A hydrotalcite aramid separator composite material, its preparation method and application

Abstract

The present invention relates to the technical field of battery separators, and particularly relates to a hydrotalcite aramid separator composite material, a preparation method thereof, and an application thereof. The preparation method is as follows: A metal compound for preparing hydrotalcite and an aramid separator are added to water, and the soaking temperature and soaking time are controlled. After the hydrotalcite grows in-situ on the aramid separator, it is rinsed with clear water and dried to obtain the hydrotalcite aramid separator composite material. The hydrotalcite aramid separator composite material of the present invention has a relatively high specific surface area, provides a large number of lithium ion adsorption sites, is beneficial to improving the ion transport rate, and provides a basis for high-rate charge and discharge. The hydrotalcite grows in-situ in the aramid separator fibers, does not increase the thickness of the separator, improves the high-temperature thermal shrinkage performance of the separator, and increases the energy density of the battery cell.

Description

Technical Field

[0001] The present invention relates to a hydrotalcite aramid separator composite material, a preparation method and an application thereof, belonging to the technical field of battery separators. Background Art

[0002] With the development of the new energy vehicle market, the technical development of batteries has become increasingly important, because the performance of batteries will directly affect the development of new energy vehicles. The separator is an important component in lithium-ion batteries. Indicators such as the thermal stability, flame retardancy and ionic conductivity of the separator will directly affect the application effect and service life of the battery. Therefore, the development of separators with excellent performance is of great significance for the development of batteries.

[0003] As a new type of heat-resistant separator material, aramid separators can significantly improve the safety performance, rate performance, cycle life and manufacturing efficiency of power batteries due to their excellent heat resistance, insulation, flame retardancy and thermal stability. Chinese Patent Application CN114479654A discloses a preparation method of an organic intercalated hydrotalcite-aramid coating solution and its application in the coating of lithium battery separators. An organic intercalated hydrotalcite is added to the aramid polymerization reaction to obtain an organic intercalated hydrotalcite-aramid coating solution. The organic intercalated hydrotalcite-aramid coating solution is coated on a base film, and then washed with water and dried to obtain a battery separator. However, due to the unique coating process of aramid separators, the advantage of the shrinkage performance of aramid separators at high temperatures is not obvious, and it is easy to cause the battery separator to be thicker, which cannot meet the growing battery demand. Therefore, there is an urgent need for new materials and new processes for product iteration and update. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a hydrotalcite aramid separator composite material, a preparation method and an application thereof. The separator composite material prepared by the preparation method improves the heat resistance and ionic conductivity performance without changing the original thickness of the aramid separator, and the preparation process is simple.

[0005] The technical solution for solving the above technical problems of the present invention is as follows: A preparation method of a hydrotalcite aramid separator composite material, the preparation method is: adding a metal compound for preparing hydrotalcite and an aramid separator into water, controlling the soaking temperature and soaking time. After the hydrotalcite grows in-situ on the aramid separator, it is rinsed with clear water and dried to obtain the hydrotalcite aramid separator composite material.

[0006] Further, the hydrotalcite is a double-metal layered hydroxide or a single-metal layered hydroxide; the size of the hydrotalcite is 100~1000 nm.

[0007] Further, the hydrotalcite is at least one of cobalt oxide containing nickel, aluminum oxide containing nickel, magnesium oxide containing nickel, iron oxide containing nickel, nickel oxide containing iron, cobalt oxide containing iron, calcium oxide containing iron, magnesium oxide containing iron, aluminum oxide containing iron, sodium oxide containing iron, nickel oxide containing cobalt, iron oxide containing cobalt, aluminum oxide containing cobalt, magnesium oxide containing cobalt, zirconium oxide containing cobalt, and sodium oxide containing cobalt.

[0008] Further, the metal compound for preparing the hydrotalcite is selected from at least one of a first metal compound and a second metal compound;

[0009] The first metal compound is selected from at least one of cobalt-containing oxides, cobalt-containing sulfides, cobalt-containing chlorides, cobalt-containing sulfates, cobalt-containing nitrates, cobalt-containing carbonates, magnesium oxides, magnesium-containing sulfides, magnesium-containing chlorides, magnesium-containing sulfates, magnesium-containing nitrates, and magnesium-containing carbonates;

[0010] The second metal compound is selected from at least one of nickel-containing oxides, nickel-containing sulfides, nickel-containing chlorides, nickel-containing sulfates, nickel-containing nitrates, nickel-containing carbonates, aluminum-containing oxides, aluminum-containing chlorides, aluminum-containing sulfides, aluminum-containing hydroxides, aluminum-containing sulfates, aluminum-containing nitrates, and aluminum-containing carbonates.

[0011] Further, the metal compound for preparing the hydrotalcite is a first metal compound and a second metal compound, and the mass ratio of the first metal compound to the second metal compound is 1:(2 - 6).

[0012] Preferably, the metal compound is nickel chloride and cobalt chloride.

[0013] Further, for every 30*30 cm aramid separator, the addition amount of the metal compound is 2 - 12 g; the mass ratio of the metal compound to water is 1:(75 - 200).

[0014] Further, in the preparation method, an alkali is added to the water, and the alkali is at least one of sodium hydroxide and calcium oxide; the mass ratio of the metal compound to the alkali is 1:(0.5 - 6).

[0015] Further, the soaking temperature is 20 - 80°C, and the soaking time is 20 s - 1 h.

[0016] A hydrotalcite aramid separator composite material, and the hydrotalcite aramid separator composite material is prepared according to the preparation method described in the present invention.

[0017] An application of a hydrotalcite aramid separator composite material, and the hydrotalcite aramid separator composite material is used as a separator material for lithium-ion batteries.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) The hydrotalcite aramid separator composite material of the present invention has high ionic conductivity (≥0.5 mS / cm 2 ), good heat resistance (maximum thermal shrinkage at 200°C for 1 hour: MD ≤ 10.0%, TD ≤ 9.7%, minimum thermal shrinkage: MD ≤ 4.0%, TD ≤ 3.2%), and a wide electrochemical stability window. The hydrotalcite in the preparation method of the present invention is nanoscale-anchored on each fiber of the aramid separator. Without significantly increasing the original thickness of the aramid separator, it effectively increases the specific surface area of the separator, improves thermal stability and mechanical stability, and further improves the cycle stability and safety performance of lithium batteries (high-temperature thermal box, acupuncture, extrusion, and heavy object impact) on the premise of ensuring the electrical performance of the battery.

[0020] (2) The hydrotalcite aramid separator composite material of the present invention has high ionic conductivity, which can improve the fast charging and rate performance of lithium batteries.

[0021] (3) The preparation method of the present invention is to prepare the hydrotalcite aramid separator composite material by a one-step in-situ growth technique. By reasonably controlling the content ratio of the bimetal, the soaking time, and the soaking temperature, the aramid separator is used as the carrier and the anchoring point of the hydrotalcite aramid separator composite material. Finally, the hydrotalcite aramid separator composite material is obtained, and then the excess ions are removed by washing with water to obtain a pure product. The preparation process is simple and highly operable.

[0022] (4) During the preparation process of the hydrotalcite aramid separator composite material of the present invention, the role of the aramid separator as the carrier and the anchoring point of the hydrotalcite aramid separator composite material is fully utilized. On the one hand, during the in-situ growth process, the separator provides the position for ionic anchoring as the fiber main body, and maintains the uniform distribution and consistency of the structure during the growth of hydrotalcite in the solution. On the other hand, the aramid separator is insoluble in water, and no additional cleaning agent needs to be added during the later cleaning process. Only green and environmentally friendly water is needed for washing to obtain a pure product.

[0023] (5) The method for preparing the hydrotalcite aramid separator composite material of the present invention is simple, reliable, has good repeatability, is environmentally friendly, and has low cost, and has broad prospects for industrial application in batteries. The hydrotalcite aramid separator composite material of the present invention is particularly suitable for use as a separator material for lithium-ion batteries. The prepared lithium-ion battery has good cycle life, high safety performance, and rate performance. Description of the Drawings

[0024] Figure 1 It is a scanning electron microscope image of the hydrotalcite aramid separator composite material prepared in Example 2. Detailed Embodiments

[0025] The following is a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing the specific embodiments and are not intended to limit the present invention.

[0027] A preparation method of a hydrotalcite aramid separator composite material, the preparation method being: adding a metal compound for preparing hydrotalcite and an aramid separator to water, controlling the soaking temperature and soaking time, and after the hydrotalcite grows in-situ on the aramid separator, rinsing with clear water and drying to obtain the hydrotalcite aramid separator composite material, wherein the drying temperature is: 70 °C.

[0028] Specifically, the hydrotalcite is a double-metal layered hydroxide or a single-metal layered hydroxide; the size of the hydrotalcite is 100-1000 nm.

[0029] Preferably, the hydrotalcite is a double-metal layered hydroxide.

[0030] Specifically, the hydrotalcite is at least one of cobalt oxide containing nickel, aluminum oxide containing nickel, magnesium oxide containing nickel, iron oxide containing nickel, nickel oxide containing iron, cobalt oxide containing iron, calcium oxide containing iron, magnesium oxide containing iron, aluminum oxide containing iron, sodium oxide containing iron, nickel oxide containing cobalt, iron oxide containing cobalt, aluminum oxide containing cobalt, magnesium oxide containing cobalt, zirconium oxide containing cobalt, and sodium oxide containing cobalt.

[0031] More specifically, the hydrotalcite is at least one of magnesium-aluminum hydrotalcite, nickel-cobalt hydrotalcite, calcium-magnesium hydrotalcite, cobalt-cobalt hydrotalcite, nickel-aluminum hydrotalcite, calcium-aluminum hydrotalcite, nickel-nickel hydrotalcite, cobalt-aluminum hydrotalcite, nickel-iron hydrotalcite, cobalt-iron hydrotalcite, magnesium-iron hydrotalcite, and iron-iron hydrotalcite.

[0032] Preferably, the hydrotalcite is nickel-cobalt hydrotalcite.

[0033] Specifically, the metal compound for preparing the hydrotalcite is selected from at least one of a first metal compound and a second metal compound;

[0034] The first metal compound is selected from at least one of cobalt-containing oxides, cobalt-containing sulfides, cobalt-containing chlorides, cobalt-containing sulfates, cobalt-containing nitrates, cobalt-containing carbonates, magnesium oxides, magnesium-containing sulfides, magnesium-containing chlorides, magnesium-containing sulfates, magnesium-containing nitrates, and magnesium-containing carbonates;

[0035] The second metal compound is selected from at least one of nickel-containing oxides, nickel-containing sulfides, nickel-containing chlorides, nickel-containing sulfates, nickel-containing nitrates, nickel-containing carbonates, aluminum-containing oxides, aluminum-containing chlorides, aluminum-containing sulfides, aluminum-containing hydroxides, aluminum-containing sulfates, aluminum-containing nitrates, and aluminum-containing carbonates.

[0036] Preferably, the metal compounds for preparing the hydrotalcite are a first metal compound and a second metal compound, and the mass ratio of the first metal compound to the second metal compound is 1:(2 - 6).

[0037] More preferably, the metal compounds for preparing the hydrotalcite are nickel chloride and cobalt chloride.

[0038] Specifically, for every 30*30 cm aramid separator, the addition amount of the metal compound is 2 - 6 g; the mass ratio of the metal compound to water is 1:(75 - 200).

[0039] Specifically, in the preparation method, an alkali is added to the water, and the alkali is at least one of sodium hydroxide and calcium oxide; the mass ratio of the metal compound to the alkali is 1:(0.5 - 6).

[0040] Specifically, the soaking temperature is 20 - 80 °C, and the soaking time is 20 s - 1 h.

[0041] More specifically, the soaking temperature is T , in units of °C; the soaking time is Y, in units of s; then Y = y ± 8, y = -2585ln( T ). And the multiple of the addition amount of the alkali to the mass of the metal oxide is C (that is, the mass ratio of the metal compound to the alkali is 1: C ); then C ≤(-0.05 Y + 7). The relationship between the soaking temperature and the soaking time, and the soaking temperature and the alkali dosage according to the above formula is more conducive to efficiently obtaining a hydrotalcite aramid separator composite material with excellent performance.

[0042] Specifically, the aramid separator is any one of meta-aramid separator, para-aramid separator, bio-based aramid separator, meta-aramid ceramic separator, para-aramid ceramic separator, bio-based aramid ceramic separator, meta-aramid fiber separator, para-aramid fiber separator, and polyacrylonitrile separator.

[0043] More specifically, the aramid separator used in the examples of the present invention is a meta-aramid separator (specific model: THM0722 of Yantai Taihe New Materials Battery New Materials Technology Co., Ltd.).

[0044] A hydrotalcite aramid separator composite material, and the hydrotalcite aramid separator composite material is prepared according to the preparation method described in the present invention.

[0045] An application of a hydrotalcite aramid separator composite material, and the hydrotalcite aramid separator composite material is used as a separator material for lithium-ion batteries.

[0046] Example 1

[0047] Preparation of a hydrotalcite aramid separator composite material:

[0048] Add 1 g of cobalt chloride and 3 g of nickel chloride to 300 g of water. After stirring evenly, add an aramid separator with a size of 30*30 cm. Soak it statically at 55 °C for 980 s, then rinse it with clear water and dry it to obtain the hydrotalcite aramid separator composite material.

[0049] Example 2

[0050] Preparation of a hydrotalcite aramid separator composite material:

[0051] Add 1 g of cobalt chloride, 3 g of nickel chloride, and 2 g of calcium oxide to 300 g of water. After stirring evenly, add an aramid separator with a size of 30*30 cm. Soak it statically at 55 °C for 980 s, then rinse it with clear water and dry it to obtain the hydrotalcite aramid separator composite material.

[0052] Example 3

[0053] Preparation of a hydrotalcite aramid separator composite material:

[0054] Add 1 g of cobalt oxide, 2 g of aluminum hydroxide, and 8 g of sodium hydroxide to 300 g of water. After stirring evenly, add an aramid separator with a size of 30*30 cm. Soak it statically at 80 °C for 20 s, then rinse it with clear water and dry it to obtain the hydrotalcite aramid separator composite material.

[0055] Example 4

[0056] Preparation of a hydrotalcite aramid separator composite material:

[0057] Add 1 g of cobalt oxide, 2 g of aluminum hydroxide, and 6 g of calcium oxide to 300 g of water. After stirring evenly, add an aramid separator with a size of 30*30 cm. Soak it statically at 80 °C for 20 s, then rinse it with clear water and dry it to obtain the hydrotalcite aramid separator composite material.

[0058] Example 5

[0059] Preparation of a hydrotalcite aramid separator composite material:

[0060] Add 0.5 g of magnesium oxide and 3 g of aluminum chloride to 700 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 20 °C, let it stand and soak for 1 h, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0061] Example 6

[0062] Preparation of a hydrotalcite aramid separator composite material:

[0063] Add 0.5 g of magnesium oxide, 3 g of aluminum chloride, and 21 g of calcium oxide to 700 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 20 °C, let it stand and soak for 1 h, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0064] Example 7

[0065] Preparation of a hydrotalcite aramid separator composite material:

[0066] Add 2 g of magnesium oxide and 4 g of aluminum chloride to 600 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 40 °C, let it stand and soak for 0.5 h, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0067] Example 8

[0068] Preparation of a hydrotalcite aramid separator composite material:

[0069] Add 1 g of nickel sulfate and 3 g of aluminum sulfate to 400 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 40 °C, let it stand and soak for 0.5 h, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0070] Example 9

[0071] Preparation of a hydrotalcite aramid separator composite material:

[0072] Add 1 g of nickel carbonate and 2 g of magnesium carbonate to 300 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 60 °C, let it stand and soak for 750 s, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0073] Example 10

[0074] Preparation of a hydrotalcite aramid separator composite material:

[0075] Add 1 g of cobalt chloride and 3 g of nickel chloride to 300 g of water. After stirring evenly, add a 30*30 cm aramid separator. At 55 °C, let it stand and soak for 1 h, then rinse with clean water and dry to obtain a hydrotalcite aramid separator composite material.

[0076] Example 11

[0077] Preparation of a hydrotalcite aramid separator composite material:

[0078] Add 1 g of cobalt chloride, 3 g of nickel chloride, and 20 g of calcium oxide to 300 g of water. After stirring evenly, add a 30*30 cm aramid separator. Soak it statically at 55 °C for 980 s, then rinse with clear water and dry to obtain the hydrotalcite aramid separator composite material.

[0079] Example 12

[0080] Preparation of a hydrotalcite aramid separator composite material:

[0081] Add 4 g of cobalt chloride to 300 g of water. After stirring evenly, add a 30*30 cm aramid separator. Soak it statically at 55 °C for 980 s, then rinse with clear water and dry to obtain the hydrotalcite aramid separator composite material.

[0082] Comparative Example 1

[0083] Synthesize NiCo-LDH nanosheets: Add 1 g of nickel nitrate, 3 g of cobalt nitrate, and 6 g of sodium hydroxide to 1 L of water. Stir evenly, heat to 70 °C, keep for 1 h, then wash and dry at 70 °C for 1 h to obtain NiCo-LDH nanosheets.

[0084] Mix the synthesized NiCo-LDH nanosheets into 1 L of water, evenly coat them on the surface of the aramid separator, and dry after standing for 1 hour to obtain the product.

[0085] Comparative Example 2

[0086] Prepare the hydrotalcite aramid separator composite material using the same method as in Example 1, except that: increase the addition amount of the metal compound. The addition amount of the metal compound in this Comparative Example 2 is 8 g (higher than the dosage defined in the present invention). The specific preparation process is as follows:

[0087] Add 2 g of cobalt chloride and 6 g of nickel chloride to 300 g of water. After stirring evenly, add a 30*30 cm aramid separator. Soak it statically at 55 °C for 980 s, then rinse with clear water and dry to obtain the hydrotalcite aramid separator composite material.

[0088] Comparative Example 3

[0089] Prepare the hydrotalcite aramid separator composite material using the same method as in Example 4, except that: increase the addition amount of the base. In this Comparative Example 3, the mass ratio of the metal compound to the base is 1:15 (higher than the dosage defined in the present invention). The specific preparation process is as follows:

[0090] Add 1 g of cobalt hydroxide, 2 g of aluminum hydroxide, and 45 g of sodium hydroxide to 300 g of water. After stirring evenly, add an aramid separator with a size of 30 * 30 cm. Soak it statically at 80 °C for 20 s, then rinse it with clean water and dry it to obtain a hydrotalcite aramid separator composite material.

[0091] Comparative Example 4

[0092] Prepare the hydrotalcite aramid separator composite material by the same method as in Example 1, except that: increase the soaking temperature. In this Comparative Example 4, the soaking temperature is 90 °C. The specific preparation process is as follows:

[0093] Add 1 g of cobalt chloride and 3 g of nickel chloride to 300 g of water. After stirring evenly, add an aramid separator with a size of 30 * 30 cm. Soak it statically at 90 °C for 980 s, then rinse it with clean water and dry it to obtain a hydrotalcite aramid separator composite material.

[0094] Comparative Example 5

[0095] Prepare the hydrotalcite aramid separator composite material by the same method as in Example 1, except that: decrease the soaking temperature. In this Comparative Example 4, the soaking temperature is 10 °C. The specific preparation process is as follows:

[0096] Add 1 g of cobalt chloride and 3 g of nickel chloride to 300 g of water. After stirring evenly, add an aramid separator with a size of 30 * 30 cm. Soak it statically at 10 °C for 980 s, then rinse it with clean water and dry it to obtain a hydrotalcite aramid separator composite material.

[0097] Perform heat resistance tests on the separator composite materials prepared in the above examples and comparative examples. The test methods involved are as follows:

[0098] Thickness test: GB / T 6672-2001 "Plastics - Films and Sheets - Determination of Thickness by Mechanical Measurement";

[0099] Film breaking temperature: GB / T 36800.1-2018 "Plastics - Thermomechanical Analysis (TMA) - Part 1: General Principles";

[0100] Thermal shrinkage rate: Conduct the test according to GB / T 36363-2018. Draw a line of 10.0 cm × 10.0 cm on the separator along the MD×TD direction. After sandwiching the separator between two A4 papers, put it into the oven. Measure three samples at the same temperature, and take the average value as the test result.

[0101] The specific test results are shown in Table 1 below.

[0102] Table 1 Test Results of Thickness and Heat Resistance of Separator Composite Materials

[0103]

[0104] Note: In Table 1, MD represents the longitudinal direction and TD represents the transverse direction.

[0105] In addition, a method for preparing a lithium-ion battery using a hydrotalcite aramid separator composite material and testing its performance: The separator composite materials prepared in the above examples and comparative examples were punched into separators of standard size using a standard stamping machine, and a 2032 button cell was assembled using a lithium metal sheet and graphite as the counter electrodes. The electrolyte used was 1.0 M LiPF6 / EC / DEC, and the charge-discharge current density used for testing the cycle performance was 1C. The specific test results are shown in Table 2 below.

[0106] Table 2 Test Results of Battery Performance

[0107]

[0108] Figure 1 is a scanning electron microscope image (SEM) of the hydrotalcite aramid separator composite material prepared in Example 2. From Figure 1 it can be seen that the hydrotalcite nanosheets grow uniformly on each fiber of the aramid separator, and the size of each hydrotalcite nanosheet is in the nanometer range, thus not increasing the thickness of the separator itself. Secondly, due to the in-situ growth of hydrotalcite on each fiber, the heat-resistant characteristics of hydrotalcite are perfectly combined with the aramid separator, which can greatly improve the heat-resistant characteristics of the separator. Finally, the in-situ growth of hydrotalcite on the fibers of the aramid separator will not cause agglomeration and accumulation, nor will it cause powder dropping under physical mixing, and it will not contaminate the battery assembly line, greatly improving the assembly efficiency.

[0109] From the data in Table 1 and Table 2 above, it can be seen that: The hydrotalcite aramid separator composite materials prepared in Examples 1 - 12 using the preparation method of the present invention are based on the aramid separator, and by using the in-situ growth method of hydrotalcite nanomaterials, the hydrotalcite nanosheets with heat-resistant characteristics are evenly distributed on each fiber of the aramid separator, giving full play to the heat-resistant characteristics of aramid and hydrotalcite. At the same time, numerous active hydroxyl groups and interlayer anions on the surface of the hydrotalcite main board provide a large number of adsorption sites, accelerating the transmission speed of lithium ions, broadening the transmission path of lithium ions, further improving the ionic conductivity of the separator. When applied to lithium-ion batteries, it can improve the cycle stability and safety performance of lithium batteries.

[0110] From the data comparison of Examples 1, 5 and Examples 2, 3, 4, 6, it can be seen that: During the preparation process of Examples 2, 3, 4 and 6, adding an appropriate amount of alkali can make the hydrotalcite adhere more evenly to the aramid separator, and the finally obtained hydrotalcite aramid separator composite material has better heat-resistant performance and better application effect in lithium-ion batteries.

[0111] From the data comparison between Example 1 and Example 10, it can be seen that when the soaking temperature and soaking time satisfy Y = y ± 8, where y = -2585ln( T ), it is more conducive to efficiently obtaining a hydrotalcite aramid separator composite material with excellent performance. From the data comparison between Example 2 and Example 11, it can be seen that there is a correspondence between the soaking temperature and the alkali dosage C ≤ (-0.05 Y +7), which is more conducive to efficiently obtaining a hydrotalcite aramid separator composite material with excellent performance. Because of the mutual cooperation among the soaking temperature, soaking time, and alkali dosage, the in-situ growth rate and growth state of hydrotalcite can be controlled, which is more conducive to the uniform distribution of hydrotalcite on the aramid separator, and ultimately improves the heat resistance and battery application performance of the hydrotalcite aramid separator composite material.

[0112] From the data comparison between Example 1 and Example 12, it can be seen that compared with the single-metal layered hydroxide in Example 12, the double-metal layered hydroxide on the aramid separator in Example 1 is more conducive to improving the heat resistance and battery application performance of the aramid separator composite material.

[0113] From the data comparison between Example 1 and Comparative Example 1, it can be seen that the preparation method of the present invention grows and introduces hydrotalcite in-situ on the aramid separator. Compared with the coating method in Comparative Example 1, it is more conducive to the uniform distribution and consistency of hydrotalcite, and ultimately improves the application performance of the hydrotalcite aramid separator composite material.

[0114] From the data comparison between Example 1 and Comparative Example 2, it can be seen that if the addition amount of the metal compound is too much, the heat resistance of the hydrotalcite aramid separator composite material will decrease. Because too much dosage of the metal compound will affect the uniform distribution of hydrotalcite on the aramid separator, and the problem of hydrotalcite accumulation is likely to occur on the aramid separator, ultimately leading to the performance degradation of the hydrotalcite aramid separator composite material.

[0115] From the experimental comparison between Example 4 and Comparative Example 3, it can be seen that too much addition of alkali will also cause the performance of the aramid separator composite material to deteriorate. Because too strong alkalinity will accelerate the growth rate of hydrotalcite nanosheets, resulting in too short nucleation time of hydrotalcite, and agglomeration and accumulation have occurred, causing hydrotalcite to fall off and the ionic conductivity to decrease. And too strong alkalinity will corrode the separator, causing the separator to be damaged.

[0116] From the data comparison between Example 1 and Comparative Example 4, it can be seen that if the soaking temperature is too high, the heat resistance of the hydrotalcite aramid separator composite material will decrease. Because too high temperature makes the growth rate of hydrotalcite too fast, and it is easy to be unevenly distributed on the aramid separator.

[0117] It can be seen from the data comparison between Example 1 and Comparative Example 5 that if the soaking temperature is too low, sufficient hydrotalcite cannot be formed in situ on the aramid separator, which will also cause the aramid separator composite material to fail to meet the better heat resistance requirements. Therefore, using the temperature conditions defined in the present invention is more conducive to obtaining a hydrotalcite aramid separator composite material with excellent performance.

[0118] In summary, the hydrotalcite aramid separator composite material described in the present invention has nano-scale hydrotalcite nanosheets with a large specific surface area. At the same time, a large number of active hydroxyl groups and interlayer anions on the surface of the hydrotalcite can provide a large number of lithium ion adsorption sites, which is beneficial to improving the ion transport rate, broadening the ion transport path, and providing the basis for high-rate charge and discharge. The hydrotalcite grows in situ in the aramid separator fibers, does not increase the separator thickness, improves the high-temperature thermal shrinkage performance of the separator, and enhances the energy density, long cycle performance, and high-rate discharge capacity of the battery cell.

[0119] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the various technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0120] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A method for preparing a hydrotalcite aramid diaphragm composite material, characterized in that: The preparation method comprises: adding a metal compound for preparing hydrotalcite and an aramid membrane into water, controlling the soaking temperature and soaking time, and after the hydrotalcite is in-situ grown on the aramid membrane, washing with clean water and drying to obtain the hydrotalcite aramid membrane composite material; The hydrotalcite is a double metal layered hydroxide or a single metal layered hydroxide; the size of the hydrotalcite is 100-1000 nm; For each 30*30cm aramid diaphragm, the amount of the metal compound added is 2-6g; the mass ratio of the metal compound to water is 1:(75-200); In the preparation method, alkali or calcium oxide is added to the water, and the mass ratio of the metal compound to the alkali or calcium oxide is 1: (0.5-6); The soaking temperature is 20-80°C, and the soaking time is 20s-1h; The metal compound used to prepare the hydrotalcite is a first metal compound and a second metal compound; The first metal compound is selected from at least one of cobalt-containing oxides, cobalt-containing sulfides, cobalt-containing chlorides, cobalt-containing sulfates, cobalt-containing nitrates, cobalt-containing carbonates, magnesium oxides, magnesium-containing sulfides, magnesium-containing chlorides, magnesium-containing sulfates, magnesium-containing nitrates, and magnesium-containing carbonates; The second metal compound is selected from at least one of nickel-containing oxides, nickel-containing sulfides, nickel-containing chlorides, nickel-containing sulfates, nickel-containing nitrates, nickel-containing carbonates, aluminum-containing oxides, aluminum-containing chlorides, aluminum-containing sulfides, aluminum-containing hydroxides, aluminum-containing sulfates, aluminum-containing nitrates, and aluminum-containing carbonates.

2. The method for preparing a hydrotalcite aramid diaphragm composite material according to claim 1, characterized in that: The mass ratio of the first metal compound to the second metal compound is 1:(2-6).

3. The method for preparing a hydrotalcite aramid diaphragm composite material according to claim 1, characterized in that: The base is sodium hydroxide.

4. A hydrotalcite aramid diaphragm composite material, characterized in that: The hydrotalcite aramid diaphragm composite material is prepared according to the preparation method according to any one of claims 1-3.

5. An application of a hydrotalcite aramid diaphragm composite material according to claim 4, characterized in that: The hydrotalcite aramid diaphragm composite material is used as a lithium ion battery diaphragm material.

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