RU2307428C2 - Nonwoven microporous material for chemical power supply separators and method for its production - Google Patents

Abstract

FIELD: materials for plate separators of chemical current supplies and storage batteries.

SUBSTANCE: proposed nonwoven material for alkali current supply separators is made of extremely thin polysulphone fiber having pore diameter of maximum 6 μm and surface density of 26 - 39 g/cm². Method for producing such material includes electric formation of extremely thin polysulphone fibers and their compression followed by treatment with surface-active material.

EFFECT: enhanced moisture and alkali absorption capacity, reduced electrical resistance, and enhanced chemical stability.

4 cl, 1 ex

Description

The invention relates to materials used as interelectrode separators in chemical current sources and electric energy batteries.

Known film separators containing elastomers selected from the group of copolymers of acrylonitrile with butadiene styrene, polyesters and the group of polyvinylidene fluoride, and its copolymers, polymethyl methacrylate, polyvinyl chloride having a porosity of 30-95% and a pore diameter of 0.1-5 microns (US 6274276, 14.08 .2001).

However, the electrical resistance of a battery with such a porous membrane is high.

To increase the specific volumetric electric capacitance and reduce electric resistance, separators are used, made of thin polymer fibers.

For example, materials for separators made of polystyrene, polyolefin, polycarbonate fibers with a fiber diameter of 0.05-20 μm and an average pore diameter of 0.5-15 μm are known (US 4137379, 01/30/1979).

Also known is material for separators of ultra-thin polypropylene fibers, where 10% of the fibers have a diameter of less than 1 μm, and most fibers with a diameter less than or equal to 5 μm, while the porosity of the material is about 90% (US 5962161, 05.10.1999).

The disadvantage of such materials is the low resistance to germination of dendrites.

The closest in technical essence and the achieved result is a fibrous non-woven material for separators of alkaline batteries made of polyaryl sulfone obtained by electrospinning fibers with a diameter of 0.6-2 microns and characterized by a pore diameter of 2-3 microns (RU 95108510 A1, 04/27/1997).

However, the known material has high conductivity values.

The closest in technical essence and the achieved result is also a method for producing a non-woven fibrous material for separators, comprising forming polysulfone fibers and treating the fiber with an impregnating composition, containing (wt.%): Surfactant 0.2-1.0; phenylglycine 0.5-1.5; the solvent is 97.5-99.3, and the treatment with the impregnating composition is carried out at 60-70 ° C for 3-20 minutes (RU 1781737, 12/15/1992).

This method is inefficient due to the long processing time, roads, and the electrical resistance of the resulting separator is high.

The objective of the present invention is to develop a microporous material for separators of alkaline chemical current sources capable of withstanding a large number of charge-discharge cycles having high alkalinity, low electrical resistance, as well as the development of a method for producing this material.

The problem is solved by the described non-woven microporous material for alkaline battery separators, which is made in three layers: the inner layer consists of fibers with a diameter of 0.3-3.0 microns, and the outer layers of fibers with a diameter of 4-8 microns, with a surface density of 26 -39 g / m ² . The resulting material has a surface density of 26-34 g / m ² , air flow resistance of at least 12 Pa at a flow rate of 1 cm / s, pore diameter of not more than 6 μm, alkali absorption of at least 150%, electrical resistance of not more than 0.05 Ohm · cm ^-1 , tensile strength not less than 0.5 kgf.

The problem is also solved by the described method for producing non-woven material for alkaline battery separators, including the electrospinning of thin-fibrous material from a solution of polysulfone in an organic solvent, the material being made three-layer: the inner layer of fibers with a diameter of 0.3-3.0 microns, and the outer layers of glued together fibers with a diameter of 4-8 microns, pressing is carried out to a material thickness of 40-60 microns, followed by pressing of this material under pressure and surface impregnation -active substance.

Typically, electroforming is carried out from a solution of polysulfone in a solvent selected from the series: dichloroethane, ethyl acetate, butyl acetate, cyclohexanone, or a mixture thereof in an amount of up to 90%.

Preferably, the pressing is carried out under pressure, 200-400 kg / cm ² are carried out at a temperature of 20-25 ° C. to a material thickness of 40-60 μm.

Below are examples of obtaining the claimed material and its characteristics.

Example

A 13% solution of polysulfone in dichloroethane is prepared with the addition of 1% cyclohexanone.

The obtained spinning solution is fed to the capillaries of different hydrodynamic resistance of the fiber electrospinning unit and the process is conducted with the following parameters:

potential difference 120 kV distance between electrodes 30 cm volumetric flow per capillary 3 · 10 ^-3 cm ³ / s

Of the fibers with a diameter of 0.9-1.1 μm, an inner layer with a surface density of 10 g / cm ^{2 is formed} . Glued layers with a surface density of 9 g / cm ² are formed from fibers with a diameter of 4.0-5.0 μm. The total surface density of the material is 28 g / cm ² .

Then the material is pressed under a pressure of 250 kg / cm ² at a temperature of 25 ° C to a thickness of 50 μm and moistened with an aqueous solution of surfactant OP-10 with a concentration of 5 g / l, followed by drying at normal temperature.

The obtained separation material of the type FPSF-6C has the following characteristics:

pore diameter 5 microns alkalinity 155% electrical resistance 0.045 Ohm · cm ² breaking load 0.6 kgf

Similarly to the above example, materials were obtained in the entire interval of the declared parameters.

The use of the obtained separation materials in alkaline batteries provides up to 1000 cycles of "charge-discharge" to the circuit. They have alkali absorption 2 times higher, and electrical resistance is 2.5 times lower than that of the prototype.

Claims (4)

1. Non-woven microporous material for separators of alkaline chemical current sources, made of ultra-thin polysulfone fiber, characterized in that it contains three layers, while the inner layer is formed of fibers with a diameter of 0.3-3 microns, the outer layers of glued fibers with a diameter 4-8 microns, while it has a pore diameter of not more than 6 microns and a surface density of 26-39 g / m ² . 2. The nonwoven material according to claim 1, characterized in that it has an alkalinity of at least 150%, an electrical resistance of not more than 0.05 Ohm · cm ² . 3. A method of producing a nonwoven microporous material for separators of alkaline chemical current sources from polysulfone fibers by treating a fibrous polymeric material with an impregnating surfactant material, characterized in that the electroforming of ultrafine fibers is carried out from a solution of polysulfone in an organic solvent, the material is made three-layer, where the inner layer is formed of fibers with a diameter of 0.3-3.0 microns, the outer layers of glued together fibers with a diameter of 4-8 microns, after which l pressed to a thickness of 40-60 microns and carry out its impregnation. 4. The method according to claim 3, characterized in that the molding is carried out from a solution of polysulfone in an organic solvent selected from the series: dichloroethane, ethyl acetate, butyl acetate, cyclohexanone or mixtures thereof.