Battery pack manufacturing method

Abstract

This ensures electrical connection between multiple battery cells that make up a battery stack housed in a battery case. [Solution] In a battery stack, adjacent first and second battery cells are arranged. Subsequently, a restraining load is applied to the battery stack from both sides in the direction of arrangement of the first and second battery cells. Next, the battery stack with the restraining load applied is housed in a battery case. After arranging the first and second battery cells and before applying the restraining load to the battery stack, a contact pressure sensor is installed between the first and second battery cells and at the location that receives the restraining load applied to the battery stack. After the battery stack is housed in the battery case, the detected value of the contact pressure sensor is acquired. Then, based on the change in the detected value, the electrical connections between the multiple battery cells constituting the battery stack are inspected.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a battery package mounted on a vehicle.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a battery module in which a battery stack is housed in a battery case. In this conventional method, a shim is disposed between the battery case and the battery stack so that the pressurized state of the battery stack is maintained by the inner surfaces of the battery case located at both ends in the longitudinal direction of the battery stack. The purpose of disposing this shim is to absorb dimensional variations in the longitudinal direction of the battery stack and to ensure pressurization of the battery stack by the inner surface of the battery case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, regarding the battery stack housed in the battery case, there is a problem that it is difficult to ensure the quality of the electrical connection between a plurality of battery cells constituting the battery stack. In this regard, it is also possible to manage the electrical connection by applying a voltage sensor to the battery stack housed in the battery case to measure the voltage. However, even if there is a poor connection (for example, only a light contact) at the connection portion between a plurality of battery cells, the voltage of the battery stack can be detected. Therefore, with the method of measuring the voltage of the battery stack housed in the battery case, it is not possible to guarantee the conduction area (resistance value) of the connection portion.

[0005] One object of this disclosure is to provide a technology that can ensure electrical connections between multiple battery cells constituting a battery stack housed in a battery case. [Means for solving the problem]

[0006] This disclosure relates to a method for manufacturing a battery pack, which includes a battery stack housed in a battery case, and has the following features: The method of the present disclosure includes the steps of: arranging adjacent first and second battery cells in a battery stack; applying a restraining load to the battery stack from both sides in the direction of arrangement of the first and second battery cells; and housing the battery stack with the restraining load applied in a battery case. The method of the present disclosure further includes the steps of: installing a contact pressure sensor between the first and second battery cells and at a location that receives the restraining load applied to the battery stack, after the step of arranging the first and second battery cells and before the step of applying a restraining load to the battery stack; acquiring a detected value from the contact pressure sensor after the step of housing the battery stack in a battery case; and inspecting the electrical connections between the plurality of battery cells constituting the battery stack based on the change in the detected value.

[0007] In this disclosure, the battery stack may include a plate member provided between the end face of a first battery cell and the end face of a second battery cell. In this case, during the process of installing the contact pressure sensor, the contact pressure sensor may be installed between the end face of the first battery cell and the end face of the second battery cell, and in a location that does not interfere with the plate member.

[0008] In this disclosure, the end face of the first battery cell may be provided with a first terminal indicating the external terminal of the positive or negative electrode of the first battery cell, and the end face of the second battery cell facing the end face of the first battery cell may be provided with a second terminal indicating the external terminal of the positive or negative electrode of the second battery cell, which is paired with the first terminal. Here, the first terminal may have a terminal surface parallel to the end face of the first battery cell, and the second terminal may have a terminal surface parallel to the end face of the second battery cell. In this case, in the step of installing the contact pressure sensor, the contact pressure sensor may be installed between the terminal surface of the first terminal and the terminal surface of the second terminal.

[0009] In this disclosure, the battery stack may include a plate member provided between the end face of a first battery cell and the end face of a second battery cell. In this case, the area of ​​the end face of the plate member facing the end face of the first battery cell may be smaller than the area of ​​the end face of the first battery cell, and the area of ​​the end face of the plate member facing the end face of the second battery cell may be smaller than the area of ​​the end face of the second battery cell. Furthermore, a first terminal may be provided outside the region of the end face of the first battery cell that faces the end face of the plate member, and a second terminal may be provided outside the region of the end face of the second battery cell that faces the end face of the plate member.

[0010] In this disclosure, the sum of the thickness of the first battery cell in the direction of arrangement of the first and second terminals and the thickness of the second battery cell in the same direction of arrangement may be greater than or equal to a thickness predetermined as the distance in the same direction of arrangement between the end face of the first battery cell and the end face of the second battery cell when the battery stack is housed in the battery case, and less than or equal to the thickness in the same direction of arrangement of the plate member provided between the end face of the first battery cell and the end face of the second battery cell. [Effects of the Invention]

[0011] According to this disclosure, after the process of arranging the first and second battery cells, a contact pressure sensor is installed between the first and second battery cells and at a location that receives a restraining load applied to the battery stack. Then, a restraining load is applied to the battery stack from both sides in the direction of arrangement of the first and second terminals. As a result, in the battery stack housed in the battery case, the contact pressure sensor remains present between the first and second battery cells.

[0012] According to this disclosure, after the battery stack is housed in the battery case, a pressure sensor reading is acquired, and the electrical connections between the battery cells constituting the battery stack are inspected based on the change in this pressure sensor reading. The pressure sensor detects the pressure (i.e., restraining load) applied to the location where it is installed. This pressure sensor reading changes if there is poor contact (e.g., only light contact) at the connection between the battery cells. Therefore, it is possible to ensure electrical connections through inspection based on the change in the pressure sensor reading. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram illustrating an example of a typical battery pack manufacturing method. [Figure 2] This figure shows a first configuration example of a battery cell with a contact pressure sensor applied to the method according to the embodiment. [Figure 3] This figure illustrates a first example of the method according to the embodiment. [Figure 4] This figure illustrates the challenges of the battery pack manufacturing method described in Figure 1. [Figure 5] This figure shows a second example configuration of a battery cell with a contact pressure sensor applied to the method according to the embodiment. [Figure 6] This figure illustrates a second example of the method according to the embodiment. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below with reference to the drawings. However, structures and the like described in the embodiments below are not necessarily essential to the present invention unless specifically stated or clearly defined in principle.

[0015] The battery pack manufactured by the method according to the embodiments of this disclosure is mounted on a vehicle. Examples of such vehicles include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that run using electricity supplied from the battery pack. The battery pack is mounted, for example, on the underbody of the vehicle.

[0016] Figure 1 illustrates an example of a general battery pack manufacturing method. Figure 1 shows the lower case 11 of the battery pack 1. The lower case 11 is combined with an upper cover (not shown) to form the battery pack 1. The X-axis shown in Figure 1 corresponds to, for example, the front-to-rear direction of the vehicle, and the Y-axis, which is perpendicular to the X-axis, corresponds to, for example, the left-to-right direction of the vehicle. More specifically, the positive direction of the X-axis corresponds to the front direction of the vehicle, and the positive direction of the Y-axis corresponds to the left direction of the vehicle.

[0017] In the example shown in Figure 1, the lower case 11 has four spaces 12 formed in the X-axis direction. Three of these spaces 12 each house three battery stacks 2. These battery stacks 2 are made up of multiple battery cells stacked on top of each other. The total number NC of battery cells that make up one battery stack 2 is predetermined. The total number NC is, for example, 20 to 50 cells.

[0018] Also shown in FIG. 1 is a single battery stack 2 outside the lower case 11. In the example shown in FIG. 1, first, outside the lower case 11, a plurality of battery cells are arranged in a certain direction. During this arrangement, plate materials are appropriately arranged on the side surfaces of the battery cells. As the plate member, a cooling plate having a function of cooling the battery cells is exemplified. An aggregate of these cells in a state where a predetermined number (total number NC) of battery cells are arranged corresponds to the battery stack 2 shown in FIG. 1.

[0019] In the example shown in FIG. 1, subsequently, a restraining load is applied to these battery cells from both side surfaces in the arrangement direction of the plurality of battery cells. Then, the stack of a plurality of battery cells (that is, the battery stack 2) is subjected to a restraining load from both side surfaces in the stacking direction of these cells (that is, the longitudinal direction of the battery stack 2). Subsequently, while maintaining the state where the restraining load is applied to the battery stack 2, the battery stack 2 is inserted into the space 12. Thereby, the battery stack 2 is accommodated in the lower case 11.

[0020] The method described with reference to FIG. 1 is also called the CTP (Cell To Package) method. The CTP method has an advantage that it can increase the cell filling rate compared to the MTP (Module To Pack) method in which a plurality of battery cells are grouped into a module and then a battery pack is manufactured via a restraining member. However, the CTP method has a problem that it is difficult to ensure the quality of the electrical connection between a plurality of battery cells.

[0021] Therefore, in the method according to an embodiment, at least one contact pressure sensor is provided between two adjacent battery cells and at a location that receives the restraining load applied to the battery stack 2. Then, after the battery stack 2 is accommodated in the lower case 11, the detection value of this contact pressure sensor is acquired to inspect the electrical connection between the plurality of battery cells. The detection value of the contact pressure sensor changes when there is a poor connection (for example, only a light contact) at the connection part between the plurality of battery cells. Therefore, according to the inspection based on the change in the detection value of the contact pressure sensor, it becomes possible to ensure the electrical connection between the plurality of battery cells.

[0022] Figure 2 shows an example configuration of a battery cell with a contact pressure sensor applied to the method according to the embodiment. In the example shown in Figure 2, a contact pressure sensor 22 is provided on the end face 211 of the battery cell 21. Examples of contact pressure sensors 22 include load cell sensors and tactile sensors. However, single-point measuring sensors such as strain gauges, piezoresistive sensors, and force sensors, or surface measuring sensors such as force sensing mats, microfluidic pressure sensors, and flexible dielectric sensors may also be used as the contact pressure sensor 22. Note that the Z-axis shown in Figure 2 corresponds, for example, to the vertical direction of the vehicle. More specifically, the positive direction of the Z-axis corresponds to the upward direction of the vehicle.

[0023] Figure 2 shows a view of the end face 211 along line AA. As can be seen from this view, the end face of the contact pressure sensor 22 has a square shape (hollow rectangle). The end face of the contact pressure sensor 22 has a size approximately equal to the size of the end face 211. The reason the end face of the contact pressure sensor 22 has a square shape is that a plate member 23 (for example, a cooling plate) is provided in the opening. The end face 211 on which the plate member 23 is provided is the same as the end face on which the contact pressure sensor 22 is provided. The thickness of the contact pressure sensor 22 in the direction of arrangement of the battery cells 21 is less than or equal to the thickness of the plate member 23, and is greater than or equal to the distance (design value) between the end face 211 when the battery stack 2 is housed in the lower case 11 and the end face of another battery cell 21 facing this end face 211.

[0024] The shape of the end face of the contact pressure sensor 22 shown in Figure 2 is just one example, and the shape of the end face of the contact pressure sensor 22 can be arbitrarily changed as long as it does not interfere with the plate member 23. For example, the shape of the end face of the contact pressure sensor 22 may be U-shaped, L-shaped, or straight. Also, the installation position of the contact pressure sensor 22 shown in Figure 2 is just one example, and the installation position can be arbitrarily changed as long as it does not interfere with the plate member 23 on the end face 211.

[0025] Figure 3 illustrates a method according to an embodiment. In the example shown in Figure 3, first, a plurality of battery cells 21 are arranged in a certain direction (for example, in the X-axis direction). In this arrangement, a contact pressure sensor 22 is installed between the first battery cell 21 and the second battery cell 21. Here, the second battery cell 21 is the battery cell 21 facing the first battery cell 21. The contact pressure sensor 22 is installed between the end face 211 of the first battery cell 21 and the end face 212 of the second battery cell 21. Note that the first battery cell 21 and the second battery cell 21 that sandwich the contact pressure sensor 22 can be set arbitrarily.

[0026] In the example shown in Figure 3, after the contact pressure sensor 22 is installed, a restraining load (approximately 10-20 kN) is applied from both sides in the stacking direction of these cells (i.e., the longitudinal direction of the battery stack 2). End plates 26 of the battery stack 2 are positioned on both sides of the battery stack 2 to which the restraining load is applied.

[0027] In the example shown in Figure 3, the battery stack 2 is then inserted into space 12 while maintaining a restraining load (approximately 10-20 kN) applied to it. This step is the same as the example described in Figure 1.

[0028] In the example shown in Figure 3, the electrical connections between multiple battery cells 21 are then inspected. For the electrical connection inspection, the measuring instrument 3 is first connected to the battery stack 2 housed in the lower case 11. The measuring instrument 3 is connected to the contact pressure sensor 22. The measuring instrument 3 acquires the output signal from the contact pressure sensor 22 and detects changes in the detected pressure. For example, if the rate of change of the detected pressure falls below a reference value, it is determined that there is no problem with the electrical connection. On the other hand, if the detected pressure exceeds the reference value, it is determined that there is a problem with the electrical connection. Thus, as shown in the example in Figure 3, it is possible to guarantee the electrical connections between multiple battery cells 21.

[0029] By the way, the CTP method has the following challenge in addition to the challenge of quality assurance regarding electrical connections. This second challenge will be explained with reference to Figure 4. Figure 4 shows the battery stack 2 housed in the lower case 11 using the method described in Figure 1.

[0030] In the example shown in Figure 4, a busbar 4 is attached to the battery stack 2 housed in the lower case 11. The busbar 4 is a conductive member for electrically connecting multiple battery cells, such as connecting the external terminal (e.g., positive terminal) of a first battery cell to that of a second battery cell adjacent to the first battery cell (e.g., negative terminal), and connecting the external terminal (e.g., positive terminal) of a second battery cell adjacent to the second battery cell to that of a third battery cell adjacent to the second battery cell (e.g., negative terminal).

[0031] However, if a busbar 4 is provided, the two battery cells 21 that have come close together due to the application of a restraining load will be separated by the length of the busbar 4 connecting them. In particular, increasing the total number NC of battery cells 21 constituting the battery stack 2 can increase the cell filling rate Φ (for example, the total volume of battery cells / the volume of the battery stack 2) and improve the energy density of the battery stack 2, but the presence of the busbar 4 hinders this, which is a problem.

[0032] Therefore, in the method according to the embodiment, the external terminals provided on the battery cell 21 are provided on the end faces in the direction of arrangement of the battery cell 21. Then, a restraining load is applied to the battery stack 2 with the external terminals of two adjacent battery cells 21 in contact. Figure 5 is a diagram showing a second example of the configuration of a battery cell with a contact pressure sensor applied to the method according to the embodiment. In the example shown in Figure 5, an external terminal (e.g., a positive terminal) 24 is provided on the end face 211 of the battery cell 21, and an external terminal (e.g., a negative terminal) 25 is provided on the end face 212 of the battery cell 21.

[0033] Both external terminals 24 and 25 have a plate shape. External terminals 24 and 25 are the same size. The thickness of each external terminal 24 and 25 in the arrangement direction of the battery cells 21 is less than or equal to half the thickness of each plate member 23 (e.g., cooling plate) provided adjacent to the end faces 211 and 212. Also, the thickness of each external terminal 24 and 25 is more than half the distance (design value) between end faces 211 and 212 when the battery stack 2 is housed in the lower case 11. In other words, the sum of the thicknesses of external terminals 24 and 24 is greater than or equal to the distance between end faces 211 and 212 when the battery stack 2 is housed in the lower case 11, and less than or equal to the thickness of the plate member 23.

[0034] Figure 5 also shows arrow views of end face 211 along line BB and end face 212 along line CC. As can be seen from the arrow view along line BB, both end face 211 and the end face of the adjacent plate member 23 are square in shape, but the area of ​​the latter is smaller than that of the former. The external terminal 24 is located outside the area of ​​end face 211 that faces the end face of the plate member 23. Therefore, it can be said that an area for providing the external terminal 24 is secured on end face 211. The same can be seen from the arrow view of end face 212 along line CC. That is, an area for providing the external terminal 25 is secured on end face 212.

[0035] In the example shown in Figure 5, the external terminals 24 and 25 are located at the center of the ends of the end faces 211 and 212 in the Z-axis direction, respectively. In the Y-axis and Z-axis directions, the position of external terminal 24 coincides with the position of external terminal 25. Therefore, when multiple battery cells 21 are arranged, the external terminals 24 (e.g., positive terminal) and the corresponding external terminals 25 (e.g., negative terminal) will face each other between two adjacent battery cells 21 (first and second battery cells). Note that the positions of external terminals 24 and 25 can be changed to any position as long as their positions coincide in the YZ plane (i.e., the plane perpendicular to the direction of arrangement of the battery cells).

[0036] Furthermore, the shape of the end face of the plate member 23 shown in Figure 5 is just one example, and its shape can be arbitrarily modified as long as the external terminals 24 and 25 do not interfere with the plate member 23. For example, the shape of the end face of the plate member 23 may be such that two of the four sides constituting the end face of the plate member 23 are equal in length to those of the end face 211 (or end face 212), and the area corresponding to where the external terminals 24 and 25 are provided is narrow (rectangular). Alternatively, the length of all four sides constituting the end face of the plate member 23 may be equal to those of the end face 211 (or end face 212), and only the area where the external terminals 24 and 25 are provided may be cut out (perforated shape).

[0037] In the example shown in Figure 5, the contact pressure sensor 22 is also installed on the terminal surface of the external terminal 24. Examples of the contact pressure sensor 22 include the various sensors described in the explanation of Figure 2. The end face of the contact pressure sensor 22 shown in Figure 5 is rectangular. However, the shape of the contact pressure sensor 22 shown in Figure 5 is just one example, and its shape can be arbitrarily changed as long as it can be installed on the terminal surface of the external terminal 24.

[0038] Figure 6 illustrates a second example of the method according to the embodiment. In the second example, first, a plurality of battery cells 21 are arranged in a certain direction (for example, in the X-axis direction). In this arrangement, a contact pressure sensor 22 is installed between the terminal surface of the first external terminal 24 (first terminal) provided on the first battery cell 21 (first battery cell) and the terminal surface of the second external terminal 25 (second terminal) provided on the second battery cell 21 (second battery cell). The first external terminal 24 and the second external terminal 25 that sandwich the contact pressure sensor 22 can be set arbitrarily.

[0039] In the second example, a restraining load (approximately 10-20 kN) is then applied from both sides of the battery cell 21 in the stacking direction (i.e., the longitudinal direction of the battery stack 2). As explained in Figure 5, the position of the external terminal 24 coincides with the position of the external terminal 25 in the Y-axis and Z-axis directions. Also, the terminal faces of the external terminals 24 and 25 are parallel to the end faces 211 and 212, respectively. Therefore, when multiple battery cells 21 are arranged and the contact pressure sensor 22 is installed, and then these battery cells 21 are moved in the arrangement direction from the other end face of the battery stack 2 while fixing one end face of the battery stack 2, the terminal face of the first external terminal 24 is aligned with the terminal face of the second external terminal 25 via the contact pressure sensor 22. Note that the terminal face of the first external terminal 24, on which the contact pressure sensor 22 is not installed, is directly aligned with the terminal face of the second external terminal 25.

[0040] In the second example, the terminal surfaces of the first external terminal 24 and the second external terminal 25 are brought together so that these external terminals make direct or indirect contact. In the second example, the battery stack 2 is then inserted into the space 12 while maintaining a restraining load (approximately 10-20 kN) applied to the battery stack 2. This step is the same as the example described in Figure 1. In the second example, the electrical connections between the multiple battery cells 21 are then checked. This step is the same as the first example described in Figure 3.

[0041] Thus, the second example shown in Figure 6 provides the same effect as the first example described in the third example. In addition, the second example also provides the following effect: it is possible to establish electrical connections between the external terminals 24 and 25 without providing busbars 4 on the sides of the battery stack 2. In other words, it is possible to solve the problem described in Figure 5. This also leads to the omission of the process of providing busbars 4, which is expected to improve the manufacturing efficiency of the battery pack 1. Furthermore, by reducing the thickness of the external terminals 24 and 25 in the direction of the arrangement of multiple battery cells 21, it is possible to increase the total number of battery cells 21 constituting the battery stack 2 and improve the energy density of the battery stack 2.

[0042] Furthermore, the example shown in Figure 3 and the example shown in Figure 6 can be combined. Specifically, the external terminals 24 and 25 in the second configuration example described in Figure 5 are combined with the shape of the end face of the contact pressure sensor 22 in the first configuration example described in Figure 2 (U-shaped, L-shaped, straight, etc.). In this case, the contact pressure sensor 22 can be provided in a location that does not interfere with the plate member 23 and the external terminals 24. Therefore, with this combination example, it is possible to provide both the external terminals 24 and the contact pressure sensor 22 on the end face 211 of the battery cell 21 while obtaining the same additional effect as in the second example. [Explanation of Symbols]

[0043] 1...Battery pack, 2...Battery stack, 11...Lower case, 12...Space, 21...Battery cell, 22...Contact pressure sensor, 23...Plate member, 24,25...External terminals, 26...End plate, 211,212...End face, 3...Measuring instrument, 4...Bus bar

Claims

1. A method for manufacturing a battery pack, which includes a battery stack housed in a battery case, The process involves arranging adjacent first and second battery cells in the aforementioned battery stack, A step of applying a restraining load to the battery stack from both sides in the arrangement direction of the first and second battery cells, The process includes housing the battery stack, with the aforementioned restraining load applied, into the battery case, After the step of arranging the first and second battery cells, and before the step of applying a restraining load to the battery stack, a step of installing a contact pressure sensor between the first and second battery cells and at a location that receives the restraining load applied to the battery stack, The steps include: after the step of housing the battery stack in the battery case, acquiring the detected value of the contact pressure sensor; The process further includes inspecting the electrical connections between a plurality of battery cells constituting the battery stack based on the change in the detected value. A method for manufacturing a battery pack characterized by the following:

2. The method according to claim 1, The battery stack includes a plate member provided between the end face of the first battery cell and the end face of the second battery cell, In the step of installing the contact pressure sensor, the contact pressure sensor is installed between the end face of the first battery cell and the end face of the second battery cell, and in a location that does not interfere with the plate member. A method for manufacturing a battery pack characterized by the following:

3. The method according to claim 1, The end face of the first battery cell is provided with a first terminal indicating the external terminal of the positive or negative electrode of the first battery cell, and the end face of the second battery cell facing the end face of the first battery cell is provided with a second terminal indicating the external terminal of the positive or negative electrode of the second battery cell, which is paired with the first terminal. The first terminal has a terminal surface parallel to the end face of the first battery cell, and the second terminal has a terminal surface parallel to the end face of the second battery cell. In the step of installing the contact pressure sensor, the contact pressure sensor is installed between the terminal surface of the first terminal and the terminal surface of the second terminal. A method for manufacturing a battery pack characterized by the following:

4. The method according to claim 3, The battery stack includes a plate member provided between the end face of the first battery cell and the end face of the second battery cell, The area of ​​the end face of the plate member facing the end face of the first battery cell is smaller than the area of ​​the end face of the first battery cell, and the area of ​​the end face of the plate member facing the end face of the second battery cell is smaller than the area of ​​the end face of the second battery cell. The first terminal is provided on the outer side of the region of the end face of the first battery cell that faces the end face of the plate member, and the second terminal is provided on the outer side of the region of the end face of the second battery cell that faces the end face of the plate member. A method for manufacturing a battery pack characterized by the following:

5. The method according to claim 3 or 4, The sum of the thickness of the first terminal and the thickness of the second terminal in the aforementioned arrangement direction is greater than or equal to a thickness predetermined as the distance in the aforementioned arrangement direction between the end face of the first battery cell and the end face of the second battery cell when the battery stack is housed in the battery case, and less than or equal to the thickness in the aforementioned arrangement direction of the plate member provided between the end face of the first battery cell and the end face of the second battery cell. A method for manufacturing a battery pack characterized by the following:

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