Cooling structure between battery cells, battery module, and battery pack

Abstract

To efficiently suppress a temperature rise of an adjacent battery cell even in a case where an abnormally heated battery cell is generated.SOLUTION: In a cooling structure between battery cells, a multilayered structure of cell / metal member / heat insulation layer / metal layer / cell is formed from tabular metal members and a heat insulation layer disposed between the tabular metal members and further, included is a cooling member existing in the vicinity of a plurality of battery cells. One end of each of the tabular metal members is in contact with the cooling members. Two metal members constituting the multilayered structure has the same heat conductivity and thickness, and a ratio of thicknesses of metal member / heat insulation layer / metal layer is within a specific range. The metal member is substantially concave-shaped by connecting lower parts of metal members thermally in contact with side faces of adjacent heat insulation members with each other. The substantially concave-shaped metal member is inserted between adjacent heat insulation members, and the battery cells are disposed in a substantially concave-shaped recess.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cooling structure between battery cells, a battery module, and a battery pack.

Background Art

[0002] In order to obtain a large storage capacity and high output, electric vehicles use a large number of battery cells (for example, lithium ion secondary batteries, etc.). There are cylindrical, rectangular, laminated types, etc. for battery cells, but for electric vehicles, rectangular ones with high mechanical strength and a good balance of energy density, size, etc. are often adopted. In electric vehicles using rectangular battery cells (hereinafter also simply referred to as "battery cells"), a plurality of battery modules, which are configured by densely arranging a large number of battery cells in parallel or in series in a limited space, are used, and these battery modules are connected to form a battery pack and are mounted on the vehicle. During the process of repeated charging and discharging, the battery cells generate a large amount of heat, and if left as it is, the progress of deterioration is accelerated. Therefore, a structure or mechanism for cooling the battery cells by air cooling, water cooling, etc. is provided in the battery module.

[0003] However, even if such a cooling structure or cooling mechanism is provided, the battery cells may deteriorate during the repeated charge and discharge process, or external heat or impact may be applied, causing some of the battery cells to generate abnormal heat. In this case, a large amount of heat is transmitted from the abnormally heated battery cell to the adjacent battery cells, and the propagation of such heat may damage the entire battery module. As a countermeasure, for example, in Patent Document 1, a technique for suppressing damage to the battery module by providing a separator between adjacent battery cells is disclosed. As an example of the separator between cells in this document, a laminated structure of a heat insulating member / a heat conducting member / a heat insulating member is described. Thereby, the heat transfer between adjacent cells can be suppressed by the heat insulating member, and further, by bringing the end of the heat conducting member or the lower part of the battery cell into contact with a cooling plate or the like, the heat generated by abnormal heat generation is transferred and dispersed to other parts to suppress the propagation of abnormal heat generation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in recent years, the battery cells for electric vehicles have been made to have a higher energy density, and when abnormal heat generation occurs, the temperature rise of the heat-generating cell becomes even higher, and heat transfer between adjacent cells is likely to occur. Therefore, more than ever, a heat transfer control technology (cooling technology) for suppressing damage to the battery module during abnormal heat generation has been desired.

[0006] On the one hand, in order to reduce the cost of battery modules, there is also a trend in some cases to change the material of the casing of battery cells from aluminum-based materials such as aluminum alloys to iron-based materials such as steel. The iron-based material has a thermal conductivity that is about 1 / 5 to 1 / 10 lower than that of the aluminum-based material. Therefore, when an iron-based material is used for the casing, even when using a battery module in which the battery case is brought into contact with a cooling mechanism such as a cooling plate to enhance the cooling capacity, it becomes difficult to transfer and disperse the heat from the abnormally heated battery cell to other parts through the cooling plate.

[0007] In addition, the iron-based material has a higher melting point than the aluminum-based material. Due to the high energy density of recent battery cells for electric vehicles, the maximum temperature during abnormal heating may reach 700 to 800 °C or higher, exceeding the melting point of the aluminum-based material (about 660 °C), which may lead to a very dangerous situation where the casing itself melts and falls off. However, for an iron-based material with a melting point of about 1500 °C, such melting and falling off of the casing does not occur, so it can be said that the iron-based material is safer than the aluminum-based material.

[0008] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to more efficiently suppress the temperature rise of adjacent battery cells compared to the prior art, even when an abnormally heated battery cell occurs and even when the material of the casing of the battery cell at that time is an iron-based material such as steel. The present invention provides a cooling structure between battery cells, a battery module having the cooling structure between battery cells, and a battery pack.

[0009] Also, the closer the distance between battery cells, the more compact the design of the battery pack or battery module can be, which is preferable in terms of size reduction. On the other hand, considering aspects such as preventing abnormal heat generation and the ease of installing a cooling structure, a certain distance is required. Therefore, the distance between battery cells needs to be designed considering these balances, and different distances are designed for each type of battery.

[0010] Accordingly, the main object of the present invention is, among the above-mentioned problems, particularly, to provide a cooling structure between battery cells, a battery module having the cooling structure between battery cells, and a battery pack that can more efficiently suppress the temperature rise of adjacent battery cells compared to the prior art under the same situation where the distance between battery cells is the same.

[0011] In a battery cell, since it is important to prevent abnormal heat generation, it is common to use an aluminum-based material with excellent thermal conductivity for the casing, and the above problems could not occur. The above problems can occur only when an attempt is made to use an iron-based material for the casing.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, the present inventors have found that a multi-layer structure of "a layer of a metal member with high thermal conductivity that thermally contacts one side surface of a battery cell / a heat insulating layer disposed between the layers / a layer of a metal member with high thermal conductivity that thermally contacts the other side surface of the battery cell" (hereinafter, may be abbreviated as "A structure") is provided between adjacent battery cells, a predetermined thickness is set for each layer, and one end of the metal member with high thermal conductivity is connected to a cooling mechanism. Thus, it has been found that even when an abnormally heated battery cell occurs, the rising temperature of adjacent battery cells can be reduced more efficiently than in the prior art.

[0013] Also, under the above conditions, instead of the A structure, a multilayer structure of "a layer of a member with high thermal conductivity arranged between layers of heat insulating members in thermal contact with one battery cell side surface / a layer of a member with high thermal conductivity arranged between layers of heat insulating members in thermal contact with the other battery cell side surface" (hereinafter sometimes abbreviated as "B structure") is provided between adjacent battery cells, and this case was also examined. Then, both the above A structure and B structure were compared.

[0014] As a result, at the initial stage of abnormal heat generation, there is almost no difference in the cooling capacity between the A structure and the B structure, but a difference occurs over time, and it was also found that the cooling capacity is higher when the A structure is used than when the B structure is used. In addition, it was found that the A structure has an improved cooling capacity when a single layer of a member with high thermal conductivity is simply provided between the battery cells by making the thickness of each member equal to or greater than a predetermined value.

[0015] Furthermore, paying attention to the thermal resistance at the contact interface between the battery cell and the metal member, it was found that it is preferable to control the ratio of the thermal resistance value at the contact interface to the thermal resistance value of the metal member to be equal to or less than a predetermined value, because the cooling capacity is further improved.

[0016] Note that Patent Document 2 discloses a structure similar to the above A structure. However, in such Patent Document 2, the invention is made with the intention of reflecting electromagnetic waves, and the aspect of conducting heat as focused on in the present invention is not disclosed. Also, in the above Patent Document 2, the thickness of the heat insulating material is 0.1 to 3 mm, which is thinner than that of the present invention to be described in detail below. From such a perspective, it can be seen that what is focused on in the above Patent Document 2 is the reflection of electromagnetic waves and not the conduction of heat. Also, in the above Patent Document 2, the control of the thermal resistance at the contact interface is not considered at all.

[0017] In addition, Patent Document 3 discloses an invention intended for heat conduction, similar to the present invention. In Patent Document 3, sheets or foils such as graphite sheets are used as the heat conductive material, and the thickness thereof is also extremely thin, 0.02 mm in the example, which is different from the present invention. Further, in Patent Document 3, the control of the thermal resistance at the contact interface is not considered at all.

[0018] The gist of the present invention completed based on the above findings is as follows.

[0019] (1) A cooling structure between adjacent battery cells in a plurality of rectangular battery cells arranged with two side faces facing each other, comprising: a plate-shaped metal member having a thermal conductivity of 100 w / m·K or more and a thickness of 0.3 mm or more, and thermally contacting each of the opposing side faces of the adjacent battery cells; and a heat insulating layer having at least one of a heat insulating member or a gas layer having a thermal conductivity of 1.0 W / m·K or less and a thickness of 0.5 mm or more, which is disposed between the plate-shaped metal members thermally contacting each of the opposing side faces of the adjacent battery cells, so as to form a multi-layer structure of battery cell / plate-shaped metal member / heat insulating layer / plate-shaped metal member / battery cell between the adjacent battery cells. Further, it includes a cooling member that thermally contacts each of the plurality of rectangular battery cells or exists in the vicinity of each of the plurality of rectangular battery cells. Each of the plate-shaped metal members has at least one end thermally contacting the cooling member. The two plate-shaped metal members constituting the multi-layer structure have the same thermal conductivity and thickness, and the ratio of the thicknesses of the plate-shaped metal member / heat insulating layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0. The lower portions of the plate-shaped metal members thermally contacting the respective side faces of the adjacent heat insulating members are connected to form a substantially concave shape, and the substantially concave-shaped plate-shaped metal member is inserted between the adjacent heat insulating members, and the battery cell is disposed in the recess of the substantially concave shape. A cooling structure between battery cells. (2) A cooling structure between adjacent battery cells in a plurality of rectangular battery cells arranged such that two sides face each other, comprising: a plate-shaped metal member having a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more, and thermally contacting respective opposing sides of the adjacent battery cells; and a heat insulating layer disposed between the plate-shaped metal members that thermally contact respective opposing sides of the adjacent battery cells, the heat insulating layer having at least one of a heat insulating member or a gas layer with a thermal conductivity of 1.0 W / m·K or less and a thickness of 0.5 mm or more. The adjacent battery cells form a multi-layer structure of battery cell / plate-shaped metal member / heat insulating layer / plate-shaped metal member / battery cell. Further, a cooling member that thermally contacts each of the plurality of rectangular battery cells or exists in the vicinity of each of the plurality of rectangular battery cells is provided. Each of the plate-shaped metal members has at least one end thermally contacting the cooling member. The two plate-shaped metal members constituting the multi-layer structure have the same thermal conductivity and thickness, and the ratio of the thicknesses of the plate-shaped metal member / heat insulating layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0. The plate-shaped metal member is processed so that its cross-sectional shape is concave, is inserted between adjacent battery cells, and the heat insulating layer is disposed in the concave depression. A cooling structure between battery cells. (3) The cooling structure between battery cells according to (1) or (2), wherein the thickness of the plate-shaped metal member is 0.5 mm or more, and the thickness of the heat insulating layer is 1.0 mm or more. (4) In each of the plurality of rectangular battery cells, on a side surface parallel to the direction in which the plurality of rectangular battery cells are arranged, there is further a second plate-shaped metal member having a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more. The second plate-shaped metal member thermally contacts the side surface of the battery cell and has at least one end thermally contacting the cooling member. The cooling structure between battery cells according to any one of (1) to (3). (5) The distance between adjacent battery cells is 1.5 to 5.0 mm, and it is the cooling structure between battery cells according to any one of (1) to (4). (6) The side surface of the battery cell is composed of a steel material, and it is the cooling structure between battery cells according to any one of (1) to (5). (7) The plate-shaped metal member and the cooling member are in thermal contact via an adhesive or grease having a thermal conductivity of 1.0 W / m·K or more, and the adhesive or grease having a thermal conductivity of 1.0 W / m·K or more is an adhesive or grease that cures at room temperature, and it is the cooling structure between battery cells according to any one of (1) to (6). (8) The square battery cell is composed of laminated laminate-type battery cells, and it is the cooling structure between battery cells according to any one of (1) to (7). (9) The material of the plate-shaped metal member is at least any one of aluminum, aluminum alloy, copper, or copper alloy, and it is the cooling structure between battery cells according to any one of (1) to (8). (10) A battery module having the cooling structure between battery cells according to any one of (1) to (9). (11) A battery pack having the cooling structure between battery cells according to any one of (1) to (9).

Effect of the Invention

[0020] As described above, according to the present invention, even when an abnormally heated battery cell occurs, and even when the material of the casing of the battery cell at that time is an iron-based material such as steel, the temperature rise of adjacent battery cells can be suppressed more efficiently compared with the prior art under the same situation of the distance between battery cells.

Brief Description of the Drawings

[0021]

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Mode for Carrying Out the Invention

[0022] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, for components having substantially the same functional configuration, the same reference numerals are given to omit duplicate explanations.

[0023] <Overall Structure of the Cooling Structure between Battery Cells> FIG. 1 is a schematic diagram (cross-sectional view in the longitudinal direction of the battery module) showing an embodiment of the cooling structure in the present invention. With this cooling structure, the temperature rise in the battery cells adjacent to the abnormally overheating battery cell can be suppressed lower than in the conventional cooling structure.

[0024] In the structure of FIG. 1, a rectangular battery cell (hereinafter, the "rectangular battery cell" is simply abbreviated as the "battery cell") 10 made of iron or aluminum is arranged in a plurality with two side surfaces (the side surfaces with the largest area) of each battery cell 10 facing each other (only some cells are shown in the figure). The battery cell may be composed of laminated laminate-type battery cells.

[0025] On each side surface of adjacent battery cells 10, there is a plate-shaped metal member 20 (hereinafter, may be simply abbreviated as the "metal member 20") having a thermal conductivity of 100 w / m·K or more (in the normal temperature range of 25 °C) and a thickness of 0.3 mm or more, which is in thermal contact. Therefore, the two plate-shaped metal members 20 are adjacent to each other in the same manner as the adjacent battery cells 10. Between these two adjacent plate-shaped metal members 20, there is a heat insulation layer 30 having at least one of a heat insulation member or a gas layer having a thermal conductivity of 1.0 W / m·K or less (in the normal temperature range of 25 °C) and a thickness of 0.5 mm or more.

[0026] Here, in the embodiment of the present invention, "being in thermal contact" includes not only direct contact between two members but also a state where the two members are "connected so as to enable heat conduction" with another member sandwiched between them. Details will be described later.

[0027] The interval between adjacent battery cells 10 is required to be as small as possible for the compactification and high density of a battery module or a battery pack composed of a plurality of battery cells, and usually is 10 mm or less. In the present embodiment, when the interval between adjacent battery cells 10 is 1.5 mm or more, the difference in the cooling effect from the prior art becomes more significant.

[0028] Also, the lower end of the plate-shaped metal member 20 is in thermal contact with the upper surface of the cooling member 40 existing below the battery cell 10. In this embodiment, the cooling member 40 is composed of a cooling plate 41 that is water-cooled and a thin heat transfer sheet 42 adhered thereon for electrical insulation. The cooling member 40 that is in thermal contact with the plate-shaped metal member 20 may be present in the vicinity of the battery cell 10, and may be present above or on the side in addition to below. That is, the cooling member 40 may be present at a position where the end of the metal member 20 and the cooling member 40 can easily come into contact by being present in the vicinity of the battery cell 10. Further, the cooling member 40 may be in thermal contact with the battery cell 10 to directly cool the battery cell 10. For improving the cooling ability, it is preferable that the cooling member 40 is present at a plurality of positions among below, above, and on the side. For example, in the example shown in FIG. 2, in addition to the plate-shaped metal member 20, a second plate-shaped metal member 60 located above the battery cell 10 and a third plate-shaped metal member 70 located on the side of the battery cell 10 are illustrated when provided. Also, for simplifying the structure, it is preferable that the plate-shaped metal member 20 is present only below the battery cell 10.

[0029] Also, preferably, as shown in FIG. 1, the battery cell 10 is placed on the cooling member 40 existing below it, and the lower surface of the battery cell 10 and the upper surface of the cooling member 40 may be in thermal contact.

[0030] Furthermore, in each battery cell 10, in addition to the two sides (the two long-side sides) of the side surface with the largest area, for the remaining two side surfaces (the two short-side sides) that are side surfaces parallel to the direction in which a plurality of rectangular battery cells 10 are arranged side by side (side surfaces extending in the same direction), it is preferable that a plate-shaped metal member 20 having a thermal conductivity of 100 w / m·K or more and a thickness of 0.3 mm or more is in thermal contact and is also in thermal contact with the upper surface of the cooling member 40 existing below it (not shown).

[0031] Note that a heat insulating member having a thermal conductivity of 1.0 W / m·K or less and a thickness of 1.0 mm or more may be provided on the metal member 20 (not shown). In this case, plate-like metal members 20 may be installed on both sides of the short side of each battery cell 10, but as shown in FIG. 2, one plate-like metal member 20 may be installed on each of the two short side surfaces of the battery cell 10 across all the battery cells 10 constituting the battery module.

[0032] By having such a structure, when some of the plurality of battery cells 10 start to abnormally generate heat, the heat can be released to the cooling member 40 present in the vicinity through the metal member 20. Further, the heat insulating member can suppress the heat transfer to the adjacent battery cells 10 and effectively suppress the temperature rise of the adjacent battery cells 10.

[0033] In particular, this cooling structure can effectively suppress the temperature rise of adjacent battery cells 10 even when steel materials are used for the casings of the battery cells 10 and the side surfaces of adjacent battery cells 10 are made of a steel material whose thermal conductivity is one digit smaller than that of an aluminum material for cost reduction and the like. Therefore, when this cooling structure is applied to battery cells in which steel materials are used on the side surfaces of the cells, the difference in effect from the prior art becomes more prominent, which is preferable.

[0034] <Regarding the plate-like metal member> The plate-shaped metal member 20 needs to have a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more in order to efficiently release the heat of the battery cell 10 that has started to generate abnormal heat to the cooling member 40 present in the vicinity. In addition to the superiority in relative cooling capacity compared to the prior art, from the aspect of making the value of the reaching temperature itself lower, the thickness of the plate-shaped metal member 20 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. On the other hand, the thickness of the plate-shaped metal member 20 is determined while considering the interval between adjacent battery cells 10 and the thickness of the heat insulation layer 30, but substantially, about 5.0 mm is the upper limit. The thickness of the plate-shaped metal member 20 is preferably 5.0 mm or less, and more preferably 2.0 mm or less. Also, the thermal conductivity is preferably 150 W / m·K or more. On the other hand, the thermal conductivity of the plate-shaped metal member 20 is substantially about 420 W / m·K as the upper limit. The plate-shaped metal member 20 is more preferably such that the thickness is 1.0 mm or more and the thermal conductivity is 150 W / m·K or more.

[0035] The thickness of the plate-shaped metal member 20 does not necessarily have to be a constant thickness, and the shape of the metal member may be tapered, have steps, or have irregularities. In these cases, as the plate thickness value described above, the average value can be used. This average value of the plate thickness can be calculated as (the volume of the plate-shaped metal member 20) ÷ (the projected area of the plate-shaped metal member 20 in the plate thickness direction).

[0036] The material of the metal member is not particularly limited. However, from the balance of high thermal conductivity and low cost, as the material of the metal member, aluminum, aluminum alloy, copper, and copper alloy (including chalcopyrite) are preferable.

[0037] The range of the metal member 20 that is in thermal contact with the side surface (the side surface with the largest area) of the battery cell 10 may be partial, but it is preferably 70% or more of the area of the side surface of the battery cell 10, and more preferably 90% or more. Also, since it is considered that the temperature rise of the battery cell 10 during abnormal heat generation usually becomes higher in the part farther from the cooling member 40, it is preferable that the metal member 20 is in thermal contact from the part farther from the cooling member 40. In the cooling structure of FIG. 1, since the cooling member 40 is installed below, the metal member 20 is preferably installed so as to be in thermal contact from above the side surface of the battery cell 10 as shown in FIG. 1. More specifically, it is more preferable that the metal member 20 is installed so as to be in thermal contact in 90% or more of the vertical length of the side surface of the battery cell 10.

[0038] Also, as shown in FIG. 3A, after connecting the lower parts of the plate-shaped metal members 20 that are in thermal contact with the respective side surfaces of the adjacent heat insulating members 30 to form a concave shape (in other words, after making the cross-sectional shape of the plate-shaped metal member 20 into a concave shape), the such metal member 20 may be inserted between the adjacent heat insulating members 30, and further, the battery cell 10 may be installed in the depression of the plate-shaped metal member 20. By doing so, since a desired heat insulating state can be realized only by inserting the metal member 20 in which the battery cell 10 is installed between the adjacent heat insulating members 30, the productivity is further improved.

[0039] At this time, the corners of the concave-shaped metal member 20 may be right-angled as shown in FIG. 3A, or may be in a curved state as shown in FIG. 3B.

[0040] <Regarding the heat insulating layer> When some of the battery cells 10 generate abnormal heat, the heat insulating layer 30 needs to have a thermal conductivity of 1.0 W / m·K or less and a thickness of 0.5 mm or more in order to suppress the transfer of heat to adjacent battery cells 10. The higher the heat insulation ability of the heat insulating layer 30, the more the initial temperature rise in the battery cells adjacent to the abnormally heated battery cell can be suppressed. Therefore, from the viewpoint of suppressing the initial temperature rise, the thermal conductivity of the heat insulating layer 30 is preferably 0.1 W / m·K or less, and more preferably 0.06 W / m·K or less. In addition, the lower limit of the thermal conductivity of the heat insulating layer 30 is substantially about 0.02 W / m·K. Similarly, from the viewpoint of suppressing the initial temperature rise, the thickness of the heat insulating layer 30 is preferably 1.0 mm or more, and more preferably 1.5 mm or more. On the other hand, the thickness of the heat insulating layer 30 is determined while considering the interval between adjacent battery cells 10 and the thickness of the plate-shaped metal member 20, but the upper limit is substantially about 10.0 mm. The thickness of the heat insulating layer 30 is preferably 5.0 mm or less, and more preferably 2.0 mm or less.

[0041] The material of the heat insulating layer 30 is not particularly limited, but heat insulating members such as glass wool, rock wool, urethane foam, foamed rubber, non-woven fabric, polystyrene, resins such as polypropylene and polybutylene terephthalate, etc. can be used. Further, the heat insulating layer 30 may be a gas layer in which a gas such as air exists in the space. Furthermore, the heat insulating layer 30 may be such that a member capable of holding a gas layer such as a porous member or the like is used between adjacent metal members 20 so that a gas such as air exists inside the pores.

[0042] The heat insulating layer 30 only needs to exist between two adjacent plate-shaped metal members 20. When a heat insulating member is used as the heat insulating layer 30, the heat insulating layer (heat insulating member) 30 may be in contact with the metal member 20 or may have a gap and be separated therefrom. Also, one side surface of the heat insulating layer (heat insulating member) 30 may be in contact with the metal member 20, and the other side surface may have a gap and be separated from the metal member 20. When the heat insulating member 30 and the metal member 20 are brought into contact with each other, the two can be fixed using an adhesive.

[0043] Alternatively, it is also possible to simply sandwich a heat insulating layer (heat insulating member) 30 between two adjacent plate-shaped metal members 20. In this case, it is preferable to sandwich a heat insulating layer (heat insulating member) 30 having a relatively high resilience elasticity between two adjacent plate-shaped metal members 20 and use it to press the metal members 20. As a result, the metal members 20 are pressed against the side surfaces of the battery cells 10, so that the contact resistance (thermal resistance) is reduced and the cooling effect is further improved.

[0044] Also, even when the heat insulating layer 30 is only a gas layer such as air (only voids), if the gas layer is not actively convected, the influence of radiant heat is extremely small in the temperature range of about 100°C. Therefore, the space between the plate-shaped metal members 20 is insulated by the low thermal conductivity of the gas layer. For example, when the heat insulating layer 30 is an air layer, there is no significant difference in the heat insulating effect compared to the case of glass wool. However, when the heat insulating layer 30 is only a gas layer, since a temperature gradient exists around the battery cell 10, natural convection of the gas occurs, and an increase in the heat transfer rate between the plate-shaped metal members 20 due to convective heat transfer may occur depending on the surrounding structure. Therefore, it is more preferable to use a heat insulating member for the heat insulating layer 30.

[0045] When there is a gap between the heat insulating layer (heat insulating member) 30 and the metal member 20, the air layer existing in such a gap, together with the heat insulating member 30, will bear the heat insulating effect between two adjacent plate-shaped metal members 20. In this case, the heat insulating layer (heat insulating member) 30 can be fixed to the lower cooling structure 40 with an adhesive or the like. Alternatively, it is also possible to simply place the heat insulating member 30 between two adjacent plate-shaped metal members 20.

[0046] The installation position and area of the heat insulation layer (heat insulation member) 30 are preferably at least such that they cover the entire surface of the metal member 20. This is because when abnormal heat generation occurs in the battery cell 10, heat dissipation from the side surface of the metal member 20 is suppressed, and heat of the battery cell 10 can be efficiently transferred from the metal member 20 to the cooling member 40. Furthermore, it is more preferable to arrange it so as to face the entire side surface of the battery cell 10, because heat transfer to adjacent battery cells 10 can be suppressed.

[0047] Furthermore, as shown in FIG. 4, the lower portions of the plate-shaped metal members 20 that are in thermal contact with the respective side surfaces of adjacent battery cells 10 are connected to form a concave shape (in other words, the cross-sectional shape of the plate-shaped metal member 20 is made concave), and such a metal member 20 is inserted between the battery cells 10. Further, a heat insulation layer (heat insulation member) 30 may be installed in the depression of the plate-shaped metal member 20. By doing so, a desired heat insulation state can be realized only by inserting the metal member 20 between adjacent battery cells 10, so productivity is further improved. In addition, the heat insulation layer (heat insulation member) 30 can be stably installed. The height of the connection portion at the lower part of the metal member 20 is preferably 1 / 4 or less of the height of the entire metal member 20 in order to sufficiently maintain the heat insulation effect of the heat insulation member 30.

[0048] <Regarding the multi-layer structure> In the present embodiment, as illustrated in FIG. 2, a multi-layer structure of battery cell 10 / plate-shaped metal member 20 / heat insulation layer 30 / plate-shaped metal member 20 / battery cell 10 is formed between adjacent battery cells. In this multi-layer structure, the characteristics of each of the plate-shaped metal member 20 / heat insulation layer 30 / plate-shaped metal member 20 are as described above. As long as it is within the above-described range, there is no limitation on the entire multi-layer structure. For example, the two plate-shaped metal members 20 existing between adjacent cells may have different thermal conductivities and thicknesses from each other. However, if the characteristics of both are the same, it is preferable in terms of the balance of the entire cooling structure, suppression of temperature non-uniformity, and ease of manufacture.

[0049] When the thermal conductivities and thicknesses of two adjacent plate-shaped metal members 20 are the same, regarding the ratio of the thicknesses of the plate-shaped metal member 20 / thermal insulation layer 30 / plate-shaped metal member 20, when the thickness of the plate-shaped metal member 20 is taken as 1.0, the thickness of the thermal insulation layer 30 is preferably 0.2 to 4.0, and more preferably 0.5 to 3.0. That is, the ratio of the thicknesses of the plate-shaped metal member 20 / thermal insulation layer 30 / plate-shaped metal member 20 is preferably 1.0:0.2 to 4.0:1.0, and more preferably 1.0:0.5 to 3.0:1.0.

[0050] <Regarding thermal contact> (Thermal contact between the side surface of the battery cell and the plate-shaped metal member) In the present embodiment, in the situation where the side surface of the battery cell 10 and the plate-shaped metal member 20 are in thermal contact, in addition to the case where they are in direct contact, the case where they are connected (in contact) through a contact member such as an adhesive, grease, or a thin sheet (not shown) so that heat conduction is possible between them is also included.

[0051] Even when they are in direct contact, there is a contact resistance at the contact interface caused by slight differences in the surface roughness and curvature of the two. Therefore, the thermal resistance from the surface of the battery cell 10 to the surface of the heat insulating material side of the plate-shaped metal member 20 is larger than the thermal resistance of the plate-shaped metal member 20 alone. The thermal resistance Rs at the contact interface is preferably Rs / Rm≦3.0, more preferably Rs / Rm≦1.5, and even more preferably Rs / Rm≦1.0, compared to the thermal resistance Rm of the plate-shaped metal member 20 alone. Note that the thermal resistance Rs at the contact interface is expressed in L / λ or 1 / h [m 2 ·K / W]. Here, when a contact member is used, the above L represents the thickness of the contact member present at the contact interface, the above λ represents the thermal conductivity of the contact member, and the above h represents the heat transfer coefficient at the contact interface.

[0052] In order to reduce the thermal resistance Rs at the contact interface, in the case of direct contact, the surface roughness (asperities) of the side surface of the battery cell 10 and the plate-shaped metal member 20 can be reduced by polishing or the like, or the pressing pressure of the plate-shaped metal member 20 against the side surface of the battery cell 10 can be increased, etc.

[0053] Also, the side surface of the battery cell 10 and the plate-shaped metal member 20 can be brought into thermal contact via an adhesive or grease. By using an adhesive or grease, the asperities on the surfaces of both can be filled, and the substantial contact area can be easily increased, which is preferable. When using an adhesive or grease, it is preferable to use a high thermal conductivity one with a thermal conductivity of 1.0 W / m·K or more. The thermal conductivity of the adhesive or grease is more preferably 2.0 W / m·K or more, and even more preferably 4.0 W / m·K or more. On the other hand, the thermal conductivity of the adhesive or grease is substantially limited to about 10.0 W / m·K as the upper limit. It is preferable to apply the adhesive or grease thinly enough to fill the asperities of both, as this can reduce the thermal resistance. The adhesive or grease preferably has a coating thickness of, for example, about 0.01 to 0.2 mm according to the degree of asperities.

[0054] Also, the side surface of the battery cell 10 and the plate-shaped metal member 20 can be brought into thermal contact via a thin sheet such as a heat transfer sheet. A heat transfer sheet made of a soft material such as silicone rubber can fill the asperities on the surfaces of both, similar to an adhesive or grease, and can easily increase the substantial contact area, which is preferable. Also, using a heat transfer sheet with electrical insulation can ensure better electrical insulation between cells. Since the heat transfer sheet is often thicker than an adhesive or grease, a higher thermal conductivity is preferable. For example, the thermal conductivity of the heat transfer sheet is preferably 2 W / m·K or more, and more preferably 10 W / m·K or more. On the other hand, the thermal conductivity of the heat transfer sheet is substantially limited to about 50 W / m·K as the upper limit.

[0055] Furthermore, a ceramic filler or the like may be further mixed with the adhesive, grease, or heat transfer sheet, and the mixture may be used after improving the heat transfer characteristics and imparting electrical insulation characteristics.

[0056] A lithium-ion secondary battery, which is one of the typical battery cells, is known to expand and contract during charging and discharging. At this time, grease, which behaves similarly to a liquid, may cause a "pump-out phenomenon" in which it is pushed out of the gap due to repeated expansion and contraction. To prevent such a pump-out phenomenon, it is more preferable to use an adhesive that becomes solid after curing (more specifically, an adhesive that cures at room temperature) or a heat transfer sheet that is solid. In particular, since the adhesive cures according to the shape and gap, it is possible to conduct heat from the battery cell 10 without being affected by factors such as thickness, shape, distortion, and surface unevenness. Among them, a soft and elastic adhesive is particularly preferable because it can easily deform even with expansion and contraction and will not crack or break even with repeated expansion and contraction.

[0057] From the perspective of heat conduction, the thickness of such an adhesive, grease, or heat transfer sheet is preferably thin, and from the perspective of coping with expansion and contraction, a thicker thickness is preferable. Considering such a trade-off relationship, the thickness of the adhesive, grease, or heat transfer sheet is preferably 1 μm or more, more preferably 5 μm or more. Also, the thickness of the adhesive, grease, or heat transfer sheet is preferably 2 mm or less, more preferably 500 μm or less.

[0058] When the side surface of the battery cell 10 and the plate-shaped metal member 20 are brought into thermal contact via a contact member such as an adhesive, grease, or heat transfer sheet, similar to the case of direct contact, the thermal resistance Rs of the adhesive, grease, or heat transfer sheet is preferably Rs / Rm ≦ 1.5, more preferably Rs / Rm ≦ 0.8, and even more preferably Rs / Rm ≦ 0.5, compared to the thermal resistance Rm of the plate-shaped metal member 20 alone. In this case, the adjustment of Rs / Rm can be achieved by material selection (thermal conductivity) and thickness setting.

[0059] (Thermal Contact between the End of a Plate-Shaped Metal Member and a Cooling Member) In this embodiment, in the situation where one end of the plate-shaped metal member 20 (in FIG. 1, due to the rectangular plate shape, among the four ends, the end existing on the cooling member side) and the cooling member 40 are in thermal contact, similar to the thermal contact between the side surface of the battery cell and the plate-shaped metal member, in addition to the case where the two are in direct contact, there is also a case where the two are connected (in contact) so as to be thermally conductive through an adhesive, grease, or a thin heat transfer sheet. FIG. 1 shows an example using a thin sheet (heat transfer sheet 41).

[0060] In FIG. 1, one end of the plate-shaped metal member 20 is placed directly on the heat transfer sheet 41 that constitutes the upper surface of the cooling member 40 and is in thermal contact. Here, as shown in FIG. 5, the plate-shaped metal member 20 may be inserted into the inside of the cooling member 40. The structure as shown in FIG. 5 can be realized, for example, by providing a groove portion in the cooling member 40 and fitting the end of the plate-shaped metal member 20 into the groove portion to make thermal contact. By adopting such a structure, it is possible to increase the contact area between the plate-shaped metal member 20 and the cooling member 40 or reduce the substantial thermal resistance between the plate-shaped metal member 20 and the cooling member 40, and it becomes possible to more reliably cool the abnormally heated battery cell 10. In FIG. 5, the heat transfer sheet 50 installed between the plate-shaped metal member 20 and the side surface of the battery cell 10 is extended together with the plate-shaped metal member 20 and embedded in the groove portion of the cooling member 40 together with the plate-shaped metal member 20 to ensure the thermal contact between the cooling member 40 and the plate-shaped metal member 20.

[0061] <Regarding Cooling Characteristics>[[]] By adopting the structure of this embodiment, the cooling capacity can be improved compared with the prior art. Here, the cooling characteristics in the structure of this embodiment shown in FIG. 1 are clarified by comparing with the prior art shown in FIGS. 6 to 8.

[0062] The cooling structure shown in Fig. 6 is obtained by swapping the positions of the metal and the heat insulating material in the cooling structure of Fig. 1 (the thickness of the metal member is the same as the total thickness of the two metal members in Fig. 1, and the total thickness of the two heat insulating members is the same as the thickness of the heat insulating layer in Fig. 1). Other structures are the same as those in Fig. 1. That is, it has a multi-layer structure of "cell / heat insulating member / metal member / heat insulating member / cell", and one end of the metal member is in thermal contact with the lower cooling member. The cooling structures shown in Figs. 7 and 8 respectively show a cooling structure in which only the metal member 20 is installed between the battery cells, and a cooling structure in which only the heat insulating member 30 is installed (the thicknesses of the metal member and the heat insulating member are the same as the thickness of the multi-layer structure in Fig. 1). Other structures are the same as those in Fig. 1 (in Fig. 7, the metal member is in thermal contact with the lower cooling member).

[0063] Fig. 9 is a temperature history diagram schematically showing the differences in cooling characteristics when using the cooling structures of Fig. 1 and Figs. 6 to 8, and represents the change over time of the temperature (at the hottest part considered) in the battery cell adjacent to the battery cell where abnormal heat generation occurred.

[0064] It can be seen that the cooling structure of the present embodiment in Fig. 1 finally has the lowest temperature and the best cooling ability. The cooling structure of Fig. 5 shows the same temperature change as the cooling structure of Fig. 1 until midway, but starts to deviate in the higher temperature direction from around 1000 seconds, and the temperature becomes higher than that of the cooling structure of Fig. 1. In the cooling structure with only the metal member installed in Fig. 7, the temperature rises fastest initially, but the temperature rise is alleviated midway and becomes the second lowest temperature after Figs. 1 and 6. In the cooling structure with only the heat insulating member installed in Fig. 8, although the temperature rise is slower than that of the cooling structure with only the metal member installed in Fig. 7 initially, it is reversed around 1000 seconds and finally results in the highest temperature. It should be noted that in the cooling structure of Fig. 8, when the heat insulating member is only an air layer, it is found that the temperature change result is substantially the same as that in the case of only the heat insulating member.

[0065] As described above, it was found that the cooling ability of the cooling structure in Fig. 1 cannot be easily predicted from the cooling abilities of the cooling structures in Figs. 6 to 8.

[0066] The superiority of the cooling capacity of the cooling structure according to the present invention is exhibited when a plate-shaped metal member having a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more and a heat insulating layer having a thermal conductivity of 1.0 W / m·K or less and a thickness of 0.5 mm or more are used. Outside such a range, no superiority occurs, and in some cases, it has also been found that a phenomenon occurs in which the structure of FIG. 7 in which only the metal member exists results in a lower maximum temperature.

[0067] <Regarding the manufacturing method of the cooling structure> The manufacturing method of the present embodiment is not particularly limited. Thermal contact of the plate-shaped metal member 20 with the side surface of the adjacent battery cell 10, thermal contact of at least one end of the plate-shaped metal member 20 with the cooling member 40, installation of the heat insulating layer 30 between the adjacent plate-shaped metal members 20, etc. may be appropriately performed.

[0068] <Regarding the evaluation method of thermal conductivity> (Evaluation method of the thermal conductivity of the plate-shaped metal member) If the material of the plate-shaped metal member 20 is known, the thermal conductivity can be specified as a physical property value unique to the material.

[0069] When the material of the plate-shaped metal member 20 is unknown or the physical property value of the thermal conductivity is not known even if the material is known, it is measured by the Straight Fin Temperature Fitting (SFTF) method. With reference to FIGS. 10 and 11, the measurement method of the thermal conductivity of the plate-shaped metal member 20 will be briefly described.

[0070] Here, when the plate-shaped metal member 20 is already disposed on the surface of the battery cell 10, the thermal conductivity is measured after removing the plate-shaped metal member 20 from the surface of the battery cell 10. Further, when the plate-shaped metal member 20 is disposed on the surface of the battery cell 10 via a heat transfer sheet, the thermal conductivity is measured after removing the plate-shaped metal member 20 from the heat transfer sheet.

[0071] Specifically, when the plate-shaped metal member 20 is in contact with the battery cell 10 via grease, the plate-shaped metal member 20 can be peeled off in the vertical direction of the battery cell 10 and the grease can be wiped off, so that it can be used for measurement. Also, when the plate-shaped metal member 20 is adhered to the battery cell 10 with an adhesive, the plate-shaped metal member 20 is peeled off from the battery cell 10 using an instrument such as a scraper, and the surface where the adhesive exists is polished to expose the surface of the plate-shaped metal member 20 and smooth the surface. Even when the plate-shaped metal member 20 is in contact with the heat transfer sheet, the plate-shaped metal member 20 is similarly peeled off and used for measurement.

[0072] Thereafter, the surface of the plate-shaped metal member 20 that is closest to the surface of the battery cell 10 is used as the measurement surface, and all parts except this measurement surface and the part where heat flux is input are covered with a heat insulating material. Thereby, a test piece of the plate-shaped metal member 20 to be used for the SFTF method can be obtained.

[0073] FIG. 10 is an explanatory diagram for explaining the principle of the SFTF method. For a flat plate test piece with a length Lt [m], a cross-sectional area A [m 2 =H×t, and a perimeter P [m]=2×(Lt + H + t) as shown in the upper part of FIG. 10, when one end is heated and the other end is cooled, the boundary temperature T 0 =T x0 at the heat flux input site and the temperature rise distribution T i (i = 1 to n: number of temperature measurement points) from the ambient air of the test piece are measured.

[0074] On the other hand, the analytical solution T xi of the temperature distribution of the straight fin that gives the temperature distribution of the straight fin is given by the following formula (101) using the boundary conditions of fixing the temperature at one end of the test piece and insulating one end face. Therefore, the obtained measured value Txi is compared with the analytical solution Tx of the temperature rise of the straight fin given by formula (101), and the standard deviation σ defined by the following formula (103) is calculated, and the parameter m in the analytical formula is determined so that this standard deviation is minimized.

[0075] Also, let the in-plane thermal conductivity of the sample of interest (the thermal conductivity in the length Lt direction in Fig. 10) be k. p Then, if we express it as such, the parameter m in the analytical formula represented by Equation (101) is the average heat transfer coefficient h from the test piece surface to the surrounding air. m Using this, it is expressed as in the following Equation (105).

[0076] Also, the average heat transfer coefficient h m is expressed as in the following Equations (107) to (111) using the theoretical formulas for the natural convection heat transfer coefficient and the radiative heat transfer coefficient of a vertical flat plate. Here, in the following Equations (107) to (111), h nm is the natural convection heat transfer coefficient for a vertical flat plate of height H, and h rm is the radiative heat transfer coefficient from the surface with emissivity ε. Also, k a , v a , β, and Pr are the thermal conductivity, kinematic viscosity coefficient, expansion rate, and Prandtl number of air, respectively. Also, g is the gravitational acceleration, and σ’ is the Stefan–Boltzmann constant (=5.67×10 -8 W / m 2 ·K 4 ). T m , T a are the average temperature of the test piece and the outside air expressed in absolute temperature, respectively. ΔTm is the average temperature rise of the test piece, and it can be obtained by ΔT 0 ·φ using the fin efficiency φ(0.8) and the temperature rise ΔT at x = 0. 0

[0077]

Equation

[0078] When measuring the thermal conductivity of an actual metal member, the target metal member is cut out to a size of 20 mm in width × 200 mm in length, and then a laminated structure as shown in Fig. 11 is formed. A heater is installed at one end, and the heater output is set to 1.6 W at 10 V. Then, the in-plane temperature distribution of the metal member is photographed with a thermal camera, the obtained thermal image is converted into a temperature distribution, and the relationship between the test length and the surface temperature is confirmed. By analyzing the obtained relationship between the test length and the surface temperature by the above linear fin temperature distribution fitting method, the thermal conductivity of the metal member of interest can be obtained. In addition, when the size of the metal member is small and it cannot be cut out to a size of 20 mm in width × 200 mm in length, the test piece can be made smaller, such as 20 mm in width × 100 mm in length, and measured.

[0079] Also, in a structure where a heat transfer sheet exists between a battery cell and a plate-shaped metal member, the method for measuring the thermal conductivity of this heat transfer sheet can be carried out in the same manner as the method for measuring the thermal conductivity of the plate-shaped metal member described above.

[0080] (Method for Evaluating Thermal Conductivity of Adhesive and Grease) The thermal conductivities of adhesives and greases can be measured by the following thermal resistance measurement method conforming to ASTM5470.

[0081] As shown in the left figure of Fig. 12, the sample of interest is sandwiched between the upper meter bar and the lower meter bar, and power is applied to the heater on the upper meter bar side. On the other hand, the test head on the lower meter bar side is maintained at a constant temperature by a method such as water cooling. Then, the thermal resistance of the sample is obtained from the relationship between the positions and temperatures of the upper meter bar and the lower meter bar. Specifically, thermocouples are attached to the positions shown as T1 to T4 in the figure, and based on the temperature gradient calculated from the temperatures obtained at T1 to T2, the surface temperature on the upper meter bar side of the sample is calculated, and based on the temperature gradient calculated from the temperatures obtained at T3 to T4, the surface temperature on the lower meter bar side of the sample is calculated. Thereby, the temperature difference ΔT inside the sample is calculated. Also, the thermal resistance of the sample can be obtained by using the heat generation amount Q [W] from the heater.

[0082] While changing the thickness of the sample, calculate the thermal resistance of the sample as described above, and plot the obtained results on a coordinate plane defined by the thickness and thermal resistance of the sample as shown in the lower part of FIG. 12. Then, linearly approximate the distribution of the obtained plots by the least squares method and calculate the slope of the line. The reciprocal of the obtained slope is the thermal conductivity of the sample of interest.

[0083] Unlike the transistor method and the model heater method, the above-described method for measuring thermal conductivity can change the applied pressure on the upper meter bar side, so it is possible to reproducibly evaluate the thermal resistance with respect to the applied pressure. In actual measurement, thin films with thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm are fabricated and cut into 20 mm squares. Then, the cut samples may be sandwiched between the meter bars for measurement. At this time, the material of the meter bar is SUS304 (20 mm square), and the load during measurement is 3 kg / cm 2 Let it be. Then, calculate the slope from the relationship between the thermal resistance and the thickness, and calculate the thermal conductivity from the reciprocal of the slope.

[0084] Also, when only a small amount of the adhesive or grease of interest is obtained, dissolve the adhesive or grease of interest in an appropriate organic solvent and extract the filler particles that did not dissolve. By subjecting the extracted filler particles to component analysis by fluorescent X-ray and crystal structure analysis by X-ray diffraction, the type of filler particles is identified. Regarding the composition of the matrix resin, the type of matrix resin is identified by observing the obtained resin solution by infrared spectroscopy. Also, the thermal conductivity can be calculated by the following formula (121) from the extracted filler amount and matrix amount.

[0085] Here, in the following formula (121), λ matrix is the thermal conductivity of the matrix resin, λ filler is the thermal conductivity of the filler particles, and λ composite is the thermal conductivity of the composite. Also, φ is the filler content (volume fraction), and x is the filler shape factor (when it is a true sphere, x = 2 and is the minimum).

[0086] [Number]

[0087] [Regarding the method for evaluating thermal resistance] The thermal resistance (Rm) of a plate-shaped metal member can be obtained from the thermal conductivity (λm) of the plate-shaped metal member determined by the above-described evaluation method and the thickness (Lm) of the plate-shaped metal member, according to Rm = Lm / λm.

[0088] Also, the thermal resistance (Rs) of an adhesive, grease, or heat transfer sheet can be obtained from the thermal conductivity (λs) of the adhesive, grease, or heat transfer sheet determined by the above-described evaluation method and the thickness (Ls) of the adhesive, grease, or heat transfer sheet, according to Rs = Ls / λs.

[0089] By obtaining Rm and Rs using such an evaluation method, the above-described Rs / Rm can be calculated.

[0090] [Regarding battery modules and battery packs] Any battery module and battery pack having the cooling structure between battery cells in the above-described embodiment of the present invention may be used. The battery pack may be not only one in which a plurality of battery packs are arranged in parallel in the horizontal or vertical direction, but also a single battery module. [Examples]

[0091] Hereinafter, while showing examples and comparative examples, the cooling structure between battery cells according to the present invention, and battery cell modules and battery packs having the cooling structure will be described with specific examples. Note that the examples shown below are merely examples of the present invention, and the present invention is not limited to the following examples.

[0092] [Battery cells and battery modules] For the battery cells, rectangular cells (length 27 mm × width 170 mm × height 115 mm) with a steel casing were used. Eight of these cells were arranged linearly so as to face each other to fabricate a battery module. Four types of the battery module were prepared with the gaps between the cells being 0.5 mm, 2 mm, 3 mm, and 5 mm.

[0093] [Charge and Discharge Test Device] For the charge and discharge test of the fabricated module, EVT60V120A manufactured by Nippon Steel & Sumikin Tex-en Co., Ltd. was used.

[0094] [Cooling Device] As the cooling device that functions as a heat cooling mechanism, a self-made water cooling device (length 190 mm × width 400 mm × height 40 mm) was used. The battery module was placed on it to perform charge and discharge of the battery. The battery cell cooling mechanism realized in this way has a structure generally exemplified in the cross-sectional view of FIG. 1 (longitudinal cross-section of the battery module).

[0095] [Metal Member and Heat Insulation Layer] As the plate-shaped metal member, a plate made of aluminum with a thermal conductivity of 235 W / m·K at room temperature was used. In the example of the present invention, Shin-Etsu Chemical Co., Ltd.'s silicone grease (G-777, thermal conductivity at room temperature: 3.3 W / (m·K)), Cemedine Co., Ltd.'s adhesive (SX1008, thermal conductivity at room temperature: 1.7 W / (m·K), abbreviated as "adhesive 1" in Table 1 below), or Cemedine Co., Ltd.'s adhesive (RH96L, thermal conductivity at room temperature: 2.1 W / (m·K), abbreviated as "adhesive 2" in Table 1 below) was thinly applied (about 0.02 mm thick) and attached to the cell. At this time, in the rectangular parallelepiped-shaped square cell, the aluminum plate was attached to substantially the entire side surface of the cell on the surface to be attached (excluding several millimeters at the upper end and several millimeters at the left and right ends. Area ratio: 95% or more). Also, the attached aluminum plate was connected to a water cooling device installed under the battery module via Shin-Etsu Chemical Co., Ltd.'s silicone grease (G-777, thermal conductivity at room temperature: 3.3 W / (m·K)) (applied about 0.1 mm). The ratio (Rs / Rm) of the thermal resistance of the metal member to the thermal resistance Rs of the grease or adhesive is shown in Table 1 below.

[0096] As the heat insulating member in the heat insulating layer, glass wool with a thermal conductivity of 0.05 W / m·K at room temperature or Nichias Corporation's fireproof cloth (TOMBO No. 8300, thermal conductivity at room temperature: 0.10 W / m·K) adjusted to a desired thickness was used.

[0097] [Regarding the multilayer structure] As the structure between adjacent cells, in the example of the present invention, a multilayer structure of cell / aluminum plate / glass wool / aluminum plate / cell was adopted. As comparative examples (prior art), a multilayer structure of cell / glass wool / aluminum plate / glass wool / cell, a single aluminum plate structure, and a single glass wool structure were adopted. The thicknesses of the respective members in each structure are shown in Table 1 below.

[0098] In addition, the cooling capacity was also measured for the cooling structure generally exemplified in the cross-sectional view of FIG. 4 and the cooling structure in which the surface on the short side of the cell was brought into contact with an aluminum plate as shown in FIG. 2. These conditions are also shown in Table 1 below. For the example with a gap of 0.5 mm between cells, since it was obvious that it would result in a bad evaluation without even measuring the cooling capacity, no evaluation was performed below.

[0099] ◇Cooling performance evaluation (temperature evaluation at the time of abnormal heat generation in the cell) Thermocouples were attached to arbitrary positions on the cell surface using Kapton tape, and the temperature rise accompanying charge and discharge was measured. Evaluation was performed for the combinations of the example of the present invention and the comparative example (prior art) shown in Table 1. Using the module in which the above eight cells were connected in series, when the two central cells generated heat at a constant calorific value of 500 kW / h in an environment of 25°C (simulating abnormal heat generation), the temperature of the adjacent cell at 2000 seconds after the start of heating (three points were measured at equal intervals in the height direction of the cell: positions 20 mm, 50 mm, and 80 mm from the top) was taken as the temperature of the hottest part. As a result, the example with a lower temperature than any of the comparative examples after 2000 seconds was taken as the example of the present invention. In addition, although it has a multi-layer structure of cell / aluminum plate / glass wool / aluminum plate / cell, the example in which the thickness of the aluminum plate was thin and the temperature was higher than that of the comparative example was taken as a reference example.

[0100] As a result of the study by the present inventors, it was found that a change in characteristics began to occur around 1000 to 2000 seconds after the start of measurement, and the behavior in such a range was important for performance evaluation. It was also found that the characteristics saturated after exceeding 2000 seconds from the start of measurement and the performance of the battery cell was determined. In addition, assuming that the battery cell is mounted on an electric vehicle, it is necessary to secure time for the passengers to evacuate when the battery cell is about to be in a dangerous state, so an early judgment is required. Based on this point, as described above, the judgment was made at 2000 seconds after the start of measurement.

[0101] Also, with the cell interval of 5 mm as a reference to Comparative Example 1, the cell interval of 3 mm as a reference to Comparative Example 4, and the cell interval of 2 mm as a reference to Comparative Example 6, the cooling performances of the inventive examples, reference examples, and comparative examples at each cell interval were compared. In the comparison, the comparison was made based on the maximum cell temperature after 2000 seconds, and it was expressed as the battery temperature reduction rate of the formula shown below.

[0102] Battery cell temperature reduction rate (%) (in the case of the inventive example) =[(Maximum cell temperature of the reference comparative example - Maximum cell temperature of the inventive example) / Maximum cell temperature of the reference comparative example] × 100 Battery cell temperature reduction rate (%) (in the case of the reference example) =[(Maximum cell temperature of the reference comparative example - Maximum cell temperature of the reference example) / Maximum cell temperature of the reference comparative example] × 100 Battery cell temperature reduction rate (%) (in the case of the comparative example) =[(Maximum cell temperature of the reference comparative example - Maximum cell temperature of the comparative example) / Maximum cell temperature of the reference comparative example] × 100

[0103] Also, those with the above temperature reduction rate of 10% or more were rated as "A", those with 5% or more and less than 10% were rated as "B", those with more than 0% and less than 5% were rated as "C", and those with 0% or less were rated as "D" for evaluation. In addition, those showing excellent performance compared to the case of the multi-layer structure of cell / glass wool / aluminum plate / glass wool / cell (that is, the above B structure) are regarded as "qualified".

[0104]

Table 1

[0105] [Comparison results of cooling performance] Figure 13 shows the results when the distance between cells is 5.0 mm. For Comparative Example 1 [thermal insulation member 1.0 mm / Al 3.0 mm / thermal insulation member 1.0 mm] and Comparative Example 2 [Al 5.0 mm only], in the examples of the present invention, Example 1 of the present invention [Al 1.5 mm / thermal insulation member 2.0 mm / Al 1.5 mm], Example 2 of the present invention [Al 2.25 mm / thermal insulation member 0.5 mm / Al 2.25 mm], Example 3 of the present invention [Al 2.0 mm / thermal insulation member 1.0 mm / Al 2.0 mm], and Example 4 of the present invention [Al 1.0 mm / thermal insulation member 3.0 mm / Al 1.0 mm], the temperature of adjacent cells after 2000 seconds is lower than that of the comparative examples. It can be seen that the examples of the present invention have higher cooling performance than the prior art. Also, in Reference Example 1 [Al 0.25 mm / thermal insulation member 4.5 mm / Al 0.25 mm] where the thickness of the aluminum plate is thin, the temperature of adjacent cells after 2000 seconds is higher than that of Comparative Example 1, and the cooling performance is lower than that of the prior art. Also, although not shown in Figure 13, in Example 12 and Example 13 of the present invention where the cell and the metal member are adhered with an adhesive instead of grease, and in Example 14 of the present invention where the thermal insulation member is replaced with glass wool to form a refractory cloth, the cooling performance is also higher than that of the prior art.

[0106] Figure 14 shows the results when the distance between cells is 3 mm. For Comparative Example 3 [thermal insulation member 1.0 mm / Al 1.0 mm / thermal insulation member 1.0 mm], Comparative Example 4 [thermal insulation member 0.5 mm / Al 2.0 mm / thermal insulation member 0.5 mm], and Comparative Example 5 [Al 3.0 mm only], in the examples of the present invention, Example 5 of the present invention [Al 0.5 mm / thermal insulation member 2.0 mm / Al 0.5 mm] and Example 6 of the present invention [Al 1.0 mm / thermal insulation member 1.0 mm / Al 1.0 mm], the temperature of adjacent cells after 2000 seconds is lower than that of any of the comparative examples. It can be seen that the cooling performance is higher than that of the prior art.

[0107] Figure 15 shows the results when the cell gap is 2 mm. For Comparative Example 6 [thermal insulation member 0.5 mm / Al 1.0 mm / thermal insulation member 0.5 mm] and Comparative Example 7 [only Al 2.0 mm], Example 7 of the present invention [Al 0.5 mm / thermal insulation member 1.0 mm / Al 0.5 mm], which is an example of the present invention, shows that the temperature of adjacent cells after 2000 seconds is lower than that of any of the comparative examples, indicating that the cooling performance is higher than that of the prior art.

[0108] Figure 16 shows the results of Example 8 of the present invention ([Al 1.5 mm / thermal insulation member 2.0 mm / Al 1.5 mm], where the lower parts of two aluminum plates are connected at 25% of the height in the height direction and integrated) in the case where the lower part of the metal member is connected (U-shaped metal member) at a cell interval of 5 mm (the structure of Figure 4), compared with Example 1 and Comparative Example 1. In Example 8 of the present invention, although the temperature of adjacent cells after 2000 seconds is slightly higher than that of Example 1, it is lower than that of Comparative Example 1, indicating that the cooling performance is higher than that of the prior art.

[0109] Figure 17 shows a comparison between Example 9 of the present invention ([Al 1.5 mm / thermal insulation member 2.0 mm / Al 1.5 mm] + Al provided on the short side surface) and Example 1 of the present invention in the case where aluminum plates (3 mm thick) are adhered to the side surfaces of all short sides of 8 battery cells via grease and the entire side surface of the battery module is covered with an aluminum plate (the structure of Figure 2). It can be seen that in Example 9 of the present invention, the temperature of adjacent cells after 2000 seconds is lower than that of Example 1, and the cooling performance is further improved.

[0110] As is clear from Table 1 above and Figures 13 to 17, those corresponding to the examples of the present invention all receive evaluations of "A" or "B", indicating that the cooling capacity is superior to that of the prior art.

[0111] [Regarding the influence of the type (thermal conductivity) of the plate-shaped metal member] Figure 18 shows the results when the metal member is changed to duralumin (thermal conductivity: 110 W / m·K at room temperature) and cast iron (thermal conductivity: 50 W / m·K at room temperature).

[0112] In Invention Example 10, the same conditions as in Example 1 were used except that the metal member was made of duralumin. In Comparative Example 8, the same conditions as in Comparative Example 1 were used except that the metal member was made of duralumin. Comparing the two, it can be seen that in Invention Example 10, the temperature of the adjacent cell after 2000 seconds is lower than that in Comparative Example 8, and the cooling performance is higher than that of the prior art. However, compared with Example 1 of the present invention, the temperature in Invention Example 10 has risen overall, and it can be seen that the thermal conductivity of the metal member is preferably 150 w / m·K or more.

[0113] In addition, in Reference Example 2, the same conditions as in Example 1 were used except that the metal member was made of cast iron. In Comparative Example 9, the same conditions as in Comparative Example 1 were used except that the metal member was made of cast iron. Comparing the two, although the temperature of the adjacent cell after 2000 seconds in Reference Example 2 is lower than that in Comparative Example 9, the maximum temperature of the adjacent cell exceeds 200°C. Therefore, it cannot be said that the temperature rise of the adjacent battery cells is efficiently suppressed, and it is used as a reference example.

[0114] [Influence of the type (thermal conductivity) of the heat insulation member in the heat insulation layer] Figure 19 shows the results when the heat insulation member of the heat insulation layer is changed to a glass plate (thermal conductivity: 0.9 W / m·K at room temperature).

[0115] In Invention Example 11, the same conditions as in Example 1 were used except that the heat insulation member was made of a glass plate. In Comparative Example 10, the same conditions as in Comparative Example 1 were used except that the heat insulation member was made of a glass plate. Comparing the two, it can be seen that in Invention Example 11, the temperature of the adjacent cell after 2000 seconds is lower than that in Comparative Example 10, and the cooling performance is higher than that of the prior art. However, compared with Example 1 of the present invention, the temperature in Invention Example 10 has risen overall, and it can be seen that the thermal conductivity of the heat insulation member is preferably 0.1 W / m·K or less.

[0116] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present invention.

Explanation of Reference Numerals

[0117] 1 Cooling structure of battery cell 2 Multilayer structure 10 Battery cell 20 Plate-shaped metal member 30 Heat insulation layer (heat insulation member or gas layer) 40 Cooling member 41 Cooling plate 42 Heat transfer sheet 50 Heat transfer sheet 60 Second plate-shaped metal member 70 Third plate-shaped metal member 100 Battery module

Claims

1. A cooling structure between adjacent battery cells in a plurality of rectangular battery cells arranged side by side with two side surfaces facing each other, comprising: A plate-shaped metal member having a thermal conductivity of 100 w / m·K or more and a thickness of 0.3 mm or more, and in thermal contact with each of the opposing side surfaces of the adjacent battery cells; A heat insulating layer is disposed between plate-shaped metal members that are in thermal contact with the opposing side surfaces of the adjacent battery cells, and has at least one of a heat insulating member or a gas layer having a thermal conductivity of 1.0 W / m K or less and a thickness of 0.5 mm or more; Due to The adjacent battery cells form a multi-layer structure of battery cell / plate-shaped metal member / insulating layer / plate-shaped metal member / battery cell, Further, a cooling member in thermal contact with each of the plurality of rectangular battery cells or in the vicinity of each of the plurality of rectangular battery cells; Equipped with At least one end of each of the plate-shaped metal members is in thermal contact with the cooling member, The two plate-shaped metal members constituting the multi-layer structure have the same thermal conductivity and thickness, and the ratio of the thickness of the plate-shaped metal member / thermal insulation layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0; The plate-shaped metal member has a generally concave shape in which lower portions of the plate-shaped metal member that are in thermal contact with the respective side surfaces of the adjacent heat insulating members are connected to each other, The substantially concave plate-like metal member is inserted between the adjacent heat insulating members, A cooling structure between battery cells, wherein the battery cell is disposed in the generally concave recess.

2. A cooling structure between adjacent battery cells in a plurality of rectangular battery cells arranged side by side with two side surfaces facing each other, comprising: A plate-shaped metal member having a thermal conductivity of 100 w / m·K or more and a thickness of 0.3 mm or more, and in thermal contact with each of the opposing side surfaces of the adjacent battery cells; A heat insulating layer is disposed between plate-shaped metal members that are in thermal contact with the opposing side surfaces of the adjacent battery cells, and has at least one of a heat insulating member or a gas layer having a thermal conductivity of 1.0 W / m K or less and a thickness of 0.5 mm or more; Due to The adjacent battery cells form a multi-layer structure of battery cell / plate-shaped metal member / insulating layer / plate-shaped metal member / battery cell, Further, a cooling member in thermal contact with each of the plurality of rectangular battery cells or in the vicinity of each of the plurality of rectangular battery cells; Equipped with At least one end of each of the plate-shaped metal members is in thermal contact with the cooling member, The two plate-shaped metal members constituting the multi-layer structure have the same thermal conductivity and thickness, and the ratio of the thickness of the plate-shaped metal member / thermal insulation layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0; The plate-shaped metal member is processed so that its cross-sectional shape is concave, and is inserted between adjacent battery cells, A cooling structure between battery cells, wherein the insulating layer is disposed in the concave recess.

3. The thickness of the plate-shaped metal member is 0.5 mm or more, The cooling structure between battery cells according to claim 1 or 2, wherein the insulating layer has a thickness of 1.0 mm or more.

4. In each of the plurality of rectangular battery cells, A second plate-shaped metal member having a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more is further present on a side parallel to the direction in which the plurality of rectangular battery cells are arranged, The cooling structure between battery cells described in any one of claims 1 to 3, wherein the second plate-shaped metal member is in thermal contact with a side surface of the battery cell and at least one end portion is in thermal contact with the cooling member.

5. The cooling structure between battery cells according to any one of claims 1 to 4, wherein the gap between the adjacent battery cells is 1.5 to 5.0 mm.

6. The cooling structure between battery cells according to any one of claims 1 to 5, wherein a side surface of the battery cell is made of a steel material.

7. the plate-shaped metal member and the cooling member are in thermal contact with each other via an adhesive or grease having a thermal conductivity of 1.0 W / m K or more; The cooling structure between battery cells according to any one of claims 1 to 6, wherein the adhesive or grease having a thermal conductivity of 1.0 W / m·K or more is an adhesive or grease that hardens at room temperature.

8. The cooling structure between battery cells according to any one of claims 1 to 7, wherein the rectangular battery cell is configured by stacking laminate-type battery cells.

9. 9. The cooling structure between battery cells according to claim 1, wherein the material of the plate-shaped metal member is at least one of aluminum, an aluminum alloy, copper, and a copper alloy.

10. A battery module having the cooling structure between battery cells according to any one of claims 1 to 9.

11. A battery pack having the cooling structure between battery cells according to any one of claims 1 to 9.

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