JPS6043623B2 - Battery separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery separator, and its feature is that when embossing a microporous thin film sheet containing synthetic resin, the protrusions are shaped into a specific size, e.g. 1
Diamond shape with side ~10-fWL range, or diameter 1-10Tfg
n circle, etc., and the width between the convex parts is 0.2 to 2 Tf.
r! An object of the present invention is to provide a battery separator by connecting linear protrusions with a height lower than the protrusions at n.

Conventional thin microporous sheets of O, 5 wrIn or less are thin, and glass mats or nonwoven fabrics are used as spacers to maintain the gap between the cathode and anode plates, or ribs are added to the sheet surface. It had been.

However, when a glass mat is used in combination, there are drawbacks such as inconvenience in handling during battery assembly and high cost. On the other hand, the method of attaching ribs also had the disadvantage that it was difficult to attach ribs. In order to eliminate these drawbacks, the microporous thin film sheet is embossed to create irregularities, and when embossing, the porosity of the embossed parts is reduced to zero or is reduced compared to other parts. A method has been proposed to use it. However, when a device with a simple protrusion like this is placed between the positive and negative electrodes as shown in Figure 4, the gas generated during battery charging and discharging is trapped between the back of the protrusion and the electrode plate. This has the disadvantage that it accumulates, hinders the movement of ions, increases electrical resistance, and deteriorates charging voltage characteristics. The present invention relates to improvement of these embossed separators, and the embossed shape of the separator obtained by embossing a microporous thin film sheet has a plurality of convex portions having a certain interval and a shape connecting the convex portions. This separator is characterized by consisting of suitable biaxial linear protrusions that are lower in height than the protrusions, and by using this separator, it is possible to prevent the accumulation of gas generated from the battery electrode plates. Because the electrolyte has good fluidity and mechanical elasticity, it provides storage batteries with good performance.

That is, the present invention has good high rate discharge pressure characteristics, sustained characteristics,
Moreover, it is possible to provide a separator for making a battery with good life characteristics.

The feature of the separator of the present invention is that a thin sheet with a thickness of 10.5 mm or less is deformed to obtain an apparent thickness while taking advantage of its thinness, resulting in low electrical resistance and good high rate discharge characteristics. 2. It has many relatively small convex parts, so it is highly elastic, and has the power to pressurize the active material when placed between the electrode plates.
Despite using a thin separator of 0.5 Twt or less, it has almost the same effect of preventing active material from falling off as a separator made by laminating a 0.4-thick glass mat to a 0.7 wm separator, as shown in Figure 3. It is more effective in preventing the active material from falling off than corrugated separators, and has a longer lifespan.

In order to exhibit the above 12 characteristics, the present invention has the following structure.

That is, by providing biaxially linear protrusions connecting the protrusions formed on the separator and having a height lower than the protrusions, the space formed by the anode plate and the separator and the cathode The spaces formed between the plates and the separators each have a continuous passageway, which facilitates the flow of electrolyte and the movement of gas, which has the effect of smoothing battery reactions and improving battery performance. . Furthermore, since the linear protrusions extend in biaxial directions, it has good bendability and is particularly suitable for a type of separator that wraps around electrode plates.

To explain the present invention with reference to drawings, FIG. 1A is a partial plan view of an embodiment of the present invention, FIG. 1A is a partial perspective view thereof, and FIG. It is.

In the figure, 1 is an embossed protrusion, and 2 is a linear protrusion that connects the protrusions and is lower in height than the protrusions, and extends in biaxial directions. 3 is the web.

The figure shows one embodiment of the present invention, and the shape of the convex part is a rhombus. However, as shown in the example below, if the size is within a certain range, a circle, an ellipse, or a square contract can be formed. It may be similar to a rectangle or the like, and the protrusions connecting the protrusions also have a width of 0.
It may be within the range of 2 to 2 days. Further, it is appropriate that the distance between the convex portions (the distance connecting the centers of the convex portions) is in the range of 4 to 20 WrIi. Examples are shown below.

Example 1 A microporous thin film sheet with a thickness of 0.2Tn1n was prepared by using a microporous thin film sheet having protrusions such that the shape of the tip was a diamond shape of 2 wm on a side, the distance between the protrusions was 5 m, and the protrusions were connected to each other at the tips. The sheet is embossed with a roll that has a pattern of connected linear protrusions with a width of 0.2 mm and lower than the height of the protrusions, and the sheet has diamond-shaped protrusions and linear protrusions connecting the protrusions. It was used as a separator to provide an opening.

This separator has an electrical resistance of 1.2■ in dilute sulfuric acid of 0.
The resistance is extremely low at 0.010 (Ω/d/sheet), and the oxidation resistance is 130H/sheet, which is equivalent to or higher than that of conventional phenol-treated paper separators. Moreover, the elasticity of this separator was large, and when a load of 20 k9/100 cIt was applied, the change over time was 15% in 3 months, which was comparable to the elasticity of glass mat. When the battery was assembled and tested in such a manner that the linear protrusions connecting the protrusions were oblique in the vertical direction, the elastic protrusions provided on the separator caused the electrode plates to Because the gaps are maintained and the protrusions are connected by protrusions that are lower in height than the protrusions, the movement of the electrolyte is rapid, and the gas generated from the electrode plates is prevented from flowing between the plates and the separator. It can easily move through the space formed between the poles and remove them from the pole group, and exhibits characteristics not found in conventional separators, especially in high rate discharge, with a capacity improvement of 20% and voltage characteristics of 10%. % increase.The life performance was 30% greater than that of a working pond using a ribbed separator.Also, the linear protrusions connecting the protrusions are oblique to the vertical direction, which increases the gas This is also one of the reasons why the embossed separator has become easier to remove.Furthermore, compared to conventional ribbed separators or separators combined with glass mats, the embossed separator is simply a deformation of the sheet, so there is no additional material and the cost is 30 to 30 yen. It became possible to reduce costs by 40%.Example 2 A microporous thin film sheet with a thickness of 0.1 m was made with a tip shape of 3 in diameter.
It has protrusions that look like a circle on the skin, and the distance between the protrusions is 6Tn.
! R, and the protrusions are embossed with a roll having a pattern in which the protrusions are connected by linear protrusions with a width of 1 Tfa at the tip and lower than the height of the protrusions to form circular protrusions on the sheet. The separator is provided with linear protrusions that connect the protrusions and the protrusions.

The electrical resistance of this separator in dilute sulfuric acid of 1.2ω is 0.
It has an extremely low resistance of 0,008 (Ω/d/sheet) and an oxidation resistance of 120H/sheet, making it suitable for use as a storage battery separator, as in Example 1. As in Example 1, this separator was assembled into a battery so that the protrusions were in contact with the anode, and the linear protrusions connecting the protrusions were oblique in the vertical direction. The capacity increased by 20% and the voltage characteristics increased by 10%. The life performance was 25% greater than that of the ribbed separator. Example 3 1% by volume of high molecular weight polyethylene, 1% by volume of silica and 1% by volume of carbon black as fillers, and 6% by volume of petroleum oil as a plasticizer were uniformly mixed to form a mixture. The mixture was formed into a sheet by an appropriate method, and the sheet was immersed in a solvent hexane to extract petroleum oil to form a thin microporous sheet.

The sheet was formed by linear protrusions with a tip shape of a rhombus of 27r0n on a side, a distance of 5wrm between the protrusions, and a width of 0.2wn at the tip and a height lower than the height of the protrusions. The sheet was embossed with a roll having a connected pattern to form a separator in which diamond-shaped protrusions and linear protrusions connecting the protrusions were provided on the sheet. The embossed separator thickness was 0.8Tr0n. This separator is -1.2
The electrical resistance in 0Ci dilute sulfuric acid is 0.0017 (Ω/c!t
/sheet), and the oxidation resistance was 450H/sheet or more.
However, the elasticity of the separator was somewhat weak;
Examples 1 and 2 are also suitable as separators for storage batteries.

Example 4 After making paper by uniformly mixing 20% acrylonitrile fiber and 20% glass fiber, polyethylene 2 was added as a binder.
A mixture of 0% white carbon and 40% white carbon as filler was applied to the sheet and suitably treated to form a microporous sheet.

The sheet was embossed with a roll having the same shape as that used in Example 3, and a separator was prepared in which the sheet was provided with diamond-shaped protrusions and linear protrusions connecting the protrusions. The electrical resistance of this separator in 1.20Ci dilute sulfuric acid is 0.00.
13 (Ω/Cll/sheet), and the oxidation resistance was 80H/sheet. However, this separator also had poor elasticity, but was suitable as a separator for storage batteries as in Examples 1 and 2.

As described above, the shape and size of the protrusions, the shape of the linear protrusions connecting the protrusions, and the spacing between the protrusions have an effect on the characteristics of the separator, which in turn has an effect on the battery performance.

Examples for other shapes are summarized in Table 1. To describe the features of the present invention in more detail, the sheet can be simply . As shown in FIG. 4, in the conventional type having a convex portion, when the two electrode plates are sandwiched, the space 6 formed between the concave portion on the back side of the convex portion 4 and the electrode plate 5 becomes a sealed shape. The electrolyte inside this is difficult to flow, and the gas trapped inside has no place to escape and stays there. However, this results in hindering the flow of ions and significantly impeding the battery discharge performance.In contrast, the present invention has linear protrusions that connect the protrusions and are lower in height than the protrusions. , is formed between the electrode plates and the separator when a separator is placed between the electrode plates. Space can be made continuous.

That is, although it has many convex portions in order to obtain elasticity, it allows the electrolyte to flow and removes gas pockets, and is extremely effective as a separator in improving battery performance.

[Brief explanation of the drawing]

Fig. 1A is a partial plan view of one embodiment of the present invention, the opening of Fig. 1 is a partial perspective view, Fig. 2 is a sectional view A-A'' of Fig.
The figure is a perspective view of a conventional corrugated separator, FIG. 4A is a perspective view of a conventional embossed separator, and the opening in FIG.
It is a partial sectional view showing this in combination with an electrode plate. 1... Embossed convex part, 2...
- Linear convexity, 3... Web, 4... Convex portion, 5... Pole plate, 6... Space.

Claims (1)

[Claims] 1. A microporous thin film sheet made of synthetic resin is provided with a plurality of protrusions and linear protrusions that connect the protrusions and are lower in height than the protrusions in biaxial directions. A battery separator featuring: 2. The battery separator according to claim 1, wherein the shape of the convex portion is a rhombus with a side of 1 to 10 mm or a shape similar in size to this. 3. The battery separator according to claim 1, wherein the distance between the convex portions is 4 to 20 mm. 4. The battery separator according to claim 1, wherein the width of the linear protrusions connecting the protrusions is 0.2 to 2 mm. 5. The battery separator according to claim 1, wherein the linear protrusions connecting the protrusions are oblique with respect to the vertical direction during use.