the transformation of MnO2 to Mn3O4 structure, but also can selenium-dope the Mn3O4 structure while retaining the original nanoflower morphology of MnO2. Selenium doping can make Mn3O4 have better conductivity, more active sites and more stable structure, thereby alleviating the internal stress and volume change caused by zinc ion insertion and extraction, and showing more excellent zinc storage performance. Compared with the hydrothermal method, this synthesis method has better safety and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD pattern of selenium-doped Mn3O4 nanoflowers prepared in Example 1.

[0021] Figure 2 This is the SEM image of the selenium-doped Mn3O4 nanoflowers prepared in Example 1.

[0022] Figure 3 This is the element distribution diagram of the selenium-doped Mn3O4 nanoflowers prepared in Example 1.

[0023] Figure 4 This is the XRD pattern of selenium-doped Mn3O4 nanoflowers prepared in Example 2.

[0024] Figure 5 This is the XRD pattern of selenium-doped Mn3O4 nanoflowers prepared in Example 4.

[0025] Figure 6 This is the XRD diagram of the MnO2 nanoflowers prepared in Comparative Example 1.

[0026] Figure 7 This is the XRD pattern of the sample material prepared in Comparative Example 2.

[0027] Figure 8 This is the XRD pattern of the sample material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0028] The present application is further described below in conjunction with specific embodiments.

[0029] It should be noted that the terms such as "upper", "lower", "left", "right", "middle", etc. cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of this application without substantially changing the technical content.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0031] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0032] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0033] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" expressly includes only A, only B, only C, and combinations of each thereof.

[0034] Concentration, amount and other numerical data can be presented in range format herein.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges contained in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including single numerals (such as 2,3,4) and sub-ranges (such as 1 to 3,2 to 4, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all the above-mentioned values ​​and ranges.In addition, no matter how the breadth of the described range or feature is, this explanation should be applicable.

[0035] Example 1

[0036] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70℃ drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder and 20mg of selenium powder were fully ground, calcined at 350℃ in a nitrogen atmosphere for 2h with a heating rate of 5℃ / min to obtain selenium-doped Mn3O4 nanoflowers, whose XRD is as follows: Figure 1 shown. Figure 2 This is the SEM image of selenium-doped Mn3O4 nanoflowers. Figure 3 The element distribution map shows that Selenium is uniformly doped into the Mn3O4 nanoflowers.

[0037] The selenium-doped Mn3O4 nanoflower prepared in Example 1 was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, and N-methyl-2-pyrrolidone solution was added. After electric stirring, it was coated on graphite paper, dried in a vacuum oven at 90°C for 12 hours, and punched into a circular electrode sheet with a diameter of 11mm as the positive electrode sheet. The metal zinc sheet was used as the electrode, Whatman glass fiber (GF / D) was used as the diaphragm, and the electrolyte was 2mol / L ZnSO4·7H2O+0.1mol / L MnSO4 solution. CR2032 button batteries were assembled in air. Under a constant temperature environment of 25°C, the zinc positive electrode cycle test was carried out at a current density of 0.2A / g and a cut-off voltage of 0.8-1.8V. After 100 cycles of the selenium-doped Mn3O4 nanoflower positive electrode material, the discharge specific capacity remained at 315.1mAh / g.

[0038] Example 2

[0039] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70°C drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder and 10mg of selenium powder were fully ground, calcined at 350°C in a nitrogen atmosphere for 2h with a heating rate of 5°C / min to obtain selenium-doped Mn3O4 nanoflowers, whose XRD is as follows: Figure 4 As shown, there are certain impurities.

[0040] The selenium-doped Mn3O4 nanoflower prepared in Example 2 was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, and N-methyl-2-pyrrolidone solution was added. After electric stirring, it was coated on graphite paper, dried in a vacuum oven at 90°C for 12 hours, and punched into a circular electrode sheet with a diameter of 11mm as the positive electrode sheet. The metal zinc sheet was used as the electrode, Whatman glass fiber (GF / D) was used as the diaphragm, and the electrolyte was 2mol / L ZnSO4·7H2O+0.1mol / L MnSO4 solution. CR2032 button batteries were assembled in air. Under a constant temperature environment of 25°C, the zinc positive electrode cycle test was carried out at a current density of 0.2A / g and a cut-off voltage of 0.8-1.8V. After 100 cycles of the selenium-doped Mn3O4 nanoflower positive electrode material, the discharge specific capacity remained at 224.6mAh / g.

[0041] Example 3

[0042] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70℃ drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder and 40mg of selenium powder were fully ground, calcined at 350℃ in a nitrogen atmosphere for 2h with a heating rate of 5℃ / min to obtain selenium-doped Mn3O4 nanoflowers, whose XRD is as follows: Figure 5 As shown, there are certain impurities.

[0043] The selenium-doped Mn3O4 nanoflower prepared in Example 3 was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, and N-methyl-2-pyrrolidone solution was added. After electric stirring, it was coated on graphite paper, dried in a vacuum oven at 90°C for 12 hours, and punched into a circular electrode sheet with a diameter of 11mm as the positive electrode sheet. The metal zinc sheet was used as the electrode, Whatman glass fiber (GF / D) was used as the diaphragm, and the electrolyte was 2mol / L ZnSO4·7H2O+0.1mol / L MnSO4 solution. CR2032 button batteries were assembled in air. Under a constant temperature environment of 25°C, the zinc positive electrode cycle test was carried out at a current density of 0.2A / g and a cut-off voltage of 0.8-1.8V. After 100 cycles of the selenium-doped Mn3O4 nanoflower positive electrode material, the discharge specific capacity remained at 174.4mAh / g.

[0044] Comparative Example 1

[0045] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70℃ drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder was calcined at 350℃ in a nitrogen atmosphere for 2h with a heating rate of 5℃ / min, and MnO2 nanoflower powder was still obtained, and its XRD is as follows Figure 6 shown.

[0046] The MnO2 nanoflower powder prepared in Comparative Example 1 was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, and N-methyl-2-pyrrolidone solution was added. After electric stirring, it was coated on graphite paper, dried in a vacuum oven at 90°C for 12 hours, and punched into a circular electrode sheet with a diameter of 11mm as the positive electrode sheet. The metal zinc sheet was used as the electrode, Whatman glass fiber (GF / D) was used as the diaphragm, and the electrolyte was 2mol / L ZnSO4·7H2O+0.1mol / L MnSO4 solution. CR2032 button batteries were assembled in air. Under a constant temperature environment of 25°C, the zinc positive electrode cycle test was carried out at a current density of 0.2A / g and a cut-off voltage of 0.8-1.8V. After 100 cycles of the MnO2 nanoflower powder positive electrode material, the discharge specific capacity remained at 115.6mAh / g.

[0047] Comparative Example 2

[0048] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70℃ drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder and 20mg of sulfur powder were fully ground, calcined at 350℃ in a nitrogen atmosphere for 2h, and the heating rate was 5℃ / min. The XRD characteristics of the obtained sample are as follows: Figure 7 As shown, its structure is not that of Mn3O4, and there are certain impurities.

[0049] Comparative Example 3

[0050] 2mmol potassium permanganate (KMnO4) and 3mmol manganese chloride tetrahydrate (MnCl2·4H2O) were added to 100ml deionized water to obtain solution A and solution B respectively. Solution A was added dropwise to solution B at a dripping rate of 10ml / min using a peristaltic pump, stirred thoroughly for 30 minutes and allowed to stand for 6h. After the reaction, the black precipitate was repeatedly washed with deionized water, and then vacuum dried in a 70℃ drying oven for 12h to obtain MnO2 nanoflower powder. 200mg of MnO2 nanoflower powder and 20mg of tellurium powder were fully ground, calcined at 350℃ in a nitrogen atmosphere for 2h, and the heating rate was 5℃ / min. The XRD characteristics of the obtained sample are as follows: Figure 8 As shown, its structure is not that of Mn3O4, and there are certain impurities.

[0051] The above embodiments are only specific embodiments of the present invention and are not intended to limit its scope. Those skilled in the art may make many possible modifications based on the prior art, or modify them into equivalent embodiments with equivalent changes. Without departing from the spirit and technical solution of the present invention, various modifications and improvements made by those of ordinary skill in the art to the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing selenium-doped Mn3O4 nanoflowers, characterized in that: The following steps are involved: a. Add potassium permanganate solution dropwise into manganese salt solution under stirring and let stand for a while; b. Centrifugally filtering the solid-liquid mixture and vacuum drying to obtain MnO2 nanoflower powder; c. Grind a certain mass of MnO2 nanoflower powder and selenium powder thoroughly, and calcine them in an inert gas to obtain selenium-doped Mn3O4 nanoflowers.

2. The method according to claim 1, characterized in that In step a, the manganese salt is one or more of manganese chloride, manganese sulfate, manganese acetate and manganese nitrate.

3. The method according to claim 1, characterized in that In step a, the molar ratio of potassium permanganate to manganese salt is 2:

3.

4. The method according to claim 1, characterized in that In step a, the dropping speed is 5-20 ml / min.

5. The method according to claim 1, characterized in that In step a, the standing time is 3-9h.

6. The method according to claim 1, characterized in that In step c, the mass ratio of MnO2 nano flower powder to selenium powder is 200:10~40.

7. The method according to claim 1, characterized in that In step c, the protective atmosphere is any one of nitrogen, argon, and argon-hydrogen mixed gas.

8. The method according to claim 1, characterized in that In step c, the calcination temperature is 300-400° C., preferably 350±20° C.; and the calcination time is 1-3 hours.

9. A selenium-doped Mn3O4 nanoflower prepared by the method according to any one of claims 1 to 8.

10. Use of selenium-doped Mn3O4 nanoflowers prepared by the method according to any one of claims 1 to 8 as positive electrode materials for zinc ion batteries.

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