A functional composite material for lithium ion battery separators and a production process thereof

Abstract

This invention relates to the field of lithium-ion batteries, specifically to a functional composite material for lithium-ion battery separators and its manufacturing process. It addresses the problem of poor high-temperature stability and electrochemical performance of existing polyolefin separators, which significantly negatively impact the performance of lithium-ion batteries. The manufacturing process utilizes a functional composite material to treat the surface of the polyolefin separator, forming a functional protective layer. This allows the polyolefin separator to maintain stable performance at high temperatures, effectively preventing short circuits caused by high temperatures in lithium-ion batteries, improving their reliability and safety. Furthermore, it significantly enhances the conductivity of the polyolefin separator, thereby improving the electrochemical performance of the lithium-ion battery and significantly improving its overall performance. This broadens the application prospects of lithium-ion batteries. Moreover, the manufacturing process is simple, easy to operate, and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more specifically to a functional composite material for lithium-ion battery separators and its manufacturing process. Background Technology

[0002] As an important component of modern energy storage systems, the market demand for lithium-ion batteries is increasing year by year. However, due to the frequent occurrence of accidents such as spontaneous combustion and explosion caused by the thermal runaway of lithium-ion batteries, which seriously damage people's property and personal safety, people are paying more and more attention to the safety of lithium-ion batteries.

[0003] As a crucial component of lithium-ion batteries, the separator not only isolates the positive and negative electrodes and prevents short circuits, but also allows lithium ions to freely pass through the electrolyte. Currently, the mainstream lithium-ion battery separator materials on the market are mainly polyolefin materials, represented by polyethylene (PE) and polypropylene (PP). However, polyolefin separators have poor thermal stability and are prone to thermal shrinkage at high temperatures. This shrinkage may cause the positive and negative electrode materials inside the lithium-ion battery to come into contact, thus triggering a short circuit. A short circuit will rapidly increase the heat and pressure inside the lithium-ion battery, causing the internal temperature to rise further and creating safety hazards. In addition, due to its low surface polarity, polyolefin separators have poor wettability to the electrolyte, hindering lithium ion transport and limiting the battery's electrochemical performance.

[0004] The current polyolefin separators suffer from poor high-temperature stability and electrochemical performance, which significantly negatively impacts the performance of lithium-ion batteries. Therefore, developing a functional composite material and its manufacturing process for lithium-ion battery separators is of great significance. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a functional composite material for lithium-ion battery separators and its production process, which solves the problem that the existing polyolefin separators have poor high-temperature stability and electrochemical performance, which have a significant adverse impact on the performance of lithium-ion batteries.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A functional composite material for lithium-ion battery separators comprises the following components in parts by weight:

[0008] 1.5-4.5 parts of high-temperature stabilizer, 11-17 parts of conductive enhancer, 10-15 parts of polyvinylidene fluoride, 2-3 parts of polyethylene glycol, 0.8-1.6 parts of sodium carboxymethyl cellulose, and 70-80 parts of anhydrous acetone;

[0009] The high-temperature stabilizer is prepared by the following steps:

[0010] Step a1: Hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide, and N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred for 10-20 min at a temperature of 25-30℃ and a stirring rate of 200-300 r / min. Then, the temperature was raised to 100-110℃ and the mixture was stirred for 3-5 h. After the reaction was completed, the reaction product was cooled to room temperature, and the solvent was removed by rotary evaporation. The product was then added to dichloromethane and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried for 3-4 h at a temperature of 80-85℃ to obtain the organophosphorus nitrogen sulfonic acid intermediate.

[0011] Step a2: Add the organophosphorus nitrogen sulfonic acid intermediate, lithium hydroxide, and deionized water to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir the reaction at 25-30℃ and 200-300 r / min for 10-20 min. Then raise the temperature to 50-55℃ and continue stirring for 10-15 h. After the reaction is complete, cool the reaction product to room temperature, then remove the solvent by rotary evaporation. Wash the product 2-3 times with dichloromethane and anhydrous ethanol in sequence, and then place it in a vacuum drying oven and dry it at 50-55℃ for 5-6 h to obtain the high-temperature stabilizer.

[0012] As a further embodiment of the present invention: the ratio of hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide and N,N-dimethylformamide used in step a1 is 10 mmol: 60 mmol: 0.5-1.5 g: 0.2-0.4 g: 80-100 mL.

[0013] As a further aspect of the present invention: the ratio of the organophosphorus nitrogen sulfonic acid intermediate, lithium hydroxide and deionized water in step a2 is 10 mmol: 100-120 mmol: 100-120 mL.

[0014] As a further aspect of the present invention: the conductivity enhancer is prepared by the following steps:

[0015] Step b1: Add carbon nanotubes, concentrated sulfuric acid, and concentrated nitric acid to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. Stir the reaction at 25-30℃ and 200-300 r / min for 10-20 min. Then, heat to reflux and continue stirring for 6-8 h. After the reaction is complete, cool the reaction product to room temperature, centrifuge, and wash the precipitate 2-3 times with deionized water and anhydrous acetone. Then, place it in a vacuum drying oven and dry at 90-100℃ for 3-4 h to obtain acidified carbon nanotubes.

[0016] Step b2: Add acidified carbon nanotubes, boric acid, and glycerol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 25-30℃ and 200-300 r / min for 10-20 min. Then, raise the temperature to 150-160℃ and continue stirring for 1-2 h. After the reaction is complete, cool the reaction product to room temperature and place it in a tube furnace. Purge with nitrogen and hold at 250-260℃ for 2-3 h. Then, raise the temperature to 550-560℃ and hold for 2-3 h. Finally, raise the temperature to 1500-1600℃ and hold for 2-3 h. Then, cool with the furnace to obtain the conductivity enhancer.

[0017] As a further aspect of the present invention: the ratio of carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid used in step b1 is 5g:90-100mL:30-40mL.

[0018] As a further aspect of the present invention: the carbon nanotubes in step b1 have a diameter of 45-65 nm and a length of 6-16 μm.

[0019] As a further aspect of the present invention: the concentrated sulfuric acid in step b1 has a mass fraction of 98%.

[0020] As a further aspect of the present invention: the concentrated nitric acid in step b1 has a mass fraction of 67%.

[0021] As a further aspect of the present invention: the ratio of the acidified carbon nanotubes, boric acid and glycerol used in step b2 is 2g:8-10g:70-80g.

[0022] As a further aspect of the present invention: a manufacturing process for a functional composite material for lithium-ion battery separators, comprising the following steps:

[0023] Step 1: Weigh out 1.5-4.5 parts by weight of high temperature stabilizer, 11-17 parts by weight of conductive enhancer, 10-15 parts by weight of polyvinylidene fluoride, 2-3 parts by weight of polyethylene glycol, 0.8-1.6 parts by weight of sodium carboxymethyl cellulose and 70-80 parts by weight of anhydrous acetone, and set aside.

[0024] Step 2: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 10-20 minutes at a temperature of 25-30℃ and a stirring rate of 200-300 r / min. Then, raise the temperature to 60-65℃ and continue stirring for 2-3 hours. After that, add high-temperature stabilizer, conductive reinforcing agent, polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 2-3 hours. Then, let it stand for 1-2 hours to obtain the functional composite material.

[0025] As a further aspect of the present invention: the polyethylene glycol is PEG-400.

[0026] The beneficial effects of this invention are:

[0027] This invention discloses a functional composite material for lithium-ion battery separators and its manufacturing process. The process involves adding polyvinylidene fluoride (PVDF) and anhydrous acetone to a mixer and stirring. Then, a high-temperature stabilizer, a conductivity enhancer, polyethylene glycol, and sodium carboxymethyl cellulose are added and the mixture is stirred further. After standing, the mixture is allowed to settle, yielding the functional composite material. This manufacturing process utilizes the functional composite material to treat the surface of the polyolefin separator, forming a functional protective layer. This allows the polyolefin separator to maintain stable performance at high temperatures, effectively preventing short circuits caused by high temperatures in the lithium-ion battery. This characteristic enables the lithium-ion battery to be used over a wider temperature range, improving its reliability and safety. It also significantly improves the conductivity of the polyolefin separator, thereby enhancing the electrochemical performance of the lithium-ion battery. This characteristic results in higher energy density and longer lifespan for the lithium-ion battery. The use of this functional composite material significantly improves the overall performance of the lithium-ion battery by enhancing the high-temperature stability and electrochemical performance of the polyolefin separator, making lithium-ion batteries more widely applicable in electric vehicles, energy storage systems, and other fields. Moreover, this manufacturing process is simple, easy to operate, and suitable for large-scale industrial production.

[0028] In the preparation of functional composite materials for lithium-ion battery separators, a high-temperature stabilizer was first prepared. This was achieved by reacting hexachlorocyclotriphosphazene with aniline-2,5-bissulfonic acid. The chlorine atom on the hexachlorocyclotriphosphazene reacts with the amino group on the aniline-2,5-bissulfonic acid, simultaneously introducing a large number of sulfonic acid groups to obtain an organophosphorus sulfonic acid intermediate. This intermediate then reacts with lithium hydroxide, where the sulfonic acid groups combine with lithium atoms to form lithium sulfonate groups, yielding the high-temperature stabilizer. The molecular structure of this stabilizer contains a large amount of phosphorus. At high temperatures, the organophosphorus decomposes into phosphoric acid or anhydride, promoting dehydration and endothermic dehydrogenation on the material surface to form a dense carbon layer. This layer blocks oxygen contact and heat transfer between the material and the external environment. It decomposes to release some free radicals, which then capture highly reactive free radicals in the flame zone, interrupting the combustion chain reaction. The molecular structure of this high-temperature stabilizer also contains a large amount of nitrogen. At high temperatures, organic nitrogen decomposes to form non-flammable gases, thereby diluting the concentration of flammable gases. The molecular structure of this high-temperature stabilizer also contains a large number of lithium sulfonate groups, which endow it with high-temperature stability. At the same time, sulfur can act as a catalyst to promote the formation of the carbon layer. During combustion, it can also generate sulfur dioxide, thereby diluting the concentration of flammable gases and inhibiting combustion. Furthermore, it introduces a large number of lithium ions to achieve a lithium-rich strategy, providing a large number of mobile free lithium ions to improve conductivity. Therefore, adding a high-temperature stabilizer can significantly improve the high-temperature flame retardant performance and electrochemical performance of lithium-ion battery separators.

[0029] In the process of preparing functional composite materials for lithium-ion battery separators, a conductive reinforcing agent was also prepared. Carbon nanotubes were treated with concentrated sulfuric acid and concentrated nitric acid to remove impurities and introduce a large number of hydroxyl and carboxyl groups, resulting in acidified carbon nanotubes. Then, using the acidified carbon nanotubes and boric acid as raw materials, boron atoms were introduced into the acidified carbon nanotubes to obtain the conductive reinforcing agent. Carbon nanotubes possess excellent mechanical properties and high electrical conductivity. Loading them onto lithium-ion battery separators can improve the structural stability of the separator and promote the uniform storage and transport of lithium ions, thereby reducing interfacial impedance and improving the electrochemical performance of lithium-ion batteries. Furthermore, after acidification, the abundant hydroxyl and carboxyl groups on their surface enhance the interaction between the separator and the electrolyte, improving the electrolyte wettability of the separator and facilitating lithium ion transport. Doping with boron atoms increases the number of active sites, further improving conductivity. Therefore, adding a conductive reinforcing agent can significantly improve the electrochemical performance of lithium-ion battery separators. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] This embodiment describes a production process for a functional composite material used in lithium-ion battery separators, including the following steps:

[0033] Step S1: 10 mmol hexachlorocyclotriphosphazene, 60 mmol aniline-2,5-disulfonic acid, 0.5 g tetrabutylammonium bromide, 0.2 g potassium iodide, and 80 mL N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred at 25 °C and 200 r / min for 10 min. The mixture was then heated to 100 °C and stirred for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and the solvent was removed by rotary evaporation. The product was then added to dichloromethane and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 80 °C for 3 h to obtain the organophosphorus nitrogen sulfonic acid intermediate.

[0034] Step S2: 10 mmol of organophosphorus sulfonic acid intermediate, 100 mmol of lithium hydroxide and 100 mL of deionized water were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 25 °C and 200 r / min for 10 min. Then the temperature was raised to 50 °C and the mixture was stirred for 10 h. After the reaction was completed, the reaction product was cooled to room temperature. The solvent was then removed by rotary evaporation. The product was then washed twice with dichloromethane and anhydrous ethanol. Finally, it was placed in a vacuum drying oven and dried at 50 °C for 5 h to obtain a high-temperature stabilizer.

[0035] Step S3: Add 5g of carbon nanotubes with a diameter of 45-65nm and a length of 6-16μm, 90mL of 98% concentrated sulfuric acid and 30mL of 67% concentrated nitric acid to a three-necked flask equipped with a stirrer, thermometer and reflux condenser. Stir the reaction at 25℃ and 200r / min for 10min. Then heat to reflux and continue stirring for 6h. After the reaction is completed, cool the reaction product to room temperature and centrifuge. Wash the precipitate twice with deionized water and anhydrous acetone, and then place it in a vacuum drying oven and dry at 90℃ for 3h to obtain acidified carbon nanotubes.

[0036] Step S4: Add 2g of acidified carbon nanotubes, 8g of boric acid and 70g of glycerol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 25°C and 200r / min for 10min. Then, raise the temperature to 150°C and continue stirring for 1h. After the reaction is complete, cool the reaction product to room temperature and place it in a tube furnace. Purge with nitrogen and keep at 250°C for 2h. Then, raise the temperature to 550°C and keep at 550°C for 2h. Then, raise the temperature to 1500°C and keep at 1500°C for 2h. Then, cool the product with the furnace to obtain the conductive enhancer.

[0037] Step S5: Weigh out 1.5 parts of high temperature stabilizer, 11 parts of conductive enhancer, 10 parts of polyvinylidene fluoride, 2 parts of PEG-400 polyethylene glycol, 0.8 parts of sodium carboxymethyl cellulose and 70 parts of anhydrous acetone according to the following weight proportions, and set aside for later use.

[0038] Step S6: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 10 minutes at a temperature of 25°C and a stirring rate of 200 r / min. Then, heat the mixture to 60°C and continue stirring for 2 hours. After that, add a high-temperature stabilizer, a conductive reinforcing agent, PEG-400 polyethylene glycol, and sodium carboxymethyl cellulose and continue stirring for 2 hours. Then, let it stand for 1 hour to obtain a functional composite material.

[0039] Example 2:

[0040] This embodiment describes a production process for a functional composite material used in lithium-ion battery separators, including the following steps:

[0041] Step S1: 10 mmol hexachlorocyclotriphosphazene, 60 mmol aniline-2,5-disulfonic acid, 1.0 g tetrabutylammonium bromide, 0.3 g potassium iodide, and 90 mL N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred at 28 °C and 250 r / min for 15 min. The mixture was then heated to 105 °C and stirred for another 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and the solvent was removed by rotary evaporation. The product was then added to dichloromethane and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 82 °C for 3.5 h to obtain the organophosphorus nitrogen sulfonic acid intermediate.

[0042] Step S2: 10 mmol of organophosphorus sulfonic acid intermediate, 110 mmol of lithium hydroxide and 110 mL of deionized water were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 28 °C and 250 r / min for 15 min. Then the temperature was raised to 52 °C and the mixture was stirred for 12 h. After the reaction was completed, the reaction product was cooled to room temperature. The solvent was then removed by rotary evaporation. The product was then washed twice with dichloromethane and anhydrous ethanol. Finally, it was placed in a vacuum drying oven and dried at 52 °C for 5.5 h to obtain a high-temperature stabilizer.

[0043] Step S3: Add 5g of carbon nanotubes with a diameter of 45-65nm and a length of 6-16μm, 95mL of 98% concentrated sulfuric acid and 35mL of 67% concentrated nitric acid to a three-necked flask equipped with a stirrer, thermometer and reflux condenser. Stir the reaction at 28℃ and 250r / min for 15min. Then heat to reflux and continue stirring for 7h. After the reaction is completed, cool the reaction product to room temperature and centrifuge. Wash the precipitate twice with deionized water and anhydrous acetone, and then place it in a vacuum drying oven and dry at 95℃ for 3.5h to obtain acidified carbon nanotubes.

[0044] Step S4: Add 2g of acidified carbon nanotubes, 9g of boric acid and 75g of glycerol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 28℃ and 250r / min for 15min. Then, raise the temperature to 155℃ and continue stirring for 1.5h. After the reaction is complete, cool the reaction product to room temperature and place it in a tube furnace. Purge with nitrogen and keep at 255℃ for 2.5h. Then, raise the temperature to 555℃ and keep at 555℃ for 2.5h. Then, raise the temperature to 1550℃ and keep at 1550℃ for 2.5h. Finally, cool the furnace to obtain the conductivity enhancer.

[0045] Step S5: Weigh out 3 parts of high-temperature stabilizer, 14 parts of conductive enhancer, 12.5 parts of polyvinylidene fluoride, 2.5 parts of PEG-400 polyethylene glycol, 1.2 parts of sodium carboxymethyl cellulose and 75 parts of anhydrous acetone according to the following weight proportions, and set aside for later use;

[0046] Step S6: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 15 minutes at a temperature of 28°C and a stirring rate of 250 r / min. Then, heat the mixture to 62°C and continue stirring for 2.5 hours. After that, add a high-temperature stabilizer, a conductive reinforcing agent, PEG-400 polyethylene glycol, and sodium carboxymethyl cellulose and continue stirring for 2.5 hours. Then, let the mixture stand for 1.5 hours to obtain a functional composite material.

[0047] Example 3:

[0048] This embodiment describes a production process for a functional composite material used in lithium-ion battery separators, including the following steps:

[0049] Step S1: 10 mmol hexachlorocyclotriphosphazene, 60 mmol aniline-2,5-disulfonic acid, 1.5 g tetrabutylammonium bromide, 0.4 g potassium iodide, and 100 mL N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred at 30 °C and 300 r / min for 20 min. The mixture was then heated to 110 °C and stirred for another 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and the solvent was removed by rotary evaporation. The product was then added to dichloromethane and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 85 °C for 4 h to obtain the organophosphorus nitrogen sulfonic acid intermediate.

[0050] Step S2: 10 mmol of organophosphorus sulfonic acid intermediate, 120 mmol of lithium hydroxide and 120 mL of deionized water were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 30 °C and 300 r / min for 20 min. Then the temperature was raised to 55 °C and the mixture was stirred for 15 h. After the reaction was completed, the reaction product was cooled to room temperature. The solvent was then removed by rotary evaporation. The product was then washed three times with dichloromethane and anhydrous ethanol. Finally, it was placed in a vacuum drying oven and dried at 55 °C for 6 h to obtain a high-temperature stabilizer.

[0051] Step S3: Add 5g of carbon nanotubes with a diameter of 45-65nm and a length of 6-16μm, 100mL of 98% concentrated sulfuric acid and 40mL of 67% concentrated nitric acid to a three-necked flask equipped with a stirrer, thermometer and reflux condenser. Stir the reaction at 30℃ and 300r / min for 20min. Then heat to reflux and continue stirring for 8h. After the reaction is completed, cool the reaction product to room temperature and centrifuge. Wash the precipitate three times with deionized water and anhydrous acetone. Then place it in a vacuum drying oven and dry at 100℃ for 4h to obtain acidified carbon nanotubes.

[0052] Step S4: Add 2g of acidified carbon nanotubes, 10g of boric acid and 80g of glycerol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 30℃ and 300r / min for 20min. Then, raise the temperature to 160℃ and continue stirring for 2h. After the reaction is completed, cool the reaction product to room temperature and place it in a tube furnace. Purge with nitrogen and keep at 260℃ for 3h. Then, raise the temperature to 560℃ and keep at 560℃ for 3h. Then, raise the temperature to 1600℃ and keep at 1600℃ for 3h. Then, cool with the furnace to obtain the conductive enhancer.

[0053] Step S5: Weigh out 4.5 parts of high-temperature stabilizer, 17 parts of conductive enhancer, 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethyl cellulose and 80 parts of anhydrous acetone according to the following weight proportions, and set aside for later use.

[0054] Step S6: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 20 minutes at 30°C and 300 r / min. Then, heat to 65°C and continue stirring for 3 hours. After that, add high-temperature stabilizer, conductive reinforcing agent, PEG-400 polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 3 hours. Then, let stand for 2 hours to obtain the functional composite material.

[0055] Comparative Example 1:

[0056] This comparative example illustrates a manufacturing process for a functional composite material used in lithium-ion battery separators, comprising the following steps:

[0057] Step S1: Weigh out 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethyl cellulose and 80 parts of anhydrous acetone according to the weight ratio, and set aside.

[0058] Step S2: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 20 minutes at a temperature of 30°C and a stirring rate of 300 r / min. Then, heat the mixture to 65°C and continue stirring for 3 hours. After that, add PEG-400 polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 3 hours. Then, let it stand for 2 hours to obtain the functional composite material.

[0059] Comparative Example 2:

[0060] This comparative example illustrates a manufacturing process for a functional composite material used in lithium-ion battery separators, comprising the following steps:

[0061] Step S1: 10 mmol hexachlorocyclotriphosphazene, 60 mmol aniline-2,5-disulfonic acid, 1.5 g tetrabutylammonium bromide, 0.4 g potassium iodide, and 100 mL N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Nitrogen gas was introduced for protection, and the mixture was stirred at 30 °C and 300 r / min for 20 min. The mixture was then heated to 110 °C and stirred for another 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and the solvent was removed by rotary evaporation. The product was then added to dichloromethane and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 85 °C for 4 h to obtain the organophosphorus nitrogen sulfonic acid intermediate.

[0062] Step S2: 10 mmol of organophosphorus sulfonic acid intermediate, 120 mmol of lithium hydroxide and 120 mL of deionized water were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 30 °C and 300 r / min for 20 min. Then the temperature was raised to 55 °C and the mixture was stirred for 15 h. After the reaction was completed, the reaction product was cooled to room temperature. The solvent was then removed by rotary evaporation. The product was then washed three times with dichloromethane and anhydrous ethanol. Finally, it was placed in a vacuum drying oven and dried at 55 °C for 6 h to obtain a high-temperature stabilizer.

[0063] Step S3: Weigh out 4.5 parts of high temperature stabilizer, 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethyl cellulose and 80 parts of anhydrous acetone according to the following weight proportions, and set aside for later use;

[0064] Step S4: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 20 minutes at 30°C and 300 r / min. Then, heat to 65°C and continue stirring for 3 hours. After that, add high-temperature stabilizer, PEG-400 polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 3 hours. Then, let stand for 2 hours to obtain the functional composite material.

[0065] Comparative Example 3:

[0066] This comparative example illustrates a manufacturing process for a functional composite material used in lithium-ion battery separators, comprising the following steps:

[0067] Step S1: Add 5g of carbon nanotubes with a diameter of 45-65nm and a length of 6-16μm, 100mL of 98% concentrated sulfuric acid and 40mL of 67% concentrated nitric acid to a three-necked flask equipped with a stirrer, thermometer and reflux condenser. Stir the reaction at 30℃ and 300r / min for 20min. Then heat to reflux and continue stirring for 8h. After the reaction is completed, cool the reaction product to room temperature and centrifuge. Wash the precipitate three times with deionized water and anhydrous acetone. Then place it in a vacuum drying oven and dry at 100℃ for 4h to obtain acidified carbon nanotubes.

[0068] Step S2: Add 2g of acidified carbon nanotubes, 10g of boric acid and 80g of glycerol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 30℃ and 300r / min for 20min. Then, raise the temperature to 160℃ and continue stirring for 2h. After the reaction is completed, cool the reaction product to room temperature and place it in a tube furnace. Purge with nitrogen and keep at 260℃ for 3h. Then, raise the temperature to 560℃ and keep at 560℃ for 3h. Then, raise the temperature to 1600℃ and keep at 1600℃ for 3h. Then, cool with the furnace to obtain the conductivity enhancer.

[0069] Step S3: Weigh out 17 parts by weight of conductive reinforcing agent, 15 parts by weight of polyvinylidene fluoride, 3 parts by weight of PEG-400 polyethylene glycol, 1.6 parts by weight of sodium carboxymethyl cellulose and 80 parts by weight of anhydrous acetone, and set aside.

[0070] Step S4: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 20 minutes at 30°C and 300 r / min. Then, heat to 65°C and continue stirring for 3 hours. Then, add conductive reinforcing agent, PEG-400 polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 3 hours. Then, let stand for 2 hours to obtain the functional composite material.

[0071] Comparative Example 4:

[0072] This comparative example illustrates a manufacturing process for a functional composite material used in lithium-ion battery separators, comprising the following steps:

[0073] Step S1: Weigh out 4.5 parts by weight of hexachlorocyclotriphosphazene, 17 parts of carbon nanotubes with a diameter of 45-65 nm and a length of 6-16 μm, 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethyl cellulose and 80 parts of anhydrous acetone, and set aside.

[0074] Step S2: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 20 minutes at 30°C and 300 r / min. Then, heat to 65°C and continue stirring for 3 hours. After that, add hexachlorocyclotriphosphazene, carbon nanotubes, PEG-400 polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 3 hours. Then, let stand for 2 hours to obtain the functional composite material.

[0075] The functional composite materials of Examples 1-3 and Comparative Examples 1-4 were uniformly coated onto the PP separator (Ce lgard 2500) using a 15 μm coating applicator. The coated materials were then placed in a vacuum drying oven and dried at 50 °C for 12 h to obtain the lithium-ion battery separators of the experimental examples. The lithium-ion battery separators of the blank examples were untreated PP separators (Ce lgard 2500).

[0076] The performance of the lithium-ion battery separators from the experimental and blank examples was tested, and the test results are shown in the table below:

[0077]

[0078] Referring to the data in the table above, and based on the comparison between the experimental examples and blank examples of Examples 1-3 and Comparative Examples 1-4, it can be seen that the lithium-ion battery separator prepared by treating the PP separator with the functional composite material of this application has excellent heat resistance and flame retardant properties, greatly improves the high-temperature stability of lithium-ion batteries, and significantly improves the electrochemical performance of lithium-ion battery separators.

[0079] The heat resistance test method is as follows: the lithium-ion battery separator is cut into a size of 4cm×5cm, and then placed in a vacuum drying oven. The area change is measured after drying at 120℃ and 150℃ for 1 hour, and the heat shrinkage rate at 120℃ and 150℃ is obtained respectively.

[0080] The flame retardant performance test method is as follows: cut the lithium-ion battery separator into a size of 6cm×5cm, and then test the limiting oxygen index.

[0081] The electrochemical performance testing method is as follows: the lithium-ion battery separator is assembled into a "steel sheet / separator / steel sheet" system battery between two stainless steel discs with a diameter of 16 mm, and the ionic conductivity is tested at a temperature of 25℃.

[0082] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A functional composite material for lithium-ion battery separators, characterized in that, Includes the following components by weight: 1.5-4.5 parts of high-temperature stabilizer, 11-17 parts of conductive enhancer, 10-15 parts of polyvinylidene fluoride, 2-3 parts of polyethylene glycol, 0.8-1.6 parts of sodium carboxymethyl cellulose, and 70-80 parts of anhydrous acetone; The high-temperature stabilizer is prepared by the following steps: Step a1: Hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide and N,N-dimethylformamide were stirred and reacted. After the reaction was completed, the reaction product was cooled, then evaporated by rotary evaporation, and then added to dichloromethane. After vacuum filtration, the filter cake was dried to obtain the organophosphorus nitrogen sulfonic acid intermediate. Step a2: The organophosphorus nitrogen sulfonic acid intermediate, lithium hydroxide and deionized water are stirred and reacted. After the reaction is completed, the reaction product is cooled, then rotary evaporated, washed and dried to obtain a high temperature stabilizer.

2. The functional composite material for lithium-ion battery separators according to claim 1, characterized in that, The ratio of hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide, and N,N-dimethylformamide used in step a1 is 10 mmol: 60 mmol: 0.5-1.5 g: 0.2-0.4 g: 80-100 mL.

3. The functional composite material for lithium-ion battery separators according to claim 1, characterized in that, The ratio of the organophosphorus nitrogen sulfonic acid intermediate, lithium hydroxide, and deionized water in step a2 is 10 mmol: 100-120 mmol: 100-120 mL.

4. The functional composite material for lithium-ion battery separators according to claim 1, characterized in that, The conductivity enhancer is prepared by the following steps: Step b1: Carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid are stirred and reacted. After the reaction is completed, the reaction product is cooled, then centrifuged, and the precipitate is washed and dried to obtain acidified carbon nanotubes. Step b2: Acidified carbon nanotubes, boric acid and glycerol are stirred and reacted. After the reaction is completed, the reaction product is cooled and then placed in a tube furnace for heat preservation. After cooling with the furnace, a conductive enhancer is obtained.

5. A functional composite material for lithium-ion battery separators according to claim 4, characterized in that, The ratio of carbon nanotubes, concentrated sulfuric acid, and concentrated nitric acid used in step b1 is 5g:90-100mL:30-40mL.

6. The functional composite material for lithium-ion battery separators according to claim 4, characterized in that, The carbon nanotubes in step b1 have a diameter of 45-65 nm and a length of 6-16 μm; the concentrated sulfuric acid has a mass fraction of 98%; and the concentrated nitric acid has a mass fraction of 67%.

7. The functional composite material for lithium-ion battery separators according to claim 4, characterized in that, The ratio of acidified carbon nanotubes, boric acid, and glycerol used in step b2 is 2g:8-10g:70-80g.

8. A manufacturing process for a functional composite material used in lithium-ion battery separators, characterized in that, The method for preparing the functional composite material for lithium-ion battery separators as described in any one of claims 1-7 comprises the following steps: Step 1: Weigh out 1.5-4.5 parts by weight of high temperature stabilizer, 11-17 parts by weight of conductive enhancer, 10-15 parts by weight of polyvinylidene fluoride, 2-3 parts by weight of polyethylene glycol, 0.8-1.6 parts by weight of sodium carboxymethyl cellulose and 70-80 parts by weight of anhydrous acetone, and set aside. Step 2: Add polyvinylidene fluoride and anhydrous acetone to a mixer and stir for 10-20 minutes at a temperature of 25-30℃ and a stirring rate of 200-300 r / min. Then, raise the temperature to 60-65℃ and continue stirring for 2-3 hours. After that, add high-temperature stabilizer, conductive reinforcing agent, polyethylene glycol and sodium carboxymethyl cellulose and continue stirring for 2-3 hours. Then, let it stand for 1-2 hours to obtain the functional composite material.

9. The production process of a functional composite material for lithium-ion battery separators according to claim 8, characterized in that, The polyethylene glycol is PEG-400.

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