阅读说明：本技术 一种隔膜及电池 (Diaphragm and battery ) 是由 王翔 彭冲 李俊义 徐延铭 于 2021-07-15 设计创作，主要内容包括：本申请公开了一种隔膜及电池,涉及锂离子电池技术领域,该隔膜包括：隔膜本体和涂覆于所述隔膜本体上的阻燃涂层；其中,所述阻燃涂层包括自由基捕捉剂和包裹所述自由基捕捉剂的聚合物；所述自由基捕捉剂为2,2-二苯基-1-三硝基苯肼、对苯醌、四甲基苯醌、2-甲基-2-亚硝基甲烷和苯基-N-叔丁基硝酮中的至少一种；所述聚合物的熔点温度或者粘流温度低于所述隔膜的热失效临界温度。这样,当电池的温度较高时,包裹在自由基捕捉剂外层的聚合物被高温熔化,使得自由基捕捉剂与电解液融合,对电解液分解产生的氧自由基进行捕获,从而避免电池发生爆炸。(The application discloses diaphragm and battery relates to lithium ion battery technical field, and this diaphragm includes: the diaphragm comprises a diaphragm body and a flame-retardant coating coated on the diaphragm body; wherein the flame retardant coating comprises a free radical scavenger and a polymer encapsulating the free radical scavenger; the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butyl nitrone; the melting point temperature or viscous flow temperature of the polymer is below the thermal failure critical temperature of the separator. Therefore, when the temperature of the battery is higher, the polymer wrapped on the outer layer of the free radical scavenger is melted at high temperature, so that the free radical scavenger is fused with the electrolyte to capture oxygen radicals generated by decomposition of the electrolyte, and the explosion of the battery is avoided.)

1. A septum, comprising: the diaphragm comprises a diaphragm body and a flame-retardant coating coated on the diaphragm body;

wherein the flame retardant coating comprises a free radical scavenger and a polymer encapsulating the free radical scavenger;

the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butyl nitrone;

the melting point temperature or viscous flow temperature of the polymer is below the thermal failure critical temperature of the separator.

2. The separator of claim 1, wherein the flame retardant coating is applied to a first surface and/or a second surface of the separator body, the first surface and the second surface being opposite sides of the separator body.

3. The separator of claim 1, wherein the flame retardant coating is applied at a thickness ranging from 1 micron to 8 microns.

4. The separator according to claim 1, wherein the polymer is any one of polypropylene, polyethylene, and a silicon-based polymer.

5. The membrane of claim 4, wherein the polymer has a melting point temperature or viscous flow temperature in the range of 90 ℃ to 130 ℃.

6. A membrane according to any one of claims 1 to 5, characterized in that the preparation method of the membrane comprises:

adding the polymer into a solvent, heating, and stirring after the polymer is dissolved to obtain a first solution, wherein the melting point temperature or viscous flow temperature of the polymer is lower than the thermal failure critical temperature of the diaphragm;

adding the free radical scavenger into the solvent and stirring to obtain a second solution, wherein the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butylnitrone;

adding the second solution to the rapidly stirred first solution to obtain a third solution of the polymer coated with the radical scavenger;

adding the mesoacid amide into the third solution, stirring, and evaporating the solvent to obtain a particle substance of the polymer-coated free radical scavenger;

adding the granular substance into a carboxymethyl cellulose solution, stirring, and adding a polyacrylic acid aqueous solution to obtain the flame-retardant coating;

and coating the flame-retardant coating on a diaphragm body to obtain the diaphragm.

7. The membrane of claim 6, wherein the solvent is at least one of xylene, toluene, and decalin.

8. The membrane of claim 6, wherein the concentration of the polymer in the first solution ranges from 1% to 4%.

9. A battery, comprising: a positive electrode sheet, a negative electrode sheet, and the separator according to any one of claims 1 to 8.

10. The battery according to claim 9, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, and the separator, the positive electrode sheet, and the negative electrode sheet are wound.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a diaphragm and a battery.

Background

The lithium ion battery has the advantages of high energy density, low self-discharge, no memory effect and the like, and is widely applied to the fields of mobile phones, flat plates, power industries and the like. When the lithium ion battery is abused in the using process, a large amount of gas can be decomposed from the electrolyte of the lithium ion battery, so that the battery explodes. In order to solve the problem, in the prior art, a flame retardant is usually directly added into the electrolyte, and the flame retardant can release free radicals at high temperature to capture oxygen radicals generated by decomposition of the electrolyte, so that the problem of battery explosion is solved. However, in this way, the required amount of the flame retardant is large, which greatly increases the viscosity of the electrolyte, thereby causing the performance of the battery to be reduced.

Disclosure of Invention

The embodiment of the invention provides a diaphragm and a battery, and aims to solve the problem that the viscosity of an electrolyte is greatly improved and the performance of the battery is reduced in the conventional mode of directly adding a flame retardant into the electrolyte.

In a first aspect, embodiments of the present application provide a membrane, including: the diaphragm comprises a diaphragm body and a flame-retardant coating coated on the diaphragm body;

wherein the flame retardant coating comprises a free radical scavenger and a polymer encapsulating the free radical scavenger;

the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butyl nitrone;

the melting point temperature or viscous flow temperature of the polymer is below the thermal failure critical temperature of the separator.

Optionally, the flame retardant coating is applied to a first surface and/or a second surface of the separator body, the first surface and the second surface being opposite sides of the separator body.

Optionally, the flame retardant coating layer has a coating thickness ranging from 1 micron to 8 microns.

Optionally, the polymer is any one of polypropylene, polyethylene and a silicon-based polymer.

Optionally, the melting point temperature or viscous flow temperature of the polymer ranges from 90 ℃ to 130 ℃.

Optionally, the preparation method of the separator comprises:

adding the polymer into a solvent, heating, and stirring after the polymer is dissolved to obtain a first solution, wherein the melting point temperature or viscous flow temperature of the polymer is lower than the thermal failure critical temperature of the diaphragm;

adding the free radical scavenger into the solvent and stirring to obtain a second solution, wherein the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butylnitrone;

adding the second solution to the rapidly stirred first solution to obtain a third solution of the polymer coated with the radical scavenger;

adding the mesoacid amide into the third solution, stirring, and evaporating the solvent to obtain a particle substance of the polymer-coated free radical scavenger;

adding the granular substance into a carboxymethyl cellulose solution, stirring, and adding a polyacrylic acid aqueous solution to obtain the flame-retardant coating;

and coating the flame-retardant coating on a diaphragm body to obtain the diaphragm.

Alternatively, the solvent is xylene, toluene or decalin.

Optionally, the concentration of the polymer in the first solution ranges from 1% to 4%.

In a second aspect, an embodiment of the present application provides a battery, including: a positive electrode sheet, a negative electrode sheet, and a separator as described in the first aspect.

Optionally, the separator is located between the positive electrode sheet and the negative electrode sheet, and the separator, the positive electrode sheet and the negative electrode sheet are wound.

In an embodiment of the present application, the diaphragm includes: the diaphragm comprises a diaphragm body and a flame-retardant coating coated on the diaphragm body; wherein the flame retardant coating comprises a free radical scavenger and a polymer encapsulating the free radical scavenger; the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butyl nitrone; the melting point temperature or viscous flow temperature of the polymer is below the thermal failure critical temperature of the separator. Therefore, when the temperature of the battery is lower, the free radical trapping agent is wrapped by the polymer and is positioned on the diaphragm body, and the viscosity of the electrolyte cannot be influenced; when the temperature of the battery is higher, the polymer wrapped on the outer layer of the free radical scavenger is melted at high temperature, so that the free radical scavenger is fused with the electrolyte to capture oxygen radicals generated by decomposition of the electrolyte, and the battery is prevented from exploding. Therefore, by using the separator, not only can the performance of the battery be guaranteed when the temperature of the battery is low, but also the safety of the battery can be improved when the temperature of the battery is high.

Drawings

FIG. 1 is a schematic structural diagram of a diaphragm provided in an embodiment of the present application;

fig. 2 is a flowchart of a method for manufacturing a separator provided in an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. Without conflict, the embodiments and features of the embodiments described below may be combined with each other. On the basis of the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort belong to the protection scope of the present application.

The embodiment of the application provides a diaphragm. Referring to fig. 1, fig. 1 is a schematic structural diagram of a diaphragm provided in an embodiment of the present application. As shown in fig. 1, the diaphragm includes: a separator body 100 and a flame retardant coating 200 coated on the separator body 100;

wherein the flame retardant coating 200 comprises a radical scavenger and a polymer encapsulating the radical scavenger;

the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butyl nitrone;

the melting point temperature or viscous flow temperature of the polymer is below the critical temperature for thermal failure of the separator.

Specifically, the separator body 100 has a main function of separating a positive electrode sheet and a negative electrode sheet of a battery, preventing short circuit due to contact between the two electrodes, and a function of allowing electrolyte ions to pass therethrough. The material of the separator body 100 is electrically non-conductive, and the physical and chemical properties thereof have a great influence on the performance of the battery. The separator body 100 used differs depending on the type of battery. In the lithium ion battery system, since the electrolyte is an organic solvent, a material resistant to the organic solvent is required for the separator body 100. A polyolefin porous film having high strength and being thinned can be generally used as the separator body 100. The flame retardant coating 200 may include a radical scavenger and a polymer coating the radical scavenger, and is used to release the radical scavenger in the polymer after the polymer is melted due to a high temperature of the electrolyte, so as to scavenge oxygen radicals generated by decomposition of the electrolyte, and thus the flame retardant coating 200 may achieve the effects of preventing combustion and preventing explosion. Specifically, the radical scavenger is a substance that can react with an active radical to form a radical or a stable molecule that can exist stably. The radical scavenger may be any one or a combination of any more of 2, 2-diphenyl-1-trinitrophenylhydrazine (DPPH), p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane, and phenyl-N-tert-butylnitrone, and the like, and the present application is not particularly limited. When the free radical scavenger is prepared by blending 2, 2-diphenyl-1-trinitrophenyl hydrazine (DPPH) and one or more of p-benzoquinone, tetramethyl benzoquinone, 2-methyl-2-nitrosomethane, phenyl-N-tert-butyl nitrone and the like, the percentage of the 2, 2-diphenyl-1-trinitrophenyl hydrazine in the free radical scavenger is preferably more than 50%, so that the performance of the free radical scavenger can be optimal.

The thermal failure critical temperature of the separator is the critical temperature of the failure state reached by the separator under the condition of thermal shrinkage. That is, the thermal failure critical temperature of the separator is a temperature at which the separator shrinks by heat to a critical state where the positive electrode sheet and the negative electrode sheet are not completely separated. If the temperature in the battery reaches the thermal failure critical temperature of the diaphragm, the diaphragm can be seriously shrunk, and the positive plate and the negative plate in the battery are short-circuited to fail.

It is noted that the polymer in this application is a low melting point polymer such that the polymer reaches its melting point temperature or viscous flow temperature before the temperature within the cell reaches the critical temperature for thermal failure of the separator. The polymer may be a crystalline polymer, such as Polypropylene (PP), Polyethylene (PE), etc., or may be a non-crystalline polymer, such as a silicon-based polymer, etc. When the polymer in this application is a crystalline polymer, the melting point temperature corresponds to the temperature at which the crystalline polymer can be transformed from a solid state to a liquid state; when amorphous polymers are used as polymers in the present application, the viscous flow temperature corresponds to the temperature at which the amorphous polymer can be transformed from a high-elastic state to a viscous state.

In the embodiment, since the flame retardant coating 200 is coated on the separator body 100, when the temperature of the battery is low, the radical scavenger is wrapped by the polymer and is located on the separator body, and the viscosity of the electrolyte is not affected; when the temperature of the battery is higher, the polymer wrapped on the outer layer of the free radical scavenger is melted at high temperature, so that the free radical scavenger is fused with the electrolyte to capture oxygen radicals generated by decomposition of the electrolyte, and the battery is prevented from exploding. Therefore, by using the separator, not only can the performance of the battery be guaranteed when the temperature of the battery is low, but also the safety of the battery can be improved when the temperature of the battery is high.

Further, the flame retardant coating layer 200 is applied to a first surface and/or a second surface of the separator body 100, the first surface and the second surface being opposite to each other of the separator body 100.

Specifically, the flame retardant coating 200 may be coated on one surface of the diaphragm body 100, such as a first surface or a second surface of the diaphragm body 100; it may also be coated on both surfaces of the diaphragm body 100, such as the first surface and the second surface of the diaphragm body 100, which is not particularly limited in this application. The first surface here may refer to one surface that is in contact with a positive electrode tab in the battery, and the second surface may refer to one surface that is in contact with a negative electrode tab in the battery.

In one embodiment, the flame retardant coating layer 200 may be coated on both the first surface and the second surface of the separator body 100, such that when the temperature inside the battery reaches the melting point temperature or the viscous flow temperature of the polymer, the flame retardant coating layer 200 on both sides of the separator body 100 may release the radical scavenger, so that the radical scavenger can be rapidly distributed at different positions of the electrolyte.

Further, the flame retardant coating layer 200 is applied at a thickness ranging from 1 to 8 micrometers.

It should be noted that the thicker the coating thickness of the flame retardant coating layer 200 is, the higher the content of the radical scavenger in the battery is, and the better the flame retardant effect is. But in order to ensure that the volume of the roll core structure in the battery is not influenced by the thickness of the diaphragm, the coating thickness of the flame-retardant coating layer 200 can be set within the range of 1-8 microns, so that the volume of the roll core structure is not greatly influenced by the diaphragm, and a better flame-retardant effect can be achieved.

Further, the polymer is any one of polypropylene, polyethylene and silicon-based polymers.

In one embodiment, since the melting point temperature of polypropylene and polyethylene and the viscous flow temperature of silicon-based polymer are low, any one of polypropylene, polyethylene and silicon-based polymer can be selected as the polymer in the present application. Thus, when the internal temperature of the battery reaches a lower temperature, the polymer can be melted, and the free radical scavenger wrapped in the polymer can be released.

Further, the melting point temperature or viscous flow temperature of the polymer ranges from 90 ℃ to 130 ℃.

It should be noted that different types of polymers have different melting point temperatures or viscous flow temperatures. In this embodiment, a polymer having a melting point temperature or a viscous flow temperature in a range of 90 ℃ to 130 ℃, such as polypropylene, polyethylene, or a silicon-based polymer, may be selected, and mixed with the radical scavenger to form the flame retardant coating 200.

Referring to fig. 2, fig. 2 is a flowchart of a method for manufacturing a separator provided in an embodiment of the present application. The preparation method of the diaphragm comprises the following steps:

step 201, adding a polymer into a solvent, heating, and stirring after the polymer is dissolved to obtain a first solution, wherein the melting point temperature or viscous flow temperature of the polymer is lower than the thermal failure critical temperature of a diaphragm;

step 202, adding a free radical scavenger into a solvent and stirring to obtain a second solution, wherein the free radical scavenger is at least one of 2, 2-diphenyl-1-trinitrophenylhydrazine, p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane and phenyl-N-tert-butylnitrone;

step 203, adding the second solution into the rapidly stirred first solution to obtain a third solution of the polymer-coated free radical scavenger;

step 204, adding the mesoacid amide into the third solution, stirring, and evaporating the solvent to dryness to obtain a polymer-coated free radical scavenger particle substance;

step 205, adding the granular substances into a carboxymethyl cellulose solution, stirring, and adding a polyacrylic acid aqueous solution to obtain a flame-retardant coating;

and step 206, coating the flame-retardant coating on the diaphragm body to obtain the diaphragm.

The step 201 may be executed simultaneously with the step 202, may be executed prior to the step 202, or may be executed after the step 202, which is not limited in this application.

Specifically, the polymer may be a crystalline polymer, such as Polypropylene (PP), Polyethylene (PE), and the like, or may be an amorphous polymer, such as a silicon-based polymer, and the like. Adding the polymer into a solvent, heating the solvent to the melting point temperature or viscous flow temperature of the polymer, and fully stirring after the polymer is dissolved in the solvent to obtain a first solution.

The radical scavenger may be any one or a combination of any more of 2, 2-diphenyl-1-trinitrophenylhydrazine (DPPH), p-benzoquinone, tetramethylbenzoquinone, 2-methyl-2-nitrosomethane, and phenyl-N-tert-butylnitrone, and the present application is not particularly limited thereto. The radical scavenger is added to the solvent and sufficiently stirred to obtain a second solution.

Thus, the second solution is added to the rapidly stirred first solution to obtain a third solution of polymer-encapsulated radical scavenger. Then stirring the third solution at a low speed, adding the mesoacid amide, fully stirring, and evaporating the solvent to dryness to obtain a polymer-coated free radical scavenger particle substance; then adding the granular substance into a carboxymethyl cellulose (CMC) solution, dispersing the granular substance through the CMC, adding a polyacrylic acid aqueous solution, and adhering the dispersed granular substance through the polyacrylic acid aqueous solution to obtain the flame-retardant coating. And finally, coating the flame-retardant coating on the first surface and/or the second surface of the diaphragm body to obtain the diaphragm.

The diaphragm prepared by the preparation method of the embodiment can be positioned on the diaphragm body and the free radical scavenger is wrapped by the polymer when the temperature of the battery is low, so that the viscosity of the electrolyte cannot be influenced; when the temperature of the battery is higher, the polymer wrapped on the outer layer of the free radical scavenger is melted at high temperature, so that the free radical scavenger is fused with the electrolyte to capture oxygen free radicals generated by decomposition of the electrolyte, and the battery is prevented from exploding. Therefore, by using the separator, not only can the performance of the battery be guaranteed when the temperature of the battery is low, but also the safety of the battery can be improved when the temperature of the battery is high.

Further, the solvent is xylene, toluene or decalin.

Specifically, any one of xylene, toluene and decalin can be selected as a solvent to participate in the preparation process of the first solution and the second solution. Because the substance has a low boiling point, after the first solution and the second solution are mixed to obtain a third solution, the solvent can be evaporated by heating the third solution to dryness to obtain the polymer-coated free radical scavenger particle substance.

Further, the concentration of the polymer in the first solution ranges from 1% to 4%.

Specifically, when the polymer is added into the solvent to prepare the first solution, the polymer may be mixed according to a pre-calculated ratio, so that the concentration of the polymer in the first solution ranges from 1% to 4%, and thus, when the first solution is mixed with the second solution, the polymer is beneficial to being capable of wrapping the radical scavenger in the second solution.

In addition, this application embodiment also provides a battery, and this battery includes: positive plate, negative plate and the diaphragm.

Alternatively, the separator is located between the positive electrode sheet and the negative electrode sheet, and the separator, the positive electrode sheet and the negative electrode sheet are wound.

It should be noted that the specific embodiment of the battery is the same as the embodiment of the separator described above, and the same technical effects can be achieved, and are not described herein again.

The following examples are provided to further illustrate the advantageous effects of the present invention.

Example 1:

and winding the conventional separator (i.e. the separator body without the flame-retardant coating) and the positive plate and the negative plate into a battery. The pass rate of the safety test was 40%.

Example 2:

heating polyethylene in xylene to 120 ℃ to dissolve the polyethylene, wherein the concentration is 2 percent, obtaining a first solution, stirring the first solution at a high speed, and dissolving 2, 2-diphenyl-1-trinitrophenylhydrazine in the xylene solution to obtain a second solution; adding the second solution into the first solution which is rapidly stirred to obtain a third solution of the polymer-coated radical scavenger, stirring at a low speed, adding the mesoacid amide, and evaporating the solvent to finally obtain polyethylene-coated radical scavenger small particles; dispersing the small particles in CMC solution, uniformly coating on a diaphragm to obtain a final diaphragm, and winding the final diaphragm, the positive plate and the negative plate into a battery. The pass rate of the safety test is 100%.

Example 3:

heating polyethylene in xylene to 120 ℃ to dissolve the polyethylene, wherein the concentration of the polyethylene is 2 percent to obtain a first solution, stirring the first solution at a high speed, and dissolving p-benzoquinone in the xylene solution to obtain a second solution; adding the second solution into the first solution which is rapidly stirred to obtain a third solution of the polymer-coated radical scavenger, stirring at a low speed, adding the mesoacid amide, and evaporating the solvent to finally obtain polyethylene-coated radical scavenger small particles; dispersing the small particles in CMC solution, uniformly coating on a diaphragm to obtain a final diaphragm, and winding the final diaphragm, the positive plate and the negative plate into a battery. The pass rate of the safety test was 90%.

Example 4:

heating polyethylene in xylene to 120 ℃ to dissolve the polyethylene, wherein the concentration of the polyethylene is 2 percent to obtain a first solution, stirring at a high speed, and dissolving tetramethyl benzoquinone in the xylene solution to obtain a second solution; adding the second solution into the first solution which is rapidly stirred to obtain a third solution of the polymer-coated radical scavenger, stirring at a low speed, adding the mesoacid amide, and evaporating the solvent to finally obtain polyethylene-coated radical scavenger small particles; dispersing the small particles in CMC solution, uniformly coating on a diaphragm to obtain a final diaphragm, and winding the final diaphragm, the positive plate and the negative plate into a battery. The pass rate of the safety test was 95%.

Example 5:

heating polyethylene in xylene to 120 ℃ to dissolve the polyethylene, wherein the concentration of the polyethylene is 2 percent to obtain a first solution, stirring the first solution at a high speed, and dissolving 2-methyl-2-nitrosomethane in the xylene solution to obtain a second solution; adding the second solution into the first solution which is rapidly stirred to obtain a third solution of the polymer-coated radical scavenger, stirring at a low speed, adding the mesoacid amide, and evaporating the solvent to finally obtain polyethylene-coated radical scavenger small particles; dispersing the small particles in CMC solution, uniformly coating on a diaphragm to obtain a final diaphragm, and winding the final diaphragm, the positive plate and the negative plate into a battery. The pass rate of the safety test was 95%.

Example 6:

heating polyethylene in xylene to 120 ℃ to dissolve the polyethylene, wherein the concentration is 2 percent, obtaining a first solution, stirring at a high speed, and dissolving phenyl-N-tert-butyl nitrone in the xylene solution to obtain a second solution; adding the second solution into the first solution which is rapidly stirred to obtain a third solution of the polymer-coated radical scavenger, stirring at a low speed, adding the mesoacid amide, and evaporating the solvent to finally obtain polyethylene-coated radical scavenger small particles; dispersing the small particles in CMC solution, uniformly coating on a diaphragm to obtain a final diaphragm, and winding the final diaphragm, the positive plate and the negative plate into a battery. The pass rate of the safety test was 95%.

The safety tests of examples 1 to 6 above, all of which were conducted at 130 ℃ for 1 hour at full charge, judged whether the battery ignited or exploded.

As can be seen from the above examples 1 to 6, example 1 differs from examples 2, 3, 4, 5 and 6 in that: example 1 used a conventional separator, while examples 2 to 6 used separators coated with a flame retardant coating. By comparison, the safety test was shown to pass much higher with the separator coated with the flame retardant coating than with the conventional separator.

The difference between examples 2 to 6 is that: the radical scavenger used in example 2 was 2, 2-diphenyl-1-trinitrophenylhydrazine, the radical scavenger used in example 3 was p-benzoquinone, the radical scavenger used in example 4 was tetramethylbenzoquinone, the radical scavenger used in example 5 was 2-methyl-2-nitrosomethane, and the radical scavenger used in example 6 was phenyl-N-tert-butylnitrone. By comparison, it is known that 2, 2-diphenyl-1-trinitrophenylhydrazine is better as a radical scavenger, and the radical scavenger of other substances has a closer effect.

The embodiments described above are described with reference to the drawings, and various other forms and embodiments are possible without departing from the principles of the present application, so that the present application is not to be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. In the drawings, the size and relative sizes of components may be exaggerated for clarity. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, components, and/or components, but do not preclude the presence or addition of one or more other features, integers, components, and/or groups thereof. Unless otherwise indicated, a range of values, when stated, includes the upper and lower limits of the range and any subranges therebetween.

While the foregoing is directed to the preferred embodiment of the present application, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the principles of the disclosure and, therefore, the scope of the disclosure is to be defined by the appended claims.