Method for laser-induced synthesis of hollow carbon spheres from al- metal organic frameworks and applications thereof

Abstract

The application provides a method for synthesizing hollow carbon spheres by laser-induced aluminum metal organic framework and application thereof, and the method comprises the following steps: S1, obtaining double-pyramid-shaped Al-MOF by a hydrothermal method, and drying the double-pyramid-shaped Al-MOF under vacuum conditions to obtain dry double-pyramid-shaped Al-MOF powder; S2, placing the dry double-pyramid-shaped Al-MOF powder between two glass slides; S3, irradiating and treating the double-pyramid-shaped Al-MOF powder by laser, and the double-pyramid-shaped Al-MOF is induced to transform into hollow carbon spheres by laser, thereby obtaining hollow carbon sphere powder; and S4, mixing the obtained hollow carbon sphere powder with sublimed sulfur powder, and then heating to obtain a hollow carbon sphere / sulfur composite material. The application has the beneficial effect that the double-pyramid-shaped Al-MOF is induced to transform into hollow carbon spheres by laser induction technology, the hollow carbon sphere structure can promote the penetration of electrolytes, promote the transmission of electrons / ions, improve the utilization rate of sulfur, prevent the shuttle of polysulfides, and buffer the expansion of the electrode during the cycle.

Description

Technical Field

[0001] This invention relates to the field of Al-MOF (aluminum-based metal-organic framework) preparation technology, and in particular to a method for laser-induced synthesis of hollow carbon spheres from aluminum metal-organic frameworks and its application. Background Technology

[0002] Metal-organic frameworks (MOFs) possess characteristics such as high specific surface area, tunable pore size, diverse structures, and porous structures, leading to their wide application in adsorption, catalysis, ion exchange, and energy storage. In particular, MOFs can serve as sulfur hosts in the composite cathode of lithium-sulfur batteries (Li-S batteries), where sulfur molecules can be tightly immobilized within the porous MOF structure. Metal nodes and functional groups can provide more effective binding sites for polysulfides. However, MOF materials in lithium-sulfur batteries suffer from problems such as rapid capacity decay, limited ion diffusion, and poor rate performance. Summary of the Invention

[0003] In view of this, in order to solve the problems of rapid capacity decay, limited ion diffusion and poor rate performance of MOF materials in lithium-sulfur batteries, embodiments of the present invention provide a method for synthesizing hollow carbon spheres by laser-induced aluminum metal-organic frameworks and its application.

[0004] First, embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, characterized by comprising the following steps: S1. Obtain double pyramidal Al-MOF by hydrothermal method, and dry the double pyramidal Al-MOF under vacuum conditions to obtain dry double pyramidal Al-MOF powder. S2. Place the dried double pyramidal Al-MOF powder between two glass slides; S3. By irradiating the double pyramidal Al-MOF powder with a laser, the double pyramidal Al-MOF is induced by the laser to transform into hollow carbon spheres, thus obtaining hollow carbon sphere powder. S4. Mix the obtained hollow carbon sphere powder with sublimed sulfur powder, and then heat to obtain hollow carbon sphere / sulfur composite material.

[0005] Furthermore, in step S3, the power of the laser irradiating the double pyramidal Al-MOF powder is 15-35W, the laser moving speed is 10-100mm / second, and the laser frequency is 20 kHz.

[0006] Furthermore, in step S3, a glass slide containing Al-MOF powder is placed inside a laser, and the double pyramid-shaped Al-MOF powder is irradiated by the laser.

[0007] Furthermore, in step S1, the hydrothermal temperature of the hydrothermal method is 120-140℃, the vacuum drying temperature is 60-80℃, and the heat preservation time is 7-8 hours.

[0008] Furthermore, in step S4, the heating temperature is 155°C and the holding time is 10-12 hours.

[0009] Furthermore, in step S4, hollow carbon spheres and sublimated sulfur powder are mixed at a mass ratio of 4:6.

[0010] Furthermore, in step S2, the dried double pyramidal Al-MOF powder is placed into the groove of one of the glass slides, and then another glass slide is placed on top of the groove.

[0011] Furthermore, the groove is a rectangular groove with a length, width, and height of 2cm × 2cm × 0.5cm.

[0012] Furthermore, embodiments of the present invention also provide a hollow carbon sphere / sulfur composite material prepared by the above-described laser-induced aluminum metal-organic framework synthesis method for hollow carbon spheres.

[0013] Furthermore, embodiments of the present invention also provide the application of the hollow carbon sphere / sulfur composite material prepared by the above-described laser-induced aluminum metal-organic framework synthesis method in the positive electrode of a lithium-sulfur battery, wherein the positive electrode of the lithium-sulfur battery includes the hollow carbon sphere / sulfur composite material.

[0014] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The method for synthesizing hollow carbon spheres by laser-induced aluminum metal-organic framework and its application, through laser-induced technology, induces double pyramidal Al-MOF to be transformed into hollow carbon spheres. The hollow carbon sphere structure can promote electrolyte penetration, promote electron / ion transfer, improve sulfur utilization, prevent polysulfide shuttle, and buffer electrode expansion during cycling. The hollow carbon sphere / sulfur composite material prepared by this laser-induced aluminum metal-organic framework method is applied to the positive electrode of lithium-sulfur batteries, enhancing the conductivity and sulfur loading of the lithium-sulfur battery positive electrode, promoting electrolyte penetration, improving the electrolyte / electrode contact area, and promoting electron / ion transport, so that the lithium-sulfur battery positive electrode has high capacity, excellent rate performance and stable cycle performance. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the principle of laser irradiation treatment of double pyramidal Al-MOF powder in this invention. Figure 2 This is a SEM (scanning electron microscope) image of Al-MOF obtained by hydrothermal method in Example 1 of the present invention; Figure 3This is a SEM image of the hollow carbon spheres prepared in Example 1 of this invention; Figure 4 This refers to the laser-induced process for obtaining hollow carbon spheres in Embodiment 1 of the present invention. Figure 5 This is an electrochemical performance diagram of the lithium-sulfur battery cathode prepared by the hollow carbon sphere / sulfur composite material in Example 1 of the present invention. Figure 6 This is an X-ray diffraction test pattern of the hollow carbon sphere of Embodiment 1 of the present invention; Figure 7 This is a cycle test performance diagram of the lithium-sulfur battery cathode made of the hollow carbon sphere / sulfur composite material of Example 1 of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0017] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0018] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0019] Example 1 Embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, comprising the following steps: S1. The double-pyramid Al-MOF obtained under hydrothermal conditions is dried under vacuum to obtain dried double-pyramid Al-MOF powder. The hydrothermal temperature is 120-140℃, the vacuum drying temperature is 60-80℃, and the holding time is 7-8 hours. In this embodiment, the hydrothermal temperature is 140℃, the vacuum drying temperature is 70℃, and the vacuum drying time is 7 hours.

[0020] like Figure 1 and 2 As shown, the Al-MOF obtained by the hydrothermal method in this embodiment exhibits a double pyramid shape, uniform size, and smooth surface.

[0021] S2. Place the dried double-pyramid Al-MOF powder between two glass slides. One of the glass slides has a groove. Place the dried double-pyramid Al-MOF powder on the glass slide, filling the groove completely. Then cover the groove with the other glass slide. In this embodiment, the glass slide is made of quartz glass, and the groove is a rectangular groove with dimensions of 2cm × 2cm × 0.5cm.

[0022] S3. The double-pyramid-shaped Al-MOF powder is irradiated with a laser, causing the double-pyramid-shaped Al-MOF to be induced to transform into hollow carbon spheres, thus obtaining hollow carbon sphere powder. Specifically, as shown... Figure 4 As shown, a glass slide containing Al-MOF powder is placed inside a laser, and the laser source is focused on the double pyramidal Al-MOF powder. The laser power is set, and the double pyramidal Al-MOF powder is irradiated by the laser. The powder is then scraped off the glass slide using a key to obtain hollow carbon sphere powder.

[0023] The laser power used to irradiate the double-pyramid-shaped Al-MOF powder is 15-35W, the laser movement speed is 10-100mm / s, and the laser frequency is 20kHz. In this embodiment, the laser power is 15W and the laser movement speed is 30 mm / s.

[0024] like Figure 3 The hollow carbon spheres shown are uniformly distributed and have smooth surfaces.

[0025] S4. Mix the obtained hollow carbon sphere powder with sublimed sulfur powder, and then heat to obtain a hollow carbon sphere / sulfur composite material. Specifically, weigh 100 mg of hollow carbon sphere powder and 150 mg of sublimed sulfur powder, grind and mix them evenly, place the ground sample in a reaction vessel, and place the reaction vessel in an oven at 155°C for 12 hours to complete the sulfur loading process and obtain the hollow carbon sphere / sulfur composite material.

[0026] Example 2 Embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, comprising the following steps: S1. The double-pyramid Al-MOF obtained under hydrothermal conditions is dried under vacuum conditions to obtain dried double-pyramid Al-MOF powder. In this embodiment, the hydrothermal temperature is selected as 140℃, the vacuum drying temperature is selected as 70℃, and the vacuum drying time is 7 hours.

[0027] S2. Place the dried double pyramidal Al-MOF powder between two glass slides. One of the glass slides has a groove. Place the dried double pyramidal Al-MOF powder on the glass slide so that the powder completely fills the groove, and then cover the groove with the other glass slide.

[0028] S3. Place a glass slide containing Al-MOF powder inside a laser, focusing the laser light source onto the double-pyramid Al-MOF powder. Set the laser power and irradiate the double-pyramid Al-MOF powder with the laser. Use a key to scrape the powder off the glass slide to obtain hollow carbon sphere powder. In this embodiment, the laser power is selected as 25W, the laser movement speed is selected as 30mm / second, and the laser frequency is 20kHz.

[0029] S4. Weigh 100 mg of hollow carbon sphere powder and 150 mg of sublimed sulfur powder, grind and mix them evenly, place the ground sample in a reaction vessel, place the reaction vessel in an oven at 155℃ and heat for 12 hours to complete the sulfur loading process and obtain hollow carbon sphere / sulfur composite material.

[0030] Example 3 Embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, comprising the following steps: S1. The double-pyramid Al-MOF obtained under hydrothermal conditions is dried under vacuum conditions to obtain dried double-pyramid Al-MOF powder. In this embodiment, the hydrothermal temperature is selected as 140℃, the vacuum drying temperature is selected as 70℃, and the vacuum drying time is 7 hours.

[0031] S2. Place the dried double pyramidal Al-MOF powder between two glass slides. One of the glass slides has a groove. Place the dried double pyramidal Al-MOF powder on the glass slide so that the powder completely fills the groove, and then cover the groove with the other glass slide.

[0032] S3. Place a glass slide containing Al-MOF powder inside a laser, focusing the laser light source onto the double-pyramid Al-MOF powder. Set the laser power and irradiate the double-pyramid Al-MOF powder with the laser. Use a key to scrape the powder off the glass slide to obtain hollow carbon sphere powder. In this embodiment, the laser power is 35W, the laser movement speed is 50mm / second, and the laser frequency is 20kHz.

[0033] S4. Weigh 100 mg of hollow carbon sphere powder and 150 mg of sublimed sulfur powder, grind and mix them evenly, place the ground sample in a reaction vessel, place the reaction vessel in an oven at 155℃ and heat for 12 hours to complete the sulfur loading process and obtain hollow carbon sphere / sulfur composite material.

[0034] Example 4 Embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, comprising the following steps: S1. The double-pyramid Al-MOF obtained under hydrothermal conditions is dried under vacuum conditions to obtain dried double-pyramid Al-MOF powder. In this embodiment, the hydrothermal temperature is selected as 140℃, the vacuum drying temperature is selected as 70℃, and the vacuum drying time is 7 hours.

[0035] S2. Place the dried double pyramidal Al-MOF powder between two glass slides. One of the glass slides has a groove. Place the dried double pyramidal Al-MOF powder on the glass slide so that the powder completely fills the groove, and then cover the groove with the other glass slide.

[0036] S3. Place a glass slide containing Al-MOF powder inside a laser, focusing the laser light source onto the double-pyramid Al-MOF powder. Set the laser power and irradiate the double-pyramid Al-MOF powder with the laser. Use a key to scrape the powder off the glass slide to obtain hollow carbon sphere powder. In this embodiment, the laser power is 35W, the laser movement speed is 100mm / second, and the laser frequency is 20kHz.

[0037] S4. Weigh 100 mg of hollow carbon sphere powder and 150 mg of sublimed sulfur powder, grind and mix them evenly, place the ground sample in a reaction vessel, place the reaction vessel in an oven at 155℃ and heat for 12 hours to complete the sulfur loading process and obtain hollow carbon sphere / sulfur composite material.

[0038] Example 5 Embodiments of the present invention provide a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks, comprising the following steps: S1. The double-pyramid Al-MOF obtained under hydrothermal conditions is dried under vacuum conditions to obtain dried double-pyramid Al-MOF powder. In this embodiment, the hydrothermal temperature is selected as 140℃, the vacuum drying temperature is selected as 70℃, and the vacuum drying time is 7 hours.

[0039] S2. Place the dried double pyramidal Al-MOF powder between two glass slides. One of the glass slides has a groove. Place the dried double pyramidal Al-MOF powder on the glass slide so that the powder completely fills the groove, and then cover the groove with the other glass slide.

[0040] S3. Place a glass slide containing Al-MOF powder inside a laser, focusing the laser light source onto the double-pyramid Al-MOF powder. Set the laser power and irradiate the double-pyramid Al-MOF powder with the laser. Use a key to scrape the powder off the glass slide to obtain hollow carbon sphere powder. In this embodiment, the laser power is 15W, the laser movement speed is 30mm / second, and the laser frequency is 20kHz.

[0041] S4. Weigh 100 mg of hollow carbon sphere powder and 150 mg of sublimed sulfur powder, grind and mix them evenly, place the ground sample in a reaction vessel, place the reaction vessel in an oven at 155℃ and heat for 12 hours to complete the sulfur loading process and obtain hollow carbon sphere / sulfur composite material.

[0042] In addition, in various embodiments of the present invention, the prepared hollow carbon sphere / sulfur composite material, conductive carbon black and polyvinylidene fluoride are mixed in an N-methylpyrrolidone solution at a mass ratio of 7:2:1 to prepare a uniform slurry. Then, the slurry is coated onto aluminum foil with a 90mm or 120mm scraper. The aluminum foil coated with slurry is dried in an oven at 70°C for 12 hours. 12mm electrode sheets are cut out using a cutting machine. Lithium metal sheets are selected as counter electrodes. The battery is assembled in an argon-filled glove box to form a coin-type lithium-sulfur battery.

[0043] Results and Analysis: Depend on Figure 5 The electrochemical performance graph of the lithium-sulfur battery cathode prepared by the hollow carbon sphere / sulfur composite material in Example 1 shows two oxidation peaks, corresponding to the two-step oxidation of lithium sulfide to sulfur. In addition, two reduction peaks are also present on the CV curve (capacitance-voltage characteristic curve).

[0044] Depend on Figure 6 The X-ray diffraction pattern of the hollow carbon spheres in Example 1 clearly shows the presence of carbon characteristic peaks. Hollow carbon spheres can increase the sulfur loading and improve the conductivity of the composite electrode, thereby enhancing its electrochemical performance.

[0045] Figure 7 The graph shows the cycle performance of the lithium-sulfur battery cathode prepared from the hollow carbon sphere / sulfur composite material of Example 1. The graph reveals that the initial specific capacity of the hollow carbon sphere / sulfur cathode is 1077.8 mAh g⁻¹. -1After 150 cycles, the specific capacity of the hollow carbon sphere / sulfur cathode was 395.7 mAh g. -1 .

[0046] The hollow carbon sphere / sulfur composite materials prepared in Examples 2-5, and the lithium-sulfur battery cathodes made from the hollow carbon sphere / sulfur composite materials, have the same performance characteristics as those in Example 1.

[0047] This invention discloses a method for synthesizing hollow carbon spheres using laser-induced aluminum metal-organic frameworks and its application. Laser-induced transformation of double-pyramidal Al-MOFs into hollow carbon spheres is achieved. The hollow carbon sphere structure promotes electrolyte permeation, electron / ion transfer, sulfur utilization, prevents polysulfide shuttle, and buffers electrode expansion during cycling. The hollow carbon sphere / sulfur composite material prepared using this laser-induced aluminum metal-organic framework method is applied to the cathode of lithium-sulfur batteries, enhancing the conductivity and sulfur loading of the lithium-sulfur battery cathode, promoting electrolyte permeation, improving the electrolyte / electrode contact area, and promoting electron / ion transport. This results in lithium-sulfur battery cathodes exhibiting high capacity, excellent rate performance, and stable cycle performance.

[0048] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0049] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for laser-induced synthesis of hollow carbon sphere / sulfur composite materials from aluminum metal-organic frameworks, characterized in that, Includes the following steps: S1. Obtain double pyramidal Al-MOF by hydrothermal method, and dry the double pyramidal Al-MOF under vacuum conditions to obtain dry double pyramidal Al-MOF powder. S2. Place the dried double pyramidal Al-MOF powder between two glass slides; S3. The double pyramidal Al-MOF powder is treated by laser irradiation. The double pyramidal Al-MOF is induced by laser to transform into hollow carbon spheres, and hollow carbon sphere powder is obtained. The power of the laser irradiating the double pyramidal Al-MOF powder is 15-35W, the laser moving speed is 10-100mm / second, and the laser frequency is 20kHz. S4. Mix the obtained hollow carbon sphere powder with sublimed sulfur powder, and then heat to obtain hollow carbon sphere / sulfur composite material.

2. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 1, characterized in that: In step S3, a glass slide containing Al-MOF powder is placed inside a laser, and the double pyramid-shaped Al-MOF powder is irradiated by the laser.

3. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 1, characterized in that: In step S1, the hydrothermal temperature of the hydrothermal method is 120-140℃, the vacuum drying temperature is 60-80℃, and the drying time is 7-8 hours.

4. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 1, characterized in that: In step S4, the heating temperature is 155℃ and the heating time is 10-12 hours.

5. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 1, characterized in that: In step S4, hollow carbon spheres and sublimed sulfur powder are mixed at a mass ratio of 4:

6.

6. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 1, characterized in that: In step S2, the dried double pyramidal Al-MOF powder is placed into the groove of one of the glass slides, and then another glass slide is placed on top of the groove.

7. The method for synthesizing hollow carbon sphere / sulfur composite materials using laser-induced aluminum metal-organic frameworks as described in claim 6, characterized in that: The groove is a rectangular groove with a length, width, and height of 2cm × 2cm × 0.5cm.

8. Hollow carbon sphere / sulfur composite material prepared by the method of laser-induced aluminum metal-organic framework synthesis of hollow carbon sphere / sulfur composite material according to any one of claims 1-7.

9. The application of the hollow carbon sphere / sulfur composite material as described in claim 8 in the positive electrode of a lithium-sulfur battery, characterized in that: The positive electrode of the lithium-sulfur battery includes the hollow carbon sphere / sulfur composite material.

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