阅读说明：本技术 一种以纳米二氧化硅为填料的pvdf隔膜 (PVDF (polyvinylidene fluoride) diaphragm taking nano silicon dioxide as filler ) 是由 刘方 刘瑾豪 李越旺 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种以纳米二氧化硅为填料的PVDF隔膜,包括一复合膜,该复合膜由基膜以及至少一层涂覆在基膜单面或者两侧面上的涂层组成,该涂层为纳米二氧化硅填充PVDF涂层,纳米二氧化硅硅氧四面体形成的立体网状结构将涂层与基膜粘接固定。本发明的产品涂层与基材形成一个立体网状结构,增强了涂层与隔膜的结合力,大大提升隔膜的耐热性能,使锂离子电池的安全性能进一步提升。(The invention discloses a PVDF diaphragm taking nano-silica as a filler, which comprises a composite membrane, wherein the composite membrane consists of a base membrane and at least one layer of coating coated on one side or two sides of the base membrane, the coating is a PVDF coating filled with the nano-silica, and the coating and the base membrane are bonded and fixed by a three-dimensional net structure formed by nano-silica-oxygen tetrahedrons. The coating and the base material of the product form a three-dimensional net structure, so that the binding force of the coating and the diaphragm is enhanced, the heat resistance of the diaphragm is greatly improved, and the safety performance of the lithium ion battery is further improved.)

1. A PVDF diaphragm taking nano-silica as a filler is characterized in that: the composite membrane comprises a composite membrane, wherein the composite membrane consists of a base membrane (1) and at least one coating (2) coated on one side or two sides of the base membrane, the coating (2) is a PVDF coating filled with nano silicon dioxide, and the coating (2) is bonded and fixed with the base membrane (1) through a three-dimensional net structure formed by nano silicon dioxide silicon four-sided bodies.

2. PVDF membrane with nanosilica as filler according to claim 1, characterized in that: the nano-silica filled PVDF coating is a coating coated after mixing nano-silica and PVDF, or the nano-silica filled PVDF coating is a combination of the nano-silica coating and the PVDF.

3. PVDF membrane with nanosilica as filler according to claim 1, characterized in that: the base membrane (1) is a polyolefin porous base membrane, and the thickness of the polyolefin porous base membrane is 5-25 mu m.

4. PVDF membrane with nanosilica as filler according to claim 1, characterized in that: the thickness of the composite membrane is 7-30 μm.

5. PVDF membrane with nanosilica as filler according to claim 1, characterized in that: the number of the coating layers (2) on one side or both sides of the base film (1) is 1-3.

6. PVDF membrane with nanosilica as filler according to claim 5, characterized in that: the thickness of each layer of nano silicon dioxide filled PVDF coating is 1-5 mu m.

Technical Field

The invention relates to a diaphragm, in particular to a PVDF diaphragm taking nano silicon dioxide as a filler.

Background

The PVDF is coated on the diaphragm, so that the bonding performance of the diaphragm and a pole piece is improved, the cycle performance of the lithium ion battery is obviously improved, but the application of the PVDF in the lithium ion battery, particularly in the aspect of power batteries, is limited due to poor heat resistance. In the prior art, nanometer alumina is generally used for filling PVDF coating diaphragm to improve the heat resistance of the diaphragm so as to improve the safety performance of the lithium ion battery. However, the characteristics of the planar structure of the nano aluminum oxide cause the problems of general adhesion between the product coating and the diaphragm, small improvement of heat resistance and the like.

Lithium ion batteries are receiving more and more attention from people due to the characteristics of large energy density, high working voltage, long cycle life, low self-discharge rate and the like, and the application range of the lithium ion batteries is gradually expanded. In the structure of the lithium battery, the diaphragm is one of key inner-layer components, separates positive and negative electrodes, prevents the two electrodes from contacting and short-circuiting, and has the function of providing electrolyte ions for passing through.

With the development of power automobiles, the energy density becomes the biggest challenge of the development of the current lithium ion batteries, and people expect that the energy density of the batteries can reach a brand new magnitude, so that the endurance time or endurance mileage of products does not become a main factor troubling the products any more. And the lithium ion battery has higher and higher requirements on the heat resistance, the liquid absorption/retention rate and the like of the diaphragm under high energy density. The existing main solution is to coat a functional coating layer on the surface of the polyolefin diaphragm, mainly including ceramic coating, PVDF coating, ceramic-filled PVDF coating, and the like, wherein the ceramic-filled PVDF coating has the advantages of both the ceramic coating and the PVDF coating, and is the mainstream in the existing coating technology, and the application of the coating technology is generally the nano-alumina-filled PVDF coating technology.

The PVDF is coated on the diaphragm, so that the bonding performance of the diaphragm and a pole piece is improved, the cycle performance of the lithium ion battery is obviously improved, but the application of the PVDF in the lithium ion battery, particularly in the aspect of power batteries, is limited due to poor heat resistance. In the prior art, nanometer alumina is generally used for filling PVDF coating diaphragm to improve the heat resistance of the diaphragm so as to improve the safety performance of the lithium ion battery. However, the characteristics of the planar structure of the nano aluminum oxide cause the problems of general adhesion between the product coating and the diaphragm, small improvement of heat resistance and the like.

Disclosure of Invention

The PVDF membrane takes nano silicon dioxide as a filler, the PVDF coating is filled with the nano silicon dioxide, the nano silicon dioxide is easy to disperse, the suspension liquid is good in stability, the three-dimensional network structure formed by silica tetrahedrons enables the coating and the base membrane to be bonded more firmly, the formed network framework support also greatly improves the heat resistance of the membrane, and the safety performance of the lithium ion battery is further improved.

The invention is realized by the following technical scheme: the PVDF membrane with the nano silicon dioxide as the filler comprises a composite membrane, wherein the composite membrane consists of a base membrane and at least one layer of coating coated on one side or two sides of the base membrane, the coating is a PVDF coating filled with the nano silicon dioxide, and the coating and the base membrane are bonded and fixed by a three-dimensional net structure formed by nano silicon dioxide four-sided bodies.

As a preferred technical solution, the nano-silica filled PVDF coating is a coating coated after mixing nano-silica and PVDF, or the nano-silica filled PVDF coating is a combination of a nano-silica coating and a PVDF coating.

As a preferable technical scheme, the base membrane is a polyolefin porous base membrane, and the thickness of the polyolefin porous base membrane is 5-25 μm.

As a preferable technical scheme, the thickness of the composite membrane is 7-30 μm.

As a preferred technical scheme, the number of coating layers positioned on one side or both sides of the base film is 1-3.

As a preferred technical scheme, the thickness of each layer of nano silicon dioxide filled PVDF coating is 1-5 μm.

The invention has the beneficial effects that: the coating and the base material of the product form a three-dimensional net structure, so that the binding force of the coating and the diaphragm is enhanced, the heat resistance of the diaphragm is greatly improved, and the safety performance of the lithium ion battery is further improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of the present invention.

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

As shown in fig. 1, the PVDF membrane using nano-silica as a filler of the invention includes a composite membrane, the composite membrane is composed of a base membrane 1 and at least one coating layer 2 coated on one side or two sides of the base membrane, the coating layer 2 is a PVDF coating layer filled with nano-silica, and the coating layer 2 is bonded and fixed with the base membrane 1 by a three-dimensional network structure formed by nano-silica four-silica faces.

In this embodiment, the nano-silica-filled PVDF coating is a coating applied after mixing nano-silica and PVDF, or the nano-silica-filled PVDF coating is a combination of a nano-silica coating and a PVDF coating.

Wherein, the basement membrane 1 is a polyolefin porous basement membrane, the thickness of the polyolefin porous basement membrane is 5-25 μm, and the thickness of the composite membrane is 7-30 μm.

The number of the coating layers 2 on one side or both sides of the base film 1 is 1-3, in the embodiment, the coating layers are arranged on both sides of the base film, the number of the coating layers is 1, and the thickness of each layer of the nano silicon dioxide filled PVDF coating is 1-5 μm.

The invention has the beneficial effects that: the PVDF coating is filled with the nano silicon dioxide, the nano silicon dioxide is easy to disperse, the suspension liquid is good in stability, the three-dimensional net structure formed by the silica tetrahedron enables the coating and the base film to be bonded more firmly, the formed net framework support also greatly improves the heat resistance of the diaphragm, and the safety performance of the lithium ion battery is further improved.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that are not thought of through the inventive work should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.