Silicon quantum dots SiQDs / COF supported by covalent organic frameworks BTCA-PA Preparation method and application

Abstract

The present invention discloses a preparation method and application of silicon quantum dots SiQDs / COF with covalent organic framework as a carrier BTCA‑PA The preparation method comprises adding an aqueous solution of PEI to an aqueous solution of nanosilicon, stirring and centrifuging at room temperature; freeze-drying the obtained brown solid to obtain PEI-modified nanosilicon (Si-PEI); adding it to a mixed solution of o-dichlorobenzene / n-butanol for dispersion and dissolution, then adding p-phenylenediamine and trimesoylbenzene, followed by ultrasonic dispersion, and then adding glacial acetic acid to obtain a mixed solution. Transfer the mixed solution to a high-pressure reaction kettle, add glacial acetic acid and deionized water to the mixed solution and react to obtain a precipitate; centrifuge and wash the precipitate, and then perform vacuum freeze-drying and grinding to obtain a pale yellow powder, thus obtaining SiQDs / COF BTCA‑PA The synthesis method of the invention is simple and has good effects. The synthesized product of the invention can effectively alleviate the volume expansion of nanosilicon, improve the stability and reversibility of the electrode material, and can be used as the anode material of a lithium-ion battery

Description

Technical Field

[0001] The present invention belongs to the field of material chemistry, and specifically relates to silicon quantum dots SiQDs / COF with covalent organic framework as carrier BTCA-PA Preparation method and application. Background Art

[0002] Silicon nanoparticles have an ultra-high theoretical capacity in the field of energy storage, but their severe volume expansion greatly limits their application. Today, commercial silicon-based negative electrode materials are made of nano-silicon and graphite in a mass ratio of 1:9. A small amount of silicon doped in graphite can increase the experimental capacity of graphite, and a small amount of silicon doping can only reduce its expansion rate, but it is essentially unable to solve the volume expansion of nano-silicon of about 400% during the charge and discharge process, which causes a large capacity loss of electrode materials. Moreover, nano-silicon has no base material as support and directly contacts the electrolyte material. The solid electrolyte interface film (SEI film) produced exists directly on the surface of silicon, which will break as the volume of silicon nanoparticles expands, thereby further forming a new SEI film, further reducing the experimental capacity of the material. Summary of the invention

[0003] Based on the above-mentioned background technology problems, it is necessary to develop a silicon quantum dot material that can alleviate the volume expansion of silicon. Covalent organic framework materials have a large specific surface area and more pores, and are excellent carriers of silicon quantum dots. Combining silicon quantum dots with covalent organic framework materials is an ideal solution.

[0004] The present invention aims to provide a silicon quantum dot SiQDs / COF with a covalent organic framework as a carrier. BTCA-PA The preparation method comprises the following steps:

[0005] (1) Ultrasonic dispersion of nano-silicon in tertiary water to obtain a nano-silicon aqueous solution;

[0006] (2) Ultrasonic dispersion of polyethyleneimine (PEI) in tertiary water to prepare a PEI aqueous solution;

[0007] (3) adding the PEI aqueous solution to the nano-silicon aqueous solution and stirring at room temperature, and then centrifuging three times with water; freeze-drying the obtained brown solid and grinding it into powder to obtain powdered PEI-modified nano-silicon (Si-PEI);

[0008] (4) adding the PEI-modified nano-silicon (Si-PEI) and polyvinyl pyrrolidone (PVP) to a mixed solution of o-dichlorobenzene / n-butanol (v / v=1:1), performing a first ultrasonic dispersion to completely dissolve, then adding p-phenylenediamine and triformylbenzene, performing a second ultrasonic dispersion, then adding glacial acetic acid and stirring at room temperature to obtain a mixed solution; transferring the mixed solution to an autoclave, adding glacial acetic acid and deionized water to the mixed solution, placing the autoclave in an oven at 120°C for reaction for 5 days, and obtaining a precipitate;

[0009] (5) The precipitate was centrifuged and washed with acetone as a detergent, and then vacuum-freeze-dried and ground to obtain a light yellow powder to obtain SiQDs / COF BTCA-PA .

[0010] Preferably, in step (1), the concentration of the nano-silicon aqueous solution is 5-10 mg / mL; in step (2), the concentration of the PEI aqueous solution is 50-100 mg / mL.

[0011] Preferably, in step (3), the stirring time at room temperature is 1 h and the rotation speed is 500 r / min.

[0012] Preferably, in step (4), the first ultrasonic dispersion is performed for 30 min, and the second ultrasonic dispersion is performed for 5 min.

[0013] Preferably, in step (4), the stirring time at room temperature is 4 h, the rotation speed is 500 r / min, and the lining of the high-pressure reactor is polytetrafluoroethylene.

[0014] Preferably, in step (4), the PEI-modified nano-silicon (Si-PEI) is 6-10 mg, the polyvinyl pyrrolidone (PVP) is 40-50 mg, and the o-dichlorobenzene / n-butanol mixed solution is 10 mL.

[0015] Preferably, in step (4), the amount of p-phenylenediamine is 5 mg, and the amount of trimesophenone is 5 mg.

[0016] Silicon quantum dots SiQDs / COF with covalent organic framework as carrier obtained according to the method BTCA-PA , used in the field of energy storage, and can be applied to negative electrode materials of lithium-ion batteries.

[0017] Through the above method, a large number of silicon quantum dots SiQDs / COF with covalent organic framework as carrier were successfully prepared. BTCA-PA The composite material is synthesized by mixing nano-silicon, polyethyleneimine, polyvinyl pyrrolidone, p-phenylenediamine and triformylbenzene uniformly at room temperature and then further crystallizing at high temperature.

[0018] Silicon quantum dots SiQDs / COF prepared by the present invention with covalent organic framework as carrier BTCA-PA The material can effectively slow down the huge volume expansion of silicon during the charging and discharging process of lithium-ion batteries, thereby improving the stability and reversibility of electrode materials. The silicon quantum dots prepared by the present invention have a small size of only about 5 nm, so their volume expansion can be greatly slowed down. In addition, the periphery of quantum silicon is supported by a covalent organic framework material as a substrate, which can provide limited space for the expansion of silicon, thereby effectively alleviating its volume expansion and the pulverization of electrode materials during the charging and discharging process of lithium-ion batteries. And the silicon quantum dots SiQDs / COF prepared by the present invention with a covalent organic framework as a carrier BTCA-PA , avoiding direct contact between silicon and electrolyte, can produce a stable solid electrolyte interface film (SEI film), effectively promote the transmission of lithium ions and greatly reduce the loss of capacity. Silicon quantum dots SiQDs / COF based on covalent organic framework BTCA-PA It can effectively alleviate the volume expansion of nano-silicon, improve the stability and reversibility of electrode materials, and has great development prospects in the field of energy storage.

[0019] The gain effect of the present invention is:

[0020] 1. The preparation method is simple; the composite material is prepared by mixing nano-silicon, polyethyleneimine, polyvinyl pyrrolidone, p-phenylenediamine and triformylbenzene uniformly at room temperature and then further crystallizing at high temperature.

[0021] 2. Good preparation effect; through SEM and TEM, it can be seen that the synthesized composite material has a uniform morphology and is loaded on COF BTCA-PA The silicon quantum dots in the nanostructured ... BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 :SiQDs / COF BTCA-PA Scanning electron microscope image of .

[0023] Figure 2(a): SiQDs / COF BTCA-PA Transmission electron microscopy images at different magnifications (0.2 mm).

[0024] Figure 2(b): SiQDs / COF BTCA-PA Transmission electron microscopy images at different magnifications (20 nm).

[0025] Figure 2(c): SiQDs / COF BTCA-PA Transmission electron microscopy images at different magnifications (2 nm).

[0026] Figure 3 :SiQDs / COF BTCA-PA X-ray diffraction pattern of .

[0027] Figure 4 :SiQDs / COF BTCA-PA Infrared spectrum of .

[0028] Figure 5 :SiQDs / COF BTCA-PA Thermogravimetric curve.

[0029] Figure 6 :SiQDs / COF BTCA-PA Nitrogen adsorption-desorption isotherm curve, and the inset is the pore size distribution diagram. DETAILED DESCRIPTION

[0030] Example 1

[0031] (1) Weigh 100 mg of nano-silicon and disperse it in 20 mL of tertiary water. Ultrasonicate for more than 10 min until the silicon is completely dispersed in the tertiary water to prepare a nano-silicon aqueous solution. The concentration of nano-silicon in the aqueous solution is 5 mg / mL.

[0032] (2) Weigh 500 mg of polyethyleneimine (PEI) and disperse it in 5 mL of tertiary water. Ultrasonic dispersion is performed for 10 min to prepare a PEI aqueous solution. The concentration of polyethyleneimine in the aqueous solution is 100 mg / mL.

[0033] (3) Slowly add 1 mL of PEI aqueous solution to the silicon aqueous solution, stir the solution at room temperature for 1 h at a speed of 500 r / min, and centrifuge it three times. Freeze-dry the obtained brown solid for 6 h, grind it into powder and store it in a desiccator to obtain powdered PEI-modified nanosilicon (Si-PEI).

[0034] (4) Weigh 6 mg of Si-PEI and 40 mg of polyvinylpyrrolidone (PVP) and add them to 10 mL of o-dichlorobenzene / n-butanol mixed solution (v / v=1:1). Ultrasonic dispersion was performed for 30 min to completely dissolve the solid. 5 mg of p-phenylenediamine and 5 mg of triphenylene were added to the solution and ultrasonic dispersion was performed for 5 min. 100 mL of glacial acetic acid was added and stirred at room temperature for 4 h at a speed of 500 r / min. The above solution was transferred to a 25 mL polytetrafluoroethylene-lined autoclave, and 400 mL of glacial acetic acid and 480 mL of deionized water were added dropwise to the solution. The autoclave was placed in an oven at 120°C for 5 days.

[0035] (5) The obtained precipitate is centrifuged and washed several times using acetone as a detergent, and then the obtained precipitate is freeze-dried and ground to obtain a light yellow powder, thus obtaining silicon quantum dots SiQDs / COF with a covalent organic framework as a carrier. BTCA-PA .

[0036] Example 2

[0037] (1) Weigh 100 mg of nano-silicon and disperse it in 10 mL of tertiary water. Ultrasonicate for more than 10 min until the silicon is completely dispersed in the tertiary water to prepare a nano-silicon aqueous solution. The concentration of nano-silicon in the aqueous solution is 10 mg / mL.

[0038] (2) Weigh 500 mg of polyethyleneimine (PEI) and disperse it in 10 mL of water. Ultrasonic dispersion is performed for 10 min to prepare a PEI aqueous solution. The concentration of polyethyleneimine in the aqueous solution is 50 mg / mL.

[0039] (3) Slowly add 1 mL of PEI aqueous solution to the silicon aqueous solution, stir the solution at room temperature for 1 h at a speed of 500 r / min, and centrifuge it three times. Freeze-dry the obtained brown solid for 6 h, grind it into powder and store it in a desiccator to obtain powdered PEI-modified nanosilicon (Si-PEI).

[0040] (4) Weigh 6 mg of Si-PEI and 40 mg of polyvinylpyrrolidone (PVP) and add them to 10 mL of o-dichlorobenzene / n-butanol mixed solution (v / v=1:1). Ultrasonic dispersion was performed for 30 min to completely dissolve the solid. 5 mg of p-phenylenediamine and 5 mg of triphenylene were added to the solution and ultrasonic dispersion was performed for 5 min. 100 mL of glacial acetic acid was added and stirred at room temperature for 4 h at a speed of 500 r / min. The above solution was transferred to a 25 mL polytetrafluoroethylene-lined autoclave, and 400 mL of glacial acetic acid and 480 mL of deionized water were added dropwise to the solution. The autoclave was placed in an oven at 120°C for 5 days.

[0041] (5) The obtained precipitate is centrifuged and washed several times using acetone as a detergent, and then the obtained precipitate is freeze-dried and ground to obtain a light yellow powder, thus obtaining silicon quantum dots SiQDs / COF with a covalent organic framework as a carrier. BTCA-PA .

[0042] Example 3

[0043] (1) Weigh 100 mg of nano-silicon and disperse it in 20 mL of tertiary water. Ultrasonicate for more than 10 min until the silicon is completely dispersed in the tertiary water to prepare a nano-silicon aqueous solution. The concentration of nano-silicon in the aqueous solution is 5 mg / mL.

[0044] (2) Weigh 500 mg of polyethyleneimine (PEI) and disperse it in 5 mL of tertiary water. Ultrasonic dispersion is performed for 10 min to prepare a PEI aqueous solution. The concentration of polyethyleneimine in the aqueous solution is 100 mg / mL.

[0045] (3) Slowly add 1 mL of PEI aqueous solution to the silicon aqueous solution, stir the solution at room temperature for 1 h at a speed of 500 r / min, and centrifuge it three times. Freeze-dry the obtained brown solid for 6 h, grind it into powder and store it in a desiccator to obtain powdered PEI-modified nanosilicon (Si-PEI).

[0046] (4) Weigh 10 mg of Si-PEI and 50 mg of polyvinylpyrrolidone (PVP) and add them to 10 mL of o-dichlorobenzene / n-butanol mixed solution (v / v=1:1). Ultrasonic dispersion was performed for 30 min to completely dissolve the solid. 5 mg of p-phenylenediamine and 5 mg of triphenylene were added to the solution and ultrasonic dispersion was performed for 5 min. 100 mL of glacial acetic acid was added and stirred at room temperature for 4 h at a speed of 500 r / min. The above solution was transferred to a 25 mL polytetrafluoroethylene-lined autoclave, and 400 mL of glacial acetic acid and 480 mL of deionized water were added dropwise to the solution. The autoclave was placed in an oven at 120°C for 5 days.

[0047] (5) The obtained precipitate is centrifuged and washed several times using acetone as a detergent, and then the obtained precipitate is freeze-dried and ground to obtain a light yellow powder, thus obtaining silicon quantum dots SiQDs / COF with a covalent organic framework as a carrier. BTCA-PA .

[0048] Example 4

[0049] (1) Weigh 100 mg of nano-silicon and disperse it in 10 mL of tertiary water. Ultrasonicate for more than 10 min until the silicon is completely dispersed in the tertiary water to prepare a nano-silicon aqueous solution. The concentration of nano-silicon in the aqueous solution is 10 mg / mL.

[0050] (2) Weigh 500 mg of polyethyleneimine (PEI) and disperse it in 10 mL of water. Ultrasonic dispersion is performed for 10 min to prepare a PEI aqueous solution. The concentration of polyethyleneimine in the aqueous solution is 50 mg / mL.

[0051] (3) Slowly add 1 mL of PEI aqueous solution to the silicon aqueous solution, stir the solution at room temperature for 1 h at a speed of 500 r / min, and centrifuge it three times. Freeze-dry the obtained brown solid for 6 h, grind it into powder and store it in a desiccator to obtain powdered PEI-modified nanosilicon (Si-PEI).

[0052] (4) Weigh 10 mg of Si-PEI and 50 mg of polyvinylpyrrolidone (PVP) and add them to 10 mL of o-dichlorobenzene / n-butanol mixed solution (v / v=1:1). Ultrasonic dispersion was performed for 30 min to completely dissolve the solid. 5 mg of p-phenylenediamine and 5 mg of triphenylene were added to the solution and ultrasonic dispersion was performed for 5 min. 100 mL of glacial acetic acid was added and stirred at room temperature for 4 h at a speed of 500 r / min. The above solution was transferred to a 25 mL polytetrafluoroethylene-lined autoclave, and 400 mL of glacial acetic acid and 480 mL of deionized water were added dropwise to the solution. The autoclave was placed in an oven at 120°C for 5 days.

[0053] (5) The obtained precipitate is centrifuged and washed several times using acetone as a detergent, and then the obtained precipitate is freeze-dried and ground to obtain a light yellow powder, thus obtaining silicon quantum dots SiQDs / COF with a covalent organic framework as a carrier. BTCA-PA .

[0054] Scanning electron microscopy and transmission electron microscopy show that the material has a relatively uniform morphology, presenting uniformly in the form of nanoparticles. High-resolution transmission electron microscopy shows that the size of the black nanoparticles is 2-5 nm, which is in the quantum size range, and has uniform lattice fringes. The lattice fringes were measured and found to have a lattice spacing of 1.98 nm, corresponding to the 220 crystal plane of silicon.

Claims

1. Silicon quantum dots SiQDs / COF based on covalent organic framework BTCA-PA The preparation method comprises the following steps: (1) Ultrasonic dispersion of nano-silicon in tertiary water to obtain a nano-silicon aqueous solution; (2) Ultrasonic dispersion of polyethyleneimine (PEI) in tertiary water to prepare a PEI aqueous solution; (3) adding the PEI aqueous solution to the nano-silicon aqueous solution and stirring at room temperature, and then centrifuging three times with water; freeze-drying the obtained brown solid and grinding it into powder to obtain powdered PEI-modified nano-silicon (Si-PEI); (4) adding the PEI-modified nano-silicon (Si-PEI) and polyvinyl pyrrolidone (PVP) to a mixed solution of o-dichlorobenzene / n-butanol (v / v=1:1), performing a first ultrasonic dispersion to completely dissolve, then adding p-phenylenediamine and triformylbenzene, performing a second ultrasonic dispersion, then adding glacial acetic acid and stirring at room temperature to obtain a mixed solution; transferring the mixed solution to an autoclave, adding glacial acetic acid and deionized water to the mixed solution, placing the autoclave in an oven at 120°C for reaction for 5 days, and obtaining a precipitate; (5) The precipitate was centrifuged and washed with acetone as a detergent, and then vacuum-freeze-dried and ground to obtain a light yellow powder to obtain SiQDs / COF BTCA-PA .

2. The method according to claim 1, characterized in that: In step (1), the concentration of the nano-silicon aqueous solution is 5-10 mg / mL; in step (2), the concentration of the PEI aqueous solution is 50-100 mg / mL.

3. The method according to claim 1, characterized in that: In step (3), the stirring time at room temperature is 1 h and the rotation speed is 500 r / min.

4. The method according to claim 1, characterized in that: In step (4), the first ultrasonic dispersion time is 30 min, and the second ultrasonic dispersion time is 5 min.

5. The method according to claim 1, characterized in that: In step (4), the stirring time at room temperature is 4 h, the rotation speed is 500 r / min, and the lining of the high-pressure reactor is polytetrafluoroethylene.

6. The method according to claim 1, characterized in that: In step (4), the PEI-modified nano-silicon (Si-PEI) is 6-10 mg, the polyvinyl pyrrolidone (PVP) is 40-50 mg, and the o-dichlorobenzene / n-butanol mixed solution is 10 mL.

7. The method according to claim 1, characterized in that: In step (4), the amount of p-phenylenediamine is 5 mg, and the amount of triphenylene is 5 mg.

8. Silicon quantum dots SiQDs / COF with covalent organic framework as carrier obtained by the method according to any one of claims 1 to 7 BTCA-PA .

9. The silicon quantum dots SiQDs / COF with a covalent organic framework as a carrier according to claim 8 BTCA-PA , characterized in that: The silicon quantum dots SiQDs / COF with covalent organic framework as carrier BTCA-PA Applied in the field of energy storage, it can be used as negative electrode material for lithium-ion batteries.

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