Preparation method and application of manganese-doped cobalt-nickel layered double hydroxide electrode material

Abstract

The invention discloses a preparation method and application of a manganese-doped cobalt-nickel layered double hydroxide electrode material, and the method comprises the following steps: mixing and dissolving a cobalt salt and a nickel salt in water to prepare a cobalt salt solution, adding pretreated manganese powder under a stirring condition, uniformly mixing, covering with a preservative film, standing and storing for 24 hours, and drying to obtain the manganese-doped cobalt-nickel layered double hydroxide electrode material. And centrifugally separating the generated product, washing with deionized water for three times, and drying to obtain the manganese-doped cobalt-nickel layered double hydroxide. The manganese-doped cobalt-nickel layered double hydroxide electrode material overcomes the defects that cobalt-nickel double hydroxide has high surface energy and is easy to gather, so that the specific surface area of the electrode material is small and the like to a certain extent, the electrochemical charge transfer efficiency is promoted, and the adsorption capacity of electrolyte is enhanced, so that good electrochemical performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic functional materials, and in particular relates to a preparation method and application of a manganese-doped cobalt-nickel layered double hydroxide electrode material. Background Art

[0002] Layered double hydroxide (LDH) is a typical hydrotalcite material. Its unique three-dimensional hierarchical porous structure and large specific surface area make it an extremely attractive supercapacitor electrode material with its low cost and high specific capacity. Among them, cobalt nickel layered double hydroxide (NiCo-LDHs) has abundant active sites and has the characteristics of high specific capacitance, good electrochemical stability and low toxicity, and is considered to be a promising pseudocapacitive electrode material. Cobalt nickel double hydroxide (NiCo-LDHs) has the disadvantages of easy agglomeration and poor conductivity, which limits its electrochemical performance. In order to effectively overcome these problems, its conductivity is improved by doping or ion exchange, and compounding with other conductive materials. For example, the patent discloses a wine lees porous carbon / cobalt nickel hydroxide electrode material and its preparation process (publication number: CN 112289591 A, application date: 2020-10-23). ​​The method is to prepare carbonized wine lees porous carbon as a substrate material, and then obtain cobalt nickel double metal hydroxide after hydrothermal reaction with cobalt nitrate hexahydrate, nickel nitrate hexahydrate, urea and polyvinyl pyrrolidone. Cobalt and nickel elements are loaded on the surface of wine lees porous carbon in the form of Co-Ni-LDH, and finally obtain wine lees porous carbon / cobalt nickel hydroxide electrode material. In order to effectively overcome these problems, some researchers have proposed a modification strategy. By introducing a third metal element (such as V, Mn or Cr), the charge density of the laminate can be adjusted, the bandwidth of the material can be changed, the conductivity can be improved, and sufficient active sites can be provided, thereby obtaining excellent performance (Regeneration Mechanism, Modification Strategy, and Environment Application of Layered Double Hydroxides: Insights Based on Memory Effect. Coord. Chem. Rev. 2022, 450 , 214253 DOI: 10.1016 / j.ccr.2021.214253).

[0003] According to existing reports, the process basically uses the hydrothermal method, which is complex, energy-intensive, and difficult to mass-produce, hindering its industrial application. Therefore, developing a high-specific-surface-area porous structure for electrode materials based on new mechanisms and pathways has become an important and challenging topic in related research. Summary of the invention

[0004] In view of this, in order to solve the above problems, the present invention provides a preparation method and application of a sheet-like manganese-doped cobalt-nickel double hydroxide electrode material. In the present invention, manganese powder is added to a mixed aqueous solution of cobalt and nickel salts at room temperature, and the product is centrifuged, washed and dried after standing for 24 hours to obtain a manganese-doped cobalt-nickel double hydroxide electrode material. The method has the advantages of mild reaction conditions, simple process, low energy consumption and short time consumption. To a certain extent, it overcomes the disadvantages of cobalt-nickel double hydroxide having a high surface energy, easy aggregation, and a small specific surface area of ​​the electrode material, promotes the electrochemical charge transfer efficiency, and enhances the adsorption capacity of the electrolyte, thereby obtaining good cycle performance.

[0005] In order to solve the above technical problems, the present application discloses a preparation method and application of a manganese-doped cobalt-nickel layered double hydroxide electrode material, comprising the following steps: Step 1, dissolving cobalt salt and nickel salt in water to obtain a mixed solution of cobalt and nickel salts; Step 2: Add the pretreated manganese powder under stirring, cover with plastic wrap and react for 24 hours.

[0006] Step 3, the green flocculent precipitate prepared in step 2 is centrifuged, washed three times with deionized water, and dried to obtain a manganese-doped cobalt-nickel layered double hydroxide electrode material; Furthermore, in step 1, the concentration of the cobalt salt and nickel salt solution is 0.01-1.00 mol / L.

[0007] Furthermore, the cobalt salt in step 1 is selected from one of cobalt nitrate, chlorine chloride or cobalt acetate, and the nickel salt is selected from one of nickel nitrate, nickel chloride or nickel acetate. Furthermore, in step 2, the molar ratio of the cobalt salt to the nickel salt is 1:4-1:20; the molar ratio of the nickel salt to the manganese powder is 1:0.6-1:2.

[0008] Furthermore, the stirring conditions in step 2 include a temperature of 20-25° C. and a rotation speed of 180-220 r / min.

[0009] Furthermore, the drying temperature in step 3 is 50-70°C.

[0010] The invention also discloses a manganese-doped cobalt-nickel layered double hydroxide electrode material prepared by the above preparation method.

[0011] The present invention also discloses an application of the above-mentioned manganese-doped cobalt-nickel layered double hydroxide electrode material in a supercapacitor, wherein the prepared manganese-doped cobalt-nickel layered double hydroxide electrode material is uniformly mixed with acetylene black and PTFE in a mass ratio of 80:10:10 to form a paste, and the paste is uniformly coated on a 1 cm 2The foamed nickel current collector was pressed into sheets under a pressure of 10 MPa to prepare CoNiMn-LDH electrode material; the CoNiMn-LDH electrode material was used as the positive electrode, the activated carbon was used as the negative electrode, and a 3 mol / L KOH solution was used as the electrolyte.

[0012] Compared with the prior art, the present invention can achieve the following technical effects: 1) The present invention utilizes metallic manganese for doping through redox reaction. This special doping method can effectively improve the performance of cobalt nickel double hydroxide supercapacitors.

[0013] 2) The manganese-doped cobalt-nickel double hydroxide electrode material obtained in the present invention can reach a capacity of 745.0 C / g after being used in a supercapacitor.

[0014] 3) The preparation conditions of the present invention are all carried out at room temperature, without the need for complicated processes such as heating and hydrothermal processes.

[0015] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a SEM picture of the manganese-doped cobalt-nickel layered double hydroxide prepared in Example 1 of the present invention; Figure 2 is the XRD spectrum of the manganese-doped cobalt-nickel layered double hydroxide prepared in Example 1 of the present invention; Figure 3 is a TEM photograph of the manganese-doped cobalt-nickel layered double hydroxide prepared in Example 1 of the present invention; Figure 4 This is the EPR spectrum of the manganese-doped cobalt-nickel layered double hydroxide prepared in Example 1 of the present invention; Figure 5 1 is a graph showing the specific capacity of manganese-doped cobalt-nickel layered double hydroxides prepared at different current densities using different ratios of cobalt salt and nickel salt prepared in Example 1 of the present invention; Figure 6 This is a cycle stability diagram of the manganese-doped cobalt-nickel layered double hydroxide prepared in Example 1 of the present invention at a current density of 5 A / g. DETAILED DESCRIPTION

[0017] The following will describe the implementation methods of the present invention in detail with reference to the embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0018] The present application discloses a preparation method and application of a manganese-doped cobalt-nickel layered double hydroxide electrode material, comprising the following steps: Step 1, dissolving cobalt salt and nickel salt in water to prepare a 0.01-1.00 mol / L cobalt salt and nickel salt mixed aqueous solution, wherein the cobalt salt is cobalt nitrate, cobalt chloride and cobalt acetate, and the molar ratio of the cobalt salt solution to the nickel salt is 1:4-1:20.

[0019] Step 2: Add manganese powder and stir at room temperature (20-25°C) at a speed of 180-220 r / min. The molar ratio of nickel salt to manganese powder is 1:0.6-1:2. The ratio of nickel salt to manganese powder is the key to the experiment. Under appropriate conditions, a green flocculent precipitate is formed. Cover with plastic wrap and let stand for 24 hours.

[0020] Step 3: centrifuge the obtained green flocculent precipitate, wash it three times with deionized water, and dry it at 50-70° C. to obtain a manganese-doped cobalt-nickel layered double hydroxide electrode material.

[0021] In this preparation method, 1. Manganese powder is used instead of manganese salt. If manganese salt is used directly, it is difficult to self-hydrolyze to form OH - , which makes it difficult to form cobalt-nickel double hydroxide, and the resulting product has poor performance as a supercapacitor positive electrode material.

[0022] 2. The reason why manganese is doped with cobalt-nickel double hydroxide is that manganese hydroxide is stable in strong alkaline solution. 2+ The phase change of cobalt nickel double hydroxide during the charging and discharging process is inhibited to a certain extent.

[0023] 3. The ratio of nickel salt to manganese powder is the key to the experiment. The molar ratio is 1:0.6-1:2. It is difficult to form a two-dimensional layered double hydroxide material with a large specific surface area if the molar ratio is greater or less than this range.

[0024] 4. The substance obtained by centrifugation is the green flocs on the upper layer of the mixed solution after standing for 24 hours, not the black substance at the bottom.

[0025] Example 1 Cobalt chloride and nickel chloride were mixed and dissolved in deionized water, the molar ratio of cobalt chloride to nickel chloride was 1:9, the concentration of the mixed aqueous solution of cobalt salt and nickel salt was 0.050 mol / L, and manganese powder was added under stirring conditions of 200 r / min and 25 °C, the molar ratio of nickel chloride to manganese powder was 1:1.1. After the mixed solution was stirred for a period of time, a green flocculent precipitate was formed, and the mixture was covered with plastic wrap and allowed to stand for 24 h. The product was centrifuged, washed three times with deionized water, and dried at 70 °C to obtain a manganese-doped cobalt-nickel layered double hydroxide electrode material. The scanning electron microscope photo of the obtained product is shown in FIG. Figure 1 As shown in the XRD spectrum Figure 2 As shown in the TEM images Figure 3 The EPR spectrum of manganese-doped cobalt-nickel double hydroxide is shown in Figure 4 As shown in Figure 2, the electronic paramagnetic signal at g = 2.003 is generated by electrons captured by oxygen vacancies. The specific capacity of the prepared manganese-doped cobalt-nickel layered double hydroxide at different current densities is shown in Figure 2. Figure 5 As shown in Figure 2, its specific capacity can reach 741.4 C / g at a current density of 1 A / g. The cycle performance of the prepared manganese-doped cobalt-nickel layered double hydroxide electrode material assembled into a supercapacitor is shown in Figure 2. Figure 6 As shown in Figure 2, the capacity retention rate is as high as 85.5% after 10,000 cycles at a current density of 5 A / g.

[0026] Example 2 Cobalt chloride and nickel chloride were mixed and dissolved in deionized water, the molar ratio of cobalt chloride to nickel chloride was 1:4, the concentration of the mixed aqueous solution of cobalt salt and nickel salt was 0.050 mol / L, and manganese powder was added under stirring conditions of 210 r / min and 23 °C, the molar ratio of nickel chloride to manganese powder was 1:1.25. After stirring the mixed solution for a period of time, a green flocculent precipitate was formed, and the mixture was covered with plastic wrap and allowed to stand for 24 h. The product was separated by centrifugation, washed three times with deionized water, and dried at 65 °C to obtain a manganese-doped cobalt-nickel layered double hydroxide electrode material. The specific capacity diagram of the prepared manganese-doped cobalt-nickel layered double hydroxide at different current densities is shown in Figure 2. Figure 5 As shown in the figure, its specific capacity can reach 663.0 C / g at a current density of 1 A / g.

[0027] Example 3 Cobalt chloride and nickel chloride were mixed and dissolved in deionized water, the molar ratio of cobalt chloride to nickel chloride was 1:19, the concentration of the mixed aqueous solution of cobalt salt and nickel salt was 0.050 mol / L, and manganese powder was added under stirring conditions of 190 r / min and 21 °C, the molar ratio of nickel chloride to manganese powder was 1:1.05. After stirring the mixed solution for a period of time, a green flocculent precipitate was formed, and the mixture was covered with plastic wrap and allowed to stand for 24 h. The product was separated by centrifugation, washed three times with deionized water, and dried at 60 °C to obtain a manganese-doped cobalt-nickel layered double hydroxide electrode material. The specific capacity diagram of the prepared manganese-doped cobalt-nickel layered double hydroxide at different current densities is shown in Figure 2. Figure 5 As shown, its specific capacity can reach 673.1 C / g at a current density of 1 A / g.

[0028] The above description shows and describes several preferred embodiments of the invention, but as mentioned above, it should be understood that the invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. Changes and modifications made by those skilled in the art should be within the scope of protection of the claims attached to the invention without departing from the spirit and scope of the invention.

Claims

1. A method for preparing a manganese-doped cobalt-nickel layered double hydroxide electrode material, characterized in that: The following steps are involved: Step 1, dissolving cobalt salt and nickel salt in water to obtain a mixed solution of cobalt and nickel salts; Step 2: Add the pretreated manganese powder under stirring, cover with plastic wrap and react for 24 hours.

2. Step 3, the green flocculent precipitate prepared in step 2 is centrifuged, washed three times with deionized water, and dried to obtain manganese-doped cobalt-nickel layered double hydroxide; The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that The concentration of cobalt salt and nickel salt solution is 0.01-1.00 mol / L.

3. The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that: The cobalt salt in step 1 is selected from one of cobalt nitrate, chlorine chloride or cobalt acetate, and the nickel salt is selected from one of nickel nitrate, nickel chloride or nickel acetate.

4. The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that: The molar ratio of the cobalt salt to the nickel salt is 1:4-1:20; the molar ratio of the nickel salt to the manganese powder is 1:0.6-1:

2.

5. The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that: The stirring conditions in step 2 are a temperature of 20-25° C. and a rotation speed of 180-220 r / min.

6. The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that: The temperature of the static storage is 20-25°C.

7. The method for preparing the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 1, characterized in that The drying temperature in step 3 is 50-70°C.

8. A manganese-doped cobalt-nickel layered double hydroxide electrode material prepared by the preparation method according to any one of claims 1 to 7.

9. An application of the manganese-doped cobalt-nickel layered double hydroxide electrode material according to claim 8 in a supercapacitor, characterized in that: The following steps are involved: The prepared manganese-doped cobalt-nickel layered double hydroxide electrode material was uniformly mixed with acetylene black and PTFE in a mass ratio of 80:10:10 to form a paste, which was evenly coated on a 1 cm 2 The foamed nickel current collector was pressed into a sheet under a pressure of 10 MPa to prepare a CoNiMn-LDH electrode sheet, and a 3 mol / L KOH solution was used as the electrolyte.

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