阅读说明：本技术 一种导热导电材料涂覆隔膜及其制备方法 (Heat-conducting and electric-conducting material coated diaphragm and preparation method thereof ) 是由 王素清 黄子宇 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种导热导电材料涂覆隔膜及其制备方法。所述隔膜包括基底膜和涂覆层,所用基底膜为聚烯烃多孔膜,所用的涂覆层包含球形颗粒和粘合剂等多种助剂。制备步骤包括：(1)将导电导热颗粒、分散剂和润湿剂加入到粘合剂溶液中,搅拌混合,得涂覆浆料；(2)将步骤(1)所述的涂覆浆料涂覆于聚烯烃多孔基底膜上,干燥后再真空烘干,得到导热导电材料涂覆隔膜。球形颗粒为导热导电材料,优良的导电性使涂覆层作为集流体的存在,减少电极的阻抗,提高电池的电化学性能,另一方面导热性质可辅助扩散电池在运行过程产生的热量,使界面热量均匀,提高电池稳定性。(The invention discloses a heat-conducting and electric-conducting material coated diaphragm and a preparation method thereof. The diaphragm comprises a base film and a coating layer, wherein the base film is a polyolefin porous film, and the coating layer contains spherical particles, an adhesive and other various auxiliaries. The preparation method comprises the following steps: (1) adding the conductive and heat-conductive particles, the dispersing agent and the wetting agent into the adhesive solution, and stirring and mixing to obtain coating slurry; (2) and (2) coating the coating slurry obtained in the step (1) on a polyolefin porous base membrane, drying, and then drying in vacuum to obtain the heat-conducting and electric-conducting material coating membrane. The spherical particles are made of heat-conducting and electric-conducting materials, the coating layer is made of a current collector due to excellent electric conductivity, the impedance of an electrode is reduced, the electrochemical performance of the battery is improved, and on the other hand, the heat generated by the battery in the operation process can be diffused in an auxiliary mode due to the heat-conducting property, so that the interface heat is uniform, and the stability of the battery is improved.)

1. A preparation method of a heat-conducting and electric-conducting material coating diaphragm is characterized by comprising the following steps,

(1) adding the conductive and heat-conductive particles, the dispersing agent and the wetting agent into the adhesive solution, and stirring and mixing to obtain coating slurry;

(2) and (2) coating the coating slurry obtained in the step (1) on a polyolefin porous base membrane, drying, and then drying in vacuum to obtain the heat-conducting and electric-conducting material coating membrane.

2. The production method according to claim 1,

the adhesive solution in the step (1) is obtained by mixing and stirring an adhesive and a solvent.

3. The production method according to claim 2,

the adhesive is one or more of polyvinyl alcohol, styrene-butadiene rubber, polyvinylidene fluoride-hexafluoropropylene, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride and polyacrylonitrile.

4. The production method according to claim 2,

the solvent is one or more of water, dimethylacetamide, dimethylformamide, chloroform, dimethyl sulfoxide, dichloromethane, nitrogen methyl pyrrolidone and acetone.

5. The production method according to claim 1,

the heat-conducting and electric-conducting particles in the step (1) are one or more of silicon carbide, magnesium diboride, tungsten carbide, titanium carbide, silicon nitride and titanium nitride; the particle size of the heat-conducting and electric-conducting particles is 0.02-5 microns.

6. The production method according to claim 1,

the dispersant in the step (1) is one or more of sodium polyacrylate, sodium carboxymethyl cellulose, polyethylene glycol and sodium polymethacrylate.

7. The production method according to claim 1,

the wetting agent in the step (1) is one or more of sodium dodecyl sulfate, fluorinated alkyl ethoxy alcohol ether, fatty alcohol-polyoxyethylene ether and hydroxyethyl sodium sulfonate.

8. The production method according to claim 1,

and (3) uniformly casting the heat-conducting and electric-conducting coating slurry on one side or two sides of the polyolefin porous base membrane by using a scraper and a casting machine in the coating of the step (2).

9. The method according to claim 1,

the drying temperature in the step (2) is 50-70 ℃, and the vacuum drying temperature is 50-70 ℃.

10. The thermally and electrically conductive material-coated separator prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of lithium ion battery diaphragm modification, and particularly relates to a heat-conducting and electric-conducting material coated diaphragm and a preparation method thereof.

Background

In recent years, with the rapid development of the world economy and the increase of the population, the use of energy in various countries is increasingly emphasized. Because the traditional fossil energy belongs to non-renewable energy and has a huge environmental pollution problem in the use process, many countries focus on developing clean energy storage technology. The lithium ion battery has the characteristics of excellent energy density, long service life, no memory effect and the like, has become a popular energy storage device in the international market, and is widely applied to tools such as mobile phones, notebook computers, new energy automobiles and the like.

The diaphragm is an important component in the liquid lithium ion battery, accounts for about 20% of the manufacturing cost of the battery, and has the functions of isolating the positive electrode and the negative electrode, preventing the short circuit of the battery and facilitating the movement of lithium ions. The traditional diaphragm adopts polyolefin such as polyethylene, polypropylene and the like as raw materials, and the materials have low cost and are suitable for large-scale production. In the prior art, the heat of the battery is mainly conducted out by a current collector of an electrode, a diaphragm is positioned between an anode and a cathode, and the generated heat cannot be diffused out due to poor heat conductivity of a polymer per se, so that local heat accumulation is caused. Patent CN 110571394 a discloses a ceramic slurry and a ceramic-coated separator, in which inorganic particles (alumina, boehmite, silica, titania, calcium carbonate, barium sulfate and magnesium oxide) are used to coat and modify the separator, but the inorganic particles used do not have thermal conductivity and electrical conductivity, cannot exert the functions of diffusing heat and improving ion and electron transport, and do not significantly improve the battery performance. In addition, the electric conductor is constructed on the surface of the diaphragm, so that ion and electron transmission paths can be further enriched, the impedance of the battery is reduced, and the electrochemical performance of the battery is optimized.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a heat conductive and electrically conductive material coated separator and a method for preparing the same. According to the invention, the polyolefin diaphragm is coated with the heat-conducting and electricity-conducting material, so that the generated heat can be conducted out under the condition of high-rate operation of the battery, the operation stability of the battery is improved, and the conductive layer enables the coating layer to serve as a current collector to reduce the impedance of an electrode and optimize the performance of the battery.

The purpose of the invention is realized by the following technical scheme.

A preparation method of a heat-conducting and electric-conducting material coating diaphragm comprises the following steps,

(1) adding the conductive and heat-conductive particles, the dispersing agent and the wetting agent into the adhesive solution, and stirring and mixing to obtain coating slurry;

(2) and (2) coating the coating slurry obtained in the step (1) on a polyolefin porous base membrane, drying, and then drying in vacuum to obtain the heat-conducting and electric-conducting material coating membrane.

Preferably, the adhesive solution in the step (1) is obtained by mixing and stirring an adhesive and a solvent; preferably, the adhesive is one or more of polyvinyl alcohol, styrene-butadiene rubber, polyvinylidene fluoride-hexafluoropropylene, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride and polyacrylonitrile, and the solvent is one or more of water, dimethylacetamide, dimethylformamide, chloroform, dimethyl sulfoxide, dichloromethane, nitrogen methyl pyrrolidone and acetone.

Preferably, the heat-conducting and electric-conducting particles in the step (1) are one or more of silicon carbide, magnesium diboride, tungsten carbide, titanium carbide, silicon nitride and titanium nitride; the particle size of the heat-conducting and electric-conducting particles is 0.02-5 microns; further preferably, the particle size of the heat and electricity conducting particles is one or more of 20-40 nm, 100-200 nm, 300-500 nm, 1 micron and 2-5 microns.

Preferably, the dispersant in the step (1) is one or more of sodium polyacrylate, sodium carboxymethyl cellulose, polyethylene glycol and sodium polymethacrylate.

Preferably, the wetting agent in the step (1) is one or more of sodium dodecyl sulfate, fluorinated alkyl ethoxy alcohol ether, fatty alcohol-polyoxyethylene ether and sodium hydroxyethyl sulfonate.

Preferably, the coating in step (2) uses a doctor blade and a casting machine to uniformly cast the thermally and electrically conductive coating slurry on one side or both sides of the polyolefin porous base film.

Preferably, the drying temperature in the step (2) is 50-70 ℃, and the vacuum drying temperature is 50-70 ℃.

The heat-conducting and electric-conducting material prepared by the preparation method coats the diaphragm.

Compared with the prior art, the invention has the following advantages:

the lithium ion battery diaphragm coated with the heat-conducting and electric-conducting material plays the functions of heat conduction of the coating and enrichment of an ion electron transmission path, heat generated in battery operation is diffused from the space between a positive electrode and a negative electrode, the impedance of the electrodes can be reduced, and the electrochemical performance of the battery is improved.

Drawings

FIG. 1 is a schematic representation of the structure of a coated separator prepared in example 1;

FIG. 2 is a surface SEM photograph of the coated separator prepared in example 2;

fig. 3 is a graph of electrochemical performance at 1C rate (cycling) for a lithium battery assembled using an electrically and thermally conductive coated separator and an uncoated base film in example 2.

Detailed Description

To further illustrate the present invention, the following description is given with reference to specific examples and accompanying drawings, but the practice of the present invention is not limited thereto.

Example 1

The selected adhesive is polyvinyl alcohol, the first solvent is water, 2 g of polyvinyl alcohol is added into 80 g of water, and a transparent polyvinyl alcohol solution is obtained after stirring by a mechanical stirrer. The heat-conducting and electric-conducting material is silicon carbide, the particle size is 300-500 nanometers, the dispersing agent is sodium carboxymethylcellulose, the wetting agent is sodium dodecyl sulfate, 17 g of titanium carbide, 0.5 g of carboxymethyl cellulose and 0.5 g of sodium dodecyl benzene sulfonate are added into a polyvinyl alcohol solution, and the coating solution is obtained after stirring. And (3) selecting a 16-micron polyethylene film as a base film, uniformly coating the coating solution on one side of the base film by using a casting machine and a scraper, drying in an oven at the controlled temperature of 50 ℃, transferring to a vacuum oven for drying after drying at the controlled temperature of 60 ℃, and taking out after drying to obtain the diaphragm for the lithium ion battery with the heat-conducting and electric-conducting coating layer. The coating thickness was measured using a micrometer to give a coating layer of 5 microns thickness.

The structure of the coated membrane prepared in example 1 is schematically shown (fig. 1), and it can be seen from the figure that after coating, the particles are tightly adhered to the surface of the substrate and uniformly dispersed so as to exert the functions of heat conduction and electricity conduction.

Example 2

The selected adhesive is polyvinyl alcohol, the first solvent is water, 2 g of polyvinyl alcohol is added into 80 g of water, and a transparent polyvinyl alcohol solution is obtained after stirring by a mechanical stirrer. The heat-conducting and electric-conducting material is silicon carbide, the particle size is 100-200 nanometers, the dispersing agent is sodium carboxymethylcellulose, the wetting agent is sodium dodecyl sulfate, 17 g of titanium nitride, 0.5 g of carboxymethyl cellulose and 0.5 g of sodium dodecyl benzene sulfonate are added into a polyvinyl alcohol solution, and the coating solution is obtained after stirring. And (3) selecting a 16-micron polyethylene film as a base film, uniformly coating the coating solution on one side of the base film by using a casting machine and a scraper, drying in an oven at the controlled temperature of 50 ℃, transferring to a vacuum oven for drying after drying at the controlled temperature of 60 ℃, and taking out after drying to obtain the diaphragm for the lithium ion battery with the heat-conducting and electric-conducting coating layer. The coating thickness was measured using a micrometer to give a coating layer of 5 microns thickness.

In the SEM image (fig. 2) of the surface of the coated separator obtained in example 2, it can be seen that the coated particles are uniformly dispersed on the surface, and there is no agglomeration phenomenon, and on the one hand, the ion transport is not hindered, and on the other hand, the function thereof can be exerted to a greater extent.

Electrochemical performance at 1C rate of lithium battery assembled using electrically and thermally conductive coated separator and uncoated base film in example 2 (fig. 3), (cathode: phosphorus)Lithium iron phosphate, negative electrode: lithium sheet, electrolyte: 1M LiPF₆After 100 cycles of the + EC/DEC (v/v) battery, the battery equipped with the coated film released a higher specific capacity due to the improvement of the coating layer).

Example 3

The selected adhesive is polyvinyl alcohol, the first solvent is water, 4 g of polyvinyl alcohol is added into 80 g of water, and a transparent polyvinyl alcohol solution is obtained after stirring by a mechanical stirrer. The selected heat-conducting and electric-conducting material is titanium nitride, the particle size is 100-200 nanometers, the selected dispersing agent is sodium carboxymethyl cellulose, the selected wetting agent is sodium dodecyl sulfate, 15 g of titanium nitride, 0.5 g of sodium carboxymethyl cellulose and 0.5 g of sodium dodecyl benzene sulfonate are added into a polyvinyl alcohol solution, and the coating solution is obtained after stirring. Selecting a 25-micron polypropylene film as a base film, uniformly coating the coating solution on one side of the base film by using a casting machine and a scraper, putting the base film into an oven for drying, controlling the temperature to be 50 ℃, after drying, transferring the base film into a vacuum oven for drying, controlling the temperature to be 60 ℃, and taking out after drying to obtain the diaphragm for the lithium ion battery with the heat-conducting and electric-conducting coating layer. The coating thickness was measured using a micrometer to give a coating layer of 3 microns thickness.

Example 4

The selected adhesive is polyvinyl alcohol, the first solvent is water, 4 g of polyvinyl alcohol is added into 80 g of water, and a transparent polyvinyl alcohol solution is obtained after stirring by a mechanical stirrer. The selected heat-conducting and electric-conducting material is titanium nitride, the particle size is 20-40 nanometers and 100-200 nanometers, the ratio of the titanium nitride to the particle size is 3/2, the selected dispersing agent is sodium carboxymethyl cellulose, the wetting agent is sodium dodecyl sulfate, 15 g of titanium nitride, 0.5 g of sodium carboxymethyl cellulose and 0.5 g of sodium dodecyl benzene sulfonate are added into polyvinyl alcohol solution, and the coating solution is obtained after stirring. Selecting a 15-micron polyethylene film as a base film, uniformly coating the coating liquid on two sides of the base film by using a casting machine and a scraper, putting the base film into an oven for drying, controlling the temperature to be 50 ℃, after drying, transferring the base film into a vacuum oven for drying, controlling the temperature to be 60 ℃, and taking out after drying to obtain the diaphragm for the lithium ion battery with the heat-conducting and electric-conducting coating layer. The coating thickness was measured using a micrometer to give a coating layer of 5 microns thickness.

Example 5

The selected adhesive is polyacrylic acid, the first solvent is water, 4 g of polyacrylic acid is added into 80 g of water, and a transparent polyacrylic acid solution is obtained after stirring by a mechanical stirrer. The selected heat-conducting and electric-conducting material is tungsten carbide, the particle size is 300-500 nanometers, the selected dispersing agent is sodium carboxymethyl cellulose, the selected wetting agent is sodium dodecyl sulfate, 15 g of tungsten carbide, 0.4 g of carboxymethyl cellulose and 0.6 g of sodium dodecyl benzene sulfonate are added into the polyacrylic acid solution, and the coating solution is obtained after stirring. And (3) selecting a 12-micron polyethylene film as a base film, uniformly coating the coating solution on one side of the base film by using a casting machine and a scraper, drying in an oven at the controlled temperature of 50 ℃, transferring to a vacuum oven for drying after drying at the controlled temperature of 60 ℃, and taking out after drying to obtain the diaphragm for the lithium ion battery with the heat-conducting and electric-conducting coating layer. The coating thickness was measured using a micrometer to give a coating layer of 3 microns thickness.

The above description is only an exemplary description of the technical idea of the present invention, and the present invention is not limited to the above-described embodiments. It is within the technical scope of the present invention that any modification or variation of the technical method and process of the present invention may be made by those skilled in the art.