Ultrathin high-temperature-resistant ceramic coating diaphragm and preparation method thereof

Abstract

The invention discloses an ultrathin high-temperature-resistant ceramic coating diaphragm and a preparation method thereof.The ultrathin high-temperature-resistant ceramic coating diaphragm comprises a base membrane and a coating on the base membrane, the coating is obtained by coating slurry, and the method for preparing the slurry comprises the steps that nano ceramic, a solution containing a modified organic binder, a dispersing agent, a functional auxiliary agent and third water are mixed to be uniform, and the slurry is obtained; the functional auxiliary agent is a mixture of carbomer and hydroxypropyl methyl cellulose; the method for preparing the solution containing the modified organic binder comprises the following steps: uniformly mixing an acrylate monomer, an organic silicon monomer, an emulsifier and first water at room temperature to obtain a pre-emulsion; and mixing a part of the pre-emulsion with second water, adding an initiator, dropwise adding the residual pre-emulsion at a constant speed, and adding a cross-linking agent to obtain a solution containing the modified organic binder. The ultrathin high-temperature-resistant ceramic coating diaphragm disclosed by the invention has relatively low hole closing temperature and relatively good heat resistance and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to an ultra-thin high-temperature resistant ceramic-coated separator and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, the requirements for energy density and safety performance of power batteries and energy storage batteries are constantly increasing. As a key component of the battery, the performance of the separator directly affects the battery's cycle life and safe service capability. Although the mainstream polyolefin separators (such as polyethylene membranes and polypropylene membranes) have good ion conductivity and mechanical strength, their high-temperature resistance is poor. When the battery experiences thermal runaway, the separator is prone to melting and shrinkage, leading to a short circuit between the positive and negative electrodes, which can cause safety accidents such as fires and explosions.

[0003] To improve the high-temperature resistance of polyolefin separators, those skilled in the art generally coat the polyolefin separator with a coating slurry to form a ceramic coating, thus obtaining a ceramic-coated separator. However, this modification method has two major problems: First, the coating slurry has poor stability, and the ceramic particles in the coating slurry are prone to agglomeration, resulting in insufficient coating density and easy shrinkage at high temperatures; Second, the coating is too thick. To improve heat resistance, the thickness of the ceramic coating in the prior art is generally set at 2~5μm. However, an excessively thick coating will significantly increase the interfacial impedance of the separator, hinder rapid ion transport, increase the internal resistance of the battery, and reduce the energy density of the battery.

[0004] Therefore, developing a ceramic-coated separator with a thin coating that combines high temperature resistance and adhesion is key to obtaining high-energy-density batteries. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an ultra-thin high-temperature resistant ceramic coating diaphragm.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned ultrathin high-temperature resistant ceramic coating diaphragm.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] An ultrathin high-temperature resistant ceramic-coated diaphragm includes: a base membrane and a coating on the base membrane, wherein the coating is obtained by coating with a slurry. The method for preparing the slurry includes: mixing nano-ceramics, a solution containing a modified organic binder, a dispersant, a functional additive, and a third water until homogeneous to obtain the slurry, wherein the functional additive is a mixture of carbomer and hydroxypropyl methylcellulose (HPMC).

[0009] A method for preparing a solution containing a modified organic binder includes: mixing acrylate monomers, organosilicon monomers, emulsifiers, and first water at room temperature until homogeneous to obtain a pre-emulsion; mixing a portion of the pre-emulsion (70-80 wt% of the total mass of the pre-emulsion) with second water, keeping the mixture at 75-80°C for 8-12 minutes, adding an initiator, keeping the mixture at 75-80°C for 5-15 minutes, uniformly adding the remaining pre-emulsion (dropping rate 2-3 mL / min), continuing to keep the mixture at 75-80°C for 2-3 hours after the addition is complete, cooling the mixture to 50-60°C, adding a crosslinking agent, and keeping the mixture at 75-80°C for 30-45 minutes to obtain a solution containing a modified organic binder.

[0010] In the method for preparing a solution containing a modified organic binder, the ratio of acrylate monomer, organosilicon monomer, emulsifier, first water, second water, initiator and crosslinking agent by mass parts is (25~35):(5~10):(1~2):(30~40):(20~30):(0.3~0.6):(0.5~1).

[0011] In the method for preparing a solution containing a modified organic binder, the organosilicon monomer is at least one of γ-methacryloyloxypropyltrimethoxysilane and vinyltrimethoxysilane.

[0012] In the method for preparing a solution containing a modified organic binder, the initiator is ammonium persulfate.

[0013] In the method for preparing a solution containing a modified organic binder, the crosslinking agent is an aziridine crosslinking agent.

[0014] In the method for preparing a solution containing a modified organic binder, the emulsifier is one or a mixture of two of sodium dodecyl sulfate (SDS) and nonylphenol polyoxyethylene ether (NP-10).

[0015] In the above technical solution, the ratio of carbomer to hydroxypropyl methylcellulose (HPMC) by mass parts is (0.5~2):(1~3).

[0016] In the above technical solution, the ratio of nano-ceramics, solution containing modified organic binder, dispersant, functional additive and third water by mass parts is (5~30): (5~10): (0.1~1): (0.5~3): (55~88).

[0017] In the above technical solution, the viscosity of the slurry is 300~800 mPa·s (25℃).

[0018] In the above technical solution, the dispersant is a polycarboxylate.

[0019] In the above technical solution, the nanoceramic is nano-alumina.

[0020] In the above technical solution, the method for preparing the slurry includes the following steps:

[0021] Step 1: Mix the functional additive and the third water until homogeneous to obtain the first system;

[0022] In step 1, the functional additive and the third water are mixed and stirred until homogeneous. The stirring speed is 300~500 rpm, and the stirring time is 15~20 min.

[0023] Step 2: Mix the first system, the solution containing the modified organic binder, and the dispersant until homogeneous to obtain the second system;

[0024] In step 2, the first system, the solution containing the modified organic binder, and the dispersant are mixed and stirred until homogeneous. The stirring speed is 500~800 rpm, and the stirring time is 10~20 min.

[0025] Step 3: Mix the second system and the nano-ceramics until homogeneous to obtain a slurry.

[0026] In step 3, the second system and the nano-ceramic are mixed, stirred, and then sonicated until homogeneous. The stirring speed is 1500~2000 rpm, the stirring time is 1~2 h, the sonication power is 300~500 W, and the sonication time is 30~60 min.

[0027] The preparation method of the above-mentioned ultrathin high-temperature resistant ceramic coating diaphragm includes: coating a slurry onto a base membrane, drying it, obtaining a coating on the base membrane, and obtaining an ultrathin high-temperature resistant ceramic coating diaphragm.

[0028] In the above technical solution, the thickness of the coating on one side is 1~1.5μm.

[0029] In the above technical solution, the coating method is one of microgravure coating and slot extrusion coating.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention selects nano-alumina as the main filler. Its excellent nanoscale monodispersity enables it to be uniformly dispersed in the slurry. At the same time, carbomer, with its three-dimensional network gel structure and high thixotropy, can further enhance the steric hindrance effect between nano-alumina particles and inhibit particle agglomeration. Hydroxypropyl methylcellulose plays an excellent role in film formation and interfacial adhesion, promoting the tight bonding between nano-alumina particles and the base membrane surface. Under the synergistic effect, nano-alumina constructs a three-dimensional rigid heat-resistant skeleton with low porosity, dense structure and uniformity on the base membrane surface. This three-dimensional rigid heat-resistant skeleton can effectively improve the thermal stability of the diaphragm and prevent the diaphragm from shrinking at high temperature.

[0032] 2. The method for preparing a solution containing a modified organic binder in this invention uses water as the dispersion medium, completely eliminating the organic solvent system relied upon in traditional binder preparation, thus eliminating VOC emissions and pollution at the source. Simultaneously, through the copolymerization reaction of acrylate monomers and organosilicon monomers, siloxane bonds are introduced into the polymer backbone. These siloxane bonds can further crosslink at high temperatures, forming an inorganic-organic hybrid network, endowing the coating with excellent high-temperature resistance. The molecular structure of the modified organic binder simultaneously has an affinity for both polar inorganic ceramic particles and non-polar base film, forming a strong chemical bond and physical anchor at the interface, solving the industry pain point of easy peeling of traditional coatings. Attached Figure Description

[0033] Figure 1 SEM image of the ultrathin high-temperature resistant ceramic coating membrane prepared in Example 1. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0035] Nano-alumina: white powder, D50=300nm.

[0036] Polycarboxylate: Purchased from Jiangsu Nantong Congyuan Chemical Co., Ltd., model number 5040.

[0037] Carbomer: Purchased from Hubei Xindesheng Materials Technology Co., Ltd., model number 941.

[0038] Aziridine crosslinking agent: purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., model P-350.

[0039] The base film is a polyethylene (PE) film with a thickness of 7μm, but other thicknesses can also be used.

[0040] Closed-pore temperature: Tested using a diaphragm closed-pore rupture tester. The specific test method is as follows: the diaphragm is cut into 40mm*40mm samples, soaked (i.e., wetted) with electrolyte, and heated from room temperature at a rate of 5℃ / min. The resistance during the heating process is measured, and the temperature at which the resistance suddenly increases to 1000 Ω is recorded as the closed-pore temperature. Electrolyte: The electrolyte is a mixture of electrolyte and solvent. The electrolyte is LiPF6, with a concentration of 1M. The solvent is a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1.

[0041] The acrylate monomer is methyl acrylate.

[0042] Example 1

[0043] A method for preparing an ultrathin high-temperature resistant ceramic-coated separator includes: coating a slurry onto a base film using a microgravure coating method, drying at 60°C for 1 min, and obtaining a coating with a single-sided thickness of 1.5 μm on the base film, thus obtaining an ultrathin high-temperature resistant ceramic-coated separator. The method for preparing the slurry includes the following steps:

[0044] Step 1: Mix the functional additive and the third water, and stir at 500 rpm for 20 minutes at room temperature until homogeneous to obtain the first system. The functional additive is a mixture of carbomer and hydroxypropyl methylcellulose (HPMC). By mass, the ratio of carbomer to hydroxypropyl methylcellulose (HPMC) is 1:2.

[0045] Step 2: Mix the first system, the solution containing the modified organic binder, and the dispersant, and stir at 800 rpm for 10 minutes at room temperature until homogeneous to obtain the second system, wherein the dispersant is a polycarboxylate.

[0046] A method for preparing a solution containing a modified organic binder includes: mixing acrylate monomers, organosilicon monomers, emulsifiers, and first water at room temperature until homogeneous to obtain a pre-emulsion; mixing a portion of the pre-emulsion (80 wt% of the total mass of the pre-emulsion) with the second water, incubating at 75°C for 10 minutes, adding an initiator (for initiating the copolymerization of acrylate monomers and organosilicon monomers), incubating at 75°C for 10 minutes, and then uniformly adding the remaining 20 wt% of the pre-emulsion to the system at a dropping rate of 3 mL / min. After the dropping is completed, continue... The mixture was kept at 75℃ for 2 hours, then cooled to 50℃, and a crosslinking agent was added. The mixture was then kept at 75℃ for 30 minutes to obtain a solution containing the modified organic binder. The mass ratio of acrylate monomer, organosilicon monomer, emulsifier, primary water, secondary water, initiator, and crosslinking agent was 30:7:1.5:38:25:0.5:0.6. The organosilicon monomer was γ-methacryloyloxypropyltrimethoxysilane, the initiator was ammonium persulfate, the crosslinking agent was an aziridine crosslinking agent, and the emulsifier was sodium dodecyl sulfate (SDS). The preparation of the solution containing the modified organic binder was carried out under stirring conditions at a speed of 1000 rpm.

[0047] Step 3: Mix the second system with nano-ceramics (nano-alumina), stir at room temperature and then sonicate until homogeneous (stirring speed is 2000 rpm, stirring time is 1 h, sonication power is 300 W, sonication time is 30 min) to obtain a slurry with a viscosity of 500 mPa·s (25℃).

[0048] The ratio of nano-ceramics, solution containing modified organic binder, dispersant, functional additives and third water by mass parts is 20:6:0.3:1:60.

[0049] Example 2

[0050] The preparation method of an ultrathin high-temperature resistant ceramic coating membrane is basically the same as that in Example 1, except that the ratio of "by mass parts, nano-ceramics, solution containing modified organic binder, dispersant, functional additives and third water is 20:6:0.3:1:60" is replaced with "by mass parts, nano-ceramics, solution containing modified organic binder, dispersant, functional additives and third water is 10:9:0.3:1:60".

[0051] Example 3

[0052] The preparation method of an ultrathin high-temperature resistant ceramic coating membrane is basically the same as that in Example 1, except that "the organosilicon monomer is γ-methacryloyloxypropyltrimethoxysilane" is replaced with "the organosilicon monomer is vinyltrimethoxysilane".

[0053] Comparative Example 1

[0054] A method for preparing a ceramic-coated diaphragm is basically the same as that in Example 1, except that no functional additives are added. The viscosity of the slurry prepared in Comparative Example 1 is 380 mPa·s (25°C). Local sagging occurred during coating, and the coating cracked slightly after drying.

[0055] Comparative Example 2

[0056] A method for preparing a ceramic-coated diaphragm is basically the same as in Example 1, except that the ratio of "by mass parts, nano-ceramics, solution containing modified organic binder, dispersant, functional additives and third water is 20:6:0.3:1:60" is replaced with "by mass parts, nano-ceramics, solution containing modified organic binder, dispersant, functional additives and third water is 10:9:0.3:6:60". The viscosity of the slurry prepared in Comparative Example 2 is 850 mPa·s (25℃), which is too thick. During coating, the slurry has poor fluidity, and bubbles and scratches appear on the coating.

[0057] Comparative Example 3

[0058] A method for preparing a ceramic-coated diaphragm is basically the same as in Example 1, except that "the functional additive is a mixture of carbomer and hydroxypropyl methylcellulose (HPMC)" is replaced with "the functional additive is carbomer". That is, hydroxypropyl methylcellulose (HPMC) was not introduced in Comparative Example 3.

[0059] Comparative Example 4

[0060] A method for preparing a ceramic-coated diaphragm is basically the same as that in Example 1, except that "the functional additive is a mixture of carbomer and hydroxypropyl methylcellulose (HPMC)" is replaced with "the functional additive is hydroxypropyl methylcellulose (HPMC)".

[0061] Comparative Example 5

[0062] A method for preparing a ceramic-coated diaphragm is basically the same as in Example 1, except that "solution containing modified organic binder" is replaced with "polyvinyl alcohol". The polyvinyl alcohol is PVA 2488.

[0063] The test results of the ultrathin high-temperature resistant ceramic-coated diaphragms prepared in Examples 1-3 and the ceramic-coated diaphragms prepared in Comparative Examples 1-5 are shown in Table 1.

[0064] Table 1

[0065]

[0066] As shown in Table 1, the overall performance of the ultrathin high-temperature resistant ceramic coating membranes prepared in Examples 1-3 is far superior to that of Comparative Examples 1-5.

[0067] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An ultra-thin high temperature resistant ceramic coated separator, characterized in that, The application relates to a base film and a coating layer on the base film, wherein the coating layer is obtained by coating a slurry, and a method for preparing the slurry comprises the following steps: mixing nano ceramic, a solution containing a modified organic binder, a dispersant, a functional auxiliary agent and third water to be uniform to obtain the slurry, wherein the functional auxiliary agent is a mixture of carbomer and hydroxypropyl methyl cellulose. The method for preparing the solution containing the modified organic binder comprises the following steps: mixing acrylate monomers, silicone monomers, an emulsifier and first water at room temperature to be uniform to obtain a pre-emulsion; mixing a part of the pre-emulsion and second water, keeping at 75-80 DEG C for 8-12 minutes, adding an initiator to initiate copolymerization of the acrylate monomers and the silicone monomers, keeping at 75-80 DEG C for 5-15 minutes, uniformly dropping the rest of the pre-emulsion, continuing to keep at 75-80 DEG C for 2-3 hours after dropping is completed, cooling to 50-60 DEG C, adding a crosslinking agent, keeping at 75-80 DEG C for 30-45 minutes to obtain the solution containing the modified organic binder. The ratio of the nano ceramic, the solution containing the modified organic binder, the dispersant, the functional auxiliary agent and the third water is (5-30) : (5-10) : (0.1-1) : (0.5-3) : (55-88) in mass fraction.

2. The ultra-thin high temperature resistant ceramic coated separator of claim 1, wherein, The ratio of the carbomer and the hydroxypropyl methyl cellulose is (0.5-2) : (1-3) in mass fraction.

3. The ultra-thin high temperature resistant ceramic coated separator of claim 1, wherein, The viscosity of the slurry is 300-800 mPa.s.

4. The ultra-thin high temperature resistant ceramic coated separator of claim 1, wherein, The dispersant is polycarboxylate, and the nano ceramic is nano alumina.

5. The ultra-thin, high temperature resistant ceramic coated separator of claim 1, wherein, In the method for preparing the solution containing the modified organic binder, the ratio of the acrylate monomers, the silicone monomers, the emulsifier, the first water, the second water, the initiator and the crosslinking agent is (25-35) : (5-10) : (1-2) : (30-40) : (20-30) : (0.3-0.6) : (0.5-1) in mass fraction.

6. The ultra-thin, high temperature resistant ceramic coated separator of claim 1, wherein, The silicone monomers are at least one of gamma-methacryloxypropyl trimethoxysilane and vinyl trimethoxysilane.

7. The ultra-thin, high temperature resistant ceramic coated separator of claim 1, wherein, The initiator is ammonium persulfate, the crosslinking agent is an aziridine crosslinking agent, and the emulsifier is a mixture of one or both of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether.

8. The ultra-thin, high temperature resistant ceramic coated separator of claim 1, wherein, The application relates to a base film and a coating layer on the base film, wherein the coating layer is obtained by coating a slurry, and a method for preparing the slurry comprises the following steps: mixing nano ceramic, a solution containing a modified organic binder, a dispersant, a functional auxiliary agent and third water to be uniform to obtain the slurry, wherein the functional auxiliary agent is a mixture of carbomer and hydroxypropyl methyl cellulose.

9. The method of claim 1, wherein the ultra-thin high temperature resistant ceramic coating separator is prepared by the steps of: The coating layer is obtained by coating the slurry on the base film and drying. The single-side thickness of the coating layer is 1-1.5 microns.

10. The method of claim 9, wherein, The application relates to a base film and a coating layer on the base film, wherein the coating layer is obtained by coating a slurry, and a method for preparing the slurry comprises the following steps: mixing nano ceramic, a solution containing a modified organic binder, a dispersant, a functional auxiliary agent and third water to be uniform to obtain the slurry, wherein the functional auxiliary agent is a mixture of carbomer and hydroxypropyl methyl cellulose.

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