Functionalized aramid nanofiber-based battery separator and preparation method and application thereof

Abstract

The application discloses a kind of functional aramid nanofiber-based battery separators and its preparation method and application, aramid nanofiber film is prepared using aramid nanofiber, and the surface thereof is functionally modified to obtain functional aramid nanofiber-based battery separator.The separator has unique nano-scale structure, high strength and high modulus, good temperature resistance, and rich pore structure characteristics.Compared with the current commercial polyolefin separator, the battery separator provided by the application has significantly improved temperature resistance, electrolyte wettability and mechanical properties.After the surface of the separator is functionally modified, it has more active groups, which can adsorb the products generated during the battery reaction through physical adsorption and chemical bonding, improve the battery reaction activity, increase the discharge capacity during the battery charge and discharge cycle, and reduce the average capacity decay rate per cycle.The separator has high mechanical strength, excellent temperature resistance and surface functional groups, and has wide application prospects in the fields of lithium-ion batteries, lithium-sulfur batteries and the like.

Description

Technical Field

[0001] This invention belongs to the field of battery separators, specifically relating to a functionalized aramid nanofiber-based battery separator, its preparation method, and its application. Background Technology

[0002] In recent years, with the development of new energy vehicles towards higher energy density and higher discharge capacity, research on high-performance battery materials has become increasingly extensive. As one of the four basic components of battery materials, the separator plays a crucial role in preventing contact between the positive and negative electrodes and transporting lithium ions. Currently, the battery separator materials widely used in commercial batteries are mainly polyethylene (PE), polypropylene (PP), and their composites (PP / PE / PP). Polyolefin materials have simple preparation processes, low prices, and excellent chemical properties, but they suffer from poor mechanical strength, poor electrolyte wettability, and poor high-temperature resistance. They gradually shrink when the temperature rises above 120℃, and thermal pores appear when the temperature exceeds 160℃, making it difficult to inhibit the growth of lithium dendrites and seriously threatening battery safety. Therefore, the development of high-performance battery separator materials is urgently needed.

[0003] In the existing battery separator preparation process, the main focus is on optimizing and modifying commercial polyolefin separators to change the thermal stability and electrolyte wettability of the separator, thereby improving the discharge capacity of the battery. (1) The invention patent with publication number CN111628134A proposes to add a modified coating to the polyethylene matrix microporous membrane. In the modified and reinforced coating, the addition of nano-inorganic powder can enhance the polyethylene matrix microporous membrane, thereby reducing the thermal shrinkage performance of the polyethylene matrix microporous membrane, effectively improving the charge and discharge performance of the lithium-ion battery, reducing the influence of the coating on lithium-ion transport, and improving the performance of the lithium-ion battery separator. However, this modification method modifies the surface of the polyolefin separator, which reduces the cycle life of the battery during the charge and discharge process. (2) The invention patent with authorization publication number CN107658408B addresses the problem of low high-temperature integrity of existing polypropylene or polyethylene porous separators, as well as the unreasonable pore structure of existing electrospun separators. The proposed composite multilayer polyolefin lithium battery separator has a PET and PVDF-HFP composite coating electrospun on the surface of the polyolefin porous separator. PVDF-HFP improves the wettability of the separator due to its swelling properties in the electrolyte. Therefore, the composite multilayer polyolefin lithium battery separator has high temperature resistance and high electrolyte wettability. However, this method requires electrospinning, which is complex, has high preparation cost, and uses many components, which affects the lithium ion transport speed of the separator. (3) The invention patent with publication number CN111244361A proposes a polyolefin separator with an ordered mesoporous silica coating on the surface of the polyolefin separator and its preparation method and application. However, the preparation process of this composite separator is complex, and the use of adhesives and thickeners has a great impact on the performance of the separator.

[0004] Para-aramid fibers possess excellent properties such as temperature resistance, flame retardancy, and superior mechanical properties, making them widely applicable in specialty materials and military fields. Para-aramid nanofibers (ANFs), as a newly emerging nanoscale material in recent years, retain the high strength and high modulus characteristics of macroscopic aramid fibers due to their unique nanoscale structure and large aspect ratio. They serve as a novel nanostructural building block, playing a crucial role in interface reinforcement and material toughening. ANFs can form a cross-linked network structure through strong hydrogen bonding, exhibiting excellent film-forming properties. ANF films possess superior porosity, playing a vital role in suppressing lithium dendrite penetration of the separator and improving lithium-ion transport rates, thus significantly enhancing the overall performance of battery separators. Summary of the Invention

[0005] The purpose of this invention is to provide a functionalized aramid nanofiber-based battery separator, its preparation method, and its application, in order to overcome the problems of poor mechanical properties, easy shrinkage and deformation, smooth surface, lack of active groups, and easy puncture by lithium dendrites in commercial polyolefin separators. This invention uses a new method to develop a novel aramid nanofiber-based battery separator with excellent temperature resistance, high mechanical strength, high electrolyte wettability, and functionalization, which has broad application prospects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a functionalized aramid nanofiber-based battery separator includes the following steps:

[0008] S1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0009] S2: The aramid nanofiber gel is hydroxylated using a hydroxylation modifier, and then hydroxylated aramid nanofiber films are prepared by dispersion, vacuum-assisted filtration, and layer-by-layer self-assembly.

[0010] S3: After surface oxidation treatment, hydroxylated aramid nanofiber film is activated to obtain surface carboxylated aramid nanofiber film.

[0011] S4: After activating the surface carboxylated aramid nanofiber film, functionalized aramid nanofiber-based battery separators are obtained by self-assembly alternating impregnation method.

[0012] Further, in S1, the mass concentration of the aramid nanofiber / dimethyl sulfoxide dispersion is 0.1% to 0.5%.

[0013] Furthermore, in S2, the hydroxylation modifier is a phosphoric acid solution with a mass concentration of 85%, and the ratio between the aramid nanofiber gel and the phosphoric acid solution is 1g:200ml.

[0014] Furthermore, the hydroxylation modification treatment is performed at a temperature of 40℃ to 60℃ for 1 hour.

[0015] Furthermore, in S3, the surface oxidation treatment employs an oxidant and a catalyst, wherein the oxidant is a hydrogen peroxide solution with a mass concentration of 0.1%, and the catalyst is ferric chloride.

[0016] Furthermore, in S3, the activation treatment uses a lithium hydroxide solution with a molar concentration of 0.1 mol / L.

[0017] Furthermore, in S4, the activation treatment uses a lithium hydroxide solution with a molar concentration of 0.1 mol / L, and the activation treatment time is 10 min.

[0018] Furthermore, in S4, the impregnation solution used in the self-assembly alternating impregnation method is a polydiallyldimethylammonium chloride solution and a sodium terephthalate sulfonate solution;

[0019] The mass concentration of the polydiallyldimethylammonium chloride solution is 20%, and the mass concentration of the sodium poly(p-styrene sulfonate) solution is 30%.

[0020] The single immersion time of the polydiallyldimethylammonium chloride solution is 10 min to 15 min, and the single immersion time of the sodium poly(p-styrene sulfonate) solution is 15 min to 25 min.

[0021] A functionalized aramid nanofiber-based battery separator is obtained by the above-mentioned preparation method of a functionalized aramid nanofiber-based battery separator. The battery separator has an average thickness of 35 μm, a porosity of 52%, an electrolyte absorption rate of 198%, a tensile strength of 138 MPa, and a maximum decomposition temperature of 486 °C.

[0022] Application of a functionalized aramid nanofiber-based battery separator in lithium-ion and lithium-sulfur batteries.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] This invention provides a method for preparing a functionalized aramid nanofiber-based battery separator. Using aramid nanofibers, which possess unique nanoscale structures, high strength and modulus, high specific surface area, high aspect ratio, and excellent temperature resistance, as raw materials, a novel high-performance aramid nanofiber-based battery separator is prepared. The surface of the obtained aramid nanofiber-based battery separator is treated with carboxylation and a self-assembly alternating impregnation method to functionalize the separator. This significantly reduces the internal resistance of the separator and, during battery charge-discharge cycles, inhibits the growth and penetration of lithium dendrites through physical adsorption or chemical bonding, thereby improving the battery's discharge capacity. This method meets the application requirements of batteries with high cycle stability, high safety, and high rate performance, laying the foundation for its large-scale production and application.

[0025] This invention provides a functionalized aramid nanofiber-based battery separator with a multi-layered and distinct Z-axis hierarchical structure. During battery charge-discharge cycles, it provides more pore structures, improving the free transport speed of lithium ions. The multi-layered structure can inhibit the growth of lithium dendrites and resist the damage of lithium dendrites to the separator structure. When the temperature rises, the Z-axis hierarchical structure can hinder external force damage and improve the temperature resistance of the separator. It can meet the application requirements of separators in fields such as lithium-ion batteries and lithium-sulfur batteries, and improves the overall energy density, charge-discharge capacity, cycle stability and overall safety of the battery.

[0026] This invention provides an application of a functionalized aramid nanofiber-based battery separator in the field of battery separators. Compared with currently commercially available polyolefin materials, the separator material prepared by this invention has significantly improved temperature resistance, and does not exhibit dimensional shrinkage or thermal pore blockage, ensuring battery safety. In addition, the electrolyte wettability and mechanical strength of the ANF-based battery separator are improved, exhibiting excellent electrolyte wettability and mechanical strength. This provides a new approach for the preparation of next-generation battery separators and has broad application prospects in lithium-sulfur batteries and lithium-ion batteries. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a flowchart illustrating the preparation process of the surface-carboxylated aramid nanofiber thin film of the present invention.

[0029] Figure 2 This is a flowchart illustrating the preparation process of functionalized aramid nanofiber-based battery separators using the self-assembly surface alternating impregnation method of this invention.

[0030] Figure 3This is a comparison chart of the mechanical properties of the functionalized aramid nanofiber-based battery separator and the PP separator prepared in Example 2 of the present invention.

[0031] Figure 4 This is a comparison chart of the temperature resistance of the functionalized aramid nanofiber-based battery separator and the PP separator prepared in Example 2 of the present invention. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below:

[0033] A method for preparing a functionalized aramid nanofiber-based battery separator involves preparing an aramid nanofiber thin film using aramid nanofibers and then performing functionalization modification treatment on its surface to obtain the functionalized aramid nanofiber-based battery separator.

[0034] A method for preparing a functionalized aramid nanofiber-based battery separator includes the following steps:

[0035] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion, and obtain an aramid nanofiber gel by protonation reduction and washing; wherein the mass concentration of the aramid nanofiber / dimethyl sulfoxide dispersion is 0.1-0.5%.

[0036] Step 2: The obtained aramid nanofiber gel was hydroxylated and modified, and then hydroxylated aramid nanofiber films were prepared by dispersion, vacuum-assisted filtration and layer-by-layer self-assembly. The hydroxylation modifier was 85% phosphoric acid, and the ratio of aramid nanofiber to phosphoric acid was 1g aramid nanofiber to 200ml 85% phosphoric acid. The modification temperature was 40-60℃ and the modification time was 1h.

[0037] Step 3: The hydroxylated aramid nanofiber membrane is subjected to surface oxidation treatment to prepare a surface carboxylated aramid nanofiber film; wherein, the oxidant used in the preparation of the carboxylated aramid nanofiber film is hydrogen peroxide with a mass concentration of 0.1%, the catalyst is ferric chloride, and after the carboxylation modification is completed, it is activated by lithium hydroxide with a molar concentration of 0.1 mol / L, and the treatment conditions are: drying in a vacuum drying oven at 60℃ for 4 hours.

[0038] Step 4: The carboxylated aramid nanofiber membrane is subjected to a surface self-assembly alternating impregnation method to obtain a functionalized aramid nanofiber-based battery membrane. Before the self-assembly alternating impregnation method, an activation treatment is performed using lithium hydroxide with a molar concentration of 0.1 mol / L and a treatment time of 10 min. The impregnation solution is polydiallyldimethylammonium chloride (PDDA) and sodium poly(p-phenylene sulfonate) sulfonate (PSS). The mass concentration percentage of PDDA in the impregnation solution is 20%, and the mass concentration percentage of PSS is 30%. The treatment time of PDDA is 10–15 min, and the treatment time of PSS is 15–25 min.

[0039] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0040] The following detailed descriptions are all illustrative of embodiments and are intended to provide a further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the present invention.

[0041] Example 1

[0042] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.1%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0043] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 40℃ for 1h. After the reaction, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0044] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0045] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 10 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 15 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 10 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0046] Example 2

[0047] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.2%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0048] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 45℃ for 1h, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0049] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0050] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 12 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 20 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 12 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0051] Example 3

[0052] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.3%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0053] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 50℃ for 1h, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0054] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0055] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 25 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0056] Example 4

[0057] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.4%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0058] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 55℃ for 1h, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0059] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0060] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 10 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 25 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 10 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0061] Example 5

[0062] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.5%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0063] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 60℃ for 1h. After the reaction, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0064] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0065] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 20 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0066] Example 6

[0067] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.2%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0068] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 40℃ for 1h. After the reaction, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0069] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0070] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% sodium terephthalate sulfonate (PSS) for 15 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% polydiallyldimethylammonium chloride (PDDA) for 15 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0071] Example 7

[0072] Step 1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion with a mass concentration of 0.25%, and obtain an aramid nanofiber gel by protonation reduction and washing;

[0073] Step 2: Take 1g of the obtained aramid nanofiber gel, add 200ml of 85% phosphoric acid, stir and react at 50℃ for 1h, wash with a large amount of deionized water until neutral, then disperse, vacuum-assisted filtration and layer-by-layer self-assembly method to prepare hydroxylated aramid nanofiber film.

[0074] Step 3: The hydroxylated aramid nanofiber membrane was placed in hydrogen peroxide containing 0.1% ferric chloride for oxidation treatment. After oxidation treatment, it was activated with 0.1 mol / L lithium hydroxide and dried in a vacuum drying oven at 60°C for 4 hours to obtain the carboxylated aramid nanofiber membrane.

[0075] Step 4: The carboxylated aramid nanofiber separator obtained in Step 3 was activated with 0.1 mol / L lithium hydroxide for 10 min, then immersed in 20% (w / w) polydiallyldimethylammonium chloride (PDDA) for 12 min, washed with deionized water, soaked in deionized water for 10 min, removed and immersed in 30% (w / w) sodium terephthalate sulfonate (PSS) for 25 min, washed with deionized water and naturally dried to obtain a negative-functionalized aramid nanofiber-based battery separator. The negative-functionalized aramid nanofiber-based battery separator was then immersed in 20% (w / w) polydiallyldimethylammonium chloride (PDDA) for 25 min, washed with deionized water and naturally dried to obtain a positive-functionalized aramid nanofiber-based battery separator.

[0076] The functionalized aramid nanofiber-based battery separator prepared in Example 2 of this invention was characterized by the following indicators: 1. Average thickness of battery separator: 35 μm; 2. Porosity of battery separator: 52%; 3. Electrolyte absorption rate of battery separator: 198%; 4. Tensile strength: 138 MPa; 5. Maximum decomposition temperature: 486 °C.

[0077] This invention utilizes novel processes and methods to develop and produce a functionalized aramid nanofiber-based battery separator. This separator possesses high mechanical strength, excellent temperature resistance, and outstanding electrolyte wettability and absorption. It overcomes the shortcomings of traditional commercial polyolefin separators, such as poor temperature resistance, easy shrinkage and deformation, difficulty in electrolyte wettability, and low ionic conductivity. The functionalized separator prepared has functional groups on its surface that physically adsorb and chemically crosslink lithium dendrite formation and puncture, ultimately resulting in a significant improvement in battery capacity. It has broad application prospects in lithium-sulfur batteries and lithium-ion batteries.

[0078] The embodiments described above are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in this application can be arbitrarily combined with each other without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing a functionalized aramid nanofiber-based battery separator, characterized in that, Includes the following steps: S1: Prepare an aramid nanofiber / dimethyl sulfoxide dispersion, and obtain an aramid nanofiber gel by protonation reduction and washing; S2: The aramid nanofiber gel is hydroxylated using a hydroxylation modifier, and then hydroxylated aramid nanofiber films are prepared by dispersion, vacuum-assisted filtration, and layer-by-layer self-assembly. S3: After surface oxidation treatment, hydroxylated aramid nanofiber film is activated to obtain surface carboxylated aramid nanofiber film. S4: After activating the surface carboxylated aramid nanofiber film, functionalized aramid nanofiber-based battery separators are obtained by self-assembly alternating impregnation method.

2. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S1, the mass concentration of the aramid nanofiber / dimethyl sulfoxide dispersion is 0.1% to 0.5%.

3. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S2, the hydroxylation modifier is a phosphoric acid solution with a mass concentration of 85%, and the ratio between the aramid nanofiber gel and the phosphoric acid solution is 1g:200ml.

4. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, The hydroxylation modification treatment was performed at a temperature of 40℃ to 60℃ for 1 hour.

5. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S3, the surface oxidation treatment uses an oxidant and a catalyst. The oxidant is a hydrogen peroxide solution with a mass concentration of 0.1%, and the catalyst is ferric chloride.

6. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S3, the activation treatment uses a lithium hydroxide solution with a molar concentration of 0.1 mol / L.

7. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S4, the activation treatment uses a lithium hydroxide solution with a molar concentration of 0.1 mol / L and the activation treatment time is 10 min.

8. The method for preparing a functionalized aramid nanofiber-based battery separator according to claim 1, characterized in that, In S4, the impregnation solution used in the self-assembly alternating impregnation method is a polydiallyldimethylammonium chloride solution and a sodium terephthalate sulfonate solution; The mass concentration of the polydiallyldimethylammonium chloride solution is 20%, and the mass concentration of the sodium poly(p-styrene sulfonate) solution is 30%. The single immersion time of the polydiallyldimethylammonium chloride solution is 10 min to 15 min, and the single immersion time of the sodium poly(p-styrene sulfonate) solution is 15 min to 25 min.

9. A functionalized aramid nanofiber-based battery separator, characterized in that, The battery separator is prepared by any one of claims 1 to 8, and has an average thickness of 35 μm, a porosity of 52%, an electrolyte absorption rate of 198%, a tensile strength of 138 MPa, and a maximum decomposition temperature of 486 °C.

10. The application of the functionalized aramid nanofiber-based battery separator as described in claim 9 in lithium-ion batteries and lithium-sulfur batteries.

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