Bipolar battery structure

Abstract

The invention provides a bipolar battery structure capable of inhibiting flux from seeping to a conductive adhesive side during brazing. The bipolar battery structure is formed by alternately stacking battery modules and coolers. The cooler is provided with: a first metal plate having a convex surface section bonded to the bottom surface of the upper battery module via a conductive adhesive, and a pair of first flange sections disposed on both sides of the convex surface section; a second metal plate having a concave surface portion bonded to the top surface of the lower battery module via a conductive adhesive, and a pair of second flange portions disposed on both sides of the concave surface portion; and a metal wave plate disposed between the first metal plate and the second metal plate to form a refrigerant flow path. The first metal plate, the second metal plate, and the metal corrugated plate are joined by brazing. A first engagement protrusion that engages with the bottom surface recess of the upper battery module is disposed on the outer side of the first flange portion, and a second engagement protrusion that engages with the top surface recess of the lower battery module is disposed on the outer side of the second flange portion.

Description

Technical Field

[0001] This invention relates to a bipolar battery structure. Background Technology

[0002] Conventionally, the technology described in Patent Document 1 is an example of this technical field. The bipolar battery structure described in Patent Document 1 consists of a battery module and a cooler stacked together, and the battery module is cooled by a refrigerant flowing through the cooler.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-133874 Summary of the Invention

[0004] In manufacturing the aforementioned bipolar battery structure, from the viewpoint of ensuring sealing, it is preferable to join multiple metal plates together by brazing to form a cooler. Furthermore, to secure the cooler and battery module, a conductive adhesive is applied between them for bonding. However, when brazing the metal plates, flux needs to be applied to the metal plates to remove the natural oxide film. Therefore, during brazing, flux may seep onto the conductive adhesive coating surface, remaining as residue and potentially causing an increase in resistance.

[0005] This invention was made to solve this technical problem, and its purpose is to provide a bipolar battery structure that can suppress flux leakage to the conductive binder side during brazing.

[0006] The bipolar battery structure of this invention comprises multiple battery modules and multiple coolers stacked alternately. Each cooler includes: a first metal plate having a convex portion bonded to the bottom surface of one of a pair of adjacent battery modules along the stacking direction via a conductive adhesive, and a pair of first flanges disposed on both sides of the convex portion; a second metal plate having a concave portion bonded to the top surface of the other pair of adjacent battery modules via a conductive adhesive, and a pair of second flanges disposed on both sides of the concave portion; and a metal corrugated plate disposed between the first metal plate and the second metal plate. The convex and concave portions form a refrigerant flow path. The first metal plate, the second metal plate, and the metal corrugated plate are joined by brazing with the end of the metal corrugated plate clamped between the first flange and the second flange. A first engaging protrusion is provided on the outer side of the first flange of the first metal plate to engage with the bottom surface recess of the bottom surface of the battery module, and / or a second engaging protrusion is provided on the outer side of the second flange of the second metal plate to engage with the top surface recess of the top surface of the battery module.

[0007] In the bipolar battery structure of this invention, a first engaging protrusion is disposed on the outer side of the first flange of the first metal plate, engaging with the bottom recess of the battery module bonded to the first metal plate, and / or a second engaging protrusion is disposed on the outer side of the second flange of the second metal plate, engaging with the top recess of the battery module bonded to the second metal plate. Furthermore, the first engaging protrusion and / or the second engaging protrusion can suppress flux leakage into the conductive adhesive side during brazing. As a result, an increase in resistance caused by flux leakage can be prevented, and electrical conductivity can be ensured.

[0008] In the bipolar battery structure of the present invention, it is preferable that the first engaging protrusion is disposed on the outer side of the first flange portion of the first metal plate, and the second engaging protrusion is disposed on the outer side of the second flange portion of the second metal plate. In this case, the first engaging protrusion prevents flux from seeping into the conductive adhesive between the first metal plate and the bottom surface of the battery module, and the second engaging protrusion prevents flux from seeping into the conductive adhesive between the second metal plate and the top surface of the battery module, thereby improving the effect of suppressing flux seepage into the conductive adhesive side during brazing. Furthermore, by engaging the first engaging protrusion with the bottom recess of the battery module and engaging the second engaging protrusion with the top recess of the battery module, the battery module and the cooler in the stacking direction can be easily positioned, and positional displacement of the battery module and the cooler in a direction orthogonal to the stacking direction can be prevented.

[0009] In the bipolar battery structure of the present invention, preferably, the first engaging protrusion has a first bent portion that bends from the first flange toward the bottom surface of the battery module, and the second engaging protrusion has a second bent portion that bends from the second flange toward the top surface of the battery module, wherein the first metal plate, the second metal plate, and the metal corrugated plate are respectively formed of aluminum.

[0010] In a direction orthogonal to the stacking direction, the metal corrugated plate is disposed on the inner side of the first and second bends such that the distance from its end face to the first bend and the distance from its end face to the second bend are both L or more, where L = (σcosθ) / (4.9ρt), σ is the surface tension coefficient between the flux and aluminum, θ is the contact angle between the flux and aluminum, ρ is the density of the flux, and t is the thickness of the metal corrugated plate in the stacking direction. This reliably suppresses the flux seeping into the conductive adhesive between the first metal plate and the bottom surface of the battery module via the first engaging protrusion, and reliably suppresses the flux seeping into the conductive adhesive between the second metal plate and the top surface of the battery module via the second engaging protrusion.

[0011] Invention Effects

[0012] According to the present invention, it is possible to suppress the seepage of flux into the conductive adhesive side during brazing. Attached Figure Description

[0013] Figure 1 This is a schematic cross-sectional view showing the bipolar battery structure involved in the embodiment.

[0014] Figure 2 yes Figure 1 An enlarged view of part A.

[0015] Figure 3 This is a schematic cross-sectional view used to illustrate the length L where no flux seepage occurs.

[0016] Figure 4 This is a schematic diagram used to illustrate the amount of liquid intrusion based on capillary phenomena.

[0017] Figure 5 This is a schematic cross-sectional view used to illustrate the problem of conventional bipolar battery structures (flux leakage).

[0018] Figure 6 This is a schematic cross-sectional view used to illustrate the problem (positional offset) of previous bipolar battery structures. Detailed Implementation

[0019] Hereinafter, embodiments of the bipolar battery structure according to the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are labeled with the same symbols, and repeated descriptions thereof are omitted.

[0020] Figure 1 This is a schematic cross-sectional view showing the bipolar battery structure involved in the embodiment. Figure 2 yes Figure 1 The enlarged view of part A is shown. The bipolar battery structure 1 of this embodiment is formed by alternately stacking multiple battery modules 2 and multiple coolers 3 along one direction (stack direction). Furthermore, the bipolar battery structure 1 will be described below with the stacking direction of the battery modules 2 and coolers 3 being the vertical direction of each figure, and the length direction of the battery modules 2 or coolers 3 being the horizontal direction of each figure. However, these directions are merely convenient directions corresponding to the states shown in the figures and do not limit the orientation or configuration of the bipolar battery structure 1.

[0021] Battery module 2 is a module comprising multiple stacked battery cells. Although not shown, each battery cell has bipolar electrodes, and current collectors and separators coated with positive and negative electrode active materials are alternately stacked on both sides. Furthermore, each battery cell is configured to directly conduct electricity in the stacking direction of the bipolar electrodes. In battery module 2, the stacking direction of the battery cells is the same as the direction in which the current flows. In this embodiment, the stacking direction of the battery cells is the same as the stacking direction of battery module 2 and cooler 3.

[0022] A top surface recess 21 is provided on the top surface (i.e., upper surface) 2a of the battery module 2, which can engage with the second engaging protrusion 323 of the cooler 3 described later. The top surface recess 21 is respectively disposed on two edges in the length direction of the battery module 2 (see reference). Figure 1 The top surface recess 21 extends along the width direction of the battery module 2 and is formed across the entire width of the battery module 2. That is, the top surface recess 21 is a groove formed on the top surface 2a of the battery module 2 across the entire width of the battery module 2. In addition, the width direction refers to the direction orthogonal to the stacking direction and the length direction.

[0023] Corresponding to the top surface recess 21, a bottom surface recess 22 is provided on the bottom surface (i.e., the lower surface) 2b of the battery module 2, which can engage with the first engaging protrusion 313 of the cooler 3 described later. The bottom surface recesses 22 are respectively disposed on two edges in the length direction of the battery module 2, so that they are in the same position as the top surface recess 21 in the stacking direction (see reference). Figure 1 The bottom recess 22, like the top recess 21, is a groove formed across the entire width of the battery module 2.

[0024] The cooler 3 is a flat box-shaped device with a space for refrigerant to circulate inside. The refrigerant flowing through it absorbs heat from the battery module 2, thereby cooling the battery module 2. Figure 1 As shown, the cooler 3 is disposed between adjacent upper and lower battery modules 2 in the stacking direction and absorbs heat from the upper and lower battery modules 2.

[0025] The cooler 3 includes: a first metal plate 31, which is bonded to the bottom surface 2b of the upper battery module 2 of the pair of upper and lower battery modules 2; a second metal plate 32, which is bonded to the top surface 2a of the lower battery module 2; and a metal corrugated plate 33, which is disposed between the first metal plate 31 and the second metal plate 32.

[0026] The first metal plate 31 has a convex cross-section and includes a convex portion 311 located at the center of the first metal plate 31 and coinciding with the bottom surface 2b of the upper battery module 2, and a pair of first flange portions 312 located on the left and right sides of the convex portion 311. The convex portion 311 is the planar portion of the first metal plate 31 that contacts the bottom surface 2b of the upper battery module 2, and is formed to be larger than other portions such as the first flange portions 312 in order to improve the heat absorption rate. On the other hand, the first flange portions 312 are parallel to the convex portion 311.

[0027] Furthermore, a first engaging protrusion 313 is disposed on the outer side of the first flange portion 312 of the first metal plate 31, which engages with the bottom surface recess 22 of the upper battery module 2. The first engaging protrusion 313 is integrally formed with the first flange portion 312 and is located on the side away from the convex portion 311. The first engaging protrusion 313 protrudes from the first flange portion 312 to the bottom surface 2b of the upper battery module 2 and has an inverted "V" shape in cross-section. Moreover, when the first engaging protrusion 313 is engaged with the bottom surface recess 22, its inverted "V" shaped front end is inserted into the interior of the bottom surface recess 22. Furthermore, the first engaging protrusion 313 has a first bent portion 313a that bends from the first flange portion 312 toward the bottom surface 2b of the upper battery module 2 (see reference). Figure 2 ).

[0028] The first metal plate 31 having this structure is formed, for example, by stamping a metal plate such as aluminum, aluminum alloy, or stainless steel.

[0029] The second metal plate 32 has a concave cross-section and includes a concave portion 321 located at the center of the second metal plate 32 and coinciding with the top surface 2a of the lower battery module 2, and a pair of second flange portions 322 located on the left and right sides of the concave portion 321. The concave portion 321 is the planar portion of the second metal plate 32 that contacts the top surface 2a of the lower battery module 2, and is formed to be larger than other portions such as the second flange portions 322 to improve the heat absorption rate of the lower side. On the other hand, the second flange portions 322 are parallel to the concave portion 321.

[0030] Furthermore, a second engaging protrusion 323 is disposed on the outer side of the second flange portion 322 of the second metal plate 32, which engages with the top surface recess 21 of the lower battery module 2. The second engaging protrusion 323 is integrally formed with the second flange portion 322 and is located on the side away from the recess portion 321. The second engaging protrusion 323 protrudes from the second flange portion 322 to the top surface 2a of the lower battery module 2 and has an inverted "V" shape in cross-section. Moreover, when the second engaging protrusion 323 is engaged with the top surface recess 21, its inverted "V" shaped front end is inserted into the interior of the top surface recess 21. Furthermore, the second engaging protrusion 323 has a second bent portion 323a that bends from the second flange portion 322 toward the top surface 2a of the lower battery module 2 (see reference). Figure 2 ).

[0031] The second metal plate 32 having this structure is formed, for example, by stamping a metal plate such as aluminum, aluminum alloy, or stainless steel.

[0032] The metal corrugated plate 33 is formed into a corrugated cross-section by alternating multiple recesses 331 and protrusions 332. The bottom of the recesses 331 is planar and contacts the concave portion 321 of the second metal plate 32. On the other hand, the top of the protrusions 332 is also planar and contacts the convex portion 311 of the first metal plate 31. These recesses 331 and protrusions 332 are arranged within a space surrounded by the convex portion 311 of the first metal plate 31 and the concave portion 321 of the second metal plate 32, and the convex portion 311 and concave portion 321 form a refrigerant flow path.

[0033] Furthermore, the metal corrugated plate 33 has a pair of third flange portions 333 disposed on the left and right sides of the region where a plurality of recesses 331 and protrusions 332 are formed. The metal corrugated plate 33 having this structure is formed, for example, by stamping a metal plate such as aluminum, aluminum alloy, or stainless steel, similar to the first metal plate 31 and the second metal plate 32.

[0034] like Figure 1 As shown, the first metal plate 31, the second metal plate 32, and the metal corrugated plate 33 are joined by welding with the end of the third flange 333 clamped between the first flange 312 and the second flange 322. Specifically, the first flange 312 and the second flange 322 are joined to the first engaging protrusion 313 by solder with flux (in other words, solder 34 and flux 35).

[0035] When performing brazing, such as Figure 3 As shown in (a), firstly, solder 34 is disposed on the upper and lower surfaces of the third flange portion 333 of the metal corrugated plate 33, and flux 35 is applied to the surface of each solder 34 facing the first flange portion 312 or the second flange portion 322. Next, with the solder 34 and flux 35 respectively positioned between the third flange portion 333 and the first flange portion 312, and between the third flange portion 333 and the second flange portion 322, the metal corrugated plate 33 is clamped by the first metal plate 31 and the second metal plate 32, and the first flange portion 312, the second flange portion 322, and the third flange portion 333 are brazed together.

[0036] In addition, the solder 34 uses a metal material (e.g., aluminum alloy) with a melting point lower than that of the first metal plate 31, the second metal plate 32, and the metal corrugated plate 33. The flux 35 uses, for example, a non-corrosive flux.

[0037] The cooler 3, constructed as described above, is fixed to the upper and lower battery modules 2 by a conductive adhesive 36 while being sandwiched between them. Specifically, the cooler 3 is fixed to the upper and lower battery modules 2 by bonding the convex portion 311 of the first metal plate 31 to the bottom surface 2b of the upper battery module 2 with the conductive adhesive 36, and by bonding the concave portion 321 of the second metal plate 32 to the top surface 2a of the lower battery module 2 with the conductive adhesive 36.

[0038] like Figure 1 and Figure 2 As shown, the conductive adhesive 36 is intermittently applied to the convex portion 311 or the concave portion 321 at certain intervals. Alternatively, the conductive adhesive 36 can be applied to the entire surface of the convex portion 311 or the entire surface of the concave portion 321. Furthermore, the conductive adhesive 36 can also be applied to the first engaging protrusion 313 and the second engaging protrusion 323, but this application can be omitted. For example, silver paste can be used as the conductive adhesive 36.

[0039] In the bipolar battery structure 1 of this embodiment, a first engaging protrusion 313 is disposed on the outer side of the first flange portion 312 of the first metal plate 31, engaging with the bottom surface recess 22 of the upper battery module 2 bonded to the first metal plate 31. A second engaging protrusion 323 is disposed on the outer side of the second flange portion 322 of the second metal plate 32, engaging with the top surface recess 21 of the lower battery module 2 bonded to the second metal plate 32. The first engaging protrusion 313 and the second engaging protrusion 323 can suppress the leakage of flux 35 into the conductive adhesive 36 during brazing. As a result, the increase in resistance caused by the leakage of flux 35 can be prevented, and the conductivity of the bipolar battery structure 1 can be ensured.

[0040] For example, in Figure 5 In the conventional cooler 3A shown in (a), neither the first metal plate 31A nor the second metal plate 32A has the aforementioned engaging protrusions (first engaging protrusion 313 and second engaging protrusion 323). Furthermore, in the longitudinal direction, the end faces of the first metal plate 31A, the second metal plate 32A, and the metal corrugated plate 33 are coplanar. Moreover, when the third flange portion 333 is brazed while being held by the first flange portion 312A and the second flange portion 322A, flux 35 seeps out due to capillary action to the upper surface of the first flange portion 312A and the lower surface of the second flange portion 322A (see reference). Figure 5 (b) This residue seeps into the conductive adhesive side and becomes a residue, leading to increased resistance.

[0041] To address this issue in this embodiment, first engaging protrusions 313 are provided on the first metal plate 31 to engage with the bottom recess 22 of the upper battery module 2, and second engaging protrusions 323 are provided on the second metal plate 32 to engage with the top recess 21 of the lower battery module 2. The first engaging protrusions 313 prevent flux 35 from seeping into the conductive adhesive 36 between the convex portion 311 and the bottom surface 2b of the upper battery module 2, and the second engaging protrusions 323 prevent flux 35 from seeping into the conductive adhesive 36 between the recessed portion 321 and the top surface 2a of the lower battery module 2.

[0042] Furthermore, by engaging the first engaging protrusion 313 with the bottom recess 22 of the upper battery module 2 and engaging the second engaging protrusion 323 with the top recess 21 of the lower battery module 2, the battery module 2 and the cooler 3 in the stacking direction can be easily positioned, and the positional displacement of the battery module 2 and the cooler 3 in the length direction can be prevented.

[0043] For example, in Figure 6 In the conventional bipolar battery structure 1A shown, when multiple battery modules 2 and coolers 3A are stacked, the battery modules 2 and coolers 3A are prone to positional misalignment because there are no positioning structures for the battery modules 2 and coolers 3A in the stacking direction or structures to restrict their movement in the length direction. If this positional misalignment occurs, the conductive area decreases, resulting in a reduction in the battery pack's capacity.

[0044] To address this issue, in this embodiment, a top surface recess 21 is provided on the top surface 2a of the battery module 2, a bottom surface recess 22 is provided on the bottom surface 2b, a first engaging protrusion 313 that engages with the bottom surface recess 22 is provided on the first metal plate 31, and a second engaging protrusion 323 that engages with the top surface recess 21 is provided on the second metal plate 32. Furthermore, when stacking the battery module 2 and the cooler 3, by engaging the first engaging protrusion 313 with the bottom surface recess 22 of the upper battery module 2 and engaging the second engaging protrusion 323 with the top surface recess 21 of the lower battery module 2, the battery module 2 and the cooler 3 can be easily positioned in the stacking direction, and the positional shift of the battery module 2 and the cooler 3 in the length direction can be prevented.

[0045] Furthermore, in the bipolar battery structure 1 of this embodiment, when the first metal plate 31, the second metal plate 32, and the metal corrugated plate 33 are each formed of aluminum, such as Figure 3As shown, the distance from the end face 33a of the metal corrugated plate 33 to the first bend 313a and the distance from the end face 33a of the metal corrugated plate 33 to the second bend 323a are both L or more. In this embodiment, L refers to the length at which flux seepage does not occur, and is calculated by L = (σcosθ) / (4.9ρt). σ is the surface tension coefficient between the flux liquid and aluminum, θ is the contact angle between the flux liquid and aluminum, ρ is the density of the flux liquid, and t is the thickness of the metal corrugated plate 33 in the stacking direction. Furthermore, in Figure 3 In the diagram, (a) represents the state with flux applied (i.e., the state before brazing), and (b) represents the state with the flux diluted (i.e., the state after brazing).

[0046] Here, based on Figure 4 The length L where flux leakage does not occur is described in detail.

[0047] like Figure 4 As shown, typically, the amount of liquid 11 penetrating into the gap between the two plates 10, h, through capillary action, is calculated using h = (2σcosθ) / (gρt) = (σcosθ) / (4.9ρt). Here, σ is the surface tension coefficient (unit: N / m), θ is the contact angle (unit: deg), and ρ is the density of the liquid (unit: g / m³). 3 ), t is the gap (unit: m), g is the gravitational acceleration (9.8 kg / m). 2 ).

[0048] Referring to the aforementioned intrusion amount h, in this embodiment, the distance from the end face 33a of the metal corrugated plate 33 to the first bend 313a and the distance from the end face 33a of the metal corrugated plate 33 to the second bend 323a are both set to L or more. Furthermore, L = (σcosθ) / (4.9ρt), where σ is the surface tension coefficient between the flux and aluminum (unit: N / m), θ is the contact angle between the flux and aluminum (unit: deg), and ρ is the density of the flux (unit: g / m³). 3 ), where t is the thickness of the metal corrugated plate in the stacking direction (unit: m).

[0049] Furthermore, when the surface tension coefficient between the flux and aluminum is σ = 23 mN / m, the contact angle between the flux and aluminum is θ = 10°, and the density of the flux is ρ = 0.79 g / cm³, the desired surface tension is achieved. 3 When the thickness of the metal corrugated plate in the stacking direction is t = 0.8 mm, L = 7 mm.

[0050] Thus, the distances from the end face 33a of the metal corrugated plate 33 to the first bend 313a and from the end face 33a of the metal corrugated plate 33 to the second bend 323a are both set to L or more, so the intrusion of flux 35 caused by capillary action is limited to the aforementioned L range. In other words, even if flux 35 intrudes beyond the end face 33a due to capillary action, its intrusion will not exceed the aforementioned L. Therefore, flux 35 can be reliably suppressed from seeping into the conductive adhesive 36 side between the convex part 311 and the bottom surface 2b of the upper battery module 2, and from seeping into the conductive adhesive 36 side between the concave part 321 and the top surface 2a of the lower battery module 2.

[0051] Furthermore, even if flux 35 seeps out beyond L, it will accumulate due to gravity in the concave portion of the second engaging protrusion 323, which has an inverted "V" shaped cross section, thus preventing further seepage to the conductive adhesive 36 side.

[0052] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Various design changes can be made without departing from the spirit of the present invention as set forth in the claims.

[0053] Symbol Explanation

[0054] 1-Bipolar battery structure, 2-Battery module, 2a-Top surface, 2b-Bottom surface, 3-Cooler, 21-Top surface recess, 22-Bottom surface recess, 31-First metal plate, 32-Second metal plate, 33-Metal corrugated plate, 33a-End face, 34-Solder, 35-Fluoride, 311-Convex part, 312-First flange, 313-First engaging protrusion, 313a-First bending part, 321-Concave part, 322-Second flange, 323-Second engaging protrusion, 323a-Second bending part, 331-Concave part, 332-Convex part, 333-Third flange.

Claims

1. A bipolar battery structure which is formed by alternately stacking a plurality of battery modules and a plurality of coolers, the bipolar battery structure characterized by, the cooler is provided with: a first metal plate having a convex portion adhered to a bottom surface of one of a pair of battery modules adjacent in a stacking direction via a conductive adhesive and a pair of first flange portions disposed on both sides of the convex portion; a second metal plate having a concave portion adhered to a top surface of the other of the pair of battery modules adjacent in the stacking direction via a conductive adhesive and a pair of second flange portions disposed on both sides of the concave portion; and a metal wave plate disposed between the first metal plate and the second metal plate and forming a refrigerant flow path with the convex portion and the concave portion, the first metal plate, the second metal plate, and the metal wave plate are joined by brazing in a state where end portions of the metal wave plate are sandwiched between the first flange portions and the second flange portions, a first engagement protrusion which engages with a bottom surface recess provided on the bottom surface of the battery module is disposed on an outer side of the first flange portion of the first metal plate, or / and, a second engagement protrusion which engages with a top surface recess provided on the top surface of the battery module is disposed on an outer side of the second flange portion of the second metal plate.

2. The bipolar battery structure according to claim 1, characterized in that, the first engagement protrusion is disposed on the outer side of the first flange portion of the first metal plate, and the second engagement protrusion is disposed on the outer side of the second flange portion of the second metal plate.

3. The bipolar battery structure according to claim 2, characterized in that, the first engagement protrusion has a first bent portion bent toward the bottom surface side of the battery module from the first flange portion, and the second engagement protrusion has a second bent portion bent toward the top surface side of the battery module from the second flange portion, when the first metal plate, the second metal plate, and the metal wave plate are each formed of aluminum, in a direction orthogonal to the stacking direction, the metal wave plate is disposed inside the first bent portion and the second bent portion in such a manner that a distance from an end surface thereof to the first bent portion and a distance from the end surface to the second bent portion are each L or more, L = (σ cos θ) / (4.9pt), σ is a surface tension coefficient of a flux liquid with respect to aluminum, θ is a contact angle of the flux liquid with respect to aluminum, p is a density of the flux liquid, and t is a thickness of the metal wave plate in the stacking direction.

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