Battery pack

Abstract

To provide a battery pack that can improve safety in the event of thermal runaway of battery cells. [Solution] The battery pack comprises a housing, a first battery cell, at least one second battery cell, an insulating section, and a gas path. The first battery cell is housed in the housing. The second battery cell is housed in the housing, has a full charge capacity smaller than that of the first battery cell, and has an opening / closing section that releases internal pressure to the outside. The insulating section is disposed between the first battery cell and the second battery cell. The gas path connects the outside of the housing to the opening / closing section.

Description

Technical Field

[0001] The present invention relates to a battery pack.

Background Art

[0002] Conventionally, a secondary battery module (hereinafter referred to as a module) in which a plurality of secondary battery cells (hereinafter referred to as battery cells) are arranged and housed in a module case and electrically connected by a conductive member is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the battery cells in a secondary battery module are repeatedly charged, lithium may precipitate inside the battery cells, break through the separator, and cause internal short circuit due to contact between the positive and negative electrodes. When an internal short circuit occurs, the temperature of the battery cell rises and thermal runaway occurs, and the heat due to the thermal runaway may also be transmitted to other adjacent battery cells, leading to a possible thermal chain reaction where other battery cells experience thermal runaway. Also, since there are multiple battery cells housed in the module, it is difficult to predict which battery cell will experience thermal runaway first.

[0005]

[0006] ​One of the objectives of the present invention is to provide a battery pack that can improve safety in the event of thermal runaway of a battery cell. [Means for solving the problem]

[0007] To achieve the above objective, the battery pack according to the present invention comprises a housing, a first battery cell, at least one second battery cell, a heat insulating section, and a gas passage. The first battery cell is housed in the housing. The second battery cell is housed in the housing, has a full charge capacity smaller than that of the first battery cell, and has an opening / closing section that releases internal pressure to the outside. The heat insulating section is disposed between the first battery cell and the second battery cell. The gas passage connects the outside of the housing to the opening / closing section. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a battery pack that can improve safety in the event of thermal runaway of a battery cell. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the configuration of a battery pack according to an embodiment. [Figure 2] Figure 2 illustrates the relationship between the full charge capacity of a battery cell during overcharging and the time it takes for thermal runaway to occur. [Figure 3] Figure 3 illustrates the relationship between the full charge capacity of a battery cell and the time it takes for thermal runaway to occur during repeated charging and discharging. [Modes for carrying out the invention]

[0010] [Embodiment] The embodiment of the battery pack 1 will be described in detail below with reference to the attached drawings. The configuration of the embodiment described below, as well as the operation and results (effects) brought about by said configuration, are merely examples and are not limited to the contents described below. In this specification, ordinal numbers are used only to distinguish parts and materials and do not indicate order or priority.

[0011] The outline and structure of the battery pack 1 according to this embodiment will be described below. Figure 1 is a diagram showing an example of the configuration of the battery pack 1 according to this embodiment. The battery pack 1 according to this embodiment is For example, it may be installed in a vehicle and generate power for driving the vehicle's motor. The battery pack 1 may supply power to devices other than vehicles.

[0012] The battery pack 1 comprises a housing 11, a plurality of first battery cells 12, second battery cells 13, an insulating section 15, and a gas passage 16. The housing 11 is formed in the shape of a roughly rectangular parallelepiped box. The housing 11 houses a plurality of battery cells. In this embodiment, the battery cells housed in the housing 11 are distinguished as a plurality of first battery cells 12 and second battery cells 13.

[0013] Multiple first battery cells 12 are housed in a casing 11. Each of the multiple first battery cells 12 has an opening / closing section 121 that releases internal air pressure to the outside. Multiple adjacent first battery cells 12 constitute a battery module 12a. In this embodiment, the battery pack 1 has three battery modules 12a. The number of battery modules 12a is not limited to this; it may be two or fewer, or four or more. Also, each of the multiple first battery cells 12 is a secondary battery.

[0014] The second battery cell 13 is housed in the casing 11 and has a full charge capacity smaller than that of the first battery cell 12. The second battery cell 13 has an opening / closing section 131 that releases internal air pressure to the outside. In this embodiment, there is one second battery cell 13, but the number of second battery cells 13 is not limited to this and may be two or more. Also, the second battery cell 13 is a rechargeable battery.

[0015] The first battery cell 12 is, for example, a new battery cell. The second battery cell 13 is, for example, a battery cell whose full charge capacity has been reduced due to overcharging or repeated charging and discharging of the first battery cell 12.

[0016] In each battery module 12a, each of the plurality of first battery cells 12 is connected in series to generate DC power. In each battery module 12a, each of the plurality of first battery cells 12 may be connected in parallel.

[0017] In the present embodiment, the plurality of first battery cells 12 and second battery cells 13 are rectangular battery cells, and the opening / closing portions 121 and 131 are safety valves. The plurality of first battery cells 12 and second battery cells 13 are not limited to rectangular battery cells, and may be, for example, cylindrical or laminated battery cells.

[0018] In any of the above-described types of battery cells, the plurality of first battery cells 12 and second battery cells 13 are provided with portions corresponding to the opening / closing portions 121 and 131, and have a structure that can release the internal air pressure caused by the high-temperature gas to the outside from the portion.

[0019] Here, referring to FIG. 2, the relationship between the full charge capacity of the battery cell and the time when thermal runaway occurs during overcharging will be described. FIG. 2 is a diagram for explaining the relationship between the full charge capacity of the battery cell and the time when thermal runaway occurs during overcharging.

[0020] In FIG. 2, during overcharging of the battery pack 1, it is shown that the battery cell (second battery cell 13) with a small full charge capacity has a surface temperature that rises faster than that of a new battery cell and a battery cell (first battery cell 12) with a large full charge capacity, and thermal runaway occurs.

[0021] Generally, when the full charge capacity of a battery cell decreases due to overcharging or the like, lithium is likely to precipitate inside the battery cell, and thermal runaway is likely to occur relatively early due to an internal short circuit.

[0022] Since the second battery cell 13 has a smaller full charge capacity than the first battery cell 12, when the battery pack 1 is overcharged, lithium deposits first inside the second battery cell 13, causing an internal short circuit, which raises the surface temperature and leads to thermal runaway. Therefore, when the battery pack 1 is overcharged, detecting the thermal runaway in the second battery cell 13 at the moment it occurs can suppress the occurrence of a heat chain reaction in the first battery cell 12.

[0023] Next, referring to Figure 3, we will explain the relationship between the full charge capacity of a battery cell and the time it takes for thermal runaway to occur during repeated charging and discharging. Figure 3 is a diagram illustrating the relationship between the full charge capacity of a battery cell and the time it takes for thermal runaway to occur during repeated charging and discharging.

[0024] Figure 3 shows that during repeated charging and discharging of the battery pack 1, the battery cell with a small full charge capacity (second battery cell 13) experiences a faster surface temperature rise and thermal runaway than a new battery cell and a battery cell with a large full charge capacity (first battery cell 12).

[0025] Generally, as battery cells lose their full charge capacity due to repeated charging and discharging, lithium is more likely to deposit inside the battery cell, making it easier for thermal runaway to occur relatively quickly due to internal short circuits.

[0026] Since the second battery cell 13 has a smaller full charge capacity than the first battery cell 12, during repeated charging and discharging of the battery pack 1, lithium deposits first inside the second battery cell 13, causing an internal short circuit, which in turn causes the surface temperature to rise and leads to thermal runaway. Therefore, during repeated charging and discharging of the battery pack 1, by detecting thermal runaway when it occurs in the second battery cell 13, it is possible to suppress the occurrence of a heat chain reaction in the first battery cell 12.

[0027] In other words, the battery pack 1 intentionally includes a second battery cell 13 among the multiple first battery cells 12, which has a smaller full charge capacity than the first battery cells 12. This allows the battery pack 1 to identify the first battery cell (the second battery cell 13) that experiences thermal runaway during overcharging or repeated charge-discharge cycles, thereby detecting the thermal runaway and suppressing the occurrence of a heat chain reaction in the first battery cells 12.

[0028] Returning to Figure 1, inside the housing 11, the first battery cell 12 and the second battery cell 13 are spaced apart from each other. More specifically, a space S is provided between the second battery cell 13 and the first battery cell 12, which is relatively close to the second battery cell 13.

[0029] Generally, in a secondary battery module, if the temperature of a battery cell rises due to repeated charging and discharging, causing thermal runaway, other battery cells adjacent to the cell experiencing thermal runaway are heated by the radiant heat from that cell. The greater the distance between the cell experiencing thermal runaway and the adjacent battery cells, the less heat is generated by radiant heat.

[0030] In this embodiment, if thermal runaway occurs in the second battery cell 13, the space S provided between the second battery cell 13 and the first battery cell 12, which is relatively close to the second battery cell 13, reduces the thermal impact on the first battery cell 12 due to radiant heat from the second battery cell 13, thereby suppressing the heating of the first battery cell 12 by radiant heat.

[0031] In other words, the battery pack 1 can suppress the generation of a heat chain from the second battery cell 13 to the first battery cell 12.

[0032] The heat insulating section 15 is positioned between the first battery cell 12 and the second battery cell 13. More specifically, the heat insulating section 15 is formed in the shape of a roughly rectangular box, and the second battery cell 13 is covered by the heat insulating section 15. The heat insulating section 15 is made of, for example, an insulating material, and suppresses the transfer of radiant heat generated when the second battery cell 13 experiences thermal runaway to the first battery cell 12.

[0033] Therefore, if the second battery cell 13 experiences thermal runaway and becomes overheated, the first battery cell 12 adjacent to the second battery cell 13 where the thermal runaway occurred is less affected by the radiant heat from the thermal runaway of the second battery cell 13.

[0034] In other words, the battery pack 1 can suppress the generation of a heat chain from the second battery cell 13 to the first battery cell 12.

[0035] The gas path 16 connects the outside of the housing 11 to the opening / closing section 131. More specifically, the gas path 16 connects the outside of the housing 11 to the inside of the heat-insulating section 15. The gas path 16 is formed, for example, in a hollow, substantially cylindrical shape. The gas path 16 releases the pressure (atmospheric pressure) caused by the high-temperature gas generated from the second battery cell 13 when thermal runaway occurs to the outside of the housing 11.

[0036] Generally, when the temperature of a battery cell rises and thermal runaway occurs, high-temperature gas is generated inside the battery cell and is discharged through safety valves or other mechanisms provided in the battery cell. The high-temperature gas discharged from the safety valves or other mechanisms of the battery cell spreads around the battery cell where thermal runaway occurred and transfers heat to other battery cells arranged around it. This heat transfer by the high-temperature gas may cause a heat chain reaction to occur from the battery cell where thermal runaway occurred to other battery cells.

[0037] On the other hand, in the above-described configuration, if the second battery cell 13 experiences thermal runaway and becomes overheated, the high-temperature gas generated from the second battery cell 13 is discharged from the opening / closing section 121 of the second battery cell 13, fills the inside of the heat-insulating section 15, and is released to the outside of the housing 11 via the gas path 16.

[0038] Therefore, the first battery cell 12 housed inside the casing 11 is less affected by the high-temperature gas generated from the second battery cell 13. In other words, the battery pack 1 can suppress the heat chain from the high-temperature gas generated from the second battery cell 13 to the first battery cell 12.

[0039] Furthermore, the second battery cell 13 is positioned closer to the edge of the housing 11 than the adjacent first battery cell 12. Also, a space S exists between the second battery cell 13 and the adjacent first battery cell 12. With this configuration, if the second battery cell 13 overheats, the radiant heat emitted from the second battery cell 13 will decrease in heat as it travels through the space S, making it difficult for it to reach the first battery cell 12.

[0040] Therefore, if the second battery cell 13 experiences thermal runaway and becomes overheated, the first battery cell 12 adjacent to the second battery cell 13 experiencing thermal runaway is less affected by the radiant heat from the second battery cell 13's thermal runaway. In other words, the battery pack 1 can suppress the generation of a heat chain from the second battery cell 13 to the first battery cell 12.

[0041] Furthermore, the gas path 16 connecting the outside of the housing 11 and the inside of the insulation section 15 follows the shortest path between the two. Therefore, the gas path 16 can be made shorter as it approaches the ends of the housing 11. By making the length of the gas path 16 shorter, the manufacturing cost of the battery pack 1 can be reduced.

[0042] In other words, by positioning the second battery cell 13 closer to the edge of the housing 11 than the adjacent first battery cell 12, the battery pack 1 can shorten the gas path 16 compared to when the second battery cell 13 is closer to the adjacent first battery cell 12, and consequently, manufacturing costs can be reduced.

[0043] [Differentiation] The heat insulating section 15 is disposed between the first battery cell 12 and the second battery cell 13, and does not necessarily have to cover the second battery cell 13. Even in this case, the heat insulating section 15 suppresses the transfer of radiant heat generated from the second battery cell 13 to the first battery cell 12 in the event of thermal runaway of the second battery cell 13.

[0044] Therefore, if the second battery cell 13 experiences thermal runaway and becomes overheated, the first battery cell 12 is less affected by the heat caused by the thermal runaway of the second battery cell 13. In other words, the battery pack 1 can suppress the generation of a heat chain from the second battery cell 13 to the first battery cell 12.

[0045] In the above embodiment, the battery pack 1 comprises a housing 11, a first battery cell 12, at least one second battery cell 13, a heat insulating section 15, and a gas passage 16. The first battery cell 12 is housed in the housing 11. The second battery cell 13 is housed in the housing 11, has a full charge capacity smaller than that of the first battery cell 12, and has an opening / closing section 131 that releases internal pressure to the outside. The heat insulating section 15 is disposed between the first battery cell 12 and the second battery cell 13. The gas passage 16 connects the outside of the housing 11 to the opening / closing section 131.

[0046] Generally, battery cells whose full charge capacity has decreased due to overcharging or repeated charging and discharging are prone to thermal runaway relatively quickly. In the above configuration, the battery pack 1 comprises a first battery cell 12 and a second battery cell 13 whose full charge capacity is smaller than that of the first battery cell 12 and which is prone to thermal runaway relatively quickly. The battery pack 1 also comprises an insulating section 15 disposed between the first battery cell 12 and the second battery cell 13, and a gas path 16 that connects the outside of the housing 11 to the opening / closing section 131.

[0047] In the above configuration, during overcharging or repeated charging and discharging, thermal runaway first occurs in the second battery cell 13, which has a full charge capacity smaller than that of the first battery cell 12. Here, the first battery cell 12 is protected from the effects of radiant heat generated from the second battery cell 13, which has become hot due to thermal runaway, by the heat insulating section 15 disposed between it and the second battery cell 13.

[0048] Furthermore, the high-temperature gas generated from the second battery cell 13, which has become overheated due to thermal runaway, is released to the outside of the housing 11 through the gas path 16 via the opening / closing section 131 of the second battery cell 13. As a result, the first battery cell 12, which is housed inside the housing 11, is less affected by the high-temperature gas generated from the second battery cell 13.

[0049] In other words, if the second battery cell 13, which is relatively prone to thermal runaway, experiences thermal runaway and becomes hot, the first battery cell 12, which is not experiencing thermal runaway, will be less affected by the heat from the second battery cell 13's thermal runaway, thus suppressing the occurrence of a heat chain from the second battery cell 13 to the first battery cell 12. Consequently, the battery pack 1 can improve safety in the event of thermal runaway in the battery cells.

[0050] Furthermore, in this embodiment, the first battery cell 12 and the second battery cell 13 are spaced apart from each other.

[0051] In the above configuration, the first battery cell 12 and the second battery cell 13 are spaced apart from each other. Therefore, even if the second battery cell 13 experiences thermal runaway and becomes extremely hot, the radiant heat emitted from the second battery cell 13 is unlikely to be transferred to the first battery cell 12.

[0052] In other words, if the second battery cell 13, which is relatively prone to thermal runaway, experiences thermal runaway and becomes hot, the first battery cell 12, which is not experiencing thermal runaway, will be less affected by the heat from the second battery cell 13's thermal runaway, thus suppressing the occurrence of a heat chain from the second battery cell 13 to the first battery cell 12. Consequently, the battery pack 1 can improve safety in the event of thermal runaway in the battery cells.

[0053] In this embodiment, the second battery cell 13 is covered by the heat insulating section 15. The gas passage 16 connects the outside of the housing 11 to the inside of the heat insulating section 15.

[0054] Generally, when a battery cell's temperature rises and thermal runaway occurs, high-temperature gas is released from safety valves or other mechanisms within the battery cell. This released high-temperature gas spreads around the cell experiencing thermal runaway and transfers heat to other battery cells located around it. This heat transfer by the high-temperature gas can potentially cause a heat chain reaction, spreading from the cell experiencing thermal runaway to other cells.

[0055] On the other hand, in the above-described configuration, the second battery cell 13 is covered by the heat insulating section 15. Therefore, if the second battery cell 13 experiences thermal runaway and becomes hot, the radiant heat emitted from the second battery cell 13 is less likely to be transferred to the first battery cell 12.

[0056] Furthermore, the high-temperature gas generated from the second battery cell 13, which has become overheated due to thermal runaway, is discharged from the opening / closing section 131 of the second battery cell 13, fills the inside of the heat-insulating section 15, and is released to the outside of the housing 11 via the gas path 16. As a result, the first battery cell 12 housed inside the housing 11 is less affected by the high-temperature gas generated from the second battery cell 13.

[0057] In other words, if the second battery cell 13, which is relatively prone to thermal runaway, experiences thermal runaway and becomes hot, the first battery cell 12, which is not experiencing thermal runaway, will be less affected by the heat from the second battery cell 13's thermal runaway, thus suppressing the occurrence of a heat chain from the second battery cell 13 to the first battery cell 12. Consequently, the battery pack 1 can improve safety in the event of thermal runaway in the battery cells.

[0058] Furthermore, in this embodiment, the second battery cell 13 is positioned closer to the end of the housing 11 than the adjacent first battery cell 12.

[0059] In the above configuration, the second battery cell 13 is positioned closer to the edge of the housing 11 than the adjacent first battery cell 12. Therefore, if the second battery cell 13 overheats and becomes hot, the radiant heat emitted from the second battery cell 13 is less likely to be transferred to the first battery cell 12, which is further away from the edge of the housing 11 than the second battery cell 13.

[0060] Furthermore, the high-temperature gas generated from the second battery cell 13, which has become overheated due to thermal runaway, is less likely to transfer heat to the first battery cell 12, which is further away from the second battery cell 13 than the edge of the housing 11.

[0061] In other words, if the second battery cell 13, which is relatively prone to thermal runaway, experiences thermal runaway and becomes hot, the first battery cell 12, which is not experiencing thermal runaway, will be less affected by the heat from the second battery cell 13's thermal runaway, thus suppressing the occurrence of a heat chain from the second battery cell 13 to the first battery cell 12. Consequently, the battery pack 1 can improve safety in the event of thermal runaway in the battery cells.

[0062] Although embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Moreover, this embodiment is included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0063] 1 Battery pack 11 cabinets 12. First battery cell 12a battery module 13. Second battery cell 15. Insulation section 16 Gas routes 121, 131 Opening / Closing Section S space

Claims

1. The casing and A first battery cell housed in the aforementioned housing, A second battery cell, housed in the aforementioned casing, having a full charge capacity smaller than that of the first battery cell, and having an opening / closing section for releasing internal air pressure to the outside, A heat insulating section disposed between the first battery cell and the second battery cell, A gas path connecting the outside of the housing and the opening / closing part, Equipped with, Battery pack.

2. The first battery cell and the second battery cell are spaced apart from each other. The battery pack according to claim 1.

3. The second battery cell is covered by the heat insulating portion. The gas path connects the outside of the housing and the inside of the heat-insulating section. The battery pack according to claim 1 or 2.

4. The second battery cell is positioned closer to the end of the housing than the adjacent first battery cell. The battery pack according to claim 3.

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