An aramid aqueous dispersion nano-microsphere, a coating slurry, a separator and a preparation method thereof

Abstract

The present invention relates to the technical field of lithium battery separators, and particularly relates to an aramid water-dispersed nano-microsphere, a coating slurry, a separator and a preparation method thereof. The preparation method of the aramid water-dispersed nano-microsphere is as follows: A diamine monomer, a first dispersant and an acid-binding agent are dissolved in deionized water to obtain an aqueous phase system, and a dicarbonyl chloride monomer is dissolved in chloroform to obtain an oil phase system; Under the condition of high-speed homogenization, the oil phase system is slowly added to the aqueous phase system for polymerization reaction, and finally, after solid-liquid separation, washing with water and formulation, an aqueous system of aramid water-dispersed nano-microspheres is obtained. The present invention prepares nano-scale water-dispersed microspheres with a large specific surface area by means of interfacial polymerization, and the microspheres have controllable particle size, good thermal stability and can be stably dispersed in water, which can greatly improve the liquid absorption rate of the separator. The aramid water-dispersed nano-microspheres and ceramic particles act together to prepare a coated separator with a high film-breaking temperature, low thermal shrinkage and good electrolyte wettability.

Description

Technical Field

[0001] The present invention relates to an aramid water-dispersed nano-microsphere, a coating slurry, a separator and a preparation method thereof, and belongs to the technical field of lithium battery separators. Background Art

[0002] In recent years, with the rapid upgrading of lithium-ion battery technology, lithium-ion batteries have become the mainstream power batteries used in 3C devices (communication products, computer products, consumer electronic products), as well as new energy vehicles, large-scale energy storage devices, etc. As an important component of lithium-ion batteries, the separator plays a crucial role in the performance of lithium-ion batteries. The separator serves to separate the positive and negative electrode materials and prevent short circuits. Although the separator does not participate in any chemical reactions during charge and discharge, it affects the battery's rate performance, cycle stability, and high-temperature safety.

[0003] Currently, the mainstream lithium-ion battery separators used in the market are mainly polyolefin microporous membranes, namely dry-stretched PP membranes, wet-stretched PE membranes, and three-layer composite membranes of the above two. As a lithium-ion battery separator, polyolefin separators have excellent mechanical properties, good electrochemical stability, and a thermal shut-off temperature with good safety characteristics. However, its inherent drawbacks such as poor thermal dimensional stability, insufficient liquid wettability, and low porosity are not conducive to the rapid and complete filling of the internal space of the separator with the electrolyte, affecting the ion transport rate, and restricting the development of lithium ions in terms of high energy and power density, high working voltage, wide temperature range, and fast charge and discharge speed. Existing polyolefin separators are difficult to meet the above requirements, and with the increase in the energy density of power batteries, it is bound to cause a decrease in the heat dissipation area, resulting in serious safety hazards. Therefore, in order to adapt to the rapid development of lithium-ion batteries, current research focuses on modifying the separator.

[0004] Surface coating has become one of the important means for modifying polyolefin separators due to its mature, simple, and efficient technology. In recent years, there have been more and more studies on coating modifications with inorganic ceramics, PVDF, aramid, etc. Although the thermal stability and wettability of the coated separators have been improved to a certain extent. However, there are still many problems in these studies. For example, the compatibility between the inorganic coating and the organic base film is poor, the inorganic particles are prone to fall off, the density of the inorganic particles is large, and the coating weight increases too much, which is not conducive to the improvement of the battery energy density; the heat resistance of polymers such as PVDF is still not high enough. Among them, aramid has been unanimously recognized by the domestic and foreign markets because of its high strength, high modulus, high temperature resistance, chemical corrosion resistance and other characteristics. Coating it on the battery separator can endow it with a relatively high membrane-breaking temperature, low thermal shrinkage, and good electrolyte wettability.

[0005] At present, aramid coating is mainly oil-based coating. The coating slurry is made by dispersing aramid stock solution with organic solvents. Oil-based coating has the advantages of high bonding performance and good comprehensive performance, but it has the disadvantages of complex process control, large pollution, and high cost. In view of the defects and deficiencies of oil-based coating, water-based aramid coating slurry emerges as the times require and has the advantages of low air permeability increase, low pollution, and low price. However, water-based aramid coating slurry has problems such as poor dispersibility, low bonding performance, and complex preparation process. At present, the water-based coating slurry mainly composed of aramid nanofibers is prepared by crushing and grinding large-size fibers and then dispersing them in water. The prepared aramid nanofibers have the disadvantages of large size, difficult to control, and poor dispersibility in water, making it unable to disperse well on the surface of the separator, resulting in uneven surface of the separator and unstable comprehensive performance, which hinders its application in the field of separator coating. Summary of the Invention

[0006] In view of the deficiencies of the existing technology, the present invention provides an aramid water-dispersed nano-microsphere, a coating slurry, a separator and a preparation method. By means of interfacial polymerization, a nano-scale water-dispersed microsphere with a large specific surface area is prepared. The water-dispersed microsphere prepared by interfacial polymerization has a controllable particle size, more uniform particle size, can be stably dispersed in water, and has good thermal stability. The aramid nano-microsphere and ceramics are mixed to prepare a coating slurry, which not only exerts the high heat resistance and strong puncture resistance of ceramics, but also the addition of aramid nano-microspheres overcomes the problems of poor compatibility between ceramic particles and the base film and easy shedding of inorganic particles, can significantly improve the wettability of the electrolyte, the liquid absorption rate of the electrolyte, the ionic conductivity and porosity of the separator, so that the battery has good cycle performance and high specific capacity, and the preparation process is simple and can be widely applied in industrialization;

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A preparation method of aramid water-dispersed nano-microspheres, and the preparation method of the aramid water-dispersed nano-microspheres is as follows:

[0008] Dissolve diamine monomers, a first dispersant and an acid-binding agent in deionized water to obtain an aqueous phase system, and dissolve dicarboxylic acid chloride monomers in chloroform to obtain an oil phase system;

[0009] Under the condition of high-speed homogenization, slowly add the oil phase system to the aqueous phase system, and carry out a polymerization reaction under the condition of high-speed homogenization to obtain a polymer, and finally obtain the aqueous system of the aramid water-dispersed nano-microspheres after solid-liquid separation, washing with water, and adding water for formulation.

[0010] Further, the diamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, and 4,4-diaminodiphenyl ether;

[0011] The dicarboxylic acid chloride monomer is at least one of terephthaloyl chloride and isophthaloyl chloride;

[0012] The acid-binding agent is at least one of 2-methylpyridine, calcium hydroxide, and sodium carbonate.

[0013] Furthermore, the first dispersant is at least one of polyvinylpyrrolidone and polyvinyl alcohol.

[0014] Furthermore, the speed of high-speed homogenization is 2000 rpm - 10000 rpm.

[0015] Furthermore, the molar ratio of the dicarbonyl chloride monomer to the diamine monomer is (0.95 - 1.05):1;

[0016] The added mass of the first dispersant is 4% - 15% of the total mass of the diamine monomer and the dicarbonyl chloride monomer;

[0017] The solid content of the polymer is 5 - 15 wt%.

[0018] The present invention also discloses an aramid water-dispersed nano microsphere coating slurry. By weight, the coating slurry includes: 8 - 20 parts of aramid water-dispersed nano microspheres, 20 - 40 parts of ceramic particles, 2 - 8 parts of binder, 0.5 - 4 parts of second dispersant, 0.5 - 2 parts of wetting agent, and 26 - 69 parts of deionized water;

[0019] The aramid water-dispersed nano microspheres are prepared according to the preparation method described in the present invention.

[0020] Furthermore, the particle size of the aramid water-dispersed nano microspheres is 60 - 400 nm;

[0021] The particle size of the ceramic particles is 100 - 800 nm.

[0022] Furthermore, the ceramic particles are at least one of alumina, silica, and boehmite;

[0023] The binder is at least one of aqueous polyacrylate and modified polyacrylic acid;

[0024] The second dispersant is at least one of ammonium polyacrylate, sodium polyacrylate, and styrene-maleic anhydride ester;

[0025] The wetting agent is at least one of polyether-modified silicone, fatty alcohol polyoxyethylene ether, and modified succinic acid.

[0026] The present invention also discloses a preparation method of an aramid water-dispersed nano microsphere coating slurry. The preparation method of the coating slurry is as follows:

[0027] Deionized water, a second dispersant, ceramic particles, and a wetting agent are ground and dispersed to obtain a mixed solution. Then, an aqueous system of aramid water-dispersed nano-microspheres is added to the mixed solution, and the mixture is stirred and mixed evenly at a rotation speed of 1000 - 1200 rpm to obtain an aramid water-dispersed nano-microsphere coating slurry.

[0028] The present invention also discloses a lithium battery coated separator. The aramid water-dispersed nano-microsphere coating slurry is coated on both sides of a base film, and the lithium battery coated separator is obtained after shaping and drying.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. Through an interfacial polymerization method, the reaction is carried out under high-speed homogenization conditions in the present invention, and water-dispersed nano-microspheres with controllable particle size, uniform dispersion, and good thermal stability can be obtained. After filtration, washing, and preparation, the water-dispersed nano-microspheres for coating slurry are directly prepared, fundamentally solving the problems of poor dispersion, low bonding performance, and complex preparation process of traditional aqueous aramid nanofiber slurries.

[0031] 2. The aramid water-dispersed nano-microsphere coating slurry prepared in the present invention is an aqueous coating slurry. The aramid nano water-dispersed microspheres and ceramic particles in the slurry act synergistically, not only ensuring the high heat resistance and strong puncture resistance of the coated separator, but also improving its electrolyte wettability, electrolyte liquid absorption rate, ionic conductivity, and porosity of the separator, solving the problems of powder shedding and low liquid absorption rate of aqueous ceramic coatings.

[0032] 3. By mixing aramid nano-microspheres with ceramics to prepare a coating slurry, the high heat resistance and strong puncture resistance of ceramics are exerted. The addition of aramid nano-microspheres also overcomes the problems of poor compatibility between ceramic particles and the base film and easy shedding of inorganic particles, and can significantly improve the electrolyte wettability, electrolyte liquid absorption rate, ionic conductivity, and porosity of the separator, thereby enabling the battery to have good cycle performance and high specific capacity. Description of the Drawings

[0033] Figure 1 It is a scanning electron microscope image of the aramid water-dispersed microspheres prepared in Example 6;

[0034] Figure 2 It is a thermogravimetric curve of the aramid water-dispersed microspheres prepared in Example 6;

[0035] Figure 3 It is a scanning electron microscope image of the lithium battery coated separator prepared in Example 6;

[0036] Figure 4 It is a comparison diagram of the battery application effects of the lithium battery coated separators prepared in Example 1 and Example 6 and a commercially available separator;

[0037] Figure 5 It is a scanning electron microscope image of the aramid water-dispersed microspheres prepared in Comparative Example 5. Detailed implementation manners

[0038] The following makes a detailed description of the detailed implementation manners of the present invention. The present invention can be implemented in many other ways different from those described herein. 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.

[0039] 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 implementation manners and are not intended to limit the present invention.

[0040] A preparation method of aramid water-dispersed nano microspheres, and the preparation method of the aramid water-dispersed nano microspheres is as follows:

[0041] Dissolve a diamine monomer, a first dispersant and an acid-binding agent in deionized water to obtain an aqueous phase system, and dissolve a dicarboxylic acid chloride monomer in chloroform to obtain an oil phase system;

[0042] Under the condition of high-speed homogenization, slowly add the oil phase system to the aqueous phase system, and carry out a polymerization reaction under the condition of high-speed homogenization to obtain a polymer. Finally, after solid-liquid separation, washing with water, and adding water for formulation, the aqueous system of the aramid water-dispersed nano microspheres can be obtained.

[0043] Specifically, the diamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, and 4,4-diaminodiphenyl ether;

[0044] The dicarboxylic acid chloride monomer is at least one of terephthaloyl chloride and isophthaloyl chloride;

[0045] The acid-binding agent is at least one of 2-methylpyridine, calcium hydroxide, and sodium carbonate.

[0046] Specifically, the first dispersant is at least one of polyvinylpyrrolidone (PVP-K30, purchased from Tianjin Ruijinte Chemical Co., Ltd.) and polyvinyl alcohol (PVA, purchased from Shandong Keyuan Biochemical Co., Ltd.).

[0047] Specifically, the speed of the high-speed homogenization is 2000 rpm - 10000 rpm.

[0048] Specifically, the addition speed of the oil phase system to the aqueous phase system is 20 - 100 g / min.

[0049] More specifically, the high-speed homogenization speed is R, with the unit of rpm; the addition speed of the oil phase system is v, with the unit of g / min; then R = r ±100, r = 1340exp(0.02v ), the high-speed homogenization speed and the oil phase system addition speed satisfy this relationship, which is more conducive to obtaining aramid water-dispersible nano-microspheres with high particle size uniformity.

[0050] Specifically, the molar ratio of the diformyl chloride monomer to the diamine monomer is (0.95-1.05):1;

[0051] The added mass of the first dispersant is 4%-15% of the total mass of the diamine monomer and the diformyl chloride monomer;

[0052] The solid content of the polymer is 5-15wt%.

[0053] More specifically, the acid binding agent mainly functions to absorb the acid generated in the system during the polymerization reaction, and its usage is not strictly limited.

[0054] More specifically, the amount of the first dispersant added and the high-speed homogenization speed will affect the particle size of the aramid water-dispersible nano-microspheres. The faster the high-speed homogenization speed, the smaller the particle size of the aramid water-dispersible nano-microspheres. Under the condition of a high-speed homogenization speed of 4000-5000rpm, when the amount of the first dispersant added is 4%-5% of the total mass of the diamine monomer and the diformyl chloride monomer, aramid water-dispersible nano-microspheres with a particle size range of 260-400nm can be obtained; when the amount of the first dispersant added is 8%-10% of the total mass of the diamine monomer and the diformyl chloride monomer, aramid water-dispersible nano-microspheres with a particle size range of 180-240nm can be obtained; when the amount of the first dispersant added is 12%-15% of the total mass of the diamine monomer and the diformyl chloride monomer, aramid water-dispersible nano-microspheres with a particle size range of 60-180nm can be obtained. Aramid water-dispersible nano-microspheres with a suitable particle size range can be selected according to the requirements of the diaphragm coating thickness.

[0055] More specifically, when preparing the aqueous phase system, the mass ratio of the diamine monomer to deionized water is 1:(10-40); when preparing the oil phase system, the mass ratio of the diformyl chloride monomer to chloroform is 1:(2.8-10.5).

[0056] More specifically, the reaction temperature of the polymerization reaction is 5-10°C.

[0057] More specifically, in the embodiment of the present invention, water is added during the preparation process to obtain aramid water-dispersible nano-microspheres with a solid content of 20%.

[0058] A coating slurry for aramid water-dispersible nano-microspheres, comprising, by weight: 8-20 parts of aramid water-dispersible nano-microspheres, 20-40 parts of ceramic particles, 2-8 parts of a binder, 0.5-4 parts of a second dispersant, 0.5-2 parts of a wetting agent, and 26-69 parts of deionized water;

[0059] The aramid water-dispersed nano-microspheres are prepared according to the preparation method described in the present invention.

[0060] More specifically, the mass percentages of the components in the coating slurry with respect to the mass of the coating slurry are as follows:

[0061] Aramid water-dispersed nano-microspheres: 8-20 wt%;

[0062] Ceramic particles: 20-40 wt%;

[0063] Binder: 2-8 wt%;

[0064] Dispersant: 0.5-4 wt%;

[0065] Wetting agent: 0.5-2 wt%;

[0066] Deionized water: 26-69 wt%.

[0067] The total weight of the above components satisfies 100 wt%.

[0068] Specifically, the particle size of the aramid water-dispersed nano-microspheres is 60-400 nm;

[0069] The particle size of the ceramic particles is 100-800 nm.

[0070] Specifically, the ceramic particles are at least one of alumina, silica, and boehmite;

[0071] The binder is at least one of aqueous polyacrylate (model FC-05, purchased from Dongguan Yixing New Material Technology Co., Ltd.) and modified polyacrylic acid (model 8501, purchased from Rongdong New Materials);

[0072] The second dispersant is at least one of ammonium polyacrylate (model DURAMAX D-3019, purchased from Dow Chemical Co., Ltd.), sodium polyacrylate (model HT-5000, purchased from Nantong Hantai Chemical Co., Ltd.), and styrene-maleic anhydride ester (model SMA, purchased from Luoyang Yefang New Material Technology Co., Ltd.);

[0073] The wetting agent is at least one of polyether-modified silicone (model Xinnuo® LD 1710, purchased from Anhui Jiazhixin Nuo Chemical Co., Ltd.), fatty alcohol polyoxyethylene ether (model AEO-9, purchased from Guangzhou Xiangmei Chemical Technology Co., Ltd.), and modified succinic acid (model OT-75, purchased from Nantong Chenrun Chemical Co., Ltd.).

[0074] A preparation method of an aramid water-dispersed nano-microsphere coating slurry, and the preparation method of the coating slurry is as follows:

[0075] Deionized water, a second dispersant, ceramic particles, and a wetting agent are ground and dispersed to obtain a mixed solution. Then, an aqueous system of aramid water-dispersed nanospheres is added to the mixed solution, and the mixture is stirred and mixed evenly at a rotation speed of 1000 - 1200 rpm to obtain an aramid water-dispersed nanosphere coating slurry.

[0076] When preparing the mixed solution, the process of grinding and dispersing can not only play a role in uniform dispersion but also adjust the particle size of the ceramic particles. The particle size of the aramid water-dispersed nanospheres and the ceramic particles being mutually matched is more conducive to obtaining a separator with excellent battery application performance and is more conducive to the ionic conductivity and porosity of the separator.

[0077] More specifically, when preparing the mixed solution, the grinding and dispersing time is 10 - 60 min.

[0078] Preferably, when the particle size of the aramid water nanospheres used is 60 - 180 nm, the grinding time is 10 - 20 min; when the particle size of the aramid water nanospheres used is 180 - 240 nm, the grinding time is 20 - 40 min; when the particle size of the aramid water nanospheres used is 240 - 400 nm, the grinding time is 40 - 60 min.

[0079] A lithium battery coated separator is obtained by coating the aramid water-dispersed nanosphere coating slurry on both sides of a base film and then subjecting it to shaping and drying.

[0080] Preferably, the thickness of the lithium battery coated separator is 6 - 14 μm.

[0081] More specifically, the base film used in the embodiments of the present invention is a PE base film with a thickness of 7 μm, but this does not limit the technical solution of the present invention.

[0082] Example 1

[0083] (1) Preparation of aramid water-dispersed nanospheres: 20 g of m-phenylenediamine monomer, 2.79 g of the first dispersant PVP, and 32.72 g of the acid-binding agent 2-methylpyridine are dissolved in 210 g of deionized water to obtain an aqueous phase system. 35.71 g of isophthaloyl chloride monomer is dissolved in 105 g of chloroform to obtain an oil phase system. The oil phase system is slowly added to the aqueous phase system under high-speed homogenization conditions of 5000 rpm, and the addition rate of the oil phase system is 65 g / min. A homogeneous reaction is carried out at 5°C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, 20% solid content aramid water-dispersed nanospheres can be obtained.

[0084] (2) The content of each component for preparing the aramid polyamide water-dispersed nanosphere coating slurry is as follows:

[0085] Aramid water-dispersed nanospheres: 20 wt%

[0086] Ceramic particles: 20 wt%;

[0087] Binder: 8 wt%;

[0088] Second dispersant: 2 wt%;

[0089] Wetting agent: 1 wt%;

[0090] Deionized water: 49 wt%.

[0091] Preparation of aramid aqueous dispersion nano microsphere coating slurry: According to the composition, deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate and modified succinic acid were added to the stirring tank in sequence, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 40 min. Then, an aqueous system of aramid aqueous dispersion nano microspheres with a solid content of 20% was added to the mixed solution, and stirring and mixing were carried out at a rotation speed of 1000 rpm for 30 min to obtain an aramid aqueous dispersion nano microsphere coating slurry with a solid content of 51%;

[0092] (3) The obtained aramid aqueous dispersion nano microsphere coating slurry was coated on both sides of the base film, and after shaping and drying, a lithium battery coated separator was obtained. The thickness of the lithium battery coated separator was 10 μm.

[0093] Example 2

[0094] (1) Preparation of aramid aqueous dispersion nano microspheres: 20 g of p-phenylenediamine monomer, 2.97 g of the first dispersant PVA and 29.26 g of the acid-binding agent pyridine were dissolved in 356 g of deionized water to obtain an aqueous phase system. 39.47 g of terephthaloyl chloride monomer was dissolved in 178 g of chloroform to obtain an oil phase system. The oil phase system was slowly added to the aqueous phase system under the condition of high-speed homogenization at 2000 rpm, and the addition speed of the oil phase system was 20 g / min. And a homogeneous reaction was carried out at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing and formulation, 20% solid content aramid aqueous dispersion nano microspheres could be obtained.

[0095] (2) The contents of each component for preparing the aromatic polyamide aqueous dispersion nano microsphere coating slurry were:

[0096] Aramid aqueous dispersion nano microspheres: 8 wt%;

[0097] Ceramic particles: 40 wt%;

[0098] Binder: 6 wt%;

[0099] Second dispersant: 4 wt%;

[0100] Wetting agent: 0.5 wt%;

[0101] Deionized water: 49.5 wt%.

[0102] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the formulation composition, deionized water, boehmite, waterborne polyacrylate, styrene-maleic anhydride ester, and fatty alcohol polyoxyethylene ether were successively added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 60 min. Then, an aqueous system of aramid water-dispersed nano microspheres with a solid content of 20% was added to the mixed solution, and stirring and mixing were carried out at a rotation speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 50.5%;

[0103] (3)Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and after shaping and drying, a lithium battery coated separator is obtained. The thickness of the lithium battery coated separator is 10 μm.

[0104] Example 3

[0105] (1)Preparation of aramid water-dispersed nano microspheres: Dissolve 20 g of 4,4-diaminodiphenyl ether monomer, 2.02 g of the first dispersant PVA, and 27.41 g of the acid-binding agent calcium hydroxide in 336 g of deionized water to obtain an aqueous phase system. Dissolve 20.3 g of terephthaloyl chloride monomer in 168 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 6000 rpm, slowly add the oil phase system to the aqueous phase system at a rate of 75 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain white solid powder. After three times of filtration, washing, and formulation, 20% solid content aramid water-dispersed nano microspheres can be obtained.

[0106] (2)The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0107] Aramid water-dispersed nano microspheres: 8 wt%;

[0108] Ceramic particles: 20 wt%;

[0109] Binder: 2 wt%;

[0110] Second dispersant: 0.5 wt%;

[0111] Wetting agent: 0.5 wt%;

[0112] Deionized water: 69 wt%.

[0113] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the formula composition, deionized water, silicon dioxide, water-based polyacrylate, sodium polyacrylate and polyether-modified silicone were sequentially added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 30 min. Then, a water system of 20% solid content aramid water-dispersed nano microspheres was added to the mixed solution, and stirring and mixing were carried out at a speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 31%;

[0114] (3)Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and after shaping and drying, a lithium battery coated separator is obtained. The thickness of the lithium battery coated separator is 10 μm.

[0115] Example 4

[0116] (1)Preparation of aramid water-dispersed nano microspheres: 20 g of p-phenylenediamine monomer, 2.84 g of the first dispersant PVP and 26.86 g of the acid-binding agent calcium hydroxide were dissolved in 758 g of deionized water to obtain an aqueous phase system, and 36.84 g of terephthaloyl chloride monomer was dissolved in 379 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 8000 rpm, the oil phase system was slowly added to the aqueous phase system at a rate of 89 g / min, and homogenization reaction was carried out at 5 °C for 2 h to obtain white solid powder. After three times of filtration, washing and formulation, 20% solid content aramid water-dispersed nano microspheres can be obtained.

[0117] (2)The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0118] Aramid water-dispersed nano microspheres: 20 wt%;

[0119] Ceramic particles: 40 wt%;

[0120] Binder: 8 wt%;

[0121] Second dispersant: 4 wt%;

[0122] Wetting agent: 2 wt%;

[0123] Deionized water: 26 wt%.

[0124] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the formula composition, deionized water, alumina, modified polyacrylic acid, styrene-maleic anhydride ester and polyether-modified silicone were sequentially added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 20 min. Then, a water system of 20% solid content aramid water-dispersed nano microspheres was added to the mixed solution, and stirring and mixing were carried out at a speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 74%;

[0125] (3) Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and obtain a lithium battery coated separator after shaping and drying. The thickness of the lithium battery coated separator is 10 μm.

[0126] Example 5

[0127] (1) Preparation of aramid water-dispersed nano microspheres: Dissolve 20 g of m-phenylenediamine monomer, 2.92 g of the first dispersant PVP, and 29.26 g of the acid-binding agent pyridine in 324 g of deionized water to obtain an aqueous phase system. Dissolve 38.34 g of isophthaloyl chloride monomer in 162 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 7000 rpm, slowly add the oil phase system to the aqueous phase system. The addition rate of the oil phase system is 82 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, 20% solid content aramid water-dispersed nano microspheres can be obtained.

[0128] (2) The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0129] Aramid water-dispersed nano microspheres: 15 wt%;

[0130] Ceramic particles: 30 wt%;

[0131] Binder: 6 wt%;

[0132] Second dispersant: 2 wt%;

[0133] Wetting agent: 1 wt%;

[0134] Deionized water: 46 wt%.

[0135] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the formula composition, add deionized water, silicon dioxide, water-based polyacrylate, sodium polyacrylate, and modified succinic acid to the stirring tank in sequence, and carry out grinding and dispersion to obtain a mixed solution, where the grinding time is 15 min. Then add the aqueous system of 20% solid content aramid water-dispersed nano microspheres to the mixed solution, and stir and mix at a rotation speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 54%;

[0136] (3) Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and obtain a lithium battery coated separator after shaping and drying. The thickness of the lithium battery coated separator is 10 μm.

[0137] Example 6

[0138] (1)Preparation of aramid aqueous dispersion nanospheres: Dissolve 20 g of m-phenylenediamine monomer, 2.84 g of the first dispersant PVA, and 33.75 g of the acid-binding agent 2-methylpyridine in 379 g of deionized water to obtain an aqueous phase system. Dissolve 36.84 g of isophthaloyl chloride monomer in 189 g of chloroform to obtain an oil phase system. Slowly add the oil phase system to the aqueous phase system under the condition of high-speed homogenization at 10,000 rpm. The addition rate of the oil phase system is 100 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, 20% solid content aramid aqueous dispersion nanospheres can be obtained.

[0139] (2)The contents of the components for preparing the coating slurry of aromatic polyamide aqueous dispersion nanospheres are as follows:

[0140] Aramid aqueous dispersion nanospheres: 12 wt%;

[0141] Ceramic particles: 25 wt%;

[0142] Binder: 7 wt%;

[0143] Second dispersant: 2.5 wt%;

[0144] Wetting agent: 1.5 wt%;

[0145] Deionized water: 52 wt%.

[0146] Preparation of the coating slurry of aramid aqueous dispersion nanospheres: According to the formulation composition, add deionized water, alumina, water-based polyacrylate, ammonium polyacrylate, and fatty alcohol polyoxyethylene ether to the stirring tank in sequence, and carry out grinding and dispersion to obtain a mixed solution, where the grinding time is 10 min. Then add the water system of 20% solid content aramid aqueous dispersion nanospheres to the mixed solution, and stir and mix at a rotation speed of 1,000 rpm for 30 min to obtain a coating slurry of aramid aqueous dispersion nanospheres with a solid content of 48%;

[0147] (3)Coat the obtained coating slurry of aramid aqueous dispersion nanospheres on both sides of the base film, and obtain a lithium battery coating separator after shaping and drying. The thickness of the lithium battery coating separator is 10 μm.

[0148] Example 7

[0149] (1)Preparation of aramid water-dispersed nano-microspheres: Dissolve 20 g of m-phenylenediamine monomer, 5.57 g of dispersant PVP, and 32.72 g of acid-binding agent 2-methylpyridine in 210 g of deionized water to obtain an aqueous phase system. Dissolve 35.71 g of isophthaloyl chloride monomer in 105 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 5000 rpm, slowly add the oil phase system to the aqueous phase system at a rate of 65 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, aramid water-dispersed nano-microspheres with a solid content of 20% can be obtained.

[0150] (2)The contents of each component of the slurry for coating aromatic polyamide water-dispersed nano-microspheres are as follows:

[0151] Aramid water-dispersed nano-microspheres: 20 wt%;

[0152] Ceramic particles: 20 wt%;

[0153] Binder: 8 wt%;

[0154] Second dispersant: 2 wt%;

[0155] Wetting agent: 1 wt%;

[0156] Deionized water: 49 wt%.

[0157] Preparation of the slurry for coating aramid water-dispersed nano-microspheres: According to the formula composition, add deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate, and modified succinic acid to the stirring tank in sequence, and carry out grinding and dispersion to obtain a mixed solution, where the grinding time is 30 min. Then add the aqueous system of aramid water-dispersed nano-microspheres with a solid content of 20% to the mixed solution, and stir and mix at a speed of 1000 rpm for 30 min to obtain a slurry for coating aramid water-dispersed nano-microspheres with a solid content of 51%;

[0158] (3)Coat the obtained slurry for coating aramid water-dispersed nano-microspheres on both sides of the base film, and obtain a lithium battery coated separator after shaping and drying. The thickness of the lithium battery coated separator is 10 μm.

[0159] Example 8

[0160] (1)Preparation of aramid water-dispersed nano-microspheres: 20 g of m-phenylenediamine monomer, 8.35 g of dispersant PVP, and 32.72 g of acid-binding agent 2-methylpyridine were dissolved in 210 g of deionized water to obtain an aqueous phase system. 35.71 g of isophthaloyl chloride monomer was dissolved in 105 g of chloroform to obtain an oil phase system. The oil phase system was slowly added to the aqueous phase system under the condition of high-speed homogenization at 5000 rpm, and the addition rate of the oil phase system was 65 g / min. Homogeneous reaction was carried out at 5 °C for 2 h to obtain white solid powder. After three times of filtration, washing, and formulation, aramid water-dispersed nano-microspheres with a solid content of 20% could be obtained.

[0161] (2)The contents of each component of the aromatic polyamide water-dispersed nano-microsphere coating slurry are as follows:

[0162] Aramid water-dispersed nano-microspheres: 20 wt%;

[0163] Ceramic particles: 20 wt%;

[0164] Binder: 8 wt%;

[0165] Second dispersant: 2 wt%;

[0166] Wetting agent: 1 wt%;

[0167] Deionized water: 49 wt%.

[0168] Preparation of aramid water-dispersed nano-microsphere coating slurry: According to the formula composition, deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate, and modified succinic acid were sequentially added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 18 min. Then, an aqueous system of aramid water-dispersed nano-microspheres with a solid content of 20% was added to the mixed solution, and stirring and mixing were carried out at a rotation speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano-microsphere coating slurry with a solid content of 51%;

[0169] (3)The obtained aramid water-dispersed nano-microsphere coating slurry was coated on both sides of the base film, and a lithium battery coating separator was obtained after shaping and drying. The thickness of the lithium battery coating separator was 10 μm.

[0170] Example 9

[0171] (1)Preparation of aramid water-dispersed nano-microspheres: Dissolve 20 g of m-phenylenediamine monomer, 2.79 g of the first dispersant PVP, and 32.72 g of the acid-binding agent 2-methylpyridine in 210 g of deionized water to obtain an aqueous phase system. Dissolve 35.71 g of isophthaloyl chloride monomer in 105 g of chloroform to obtain an oil phase system. Slowly add the oil phase system to the aqueous phase system under the condition of high-speed homogenization at 5000 rpm. The addition rate of the oil phase system is 100 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, aramid water-dispersed nano-microspheres with a solid content of 20% can be obtained.

[0172] (2)The contents of the components for preparing the aramid water-dispersed nano-microsphere coating slurry are as follows:

[0173] Aramid water-dispersed nano-microspheres: 20 wt%;

[0174] Ceramic particles: 20 wt%;

[0175] Binder: 8 wt%;

[0176] Second dispersant: 2 wt%;

[0177] Wetting agent: 1 wt%;

[0178] Deionized water: 49 wt%.

[0179] Preparation of aramid water-dispersed nano-microsphere coating slurry: According to the formula composition, sequentially add deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate, and modified succinic acid to a stirring tank, and carry out grinding and dispersion to obtain a mixed solution, where the grinding time is 40 min. Then add the aqueous system of 20% solid content aramid water-dispersed nano-microspheres to the mixed solution, and stir and mix at a rotation speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano-microsphere coating slurry with a solid content of 51%;

[0180] (3)Coat the obtained aramid water-dispersed nano-microsphere coating slurry on both sides of the base film, and obtain a lithium battery coated separator after shaping and drying. The thickness of the lithium battery coated separator is 10 μm.

[0181] Example 10

[0182] (1)Preparation of aramid aqueous dispersion nano - microspheres: Dissolve 20 g of 4,4 - diamino - diphenyl ether monomer, 2.02 g of the first dispersant PVA, and 27.41 g of the acid - binding agent calcium hydroxide in 336 g of deionized water to obtain an aqueous phase system. Dissolve 20.3 g of terephthaloyl chloride monomer in 168 g of chloroform to obtain an oil - phase system. Under the condition of high - speed homogenization at 6000 rpm, slowly add the oil - phase system to the aqueous phase system at a rate of 75 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three - time filtration, washing, and formulation, 20% solid - content aramid aqueous dispersion nano - microspheres can be obtained.

[0183] (2)The contents of each component of the aramid - based polyamide aqueous dispersion nano - microsphere coating slurry are as follows:

[0184] Aramid aqueous dispersion nano - microspheres: 8 wt%;

[0185] Ceramic particles: 20 wt%;

[0186] Binder: 2 wt%;

[0187] Second dispersant: 0.5 wt%;

[0188] Wetting agent: 0.5 wt%;

[0189] Deionized water: 69 wt%.

[0190] Preparation of aramid aqueous dispersion nano - microsphere coating slurry: According to the formulation composition, add deionized water, silica, water - borne polyacrylate, sodium polyacrylate, and polyether - modified silicone to the stirring tank in sequence, and carry out grinding and dispersion to obtain a mixed solution, where the grinding time is 60 min. Then add the aqueous system of 20% solid - content aramid aqueous dispersion nano - microspheres to the mixed solution, and stir and mix at a speed of 1000 rpm for 30 min to obtain an aramid aqueous dispersion nano - microsphere coating slurry with a solid content of 31%.

[0191] (3)Coat the obtained aramid aqueous dispersion nano - microsphere coating slurry on both sides of the base film, and obtain a lithium - ion battery coating separator after shaping and drying. The thickness of the lithium - ion battery coating separator is 10 μm.

[0192] Comparative Example 1

[0193] Prepare a lithium - ion battery coating separator by the same method as in Example 6, except that: the aramid aqueous dispersion nano - microspheres are not added to the coating slurry in this Comparative Example 1. The specific process is as follows:

[0194] (1)The contents of each component of the coating slurry are as follows:

[0195] Ceramic particles: 37 wt%;

[0196] Binder: 7 wt%;

[0197] Second dispersant: 2.5 wt%

[0198] Wetting agent: 1.5 wt%

[0199] Deionized water: 52 wt%

[0200] Preparation of aramid aqueous dispersion nano microsphere coating slurry: According to the formula composition, deionized water, alumina, waterborne polyacrylate, ammonium polyacrylate and fatty alcohol polyoxyethylene ether are added to the stirring tank in sequence, and grinding and dispersion are carried out to obtain a mixed solution, where the grinding time is 10 min, and then stirring and mixing are carried out at a speed of 1000 rpm for 30 min to obtain a coating slurry with a solid content of 48%.

[0201] (3) The obtained coating slurry is coated on both sides of the base film, and after shaping and drying, a lithium battery coated separator is obtained, and the thickness of the lithium battery coated separator is 10 μm.

[0202] Comparative Example 2

[0203] A lithium battery coated separator is prepared by the same method as in Example 6, except that: ceramic particles are not added to the coating slurry of this Comparative Example 1, and the specific process is as follows:

[0204] (1) Preparation of aramid aqueous dispersion nano microspheres: 20 g of m-phenylenediamine monomer, 2.84 g of the first dispersant PVA and 33.75 g of the acid-binding agent 2-methylpyridine are dissolved in 379 g of deionized water to obtain an aqueous phase system, and 36.84 g of isophthaloyl chloride monomer is dissolved in 189 g of chloroform to obtain an oil phase system. The oil phase system is slowly added to the aqueous phase system under the condition of high-speed homogenization at 10000 rpm, the addition speed of the oil phase system is 100 g / min, and a homogeneous reaction is carried out at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing and formulation, 20% solid content aramid aqueous dispersion nano microspheres can be obtained.

[0205] (2) The contents of each component for preparing the aromatic polyamide aqueous dispersion nano microsphere coating slurry are as follows:

[0206] Aramid aqueous dispersion nano microspheres: 37 wt%

[0207] Binder: 7 wt%

[0208] Second dispersant: 2.5 wt%

[0209] Wetting agent: 1.5 wt%

[0210] Deionized water: 52 wt%

[0211] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the formula composition, deionized water, water-based polyacrylate, ammonium polyacrylate, and fatty alcohol polyoxyethylene ether were successively added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 10 min. Then, an aqueous system of aramid water-dispersed nano microspheres with a solid content of 20% was added to the mixed solution, and stirring and mixing were carried out at a speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 48%.

[0212] (3)Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and after shaping and drying, a lithium battery coated separator is obtained. The thickness of the lithium battery coated separator is 10 μm.

[0213] Comparative Example 3

[0214] A lithium battery coated separator was prepared by the same method as in Example 1, except that: the amount of the first dispersant added was reduced (in this Comparative Example 3, the added mass of the first dispersant was 3% of the total mass of the diamine monomer and the dichloride monomer, which was lower than the dosage defined in the present invention). The specific preparation process is as follows:

[0215] (1)Preparation of aramid water-dispersed nano microspheres: Dissolve 20 g of m-phenylenediamine monomer, 1.67 g of the first dispersant PVP, and 32.72 g of the acid-binding agent 2-methylpyridine in 210 g of deionized water to obtain an aqueous phase system. Dissolve 35.71 g of isophthaloyl chloride monomer in 105 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 5000 rpm, slowly add the oil phase system to the aqueous phase system at a rate of 65 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing, and formulation, aramid water-dispersed nano microspheres with a solid content of 20% can be obtained.

[0216] (2)The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0217] Aramid water-dispersed nano microspheres: 20 wt%;

[0218] Ceramic particles: 20 wt%;

[0219] Binder: 8 wt%;

[0220] Second dispersant: 2 wt%;

[0221] Wetting agent: 1 wt%;

[0222] Deionized water: 49 wt%.

[0223] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the composition, deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate and modified succinic acid were successively added to a stirring tank, and ground and dispersed to obtain a mixed solution, where the grinding time was 40 min. Then, an aqueous system of aramid water-dispersed nano microspheres with a solid content of 20% was added to the mixed solution, and stirred and mixed at a speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 51%.

[0224] (3)Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and obtain a lithium battery coated separator after shaping and drying. The thickness of the lithium battery coated separator is 10 μm.

[0225] Comparative Example 4

[0226] A lithium battery coated separator was prepared by the same method as in Example 1, except that: the type of the first dispersant was changed (in this Comparative Example 4, sodium dodecyl sulfate was used as the first dispersant). The specific preparation process is as follows:

[0227] (1)Preparation of aramid water-dispersed nano microspheres: Dissolve 20 g of m-phenylenediamine monomer, 2.79 g of the first dispersant sodium dodecyl sulfate and 32.72 g of the acid-binding agent 2-methylpyridine in 210 g of deionized water to obtain an aqueous phase system. Dissolve 35.71 g of isophthaloyl chloride monomer in 105 g of chloroform to obtain an oil phase system. Under the condition of high-speed homogenization at 5000 rpm, slowly add the oil phase system to the aqueous phase system at a rate of 65 g / min, and carry out a homogenization reaction at 5 °C for 2 h to obtain a white solid powder. After three times of filtration, washing and preparation, aramid water-dispersed nano microspheres with a solid content of 20% can be obtained.

[0228] (2)The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0229] Aramid water-dispersed nano microspheres: 20 wt%;

[0230] Ceramic particles: 20 wt%;

[0231] Binder: 8 wt%;

[0232] Second dispersant: 2 wt%;

[0233] Wetting agent: 1 wt%;

[0234] Deionized water: 49 wt%.

[0235] Preparation of aramid water-dispersed nano microsphere coating slurry: According to the composition, deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate and modified succinic acid were successively added to a stirring tank, and grinding and dispersion were carried out to obtain a mixed solution, where the grinding time was 40 min. Then, an aqueous system of aramid water-dispersed nano microspheres with a solid content of 20% was added to the mixed solution, and stirring and mixing were carried out at a rotation speed of 1000 rpm for 30 min to obtain an aramid water-dispersed nano microsphere coating slurry with a solid content of 51%.

[0236] (3)Coat the obtained aramid water-dispersed nano microsphere coating slurry on both sides of the base film, and after shaping and drying, a lithium battery coated separator is obtained, and the thickness of the lithium battery coated separator is 10 μm.

[0237] Comparative Example 5

[0238] A lithium battery coated separator was prepared by the same method as in Example 1, except that: in this Comparative Example 5, aramid nano microspheres were prepared by a conventional polymerization method, and the specific process was as follows:

[0239] (1)Preparation of aramid nano microspheres:

[0240] Dissolve 20 g of m-phenylenediamine monomer in DMAC, and add terephthaloyl chloride monomer in two batches for polymerization reaction. The total addition amount of terephthaloyl chloride monomer is 35.71 g. Control the polymerization reaction temperature at 5 °C and the stirring speed at 800 rpm. After the reaction is completed, carry out neutralization treatment and filter to remove unreacted reagents to obtain a polymerization stock solution with a solid content of 16%.

[0241] Mix the polymerization stock solution and water according to a mass ratio of 1:10, carry out high-speed shearing (5000 rpm) in a precipitation device, and after washing, aramid nano microspheres are obtained. After formulation, aramid nano microspheres with a solid content of 20% can be obtained.

[0242] (2)The contents of the components for preparing the aromatic polyamide water-dispersed nano microsphere coating slurry are as follows:

[0243] Aramid nano microspheres: 20 wt%;

[0244] Ceramic particles: 20 wt%;

[0245] Binder: 8 wt%;

[0246] Second dispersant: 2 wt%;

[0247] Wetting agent: 1 wt%;

[0248] Deionized water: 49 wt%.

[0249] Preparation of aramid nanofiber microsphere coated slurry: According to the composition, deionized water, alumina, modified polyacrylic acid, ammonium polyacrylate and modified succinic acid were successively added to a stirring tank, and ground and dispersed to obtain a mixed solution, where the grinding time was 40 min. Then, an aqueous system of aramid nanofiber microspheres with a solid content of 20% was added to the mixed solution, and stirred and mixed at a speed of 1000 rpm for 30 min to obtain an aramid nanofiber microsphere coated slurry with a solid content of 51%.

[0250] (3)The obtained aramid nanofiber microsphere coated slurry was coated on both sides of the base film, and after shaping and drying, a lithium battery coated separator was obtained, and the thickness of the lithium battery coated separator was 10 μm.

[0251] The aramid aqueous dispersed nanofibers and lithium battery coated separators prepared in the above examples and comparative examples were tested for performance indicators. The specific test results are shown in Table 1 below. The test methods involved are as follows:

[0252] The particle size distribution of aramid aqueous dispersed nanofibers was tested according to the standard GB / T 19077-2016;

[0253] The thermal stability of aramid aqueous dispersed nanofibers was tested according to the standard GB / T 33047.1-2016;

[0254] The air permeability of the coated separator was tested according to the standard GB / T 36363-2018;

[0255] The thermal shrinkage performance of the coated separator was tested at 150 °C according to the standard GB / T 2027-2004;

[0256] The liquid absorption rate of the coated separator can be tested with reference to the standard QB / T 2303.11-2008 "Battery Separating Paper - Part 11: Determination of Liquid Absorption Rate".

[0257] Table 1 Performance test data

[0258]

[0259] It can be seen from the above table data that: The aramid aqueous dispersed nanofibers prepared by the preparation method described in the present invention in Examples 1-10 have the advantages of controllable particle size, uniform particle size distribution, and good thermal stability, and can be stably dispersed in water. When used in combination with ceramic particles in a lithium battery coated separator, a water-based aramid coated separator with a relatively high film-breaking temperature, low thermal shrinkage, and good electrolyte wettability can be prepared, and the problem of powder falling off of the coated separator can be solved. In addition, the preparation process is simple and can be widely applied to industrial production. Figure 1 Figure 32 shows the scanning electron microscope image of the aramid aqueous dispersed microspheres prepared in Example 6. From Figure 1It can be seen that the aramid water-dispersed microspheres prepared by the preparation method of the present invention have good dispersibility and uniform particle size distribution; Figure 2 is the thermogravimetric curve of the aramid water-dispersed microspheres prepared in Example 6. It can be seen from Figure 2 that the initial decomposition temperature of the aramid nano-microspheres is higher than 430 °C, and the microspheres have good thermal stability, which can meet the application requirements of lithium battery coating diaphragms; Figure 3 is the scanning electron micrograph of the lithium battery coating diaphragm prepared in Example 6. It can be seen from Figure 3 that the aramid water-dispersed nano-microspheres and ceramics are uniformly mixed and dispersed on the surface of the base film, and the film surface is flat.

[0260] It can be seen from the data of Example 1, Example 7, and Example 8 that: for the preparation method of the aramid water-dispersed nano-microspheres of the present invention, the particle size of the aramid water-dispersed nano-microspheres can be controlled by adjusting the addition amount of the first dispersant. It is more conducive to actual production applications, provides very clear guidance for the production of nano-microspheres with target particle sizes, and improves production efficiency.

[0261] It can be seen from the comparison of the data of Example 9 and Example 1 that: in Example 1, the high-speed homogenization speed and the addition speed of the oil phase system cooperate with each other, which is more conducive to obtaining aramid water-dispersed nano-microspheres with higher particle size uniformity.

[0262] It can be seen from the comparison of the data of Example 10 and Example 3 that: when the grinding time and the particle size of the aramid water-dispersed nano-microspheres match each other, it is more conducive to obtaining a lithium battery coating diaphragm with excellent performance.

[0263] It can be seen from the comparison of the data of Comparative Example 1, 2 and Example 6 that: in the coating slurry, the aramid water-dispersed nano-microspheres and ceramic particles need to cooperate synergistically to prepare a lithium battery coating diaphragm with more excellent performance. If the aramid water-dispersed nano-microspheres are not added, it is found in the experiment that the diaphragm is prone to powder falling, and the liquid absorption rate will be reduced, thus affecting the electrolyte wettability of the diaphragm. If the ceramic particles are not added, the thermal shrinkage of the diaphragm will be reduced, affecting the high-temperature resistance of the diaphragm.

[0264] It can be seen from the comparison of the data of Comparative Example 3 and Example 1 that: if the addition amount of the first dispersant is reduced, the emulsification will be uniform, resulting in an increase in the particle size and uneven distribution of the water-dispersed microspheres.

[0265] It can be seen from the comparison of the data of Comparative Example 4 and Example 1 that: if sodium dodecyl sulfate is used as the first dispersant, a stable emulsion structure cannot be formed, resulting in uneven particle size distribution. Therefore, using the first dispersant defined in the present invention is more conducive to obtaining aramid water-dispersed nano-microspheres with uniform particle size distribution by interfacial polymerization, and finally obtaining a lithium battery coating diaphragm with excellent performance.

[0266] From the data comparison between Comparative Example 5 and Example 1, it can be seen that: by means of interfacial polymerization, the present invention is more conducive to preparing aramid nanofiber aqueous dispersion microspheres with a large specific surface area, and the microsphere particle size is controllable, the thermal stability is good, and they can be stably dispersed in water, which is more conducive to being applied in lithium battery separators, can greatly improve the liquid absorption rate of the separators, and the preparation process is simple and the raw materials are simple, and it can be widely applied in industrialization. Moreover, from Figure 1 and Figure 5 It can also be clearly seen from the comparison that the aramid nanofiber aqueous dispersion microspheres obtained by the preparation method described in the present invention are more uniform.

[0267] In addition, the lithium battery coated separators prepared in Example 1 and Example 6 were assembled into lithium batteries respectively with two commonly used commercially available lithium battery separators by the same method, and the battery performance tests were carried out.

[0268] The battery performance test results are as Figure 4 shown. From Figure 4 the comparison of the battery performance tests between the two commonly used commercially available lithium battery separators and the lithium battery coated separators prepared in Example 1 and Example 6, it can be seen that: when the separators of Example 1 and Example 6 prepared by the preparation method of the present invention are applied to the batteries, the rate performance, high and low temperature rate and cycle performance of the batteries are all improved.

[0269] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, all possible combinations of the 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 as the scope recorded in this specification.

[0270] 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 aramid water-dispersible nanospheres, characterized in that: The preparation method of the aramid water-dispersible nano-microspheres is as follows: The diamine monomer, the first dispersant and the acid binding agent are dissolved in deionized water to obtain an aqueous phase system, and the diformyl chloride monomer is dissolved in chloroform to obtain an oil phase system; the added mass of the first dispersant is 4%-15% of the total mass of the diamine monomer and the diformyl chloride monomer; the first dispersant is at least one of polyvinyl pyrrolidone and polyvinyl alcohol; The oil phase system is slowly added to the water phase system under high-speed homogenization conditions, and a polymerization reaction is carried out under high-speed homogenization conditions to obtain a polymer. Finally, after solid-liquid separation, water washing and blending, the water system of the aramid water-dispersible nano-microspheres can be obtained; the speed of the high-speed homogenization is 2000rpm-10000rpm.

2. The method for preparing aramid water-dispersible nanospheres according to claim 1, characterized in that: The diamine monomer is at least one of p-phenylenediamine, m-phenylenediamine and 4,4-diaminodiphenyl ether; The diphthaloyl chloride monomer is at least one of terephthaloyl chloride and isophthaloyl chloride; The acid binding agent is at least one of 2-methylpyridine, calcium hydroxide and sodium carbonate.

3. The method for preparing aramid water-dispersible nanospheres according to claim 1, characterized in that: The molar ratio of the diformyl chloride monomer to the diamine monomer is (0.95-1.05):1; The solid content of the polymer is 5-15wt%.

4. A slurry for coating aramid water-dispersible nano-microspheres, characterized in that: The coating slurry comprises, by weight: 8-20 parts of aramid water-dispersible nano-microspheres, 20-40 parts of ceramic particles, 2-8 parts of a binder, 0.5-4 parts of a second dispersant, 0.5-2 parts of a wetting agent, and 26-69 parts of deionized water; The aramid water-dispersible nanospheres are prepared according to the preparation method described in any one of claims 1 to 3.

5. The aramid water-dispersible nano-microsphere coating slurry according to claim 4, characterized in that: The particle size of the aramid water-dispersible nano-microspheres is 60-400 nm; The particle size of the ceramic particles is 100-800nm.

6. The aramid water-dispersible nano-microsphere coating slurry according to claim 4, characterized in that: The ceramic particles are at least one of alumina, silica, and boehmite; The binder is at least one of waterborne polyacrylate and modified polyacrylic acid; The second dispersant is at least one of ammonium polyacrylate, sodium polyacrylate, and styrene-maleic anhydride ester; The wetting agent is at least one of polyether-modified siloxane, fatty alcohol polyoxyethylene ether and modified succinic acid.

7. A method for preparing the aramid water-dispersible nano-microsphere coating slurry according to any one of claims 4 to 6, characterized in that: The preparation method of the coating slurry is: Deionized water, a second dispersant, ceramic particles and a wetting agent are ground and dispersed to obtain a mixed solution, and then a water system of aramid water-dispersible nano-microspheres is added to the mixed solution, and the mixture is stirred and mixed at a speed of 1000-1200 rpm to obtain a aramid water-dispersible nano-microsphere coating slurry.

8. A lithium battery coated diaphragm, characterized in that: The aramid water-dispersible nano-microsphere coating slurry described in any one of claims 4 to 6 is coated on both sides of the base film, and the lithium battery coated diaphragm is obtained after shaping and drying.

Images