阅读说明：本技术 一种高粘结性隔膜用水系浆料及应用其制造的锂离子电池隔膜 (High-cohesiveness water-based slurry for diaphragm and lithium ion battery diaphragm manufactured by using same ) 是由 李雪 王晓明 郭维东 王志彬 于 2019-10-22 设计创作，主要内容包括：本发明涉及锂离子电池隔膜涂敷技术领域,具体涉及一种高粘结性隔膜用水系浆料及应用其制造的锂离子电池隔膜,所述水系浆料包括如下重量份的原料：PVDF类聚合物5-15％、PMMA共聚物1-2.5％、粘合剂3-5％、稳定剂6-10％、润湿剂0.1-0.2％、分散剂0.1-0.3％和余量为去离子水。本发明利用粒径和性质不同的PVDF类聚合物和PMMA共聚物的极性和空间位阻,使制得的水系浆料中胶粒能形成相间形式,涂覆于隔膜表面提升隔膜的粘结力,降低了因大量PMMA共聚物溶胀导致黑斑析锂的风险；将制得的水系浆料应用到锂离子电池隔膜中,可增强锂离子电池隔膜与极片的粘结力强,有效提升制得锂电池的稳定性和安全性能。(The invention relates to the technical field of lithium ion battery diaphragm coating, in particular to a high-cohesiveness water-based slurry for a diaphragm and a lithium ion battery diaphragm manufactured by applying the water-based slurry, wherein the water-based slurry comprises the following raw materials in parts by weight: 5-15% of PVDF polymer, 1-2.5% of PMMA copolymer, 3-5% of adhesive, 6-10% of stabilizer, 0.1-0.2% of wetting agent, 0.1-0.3% of dispersant and the balance of deionized water. According to the invention, the polarity and the steric hindrance of the PVDF polymer and the PMMA copolymer with different particle sizes and properties are utilized, so that colloidal particles in the prepared water system slurry can form an interphase form, the colloidal particles are coated on the surface of the diaphragm to improve the binding power of the diaphragm, and the risk of black spot lithium precipitation caused by swelling of a large amount of PMMA copolymer is reduced; the prepared water system slurry is applied to the lithium ion battery diaphragm, so that the strong bonding force between the lithium ion battery diaphragm and a pole piece can be enhanced, and the stability and the safety performance of the prepared lithium battery are effectively improved.)

1. A high-cohesiveness water-based slurry for a diaphragm is characterized in that: the feed comprises the following raw materials in parts by weight:

the balance being deionized water.

2. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the PVDF polymer is at least one of polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene, polyvinyl alcohol resin, polyvinyl butyral and vinylidene fluoride-hexafluoropropylene.

3. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the PMMA copolymer is at least one of methyl methacrylate-methacrylic acid copolymer, methyl methacrylate-ethacrylic acid copolymer, methyl methacrylate-ethyl methacrylate copolymer and methyl methacrylate-butyl methacrylate copolymer.

4. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the stabilizer is at least one of hydroxypropyl methylcellulose, sodium carboxymethylcellulose and methylcellulose.

5. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the adhesive is at least one of styrene-butadiene rubber, polyurethane, epoxy resin, acrylic polymer and acrylonitrile polymer.

6. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the wetting agent is at least one of siloxane, glycerol and N-methyl pyrrolidone.

7. A high-adhesiveness water-based paste for separators as claimed in claim 1, wherein: each part of the dispersing agent is at least one of ethanol, polyethylene glycol and isopropanol.

8. A high-cohesiveness aqueous slurry for separators as set forth in any one of claims 1 to 7, wherein: the aqueous slurry is prepared by the following steps:

1) adding deionized water, PVDF polymer, PMMA copolymer and binder into a stirrer according to the weight ratio, and stirring to obtain a mixture A for later use;

2) adding a stabilizer into the mixture A, and stirring while keeping the stirring speed unchanged to obtain a stable dispersion system B;

3) and adding a dispersing agent into the dispersion system B, stirring under the same stirring condition, adding a wetting agent, reducing the stirring speed, stirring, and filtering to obtain the finished product of the water-based slurry.

9. A high-adhesiveness water-based paste for separators as claimed in claim 8, wherein: the stirring speed in the step 1) is 1000-1500r/min of rotation speed and 30-40r/min of revolution speed; the stirring time in the step 2) is 30-60 min; the stirring time after the dispersant is added into the dispersion system B in the step 3) is 1.5 to 2 hours, the stirring speed after the wetting agent is added is 10 to 20r/min of revolution speed, 200r/min of rotation speed and 25 to 35min of stirring speed.

10. A lithium ion battery diaphragm containing a high-cohesiveness water-based slurry coating for diaphragms is characterized in that: the lithium ion battery diaphragm is obtained by coating the water-based slurry for the high-adhesion diaphragm of claims 1 to 7 on the surface of a polyethylene base film at a speed of 40 to 60m/min by utilizing a micro-gravure coating mode, wherein the coating thickness is 1 mu m, and finally, drying at the temperature of 40 to 50 ℃ for 0.5 to 3.0 min.

Technical Field

The invention relates to the technical field of lithium ion battery diaphragm coating, in particular to a high-cohesiveness water-based slurry for a diaphragm and a lithium ion battery diaphragm manufactured by applying the same.

Background

The lithium ion battery diaphragm is used as an important component of the lithium ion battery, and the property of the diaphragm directly determines the capacity, the cycle performance, the charge-discharge current density and the safety of the battery. The adhesion between the diaphragm and the pole piece is also an important index for evaluating the quality of the diaphragm, and the direct bonding influences the hardness and the shape retention capability of the battery core. However, with the current demands of power and energy storage systems for high output and high capacity of batteries and the demands of 3C lithium battery rapid charging performance, the adhesion force of the diaphragm and the pole piece cannot meet the demands of these developments, so that the development of a more stable and more adhesive lithium ion battery diaphragm is urgently needed, and deformation and battery softening caused by thermal shock or other factors are reduced to the maximum extent.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide the water system slurry for the high-adhesion diaphragm, and the water system slurry for the high-adhesion diaphragm is prepared by utilizing the PVDF polymer and the PMMA copolymer with different particle sizes and properties, and the colloidal particles in the prepared water system slurry can form an interphase form and are coated on the surface of the ceramic diaphragm due to the polarity and the steric hindrance of the PVDF polymer and the PMMA copolymer, so that the higher adhesion is met, the risk of lithium precipitation caused by the swelling of a large amount of PMMA copolymer is reduced, and the stability and the safety performance of a lithium ion battery in use are improved.

The invention also aims to provide the application of the high-adhesion water-based slurry for the diaphragm in the lithium ion battery diaphragm, the lithium ion battery diaphragm using the water-based slurry has strong adhesion with a pole piece, and the stability and the safety performance of the prepared lithium battery in use are effectively improved.

The purpose of the invention is realized by the following technical scheme: the high-cohesiveness water-based slurry for the diaphragm comprises the following raw materials in parts by weight:

the aqueous slurry is prepared by the following steps:

1) adding deionized water, PVDF polymer, PMMA copolymer and adhesive into a stirrer with the rotation rate of 1000-1500r/min and the revolution rate of 30-40r/min according to the weight ratio, and stirring for 30-60min to obtain a mixture A for later use;

2) adding a stabilizer into the mixture A, and stirring for 30-60min while keeping the stirring speed unchanged to obtain a stable dispersion system B;

3) adding a dispersing agent into the dispersion system B, and stirring for 1.5-2h under the same stirring condition; then adding a wetting agent, reducing the stirring speed until the revolution speed is 10-20r/min, the rotation speed is 100-.

The water system slurry prepared by the method can form an interphase form by utilizing the polarity and steric hindrance of the PVDF polymer and the PMMA copolymer with different particle sizes and properties, and is coated on the surface of the ceramic diaphragm, so that higher cohesive force is met, the risk of black spot lithium precipitation caused by swelling of a large amount of PMMA copolymer is reduced, and the stability and the safety performance of a lithium ion battery in use are improved. In addition, the step 1) in the preparation process of the water system slurry mainly aims at enabling colloidal particles in the prepared water system slurry to form an interphase form by utilizing the polarity and the steric hindrance of the PVDF polymer and the PMMA copolymer and coating the colloidal particles on the surface of the ceramic diaphragm, so that higher cohesive force is met; meanwhile, the rotation rate of 1000-; the addition of the adhesive can effectively improve the adhesiveness of a slurry system, is beneficial to firmly combining the water system slurry and the matrix diaphragm when the water system slurry is coated on the diaphragm, and effectively improves the stability and safety performance of the prepared lithium battery in use.

Preferably, each part of the PVDF polymer is at least one of polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene, polyvinyl alcohol resin, polyvinyl butyral and vinylidene fluoride-hexafluoropropylene; more preferably, the PVDF polymer is a mixture of modified polyvinylidene fluoride, polyvinyl alcohol resin, polyvinyl butyral and vinylidene fluoride-hexafluoropropylene in a weight ratio of 0.8-1.2:0.4-0.8:0.6-1.0: 0.1-0.5; the modified polyvinylidene fluoride is prepared by the following method: s1, adding 20-30 parts of polyvinylidene fluoride into 1-5 parts of N-methyl pyrrolidone and 4-8 parts of hydroxyethyl methacrylate solution, introducing ozone, and stirring for 20-40min to obtain a mixture solution for later use; s2, placing the mixture liquid obtained in the step S1 in a water bath, heating to 50-60 ℃ under the protection of nitrogen, stirring for 1-3h, and finally standing, filtering and drying to obtain the modified polyvinylidene fluoride.

The polyvinylidene fluoride used in the invention has stable chemical property and good heat resistance, but the membrane surface prepared from the polyvinylidene fluoride has strong hydrophobicity and is easy to generate adsorption pollution, so that the polyvinylidene fluoride needs to be modified, and the surface hydrophilic ability of the polyvinylidene fluoride modified by the method is enhanced, thus being beneficial to the dispersion of the polyvinylidene fluoride in slurry; the polyvinyl alcohol resin can avoid the characteristic of weak bonding property of pure PVDF, and can synergistically modify the excellent bonding property of polyvinylidene fluoride, polyvinyl butyral and vinylidene fluoride-hexafluoropropylene, so that the bonding property of the prepared water-based slurry can be further enhanced, and the bonding force of the lithium ion battery diaphragm and the pole piece prepared by the water-based slurry is favorably utilized.

Preferably, each part of the PMMA copolymer is at least one of a methyl methacrylate-methacrylic acid copolymer, a methyl methacrylate-ethacrylic acid copolymer, a methyl methacrylate-ethyl methacrylate copolymer and a methyl methacrylate-butyl methacrylate copolymer; more preferably, the PMMA copolymer is a mixture of a methyl methacrylate-methacrylic acid copolymer, a methyl methacrylate-ethacrylic acid copolymer, a methyl methacrylate-ethyl methacrylate copolymer and a methyl methacrylate-butyl methacrylate copolymer in a weight ratio of 0.6-1.0:0.8-1.2:0.1-0.5: 0.4-0.8.

According to the invention, the PMMA copolymer is adopted, so that the defect that color spots are easy to precipitate when pure PMMA is used for preparing the slurry can be avoided, and the polarity and the steric hindrance of the PMMA copolymer are utilized to enable colloidal particles in the prepared water system slurry to form an interphase form when the PMMA copolymer is compounded with the PVDF polymer, so that the prepared water system slurry can be coated on the surface of a ceramic diaphragm, and therefore, higher binding power is met, and the stability and the safety performance of the prepared lithium battery are effectively improved when the lithium battery.

Preferably, each part of the stabilizer is at least one of hydroxypropyl methylcellulose, sodium carboxymethyl cellulose and methylcellulose; more preferably, the stabilizer is a mixture of sodium carboxymethyl cellulose, methylcellulose and 4% of hydroxypropyl methylcellulose in a weight ratio of 0.6-1.0:0.8-1.2: 0.1-0.5. Each part of the adhesive is at least one of styrene-butadiene rubber, polyurethane, epoxy resin, acrylic polymer and acrylonitrile polymer; more preferably, the adhesive is a mixture of styrene-butadiene rubber, epoxy resin and acrylonitrile polymer in a weight ratio of 0.8-1.2:0.6-1.0: 0.4-0.8.

The hydroxypropyl methyl cellulose adopted in the invention can be dissolved in cold water to form transparent viscous solution, and has the characteristics of thickening, bonding, dispersing, emulsifying, film forming, suspending, adsorbing, gelling, surface activity, moisture retention, protective colloid and the like; the methyl cellulose is quite stable in aqueous solution at normal temperature, can be gelled at high temperature, can be mutually transformed with the solution along with the temperature, has excellent wettability, dispersibility, adhesiveness, thickening property, emulsifying property, water-retaining property and film-forming property, is beneficial to firmly combining water-based slurry and a substrate diaphragm when the water-based slurry is sprayed on the diaphragm, and strengthens the adhesive force between the lithium ion battery diaphragm and a pole piece; the adopted binder can well ensure that the water system slurry is uniformly coated on the surface of the substrate diaphragm and is not easy to fall off.

Preferably, each part of the wetting agent is at least one of siloxane, glycerol and N-methyl pyrrolidone; more preferably, the humectant is a mixture of silicone, glycerin and N-methyl pyrrolidone in a weight ratio of 0.8-1.2:0.4-0.8: 0.6-1.0. Each part of the dispersing agent is at least one of ethanol, polyethylene glycol and isopropanol; more preferably, the dispersing agent is a mixture of polyethylene glycol, isopropanol and 99% of ethanol by weight ratio of 0.4-0.8:0.8-1.2: 0.6-1.0.

The wetting agent adopted in the invention has the advantages of heat resistance, cold resistance, small viscosity change along with temperature, small surface tension, heat conductivity and the like, and can further assist in improving the caking property, the flame retardance and the electric conductivity of the prepared ceramic slurry in the process of preparing the water system slurry; the dispersing agent is a mixture consisting of polyethylene glycol, isopropanol and ethanol with the mass fraction of 99% according to the weight ratio of 0.4-0.8:0.8-1.2:0.6-1.0, and can increase the repulsive force among particles so as to overcome the agglomeration caused by the van der Waals attractive force among the particles.

The invention also provides a lithium ion battery diaphragm containing the high-adhesion water-based slurry coating for the diaphragm, which is obtained by coating the high-adhesion water-based slurry for the diaphragm on the surface of a polyethylene base film by a micro gravure coating mode at the speed of 40-60m/min, wherein the coating thickness is 1 mu m, and finally drying at the temperature of 40-50 ℃ for 0.5-3.0 min.

The lithium ion battery diaphragm using the water system slurry has strong binding power with the pole piece, and the stability and the safety performance of the prepared lithium battery during use are effectively improved.

The invention has the beneficial effects that: according to the invention, by utilizing the polarity and steric hindrance of the PVDF polymer and the PMMA copolymer with different particle sizes and properties, colloidal particles in the prepared water system slurry can form an interphase form and can be coated on the surface of the diaphragm, so that higher binding power is met, the risk of lithium precipitation caused by the swelling of a large amount of PMMA copolymer is reduced, and the stability and safety performance of the lithium ion battery in use are improved; the prepared water system slurry is applied to the lithium ion battery diaphragm, so that the strong bonding force between the lithium ion battery diaphragm and the pole piece can be enhanced, and the dry pressing bonding force between the diaphragm and the pole piece with the stability and safety performance when the prepared lithium battery is used is effectively improved.

Drawings

FIG. 1 is a graph comparing the dry press adhesion of aqueous slurry coating to a pole piece in accordance with the present invention.

Detailed Description

For the understanding of those skilled in the art, the present invention will be further described with reference to the following examples and the accompanying fig. 1, and the description of the embodiments is not intended to limit the present invention.