Functional composite material for lithium ion battery diaphragm and production process of functional composite material

Abstract

The invention relates to the field of lithium ion batteries, in particular to a functional composite material for a lithium ion battery diaphragm and a production process of the functional composite material, which are used for solving the problems that an existing polyolefin diaphragm is poor in high-temperature stability and electrochemical performance and has relatively great adverse effects on the performance of a lithium ion battery. According to the production process, the functional composite material is used for treating the polyolefin diaphragm, so that a functional protection layer can be formed on the surface of the polyolefin diaphragm, the polyolefin diaphragm can keep stable performance in a high-temperature environment, short circuit of the lithium ion battery caused by high temperature is effectively prevented, and the reliability and the safety of the lithium ion battery are improved; meanwhile, the conductivity of the polyolefin diaphragm can be remarkably improved, the electrochemical performance of the lithium ion battery is further improved, the overall performance of the lithium ion battery is remarkably improved, the lithium ion battery has a wider application prospect, and the production process is simple, easy to operate and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and particularly to a functional composite material for a lithium-ion battery separator and its production process. Background Art

[0002] As an important part of modern energy storage systems, the market demand for lithium-ion batteries is increasing year by year. However, due to the easy occurrence of thermal runaway in lithium-ion batteries, accidents such as spontaneous combustion and explosion occur frequently, seriously damaging people's property and personal safety, making people pay more and more attention to the safety issues of lithium-ion batteries.

[0003] As an important part of lithium-ion batteries, the separator not only plays the role of isolating the positive and negative electrodes and preventing short circuits, but also undertakes the task of allowing lithium ions in the electrolyte to pass freely. 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. The short circuit will quickly increase the heat and pressure inside the lithium-ion battery, resulting in a further increase in the internal temperature of the lithium-ion battery, and thus posing a safety hazard. In addition, due to the low surface polarity of polyolefin separators, the wettability of the electrolyte is poor, which hinders the transmission of lithium ions and limits the electrochemical performance of the battery.

[0004] How to improve the poor high-temperature stability and electrochemical performance of current polyolefin separators has a greater adverse impact on the performance of lithium-ion batteries. Therefore, it is of great significance to develop a functional composite material for a lithium-ion battery separator and its production process. Summary of the Invention

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

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A functional composite material for a lithium-ion battery separator 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] Among them, the high-temperature stabilizer is prepared by the following steps:

[0010] Step a1: Add hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide, and N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 10 - 20 min under the conditions of a temperature of 25 - 30°C and a stirring rate of 200 - 300 r / min. Then, raise the temperature to 100 - 110°C and continue stirring and reacting for 3 - 5 h. After the reaction ends, cool the reaction product to room temperature. Then, remove the solvent by rotary evaporation. Then, add it to dichloromethane. Then, perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 3 - 4 h under the conditions of a temperature of 80 - 85°C to obtain an organophosphorus-nitrogen sulfonic acid intermediate;

[0011] Step a2: Add the organophosphorus-nitrogen sulfonic acid intermediate, lithium hydroxide, and deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 10 - 20 min under the conditions of a temperature of 25 - 30°C and a stirring rate of 200 - 300 r / min. Then, raise the temperature to 50 - 55°C and continue stirring and reacting for 10 - 15 h. After the reaction ends, cool the reaction product to room temperature. Then, remove the solvent by rotary evaporation. Then, wash it with dichloromethane and absolute ethanol 2 - 3 times in sequence. Then, place it in a vacuum drying oven and dry it for 5 - 6 h under the conditions of a temperature of 50 - 55°C to obtain a high-temperature stabilizer.

[0012] As a further scheme of the present invention: The dosage ratio of the hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide, and N,N-dimethylformamide 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 scheme of the present invention: The dosage 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 scheme of the present invention: The conductive enhancer is prepared by the following steps:

[0015] Step b1: Add carbon nanotubes, concentrated sulfuric acid, and concentrated nitric acid into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and react for 10 - 20 min under the conditions of a temperature of 25 - 30 °C and a stirring rate of 200 - 300 r / min. Then, raise the temperature to the reflux condition and continue to stir and react for 6 - 8 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with deionized water and anhydrous acetone 2 - 3 times successively, and then place it in a vacuum drying oven and dry it at a temperature of 90 - 100 °C for 3 - 4 h to obtain acidified carbon nanotubes;

[0016] Step b2: Add acidified carbon nanotubes, boric acid, and glycerol into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 10 - 20 min under the conditions of a temperature of 25 - 30 °C and a stirring rate of 200 - 300 r / min. Then, raise the temperature to 150 - 160 °C and continue to stir and react for 1 - 2 h. After the reaction is completed, cool the reaction product to room temperature, then place it in a tube furnace, introduce nitrogen for protection, and keep it at a temperature of 250 - 260 °C for 2 - 3 h. Then, raise the temperature to 550 - 560 °C and continue to keep it for 2 - 3 h. Then, raise the temperature to 1500 - 1600 °C and continue to keep it for 2 - 3 h. Then, cool it with the furnace to obtain a conductive enhancer.

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

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

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

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

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

[0022] As a further scheme of the present invention: A production process of a functional composite material for a lithium-ion battery separator includes the following steps:

[0023] Step 1: Weigh 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 according to parts by weight for standby.

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

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

[0026] The beneficial effects of the present invention:

[0027] A functional composite material for a lithium - ion battery separator and its production process of the present invention, by adding polyvinylidene fluoride and anhydrous acetone into a mixer for stirring and mixing, then adding the high - temperature stabilizer, conductive enhancer, polyethylene glycol and sodium carboxymethyl cellulose and continuing to stir and mix, and then letting it stand, to obtain the functional composite material; this production process uses the functional composite material to process the separator, which can form a functional protective layer on the surface of the polyolefin separator, enabling the polyolefin separator to maintain stable performance in a high - temperature environment, effectively preventing the short - circuit of the lithium - ion battery caused by high temperature. This characteristic enables the lithium - ion battery to be used in a wider temperature range, improving the reliability and safety of the lithium - ion battery. It can also significantly improve the conductive performance of the polyolefin separator, thereby improving the electrochemical performance of the lithium - ion battery. This characteristic enables the lithium - ion battery to have a higher energy density and a longer service life; 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, which makes the lithium - ion battery have a wider application prospect in fields such as electric vehicles and energy storage systems; moreover, this production process is simple, easy to operate and suitable for large - scale industrial production.

[0028] In the process of preparing a functional composite material for a lithium-ion battery separator, a high-temperature stabilizer was first prepared. First, hexachlorocyclotriphosphazene and aniline-2,5-disulfonic acid were reacted. The chlorine atoms on hexachlorocyclotriphosphazene reacted with the amino groups on aniline-2,5-disulfonic acid, and a large number of sulfonic acid groups were introduced simultaneously to obtain an organophosphorus-nitrogen sulfonic acid intermediate. Then, the organophosphorus-nitrogen sulfonic acid intermediate and lithium hydroxide were reacted. The sulfonic acid groups on the organophosphorus-nitrogen sulfonic acid intermediate combined with lithium atoms to form lithium sulfonate groups, and the high-temperature stabilizer was obtained. The molecular structure of this high-temperature stabilizer contains a large amount of phosphorus elements. At high temperatures, organophosphorus decomposes into phosphoric acid or acid anhydride, promoting dehydration and endothermic dehydrogenation on the material surface to form a dense carbon layer, blocking the contact between the material and external oxygen and heat transfer, and some free radicals will be decomposed when heated, and then capture the highly active free radicals in the flame zone to interrupt the combustion chain reaction. The molecular structure of this high-temperature stabilizer also contains a large amount of nitrogen elements. At high temperatures, organonitrogen will decompose to form non-combustible gases, thereby diluting the concentration of combustible gases. The molecular structure of this high-temperature stabilizer also contains a large amount of lithium sulfonate groups, endowing it with high-temperature stability. At the same time, sulfur elements can act as catalysts to promote the formation of the carbon layer and can also generate sulfur dioxide during combustion to dilute the concentration of combustible gases, thereby suppressing combustion, and a large number of lithium ions are introduced to implement the strategy of lithium enrichment to provide a large number of mobile free lithium ions to improve the conductivity. Therefore, adding the high-temperature stabilizer can significantly improve the high-temperature flame retardant performance and electrochemical performance of the lithium-ion battery separator.

[0029] In the process of preparing a functional composite material for a lithium-ion battery separator, a conductive enhancer was also prepared. Concentrated sulfuric acid and concentrated nitric acid were used to treat carbon nanotubes. While removing the impurities on the carbon nanotubes, a large number of hydroxyl groups and carboxyl groups were introduced to obtain acidified carbon nanotubes. Then, acidified carbon nanotubes and boric acid were used as raw materials to introduce boron atoms into the acidified carbon nanotubes to obtain the conductive enhancer. Carbon nanotubes have excellent mechanical properties and high electrical conductivity. After being loaded on the lithium-ion battery separator, they can improve the structural stability of the lithium-ion battery separator, and at the same time can promote the uniform storage and transmission of lithium ions, thereby reducing the interfacial impedance and improving the electrochemical performance of the lithium-ion battery. And after acidification, the rich hydroxyl groups and carboxyl groups on its surface enhance the interaction between the separator and the electrolyte, can improve the electrolyte wettability of the separator, thereby facilitating the transmission of lithium ions. After doping boron atoms into it, the active sites can be increased, further improving its electrical conductivity. Therefore, adding the conductive enhancer can significantly improve the electrochemical performance of the lithium-ion battery separator. Specific embodiments

[0030] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] This embodiment is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0033] Step S1: Add 10 mmol of hexachlorocyclotriphosphazene, 60 mmol of aniline-2,5-disulfonic acid, 0.5 g of tetrabutylammonium bromide, 0.2 g of potassium iodide, and 80 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection, and stir and react for 10 min under the conditions of a temperature of 25°C and a stirring rate of 200 r / min. Then, continue to stir and react for 3 h under the condition of raising the temperature to 100°C. After the reaction is completed, cool the reaction product to room temperature, then remove the solvent by rotary evaporation, then add it to dichloromethane, and then perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 3 h under the condition of a temperature of 80°C to obtain an organophosphorus-nitrogen-sulfonic acid intermediate;

[0034] Step S2: Add 10 mmol of the organophosphorus-nitrogen-sulfonic acid intermediate, 100 mmol of lithium hydroxide, and 100 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection, and stir and react for 10 min under the conditions of a temperature of 25°C and a stirring rate of 200 r / min. Then, continue to stir and react for 10 h under the condition of raising the temperature to 50°C. After the reaction is completed, cool the reaction product to room temperature, then remove the solvent by rotary evaporation, then wash it twice with dichloromethane and absolute ethanol in sequence, and then place it in a vacuum drying oven and dry it for 5 h under the condition of a temperature of 50°C to obtain a high-temperature stabilizer;

[0035] Step S3: Add 5 g of carbon nanotubes with a diameter of 45 - 65 nm and a length of 6 - 16 μm, 90 mL of concentrated sulfuric acid with a mass fraction of 98%, and 30 mL of concentrated nitric acid with a mass fraction of 67% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and react for 10 min under the conditions of a temperature of 25°C and a stirring rate of 200 r / min. Then, continue to stir and react for 6 h under the condition of raising the temperature to reflux. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate twice with deionized water and absolute acetone in sequence, and then place it in a vacuum drying oven and dry it for 3 h under the condition of a temperature of 90°C to obtain acidified carbon nanotubes;

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

[0037] Step S5: Weigh 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 part of sodium carboxymethylcellulose, and 70 parts of anhydrous acetone by weight, and set aside;

[0038] Step S6: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 10 min under the conditions of a temperature of 25°C and a stirring rate of 200 r / min. Then, continue to stir and mix for 2 h under the condition of raising the temperature to 60°C. Then, add the high-temperature stabilizer, conductive enhancer, PEG-400 polyethylene glycol, and sodium carboxymethylcellulose and continue to stir and mix for 2 h. Then, let it stand for 1 h to obtain a functional composite material.

[0039] Example 2:

[0040] This example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0041] Step S1: Add 10 mmol of hexachlorocyclotriphosphazene, 60 mmol of aniline-2,5-disulfonic acid, 1.0 g of tetrabutylammonium bromide, 0.3 g of potassium iodide, and 90 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube. Introduce nitrogen for protection, stir and react for 15 min under the conditions of a temperature of 28°C and a stirring rate of 250 r / min. Then, continue to stir and react for 4 h under the condition of raising the temperature to 105°C. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then add it into dichloromethane, then perform vacuum filtration, and place the filter cake in a vacuum drying oven and dry it for 3.5 h under the condition of a temperature of 82°C to obtain an organophosphorus-nitrogen-sulfonic acid intermediate;

[0042] Step S2: Add 10 mmol of the organophosphorus-nitrogen sulfonic acid intermediate, 110 mmol of lithium hydroxide, and 110 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube. Introduce nitrogen for protection. Stir and react for 15 min under the conditions of a temperature of 28 °C and a stirring rate of 250 r / min. Then, continue to stir and react for 12 h under the condition of raising the temperature to 52 °C. After the reaction is completed, cool the reaction product to room temperature. Then, remove the solvent by rotary evaporation. Then, wash it twice with dichloromethane and absolute ethanol successively. Then, place it in a vacuum drying oven and dry it for 5.5 h under the condition of a temperature of 52 °C to obtain a high-temperature stabilizer;

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

[0044] Step S4: Add 2 g of acidified carbon nanotubes, 9 g of boric acid, and 75 g of glycerol into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 15 min under the conditions of a temperature of 28 °C and a stirring rate of 250 r / min. Then, continue to stir and react for 1.5 h under the condition of raising the temperature to 155 °C. After the reaction is completed, cool the reaction product to room temperature. Then, place it in a tube furnace, introduce nitrogen for protection, and keep it warm for 2.5 h under the condition of a temperature of 255 °C. Then, raise the temperature to 555 °C and continue to keep it warm for 2.5 h. Then, raise the temperature to 1550 °C and continue to keep it warm for 2.5 h. Then, cool it with the furnace to obtain a conductive enhancer;

[0045] Step S5: Weigh 3 parts of the high-temperature stabilizer, 14 parts of the 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 by weight for standby;

[0046] Step S6: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 15 min under the conditions of a temperature of 28 °C and a stirring rate of 250 r / min, then continue to stir and mix for 2.5 h under the condition of heating up to 62 °C, then add a high-temperature stabilizer, a conductive enhancer, PEG-400 polyethylene glycol, and sodium carboxymethylcellulose and continue to stir and mix for 2.5 h, and then let it stand for 1.5 h to obtain a functional composite material.

[0047] Example 3:

[0048] This example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0049] Step S1: Add 10 mmol of hexachlorocyclotriphosphazene, 60 mmol of aniline-2,5-disulfonic acid, 1.5 g of tetrabutylammonium bromide, 0.4 g of potassium iodide, and 100 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe, introduce nitrogen protection, stir and react for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min, then continue to stir and react for 5 h under the condition of heating up to 110 °C. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then add it to dichloromethane, and then perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 4 h under the condition of a temperature of 85 °C to obtain an organophosphorus-nitrogen-sulfonic acid intermediate;

[0050] Step S2: Add 10 mmol of the organophosphorus-nitrogen-sulfonic acid intermediate, 120 mmol of lithium hydroxide, and 120 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe, introduce nitrogen protection, stir and react for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min, then continue to stir and react for 15 h under the condition of heating up to 55 °C. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then wash it 3 times with dichloromethane and anhydrous ethanol in sequence, and then place it in a vacuum drying oven and dry it for 6 h under the condition of a temperature of 55 °C to obtain a high-temperature stabilizer;

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

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

[0053] Step S5: Weigh 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 by weight, and set aside;

[0054] Step S6: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 20 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min. Then, raise the temperature to 65°C and continue stirring and mixing for 3 h. Then, add the high-temperature stabilizer, conductive enhancer, PEG - 400 polyethylene glycol, and sodium carboxymethyl cellulose and continue stirring and mixing for 3 h. Then, let it stand for 2 h to obtain a functional composite material.

[0055] Comparative Example 1:

[0056] This comparative example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0057] Step S1: Weigh 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 by weight, and set aside;

[0058] Step S2: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min, then continue to stir and mix for 3 h under the condition of heating to 65 °C, then add PEG-400 polyethylene glycol and sodium carboxymethylcellulose and continue to stir and mix for 3 h, and then let it stand for 2 h to obtain a functional composite material.

[0059] Comparative Example 2:

[0060] This comparative example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0061] Step S1: Add 10 mmol of hexachlorocyclotriphosphazene, 60 mmol of aniline-2,5-disulfonic acid, 1.5 g of tetrabutylammonium bromide, 0.4 g of potassium iodide, and 100 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube, introduce nitrogen protection, stir and react for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min, then continue to stir and react for 5 h under the condition of heating to 110 °C. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then add it to dichloromethane, then vacuum filter, place the filter cake in a vacuum drying oven, and dry it for 4 h under the condition of a temperature of 85 °C to obtain an organophosphorus-nitrogen sulfonic acid intermediate;

[0062] Step S2: Add 10 mmol of the organophosphorus-nitrogen sulfonic acid intermediate, 120 mmol of lithium hydroxide, and 120 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube, introduce nitrogen protection, stir and react for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min, then continue to stir and react for 15 h under the condition of heating to 55 °C. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then wash it 3 times with dichloromethane and anhydrous ethanol in sequence, and then place it in a vacuum drying oven and dry it for 6 h under the condition of a temperature of 55 °C to obtain a high-temperature stabilizer;

[0063] Step S3: Weigh 4.5 parts of the high-temperature stabilizer, 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethylcellulose, and 80 parts of anhydrous acetone by weight for standby;

[0064] Step S4: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 20 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min, then continue to stir and mix for 3 h under the condition of heating to 65°C, then add a high-temperature stabilizer, PEG-400 polyethylene glycol, and sodium carboxymethylcellulose and continue to stir and mix for 3 h, and then let it stand for 2 h to obtain a functional composite material.

[0065] Comparative Example 3:

[0066] This comparative example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0067] Step S1: Add 5 g of carbon nanotubes with a diameter of 45 - 65 nm and a length of 6 - 16 μm, 100 mL of concentrated sulfuric acid with a mass fraction of 98%, and 40 mL of concentrated nitric acid with a mass fraction of 67% into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and react for 20 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min, then continue to stir and react for 8 h under the condition of heating to reflux. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with deionized water and anhydrous acetone three times respectively, and then place it in a vacuum drying oven and dry for 4 h under the condition of a temperature of 100°C to obtain acidified carbon nanotubes;

[0068] Step S2: Add 2 g of acidified carbon nanotubes, 10 g of boric acid, and 80 g of glycerol into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 20 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min, then continue to stir and react for 2 h under the condition of heating to 160°C. After the reaction is completed, cool the reaction product to room temperature, then place it in a tubular furnace, introduce nitrogen for protection, and keep it warm for 3 h under the condition of a temperature of 260°C, then heat it to 560°C and continue to keep it warm for 3 h, then heat it to 1600°C and continue to keep it warm for 3 h, and then cool it with the furnace to obtain a conductive enhancer;

[0069] Step S3: Weigh 17 parts of conductive enhancer, 15 parts of polyvinylidene fluoride, 3 parts of PEG-400 polyethylene glycol, 1.6 parts of sodium carboxymethylcellulose, and 80 parts of anhydrous acetone according to weight, and set aside;

[0070] Step S4: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 20 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min, then continue to stir and mix for 3 h under the condition of heating to 65°C, then add the conductive enhancer, PEG-400 polyethylene glycol, and sodium carboxymethylcellulose and continue to stir and mix for 3 h, and then let it stand for 2 h to obtain a functional composite material.

[0071] Comparative Example 4:

[0072] This comparative example is a production process of a functional composite material for a lithium-ion battery separator, including the following steps:

[0073] Step S1: Weigh 4.5 parts 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 carboxymethylcellulose, and 80 parts of anhydrous acetone, and set aside;

[0074] Step S2: Add polyvinylidene fluoride and anhydrous acetone to a mixer, stir and mix at a temperature of 30°C and a stirring rate of 300 r / min for 20 min, then continue to stir and mix at a temperature of 65°C for 3 h, then add hexachlorocyclotriphosphazene, carbon nanotubes, PEG - 400 polyethylene glycol, and sodium carboxymethylcellulose and continue to stir and mix for 3 h, and then let it stand for 2 h to obtain a functional composite material.

[0075] Use a 15 - μm film applicator to evenly coat the functional composite materials of Examples 1 - 3 and Comparative Examples 1 - 4 on a PP separator (Celgard 2500), and then place it in a vacuum drying oven and dry it at a temperature of 50°C for 12 h to obtain the lithium-ion battery separators of the experimental examples; among them, the lithium-ion battery separator of the blank example is an untreated PP separator (Celgard 2500).

[0076] Perform performance tests on the lithium-ion battery separators of the experimental examples and the blank example, and the test results are shown in the following table:

[0077]

[0078] Referring to the data in the above table, based on the comparison between the experimental examples and the blank examples of Examples 1 - 3 and Comparative Examples 1 - 4, it can be known that after the PP separator is treated with the functional composite material of the present application, the prepared lithium-ion battery separator has excellent heat resistance and flame retardancy, greatly improves the high-temperature stability of the lithium-ion battery, and at the same time significantly improves the electrochemical performance of the lithium-ion battery separator.

[0079] Among them, the heat resistance test method is: Cut the lithium-ion battery separator into a size of 4 cm × 5 cm, and then place it in a vacuum drying oven, and measure its area change when dried at a temperature of 120°C and 150°C for 1 h to obtain the thermal shrinkage rate at 120°C and the thermal shrinkage rate at 150°C respectively.

[0080] Among them, the flame retardancy test method is: Cut the lithium-ion battery separator into a size of 6 cm × 5 cm, and then test the limiting oxygen index.

[0081] Among them, the method for testing the electrochemical performance is as follows: An ion-conductivity test is carried out on a lithium-ion battery separator at 25°C by assembling it into a system battery of "steel sheet / separator / steel sheet" with two stainless-steel wafers each having a diameter of 16 mm in the middle.

[0082] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0083] The above content is only an illustration and description of the present invention. Those skilled in the art to which this technology belongs may make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the invention or exceed the scope defined by this application, they should all fall within the protection scope of the present invention.

Claims

1. A functional composite material for lithium-ion battery separator, characterized in that: It comprises the following components in parts 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; Wherein, the high temperature stabilizer is prepared by the following steps: Step a1: stirring hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide and N,N-dimethylformamide for reaction, cooling the reaction product after the reaction, then rotary evaporating, then adding it to dichloromethane, then vacuum filtering, and drying the filter cake to obtain an organic phosphorus nitrogen sulfonic acid intermediate; Step a2: stirring the organic phosphorus nitrogen sulfonic acid intermediate, lithium hydroxide and deionized water for reaction, cooling the reaction product after the reaction is completed, and then rotary evaporating, washing and drying to obtain a high temperature stabilizer.

2. The functional composite material for lithium-ion battery separator according to claim 1, characterized in that: The usage ratio of the hexachlorocyclotriphosphazene, aniline-2,5-disulfonic acid, tetrabutylammonium bromide, potassium iodide and N,N-dimethylformamide 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 separator according to claim 1, characterized in that: The usage ratio of the organic phosphorus 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 separator according to claim 1, characterized in that: The conductive enhancer is prepared by the following steps: Step b1: stirring the carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid to react, cooling the reaction product after the reaction is completed, then centrifuging, washing and drying the precipitate to obtain acidified carbon nanotubes; Step b2: stirring the acidified carbon nanotubes, boric acid and glycerol for reaction, cooling the reaction product after the reaction is completed, and then placing it in a tubular furnace for heat preservation, and then cooling it with the furnace to obtain a conductive enhancer.

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

6. The functional composite material for lithium-ion battery separator 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 mass fraction of the concentrated sulfuric acid is 98%; and the mass fraction of the concentrated nitric acid is 67%.

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

8. A production process for a functional composite material for lithium-ion battery separators, characterized in that: The following steps are involved: Step 1: Weigh 1.5-4.5 parts of high temperature stabilizer, 11-17 parts of conductivity 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 according to weight parts, and set aside; Step 2: Add polyvinylidene fluoride and anhydrous acetone into a mixer, stir and mix for 10-20 minutes at a temperature of 25-30°C and a stirring rate of 200-300r / min, then heat to 60-65°C and continue stirring and mixing for 2-3 hours, then add high temperature stabilizer, conductive enhancer, polyethylene glycol and sodium carboxymethyl cellulose and continue stirring and mixing for 2-3 hours, then let stand for 1-2 hours to obtain a functional composite material.

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

Images