阅读说明：本技术 极性聚烯烃隔膜及其制备方法 (Polar polyolefin separator and preparation method thereof ) 是由 陶晶 王志豪 陈强 杨影杰 袁其振 于 2019-08-28 设计创作，主要内容包括：本发明公开了一种极性聚烯烃隔膜及其制备方法,所述极性聚烯烃隔膜主要由极性聚合物和聚烯烃材料共混组成,所述聚烯烃材料为偶联剂接枝的聚烯烃材料。本发明改善了聚烯烃隔膜的电解液浸润性、吸液保液率和离子电导率,又能使聚烯烃与极性聚合物熔融共混形成稳定均相体系,减少了增容剂的引入。(The invention discloses a polar polyolefin diaphragm and a preparation method thereof. The invention improves the electrolyte wettability, the liquid absorption and retention rate and the ionic conductivity of the polyolefin diaphragm, can also ensure that the polyolefin and the polar polymer are melted and blended to form a stable homogeneous system, and reduces the introduction of a compatibilizer.)

1. A polar polyolefin separator characterized by: the polar polyolefin diaphragm is mainly formed by blending a polar polymer and a polyolefin material, wherein the polyolefin material is a coupling agent grafted polyolefin material.

2. The polar polyolefin separator according to claim 1, wherein: the polar polymer is a polymer containing polar functional groups, and the polar functional groups comprise one or more of ether groups, amide groups, ester groups, sulfonic acid groups and hydroxyl groups.

3. The polar polyolefin separator according to claim 2, wherein: the polar polymer comprises one or more of polyether/polyolefin block polymer, block polyether amide resin, polyvinyl acetate, secondary alkyl sulfonic acid compound and polyvinyl alcohol.

4. The polar polyolefin separator according to claim 1, wherein: the polyolefin material comprises polyethylene powder, polypropylene powder or mixed powder of polyethylene and polypropylene.

5. The polar polyolefin separator according to claim 1, wherein: the coupling agent comprises one or more of gamma-aminopropyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and a perfluorophenyl azide compound.

6. A polar polyolefin separator according to any one of claims 1 to 5, characterized in that: the mass ratio of the polar polymer to the polyolefin material is 1:100-20: 100.

7. The method for preparing a polar polyolefin separator according to any one of claims 1 to 6, wherein: the method comprises the following steps: firstly, mixing a polyolefin material and a coupling agent for grafting reaction, then mixing the polyolefin material grafted by the coupling agent with a polar polymer and a plasticizer for melt extrusion, and then at least carrying out the steps of sheet casting, longitudinal stretching, transverse stretching, extraction and heat setting to obtain the polar polyolefin diaphragm.

8. The method for preparing a polar polyolefin separator according to claim 7, wherein: the specific steps of mixing the polyolefin material and the coupling agent for grafting reaction are as follows: mixing and stirring a polyolefin material and a silane coupling agent, adding an initiator, and carrying out grafting reaction under an ice bath condition to obtain a coupling agent grafted polyolefin material; or mixing and stirring the polyolefin material and the perfluorophenyl azide, and carrying out grafting reaction under the ultraviolet radiation condition to obtain the coupling agent grafted polyolefin material.

9. The method for preparing a polar polyolefin separator according to any one of claims 1 to 6, wherein: the method comprises the following steps: firstly, mixing a polyolefin material and a coupling agent for grafting reaction, then mixing the polyolefin material grafted by the coupling agent with a polar polymer for melting and extruding, and then at least carrying out the steps of sheet casting, annealing, stretching and heat setting to obtain the polar polyolefin diaphragm.

10. The method for preparing a polar polyolefin separator according to claim 9, wherein: the specific steps of mixing the polyolefin material and the coupling agent for grafting reaction are as follows: mixing and stirring a polyolefin material and a silane coupling agent, adding an initiator, and carrying out grafting reaction under an ice bath condition to obtain a coupling agent grafted polyolefin material; or mixing and stirring the polyolefin material and the perfluorophenyl azide, and carrying out grafting reaction under the ultraviolet radiation condition to obtain the coupling agent grafted polyolefin material.

Technical Field

The invention belongs to the field of lithium battery diaphragm materials, and particularly relates to a polar polyolefin diaphragm and a preparation method thereof.

Background

The lithium ion battery diaphragm is one of the core materials of the lithium ion battery, and in the lithium ion battery, the lithium ion battery diaphragm mainly has two functions: separating the positive and negative electrode materials of the battery to prevent the two electrodes from being in direct contact and short circuit; and secondly, the porous structure of the diaphragm can hold a large amount of electrolyte, so that the lithium ions can be rapidly conducted in the diaphragm.

According to the difference of the forming method, the lithium ion battery diaphragm is divided into a wet diaphragm and a dry diaphragm, and the lithium ion battery diaphragm relates to a diaphragm made of polyethylene and polypropylene as main materials. The traditional polyolefin diaphragm is a non-polar material, has poor wettability with electrolyte and seriously influences the stable application of the diaphragm in a battery.

In recent years, researchers have attempted to improve the wettability of a separator with an electrolyte by modifying polyolefin from a material viewpoint based on many limitations of polyolefin separators. For example, by an in-situ blending method (CN109244336A), an aliphatic high polymer having polar groups is added to a high molecular weight polyethylene, and the two substances form a stable homogeneous system in a plasticizing stage through the effect of a compatibilizer, so that the porous structures on the surface and inside of the obtained separator are both infiltrated by a large amount of electrolytes, thereby greatly improving the overall electrophilic electrolyte performance. However, further research shows that the effect is not ideal when the compatibilizer is used to melt and blend polyolefin and polar materials to form a stable homogeneous system, and the blending of the compatibilizer, the polyolefin and the polar materials has high requirements on an extrusion process and is not beneficial to cost control.

Disclosure of Invention

In view of the above, the present invention provides a polar polyolefin separator and a preparation method thereof, which can improve the electrolyte wettability, the liquid absorption and retention rate, and the ionic conductivity of the polyolefin separator, and can also melt and blend polyolefin and a polar polymer to form a stable homogeneous system, thereby reducing the introduction of a compatibilizer.

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

the invention discloses a polar polyolefin diaphragm which is mainly formed by blending a polar polymer and a polyolefin material, wherein the polyolefin material is a polyolefin material grafted by a coupling agent.

As a preferable technical scheme, the polar polymer is a polymer containing a polar functional group, and the polar functional group comprises one or more of an ether group, an amide group, an ester group, a sulfonic group and a hydroxyl group.

As a preferred technical scheme, the polar polymer comprises one or more of polyether/polyolefin block polymer, block polyether amide resin, polyvinyl acetate, secondary alkyl sulfonic acid compound and polyvinyl alcohol.

As a preferred technical solution, the polyolefin material includes polyethylene powder, polypropylene powder or a mixed powder of polyethylene and polypropylene.

As a preferable technical scheme, the coupling agent comprises one or more of gamma-aminopropyl triethoxysilane, gamma-methacryloxypropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane and a perfluorinated phenyl azide compound.

As a preferred technical scheme, the mass ratio of the polar polymer to the polyolefin material is 1:100-20: 100.

The invention also discloses a preparation method (wet method) of the polar polyolefin diaphragm, which comprises the following steps: firstly, mixing a polyolefin material and a coupling agent for grafting reaction, then mixing the polyolefin material grafted by the coupling agent with a polar polymer and a plasticizer for melt extrusion, and then at least carrying out the steps of sheet casting, longitudinal stretching, transverse stretching, extraction and heat setting to obtain the polar polyolefin diaphragm;

the invention also discloses a preparation method (dry method) of another polar polyolefin diaphragm, which comprises the following steps: firstly, mixing a polyolefin material and a coupling agent for grafting reaction, then mixing the polyolefin material grafted by the coupling agent with a polar polymer for melting and extruding, and then at least carrying out the steps of sheet casting, annealing, stretching and heat setting to obtain the polar polyolefin diaphragm.

In the preparation method, the specific steps of mixing the polyolefin material and the coupling agent for grafting reaction are as follows: mixing and stirring a polyolefin material and a silane coupling agent, adding an initiator, and carrying out grafting reaction under an ice bath condition to obtain a coupling agent grafted polyolefin material; or mixing and stirring the polyolefin material and the perfluorophenyl azide, and carrying out grafting reaction under the ultraviolet radiation condition to obtain the coupling agent grafted polyolefin material.

The invention has the beneficial effects that:

the polyolefin material is grafted by the coupling agent, so that the homogeneous phase capacity of the polyolefin material and the polar polymer in a molten state is improved, then the polyolefin material and the polar polymer are blended, and the polar functional group is introduced into the polyolefin diaphragm, so that the surface tension of the polyolefin diaphragm is improved, the wettability of a base film and electrolyte is improved, and the liquid absorption and retention rate and the ionic conductivity are improved. The invention improves the electrolyte wettability, the liquid absorption and retention rate and the ionic conductivity of the polyolefin diaphragm, can also ensure that the polyolefin and the polar polymer are melted and blended to form a stable homogeneous system, and reduces the introduction of a compatibilizer.

Detailed Description

The present invention is further described with reference to specific examples to enable those skilled in the art to better understand the present invention and to practice the same, but the examples are not intended to limit the present invention.