JP2019133778A - Battery pack and battery system including the same - Google Patents

Abstract

To provide a battery pack in which breakdown of laminate film during normal time is prevented without providing a complex mechanism, and a determination can be made whether or not the laminate film is broken by a sharp part.SOLUTION: A battery pack includes a secondary battery 50 covered with a laminate film, a sharp part 80 for releasing internal pressure of the secondary battery 50, by breaking the laminate film upon expansion of the secondary battery 50, and a liquid leakage detection sensor 90 for detecting leakage of electrolyte. An outer case 20 receiving the secondary battery 50 has irregular shape constituted of the inner walls of the protrusions 22A and recesses 22B, and this irregular shape functions as a holding mechanism for separating the laminate film and the sharp part 80 when the secondary battery 50 is not expanded. With such an arrangement, breakdown of the laminate film can be prevented during normal time. Furthermore, since the liquid leakage detection sensor 90 is provided, a determination can be made whether or not the laminate film is broken by the sharp part 80.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a battery pack and a battery system including the same, and more particularly to a battery pack using a secondary battery covered with a laminate film and a battery system including the same.

  As a battery pack using a secondary battery such as a lithium ion battery, a battery pack including a secondary battery covered with a laminate film and an outer case for housing the secondary battery is widely known. When the temperature rises, the secondary battery covered with the laminate film increases in internal pressure, which may cause the entire battery to expand. However, since the laminate film itself cannot be provided with a gas valve, if the internal pressure becomes abnormally high, the main body device using the outer case or the battery pack may be damaged due to the expansion of the laminate film.

  In order to solve this problem, Patent Documents 1 and 2 propose a method of releasing the internal pressure of the secondary battery by breaking the laminate film with a sharp portion when the laminate film expands.

JP2012-74300A Japanese Patent No. 4686833

  However, in the battery pack described in Patent Document 1, since the laminate film and the sharp portion are always in a contactable relationship, the laminate film may be unintentionally damaged by vibration or impact. On the other hand, in the battery pack described in Patent Document 2, damage to the laminate film at normal times is prevented by covering the tip of the sharp portion with a shutter. However, the battery pack described in Patent Document 2 has a problem that the configuration is complicated because a drive mechanism and a control mechanism for opening and closing the shutter are required.

  Moreover, since the battery packs described in Patent Documents 1 and 2 cannot determine whether or not the laminate film has actually been broken by the sharp part, it has been difficult to ensure sufficient reliability.

  Accordingly, the present invention provides a battery pack capable of preventing damage to the laminate film during normal times without providing a complicated mechanism and determining whether or not the laminate film is torn by the sharp part, and a battery system including the battery pack. The purpose is to provide.

  The battery pack according to the present invention releases the internal pressure of the secondary battery by breaking the laminate film when the secondary battery is expanded, and the secondary battery in which the electrolytic solution is sealed and at least partially covered with the laminate film. A sharp portion, a holding mechanism that separates the laminate film and the sharp portion when the secondary battery is not expanded, and a liquid leakage detection sensor that detects leakage of the electrolytic solution are provided.

  According to the present invention, since the laminate film and the sharp part are separated by the holding mechanism at the time of non-expansion, it is possible to prevent the laminate film from being damaged in a normal state without providing a complicated mechanism. In addition, since the liquid leakage detection sensor that detects the leakage of the electrolytic solution is provided, it can be determined whether or not the laminate film has been torn by the sharp part. Thereby, it becomes possible to provide a highly reliable battery pack.

  The battery pack according to the present invention further includes an exterior case that accommodates the secondary battery, and the inner wall of the exterior case is provided with a recess that functions as a holding mechanism by accommodating the sharp portion, and the depth of the recess is The height of the sharp part may be larger. According to this, even when the secondary battery expands slightly with normal charging / discharging, the sharp part does not come into contact with the laminate film. It becomes possible to prevent.

  In the present invention, the exterior case includes first and second top plates that overlap each other when viewed from the thickness direction, and the first top plate includes the first convex portion and the first height that are different from each other in the thickness direction. The second top plate has a second convex portion and a second concave portion having different heights in the thickness direction, and the first convex portion is a second convex portion as viewed from the thickness direction. The second convex portion may overlap the concave portion, and the second convex portion may overlap the first concave portion when viewed from the thickness direction. According to this, since the top plate of the exterior case has a concavo-convex shape, heat dissipation and mechanical strength are enhanced by increasing the surface area. In addition, even when a plurality of battery packs are stacked, the protrusions do not interfere with each other, so that a plurality of storage batteries can be stacked at a high density.

  In the present invention, the sharp part and the liquid leakage detection sensor may be arranged on the inner wall of the convex part of the second top plate. According to this, since the step between the convex part and the concave part of the second top plate functions as a holding mechanism as it is, it is not necessary to provide a holding mechanism separately.

  In the present invention, the liquid leakage detection sensor may be disposed in the lower part in the direction of gravity in the outer case. According to this, it is possible to reliably detect leakage of the electrolyte regardless of the orientation of the battery pack during actual use.

  In the present invention, the liquid leakage detection sensor may include two or more electrodes arranged near the tip of the sharp part. According to this, it becomes possible to immediately detect the electrolyte solution leaking from the portion pierced by the sharp portion.

  In the present invention, the secondary battery may have a sealing portion in which a laminate film is sealed, and the liquid leakage detection sensor may be disposed in the vicinity of the sealing portion. According to this, it is possible to detect leakage of the electrolytic solution caused by peeling of the sealing portion.

  The battery pack according to the present invention may include a plurality of liquid leakage detection sensors, and the plurality of liquid leakage detection sensors may be connected in parallel. According to this, it becomes possible to detect the leakage of the electrolyte more reliably.

  In the present invention, the secondary battery may be a lithium ion secondary battery. According to this, it becomes possible to obtain a high battery capacity.

  A battery system according to the present invention includes a plurality of the above-described battery packs, and the plurality of battery packs are connected in series or in parallel. According to the present invention, a larger voltage or current can be supplied.

  Thus, according to the present invention, there is provided a battery pack capable of preventing damage to the laminate film during normal time without providing a complicated mechanism and determining whether the laminate film has been torn by the sharp part. It is possible to provide a battery system provided.

FIG. 1 is a schematic perspective view showing an appearance of a battery pack 10 according to a preferred embodiment of the present invention. FIG. 2 is an exploded perspective view of the exterior case 20. FIG. 3 is a perspective view showing the secondary battery 50 accommodated in the outer case 20. FIG. 4 is a schematic exploded perspective view of the secondary battery 50. FIG. 5 is a schematic cross-sectional view along the line AA shown in FIG. FIG. 6 is an xz cross-sectional view of the battery pack 10 when not expanded. FIG. 7 is an xz sectional view of the battery pack 10 during expansion. FIG. 8 is a schematic perspective view showing an example of the layout of the detection electrodes 91 and 92. FIG. 9 is a partial cross-sectional view showing an example in which the detection electrodes 91 and 92 are formed on the surface of the cover 81. FIG. 10 is an xz cross-sectional view of the battery pack 10 according to an example in which another liquid leakage detection sensor 90 is added. FIG. 11 is a plan cross-sectional view of the battery pack 10 according to an example in which the leak detection sensor 90 is disposed in the vicinity of the sealing portion 54a. It is a circuit diagram which shows the example which connected the some leak detection sensor 90 in parallel. FIG. 13 is a schematic perspective view showing a state in which a plurality of battery packs 10 are stacked. FIG. 14 is an xz sectional view showing a state in which a plurality of battery packs 10 are stacked.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing an appearance of a battery pack 10 according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the battery pack 10 according to the present embodiment includes an outer case 20, a positive terminal 31, a negative terminal 32, detection terminals 33 and 34, and a gas valve 40. Accommodates a secondary battery 50 such as a lithium ion battery described later. The outer case 20 is preferably made of a material having high thermal conductivity, for example, a metal such as aluminum (Al).

  The exterior case 20 has a substantially box shape with the z direction as the thickness direction, and the first top plate 21 and the second top plate 22 constituting the xy plane have an uneven shape. In the battery pack 10 according to the present embodiment, since the top plate of the outer case 20 has such a concavo-convex shape, the surface area increases as compared with the case where the surface of the top plate is flat. Thereby, not only the heat dissipation is improved, but also the mechanical strength is improved. Although not particularly limited, the side surfaces (xz plane and yz plane) do not have an uneven shape. The positive electrode terminal 31, the negative electrode terminal 32, the detection terminals 33 and 34, and the gas valve 40 described above are formed on the xz plane.

  In the present embodiment, the first top plate 21 is provided with two convex portions 21A and two concave portions 21B that extend in the y direction, and the second top plate 22 has two convex portions that extend in the y direction. 22A and two recesses 22B are provided. The convex portion refers to a portion protruding in the z direction, and the concave portion refers to a portion recessed in the z direction. Therefore, the height of the convex portion and the concave portion is different from each other in the z direction. As shown in FIG. 1, the convex portion 21A overlaps with the concave portion 22B when viewed from the z direction, and the convex portion 22A overlaps with the concave portion 21B when viewed from the z direction. In the present embodiment, the height in the z direction of the step formed by the convex portion 21A and the concave portion 21B is equal to the height in the z direction of the step formed by the convex portion 22A and the concave portion 22B. Further, the width W1 of the convex portions 21A and 22A in the x direction is designed to be substantially the same as or slightly narrower than the width W2 of the concave portions 21B and 22B in the x direction.

  FIG. 2 is an exploded perspective view of the outer case 20, and FIG. 3 is a perspective view showing the secondary battery 50 accommodated in the outer case 20.

  As shown in FIG. 2, the outer case 20 includes a sealing plate 23 that forms an xz plane, and the inside is sealed by welding the sealing plate 23 to the main body of the outer case 20. In the manufacturing process of the battery pack 10, first, the main body of the exterior case 20 is prepared, and after the secondary battery 50 shown in FIG. 3 is accommodated therein, the sealing plate 23 is welded. When attaching the sealing plate 23, the positive electrode tab 51 provided on the secondary battery 50 is connected to the positive terminal 31 of the sealing plate 23, and the negative electrode tab 52 provided on the secondary battery 50 is connected to the sealing plate 23. Connected to the negative terminal 32. As a result, the secondary battery 50 can be charged / discharged via the positive electrode terminal 31 and the negative electrode terminal 32. The interior of the outer case 20 is basically sealed, but when the internal pressure increases to a predetermined value or more, the internal pressure is lowered by automatically opening the gas valve 40.

  4 is a schematic exploded perspective view of the secondary battery 50, and FIG. 5 is a schematic cross-sectional view taken along the line AA shown in FIG.

  The secondary battery 50 is, for example, a lithium ion secondary battery, and includes a laminate 53 and a bag-like laminate film 54 that accommodates the laminate 53 together with an electrolyte (not shown) as shown in FIG. A positive electrode tab 51 and a negative electrode tab 52 are led out from the laminate film 54. The stacked body 53 has a structure in which a plurality of positive electrodes 71 and a plurality of negative electrodes 72 are stacked via a separator 73. The separator 73 is an insulating film in which minute holes that transmit lithium ions contained in the electrolytic solution are formed.

The positive electrode 71 has a structure in which a positive electrode active material is formed on the surface of the positive electrode current collector, and a part of the positive electrode current collector is led out from the laminate film 54 to constitute the positive electrode tab 51. The positive electrode tab 51 may be another metal body connected to the positive electrode current collector. The positive electrode current collector is made of, for example, aluminum (Al), and the positive electrode active material is made of a material capable of inserting and extracting lithium ions, such as LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ .

  The negative electrode 72 has a structure in which a negative electrode current collector is formed on the surface of the negative electrode current collector, and a part of the negative electrode current collector is led out from the laminate film 54 to constitute the negative electrode tab 52. The negative electrode tab 52 may be another metal body connected to the negative electrode current collector. The negative electrode current collector is made of, for example, copper (Cu), and the negative electrode active material is made of, for example, graphite.

  The laminate 53 having such a structure is accommodated in a bag-like laminate film 54 together with the electrolytic solution. The laminate film 54 has a structure in which an insulating film is laminated on both surfaces of a metal film, and the laminate 53 and the electrolytic solution are sealed by processing into a bag shape. As a method of processing the laminate film 54 into a bag shape, one end of the laminate film 54 is folded into two, and then the three overlapping sides are heated to thereby end the upper insulating film and the lower insulating film. The end portions of the upper insulating film and the lower insulating film may be bonded to each other by heating four sides after the two laminated films 54 are stacked. It doesn't matter. Reference numeral B shown in FIG. 4 indicates a region overlapping the laminated body 53, and by heating three or four sides on the outside, the upper and lower insulating films are bonded to form a laminated film 54 sealed in a bag shape. The

  As shown in FIG. 2, the inner wall of the exterior case 20 has a shape reflecting the uneven shape of the top plates 21 and 22. That is, the height in the z direction is enlarged at the portions where the convex portions 21A and 22A are formed, and the height in the z direction is reduced at the portions where the concave portions 21B and 22B are formed. On the other hand, the xy plane of the secondary battery 50 is substantially flat as shown in FIG. For this reason, as shown in FIG. 6 which is an xz sectional view of the battery pack 10, when the secondary battery 50 is accommodated in the exterior case 20, a space 60 is formed between the secondary battery 50 and the convex portions 21A and 22A. Is done. The space 60 can also be formed between the secondary battery 50 and the recesses 21B and 22B, but even in this case, the space 60 formed between the secondary battery 50 and the projections 21A and 22A The interval in the z direction is wider than the interval in the z direction of the space 60 formed between the secondary battery 50 and the recesses 21B and 22B.

  The convex portions 21A and 22A constitute a concave portion when viewed from the inside of the outer case 20, and the concave portions 21B and 22B constitute a convex portion when viewed from the inside of the outer case 20. And as shown in FIG. 6, the sharp part 80 which has a sharp front-end | tip is arrange | positioned at the recessed part comprised by the inner wall of 22 A of convex parts. The tip of the sharp part 80 faces the laminate film 54 constituting the secondary battery 50, but the height h of the sharp part 80 is lower than the depth H of the concave part of the inner wall constituting the convex part 22A. In a normal time when the battery 50 is not expanded, the tip of the sharp portion 80 does not come into contact with the laminate film 54. Further, when the secondary battery 50 is charged / discharged, the secondary battery 50 may slightly expand along with this, but the difference between the depth H of the concave portion and the height h of the sharp portion 80 is to some extent. If secured, the tip of the sharp portion 80 does not come into contact with the laminate film 54 due to expansion of the secondary battery 50 caused by normal charge / discharge. The inner walls of the secondary battery 50 and the outer case 20 may or may not be fixed to each other. When fixing both, as shown in FIG. 6, it is preferable to fix the secondary battery 50 to the inner wall of the recessed part 21B which overlaps with the sharp part 80 in plan view using an adhesive 55 or the like. According to this, it becomes possible to ensure a sufficient distance between the tip of the sharp part 80 and the laminate film 54 in a normal state.

  And if the internal pressure of the secondary battery 50 increases abnormally due to the temperature rise, the secondary battery 50 expands. The space 60 acts as a margin for a certain degree of expansion, but when the secondary battery 50 further expands, the laminate film 54 comes into contact with the tip of the sharp portion 80 as shown in FIG. As a result, the laminate film 54 is torn and a hole is formed, and gas is released from this, so that the internal pressure is released. The released gas is released into the atmosphere through a gas valve 40 provided in the outer case 20.

  Thus, in this embodiment, since the sharp part 80 is provided in the inner wall part of the exterior case 20, the internal pressure of the secondary battery 50 can be obtained by breaking the laminate film 54 when the secondary battery 50 is expanded. Can be released. In addition, since the uneven shape of the top plate 22 functions as a holding mechanism that separates the laminate film 54 and the sharp portion 80 when the secondary battery 50 is not expanded, it does not expand without providing a complicated mechanism such as a shutter. It is possible to prevent the laminate film 54 from being damaged.

  Furthermore, the battery pack 10 according to the present embodiment includes a liquid leakage detection sensor 90 that detects leakage of the electrolytic solution. The liquid leakage detection sensor 90 is a sensor that determines the presence or absence of liquid leakage based on the impedance between the pair of detection electrodes 91 and 92. As shown in FIG. Provided. For this reason, when the laminate film 54 is torn by the sharp portion 80, it can be immediately determined whether or not the electrolyte has leaked.

  FIG. 8 is a schematic perspective view showing an example of the layout of the detection electrodes 91 and 92.

  In the example shown in FIG. 8, the detection electrodes 91 and 92 are formed on the surface of the sharp portion 80 having a conical shape, and both are insulated by a predetermined gap G. For this reason, in normal times, the impedance between the detection electrode 91 and the detection electrode 92 is sufficiently high. However, when the laminate film 54 is broken by the sharp portion 80 and the electrolytic solution leaks from here, the detection electrode 91 and the detection electrode 92 are conducted through the electrolytic solution. Thereby, since the impedance between the detection electrode 91 and the detection electrode 92 is lowered, it is possible to detect leakage of the electrolytic solution by a detection circuit (not shown). The detection circuit may be disposed inside the outer case 20, or the detection electrodes 91 and 92 may be connected to the detection terminals 33 and 34, respectively, and connected to an external detection circuit.

  Further, if tin or an alloy containing this is plated on at least a portion of the detection electrodes 91 and 92 that constitutes the gap G, a part of the plating is caused by migration when the electrolytic solution adheres to the detection electrodes 91 and 92. Moving to the gap G, the detection electrodes 91 and 92 are easily short-circuited. For this reason, if the detection electrodes 91 and 92 are plated with tin or an alloy containing the same, leakage of the electrolyte can be detected by plating migration even when the electrolyte does not drop into the gap G. It becomes possible.

  A part of the sharp part 80 may be constituted by the outer case 20 itself. Here, when the exterior case 20 is made of a metal material, as shown in FIG. 9, a part of the exterior case 20 is deformed inward to form a conical sharp portion 80, and It is preferable to cover the sharp portion 80 with a cover 81 made of an insulating material such as resin. If the detection electrodes 91 and 92 are formed on the surface of the cover 81, it is possible to prevent a short circuit between the detection electrodes 91 and 92 and the metal outer case 20.

  Further, as shown in FIG. 10, another liquid leakage detection sensor 90 including detection electrodes 91 and 92 may be disposed on the inner wall portion of the convex portion 21 </ b> A of the upper top plate 21. As described above, if the liquid leakage detection sensors 90 are arranged on both inner walls of the top plates 21 and 22, respectively, the top plate 21 is used in a state where it is located on the lower side in the direction of gravity during actual use. However, since the leaked electrolytic solution reaches the liquid leakage detection sensor 90 provided on the top plate 21, the leakage of the electrolytic solution can be detected more reliably.

  Furthermore, as shown in FIG. 11, when the sealing part 54a by thermocompression bonding exists on the three sides of the laminate film 54, one or two or more leak detection sensors 90 are arranged in the vicinity of the sealing part 54a. It doesn't matter. Since the sealing portion 54a of the laminate film 54 may cause electrolyte leakage due to peeling of the crimped portion, if the leakage detection sensor 90 is disposed in the vicinity of the sealing portion 54a, the sealing portion 54a is separated from the sealing portion 54a. It becomes possible to quickly detect the leakage.

  When a plurality of leak detection sensors 90 are arranged, a plurality of leak detection sensors 90 may be connected in parallel as shown in FIG. In the example shown in FIG. 12, the detection electrodes 91 and 92 of each leakage detection sensor 90 are connected to the wirings 91L and 92L, respectively. According to this, if the impedance of any one of the plurality of leak detection sensors 90 decreases, the impedance between the wiring 91L and the wiring 92L decreases. Can be detected.

  13 and 14 are views showing a state in which a plurality of battery packs 10 are stacked, FIG. 13 is a schematic perspective view, and FIG. 14 is an xz sectional view.

  As shown in FIGS. 13 and 14, when a plurality of battery packs 10 are stacked in the z direction, the convex portion 21A of the battery pack 10 located in the lower stage is fitted into the concave portion 22B of the battery pack 10 located in the upper stage, The convex part 22A of the battery pack 10 located in the upper stage is fitted into the concave part 21B of the battery pack 10 located in the lower stage. That is, since the convex portions and the concave portions are fitted without interference between the convex portions provided on the upper and lower battery packs 10, a plurality of battery packs 10 can be stacked with high density in the z direction. In addition, since the outer casings 20 constituting the upper and lower battery packs 10 come into contact with each other in a wider range, even if some battery packs 10 are overheated, the outer casings 20 of the other battery packs 10 It is possible to effectively dissipate heat.

  In the example shown in FIGS. 13 and 14, a plurality of battery packs 10 are arranged not only in the z direction but also in the x direction, so that from a large number (12 in the example shown in FIG. 13) of battery packs 10. A battery system is configured. The plurality of battery packs 10 constituting this battery system are connected in parallel or in series as necessary, thereby ensuring a necessary battery capacity or voltage. In this embodiment, since the yz surface of the battery pack 10 is flat, the exterior cases 20 of the battery packs 10 adjacent to each other in the x direction can be brought into contact in a wide range.

  As described above, in the battery pack 10 according to the present embodiment, the sharp portion 80 is provided inside the outer case 20, and the uneven shape of the top plate 22 functions as a holding mechanism. It plays the role which separates the laminate film 54 and the sharp part 80 at the time of non-expansion. Thereby, the laminate film 54 can be reliably broken by the sharp portion 80 when the secondary battery 50 is expanded while preventing the unintended damage of the laminate film 54 due to vibration or impact. Moreover, in the battery pack 10 according to the present embodiment, when the laminate film 54 is broken by the sharp portion 80 and the electrolyte solution leaks, the leak detection sensor 90 can detect this, so that the electrolyte solution leaks. It is also possible to detect electrically.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, the case where the present invention is applied to a lithium ion secondary battery has been described as an example. However, the subject of the present invention is not limited to a lithium ion secondary battery, and other types of battery packs are used. It is also possible to apply to.

  Moreover, in the said embodiment, although the whole secondary battery 50 is covered with the laminate film 54, when only a part is covered with the laminate film 54, facing the part which the laminate film 54 exposes, The sharp part 80 may be disposed.

DESCRIPTION OF SYMBOLS 10 Battery pack 20 Exterior case 21 1st top plate 22 2nd top plate 21A, 22A Convex part 21B, 22B Concave 23 Sealing plate 31 Positive electrode terminal 32 Negative electrode terminal 33, 34 Detection terminal 40 Gas valve 50 Secondary battery 51 Positive electrode tab 52 Negative electrode tab 53 Laminate 54 Laminate film 54a Sealing portion 55 Adhesive 60 Space 71 Positive electrode 72 Negative electrode 73 Separator 80 Sharp portion 81 Cover 90 Liquid leakage detection sensors 91 and 92 Detection electrodes 91L and 92L Wiring G Gap

Claims (10)

A secondary battery in which an electrolyte is enclosed and at least a part of which is covered with a laminate film;
A sharp part that releases the internal pressure of the secondary battery by breaking the laminate film during expansion of the secondary battery,
A holding mechanism for separating the laminate film and the sharp part when the secondary battery is not expanded;
A battery pack, comprising: a leak detection sensor that detects leakage of the electrolyte. An outer case for housing the secondary battery;
The inner wall of the outer case is provided with a recess that functions as the holding mechanism by accommodating the sharp part,
The battery pack according to claim 1, wherein a depth of the recess is greater than a height of the sharp part. The exterior case has first and second top plates that overlap each other when viewed from the thickness direction,
The first top plate has a first convex portion and a first concave portion having different heights in the thickness direction,
The second top plate has a second convex portion and a second concave portion having different heights in the thickness direction,
The first convex portion overlaps with the second concave portion when viewed from the thickness direction,
2. The battery pack according to claim 1, wherein the second convex portion overlaps the first concave portion when viewed from the thickness direction.   The battery pack according to claim 3, wherein the sharp part and the liquid leakage detection sensor are arranged on an inner wall of the convex part of the second top plate.   5. The battery pack according to claim 2, wherein the leak detection sensor is disposed at a lower portion in the direction of gravity in the exterior case. 6.   6. The battery pack according to claim 1, wherein the liquid leakage detection sensor includes two or more electrodes disposed in the vicinity of a tip of the sharp part. The secondary battery has a sealing portion in which the laminate film is sealed,
The battery pack according to claim 1, wherein the leak sensor is disposed in the vicinity of the sealing portion.   The battery pack according to any one of claims 1 to 7, wherein a plurality of the leakage detection sensors are provided, and the plurality of leakage detection sensors are connected in parallel.   The battery pack according to claim 1, wherein the secondary battery is a lithium ion secondary battery.   A battery system comprising a plurality of battery packs according to any one of claims 1 to 9, wherein the plurality of battery packs are connected in series or in parallel.

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