CN116554528A - Preparation method and production device of ceramic grafted diaphragm for secondary battery - Google Patents

Abstract

A preparation method and production device for a ceramic graft diaphragm used in a secondary battery, using a pulse plasma process to treat the diaphragm substrate in an oxygen-containing atmosphere, that is, introducing a base such as a peroxy group on the basis of ensuring the mechanical strength of the diaphragm. group, and then place the treated diaphragm in a mixed solution of a coupling agent containing unsaturated bond groups and nano-oxide ceramic particles, and decompose the peroxy group under heating conditions to generate oxygen free radicals to initiate The grafting reaction with the unsaturated group on the coupling agent also causes the dehydration condensation reaction of the siloxy group on the coupling agent, the hydroxyl group, carboxyl group, epoxy group on the diaphragm and the hydroxyl group on the surface of the inorganic nano oxide. The production device of the present invention has simple structure, low cost, convenient maintenance, simple and easy-to-operate preparation method, and the prepared ceramic grafted diaphragm has excellent thermal stability and electrolyte affinity, which solves the problem of poor thermal stability of polyolefin diaphragms on the market and insufficient wettability of the electrolyte.

Description

A preparation method and production device of a ceramic graft separator for secondary batteries

technical field

The invention belongs to the technical field of battery diaphragms, and relates to a preparation method and a production device for a ceramic grafted diaphragm used in a secondary battery.

Background technique

Lithium-ion batteries have the advantages of high energy density, long cycle life, and no memory effect, and are widely used in various fields such as portable electronic devices, electric vehicles, drones, medical equipment, and security equipment. Separator is one of the four key raw materials of lithium-ion batteries. Its quality directly affects the capacity, cycle life and safety performance of the battery. For power batteries with high energy density, the polyolefin separators currently on the market cannot meet the demand due to their poor thermal stability and electrolyte wettability.

At present, in the industry, the diaphragm is often coated to improve the performance of the diaphragm. For example, the Chinese patent "Manufacturing method of a high-safety ceramic coating diaphragm" whose patent publication number is CN106953049A includes the following steps: 1) Preparation of modified alkaline ceramic powder: mix and stir short carbon chain phosphoric acid and solvent evenly , then add alkaline ceramic powder and stir evenly to obtain a grafting solution, then heat up to 150°C-200°C and stir for 5-10h, after rinsing, filtering, and vacuum drying, a modified alkaline ceramic powder is obtained; 2) modification Preparation of ceramic slurry: Mix and stir the modified alkaline ceramic powder prepared in step 1), deionized water and binder for 0.5-3 hours to obtain modified ceramic slurry; 3) Coating: the The obtained modified ceramic slurry is coated on one side or both sides of the polyolefin base film, and the modified ceramic coating is formed after drying to obtain a high-safety ceramic coated diaphragm. The invention enhances the mechanical properties of the diaphragm, maintains the gas permeability of the diaphragm, maintains the thermal stability of the alkaline ceramic coating, and improves the conductivity and safety performance of the lithium battery. In the method, modified alkaline ceramic powder and binder are formulated into slurry in deionized water and coated on the polyolefin base film to obtain a ceramic coated diaphragm, which can improve the conductivity and safety performance of the lithium battery. However, this type of method has high requirements for equipment, complex performance control, uneven distribution of ceramic particles and easy detachment, and reduced porosity of the separator, and the thickness of the separator after coating will increase by 2 to 3 microns, which will increase the energy density of the battery. reduce.

In addition, there is also a method of radiation modification to improve the properties of the diaphragm, such as the Chinese patent "A boron-containing modified diaphragm, its preparation method and application, and a battery containing the diaphragm" with the patent publication number CN112928387A. The diaphragm is irradiated and grafted with gamma rays to obtain a boron-containing modified diaphragm, which improves the lithium ion migration number of the diaphragm. However, high-energy ray irradiation will greatly affect the mechanical properties of the separator, which increases the probability of rupture of the separator during battery use. Moreover, such methods involve electromagnetic radiation equipment, and long-term use has a certain impact on the surrounding environment and practitioners.

Contents of the invention

The first technical problem to be solved by the present invention is to provide a production device for ceramic grafted separators for secondary batteries, which has the advantages of simple structure, convenient operation, low cost and easy maintenance.

The second technical problem to be solved by the present invention is to provide a method for preparing a ceramic graft separator for secondary batteries, the process is simple and easy to operate, and is environmentally friendly, and the prepared ceramic graft separator has excellent thermal stability and Electrolyte affinity, suitable for large-scale production.

The technical scheme adopted by the present invention to solve the above-mentioned first technical problem is: a production device for ceramic grafted diaphragms for secondary batteries, which is characterized in that it includes a pulse plasma device and a soaking graft device, and the pulse plasma device includes The reaction chamber is equipped with a plasma processing area and a rewinding and unwinding system. The plasma processing area is set in the middle of the reaction chamber and connected to the pulse power supply. The rewinding and unwinding system includes a rewinding shaft and an unwinding shaft. On both sides of the treatment area, a vacuum pump and a plasma source are arranged outside the reaction chamber; the soaking and grafting device includes a reaction pool filled with grafting solution and a rewinding and unwinding mechanism. The rewinding and unwinding mechanism includes an unwinding roller and a winding roller and guide rollers, the unwinding roller is set on the left side of the upper end of the reaction pool, the winding roll is set on the right side outside the upper end of the reaction pool, and the diaphragm on the unwinding roll enters the reaction pool from the left end of the reaction pool to carry out grafting reaction. After the branch reaction, the diaphragm comes out from the right end of the reaction tank and is wound up on the winding roller.

Further, the reaction chamber is a rectangular chamber, the reaction pool is a rectangular pool with an open upper end, and there are three guide rollers, two of which are set on the left and right sides of the reaction pool near the bottom of the pool, and the third is set on the right end of the reaction pool Above, the production device also includes a flushing device and a drying device. After the grafting reaction, the diaphragm is wound up on the winding roller after being processed by the flushing device and the drying device.

The technical scheme adopted by the present invention to solve the above-mentioned second technical problem is: a kind of preparation method for the ceramic graft separator of secondary battery, it is characterized in that comprising the following steps:

1) Treat the separator substrate in an oxygen-containing atmosphere using a pulsed plasma process:

Place the diaphragm base material in the unwinding system of the pulse plasma device, turn on the vacuum pump, and feed the plasma source. The plasma source is gas or liquid containing oxygen, and the gas flow rate is adjusted to 10-400mL/min. When the air pressure is lower than 10Pa, turn on the pulse plasma discharge power supply and adjust the output power to 10-300W, the pulse frequency is 0-10000Hz, the duty cycle is 5-95%, and the winding and unwinding system is turned on at the same time, and the running speed is 1-10m /min, the temperature inside the reaction chamber is 20-60°C. After all the diaphragms have passed through the plasma treatment area, they are taken out to obtain diaphragms containing groups such as hydroxyl, carboxyl, epoxy or/and peroxy groups;

2) Place the treated diaphragm in the grafting solution soaking the grafting device for grafting reaction:

The diaphragm after step 1) is passed through the grafting solution through the winding and unwinding mechanism. The grafting solution is a mixed solution of coupling agent grafting monomers containing unsaturated bond groups and nano-oxide ceramic particles, which is pH The acidic system aqueous solution with a value of 0-6, the mass percentage of the grafting monomer of the coupling agent contained in the grafting solution is 1%-5%, and the mass percentage of the nano-oxide ceramic particles contained is 1%-20%, The temperature of the grafting reaction is 40-80°C, and the reaction time is 2-20 hours;

3) The diaphragm is sent out through the winding and unwinding mechanism, and then passes through the washing device and the drying device in sequence, and finally the ceramic grafted diaphragm is obtained by winding.

Preferably, the plasma source in step 1) includes air, oxygen, water vapor or ozone; the diaphragm substrate includes one of polyethylene, polypropylene, and polyethylene/polypropylene composite diaphragm, with a thickness of 5-20 microns.

Further preferably, the plasma source uses oxygen with a flow rate of 50-100 mL/min.

Preferably, the discharge output power of the pulse plasma device in step 1) is 50W, the pulse frequency is 100Hz, the duty cycle is 30%, the diaphragm winding speed is 2m/min during plasma treatment, and the temperature inside the reaction chamber is 25°C .

Preferably, the coupling agent grafting monomer of the step 2) adopts vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-form One or more of acryloyloxypropyltrimethoxysilane; one or more of aluminum oxide, silicon oxide, titanium oxide, and zirconium oxide are used as nano-inorganic oxides, and the particle size is 50-100nm.

Further preferably, vinyltrimethoxysilane or vinyltriethoxysilane is used as the grafting monomer of the coupling agent; aluminum oxide is used as the nano-inorganic oxide with a particle size of 50 nm.

Further, the pH regulator of the grafting solution in step 2) is one or more of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid.

Preferably, the pH value of the grafting solution in step 2) is 1, the grafting solution contains a coupling agent grafting monomer mass percent of 2%, and the contained nano-oxide ceramic particles contain a mass percent of 2%; The temperature during the grafting reaction was 70°C.

Further, the flushing system in step 3) is pure water flushing, and the drying system is hot air drying at 70±5°C.

Finally, the secondary batteries include lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries.

Compared with the prior art, the present invention has the advantages of:

1. The diaphragm substrate is treated with pulse plasma technology, that is, hydroxyl groups, carboxyl groups, epoxy groups, peroxyl groups and other groups are introduced on the basis of ensuring the mechanical strength of the diaphragm, and then the treated diaphragm is placed in a place containing unsaturated bond groups. In the mixed solution of the coupling agent of the group and the nano-oxide ceramic particles, under the condition of heating, the peroxy group is decomposed to generate oxygen free radicals, thereby initiating the grafting reaction between the membrane and the unsaturated group on the coupling agent, Simultaneously, dehydration condensation reaction occurs between the siloxy groups on the coupling agent, the hydroxyl groups, carboxyl groups, epoxy groups on the diaphragm and the hydroxyl groups on the surface of the inorganic nano oxide. The thickness of the ceramic layer of the ceramic grafted separator can be as low as 100nm, which is much smaller than the ceramic layer (~2μm) of the ceramic coated separator on the market. Therefore, the ceramic grafted separator has a great weight advantage, which is conducive to the realization of high safety and high specific energy. secondary ion battery;

2. The ceramic layer of the ceramic grafted membrane of the present invention is chemically bonded to the base membrane, without the risk of falling off, and no organic solvent is used in the preparation process, which is conducive to environmental protection;

3. The production device of the present invention is simple in structure, low in cost, easy to maintain, and the preparation method is simple and easy to operate. The prepared ceramic grafted diaphragm has excellent thermal stability and electrolyte affinity, which solves the problem of polyolefin diaphragm on the market. The disadvantages of poor stability and insufficient electrolyte wettability, thereby improving the safety and rate performance of batteries using these separators, are suitable for large-scale production.

Description of drawings

Fig. 1 is the structural representation of the production device of the ceramic graft diaphragm that is used for secondary battery provided by the present invention;

Fig. 2a, 2b, 2c are the scanning electron micrographs of the diaphragm of comparative example 1, comparative example 2, embodiment 1 respectively;

Fig. 3 is the infrared spectrogram of comparative example 1 and embodiment 1;

Fig. 4 is the stress-strain curve of comparative example 1, comparative example 2, embodiment 1;

Fig. 5 is the photograph of comparative example 1, comparative example 3, embodiment 1 after being heated at 150 ℃;

FIG. 6 is the Nyquist plot (Nyquistplot) of Comparative Example 1, Comparative Example 2, and Example 1 when the number of diaphragms is 1.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a production device for ceramic grafted diaphragms for secondary batteries includes a pulse plasma device A, a soaking graft device B, a flushing device C and a drying device D, wherein the pulse plasma device A includes a reaction The cabin body 1, the reaction cabin body 1 is a rectangular cabin, the plasma processing area 3 and the unwinding system are arranged in the reaction cabin body 1, the plasma processing area 3 is arranged in the middle position in the reaction cabin body 1, and is connected with the pulse power supply 2, The rewinding and unwinding system includes a rewinding shaft 7 and an unwinding shaft 6 , which are respectively arranged on both sides of the plasma processing area 3 , and a vacuum pump 4 and a plasma source 5 are arranged outside the reaction chamber 1 . Soaking and grafting device B comprises a reaction tank 8 that is filled with grafting solution and a rewinding and unwinding mechanism, the reaction tank 8 is a rectangular tank with an upper end opening, and the rewinding and unwinding mechanism includes an unwinding roller 9, a winding roller 20 and a guide Roller 30, unwinding roller 9 is arranged on the left side of the upper end of the reaction tank, winding roller 20 is arranged on the right side outside the upper end of the reaction tank 8, and there are three guide rollers 30, two of which are arranged in the reaction tank 8 near the bottom of the pool The left and right sides of the reaction tank 8, the third one is set above the right end of the reaction tank 8, the diaphragm 10 on the unwinding roller 9 enters the reaction tank 8 from the left end of the reaction tank 8 for grafting reaction, and the diaphragm 10 after the grafting reaction goes out to react The pool 8 is wound up on the winding roller 20 after being processed by the washing device C and the drying device D.

Example 1

A polyethylene diaphragm 10 with a thickness of 9 microns is placed in the unwinding device in the pulse plasma device A, as shown in Figure 1, the vacuum pump 4 is turned on, oxygen is introduced, and the gas flow rate is adjusted to be 100mL/min. When the air pressure is lower than 10Pa, turn on the pulse plasma discharge power supply 2 and adjust the output power to 50W, the working frequency is 100Hz, the duty cycle is 30%, and the temperature inside the reaction chamber is 25°C. At the same time, open the winding and unwinding device, and the running speed is 2m/min. After all the separators 10 have passed through the plasma treatment area 3, they are taken out to obtain polyethylene separators containing hydroxyl groups, carboxyl groups, epoxy groups, peroxy groups and other groups.

The above-mentioned diaphragm 10 is entered into the reaction tank 8 by the rewinding and unwinding mechanism, and it is passed through the grafting solution. The grafting solution is nano-alumina (50nm in particle size) containing 2% mass fraction and vinyl trimethoxyl containing 2% mass fraction. An aqueous solution of silane, the grafting solution has been adjusted to pH 1 with hydrochloric acid. The temperature of the solution is 70°C, and each membrane 10 passes through the grafting solution for about 4 hours, and then the membrane 10 passes through the guide roller 30 and passes through the washing device C (rinsing with pure water) and the drying device D (drying with hot air at 70°C) in sequence. dry), and finally obtained alumina-grafted polyethylene separator by winding.

FIG. 2 b is a scanning electron microscope image of the basement membrane after pulsed plasma treatment. It can be seen that there is no obvious fracture of the surface fibers, indicating that the pulse method used in the present invention has little damage to the diaphragm 10 . Fig. 2c is the scanning electron micrograph of the polyethylene diaphragm of the aluminum oxide grafting that embodiment 1 gains, as seen from the figure, its surface does not have bulky oxide particle, shows that the oxide particle on the grafting of this method is nanoscale, not It will greatly increase the weight and thickness of the diaphragm, and will not block the pores of the diaphragm. Fig. 3 is the infrared spectrogram of base film and the ceramic grafted membrane of embodiment 1 gained, can see from the figure that the infrared spectrum of gained grafted membrane product has the obvious absorption peak of aluminum oxide, shows that aluminum oxide has been successfully grafted onto the membrane. Figure 4 shows the stress-strain curves of the base film and the alumina-grafted separator obtained in Example 1. The mechanical strength and elongation at break of the alumina-grafted polyethylene separator obtained in Example 1 only decreased compared to the base film It can be seen that the method used in the present invention has little influence on the mechanical properties of the diaphragm 10. It can also be seen that the mechanical properties of the diaphragm 10 after alumina grafting are better than those of the membrane only treated with plasma. A certain improvement. Figure 5 is a photo of the base film, commercial ceramic coated diaphragm, and the ceramic grafted diaphragm obtained in Example 1 after heating at 150 ° C for 1 hour. Obviously, the thermal stability of the alumina grafted polyethylene diaphragm obtained in Example 1 Much larger than ungrafted polyethylene separators and larger than commercially available ceramic coated separators. Fig. 6 is the Nyquist plot (Nyquist plot) that the impedance test of the base film, the film only through pulse plasma treatment, the ceramic graft diaphragm obtained in Example 1 is carried out when the number of diaphragms is 1, the oxidation obtained in Example 1 The aluminum-grafted polyethylene separator exhibited the smallest ionic impedance because the grafted alumina improved the affinity of the separator to the electrolyte and ceramic particles did not block the separator pores.

The test mode of this embodiment is:

Infrared spectrum test

Wash the diaphragm with ethanol, dry it, cut it into a disc with a diameter of 15 mm, and fix it in a circular fixture for infrared spectrum testing. The test environment is room temperature, and the wave number is 400-4000 cm ^-1 .

Tensile strength, elongation at break test

According to the provisions of GB/T 1040.3-2006, that is, a type 2 sample (rectangular) with a width of (15±0.1) mm is clamped in the fixture, the initial distance between the fixtures is (100±5) mm, and the test speed is ( 250±10)mm/min.

Heat Shrinkage Test

Carry out in accordance with the provisions of GB/T 36363-2018, that is, cut a square diaphragm of 100mm×diaphragm width in the longitudinal direction of the film roll, and make a longitudinal and horizontal mark. Put the stainless steel plate and two pieces of quantitative filter paper in the middle of the oven, control the temperature so that the stainless steel and filter paper reach (150±1)°C, and then place the diaphragm flat on one of the quantitative filter papers on the stainless steel plate in the middle of the blast-type incubator. After finishing, use another piece of quantitative filter paper to press it, close the door of the incubator, and start timing. After keeping at a temperature of 150°C for 1h±6min, take out the diaphragm, and after the diaphragm returns to room temperature, measure the longitudinal and transverse marking lengths again, and calculate the longitudinal and transverse shrinkage rates of the diaphragm respectively (the reduced length of the diaphragm/the original length of the diaphragm) , take the average of the three test results as the thermal shrinkage rate of the diaphragm.

Ionic Conductivity Test

Carry out according to the regulations of GB/T 36363-2018, that is, cut 4 diaphragms that match the resistance test mold, put the diaphragm into lithium hexafluorophosphate (LiPF ₆ ), ethylene carbonate (EC), carbonic acid with a concentration of 1.0mol/L Ethyl methyl ester (EMC), dimethyl carbonate (DMC) in the electrolyte solution with a volume ratio of 1:1:1, keep sealed, and soak for 2 hours. Inject the electrolyte into the resistance test mold, put a layer of diaphragm, and test its AC resistance. Then put in layer 1, and test its AC impedance resistance until it is placed in layer 4, and measure four AC impedance resistances respectively. During the test, it is necessary to ensure that the electrolyte in the resistance test mold can fully soak the placed separator. Draw a curve with the number of diaphragm layers as the abscissa and the diaphragm resistance as the ordinate, and calculate the slope and linear fitting degree of the curve. When the linear fitting degree is greater than 0.99, the ionic conductivity σ of the diaphragm is calculated according to the following formula.

σ=d/(k*S)

Where d is the thickness of a layer of diaphragm in micrometers (μm), k is the slope of the curve when the fitting degree is greater than 0.99, and S is the area of the diaphragm cut out during the test, in square centimeters (cm ² ).

Example 2

The procedure is the same as that in Example 1, except that the parameters of the plasma treatment are 200W power, 1Hz, 20% duty cycle, and 5m/min operating speed.

Example 3

The procedure is the same as in Example 1, except that the gas flow rate used is 5 mL/min.

Example 4

The procedure is the same as in Example 1, except that the plasma gas source is water vapor.

Example 5

The procedure was the same as in Example 1, except that a polypropylene separator with a thickness of 16 microns was used.

Example 6

The procedure is the same as in Example 1, except that the pH of the hydrolyzed solution is 4, and the time for the diaphragm to pass through the solution is 10 hours.

Example 7

The procedure is the same as in Example 1, except that the mass fraction of alumina in the hydrolyzed solution is 10%, the mass fraction of the coupling agent is 1%, and the time for the diaphragm to pass through the solution is 14 hours.

Example 8

The procedure is the same as that in Example 1, except that the oxide added in the solution is nano-titanium oxide, and the coupling agent is vinyltriethoxysilane.

Comparative example 1

The polyethylene separator with a thickness of 9 microns was used as the separator of Comparative Example 1 without any treatment.

Comparative example 2

The procedure is the same as in Example 1, except that the diaphragm is taken out after pulse plasma treatment, and the obtained polyethylene diaphragm containing groups such as hydroxyl groups, carboxyl groups, epoxy groups, and peroxy groups on the surface is used as comparative example 2. diaphragm.

Comparative example 3

The commercially available ceramic-coated separator (2 μm Al ₂ O ₃ and 2 μm PVDF-coated 12 μm PE separator) without any treatment was used as the separator of Comparative Example 3.

Table 1 is the performance comparison between the embodiment 1-8 prepared by the method of the present invention and the comparative example 1-3

It can be seen from Table 1 that the ceramic graft separator prepared in the embodiment of the present invention has excellent thermal stability and electrolyte affinity, which solves the shortcomings of poor thermal stability and insufficient electrolyte wettability of polyolefin separators on the market. Thereby improving the safety and rate performance of batteries using these separators.

The above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (12)

1. A production device for a ceramic grafted separator of a secondary battery, characterized in that: the device comprises a pulse plasma device and a soaking grafting device, wherein the pulse plasma device comprises a reaction cabin body, a plasma treatment area and a winding and unwinding system are arranged in the reaction cabin body, the plasma treatment area is arranged in the middle position in the reaction cabin body and is connected with a pulse power supply, the winding and unwinding system comprises a winding shaft and a unwinding shaft which are respectively arranged at two sides of the plasma treatment area, and a vacuum pump and a plasma source are arranged outside the reaction cabin body; the soaking grafting device comprises a reaction tank filled with grafting solution and a winding and unwinding mechanism, wherein the winding and unwinding mechanism comprises an unwinding roller, a winding roller and a guide roller, the unwinding roller is arranged on the left side of the upper end of the reaction tank, the winding roller is arranged on the right side outside the upper end of the reaction tank, a diaphragm on the unwinding roller enters the reaction tank from the left end of the reaction tank to carry out grafting reaction, and the diaphragm after grafting reaction is wound on the winding roller after coming out from the right end of the reaction tank.

2. The production device according to claim 1, wherein: the reaction cabin body is a rectangular cabin, the reaction tank is a rectangular tank with an opening at the upper end, three guide rollers are arranged, two guide rollers are arranged on the left side and the right side of the reaction tank, which are close to the bottom of the reaction tank, the third guide roller is arranged above the right end of the reaction tank, the production device further comprises a flushing device and a drying device, and the diaphragm after the grafting reaction is rolled on the rolling roller after being treated by the flushing device and the drying device.

3. A method for preparing a ceramic grafted separator for a secondary battery, comprising the steps of:

1) Treating the separator substrate in an oxygen-containing atmosphere using a pulsed plasma process:

placing a diaphragm substrate in a winding and unwinding system in a pulse plasma device, opening a vacuum pump, introducing a plasma source which is gas or liquid containing oxygen elements, regulating the gas flow to be 10-400 mL/min, when the gas pressure in a reaction chamber is lower than 10Pa, starting a pulse plasma discharge power supply, regulating the output power to be 10-300W, regulating the pulse frequency to be 0-10000 Hz, and simultaneously starting the winding and unwinding system, wherein the duty ratio is 5-95%, the operation speed is 1-10 m/min, the temperature in the reaction chamber is 20-60 ℃, and taking out the diaphragm after all diaphragms pass through a plasma treatment area to obtain the diaphragm containing hydroxyl, carboxyl, epoxy or/and peroxy groups;

2) Placing the treated diaphragm into a grafting solution of a soaking grafting device for grafting reaction:

the diaphragm treated in the step 1) passes through a grafting solution through a winding and unwinding mechanism, wherein the grafting solution is a mixed solution of coupling agent grafting monomers containing unsaturated bond groups and nano oxide ceramic particles, the grafting solution is an acidic system aqueous solution with the pH value of 0-6, the mass percent of the coupling agent grafting monomers contained in the grafting solution is 1-5%, the mass percent of the nano oxide ceramic particles contained in the grafting solution is 1-20%, the grafting reaction temperature is 40-80 ℃, and the reaction time is 2-20 hours;

3) The diaphragm is delivered out through the winding and unwinding mechanism and sequentially passes through the flushing device and the drying device, and finally the ceramic grafted diaphragm is obtained through winding.

4. A method of preparation according to claim 3, characterized in that: the plasma source of step 1) comprises air, oxygen, water vapor or ozone; the membrane substrate comprises one of polyethylene, polypropylene and polyethylene/polypropylene composite membrane, and has a thickness of 5-20 micrometers.

5. The method of manufacturing according to claim 4, wherein: the plasma source adopts oxygen, and the flow is 50-100 mL/min.

6. A method of preparation according to claim 3, characterized in that: the discharge output power of the pulse plasma device in the step 1) is 50W, the pulse frequency is 100Hz, the duty ratio is 30%, the diaphragm winding speed during plasma treatment is 2m/min, and the temperature in the reaction chamber body is 25 ℃.

7. A method of preparation according to claim 3, characterized in that: the coupling agent grafting monomer of the step 2) adopts one or more of vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tri (beta-methoxyethoxy) silane and gamma-methacryloxypropyl trimethoxy silane; the nanometer inorganic oxide adopts one or more of alumina, silica, titania and zirconia, and the grain diameter is 50-100 nm.

8. The method of manufacturing according to claim 7, wherein: the coupling agent grafting monomer adopts vinyl trimethoxy silane or vinyl triethoxy silane; the nanometer inorganic oxide adopts alumina with the grain diameter of 50nm.

9. A method of preparation according to claim 3, characterized in that: the pH value regulator of the grafting solution in the step 2) is one or more of hydrochloric acid, sulfuric acid, nitric acid and acetic acid.

10. A method of preparation according to claim 3, characterized in that: the pH value of the grafting solution in the step 2) is 1, the mass percentage of the coupling agent grafting monomer contained in the grafting solution is 2%, and the mass percentage of the nano oxide ceramic particles contained in the grafting solution is 2%; the grafting reaction temperature was 70 ℃.

11. A method of preparation according to claim 3, characterized in that: the washing device in the step 3) is pure water washing, and the drying device is used for drying by hot air at 70+/-5 ℃.

12. The method of manufacturing according to claim 1, characterized in that: the secondary battery comprises a lithium ion battery, a sodium ion battery and a zinc ion battery.