CN112271406A - Boron nitride fiber coated diaphragm for lithium ion battery and preparation method thereof - Google Patents
Boron nitride fiber coated diaphragm for lithium ion battery and preparation method thereof Download PDFInfo
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- CN112271406A CN112271406A CN202011194944.9A CN202011194944A CN112271406A CN 112271406 A CN112271406 A CN 112271406A CN 202011194944 A CN202011194944 A CN 202011194944A CN 112271406 A CN112271406 A CN 112271406A
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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Abstract
The invention discloses a boron nitride fiber coated diaphragm for a lithium ion battery and a preparation method thereof. The invention adopts a two-step method to prepare the boron nitride fiber coated diaphragm: firstly, preparing a high-activity boron nitride fiber material with a hexagonal structure by a chemical activation method; and secondly, coating the prepared boron nitride fiber on the surface of the polyolefin diaphragm by a press molding method to prepare the boron nitride fiber coated diaphragm. The chemical activation method used by the invention can overcome the defects that the existing synthesis process needs strong acid and strong alkali treatment and the process is complex. The method has the advantages of low preparation temperature, simple process, no use of strong acid for activation, and small pollution, and is suitable for large-scale industrial production. The boron nitride fiber coated diaphragm prepared by the invention has high thermal stability, high thermal conductivity and good mechanical stability, and lithium ions can rapidly pass through the diaphragm, so that the requirement of a high-power lithium ion battery can be met, and the diaphragm has wide prospects in the field of high-power electronic packaging application.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a boron nitride fiber coated diaphragm for a lithium ion battery and a preparation method thereof.
Background
As the world seeks to more efficiently utilize energy resources, improving battery technology is a high priority. The lithium ion battery technology has high application requirements in some fields, such as electric vehicles, hybrid electric vehicles and power grids, and plays an important role in the aspect of power supply of high-energy and power density devices. However, battery safety is a serious and challenging problem currently faced, especially the risk of battery fire and explosion increases significantly, and the existing safety problems of lithium ion batteries rise to an extreme level, such as battery fire and explosion of samsung Note7, battery fire of tesla electric vehicles, and battery problems of boeing 787 dream passenger aircraft. Therefore, the safety problem of the lithium battery is used for solution.
Lithium ion batteries consist of three functional components: electrodes (anode and cathode), separator, and electrolyte. The diaphragm is arranged between the two electrodes to prevent the two electrodes from being in electric contact, and simultaneously allows ion transmission, and in the prior art, the thermal stability of the diaphragm is poor, and the safety failure of lithium ions is mainly caused by thermal runaway caused by overheating; the battery is initially overheated due to overhigh external temperature and high-current and high-rate charge and discharge, and the commercial polyolefin diaphragm begins to shrink under the extreme overheating environment, so that the battery is finally short-circuited; the initial short accelerates the uncontrolled exothermic reaction, further decomposing the solid electrolyte interface layer, electrolyte and electrodes, releasing a large amount of heat, even at temperatures above 200 ℃. Thus, severe thermal runaway can cause fires and explosions. The basic problem with commercial polyolefin separators (including polyethylene and polypropylene) is their low melting point (melting point of PE around 135 ℃ and melting point of PP around 165 ℃); at higher operating temperatures, polyolefin lithium ion battery separators can develop significant dimensional instability that can cause internal short circuits when the battery is operated at higher current rates; since the battery separator is a main component for preventing short circuits, thermal stability of the battery separator is important.
In order to improve the thermal stability of lithium ion battery separators, many safety materials have been developed for modifying commercial polyolefin battery separators. In the prior art, inorganic nanoparticles (such as SiO) are mainly used2、Al2O3、Al(OH)3、Mg(OH)2Zeolite, ZrO2And TiO2) The thermal stability of the polyolefin battery diaphragm is improved by coating the modified polyolefin battery diaphragm, but the thermal stability improvement effect is not obvious, and the battery diaphragm modified by the inorganic nano particles is brittle and has low flexibility (mechanical instability), cracks can be generated in the battery assembly process, and short circuit can be immediately generated in the battery operation process; in the prior art, substitutes of some polyolefin battery separators are also explored, such as non-woven fabric separators, and although the non-woven fabric separators have good thermal stability, the separators all have a macroporous structure, so that internal short circuit, self-discharge and even electrolyte leakage are easily caused.
Therefore, the battery separator in the prior art cannot well balance other important parameters such as mechanical stability and cycle performance under high current rate and high temperature with thermal stability. Therefore, improvements in existing battery separators are needed to improve thermal stability, mechanical stability, etc., and thus improve safety and reliability of lithium ion batteries. Therefore, the development of a battery separator having high performance is essential to achieve safe and reliable performance of a lithium battery.
Disclosure of Invention
The invention aims to provide a boron nitride fiber-coated diaphragm which is low in preparation cost, easy to industrially produce, high in thermal stability, excellent in mechanical stability and capable of allowing lithium ions to rapidly pass through, and a preparation method thereof, aiming at the defects of the prior art, and the prepared boron nitride fiber-coated diaphragm can be applied to a lithium ion battery.
The purpose of the invention can be realized by the following technical scheme:
a boron nitride fiber coated diaphragm comprises a polyolefin diaphragm and a boron nitride fiber film layer coated on the surface of the polyolefin diaphragm.
The preparation method of the boron nitride fiber-coated membrane comprises the following steps: preparing high-activity boron nitride fibers by a chemical activation method; and then coating the boron nitride fiber on the surface of the polyolefin diaphragm by a compression molding method to prepare the obtained boron nitride fiber coated diaphragm.
Preferably, the preparation process of the boron nitride fiber is as follows:
s1, placing a certain volume part of boron trifluoride diethyl etherate solution in a horizontal tube furnace, heating to a certain temperature at a certain heating rate by taking ammonia as reaction gas, and reacting for a period of time at the temperature to obtain a product A;
s2, cooling the product A obtained in the step S1, placing the product A into an alkaline aqueous solution with the pH value of 7.5-8.5, uniformly stirring, heating and reacting for a period of time to obtain a mixed solution, cooling and filtering the mixed solution, filtering and collecting solid powder in the mixed solution, and washing the solid powder with deionized water until the surface of the solid powder is neutral to obtain a product B;
s3, placing the product B obtained in the step S2 in an ethanol water solution, stirring and mixing uniformly, heating and reacting for a period of time to obtain a mixed solution, cooling the mixed solution, filtering and collecting solid matters in the mixed solution, and obtaining the high-activity boron nitride fiber.
Preferably, in the step S1, the temperature of the heating reaction is 300 to 700 ℃; the heating reaction time is 1-3 h; the heating rate is 1-5 ℃/min; the gas flow of the ammonia gas is 50-500 mL/min.
Preferably, the volume part of the boron trifluoride ethyl ether solution is 1-10 parts; the volume concentration of the boron trifluoride diethyl etherate solution is 20-45%; the volume part of the alkaline aqueous solution is 10-100 parts; the alkaline aqueous solution is an inorganic alkaline aqueous solution.
Preferably, in the step S2, the stirring time is 0.5 to 3 hours; the heating reaction temperature is 65-85 ℃, and the heating reaction time is 0.2-3 h.
Preferably, in the step S3, the stirring time is 1 to 3 hours; the heating reaction temperature is 70-80 ℃, and the heating reaction time is 1-3 h; the ethanol water solution is 25-45% of ethanol water solution by volume concentration.
Preferably, the specific process of coating the boron nitride fiber on the surface of the polyolefin diaphragm by a press molding method is as follows: adding a certain mass of binder into a certain volume of deionized water, and continuously stirring for 0.5-2 h at the temperature of 70-90 ℃ to obtain a binder suspension; then adding a certain mass of boron nitride fibers into the binder suspension, and carrying out ultrasonic treatment for 40-120 min to obtain boron nitride slurry; and uniformly coating the boron nitride slurry on the surface of the polyolefin diaphragm, drying at room temperature for 5-12 h, and flattening by using a pressing wheel to obtain the boron nitride fiber coated diaphragm.
Preferably, the binder is polyvinyl alcohol, the concentration of the binder in the boron nitride slurry is 0.001-0.2 g/mL, and the concentration of the boron nitride in the boron nitride slurry is 0.001-0.02 g/mL.
The application of the boron nitride fiber-coated membrane is to a lithium ion battery membrane.
The invention relates to a boron nitride fiber coated diaphragm for a lithium ion battery and a preparation method thereof. According to the invention, the boron nitride fiber coated diaphragm is prepared by adopting a two-step method, in the first step, the boron nitride fiber material with high activity and a hexagonal structure is prepared by a chemical activation method, the boron nitride prepared by the chemical activation method has high crystallinity, the boron nitride fiber with a porous channel structure is formed, a good heat conduction channel can be formed, the heat conduction capability of the boron nitride is fully exerted, and the boron nitride fiber coated diaphragm is good in thermal stability and high in mechanical strength; and secondly, coating the prepared boron nitride fiber on the surface of the polyolefin diaphragm by a press molding method to prepare the boron nitride fiber coated diaphragm. The chemical activation method process used by the invention can obtain the high-activity boron nitride fiber without using strong acid and strong alkali for treatment and using a complex process, overcomes the defects that the existing active boron nitride preparation process needs strong acid and strong alkali for treatment and the process is complex, and the obtained boron nitride fiber material is the boron nitride fiber with a hexagonal structure; the cladding of fibrous structure's boron nitride fibre is on polyolefin diaphragm surface, can provide lithium ion's passageway, help lithium ion's quick pass through, and fibrous structure's boron nitride fibre evenly distributed is on the diaphragm surface, form the heat conduction passageway, make boron nitride's heat conductivity obtain full play, make the heat conductivity of diaphragm show the promotion, the thermal stability is showing and improves, the degree of crystallinity of hexagonal structure's boron nitride, mechanical stability is good, the cladding of boron nitride fibre prepared through the pressure moulding method is on polyolefin diaphragm surface, make the mechanical stability of preparing the boron nitride fibre cladding diaphragm good, mechanical strength is high.
The invention has the beneficial effects that:
1. the boron nitride fiber-coated diaphragm prepared by the invention has good thermal stability, the thermal conductivity is obviously improved, and lithium ions can rapidly pass through the diaphragm, so that the requirement of a high-power lithium ion battery can be met;
2. the boron nitride fiber-coated diaphragm prepared by the invention has high mechanical strength and has wide prospect in the application field of high-rate lithium ion electronic diaphragms;
3. the raw materials adopted by the invention are boron trifluoride diethyl etherate solution and ammonia gas, which belong to industrial products, and have low price, easy obtainment and low production cost;
4. the method has the advantages of low preparation temperature, simple process, no use of strong acid for activation, and small pollution, and is suitable for large-scale industrial production.
Drawings
FIG. 1 is an X-ray powder diffraction pattern of a boron nitride fiber material prepared in example 1 of the present invention;
FIG. 2 is a graph showing the comparison of the thermal stability of the boron nitride fiber-coated membrane and the pure polypropylene membrane in example 1 of the present invention;
FIG. 3 is a graph comparing the mechanical stability of the boron nitride fiber-coated membrane and the pure polypropylene membrane in example 1 of the present invention.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
Example 1
1. Putting 10 ml of boron trifluoride diethyl etherate solution with volume concentration of 45% in a horizontal tube furnace, introducing ammonia gas serving as reaction gas into the horizontal tube furnace, wherein the gas flow is 50ml/min, heating to 300 ℃ at the heating rate of 1 ℃ per minute, and reacting for 1 hour at the temperature to obtain a product A which is collapse type boron nitride fiber;
2. after the product obtained in the step 1 is cooled to room temperature, placing the product into 10 ml of alkaline aqueous solution with the pH value of 7.5, stirring for 0.5 hour, heating to 65 ℃, reacting for 0.2 hour at the temperature to obtain mixed solution, cooling the obtained mixed solution to room temperature, filtering the mixed solution to obtain solid powder, and washing the solid powder with deionized water until the surface of the solid powder is neutral to obtain a product B;
3. placing the product B obtained in the step 2 into an ethanol water solution, wherein the volume concentration of ethanol is 25%, and the ethanol is added to graft a hydroxyl functional group on the surface of the boron nitride, so that the boron nitride fiber can better coat the polypropylene diaphragm; stirring for 1 hour, heating to 70 ℃, reacting for 1 hour at the temperature, cooling the mixed solution to room temperature, filtering the mixed solution, and filtering and collecting solid matters to obtain the high-activity boron nitride fiber.
4. Adding 0.1 g of polyvinyl alcohol binder into 50ml of deionized water, continuously stirring for 0.5 hour at the temperature of 70 ℃ to obtain binder suspension, then adding 0.1 g of boron nitride fiber prepared in the step 3 into the binder suspension, and performing ultrasonic treatment for 40min to obtain boron nitride slurry; placing a polypropylene diaphragm on a flat surface, and then uniformly dispersing boron nitride slurry on the surface; drying for 5 hours at room temperature, and then flattening by a pressing wheel to obtain the product, namely the boron nitride fiber coated diaphragm.
As shown in fig. 1, the X-ray powder diffraction pattern of the boron nitride fiber prepared in step 3 is clear in diffraction peak and narrow in half-peak width, which indicates that the hexagonal boron nitride material prepared by the chemical activation method has high crystallinity.
As shown in fig. 2, curve a in fig. 2 is a graph of the weight of the pure polypropylene membrane changing with temperature, curve b in fig. 2 is a graph of the weight of the boron nitride fiber coated membrane changing with temperature, it can be seen from the graph that the decomposition temperature of the boron nitride fiber coated membrane is about 420 ℃, and the thermal conductivity is tested to be as high as 10W/m.k; the decomposition temperature of the pure polypropylene diaphragm is about 175 ℃, and the heat conductivity of the pure polypropylene diaphragm is 0.22W/m.K; through comparative analysis, the thermal stability and the thermal conductivity of the boron nitride fiber coated diaphragm are greatly improved, and the boron nitride fiber coated diaphragm has wide prospects in the field of electronic packaging application.
As shown in fig. 3, curve a in fig. 3 is a curve of the variation of the tensile strength of the boron nitride fiber-coated membrane with temperature; curve b in fig. 3 is a curve of tensile strength of the pure polypropylene separator as a function of temperature; as can be seen from the figure, the tensile strength of the boron nitride fiber coated diaphragm can still be maintained at 220MPa when the temperature is up to 300 ℃; the mechanical strength of the pure polypropylene diaphragm at room temperature is 100MPa, and the tensile strength of the pure polypropylene diaphragm at 300 ℃ is only 50 MPa; fig. 3 illustrates that the boron nitride fiber coating of the present invention has excellent mechanical stability and mechanical strength, and has a wide prospect in the application field of high-rate lithium ion batteries.
Example 2
Example 2 the procedure of example 1 was substantially the same, except that 50ml of boron trifluoride diethyl etherate was used in step 1; the volume concentration of boron trifluoride diethyl etherate solution is 30%; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 3
Example 3 the same operations as example 1 were carried out except that in step 1, 100ml of boron trifluoride diethyl etherate was used; the volume concentration of boron trifluoride diethyl etherate solution is 20%; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 4
Example 4 the operations were substantially the same as example 1, except that in step 1, the gas flow rate of ammonia gas was 50 mL/min; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 5
Example 5 the operations of example 1 were substantially the same, except that in step 1, the gas flow rate of ammonia gas was 100 mL/min; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 6
Example 6 the operations of example 1 were substantially the same except that in step 1, the temperature of the heating reaction was 500 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 7
Example 7 the operations of example 1 were substantially the same except that in step 1, the temperature of the heating reaction was 700 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 8
Example 8 the operations of example 1 were substantially the same, except that in step 1, the heating reaction was carried out for 2 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 9
Example 9 the operations of example 1 were substantially the same except that in step 1, the heating reaction was carried out for 3 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 10
Example 10 the same operations as in example 1 were carried out except that in step 2, the aqueous alkaline solution had a pH of 8; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 11
Example 11 the same operations as example 1 were carried out except that in step 2, the aqueous alkaline solution had a pH of 8.5; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 12
Example 12 the operations were substantially the same as example 1, except that in step 2, the stirring time was 2 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 13
Example 13 the operations were substantially the same as example 1, except that in step 2, the stirring time was 3 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 14
Example 14 the operations of example 1 were substantially the same, except that in step 2, the temperature of the heating reaction was 75 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 15
Example 15 the operations of example 1 were substantially the same except that in step 2, the temperature of the heating reaction was 85 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 16
Example 16 was substantially the same as example 1 except that in step 2, the heating reaction was carried out for 1.5 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 17
Example 17 was substantially the same as example 1 except that in step 2, the heating reaction was carried out for 3 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 18
Example 18 the same operations as example 1 except that in step 3, the ethanol concentration in the aqueous ethanol solution was 30% by volume; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 19
Example 19 the same operations as example 1, except that in step 3, the ethanol concentration in the aqueous ethanol solution was 45% by volume; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 20
Example 20 the operations were substantially the same as in example 1, except that in step 3, the stirring time was 2 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 21
Example 21 the operations were substantially the same as example 1, except that in step 3, the stirring time was 3 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 22
Example 22 the operations of example 1 were substantially the same, except that in step 3, the temperature of the heating reaction was 75 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 23
Example 23 the same operations as example 1 were carried out except that in step 3, the temperature of the heating reaction was 80 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 24
Example 24 substantially the same as example 1 except that in step 3, the heating reaction was carried out for 2 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 25
Example 25 the operations of example 1 were substantially the same except that in step 3, the heating reaction was carried out for 3 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 26
Example 26 the same operations as example 1, except that in step 4, the polyvinyl alcohol binder mass was 1 gram; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 27
Example 27 the same as example 1 except that in step 4, the polyvinyl alcohol binder mass was 10 grams; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 28
Example 28 the same procedure as in example 1 was followed except that in step 4, the volume of deionized water was 75 ml; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 29
Example 29 the same procedure as in example 1 was followed except that in step 4, the volume of deionized water was 100 ml; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 30
Example 30 the operations of example 1 were substantially the same, except that in step 4, the temperature of the heating reaction was 85 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 31
Example 31 the operations of example 1 were substantially the same except that in step 4, the temperature of the heating reaction was 90 ℃; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 32
Example 32 the operations of example 1 were substantially the same, except that in step 4, the stirring time was 1 hour; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 33
Example 33 the same operations as example 1 were carried out except that in step 4, the stirring time was 2 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 34
Example 34 the operations of example 1 were substantially the same, except that in step 4, the sonication time was 80 minutes; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 35
Example 35 the operations of example 1 were substantially the same, except that in step 4, the sonication time was 120 minutes; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 36
Example 36 the operations of example 1 were substantially the same, except that in step 4, the drying time was 9 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
Example 37
Example 37 was substantially the same as example 1 except that in step 4, the drying time was 12 hours; the decomposition temperature of the obtained boron nitride fiber coated diaphragm is close to 420 ℃, and the thermal conductivity reaches more than 10W/m.K; the tensile strength reaches 220MPa at 300 ℃.
The above is not relevant and is applicable to the prior art.
While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.
Claims (10)
1. The boron nitride fiber-coated diaphragm is characterized by comprising a polyolefin diaphragm and a boron nitride fiber film layer coated on the surface of the polyolefin diaphragm.
2. A method for preparing a boron nitride fiber-coated membrane according to claim 1, comprising the steps of: preparing high-activity boron nitride fibers by a chemical activation method; and then coating the boron nitride fiber on the surface of the polyolefin diaphragm by a compression molding method to prepare the obtained boron nitride fiber coated diaphragm.
3. The method for preparing a boron nitride fiber-coated membrane according to claim 2, wherein the boron nitride fiber is prepared by the following steps:
s1, placing a certain volume part of boron trifluoride diethyl etherate solution in a horizontal tube furnace, heating to a certain temperature at a certain heating rate by taking ammonia as reaction gas, and reacting for a period of time at the temperature to obtain a product A;
s2, cooling the product A obtained in the step S1, placing the product A into an alkaline aqueous solution with the pH value of 7.5-8.5, uniformly stirring, heating and reacting for a period of time to obtain a mixed solution, cooling and filtering the mixed solution, filtering and collecting solid powder in the mixed solution, and washing the solid powder with deionized water until the surface of the solid powder is neutral to obtain a product B;
s3, placing the product B obtained in the step S2 in an ethanol water solution, stirring and mixing uniformly, heating and reacting for a period of time to obtain a mixed solution, cooling the mixed solution, filtering and collecting solid matters in the mixed solution, and obtaining the high-activity boron nitride fiber.
4. The method according to claim 3, wherein in step S1, the temperature of the heating reaction is 300-700 ℃; the heating reaction time is 1-3 h; the heating rate is 1-5 ℃/min; the gas flow of the ammonia gas is 50-500 mL/min.
5. The method for preparing a boron nitride fiber-coated membrane according to claim 3, wherein the boron trifluoride ethyl ether solution is 1 to 10 parts by volume; the volume concentration of the boron trifluoride diethyl etherate solution is 20-45%; the volume part of the alkaline aqueous solution is 10-100 parts; the alkaline aqueous solution is an inorganic alkaline aqueous solution.
6. The method for preparing the boron nitride fiber-coated membrane according to claim 3, wherein in the step S2, the stirring time is 0.5-3 h; the heating reaction temperature is 65-85 ℃, and the heating reaction time is 0.2-3 h.
7. The method for preparing the boron nitride fiber-coated membrane according to claim 3, wherein in the step S3, the stirring time is 1-3 h; the heating reaction temperature is 70-80 ℃, and the heating reaction time is 1-3 h; the ethanol water solution is 25-45% of ethanol water solution by volume concentration.
8. The method for preparing the boron nitride fiber-coated membrane according to any one of claims 2 to 7, wherein the specific process of coating the boron nitride fiber on the surface of the polyolefin membrane by a compression molding method is as follows: adding a certain mass of binder into a certain volume of deionized water, and continuously stirring for 0.5-2 h at the temperature of 70-90 ℃ to obtain a binder suspension; then adding a certain mass of boron nitride fibers into the binder suspension, and carrying out ultrasonic treatment for 40-120 min to obtain boron nitride slurry; and uniformly coating the boron nitride slurry on the surface of the polyolefin diaphragm, drying at room temperature for 5-12 h, and flattening by using a pressing wheel to obtain the boron nitride fiber coated diaphragm.
9. The method according to claim 8, wherein the binder is polyvinyl alcohol, the concentration of the binder in the boron nitride slurry is 0.001-0.2 g/mL, and the concentration of the boron nitride in the boron nitride slurry is 0.001-0.02 g/mL.
10. Use of the boron nitride fiber-coated separator according to claim 9 for a lithium ion battery separator.
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| US20170162848A1 (en) * | 2014-06-30 | 2017-06-08 | Chengdu Zhongke Laifang Power Science & Technology Co., Ltd. | Water-based composition used for modifying diaphragm for lithium ion batteries and modified diaphragm and batteries |
| CN106848163A (en) * | 2017-03-13 | 2017-06-13 | 厦门大学 | A kind of ceramic coating membrane and its preparation method and application |
| CN107326722A (en) * | 2017-05-05 | 2017-11-07 | 华南理工大学 | A kind of preparation method of lithium battery diaphragm paper |
| CN109133942A (en) * | 2018-09-17 | 2019-01-04 | 河北工业大学 | A kind of preparation method of the active nitride boron fibre of high-specific surface area |
| CN110718659A (en) * | 2019-10-21 | 2020-01-21 | 重庆云天化纽米科技股份有限公司 | Boron nitride coated battery separator and method of making same |
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Patent Citations (5)
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|---|---|---|---|---|
| US20170162848A1 (en) * | 2014-06-30 | 2017-06-08 | Chengdu Zhongke Laifang Power Science & Technology Co., Ltd. | Water-based composition used for modifying diaphragm for lithium ion batteries and modified diaphragm and batteries |
| CN106848163A (en) * | 2017-03-13 | 2017-06-13 | 厦门大学 | A kind of ceramic coating membrane and its preparation method and application |
| CN107326722A (en) * | 2017-05-05 | 2017-11-07 | 华南理工大学 | A kind of preparation method of lithium battery diaphragm paper |
| CN109133942A (en) * | 2018-09-17 | 2019-01-04 | 河北工业大学 | A kind of preparation method of the active nitride boron fibre of high-specific surface area |
| CN110718659A (en) * | 2019-10-21 | 2020-01-21 | 重庆云天化纽米科技股份有限公司 | Boron nitride coated battery separator and method of making same |
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