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 technology]

[0002] Electric vehicles use a large number of battery cells (e.g., lithium-ion secondary batteries) to obtain a large storage capacity and high output. Battery cells come in various types, including cylindrical, prismatic, and laminated. Prismatic cells are commonly used for electric vehicles because they have high mechanical strength and a good balance of energy density and size. Electric vehicles that use prismatic battery cells (hereinafter simply referred to as "battery cells") use multiple battery modules in a limited space, each consisting of a large number of battery cells densely arranged in parallel or series. These battery modules are connected to form a battery pack and are installed on the vehicle. Battery cells generate a large amount of heat during repeated charging and discharging, which accelerates their deterioration if left untreated. Therefore, the battery module is equipped with a structure or mechanism for cooling the battery cells using air cooling, water cooling, or other methods.

[0003] However, even with such cooling structures and mechanisms, some battery cells may become abnormally hot due to deterioration during repeated charging and discharging, or due to external heat or impact. In this case, a large amount of heat is transferred from the abnormally hot battery cell to adjacent battery cells, and the heat spreads, damaging the entire battery module. As a countermeasure, for example, Patent Document 1 discloses a technology for suppressing damage to the battery module by providing an inter-battery separator between adjacent battery cells. An example of an inter-battery separator in this document is a stacked structure of a heat insulating member / thermal conductive member / thermal conductive member. This structure can suppress heat transfer between adjacent cells using the heat insulating member. Furthermore, by contacting the ends of the thermal conductive member or the bottom of the battery cell with a cooling plate or the like, the heat generated by the abnormal heat generation is transferred and dispersed to other parts, thereby suppressing the spread of the abnormal heat generation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167689 [Patent Document 2] International Publication No. 2019 / 167612 [Patent Document 3] China Patent Publication No. 105489965 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, the energy density of battery cells for electric vehicles has increased, and when abnormal heat is generated, the temperature rise of the heat-generating cell becomes even greater, making it easier for heat to spread between adjacent cells. Therefore, there has been a greater need than ever before for heat transfer control technology (cooling technology) that can prevent damage to battery modules when abnormal heat is generated.

[0006] Meanwhile, in order to reduce the cost of battery modules, there has been a trend in some areas to use iron-based materials such as steel for the casings of battery cells, rather than aluminum-based materials such as aluminum alloys. Iron-based materials have thermal conductivity that is approximately 1 / 5 to 1 / 10 lower than that of aluminum-based materials. Therefore, when an iron-based material is used for the casing, even if a battery module is used in which the cooling capacity is enhanced by bringing the battery case into contact with a cooling mechanism such as a cooling plate, it becomes difficult to transfer and disperse heat from abnormally heated battery cells to other parts through the cooling plate.

[0007] Furthermore, iron-based materials have a higher melting point than aluminum-based materials. Due to the recent trend toward higher energy in battery cells for electric vehicles, the maximum temperature in the event of abnormal heat generation can reach 700-800°C or higher, which could exceed the melting point of aluminum-based materials (approximately 660°C) and lead to a very dangerous situation in which the casing itself melts. However, with iron-based materials, which have a melting point of around 1500°C, this type of casing melt-through does not occur, so it can be said that iron-based materials are safer than aluminum-based materials.

[0008] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is 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 temperature rises in adjacent battery cells compared to conventional technology, even if a battery cell generates abnormal heat and even if the casing of the battery cell at that time is made of an iron-based material such as steel.

[0009] Furthermore, the narrower the spacing between battery cells, the more compact the battery pack or battery module can be designed, which is preferable in terms of size reduction. However, a certain amount of spacing is necessary to prevent abnormal heat generation and to facilitate the installation of cooling structures. Therefore, the spacing between battery cells must be designed with these factors in mind, and the spacing is designed differently for each type of battery.

[0010] Therefore, the main object of the present invention is to provide a cooling structure between battery cells, and a battery module and a battery pack having the cooling structure between battery cells, which can more efficiently suppress temperature rises in adjacent battery cells than conventional techniques, particularly when the spacing between battery cells is the same, in the above-mentioned problem.

[0011] Since it is important to prevent abnormal heat generation in battery cells, aluminum-based materials with excellent thermal conductivity are generally used for the casing, and the above-mentioned problems would not have occurred.The above-mentioned problems would only have occurred if an iron-based material had been used for the casing. [Means for solving the problem]

[0012] As a result of intensive research into solving the above problems, the inventors came up with the idea of ​​providing a multilayer structure (hereinafter sometimes abbreviated as "Structure A") between adjacent battery cells, consisting of "a layer of metal material with high thermal conductivity in thermal contact with the side surface of one battery cell / a heat insulating layer disposed between them / a layer of metal material with high thermal conductivity in thermal contact with the side surface of the other battery cell," with each layer having a predetermined thickness and one end of the metal material with high thermal conductivity connected to a cooling mechanism.The inventors have found that this makes it possible to reduce the temperature rise of adjacent battery cells more efficiently than conventional techniques, even in the event of an abnormally hot battery cell.

[0013] Additionally, under the above conditions, we also investigated the case where, instead of Structure A, a multi-layer structure was provided between adjacent battery cells, consisting of "a layer of heat insulating material in thermal contact with the side of one battery cell, a layer of material with high thermal conductivity placed between them, and a layer of heat insulating material in thermal contact with the side of the other battery cell" (hereinafter sometimes abbreviated as "Structure B"). Then, we compared both Structure A and Structure B.

[0014] As a result, it was found that in the early stages of abnormal heat generation, there was almost no difference in cooling capacity between Structure A and Structure B, but as time passed, differences arose, and Structure A had a higher cooling capacity than Structure B. It was also found that Structure A had a higher cooling capacity when the thickness of each component was above a certain value, compared to when a single layer of a component with high thermal conductivity was simply placed between battery cells.

[0015] Furthermore, when we focused on the thermal resistance at the contact interface between the battery cell and the metal member, we found that controlling the ratio of the thermal resistance value at the contact interface to the thermal resistance value of the metal member to a predetermined value or less is preferable, as this further improves cooling capacity.

[0016] Incidentally, Patent Document 2 discloses a structure similar to Structure A, but Patent Document 2 was invented with the intention of reflecting electromagnetic waves, and does not disclose the aspect of heat conduction that is the focus of the present invention. Furthermore, Patent Document 2 discloses that the thickness of the heat insulating material is 0.1 to 3 mm, which is thinner than that of the present invention, which will be described in detail below. From this perspective, it can be seen that Patent Document 2 focuses on the reflection of electromagnetic waves, and does not intend to conduct heat. Furthermore, Patent Document 2 does not consider at all the control of the thermal resistance of the contact interface.

[0017] Furthermore, Patent Document 3 discloses an invention similar to the present invention, which is intended to conduct heat. In Patent Document 3, a sheet or foil such as a graphite sheet is used as the thermally conductive material, and the thickness of the sheet or foil is very thin, at 0.02 mm in the examples, which is different from the present invention. Furthermore, Patent Document 3 does not consider at all the control of the thermal resistance of the contact interface.

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

[0019] (1) A cooling structure between adjacent battery cells in a plurality of prismatic battery cells arranged side by side with two side surfaces facing each other, the cooling structure 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; 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, disposed between the plate-shaped metal members in thermal contact with each of the opposing side surfaces of the adjacent battery cells, forming a multilayer structure of battery cell / plate-shaped metal member / heat insulating layer / plate-shaped metal member / battery cell between the adjacent battery cells; and and a cooling member in thermal contact with each of the plurality of rectangular battery cells or present in the vicinity of each of the plurality of rectangular battery cells, wherein 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 multilayer structure have the same thermal conductivity and thickness, and the thickness ratio of plate-shaped metal member / insulating layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0, the plate-shaped metal members are formed into a substantially concave shape by connecting lower parts of the plate-shaped metal members that are in thermal contact with side surfaces of adjacent insulating members, the substantially concave-shaped plate-shaped metal member is inserted between the adjacent insulating members, and the battery cell is arranged in the substantially concave depression. (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, the cooling structure 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; and a heat insulating layer disposed between the plate-shaped metal members in thermal contact with each of the opposing side surfaces of the adjacent battery cells, the 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, whereby the adjacent battery cells are cooled in a battery cell / plate-shaped metal member / heat insulating layer / plate-shaped metal member / battery a cooling structure between battery cells, which forms a multilayer structure called rectangular battery cells, and further comprises a cooling member that is in thermal contact with each of the plurality of rectangular battery cells or that is present in the vicinity of each of the plurality of rectangular battery cells, wherein 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 that make up the multilayer structure have the same thermal conductivity and thickness, and the ratio of plate-shaped metal member / insulating layer / thickness of 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, with the insulating layer being disposed in the recess of the concave shape. (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) The cooling structure between battery cells described in any one of (1) to (3), wherein 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 of each of the plurality of rectangular battery cells that is parallel to the direction in which the plurality of rectangular battery cells are arranged side by side, and the second plate-shaped metal member is in thermal contact with the side of the battery cell, and at least one end of the second plate-shaped metal member is in thermal contact with the cooling member. (5) The cooling structure between battery cells according to any one of (1) to (4), wherein the interval between the adjacent battery cells is 1.5 to 5.0 mm. (6) The cooling structure between battery cells according to any one of (1) to (5), wherein the side surfaces of the battery cells are made of a steel material. (7) A cooling structure between battery cells described in any one of (1) to (6), wherein 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 hardens at room temperature. (8) The cooling structure between battery cells according to any one of (1) to (7), wherein the prismatic battery cell is configured by stacking laminated battery cells. (9) The cooling structure between battery cells according to any one of (1) to (8), 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 (1) to (9). (11) A battery pack having the cooling structure between battery cells according to any one of (1) to (9). [Effects of the Invention]

[0020] As described above, according to the present invention, even if a battery cell generates abnormal heat, and even if the casing of the battery cell is made of an iron-based material such as steel, it is possible to more efficiently suppress the temperature rise of adjacent battery cells than with conventional technology, provided that the spacing between the battery cells remains the same. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an explanatory diagram (a cross-sectional view in the longitudinal direction of a battery module) that schematically illustrates a battery cell cooling structure according to an embodiment of the present invention. [Figure 2]1 is an explanatory diagram schematically illustrating a battery module according to an embodiment of the present invention; [Figure 3A] FIG. 10 is an explanatory diagram (a cross-sectional view in the longitudinal direction of a battery module) that schematically illustrates another example of a battery cell cooling structure according to an embodiment of the present invention. [Figure 3B] FIG. 10 is an explanatory diagram (a cross-sectional view in the longitudinal direction of a battery module) that schematically illustrates another example of a battery cell cooling structure according to an embodiment of the present invention. [Figure 4] FIG. 10 is an explanatory diagram (a cross-sectional view in the longitudinal direction of a battery module) that schematically illustrates another example of a battery cell cooling structure according to an embodiment of the present invention. [Figure 5] 3 is an explanatory diagram illustrating an example of thermal contact between a metal member and a cooling member in a battery cell cooling structure according to an embodiment of the present invention. FIG. [Figure 6] FIG. 1 is a schematic diagram (a cross-sectional view in the longitudinal direction of a battery module) for explaining a conventional battery cell cooling structure (a comparative example). [Figure 7] 10 is a schematic diagram (cross-sectional view in the longitudinal direction of the battery module) for explaining a battery cell cooling structure (comparative example) in which only a metal member or a heat insulating member is installed between adjacent battery cells. FIG. [Figure 8] FIG. 10 is a schematic diagram (cross-sectional view in the longitudinal direction of the battery module) for explaining a battery cell cooling structure (comparative example) in which a gap (air layer) is provided between adjacent battery cells. [Figure 9] FIG. 1 is a temperature history diagram comparing the cooling characteristics of the battery cell cooling structures shown in FIG. 1, FIGS. 6 to 8, etc. [Figure 10] FIG. 2 is an explanatory diagram for explaining a method for measuring the thermal conductivity of a metal member. [Figure 11] FIG. 2 is an explanatory diagram for explaining a method for measuring the thermal conductivity of a metal member. [Figure 12] FIG. 1 is an explanatory diagram for explaining a method for measuring the thermal conductivity of an adhesive and a grease. [Figure 13]FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (cell spacing 5 mm). [Figure 14] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (cell spacing 3 mm). [Figure 15] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (cell spacing 2 mm). [Figure 16] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (cell spacing 5 mm, metal member U-shaped). [Figure 17] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (cell spacing 5 mm, metal members also on the side surfaces on the short sides of the cells). [Figure 18] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an embodiment (using duralumin or cast iron for the metal member). [Figure 19] FIG. 10 is a diagram showing the results of cooling characteristics of an example of the present invention and a comparative example in an example (using a glass plate as a heat insulating layer). DETAILED DESCRIPTION OF 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 drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0023] <Overall structure of the cooling structure between battery cells> 1 is a schematic diagram (a longitudinal cross-sectional view of a battery module) showing one embodiment of the cooling structure of the present invention. This cooling structure can suppress the temperature rise in battery cells adjacent to an abnormally heated battery cell to a lower level than conventional cooling structures.

[0024] In the structure shown in Fig. 1, a plurality of prismatic battery cells 10 (hereinafter, "prismatic battery cells" will be abbreviated simply as "battery cells") with casings made of iron or aluminum are arranged side by side with their two side surfaces (the sides with the largest surface area) facing each other (only some of the cells are shown in the figure). The battery cells may be constructed by stacking laminated battery cells.

[0025] A plate-shaped metal member 20 (hereinafter sometimes simply referred to as "metal member 20") having a thermal conductivity of 100 W / m·K or more (at room temperature of 25°C) and a thickness of 0.3 mm or more is in thermal contact with each side surface of adjacent battery cells 10. Therefore, the two plate-shaped metal members 20 are adjacent to each other, just like adjacent battery cells 10. Between these two adjacent plate-shaped metal members 20, there is a heat insulating layer 30 having at least either a heat insulating member or a gas layer having a thermal conductivity of 1.0 W / m·K or less (at room temperature of 25°C) and a thickness of 0.5 mm or more.

[0026] In the embodiments of the present invention, "being in thermal contact" does not necessarily mean direct contact between two members, but also includes a state in which two members are "connected so as to enable thermal conduction" with another member sandwiched between them. Details will be described later.

[0027] The gap between adjacent battery cells 10 is required to be as small as possible to make battery modules and battery packs made up of multiple battery cells more compact and dense, and is usually 10 mm or less. In this embodiment, when the gap between adjacent battery cells 10 is 1.5 mm or more, the difference in cooling effect compared to conventional techniques becomes greater.

[0028] Furthermore, the lower end of the plate-shaped metal member 20 is in thermal contact with the upper surface of a cooling member 40 located below the battery cell 10. In this embodiment, the cooling member 40 is composed of a water-cooled cooling plate 41 and a thin heat-transfer sheet 42 adhered thereon for electrical insulation. The cooling member 40, which is in thermal contact with the plate-shaped metal member 20, only needs to be located near the battery cell 10, and may be located above or to the side, in addition to below. In other words, the cooling member 40 only needs to be located near the battery cell 10 so that the end of the metal member 20 and the cooling member 40 can easily come into contact with each other. The cooling member 40 may also be in thermal contact with the battery cell 10 and directly cool the battery cell 10. In order to improve cooling performance, it is preferable that the cooling member 40 be located in multiple positions among below, above, and to the side. 2 illustrates a case in which, in addition to the plate-shaped metal member 20, a second plate-shaped metal member 60 positioned above the battery cell 10 and a third plate-shaped metal member 70 positioned to the side of the battery cell 10 are provided. In order to simplify the structure, it is preferable that the plate-shaped metal member 20 be present only below the battery cell 10.

[0029] Preferably, as shown in FIG. 1, the battery cell 10 is placed on a cooling member 40 located below it, and the lower surface of the battery cell 10 and the upper surface of the cooling member 40 are in thermal contact with each other.

[0030] Furthermore, in each battery cell 10, in addition to the two sides with the largest area (the two long sides), the remaining two sides (the two short sides) that are parallel to the direction in which the multiple rectangular battery cells 10 are arranged side by side (sides extending in the same direction) are preferably in thermal contact with 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, and also in thermal contact with the upper surface of the cooling member 40 located below (not shown).

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

[0032] With this structure, when some of the multiple battery cells 10 begin to generate abnormal heat, the heat can be released to the nearby cooling member 40 through the metal member 20. Furthermore, the heat insulating member suppresses the transfer of heat to adjacent battery cells 10, and can efficiently suppress the temperature rise of the adjacent battery cells 10.

[0033] In particular, this cooling structure can efficiently suppress the temperature rise of adjacent battery cells 10 even when steel is used for the casing of the battery cells 10 to reduce costs, etc., and the side surfaces of adjacent battery cells 10 are made of steel material whose thermal conductivity is one order of magnitude lower than that of aluminum material. Therefore, when this cooling structure is applied to battery cells in which steel material is used for the side surfaces of the cells, the difference in effect from conventional techniques becomes more significant, making it preferable.

[0034] <About plate-shaped metal components> The plate-shaped metal member 20 must have a thermal conductivity of 100 W / m·K or more and a thickness of 0.3 mm or more to efficiently dissipate heat from a battery cell 10 that has begun to generate abnormal heat to a nearby cooling member 40. In addition to its superior cooling capacity compared to conventional technology, the thickness of the plate-shaped metal member 20 is preferably 0.5 mm or more, more preferably 1.0 mm or more, from the perspective of lowering the ultimate temperature itself. The thickness of the plate-shaped metal member 20 is determined taking into account the spacing between adjacent battery cells 10 and the thickness of the insulating layer 30, but is practically limited to approximately 5.0 mm. The thickness of the plate-shaped metal member 20 is preferably 5.0 mm or less, more preferably 2.0 mm or less. The thermal conductivity of the plate-shaped metal member 20 is preferably 150 W / m·K or more. The thermal conductivity of the plate-shaped metal member 20 is practically limited to approximately 420 W / m·K. It is even more preferable that the plate-shaped metal member 20 has a thickness of 1.0 mm or more and a thermal conductivity of 150 W / m·K or more.

[0035] The thickness of the plate-shaped metal member 20 does not necessarily have to be constant, and the shape of the metal member may be tapered, have steps, or have unevenness. In these shapes, the average value can be used as the above-mentioned plate thickness value. This average plate thickness value can be calculated by (volume of the plate-shaped metal member 20) / (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, but aluminum, aluminum alloy, copper, and copper alloy (including chalcopyrite) are preferred as the material of the metal member in terms of the balance between high thermal conductivity and low cost.

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

[0038] 3A, the lower portions of plate-shaped metal members 20 that are in thermal contact with the respective side surfaces of adjacent heat insulating members 30 may be connected to form a concave shape (in other words, the cross-sectional shape of the plate-shaped metal member 20 may be made concave), and then the metal members 20 may be inserted between the adjacent heat insulating members 30, and further, battery cells 10 may be placed in the recesses of the plate-shaped metal members 20. In this way, the desired heat insulating state can be achieved simply by inserting the metal members 20 with the battery cells 10 placed thereon between the adjacent heat insulating members 30, further improving productivity.

[0039] In this case, the corners of the concave metal member 20 may be right angles as shown in FIG. 3A, or may be curved as shown in FIG. 3B.

[0040] <About the heat insulating layer> The 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 to suppress heat transfer to adjacent battery cells 10 when some battery cells 10 abnormally heat up. The higher the insulating ability of the insulating layer 30, the more effectively it can suppress the initial temperature rise in battery cells adjacent to the abnormally heated battery cell. Therefore, from the viewpoint of suppressing the initial temperature rise, the thermal conductivity of the insulating layer 30 is preferably 0.1 W / m·K or less, and more preferably 0.06 W / m·K or less. The thermal conductivity of the insulating layer 30 is essentially limited to approximately 0.02 W / m·K. Similarly, from the viewpoint of suppressing the initial temperature rise, the thickness of the insulating layer 30 is preferably 1.0 mm or more, and more preferably 1.5 mm or more. The thickness of the insulating layer 30 is determined taking into consideration the spacing between adjacent battery cells 10 and the thickness of the plate-shaped metal member 20, but is essentially limited to approximately 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 insulating layer 30 is not particularly limited, and insulating materials such as glass wool, rock wool, urethane foam, foamed rubber, nonwoven fabric, polystyrene, and resins such as polypropylene and polybutylene terephthalate can be used. The insulating layer 30 may also be a gas layer in which a gas such as air exists in a space. Furthermore, the insulating layer 30 may be formed by using a material capable of retaining a gas layer, such as a porous material, between adjacent metal members 20, so that a gas such as air exists inside the pores.

[0042] The heat insulating layer 30 may be present 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 be separated from the metal member 20 with a gap therebetween. Also, one side of the heat insulating layer (heat insulating member) 30 may be in contact with the metal member 20, and the other side may be separated from the metal member 20 with a gap therebetween. When the heat insulating member 30 and the metal member 20 are in contact with each other, they can be fixed together using an adhesive.

[0043] Alternatively, the heat insulating layer (heat insulating member) 30 may simply be sandwiched between two adjacent plate-shaped metal members 20. In this case, it is preferable to sandwich the heat insulating layer (heat insulating member) 30, which has a relatively high resilience, between the two adjacent plate-shaped metal members 20 and use it to press the metal members 20. This causes the metal members 20 to be pressed against the side surfaces of the battery cell 10, reducing contact resistance (thermal resistance) and further improving the cooling effect.

[0044] Furthermore, even if the insulating layer 30 is only a gas layer such as air (only voids), the influence of radiant heat is minimal in the temperature range of around 100°C unless the gas layer is actively convected, and therefore the gap between the plate-shaped metal members 20 is insulated by the low thermal conductivity of the gas layer. For example, if the insulating layer 30 is an air layer, there is no significant difference in the insulating effect compared to when it is glass wool. However, if the insulating layer 30 is only a gas layer, a temperature gradient occurs around the battery cell 10, which can cause natural convection of the gas, and the heat transfer coefficient between the plate-shaped metal members 20 can increase due to convective heat conduction, depending on the surrounding structure. For this reason, it is more preferable to use an insulating material for the 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 present in the gap, together with the heat insulating member 30, provides a heat insulating effect between the two adjacent plate-shaped metal members 20. In this case, the heat insulating layer (heat insulating member) 30 can be fixed to the cooling structure 40 below with an adhesive or the like. Alternatively, the heat insulating member 30 may simply be placed between the two adjacent plate-shaped metal members 20.

[0046] The installation position and area of ​​the heat insulating layer (heat insulating member) 30 are preferably set to a position and size that covers at least the entire surface of the metal member 20. This is because, when the battery cell 10 generates abnormal heat, heat radiation from the side surface of the metal member 20 can be suppressed, and the 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 the heat insulating layer (heat insulating member) 30 so that it faces the entire side surface of the battery cell 10, as this can suppress the transfer of heat to adjacent battery cells 10.

[0047] Furthermore, as shown in FIG. 4 , the lower portions of plate-shaped metal members 20 that are in thermal contact with the respective side surfaces of adjacent battery cells 10 may be connected to form a concave shape (in other words, the cross-sectional shape of the plate-shaped metal member 20 may be made concave), and the metal members 20 may be inserted between the battery cells 10. Furthermore, a heat insulating layer (heat insulating member) 30 may be installed in the recess of the plate-shaped metal member 20. This allows the desired thermal insulation state to be achieved simply by inserting the metal member 20 between adjacent battery cells 10, further improving productivity. In addition, the heat insulating layer (heat insulating member) 30 can be installed stably. It is preferable that the height of the connecting portion of the lower portion of the metal member 20 be equal to or less than ¼ of the overall height of the metal member 20 in order to sufficiently maintain the heat insulating effect of the heat insulating member 30.

[0048] <About the multi-layer structure> In this embodiment, as illustrated in FIG. 2 , adjacent battery cells form a multi-layer structure of battery cell 10 / plate-shaped metal member 20 / insulating layer 30 / plate-shaped metal member 20 / battery cell 10. In this multi-layer structure, the characteristics of each of the plate-shaped metal member 20 / insulating layer 30 / plate-shaped metal member 20 are as described above. There are no limitations on the multi-layer structure as a whole, as long as they are within the above-described ranges. For example, the two plate-shaped metal members 20 present between adjacent cells may have different thermal conductivities and thicknesses. However, if the characteristics of both are the same, the cooling structure as a whole will be well-balanced, and this is preferable in terms of suppressing temperature non-uniformity and facilitating production.

[0049] When two adjacent plate-shaped metal members 20 have the same thermal conductivity and thickness, the thickness ratio of the plate-shaped metal member 20 / thermal insulating layer 30 / plate-shaped metal member 20 is preferably 0.2 to 4.0, and more preferably 0.5 to 3.0, when the thickness of the plate-shaped metal member 20 is 1.0. In other words, the thickness ratio of the plate-shaped metal member 20 / thermal insulating 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] <About thermal contact> (Thermal contact between the side of the battery cell and the plate-shaped metal member) In this embodiment, the situation in which the side surface of the battery cell 10 and the plate-shaped metal member 20 are in thermal contact includes not only the case in which they are in direct contact with each other, but also the case in which they are connected (in contact) in a manner that allows thermal conduction via a contact member such as adhesive, grease, or a thin sheet (not shown).

[0051] Even when they are in direct contact, there is contact resistance at the contact interface caused by slight differences in the roughness and curvature of the surfaces 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. The thermal resistance Rs at the contact interface is expressed as a function of L / λ or 1 / h [m 2 ·K / W]. Here, when a contact member is used, the above L indicates the thickness of the contact member present at the contact interface, the above λ indicates the thermal conductivity of the contact member, and the above h indicates 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 (irregularities) 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.

[0053] Alternatively, the side surface of the battery cell 10 and the plate-shaped metal member 20 can be thermally contacted via adhesive or grease. Using adhesive or grease is preferable because it can fill in the irregularities on the surfaces of both materials and easily increase the effective contact area. When using adhesive or grease, it is preferable to use one with high thermal conductivity, with a thermal conductivity of 1.0 W / m·K or higher. The thermal conductivity of the adhesive or grease is more preferably 2.0 W / m·K or higher, and even more preferably 4.0 W / m·K or higher. Meanwhile, the upper limit of the thermal conductivity of the adhesive or grease is essentially about 10.0 W / m·K. It is preferable to apply the adhesive or grease thinly enough to fill in the irregularities on both materials, as this reduces thermal resistance. Depending on the degree of irregularity, it is preferable to apply the adhesive or grease to a thickness of, for example, about 0.01 to 0.2 mm.

[0054] Alternatively, the side of the battery cell 10 and the plate-shaped metal member 20 can be thermally contacted via a thin sheet such as a heat transfer sheet. Heat transfer sheets made of soft materials such as silicone rubber are preferred because, like adhesives and grease, they can fill in the irregularities on the surfaces of both materials, easily increasing the effective contact area. Furthermore, using an electrically insulating heat transfer sheet can also ensure better electrical insulation between cells. Heat transfer sheets are often thicker than adhesives and greases, so a higher thermal conductivity is preferable. For example, the thermal conductivity of a heat transfer sheet is preferably 2 W / m·K or higher, and more preferably 10 W / m·K or higher. However, the thermal conductivity of a heat transfer sheet is practically limited to approximately 50 W / m·K.

[0055] The adhesive, grease, or heat transfer sheet may further contain a ceramic filler or the like to improve the heat transfer properties or to impart electrical insulation properties to the adhesive, grease, or heat transfer sheet.

[0056] Lithium-ion secondary batteries, a typical type of battery cell, are known to expand and contract during charging and discharging. This can cause a "pump-out" phenomenon, in which grease, which behaves like a liquid, is forced out of gaps due to repeated expansion and contraction. To prevent this pump-out phenomenon, it is preferable to use an adhesive that solidifies after curing (more specifically, an adhesive that solidifies at room temperature) or a solid heat transfer sheet. In particular, the adhesive hardens to conform to the shape and gaps, allowing heat to be conducted from the battery cell 10 without being affected by thickness, shape, distortion, or surface irregularities. Among these, soft and elastic adhesives are particularly preferable because they easily deform in response to expansion and contraction and do not crack or break even with repeated expansion and contraction.

[0057] The thickness of such adhesives, greases, and heat transfer sheets is preferably thin from the viewpoint of thermal conduction, but thick from the viewpoint of expansion and contraction compatibility. In consideration of this trade-off, the thickness of the adhesives, greases, and heat transfer sheets is preferably 1 μm or more, and more preferably 5 μm or more. Furthermore, the thickness of the adhesives, greases, and heat transfer sheets is preferably 2 mm or less, and more preferably 500 μm or less.

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

[0059] (Thermal contact between the edge of the plate-shaped metal member and the cooling member) In this embodiment, the situation in which one end of the plate-shaped metal member 20 (in FIG. 1, since it is a rectangular plate, of the four ends, the end on the cooling member side) is in thermal contact with the cooling member 40 includes not only a case in which the two are in direct contact, as in the thermal contact between the side of the battery cell and the plate-shaped metal member, but also a case in which the two are connected (in contact) so as to be thermally conductive via adhesive, grease, or a thin heat transfer sheet. FIG. 1 shows an example in which a thin sheet (heat transfer sheet 41) is used.

[0060] In FIG. 1 , one end of the plate-shaped metal member 20 is directly placed on the heat transfer sheet 41 that forms the upper surface of the cooling member 40, making thermal contact with it. Here, as shown in FIG. 5 , the plate-shaped metal member 20 may be configured to extend into the interior of the cooling member 40. The structure shown in FIG. 5 can be realized, for example, by providing a groove in the cooling member 40 and fitting the end of the plate-shaped metal member 20 into the groove to make thermal contact with it. This structure can increase the contact area between the plate-shaped metal member 20 and the cooling member 40 and reduce the effective thermal resistance between the plate-shaped metal member 20 and the cooling member 40, thereby more reliably cooling an abnormally heated battery cell 10. In FIG. 5 , the heat transfer sheet 50 installed between the plate-shaped metal member 20 and the side of the battery cell 10 is extended together with the plate-shaped metal member 20 and embedded in the groove of the cooling member 40 together with the plate-shaped metal member 20, thereby ensuring thermal contact between the cooling member 40 and the plate-shaped metal member 20.

[0061] <Cooling characteristics> The structure of this embodiment can improve cooling capacity compared to the conventional technology. Here, the cooling characteristics of the structure of this embodiment shown in Fig. 1 will be made clear by comparing it with the conventional technology shown in Figs.

[0062] The cooling structure shown in FIG. 6 is the cooling structure of FIG. 1, with the positions of the metal and the insulating material swapped (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 insulating members is the same as the thickness of the insulating layer in FIG. 1). The rest of the structure is the same as that of FIG. 1. That is, it has a multi-layer structure of "cell / insulating member / metal member / insulating member / cell," and one end of the metal member is in thermal contact with the cooling member below. The cooling structures shown in FIG. 7 and FIG. 8 respectively show a cooling structure in which only a metal member 20 is installed between battery cells, and a cooling structure in which only an insulating member 30 is installed (the thicknesses of the metal member and the insulating member are the same as the thicknesses of the multi-layer structure in FIG. 1). The rest of the structure is the same as that of FIG. 1 (in FIG. 7, the metal member is in thermal contact with the cooling member below).

[0063] Figure 9 is a temperature history diagram that schematically shows the difference in cooling characteristics when using the cooling structures of Figure 1 and Figures 6 to 8, and shows the change over time in temperature (at the part that is thought to be the hottest) in the battery cell adjacent to the battery cell in which abnormal heat generation occurred.

[0064] The cooling structure of this embodiment shown in Figure 1 ultimately achieved the lowest temperature, demonstrating the best cooling capacity. The cooling structure shown in Figure 5 exhibited similar temperature changes to the cooling structure shown in Figure 1 until halfway through, but began to deviate toward a higher temperature around 1000 seconds, resulting in a higher temperature than the cooling structure shown in Figure 1. The cooling structure shown in Figure 7, which includes only a metal component, initially showed the fastest temperature rise, but the temperature increase slowed down and resulted in the next lowest temperature after Figures 1 and 6. The cooling structure shown in Figure 8, which includes only a heat insulating component, initially showed a slower temperature rise than the cooling structure shown in Figure 7, but this trend reversed around 1000 seconds, ultimately resulting in the highest temperature. It was also found that the cooling structure shown in Figure 8, which uses only an air layer as the heat insulating component, showed a temperature transition similar to that of the heat insulating component alone.

[0065] As described above, it has been found that the cooling capacity of the cooling structure of FIG. 1 cannot be easily predicted from the cooling capacity of the cooling structures of FIGS.

[0066] The cooling capacity advantage of the cooling structure according to the present invention is demonstrated when a plate-shaped metal member with a thermal conductivity of 100 W / m K or more and a thickness of 0.3 mm or more is used, and a heat insulating layer with a thermal conductivity of 1.0 W / m K or less and a thickness of 0.5 mm or more is used. Outside this range, the advantage is not realized, and in some cases, it has been found that the structure shown in Figure 7, which contains only a metal member, results in a lower maximum temperature.

[0067] <About the manufacturing method of the cooling structure> The manufacturing method of this embodiment is not particularly limited, and may be carried out as appropriate by bringing the plate-shaped metal member 20 into thermal contact with the side surfaces of adjacent battery cells 10, bringing at least one end of the plate-shaped metal member 20 into thermal contact with the cooling member 40, and providing a heat insulating layer 30 between adjacent plate-shaped metal members 20.

[0068] <Method for evaluating thermal conductivity> (Method for evaluating the thermal conductivity of plate-shaped metal members) If the material of the plate-shaped metal member 20 is known, the thermal conductivity of the plate-shaped metal member 20 can be determined as a physical property value inherent to the material.

[0069] When the material of the plate-shaped metal member 20 is unknown, or when the material is known but the physical property value of thermal conductivity is not publicly known, the temperature is measured by the Straight Fin Temperature Fitting (SFTF) method. The method for measuring the thermal conductivity of the plate-shaped metal member 20 will be briefly described with reference to Figures 10 and 11.

[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. 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 direction perpendicular to the battery cell 10 and the grease can be wiped off for measurement. When the plate-shaped metal member 20 is bonded to the battery cell 10 with an adhesive, the plate-shaped metal member 20 is peeled off from the battery cell 10 using a tool such as a scraper, and the surface where the adhesive is present is polished to expose and smooth the surface of the plate-shaped metal member 20. When the plate-shaped metal member 20 is in contact with a heat transfer sheet, the plate-shaped metal member 20 is also peeled off for measurement in the same way.

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

[0073] Fig. 10 is an explanatory diagram for explaining the principle of the SFTF method. As shown in the upper part of Fig. 10, the length Lt [m], the cross-sectional area A [m 2 ]=H×t, perimeter length P[m]=2×(Lt+H+t) of a flat plate specimen. When one end of the specimen is heated and the other end is cooled, the boundary temperature T0 at the heat flow input point is calculated as follows: x0 and the temperature rise distribution T from the surrounding air of the test specimen i (i=1 to n: number of temperature measurement points) and are measured.

[0074] On the other hand, the analytical solution for the temperature distribution of the straight fin, T xi The analytical equation for the temperature distribution in a straight fin is given by the following equation (101), using the boundary conditions of a fixed temperature at one end of the test piece and an insulated one end.The measured values ​​Txi are then compared with the analytical solution Tx for the temperature rise of the straight fin given by equation (101), and the standard deviation σ defined by the following equation (103) is calculated.The parameter m in the analytical equation is then determined so that this standard deviation is minimized.

[0075] In addition, the in-plane thermal conductivity of the sample (thermal conductivity in the length Lt direction in Figure 10) is k p Then, the parameter m in the analytical formula (101) is the average heat transfer coefficient h from the test specimen surface to the surrounding air. m Using this, it is expressed as the following equation (105).

[0076] Also, the average heat transfer coefficient h m is expressed as the following equations (107) to (111) using the theoretical equations for the natural convection heat transfer coefficient and radiation heat transfer coefficient of a vertical flat plate. nm is the natural convection heat transfer coefficient for a vertical plate of height H, and h rm is the radiative heat transfer coefficient from a surface with emissivity ε. Also, k a , v a , β, and Pr are the thermal conductivity, dynamic viscosity, expansion coefficient, 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 specimen and the ambient temperature, expressed in absolute degrees, respectively. ΔTm is the average temperature rise of the test specimen, which can be calculated as ΔT0·φ using the fin efficiency φ(0.8) and the temperature rise ΔT0 at x=0.

[0077]

number

[0078] To measure the thermal conductivity of an actual metal component, the target metal component is cut to a size of 20 mm wide x 200 mm long, and then a laminated structure like that shown in Figure 11 is constructed. A heater is installed at one end, and the heater output is set to 1.6 W at 10 V. The temperature distribution within the metal component's surface is then captured with a thermal camera. The thermal image is converted to a temperature distribution, and the relationship between the test length and surface temperature is confirmed. The thermal conductivity of the target metal component can be obtained by analyzing this relationship using the linear fin temperature distribution fitting method described above. If the metal component is too small to be cut to a size of 20 mm wide x 200 mm long, a smaller test piece, such as 20 mm wide x 100 mm long, can be used for measurement.

[0079] Furthermore, in a structure in which a heat transfer sheet is present between a battery cell and a plate-shaped metal member, the method for measuring the thermal conductivity of this heat transfer sheet can be performed in the same manner as the method for measuring the thermal conductivity of the plate-shaped metal member described above.

[0080] (Method for evaluating the thermal conductivity of adhesives and greases) The thermal conductivity of adhesives and greases can be measured by the following thermal resistance measurement method in accordance with ASTM 5470.

[0081] As shown in the left diagram of Figure 12, the sample of interest is sandwiched between the upper and lower meter bars, and power is applied to the heater on the upper meter bar side. Meanwhile, the test head on the lower meter bar side is maintained at a constant temperature by water cooling or other methods. The thermal resistance of the sample is then calculated from the relationship between the positions and temperatures of the upper and lower meter bars. Specifically, thermocouples are attached at the positions indicated by T1 to T4 in the diagram. The surface temperature of the upper meter bar side of the sample is calculated based on the temperature gradient calculated from the temperatures obtained at T1 to T2, and the surface temperature of the lower meter bar side of the sample is calculated based on the temperature gradient calculated from the temperatures obtained at T3 to T4. This allows the temperature difference ΔT within the sample to be calculated. The thermal resistance of the sample can also be calculated using the heat generation amount Q [W] from the heater.

[0082] The thermal resistance of the sample is calculated as described above while changing the sample thickness, and the results are plotted on a coordinate plane defined by the sample thickness and thermal resistance, as shown in the bottom of Figure 12. The distribution of the plots obtained is then linearly approximated using the least squares method, and the slope of the line is calculated. The reciprocal of the obtained slope is the thermal conductivity of the sample of interest.

[0083] Unlike the transistor method or model heater method, the above-mentioned method for measuring thermal conductivity allows for the application of different pressures to the upper meter bar, making it possible to evaluate the thermal resistance against the applied pressure with good reproducibility. In actual measurements, thin films with thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm are prepared and cut into 20 mm squares. The cut samples are then sandwiched between the meter bars and measured. In this case, the material of the meter bar is SUS304 (20 mm square), and the load during measurement is 3 kg / cm. 2 Then, calculate the slope from the relationship between thermal resistance and thickness, and calculate the thermal conductivity from the reciprocal of the slope.

[0084] If only a small amount of the adhesive or grease of interest is obtained, the adhesive or grease is dissolved in an appropriate organic solvent and the undissolved filler particles are extracted. The extracted filler particles are subjected to component analysis using fluorescent X-rays and crystal structure analysis using X-ray diffraction to identify the type of filler particles. Furthermore, the composition of the matrix resin is identified by observing the obtained resin solution using infrared spectroscopy. Furthermore, the thermal conductivity can be calculated from the extracted filler amount and matrix amount using the following equation (121).

[0085] Here, in the following equation (121), λ matrix is the thermal conductivity of the matrix resin, and λ filler is the thermal conductivity of the filler particles, and λ composite is the thermal conductivity of the composite, φ is the filler content (volume fraction), and x is the shape factor of the filler (minimum at x=2 for a perfect sphere).

[0086]

number

[0087] <Method for evaluating thermal resistance> The thermal resistance (Rm) of a plate-shaped metal member can be calculated from the thermal conductivity (λm) of the plate-shaped metal member calculated using the above-mentioned evaluation method and the thickness (Lm) of the plate-shaped metal member, using the formula Rm=Lm / λm.

[0088] In addition, the thermal resistance (Rs) of the adhesive, grease, and heat transfer sheet can be calculated from the thermal conductivity (λs) of the adhesive, grease, and heat transfer sheet determined using the evaluation method described above and the thickness (Ls) of the adhesive, grease, and heat transfer sheet, using the formula Rs = Ls / λs.

[0089] By determining Rm and Rs using this evaluation method, the above-mentioned Rs / Rm can be calculated.

[0090] <About battery modules and battery packs> Any battery module or battery pack may be used as long as it has the cooling structure between battery cells according to the above-described embodiment of the present invention. The battery pack may be configured not only by a plurality of battery packs arranged in parallel in the horizontal or vertical direction, but also by a single battery module. [Example]

[0091] The following describes the cooling structure between battery cells according to the present invention, as well as the battery cell module and battery pack having the cooling structure, using specific examples and comparative examples. Note that the examples shown below are merely examples of the present invention, and the present invention is not limited to the examples below.

[0092] [Battery cells and battery modules] The battery cells were rectangular cells (27mm long x 170mm wide x 115mm high) with steel casings, and eight of these cells were arranged in a straight line facing each other to create a battery module. Four types of battery modules were prepared with inter-cell gaps of 0.5mm, 2mm, 3mm, and 5mm.

[0093] [Charge / discharge test equipment] A charge / discharge test of the fabricated module was carried out using EVT60V120A manufactured by Nippon Steel Texeng Co., Ltd.

[0094] [Cooling device] A homemade water-cooling device (190mm long x 400mm wide x 40mm high) was used as the cooling device that functions as a thermal cooling mechanism, and the battery module was placed on top of it to charge and discharge the battery. The battery cell cooling mechanism realized in this way has a structure roughly as shown in the cross-sectional view (longitudinal cross section of the battery module) in Figure 1.

[0095] [Metal components and thermal insulation layer] The plate-shaped metal member used was an aluminum plate with a thermal conductivity of 235 W / m·K at room temperature. In this example, the aluminum plate was thinly coated (approximately 0.02 mm thick) with one of the following adhesives: silicone grease (G-777, thermal conductivity of 3.3 W / (m·K) at room temperature), adhesive (SX1008, thermal conductivity of 1.7 W / (m·K) at room temperature, abbreviated as "Adhesive 1" in Table 1 below), or adhesive (RH96L, thermal conductivity of 2.1 W / (m·K) at room temperature, abbreviated as "Adhesive 2" in Table 1 below) manufactured by Shin-Etsu Chemical Co., Ltd., and then attached to the cell. For rectangular cells, the aluminum plate was attached to almost the entire side of the cell (excluding a few millimeters of the top edge and a few millimeters of each edge; an area ratio of 95% or more). The attached aluminum plate was then connected (applied approximately 0.1 mm) to a water cooling device installed under the battery module via silicone grease (G-777, thermal conductivity at room temperature: 3.3 W / (m·K)) manufactured by Shin-Etsu Chemical Co., Ltd. The ratio of the thermal resistance of the metal component to the thermal resistance of the grease or adhesive (Rs / Rm) is shown in Table 1 below.

[0096] The insulating material used in the insulation layer was glass wool with a thermal conductivity of 0.05 W / m K at room temperature, or fire-resistant cloth manufactured by Nichias Corporation (TOMBO No. 8300, with a thermal conductivity of 0.10 W / m K at room temperature) adjusted to the desired thickness.

[0097] [About the multi-layer structure] The structure between adjacent cells in the example of the present invention was a multi-layer structure of cell / aluminum plate / glass wool / aluminum plate / cell. Comparative examples (prior art) were a multi-layer structure of cell / glass wool / aluminum plate / glass wool / cell, a structure using only aluminum plate, and a structure using only glass wool. The thickness of each member in each structure is shown in Table 1 below.

[0098] The cooling capacity was also measured for a cooling structure roughly as shown in the cross section of Figure 4, and a cooling structure in which the short side surfaces of the cells are in contact with an aluminum plate as shown in Figure 2. These conditions are also shown in Table 1 below. Note that the example with a 0.5 mm gap between cells was not evaluated below because it was clear that it would be poorly rated without even needing to measure the cooling capacity.

[0099] ◇ Cooling performance evaluation (temperature evaluation when abnormally heated cells occur) Thermocouples were attached at random positions on the cell surface using Kapton tape, and the temperature rise associated with charge and discharge was measured. The combinations of the present invention and comparative examples (prior art) shown in Table 1 were evaluated. Using a module with eight connected cells, the two central cells generated heat at a constant rate of 500 kW / h in a 25°C environment (simulating abnormal heat generation). The temperature of the hottest adjacent cell (measured at three equally spaced points along the cell height: 20 mm, 50 mm, and 80 mm from the top) 2000 seconds after heating began was recorded. The sample with a lower temperature than any of the comparative examples after 2000 seconds was designated the present invention. Furthermore, a sample with a multilayer structure of cell / aluminum plate / glass wool / aluminum plate / cell, but with a thinner aluminum plate, was designated the reference example.

[0100] The inventors' investigations revealed that the characteristics begin to change approximately 1,000 to 2,000 seconds after the start of measurement, and that behavior within this range is important for performance evaluation. Furthermore, it was also found that the characteristics saturate and the performance of the battery cell is determined after 2,000 seconds from the start of measurement. Furthermore, assuming that the battery cell is installed in an electric vehicle, early judgment is required because it is necessary to ensure that occupants have time to evacuate if the battery cell is approaching a dangerous state. Taking this into consideration, it was decided to make the judgment 2,000 seconds after the start of measurement, as described above.

[0101] Furthermore, the cooling performance of the invention examples, reference examples, and comparative examples at each cell spacing was compared, with Comparative Example 1 as the standard when the cell spacing was 5 mm, Comparative Example 4 as the standard when the cell spacing was 3 mm, and Comparative Example 6 as the standard when the cell spacing was 2 mm. The comparison was made based on the maximum cell temperature after 2000 seconds, and expressed as a battery temperature reduction rate using the following formula:

[0102] Battery cell temperature reduction rate (%) (in the present invention) = [(Maximum cell temperature of the comparative example serving as a reference - Maximum cell temperature of the example of the present invention) / Maximum cell temperature of the comparative example serving as a reference] × 100 Battery cell temperature reduction rate (%) (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] x 100 Battery cell temperature reduction rate (%) (comparison example) = [(Maximum cell temperature of the reference comparative example - Maximum cell temperature of the comparative example) / Maximum cell temperature of the reference comparative example] x 100

[0103] Furthermore, the temperature reduction rate was evaluated as follows: a temperature reduction rate of 10% or more was given a rating of "A," a temperature reduction rate of 5% or more but less than 10% was given a rating of "B," a temperature reduction rate of more than 0% but less than 5% was given a rating of "C," and a temperature reduction rate of 0% or less was given a rating of "D." Note that a structure that showed superior performance compared to the multilayer structure of cell / glass wool / aluminum plate / glass wool / cell (i.e., the above-mentioned structure B) was given a "pass" rating.

[0104] [Table 1]

[0105] [Cooling performance comparison results] Figure 13 shows the results when the cell spacing was 5.0 mm. Compared to Comparative Example 1 [1.0 mm insulation / 3.0 mm Al / 1.0 mm insulation] and Comparative Example 2 [5.0 mm Al only], the temperatures of adjacent cells after 2000 seconds were all lower in the present invention examples: Invention Example 1 [1.5 mm Al / 2.0 mm Al / 1.5 mm Al], Invention Example 2 [2.25 mm Al / 0.5 mm Al / 2.25 mm Al], Invention Example 3 [2.0 mm Al / 1.0 mm Al / 2.0 mm Al], and Invention Example 4 [1.0 mm Al / 3.0 mm Al / 1.0 mm Al]. It can be seen that the invention examples have higher cooling performance than the prior art. Furthermore, in Reference Example 1 [Al 0.25 mm / insulating member 4.5 mm / Al 0.25 mm], which had a thinner aluminum plate, the temperature of the adjacent cells after 2000 seconds was higher than in Comparative Example 1, and the cooling performance was lower than that of the prior art. Furthermore, although not shown in Fig. 13, Invention Examples 12 and 13, in which the cells and metal members were bonded with adhesive instead of grease, and Invention Example 14, in which the insulating member was replaced with fireproof cloth instead of glass wool, also had higher cooling performance than the prior art.

[0106] Figure 14 shows the results when the cell spacing was 3 mm. Compared to Comparative Example 3 (1.0 mm heat insulating member / 1.0 mm aluminum / 1.0 mm heat insulating member), Comparative Example 4 (0.5 mm heat insulating member / 2.0 mm aluminum / 0.5 mm heat insulating member), and Comparative Example 5 (3.0 mm aluminum only), the temperatures of adjacent cells after 2000 seconds were lower in Invention Example 5 (0.5 mm aluminum / 2.0 mm aluminum / 0.5 mm aluminum) and Invention Example 6 (1.0 mm aluminum / 1.0 mm aluminum / 1.0 mm aluminum), indicating that the cooling performance was higher than that of conventional technology.

[0107] Figure 15 shows the results when the cell spacing was 2 mm. Compared to Comparative Example 6 (insulating member 0.5 mm / Al 1.0 mm / insulating member 0.5 mm) and Comparative Example 7 (Al 2.0 mm only), the temperature of adjacent cells in Example 7 (Al 0.5 mm / insulating member 1.0 mm / Al 0.5 mm), which is an example of the present invention, was lower than either of the comparative examples, demonstrating that the cooling performance was higher than that of conventional technology.

[0108] Figure 16 shows the results of Example 8 of the present invention ([Al 1.5 mm / insulating member 2.0 mm / Al 1.5 mm], where the lower parts of the two aluminum plates are connected together over 25% of their height) when the cell spacing is 5 mm and the lower parts of the metal members are connected (U-shaped metal member) (structure of Figure 4), in comparison with Example 1 and Comparative Example 1. In Example 8 of the present invention, the temperature of the adjacent cells after 2000 seconds is slightly higher than in Example 1, but lower than in Comparative Example 1, and it is clear that the cooling performance is higher than that of conventional technology.

[0109] Figure 17 shows a comparison between Example 9 of the present invention ([Al 1.5 mm / insulating material 2.0 mm / Al 1.5 mm] + Al provided on the short side surfaces) in which aluminum plates (3 mm thick) were adhered via grease to the short side surfaces of all eight battery cells, covering the entire side surface of the battery module with aluminum plates (structure of Figure 2), and Example 1 of the present invention. It can be seen that the temperature of the adjacent cells after 2000 seconds is lower in Example 9 of the present invention than in Example 1 of the present invention, demonstrating even better cooling performance.

[0110] As is clear from Table 1 above and FIGS. 13 to 17, all of the examples according to the present invention were rated with a rating of "A" or "B," indicating that they have better cooling capacity than the prior art.

[0111] [Influence of the type of plate-shaped metal material (thermal conductivity)] Figure 18 shows the results when the metal material was 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] Inventive Example 10 was produced under the same conditions as Example 1, except that the metal member was made of duralumin, and Comparative Example 8 was produced under the same conditions as Comparative Example 1, except that the metal member was made of duralumin. Comparing the two, it can be seen that in Inventive Example 10, the temperature of the adjacent cells after 2000 seconds was lower than in Comparative Example 8, indicating that the cooling performance is higher than that of the prior art. However, compared to Inventive Example 1, the temperature in Inventive Example 10 was higher overall, indicating that a thermal conductivity of 150 w / m K or higher for the metal member is preferable.

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

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

[0115] Inventive Example 11 was prepared under the same conditions as Example 1, except that a glass plate was used as the insulating member, and Comparative Example 10 was prepared under the same conditions as Comparative Example 1, except that a glass plate was used as the insulating member. Comparing the two, it can be seen that in Inventive Example 11, the temperature of the adjacent cells after 2000 seconds was lower than in Comparative Example 10, indicating that Inventive Example 11 has better cooling performance than the prior art. However, compared to Inventive Example 1, the temperature in Inventive Example 10 was higher overall, indicating that the thermal conductivity of the insulating member should preferably be 0.1 W / m K or less.

[0116] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0117] 1. Battery cell cooling structure 2. Multi-layer structure 10 battery cells 20 Plate-shaped metal parts 30 Insulation layer (insulation material 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, 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, the plate-shaped metal member being in thermal contact with each of the opposing side surfaces of the adjacent battery cells; a heat insulating layer disposed between plate-shaped metal members that are in thermal contact with the opposing side surfaces of the adjacent battery cells, the 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; Therefore, 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 is in thermal contact with each of the plurality of prismatic battery cells or that is present in the vicinity of each of the plurality of prismatic 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 multilayer structure have the same thermal conductivity and thickness, and the ratio of the thickness of the plate-shaped metal member / thermal insulating layer / plate-shaped metal member is 1.0:0.2 to 4.0:1.0; the plate-shaped metal members are connected at their lower portions to each other, the lower portions being in thermal contact with the side surfaces of the adjacent heat insulating members, and have a generally concave shape; The substantially concave plate-like metal member is inserted between the adjacent heat insulating members, a cooling structure between battery cells, in which 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, 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, the plate-shaped metal member being in thermal contact with each of the opposing side surfaces of the adjacent battery cells; a heat insulating layer disposed between plate-shaped metal members that are in thermal contact with the opposing side surfaces of the adjacent battery cells, the 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; Therefore, 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 is in thermal contact with each of the plurality of prismatic battery cells or that is present in the vicinity of each of the plurality of prismatic 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 multilayer structure have the same thermal conductivity and thickness, and the ratio of the thickness of the plate-shaped metal member / thermal 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, and is inserted between the adjacent battery cells; A cooling structure between battery cells, wherein the heat insulating layer is disposed in the concave depression.

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 heat insulating layer has a thickness of 1.0 mm or more.

4. In each of the plurality of prismatic 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 surface 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 thereof 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 the side surfaces of the battery cells are 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; 7. The cooling structure between battery cells according to claim 1, 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 prismatic battery cell is configured by stacking laminated 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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