CN111211277A

CN111211277A - Preparation method of PMMA gel coating diaphragm

Info

Publication number: CN111211277A
Application number: CN202010100807.8A
Authority: CN
Inventors: 王志豪; 陶晶; 杜辉; 王思双
Original assignee: Chongqing Yuntianhua Newmi Tech Co ltd
Current assignee: Chongqing Yuntianhua Newmi Tech Co ltd
Priority date: 2020-02-19
Filing date: 2020-02-19
Publication date: 2020-05-29
Anticipated expiration: 2040-02-19
Also published as: CN111211277B

Abstract

The invention discloses a preparation method of a PMMA gel coating diaphragm, which comprises the following steps: (1) mixing PMMA powder with water according to the mass ratio of 4:6-9:1, adding a grafting agent, grinding, and stirring and dispersing to obtain a grafted PMMA dispersion liquid; (2) diluting the grafted PMMA dispersion liquid to prepare coating slurry; (3) feeding the diaphragm into a coating device, and coating by using the coating slurry; (4) and drying and rolling the coated diaphragm to obtain the PMMA gel coated diaphragm. According to the invention, by a high-solid-content grinding grafting method, the grafting rate of the grafting agent on the surface of PMMA is greatly improved, so that the uniformity and stability of PMMA slurry are improved, the coating quality is further improved, and the prepared coating membrane has high ionic conductivity and excellent bonding performance.

Description

Preparation method of PMMA gel coating diaphragm

Technical Field

The invention belongs to the field of lithium battery diaphragm materials, and particularly relates to a preparation method of a PMMA gel coating diaphragm.

Background

The lithium ion battery as a secondary rechargeable battery has the advantages of high energy density, long cycle life, no memory effect, environmental protection and the like, and is widely applied to portable electronic equipment, electric tools, electric vehicles, energy storage and the like. The diaphragm is one of three main materials in the lithium ion battery, and is directly related to the cycle life, safety, current density and the like of the battery.

With the increasing demands of consumers on the long service life, high multiplying power, high safety and light weight of the battery, the traditional lithium ion battery diaphragm cannot meet the requirements, the application field of the traditional ceramic coating diaphragm used in the battery is limited, the problem that the swelling and formation thickness of the polymer battery are increased greatly cannot be solved, the PVDF coating diaphragm can improve the problems of swelling and thickness increase of the battery, but the multiplying power, circulation and other performances of the battery can be influenced, the difficult problem can be well solved by using the PMMA coating, and the PMMA coating diaphragm has an important effect on the improvement of the industrial chain structure.

However, in the production process of the PMMA coated diaphragm, the problems of nonuniform and unstable PMMA slurry dispersion can occur, so that the PMMA coating has poor quality and a plurality of defects, and the performance of the PVDF coated diaphragm is directly influenced.

Disclosure of Invention

In view of this, the invention aims to provide a preparation method of a PMMA gel coated membrane, which can improve the uniformity and stability of PMMA slurry, and further improve the coating quality and membrane performance.

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

the invention provides a preparation method of a PMMA gel coating diaphragm, which comprises the following steps:

(1) mixing PMMA powder with water according to the mass ratio of 4:6-9:1, adding a grafting agent, grinding, and stirring and dispersing to obtain a grafted PMMA dispersion liquid;

(2) diluting the grafted PMMA dispersion liquid prepared in the step (1) to prepare coating slurry;

(3) sending the diaphragm into a coating device, and coating by using the coating slurry prepared in the step (2);

(4) and (4) drying and rolling the diaphragm coated in the step (3) to obtain the PMMA gel coating diaphragm.

In a preferable embodiment, in the step (1), the PMMA powder and water are mixed in a mass ratio of 6:4 to 8: 2.

As a preferred technical scheme, in the step (1), the grafting agent is one or more of a silane coupling agent or a complex coupling agent.

As a preferable technical scheme, in the step (1), the added grafting agent accounts for 0.5-4% of the mass of the PMMA powder.

As a preferable technical scheme, in the step (1), one or more of a planetary ball mill, a vertical mill and a horizontal mill are used in combination in the grinding process, and the grinding time is 0.5-2 h.

As a preferable technical scheme, in the step (1), the stirring and dispersing process is dispersed for 2-4h at the stirring speed of 700-1500 r/min.

As a preferable technical scheme, in the step (2), the graft PMMA dispersion is diluted by a sodium carboxymethyl cellulose solution until the PMMA content is 0.2-15 wt%, and then an auxiliary agent is added to prepare a coating slurry.

Preferably, in the step (3), the separator is a polyolefin-based film or a ceramic separator in which a coating layer of inorganic ceramic particles is coated on the polyolefin-based film.

As a preferable technical scheme, in the step (3), the polyolefin-based film is a polyethylene film, a polypropylene film or a polyethylene and polypropylene composite film with the thickness of 4-32 μm and the porosity of 30-80%.

As a preferable technical scheme, in the step (3), the thickness of the coating is 0.1-3 μm.

The invention has the beneficial effects that:

according to the invention, by a high solid content grinding grafting method, the contact efficiency of the grafting agent and the surface of PMMA powder is obviously improved, the grafting rate of the grafting agent on the surface of PMMA is greatly improved, and the PMMA surface carries more charges due to the improvement of the grafting rate, so that the interparticle repulsion force is increased, and the dispersion stability of the slurry is facilitated, thereby improving the uniformity and stability of the PMMA slurry, further improving the coating quality, and the prepared coating diaphragm has high ionic conductivity and excellent bonding performance.

Drawings

In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1 is a scanning electron micrograph of a PMMA gel coated septum prepared in example 1.

Detailed Description

The present invention is further described with reference to the following drawings and specific examples so that those skilled in the art can better understand the present invention and can practice the present invention, but the examples are not intended to limit the present invention.

Example 1:

(1) mixing PMMA powder with water according to a mass ratio of 4:6, adding a KH-550 grafting agent accounting for 1% of the mass of the PMMA powder, grinding for 0.5h by using a horizontal grinder, and dispersing for 2h at a stirring speed of 1000r/min by using a stirrer to obtain a grafted PMMA dispersion liquid;

(2) diluting the grafted PMMA dispersion liquid prepared in the step (1) with a sodium carboxymethylcellulose solution until the PMMA content is 0.6 wt%, and then adding a dispersing agent, a polyacrylic acid adhesive emulsion and a fluorocarbon surfactant to prepare coating slurry;

(3) taking a ceramic diaphragm with one side coated with an inorganic ceramic particle coating, sending the diaphragm into a coating device, and carrying out double-side coating by using the coating slurry prepared in the step (2);

FIG. 1 is a scanning electron microscope image of a PMMA gel coated membrane prepared in example 1, from which it can be seen that PMMA is uniformly dispersed on the membrane surface without agglomeration.

Example 2:

example 2 differs from example 1 in that: in the step (1), PMMA powder and water are mixed according to the mass ratio of 6: 4.

Example 3:

example 3 differs from example 1 in that: in the step (1), a planetary ball mill is adopted for grinding.

Example 4:

example 4 differs from example 1 in that: in the step (2), the graft PMMA dispersion is diluted with a sodium carboxymethyl cellulose solution until the PMMA content is 2 wt%.

Comparative example 1:

(1) mixing PMMA powder with sodium carboxymethylcellulose solution until the content of PMMA is 0.6 wt%, adding KH-550 grafting agent accounting for 1% of the mass of the PMMA powder, and dispersing for 2h at the stirring speed of 1000r/min by using a stirrer to obtain PMMA dispersion liquid;

(2) adding a dispersing agent, polyacrylic acid adhesive emulsion and fluorocarbon surfactant into the PMMA dispersion liquid prepared in the step (1) to prepare coating slurry;

The separators prepared in examples 1 to 4 and comparative example 1 were subjected to performance tests under the same conditions, and the results are shown in table 1.

TABLE 1 comparison of results of membrane Performance tests

From the performance indexes of table 1, the grafting ratio of examples 1 to 4 is much higher than that of comparative example 1 by using a high solid content grinding and grafting method, so that the uniformity and stability of PMMA slurry are improved, the coating quality is improved, the thickness is uniform, the air permeability is less increased, the pore blocking probability of the diaphragm is low, the ionic conductivity of the diaphragm is high, and the adhesion performance is excellent.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.

Claims

1. A preparation method of a PMMA gel coating diaphragm is characterized by comprising the following steps: the method comprises the following steps:

2. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (1), PMMA powder and water are mixed according to the mass ratio of 6:4-8: 2.

3. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (1), the grafting agent is one or more of a silane coupling agent or a complex coupling agent.

4. A method of preparing a PMMA gel coated membrane according to claim 3, wherein: in the step (1), the added grafting agent accounts for 0.5-4% of the mass of the PMMA powder.

5. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (1), one or more of a planetary ball mill, a vertical grinder and a horizontal grinder are used in a matching way in the grinding process, and the grinding time is 0.5-2 h.

6. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (1), the stirring and dispersing process is carried out for 2-4h at a stirring speed of 700-1500 r/min.

7. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (2), the grafted PMMA dispersion liquid is diluted by adopting a sodium carboxymethyl cellulose solution until the PMMA content is 0.2-15 wt%, and then an auxiliary agent is added to prepare coating slurry.

8. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (3), the diaphragm is a polyolefin-based film or a ceramic diaphragm coated with an inorganic ceramic particle coating on the polyolefin-based film.

9. A method of preparing a PMMA gel coated membrane according to claim 8, wherein: in the step (3), the polyolefin base film is a polyethylene film, a polypropylene film or a polyethylene and polypropylene composite film with the thickness of 4-32 μm and the porosity of 30-80%.

10. A method of preparing a PMMA gel coated membrane according to claim 1, wherein: in the step (3), the thickness of the coating is 0.1-3 μm.