A Mn2O3@MXene cathode material, its preparation method, and its application in aqueous magnesium ion capacitors.

Abstract

This invention belongs to the technical field of capacitor cathode materials, and discloses a Mn2O3@MXene cathode material, its preparation method, and its application in aqueous magnesium-ion capacitors. An MXene (Ti3C2) colloidal solution is added to a deionized aqueous solution of manganese acetate and citric acid, stirred, and the pH value of the solution is adjusted. The solution is then transferred to a reaction vessel to prepare a precursor using a hydrothermal method, followed by high-temperature calcination and annealing to successfully prepare the cathode. MXene is a 2D layered material with a large spacing, which can establish a good conductive system, provide abundant active centers, and provide unobstructed conductive channels for rapid charge transfer, further improving specific capacitance. The synthesis process of the Mn2O3@MXene cathode material in this invention is simple, and the selected reactants are characterized by low toxicity and low cost, effectively reducing environmental pollution. It is expected to become a novel aqueous magnesium-ion capacitor energy storage device.

Description

Technical Field

[0001] This invention belongs to the technical field of positive electrode materials for aqueous capacitors, specifically relating to a Mn2O3@MXene positive electrode material, its preparation method, and its application in aqueous magnesium ion capacitors. Background Technology

[0002] With the development of the times, the increased consumption of traditional energy sources has led to an energy shortage crisis. The global demand for renewable and clean energy is constantly growing, prompting people to seek reliable and sustainable electrochemical energy storage devices. Lithium-ion batteries have become deeply integrated into our lives; electric vehicles, smartwatches, smartphones, and even spacecraft all use lithium-ion batteries as a power source to some extent. Although lithium-ion batteries currently dominate energy storage devices due to their high energy density and technological maturity, their limited lithium resources and the increased safety risks associated with using organic electrolytes make them unsuitable for large-scale grid energy applications. Aqueous rechargeable batteries, on the other hand, offer advantages such as abundant resources, low cost, high safety, and high ionic conductivity, providing a broad prospect for next-generation large-scale energy storage. Among various aqueous batteries and energy storage devices, aqueous magnesium-ion batteries are abundant, which can effectively reduce costs, and their theoretical specific capacity is high (3833 mAh cm⁻¹). -3 Magnesium ions (MgIs) possess a low reduction potential (-2.4V compared to a standard hydrogen electrode), which has attracted considerable research interest. In aqueous electrolytes, the strong dipole water molecules lead to rapid diffusion kinetics of magnesium ions, resulting in excellent electrochemical performance. Furthermore, according to the diagonal rule, magnesium ions are most similar in size to lithium ions and can provide twice as many electrons as monovalent lithium ions. More importantly, magnesium electrodes do not form dendritic structures during charge and discharge, which significantly improves the safety and cycle life of magnesium-ion batteries. Therefore, aqueous magnesium-ion batteries and various energy storage devices show great promise and are expected to become candidates for next-generation green energy storage systems. Summary of the Invention

[0003] The purpose of this invention is to provide a Mn2O3@MXene cathode material, its preparation method, and its application in aqueous magnesium ion capacitors, thereby improving its specific capacitance.

[0004] The technical solution adopted in this invention is as follows:

[0005] A Mn2O3@MXene cathode material is prepared by the following steps: MXene (Ti3C2) material is added to deionized water and stirred for 20 min to obtain a blackish-gray MXene (Ti3C2) colloidal solution. The MXene (Ti3C2) colloidal solution is added to an aqueous solution of manganese acetate and citric acid, stirred, and the pH of the solution is adjusted to 10. Then, the solution is magnetically stirred for 30 min. The mixed solution is then transferred to a reaction vessel for hydrothermal reaction. After the reaction is completed, the precipitate is collected and washed three times with deionized water. After drying in a vacuum drying oven at 60℃ for 12 h, the precipitate is taken out and calcined in a muffle furnace to obtain the Mn2O3@MXene cathode material.

[0006] Preferably, the preparation method of the Mn2O3@MXene cathode material mentioned above includes the following steps: weigh 4g of lithium fluoride and add it to 40mL of 9M hydrochloric acid solution, stir for 30min, then weigh 2g of MAX(Ti3AlC2) and slowly add it to the above solution, stir for 72h, filter and wash with a large amount of deionized water until the pH of the supernatant is 7, transfer the washed product to a vacuum drying oven at 60℃ and dry for 12h to obtain the MXene(Ti3C2) material.

[0007] Preferably, in the above-mentioned Mn2O3@MXene cathode material, the mass ratio of MXene (Ti3C2) material to deionized water is 2:1.

[0008] Preferably, in the above-mentioned Mn2O3@MXene cathode material, the aqueous solution of manganese acetate and citric acid has a mass ratio of manganese acetate:citric acid:deionized water = 1:0.5:100.

[0009] Preferably, in the above-mentioned Mn2O3@MXene cathode material, the hydrothermal reaction condition is maintained at 150°C for 3 hours.

[0010] Preferably, in the above-mentioned Mn2O3@MXene cathode material, the calcination is carried out at 500°C for 1 hour.

[0011] The application of any of the above-mentioned Mn2O3@MXene cathode materials in aqueous magnesium ion capacitors.

[0012] Preferably, the above application method includes the following steps:

[0013] 1) Grind and mix Mn2O3@MXene cathode material with binder and conductive material at a mass ratio of 8:1:1, coat evenly on carbon paper, and dry in a vacuum drying oven at 60℃ for 12h to obtain Mn2O3@MXene cathode sheet;

[0014] 2) Cut the Mn2O3@MXene positive electrode and the activated carbon negative electrode coated on the current collector separately, and then assemble them in the following order: negative electrode shell, activated carbon negative electrode, diaphragm containing magnesium salt electrolyte, Mn2O3@MXene positive electrode, gasket, spring plate, and positive electrode shell to obtain an aqueous magnesium ion capacitor based on Mn2O3@MXene positive electrode.

[0015] Preferably, in the above-described applications, the current collector is any one of copper foil, titanium foil, carbon paper, and stainless steel mesh.

[0016] Preferably, in the above-described applications, the magnesium salt is any one of magnesium sulfate, magnesium chloride, and magnesium nitrate.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention provides a porous structure Mn2O3@MXene as the positive electrode material for an aqueous magnesium ion capacitor. The design of this aqueous magnesium ion capacitor has the following advantages: the surface of MXene has many functional groups (-OH, -O, -F), which gives it good hydrophilicity. This effectively promotes the penetration of electrolyte into the positive electrode material, thereby accelerating the insertion / extraction of magnesium ions, achieving faster charging and discharging, and thus improving electrochemical performance.

[0019] 2. In this invention, MXene is a 2D layered material with a large spacing, which can establish a good conductive system, provide abundant active centers, and provide unobstructed conductive channels for rapid charge transfer. The discharge specific capacitance of Mn2O3@MXene is increased by 25.2 F g. -1 The discharge specific capacitance reaches 194.96 F g. -1 It is 1.15 times that of the original Mn2O3.

[0020] 3. In this invention, the synthesis process of Mn2O3@MXene material is simple, and the selected reactants are characterized by low toxicity and low cost, which can effectively reduce environmental pollution and is expected to become a new type of aqueous magnesium ion capacitor energy storage device.

[0021] 4. The capacitor provided by this invention has the characteristics of low cost and environmental friendliness, and also has high stability. It is expected to be mass-produced and become the next generation of green energy storage system. Attached Figure Description

[0022] Figure 1 This is a comparison of XRD patterns of Mn2O3@MXene prepared in this invention and original Mn2O3.

[0023] Figure 2 This is the SEM spectrum of Mn2O3@MXene prepared in this invention.

[0024] Figure 3 This is a cyclic voltammetry curve of an aqueous magnesium ion capacitor assembled with Mn2O3@MXene as the positive electrode and activated carbon as the negative electrode, prepared in this invention.

[0025] Figure 4 This is a comparison diagram of the discharge specific capacitance of an aqueous magnesium ion capacitor assembled with Mn2O3@MXene prepared in this invention and raw Mn2O3 as the positive electrode and activated carbon as the negative electrode, respectively. Detailed Implementation

[0026] Example 1

[0027] The preparation method of MXene (Ti3C2) material is as follows:

[0028] Weigh 4g of lithium fluoride and add it to 40mL of 9M hydrochloric acid solution. Stir for 30min. Then weigh 2g of MAX(Ti3AlC2) and slowly add it to the above solution. Stir for 72h and then filter and wash with a large amount of deionized water until the pH of the supernatant is 7. Transfer the washed product to a vacuum drying oven at 60℃ and dry for 12h to obtain MXene(Ti3C2) material.

[0029] Example 2

[0030] (I) Mn2O3@MXene cathode material, the preparation method is as follows:

[0031] First, weigh 100 mg of MXene (Ti3C2) material and add it to 50 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0032] (II) Testing

[0033] Figure 1 These are the XRD patterns of Mn2O3@MXene and Mn2O3 prepared according to this invention. Figure 1As can be seen, the positions of Mn2O3@MXene are basically consistent with those of the standard card PDF#41-1442, but some peaks are shifted. This may be due to recombination with MXene. Some marked peaks are new peaks generated after recombination with MXene (Ti3C2).

[0034] Figure 2 This is the SEM spectrum of the Mn2O3@MXene cathode material prepared in this invention. Figure 2 It can be seen that spherical Mn2O3 grows on MXene with a plate-like structure.

[0035] Example 3

[0036] The preparation method of Mn2O3@MXene cathode material is as follows:

[0037] First, weigh 200 mg of MXene (Ti3C2) material and add it to 100 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0038] Example 4

[0039] The preparation method of Mn2O3@MXene cathode material is as follows:

[0040] First, weigh 300 mg of MXene (Ti3C2) material and add it to 150 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0041] Example 5

[0042] The preparation method of Mn2O3@MXene cathode material is as follows:

[0043] First, weigh 400 mg of MXene (Ti3C2) material and add it to 200 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0044] Example 6

[0045] The preparation method of Mn2O3@MXene cathode material is as follows:

[0046] First, weigh 500 mg of MXene (Ti3C2) material and add it to 250 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0047] Example 7

[0048] The preparation method of Mn2O3@MXene cathode material is as follows:

[0049] First, weigh 600 mg of MXene (Ti3C2) material and add it to 300 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0050] Example 8

[0051] The preparation method of Mn2O3@MXene cathode material is as follows:

[0052] First, weigh 700 mg of MXene (Ti3C2) material and add it to 350 mL of deionized water. Stir for 20 min to obtain a dark gray colloidal solution, denoted as solution A. Weigh 1 g of manganese acetate and 0.5 g of citric acid and dissolve them in 100 mL of deionized water to form solution B. Add solution A to solution B. While stirring, add 5 M sodium hydroxide aqueous solution dropwise. Dip a glass rod into the mixture and wet pH test paper. Compare the pH with a standard colorimetric card to make the pH of the solution equal to 10. Stir magnetically for 30 min. Transfer the mixed solution to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene. Maintain the temperature at 150 °C for 3 h. After the reactor cools to room temperature, collect the precipitate by centrifugation. Wash the precipitate three times with deionized water. Transfer the washed precipitate to a vacuum drying oven at 60 °C and dry for 12 h. The resulting dark gray powder is then transferred to a muffle furnace and calcined at 500 °C for 1 h to prepare the Mn2O3@MXene cathode material.

[0053] Example 9

[0054] An aqueous magnesium ion capacitor based on Mn2O3@MXene cathode material is prepared by the following method:

[0055] Electrode sheets were prepared using the Mn2O3@MXene cathode material obtained in Example 2. These sheets, along with activated carbon, served as the positive and negative electrodes of an aqueous magnesium ion capacitor, respectively. They were separated by a membrane containing electrolyte and finally encapsulated into a button-type device.

[0056] (I) The preparation method is as follows:

[0057] 1) Grind and mix Mn2O3@MXene cathode material with binder and conductive material at a mass ratio of 8:1:1, coat evenly on carbon paper, and dry in a vacuum drying oven at 60℃ for 12h to obtain Mn2O3@MXene cathode sheet;

[0058] 2) Cut the Mn2O3@MXene positive electrode and the activated carbon negative electrode coated on carbon paper into 12mm small round pieces. Then assemble them in the following order: negative electrode shell, activated carbon negative electrode, separator containing an appropriate amount of 0.5M MgSO4 electrolyte, Mn2O3@MXene positive electrode, gasket, spring sheet, and positive electrode shell. Package them into a button-type device to obtain an aqueous magnesium ion capacitor based on Mn2O3@MXene positive electrode material.

[0059] (II) Performance Testing

[0060] Figure 3 These are the cyclic voltammetry curves of a button-type device assembled using Mn2O3@MXene as the positive electrode and activated carbon as the negative electrode, prepared in this invention. Figure 3As can be seen, based on the cyclic voltammetry curve of the aqueous magnesium ion capacitor obtained from the Mn2O3@MXene cathode material in Example 2, the Mn2O3@MXene cathode material did not show a significant hydrogen evolution trend at around 1.9V, and its voltage range can be considered to be 0-1.9V.

[0061] Figure 4 This is a comparison of the discharge specific capacitance of button-type devices assembled with Mn2O3@MXene and Mn2O3 as the positive electrode and activated carbon as the negative electrode, respectively. Figure 4 It can be seen that the discharge specific capacitance increased by 25.2 Fg after Mn2O3 was combined with MXene. -1 The discharge specific capacitance reaches 194.96 F g. -1 It is 1.15 times that of the original Mn2O3.

Claims

1. The application of a Mn2O3@MXene cathode material in an aqueous magnesium ion capacitor, characterized in that, The method includes the following steps: 1) Grind and mix Mn2O3@MXene cathode material with binder and conductive material at a mass ratio of 8:1:1, coat evenly on carbon paper, and dry in a vacuum drying oven at 60 ℃ for 12 h to obtain Mn2O3@MXene cathode sheet; 2) Cut the Mn2O3@MXene positive electrode and the activated carbon negative electrode coated on the current collector separately, and then assemble them in the following order: negative electrode shell, activated carbon negative electrode, diaphragm containing magnesium salt electrolyte, Mn2O3@MXene positive electrode, gasket, spring plate, and positive electrode shell to obtain an aqueous magnesium ion capacitor based on Mn2O3@MXene positive electrode. The preparation method of the Mn2O3@MXene cathode material includes the following steps: MXene-Ti3C2 material is added to deionized water and stirred for 20 min to obtain a blackish-gray MXene-Ti3C2 colloidal solution. The MXene-Ti3C2 colloidal solution is added to an aqueous solution of manganese acetate and citric acid, stirred, and the pH value of the solution is adjusted to 10. Then, the solution is magnetically stirred for 30 min. The mixed solution is then transferred to a reaction vessel for hydrothermal reaction. After the reaction is completed, the precipitate is collected and washed three times with deionized water. After drying in a vacuum drying oven at 60 °C for 12 h, the precipitate is taken out and transferred to a muffle furnace for calcination to obtain the Mn2O3@MXene cathode material.

2. The application according to claim 1, characterized in that, The preparation method of the MXene-Ti3C2 material includes the following steps: 4 g of lithium fluoride is weighed and added to 40 mL of 9 M hydrochloric acid solution and stirred for 30 min. Then, 2 g of MAX-Ti3AlC2 is weighed and slowly added to the above solution. After stirring for 72 h, the product is washed by vacuum filtration with a large amount of deionized water until the pH of the supernatant is 7. The washed product is then transferred to a vacuum drying oven at 60 ℃ and dried for 12 h to obtain the MXene-Ti3C2 material.

3. The application according to claim 1, characterized in that, By mass ratio, MXene-Ti3C2 material : deionized water = 2 :

1.

4. The application according to claim 1, characterized in that, In the aqueous solution of manganese acetate and citric acid, the mass ratio of manganese acetate : citric acid : deionized water is 1 : 0.5 :

100.

5. The application according to claim 1, characterized in that, The hydrothermal reaction conditions were maintained at 150 °C for 3 h.

6. The application according to claim 1, characterized in that, The calcination is carried out at 500°C for 1 hour.

7. The application according to claim 1, characterized in that, The current collector can be any one of copper foil, titanium foil, carbon paper, and stainless steel mesh.

8. The application according to claim 1, characterized in that, The magnesium salt is any one of magnesium sulfate, magnesium chloride, and magnesium nitrate.

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