阅读说明：本技术 一种自组装三维结构的金属氧化物改性的电池隔膜及其制备方法和应用 (Self-assembled three-dimensional structure metal oxide modified battery diaphragm and preparation method and application thereof ) 是由 王贤保 伍丽萍 陈子和 于 2021-08-26 设计创作，主要内容包括：本发明属于有机无机复合材料制备技术领域,具体涉及一种自组装三维结构的金属氧化物改性的电池隔膜及其制备方法和应用。该方法包括以下步骤：1)金属有机框架前驱体的制备；2)局部三维交联金属氧化物的制备；3)改性隔膜的制备：将步骤2)制得的局部三维交联金属氧化物和粘接剂、溶剂混合研磨后均匀涂覆在PP/PE/PP隔膜的一侧,经干燥后,得到自组装三维结构的金属氧化物改性的电池隔膜。本发明通过限定的金属氧化物的结构,将其与PP/PE/PP隔膜复合,应用在锂硫电池中,既能有效锚定多硫化物,又能保证锂离子的传输效率,显著提高了锂硫电池的循环稳定性。(The invention belongs to the technical field of organic-inorganic composite material preparation, and particularly relates to a self-assembled three-dimensional structure metal oxide modified battery diaphragm and a preparation method and application thereof. The method comprises the following steps: 1) preparing a metal organic framework precursor; 2) preparing local three-dimensional cross-linked metal oxide; 3) preparing a modified diaphragm: mixing and grinding the local three-dimensional cross-linked metal oxide prepared in the step 2), an adhesive and a solvent, uniformly coating the mixture on one side of a PP/PE/PP diaphragm, and drying to obtain the battery diaphragm modified by the metal oxide with the self-assembled three-dimensional structure. The invention compounds the metal oxide with a PP/PE/PP diaphragm through the limited structure of the metal oxide, and when the metal oxide is applied to the lithium-sulfur battery, the polysulfide can be effectively anchored, the transmission efficiency of lithium ions can be ensured, and the cycle stability of the lithium-sulfur battery is obviously improved.)

1. A preparation method of a battery diaphragm modified by metal oxide with a self-assembled three-dimensional structure is characterized by comprising the following steps:

1) preparing a metal organic framework precursor: dissolving transition metal salt and organic ligand in a solvent, and reacting to obtain a metal organic framework precursor;

2) preparation of local three-dimensional cross-linked metal oxide: annealing the metal organic framework precursor prepared in the step 1) in an air atmosphere to prepare a local three-dimensional crosslinked metal oxide;

3) preparing a modified diaphragm: mixing and grinding the local three-dimensional cross-linked metal oxide prepared in the step 2), an adhesive and a solvent, uniformly coating the mixture on one side of a PP/PE/PP diaphragm, and drying to obtain the battery diaphragm modified by the metal oxide with the self-assembled three-dimensional structure.

2. The method for preparing a self-assembled three-dimensional structure metal oxide modified battery separator according to claim 1, wherein in step 1):

the transition metal salts include, but are not limited to: metal cobalt salts, metal zinc salts, metal iron salts, metal nickel salts or metal copper salts;

such organic ligands include, but are not limited to: methylimidazole, 2-formylimidazole, terephthalic acid or trimesic acid;

such solvents include, but are not limited to: one or more of methanol, ethanol, deionized water or N, N-dimethylformamide.

3. The method of preparing a self-assembled three-dimensional structure metal oxide modified battery separator according to claim 1, wherein: the reaction mode in step 1) includes but is not limited to one or more of stirring, ultrasound or high-pressure hydrothermal.

4. The method of preparing a self-assembled three-dimensional structure metal oxide modified battery separator according to claim 1, wherein: the annealing time in the step 2) is 1-3 h, the annealing temperature is 420-520 ℃, and the heating rate is 2-8 ℃/min.

5. The method for preparing the self-assembled three-dimensional structure metal oxide modified battery separator according to any one of claims 1 to 4, wherein in step 3):

such adhesives include, but are not limited to: polyvinylidene fluoride, sodium carboxymethylcellulose, styrene butadiene rubber or LA 133;

such solvents include, but are not limited to: n, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide or deionized water;

the mass ratio of the adhesive to the metal oxide is 10-15 wt%, and the grinding time is 0.5-2 h.

6. A battery separator produced by the production method according to any one of claims 1 to 5.

7. Use of a battery separator according to claim 6, wherein: used for preparing lithium-sulfur batteries, lithium batteries, supercapacitors or photocatalysts.

8. Use of a battery separator according to claim 7, wherein: as a lithium sulfur battery separator.

Technical Field

The invention belongs to the technical field of organic-inorganic composite material preparation, and particularly relates to a self-assembled three-dimensional structure metal oxide modified battery diaphragm and a preparation method and application thereof.

Background

Along with the rapid development in the fields of unmanned aerial vehicles, electric vehicles, military portable power supplies and the like, a novel energy storage technology with high energy density is urgently needed, and the energy of a lithium ion batteryThe bulk density has approached a limit. Therefore, has high theoretical capacity (1672mAh g^-1) The lithium-sulfur battery is expected to become a next generation high energy storage battery after entering the field of vision of people. However, the lithium sulfur battery still has some problems such as volume expansion of sulfur, poor conductivity of sulfur, and dissolution of polysulfide. In particular, the dissolution of polysulfide, which diffuses into the electrolyte and then shuttles across the separator by concentration diffusion and electric field action, leads to a short life span of the lithium-sulfur battery, a low coulombic efficiency, and ultimately affects the commercialization of the lithium-sulfur battery.

In recent years research, sulfur has been compounded with various non-polar or polar materials to suppress the "shuttling effect" of polysulfides. Although these methods help to suppress the shuttling of polysulfides, under the condition of high sulfur loading, 10-20% of polysulfides are still inevitably dissolved into the electrolyte to cause the shuttling effect. And the preparation steps of the anode are complicated, the cost is high, and the actual industrial production is not facilitated. The research on the modification of the membrane has attracted the attention of researchers as a new strategy. At present, various polar materials are developed, and metal oxides are widely used for modification of a separator because they can effectively adsorb polysulfide due to strong polarity of oxygen in the metal oxides. For example, Chinese patent publication No. CN112768840A discloses a multifunctional diaphragm of a lithium-sulfur battery and a preparation method thereof, wherein the preparation method comprises the steps of uniformly mixing polydopamine, a carbon material, a catalytic material, a thickening agent and other auxiliaries to prepare a slurry, finally coating the slurry on the surface of a diaphragm substrate, and drying to obtain the multifunctional diaphragm of the lithium-sulfur battery. The metal oxide contained in the catalytic material can adsorb polysulfide to the coating side of the diaphragm, and shuttle of the polysulfide is prevented. Chinese patent publication CN113036311A discloses a porous carbon sphere-encapsulated vanadium oxide heterogeneous core-shell sphere structure material and a preparation method thereof, wherein polar vanadium oxide inside carbon spheres in the material can form a strong chemical bond with polysulfide to anchor the polysulfide. Chinese patent publication CN112688020A discloses a porous carbon-loaded europium oxide material, and a preparation method and application thereof, wherein the material adsorbs polysulfides by chemical action, and obstructs shuttle of polysulfides on a transmission path of polysulfide. Although these metal oxide modified membranes have achieved good results in anchoring polysulfides, it is noted that such conventional metal oxide modified membranes still have problems, such as: when the thickener, ethanol and other additives and the metal oxide are mixed to obtain the precoat, the coating is easy to form a close-packed structure, so that the lithium ion transmission efficiency is reduced, and the polysulfide further blocks a lithium ion transmission channel due to the strong adsorption effect of the metal oxide and the polysulfide, so that the reaction kinetics of the lithium-sulfur battery are reduced. In addition, the compounding of metal oxides with carbon materials or porous carbon spheres inevitably reduces the content of metal oxides per unit area, resulting in insufficient exposure of active sites, thereby affecting the adsorption of polysulfides. Therefore, structural design of the metal oxide is one of important means for solving the above problems to improve cycle stability of the lithium sulfur battery.

Disclosure of Invention

The invention provides a metal oxide modified battery diaphragm with a self-assembled three-dimensional structure, and a preparation method and application thereof, aiming at solving the problems of the prior art that a metal oxide diaphragm modified layer is densely stacked and polysulfide adsorption sites are low in exposure rate. The invention compounds the metal oxide with a PP/PE/PP diaphragm (hereinafter referred to as diaphragm) through the limited structure of the metal oxide, and the metal oxide can be applied to the lithium-sulfur battery, thereby effectively anchoring polysulfide, ensuring the transmission efficiency of lithium ions and obviously improving the cycle stability of the lithium-sulfur battery.

The technical scheme provided by the invention is as follows:

a preparation method of a battery diaphragm modified by metal oxide with a self-assembled three-dimensional structure comprises the following steps:

1) preparing a metal organic framework precursor: dissolving transition metal salt and organic ligand in a solvent, and reacting to obtain a metal organic framework precursor;

2) preparation of local three-dimensional cross-linked metal oxide: annealing the metal organic framework precursor prepared in the step 1) in an air atmosphere to prepare a local three-dimensional crosslinked metal oxide;

3) preparing a modified diaphragm: mixing and grinding the local three-dimensional cross-linked metal oxide prepared in the step 2), an adhesive and a solvent, uniformly coating the mixture on one side of a PP/PE/PP diaphragm, and drying to obtain the battery diaphragm modified by the metal oxide with the self-assembled three-dimensional structure.

Based on the technical scheme:

the battery diaphragm contains metal oxide components, so that polysulfide can be adsorbed on the side of the diaphragm coating layer to prevent the shuttle of the polysulfide;

the coating method is characterized in that a solvent volatilization induced self-assembly means is adopted, so that the ordered combination of the local three-dimensional crosslinked metal oxide and the binder is realized, and a uniform macroscopic three-dimensional structure interface is spontaneously assembled on the surface of the diaphragm by the local three-dimensional crosslinked structure, so that the problem that the reaction kinetics of the lithium-sulfur battery is reduced due to the fact that a coating forms a close-packed structure and the transmission efficiency of lithium ions is reduced and the problem that polysulfide blocks a transmission channel of the lithium ions due to the strong adsorption effect of the metal oxide and the polysulfide is solved;

the modified diaphragm has high lithium ion transmission rate and strong polysulfide adsorption effect, and the permeability of the electrolyte is improved through a uniform macroporous structure on a macroscopic three-dimensional structure interface, so that the transmission of lithium ions is promoted; meanwhile, abundant ravines on the surface of the local three-dimensional crosslinked metal oxide can expose more active sites, and polysulfide can be anchored more effectively, so that the cycle stability of the lithium-sulfur battery is improved remarkably.

Based on the technical scheme:

the metal organic framework precursor adopts transition metal ions: dissolving an organic ligand in a molar ratio of 1: 0.5-6, wherein the concentration is limited to 0.1-0.6M;

local three-dimensional crosslinking means: the metal oxide with the three-dimensional structure is locally crosslinked to form a metal oxide skeleton with the three-dimensional structure, and the skeleton, the adhesive and the solvent are mixed and ground to form a uniform macroporous structure along with the volatilization of the solvent, so that a macroscopic three-dimensional structure interface is formed.

Specifically, in step 1): the transition metal salts include, but are not limited to: metallic cobalt salts, metallic zinc salts, metallic iron salts, metallic nickel salts or metallic copper salts, and the like.

Specifically, in step 1): such organic ligands include, but are not limited to: methylimidazole, 2-formylimidazole, terephthalic acid, trimesic acid, or the like.

Specifically, in step 1): such solvents include, but are not limited to: one or more of methanol, ethanol, deionized water or N, N-dimethylformamide and the like.

Specifically, the reaction mode in step 1) includes but is not limited to one or more of stirring, ultrasound or high-pressure hydrothermal.

Specifically, the annealing time in the step 2) is 1-3 hours, the annealing temperature is 420-520 ℃, and the heating rate is 2-8 ℃/min.

Based on the technical scheme, the annealing time and temperature of the metal organic framework precursor in the air atmosphere are controlled, and the volume and the escape rate of the carbon oxide gas are controlled, so that the artificial control on the metal oxide structure is realized, and the local three-dimensional crosslinked metal oxide is obtained.

Specifically, in step 3): such adhesives include, but are not limited to: polyvinylidene fluoride, sodium carboxymethylcellulose, styrene butadiene rubber, LA133 and the like.

Specifically, in step 3): such solvents include, but are not limited to: n, N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, deionized water, or the like.

Specifically, in step 3): the mass ratio of the adhesive to the metal oxide is 10-15 wt%, the grinding time is 0.5-2 h, and the film thickness can be 200-300 μm.

Specifically, in step 3): the drying mode is vacuum drying, the drying temperature is 60-80 ℃, and the drying time is 6-8 hours.

The invention also provides the battery diaphragm prepared by the method.

The contact angle between the modified diaphragm and the electrolyte is 0 degrees, and the transmission of lithium ions can be promoted; and the abundant gullies on the surface of the local three-dimensional cross-linked metal oxide expose more active sites, which can promote the anchoring of polysulfide;

the invention also provides application of the battery diaphragm in the field of preparation of lithium-sulfur batteries, lithium batteries, supercapacitors or photocatalysis.

The battery diaphragm can improve the permeability of electrolyte due to the uniform macroporous structure on the macroscopic three-dimensional structure interface, so that the battery diaphragm can be used as a lithium battery diaphragm and a super capacitor diaphragm to improve the ion mobility; meanwhile, more active sites are exposed by abundant gullies on the surface of the local three-dimensional cross-linked metal oxide, so that the method can be used in the field of photocatalysis to improve the photocatalytic activity.

Further, the battery separator is used as a lithium-sulfur battery separator.

The contact angle between the modified diaphragm and the electrolyte is 0 degrees, so that the transmission of lithium ions is promoted; and the abundant gullies on the surface of the local three-dimensional cross-linked metal oxide expose more active sites, thus promoting the anchoring of polysulfide; the battery prepared by the modified diaphragm circulates 700 circles at 0.5 ℃, the attenuation of each circle is only 0.02 percent, and the cycle stability of the lithium-sulfur battery is obviously improved.

The invention has the following advantages and positive effects:

1. according to the invention, the annealing time and temperature of the metal organic framework precursor in the air atmosphere are controlled, and the volume and the escape rate of the carbon oxide gas are controlled, so that the artificial control of the metal oxide structure is realized, and the local three-dimensional crosslinked metal oxide is obtained.

2. The modified diaphragm prepared by the invention is prepared by uniformly coating a local three-dimensional crosslinked metal oxide, a binder and a solvent on one side of the diaphragm after mixing, and the coating method adopts a solvent volatilization induced self-assembly means to realize the ordered combination of the local three-dimensional crosslinked metal oxide and the binder, so that a local three-dimensional crosslinked structure is spontaneously assembled into a uniform macroscopic three-dimensional structure interface on the surface of the diaphragm.

3. The modified diaphragm prepared by the invention has high lithium ion transmission rate and strong polysulfide adsorption effect, and the permeability of the electrolyte is improved through a uniform macroporous structure on a macroscopic three-dimensional structure interface, so that the transmission of lithium ions is promoted; meanwhile, abundant ravines on the surface of the local three-dimensional crosslinked metal oxide can expose more active sites, and polysulfide can be anchored more effectively, so that the cycle stability of the lithium-sulfur battery is improved remarkably.

4. The invention has simple preparation process, can effectively control the size and the structure of a product, can be matched with the existing battery coating diaphragm production equipment, and is easy to realize industrialized mass production.

Drawings

FIG. 1 shows an X-ray powder diffraction pattern and a scanning electron micrograph of localized three-dimensionally crosslinked cobaltosic oxide in example 1 of the present invention;

FIG. 2 shows a scanning electron micrograph of a modified separator in example 1 of the present invention and a contact angle test chart with an electrolyte;

FIG. 3 shows a comparison graph of polysulfide adsorption experiments for the modified membranes and the comparative membranes of example 1 of the present invention;

FIG. 4 shows UV-VIS spectrophotometric test patterns after polysulfide adsorption experiments for the modified membranes and the comparative membranes of example 1 of the present invention;

FIG. 5 is a graph showing the capacity fade after 700 cycles of the modified membrane in example 1 of the present invention;

FIG. 6 shows a scanning electron microscope image of a hollow cobaltosic oxide and an agglomerated modified diaphragm and a contact angle test image of the agglomerated modified diaphragm and an electrolyte in comparative example 1 according to the present invention;

fig. 7 shows a scanning electron microscope image of the monodisperse cobaltosic oxide and the agglomerated modified diaphragm in comparative example 2 of the present invention and a contact angle test image of the agglomerated modified diaphragm and the electrolyte.

Detailed Description

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

It will be understood that when an element or component is referred to as being "connected," "positioned" or "coupled" to another element or component, it can be directly on the other element or component or intervening elements or components may also be present. The terms "left", "right", "upper", "lower" and the like as used herein are for illustrative purposes only.

Example 1

This example describes a self-assembled three-dimensional structure metal oxide modified battery separator (hereinafter referred to as modified separator) and a method for preparing the same in detail, including the following steps:

(1) preparing a metal organic framework precursor: respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in 30mL and 60mL of methanol (wherein the molar ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1:5), mixing the two solutions, performing ultrasonic reaction for 1h at 25 ℃, centrifuging, washing and drying to obtain a cobalt-based metal organic framework precursor (hereinafter referred to as ZIF-67);

(2) preparation of local three-dimensional cross-linked metal oxide: annealing ZIF-67 at a heating rate of 5 ℃/min for 1h at 470 ℃ in an air atmosphere to synthesize local three-dimensional cross-linked cobaltosic oxide (hereinafter referred to as cobaltosic oxide);

(3) preparing a modified diaphragm: mixing polyvinylidene fluoride and cobaltosic oxide according to the mass ratio of 1:8, adding N-methyl pyrrolidone, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm (hereinafter referred to as the diaphragm), and drying to obtain the modified diaphragm.

The X-ray powder diffractogram of the cobaltosic oxide prepared in this example 1 is shown in part a of fig. 1, illustrating the successful synthesis of cobaltosic oxide; the scanning electron micrograph of the cobaltosic oxide is shown as part b in figure 1, and shows a local three-dimensional cross-linked structure;

the scanning electron micrograph of the modified membrane prepared in this example 1 is shown in a part a in fig. 2, and shows a uniform macroscopic three-dimensional structure interface; a contact angle test chart of the modified diaphragm and the electrolyte is shown in a part b in fig. 2, the contact angle of the modified diaphragm and the electrolyte is 0 degrees, and the fact that the modified diaphragm has a uniform macroporous interface is beneficial to enhancing the permeability of the electrolyte, so that the transmission of lithium ions is promoted;

a comparison graph of the polysulfide adsorption experiment of the modified membrane and the comparison membrane prepared in this example 1 is shown in fig. 3, and for the modified membrane (part a in fig. 3), the color of the solution on the right side does not change significantly within 12 hours, which indicates that more active sites are exposed by rich ravines on the surface of cobaltosic oxide, and the polysulfide is strongly adsorbed, thereby hindering the shuttling effect. In contrast, for the separator (part b in fig. 3), some polysulfides were observed within 2 h. Then at 6h, almost all the solution on the right became tan. After 12h, the right tube was filled with polysulfide, indicating that the polysulfide can easily shuttle through the membrane;

the experimental method of polysulfide adsorption experiment is as follows: the adsorption experiment was carried out using an H-type electrolytic cell device in which the solution on the left side was 50ml of a polysulfide solution having a concentration of 10mM, the solution on the right side was 50ml of a polysulfide-free mixed solution of 1, 3-dioxolane and ethylene glycol dimethyl ether (volume ratio 1:1), the separators in the middle of the electrolytic cell were a modified separator and a comparative separator, respectively, the H-type electrolytic cell device was placed on a horizontal surface, observed for 12 hours, and the change in the permeation of polysulfide was recorded with a video camera;

the material of the comparison diaphragm is a PP/PE/PP diaphragm, namely a polypropylene/polyethylene/polypropylene composite diaphragm;

the modified membrane prepared in example 1 and the right solution of the comparative membrane after the adsorption experiment were subjected to uv-visible spectrophotometry, and the test chart is shown in fig. 4, in which the modified membrane had very little polysulfide absorption peak. In contrast, for the comparative membrane, the absorption peak of polysulfide can be clearly observed, indicating that the modified membrane has extremely strong adsorption capacity to polysulfide, which is consistent with the adsorption experiment result;

the graph of the capacity fading condition of the battery prepared by the modified diaphragm in the embodiment 1 after 700 cycles at 0.5C is shown in fig. 5, and at 0.5C, the fading of each cycle is only 0.02%, so that the battery has a better capacity retention rate, and the realization of a stable lithium-sulfur battery is possible;

the positive plate of the lithium-sulfur battery adopts sulfur powder: conductive carbon black: grinding and size mixing polyvinylidene fluoride according to the mass ratio of 7:2:1, coating on an aluminum foil by using a scraper, and drying to obtain a positive pole piece; the electrolyte is a mixed solution (volume ratio is 1:1) of 1, 3-dioxolane and glycol dimethyl ether with the concentration of 1M lithium bistrifluoromethanesulfonimide, and the electrolyte simultaneously contains 1% of anhydrous lithium nitrate as an additive; a metal lithium sheet is used as a negative electrode; the CR2032 button cell was assembled in a glove box filled with argon by a conventional method and tested for electrochemical performance.

Example 2

This example describes a self-assembled three-dimensional structure metal oxide modified battery separator (hereinafter referred to as modified separator) and a method for preparing the same in detail, including the following steps:

(1) preparing a metal organic framework precursor: respectively dissolving zinc nitrate hexahydrate and 2-methylimidazole in 30mL and 60mL of methanol (wherein the molar ratio of the zinc nitrate hexahydrate to the 2-methylimidazole is 1:5), mixing the two solutions, carrying out ultrasonic reaction for 1h at 25 ℃, and carrying out centrifugal washing and drying to obtain a zinc-based metal organic framework precursor (hereinafter referred to as ZIF-8);

(2) preparation of local three-dimensional cross-linked metal oxide: annealing ZIF-8 at 470 ℃ for 1h at the heating rate of 5 ℃/min in the air atmosphere to synthesize local three-dimensional cross-linked zinc oxide (hereinafter referred to as zinc oxide);

(3) preparing a modified diaphragm: mixing polyvinylidene fluoride and zinc oxide according to the mass ratio of 1:8, adding N, N-dimethylformamide, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm, and drying to obtain the modified diaphragm.

Example 3

This example describes a self-assembled three-dimensional structure metal oxide modified battery separator (hereinafter referred to as modified separator) and a method for preparing the same in detail, including the following steps:

(1) preparing a metal organic framework precursor: dissolving ferric chloride hexahydrate and terephthalic acid in 30mL of N, N-dimethylformamide (wherein the molar ratio of the ferric chloride hexahydrate to the terephthalic acid is 2:1), stirring for 30min, then putting the solution into a reaction kettle, reacting for 12h at 110 ℃, and centrifugally washing and drying to obtain an iron-based metal organic framework precursor (hereinafter referred to as Fe-MOF);

(2) preparation of local three-dimensional cross-linked metal oxide: annealing Fe-MOF in air atmosphere at a heating rate of 2 ℃/min for 2h at 400 ℃ to synthesize local three-dimensional cross-linked ferric oxide (hereinafter referred to as ferric oxide);

(3) preparing a modified diaphragm: mixing LA133 and ferric oxide according to the mass ratio of 1:9, adding deionized water, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm, and drying to obtain the modified diaphragm.

Example 4

This example describes a self-assembled three-dimensional structure metal oxide modified battery separator (hereinafter referred to as modified separator) and a method for preparing the same in detail, including the following steps:

(1) preparing a metal organic framework precursor: dissolving copper nitrate trihydrate and trimesic acid in a mixed solution consisting of 15mL of N, N-dimethylformamide, 15mL of ethanol and 15mL of deionized water (wherein the molar ratio of the copper nitrate trihydrate to the trimesic acid is 2:1), stirring for 15min, then putting the solution into a reaction kettle, reacting for 20h at 85 ℃, and centrifugally washing and drying to obtain a copper-based metal organic framework precursor (hereinafter referred to as Cu-MOF);

(2) preparation of local three-dimensional cross-linked metal oxide: annealing Cu-MOF for 3h at the temperature rise rate of 5 ℃/min and the temperature of 400 ℃ in the air atmosphere to synthesize local three-dimensional cross-linked copper oxide (hereinafter referred to as copper oxide);

(3) preparing a modified diaphragm: mixing sodium carboxymethylcellulose and copper oxide according to the mass ratio of 1:7, adding deionized water, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm, and drying to obtain the modified diaphragm.

Comparative example 1

The comparison example elaborates the modified diaphragm of the agglomeration type lithium-sulfur battery (hereinafter referred to as agglomeration modified diaphragm) and the preparation method thereof, and comprises the following steps:

(1) preparing a metal organic framework precursor: respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in 30mL and 60mL of methanol (wherein the molar ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1:5), mixing the two solutions, performing ultrasonic reaction at 25 ℃ for 1h, and performing centrifugal washing and drying to obtain a cobalt-based metal organic framework precursor (hereinafter referred to as ZIF-67);

(2) preparation of hollow metal oxide: annealing ZIF-67 at a temperature rise rate of 5 ℃/min for 1h at 370 ℃ in an air atmosphere to synthesize hollow cobaltosic oxide;

(3) preparing an agglomerated modified diaphragm: mixing polyvinylidene fluoride and hollow cobaltosic oxide according to the mass ratio of 1:8, adding N-methyl pyrrolidone, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm (hereinafter referred to as the diaphragm), drying, and mutually stacking the hollow cobaltosic oxide to generate an agglomeration effect to obtain the agglomeration modified diaphragm.

The scanning electron micrograph of the hollow cobaltosic oxide prepared in the comparative example 1 is shown as part a in fig. 6, and the presented hollow structure is similar to the structure of the original ZIF-67; the scanning electron microscope image of the agglomerated modified diaphragm prepared in the comparative example 1 is shown as part b in fig. 6, and hollow cobaltosic oxide is stacked with each other to generate an agglomeration effect; the contact angle test chart of the agglomerated modified diaphragm and the electrolyte is shown in part c in fig. 6, the contact angle of the agglomerated modified diaphragm and the electrolyte is 6.9 degrees, the agglomeration modified diaphragm is not beneficial to the permeation of the electrolyte, and the lithium ion transmission performance is reduced.

Comparative example 2

The comparison example elaborates the modified diaphragm of the agglomeration type lithium-sulfur battery (hereinafter referred to as agglomeration modified diaphragm) and the preparation method thereof, and comprises the following steps:

(1) preparing a metal organic framework precursor: respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in 30mL and 60mL of methanol (wherein the molar ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1:5), mixing the two solutions, performing ultrasonic reaction at 25 ℃ for 1h, and performing centrifugal washing and drying to obtain a cobalt-based metal organic framework precursor (hereinafter referred to as ZIF-67);

(2) preparation of monodisperse metal oxide: annealing ZIF-67 at the temperature rising rate of 5 ℃/min for 1h at the temperature of 570 ℃ in the air atmosphere to synthesize monodisperse cobaltosic oxide;

(3) preparing an agglomerated modified diaphragm: mixing polyvinylidene fluoride and monodisperse cobaltosic oxide according to the mass ratio of 1:8, adding N-methyl pyrrolidone, grinding for 1.2h, uniformly coating on one side of a PP/PE/PP diaphragm (hereinafter referred to as the diaphragm), drying, and mutually stacking the monodisperse cobaltosic oxide to generate an agglomeration effect to obtain the agglomeration modified diaphragm.

The scanning electron micrograph of the monodisperse cobaltosic oxide prepared in comparative example 1 is shown as part a in fig. 7, and shows a monodisperse structure; the scanning electron microscope image of the agglomerated modified diaphragm prepared in the comparative example 1 is shown in part b in fig. 7, and the monodisperse cobaltosic oxide is stacked with each other to generate an agglomeration effect; the contact angle test chart of the agglomeration modified diaphragm and the electrolyte is shown in part c in fig. 7, the contact angle of the agglomeration modified diaphragm and the electrolyte is 5 degrees, the agglomeration modified diaphragm is not beneficial to the permeation of the electrolyte, and the transmission performance of lithium ions is reduced.

The foregoing is merely a preferred embodiment of this invention and is not intended to limit the invention in any manner; those skilled in the art can readily practice the invention as shown and described in the drawings and detailed description herein; however, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the scope of the invention as defined by the appended claims; meanwhile, any changes, modifications, and evolutions of the equivalent changes of the above embodiments according to the actual techniques of the present invention are still within the protection scope of the technical solution of the present invention.