JPH10162795A - Pack battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat radiating efficiency of batteries, reduce a temperature difference between individual batteries, and improve cycle service life performance by arranging plural ventilating holes in a place where a vessel inside surface of a pack battery and a cylindrical battery cannot substantially contact with each other. SOLUTION: In this pack battery, for example, battery groups where cells are connected by two pieces in parallel to each other, are connected by three pieces in series to each other, and batteries 2 are arranged and housed in a resinous vessel 3. A positive electrode external terminal and a negative electrode external terminal are arranged in the vessel 3. Ventilating holes 1 are also arranged in a plurality in a position close to a peripheral surface of the batteries 2 in a place where the cylindrical batteries 2 cannot substantially contact with them on a wall surface of the vessel 3 opposed to a cylindrical battery peripheral surface. In such constitution, the batteries 2 do not block up the ventilating holes 1, and the inside of the vessel 3 is always smoothly ventilated, and a temperature rise in the batteries 2 is restrained, and temperatures of plural batteries 2 in the vessel 3 can be uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a battery pack containing a plurality of cylindrical secondary batteries such as a nickel-cadmium battery, a nickel-hydrogen battery and a lithium ion battery.

[0002]

2. Description of the Related Art In recent years, information devices such as notebook personal computers and word processors, mobile communication devices such as mobile phones, video cameras,
Demand for AV equipment such as liquid crystal televisions is rapidly increasing. As a power source, sealed small secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries are often used, and among them, non-aqueous electrolyte secondary batteries represented by lithium-ion secondary batteries are high in capacity. Utilizing characteristics such as voltage, high energy density, and light weight, it is widely used in various fields. In many cases, batteries used as power sources for the various devices include a plurality of batteries connected in series and / or.
Alternatively, it is used in a battery pack connected in parallel and hermetically sealed.

[0003]

Since a plurality of batteries are installed in a single container so as to be adjacent to each other and are sealed, heat generated by Joule heat during charging / discharging of the batteries is trapped. In addition, the ambient temperature of the battery pack may be significantly increased by the operation of the device. As described above, the temperature of the battery pack greatly changes depending on the magnitude of the charge / discharge current, the use state of the equipment used, and the like. Further, in a device such as a notebook computer in which the occupied volume of the battery pack is large, the temperature difference between the individual batteries in the battery pack becomes large. In general, the charge and discharge characteristics of a battery change with temperature.If the temperature difference between the individual batteries in the battery pack increases, the performance variation between the batteries increases, and as a result, the battery with the lowest performance is the entire battery pack. Dominates performance. This tendency is noticeable in non-aqueous electrolyte secondary batteries represented by lithium secondary batteries. The reason is that the non-aqueous electrolyte secondary battery is a nickel-cadmium battery or a nickel-cadmium battery in which the electrolyte is an aqueous solution.
This is because the degree of deterioration of the battery due to overcharge and overdischarge is greater than that of a hydrogen battery, a lead storage battery, or the like. An object of the present invention is to provide a battery pack having improved cycle life performance by improving the heat radiation efficiency of the battery and reducing the temperature difference between the individual batteries.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a battery pack according to the present invention in which a plurality of cylindrical batteries 2 are stored in a container 3, or a plurality of cylindrical batteries 2 are stored in a container 3. Each of the battery packs housed such that a part of the side surface of each cylindrical battery 2 is exposed from the container 3 is provided with a plurality of ventilation holes at locations where the inner surface of the container 3 and the cylindrical battery 3 cannot substantially contact each other. 1 is provided. By adopting this configuration, the air permeability in the pack is dramatically improved. For this reason, heat is dissipated and the heat does not partially remain, so that the temperature difference between the individual batteries 2 in the container 3 can be reduced, and the absolute temperature rise of the entire battery pack can be suppressed. As a result, variations in the characteristics of the battery 2 are suppressed, and the cycle life performance is improved. Further, the safety is improved because the temperature rise of the battery 2 is suppressed. In the above configuration, it is preferable that a portion where the cylindrical battery cannot substantially contact exists on the container wall surface facing the peripheral surface of the cylindrical battery. The reason for this is that the location of the ventilation hole is an adjacent portion (space) between the batteries heated by the batteries and has a strong air current, so that the air permeability in the pack is dramatically improved. Therefore, heat dissipation proceeds, and heat does not partially remain.

[0005] In the above structure, it is preferable that a cover is arranged outside or inside the ventilation hole. The reason is that by employing this configuration, it is possible to realize a configuration in which foreign substances hardly enter through the ventilation holes. Even if foreign matter enters the container, the position of the ventilation hole is the container wall surface facing the peripheral surface of the cylindrical battery, so that compared to the case where the ventilation hole is located at the upper end and / or lower end of the cylindrical battery, The probability of the presence of the foreign matter at the electrical connection is reduced. Therefore, even if the foreign substance is a conductive material, a catastrophic failure is unlikely to occur and safety is improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to an example of a battery pack using a cylindrical lithium secondary battery as a unit cell. First, a method for manufacturing a unit cell will be described. A paste-like solution mainly composed of a lithium-cobalt composite oxide is applied to both surfaces of a 20 μm-thick aluminum foil on the positive electrode plate,
After drying and rolling, a product cut to a width of 54 mm was used. A negative electrode plate was prepared by applying a paste-like solution mainly composed of a carbon material to both surfaces of a 10-μm-thick copper foil, drying and rolling, and then cutting the resultant to a width of 56 mm. The positive electrode plate and the negative electrode plate were wound through a separator made of a microporous polyethylene film having a thickness of 25 μm and a width of 58 mm to form a wound group. The wound group is inserted into a can, and a tab terminal previously welded to the negative electrode current collector is welded to the bottom of the can. Next, after injecting 5 ml of an electrolytic solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l into a solvent in which propylene carbonate and dimethyl carbonate are mixed at a volume ratio of 30:70, the positive electrode tab previously fused to the positive electrode current collector was injected. The terminal was welded to the positive electrode cap, the positive electrode cap was placed on the upper part of the can, and the upper part of the can was caulked via an insulating gasket to seal the battery.

Next, a method of manufacturing a battery pack using the above-described unit cell will be described. As shown in the cross-sectional view of FIG. 1, the battery 2 is arranged and housed in a resin container 3, and a battery pack is prepared by connecting three battery groups in which two unit cells manufactured as described above are connected in parallel. Obtained. The container 3 of FIG. 1 is provided with a positive external terminal and a negative external terminal (not shown). Also, as shown in the figure, a ventilation hole 1 having a diameter of 2 mm is formed on a wall of the container 3 facing the peripheral surface of the cylindrical battery 2 where the cylindrical battery 2 cannot substantially contact.
Were provided. In the above configuration, the battery 2 does not block the ventilation hole 1, the ventilation in the container 3 is always performed smoothly, the temperature rise of the battery 2 is suppressed, and the plurality of batteries 2 in the container 3 are suppressed.
The temperature can be made uniform. The ventilation hole 1 is located at a position close to the peripheral surface of the cylindrical battery 2. In general, the peripheral surface of a cylindrical battery occupies most of the surface area of the battery. Therefore, by ventilating the periphery, the temperature rise of the battery 2 can be suppressed most efficiently. Alternatively, the temperature of the plurality of batteries 2 in the container 3 can be made more uniform. By making the temperatures of the plurality of batteries 2 in the container 3 uniform, the characteristics of the batteries 2 in the container 3 can be made equal. In any battery system, the overcharge area and the overdischarge area differ depending on the temperature. If a plurality of cells are connected in parallel and / or in series and some of the cells have different overcharge regions and overdischarge regions, the deterioration of a specific battery alone will proceed more quickly. As described above, the battery with the worst characteristics governs the characteristics of the whole battery pack. In particular, non-aqueous electrolyte secondary batteries containing an organic solvent or the like in the electrolyte are overcharged, and the deterioration of the battery due to overdischarge is more severe than that of the aqueous electrolyte battery. It is particularly effective.

The structure of the ventilation hole 1 of the present invention is preferably a structure in which a cover is disposed outside or inside the ventilation hole 1 in addition to the structure in which the ventilation hole 1 shown in FIG. For example, as shown in FIG. 2 and FIG. 3, a structure in which a part of a wall surface is deformed and projected outward or inward to form a cover and a ventilation hole 1 is formed. By adopting the configuration shown in FIGS. 2 and 3, it is possible to make it difficult to mix foreign matter into the container 3, thereby preventing a short circuit accident or the like. Comparing the configurations of FIGS. 2 and 3, it can be said that the configuration in which the cover is provided on the inside of the ventilation hole 1 is preferable because it is less bulky and the volume energy density of the battery pack becomes higher.

In practicing the present invention, a plurality of cylindrical batteries are housed in a container, and a pack battery housed so that a part of the side surface of each cylindrical battery is exposed from the container is provided with the ventilation hole having the above-described structure. Applicable.

[0010]

EXAMPLE Two cylindrical lithium secondary batteries described in the embodiment of the invention were connected in parallel, and three of them were connected in series. The 2-parallel 3-series battery group was housed in a resin container as shown in FIG. 1 to obtain a battery pack. In this battery pack, five ventilation holes 1 having a diameter of 2 mm are provided on one side of the wall of the container 3 facing the peripheral surface of the cylindrical battery 3 at a position where it cannot substantially contact the cylindrical battery 3. Was. This battery pack is called Example 1. For comparison, ventilation hole 1
As shown in FIG. 4, a battery pack having a cylindrical battery 3 on the wall surface of the container 3 substantially in contact with the peripheral surface of the battery 3 was manufactured. Ventilation hole 1
Except for the arrangement position of, it was manufactured under exactly the same conditions as in Example 1. This battery pack is called a comparative example. Further, as shown in FIG. 6, a conventional battery pack was manufactured under exactly the same conditions as in the battery pack of Example 1 except that no ventilation hole 1 was provided. Each of the above-mentioned battery packs is 2800 mAh-
There is an initial characteristic of 10.8V.

The manufactured battery pack was set at a set voltage of 12.6.
V, a constant voltage charge was performed at a limited current of 2800 mA for 2.5 hours to obtain a fully charged state, and then a temperature change during charge and discharge, a cycle life test, and a high-temperature storage test were performed. The measurement of the temperature change at the time of charging / discharging is performed by fixing two thermocouples to the side of each of the six batteries housed in the battery pack with tape.
The battery pack was allowed to stand under each condition to perform charging and discharging, and the temperature change of each cell and the temperature difference between individual batteries in the battery pack were measured. The discharge is performed at a current of 2800 mA (corresponding to 1 CmA) until the discharge end voltage reaches 7.5 V, after which the set voltage is 12.6 V and the limited current is 2800 mA (1 Cm).
In A), constant voltage charging was performed for 2.5 hours. Table 1 shows the installation conditions of the battery pack, the ambient temperature, the maximum temperature of the battery during charging and discharging, and the maximum temperature difference between the batteries. The items indicated as "partial heating temperature" in the battery pack installation conditions in the table indicate the conditions for the test in which the individual cells constituting the battery pack are charged and discharged after having a temperature difference. is there. A method of giving a temperature difference to individual cells constituting a battery pack is to wind a heater capable of setting a temperature around a part of the battery pack and heat it. The partial heating temperature in the table indicates a temperature difference after heating in a standing state for one hour, and charging / discharging is started from this state.

[0012]

[Table 1]

As shown in Table 1, the maximum temperature of the battery of Example 1 was lower than that of the comparative example and the conventional example under any conditions.
Also, the temperature difference between the individual batteries in the container is small. It can be seen that heat was easily released because holes were formed in the wall of the container 3 where the inner surface of the container 3 could not substantially contact the cylindrical battery 3 to improve air permeability. Even under the condition that a temperature difference is given between the individual batteries in the battery pack, the temperature difference between the individual batteries in the battery pack of Example 1 is smaller than that of the comparative example and the conventional example.
The reason why the battery pack of the comparative example cannot obtain a better heat radiation effect than the battery pack of the first embodiment is that the ventilation hole 1 of the battery pack of the comparative example may be closed by the cylindrical battery peripheral surface, and It is considered that was not good.

Next, assuming a battery pack incorporated in a small device, that is, assuming that the battery in the battery pack is warmed from the outside, a heater is wound around a part of the battery pack and the battery pack itself is initialized. A cycle life test was performed with a temperature difference of 10 ° C. Charge and discharge conditions are ambient temperature 2
5 ° C., discharge is discharge current 560 mA 0.2 CmA), discharge end voltage 7.5 V, charge is constant current constant voltage charge with set voltage 12.6 V, limited current 2800 mA (1 CmA), and charge time 2.5 hours. After that, the rest was one cycle for 30 minutes. As a result of the cycle life test, as shown in FIG. 5, the pack battery of the example had an initial capacity of about 8 even after 200 cycles.
There is 0% capacity, and the change in capacity is stable. On the other hand, the capacity of the battery pack of the comparative example reaches about 70% of the initial capacity in 200 cycles, and the capacity of the battery pack of the conventional example changes at a lower level. This is considered to be due to the fact that the variation in the capacity between the batteries becomes large due to the temperature variation in the battery pack, and as a result, the battery with a small capacity dominate the capacity of the whole battery pack, and the capacity reduction occurred early. Therefore, suppressing the temperature difference between the individual batteries in the battery pack makes the load on the batteries uniform during operation of the device, and as a result, the cycle life is improved.

Next, the possibility of foreign matter entering the pack was evaluated. A glass bead with a particle size of 1 mm
The weight of the glass beads dropped into the container after being dropped by 00 g is measured. The object of comparison is one in which a cover is arranged outside or inside the ventilation hole. Specifically, a part of the wall surface is deformed and projected to the outside of the container 3 as shown in FIG. 2 to form a cover and a ventilation hole 1 (Example 2). A battery pack (Example 3) having a structure in which a cover is formed and a ventilation hole 1 is formed by deforming and projecting a part of the wall surface into the inside of the container 3 as shown in FIG. As a result, the beads mixed in the battery pack containers 3 of Example 2 and Example 3 contained 0.2%.
The amount of beads mixed into the battery pack container 3 of Example 1 was 4 g with respect to g. As can be seen from the above, by adopting a structure in which the cover is arranged outside or inside one of the ventilation holes, the possibility that foreign matters enter the container 3 is considerably reduced.

In this embodiment, a pack battery containing a lithium ion secondary battery is used. However, a similar effect can be obtained with a pack battery containing a cylindrical battery such as a nickel-cadmium battery or a nickel-hydrogen battery. Further, as in the comparative example, a hole was formed in the peripheral part of the cylindrical battery, and
A pack container having a hole as described above is more preferable. Further, even when the battery pack is housed in a container formed in such a shape that a part of the peripheral surface of the cylindrical battery is exposed, securing a hole in the place as in the embodiment 1 has a heat dissipation effect. .

[0017]

According to the present invention, it is possible to provide a battery pack having improved cycle life performance by improving the heat radiation efficiency of the battery pack and reducing the temperature difference between the individual batteries.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a battery pack of the present invention.

FIG. 2 is a cross-sectional view of an example of the battery pack of the present invention.

FIG. 3 is a sectional view of an example of the battery pack of the present invention.

FIG. 4 is a sectional view of an example of a battery pack of a comparative example.

FIG. 5 is a diagram showing the relationship between the number of charge / discharge cycles of a battery pack and the capacity retention ratio.

FIG. 6 is a cross-sectional view of an example of a conventional battery pack.

[Explanation of symbols]

 1. Ventilation hole 2. Battery 3. container

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shinkazu Tanaka 2-8-7 Nihonbashi Honcho, Chuo-ku, Tokyo Inside Shin-Kobe Electric Co., Ltd.

Claims (5)

[Claims] 1. A battery pack in which a plurality of cylindrical batteries are housed in a container, wherein the container wall has a plurality of ventilation holes at locations where the cylindrical batteries cannot substantially contact. Battery pack. 2. A battery pack in which a plurality of cylindrical batteries are housed in a container, and a part of the side surface of each cylindrical battery is housed so as to be exposed from the container, wherein the cylindrical battery is substantially formed on the container wall. A battery pack having a plurality of ventilation holes at locations where it cannot contact the battery. 3. The battery pack according to claim 1, wherein the portion where the cylindrical battery cannot substantially contact exists on the wall of the container facing the peripheral surface of the cylindrical battery. 4. The battery pack according to claim 1, wherein a cover is arranged outside or inside the ventilation hole. 5. The battery pack according to claim 1, wherein the cylindrical battery is a non-aqueous electrolyte secondary battery.