JPS6139452A - Separator for alkaline battery - Google Patents

Abstract

PURPOSE:To prevent a short circuit due to fragments of a drop from occurring, by forming a polyolefin resin porous film in both upper and lower parts of a separator using a polyamide fabric or a nonwoven fabric. CONSTITUTION:Both upper and lower parts in the longitudinal direction of a polyamide fabric or a nonwoven fabric constituting a separator 2 are made up of each polyolefin resin porous film 1. For example, after a film 1 composed of 6-nylon web and polyethylene is impregnated in an aqueous solution of polyvinyl alcohol, the film 1 composed of polyethylene is sandwiched with the 6-nylon web and dried up. This film is pressed with a heated roll and the separator 2 of the nonwoven fabric is produced. With this constitution, not only weight per unit area increases but also a perfect network structure is secured, while such an inorganic substance as fine silicic acid is mixed in the film so that penetration in the separator due to fragments of a drop is reduced, thus a short circuit is preventable from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improved separator for alkaline storage batteries that is improved to prevent short circuits between cathode and anode plates.

Conventional technology Characteristics required for alkaline storage battery separators include good electrolyte retention capacity, high liquid absorption speed, no obstruction to the passage of generated gases and charged ions, and no debris or oxides that fall off from the electrodes. It is possible to prevent the movement of particles, has no through holes, and is porous and has low internal resistance.

Conventional separators for alkaline storage batteries have a structure in which a mixture of high-melting point and low-melting point polyamide fibers or a single web of thermoplastic fibers is hot-pressed with heated rolls and welded together at the contact points and intersection points of the fibers. . As described above, conventional separators use so-called heat-welding fibers, the fibers of which are entirely made of a low-melting resin, as a nonwoven fabric binder.

When welding the rolled nonwoven fabric, there are many bonding points on the surface near the heat source, but inside there are fewer bonding points and the bonding becomes loose.

Although there are more welding points in the large female area, overall, a homogeneous structure with an average pore size of 0.1μ or less and a maximum pore diameter of 1μ or less, like the strong network structure of a synthetic resin film, has not been created. do not have.

Problems that the invention aims to solve: Therefore, when winding the electrode plate, pieces that fall off from the electrode plate (
If there is a sintered body containing an active material, this may become embedded in the separator and cause a short circuit, or dendrites may grow from the active material, causing a short circuit early during battery use. Further, these falling fragments frequently occur at the upper and lower parts of the electrode plate in the longitudinal direction (near the cut portion of the electrode plate) when the electrode plate is wound.

In addition, to explain the causes of short circuits mentioned above, since the polyamide fibers are bonded by heat welding, uneven bonding occurs, and a strong network is formed throughout the separator. It is often said that fragments that fall off from the pierced electrode can easily penetrate inside and reach the opposite electrode. Furthermore, even when dendrites grow from the active material, there is a breakthrough in the electrode plate, and 6
It can be said that conventional batteries with a large number of batteries are susceptible to short circuits.

Means for Solving the Problems The present invention eliminates the above-mentioned drawbacks.The upper and lower parts of the polyamide thread woven fabric or non-woven fabric constituting the separator in the longitudinal direction are formed of a polyolefin film, and the falling objects are removed. This prevents short circuits caused by debris.

Function When using a polyolefin film compared to conventional polyamide yarn woven fabrics or non-woven fabrics, not only does the weight per unit area increase, but it also has a complete network structure, and the film contains particles such as finely divided silicic acid. The inclusion of inorganic substances reduces the penetration of the separator by fragments of fallen objects and prevents short circuits.

Example 6 A mixed fiber web consisting of 50 pieces of nylon fibers with 2 denier 38 length cuts and 50 pieces of 6 nylon fibers with 3 denier 51 pieces cut, with a basis weight of 801~ and a thickness of 1.6 mm was prepared. The average film thickness of the film 1 made of polyethylene is 0.221t.
ll, basis weight 130 l, fine powder silicic acid 34.51, maximum pore diameter 1μ, average pore diameter 0.08μ. The film 1 made of the 6-nylon web and polyethylene is impregnated with a 1.2-inch aqueous solution of polyvinyl alcohol, and then the film 1 made of polyethylene is sandwiched between the 6-nylon web and dried as shown in FIG. This is hot pressed with a roll heated to 1500°C to a thickness of 0.22 to 0.25flll.
A nonwoven fabric separator 2 shown in FIG. 1 was obtained.

In addition, as a conventional product, 6 nylon fiber m3 denier 511
A mixed web of 1 cut of 50 mm and 6 nylon fibers of 2 denier and 38 mm of cut with a fiber basis weight of 801/rrt 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 with a non-solvent to solidify the dissolved nylon 6 and bond the fibers together.
After washing the web, dry it at 110C and continue with 1
Heat-press with a roll heated to 45C to obtain a thickness of 0.20-0.
A 25 m separator was obtained.

When a battery was assembled using these two separators, the separator 2 according to the present invention was placed at the upper part of the electrode plate in the longitudinal direction.
In the battery in which the polyethylene film 1 was applied to the lower part, the short-term occurrence rate during battery assembly was reduced to 63 inches compared to the battery in which a conventional separator was used. In addition, in the separator 2 of the present invention, since there is a portion made only of polyethylene film, the amount of electrolyte retained in the upper and lower portions of the electrode plate is slightly reduced, but a life test showed that there was no problem in practical use.

Effects of the Invention As mentioned above, the present invention has great industrial value as it reduces the incidence of short circuits.

[Brief explanation of the drawing]

Fig. 1 is a schematic view of a separator having a polyolefin film according to the present invention in the upper and lower portions of the separator in the longitudinal direction, and Fig. 2 is a cross-sectional view of a web in which the polyolefin film is sandwiched between polyamide nonwoven fabrics before being heat-pressed. It is. 1 is film, 2 is separator

Claims (1)

[Claims] A separator for an alkaline storage battery, characterized in that the separator is made of a polyamide woven fabric or a nonwoven fabric, and includes a polyolefin resin porous membrane formed on the upper and lower parts of the separator.