WO2011077640A1 - Valve-regulated lead acid battery - Google Patents

Abstract

A valve-regulated lead acid battery, in which a positive electrode active material has a specific surface area of 1.5 to 4.5 m²/g inclusive and a separator (4) has an average pore diameter of 1.5 to 2.5 μm inclusive.

Description

Control valve type lead acid battery

The present invention relates to a control valve type lead acid battery (hereinafter, simply referred to as “battery”).

¡Control valve type lead-acid batteries are broadly divided into trickle and cycle applications. In trickle applications, the battery is always charged and discharged only during a power failure, as represented by an uninterruptible power supply. In the cycle application, as represented by a power source for an electric vehicle, a charge / discharge cycle in which the battery is fully charged after receiving a deep discharge is repeated.

Conventionally, control valve-type lead-acid batteries have been mainly used for trickle applications. In recent years, the demand for a control valve type lead storage battery as a power source for electric vehicles has increased, and there is a demand for extending the life of the control valve type lead storage battery during cycle use.

Various studies have been made for the purpose of improving the cycle life characteristics of control valve type lead-acid batteries. For example, Patent Document 1, a specific surface area of the cathode active material and 5.0m ² /g~8.0m ² / g, and a specific surface area of the anode active material and 0.8m ² /g~1.4m ² / g Moreover, it is shown that a lead-acid battery having excellent cycle life characteristics can be obtained by pressurizing at a group pressure of 50 kg / dm ² or more in a state where the electrode group is housed in the battery case.

Japanese Patent Laid-Open No. 2003-338312

In the technique of Patent Document 1, since the group pressure is higher than before, it is necessary to increase the strength of the battery case such as increasing the thickness of the battery case.

Further, in the technique of Patent Document 1, since the positive electrode active material may be softened, further improvement in cycle life characteristics is required.

The present invention provides a control valve type lead storage battery having excellent cycle life characteristics.

In the control valve type lead acid battery according to the present invention, the specific surface area of the positive electrode active material is 1.5 m ² / g or more and 4.5 m ² / g or less, and the average pore diameter of the separator is 1.5 μm or more and 2.5 μm or less. . Thereby, the control valve type lead acid battery excellent in cycle life characteristics can be provided, without raising the pressure (group pressure) given to an electrode group etc. when accommodating an electrode group in a battery case.

If the specific surface area of the positive electrode active material is 2.0 m ² / g or more and 3.5 m ² / g or less, further excellent cycle life characteristics can be obtained.

In this specification, the “specific surface area” is a specific surface area in a fully charged state, that is, a specific surface area of the active material after chemical conversion, and is measured according to the BET (Brunauer-Emmett-Teller) method.

In this specification, the “average pore diameter” means the separator pore diameter when the separator is assembled to the battery, that is, the dimension of the separator when the dimension between the positive electrode plate and the negative electrode plate is reduced to the state assembled to the battery. It is a pore diameter and is a median diameter measured by a liquid injection method. In the liquid injection method, a known liquid (for example, a liquid having a specific gravity similar to that of water) can be used as the liquid used when measuring the pore diameter of the separator.

According to the present invention, the cycle life characteristics are improved.

FIG. 1 is a cross-sectional view of a control valve type lead storage battery according to an embodiment of the present invention. FIG. 2 is a table showing values of the specific surface area of the positive electrode active material and the average pore diameter of the separator in the battery produced in the example. FIG. 3 is a table showing the value of the specific surface area of the positive electrode active material and the average pore diameter of the separator in the battery produced in the example. FIG. 4 is a table showing the results of the cycle life test for the battery shown in FIG. FIG. 5 is a table showing the results of the cycle life test for the battery shown in FIG. FIG. 6 is a graph showing the results shown in FIG. 4 and FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below.

FIG. 1 is a cross-sectional view of a control valve type lead storage battery according to an embodiment of the present invention.

As shown in FIG. 1, the control valve type lead storage battery 10 according to the present embodiment is configured such that a positive electrode plate 2 and a negative electrode plate 3 are accommodated in a battery case 1 via a separator 4. The battery case 1 may be a battery case known as a battery case of a control valve type lead-acid battery, and is closed with a lid 5.

The lid 5 includes a control valve 8 composed of a valve cylinder 5a, a valve body 6 and a valve pressing plate 7. The valve cylinder 5 a is provided on the lid 5 and extends in the longitudinal direction of the battery case 1. The valve body 6 is attached to the valve cylinder 5a. The valve pressing plate 7 is provided on the outer side of the lid 5 with respect to the valve body 6, and prevents the valve body 6 from dropping from the valve cylinder 5 a and applies an appropriate valve opening pressure to the control valve 8.

The configuration of the control valve 8 is not limited to the above configuration and the configuration shown in FIG.

Further, the battery 10 may have a strap for connecting the same polar plates, and the battery case 1 preferably has a positive terminal and a negative terminal. Moreover, when the battery 10 is a monoblock type control valve type lead acid battery, it is preferable that the single cells are connected to each other via an inter-cell connector or the like.

In the positive electrode plate 2, a positive electrode current collector (not shown) is filled with a positive electrode active material (not shown). In the negative electrode plate 3, the negative electrode current collector (not shown) is filled with a negative electrode active material (not shown). Z).

The current collector may be a known current collector as a current collector of a control valve type lead storage battery, and may be made of a Pb alloy. For example, the positive electrode current collector is made of a Pb alloy containing 1.0% by mass or more and 2.2% by mass or less of Sn and 0.05% by mass or more and 0.15% by mass or less of Ca. , And a Pb alloy containing 0 mass% or more and 1.0 mass% or less of Sn and 0.05 mass% of Ca. Such a current collector may be a grid (casting grid) made by casting, a grid made of expanded metal (expanded grid), or a grid (punching grid) made by punching. A foil in which through holes are formed may be used.

The positive electrode active material is lead dioxide. This positive electrode active material has a specific surface area of 1.5 m ² / g or more and 4.5 m ² / g or less, and a specific surface area of 2.0 m ² / g or more and 3.5 m ² / g or less. Preferably it is.

The positive electrode plate 2 is manufactured according to the following method. Water and dilute sulfuric acid are added and kneaded to a lead powder (mixture of metallic lead and lead oxide) obtained by a known technique. Thereby, a paste-like positive electrode active material is obtained. After filling the paste-like positive electrode active material into the positive electrode current collector, aging, drying, and chemical conversion are performed according to a known method. Thereby, the positive electrode 2 is obtained.

In order to change the specific surface area of the positive electrode active material, the amount of water or dilute sulfuric acid relative to the lead powder may be adjusted, or the sulfuric acid concentration in the dilute sulfuric acid may be adjusted. Carbon may be added to the paste-like positive electrode active material. When carbon is added to the paste-like positive electrode active material, the carbon is oxidized during the formation, and vacancies are formed in the positive electrode active material. Further, tin sulfate, tin oxide, phosphate, or the like may be added to the paste-like positive electrode active material.

The negative electrode active material is metallic lead, and the specific surface area may be a value known as the specific surface area of the negative electrode active material of the control valve type lead-acid battery, for example, 0.7 m ² / g or more and 2.0 m ² / g. It is as follows. The negative electrode plate 3 can be manufactured according to a known manufacturing method as a manufacturing method of the negative electrode plate 3 of the control valve type lead-acid battery.

In addition, it is preferable that the capacity | capacitance of a negative electrode active material is larger than the capacity | capacitance of a positive electrode active material so that the oxygen gas generated at the side of the positive electrode plate 2 at the time of charge can be absorbed with the negative electrode plate 3. The capacity difference may be a capacity difference known as a capacity difference of the control valve type lead storage battery.

Further, the group pressure may be set so that the positive electrode plate 2 and the negative electrode plate 3 are in close contact with the separator 4. The group pressure may be a known value as the group pressure of the control valve type lead storage battery, and may be, for example, 11.0 kPa or more and 40.0 kPa or less. If the group pressure is less than 11.0 kPa, the positive electrode plate 2 or the negative electrode plate 3 may not adhere to the separator 4. On the other hand, if the group pressure exceeds 40.0 kPa, the battery case 1 may need to be strengthened.

The separator 4 only needs to be chemically stable with respect to the electrolytic solution (dilute sulfuric acid), can hold a predetermined amount of the electrolytic solution, and can prevent a short circuit between the positive electrode plate 2 and the negative electrode plate 3. good. An example of a material that satisfies all of these requirements is a glass mat.

The separator 4 has an average pore diameter of 1.5 μm or more and 2.5 μm or less. In order to change the average particle diameter of the separator 4, the diameter of the glass fiber, the basis weight of the glass fiber (the mass of the glass fiber), the content of the binder and the compression amount (before the electrode group is put in the battery case 1) At least one of the degree of compression in the group compression step may be changed, or silica or the like may be added to the separator 4.

The electrolytic solution (not shown) is impregnated and held in the pores formed in the positive electrode active material, the negative electrode active material, and the separator 4, and has a known composition as the composition of the electrolytic solution in the control valve type lead storage battery. If you do. The battery case 1 may contain an amount of free electrolyte that does not interfere with the oxygen gas absorption reaction by the negative electrode plate 3. Here, the free electrolytic solution is an electrolytic solution that is not impregnated in any of the positive electrode active material, the negative electrode active material, and the separator 4.

The positive electrode active material in the present embodiment has a specific surface area of 1.5 m ² / g or more and 4.5 m ² / g or less. Thus, since the specific surface area of the positive electrode active material in this embodiment is smaller than the specific surface area of the conventional positive electrode active material (for example, the specific surface area in Patent Document 1), softening of the positive electrode active material due to repeated charge and discharge is prevented. Is done. However, the reaction area of the positive electrode active material is reduced and the reaction efficiency is reduced. In order to prevent this, in this embodiment, the average pore diameter of the separator 4 is set to 1.5 μm or more and 2.5 μm or less to ensure the amount of the electrolyte solution in contact with the positive electrode active material. Further, if the specific surface area of the positive electrode active material is 2.0 m ² / g or more and 3.5 m ² / g or less when the average pore size of the separator 4 is 1.5 μm or more and 2.5 μm or less, the cycle life characteristics are further improved. improves. This will be specifically described below.

If the specific surface area of the positive electrode active material is less than 1.5 m ² / g, the reason why the cycle life characteristics are deteriorated cannot be stated, but the following may be considered. Generally, when a lead storage battery is discharged, lead sulfate is deposited on the positive electrode plate 2 side, so that the reaction area of the positive electrode active material is reduced by the discharge. Here, when the specific surface area of a positive electrode active material is less than 1.5 m < ² > / g, it is thought that the reaction area of the positive electrode active material after discharge becomes remarkably small. For this reason, charging after discharging becomes extremely difficult, resulting in a decrease in charge acceptability. Therefore, it reaches the lifetime.

The following can be considered as the reason why the cycle life characteristics are lowered when the specific surface area of the positive electrode active material exceeds 4.5 m ² / g. In general, when a lead storage battery is repeatedly charged and discharged, the positive electrode active material is coarsened, thereby softening the positive electrode active material. Then, the bond strength between the positive electrode active materials is reduced, and the positive electrode active materials are dropped off. Here, since the diameter of a positive electrode active material will become small when the specific surface area of a positive electrode active material exceeds 4.5 m < ² > / g, the fall of the contact area of positive electrode active materials will be caused. Therefore, it is considered that the bonding force between the positive electrode active materials is weak even before repeated charging and discharging. Therefore, when the lead storage battery including the positive electrode active material is repeatedly charged and discharged, the bonding force between the positive electrode active materials is remarkably reduced, and therefore, the positive electrode active material is easily dropped or the timing at which the positive electrode active material is dropped is accelerated. .

When the average pore diameter of the separator 4 is less than 1.5 μm, the amount of electrolyte solution that can be held by the separator 4 increases. Therefore, at least half or more of the electrolytic solution supplied into the battery case 1 is absorbed by the separator 4, thereby reducing the amount of the electrolytic solution present on the surface of the positive electrode active material or the negative electrode active material. Therefore, the discharge reaction is difficult to occur.

In addition, when the average pore diameter of the separator 4 is less than 1.5 μm, it is difficult for oxygen gas generated on the positive electrode plate 2 side during charging to move to the negative electrode plate 3 side. Therefore, the hydrogen gas generation reaction on the negative electrode plate 3 side cannot be suppressed, and the internal pressure of the battery case 1 is increased. Therefore, the control valve 8 opens and causes liquid leakage. Thereby, since the water | moisture content in electrolyte solution leaks out of the battery case 1, the sulfuric acid which is one of the reaction materials of a battery reaction reduces. At the same time, since the closed state is released when the control valve 8 is opened, the negative electrode plate 3 cannot absorb the oxygen gas generated in the positive electrode plate 2. Therefore, oxygen gas continues to be generated from the positive electrode plate 2, hydrogen gas continues to be generated from the negative electrode plate 3 (the control valve 8 continues to open), and the electrolytic solution decreases at an accelerated rate. Therefore, the lifetime is reached.

When the average pore diameter of the separator 4 exceeds 2.5 μm, the amount of electrolyte solution that can be held by the separator 4 decreases. Therefore, the amount of electrolyte that can be supplied to the battery case 1 is reduced. Therefore, even in this case, the amount of the electrolytic solution present on the surface of the positive electrode active material or the negative electrode active material is reduced, so that the discharge reaction is less likely to occur.

Further, when the average pore diameter of the separator 4 exceeds 2.5 μm, the mechanical strength of the separator 4 is reduced. As long as the separator 4 has a predetermined mechanical strength, the separator 4 can prevent the positive electrode active material from having a decreased bonding force between the particles. However, if the mechanical strength of the separator 4 is low, it is difficult for the separator 4 to prevent the positive electrode active material from dropping with a reduced bonding force between the particles.

As described above, when the average pore diameter of the separator 4 is 1.5 μm or more and 2.5 μm or less, the amount of the electrolyte present in the vicinity of the surface of the positive electrode active material or the like can be ensured. Furthermore, if the specific surface area of the positive electrode active material is 2.0 m ² / g or more and 3.5 m ² / g or less, softening of the positive electrode active material due to repeated charge and discharge is prevented while ensuring a sufficient reaction area of the positive electrode active material. it can. Therefore, it is considered that the effect obtained by optimizing the average pore diameter of the separator 4 is sufficiently exhibited.

In this example, a control valve type lead-acid battery was prepared by variously changing the specific surface area of the positive electrode active material and the average pore diameter of the separator, and a cycle life test was performed on the battery.

1. First, a current collector was prepared. A sheet made of a Pb alloy containing 1.6% by mass of Sn and 0.06% by mass of Ca was prepared, and this sheet was expanded. In this way, a positive electrode current collector was obtained. Moreover, the sheet | seat which consists of a Pb alloy containing 0.25 mass% Sn and 0.07 mass% Ca was prepared, and the expansion process was performed with respect to this sheet | seat. In this way, a negative electrode current collector was obtained.

Next, a paste-like active material was prepared. Water was added to and kneaded with lead powder (lead powder is composed of 30% by mass of Pb and 70% by mass of PbO), and further, kneaded while dropping dilute sulfuric acid having a sulfuric acid concentration of 40% by mass. In this way, a paste-like positive electrode active material was obtained. In addition, carbon (conducting aid), barium sulfate (shrinking agent) and lignin sulfonic acid sodium salt (shrinking agent) are added to and mixed with the above lead powder, water is added and kneaded, and further dilute sulfuric acid is added dropwise While kneading. In this way, a paste-like negative electrode active material was obtained. Each kneading was performed using a ball mill.

After filling the positive electrode current collector with the paste-like positive electrode active material, the electrode plate was aged and dried. Thereby, an unformed positive electrode plate was obtained. Similarly, a negative electrode current collector was filled with a paste-like negative electrode active material, and this electrode plate was aged and dried. Thereby, an unformed negative electrode plate was obtained. The unformed positive electrode plate had a height (up and down direction of FIG. 1) of 67.0 mm, a width of 44.5 mm, and a thickness (left and right direction of FIG. 1) of 3.00 mm. The unformed negative electrode plate had a height (up and down direction of FIG. 1) of 68.0 mm, a width of 44.5 mm, and a thickness (left and right direction of FIG. 1) of 1.90 mm.

A single cell was produced using 6 unformed positive plates and 7 unformed negative plates. At this time, a separator made of glass fiber was disposed between the unformed positive electrode plate and the unformed negative electrode plate. In this way, three single cells were produced. Each single cell was accommodated in the cell chamber of the battery case, the single cells were connected in series, and a predetermined single cell was connected to the terminal of the battery case. Then, after inject | pouring electrolyte solution in each cell chamber, the positive electrode plate was electrolytically oxidized and the negative electrode plate was electrolytically reduced. In this way, a monoblock type control valve type lead storage battery (6V15Ah) was produced.

In this example, the specific surface area of the negative electrode active material was 1.0 m ² / g in any battery. Moreover, the specific surface area of the positive electrode active material was as shown in FIGS. Note that when the amount of water and dilute sulfuric acid added to the lead powder was increased to produce a paste-like positive electrode active material, the specific surface area of the positive electrode active material increased.

In this example, the average pore diameter of the separator was as shown in FIGS. In addition, the diameter of the glass fiber and the basis weight of the glass fiber were changed to change the average pore diameter of the separator.

In this example, the group pressure applied to the separator was 14.7 kPa (20 kgf / dm ² when converted to a non-SI unit system).

2. Cycle life test (1) Test method The following cycle life test was performed on each battery shown in FIGS. After performing high rate discharge (constant current discharge at 5.00 A, discharge end voltage is 5.25 V) in an atmosphere at 25 ° C. for 2 hours, constant current and constant voltage charge (charge voltage is 7.35 V, initial charge current) Was 4.50 A) for 12 hours. This was defined as one cycle, and the life was reached when the discharge capacity at high rate discharge reached 60%.

(2) Results and discussion The results are shown in FIGS. In FIG. 6, the average pore diameter of the separator is expressed as “d”.

From the results shown in FIGS. 4 to 6, when the specific surface area of the positive electrode active material is less than 1.5 m ² / g, or the specific surface area of the positive electrode active material is more than 4.5 m ² / g, the cycle life characteristics are deteriorated. did. The reason is considered as described in the above embodiment.

Further, when the average pore diameter of the separator was less than 1.5 μm, or when the average pore diameter of the separator was more than 2.5 μm, the cycle life characteristics were deteriorated. The reason is considered as described in the above embodiment.

On the other hand, if the specific surface area of the positive electrode active material is 1.5 m ² / g or more and 4.5 m ² / g or less and the separator has an average pore diameter of 1.5 μm or more and 2.5 μm or less, the average pore diameter of the separator is It was higher than the maximum value of the number of cycles (for example, the number of cycles of the battery D6) when it was outside the range of 1.5 μm to 2.5 μm. In addition, when the average pore size of the separator is 1.5 μm or more and 2.5 μm or less, if the specific surface area of the positive electrode active material is 2.0 m ² / g or more and 3.5 m ² / g or less, the number of cycles is 700. Thus, the cycle life characteristics were remarkably improved. The reason is considered as described in the above embodiment.

Further, as can be seen from FIG. 6, when the average pore diameter of the separator is outside the range of 1.5 μm or more and 2.5 μm or less, the specific surface area of the positive electrode active material is changed from 1.2 m ² / g to 1.5 m ² / g. Even if it was changed or the specific surface area of the positive electrode active material was changed from 4.5 m ² / g to 5.0 m ² / g, the cycle life characteristics were only slightly improved. However, when the average pore diameter of the separator is 1.5 μm or more and 2.5 μm or less, the specific surface area of the positive electrode active material is changed from 1.2 m ² / g to 1.5 m ² / g, or the ratio of the positive electrode active material When the surface area was changed from 4.5 m ² / g to 5.0 m ² / g, the cycle life characteristics were remarkably improved (the number of cycles became about 1.5 times or more). This is what the present inventor has discovered for the first time, and far exceeds the range that the inventor had originally anticipated. As a reason why such a result is obtained, the present inventor believes that there is a synergistic effect by optimization of the specific surface area of the positive electrode active material and optimization of the average pore diameter of the separator.

The present inventor confirmed that the same results as those shown in FIGS. 4 to 6 can be obtained if the specific surface area of the negative electrode active material is 0.7 m ² / g or more and 2.0 m ² / g or less. ing. That is, the results shown in FIGS. 4 to 6 are not limited to the case where the specific surface area of the negative electrode active material is 1.0 m ² / g.

Further, the present inventor has confirmed that the same results as those shown in FIGS. 4 to 6 can be obtained when the group pressure applied to the separator is 11.0 kPa or more and 40.0 kPa or less. That is, the results shown in FIGS. 4 to 6 are not limited to the case where the group pressure is 14.7 kPa.

As described above, the present invention is useful for a control valve type lead-acid battery and is suitable for cycle applications such as a power source for an electric vehicle.

1 Battery case 2 Positive electrode plate 3 Negative electrode plate 4 Separator 5 Lid 5a Valve cylinder 6 Valve body 7 Valve retainer plate 8 Control valve 10 Battery (Control valve type lead acid battery)

Claims (3)

A control valve type lead acid battery comprising a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate,
The positive electrode plate has a positive electrode active material having a specific surface area of 1.5 m ² / g or more and 4.5 m ² / g or less,
A control valve type lead acid battery in which an average pore diameter of the separator is 1.5 μm or more and 2.5 μm or less. It is a control valve type lead acid battery according to claim 1,
A control valve type lead-acid battery, wherein the positive electrode active material has a specific surface area of 2.0 m ² / g or more and 3.5 m ² / g or less. It is a control valve type lead acid battery according to claim 1,
The separator is a control valve type lead storage battery made of glass fiber.

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