阅读说明：本技术 一种双重闭孔隔膜及其制备方法和应用 (Dual-closed-pore diaphragm and preparation method and application thereof ) 是由 袁海朝 徐锋 贾亚峰 李青 刘志强 于 2021-07-01 设计创作，主要内容包括：本发明公开了一种双重闭孔隔膜的制备方法,包括以下步骤：步骤1：将PE粉溶于苯乙烯后,通过粒子溅射方式造粒得PE粒子；步骤2：向去离子水中加入阻燃无机粉末、PE粒子和分散剂,混合搅拌均匀后加入增稠剂、消泡剂和粘结剂,搅拌均匀得水系浆料；步骤3：将所得水系浆料通过微凹版辊涂的方式涂覆在PE基膜的一侧或两侧,烘干得双重闭孔隔膜。该双重闭孔隔膜采用PE基膜,结合无机粒子和有机粒子的复合涂层,是隔膜同时具有耐高温性能和闭孔性能。当它遭受130℃以上高温时,有机粒子会开始融化填充封闭涂层内部的孔隙,阻断锂离子迁移,提高电池安全性能。(The invention discloses a preparation method of a double-closed-pore diaphragm, which comprises the following steps: step 1: dissolving PE powder in styrene, and granulating in a particle sputtering mode to obtain PE particles; step 2: adding flame-retardant inorganic powder, PE particles and a dispersing agent into deionized water, mixing and stirring uniformly, adding a thickening agent, a defoaming agent and a binder, and stirring uniformly to obtain a water system slurry; and step 3: and coating the obtained water system slurry on one side or two sides of the PE base film in a micro gravure roll coating mode, and drying to obtain the double closed-cell diaphragm. The double-closed-pore diaphragm adopts a PE base film and is combined with a composite coating of inorganic particles and organic particles, so that the diaphragm has high temperature resistance and closed-pore performance. When the lithium ion battery is subjected to high temperature of more than 130 ℃, the organic particles can begin to melt and fill the pores in the sealing coating, so that the lithium ion migration is blocked, and the safety performance of the battery is improved.)

1. A preparation method of a double closed-cell diaphragm is characterized by comprising the following steps: the method comprises the following steps:

step 1: preparation of PE particles

Dissolving PE powder in styrene, and granulating in a particle sputtering mode to obtain PE particles;

step 2: preparation of the slurry

Adding flame-retardant inorganic powder, PE particles and a dispersing agent into deionized water, mixing and stirring uniformly, adding a thickening agent, a defoaming agent and a binder, and stirring uniformly to obtain a water system slurry;

and step 3: preparation of coated separator

And coating the obtained water system slurry on one side or two sides of the PE base film, and drying to obtain the double closed-cell diaphragm.

2. The method of claim 1, wherein: in the step 1, the viscosity average molecular weight of the PE powder is 30-200 ten thousand.

3. The method of claim 2, wherein: the particle size of the PE particles is 0.1-2.0 μm.

4. The method of claim 1, wherein: in step 2, the flame-retardant inorganic powder is alumina powder or boehmite powder.

5. The method of claim 4, wherein: the particle size of the flame-retardant inorganic powder is 0.2-2.0 μm.

6. The method of claim 5, wherein: the dispersing agent is one of fatty acids, fatty amides, esters and low molecular waxes; the thickening agent is one of PVA, PEG, PVP and CMC; the defoaming agent is one of alcohol and polyether modified polydimethylsiloxane emulsion; the binder is polyacrylate.

7. The method of claim 6, wherein: the mass of the PE particles accounts for 1-6% of the total mass of the PE particles and the flame-retardant inorganic powder.

8. The method of claim 7, wherein: the total mass of the PE particles and the flame-retardant inorganic powder, and the mass ratio of the dispersing agent, the thickening agent, the defoaming agent and the binder are (80-120): (1.2-1.8): (1-5): (1-5): (3-8).

9. The dual closed-cell membrane prepared by the preparation method of any one of claims 1 to 8, wherein the gas permeability value after being baked at 135 ℃ for 30min is 650-700s/100 ml.

10. Use of the dual closed-cell separator of claim 9 in a lithium battery.

Technical Field

The invention relates to the technical field of lithium battery diaphragms, in particular to a double-closed-pore diaphragm and a preparation method and application thereof.

Background

The battery mainly comprises a positive electrode material, a negative electrode material, electrolyte and a diaphragm, wherein the diaphragm is an important component of the battery, and the diaphragm mainly comprises a microporous film or a non-woven fiber sheet, separates the positive electrode and the negative electrode of the battery in the battery, plays a role in preventing short circuit of the two electrodes, and has electronic insulation property and ionic conductivity. Under the condition of temperature rise, the diaphragm has the protection effect of micropore self-closing, and can prevent the battery from being exploded due to short circuit, so the research on the closed pore performance of the diaphragm is very important for improving the safety of the battery.

Disclosure of Invention

The invention aims to provide a double-closed-pore diaphragm aiming at the defect of low closed-pore performance of the diaphragm in the prior art. The double-closed-pore diaphragm adopts a PE base film and is combined with a composite coating of inorganic particles and organic particles, so that the diaphragm has high temperature resistance and closed-pore performance. When the lithium ion battery is subjected to high temperature of more than 130 ℃, the organic particles can begin to melt and fill the pores in the sealing coating, so that the lithium ion migration is blocked, and the safety performance of the battery is improved.

Another object of the present invention is to provide a method for preparing the above dual closed-cell separator.

The technical scheme adopted for realizing the purpose of the invention is as follows:

a method of making a dual closed-cell membrane, comprising the steps of:

step 1: preparation of PE particles

Dissolving PE powder in styrene, and granulating in a particle sputtering mode to obtain PE particles with small particle size;

step 2: preparation of the slurry

Adding flame-retardant inorganic powder, PE particles and a dispersing agent into deionized water, mixing and stirring uniformly, adding a thickening agent, a defoaming agent and a binder, and stirring uniformly to obtain a water system slurry;

and step 3: preparation of coated separator

And coating the obtained water system slurry on one side or two sides of the PE base film in a micro gravure roll coating mode, and drying to obtain the double closed-cell diaphragm.

In the above technical scheme, in the step 1, the viscosity average molecular weight of the PE powder is 30 to 200 ten thousand.

In the above technical solution, the particle size of the PE particles is 0.1 to 2.0 μm. The PE particles in the particle size range do not influence the integrity of the inorganic coating, meanwhile, the particle size of the PE particles is smaller than that of the flame-retardant inorganic powder, the PE particles are filled in gaps among the inorganic particles, and the gaps among the inorganic particles are blocked after the PE particles are melted.

In the above technical scheme, in step 2, the flame-retardant inorganic powder is alumina powder or boehmite powder. The alumina powder or boehmite powder is high-temperature-resistant flame-retardant inorganic powder, so that the prepared diaphragm has both heat resistance and pore-closing performance.

In the above technical scheme, the particle size of the flame-retardant inorganic powder is 0.2-2.0 μm.

In the technical scheme, the dispersing agent is one of fatty acids, aliphatic amides, esters and low molecular waxes; the thickening agent is one of PVA, PEG, PVP and CMC; the defoaming agent is one of alcohol and polyether modified polydimethylsiloxane emulsion; the binder is polyacrylate.

In the technical scheme, the mass of the PE particles accounts for 1-6% of the total mass of the PE particles and the flame-retardant inorganic powder. The addition amount of the PE particles is only the amount of filling the gaps of the inorganic coating, and the integrity of the inorganic coating is influenced by the excessive addition amount, so that the high-temperature resistance of the inorganic coating is influenced.

In the technical scheme, the mass ratio of the total mass of the PE particles and the flame-retardant inorganic powder to the mass of the dispersant thickener, the defoaming agent and the binder is (80-120): (1.2-1.8): (1-5): (1-5): (3-8).

On the other hand, the air permeability value of the dual-closed-pore membrane prepared by the preparation method is 650-700s/100ml after being baked at 135 ℃ for 30min, and the air permeability value of the membrane after being closed is effectively improved by filling the internal gaps of the coating with the organic particles.

On the other hand, the application of the double-closed-pore diaphragm in the lithium battery can thoroughly block the migration of lithium ions and improve the safety performance of the battery.

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

1. according to the double-closed-pore diaphragm provided by the invention, the organic particles are used for filling the internal gaps of the coating, so that the ventilation value of the diaphragm after being closed is effectively improved.

2. The double-closed-pore diaphragm provided by the invention combines heat-resistant flame-retardant inorganic powder such as alumina powder or boehmite powder, and has heat resistance and closed-pore performance.

3. When the double-closed-pore diaphragm provided by the invention is applied to a lithium battery, the migration of lithium ions can be thoroughly blocked, and the safety performance of the battery is improved.

Detailed Description

The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

A method of making a dual closed-cell membrane, comprising the steps of:

step 1: preparation of PE particles

Firstly, 950g of styrene is weighed by a beaker to be used as a solvent, then 50g of PE powder with the viscosity-average molecular weight of 50 ten thousand is weighed and placed in the beaker, a stirrer is used for stirring at the speed of 500RPM/min to promote the dissolution of the PE powder, and the dissolution time is 60min until a transparent and stable solution a is formed;

then, putting the solution a into a stainless steel watering can for standby; preparing a water tank filled with deionized water, and quickly spraying the PE solution a into the water tank in a particle sputtering mode by using a spraying pot; the solution a contacts deionized water in a particle form and then enters the interior of the solution a, and is coagulated into PE particles b by the principle of phase separation. (ii) a

Finally, screening the obtained large number of PE particles b through a 8000-mesh screen to obtain PE particles c with the particle size of below 1.6 um;

step 2: preparation of the slurry

Adding 9.6kg of alumina powder, 0.18kg of PE particles c and 110g of sodium polyacrylate into 13kg of deionized water, mixing and stirring for 1.0h to uniformly disperse the alumina powder, adding 1.8kg of sodium carboxymethylcellulose (CMC), 0.06kg of isopropanol and 1.0kg of polymethyl acrylate, and uniformly stirring to obtain water-based slurry d;

and step 3: preparation of coated separator

Coating the water system slurry d on one side of a base film with the thickness of 9umPE in a micro gravure roll coating mode, and then baking the base film in a baking oven at the temperature of 90 ℃ for 4min to form a coating of 3um, thereby preparing the coating diaphragm of '9 umPE base film +3um alumina & PE particles', namely the double closed-cell diaphragm.

Comparative example 1

Comparative example 1 compared to example 1, the slurry contained no PE particles.

A method of making a separator comprising the steps of:

step a: preparation of the slurry

Adding 9.6kg of alumina powder and 110g of sodium polyacrylate into 13kg of deionized water, mixing and stirring for 1.0h to uniformly disperse the alumina powder and the sodium polyacrylate, and then adding 1.8kg of sodium carboxymethylcellulose (CMC), 0.06kg of isopropanol and 1.0kg of polymethyl acrylate, and stirring uniformly to obtain water-based slurry;

step b: preparation of coated separator

Coating the water system slurry on one side of a base film with the thickness of 9umPE in a micro gravure roll coating mode, and then baking the base film in a baking oven at the temperature of 90 ℃ for 4min to form a coating of 3um, thereby preparing the coating diaphragm of '9 umPE base film +3um aluminum oxide'.

Example 2

A method of making a dual closed-cell membrane, comprising the steps of:

step 1: preparation of PE particles

Firstly, 970g of styrene is weighed in a beaker to be used as a solvent, then 30g of PE powder with 50 ten thousand molecular weight is weighed and placed in the beaker, and stirring is carried out by a stirrer at the speed of 600RPM/min to promote the dissolution of the PE powder, wherein the dissolution time is 50 min. Until a transparent stable solution a is formed;

then, the solution a was charged into a stainless steel watering can for use. In addition, a water bath filled with deionized water was prepared, and the solution a of PE was rapidly sprayed as a particle sputter into the water bath using a spray can. The solution a contacts deionized water in a particle form and then enters the interior of the solution a, and is condensed into PE organic particles b of one particle by the phase separation principle;

finally, screening the particle size of the obtained large amount of PE organic particles b through a 8000-mesh screen to finally obtain PE particles c with the particle size of below 1.6 um;

step 2: preparation of the slurry

Adding 11kg of alumina powder, 0.4kg of PE particles c and 120g of sodium pyrophosphate into 14kg of deionized water, mixing and stirring for 1.5h to uniformly disperse the alumina powder, then adding 0.9kg of PVP, 0.03kg of isopropanol and 1.5kg of polyethyl acrylate, and uniformly stirring to obtain water system AL2O3& PE particles slurry d;

and step 3: preparation of coated separator

Coating the slurry d on one side of a 9umPE base film in a micro gravure roll coating mode, and then baking the coated film in an oven at 85 ℃ for 5min to form a 3um coating, thereby preparing the coating diaphragm of '9 umPE base film +3um alumina & PE particles'.

Example 3

A method of making a dual closed-cell membrane, comprising the steps of:

step 1: preparation of PE particles

Firstly, 950g of styrene is weighed by a beaker to be used as a solvent, then 50g of PE powder with the viscosity-average molecular weight of 50 ten thousand is weighed and placed in the beaker, a stirrer is used for stirring at the speed of 500RPM/min to promote the dissolution of the PE powder, and the dissolution time is 60min until a transparent and stable solution a is formed;

then, putting the solution a into a stainless steel watering can for standby; preparing a water tank filled with deionized water, and quickly spraying the PE solution a into the water tank in a particle sputtering mode by using a spraying pot; the solution a contacts deionized water in a particle form and then enters the interior of the solution a, and is coagulated into PE particles b by the principle of phase separation. (ii) a

Finally, screening the obtained large number of PE particles b through a 8000-mesh screen to obtain PE particles c with the particle size of below 1.6 um;

step 2: preparation of the slurry

Adding 11.0kg of alumina powder, 0.3kg of PE particles c and 130g of sodium pyrophosphate into 15kg of deionized water, mixing and stirring for 1.2h to uniformly disperse the alumina powder, then adding 1.6kg of PVA, 0.05kg of ethanol and 0.8kg of polyethyl acrylate, and uniformly stirring to obtain water system AL2O3& PE particles slurry d;

and step 3: preparation of coated separator

Coating the slurry d on one side of a 12umPE base film in a micro gravure roll coating mode, and then baking the coating in an oven at 80 ℃ for 6min to form a coating of 3um, thereby preparing the coating diaphragm of '12 umPE base film +4um alumina & PE particles', namely the double closed-cell diaphragm.

The results of the characteristic test of the dual closed-cell separators prepared in examples 1 to 3 and the separator prepared in comparative example 1 are shown in the following table:

as can be seen from the above table, the dual closed-cell membranes prepared by the preparation methods of examples 1 to 3, in which the PE particles are added, have significantly improved air permeability values after closing compared to comparative example 1. This indicates that the closed cell effect is significantly improved, thereby significantly improving the safety performance of the battery.

The dual closed cell membranes of the present invention were prepared according to the process parameter adjustments of the present disclosure and exhibited substantially the same performance as example 1.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.