CN117748050A - Preparation method of high heat-resistant polyether ketone nitrile/polyvinylidene fluoride lithium battery diaphragm - Google Patents

Abstract

A preparation method of a high heat-resistant polyether-ketone-nitrile/polyvinylidene fluoride lithium battery diaphragm belongs to the technical field of lithium ion battery materials. According to the invention, the polyether ketone nitrile copolymer is synthesized through nucleophilic substitution polycondensation reaction, and is blended with polyvinylidene fluoride, and then phase separation is carried out by adopting a non-solvent to obtain the high heat-resistant polyether ketone nitrile/polyvinylidene fluoride lithium battery diaphragm. In the battery diaphragm, the crystallinity of the blend film can be reduced by the polyether ketone nitrile, and the affinity of the blend film with the liquid electrolyte is enhanced by the polar carboxyl and the oxygen ether bond on the polyether ketone main chain, so that the introduction of the cyano group in the polyether ketone nitrile is beneficial to improving the absorption rate of the electrolyte, and the electrochemical window is widened, so that the diaphragm has high ionic conductivity, good electrolyte wettability and strong heat resistance.

Description

Preparation method of highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator

Technical field

The invention belongs to the technical field of lithium-ion battery materials, and specifically relates to a method for preparing a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator.

Background technique

With the development of high-performance lithium-ion battery technology, higher requirements have been put forward for separator modification design. As an important safety component, separators play a key role in the safety performance and electrochemical performance of batteries. The separator not only effectively isolates the positive and negative electrodes to avoid short circuits, but also provides an unobstructed path for lithium ions to pass through the liquid electrolyte. Qualified separators should have appropriate porosity, good electrochemical stability and thermal stability. Polyolefin separators are one of the most common commercial separator materials due to their high mechanical properties, excellent electrochemical stability and low price, such as polypropylene (PP) and polyethylene (PE). However, polyolefin separators have low melting points and poor electrolyte wetting, and are prone to severe dimensional shrinkage at high temperatures, leading to internal short circuits and further inducing thermal runaway in LIBS.

In order to make up for the shortcomings of polyolefin separators and meet the needs of high-performance lithium-ion batteries, domestic and foreign researchers mainly use methods to modify polyolefin separators, such as chemical grafting and inorganic or organic coating on the surface to modify polyolefin separators. Olefin separator. However, the use of chemical graft modification will increase the number of subsequent processing steps and easily cause the membrane pores to be blocked; coating the surface of the PE membrane with inorganic nanoparticles can improve its thermal stability, but this method can easily lead to the formation of pores on the membrane surface. Closed pore phenomenon, and the preparation process is difficult to accurately control. Therefore, developing a new material to replace polyolefin separators is a top priority.

Chinese patent application number 201810504179.2 discloses a method for manufacturing a composite separator for lithium-ion power batteries. The mixture of polyaryl ether nitrile and polyvinyl alcohol is made into a non-woven fiber layer through an electrospinning process, and then functional groups are introduced. Coating a layer of inorganic particles on the substrate enhances the heat resistance of the separator, but this easily causes the pores in the separator to close, and the manufacturing process is complex and difficult to control. The Chinese patent application number 202310804126.3 discloses a method for preparing a functional power battery electrospun lithium replenishing separator. It uses electrospinning technology to combine a lithium replenishing agent and a polyvinylidene fluoride electrospinning separator to increase electrolysis. However, due to the high crystallinity and interface resistance of polyvinylidene fluoride, the safety performance of the battery will be limited.

Contents of the invention

The purpose of the present invention is to propose a method for preparing a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator in view of the problems existing in the background technology. The present invention synthesizes polyether ketone nitrile copolymer through nucleophilic substitution condensation polymerization reaction. After blending with polyvinylidene fluoride, a non-solvent induced phase separation method is used to prepare a high heat-resistant lithium battery separator, and by preparing different compound ratios Polyetherketonenitrile/polyvinylidene fluoride separator Study the effect of polyetherketonenitrile on the structure and performance of the separator. In addition, the changes in thermal stability and electrolyte absorption rate of polyetherketonenitrile/polyvinylidene fluoride composite separators prepared by different annealing treatments were studied.

In order to achieve the above objects, the technical solutions adopted by the present invention are as follows:

A method for preparing a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator, including the following steps:

Step 1. Synthesis of polyetherketonenitrile:

1.1 Add 4,4'-biphenyldiphenol, 2,6-dichlorobenzonitrile and 4,4'-difluorodiphenol to a three-necked flask equipped with a thermometer, water separator, condensation reflux device and mechanical stirring device. Benzophenone is used as a reactant, potassium carbonate is added as a catalyst to obtain a mixture powder; toluene is injected into the water separator; among them, 4,4'-difluorobenzophenone, 4,4'-biphenyldiphenol, 2 , the molar ratio of 6-dichlorobenzonitrile and potassium carbonate is 1:3: (2.1～2.4): 4.2;

1.2 Add a mixed solvent of N-methylpyrrolidone and toluene to the mixture powder obtained in step 1.1, stir and mix evenly to obtain mixed liquid A; in the mixed solvent, the volume ratio of N-methylpyrrolidone and toluene is 3:1; where , the molar ratio of the toluene injected in the water separator in step 1.1 and the toluene added to the mixture powder in step 1.2 is 1: (1.35~1.8);

1.3 The mixed liquid A obtained in step 1.2 is heated and refluxed at 140°C for 2 to 5 hours to release the toluene in the water separator, then the temperature is raised to 150 to 159°C and kept at 150 to 159°C for 1 to 2 hours, and the temperature is raised to 160 to 169 ℃ and keep it at 160~169°C for 1~2h, raise the temperature to 170~179°C and keep it at 170~179°C for 1~2h, raise the temperature to 180~190°C and keep it at 180~190°C for 1~2h, proceed Dehydration and condensation reaction. When the viscosity no longer increases, pour the resulting reaction solution into deionized water and stir to obtain a strip solid;

1.4 The strip solid obtained in step 1.3 is soaked in 10wt% hydrochloric acid solution for 24 hours, then crushed, and then washed with deionized water 3 to 5 times until the solution becomes neutral; the washed powder is dried in an oven at 100°C for 24 to After 48h, polyetherketonenitrile powder was obtained;

Step 2. Prepare polyetherketonenitrile/polyvinylidene fluoride hot blend solution:

2.1 Add N-methylpyrrolidone and the polyetherketonenitrile powder obtained in step 1 into a three-necked bottle, heat and stir at 140-150°C for 2-5 hours to obtain a uniform solution B;

2.2 Add polyvinylidene fluoride and N-methylpyrrolidone to solution B obtained in step 2.1, and continue heating and stirring at 140 to 150°C for 2 hours to obtain a polyetherketonenitrile/polyvinylidene fluoride hot blend solution; where , the mass ratio of polyetherketonenitrile and polyvinylidene fluoride is 1: (0.25~4), the solid-liquid ratio of the mixed solid powder of polyetherketonenitrile powder and polyvinylidene fluoride and N-methylpyrrolidone is 1g (15～35)mL;

Step 3. Use a non-solvent-induced phase separation method to prepare a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator:

3.1 Pour the polyetherketonenitrile/polyvinylidene fluoride hot blend solution obtained in step 2 onto a clean, flat glass plate, and use a four-sided film applicator to cast a wet film;

3.2 Directly immerse the glass plate with the wet film obtained in step 3.1 into the coagulation bath for 10 to 20 minutes to separate and form a separator with a porous structure, and then soak the separator in deionized water; where, the coagulation bath is a non-porous membrane with a volume ratio of 1:1. A mixture of hydroethanol and deionized water;

3.3 Dry the separator obtained after the treatment in step 3.2 at room temperature to obtain the high heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a method for preparing a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator. The polyetherketonenitrile copolymer is synthesized through a nucleophilic substitution condensation polymerization reaction. After blending with polyvinylidene fluoride, A highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator was obtained using non-solvent-induced phase separation. In this battery separator, polyetherketonenitrile can reduce the crystallinity of the blend film, and the polar carboxyl groups and oxygen ether bonds on the polyetherketone main chain enhance its affinity with the liquid electrolyte. The cyano group in polyetherketonenitrile The introduction helps to increase the absorption rate of the electrolyte and broaden the electrochemical window, making the separator have high ionic conductivity, good electrolyte wettability and strong heat resistance.

Description of drawings

Figure 1 is the synthesis route of polyetherketonenitrile in step 1;

Figure 2 shows the electrolyte wettability of the polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared in Example 3 and Comparative Example 8;

Figure 3 shows the heat resistance stability of polyetherketonenitrile/polyvinylidene fluoride lithium battery separators prepared in Examples 1 to 3 and Comparative Examples 4 to 6 and Comparative Examples 7 and 8;

Figure 4 shows the battery cycle performance of the polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared in Example 3 and Comparative Example 8.

Detailed ways

The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and examples.

Example 1

A method for preparing a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator, including the following steps:

Step 1. Synthesis of polyetherketonenitrile:

1.1 Add 4,4'-biphenyldiphenol, 2,6-dichlorobenzonitrile and 4,4'-difluorodiphenol into a three-necked flask equipped with a thermometer, water separator, condensation reflux device and mechanical stirring device. Benzophenone is used as a reactant, potassium carbonate is added as a catalyst to obtain a mixture powder; toluene is injected into the water separator; among them, 4,4'-difluorobenzophenone, 4,4'-biphenyldiphenol, 2 , the molar ratio of 6-dichlorobenzonitrile and potassium carbonate is 1:3:2.2:4.2;

1.2 Add a mixed solvent of N-methylpyrrolidone and toluene to the mixture powder obtained in step 1.1, stir and mix evenly to obtain mixed liquid A; in the mixed solvent, the volume ratio of N-methylpyrrolidone and toluene is 3:1; where , the molar ratio of the toluene injected in the water separator in step 1.1 and the toluene added to the mixture powder in step 1.2 is 1:1.8;

1.3 Mixed solution A obtained in step 1.2 is heated to reflux at 140°C for 3 hours, releasing 3 to 5 mL of toluene in the water separator every 8 to 10 minutes, and then heated to 155°C at a heating rate of 2 to 5°C/min and heated at 155°C. Keep the temperature at 165°C for 2 hours, raise the temperature to 165°C and keep it at 165°C for 2 hours, raise the temperature to 175°C and keep it at 175°C for 2 hours, raise the temperature to 185°C and keep it at 185°C for 2 hours, and carry out dehydration and condensation reaction until the viscosity no longer increases. When, the reaction solution obtained is poured into deionized water and stirred to obtain a strip solid;

1.4 The strip solid obtained in step 1.3 is soaked in 10wt% hydrochloric acid solution for 24 hours, then crushed, and then washed with deionized water 3 to 5 times until the solution becomes neutral; the washed powder is dried in an oven at 100°C for 36 hours. Polyetherketonenitrile powder is obtained;

Step 2. Prepare polyetherketonenitrile/polyvinylidene fluoride hot blend solution:

2.1 Add N-methylpyrrolidone and the polyetherketonenitrile powder obtained in step 1 into a three-necked flask, heat and stir at 150°C for 5 hours to obtain a uniform solution B; add 10 mL of N to 1g of polyetherketonenitrile powder. - Methylpyrrolidone;

2.2 Add polyvinylidene fluoride and N-methylpyrrolidone to the solution B obtained in step 2.1, and continue to heat and stir at 150°C for 2 hours to obtain a polyetherketonenitrile/polyvinylidene fluoride blend hot solution; where, poly(vinylidene fluoride) and N-methylpyrrolidone are added. The mass ratio of ether ketone nitrile and polyvinylidene fluoride is 1: (0.25~4), and 16.25 mL of N-methylpyrrolidone is added to 1g of the mixed solid powder of polyether ketone nitrile powder and polyvinylidene fluoride;

Step 3. Use a non-solvent-induced phase separation method to prepare a highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator:

3.1 Pour the polyetherketonenitrile/polyvinylidene fluoride hot blend solution obtained in step 2 onto a clean, flat glass plate, and use a four-sided film applicator to cast a wet film;

3.2 Directly immerse the glass plate with wet film obtained in step 3.1 into the coagulation bath for 15 minutes to separate and form a separator with a porous structure, and then soak the separator in deionized water; where the coagulation bath is absolute ethanol with a volume ratio of 1:1 and deionized water mixture;

3.3 Dry the separator obtained after the treatment in step 3.2 at room temperature to obtain the high heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator.

Example 2

Compared with Embodiment 1, the differences between this embodiment and Embodiment 1 are:

The process of preparing the polyetherketonenitrile/polyvinylidene fluoride hot blend solution in step 2 is adjusted as follows:

2.1 Add N-methylpyrrolidone and the polyetherketonenitrile powder obtained in step 1 into a three-necked flask, heat and stir at 150°C for 5 hours to obtain a uniform solution B; add 10 mL of N to 1g of polyetherketonenitrile powder. - Methylpyrrolidone;

2.2 Add polyvinylidene fluoride and N-methylpyrrolidone to the solution B obtained in step 2.1, and continue to heat and stir at 150°C for 2 hours to obtain a polyetherketonenitrile/polyvinylidene fluoride blend hot solution; where, poly(vinylidene fluoride) and N-methylpyrrolidone are added. The mass ratio of ether ketone nitrile and polyvinylidene fluoride is 1: (0.25~4). 20 mL of N-methylpyrrolidone is added to 1g of the mixed solid powder of polyether ketone nitrile powder and polyvinylidene fluoride; the rest of the process is as follows Example 1 is exactly the same.

Example 3

Compared with Embodiment 1, the differences between this embodiment and Embodiment 1 are:

The process of preparing the polyetherketonenitrile/polyvinylidene fluoride hot blend solution in step 2 is adjusted as follows:

2.1 Add N-methylpyrrolidone and the polyetherketonenitrile powder obtained in step 1 into a three-necked flask, heat and stir at 150°C for 5 hours to obtain a uniform solution B; among which, add 10mL of N to 1g of polyetherketonenitrile powder. -Methylpyrrolidone;

2.2 Add polyvinylidene fluoride and N-methylpyrrolidone to the solution B obtained in step 2.1, and continue to heat and stir at 150°C for 2 hours to obtain a polyetherketonenitrile/polyvinylidene fluoride blend hot solution; where, poly(vinylidene fluoride) and N-methylpyrrolidone are added. The mass ratio of ether ketone nitrile and polyvinylidene fluoride is 1: (0.25~4). 35 mL of N-methylpyrrolidone is added to 1g of the mixed solid powder of polyether ketone nitrile powder and polyvinylidene fluoride; the rest of the process is as follows Example 1 is exactly the same.

Comparative example 1

Step 1. Mix polyvinylidene fluoride and N-methylpyrrolidone, heat and stir at 150°C for 2 hours to obtain a hot polyvinylidene fluoride solution; add 10 mL of N-methylpyrrolidone to 1g of polyvinylidene fluoride powder. pyrrolidone;

Step 2. Use non-solvent induced phase separation method to prepare polyvinylidene fluoride lithium battery separator:

2.1 Pour the polyvinylidene fluoride hot solution obtained in step 1 onto a clean, flat glass plate, and use a four-sided film applicator to cast a wet film;

2.2 Directly immerse the glass plate with wet film obtained in step 2.1 into the coagulation bath for 15 minutes to separate and form a separator, and then soak the separator in deionized water; where the coagulation bath is absolute ethanol and deionized water with a volume ratio of 1:1 mixture;

2.3 Dry the separator obtained after step 2.2 at room temperature to obtain a polyvinylidene fluoride lithium battery separator.

Comparative example 2

The difference between this comparative example and Example 1 is that in step 3.3, the separator obtained after step 3.2 is dried at room temperature and then heat-treated at 120°C for 5 hours; the remaining steps are the same as in Example 1.

Comparative example 3

The difference between this comparative example and Example 2 is that in step 3.3, the separator obtained after step 3.2 is dried at room temperature and then heat-treated at 120°C for 5 hours; the remaining steps are the same as in Example 2.

Comparative example 4

The difference between this comparative example and Example 3 is that in step 3.3, the separator obtained after step 3.2 is dried at room temperature and then heat-treated at 120°C for 5 hours; the remaining steps are the same as in Example 3.

Comparative example 5

The difference between this comparative example and Example 3 is that in step 3.3, the separator obtained after step 3.2 is dried at room temperature and then heat-treated at 200°C for 2 hours; the remaining steps are the same as in Example 3.

Comparative example 6

The difference between this comparative example and Comparative Example 1 is that in step 2.3, the separator obtained after step 2.2 is dried at room temperature and then heat-treated at 120°C for 5 hours; the remaining steps are exactly the same as in Comparative Example 1.

Comparative example 7

A polyetherketone nitrile lithium battery separator, the preparation method of which includes:

Step 1. Synthesis of polyetherketonenitrile:

1.1 Add 4,4'-biphenyldiphenol, 2,6-dichlorobenzonitrile and 4,4'-difluorodiphenol to a three-necked flask equipped with a thermometer, water separator, condensation reflux device and mechanical stirring device. Benzophenone is used as a reactant, potassium carbonate is added as a catalyst to obtain a mixture powder; toluene is injected into the water separator; among them, 4,4'-difluorobenzophenone, 4,4'-biphenyldiphenol, 2 , the molar ratio of 6-dichlorobenzonitrile and potassium carbonate is 1:3:2.2:4.2;

1.2 Add a mixed solvent of N-methylpyrrolidone and toluene to the mixture powder obtained in step 1.1, stir and mix evenly to obtain mixed liquid A; in the mixed solvent, the volume ratio of N-methylpyrrolidone and toluene is 3:1; where , the molar ratio of the toluene injected in the water separator in step 1.1 and the toluene added to the mixture powder in step 1.2 is 1:1.8;

1.3 Mixed solution A obtained in step 1.2 is heated to reflux at 140°C for 3 hours, releasing 3 to 5 mL of toluene in the water separator every 8 to 10 minutes, and then heated to 155°C at a heating rate of 2 to 5°C/min and heated at 155°C. Keep the temperature at 165°C for 2 hours, raise the temperature to 165°C and keep it at 165°C for 2 hours, raise the temperature to 175°C and keep it at 175°C for 2 hours, raise the temperature to 185°C and keep it at 185°C for 2 hours, and carry out dehydration and condensation reaction until the viscosity no longer increases. When, the reaction solution obtained is poured into deionized water and stirred to obtain a strip solid;

1.4 The strip solid obtained in step 1.3 is soaked in 10wt% hydrochloric acid solution for 24 hours, then crushed, and then washed with deionized water 3 to 5 times until the solution becomes neutral; the washed powder is dried in an oven at 100°C for 36 hours. Polyetherketonenitrile powder is obtained;

Step 2. Prepare polyetherketonenitrile hot solution:

Add N-methylpyrrolidone and the polyetherketonenitrile powder obtained in step 1 into a three-necked flask, heat and stir at 150°C for 5 hours to obtain a polyetherketonenitrile hot solution; where, 10 mL of polyetherketonenitrile powder is added to 1g of polyetherketonenitrile powder. N-methylpyrrolidone;

Step 3. Use non-solvent induced phase separation method to prepare polyetherketone nitrile lithium battery separator:

3.1 Pour the hot polyetherketonenitrile solution obtained in step 2 onto a clean, flat glass plate, and use a four-sided film applicator to cast a wet film;

3.2 Directly immerse the glass plate with wet film obtained in step 3.1 into the coagulation bath for 15 minutes to separate and form a separator, and then soak the separator in deionized water; where the coagulation bath is absolute ethanol and deionized water with a volume ratio of 1:1 mixture;

3.3 Dry the separator obtained after the treatment in step 3.2 at room temperature to obtain the polyetherketone nitrile lithium battery separator.

Comparative example 8

Commercially available Celgard 2400 separator.

Various properties of the lithium battery separators prepared in the above examples and comparative examples were tested, and the results are shown in Table 1 and Table 2.

Table 1 Melting point and melting enthalpy of battery separator

sample name Melting point 1/℃ Melting enthalpy/(J/g) Melting point 2/℃ Melting enthalpy 2/(J/g) Melting point 3/℃ Melting enthalpy 3/(J/g) Example 1 164.7 43.80 305.3 0.04 Example 2 163.8 24.30 307.7 0.25 Example 3 162.9 7.07 300.4 1.47 Comparative example 1 163.9 58.12 - - Comparative example 2 165.1 33.45 306.3 0.18 Comparative example 3 163.5 29.15 307.0 0.47 Comparative example 4 163.0 6.40 301.8 1.40 Comparative example 5 170.0 2.70 179 0.83 301.3 1.51 Comparative example 6 165.2 55.39 Comparative example 7 170.2 87.17 Comparative example 8 311.7 0.25

Table 2 Battery separator performance

As can be seen from Table 1, as the proportion of polyvinylidene fluoride increases, the melting enthalpy increases, which indicates that polyvinylidene fluoride can promote the crystallization of the composite separator. Moreover, the crystallinity of the composite film is smaller than that of polyvinylidene fluoride, which is due to the increase in the amorphous area of polyvinylidene fluoride, and lower crystallinity can improve conductivity. After some composite separators are treated at 120°C, the melting point of polyvinylidene fluoride is almost not affected, but the crystallinity is reduced. In order to confirm the crystallinity of the composite separator, after treating Example 3 in a high-temperature oven at 200°C for 2 hours, it was observed that the melting point of polyvinylidene fluoride in Example 3 changed to two points, 166.9°C and 179°C respectively. The melting point of the vinylidene fluoride component increased by 10%, which was due to the increase in the alpha phase content in polyvinylidene fluoride. As can be seen from Table 2, compared with Comparative Example 7, the highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared in the embodiment of the present invention has good heat resistance, and also has 55.54% to 89.86% High porosity, high-efficiency electrolyte absorption rate of 210% to 435% and ionic conductivity of 0.301 to 0.600*10 ^-3 S/cm.

Figure 2 shows the electrolyte wettability of the polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared in Example 3 and Comparative Example 8; it can be seen from Figure 2 that the high heat-resistant polyetherketonenitrile prepared in Examples of the present invention /Polyvinylidene fluoride lithium battery separator shows good electrolyte wettability, and the electrolyte can be spread well on the film. Compared with Comparative Examples 7 and 8, the highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared by the present invention has higher electrolyte wettability.

Figure 3 shows the heat resistance stability of the polyetherketonenitrile/polyvinylidene fluoride lithium battery separators prepared in Examples 1 to 3 and Comparative Examples 4 to 6 and Comparative Examples 7 and 8; as can be seen from Figure 3, the Compared with Example 7 and Comparative Example 8, the highly heat-resistant polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared by the present invention has good flame retardancy and heat resistance and can meet lithium ion safety standards.

Figure 4 shows the battery cycle performance of the polyetherketonenitrile/polyvinylidene fluoride lithium battery separator prepared in Example 3 and Comparative Example 8; it can be seen from Figure 4 that compared with Comparative Example 8, the high-resistant membrane prepared in the Example of the present invention has The specific capacity of the battery assembled with the thermal polyetherketonenitrile/polyvinylidene fluoride lithium battery separator is relatively high, reaching about 160mAh g ^-1 , and the initial discharge specific capacity is 169.1mAh g ^-1 at a current density of 0.5C. After 45 cycles, the battery's capacity retention rate was 86.64%, and the battery's specific discharge capacity was 146.5mAhg ^-1 . The high-temperature-resistant polyetherketonenitrile/polyvinylidene fluoride film of the present invention is used as a lithium-ion battery separator, and the battery performance is significantly better than the Celgard 2400 separator.

Claims (1)

1. The preparation method of the high heat-resistant polyether-ketone-nitrile/polyvinylidene fluoride lithium battery diaphragm is characterized by comprising the following steps of:

step 1, synthesizing polyether ketone nitrile:

1.1 adding 4,4 '-biphenol, 2, 6-dichlorobenzonitrile and 4,4' -difluorobenzophenone as reactants and adding potassium carbonate as a catalyst into a three-necked bottle to obtain mixture powder; injecting toluene into a water separator; wherein, the mole ratio of 4,4 '-difluorobenzophenone, 4' -biphenol, 2, 6-dichlorobenzonitrile and potassium carbonate is 1:3: (2.1-2.4): 4.2;

1.2 adding a mixed solvent of N-methylpyrrolidone and toluene into the mixture powder obtained in the step 1.1, and stirring and uniformly mixing to obtain a mixed solution A; in the mixed solvent, the volume ratio of N-methyl pyrrolidone to toluene is 3:1; wherein, the molar ratio of toluene injected in the water separator in the step 1.1 and toluene added in the mixture powder in the step 1.2 is 1 (1.35-1.8);

1.3 heating and refluxing the mixed solution A obtained in the step 1.2 at 140 ℃ for 2-5 hours, releasing toluene in a water separator, then heating to 150-159 ℃ and preserving heat for 1-2 hours at 150-159 ℃, heating to 160-169 ℃ and preserving heat for 1-2 hours at 160-169 ℃, heating to 170-179 ℃ and preserving heat for 1-2 hours at 170-179 ℃, heating to 180-190 ℃ and preserving heat for 1-2 hours at 180-190 ℃, pouring the obtained reaction solution into deionized water, and stirring to obtain strip-shaped solid;

1.4 soaking the strip-shaped solid obtained in the step 1.3 in hydrochloric acid solution for 24 hours, crushing, and washing with deionized water to neutrality; drying the washed powder in a baking oven to obtain polyether ketone nitrile powder;

step 2, preparing a polyether ketone nitrile/polyvinylidene fluoride blending hot solution:

2.1 adding N-methyl pyrrolidone and the polyether ketone nitrile powder obtained in the step 1 into a three-necked bottle, heating and stirring for 2-5 h at 140-150 ℃ to obtain a uniform solution B;

2.2 adding polyvinylidene fluoride and N-methyl pyrrolidone into the solution B obtained in the step 2.1, and continuously heating and stirring for 2 hours at 140-150 ℃ to obtain a polyether ketone nitrile/polyvinylidene fluoride blending hot solution; wherein, the mass ratio of the polyether ketone nitrile to the polyvinylidene fluoride is 1: (0.25-4), wherein the solid-to-liquid ratio of the mixed solid powder of the polyether ketone nitrile powder and the polyvinylidene fluoride to the N-methyl pyrrolidone is 1g: (15-35) mL;

step 3, preparing the high heat-resistant polyether ketone nitrile/polyvinylidene fluoride lithium battery diaphragm by adopting a non-solvent induced phase separation method:

3.1 pouring the polyether-ketone-nitrile/polyvinylidene fluoride blending hot solution obtained in the step 2 on a clean and flat glass plate, and casting a wet film by using a four-side film coater;

3.2 immersing the glass plate with the wet film obtained in the step 3.1 into a coagulating bath for 10-20 min, separating to form a diaphragm with a porous structure, and immersing the diaphragm into deionized water; wherein, the coagulating bath is a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:1;

and 3.3, airing the diaphragm obtained after the treatment in the step 3.2 at room temperature, and obtaining the high heat-resistant polyether-ketone-nitrile/polyvinylidene fluoride lithium battery diaphragm.