Zif-8 materials, preparation systems, preparation methods, single atom catalysts, battery separator membranes, and applications thereof

Abstract

The application discloses a ZIF-8 material and a preparation system, a preparation method, a single-atom catalyst, a battery isolation film and application thereof. The preparation system of the ZIF-8 material comprises metal ions, ligand molecules and a solvent; wherein the metal ions are zinc ions, the ligand molecules are 2-methyl imidazole, and the solvent is water; in the preparation system, the molar ratio of the metal ions, the ligand molecules and the solvent is 1:a:z, wherein 7 < a < 13 and 310 < z < 600.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal organic framework materials and secondary batteries, and more particularly to a ZIF-8 material and a preparation system, a preparation method, a single-atom catalyst, a battery separator, and applications thereof, and further relates to a battery cell and a power utilization device. BACKGROUND

[0002] The statements herein are provided only to complement the background of the present application and are not necessarily prior art.

[0003] A zeolitic imidazolate framework (ZIF material) is a kind of metal organic framework (MOF) material. The ZIF material is a kind of porous crystalline material with a zeolite topology formed by complexing divalent transition metal ions with imidazole-based ligands, and the divalent transition metal ions involved are usually zinc ions or cobalt ions. When zinc ions are used to provide divalent transition metal ions, a ZIF-8 material can be obtained, which has excellent properties such as large specific surface area, high porosity, ultrahigh thermal stability, and chemical stability, and has wide applications in various fields such as gas storage, gas separation, catalytic reaction, optics, magnetic materials, and sensing.

[0004] However, the current preparation process of the ZIF-8 material generally has problems such as long cycle and large raw material consumption. SUMMARY

[0005] In view of the above problems, the present application provides a ZIF-8 material and a preparation system, a preparation method, a single-atom catalyst, a battery separator, and applications thereof (including applications as a material or element of a battery cell and a power utilization device), the preparation system and the preparation method provided by the present application use an unexpectedly discovered scheme with extremely low ligand dosage and extremely low water dosage, and nanoscale ZIF-8 particles with high particle dispersity and uniform particle size are prepared, which can significantly shorten the process cycle and reduce the raw material consumption.

[0006] In a first aspect, the present application provides a preparation system of a ZIF-8 material, which comprises metal ions, ligand molecules, and a solvent;

[0007] The metal ions are zinc ions, the ligand molecules are 2-methyl imidazole, and the solvent is water.

[0008] In the preparation system, the molar ratio of the metal ions, the ligand molecules, and the solvent is 1:a:z, wherein 7

[0009] Through long-term and large-scale experimental exploration, the inventors of the present application accidentally found that ZIF-8 nanoparticles can still be prepared under the condition of extremely low ligand dosage and extremely low water dosage, and the particles have high dispersibility, controllable particle size and good uniformity of particle size distribution, when studying the preparation of ZIF-8 material by co-precipitation method. The preparation system breaks the design principle of high ligand dosage and high water dosage in traditional preparation system design, and uses a ligand dosage far lower than the traditional design and a water dosage far lower than the traditional scheme, which can significantly reduce the residual ligand and solvent treatment cost, shorten the process cycle and reduce the raw material consumption. Further, based on the characteristics of high dispersibility, controllable particle size and good uniformity of particle size distribution of ZIF-8 nanoparticles in ZIF-8 material, the ZIF-8 material provided by the present application can provide high-quality raw materials in various applications, including but not limited to preparing single-atom catalysts with high catalytic activity and preparing battery separator membranes with high thermal stability. In some embodiments, a satisfies 8≤a≤12.

[0010] In some embodiments, a satisfies 8≤a≤12.

[0011] Preferably, a satisfies 9≤a≤12.

[0012] Preferably, a satisfies 9≤a≤12.

[0013] Preferably, a satisfies 9≤a≤12.

[0014] In some embodiments, z satisfies 310

[0015] Preferably, z satisfies 310

[0016] Preferably, z satisfies 310

[0017] Preferably, z satisfies 310

[0018] Preferably, z satisfies 310

[0019] Preferably, z satisfies 310

[0020] Preferably, z satisfies 310

[0021] In some embodiments, the molar ratio z / a of the ligand molecules and the solvent satisfies 30 < (z / a) < 44;

[0022] Preferably, z / a satisfies 32 ≤ (z / a) ≤ 40;

[0023] More preferably, z / a satisfies 33 ≤ (z / a) ≤ 39;

[0024] More preferably, z / a satisfies 34 ≤ (z / a) ≤ 36;

[0025] More preferably, z / a satisfies 34 ≤ (z / a) ≤ 35.

[0026] The above z / a is equal in value to the ratio of the total molar amount of water to the molar amount of ligand in the preparation system. In the present application, controlling z / a in a suitable range can regulate the particle size of ZIF-8 nanoparticles. A smaller z / a value is conducive to obtaining smaller primary particle size, and is more conducive to preparing high-performance single-atom catalysts and high-performance battery separator membranes. However, z / a should not be too small, otherwise the aggregation of primary particles will lead to the presence of larger secondary particles.

[0027] In some embodiments, the zinc ions are from a soluble zinc salt;

[0028] Preferably, the soluble zinc salt comprises one or more of zinc acetate, zinc chloride, zinc nitrate and zinc sulfate.

[0029] The soluble zinc salt can be used to provide zinc ions, which further react with the ligand 2-methylimidazole to generate ZIF-8 nanoparticles, i.e., 2-methylimidazole zinc ZIF-8 nanoparticles.

[0030] In a second aspect, the present application provides a preparation method of ZIF-8 material, comprising the following steps:

[0031] Mixing a zinc source solution with a ligand solution to prepare the preparation system of the ZIF-8 material of the first aspect of the present application;

[0032] Carrying out a coordination reaction on the preparation system to prepare ZIF-8 nanoparticles;

[0033] In the preparation system,

[0034] The molar ratio of zinc ions in the preparation system to water in the zinc source solution is 1: b;

[0035] The molar ratio of zinc ions in the preparation system to water in the ligand solution is 1: c;

[0036] In the preparation system, the molar ratio of zinc ions, the ligand molecules and water is 1: a: (b+c).

[0037] The application provides a preparation method of ZIF-8 material, wherein the relative amounts of zinc ions, ligands (2-methylimidazole) and solvents (water) are controlled in a specific range by using the preparation system of the ZIF-8 material provided in the first aspect of the application, so that the ZIF-8 material with high particle dispersity, controllable particle size and good uniformity of particle size distribution can be prepared under the condition of extremely low ligand amount and extremely low water amount, and high yield and high yield can also be achieved, which is suitable for large-scale production.

[0038] In some embodiments, b satisfies 100 < b < 200;

[0039] Preferably, b satisfies 100 ≤ b ≤ 150;

[0040] More preferably, b satisfies 110 ≤ b ≤ 140;

[0041] More preferably, b satisfies 115 ≤ b ≤ 140.

[0042] The above b is equal in value to the ratio of the water molar amount in the zinc source solution to the zinc ion molar amount, and the zinc source solution has a suitable zinc ion concentration by controlling b in a suitable value range in the application, so that local concentration unevenness can be avoided when mixed with the ligand solution, and the particle size and distribution uniformity of primary particles can be better controlled.

[0043] In some embodiments, c satisfies 160 < c < 410;

[0044] Preferably, c satisfies 200 ≤ c ≤ 300;

[0045] More preferably, c satisfies 205 ≤ c ≤ 300;

[0046] More preferably, c satisfies 220 ≤ c ≤ 280;

[0047] More preferably, c satisfies 250 ≤ c ≤ 280.

[0048] The above c is equal in value to the ratio of the water molar amount in the ligand solution to the zinc ion molar amount in the zinc source solution, and the total amount of water in the preparation system and the concentration of the ligand solution can be flexibly adjusted by adjusting the value of c. The primary particle size and distribution uniformity of ZIF-8 nanoparticles can be more finely controlled by adjusting c in a suitable value range. For a certain ligand molar amount, the smaller the value of c, the higher the concentration of the ligand solution, and the smaller the primary particle size. However, if the value of c is too small, the primary particles may also agglomerate to form secondary particles with larger particle size.

[0049] In some embodiments, the reaction temperature for the coordination reaction of the preparation system is selected from 5°C to 40°C.

[0050] Preferably, the reaction temperature for the coordination reaction is selected from 5°C to 37°C.

[0051] More preferably, the reaction temperature for the coordination reaction is selected from 5°C to 30°C.

[0052] More preferably, the reaction temperature for the coordination reaction is selected from 15°C to 40°C.

[0053] More preferably, the reaction temperature for the coordination reaction is selected from 15°C to 35°C.

[0054] More preferably, the reaction temperature for the coordination reaction is selected from 20°C to 30°C.

[0055] In some embodiments, the reaction time for the coordination reaction of the preparation system is selected from 3h to 30h.

[0056] Preferably, the reaction time for the coordination reaction is selected from 12h to 24h.

[0057] By adjusting the reaction temperature of the coordination reaction, the primary particle size of the ZIF-8 nanoparticles can be affected. When the reaction temperature is higher, the primary particle size is generally larger; when the reaction temperature is too high, the primary particles are prone to agglomeration; if the reaction temperature is lower, the reaction rate will be slower. Further, the reaction time of the coordination reaction can be adjusted in combination with the reaction temperature, both to ensure the full progress of the coordination reaction and to avoid the agglomeration of the primary particles.

[0058] In some embodiments, the mixing of the zinc source solution and the ligand solution includes: adding the zinc source solution to the ligand solution under stirring conditions.

[0059] In some embodiments, the stirring conditions include: the stirring speed is selected from 200rpm to 800rpm.

[0060] Mixing the zinc source solution and the ligand solution under stirring conditions can make the reactants more uniformly dispersed in the system, avoiding local agglomeration of primary particles due to too high local concentration of reactants. By controlling the appropriate stirring speed, the reactants in the system can be uniformly and sufficiently mixed, and local shear force that may cause agglomeration of primary particles can be avoided.

[0061] In a third aspect, the present application provides a ZIF-8 material, wherein the ZIF-8 material comprises ZIF-8 nanoparticles; the D v 90 and D v10 nm. v 90 nm v 10 nm. v 90 nm v 10 nm.

[0062] Preferably, (D v 90 nm v 10 nm.

[0063] More preferably, (D v 90 nm v 10 nm.

[0064] More preferably, (D v 90 nm v 10 nm.

[0065] More preferably, (D v 90 nm v 10 nm.

[0066] More preferably, (D v 90 nm v 10 nm.

[0067] More preferably, (D v 90 nm v 10 nm.

[0068] The ZIF-8 material provided in the present application has ZIF-8 nanoparticles with uniform particle size distribution. (D v 90 nm v 10 nm.

[0069] In some embodiments, the average particle size d1 of primary particles of the ZIF-8 nanoparticles satisfies d1≤800 nm;

[0070] Preferably, the average particle size d1 of primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤d1≤800 nm;

[0071] More preferably, the average particle size d1 of primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤d1≤500 nm;

[0072] More preferably, the average particle size d1 of primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤d1≤480 nm;

[0073] More preferably, the average particle size d1 of primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤d1≤450 nm;

[0074] Preferably, the average particle size dl of the primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤dl≤300 nm.

[0075] Preferably, the average particle size dl of the primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤dl≤250 nm.

[0076] Preferably, the average particle size dl of the primary particles of the ZIF-8 nanoparticles satisfies 10 nm≤dl≤200 nm.

[0077] The ZIF-8 material provided in the present application has the primary particles of the ZIF-8 nanoparticles in nanometer scale and controllable particle size.

[0078] In some embodiments, the D90 of the ZIF-8 nanoparticles satisfies 90≤100000 nm. v 90≤100000 nm.

[0079] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≥10 nm. v 90≥10 nm.

[0080] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤4500 nm. v 90≤4500 nm.

[0081] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤4500 nm. v 90≤4500 nm.

[0082] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤2000 nm. v 90≤2000 nm.

[0083] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤1500 nm. v 90≤1500 nm.

[0084] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤1000 nm. v 90≤1000 nm.

[0085] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤800 nm. v 90≤800 nm.

[0086] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤650 nm. v 90≤650 nm.

[0087] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤600 nm. v 90≤600 nm.

[0088] Preferably, the D90 of the ZIF-8 nanoparticles satisfies 90≤550 nm. v 90≤550 nm.

[0089] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 90≤500nm.

[0090] The ZIF-8 material provided in the present application has a narrow distribution range of the ZIF-8 nanoparticles, 90% of the volume of the nanoparticles are within the controllable nanometer scale.

[0091] In some embodiments, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50<3000nm;

[0092] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤3000nm;

[0093] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤2000nm;

[0094] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤1500nm;

[0095] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤1000nm;

[0096] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤800nm;

[0097] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤650nm;

[0098] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v 50≤600nm;

[0099] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤D v50 ≤550nm;

[0100] Preferably, the D90 of the ZIF-8 nanoparticles is less than 500 nm. v 50nm≤Dv 50≤500nm.

[0101] The ZIF-8 nanoparticles in the ZIF-8 material provided by the present application have an ideal average particle size, neither too large to adversely affect the preparation of high-performance monatomic catalysts and high-performance battery separator membranes and other applications, nor too small to easily agglomerate.

[0102] In some embodiments, the D v 10≥10nm;

[0103] Preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10<800nm;

[0104] More preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10≤700nm;

[0105] More preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10≤500nm;

[0106] More preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10≤350nm;

[0107] More preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10≤300nm;

[0108] More preferably, the D v 10 of the ZIF-8 nanoparticles satisfies 10nm≤D v 10≤250nm.

[0109] By jointly controlling the D v 10 and the D v 90, it can be ensured that the ZIF-8 nanoparticles have a relatively narrow particle size distribution, and the narrower the particle size distribution, the more uniform the particle size, which is more advantageous for the preparation of high-performance monatomic catalysts and high-performance battery separator membranes and other applications.

[0110] In a fourth aspect, the present application provides a preparation method of a monatomic catalyst, comprising the following steps:

[0111] mixing the ZIF-8 material sacrificial precursor with a metal salt solution, solid-liquid separation, collecting the solid phase, drying, to obtain a metal salt loaded ZIF-8 material; wherein the ZIF-8 material sacrificial precursor comprises the ZIF-8 material prepared by the preparation method of the second aspect of the present application or the ZIF-8 material of the third aspect of the present application, and the metal element M in the metal salt solution comprises one or more of Co, Fe, Mn, Ni, Cu, Pt and Zn;

[0112] calcining the metal salt loaded ZIF-8 material in an inert gas atmosphere, cooling, to obtain a ZIF-8 derived single-atom catalyst, wherein the single-atom metal site type of the ZIF-8 derived single-atom catalyst is selected from any one of M-N4-C, M-N3-C, M-N2-C and M-N1-C.

[0113] The ZIF-8 nanoparticles in the ZIF-8 material prepared (second aspect) or provided (third aspect) in the present application are 2-methyl imidazole zinc ZIF-8 nanoparticles, which have small primary particle sizes and uniform particle size distribution, can adsorb more metal sites as a sacrificial precursor, so that the metal content in the obtained carbon-based single-atom catalyst is higher, the catalytic site density is higher, and thus the catalytic activity is more favorable to be improved. Further, the primary particles of the obtained carbon-based single-atom catalyst can inherit the morphology and particle size of the ZIF-8 precursor, so that the catalytic sites of the prepared carbon-based single-atom catalyst can be better exposed to the reactants and solvents, thereby giving it higher catalytic activity.

[0114] In some embodiments, the solvent in the metal salt solution comprises one or more of methanol, ethanol, water and N,N-dimethylformamide.

[0115] In some embodiments, the metal salt in the metal salt solution is selected from one or more of cobalt nitrate, iron nitrate, iron chloride, nickel nitrate, nickel acetylacetonate, sodium chloroplatinate, iron acetylacetonate, copper nitrate and copper sulfate.

[0116] In some embodiments, the temperature for mixing the ZIF-8 material sacrificial precursor with the metal salt solution is selected from 10°C to 60°C, preferably, the mixing time is selected from 1h to 12h, and more preferably, the mixing time is selected from 2h to 6h.

[0117] The drying temperature is selected from 95°C to 105°C, and preferably, the drying time is selected from 5h to 10h.

[0118] The step of calcining the metal salt loaded ZIF-8 material in an inert gas atmosphere, cooling, comprises: heating the metal salt loaded ZIF-8 material to a calcination temperature under an inert gas, holding, and cooling,

[0119] Preferably, the inert gas atmosphere is selected from a nitrogen atmosphere or an argon atmosphere;

[0120] Preferably, the heating rate is selected from 4℃ / min to 6℃ / min.

[0121] Preferably, the calcination temperature is selected from 800℃ to 1000℃.

[0122] Preferably, the holding time is selected from 1.5h to 2.5h.

[0123] Preferably, the cooling mode is furnace cooling.

[0124] Preferably, the cooling is to 4℃ to 40℃.

[0125] In some embodiments, the average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst satisfies 5nm≤d2≤700nm.

[0126] Using the ZIF-8 material prepared (second aspect) or provided (third aspect) in the foregoing of the present application as a sacrificial precursor, further comprehensive regulation of process parameters such as metal salt type, solvent type, reaction temperature in the reaction system can control the average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst to be in a suitable nanometer scale, so that the ZIF-8 derived single-atom catalyst has higher metal content, higher catalytic site density, and higher catalytic activity.

[0127] In the fifth aspect, the present application provides a single-atom catalyst, which is prepared according to the preparation method of the fourth aspect of the present application. The provided single-atom catalyst is a ZIF-8 derived single-atom catalyst, the primary particles of which have a suitable nanometer scale, controllable particle size, and good particle size distribution uniformity, and further have high metal content, high catalytic site density, and high catalytic activity.

[0128] In the sixth aspect, the present application provides a battery separator, which comprises a porous substrate and a porous coating layer arranged on at least one surface of the porous substrate, and the porous coating layer comprises the ZIF-8 material prepared by the preparation method of the second aspect of the present application or the ZIF-8 material of the third aspect of the present application.

[0129] In some embodiments, the weight percentage content of the ZIF-8 material in the porous coating layer is selected from 40% to 90%.

[0130] In some embodiments, the porous coating layer can further comprise one or more of a binder, inorganic particles, a stabilizer, a wetting agent, a rheology modifier, an antifoaming agent, a thickening agent, a pH adjuster, and a preservative.

[0131] Preferably, the inorganic particle comprises one or more of the following group: boehmite, molecular sieve, zeolite, alumina, aluminum oxyhydroxide, silicon dioxide, aluminum nitride, silicon carbide, magnesium oxide, calcium oxide, zinc oxide, zirconium dioxide, titanium dioxide.

[0132] In some embodiments, the thickness of the porous coating is selected from 0.5 μm to 12 μm.

[0133] When the battery separator is prepared using the ZIF-8 material prepared or provided by the aforementioned preparation (second aspect) or provision (third aspect) of the present application, the ZIF-8 nanoparticles with small primary particles and uniform particle size distribution can be uniformly coated on the surface of the separator, which can effectively inhibit the thermal shrinkage of the separator at a lower coating thickness; the obtained separator also has good electrolyte wettability and good electrolyte retention rate; when the lithium ion battery is prepared using the separator, the battery has low expansion rate, good rate performance, good cycle performance and high safety.

[0134] In a seventh aspect, the present application provides the use of the ZIF-8 material prepared by the preparation method of the second aspect of the present application or the ZIF-8 material of the third aspect of the present application in the preparation of a carbon-based single-atom catalyst or a lithium ion battery separator.

[0135] In the ZIF-8 material prepared or provided by the aforementioned preparation (second aspect) or provision (third aspect) of the present application, the ZIF-8 nanoparticles have small primary particle size, uniform particle size distribution and good particle dispersibility; when the ZIF-8 material is used to prepare a carbon-based single-atom catalyst, the metal content is high, the catalytic site density is high, and the catalytic activity is high; when the ZIF-8 material is used to prepare a lithium ion battery separator, it can be uniformly distributed on the surface of the separator at a suitable surface density, which can effectively inhibit the thermal shrinkage of the separator at a lower coating thickness; the obtained separator also has good electrolyte wettability and good electrolyte retention rate.

[0136] In an eighth aspect, the present application provides a battery monomer comprising a positive electrode sheet, a battery separator of the sixth aspect of the present application and a negative electrode sheet, the battery separator being arranged between the negative electrode sheet and the positive electrode sheet.

[0137] When the battery separator of the sixth aspect of the present application is used to prepare a lithium ion battery, the battery monomer has low expansion rate, good rate performance, good cycle performance and high safety.

[0138] In a ninth aspect, the present application provides an electric device comprising the battery monomer of the eighth aspect of the present application.

[0139] The electric device prepared using the battery monomer of the eighth aspect of the present application can have the remarkable advantages of fast charging, long endurance, long service life and high safety.

[0140] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0141] To better describe and illustrate the embodiments or examples of the application disclosed herein, reference can be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments or examples, and the best mode of these applications as presently understood. Moreover, in all the drawings, like reference numerals refer to like parts throughout the several views. In the drawings:

[0142] Figure 1 is a SEM image of ZIF-8 nanoparticles in an embodiment of the application;

[0143] Figure 2 is a nanoparticle size distribution graph of ZIF-8 material in an embodiment of the application, with the horizontal axis representing particle size (μm) and the vertical axis representing volume percentage content (%);

[0144] Figure 3 is an XRD spectrum of ZIF-8 material prepared in an embodiment of the application, with the horizontal axis representing 2θ diffraction angle (unit: °) and the vertical axis representing diffraction peak intensity;

[0145] Figure 4 is an atomic resolution HAADF-STEM image of ZIF-8 derived single-atom catalyst in an embodiment of the application, wherein the circled part shows single-atom sites;

[0146] Figure 5 is a SEM image of ZIF-8 nanoparticles (left) and a morphology image of ZIF-8 derived single-atom catalyst (right) used in preparation of ZIF-8 derived single-atom catalyst in an embodiment of the application;

[0147] Figure 6 is an oxygen reduction test graph of ZIF-8 derived single-atom catalyst in an embodiment of the application, wherein the horizontal axis represents potential (V vs. RHE) and the vertical axis represents current density;

[0148] Figure 7 is a SEM image of ZIF-8 nanoparticles (left) and a morphology image of ZIF-8 nanoparticles on the surface of a separation membrane used in preparation of the separation membrane in an embodiment of the application;

[0149] Figure 8Figure 1 is a contrast diagram of the appearance of a separator film prepared by using ZIF-8 material in an embodiment of the present application before and after being placed at 150℃ for 1h, wherein the left side corresponds to the original composite separator before heating, and the right side corresponds to after heating;

[0150] Figure 9 Figure 2 is a schematic diagram of a battery cell in an embodiment of the present application;

[0151] Figure 10 Figure 3 is an exploded view of the battery cell in an embodiment of the present application shown in Figure 2; Figure 1

[0152] Figure 11 Figure 4 is a schematic diagram of a use device using a secondary battery as a power source in an embodiment of the present application.

[0153] BRIEF DESCRIPTION OF DRAWINGS

[0154] 5, secondary battery; 51, housing; 52, electrode assembly; 53, cover plate; 6, use device. DETAILED DESCRIPTION

[0155] Hereinafter, embodiments of the ZIF-8 material and its preparation system, preparation method, single-atom catalyst, battery separator, and application of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters that are already well known, repeated descriptions of practically identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided in order for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0156] ​The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all combinations of any two of the range limits, unless otherwise indicated. For example, a range of "1 to 10" is intended to include any number from 1 to 10, including the integers 1 and 10. Unless otherwise indicated, the use of "or" in the disclosed aspects herein is the inclusive, and not the exclusive use. Only the context, and not the number of times an item is used, can determine that it is the exclusive use. For example, the phrase "A uses B or C" means that A can use B, or A can use C, or A can use both B and C. Also, the use of the term "one" or "a" or "the" is intended to be singular as well as plural, unless only the singular form is used. For example, the phrase "one or more of A, B, and C" means that A, B, or C can be present, and that one of A, B, and C can be present, and that two of A, B, and C can be present, and that all of A, B, and C can be present.

[0157] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0158] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0159] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0160] Unless otherwise specified, "including" and "including" mentioned in the present application means open, and can also be closed. For example, "including" and "including" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0161] If not specifically stated otherwise, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0162] In this application, "plurality", "a plurality of", "multiple", "a plurality of times", and the like, if not specifically limited, refer to greater than or equal to 2 in number. For example, "one or more" means one or greater than or equal to two.

[0163] As used herein, "combinations thereof", "any combination thereof", "any combination manner thereof", and the like, include all suitable combination manners of any two or more of the listed items.

[0164] As used herein, "suitable combination manner", "suitable manner", "any suitable manner", and the like, "suitable" is subject to the implementation of the technical solutions of the present application.

[0165] As used herein, "preferably", "more preferably", "even more preferably", "suitably", and the like, only describe the embodiments or examples with better effects, and it should be understood that they do not constitute a limitation on the protection scope of the present application. If there are multiple "preferably" in a technical solution, and there is no special description, and there is no contradictory relationship or mutual restriction, each "preferably" is independent.

[0166] In this application, "further", "more further", "particularly", and the like are used for description purposes, indicating differences in content, but should not be understood as limiting the protection scope of the present application.

[0167] In this application, in the terms "first aspect", "second aspect", "third aspect", "fourth aspect", and the like, the terms "first", "second", "third", "fourth", and the like are only for description purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0168] In this application, w / w represents the weight ratio. For example, "ethylene carbonate (EC) : methyl ethyl carbonate (EMC) = 1:1 (w / w)" means that the weight ratio of EC and EMC is 1:1.

[0169] In the present application, wt%, %(w / w), %(w / v), %(v / v) all represent percentage concentration, and have the following meanings respectively. If not specifically stated, for gas-gas mixture, it means volume percentage %(v / v), for solid-solid mixture, it means mass percentage wt%, for liquid-liquid mixture, it means volume percentage %(v / v), for solid-liquid mixture, it means mass percentage wt% or %(w / w) or mass volume percentage %(w / v).

[0170] If not specifically stated, wt% means mass percentage, which means the mass percentage of a specific component in a mixture.

[0171] If not specifically stated, %(w / w) can mean mass percentage, which has the same meaning as wt%, and %(w / w) can also mean mass percentage, which means the relative mass ratio when a given mass of a certain substance is mixed with a given mass of another substance, described in percentage form, for example, mass m1 of substance A and mass m2 of substance B are mixed, then the mass concentration of substance A relative to substance B is m1 / (m1+m2)×100%. The two meanings can be distinguished by the mass base.

[0172] If not specifically stated, %(w / v) means mass volume percentage, which means the mass to volume ratio when a given mass of a certain substance is mixed with a given volume of a certain liquid substance, described in percentage form, for example, mass m1 (unit g) of substance A is mixed with volume v2 (unit mL) of liquid substance B, then the mass volume percentage of substance A relative to substance B is (m1 / v2)×100%, for example, a 5% (w / v) aqueous solution of substance A means the corresponding percentage concentration when 5 grams of substance A is mixed with 100 milliliters of water.

[0173] If not specifically stated, %(v / v) means volume percentage, which means the volume to volume ratio when a given volume of a certain substance is mixed with a given volume of another substance, described in percentage form, for example, volume v1 of substance A is mixed with volume v2 of liquid substance B, then the volume percentage of substance A relative to substance B is (v1 / v2)×100%. Here, substance A and substance B are usually both liquid or both gaseous.

[0174] Zeolite-like imidazolate framework material (ZIF material) is a kind of metal organic framework material. The metal ion (Zn 2+ or CO 2+The difference in ZIF material structure can be caused by different ligand (benzimidazole or 2-methylimidazole) and solvent type (water, dimethylformamide, methanol, etc.). ZIF-8 is a special ZIF material, and its complex component is connected by coordination bond between zinc ion and N in 2-methylimidazole (as shown in the following formula), which has high thermal stability and chemical stability similar to zeolite characteristics.

[0175]

[0176] At present, the common method for synthesizing nano-sized ZIF-8 particles with uniform particles is the co-precipitation method with methanol or water as solvent. The principle is to add ligand (2-methylimidazole) and solvent (methanol or water) far exceeding the molar amount of zinc ion, and usually some special additives (such as polyethylene glycol, surfactant, etc.) are added to play the role of morphology control, crystal control, and prevention of agglomeration, so that the coordination reaction between zinc ion and ligand occurs to generate complex (2-methylimidazole zinc), and the generated complex is precipitated from the solution, and after the treatment steps such as solid-liquid separation, ZIF-8 material can be obtained. In addition, during the preparation process, the primary particles of the generated ZIF-8 nanoparticles are prone to agglomeration. Using methanol as solvent can greatly increase the cost and risk of production, and using water as solvent requires using ligand (2-methylimidazole) and additives far exceeding the molar amount of zinc ion to reduce the formation of impurities and the occurrence of agglomeration. Therefore, it is generally believed that it is difficult to obtain ZIF-8 material with good particle dispersion, controllable particle size, and good particle size distribution uniformity when using water as solvent under the conditions of no additives and low 2-methylimidazole dosage.

[0177] In view of the above-mentioned common technical problems, in a first aspect, the present application provides a preparation system of ZIF-8 material, which comprises metal ions, ligand molecules and solvent; wherein the metal ions are zinc ions, the ligand molecules are 2-methylimidazole, and the solvent is water; in the preparation system, the ligand (2-methylimidazole) and solvent (water) used are far lower than the amount used in the traditional design principle, and ZIF-8 nanoparticles can still be prepared, and the particle dispersion is high, the particle size is controllable, and the particle size distribution uniformity is good. The preparation system can significantly reduce raw material consumption and shorten process cycle.

[0178] In this application, the term "ZIF-8 material preparation system" refers to a reaction system composed of raw materials for preparing ZIF-8 materials. The ZIF-8 material of this application can be prepared using the substances contained in this reaction system. The "raw materials for preparing ZIF-8 materials" include reactants that directly participate in the coordination reaction, and substances that provide a reaction environment for the ligand reaction. The "reactants that directly participate in the coordination reaction" are metal ions and ligand molecules, and the "substances that provide a reaction environment for the ligand reaction" include at least a solvent. The substances in this reaction system can be a composition mixed in the same container, but controlled storage conditions are allowed to prevent the coordination reaction from occurring; alternatively, they can be provided separately or in free combination in multiple pre-prepared containers, and then mixed before use. For example, the substance providing the metal ions (metal salt), ligand molecules, and solvent can be pre-prepared in different containers, or the metal salt and solvent can be pre-combined in one container, or the ligand molecules and solvent can be pre-combined in one container. When preparing the ZIF-8 material of this application, the aforementioned related substances should be provided in a complete set. When the relevant substances are mixed in the preset amounts, a coordination reaction will occur between the metal ions and ligand molecules, consuming both metal ions and ligand molecules while generating a complex.

[0179] In some embodiments, this application provides a ZIF-8 material preparation system comprising metal ions, ligand molecules, and a solvent;

[0180] Wherein, the metal ion is zinc ion, the ligand molecule is 2-methylimidazole, and the solvent is water;

[0181] In the preparation system described above, the molar ratio of the metal ion, the ligand molecule, and the solvent is 1:a:z, where 7 < a < 13 and 310 < z < 600.

[0182] ZIF-8 exhibits certain stability in terms of crystal structure, pore size, cage size, BET specific surface area (specific surface area measured by the BET method), and pore volume. For example, a typical ZIF-8 has a zeolite topology with a pore size of 0.34 nm, a cage size of 1.2 nm, and a BET specific surface area >1000 m². 2 / g, pore volume is 0.66cm³ 3 / g. You can refer to the methods described in the literature such as "Park KS eta1. Exceptional chemical and thermal stability of zeolitic imidazolateframeworks[J]PNAS,2006,103(27):10186-10191" to characterize the basic properties of ZIF-8 and then determine whether ZIF-8 has been obtained.

[0183] Through extensive and long-term experimental research, the inventors of this application unexpectedly discovered, while studying the co-precipitation method for preparing ZIF-8 materials, that ZIF-8 nanoparticles could still be obtained with extremely low ligand and water content, exhibiting high particle dispersibility, controllable particle size, and good particle size distribution uniformity. This formulation system breaks away from the traditional design principle of high ligand and high water content, employing significantly lower ligand and water content than conventional designs. This significantly reduces residual ligand and solvent treatment costs, shortens the process cycle, and reduces raw material consumption. Furthermore, the ZIF-8 nanoparticles provided in this application exhibit high dispersibility, controllable particle size, and good particle size distribution uniformity. Therefore, the ZIF-8 material provided in this application can provide high-quality raw materials for various applications, including but not limited to the preparation of highly catalytically active single-atom catalysts and battery separators with high thermal stability.

[0184] Parameter 'a': Numerically equal to the ratio of the molar amount of ligand to the molar amount of zinc ions in the formulation system. A smaller 'a' value indicates a smaller amount of ligand, and vice versa. In traditional aqueous systems, 'a' is typically greater than 20.

[0185] In some embodiments, a satisfies 8 ≤ a ≤ 12.

[0186] In some embodiments, a satisfies 9 ≤ a ≤ 12.

[0187] In some embodiments, a satisfies 10 ≤ a ≤ 12.

[0188] In some embodiments, 'a' may also be selected from any one of the following values ​​or an interval consisting of any two of the following values: 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.2, 9.4, 9.5, 9.6, 9.8, 10, 10.2, 10.4, 10.5, 10.6, 10.8, 11, 11.2, 11.4, 11.5, 11.6, 11.8, 11.9, etc.

[0189] In this application, by controlling 'a' within an unexpectedly low range, the particle size of the prepared ZIF-8 nanoparticles can be precisely controlled to achieve a suitable nanoscale size. However, if the value of 'a' is too small, it can easily lead to a larger size of the ZIF-8 nanoparticles.

[0190] The parameter z is numerically equal to the ratio of the total molar amount of water to the molar amount of zinc ions in the prepared system. A smaller z value indicates less water usage, and vice versa. In traditional aqueous systems, z is typically greater than 1000.

[0191] In some embodiments, z satisfies 310 < z < 500.

[0192] In some embodiments, z satisfies 310 < z < 460.

[0193] In some embodiments, z satisfies 320≤z≤450.

[0194] In some embodiments, z satisfies 340≤z≤450.

[0195] In some embodiments, z satisfies 340≤z≤420.

[0196] In some embodiments, z satisfies 400≤z≤420.

[0197] In some embodiments, z may also be selected from any one of the following values ​​or an interval consisting of any two of the following values: 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 330, 340, 342, 344, 345, 346, 348, 350, 360, 370, 380, 390, 400, 410, 411, 412, 415, 420, 425, 430, 440, 450, 460, 470, 480, 482, 484, 485, 486, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, etc.

[0198] In this application, controlling z within an unexpectedly low value range can prevent the aggregation of ZIF-8 nanoparticles, thus achieving high dispersion of ZIF-8 nanoparticles. Higher particle dispersion and less aggregation make it easier to obtain high-performance single-atom catalysts and high-performance battery separators. However, if the z value is too small, it can easily lead to the aggregation of ZIF-8 particles.

[0199] The parameter z / a is numerically equal to the ratio of the total molar amount of water to the molar amount of ligands in the formulation system. The larger the z / a value, the higher the excess of water compared to the excess of ligands; conversely, the smaller the z / a value, the lower the excess of water compared to the excess of ligands.

[0200] In some embodiments, the molar ratio z / a of the ligand molecule and the solvent satisfies 30 < (z / a) < 44;

[0201] In some embodiments, z / a satisfies 32≤(z / a)≤40.

[0202] In some embodiments, z / a satisfies 33≤(z / a)≤39.

[0203] In some embodiments, z / a satisfies 34≤(z / a)≤36.

[0204] In some embodiments, z / a satisfies 34≤(z / a)≤35.

[0205] In some embodiments, z / a may also be selected from any one of the following values ​​or an interval consisting of any two of the following values: 30.5, 30.8, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41, 41.5, 42, 42.5, 43, 43.5, etc.

[0206] In this application, controlling the z / a ratio within a suitable range allows for the regulation of the ZIF-8 nanoparticle size. A smaller z / a value is beneficial for obtaining smaller primary particle sizes, which is more conducive to preparing high-performance single-atom catalysts and high-performance battery separators. However, z / a should not be too small, as this may cause primary particle agglomeration and lead to the formation of larger secondary particles.

[0207] The aforementioned a and z values ​​can be combined in any suitable manner to achieve synergistic control over the amounts of zinc ions, ligand molecules, and solvent water. Through fine adjustment, ZIF-8 materials with good particle dispersibility, nanoscale size, controllable particle size, and uniform particle size distribution can be prepared with extremely low ligand and even lower water content. This is more conducive to the preparation of high-performance single-atom catalysts and high-performance battery separators.

[0208] In some embodiments, zinc ions are derived from soluble zinc salts.

[0209] In this application, "soluble zinc salt" refers to a zinc salt that is soluble in water.

[0210] In some embodiments, the preparation system consists of a soluble zinc salt, ligand molecules, and water. In this case, the preparation system provided in this application does not include the special additives required in conventional systems. In conventional systems, for example, polyethylene glycol is added to provide a template agent to induce ZIF-8 growth and control the grain morphology, or surfactants are added to control crystal face growth to obtain a specific crystal form. The ZIF-8 material preparation system provided in this application can significantly simplify the process formulation, reduce raw material consumption, and shorten the process cycle.

[0211] In some embodiments, the soluble zinc salt includes one or more of zinc acetate, zinc chloride, zinc nitrate, zinc sulfate, etc.

[0212] In some embodiments, the soluble zinc salt is selected from one or more of zinc acetate, zinc chloride, zinc nitrate, zinc sulfate, etc.

[0213] In some embodiments, the soluble zinc salt includes one or both of zinc acetate and zinc nitrate.

[0214] In some embodiments, the soluble zinc salt is zinc acetate.

[0215] In some embodiments, the soluble zinc salt is zinc nitrate.

[0216] Soluble zinc salts can be used to provide zinc ions, which further coordinate with the ligand 2-methylimidazole to generate ZIF-8 nanoparticles, namely 2-methylimidazole zinc ZIF-8 nanoparticles.

[0217] Secondly, this application provides a method for preparing ZIF-8 material, which can be used to prepare ZIF-8 material using the ZIF-8 material preparation system described in the first aspect of this application.

[0218] In some embodiments, this application provides a method for preparing ZIF-8 material, which includes the following steps:

[0219] The zinc source solution and the ligand solution were mixed to prepare the ZIF-8 material preparation system described in the first aspect of this application.

[0220] The preparation system was subjected to a coordination reaction to obtain ZIF-8 nanoparticles.

[0221] in,

[0222] The molar ratio of zinc ions to water in the zinc source solution in the preparation system is 1:b;

[0223] The molar ratio of zinc ions to water in the ligand solution in the preparation system is 1:c;

[0224] In the preparation system described above, the molar ratio of zinc ions, the ligand molecules, and water is 1:a:(b+c).

[0225] In this application, unless otherwise specified, "zinc source solution" refers to an aqueous solution containing zinc ions.

[0226] In this application, unless otherwise specified, "ligand solution" means an aqueous solution containing ligand (2-methylimidazole).

[0227] The method for preparing ZIF-8 material provided in this application utilizes the ZIF-8 material preparation system provided in the first aspect of this application to control the relative amounts of zinc ions, ligands (2-methylimidazole), and solvent (water) within a specific range. As a result, ZIF-8 material with high particle dispersibility, controllable particle size, and uniform particle size distribution can be obtained with extremely low ligand and water amounts. Raw material consumption is reduced, and the amount of solvent and excess ligand that needs to be processed decreases by an order of magnitude, thereby greatly shortening the process cycle, significantly reducing production costs, and achieving high yield and productivity, making it suitable for large-scale production.

[0228] In some embodiments, the zinc source solution is a mixture of soluble zinc salt and water.

[0229] In some embodiments, the ligand solution is a mixture of 2-methylimidazole and water.

[0230] In some embodiments, the zinc source solution is a mixture of soluble zinc salt and water, and the ligand solution is a mixture of 2-methylimidazole and water. In this case, the preparation system consists of soluble zinc salt, ligand molecules (2-methylimidazole), and water. The preparation system provided in this application does not include the special additives required in conventional systems. ZIF-8 materials with high particle dispersibility, controllable particle size, and uniform particle size distribution can be prepared with extremely low ligand and water consumption and without the need for special additives (such as polyethylene glycol, surfactants, etc.). The formulation is simple, raw material consumption is low, and the process cycle for handling excess ligands and solvents is significantly shortened, reducing costs. Furthermore, high yield and productivity can be achieved, making it suitable for large-scale production.

[0231] Parameter b: Numerically equal to the ratio of the molar amount of water to the molar amount of zinc ions in the zinc source solution. The smaller the b value, the higher the concentration of zinc ions in the zinc salt solution; conversely, the larger the b value, the lower the concentration of zinc ions in the zinc source solution.

[0232] In some embodiments, b satisfies 100 < b < 200.

[0233] In some embodiments, b satisfies 100≤b≤150.

[0234] In some embodiments, b satisfies 110≤b≤140.

[0235] In some embodiments, b satisfies 115 ≤ b ≤ 140.

[0236] In some embodiments, b may also be selected from any one of the following values ​​or an interval consisting of any two of the following values: 101, 102, 103, 104, 105, 110, 112, 114, 115, 120, 125, 130, 135, 136, 137, 138, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 198, 199, etc.

[0237] In this application, controlling b within a suitable numerical range allows the zinc source solution to have a suitable zinc ion concentration, thereby avoiding local concentration unevenness when mixed with the ligand solution, enabling ZIF-8 to have a suitable nucleation and growth rate, and thus better controlling the particle size and distribution uniformity of the primary particles.

[0238] Parameter c: Numerically equal to the ratio of the molar amount of water in the ligand solution to the molar amount of zinc ions in the zinc source solution. Given a specific amount of ligand, a larger c value indicates a lower ligand concentration in the ligand solution, and vice versa.

[0239] In some embodiments, c satisfies 160 < c < 410.

[0240] In some embodiments, c satisfies 200≤c≤300.

[0241] In some embodiments, c satisfies 205≤c≤300.

[0242] In some embodiments, c satisfies 220≤c≤280.

[0243] In some embodiments, c satisfies 250≤c≤280.

[0244] In some embodiments, c may also be selected from any one of the following values ​​or an interval consisting of any two of the following values: 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 175, 180, 185, 190, 195, 200, 205, 206, 208, 210, 215, 220, 222, 224, 225, 226, 22 8, 230, 235, 240, 245, 250, 255, 260, 265, 270, 274, 275, 280, 285, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, etc.

[0245] The value of 'c' is numerically equal to the ratio of the molar amount of water in the ligand solution to the molar amount of zinc ions in the zinc source solution. This application allows for flexible adjustment of both the total amount of water in the preparation system and the concentration of the ligand solution by adjusting the value of 'c'. Within a suitable numerical range, controlling the value of 'c' allows for more precise control over the primary particle size and distribution uniformity of ZIF-8 nanoparticles. For a given molar amount of ligand, a smaller 'c' value results in a higher ligand solution concentration, making it easier to obtain small-sized primary particles. However, if the 'c' value is too small, it may lead to the aggregation of primary particles, forming larger secondary particles.

[0246] In some embodiments, the reaction temperature for the coordination reaction of the preparation system is selected from 5°C to 40°C.

[0247] In some embodiments, the reaction temperature for carrying out the coordination reaction is selected from 5°C to 37°C.

[0248] In some embodiments, the reaction temperature for carrying out the coordination reaction is selected from 5°C to 30°C.

[0249] In some embodiments, the reaction temperature for carrying out the coordination reaction is selected from 15°C to 40°C.

[0250] In some embodiments, the reaction temperature for carrying out the coordination reaction is selected from 15°C to 35°C.

[0251] In some embodiments, the reaction temperature for carrying out the coordination reaction is selected from 20°C to 30°C.

[0252] In some embodiments, the reaction temperature for carrying out the coordination reaction may also be selected from any one of the following temperatures or a temperature range consisting of any two of the following: 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 12℃, 15℃, 16℃, 18℃, 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc.

[0253] In some embodiments, the reaction temperature for carrying out the coordination reaction can also be selected from 5℃~20℃, 10℃~20℃, 5℃~26℃, 10℃~26℃, 15℃~26℃, 16℃~26℃, 15℃~25℃, 10℃~25℃, 20℃~35℃, etc.

[0254] In some embodiments, the reaction time for the coordination reaction of the preparation system is selected from 3h to 30h.

[0255] In some embodiments, the reaction time for the coordination reaction is selected from 12h to 24h.

[0256] In some embodiments, the reaction time for the coordination reaction may also be selected from any one of the following durations or an interval consisting of any two durations: 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 12h, 14h, 15h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, etc.

[0257] In some embodiments, the reaction is carried out overnight (e.g., 12h to 18h).

[0258] In some embodiments, the reaction time for the coordination reaction can also be selected from 4h to 24h, 4h to 18h, 4h to 16h, etc.

[0259] The primary particle size of ZIF-8 nanoparticles can be affected by adjusting the reaction temperature of the coordination reaction. Higher reaction temperatures generally result in larger primary particle sizes; excessively high temperatures can also lead to particle agglomeration; and lower reaction temperatures result in a slower reaction rate. Furthermore, the reaction time of the coordination reaction can be adjusted in conjunction with the reaction temperature to ensure the coordination reaction proceeds fully while preventing particle agglomeration.

[0260] In some embodiments, mixing the zinc source solution with the ligand solution includes adding the zinc source solution to the ligand solution under stirring conditions. In some embodiments, the stirring conditions include a stirring speed selected from 200 rpm to 800 rpm. The stirring speed can be selected from any one of the following stirring speeds or a range of any two stirring speeds: 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, and 800 rpm. The addition rate of the zinc source solution is preferably such that it is more conducive to the dispersion of the reactants and does not result in excessively high local concentrations.

[0261] In some embodiments, mixing the zinc source solution with the ligand solution includes adding the ligand solution to the zinc source solution under stirring conditions. In some embodiments, the stirring conditions include a stirring speed selected from 200 rpm to 800 rpm. The stirring speed can be selected from any one of the following stirring speeds or a range of any two stirring speeds: 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, and 800 rpm. The addition rate of the ligand solution is preferably such that it is more conducive to the dispersion of the reactants and does not result in excessively high local concentrations.

[0262] Mixing the zinc source solution and ligand solution under stirring conditions, compared to direct mixing, allows for more uniform dispersion of the reactants in the system, avoiding localized primary particle agglomeration caused by excessively high local concentrations of reactants. By controlling an appropriate stirring speed, the reactants in the system can be mixed uniformly and thoroughly, while avoiding excessive local shear forces that could trigger primary particle agglomeration.

[0263] Thirdly, this application provides a ZIF-8 material, which can be prepared by the preparation method of the second aspect. The ZIF-8 nanoparticles in this ZIF-8 material have nanoscale characteristics, small particle size, good uniformity of particle size distribution, good particle dispersibility, and little or no agglomeration of primary particles.

[0264] In some embodiments, this application provides a ZIF-8 material, wherein the ZIF-8 material comprises ZIF-8 nanoparticles; the D of the ZIF-8 nanoparticles... v90 With D v The difference of 10 (D) v 90-D v 10) Satisfies (D) v 90-D v 10) <4000nm.

[0265] In some embodiments, (D) v 90-D v 10)≤3500nm.

[0266] In some embodiments, (D) v 90-D v 10)≤1500nm.

[0267] In some embodiments, (D) v 90-D v 10)≤1000nm.

[0268] In some embodiments, (D) v 90-D v 10)≤500nm.

[0269] In some embodiments, (D) v 90-D v 10)≤350nm.

[0270] In some embodiments, (D) v 90-D v 10)≤300nm.

[0271] In some embodiments, (D) v 90-D v10) The particle size distribution width can be less than or equal to any of the following: 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 380nm, 400nm, 420nm, 440nm, 450nm, 460nm, 480nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc. Further, in some embodiments, (D v 90-D v 10) The particle size distribution width can be greater than or equal to any of the following: 10nm, 20nm, 30nm, 50nm, 50nm, etc.

[0272] In the context of this application, the volumetric cumulative distribution particle size D can be used. v 90. D v 50. D v The particle size of ZIF-8 nanoparticles is characterized by 10 parameters. Specifically, Dv90 refers to the particle size corresponding to a cumulative volume distribution percentage of 90%; Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%; and Dv10 refers to the particle size corresponding to a cumulative volume distribution percentage of 10%. v 90. D v 50. D v 10 can be obtained separately from the cumulative volume distribution curves of particle size, which, unless otherwise specified, are accumulated from zero on the smaller particle size side. Those skilled in the art will understand that D... v 90. D v 50. D v The meaning of 10 can be determined using instruments and methods known in the field. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0273] The ZIF-8 material provided in this application has ZIF-8 nanoparticles with uniform particle size distribution. (D) v 90-D v The smaller the value of 10, the more uniform the particle size distribution of ZIF-8 nanoparticles.

[0274] The ZIF-8 nanoparticles provided in this application can be formed by the aggregation of multiple primary particles.

[0275] In some embodiments, the average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies d1≤800nm.

[0276] In some embodiments, the average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies any of the following conditions: 10nm≤d1≤800nm, 10nm≤d1≤500nm, 10nm≤d1≤480nm, 10nm≤d1≤450nm, 10nm≤d1≤300nm, 10nm≤d1≤250nm, 10nm≤d1≤200nm, etc.

[0277] In some embodiments, the average particle size d1 of the primary particles of the ZIF-8 nanoparticles is selected from any one of the following values ​​or a range between any two of the following values: 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 90nm, 100nm, 120nm, 150nm, 160nm, 180nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc.

[0278] In some embodiments, the average particle size d1 of the primary particles of the ZIF-8 nanoparticles may also satisfy any of the following conditions: 50nm≤d1≤800nm, 50nm≤d1≤500nm, 50nm≤d1≤480nm, 50nm≤d1≤450nm, 50nm≤d1≤300nm, 50nm≤d1≤250nm, 50nm≤d1≤200nm, etc.

[0279] In this application, "primary particle" and "secondary particle" are terms well known in the art. "Primary particle" refers to a single crystal grain. "Secondary particle" refers to an aggregated particle composed of two or more primary particles. Primary and secondary particles can be easily distinguished by taking SEM images using a scanning electron microscope.

[0280] The ZIF-8 nanoparticles in the ZIF-8 material provided in this application have a primary single crystal size at the nanoscale and a controllable particle size.

[0281] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤100000nm.

[0282] In some embodiments, the D of the ZIF-8 nanoparticles v 90 ≥ 10 nm.

[0283] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤4500nm.

[0284] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤4500nm.

[0285] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤2000nm.

[0286] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤1500nm.

[0287] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤1000nm.

[0288] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤800nm.

[0289] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤650nm.

[0290] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤600nm.

[0291] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤550nm.

[0292] In some embodiments, the D of the ZIF-8 nanoparticles v 90≤500nm.

[0293] In some embodiments, the D of the ZIF-8 nanoparticles v 90 can be less than or equal to any of the following particle size distribution widths: 400nm, 420nm, 440nm, 450nm, 460nm, 480nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc. Further, in some embodiments, the D of the ZIF-8 nanoparticles... v 90 can be greater than or equal to any of the following particle size distribution widths: 10nm, 20nm, 30nm, 40nm, 50nm, etc.

[0294] The ZIF-8 nanoparticles in the ZIF-8 material provided in this application have a narrow distribution range, with 90% of the volume of nanoparticles within a controllable nanoscale.

[0295] In some embodiments, the D of the ZIF-8 nanoparticles v 50 < 3000nm.

[0296] In some embodiments, the D of the ZIF-8 nanoparticles v 50 can satisfy any of the following conditions: 50nm ≤ D v 50≤3000nm, 50nm≤D v 50≤2000nm, 50nm≤D v 50≤1500nm, 50nm≤D v 50≤1000nm, 50nm≤D v 50≤800nm, 50nm≤D v 50≤650nm, 50nm≤D v 50≤600nm, 50nm≤D v 50≤550nm, 50nm≤D v 50≤500nm, etc.

[0297] In some embodiments, the D of the ZIF-8 nanoparticles v 50 can be less than or equal to any of the following particle size distribution widths: 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 380nm, 400nm, 420nm, 440nm, 450nm, 460nm, 480nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, etc. Further, in some embodiments, the D of the ZIF-8 nanoparticles... v 50 can be greater than or equal to any of the following particle size distribution widths: 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

[0298] The ZIF-8 nanoparticles in the ZIF-8 material provided in this application have an ideal average particle size, which is neither too large to adversely affect applications such as the preparation of high-performance single-atom catalysts and high-performance battery separators, nor too small to easily agglomerate.

[0299] In some embodiments, the D of the ZIF-8 nanoparticles v 10≥10nm.

[0300] In some embodiments, the D of the ZIF-8 nanoparticles v 10 can satisfy any of the following conditions: 10nm≤D v 10 < 800 nm, 10 nm ≤ D v10≤700nm, 10nm≤D v 10≤500nm, 10nm≤D v 10≤350nm, 10nm≤D v 10≤300nm, 10nm≤D v 10≤250nm, etc.

[0301] In some embodiments, the D of the ZIF-8 nanoparticles v The particle size distribution width can be less than or equal to any of the following: 200nm, 210nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm, 320nm, 340nm, 350nm, 360nm, 380nm, 400nm, 420nm, 440nm, 450nm, 460nm, 480nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc. Further, in some embodiments, the D0 of the ZIF-8 nanoparticles... v 10 can be greater than or equal to any of the following particle size distribution widths: 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

[0302] Through joint control of D v 10 and D v A particle size distribution of 90 ensures that ZIF-8 nanoparticles have a narrower particle size distribution. The narrower the particle size distribution, the more uniform the particle size, which is more advantageous for applications such as the preparation of high-performance single-atom catalysts and high-performance battery separators.

[0303] Fourthly, this application provides a method for preparing a single-atom catalyst, which includes the following steps S410 and S420:

[0304] S410: The ZIF-8 material sacrificial precursor is mixed with a metal salt solution, the solid and liquid phases are separated, the solid phase is collected and dried to obtain the metal salt-loaded ZIF-8 material; wherein, the ZIF-8 material sacrificial precursor includes the ZIF-8 material prepared by the preparation method described in the second aspect of this application or the ZIF-8 material described in the third aspect of this application, and the metal element M in the metal salt solution includes one or more of Co, Fe, Mn, Ni, Cu, Pt and Zn;

[0305] S420: The ZIF-8 material loaded with metal salt is calcined in an inert gas atmosphere and cooled to prepare a ZIF-8 derived single-atom catalyst. The single-atom metal site type of the ZIF-8 derived single-atom catalyst is selected from any one of M-N4-C, M-N3-C, M-N2-C and M-N1-C.

[0306] The ZIF-8 nanoparticles in the ZIF-8 material prepared (second aspect) or provided (third aspect) of this application are 2-methylimidazolium zinc ZIF-8 nanoparticles. These nanoparticles have small primary particle size and uniform particle size distribution. As a sacrificial precursor, they can adsorb more metal sites, resulting in a higher metal content and higher catalytic site density in the obtained carbon-based single-atom catalyst, which is more conducive to improving catalytic activity. Furthermore, the primary particles of the obtained carbon-based single-atom catalyst can inherit the morphology and particle size of the ZIF-8 precursor, allowing the catalytic sites of the prepared carbon-based single-atom catalyst to be better exposed to reactants and solvents, thus endowing it with higher catalytic activity.

[0307] In some embodiments, the ratio of the sacrificial precursor to the metal salt solution in the ZIF-8 material can be appropriately selected by those skilled in the art based on the type of single-atom metal site. In single-atom metal site types such as M-N4-C, M-N3-C, M-N2-C, and M-N1-C, the metal element M originates from the metal salt in the metal salt solution, and the nitrogen element N originates from the ligand in the ZIF-8 material. A suitable ratio of raw materials can be selected according to the requirements of the single-atom metal site type.

[0308] In some embodiments, the solvent in the metal salt solution includes one or more of methanol, ethanol, water, N,N-dimethylformamide, etc.

[0309] In some embodiments, the metal salt in the metal salt solution is selected from one or more of cobalt nitrate, ferric nitrate, ferric chloride, nickel nitrate, nickel acetylacetonate, sodium chloroplatinate, ferric acetylacetonate, copper nitrate, and copper sulfate.

[0310] In some embodiments, the temperature at which the ZIF-8 material sacrificial precursor is mixed with the metal salt solution is selected from 10°C to 60°C. The mixing temperature can also be selected from any one or any two of the following temperatures: 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc. The mixing temperature can also be selected from 20°C to 30°C, etc. Further, the mixing time can be 1 hour to 12 hours. Non-limiting examples of mixing times include 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0311] In some embodiments, the drying temperature is selected from 95°C to 105°C. The drying temperature may also be selected from any one of the following temperatures or a range of any two of the following temperatures: 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc.

[0312] In some embodiments, the drying time is selected from 5h to 10h. Non-limiting examples of drying time include 5h, 6h, 7h, 8h, 9h, 10h, etc.

[0313] In some embodiments, the drying temperature is selected from 95°C to 105°C, and in some embodiments, the drying time is selected from 5h to 10h.

[0314] In some embodiments, the step of calcining the metal salt-loaded ZIF-8 material in an inert gas atmosphere and then cooling it includes: heating the metal salt-loaded ZIF-8 material to the calcination temperature under an inert gas atmosphere, holding it at that temperature, and then cooling it.

[0315] In some embodiments, the inert gas atmosphere is selected from a nitrogen atmosphere or an argon atmosphere.

[0316] In some embodiments, the heating rate is selected from 4°C / min to 6°C / min. Non-limiting examples include 4°C / min, 4.5°C / min, 5°C / min, 5.5°C / min, 6°C / min, etc.

[0317] In some embodiments, the calcination temperature is selected from 880°C to 920°C. Non-limiting examples include 880°C, 890°C, 900°C, 910°C, 920°C, etc.

[0318] In some embodiments, the heat preservation time is selected from 1.5h to 2.5h. Non-limiting examples include 1.5h, 2h, 2.5h, etc.

[0319] In some embodiments, the cooling method is furnace-in-furnace cooling.

[0320] In some embodiments, the temperature is cooled to 4°C to 40°C. Non-limiting examples include 4°C, 5°C, 6°C, 8°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.

[0321] In some embodiments, the average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst satisfies 5nm ≤ d2 ≤ 700nm. In some embodiments, the average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst is selected from any one of the following values ​​or a range consisting of any two of the following values: 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc.

[0322] Using the ZIF-8 material prepared (second aspect) or provided (third aspect) as a sacrificial precursor, and by further comprehensively controlling the process parameters such as the type of metal salt, the type of solvent, and the reaction temperature in the reaction system, the average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst can be controlled at a suitable nanoscale, thereby enabling the ZIF-8 derived single-atom catalyst to have higher metal content, higher catalytic site density, and higher catalytic activity.

[0323] In some embodiments, the prepared single-atom catalyst is a carbon-based single-atom catalyst.

[0324] In some embodiments, the onset potential of the prepared carbon-based single-atom catalyst at 1600 rpm is selected from 1V to 1.1V, for example 1.02V, 1.04V, 1.05V, 1.06V, 1.08V, etc.

[0325] In some embodiments, the limiting current at 1600 rpm of the prepared carbon-based single-atom catalyst is selected from -5 mA / cm². 2 ~-6mA / cm 2 For example, -5.2mA / cm 2 -5.4mA / cm 2 -5.5mA / cm 2 -5.6mA / cm 2 -5.8mA / cm 2 wait.

[0326] In some embodiments, the half-wave potential of the prepared carbon-based single-atom catalyst at 1600 rpm is selected from 0.85V to 0.95V, for example 0.89V, 0.9V, and 0.91V. Fifthly, this application provides a single-atom catalyst prepared according to the preparation method described in the fourth aspect of this application.

[0327] In some embodiments, the single-atom catalyst is a carbon-based single-atom catalyst.

[0328] The provided single-atom catalyst is a ZIF-8 derived single-atom catalyst. Its primary particles have suitable nanoscale, controllable particle size, and uniform particle size distribution. Furthermore, it has high metal content, high catalytic site density, and high catalytic activity.

[0329] In a sixth aspect, this application provides a battery separator, which includes a porous substrate and a porous coating (also referred to as a ZIF-8 coating) disposed on at least one surface of the porous substrate, wherein the porous coating includes a ZIF-8 material prepared by the preparation method described in the second aspect of this application or a ZIF-8 material described in the third aspect of this application.

[0330] When using the ZIF-8 material prepared (second aspect) or provided (third aspect) in this application to prepare a battery separator, the ZIF-8 nanoparticles with small primary particles and uniform particle size distribution can be uniformly coated on the surface of the separator. At this time, the surface of the separator is uniformly covered with the aforementioned ZIF-8 material. The separator can effectively suppress the thermal shrinkage of the separator with a low coating thickness. The obtained separator also has good electrolyte impregnation and good electrolyte retention. When lithium-ion batteries are prepared using this separator, the battery has low expansion rate, good rate performance, good cycle performance, and high safety.

[0331] Unless otherwise specified, the terms "separator" and "membrane" as used in this application refer to battery separators.

[0332] In some embodiments, the weight percentage of the ZIF-8 material in the porous coating is selected from 40% to 90%. The weight percentage of the ZIF-8 material in the porous coating may also be selected from any one percentage or a range of any two of the following: 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. The weight percentage of the ZIF-8 material in the porous coating may also be selected from 80% to 90%, 84% to 86%, etc.

[0333] The ZIF-8 content in the porous coating affects the thermal stability and lithium-ion transport rate of the composite separator. By controlling the ZIF-8 content in the porous coating, higher battery rate performance and thermal stability can be achieved. Increasing the ZIF-8 content decreases the lithium-ion transport rate and reduces the battery rate performance. Conversely, lower ZIF-8 content results in a higher thermal shrinkage rate of the composite separator and reduced battery thermal stability.

[0334] In some embodiments, the porous coating further includes one or more of the following: binder, inorganic particles, stabilizer, wetting agent, rheology modifier, defoamer, thickener, pH adjuster, and preservative.

[0335] In some embodiments, the inorganic particles comprise one or more of the following: boehmite, molecular sieve, zeolite, alumina, alumina hydroxyl, silicon dioxide, aluminum nitride, silicon carbide, magnesium oxide, calcium oxide, zinc oxide, zirconium dioxide, and titanium dioxide.

[0336] Porous substrates

[0337] In some embodiments, any well-known porous substrate with good chemical and mechanical stability can be selected.

[0338] In some embodiments, the porous substrate may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0339] In some embodiments, the porous substrate may be selected from polymer membranes comprising any of the following materials: polyolefins (e.g., ethylene-propylene copolymers), glass fibers, aramid fibers, polyvinyl alcohol, cellulose, polyethylene oxide, polytetrafluoroethylene, polyallylamine, polyacrylonitrile, polyurethane, polymethyl methacrylate, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polycarbonate, polyetheretherketone, polysulfone, polyphenylene ether, polystyrene, polynaphthalene, and any two or more physical mixtures or copolymers of the above materials, wherein the polyolefin may include polypropylene, polyethylene, and physical mixtures or copolymers thereof.

[0340] The battery separator provided in this application is a multilayer composite membrane, also known as a composite separator, which has a ZIF-8 porous coating laminated on a porous substrate. This ZIF-8 porous coating is obtained by applying a coating solution containing any suitable ZIF-8 material to at least one surface of the porous substrate (it can be single-sided or double-sided coating) to form a wet coating, followed by drying. After drying, the aforementioned porous coating is formed on the surface of the porous substrate.

[0341] In some embodiments, the thickness of the wet coating is selected from 0.5 μm to 12 μm. The thickness of the wet coating may also be selected from any one or any two of the following thicknesses: 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, etc. The thickness of the coating may also be selected from 8 μm to 12 μm, 9 μm to 11 μm, etc.

[0342] In some embodiments, the drying method is oven drying. Non-limiting examples of drying temperatures include 75°C–85°C, 75°C, 76°C, 78°C, 80°C, 82°C, 84°C, 85°C, 86°C, etc. Non-limiting examples of drying times include 55–65 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, etc.

[0343] In some embodiments, the thickness of the porous coating is selected from 0.5 μm to 12 μm. The thickness of the porous coating may also be selected from any one or any two of the following thicknesses: 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, etc. The thickness of the porous coating may also be selected from 8 μm to 12 μm, 9 μm to 11 μm, etc.

[0344] The thickness of the porous coating affects the lithium-ion transport rate and thermal stability of the separator. By adjusting the thickness of the porous coating, a suitable lithium-ion transport rate and thermal stability of the separator can be obtained. If the thickness increases, the lithium-ion transport rate of the separator decreases, and the rate performance of the battery deteriorates. If it is too thin, the composite separator has a higher thermal shrinkage rate, and the thermal stability of the battery decreases.

[0345] In some embodiments, the areal density of the battery separator is selected from 0.7 g / cm³. 2 ~0.9g / cm 2 The areal density of the separator can also be selected from any one of the following densities or a range consisting of any two densities: 0.7 g / cm³ 2 0.75g / cm 2 0.8g / cm 2 0.85g / cm 2 0.9g / cm 2 wait.

[0346] In this application, unless otherwise specified, the term "areal density" refers to the areal density obtained by dividing the total mass of the ZIF-8 coating on both sides of the battery separator by the coating area; that is, it refers to the total areal density calculated from the ZIF-8 coating on both sides. Unless otherwise specified, the test temperature is 20–30°C, more specifically, 25°C.

[0347] For information on the areal density of the battery separator of this application, please refer to Test Example 3.2.1 and related test results in the Specific Embodiments section below.

[0348] The areal density of the separator affects its lithium-ion transport rate and thermal stability. By adjusting the areal density, suitable lithium-ion transport rates and thermal stability can be achieved. Increasing the areal density decreases the lithium-ion transport rate and reduces the battery's rate performance. Conversely, decreasing the areal density results in a higher thermal shrinkage rate of the composite separator and reduced battery thermal stability.

[0349] In this application, the longitudinal thermal shrinkage rate and transverse thermal shrinkage rate of the battery separator can be tested by the following method: a rectangular separator sheet with a certain length and width is placed in a constant temperature and humidity chamber at a specific temperature. After being kept at the temperature for a certain period of time, the separator sample is taken out and placed for a certain period of time. The percentage of the change in length and width in the direction relative to the initial value is then measured, and the longitudinal thermal shrinkage rate (MD) and transverse thermal shrinkage rate (TD) are calculated.

[0350] In some implementations, the following measurement method is used: A uniformly flat separator is cut into rectangular pieces 25cm long and 10cm wide. These pieces are placed in a constant temperature and humidity chamber at 150°C for 1 hour. Afterward, the separator samples are removed and left to stand for 30 minutes. The length and width are then measured, and the heat shrinkage rate is calculated as a percentage of the dimensional change to the initial size. The change in length corresponds to the longitudinal heat shrinkage rate. The change in width corresponds to the transverse heat shrinkage rate.

[0351] In some embodiments, the longitudinal thermal shrinkage rate of the battery separator film after heating at 150°C for 1 hour is selected from 0% to 2%, with non-limiting examples such as 1%, 1.2%, 1.5%, 1.6%, 1.8%, etc. Further, the length × width dimensions of the test sample can be 25cm × 10cm.

[0352] In some embodiments, the lateral thermal shrinkage rate of the battery separator film heated at 150°C for 1 hour is selected from 0% to 1%, with non-limiting examples such as 0.5%, 0.6%, 0.8%, etc. Further, the test area can be 25cm × 10cm.

[0353] For information on the thermal shrinkage rate of the battery separator of this application, please refer to Test Example 3.2.2 and related test results in the Specific Embodiments section below.

[0354] In this application, the electrolyte wetting performance of the battery separator can be measured using the following method: One drop (approximately 0.05 mL) of a proton-type hydrophilic electrolyte (a 1M lithium hexafluorophosphate (LiPF6) solution in ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1:1 (w / w)) is dropped onto a horizontally placed separator. After 5 minutes, the approximate area of ​​electrolyte wetting is calculated using a grid method. Specifically, the grid method is measured as follows: after 5 minutes, a photograph is taken of the upper surface of the separator from directly above, and then an area of ​​0.1 cm² is used in the photograph. 2The grid covers all areas showing electrolyte wetting marks. Squares completely occupied by electrolyte wetting marks are labeled "fully wetted," as are squares with an electrolyte wetting area equal to or greater than half the area. Squares with an electrolyte wetting area less than half the area are labeled "unwetting." The final electrolyte wettability of the diaphragm is equal to the number of fully wetted squares multiplied by 0.1, expressed in square centimeters. Unless otherwise specified, the test temperature is 20–30°C, or even 25°C.

[0355] In some embodiments, the electrolyte wetting properties of the battery separator measured using the above method are selected from 7cm. 2 ~10cm 2 Non-restrictive examples include 7cm 2 8cm 2 8.5cm 2 8.8cm 2 9cm 2 10cm 2 wait.

[0356] For further information on the electrolyte wettability of the battery separator of this application, please refer to Test Example 3.2.3 and related test results in the Specific Embodiments section below.

[0357] In this application, the electrolyte retention rate can be measured using the following method: Take a diaphragm with dimensions of 10cm × 10cm, weigh the dry weight W0 of the diaphragm, then immerse the diaphragm in the electrolyte for 10 hours, and let it stand in a sealed container for 1 hour to allow the electrolyte in the diaphragm to reach saturation. Then weigh the wet weight W of the diaphragm, and calculate its electrolyte retention rate based on the following formula. It can be seen that the electrolyte retention rate not only characterizes the capacity of the diaphragm to hold the electrolyte, but also reflects the diaphragm's ability to retain the electrolyte. Electrolyte retention rate = [(W-W0) / W0] × 100%. Unless otherwise specified, the test temperature is 20–30℃, further such as 25℃.

[0358] In some embodiments, the electrolyte retention rate of the battery separator measured by the above method is selected from 200% to 400%, and non-limiting examples include 250%, 300%, 350%, etc.

[0359] For further information on the electrolyte retention rate of the battery separator in this application, please refer to Test Example 3.2.4 and related test results in the Specific Embodiments section below.

[0360] Seventhly, this application provides the application of ZIF-8 material prepared by the preparation method described in the second aspect of this application or ZIF-8 material described in the third aspect of this application in the preparation of carbon-based single-atom catalysts or lithium-ion battery separators.

[0361] ZIF-8 materials have many applications, including but not limited to being used as sacrificial precursors in the preparation of single-atom catalysts and as coating materials in the preparation of composite battery separators. Using more uniform nano-sized ZIF-8 particles offers significant advantages. For example, single-atom catalysts prepared using more uniform nano-sized ZIF-8 particles as sacrificial precursors have more active sites, which are more exposed in the reactants. Furthermore, composite battery separators obtained using more uniform nano-sized ZIF-8 particles as coating materials have thinner layers and higher volumetric energy density.

[0362] In the ZIF-8 material prepared (second aspect) or provided (third aspect) as described above in this application, the ZIF-8 nanoparticles have small primary particle size, uniform particle size distribution, and good particle dispersibility. When the ZIF-8 material is used to prepare carbon-based single-atom catalysts, it has high metal content, high catalytic site density, and high catalytic activity. When the ZIF-8 material is used to prepare lithium-ion battery separators, it can be uniformly distributed on the surface of the separator with a suitable areal density, effectively suppressing the thermal shrinkage of the separator with a low coating thickness. The resulting separator also has good electrolyte wettability and good electrolyte retention.

[0363] Eighthly, this application provides a battery cell comprising a positive electrode sheet, a battery separator as described in the sixth aspect of this application, and a negative electrode sheet, wherein the battery separator is disposed between the negative electrode sheet and the positive electrode sheet.

[0364] When lithium-ion batteries are prepared using the battery separator provided in the sixth aspect of this application, the battery cells exhibit low expansion rate, good rate performance, good cycle performance, and high safety.

[0365] In some embodiments, the battery cell is a secondary battery.

[0366] In some embodiments, the battery cell is a lithium-ion secondary battery.

[0367] In this application, the battery expansion rate can be tested using the following method: A charge-discharge test is performed on a secondary battery (such as a lithium-ion secondary battery) including the aforementioned battery separator. 1000 ppm water is added to the electrolyte to accelerate gas production. The battery volume before charge-discharge is measured using the water displacement method and recorded as V1. After 100 charge-discharge cycles, the battery volume is measured and recorded as V2. The battery expansion rate P = (V2 - V1) / V1 × 100%. Unless otherwise specified, the test temperature is 20–30°C, or more specifically, 25°C.

[0368] In some embodiments, according to the above test method, the battery expansion rate of the secondary battery (such as a lithium-ion secondary battery) including the aforementioned battery separator is selected from 5% to 15%, and non-limiting examples include 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, etc.

[0369] For information on the battery expansion rate of the battery cell (which may further be a lithium-ion secondary battery) of this application, please refer to Test Example 3.2.8 and related test results in the Specific Embodiments section below.

[0370] In this application, the rate performance of the battery can be tested using the following method: At a certain temperature (e.g., 20–30°C, or more specifically, 25°C), the battery cell is placed in the test channel of an Arbin electrochemical workstation and charged at a constant current rate of 0.1C to the charging cutoff voltage of 4.3V. Then, it is charged at a constant voltage for 30 minutes. Afterward, it is discharged at a constant current rate of 0.1C and 1C to the discharge cutoff voltage of 2.8V, respectively. The discharge capacity is recorded as the 0.1C capacity and the 1C capacity, respectively. The rate performance is calculated as: 1C capacity / 0.1C capacity × 100%. Here, 1C corresponds to 180 mAh / g. Unless otherwise specified, the test temperature is 20–30°C, or more specifically, 25°C.

[0371] In some embodiments, the rate performance (1C capacity / 0.1C capacity × 100%) of a secondary battery (such as a lithium-ion secondary battery) including the aforementioned battery separator at 25°C is selected from 90% to 99%, and non-limiting examples include 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0372] For the rate performance of the battery cell (which may further be a lithium-ion secondary battery) of this application, please refer to Test Example 3.2.5 and related test results in the Specific Embodiments section below.

[0373] In this application, the battery cycle performance can be tested using the following method: The cell is placed in the test channel of an Arbin electrochemical workstation and charged at a constant current rate of 1C to the charging cutoff voltage of 4.3V. After resting for 5 minutes, it is discharged at a constant current rate of 1C to the discharge cutoff voltage of 28V. The discharge capacity is recorded, and then the cell is allowed to rest for another 5 minutes. This cycle is repeated 100 times. The capacity retention rate after 100 cycles is calculated as: (Capacity of the 100th cycle / Capacity of the 1st cycle) × 100%.

[0374] In some embodiments, the capacity retention rate of a secondary battery (such as a lithium-ion secondary battery) including the aforementioned battery separator after 100 cycles is selected from 85% to 95%, and is not limited to 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, etc.

[0375] In this application, the "capacity retention rate after 100 cycles" of a secondary battery (preferably a lithium-ion secondary battery) generally refers to the test value under conditions of 20°C to 30°C, or more specifically, 25°C, unless otherwise specified.

[0376] Regarding the capacity retention rate of the battery cell (which can further be a lithium-ion secondary battery) after 100 cycles, please refer to Test Example 3.2.6 and related test results in the Specific Embodiments section below.

[0377] In some embodiments, the secondary battery (such as a lithium-ion secondary battery) including the aforementioned battery separator is subjected to a hot box test, which ensures extremely high safety.

[0378] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through. This separator can be the battery separator provided in aspect six of this application.

[0379] Positive electrode sheet

[0380] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0381] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0382] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0383] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0384] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0385] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0386] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0387] Negative electrode sheet

[0388] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0389] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0390] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0391] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0392] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0393] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0394] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0395] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0396] electrolytes

[0397] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0398] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0399] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0400] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0401] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0402] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0403] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0404] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0405] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 9 This is an example of a square-structured secondary battery 5.

[0406] In some implementations, refer to Figure 10 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0407] Ninthly, this application provides an electrical device that includes the battery cell described in the eighth aspect of this application.

[0408] The battery cell manufacturing device provided in the eighth aspect of this application has significant advantages such as fast charging, long battery life, long service life, and high safety.

[0409] The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices may include, for example, mobile phones and laptops; electric vehicles may include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0410] As the electrical device, the battery cells can be selected according to its usage requirements.

[0411] Figure 11 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0412] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0413] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims.

[0414] The following describes some embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the description above, or according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially, or can be synthesized using conventional methods from commercially available products.

[0415] In the following examples, room temperature refers to 20°C to 30°C.

[0416] Example 1. Preparation of 2-methylimidazolium zinc ZIF-8 nanoparticles

[0417] 1.1. Preparation Example

[0418] In Experiment 1-1, 1 mol of zinc acetate was dissolved in 137 mol of water, and 12 mol of 2-methylimidazole was dissolved in 274 mol of water. The resulting zinc acetate solution was then rapidly added to the 2-methylimidazole solution within 1 minute. After stirring and reacting at 25°C for 12 hours, the resulting suspension was filtered, washed three times with deionized water, and dried in a vacuum oven at 80°C for 12 hours to obtain approximately 200 g of ZIF-8 nanoparticles (2-methylimidazole zinc ZIF-8).

[0419] Experimental Examples 1-2 to 1-9 used the same method as Experimental Example 1-1, with the only differences being the type and amount of raw materials, reaction temperature, and reaction time, as detailed in Table 1.

[0420] Experimental Examples 1-10 used the same method as Experimental Examples 1-3, the only difference being the mixing method of the zinc source solution and the ligand solution. In Experimental Examples 1-10, the ligand solution was added to the zinc source solution.

[0421] Comparative Examples 1-1 to 1-6 used essentially the same methods as Experimental Example 1-1, with the differences shown in Table 1. Parameters not listed in Table 1 are consistent with those in Experimental Example 1-1.

[0422] 1.2. Test Case

[0423] 1.2.1. Morphological Testing

[0424] All 2-methylimidazolium zinc ZIF-8 samples from the examples and comparative examples were tested using a scanning electron microscope (SEM) and then tested according to standard JY / T010-1996 to observe the morphology of the samples.

[0425] 1.2.2. Particle size testing

[0426] Sample to be tested: The sample in the wet filter cake remaining after vacuum filtration and washing.

[0427] (1) Average particle size of primary particles: The average particle size of primary particles is the average value of more than 30 particles measured by electron microscopy. For irregular particles, the smallest dimension is taken, such as the smaller width of cuboid particles instead of the height.

[0428] (2) Particle size type: D of secondary particles v 10. D v 50. D v 90 tests.

[0429] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8%–12% opacity), add 20 mL of anhydrous ethanol, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO13320:2009 standard. To avoid agglomeration during the drying process affecting the particle size test, use a washed and moistened sample for dispersion testing.

[0430] (3) Purity: X-ray diffraction tests were performed on the samples. The obtained X-ray diffraction pattern was compared with the ZIF-8 standard pattern of 2-methylimidazolium zinc. If no other impurity peaks were found, the purity was marked as "O"; otherwise, it was marked as "×". A Brucker D8A_A25 X-ray powder diffractometer from Brucker AXS (Germany) was used, with CuKα rays as the radiation source, and the wavelength of the rays was... The 2θ angle was scanned in the range of 5° to 60°, and the scanning rate was 4° / min for testing.

[0431] 1.3. Test Results

[0432] The test results of the ZIF-8 materials prepared in each experimental example and comparative example can be found in Table 1 and Figure 1 , Figure 2 , Figure 3 .

[0433] The ZIF-8 nanoparticles prepared in each experimental example (Examples 1-1 to 1-10) were uniform in size and narrowly distributed. For example, Figure 1 , Figure 2 The images show SEM images and particle size distribution diagrams of the ZIF-8 nanoparticles prepared in Experimental Examples 1-2.

[0434] According to X-ray diffraction results, all experimental examples (Examples 1-1 to 1-10) yielded a pure ZIF-8 phase, while Comparative Examples 1-2 and 1-8 contained more impurities. Figure 3 The XRD pattern of the ZIF-8 material prepared in Experimental Example 1-1 is compared with the standard XRD pattern of 2-methylimidazolium zinc ZIF-8.

[0435] Based on Comparative Examples 1-2 and 1-3, it can be seen that reducing the amount of ligand alone (Comparative Example 1-2) or reducing the amount of ligand too much (Comparative Example 1-3) will result in the inability to obtain pure-phase ZIF-8 materials.

[0436] Based on Comparative Examples 1-4 and 1-5, it can be seen that if the reaction temperature (the temperature of the coordination reaction) is high, such as 55℃ in Comparative Example 1-4 or 42℃ in Comparative Example 1-5, it will lead to an increase in the particle size (d1, D) of ZIF-8 nanoparticles. v 10. D v 50. D v 90) The size of the particles increases significantly, and the uniformity of the particle size distribution deteriorates significantly.

[0437] According to Comparative Examples 1-6, it can be seen that if the reaction temperature (the temperature of the coordination reaction) is too low, the particle size of ZIF-8 nanoparticles will also increase.

[0438] Table 1.

[0439]

[0440]

[0441] Note 1: In Table 1, the molar amount of zinc source is 1 mol. Therefore, the molar amount of water in the zinc source solution is numerically equal to a, the molar amount of water in the ligand solution is numerically equal to b, and the total amount of water used in the ZIF-8 material preparation system is numerically equal to a+b.

[0442] Note 2: In Table 1, since the nanoparticles prepared in Comparative Examples 1-2 and 1-3 are not pure phases, the prepared samples already contain impurity particles such as zinc oxide. Therefore, the D… v50 This does not represent the particle size of the pure phase of ZIF-8.

[0443] Example 2. Preparation of ZIF-8 derived single-atom catalyst

[0444] 2.1. Preparation Example

[0445] Example 2-1: 2 g of the ZIF-8 material prepared in Example 1-3 was added to 100 mL of a 2 mmol / L cobalt nitrate methanol solution. After stirring for 12 hours, the moist solid was filtered off and then dried at 100 °C for 8 hours to obtain the 2-methylimidazolium zinc ZIF-8 material loaded with metal salt. The 2-methylimidazolium zinc ZIF-8 material loaded with metal salt was heated to 900 °C at 5 °C / min and held for 2 hours in a tube furnace under argon atmosphere, followed by natural cooling to room temperature to obtain the ZIF-8 derived single-atom catalyst.

[0446] Experiments 2-2 to 2-3 used the same method as Experiment 2-1, with the only difference being the parameters shown in Table 2.

[0447] Experiment 2-4 uses the same method as Experiment 2-1, except that the inert gas atmosphere used for calcination in the tube furnace is different; Experiment 2-4 uses a nitrogen atmosphere.

[0448] Comparative Examples 2-1 to 2-7 used essentially the same methods as Experimental Example 2-1, with the only difference being the parameters shown in Table 2.

[0449] 2.2. Test Case

[0450] Test parameters: initial potential, limiting current, half-wave potential.

[0451] The ZIF-8-derived single-atom catalysts prepared in each example were ultrasonically dispersed in ethanol to obtain a slurry with a concentration of 2 mg / mL. 50 μL of this slurry was then dropped onto a surface with an area of ​​0.196 cm². 2 A catalyst-loaded working electrode was obtained by adding 5 μL of 0.1 wt% Nafion binder solution to a rotating disk electrode and allowing it to dry. The working electrode was then placed in a continuously saturated 0.1 M KOH solution with O2 continuously passed through it. The rotation speed was set to 1600 rpm, with saturated Ag / AgCl as the reference electrode and a platinum sheet as the counter electrode. A linear sweep voltammetry test was performed at 10 mV / s.

[0452] 2.3. Test Results

[0453] The test results of the ZIF-8 derived single-atom catalysts prepared in each experimental example and comparative example can be found in Table 2 and Figure 4 , Figure 5 , Figure 6 .

[0454] Figure 4 This is an atomic-resolution HAADF-STEM image of the ZIF-8 derived single-atom catalyst (Example 2-1) prepared using the ZIF-8 material from Examples 1-3. Some single-atom sites are circled. It can be seen that the morphology of the derived single-atom catalyst basically maintains the rhombic dodecahedral nanoparticle morphology of Examples 1-3, which allows the single-atom sites to be fully exposed in the reactants, thus exhibiting high catalytic activity.

[0455] Figure 5 The images show SEM images (left) of ZIF-8 nanoparticles prepared in Experimental Examples 1-3 and morphology images (right) of ZIF-8-derived single-atom catalysts (Experimental Example 2-1) prepared using the ZIF-8 material from Experimental Examples 1-3.

[0456] Figure 6This is a graph showing the oxygen reduction performance of a ZIF-8-derived single-atom catalyst (Experimental Example 2-1) prepared using the ZIF-8 material from Experimental Example 1-3. The horizontal axis represents potential (V relative to RHE), and the vertical axis represents current density. According to the test results, the single-atom catalyst derived from Comparative Example 2-1, which uses a larger particle size precursor, exhibits worse oxygen reduction performance, reflected in its lower limiting plateau current density and smaller onset potential.

[0457] Due to the presence of a large amount of ligand residue in Comparative Example 1-1, the onset potential and limiting current performance of the prepared ZIF-8 derived single-atom catalyst deteriorated.

[0458] Table 2.

[0459]

[0460] Example 3. Preparation of separator and secondary battery

[0461] 3.1. Preparation Example

[0462] 3.1.1. Experimental Example 3-1:

[0463] (1) Preparation of the separator: A 16 μm thick PP-PE copolymer microporous film (denoted as PP-PE bare separator) produced by Zhuogao Electronic Technology Co., Ltd. was used as the substrate layer, with an average pore size of 80 nm. The 2-methylimidazolium zinc ZIF-8 material prepared in Examples 1-3, the adhesive polymethyl acrylate (produced by Hubei Nuona Co., Ltd.), the adhesive acrylic-acrylate-acrylonitrile copolymer (produced by Hubei Nuona Co., Ltd.), the stabilizer sodium carboxymethyl cellulose (chemically pure), and the wetting agent polyoxyethylene ether (produced by Hubei Nuona Co., Ltd.) were mixed uniformly in a weight ratio of 85:6:3:3:3. Water was added during mixing to form a water-based coating with a solid content of 9%. This slurry was applied to both surfaces of the 16 μm thick PP-PE copolymer microporous film substrate layer by a scraping method, forming a wet coating on the surface. The coating was then transferred to an oven and dried at 80°C for 60 minutes to obtain a separator with a ZIF-8 coating on both surfaces. The thickness of the wet coating can be adjusted to obtain separators with different areal densities, i.e., the target separator.

[0464] (2) Preparation of secondary batteries

[0465] Active material LiNi 0.8 Co 0.1 Mn 0.1O2, conductive agent acetylene black (Denka), and binder polyvinylidene fluoride (Arkema, HSV 900) were thoroughly mixed in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3 to obtain a slurry with a solid content of 30%. A 250 μm thick wet coating was formed on one side of an aluminum (Al) foil with a thickness of 12 μm using a transfer coating method. The coating was then transferred into an oven and dried at 150°C for 60 minutes. Finally, the coating was cold-pressed using a roller press at a pressure of 60 tons to obtain the positive electrode sheet.

[0466] The active material graphite, the conductive agent acetylene black, and the binder polyvinylidene fluoride were thoroughly mixed in an N-methylpyrrolidone solvent system at a weight ratio of 95:2:3 to obtain a slurry with a solid content of 15%. The slurry was then coated onto one side of a copper (Cu) foil with a thickness of 12 μm using a doctor blade to form a wet coating with a thickness of 120 μm. The coating was then transferred to an oven and dried at 150°C for 60 minutes. Finally, the coating was cold-pressed at a pressure of 50 tons using a cold press to obtain the negative electrode sheet.

[0467] The positive electrode, separator, and negative electrode are rolled up in sequence to form a wound stacked structure with dimensions of 16cm × 10cm × 2.8cm. The bare cell is placed in a soft package made of aluminum-plastic film, 150g of electrolyte is injected into it, and then it is sealed to obtain the cell. The electrolyte is a 1M LiPF6 EC / DMC mixed solution, wherein the EC / DMC volume ratio is 1:1.

[0468] 3.1.3. Comparative Example

[0469] Comparative Examples 3-1 to 3-7 used essentially the same method as Experimental Example 3-1, with the only difference being the parameters shown in Table 3.

[0470] 3.2. Test Case

[0471] 3.2.1. The test method for the density of the ZIF-8 coating layer is as follows:

[0472] A square coated diaphragm (i.e., the release diaphragm) measuring 10cm × 10cm and the bare diaphragm before coating were weighed separately to obtain the total mass of the ZIF-8 coatings on both sides. This total mass was then divided by the coating area to obtain the areal density. This areal density is the total areal density of the coatings on both sides. This areal density is adjusted by controlling the thickness of the wet coating.

[0473] 3.2.2. Thermal shrinkage rate

[0474] A uniformly flat release liner was cut into rectangular pieces 25cm long and 10cm wide. These pieces were then placed in a constant temperature and humidity chamber at 150℃ for 1 hour. After removing the liner samples and allowing them to stand for 30 minutes, their length and width were measured. The heat shrinkage rate was calculated as a percentage of the dimensional change to the initial size. The change in length corresponds to the longitudinal heat shrinkage rate, and the change in width corresponds to the transverse heat shrinkage rate.

[0475] 3.2.3. The method for measuring the electrolyte wettability of the diaphragm is as follows:

[0476] One drop (approximately 0.05 mL) of a proton-type hydrophilic electrolyte (1 M lithium hexafluorophosphate (LiPF6) in a 1:1 (w / w) solution of ethylene carbonate (EC): ethyl methyl carbonate (EMC)) was dropped onto a horizontally placed diaphragm. After 5 minutes, the approximate area of ​​electrolyte wetting was determined using the grid method. Specifically, the grid method was performed as follows: after 5 minutes, a photograph was taken of the upper surface of the diaphragm from directly above, and then the area was measured using a 0.1 cm² area from the photograph. 2 The grid covers all areas showing electrolyte wetting marks. Squares completely occupied by electrolyte wetting marks are labeled "fully wetted," as are squares with an electrolyte wetting area equal to or greater than half the area. Squares with an electrolyte wetting area less than half the area are labeled "unwetting." The final electrolyte wettability of the diaphragm is equal to the number of fully wetted squares multiplied by 0.1, expressed in square centimeters. The test temperature is 25℃.

[0477] 3.2.4. Electrolyte retention rate test

[0478] Take a 10cm × 10cm membrane and weigh its dry weight W0. Then, immerse the membrane in electrolyte for 10 hours and let it stand in a sealed container for 1 hour to allow the electrolyte in the membrane to reach saturation. Weigh the membrane's wet weight W and calculate its electrolyte retention rate using the following formula. It can be seen that the electrolyte retention rate not only characterizes the capacity of the membrane to hold electrolyte but also reflects the membrane's ability to retain electrolyte. The test temperature was 25℃. Electrolyte retention rate = [(W - W0) / W0] × 100%.

[0479] 3.2.5. The measurement method for rate performance is as follows:

[0480] The battery cell was placed in the test channel of the Arbin electrochemical workstation and charged at a constant current rate of 0.1C to the charging cutoff voltage of 4.3V. It was then charged at a constant voltage for 30 minutes, followed by constant current discharge at 0.1C and 1C rates to the discharge cutoff voltage of 2.8V. The discharge capacity was recorded as the 0.1C capacity and the 1C capacity, respectively. Rate performance = 1C capacity / 0.1C capacity × 100%. Here, 1C corresponds to 180mAh / g. The test temperature was 25℃.

[0481] 3.2.6. The method for measuring cycle performance is as follows:

[0482] The battery cell was placed in the test channel of the Arbin electrochemical workstation and charged at a constant current rate of 1C to the charging cutoff voltage of 4.3V. After resting for 5 minutes, it was discharged at a constant current rate of 1C to the discharge cutoff voltage of 2.8V. The discharge capacity was recorded, and then it was allowed to rest for another 5 minutes. This cycle was repeated 100 times. The capacity retention rate after 100 cycles = (capacity of the 100th cycle / capacity of the 1st cycle) × 100%. The test temperature was 25℃.

[0483] 3.2.7. The measurement method for the hot box test is as follows:

[0484] Store the battery at 150°C for 1 hour, and then check whether it will cause the battery to explode or burst. The sample that passes the hot box test is marked "O", while the sample that explodes or bursts is marked "×".

[0485] 3.2.8. The battery swelling rate test method is as follows:

[0486] The obtained cells were assembled into pouch cells for charge-discharge testing. 1000 ppm water was added to the electrolyte to accelerate gas production. The battery volume before charge-discharge was measured using the water displacement method and recorded as V1. After 100 charge-discharge cycles, the battery volume was measured and recorded as V2. The battery expansion rate P = (V2 - V1) / V1 × 100%. The test temperature was 25℃.

[0487] 3.3. Test Results

[0488] The test results of the separators and secondary batteries prepared in each experimental example and comparative example can be found in Table 3 and Figure 7 , Figure 8 .

[0489] Figure 7 The images show SEM images of the ZIF-8 nanoparticles used in the separator in Experiment 3-1 (left, Experiment 1-3), and the morphology of the ZIF-8 nanoparticles on the separator surface. It can be seen that the ZIF-8 nanoparticles are uniformly distributed on the separator surface.

[0490] Figure 8The images show a comparison of the appearance of the separator prepared using ZIF-8 material (Examples 1-3) in Experiment 3-1 before and after being placed at 150°C for 1 hour. The left side corresponds to the original composite separator before heating, and the right side corresponds to the separator after heating. According to the test results, the composite separator based on ZIF-8 nanoparticles prepared in Experiment 1-3 did not show significant shrinkage after being placed at 150°C for 1 hour. Its longitudinal shrinkage rate and transverse shrinkage rate were 16% and 0.8%, respectively, demonstrating extremely high thermal stability.

[0491] Comparing Experiment 3-1 with the bare PP-PE separator, it can be found that the bare PP-PE separator without the ZIF-8 material of this application has a relatively high heat recovery rate in both the longitudinal and transverse directions. In addition, the separator has poor electrolyte wetting performance, almost no ability to retain electrolyte, poor rate performance and cycle performance, and poor hot box test results.

[0492] Comparing Experimental Example 3-1 with Comparative Examples 3-1 and 3-2, it can be found that at 0.8 mg / cm³... 2 Under the condition of areal density, the ZIF-8 particles with larger Dv50 and poorer dispersibility are unevenly distributed on the separator, which easily leads to local agglomeration. This results in a large thermal shrinkage rate of the composite separator, poor electrolyte wetting performance, poor electrolyte retention, poor rate performance and cycle performance of the resulting battery, and unsatisfactory hot box test results.

[0493] Comparing Experimental Example 3-1 with Comparative Example 3-3, it can be found that the ZIF-8 particles prepared using the conventional ligand dosage have a large amount of residual 2-methylimidazolium ligand, resulting in poor rate performance and cycle performance of the obtained battery.

[0494] Comparing Experiment 3-1 with Comparative Examples 3-4 and 3-5, it can be found that excessively high reaction temperature leads to larger Dv50 of ZIF-8 particles and poorer dispersion, resulting in uneven distribution on the separator and easy local agglomeration. This leads to a larger thermal shrinkage rate of the resulting composite separator, poor electrolyte wetting performance, poor electrolyte retention, and poor rate performance and cycle performance of the resulting battery.

[0495] Comparing Experimental Example 3-1 with Comparative Example 3-6, it can be found that if the surface density of the composite separator is too low, the content of ZIF-8 particles will be too low, resulting in a large thermal shrinkage rate of the obtained composite separator and poor electrolyte wetting performance, poor electrolyte retention ability, poor cycle performance of the obtained battery, and unsatisfactory hot box test results.

[0496] Comparing Experiment 3-1 with Comparative Example 3-7, it can be found that when the areal density is too high, the ZIF-8 particle content is too high, which affects the lithium-ion transport rate and results in poor rate performance of the obtained battery.

[0497] Table 3.

[0498]

[0499] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0500] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. The above-described embodiments only illustrate several embodiments of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing ZIF-8 material, comprising the following steps: A zinc source solution and a ligand solution were mixed to prepare a ZIF-8 material preparation system. The ZIF-8 material preparation system contains metal ions, specifically zinc ions, and is composed of a soluble zinc salt, ligand molecules, and a solvent. The ligand molecule is 2-methylimidazole, and the solvent is water; in the preparation system of the ZIF-8 material, the molar ratio of the metal ion, the ligand molecule and the solvent is 1:a:z, where 9 ≤a ≤ 12, 311 ≤ z ≤ 420; The ZIF-8 material preparation system was subjected to a coordination reaction at a temperature selected from 5 °C to 40 °C and a reaction time selected from 4 h to 30 h to obtain ZIF-8 nanoparticles. The obtained ZIF-8 nanoparticles include primary particles with a rhombic dodecahedral nanoparticle morphology. The D of the ZIF-8 nanoparticles... v 50 satisfies 50 nm ≤ D v The average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies 100 nm ≤ d1 ≤ 500 nm; the D of the ZIF-8 nanoparticles is 50 nm ≤ 650 nm. v 90 and D v The difference of 10 (D) v 90-D v 10) Satisfies (D) v 90-D v 10) ≤ 1000 nm; In the ZIF-8 material preparation system, the molar ratio of zinc ions to water in the zinc source solution is 1:b, and 100 ≤ b ≤ 150; The molar ratio of zinc ions to water in the ligand solution in the ZIF-8 material preparation system is 1:c, and 205 ≤ c ≤ 300.

2. The method for preparing ZIF-8 material as described in claim 1, wherein, a satisfies 10 ≤ a ≤ 12.

3. The method for preparing ZIF-8 material as described in claim 1, wherein, a satisfies 11 ≤ a ≤ 12.

4. The method for preparing ZIF-8 material as described in claim 3, wherein, z satisfies 400 ≤ z ≤ 420.

5. The method for preparing ZIF-8 material as described in claim 1, wherein, a satisfies 11.5 ≤ a ≤ 12.

6. The method for preparing ZIF-8 material as described in claim 1, wherein, z satisfies 312 ≤ z ≤ 411.

7. The method for preparing ZIF-8 material as described in claim 1, wherein, z satisfies 340 ≤ z ≤ 420.

8. The method for preparing the ZIF-8 material as described in claim 7, wherein, z satisfies 342≤ z ≤ 411.

9. The method for preparing ZIF-8 material as described in claim 1, wherein, z satisfies 400 ≤ z ≤ 420.

10. The method for preparing the ZIF-8 material as described in claim 9, wherein, z satisfies 410 ≤ z ≤ 420.

11. The method for preparing ZIF-8 material as described in claim 5, wherein, z satisfies 400 ≤ z ≤ 415.

12. The method for preparing ZIF-8 material as described in claim 11, wherein, z satisfies 410 ≤ z ≤ 415.

13. The method for preparing ZIF-8 material as described in claim 11, wherein, z satisfies 410 ≤ z ≤ 412.

14. The method for preparing ZIF-8 material as described in claim 1, wherein, a=12 and z=411, or a=10 and z=342.

15. The method for preparing ZIF-8 material as described in claim 1, wherein, The molar ratio z / a of the ligand molecule and the solvent satisfies 32 ≤ (z / a) ≤ 40.

16. The method for preparing ZIF-8 material as described in claim 1, wherein, z / a satisfies 32 ≤ (z / a) ≤ 36.

17. The method for preparing ZIF-8 material as described in claim 1, wherein, z / a satisfies 34 ≤ (z / a) ≤ 35.

18. The method for preparing ZIF-8 material as described in claim 1, wherein, z / a satisfies 34 ≤ (z / a) ≤ 34.

5.

19. The method for preparing ZIF-8 material as described in claim 1, wherein, The soluble zinc salts include one or more of zinc acetate, zinc chloride, zinc nitrate, and zinc sulfate.

20. The method for preparing ZIF-8 material as described in claim 1, wherein, b satisfies 110 ≤ b ≤ 140.

21. The method for preparing ZIF-8 material as described in claim 1, wherein, c satisfies 220 ≤ c ≤ 280.

22. The method for preparing ZIF-8 material as described in claim 1, wherein, The reaction temperature for carrying out the coordination reaction is selected from 20 °C to 30 °C.

23. The method for preparing ZIF-8 material as described in claim 1, wherein, The reaction time for the coordination reaction of the ZIF-8 material preparation system is selected from 12 h to 30 h.

24. The method for preparing ZIF-8 material as described in claim 1, wherein, The reaction time for the coordination reaction is selected from 12 h to 24 h.

25. The method for preparing ZIF-8 material as described in claim 1, wherein, The mixing of the zinc source solution and the ligand solution includes: adding the zinc source solution to the ligand solution under stirring conditions.

26. The method for preparing ZIF-8 material as described in claim 25, wherein, The stirring conditions include a stirring speed selected from 200 rpm to 800 rpm.

27. The method for preparing ZIF-8 material as described in claim 1, wherein, After coordination reaction, ZIF-8 nanoparticles were obtained by solid-liquid separation.

28. The method for preparing ZIF-8 material as described in claim 1, wherein, (D v 90-D v 10) ≤ 500 nm。 29. The method for preparing ZIF-8 material as described in claim 1, wherein, (D v 90-D v 10) ≤ 350 nm。 30. The method for preparing ZIF-8 material as described in claim 1, wherein, (D v 90-D v 10) ≤ 300 nm。 31. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies 160 nm ≤ d1 ≤ 500 nm.

32. The method for preparing ZIF-8 material as described in claim 31, wherein, The average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies 180 nm ≤ d1 ≤ 350 nm.

33. The method for preparing ZIF-8 material as described in claim 31, wherein, The average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies 180 nm ≤ d1 ≤ 250 nm.

34. The method for preparing ZIF-8 material as described in claim 31, wherein, The average particle size d1 of the primary particles of the ZIF-8 nanoparticles satisfies 180 nm ≤ d1 ≤ 200 nm.

35. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The D of the ZIF-8 nanoparticles v 90 ≤ 1500 nm.

36. The method for preparing ZIF-8 material as described in claim 35, wherein, The D of the ZIF-8 nanoparticles v 90 ≤1000 nm.

37. The method for preparing ZIF-8 material as described in claim 35, wherein, The D of the ZIF-8 nanoparticles v 90 ≤ 650nm.

38. The method for preparing ZIF-8 material as described in claim 35, wherein, The D of the ZIF-8 nanoparticles v 90 ≤ 500nm.

39. The method for preparing ZIF-8 material as described in claim 35, wherein, The D of the ZIF-8 nanoparticles v 90 ≤ 450nm.

40. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The D of the ZIF-8 nanoparticles v 50 satisfies 50 nm ≤ D v 50 ≤ 500 nm.

41. The method for preparing ZIF-8 material as described in claim 40, wherein, The D of the ZIF-8 nanoparticles v 50 satisfies 300nm ≤ D v 50 ≤ 400 nm.

42. The method for preparing ZIF-8 material as described in claim 41, wherein, The D of the ZIF-8 nanoparticles v 50 satisfies 300nm ≤ D v 50 ≤ 330 nm.

43. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The D of the ZIF-8 nanoparticles v 10 satisfies 100 nm ≤ D v 10 ≤ 350 nm.

44. The method for preparing ZIF-8 material as described in claim 43, wherein, The D of the ZIF-8 nanoparticles v 10 satisfies 100nm ≤ D v 10 ≤ 300 nm.

45. The method for preparing ZIF-8 material as described in claim 43, wherein, The D of the ZIF-8 nanoparticles v 10 satisfies 100nm ≤ D v 10 ≤ 250 nm.

46. ​​The method for preparing ZIF-8 material as described in claim 43, wherein, The D of the ZIF-8 nanoparticles v 10 satisfies 100nm ≤ D v 10 ≤ 240 nm.

47. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The ZIF-8 nanoparticles satisfy the following conditions: 180 nm ≤ d1 ≤ 250 nm; 300 nm ≤ D v 50 ≤ 440 nm; D v 90 ≤ 650 nm.

48. The method for preparing the ZIF-8 material according to any one of claims 1 to 30, wherein, The ZIF-8 nanoparticles satisfy the following conditions: 180 nm ≤ d1 ≤ 200 nm; 300 nm ≤ D v 50 ≤ 380 nm; D v 90 ≤ 450 nm.

49. The method for preparing ZIF-8 material as described in claim 47, wherein, The ZIF-8 nanoparticles satisfy the following condition: 300 nm ≤ D v 50 ≤ 330 nm; D v 90 ≤ 450 nm.

50. A ZIF-8 material, which is a ZIF-8 material prepared by the preparation method of any one of claims 1 to 49.

51. A method for preparing a single-atom catalyst, comprising the following steps: ZIF-8 material is prepared by the preparation method of ZIF-8 material according to any one of claims 1 to 49; the ZIF-8 material is used as a sacrificial precursor for ZIF-8 material. The ZIF-8 material sacrificial precursor was mixed with a metal salt solution, subjected to solid-liquid separation, and the solid phase was collected and dried to obtain the metal salt-loaded ZIF-8 material; wherein... The metal element M in the metal salt solution includes one or more of Co, Fe, Mn, Ni, Cu, Pt, and Zn; The ZIF-8 material loaded with metal salt was calcined in an inert gas atmosphere and cooled to prepare a ZIF-8 derived single-atom catalyst. The single-atom metal site type of the ZIF-8 derived single-atom catalyst was selected from any one of M-N4-C, M-N3-C, M-N2-C and M-N1-C.

52. The method for preparing the single-atom catalyst according to claim 51, wherein, The solvent in the metal salt solution includes one or more of methanol, ethanol, water, and N,N-dimethylformamide.

53. The method for preparing the single-atom catalyst according to claim 51, wherein, The metal salt in the metal salt solution is selected from one or more of cobalt nitrate, ferric nitrate, ferric chloride, nickel nitrate, nickel acetylacetonate, sodium chloroplatinate, ferric acetylacetonate, copper nitrate, and copper sulfate.

54. The method for preparing the single-atom catalyst according to claim 51, wherein, The temperature for mixing the ZIF-8 material sacrificial precursor with the metal salt solution is selected from 10 °C to 60 °C, and the mixing time is selected from 1 h to 12 h. The drying temperature is selected from 95 °C to 105 °C, and the drying time is selected from 5 h to 10 h; The step of calcining and cooling the ZIF-8 material loaded with metal salt in an inert gas atmosphere includes: heating the ZIF-8 material loaded with metal salt to the calcination temperature under an inert gas atmosphere, holding at that temperature, and then cooling. The inert gas atmosphere is selected from nitrogen atmosphere or argon atmosphere; The heating rate is selected from 4 °C / min to 6 °C / min; The calcination temperature is selected from 800 °C ~ 1000 °C; The heat preservation time is selected from 1.5 h to 2.5 h; The cooling method is furnace-in-flight cooling; Cool to 4 °C ~ 40 °C.

55. The method for preparing the single-atom catalyst according to claim 51, wherein, The average particle size d2 of the primary particles of the ZIF-8 derived single-atom catalyst satisfies 5 nm ≤ d2 ≤ 700 nm.

56. A single-atom catalyst, prepared by the method of any one of claims 51 to 55.

57. A method for preparing a battery separator, wherein, The battery separator includes a porous substrate and a porous coating disposed on at least one surface of the porous substrate, wherein the porous coating includes ZIF-8 material; The ZIF-8 material is prepared using the ZIF-8 material preparation method described in any one of claims 1 to 49.

58. The method for preparing the battery separator as described in claim 57, wherein, The weight percentage of the ZIF-8 material in the porous coating is selected from 40% to 90%.

59. The method for preparing the battery separator as described in claim 57, wherein, The thickness of the porous coating is selected from 0.5 μm to 12 μm.

60. The method for preparing the battery separator as described in claim 57, wherein, The porous coating also includes one or more of the following: binder, inorganic particles, stabilizer, wetting agent, rheology modifier, defoamer, thickener, pH adjuster, and preservative; The inorganic particles are composed of one or more of the following: boehmite, molecular sieve, zeolite, alumina, alumina hydroxyl, silicon dioxide, aluminum nitride, silicon carbide, magnesium oxide, calcium oxide, zinc oxide, zirconium dioxide, and titanium dioxide.

61. Applications of ZIF-8 materials in the preparation of carbon-based single-atom catalysts or lithium-ion battery separators, among which, The ZIF-8 material is prepared using the ZIF-8 material preparation method described in any one of claims 1 to 49.

62. A method for preparing a single battery cell, wherein, The battery cell includes a positive electrode sheet, a battery separator, and a negative electrode sheet stacked together, with the battery separator sheet disposed between the negative electrode sheet and the positive electrode sheet; The battery separator is prepared by the method described in any one of claims 57 to 60.

63. A battery cell prepared by the method of preparation of the battery cell according to claim 62.

64. A method for preparing an electrical device, wherein, The electrical device includes a battery cell; wherein the battery cell is prepared using the method for preparing the battery cell according to claim 62.

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