Lithium ion battery ceramic composite diaphragm based on fluorinated azide comprehensive crosslinking and preparation method of lithium ion battery ceramic composite diaphragm

Abstract

The invention provides a lithium ion battery ceramic composite diaphragm based on fluorinated azide comprehensive crosslinking and a preparation method of the lithium ion battery ceramic composite diaphragm. The lithium ion battery ceramic composite diaphragm comprises a base membrane and a coating coated on at least one side surface of the base membrane, the coating is prepared from the following components in parts by mass: 20 to 40 parts of ceramic particles, 1 to 5 parts of PAA aqueous solution, 0.1 to 1 part of fluorinated azide, 0.1 to 1 part of surfactant and 70 to 100 parts of deionized water. Through a cross-linked structure formed by the fluorinated azide, the base membrane and the PAA binder system, the bonding strength of the coating is remarkably improved, and the technical problem that the coating of the traditional ceramic composite diaphragm is easy to fall off is solved. Meanwhile, by utilizing the high-temperature-resistant characteristic of the ceramic particles and the supporting effect of the cross-linked network, the thermal shrinkage rate of the diaphragm is remarkably reduced, and the risk of thermal runaway of the battery is effectively avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery separator, in particular to a lithium ion battery ceramic composite separator based on fluorinated azide compound comprehensive cross-linking and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have been widely used in portable electronic devices, electric vehicles and energy storage systems due to their high energy density, long cycle life and no memory effect. Currently, polyolefin separators are commonly used in commercial lithium ion batteries. Although such separators have excellent mechanical properties and ion conductivity, they have the defect of insufficient thermal stability. When the battery overheats, the polyolefin separator is prone to melt and shrink, causing the positive and negative electrodes to directly contact, leading to short circuit, fire and even explosion. To improve this problem, researchers have developed ceramic composite separators by coating a layer of high-temperature resistant ceramic particles on the surface of the polyolefin substrate, significantly improving the thermal stability of the separator.

[0003] However, the existing ceramic composite separator still has the following limitations: first, the interface bonding force between the ceramic particles and the polyolefin substrate is weak. Under the mechanical stress (such as extrusion and winding) during battery assembly and the swelling effect of electrolyte during long-term cycling, the ceramic coating is prone to fall off or crack, resulting in a decrease in thermal stability and a shortening of the battery cycle life. Second, when the amount of high molecular binder added to enhance the stability of the coating is excessive, it will block the pores between the ceramic particles, reduce the ion conductivity of the separator, and thus damage the rate performance and energy density of the battery. Therefore, it is of great significance to develop a ceramic composite separator preparation technology that has high interface bonding strength, excellent thermal stability, high ion conductivity and electrolyte corrosion resistance, in order to improve the safety performance and cycle stability of lithium ion batteries. SUMMARY

[0004] In view of the above shortcomings of the prior art, the present application provides a lithium ion battery ceramic composite separator based on fluorinated azide compound comprehensive cross-linking and a preparation method thereof, to solve the problems of weak bonding force between the coating and the base film, electrolyte wettability, ion conductivity, thermal stability and other aspects of the existing ceramic composite separator, and to improve the overall performance of lithium ion batteries.

[0005] The technical scheme provided by the present application is a lithium ion battery ceramic composite separator based on fluorinated azide compound comprehensive cross-linking, which comprises a base film and a coating layer coated on at least one side of the base film. The coating layer is prepared from the following components by mass fraction: ceramic particles 20-40 parts, PAA aqueous solution 1-5 parts, fluorinated azide compound 0.1-1 parts, surfactant 0.1-1 parts, and deionized water 70-100 parts.

[0006] Furthermore, the fluorinated azide compound is at least one selected from perfluorooctylsulfonyl azide, perfluorobutylsulfonyl azide, perfluorohexylsulfonyl azide, fluoroalkyl acyl azide, and fluorobenzenesulfonyl azide.

[0007] Furthermore, the ceramic particles are selected from one of alumina, silicon dioxide, zirconium oxide, titanium dioxide, or boehmite, and the D50 particle size of the ceramic particles is 50-200 nm.

[0008] Furthermore, the concentration of the PAA aqueous solution is 10-20 wt%.

[0009] Furthermore, the surfactant is at least one of the following: disodium dodecyl sulfosuccinate, disodium lauryl polyoxyethylene ether sulfosuccinate, disodium isooctyl sulfosuccinate, and disodium stearyl sulfosuccinate.

[0010] Furthermore, the base film is selected from one of PP, PE, PP / PE / PP, PE / PP / PE, and non-woven membrane, the thickness of the base film is 4-100um, and the thickness of the coating is 1-10um.

[0011] Another technical solution provided by this invention: a method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds, comprising the following steps:

[0012] (1) Add ceramic particles, PAA aqueous solution, surfactant and deionized water to a stirring device in the mass fraction ratio, and stir at 200-500 rpm for 30-60 min at room temperature to obtain a premixed slurry; add composite azide to the premixed slurry, continue stirring at 200-500 rpm for 20-40 min, and then use ultrasonic dispersion treatment for 15-30 min with ultrasonic power of 300-500 W to obtain a uniform ceramic slurry;

[0013] (2) The ceramic slurry prepared in step (1) is coated on the surface of the base film and cured by ultraviolet light to obtain a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds.

[0014] Furthermore, the coating method in step (2) is one of gravure coating, extrusion coating, wire rod coating, scraping coating, casting, or dip coating.

[0015] Furthermore, the wavelength of the ultraviolet light is 254 nm, and the irradiation intensity is 10-50 mW / cm². 2 The irradiation time is 1-20 minutes.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention significantly improves coating bonding strength through the cross-linked structure formed by fluorinated azide, the base membrane, and the PAA binder system, solving the technical problem of easy coating detachment in traditional ceramic composite separators. Simultaneously, by utilizing the high-temperature resistance of ceramic particles and the supporting effect of the cross-linked network, the thermal shrinkage rate of the separator is significantly reduced, effectively mitigating the risk of battery thermal runaway. Furthermore, the fluorinated cross-linked structure endows the separator with excellent resistance to electrolyte immersion, ensuring coating stability and ion conductivity during long-term use; and by optimizing the formulation to maintain continuous lithium-ion transport channels, high ion conductivity is maintained while ensuring coating stability, overcoming the problem of decreased ion conductivity caused by the addition of binders in traditional processes.

[0018] At the preparation and application levels, this invention also possesses significant advantages. The formulation is scientifically designed, and the selected ceramic particles, fluorinated azides, surfactants, and other components exhibit good compatibility. A uniform slurry can be prepared using conventional stirring and ultrasonic dispersion processes, and the coating method is flexible and can be selected to adapt to different production needs. The UV curing process eliminates the need for high-temperature sintering, simplifying the production process, improving production efficiency, reducing energy consumption and production costs, and facilitating large-scale production. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, specific implementation examples are provided below to further illustrate the technical solutions of this invention. However, the specific details of the embodiments are only for illustrating this invention and do not represent all technical methods under the concept of this invention. Therefore, they should not be construed as limiting the overall technical solution of this invention.

[0020] It should be noted that, unless otherwise specified, the experimental methods used in the examples are conventional methods, and the materials and reagents used in the examples are commercially available unless otherwise specified.

[0021] Example 1

[0022] A method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds includes the following steps:

[0023] (1) Ceramic slurry: Alumina ceramic particles, PAA aqueous solution (concentration of 10wt%), surfactant disodium dodecyl sulfosuccinate and deionized water were added to the stirring device in the mass ratio, and stirred at 500 rpm for 30 min at room temperature to obtain a premixed slurry; the composite azide perfluorooctyl sulfonyl azide was added to the premixed slurry, and stirring was continued at 500 rpm for 40 min, followed by ultrasonic dispersion treatment for 30 min with an ultrasonic power of 500 W to obtain a uniform alumina ceramic slurry;

[0024] (2) The alumina ceramic slurry prepared in step (1) is coated onto the surface of a 12µm PP base film using a gravure printing process, and then cured by ultraviolet light irradiation (UV wavelength is 254nm, irradiation intensity is 50mW / cm). 2 With an irradiation time of 10 min, a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds was obtained.

[0025] The above components, by mass, are: 30 parts alumina ceramic, 2 parts 10wt% PAA aqueous solution, 0.5 parts perfluorooctyl sulfonyl azide compound, 0.3 parts disodium dodecyl sulfosuccinate surfactant, and 100 parts deionized water.

[0026] Example 2

[0027] A method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds includes the following steps:

[0028] (1) Ceramic slurry: Alumina ceramic particles, PAA aqueous solution (concentration of 12wt%), surfactant disodium isooctyl sulfosuccinate and deionized water were added to the stirring device in the following weight ratios and stirred at 400 rpm for 40 min to obtain a premixed slurry; Perfluorohexyl sulfonyl azide was added to the premixed slurry and stirred at 400 rpm for 30 min, and then ultrasonically dispersed for 20 min with an ultrasonic power of 400 W to obtain a uniform alumina ceramic slurry;

[0029] (2) The alumina ceramic slurry prepared in step (1) is applied to the surface of a 12µm PE base film by gravure coating, and then cured by ultraviolet light irradiation (UV wavelength is 254nm, irradiation intensity is 40mW / cm). 2 With an irradiation time of 12 min, a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds was obtained.

[0030] The above components, by mass parts, are: 25 parts alumina ceramic, 2.5 parts 12wt% PAA aqueous solution, 0.55 parts perfluorohexylsulfonyl azide compound, 0.25 parts disodium isooctylsulfosuccinate surfactant, and 90 parts deionized water.

[0031] Example 3

[0032] A method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds includes the following steps:

[0033] (1) Ceramic slurry: Ceramic particles silica, PAA aqueous solution (concentration of 10wt%), surfactant disodium lauryl ether sulfosuccinate and deionized water were added to the stirring device in the following weight ratios. The mixture was stirred at 300 rpm for 30 min to obtain a premixed slurry. The composite azide fluoroalkyl acyl azide was added to the premixed slurry and stirred at 300 rpm for 35 min. Then, ultrasonic dispersion was performed for 25 min with an ultrasonic power of 450 W to obtain a uniform silica ceramic slurry.

[0034] (2) The silica ceramic slurry prepared in step (1) is applied to the surface of a 12µm PE base film by gravure coating, and then cured by ultraviolet light irradiation (UV wavelength is 254nm, irradiation intensity is 45mW / cm). 2 With an irradiation time of 8 minutes, a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds was obtained.

[0035] The above components, by mass parts, are: 28 parts silicon dioxide ceramic, 1.5 parts 10wt% PAA aqueous solution, 0.6 parts fluoroalkyl acyl azide compound, 0.1 parts disodium lauryl polyoxyethylene ether sulfosuccinate surfactant, and 95 parts deionized water.

[0036] Example 4

[0037] A method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds includes the following steps:

[0038] (1) Ceramic slurry: Boehmite ceramic particles, PAA aqueous solution (concentration of 13wt%), surfactant disodium stearyl sulfosuccinate and deionized water were added to the stirring device in the following weight ratios and stirred at 450 rpm for 35 min to obtain a premixed slurry; Perfluorooctyl sulfonyl azide was added to the premixed slurry and stirred at 450 rpm for 30 min, and then ultrasonically dispersed for 30 min with an ultrasonic power of 400 W to obtain a uniform boehmite ceramic slurry;

[0039] (2) The boehmite ceramic slurry prepared in step (1) was applied to the surface of a 12µm PP / PE / PP base film by gravure coating, and then cured by UV light irradiation (UV wavelength 254nm, irradiation intensity 45mW / cm). 2 With an irradiation time of 12 min, a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds was obtained.

[0040] The above components, by mass, are: 30 parts silica ceramic, 2.5 parts 13wt% PAA aqueous solution, 0.7 parts fluoroalkyl acyl azide compound, 0.15 parts disodium stearyl sulfosuccinate surfactant, and 100 parts deionized water.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that no fluorinated azide is added.

[0043] Comparative Example 2

[0044] The difference from Example 1 is that PAA is replaced with PVDF.

[0045] Performance testing:

[0046] The coating adhesion strength, ionic conductivity, thermal shrinkage rate, and air permeability increment of the diaphragm in the example were measured, and the results are shown in Table 1.

[0047] Table 1 Performance Test Results

[0048] Coating bond strength N / m Ionic conductivity (mS / cm) Machine direction thermal shrinkage (130°C / 1h; %) Air permeability increment Sec / 100ml Example 1 27 9.1*10 -2 ]]> MD: 0.5% TD: 0% 11 Example 2 49 8.2*10 -1 ]]> MD: 1.1% TD: 0.9% 7 Example 3 52 8.6*10 -1 ]]> MD: 1.2% TD: 1.0% 6 Example 4 34 8.7*10 -2 ]]> MD: 0.6% TD: 0% 10 Comparative Example 1 12 3.4*10 -3 ]]> MD: 3.4% TD: 0.3% 25 Comparative Example 2 13 2.6*10 -3 ]]> MD: 3.5% TD: 0.3% 24

[0049] The test results above show that the cross-linking structure formed by the fluorinated azide compound, the base film, and the PAA (polyacrylic acid) binder system significantly improves the coating bonding strength, maintains high ionic conductivity while ensuring coating stability, and significantly reduces the thermal shrinkage rate of the separator by utilizing the high temperature resistance of ceramic particles and the supporting effect of the cross-linking network, effectively avoiding the risk of battery thermal runaway.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds, characterized in that, The coating comprises a base film and a coating applied to at least one side of the base film, the coating being prepared from the following components in parts by mass: 20-40 parts ceramic particles, 1-5 parts aqueous PAA solution, 0.1-1 parts fluorinated azide compound, 0.1-1 parts surfactant, and 70-100 parts deionized water.

2. The lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds according to claim 1, characterized in that, The fluorinated azide compound is at least one of perfluorooctylsulfonyl azide, perfluorobutylsulfonyl azide, perfluorohexylsulfonyl azide, fluoroalkyl acyl azide, and fluorobenzenesulfonyl azide.

3. The lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds according to claim 1, characterized in that, The ceramic particles are selected from one of alumina, silicon dioxide, zirconium oxide, titanium dioxide or boehmite, and the D50 particle size of the ceramic particles is 50-200 nm.

4. The lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds according to claim 1, characterized in that, The concentration of the PAA aqueous solution is 10-20 wt%.

5. The lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds according to claim 1, characterized in that, The surfactant is at least one of the following: disodium dodecyl sulfosuccinate, disodium lauryl polyoxyethylene ether sulfosuccinate, disodium isooctyl sulfosuccinate, and disodium stearyl sulfosuccinate.

6. The lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds according to claim 1, characterized in that, The base film is selected from one of PP, PE, PP / PE / PP, PE / PP / PE, and non-woven membrane. The thickness of the base film is 4-100um, and the thickness of the coating is 1-10um.

7. A method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Add ceramic particles, PAA aqueous solution, surfactant and deionized water to the stirring device in the mass fraction ratio, and stir at 200-500 rpm for 30-60 min at room temperature to obtain premixed slurry; Add the composite azide to the premixed slurry, continue stirring at 200-500 rpm for 20-40 min, and then perform ultrasonic dispersion treatment for 15-30 min with an ultrasonic power of 300-500 W to obtain a uniform ceramic slurry. (2) The ceramic slurry prepared in step (1) is coated on the surface of the base film and cured by ultraviolet light to obtain a lithium-ion battery ceramic composite separator based on the comprehensive cross-linking of fluorinated azide compounds.

8. The method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds according to claim 7, characterized in that, The coating method in step (2) is one of gravure coating, extrusion coating, wire rod coating, scraping coating, casting, or dip coating.

9. The method for preparing a lithium-ion battery ceramic composite separator based on the comprehensive crosslinking of fluorinated azide compounds according to claim 7, characterized in that, The ultraviolet light has a wavelength of 254 nm and an irradiation intensity of 10-50 mW / cm². 2 The irradiation time is 1-20 minutes.