CN108842303B - Boehmite/polyacrylonitrile composite nanofiber membrane as well as preparation method and application thereof - Google Patents
Boehmite/polyacrylonitrile composite nanofiber membrane as well as preparation method and application thereof Download PDFInfo
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- D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
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Abstract
The invention discloses a boehmite/polyacrylonitrile composite nanofiber membrane as well as a preparation method and application thereof. The preparation method comprises the steps of preparing boehmite sol by a sol-gel method for controlling the hydrolysis of aluminum alkoxide to form sol, then stirring and mixing the boehmite sol and polyacrylonitrile solution to obtain homogeneous spinning solution, and spinning the homogeneous spinning solution into the boehmite/polyacrylonitrile composite nanofiber membrane with the porous three-dimensional network structure by an electrostatic spinning method. The boehmite/polyacrylonitrile composite nanofiber membrane is applied as a membrane material of a lithium ion battery, has excellent lyophilic performance, heat resistance and mechanical performance, and can obviously improve the electrochemical performance of the lithium ion battery. In addition, the preparation method disclosed by the invention is simple in process, green and environment-friendly, low in cost, good in repeatability and good in application prospect.
Description
Technical Field
The invention relates to the technical field of preparation of lithium battery diaphragms, in particular to a preparation method of a boehmite/polyacrylonitrile composite nanofiber diaphragm.
Background
The lithium ion battery diaphragm is a porous film, separates positive and negative electrodes to prevent the internal short circuit of the battery, but allows the rapid passing of ion flow, thereby completing the rapid transmission of lithium ions between the positive and negative electrodes in the electrochemical charging and discharging process. The traditional commercial diaphragm of the lithium battery is mainly a polyolefin diaphragm manufactured by a dry method or a wet method, and the diaphragm has the defects of poor lyophilic performance, poor heat resistance and the like, so that the electrochemical performance of the battery is influenced.
Boehmite is a main component of bauxite, is an important chemical raw material, has a unique crystal structure, and is widely applied to various fields such as catalysts, adsorbents, inorganic flame retardants and the like.
Chinese patent application 2014108301100 discloses an aqueous multilayer separator for lithium ion batteries. The multilayer diaphragm is composed of a polymer base material, an inorganic particle coating and an organic particle coating, and the prepared inorganic or organic slurry is coated on the polymer base material by a coating method, so that the high-temperature resistance and the mechanical property of the diaphragm are improved to a certain extent by the method. However, because a multilayer coating process is adopted, and the inorganic particles and the binder are simply and physically blended, the problems of poor interlayer matching property and insufficient binding property are easily caused, so that the whole body is peeled off, and the hidden trouble of powder falling exists. In addition, because the base film adopts the microporous film, the situation that inorganic particles block micropores in the coating process possibly causes the problems of low porosity and the like, and the safety and the electrochemical performance of the battery are not improved.
Chinese patent application 201680020283 discloses a composite separator for a lithium secondary battery and a method for manufacturing the same. The composite separator for a lithium secondary battery includes: porous basic unit, heat-resisting layer and fusing layer. The process adopts a simultaneous coating method, and utilizes a multilayer groove coating die to simultaneously coat heat-resistant layer slurry and fusion layer slurry on one side or two sides of a microporous base film to form a multilayer composite diaphragm. The thermal stability and the service life of the diaphragm prepared by the method are improved, but the process still adopts the polyolefin microporous membrane as a base membrane material, and the polyolefin microporous membrane is modified by introducing inorganic/organic particle coating, so that the problem of porosity reduction caused by the situation that the micropores are blocked by inorganic particles still exists, and the transmission of lithium ions is not facilitated, thereby influencing the electrochemical performance of the battery.
Disclosure of Invention
Aiming at the defects of the existing commercial diaphragm, the invention provides a diaphragm which overcomes the problem of powder falling in the existing multilayer coating technology; the nano-fiber diaphragm has a porous network structure, the porosity reaches 70-85%, and the ionic conductivity reaches 1.5mS cm-1～3.0mS cm-1Boehmite/polyacrylonitrile composite nano-fiber diaphragm with a contact angle of 0-15 degrees and a preparation method thereof.
The invention also aims to provide the application of the boehmite/polyacrylonitrile composite nanofiber membrane as a lithium ion battery membrane.
The diaphragm has a porous three-dimensional network structure, and the composite nanofiber has a high specific surface area, so that the mechanical property and lyophilic property of the diaphragm are improved. The good thermal conductivity and flame retardance of the boehmite also effectively improve the heat resistance of the composite diaphragm. The application of the composite diaphragm in the lithium ion battery greatly improves the safety performance and the cycle performance of the battery due to the good lyophilic performance and thermodynamic performance of the composite diaphragm.
Boehmite has the characteristics of high heat-resistant temperature, good compatibility with organic matters and the like; the hardness is low, the abrasion to machinery can be reduced, and the cost is advantageous; meanwhile, boehmite is used as an inorganic flame retardant, and the heat resistance of the material can be effectively improved through compounding with a high polymer material. Due to the excellent thermal conductivity of the boehmite, the heat conduction problem of the lithium ion battery can be improved, and the flame retardance can prevent the battery from being combusted and exploded in a large range; boehmite is a layered structure, and when the material abnormally generates heat, boehmite expands to close a conduction hole, thereby blocking current. When the temperature drops, the material shrinks in volume and the current conduction hole reopens. Therefore, the boehmite can effectively improve the safety performance of the lithium ion battery and provide possibility for application of high-energy batteries such as power batteries.
The nanofiber membrane prepared by the electrostatic spinning method has a spatial network structure, higher porosity and good mechanical properties, and is an ideal lithium battery diaphragm material.
The boehmite sol is obtained by an aluminum alkoxide hydrolysis method, and then is mixed with a polyacrylonitrile solution to form a homogeneous spinning solution, and the boehmite/polyacrylonitrile composite nanofiber membrane is prepared by an electrostatic spinning method. The composite diaphragm prepared by the invention has a porous three-dimensional network structure, has excellent liquid absorption performance, heat resistance and mechanical performance, and has good electrochemical performance under an assembled lithium battery.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane comprises the following steps:
1) adding aluminum alkoxide into deionized water, stirring for 3-4 h at 60-80 ℃, adding a dilute nitric acid solution when white precipitates appear, adjusting the pH of the solution to 2-5, and continuously heating, refluxing and stirring for 8-12 h at 90-100 ℃ to obtain stable boehmite sol;
2) adding polyacrylonitrile powder into an organic solvent, firstly swelling for 8-12 h at room temperature, and then stirring for 5-6 h at 70-90 ℃ to obtain a polyacrylonitrile solution; the organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone and acetone;
3) after the polyacrylonitrile solution is cooled to room temperature, adding the boehmite sol obtained in the step 1) into the polyacrylonitrile solution, mixing and stirring for 5-6 hours at 70-90 ℃, naturally cooling to room temperature, and standing for 1-2 hours to obtain a boehmite/polyacrylonitrile spinning solution; then obtaining a boehmite/polyacrylonitrile composite diaphragm by an electrostatic spinning method, and carrying out vacuum drying at 80-160 ℃ to remove an organic solvent and water; the mass ratio of the boehmite sol to the polyacrylonitrile powder is controlled to be 1-5: 10.
To further achieve the object of the present invention, preferably, in step 1), the aluminum alkoxide is one or more of aluminum isopropoxide, aluminum sec-butoxide, and boehmite.
Preferably, in step 3), the conditions of electrostatic spinning are as follows: the temperature is 15-30 ℃; the voltage is as follows: 10-25 kV; the flow rate is: 0.05-1.5 mL/h; the receiving distance is: 14-18 cm; the needle head moves back and forth: 15-35 cm/min; the spinning time is 8-15 h; the diameter of the needle head is as follows: 0.15-0.25 mm.
Preferably, in the step 1), the mass ratio of the aluminum alkoxide to the deionized water is 1-5: 100, and the mass ratio of the aluminum alkoxide to the dilute nitric acid is 1: 0.1-0.5.
Preferably, in the step 1), the first stirring and the second stirring are mechanical stirring or magnetic stirring, and the stirring speed is 400-1000 r/min.
Preferably, in the step 2), the mass ratio of the polyacrylonitrile powder to the organic solvent is 0.5-2: 10.
Preferably, in the step 2), the stirring is mechanical stirring or magnetic stirring, and the stirring speed is 600-1000 r/min.
Preferably, in the step 3), the absolute vacuum degree of the vacuum drying is-0.1 to-0.05 MPa, and the time of the vacuum drying is 8 to 15 hours.
The boehmite/polyacrylonitrile composite nanofiber membrane is prepared by the preparation method, has a porous three-dimensional network structure, has the porosity of 70-85%, the average fiber diameter of 250-400 nm, the thickness of 40-70 mu m, the contact angle of 0-15 degrees, the shrinkage rate of 0-10% at 135 ℃, and the ionic conductivity of 1.5mScm-1～3.0mS cm-1。
The boehmite/polyacrylonitrile composite nanofiber membrane is applied as a lithium ion battery membrane.
Compared with the prior art, the invention has the following advantages:
1) the boehmite/polyacrylonitrile composite nanofiber membrane is prepared by compounding boehmite sol and polyacrylonitrile solution and adopting an electrostatic spinning method. The diaphragm has a porous three-dimensional network structure, and the composite nanofiber has a high specific surface area, so that the mechanical property and lyophilic property of the diaphragm are improved. The good thermal conductivity and flame retardance of the boehmite also effectively improve the heat resistance of the composite diaphragm. The application of the composite diaphragm in the lithium ion battery greatly improves the safety performance and the cycle performance of the battery due to the good lyophilic performance and thermodynamic performance of the composite diaphragm.
2) The preparation method has the advantages of simple preparation process, mild conditions, convenient operation and low cost, and the prepared boehmite/polyacrylonitrile nano-fiber composite membrane has excellent comprehensive properties such as heat resistance, electrochemical properties and the like.
3) According to the invention, aluminum alkoxide hydrolysis and a sol-gel method are adopted to prepare boehmite sol, and then the boehmite sol and polyacrylonitrile solution are compounded to obtain homogeneous spinning solution, and the porous nanofiber composite diaphragm is prepared by an electrostatic spinning technology. The composite diaphragm obtained by spinning can be directly molded, and boehmite particles are firmly embedded into polyacrylonitrile fibers, so that the problems of insufficient cohesiveness and powder falling of the existing multilayer coating technology are solved.
4) The nanofiber membrane prepared by the electrostatic spinning method has a porous network structure, so that the porosity of the membrane is remarkably improved and is far higher than that of the membrane prepared by the prior art; and the composite diaphragm is directly molded and has good repeatability.
Drawings
Fig. 1 is an SEM image of a boehmite/polyacrylonitrile composite nanofiber membrane prepared in example 1, in which fig. 1a) and 1b) are SEM images at 5000 times and 50000 times, respectively;
FIG. 2 is a contact angle test chart of the boehmite/polyacrylonitrile composite nanofiber membrane and Celgard2400 type single-layer PP membrane prepared in example 1; wherein, the graph of FIG 2a) and the graph of FIG 2b) are contact angle test graphs from 0s to 2s of the boehmite/polyacrylonitrile composite nano-fiber diaphragm respectively; fig. 2c) and fig. 2d) are contact angle test plots from 0s to 2s for Celgard2400 type monolayer PP separator, respectively.
FIG. 3 is a DSC of boehmite/polyacrylonitrile composite nanofiber membrane prepared in example 1 and a PP membrane;
fig. 4 is a cycle performance diagram of a button cell assembled with a PP separator, respectively, of the boehmite/polyacrylonitrile composite nanofiber separator prepared in example 1.
Detailed Description
For better understanding of the present invention, the present invention will be further described with reference to the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto.
Example 1
A preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane comprises the following steps:
(1) slowly adding 1 part of aluminum sec-butoxide into 100 parts of deionized water in parts by mass, stirring for 4 hours at 80 ℃, adding 0.1 part of dilute nitric acid solution when white precipitates appear, adjusting the pH value of the solution to be 3, and continuously refluxing and magnetically stirring for 12 hours at 90 ℃ and 800r/min to obtain stable boehmite sol;
(2) adding 1 part of polyacrylonitrile powder into 10 parts of N, N-dimethylformamide in parts by mass, firstly swelling at room temperature for 12 hours, and then magnetically stirring at 80 ℃ and 800r/min for 6 hours to obtain a polyacrylonitrile solution;
(3) cooling polyacrylonitrile solution to room temperature by mass parts, adding 1 part of boehmite sol into 10 parts of polyacrylonitrile solution, magnetically stirring for 6 hours at 80 ℃ under 1000r/min, uniformly mixing, naturally cooling to room temperature, standing for 2 hours to obtain boehmite/polyacrylonitrile spinning solution, then obtaining a boehmite/polyacrylonitrile composite diaphragm by an electrostatic spinning method (temperature: 25 ℃, voltage: 16kV, receiving distance: 16cm, flow rate: 0.64mL/h, needle size: 0.21mm, needle reciprocating speed: 20cm/min, time 8 hours), and drying in vacuum for 12 hours at 80 ℃ and-0.01 MPa absolute vacuum degree to remove redundant solvent.
A Celgard 2400-type monolayer PP membrane (Celgard Corp., USA) was used as a comparative example, with a thickness of 25 μm and a porosity of 41%.
Fig. 1 is an SEM image of the boehmite/polyacrylonitrile composite nanofiber membrane prepared in example 1, in which fig. 1a) and 1b) are SEM images at 5000 times and 50000 times, respectively. As can be seen from FIG. 1, the boehmite/polyacrylonitrile nano-fiber composite membrane has a porous three-dimensional network structure, the porosity of the membrane reaches 85%, the average fiber diameter is 390 +/-50 nm, and the thickness of the membrane is 45 μm measured by a micrometer.
And (3) carrying out contact angle test on the diaphragm by using an OCA40Micro surface tension surface contact angle tester. In fig. 2, fig. 2a) and fig. 2b) are respectively a contact angle of the boehmite/polyacrylonitrile composite nanofiber membrane from 0s to 2s, the contact angle is from 70.1 degrees, and the change is 6 degrees after 2 s; in fig. 2, fig. 2c) and fig. 2d) show that the contact angle of the Celgard2400 type single-layer PP separator is from 0s to 2s, the contact angle is from 103.1 degrees, and the change after 2s is 101.5 degrees, which indicates that the boehmite/polyacrylonitrile nano-fiber composite separator has more excellent wetting performance than the PP separator. The liquid absorption rate of the composite diaphragm can be up to 1247 percent (only 169 percent of Celgard2400 type single-layer PP diaphragms) by a wet weight method.
And testing the thermal stability of the diaphragm by using Differential Scanning Calorimetry (DSC), wherein the temperature range is 100-250 ℃, and the heating rate is 10 ℃/min. As can be seen from FIG. 3, at a temperature of 167 ℃, the PP membrane has a larger endothermic peak, while the boehmite/polyacrylonitrile nanofiber composite membrane has no obvious peak, which indicates that the composite membrane has more excellent thermal stability.
The boehmite/polyacrylonitrile nano-fiber composite membrane and the comparative PP membrane are assembled into the CR2016 button cell in the glove box, and the charge-discharge cycle is performed for 100 times at the rate of 0.5C, and as can be seen from figure 4, the cell using the boehmite/polyacrylonitrile nano-fiber composite membrane has better cycle performance than the PP membrane, the capacity retention rate reaches 87.68%, and the PP membrane is only 55.73%.
The prior art has the problems of insufficient cohesiveness of the diaphragm, low porosity and the like, and also has the hidden trouble of powder falling, which is not beneficial to improving the safety and the electrochemical performance of the battery. In the embodiment, aluminum alkoxide is hydrolyzed, boehmite sol is prepared by a sol-gel method, and then the boehmite sol and polyacrylonitrile solution are compounded to form homogeneous spinning solution, and the porous nanofiber composite membrane is obtained through electrostatic spinning. The composite diaphragm is directly formed through electrostatic spinning, multilayer coating modification is not needed, boehmite particles are more firmly embedded into polyacrylonitrile fibers, and the problem of 'powder falling' caused by insufficient cohesiveness in the existing coating technology is solved; meanwhile, the nanofiber membrane prepared by the electrostatic spinning method has a porous network structure, and the porosity of the membrane is improved more remarkably. Therefore, the composite diaphragm prepared by the embodiment can effectively overcome the defects of the prior art, and obviously improves the safety performance and the electrochemical performance of the battery.
Example 2
A preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane comprises the following steps:
(1) slowly adding 2 parts of aluminum isopropoxide into 100 parts of deionized water in parts by mass, stirring for 4 hours at 80 ℃, adding 0.2 part of dilute nitric acid solution when white precipitates appear, adjusting the pH value of the solution to be 3.5, and continuously refluxing and magnetically stirring for 12 hours at 90 ℃ and 900r/min to obtain stable boehmite sol;
(2) adding 0.5 part of polyacrylonitrile powder into 8 parts of N, N-dimethylformamide and 2 parts of acetone in parts by mass, firstly swelling at room temperature for 12 hours, and then magnetically stirring at 80 ℃ and 800r/min for 6 hours to obtain a polyacrylonitrile solution;
(3) cooling polyacrylonitrile solution to room temperature by mass parts, adding 2 parts of boehmite sol into 10 parts of polyacrylonitrile solution, magnetically stirring for 6 hours at 80 ℃ under 1000r/min, uniformly mixing, naturally cooling to room temperature, standing for 2 hours to obtain boehmite/polyacrylonitrile spinning solution, then obtaining a boehmite/polyacrylonitrile composite diaphragm by an electrostatic spinning method (temperature: 25 ℃, voltage: 15kV, receiving distance: 15cm, flow rate: 0.58mL/h, needle size: 0.21mm, needle back-and-forth speed: 25cm/min, time 8 hours), and drying in vacuum for 12 hours at 80 ℃ and-0.01 MPa absolute vacuum degree to remove redundant solvent.
Example 3
A preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane comprises the following steps:
(1) adding 1 part of aluminum sec-butoxide and 2 parts of aluminum isopropoxide into 100 parts of deionized water by mass, stirring for 4 hours at 80 ℃, adding 0.3 part of dilute nitric acid solution when white precipitates appear, adjusting the pH value of the solution to be 3, and continuously refluxing and magnetically stirring for 12 hours at 90 ℃ and 800r/min to obtain stable boehmite sol;
(2) adding 1.5 parts of polyacrylonitrile powder into 10 parts of N, N-dimethylacetamide by mass, firstly swelling at room temperature for 12 hours, and then magnetically stirring at 80 ℃ and 900r/min for 6 hours to obtain a polyacrylonitrile solution;
(3) according to the mass portion, when the polyacrylonitrile solution is cooled to the room temperature, 3 portions of boehmite sol are added into 10 portions of polyacrylonitrile solution, magnetic stirring is carried out for 6 hours at 80 ℃ and 1000r/min, the mixture is uniformly mixed, the mixture is naturally cooled to the room temperature and stands for 2 hours, boehmite/polyacrylonitrile spinning solution is obtained, then a boehmite/polyacrylonitrile composite diaphragm is obtained by an electrostatic spinning method (the temperature is 25 ℃, the voltage is 16.8kV, the receiving distance is 16cm, the flow rate is 0.73mL/h, the size of a needle is 0.23mm, the reciprocating speed of the needle is 25cm/min, the time is 12 hours), and the redundant solvent is removed by vacuum drying at 80 ℃ and-0.01 MPa absolute vacuum degree for 12 hours.
Example 4
A preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane comprises the following steps:
(1) adding 3 parts of boehmite into 100 parts of deionized water by mass, stirring for 4 hours at 80 ℃, adding 0.3 part of dilute nitric acid solution when white precipitates appear, adjusting the pH value of the solution to be 3, and continuously refluxing and magnetically stirring for 12 hours at 90 ℃ and 800r/min to obtain stable boehmite sol;
(2) adding 1 part of polyacrylonitrile powder into 10 parts of N-methyl pyrrolidone in parts by mass, firstly swelling at room temperature for 12 hours, and then magnetically stirring at 80 ℃ and 800r/min for 6 hours to obtain a polyacrylonitrile solution;
(3) cooling polyacrylonitrile solution to room temperature by mass parts, adding 4 parts of boehmite sol into 10 parts of polyacrylonitrile solution, magnetically stirring for 6 hours at 80 ℃ under 1000r/min, uniformly mixing, naturally cooling to room temperature, standing for 2 hours to obtain boehmite/polyacrylonitrile spinning solution, then obtaining the boehmite/polyacrylonitrile composite diaphragm by an electrostatic spinning method (temperature: 30 ℃, voltage: 17.5kV, receiving distance: 17cm, flow rate: 0.58mL/h, needle size: 0.22mm, needle reciprocating speed: 30cm/min, time 10 hours), and drying in vacuum for 12 hours under absolute vacuum degree of-0.01 MPa at 80 ℃ to remove redundant solvent.
For the above examples and PP separators, various physical and electrochemical performance tests are shown in table 1 below. Wherein the PP diaphragm is a Celgard2400 type single-layer diaphragm.
The thickness of the composite diaphragm is measured by a micrometer;
the porosity is measured and calculated by using an n-butanol method, different diaphragms are respectively soaked in the n-butanol for 1 hour, and the weight of the diaphragms before and after liquid absorption is weighed, wherein the equation is as follows:
porosity (%) — (weight after imbibition-weight before imbibition) × 100%/(density of n-butanol × volume of separator);
the liquid absorption rate is measured by respectively weighing the weight of the diaphragm before and after liquid absorption after the diaphragm is soaked in electrolyte for 1h in a glove box and calculating, and the equation is as follows:
liquid absorption rate (%) (weight after liquid absorption-weight before liquid absorption) × 100%/(weight before liquid absorption);
and (3) testing the shrinkage rate of the diaphragm, namely cutting the diaphragm into circular sheets with the diameter of 19mm by using a sheet punching machine, placing different diaphragms in an air-blowing drying oven, heating for 1h at 135 ℃, measuring the areas of the diaphragms before and after heating, and calculating according to an equation:
shrinkage (%) (area of the separator before heating-area of the separator after heating) × 100%/(area of the separator before heating);
the ionic conductivity is obtained by assembling different diaphragms into a stainless steel sheet | diaphragm | stainless steel sheet CR2016 type blocking battery, measuring the impedance of the different diaphragms by a Gamry electrochemical workstation respectively and calculating by an equation:
ionic conductivity ═ membrane thickness/(membrane volume resistance × membrane area);
different diaphragms are assembled into a CR2016 type battery in a glove box, and electrochemical properties such as discharge specific capacity, charge-discharge efficiency, cycle rate and the like of the battery are tested by a Xinwei battery comprehensive performance tester.
TABLE 1
As can be seen from the test results in table 1, the PP separators in examples 1 to 4 have more excellent porosity, liquid absorption rate, and ionic conductivity, and also have low shrinkage, good heat stability, and excellent electrochemical properties.
According to the invention, aluminum alkoxide hydrolysis and a sol-gel method are adopted to prepare boehmite sol, and then the boehmite sol and polyacrylonitrile solution are compounded to obtain homogeneous spinning solution, and the porous nanofiber composite diaphragm is prepared by an electrostatic spinning technology. The composite diaphragm obtained by spinning can be directly molded, and boehmite particles are firmly embedded into polyacrylonitrile fibers, so that the problems of insufficient cohesiveness and powder falling of the existing multilayer coating technology are solved; meanwhile, the nanofiber membrane prepared by the electrostatic spinning method has a porous network structure, so that the porosity of the membrane is remarkably improved and is far higher than that of the membrane prepared by the prior art; and the composite diaphragm is directly molded, the preparation process is simpler, and the repeatability is good. Therefore, the nanofiber composite diaphragm prepared by the method can effectively overcome the defects of the prior art, and can remarkably improve the safety performance and the electrochemical performance of the battery.
In conclusion, the boehmite/polyacrylonitrile composite nanofiber diaphragm prepared by the method not only can meet the basic requirements of lithium ion battery diaphragms, but also can effectively improve the mechanical property, lyophilic property, heat resistance and electrochemical property of the diaphragms. The preparation method disclosed by the invention is simple in preparation process, mild in condition, convenient to operate and low in cost, and the prepared boehmite/polyacrylonitrile nano-fiber composite diaphragm is excellent in comprehensive performances such as heat resistance and electrochemical performance and has a good application prospect.
The above embodiments are not intended to limit the present invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (9)
1. A preparation method of a boehmite/polyacrylonitrile composite nanofiber membrane is characterized by comprising the following steps:
1) adding aluminum alkoxide into deionized water, stirring for 3-4 h at 60-80 ℃, adding a dilute nitric acid solution when white precipitates appear, adjusting the pH of the solution to 2-5, and continuously heating, refluxing and stirring for 8-12 h at 90-100 ℃ to obtain stable boehmite sol;
2) adding polyacrylonitrile powder into an organic solvent, firstly swelling for 8-12 h at room temperature, and then stirring for 5-6 h at 70-90 ℃ to obtain a polyacrylonitrile solution; the organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone and acetone; the mass ratio of the polyacrylonitrile powder to the organic solvent is 0.5-2: 10;
3) after the polyacrylonitrile solution is cooled to room temperature, adding the boehmite sol obtained in the step 1) into the polyacrylonitrile solution, mixing and stirring for 5-6 hours at 70-90 ℃, naturally cooling to room temperature, and standing for 1-2 hours to obtain a boehmite/polyacrylonitrile spinning solution; then obtaining a boehmite/polyacrylonitrile composite nanofiber membrane by an electrostatic spinning method, and carrying out vacuum drying at 80-160 ℃ to remove an organic solvent and water; controlling the mass ratio of the boehmite sol to the polyacrylonitrile powder to be 1-5: 10;
the boehmite/polyacrylonitrile composite nanofiber membrane has a porous three-dimensional network structure, the porosity is 70-85%, the average fiber diameter is 250-400 nm, the thickness is 40-70 mu m, the contact angle is 0-15 ℃, the shrinkage at 135 ℃ is 0-10%, and the ionic conductivity is 1.5mS cm-1~3.0mS cm-1。
2. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, wherein in the step 3), the electrostatic spinning conditions are as follows: the temperature is 15-30 ℃; the voltage is as follows: 10-25 kV; the flow rate is: 0.05-1.5 mL/h; the receiving distance is: 14-18 cm; the needle head moves back and forth: 15-35 cm/min; the spinning time is 8-15 h; the diameter of the needle head is as follows: 0.15-0.25 mm.
3. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, wherein in step 1), the aluminum alkoxide is one or more of aluminum isopropoxide and aluminum sec-butoxide.
4. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, wherein in the step 1), the mass ratio of the aluminum alkoxide to the deionized water is 1-5: 100, and the mass ratio of the aluminum alkoxide to the dilute nitric acid is 1: 0.1-0.5.
5. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, wherein in the step 1), the first stirring and the second stirring are mechanical stirring or magnetic stirring, and the stirring speed is 400-1000 r/min.
6. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, characterized in that in the step 2), the stirring is mechanical stirring or magnetic stirring, and the stirring speed is 600-1000 r/min.
7. The preparation method of the boehmite/polyacrylonitrile composite nanofiber membrane according to claim 1, wherein in the step 3), the absolute vacuum degree of vacuum drying is-0.1 to-0.05 MPa, and the time of vacuum drying is 8 to 15 hours.
8. A boehmite/polyacrylonitrile composite nanofiber membrane prepared by the preparation method of any one of claims 1-7, wherein the boehmite/polyacrylonitrile composite nanofiber membrane has a porous three-dimensional network structure, the porosity is 70% -85%, the average fiber diameter is 250-400 nm, the thickness is 40-70 μm, the contact angle is 0-15%, the shrinkage at 135 ℃ is 0% -10%, and the ionic conductivity is 1.5mS cm-1~3.0mS cm-1。
9. The use of the boehmite/polyacrylonitrile composite nanofiber membrane described in claim 8 as a lithium ion battery membrane.
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| CN110137422A (en) * | 2019-05-30 | 2019-08-16 | 湖南电将军新能源有限公司 | A kind of lithium ion battery composite separation membrane and preparation method thereof |
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| CN113493958B (en) * | 2020-04-05 | 2023-02-28 | 北京化工大学 | Polyimide nanofiber membrane coaxially coated with boehmite and preparation method thereof |
| CN112127011B (en) * | 2020-09-28 | 2023-01-03 | 湘潭大学 | Polyacrylonitrile/cellulose composite fiber membrane and preparation method and application thereof |
| CN112999896B (en) * | 2021-03-11 | 2023-12-22 | 西西埃热能(南京)有限公司 | Boehmite modified adsorption film and preparation method and application thereof |
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| CN115814754B (en) * | 2022-12-14 | 2024-08-02 | 江西宝弘纳米科技有限公司 | Boehmite modified adsorbent and preparation method and application thereof |
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