CN110707383A - A kind of preparation method and using method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery - Google Patents

Abstract

A preparation method of an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries and a use method thereof belong to the field of lithium-sulfur batteries. The described dimethylformamide is added to the weighed vanadyl acetylacetonate of the present invention, magnetically stirred for a certain period of time, and after fully dissolving, the described 4-4 diaminodiphenyl ether is added, and after a certain period of ultrasonication , under the condition of mechanical stirring, the pyromellitic anhydride is added in stages, and after stirring for a certain period of time, a precursor solution is obtained, and then high temperature treatment is performed after electrospinning, and it is converted into amorphous containing Nanofibrous webs of vanadium oxide and used as an additive layer for lithium-sulfur batteries. The fiber interlayer has a good confinement effect on the intermediate products of lithium-sulfur batteries and provides good electrical conductivity, and no binder and conductive agent need to be added during the preparation of the interlayer. The performance of the battery has been greatly improved.

Description

A kind of preparation method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery and how to use it

technical field

The invention belongs to the field of lithium-sulfur batteries; in particular, it relates to a preparation method of an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries and a method for using the same.

Background technique

In recent years, the excessive exploitation and use of non-renewable energy sources such as fossil fuels have caused serious environmental pollution and global warming. Therefore, the development of renewable and clean energy technologies is a major problem for scientists in the 21st century. Lithium-ion batteries with high energy density and long cycle life have been widely used in mobile phones, computers and new energy vehicles in the past 20 years. However, with the increasing cost caused by the shortage of lithium resources and the higher demand for technical parameters such as the specific capacity and cycle performance of lithium-ion batteries, scientists have been working on developing more ideal secondary batteries, in which the theory of lithium-sulfur batteries The energy density (~2600Wh·kg ^-1 ) is much higher than the existing commercial lithium-ion battery (~500Wh·kg ^-1 ), and the content of sulfur element in the earth's crust is high, the price is cheap, and it is non-polluting to the environment, which is regarded as The most ideal replacement battery for lithium ion in the future.

However, lithium-sulfur batteries still face many challenges. The most critical problem is that the lithium polysulfide generated during the discharge process will dissolve in the electrolyte, which greatly reduces the utilization rate of active material sulfur and reduces the cycle performance of the battery. . At present, many materials have been developed to be used as sulfur supports in positive electrodes, including carbon materials, metal oxides, etc. These materials solve the problem of polysulfide dissolution to a certain extent. However, the addition of these carbon or metal compounds reduces the energy density of the electrodes, so more and more attention has been paid to bare sulfur cathodes in recent years.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries and a method for using the same.

The present invention is achieved through the following technical solutions:

A preparation method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery, comprising the following steps:

Step 1. Weigh a certain quality of vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether and pyromellitic anhydride respectively according to a certain material-to-liquid ratio, and set aside for use;

Step 2. Add the dimethylformamide to the vanadyl acetylacetonate weighed in step 1, stir magnetically for a certain period of time, and after fully dissolving, add the 4-4 diaminodiphenyl ether , after sonicating for a certain period of time, under the condition of mechanical stirring, the pyromellitic anhydride is added in stages, and after stirring for a certain period of time, a precursor solution is obtained, which is ready for use;

Step 3. Electrospin the precursor solution prepared in Step 2 to obtain polymer fibers, which are ready for use;

Step 4. The polymer fibers prepared in step 3 are placed in a tube furnace for heat treatment, heated to a range of 250-300 °C at a rate of 5 °C min ^-1 and maintained for 1-2 h, and then under the protection of argon gas , rise to the range of 650-900°C at a rate of 5-10°C min ^-1 and hold for 1-2 hours, then drop to 300°C at a rate of 5-10°C min ^-1 , and finally anneal to room temperature to obtain a An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 1, vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether, pyromellitic tetrakis The solid-liquid ratio of formic anhydride is 1.0-1.2g:10-15ml:1.0-1.2g:1.08-1.2g.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 2, the magnetic stirring time of the dimethylformamide is added to the vanadyl acetylacetonate for 10-20 minutes, and the ultrasonic Time 15-20min, mechanical stirring time 20-30min.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 3, the electrospinning conditions are in a temperature environment of 35°C, the applied voltage is 17kV, and the flow rate is 0.4ml·h ^{- 1} , the humidity is 40%, the distance between the metal nozzle and the aluminum foil collector is 14cm.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 4, the heat treatment process is to raise the temperature to a range of 300° C. at a rate of 5° C. min ⁻¹ and hold for 1 h, and then Under the protection of argon, it was raised to the range of 900°C at a rate of 10°C min ^-1 and held for 2 h, then decreased to 300°C at a rate of 5°C min ^-1 , and finally annealed to room temperature.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention prepares the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries is made into a circular interlayer, which is placed between the separator and the positive electrode of the lithium-sulfur battery.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention prepares the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The preparation method of the positive electrode is to use the sublimated sulfur powder as the positive electrode active material, Super-P as the conductive agent, and PVDF as the binder. After manual grinding in a mortar for 20 minutes, add 5% NMP solution and stir magnetically for 6h until black uniform. The paste slurry was then evenly spread on an aluminum sheet with a diameter of 12 mm with a glass rod, and then dried in a vacuum oven at 60 °C for 24 hours to prepare a positive electrode.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention prepares the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The mass ratio of sublimed sulfur powder, Super-P and PVDF is 7:2:1.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention prepares the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The diaphragm is a pp film.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention prepares the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the A method of making circular interlayers from amorphous vanadium oxide/carbon fiber materials for lithium-sulfur batteries is to use a small punching machine to cut them into 16mm black circular sheets.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 2, 4-4 diaminodiphenyl ether and pyromellitic anhydride undergo a polycondensation reaction to form a soluble high molecular weight Polyamic acid (PAA, polyamide acid), the theoretical calculation shows that the molecular weight of the polyamic acid obtained is the largest when the mass ratio of the two is 1:1, but a small amount of water will be removed during the reaction process, so the pyromellitic anhydride The content is increased slightly, eventually bringing it to maximum viscosity.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, the nanofibers prepared by electrospinning technology in step 3 not only have high specific surface area and good electrochemical performance , and has excellent mechanical properties. Using it as an additive layer between the lithium-sulfur battery separator and the sulfur cathode can effectively inhibit the dissolution of polysulfides, thereby achieving high performance of the lithium-sulfur battery.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, in step 4, the polyamic acid polymer fiber undergoes a stepwise imidization reaction in the range of 250-300° C. during the heating process Converted into pale yellow polyimide (PI, Polyimide) fiber.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention utilizes vanadyl acetylacetonate and polyamic acid as electrospinning precursors, and converts them into carbon-containing materials through high temperature carbonization and other steps. Nanofibrous webs of amorphous vanadium oxide and used as an additive layer for lithium-sulfur batteries. The fiber interlayer has a good confinement effect on the intermediate product (polysulfide) of the lithium-sulfur battery and provides good electrical conductivity, and the preparation of the interlayer does not require the addition of binders and conductive agents. The subsequent battery performance tests also proved that The interlayer greatly improves the performance of lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention, the obtained amorphous vanadium oxide interlayer and a pure sulfur electrode are assembled into a button-type lithium-sulfur battery, and the electrochemical performance is tested. . The measured rate performance shows that the first cycle discharge capacity of the battery is as high as 1236mA h·g ^-1 at a current density of 0.1C, and its capacity remains above 700mA h·g ^-1 at a large current density of 2C; It is fully demonstrated that the amorphous vanadium oxide carbon fiber interlayer provided by the present invention has a good inhibitory effect on the shuttle effect of the lithium-sulfur battery, and the battery has excellent rate performance. At the same time, the present invention tests the service life of the obtained button-type lithium-sulfur battery, and the results show that the capacity of the battery can still be maintained at 769mA h·g ^-1 after being charged and discharged 700 times at a high current density of 1C (1C=1675mA/g). This shows that the amorphous vanadium oxide carbon fiber interlayer provided by the present invention has high research value in improving the electrochemical performance of the lithium-sulfur battery.

Description of drawings

1 is a process flow diagram of a method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the present invention;

2 is a schematic diagram of the sandwich structure of a button-type lithium-sulfur battery according to a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to the present invention;

3 is a SEM image of 2200 times the size of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

4 is a 5000-fold SEM picture of an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

5 is a 50,000-fold SEM picture of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

6 is a photo of the element distribution of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

Fig. 7 is the 8000 times transmission electron microscope photograph of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery prepared by the method of the specific embodiment;

8 is a 20,000-times transmission electron microscope photograph of an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

9 is an X-ray diffraction pattern of an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

10 is the XPS spectrum of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method in Embodiment 1;

Fig. 11 is the charge-discharge curve of the amorphous vanadium oxide/carbon fiber material according to the second embodiment for the lithium-sulfur battery at the 1st, 100th, 300th, 500th and 700th times;

12 is a rate performance curve of the amorphous vanadium oxide/carbon fiber material according to Embodiment 2 used in a lithium-sulfur battery;

FIG. 13 is a cycle performance curve of the amorphous vanadium oxide/carbon fiber material according to Embodiment 2 used in a lithium-sulfur battery at a charge-discharge current density of 1C for the first 700 cycles.

Detailed ways

Specific implementation one:

A preparation method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery, comprising the following steps:

Step 1. Weigh a certain quality of vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether and pyromellitic anhydride respectively according to a certain material-to-liquid ratio, and set aside for use;

Step 2. Add the dimethylformamide to the vanadyl acetylacetonate weighed in step 1, stir magnetically for a certain period of time, and after fully dissolving, add the 4-4 diaminodiphenyl ether , after sonicating for a certain period of time, under the condition of mechanical stirring, the pyromellitic anhydride is added in stages, and after stirring for a certain period of time, a precursor solution is obtained, which is ready for use;

Step 3. Electrospin the precursor solution prepared in Step 2 to obtain polymer fibers, which are ready for use;

Step 4. The polymer fibers prepared in step 3 are placed in a tube furnace for heat treatment, heated to a range of 250-300 °C at a rate of 5 °C min ^-1 and maintained for 1-2 h, and then under the protection of argon gas , rise to the range of 650-900°C at a rate of 5-10°C min ^-1 and hold for 1-2 hours, then drop to 300°C at a rate of 5-10°C min ^-1 , and finally anneal to room temperature to obtain a An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, in step 1, vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether, homophenylene The solid-liquid ratio of tetracarboxylic anhydride is 1.0-1.2g:10-15ml:1.0-1.2g:1.08-1.2g.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, in step 2, the magnetic stirring time for adding the dimethylformamide to the vanadyl acetylacetonate is 10-20 min, Ultrasonic time 15-20min, mechanical stirring time 20-30min.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, in step 3, the electrospinning conditions are in a temperature environment of 35°C, the applied voltage is 17kV, and the flow rate is 0.4ml·h ^-1 , the humidity is 40%, and the distance between the metal nozzle and the foil collector is 14cm.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment, in step 4, the heat treatment process is to raise the temperature to a range of 300°C at a rate of 5°C min ^-1 and keep it for 1 hour, Then, under the protection of argon, it was raised to the range of 900°C at a rate of 10°C min ^-1 and held for 2 h, then lowered to 300°C at a rate of 5°C min ^-1 , and finally annealed to room temperature.

A method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment, FIG. 3 to FIG. 5 are the amorphous vanadium oxide for a lithium-sulfur battery at different magnifications. / Scanning electron microscope picture of carbon fiber material, it can be seen from the figure that the nanofiber interlayer of the amorphous vanadium oxide/carbon fiber material prepared by electrospinning for lithium-sulfur batteries has a smooth surface and a diameter of about is 0.5 μm, and the size of the fibers is relatively uniform.

A method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, FIG. 6 is a photo of the element distribution of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries, FIG. 6-b It is a photo of the distribution of carbon elements, 6-c is a photo of the distribution of oxygen elements, and 6-d is a photo of the distribution of vanadium elements. It can be seen from the figure that the distribution of each element is uniform.

A method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment, FIG. 7 and FIG. 8 are the transmission of the amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery at different magnifications Electron microscope photo, it can be seen from the figure that the nanofiber interlayer of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by electrospinning has a smooth surface, the diameter of the fiber is about 0.5 μm, and There are no vanadium oxide crystal particles inside the fiber.

A method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, FIG. 9 is an X-ray diffraction pattern of the prepared amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries, obtained from As can be seen in FIG. 9 , the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries is an amorphous vanadium oxide carbon fiber.

A preparation method of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, FIG. 10 is the XPS spectrum of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries, from FIG. From the analysis of the XPS spectrum of V2p of 10, the binding energy peaks at 523.98 eV and 516.38 eV are attributed to V ⁴⁺ and the undecomposed vanadyl acetylacetonate.

Specific implementation two:

According to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 1, the method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery is prepared, The described amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery is made into a circular interlayer, which is placed between the separator and the positive electrode of the lithium-sulfur battery.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment is a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The preparation method of the positive electrode is to use the sublimated sulfur powder as the positive electrode active material, Super-P as the conductive agent, PVDF as the binder, after manual grinding in a mortar for 20 minutes, add 5% NMP solution, magnetic stirring for 6h to black Homogeneous paste slurry, and then evenly spread it on an aluminum sheet with a diameter of 12 mm with a glass rod, and then dried in a vacuum oven at 60 °C for 24 hours to prepare a positive electrode.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment is a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The mass ratio of sublimed sulfur powder, Super-P, and PVDF is 7:2:1.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment is a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the The diaphragm is pp film.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment is a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the A method of making circular interlayers from amorphous vanadium oxide/carbon fiber materials for lithium-sulfur batteries is to use a small punching machine to cut them into 16mm black circular sheets.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment The method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery prepared by using a metal The lithium sheet is the negative electrode, and the pp film is the diaphragm. Commercial lithium-sulfur electrolyte is selected, and it is added dropwise to both sides of the diaphragm with a pipette (30 μL is added dropwise to each battery). Assembly of the entire battery is done in the glove box.

The method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment is a method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery, the An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries was fabricated into a circular interlayer with a diameter of 16 mm.

A method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment A method for using the amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery prepared, Figure 11 For the described amorphous vanadium oxide/carbon fiber material used for lithium-sulfur batteries in the 1st, 100th, 300th, 500th and 700th charge-discharge curves, it can be seen from Fig. 11 that under the activation of a small current density of 0.1C, the The first discharge capacity of the battery can reach more than 1200mAh·g ^-1 . After charging and discharging at a high current density of 1C, the 100th, 300th, 500th and 700th discharge capacity of the battery can still reach a high capacity of more than 700mAh·g ^-1 , and the capacity does not decay significantly.

A method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment A method for using an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery prepared, Figure 12 is the rate performance curve of the amorphous vanadium oxide/carbon fiber material used in the lithium-sulfur battery. It can be seen from Figure 12 that the battery can contribute more than 1000mAh·g ^-1 at a small charge-discharge current density of 0.1C. specific capacity. When the current density is increased to the large current density of 1C and 2C, the battery can still maintain the capacity of about 850mAh·g ^-1 and 700mAh·g ^-1 , showing very excellent rate performance.

A method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment A method for using the amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery prepared, Figure 13 It is the cycle performance curve of the amorphous vanadium oxide/carbon fiber material used for the lithium-sulfur battery under the charge-discharge current density of 1C for the first 700 times. It can maintain a high specific capacity of about 900mAh·g ^-1 , and the capacity does not rapidly decay after 700 long cycles, which indicates that the interlayer used in lithium-sulfur batteries can greatly improve the cycle stability of the battery.

Specific implementation three:

A preparation method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery, comprising the following steps:

Step 1. Weigh a certain quality of vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether and pyromellitic anhydride respectively according to a certain material-to-liquid ratio, and set aside for use;

Step 2. Add the dimethylformamide to the vanadyl acetylacetonate weighed in step 1, stir magnetically for a certain period of time, and after fully dissolving, add the 4-4 diaminodiphenyl ether , after sonicating for a certain period of time, under the condition of mechanical stirring, the pyromellitic anhydride is added in stages, and after stirring for a certain period of time, a precursor solution is obtained, which is ready for use;

Step 3. Electrospin the precursor solution prepared in Step 2 to obtain polymer fibers, which are ready for use;

Step 4. The polymer fibers prepared in step 3 are placed in a tube furnace for heat treatment, heated to a range of 250-300 °C at a rate of 5 °C min ^-1 and maintained for 1-2 h, and then under the protection of argon gas , rise to the range of 650-900°C at a rate of 5-10°C min ^-1 and hold for 1-2 hours, then drop to 300°C at a rate of 5-10°C min ^-1 , and finally anneal to room temperature to obtain a An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, in step 2, 4-4 diaminodiphenyl ether and pyromellitic anhydride undergo a polycondensation reaction to form a soluble high molecular weight The molecular weight of the obtained polyamic acid (PAA) is the largest when the mass ratio of the two is 1:1, but a small amount of water will be removed during the reaction, so the content of pyromellitic anhydride is slightly increase until it reaches its maximum viscosity.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, the nanofibers prepared by electrospinning technology in step 3 not only have high specific surface area and good electrochemical performance It has excellent mechanical properties and can be used as an additive layer between the lithium-sulfur battery separator and the sulfur cathode to inhibit the dissolution of polysulfides, thereby achieving high performance of lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery described in this embodiment, the polyamic acid polymer fiber is gradually imidized during the heating process in the range of 250-300° C. in step 4. The reaction converted to pale yellow polyimide (PI) fibers.

The method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment uses vanadyl acetylacetonate and polyamic acid as electrospinning precursors, which are converted into Nanofibrous webs containing amorphous vanadium oxide and used as additive layers for lithium-sulfur batteries. The fiber interlayer has a good confinement effect on the intermediate product (polysulfide) of the lithium-sulfur battery and provides good electrical conductivity, and the preparation of the interlayer does not require the addition of binders and conductive agents. The subsequent battery performance tests also proved that The interlayer greatly improves the performance of lithium-sulfur batteries.

In the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries described in this embodiment, the obtained amorphous vanadium oxide interlayer and a pure sulfur electrode are assembled to form a button-type lithium-sulfur battery, and the electrochemical performance is carried out. test. The measured rate performance shows that the first cycle discharge capacity of the battery is as high as 1236mA h·g ^-1 at a current density of 0.1C, and its capacity remains above 700mA h·g ^-1 at a large current density of 2C; It is fully demonstrated that the amorphous vanadium oxide carbon fiber interlayer provided by the present invention has a good inhibitory effect on the shuttle effect of the lithium-sulfur battery, and the battery has excellent rate performance. At the same time, the present invention tests the service life of the obtained button-type lithium-sulfur battery, and the results show that the capacity of the battery can still be maintained at 769mA h·g ^-1 after being charged and discharged 700 times at a high current density of 1C (1C=1675mA/g). This shows that the amorphous vanadium oxide carbon fiber interlayer provided by the present invention has high research value in improving the electrochemical performance of the lithium-sulfur battery.

Specific implementation four:

According to the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to Embodiment 3, in step 1, vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether, The solid-liquid ratio of pyromellitic anhydride is 1.0-1.2g:10-15ml:1.0-1.2g:1.08-1.2g.

Specific implementation five:

According to the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to the third embodiment, in step 2, the magnetic stirring time of adding the dimethylformamide to the vanadyl acetylacetonate is 10- 20min, ultrasonic time 15-20min, mechanical stirring time 20-30min.

Specific implementation six:

According to the method for preparing an amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries according to Embodiment 3, in step 3, the electrospinning conditions are in a temperature environment of 35°C, the applied voltage is 17kV, and the flow rate is 0.4ml · h ⁻¹ , humidity 40%, distance from metal nozzle to foil collector 14 cm.

Specific implementation seven:

According to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 3, the heat treatment process in step 4 is to heat up to a temperature of 300°C at a rate of 5°C min ^-1 and keep 1h, then under the protection of argon, it was raised to the range of 900°C at a rate of 10°C min ^-1 and held for 2h, then lowered to 300°C at a rate of 5°C min ^-1 , and finally annealed to room temperature.

Eighth specific implementation:

Use of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared according to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiments 3 to 7 In the method, the amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery is made into a circular interlayer, which is placed between the separator and the positive electrode of the lithium-sulfur battery.

Specific implementation nine:

The method of using the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared according to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 9, The preparation method of the positive electrode is to use the sublimated sulfur powder as the positive electrode active material, Super-P as the conductive agent, and PVDF as the binder. After manual grinding in a mortar for 20 minutes, add 5% NMP solution and stir magnetically for 6 hours. To black uniform paste slurry, then use a glass rod to spread it evenly on an aluminum sheet with a diameter of 12mm, and then dry it in a vacuum oven at 60°C for 24 hours to prepare a positive electrode.

Specific implementation ten:

The method of using the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared according to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 9, The mass ratio of the sublimated sulfur powder, Super-P and PVDF is 7:2:1.

Specific implementation eleven:

The method of using the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared according to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 9, The diaphragm is a pp film.

Twelve specific implementations:

The method of using the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared according to the method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to Embodiment 9, The described method for making a circular interlayer from an amorphous vanadium oxide/carbon fiber material used in a lithium-sulfur battery is to use a small punching machine to cut it into a 16mm black circular sheet.

Claims (10)

1. a preparation method for the amorphous vanadium oxide/carbon fiber material of lithium-sulfur battery, is characterized in that: comprise the steps: Step 1. Weigh a certain quality of vanadyl acetylacetonate, dimethylformamide, 4-4 diaminodiphenyl ether and pyromellitic anhydride respectively according to a certain material-to-liquid ratio, and set aside for use; Step 2. Add the dimethylformamide to the vanadyl acetylacetonate weighed in step 1, stir magnetically for a certain period of time, and after fully dissolving, add the 4-4 diaminodiphenyl ether , after sonicating for a certain period of time, under the condition of mechanical stirring, the pyromellitic anhydride is added in stages, and after stirring for a certain period of time, a precursor solution is obtained, which is ready for use; Step 3. Electrospin the precursor solution prepared in Step 2 to obtain polymer fibers, which are ready for use; Step 4. The polymer fibers prepared in step 3 are placed in a tube furnace for heat treatment, heated to a range of 250-300 °C at a rate of 5 °C min ^-1 and maintained for 1-2 h, and then under the protection of argon gas , rise to the range of 650-900°C at a rate of 5-10°C min ^-1 and hold for 1-2 hours, then drop to 300°C at a rate of 5-10°C min ^-1 , and finally anneal to room temperature to obtain a An amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries. 2. the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 1, is characterized in that: in step 1, vanadyl acetylacetonate, dimethylformamide, 4-4 two The solid-liquid ratio of aminodiphenyl ether and pyromellitic anhydride is 1.0-1.2g:10-15ml:1.0-1.2g:1.08-1.2g. 3. the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 1, is characterized in that: in step 2, in the vanadyl acetylacetonate, add described dimethylformamide The magnetic stirring time is 10-20min, the ultrasonic time is 15-20min, and the mechanical stirring time is 20-30min. 4. the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 1, is characterized in that: in step 3, electrospinning condition is under 35 ℃ of temperature environment, and the applied voltage is 17kV , the flow rate was 0.4 ml·h ^-1 , the humidity was 40%, and the distance between the metal nozzle and the aluminum foil collector was 14 cm. 5. the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 1, is characterized in that: in step 4, heat treatment process is to be heated to 300 ℃ at the rate of 5 ℃ min ^-1 within the range of 900 °C for 1 h, then under the protection of argon gas, it was raised to the range of 900 °C at a rate of 10 °C min ^-1 and maintained for 2 h, then decreased to 300 °C at a rate of 5 °C min ^-1 , and finally annealed to room temperature. 6. A kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery prepared by the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 1-5 The use method is characterized in that: the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries is made into a circular interlayer, which is placed between the separator and the positive electrode of the lithium-sulfur battery. 7. a kind of using method of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery prepared by the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 6 , is characterized in that: the preparation method of the positive electrode is to use the sublimated sulfur powder as the positive electrode active material, Super-P as the conductive agent, PVDF as the binder, after manual grinding in a mortar for 20 minutes, add 5% NMP The solution was magnetically stirred for 6 hours to a black uniform paste slurry, and then evenly spread on an aluminum sheet with a diameter of 12 mm with a glass rod, and then dried in a vacuum oven at 60 °C for 24 hours to obtain a positive electrode. 8. the described a kind of using method of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery prepared by the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 7 , is characterized in that: the mass ratio of described sublimation sulfur powder, Super-P, PVDF is 7:2:1. 9. the described a kind of using method of the amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery prepared by the preparation method of a kind of amorphous vanadium oxide/carbon fiber material for lithium-sulfur battery according to claim 6 , which is characterized in that: the diaphragm is a pp film. 10. A method of using the amorphous vanadium oxide/carbon fiber material for lithium-sulfur batteries prepared by a method for preparing an amorphous vanadium oxide/carbon fiber material for a lithium-sulfur battery according to claim 6 , characterized in that: the method for making a circular interlayer from an amorphous vanadium oxide/carbon fiber material used in a lithium-sulfur battery is to use a small punching machine to cut it into a 16mm black circular sheet.

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