Manganese-aluminum layered double hydroxide asymmetric supercapacitor and preparation method thereof

Abstract

The invention discloses a manganese-aluminum layered double hydroxide asymmetric supercapacitor and a preparation method thereof, and belongs to the field of new energy material preparation, and the method comprises the steps: taking foamed nickel as a carrier, and preparing a positive electrode material MnAl-LDH of a manganese-aluminum hydroxide two-dimensional layered nanosheet structure through a one-step hydrothermal method; the structure of the material provides an electron transmission channel, increases active sites and improves conductivity. And the specific surface area of the electrode material is greatly increased. The asymmetric supercapacitor MnAl-LDH-coated NC / / AC is formed by assembling the MnAl-LDH-coated NC / AC and the activated carbon, so that the problem of low energy density of a supercapacitor in the prior art is solved. Compared with other non-equivalent supercapacitor electrode materials, the electrode material has higher energy density and power density, and meanwhile, the electrode material prepared by the invention is high in activity, stable in structure and high in cycle efficiency, and is an electrode with high area specific capacitance and high catalytic efficiency. The preparation method has the advantages of simplicity, environmental friendliness, low cost, high efficiency and the like.

Description

Technical Field

[0001] This invention belongs to the field of new energy material preparation technology, and relates to a manganese-aluminum layered double hydroxide asymmetric supercapacitor and its preparation method, more specifically, to a MnAl-LDH supercapacitor and its preparation method. Background Technology

[0002] Supercapacitors are an innovative energy storage solution that is gaining popularity due to their high power density, rapid charge / discharge capabilities, and extended lifespan. Traditional symmetric supercapacitors have limitations in energy density, hindering their ability to meet the growing energy storage demands. Asymmetric supercapacitors (ASCs) can address this problem. With the development of portable electronic devices, electric vehicles, and smart grids, energy storage systems must be upgraded. These devices require high energy concentration and power density to enable rapid charge / discharge and ensure continuous operation. Traditional symmetric supercapacitors sometimes fail to meet these standards due to limitations in electrode materials. In such cases, ASCs represent an effective energy storage solution. These devices have become a focus of contemporary research by combining a variety of electrode materials, expanding the operating voltage range and increasing energy density. ASC electrode materials possess unique electrochemical properties. The positive electrode material exhibits a higher redox potential, accelerating the Faraday process during charging and facilitating the storage of large amounts of charge. Conversely, the negative electrode material has a lower redox potential and accumulates charge through double-layer capacitance or pseudo-capacitance. During charging and discharging, the positive and negative electrode materials function at different voltage levels, enabling ASCs to operate over a wider voltage range and increase energy density. The positive electrode material is composed of transition metal oxides, while the negative electrode material is composed of carbon-based compounds and conductive polymers. Binary layered double hydroxide electrode materials have become a research hotspot due to their large specific surface area, numerous active sites, and stable structure. Recent studies have shown that MnAl-LDH has advantages such as affordability, environmental friendliness, low manufacturing cost, and low toxicity. Therefore, MnAl-LDH has received more attention in recent years and has become a more feasible and suitable alternative electrode component for high-performance supercapacitors. The two-dimensional nanolayered structure of MnAl-LDH can perfectly combine Mn and Al hydroxides, fully leveraging their synergistic effect. This will result in higher conductivity and ultra-high capacity than single hydroxides. However, some challenges remain. Different MnAl ratios can cause stacking of the two-dimensional nanolayered structure, making the contact between the active material and the electrolyte unstable, leading to significant differences in electrochemical performance. The spatial limitation of the two-dimensional structure of MnAl-LDH supercapacitors restricts ion diffusion and results in low charge-discharge retention, limiting charge transport rates and affecting charge-discharge performance. This also limits the rate performance and cycle stability of the supercapacitor. To address the above problems, the present invention provides the following technical solution. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a manganese-aluminum layered double hydroxide asymmetric supercapacitor, which solves the shortcomings of the MnAl-LDH electrode material prepared in the prior art, such as the instability of the two-dimensional nanolayered structure, low charge-discharge performance, and poor cycle stability in supercapacitor applications. At the same time, the method also solves the shortcomings of the existing synthesis technology, such as harsh synthesis conditions, cumbersome operation, high energy consumption, and environmental pollution.

[0004] Another object of the present invention is to provide a supercapacitor prepared by the above method.

[0005] The objective of this invention can be achieved through the following technical solutions: A manganese-aluminum layered double hydroxide asymmetric supercapacitor and its preparation method include the following steps: S1. Cut the nickel foam into 1.0×1.5cm2 pieces, sonicate with dilute hydrochloric acid for 10 minutes, wash with acetone and deionized water, and finally dry to obtain the nickel foam matrix; S2. Weigh 0.1 mmol Cl2H8MnO4 and Al(NO3)3·9H2O and dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor MnAl-LDH. S3. Weigh 2.0 mmol Cl2H8MnO4 and Al(NO3)3·9H2O, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B; S4. Place the precursor MnAl-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner, place it in an oven for heat treatment, cool it to 20℃, take it out and wash it three times with anhydrous ethanol and deionized water respectively. S5. Dry in a vacuum oven at 60°C for 12 hours and then cool to room temperature to obtain the MnAl-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in different proportions and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. The positive and negative electrode materials obtained in (5) and (7) are separated by a diaphragm and added to the KOH solution in (8) to assemble a supercapacitor.

[0006] Furthermore, in step S3, the molar ratio of Cl2H8MnO4 to Al(NO3)3·9H2O is 7:1, 5:1, 3:1, 1:1, or 1:3.

[0007] Furthermore, in step S4, the heat treatment conditions inside the oven are 140℃ for 16 hours.

[0008] Furthermore, in step S6, the ratio of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) is 8:1:1, 7:1:2, or 7:2:1.

[0009] The present invention also discloses a Mn3Al1-LDH supercapacitor electrode material, which is prepared by the above-described preparation method.

[0010] The beneficial effects of this invention are: 1. This invention discloses a method for preparing a high-performance non-isolated supercapacitor electrode material, Mn3Al1-LDH. MnAl-LDH is prepared via a one-step hydrothermal method, and the structure of the nanomaterial is controlled by adjusting the ratio of binary layered hydroxides. Mn3Al1-LDH exhibits an optimal two-dimensional layered structure, reducing nanosheet stacking. This special structure provides excellent electron transport channels, significantly increasing the specific surface area of ​​the electrode material, increasing the active sites and conductivity, resulting in faster electrolyte ion transfer and higher specific capacity. Simultaneously, the method of adjusting the ratio of binary metal ions solves the problem of difficult particle morphology control in existing technologies. Compared with traditional single-unit hydroxide electrodes, Mn3Al1-LDH exhibits significantly increased electrocatalytic activity and enhanced stability, making it an electrode with excellent electrochemical performance.

[0011] 2. The preparation method of this invention adopts a simple one-step hydrothermal method to prepare MnAl-LDH electrode material. Compared with other methods, it has the advantages of simple operation, environmental friendliness, low cost and high efficiency. Moreover, the electrode efficiency and conductivity of the prepared electrode material are significantly improved, thereby increasing the specific capacitance.

[0012] 3. The electrode material in this invention exhibits high electrocatalytic activity and cycle stability for redox reactions in alkaline media. Furthermore, the high specific surface area of ​​this electrode material is crucial for achieving high-energy-density electrochemical capacitor energy storage. The Mn3Al1-LDH composite material achieves this at 1 A·g -1 It can provide 3755 F·g at current density-1 High specific capacitance, at 10 A·g -1 It can provide 3325 F·g at current density -1 The Mn3Al1-LDH@NC / / AC supercapacitor exhibits high specific capacitance and a specific capacitance retention rate of 88.5%. The prepared electrode materials were assembled into a non-conductive supercapacitor. After 5000 charge-discharge cycles, the Mn3Al1-LDH@NC / / AC supercapacitor achieved a coulombic efficiency of 99.4% and a capacitance retention rate of 90.8%; simultaneously, it achieved an energy density of 262 Wh·kg⁻¹. -1 It has 825 W·kg -1 Its power density is higher than that of other manganese-based supercapacitors. Attached Figure Description

[0013] The invention will now be further described with reference to the accompanying drawings.

[0014] Figure 1 SEM and TEM images of the Mn3Al1-LDH electrode material; Figure 2 Comparison of CV values ​​for pure nickel foam (NF), Mn3Al1-LDH, and Mn5Al1-LDH electrode materials; Figure 3 Comparison of GCD values ​​for pure nickel foam (NF), Mn3Al1-LDH, and Mn5Al1-LDH electrode materials; Figure 4 EIS curves of Mn3Al1-LDH and Mn5Al1-LDH electrode materials; Figure 5 The graph shows the change in specific capacitance retention rate of the Mn3Al1-LDH@NF / / AC supercapacitor after 5000 constant current charge-discharge cycles at 10A / g. Figure 6 The diagram shows the energy density and power density of the Mn3Al1-LDH@NF / / AC supercapacitor in this embodiment compared to similar supercapacitors. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1 A supercapacitor prepared using a MnAl-LDH supercapacitor electrode material is described below: S1. First, cut the nickel foam into 1.0×1.5cm pieces. 2 The size was determined by sonication with dilute hydrochloric acid for 10 minutes, followed by cleaning with acetone and deionized water, and finally drying to obtain a nickel foam matrix. S2. Weigh 0.05 mmol Cl2H8MnO4 and 0.05 mmol Al(NO3)3·9H2O, dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor MnAl-LDH. S3. Weigh 3.0 mmol Cl2H8MnO4 and 1.0 mmol Al(NO3)3·9H2O, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B. S4. Place the precursor MnAl-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner, place it in an oven for heat treatment, and then cool it to 20℃. Remove the foamed nickel and wash it three times with anhydrous ethanol and deionized water respectively. S5. The prepared nickel foam sample was dried in a vacuum oven at 60°C for 12 hours and then cooled to room temperature to obtain the Mn3Al1-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. Separate the positive and negative electrode materials obtained in S5 and S7 with a diaphragm and add them to the KOH solution in S8 to assemble a supercapacitor.

[0017] In this embodiment, the Mn3Al1-LDH electrode exhibits excellent specific capacitance, at 1 A·g -1 It possesses a high specific capacitance of 3755 F·g⁻¹ at current density, and at 10 A·g -1 It has 3325 F·g at current density -1 It exhibits a high specific capacitance with a retention rate of 88.5%. When assembled with an activated carbon anode, it forms an asymmetric supercapacitor, Mn3Al1-LDH@NC / / AC, achieving a capacitance of 1 A·g. -1 It has 192 F·g at current density-1 High specific capacitance, and at 10 A·g -1 It has 103 F·g at current density -1 It has a high specific capacity and an energy density of 262 Wh·kg⁻¹. -1 It has 825 W·kg -1 The power density is high; and after 5000 charge-discharge cycles, the coulombic efficiency of the Mn3Al1-LDH@NC / / AC supercapacitor is 99.4%, and the capacitance retention rate is 90.8%.

[0018] Figure 1 The image shows the scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Mn3Al1-LDH in this embodiment, along with their elemental distribution maps. Figure 2 This is a CV comparison chart of Mn3Al1-LDH, pure nickel foam (NF), and Mn5Al1-LDH in this embodiment; Figure 3 This is a comparison chart of GCD values ​​for Mn3Al1-LDH, pure nickel foam (NF), and Mn5Al1-LDH in this embodiment; Figure 4 This is a comparison chart of EIS values ​​for Mn3Al1-LDH and Mn5Al1-LDH in this embodiment; Figure 5 This is a long-cycle diagram of the Mn3Al1-LDH@NF / / AC supercapacitor assembled in this embodiment; Figure 6 This is a comparison chart of the energy density and power density of the Mn3Al1-LDH@NF / / AC supercapacitor assembled in this embodiment; Example 2 A supercapacitor prepared from MnAl-LDH electrode material includes the following steps: S1. Cut the nickel foam into 1.0×1.5cm pieces. 2 The size was determined by sonication with dilute hydrochloric acid for 10 minutes, followed by cleaning with acetone and deionized water, and finally drying to obtain a nickel foam matrix. S2. Weigh 0.05 mmol Cl2H8MnO4 and 0.05 mmol Al(NO3)3·9H2O and dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor Mn5Al1-LDH. S3. Weigh 3.33 mmol Cl2H8MnO4 and 0.67 mmol Al(NO3)3·9H2O, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B. S4. Place the precursor Mn5Al1-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner. After heat treatment in an oven, cool to 20℃. Remove the foamed nickel and wash it three times with anhydrous ethanol and deionized water respectively. S5. The prepared nickel foam sample was dried in a vacuum oven at 60°C for 12 hours and then cooled to room temperature to obtain the Mn5Al1-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1 and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. Separate the positive and negative electrode materials obtained in S5 and S7 with a diaphragm and add them to the KOH solution in S8 to assemble a Mn5Al1-LDH@NF / / AC supercapacitor.

[0019] In this embodiment, the Mn5Al1-LDH electrode exhibits a relatively good specific capacitance, at 1 A·g -1 It has 1635 F·g at current density -1 Specific capacitance, and at 10 A·g -1 It has 1350 F·g at current density -1 Its specific capacitance has a retention rate of 82.5%.

Claims

1. A method for preparing a manganese-aluminum layered double hydroxide asymmetric supercapacitor, characterized in that, Includes the following steps: S1. Cut the nickel foam into 1.0×1.5cm pieces. 2 The size was determined by sonication with dilute hydrochloric acid for 10 minutes, followed by cleaning with acetone and deionized water, and finally drying to obtain a nickel foam matrix. S2. Weigh 0.05 mmol Cl2H8MnO4 and 0.05 mmol Al(NO3)3·9H2O and dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor MnAl-LDH. S3. Weigh Cl2H8MnO4 and Al(NO3)3·9H2O in a molar ratio of 7:1, 5:1, 3:1, 1:1 or 1:3, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B. S4. Place the precursor MnAl-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner, place it in an oven for heat treatment, and then cool it to 20℃. Remove the foamed nickel and wash it three times with anhydrous ethanol and deionized water respectively. S5. The prepared nickel foam sample was dried in a vacuum oven at 60°C for 12 hours and then cooled to room temperature to obtain the MnAl-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, 7:1:2, or 7:2:1 and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. Separate the positive and negative electrode materials obtained in S5 and S7 with a diaphragm and add them to the KOH solution in S8 to assemble a supercapacitor.

2. The method for preparing a manganese-aluminum layered double hydroxide asymmetric supercapacitor according to claim 1, characterized in that, In step S4, the heat treatment conditions inside the oven are 140℃ for 16 hours.

3. The method for preparing a manganese-aluminum layered double hydroxide asymmetric supercapacitor according to any one of claims 1 to 2, characterized in that, Follow these steps: S1. First, cut the nickel foam into 1.0×1.5cm pieces. 2 The size was determined by sonication with dilute hydrochloric acid for 10 minutes, followed by cleaning with acetone and deionized water, and finally drying to obtain a nickel foam matrix. S2. Weigh 0.05 mmol Cl2H8MnO4 and 0.05 mmol Al(NO3)3·9H2O, dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor MnAl-LDH. S3. Weigh 3.0 mmol Cl2H8MnO4 and 1.0 mmol Al(NO3)3·9H2O, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B. S4. Place the precursor MnAl-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner, place it in an oven for heat treatment, and then cool it to 20℃. Remove the foamed nickel and wash it three times with anhydrous ethanol and deionized water respectively. S5. The prepared nickel foam sample was dried in a vacuum oven at 60°C for 12 hours and then cooled to room temperature to obtain the Mn3Al1-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. Separate the positive and negative electrode materials obtained in S5 and S7 with a diaphragm and add them to the KOH solution in S8 to assemble a supercapacitor.

4. A method for preparing a manganese-aluminum layered double hydroxide asymmetric supercapacitor according to any one of claims 1 to 2, characterized in that, Follow these steps: S1. Cut the nickel foam into 1.0×1.5cm pieces. 2 The size was determined by sonication with dilute hydrochloric acid for 10 minutes, followed by cleaning with acetone and deionized water, and finally drying to obtain a nickel foam matrix. S2. Weigh 0.05 mmol Cl2H8MnO4 and 0.05 mmol Al(NO3)3·9H2O and dissolve them in 100 mL of deionized water to obtain a 1 mol / L mixed solution A. Immerse the nickel foam matrix in the mixed solution A at room temperature for 15 minutes and remove it. Repeat the above steps three times and dry to obtain the precursor Mn5Al1-LDH. S3. Weigh 3.33 mmol Cl2H8MnO4 and 0.67 mmol Al(NO3)3·9H2O, dissolve them in 60 mL of deionized water, and then weigh 4.0 mmol CO(NH2)2 and 8.0 mmol NH4F and mix them to obtain mixed solution B. S4. Place the precursor Mn5Al1-LDH and mixed solution B together in a 100ml stainless steel reactor with a PTFE liner. After heat treatment in an oven, cool to 20℃. Remove the foamed nickel and wash it three times with anhydrous ethanol and deionized water respectively. S5. The prepared nickel foam sample was dried in a vacuum oven at 60°C for 12 hours and then cooled to room temperature to obtain the Mn5Al1-LDH cathode material for supercapacitors. S6. Mix 50 mg of activated carbon powder (AC), acetylene black, and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1 and add n-methyl-2-pyrrolidone (NMP) dropwise. Stir magnetically for 12 h to obtain mixture C. S7. The mixture C is uniformly coated on the nickel foam and dried in a vacuum oven at 60°C for 12 hours to obtain the AC negative electrode material of the supercapacitor. S8. Weigh a certain amount of KOH and dissolve it in deionized water to prepare a 6 mol / L KOH solution; S9. Separate the positive and negative electrode materials obtained in S5 and S7 with a diaphragm and add them to the KOH solution in S8 to assemble a Mn5Al1-LDH@NF / / AC supercapacitor.

5. A manganese-aluminum layered double hydroxide asymmetric supercapacitor, prepared according to any one of claims 1 to 4.

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