JP2006210058A - Lead acid storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead acid storage battery which prevents an ear portion from fracturing and reaching the end of its usefulness suddenly, especially the lead acid storage battery suitable for a vehicle that has to stop at idle running. <P>SOLUTION: This is the lead acid storage battery in which the thickness of the ear portion of a negative electrode lattice plate is the thickness or more of the outer frame lattice of the negative electrode lattice plate and in which Al is contained 2-50 g/l in sulfate conversion in the electrolytic liquid. Since the lead acid storage battery has made the thickness of the ear portion of the negative electrode lattice plate same or more than the thickness of the outer frame lattice of the negative electrode lattice plate, the quantity of lead sulfate produced at the negative electrode lattice plate ear portion is reduced and since Al is contained appropriately in the electrolytic liquid, the crystal grain of the lead sulfate produced at the negative electrode lattice plate ear portion is made minute, and thereby lead sulfate hardly comes off from the negative electrode lattice plate ear portion, and oxidation by oxygen generated from the positive electrode side at the time of charging is prevented, and furthermore, since Al suppresses sulfation, thinning (fracture) of the ear portion is prevented. The lead acid storage battery exerts its effect remarkably in a vehicle that has to stop at idle running. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lead-acid battery that is particularly suitable for an idling stop vehicle, in which the ears of a negative electrode grid plate are thinned and ruptured to prevent a sudden life.

  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, there has been a demand for an idling stop that stops the engine while the vehicle is stopped due to a signal, etc., for the purpose of improving the fuel efficiency of automobiles and reducing exhaust emissions. And since the electric power is supplied not from the generator but from the lead storage battery while the engine is stopped, the lead storage battery has come to be discharged deeper than before (Patent Document 1).
In addition, since an overcharge prevention system for reducing the load on the generator by terminating charging before overcharging has been introduced, lead storage batteries are often used in an insufficiently charged state.

  In this way, since lead-acid batteries have been used in deep discharge and chronic undercharge conditions, concentrated sulfuric acid settles at the bottom of the electrode plate (stratification phenomenon) and does not contribute to the battery reaction. Sulfation generated by crystalline lead sulfate (discharge product) was generated, and the charging efficiency was likely to be lowered. The battery life decreased rapidly by repeating the vicious cycle of the decrease in charging efficiency and the occurrence of sulfation.

  As a measure to improve this, a method of adding a large amount of carbon to the negative electrode to form a conductive path in the gap between lead sulfates was proposed (Non-Patent Document 1). No life extension was observed.

  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 lattice plate ear part and the upper part of the negative electrode lattice plate whose polarization was smaller than the negative electrode part deteriorated by sulfation became active material, The ears broke down, causing the worst situation where the lead-acid battery suddenly reached the end of its life.

  Incidentally, when the occurrence of thinning due to the sulfation of the negative electrode grid plate ear was examined, when the remaining battery life was about 20%, the amount of lead sulfate in the negative electrode active material increased to around 50%, and the negative electrode grid The plate 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, it was found that the deterioration of the negative electrode progressed to the end of its lifetime.

  Of course, it is desirable that the lead-acid battery has a negative electrode that gradually deteriorates to reach the end of its life, and the situation where the ear part suddenly reaches the end of life is a situation that should be avoided particularly as a lead-acid battery for automobiles. Note that the thinning of the ears or the like occurs even in a control valve type lead acid battery with a small amount of electrolyte or a liquid type lead acid battery that contains a large amount of electrolyte.

Japanese Patent Laid-Open No. 2003-338312 K. Nakamura, et al., “Failure models of valve-regulated lead / acid batteries”, Journal of Power Sources, (USA), 1996, Vol. 59, p. 153-157

  The present inventors have extensively investigated the cause of thinning in preventing thinning of the negative electrode lattice plate ear. As a result, the thinning of the negative electrode lattice plate ears, in addition to the sulfation, when the lead sulfate generated in the negative electrode lattice plate ears reaches a certain amount, the ears are exposed, and the exposed portion becomes the positive electrode during charging. It has been found that it proceeds also by oxidation with oxygen generated from the side. Then, it has been found that the removal of the lead sulfate is greatly improved by both reducing the surface area of the negative electrode lattice plate ear and adding Al to the electrolytic solution, and further studies are made to complete the present invention. It came.

  An object of the present invention is to provide a lead-acid battery that is particularly suitable for an idling stop vehicle, in which the ear portion is prevented from breaking and suddenly reaching the end of its life.

  The thickness of the ear | edge part of a negative electrode grid plate is more than the thickness of the outer frame grid of the said negative electrode grid plate, and 2-50 g / l of Al is contained in electrolyte solution in conversion of a sulfate. It is the lead acid battery characterized by this.

  The invention according to claim 2 is the lead acid battery according to claim 1, wherein the lead acid battery is for an idling stop vehicle.

In the lead storage battery of the present invention, since the thickness of the negative electrode grid plate ear portion is made larger than the thickness of the outer frame lattice of the negative electrode lattice plate, the amount of lead sulfate produced in the negative electrode lattice plate ear portion is reduced, and the electrolyte solution Since an appropriate amount of Al is contained in the lead sulfate crystal grains formed in the negative electrode lattice plate ears, the lead sulfate is difficult to fall off from the negative electrode lattice plate ears. Oxidation is prevented, and since Al suppresses sulfation, thinning (breaking) of the ear is prevented. Since the thinning is likely to occur in an insufficiently charged state, the present invention is particularly effective in a lead-acid battery for an idling stop vehicle.
INDUSTRIAL APPLICABILITY The present invention is a lead storage battery that can cope with improvement in fuel consumption of automobiles and the like that will become more important in the future due to global environmental problems, and operates stably, and its industrial value is extremely large.

In the present invention, the reason for making the thickness of the negative electrode lattice plate ears greater than the thickness of the outer frame lattice is to reduce the surface area of the negative electrode lattice plate ears, reduce the amount of lead sulfate produced in the ears, This is to make it difficult to drop off the ear. The reason for making the thickness of the negative electrode lattice plate ear portion equal to or greater than the outer frame lattice thickness is that the effect cannot be sufficiently obtained if the thickness of the ear portion is less than the outer frame lattice thickness.
It is desirable to make the thickness of the negative electrode grid plate ears 3% or more thicker than the thickness of the outer frame grid, since the effect is remarkable. Here, the outer frame lattice is a portion that forms the outer periphery of the negative electrode lattice plate, and is a portion that becomes a base portion of the ear portion. Note that the cross-sectional area of the ear portion is kept constant in order to secure a predetermined energization amount.

  In the present invention, the reason why Al is contained in the electrolytic solution is that when Al is contained in the electrolytic solution, the lead sulfate crystal grains generated in the negative electrode grid plate ears become finer and lead sulfate is less likely to fall off the ears. It is. The Al also has a function of suppressing sulfation by suppressing or making unstable lead sulfate crystal growth.

  The reason why the content of Al is regulated to 2 to 50 g / l in terms of sulfate is that the effect cannot be sufficiently obtained when the content is less than 2 g / l, and the effect is saturated when the content exceeds 50 g / l. This is because the conductivity of the battery deteriorates and the battery characteristics deteriorate, which is disadvantageous in terms of cost.

  In the present invention, it is desirable to improve the charge / discharge characteristics by adding carbon, lignin, barium sulfate or the like to the negative electrode. The addition amount of the carbon, lignin, and barium sulfate is 0.05 to 3 parts by weight, 0.1 to 1 part by weight, and 0.5 to 5 parts by weight, respectively, with respect to 100 parts by weight of the negative electrode active material. If the amount is less than the lower limit, the effect cannot be sufficiently obtained, and even if the amount exceeds the upper limit, the effect is saturated, which is disadvantageous in terms of cost.

  In the present invention, if the specific gravity of the electrolytic solution at 20 ° C. is less than 1.270, there is a case where sulfate ions are insufficient at an early stage due to insufficient charging and a sufficient discharge capacity may not be obtained. As a result, a sufficient discharge capacity may not be obtained, and the electrolyte may be reduced due to gas generation. Accordingly, the specific gravity of the electrolyte is preferably 1.270 to 1.320.

(1) Production of negative electrode non-formed sheet An appropriate amount of acetylene black powder and barium sulfate powder having a specific surface area of 70 m ² / g was added as carbon powder to the lead powder produced by the ball mill method and dry-mixed. An appropriate amount of lignin as an aqueous solution was added thereto, and then ion-exchanged water was added to about 10 parts by weight with respect to 100 parts by weight of lead powder to knead to prepare a water paste, and further 10 parts by weight of diluted sulfuric acid having a specific gravity of 1.36. In addition, kneading was performed to prepare a negative electrode active material paste having a cup density of 140 g / 2 in ³ . Next, the negative electrode active material paste was filled in a negative electrode cast lattice plate made of Pb—Ca alloy, then aged in an atmosphere of 40 ° C. and 95% humidity for 24 hours, and then dried to prepare a negative electrode unformed plate.
The thickness of the outer frame lattice of the cast lattice plate was 1.20 mm, and the thickness of the ear portion was variously changed in the range of 1.20 to 1.30 mm.

(2) Preparation of positive electrode unformed plate Approximately 10 parts by weight of ion-exchanged water is added to 100 parts by weight of lead oxide and kneaded. A positive electrode active material paste of 130 g / 2 in ³ was prepared. Next, the Pb—Ca alloy positive electrode cast lattice plate was filled with the paste, then aged in an atmosphere of 40 ° C. and humidity of 95% for 24 hours, and then dried to prepare a positive electrode unformed plate.

(3) Battery assembly, adjustment of electrolyte solution and formation of battery case A polyethylene separator was combined with both the positive and negative unformed plates, and the plates were welded together by the COS method to form a plate group. This was put into a battery case made of polypropylene and covered with heat seal, and then an electrolyte was injected from the liquid port of the battery case lid, followed by battery case formation to produce a lead storage battery of D23 size, 50 Ah, 12 V. . In the electrolytic solution, 20 g / l of hydrated Al sulfate is added to dilute sulfuric acid having a specific gravity of 1.200 in terms of (Al ₂ (SO ₄ ) ₃ ), and the specific gravity is adjusted after the chemical conversion is completed. It was set as the electrolyte solution.

(4) Idling stop life test Each of the obtained lead-acid batteries was fully charged at 25 ° C. and a 5 hour rate current, then at the same temperature, a constant current discharge of 45 A-59 seconds and 300 A-1 seconds, and 100 A-60 An idling stop life test was performed in which a constant current / constant voltage charge with an upper limit voltage of 14.2 V was taken as one cycle per second. The number of cycles when the voltage during constant current discharge fell below 7.2 V was defined as the battery life.
A life cycle of 30,000 times or more was judged good and less than 30,000 times was judged as bad.
Moreover, the lead storage battery after the test was disassembled, and the thinned state of the negative electrode lattice plate ear and the upper portion of the negative electrode lattice plate was observed. Those in which thinness was not observed were judged as good (◯), those in which thinness was observed were judged as bad (Δ), and those in which the ears were broken were judged as extremely poor (×).

The ear thickness of the negative electrode cast lattice plate is set to 1.25 mm, dilute sulfuric acid having a specific gravity of 1.200, and hydrated Al sulfate in terms of (Al ₂ (SO ₄ ) ₃ ) in the electrolyte, 2 to 50 g / l. A lead storage battery was produced by the same method as in Example 1 except that the added electrolyte was used, and a cycle life test and a state observation after the test were conducted by the same method as in Example 1.

  [Comparative Example 1] A lead-acid battery was manufactured in the same manner as in Example 1 except that the thickness of the ear portion of the negative electrode cast grid plate in Example 1 was 1.15 mm (conventional thickness). The cycle life test and the state observation after the test were performed by the same method.

  [Comparative Example 2] A lead-acid battery was produced by the same method as in Example 1 except that no aluminum sulfate hydrate was added to the electrolyte in Example 1, and a cycle life test was conducted by the same method as in Example 1. And the state observation after the test was performed.

The results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.
The cycle life times are rounded down to the nearest 1000 times.

  As is clear from Table 1, the lead storage batteries of Examples of the present invention (Examples 1 and 2) were all excellent at a cycle life of 30,000 times or more. Further, almost no thinning was observed at the edge of the negative electrode grid plate or the upper part of the negative electrode lattice plate. This is because the surface area of the ear portion was reduced and Al was contained in the electrolytic solution, so that lead sulfate was not easily removed from the ear portion, and Al in the electrolytic solution suppressed sulfation.

  In contrast, Comparative Example 1 was inferior in cycle life. When dismantled, the ears of the negative grid plate were extremely thin. The reason for this thinning is that the surface area of the ear portion is large, so that the amount of lead sulfate produced is large and it is easy to fall off.

  Comparative Example 2 suddenly reached the end of its life during the cycle life test. When dismantled, the ears were broken. This is because Al was not contained in the electrolytic solution, and lead sulfate in the negative electrode grid plate ear portion was easily dropped and sulfation was easily generated.

In Examples 1 and 2 described above, the liquid lead-acid battery using a cast lattice plate as the negative electrode lattice plate has been described. However, in the present invention, the negative electrode lattice plate expands or punches a rolled material or an extruded material. Even if the lead storage battery is a control valve type lead storage battery, the same effect can be obtained.

Claims (2)

  The lead-acid battery characterized in that the thickness of the ear part of the negative electrode grid plate is equal to or greater than the thickness of the outer frame grid of the negative electrode grid plate, and Al is contained in the electrolyte in an amount of 2 to 50 g / l in terms of sulfate. . The lead acid battery according to claim 1, wherein the lead acid battery is for an idling stop vehicle.