CN114300277B - A kind of aluminum manganese oxide and its application as positive electrode material in aqueous magnesium ion capacitor - Google Patents

Abstract

The invention discloses an aluminum manganese oxide and its application as a positive electrode material in a water system magnesium ion capacitor. Add manganese sulfate, aluminum sulfate and potassium permanganate into deionized water, stir to dissolve, add sulfuric acid drop by drop, continue stirring for 24 hours, then transfer the resulting mixed solution into a reaction kettle for hydrothermal reaction to obtain aluminum manganese oxide. Aluminum-manganese oxide is used as the positive electrode material in water-based magnesium ion capacitors. It can be concluded from electrochemical tests that a single aluminum-manganese oxide has a high specific capacity. And after assembling it with activated carbon into a device, a higher capacitance can still be achieved. The invention has the advantages of simple synthesis process, energy saving, environmental protection and low price, and is expected to become a novel energy storage device.

Description

A kind of aluminum manganese oxide and its application as positive electrode material in aqueous magnesium ion capacitor application

technical field

The invention belongs to the technical field of materials, and in particular relates to an aluminum-manganese oxide and its application as a positive electrode material in a water-based magnesium ion capacitor.

Background technique

With the rapid development of renewable energy such as solar energy, biomass energy, hydropower, and wind energy, as well as the construction of smart grids and the development of micro-grid technology and energy interconnection, energy storage technology is a new challenge that will change the global energy landscape. Electrochemical energy storage has been highly valued due to its application flexibility, high conversion efficiency, and high power density, and is considered to be an important form of energy storage in the future. Among all electrochemical energy storage systems, batteries of different kinds and functions are widely used in daily life and have enabled the wireless revolution of mobile phones, laptops and electronic devices. Among traditional batteries, lead-acid and nickel-metal hydride batteries show low energy density, and their corresponding organic electrolytes also cause serious environmental pollution, so they do not meet the requirements of sustainable development. Although lithium-ion batteries have high power density and energy density, their corresponding organic electrolytes are highly flammable and explosive, threatening human health and public safety. At the same time, the limited supply and high cost of lithium resources also restrict its widespread use. Therefore, green and safe energy storage systems and their applicable electrode materials have become the focus of battery research. Rechargeable magnesium-ion battery systems are a promising system that has been intensively studied due to their similar electrochemical properties to lithium and low cost. Among them, Mg-ion batteries are particularly attractive due to their dendrite-free nature, abundant crustal reserves (~2.9%), high theoretical capacity (~3833 mAh/cm ³ ), and low reduction voltage (-2.37 V vs standard hydrogen electrode). Nevertheless, a major problem still exists in Mg-ion batteries, that is, the strong electrostatic interaction between Mg ions and hosts causes slow solid-state diffusion and strong polarization effects, thus requiring proper selection of electrode materials and electrolytes. Magnesium ions in organic electrolytes must be separated from solvated species before intercalation, severely affecting their diffusion kinetics. At the same time, organic electrolytes are flammable and toxic, so rechargeable aqueous magnesium solutions are obviously a better choice. However, only a few reports on aqueous rechargeable Mg-ion batteries are available.

Contents of the invention

The object of the present invention is to provide an aluminum manganese oxide and its application as a positive electrode material in an aqueous magnesium ion capacitor, and the specific capacitance of the provided aqueous magnesium ion capacitor can be significantly improved.

The technical scheme adopted in the present invention is: an aluminum manganese oxide, the preparation method comprising the following steps: adding manganese sulfate, aluminum sulfate and potassium permanganate into deionized water, stirring and dissolving, adding sulfuric acid drop by drop, and continuing to stir for 24 hours , move the obtained mixed solution into a reaction kettle, and carry out hydrothermal reaction to obtain a new type of positive electrode material, aluminum manganese oxide.

Preferably, the above-mentioned aluminum manganese oxide has a molar ratio of manganese sulfate:aluminum sulfate:potassium permanganate=1:0.24˜3.6:0.8.

Preferably, for the aforementioned aluminum manganese oxide, the hydrothermal reaction is carried out at 180° C. for 24 hours.

The invention provides an application of an aluminum manganese oxide as a positive electrode material in a water system magnesium ion capacitor.

A kind of water system magnesium ion capacitor based on aluminum manganese oxide, with aluminum manganese oxide as positive electrode material, preparation method comprises the following steps:

1) Preparation of the positive electrode: After mixing the aluminum manganese oxide with the binder and the conductive material evenly, add a small amount of NMP as a solvent dropwise, after mixing evenly, directly smear it on the substrate carbon paper, dry it in a vacuum oven, take it out, A positive electrode sheet coated with aluminum manganese oxide is obtained;

2) Preparation of negative electrode: After mixing activated carbon with binder and conductive material evenly, add a small amount of NMP as a solvent dropwise, after mixing evenly, apply it directly on the substrate carbon paper, dry it in a vacuum oven, take it out, and apply it Negative pole piece with activated carbon;

3) Preparation of water-based magnesium ion capacitor: Put the positive electrode piece into the positive electrode shell, make the side coated with aluminum manganese oxide contact the diaphragm, then put the diaphragm, then drop the electrolyte, and then put the negative electrode above the diaphragm For the pole piece, make the side coated with activated carbon contact the diaphragm, then put in the gasket and shrapnel in turn, and finally buckle the negative electrode shell and package it to obtain a water-based magnesium ion capacitor.

Preferably, the binder is PVDF or CMC.

Preferably, the conductive material is Super P or acetylene black.

Preferably, the electrolyte is one of magnesium sulfate aqueous solution, magnesium chloride aqueous solution, and magnesium nitrate aqueous solution.

Preferably, the diaphragm is one of cellulose diaphragm, polypropylene film, diaphragm paper and polymer semipermeable membrane.

The beneficial effects of the present invention are:

1. The present invention designs a novel water-based magnesium ion asymmetric capacitor, using aluminum-manganese oxide and activated carbon as positive and negative materials respectively. It has the following advantages: first, metal aluminum is an ideal doping element for metal oxides, and has high cost-effectiveness and low toxicity. More importantly, trivalent aluminum ions can combine with oxygen atoms to form stable Al-O chemical bonds. Second, since the ionic radius of Al ³⁺ (53.5pm) is very close to that of Mn ⁴⁺ (53pm), Al ³⁺ is a more suitable cation for manganese dioxide substitution doping, and can easily reduce the band gap to generate new Molecular orbitals and the introduction of impurity levels into manganese dioxide.

2. In the present invention, the discharge time of the new aluminum-manganese oxide is increased by 2208 seconds after aluminum doping, and the specific capacitance is as high as 259.58F/g, which is about 1.8 times larger than that of the original manganese dioxide.

3. In the present invention, the selected material has good pseudocapacitive performance, and is cheap, environmentally friendly and recyclable. At the same time, it also has a high theoretical specific capacitance value and good stability in the electrolyte environment.

4. The present invention adopts a combination of a new positive electrode material, aluminum manganese oxide, and activated carbon, which fully breaks the conventional combination form. Moreover, it shows superior performance in terms of specific capacitance. The method has the advantages of simple synthesis process and assembly process, saving and environmental protection, and low price. It is expected to become an ideal material and device for energy storage in the future.

Description of drawings

Fig. 1 is the XRD spectrogram of manganese dioxide and aluminum manganese oxide prepared in the present invention.

Fig. 2 is the SEM spectrogram of the aluminum manganese oxide prepared in the present invention.

Fig. 3 is the cyclic voltammetry curve of aluminum manganese oxide and activated carbon asymmetric water system magnesium ion capacitor prepared by the present invention.

Fig. 4 is the specific capacitance diagram of the aluminum manganese oxide and activated carbon asymmetric water system magnesium ion capacitor prepared by the present invention.

Detailed ways

Example 1

(1) aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.0024mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

(2) comparative example, the preparation method of manganese dioxide is as follows:

Weigh 0.01mol of manganese sulfate monohydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue stirring for 24h, and transfer the resulting mixed solution into Put it into the reaction kettle, and conduct a hydrothermal reaction at 180°C for 24 hours to obtain manganese dioxide material.

(3) Detection

Fig. 1 is the XRD spectrogram of manganese dioxide and aluminum manganese oxide prepared in the present invention. It can be seen from Figure 1 that after Al doping, the XRD spectrum of the sample did not show obvious changes, and the shift of individual peaks indicated that Al ions were successfully doped into MnO ₂ .

Fig. 2 is the SEM spectrogram of the aluminum manganese oxide prepared in the present invention. It can be seen from Figure 2 that due to the combination of trivalent aluminum ions and oxygen atoms to form a stable Al-O chemical bond, the sample gradually condenses from a single nanorod into a cluster.

Example 2

Aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.0192mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

Example 3

Aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.024mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

Example 4

Aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.0264mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

Example 5

Aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.0288mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

Example 6

Aluminum manganese oxide, the preparation method is as follows:

Weigh 0.01mol of manganese sulfate monohydrate, 0.036mol of aluminum sulfate octadecahydrate and 0.008mol of potassium permanganate into 50mL of deionized water, stir and dissolve, then add 20mL of sulfuric acid with a concentration of 0.2mol/L dropwise, continue After stirring for 24 hours, the obtained mixed solution was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180° C. for 24 hours to obtain aluminum manganese oxide Al _x MnO ₂ .

Example 7

(1) A kind of water system magnesium ion capacitor based on aluminum manganese oxide, the preparation method is as follows:

1) Preparation of the positive electrode: Mix 80 mg of aluminum manganese oxide Al _x MnO ₂ obtained in Example 5 with 10 mg of PVDF and 10 mg of Super P, and drop a small amount of NMP as a solvent to make the binder fully contact with other substances and distribute evenly. Then apply directly to the backing carbon paper. Put it into a vacuum drying oven for drying, take it out, and get the positive pole piece coated with aluminum manganese oxide;

2) Preparation of negative electrode: After mixing 80mg of activated carbon with 10mg of PVDF and 10mg of Super P evenly, a small amount of NMP was added dropwise as a solvent to fully contact the binder with other substances and distribute them evenly. Then apply directly to the backing carbon paper. Put it into a vacuum drying oven for drying, take it out, and get a negative electrode sheet coated with activated carbon;

3) Preparation of water-based magnesium ion capacitor: put the positive electrode piece into the positive electrode shell, make the side coated with aluminum manganese oxide contact the diaphragm, then put the cellulose diaphragm, and then drip sulfuric acid with a concentration of 0.5mol/L Magnesium electrolyte, and then put the negative pole piece on the top of the diaphragm, so that the side coated with activated carbon contacts the diaphragm, then put in the gasket and shrapnel in turn, and finally buckle the negative electrode shell, and pack it into a button-type device with a thickness of 40 μm, that is Aqueous magnesium ion capacitors were obtained.

(2) Performance test

In the comparative example, the manganese dioxide material was used as the positive electrode material, and the aqueous magnesium ion capacitor containing manganese dioxide was prepared as above.

Fig. 3 is the cyclic voltammetry curve of the aluminum manganese oxide and activated carbon asymmetric aqueous magnesium ion capacitor prepared in the present invention. It can be seen from Fig. 3 that the aluminum manganese oxide Al _{x MnO} obtained in Example 5 does not show obvious hydrogen evolution trend at about 1.9V after aluminum doping, and there is an obvious voltage plateau, and it can be seen that Its capacity is larger than that of pristine _MnO2 oxide.

Fig. 4 is the specific capacitance diagram of the aluminum manganese oxide and activated carbon asymmetric water system magnesium ion capacitor prepared by the present invention. As can be seen from Fig. 4, the aluminum manganese oxide Al _x MnO obtained in Example ₅ is increased by 2208 seconds after aluminum doping, and the specific capacitance is as high as 259.58 F/g, which is about 1.8 times higher than that of the original manganese dioxide. times.

Claims (7)

1. The water system magnesium ion capacitor based on the aluminum manganese oxide is characterized in that the aluminum manganese oxide is used as a positive electrode material, and the preparation method comprises the following steps:

1) Preparation of positive electrode: uniformly mixing aluminum-manganese oxide, a binder and a conductive material, dropwise adding a small amount of NMP as a solvent, uniformly mixing, directly coating on carbon paper of a substrate, drying in a vacuum drying oven, and taking out to obtain a positive electrode plate coated with aluminum-manganese oxide;

the preparation method of the aluminum manganese oxide comprises the following steps: adding manganese sulfate, aluminum sulfate and potassium permanganate into deionized water, stirring and dissolving, then adding sulfuric acid dropwise, continuing stirring for 24 hours, transferring the obtained mixed solution into a reaction kettle, and performing hydrothermal reaction to obtain aluminum manganese oxide;

2) Preparation of the negative electrode: uniformly mixing active carbon, a binder and a conductive material, dropwise adding a small amount of NMP as a solvent, uniformly mixing, directly coating on carbon paper, drying in a vacuum drying oven, and taking out to obtain a negative electrode plate coated with the active carbon;

3) Preparation of a water-based magnesium ion capacitor: placing the positive electrode plate into a positive electrode shell, enabling one surface coated with aluminum-manganese oxide to contact a diaphragm, then placing the diaphragm, then dripping electrolyte, then placing the negative electrode plate above the diaphragm, enabling one surface coated with active carbon to contact the diaphragm, then sequentially placing a gasket and an elastic sheet, finally buckling the negative electrode shell, and packaging to obtain the water-based magnesium ion capacitor.

2. An aluminum manganese oxide based aqueous magnesium ion capacitor according to claim 1 wherein said binder is PVDF or CMC.

3. The aluminum manganese oxide-based aqueous magnesium ion capacitor according to claim 1, wherein the conductive material is Super P or acetylene black.

4. The aluminum manganese oxide-based aqueous magnesium ion capacitor of claim 1 wherein said electrolyte is one of an aqueous magnesium sulfate solution, an aqueous magnesium chloride solution and an aqueous magnesium nitrate solution.

5. The aluminum manganese oxide-based aqueous magnesium ion capacitor according to claim 1, wherein the separator is one of a cellulose separator, a polypropylene film, a separator paper, and a polymeric semipermeable membrane.

6. The aluminum-manganese oxide-based aqueous magnesium ion capacitor according to claim 1, wherein the molar ratio of manganese sulfate to aluminum sulfate to potassium permanganate=1 is 0.24 to 3.6 to 0.8.

7. An aluminum manganese oxide based aqueous magnesium ion capacitor according to claim 1 wherein said hydrothermal reaction is at 180 ℃ for 24 hours.