Separation member, battery pack, and heat transfer control method for battery pack

Abstract

The present invention provides a separation member, a battery pack, and a heat transfer control method for a battery pack that can control heat transfer between single cells in a battery pack including a plurality of single cells. A separation member is used to separate single cells constituting a battery pack and has two surfaces in the thickness direction. When the average temperature of one of the two surfaces exceeds 180 °C, the thermal resistance per unit area (θ1) in the thickness direction satisfies the following formula 1, and when the average temperatures of both of the two surfaces do not exceed 80 °C, the thermal resistance per unit area (θ2) in the thickness direction satisfies the following formula 2. θ1 ≥ 5.0 × 10 ‑3 [m 2 ·K / W] (Formula 1) θ2 ≤ 4.0 × 10 ‑3 [m 2 ·K / W] (Formula 2).

Description

[0001] This application is a divisional application of an application with an application date of December 27, 2017, an application number of 201780080853.2, and an invention title of "Partition member, battery pack, and heat transfer control method for battery pack". Technical Field

[0002] The present invention relates to a partition member, a battery pack, and a heat transfer control method for a battery pack. Background Art

[0003] In recent years, for secondary batteries that have seen a rapid increase in applications as power sources for vehicles and the like, research on increasing the energy density of secondary batteries has been underway for the purpose of improving the degree of freedom when mounted in a limited space such as a vehicle and extending the cruising range that can be traveled on a single charge.

[0004] On the other hand, the safety of secondary batteries tends to be in conflict with the energy density, and there is a tendency that the higher the energy density of the secondary battery, the lower its safety. For example, in a secondary battery mounted on an electric vehicle with a cruising range of several hundred kilometers, when the secondary battery is damaged due to overcharging, internal short circuit, etc., the surface temperature of the battery can exceed several hundred degrees Celsius and sometimes approach 1000°C.

[0005] Secondary batteries used as power sources for vehicles and the like are usually used in the form of a battery pack composed of a plurality of single batteries (hereinafter also referred to as "battery cells"). Therefore, when one of the batteries is damaged and reaches the above temperature range, there is a concern that its heat generation may cause damage to adjacent batteries and the damage may spread chain-reaction to the entire battery pack. To prevent such chain damage between batteries, various techniques have been proposed, such as a technique for cooling a damaged battery and a technique for suppressing heat transfer from a damaged battery to an undamaged battery.

[0006] For example, Patent Document 1 studies a method for cooling an abnormally heated battery. Specifically, a battery assembly is disclosed in which a cooling unit containing a cooling material is provided near a single battery, a sealing portion is formed in the cooling unit with a sealed sheet-like portion, and an opening portion is provided in a part of the sealing portion, and the opening portion will open when the single battery abnormally heats up.

[0007] In addition, Patent Document 2 has studied the structure of a coolant storage portion and a coolant discharge mechanism for cooling a battery that abnormally generates heat. Specifically, a battery assembly is disclosed, which includes: a battery cell composed of a plurality of single cells; a housing having a storage portion with at least one open end, in which the battery cell is stored; a lid having an opening portion, which covers the open end in the housing; and a heat absorption member having a heat absorption agent and an outer packaging film that encloses the heat absorption agent, and is disposed in contact with the side surface of the battery cell. Among them, the outer packaging film has a laminated structure of a resin layer and a metal film, the metal film has a melting point higher than the softening temperature of the resin layer, and is melted by the heat generated by the single cell.

[0008] In addition, Patent Document 3 discloses a method in which a partition member disposed between batteries is composed of a fusible base material and a thermosetting resin, and heat conduction caused by the partition member is suppressed by melting the base material, thereby suppressing heat transfer from an abnormally heated battery to an adjacent battery.

[0009] Furthermore, Patent Document 4 discloses a method in which a partition member disposed between power storage elements is composed of the following components, thereby suppressing heat transfer from an abnormally heated battery to an adjacent battery. The components include: a base material formed of a resin; and a foaming agent that is held on the base material and thermally decomposes as the power storage element generates heat and the temperature rises.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent No. 5352681 Gazette

[0013] Patent Document 2: Japanese Patent No. 4900534 Gazette

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2010-97693 Gazette

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 2010-165597 Gazette Summary of the Invention

[0016] Problems to be Solved by the Invention

[0017] The inventors of the present invention have studied the above prior art in detail, and as a result, it has been found that in terms of quantitatively considering the calorific value of the single cells constituting the battery pack and the heat transfer influence brought by components other than the batteries constituting the battery pack, the research on the thermal resistance value required to prevent chain damage between batteries is not sufficient.

[0018] Although the method of cooling a battery with abnormal heat generation has been studied in detail in the above-mentioned Patent Document 1, the calorific value of the battery cell with abnormal heat generation and the cooling capacity of the coolant have not been quantitatively studied. In addition, the calorific value of the battery with abnormal heat generation and the cooling capacity of the coolant have not been quantitatively studied in the above-mentioned Patent Document 2.

[0019] Furthermore, in the above-mentioned Patent Document 3, the change in the thermal resistance value of the partition member due to the melting of the base material has not been quantitatively studied. In addition, in the above-mentioned Patent Document 4, the change in the thermal resistance of the partition member caused by the foaming agent that thermally decomposes with the temperature rise accompanying heat generation has not been quantitatively studied. In addition, even when the thermal resistance of these partition members changes, if the temperature region of the change, the thermal resistance values before and after the change, etc. are not reasonably designed, although a part of the heat transfer from the battery with abnormal heat generation to the adjacent battery is suppressed, it is considered that it is difficult to prevent the adjacent battery from reaching the abnormal heat generation state as a result. In addition, the following aspect has not been considered: the single cells constituting the battery pack are connected by bus bars, and usually bus bars use metals that are good conductors of heat. Therefore, even when heat transfer between the batteries caused by the melting of the base material of the partition member provided between the batteries is suppressed, heat transfer between the batteries caused by the bus bars cannot be avoided.

[0020] An object of the present invention is to provide a partition member, a battery pack, and a control method for a battery pack that can control heat transfer between single cells in a battery pack including a plurality of single cells.

[0021] Solutions for Solving the Problems

[0022] The inventors of the present invention focused on the thermal resistance value required to prevent chain damage between batteries, which has not been fully studied in these prior arts, and studied its conditions in detail. As a result, it was found that in a partition member that separates single cells constituting a battery pack and has two surfaces in the thickness direction, it is important to appropriately control the thermal resistance value according to whether the average temperature of each of the two surfaces is the same as the temperature of the battery cell in the normal state or the same as the temperature of the battery cell in the abnormal heat generation state, and thus the present invention was completed. The present invention is as follows.

[0023] [1] A partition member for separating single cells constituting a battery pack and having two surfaces in the thickness direction. When the average temperature of one of the two surfaces exceeds 180 °C, the thermal resistance per unit area (θ 1 ) satisfies the following formula 1, and when the average temperatures of both of the two surfaces do not exceed 80 °C, the thermal resistance per unit area (θ 2 ) satisfies the following formula 2.

[0024] θ1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1)

[0025] θ 2 ≤4.0×10 -3 [m 2 ·K / W] (Equation 2)

[0026] [2] The partitioning member according to [1], wherein, when the average temperature of one of the two surfaces is 180 °C or higher, the thermal conductivity in the thickness direction is 2.0×10 -2 W / m·K or higher and 2.0 W / m·K or lower, and,

[0027] when the average temperatures of both of the two surfaces are 80 °C or lower, the thermal conductivity in the thickness direction is 5.0×10 -2 W / m·K or higher and 50 W / m·K or lower.

[0028] [3] The partitioning member according to [1] or [2], wherein, when the thickness of the single cell is L [mm], the thickness in the thickness direction is L / 50 mm or higher and L / 10 mm or lower.

[0029] [4] The partitioning member according to any one of [1] to [3], wherein, when the average temperature of one of the two surfaces exceeds 180 °C and is 300 °C or lower, the thermal resistance per unit area in the thickness direction (θ 1 ) satisfies the following Equation 1, and,

[0030] when the average temperatures of both of the two surfaces do not exceed 80 °C, the thermal resistance per unit area in the thickness direction (θ 2 ) satisfies the following Equation 2.

[0031] [5] A battery pack, comprising the partitioning member according to any one of [1] to [4].

[0032] [6] A battery pack, comprising:

[0033] a plurality of single cells, including a first single cell, a second single cell, and a third single cell;

[0034] a first partitioning member for partitioning between the first single cell and the second single cell; and a second partitioning member for partitioning between the second single cell and the third single cell,

[0035] When heat from the first single cell that has reached an abnormally high temperature state causes the second single cell to deviate from its normal state, the heat transferred from the first single cell to the second single cell via the first partition member is suppressed by the first partition member, and the heat transferred from the first single cell to the third single cell that maintains the normal state is not suppressed by the second partition member.

[0036] [7] The battery pack according to [6], wherein the thermal resistance per unit area of the first partition member is increased, so that the heat transferred from the first single cell to the second single cell is suppressed.

[0037] [8] The battery pack according to [6] or [7], wherein even when the second single cell deviates from the normal state, the thermal resistance per unit area of the second partition member does not increase, and the heat transferred from the first single cell to the third single cell is not suppressed.

[0038] [9] A heat transfer control method for a battery pack, which is a heat transfer control method for a battery pack that separates single cells by a partition member, wherein

[0039] the partition member has two surfaces in the thickness direction, one of which is the first surface opposite to the first single cell, and the other is the second surface opposite to the second single cell.

[0040] When the average temperature of the first surface does not exceed 80 °C, the thermal resistance per unit area (θ 2 ) in the thickness direction satisfies the following formula 2, and the heat from the first single cell is transferred to the second single cell via the partition member.

[0041] When the first single cell reaches an abnormally high temperature state, and due to the heat transferred from the first single cell via the partition member, the second single cell deviates from the normal state, and the heat from the first single cell causes the average temperature of the first surface to exceed 180 °C, the thermal resistance per unit area (θ 1 ) in the thickness direction satisfies the following formula 1, thereby suppressing the heat transferred from the first single cell via the partition member.

[0042] θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Formula 1)

[0043] θ 2 ≤4.0×10 -3 [m 2 ·K / W] (Formula 2)

[0044] Effects of the Invention

[0045] According to the present invention, in a battery pack including a plurality of single cells, heat transfer between the single cells can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 FIG. is an illustration of a partition member.

[0047] Figure 2 FIG. is an illustration of a partition member having a comb-like structure.

[0048] Figure 3 FIG. is an illustration of a battery pack.

[0049] Figure 4 FIG. is an illustration of a heat transfer path of a battery pack.

[0050] Figure 5 FIG. is an example of a bag-like structure as an example of an embodiment of the present invention.

[0051] Figure 6 FIG. is a modified example of a bag-like structure as an example of an embodiment of the present invention.

[0052] Figure 7 FIG. is a graph showing the internal temperature change of the battery cell in Comparative Example 1.

[0053] Figure 8 FIG. is a graph showing the change in the surface average temperature of the partition member in Comparative Example 1.

[0054] Figure 9 FIG. is a graph showing the change in the thermal resistance of the partition member in Comparative Example 1.

[0055] Figure 10 FIG. is a graph showing the internal temperature change of the battery cell in Example 1.

[0056] Figure 11 FIG. is a graph showing the change in the surface average temperature of the partition member in Example 1.

[0057] Figure 12 FIG. is a graph showing the change in the thermal resistance of the partition member in Example 1.

[0058] Figure 13 FIG. is a graph showing the internal temperature change of the battery cell in Comparative Example 2.

[0059] Figure 14 FIG. is a graph showing the change in the surface average temperature of the partition member in Comparative Example 2.

[0060] Figure 15 FIG. is a graph showing the change in the thermal resistance of the partition member in Comparative Example 2.

[0061] Figure 16 It is a graph showing the temperature change inside the battery cell in Comparative Example 3.

[0062] Figure 17 It is a graph showing the change in the average surface temperature of the separator in Comparative Example 3.

[0063] Figure 18 It is a graph showing the change in the thermal resistance of the separator in Comparative Example 3.

[0064] Figure 19 It is a graph showing the temperature change inside the battery cell in Comparative Example 4.

[0065] Figure 20 It is a graph showing the change in the average surface temperature of the separator in Comparative Example 4.

[0066] Figure 21 It is a graph showing the change in the thermal resistance of the separator in Comparative Example 4. DETAILED DESCRIPTION

[0067] Hereinafter, embodiments of the present invention will be described in detail. The description of the technical features described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents as long as it exceeds its gist.

[0068] <Separator>

[0069] The separator of the present invention is a separator for separating single cells constituting a battery pack. The separator separates the single cells constituting the battery pack and has two surfaces in the thickness direction. When the average temperature of one of the two surfaces exceeds 180°C, the thermal resistance per unit area (θ 1 ) in the thickness direction satisfies the following formula 1, and when the average temperatures of both of the two surfaces do not exceed 80°C, the thermal resistance per unit area (θ 2 ) in the thickness direction satisfies the following formula 2.

[0070] θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Formula 1)

[0071] θ 2 ≤4.0×10 -3 [m 2 ·K / W] (Formula 2)

[0072] θ 1 is preferably 1.0×10 -2 or more, and more preferably 2.0×10-2 Above. On the other hand, θ 2 is preferably 2.0×10 -3 or less, more preferably 1.0×10 -3 or less. Additionally, preferably, when the average temperature of one of the two surfaces in the thickness direction of the aforementioned partition member that separates the individual cells constituting the battery pack exceeds 160°C, the thermal resistance per unit area (θ 1 ) satisfies the above formula 1, and when the average temperatures of both of the aforementioned two surfaces do not exceed 100°C, the thermal resistance per unit area (θ 2 ) satisfies the above formula 2.

[0073] The partition member separates the individual cells constituting the battery pack. Figure 1 It is a diagram illustrating the partition member. Figure 1 In Figure 1 , a partition member 1 (referred to as partition member 1A in the

[0074] description) in the form of a rectangular parallelepiped (plate) having a height, a length, and a thickness (width) is illustrated. The partition member 1A has two surfaces, surface 1a and surface 1b, facing in opposite directions in the thickness direction.

[0075] In Figure 1 the example shown, surface 1a and 1b can be used as "the two surfaces in the thickness direction that separate the individual cells constituting the battery pack". However, depending on the partitioning method using the partition member 1A, one of "the two surfaces in the thickness direction that separate the individual cells constituting the battery pack" may not face the unit cell.

[0076] In the present invention, the thermal resistance per unit area (θ) of the partition member refers to the heat transfer resistance per unit cross-sectional area in the thickness direction of the partition member. The thermal resistance per unit area (θ) of the partition member can be expressed using the thermal conductivity (k [W / m·K]) in the thickness direction of the material used as the partition member and the thickness (d [m]) of the partition member.

[0077] For Figure 1The thermal resistance (θ) per unit area of the partition member 1A shown will be described. To simplify the description, it is assumed that the partition member 1A is formed of a single material and has a constant density. Let the thermal conductivity in the thickness direction of the partition member 1A be k [W / m·K], and the thickness of the partition member 1A be d [m]. Further, let the average surface temperature of the surface 1b of the partition member 1A be T 1 [°C], and let the average surface temperature of the surface 1a be T 2 [°C].

[0078] T 2 is lower than T 1 , a surface temperature difference T 1 - T 2 is generated between the surface 1b side and the surface 1a side of the partition member 1A. In this case, the heat flux (thermal flux) q per unit cross-sectional area of the partition member 1A can be expressed by the following equation (1).

[0079] q = k(T 1 - T 2 ) / d [W / m 2 (1)

[0080] Here, the heat flux (q) can be expressed by the following equation (2) using the thermal resistance (θ) per unit area.

[0081] q = (1 / θ)(T 1 - T 2 ) (2)

[0082] From equations (1) and (2), the thermal resistance (θ) per unit area can be expressed using the thermal conductivity (k) in the thickness direction of the partition member 1A and the thickness (d) of the partition member. That is, the thermal resistance (θ) per unit area can be expressed by the following equation (3).

[0083] θ = d / k [m 2 ·K / W] (3)

[0084] The shape (structure) of the partition member 1 is not limited to a cuboid. As long as it has a shape in the thickness direction, even when the partition member has a comb structure, a hollow structure, a lattice structure, etc., the thermal resistance of the partition member 1 can be expressed by the above formula (3). In addition, the partition member 1 is not limited to being formed of a single material, and may also be formed of a combination of multiple materials. Even when formed of a combination of multiple materials, the thermal resistance per unit area of the partition member 1 can be expressed by the above formula (3). The combination of materials can be selected from, for example, polyethylene, chlorinated polyethylene, ethylene vinyl chloride copolymer, ethylene vinyl acetate copolymer, polyvinyl acetate, polypropylene, polybutene, polybutadiene, polymethylpentene, polystyrene, poly-α-methylstyrene, poly-p-vinylphenol, ABS resin, SAN resin, AES resin, AAS resin, methacrylic resin, norbornene resin, polyvinyl chloride, acrylic-modified polyvinyl chloride, polyvinylidene chloride, polyallylamine, polyethylene ether, polyvinyl alcohol, ethylene vinyl alcohol copolymer, petroleum resin, thermoplastic elastomer, thermoplastic polyurethane resin, polyacrylonitrile, polyvinyl butyral, phenolic resin, epoxy resin, urea resin, melamine resin, furan resin, unsaturated polyester resin, diallyl phthalate, guanamine, ketone resin, cellulose acetate, cellophane, cellulose nitrate, acetyl cellulose, nylon, polyamide, polyacetal, polyoxymethylene, polycarbonate, polycarbonate / ABS alloy, polycarbonate / polyester alloy, polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate, polyamideimide, polyetherimide, polyetheretherketone, ultra-high molecular weight polyethylene, isotactic polystyrene, liquid crystal polymer, polyimide, fluororesin, Teflon (registered trademark), tetrafluoroethylene perfluoroalkoxy vinyl ether, tetrafluoroethylene-hexafluoroethylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, polyaminobismaleimide, polytriazine, crosslinked polyamideimide, etc. and combined with two or more materials.

[0085] Figure 2 An example of the partition member 1 having a comb structure (referred to as the partition member 1B in the Figure 2 description). As Figure 2 shown, the entire partition member 1B is formed in a plate shape, and its cross section is formed in a comb shape. The partition member 1B also has two surfaces facing in opposite directions in the thickness direction, namely, surface 1c and surface 1d. Surface 1c is a striped uneven surface, and surface 1d is a flat surface. Thus, the cross section obtained by cutting the partition member 1B with a surface in the thickness direction is in a comb shape. Surface 1c and surface 1d can be treated in the same manner as surface 1a and surface 1b.

[0086] Figure 2The method for obtaining the thermal resistance (θ) per unit area of the partition member 1B shown is as follows. The average temperature of each surface of surface 1c and surface 1d can be used as T in the above formulas (1) and (2). 1 and T 2 . Additionally, the average value of the heat flux per unit cross-sectional area of the partition member 1B can be used as the heat flux (q) in the above formulas (1) and (2).

[0087] Furthermore, as the thermal conductivity (k), the composite thermal conductivity calculated considering the structure and material type of the partition member 1B is used as the thermal conductivity (k) in the above formulas (1) and (3). Thus, the thermal resistance (θ) per unit area can be expressed by the above formula (3). In this way, the thermal resistance (θ) per unit area can use the effective thermal resistance per unit area calculated considering the structure and material type of the partition member 1B.

[0088] It should be noted that the composite thermal conductivity can be calculated, for example, by the following method. First, find the composite thermal resistance (R) of a composite member of n materials with thermal conductivity: k n [W / m·K], thickness: d n [m], and thermal resistance: R n (n = 1, 2,... n). When n materials are arranged in series, the thermal resistance (R) can be expressed by the following formula (4).

[0089] R = R 1 +R 2 +R 3 +……+R n (4)

[0090] In addition, when n materials are arranged in parallel, the thermal resistance (R) can be expressed by the following formula (5).

[0091] 1 / R = 1 / R 1 +1 / R 2 +1 / R 3 +……+1 / R n (5)

[0092] Next, calculate the composite thermal conductivity of the composite member when n materials are arranged in series. At this time, the cross-sectional areas (A n ) in the heat transfer direction of the n materials are set to be all equal. That is, when setting A 1 = A 2 = A 3 = …… = A n = A[m 2 , the thermal resistance (R n ) of each material is expressed by the following formula (6) using the thermal resistance (θ n ) per unit cross-sectional area.

[0093] R n = θ n / A (6)

[0094] Using equations (6) and (3) to transform equation (4), the following equation (7) can be obtained.

[0095] R = (θ 1 + θ 2 + θ 3 + …… + θ n ) / A

[0096] = (d 1 / k 1 + d 2 / k 2 + d 3 / k 3 + …… + d n / k n ) / A (7)

[0097] When the composite thermal conductivity of the composite component is set to κ, the total thickness of the composite component is Σd n , so the composite thermal conductivity (κ) can also be expressed as the following equation (8).

[0098] R = (Σd n / κ) / A (8)

[0099] Through equations (7) and (8), the composite thermal conductivity (κ) can be expressed as follows.

[0100] κ = Σd n / Σ(d n / k n )

[0101] = (d 1 + d 2 + d 3 + …… + d n ) / (d 1 / k 1 + d 2 / k 2 + d 3 / k 3 + …… + d n / k n )

[0102] In addition, calculate the composite thermal conductivity of the composite component when n materials are arranged in parallel. At this time, the thicknesses of the n materials in the heat transfer direction are set to be all equal. That is, set d 1 = d 2 = d 3 = …… = d n = d[m]. The cross-sectional areas of the n materials in the heat transfer direction are respectively set to An [m 2 , the thermal resistance (R n ) of each material can be expressed using the thermal resistance per unit cross-sectional area (θ n ) as follows.

[0103] R n = θ n / A n (9)

[0104] By transforming Equation (5) using Equations (9) and (3), the following Equation (10) can be obtained.

[0105] 1 / R = A 1 / θ 1 + A 2 / θ 2 + A 3 / θ 3 + …… + A n / θ n

[0106] = (A 1 k 1 + A 2 k 2 + A 3 k 3 + …… + A n k n ) / d (10)

[0107] When the combined thermal conductivity of the composite member is set to κ, the total cross-sectional area of the composite member is ΣA n , so the combined thermal conductivity (κ) can also be expressed by the following Equation (11).

[0108] R = (d / κ) / ΣA n (11)

[0109] The combined thermal conductivity (κ) can be expressed as follows using Equations (10) and (11).

[0110] κ = Σ(A n k n ) / ΣA n

[0111] = (A 1 k 1 + A 2 k 2 + A 3 k 3 + …… + A n k n ) / (A 1 + A 2 + A 3 + …… + An )

[0112] Even for a partition member having a comb-like structure such as the partition member 1B, or even for a partition member having a hollow structure, a lattice structure, etc., the composite thermal conductivity can be calculated by giving the thermal conductivity of air as the material of the hollow portion, the thickness, and the cross-sectional area of the hollow portion.

[0113] Preferably, it is set as follows: when the average temperature of one of the two surfaces in the thickness direction that partitions between the single cells constituting the battery pack of the partition member 1 (for example, any one of the surfaces 1a to 1d) exceeds 180°C, the thermal conductivity in its thickness direction is 2.0×10 -2 W / m·K or more and 2.0 W / m·K or less, and when the average temperature of the aforementioned surface (for example, any one of the surfaces 1a to 1d) does not exceed 80°C, the thermal conductivity in its thickness direction is 5.0×10 -2 W / m·K or more and 50 W / m·K or less.

[0114] In addition, when the thickness of the single cell constituting the battery pack is L [mm], the thickness is preferably L / 50 mm or more and L / 10 mm or less. Here, the assumed range of the thickness (L) of the single cell constituting the battery pack is usually 10 mm ≤ L ≤ 100 mm, and preferably 15 mm ≤ L ≤ 80 mm.

[0115] It should be noted that it is possible to confirm whether a certain partition member belongs to the partition member of the present invention in the following manner.

[0116] [1. Determine the thermal resistance (θ 1 )]

[0117] 1-1) Determine the center of gravity of the partition member to be confirmed. Then, draw a perpendicular line from this center of gravity to one surface of the partition member, and take the point of intersection as the first point. Heat the entire surface including this first point to 160°C. It should be noted that as long as this heating method can control the temperature and heat so that the entire surface including a certain first point becomes 160 to 300°C, the method is not limited.

[0118] 1-2) Based on the first point, take the following point on the other surface as the second point: the second point is located at a position symmetric to the first point with respect to the dividing surface that bisects the aforementioned partition member in the aforementioned thickness direction.

[0119] 1-3) Based on the first point and the second point, raise the temperature of the surface including the first point from 160°C to 300°C. Here, when the temperature of the entire system reaches a steady state at each temperature of 160°C, 180°C, 210°C, 240°C, 270°C, and 300°C, the thermal resistance (θ 1)。

[0120] [2. Determine the thermal resistance (θ 2 )]

[0121] 2-1) For the surface including the aforementioned point 1, heat the entire surface to 100 °C. It should be noted that as long as the heating method can control the temperature and heat so that the entire surface including the aforementioned point 1 becomes 20 - 1000 °C, the method is not limited.

[0122] 2-2) Determine point 2 in the same manner as 1-2).

[0123] 2-3) Based on point 1 and point 2, cool the surface including point 1 from 100 °C to 20 °C. Here, when the temperature of the entire system reaches a steady state at each temperature of 80 °C, 60 °C, 40 °C, and 20 °C, obtain the thermal resistance (θ 2 ) by the aforementioned method.

[0124] [3. Confirm the separating member]

[0125] 3-1) Using the thermal resistance values obtained in 1-3) and 2-3) above, confirm whether the above formula 1 is satisfied at each temperature higher than 180 °C, and whether the above formula 2 is satisfied at each temperature lower than 80 °C. Confirm whether a certain separating member belongs to the separating member of the present invention by confirming whether formula 1 and formula 2 are satisfied at the above respective temperatures. It should be noted that as described above, the separating member of the present invention preferably satisfies the above formula 1 at each temperature higher than 160 °C, and preferably satisfies the above formula 2 at each temperature lower than 100 °C.

[0126] <Battery pack>

[0127] The separating member 1 is one of the constituent elements constituting the battery pack. The battery pack applicable to the present invention is applicable to, for example, electric vehicles (EV, Electric Vehicle), hybrid electric vehicles (HEV, Hybrid Electric Vehicle), plug-in hybrid electric vehicles (PHEV, Plug-in Hybrid Electric Vehicle), electric heavy machinery, electric motorcycles, electric assist bicycles, ships, airplanes, trains, uninterruptible power supplies (UPS, Uninterruptible Power Supply), home power storage systems, battery packs mounted in battery systems for stabilizing power systems using renewable energy such as wind energy / solar energy / tidal energy / geothermal energy, etc. In addition, the battery pack can also be used as a power source for supplying power to devices other than the above EVs, etc.

[0128] Figure 3 is a diagram illustrating the battery pack. In Figure 3Among them, a simple battery pack connecting three battery cells is illustrated as the battery pack 10. The battery pack can be formed by connecting a corresponding number of single cells (also referred to as battery cells) in series, in parallel, or in a combined series and parallel manner according to the desired output power. The number of battery cells is appropriately set according to the required power. Figure 3 In the example of, each single cell is connected in series, and a separating member is disposed between the single cells.

[0129] In Figure 3 In the illustration of the battery pack 10 shown, the battery pack 10 includes: battery cell 21 (Cell1: the first single cell), battery cell 22 (Cell2: the second single cell), battery cell 23 (Cell3: the third single cell); and separating members 11 (Spacer1: the first separating member) and 12 (Spacer2: the second separating member) disposed between the battery cells for separating between the battery cells. The battery pack 10 further includes a bus bar 3 and a housing 4. In the following description, when not distinguishing between the separating member 11 and the separating member 12, they are referred to as the separating member 1. In addition, when not distinguishing between the battery cell 21, the battery cell 22, and the battery cell 23, the expression of battery cell 2 is used. It should be noted that in the present invention, the first single cell, the second single cell, and the third single cell, as well as the first separating member and the second separating member, refer to the relative positional relationship as Figure 3 shown. When a certain single cell reaches an abnormal heating state, that single cell is regarded as the first single cell, and thereby the second single cell and the third single cell, as well as the first separating member and the second separating member, are determined.

[0130] (Battery cell / Single cell)

[0131] The battery cell 2 is, for example, a lithium-ion secondary battery having a positive electrode, a negative electrode, and an electrolyte that can absorb and release lithium ions. In addition to the lithium-ion secondary battery, secondary batteries such as lithium-ion all-solid-state batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries can be applied.

[0132] (Separating member)

[0133] The separating member 1 can be applied to the separating member described by Figure 1 and Figure 2 for explanation.

[0134] (Bus bar, Housing)

[0135] The bus bar 3 is a conductor bar for supplying the power output from the battery cell to a load (e.g., a motor), and is formed of a conductor such as aluminum. The housing 4 accommodates the partition member 1 and the battery cell 2. The housing 4 can be formed of, for example, metal, resin (polypropylene, etc.), or a combination of metal and resin. The housing can be constructed as follows: the battery cell 2 and the partition member 1 are fixed by clamping the end plates of the plurality of battery cells 2 with the partition members 1 inserted between the battery cells, and the end plates are connected by a connecting plate.

[0136] <Heat Generation and Heat Transfer in Battery Pack>

[0137] Some or all of the chemical substances used to form the electrodes, electrolyte, etc. constituting the battery cell 2 undergo decomposition reactions inside the battery cell 2 as the heat is generated, thereby raising the temperature of the battery cell 2, and sometimes some or all of the battery cell 2 may reach above 200° C. This state is called an “abnormal heat state”.

[0138] Generally, it is known that the safety of the positive electrode material among the materials constituting the battery cell 2 is largely affected by the stability of the crystal structure after delithiation due to charging. LiCoO, which is generally used as the positive electrode material, 2 、Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 ) 2 、Li(Ni 0.8 Co 0.15 Al 0.05 ) 2 Materials such as positive electrodes will undergo crystal destruction accompanied by oxygen release at high temperatures when in a charged state. Oxygen released from the positive electrode will cause oxidation of the electrolyte, etc., accompanied by a violent exothermic reaction. Based on structural analysis using radiant light, it is reported that the above-mentioned positive electrode materials will undergo a crystal phase transition at around 200°C. Therefore, the fact that a part of the battery cell 2 or even the entire area reaches 200°C or above means that the crystal destruction of the positive electrode is ongoing, in other words, the battery cell 2 is in a thermal runaway state (Reference 1: High Safety Technology and Materials for Lithium-ion Batteries CMC Publishing, page 44; Reference 2: J. Dahn et al., Electrochemistry Communication, 9, 2534-2540 (2007); Reference 3: Hironori Kobayashi, "Evaluation and Analysis Technology of Positive Electrode Materials for Lithium-ion Secondary Batteries Using Radiant Light" Spring-8 Utilization Promotion Council Glass and Ceramics Research Group (2nd) (2011)).

[0139] In addition, regarding the safety of the negative electrode material among the materials constituting the battery cell 2, it is known that the charged negative electrode (lithium-embedded carbon negative electrode) basically exhibits the same strong reducibility as metallic lithium, and a protective film is formed on the surface of the negative electrode by reaction with the electrolyte, thereby suppressing further reactions. Therefore, the chemical composition, structure, and thermal stability of this protective film will greatly affect the thermal stability of the charged negative electrode when the temperature rises. Generally, the reaction between the charged negative electrode and the electrolyte can be explained by the formation of the protective film and the subsequent explosive reduction decomposition reaction caused by the destruction of the film. It has been reported that generally, the protective film formation reaction on the negative electrode starts around 130°C, and the subsequent film decomposition reaction occurs around 200°C, eventually reaching the explosive reduction decomposition reaction. Therefore, the situation where a part or the entire area of the battery cell 2 reaches 200°C or higher means that the film on the surface of the negative electrode is being destroyed, that is, the battery cell 2 is in a thermal runaway state (Reference 4: Battery Handbook, 1st Edition, Ohmsha, Ltd., p. 591; Reference 5: The Cutting Edge of High-Safety Technology and Evaluation Technology for Lithium-Ion Batteries, CMC Publishing, p. 90).

[0140] In addition, the state in which the chemical substances used to form the electrodes, electrolytes, etc. constituting the battery cell 2 do not undergo a decomposition reaction with a heat generation rate above a certain level inside the battery cell 2 is called the "normal state". Here, the heat generation state of the battery cell 2 can be evaluated using ARC (Accelerating rate calorimetry), which is a means of quantitatively measuring the thermal behavior when a reactive chemical substance undergoes self-heating decomposition under adiabatic conditions. For example, Dahn et al. defined the situation where the heat generation rate observed in ARC exceeds 0.04°C / minute as a self-heating reaction occurring inside the battery cell, and this definition can be followed (Reference 6: J. Dahn et al., Electrochimica Acta, 49, 4599 - 4604 (2004)). In addition, the battery cell 2 in the normal state is called a "single cell maintaining the normal state", and the battery cell 2 that deviates from the normal state and has not reached the abnormal heat generation state is called a "single cell deviating from the normal state". The heat generated inside the battery cell 2 is transmitted to other battery cells 2 through various transmission paths.

[0141] In addition, the battery cell 2 in the normal state is called a "single cell maintaining the normal state", and the battery cell 2 that deviates from the normal state and has not reached the abnormal heat generation state is called a "single cell deviating from the normal state". The heat generated inside the battery cell 2 is transmitted to other battery cells 2 through various transmission paths.

[0142] Figure 4 is a diagram illustrating the heat transfer paths of the battery pack. In Figure 4In the example, when the battery cell 21 at the left end of the battery pack 10 generates abnormal heat, the heat generated in the battery cell 21 is transferred to other battery cells 22 and 23 not only through (1) the partition member 11 arranged between the battery cells, (2) the bus bar 3, and (3) the housing 4 of the battery pack 10 in contact with the battery cell, but also generates heat outside the housing of the battery pack 10.

[0143] Assume that the upper limit value of the surface average temperature when the battery cell 2 in contact with or close to the partition member 1 deviates from the normal state and does not reach the abnormal heat generation state is 180 °C. Here, the melting temperature of common insulating materials is known to be 160 - 200 °C. Therefore, when the surface average temperature of the battery cell 2 exceeds 180 °C, there is a risk that a part of the common insulating material constituting the battery cell 2 will melt and reach the abnormal heat generation state. When the average temperature of one of the two surfaces in the thickness direction for partitioning between the battery cells 2 constituting the battery pack 10 of the partition member 1 exceeds 180 °C, by controlling so that the thermal resistance (θ 1 ) satisfies the aforementioned (Equation 1), the heat transfer through the partition member 1 is restricted, and its spread to the battery cell 2 in contact with or close to the partition member 1 can be suppressed. The material of the common insulating material is, for example, polyethylene, polypropylene, etc. (Reference 7: Japanese Patent Laid-Open No. 2013-35293; Reference 8: Japanese Patent Laid-Open No. 2015-208894).

[0144] Assume that the upper limit value of the surface average temperature when the battery cell 2 in contact with or close to the partition member 1 does not deviate from the normal state is 80 °C. Here, the boiling point of the common electrolyte components is 90 °C or higher as shown in Table 1 below. The common electrolyte components are, for example, ethylene carbonate (EC), diethyl carbonate, dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). When the surface average temperature of the battery cell 2 is lower than 80 °C, the common electrolyte constituting the battery cell 2 itself does not reach boiling. When the average temperatures of both of the two surfaces in the thickness direction for partitioning between the single cells constituting the battery pack of the partition member 1 are lower than 80 °C, by controlling so that the thermal resistance (θ 2 ) satisfies the aforementioned (Equation 2), the heat transfer through the partition member 1 is promoted. When all the battery cells 2 are in the normal state, the heat transfer resistance of the partition member 1 is lower than that of conventional products, so it is effective for equalizing the temperature between the battery cells 2 in the battery pack 10, and the effect of weakening the deterioration of the battery cell 2 due to temperature unevenness can be expected.

[0145] [Table 1]

[0146] EC DMC EMC DEC Density g / ml 1.385 1.063 1.007 0.970 Molecular Weight g / mol 88.06 90.08 104.11 118.13 Boiling Point ℃ 238 90 108 127

[0147] <Control Method of Thermal Resistance (θ) per Unit Area>

[0148] A method for controlling the thermal resistance (θ) per unit area by the surface temperature of the partition member 1 will be described. First, materials A and B that make up the partition member 1 are exemplified as follows.

[0149] Material A is a material whose thermal resistance (θ) per unit area satisfies the aforementioned (Equation 1). For Material A, the thermal conductivity is set to: k ≤ 0.20 [W / m·K], and the thickness is: d = 1.0 [mm]. That is, the thermal resistance per unit area: θ = d / k ≥ (1.0×10 -3 ) / 0.20 = 5.0×10 -3 [m 2 ·K / W]. Material A is, for example, a resin plate made of polycarbonate or butyl rubber.

[0150] In addition, Material B is a material whose thermal resistance (θ) per unit area satisfies the aforementioned (Equation 2). For Material B, the thermal conductivity is set to: k ≥ 0.25 [W / m·K], and the thickness is: d = 1.0 [mm]. That is, the thermal resistance per unit area: θ = d / k ≤ (1.0×10 -3 ) / 0.25 = 4.0×10 -3 [m 2 ·K / W]. Regarding Material B, for example, in the case of a solid, it is ceramics, a glass plate, polyethylene, etc., and in the case of a liquid, it is water, ethylene glycol, glycerol, etc.

[0151] As the partition member 1 whose thermal resistance (θ) per unit area satisfies the above (Equation 1) at a temperature T [°C] or higher and satisfies the above (Equation 2) at a temperature lower than T [°C], the following two examples are shown. In the first example, the partition member 1 includes a bag-shaped structure, and the bag-shaped structure is a substantially rectangular parallelepiped ( Figure 5 ) that is hollow inside and formed of Material A having a melting point at a temperature higher than T [°C]. The inside of the bag-shaped structure is filled with Material B in a liquid state at T [°C], and an opening for communicating the inside and the outside is provided on the lower surface of the bag-shaped structure, and the opening is closed by a plug formed of, for example, Material C having a melting point near T [°C]. It is designed such that at a temperature near T [°C], when the plug formed of Material C melts, an opening is formed, and the Material B filled inside flows out of the opening to the outside. The outer shape of the bag-shaped structure can have a shape other than a rectangular parallelepiped. In addition, in Figure 5In this case, although the opening is provided on the lower surface of the bag-like structure, the opening may also be provided on the side surface as long as Material B flows out of the opening to the outside of the bag-like structure. It should be noted that the partition member 1 may also be a structure formed by arranging a plurality of bag-like structures filled with the above-mentioned Material B in the length direction or the height direction. In addition, a plug is not necessary. The melting point of Material C may be the same as or lower than that of Material B. In some cases, the plug may be formed of Material B. Material B may not necessarily be in a liquid state at T [°C], and other fluid states besides liquid are also possible.

[0152] In the case of the partition member 1 of the bag-like structure as described above, when the surface temperature is less than T [°C], using Material B in the bag-like structure, the thermal resistance (θ) per unit area satisfies the above (Equation 2). In addition, when the surface temperature of the partition member 1 becomes T [°C] or higher, since Material B flows out to the outside of the bag-like structure, the partition member 1 is composed of Material A, and the thermal resistance (θ) per unit area of the partition member 1 satisfies the above (Equation 1).

[0153] Next, a second example will be described. In the second example, the partition member 1 has the following structure: inside the Figure 5 bag-like structure, a lattice-shaped frame ( Figure 6 ) is provided. Inside the bag-like structure, the portion other than the frame is filled with Material B in a liquid state at T [°C], and the lower surface of the bag-like structure is closed by a plug formed of Material C having a melting point near T [°C]. Design is carried out such that when the plug formed of Material C melts near T [°C], Material B filled in the space portion of the bag-like structure flows out to the outside from the opening formed due to the melting of the plug. The frame plays a role in maintaining the rigidity (strength) of the bag-like structure when Material B flows out. In the case of the partition member 1 of such a bag-like structure, when the surface temperature is lower than T [°C], using Material B filled in the space portion of the bag-like structure, the thermal resistance per unit area satisfies the above (Equation 2). In addition, when the surface temperature of the partition member 1 becomes T [°C] or higher, Material B flows out to the outside of the bag-like structure, so the partition member 1 is composed of Material A, and the thermal resistance (θ) per unit area of the partition member 1 satisfies the above (Equation 1).

[0154] <Thermal transfer control between battery cells>

[0155] Heat transfer between the battery cells 2 that make up the battery pack 10 is controlled as follows: Heat transfer from a battery cell 2 that has reached an abnormal overheating state to a battery cell 2 that has deviated from the normal state is suppressed, and heat transfer from a battery cell 2 that has reached an abnormal overheating state to a battery cell 2 that remains in the normal state without passing through the electrode body of a battery cell 2 that has deviated from the normal state, and heat transfer from a battery cell 2 that has deviated from the normal state to a battery cell 2 that remains in the normal state are not suppressed. Note that the electrode body of the battery cell 2 is a structure including an electrode, a separator, and an electrolytic solution, that is, the main body of the battery.

[0156] For example, in Figure 4 , it is assumed that the battery cell 21 has reached an abnormal overheating state, the battery cell 22 has deviated from the normal state, and the battery cell 23 remains in the normal state. In this case, control is performed as follows: Heat transfer from the battery cell 21 to the battery cell 22 is suppressed, and heat transfer from the battery cell 21 to the battery cell 23 without passing through the electrode body of the battery cell 22 and heat transfer from the battery cell 22 to the battery cell 23 are not suppressed.

[0157] Heat transfer between the battery cells 2 can be controlled by the switching function of the partition member 1. That is, since the heat transfer resistance of the partition member 11 provided between the battery cell 22 that has deviated from the normal state and the battery cell 21 that has reached an abnormal overheating state increases, the amount of heat transferred from the battery cell 21 to the battery cell 22 decreases. In addition, since the heat transfer resistance of the partition member 12 provided between the battery cell 22 that has deviated from the normal state and the battery cell 23 that remains in the normal state does not increase, the amount of heat transferred from the battery cell 22 to the battery cell 23 and the amount of heat transferred from the battery cell 21 to the battery cell 23 without passing through the electrode body of the battery cell 22 do not decrease. Note that among the heat emitted from the battery cell 21, the heat transferred to the battery cell 23 without passing through the electrode body of the battery cell 22 can be transferred through a structure of the battery cell 2 or the battery pack 10 other than the partition member 1 and other than the electrode body of the battery cell 22 (for example, a bus bar 3 and the outer wall of the housing 4, etc.).

[0158] In this way, according to the partition member 1 of the present embodiment, the heat emitted from the battery cell 21 that has reached an abnormal overheating state is controlled so that the heat transferred to the battery cell 22 that has deviated from the normal state is suppressed and transferred to the battery cell 23 that remains in the normal state, and the temperatures of the respective battery cells 2 in the battery pack 10 are equalized. Therefore, it is possible to suppress the battery cells 2 other than the battery cell 2 that has reached an abnormal overheating state from reaching an abnormal overheating state.

[0159] Examples

[0160] Next, the specific embodiments of the present invention will be further described in detail through examples, but the present invention is not limited to these examples.

[0161] In the following examples and comparative examples, among the heat transfer paths from the abnormally heated battery cell to other battery cells, focusing on the heat transfer through the partition member 1 disposed between the battery cells, the possibility of suppressing the spread of fire between battery cells brought about by the partition member 1 was studied. For the battery pack to be evaluated, a Figure 3 simple battery pack model with three battery cells connected in a two-dimensional coordinate system as shown was constructed, and the battery cell 21 at the left end was given a calorific value equivalent to 1.3×10 9 [J / m 3 (total calorific value inferred from the heat evaluation of the battery cell 2 using an NMC-based positive electrode). Under the conditions of the following examples and comparative examples, the heat conduction equation was analyzed by the finite element method, and thus the temperature in each battery cell 2, as well as the surface average temperature and the thermal resistance per unit area of the partition member 1 were calculated. Here, in the analysis, COMSOL Multiphysics, which is a commonly used physical simulation software manufactured by COMSOL AB, was used, and the analysis was carried out with reference to the following References 9 and 10. It should be noted that for the heat transfer path between the battery cells, the path described in Figure 4 was assumed (Reference 9: Japanese Patent Laid-Open No. 2006-010648; Reference 10: R.M. Spotnitz et al., J. Power Sources 163, 1080-1086, (2007)).

[0162] In addition, Figure 3 when the battery cell 21 at the left end was abnormally heated, the internal temperatures of the adjacent battery cells 22 and 23, as well as the surface average temperature and the thermal resistance per unit area of the partition member 1 were calculated, and the effects such as suppressing the spread of fire brought about by the change in the heat transfer resistance of the partition member 1 were evaluated. It should be noted that the internal temperature of each battery cell 2 was assumed to be the temperature obtained by measuring the internal average temperature of the electrode body (a structure including an electrode, a separator, and an electrolyte).

[0163] (Comparative Example 1)

[0164] In Comparative Example 1, it was assumed that the partition member 1 was a conventional resin-made partition member such as polypropylene (PP), the film thickness was set to 1 mm, and the thermal conductivity was 0.24 W / m·K. It was assumed that the bus bar 3 was an aluminum bus bar, and the thermal conductivity was set to 237 W / m·K. It was assumed that the housing 4 was a conventional resin-made housing such as polypropylene, and the thermal conductivity was set to 0.24 W / m·K. Under the above conditions, the temperature in each battery cell 2, as well as the surface average temperature and the thermal resistance per unit area of the partition member 1 were calculated.

[0165] Figure 7 It is a graph showing the change in the internal temperature of the battery cell in Comparative Example 1. The vertical axis represents the absolute temperature [K] inside the battery cell 2, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heating state. Approximately 150 seconds after the battery cell 21 reaches the abnormal heating state, the internal temperatures of the battery cells 22 and 23 exceed 1000K, indicating that a fire spread from the abnormally heating battery cell 21 to the battery cells 22 and 23 has occurred.

[0166] Figure 8 It is a graph showing the change in the average surface temperature of the partition member in Comparative Example 1. Note that the average surface temperature of the partition member 1 is taken as the average temperature of the surface on the side of the abnormally heating battery cell 21. The vertical axis represents the average surface temperature [°C] of the partition member 1, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heating state. It is estimated that immediately after the battery cell 21 reaches the abnormal heating state, the average surface temperature of the partition member 11 (Spacer1) rises sharply to 400°C, and approximately 150 seconds later, the average surface temperature of the partition member 12 (Spacer2) also rises sharply and exceeds 700°C.

[0167] Figure 9 It is a graph showing the change in the thermal resistance per unit area of the partition member in Comparative Example 1. The vertical axis represents the thermal resistance per unit area (m 2 ·K / W), and the horizontal axis represents the average surface temperature (°C) of the partition member 1. The value of the thermal resistance per unit area (θ 1 ) at an average surface temperature of 190°C of the partition member 11 (Spacer1) and the partition member 12 (Spacer2) is 4.2×10 -3 m 2 ·K / W, and the value of the thermal resistance per unit area (θ 2 ) at an average temperature of 70°C is 4.2×10 -3 m 2 ·K / W. That is, the partition member 1 in Comparative Example 1 does not satisfy any of the above conditions (Equation 1) and (Equation 2) regarding the thermal resistance per unit area.

[0168] (Example 1)

[0169] In Example 1, it is assumed that the partition member 1 is a high-performance partition member having a conversion function in which the thermal conductivity changes at the moment when the surface temperature on the side of the abnormally heating battery cell reaches a specified temperature, and the film thickness is set to 1.0 mm. Various conditions of the bus bar 3 and the housing 4 are the same as those in Comparative Example 1.

[0170] The partition member 1 having a conversion function can be, for example, a structure designed in the following manner: inside a bag-shaped structure made of the material A having a melting point of around 150°C among the above materials, a substance in a liquid state at 150°C in the material B is enclosed. When a part of the bag-shaped structure made of the material A melts at 150°C, the material B enclosed inside flows out to the outside of the bag-shaped structure. With this structure, the conversion temperature of the partition member 1 is set to 150°C, the initial thermal conductivity is set to 1.0 W / m·K, and the thermal conductivity after conversion is set to 0.10 W / m·K. The temperature in each battery cell 2, as well as the surface average temperature and the thermal resistance per unit area of the partition member 1, are estimated.

[0171] Figure 10 It is a graph showing the temperature change inside the battery cell in Example 1. The vertical axis represents the absolute temperature [K] inside the battery cell 2, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heat generation state. After the battery cell 21 reaches the abnormal heat generation state, the internal temperatures of the battery cells 22 and 23 gradually rise but do not reach the abnormal heat generation state, and converge at around 430 K, showing the possibility of suppressing the spread of fire between the battery cells 2.

[0172] Figure 11 It is a graph showing the change in the surface average temperature of the partition member in Example 1. The vertical axis represents the surface average temperature (°C) of the partition member 1, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heat generation state. It is estimated that immediately after the battery cell 21 reaches the abnormal heat generation state, the surface average temperature of the partition member 11 (Spacer1) rises sharply and exceeds 400°C, but the surface average temperature of the partition member 12 (Spacer2) does not rise sharply and converges at around 160°C.

[0173] Figure 12 It is a graph showing the change in the thermal resistance per unit area of the partition member in Example 1. The vertical axis represents the thermal resistance per unit area [m 2 ·K / W], and the horizontal axis represents the surface average temperature [°C] of the partition member 1. The value of the thermal resistance per unit area (θ 1 ) of the partition member 11 (Spacer1) and the partition member 12 (Spacer2) at a surface average temperature of 190°C is 1.0×10 -2 m 2 ·K / W, and the value of the thermal resistance per unit area (θ 2 ) at an average temperature of 70°C is 1.0×10 -3 m 2 ·K / W. That is, the partition member 1 in Example 1 satisfies any one of the above conditions (Equation 1) and (Equation 2) regarding the thermal resistance per unit area.

[0174] (Comparative Example 2)

[0175] Comparative Example 2 and Comparative Example 3 are examples in which the partition member 1 having no conversion function is assumed in order to confirm the importance of the conversion function of the partition member 1. In Comparative Example 2, it is assumed that the partition member 1 has a lower thermal conductivity than the partition member 1 in Comparative Example 1, the film thickness is set to 1.0 mm, and the thermal conductivity is 0.10 W / m·K. Various conditions of the bus bar 3 and the housing 4 are the same as those in Comparative Example 1.

[0176] Figure 13 It is a graph showing the change in the internal temperature of the battery cell in Comparative Example 2. The vertical axis represents the absolute temperature [K] inside the battery cell 2, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heat generation state. The results show that, compared with Comparative Example 1 using the ordinary resin-made partition member 1, although the time required for the spread of combustion from the abnormally heated battery cell 21 to the battery cells 22 and 23 is extended, the spread of combustion is not suppressed.

[0177] Figure 14 It is a graph showing the change in the surface average temperature of the partition member in Comparative Example 2. The vertical axis represents the surface average temperature [°C] of the partition member 1, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heat generation state. After the battery cell 21 reaches the abnormal heat generation state, the surface average temperature of the partition member 11 (Spacer1) starts to rise after about 250 seconds. Based on this result, it is presumed that in the case of improving the heat insulation of the partition member 1, since the heat generation of the battery cell 21 is not efficiently removed in the initial stage when the battery cell 21 reaches the abnormal heat generation state, the spread of combustion is not suppressed.

[0178] Figure 15 It is a graph showing the change in the thermal resistance per unit area of the partition member in Comparative Example 2. The vertical axis represents the thermal resistance per unit area [m 2 ·K / W], and the horizontal axis represents the surface average temperature [°C] of the partition member 1. The value of the thermal resistance per unit area (θ 1 ) of the partition member 11 (Spacer1) and the partition member 12 (Spacer2) at the surface average temperature of 190 °C is 1.0×10 -2 m 2 ·K / W, and the value of the thermal resistance per unit area (θ 2 ) at the average temperature of 70 °C is 1.0×10 -2 m 2 ·K / W. That is, although the partition member 1 in Comparative Example 2 satisfies the condition of the above (Equation 1) regarding the thermal resistance per unit area, it does not satisfy the condition of (Equation 2).

[0179] (Comparative Example 3)

[0180] In Comparative Example 3, the partition member 1 is assumed to have a higher thermal conductivity than that of Comparative Example 1, and the film thickness is set to 1.0 mm and the thermal conductivity is set to 1.0 W / m·K. Various conditions of the bus bar 3 and the case 4 are the same as those of Comparative Example 1.

[0181] Figure 16 : is a graph showing the change in the internal temperature of the battery cell in Comparative Example 3. The vertical axis represents the absolute temperature [K] inside the battery cell 2, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heating state. The results show that, compared with Comparative Example 1 using a conventional resin partition member 1, the time required for the abnormal heating of the battery cell 21 to spread to the battery cells 22 and 23 is shortened, and the battery cells 22 and 23 basically generate abnormal heating at the same time as the battery cell 21.

[0182] Figure 17 : This is a graph showing the change in the average surface temperature of the partition member in Comparative Example 3. The vertical axis represents the average surface temperature of the partition member 1 (°C), and the horizontal axis represents the time (seconds) after the battery cell 21 reaches the abnormal heating state. It is estimated that just after the battery cell 21 reaches the abnormal heating state, the average surface temperature of the partition member 11 (Spacer1) and the partition member 12 (Spacer2) rises sharply, and the average surface temperature exceeds 600°C within 100 seconds. Based on this result, it is estimated that when the heat conductivity of the partition member 1 is improved, the heat generated by the abnormal heating of the battery cell 21 will quickly spread to the adjacent battery cells 22 and 23, so the spread of fire is not suppressed.

[0183] Figure 18 : is a graph showing the change in thermal resistance per unit area of ​​the partition member in Comparative Example 3. The vertical axis represents the thermal resistance per unit area [m 2 ·K / W], and the horizontal axis represents the average surface temperature (°C) of the partition member 1. The thermal resistance (θ) per unit area of ​​the partition member 11 (Spacer1) and the partition member 12 (Spacer2) at an average surface temperature of 190°C 1 ) is 1.0×10 -3 m 2 K / W, thermal resistance per unit area at an average temperature of 70°C (θ 2 ) is 1.0×10 -3 m 2 ·K / W. That is, the partition member 1 in Comparative Example 3 does not satisfy the condition of the above-mentioned (Formula 1) concerning the thermal resistance per unit area, but satisfies the condition of (Formula 2).

[0184] (Comparative Example 4)

[0185] Comparative Example 4 shows an example in which even a high-performance partition member having a function of converting a change in thermal conductivity can cause a battery cell that generates abnormal heat to spread to other battery cells because the thermal resistance per unit area before and after the change is not within an appropriate range.

[0186] In Comparative Example 4, the film thickness of the partition member 1 was set to 1.0 mm, the switching temperature was set to 150° C., the initial thermal conductivity was set to 0.24 W / m·K, and the thermal conductivity after switching was set to 0.10 W / m·K. The various conditions regarding the bus bar 3 and the case 4 were the same as those in Comparative Example 1.

[0187] Figure 19 This is a graph showing the change in the internal temperature of the battery cells in Comparative Example 4. The vertical axis represents the absolute temperature [K] inside the battery cell 2, and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heating state. The results show that after the battery cell 21 reaches the abnormal heating state, about 600 seconds later, the internal temperatures of the battery cells 22 and 23 exceed 1200K, and the fire spreads from the abnormally heated battery cell 21 to the battery cells 22 and 23.

[0188] Figure 20 This is a graph showing the change in the average surface temperature of the partition member in Comparative Example 4. The vertical axis represents the average surface temperature of the partition member 1 [°C], and the horizontal axis represents the time [seconds] after the battery cell 21 reaches the abnormal heating state. It is estimated that the average surface temperature of the partition member 11 (Spacer1) rises sharply and exceeds 400°C just after the battery cell 21 reaches the abnormal heating state, and about 600 seconds later, the average surface temperature of the partition member 12 (Spacer2) also rises sharply and exceeds 800°C. Based on this result, it is estimated that even if the partition member 1 has a conversion function, if the thermal conductivity of the partition member 1 is not properly controlled, the spread of fire cannot be suppressed.

[0189] Figure 21 : is a graph showing the change in thermal resistance per unit area of ​​the partition member in Comparative Example 4. The vertical axis represents thermal resistance per unit area [m 2 ·K / W], and the horizontal axis represents the average surface temperature of the partition member 1 [°C]. The thermal resistance per unit area (θ) of the partition member 11 (Spacer1) and the partition member 12 (Spacer2) at an average surface temperature of 190°C 1 ) is 1.0×10 -2 [m 2 ·K / W], thermal resistance per unit area at an average temperature of 70°C (θ 2 ) is 4.2×10 -3 [m 2·K / W]. That is, although the partition member 1 in Comparative Example 4 satisfies the condition of the above (Equation 1) regarding the thermal resistance per unit area, it does not satisfy the condition of (Equation 2).

[0190] Explanation of Reference Numerals in the Drawings

[0191] 10 Battery pack

[0192] 1, 1A, 1B, 11, 12 Partition members

[0193] 2, 21, 22, 23 Battery cells, single cells

[0194] 3 Bus bar

[0195] 4 Housing

Claims

1. A partition member, wherein, the partition member is used to partition between single cells constituting a battery pack and has two surfaces in the thickness direction, the partition member includes an opening that communicates its interior and exterior at a specified temperature, the partition member contains a material with a thermal conductivity of 0.25 [W / m·K] or more inside a structure, and the structure contains a material having a melting point at a temperature higher than 150°C, the partition member is configured such that the material contained in the partition member can be discharged from the interior to the exterior, When the average temperature of one of the two surfaces exceeds 180°C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 1 satisfies the following formula (1), and When the average temperature on both sides of the two surfaces does not exceed 80 °C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 2 satisfies the following formula (2), θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1) θ 2 ≤4.0×10 -3 [m 2 ·K / W] (Equation 2); Among them, when the average temperature of one of the two surfaces is 180 °C or higher, the thermal conductivity in the thickness direction is 2.0×10 -2 W / m·K or higher and 2.0 W / m·K or lower, and When the average temperature on both sides of the two surfaces is 80°C or lower, the thermal conductivity in the thickness direction is 5.0×10 -2 W / m·K or more and 50 W / m·K or less.

2. A partition member, wherein, the partition member is used to partition between single cells constituting a battery pack and has two surfaces in the thickness direction, the partition member includes an opening that communicates its interior and exterior at a specified temperature, the partition member contains a material with a thermal conductivity of 0.25 [W / m·K] or more inside a structure, and the structure contains a material having a melting point at a temperature higher than 150°C, the partition member is configured such that the material contained in the partition member can be discharged from the interior to the exterior, When the average temperature of one of the two surfaces exceeds 180°C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 1 satisfies the following formula (1), and When the average temperature on both sides of the two surfaces does not exceed 80 °C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 2 satisfies the following formula (2), θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1) θ 2 ≤4.0×10 -3 [m 2 ·K / W] (Equation 2); wherein, when the thickness of the single cell is L [mm], the thickness in the thickness direction is L / 50 mm or more and L / 10 mm or less.

3. A partition member, wherein, the partition member is used to partition between single cells constituting a battery pack and has two surfaces in the thickness direction, the partition member includes an opening that communicates its interior and exterior at a specified temperature, the partition member contains a material with a thermal conductivity of 0.25 [W / m·K] or more inside a structure, and the structure contains a material having a melting point at a temperature higher than 150°C, the partition member is configured such that the material contained in the partition member can be discharged from the interior to the exterior, When the average temperature of one of the two surfaces exceeds 180 °C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 1 satisfies the following formula (1), and When the average temperature on both sides of the two surfaces does not exceed 80 °C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 2 satisfies the following formula (2), θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1) θ 2 ≤ 4.0×10 -3 [m 2 ·K / W] (Equation 2), When the average temperature of one of the two surfaces exceeds 180°C and is below 300°C, the thermal resistance θ per unit area in the thickness direction 1 satisfies the above formula (1), and When the average temperature on both sides of the two surfaces does not exceed 80 °C, the thermal resistance θ per unit area in the thickness direction 2 satisfies the above formula (2).

4. The partition member according to any one of claims 1 to 3, wherein, the material with a thermal conductivity of 0.25 [W / m·K] or more contains a substance that is in a liquid state or a fluid state other than liquid at 150°C or higher.

5. The partition member according to claim 4, wherein, the material with a thermal conductivity of 0.25 [W / m·K] or more is at least one material selected from water, ethylene glycol, and glycerol.

6. A battery pack comprising the partition member according to any one of claims 1 to 5.

7. A battery pack, which comprises: a plurality of single cells, including a first single cell, a second single cell, and a third single cell; a first partition member for partitioning between the first single cell and the second single cell; and a second partition member for partitioning between the second single cell and the third single cell, the partition member includes an opening that communicates its interior and exterior at a specified temperature, the partition member contains a material with a thermal conductivity of 0.25 [W / m·K] or more inside a structure, and the structure contains a material having a melting point at a temperature higher than 150°C, the partition member is configured such that the material contained in the partition member can be discharged from the interior to the exterior, When heat from the first single cell that has reached an abnormally high temperature state causes the second single cell to deviate from its normal state, the heat transferred from the first single cell to the second single cell through the first partition member is suppressed by the first partition member, and the heat transferred from the first single cell to the third single cell that maintains the normal state is not suppressed by the second partition member.

8. The battery pack according to claim 7, wherein the thermal resistance per unit area of the first partition member increases, so that the heat transferred from the first single cell to the second single cell is suppressed.

9. The battery pack according to claim 7, wherein even when the second single cell deviates from the normal state, the thermal resistance per unit area of the second partition member does not increase, and the heat transferred from the first single cell to the third single cell is not suppressed.

10. The battery pack according to any one of claims 7 to 9, wherein the material having a thermal conductivity of 0.25 [W / m·K] or more is a substance that is in a liquid state or a fluid state other than liquid at 150°C or higher.

11. The battery pack according to claim 10, wherein the material having a thermal conductivity of 0.25 [W / m·K] or more is at least one material selected from water, ethylene glycol, and glycerol.

12. A battery pack, comprising a single cell and a partition member, wherein the partition member includes an opening that communicates its interior and exterior at a specified temperature, the partition member contains a material having a thermal conductivity of 0.25 [W / m·K] or more inside a structure, and the structure contains a material having a melting point at a temperature higher than 150°C, the partition member is configured such that the material contained in the partition member can be discharged from the interior to the exterior. When the surface temperature of the partition member exceeds 180 °C, the thermal resistance θ per unit area and per 1.0 mm thickness of the surface of the partition member that contacts or is close to the single cell 1 satisfies the following formula (1), When the surface temperature of the partition member does not exceed 80 °C, the thermal resistance θ per unit area and per 1.0 mm thickness of the surface of the partition member that contacts or is close to the single cell 2 satisfies the following formula (2), θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1) θ 2 ≤ 4.0×10 -3 [m 2 ·K / W] (Formula 2).

13. The battery pack according to claim 12, wherein the material having a thermal conductivity of 0.25 [W / m·K] or more is a substance that is in a liquid state or a fluid state other than liquid at 150°C or higher.

14. The battery pack according to claim 13, wherein the material having a thermal conductivity of 0.25 [W / m·K] or more is at least one material selected from water, ethylene glycol, and glycerol.

15. The battery pack according to any one of claims 12 to 14, wherein the partition member includes a bag-shaped structure.

16. The battery pack according to any one of claims 12 to 14, wherein the surface of the partition member that contacts or is close to the single cell is the surface of the bag-shaped structure.

17. The battery pack according to any one of claims 12 to 14, wherein a liquid or a fluid state other than liquid filled inside the partition member is discharged to the exterior so as to satisfy the thermal resistance of Equation 2.

18. A heat transfer control method for a battery pack, which is a heat transfer control method for a battery pack that separates single cells by a partition member, wherein the partition member includes an opening that communicates its interior and exterior at a specified temperature, The separation member contains a material having a thermal conductivity of 0.25 [W / m·K] or more inside the structure, and the structure contains a material having a melting point at a temperature higher than 150°C. The separation member is configured such that the material contained in the separation member can be discharged from the inside to the outside. The separation member has two surfaces in the thickness direction, one of which is a first surface facing the first single cell, and the other is a second surface facing the second single cell. When the average temperature of the first surface does not exceed 80°C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 2 satisfies the following formula (2), and heat from the first single cell is transferred to the second single cell through the partition member. When the first single cell reaches an abnormal heat generation state, and the heat transferred from the first single cell through the separation member causes the second single cell to deviate from the normal state, and the heat from the first single cell causes the average temperature of the first surface to exceed 180 °C, the thermal resistance θ per unit area and per 1.0 mm thickness in the thickness direction 1 satisfies the following formula (1), thereby suppressing the amount of heat transferred from the first single cell through the separation member. θ 1 ≥5.0×10 -3 [m 2 ·K / W] (Equation 1) θ 2 ≤ 4.0×10 -3 [m 2 ·K / W] (Formula 2).

19. The heat transfer control method for a battery pack according to claim 18. wherein The material having a thermal conductivity of 0.25 [W / m·K] or more contains a substance that is in a liquid state or a fluid state other than liquid at 150°C or higher.

20. The heat transfer control method for a battery pack according to claim 19. wherein The material having a thermal conductivity of 0.25 [W / m·K] or more is at least one material selected from water, ethylene glycol, and glycerol.

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