KR100389123B1 - Separator for alkali secondary battery and preparation method thereof - Google Patents

Abstract

PURPOSE: A separator for an alkali secondary battery and its preparation method are provided, to prevent an electrolyte solution from being dried after charge/discharge for a long time for improving the lifetime of a battery and to prevent a free electrolyte solution from being generated for improving the capacity of a battery. CONSTITUTION: The separator comprises a polyolefin-based or nylon-based nonwoven whose surface has spacers having a diameter of 50-100 micrometers. The method comprises the steps of placing a glass bead(spacer) having a diameter of 50-100 micrometers on the surface of a polyolefin-based or nylon-based nonwoven, and mechanically compressing the glass bead. Preferably the compression pressure is 5-7 kgf/cm¬2.

Description

Separators for alkaline secondary batteries and manufacturing method thereof

The present invention relates to a separator for an alkaline secondary battery and a method of manufacturing the same, and more particularly, such as nickel-cadmium, nickel-cadmium, nickel-zinc, nickel-hydrogen, silver-zinc 7 secondary batteries, and the like. In an alkaline secondary battery using an aqueous solution as an electrolytic solution, the present invention relates to improving the separator in charge of containing and maintaining the alkaline electrolytic solution and improving the life of the battery.

In order to be used as a separator for alkaline secondary batteries, it has to have good affinity with electrolyte solution, excellent absorption rate and liquid absorption, and good chemical stability such as alkali resistance and oxidation resistance that can withstand repeated use such as long-term layer discharge. Various performances and characteristics are required, such as low internal resistance and good air permeability, which does not interfere with the passage of gas generated from the electrode.

Up to now, most of the separators for alkaline secondary batteries have been polyolefins such as polyethylene and polypropylene, and nylon nonwoven fabrics such as polyamide. However, when these nonwoven fabrics are used in batteries, they are mostly applied in the longitudinal direction. to be.

However, in the case of using a conventional non-woven separator, as the secondary rechargeable batteries gradually increase in size, the charge and discharge process is repeated, which causes the electrolyte to dry out due to the densities of the electrodes due to skelling of the electrodes. Thus, the separator has a nearly one-dimensional structure. This is because most of the existing nonwoven fabrics have an ordinary fiber type structure, so that the nonwoven fabric has almost one-dimensional structure due to the phenomenon of swelling of the national board during the heavy discharge process. The electrons do not sufficiently recapture and deterioration of the electrode is accelerated, resulting in shortening of the battery life.

In an attempt to solve the cycle life of such a battery using a nonwoven fabric, Japanese Patent Publication No. 6-163023 describes that a mixture of aniline and propylene rubber was used as a porous porous membrane. The porosity is about 50%, which drops considerably, and the impregnation height of the electrolyte is also considerably dropped.

In addition, Japanese Patent Publication No. 6-163020 introduced a carboxyl group and a sulfonic acid group in an NBR-melanin crosslinking resin on the surface of a nonwoven fabric sheet to produce an alkaline battery separator that is stable even in charge and discharge repeats over a long period of time. This was able to improve the absorption rate and the liquid absorption to some extent, but since the introduced functional group is an acid functional group, it has a problem that it is difficult to achieve the original effect because it acts and neutralizes with the alkaline electrolyte after long-term use.

Accordingly, an object of the present invention is to provide a separator for an alkaline secondary battery, which not only solves the above problems but also improves the moisture content and absorption rate of the electrolyte solution significantly compared to the conventional separator.

On the other hand, another object of the present invention is to provide a method for manufacturing the separator for alkaline secondary batteries.

The separator for alkaline secondary batteries of the present invention for achieving the above object consists of a spacer formed on the surface of a nonwoven fabric.

Hereinafter, the configuration of the present invention will be described in more detail with reference to the accompanying drawings.

In order to be used as a separator of an alkaline secondary battery, various characteristics are required as described above, but existing separators do not fully satisfy these characteristics. In other words, when the charging / discharging process is repeated using a separator made of a general nonwoven fabric, the electrolyte dries out due to swelling of the electrode, and the separator has a nearly one-dimensional structure. Significantly lowered, the battery capacity is not sufficiently reduced to shorten the life of the battery.

Therefore, in the present invention, the nonwoven fabric has a three-dimensional structure as described above by using a spacer that does not cause any reaction with the alkaline solution and does not have any risk of dropping out of the electrolyte during the charging and discharging process. As a result, the battery retains the absorption rate as well as the retention rate of the electrolyte, thereby allowing the battery to exhibit its service life.

In short, the separator of the present invention is characterized in that a spacer is formed on the surface of the nonwoven fabric. That is, in order to improve the absorption rate and liquid retention of the electrolyte when used in an alkaline secondary battery, the present invention regulates the moisture content of the electrolyte, but prevents the nonwoven fabric from becoming almost one-dimensional while undergoing charge and discharge for a long time. Spacers are used to prevent the condition. Glass beads are preferable as the spacer used, but other similar bell tower spacers may also be used. The size of the spacer used is preferably about 50 μm to 100 μm in diameter. If the diameter of the spacer is 50 µm or less, the moisture content of the nonwoven fabric is significantly lowered as in the case of not using the spacer. In addition, when the diameter of the spacer is 100 μm or more, the volume expansion of the positive electrode is deepened by overlapping with the swelling of the nickel electrode, and the battery casing is severely deformed, thereby reducing the capacity of the battery.

On the other hand, the method of manufacturing the separator of the present invention is characterized by placing a spacer on the surface of the nonwoven fabric and pressing it by a mechanical method. That is, the method cleans and dries the glass beads having a diameter of about 50 μm to 100 μm, and then places the glass beads on a nonwoven fabric to be used, for example, a polyamide nonwoven fabric, and mechanically pressurizes the glass beads. It is to be seated. At this time, the pressure applied to the glass beads is about 5 ~ 7 / Kgf / ㎠. If the nonwoven fabric manufactured by applying the pressure of 5Kgf / ㎠ or less, glass beads fall off and show no improvement effect. In addition, when applying a pressure of 7Kgf / ㎠ or more, the fibers forming the nonwoven fabric are separated from each other to increase the pore size (pore size) there is a problem that the moisture content of the electrolyte is significantly reduced.

Hereinafter, the manufacturing process of the separator of the present invention will be described in more detail with reference to the production examples, and the effects of the present invention will be described in more detail with reference to Examples and Comparative Examples.

Preparation Example 1

Glass beads having a diameter of about 75 μm were washed thoroughly and then dried in a dry oven for 5 minutes. Then 100 beads per cm 2 are geographicly wrapped around the polyamide nonwoven fabric to be used using # 100 sieves, and then rolling it under a pressure of 6 Kgf / cm 2 using a stainless roll. The glass beads were physically placed on the surface of the polyamide nonwoven fabric, thereby preparing the separator of the present invention.

As a result of X-ray analysis to confirm the glass bead distribution on the nonwoven fabric, it was confirmed that up to 30 glass beads per 50 cm2 of nonwoven fabric were located. In addition, it was confirmed that the separator of the present invention has no problem in use through alkali resistance test, ventilation test, and compression test. That is, it was found that the specimen 10 cm × 10 cm non-woven fabric was left for 20 days in a KOH solution having a specific gravity of 1.3 for 30 days, and then there was almost no drop of non-glass beads measured the degree of glass beads drop compared to the sound insulation weight. In addition, the nonwoven fabric having a diameter of 8cm was cut into a circle and installed in a 5cm diameter tuyere, and forcedly exhausted for 10 seconds at a speed of 10m / sec to confirm the degree of dropping of the glass beads.

On the other hand, to determine the crimping degree, cut the piece into 10cm × 10cm size, place it between the stainless plate and press the pressure gauge to the usable range of 0 ~ 2.5atm using the pressure gauge. After repeating, the weight difference of the glass cloth was measured by comparing the weight difference of the nonwoven fabric. As a result, it was found that there was almost no drop of the glass beads.

Example 1

1 is a block diagram of an alkaline secondary battery according to the present invention, in which 1 is a nickel sintered electrode, 2 is a zinc electrode, 3 is a polyamide nonwoven fabric, 4 is a polypropylene microporous film, 5 is a cotton nonwoven fabric, 6 Ag is a polypropylene film coated with Ag, and the drawings will be described a manufacturing process of the alkaline secondary battery according to the present invention.

The anode used in this embodiment is a nickel sintered electrode 1, and the cathode is a zinc electrode 2 produced by a dry compaction method.

In the negative electrode active material, zinc oxide (80 wt%) and zinc powder (10 wt%) were added PTFE (polytetrafluoroethylene) resin, ethylene oxide resin (5 wt%), lead oxide (2 wt%), and cadmium oxide (3 wt%) and kneaded well in a kneader. It was prepared using.

The nickel sintered electrode 1 is a sintered substrate having a porosity of 75%, and a current collector in which a nickel plate is expanded is used. The electrolyte solution can suppress the production of zinc dendrites and 25% potassium sorbate for the purpose of improving charging efficiency and battery life while maximally suppressing the zinc active material being excessively eluted in the electrolyte solution without saturating zinc oxide. An electrolyte solution of 5% lithium hydroxide was used.

Meanwhile, a hydrophilic polyamide nonwoven fabric 3 treated with glass beads prepared in 1 was used as a separator so that the nickel sintered electrode 1 had a sufficient capacity and a sufficient electrolyte solution. The propylene microporous membrane 4 was used.

Also, a nonwoven fabric (5) was used for the zinc electrode (2), and Ag-coated polypropylene was used for the inhibition of penetration of zinc dendrites and the rapid absorption of oxygen gas from the nickel sintered electrode (1). Membrane 6 was used.

The electrode of the test battery used in this example was 6 cm in width and 4 cm in size, and two nickel electrodes were used as one sheet, and two sheets were used. The capacity was 3.4 Ah. The same size as the nickel electrode was used for three zinc electrodes, and the capacity was 11.7 Ah, and the capacity ratio of the negative electrode and the positive electrode was 3.45: 1, which was the rate of positive electrode capacity.

The battery A of the example of the present invention was manufactured through the above-described process, and the charge / discharge cycle characteristics of the battery were examined as follows.

First, the battery of the present example was charged and discharged at 80% DOC at 90% charge. In other words, the layer was carried out in three stages and discharged at a discharge rate of 3 hours until the battery voltage reached 1.2 V. The battery capacity was calculated. The cycle life was calculated until 60% of the rated capacity.

In addition, the amount of the electrolyte was regulated to 1.4 ml / Zn, Ah for the battery of the present embodiment, and the electrode was left at atmospheric pressure for 24 hours after the injection of the electrolyte so that the electrode was sufficiently aged with the electrolyte. Thereafter, a pressure gauge was used to measure the internal pressure during charging.

Comparative Example 1

In this comparison, a battery B was prepared in the same manner as in Example 1, except that a general nonwoven fabric without using glass beads was used as a separator, which was introduced for comparison with the present invention. The cycle life and the internal pressure change of the battery were measured using the same measurement method as 1.

2 is a graph comparing capacity retention ratios according to charge / discharge cycles of batteries according to the related art and the present invention. According to FIG. 2, it can be seen that the charge / discharge cycle life is improved in the battery using the nonwoven fabric of the present invention to which glass beads are added, compared to the conventional battery using the general nonwoven fabric.

3 is a graph comparing the change in the internal pressure of the battery according to the charge and discharge cycle for the battery according to the prior art and technology. According to FIG. 3, the battery using the nonwoven fabric of the present invention to which glass beads are added has superior internal pressure characteristics of the battery according to the cycle during charging, compared to a conventional battery using a conventional nonwoven fabric. This is because it is effectively absorbed.

Therefore, by using the alkaline secondary electron separator of the present invention, since the drying phenomenon of the electrolyte solution hardly appears even after a long time of charge and discharge, the battery can exhibit its full capacity, and thus the battery life becomes longer. In addition, in general separators, the separator is squeezed due to the swelling during charging, and thus a lot of glass electrolyte is generated. However, the separator of the present invention is almost free of electrolyte because there is no crimping phenomenon, and thus the permeation of the generated oxygen gas is very easy. The capacity of the battery can be maximized.

1 is a block diagram of an alkali secondary electron according to the present invention,

2 is a graph comparing capacity change rate according to charge and discharge cycles for the former and the electron according to the present invention;

3 is a graph comparing the change in the internal pressure of the battery according to the charge and discharge cycle for the former and the electron according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: nickel sintered electrode 2: zinc electrode

3: polyamide nonwoven fabric 4: polypropylene filtration microporous membrane

5: cotton nonwoven fabric 6: Ag coated polypropylene film

Claims (3)

A separator for alkaline secondary batteries, wherein a spacer having a diameter of 50 to 100 μm is formed on a surface of a polyolefin-based or nylon-based nonwoven fabric. A method for producing a separator for alkaline secondary batteries, characterized by placing a spacer, which is a glass bead having a diameter of 50 to 100 μm, on a surface of a polyolefin-based or nylon-based nonwoven fabric, and pressing it by a mechanical method. The method of manufacturing a separator for alkaline secondary batteries according to claim 2, wherein the pressure during compression is 5 to 7 kgf / cm 2.