JPS6113558A - Separator for alkaline storage battery - Google Patents

Abstract

PURPOSE:To prevent short caused by active material especially in the starting part of winding of plate by using polyamide base woven fabric or nonwoven fabric in the outer layers and using a polyolefin porous film in a part of at least one layer of the inner layers. CONSTITUTION:An outer layer 1 consists of polyamide base nonwoven fabric to retain electrolyte and brings a plate into good contact with a separator. A part of the polyamide base nonwoven fabric 3 is replaced with a polyolefin porous film 2. Thereby, short caused by coming off of active material in the starting part of winding is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a zeparator for alkaline storage batteries that prevents short circuits between negative and positive electrode plates.

Conventional technology Characteristics required for alkaline storage battery separators include good electrolyte retention capacity, high liquid absorption rate, no obstruction to the passage of generated gases and charged ions, and no obstruction to debris or oxidation that falls off from electrodes. It can prevent objects from moving, has no through holes, is porous, and has low internal resistance.

Conventional alkaline storage battery separators are a mixed web or structure of high melting point and low melting point polyamide fibers. These separators use, as a nonwoven fabric binder, so-called heat-fusible fibers whose entire fibers are made of a low-melting-point resin. For this reason, when the nonwoven fabric is fused, there are many bonding points on the surface where the heat source is nearby, but inside there are fewer bonding points and the bonding becomes loose. Furthermore, although there are many fusion points in the surface area, overall, a homogeneous structure with an average pore size of 0.1 μm or less and a maximum pore size of 1 μm or less, like the network structure of a synthetic resin film, cannot be created.

Problems to be Solved by the Invention Therefore, when winding an electrode plate, if there are pieces (sintered body impregnated with active material) that fall off from the electrode plate at the beginning of winding or at the side edges, This debris embedded in the separator and caused a short circuit, and dendrites grew from the active material.
This may cause a short circuit while the battery is in use. This is because polyamide fibers are bonded by heat fusion, which causes uneven bonding and does not form a strong network across the inside of the separator, making it easy for debris to fall off from the electrode plates that penetrate the surface layer of the separator. Often times we reach the opposite end of the spectrum. Furthermore, even when dendrites grow from the active material, the growth is likely to occur because of the uneven bonding.

Means for Solving the Problems The present invention is intended to solve the above-mentioned short circuit, and uses polyamide woven fabric or non-woven fabric for the upper and lower outer layers as the fiber layers constituting the separator, and for the inner layer. At least one layer of the inner layer uses a web in which part of the polyamide woven fabric or nonwoven fabric is replaced with a polyolefin resin porous membrane, and the sandwich structure web made of these is heated and pressurized, and as a result, part of the inner layer is heated and pressurized. It is made of polyolefin film and has a strong network structure.

Function: Particularly at the beginning of winding of the electrode plate, the active material of the electrode plate is prevented from penetrating and causing a short circuit.

The exception layer 1 is a polyamide nonwoven fabric, and is necessary for retaining the electrolyte and for sufficient contact between the electrode plates and the separator. In addition, the polyolefin film 2 replaces a part of the polyamide nonwoven fabric 3, and by using the polyamide nonwoven fabric 3 at the beginning of winding of the electrode plate, it is possible to prevent short circuits caused by debris that often falls off at the beginning of winding. It is something.

This will be explained in more detail.

First 6 nylon fiber 2 denier 38■ cut so%, 6
Prepare a mixed fiber web of 50 pieces of 3-denier 51-fin cut nylon fiber, with a basis weight of 7 m1 and a thickness of 1 O. In addition to this, polyethylene film, average film thickness 0
．． 08m+, a maximum pore diameter of 1μ or less, and an average pore diameter of 0.09μ are prepared. The nylon 6 web and polyethylene film are laminated as shown in Figure 2, with the nylon 6 web 4 placed on the upper and lower outer layers, and the nylon 6 web 5 placed on both sides of the polyethylene film 2 as the inner layer. . This laminated web was impregnated with a 129 g aqueous solution of polyvinyl alcohol and dried to produce a nonwoven fabric with a solid coverage of 5 cm. This was hot-pressed with a roll heated to 150°C to obtain a nonwoven fabric separator having a thickness of 0.22 to 0.25 m and shown in FIG. 1.

A comparative example is also shown to clarify the difference with conventional products.

6 nylon fiber 2 denier 38cm cut 50cm, 6 nylon fiber 3 denier 51m cut 50cm mixed fiber web with fiber basis weight 80? /- is immersed in a zinc chloride solution, which is a fiber solvent, to slightly dissolve the fiber surface. After removing the solvent, it is impregnated and dissolved in a non-vehicle to coagulate the 96 nylon to bond between the fibers, and the web is washed.
The separator was dried at 10°C and then hot-pressed using rolls heated to 145°C to obtain a separator with a thickness of 0.20 to 0.25 mm.

When a battery was assembled using these two types of separators, it was found that the battery in which the separator according to the present invention was used so that the film part was in contact with the beginning of winding of the electrode plate was faster to assemble than the battery in which the conventional separator was used. The short circuit occurrence rate is 3
The number has decreased to 2. In addition, we conducted a charge/discharge life test on a battery using the separator according to the present invention, and found that since the outer layer of the separator is covered with a nonwoven fabric, there was no problem that the amount of liquid retained was insufficient, and compared to conventional batteries, the battery The characteristics were the same or better.

Effects of the Invention According to the present invention, it is possible to prevent short circuits due to the active material, particularly at the beginning of winding of the electrode plate.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a separator according to the present invention having a polyolefin film between polyamide nonwoven fabrics, and FIG. 2 is a sectional view of a laminated web having a polyolefin film between polyamide fiber nonwoven fabrics. 1 is outer layer, 2 is polyolefin film, 3 is polyamide nonwoven fabric

Claims (1)

[Claims] A separator for an alkaline storage battery, characterized in that the separator is made of polyamide-based woven fabric or non-woven fabric, is laminated in three or more layers, and a portion of the inner layer is made of a polyolefin-based resin porous membrane.