Lithium battery diaphragm coated with aramid nanofiber and preparation method of lithium battery diaphragm

Abstract

The invention discloses a lithium battery diaphragm coated with aramid nanofibers and a preparation method of the lithium battery diaphragm, and belongs to the technical field of lithium ion battery materials, the aramid nanofibers with a unique nanoscale structure and excellent mechanical properties and thermal stability are used as a functional coating matrix, zirconium oxide with high hardness and high wear resistance is used as a functional filler, and the lithium battery diaphragm coated with the aramid nanofibers is prepared. A coating design is carried out through a plasma etching technology, and the functionalized lithium battery diaphragm with high safety, high mechanical strength and excellent thermal stability is prepared. The preparation method specifically comprises the following steps: carrying out plasma etching on a PP base membrane, preparing aramid nanofiber dispersion liquid, preparing ANF / ZrO2 / DMSO composite slurry, coating the PP base membrane, carrying out post-treatment and the like, so as to obtain the lithium battery diaphragm. According to the lithium battery diaphragm, the inherent defects of a traditional lithium battery diaphragm in the aspects of thermal safety, mechanical strength, electrolyte wettability and the like can be overcome. The preparation process is simple and controllable, and the obtained functional diaphragm has wide application prospects in the high-end fields of power lithium batteries, energy storage batteries and the like.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, specifically relating to a lithium battery separator coated with aramid nanofibers and its preparation method. Background Technology

[0002] Lithium-ion batteries mainly consist of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging, lithium ions move from the positive electrode to the negative electrode; during discharging, they move from the negative electrode back to the positive electrode, and electrons output electrical energy through the external circuit. The separator, as a key component, primarily functions to isolate the positive and negative electrodes to prevent short circuits, and to allow lithium ions to pass through through micropores to form a circuit. Although it does not directly participate in electrochemical reactions, the performance of the separator has a significant impact on battery safety and electrochemical behavior. Its pore structure and ion conductivity affect charge and discharge efficiency, while its mechanical strength relates to battery safety. The separator is a component with high technological barriers in lithium-ion batteries, typically accounting for 10%–14% of the cost, and up to 20% in high-end batteries.

[0003] Currently, commercially available lithium-ion battery separators are mainly microporous polyolefin separators based on PE and PP. These separators are manufactured primarily using dry and wet processes. Due to their lower cost, good mechanical properties, and excellent chemical and electrochemical stability, they are widely used in lithium-ion batteries. However, their poor heat resistance, susceptibility to thermal shrinkage, and low affinity for electrolytes are becoming increasingly prominent issues. These problems not only affect battery performance at high temperatures but may also become bottlenecks restricting further performance improvements. Therefore, developing separators suitable for high-performance lithium-ion batteries is particularly important.

[0004] Aramid nanofibers (ANFs), a novel nanopolymer fiber material developed in recent years, retain the excellent mechanical properties and thermal stability of conventional macroscopic para-aramid fibers. Simultaneously, their nanoscale (diameter 10-20 nm, length 3-10 μm) endows them with new connotations and characteristics. Although ANF membranes exhibit significant advantages in thermal stability and mechanical strength, their ionic conductivity still requires further optimization. While single inorganic coatings enhance ion migration, they struggle to simultaneously provide flexible support and dendrite physical barrier.

[0005] In summary, existing technologies, whether traditional polyolefin separators, their inorganically coated modified separators, or novel aramid nanofiber-based separators, struggle to achieve an ideal balance between high-temperature dimensional stability, electrolyte compatibility, high mechanical strength, high ionic conductivity, and good process feasibility. In particular, how to construct a functional coating that is firmly bonded to the base membrane, has a uniform structure, and possesses both rigidity and flexibility, thereby systematically improving the overall performance of the separator, remains a key problem that urgently needs to be solved in the current lithium-ion battery separator technology field. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium battery separator coated with aramid nanofibers and its preparation method, overcoming the problems of poor heat resistance, easy heat shrinkage, and low affinity for electrolyte in existing battery separators.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, a lithium battery separator coated with aramid nanofibers is provided, comprising a polypropylene base film and an ANF / ZrO2 coating, wherein the surface of the polypropylene base film is coated with an ANF / ZrO2 coating. The mass ratio of aramid nanofibers to ZrO2 in the ANF / ZrO2 coating is (50~90):(50~10).

[0008] In some embodiments, the thickness of the lithium battery separator coated with aramid nanofibers is 19-25 μm, the thickness of the polypropylene base film is 16-20 μm, and the thickness of the ANF / ZrO2 coating is 3-5 μm. The lithium battery separator has a tensile strength of 108.2~160.3 MPa; a porosity of 65%~84%; and a room temperature ionic conductivity of 0.33~0.71 mS / cm. - ¹.

[0009] Secondly, a method for preparing a lithium battery separator coated with aramid nanofibers, comprising the following steps: The polypropylene base film was pretreated by plasma etching to obtain a surface-activated and roughened polypropylene base film. Para-aramid short fibers, potassium hydroxide, dimethyl sulfoxide, and deionized water were mixed and stirred to obtain an ANF / DMSO dispersion. ZrO2 nanoparticles were added to a DMSO solution and ultrasonically treated to obtain a ZrO2 / DMSO dispersion. The ANF / DMSO dispersion and the ZrO2 / DMSO dispersion were then mixed and stirred to obtain an ANF / ZrO2 / DMSO composite slurry. The ANF / ZrO2 / DMSO composite slurry was high-pressure sprayed onto the surface of a plasma-etched polypropylene base film, then soaked in deionized water and dried to obtain a lithium battery separator coated with aramid nanofibers.

[0010] In some embodiments, the plasma etching technique is used to pretreat the polypropylene substrate film for 60-90 seconds.

[0011] In some embodiments, the ratio of the para-aramid chopped fibers, potassium hydroxide, and dimethyl sulfoxide is 1 g: 1.5 g: 200 mL, and the volume ratio of dimethyl sulfoxide to deionized water is 1:25.

[0012] In some embodiments, the mass concentration of the ANF / DMSO dispersion is 0.5%.

[0013] In some embodiments, the aramid nanofibers in the ANF / DMSO dispersion have a diameter of 12-15 nm and a length of 4-7 μm.

[0014] In some embodiments, the ultrasonic treatment has a power of 500-1500 W and a duration of 20-40 min.

[0015] In some embodiments, the high-pressure spraying pressure is 0.2~0.5 MPa, the atomized particle size is 10~50 μm, and the spraying distance is 50~70 cm.

[0016] In some embodiments, the ZrO2 nanoparticles have a particle size of 50-100 nm.

[0017] In some embodiments, the drying temperature is 50~80°C and the time is 3~7 min.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a lithium battery separator coated with aramid nanofibers, which consists of a polypropylene base film and an ANF / ZrO2 coating. The surface of the polypropylene base film is coated with an ANF / ZrO2 coating, and the mass ratio of aramid nanofibers to ZrO2 in the ANF / ZrO2 coating is (50~90):(50~10). By using aramid nanofibers with nanoscale structure, high strength, large aspect ratio and high temperature resistance as the matrix, the microstructure of the aramid nanofiber-based functional coating is controlled by high-pressure spraying pore gradient control technology.

[0019] Furthermore, the thickness of the lithium battery separator coated with aramid nanofibers is 19-25 μm, the thickness of the polypropylene base film is 16-20 μm, and the thickness of the ANF / ZrO2 coating is 3-5 μm; the tensile strength of the lithium battery separator is 108.2-160.3 MPa, the porosity is 65%-84%, and the room temperature ionic conductivity is 0.33-0.71 mS / cm. -¹ By controlling the concentration of aramid nanofibers, the proportion of inorganic particles, and the dispersion process, a porous structure conducive to high-speed, homogeneous ion transport is directionally constructed while ensuring coating uniformity and strong interfacial adhesion, effectively balancing the contradiction between high porosity and high mechanical strength. This provides a new path to overcome the technological bottlenecks of high-safety, high-energy-density lithium-ion battery separators.

[0020] This invention provides a method for preparing an aramid nanofiber-based functionalized lithium battery separator. ZrO2 nanoparticles are added to a DMSO solution and ultrasonically treated to obtain a ZrO2 / DMSO dispersion. The resulting ANF / DMSO dispersion and ZrO2 / DMSO dispersion are then mixed and stirred to obtain an ANF / ZrO2 / DMSO composite slurry. This method fully utilizes the excellent thermal stability and mechanical properties of ANF itself, and by introducing inorganic particles (i.e., ZrO2) with high thermal conductivity and high hardness, the thermal stability, puncture resistance, and flame retardancy of the composite separator are significantly improved. ANF and the inorganic particles interact through physical adsorption and... Hydrogen bonding forms a stable "organic-inorganic" interpenetrating network structure, endowing the separator with excellent high-temperature dimensional stability and cycle durability, meeting the stringent high-temperature safety requirements of high-energy-density lithium batteries. The ANF / ZrO2 / DMSO composite slurry is high-pressure sprayed onto the surface of a plasma-etched polypropylene base film. In constructing the ANF / inorganic particle composite coating, an innovative high-pressure spraying process is employed. Utilizing the stable dispersion of ANF in DMSO and the spatial effect of its nanofiber network, the agglomeration of inorganic particles such as ZrO2 is effectively suppressed, achieving highly uniform dispersion of inorganic fillers in the ANF matrix. Therefore, this invention, through coating design, constructs a highly wear-resistant, low-impedance ANF / ZrO2 layer on the PP base film surface. An aramid nanofiber-based coated separator with high strength, good wettability, and good heat resistance is prepared. This achieves the goal of overcoming the defects of traditional commercial polyolefin separators, such as poor heat resistance, low mechanical strength, poor wettability, and lithium dendrite puncture. The preparation process is simple and easy to implement, and it has broad application prospects in the lithium battery field.

[0021] Furthermore, the ANF / ZrO2 / DMSO composite slurry was high-pressure sprayed onto the surface of a plasma-etched polypropylene base film. The plasma etching time was 60-90 s. Before coating, the polypropylene base film underwent surface pretreatment using plasma etching technology. Through physical bombardment and chemical activation, polar groups were introduced onto the base film surface, increasing surface roughness and significantly enhancing the interfacial adhesion between the ANF / ZrO2 coating and the PP base film. This effectively prevented the coating from peeling or detaching during battery cycling, thereby improving the overall structural stability and long-term reliability of the separator. This process is simple, environmentally friendly, does not introduce impurities, and has good compatibility with subsequent spraying processes, providing a reliable interface engineering foundation for the preparation of high-performance composite separators.

[0022] Furthermore, the high-pressure spraying pressure is 0.2~0.5 MPa and the spraying distance is 50~70 cm. By precisely controlling the spraying parameters, a composite functional layer with uniform pore size distribution and ordered microstructure is constructed on the surface of the PP base film. This structure not only significantly enhances the mechanical strength and heat resistance of the membrane, but also effectively optimizes the ion transport path and improves ion conductivity and lithium ion transference number. Attached Figure Description

[0023] Figure 1 This is a SEM image of the lithium battery separator surface coated with aramid nanofibers obtained in Example 3 of the present invention. Figure 2 This is a SEM image of the lithium battery separator surface coated with aramid nanofibers obtained in Example 3 of the present invention. Figure 3 This is a SEM image of the cross-section of the lithium battery separator coated with aramid nanofibers obtained in Example 3 of the present invention. Figure 4 The stress-strain curve of the lithium battery separator coated with aramid nanofibers obtained in Example 3 of the present invention is shown. Detailed Implementation

[0024] The embodiments of the present invention will be described in further detail below: A lithium-ion battery separator coated with aramid nanofibers is disclosed. The separator uses a polypropylene (PP) microporous base membrane as a support layer, on which an aramid nanofiber / zirconia (ANF / ZrO2) coating is constructed. An ANF / ZrO2 layer B is coated on one side of the PP base membrane A. The mass ratio of aramid nanofibers to ZrO2 in the ANF / ZrO2 coating is (50~90):(50~10). The total thickness of the separator is 19~25 μm, of which the PP base membrane thickness is 16~20 μm and the ANF / ZrO2 coating thickness is 3~5 μm. The tensile strength is 108.2~160.3 MPa; the porosity is 65%~84%; and the room temperature ionic conductivity is 0.33~0.71 mS / cm. - ¹.

[0025] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and a certain amount of deionized water were used as raw materials, with the volume ratio of deionized water to dimethyl sulfoxide being (1:25). During preparation, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1200 r / min to 1500 r / min for 5 to 20 min to ensure complete dissolution. Subsequently, the aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 2 to 4 h. After the reaction, a homogeneous and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained, wherein the aramid nanofibers had a diameter of approximately 12 to 15 nm and a length distribution of 4 to 7 μm.

[0026] Step 2: Preparation of composite coating slurry. ANF / ZrO2 / DMSO composite slurry preparation: Take a certain amount of the ANF / DMSO dispersion prepared in Step 1. Add ZrO2 nanoparticles slowly to the DMSO dispersion at a mass ratio of (50~90):(50~10) to obtain a ZrO2 / DMSO dispersion. Then, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 20~40 min. Finally, mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain a stable ANF / ZrO2 / DMSO composite slurry.

[0027] Step 3: Base film treatment and high-pressure spraying. The polypropylene base film is pretreated with plasma etching technology for 60-90 seconds. Then, a high-pressure spray gun is used to spray the pretreated polypropylene (PP) base film. First, the PP base film is fixed on the spraying platform. Using an ANF / ZrO2 / DMSO composite slurry, spraying is performed at a pressure of 0.2 MPa-0.5 MPa, maintaining a distance of 50 cm-70 cm between the spray gun and the base film, until a uniform coating is formed on the base film surface.

[0028] Step 4: Post-processing and finished product preparation. The coated separator obtained in Step 3 is completely immersed in a large amount of deionized water for 12 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing the ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving coating structure curing. Afterwards, the separator is removed and placed in a vacuum drying oven at 50-80℃ for 3-7 minutes to quickly remove residual moisture, ultimately obtaining a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0029] This invention discloses a lithium-ion battery separator coated with aramid nanofibers and its preparation method. Addressing the problems of poor thermal stability, insufficient electrolyte wettability, and limited mechanical strength in current commercially available polyolefin separators, this invention innovatively proposes using aramid nanofibers, which possess excellent mechanical properties, superior heat resistance, and abundant polar groups, as the functional coating matrix material. By introducing nano-inorganic particles (ZrO2) with high ion conductivity, a "rigid-flexible" composite functional coating is constructed on the surface of a PP separator using high-pressure spraying technology. The synergistic mechanism between ANF and inorganic particles, the gradient regulation of the coating pore structure, and their influence on interfacial impedance, ionic conductivity, and lithium dendrite suppression are systematically studied. The aim is to significantly improve the thermal stability, electrolyte affinity, mechanical strength, and electrochemical cycle performance of the separator, providing new ideas and technical support for the development of novel lithium-ion battery separators with high safety and long lifespan.

[0030] The present invention will be further described in detail below with reference to embodiments: Example 1 A lithium-ion battery separator coated with aramid nanofibers is disclosed, comprising a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 90:10; the total thickness of the separator is 21 μm (16 μm for the PP base film and 5 μm for the ANF / ZrO2 layer), the tensile strength is 145.6 MPa, the porosity is 65%, and the room temperature ionic conductivity is 0.33 mS / cm. - ¹.

[0031] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In the preparation, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1350 r / min for 14 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 3.3 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0032] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 72 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.04 g of ZrO2 nanoparticles (50 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 90:10 to obtain a ZrO2 / DMSO dispersion. Subsequently, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 28 min (power 1100 W). Mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry.

[0033] Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 60 s. A high-pressure spray gun was then used to coat the pretreated PP base film (16 μm thick). The PP base film was fixed on the spraying platform, and an ANF / ZrO2 / DMSO composite slurry was applied at a spraying pressure of 0.36 MPa, maintaining a distance of 59 cm between the spray gun and the base film, until a uniform coating was formed on the base film surface.

[0034] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 15 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing the ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving coating structure curing. Afterward, the separator was removed and placed in a vacuum drying oven at 60 °C for 4 minutes to rapidly remove residual moisture, ultimately yielding a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0035] Example 2 A lithium-ion battery separator coated with aramid nanofibers is disclosed, comprising a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 80:20; the total thickness of the separator is 19 μm (16 μm for the PP base film and 3 μm for the ANF / ZrO2 layer), the tensile strength is 160.3 MPa, the porosity is 67%, and the room temperature ionic conductivity is 0.61 mS / cm. - ¹.

[0036] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In the preparation process, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1450 r / min for 18 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 2 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0037] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 64 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.08 g of ZrO2 nanoparticles (50 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 80:20 to obtain a ZrO2 / DMSO dispersion. Then, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 30 min (1000 W power). Mix the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry. Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 80 s. A high-pressure spray gun was then used to coat the pretreated PP base film (16 μm thick). The PP base film was fixed on the spraying platform, and an ANF / ZrO2 / DMSO composite slurry was applied at a spraying pressure of 0.38 MPa, maintaining a distance of 62 cm between the spray gun and the base film, until a uniform coating was formed on the base film surface.

[0038] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 16 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing the ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving the curing of the coating structure. Afterward, the separator was removed and placed in a vacuum drying oven at 70 °C for 5 minutes to rapidly remove residual moisture, ultimately yielding a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0039] Example 3 like Figures 1-3 As shown, a lithium battery separator coated with aramid nanofibers is disclosed. The separator consists of a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 70:30; the total thickness of the separator is 22 μm (18 μm for the PP base film and 4 μm for the ANF / ZrO2 layer), the tensile strength is 134.1 MPa, the porosity is 84%, and the room temperature ionic conductivity is 0.71 mS / cm. - ¹.

[0040] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In the preparation process, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1400 r / min for 15 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 3 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0041] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 56 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.12 g of ZrO2 nanoparticles (50 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 70:30 to obtain a ZrO2 / DMSO dispersion. Subsequently, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 25 min (power 1200 W). Mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry.

[0042] Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 80 s. A high-pressure spray gun was then used to coat the pretreated PP base film (18 μm thick). First, the PP base film was fixed on the spraying platform. Using an ANF / ZrO2 / DMSO composite slurry, a spraying pressure of 0.4 MPa was applied while maintaining a distance of 55 cm between the spray gun and the base film until a uniform coating was formed on the base film surface.

[0043] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 10 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving coating structure curing. Afterward, the separator was removed and placed in a vacuum drying oven at 50°C for 7 minutes to rapidly remove residual moisture, ultimately yielding a structurally complete and high-performance functionalized aramid nanofiber composite lithium battery separator, i.e., a lithium battery separator coated with aramid nanofibers.

[0044] Example 4 A lithium-ion battery separator coated with aramid nanofibers is disclosed. The separator comprises a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 60:40; the total thickness of the separator is 24 μm (20 μm for the PP base film and 4 μm for the ANF / ZrO2 layer); the tensile strength is 121.5 MPa; the porosity is 81%; and the room temperature ionic conductivity is 0.36 mS / cm. - ¹.

[0045] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In the preparation process, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1200 r / min for 5 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 4 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0046] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 48 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.16 g of ZrO2 nanoparticles (50 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 60:40 to obtain a ZrO2 / DMSO dispersion. Then, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 35 min (800 W power). Mix the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry. Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 60 s. A high-pressure spray gun was then used to coat the pretreated PP base film (20 μm thick). First, the PP base film was fixed on the spraying platform. Using an ANF / ZrO2 / DMSO composite slurry, a spraying pressure of 0.3 MPa was applied while maintaining a distance of 60 cm between the spray gun and the base film until a uniform coating was formed on the base film surface.

[0047] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 12 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving coating structure curing. Afterward, the separator was removed and placed in a vacuum drying oven at 60°C for 5 minutes to rapidly remove residual moisture, ultimately yielding a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0048] Example 5 A lithium-ion battery separator coated with aramid nanofibers is disclosed. The separator comprises a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 50:50; the total thickness of the separator is 20 μm (16 μm for the PP base film and 4 μm for the ANF / ZrO2 layer); the tensile strength is 114.5 MPa; the porosity is 73%; and the room temperature ionic conductivity is 0.65 mS / cm. - ¹.

[0049] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In preparation, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1500 r / min for 10 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 2.5 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0050] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 40 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.2 g of ZrO2 nanoparticles (50 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 50:50 to obtain a ZrO2 / DMSO dispersion. Subsequently, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 40 min (power 700 W). Mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry.

[0051] Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated for 90 s using plasma etching technology. A high-pressure spray gun was then used to coat the pretreated PP base film (16 μm thick). First, the PP base film was fixed on the spraying platform. Using an ANF / ZrO2 / DMSO composite slurry, a spraying pressure of 0.35 MPa was applied while maintaining a distance of 65 cm between the spray gun and the base film until a uniform coating was formed on the base film surface.

[0052] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 15 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing the ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving the curing of the coating structure. Afterward, the separator was removed and placed in a vacuum drying oven at 70°C for 3 minutes to rapidly remove residual moisture, ultimately yielding a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0053] Example 6 A lithium-ion battery separator coated with aramid nanofibers is disclosed. The separator comprises a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 70:30; the total thickness of the separator is 25 μm (20 μm for the PP base film and 5 μm for the ANF / ZrO2 layer); the tensile strength is 126.1 MPa; the porosity is 68%; and the room temperature ionic conductivity is 0.59 mS / cm. - ¹.

[0054] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In the preparation, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1450 r / min for 20 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 4 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0055] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 56 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.12 g of ZrO2 nanoparticles (80 nm in diameter) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 70:30 to obtain a ZrO2 / DMSO dispersion. Subsequently, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 20 min (power 500 W). Mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry.

[0056] Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 70 s. A high-pressure spray gun was then used to coat the pretreated PP base film (20 μm thick). First, the PP base film was fixed on the spraying platform. Using an ANF / ZrO2 / DMSO composite slurry, a spraying pressure of 0.2 MPa was applied while maintaining a distance of 50 cm between the spray gun and the base film until a uniform coating was formed on the base film surface.

[0057] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 16 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving the curing of the coating structure. Afterward, the separator was removed and placed in a vacuum drying oven at 80°C for 5 minutes to quickly remove residual moisture, ultimately yielding a structurally complete and high-performance functionalized aramid nanofiber composite lithium battery separator, i.e., a lithium battery separator coated with aramid nanofibers.

[0058] Example 7 A lithium-ion battery separator coated with aramid nanofibers is disclosed. The separator comprises a polypropylene (PP) base film and an ANF / ZrO2 coating; wherein the mass ratio of ANF to ZrO2 is 50:50; the total thickness of the separator is 21 μm (16 μm for the PP base film and 5 μm for the ANF / ZrO2 layer); the tensile strength is 108.2 MPa; the porosity is 71%; and the room temperature ionic conductivity is 0.36 mS / cm. - ¹.

[0059] A method for preparing a lithium battery separator coated with aramid nanofibers includes the following steps: Step 1: Preparation of ANF / DMSO dispersion The raw materials used were 1 g of 6 mm long para-aramid chopped fibers (PPTA), 1.5 g of potassium hydroxide (KOH), 200 mL of dimethyl sulfoxide (DMSO), and 8 mL of deionized water (the volume ratio of deionized water to dimethyl sulfoxide was 1:25). In preparation, potassium hydroxide was added first, followed by deionized water, and the mixture was stirred in a sealed beaker at 1450 r / min for 18 min using a magnetic stirrer to ensure complete dissolution. Subsequently, the para-aramid chopped fibers and dimethyl sulfoxide were added sequentially, and the reaction was continued with stirring at the same speed for 3.2 h. After the reaction, a uniform and stable aramid nanofiber / DMSO dispersion (ANF / DMSO) with a mass concentration of 0.5% was obtained. The aramid nanofibers had a diameter distribution of 12-15 nm and a length distribution of 4-7 μm. The diameters included 12 nm, 13 nm, 14 nm, and 15 nm, and the lengths included 4 μm, 5 μm, 6 μm, and 7 μm. The average diameter was 13.5 nm and the average length was 5.5 μm.

[0060] Step 2: Preparation of composite coating slurry Preparation of ANF / ZrO2 / DMSO composite slurry: Take 40 mL of the ANF / DMSO dispersion prepared in step one, and slowly add 0.2 g of ZrO2 nanoparticles (particle size 100 nm) to the DMSO solution at a mass ratio of aramid nanofibers to ZrO2 nanoparticles of 50:50 to obtain a ZrO2 / DMSO dispersion. Subsequently, place the ZrO2 / DMSO dispersion in an ultrasonic disperser and perform ultrasonic treatment for 30 min (power 1500 W). Mix and stir the obtained ANF / DMSO dispersion and ZrO2 / DMSO dispersion to obtain the ANF / ZrO2 / DMSO composite slurry.

[0061] Step 3: Base film treatment and high-pressure spraying The polypropylene (PP) base film was pretreated with plasma etching for 60 s. A high-pressure spray gun was then used to coat the pretreated PP base film (16 μm thick). The PP base film was fixed on the spraying platform, and an ANF / ZrO2 / DMSO composite slurry was applied at a spraying pressure of 0.5 MPa, maintaining a distance of 70 cm between the spray gun and the base film, until a uniform coating was formed on the base film surface.

[0062] Step 4: Post-processing and finished product preparation The coated separator obtained in step three was completely immersed in a large amount of deionized water for 16 hours. This process aims to replace and completely remove the DMSO solvent in the system, while simultaneously causing the ANF to undergo protonation reduction, strengthening its intermolecular hydrogen bonding and achieving the curing of the coating structure. Afterward, the separator was removed and placed in a vacuum drying oven at 70 °C for 5 minutes to rapidly remove residual moisture, ultimately yielding a functionalized aramid nanofiber composite lithium battery separator with a complete structure and excellent performance.

[0063] Taking Example 3 as an example, the lithium battery separator coated with aramid nanofibers prepared according to the present invention was tested. See [link to example]. Figure 4 Its tensile strength is 134.1 MPa, its porosity is 84%, and its room temperature ionic conductivity is 0.71 mS / cm. - ¹. It exhibits excellent thermal stability and electrolyte wettability. This means the composite aramid nanofiber coated separator possesses high safety and high mechanical strength, and has broad application prospects in high-end fields such as power lithium batteries and energy storage batteries.

Claims

1. A lithium battery separator coated with aramid nanofibers, characterized in that, It consists of a polypropylene base film and an ANF / ZrO2 coating. The surface of the polypropylene base film is coated with an ANF / ZrO2 coating. The mass ratio of aramid nanofibers to ZrO2 in the ANF / ZrO2 coating is (50~90):(50~10).

2. The lithium battery separator coated with aramid nanofibers according to claim 1, characterized in that, The thickness of the lithium battery separator coated with aramid nanofibers is 19~25 μm, the thickness of the polypropylene base film is 16~20 μm, and the thickness of the ANF / ZrO2 coating is 3~5 μm. The lithium battery separator has a tensile strength of 108.2~160.3 MPa, a porosity of 65%~84%, and a room temperature ionic conductivity of 0.33~0.71 mS / cm. - ¹.

3. A method for preparing a lithium battery separator coated with aramid nanofibers, characterized in that, The method for preparing a lithium battery separator coated with aramid nanofibers as described in any one of claims 1 to 2 includes the following steps: Potassium hydroxide was dissolved in deionized water, and then para-aramid short fibers and dimethyl sulfoxide were added and mixed and stirred to obtain an ANF / DMSO dispersion. ZrO2 nanoparticles were added to a DMSO solution and ultrasonically treated to obtain a ZrO2 / DMSO dispersion. The ANF / DMSO dispersion and the ZrO2 / DMSO dispersion were then mixed and stirred to obtain an ANF / ZrO2 / DMSO composite slurry. The ANF / ZrO2 / DMSO composite slurry was high-pressure sprayed onto the surface of a plasma-etched polypropylene base film, then soaked in deionized water and dried to obtain a lithium battery separator coated with aramid nanofibers.

4. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The plasma etching time is 60~90 s.

5. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The ratio of the para-aramid short-cut fibers, potassium hydroxide, and dimethyl sulfoxide is 1g:1.5g:200mL, and the volume ratio of the deionized water to dimethyl sulfoxide is 1:

25.

6. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The conditions for dissolving potassium hydroxide in deionized water include: stirring at a mechanical stirring speed of 1200–1500 r / min for 5–20 min; The mixing and stirring time is 2-4 hours.

7. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The mass concentration of the ANF / DMSO dispersion is 0.5%, and the aramid nanofibers in the ANF / DMSO dispersion have a diameter of 12~15 nm and a length of 4~7 μm.

8. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The ultrasonic treatment has a power of 500~1500 W and a duration of 20~40 min; The high-pressure spraying pressure is 0.2~0.5 MPa, and the spraying distance is 50~70 cm.

9. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The ZrO2 nanoparticles have a particle size of 50 nm.

10. The method for preparing a lithium battery separator coated with aramid nanofibers according to claim 3, characterized in that, The drying temperature is 50~80℃, and the time is 3~7 min; The soaking time in deionized water is 10h to 16h.

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