JP7639800B2 - Energy Storage Devices - Google Patents

Description

The present invention relates to an electricity storage device.

In power storage devices such as lithium ion secondary batteries, it has been proposed to apply a confining pressure to the power storage cells in order to prevent the cells from shifting out of position and ensure output performance (for example, Patent Document 1).

JP 2017-103083 A

However, when an unexpected event such as overcharging or a short circuit occurs, gas may be generated inside the storage cell due to the decomposition of the electrolyte. As in Patent Document 1, when a restraining pressure is applied to the storage cell, the gas pressure inside the storage cell may concentrate, causing damage to the exterior body, which may result in the gas being released outside the storage cell.

In consideration of the above, the present invention aims to provide an energy storage device that can improve safety when an abnormality in an energy storage cell is detected or predicted.

The energy storage device described in claim 1 comprises an energy storage cell formed in a plate shape, a cell restraint section that applies a restraint pressure to the energy storage cell along a plate thickness direction and is deformable when an abnormality in the energy storage cell is detected or predicted, thereby reducing the restraint pressure, and a restraint control section that detects at least one of temperature, voltage, and water ingress in the energy storage cell, and deforms the cell restraint section to reduce the restraint pressure when an abnormality in the energy storage cell is detected or predicted from the detection result .

In the energy storage device described in claim 1, the cell restraining portion applies a restraining pressure to the plate-shaped energy storage cell in the plate thickness direction. This prevents the energy storage cell from shifting position and stabilizes the expansion and contraction of the energy storage cell due to charging and discharging, thereby ensuring output performance. Here, the restraining control portion detects at least one of the temperature, voltage, and water ingress of the energy storage cell, and when an abnormality in the energy storage cell is detected or predicted from the detection result , the cell restraining portion is deformed to reduce the restraining pressure of the energy storage cell. This suppresses concentration of gas pressure in the energy storage cell and prevents damage to the exterior body, thereby improving safety.

The power storage device according to a second aspect of the present invention has the configuration according to the first aspect, wherein the power storage cell includes an all-solid-state battery element in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated, and an exterior body made of a laminate film that covers the all-solid-state battery element.

In the all-solid-state battery storage device described in claim 2, the storage cell constitutes an all-solid-state battery element having a solid electrolyte layer. It is known that storage cells constituting such all-solid-state battery elements are easier to thin than conventional lithium ion secondary batteries using liquid electrolytes, and contribute to miniaturization of devices. Here, by forming the exterior body from a laminate film, when gas is generated in the storage cell, the exterior body can be flexibly deformed in response to the device package. This makes it easy to disperse gas pressure and effectively suppresses concentration of gas pressure. As a result, it is possible to improve safety while miniaturizing the storage device.

The energy storage device described in claim 3 has a stack of a plurality of the energy storage cells stacked in the plate thickness direction in the configuration described in claim 1 or claim 2, and the cell restraint section applies the restraint pressure to the stack in the stacking direction.

The all-solid-state battery energy storage device described in claim 3 has a stack in which multiple energy storage cells are stacked in the plate thickness direction, and the cell restraint section applies a restraining pressure to the stack in the stacking direction. Therefore, when an abnormality in the energy storage cell is detected or predicted, the restraining pressure on the stack is reduced to provide a gap between the electrodes of each energy storage cell. This suppresses heat transfer between the electrodes and improves safety.

The energy storage device of claim 4 has the configuration of claim 1, wherein the cell restraint portion has a first restraint portion arranged on one side of the storage cell in the plate thickness direction, a second restraint portion arranged on the other side of the storage cell in the plate thickness direction, and a connecting portion that connects the first restraint portion and the second restraint portion and deforms when an actuator is driven to displace the first restraint portion relative to the second restraint portion in the plate thickness direction, and when an abnormality in the storage cell is detected or predicted, the restraint control portion deforms the connecting portion so as to displace the first restraint portion in a direction away from the second restraint portion, thereby reducing the restraint pressure.

In the all-solid-state battery energy storage device according to claim 4, the energy storage cell can be restrained from both sides in the plate thickness direction by the first restraining portion and the second restraining portion. When an abnormality in the energy storage cell is detected or predicted , the restraint control portion drives the actuator to deform the connecting portion, thereby separating the first restraint portion from the second restraint portion and reducing the restraint pressure. With this configuration, it is possible to reliably reduce the restraint pressure when an abnormality occurs.

As described above, the energy storage device according to the present invention has the effect of improving safety when detecting or predicting an abnormality in an energy storage cell.

1 is a schematic diagram showing a vehicle including an electricity storage device according to an embodiment of the present invention. FIG. 2 is a perspective view that illustrates a schematic diagram of the electricity storage device illustrated in FIG. 1 . 3 is a vertical cross-sectional view showing a stacked structure of the power storage cell shown in FIG. 2. 5A and 5B are schematic diagrams for explaining the operation of an actuator, in which (A) shows a constrained state of a storage cell, and (B) shows a state in which the constraint of the storage cell is released. FIG. 2 is a block diagram of a restraint pressure control ECU. 4 is a flowchart showing an example of a restraining pressure control process executed by a restraining pressure control ECU. 1A and 1B are schematic diagrams showing a cell restraint section for a modified example of this embodiment, in which (A) shows a restrained state of a storage cell, and (B) shows a state in which the restraint of the storage cell is released.

Below, an electric storage device 20 according to one embodiment of the present invention will be described with reference to Figures 1 to 6.

The vehicle 10 shown in FIG. 1 includes an electricity storage device 20, a restraining pressure control ECU 40, and a drive source 50. The vehicle 10 includes an electric motor (not shown) as the drive source 50 for traveling, and the electric motor is driven by electricity stored in the electricity storage device 20.

As shown in FIG. 2, the energy storage device 20 has a laminate 24 that constitutes an energy storage module and a housing 22 in which the laminate 24 is housed.

The stack 24 includes a plurality of storage cells 26 formed in a plate shape, end plates 28 arranged at the ends of the stack 24, and sheet-shaped insulating members 29 arranged between the storage cells 26 and between the storage cells 26 and the end plates 28.

The multiple storage cells 26 are stacked in the plate thickness direction. Two end plates 28 are arranged at one end and the other end in the stacking direction.

In addition, when the stack 24 is mounted, a cell restraint section 60 is attached to apply a predetermined restraining pressure to the stack 24 along the stacking direction (i.e., the plate thickness direction of the storage cells 26).

As shown in FIG. 3, each storage cell 26 is a lithium ion secondary battery, and the positive electrode layer 30P, the solid electrolyte layer 33, and the negative electrode layer 30N are stacked to form the all-solid-state battery element 30. Note that FIG. 3 shows the stacking direction H1 of each layer of the all-solid-state battery element 30 and the surface direction W1 of each layer.

The positive electrode layer 30P is composed of a positive electrode collector layer 31 having a positive electrode collector tab 31A and a positive electrode active material layer 32. The negative electrode layer 30N is composed of a negative electrode active material layer 34 and a negative electrode collector layer 35 having a negative electrode collector tab 35A.

The material of the positive electrode collector layer 31 may be, for example, but is not limited to, SUS, aluminum, copper, nickel, iron, titanium, or carbon.

The positive electrode active material layer 32 includes at least a positive electrode active material, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or lithium manganese oxide (LiMn ₂ O ₄ ), but is not limited thereto.

The solid electrolyte layer 33 contains at least a solid electrolyte. The material of the solid electrolyte is not particularly limited, and any material that can be used as a solid electrolyte in an all-solid-state battery can be used.

The negative electrode active material layer 34 contains lithium titanate (LTO), a binder that bonds the LTO particles together, and a conductive additive.

The material used for the negative electrode collector layer 35 is, for example, the material used for the positive electrode collector layer 31.

The storage cell 26 is constituted of one all-solid-state battery element 30 by stacking a positive electrode collector layer 31, a positive electrode active material layer 32, a solid electrolyte layer 33, a negative electrode active material layer 34, and a negative electrode collector layer 35 in this order. Note that FIG. 3 illustrates a configuration in which one storage cell 26 includes one all-solid-state battery element 30, but this is not limited thereto, and one storage cell may be constituted of a stack of multiple all-solid-state battery elements 30. In this case, the positive electrode collector layer 31 and the negative electrode collector layer 35 may be shared between adjacent all-solid-state battery elements, and multiple elements may be stacked in the reverse order of stacking the layers.

The all-solid-state battery element 30 is covered with an exterior body 38. The exterior body 38 can be made of a laminate film or a rectangular can, but in one example of this embodiment, it is made of an exterior body made of a laminate film. When the exterior body 38 is made of a laminate film, it is preferable in that when gas is generated in the all-solid-state battery element 30, the exterior body 38 can be flexibly deformed to disperse the gas pressure.

A laminate film is made of resin-laminated metal foil that has a resin film on one or both sides of the metal foil. For example, resin-laminated metal foil has a resin film laminated on one side of the metal foil to impart mechanical strength, and a resin film with heat sealability laminated on the opposite side.

The metal foil in the resin-laminated metal foil may be, for example, a foil made of aluminum, an aluminum alloy, or the like. The resin film for maintaining mechanical strength may be, for example, a film made of polyester, nylon, or the like. The resin film having heat sealability may be, for example, a film made of polyolefin, or more specifically, a film made of polyethylene, polypropylene, or the like.

The exterior body 38 is made by placing two laminate films facing each other with the heat-sealable resin film on the inside, and placing the all-solid-state battery element 30 in the gap between them. The four outer edges of the laminate film are sealed by heat sealing to form a bag-shaped exterior body. As a result, the all-solid-state battery element 30 is housed inside the exterior body 38 made of the laminate film.

In the energy storage device 20, multiple storage cells 26 are stacked in the plate thickness direction with a sheet-like insulating member 29 sandwiched between them. The stacked multiple storage cells 26 are then sandwiched between two end plates 28 on both sides in the stacking direction to form a stack 24.

A cell restraining section 60 is attached to the stack 24. The cell restraining section 60 is attached so as to clamp the stack 24 from both sides in the stacking direction, and applies a predetermined restraining pressure to the stack 24 from both sides in the stacking direction. This allows the stacked multiple storage cells 26 to be integrated, and a predetermined restraining pressure is applied to each storage cell 26 along the plate thickness direction.

As shown in Figures 4(A) and 4(B), the cell restraint portion 60 includes a first restraint portion 62, a second restraint portion 64, and a connecting portion 66.

The first restraining portion 62 is disposed on one side of the stacking direction of the laminate 24. The second restraining portion 64 is disposed opposite the first restraining portion 62 on the other side of the stacking direction of the laminate 24. The connecting portion 66 extends in the stacking direction and connects the first restraining portion 62 and the second restraining portion 64. That is, the laminate 24 is inserted into and clamped in the contained space formed by the first restraining portion 62, the second restraining portion 64, and the connecting portion 66.

The connecting portion 66 has a first connecting body 661 extending from an end of the first restraining portion 62 and a second connecting body 662 extending from an end of the second restraining portion 64. The first connecting body 661 and the second connecting body 662 are connected in the stacking direction via the actuator 54.

The actuator 54 has a motor 56 as a drive source provided in the second connecting body 662, and a shaft 58 connected to the output shaft of the motor 56. The shaft 58 has a male thread provided on the outer periphery that screws into a screw hole in the first connecting body 661, and the shaft 58 rotates when driven by the motor 56, displacing the first connecting body 661 in the axial direction relative to the second connecting body 662. In other words, the connecting portion 66 is deformed by the drive of the actuator 54 so as to extend in the stacking direction of the stack 24. As a result, the first restraining portion 62 moves relative to the second restraining portion 64 in the stacking direction, and the restraining pressure applied to the stack 24 can be changed.

The driving of the actuator 54 is controlled by the restraining pressure control ECU 40 .
The configuration of the restraint pressure control ECU 40 will now be described.

As shown in FIG. 5, the restraint pressure control ECU 40 includes, as hardware components, a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a storage 44, a communication interface (I/F) 45, and an input/output interface (I/F) 46. The CPU 41, ROM 42, RAM 43, storage 44, communication I/F 45, and input/output I/F 46 are connected to each other via an internal bus 47 so as to be able to communicate with each other.

The CPU 41 is a central processing unit that executes various programs and controls each part. The CPU 41 reads the programs from the ROM 42 or the storage 44, and executes the programs using the RAM 43 as a working area. The CPU 41 controls each component and performs various calculation processes according to the programs recorded in the ROM 42 or the storage 44.

The ROM 42 stores various programs and data. The RAM 43 temporarily stores programs or data as a working area. The storage 44 is composed of a storage device such as a HDD (Hard Disk Drive) or SSD (Solid State Drive), and stores various programs and data.

The communication I/F 45 is an interface that allows the restraint pressure control ECU 40 to communicate with other devices.

The input/output I/F 46 is an interface for communicating with each device mounted on the vehicle 10. In this embodiment, the abnormality detection sensor 52 and the actuator 54 are connected to the input/output I/F 46.

The abnormality detection sensor 52 is a sensor for detecting or predicting an abnormality in the power storage cell 26, and may be configured as a single sensor or a sensor group combining a plurality of sensors. The abnormality detection sensor 52 is configured to include at least one of a temperature sensor, a voltage sensor, and a water ingress detection sensor, for example. The temperature sensor may be provided so as to be able to detect the temperature of a single power storage cell 26, or may be provided so as to detect the temperature inside the housing 22 of the power storage device 20. The water ingress detection sensor is provided so as to detect, for example, the presence or absence of water ingress into the housing 22. These sensors can detect an abnormality or prediction of an abnormality in the power storage cell 26 based on a fire occurring inside or outside the housing 22, the occurrence of water ingress into the housing 22, an abnormal temperature rise of the power storage cell 26, overcharging of the power storage cell 26, or the like .

The restraint pressure control ECU 40 also has, as its functional components, an acquisition unit 410 and a restraint pressure control unit 420. The functions of the acquisition unit 410 and the restraint pressure control unit 420 are realized by the CPU 41 reading and executing a program stored in the ROM 42.

The acquisition unit 410 has the function of acquiring the detection value of the anomaly detection sensor 52.

The restraining pressure control unit 420 has a function of driving the actuator 54 when an abnormality in the storage cell 26 is detected or predicted based on the detection value acquired by the acquisition unit 410. Specifically, the restraining pressure control unit 420 drives the actuator 54 to displace the first restraining portion 62 from the restraining position shown in FIG. 4(A) to the released restraint position shown in FIG. 4(B). At the released restraint position, the first restraining portion 62 is displaced in a direction away from the second restraining portion 64 along the stacking direction, relative to the restraining position. This reduces the restraining pressure applied to the stack 24.

(Operation)
Next, an example of the restraint pressure control process executed by the restraint pressure control ECU 40 will be described with reference to the flowchart shown in Fig. 6. This restraint pressure control process is started, for example, when the ignition switch of the vehicle is turned ON, and is performed by the CPU 41 reading a program from the RO 42 or the storage 44, expanding it in the RAM 43, and executing it.

As shown in FIG. 6, in step S101, the CPU 41 acquires sensor information. Specifically, the CPU 41 acquires the detection value detected by the anomaly detection sensor 52 through the function of the acquisition unit 410.

In step S102, the CPU 41 determines whether the acquired detection value is an abnormal value. Whether the detection value is abnormal is determined based on a preset threshold. If the CPU 41 determines that an abnormal value has been detected, the process proceeds to step S103. On the other hand, if the CPU 41 determines that an abnormal value has not been detected, the process returns to step S101.

In step S103, the CPU 41 releases the energy storage cell 26. Specifically, the actuator 54 is driven based on the function of the restraining pressure control unit 420. By driving the actuator 54, the first restraining portion 62 of the cell restraining unit 60 is displaced in a direction away from the second restraining portion 64, reducing the restraining pressure on the stack 24 and thus the energy storage cell 26, and then the restraining pressure control process is terminated.

By reducing the confining pressure, gaps are provided between the stacked storage cells 26. This suppresses heat transfer between the electrodes of the storage cells 26 (positive electrode current collector tab 31A or negative electrode current collector tab 35A) in the event of an abnormal temperature rise in the storage cells 26 due to a short circuit caused by flooding or a fire. Furthermore, in the event that flammable gas or the like is generated inside the storage cells 26, the exterior body 38 of the storage cells 26 becomes deformable, suppressing the concentration of gas pressure.

As described above, in the energy storage device 20 according to this embodiment, the cell restraining portion 60 applies a restraining pressure to the plate-shaped energy storage cell 26 along the plate thickness direction. This prevents the energy storage cell 26 from shifting out of position and stabilizes the expansion and contraction of the energy storage cell 26 due to charging and discharging, thereby ensuring output performance. Here, when an abnormality in the energy storage cell 26 is detected or predicted, the cell restraining portion 60 deforms to reduce the restraining pressure of the energy storage cell 26. This suppresses the concentration of gas pressure inside the energy storage cell 26 and prevents damage to the exterior body 38, improving safety.

In the energy storage device 20, the storage cell 26 constitutes an all-solid-state battery element 30 having a solid electrolyte layer 33. The storage cell 26 constituting such an all-solid-state battery element 30 is known to be easier to thin than conventional lithium ion secondary batteries using liquid electrolytes, and can contribute to the miniaturization of the device. Here, by forming the exterior body 38 from a laminate film, when gas is generated in the storage cell 26, the exterior body 38 can be flexibly deformed in response to the device package. This makes it easy to disperse gas pressure, and can effectively suppress concentration of gas pressure. As a result, the safety of the energy storage device 20 can be improved while miniaturizing the device.

The energy storage device 20 has a stack 24 including a plurality of energy storage cells 26 stacked in the plate thickness direction, and the cell restraint section 60 applies a restraining pressure to the stack 24 along the stacking direction. Therefore, when an abnormality in the energy storage cell 26 is detected or predicted, a gap is provided between the electrodes of each energy storage cell 26 by reducing the restraining pressure on the stack 24. This suppresses heat transfer between the electrodes, improving safety.

In the energy storage device 20, the energy storage cell 26 can be restrained from both sides in the plate thickness direction by the first restraining portion 62 and the second restraining portion 64. Furthermore, when an abnormality in the energy storage cell 26 is detected or predicted, the actuator 54 is driven to deform the connecting portion 66. This causes the first restraining portion 62 to move away from the second restraining portion 64, reducing the restraining pressure. This configuration ensures that the restraining pressure is reduced when an abnormality occurs.

(Modification of cell restraint portion)
Next, a power storage device 70 including a cell restraining unit 72 according to a modified example will be described with reference to Figures 7(A) and 7(B). Note that the same components as those in the first embodiment described above are given the same reference numbers and the description thereof will be omitted.

The cell restraint portion 72 according to the modified example is disposed inside the housing 22 on one side of the stack 24 (energy storage cells 26) in the stacking direction. The shape of the cell restraint portion 72 is not particularly limited, but as an example, it is formed in a plate or rod shape extending along the surface direction of the stack 24, and both ends in the longitudinal direction are supported by the housing 22. When the stack 24 is housed inside the housing 22, the cell restraint portion 72 is pressed against the opposing surface of the housing 22, thereby applying a restraining pressure along the stacking direction to the stack 24.

The cell restraint portion 72 in this modified example is characterized in that it is molded using a material that melts in a situation in which an abnormality in the storage cell 26 is detected or predicted.

For example, the cell restraint portion 72 can be formed using a material that is melted when heated to a temperature above a threshold value. As a result, when the cell restraint portion 72 is heated due to a fire or an abnormal temperature rise in the storage cell 26, the heated portion of the cell restraint portion 72 melts, and the support state by the housing 22 is released.

The cell restraint portion 72 may also be formed using a material that melts when moisture above a threshold level penetrates it. In this case, if the inside of the housing 22 becomes flooded for some reason, the flooded portion of the cell restraint portion 72 melts, and the support state by the housing 22 is released. In other words, flooding inside the housing 22 may cause a short circuit to the storage cell 26. Therefore, flooding inside the housing 22 can be used to detect or predict an abnormal state of the storage cell 26.

When the cell restraining portion 72 is released from the support state by the housing 22 due to melting, the cell restraining portion 72 loses the reaction surface, and the restraining pressure on the stack 24 is reduced. This provides gaps between the energy storage cells 26, and the same effects as those of the above embodiment can be achieved. In addition, this modified example can be implemented without a high-precision sensor group or precise control processing, and therefore manufacturing costs can be reduced.
[supplementary explanation]

Although one embodiment of the present invention has been described above, the present invention is not limited to this. Each configuration of the present invention can be modified in various ways without departing from the spirit of the invention. For example, in the above embodiment and modified example, the power storage device 20, 70 is configured to house multiple power storage cells 26, but the present invention is not limited to this. A cell restraint portion may be attached to a single power storage cell.

In addition, in the above embodiment and modified example, the case where the storage cell constitutes an all-solid-state battery element has been described, but this is not limited to this. The configuration of the present invention can also be applied to a storage cell that has a liquid electrolyte layer.

20 Electricity storage device 22 Housing 24 Laminated body 26 Electricity storage cell 30 All-solid-state battery element 30P Positive electrode layer 30N Negative electrode layer 33 Solid electrolyte layer 54 Actuator 60 Cell restraining portion 62 First restraining portion 64 Second restraining portion 66 Connection portion 72 Cell restraining portion

Claims (4)

A storage cell formed in a plate shape;
A cell restraining portion that applies a restraining pressure to the energy storage cell along a plate thickness direction and is deformable when an abnormality in the energy storage cell is detected or predicted, and reduces the restraining pressure by deforming ;
a restraint control unit that detects at least one of a temperature, a voltage, and water ingress in the power storage cell, and deforms the cell restraint unit to reduce the restraint pressure when an abnormality in the power storage cell is detected or predicted from a detection result;
A power storage device having the above structure. The storage cell is
an all-solid-state battery element in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated;
The power storage device according to claim 1 , further comprising: an exterior body including a laminate film that covers the all-solid-state battery element. A stack of a plurality of the storage cells in a plate thickness direction is provided,
The power storage device according to claim 1 , wherein the cell restraining portion applies the restraining pressure to the stack in a stacking direction. The cell restraint portion is
A first restraint portion arranged on one side in a plate thickness direction of the energy storage cell;
A second restraint portion arranged on the other side in a plate thickness direction of the energy storage cell;
a connecting portion that connects the first restraining portion and the second restraining portion and is deformed by driving an actuator to relatively displace the first restraining portion in a plate thickness direction with respect to the second restraining portion,
The energy storage device according to claim 1 , wherein the restraint control unit, when an abnormality in the energy storage cell is detected or predicted, deforms the connecting portion so as to displace the first restraint portion in a direction away from the second restraint portion, thereby reducing the restraint pressure.