JP2010020905A - Lead-acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of rapid degradation of lifetime of a lead-acid battery by lowering of charge efficiency and arising sulfation coming from a stratification phenomenon in which a specific gravity of electrolyte liquid becomes higher at the lower part of the electrode plate due to usage in insufficient charge condition, by being used under a deep discharge and chronic insufficient charging condition resulting to lower charge efficiency. <P>SOLUTION: A negative electrode plate and a positive electrode plate are set so that a grid area of current collectors is at least 40% for a middle 1/3 part and 20 to 80% for a lower 1/3 part to that of an upper 1/3 part in height direction of the current collector lattice. And thickness of a negative electrode plate and a positive electrode plate becomes thinner from an upper part to a lower part. When an upper part thickness of the electrode plate is T, a height of the electrode plate is H, a lower part thickness of the electrode plate is t, and a thickness of the electrode plate at height Y is X, Y=(H/(T-t))X-HT/(T-t), where H/(T-t) is set as 97 to 290, and HT/(T-t) is set as 155 to 464. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an automotive lead acid battery for idling stop applications.

Lead-acid batteries for automobiles, as called SLI batteries, are mainly used for starters (start-ups), lighting, and ignition, and in addition, they are used for the power supply of more than 100 motors installed in luxury cars. Other than the starter, since the engine drives the generator to supply power, the lead-acid battery is not discharged so deeply. Instead, it is charged by the generator during driving and may be left in a fully charged state. There were many.
However, in recent years, for the purpose of improving the fuel efficiency of automobiles and reducing exhaust emissions, an idling stop has been required to stop the engine while it is stopped due to a signal, etc. When the engine is stopped, power is not supplied from the generator. Since it is supplied from a lead storage battery, the lead storage battery has come to be discharged deeper than before (Patent Document 1).
In addition, since an overcharge prevention system that reduces the load on the generator by terminating charging before overcharging is introduced, it is often used in an insufficiently charged state when the charging efficiency is low. In this way, lead-acid batteries are used in deep discharge and chronic undercharged conditions, especially when used for long periods in undercharged conditions, when concentrated sulfuric acid settles and the specific gravity of the electrolyte is below the electrode plate. As a result, a stratification phenomenon that became so high occurred that, as a result, coarse crystals of lead sulfate that did not contribute to the battery reaction were formed (sulfation) on the negative electrode, resulting in a decrease in charging efficiency. The battery life decreased rapidly due to the repeated vicious circle of the reduction in charging efficiency and the generation of sulfation.
As a measure for improving this, a method was proposed in which a large amount of carbon was added to the negative electrode to form a conductive path in the lead sulfate gap. It was.
In response to the idling stop, the automobile side has been modified to restart the engine with less power. However, because the engine started even in the state where sulfation progressed due to this modification, the negative electrode ear part and the upper part of the negative electrode grid plate whose polarization was smaller than the negative electrode active material part deteriorated by sulfation became active material, thinned, and fractured This led to the worst life mode in which lead-acid batteries suddenly reached the end of their lives.
In addition, with the increase in the number of engine starts due to idling stop and the decrease in the state of charge due to the charge control, the discharge distribution of the electrode plate becomes non-uniform, and the thinning of the negative electrode ear portion with smaller polarization is accelerated. For this reason, uniform discharge distribution is an important issue as a measure against thinning of the negative electrode ear.
The thinning of the ears or the like occurs even in a control valve type lead acid battery (Patent Document 1) with a small amount of electrolyte or a liquid type lead acid battery containing a large amount of electrolyte.
So far, a method has been proposed in which the ear is corroded by oxygen generated from the positive electrode side during charging by arranging a mat body or the like on the ear and holding the electrolyte there (Patent Document). 2 and 3), however, the thinning of the ears could not be prevented by this method.

Japanese Patent Laid-Open No. 2003-338312 Japanese Patent Laid-Open No. 4-249064 JP-A-8-162149

For these reasons, the present inventors investigated the thinness of the negative electrode ear. As a result, the following was found. That is, when the remaining battery life is about 20%, the amount of lead sulfate in the negative electrode active material increases to around 50%, and the negative electrode ear begins to thin. Thereafter, lead sulfate increases rapidly, and when the amount of lead sulfate reaches 80 to 90%, the thickness of the ear portion becomes about 10% of the original thickness, and is easily broken. At that time, the deterioration of the negative electrode also progresses to the end of its lifetime.
By the way, it is desirable for the battery life mode that the negative electrode gradually deteriorates to reach the life, and sudden life due to the breaking of the ear should be avoided as a lead acid battery for automobiles. It is necessary to delay the partial breakage from the life due to the deterioration of the negative electrode.
An object of the present invention is to provide a long-life lead-acid battery in which the deterioration of the negative electrode is delayed and the ear part breakage is further delayed and the life is not suddenly shortened.

According to the first aspect of the present invention, the area of the grids of the current collector for the negative electrode plate and the positive electrode plate formed by the expanding manufacturing method is smaller than the upper part 1/3 in the current collector grid height direction. 3 is 40% or more, and the lower 1/3 is 20 to 80%.
The invention according to claim 2 is a negative electrode plate and a positive electrode plate whose thickness decreases from the upper part toward the lower part, the upper thickness of the electrode plate is T, the height of the electrode plate is H, and the lower part of the electrode plate Assuming that the thickness is t and the thickness of the electrode plate at a height Y where the electrode plate is X is X, the equation is as shown in Equation 1, the slope H / (Tt) is 97 to 290, and the Y intercept HT / (Tt). Is a lead acid battery characterized by being 155-464.
Y = (H / (T−t)) X−HT / (T−t) (Equation 1)

The invention according to claim 1 increases the current collection efficiency of the lower part of the electrode plate by reducing the area of the grid of the current collector from the upper part to the lower part, and makes the discharge distribution and the charge efficiency of the entire electrode plate uniform. I can do it. Similarly, in the invention according to claim 2, the discharge distribution and the charging efficiency of the entire electrode plate can be made uniform by decreasing the thickness of the electrode plate from the upper part to the lower part. Thereby, the difference in polarization between the negative electrode active material and the negative electrode ear can be suppressed, and the active material can be prevented from being formed by the ear discharge. It is important to make the discharge distribution uniform throughout the electrode plate, and the effect of the invention is exhibited only when the current collection efficiency above and below the electrode plate is balanced.
The present invention responds to the improvement in fuel efficiency of transportation equipment such as automobiles, which occupy a large amount of fossil fuel consumption, due to the inevitably required energy saving and natural energy use due to global environmental problems becoming increasingly important in the 21st century. To provide a lead storage battery that is economical and stable for a long period of time, and its industrial value is extremely high

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the following Example at all, In the range which does not change the summary, it can change suitably and can implement.

  Hereinafter, embodiments of the present invention will be described in detail.

(Comparative example)
The lead acid battery of the comparative example was produced as follows.
15 kg of red lead and 110 L of dilute sulfuric acid (specific gravity 1.26: same as below 20 ° C.) were put into a kneading mixer to make red lead slurry. The red lead slurry and 850 kg of lead powder were put into a paste kneader and kneaded with 100 L of water to make a positive electrode active material paste. Next, 85 g of this positive electrode active material paste was filled in an expanded current collector made of a calcium alloy, left to mature for 18 hours at a temperature of 40 ° C. and a humidity of 95%, and then left at a temperature of 60 ° C. for 12 hours. And dried to produce an unformed positive electrode plate. The grid of the expanded current collector has a rhombus shape with a width of 17 mm and a height of 12 mm, and an opening area (hereinafter referred to as area) of 102 mm ² .

Next, the negative electrode plate is prepared by kneading lead powder, 15 wt% diluted sulfuric acid (specific gravity 1.26) with respect to the lead powder, and 12 wt% water with respect to the lead powder. It was. Next, 80 g of negative electrode active material paste was filled in an expanded current collector of calcium alloy, left to mature at a temperature of 50 ° C. and a humidity of 95% for 18 hours, and then left to stand at a temperature of 110 ° C. for 2 hours to dry. Thus, an unformed negative electrode plate was produced.
Eight unformed negative electrode plates and seven unformed positive electrode plates were alternately laminated via separators to form each electrode plate group.
In the chemical conversion, charging was performed in an atmosphere of 25 ° C. with a constant current of 22.5 A for 12 hours. The specific gravity of sulfuric acid used for charging was 1.240, and 700 ml of each cell was injected.
By the above procedure, a comparative example 80D26 type lead-acid battery for automobile (described in JIS D5301) having a rated voltage of 12 V and a rated capacity (5 hour rate capacity) of 55 Ah was produced.

(Embodiment 1)
The lead storage battery of Embodiment 1 was produced as follows.
The positive electrode active material paste and the negative electrode active material paste were produced in the same manner as in the comparative example. An expanded current collector of calcium alloy forms a diamond-shaped cell by cutting a lead-calcium alloy sheet with a stepped upper blade and developing the sheet in the width direction of the sheet. By changing the shape of the upper blade, the shape of the grid in the vertical direction of the current collector can be changed.
In the current collector of the present embodiment, the upper part 1/3 in the height direction has a rhombus shape with a width of 17 mm and a height of 12 mm and a square with an area of 102 mm ² , and the central part 1/3 has a width of 17 mm and a height of 9 mm. The grid has a rhombus shape and an area of 76.5 mm ² , and the lower third is a rhombus shape having a width of 17 mm and a height of 6 mm and an area of 51 mm ² . The current collector was filled with paste, and after aging, an 80D26 type automotive lead-acid battery (described in JIS D5301) of Embodiment 1 was produced in the same manner as in the comparative example.

(Embodiment 2)
The lead storage battery of Embodiment 2 was produced as follows.
The positive electrode active material paste and the negative electrode active material paste were produced in the same manner as in the comparative example. The positive expanded current collector of the calcium alloy was expanded in the same manner as in the first embodiment, and the intersection portion of the current collector was pressed with a thickness of 1.6 mm at the upper part 1/3 in the height direction, and the central part 1/3. Was pressed with a thickness of 1.2 mm, and the lower 1/3 was pressed with a thickness of 0.8 mm and then filled with paste. The filling thickness of the electrode plate was adjusted so that the electrode plate became thinner at a constant rate toward the lower part of the electrode plate so that the uppermost electrode plate had a thickness of 1.6 mm and the lowermost electrode plate had a thickness of 0.9 mm. At this time, when the upper thickness of the electrode plate is T, the electrode plate height is H, the electrode plate lower thickness is t, and the electrode plate thickness at the height Y with the electrode plate is X, H / (T−t) The value is 166 because the electrode plate height H is 116 mm, and HT / (T−t) is 265.
The negative electrode current collector is expanded in the same manner as in the first embodiment, and then the intersection part of the current collector is pressed with a thickness of 1.2 mm at the upper part 1/3 in the height direction and the central part 1/3 is 0.9 mm. The lower 1/3 was pressed with a thickness of 0.6 mm, and then the paste was filled. The filling thickness of the electrode plate was adjusted so that the uppermost electrode plate was 1.3 mm thick and the lowermost electrode plate was 0.8 mm so that the electrode plate became thinner at a constant rate toward the lower electrode plate. The value of H / (T−t) at this time is 232 because the electrode plate height H is 116 mm, and HT / (T−t) is 302. After aging, the 80D26 type automotive lead-acid battery (described in JIS D5301) of Embodiment 2 was produced in the same manner as in the comparative example.

  FIG. 1 shows the number of life cycles of Embodiments 1 and 2 with the comparative example being 100% for the life cycle number of the idling stop life test of SBA regulations (SBA S 0101). The test conditions were 45A at an ambient temperature of 25 ° C., 59 seconds of discharge, 300A, 1 second of discharge, and then charge / discharge repeated for 14 seconds at 14V for 60 seconds. The charge was repeated for 40 to 48 hours every 3600 cycles. Insert. The life cycle is a cycle in which the voltage during discharge becomes less than 7.2V.

  The vertical axis of FIG. 1 shows the cycle number ratio of the first embodiment and the second embodiment when the life cycle number of the comparative example is 100. In Embodiment 1, since the grid shape of the current collector is made smaller from the upper part of the electrode plate toward the lower part, the current collecting property at the lower part of the electrode plate is improved as compared with the upper part of the electrode plate. In the actual charging / discharging, the closer to the current collecting portion, the better the current collecting property, that is, the current collecting property is improved toward the upper part of the electrode plate which is the current collecting portion. Since the electrode plate No. 1 can secure a uniform current collecting property on the entire surface of the electrode plate, the active material of the entire electrode plate is uniformly used for charging and discharging, and the life cycle is improved. In particular, Comparative Example 1 resulted in a short life due to breakage of the negative electrode ear portion due to sulfation at the bottom of the electrode plate by repeating non-uniform charge / discharge cycles. In the second embodiment, the principle of the effect is the same as that in the first embodiment. By reducing the thickness of the electrode plate by reducing the thickness toward the lower part of the electrode plate, the charge / discharge distribution which is usually non-uniform is improved. The life cycle was improved by making the pressure uniform.

  FIG. 2 shows the current value at 5 seconds of the first embodiment and the second embodiment when the comparative example of the charge acceptance test is 100. This is a test in which the battery capacity is adjusted to SOC (State of Charge) 90% and left at 25 ° C. for 6 hours and then charged at a constant voltage of 14.0 V. The larger the value of the current at the 5th second, the better the power receiving ability, and in Embodiments 1 and 2, the chargeability is greatly improved compared to the comparative example. This is a result of the fact that the current distribution is made uniform, the discharge distribution is uniform over the entire active material of the electrode plate, and the charge acceptance is improved. This improvement in charge acceptance is considered to be due to the fact that the hydrogen and oxygen generation reactions, which are side reactions during charging, can be suppressed as the discharge state before charging is uniformly discharged over the entire electrode plate. This improvement in charge acceptability can also be said to be an effect of improving the cycle characteristics shown in FIG.

  FIG. 3 shows a negative electrode plate and a positive electrode plate whose thickness is reduced from the upper part toward the lower part. The upper thickness of the electrode plate is T, the height of the electrode plate is H, and the lower thickness of the electrode plate is t. The relationship between the t / T and the current at the 5th second of the charge acceptance test. Since the effect of the invention is great when the ratio of the lower thickness to the upper thickness is 0.25 to 0.75, when the electrode plate thickness at the height Y where the electrode plate is X is X, the relationship between X and Y Y = (H / (T−t)) X−HT / (T−t), the slope H / (T−t) of this equation is 97 to 290, and the Y intercept HT / (T−t) is 155. In the case of ˜464, an effect is brought about by charge acceptance.

  FIG. 4 shows the relationship between the ratio of the grid area to the grid area of the upper third of the current collector in the height direction and the current at the fifth second in the charge acceptance test. It can be seen that the current at the 5th second is large when the lower area ratio relative to the upper grid area is 20 to 80%. Further, the central area ratio with respect to the upper grid area is 40% or more, and the current at the 5th second is large, and it can be seen that the ratio of these square areas is more effective.

It is a figure which shows the comparative example ratio of the life cycle number in an idling stop life test. It is a figure which shows the comparative example ratio of 14V constant voltage charge 5 second current value in 25 degreeC and a charge acceptance test. It is the figure which showed the relationship between the ratio of upper electrode board thickness T and lower electrode board thickness t, the relationship of t / T, and the 14-V constant voltage charge 5 second current value in a charge acceptance test. It is the figure which showed the relationship between the center area | region and lower cell area ratio with respect to the upper cell area of an electrical power collector, and the 14V constant voltage charge 5 second current value in a charge acceptance test.

Claims (2)

A current collector for a negative electrode plate and a positive electrode plate formed by an expanding manufacturing method, wherein the area of the grid of the current collector is 40 in the central portion 1/3 with respect to the upper third in the current collector height direction. % Or more, and the lower 1/3 is 20 to 80%. A negative electrode plate and a positive electrode plate whose thickness decreases from the upper part toward the lower part. The upper thickness of the electrode plate is T, the height of the electrode plate is H, the lower thickness of the electrode plate is t, Assuming that the electrode plate thickness at a certain height Y is X, there is a relationship of Formula 1, the slope H / (Tt) is 97 to 290, and the Y intercept HT / (Tt) is 155 to 464. The lead acid battery according to claim 1.
Y = (H / (T−t)) X−HT / (T−t) (Equation 1)

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