Hap-anf composite diaphragm and preparation method and application thereof

Abstract

This invention discloses a HAP-ANF composite separator, its preparation method, and its applications, belonging to the fields of polymer fibers and lithium-ion batteries. The HAP-ANF composite separator is produced by mixing aramid nanofibers and hydroxyapatite nanofibers using a wet papermaking process. The production process is simple and feasible, avoiding problems such as loose paper structure, poor interfacial bonding, and low mechanical and compressive strength caused by the large dimensional differences in aramid separator paper components. The prepared HAP-ANF composite separator has high temperature resistance and flame retardancy, effectively improving battery safety and stability. It can be used to manufacture thinner, lighter, and more compact high-capacity batteries, offering significant development opportunities in the new energy and high-end consumer goods sectors, thus achieving higher-quality development in the aramid fiber industry.

Description

Technical Field

[0001] This invention belongs to the field of polymer fibers and lithium-ion batteries, specifically relating to a HAP-ANF composite separator, its preparation method, and its application. Background Technology

[0002] As one of the four major components of a lithium-ion battery, the separator plays a crucial role in isolating the positive and negative electrodes, blocking electrons, and allowing lithium ions to pass through. Although the separator does not directly participate in the chemical reactions within the battery, it has a significant impact on the battery's electrochemical performance, cycle life, and safety. Currently, news reports of fires and explosions involving electric vehicles and new energy vehicles are frequent, making battery safety a primary concern for consumers when choosing to purchase new energy vehicles and electric scooters. Therefore, developing battery separators that can improve battery safety and efficiency is of great importance. While battery technology is crucial, automotive safety also requires a focus on specific materials research. The thermal safety temperature of the separator largely depends on the substrate used to prepare it. Currently, commercially available polyolefin separators possess excellent electrochemical performance, corrosion resistance, and superior pore size. However, the inherent poor thermal stability, low strength, and poor wettability of polyolefin materials limit their application in high-performance lithium-ion power batteries and severely impact battery cycle life, failing to meet the demands of power battery use.

[0003] To further improve the mechanical properties and thermal stability of separators, aramid nanofibers, with their high temperature resistance, high strength and modulus, acid and alkali resistance, and high insulation, have become a novel material of widespread interest to researchers. Aramid nanofibers possess excellent properties such as high strength, high modulus, good stability, degradation resistance, high temperature resistance, corrosion resistance, low density, and good flexibility, meeting the performance requirements of lithium-ion battery separators. Based on this, multiple research groups and teams have focused on the preparation and application of high-performance aramid paper-based lithium-ion battery separators. Using wet molding technology, they have prepared lithium-ion battery separators with excellent comprehensive performance, including controllable structure, high porosity, suitable pore size, good electrolyte wettability, and high ionic conductivity. They have also found that these separators effectively inhibit lithium dendrite puncture of the separator.

[0004] In terms of application, the thickness of battery separators should be as thin as possible to facilitate the efficient passage of lithium ions. However, excessively thin separators are prone to puncture, tearing, and breakage. Therefore, ensuring both thinness and high strength of the separator is a pressing issue. Based on currently available research, many researchers have begun using differentiated aramid fibers to prepare lithium-ion battery separators. Chinese invention patent application CN115207559A, published on October 18, 2022, uses differentiated aramid fibers as raw material to prepare a high-performance aramid separator through wet molding. High-temperature hot pressing further strengthens the fiber bonding in the separator, significantly improving its strength and puncture resistance. Chinese invention patent application CN114865219A, published on August 5, 2022, uses a spray method to coat the surfaces of polypropylene or polyethylene with an aramid composite slurry, resulting in a coating only 0.5–4 micrometers thick. This improves the ductility of the prepared separator, leading to a longer battery life, better safety, and lower cost. Based on existing research, it can be inferred that the focus of research is on how to improve the thermal stability and strength of battery separators while ensuring good porosity and high liquid absorption rate.

[0005] Hydroxyapatite is a green, stable, and widely available inorganic material with high strength, high temperature resistance, good flame retardancy, and good electrolyte wettability. It maintains its structural integrity even at 1000℃. The surface hydration layer of an aqueous dispersion of hydroxyapatite nanowires prepared via hydrothermal synthesis has numerous hydrogen bonds, exhibiting excellent compatibility with water molecules. Currently, there are few lithium-ion battery separators prepared using aramid fibers and hydroxyapatite; therefore, the preparation of lithium-ion battery separators using aramid fibers and hydroxyapatite represents an emerging field.

[0006] To address the aforementioned issues encountered in the development of lithium battery separator technology, the current bottleneck lies in the ability to uniformly and efficiently prepare high-performance aramid separators while ensuring appropriate porosity and high liquid absorption rate.

[0007] Therefore, the current challenge is to improve the thermal stability and strength of the battery separator while ensuring good porosity and high liquid absorption rate. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of how to improve the thermal stability and strength of battery separators while ensuring good porosity and high liquid absorption rate. It provides a HAP-ANF composite separator, its preparation method and application. The composite separator prepared using hydroxyapatite nanowires and aramid nanofibers has high flexibility, good mechanical strength, rich pore structure, excellent electrolyte wettability, high thermal stability and flame retardancy.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a HAP-ANF composite membrane includes using calcium chloride, oleic acid, sodium oleate, ethanol, sodium hydroxide, and sodium dihydrogen phosphate as raw materials. The raw materials are prepared by hydrothermal synthesis to obtain a hydrothermal synthesis product. The hydrothermal synthesis product is then heated, stirred, and washed to obtain an aqueous dispersion of hydroxyapatite nanowires. Para-aramid fibers are prepared in a dimethyl sulfoxide (DMSO) alkaline solution system to obtain an aramid nanofiber / DMSO solution. This aramid nanofiber / DMSO solution is protonated to obtain an aqueous dispersion of aramid nanofibers. The hydrothermal synthesis product is mixed with the aramid nanofiber / DMSO solution, and then heated, stirred, and washed several times to obtain a mixed dispersion A. The aqueous dispersion of hydroxyapatite nanowires is mixed with the aramid nanofiber / DMSO solution, and then heated, stirred, and washed several times to obtain a mixed dispersion B. The aqueous dispersion of hydroxyapatite nanowires is mixed with the aqueous dispersion of aramid nanofibers to obtain a mixed dispersion C. The concentration of mixed dispersions A, B, or C is adjusted, and then wet-processed to obtain the HAP-ANF composite membrane.

[0011] Furthermore, the mass concentration of the aramid nanofiber / dimethyl sulfoxide solution is 0.2% to 1%; the mass concentration of the aramid nanofiber aqueous dispersion is 1% to 2%; the hydrothermal synthesis product is heated using alcohol, and the washing process uses deionized water; the temperature of the hydrothermal synthesis method is 150℃ to 250℃, and the synthesis reaction time of the hydrothermal synthesis method is 20 to 36 hours.

[0012] Furthermore, the mass concentration of the aramid nanofiber / dimethyl sulfoxide solution is 0.2% to 1%; the mass concentration of the aramid nanofiber aqueous dispersion is 0.5% to 5%; the hydrothermal synthesis product is heated using alcohol, and the washing process uses deionized water; the temperature of the hydrothermal synthesis method is 180℃ to 200℃, and the synthesis reaction time of the hydrothermal synthesis method is 22 to 25 hours.

[0013] Furthermore, the para-aramid fiber is a chopped para-aramid fiber with an average length of 3-20 mm and an average diameter of 6-15 μm.

[0014] Furthermore, the para-aramid fiber is a chopped para-aramid fiber with an average length of 3-12 mm and an average diameter of 8-12 μm.

[0015] Furthermore, the raw materials are oleic acid, ethanol, calcium chloride, sodium hydroxide, and sodium dihydrogen phosphate, or sodium oleate, calcium chloride, and sodium dihydrogen phosphate; the average diameter of the hydroxyapatite nanowires in the aqueous dispersion is 100 nm, and the length of the hydroxyapatite nanowires in the aqueous dispersion is 30 μm; the mass concentration of the mixed dispersion A, B, or C is 1% to 5%.

[0016] Furthermore, the adjustment is carried out using magnetic stirring, and the wet papermaking process specifically involves vacuum filtration followed by heating and drying. The vacuum pressure is -0.1 MPa, the heating and drying temperature is 65–85°C, and the heating and drying time is 5–10 minutes.

[0017] Furthermore, the mass ratio of hydroxyapatite nanowires to aramid nanofibers in the mixed dispersion A, B or C is (50-10):(50-90).

[0018] A HAP-ANF composite membrane is prepared using the preparation method described above. The thickness of the composite membrane is 22 μm to 25 μm, the porosity of the composite membrane is above 60%, and the liquid absorption rate of the composite membrane is above 200%.

[0019] Application of a HAP-ANF composite separator in the preparation of lithium-ion batteries.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] This invention produces HAP-ANF composite separators by mixing aramid nanofibers and hydroxyapatite nanofibers and using a wet papermaking process. The production process is simple and feasible, avoiding the problems of loose paper structure, poor interfacial bonding, low mechanical strength and compressive strength caused by the large differences in the dimensional composition of existing aramid separator paper. By using aramid nanofibers and hydroxyapatite nanowires as the main raw materials, the toughness of aramid fiber separators and the high temperature resistance of hydroxyapatite nanowires are combined, enabling the HAP-ANF composite separator to work stably without shrinking at temperatures above 200°C, thus giving the HAP-ANF composite separator the ability to work stably in high-temperature environments.

[0022] This invention introduces hydroxyapatite nanowires into aramid nanofibers, which significantly improves the interfacial bonding strength of aramid fiber-based materials and significantly enhances the electrolyte wettability of aramid nanofiber separators. This not only provides new ideas and theoretical guidance for the preparation of high-performance battery separator paper, but also helps to enrich the existing hydroxyapatite composite material preparation technology and theory.

[0023] This invention employs a wet papermaking process in the preparation of the diaphragm, which is simple and convenient to operate, providing a simple approach and feasible solution for the subsequent industrial production of diaphragms.

[0024] The HAP-ANF composite separator prepared by this invention has high temperature resistance and flame retardancy, which can effectively improve the safety and stability of the battery. It can be used to manufacture lighter, thinner, and more compact high-capacity batteries, and has great development opportunities in the fields of new energy and high-end consumer products, so as to achieve higher quality development of the aramid fiber industry. Attached Figure Description

[0025] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is a scanning electron microscope image of the composite membrane in Embodiment 4 of the present invention.

[0027] Figure 2 The image shows the XRD pattern of hydroxyapatite nanowires in the HAP NWs / H2O dispersion prepared in this embodiment of the invention.

[0028] Figure 3 This is a scanning electron microscope image of the composite membrane in Embodiment 1 of the present invention. Detailed Implementation

[0029] The present invention will now be described in further detail:

[0030] A method for preparing a HAP-ANF composite separator involves wet papermaking using a dispersion of hydroxyapatite nanowires (HAP NWs) and aramid nanofibers (ANFs), wherein the mass ratio of HAP NWs to ANFs is (50–10):(50–90). The raw materials are processed through steps including preparation, mixing, and molding to obtain a HAP-ANF composite separator. The composite separator has a thickness of 22 μm–25 μm, a porosity of over 60%, and a liquid absorption rate of over 200%.

[0031] A method for preparing a HAP-ANF composite membrane includes the following steps:

[0032] (1) Preparation of HAP NWs: Hydrothermal synthesis was performed using oleic acid, ethanol, calcium chloride, sodium hydroxide, and sodium dihydrogen phosphate, or sodium oleate, calcium chloride, and sodium dihydrogen phosphate, as raw materials. The hydrothermal synthesis temperature was limited to 180℃~200℃ or 150℃~250℃, and the reaction time was 22~25 hours or 20~36 hours. The hydrothermal synthesis product was then heated and stirred with alcohol and washed with deionized water to obtain a HAP NWs / H2O dispersion. The average diameter of the HAP NWs in the HAP NWs / H2O dispersion was 100 nm, and the length was 30 μm. Figure 2 The image shows the XRD pattern of HAP NWs in the prepared HAP NWs / H2O dispersion.

[0033] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 3-20 mm or 3-12 mm and an average diameter of 6-15 μm or 8-12 μm were used as raw materials to prepare aramid nanofibers using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.2%-1%. Then, deionized water was injected to obtain an ANFs / H2O dispersion with a concentration of 0.5%-5% or 1%-2%.

[0034] (3) Preparation of the mixed slurry: The HAP NWs prepared in step (1) and ANFs prepared in step (2) are mixed using one of the following three methods: the hydrothermal synthesis product is directly mixed with ANF / DMSO; the HAP NWs / H2O dispersion obtained after washing the hydrothermal synthesis product is mixed with ANF / DMSO through a protonation process; the HAPNWs / H2O dispersion obtained after washing the hydrothermal synthesis product is mixed with the ANFs / H2O dispersion. Then, the mixed dispersion is obtained by heating, stirring and washing with alcohol and deionized water 3 to 5 times.

[0035] (4) Fabrication and molding of composite membrane: The concentration of the mixed dispersion obtained in step (3) is adjusted to 1-5% or 0.2%-0.5% by magnetic stirring. Then, wet fabrication is carried out by vacuum filtration. After drying at 65-85℃ for 5-10 minutes under a pressure of -0.1MPa, a HAP-ANF composite membrane is obtained.

[0036] Application of a HAP-ANF composite separator in the preparation of lithium-ion batteries.

[0037] The present invention will be further described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and raw material ratios in the embodiments of the present invention can be combined with each other. All technical terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terminology used in the present invention is only for describing specific embodiments and is not intended to limit the exemplary embodiments of the present invention.

[0038] Example 1

[0039] A HAP-ANF composite separator is prepared by wet papermaking using a dispersion of HAP NWs and ANFs, wherein the mass ratio of HAP NWs to ANFs is 50:50. The raw materials are processed through steps such as preparation, mixing, and molding to obtain the HAP-ANF composite separator. The composite separator has a thickness of 22 μm, a porosity of 83%, and a liquid absorption rate of 320%.

[0040] A method for preparing a HAP-ANF composite membrane includes the following steps:

[0041] (1) Preparation of HAP NWs: Using oleic acid, ethanol, calcium chloride, sodium hydroxide, and sodium dihydrogen phosphate (mass ratio 12:12:0.22:1:0.28) as raw materials, a hydrothermal synthesis method was used to prepare the product. The hydrothermal synthesis method was limited to a temperature of 180℃ and a reaction time of 22 hours. The product was then washed with alcohol and deionized water under heating and stirring to obtain a HAP NWs / H2O dispersion. The average diameter of the HAP NWs in the HAP NWs / H2O dispersion was 100 nm, and the length of the HAP NWs was 30 μm.

[0042] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 3 mm and an average diameter of 6 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.2%. Then, deionized water was injected to obtain an ANFs / H2O dispersion with a concentration of 0.5% through a protonation process.

[0043] (3) Preparation of mixed slurry: The hydrothermal synthesis product obtained in step (1) is directly mixed with the ANF / DMSO solution obtained in step (2); then the mixture is heated, stirred and washed 5 times with alcohol and deionized water to obtain a mixed dispersion.

[0044] (4) Fabrication and molding of the composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 1% using magnetic stirring, and then wet fabrication was performed by vacuum filtration. After drying at 65°C for 10 minutes under a pressure of -0.1 MPa, a HAP-ANF composite membrane was obtained. Figure 1 The image shown is a scanning electron microscope (SEM) image of the composite membrane prepared in this embodiment.

[0045] Lithium-ion batteries were prepared using HAP-ANF composite separators.

[0046] Example 2

[0047] A HAP-ANF composite separator and its preparation method are disclosed. The method involves wet-processing of a dispersion of HAP NWs and ANFs into paper, wherein the mass ratio of HAP NWs to ANFs is 40:60. The raw materials are processed through steps such as preparation, mixing, and molding to obtain a HAP-ANF composite separator with a thickness of 23 μm, a porosity of 78%, and a liquid absorption rate of 300%.

[0048] A HAP-ANF composite membrane and its preparation method, comprising the following steps:

[0049] 1) Preparation of HAP NWs: Using oleic acid, ethanol, calcium chloride, sodium hydroxide and sodium dihydrogen phosphate (mass ratio of 12:12:0.22:1:0.28) as raw materials, a hydrothermal synthesis method was used to prepare the hydrothermal synthesis product. The limited temperature of the hydrothermal synthesis method was 200℃ and the synthesis reaction time was 25 hours. The hydrothermal synthesis product was then washed with alcohol and deionized water under heating and stirring to obtain the HAP NWs / H2O dispersion.

[0050] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 10 mm and an average diameter of 8 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.5%. Then, deionized water was injected and protonated to obtain an ANFs / H2O dispersion with a concentration of 5%.

[0051] (3) Preparation of mixed slurry: The HAP NWs / H2O dispersion obtained in step (1) is mixed with the ANF / DMSO solution obtained in step (2) through a protonation process; then the mixed dispersion is obtained by heating, stirring and washing with alcohol and deionized water 5 times.

[0052] (4) Fabrication and molding of composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 3% by magnetic stirring, and then wet fabrication was carried out by vacuum filtration. After drying at 70°C for 9 minutes under a pressure of -0.1MPa, a HAP-ANF composite membrane was obtained.

[0053] Example 3

[0054] A HAP-ANF composite separator and its preparation method are disclosed. The method involves wet-processing of a dispersion of HAP NWs and ANFs into paper, wherein the mass ratio of HAP NWs to ANFs is 40:60. The raw materials are processed through steps such as preparation, mixing, and molding to obtain a HAP-ANF composite separator with a thickness of 23 μm, a porosity of 78%, and a liquid absorption rate of 300%.

[0055] A HAP-ANF composite membrane and its preparation method, comprising the following steps:

[0056] 1) Preparation of HAP NWs: Using oleic acid, ethanol, calcium chloride, sodium hydroxide and sodium dihydrogen phosphate (mass ratio of 12:12:0.22:1:0.28) as raw materials, a hydrothermal synthesis method was used to prepare the hydrothermal synthesis product. The limited temperature of the hydrothermal synthesis method was 190℃ and the synthesis reaction time was 24 hours. The hydrothermal synthesis product was then washed with alcohol and deionized water under heating and stirring to obtain the HAP NWs / H2O dispersion.

[0057] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 12 mm and an average diameter of 10 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.5%. Then, deionized water was injected and protonated to obtain an ANFs / H2O dispersion with a concentration of 1%.

[0058] (3) Preparation of mixed slurry: The HAP NWs / H2O dispersion obtained in step (1) is mixed with the ANFs / H2O dispersion obtained in step (2); then the mixed dispersion is obtained by heating, stirring and washing with alcohol and deionized water 4 times.

[0059] (4) Fabrication and molding of composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 5% by magnetic stirring, and then wet fabrication was carried out by vacuum filtration. After drying at 70°C for 9 minutes under a pressure of -0.1MPa, a HAP-ANF composite membrane was obtained.

[0060] Example 4

[0061] A HAP-ANF composite separator and its preparation method are disclosed. The method involves wet papermaking using a dispersion of HAP NWs and ANFs, wherein the mass ratio of HAP NWs to ANFs is 30:70. The raw materials are processed through steps including preparation, mixing, and molding to obtain a HAP-ANF composite separator with a thickness of 24 μm, a porosity of 75%, and a liquid absorption rate of 280%.

[0062] A HAP-ANF composite membrane and its preparation method, comprising the following steps:

[0063] (1) Preparation of HAP NWs: Sodium oleate, calcium chloride and sodium dihydrogen phosphate (mass ratio of 24:2.2:2.8) were used as raw materials to prepare the hydrothermal synthesis product by hydrothermal synthesis method. The limited temperature of hydrothermal synthesis method was 150℃ and the synthesis reaction time was 20 hours. The hydrothermal synthesis product was then washed with alcohol and deionized water by heating and stirring to obtain HAP NWs / H2O dispersion.

[0064] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 15 mm and an average diameter of 12 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.6%. Then, deionized water was injected and protonated to obtain an ANFs / H2O dispersion with a concentration of 2%.

[0065] (3) Preparation of mixed slurry: The HAP NWs / H2O dispersion obtained in step (1) is mixed with the ANF / DMSO solution obtained in step (2) through a protonation process; then the mixed dispersion is obtained by heating, stirring and washing three times with alcohol and deionized water.

[0066] (4) Fabrication and molding of composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 0.2% by magnetic stirring, and then wet fabrication was carried out by vacuum filtration. After drying at 75°C for 8 minutes under a pressure of -0.1MPa, a HAP-ANF composite membrane was obtained.

[0067] The HAP-ANF composite diaphragm prepared in Example 4 of this invention was tested and characterized. Some of its indicators are as follows: 1. Diaphragm paper thickness is 21 μm; 2. Porosity is 75%; 3. Liquid absorption rate is 255%; 4. Tensile strength is 21 MPa.

[0068] Example 5

[0069] A HAP-ANF composite separator and its preparation method are disclosed. The method involves wet-processing of a dispersion of HAP NWs and ANFs into paper, wherein the mass ratio of HAP NWs to ANFs is 20:80. The raw materials are processed through steps such as preparation, mixing, and molding to obtain a HAP-ANF composite separator with a thickness of 25 μm, a porosity of 65%, and a liquid absorption rate of 238%.

[0070] A HAP-ANF composite membrane and its preparation method, comprising the following steps:

[0071] (1) Preparation of HAP NWs: Sodium oleate, calcium chloride and sodium dihydrogen phosphate (mass ratio of 24:2.2:2.8) were used as raw materials to prepare the hydrothermal synthesis product by hydrothermal synthesis method. The limited temperature of hydrothermal synthesis method was 200℃ and the synthesis reaction time was 28 hours. The hydrothermal synthesis product was then washed with alcohol and deionized water by heating and stirring to obtain HAP NWs / H2O dispersion.

[0072] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 20 mm and an average diameter of 15 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 1%. Then, a deionized water protonation process was injected to obtain an ANFs / H2O dispersion with a concentration of 1.5%.

[0073] (3) Preparation of mixed slurry: The hydrothermal synthesis product obtained in step (1) is directly mixed with the ANF / DMSO solution obtained in step (2); then the mixture is heated, stirred and washed 5 times with alcohol and deionized water to obtain a mixed dispersion.

[0074] (4) Fabrication and molding of the composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 0.5% using magnetic stirring, and then wet fabrication was performed by vacuum filtration. After drying at 85°C for 5 minutes under a pressure of -0.1 MPa, a HAP-ANF composite membrane was obtained. Figure 1 The image shown is a scanning electron microscope image of the HAP-ANF composite membrane prepared in Example 4 of this invention.

[0075] Example 6

[0076] A HAP-ANF composite separator and its preparation method are disclosed. The method involves wet-processing of a dispersion of HAP NWs and ANFs into paper, wherein the mass ratio of HAP NWs to ANFs is 10:90. The raw materials are processed through steps such as preparation, mixing, and molding to obtain a HAP-ANF composite separator with a thickness of 23 μm, a porosity of 60%, and a liquid absorption rate of 200%.

[0077] A HAP-ANF composite membrane and its preparation method, comprising the following steps:

[0078] 1) Preparation of HAP NWs: Sodium oleate, calcium chloride and sodium dihydrogen phosphate (mass ratio of 24:2.2:2.8) were used as raw materials to prepare the hydrothermal synthesis product. The hydrothermal synthesis method was limited to a temperature of 250℃ and a reaction time of 36 hours. The hydrothermal synthesis product was then washed with alcohol and deionized water under heating and stirring to obtain a HAP NWs / H2O dispersion.

[0079] (2) Preparation of ANFs: Para-aramid short-cut fibers with an average length of 18 mm and an average diameter of 12 μm were used as raw materials. Aramid nanofibers were prepared using a dimethyl sulfoxide alkaline solution system to obtain an ANFs / DMSO solution with a concentration of 0.5%. Then, deionized water was injected to obtain an ANFs / H2O dispersion with a concentration of 2.5% through a protonation process.

[0080] (3) Preparation of mixed slurry: The HAP NWs / H2O dispersion obtained in step (1) is mixed with the ANFs / H2O dispersion obtained in step (2); then the mixed dispersion is obtained by heating, stirring and washing three times with alcohol and deionized water.

[0081] (4) Fabrication and molding of composite membrane: The concentration of the mixed dispersion obtained in step (3) was adjusted to 0.3% by magnetic stirring, and then wet fabrication was carried out by vacuum filtration. After drying at 70°C for 9 minutes under a pressure of -0.1MPa, a HAP-ANF composite membrane was obtained.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A method for preparing a HAP-ANF composite membrane, characterized in that, Using calcium chloride, oleic acid, sodium oleate, ethanol, sodium hydroxide, and sodium dihydrogen phosphate as raw materials, a hydrothermal synthesis product was prepared from the raw materials using a hydrothermal synthesis method. The hydrothermal synthesis product was then heated, stirred, and washed to obtain an aqueous dispersion of hydroxyapatite nanowires. An aramid nanofiber / dimethyl sulfoxide solution was prepared from para-aramid fibers in a dimethyl sulfoxide alkaline solution system. This aramid nanofiber / dimethyl sulfoxide solution was protonated to obtain an aqueous dispersion of aramid nanofibers. The hydrothermal synthesis product was mixed with the aramid nanofiber / dimethyl sulfoxide solution, and then heated, stirred, and washed several times to obtain mixed dispersion A. The aqueous dispersion of hydroxyapatite nanowires was mixed with the aramid nanofiber / dimethyl sulfoxide solution, and then heated, stirred, and washed several times to obtain mixed dispersion B. The aqueous dispersion of hydroxyapatite nanowires was mixed with the aqueous dispersion of aramid nanofibers to obtain mixed dispersion C. After adjusting the concentration of mixed dispersions A, B, or C, a wet papermaking process was used to obtain a HAP-ANF composite membrane. The mass concentration of the aramid nanofiber / dimethyl sulfoxide solution is 0.2%~1%; the mass concentration of the aramid nanofiber aqueous dispersion is 1%~2%; the hydrothermal synthesis product is heated with alcohol, and the washing is done with deionized water; the temperature of the hydrothermal synthesis method is 150℃~250℃, and the synthesis reaction time of the hydrothermal synthesis method is 20~36 hours. The mass concentration of the aramid nanofiber / dimethyl sulfoxide solution is 0.2%~1%; the mass concentration of the aramid nanofiber aqueous dispersion is 0.5%~5%; the hydrothermal synthesis product is heated using alcohol, and the washing process uses deionized water; the temperature of the hydrothermal synthesis method is 180℃~200℃, and the synthesis reaction time of the hydrothermal synthesis method is 22~25 hours. The para-aramid fiber is a chopped para-aramid fiber with an average length of 3-20 mm and an average diameter of 6-15 μm. The para-aramid fiber is a chopped para-aramid fiber with an average length of 3-12 mm and an average diameter of 8-12 μm. The hydroxyapatite nanowires in the aqueous dispersion have an average diameter of 100 nm and a length of 30 μm; the mass concentration of the mixed dispersion A, B, or C is 1% to 5%. The adjustment is carried out using magnetic stirring. The wet papermaking process specifically involves vacuum filtration followed by heating and drying. The vacuum pressure is -0.1 MPa, the heating and drying temperature is 65~85℃, and the heating and drying time is 5~10 min. The mass ratio of hydroxyapatite nanowires to aramid nanofibers in the mixed dispersion A, B or C is (50~10):(50~90).

2. A HAP-ANF composite membrane, prepared by the method according to any one of claims 1, characterized in that, The composite membrane has a thickness of 22μm to 25μm, a porosity of over 60%, and a liquid absorption rate of over 200%.

3. The application of the HAP-ANF composite separator according to claim 2 in the preparation of lithium-ion batteries.

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