阅读说明：本技术 一种金属有机框架mof-808膜基功能性夹层材料的制备方法及应用 (Preparation method and application of metal organic framework MOF-808 film-based functional interlayer material ) 是由 吴飞超 王鑫瑶 郑少宁 于 2020-12-25 设计创作，主要内容包括：本发明为一种金属有机框架MOF-808膜基功能性夹层材料的制备方法及应用。该方法包括如下步骤：将八水合氧氯化锆和均苯三甲酸溶于去离子水中,常温下磁力搅拌30-60min,然后加入三氟乙酸,超声30-60min得到合成液；然后将碳纳米管(CNT)薄膜圆片垂直浸没于上述合成液中,110-130℃生长3-5h,得到MOF-808/CNT膜。本发明得到的MOF-808/CNT膜夹层材料操作简单,易于放大,适合工业化生产；用于锂硫电池中正极与隔膜之间的夹层材料,可以显著提高锂硫电池性能,其可逆容量可达到1292mAh g～(-1),且循环性能稳定。(The invention relates to a preparation method and application of a metal organic framework MOF-808 film-based functional interlayer material. The method comprises the following steps: dissolving zirconium oxychloride octahydrate and trimesic acid in deionized water, magnetically stirring at normal temperature for 30-60min, adding trifluoroacetic acid, and performing ultrasonic treatment for 30-60min to obtain a synthetic solution; then vertically immersing a Carbon Nano Tube (CNT) film wafer into the synthetic solution, and growing for 3-5h at 110-130 ℃ to obtain the MOF-808/CNT film. The MOF-808/CNT film interlayer material obtained by the invention is simple to operate, easy to amplify and suitable for industrial production; the material is used for an interlayer material between a positive electrode and a diaphragm in a lithium-sulfur battery, can obviously improve the performance of the lithium-sulfur battery, and has reversible capacity of 1292mAh g ‑1 And the cycle performance is stable.)

1. A method for preparing a metal organic framework MOF-808 film-based functional interlayer material is characterized by comprising the following steps:

dissolving zirconium oxychloride octahydrate and trimesic acid in deionized water, magnetically stirring at normal temperature for 30-60min, adding trifluoroacetic acid, and performing ultrasonic treatment for 30-60min to obtain a synthetic solution; then vertically immersing a CNT film wafer into the synthetic liquid, and growing for 3-5h at 110-130 ℃ to obtain an MOF-808/CNT film, namely a metal organic framework MOF-808 film-based functional interlayer material;

wherein the molar ratio of the materials in the synthetic liquid is that zirconium oxychloride octahydrate: trimesic acid: trifluoroacetic acid: water (2-3) 1 (60-70) 500-600.

2. Use of a metal organic framework MOF-808 film-based functional interlayer material prepared by the method of claim 1, for an interlayer material between a positive electrode and a separator in a lithium sulfur battery.

Technical Field

The technical scheme of the invention relates to a preparation method and application of a metal organic framework MOF-808 film-based interlayer material, belonging to the technical field of lithium-sulfur batteries.

Background

With the increasing exhaustion of fossil energy, the development of new renewable clean energy becomes the focus of attention. The lithium-sulfur secondary battery (lithium-sulfur battery for short) with simple substance sulfur or sulfur-containing compound as the anode and metallic lithium as the cathode has ultrahigh theoretical specific capacity (1675mAh g)^-1) And energy density (2600Wh kg)^-1) Far exceeding the current lithium ion batteries. In addition, the anode material sulfur is nontoxic and has low cost. Therefore, the lithium-sulfur battery is considered as the next generation energy storage battery with the most development potential and has wide application prospect.

However, the current commercial application of lithium sulfur batteries still faces a number of technical challenges, such as the insulation of sulfur, volume expansion, the "shuttling effect" of polysulfides, and the like. Among them, polysulfide (S) generated from the positive electrode during charge and discharge_n ^2-And n is more than or equal to 2 and less than or equal to 8) is easily dissolved in the electrolyte, passes through the diaphragm under the combined action of potential difference and chemical potential difference, diffuses to the negative electrode, and reacts with the negative electrode metal lithium to cause shuttle effect, which not only causes irreversible loss of the battery electrode material, but also causes volume expansion effect in the charging and discharging process and attenuation of the battery performance and service life, and becomes a main technical bottleneck for hindering the commercial application of the lithium-sulfur battery.

In order to solve the above problems, the introduction of a functional interlayer material between the positive electrode and the separator can act as a polysulfide barrier layer to prevent polysulfide from diffusing out of the positive electrode region, thereby improving the utilization rate of active substances and the electrochemical performance of the battery, and is an effective strategy and research hotspot for inhibiting the shuttle effect of polysulfide. These functional interlayer materials are typically constructed based on porous materials. In particular, Metal Organic Frameworks (MOFs) have the characteristics of regular pore channels, large specific surface area, good repairability and the like, and have unique advantages when being used as an interlayer material of a lithium-sulfur battery. Currently, research mainly utilizes MOFs such as ZIF-8, ZIF-67, MIL-125(Ti) and the like or derived materials thereof to adsorb or catalytically convert polysulfides, so as to design functional interlayer materials of lithium-sulfur batteries. Because of the limited adsorption or catalytic sites of MOFs materials, there is a certain upper limit to the suppression of the shuttle effect. Furthermore, to increase the conductivity, the MOFs generally need to be carbonized at high temperature, which destroys the active metal sites and the porous structure of the MOFs material, reducing its ability to bind polysulfides. Therefore, how to design the lithium-sulfur battery interlayer material based on the original MOFs according to the characteristics of the MOFs material has important significance for inhibiting the shuttle effect and improving the performance of the lithium-sulfur battery.

Disclosure of Invention

The invention provides a preparation method and application of a metal organic framework MOF-808 film-based functional interlayer material aiming at the defects in the prior art. The method uses a Carbon Nanotube (CNT) thin film as a substrate material, and prepares a MOF-808 film on the substrate material by an in-situ solvothermal method. The MOF-808/CNT film interlayer material obtained by the invention can obviously improve the performance of a lithium-sulfur battery, and the reversible capacity of the material can reach 1292mAh g^-1And the cycle performance is stable.

The technical scheme of the invention is as follows:

a method for preparing a metal organic framework MOF-808 film-based functional interlayer material, comprising the following steps:

dissolving zirconium oxychloride octahydrate and trimesic acid in deionized water, magnetically stirring at normal temperature for 30-60min, adding trifluoroacetic acid, and performing ultrasonic treatment for 30-60min to obtain a synthetic solution; then vertically immersing a CNT film wafer into the synthetic liquid, and growing for 3-5h at 110-130 ℃ to obtain an MOF-808/CNT film;

wherein the molar ratio of the materials in the synthetic liquid is that zirconium oxychloride octahydrate: trimesic acid: trifluoroacetic acid: water (2-3) 1 (60-70) 500-600);

the application of the metal organic framework MOF-808/CNT film is used for an interlayer material between a positive electrode and a diaphragm in a lithium-sulfur battery.

The above method for preparing the MOF-808/CNT sandwich material for lithium sulfur batteries is commercially available, and the equipment and process used are well known to those skilled in the art.

The invention has the beneficial effects that:

(1) the MOF-808/CNT membrane prepared by the invention is a continuous MOF-808 separation membrane material reported for the first time, and can obviously improve the specific capacity and the cycling stability of a lithium-sulfur battery when being used as a lithium-sulfur battery interlayer material.

(2) The main pore size of the MOF-808 is 1.68nm, the MOF-808 can play a role in selective sieving, lithium ions are allowed to pass through to block polysulfide, so that a shuttle effect can be effectively inhibited, meanwhile, the MOF-808 film is a polar material, so that the infiltration of electrolyte and the lithium ion conduction are facilitated, the reaction kinetics of the battery are accelerated, in addition, the MOF-808 can play a role in catalysis, the transformation of polysulfide is promoted, a CNT carrier has good conductivity, not only can play a role of a carrier, but also can be used as a second current collector to improve the utilization rate of sulfur, so that the MOF-808/CNT film interlayer material can obviously improve the performance of the lithium sulfur battery, and the reversible capacity of the MOF-808/CNT^-1And the cycle performance is stable.

(3) The experimental operation of the invention is simple and easy, the required interlayer material can be obtained by a simple in-situ method and a reaction for hours, and the method is easy to amplify and suitable for industrial production.

Drawings

FIG. 1 is a surface Scanning Electron Microscope (SEM) image of the MOF-808 film made in example 1.

FIG. 2 is a SEM image of a cross-section of the MOF-808 film prepared in example 1.

FIG. 3 is an X-ray diffraction pattern of the MOF-808 film made in example 1.

FIG. 4 is a charge and discharge curve at 0.2C current density for a lithium sulfur battery using the MOF-808/CNT film made in example 1 as an interlayer.

FIG. 5 is a surface SEM image of a MOF-808 film made in example 2.

FIG. 6 is a surface SEM image of a MOF-808 film made by comparative example 1.

FIG. 7 is a surface SEM image of a MOF-808 film made by comparative example 2.

Detailed Description

The invention is described in more detail below with reference to specific examples, without limiting the scope of the invention.

The invention is further illustrated with reference to the following figures and examples.

In the designation of the MOF-808 film-based interlayer material, MOF means a metal organic framework, and 808 is an industry custom sequence number.

The carbon nanotube film is a known material, and is prepared from Chengdu good materials science and technology company, model number is JCSWCFM, and conductivity is (3-8) x10⁴S/m, thickness 25-35 μm.

Example 1:

synthesis of MOF-808 film material on Carbon Nanotube (CNT) thin film and its application in lithium sulfur batteries:

1.45g of zirconium oxychloride octahydrate (4.5mmol) and 0.42g of trimesic acid (2mmol) are dissolved in 20mL (1111mmol) of deionized water, magnetic stirring is carried out at normal temperature for 1h, then 10mL of trifluoroacetic acid (134mmol) is added, and ultrasonic treatment is carried out for 1h to obtain a synthetic solution. Transferring the synthetic solution into a stainless steel hydrothermal reaction kettle with a polytetrafluoroethylene lining, and vertically immersing a carbon nanotube film wafer which is cut into a diameter of 19mm by a cutting machine into the synthetic solution. And (3) placing the hydrothermal reaction kettle in an oven, heating for 3 hours at 120 ℃, and naturally cooling to room temperature. After the material is taken out, the material is washed for a plurality of times by deionized water and absolute ethyl alcohol and dried at the temperature of 60 ℃. In order to avoid the impedance increase caused by the insulating MOF-808 material, the MOF-808 film layer on one side is scraped by a scraper and then is used as an interlayer material of the lithium-sulfur battery. The battery case model adopted is CR2032, and the assembly sequence is as follows: positive electrode can, positive electrode sheet (CNT/S), interlayer obtained in this example (MOF-808 film layer facing the positive electrode), commercial separator Celgard 2400, lithium sheet, gasket, spring sheet, negative electrode can.

FIG. 1 is an SEM image of the surface of MOF-808 film on CNT carrier prepared in this example, which shows the dense MOF-808 film formed by cross-linked growth of MOF-808 crystal grains obtained by the present invention.

FIG. 2 is a SEM cross-sectional view of a MOF-808/CNT film made according to this example, having an overall interlayer thickness of about 35-45 μm, wherein the thickness of the MOF-808 film is about 4 μm and the film layer serves as a selective sieving for polysulfides.

FIG. 3 is an XRD pattern of the MOF-808/CNT film obtained in this example, which is consistent with characteristic peaks of MOF-808 reported in the literature.

FIG. 4 is a graph showing the charge and discharge curves at 0.2C current density for a lithium sulfur battery using the MOF-808/CNT film sandwiched in this example. It can be seen from the figure that at 0.2C current density, the first discharge capacity of the material is as high as 1292mAh g^-1And the cycle performance is stable.

The MOF-808 film obtained by the embodiment can effectively prevent migration of polysulfide and allow free passage of lithium ions; the MOF-808 film is a polar material, so that the infiltration of electrolyte and the lithium ion conduction are facilitated, and the reaction kinetics of the battery are accelerated; MOF-808 can also act as a catalyst, promoting the conversion of polysulfides; the CNT carrier has good conductivity, not only can play a role of a carrier, but also can play a role of a second current collector, and utilization of sulfur is improved. This is also confirmed in the charge-discharge curve of FIG. 4, where the first discharge capacity is up to 1292mAh g after addition of the interlayer material^-1And the discharge capacity after 100 times of circulation is 903mAh g^-1The capacity retention rate was 69.9%.

Example 2:

the procedure is as in example 1, except that in the synthesis process 1.93g zirconium oxychloride octahydrate (6mmol) and 0.42g trimesic acid (2mmol) are dissolved in 21.6mL (1200mmol) deionized water, magnetic stirring is carried out at room temperature for 30min, then 10.4mL trifluoroacetic acid (140mmol) is added, the synthesis temperature is changed from 120 ℃ to 110 ℃, and the other procedures are the same as in example 1.

FIG. 5 is a surface SEM image of the MOF-808 film obtained in this example, which shows that the film is still dense and continuous, and when the film is used as an interlayer of a lithium-sulfur battery, the first discharge capacity is 1185mAh g^-1And the discharge capacity after 100 times of circulation is 834mAh g^-1The capacity retention rate was 70.4%.

Comparative example 1:

the other procedure was the same as in example 1 except that the support was changed from a CNT thin film to another polyvinylidene fluoride (PVDF) film that can be used in a lithium sulfur battery.

After synthesis, only a few MOF-808 particles are obtained on the surface of the carrier, and a continuous MOF-808 film is not obtained, and the film layer does not have the selective sieving effect on polysulfide. The reason is that PVDF is an organic polymer material and has great property difference with MOF-808, so that MOF-808 crystal grains are difficult to nucleate on the surface of the PVDF membrane in a homogeneous phase manner to form a continuous membrane layer.

Comparative example 2:

the other steps are the same as example 1, except that the synthesis temperature is changed from 120 ℃ to 100 ℃.

After synthesis, only some MOF-808 grains are obtained on the surface of the CNT, a continuous MOF-808 film is not obtained, and the film layer does not have selective sieving effect on polysulfide. The reason is that the growth temperature is too low, the MOF-808 crystal grains are not sufficiently grown, and a continuous MOF-808 film is difficult to form.

It can be seen from the above examples and comparative examples that the CNT support and the synthesis process conditions adopted in the present invention are favorable for the formation of the continuous MOF-808 film, and the specific capacity and cycle performance of the lithium-sulfur battery can be significantly improved when the film layer is used as the interlayer material of the lithium-sulfur battery.

The invention is not the best known technology.