JP2003197159A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell and a battery pack excellent in heat radiation performance. <P>SOLUTION: In relation to a battery provided with a power generation element composed by rolling a strip positive electrode plate and a strip negative electrode plate through a separator, and structured by housing it in a battery jar, this cell is characterized by that the outer shape of the battery jar is a frustum of a circular cone wherein the upper part is larger than the lower part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly to a wound type battery.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional wound type cell. 1A is a side view of the unit cell 10, and FIG. 1B is a top view thereof. The outer shape of the battery case 15 is cylindrical, and the positive electrode terminal 1 and the negative electrode terminal 2 are provided on one end surface thereof.

FIG. 2 shows a battery case of a conventional wound type assembled battery. 2A is a side view, FIG. 2B is a top view, and FIG.
2C is a sectional view taken along line AA of FIG. The battery case 2
0 is often made of resin, and two or more cell chambers 21
(In FIG. 2, there are six cell chambers). These battery cases are known from US Pat. No. 5,283,137 and the like. The resin battery container having such a shape can be easily produced in large quantities by molding, and since the outer walls of adjacent cell chambers are joined to each other, they have the advantage of high strength.

Another method for forming an assembled battery is to combine a plurality of the unit cells 10 shown in FIG. 1 and store them in a frame, as disclosed in JP-A-9-7564. A perspective view thereof is shown in FIG. 3 (illustration of terminals is omitted in FIG. 3).

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As described in 564, when using the battery,
It is necessary to consider heat dissipation so that the battery temperature does not become too high. This is because the normal battery has a shorter life when the temperature of the power generation element rises.

In particular, in the assembled battery as shown in FIG. 2 or FIG. 3, in order to make the assembled battery compact, when the cells are arranged adjacent to each other, the heat generated by charging / discharging is not easily dissipated, and the heat is generated by the battery. Easy to accumulate in the element.

Particularly in a lead battery, when it is subjected to a charge / discharge cycle in which overcharging is not often performed, such as used in a hybrid electric vehicle, under high temperature conditions, lead sulfate accumulates on the negative electrode plate for charging. Life often comes from the phenomenon of sulfation, which makes acceptance very difficult.

In order to solve this problem, if the outer walls of the adjacent cell chambers are not joined to each other or the outer casings of the unit cells are arranged so as not to be in contact with each other, an extra space is required for the assembled battery, resulting in an increase in size. Alternatively, in the case of the battery case as shown in FIG. 2, the strength of each cell chamber portion becomes low, and each cell chamber may be damaged when the power generating element is inserted. Further, not only in the case of the assembled battery but also in the unit cell, when it is used by being housed in a storage container or the like having poor heat dissipation, the same problem as the assembled battery occurs.

The present invention has been made to solve the above problems, and provides a single battery or an assembled battery having excellent heat dissipation performance.

[0010]

A first aspect of the present invention, which has been made to solve the above-mentioned problems, comprises a power generating element in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound around a separator, and a battery case is provided. In a battery configured to be housed, an outer shape of the battery case is a truncated cone shape having a large upper portion.

A second aspect of the present invention is configured such that a power generating element, which is formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate around a separator, is housed in a battery case having two or more cell chambers. In the assembled battery, the outer shape of the cell chamber is a truncated cone shape having a large upper portion.

A third invention is an assembled battery comprising a plurality of the unit cells according to claim 1 combined.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of a cell according to the present invention is shown in FIG. FIG. 4A is a side view of the unit cell 40, and FIG. 4B is a top view thereof. The outer shape of the battery case 16 is a truncated cone shape having a larger upper portion, and the positive electrode terminal 1 and the negative electrode terminal 2 are provided on one end surface of the larger one. FIG. 5 is a sectional view of the battery case of the unit cell according to the present invention. In the present invention, since the outer shape of the unit cell 40 may be a truncated cone shape, the inside of the unit cell battery case may be provided with a truncated cone-shaped space as shown in FIG. It is also possible to provide a cylindrical space as shown in FIG.

FIG. 6 shows a storage configuration of a conventional unit cell and a unit cell according to the present invention. FIG. 6 (A) shows a state in which a conventional unit cell is stored, in which a storage space for the unit cell 10 is provided in a case 61,
Devices and members 62 are often arranged in the vicinity of the storage section. In such a case, there is almost no gap between the storage unit of the unit cell 10 and the device or member 62, and it is difficult to dissipate heat even if an airflow exists. On the other hand, when the unit cell according to the present invention is used, as shown in FIG. 6 (B), a gap can be provided between the storage unit of the unit cell 40 and the device or member 62, and a refrigerant such as gas or liquid. And the heat dissipation of the lower part of the unit cell is improved.

Next, the case where the battery case for the assembled battery is used will be described. FIG. 7 is an example of the battery pack battery case 30 according to the present invention.
7A is a side view, FIG. 7B is a top view, and FIG. 7C.
FIG. 8 is a sectional view taken along line AA of FIG. The battery case 30 is often made of resin and has two or more cell chambers 21 (six cell chambers in FIG. 2). As compared with FIG. 2 of the conventional example, FIG.
The feature of the present invention is that the lower interval b is wider than the upper interval a (a = 0 in the drawing) outside each cell chamber of the battery case. Further, the battery case internal space in FIG. 7C has a shape as shown in FIG. 5B, but the shape is not particularly limited to the shape of FIG. 7C. Further, when such a battery case is used, a power generating element can be housed in each cell chamber to form an assembled battery, or a single battery can be housed in each cell chamber to form an assembled battery.

Examples other than FIG. 7 are shown in FIGS. 8A, 8B, and 8C. 8A and 8B are bottom views.
(C) is a side view. The truncated cone shape described in the present invention is not limited to a mathematical truncated cone shape, but may be a polygonal (desirably hexagonal or more) frustum (FIG. 8A), an elliptical frustum (FIG. 8B), or the like. It also includes a shape or a combination of an upper cylindrical shape and a lower truncated cone shape as illustrated in FIG. 8C.
In this case, in order to maintain the strength, it is desirable that the outsides of the adjacent cell chambers are joined to each other in the upper part of the battery case.

Although not particularly shown, when the unit cell shown in FIG. 4 is assembled into the assembled battery as shown in FIG. 3, the upper portion of the unit cell has no space between adjacent unit cells ( Alternatively, it is possible to obtain an assembled battery having a configuration in which there is a space below the unit cells (or a width is narrow).

In the case of such a structure, the reason why the life is unlikely to be extended due to sulfation even if the incomplete charge / discharge cycle is carried out, especially in the lead battery, will be described below.

The charging / discharging reaction of the battery is represented by the following formula. PbO ₂ + 2H ₂ SO ₄ + Pb <-> 2PbSO ₄ +
2H ₂ 0 As is clear from the above reaction formula, both lead dioxide, which is a positive electrode active material, and lead, which is a negative electrode active material, are converted to lead sulfate by discharge, and lead sulfate, which is a discharge product, is discharged on the positive electrode by charging. It becomes lead, and at the negative electrode it becomes lead.

In the incomplete charging / discharging cycle, lead sulfate is slightly contained in both the positive and negative electrodes for two reasons that it is not overcharged as the charging / discharging cycle progresses and the charging efficiency of the battery is not 100%. It accumulates one by one. However, the lead sulfate accumulated in the positive electrode active material has a large BET specific surface area because the positive electrode active material is an oxide, and the active material particles are fine, so that a large amount of electrons can be transferred and received. Since the negative electrode active material is a reductant, the BET specific surface area is smaller than that of the positive electrode active material, and the active material particles are larger, so that the number of places where electrons can be transferred is smaller than that of the positive electrode active material. For this reason, dissolved lead ions are relatively easily deposited as lead dioxide on the positive electrode during charging.
In other words, lead sulfate is less likely to become coarse and unevenly distributed. On the other hand, in the negative electrode, there are few parts that can be deposited as lead in the negative electrode during charging, so lead sulfate tends to become coarse and unevenly distributed. In this way, the state in which coarsened and unevenly distributed lead sulfate is accumulated in the negative electrode plate is called sulfation.In this state, it becomes very difficult to return the negative electrode active material to the original lead. In the case of, the life is judged.

Sulfation usually occurs at a position away from the current collecting ear, that is, at the lower part of the electrode plate where the voltage drop caused by the resistance of the current collector is large. Also, as is well known, the resistance of metal increases as the temperature rises, so that sulfation is more likely to occur as the heat dissipation of the battery is poor and the temperature rises easily. Particularly in a module battery, the temperature rise is more likely to occur than in the case of a single cell due to the heat generation of the battery power generation element housed in the adjacent cell chamber.

According to the present invention, the portion corresponding to the lower portion of the electrode plate of the battery case is provided with a wider space than that of the upper portion, so that heat dissipation of the lower portion of the electrode plate is promoted and the temperature of the lower portion of the electrode plate is lowered, thereby generating electricity. The resistance of the collector of the element is reduced to prevent sulfation. Further, the present invention can be applied to all the batteries in which the temperature rise of the power generation element may adversely affect the battery performance, regardless of the above-mentioned lead battery alone.

[0023]

EXAMPLE A positive electrode plate and a negative electrode plate made of a band-shaped current collector were wound around a separator to form a plurality of 10 Ah battery power generating elements, and the battery power generating elements were placed in a battery case as shown in FIG. Conventional 12V battery pack (module X)
And each of the 12V assembled batteries (module Y) according to the present invention, in which the battery power generating elements are housed in a battery case as shown in FIG. Here, the battery case used for module X has an outer diameter of 47.5 mm at the upper and lower portions and a height of 10 mm.
It was 4 mm, and there was no space between the upper and lower parts outside the adjacent cell chamber, whereas the battery case used for module Y had an upper outer diameter of φ47.5 mm and a lower outer diameter of φ4.
The height was 7.0 mm and the height was 104 mm. No space was provided in the upper part outside the adjacent cell chambers, and a space of 1 mm was provided in the lower part.

The module X and the module Y are discharged in the gas phase at 30 ° C. for 60 seconds at 30 A and then for 2 seconds at 90 A, and a constant voltage low with a maximum voltage of 14 V and a maximum current of 30 A. Charge and discharge under the charging condition of charging with an electric current for 180 seconds (charging electricity quantity is 90 to 10
It will be about 0%. ) Was repeated, and after charging was completed every 1000 cycles, it was subjected to a charge / discharge cycle life test in which uniform charging was performed at 1 A for 5 hours. The life condition was the time when the terminal voltage of the battery during discharging fell below 8.5V.

The test results are shown in FIG. The conventional module X has reached the end of life at about 60,000 cycles, while the module Y according to the present invention has reached the end of life at about 8000.
It was 0 cycle. The test data is the average value of the test battery.

At the time when the module X reaches the end of its life, two tests of the modules Y that have not reached the end of life are stopped, and the module X that has reached the end of life and the module Y whose life test has been stopped halfway are disassembled. did. Immediately after dismantling, the positive and negative electrode plates are washed with water and dried, and the central portion of the strip-shaped positive and negative electrode plates is approximately 10%.
The degree was divided into upper and lower parts and the amount of lead sulfate was analyzed. The test results are shown in Table 1.

[0027]

[Table 1]

In module X, as much as 60% of lead sulfate accumulated in the lower part of the negative electrode plate in about 60,000 cycles, and it can be said that the cause of the life is sulfation. On the other hand, in the module Y, the amount of lead sulfate accumulated in the lower part of the negative electrode plate was only 30% even after about 60,000 cycles, and it was still in a chargeable and dischargeable state.

In addition to the above-mentioned examples, various examinations were carried out for the capacity of the wound-type battery power generating element (height, number of windings, etc.), the interval of the lower part of the battery case, etc. The one with a space below the battery case or the one with a wide space had a better charge / discharge cycle life performance in an incomplete charge / discharge cycle.

Although the lead battery has been described in the above embodiment,
Although other batteries have different life test conditions and deterioration factors, the battery employing the configuration of the present invention is superior in life performance.

[0031]

According to the present invention, it is possible to provide a battery having excellent heat dissipation performance.

[Brief description of drawings]

FIG. 1 Conventional unit cell

[Fig. 2] Conventional battery pack battery case

FIG. 3 Conventional battery pack

FIG. 4 Single cell according to the invention

FIG. 5 is a cross section of a unit cell according to the present invention.

FIG. 6 Example of storing single cells

FIG. 7: A battery pack battery case according to the present invention

FIG. 8 is an assembled battery case according to the present invention.

[Figure 9] Life test results

[Explanation of symbols]

1 Positive terminal 2 Negative electrode terminal 10 Conventional cells 15 Conventional battery case 16 Battery case according to the present invention 20 Conventional battery pack battery case 21 cell room 30 Battery pack battery according to the present invention 40 Single cell according to the invention 61 cases 62 Equipment and members

Claims (3)

[Claims] 1. A battery comprising a power generation element in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed therebetween, and the power generation element is housed in a battery case. A single battery characterized by having a trapezoidal shape. 2. An assembled battery constructed by housing a power generation element, in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed between them, in a battery case having two or more cell chambers, An assembled battery, wherein the outer shape of the cell chamber is a truncated cone shape having a large upper portion. 3. An assembled battery comprising a plurality of the unit cells according to claim 1 combined.