power storage device

Abstract

The present application provides a power storage device that does not cause an electrical short circuit at the positive electrode terminal and the negative electrode terminal outside the battery module even if electrolyte leaks from the laminated package of the battery module. A power storage device includes a battery module, a battery pack, a cooling flow path, and a cold medium outflow unit. The battery module seals a laminate structure body in which a positive electrode layer and a negative electrode layer sandwich a separator impregnated in electrolyte within a laminated package, and terminals that are in conduction with the positive electrode layer and the negative electrode layer, respectively, protrude to the outside. The battery pack houses the battery module. The cooling flow path circulates a non-conductive cold medium around the battery module to cool. The cold medium outflow unit causes the cold medium to flow from the cold medium flow path to the surroundings of the battery module in response to detection of leakage of electrolyte by a leakage sensor that detects leakage of electrolyte from the battery module, and mixes the cold medium in the electrolyte leaked from the battery module in the battery pack to reduce the conductivity of the electrolyte.

Description

Technical Field

[0001] The present invention relates to an energy storage device having a battery module, and more specifically, to a structure for dealing with electrolyte leakage from the battery module. Background Technology

[0002] Energy storage devices with battery modules are sometimes mounted on mobile bodies or portable devices and moved, so various structures have been proposed to cope with the impacts that may occur during movement. For example, Japanese Patent Application Publication No. 2023-177537 discloses an energy storage device having a structure that can suppress damage to the energy storage stack when subjected to an external impact. The structure comprises: an energy storage stack containing a plurality of energy storage modules arranged in a first direction; a pair of constraint plates clamping the energy storage stack in the first direction; a pair of sidewall portions facing each other in a second direction orthogonal to the first direction, with the energy storage stacks positioned between each other; and a plurality of stop members disposed between the energy storage stack and the pair of sidewall portions on both outer sides of the energy storage stack in the second direction. The pair of constraint plates each have an outer main surface located on the opposite side of the side where the energy storage stack is located. A plurality of reinforcing portions are provided on the outer main surfaces of the pair of constraint plates in a manner extending along the second direction and arranged in a third direction orthogonal to the first and second directions. The plurality of stop members are disposed at the two end sides of the corresponding reinforcing portions in the second direction, respectively, at a position overlapping with the corresponding reinforcing portions in the first direction. Summary of the Invention

[0003] As the energy storage element in an energy storage device, battery modules of secondary batteries such as lithium-ion batteries are sometimes used. Various forms of battery modules exist in these secondary battery modules. A typical liquid-state battery module has the following structure: a laminated structure is formed, consisting of a positive electrode active material layer and a negative electrode active material layer sandwiching a heat-insulating film impregnated with electrolyte. The positive electrode active material layer is coated on a current-collecting foil (positive electrode foil), which may be a metal foil, and the negative electrode active material layer is coated on a current-collecting foil (negative electrode foil), which may also be a metal foil. This laminated structure is housed and sealed within a package (laminated package) formed of laminated material. Conductive areas, connected to the positive and negative electrode foils, are formed in the areas of the package corresponding to the positive and negative electrode foils, respectively. Furthermore, current-collecting plates with positive and negative terminals for external electrical connection are attached to these conductive areas. The battery module with the positive and negative terminals is then configured and housed in an external container (battery pack).

[0004] In the energy storage device obtained by housing the battery module in the battery pack as described above, due to the insufficient mechanical strength of the battery pack and inertial forces, mechanical stress is applied to the battery module, causing damage to the laminated packaging and leakage of the internal electrolyte. If the positive and negative terminals on the outside of the battery module are immersed in the electrolyte, a short circuit will occur. Therefore, a structure that does not cause a short circuit even if the positive and negative terminals on the outside of the battery module are immersed in the electrolyte is advantageous.

[0005] Thus, the object of the present invention is that, in an energy storage device obtained by housing the liquid system battery module as described above in a battery pack, even if the electrolyte leaks from the laminated packaging of the battery module, no short circuit will occur at the positive and negative terminals on the outside of the battery module.

[0006] Regarding this point, in the energy storage devices described above, a structure for cooling the battery module is sometimes housed within the battery pack. Typically, this cooling structure forms a flow path for a cooling medium around the battery module, absorbing heat by allowing the cooling medium to flow through this path. This cooling medium is generally a non-conductive liquid; therefore, if the electrolyte leaks to the outside of the battery module, allowing the cooling medium to flow into the battery pack to dilute the leaked electrolyte can suppress short circuits even if the positive and negative terminals are immersed in the electrolyte. This understanding is applied in the present invention.

[0007] According to the present invention, the above-mentioned problem is achieved by the following energy storage device, which has a battery module, a battery pack, and a cooling structure. In the battery module, a laminated structure in which a positive electrode layer and a negative electrode layer are sandwiched between opposite membranes and an electrolyte is filled between the positive and negative electrode layers is housed and sealed within a laminated package. Terminals electrically connected to the positive and negative electrode layers protrude outwards. The battery pack is an outer container housing the battery module. The cooling structure is configured to have a cold medium flow path disposed within the battery pack around the battery module, in which a non-conductive cold medium flowing through the cold medium flow path can absorb heat from the battery module.

[0008] The energy storage device includes:

[0009] A leakage sensor for detecting leakage of the electrolyte from the battery module; and

[0010] In response to the detection of electrolyte leakage by the leakage sensor, a cold medium outflow unit is established to allow the cold medium to flow from the cold medium flow path to the area surrounding the battery module within the battery pack.

[0011] The energy storage device is configured such that when the electrolyte leaks from the battery module, the cold medium flowing out from the cold medium flow path mixes with the leaked electrolyte, thereby reducing the conductivity of the electrolyte.

[0012] In the above structure, the "battery module" is typically a module that houses and seals a liquid-system secondary battery, such as a lithium-ion secondary battery, within a laminated package. Here, the secondary battery is typically a laminated structure consisting of a positive electrode layer and a negative electrode layer formed by coating positive and negative electrode active material layers onto positive and negative electrode foils respectively, with a separator sandwiched between them and electrolyte filling the space between them. Positive and negative terminals, respectively electrically connected to the positive and negative electrode foils, are provided outside the laminated package. The positive electrode foil, positive electrode active material layer, negative electrode foil, negative electrode active material layer, separator, and electrolyte can be formed in a conventional manner. Typically, a conductive region is formed on the surface of the laminated package opposite the positive and negative electrode foils, and current collectors are attached to these conductive regions for terminals to be electrically connected to the outside, but this is not a limitation. Furthermore, the battery modules are housed within a battery pack, which serves as the outer casing. To cool the battery modules, a cooling structure is formed within the battery pack by arranging a non-conductive cooling medium flow path around the battery modules. The cooling medium can be, for example, a non-conductive liquid primarily composed of ethylene glycol containing rust inhibitors, or ATF (Automatic Transmission Fluid). Typically, the liquid temperature is around 30°C, and cooling is implemented to keep the battery temperature below 65°C to prevent battery performance degradation.

[0013] In the structure of the energy storage device that includes battery modules and a cooling structure within the battery pack as described above, in the case of this invention, a leakage sensor is further provided for detecting electrolyte leakage from the battery modules; and a cold medium outflow unit that, in response to the detection of electrolyte leakage by the leakage sensor, causes a cold medium to flow from a cold medium flow path to the vicinity of the battery modules within the battery pack. Here, the leakage sensor can be any type of sensor that detects leakage when in contact with the electrolyte. Specifically, for example, it can be composed of two metal components or wires, through which a small current flows if a conductive liquid is attached between the electrodes, thereby detecting the contact of the conductive liquid. Thus, electrolyte leakage from the battery modules is detected by detecting the contact between the leakage sensor and the electrolyte. Furthermore, if electrolyte leakage is detected by the leakage sensor, this information is transmitted to the cold medium outflow unit, and the cold medium flows from the cold medium flow path to the vicinity of the battery modules within the battery pack. The cold medium flowing from the cold medium flow path mixes with the leaked electrolyte, thereby reducing the conductivity of the electrolyte.

[0014] According to the structure of the present invention described above, if the electrolyte leaks from the battery module for some reason, the cold medium flows out from the cold medium flow path into the battery pack and mixes with the leaked electrolyte. The conductivity of the electrolyte decreases, so even if the leaked electrolyte comes into contact with the positive and negative terminals located on the outside of the laminated packaging, a short circuit can be avoided.

[0015] In the above structure, the cold medium outflow unit can be a solenoid valve disposed in the cold medium flow path. The solenoid valve is configured to allow the cold medium flowing in the cold medium flow path to flow out to the outside of the cold medium flow path in response to the detection of electrolyte leakage by the leakage sensor. Typically, the cold medium flow path can consist of an inlet flow path for introducing cold medium from outside the battery pack, a flow path (heat exchange flow path) for allowing the cold medium to flow along the outer surface of the battery module in a manner that exchanges heat with the surface of the battery module, and an outlet flow path for subsequently discharging the cold medium out of the battery pack. The solenoid valve is disposed in the inlet flow path or the outlet flow path. Typically, it can be configured to allow the cold medium to flow in the heat exchange flow path, and to switch the flow of the cold medium to flow out from the inlet flow path or the outlet flow path to the vicinity of the battery module when electrolyte leaks from the battery module.

[0016] Furthermore, in the above structure, the leakage sensor can be installed in various locations. For example, the leakage sensor can be installed along a portion of the bottom surface of the battery pack or along the entire circumference of the battery module. Since electrolyte leaking from the battery module first accumulates on the bottom surface of the battery pack, it is expected that the leakage can be detected more reliably regardless of where the electrolyte leaks from the battery module. Alternatively, the leakage sensor can be installed on the side of the battery module. Electrolyte leakage from the battery module tends to occur at the sealing weld of the laminated packaging located on the side of the battery module; therefore, by installing the leakage sensor on the side of the battery module, it is expected that electrolyte leakage can be detected more quickly. Furthermore, on the lower surface of the battery module, electrolyte leakage may occur due to damage to the laminated packaging, etc. Therefore, to detect this situation, the leakage sensor can also be installed in the liquid accumulation area formed on the bottom surface of the battery pack on the lower side of the battery module.

[0017] Thus, according to the structure of the present invention, in an energy storage device obtained by housing a liquid-system battery module in a battery pack, even if the electrolyte leaks from the laminated packaging of the battery module, the electrolyte is diluted by a cooling medium, and its conductivity decreases. Therefore, even if the leaked liquid comes into contact with the positive and negative terminals on the outside of the battery module, a short circuit can be avoided. The structure of the present invention can be used in energy storage devices that utilize various liquid-system battery modules.

[0018] Other objects and advantages of the present invention will become more apparent from the following description of preferred embodiments of the invention. Attached Figure Description

[0019] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, wherein the same reference numerals denote the same elements.

[0020] Figure 1A This is a schematic cross-sectional view of one embodiment of the energy storage device.

[0021] Figure 1B This is a schematic top view of one embodiment of the energy storage device.

[0022] Figure 1C This is a schematic top view of another embodiment of the energy storage device.

[0023] Figure 1D This is a schematic top view of another embodiment of the energy storage device.

[0024] Figure 2A This is a schematic cross-sectional view of one embodiment of the energy storage device.

[0025] Figure 2B This is a schematic cross-sectional view of one embodiment of the energy storage device.

[0026] Figure 2C This is a schematic cross-sectional view of one embodiment of the energy storage device.

[0027] Figure 2D This is a schematic cross-sectional view of one embodiment of the energy storage device.

[0028] Figure 3A This is a schematic cross-sectional view of another embodiment of the energy storage device.

[0029] Figure 3B This is a schematic top view of the adhesive layer beneath the current collector.

[0030] Figure 4 This is a schematic top view of another embodiment of the energy storage device.

[0031] Figure 5A This is a schematic cross-sectional view of the energy storage device using this embodiment, and a diagram illustrating the operation when electrolyte leaks from the battery module.

[0032] Figure 5B This is a schematic cross-sectional view of the energy storage device using this embodiment, and a diagram illustrating the operation when electrolyte leaks from the battery module.

[0033] Figure 5C This is a schematic cross-sectional view of the energy storage device using this embodiment, and a diagram illustrating the operation when electrolyte leaks from the battery module. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and some preferred embodiments. In the drawings, the same reference numerals denote the same parts.

[0035] Basic structure of energy storage devices

[0036] Reference Figure 1A , Figure 1BThe structure of this embodiment can be applied to an energy storage device 1. The structure of the energy storage device 1 is as follows: a battery module 3, which houses and seals a liquid-system secondary battery such as a lithium-ion secondary battery within a laminated package, is disposed on the bottom surface inside a barrel-shaped battery pack 2, which serves as an outer container. More specifically, the battery module 3 can have the following structure: In a conventional manner, a laminated structure is housed and sealed within a laminated package. The laminated structure is formed by coating a positive electrode active material layer and a negative electrode active material layer onto a positive electrode foil and a negative electrode foil, respectively, with a separator sandwiched between them and an electrolyte filled between them. The positive electrode layer, negative electrode layer, separator, and electrolyte can be modulated using materials commonly used in the art. When sealing a laminated structure with a laminated package, it can typically be in the following state: a sheet-shaped laminated structure is sandwiched between an upper portion formed by a thin box protruding upwards and a lower portion formed by a thin box protruding downwards, housed within the upper and lower box-shaped portions. The edges of the upper and lower portions are bonded together to seal the laminated structure in a way that prevents electrolyte leakage. The laminated material forming the laminated package can be a thin film material commonly used in the art, such as applying resin layers to both sides of aluminum foil. Furthermore, in the central region of the laminated package, which forms the upper and lower surfaces of the battery module 3, conductive foil is exposed. For these upper and lower conductive foils, a current collector 5 having terminals 5a for external electrical connection is adhered via a conductive adhesive layer 4. Furthermore, in the stacked structure within the battery module 3, multiple battery cells consisting of a positive electrode layer, a separator, and a negative electrode layer can be stacked in series. In this case, the voltage monitoring terminal 3b, used to monitor the voltage of each cell, can be provided separately from the terminal 5a. The battery module 3, to which the current collector 5 is attached, is fixed to the support platform 2a located on the bottom surface of the battery pack 2 by a further adhesive layer 4 applied to the lower surface of the current collector 5. Additionally, a cooling plate 6 for cooling the battery module is disposed above the upper current collector 5. A cooling medium flow path can be formed within the cooling plate 6. The cooling medium is fed into the cooling medium flow path from the inlet flow path 6b, flows within the cooling plate 6, absorbs the heat emitted by the battery module 3, and is discharged to the outside from the outlet flow path 6a. The cooling medium can be, for example, a non-conductive liquid with ethylene glycol as its main component containing rust inhibitors, or it can be ATF (Automatic Transmission Fluid). Typically, the liquid temperature is around 30°C. To prevent battery performance degradation, cooling is implemented to keep the battery temperature below 65°C. Terminal 5a, mounted on the current collector 5, is connected to an external wire (not shown) through which the battery is charged and discharged.

[0037] Structure when electrolyte leaks

[0038] In the battery module 3 of the energy storage device 1 described above, the laminated structure constituting the battery is sealed within a laminated package. Therefore, the electrolyte should not leak out of the battery module 3. However, when the energy storage device 1 is subjected to mechanical impact or other forces that cause the welded portion 3a of the laminated package of the battery module 3 to detach or other parts to break, the electrolyte may leak into the battery module 3. If the electrolyte comes into contact with the terminal 5a, a short circuit will occur. Therefore, in this embodiment, a structure is provided to prevent such short circuits caused by electrolyte leakage.

[0039] Specifically, such as Figure 1A , Figure 1B As shown, a leakage sensor 7 for detecting contact with electrolyte is provided on the outside of the battery module 3; and a solenoid valve (cold medium outflow unit) 8 for causing the cold medium flowing in the cooling plate to flow out to the surrounding area of ​​the battery module 3 in response to the detection of contact with electrolyte by the leakage sensor 7.

[0040] The leakage sensor 7 can be a sensor that detects contact with the electrolyte in any form. Typically, for example, as illustrated in the Summary of the Invention section, it can be composed of two metal components or wires, through which a small current flows if a conductive liquid is attached between the electrodes, thereby enabling the detection of the contact of the conductive liquid.

[0041] The leakage sensor 7 can be placed at various locations around the battery module 3. In one embodiment, such as... Figure 1A , Figure 1B As shown, it can be configured on the bottom surface of the battery pack 2. As mentioned above, leaked electrolyte accumulates on the bottom surface of the battery pack 2; therefore, by configuring the leakage sensor 7 on the bottom surface of the battery pack 2, electrolyte leakage can be detected more reliably. Furthermore, the configuration location in the battery module 3 can be near areas where electrolyte is prone to leakage, such as near a corner of the battery module 3. Moreover, as... Figure 1C In that case, the leakage sensor 7 can be configured at multiple locations such as the four corners of the battery module 3, or it can also be configured as follows: Figure 1D Such a configuration covers almost the entire circumference of battery module 3. Placing the leakage sensor 7 only near areas where electrolyte is prone to leakage can keep costs low. On the other hand, by placing the leakage sensor 7 around almost the entire circumference of battery module 3, electrolyte leakage can be detected more reliably.

[0042] In addition, such as Figure 2A , Figure 2B As shown, the leakage sensor 7 can be disposed at an appropriate location below or above the welded portion 3a in the side of the battery module 3, or, as... Figure 2C , Figure 2DAs shown, the leakage sensor 7 can also be disposed around the entire circumference of the welded portion 3a on the side of the battery module 3, below or above it. In the battery module 3, electrolyte tends to leak from the vicinity of the welded portion 3a; therefore, by disposing of the leakage sensor 7 on the side of the battery module 3, electrolyte leakage can be detected more quickly.

[0043] Furthermore, since electrolyte leakage from the lower surface of the battery module 3 is also possible, multiple through holes 5s can be perforated in the current collector 5 on the lower surface of the battery module 3 to detect this situation. A liquid accumulation portion 4s is formed on the adhesive layer 4 below the current collector 5 on the lower surface, and a leakage sensor 7 is disposed in this liquid accumulation portion 4s. According to this structure, if electrolyte leaks from the lower surface of the battery module 3, it accumulates in the liquid accumulation portion 4s through the through holes 5s in the current collector 5 on the lower surface, and thus, upon contact with the leakage sensor 7, the electrolyte leakage can be detected.

[0044] Refer again Figure 1A , Figure 1B If electrolyte leaks from battery module 3 and comes into contact with the aforementioned leakage sensor 7, detecting the leakage, this information is sent to control unit 10 in any manner. Control unit 10 then sends a control command to solenoid valve 8, which is located in the outlet flow path 6a or inlet flow path 6b of the cooling medium. Control unit 10 can be any form of electronic circuit device or circuit device capable of receiving signals from sensor 7 and sending control commands to solenoid valve 8. Furthermore, if solenoid valve 8 receives a control command, it causes the cooling medium flowing in outlet flow path 6a or inlet flow path 6b to flow around battery module 3 within battery pack 2. Moreover, solenoid valve 8 may only be located in outlet flow path 6a, but... Figure 4 As shown, it can also be set in the inlet flow path 6b, thereby enabling the cold medium to flow out to the surrounding area of ​​the battery module 3 more quickly.

[0045] During the process from electrolyte leakage to electrolyte dilution by the cooling medium, firstly, as... Figure 5A As shown, if electrolyte Ls leaks from battery module 3, it comes into contact with leakage sensor 7, and this information is transmitted to control unit 10. Control unit 10 then sends a control command to solenoid valve 8, such as... Figure 5B As shown, solenoid valve 8 releases the cooling medium cl into battery pack 2. Thus, as... Figure 5C As shown, the leaked electrolyte mixes with the cooling medium, which is a non-conductive liquid. Therefore, the conductivity of the mixture is greatly reduced, which can prevent electrical short circuits between terminals.

[0046] Thus, according to this embodiment, in the energy storage device obtained by housing the liquid battery module as described above in the battery pack, when the electrolyte leaks from the laminated packaging of the battery module, the leaked electrolyte is diluted by a cooling medium, so that the mixture becomes non-conductive, and even if the positive and negative terminals on the outside of the battery module come into contact with the liquid, no electrical short circuit can be generated.

[0047] The above description is made in connection with the embodiments of the present invention, but many modifications and changes can be easily made by those skilled in the art. The present invention is not limited to the embodiments illustrated above, and can obviously be applied to various devices without departing from the concept of the present invention.

Claims

1. An energy storage device comprising a battery module, a battery pack, and a cooling structure. In the battery module, a laminated structure consisting of a positive electrode layer and a negative electrode layer sandwiching a separator, with electrolyte filling the space between the positive and negative electrode layers, is housed and sealed within a laminated package. Terminals electrically connected to the positive and negative electrode layers protrude outwards. The battery pack is an external container for housing the battery module. The cooling structure is configured to have a cold medium flow path disposed within the battery pack and surrounding the battery module, wherein a non-conductive cold medium flowing through the cold medium flow path can absorb heat from the battery module. The energy storage device includes: A leakage sensor for detecting leakage of the electrolyte from the battery module; and In response to the detection of electrolyte leakage by the leakage sensor, a cold medium outflow unit is established to allow the cold medium to flow from the cold medium flow path to the area surrounding the battery module within the battery pack. The energy storage device is configured such that when the electrolyte leaks from the battery module, the cold medium flowing out from the cold medium flow path mixes with the leaked electrolyte, thereby reducing the conductivity of the electrolyte.

2. The energy storage device according to claim 1, wherein the cold medium outflow unit is a solenoid valve disposed in the cold medium flow path, the solenoid valve being configured to, in response to the detection of electrolyte leakage by the leakage sensor, cause the cold medium flowing in the cold medium flow path to flow out to the outside of the cold medium flow path.

3. The energy storage device according to claim 1, wherein the leakage sensor is disposed on the bottom surface of the battery pack.

4. The energy storage device according to claim 1, wherein the leakage sensor is disposed on the side of the battery module.

5. The energy storage device according to claim 1, wherein the leakage sensor is disposed within the liquid accumulation section, and the liquid accumulation section is formed on the bottom surface of the battery pack on the lower side of the battery module.

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