阅读说明：本技术 一种锂离子电池隔离膜 (Lithium ion battery isolating membrane ) 是由 孙先维 赖旭伦 晋沛沛 符宽 李富 陈杰 杨山 郑明清 于 2020-12-21 设计创作，主要内容包括：本发明属于锂离子电池技术领域,尤其涉及一种锂离子电池隔离膜,包括基膜、陶瓷涂层和聚合物涂层,所述陶瓷涂层设置于所述基膜的一面,所述聚合物涂层设置于所述基膜的另一面以及所述陶瓷涂层的表面；所述陶瓷涂层包括陶瓷颗粒、纳米纤维和抗静电剂A,所述聚合物涂层包括高分子材料和抗静电剂B。相比于现有技术,本发明的隔离膜热稳定性好、电解液浸润性好,且具有抗静电作用。(The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery isolating membrane which comprises a base membrane, a ceramic coating and a polymer coating, wherein the ceramic coating is arranged on one surface of the base membrane, and the polymer coating is arranged on the other surface of the base membrane and the surface of the ceramic coating; the ceramic coating comprises ceramic particles, nano fibers and an antistatic agent A, and the polymer coating comprises a high molecular material and an antistatic agent B. Compared with the prior art, the isolating membrane has the advantages of good thermal stability, good electrolyte wettability and antistatic effect.)

1. The lithium ion battery isolating membrane is characterized by comprising a base membrane, a ceramic coating and a polymer coating, wherein the ceramic coating is arranged on one side of the base membrane, and the polymer coating is arranged on the other side of the base membrane and the surface of the ceramic coating; the ceramic coating comprises ceramic particles, nano fibers and an antistatic agent A, and the polymer coating comprises a high molecular material and an antistatic agent B.

2. The lithium ion battery separator according to claim 1, wherein the antistatic agent a coats the surfaces of the ceramic particles and the nanofibers, and the antistatic agent B coats the surface of the polymer material.

3. The lithium ion battery isolation membrane of claim 1, wherein the ceramic coating is formed by coating and drying ceramic slurry with a solid content of 26-35%, and the ceramic slurry specifically comprises ceramic particles, a thickening agent, nanofibers, a dispersing agent, a binder and an antistatic agent A; the ceramic particles account for 10-50% of the total mass of the ceramic slurry, and the antistatic agent A accounts for 0.2-10% of the total mass of the ceramic slurry.

4. The lithium ion battery isolation membrane of claim 1, wherein the polymer coating is formed by coating and drying polymer slurry with the solid content of 3-8%, and the polymer slurry comprises a high polymer material, a thickening agent, a dispersing agent, a binder and an antistatic agent B; the polymer material accounts for 20-80% of the total mass of the polymer slurry, and the antistatic agent B accounts for 0.2-10% of the total mass of the polymer slurry.

5. The lithium ion battery separator according to any of claims 1-3, wherein the ceramic particles comprise SiO₂、Al₂O₃、CaO、TiO₂、MgO、ZnO、SnO₂、ZrO₂、AlOOH、Mg(OH)₂And BaSO₄At least one of; the particle size of the ceramic particles is 0.5-1.2 μm.

6. The lithium ion battery separator according to any of claims 1 to 3, wherein the nanofibers comprise at least one of methylcellulose, carboxymethylcellulose, hydroxyethylcellulose and hydroxypropylmethylcellulose, and have a relative molecular weight of 10000 to 200000, a diameter of 5 to 1000nm and a length of 5 to 1000 nm.

7. The lithium ion battery separator according to claim 1 or 4, wherein the glass transition temperature of the polymer material is 30 to 100 ℃ and the particle size is 0.3 to 0.8 μm.

8. The lithium ion battery separator according to claim 1, wherein the antistatic agent A and the antistatic agent B are at least one of a derivative of an amine, a quaternary ammonium salt, a sulfate, a phosphate, and a derivative of polyethylene glycol, respectively.

9. The lithium ion battery separator according to claim 1, wherein the polymer coating has a thickness of 0.2 to 10 μm and a coating areal density of 0.05 to 5.0g/m²。

10. The lithium ion battery separator according to claim 1, wherein the base film is a PE film, a PP film or a PE/PP/PE composite film, the base film has a melting point of 130 to 160 ℃, a thickness of 3 to 20 μm, a porosity of 20 to 50%, and an air permeability of 30 to 400sec/100 cc.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery isolating membrane.

Background

The lithium ion battery has the characteristics of high working voltage, large energy density, long cycle life, no memory effect and no pollution, has the advantages of safety, reliability, quick charge and discharge and the like, is a main power supply of various electronic products, is a green and environment-friendly secondary battery without pollution, meets the development requirements of energy and environment protection in various countries at present, and is rapidly increased in the use amount of various industries.

The four key materials of the lithium ion battery are a positive electrode material, a negative electrode material, electrolyte and a diaphragm. The diaphragm has the main functions of isolating the positive electrode and the negative electrode and preventing electrons from passing through, and can allow ions to pass through, so that the lithium ions are rapidly transmitted between the positive electrode and the negative electrode in the charging and discharging process. The battery is manufactured by winding a piece of isolating film, a piece of anode, a piece of isolating film and a piece of cathode in a superposition manner, and then in the winding process, because the static electricity of the isolating film is large or the static electricity removing capability of equipment is weak, after the winding is finished, the pole piece is taken out when the needle is drawn due to the electrostatic adsorption of the isolating film on the winding needle and the pole piece, so that the size is abnormal, the pole lug is staggered, and the like, the battery core is scrapped, and the material cost loss is large.

The isolation film is used as an insulating high polymer material, the dielectric constant is 2.0-2.4, on one hand, the isolation film is coated and processed under the condition of low humidity, the capacity is easy to generate large static electricity, and on the other hand, even if the static electricity removing device is installed on equipment, the static electricity of the isolation film is difficult to be completely removed by the equipment in the high-speed production process. Therefore, the process of winding the isolating film into the battery cell faces the problem that the isolating film brings out the pole piece when the needle is drawn, so that the whole battery cell is scrapped, and the material cost loss is very high.

Disclosure of Invention

The invention aims to: aiming at the defects of the prior art, the lithium ion battery isolating membrane is good in thermal stability and electrolyte wettability and has an antistatic effect.

In order to achieve the purpose, the invention adopts the following technical scheme:

a lithium ion battery isolating membrane comprises a base membrane, a ceramic coating and a polymer coating, wherein the ceramic coating is arranged on one side of the base membrane, and the polymer coating is arranged on the other side of the base membrane and the surface of the ceramic coating; the ceramic coating comprises ceramic particles, nano fibers and an antistatic agent A, and the polymer coating comprises a high molecular material and an antistatic agent B.

As an improvement of the lithium ion battery isolating membrane, the antistatic agent A is coated on the surfaces of the ceramic particles and the nanofiber, and the antistatic agent B is coated on the surface of the high polymer material.

As an improvement of the lithium ion battery isolating membrane, the ceramic coating is formed by coating and drying ceramic slurry with the solid content of 26-35%, and the ceramic slurry specifically comprises ceramic particles, a thickening agent, nano fibers, a dispersing agent, an adhesive and an antistatic agent A; the ceramic particles account for 10-50% of the total mass of the ceramic slurry, and the antistatic agent A accounts for 0.2-10% of the total mass of the ceramic slurry.

As an improvement of the lithium ion battery isolating membrane, the polymer coating is formed by coating and drying polymer slurry with the solid content of 3-8%, and the polymer slurry comprises a high molecular material, a thickening agent, a dispersing agent, an adhesive and an antistatic agent B; the polymer material accounts for 20-80% of the total mass of the polymer slurry, and the antistatic agent B accounts for 0.2-10% of the total mass of the polymer slurry.

As an improvement of the lithium ion battery isolating membrane, the ceramic particles comprise SiO₂、Al₂O₃、CaO、TiO₂、MgO、ZnO、SnO₂、ZrO₂、AlOOH、Mg(OH)₂And BaSO₄At least one of; the particle size of the ceramic particles is 0.5-1.2 μm.

As an improvement of the lithium ion battery isolating membrane, the nano-fiber comprises at least one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, and the nano-fiber has a relative molecular weight of 10000-200000, a diameter of 5-1000 nm and a length of 5-1000 nm.

As an improvement of the lithium ion battery isolating membrane, the glass transition temperature of the high polymer material is 30-100 ℃, and the particle size is 0.3-0.8 mu m.

As an improvement of the lithium ion battery isolating membrane, the antistatic agent A and the antistatic agent B are respectively at least one of amine derivatives, quaternary ammonium salts, sulfuric esters, phosphate esters and polyethylene glycol derivatives.

As an improvement of the lithium ion battery isolating membrane, the thickness of the polymer coating is 0.2-10 mu m, and the coating surface density is 0.05-5.0g/m²。

As an improvement of the lithium ion battery isolating membrane, the base membrane is a PE membrane, a PP membrane or a PE/PP/PE composite membrane, the melting point of the base membrane is 130-160 ℃, the thickness of the base membrane is 3-20 mu m, the porosity of the base membrane is 20-50%, and the air permeability of the base membrane is 30-400 sec/100 cc.

Compared with the prior art, the invention has the beneficial effects that:

1) the isolating membrane is provided with the ceramic coating, ceramic particles and nano fibers in the ceramic coating form compact network structure distribution, so that a framework can be formed, the shrinkage of a base membrane can be inhibited under a high-temperature condition, the thermal stability of the coating is improved, and meanwhile, the pores of the coating formed by the network structure are larger, and the absorption and storage of electrolyte can be improved.

2) The isolating membrane is provided with the ceramic coating, and the nano fibers in the ceramic coating contain stronger polar functional groups, so that the infiltration of electrolyte can be improved, and the problem of insufficient interface of electrolyte circulating for a long time in a battery cell can be solved.

3) The isolating membrane is provided with the ceramic coating and the polymer coating, and the antistatic agent A and the antistatic agent B are respectively arranged in the two coatings, so that the isolating membrane has an antistatic effect, not only can the generation of static electricity in the coating and cutting processes be reduced, but also the conduction and the release of the static electricity can be accelerated, further the equipment investment of the coating and cutting processes on a static eliminator can be reduced, the cost is saved, the bad core pulling in the winding process can be reduced, and the production yield is improved.

Drawings

FIG. 1 is a schematic view of the structure of the separator of the present invention.

Fig. 2 is a schematic view of the structure of the ceramic particles coated with the antistatic agent a in the present invention.

Fig. 3 is a schematic structural view of nanofibers coated with antistatic agent a in the present invention.

FIG. 4 is a schematic structural diagram of a polymer material coated with an antistatic agent B according to the present invention.

Fig. 5 is a graph showing the cycle curves of the batteries manufactured using the separators of example 1 and comparative example 1 in the present invention.

Wherein: 1-base film, 2-ceramic coating, 3-polymer coating, 21-ceramic particles, 22-nano fibers, 23-antistatic agent A, 31-high molecular material and 32-antistatic agent B.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings.

As shown in fig. 1, the lithium ion battery isolation membrane comprises a base membrane 1, a ceramic coating 2 and a polymer coating 3, wherein the ceramic coating 2 is arranged on one side of the base membrane 1, and the polymer coating is arranged on the other side of the base membrane 1 and the surface of the ceramic coating 2; the ceramic coating 2 comprises ceramic particles 21, nano-fibers 22 and an antistatic agent A23, and the polymer coating 3 comprises a high molecular material 31 and an antistatic agent B32.

Further, as shown in fig. 2 to 3, the antistatic agent a23 is coated on the surface of the ceramic particle 21 and the surface of the nanofiber 22, and as shown in fig. 4, the antistatic agent B32 is coated on the surface of the polymer material 31. The antistatic agent A23 is coated on the surface of the ceramic particles 21 and the surface of the nano-fiber 22, and is distributed in a fine layered or rib shape in the coating to form a conductive layer, so that static charge is leaked by taking the conductive layer as a passage, and the volume resistivity of the material is reduced to achieve the antistatic effect. The molecules of the antistatic agent B32 are attached to the surface of the polymer material 31 by coating, spraying or dipping, and the like, so that certain lubricity is provided to the surface of the polymer material 31, the friction coefficient is reduced, and the generation of static charge is inhibited and reduced.

Further, the ceramic coating 2 is formed by coating and drying ceramic slurry with the solid content of 26-35%, wherein the ceramic slurry specifically comprises ceramic particles, a thickening agent, nano fibers, a dispersing agent, an adhesive and an antistatic agent A; the ceramic particles account for 10-50% of the total mass of the ceramic slurry, and the antistatic agent A accounts for 0.2-10% of the total mass of the ceramic slurry.

Further, the polymer coating 3 is formed by coating and drying polymer slurry with the solid content of 3-8%, wherein the polymer slurry comprises a high polymer material, a thickening agent, a dispersing agent, an adhesive and an antistatic agent B; the polymer material accounts for 20-80% of the total mass of the polymer slurry, and the antistatic agent B accounts for 0.2-10% of the total mass of the polymer slurry.

Further, the ceramic particles comprise SiO₂、Al₂O₃、CaO、TiO₂、MgO、ZnO、SnO₂、 ZrO₂、AlOOH、Mg(OH)₂And BaSO₄At least one of; the ceramic particles have a particle size of 0.5 to 1.2 μm. The above ceramic particles have good thermal stability. When the particle size of the ceramic particles is too large, the thickness of the coating is too thick, and the uniformity of the coating is deteriorated; and if the particle size of the ceramic particles is smaller to a certain degree, the risk of blocking the pores exists, and the lithium ion conduction is hindered.

Further, the nano-fiber comprises at least one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, and has a relative molecular weight of 10000-200000, a diameter of 5-1000 nm and a length of 5-1000 nm. The nanofiber forms a network structure, so that the pores of the coating are improved, and the nanofiber has stronger polarity, so that the capability of the coating for absorbing electrolyte can be improved.

Furthermore, the glass transition temperature of the polymer material is 30-100 ℃, and the particle size is 0.3-0.8 μm. Specifically, the polymer material may be PVDF, PMMA, or the like. The glass transition temperature of the high polymer material is 30-100 ℃, and after the battery core is formed by dry pressing or wet pressing, the adhesion between the isolation film and the pole piece can be improved, and the hardness of the battery core is improved. In addition, when the particle size of the polymer material is larger, the thickness of the coating is thicker, and the uniformity of the coating is worse; however, if the particle size of the polymer material is too small to a certain extent, the risk of blocking the pores is present, which hinders the lithium ion conduction.

Further, the antistatic agent a and the antistatic agent B are at least one of amine derivatives, quaternary ammonium salts, sulfuric esters, phosphoric esters, and polyethylene glycol derivatives, respectively. When the antistatic agent A is a nonionic compound, hydrophobic groups of the antistatic agent A are attached to the surface of the material, and hydrophilic groups arranged outwards absorb trace moisture in the environment, so that a conductive layer is formed because water is a liquid with a high dielectric constant, and trace electrolyte contained in the fiber also reduces the surface resistance to a certain extent; when the antistatic agent A is an ionic compound, it has an ionic conduction action by itself. The coating is distributed in a fine layered or rib shape to form a conductive layer, static charge is leaked by taking the conductive layer as a passage, the volume resistivity of the material is reduced to achieve an antistatic effect, and when an isolating film is in contact with a pole piece or a winding needle, the static charge can be directly conducted out. The antistatic agent B has one smooth molecular layer on the surface, and is adhered to the surface of polymer material and combined with the polymer layer via covalent bond, so as to endow the surface of material with certain lubricity, lower friction coefficient, and inhibit and reduce static charge.

Further, the adhesive may be one or more of polyacrylates, polyacrylonitrile, polyvinyl alcohol, silicones, epoxies, and polyurethanes, without limitation.

Further, the thickness of the polymer coating 3 is 0.2-10 μm, and the coating surface density is 0.05-5.0g/m²。

Further, the base film 1 is a PE film, a PP film or a PE/PP/PE composite film, the melting point of the base film 1 is 130-160 ℃, the thickness is 3-20 μm, the porosity is 20-50%, and the air permeability is 30-400 sec/100 cc.

Embodiments of the present invention are illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the claimed invention.

Example 1

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, nano-fibers (methylcellulose with the relative molecular weight of 10000-200000, the diameter of 5-1000 nm and the length of 5-1000 nm), a dispersing agent, a polyacrylate adhesive and an antistatic agent A (amine derivative) according to the dry weight mass ratio of 89.5:0.5:0.5:0.01:5:0.5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent, a polyacrylate adhesive and an antistatic agent B (amine derivative) according to a dry weight mass ratio of 89.5:0.5:0.01:5:0.5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Example 2

The difference from example 1 is: antistatic agent A and antistatic agent B are both quaternary ammonium salts.

The rest is the same as embodiment 1, and the description is omitted here.

Example 3

The difference from example 1 is: antistatic agent A and antistatic agent B are both sulfates.

The rest is the same as embodiment 1, and the description is omitted here.

Example 4

The difference from example 1 is: both antistatic agent A and antistatic agent B are phosphate esters.

The rest is the same as embodiment 1, and the description is omitted here.

Example 5

The difference from example 1 is: both antistatic agent A and antistatic agent B are derivatives of polyethylene glycol.

The rest is the same as embodiment 1, and the description is omitted here.

Example 6

The difference from example 1 is: the nanofiber is carboxymethyl cellulose.

The rest is the same as embodiment 1, and the description is omitted here.

Example 7

The difference from example 1 is: the nanofiber is hydroxyethyl cellulose.

The rest is the same as embodiment 1, and the description is omitted here.

Example 8

The difference from example 1 is: the nano-fiber is carboxymethyl cellulose and hydroxypropyl methyl cellulose.

The rest is the same as embodiment 1, and the description is omitted here.

Example 9

The difference from example 1 is: the polymer material is PVDF.

The rest is the same as embodiment 1, and the description is omitted here.

Example 10

The difference from example 1 is: the high molecular material is PVDF and PMMA.

The rest is the same as embodiment 1, and the description is omitted here.

Comparative example 1

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, a dispersing agent and a polyacrylate adhesive according to the dry weight mass ratio of 89.5:0.5:0.01:5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent and a polyacrylate adhesive according to a dry weight mass ratio of 89.5:0.5:0.01:5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Comparative example 2

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, a dispersing agent, a polyacrylate adhesive and an antistatic agent A (amine derivative) according to the dry weight mass ratio of 89.5:0.5:0.01:5:0.5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent, a polyacrylate adhesive and an antistatic agent B (amine derivative) according to a dry weight mass ratio of 89.5:0.5:0.01:5:0.5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Comparative example 3

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, nano-fibers (methylcellulose with the relative molecular weight of 10000-200000, the diameter of 5-1000 nm and the length of 5-1000 nm), a dispersing agent and a polyacrylate adhesive according to the dry weight mass ratio of 89.5:0.5:0.5:0.01:5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent and a polyacrylate adhesive according to a dry weight mass ratio of 89.5:0.5:0.01:5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Comparative example 4

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, nano-fibers (methylcellulose with the relative molecular weight of 10000-200000, the diameter of 5-1000 nm and the length of 5-1000 nm), a dispersing agent, a polyacrylate adhesive and an antistatic agent A (amine derivative) according to the dry weight mass ratio of 89.5:0.5:0.5:0.01:5:0.5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent and a polyacrylate adhesive according to a dry weight mass ratio of 89.5:0.5:0.01:5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Comparative example 5

Preparing the lithium ion battery isolation membrane:

taking a PE film with the thickness of 12 mu m and the porosity of 35 percent as a base film, coating a heat-resistant ceramic coating on one surface of the base film, and coating a layer of PE film with the thickness of 6 mu m and the coating surface density of 1.2g/m on the other surface of the base film and the surface of the ceramic coating²The polymer coating of (1), wherein:

ceramic coating: mixing and stirring alumina (with the particle size of 0.8 mu m), a thickening agent, nano-fibers (methylcellulose with the relative molecular weight of 10000-200000, the diameter of 5-1000 nm and the length of 5-1000 nm), a dispersing agent and a polyacrylate adhesive according to the dry weight mass ratio of 89.5:0.5:0.5:0.01:5 to form ceramic slurry with the solid content of 30%, coating the ceramic slurry on one surface of a base film in a gravure coating mode, and drying to obtain a ceramic coating;

polymer coating: mixing and stirring PMMA (particle size of 0.5 mu m), a thickening agent, a dispersing agent, a polyacrylate adhesive and an antistatic agent B (amine derivative) according to a dry weight mass ratio of 89.5:0.5:0.01:5:0.5 to form polymer slurry with the solid content of 5%, respectively coating the polymer slurry on the other surface of the base film and the surface of the ceramic coating in a gravure coating mode, and drying to obtain the polymer coating.

Performance testing

1) The separators obtained in examples and comparative examples were kept at a constant temperature of 150 ℃ for 0.5 hour, and taken out to calculate the transverse shrinkage and the longitudinal shrinkage of the separators.

2) And (3) matching the isolating membranes prepared in the examples and the comparative examples with a positive plate (active material is lithium cobaltate) and a negative plate (active material is graphite) to prepare the lithium ion battery, testing the cycle performance of the lithium ion battery, and calculating the cycle capacity retention rate of the lithium ion battery.

The results of the above tests are shown in table 1. In addition, the cycle profiles of the batteries manufactured using the separators of example 1 and comparative example 1 are shown in fig. 5.

TABLE 1 test results

As can be seen from the test results of table 1:

1) the shrinkage of the barrier films prepared in examples 1-10 and comparative examples 3-5 is significantly less than that of the barrier films prepared in comparative examples 1-2. The isolating membrane is added with ceramic particles and nano fibers in a ceramic coating, the ceramic particles and the nano fibers form compact network structure distribution, so that a framework can be formed to inhibit the shrinkage of a base membrane under a high-temperature condition, and the thermal stability is improved.

2) The capacity retention rate of the lithium ion battery adopting the isolating films prepared in the examples 1-10 and the comparative examples 3-5 after 500 weeks of circulation is obviously superior to that of the lithium ion battery adopting the comparative examples 1-2. The isolating membrane is characterized in that ceramic particles and nano fibers are added in the ceramic coating of the isolating membrane, the ceramic particles and the nano fibers form compact network structure distribution, pores formed by the network structure are larger, and the absorption and storage of electrolyte can be improved; and the nanofiber contains stronger polar functional groups, so that the wettability of the electrolyte can be improved, and the problem of insufficient electrolyte of long-term circulation of the battery is solved.

3) The production yield of the separator of examples 1 to 10 for the preparation of batteries was significantly higher than that of comparative examples 1 to 5, wherein the worst of comparative examples 1 and 3, the next to comparative examples 4 to 5, and the slightly better of comparative example 2. This is because the antistatic agent was not added to both the ceramic coating and the polymer coating in comparative examples 1 and 3, while the antistatic agent was added to one of the ceramic coating and the polymer coating in comparative examples 4 to 5. The antistatic agent has an antistatic effect, can reduce the generation of static electricity in the coating and cutting processes, can accelerate the conduction and the release of the static electricity, can further reduce the equipment investment of the coating and cutting processes on the static eliminator, saves the cost, can also reduce the loose core defect in the winding process, and improves the production yield.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.