Battery module and method for manufacturing battery module

Abstract

To provide a battery module having high welding strength on the inner surface side of a battery case and high pressure resistance.SOLUTION: There is provided a battery module in which multiple battery elements are accommodated inside a resin battery case 10. The battery case 10 includes a case body 12 having an accommodation space 11 in which the battery elements are accommodated and an opening that connects the accommodation space 11 to the outside, and a lid body 2 that is welded to an opening edge portion 18a of the case body 12 and closes the opening, and at a welded portion 40 between the case body 12 and the lid body 2, a molten layer 41 consisting of the molten resin of the case body 12 and the molten resin of the lid body 2 is thicker on the inner surface 10a side of the battery case 10 than on the outer surface 10b side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery module and a method for manufacturing a battery module. [Background technology]

[0002] Secondary batteries used as power sources for electrically powered vehicles such as electric cars and hybrid cars are used in the form of a battery module in which a plurality of secondary batteries are electrically connected to increase charge / discharge capacity and output power. Generally, this type of secondary battery includes a battery case in which battery elements are housed. For example, Patent Document 1 discloses a battery module having single cells in which a resin battery case constitutes an integrated battery case, and the integrated battery case is divided by partitions into a plurality of battery cases in which battery elements (electrode groups, current collectors, electrolyte) are housed.

[0003] The battery module described in Patent Document 1 has a resin integrated battery case and a lid that form a case, and the top opening of the integrated battery case is sealed with the lid while battery elements are housed in multiple battery cases separated by partitions. In this battery module, the lid is attached to the opening of the integrated battery case by welding the integrated battery case and the lid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-211197 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the battery module described in Patent Document 1, gases such as hydrogen are generated in each cell during use. When the internal pressure of the battery case increases due to the generation of gas, a load is applied to the side wall of the case, and a strong force that can separate the welded portion between the integrated battery case and the lid is applied, particularly on the inner surface of the case. Therefore, there is a risk that the case will be damaged when the internal pressure of the battery case increases.

[0006] In addition, when the integrated battery case and the lid are welded, burrs are formed on both the inner and outer sides of the case at the welded portion, and if the internal pressure of the battery case increases as described above, cracks may occur starting from the base of the burrs formed on the inner side of the case, which may damage the case.

[0007] In this way, in a battery module in which the case is joined by welding the integrated battery container and the lid, there is a risk that the case will break when the internal pressure rises due to insufficient strength of the welded portion on the inner surface of the case. In other words, conventional battery modules have room for improvement in terms of pressure resistance.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide a battery module having high welding strength on the inner surface side of the battery case and high pressure resistance, and a method for manufacturing the battery module. [Means for solving the problem]

[0009] The battery module according to the present invention, which achieves the above object, has the following characteristic configuration: A battery module in which a plurality of battery elements are housed inside a resin battery case, The battery case is a case body having an accommodation space for accommodating the battery element and an opening communicating the accommodation space with the outside; a cover body welded to an edge portion of the opening of the case body to close the opening, At the welded portion between the case body and the lid, a molten layer consisting of the molten resin of the case body and the molten resin of the lid is thicker on the inner surface side of the battery case than on the outer surface side.

[0010] According to the above characteristic configuration, the molten layer is thicker on the inner surface side of the battery case than on the outer surface side. Therefore, the welding strength between the case body and the lid is high on the inner surface side of the battery case where a strong force acts when the internal pressure rises or where cracks are likely to start, and the battery module can withstand a higher internal pressure than before. In other words, the battery module having the above characteristic configuration has a high pressure resistance.

[0011] Further characteristic configurations of the battery module according to the present invention are as follows: the welded portion has a protrusion formed on an inner surface side of the battery case at the time of welding and a protrusion formed on an outer surface side of the battery case at the time of welding, The amount of protrusion formed on the inner surface side of the battery case is smaller than the amount of protrusion formed on the outer surface side of the battery case.

[0012] According to the above characteristic configuration, the protrusions, which have higher rigidity on the inner surface side of the battery case than on the outer surface side, protrude less, thereby suppressing stress concentration caused by differences in rigidity when the internal pressure of the battery case increases. Therefore, a battery module having the above characteristic configuration has higher pressure resistance.

[0013] Further characteristic configurations of the battery module according to the present invention are as follows: The molten layer is inclined downward from the inner surface side of the battery case toward the outer surface side of the battery case.

[0014] The molten layer is formed by contacting and joining the molten surface of the case body and the molten surface of the lid when the case body and the lid are welded. Therefore, the molten layer inclined downward from the inner surface side to the outer surface side of the battery case is formed by melting and joining the case body and the lid so as to have a molten surface inclined downward from the inner surface side to the outer surface side of the battery case. Here, when the case body and the lid are melted so as to have the above-mentioned molten surface inclined downward, the molten resin flows from the inner surface side to the outer surface side of the battery case. Therefore, when the battery module has a molten layer inclined downward from the inner surface side to the outer surface side of the battery case, the protrusion amount of the protrusion generated on the inner surface side of the battery case is smaller than the protrusion amount of the protrusion generated on the outer surface side, compared to when the molten layer is not inclined. Therefore, in the battery module having the above-mentioned characteristic configuration, stress concentration when the internal pressure of the battery case increases can be further suppressed.

[0015] The manufacturing method of the battery module according to the present invention for achieving the above object is characterized by the following configuration: A method for manufacturing a battery module in which a plurality of battery elements are housed inside a battery case including a resin case body having a housing space for housing battery elements and communicating with the outside through an opening, and a resin cover body having a recessed portion opening on a rear surface and closing the opening of the case body, comprising: a melting step of melting a part of the case body and the lid by sandwiching a hot plate having one or more protrusions on at least one of the front and back surfaces between the opening edge of the case body and the lid; a joining step of welding and joining the case body and the lid body, In the melting step, the opening edge of the case body and the lid are brought into contact with the front and back surfaces of the hot plate, and the side surface of the protruding body is brought into contact with at least one of the inner wall surface of the case body and the inner wall surface of the recess in the lid, so that at least one of the melted amount of the resin constituting the case body and the melted amount of the resin constituting the lid is greater on the inner surface side of the battery case than on the outer surface side, and the generation of protrusions on the inner surface side of the battery case is suppressed and the generation of protrusions on the outer surface side of the battery case is promoted, In the joining step, the fusion portion of the case body formed in the melting step and the fusion portion of the lid body are brought into contact with each other and pressurized.

[0016] According to the above characteristic configuration, the joining step is performed after the melting amount of the resin constituting the case body and the resin constituting the lid are greater on the inner surface side of the battery case than on the outer surface side. As a result, the thickness of the molten layer consisting of the molten resin of the case body and the molten resin of the lid is thicker on the inner surface side of the battery case than on the outer surface side. Therefore, the obtained battery module has high welding strength on the inner surface side of the battery case where a strong force acts when the internal pressure increases or where it is likely to become a starting point of cracks, and can withstand higher internal pressure than conventional battery modules. Furthermore, according to the above characteristic configuration, in the melting step, the generation of protrusions on the inner surface side of the battery case is suppressed and the generation of protrusions on the outer surface side is promoted, and then the joining step is performed. As a result, in the obtained battery module, the amount of protrusions generated on the inner surface side of the battery case is smaller than the amount of protrusions generated on the outer surface side. Therefore, in the obtained battery module, the amount of protrusion of the protrusions, which are more rigid on the inner surface side of the battery case than on the outer surface side, is smaller, and stress concentration due to the difference in rigidity when the internal pressure increases is suppressed. Furthermore, in the obtained battery module, the amount of molten resin flowing toward the inner surface of the battery case is suppressed, and more resin flows toward the outer surface, resulting in a larger amount of protrusion on the outer surface than on the inner surface. As a result, the distance from the potential crack starting point (the base of the protrusion on the inner surface of the battery case) to the end of the molten layer on the outer surface of the battery case becomes longer, resulting in a stronger welded portion. In other words, according to the manufacturing method of the battery module having the above-mentioned characteristic configuration, a battery module having high pressure resistance can be manufactured.

[0017] Further characteristic configurations of the battery module according to the present invention are as follows: the hot plate has a front and rear surface, and a portion where the opening edge of the case body and the lid come into contact with the front and rear surfaces of the hot plate is inclined downward from the inner surface side to the outer surface side of the battery case, The melting process involves melting the resin constituting the case body and the resin constituting the lid body so that the opposing portions of the case body and the lid body form surfaces that slope downward from the inner surface side to the outer surface side of the battery case.

[0018] According to the above characteristic configuration, in the melting step, the molten resin easily flows from the inner surface side to the outer surface side of the battery case. Therefore, when the case body and the lid are brought into contact with each other and joined, the amount of protrusions generated on the inner surface side of the battery case is smaller than the amount of protrusions generated on the outer surface side, compared to when the resin is melted so that the opposing portions of the case body and the lid do not form inclined surfaces. Therefore, in the obtained battery module, stress concentration when the internal pressure of the battery case increases is further suppressed, and the welded parts have higher strength. Effect of the Invention

[0019] As described above, according to the battery module and the manufacturing method of the battery module of the present invention, it is possible to realize a battery module having high welding strength on the inner surface side of the battery case and high pressure resistance. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is an exploded perspective view showing a battery module according to one embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an end face of a portion II-II in FIG. [Diagram 3] 5A to 5C are schematic diagrams for explaining a manufacturing process of the battery module. [Figure 4] 5A to 5C are schematic diagrams for explaining a manufacturing process of the battery module. [Diagram 5] 11A and 11B are diagrams illustrating a state when the internal pressure of the battery module increases. [Figure 6] 10A to 10C are schematic diagrams illustrating a part of a manufacturing process of a battery module according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a battery module according to the present embodiment and a manufacturing method for the battery module will be described with reference to the drawings. In the following, an example in which the battery module includes nickel-metal hydride secondary batteries as unit cells will be described. In addition, in the following, each description and each drawing will be appropriately simplified in order to clarify the description.

[0022] [Configuration of battery module 1] Fig. 1 is an exploded perspective view showing a battery module 1 according to this embodiment. Fig. 2 is a schematic view showing an end face of part II-II in Fig. 1, but the battery element 31 accommodated in the accommodation space 11 is not shown. In the following description, the direction parallel to the height direction of the battery module 1 is defined as the Z-axis direction, the direction parallel to the longitudinal direction of the battery module 1 is defined as the X-axis direction, and the direction parallel to the thickness direction of the battery module 1 is defined as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0023] As shown in Figures 1 and 2, the battery module 1 includes a resin battery case 10 having a storage space 11 in which a battery element 31 is housed, and a single battery 30 consisting of the battery element 31 housed in the storage space 11.

[0024] [Configuration of battery case 10] 1 and 2, the battery case 10 is composed of a rectangular solid-shaped integrated battery case 12 having an opening 18 at the top formed to connect the storage space 11 with the outside, and a lid 2 that covers the opening 18 of the integrated battery case 12. In this embodiment, the integrated battery case 12 and the lid 2 are made of a weldable thermoplastic resin such as polypropylene. In this embodiment, the integrated battery case 12 corresponds to the "case body."

[0025] The integrated battery case 12 is composed of a pair of side walls 13 arranged opposite each other along the longitudinal direction (X-axis direction) and having an outer wall surface 13b with the widest area, a pair of end walls 14 connecting the ends of the side walls 13 in the longitudinal direction (X-axis direction), and a bottom 15 closing the bottom, which are integrally molded from resin. In this embodiment, the storage space 11 is a space surrounded by the lid 2, the side walls 13, the end walls 14, and the bottom 15, and the storage space 11 is equally divided and isolated by five partition walls 16, and six battery cases 17 are formed along the X-axis direction.

[0026] The outer wall surface 13b of each side wall 13 is provided with a plurality of position adjustment parts 19 used for aligning with the adjacent battery module 1, and passage forming protrusions 20 formed to protrude in the thickness direction (Y-axis direction) of the side wall 13 and form cooling passages between the adjacent battery modules 1. In this embodiment, three pairs of position adjustment parts 19 are provided.

[0027] An opening window 21 sealed by a side cover 22 is formed in each side wall 13 so as to straddle the partition wall 16. In this embodiment, three opening windows 21 are formed in one of the pair of side walls 13, and two opening windows 21 are formed in the other side wall 13. That is, in this embodiment, five opening windows 21 are formed in the battery case 10 as a whole.

[0028] A terminal mounting portion (not shown) penetrating in the thickness direction (X-axis direction) is formed on the upper end side of each end side wall 14, and a connection terminal 23 for extracting the output of the single battery 30 to the outside is attached to the terminal mounting portion.

[0029] The cover 2 has a flat plate-like portion 3 and a connection portion 5 extending downward from the lower surface of the plate-like portion 3 so that a recess 4 is formed on the lower surface side of the plate-like portion 3.

[0030] In this embodiment, the plate-shaped portion 3 is formed such that the length in the longitudinal direction (X-axis direction) is approximately the same as the long side of the side wall 13 of the integrated battery case 12, and the length in the lateral direction (Y-axis direction) is approximately the same as the short side of the end wall 14 of the integrated battery case 12. The connection portion 5 is formed at a position corresponding to the side wall 13 and the end wall 14 of the integrated battery case 12. Details will be described later, but in a state in which the battery element 31 is accommodated in each battery case 17 of the integrated battery case 12, the lower end portion 5a of the connection portion 5 is welded to the edge portion 18a of the opening 18 of the integrated battery case 12, thereby airtightly closing the opening 18 of the integrated battery case 12. The edge portion 18a of the opening 18 of the integrated battery case 12 is composed of the upper end portion 13c of the side wall 13 and the upper end portion 14c of the end wall 14 of the integrated battery case 12, and in this embodiment, the edge portion 18a of the opening 18 corresponds to the "opening edge portion".

[0031] In addition, in this embodiment, the lid body 2 is formed as a hole penetrating in the thickness direction and is equipped with a measurement section 6 into which a temperature sensor such as a thermocouple is inserted, and a discharge valve 7 for opening to release the internal pressure when the internal pressure of the battery case 10 reaches or exceeds a threshold value.

[0032] [Configuration of the cell 30] In this embodiment, the cells 30 are nickel-metal hydride secondary batteries composed of battery elements 31 housed in respective battery cases 17. The battery elements 31 are composed of an electrode group, current collector plates, and an electrolyte, which are not shown. Although detailed description will be omitted, in this embodiment, each cell 30 is electrically connected to an adjacent cell 30 via a current collector plate or a connection member that connects the current collector plates to each other. Therefore, the battery module 1 of this embodiment has a configuration in which the cells 30 are connected in series.

[0033] [Mode of welded portion 40 between integrated battery case 12 and lid 2] Next, the aspect of the welded portion 40 between the integrated battery case 12 and the lid 2 will be described. As shown in Fig. 2, the battery module 1 has the welded portion 40 formed by welding the upper end portion 13c of the side wall 13 and the upper end portion 14c of the end side wall 14 of the integrated battery case 12 to the lower end portion 5a of the connection portion 5 of the lid 2. Fig. 2 shows the welded portion 40 formed by welding the upper end portion 13c of the side wall 13 of the integrated battery case 12 to the lower end portion 5a of the connection portion 5 of the lid 2.

[0034] In this embodiment, the welded portion 40 has a molten layer 41 made of the molten resin of the integrated battery case 12 and the molten resin of the lid 2, an inner protrusion 42 formed on the inner surface 10a of the battery case 10 during welding, and an outer protrusion 43 formed on the outer surface 10b of the battery case 10 during welding. The inner surface 10a of the battery case 10 is made up of the inner wall surface 13a of the side wall 13 and the inner wall surface of the end wall 14 of the integrated battery case 12, and the inner wall surface 4a of the recess 4 of the lid 2. The outer surface 10b of the battery case 10 is made up of the outer wall surface 13b of the side wall 13 and the outer wall surface of the end wall 14 of the integrated battery case 12, and the outer wall surface 5b of the connection portion 5 of the lid 2.

[0035] The molten layer 41 is a layer formed by mixing the resin constituting the edge 18a (upper end 13c of the side wall 13 and upper end 14c of the end side wall 14) of the opening 18 of the integrated battery case 12 and the lower end 5a of the connection part 5 of the lid body 2, which melted when the integrated battery case 12 and the lid body 2 were welded together. The molten layer 41 is thicker on the side of the inner surface 10a of the battery case 10 than on the side of the outer surface 10b. Specifically, the molten layer 41 of this embodiment has a thick part 41a on the side of the inner surface 10a of the battery case 10 that is thicker than other parts. The thickness of the molten layer 41 is not particularly limited, but it is preferable that the maximum thickness Tmax of the thick part 41a is 2 to 10 times the thickness Tmin of the thinnest part of the molten layer 41.

[0036] The inner protrusion 42 is a so-called burr formed by the extrusion of molten resin constituting the edge 18a (upper end 13c of the side wall 13 and upper end 14c of the end side wall 14) of the opening 18 of the integrated battery case 12 and the lower end 5a of the connection portion 5 of the lid 2 onto the inner surface 10a of the battery case 10 when the integrated battery case 12 and the lid 2 are welded together. On the other hand, the outer protrusion 43 is a burr formed by the extrusion of molten resin onto the outer surface 10b of the battery case 10.

[0037] In this embodiment, the amount of protrusion of the inner protrusion 42 is smaller than the amount of protrusion of the outer protrusion 43. The "amount of protrusion" of the protrusion means the amount of resin forming the inner protrusion 42 and the outer protrusion 43, and more specifically, the weight of the resin. Therefore, in this embodiment, the amount (weight) of each resin forming the inner protrusion 42 and the outer protrusion 43 is smaller than the amount of resin forming the inner protrusion 42.

[0038] In this embodiment, burr removal is performed on the outer protrusions 43. Specifically, the shape of the outer protrusions 43 in this embodiment is corrected by pressing a hot plate against the outer protrusions 43.

[0039] [Manufacturing method of battery module 1] Next, a manufacturing method of the battery module 1 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 and Fig. 4 are schematic diagrams showing the manufacturing process of the battery module 1.

[0040] The manufacturing method for the battery module 1 includes a melting process in which a hot plate 50 having multiple protrusions 52, 53, 54, 55 on its front and back surfaces is sandwiched between the edge 18a of the opening 18 of the integrated battery case 12 and the lid body 2, thereby melting a portion of the integrated battery case 12 and the lid body 2, and a joining process in which the integrated battery case 12 and the lid body 2 are welded and joined together.

[0041] In the melting process of this embodiment, the edge 18a of the opening 18 of the integrated battery case 12 and the lid body 2 are brought into contact with the front and back surfaces of the hot plate 50, and the side surfaces 52a, 53a, 54a, 55a of the protrusions 52, 53, 54, 55 are brought into contact with the inner wall surface 13a of the side wall 13 and the inner wall surface of the end wall 14 of the integrated battery case 12, and the inner wall surface 4a of the recess 4 in the lid body 2, so that the amount of melted resin constituting the integrated battery case 12 and the amount of melted resin constituting the lid body 2 are greater on the inner surface 10a than on the outer surface 10b of the battery case 10, and the occurrence of an inner protrusion 42 toward the inner surface 10a of the battery case 10 is suppressed and the occurrence of an outer protrusion 43 toward the outer surface 10b of the battery case 10 is promoted. In this embodiment, the hot plate 50 used has two protrusions 52, 53 formed on an upper surface 51a (front surface) of a flat body 51, and two protrusions 54, 55 formed on a lower surface 51b (rear surface).

[0042] In the joining step of this embodiment, the casing-side welded portion M1 of the integrated casing 12 formed in the melting step and the lid-side welded portion M2 of the lid 2 are brought into contact with each other and pressurized.

[0043] Specifically, when manufacturing the battery module 1 of this embodiment, as shown in FIG. 3(a), first, the tip of the upper end portion 13c of the side wall 13 of the integrated battery case 12 and the tip of the upper end portion 14c of the end side wall 14 are arranged to face the tip of the lower end portion 5a of the connection portion 5 in the lid body 2.

[0044] Next, a hot plate 50 is inserted between the integrated battery case 12 and the lid 2, and the integrated battery case 12 and the lid 2 are brought into contact with the hot plate 50, thereby melting a part of the integrated battery case 12 and a part of the lid 2. Specifically, the tip of the lower end 5a of the connection part 5 of the lid 2 is brought into contact with the upper surface 51a (surface) of the main body 51 of the hot plate 50, and the side surfaces 52a and 53a of the protruding bodies 52 and 53 of the hot plate 50 that face the inner wall surface 4a of the recess 4 of the lid 2 are brought into contact with the inner wall surface 4a of the recess 4. In addition, the lower surface 51b (rear surface) of the main body 51 of the hot plate 50 is brought into contact with the tip of the upper end 13c of the side wall 13 of the integrated battery case 12 and the tip of the upper end 14c of the end side wall 14, and the side surfaces 54a and 55a of the protruding bodies 54 and 55 of the hot plate 50, which face the inner wall surface 13a of the integrated battery case 12, are brought into contact with the inner wall surface 13a of the integrated battery case 12 (FIG. 3(b)). FIG. 3(b) illustrates a state in which the tip of the upper end 13c of the side wall 13 is brought into contact with the upper surface 51a of the hot plate 50. As a result, as shown in FIG. 3(b), the area where the hot plate 50 is in contact melts, and the amount of melted resin of the integrated battery case 12 and the amount of melted resin of the lid 2 are greater on the inner surface 10a side than on the outer surface 10b side of the battery case 10. Furthermore, because the inner wall surface 13a of the integrated battery case 12 and the inner wall surface 4a of the recess 4 in the lid 2 are in contact with the side surfaces 52a, 53a, 54a, 55a of the protruding bodies 52, 53, 54, 55, the amount of molten resin flowing toward the inner surface 10a of the battery case 10 is suppressed, and more resin flows toward the outer surface 10b. Therefore, the generation of the inner protrusions 42 is suppressed, and the generation of the outer protrusions 43 is promoted, so that the amount of protrusion of the inner protrusions 42 is smaller than the amount of protrusion of the outer protrusions 43.

[0045] Next, the hot plate 50 is separated from the integrated battery case 12 and the lid body 2, and the hot plate 50 is removed from between the integrated battery case 12 and the lid body 2. Then, as shown in Fig. 4(a), the tip of the lower end 5a of the connection part 5 of the lid body 2 is pressed against the tip of the upper end part 13c of the side wall 13 of the integrated battery case 12 and the tip of the upper end part 14c of the end side wall 14, to weld the lid body 2 to the edge part 18a of the opening 18 of the integrated battery case 12. As a result, the thickness of the molten layer 41 is thicker on the inner surface 10a side of the battery case 10 than on the outer surface 10b side, and a welded part 40 having an inner protrusion 42 that protrudes less than the outer protrusion 43 is formed.

[0046] Thereafter, a hot plate 56 is pressed against the outer protrusion 43 to correct the shape of the outer protrusion 43 (FIG. 4(b)).

[0047] In this way, according to the manufacturing method of the battery module 1 of this embodiment, it is possible to suitably manufacture a battery module 1 in which the thickness of the molten layer 41 is thicker on the inner surface 10a side of the battery case 10 than on the outer surface 10b side, and in which an inner protrusion 42 is formed that protrudes less than the outer protrusion 43.

[0048] In the battery module 1 having the above configuration, as shown in Fig. 5, the molten layer 41 has a thick portion 41a on the side of the inner surface 10a of the battery case 10 that is thicker than other portions. In other words, the molten layer 41 is thicker on the side of the inner surface 10a of the molten battery case 10 than on the side of the outer surface 10b. This increases the welding strength between the integrated battery case 12 and the lid 2 on the side of the inner surface 10a of the battery case 10 where the base portion B of the inner protrusion 42, which is likely to be a crack starting point or where a strong force acts when the internal pressure increases with the use of the battery module 1, is present. Therefore, the molten layer 41 can withstand a high internal pressure compared to a case in which the molten layer 41 has a constant thickness.

[0049] In the battery module 1 of the present embodiment, the inner protrusions 42 protrude less than the outer protrusions 43. That is, in the battery module 1, the protrusions having higher rigidity protrude less on the inner surface 10a side of the battery case 10 than on the outer surface 10b side. This makes it possible to suppress stress concentration caused by the difference in rigidity when the internal pressure of the battery case 10 increases.

[0050] Furthermore, in the battery module 1 of this embodiment, the amount of molten resin flowing toward the inner surface 10a of the battery case 10 is suppressed during manufacturing, and more resin flows toward the outer surface 10b, so that the outer protrusions 43 protrude more than the inner protrusions 42. Therefore, compared to a case in which the amount of molten resin flowing toward the inner surface 10a of the battery case 10 is not suppressed, the linear distance R from the base B of the inner protrusion 42 to the end 41b of the molten layer 41 on the outer surface 10b side of the battery case 10 is longer, and the welded part 40 has high strength.

[0051] As described above, the battery module 1 according to this embodiment has high pressure resistance, and the manufacturing method of the battery module 1 according to this embodiment can suitably manufacture the battery module 1 having high pressure resistance.

[0052] [Another embodiment] [1] In the above embodiment, the molten layer 41 has the thick portion 41a on the inner surface 10a side of the battery case 10, and the molten layer 41 is thicker on the inner surface 10a side of the battery case 10 than on the outer surface 10b side of the battery case 10, but the present invention is not limited to this embodiment. For example, the thickness of the molten layer 41 may be continuously or stepwise decreased from the inner surface 10a side to the outer surface 10b side of the battery case 10, so that the thickness of the molten layer 41 is thicker on the inner surface 10a side of the battery case 10 than on the outer surface 10b side of the battery case 10.

[0053] [2] In the above embodiment, the melting step is performed using the hot plate 50 having two protrusions 52, 53, 54, 55 formed on each of the upper and lower surfaces, but the present invention is not limited to this embodiment. For example, protrusions may be formed on only one of the upper and lower surfaces. Even in this case, the melting amount of the resin constituting either the integrated battery case 12 or the lid body 2 can be made greater on the inner surface 10a side of the battery case 10 than on the outer surface 10b side, and the generation of the outer protrusions 43 can be promoted while suppressing the generation of the inner protrusions 42, so that the protrusion amount of the inner protrusions 42 is smaller than the protrusion amount of the outer protrusions 43. Alternatively, a hot plate may be used in which a protruding body having two side surfaces that can contact the two inner wall surfaces 4a of the recess 4 in the lid 2 or the two inner wall surfaces 13a of the integrated battery case 12 is formed on at least one of the upper and lower surfaces. In this case, as in the above, the amount of molten resin can be made larger on the outer surface 10b side than on the inner surface 10a side of the battery case 10, and the generation of the outer protrusions 43 can be promoted while suppressing the generation of the inner protrusions 42, so that the amount of protrusion of the inner protrusions 42 is smaller than the amount of protrusion of the outer protrusions 43.

[0054] [3] In the above embodiment, the hot plate 50 is described as being formed with a flat main body 51 and a plurality of protrusions 52, 53, 54, 55 on the front and back sides of the main body 51, but is not limited to this embodiment. FIG. 6 is a schematic diagram for explaining the melting step of the manufacturing method of the battery module according to another embodiment. For example, as shown in FIG. 6, in the melting step, the hot plate 60 may have a main body 61 and four protruding bodies 62, 63, 64, 65, and the portions 61a, 61b of the front and back surfaces of the main body 61 that contact the edge 18a of the opening 18 of the integrated battery case 12 (the tip of the upper end 13c of the side wall 13 and the tip of the upper end 14c of the end side wall 14) and the lid body 2 (the tip of the lower end 5a of the connection portion 5) are inclined downward from the inner surface 10a side to the outer surface 10b side of the battery case 10. In other words, the hot plate 60 may have a surface that contacts the mutually opposing portions of the integrated battery case 12 and the lid body 2 on the front and back surfaces of the main body 61 that is inclined downward from the inner surface 10a side to the outer surface 10b side of the battery case 10. In this case, in the melting process, the resins constituting the integrated battery case 12 and the lid body 2 are melted so that the opposing portions of the integrated battery case 12 and the lid body 2 form surfaces that slope downward from the inner surface 10a side to the outer surface 10b side of the battery case 10. In this embodiment, the molten resin easily flows from the inner surface 10a side to the outer surface 10b side of the battery case 10 in the melting step. Therefore, compared to a case in which the resin is melted so that the mutually opposing portions of the integrated battery case 12 and the lid 2 do not form inclined surfaces, the protrusion amount of the inner protrusions 42 is smaller than the protrusion amount of the outer protrusions 43. Therefore, in the obtained battery module 1, stress concentration when the internal pressure of the battery case 10 increases is further suppressed, and the welded parts 40 have higher strength.

[0055] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0056] 1: Battery module 2: Lid 4: Recess 4a: Inner wall surface 10: Battery case 10a: Inner surface 10b: External surface 11: Containment space 12: Integrated battery case (case body) 13a: Inner wall surface 18 :Aperture 18a: Edge (opening edge) 40: Welded part 41: Melting layer 42 :Inner protrusion 43 : Lateral process 50: Hot plate 50a:Top surface (surface) 50b:Bottom side (back side) 52, 53, 54, 55: protruding body 52a, 53a, 54a, 55a: Side M1: Welded part on the container side M2: Lid side melting part

Claims

1. A battery module in which a plurality of battery elements are housed inside a resin battery case, The battery case is a case body having an accommodation space for accommodating the battery element and an opening communicating the accommodation space with the outside; a cover body welded to an edge portion of the opening of the case body to close the opening, A battery module, wherein at the welded portion between the case body and the lid, a molten layer consisting of the molten resin of the case body and the molten resin of the lid is thicker on the inner surface side of the battery case than on the outer surface side.

2. the welded portion has a protrusion formed on an inner surface side of the battery case at the time of welding and a protrusion formed on an outer surface side of the battery case at the time of welding, The battery module according to claim 1 , wherein a protrusion amount generated on an inner surface side of the battery case is smaller than a protrusion amount generated on an outer surface side of the battery case.

3. The battery module according to claim 1 , wherein the melting layer is inclined downward from an inner surface side of the battery case toward an outer surface side of the battery case.

4. A method for manufacturing a battery module in which a plurality of battery elements are housed inside a battery case including a resin case body having a housing space for housing battery elements and communicating with the outside through an opening, and a resin cover body having a recessed portion opening on a rear surface and closing the opening of the case body, comprising: a melting step of melting a part of the case body and the lid by sandwiching a hot plate having one or more protrusions on at least one of the front and back surfaces between the opening edge of the case body and the lid; a joining step of welding and joining the case body and the lid body, In the melting step, the opening edge of the case body and the lid are brought into contact with the front and back surfaces of the hot plate, and the side surface of the protruding body is brought into contact with at least one of the inner wall surface of the case body and the inner wall surface of the recess in the lid, so that at least one of the melted amount of the resin constituting the case body and the melted amount of the resin constituting the lid is greater on the inner surface side of the battery case than on the outer surface side, and the generation of protrusions on the inner surface side of the battery case is suppressed and the generation of protrusions on the outer surface side of the battery case is promoted, In the joining step, the molten portion of the case body formed in the melting step and the molten portion of the lid body are brought into contact with each other and pressurized.

5. the hot plate has a front and rear surface, and a portion where the opening edge of the case body and the lid come into contact with the front and rear surfaces of the hot plate is inclined downward from the inner surface side to the outer surface side of the battery case, 5. The method for manufacturing a battery module according to claim 4, wherein in the melting process, the resin constituting the case body and the resin constituting the lid body are melted so that the opposing portions of the case body and the lid body form surfaces that slope downward from the inner surface side to the outer surface side of the battery case.

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