Battery pack

Abstract

To provide a battery pack in which joints in a battery case are resistant to corrosion.SOLUTION: A battery pack is configured to be mountable on a vehicle. The battery pack includes a battery case, battery cells housed in the battery case, and a protective layer formed on the battery case. The battery case includes a first case portion, a second case portion, and a joint portion. The first case portion and the second case portion form the outer surface of the battery case. The joint portion joins the first case portion and the second case portion. The protective layer is formed so as to be in close contact with the joint portion from the outside of the battery case.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a battery pack that can be mounted in a vehicle. [Background technology]

[0002] For example, a battery pack that can be mounted on a vehicle is described in Patent Document 1. The battery pack described in Patent Document 1 includes a battery case and battery cells housed in the battery case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-120244 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present invention have considered configuring this type of battery pack so that the battery case has two parts that form the outer surface of the battery case and a joint that joins these parts. However, it has been found that when the battery case is configured in this way, the joint may not have excellent corrosion resistance.

[0005] One aspect of the present disclosure provides a battery pack in which joints in a battery case are less susceptible to corrosion. [Means for solving the problem]

[0006] One aspect of the present disclosure is a battery pack configured to be mountable on a vehicle. The battery pack includes a battery case, battery cells housed in the battery case, and a protective layer formed on the battery case. The battery case has a first case portion, a second case portion, and a joint portion. The first case portion and the second case portion form an outer surface of the battery case. The joint portion joins the first case portion and the second case portion. The protective layer is formed so as to be in close contact with the joint portion from the outside of the battery case.

[0007] With this configuration, the joints in the battery case of the battery pack can be made less susceptible to corrosion.

[0008] In one aspect of the present disclosure, the first case part and the second case part may constitute an upper surface of an outer surface of the battery case. Even in such a configuration in which the joints are relatively likely to have poor corrosion resistance, the joints in the battery case can be made less susceptible to corrosion.

[0009] In one aspect of the present disclosure, the joint portion and the protective layer may be formed at positions that do not overlap with the battery cell in a top view. With this configuration, deterioration of the protective layer due to heat from the battery cell can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic perspective view of a battery pack. [Diagram 2] 2 is a schematic cross-sectional view of the battery pack when mounted under a vehicle. FIG. [Diagram 3] FIG. 2 is a schematic top view of the battery pack. [Figure 4] FIG. 13 is a schematic perspective view showing a modified example of a joint portion. [Diagram 5] Fig. 5A is a schematic cross-sectional view showing a first modified example of the protective layer, and Fig. 5B is a schematic cross-sectional view showing a second modified example of the protective layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0012] [1. Configuration] The battery pack 1 shown in Figs. 1 to 3 is configured to be mountable on a vehicle such as an electric car. For example, as shown in Fig. 2, the battery pack 1 is disposed below a floor panel F of the vehicle. The floor panel F is a member that constitutes the floor of the vehicle interior. When mounted on the vehicle, the battery pack 1 supplies power to, for example, a motor for running the vehicle. Note that "upper" and "lower" in this description and the drawings refer to upper and lower when the battery pack 1 is mounted on the vehicle.

[0013] As shown in FIGS. 1 and 2, the battery pack 1 includes a battery case 2, a plurality of battery cells 3, and a protective layer 4.

[0014] The battery case 2 is a member that houses a plurality of battery cells 3. In this embodiment, each of the plurality of battery cells 3 is a rectangular plate-shaped member. The plurality of battery cells 3 are housed in the battery case 2 in a stacked or aligned state.

[0015] The battery case 2 of this embodiment has a generally rectangular parallelepiped outer shape. The battery case 2 is made of metal. The battery case 2 is preferably made of a metal having high corrosion resistance. Examples of the metal having high corrosion resistance include zinc-containing plated steel and stainless steel.

[0016] The battery case 2 has an upper member 21 and a lower member 22. The upper member 21 and the lower member 22 are members that form an accommodation space 23 for accommodating the battery cells 3.

[0017] The upper member 21 is a box-shaped member that is open downward. The upper member 21 has a ceiling wall 211, a side wall 212, and a flange 213.

[0018] The ceiling wall 211 is a plate-like portion constituting the upper surface of the outer surface of the battery case 2. The ceiling wall 211 in this embodiment is generally rectangular. A plurality of ribs 214 are formed on the upper surface of the ceiling wall 211. The ribs 214 are groove-like portions. The ribs 214 in this embodiment extend linearly. Note that the ribs 214 are not shown in Figs. 2 and 3.

[0019] 1 and 2, the side wall 212 is a plate-like portion extending from the outer periphery of the ceiling wall 211 to the lower surface side of the ceiling wall 211. The side wall 212, together with a side wall 222 of the lower member 22 described later, constitutes a side surface of the outer surface of the battery case 2.

[0020] The flange 213 is a plate-like portion extending outward from the edge of the side wall 212 on the side opposite the ceiling wall 211. Here, the "outside" can be rephrased as the side opposite the ceiling wall 211 across the side wall 212. The flange 213 is formed with a plurality of insertion holes 215 for inserting the fasteners 5. Specific examples of the fasteners 5 include bolts, rivets, etc.

[0021] The upper member 21 is configured by joining a first case portion 21a and a second case portion 21b by a joining portion 21c. That is, the upper member 21 has the first case portion 21a, the second case portion 21b, and the joining portion 21c.

[0022] The first case part 21a and the second case part 21b are parts that constitute the outer surface of the battery case 2. In other words, the first case part 21a and the second case part 21b in this embodiment are each part when the upper member 21 is divided into two in a top view. That is, the first case part 21a and the second case part 21b in this embodiment constitute a part of the upper surface and a part of the side surface of the outer surface of the battery case 2, respectively.

[0023] The joint portion 21c is a portion that joins the first case portion 21a and the second case portion 21b. The joint portion 21c joins the first case portion 21a and the second case portion 21b by, for example, welding. When the first case portion 21a and the second case portion 21b are joined by welding, the joint portion 21c is also called a weld line. Note that, when the first case portion 21a and the second case portion 21b are joined by welding, the method of joining the first case portion 21a and the second case portion 21b is not particularly limited.

[0024] 3, the joints 21c are disposed in positions that do not overlap with the multiple battery cells 3 when viewed from above. The joints 21c in this embodiment extend linearly when viewed from above.

[0025] In this embodiment, the first case part 21a and the second case part 21b respectively constitute a part of the upper surface and a part of the side surface of the battery case 2, and therefore the joint part 21c that joins them also constitutes a part of the upper surface and a part of the side surface of the battery case 2. The ceiling wall 211, the side wall 212, and the flange 213 all include a part of the first case part 21a, the second case part 21b, and the joint part 21c.

[0026] 1 and 2, the lower member 22 is a box-shaped member that is open at the top. The lower member 22 has a bottom wall 221, a side wall 222, and a flange 223.

[0027] The bottom wall 221 is a plate-like portion that constitutes the lower surface of the outer surface of the battery case 2. The bottom wall 221 in this embodiment has a generally rectangular shape.

[0028] The side wall 222 is a plate-like portion extending from the outer periphery of the bottom wall 221 to the upper surface side of the bottom wall 221. The side wall 222, together with the side wall 212 of the upper member 21 described above, constitutes a side surface of the outer surface of the battery case 2.

[0029] The flange 223 is a plate-like portion extending outward from an edge of the side wall 222 opposite the bottom wall 221. Here, the "outside" can be rephrased as the side opposite the bottom wall 221 across the side wall 222. The flange 223 is formed with a plurality of insertion holes 224 for inserting the fasteners 5 therethrough. The insertion holes 224 communicate with the insertion holes 215 of the upper member 21 when the lower member 22 is disposed below the upper member 21.

[0030] The upper member 21 and the lower member 22 are arranged so as to be vertically overlapped. Specifically, the upper member 21 is arranged above the lower member 22 so that the flanges 213, 223 are in contact with each other and the ceiling wall 211 and the bottom wall 221 face each other with a gap therebetween. The ceiling wall 211 and the side wall 212 of the upper member 21 and the bottom wall 221 and the side wall 222 of the lower member 22 form an accommodation space 23. A fastener 5 is inserted into the insertion holes 215, 224 of the upper member 21 and the lower member 22. The upper member 21 is fixed to the lower member 22 by the fastener 5.

[0031] The protective layer 4 is a layer that protects at least the joint portion 21c of the battery case 2 from corrosive substances. A corrosive substance is a substance that can corrode the battery case 2. Specific examples of corrosive substances include water such as rainwater and salt water, acids contained in snow-melting agents, and oxygen contained in the air. Acids, for example, when coexisting with water, tend to corrode the battery case 2.

[0032] The protective layer 4 has a property of suppressing the permeation of corrosive substances. Specific examples of the property of suppressing the permeation of corrosive substances include water resistance and poor oxygen permeability. The protective layer 4 can be mechanically, chemically, or physically bonded to the joint 21c. The mechanical bond is a bond formed by the protective layer 4 entering the unevenness of the surface of the joint 21c (so-called anchor effect). The chemical bond is a bond formed by chemical bonds (e.g., covalent bonds) between atoms of the joint 21c and the protective layer 4. The physical bond is a bond formed by intermolecular interactions (e.g., hydrogen bonds, electrostatic interactions, van der Waals forces) between the joint 21c and the protective layer 4.

[0033] The protective layer 4 is, for example, a coating film, an adhesive film, or a pressure-sensitive adhesive film. The coating film is a film formed by applying a coating material. A specific example of the coating material is a cationic coating material. The adhesive film is a film formed by applying an adhesive. A specific example of the adhesive is a urethane adhesive, a modified silicone adhesive, an epoxy adhesive, and the like. The pressure-sensitive adhesive film is a film formed by applying an adhesive. A specific example of the adhesive is a urethane adhesive.

[0034] The protective layer 4 is formed on the battery case 2 so as to be in close contact with at least the joint portion 21c from the outside (more specifically, the upper side) of the battery case 2. Being in close contact with the joint portion 21c can also be said to be attached to the joint portion 21c without any gaps. The protective layer 4 exerts high adhesion to the joint portion 21c by being mechanically, chemically, or physically bonded to the joint portion 21c.

[0035] In this embodiment, as shown in Fig. 3, the protective layer 4 is formed so as to be in close contact with the entire joint portion 21c. The protective layer 4 extends linearly in a top view. The protective layer 4 is formed so as not to overlap with the multiple battery cells 3 in a top view.

[0036] In this embodiment, the protective layer 4 is formed to be in close contact with the joint portion 21c as well as with the area of ​​the first case portion 21a and the second case portion 21b adjacent to the joint portion 21c. In other words, the protective layer 4 is not formed on the first case portion 21a and the second case portion 21b except for the area of ​​the first case portion 21a and the second case portion 21b adjacent to the joint portion 21c.

[0037] [2. Effects] (2a) When the battery pack 1 is mounted on a vehicle, the battery case 2 may come into contact with a corrosive substance. For example, when the battery pack 1 is placed under a floor panel F of the vehicle as shown in Fig. 2, the battery case 2 may be covered with rainwater that is splashed up from the tires while the vehicle is traveling. As described above, rainwater corresponds to an example of a corrosive substance.

[0038] In the battery case 2, among the first case part 21a, the second case part 21b, and the joint part 21c, the joint part 21c is relatively susceptible to corrosion. Therefore, the protective layer 4 is formed on the battery case 2 so as to be in close contact with the joint part 21c from the outside of the battery case 2. According to this configuration, since the protective layer 4 is formed so as to be in close contact with the joint part 21c, it is possible to suppress the intrusion of corrosive substances into the boundary surface between the joint part 21c and the protective layer 4. Therefore, it is possible to make the joint part 21c less likely to come into contact with corrosive substances. As a result, it is possible to make the joint part 21c less likely to corrode.

[0039] (2b) Furthermore, the strength of the joint portion 21c may be lower than that of the first case portion 21a and the second case portion 21b. According to the above-described configuration, the protective layer 4 is formed so as to be in close contact with the joint portion 21c, thereby reinforcing the joint portion 21c.

[0040] (2c) The protective layer 4 may be formed, for example, on the entire outer surface of the battery case 2. That is, the protective layer 4 may be formed from the outside of the battery case 2 so as to be in close contact with, for example, the entire first case part 21a, the entire second case part 21b, and the entire joint part 21c. In this case, it is possible to make it difficult for not only the joint part 21c but also the first case part 21a and the second case part 21b to come into contact with a corrosive substance. On the other hand, in manufacturing the battery pack 1, the time and cost required for forming the protective layer 4 tend to increase. For example, when the protective layer 4 is a coating, it often takes time for the paint to dry. In addition, a large amount of carbon dioxide may be emitted when the paint dries.

[0041] Therefore, in this embodiment, the protective layer 4 is not formed on the first case part 21a and the second case part 21b except for the region adjacent to the joint part 21c. With such a configuration, it is possible to reduce the time and cost required for forming the protective layer 4 while making it difficult for the joint part 21c, which is relatively susceptible to corrosion, to come into contact with a corrosive substance. Furthermore, the weight of the battery pack 1 can be reduced by the amount of the reduced protective layer 4.

[0042] (2d) In this embodiment, the protective layer 4 is formed so as to adhere to the joint portion 21c as well as to the areas of the first case portion 21a and the second case portion 21b adjacent to the joint portion 21c.

[0043] For example, when the joint 21c joins the first case part 21a and the second case part 21b by welding, the region adjacent to the joint 21c in the first case part 21a and the second case part 21b may have a slightly different composition compared to the other regions due to heat during welding. In this case, the region adjacent to the joint 21c in the first case part 21a and the second case part 21b may have a lower corrosion resistance compared to the other regions.

[0044] However, according to the above-mentioned configuration, since the protective layer 4 is formed so as to be in close contact with the area adjacent to the joint portion 21c in the first case portion 21a and the second case portion 21b, the area can also be made less susceptible to contact with corrosive substances. Therefore, even if the corrosion resistance of the area is reduced, the area can be made less susceptible to corrosion.

[0045] (2e) The battery case 2 is made of, for example, a metal having high corrosion resistance. With such a configuration, even if the protective layer 4 is not formed on the first case part 21a and the second case part 21b, it is possible to make the first case part 21a and the second case part 21b less susceptible to corrosion.

[0046] (2f) The first case part 21a and the second case part 21b constitute the upper surface of the outer surface of the battery case 2. With this configuration, corrosive substances are more likely to accumulate on the surfaces of the first case part 21a and the second case part 21b than when the first case part 21a and the second case part 21b constitute, for example, the side surface or the lower surface of the outer surface of the battery case 2. When corrosive substances accumulate on the surfaces of the first case part 21a and the second case part 21b, the joint part 21c that joins them is more likely to come into contact with the corrosive substances. That is, a problem that the joint part 21c may not have excellent corrosion resistance is likely to occur. Therefore, it is more useful to form the protective layer 4 so as to be in close contact with the joint part 21c, thereby making it difficult for the joint part 21c to come into contact with the corrosive substances.

[0047] (2g) In addition, when the first case part 21a and the second case part 21b form the upper surface of the battery case 2, the joint part 21c that joins them also forms the upper surface of the battery case 2. The protective layer 4 is formed so as to be in close contact with the joint part 21c from the upper side of the battery case 2.

[0048] According to this configuration, for example, when the battery pack 1 is disposed below the floor panel F of the vehicle as shown in Fig. 2, the protective layer 4 is located between the floor panel F and the battery case 2. Therefore, when the battery case 2 bulges due to heat from the battery cells 3, the protective layer 4 can prevent the battery case 2 from coming into contact with the floor panel F. In other words, it becomes possible for the protective layer 4 to function as a buffer member.

[0049] (2h) The bonding portion 21c and the protective layer 4 are formed in a position that does not overlap the battery cell 3 in a top view. This configuration makes the bonding portion 21c and the protective layer 4 less susceptible to the effects of heat from the battery cell 3. Therefore, deterioration of the protective layer 4 due to heat from the battery cell 3 can be suppressed.

[0050] 3. Other embodiments Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

[0051] (3a) In the above embodiment, the protective layer 4 is formed on the battery case 2 so as to be in close contact with at least the joint 21c. Specifically, the protective layer 4 is formed on the battery case 2 so as to be in close contact with the entire joint 21c and the areas of the first case part 21a and the second case part 21b adjacent to the protective layer 4. However, the range in which the protective layer is formed on the battery case 2 is not particularly limited. For example, the protective layer may be formed so as to be in close contact only with the entire joint 21c. Also, for example, the protective layer may be formed so as to be in close contact with the entire joint 21c, the entire first case part 21a, and the entire second case part 21b (i.e., so as to be in close contact with the entire outer surface of the battery case 2).

[0052] (3b) In the above embodiment, the joint 21c extends linearly in top view. However, the shape of the joint is not particularly limited. For example, like the joint 24c in the upper member 24 shown in FIG. 4, the joint 24c that joins the first case portion 24a and the second case portion 24b may extend while being bent at least at one point in top view. Note that FIG. 4 shows the upper member 24 in a state where a protective layer is not formed.

[0053] (3c) In the above embodiment, the joints 21c are formed at positions that do not overlap the battery cells 3 in a top view. However, the arrangement of the joints in the upper member 21 is not particularly limited. For example, the joints may be formed at positions that overlap the battery cells 3 in a top view, in addition to or instead of the positions in the above embodiment. In that case, the protective layer may also be formed at positions that overlap the battery cells 3 in a top view, in addition to or instead of the positions in the above embodiment, so as to correspond to the positions of the joints. In other words, the arrangement of the protective layer in the upper member 21 is also not particularly limited.

[0054] (3d) In the above embodiment, the protective layer 4 extends linearly along the linearly extending joint 21c in top view. However, the shape of the protective layer is not particularly limited and may be changed as appropriate depending on, for example, the shape of the joint.

[0055] (3e) The cross-sectional shape perpendicular to the extension direction of the protective layer is not particularly limited. For example, as in the above embodiment shown in FIG. 2, the cross-sectional shape perpendicular to the extension direction of the protective layer 4 may be rectangular. For example, as in a first modified example shown in FIG. 5A, the cross-sectional shape perpendicular to the extension direction of the protective layer 4A may be triangular. For example, as in a second modified example shown in FIG. 5B, the cross-sectional shape perpendicular to the extension direction of the protective layer 4B may be semicircular.

[0056] (3f) In the above embodiment, the protective layer 4 has a property of suppressing the permeation of corrosive substances. The protective layer may further have, for example, elasticity. In the case where the protective layer can function as a buffer member as in the above embodiment, it is useful for the protective layer to have elasticity.

[0057] (3g) In the above embodiment, the rib 214 is formed on the ceiling wall 211 of the upper member 21. When the rib is formed on the ceiling wall of the upper member in this way, the shape of the rib is not particularly limited. For example, the rib may be a groove-shaped portion (so-called concave rib) as in the above embodiment, or a portion protruding from the ceiling wall (so-called convex rib). For example, the rib may be a portion extending linearly as in the above embodiment, or a portion extending curvedly (e.g., wavy). For example, when multiple ribs are formed as in the above embodiment, the multiple ribs may be formed side by side as in the above embodiment, or may be formed to spread radially. For example, the ceiling wall of the upper member does not necessarily have to have a rib formed.

[0058] (3h) In the above embodiment, the upper member 21 has the first case portion 21a and the second case portion 21b. However, the upper member may have, for example, three or more case portions, or four or more case portions.

[0059] (3i) In the above embodiment, the first case part 21a and the second case part 21b form the upper surface of the battery case 2. That is, the part forming the upper surface of the battery case 2 (the ceiling wall 211 in the above embodiment) is configured to include the first case part 21a and the second case part 21b. However, in the battery case 2, the part formed to include two or more case parts is not limited to the part forming the upper surface of the battery case 2. For example, in addition to or instead of the part forming the upper surface of the battery case 2, the part forming the side surface or the lower surface of the battery case 2 (the side walls 212, 222 or the bottom wall 221 in the above embodiment) may be configured to include two or more case parts.

[0060] (3j) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. [Explanation of symbols]

[0061] REFERENCE SIGNS LIST 1...battery pack, 2...battery case, 21...upper member, 21a...first case part, 21b...second case part, 21c...joint part, 22...lower member, 23...accommodation space, 3...battery cell, 4...protective layer, F...floor panel.

Claims

1. A battery pack configured to be mountable in a vehicle, A battery case; A battery cell accommodated in the battery case; A protective layer formed on the battery case; Equipped with The battery case includes: A first case portion and a second case portion that configure an outer surface of the battery case; a joint portion that joins the first case portion and the second case portion; having The protective layer is formed so as to be in close contact with the joint portion from the outside of the battery case.

2. 2. The battery pack according to claim 1, The first case portion and the second case portion form an upper surface of an outer surface of the battery case.

3. The battery pack according to claim 1 or 2, The joint portion and the protective layer are formed at positions that do not overlap with the battery cells in a top view of the battery pack.

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