CN108039440A - Viscous diaphragm for power battery and preparation method thereof - Google Patents

Abstract

The invention also discloses an adhesive diaphragm for a power battery, wherein at least one surface of the base film is coated with an oxide coating, and at least one surface of the base film coated with the oxide coating is coated with a viscous slurry layer. The invention also discloses a method for preparing a viscous diaphragm for a power battery, comprising: mixing an inorganic solid oxide, an auxiliary agent, and water to obtain a pre-dispersion of the inorganic solid oxide; coating the pre-dispersion of the inorganic solid oxide on The surface of the base film is dried to obtain the first diaphragm; the viscous polymer solution, the adhesion promoter and the wetting agent are mixed to obtain the viscous slurry; the viscous slurry is coated on the surface of the first diaphragm and dried to obtain the viscous diaphragm. The invention adopts the water-based viscous diaphragm as the diaphragm of the power battery, and bonds the positive and negative plates of the electrodes together, which not only effectively avoids the misalignment of the diaphragm and the poles caused by battery drop and collision, but also has high safety, and can reduce lithium ion intercalation, The "dead zone" in the de-intercalation process is of great significance for the improvement of the battery interface.

Description

A kind of viscous diaphragm for power battery and preparation method thereof

technical field

The invention relates to the technical field of power battery diaphragms, in particular to a viscous diaphragm for power batteries and a preparation method thereof.

Background technique

Lithium-ion batteries are widely used in large-scale applications such as national defense industry, electric industry, and space technology because of their advantages such as high energy density, high working voltage, long cycle life, and no memory effect.

Lithium-ion batteries are mainly composed of positive and negative electrode materials, electrolyte, diaphragm, and casing. As one of the key materials of lithium-ion batteries, the diaphragm is characterized by blocking the positive and negative electrodes, preventing short circuit, allowing only lithium ions to pass through and not allowing electrons to pass through. The performance of the diaphragm determines the interface structure and internal resistance of the battery, which directly affects the battery. Capacity, cycle and safety performance and other characteristics.

Power lithium-ion batteries have higher and higher requirements for battery safety performance. With the increase of energy density of lithium-ion batteries, the diaphragm is gradually becoming lighter and thinner. However, the gap between the existing lithium-ion diaphragm and the positive and negative electrodes is large, and the positive and negative electrodes It is easy to slide and displace between sheets, and the positive and negative poles of the battery are easy to contact and short circuit, which is poor in safety. In addition, lithium ions are prone to produce "dead zones" during the intercalation and deintercalation process, which needs to be solved urgently.

Contents of the invention

Based on the technical problems existing in the background technology, the present invention proposes a viscous separator for a power battery and its preparation method. The obtained separator bonds the positive and negative electrodes of the electrode together, which not only effectively prevents the battery from falling and colliding with the separator and the electrode. Dislocation phenomenon, high safety, and can reduce the "dead zone" in the process of lithium ion intercalation and deintercalation. In addition, the obtained separator has low thermal shrinkage, the diaphragm and the pole piece are tightly connected, good safety performance, and wettability to the electrolyte , Strong liquid absorption and liquid retention capacity.

The present invention provides an adhesive separator for a power battery, at least one surface of a base film is coated with an oxide coating, and at least one surface of the base film coated with the oxide coating is coated with a viscous slurry layer.

Preferably, the thickness of the base film is 12 μm-16 μm.

Preferably, the thickness of the oxide coating is 2-4 μm.

Preferably, the total thickness of the viscous separator for the power battery is 16-18 μm.

Preferably, the base film is a polyethylene film.

Preferably, the oxide coating comprises an inorganic solid oxide and a promoter. Further preferably, the inorganic solid oxide is at least one of boehmite, SiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ .

A kind of preparation method of the viscous diaphragm for power battery proposed by the present invention comprises the following steps:

S1, mixing the inorganic solid oxide, additives, and water to obtain a pre-dispersion of the inorganic solid oxide;

S2. Coating the inorganic solid oxide pre-dispersion on the surface of the base film and drying to obtain the first separator;

S3, mixing the viscous polymer solution, the adhesion promoter, and the wetting agent to obtain a viscous slurry;

S4. Coating the viscous slurry on the surface of the first separator and drying it to obtain a viscous separator for a power battery.

Preferably, in S1, the mass fraction of the inorganic solid oxide predispersion liquid is 30-40%.

Preferably, in S1, the auxiliary agents include dispersants, defoamers, binders, and wetting agents.

Preferably, in S1, based on the mass of the inorganic solid oxide, the content of the dispersant is 0.3-0.6wt%, the content of the defoamer is 0.5-1.5wt%, the content of the binder is 5-10wt%, and the wetting agent The content is 0.5-0.8wt%.

Preferably, in S3, the mass fraction of the viscous slurry is 10-20%.

Further preferably, in S3, based on the mass of the viscous polymer solution, the content of the adhesion promoter is 1-5 wt%.

Further preferably, in S3, based on the mass of the viscous slurry, the content of the wetting agent is 0.1-0.5 wt%.

Preferably, in S3, the viscous polymer solution is polyvinylidene fluoride solution and/or polymethyl methacrylate solution. Further preferably, in S3, the viscous polymer solution is obtained by mixing polymethyl methacrylate and polyvinylidene fluoride at a mass ratio of 1:1-5.

Preferably, in S2 and S4, the coating method is single-side coating and/or double-side coating.

Preferably, the coating means is at least one of microgravure coating, spray coating and spot coating.

Among the present invention, dispersant, binding agent, wetting agent and defoaming agent are materials commonly used in the art, such as dispersing agent can adopt high molecular polyester material, binding agent can adopt acrylic material, and wetting agent can adopt Polyether oxygen copolymer, defoamer can use silicone resin.

Compared with the prior art, the present invention has the remarkable advantages of:

1. Compared with the traditional lithium-ion battery diaphragm, the present invention uses a viscous diaphragm as the power battery diaphragm, and the viscous diaphragm bonds the positive and negative electrodes of the electrode together, effectively reducing the thermal shrinkage performance of the diaphragm and effectively avoiding the battery The dislocation of the diaphragm and the positive and negative electrodes caused by the drop and collision reduces the incidence of short circuit and improves the safety performance of the battery. At the same time, the use of viscous diaphragm can effectively reduce the "dead zone" in the process of intercalation and deintercalation of lithium ions. ", which is of great significance for the improvement of the battery interface.

2. The present invention uses inorganic solid oxides for coating, which improves the wettability of the diaphragm to the electrolyte and the ability to absorb and retain liquid, thereby improving the cycle performance of lithium-ion batteries. is also of great significance.

3. The present invention adopts water-based viscous diaphragm coating material, which is economical and environmentally friendly.

Description of drawings

Fig. 1 is a scanning electron microscope image of the viscous diaphragm for a power battery obtained in Example 1 of the present invention.

Fig. 2 is a scanning electron microscope image of the viscous separator for a power battery obtained in Example 3 of the present invention.

Fig. 3 is a scanning electron microscope image of the viscous separator for a power battery obtained in Example 4 of the present invention.

Fig. 4 is a scanning electron microscope image of the viscous diaphragm for a power battery obtained in Example 7 of the present invention.

Detailed ways

Below, the technical solution of the present invention will be described in detail through specific examples.

Example 1

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Mix 100g of Al ₂ O ₃ powder, 0.6g of dispersant, 1g of defoamer and appropriate amount of water, stir at a speed of 1500r/min for 2h, then add 8g of binder, and stir evenly at a speed of 600r/min to obtain The mass fraction is 40% inorganic solid oxide predispersion liquid;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first separator with a coating thickness of 4 μm;

S3. Add an appropriate amount of wetting agent and 5 g of adhesion promoter to 100 g of aqueous polyvinylidene fluoride solution, and stir evenly at a speed of 500 r/min to obtain a viscous slurry with a mass fraction of 20%, and the weight of the viscous slurry and wetting agent The ratio is 100:0.4;

S4. Apply the viscous slurry to the surface of the first separator by gravure coating on both sides, and dry to obtain a viscous separator for a power battery with a total thickness of 18 μm.

The viscous diaphragm for power battery obtained in this example was scanned by an electron microscope, as shown in FIG. 1 .

Example 2

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g of Al ₂ O ₃ powder, 0.5g of dispersant, 0.8g of defoamer and appropriate amount of water at a speed of 1500r/min for 2 hours, then add 6g of binder and stir evenly at a speed of 600r/min to obtain mass Inorganic solid oxide predispersion liquid with a fraction of 35%;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first separator with a coating thickness of 3 μm;

S3. Add an appropriate amount of wetting agent and 3 g of adhesion promoter to 100 g of aqueous polyvinylidene fluoride solution, and stir evenly at 500 r/min to obtain a viscous slurry with a mass fraction of 15%, and the weight ratio of the viscous slurry to the wetting agent for 100:0.4;

S4. Apply the viscous slurry to the surface of the first separator by gravure coating on both sides, and dry to obtain a viscous separator for a power battery with a total thickness of 17 μm.

Example 3

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g boehmite powder, 0.5g dispersant, 0.8g defoamer and appropriate amount of water at a speed of 1500r/min for 2h, then add 6g of binder, stir evenly at a speed of 500r/min to obtain the mass fraction 30% inorganic solid oxide pre-dispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first separator with a coating thickness of 2 μm;

S3. Add an appropriate amount of wetting agent and 3 g of adhesion promoter to 100 g of aqueous polyvinylidene fluoride solution, and stir evenly at a speed of 500 r/min to obtain a viscous slurry with a mass fraction of 15%, and the weight of the viscous slurry and wetting agent The ratio is 100:0.4;

S4. Apply the viscous slurry on both sides of the first separator by spraying, and dry to obtain a viscous separator for a power battery with a total thickness of 16 μm.

The viscous diaphragm for power battery obtained in this example was scanned by an electron microscope, as shown in FIG. 2 .

Example 4

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g of MgO powder, 0.3g of dispersant, 0.5g of defoamer and appropriate amount of water at a speed of 1500r/min for 2 hours, then add 5g of binder, and stir evenly at a speed of 500r/min to obtain a mass fraction of 35 % inorganic solid oxide predispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first separator with a coating thickness of 3 μm;

S3. Add an appropriate amount of wetting agent and 1 g of adhesion promoter to 100 g of water-based polymethyl methacrylate solution, and stir evenly at a speed of 500 r/min to obtain a viscous slurry with a mass fraction of 10%, and the viscosity of the viscous slurry and wetting agent The weight ratio is 100:0.2;

S4. Apply the viscous slurry to the surface of the first separator by gravure coating on both sides, and dry to obtain a viscous separator for a power battery with a total thickness of 16 μm.

Electron microscope scanning was performed on the viscous diaphragm for power battery obtained in this example, as shown in FIG. 3 .

Example 5

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g _ZrO2 powder, 0.4g dispersant, 0.5g defoamer and appropriate amount of water at a speed of 2000r/min for 2h, then add 10g of binder and stir evenly at a speed of 600r/min to obtain a mass fraction of 40% inorganic solid oxide pre-dispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first diaphragm with a coating thickness of 4 μm;

S3. Add an appropriate amount of wetting agent and 4 g of adhesion promoter to 100 g of water-based polymethyl methacrylate solution, and stir evenly at a speed of 500 r/min to obtain a viscous slurry with a mass fraction of 15%, viscous slurry and wetting agent The weight ratio is 100:0.1;

S4. Apply the viscous slurry on both sides of the first separator by dot coating, and dry to obtain a viscous separator for a power battery with a total thickness of 17 μm.

Example 6

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g of Al ₂ O ₃ powder, 0.6g of dispersant, 1g of defoamer and appropriate amount of water at a speed of 1500r/min for 2h, then add 8g of binder, and stir evenly at a speed of 600r/min to obtain the mass fraction 40% inorganic solid oxide pre-dispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first diaphragm with a coating thickness of 4 μm;

S3. Mix the aqueous polymethyl methacrylate solution and the aqueous polyvinylidene fluoride solution in a mass ratio of 3:7 to obtain a mixed aqueous polymer solution; add an appropriate amount of wetting agent and 5 g of an adhesion promoter to 100 g of the mixed aqueous polymer solution , stir evenly at a speed of 500r/min to obtain a viscous slurry with a mass fraction of 20%, and the weight ratio of the viscous slurry to the wetting agent is 100:0.5;

S4. Apply the viscous slurry on the surface of the first separator by gravure coating on one side, and dry to obtain a viscous separator for power batteries with a total thickness of 17 μm.

Example 7

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g of Al ₂ O ₃ powder, 0.6g of dispersant, 1g of defoamer and appropriate amount of water at a speed of 1500r/min for 2h, then add 8g of binder, and stir evenly at a speed of 600r/min to obtain the mass fraction 40% inorganic solid oxide pre-dispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first diaphragm with a coating thickness of 4 μm;

S3. Mix the aqueous polymethyl methacrylate solution and the aqueous polyvinylidene fluoride solution at a mass ratio of 1:4 to obtain a mixed aqueous polymer solution; add an appropriate amount of wetting agent and 5 g of an adhesion promoter to 100 g of the mixed aqueous polymer solution , stir evenly at a speed of 500r/min to obtain a viscous slurry with a mass fraction of 20%, and the weight ratio of the viscous slurry to the wetting agent is 100:0.5;

S4. Apply the viscous slurry to the surface of the first separator by gravure coating on both sides, and dry to obtain a viscous separator for a power battery with a total thickness of 17 μm.

The viscous separator for the power battery obtained in this example was scanned by an electron microscope, as shown in FIG. 4 .

Example 8

A method for preparing a water-based adhesive diaphragm for a power battery, comprising the following steps:

S1. Stir 100g of Al ₂ O ₃ powder, 0.6g of dispersant, 1g of defoamer and appropriate amount of water at a speed of 1500r/min for 2h, then add 8g of binder, and stir evenly at a speed of 600r/min to obtain the mass fraction 40% inorganic solid oxide pre-dispersion;

S2. Coating the inorganic solid oxide predispersion on a polyethylene film with a thickness of 12 μm, and drying to obtain a first diaphragm with a coating thickness of 4 μm;

S3. Mix the aqueous polymethyl methacrylate solution and the aqueous polyvinylidene fluoride solution at a mass ratio of 1:1 to obtain a mixed aqueous polymer solution; add an appropriate amount of wetting agent and 5 g of an adhesion promoter to 100 g of the mixed aqueous polymer solution , stir evenly at a speed of 500r/min to obtain a viscous slurry with a mass fraction of 20%, and the weight ratio of the viscous slurry to the wetting agent is 100:0.5;

S4. Apply the viscous slurry on the surface of the first separator on both sides by spraying, and dry to obtain a viscous separator for a power battery with a total thickness of 17 μm.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (10)

1. An adhesive diaphragm for a power battery, characterized in that an oxide coating is coated on at least one surface of a base film, and a viscous slurry layer is coated on at least one surface of the base film coated with an oxide coating. 2. The adhesive diaphragm for power battery according to claim 1, wherein the thickness of the base film is 12 μm-16 μm; preferably, the thickness of the oxide coating is 2-4 μm; preferably, the total thickness of the adhesive diaphragm for power battery is 16-18 μm. 3. The viscous diaphragm for power battery according to claim 1 or 2, wherein the base film is a polyethylene film; preferably, the oxide coating includes an inorganic solid oxide and an auxiliary agent; further preferably, the inorganic solid oxide The compound is at least one of boehmite, SiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ . 4. A preparation method for an adhesive diaphragm for a power battery as claimed in any one of claims 1-3, characterized in that it comprises the following steps: S1, mixing the inorganic solid oxide, additives, and water to obtain a pre-dispersion of the inorganic solid oxide; S2. Coating the inorganic solid oxide pre-dispersion on the surface of the base film and drying to obtain the first separator; S3, mixing the viscous polymer solution, the adhesion promoter, and the wetting agent to obtain a viscous slurry; S4. Coating the viscous slurry on the surface of the first separator and drying it to obtain a viscous separator for a power battery. 5. The method for preparing an adhesive diaphragm for power batteries according to claim 4, wherein, in S1, the mass fraction of the inorganic solid oxide predispersion liquid is 30-40%. 6. According to the preparation method of the viscous diaphragm for power battery described in claim 4 or 5, it is characterized in that, in S1, the auxiliary agent includes a dispersant, an antifoaming agent, a binding agent, a wetting agent; preferably, an inorganic solid Based on the mass of the oxide, the content of the dispersant is 0.3-0.6wt%, the content of the defoamer is 0.5-1.5wt%, the content of the binder is 5-10wt%, and the content of the wetting agent is 0.5-0.8wt%. 7. The method for preparing a viscous diaphragm for a power battery according to any one of claims 4-6, wherein, in S3, the mass fraction of the viscous slurry is 10-20%; preferably, the viscous polymer solution Based on the mass, the content of the adhesion promoter is 1-5 wt %; based on the mass of the viscous slurry, the content of the wetting agent is 0.1-0.5 wt %. 8. The method for preparing an adhesive diaphragm for a power battery according to any one of claims 4-7, wherein, in S3, the adhesive polymer solution is a polyvinylidene fluoride solution and/or a polymethyl methacrylate solution; Further preferably, in S3, the viscous polymer solution is obtained by mixing polymethyl methacrylate and polyvinylidene fluoride at a mass ratio of 1:1-5. 9. The method for preparing an adhesive separator for a power battery according to any one of claims 4-8, wherein, in S2 and S4, the coating method is single-sided coating and/or double-sided coating. 10. The method for preparing an adhesive diaphragm for a power battery according to claim 9, wherein the coating means is at least one of microgravure coating, spray coating, and spot coating.