JP2001222987A - Gastight lead acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gastight lead acid battery in which the growth of dendrites is considerably suppresses and the stable electric property is obtained. SOLUTION: The gastight lead acid battery is equipped with either a woven cloth (functional woven cloth) or a non-woven cloth (functional non-woven cloth) 3 having ion exchange capability is placed adjacent to both negative and positive electrodes. With this structure, Pb2+ ion leaked from either the positive electrode 1 or the negative electrode 2 is captured in a good yield in the functional non-woven cloth 3, followed by the reasonable suppression of the growth of dendrites at the negative electrode 2, resulting in a long life lead acid battery with remarkable battery properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery in which the growth of dendrites (dendrites) is sufficiently suppressed and good battery characteristics are stably obtained.

[0002]

2. Description of the Related Art In a lead-acid battery, after an electrolyte is poured into a battery case containing an electrode group to form a battery case, or after the lead-acid battery is left for a long time after use, the electrolyte (sulfuric acid) is used. ) The low concentration causes the electrolyte to react with the lead, resulting in a lower concentration of the electrolyte, and eventually lead from the positive and negative electrodes to elute as Pb ²⁺ ions into the electrolyte, and this Pb ²⁺ ion Precipitates on the negative electrode during charging and dendrite grows. Since this dendrite protrudes and grows from the negative electrode, the distance between the positive electrode and the negative electrode is locally narrowed, and self-discharge increases,
In the worst case, the dendrite comes into contact with the positive electrode to cause a short circuit, and the battery does not function. This phenomenon tends to occur in a sealed lead-acid battery in which the amount of the electrolyte is small and the concentration of the electrolyte changes drastically.

[0003] As a remedy, there has been proposed a method of suppressing the elution of lead by increasing the concentration of the electrolytic solution, or a method of suppressing the contact of the dendrite with the positive electrode by increasing the thickness of the separator or increasing the basis weight of the active material. ing. However, the former method has problems that the battery characteristics are deteriorated and the battery life is shortened due to corrosion of the positive electrode grid. In the latter method, the resistance between the electrode plates is increased and the high-rate discharge characteristics (short-time large-current discharge) Characteristics) and the discharge characteristics at low temperatures are deteriorated.

[0004]

SUMMARY OF THE INVENTION
A cation exchange membrane is interposed at the center of the separator provided between the positive and negative electrodes of the sealed lead-acid battery, and Pb ⁺²
A method for trapping ions has been proposed (JP-A-6-32).
No. 5746). However, even with this method, dendrites may grow and short-circuit, and the effect of the cation exchange membrane is extremely small particularly when applied to a sealed lead-acid battery with a small amount of electrolyte. Therefore, the present inventors investigated the cause of dendrite growth even when a cation exchange membrane was interposed between the positive and negative electrodes. As a result, some Pb ⁺² ions eluted from the positive electrode bypassed the exchange membrane and reached near the negative electrode, and some Pb ⁺² ions eluted from the negative electrode remained near the negative electrode. Also found that these Pb ⁺² ions precipitate on the negative electrode during charging etc. and grow as dendrites to cause a short circuit,
Further research has led to the completion of the present invention. An object of the present invention is to provide a sealed lead-acid battery in which the growth of dendrite is sufficiently suppressed and good battery characteristics are stably obtained.

[0005]

According to the first aspect of the present invention,
A sealed lead-acid battery in which a woven fabric (hereinafter referred to as a functional woven fabric) or a nonwoven fabric (hereinafter referred to as a functional nonwoven fabric) having ion exchange capability is provided in contact with a positive electrode and a negative electrode.

According to a second aspect of the present invention, the woven fabric or the nonwoven fabric having the ion exchange ability is a woven fabric or a nonwoven fabric into which a functional group such as a carboxyl group is introduced. Type lead-acid battery.

According to a third aspect of the present invention, the woven or nonwoven fabric having ion exchange capability is a woven or nonwoven fabric obtained by applying an ion exchange resin to the surface of a woven or nonwoven fabric. 3. A sealed lead-acid battery according to 1 or 2.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A sealed lead-acid battery according to the present invention comprises a non-woven fabric 3 having a cation exchange capability between a positive electrode 1 and a negative electrode 2 as shown in FIG. Pb eluted from both positive and negative electrodes 1 and 2
²⁺ ions are captured by the functional nonwoven fabric 3 with good yield, and the growth of dendrites on the negative electrode 2 is sufficiently suppressed. Further, since the nonwoven fabric 3 has a good retention of the electrolytic solution, even if the nonwoven fabric 3 is brought into contact with the positive electrode 1 and the negative electrode 2, the battery characteristics such as the high-rate discharge characteristics do not deteriorate. In the present invention, the functional nonwoven fabric 3
Examples thereof include those in which the surface layer of the nonwoven fabric 10 has ion exchange capability (FIG. 1B) and those in which the functional nonwoven fabric 3 is combined on both surfaces of the nonwoven fabric 10 (FIG. 1C). In the conventional method (Japanese Patent Laid-Open No. 6-325746), when the ion exchange membrane is brought into contact with the positive electrode and the negative electrode, the ion exchange membrane is inferior in the retention of the electrolyte, and the replenishment of the electrolyte becomes insufficient. Battery characteristics cannot be obtained.

In the present invention, a functional woven fabric or a functional nonwoven fabric is obtained by adding a carboxyl group (—COO) to a woven fabric or a nonwoven fabric.
H) and a functional group for capturing a cation such as a sulfonic acid group (-SO3 H). The Pb ²⁺ ion is
For example, a carboxyl group is trapped as (-COO) 2 Pb, and a sulfonic acid group is trapped as (-SO3) 2 Pb. These are all sparingly soluble salts, and Pb
There is no re-elution of ²⁺ ions. Phosphoric acid groups (-PO3 H), phenolic hydroxyl groups (-OH) and the like can also be applied to the functional groups for capturing cations.

In the present invention, the functional woven fabric or the functional nonwoven fabric may be prepared by reacting the woven fabric or the nonwoven fabric in hot concentrated sulfuric acid to introduce a sulfone group, or immersing in a latex in which an ion exchange resin is dispersed. Alternatively, it can be produced by a method of introducing a carboxyl group by graft-polymerizing acrylic acid to a nonwoven fabric. In particular, a method of immersing in the latex in which the ion exchange resin is dispersed is preferable because of excellent workability.

In the present invention, the woven or nonwoven fabric includes
A woven or nonwoven fabric having excellent electrolytic solution retention properties such as polypropylene (PP) fiber, polyethylene (PE) fiber, and glass fiber is used. Therefore, the functional woven fabric or nonwoven fabric used in the present invention has both ion exchange capacity and electrolytic solution supply ability, and the sealed lead-acid battery of the present invention using this functional woven fabric or functional nonwoven fabric has good battery characteristics. Is obtained stably.

[0012]

The present invention will be described below in detail with reference to examples. (Example 1) A lead active material (Pb
Seven electrodes (three positive electrodes and four negative electrodes) were prepared by applying O, Pb, and PbSO4 mixed, and positive electrodes 1 and negative electrodes 2 were alternately arranged as shown in FIG. In the meantime, the functional nonwoven fabric 3 was provided in contact with the positive electrode 1 and the negative electrode 2 to form an electrode plate group 4, which was stored in the battery case 5. In FIG. 2, 6 is a lid of the battery case 5, 7 is a negative electrode terminal (a positive electrode terminal is not shown), 8 is a safety valve, and 9 is a negative electrode strap.

Any of the following a to c was used for the functional nonwoven fabric. That is, a is a nonwoven fabric prepared by mixing polypropylene (PP) fiber and polyethylene (PE) fiber in hot concentrated sulfuric acid at 95 ° C. for 5 minutes to obtain a sulfonic acid group with a basis weight of 200 g.
/ M ² and a thickness of 1 mm introduced by grafting acrylic acid onto the nonwoven fabric and introducing a carboxyl group at a basis weight of 200 g / m ² , and c denotes an ion exchange resin (sulfone resin). (Acid-based) in a latex in which sulfonic acid groups are weighed 200 g /
It is 1 mm thick introduced at m ² . The basis weight is, for example, [mn] in the case of a. Here, m is the weight per 1 m ^{2 of} the functional nonwoven fabric dried after immersion in hot concentrated sulfuric acid, and n is the weight per 1 m ² of the nonwoven fabric before immersion in hot concentrated sulfuric acid.

Then, dilute sulfuric acid having a specific gravity of 1.24 is poured into the battery case 5 containing the electrode plate group 4 and then left for 5 hours, and then the battery case is formed at a current rate of 10 hours for 20 hours. As a result, a sealed lead-acid battery having a rated capacity of 10 Ah was manufactured. The sealed lead-acid batteries were manufactured in a number of 10 for each type of the functional nonwoven fabric 3.

(Example 2) A composite comprising a glass mat (0.55 mm thick) and a functional non-woven fabric (0.2 mm thick) of any one of the above a to c was formed between the positive and negative electrodes. A sealed lead-acid battery having a rated capacity of 10 Ah was manufactured in the same manner as in Example 1 except that the battery was provided so as to be in contact with the positive electrode and the negative electrode. The basis weight of the functional nonwoven fabric is 50 g each.
/ M ² .

(Comparative Example 1) A composite in which the functional nonwoven fabric of any of the above a to c (0.2 mm in thickness) was combined on one side of a glass mat (0.75 mm in thickness) between the positive and negative electrodes, A sealed lead-acid battery was manufactured in the same manner as in Example 1, except that the negative electrode was provided with a glass mat in contact with the positive electrode. The basis weight of the functional nonwoven fabric is 50 g / m.
^{And 2} .

Comparative Example 2 A sealed lead-acid battery was manufactured in the same manner as in Example 1, except that a glass mat having a thickness of 1 mm was provided between the positive and negative electrodes instead of the functional nonwoven fabric.

The following test A was carried out for each of the sealed lead-acid batteries produced in Examples 1 and 2 and Comparative Examples 1 and 2 after formation of the battery case. Test A: The voltage was measured after leaving each of the sealed lead-acid batteries at room temperature. If the voltage drop was below the specified value, it was judged as good, and if it exceeded the specified value, it was judged as defective. Next, the following test B was performed on the battery which became a good product in the test A. Test B: Each battery which became a non-defective cell in test A was discharged at a rate current of 5 hours, left at a temperature of 40 ° C. for 6 months, then returned to room temperature, charged at a rate current of 10 hours, and charged for 15 hours. The voltage was measured for the later battery. If the voltage dropped below the specified value, it was regarded as defective. When the batteries which were defective in the tests A and B were disassembled and examined, a short circuit due to dendrite was found in each of them. Table 1 shows the number of batteries that failed in Test A or Test B, and the total defective rate (short-circuit occurrence rate).

[0019]

[Table 1]

As is clear from Table 1, N of the present invention example
o. No short circuit occurred in any of Examples 1 to 3 (Example 1), and N
o. 4 to 6 (Example 2) had a low short-circuit occurrence rate of 10%. This is because Pb ²⁺ ions eluted from both the positive and negative electrodes were captured by the functional nonwoven fabric with good yield, and the growth of dendrites was sufficiently suppressed. The sealed lead-acid battery, which became a good product in both test A and test B, was used by repeating charging and discharging many times, and all of them were excellent in high-rate discharge characteristics and stable in good battery characteristics with small self-discharge rate. Indicated. On the other hand, in Comparative Example No. 7 to 9 (Comparative Example 1) all had high short-circuit occurrence rates. This is because the functional nonwoven fabric is not in contact with the positive electrode. In addition, in Comparative Example No. No. 10 (Comparative Example 2) was a conventional battery only with a glass mat interposed, and short-circuits occurred in all tests A and B. Good results were also obtained when a latex in which an ion exchange resin was dispersed was applied to both surfaces of the glass mat so that only the surface layer of the glass mat had ion exchange capability.

[0021]

As described above, in the sealed lead-acid battery of the present invention, a functional woven fabric or a functional nonwoven fabric having both ion exchange ability and electrolyte supply ability is applied between the positive and negative electrodes. Since they are provided in contact with each other, the growth of dendrites is sufficiently suppressed, and good battery characteristics are stably obtained.
Therefore, an industrially remarkable effect is achieved.

[Brief description of the drawings]

FIGS. 1A to 1C are explanatory longitudinal sectional views showing an embodiment of a functional nonwoven fabric used in the present invention.

FIG. 2 is an explanatory longitudinal sectional view showing an embodiment of the sealed lead-acid battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Nonwoven fabric having a cation exchange ability (functional nonwoven fabric) 4 Electrode plate group 5 Battery case 6 Battery case lid 7 Negative terminal 8 Safety valve 9 Negative current collecting strap 10 Nonwoven fabric

Claims (3)

[Claims] 1. A sealed lead-acid battery characterized in that a woven or nonwoven fabric having ion exchange capability is provided in contact with a positive electrode and a negative electrode. 2. The sealed lead-acid battery according to claim 1, wherein the woven or nonwoven fabric having the ion exchange ability is a woven or nonwoven fabric into which a functional group such as a carboxyl group is introduced. 3. The woven or non-woven fabric having an ion exchange ability is a woven or non-woven fabric in which an ion exchange resin is applied to the surface of a woven or non-woven fabric.
Or the sealed lead-acid battery according to 2.