阅读说明：本技术 一种锂硫电池用正极侧隔层材料的制备方法 (Preparation method of positive electrode side interlayer material for lithium-sulfur battery ) 是由 李祥村 贺高红 郭娇 姜晓滨 吴雪梅 肖武 马沧海 于 2021-05-19 设计创作，主要内容包括：本发明公开一种锂硫电池用正极侧隔层材料的制备方法,本发明提供的隔层材料由聚丙烯腈/碳纳米管复合膜液经过溶剂相转化、在膜表面生长ZIF-67,再进行碳化还原制备多孔碳膜表面覆盖包含钴纳米颗粒的碳多面体微球的隔层材料。该隔层具有网络多孔结构,有利于多硫化物的吸附,有利于锂离子传递,表面覆盖的包含钴纳米颗粒的多面体微球平铺在膜表面,有效吸附截留多硫化物,钴纳米颗粒有利于促进多硫化物的吸附和催化转化,从而缓解锂硫电池的穿梭效应,提高电池循环稳定性、倍率性能和库伦效率。以该隔层材料制备的锂硫电池具有优异的储能性能,0.2C电流密度下循环100圈后,比容量为801.2mA h g～(-1),每圈的容量损失率为0.25％,库伦效率接近100％。(The invention discloses a preparation method of a positive electrode side interlayer material for a lithium-sulfur battery, which comprises the steps of carrying out solvent phase transformation on polyacrylonitrile/carbon nano tube composite membrane liquid, growing ZIF-67 on the surface of a membrane, and carrying out carbonization reduction to prepare the interlayer material of a porous carbon membrane, wherein the surface of the interlayer material is covered with carbon polyhedral microspheres containing cobalt nano particles. The interlayer has a network porous structure, is favorable for adsorption of polysulfide and lithium ion transfer, and is covered with cobalt-containing nanoparticlesThe polyhedral microspheres of the particles are paved on the surface of the membrane, polysulfide is effectively adsorbed and intercepted, and the cobalt nanoparticles are favorable for promoting the adsorption and catalytic conversion of the polysulfide, so that the shuttle effect of the lithium-sulfur battery is relieved, and the cycling stability, the rate capability and the coulombic efficiency of the battery are improved. The lithium-sulfur battery prepared by the interlayer material has excellent energy storage performance, and after the battery is circulated for 100 circles under the current density of 0.2C, the specific capacity is 801.2mA h g ‑1 The capacity loss rate per turn is 0.25%, and the coulombic efficiency approaches 100%.)

1. A preparation method of a positive electrode side interlayer material for a lithium-sulfur battery is characterized by comprising the following steps:

1) sequentially adding N, N-dimethylformamide, carbon nano tubes and polyacrylonitrile into a screw bottle, magnetically stirring the screw bottle at 60-80 ℃ for 10-12h to obtain a casting solution, scraping the casting solution on a glass plate by a film scraper, and putting the glass plate loaded with the film into a cobalt salt aqueous solution for phase conversion for 8-24 h;

2) vacuum drying the phase-converted membrane, placing the membrane in an aqueous solution containing 2-methylimidazole for standing reaction, taking out the membrane after the reaction is finished, washing the membrane for 3-5 times by using deionized water, and drying to obtain a [email protected] CNT @ PAN membrane;

3) and transferring the [email protected] CNT @ PAN film to a tubular furnace for carbonization reduction to obtain an interlayer material, namely Co @ CNT @ C, wherein the surface of the porous carbon film is covered with carbon polyhedral microspheres containing cobalt nanoparticles.

2. The method of claim 1, wherein the positive side barrier material comprises: in the step 1), the thickness of the film obtained by the film scraping machine is 100-300 μm.

3. The method according to claim 1, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 1), the mass ratio of the polyacrylonitrile to the N, N-dimethylformamide to the carbon nano tube is 1:18: 1-5: 18: 5.

4. The method according to claim 1, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 1), the molar concentration of the cobalt salt aqueous solution is 0.1-1.0M.

5. The method according to claim 1, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 2), the molar concentration of the 2-methylimidazole water solution is 0.1-0.5M.

6. The method according to claim 1, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 2), the vacuum drying conditions are as follows: the drying temperature is 60-90 ℃, and the drying time is 6-12 h.

7. The method according to claim 1, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 3), the carbonization-reduction conditions are as follows: the atmosphere is a mixed gas of hydrogen and argon, the temperature is increased to 280 ℃ from room temperature, the temperature is kept for 1h at 280 ℃, then the temperature is increased to 700-900 ℃, the temperature is kept for 1-5 h, and the temperature increase rate is 4-10 ℃ min^-1The cooling rate from 700-900 ℃ to room temperature is 1-10 ℃ min^-1。

8. Use of the positive electrode-side separator material obtained by the production method according to claim 1 in a lithium-sulfur battery.

Technical Field

The invention belongs to the field of positive electrode side interlayers of lithium-sulfur batteries, and particularly relates to a preparation method of an interlayer material with a CNT @ C composite carbon film covering polyhedral microspheres containing cobalt nanoparticles.

Background

Through three industrial innovations, the global economy is continuously increased and prosperous and needs more energy support, however, the proven reserves of fossil fuels such as oil, natural gas and coal are not optimistic, and the continuous increase of the global carbon emission is an immense environmental hazard. The energy structures are continuously diversified, and how to transfer to the low-carbon society more quickly is a challenge facing the world, so that renewable energy sources such as solar energy, tidal energy and the like are developed vigorously, and the unsteady-state energy sources need to be stored by a battery device with high energy density. However, most of the lithium batteries which are already industrialized at present are lithium ion batteries, and the lower specific mass capacity and the mass energy density thereof severely limit the more efficient energy storage capacity thereof.

Among lithium metal batteries, lithium sulfur batteries are rated at 1672mA h g^-1Theoretical capacity of 2600Wh kg^-1The theoretical energy density of (2) is of great interest and is an energy storage device with considerable prospect. In addition, the natural reserve of sulfur is abundant, the cost is low, and the lithium-sulfur battery is environment-friendly, so that the lithium-sulfur battery has the potential of large-scale energy storage application. The theoretical capacity of the current commercial graphite cathode lithium ion battery is only 372mA h g^-1And the practical requirements can not be met, and the lithium-sulfur battery is taken as a typical lithium metal batteryThe energy storage battery is expected to become a new generation of high-performance energy storage battery due to the characteristics of high energy density, rich sulfur resources and the like. However, the conventional lithium-sulfur battery still has the problems of low sulfur carrying capacity, shuttle effect, lithium dendrite growth common to lithium metal batteries and the like, and particularly, the existence of the shuttle effect can cause the rapid attenuation of the battery capacity and the unsatisfactory cycle life. Therefore, how to functionalize the structure of the interlayer, simplify the operation steps and effectively relieve the shuttle effect has important significance for the practical application of the lithium-sulfur battery.

Disclosure of Invention

Aiming at the problems, the invention provides a preparation method of a positive electrode side interlayer material for a lithium-sulfur battery, wherein a porous carbon film (CNT @ C) is covered with carbon polyhedral microspheres containing cobalt nanoparticles on the surface, a multifunctional interlayer material is constructed and is marked as Co @ CNT @ C, the porous carbon film is used as a support body, lithium ion and electron transfer is facilitated, polysulfide adsorption is facilitated, the carbon polyhedral microspheres containing cobalt nanoparticles covered on the surface can effectively adsorb and retain polysulfide, the shuttle effect of the lithium-sulfur battery is prevented, meanwhile, the cobalt nanoparticles are beneficial to promoting polysulfide catalytic conversion, and the cycle stability, the rate capability and the coulombic efficiency of the battery are improved. The anode side interlayer material for the lithium-sulfur battery is characterized in that polyacrylonitrile and carbon nano tubes are used as raw materials to prepare a film layer, ZIF-67 grows on the surface of the film layer by a solvent phase conversion method in a cobalt salt water solution, and then carbonization reduction is carried out, wherein the polyacrylonitrile and the carbon nano tubes are carbonized into a composite carbon-based interlayer material (CNT @ C) with a network porous structure, the ZIF-67 carbonization reduction forms carbon polyhedral microspheres containing cobalt nano particles, and the interlayer material (Co @ CNT @ C) with the surface of the porous carbon film covered with the carbon polyhedral microspheres containing the cobalt nano particles is prepared. The interlayer can effectively relieve the shuttle effect and improve the conductivity and the ion transfer rate. The lithium-sulfur battery has excellent cycle stability, rate capability, coulombic efficiency and higher charging and discharging capacity.

In order to achieve the above purpose, the invention provides the following technical scheme:

a preparation method of a positive electrode side interlayer material for a lithium-sulfur battery comprises the following steps:

1) sequentially adding N, N-dimethylformamide, carbon nano tubes and polyacrylonitrile into a screw mouth bottle, and magnetically stirring the screw mouth bottle at the temperature of 60-80 ℃ for 10-12h to obtain a membrane casting solution (polyacrylonitrile/carbon nano tube composite membrane solution); scraping the membrane casting solution on a glass plate through a membrane scraping machine, and putting the glass plate loaded with the membrane into a cobalt salt water solution for phase conversion for 8-24 h;

2) vacuum drying the phase-converted membrane material, standing in a 2-methylimidazole water solution for reaction, taking out the membrane after the reaction is finished, washing the membrane for 3-5 times by using deionized water, and drying to obtain a [email protected] CNT @ PAN membrane;

3) and transferring the [email protected] CNT @ PAN film to a tubular furnace for high-temperature carbonization reduction to obtain the positive electrode side interlayer material for the lithium-sulfur battery, which is marked as Co @ CNT @ C.

Furthermore, in the step 1), the thickness of the film obtained by the film scraping machine is 100-300 μm.

Furthermore, in the step 1), the mass ratio of the polyacrylonitrile, the N, N-dimethylformamide and the carbon nano tube is 1:18: 1-5: 18: 5. The network cross-linked pore structure barrier layer material with the structure cannot be prepared beyond the proportion range.

Furthermore, in the step 1), the molar concentration of the cobalt salt aqueous solution is 0.1-1.0M. The cobalt salt is CoCl₂Or Co (NO)₃)₂。

Further, in the step 2), the molar concentration of the 2-methylimidazole water solution is 0.1-0.5M.

Further, in step 2), the vacuum drying conditions are as follows: the drying temperature is 60-90 ℃, and the drying time is 6-12 h. Standing for 3-24 h.

Further, in step 3), the conditions of the carbonization and reduction are as follows: the atmosphere is a mixed gas of hydrogen and argon, the room temperature is raised to 280 ℃, the temperature is kept at 280 ℃ for 1h, then the temperature is raised to 700-900 ℃, the temperature is kept for 1-5 h, and the temperature raising rate is 4-10 ℃ min^-1The cooling rate from 700-900 ℃ to room temperature is 1-10 ℃ min^-1。

And 2) cutting the membrane material after vacuum drying into round pieces.

The invention also provides an application of the positive electrode side interlayer material obtained by the preparation method in a lithium-sulfur battery.

The beneficial effects of the invention include:

the invention relates to a method for preparing an interlayer material (Co @ CNT @ C) of a porous carbon film, which is characterized in that polyacrylonitrile/carbon nano tube composite film liquid is subjected to solvent phase conversion, ZIF-67 grows on the surface of the film, and then carbonization and reduction are carried out, so that the surface of the porous carbon film is covered with carbon polyhedral microspheres containing cobalt nano particles. The interlayer has a network porous supporting structure, is beneficial to the transmission of lithium ions and electrons and the adsorption of polysulfide, the surface of the film is covered with polyhedral microspheres containing cobalt nanoparticles, polysulfide is effectively adsorbed and intercepted, the shuttle effect of the lithium-sulfur battery is prevented, and the cobalt nanoparticles are beneficial to promoting the catalytic conversion of the polysulfide, so that the shuttle effect of the lithium-sulfur battery is relieved, and the cycling stability, the multiplying power performance and the coulomb efficiency of the battery are improved.

The material is applied to the lithium-sulfur battery, effectively solves the problems of serious shuttle effect and the like in the lithium-sulfur battery, improves the cycling stability, the rate capability and the coulombic efficiency of the battery, and shows excellent electrochemical performance. Co @ CNT @ C is used as a positive electrode side interlayer of the battery, and after the battery is circulated for 100 circles under the current density of 0.2C, the specific capacity is 801.2mA h g^-1The capacity loss rate of each circle is 0.25%, and the coulombic efficiency is close to 100%; after the porous carbon film (CNT @ C) is used as a battery anode side separation layer and is cycled for 100 circles under the current density of 0.2C, the specific capacity is only 699.3mA h g^-1(ii) a When the polyhedral carbon microsphere (Co-PP) containing the cobalt nanoparticles is used as a battery separator, the specific capacity is only 389.3mA h g after the battery separator is cycled for 100 circles under the current density of 0.2C^-1(ii) a In the rate capability test, the specific capacity of the Co-CNT @ C interlayer is maintained at 683.5mA h g under the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be maintained at 865.3mA h g^-1The specific capacity of the CNT @ C interlayer is maintained at 622.8mA h g at the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be maintained at 808.4mA h g^-1Whereas the Co-PP interlayer performed poorly at 2.0C current density.

Drawings

Fig. 1 is a scanning electron micrograph of the positive electrode-side separator material for a lithium-sulfur battery prepared in example 1.

FIG. 2 is a graph of the cycling performance at 0.2C current density for example 1 lithium sulfur cells assembled with a Co-CNT @ C separator and a comparative cell.

FIG. 3 is a graph of the rate performance of the lithium sulfur battery of example 1 assembled with a Co-CNT @ C separator and a comparative battery.

FIG. 4 is a graph of the charge and discharge curves of the assembled Co-CNT @ C separator lithium sulfur battery of example 1.

Detailed Description

The experimental protocol of the present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials or the apparatus can be obtained commercially without specific mention.

Example 1

1. Preparation of positive electrode side interlayer electrode material for lithium-sulfur battery

1) Adding 14g N, N-dimethylformamide, 1g of carbon nano tube and 1g of polyacrylonitrile into a silk mouth bottle in sequence, and then magnetically stirring the silk mouth bottle at 60 ℃ for 10-12h to obtain black viscous casting solution. The casting solution is scraped into a glass plate by a film scraper to form a film with the thickness of 200 mu M, and the glass plate with the film is placed into Co (NO) with the concentration of 0.2M₃)₂·6H₂Carrying out phase inversion for 8h in an O phase inversion solvent;

2) drying the phase-converted membrane material at 60 ℃ in vacuum for 12h, cutting the membrane material into membrane wafers with the diameter of 19mm, placing the cut membrane wafers into a 0.2M 2-methylimidazole water solution for standing reaction for 1h, taking out the interlayer after the reaction is finished, cleaning the interlayer with deionized water for 3-5 times, and then placing the interlayer in a 60 ℃ drying oven for drying for 12h to obtain a [email protected] CNT @ PAN membrane;

3) and transferring the dried [email protected] CNT @ PAN membrane into a tubular furnace for high-temperature carbonization and reduction, wherein the carbonization and reduction conditions are that 5% of hydrogen is mixed with 95% of argon, the room temperature is increased to 280 ℃, the temperature is kept at 280 ℃ for 1h, then the temperature is increased to 700 ℃, the temperature is kept for 3h, and the temperature increase rate is 5 ℃/min. And naturally cooling to room temperature after the completion to obtain the interlayer material (Co @ CNT @ C) of the carbon polyhedral microsphere with the cobalt nanoparticles covered on the surface of the porous carbon film.

2. Preparation of phase-inversion carbon film Material (CNT @ C) (not according to the invention)

The other conditions were unchanged and the glass plate carrying the membrane was placed in deionized water for 8h phase inversion. The battery operation effect is obviously lower than that of the integrated membrane material, as shown in figures 2 and 3.

3. Preparation of post-carbonization ZIF-67 coating Polypropylene film (Co-PP) Material (not inventive)

Weigh 8.0g Co (NO)₃)₂·6H₂Dissolving O and 9.03g of 2-methylimidazole in 400ml of ethanol respectively, and slowly pouring the 2-methylimidazole solution into Co (NO) after the 2-methylimidazole solution is completely dissolved₃)₂Stirring the mixture at room temperature for 1.0h, standing the mixture for 24h, centrifuging the mixture after the standing to obtain purple powdered ZIF-67, heating the powder to 280 ℃ at room temperature under the atmosphere of 5% hydrogen and 95% argon, keeping the temperature at 280 ℃ for 1h, heating the powder to 700 ℃ and keeping the temperature for 3h, wherein the heating rate is 5 ℃/min, and obtaining black powder. Weighing 0.03g of black powder, 0.3g of polyvinylidene fluoride and 1.3g of N, N-dimethylformamide, stirring at room temperature for 8 hours to obtain a black viscous solution, carrying out blade coating on the mixed solution on a polypropylene film through a film scraping machine, wherein the blade coating thickness is 100 mu m, and drying in a vacuum oven at 60 ℃ for 12 hours after the blade coating is finished to obtain a Co @ PP interlayer.

4. Preparation of lithium-sulfur battery by using Co-CNT @ C interlayer material

10mg of polyvinylidene fluoride is dissolved in 700 mu L N-methyl pyrrolidone, and then 90mg of C/S composite material is added and stirred to obtain C/S composite slurry. The 14. mu. L C/S composite slurry was applied to one side of an aluminum foil (a disk having a diameter of 12 mm), and dried in vacuum to obtain a positive electrode for a lithium-sulfur battery. Assembling the battery in a glove box, taking a lithium sheet as a negative electrode, taking Celgard2325 as a diaphragm, taking Co @ CNT @ C as a separation layer to be placed between the positive electrode and the Celgard2325 diaphragm, taking the electrolyte as a non-aqueous phase electrolyte, adding 1% LiNO into a 1,3 epoxy pentanes/ethylene glycol dimethyl ether (volume ratio 1:1) solution containing 1M lithium bistrifluoromethylenesulfonamide (LiTFSI), and adding 1% of LiNO₃The additive of (1).

5. Preparation of lithium-sulfur battery with CNT @ C interlayer

Other conditions were unchanged, and the Co-CNT @ C spacer was replaced with a CNT @ C spacer.

6. Preparation of lithium-sulfur battery with Co-PP interlayer

Other conditions were unchanged, and the Co-CNT @ C barrier was replaced with a Co-PP barrier.

Co @ CNT @ C, Co @ C spacer, Co @ PP spacer cell Performance test

After the battery is kept still for 12 hours, the constant current charge-discharge cycle performance test and the multiplying power performance test are completed through a blue test system, and the test voltage window is 1.7-2.8V. The current density of the multiplying power performance test is 0.1C, 0.2C, 0.5C, 1.0C, 2.0C (1C is 1675mA h g^-1). The cyclic voltammogram was measured by an electrochemical workstation at a scan rate of 0.05mV s^-1. FIG. 2 is a graph of the cycling performance of the Co @ CNT @ C separator assembled lithium sulfur battery of example 1 and a comparative battery at a current density of 0.2C, after 100 cycles at a current density of 0.2C, the specific capacity is 801.2mA h g^-1The capacity loss rate of each circle is 0.25%, the coulombic efficiency is close to 100%, and after the CNT @ C serving as the battery positive electrode side interlayer is cycled for 100 circles under the current density of 0.2C, the specific capacity is only 699.3mA h g^-1When the Co-PP film is used as a battery interlayer, the specific capacity is only 389.3mA h g after 100 cycles of circulation under the current density of 0.2C^-1. FIG. 3 is a graph of the rate performance of example 1 lithium sulfur batteries and comparative batteries incorporating Co-CNT @ C separators having specific capacities maintained at 683.5mA h g at 2.0C current densities^-1When the current density is recovered to 0.1C, the specific capacity can be maintained at 865.3mA h g^-1The specific capacity of the CNT @ C interlayer is maintained at 622.8mA h g at the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be maintained at 808.4mA h g^-1Whereas the Co-PP interlayer has essentially no performance at 2.0C current density. FIG. 4 is a graph showing the charging and discharging curves of the Co-CNT @ C separator assembled in this example, wherein two discharging plateaus can be observed, and the potential ranges are 2.4-2.3V and 2.1-2.0V; a charging platform, the potential interval is 2.4-2.2V.

Finally, it should be noted that: the above embodiment is only one of specific implementation manners of the present invention, and although the description thereof is more specific, the present invention should not be construed as limiting the scope of the present invention. It should be understood by those skilled in the art that the equivalent substitutions and modifications of the present invention can be made without departing from the technical scope of the present invention, and the present invention still belongs to the protection scope of the present invention.