阅读说明：本技术 一种电池电容器用复合隔膜及其制备方法 (Composite diaphragm for battery capacitor and preparation method thereof ) 是由 不公告发明人 于 2020-12-16 设计创作，主要内容包括：本发明公开了一种电池电容器用复合隔膜及其制备方法,包括湿法无纺布,设置在湿法无纺布基布两侧的静电纺丝层；湿法无纺布基布的孔隙率为60％-70％,厚度为20-30μm；静电纺丝层的厚度为5-15μm,孔径为200-300nm,孔隙率为50％-60％。本发明复合隔膜以湿法无纺布为基布,为电池电容器用复合隔膜提供了充足的机械强度,在基布表面设置静电纺丝层,能够提高复合隔膜的耐高温性能,同时可以很好的调节复合隔膜表面的孔隙大小,解决了普通湿法无纺布隔膜热稳定性差、难以进行空隙调节易造成电池短路等问题,也解决了纯静电纺丝隔膜力学强度差的问题。(The invention discloses a composite diaphragm for a battery capacitor and a preparation method thereof, wherein the composite diaphragm comprises wet non-woven fabrics and electrostatic spinning layers arranged on two sides of wet non-woven fabric base fabrics; the porosity of the wet non-woven base fabric is 60-70%, and the thickness is 20-30 μm; the thickness of the electrostatic spinning layer is 5-15 μm, the pore diameter is 200-300nm, and the porosity is 50-60%. The composite diaphragm provided by the invention takes the wet non-woven fabric as the base fabric, provides sufficient mechanical strength for the composite diaphragm for the battery capacitor, and the electrostatic spinning layer is arranged on the surface of the base fabric, so that the high temperature resistance of the composite diaphragm can be improved, the pore size of the surface of the composite diaphragm can be well adjusted, the problems that the common wet non-woven fabric diaphragm is poor in thermal stability, the battery is easy to short circuit due to the difficulty in adjusting the pores, and the like are solved, and the problem that the mechanical strength of a pure electrostatic spinning diaphragm is poor is also solved.)

1. The composite diaphragm for the battery capacitor is characterized by comprising wet-process non-woven fabrics and electrostatic spinning layers arranged on two sides of wet-process non-woven fabric base fabrics;

the porosity of the wet non-woven base fabric is 60-70%, and the thickness is 20-30 μm;

the thickness of the electrostatic spinning layer is 5-15 μm, the pore diameter is 200-300nm, and the porosity is 50-60%.

2. The composite separator for battery capacitors as claimed in claim 1, wherein the wet-process non-woven fabric has a tensile strength of not less than 4.0kN/m and a surface smoothness of 8 to 12 s.

3. The composite separator for battery capacitors as claimed in claim 1, wherein the wet-process non-woven fabric contains 10 to 20 mass% of the binder fiber.

4. The composite separator for battery capacitors as claimed in claim 1, wherein molten whiskers of the binder fibers are present on the surface of the wet-laid nonwoven fabric, and the diameter of the molten whiskers is smaller than the diameter of the binder fibers.

5. The composite separator for battery capacitors as claimed in claim 4, wherein the number of the wet-process non-woven fabric surface-melted whiskers is 3 to 4/mm²。

6. The composite separator for battery capacitors as claimed in claim 4, wherein the wet-process nonwoven fabric contains a host fiber, and the mass ratio of the host fiber to the binder fiber is 4: 1.

7. the composite separator for battery capacitors according to claim 1, wherein the material of the electrospun layer is one or more of PTFE, LCP, PI.

8. The composite separator for battery capacitors as claimed in claim 1, wherein the length of the host fiber is 5 to 6mm and the diameter is 8 to 9 μm.

9. A method for preparing a composite separator for a battery capacitor according to any one of claims 1 to 8, comprising the steps of:

1) preparing wet-process non-woven fabric raw materials into slurry, forming the slurry, drying and hot-pressing to obtain wet-process non-woven fabric;

2) spraying a polymer solution onto the surface of the wet-process non-woven fabric by an electrostatic spinning method, wherein the molten silk of the wet-process non-woven fabric is alternately inserted into an electrostatic spinning layer, and the electrostatic spinning parameters are as follows: receiving the voltage of 18-24KV at the distance of 15 cm;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 5-10 ℃ lower than the melting point of the bonding fiber under the conditions of linear pressure of 100-400N/cm and linear speed of 10-30m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

Technical Field

The invention belongs to the field of diaphragms, and particularly relates to a composite diaphragm for a battery capacitor and a preparation method thereof.

Background

The diaphragm is used as a key component of the battery/capacitor, has the main function of isolating the positive electrode and the negative electrode, and is used as a channel for ion transfer transportation to conduct electrons in the charging and discharging processes, so that the use safety, the energy density, the power density, the charging and discharging efficiency, the cycle use and other performances of the super capacitor/battery diaphragm are directly influenced.

In view of the current trend, the requirements for the separator material are mainly focused on two aspects: providing more sufficient safety guarantee and realizing better ion transmission capability. The diaphragm provides safety guarantee for the battery/capacitor working system mainly in the following aspects: under the condition of sudden abnormal high temperature, the physical form and the size are kept stable; the diaphragm has certain mechanical strength and thickness, and is prevented from being pierced by large particles, burrs, dendrites and the like; an electronic insulating property; does not react with the electrolyte and the electrode. In order to achieve better ion transport ability, it is required to have good ion conductivity and good liquid retention, and it is required to achieve uniformity of the microporous structure in structure.

At present, the diaphragm material mainly comprises a PP/PE diaphragm, non-woven fabrics, a non-woven fabric composite system and a PP/PE composite system. The PP/PE diaphragm is obtained by means of unidirectional stretching or bidirectional mechanical stretching, but the PP/PE diaphragm is low in melting point and poor in thermal stability, can be thermally shrunk at low temperature to cause safety problems, and is low in porosity, poor in moisture retention and liquid retention property and capable of influencing rapid charging and discharging. By coating the surface of the PP/PE diaphragm, the high-temperature obturator function of the diaphragm is increased, the lyophilic property to electrolyte is improved, and the temperature resistance and the flame retardant property of the diaphragm material are improved. However, the method of adding the surface coating increases the thickness of the diaphragm, increases the internal resistance of the diaphragm, increases the process flow, improves the cost, and simultaneously, the coating can enter the diaphragm gap to reduce the porosity.

The non-woven fabric has a natural pore structure, and the plant fibers generally have a large number of hydroxyl groups, so that the non-woven fabric has good moisture retention and liquid retention properties and higher ion permeability when being used as a separator. However, the nonwoven fabric has a large pore size and a low puncture strength. Inorganic particles are compounded in the non-woven fabric, the pore structure of the non-woven fabric is regulated and controlled through the inorganic particles, meanwhile, the thermal shrinkage of the diaphragm is also inhibited, and the wettability and the liquid absorption are improved. But it does not solve the dusting problem. Patent CN201810585774.3 carries out electrostatic spinning at PP melt-blown non-woven fabrics surface and forms LCP polymer layer, obvious improvement the high temperature resistance of diaphragm to the surface pore structure of diaphragm has effectively been regulated and control, but PP melt-blown non-woven fabrics intensity is low, can not compensate the problem that electrostatic spinning layer intensity is low, and the combined strength of both is also not enough in addition.

Disclosure of Invention

In order to solve the technical problems, the invention provides a composite diaphragm for a battery capacitor and a preparation method thereof, wherein the composite diaphragm has sufficient mechanical strength, can solve the problems that a common wet-process non-woven fabric diaphragm is poor in thermal stability, is difficult to adjust gaps, is easy to cause battery short circuit and the like, and also solves the problem that a pure electrostatic spinning diaphragm is poor in mechanical strength.

The technical scheme of the invention is realized as follows:

a composite diaphragm for a battery capacitor comprises a wet-process non-woven fabric and electrostatic spinning layers arranged on two sides of a wet-process non-woven fabric base fabric;

the porosity of the wet non-woven base fabric is 60-70%, and the thickness is 20-30 μm;

the thickness of the electrostatic spinning layer is 5-15 μm, the pore diameter is 200-300nm, and the porosity is 50-60%.

Furthermore, the wet-process non-woven fabric has the tensile strength of not less than 4.0kN/m and the surface smoothness of 8-12 s.

Furthermore, the wet-process non-woven fabric contains 10-20% of bonding fibers by mass percent.

Furthermore, the surface of the wet-process non-woven fabric is provided with melting whiskers of the bonding fibers, and the diameter of the melting whiskers is smaller than that of the bonding fibers.

Furthermore, the quantity of the wet-process non-woven fabric surface melting whiskers is 3-4/mm²。

Furthermore, the wet-process non-woven fabric contains main fibers, and the mass ratio of the main fibers to the bonding fibers is 4: 1.

further, the material of the electrostatic spinning layer is one or more of PTFE, LCP and PI.

Furthermore, the length of the main fiber is 5-6mm, and the diameter is 8-9 μm.

The invention also provides a preparation method of the composite diaphragm for the battery capacitor, which comprises the following steps:

1) preparing wet-process non-woven fabric raw materials into slurry, forming the slurry, drying and hot-pressing to obtain wet-process non-woven fabric;

2) spraying a polymer solution onto the surface of the wet-process non-woven fabric by an electrostatic spinning method, wherein the molten silk of the wet-process non-woven fabric is alternately inserted into an electrostatic spinning layer, and the electrostatic spinning parameters are as follows: receiving the voltage of 18-24KV at the distance of 15 cm;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 5-10 ℃ lower than the melting point of the bonding fiber under the conditions of linear pressure of 100-400N/cm and linear speed of 10-30m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

The invention provides a composite diaphragm for a battery capacitor and a preparation method thereof, the composite diaphragm takes wet non-woven fabric as base cloth, provides sufficient mechanical strength for the composite diaphragm for the battery capacitor, and is provided with an electrostatic spinning layer on the surface of the base cloth, so that the high temperature resistance of the composite diaphragm can be improved, the pore size of the surface of the composite diaphragm can be well adjusted, the problems of poor thermal stability, difficult gap adjustment, easy battery short circuit and the like of the common wet non-woven fabric diaphragm are solved, and the problem of poor mechanical strength of a pure electrostatic spinning diaphragm is also solved.

Detailed Description

For better understanding of the essence of the present invention, the following embodiments of the present invention are given only for illustrating how the present invention can be carried into effect and not for limiting the present invention to be carried into effect only by the following embodiments, and the modifications, substitutions and structural modifications of the present invention are made on the basis of understanding the technical solution of the present invention and the scope of the present invention is covered by the claims and the equivalents thereof.

The invention discloses a composite diaphragm for a battery capacitor, which comprises wet non-woven fabrics and electrostatic spinning layers arranged on two sides of wet non-woven fabric base fabrics;

the porosity of the wet non-woven base fabric is 60-70%, and the thickness is 20-30 μm;

the thickness of the electrostatic spinning layer is 5-15 μm, the pore diameter is 200-300nm, and the porosity is 50-60%.

The wet-process non-woven fabric is used as the base fabric, sufficient mechanical strength is provided for the composite diaphragm for the battery capacitor, the electrostatic spinning layer is arranged on the surface of the base fabric, the high-temperature resistance of the composite diaphragm can be improved, and meanwhile, the size of pores on the surface of the composite diaphragm can be well adjusted.

It should be noted that the porosity and pore size of the electrostatic spinning layer affect the rapid charge and discharge rate and safety, and if the porosity and pore size are too small, the charge and discharge rate is slow, and if the porosity and pore size are too large, the safety is affected.

Furthermore, the wet-process non-woven fabric has the tensile strength of not less than 4.0kN/m and the surface smoothness of 8-12 s.

Furthermore, the wet-process non-woven fabric contains 10-20% of bonding fibers by mass percent. The surface of the wet-process non-woven fabric is provided with melting whiskers of the bonding fibers, so that the wet-process non-woven fabric and the electrostatic spinning layer can be firmly combined, and the diameter of the melting whiskers is smaller than that of the bonding fibers. The number of the wet-process non-woven fabric surface melting whiskers is 3-4/mm²。

Furthermore, the wet-process non-woven fabric contains main fibers, and the mass ratio of the main fibers to the bonding fibers is 4: 1.

further, the material of the electrostatic spinning layer is one or more of PTFE, LCP and PI. The PTFE, LCP and PI have high melting point, good chemical stability, thermal stability and dimensional stability, insulation and large dielectric constant, so that the electrostatic spinning layer can obviously improve the thermal stability and dimensional stability of the diaphragm. In addition, the electrostatic spinning process can well adjust the pore size of the surface of the diaphragm.

Furthermore, the length of the main fiber is 5-6mm, and the diameter is 8-9 μm.

The invention also provides a preparation method of the composite diaphragm for the battery capacitor, which comprises the following steps:

1) preparing wet-process non-woven fabric raw materials into slurry, forming the slurry, drying and hot-pressing to obtain wet-process non-woven fabric;

2) spraying a polymer solution onto the surface of the wet-process non-woven fabric by an electrostatic spinning method, wherein the molten silk of the wet-process non-woven fabric is alternately inserted into an electrostatic spinning layer, and the electrostatic spinning parameters are as follows: receiving the voltage of 18-24KV at the distance of 15 cm;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 5-10 ℃ lower than the melting point of the bonding fiber under the conditions of linear pressure of 100-400N/cm and linear speed of 10-30m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

In step 1), hot pressing is performed using a hot roll, and the binder fibers melted by contact with the hot roll form short whiskers when they are separated from the hot roll, thereby forming molten whiskers.

To further illustrate the technical solution of the present invention, the following examples are specifically illustrated.

Example 1

The composite diaphragm for the battery capacitor comprises wet-process non-woven fabrics and electrostatic spinning layers arranged on two sides of wet-process non-woven fabric base fabrics;

the porosity of the wet non-woven base fabric is 60 percent, and the thickness of the wet non-woven base fabric is 20 mu m; the tensile strength of the wet-process non-woven fabric is not less than 4.0kN/m, and the surface smoothness is 8 s;

the thickness of the electrospun layer was 5 μm, the pore diameter was 200nm, and the porosity was 50%.

The wet-process non-woven fabric contains bonding fibers and main fibers, and the mass ratio of the main fibers to the bonding fibers is 4: 1, the mass percentage of bonding fibers in the wet-process non-woven fabric is 20 percent;

the surface of the wet-process non-woven fabric is provided with melting whiskers of the bonding fibers, and the diameter of the melting whiskers is smaller than that of the bonding fibers; the quantity of the wet-process non-woven fabric surface melting whiskers is 4/mm²(ii) a The main fiber is polyester fiber, the length of the polyester fiber is 5mm, and the diameter of the polyester fiber is 8 mu m; the bonding fiber is a full-melting fiber, and the melting point is 110 ℃;

the preparation method of the composite diaphragm for the battery capacitor comprises the following steps:

1) dispersing polyester fibers and bonding fibers in water, uniformly mixing to obtain slurry A, diluting the concentration of the slurry A to 0.05 wt%, screening, papermaking, and drying by a drying cylinder to obtain base paper B with the water content of 6.5%; carrying out hot pressing on the base paper B to obtain base cloth C, wherein the hot pressing condition is that the hot pressing temperature is 100 ℃, the linear pressure is 150N/cm, and the linear speed is 10 m/min;

2) preparing a PTFE solution, and forming electrostatic spinning layers with the thickness of 8 mu m on two sides of the base fabric C through electrostatic spinning;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 100 ℃, under the conditions of linear pressure of 100N/cm and linear speed of 10m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

Example 2

The composite diaphragm for the battery capacitor comprises wet-process non-woven fabrics and electrostatic spinning layers arranged on two sides of wet-process non-woven fabric base fabrics;

the porosity of the wet non-woven base fabric is 70%, and the thickness of the wet non-woven base fabric is 30 micrometers; the tensile strength of the wet-process non-woven fabric is not less than 4.0kN/m, and the surface smoothness is 12 s;

the thickness of the electrostatic spinning layer was 15 μm, the pore diameter was 300nm, and the porosity was 60%.

The wet-process non-woven fabric contains bonding fibers and main fibers, and the mass ratio of the main fibers to the bonding fibers is 4: 1, the mass percentage of bonding fibers in the wet-process non-woven fabric is 20 percent;

the surface of the wet-process non-woven fabric has melting whiskers of the bonding fibers, and the diameter of the melting whiskers is smaller than that of the bonding fibersDiameter of (d); the quantity of the wet-process non-woven fabric surface melting whiskers is 4/mm²(ii) a The main fiber is polyester fiber, the length of the polyester fiber is 6mm, and the diameter of the polyester fiber is 9 μm; the bonding fiber is a full-melting fiber, and the melting point is 110 ℃;

the preparation method of the composite diaphragm for the battery capacitor comprises the following steps:

1) dispersing polyester fibers and bonding fibers in water, uniformly mixing to obtain slurry A, diluting the concentration of the slurry A to 0.05 wt%, screening, papermaking, and drying by a drying cylinder to obtain base paper B with the water content of 6.5%; carrying out hot pressing on the base paper B to obtain base cloth C, wherein the hot pressing condition is that the hot pressing temperature is 100 ℃, the linear pressure is 150N/cm, and the linear speed is 10 m/min;

2) preparing a PTFE solution, and forming electrostatic spinning layers with the thickness of 8 mu m on two sides of the base fabric C through electrostatic spinning;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 105 ℃ under the conditions of linear pressure of 400N/cm and linear speed of 30m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

Example 3

The composite diaphragm for the battery capacitor comprises wet-process non-woven fabrics and electrostatic spinning layers arranged on two sides of wet-process non-woven fabric base fabrics;

the porosity of the wet non-woven base fabric is 65%, and the thickness of the wet non-woven base fabric is 25 micrometers; the tensile strength of the wet-process non-woven fabric is not less than 4.0kN/m, and the surface smoothness is 10 s;

the thickness of the electrospun layer was 10 μm, the pore diameter was 250nm, and the porosity was 55%.

The wet-process non-woven fabric contains bonding fibers and main fibers, and the mass ratio of the main fibers to the bonding fibers is 4: 1, the mass percentage of bonding fibers in the wet-process non-woven fabric is 20 percent;

the surface of the wet-process non-woven fabric is provided with melting whiskers of the bonding fibers, and the diameter of the melting whiskers is smaller than that of the bonding fibers; the quantity of the wet-process non-woven fabric surface melting whiskers is 3/mm²(ii) a The main fiber is polyester fiber, the length of the polyester fiber is 5.5mm, and the diameter of the polyester fiber is 8.6 mu m; the bonding fiber is a full-melting fiber, and the melting point is 110 ℃;

the preparation method of the composite diaphragm for the battery capacitor comprises the following steps:

1) dispersing polyester fibers and bonding fibers in water, uniformly mixing to obtain slurry A, diluting the concentration of the slurry A to 0.05 wt%, screening, papermaking, and drying by a drying cylinder to obtain base paper B with the water content of 6.5%; carrying out hot pressing on the base paper B to obtain base cloth C, wherein the hot pressing condition is that the hot pressing temperature is 100 ℃, the linear pressure is 150N/cm, and the linear speed is 10 m/min;

2) preparing a PTFE solution, and forming electrostatic spinning layers with the thickness of 8 mu m on two sides of the base fabric C through electrostatic spinning;

3) and (3) carrying out hot pressing on the product obtained in the step 2) at the temperature of 100 ℃ under the conditions of linear pressure of 200N/cm and linear speed of 20m/min, and cooling to obtain the composite diaphragm for the battery capacitor.

Comparative example 1

Based on example 3, the difference is that the pore size of the electrospun layer is 100 nm.

Comparative example 2

Based on example 3, the difference is that the porosity is 30%.

Comparative example 3

Based on example 3, with the difference that there is no step 2).

The transverse and longitudinal tensile strengths and puncture strengths of the composite separators for battery capacitors obtained in examples 1 to 3 and comparative examples 1 to 3 were measured, and the results are shown in table 1.

TABLE 1 test results

In conclusion, the above embodiments are merely intended to illustrate the technical solution of the present invention and not to limit, although the present invention has been described by referring to certain preferred embodiments thereof, it should be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.