KR-20260066144-A - Microporous membranes, methods for manufacturing the same, and applications

KR20260066144AKR 20260066144 AKR20260066144 AKR 20260066144AKR-20260066144-A

Abstract

The present application belongs to the field of separator material manufacturing technology, and specifically relates to a microporous membrane, a method of manufacturing the same, and an application. The microporous membrane comprises a polymer and an ionic liquid, and based on the total mass of the microporous membrane, the microporous membrane comprises 0.01 wt% to 5 wt% of an ionic liquid, and optionally comprises 0.1 wt% to 5 wt% of an ionic liquid. The present application describes that by introducing an appropriate amount of ionic liquid into the microporous membrane, the ionic liquid can be adsorbed continuously or discontinuously onto the internal fibril surface of the microporous membrane, and the ionic liquid is adsorbed onto the internal fibril surface of the microporous membrane through its lipophilic ends, thereby not only eliminating internal static electricity but also better preventing a decrease in ion conductivity, which increases the mobility of electrolyte ions and reduces lithium dendrites. When the microporous membrane of the present application is used as a battery separator, adding an appropriate amount of ionic liquid within the microporous membrane is advantageous for improving the problem of electrostatic accumulation, and furthermore, by lowering the thermal shrinkage rate of the microporous membrane, it prevents issues such as affecting battery capacity and causing electrochemical safety problems.

Inventors

첸 이핑
가오 둥보
린 루징
차이 치

Assignees

셴젠 시니어 테크놀로지 매테리얼 씨오., 엘티디.

Dates

Publication Date: 20260512
Application Date: 20231031

Claims (10)

In microporous membranes, The microporous membrane comprises a polymer and an ionic liquid, and based on the total mass of the microporous membrane, the microporous membrane comprises 0.01 wt% to 5 wt% of the ionic liquid; Optionally, the microporous membrane comprises 0.1 wt% to 5 wt% of an ionic liquid; Optionally, the microporous membrane is characterized by containing 0.3 wt% to 1.0 wt% of an ionic liquid.
In paragraph 1, A microporous membrane characterized in that the microporous membrane comprises a plurality of fibrils, and the plurality of fibrils are cross-connected to form pores, and the ionic liquid is attached to the surface of at least the fibrils inside the microporous membrane through its lipophilic ends.
In paragraph 1 or 2, a) The average pore size of the microporous membrane is 20 to 70 nm; b) The standard deviation of the pore size of the microporous membrane is 2.5 to 28 nm; c) The absolute value of the difference between the sum of the average pore size and standard deviation of the microporous membrane and the bubble point pore size within the microporous membrane is 15 nm or less; Satisfy at least one of the following, Optionally, a micropore membrane characterized by an absolute difference of 10 nm or less.
In any one of paragraphs 1 through 3, The above ionic liquid is at least one of an imidazole-based ionic liquid, a pyridine-based ionic liquid, an alkylsulfonic acid-based ionic liquid, a quaternary ammonium-based ionic liquid, a quaternary phosphonium-based ionic liquid, a pyrrolidine-based ionic liquid, and a piperidine-based ionic liquid; Optionally, the ionic liquid is 1-ethyl-3-methylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole acetate, 1-butyl-3-methylimidazole acetate, 1-octadecylsulfonate sodium salt, 1-pentadecylsulfonate sodium salt, 1-ethyl-3-methylimidazole bis(fluorosulfonyl)imide, 1-butyl-3-methyl bis(fluorosulfonyl)imide, 1-ethyl-3-methyl bis(trifluorosulfonyl)imide, 1-butyl-3-methyl bis(trifluorosulfonyl)imide, dodecyl quaternary ammonium salt, octadecyl quaternary ammonium salt, At least one of 1-ethyl-3-methyl-4,5-dicyanomidazolium-bis(trifluoromethanesulfonyl)imide and N-alkylpyridinium; Optionally, the polymer is at least one homopolymer, copolymer, or mixture of propylene, ethylene, butene, pentene, methyl methacrylate, tetrafluoroethylene, and difluoroethylene selected from propylene, ethylene, butene, pentene, methyl methacrylate, tetrafluoroethylene, and difluoroethylene; Optionally, a microporous membrane characterized in that the polymer is at least one of polyethylene, polypropylene, and ethylene-propylene copolymer.
In a method for manufacturing a microporous membrane, (1) A step of obtaining a film containing a plasticizer; (2) A step of extracting a plasticizer from a film containing the plasticizer using an extractant - wherein the extractant comprises a first ionic liquid; the extractant comprises the extractant and the plasticizer; and the concentration of the plasticizer in the extractant is sequentially reduced along the direction of movement of the film containing the plasticizer - ; (3) Washing and setting step; A method for manufacturing a microporous membrane characterized by including
In paragraph 5, In step (2) above, the concentration of the plasticizer in the extract is 7 wt% or less; Optionally, in step (2), an extract having at least three concentration gradients is installed along the direction of movement of the film containing the plasticizer; Optionally, in step (2), along the direction of movement of the film containing the plasticizer, the concentration of the plasticizer in the subsequent extract is 85 wt% or less of the concentration of the plasticizer in the previous extract; Optionally, in step (2), the temperature of the extraction is 30 to 55 ℃; Optionally, along the direction of movement of the film containing the plasticizer, the temperature of the subsequent extraction is lower than or equal to the temperature of the previous extraction; Optionally, when performing the extraction in step (2), the step of performing the first spray using the first spray solution is further included; Optionally, a manufacturing method characterized in that the first spray liquid comprises a second ionic liquid.
In any one of paragraphs 5 through 6, In the washing step of the above step (3), the washing solution comprises an ionic liquid and a washing agent, the washing agent comprises water, and the concentration of the ionic liquid in the washing solution is 10 wt% or less; Optionally, the step of spraying using a second spray solution during the above washing is further included, wherein the second spray solution comprises water; Optionally, in the washing step of step (3) above, the concentration of the ionic liquid in the washing solution is sequentially reduced along the direction of movement of the film containing the plasticizer; Optionally, along the direction of movement of the film containing the plasticizer, the ionic liquid concentration in the wash solution of the subsequent wash is 30 wt% or less of the ionic liquid concentration in the wash solution of the previous wash; Optionally, before the shaping step after washing in step (3), the step of infiltrating using an infiltration solution is further included; Optionally, the infiltration solution comprises a third ionic liquid and water; Optionally, a manufacturing method characterized in that the concentration of the ionic liquid in the infiltration solution is 0.05 to 5 wt%.
In any one of paragraphs 5 through 7, The above step (1) includes at least one of the steps of obtaining a film containing the plasticizer by a melt mixing method and stretching the film containing the plasticizer; Optionally, the temperature of the above stretching is 60 ℃ or higher; Optionally, the temperature of the above stretching is 200 ℃ or lower; Optionally, the temperature of the melt mixing is 160 ℃ or higher; Optionally, the temperature of the melt mixing is 260 ℃ or lower; Optionally, a manufacturing method characterized in that the mass fraction of the plasticizer in the film containing the plasticizer is 50 to 85 wt%.
In any one of paragraphs 5 through 8, A manufacturing method characterized in that, in step (3) above, the temperature of the mold is 100 ℃ to 135 ℃, the shrinkage rate is 0.9 or less, and optionally 0.8 or less.
In the case of batteries, The battery is characterized in that the battery comprises a separator, and the separator comprises a microporous membrane according to any one of claims 1 to 4, or a microporous membrane manufactured by a manufacturing method according to any one of claims 5 to 9.

Description

Microporous membranes, methods for manufacturing the same, and applications This application belongs to the field of membrane material manufacturing technology, and specifically relates to a microporous membrane, a method for manufacturing the same, and applications. In conventional technology, plasticizers within wet films are extracted using dichloromethane and dried to produce microporous membranes with a penetrating micropore structure. However, during the drying process, the film is prone to dimensional shrinkage, significant changes in pore size and porosity occur, and corresponding stress is generated. This internal stress is gradually released after winding, leading to a series of appearance problems caused by excessive thermal shrinkage. Currently, methods to improve shrinkage mainly involve using specific low-molecular-weight polyethylene, adjusting the stretching ratio, heat-setting means, or coating the base membrane surface; however, these methods introduce new problems such as reduced membrane strength and excessive energy consumption, and it is difficult to ensure a balance between shrinkage rate and performance characteristics such as membrane air permeability, pore size, and porosity. Furthermore, static electricity accumulates on dried microporous membranes due to friction with rollers during operation or post-processing. While current methods utilize electrostatic discharge rods, this approach cannot completely eliminate static electricity and can only remove it from the surface of the microporous membrane. High shrinkage rates and static electricity accumulation lead to separator quality issues and difficulties in the application processing of battery cells, ultimately resulting in a decrease in battery cell yield. In order to more clearly explain the specific embodiments of the present application or the technical methods of the prior art, the drawings to be used in the description of the specific embodiments or prior art below are briefly described; however, it is obvious that the drawings described below are merely some embodiments of the present application, and a person skilled in the art can obtain other drawings from these drawings without creative effort. Figure 1 is a scanning electron microscope image (magnification 20,000 times) of a microporous membrane according to Example 1 of the present application. The following examples are intended to help better understand the present application and are not limited to the best embodiments described above. The content and scope of protection of the present application are not limited by these examples. Any product identical or similar to the present application derived by anyone under the disclosure of the present application or by combining features of the present application with other prior art is included within the scope of protection of the present application. The term “longitudinal direction” as used in this application is also referred to as the MD direction and means the direction of equipment operation. The term “transverse direction” as used in this application is also referred to as the TD direction and means a direction perpendicular to the direction of operation of the equipment. The term “±” as used in this application signifies that a specific value includes its variation and corresponds to normal variation in the actual process. Where specific experimental steps or conditions are not specified in the examples, they may be performed according to the operations or conditions of ordinary experimental steps described in the literature of the art. Where the manufacturers of the reagents and equipment used are not specified, they are all ordinary reagent products available on the market. Example 1 The present embodiment provides a method for manufacturing a microporous membrane, comprising the following steps. (1) Polyethylene resin (weight average molecular weight 90W) with a mass ratio of 23:77 and liquid paraffin oil (kinematic viscosity 45 mm²/s at 40°C) are taken and fed into a double screw extruder to form a melt, the extruder temperature is set to 200±5°C and the melt is extruded through a die, and the melt is cast-cooled at 20°C to form a precursor film, and MD stretching and TD stretching are performed sequentially on the precursor film to obtain a polyethylene film containing paraffin oil; wherein the MD stretching temperature is 95°C, the MD stretching ratio is 6 times, the TD stretching temperature is 110°C, and the TD stretching ratio is 8.5 times. (2) A polyethylene film containing paraffin oil is introduced into an extraction tank using a multi-stage overflow method to extract the paraffin oil from the film; wherein, along the direction of film movement, the multi-stage overflow method comprises extraction tank 1, extraction tank 2, extraction tank 3, extraction tank 4, extraction tank 5, and extraction tank 6, and the temperatures of each extraction tank are sequentially 55 ℃, 50 ℃, 45 ℃, 40 ℃, 40 ℃, and 35