RU2279157C2 - Non-woven microporous material for separators of alkaline cells and method for its production - Google Patents

Abstract

FIELD: electrical engineering; materials for plate-to-plate separators of alkaline cells and batteries.

SUBSTANCE: proposed non-woven microporous material for alkaline-cell separators produced from extremely thin perchlorovinyl fibers is three-layer material having surface density of 26-30 g/cm² and pore diameter of maximum 6 μm. Proposed method for producing non-woven microporous material for alkaline-cell separators includes electroforming of extremely thin fibers, compression of material by applying pressure, and its treatment with surface-active material.

EFFECT: enhanced moisture and alkali absorbency, low resistance, and high chemical stability of material.

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 styrene butadiene, 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 of 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 material for a separator of chemical current sources made of perchlorovinyl ultrathin fibers with a diameter of about 1-7 μm (Yu.N. Filatov, Electroforming of fibrous materials, M .: Oil and gas, 1997, pg. 99 and 278).

Closest to the proposed method is a method of manufacturing a known material, which consists in pressing fibrous perchlorovinyl material under pressure from 100 to 400 kg / cm ² and processing with a surfactant of the type OP-7 or OP-10 (RU 166393, 09/19/1964) .

The disadvantage of this material is the low resistance to germination of dendrites and insufficient electrical conductivity, due to the low alkalinity.

The objective of the present invention is to develop a microporous material for separators of alkaline chemical current sources with increased resistance to germination of dendrites, an increase in alkalinity and a decrease in electrical resistance.

The problem is solved by the described non-woven porous material for separators of chemical power sources from ultrafine perchlorovinyl fiber, which is made of three layers, the inner layer of hydrophilic fibers with a fiber diameter of 0.3-1.3 microns, and the outer layers of hydrophilic fibers with a diameter of 4-8 microns while the surface density of the material is 26-30 g / m ² .

Mostly the material has a pore diameter of 6 μm, alkali absorption of at least 130%, water absorption of at least 1000%, electrical resistance of not more than 0.055 Ohm / cm ² , tensile strength of not less than 18 kgf / cm ² , elongation at burst of not less than 25% .

The problem is also solved by the described method of manufacturing a non-woven porous material for chemical current sources, including the electroforming of ultrafine fibers from a solution of perchlorovinyl resin in an organic solvent in the presence of surfactants in a spinning solution, the material is made three-layer, the inner layer of fibers with a diameter of 0.3 1.3 microns, and the outer layers of glued together fibers with a diameter of 4-8 microns, then they are pressed to a material thickness of 40-60 microns.

Preferably, the spinning solution contains organic solvents selected from the range: dichloroethane, ethyl acetate, butyl acetate, cyclohexanone or mixtures thereof in an amount up to 90% with additives of surfactants selected from the range: alkylarylsulfonic acid or its salts in an amount up to 5%.

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

Example

A 14% solution of perchlorovinyl in dichloroethane is prepared with the addition of 3% alkylarylsulfonic acid and 2% 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

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

Then the material is pressed at a pressure of 300 kg / cm ² at a temperature of 20 ° C to a thickness of 55 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 FPP-10SG type has the following characteristics:

pore diameter 5 microns water absorbency 1100% alkalinity 150% electrical resistance 0,050 Ohm · cm ² tensile strength 20 kgf / cm ² elongation at break 28%

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 600 charge-discharge cycles to circuit. They have alkali absorption of 1.5 times higher, and the electrical resistance is 2 times lower than that of the prototype.

Claims (4)

1. Non-woven microporous material for separators of alkaline current sources from ultrafine perchlorovinyl fiber, characterized in that it is made of three layers: the inner consists of hydrophilized fibers with a diameter of 0.3 ÷ 1.3 μm, and the outer layers are made of hydrophilized glued together fibers with a diameter of 4 ÷ 8 μm, with a surface density of 26 ÷ 30 g / cm ² and a pore diameter of not more than 6 μm. 2. The nonwoven material according to claim 1, characterized in that it has a water absorbency of at least 1000%, alkali absorbency of at least 130%, electrical resistance of not more than 0.055 Ohm.cm ² , tensile strength of at least 18 kgf / cm, elongation at a break of at least 25%. 3. A method of producing a nonwoven microporous material for separators of alkaline chemical current sources, including the formation of ultrafine fibers from a polymer solution in an organic solvent, pressing the material under pressure and processing with a surfactant, characterized in that the fibers are electroformed from a solution of polysulfone in an organic solvent, the material is made three-layer: the inner layer is made of fibers with a diameter of 0.3-3.0 microns, and the outer layers are made of diam trom 4-8 microns, pressing is carried out to a material thickness of 40-60 microns. 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.