JP2012022895A - Secondary battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery device which keeps its performance by suppressing a rise in temperature of a battery cell, and can reduce a whole size of the device.SOLUTION: The battery device comprises: a plurality of battery cells having an outer case, and each having an electrode terminal, the battery cells being disposed in the outer case so as to be arranged spaced from each other; and a plurality of conductive members for electrically connecting between the electrode terminals of the battery cells, in which the outer case is composed of metal plates and surfaces of the outer case have surface treated areas subjected to at least one of coating, surface treatment by an anodic oxidation film forming, or surface roughening processing.

Description

  Embodiments described herein relate generally to a secondary battery device having a plurality of battery cells connected in series or in parallel.

  A secondary battery device used in a vehicle such as a hybrid vehicle or an electric vehicle needs to have high output and cope with frequent output changes. Such a secondary battery device is generally configured as an assembled battery or battery module in which a plurality of battery cells are electrically connected in series or in parallel and mechanically integrated according to the required output and capacity. Has been. In a battery module, each battery cell has a positive electrode terminal and a negative electrode terminal, and among the plurality of battery cells, for example, electrode terminals of two adjacent battery cells are connected to each other by a conductive member such as a bus bar. . Further, the plurality of battery cells are accommodated in the outer case.

  The battery cell generates self-heating due to energization. When a battery module is configured by connecting a plurality of battery cells, it is necessary to limit the temperature rise of each battery cell to an allowable value or less so that all the battery cells can exhibit performance over a long period of time. . That is, it is necessary to efficiently cool all the battery cells. Therefore, battery modules are often provided with a heat dissipation mechanism. For example, a method is used in which heat is radiated to the outside of the battery module via the outer case, or heat is radiated by passing air outside the cell case. Alternatively, a method is adopted in which a plurality of ventilation holes are provided in the outer case, and the outside air is guided to the periphery of the battery cell through these ventilation holes.

JP 2009-87721 A JP 2006-139919 A

  However, when a heat dissipation mechanism that ventilates the outside of the battery module is provided, it becomes a factor that causes an increase in the size of the battery module. Usually, it is rare that a sufficient mounting space can be secured in a vehicle on which the battery module is mounted, and it is often required to reduce the size of the battery module so that the battery module can be mounted in the twisted space.

  When ventilating into the outer case through the vent hole of the outer case, it is difficult to secure sufficient cooling air necessary for cooling the battery cells. In order to reduce the size of the battery module, it is desirable to arrange a plurality of battery cells as close as possible. That is nothing but reducing the spacing between adjacent battery cells. Inevitably, the volume of the space through which the cooling air passes is reduced, and the amount of cooling air is reduced.

  There may be a case where forced cooling by ventilation is not allowed. For example, there is a case where the battery module is housed in a completely sealed casing, because the generation of air from the outside of the vehicle does not cause the component parts to be stained or corroded. In this case, it is necessary to suppress the temperature rise of the battery cell without using forced air cooling.

  Wiring conductors also tend to rise in temperature due to self-heating due to energization. Therefore, it is necessary for the wiring conductor to suppress the temperature rise. When an excessive temperature rise occurs, a part of the heat generation amount from the wiring conductor moves to the battery cell, and the battery cell is also affected.

  In addition, since an electrical insulating portion exists near the electrode terminal of the battery cell, it is essential to ensure a clean environment. That is, it is difficult to allow air containing dust, moisture, and the like to flow around the electrode terminals, and it is required to suppress the temperature rise by natural air cooling without using forced cooling.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery device capable of reducing the physique of the entire device while maintaining performance by suppressing temperature rise of the battery cell. is there.

  According to the embodiment, the battery device includes an outer case and an electrode terminal, and a plurality of battery cells arranged in the outer case with a gap between each other and the electrode terminals of the battery cell are electrically connected. A plurality of conductive members connected to each other, wherein the outer case is formed of a metal plate, and the surface of the outer case is subjected to at least one of surface treatment by coating or anodized film formation, or roughening processing It has an applied surface treatment area.

FIG. 1 is a perspective view showing a secondary battery device according to a first embodiment of the present invention. FIG. 2 is a plan view of the secondary battery device shown by cutting an outer case of the secondary battery device. FIG. 3 is an exploded perspective view of the secondary battery device showing an outer case, a battery cell, and a bus bar of the secondary battery. FIG. 4 is a plan view of the battery cell. FIG. 5 is a perspective view showing the battery cell. FIG. 6 is a cross-sectional view schematically showing the bus bar. FIG. 7 is a perspective view showing the bus bar. FIG. 8 is a diagram showing the relationship between emissivity and temperature rise in the secondary battery device.

Hereinafter, a secondary battery device according to an embodiment of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a perspective view showing a battery module according to the first embodiment as a secondary battery device, FIG. 2 is a plan view of the battery module shown by cutting a part of an outer case, and FIG. 3 is a battery module. It is a disassembled perspective view which decomposes | disassembles and shows.

  As shown in FIGS. 1, 2, and 3, the battery module 10 includes a battery group in which a plurality of, for example, ten battery cells (secondary batteries) 12 are arranged with a predetermined gap therebetween, and a battery group And a rectangular box-shaped outer case 16 that accommodates. The electrode terminals of adjacent battery cells 12 are electrically connected by a bus bar 30 as a conductive member.

  As shown in FIGS. 3, 4, and 5, each battery cell 12 is configured as a thin non-aqueous secondary battery such as a lithium ion battery, for example. The battery cell 12 includes a flat rectangular box-shaped outer container 18 formed of a metal plate material such as aluminum, and an electrode body 20 housed in the outer container 18 together with a nonaqueous electrolytic solution. The outer container 18 has a container main body 18a having an open upper end and a rectangular plate-shaped lid body 18b welded to the container main body and closing the opening of the container main body, and is formed airtight. The electrode body 20 is formed in a flat rectangular shape by, for example, winding a positive electrode plate and a negative electrode plate in a spiral shape with a separator interposed therebetween, and further compressing in a radial direction.

  A positive electrode terminal 22 and a negative electrode terminal 23 are provided at both ends of the lid body 18b in the longitudinal direction, and project from the lid body 18b. The positive electrode terminal 22 and the negative electrode terminal 23 are connected to the positive electrode and the negative electrode of the electrode body 20, respectively. A pressure release valve 24 that functions as a gas exhaust mechanism is formed at the center of the lid 18b. The pressure release valve 24 is formed to have a plate thickness about half that of the lid 18b. When gas is generated in the outer casing 18 due to an abnormal mode or the like of the battery cell 12 and the internal pressure in the outer casing rises to a predetermined value or more, the pressure release valve 24 is opened, and the inner pressure is lowered to rupture the outer casing 18. To prevent such problems.

  As shown in FIGS. 1 to 3, the outer case 16 has a rectangular plate-like bottom wall 16a, a pair of rectangular plate-like side walls 16b, front and rear end walls 16c and 16d, and a rectangular upper surface plate 16e. These are joined together to form a rectangular box shape. Each wall 16a-16d is formed, for example with metal plate materials, such as aluminum, and the upper surface board 16e is formed with the synthetic resin etc. which have insulation. When forming each wall 16a-16d with a metal plate material, you may form a thin electric insulation layer in the surface facing the battery cell 12 as needed. The electrical insulating layer is preferably a good heat conductor. A plurality of slit-shaped air holes 17 are formed in each of the side walls 16b, and these air holes 17 are arranged at predetermined intervals in the longitudinal direction and the height direction of the side wall 16b.

  An insulating sheet 28 is laid on the bottom wall 16a, and a plurality of battery cells 12 are placed on the insulating sheet. The battery cells 12 are positioned and arranged at predetermined intervals by positioning means (not shown). That is, as shown in FIGS. 1 to 3, the ten battery cells 12 are in a state where the main surfaces of the outer casing 18 face each other with a predetermined gap, and the electrode terminal side faces the same direction. In a state, they are arranged in a line. In the present embodiment, the two adjacent battery cells 12 are arranged in a state where they are inverted by 180 degrees so that the positions of the positive electrode terminal 22 and the negative electrode terminal 23 are reversed. That is, the ten battery cells 12 are arranged so that the positive electrode terminals 22 and the negative electrode terminals 23 are alternately arranged in two rows along the arrangement direction. The side surfaces of the plurality of battery cells 12 are covered with a pair of side walls 16b and front and rear end walls 1c and 16d of the outer case 16.

  Ends on the electrode terminal side of the plurality of battery cells 12 are covered with an upper surface plate 16 e of the outer case 16. The upper surface plate 16e has a plurality of openings 34 respectively facing the positive electrode terminal 22 and the negative electrode terminal 23 of the battery cell 12, and these openings 34 are arranged in two rows. Bosses 36 are respectively provided at both end portions of the upper surface plate 16e in the longitudinal direction.

  As shown in FIGS. 1 and 2, the plurality of battery cells 12 are connected in series by a plurality of bus bars 30. The bus bar 30 is formed by bending a metal plate made of a conductive material such as aluminum. As shown in FIGS. 6 and 7, the bus bar 30 includes a pair of rectangular terminal connection portions 30a and a curved connection portion 30b extending between the terminal connection portions 30a. Each terminal connection portion 30a is formed with an opening 40 with which the positive electrode terminal 22 or the negative electrode terminal 23 of the battery cell 12 is engaged.

  As shown in FIGS. 1 and 2, the bus bar 30 has one terminal connection portion 30a connected to the positive electrode terminal 22 of the battery cell 12, and the other terminal connection portion 30a connected to the negative electrode terminal of another adjacent battery cell 12. 23. The terminal connection portion 30a is welded, for example, laser welded, to the electrode terminal in a state where the positive electrode terminal 22 or the negative electrode terminal 23 is engaged in the opening 40. For welding, electron beam welding or resistance welding may be used instead of laser welding.

  An output terminal 32a on the positive electrode side is joined to the positive electrode terminal 22 of the battery cell 12 located at one end of the battery cell row. One end of the output terminal 32 a is bent upward and is disposed on the boss 36. An output terminal 32b on the negative electrode side is joined to the negative electrode terminal 23 of the battery cell 12 located at the other end of the battery cell row. One end of the output terminal 32 a is bent upward and is disposed on the boss 36. The output terminals 32a and 32b are both formed by bending a metal plate made of a conductive material such as aluminum. The bus bar 30 and the output terminals 32a and 32b joined to the electrode terminals of the battery cell 12 are respectively disposed in the corresponding openings 34 of the upper surface plate 16e.

In the battery module 10 configured as described above, outside air is introduced into the gap between the outer case 16 and the battery cell 12 through the vent hole 17 formed in the side wall 16b of the outer case 16, and the battery cell 12 is caused by this outside air. Is cooled. When such a natural air cooling method is used, as the difference between the component temperature and the ambient temperature increases, the radiation heat radiation amount from the surface of the heating element cannot be ignored. The radiant amount W _R may be expressed by the following equation.

_{W R = σ · A · ε} · (T h 4 -T anb 4) ... (1)
Where W _R : Radiation heat dissipation (W)
σ: Stefan-Boltzmann constant: 5.6687 × 10 ⁻⁸ (W / m ² K ⁴ )
A: Surface area of heating element (m ² )
ε: Emissivity of heating element surface
_Th : Absolute temperature of the heating element (K)
T _anb : Absolute temperature of atmosphere (K)
In the battery module 10, the outer case 16, the outer container 18 of the battery cell 12, and the bus bar 30 are all formed by processing a metal plate material such as aluminum. When the surface of the metal plate material constituting each member is smooth, the emissivity of the aluminum surface is small and is on the order of 0.1 or less. Since the amount of radiated heat is proportional to the emissivity, the amount of radiated heat is small when the emissivity is small. In this case, the heat radiation effect by radiation can hardly be expected, and the heat radiation means is almost limited to heat radiation by heat transfer to the ambient air.

  Even on a metal surface such as aluminum, the emissivity varies depending on the surface state. For example, when the metal surface is rough, or when a surface treatment (anodized treatment) for forming an anodic oxide film is applied to the metal surface, or when a surface treatment such as painting is performed, no treatment is performed. Compared to a smooth metal surface, the emissivity is significantly increased.

  The emissivity of the aluminum smooth surface (polished surface) is 0.1 or less, whereas the emissivity of the anodized surface is 0.8 (white) to 0.95 (black), and the emissivity of the painted surface is 0.9. The emissivity of the rough surface varies depending on the surface roughness, but reaches a maximum of about 0.8. In either case, the emissivity is much larger than the smooth surface.

  According to the present embodiment, as shown in FIGS. 1 and 2, in the battery module 10, the surfaces of the bottom wall 16a, the side wall 16b, and the front and rear end walls 16c, 16d constituting the outer case 16 are, for example, the outer surface and the inner surface. The surface treatment region 42 is formed by applying at least one of surface treatment by coating or anodized film formation, or surface roughening.

  Here, the painting means, for example, applying or spraying a paint such as paint on the surface. Roughening means that the surface is roughened by shot blasting (or sand blasting), etching, or the like. The greater the roughness of the object surface, the higher the emissivity of the object. For example, when the surface is physically roughened by shot blasting, it is desirable that the surface roughness be 50S or more (the maximum height of the roughness is 50 μm or more).

  Note that the surface treatment region may be formed by applying at least one of surface treatment and surface treatment to one of the inner surface and the outer surface, not limited to both the bottom wall 16a, the side wall 16b, and the front and rear end walls 16c and 16d. In FIG. 1 and FIG. 2, the cross-hatched or hatched region schematically shows the surface treatment region 42 to which at least one of the surface treatment or the surface processing is applied. The thickness to which the surface treatment or the surface processing is applied is sufficiently smaller than the thickness of the metal plate material constituting the outer case 16.

  When the outer case 16 of the battery module 10 is configured as described above, the emissivity on the surface of the outer case 16 is significantly increased. Therefore, in addition to heat radiation by heat transfer from the outer case 16 to the ambient air, a radiation heat radiation effect is produced in proportion to the emissivity of the outer case. Therefore, the heat radiation amount of the entire battery module 10 (total) increases.

As an example, consider the following conditions.
A: Surface area of outer case: 0.01 m ² (10 cm square)
ε: Emissivity of outer case surface: 0.8
T _h : Absolute temperature of outer case: 75 ° C. = 348K
T _anb : Absolute temperature of atmosphere: 25 ° C = _298K
h: Heat transfer coefficient of outer case surface: 10 W / m ² K
The radiant amount W _R, calculated by Equation (1) described above,
Radiation heat dissipation: W _R = 3.1W
The heat release amount W _h due to heat transfer is as follows from the following equation.
Heat transfer heat dissipation: W _h = h · A · (T _h −T _anb ) = 5 W
Under such conditions, a radiation heat radiation amount corresponding to about 60% of the heat transfer heat radiation amount can be obtained. However, since there is temperature suppression due to the radiation heat radiation effect and the temperature difference is lowered, the actual radiation heat radiation amount is somewhat smaller than the above calculated value.

  By increasing the amount of heat dissipation, the battery cell 12 can be efficiently cooled and the temperature suppression effect can be improved. Whether the battery cells 12 are arranged closer to each other or housed in a completely sealed outer case, the increase in the amount of heat dissipation due to the radiation heat dissipation effect can suppress the temperature rise value of the battery cells low. it can. As a result, it is possible to provide a battery pack capable of reducing the physique at the same time while maintaining the performance.

  FIG. 8 shows the difference in temperature rise in the battery module when the emissivity of the outer case surface is set to 0 and when the emissivity is set to 0.9. Here, FIG. 8 shows a transient temperature rise at the maximum temperature point when the battery module is operated under a specific energization condition. In FIG. 8, the horizontal axis represents time, a period from 0 s to 3600 s (: 60 min = 1 hr), and the vertical axis represents temperature. From this figure, it can be seen that the highest temperature of the battery module is lower in the direction of higher emissivity.

  According to the present embodiment, at least one of surface treatment by coating or anodic oxide film formation or surface roughening is applied to the entire surface of the exterior container 18 of each battery cell 12. 4 and 5, the hatched or cross-hatched region schematically shows the surface treatment region 44 that has been subjected to at least one of the surface treatment or the roughening process. The thickness to which the surface treatment or surface processing is applied is sufficiently smaller than the thickness of the metal plate material constituting the outer container 18.

  By performing surface treatment or surface processing on the outer container 18 of the battery cell 12 in this way, the emissivity of the outer container surface is remarkably increased, and in addition to heat radiation from the battery cell 12 by heat transfer to the cooling air or external air. Thus, a radiation heat dissipation effect proportional to the emissivity occurs. Therefore, the total (total) heat dissipation increases. The heat suppression effect of the battery module 10 can be improved by increasing the heat radiation amount from the battery cell 12 to the cooling air and the surrounding air.

  In any case where a plurality of battery cells are arranged closer to each other or stored in a completely sealed outer case, the temperature rise value of the battery cell 12 can be kept low by increasing the heat radiation amount by the radiation heat radiation effect. . As a result, it is possible to provide the battery module 10 capable of maintaining the performance and simultaneously reducing the physique.

  Furthermore, according to this embodiment, at least one of surface treatment by coating or anodic oxide film formation or roughening is applied to the entire surface of each bus bar 30. However, in the bus bar and the output terminal, the conductive part is not painted. In FIGS. 6 and 7, the hatched or cross-hatched region schematically shows the surface treatment region 46 that has been subjected to at least one of the surface treatment or the roughening process. The thickness of the surface treatment or surface treatment is sufficiently smaller than the thickness of the bus bar.

  By subjecting the bus bar 30 to surface treatment or roughening in this way, the emissivity of the bus bar surface is remarkably increased, and in addition to heat radiation by heat transfer to the surrounding air, a radiation heat radiation effect proportional to the emissivity is obtained. Arise. By increasing the amount of heat released from the bus bar to the surrounding air, the temperature suppression effect of the battery module 10 can be improved. The bus bar 30 has a small heat capacity and a small heat radiation area compared to other members, and thus easily becomes high temperature. However, by increasing the amount of heat generated by surface treatment or roughening, the temperature of the bus bar itself is increased. Can be suppressed. Thereby, it is possible to prevent the occurrence of connection failure due to thermal deformation of the bus bar, and to improve the reliability.

  According to the battery module configured as described above, the amount of radiation heat radiation can be reduced by applying at least one of surface treatment or surface roughening to the surface of the outer case 16, the outer container 18 of the battery cell 12, and the bus bar 30. The battery cell can be efficiently cooled and the temperature rise can be suppressed. Even when a plurality of battery cells 12 are arranged closer to each other or housed in a completely sealed outer case, the temperature rise value of the battery cells 12 can be kept low due to an increase in the amount of heat dissipation due to the radiation heat dissipation effect. Thereby, it is possible to provide a secondary battery device capable of reducing the physique at the same time while maintaining the performance.

  In a normal use state of the battery module, the battery cell generates heat by charging or discharging, and its temperature rises. In addition, when the battery module is abnormal, the temperature rises much larger than normal. An abnormal condition is, for example, a case where battery cell characteristics deteriorate due to secular change or failure of the temperature protection circuit, etc., and so-called heat increases, such as temperature increase, heat generation increase due to characteristic deterioration, and further temperature increase. Runaway temperature rise may occur. Measures to prevent are important. In principle, the amount of heat radiation increases as the temperature difference increases, and when the temperature increases due to thermal runaway, the temperature suppression effect by radiation radiation of the battery module according to this embodiment described above is normal use. Much more effective than Therefore, this battery module can be effectively used as one of the serious event prevention measures, and can greatly contribute to the improvement of reliability.

  In the above-described embodiment, the surface of the outer case, the outer casing of the battery cell, and the surface of the bus bar are each subjected to surface treatment or roughening. However, the present invention is not limited thereto, and the surface of the outer case, the battery cell Only one or two of the surface of the outer container and the surface of the bus bar may be subjected to at least one of surface treatment or surface roughening. Even in this case, the effect of suppressing the temperature rise of the battery cell by increasing the radiation heat radiation amount can be obtained.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
The number of battery cells constituting the battery cell group, the shape of the outer case, the structure, and the like are not limited to the above-described embodiments, and can be appropriately changed as necessary. The battery cells are not limited to being connected in series, and may be connected in parallel. For the treatment of the surface of the metal plate material, a combination of surface treatment and roughening may be used. For example, the surface of the outer case may be roughened and anodized to form a surface treatment region. The surface of the output terminal may be subjected to a surface treatment or a roughening process.

DESCRIPTION OF SYMBOLS 10 ... Battery module, 12 ... Battery cell, 16 ... Outer case, 16a ... Bottom wall,
16b ... side wall, 18 ... exterior container, 18a ... container body, 18b ... lid, 22 ... positive electrode terminal,
23 ... Negative electrode terminal, 30 ... Busbar, 32a, 32b ... Output terminal, 30a ... Terminal connection part 42, 44, 46 ... Surface treatment region

Claims (5)

An outer case, each having an electrode terminal, a plurality of battery cells arranged in the outer case side by side with a gap therebetween, and a plurality of conductive members that electrically connect the electrode terminals of the battery cell, With
The outer case is formed of a metal plate material, and the surface of the outer case has a surface treatment region to which at least one of surface treatment by coating or anodic oxide film formation or roughening is applied.   Each of the conductive members is formed of a metal plate, and the surface of the conductive member has a surface treatment region to which at least one of surface treatment by coating or anodized film formation or roughening is applied. The battery device according to 1.   Each of the battery cells has an outer container formed of a metal plate material and containing an electrode body, and the surface of the outer container is subjected to at least one of a surface treatment by coating or anodized film formation, or a roughening process. The battery device according to claim 1, further comprising a surface treatment region. An outer case, each having an electrode terminal, a plurality of battery cells arranged in the outer case side by side with a gap therebetween, and a plurality of conductive members that electrically connect the electrode terminals of the battery cell, With
Each of the conductive members is formed of a metal plate material, and the surface of the conductive member has a surface treatment region to which at least one of surface treatment by coating or anodized film formation or roughening is applied. . An outer case, and an outer container and an electrode terminal each containing an electrode body, and a plurality of battery cells arranged in the outer case side by side with a gap between each other, and between the electrode terminals of the battery cell electrically A plurality of conductive members to be connected,
The exterior container of each battery cell is made of a metal plate material, and the surface of the exterior container has a surface treatment region subjected to at least one of surface treatment by coating or anodized film formation, or surface roughening. Battery device.

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