Preparation method of aramid nanofiber-based battery diaphragm with micro-nano porous structure

文档序号：106954 发布日期：2021-10-15 浏览：13次中文

阅读说明：本技术 一种具有微纳米多孔结构的芳纶纳米纤维基电池隔膜的制备方法 (Preparation method of aramid nanofiber-based battery diaphragm with micro-nano porous structure ) 是由杨斌李卫卫张美云谭蕉君宋顺喜聂景怡王琳丁雪瑶于 2021-07-09 设计创作，主要内容包括：本发明公开了一种具有微纳米多孔结构的芳纶纳米纤维基电池隔膜的制备方法,首先制备对位芳纶纳米纤维溶液,然后在搅拌作用下注入质子化供体进行质子化还原,在真空抽滤下用混合溶剂进行多次洗涤,洗至胶状,最后分散在混合溶剂中,接着进行超声处理,并搅拌使芳纶纳米纤维均匀分散,采用真空辅助过滤和层层自组装方式将分散均匀的对位芳纶纳米纤维溶液进行抽滤,制备得到芳纶纳米纤维膜,将芳纶纳米纤维膜干燥,即得到微纳米多孔结构芳纶纳米纤维基电池隔膜。本发明制备的电池隔膜耐温性好,受热不易变形,对电解液具有良好的浸润性。(The invention discloses a preparation method of an aramid nano-fiber-based battery diaphragm with a micro-nano porous structure, which comprises the steps of firstly preparing a para-aramid nano-fiber solution, then injecting a protonation donor under the stirring action to perform protonation reduction, washing the solution for multiple times by using a mixed solvent under vacuum filtration to be colloidal, finally dispersing the solution in the mixed solvent, then performing ultrasonic treatment, stirring to uniformly disperse aramid nano-fibers, performing suction filtration on the uniformly dispersed para-aramid nano-fiber solution by adopting a vacuum auxiliary filtration and layer-by-layer self-assembly mode to prepare an aramid nano-fiber film, and drying the aramid nano-fiber film to obtain the micro-nano porous structure aramid nano-fiber-based battery diaphragm. The battery diaphragm prepared by the invention has good temperature resistance, is not easy to deform when heated, and has good wettability to electrolyte.)

1. A preparation method of an aramid fiber nanofiber-based battery diaphragm with a micro-nano porous structure is characterized by comprising the following steps:

the method comprises the following steps: mixing and stirring para-aramid fiber, dimethyl sulfoxide, potassium hydroxide and deionized water to prepare a para-aramid nanofiber solution A;

step two: injecting the p-aramid nano-fiber solution A obtained in the step one into a protonation donor under the stirring action for protonation reduction, then washing the p-aramid nano-fiber solution A with a mixed solvent for multiple times under vacuum filtration until the p-aramid nano-fiber solution A is colloidal, and then dispersing the p-aramid nano-fiber solution A in the mixed solvent to obtain a p-aramid nano-fiber solution B;

step three: carrying out ultrasonic treatment on the para-aramid nano-fiber solution B, and stirring to uniformly disperse aramid nano-fibers to obtain a para-aramid nano-fiber solution C;

step four: carrying out suction filtration on the uniformly dispersed para-aramid nano-fiber solution C by adopting a vacuum auxiliary filtration and layer-by-layer self-assembly mode to prepare an aramid nano-fiber membrane;

step five: and drying the aramid fiber nanofiber membrane to obtain the micro-nano porous structure aramid fiber nanofiber-based battery diaphragm.

2. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein in the step one, the diameter of the para-aramid nanofiber is 8-15 nm, the length of the para-aramid nanofiber is 3-8 μm, the mass ratio of the para-aramid fiber to potassium hydroxide is 1:1.5, 0.1-0.3g of the para-aramid fiber is added into each 100mL of dimethyl sulfoxide, and the volume ratio of deionized water to the dimethyl sulfoxide is 25: 1.

3. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein the protonation donor in the second step is isopropanol, anhydrous ethanol or a mixture of tert-butyl alcohol and deionized water, and the volume ratio of the isopropanol, the anhydrous ethanol or the tert-butyl alcohol to the deionized water is (1-3): (1-7).

4. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein the volume ratio of the para-aramid nanofiber solution A to the protonation donor in the second step is 1: 2.

5. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein the mixed solvent in the second step is isopropanol, absolute ethyl alcohol or a mixture of tert-butyl alcohol and deionized water, and the volume ratio of the isopropanol, the absolute ethyl alcohol or the tert-butyl alcohol to the deionized water is (1-3): (1-7).

6. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein the ultrasonic treatment conditions in the third step are as follows: the power is 90W, and the time is 30 min; the stirring conditions were: stirring by magnetic force for 12 h.

7. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein in the fifth step, the drying is heating drying or supercritical drying.

8. The preparation method of the aramid nanofiber-based battery separator with the micro-nano porous structure according to claim 7, wherein when heating and drying are adopted, the drying temperature is 105 ℃, and the drying time is 10 min.

9. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 7, wherein the preparation method is characterized in thatWhen supercritical drying is adopted, firstly soaking the aramid nano-fiber membrane in absolute ethyl alcohol for 4 hours, and additionally arranging CO₂The injection speed is 5ml/min, CO₂The injection time is 120s, the replacement speed is 5ml/s, the times are 12 times, the heating speed is 0.5 ℃/min, the air release speed is 10ml/min, the cooling temperature is set to be 12 ℃, and the heating temperature is set to be 38 ℃.

10. The preparation method of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure according to claim 1, wherein the thickness of the aramid nanofiber-based battery diaphragm with the micro-nano porous structure obtained in the step five through drying is 20-45 μm.

Technical Field

The invention belongs to the field of battery diaphragms, and particularly relates to a preparation method of an aramid nanofiber-based battery diaphragm with a micro-nano porous structure.

Background

Currently, with the development of various products such as new energy vehicles toward high-end, higher energy density, higher charge and discharge capacity and the like, research on battery materials is rapidly developed. The battery diaphragm is one of four major components of the battery, and plays an important role in the safety performance and the electrochemical performance of the battery. The separator mainly serves two purposes in the battery charging and discharging process: (1) the short circuit phenomenon caused by direct contact of the anode material and the cathode material of the battery can be effectively avoided, so that the safe use of the battery is influenced, and the danger of battery explosion is brought; (2) the ion transfer device can rapidly transfer ions in the charging and discharging process of the battery and provides a channel for the transmission of the ions. Therefore, the separator is required to have high ionic conductivity, a suitable pore size, excellent lyophilic and liquid retention properties, excellent mechanical properties, and high temperature resistance.

Currently, commercially available battery separators are mainly polypropylene microporous membranes, polyethylene microporous membranes, and membranes formed by compounding polypropylene and polyethylene membrane layers. The diaphragm material has low production cost, good strength and stable electrochemical performance, but the olefin diaphragm has poor heat-resistant stability, is easy to shrink at high temperature or high current density to cause short circuit of the battery, and has great safety risk; and the diaphragm has the problems of poor lyophilic property, ionic conductivity and the like. Therefore, it is of great significance to research and develop some novel high-performance battery separator materials to meet practical needs.

The existing battery diaphragm manufacturing process mainly optimizes and improves the production process of the polyolefin diaphragm, changes the pore structure of the diaphragm and is suitable for practical application. (1) In the invention patent CN108630862B, a membrane material, glacial acetic acid, polyvinylpyrrolidone and a diluent are mixed to obtain a homogeneous solution, the homogeneous solution is placed and defoamed in an electric heating mould at a constant temperature, a membrane casting solution is blade-coated to form a membrane, and the membrane is quenched to obtain the lithium ion battery blending microporous membrane, the pore size distribution of the membrane is more uniform, the electric conductivity is improved, the internal resistance of the battery is reduced, but the temperature resistance of the membrane is not changed in the process, and the membrane is easy to shrink when the temperature is increased, so that the application of the membrane in the high-temperature field is influenced; (2) the invention patent CN111628134A proposes that a modified coating is added to a polyethylene matrix microporous membrane, and the addition of nano inorganic micro powder in the modified reinforced coating can play a role in reinforcing 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 a lithium ion battery, reducing the influence of the coating on lithium ion transmission, and improving the performance of a lithium ion battery diaphragm, but the modification method modifies the surface of the polyolefin diaphragm, and reduces the cycle service life of the battery in the charge and discharge process of the battery; (3) the invention patent CN111129400A proposes mixing and extruding a film forming raw material and a pore-forming agent to obtain a first substrate, and cooling and forming the first substrate to obtain a second substrate; the second substrate is heated and biaxially stretched to obtain the microporous diaphragm, and the microporous diaphragm is subjected to heat setting and slitting to obtain the porous lithium battery diaphragm.

The para-aramid fiber has excellent performances such as good temperature resistance, insulativity and aging resistance, and is widely applied to the fields of special materials, military industry and the like. The para-Aramid nano-fibers (ANFs) have unique nano-scale structures (the diameter is 3-30nm, the length can reach 10 mu m at most), large length-diameter ratio and large specific surface area, so that the para-Aramid nano-fibers become a novel nano-structure building unit for building a macroscopic composite material and play important roles in interface enhancement and material toughening. The ANFs have abundant active groups on the surface, and have large length-diameter ratio and specific surface area, so that the nanometer materials have excellent characteristics. The ANFs can generate strong hydrogen bond combination to form a cross-linked network structure, has an excellent film forming effect, has the advantages of high strength, high temperature resistance, transparency, good flexibility, obvious Z-direction hierarchical structure and the like, and has huge application prospects in the fields of electric insulating materials, adsorption materials, high-temperature-resistant filtering films, supercapacitors, battery diaphragms and the like.

Disclosure of Invention

The invention aims to provide a preparation method of an aramid fiber nanofiber-based battery diaphragm with a micro-nano porous structure, which solves the problems that the traditional polyolefin battery diaphragm is poor in temperature resistance, easy to shrink and deform when heated, poor in wettability to electrolyte and the like. According to the invention, the mixed solvent is adopted to generate a micro-nano pore structure in the preparation process of the aramid nano-fiber membrane, and the para-aramid nano-fiber-based battery diaphragm with the micro-nano porous structure is researched and produced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of an aramid fiber nanofiber-based battery diaphragm with a micro-nano porous structure comprises the following steps:

the method comprises the following steps: mixing and stirring para-aramid fiber, dimethyl sulfoxide, potassium hydroxide and deionized water to prepare a para-aramid nanofiber solution A;

step three: carrying out ultrasonic treatment on the para-aramid nano-fiber solution B, and stirring to uniformly disperse aramid nano-fibers to obtain a para-aramid nano-fiber solution C;

step five: and drying the aramid fiber nanofiber membrane to obtain the micro-nano porous structure aramid fiber nanofiber-based battery diaphragm.

Further, in the first step, the diameter of the para-aramid nano-fiber is 8-15 nm, the length of the para-aramid nano-fiber is 3-8 μm, the mass ratio of the para-aramid nano-fiber to the potassium hydroxide is 1:1.5, 0.1-0.3g of para-aramid nano-fiber is added into every 100mL of dimethyl sulfoxide, and the volume ratio of deionized water to the dimethyl sulfoxide is 25: 1.

Further, the protonation donor in the second step is isopropanol, absolute ethyl alcohol or a mixture of tert-butyl alcohol and deionized water, and the volume ratio of the isopropanol, the absolute ethyl alcohol or the tert-butyl alcohol to the deionized water is (1-3): (1-7).

Further, the volume ratio of the para-aramid nano-fiber solution A to the protonation donor in the step two is 1: 2.

Further, the mixed solvent in the second step is isopropanol, absolute ethyl alcohol or a mixture of tert-butyl alcohol and deionized water, and the volume ratio of the isopropanol, the absolute ethyl alcohol or the tert-butyl alcohol to the deionized water is (1-3): (1-7).

Further, the ultrasonic treatment conditions in the third step are as follows: the power is 90W, and the time is 30 min; the stirring conditions were: stirring by magnetic force for 12 h.

Further, in the step five, the drying adopts heating drying or supercritical drying.

Further, when heat drying is adopted, the drying temperature is 105 ℃, and the drying time is 10 min.

Further, when supercritical drying is adopted, firstly, soaking the aramid nano-fiber membrane in absolute ethyl alcohol for 4 hours, and additionally arranging CO₂The injection speed is 5ml/min, CO₂The injection time is 120s, the replacement speed is 5ml/s, the times are 12 times, the heating speed is 0.5 ℃/min, the air release speed is 10ml/min, the cooling temperature is set to be 12 ℃, and the heating temperature is set to be 38 ℃.

Further, the thickness of the micro-nano porous structure aramid fiber nanofiber-based battery diaphragm obtained in the step five through drying is 20-45 microns.

Compared with the prior art, the invention has the following beneficial technical effects:

according to the invention, in the preparation process of the aramid nano-fiber membrane, the pore structure and the pore size of the membrane are regulated and controlled by the mixed solvent, so that the aramid nano-fiber-based battery membrane with a micro-nano structure is prepared, thereby replacing a commercial polyolefin membrane, solving the problems of poor temperature resistance, easy shrinkage due to heating, surface hydrophobicity and the like, and providing a new method for preparing a novel high-performance battery membrane.

The invention starts from the raw materials of the battery diaphragm, improves the characteristics of temperature difference resistance and the like of the traditional polyolefin diaphragm, selects the ANFs with more excellent performance and better film forming effect as the battery diaphragm, solves the problems that the current commercial polyolefin diaphragm has poor temperature resistance, shrinks and closes pores when being heated, and cannot meet the requirements of higher battery capacity and higher times of charge and discharge cycles (the polyolefin diaphragm shrinks at 120 ℃), greatly prolongs the service life of the battery diaphragm, improves the grade of the product, provides a new method and a theoretical basis for the preparation of a high-performance battery diaphragm material, can meet the requirements of long-term charge and discharge cycles of lithium ion batteries and lithium sulfur batteries, improves the stability of the diaphragm, and has important significance for the development of the field of new energy automobiles.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

Fig. 1 is an SEM image of the aramid nanofiber membrane obtained by the tert-butyl alcohol treatment in example 9 of the present invention, wherein (a) is an SEM image of pure ANFs, (b) is an SEM magnified image of pure ANFs, (c) is an SEM image of the ANFs after the tert-butyl alcohol treatment, and (d) is an SEM magnified image of the ANFs after the tert-butyl alcohol treatment.

Detailed Description

The invention is described in further detail below:

a preparation method of an aramid fiber nanofiber-based battery diaphragm with a micro-nano porous structure comprises the following raw materials: para-aramid nano-fiber, Isopropanol (IPA), absolute ethyl alcohol, tert-butyl alcohol and the like.

The method specifically comprises the following steps:

step (1): uniformly mixing para-aramid fiber, potassium hydroxide, dimethyl sulfoxide and deionized water according to a certain proportion at room temperature, stirring at the room temperature at the stirring speed of 1500rpm for 4 hours to prepare a para-aramid nanofiber solution A; wherein the mass ratio of the para-aramid fiber to the potassium hydroxide is 1:1.5, the volume ratio of the dimethyl sulfoxide to the deionized water is 25:1, and the diameter and the length of the para-aramid nanofiber are 8-15 nm and 3-8 microns respectively;

step (2): the method comprises the following steps of applying a certain shearing force to a para-aramid nano-fiber solution A in a DMSO/KOH system under the stirring action, injecting a mixed solvent serving as a protonation donor into the system by using an injector for protonation reduction, washing the protonation reduction system to be colloidal by using the mixed solvent under the vacuum filtration, and dispersing the colloidal mixed solvent in the mixed solvent to obtain a para-aramid nano-fiber solution B, wherein the volume ratio of the mixed solvent used for protonation reduction to the aramid nano-fiber solution is 2:1, and the mixed solvent is isopropanol, absolute ethyl alcohol or tert-butanol and deionized water in a volume ratio of (1-3): (1-7) mixing, wherein the washing times are 4 times, and the volume of a mixed solvent for dispersing the para-aramid nano-fiber solution is 300ml (the amount of the aramid nano-fiber is 0.1-0.3 g);

and (3): carrying out ultrasonic treatment on the aramid nano-fiber solution obtained in the step (2) in an ultrasonic dispersion machine, and carrying out magnetic stirring to uniformly disperse the aramid nano-fiber, wherein the ultrasonic power is 90W, the ultrasonic time is 30min, and the time for dispersing the aramid nano-fiber solution by magnetic stirring is 12 h;

and (4): carrying out suction filtration on the uniformly dispersed para-aramid nano-fiber solution C obtained in the step (3) by adopting a vacuum auxiliary filtration and layer-by-layer self-assembly mode to prepare an aramid nano-fiber membrane;

and (5): drying the aramid fiber nanofiber membrane obtained in the step (4) to obtain the micro-nano porous structure aramid fiber nanofiber-based battery diaphragm, wherein when a sheet making device is used for drying, the drying temperature is 105 ℃, and the drying time is 10 min; when supercritical drying is used, soaking the aramid fiber nano-fiber film obtained in the step (4) in absolute ethyl alcohol for 4 hours, drying the treated aramid fiber nano-fiber film on a full-automatic supercritical drying instrument, and setting CO₂The injection speed is 5ml/min, CO₂The injection time is 120s, the replacement speed is 5ml/s, the times are 12 times, the heating speed is 0.5 ℃/min, the air release speed is 10ml/min, the cooling temperature is set to be 12 ℃, and the heating temperature is set to be 38 ℃. In the drying process, absolute ethyl alcohol is required to be injected as a solvent, the injection amount of the solvent is required to completely soak the sample, and the thickness of the final aramid nano-fiber-based battery diaphragm is 20-45 microns.

The aramid nano-fibers adopted by the invention have unique nanoscale structures, large length-diameter ratio and specific surface area, the network interweaving structure formed by the aramid nano-fibers through hydrogen bonding has excellent film forming effect, and the ANFs film has the advantages of high strength, high temperature resistance, good flexibility, obvious Z-direction hierarchical structure and the like. At present, commercial battery diaphragms are mainly traditional polyolefin diaphragms, and PP, PE or PP/PE composite diaphragms are prepared by wet spinning or dry spinning. The invention develops the new material of the ANFs-based battery diaphragm which has temperature resistance, high ionic conductivity and excellent lithium ion transmission speed, improves the problems that the traditional polyolefin diaphragm has poor temperature resistance, is easy to shrink when the temperature rises, has poor wettability to electrolyte and the like, improves the grade of the product, can replace the application requirements of the polyolefin diaphragm in the fields of lithium ion batteries and lithium sulfur batteries, and becomes an excellent next-generation battery diaphragm material.

The present invention will be described in detail with reference to examples. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

The following detailed description is illustrative of the embodiments and is intended to provide further details of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.

Example 1

Step (1): taking 0.1g of para-aramid fiber, 0.15g of potassium hydroxide, 100ml of dimethyl sulfoxide and 4ml of deionized water, and carrying out stirring reaction at room temperature, wherein the stirring rotation speed is 1500rpm, and the stirring reaction time is 4 hours, so as to obtain a uniform dark red aramid nanofiber solution;

step (2): the para-aramid nano-fiber solution obtained in the step (1) is subjected to a certain shearing force under the action of magnetic stirring, 200ml of mixed solvent of isopropanol and deionized water with a volume ratio of 3:2(120ml of isopropanol and 80ml of deionized water) is injected into the system by using an injector to carry out protonation reduction, so that the para-aramid nano-fiber solution dispersed in a DMSO/KOH/mixed solvent system is obtained, the para-aramid nano-fiber solution is washed for 4 times to be colloidal by using 500ml of mixed solvent of isopropanol and deionized water with a volume ratio of 3:2(300ml of isopropanol and 200ml of deionized water) under vacuum filtration, and the para-aramid nano-fiber solution is dispersed by using 300ml of mixed solvent of isopropanol and deionized water with a volume ratio of 3:2(180ml of isopropanol and 120ml of deionized water);

and (3): carrying out ultrasonic treatment on the aramid nano-fiber solution obtained in the step (2) in a 90W ultrasonic dispersion machine for 30min, and after the ultrasonic treatment is finished, placing the aramid nano-fiber solution in a magnetic stirrer to be stirred and dispersed for 12 h;