Battery pack manufacturing method

Abstract

This improves the energy density of a battery stack housed under pressure in a battery case. [Solution] In the battery stack, adjacent first and second battery cells are arranged. In this step, a first terminal indicating the external terminal of the positive or negative electrode of the first battery cell is provided on the end face of the first battery cell, and 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, is provided on the end face of the second battery cell facing the end face of the first battery cell. 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. In this step, the restraining load is applied with the first terminal and the second terminal in contact. Subsequently, the battery stack is housed in a battery case. In this step, the battery stack is housed in the battery case with the first terminal and the second terminal in contact and the restraining load applied.

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, each of the plurality of battery cells constituting the battery stack is provided with external terminals for the positive electrode and the negative electrode. These external terminals are electrically connected between the plurality of battery cells. This electrical connection is established via a bus bar provided on the side surface of the battery stack housed in the battery case.

[0005] However, when busbars are provided on the sides of the battery stack, there is a problem in that two battery cells that have come close together due to pressurization will be separated by the length of the busbar connecting the external terminals of these battery cells. In particular, while increasing the total number of battery cells that make up the battery stack can increase the cell filling rate and improve the energy density of the battery stack, the presence of busbars hinders this.

[0006] One objective of this disclosure is to provide a technology that can improve the energy density of a battery stack housed under pressure in a battery case. [Means for solving the problem]

[0007] 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 step of arranging adjacent first and second battery cells in a battery stack. In this step, 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 method of the present disclosure also includes the step of applying a restraining load to the battery stack from both sides in the direction of arrangement of the first and second battery cells. In this step, the restraining load is applied with the first terminal and the second terminal in contact. The method of the present disclosure further includes the step of housing the battery stack in a battery case. In this step, the battery stack is housing in the battery case with the first terminal and the second terminal in contact and the restraining load applied.

[0008] In this disclosure, 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, the method of this disclosure may further include a step of aligning the terminal surface of the first terminal with the terminal surface of the second terminal after the step of arranging the first and second battery cells and before the step of applying a restraining load to the battery stack.

[0009] In this disclosure, the shape of the first terminal may be such that it engages with the second terminal. In this case, the method of this disclosure may further include the step of engaging the first terminal with the second terminal after the step of arranging the first and second battery cells and before the step of applying a restraining load to the battery stack.

[0010] 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.

[0011] 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]

[0012] According to this disclosure, when a restraining load is applied to the battery stack from both sides in the direction of the arrangement of the first and second terminals, the restraining load is applied to the battery stack in a state where the first and second terminals are in contact. Furthermore, the battery stack in a state where the first and second terminals are in contact and the restraining load is applied is housed in the battery case. As a result, the first and second terminals remain in contact with the battery stack after it is housed in the battery case.

[0013] Therefore, it becomes possible to establish an electrical connection between the first and second terminals without providing busbars on the sides of the battery stack. This also leads to the elimination of the busbar installation process, which is expected to improve the manufacturing efficiency of the battery pack. Furthermore, by reducing the thickness of the first and second terminals in the arrangement direction, it becomes possible to increase the total number of battery cells constituting the battery stack and improve the energy density of the battery stack. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram illustrating an example of a typical battery pack manufacturing method. [Figure 2] This figure illustrates the challenges of the battery pack manufacturing method described in Figure 1. [Figure 3] This figure shows an example of the configuration of a battery cell applied to the method according to the embodiment. [Figure 4] This figure illustrates a first example of the method according to the embodiment. [Figure 5] This figure illustrates a second example of the method according to the embodiment. [Modes for carrying out the invention]

[0015] 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.

[0016] 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.

[0017] FIG. 1 is a diagram for explaining an example of a method for manufacturing a general battery pack. In FIG. 1, a lower case 11 of a battery pack 1 is depicted. The lower case 11 is combined with an upper cover (not shown) to constitute the battery pack 1. Incidentally, the X-axis shown in FIG. 1 corresponds to, for example, the longitudinal direction of a vehicle, and the Y-axis orthogonal to the X-axis corresponds to, for example, the lateral direction of the vehicle. More specifically, the positive direction of the X-axis corresponds to the forward direction of the vehicle, and the positive direction of the Y-axis corresponds to the left direction of the vehicle.

[0018] In the example shown in FIG. 1, four spaces 12 are formed in the lower case 11 in the X-axis direction. Three of these spaces 12 each accommodate three battery stacks 2. These battery stacks 2 are formed by stacking a plurality of battery cells. The total number NC of battery cells constituting one battery stack 2 is set in advance. The total number NC is, for example, 20 to 50.

[0019] In FIG. 1, one battery stack 2 is also depicted 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. When arranging these, 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 battery cells in a state where a predetermined number (total number NC) of a plurality of battery cells are arranged corresponds to the battery stack 2 shown in FIG. 1.

[0020] 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 laminate of the 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 battery 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.

[0021] The method described with reference to FIG. 1 is also called the CTP (Cell To Pack) method. The CTP method has the advantage of being able to increase the cell filling rate compared to the MTP (Module To Pack) method in which a plurality of battery cells are grouped and modularized and then a battery pack is manufactured through a restraint member. However, the CTP method has the following problems. This problem will be described while referring to FIG. 2. The upper part of FIG. 2 is a diagram for explaining the first problem. In the upper part of FIG. 2, the battery stack 2 housed in the lower case 11 is depicted by the method described with reference to FIG. 1. Note that the Z-axis shown in FIG. 2 corresponds to, for example, the vertical direction of the vehicle. More specifically, the positive direction of the Z-axis corresponds to the upward direction of the vehicle.

[0022] In the example shown in the upper part of FIG. 2, the bus bar 3 is attached to the battery stack 2 housed in the lower case 11. The bus bar 3 connects an external terminal (for example, a positive terminal) provided in the first battery cell to that of the second battery cell adjacent to the first battery cell (for example, a negative terminal), and also connects an external terminal (for example, a positive terminal) provided in the second battery cell to that of the third battery cell adjacent to the second battery cell (for example, a negative terminal). It is a conductive member for electrically connecting between a plurality of battery cells.

[0023] However, when the bus bar 3 is provided, two adjacent battery cells that are brought close by the application of a restraint load will be separated by the length of the bus bar 3 that connects these battery cells. In particular, as the total number NC of the battery cells constituting the battery stack 2 increases, the cell filling rate Φ (for example, the total volume of the battery cells / the volume of the battery stack 2) can be increased to improve the energy density of the battery stack 2, but there is a problem that the presence of the bus bar 3 inhibits this.

[0024] The lower part of Figure 2 illustrates the second problem. As previously explained, a constraint load is applied to the battery stack 2 when it is inserted into the lower case 11. The direction of the load vector to which this constraint load is applied is perpendicular to the direction of gravity. However, due to the large number of components (battery cells, plate members) that make up the battery stack 2, and the dimensional variations of these components, the direction of the load vector tends to change easily. In addition, the battery stack 2 tends to undulate in the direction of gravity (negative Z-axis direction) due to the influence of gravity on the battery stack 2. Therefore, there is a problem in that it is difficult to insert the battery stack 2 into space 12 while maintaining a constant posture with the constraint load applied.

[0025] Therefore, in the method according to the embodiment, the external terminals to be provided on the battery cells are provided on the end faces in the direction of the battery cell arrangement. Then, a restraining load is applied to the battery stack 2 with the external terminals of two adjacent battery cells in contact. Figure 3 is a diagram showing an example of the configuration of a battery cell applied to the method according to the embodiment. In the example shown in Figure 3, an external terminal (e.g., a positive terminal) 22 is provided on the end face 211 of the battery cell 21, and an external terminal (e.g., a negative terminal) 23 is provided on the end face 212 of the battery cell 21.

[0026] Both external terminals 22 and 23 have a plate shape. External terminals 22 and 23 are the same size. The thickness of each external terminal 22 and 23 in the arrangement direction of the battery cells 21 is less than or equal to half the thickness of each plate member 24 (e.g., cooling plate) provided adjacent to the end faces 211 and 212. Also, the thickness of each external terminal 22 and 23 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 22 and 23 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 24.

[0027] Figure 3 also shows arrow views of end face 211 along line AA and end face 212 along line BB. As can be seen from the arrow view along line AA, both end face 211 and the end face of the adjacent plate member 24 are square in shape, but the area of ​​the latter is smaller than that of the former. The external terminal 22 is located outside the area of ​​end face 211 that faces the end face of the plate member 24. Therefore, it can be said that an area for providing the external terminal 22 is secured on end face 211. The same can be seen from the arrow view of end face 212 along line BB. That is, an area for providing the external terminal 23 is secured on end face 212.

[0028] In the example shown in Figure 3, the external terminals 22 and 23 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 22 coincides with the position of external terminal 23. Therefore, when multiple battery cells 21 are arranged, the external terminals 22 (e.g., positive terminal) and the corresponding external terminals 23 (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 22 and 23 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).

[0029] Furthermore, the shape of the end face of the plate member 24 shown in Figure 3 is just one example, and its shape can be arbitrarily modified as long as the external terminals 22, 23 and the plate member 24 do not interfere with each other. For example, the shape of the end face of the plate member 24 may be such that two of the four sides constituting the end face of the plate member 24 are equal in length to those of the end face 211 (or end face 212), and the area corresponding to where the external terminals 22, 23 are provided is narrow (rectangular). Alternatively, the length of all four sides constituting the end face of the plate member 24 may be equal to those of the end face 211 (or end face 212), and only the area where the external terminals 22, 23 are provided may be cut out (perforated shape).

[0030] Figure 4 is a diagram illustrating a first example of the method according to the embodiment. In this first example, the battery cell 21 described in Figure 3 is used. Multiple battery cells 21 are arranged in a certain direction (for example, in the X-axis direction). In this arrangement, the terminal surface 221 of the first external terminal 22 (first terminal) provided on the first battery cell 21 (first battery cell) and the terminal surface 231 of the second external terminal 23 (second terminal) provided on the second battery cell 21 (second battery cell) are aligned. Here, the second battery cell 21 is a battery cell 21 facing the first battery cell 21, and the second external terminal 23 is paired with the first external terminal 22. Furthermore, the terminal surface 221 is the end face of the first external terminal 22 that is parallel to the end face 211, and the terminal surface 231 is the end face of the second external terminal 23 that is parallel to the end face 212.

[0031] As explained in Figure 3, the position of the external terminal 22 coincides with the position of the external terminal 23 in the Y-axis and Z-axis directions. Therefore, after arranging multiple battery cells 21, if one end face of the battery stack 2 is fixed and these battery cells 21 are moved in the arrangement direction from the other end face of the battery stack 2, the terminal surface 221 of the first external terminal 22 and the terminal surface 231 of the second external terminal 23 can be easily aligned.

[0032] In the first example, the external terminals 22 and 23 come into contact when terminal surfaces 221 and 231 are aligned. After all battery cells 21 have been aligned, a restraining load (approximately 10-20 kN) is applied from both sides in the stacking direction of these battery cells (i.e., the longitudinal direction of the battery stack 2). The end plates 25 of the battery stack 2 are positioned on both sides of the battery stack 2 to which the restraining load is applied. Therefore, the external terminals 22 (or external terminals 23) of the battery cell 21 adjacent to the end plate 25 come into contact with the end face of the end plate 25.

[0033] In the first example, 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.

[0034] According to the first example, it is possible to establish electrical connections between the external terminals 22 and 23 without providing busbars 3 on the sides of the battery stack 2. In other words, it is possible to solve the first problem described in the upper part of Figure 2. This also leads to the omission of the process of providing busbars 3, which is expected to improve the manufacturing efficiency of the battery pack 1. Furthermore, by reducing the thickness of the external terminals 22 and 23 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.

[0035] Figure 5 illustrates a second example of the method according to the embodiment. In this second example, a battery cell 21 having external terminals having a different shape from the external terminals 22 and 23 described in Figure 3 is used. That is, in the example shown in Figure 5, the first battery cell 21 (first battery cell) is provided with a first external terminal 27 (first terminal) having a concave shape. The second battery cell (second battery cell) is provided with a second external terminal 28 (second terminal) having a convex shape. Here, the second battery cell 21 is a battery cell 21 facing the first battery cell 21, and the second external terminal 28 is paired with the first external terminal 27.

[0036] Furthermore, the thicknesses of the first external terminal 27 and the second external terminal 28 in the arrangement direction of the battery cell 21 are based on the maximum value in this arrangement direction. This maximum thickness is designed to be equal to the thickness of the external terminals 22 and 23 described in Figure 3. Also, the shapes of the first external terminal 27 and the second external terminal 28 shown in Figure 5 are examples, and their shapes can be arbitrarily modified as long as the first external terminal 27 and the second external terminal 28 can engage with each other. For example, if the first external terminal 27 has a stepped portion, the second external terminal 28 may have a stepped portion that engages with this stepped portion.

[0037] As explained in Figure 3, the position of external terminal 22 coincides with the position of external terminal 23 in the Y-axis and Z-axis directions. This positional relationship also holds between the first external terminal 27 and the second external terminal 28. Therefore, after arranging multiple battery cells 21, if one end face of the battery stack 2 is fixed and these battery cells 21 are moved in the arrangement direction from the other end face of the battery stack 2, the first external terminal 27 and the second external terminal 28 will engage.

[0038] In the second example, external terminals 27 and 28 engage, causing them to come into contact. After this engagement is complete in all battery cells 21, a restraining load (approximately 10-20 kN) is applied from both longitudinal sides of the battery stack 2. The contact relationship between the external terminal 27 (or external terminal 28) of a battery cell 21 adjacent to the end plate 25 and the end face of the end plate 25 is the same as that between the external terminal 22 (or external terminal 23) and the end face of the end plate 25, as explained in Figure 4.

[0039] In the second example, 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.

[0040] According to the second example, the same effect as in the first example can be obtained. In addition, in the second example, an additional effect can be expected due to the engagement of external terminals 27 and 28. That is, according to the second example, since external terminals 27 and 28 are engaged, it becomes possible to insert the battery stack 2 into space 12 while maintaining a constant posture with the constraining load applied. In other words, it becomes possible to solve the second problem described in the lower part of Figure 2. [Explanation of Symbols]

[0041] 1...Battery pack, 2...Battery stack, 3...Bus bar, 11...Lower case, 12...Space, 21...Battery cell, 22,23,27,28...External terminals, 24...Plate member, 25...End plate, 211,212,221,231...End face

Claims

1. A method for manufacturing a battery pack, which includes a battery stack housed in a battery case, A step of arranging adjacent first and second battery cells in the battery stack, wherein 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. 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, wherein the restraining load is applied to the battery stack in a state in which the first terminal and the second terminal are in contact, A step of housing the battery stack in the battery case, wherein the battery stack is housed in the battery case in a state in which the first terminal and the second terminal are in contact and the restraining load is applied, A method for manufacturing a battery pack, characterized by including the following:

2. The method according to claim 1, The first terminal has a terminal surface parallel to the end face of the first battery cell, The second terminal has a terminal surface parallel to the end face of the second battery cell. The process further includes, after the step of arranging the first and second battery cells, and before the step of applying a restraining load to the battery stack, aligning the terminal surface of the first terminal with the terminal surface of the second terminal. A method for manufacturing a battery pack characterized by the following:

3. A method according to claim 1 or 2, The shape of the first terminal is such that it engages with the second terminal. The process further includes, after the step of arranging the first and second battery cells and before the step of applying a restraining load to the battery stack, the step of engaging the first terminal and the second terminal. A method for manufacturing a battery pack characterized by the following:

4. A method according to claim 1 or 2, 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. A method according to claim 1 or 2, 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:

Images