MgCo2O4@Mn2O3 Double-Sheath Structure Electrode Material, Preparation Method, Electrode, and Supercapacitor

Abstract

The present invention discloses an MgCo2O4@Mn2O3 double-tube structure electrode material, a preparation method thereof, an electrode and a supercapacitor using the same; the MgCo2O4@Mn2O3 double-tube structure electrode material has a coaxial double-tube structure with Mn2O3 as the shell layer and MgCo2O4 as the core layer. The preparation method includes: (1) preparation of the Mn2O3 and MgCo2O4 precursor solutions; (2) electrospinning process: placing MgCo2O4 as the core layer and Mn2O3 as the shell layer on an electrospinning device respectively, and performing coaxial electrospinning to obtain a composite material; (3) drying treatment: placing the composite material in a drying oven and continuously drying it at 50-90°C for 12 hours; (4) heat treatment: placing the dried composite material in a porcelain boat, then transferring it to a tube furnace for firing, naturally cooling to room temperature, and taking it out and grinding to obtain the MgCo2O4@Mn2O3 double-tube structure electrode material; the mass specific capacitance and long-term cyclic test performance of this electrode material are significantly superior to those of the MgCo2O4 and Mn2O3 monomer electrode materials.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitors, and particularly to a MgCo2O4@Mn2O3 double-tube structure electrode material, a preparation method, an electrode, and a supercapacitor. Background Art

[0002] Supercapacitors have the advantages of high power density, long life, and low production cost, and are therefore considered to be one of the most promising candidates for energy storage systems. As a supercapacitor electrode material, MgCo2O4 has outstanding advantages such as low cost, high natural abundance, easy synthesis, environmental safety, and low toxicity. However, the actual specific capacitance of the MgCo2O4 electrode material in current supercapacitors is far lower than the theoretical value. The pure MgCo2O4 and Mn2O3 electrode materials only have 150 F / g and 250 F / g after cycling 1500 times at a current density of 10 A / g. This is because the specific surface area of the material itself is small and the number of active sites is small, resulting in insufficient reaction between the electrode material and the electrolyte, and there is no synergistic effect between the materials. Therefore, it is more exploratory and practical to prepare a MgCo2O4@Mn2O3 composite electrode material by a new method to improve the problems of insufficient specific capacitance and cycling stability of monomer materials. Summary of the Invention

[0003] An object of the present invention is to provide a MgCo2O4@Mn2O3 double-tube structure electrode material to improve the specific capacitance performance of the material based on this special structure; in terms of structure, the electrode material uses MgCo2O4 as the inner tube layer and Mn2O3 as the outer tube layer, which is sleeved outside the inner tube layer formed by MgCo2O4, and the overall forms a double-tube structure. This structure is different from conventional core-shell structure materials. The core of this structure is a tube structure. The double-tube structure electrode material can increase the specific surface area and provide more active sites.

[0004] The second object of the present invention is to provide a method for preparing a MgCo2O4@Mn2O3 double-tube structure electrode material; this method is realized through the following steps:

[0005] (1) Preparation of Mn2O3 and MgCo2O4 precursor solutions;

[0006] The preparation process of the Mn2O3 precursor solution is as follows: Weigh Mn(NO3)2·6H2O, absolute ethanol, and N,N-dimethylformamide according to a molar mass ratio of 3:53:38; dissolve the Mn(NO3)2·6H2O solution in absolute ethanol and N,N-dimethylformamide solution; stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a Mn2O3 precursor solution;

[0007] The preparation process of the MgCo2O4 precursor solution is as follows: Weigh Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol, and N,N-dimethylformamide according to the molar mass ratio of 1:2:53:38; dissolve Mg(NO3)2·6H2O and Co(NO3)2·6H2O in the absolute ethanol and N,N-dimethylformamide solution, stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous MgCo2O4 precursor solution;

[0008] (2) Electrospinning process: Place MgCo2O4 as the core layer and Mn2O3 as the shell layer on the electrospinning equipment respectively, and perform coaxial electrospinning to obtain the composite material; during the electrospinning process, keep the distance between the metal needle tip and the negative aluminum foil plate at 10 - 15 cm, set the high-voltage power supply at 15 - 18 KV, set the core layer booster rate at 1.0 - 1.4 mL / h, and set the shell layer booster rate at 1.5 - 2.0 mL / h;

[0009] (3) Drying treatment: Place the composite material in a drying oven and continuously dry it at 50 - 90 °C for 12 hours;

[0010] (4) Heat treatment: Place the composite material after drying treatment in a porcelain boat, and then transfer it to a tube furnace for firing. The tube furnace is heated from room temperature to 300 °C at a heating rate of 1.0 - 1.5 °C, hold for 3.5 - 5 hours, then heat it to 400 °C at a heating rate of 1.5 - 2.5 °C / min, continue to hold for 3.5 - 5 hours, and naturally cool to room temperature. After taking it out and grinding, the MgCo2O4@Mn2O3 double-tube structure electrode material can be obtained.

[0011] This method is based on the existing electrospinning technology combined with specific drying and heat treatment processes to prepare an electrode material with excellent performance.

[0012] The third object of the present invention is to provide an electrode of MgCo2O4@Mn2O3 double-tube structure, which is prepared by processing with the MgCo2O4@Mn2O3 double-tube structure electrode material; the performance of this electrode is improved.

[0013] The fourth object of the present invention is to provide a supercapacitor, which is prepared by processing with the MgCo2O4@Mn2O3 double-tube structure electrode material; the performance of the supercapacitor is improved. Description of the Drawings

[0014] Figure 1 It is the SEM image of the MgCo2O4@Mn2O3 coaxial core-shell double-tube structure;

[0015] Figure 2 TEM image of the MgCo2O4@Mn2O3 coaxial core-shell double-tube structure;

[0016] Figure 3 Capacity comparison diagrams of the MgCo2O4@Mn2O3, MgCo2O4, and Mn2O3 electrode materials at different current densities;

[0017] Figure 4 Long cycle comparison diagrams of MgCo2O4@Mn2O3, MgCo2O4, and Mn2O3 electrodes at a current density of 10 A / g. Detailed implementation manners

[0018] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[0019] A MgCo2O4@Mn2O3 double-tube structure electrode material, with MgCo2O4 as the inner tube layer and Mn2O3 as the outer tube layer sleeved outside the inner tube layer composed of MgCo2O4, forming a double-tube structure as a whole; its structure is as Figure 1 and Figure 2 shown. The electrode material of this structure significantly increases the specific surface area.

[0020] The preparation method of the MgCo2O4@Mn2O3 double-tube structure electrode material includes the following steps:

[0021] (1) Preparation of the Mn2O3 and MgCo2O4 precursor solutions

[0022] The preparation process of the Mn2O3 precursor solution is as follows: Weigh Mn(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide according to the molar mass ratio of 3:53:38; dissolve the Mn(NO3)2·6H2O solution in absolute ethanol and N-N dimethylformamide solution; stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous Mn2O3 precursor solution;

[0023] The preparation process of the MgCo2O4 precursor solution is as follows: Weigh Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide according to the molar mass ratio of 1:2:53:38; dissolve Mg(NO3)2·6H2O and Co(NO3)2·6H2O in absolute ethanol and N-N dimethylformamide solution, stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous MgCo2O4 precursor solution;

[0024] (2)Electrospinning process: The precursor solutions of Mn2O3 and MgCo2O4 were respectively loaded into 2 10-ml syringes. MgCo2O4 was used as the core layer and Mn2O3 as the shell layer. The syringes were respectively placed on 2 boosters and led out by a coaxial needle connected by a double hose. Adjust the distance between the metal needle and the aluminum foil of the negative electrode collecting plate, turn on the high-voltage power supply, and observe whether the spinning can be carried out smoothly. Specifically, keep the distance between the metal needle and the aluminum foil plate of the negative electrode at about 10-15 cm, set the high-voltage power supply at about 15-18 KV, set the core layer booster rate at 1.0-1.4 mL / h, set the shell layer booster rate at 1.5-2.0 mL / h, and the shell layer pushing speed should be slightly greater than that of the core layer to ensure that the solution just flows out smoothly without dripping and forms a stable Taylor cone; after electrospinning, a composite material is formed;

[0025] (3)Drying treatment: After electrospinning, use tweezers to collect the composite material on the aluminum foil plate into a clean container, and then place it in a drying oven and continuously dry it at 50-90 °C for 12 hours;

[0026] (4)Heat treatment: Place the composite material after drying treatment in a porcelain boat and then transfer it to a tubular furnace for firing. The tubular furnace is heated from room temperature to 300 °C at a heating rate of 1.0-1.5 °C to maintain the continuity and structural stability of the MgCo2O4@Mn2O3 double-tube structure material; then heat it to 400 °C at a heating rate of 1.5-2.5 °C / min and continue to hold for 3.5-5 hours to ensure the complete decomposition of PVP (K30) and facilitate the formation of good crystallization of the oxide. Naturally cool to room temperature and take out and grind to obtain the MgCo2O4@Mn2O3 double-tube structure electrode material. The heating rate, holding time and holding temperature have an important influence on the formation of the coaxial core-shell structure.

[0027] The following further elaborates the present invention by specific embodiments

[0028] Example 1

[0029] Preparation method of MgCo2O4@Mn2O3 double-tube structure electrode material:

[0030] (1)The preparation process of the Mn2O3 precursor solution is: Weigh 3 mmol of Mn(NO3)2·6H2O solution and dissolve it in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mn(NO3)2·6H2O, absolute ethanol and N-N dimethylformamide is 3:53:38), stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous Mn2O3 precursor solution;

[0031] The preparation process of the MgCo2O4 precursor solution is as follows: Weigh 1 mmol of Mg(NO3)2·6H2O and 2 mmol of Co(NO3)2·6H2O and dissolve them in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol and N-N dimethylformamide solution is 1:2:53:38). Stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), sonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and mix evenly to form the MgCo2O4 precursor solution.

[0032] (2) Electrospinning process: Load the precursor solutions of Mn2O3 and MgCo2O4 into 2 10-ml syringes respectively. MgCo2O4 is used as the core layer and Mn2O3 is used as the shell layer. Place the syringes on 2 boosters respectively and lead them out through a coaxial needle connected by a double hose. Adjust the distance between the metal needle and the negative electrode collecting plate aluminum foil, turn on the high-voltage power supply, and observe whether the fibers can be spun out smoothly. Specifically, keep the distance between the metal needle and the negative aluminum foil plate at 15 cm, set the high-voltage power supply at about 16 KV, set the core layer booster rate at 1.2 mL / h, set the shell layer booster rate at 1.5 mL / h, and the shell layer pushing speed should be slightly greater than that of the core layer to ensure that the solution just flows out smoothly without dripping and forms a stable Taylor cone; after electrospinning, a composite material is formed.

[0033] (3) Drying treatment: After electrospinning, use tweezers to collect the composite material on the aluminum foil plate into a clean container, then place it in a drying oven and dry continuously at 60 °C for 12 hours.

[0034] (4) Heat treatment: Place the dried composite material in a porcelain boat, and then transfer it to a tube furnace for firing. The tube furnace is heated from room temperature to 300 °C at a heating rate of 1.0 °C, and held for 4 hours; then heated to 400 °C at a heating rate of 2 °C / min, and continue to hold for 4 hours, and then naturally cool to room temperature. Take out and grind to obtain the MgCo2O4@Mn2O3 double-tube structure electrode material.

[0035] Example 2

[0036] Preparation method of MgCo2O4@Mn2O3 double-tube structure electrode material:

[0037] (1) The preparation process of the Mn2O3 precursor solution is as follows: Weigh 3 mmol of Mn(NO3)2·6H2O and dissolve it in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mn(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide is 3:53:38). Stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), sonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous Mn2O3 precursor solution;

[0038] The preparation process of the MgCo2O4 precursor solution is as follows: Weigh 1 mmol of Mg(NO3)2·6H2O and 2 mmol of Co(NO3)2·6H2O and dissolve them in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide solution is 1:2:53:38). Stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), sonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous MgCo2O4 precursor solution.

[0039] (2) Electrospinning process: Load the precursor solutions of Mn2O3 and MgCo2O4 into 2 10-ml syringes respectively. Use MgCo2O4 as the core layer and Mn2O3 as the shell layer. Place the syringes on 2 boosters respectively and lead them out through a coaxial needle connected by a double hose. Adjust the distance between the metal needle and the negative electrode collection plate aluminum foil, turn on the high-voltage power supply, and observe whether the fiber can be spun out smoothly. Specifically, keep the distance between the metal needle and the negative aluminum foil plate at 15 cm, set the high-voltage power supply at about 16 KV, set the core layer booster rate at 1.2 mL / h, and set the shell layer booster rate at 1.5 mL / h. The shell layer push rate should be slightly greater than the core layer to ensure that the solution just flows out smoothly without dripping and forms a stable Taylor cone; After electrospinning, a composite material is formed.

[0040] (3) Drying treatment: After electrospinning, use tweezers to collect the composite material on the aluminum foil plate into a clean container, then place it in an oven and dry continuously at 60°C for 12 hours.

[0041] (4) Heat treatment: Place the dried composite material in a porcelain boat, and then transfer it to a tube furnace for firing. The tube furnace is heated from room temperature to 300°C at a heating rate of 1.2°C, and held for 5 hours; Then heat it to 400°C at a heating rate of 1.5°C / min, continue to hold for 3.5 hours, and then cool naturally to room temperature. Take it out and grind it to obtain the MgCo2O4@Mn2O3 double-tube structure electrode material.

[0042] Example three

[0043] Preparation method of MgCo2O4@Mn2O3 double-tube structure electrode material:

[0044] (1) The preparation process of the Mn2O3 precursor solution is as follows: Weigh 3 mmol of Mn(NO3)2·6H2O solution and dissolve it in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mn(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide is 3:53:38). Stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous Mn2O3 precursor solution.

[0045] The preparation process of the MgCo2O4 precursor solution is as follows: Weigh 1 mmol of Mg(NO3)2·6H2O and 2 mmol of Co(NO3)2·6H2O and dissolve them in 3 mL of absolute ethanol and 3 mL of N-N dimethylformamide solution (the molar ratio of Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol, and N-N dimethylformamide solution is 1:2:53:38). Stir at room temperature for 1 hour, then add 2.5 g of PVP (K30), ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous MgCo2O4 precursor solution.

[0046] (2) Electrospinning process: Load the precursor solutions of Mn2O3 and MgCo2O4 into 2 separate 10 ml syringes respectively. Use MgCo2O4 as the core layer and Mn2O3 as the shell layer. Place the syringes on 2 boosters respectively, and lead them out through a coaxial needle connected by a double hose. Adjust the distance between the metal needle and the negative electrode collecting plate aluminum foil, turn on the high-voltage power supply, and observe whether the spinning can be carried out smoothly. Specifically, keep the distance between the metal needle and the negative aluminum foil plate at 15 cm, set the high-voltage power supply at about 16 KV, set the core layer booster rate at 1.2 mL / h, and set the shell layer booster rate at 1.5 mL / h. The shell layer pushing speed should be slightly greater than that of the core layer to ensure that the solution just flows out smoothly without dripping, forming a stable Taylor cone; After electrospinning, a composite material is formed.

[0047] (3) Drying treatment: After electrospinning, use tweezers to collect the composite material on the aluminum foil plate into a clean container, and then place it in an oven and dry continuously at 60 °C for 12 hours.

[0048] (4)Heat treatment: Transfer the dried composite material into a porcelain boat and then transfer it to a tube furnace for firing. The tube furnace is heated from room temperature to 300 °C at a heating rate of 1.5 °C, and held at this temperature for 3.5 hours; then it is heated to 400 °C at a heating rate of 2.5 °C / min, and held at this temperature for another 5 hours, and then naturally cooled to room temperature. After taking out and grinding, the MgCo2O4@Mn2O3 double-tube structure electrode material can be obtained.

[0049] An electrode of MgCo2O4@Mn2O3 double-tube structure material is prepared by using the MgCo2O4@Mn2O3 double-tube structure electrode material; to verify the electrode performance, the MgCo2O4@Mn2O3 double-tube structure electrode material prepared in Example 1 is used to prepare a test electrode in the following manner: The MgCo2O4@Mn2O3 double-tube structure electrode material, PVDF (binder), and acetylene black (conductive agent) are mixed evenly according to a mass ratio of 8:1:1 and coated on a 1 cm×1 cm nickel foam sheet, pressed at 10 MPa, and then vacuum dried at 60 °C for 24 h. The electrochemical test uses a three-electrode system. The counter electrode is a platinum sheet electrode, and the reference electrode is a calomel electrode. When the current density of this electrode is 1 A / g, its specific mass capacitance is 1500 F / g; measure the specific mass capacitance (F / g) of the electrodes prepared from Mn2O3, MgCo2O4, and MgCo2O4@Mn2O3 at different current densities (A / g), and form Figure 3 the comparison data in Figure 3 It can be seen that the electrodes prepared from MgCo2O4@Mn2O3 have significantly better specific mass capacitance (F / g) than the electrodes prepared from Mn2O3 and MgCo2O4 monomers at different current densities (A / g). Long-term cycling tests are carried out at a current density of 10 A / g, and the test results are as shown in Figure 4 shown. After cycling 1500 times at a current density of 10 A / g, the specific mass capacitances of the pure MgCo2O4 and Mn2O3 electrodes are only 150 F / g and 250 F / g, while the electrode prepared from MgCo2O4@Mn2O3 has 400 F / g. The specific capacitance of the MgCo2O4@Mn2O3 electrode is about 2.6 times that of the MgCo2O4 electrode and 1.6 times that of the Mn2O3 electrode.

[0050] Based on the above MgCo2O4@Mn2O3 electrode, a supercapacitor can be prepared, and the performance of the supercapacitor can be improved synchronously.

[0051] The beneficial effects of the present invention are:

[0052] The present invention combines MgCo2O4 and Mn2O3 to form a MgCo2O4@Mn2O3 double-tube structure electrode material, which has a core-shell structure and a double-tube structure, with a significantly increased specific surface area. After preparing the electrode, the mass specific capacitance is superior to that of the monomeric MgCo2O4 and Mn2O3 electrodes, and the performance is also superior to that of the monomeric electrodes under long-term cycling.

Claims

1. A MgCo2O4@Mn2O3 double-tube structure electrode material, characterized in that, MgCo2O4 is used as the inner tube layer, and Mn2O3 is used as the outer tube layer and sleeved outside the inner tube layer composed of MgCo2O4, forming a double-tube structure as a whole.

2. A method for preparing the MgCo2O4@Mn2O3 double-tube structure electrode material according to claim 1, characterized in that, It includes the following steps: (1) Preparation of the Mn2O3 and MgCo2O4 precursor solutions; where: The preparation process of the Mn2O3 precursor solution is as follows: Weigh Mn(NO3)2·6H2O, absolute ethanol, and N,N-dimethylformamide according to a molar ratio of 3:53:38; dissolve the Mn(NO3)2·6H2O solution in absolute ethanol and N,N-dimethylformamide solution; stir at room temperature for 1 hour, then add 2.5 g of PVPK30, ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous Mn2O3 precursor solution; The preparation process of the MgCo2O4 precursor solution is as follows: Weigh Mg(NO3)2·6H2O, Co(NO3)2·6H2O, absolute ethanol, and N,N-dimethylformamide according to a molar ratio of 1:2:53:38; dissolve Mg(NO3)2·6H2O and Co(NO3)2·6H2O in absolute ethanol and N,N-dimethylformamide solution, stir at room temperature for 1 hour, then add 2.5 g of PVPK30, ultrasonicate for 5 minutes, and stir with a magnetic stirrer at room temperature for 12 h to fully stir and form a homogeneous MgCo2O4 precursor solution; (2) Electrospinning processing: Place MgCo2O4 as the core layer and Mn2O3 as the shell layer on the electrospinning equipment respectively, and perform coaxial electrospinning to obtain the composite material; (3) Drying treatment: Place the composite material in a drying oven and continuously dry it at 50~90 °C for 12 hours; (4) Heat treatment: Place the composite material after drying treatment in a porcelain boat, and then transfer it to a tubular furnace for firing. The tubular furnace is heated from room temperature to 300 °C at a heating rate of 1.0~1.5 °C, hold for 3.5~5 hours, then heat up to 400 °C at a heating rate of 1.5~2.5 °C / min, continue to hold for 3.5~5 hours, and naturally cool to room temperature. Take it out and grind it to obtain the MgCo2O4@Mn2O3 double-tube structure electrode material.

3. The method for preparing the MgCo2O4@Mn2O3 double-tube structure electrode material according to claim 2, characterized in that, In step (2), during the electrospinning process, the distance between the metal needle tip and the negative aluminum foil plate is maintained at 10~15 cm, the high-voltage power supply is set at 15~18 KV, the core layer booster rate is set at 1.0~1.4 mL / h, and the shell layer booster rate is set at 1.5~2.0 mL / h.

4. A MgCo2O4@Mn2O3 double-tube structure material electrode, characterized in that, It is prepared by using the MgCo2O4@Mn2O3 double-tube structure electrode material described in claim 1.

5. A supercapacitor, characterized in that, It is prepared by using the MgCo2O4@Mn2O3 double-tube structure material electrode described in claim 4.

Images