CN118156728A - A composite diaphragm with pore size gradient effect and preparation method and application thereof - Google Patents

Abstract

The invention discloses a composite diaphragm with aperture gradient effect, a preparation method and application thereof, wherein the diaphragm is a diaphragm formed by sequentially compounding a cellulose diaphragm, a polyolefin diaphragm, a ceramic diaphragm and a nano aperture material, the polyolefin diaphragm, the cellulose diaphragm and the ceramic diaphragm are soaked in polyvinylidene fluoride and metal chloride solution according to the order of the aperture from large to small, and then the three are compounded into a film by simple rolling. Because the pore diameters of various diaphragms and materials are distributed from large to small, gradient change in pore diameter is formed, more ions can enter the diaphragm at the larger side of the pore diameter, the ion flow can be more homogenized at the side of the gradually reduced pore diameter, and the desolvation process is accelerated, so that the whole composite diaphragm has higher ion mobility.

Description

A composite diaphragm with pore size gradient effect and preparation method and application thereof

Technical Field

The invention belongs to the technical field of membrane modification, and in particular relates to a composite membrane with pore size gradient effect and a preparation method and application thereof.

Background technique

With the growing global demand for clean energy, the development of new energy technologies, especially high-performance battery technologies, has become a research hotspot. Among the many battery technologies, batteries with metals such as lithium, sodium, and zinc as negative electrodes have attracted much attention due to their high theoretical specific capacity and low reduction potential, and are expected to significantly increase the energy density of batteries. However, the high activity of these metals also brings significant challenges, especially the formation of dendrites on the surface of metal negative electrodes. The continuous growth of these dendrites will not only penetrate the battery separator, causing short circuits and potential safety accidents, but also accelerate the consumption of electrolytes, reducing the charging and discharging efficiency and life of the battery. Therefore, solving the dendrite problem in metal negative electrode batteries and improving battery safety and performance have become the focus of research. Although many studies have focused on negative electrode surface modification, uniform ion transport at the solid-liquid interface is also crucial to preventing dendrite formation. Some current solutions, such as electrolyte additives or artificial solid electrolytes, are effective to a certain extent, but the high cost and complex preparation process limit their commercial application. Therefore, it is particularly important to find a simple, low-cost and environmentally friendly modification method. In this regard, the polyolefin separators (such as polyethylene) used in traditional lithium-ion batteries have deficiencies in lithium ion and electrolyte affinity, pore distribution uniformity, and mechanical strength, all of which may lead to the formation of dendrites and battery short circuits. Therefore, it is not only necessary to modify the battery separator. However, the modification of the separator is usually mainly aimed at the doping or coating of elements, and there is little mention of the optimization of the structure of the separator itself. Only large-porosity and large-pore-size separators are used, but their desolvation in ion migration is not high, and their ion mobility is not efficient.

Summary of the invention

Based on the above problems, the present invention aims to provide a composite diaphragm with pore gradient effect and a preparation method and application thereof, so as to solve the problem of low ionic conductivity faced by existing energy storage devices at high power and high rate.

The composite diaphragm provided by the present invention is composed of three diaphragms with different pore sizes to form a complete pore gradient structure. The composite diaphragm is composed of a ceramic diaphragm, a polyolefin diaphragm, and a cellulose membrane through a binder. The pore sizes of the ceramic diaphragm, the polyolefin diaphragm, and the cellulose membrane increase in sequence. The pore size of the composite diaphragm increases from 10nm to 5um in the composite order of the ceramic diaphragm, the polyolefin diaphragm, and the cellulose membrane. Metal halides are also attached to the composite diaphragm, and the thickness of the composite diaphragm is 10~35μm.

The pore sizes of the ceramic diaphragm, polyolefin diaphragm and cellulose membrane are 0.01-1 μm, 0.05-2 μm and 0.1-5 μm respectively. The thickness of the cellulose membrane is 4-30 μm; the thickness of the polyolefin diaphragm is 4-20 μm; and the thickness of the ceramic diaphragm is 5-15 μm.

A layer of metal or covalent organic framework material with sub-nanometer pore size is deposited on the surface and in the pores of the ceramic diaphragm of the composite diaphragm, forming a four-layer pore size gradient effect.

The metal or covalent organic framework material includes but is not limited to ZIF-8, UiO-66, and COF-Go, wherein the pore size range of ZIF-8 is 0.34-1.16 nm, the pore size range of COF-GO is 0.5-1.4 nm, and the pore size range of UiO-66 is 0.8-1.1 nm.

The method for preparing the above-mentioned three-layer composite diaphragm with pore size gradient effect comprises the following steps:

Step 1, preparing a binder and a metal halide solution respectively, mixing the two and stirring them evenly to obtain a mixed solution;

Step 2, adding the polyolefin membrane, the cellulose membrane, and the ceramic membrane into the mixed solution prepared in step 1, and fully soaking them;

Step 3: Roll the membrane mixture that has been fully infiltrated in step 2 to control the thickness of the composite membrane to be 10-35 μm, and then let the prepared composite membrane stand and vacuum dry.

Furthermore, the solute of the binder is one or more of polyvinylidene fluoride, sodium alginate, sodium polyacrylate, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, and styrene butadiene rubber; the solvent of the binder is one or more of anhydrous ethanol, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and cyclohexanone; and the concentration of the binder is 1-5 mg/ml.

Furthermore, the concentration of the metal halide solution is 0.1-1 mg/ml, and the metal element in the metal halide is selected from at least one of Ni, Al, Zn, Sn, Cu, Cr, Ti, and Mg.

Furthermore, the step 2 is to immerse the polyolefin membrane, the cellulose membrane and the ceramic membrane in a mixed solution of a binder and a metal chloride solution at room temperature, and the immersion time is 4-8 hours.

Furthermore, the cellulose membrane in step 2 has a thickness of 4-30 μm and a pore size of 0.1-5 μm; the polyolefin membrane has a thickness of 4-20 μm and a pore size of 0.05-2 μm; the ceramic membrane has a thickness of 5-15 μm and a pore size of 0.01-0.1 μm.

Furthermore, in step 3, the prepared composite membrane is left to stand for 12 hours and then placed in a vacuum environment at 60 ^° C. for 12 hours to be completely dried.

The method for preparing the above-mentioned composite diaphragm with four-layer pore gradient effect is based on the step of preparing the composite diaphragm with three-layer pore gradient effect, and also includes depositing sub-nanometer pore size metal or covalent organic framework material on the surface and pores of the ceramic diaphragm by filtration or spraying on the obtained dried composite diaphragm.

The metal or covalent organic framework material includes but is not limited to ZIF-8, UiO-66, and COF-Go, wherein the pore size range of ZIF-8 is 0.34-1.16 nm, the pore size range of COF-GO is 0.5-1.4 nm, and the pore size range of UiO-66 is 0.8-1.1 nm.

The composite diaphragm with complete pore size gradient effect described in the present invention can be applied to energy storage devices including lithium/sodium/zinc metal batteries, fuel cells or supercapacitors, and the energy storage devices operate at high power and a rate not less than 3C.

Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

1. The composite diaphragm is mainly composed of polyolefin diaphragm, cellulose membrane and ceramic diaphragm, which are impregnated with metal chloride, and metal elements, chlorine elements and fluorine elements are introduced. Among the metal chlorides used, chloride ions can anchor the anions in the electrolyte to a large extent, and the lithium-philic element fluorine can reduce the migration energy barrier of lithium ions. Compared with traditional diaphragms, the composite diaphragm has a very strong affinity for electrolytes and can desolvate ions well.

2. The composite diaphragm contains rich metal elements and gradient pore size (the pore sizes of ceramic diaphragms, polyolefin diaphragms, cellulose membranes, and metal organic framework materials with nanopores are different, forming a pore gradient effect). The gradient pore design can homogenize the flow of lithium ions and can play a great advantage under high power conditions. While ensuring that a large number of ions can be accommodated, ions can be quickly conducted.

3. Under the synergistic effects of multiple factors, it can effectively regulate the distribution of lithium ions, promote the uniform deposition and stripping process of lithium metal negative electrode, inhibit the growth of lithium dendrites, significantly improve its ion conductivity and high-rate performance, and also significantly improve its flame retardancy and high-temperature resistance.

4. In the composite diaphragm, the metal chloride and metal fluoride in the inner and outer layers can bring great improvements in mechanical strength and flame retardancy, and with the introduction of polyvinylidene fluoride, the composition of the beneficial components of the SEI membrane is greatly enhanced, so that the overall liquid surface modification can be presented.

5. The preparation process of the composite diaphragm is simple, the preparation cost is low, and the effect on the energy density of the battery is small.

6. The modified preparation method of the composite diaphragm can effectively solve the challenges in cost and environment, and provide a new way to improve battery performance and safety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of the composite diaphragm in Example 1;

FIG2 is a graph showing the cycle performance of Li-NCM811 batteries prepared with different membranes at 0.5C in Example 8;

FIG. 3 is a performance diagram of some embodiments at different magnifications in Example 9.

Detailed ways

In order to better understand the technical solution of the present invention, the above-mentioned technical solution of the present invention will be described in detail below in combination with specific implementation methods and the accompanying drawings of the specification. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

This will be explained below through a specific implementation plan and product test results.

The ceramic diaphragm used in the following examples is from Hebei Jinli New Energy Technology Co., Ltd. It has aluminum oxide as the main component, and other components include silicon oxide and magnesium oxide. The thickness of the ceramic diaphragm is 5-15 μm, the average pore size of the ceramic diaphragm is 0.01-1 μm, and the porosity is 40-50%.

The polyolefin separator used in the following examples is from Asahi KASEI Co., Ltd. The thickness of the polyolefin separator is 9-20 μm. It has a porous structure with a pore size of 0.05-2 μm, and the connectivity between the pores is good. In addition, the porosity of the polyolefin separator is 40%.

The cellulose membrane (CN201911416124.7) used in the following examples is self-developed by Ningbo Rouchuang Nanotechnology Co., Ltd., and selects cellulose natural fibers and high temperature resistant and electrochemically stable materials such as aramid, polyimide fiber, polyphenylene benzobisoxazole (PBO) fiber, and polyacrylonitrile. The fibers are radially peeled off by chemical enzyme catalysis, high pressure homogenization, mechanical grinding and other processing methods to achieve nanofiberization in fineness, while maintaining good aspect ratio, thickness and pore characteristics, porosity, and other parameters. Then, the above-mentioned multiple fibers are dispersed in water to form a wet film, and then a cross-linking agent is introduced into the wet film composed of porous nanofibers to polymerize the cross-linking agent in situ, further improving the strength of the fiber nodes of the base membrane, thereby improving the mechanical properties of the diaphragm. At the same time, the solvent volatilization induces the cross-linking agent to self-assemble, and a three-dimensional mesh-like uniform pore structure is generated inside the diaphragm, further improving the porosity and pore uniformity of the diaphragm. Finally, the lithium ion conductivity is improved by coating or impregnating the cellulose membrane with a polymer solid electrolyte and an inorganic ceramic solid electrolyte. The cellulose membrane has a thickness of 5-30 μm, a porosity of 40%-75%, and a pore size of 0.1~5 μm.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

Example 1

Gradient battery separator preparation and battery assembly.

In the order of ceramic membrane, polyolefin membrane and cellulose membrane, the three material membranes are immersed in a mixture of zinc chloride and PVDF in turn. The concentration of zinc chloride solution is 1mg/ml and the concentration of PVDF solution is 2mg/ml. After 8 hours of immersion, the cellulose membrane, ceramic membrane and polyolefin membrane are compounded layer by layer in the order of pore size from large to small, and then rolled until the thickness of the composite membrane is within 35um. The rolled membrane is then left to stand for 12 hours without being disturbed to obtain a modified membrane, which is then placed in a 60℃ oven for standby use.

The modified diaphragm was then combined with different battery electrodes to form half-cells, symmetrical cells and full cells for electrochemical performance testing.

FIG1 is a schematic diagram of a battery separator designed with a gradient pore size battery separator in Example 1, wherein the pore sizes of the various layers of the separator are ranked as follows: cellulose separator>polyolefin separator>ceramic separator.

Example 2

The ceramic diaphragm, polyolefin diaphragm and cellulose membrane were immersed in a mixture of zinc chloride and PVDF, with a zinc chloride solution concentration of 1 mg/ml and a PVDF solution concentration of 2 mg/ml. After 8 hours of immersion, the cellulose diaphragm, ceramic diaphragm and polyolefin diaphragm were composited layer by layer in the order of pore size, and then rolled until the composite diaphragm thickness was within 35 um. The rolled diaphragm was then left undisturbed for 12 hours and placed in a 60°C oven for later use.

Then, the modified composite membrane is filtered or sprayed to deposit a layer of metal organic framework material with nanopore size, such as ZIF-8, on the ceramic membrane side with smaller pore size of the composite membrane. A four-layer gradient effect is formed: cellulose membrane, polyolefin membrane, ceramic membrane, and ZIF-8. The pore size of ZIF-8 is: 0.34~1.16nm.

After the ceramic diaphragm, polyolefin diaphragm, and cellulose membrane were immersed in a mixture of zinc chloride and PVDF, the pore size range did not change significantly. PVDF mainly played the role of a binder, and the introduction of zinc chloride played a role in anchoring anions and flame retardant. For example, when polysulfides are added to the electrolyte, chloride ions can inhibit the shuttle effect of polysulfides. The ZIF-8 coating on the modified diaphragm is combined with the gradient pores of the modified diaphragm to separate different solution environments at both ends. One end of the ZIF-8 pore is an external solution with a large spatial scale, and the other end is a composite diaphragm pore with micrometer-nanometer size and zinc chloride and metal oxide on the surface.

Example 3-Example 4

The operation is basically the same as that in Example 2, except that the halides used are fluoride-silver fluoride and bromide-magnesium bromide.

Example 5-Example 6

The operation is basically the same as that in Example 2, except that the nanomaterials deposited on the ceramic diaphragm side with a smaller pore size of the composite diaphragm are different. In Example 5, a layer of COF-GO covalent organic framework composite graphene oxide with a sub-nanometer pore size is deposited), and the pore size of COF-GO is 0.5~1.4nm. In Example 6, a layer of UiO-66 (metal organic framework-Zr) with a sub-nanometer pore size is deposited, and the pore size of UiO-66 is 0.8~1.1nm.

Only some of the examples are tested here, and other modification methods with nanopores composited to gradient membranes are also protected by this patent.

Example 7

This example tests the composite membranes designed based on the pore size gradient prepared in Examples 1 and 2 (the preparation method refers to the invention content), the composite membranes prepared in Examples 3 to 6, and cellulose membranes, polyolefin membranes, ceramic membranes, composite membranes of cellulose membranes and polyolefin membranes, composite membranes of polyolefin membranes and ceramic membranes, and modified membranes in which a metal or covalent organic framework material is coated on one side of the ceramic membrane after the composite of polyolefin membrane and ceramic membrane. A total of 12 types of membranes are used to assemble lithium symmetric batteries to test the lithium ion mobility and steel-to-steel batteries to test the ionic conductivity.

The composite membrane of the cellulose membrane and the polyolefin membrane, and the composite membrane of the polyolefin membrane and the ceramic membrane are composited with an adhesive. In this embodiment, the adhesive is SBR latex, silicone defoamer, sodium dodecyl sulfate wetting agent, and deionized water in a ratio of 100:1:1:1000, mixed and stirred to disperse evenly, and the adhesive solution is obtained after standing. The above test results are shown in Table 1.

Table 1

Ion mobility measures the ability of ions to move in an electrolyte. Lower ion mobility not only reduces the ionic conductivity of the electrolyte, but may also lead to severe concentration polarization effects. In order to maintain high ionic conductivity while being able to accommodate a large number of ions, high ion mobility is essential for adapting to high-power and high-rate battery operating conditions. It can be seen from Table 1 that the modified composite diaphragms prepared in Examples 1 to 6 perform better in both ionic conductivity and ion mobility than cellulose diaphragms, polyolefin diaphragms, and ceramic diaphragms. Especially when a metal or covalent organic framework structure with a smaller pore size is introduced, the ionic conductivity effect of the battery prepared by the composite diaphragm with an pore size gradient effect is more prominent.

Example 8

This example tests the cycle performance of NCM811 batteries based on different separators.

Using lithium metal as the negative electrode, NCM811 as the positive electrode, 1M LiPF6 EC/DEC (volume ratio of 1:1) as the electrolyte, and using different diaphragms, NCM811 batteries were assembled in an argon atmosphere glove box. When assembling the NCM811 battery, the side with a small pore size of the diaphragm of Examples 1 to 6 faced the negative electrode, and the side with a large pore size faced the positive electrode.

The preparation method of the NCM811 positive electrode sheet is as follows: nickel cobalt manganese (NCM), SuperP (conductive carbon black), and polyvinylidene fluoride (PVDF) binder are mixed in a mass ratio of 8:1:1, ground evenly and dispersed in polymethylpyrrolidone (NMP), then placed in a homogenizer and homogenized for 20 minutes to obtain a uniform slurry, and the slurry is scraped onto aluminum foil with a preparation device and placed in a vacuum drying oven at 80°C for 12 hours.

Taking the CR2025 button battery made of the above-mentioned polyolefin diaphragm, ceramic diaphragm, and composite diaphragm of Example 2 as an example, the diameter of this type of battery is 20 mm and the thickness is 2.5 mm. The CR2025 button battery is assembled in the order of negative electrode shell, lithium sheet, dripping electrolyte, diaphragm, dripping electrolyte, positive electrode sheet, gasket, and spring, and the battery pressure is 0.85 MPa.

The cycling performance diagram of Li-NCM811 batteries prepared with the above three types of separators at 0.5C is shown in Figure 2.

Example 9

This example tests the cycle rate performance of the NCM811 battery prepared based on different separators in Example 7.

Using lithium metal as the negative electrode, NCM811 as the positive electrode, 1M LiPF6 EC/DEC (volume ratio of 1:1) as the electrolyte, and using different diaphragms, NCM811 batteries were assembled in an argon atmosphere glove box. When assembling the NCM811 battery, the side with a small pore size of the diaphragm of Example 1 or Example 2 faced the negative electrode, and the side with a large pore size faced the positive electrode.

The preparation method of the positive electrode sheet is as follows: nickel cobalt manganese (NCM), SuperP (conductive carbon black), and polyvinylidene fluoride (PVDF) binder are mixed in a mass ratio of 8:1:1, ground evenly and dispersed in polymethylpyrrolidone (NMP), and then placed in a homogenizer for 20 minutes to obtain a uniform slurry, and the slurry is scraped onto aluminum foil with a preparation device and placed in a vacuum drying oven at 80°C for 12 hours.

Table 2 is a table of the cycle performance of the Li-NCM811 battery at different rates in Example 7. The battery using the composite separator has significantly higher rate performance than the battery using the commercial separator. The positive electrode full battery voltage is 3V-4.3V, and the test temperature is 25°C. Figure 3 is a cycle performance rate diagram of some separators in this example.

Table 2

It can be seen from Table 1 that the -OH and other groups on the surface of the ceramic particles in the single ceramic diaphragm have strong lyophilicity, thereby improving the wettability of the diaphragm for the electrolyte. However, due to the large pore size of the polyolefin diaphragm and the small size of the ceramic ions, after the adhesive is applied, the contact between the surface of the polyolefin + ceramic composite diaphragm and the electrolyte is limited, resulting in the ion conductivity of the polyolefin + ceramic composite diaphragm not being significantly improved. By coating the metal chloride on the surface of the cellulose diaphragm + polyolefin diaphragm + ceramic diaphragm through PVDF, as in Example 1, the introduction of zinc chloride plays the role of anchoring anions, which can make it easier for positively charged Li ⁺ to shuttle therein, thereby improving the mobility of lithium ions. The composite diaphragm pores have good affinity with the electrolyte, and the metal oxides in the composite diaphragm pores have affinity for the lithium ions in the lithium electrolyte, which can make the lithium ions pass through the composite diaphragm pores evenly, so that the lithium electrolyte in each pore in the composite diaphragm is evenly distributed, avoiding the lithium ions from only passing through the diaphragm from the local area of the composite diaphragm, resulting in the problem of a decrease in the rate of ion migration under high current.

The more complete the composite membrane is, the better it performs in high rate performance. For example, in Example 1, the composite membrane is composed of a ceramic membrane, a polyolefin membrane, and a cellulose membrane with increasing pore sizes, while in Example 2, the composite membrane is composed of a nano ZIF-8 material, a ceramic membrane, a polyolefin membrane, and a cellulose membrane with increasing pore sizes. In Example 2, relative to Example 1, the pore size gradient of the composite membrane pore is more perfect, and the rate of ion migration of the membrane in Example 2 under high current is improved. This is because of the unique gradient pore size design. Since the micron-nanometer pore size on one side of the composite membrane is larger, it can accommodate more ions. The pore diameter is continuously reduced to the nanometer level as the membrane composite order is continuously reduced. The lithium ion radius (0.2nm-0.3nm) in the electrolyte, the hydrated ion radius of lithium (0.76nm), the hydrated ion radius of anions (several angstroms-more than ten angstroms), the nanometer level allows the lithium ion radius and the hydrated ions of lithium to shuttle freely.

The pore size in the ZIF-8 layer is reduced to sub-nanometer level. Chloride ions and other anions in the composite diaphragm pores can inhibit anions in the electrolyte from shuttling through the diaphragm, allowing more lithium ions to pass through the composite diaphragm pores. The sub-nanometer pore size of the ZIF-8 pores is smaller than the molecular size of the solvent and larger than the radius of lithium ions. The ZIF-8 layer with sub-nanometer pores can remove the solvent molecules around lithium ions, allowing lithium ions to migrate freely in the ZIF-8 pore structure, thereby greatly accelerating the rate of ion migration. The gradient pore structure has a relatively ideal effect in the application of high-power equipment. The same is true for other materials with nanopores.

Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims (13)

1. A composite membrane with an aperture gradient effect, characterized in that the composite membrane is composited by a ceramic membrane, a polyolefin membrane, and a cellulose membrane through a binder, the pore diameters of the ceramic membrane, the polyolefin membrane, and the cellulose membrane increase in sequence, and the pore diameter of the composite membrane increases from 10 nm to 5 um in the composite order of the ceramic membrane, the polyolefin membrane, and the cellulose membrane, and metal halides are also attached to the composite membrane, and the thickness of the composite membrane is 10~35 μm. 2. The composite diaphragm according to claim 1 is characterized in that the pore sizes of the ceramic diaphragm, the polyolefin diaphragm, and the cellulose membrane are in the range of 0.01-0.1 μm, 0.05-2 μm, and 0.1-5 μm, respectively. 3. The composite membrane according to claim 2 is characterized in that a layer of metal or covalent organic framework material with sub-nanometer pore size is deposited on the surface and inside the pores of the ceramic membrane of the composite membrane. 4. The composite membrane according to claim 3 is characterized in that the metal or covalent organic framework material includes but is not limited to ZIF-8, UiO-66, COF-Go, wherein the pore size range of ZIF-8 is 0.34~1.16nm, the pore size range of COF-GO is 0.5~1.4nm, and the pore size range of UiO-66 is 0.8~1.1nm. 5. A method for preparing the composite diaphragm according to claim 1, characterized in that the preparation of the composite diaphragm comprises the following steps: Step 1, preparing a binder and a metal halide solution respectively, mixing the two and stirring them evenly to obtain a mixed solution; Step 2, adding the polyolefin membrane, the cellulose membrane, and the ceramic membrane into the mixed solution prepared in step 1, and fully soaking them; Step 3: Roll the membrane mixture that has been fully infiltrated in step 2 to control the thickness of the composite membrane to be 10-35 μm, and then let the prepared composite membrane stand and vacuum dry. 6. The preparation method according to claim 5, characterized in that the solute of the binder is one or more of polyvinylidene fluoride, sodium alginate, sodium polyacrylate, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, and styrene butadiene rubber, the solvent of the binder is one or more of anhydrous ethanol, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and cyclohexanone, and the concentration of the binder is 1-5 mg/ml. 7. The preparation method according to claim 5 is characterized in that the concentration of the metal halide solution is 0.1-1 mg/ml, and the metal element in the metal halide is selected from at least one of Ni, Al, Zn, Sn, Cu, Cr, Ti, and Mg. 8. The preparation method according to claim 5, characterized in that the infiltration time in step 2 is 4-8h. 9. The preparation method according to claim 5 is characterized in that the cellulose membrane in step 2 has a thickness of 4-30 μm and a pore size of 0.1-5 μm; the polyolefin diaphragm has a thickness of 4-20 μm and a pore size of 0.05-2 μm; the ceramic diaphragm has a thickness of 5-15 μm and a pore size of 0.01-0.1 μm. 10. The preparation method according to claim 5, characterized in that, in step 3, the prepared composite diaphragm is allowed to stand for 12 hours and then placed in a vacuum environment at 60 ^° C for 12 hours to be completely dried. 11. A method for preparing the composite membrane according to claim 3, characterized in that after step 3 of the preparation method according to claim 3, it also includes depositing a sub-nanometer pore size metal or covalent organic framework material on the surface and pores of the ceramic membrane by suction filtration or spraying on the obtained dried composite membrane. 12. The method for preparing a composite diaphragm according to claim 11, characterized in that the metal or covalent organic framework material includes but is not limited to ZIF-8, UiO-66, COF-Go, wherein the pore size range of ZIF-8 is 0.34~1.16nm, the pore size range of COF-GO is 0.5~1.4nm, and the pore size range of UiO-66 is 0.8~1.1nm. 13. An energy storage device comprising applying the composite diaphragm with pore size gradient effect as claimed in any one of claims 1 to 4 to a metal battery, fuel cell or supercapacitor including lithium/sodium/zinc.