A sodium manganate material with a MXenes-like extended layer structure and its preparation method and application

Abstract

The present invention discloses a sodium manganate material having a unique MXenes-like extended layer structure and a preparation method and application thereof. The present invention uses manganese dioxide nanotubes, first calcined to obtain a well-crystallized manganese dioxide powder with a hollow tubular structure, then ground it with a sodium salt that decomposes and generates gas, adds water to disperse ultrasound, and ultrasonically loads the manganese dioxide hollow nanotubes with sodium salt by ultrasound, and then calcines at high temperature in an oxygen atmosphere to promote the diffusion and release of carbon dioxide inside the manganese dioxide hollow tube to form a sodium manganate sodium ion battery positive electrode material that can be applied to the positive electrode of a sodium ion battery. The sodium manganate synthesized by the present invention, which is a MXenes-like extended layer structure, is conducive to the diffusion of sodium ions between layers, and has a high specific capacity and good cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery materials and relates to a sodium manganate electrode material and a preparation method thereof, and in particular to a sodium manganate material with a MXenes-like extended layer structure applied to a positive electrode of a sodium ion battery and a preparation method and application thereof. Background Art

[0002] In today's society, energy is one of the basic conditions for sustainable development. With the depletion of energy sources such as oil and natural gas, the energy crisis is becoming more and more serious. Human beings are constantly developing, researching and utilizing new energy materials. After lithium-ion batteries entered the market in the 1890s, they caused a revolution in human energy technology. A large number of lithium-ion batteries were used in human production and life, and new lithium-ion batteries with better performance were constantly being developed. However, due to the extremely low content of lithium ions in the earth's crust, with the commercialization of lithium-ion batteries, the demand for lithium has increased rapidly and the price has continued to rise. In contrast, sodium ions are abundant in the earth's crust, cheap and easy to obtain, and sodium and lithium belong to the same main group with similar physical and chemical properties. However, the radius of sodium ions (0.102nm) is slightly larger than that of lithium ions (0.076nm), and the standard electrode potential of sodium pairs (-2.87V) is higher than that of lithium pairs (-3.04V). As a result, the currently commercialized lithium-ion battery electrode materials cannot be directly converted into sodium-ion battery electrode materials. Therefore, it is of great significance to develop new low-cost and high-quality sodium-ion battery electrode materials. Summary of the invention

[0003] The purpose of the present invention is to provide a sodium manganate material, a preparation process and an application thereof which is low in cost, simple to operate and has a unique MXenes-like extended layer structure.

[0004] Provided is a sodium manganate material having a unique MXenes-like extended layer structure.

[0005] According to the above scheme, the sodium manganate material is Na 0.91 MnO 2 The distance between layers in the sodium manganate material is 10 to 30 nm.

[0006] A method for preparing a sodium manganate material having a MXenes-like extended layer structure is provided, comprising the following steps:

[0007] (1) calcining the manganese dioxide hollow nanotubes in an oxygen atmosphere to obtain a well-crystallized manganese dioxide tubular material with a hollow structure;

[0008] (2) Grinding the sodium salt that can decompose and generate gas with the above-mentioned hollow manganese dioxide tubular material, adding water, ultrasonicating, stirring and evaporating to dryness, calcining in an oxygen atmosphere, and post-treating to obtain sodium manganate powder Na with a MXenes-like expanded layer structure 0.91 MnO 2 .

[0009] According to the above scheme, the method for preparing the manganese dioxide hollow nanotubes is: preparing a high-valent manganese salt solution, adjusting the pH value of the system to acidic, and then performing a hydrothermal reaction for a period of time to obtain the manganese dioxide hollow nanotubes.

[0010] The high-valent manganese salt is one or more of potassium permanganate, sodium permanganate and potassium manganate;

[0011] The concentration of the high-valent manganese salt is 0.02-0.1 mol / L, and the pH of the system is adjusted to 1-4;

[0012] The hydrothermal reaction temperature is 100-180°C and the reaction time is 10-15h;

[0013] According to the above scheme, the calcination temperature in step (1) is 300-500°C.

[0014] According to the above scheme, the sodium salt that can be decomposed to produce gas is sodium carbonate. 0.91 MnO 2 Sheet.

[0015] According to the above scheme, the ultrasonic time is 10 min-1 h, so that the manganese dioxide with a hollow tubular structure can carry an appropriate amount of sodium salt.

[0016] According to the above scheme, the post-treatment is washing with water until it is nearly neutral and drying.

[0017] According to the above scheme, the molar ratio of sodium salt to manganese dioxide in step (2) is 0.9:1-1.1:1, the high temperature roasting temperature is 700-1000°C, and the roasting time is 10-14h.

[0018] According to the above scheme, the oxygen atmosphere flow rate in step (2) is 10-40 mL / min.

[0019] Provided is the application of the sodium manganate material having a unique MXenes-like extended layer structure as a positive electrode material for sodium ion batteries.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention uses manganese dioxide nanotubes, first calcined to obtain well-crystallized manganese dioxide powder with a hollow tubular structure, then ground the powder with sodium salt that decomposes to generate gas, added water and dispersed by ultrasound, and the manganese dioxide hollow nanotubes are loaded with sodium salt by ultrasound, and then calcined at high temperature in an oxygen atmosphere to promote the diffusion and release of carbon dioxide inside the manganese dioxide hollow tubes, thereby forming a sodium manganate sodium ion battery positive electrode material with a MXenes-like expanded layer structure that can be used for the positive electrode of a sodium ion battery.

[0022] Compared with bulk layered sodium manganate, the sodium manganate with a MXenes-like extended layer structure synthesized in the present invention has a thinner sodium manganate layer, which is beneficial to shortening the diffusion distance of sodium ions in the sodium manganate material; it has a larger interlayer spacing, between 10 and 30 nm, which is beneficial to the diffusion of sodium ions between layers, so that the sodium manganate material with a unique MXenes-like extended layer structure presents a high specific capacity of 150 mAh / g and good cycle stability (still maintaining a high specific capacity of 120 mAh / g after 100 cycles, with a retention rate of 80%).

[0023] (2) The materials prepared in the present invention are assembled into batteries with a voltage range of 2.0-4.0V at room temperature and pressure, and a charge and discharge specific capacity close to that of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to explain the present invention more clearly, the accompanying drawings related to the present invention are briefly introduced below.

[0025] Figure 1 MnO after calcination in Example 1 2 Scanning electron microscope (a) and XRD (b) diagrams show that the MnO obtained in Example 1 2 It is a hollow nanotube structure with uniform particle size and good crystallinity.

[0026] Figure 2 This is the X-ray diffraction pattern of the sodium manganate material sample prepared in Example 2. It can be seen that the prepared sodium manganate material has high purity and good crystallinity.

[0027] Figure 3 This is the scanning electron microscopy result of sodium manganate prepared in Example 2, which shows that the sodium manganate material has a MXenes-like extended layer structure with an interlayer spacing between 15-30 nm.

[0028] Figure 4 After assembling a battery with the sodium manganate prepared in Example 2 as the positive electrode, the first and second cycle cyclic voltammograms at a voltage range of 2.0-4.0 V and a scan rate of 0.12 mV / s indicate that the sodium manganate material with a unique MXenes-like extended layer structure has multiple oxidation peaks and reduction peaks during the charge and discharge process, which is consistent with its high specific capacity.

[0029] Figure 5 The first charge and discharge curve of the sodium manganate prepared in Example 1 after assembling the battery as the positive electrode shows that the sodium manganate material with a unique MXenes-like expanded layer structure exhibits a high discharge specific capacity of 115 mAh / g, and still maintains a specific capacity of 40 mAh / g after 200 cycles at a current density of 0.5 A / g, showing good cycle stability.

[0030] Figure 6 The first charge and discharge curve of the battery assembled with the sodium manganate prepared in Example 2 as the positive electrode shows that the sodium manganate material with a unique MXenes-like extended layer structure exhibits a high discharge specific capacity of 150 mAh / g.

[0031] Figure 7 The charge and discharge cycle curve of the battery assembled with the sodium manganate prepared in Example 2 as the positive electrode shows that the sodium manganate material with a unique MXenes-like extended layer structure still maintains a specific capacity of 120 mAh / g after 100 cycles, showing good cycle stability.

[0032] Figure 8 MnO after calcination in Example 2 2 Scanning electron microscope image shows that the MnO obtained in Example 2 2 It is a hollow nanotube structure with uniform particle size. DETAILED DESCRIPTION

[0033] The present invention is further described below through some specific examples, but the present invention is not limited to the scope of the specific examples.

[0034] Example 1

[0035] Dissolve 0.3g potassium permanganate in 35ml pure water, add concentrated hydrochloric acid to adjust the pH to 2, place in an oven at 140°C for reaction for 12h, filter, wash and dry, and then treat the obtained product in a tubular furnace at 500°C in an oxygen atmosphere for 2h to obtain a hollow tubular manganese dioxide material with good crystallinity.

[0036] Weigh 0.05g of manganese dioxide and 0.06g of sodium carbonate, grind and mix them thoroughly, add 10ml of deionized water, ultrasonicate for 10min, evaporate to dryness with stirring, put into a magnetic boat, react at 900℃ in an oxygen atmosphere in a tube furnace for 10h, wash the obtained product to neutrality, and dry it to obtain the target product sodium manganate (Na 0.91 MnO 2 The obtained product was used as the positive electrode material to assemble a sodium ion battery, which showed good electrochemical performance. The first charge and discharge curve of the sodium manganate prepared in Example 1 as the positive electrode after assembling the battery is shown in Figure 5, indicating that the sodium manganate material with a unique MXenes-like extended layer structure exhibits a high discharge specific capacity of 115 mAh / g, and still maintains a specific capacity of 50 mAh / g after 200 cycles at a current density of 0.5 A / g, showing good cycle stability.

[0037] MnO calcined at 500℃ in oxygen atmosphere 2 SEM and XRD Figure 1 a and 1b, it can be seen from the figure that the obtained MnO 2 It is a hollow nanotube structure with uniform particle size and good crystallinity.

[0038] Example 2

[0039] Dissolve 0.25g potassium manganate in 30ml pure water, add concentrated hydrochloric acid to adjust the pH to 1, place in an oven at 150°C for reaction for 12h, filter, wash and dry, and then treat the obtained product in a tubular furnace at 400°C in an oxygen atmosphere for 2h to obtain a hollow tubular manganese dioxide material with good crystallinity.

[0040] Weigh 0.11g of manganese dioxide and 0.13g of sodium carbonate, grind and mix them thoroughly, add 30ml of deionized water, ultrasonicate for 50min, evaporate to dryness with stirring, put into a magnetic boat, react at 850℃ in a tube furnace under oxygen atmosphere for 15h, wash the obtained product to neutrality, and dry it to obtain the target product sodium manganate. The obtained product is assembled into a sodium ion battery as a positive electrode material, showing good electrochemical performance.

[0041] MnO calcined at 400℃ in oxygen atmosphere 2 SEM images are shown in Figure 8 As can be seen from the figure, the obtained MnO 2 It is a hollow nanotube structure with uniform particle size.

[0042] The X-ray diffraction pattern of the sodium manganate material sample prepared in Example 2 is shown in Figure 2 It can be seen that the prepared sodium manganate material has high purity and good crystallinity.

[0043] Figure 3 This is the scanning electron microscopy result of sodium manganate prepared in Example 2, which shows that the sodium manganate material has a MXenes-like extended layer structure with an interlayer spacing between 15-30 nm.

[0044] Figure 4After assembling a battery with the sodium manganate prepared in Example 2 as the positive electrode, the first and second cycle cyclic voltammograms at a voltage range of 2.0-4.0 V and a scan rate of 0.12 mV / s indicate that the sodium manganate material with a unique MXenes-like extended layer structure has multiple oxidation peaks and reduction peaks during the charge and discharge process, which is consistent with its high specific capacity.

[0045] Figure 6 The first charge and discharge curve of the battery assembled with the sodium manganate prepared in Example 2 as the positive electrode shows that the sodium manganate material with a unique MXenes-like extended layer structure exhibits a high discharge specific capacity of 150 mAh / g.

[0046] Figure 7 The charge and discharge cycle curve of the battery assembled with the sodium manganate prepared in Example 2 as the positive electrode shows that the sodium manganate material with a unique MXenes-like extended layer structure still maintains a specific capacity of 120 mAh / g after 100 cycles, showing good cycle stability.

Claims

1. Sodium manganate material with a unique MXenes-like extended layer structure, characterized by: The sodium manganate material is Na 0.91 MnO2 has a MXenes-like extended layer structure, and the spacing between layers in the sodium manganate material is 10~30 nm. The preparation method includes the following steps: (1) calcining the manganese dioxide hollow nanotubes in an oxygen atmosphere to obtain a well-crystallized manganese dioxide tubular material with a hollow structure; (2) Grinding the sodium salt that can decompose and generate gas with the above-mentioned hollow manganese dioxide tubular material, adding water, ultrasonicating, stirring and evaporating to dryness, calcining in an oxygen atmosphere, and post-treating to obtain sodium manganate powder Na with a MXenes-like extended layer structure 0.91 MnO2.

2. The method for preparing the sodium manganate material having a MXenes-like extended layer structure according to claim 1, characterized in that: The following steps are involved: (1) calcining the manganese dioxide hollow nanotubes in an oxygen atmosphere to obtain a well-crystallized manganese dioxide tubular material with a hollow structure; (2) grinding the sodium salt that can decompose and generate gas with the above-mentioned manganese dioxide tubular material with a hollow structure, adding water, ultrasonicating, stirring and evaporating to dryness, calcining in an oxygen atmosphere, and post-treating to obtain sodium manganate powder Na with a MXenes-like extended layer structure. 0.91 MnO2.

3. The preparation method according to claim 2, characterized in that: The preparation method of the manganese dioxide hollow nanotubes is as follows: preparing a high-valent manganese salt solution, adjusting the pH value of the system to acidic, and then performing a hydrothermal reaction for a period of time to obtain the manganese dioxide hollow nanotubes.

4. The preparation method according to claim 3, characterized in that: The high-valent manganese salt is one or more of potassium permanganate, sodium permanganate, and potassium manganate; the concentration of the high-valent manganese salt is 0.02-0.1 mol / L, and the pH of the adjustment system is 1-4; the high-temperature hydrothermal reaction temperature of the manganese salt solution is 100-180° C., and the reaction time is 10-15h.

5. The preparation method according to claim 2, characterized in that: The calcination temperature in step (1) is 300-500°C.

6. The preparation method according to claim 2, characterized in that: The sodium salt that can be decomposed to generate gas is sodium carbonate.

7. The preparation method according to claim 2, characterized in that: The ultrasonic time is 10 min-1 h.

8. The preparation method according to claim 2, characterized in that: In the step (2), the molar ratio of sodium salt to manganese dioxide is 0.9:1-1.1:1, the high temperature roasting temperature is 700-1000° C., and the roasting time is 10-14 hours.

9. Use of the sodium manganate material with a unique MXenes-like extended layer structure as claimed in claim 1 as a positive electrode material for sodium ion batteries.

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