JP2009252535A - Control valve type lead acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control valve type lead acid battery with three or more cells linearly formed in the same direction, for solving the problem that the deterioration of the cells, particularly, the end cells caused by a difference between their conditions during using the battery precludes a high cycle life property. <P>SOLUTION: The control valve type lead acid battery comprises the three or more cells linearly formed in the same direction. The active material ratio of a negative electrode active material amount to a positive electrode active material amount for the cell, particularly, for the end cell is higher than the active material ratio for the center cell. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a valve-regulated lead-acid battery.

  In recent years, various types of electric vehicles such as electric carts and electric wheelchairs are rapidly spreading, and power sources for such electric vehicles include inexpensive control valve type lead storage batteries as compared to nickel metal hydride storage batteries and lithium secondary batteries. Widely used.

  Control valve type lead-acid batteries used in these electric vehicles are required to have high cycle life characteristics, and batteries with repeated charge / discharge cycles are softened and expanded in the active material in the positive electrode and expanded in the active material in the negative electrode. The performance deteriorates due to fixation of lead sulfate and reduction of the electrolyte contained in the battery.

  These phenomena become more prominent as the electrode plate group pressure that pressurizes the electrode plate group existing in the cell chamber is lower. In particular, in a control valve type lead-acid battery having a battery case structure in which a plurality of cells of 3 cells or more are arranged in a line in the same direction, the electrode plate group expands in accordance with charge / discharge even if the same electrode plate pressure is initially set. Since the shrinkage is repeated, the pressurizing condition to the electrode plate group changes in the end cell and the central cell as the charge / discharge cycle progresses.

  As for the electrode plate group pressure of each cell, the half surface of the electrode plate group is pressurized by the short side of the battery case in the end cell, but in the center cell, the electrode plate group is connected to the adjacent cell via the partition between the cells. It maintains the pressure and balance of the electrode group. The short side surface of the battery case where the half surface of the electrode plate group is in contact with the end cell is formed of a thermoplastic resin, and the short side surface is not able to suppress the heat and expansion force generated from the electrode plate group due to charge / discharge, and the electrode plates are laminated. There was a tendency to swell in the direction and normal electrode group pressure could not be maintained. For this reason, in the end cells located on both sides of the battery, a phenomenon in which the electrode plate group pressure is reduced as compared with the center cell is recognized.

  Furthermore, when a control valve type lead-acid battery is used in an electric vehicle, a system that receives energy generated when the vehicle stops or goes down a slope as regenerative energy is widely used. Since this regenerative charge is a large current charge, when high charge efficiency cannot be obtained depending on the state of charge of the battery, water in the electrolyte is electrolyzed and the electrolyte is reduced. As a result, if the gas absorption reaction by the negative electrode proceeds excessively, inactive lead sulfate is generated in the negative electrode active material, and the positive electrode active material that is the counter electrode of the negative electrode deteriorates and softens and expands due to the progress of the charge / discharge cycle. The short side surface of the battery case swells due to the expansion of the plate group, and the normal electrode plate group pressure cannot be maintained in the end cell.

  As the charge / discharge cycle progresses in this way, the end cell has a lower electrode group pressure than the center cell, which promotes the immobilization of the inactive lead sulfate of the negative electrode due to the gas absorption reaction. There was a problem that the service life was reached.

For this reason, in Patent Document 1, an attempt is made to increase the total amount of the negative electrode active material in the cell located in the center in order to prevent the temperature of the cell located in the center from rising and promoting the deterioration of the negative electrode. . However, when actually running on an electric vehicle, the control valve type lead-acid battery has a phenomenon that the short side surface of the battery case swells and the negative electrode deterioration of the end cell progresses due to the load pattern such as regeneration, leading to a life span. That is, it has been difficult for conventional control valve type lead-acid batteries used in electric vehicles to obtain uniform cycle life characteristics in all cells.
JP 7-169503 A

  As described above, the control valve type lead-acid battery in which a plurality of cells of 3 cells or more are linearly formed in the same direction as described above is deteriorated due to a difference in the condition of each cell during battery use. It solves the problem that high cycle life characteristics cannot be obtained due to deterioration mainly.

  In order to solve the above-mentioned problem, the invention according to claim 1 of the present invention is a negative electrode active material constituting a cell in a control valve type lead storage battery in which a plurality of cells of three or more cells are linearly formed in the same direction. The active material ratio of the amount / the amount of positive electrode active material indicates an active material ratio of the end cell> the active material ratio of the center cell.

  The invention according to claim 2 of the present invention is characterized in that the active material ratio of the end cell is 0.05 to 0.15 higher than the active material ratio of the central cell. The control valve type lead acid battery of 1 description is shown.

  According to the configuration of the present invention described above, characteristics at the same level as the center cell can be obtained by improving the characteristics of the end cells, and in particular, each cell can have a remarkable effect that uniform life characteristics can be obtained. Therefore, it is useful industrially.

  A configuration of the lead storage battery according to the embodiment of the present invention will be described.

  FIG. 1 is a configuration diagram of a control valve type lead storage battery to which the present invention is applied. A battery case 1 made of polypropylene resin is configured by a plurality of cells 2 connected in the same direction. Each cell 2 accommodates an electrode plate group 7 in which a positive electrode plate 3 and a negative electrode plate 4 are laminated via a separator 5 mainly composed of glass fibers, and an electrode plate of the same polarity is integrated with a strap 6. The connection body 9 is connected to the electrode plate group of the adjacent cell. Further, a lid 11 having an exhaust structure 10 from each cell is welded and integrated at the upper part of the battery case to constitute a battery.

Since a general lead storage battery has a 6-cell configuration, in this case, the end cell 2a is the first and sixth cells, and the central cell 2b indicates 2 to 5 cells. The end cell 2a has a connection terminal 12 and a connection body 9 for leading and extracting electricity to the outside of the battery, and the electrode plate group 7 is between the short side surface 13 and the partition wall 8 which are a part of the exterior of the battery case 1. The plate group pressure is applied. In particular, since the electrode plate group 7 of the control valve type lead-acid battery is pressurized at 20 kg / dm ² , the surface of the short side surface 13 where the half surface of the electrode plate group 7 located in the end cell 2a contacts is for reinforcement. Ribs 14 may be provided.

  The center cell 2b is housed between the partition walls 8 with the adjacent cells, but another plate group is housed on the opposite surface of the partition wall 8, so that the electrode plate is obtained by repeating the charge / discharge cycle during actual use. The expansion of the group 7 is similar to the expansion of the electrode plate group of the adjacent cell, so even if the substantial electrode plate group pressure increases, there is no direction in which the pressure escapes. It will not change.

  However, in the control valve type lead-acid battery, pressure gradually escapes toward the end cell 2a due to the expansion of the electrode plate group due to the positive electrode plate active material or the like as the charge / discharge cycle proceeds. This phenomenon is because no external pressure is applied to the short side surface 13 of the end cell 2a, and the constituent material is resin, so that the short side surface 13 swells outward, and the expansion of the center cell 2b is the end cell 2a. Will be transferred to.

  In the case of a battery in which the active material amount ratio of the positive electrode plate 3 and the negative electrode plate 4 is the same in all cells, the end cell 2a is reduced in the electrode plate group pressure by the charge / discharge cycle, and lead sulfate is fixed to the negative electrode active material by gas absorption reaction Progresses to the end of its life due to a decrease in capacity. In order to improve the life characteristics, it is necessary to suppress the amount of gas generated in the end cell 2a. In the relationship between the positive electrode that generates gas and the negative electrode active material that absorbs gas, the negative electrode active material / positive electrode active of the end cell 2a. A control valve type lead-acid battery having a structure in which the ratio of the substance is larger than that of the central cell 2b is conceivable.

  However, since the total amount of the active material of the positive electrode and the negative electrode in the substantially limited cell is almost the same, the negative electrode active material amount / positive electrode is increased by increasing the negative electrode active material amount in order to obtain a higher level of cycle life. If the active material ratio of the amount of active material becomes too high, the capacity of the storage battery will decrease due to the deterioration of the characteristics of the positive electrode. Conversely, if the active material ratio becomes small, the gas absorption capacity will decrease and charge / discharge will occur due to the decrease in electrolyte. The capacity decreases rapidly as the cycle progresses. For this reason, it is necessary to set the difference in the active material ratio between the end cell and the intermediate cell.

  As a test battery, a 12V60Ah monoblock control valve type lead storage battery in which 6 cells are arranged in the same direction was prepared. The cells on the storage battery positive terminal side are the first cells and the cells on the negative electrode terminal side are the end cells, and the second to fifth cells located in the center are configured as the central cells.

  The positive electrode plate has a height of 120 mm, a width of 100 mm, and a thickness of 1.2 mm. The negative electrode plate has the same height and width as the positive electrode plate and has a thickness of 1.0 mm, and 11 positive electrode plates / 12 negative electrode plates. An electrode plate group was constructed. The test battery was configured such that the amount of the cell active material in the center was 1000 g of the positive electrode and 950 g of the negative electrode, and the ratio of the negative electrode active material / positive electrode active material ratio was 0.95. The amount of the end cell active material of other test batteries was 960 g and 1000 g for the positive electrode, and the negative electrode was larger than the central portion, and 980 g, 1000 g, 1100 g, and 1150 g were selected, and end cells were formed by combining these.

  Table 6 shows the constituent conditions of the active material ratio for these six types of test batteries by changing the amount of the positive electrode active material and the amount of the negative electrode active material. The other test battery preparation conditions were prepared by a conventional method.

  However, NO. The end cell of the battery No. 6 has a total amount of positive electrode and negative electrode active materials of 2150 g, which is larger than the conventional 1950 g, and the electrode plate group cannot be inserted into the end cell. 1-No. The initial capacity and cycle life characteristics of 5 batteries were evaluated.

(Experiment 1)
As Experiment 1, an initial capacity test was performed. In the initial capacity test, the charged test battery was allowed to stand in a 25 ° C. atmosphere for 12 hours, and then the capacity was measured when the battery voltage was discharged at a constant current of 20 A until the battery voltage reached 9.9 V.

(Experiment 2)
As experiment 2, a cycle life test was performed. The cycle life test was performed in an atmosphere at 25 ° C. according to the following procedure.

1) Constant power charge / discharge is repeated 260 times with the charge / discharge pattern shown in Table 2 for the test battery.
In addition, in the column of charge / discharge power in Table 2, the symbol in front of the numerical value indicates-is discharge and + is charge.

  2) Pause the test battery in an open circuit for 30 minutes.

  3) The test battery is charged with the five-stage constant current charging pattern shown in Table 3.

  4) Pause the test battery for 1 hour in an open circuit.

  5) The above operations 1) to 4) are defined as one cycle, and this cycle is repeated.

  6) Stop the cycle life test every 100 cycles.

  7) Leave in a 25 ° C. atmosphere for 12 hours or more.

  8) Discharge at a constant current of 20A until the battery voltage reaches 9.9V.

  9) In 1) after performing the same charge as 3), when the battery voltage dropped to 8.4 V, the charge / discharge cycle was stopped, and the number of cycles up to that time was defined as the cycle life value. Thereafter, the capacity was confirmed while measuring the voltage of each cell under the conditions of 7) and 8).

  Table 1 shows the results of the discharge capacity, cycle life characteristics, and cells with the lowest deterioration in the discharge test after the end of the cycle life test and the low discharge voltage of the test batteries in which Experiment 1 and Experiment 2 were conducted. It shows in Table 4 with an edge cell active material ratio.

  This is a test battery that was prototyped this time. In one battery, the ratio of the all-cell positive electrode active material to the negative electrode active material was the same, and the life characteristic was 730 cycles. In the capacity check after the end of the cycle test, the discharge voltage of the sixth cell of the end cell was deteriorated to a low level, and the negative electrode active material was made non-conductive due to the decrease in the electrolyte.

  Test battery No. In No. 2, the cell deteriorated by the capacity check after the end of the cycle test was the sixth cell located in the end cell. The lifetime of the whole cell was extended to 870 cycles by extending the lifetime of the end cell compared to 1.

  Test battery No. 3 and no. No. 4 has an active material ratio of No. 2 and a difference in the ratio with the center cell is 0.05 to 0.15. The life was even longer than 2, and the deteriorated cell was the center cell in the capacity test after the end of the cycle. This is presumably because the amount of gas generated in the end cell was suppressed, and the decrease in the capacity of the negative electrode active material due to the charge / discharge cycle was reduced.

  Test battery No. No. 5 has a large active material ratio by reducing the amount of positive electrode active material in the end cell. The deterioration cell after the cycle stop was the 4th cell located in the center. However, compared with other batteries, the discharge capacity is less than the original, and the cycle life is no. 2-No. It is thought to be shorter than 4.

  Based on the above results, the first cell and the sixth cell corresponding to the end cells should be larger than the active material ratio of the negative electrode active material amount / the positive electrode active material amount of the second cell to the fifth cell corresponding to the center cell. Thus, it was confirmed that a long-life control valve type lead-acid battery capable of suppressing a decrease in capacity at the end cell was obtained. Furthermore, when the difference of the active material ratio of an edge cell and a center part cell was 0.05-0.15, it has also confirmed that a remarkable effect was acquired.

  According to the configuration of the present invention, in a plurality of cells arranged in the same direction, it is possible to provide a control valve type lead storage battery capable of obtaining a uniform life characteristic for each cell, and therefore, its industrial value is high.

Configuration diagram of control valve type lead-acid battery of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Cell 2a End cell 2b Center part cell 3 Positive electrode plate 4 Negative electrode plate 5 Separator 6 Strap 7 Electrode plate group 8 Bulkhead 9 Connection body 10 Exhaust structure 11 Lid 12 Connection terminal 13 Short side surface 14 Rib

Claims (2)

In a valve-regulated lead-acid battery in which three or more cells are linearly configured in the same direction, the active material ratio of the negative electrode active material amount / positive electrode active material amount constituting the cell is the active material ratio of the end cell> center. A valve-regulated lead-acid battery, characterized in that the active material ratio of the partial cell. The control valve type lead acid battery according to claim 1, wherein the active material ratio of the end cell is 0.05 to 0.15 higher than the active material ratio of the central cell.

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