Polyethylene diaphragm and preparation process thereof

Abstract

The invention discloses a polyethylene diaphragm and a preparation process thereof, and belongs to the technical field of lead-acid battery diaphragms.The preparation process comprises the following steps that firstly, polyethylene resin, hydrophobic modified conductive filler and liquid paraffin are mixed, feeding is conducted while mixing is conducted, heating swelling, extrusion forming and cooling qualitative treatment are conducted, then liquid paraffin is extracted out with an extracting agent, drying is conducted, and a polyethylene diaphragm is obtained; a base film is obtained; the hydrophobic modified conductive filler is a phenyl grafted conductive filler prepared by using a silane coupling agent with a conductive filler as a modification base material, and the silane coupling agent is aryl silane; and 2, sulfonating the base membrane, and drying to obtain the polyethylene diaphragm. According to the process, a polyethylene-based membrane with a porous structure is prepared through an extraction method, then the hydrophilicity of the polyethylene-based membrane is improved through sulfonation treatment, the liquid absorption rate of the diaphragm is further improved, the liquid absorption rate of the diaphragm can be further improved by adding hydrophobic modified conductive filler and then carrying out sulfonation modification in the process, and the performance of the diaphragm is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lead-acid battery separators, and particularly relates to a polyethylene separator and its preparation process. Background Art

[0002] As a classic representative of the electrochemical energy storage system, lead-acid batteries occupy an important market share in fields such as power system frequency modulation and peak shaving, backup power supplies for communication base stations, and start-stop systems for new energy vehicles due to their high safety, wide temperature range adaptability, and high recycling economy. The current mainstream separator systems include: (1) ultra-fine glass fiber (AGM) separators; (2) melt-blown polypropylene (PP) separators; (3) polyethylene (PE) separators. Among them, polyethylene separators are widely used in lead-acid batteries due to their excellent performance. It has high mechanical strength and toughness, can effectively prevent lead dendrites from penetrating, thus reducing the risk of short circuit. In addition, the polyethylene separator also has good corrosion resistance and can be used for a long time in the sulfuric acid electrolyte environment of lead-acid batteries. However, the polyethylene separator also has some limitations. Its hydrophilicity is poor, which may lead to insufficient wettability and permeability of the electrolyte. This limits the charge and discharge efficiency of the battery to a certain extent, especially in the application scenarios of fast charging and discharging.

[0003] In order to overcome these disadvantages of the polyethylene separator, a variety of modification methods are recorded in the prior art. For example, by introducing hydrophilic substances on the polyethylene separator through surface coating technology, its wettability can be significantly improved. However, this method has some limitations. The selection of coating materials and the stability of coating processes have a great impact on the modification effect. If the compatibility between the coating material and the polyethylene substrate is poor, it may lead to coating peeling or delamination, thus reducing the performance of the separator. For example, the performance of the polyethylene separator can be enhanced by adding nanomaterials. For example, nano-silica and maleic anhydride can be used for the modification of high-density polyethylene-based separators. However, the dispersion and stability of nanomaterials are a key issue. If the nanomaterials cannot be evenly dispersed in the separator, it may lead to inconsistent local performance of the separator, and even may block the pores of the separator, affecting the permeability of the electrolyte.

[0004] Although the above methods can improve the performance of the polyethylene separator to a certain extent, there are still some defects, and further research and development are still necessary to find more efficient and stable modification strategies, so as to promote the wide application of polyethylene separators in high-performance lead-acid batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyethylene separator and its preparation process to solve the problem of poor wetting performance of the polyethylene separator.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The first aspect of the present application provides a preparation process for a polyethylene separator, which includes the following steps:

[0008] First step: Mix polyethylene resin, hydrophobically modified conductive filler, and liquid paraffin, adding materials while mixing, heating to swell, extruding and forming, after cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the hydrophobically modified conductive filler uses conductive filler as the modified base material, and prepares a phenyl-grafted conductive filler using a silane coupling agent, and the silane coupling agent is aryl silane;

[0009] Second step: Sulfonate the base film and dry to obtain a polyethylene separator.

[0010] In some possible implementation manners, the sulfonation treatment includes the following steps: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, heat to 70-80 °C, react for 1-2 h, and after the reaction is completed, wash and dry.

[0011] In some possible implementation manners, the mass ratio of the polyethylene resin to the liquid paraffin is 20-70:100.

[0012] In some possible implementation manners, the mass ratio of the amount of the base film to the chlorosulfonic acid is 5-8:1.

[0013] In some possible implementation manners, the hydrophobically modified conductive filler accounts for 1% to 10% of the total mass of the polyethylene resin.

[0014] In some possible implementation manners, the extractant is one of dichloromethane and ethanol.

[0015] In some possible implementation manners, the hydrophobically modified conductive filler is prepared through the following steps:

[0016] Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution, mix the treatment solution and the conductive filler at 20 mL:1 g, while stirring, add grinding to facilitate full reaction, add hydrochloric acid to adjust the pH value to 4-5, and carry out stirring reaction at 65-70 °C under a nitrogen atmosphere. After the reaction is completed, obtain the hydrophobically modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0017] In some possible implementation manners, the aryl silane is one of phenyltrimethoxysilane, phenyltriethoxysilane, 1-naphthyltrimethoxysilane, and p-tolyltrimethylsilane.

[0018] In some possible implementation manners, the conductive filler includes at least one of carbon nanotubes, carbon black, graphene, and graphene oxide.

[0019] The second aspect of the present application provides a polyethylene separator prepared by the above preparation process.

[0020] Advantages of the present invention:

[0021] The present invention provides a preparation process for a polyethylene separator. In this process, a porous polyethylene-based film is prepared by an extraction method, and then the hydrophilicity of the polyethylene-based film is improved by sulfonation treatment, thereby improving the liquid absorption rate of the separator. During the preparation process, paraffin is used as a pore-forming agent. A high proportion of paraffin can prepare a separator with a high porosity, but its dosage should not be too high, as a high porosity will lead to a decrease in the mechanical properties of the separator, which is not conducive to its application in battery separators. In the process of the present invention, a hydrophobic modified conductive filler is also added. The conductive filler can improve the conductivity of the separator. To improve the dispersibility of the conductive filler, the present invention hydrophobically modifies the conductive filler (by phenylsilane). After adding the hydrophobic modified conductive filler and then performing sulfonation modification, the liquid absorption rate of the separator can be further improved, and the performance of the separator can be further enhanced. Specific embodiments

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0023] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0024] However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter recited in the claims.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions, and all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0026] The first aspect of the embodiment of this application provides a preparation process of a polyethylene separator, including the following steps:

[0027] The first step: Mix polyethylene resin, hydrophobically modified conductive filler and liquid paraffin, add materials while mixing, heat and swell, extrude and mold, after cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; Adding a conductive filler to construct a conductive network can reduce the resistance of the base film (polyethylene) and improve conductivity. The hydrophobically modified conductive filler uses the conductive filler as a modified base material, and uses a silane coupling agent to prepare a phenyl-grafted conductive filler, and the silane coupling agent is an aryl silane; After using phenyl silane to treat the filler, not only can the dispersibility of the conductive filler be improved, but also more sulfonation reaction sites can be provided, improving the performance of the separator. The second step: Sulfonate the base film to obtain a polyethylene separator.

[0028] In some specific embodiments, the sulfonation treatment includes the following steps: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, heat to 70-80 °C, react for 1-2 h, and after the reaction is completed, wash and dry.

[0029] In some specific embodiments, the mass ratio of the base film to chlorosulfonic acid is 5-8:1.

[0030] In some specific embodiments, the mass ratio of polyethylene resin to liquid paraffin is 20-70:100; the hydrophobically modified conductive filler accounts for 1% to 10% of the total mass of the polyethylene resin. The weight-average molecular weight (Mw) of the polyethylene resin is 300,000-700,000 g / mol.

[0031] In some specific embodiments, the extractant is one of dichloromethane and ethanol.

[0032] In some specific embodiments, the hydrophobically modified conductive filler is prepared by the following steps:

[0033] Mix phenyltrimethoxysilane, ethanol and water in a mass ratio of 2:7:1 to obtain a treatment solution, mix the treatment solution and the conductive filler at 20 mL:1 g, stir and grind at the same time to facilitate full reaction, add hydrochloric acid to adjust the pH value to 4-5, and carry out a stirring reaction at 65-70 °C under a nitrogen atmosphere. After the reaction is completed, obtain the hydrophobically modified conductive filler through centrifugation, washing with absolute ethanol and drying.

[0034] In some specific embodiments, the arylsilane is one of phenyltrimethoxysilane, phenyltriethoxysilane, 1-naphthyltrimethoxysilane, and p-tolyltrimethylsilane.

[0035] In some specific embodiments, the conductive filler includes at least one of carbon nanotubes, carbon black, graphene, and graphene oxide. The costs of different conductive fillers are different, and the resistance can be further reduced by compounding to meet different application requirements.

[0036] The second aspect of the embodiments of the present application provides a polyethylene separator prepared by the above preparation process.

[0037] The following is specifically described in conjunction with embodiments.

[0038] Example 1

[0039] This example provides a preparation process for a polyethylene separator, including the following steps:

[0040] First step: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, and while stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction is completed, perform centrifugation, wash with absolute ethanol, and dry to obtain a hydrophobic modified conductive filler.

[0041] Mix the polyethylene resin, the hydrophobic modified conductive filler, and liquid paraffin, add materials while mixing, heat and swell, extrude and mold, and after cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 60:100; the hydrophobic modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0042] Second step: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75 °C, and react for 2 h. After the reaction is completed, wash and dry to obtain a polyethylene separator. The mass ratio of the base film to the chlorosulfonic acid is 7:1.

[0043] Example 2

[0044] This example provides a preparation process for a polyethylene separator, including the following steps:

[0045] Step 1: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, and while stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65°C under a nitrogen atmosphere. After the reaction, obtain a hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0046] Mix polyethylene resin, hydrophobic modified conductive filler, and liquid paraffin, adding materials while mixing, heating and swelling, and extrusion molding. After cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of polyethylene resin to liquid paraffin is 60:100; the hydrophobic modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0047] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75°C, and react for 2 h. After the reaction, obtain a polyethylene separator through washing and drying. The mass ratio of the base film to chlorosulfonic acid is 6:1.

[0048] Example 3

[0049] This example provides a preparation process for a polyethylene separator, including the following steps:

[0050] Step 1: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, and while stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65°C under a nitrogen atmosphere. After the reaction, obtain a hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0051] Mix polyethylene resin, hydrophobic modified conductive filler, and liquid paraffin, adding materials while mixing, heating and swelling, and extrusion molding. After cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of polyethylene resin to liquid paraffin is 60:100; the hydrophobic modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0052] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75°C, and react for 2 h. After the reaction, obtain a polyethylene separator through washing and drying. The mass ratio of the base film to chlorosulfonic acid is 5:1.

[0053] Example 4

[0054] This embodiment provides a preparation process for a polyethylene diaphragm, which includes the following steps:

[0055] First step: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g. While stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4. Conduct a stirring reaction at 65°C under a nitrogen atmosphere. After the reaction, perform centrifugation, wash with absolute ethanol, and dry to obtain hydrophobically modified conductive filler.

[0056] Mix polyethylene resin, hydrophobically modified conductive filler, and liquid paraffin, adding materials while mixing. Heat to cause swelling, extrude into shape. After cooling and shaping, use an extractant to extract the liquid paraffin, and then dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 60:100; the hydrophobically modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0057] Second step: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75°C, react for 2 h. After the reaction, wash and dry to obtain a polyethylene diaphragm. The mass ratio of the base film to the chlorosulfonic acid is 8:1.

[0058] Example 5

[0059] This embodiment provides a preparation process for a polyethylene diaphragm, which includes the following steps:

[0060] First step: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g. While stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4. Conduct a stirring reaction at 65°C under a nitrogen atmosphere. After the reaction, perform centrifugation, wash with absolute ethanol, and dry to obtain hydrophobically modified conductive filler.

[0061] Mix polyethylene resin, hydrophobically modified conductive filler, and liquid paraffin, adding materials while mixing. Heat to cause swelling, extrude into shape. After cooling and shaping, use an extractant to extract the liquid paraffin, and then dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 50:100; the hydrophobically modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0062] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly heat up to 75 °C, react for 2 h, and after the reaction, obtain a polyethylene separator through washing and drying. The mass ratio of the base film to chlorosulfonic acid is 7:1.

[0063] Example 6

[0064] This example provides a preparation process for a polyethylene separator, including the following steps:

[0065] Step 1: Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, add grinding while stirring to facilitate full reaction, add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction, obtain hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0066] Mix polyethylene resin, hydrophobic modified conductive filler, and liquid paraffin, add materials while mixing, heat to swell, extrude and form, after cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 70:100; the hydrophobic modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0067] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly heat up to 75 °C, react for 2 h, and after the reaction, obtain a polyethylene separator through washing and drying. The mass ratio of the base film to chlorosulfonic acid is 7:1.

[0068] Example 7

[0069] This example provides a preparation process for a polyethylene separator, including the following steps:

[0070] Step 1: Mix phenyltriethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, add grinding while stirring to facilitate full reaction, add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction, obtain hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0071] Mix the polyethylene resin, hydrophobically modified conductive filler and liquid paraffin, adding materials while mixing, heating to swell, extruding and forming. After cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 60:100; the hydrophobically modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0072] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75 °C, react for 2 h, and after the reaction is completed, wash and dry to obtain a polyethylene separator. The mass ratio of the base film to the chlorosulfonic acid is 7:1.

[0073] Example 8

[0074] This example provides a preparation process for a polyethylene separator, including the following steps:

[0075] Step 1: Mix p-tolyltrimethylsilane, ethanol and water in a mass ratio of 2:7:1 to obtain a treatment solution, mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g, add grinding while stirring to facilitate full reaction, add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction is completed, carry out centrifugation, wash with absolute ethanol, and dry to obtain a hydrophobically modified conductive filler.

[0076] Mix the polyethylene resin, hydrophobically modified conductive filler and liquid paraffin, adding materials while mixing, heating to swell, extruding and forming. After cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 60:100; the hydrophobically modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0077] Step 2: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly raise the temperature to 75 °C, react for 2 h, and after the reaction is completed, wash and dry to obtain a polyethylene separator. The mass ratio of the base film to the chlorosulfonic acid is 7:1.

[0078] Comparative Example 1

[0079] This comparative example does not perform the second step treatment compared with Example 1, and the remaining raw materials and preparation processes are the same as those in Example 1. Specifically:

[0080] Mix phenyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g. While stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction, obtain the hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0081] Mix polyethylene resin, hydrophobic modified conductive filler, and liquid paraffin, adding materials while mixing. Heat to swell and extrude into shape. After cooling and shaping, extract the liquid paraffin with an extractant and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of polyethylene resin to liquid paraffin is 60:100; the hydrophobic modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0082] Comparative Example 2

[0083] In this comparative example, compared with Example 1, no hydrophobic modified conductive filler is added, and the other raw materials and preparation process are the same as those in Example 1. Specifically:

[0084] First step: Mix polyethylene resin and liquid paraffin, adding materials while mixing. Heat to swell and extrude into shape. After cooling and shaping, extract the liquid paraffin with an extractant and dry to obtain a base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of polyethylene resin to liquid paraffin is 60:100; the extractant is dichloromethane.

[0085] Second step: Sulfonate the base film: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly heat to 75 °C, react for 2 h. After the reaction, obtain the polyethylene separator through washing and drying. The mass ratio of the base film to chlorosulfonic acid is 7:1.

[0086] Comparative Example 3

[0087] In this comparative example, compared with Example 1, the added hydrophobic modified conductive filler is different, and the other raw materials and preparation process are the same as those in Example 1. Specifically:

[0088] First step: Mix γ-methacryloxypropyltrimethoxysilane, ethanol, and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and carbon nanotubes in a ratio of 20 mL:1 g. While stirring, add grinding to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4, and carry out a stirring reaction at 65 °C under a nitrogen atmosphere. After the reaction, obtain the hydrophobic modified conductive filler through centrifugation, washing with absolute ethanol, and drying.

[0089] Mix the polyethylene resin, hydrophobically modified conductive filler and liquid paraffin, adding materials while mixing, heating to swell, extruding and forming, after cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain the base film; the weight-average molecular weight (Mw) of the polyethylene resin is 350,000 g / mol. The mass ratio of the polyethylene resin to the liquid paraffin is 60:100; the hydrophobically modified conductive filler accounts for 2% of the total mass of the polyethylene resin. The extractant is dichloromethane.

[0090] Second step, sulfonate the base film: under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, slowly heat up to 75 °C, react for 2 h, after the reaction is completed, wash and dry to obtain the polyethylene separator. The mass ratio of the base film to the chlorosulfonic acid is 7:1.

[0091] Test the liquid absorption performance of the specimens prepared in Examples 1 - 8 and Comparative Examples 1 - 3. The liquid absorption performance includes the liquid absorption rate. Cut the separator specimens into circular pieces with a diameter of 19 mm and soak them in the electrolyte (sulfuric acid with a density of 1.24 g / cm³) for 72 h. Liquid absorption rate = (mass after soaking - mass before soaking) / mass before soaking * 100%. Test the tensile strength according to the standard GB / T 1040.3 - 2006; the results are shown in Table 1:

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from Table 1, the polyethylene separator prepared by the present invention has good wettability, a high liquid absorption rate, and good tensile strength.

[0096] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0097] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process of a polyethylene separator, characterized in that, It includes the following steps: First step: Mix polyethylene resin, hydrophobically modified conductive filler and liquid paraffin, heat to swell, extrude and form. After cooling and shaping, extract the liquid paraffin with an extractant, and dry to obtain a base film. The hydrophobically modified conductive filler uses conductive filler as the modified base material, and prepares a phenyl-grafted conductive filler by using a silane coupling agent, and the silane coupling agent is an aryl silane; Second step: Sulfonate the base film and dry to obtain a polyethylene separator.

2. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The sulfonation treatment includes the following steps: Under a nitrogen atmosphere, add the base film to a solution of 1,2-dichloroethane containing chlorosulfonic acid, heat to 70-80 °C, react for 1-2 h, and after the reaction is completed, wash and dry.

3. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The mass ratio of the polyethylene resin to the liquid paraffin is 20-70:

100.

4. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The mass ratio of the amount of the base film to the chlorosulfonic acid is 5-8:

1.

5. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The hydrophobically modified conductive filler accounts for 1% to 10% of the total mass of the polyethylene resin.

6. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The extractant is one of dichloromethane and ethanol.

7. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The hydrophobically modified conductive filler is prepared by the following steps: Mix phenyltrimethoxysilane, ethanol and water in a mass ratio of 2:7:1 to obtain a treatment solution. Mix the treatment solution and the conductive filler at 20 mL:1 g, and add grinding while stirring to facilitate full reaction. Add hydrochloric acid to adjust the pH value to 4-5, and carry out a stirring reaction at 65-70 °C under a nitrogen atmosphere. After the reaction is completed, obtain the hydrophobically modified conductive filler through centrifugation, washing with absolute ethanol and drying.

8. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The aryl silane is one of phenyltrimethoxysilane, phenyltriethoxysilane, 1-naphthyltrimethoxysilane and p-tolyltrimethylsilane.

9. The preparation process of a polyethylene diaphragm according to claim 1, characterized in that, The conductive filler includes at least one of carbon nanotubes, carbon black, graphene, and graphene oxide.

10. A polyethylene separator, characterized in that, Prepared by the preparation process according to any one of claims 1-9.

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