JP7616046B2 - Energy Storage Devices - Google Patents

Description

This application relates to an electricity storage device.

Laminated cells, in which battery elements are wrapped in a laminate film, are known as batteries with high energy density and easy handling. However, in laminated cells, electrolytes and other components may decompose and generate gas when an abnormality such as overcharging or an internal short circuit occurs. When gas is generated, the laminated cell expands. Therefore, by detecting such expansion, the current flowing through the laminated cell can be controlled, thereby improving safety. Such technology is disclosed, for example, in Patent Document 1.

Patent Document 1 discloses a battery pack in which a laminate cell is sandwiched between predetermined restraining plates and the laminate cell and the restraining plates are fixed with a band-shaped fastening member, in which an electrode tab of the laminate cell is fixed to the restraining plate connected to an external power load, and the fixation between the electrode tab and the restraining plate is released when the laminate cell expands. With such a battery pack, the external power load and the laminate cell can be electrically disconnected by releasing the fixation between the electrode tab and the restraining plate.

Patent No. 6825705

For example, in laminate cells housing lithium ion capacitors, it is common to pass a large current of 1000 W or more of power through a small cell of about 100 cc. In this case, high-temperature heat is generated in the electrode tab due to the internal resistance of the cell. The battery pack described in Patent Document 1 requires a joint that joins the restraining plate and the electrode tab, and this joint has a high contact resistance and becomes a heat generating point. This not only results in energy loss due to heat generation, but also in the problem that the contact state of the joint changes due to deformation caused by heat, resulting in an interruption of the circuit regardless of the expansion of the cell.

In view of the above, the objective of this disclosure is to provide an electricity storage device that can detect cell expansion without increasing the resistance of the cell.

As one aspect of the present disclosure for solving the above problem, the present disclosure provides an electricity storage device that includes a cell in which a battery element is packaged in an exterior body, a conductive member that covers the side surface of the cell, and a detection unit that is electrically connected to the conductive member and detects the conductive state of the conductive member by supplying a current to the conductive member, the conductive member having a structure in which the conductive state of the conductive member changes due to the expansion of the cell.

In the above-mentioned power storage device, the conductive member may have a structure in which the conductive state of the conductive member changes when a tension of 0.5 N to 300 N is applied. The conductive member may also have a slit or notch. Furthermore, the above-mentioned power storage device may include a control unit that controls the current supply to the cell, and when the detection unit detects a change in the conductive state of the conductive member, the control unit may control the current supply to the cell.

The energy storage device of the present disclosure detects cell expansion by detecting a change in the current-carrying state of the conductive member. Here, the conductive member is a member that covers the side surface of the cell and is not electrically connected to the cell. Therefore, the energy storage device of the present disclosure can detect cell expansion without increasing the resistance of the cell.

2 is a schematic diagram of a side view of the electricity storage device 100 in which the conductive member 20 is observed from the front side. FIG. 1 shows a schematic diagram of the side surface of the electricity storage device 100 observed from the side surface side of the conductive member 20. Also, the top view of the portion shown by the dotted line is indicated by an arrow. 1 is a schematic diagram for explaining a conductive member 120 arranged so as to wrap around the periphery of the cell stack 15. Also, the top view of the portion indicated by the dotted line is indicated by an arrow. FIG. 13 is a diagram showing a configuration in which a clip 121 is used as a fixing member. 13 is a diagram showing a configuration in which one of the fixing members 21 is provided in a position close to the end face of the cell stack 15. FIG. FIG. 1A is a front view of the conductive member 220. FIG. 1B is a side view of the conductive member 220. FIG. 1C is a side view of the conductive member 220 when a protective film 220c is disposed on the conductive member 220. FIG. 2 corresponds to FIG. 1 and shows the power storage device 100 after the cell stack 15 has expanded. FIG. 3 corresponds to FIG. 2 and shows the power storage device 100 after the cell stack 15 has expanded. 2 is a schematic diagram of a side view of an electricity storage device 200 in which a conductive member 20 is observed from the front side. 4 is a control flow of an embodiment of the power storage device 200.

[First embodiment]
The electricity storage device of the present disclosure will be described with reference to an electricity storage device 100 according to a first embodiment. Fig. 1 shows a schematic diagram of the side of the electricity storage device 100, in which a conductive member 20 is observed from the front side. Fig. 2 shows a schematic diagram of the side of the electricity storage device 100, in which a conductive member 20 is observed from the side side.

As shown in Figures 1 and 2, the energy storage device 100 includes a cell stack 15 in which multiple cells 10 are stacked, a conductive member 20 that covers the side surface of the cell stack 15, and a detection unit 30 that is electrically connected to the conductive member 20 and detects the current flow state of the conductive member 20 by supplying a current to the conductive member 20.

<Cell 10>
The cell 10 is a single cell in which a battery element is packaged in an exterior body 11. The battery element includes a positive electrode, a negative electrode, and an electrolyte. The type of the cell 10 is not particularly limited, and may be a liquid battery or a solid battery. The cell 10 may be a secondary battery or a capacitor. Furthermore, in the cell 10, the type of ions that move within the battery element due to charging and discharging is not particularly limited. For example, known ions such as lithium ions and sodium ions can be mentioned. An example of the cell 10 through which a large current flows and which is prone to expansion is a lithium ion capacitor. Even if the power storage device 100 uses a cell 10 that is prone to such expansion, it is possible to detect the expansion. Therefore, a lithium ion capacitor may be used for the cell 10.

The exterior body 11 is not particularly limited as long as it contains the battery element and is an exterior body that can deform due to changes in internal pressure. Examples include a laminate film and a metal housing. From the viewpoint of ease of handling, a laminate film may be used for the exterior body 11. Since a laminate film has a lower rigidity than other exterior bodies, it is prone to expanding due to an increase in the internal pressure of the cell 10. However, even if the power storage device 100 uses a cell 10 that is prone to such expansion, it is possible to detect the expansion. Therefore, a laminate film may be used for the exterior body 11. Examples of laminate films include known metal laminates such as aluminum laminates.

The cell 10 has a pair of electrode tabs (positive electrode tab 12a and negative electrode tab 12b) protruding from the exterior body 11. The positive electrode tab 12a is connected to the positive electrode sealed in the cell 10, and the negative electrode tab 12b is connected to the negative electrode sealed in the cell 10. In FIG. 1, the positive electrode tab 12a and the negative electrode tab 12b are provided on opposite sides of the cell 10. However, the energy storage device of the present disclosure is not limited to this, and the positive electrode tab 12a and the negative electrode tab 12b may be arranged on the same side of the cell or on different sides.

<Cell stack 15>
The cell stack 15 is a structure in which the cells 10 are stacked in the thickness direction. A member such as a stack plate or a heat spreader may be disposed between the stacked cells 10. In the cell stack 15, the electrode tabs of the cells 10 are connected in series. However, in the power storage device of the present disclosure, the connection method of the electrode tabs of each cell is not particularly limited, and may be in series or in parallel. From the viewpoint of passing a large current, the electrode tabs of each cell may be connected in series.

In the first embodiment, the power storage device 100 has a cell stack 15 in which multiple cells 10 are stacked, but the power storage device of the present disclosure is not limited to this and may have only one cell. The same applies to the second embodiment described below. However, from the perspective of passing a large current, the power storage device of the present disclosure may have a cell stack in which multiple cells are stacked.

<Conductive member 20>
The conductive member 20 is a member that covers the side surface of the cell stack 15. The material of the conductive member 20 is not particularly limited as long as it is a conductive member. For example, it may be a soft metal such as aluminum, or a resin having a conductive material. The conductive material is, for example, graphite, metal powder, or a conductive polymer. The type of resin is not particularly limited, and a known resin can be appropriately adopted.

The shape of the conductive member 20 is not particularly limited, and may be tape-like, band-like, or linear. A plurality of conductive members may be bundled together to form a single conductive member 20. Furthermore, in order to reinforce the conductive member 20, a resin film or the like may be attached to the surface of the conductive member 20. Furthermore, in order to fix the conductive member 20 to the cell stack 15, the resin film may have adhesive properties. This allows the conductive member 20 to be easily fixed to the side of the cell stack 15.

The side of the cell stack 15 on which the conductive member 20 is arranged is not particularly limited, and the conductive member 20 may be arranged on any side. However, in order to avoid increasing the resistance of the cell 10, it is necessary to consider not electrically connecting the conductive member 20 to the electrode tab of the cell 10. Therefore, from the viewpoint of preventing contact between the conductive member 20 and the current path (the current path formed by connecting the electrode tabs of the cells 10), the conductive member 20 may be arranged at least on the side on which the current path of the cell 10 is not arranged. This prevents energy loss due to contact between the conductive member 20 and the current path (electrode tab), and prevents a decrease in the accuracy with which the detection unit 30 detects changes in the current flow state of the conductive member 20.

The conductive member 20 may cover at least a part of the side surface of the cell stack 15. This allows the expansion of the cell 10 covered by the conductive member 20 to be detected. However, from the viewpoint of detecting the expansion of the entire cell stack 15, as shown in FIG. 1, the conductive member 20 may cover the side surface of the cell stack 15 in the thickness direction. In particular, the conductive member 20 may cover the range from one end to the other end in the thickness direction on the side surface of the cell stack 15. In addition, the conductive member 20 may not only cover only one side surface of the cell stack, but also cover other surfaces. For example, the conductive member 20 may cover one side surface and the end surface in the thickness direction of the cell stack 15. The conductive member 20 may be arranged so as to wrap around the cell stack 15. In other words, the conductive member 20 may be arranged so as to cover both opposing side surfaces and both end surfaces in the thickness direction of the cell stack 15. FIG. 3 shows a form having a conductive member 120 arranged so as to wrap around the cell stack 15.

As shown in FIG. 3, by arranging the conductive material 120 so that it wraps around the cell stack 15, the electrical conduction state of the conductive material 120 can change even if the end face of the cell stack 15 expands. Therefore, with this type of energy storage device configuration, it is possible to detect not only the expansion of the side face of the cell stack 15, but also the expansion of the end face.

The method for placing the conductive member 20 on the side is not particularly limited, and it may be attached with an adhesive or may be placed using a specified fixing member 21. In this case, the conductive member 20 may be fixed with a specified tension. An insulating adhesive may be used as the adhesive, but a conductive adhesive may be used as the adhesive for connecting the conductive member 20 and the fixing member 21. The conductive adhesive is an adhesive that contains a conductive polymer, metal, or carbon powder.

1 and 2, fixing members 21, 21 (terminals) are arranged on each end surface of the cell stack 15, and the end of the conductive member 20 is fixed to the fixing members 21, 21, respectively, so that the conductive member 20 is arranged on the side of the cell stack 15. The end of the conductive member 20 is fixed to the fixing member 21 using a conductive adhesive. Then, as shown in the upper part of FIG. 2, the connection portion 31 of the detection unit 30 is electrically connected to the end of the conductive member 20. This allows the detection unit 30 to detect changes in the current-carrying state of the conductive member 20. The connection form between the connection portion 31 and the conductive member 20 is not particularly limited, and the electrical connection may be made using a coupler or a crimp terminal.

The fixing member 21 is not particularly limited as long as it can fix the conductive member 20 and connect the conductive member 20 to the detection unit 30. As shown in FIG. 2, a terminal may be used as the fixing member 21. A clip may also be used as the fixing member. FIG. 4 shows a form in which a clip 121 is used as the fixing member.

As shown in FIG. 4, the end 20 of the conductive member 20 may be clamped and fixed by a clip 121. The clip 121 may have a predetermined locking mechanism, and the fixed state may be maintained using the locking mechanism. The end of the conductive member 20 extending from the rear of the clip 121 is electrically connected to the connection portion 31 of the detection unit 30.

1 and 2, the fixing members 21 are arranged on each end face of the cell stack 15, but the arrangement of the fixing members 21 is not limited to this. As shown in FIG. 5, one of the fixing members 21 may be provided in a position close to the end face of the cell stack 15. In the embodiment of FIG. 1 and FIG. 2, since the fixing members 21 are arranged on both end faces of the cell stack 15, none of the end faces are horizontal, and the energy storage device 100 cannot be stably placed. On the other hand, as shown in FIG. 5, the fixing member 21 on the side on which the energy storage device 100 is placed can be placed on the placement surface close to the end face of the cell stack 15, so that the energy storage device 100 can be stably placed.

Here, the conductive member 20 has a structure in which the conductive state of the conductive member 20 changes due to the expansion of the cell 10. Preferably, the conductive member 20 has a structure in which the conductive state of the conductive member 20 changes before the cell 10 expands and reaches the internal pressure limit. In the electricity storage device 100, gas may be generated inside the cell 10 due to a side reaction or thermal reaction of the battery element, causing the cell 10 to expand. Therefore, the "internal pressure limit" is the internal pressure limit at which cracks or cuts do not occur in the exterior body 11 of the cell 10 when the internal pressure changes due to the generation of gas inside the cell 10. In particular, since the sealing portion (e.g., a laminate sealing portion) of the exterior body 11 that is bonded or welded is easily opened, the internal pressure limit at which the sealing portion is not opened may be set. The "change in the current flow state" is a change in the current or voltage of the conductive member 20 detected by the detection unit 30, or an interruption of current flow. The electricity storage device 100 may have a threshold value for determining whether the current flow state of the conductive member 20 has changed. The threshold value may be set appropriately depending on the conductive member 20. This is because the threshold value changes depending on the amount of current supplied to the conductive member 20 and the material of the conductive member 20. The "structure in which the current flow state changes" is a structure in which a crack or cut occurs in the conductive member 20 before the cell 10 expands and reaches the internal pressure limit. For example, when a crack occurs in the conductive member 20, the current or voltage of the conductive member 20 detected by the detection unit 30 changes, and when the conductive member 20 is cut, the current to the conductive member 20 is cut. The threshold value for determining whether the current flow state has changed may be set based on the current flow state when a crack or cut occurs in the conductive member 20. Preferably, the threshold value is set based on the current flow state (cutoff of current flow) when the current member 20 is cut.

Since the power storage device 100 has the conductive member 20, the expansion of the cell 10 covered by the conductive member 20 changes the current-carrying state of the conductive member 20, and thus the expansion of the cell 10 can be detected. The internal pressure limit of the cell 10 varies depending on the type of cell 10, and therefore cannot be uniquely determined. Therefore, it is advisable to obtain the internal pressure limit of the cell 10 in advance through experiments or simulations. For example, the structure of the conductive member 20 may be designed so that a change in the current-carrying state occurs with a force sufficiently smaller than (internal pressure limit of the cell 10) x (coverage area of the conductive member 20 in one cell 10). The internal pressure limit of a cell 10 using a laminate film for the exterior body 11 is generally 40 kPa to 100 kPa.

The conductive member 20 has a structure in which the conductive state of the conductive member 20 changes due to the expansion of the cell 10, so that consideration must be given to preventing the conductive member 20 from easily cracking or breaking during the manufacture of the electricity storage device 100. For example, the conductive member 20 may have a structure in which the conductive state of the conductive member 20 changes when a tension of 0.5N to 300N is applied. This makes it easy to detect the expansion of the cell 10 and also makes it easy to arrange the conductive member 20 on the cell 10. If the tension of the conductive member 20 is less than 0.5N, the conductive member 20 is easily cut, making it difficult to arrange the conductive member 20 on the cell 10. If the tension of the conductive member 20 exceeds 300N, it is easy to detect the expansion of the cell 10. The tension of the conductive member can be measured by a known method, such as a test method in accordance with the international standards ASTM D882-18, D883, and D638.

The conductive member 20 may have a slit or a notch. This makes it easier for the conductive member 20 to change its electrical conduction state, and improves the accuracy of detecting the expansion of the cell 10. For example, when using a conductive member 20 with high strength, a slit or a notch may be added to the conductive member 20 to adjust its strength. The shape of the slit or notch of the conductive member 20 is not particularly limited, but a slit or a notch having an angle with respect to the thickness direction is preferable so that the electrical conduction state of the conductive member 20 can easily change. For example, the angle of the slit or the notch with respect to the thickness direction may be more than 0°, may be 10° or more, may be 30° or more, may be 45° or more, may be 60° or more, may be less than 180°, may be 170°, may be 150° or less, may be 135° or less, or may be 120° or less.

Figure 6 shows an enlarged view of the conductive member 20. As shown in Figure 6, the conductive member 20 has multiple notches 20a, which give it a shape in which hexagons are arranged continuously. In this way, the conductive member 20 may have a shape in which polygons are arranged continuously. By having the notches 20a in the conductive member 20, changes in the electrical conduction state are more likely to occur starting from the notches 20a. In other words, cracks and cuts are more likely to occur in the conductive member 20 starting from the notches 20a.

Figure 7 also shows a conductive member 220 having multiple notches 220a on its surface. (a) is a front view of the conductive member 220, and (b) is a side view of the conductive member 220. (c) is a side view of the conductive member 220 with a protective film 220c placed on it.

As shown in FIG. 7(a), the conductive member 220 has a plurality of notches 220a on its surface, and the conductive member 220 is structured such that the conductive member 220 is likely to change in its electrical conduction state starting from the notches 220a. When notches are provided on the surface of the conductive member 220, as shown in FIG. 7(b), a resin film 220b may be attached to the other surface of the conductive member 220 to improve its strength. Also, as shown in FIG. 7(c), during the manufacture of the power storage device, the conductive member 120 to which a protective film 220c that protects the surface with the notches 220a is attached may be placed on the side of the cell stack 15, and then the protective film 220c may be peeled off.

<Detection Unit 30>
The detection unit 30 is a member that is electrically connected to the conductive member 20 and detects the current-carrying state of the conductive member 20 by supplying a current to the conductive member 20. Then, by detecting a change in the current-carrying state of the conductive member 20, the expansion of the cell 10 can be detected. In FIG. 1, the detection unit 30 is electrically connected to each end of the conductive member 20. The detection unit 30 has predetermined connection parts 31, 31, and is connected to the conductive member 20 via the connection part 31. A known detection device can be appropriately adopted as the detection unit 30. The magnitude of the current and voltage flowing from the detection unit 30 to the conductive member 20 is not particularly limited, and is appropriately set to a magnitude of the current and voltage that makes it easy to detect a change in the current-carrying state of the conductive member 20.

＜Effects＞
8 and 9 correspond to FIGS. 1 and 2 and are diagrams of the electricity storage device 100 after the cell stack 15 has expanded. As shown in FIGS. 8 and 9, the expansion of the cell stack 15 (cells 10) changes the electrical conduction state of the conductive member 20. Specifically, the expansion of the cell stack 15 (cells 10) causes the conductive member 20 to break, thereby cutting off electrical conduction from the detection unit 30 to the conductive member 20. The detection unit 30 detects this change in the electrical conduction state of the conductive member 20 (cutoff of electrical conduction). Therefore, the electricity storage device 100 can detect the expansion of the cells 10.

In addition, as described above, the conductive member 20 is not electrically connected to the cell 10. Therefore, the energy storage device 100 can detect the expansion of the cell 10 without increasing the resistance of the cell 10.

<Additional Information>
By appropriately adjusting the structure of the conductive member 20, the power storage device 100 can detect the displacement of the cell stack 15 in addition to detecting the expansion of the cells 10. Typically, if the conductive member 20 has a structure in which the conductive state of the conductive member 20 changes due to the expansion of the cells 10, the detection unit 30 can detect the change in the conductive state of the conductive member 20, and the power storage device 100 can also detect the displacement of the cell stack 15.

For example, when an external force is applied to the power storage device 100, the relative position of any of the cells 10 in the cell stack 15 may shift. When the relative positions of the cells 10 shift, the electrode tabs between the cells 10 may become uncoupled, or even if the electrode tabs do not become uncoupled, a high load may be applied near the electrode tabs. When the electrode tabs become uncoupled, the power storage device 100 may become unusable. In addition, when a high load is applied near the electrode tabs, the battery element connected to the electrode tabs may be damaged. Furthermore, since a large current may flow through a limited cross-sectional area of the electrode tabs, when the electrode tabs become uncoupled due to a position shift, the electrode tabs may generate heat. Thus, a shift in the relative positions of the cells 10 is undesirable because it leads to an abnormal state of the power storage device 100. The battery pack described in Patent Document 1 does not have a means for detecting such a position shift.

On the other hand, the conductive member 20 of the energy storage device 100 may crack or break due to misalignment of the cells 10, causing a change in the electrical current state. In particular, when the conductive member 20 is attached to the side of the cell stack 15, the conductive member 20 is likely to crack or break due to misalignment of the cells 10, which in turn causes a change in the electrical current state. Therefore, the energy storage device 100 can detect a misalignment of the relative positions of the cells 10.

In addition, by having the conductive member 20, the energy storage device 100 can detect whether or not the cell 10 has been unintentionally replaced. In other words, if the cell 10 is unintentionally replaced, it is expected that the conductive member 20 will crack or break. Therefore, after the cell 10 is replaced, the detection unit 30 will detect a change in the electrical conduction state of the conductive member 20. In this way, the conductive member 20 also has the role of sealing the cell 10 (cell stack 15).

[Second embodiment]
A power storage device 200 according to a second embodiment of the power storage device of the present disclosure will be described. The power storage device 200 is configured by adding a control unit 40 to the power storage device 100. A schematic diagram of the power storage device 200 is shown in FIG.

As shown in FIG. 10, in addition to the configuration of the power storage device 100, the power storage device 200 includes a control unit 40 connected to the detection unit 30. The control unit 40 controls the power storage device 200. Specifically, the control unit 40 controls the current supply to the cell stack 15 (the amount of current supply and the stop of current supply). The control unit 40 is a known arithmetic device (computer system), such as a battery management system.

In the energy storage device 200, when the detection unit 30 detects a change in the current flow state of the conductive member 20, the control unit 40 controls the current supply to the cell stack 15. This allows the energy storage device 200 to be quickly controlled and transitioned to a safe state. Therefore, it can be said that the energy storage device 200 is a safer energy storage device.

Below, an embodiment of the control flow of the power storage device 200 by the control unit 40 is described. The control flow of the embodiment is shown in FIG. 11. However, the control of the power storage device 200 by the control unit 40 is not limited to this.

In one embodiment, the control flow repeatedly executes the following steps S1 to S4.

In process S1, the control unit 40 determines whether or not it has received information from the detection unit 30 indicating that a change in the electrical current state of the conductive member 20 has been detected. If the information has not been received, process S1 is performed again. If the information has been received, the process proceeds to process S2. "Information indicating that the electrical current state of the conductive member 20 has changed" is information indicating that the current or voltage of the conductive member 20 detected by the detection unit 30 has changed. This information indicates that an abnormal condition such as expansion or misalignment has occurred in the cell 10.

In step S2, the current supply to the cell stack 15 is controlled. For example, the current supply to the cell stack 15 (cell 10) may be reduced or cut off. A safer control is performed depending on the condition of the power storage device. After step S2, step S3 is performed.

In process S3, the temperature of the cell stack 15 is measured, and it is determined whether the measured temperature is abnormal. The temperature of the cell stack 15 is measured by a temperature measuring device (not shown). If the measured temperature is abnormal, process S4 is performed. If the measured temperature is not abnormal, the control flow ends.

In step S4, the temperature of the cell stack 15 is cooled. The cell stack 15 is cooled by a cooling device (not shown). When the temperature of the cell stack 15 has decreased to a predetermined temperature, step S4 is terminated.

REFERENCE SIGNS LIST 10 Cell 11 Exterior body 12a Positive electrode tab 12b Negative electrode tab 15 Cell stack 20, 120, 220 Conductive member 20a Notch 220a Slit 220b Resin film 220c Protective film 21, 121 Fixing member 30 Detection section 31 Connection section 40 Control section 100, 200 Electric storage device

Claims (3)

A cell in which a battery element is packaged in an exterior body;
A conductive member covering a side surface of the cell;
a detection unit electrically connected to the conductive member and supplying a current to the conductive member to detect a current-carrying state of the conductive member,
the conductive member has a structure in which a current-carrying state of the conductive member changes due to expansion of the cell ,
the conductive member is not electrically connected to the cell;
The conductive member has a shape in which hexagons are continuously arranged, and thus has a plurality of notches,
The detection unit has a connection unit that is electrically connected to an end of the conductive member when detecting a current-carrying state of the conductive member.
Energy storage device. The electric storage device according to claim 1, wherein the conductive member has a structure in which the conductive state of the conductive member changes when a tension of 0.5 N to 300 N is applied. A control unit is provided for controlling a current supply to the cell,
When the detection unit detects the energization state of the conductive member, the end of the conductive member and the connection unit are electrically connected, and when a change in the energization state of the conductive member is detected, the control unit controls the current supply to the cell.
The electricity storage device according to claim 1 or 2 .

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