JP2020140929A - Battery pack - Google Patents

Abstract

To level the temperature of cells in a battery pack (reduce the temperature difference between a cell in the center of the battery pack and a cell at the end, suppress the temperature rise of the cell in the center, and make the temperature of the cell in the battery pack equal to the temperature of the cell at the end) to extend the life of the battery pack.SOLUTION: A battery pack (100) according to the present invention includes a laminated body in which cells (110) and heat absorbing materials (130, 140) are alternately arranged and laminated, and the volume or material of the heat absorbing material (130) arranged at the center of the laminated body in the stacking direction is different from that of the heat absorbing material (140) arranged at the end of the laminated body in the stacking direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a battery pack.

Conventionally, a battery pack composed of a plurality of cells (cell cells) for in-vehicle use, industrial use, etc. has been known. In general, when a secondary battery such as a lithium-ion battery is repeatedly charged and discharged at a high temperature or left at a high temperature, the battery capacity decreases, the resistance inside the battery increases, and the output decreases. Tends to be accelerated. Therefore, some have a cooling structure in order to suppress a temperature rise due to charging / discharging of the cell.

For example, in Patent Document 1, separators (12), (32), and (42) formed in contact with the surface of a battery cell (1) in a thermally coupled state are sandwiched between a plurality of battery cells (1). The plurality of battery cells (1) are fixed so as to be laminated via separators (12), (32), and (42) provided with a cooling gap (3) between the battery cells (1). The battery blocks (10), (30), and (40), and the ventilation mechanism (9) that forcibly blows the cooling gas into the cooling gaps (3) of the battery blocks (10), (30), and (40). A vehicle battery system comprising the thermal resistance between the battery cell (1) and the separators (12), (32), (42), or separators (12), (32), (42). ) The thermal resistance of itself differs between the separators (12), (32), and (42) arranged in the stacking direction, and the difference in thermal resistance equalizes the temperature of the battery cell (1). The battery system for is disclosed.

Patent Document 2 encloses a plurality of arranged batteries, a battery accommodating case for restraining and accommodating the plurality of arranged batteries, a phase change material capable of phase change by heat from the battery, and the phase change material. A gap that can change in volume according to the deformation of the bag body is formed inside, so that the batteries are in close contact with each other or the heat conductive member in contact with the batteries. A battery module including a heat absorber sandwiched between the two and the battery module is disclosed.

Patent Document 3 describes a set battery including a plurality of cells arranged adjacent to each other, which is higher than the temperature range of the cells during normal use and has a breakdown temperature at which the cells are thermally destroyed. A phase-changing substance having a lower melting point is melted by absorbing the heat when one of the cells generates heat between the cells adjacent to each other to a temperature higher than the melting point. An assembled battery arranged in a form is disclosed.

JP-A-2010-272378 Japanese Unexamined Patent Publication No. 2013-178966 JP-A-2010-73406

The above-mentioned Patent Document 1 provides a cooling mechanism for cooling the heat of the battery cell, but when aiming at further miniaturization of the battery pack, a configuration without a cooling mechanism is advantageous.

In addition, the cell located in the center of the battery pack receives heat from the surrounding cells, and the cooling air does not reach it, or the cooling water is warmed by the heat from the surrounding cells before it reaches the center cell. Therefore, a sufficient cooling effect may not be obtained. Therefore, it is expected that the temperature of the cell located at the center of the battery pack will be higher than the temperature of the cell located at the end of the battery pack. In general, a secondary battery such as a lithium-ion battery deteriorates faster (the battery capacity decreases or the charge / discharge current decreases) when the battery is left in a high temperature state or when charging / discharging is repeated. It ends up. That is, the life of the battery pack is determined by the degree of deterioration of the cell located at the center of the battery pack, although the cell located at the end of the battery pack has little deterioration.

In Patent Document 2 and Patent Document 3, since the heat absorber or the phase change substance absorbs heat, it is not necessary to provide a cooling mechanism as in Patent Document 1, but the cell at the center and the cell at the end of the battery pack do not need to be provided. No specific study has been made on the reduction of temperature difference.

The present invention has been made in view of the above-mentioned conventional problems, and the temperature of the cells in the battery pack is leveled (the temperature difference between the cell at the center of the battery pack and the cell at the end is reduced, and the temperature difference is reduced. The purpose is to suppress the temperature rise of the cell in the center and make it equal to the temperature of the cell at the end) and extend the life of the battery pack.

One aspect of the battery pack of the present invention for achieving the above object includes a laminated body in which cells and heat absorbing materials are alternately arranged and laminated, and the heat absorbing material is arranged in the center of the laminated body in the stacking direction. It is characterized in that the volume or material is different from that of the heat absorbing material arranged at the end in the stacking direction of the laminated body.

More specific configurations of the present invention are described in the claims.

According to the present invention, the temperature of the cells in the battery pack can be leveled and the life of the battery pack can be extended.

Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

Schematic diagram of the battery pack of Example 1 of the present invention Schematic diagram showing cells (cells) constituting the battery pack of FIG. Graph showing the time course of cell temperature when the volume or material of the endothermic material (PCM) is the same A graph showing the time course of the cell temperature of Example 1 of the present invention. Schematic diagram of the battery pack of Example 2 of the present invention A graph showing the time course of the cell temperature of Example 2 of the present invention. Schematic diagram of the battery pack of Example 3 of the present invention A graph showing the time course of the cell temperature of Example 3 of the present invention. Schematic diagram of the battery pack of Example 4 of the present invention It is a figure which shows the outline of the battery pack of Embodiment 4 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of a battery pack according to a first embodiment of the present invention, and FIG. 2 is a schematic view showing cells (cell cells) constituting the battery pack of FIG. As shown in FIG. 1, the battery pack 100 of the first embodiment has a configuration in which a plurality of cells 110 are stacked. Such a battery pack 100 is mounted on a hybrid car or an electric vehicle (EV) and used as a power source thereof.

As shown in FIG. 1, the battery pack 100 has a laminated body in which cells 110 and heat absorbing materials 130 and 140 are alternately arranged and laminated. In FIG. 1, the cell 110 and the heat absorbing materials 130 and 140 are laminated in the lateral direction of the paper surface, and are arranged at the heat absorbing material 130 arranged at the center of the laminated body in the stacking direction and at the end of the laminated body in the stacking direction. The volume is different from that of the heat absorbing material 140.

As mentioned above, the temperature at the center of the battery pack tends to be higher than the temperature at the edges. Therefore, as in the present embodiment, the volume of the heat absorbing material 130 arranged at the center of the laminated body in the stacking direction is made larger than the volume of the heat absorbing material 140 arranged at the end of the laminated body in the stacking direction, thereby making the battery pack. The heat absorption amount of the heat absorbing material arranged near the central portion of the battery pack can be made larger than that of the heat absorbing material arranged near the end portion of the battery pack, and the temperature difference of the entire battery pack 100 can be reduced.

The heat absorbing materials 130 and 140 are also referred to as heat storage materials, and a phase change material (Phase Change Material, PCM) is used. PCM is a material having the property of changing from a solid to a liquid and from a liquid to a solid (repeating solidification and melting). PCM is a material that absorbs a large amount of heat in a predetermined temperature range. In this embodiment, the predetermined temperature (phase change temperature (melting point) of PCM) is higher than the environmental temperature at which the battery pack is used, and the battery is used. The temperature should be lower than the maximum temperature during normal use of the pack. Here, the environmental temperature is the temperature at which the battery pack is placed, and is about 35 ° C. in the summer in Japan. Further, in a general lithium ion battery, the temperature range during normal use is about −30 ° C. to 60 ° C., so the maximum temperature during normal use is 60 ° C. Therefore, as an example of the "predetermined temperature" (phase change temperature of PCM) of the present invention, it is 40 ° C. to 55 ° C.

PCM has a large amount of energy (latent heat of melting (kJ / kg)) in and out during a phase change. By utilizing this energy inflow and outflow, it is possible to suppress the temperature rise of the cell in a predetermined temperature range (near the phase change temperature). By using this PCM as a coolant, the cooling volume can be reduced, and power and maintenance for cooling are not required.

Specifically, the heat absorbing materials 130 and 140 are PCM-C48 (phase change temperature: about 40 ° C.) manufactured by Nippon Blower Co., Ltd. and PCM-C58 (phase change temperature: 55 ° C. or higher and 60 ° C.) manufactured by Nippon Blower Co., Ltd. (Less than), sodium acetate trihydrate (phase change temperature: 60 ° C or less), inorganic hydrate (phase change temperature: 60 ° C or less) and the like. In addition, any phase change material having the above-mentioned phase change temperature of a predetermined temperature can be used without particular limitation.

Although not shown here, it is preferable that the cells 110 and the PCMs 130 and 140 are tightly bound to each other in a plurality of cell units or the entire battery pack with a restraint bunt or the like.

The cell 110 is a lithium ion battery, and as shown in FIG. 2, is a rectangular parallelepiped square battery. The cell 110 is arranged so that the side wall portions 110c and 110d having the largest area come into contact with the PCM 130 and 140. The cell 110 has a positive electrode terminal 111 and a negative electrode terminal 112, and the positive electrode terminal 111 and the negative electrode terminal 112 of adjacent cells are electrically connected via a metal bus bar (not shown) or the like.

As described above, the temperature of the battery pack 100 of Example 1 during normal use is about −30 ° C. to 60 ° C. If the operating temperature range is exceeded and the battery is charged / discharged or left unattended, cell deterioration will be accelerated and the cell life will be shortened. In addition, the deterioration of the cell also varies due to the variation in the temperature of the cell in the battery pack. Normally, the cell located in the center of the battery pack receives the heat of the surrounding cells, and the temperature rises higher than that of the cell located at the edge of the battery pack. That is, the cell arranged at the center of the battery pack deteriorates faster than the cell arranged at the end.

Therefore, in the first embodiment, the PCM 130 arranged at the center of the battery pack 100 has a larger volume than the PCM 140 arranged at the ends in order to level the cell temperature and the deterioration in the battery pack 100. Therefore, the amount of heat absorption is increased.

FIG. 3 is a graph showing the time course of the cell temperature when the volume or material of the heat absorbing material (PCM) is the same, and FIG. 4 is a graph showing the time course of the cell temperature of Example 1 of the present invention. As can be seen by comparing FIGS. 3 and 4, in this embodiment, it can be seen that the temperature difference between the cell at the center and the cell at the end of the battery pack is small.

In Example 1, the volume of the heat absorbing materials 130 and 140 is changed to change the heat absorption amount, but the material may be changed to change the heat absorption amount.

FIG. 5 is a schematic view of the battery pack of the second embodiment of the present invention. In the configuration of the battery pack 200 shown in FIG. 5, in addition to the configuration of the first embodiment, the first heat conductor 150 (heat conduction plate a) provided in contact with the bottom surface of the laminated body is provided. As the heat conductive plate a, an aluminum plate or the like having a high thermal conductivity is used.

According to this configuration, the heat of each cell 110 and the heat absorbing materials 130 and 140 is further leveled by transferring the heat conductor 150.

FIG. 6 is a graph showing the time course of the cell temperature of Example 2 of the present invention. As shown in FIG. 6, it can be seen that the battery pack 200 of the present embodiment has a smaller temperature difference between cells than the battery pack 100 of the first embodiment.

FIG. 7 is a schematic view of the battery pack of the second embodiment of the present invention. In the configuration of the battery pack 300 shown in FIG. 7, in addition to the configuration of the second embodiment, a second heat conductor 160 (heat) provided between the cell 110 and the heat absorbing material 130 near the center of the battery pack It has a conduction plate b). The heat conductive plate b is brought into contact with the heat conductive plate a. As the heat conductive plate b, an aluminum plate or the like having a high thermal conductivity is used, similarly to the heat conductive plate a.

With this configuration, the heat accumulated in the heat absorbing material 130 can be efficiently released to the outside of the battery pack via the heat conductive plate b and the heat conductive plate a, further leveling the cell temperature and after EV charging. The cell temperature can be lowered quickly.

FIG. 8 is a graph showing the time course of the cell temperature of Example 2 of the present invention. As shown in FIG. 8, it can be seen that the battery pack 200 of the present embodiment has a smaller temperature difference between cells than the battery pack 100 of the first embodiment.

FIG. 9 is a schematic view of the battery pack of the third embodiment of the present invention. In addition to the configuration of the third embodiment, the configuration of the battery pack 400 shown in FIG. 9 is a third thermal conductor 170 (heat conductive plate c) arranged between the heat absorbing materials 130 in the vicinity of the central portion of the battery pack 400. ). With such a configuration, it is expected that the temperature difference of each cell can be further reduced as compared with Example 3.

In this embodiment, a conventional configuration in which a heat absorbing material is not provided (Comparative Example 1), a configuration in which a heat absorbing material having the same volume or material as the entire battery pack is provided between cells (Comparative Example 2), a configuration and implementation of Example 1. For the battery pack configured in Example 2, the temperature difference between the center and the end of the battery pack and the number of cycles were measured. The size of each cell was 55 mm in width, 100 mm in height, and 25 mm in width. In Comparative Example 2, the thickness of the heat absorbing material was set to 1 mm. In Examples 1 and 2, the thickness of the heat absorbing material 130 at the center of the battery pack was 1 mm, and the thickness of the heat absorbing material 140 at the end of the battery pack was 0.5 mm. The results are shown in Table 1.

In Comparative Example 1, the temperature of the cell at the center of the battery pack was 60 ° C, the temperature of the cell at the end of the battery pack was 50 ° C, and the temperature difference (variation within the battery pack) was 10 ° C. On the other hand, in Example 1, the temperature of the cell at the center of the battery pack was 53.75 ° C, the temperature of the cell at the end of the battery pack was 50 ° C, and the temperature difference (variation in the battery pack) was 3.75 ° C. In Example 2, the temperature of the cell in the center of the battery pack is 52.5 ° C, the temperature of the cell at the end of the battery pack is 50 ° C, and the temperature difference (variation in the battery pack) is 2.5 ° C, as compared with Example 1. The temperature difference can be further reduced.

Comparative Example 2, which has a configuration in which PCM having the same volume or material is provided in the battery pack, can reduce the temperature difference as compared with Comparative Example 1, but the effect is lower than that of Example 1 and Example 2.

The number of cycles was calculated from the cell temperature. Relationship between the temperature and the number of cycles, the literature: "Synergistic Effect of Charge / Discharge Cycle and Storage in Degradation of Lithium-ion Batteries for Mobile Phones" Published in: INTELEC 05-Twenty-Seventh International Telecommunications ConferenceDate of Conference: 18-22 Sept. It is shown in 2005.

In Example 1, the number of cycles is increased by 24.2% as compared with Comparative Example (number of cycles: 190 → 236, and 11.3% is increased as compared with Comparative Example 2 (number of cycles: 212 →). 236). In Example 2, the number of cycles is further increased as compared with Example 1.

As described above, according to the present invention, it has been shown that it is possible to provide a battery pack capable of leveling the temperature of cells in the battery pack and extending the life of the battery pack.

The present invention is not limited to the above-described examples, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

100, 200, 300, 400 ... Battery pack, 110 ... Cell (cell), 111 ... Positive terminal, 112 ... Negative terminal, 130, 140 ... Heat absorbing material (phase change material, PCM), 150 ... First heat conduction Body, 160 ... second heat conductor, 170 ... third heat conductor.

Claims (7)

A laminate in which cells and heat absorbing materials are alternately arranged and laminated is provided.
A battery pack characterized in that the volume or material of the heat absorbing material arranged at the center of the laminated body in the stacking direction is different from that of the heat absorbing material arranged at the end of the laminated body in the stacking direction. The first aspect of the present invention, wherein the heat absorbing material located at the central portion of the laminated body in the laminating direction has a larger heat absorption amount than the heat absorbing material located at the end portion of the laminated body in the laminating direction. Battery pack. The endothermic material is a material that absorbs a large amount of heat in a predetermined temperature range, and the predetermined temperature range is higher than the temperature of the environment in which the battery pack is used and higher than the maximum temperature during normal use of the battery pack. The battery pack according to claim 1, wherein the temperature is low. The battery pack according to claim 1, further comprising a first heat conductor provided in contact with the bottom surface of the laminated body. The battery pack according to claim 1, further comprising a second heat conductor provided between the cell and the endothermic material. The battery pack according to claim 1, wherein the heat absorbing material has two heat absorbing materials and a third heat conductor provided between the two heat absorbing materials. The battery pack according to claim 5 or 6, wherein the second heat conductor or the third heat conductor is provided in the central portion of the battery pack.

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