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CN-115548578-B - High-safety aramid fiber diaphragm and preparation method and application thereof

CN115548578BCN 115548578 BCN115548578 BCN 115548578BCN-115548578-B

Abstract

The invention discloses a high-safety aramid fiber diaphragm and a preparation method and application thereof, and the high-safety aramid fiber diaphragm comprises the following steps of (1) preparing an aramid fiber polymer solution, (2) uniformly coating an aramid fiber polymer dispersion liquid obtained by diluting the aramid fiber polymer solution on a collecting plate, then drying, washing with water after the solvent is fully volatilized, carrying out ultrasonic treatment in the washing process, further drying, carrying out biaxial stretching, and then carrying out heat setting, thus obtaining the high-safety aramid fiber diaphragm. The invention overcomes the technical problems of brittleness and easy breakage of the membrane prepared by the conventional method, and the mechanical strength and pore structure of the prepared membrane are further improved, so that the membrane can work in a high-temperature environment for a long time.

Inventors

  • CHEN KEFU
  • LI JINPENG

Assignees

  • 陈克复

Dates

Publication Date
20260512
Application Date
20221019

Claims (8)

  1. 1. The preparation method of the high-safety aramid fiber diaphragm is characterized by comprising the following steps of: (1) Preparing an aramid polymer solution; (2) Diluting the aramid polymer solution to obtain an aramid polymer dispersion liquid, uniformly coating the aramid polymer dispersion liquid on a collecting plate, then placing the collecting plate in an oven for drying treatment, quickly adding ice water for washing after the solvent is fully volatilized, carrying out ultrasonic treatment in the washing process, further drying treatment, and finally carrying out biaxial stretching and then carrying out heat setting to obtain the high-safety aramid membrane; the preparation of the aramid polymer solution comprises the steps of (1) carrying out polymerization reaction on m-phenylenediamine and m-phthaloyl chloride in an organic solvent under the condition of low temperature and protective atmosphere to obtain a neutral aramid polymer solution, wherein the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is 100 (85-120); Step (1) preparation of an aramid polymer, which comprises the steps of dissolving a cosolvent and m-phenylenediamine in N, N-dimethylacetamide under the conditions of low temperature and nitrogen protection, and then adding m-phthaloyl chloride for 2-5 times to obtain a reaction solution; the temperature of the reaction solution gradually rises along with the reaction, and an alkaline agent is added for neutralization after heat preservation treatment to prepare a neutral aramid polymer solution; The cosolvent is one or more of lithium bromide, lithium chloride, calcium chloride and calcium bromide, the heat preservation treatment is carried out at 40-80 ℃ for 0.5-12 hours, and the alkaline agent is one or more of calcium oxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, sodium hydroxide and organic amine.
  2. 2. The preparation method of claim 1, wherein the concentration of the aramid polymer dispersion in the step (2) is 5-30% by mass, and the biaxial stretching is specifically 1.3-4.0 times of transverse stretching and 1.3-4.0 times of longitudinal stretching.
  3. 3. The preparation method of claim 2, wherein the concentration of the aramid polymer dispersion liquid in the step (2) is 10-25% by mass, and the biaxial stretching is specifically 1.5-3.0 times of transverse stretching and 1.5-4.0 times of longitudinal stretching.
  4. 4. The preparation method according to claim 1,2 or 3, wherein the heat setting temperature in the step (2) is 280-330 ℃ for 1-30min, the power of the ultrasonic treatment is 200-1500W, the temperature is 30-90 ℃ and the time is 5-60min.
  5. 5. The method according to claim 1, 2 or 3, wherein the temperature of the first drying in the step (2) is 50-200 ℃, and the aramid polymer dispersion is further subjected to a vacuum defoaming pretreatment.
  6. 6. The preparation method of the coating according to claim 5, wherein the temperature of the first drying in the step (2) is 70-140 ℃, and the thickness of the coating is 20-200 μm by blade coating or spin coating.
  7. 7. The high-safety aramid separator prepared by the method of any one of claims 1 to 6.
  8. 8. The high-safety aramid separator disclosed in claim 7 is applied to the preparation of lithium batteries, lithium sulfur batteries, electrical insulation materials, adsorption filtration materials and flexible electronic device substrates.

Description

High-safety aramid fiber diaphragm and preparation method and application thereof Technical Field The invention belongs to the field of new materials, and particularly relates to a high-safety aramid fiber diaphragm and a preparation method and application thereof. Background In recent years, lithium batteries are favored because of their high endurance and the combined advantages of high cycle times, etc., and because of their great attention, some negative messages of lithium batteries are amplified. Under the conditions of overcharge and overdischarge, rapid charge and discharge, short circuit, mechanical abuse, high-temperature thermal shock and the like, dangerous side reactions in the battery are easy to generate heat, and passivation films on the surfaces of the positive electrode and the negative electrode are directly damaged. In addition, organic solvents used in lithium batteries are flammable and have low flash points, and thermal runaway due to unsafe behavior tends to ignite flammable liquid components having low flash points, resulting in boiling of the battery. When the battery is cracked and the humidity of the external environment is high, moisture and oxygen in the air can easily react with the lithium-intercalated carbon cathode violently, a large amount of heat is released, and the battery is burnt. The lithium battery safety problem is one of the most important problems in the industry, and is also the key point of the new energy industry to pay most attention to the urgent need. The lithium battery industry is also continuously exploring and developing novel battery diaphragm materials with high temperature resistance, high mechanical property and wettability. The performance of the separator has an important influence on the performance of the battery, and is generally prepared from PE (polyethylene) and PP (polypropylene) in commercial use at present, and the separator is divided into a single-layer PE film and a PP film, and a 3-layer PP film and a PE film, such as China patent technologies 201010578194.5 and 201310303894.7. However, lithium ion batteries prepared from polyolefins are increasingly inadequate for practical needs, limiting the application and development of lithium ion batteries. Particularly, the lithium ion battery has safety problems such as short circuit and the like caused by shrinkage of a diaphragm due to overhigh local temperature during high-power charge and discharge. In addition, polyolefin separators also have relatively low wettability for the electrolyte, which also results in inefficient directional movement of lithium ions within the separator, limiting the electrochemical performance of the lithium ion battery. Therefore, there is a need to develop high performance battery separator materials and key manufacturing techniques thereof. As a high-temperature-resistant special polymer material, the aramid fiber is widely applied in industry, has extremely high thermal stability (up to 400 ℃), excellent self-extinguishing property and good wettability to electrolyte, and is an alternative material of a diaphragm with excellent performance. At present, meta-aramid materials are mainly prepared by an electrostatic spinning method, such as China patent technologies 201910686373.1, 201811529222.7, 201810835751.3 and the like, but the electrostatic spinning method has some limitations, such as low efficiency, high price and low strength of the diaphragm, and is not suitable for large-scale application. There have also been researchers to improve the temperature resistance of polyolefin substrates by coating them with high temperature resistant materials such as aramid fibers, etc., as in chinese patent technologies 201821819348.3, 202110431425.8, 202210268442.9, etc., but these clearly add to the manufacturing process of battery separators. Therefore, a technology for efficiently preparing the high-safety aramid fiber diaphragm is highly urgent to develop, and the technology can be suitable for large-scale preparation and production. Disclosure of Invention The invention aims at overcoming the defects and shortcomings of the prior art and providing a preparation method of a high-safety aramid fiber diaphragm. The invention further aims to provide the high-safety aramid fiber diaphragm prepared by the method. Still another object of the present invention is to provide an application of the aramid separator for lithium batteries. The aim of the invention is achieved by the following technical scheme: The preparation method of the high-safety aramid fiber diaphragm comprises the following steps: (1) Preparing an aramid polymer solution; (2) And diluting the aramid polymer solution to obtain an aramid polymer dispersion liquid, uniformly coating the aramid polymer dispersion liquid on a collecting plate, then drying, washing with water after the solvent is fully volatilized, carrying out ultrasonic treatment in the washing process, further drying, finally carrying