JPS612263A - Lead-acid battery - Google Patents

Abstract

PURPOSE:To provide a lead-acid battery having high-temperature resistant capability, high capacity, and long life by using a separator, whose electric resistance is low, acid resistance and oxidation resistance are high, made of copolymer mainly comprising acryl-butadine-styrene and alpha-methylstyrene. CONSTITUTION:In copolymer mainly comprising acryl-butadiene-styrene and alpha-methylstyrene, the ratio of alpha-methylstyrene is limited to 10% or more, preferably 30-60%. Since part of styrene is replaced by alpha-methylstyrene unlike usual acryl-butadiene-styrene copolymer resin, heat resistance and high temperature stability of this copolymer are increased. By embossing this material, a thin, microporous separator 8 is manufactured. Webs 11 of the separator are in contact with a plate and put down swelling of the plate. Therefore, coming off of the active material is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a lead-acid battery used for automobiles and electric vehicles.

Conventional technology and its problems In recent years, lead-acid batteries for automatic i1 use electrode plates that use expanded gelatin, which increases the internal resistance of the electrode plates and makes the electrical resistance of the separator much smaller. This has become a requirement. In addition, a short circuit occurred in the seventh pallet, which could not withstand the pressing force due to the elongation and deformation of the grid during charging and discharging. In order to prevent side short circuits caused by sponge vessels generated by repeated charging and discharging, which had the disadvantage of increasing self-discharge due to dissolution of impurities contained in the separator, it is easy to heat seal, bend, and process into bags. There is a growing demand for easy separators. Furthermore, as automobiles become more compact, engine compartments become narrower, making usage conditions even hotter in the summer than before.
There is a growing demand for separators that can withstand these conditions.

On the other hand, batteries for electric vehicles used in forklifts, etc., have a deeper depth of discharge than automobile batteries, and are used for a long period of time. requested. These separators are more durable than automotive battery separators in their original shape and can withstand long-term use, and there is a growing demand for separators that are easy to bend and can be easily packaged with electrode plates or have a zigzag structure. In addition, as usage conditions become more diverse, batteries are increasingly being used in unprecedented high-temperature conditions, such as rapid charging after high-rate discharge, and there is a demand for separators that can withstand these conditions.

In response to these demands, conventionally known thin-film microporous parators are disclosed in Japanese Patent Publications No. 15078/1980, 28393/1983, 30352/1982, and 53066/1983. There is something shown.

However, although these separators are sufficient as separators for automobile batteries, they lack acid resistance and oxidation resistance as battery separators for electric vehicles. In addition, the elution of plasticizers and chlorine may harm battery performance and promote stress cranking of some synthetic resin battery containers.On the other hand, polyethylene Huikong seven pallets do not require the addition of oil. Efforts have been made to improve the oxidation resistance, but the embossed version of this type of seven-pareke has the disadvantage that it has no aggregate and the addition of oil makes it weak.

The method for manufacturing these thin film microporous separators, except for polyethylene microporous separators, is to apply a solution consisting of a synthetic resin, a solvent, and a non-solvent to a porous body, and dry it to obtain a microporous body. However, this method cannot be applied to any synthetic resin, and a method suitable for each resin is adopted.

For example, by dissolving vinyl acetate resin in tetrahydrofuran,
Even if a uniformly mixed synthetic resin solution is applied to a nonwoven fabric and dried by adding ethyl alcohol as a non-solvent, micropores cannot be obtained.

Further, even if a uniform synthetic resin solution prepared by dissolving ethylene vinyl acetate copolymer resin in tetrahydrofuran and adding and mixing isopropyl alcohol is applied to a nonwoven fabric and dried, no micropores are obtained.

This depends on the intermolecular cohesive force of the synthetic resin used and the affinity between the non-solvent and the resin.

In the same way, a homogeneous synthetic resin solution of acrylic-butadiene and styrene copolymer resin dissolved in tetrahydro-7rane and 1 m of isopropyl alcohol was applied to a nonwoven fabric, and even when dried, small particles of a few microns or less were formed. Since the pores are not uniformly formed, the separator does not satisfy the characteristics required for modern batteries.

Furthermore, a copolymer of acrylic butadiene and styrene)
A synthetic resin solution prepared by dissolving in lahydrofuran, adding isopropyl alcohol, and then adhering and drying a synthetic resin solution mixed with fine silica powder to a non-woven fabric has a larger pore size than the product of the present invention, and also has higher electrical resistance and lower oxidation resistance. It does not fully satisfy the characteristics required for a separator in recent batteries. Moreover, since the heating deformation temperature is as low as 80°C, the micropores are crushed under the operating temperature of 70 to 80°C in batteries for electric cars and automobiles. The electrical resistance of the separator increases as the micropores are crushed, and embossed products soften due to the low heating deformation temperature, resulting in an extreme decrease in elasticity, and the acid resistance and oxidation resistance deteriorate significantly at high temperatures. Ta.

The present invention provides a long-life, high-performance lead-acid battery that can withstand use at high temperatures, has the properties as a separator required for recent dual-connected lead-acid batteries. It is.

Structure of the Invention That is, in order to achieve the above object, the present invention uses a separator obtained using a copolymer mainly composed of acrylic butadiene, styrene, and α-methylstyrene, which has excellent heat resistance and flexibility. It is a lead acid battery.

A copolymer mainly composed of acrylic butadiene-styrene and α-methylstyrene is one in which the proportion of α-methylstyrene in the copolymer component is 10% or more, preferably 30 to 60%. 0 Unlike ordinary copolymer resins of acrylic, butadiene, and styrene, it is a copolymer in which a portion of the styrene is replaced with α-methylstyrene, and the inclusion of α-methylstyrene has significantly increased heat resistance. and stability at high temperatures.

The particle size and content of butadiene must be set to such an extent that the flexibility of the separator is not impaired, and the particle size is preferably 1000 Å or less and the content is preferably 60% or less.

Furthermore, as an alternative to acrylic, methyl methacrylate resin can also be used.

Example The details of the present invention will be explained below using Examples.

To explain the present invention using figures, FIG. 1 is a longitudinal cross-sectional view of a lead-acid battery showing one embodiment of the present invention. 1 is a glass mat, 2 is a thin film microporous separator 6 is a negative electrode plate, 4 is a positive electrode plate,
5 is a battery case, 6 is a battery case lid, and 7 is a positive pole. FIG. 2) is a perspective view of a lead-acid battery electrode group showing another embodiment of the civil engineering invention. 8 is an embossed thin film microporous separator.

FIG. 6 is a perspective view of an embodiment showing the shape of the separator used in the battery of the present invention after embossing, and FIG. 4 is a sectional view thereof. Reference numeral 9 indicates a groove portion where a portion of the cell is heated and the micropores are crushed, and gas generated during use of the battery passes through this portion and escapes to the top. 10 is the fourth part, and when this part is embossed, it is heated most intensely and becomes a film-like part. Reference numeral 11 denotes a separator web having micropores, and this portion contacts the electrode plate to suppress swelling of the electrode plate and prevent the active material from falling off. FIG. 5 shows a comparison of elasticity of separators used in batteries of the present invention.

(Example 1) A mixed solution consisting of 14 parts of a copolymer resin mainly composed of 0 acrylic-butadiene styrene and α-methylstyrene, 64 parts of tetrahydrofuran solvent, 20 parts of isopropyl alcohol, and 6 parts of fine silica powder was applied to a polyester nonwoven fabric. ．．
It was obtained by coating 17fl and then removing volatile components. This can be a hydrophilic microporous separator with an average pore size of 0.6μ.

Table 1 shows a comparison of the characteristics of the thin film microporous separator according to the present invention and the thin film microporous separator made of other synthetic resins.

Table 1 Comparison of characteristics of separators (Note') N0K) to (e) were obtained by the same method as in the present invention, a method of combining a synthetic resin, a solvent, and a non-solvent.

As shown in Table 1, the separator No. 1 used in the battery of the present invention has a lower electric resistance than other seven separators,
It can be seen that the separator has excellent heat resistance and oxidation resistance.

It is also seen that the MAX temperature of heat resistance is the highest compared to the others, and it has properties that can sufficiently withstand even the high-temperature use required for folded batteries.

Figure 5 shows the conventional ABS membrane separator and the heat-resistant ABS membrane separator used in the present invention.
Electrical resistance increases rapidly from around °C. This is not practical because it is in a very unstable range compared to the heat-resistant temperature range of 70 to 80° C. required for batteries in recent years.

On the other hand, the separator used in the present invention is heated to 100°C.
It is stable and has properties that can sufficiently withstand the demands of batteries.

Using this separator, embossing was performed as shown in FIG. 6.4, and the elasticity was compared in FIG. 6. This has two embossed separators.
4 hours, 20 kg/protective load was placed under the load, and the thickness change before and after the load was investigated.

It can be seen that the separator used in the battery of the present invention has less change in thickness and excellent elasticity than the separator used in the conventional battery No. 1 shown in Table 1.

This property has a great effect on battery performance, suppressing abnormal swelling of the electrode plate due to the expansion and contraction of the electrode plate that occurs during repeated charging and discharging, and reduces the falling off of the active material.

Table 2 shows a performance comparison of automotive batteries. Since the battery of the present invention uses a separator with low electrical resistance, the discharge voltage is 0.15 V higher than that of conventional lightning batteries, and its life performance is longer than that of conventional products. It is a stand.

This is because the separator used has excellent acid resistance and oxidation resistance, and has excellent elasticity, so the active material on the electrode plate is less likely to fall off.◇The synthetic resin of the separator is acrylic or butadiene. Since the main component is styrene, the polymer is thermoplastic and extremely flexible.This property allows for excellent processability such as embossing, and it can be used to wrap electrode plates in a zigzag pattern or to wrap electrode plates. It is also easy to bend when doing so.

Further, no harmful impurities are eluted into the battery electrolyte.

Furthermore, by mixing fine silica powder into the micropores, the path of the micropores becomes complicated, which prevents penetration of the lead active material, that is, greatly improves the oxidation resistance.

If the content of α-methylstyrene is less than 10%, heat resistance will not be sufficiently improved. If it exceeds 60%, the yield as a polymer decreases and the polymer exhibits unstable properties, making it unsuitable for modern batteries that require stable properties at high temperatures.

(Example 2) A mixed solution consisting of 16 parts of a copolymer resin whose main components are acrylic butadiene, styrene, and α-methylstyrene, 62 parts of tetrahydrofuran, 22 parts of isopropyl alcohol, and 3 parts of fine silica powder was applied to a polyester nonwoven fabric with 0. 25
fllc was coated and the volatile matter was removed after that, it was possible to obtain a microporous separator with an average pore diameter of 0.7μ. Third
The table shows the comparative characteristics of the rubber microporous separator used in conventional products.

Table 5 From the above results, it is clear that because the electrical resistance is low and it is made of thermoplastic synthetic resin, it has good workability such as embossing, and is easy to bend and heat seal, and can be folded into a zigzag shape as shown in Figure 2. Easy to bend and place.

Table 4 shows the performance ratio of batteries for Km electric cars.

Table 4 From the results of the above rate capacity tests, it was found that the capacity was larger than that of the rubber microporous separator, and the SBA hemorrhoid life characteristics were no different from conventional batteries.

This is thought to be due to the fact that the use of embossed separators improved degassing compared to conventional products, and that the electrical resistance of the seven separators was lower.

The separator used in the battery of the present invention has durability equivalent to or higher than conventionally used rubber microporous separators even under severe usage conditions for electric vehicles.

Also, by arranging the separators in a zigzag pattern,
Short circuits on the sides of the electrode plates can be prevented.

(Example 6) After applying the liquid mixture shown in Example 1 to one side of mackerel having a glass mat thickness of 0.7, the volatile matter was removed. by this,
A microporous separator with a glass mat on one side was obtained. A lead-acid battery using this had performance equivalent to or better than that of Example 1.

(Example 4) The microporous separator shown in Example 1 was made of glass pine) 0.5
The battery using the bonded material was a high performance battery as in Example 1.

The separator used in the battery of the present invention is made by copolymerizing 1acrylic butadiene and styrene with α-methylstyrene added thereto to impart heat resistance. As a result, while the heating deformation temperature of a conventional synthetic resin of this type is 85 to 90°C, the heat resistance was improved by 10 to 15°C. Considering that the battery usage conditions reach a maximum of 70 to 80°C, this becomes a more stable separator. In addition, the composition of the mixed liquid should be within a range that satisfies these conditions, such as uniform mixing of the liquid, ease of coating on the base material, and properties of the obtained microporous separator that can be used as a battery. The following combination is optimal.

111,100 parts, the copolymer containing acrylic butadiene and styrene as main components is 10 to 65 parts. The amount of non-solvent is 10 to 65 parts based on the sum of the solvent and the copolymer, and the amount of inorganic fine powder is 1 to 10 parts based on 100 parts of the main component, giving the best separator properties.

It goes without saying that copolymers containing acrylic butadiene, styrene, and α-methylstyrene as main components can be applied to the present invention even if they have been added with other heat resistance improvers, stabilizers, etc. do not have.

Inorganic fine powders include dry process silica, wet process silica, etc.
Any acid-resistant material may be used.

The base material to which the mixed solution is applied may be anything other than those in the examples as long as it is acid-resistant, porous, and has appropriate strength, and sheets made of synthetic pulp or the like may also be used.

The embossing of the thin film microporous separator can be applied to any shape other than those shown in FIGS. 6 and 4, as long as it can be passed between heating rolls or rubber rolls, as long as it does not cause cracks in the microporous separator.

Furthermore, since the separator of the present invention can be heat-sealed when assembled as a battery, it is also possible to wrap the electrode plate and seal both sides to form a bag-like shape.

Regarding the composition of the liquid mixture, it is also possible to add a surfactant to improve the dispersibility of the silica fine powder.

Effects of the Invention The present invention provides a high-performance, long-life lead-acid battery that can withstand use at high temperatures by using a separator with low electrical resistance and excellent acid and oxidation resistance. The value is extremely great.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a lead-acid battery showing one embodiment of the present invention. Fig. 2 is a perspective view of a lead-acid battery electrode group showing another embodiment of the present invention, and Fig. 6 shows the shape of the seven pallets used in the battery of the present invention after embossing, and the shape of the other embodiment. The perspective view and FIG. 4 are the cross-sectional views. FIG. 5 is a diagram comparing the elasticity of separators used in the present invention. FIG. 6 is a diagram comparing changes in thickness of embossed separators due to load.

Claims (5)

[Claims] (1) A copolymer mainly composed of acrylic, butadiene, styrene, and α-methylstyrene, and a solvent for the copolymer;
and a non-solvent that does not dissolve the copolymer and mixes well with the solvent, and further includes an inorganic powder, and a mixed solution is applied to an acid-resistant base material to remove volatile components. A lead-acid battery characterized by: (2) The lead-acid battery according to claim 1, which contains 10 to 60% of the copolymer α-methylstyrene. (3) The lead-acid battery according to claim 1, wherein a synthetic resin nonwoven fabric, synthetic pulp, or glass mat is used as the acid-resistant base material. (4) The lead-acid battery according to claim 1, wherein the thin film microporous separator is embossed. (5) The lead-acid battery according to claim 1, wherein the thin film microporous separator is arranged in a zigzag pattern between the positive and negative electrode plates.