Spacer and battery pack

Abstract

This spacer partitions single cells or a single cell and a member other than the single cell. The thermal conductivity λT of the spacer in the thickness direction at an average surface temperature T°C satisfies formula 1. The spacer includes an exterior material and an inner packaging material accommodated in the exterior material, the inner packaging material comprises a compositional portion including a liquid and a material that absorbs the liquid, and said material satisfies formula 2 in terms of the ratio of a liquid absorption rate 2 of the material having undergone compression under the pressure of 5 kgf / cm2 for 1 minute to a liquid absorption rate 1 of the material having undergone compression under the pressure of 0.05 kgf / cm2 for 1 minute.　Formula 1: λ40 > λ180 Formula 2: [Liquid absorption rate 2] / [Liquid absorption rate 1] ≥ 0.81

Description

Spacers and battery packs

[0001] This invention relates to a battery pack and a spacer that is housed inside the battery pack and separates the individual cells.

[0002] In recent years, secondary batteries, which are increasingly used as power sources for vehicles and other devices, are being studied for their high energy density to improve flexibility in mounting them in the limited space of vehicles and to extend the driving range on a single charge. On the other hand, the safety of secondary batteries tends to be inversely related to energy density, with safety tending to decrease as the energy density of the secondary battery increases. For example, in secondary batteries installed in electric vehicles with a driving range of several hundred kilometers, the surface temperature of the battery can exceed several hundred degrees Celsius, and in some cases even reach over 1000 degrees Celsius, if the secondary battery is damaged due to overcharging or an internal short circuit.

[0003] Secondary batteries used as power sources for vehicles and other devices are generally used as battery packs consisting of multiple individual cells. If one of the individual cells in a battery pack is damaged and reaches the temperature range described above, the heat generated can damage adjacent cells, potentially causing a chain reaction of damage to the entire battery pack. To prevent such a chain reaction of cell damage, various technologies have been proposed to install partition members between individual cells.

[0004] As a conventional spacer, for example, a spacer has been proposed that can maintain the liquid-holding capacity of the encapsulated material when the encapsulated material deforms due to pressure (Patent Document 1).

[0005] International Publication No. 2019 / 107561

[0006] The aforementioned conventional spacer contains an insulating material and a liquid as its internal structure, and the liquid is held within the insulating material by physical interactions such as surface tension. Therefore, by using a rigid insulating material containing fibers and particles, the internal structure can retain the liquid above a certain level even under pressure, and the spacer can maintain a high thermal conductivity at room temperature. However, the aforementioned conventional spacer failed to meet market requirements.

[0007] The object of the present invention is to provide a spacer that can easily maintain a high thermal conductivity at normal temperature and a laminated battery using the spacer.

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using the spacer described below, and have completed the present invention.

[0009] That is, the present invention includes the following aspects. [A1] A spacer that partitions between single cells or between a single cell and a member other than the single cell, wherein the thermal conductivity λ in the thickness direction at the surface average temperature T ° C of the spacer ４０ , １８０ , １８０ , ４０ satisfies the following formula (1), the spacer includes an exterior material and an encapsulating material housed in the exterior material, the encapsulating material includes a composition part containing a liquid and a material that absorbs the liquid, and the material has a liquid absorption rate 1 when compressed at a pressure of 0.05 kgf / cm ２ for 1 minute, and the ratio of the liquid absorption rate 2 when compressed at a pressure of 5 kgf / cm ２ for 1 minute satisfies the following formula (2). Spacer. Formula (1): λ ４０ > λ １８０ Formula (2): [Liquid absorption rate 2] / [Liquid absorption rate 1] ≥ 0.81 [A2] A spacer that partitions between single cells or between a single cell and a member other than the single cell, wherein the thermal conductivity λ in the thickness direction at the surface average temperature T ° C of the spacer Ｔ satisfies the following formula (1), the spacer includes an exterior material and an encapsulating material housed in the exterior material, and the encapsulating material includes a composition part containing a liquid and a material that can chemically interact with the liquid. Spacer. Formula (1): λ ４０ > λ １８０ [A3] The spacer according to [A1] or [A2] above, wherein the ratio of λ ４０ to λ <​​​​A spacer according to any one of [A1] to [A3] above, wherein the ratio of is 0.40 or less. [A5] A spacer according to any one of [A1] to [A4] above, wherein the composition portion comprises a gel composition. [A6] A spacer according to any one of [A1] to [A5] above, wherein the composition portion comprises a gel composition, the gel composition comprises a liquid-holding polymer, and the liquid content is 50 to 99% by mass with respect to 100% by mass of the gel composition. [A7] A spacer according to any one of [A1] to [A6] above, wherein the composition portion comprises a gel composition, the gel composition comprises a hydrogel. [A8] A spacer according to any one of [A1] to [A7] above, wherein the composition portion comprises a gel composition, the gel composition comprises a liquid-holding polymer, the liquid comprises water, and the water content A is 1 to 60% by mass with respect to 100% by mass of the gel composition. [A9] The composition portion comprises a gel composition, and the density of the gel composition at 25°C, as measured by the liquid weighing method, is 0.90 to 1.90 g / cm³. ３ The spacer according to any one of [A1] to [A8] above. [A10] The spacer according to any one of [A1] to [A9] above, wherein the composition portion comprises a gel composition, and the gel composition comprises a silicon-containing compound. [A11] The composition portion comprises a gel composition, and the gel composition comprises a polymer of a silicon-containing compound, and the polymer of the silicon-containing compound comprises SiO ４／２ Siloxane units (Q units) expressed in units, R １ SiO ３／２ Siloxane units (T units) are represented by R ２ R ３ SiO ２／２ Siloxane units (D units) represented by R ４ R ５ R ６ SiO １／２ It includes one or more units selected from the group consisting of siloxane units (M units) represented by (the above R １ ~R ６A12 A11 A11 A11 A12 [A14] The spacer according to any one of [A1] to [A13], wherein the encapsulating material further comprises a holding portion, the holding portion having an outer wall portion that contacts at least a part of the outer peripheral end surface in the planar direction of the composition portion and extends in the thickness direction, and both ends of the outer wall portion of the holding portion in the thickness direction are in contact with the exterior material. [A15] The spacer according to any one of [A1] to [A14], wherein the exterior material includes a polymer layer. [A16] The spacer according to any one of [A1] to [A15], wherein the exterior material includes a metal layer. [A17] A battery pack including a single cell and a spacer according to any one of [A1] to [A16].

[0010] [B1] A spacer that separates a single cell from another component, wherein the thermal conductivity λ in the thickness direction at the average surface temperature T°C of the spacer. Ｔ The following formula 1 is satisfied, the spacer includes an exterior material and an inner material housed in the exterior material, the inner material comprises a composition portion containing a liquid and a material that absorbs the liquid, and the material has a pressure of 0.05 kgf / cm². ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ A spacer such that the ratio of liquid absorption rates when compressed for 1 minute satisfies the following equation 2. Equation 1: λ ４０ >λ １８０Formula 2: [Liquid absorption rate 2] / [Liquid absorption rate 1] ≥ 0.81 [B2] The spacer according to [B1] above, wherein the spacer includes a sealing portion, and in a plan view from the thickness direction of the spacer, the exterior material and the composition portion overlap, and the area S1 of the first region excluding the sealing portion and the area S2 of the second region excluding the sealing portion where the exterior material and the composition portion do not overlap satisfy the following formula 3, and the burst pressure of the spacer is 9.0 MPa or more. Formula 3: 0.60 ≤ S1 / (S1 + S2) ≤ 1.00 [B3] The spacer according to [B1] or [B2] above, wherein the compression deformation rate at which the thickness of the spacer becomes 70% of the thickness when not pressurized is 0.5 MPa or more. [B4] λ in Formula 1 above ４０ λ for １８０ A spacer according to any one of [B1] to [B3] above, wherein the ratio of is less than 0.50. [B5] A spacer according to any one of [B1] to [B4] above, wherein the composition portion is a single molded body. [B6] A spacer according to any one of [B1] to [B5] above, wherein the composition portion comprises a material that can chemically interact with the liquid. [B7] A spacer according to any one of [B1] to [B6] above, wherein the composition portion comprises a gel composition. [B8] A spacer according to any one of [B1] to [B7] above, wherein the composition portion comprises a gel composition, and the 30% mass loss temperature of the gel composition is 40 to 125°C. [B9] A spacer according to any one of [B1] to [B8] above, wherein the composition portion comprises a gel composition, and the gel composition comprises a polymer that holds a liquid, and the liquid content is more than 60% by mass and 99% by mass or less based on 100% by mass of the gel composition. [B10] The composition portion comprises a gel composition, and the density of the gel composition at 25°C, as measured by the liquid weighing method, is 0.90 to 1.90 g / cm³. ３ The spacer according to any one of [B1] to [B9] above. [B11] The spacer according to any one of [B1] to [B10] above, wherein the composition portion comprises a gel composition, and the gel composition comprises a polymer of a silicon-containing compound. [B12] The composition portion comprises a gel composition, and the gel composition comprises a polymer of a silicon-containing compound, and the polymer of the silicon-containing compound is SiO ４／２ Siloxane units (Q units) expressed in units, R１ SiO ３／２ Siloxane units (T units) are represented by R ２ R ３ SiO ２／２ Siloxane units (D units) represented by R ４ R ５ R ６ SiO １／２ It includes one or more units selected from the group consisting of siloxane units (M units) represented by (the above R １ ~R ６ The spacer according to any one of [B1] to [B11] above, wherein Qx, Tx, Dx, and Mx are the molar percentages of the Q unit, T unit, D unit, and M unit, respectively, and satisfying 80 ≤ Qx ≤ 100, 0 ≤ Tx ≤ 20, 0 ≤ Dx ≤ 20, 0 ≤ Mx ≤ 20, and Qx + Tx + Dx + Mx = 100. [B13] The spacer according to any one of [B1] to [B12] above, wherein the encapsulating material further comprises a holding portion, the holding portion having an outer wall portion that contacts at least a part of the outer peripheral end surface in the surface direction of the composition portion and extends in the thickness direction. [B14] The spacer according to any one of [B1] to [B13] above, wherein the exterior material includes a metal layer, and the composition portion is in contact with the exterior material. [B15] A battery pack including a single cell and a spacer as described in any one of [B1] to [B14] above.

[0011] [C1] Thermal conductivity λ in the thickness direction at the surface mean temperature T°C Ｔ A spacer whose [W / (m·K)] satisfies the following equation 1. Equation 1: λ ４０ >λ １８０ [C2] The above λ ４０ λ for １８０ The spacer described in [C1] above, wherein the ratio of is greater than 0.00 and less than 0.90. [C3] The λ ４０ The spacer described in [C1] or [C2] above, wherein [W / (m·K)] is 0.20 or more and 1.00 or less. [C4] The λ １８０ A spacer according to any one of the above [C1] to [C3], wherein [W / (m·K)] is greater than 0.00 and less than 0.20.

[0012] [D1] Includes an outer material and an inner material housed in the outer material, wherein the inner material comprises a composition portion containing a liquid and a material that absorbs the liquid, and the material has a pressure of 0.05 kgf / cm². ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ A spacer having a ratio of liquid absorption rate 2 [liquid absorption rate 2] / [liquid absorption rate 1] of 0.81 or more and 1.0 or less when compressed for 1 minute. [D2] Includes an outer material and an inner material housed in the outer material, wherein the inner material comprises a composition part containing a liquid and a material that absorbs the liquid, and the composition part is subjected to a pressure of 0.05 kgf / cm ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ A spacer in which the ratio of liquid absorption rate 2 [liquid absorption rate 2] / [liquid absorption rate 1] when compressed for 1 minute is between 0.81 and 1.0.

[0013] [E1] A spacer comprising an outer material and an inner material contained within the outer material, wherein the inner material comprises a composition portion containing a liquid and a material chemically interactable with the liquid. [E2] The spacer according to [E1], wherein the liquid is water. [E3] The spacer according to [E1] or [E2], wherein the material chemically interactable with the liquid is a gel composition. [E4] The spacer according to any one of [E1] to [E3], wherein the 30% mass loss temperature of the material chemically interactable with the liquid is 40 to 125°C. [E5] The spacer according to any one of [E1] to [E4], wherein the mass loss rate from 30°C to 100°C calculated from the following formula is 0.76 to 1.0 mass% / °C. Formula: Mass loss rate (mass% / °C) = [Mass loss rate from 30°C to 100°C] / 70

[0014] [F1] A spacer comprising an outer material and an inner material housed in the outer material, wherein the burst pressure is 9.0 MPa or more and 50.0 MPa or less. [F2] The spacer according to [F1], wherein the outer material further comprises a sealing portion and the inner material comprises a composition portion, and in a plan view from the thickness direction, the spacer has an area S1 of a first region excluding the sealing portion and an area S2 of a second region excluding the sealing portion, where the outer material and the composition portion do not overlap. [F3] The ratio of the burst pressure P of the spacer to the area S2 of the second region P / S2 (MPa / mm ２ The spacer described in [F2] above, wherein the ratio of the burst pressure P of the spacer to the area S4 of the sealing portion in a plan view from the thickness direction is P / S4 (MPa / mm²). ２ The spacer described in [F2] or [F3] above, wherein the value is 0.0030 to 0.020.

[0015] [G1] A spacer comprising an outer material and an inner material housed within the outer material, wherein the outer material includes a sealing portion and the inner material includes a composition portion, and the area S1 of a first region where the outer material and the composition portion overlap, excluding the sealing portion, and the area S2 of a second region where the outer material and the composition portion do not overlap, excluding the sealing portion, satisfy the following formula 3. Formula 3: 0.60 ≤ S1 / (S1 + S2) ≤ 1.00

[0016] [H1] A spacer comprising an exterior material and an internal material housed in the exterior material, wherein the compressive deformation rate is 0.5 MPa or more, which is the stress at which the thickness of the spacer becomes 70% of that when not pressurized.

[0017] [I1] A spacer in which the ratio of the thickness of the spacer after applying a stress of 0.5 MPa to the thickness of the spacer before applying stress in the thickness direction is 0.10 or more and less than 0.70.

[0018] [J1] A method for manufacturing a spacer comprising an outer material and an inner material contained in the outer material, wherein the inner material comprises a gel composition, and the method includes a mixing step of preparing a sol composition comprising a metal alkoxide or metal silicate salt and a solvent, and a gelation step of manufacturing the gel composition. [J2] The method for manufacturing a spacer according to [J1], wherein the inner material further comprises a porous body, and the method further comprises a manufacturing step of the inner material comprising contacting the sol composition with the porous body. [J3] The method for manufacturing a spacer according to [J1] or [J2], wherein the inner material further comprises a porous body, and the method further comprises a manufacturing step of the inner material comprising contacting the gel composition with the porous body. [J4] The method for manufacturing a spacer according to any one of [J1] to [J3], wherein the inner material further comprises a holding portion, and the method further comprises a manufacturing step of the inner material comprising contacting the sol composition with the holding portion. [J5] The method for manufacturing a spacer according to any one of [J1] to [J4], wherein the inner material further comprises a holding portion, and the method further comprises a manufacturing step of the inner material comprising contacting the gel composition with the holding portion. [J6] A method for manufacturing a spacer according to any one of [J1] to [J5], further comprising a step of housing the internal material into the exterior material. [J7] A method for manufacturing a spacer according to any one of [J1] to [J6], further comprising a step of sealing the exterior material.

[0019] According to the present invention, it is possible to provide a spacer that can easily maintain a high thermal conductivity at room temperature and a battery pack using the spacer. The reason why the present invention is effective is not clear, but it is presumed to be due to the following mechanisms. In one embodiment of the spacer of the present invention, the composition contained in the encapsulating material has a high liquid absorption rate and can contain a large amount of liquid, so the thermal conductivity at room temperature is easily maintained. In another embodiment of the spacer of the present invention, the burst pressure is high and liquid leakage can be prevented, so the thermal conductivity at room temperature is easily maintained even under stress. In one embodiment of the spacer of the present invention, the composition contained in the encapsulating material can chemically interact with the liquid, so it can contain a large amount of liquid even under stress, and the thermal conductivity at room temperature is easily maintained. In one embodiment of the spacer of the present invention, by controlling the compression deformation rate and the thickness change rate, it can contain a large amount of liquid even under stress, and the thermal conductivity at room temperature is easily maintained. The spacer of the above embodiment can be designed to increase S1 / (S1+S2), which will be described later. Furthermore, in the spacer of the above embodiment, when an adjacent cell goes from room temperature to an abnormal state, the thermal conductivity decreases as liquid flows out of the spacer. By increasing the ratio S1 / (S1+S2), heat conduction at room temperature is more easily promoted, and insulation is more easily provided in the event of an abnormality. This makes it easier to suppress heat transfer when an abnormality occurs in a single cell.

[0020] [Correction based on Rule 91 08.01.2026] This figure shows a schematic longitudinal section of an example of a spacer member of the present invention, cut in the thickness direction. This figure shows a schematic longitudinal section of an example of the configuration of an internal material constituting the spacer, cut in the thickness direction. This figure shows a schematic longitudinal section of an example of the configuration of an internal material constituting the spacer, cut in the thickness direction. This figure shows a schematic longitudinal section of an example of the configuration of an internal material constituting the spacer, cut in the thickness direction. This figure shows a schematic plan view of an example of the configuration of an internal material constituting the spacer, viewed from the thickness direction. This figure shows a schematic plan view of an example of the configuration of an internal material constituting the spacer, viewed from the thickness direction. This figure shows a schematic longitudinal section of an example of the configuration of an internal material constituting the spacer, cut in the thickness direction. This figure shows a schematic plan view of an example of the configuration of an internal material constituting the spacer, viewed from the thickness direction. This is a schematic longitudinal section of an example of the configuration of an internal material constituting the spacer, cut in the thickness direction. This is a schematic plan view of an example of the configuration of an internal material constituting the spacer, viewed from the thickness direction. This is a cross-sectional view of the internal material shown in Figure 5A along the line A-A. This is a cross-sectional view of the internal material shown in Figure 5A along the line B-B. This figure shows a schematic plan view of an example of the configuration of an internal material constituting the spacer, viewed from the thickness direction. This figure shows a schematic longitudinal cross-sectional view of an example of the configuration of the internal material constituting the spacer, cut in the thickness direction. This is a front view of an example of the configuration of a spacer according to one embodiment of the present invention. This is a conceptual diagram showing a battery pack of the present invention. This is a plan view showing an example of a single cell. This is a front view of the single cell of Figure 10. This is a side view of the single cell of Figure 10. This is a conceptual diagram of a thermal insulation performance evaluation test apparatus.

[0021] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. In numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. "A or B" means that either A or B is included, or both are included. Unless otherwise specified, the materials exemplified in this specification can be used individually or in combination of two or more. In this specification, the content of each component in a composition means the total amount of multiple substances present in the composition if there are multiple substances corresponding to each component in the composition, unless otherwise specified.

[0022] [1. Spacer] A spacer according to one embodiment of the present invention has a thermal conductivity λ in the thickness direction at the average surface temperature T°C of the spacer. Ｔ The spacer satisfies the following equation 1. Thermal conductivity λ Ｔ [W / (m·K)] can be measured by the method described in the examples. Note that "average surface temperature" refers to the average temperature of any three points on the spacer surface that are in contact with the heating element. Equation 1: λ ４０ >λ １８０

[0023] It is presumed that the thermal conductivity switches when the average surface temperature of the spacer is 40°C because the composition contains liquid, whereas when the average surface temperature is 180°C, the liquid contained in the composition volatilizes and is replaced by air, causing the thermal conductivity to decrease.

[0024] λ ４０ The lower limit is not particularly limited, but from the viewpoint of normal heat transfer performance, it is preferably 0.20 or higher, more preferably 0.25 or higher, and even more preferably 0.30 or higher. λ ４０ There is no particular upper limit, but it is preferably 1.00 or less, more preferably 0.50 or less, and even more preferably 0.45 or less.

[0025] λ １８０The upper limit is not particularly limited, but from the viewpoint of thermal insulation under abnormal conditions, it is preferably less than 0.20, more preferably 0.15 or less, even more preferably 0.10 or less, and particularly preferably 0.05 or less. λ １８０ The lower limit is not particularly restricted, but it is preferably greater than 0.00.

[0026] From the viewpoint of effectively switching the above thermal conductivity, λ ４０ λ for １８０ The ratio is not particularly limited, but is preferably less than 0.90, more preferably less than 0.80, more preferably less than 0.70, even more preferably less than 0.60, more preferably less than 0.50, more preferably 0.40 or less, and more preferably 0.30 or less. ４０ λ for １８０ The ratio is preferably greater than 0.00.

[0027] Spacer 1, in a plan view from the thickness direction, has the area S1 of a first region where the exterior material 120 and the first inorganic layer overlap, excluding the sealing portion 120a; the area S2 of a second region where the exterior material 120 and the first inorganic layer do not overlap, excluding the sealing portion 120a; the total area S3 of the spacer (the sum of the first region, the second region, and the sealing portion); and the area S4 of the sealing portion. Preferably, S1 and S2 satisfy the following formula 3. Formula 3: 0.60 ≤ S1 / (S1 + S2)

[0028] The lower limit of S1 / (S1+S2) in the above formula 3 is 0.60, but is preferably 0.70, more preferably 0.80, even more preferably 0.82, and most preferably 0.84. The upper limit is preferably 1.00, more preferably 0.95, and even more preferably 0.90.

[0029] In a plan view from the thickness direction of the spacer, the lower limit of the ratio S1 / S3 of the area S1 of the first region to the total area S3 of the spacer is preferably 0.60, more preferably 0.65, more preferably 0.70, and more preferably 0.75, from the viewpoint of improving thermal insulation in abnormal situations. The upper limit is preferably 1.0, more preferably 0.95, and more preferably 0.90.

[0030] A spacer according to one embodiment of the present invention has a lower limit of its burst pressure P of 9.0 MPa or more. Preferably it is 10.0 MPa, more preferably 11.0 MPa, more preferably 11.5 MPa, more preferably 12.0 MPa, more preferably 12.5 MPa, more preferably 13.0 MPa, more preferably 13.5 MPa, more preferably 14.0 MPa, more preferably 14.5 MPa, more preferably 15.0 MPa, more preferably 15.5 MPa, more preferably 16.0 MPa, more preferably 20.0 MPa, and more preferably 25.0 MPa. The upper limit is preferably 50.0 MPa. The burst pressure P of the spacer can be calculated by placing a metal plate on the spacer, applying a load using a high-pressure jack, and dividing the load at the time the spacer bursts by the area of ​​the internal space within the spacer.

[0031] The ratio of the burst pressure P of the spacer to the area S2 of the second region P / S2 (MPa / mm²) ２ The lower limit of the ) is preferably 0.0050, preferably 0.0060, more preferably 0.0070, and more preferably 0.0075, from the viewpoint of extending the plateau time. The upper limit is preferably 0.020, more preferably 0.019, and more preferably 0.018.

[0032] Lower limit of the ratio P / S4 (MPa / mm) of the burst pressure P of the spacer to the area S4 of the sealing portion in a plan view from the thickness direction. ２ The upper limit is preferably 0.020 and more preferably 0.018, from the viewpoint of extending the plateau time.

[0033] A spacer according to one embodiment of the present invention includes an exterior material and an internal material housed within the exterior material. The respective components will be described below.

[0034] [1-1. Internal Material] The internal material in the spacer of the present invention is covered by an outer material. The internal material comprises a composition portion. Furthermore, from the viewpoint of achieving compressibility, it is preferable to further include a holding portion. From the viewpoint of functional integration, the internal material is preferably a single-layer structure, and from the viewpoint of functional separation, it is preferably a multi-layer structure. Here, "multiple layers" means internal material stacked in the thickness direction of the spacer. When there are multiple layers, it means that the spacer can be physically separated by applying tensile force to both ends in the thickness direction. When the multi-layer structure is adopted, it may have multiple composition portions, or it may have a single composition portion and a single holding portion. The respective configurations will be described below.

[0035] [1-1-1. Composition] One embodiment of the composition comprises a liquid and a material that absorbs the liquid, wherein the material is at a pressure of 0.05 kgf / cm². ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ It is preferable that the ratio of the liquid absorption rate 2 when compressed for 1 minute satisfies the following formula 2. The liquid absorption rate can be measured by the method of the example. Formula 2: [Liquid absorption rate 2] / [Liquid absorption rate 1] ≥ 0.81

[0036] From the viewpoint of easily maintaining a high thermal conductivity at room temperature, it is preferable that the ratio is 0.85 or higher, more preferably 0.90 or higher, and even more preferably 0.95 or higher. From the viewpoint of easily maintaining a high thermal conductivity at room temperature, it is preferable that the ratio is 1.0 or lower.

[0037] One embodiment of the composition comprises a liquid and a material that absorbs the liquid, wherein the composition is at a pressure of 0.05 kgf / cm². ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ It is preferable that the ratio of the liquid absorption rate 2 when compressed for 1 minute satisfies the following formula 2. The liquid absorption rate can be measured by the method of the example. Formula 2': [Liquid absorption rate 2] / [Liquid absorption rate 1] ≥ 0.81

[0038] From the viewpoint of easily maintaining a high thermal conductivity at room temperature, it is preferable that the ratio is 0.85 or higher, more preferably 0.90 or higher, and even more preferably 0.95 or higher. From the viewpoint of easily maintaining a high thermal conductivity at room temperature, it is preferable that the ratio is 1.0 or lower.

[0039] Furthermore, the composition portion is preferably a molded body, more preferably an aggregate of 1 to 10 molded bodies, and more preferably a single molded body. Here, "a single molded body" means a single molded body, not a form in which multiple molded bodies are aggregated, and that is physically inseparable without applying tensile force to both ends. As will be described later, it may also be a molded body made of multiple types of materials.

[0040] Another embodiment of the composition preferably includes a liquid and a material that can chemically interact with the liquid.

[0041] (Liquid) The boiling point of the liquid contained in the composition is preferably 50 to 200°C, and more preferably 80 to 180°C. The liquid preferably contains at least one selected from the group consisting of, for example, water, alcohols, esters, ethers, ketones, hydrocarbons, fluorinated compounds, and silicone oils. These can be used individually or as a mixture of two or more. The liquid may also contain additives such as antifreeze agents, preservatives, and pH adjusters. By providing antifreeze, damage to the packaging material due to expansion caused by freezing can be avoided. In addition, by adding a pH adjuster, the pH of the liquid can be changed by components leached from the powdered inorganic material, reducing the possibility of deterioration of the powdered inorganic material, the packaging material, and the liquid (water) itself. The liquid may not be limited to those listed above and may be added as needed. From the viewpoint of safety, the liquid is preferably water or alcohols, and more preferably water. The composition may further contain an excess liquid beyond the liquid that is absorbed or interacts with.

[0042] (Materials used in combination with liquid) The materials used in combination with the liquid contained in the composition are not particularly limited as long as they can hold the liquid. In one embodiment, the material can absorb the liquid by holding it in its voids. In another embodiment, the material can hold the liquid through chemical interactions such as hydrogen bonding. Specifically, materials having functional groups that interact with the liquid may be used, materials that have been surface-treated to be able to chemically interact with the liquid may be used, and known materials can be used. From the viewpoint of increasing the liquid absorption rate, materials having functional groups that interact with the liquid are preferred, and if the liquid is water or alcohols, materials having groups that can form hydrogen bonds with them are preferred, and materials having hydroxyl groups are more preferred.

[0043] (Gel Composition) One embodiment of the material used in combination with the liquid preferably includes a gel composition. By using a gel composition, the amount of liquid that can be retained can be increased. The gel composition contains at least a gel. In the present invention, "gel" refers to the storage modulus G at a strain of 0.1%. １ and loss modulus G ２ The composition satisfies the following formula 4. The storage modulus and loss modulus can be measured by known methods. The gel composition may contain, in addition to the gel, the excess liquid or known additives. Formula 4: G １ > G ２

[0044] The gel composition preferably contains a polymer that holds a liquid. From the viewpoint of easily maintaining a high thermal conductivity at room temperature, the liquid preferably constitutes 50 to 99% by mass of 100% by mass of the gel composition, more preferably 55 to 97% by mass, even more preferably 60 to 99% by mass, and especially preferably 65 to 99% by mass.

[0045] The temperature at which the gel composition loses 30% of its mass is preferably 40 to 125°C, more preferably 45 to 120°C, and even more preferably 50 to 115°C. The temperature at which the gel composition loses 30% of its mass is determined by taking a sample from a portion of the obtained gel composition. Next, a thermogravimetric differential thermal analyzer (TG-DTA) is used to perform a TG-DTA measurement on the sample, and the mass loss curve is determined when the temperature is raised from room temperature to 300°C at a rate of 5°C / min. In the obtained mass loss curve, the temperature at which the mass has decreased by 30% when the mass at the time of measurement is set to 100% is determined. The mass loss rate of the gel composition from 30°C to 100°C is preferably 0.76 to 1.0 mass% / °C, more preferably 0.78 to 1.0 mass% / °C, and even more preferably 0.80 to 1.0 mass% / °C. The above mass loss rate (mass % / °C) can be determined from the mass loss curve obtained from TG-DTA measurements similar to those for the 30% mass loss temperature, based on the following formula: Mass loss rate (mass % / °C) = [Mass loss rate from 30°C to 100°C] / 70

[0046] Examples of the polymer include organogels in which the interacting liquid is an organic solvent, or hydrogels in which the interacting liquid is water. From a safety standpoint, it is preferable that the gel composition contains a hydrogel.

[0047] From the perspective of effectively switching the thermal conductivity, especially when the liquid retained in the gel composition is water, the water content A measured by the following method is preferably 1 to 60% by mass, more preferably 1 to 50% by mass, still more preferably 1 to 40% by mass, and particularly preferably 1 to 30% by mass based on 100% by mass of the gel composition. The water content A means the amount of unfrozen water and is calculated as the value obtained by subtracting the amounts of free water and frozen-bound water from the total amount of water contained in the hydrogel measured by a differential scanning calorimeter. That is, 10 mg of the sample is sealed in an aluminum airtight container, cooled at 0.3 °C / min to a temperature range of -10 to -38 °C using a differential scanning calorimeter, held at -38 °C for 10 minutes, and the heat generation amount and heat absorption amount of the sample during the temperature increase process from -38 to 10 °C at 0.3 °C / min are measured. Let the mass of water calculated from the heat absorption amount from -38 to -5 °C during the temperature increase process be B, and the mass of water calculated from the heat absorption amount from -1 to 3 °C be C, and let A be the value obtained by subtracting the total masses B and C of water contained in the gel composition.

[0048] The gel composition preferably has a density at 25 °C measured by the liquid weighing method of 0.90 to 1.90 g / cm ３ and more preferably 0.90 to 1.70 g / cm ３ and still more preferably 0.90 to 1.50 g / cm ３ g / cm ３

[0049] From the perspective of heat resistance, the gel composition preferably contains a polymer of a silicon-containing compound, more preferably contains a silicate gel, and still more preferably is a silicate hydrogel. The polymer of the silicon-containing compound is composed of siloxane units (Q units) represented by SiO ４／２ units, siloxane units (T units) represented by R １ SiO ３／２ units, siloxane units (D units) represented by R ２ R ３ SiO ２／２ units, and R ４ R ５ R ６ SiO １／２containing at least one unit selected from the group consisting of siloxane units (M units) represented by (where the R １ ~R ６ each independently represents an alkyl group or an aryl group bonded to a silicon atom). When the molar percentages of the Q unit, T unit, D unit and M unit are Qx, Tx, Dx, Mx respectively, it is more preferable that 80 ≦ Qx ≦ 100, 0 ≦ Tx ≦ 20, 0 ≦ Dx ≦ 20, 0 ≦ Mx ≦ 20, and Qx + Tx + Dx + Mx = 100 are satisfied.

[0050] The hydrogel is a gel solid containing a siloxane bond as described above. After drying the moisture, the bonding state can be measured and analyzed in detail using a solid nuclear magnetic resonance spectroscopy (solid NMR) apparatus. As a result, the dried hydrogel is measured by solid ２９ Si-NMR, the signal area integral values derived from the Q component, T component, D component and M component are calculated, and Qx, Tx, Dx, Mx, which are the mass percentages of the tetrafunctional silane compound, trifunctional silane compound, difunctional silane compound and monofunctional silane compound respectively, may be calculated.

[0051] (Porous material) One embodiment of the material used in combination with the liquid is preferably a porous material, and more preferably contains inorganic fibers or inorganic particles. The inorganic particles are not particularly limited as long as they are within the range that achieve the effects of the present invention, and examples include silica, alumina, calcium silicate, zeolite, diatomaceous earth, shirasu balloon, clay minerals, vermiculite, mica, cement, perlite, fumed silica, and aerogel. Among these, silica particles, alumina particles, calcium silicate, zeolite, and vermiculite are preferred, and calcium silicate and zeolite are more preferred, and calcium silicate is even more preferred, as they easily contain more liquid within and between the particles. Among the types of calcium silicate, xonotlite, tobermorite, wollastonite, and gyrolite are preferred, and gyrolite is more preferred. Gyrolite, which has a petal-like structure, maintains its porous structure even when compressed and deformed, and therefore has excellent water retention properties. Clay minerals mainly include magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite. The particle size of the inorganic particles is preferably 1 / 5 or less of the thickness of the composition. These inorganic particles can be used individually or in a mixture of multiple types. The inorganic fibers are not particularly limited as long as they achieve the effects of the present invention, and examples include glass fibers, alumina fibers, rock wool, etc. The fiber system of the inorganic fibers is preferably 1 / 5 or less of the thickness of the composition. These inorganic fibers can be used individually or in a mixture of multiple types. The porous body, inorganic fibers, or inorganic particles may be used in contact with the gel composition.

[0052] [1-1-2. Holding Part] The holding part is the part that contains, houses, and holds the composition part inside. When assembling a battery pack by sandwiching spacers between individual cells, the spacers are pressed between the individual cells, and the overall length of the battery pack is adjusted by restraining the area around the cells with a belt-like member while the individual cells and spacers are stacked side by side inside the housing. In this assembly process, the holding part also functions to cushion the pressing force applied to the surface of the individual cells when the spacers are sandwiched between the individual cells. It is preferable that the holding part is in a state that deforms by compression when subjected to external force.

[0053] One embodiment of the holding portion includes a thermoplastic resin. Examples of thermoplastic resins include olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polystyrene (PS). Silicone rubber and its foam can also be used. Of these, olefin resins are preferred, and polypropylene is particularly preferred, from the viewpoint of versatility and cost. These resins may also contain heat-resistant fillers such as alumina particles and glass fibers.

[0054] The retaining portion is in contact with at least a part of the composition portion. The retaining portion may be positioned in contact with the outer peripheral end surface of the composition portion in the planar direction so as to cover a part or multiple areas of the outer peripheral end surface of the composition portion in the planar direction, or so as to cover the entire outer peripheral end surface. The retaining portion may be positioned in contact with one surface of the composition portion in the thickness direction, either partially or entirely. For example, the retaining portion may be provided on one side or both sides of the composition portion, around the entire circumference of the side of the composition portion, or partially on a part of the periphery of the composition portion. In these cases, the retaining portion may be configured such that the area of ​​the composition portion in contact with the retaining portion is greater than the area of ​​the composition portion that is not in contact with the retaining portion.

[0055] As shown in Figures 2A and 3A, in the spacer 1, the holding portion 3 has a frame-shaped outer wall portion 3a that contacts the entire outer peripheral end surface of the composition portion 4 in the planar direction and extends in the thickness direction, and has a space inside the outer wall portion 3a that has depth in the thickness direction. In this example, the outer wall portion 3a is provided in a substantially rectangular shape so as to surround the periphery of the composition portion 4 in the planar direction, but is not limited to this. The length in the thickness direction of the holding portion 3 having a space with depth in the thickness direction, that is, the length in the thickness direction of the outer wall portion 3a that contacts the outer peripheral end surface of the composition portion 4 (t3), is not particularly limited, but is preferably equal to or greater than the thickness of the composition portion 4 (t4), and is more preferably larger than the length in the thickness direction of the composition portion 4 (t4).

[0056] In the example shown in Figures 1 and 2A, the length of the holding portion 3 in the thickness direction (t3) is greater than the length of the composition portion 4 in the thickness direction (t4). With the composition portion 4 housed and held in the holding portion 3, both ends of the outer wall portion 3a of the holding portion 3 in the thickness direction are in contact with the exterior material 6, and a gap layer 5 surrounded by the holding portion 3 is secured on the upper surface side of the composition portion 4. The gap layer 5 functions to buffer and absorb the pressing force applied through the surface of the single cells 200 when the battery pack is assembled by placing spacers 1 between the single cells 200, and the pressing force applied directly from the surface of the single cells 200 when the single cells 200 expand. Furthermore, the presence of the gap layer 5 makes it less likely for the composition portion 4 housed in the holding portion 3 to collapse, ensuring shape retention. In addition, the presence of the gap layer 5 allows for the separation of the contribution of compression to external pressure between the holding portion and the composition portion.

[0057] In an internal material where the thickness of the retaining portion is greater than the thickness of the composition portion, the combination of a composition portion that controls heat transfer and a retaining portion that controls compressibility enhances the effect of excellent shape stability even at high temperatures, resistance to rupture, and stable and excellent thermal insulation when the cell becomes hot. In an internal material where the thickness of the retaining portion is greater than the thickness of the composition portion, only the retaining portion is compressed up to a certain external pressure, and above that external pressure, both the retaining portion and the composition portion are compressed together. By separating the contribution of compression to the external pressure, a spacer with desired compression characteristics can be designed.

[0058] [1-2. Exterior Material] The exterior material in the spacer of the present invention covers the inner material and preferably comes into contact with the inner material. The exterior material may be a pair of independent sheets, a pair of partially sealed sheets, or a single sheet folded in half. The spacer of the present invention is not particularly limited, but it is preferably rectangular and is a spacer formed by sealing all four sides of a pair of independent sheets, or a spacer formed by sealing all three sides of a single sheet folded in half. If the inner material includes a composition portion, it is preferable that the composition portion and the exterior material come into contact on at least one side, and more preferably that the composition portion and the exterior material come into contact on both sides. If the inner material of the spacer of the present invention includes a holding portion having an outer wall portion, it is preferable that both ends of the outer wall portion of the holding portion in the thickness direction come into contact with the exterior material. The exterior material in the spacer of the present invention may include multiple layers. The exterior material preferably includes a resin layer, and more preferably includes a metal layer. Furthermore, it is preferable that a first resin layer is included outside the metal layer, centered on the inner material, and more preferably a second layer is included inside the metal layer, and it is even more preferable that the second layer is a sealant resin layer. Furthermore, a reinforcing layer may be included between the metal layer and the second layer.

[0059] When the first intermediate layer in the aforementioned encapsulating material is a resin layer, the outer material includes a sealant resin layer and a metal layer, and it is preferable that the difference between the melting point of the resin contained in the first intermediate layer and the melting point of the resin contained in the sealant resin layer of the outer material is within 100°C, more preferably within 60°C, and even more preferably within 20°C. If the difference in melting points is within the above range, the time it takes for the liquid contained in the inorganic layer to be discharged to the outside of the spacer can be controlled with precision, and it is easier to suppress temperature rise in abnormal situations.

[0060] The thickness of the exterior material is not particularly limited, but considering the thickness of each of the above layers, from the viewpoint of mechanical strength, its thickness is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. Furthermore, in order to ensure flexibility, the thickness of the exterior material is preferably 220 μm or less, more preferably 150 μm or less, and even more preferably 110 μm or less. The resin layer (first layer), metal layer, sealant resin layer (second layer), and reinforcing layer will be described below.

[0061] (Resin layer (first layer)) One embodiment of the resin layer includes at least one of inorganic particles or a flame retardant. There are no particular limitations on the resin layer, and examples include polyolefin resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin resins such as cyclic polyolefins; polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamide resins such as nylon 6, nylon 66, nylon 12, copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolysate (EVOH), polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluororesins, acrylic resins, biodegradable resins, etc. Among these, polyamide resins such as nylon 6 and polyester resins such as polyethylene terephthalate are preferred from the viewpoint of providing heat resistance and mechanical strength as an exterior material. The resin layer may consist of a single layer or two or more layers. If there are two or more layers, different resins may be used, or the same resin may be used. If the resin layer is multilayered, all layers of the multilayer structure are included in the definition of the resin layer.

[0062] There are no particular limitations on the thickness of the resin layer, but from the viewpoint of flexibility, the thickness of the first layer is preferably 10 to 125 μm, and more preferably 10 to 40 μm. The resin layer (first layer) may contain other resins other than polyester, as long as the effects of the present invention are not impaired. Other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamide-imide resins, polyamide-bismaleimide resins, polyetherimide resins, polyetherether ketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine resins.

[0063] (Metal layer) Examples of metal layers include aluminum foil, copper foil, tin foil, nickel foil, stainless steel foil, lead foil, tin-lead alloy foil, bronze foil, iridium foil, and phosphor bronze foil. In particular, aluminum foil, copper foil, and nickel foil are preferred in terms of processability and material availability, and aluminum foil is more preferred from the viewpoint of low density and ease of handling.

[0064] While there are no particular restrictions on the thickness of the metal layer as long as it is 5 μm or more, it is preferable that it be 8 μm or more, and more preferably 12 μm or more, from the viewpoint of suppressing the occurrence of pinholes. Furthermore, from the viewpoint of ensuring flexibility, it is preferable that it be 50 μm or less, more preferably 35 μm or less, and even more preferably 20 μm or less.

[0065] (Sealant resin layer (second layer)) Examples of sealant resins include polyolefin resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin resins such as cyclic polyolefins; polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyvinyl butyral resins; acrylic resins; biodegradable resins, etc. Among these, it is preferable to use at least one selected from polyolefin resins such as high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLPDE), and polypropylene resin, in order to obtain the function of releasing the liquid inside the outer casing to the outside of the spacer in the event of abnormal heat generation. Furthermore, it is even more preferable to use unstretched polypropylene resin in order to obtain long-term storage properties within the temperature range normally used as a spacer for a battery pack and in terms of versatility.

[0066] There are no particular restrictions on the thickness of the sealant resin layer, but from the viewpoint of ensuring sealing performance, its thickness is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, in order to ensure flexibility, the thickness of the sealant resin layer is preferably 120 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less.

[0067] (Reinforcement layer) The exterior material may further include a reinforcement layer between the metal layer and the second layer. The reinforcement layer is not particularly limited and can include, for example, polyolefin resins such as homopolymers or copolymers of ethylene, propylene, butene, etc.; amorphous polyolefin resins such as cyclic polyolefins; polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamide resins such as nylon 6, nylon 66, nylon 12, copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolysate (EVOH), polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluororesins, acrylic resins, biodegradable resins, etc. Among these, polyamide resins such as nylon 6 and polyester resins such as polyethylene terephthalate are preferred from the viewpoint of providing heat resistance and mechanical strength as an exterior material, and polyamide resins such as nylon 6 are more preferred from the viewpoint of improving the pinhole resistance of the metal layer. The reinforcing layer may be a single layer or two or more layers may be laminated. In the case of two or more layers, different resin layers may be selected, or the same resin layers may be selected.

[0068] There are no particular restrictions on the thickness of the reinforcing layer, but from the viewpoint of providing mechanical strength, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. To ensure flexibility, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

[0069] [2. Battery Pack] The battery pack of the present invention includes the spacer of the present invention and a plurality of individual cells. For example, as shown in Figure 9, a plurality of individual cells 200 and spacers 1 that separate each of the individual cells 200 are stacked and housed in a housing 300, for example. The spacers 1 are provided at least between each individual cell 200 that constitute the battery pack 100, so that the individual cells 200 do not come into contact with each other. In addition to being placed between each individual cell 200, the spacers of the present invention can also be used as spacers (1A) to separate the individual cells 200 from other components. Here, "other components" means, for example, a housing that has a bottom surface and four sides and houses the individual cells and spacers that constitute the battery pack, and in Figure 9, it is the bottom of the housing. The orientation of the spacers 1 in the battery pack during use is not particularly limited, and the thickness direction of the spacers 1 may be parallel to the horizontal plane or intersect with the horizontal plane.

[0070] As described above, the spacer 1 comprises an internal material having a composition part and a holding part used as needed, and an external material that houses the internal material. In this specification, the compressive deformation rate of the spacer is the stress at which the thickness in the thickness direction of the spacer becomes 70% of that when unpressurized, and is preferably in the range of 0.1 to 20 MPa. If the stress at which the compressive deformation rate becomes 70% is 0.1 MPa or more, an appropriate stress can be applied to the single cell, and the single cell can be securely fixed. From this viewpoint, the stress at which the compressive deformation rate becomes 70% is more preferably 0.2 MPa or more, even more preferably 0.5 MPa or more, particularly preferably 0.8 MPa or more, and most preferably 1.0 MPa or more. On the other hand, regarding the upper limit, from the viewpoint of being able to absorb stress due to swelling during charging and discharging, and further, expansion during deterioration over time, thereby extending the lifespan of the cell, it is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less.

[0071] In this specification, the thickness change rate of the spacer is the ratio of the thickness of the spacer after applying a stress of 0.5 MPa to the thickness of the spacer in the thickness direction when not pressurized, and is preferably 0.10 or more and less than 0.95, more preferably 0.20 or more and less than 0.90, even more preferably 0.30 or more and 0.90 or less, especially preferably 0.40 or more and 0.90, and particularly preferably 0.50 or more and 0.90.

[0072] Spacers can be used as is to separate individual cells or cells from other components, but to make them easier to secure when separating cells or cells from other components, adhesive or double-sided tape may be applied to their surface, or pieces of resin may be attached to their surface.

[0073] (Single Cell) The single cell is preferably a lithium-ion secondary battery comprising a positive electrode and a negative electrode capable of intercalating and releasing lithium ions, as well as an electrolyte. In addition to lithium-ion secondary batteries, other secondary batteries such as lithium-ion solid-state batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lead-acid batteries can also be used. Furthermore, the single cell can be of any type, such as a prismatic single cell, a pouch-type single cell, or a cylindrical single cell.

[0074] Figure 10 is a plan view showing an example of a single cell 200 that constitutes a battery pack, Figure 11 is a front view of the single cell 200 shown in Figure 10, and Figure 12 is a right side view of the single cell 200. The single cell 200 is formed in the shape of a rectangular parallelepiped having a height direction (H), a width direction (W), and a thickness direction (D), and terminals 210 and 220 are provided on its upper surface.

[0075] The battery pack according to this embodiment, as described above, is applicable to battery packs installed in, for example, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric heavy machinery, electric motorcycles, electric assist bicycles, ships, aircraft, trains, uninterruptible power supplies (UPS), home energy storage systems, and battery storage systems for stabilizing power grids using renewable energy such as wind, solar, tidal, and geothermal power. However, the battery pack can also be used as a power source to supply power to devices other than the EVs mentioned above.

[0076] [3. Method for Producing the Gel Composition] The method for producing the hydrogel of this embodiment will be described below. For example, four different synthesis routes with different raw materials and gelation reactions can be cited. In this specification, "sol composition" means the solution and dispersion prepared in each mixing step.

[0077] (3-1. First Synthesis Route) The first synthesis route of the hydrogel of this embodiment will be described below, step by step.

[0078] (3-1-1. Mixing Step) The mixing step is a step in which a metal alkoxide (e.g., silicon alkoxide) is mixed with a solvent and hydrolyzed to produce a sol. In the mixing step, a catalyst may be added to the solvent to promote the hydrolysis reaction.

[0079] The metal alkoxide may contain at least one of the following metallic elements: silicon (Si), aluminum (Al), titanium (Ti), zirconium (Zr), hafnium (Hf), yttrium (Y), vanadium (V), cerium (Ce), lanthanum (La), neodymium (Nd), samarium (Sm), praseodymium (Pr), holmium (Ho), or molybdenum (Mo).

[0080] As a silicon alkoxide, it is sufficient to have at least one of a hydrolyzable functional group and a condensing functional group, and it may also have both a hydrolyzable functional group and a condensing functional group. For example, at least one of tetraethoxysilane, trimethoxysilane, tetramethoxysilane, triethoxysilane, tripropoxysilane, tetrapropoxysilane, and tripbutoxysilane may be used as the silicon alkoxide. In addition, silicon alkoxides having functional groups other than hydrolyzable and condensing functional groups may also be used. Examples include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylphenyldimethoxysilane, and methylphenyldiethoxysilane.

[0081] Examples of hydrolyzable functional groups include alkoxy groups. Examples of condensing functional groups (excluding those that fall under the category of hydrolyzable functional groups) include hydroxyl groups, silanol groups, carboxyl groups, and phenolic hydroxyl groups. Hydroxyl groups may be contained within hydroxyl group-containing groups such as hydroxyalkyl groups. Hydrolyzable and condensing functional groups may be used individually or in combination of two or more types.

[0082] As a solvent, for example, water or a mixture of water and an organic solvent can be used. As the organic solvent, a solvent that is miscible with water is preferable because it facilitates the solvent substitution step described later, and alcohols are preferred. Examples of alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol. Among these, methanol, ethanol, and 2-propanol are examples of alcohols with low surface tension and low boiling points that reduce interfacial tension with the gel wall. These may be used individually or in mixtures of two or more. The weight ratio of the solvent to the silicon alkoxide can be arbitrarily selected, but from the viewpoint of operability and economics, for example, 0.5 to 5.0 times is preferable.

[0083] The catalyst is not particularly limited, but an acid catalyst is preferred. Examples of acid catalysts include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromate, chloric acid, chlorous acid, and hypochlorous acid; acidic phosphates such as acidic aluminum phosphate, acidic magnesium phosphate, and acidic zinc phosphate; and organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred from an economic standpoint. These may be used individually or in combination of two or more types.

[0084] (3-1-2. Gelation Process) The gelation process involves gelling the sol obtained in the mixing process and then maturing it to obtain a wet gel. In this process, a base catalyst can be used to promote gelation. Examples of base catalysts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; and ammonium hydroxide. Among these, ammonium hydroxide (ammonia water) is superior in terms of cost-effectiveness. The above base catalysts may be used individually or in combination of two or more types.

[0085] By using a base catalyst, the dehydration condensation reaction or dealcoholization condensation reaction of metal alkoxides in the sol can be accelerated, allowing the sol to gel in a shorter time.

[0086] (3-1-3. Aging Process) The aging process may be carried out in a sealed container to prevent the solvent and base catalyst from volatilizing. Aging strengthens the bonds between the components constituting the wet gel, resulting in a wet gel with sufficient strength to suppress shrinkage during drying. Alternatively, the aging process may be carried out by impregnating the gel with a solvent. It is preferable to use the same solvent as used in the mixing process. Note that the process may be skipped and the next step may be initiated.

[0087] The maturation temperature can be, for example, 15 to 80°C, but is preferably 20 to 70°C, and more preferably 25 to 60°C. By setting the maturation temperature to 15°C or higher, a wet gel with higher strength can be obtained, and by setting the maturation temperature to 70°C or lower, the volatilization of the solvent (especially alcohols) is more easily suppressed, so maturation can be performed while suppressing volume shrinkage.

[0088] The maturation time varies depending on the maturation temperature. The maturation time can be, for example, 1 second to 24 hours, but preferably 1 second to 12 hours, and more preferably 1 to 3 hours. If the maturation time is 1 second to 3 hours, it is easier to obtain a wet gel with weak bonding, and if it is 3 to 24 hours, it is easier to obtain a wet gel with stronger bonding.

[0089] In the maturation process, the maturation temperature may be increased within the above range, or the maturation time may be extended within the above range, in order to increase the density of the resulting hydrogel or increase the strength of the bonds. Conversely, the maturation temperature may be lowered within the above range, or the maturation time may be shortened within the above range, in order to decrease the density of the resulting hydrogel or decrease the strength of the bonds.

[0090] (3-1-4. Modification Process) The modification process involves modifying the surface of the network structure with organic groups to increase the strength of the hydrogel skeleton. TMCS (Trimethylchlorosilane) is an example of an organic compound used in the modification process. Details of the modification process are described, for example, in Koji Tajiri's "Study on the Preparation of Silica Aerogel and its Modified Forms, and Evaluation of its Structure and Thermal and Mechanical Properties" (Nagoya Institute of Technology Doctoral Dissertation (2002), pp. 56-73). Note that the process may be skipped and proceeded to the next step.

[0091] The reactive groups used to modify the surface of the network structure with organic groups are preferably hydrolyzable and condensable functional groups, but are not limited to these. They may also be reactive groups in silicon alkoxides having hydrolyzable or condensable functional groups, further comprising reactive groups different from hydrolyzable and condensable functional groups (functional groups that do not fall under the category of hydrolyzable or condensable functional groups). Examples include epoxy groups, mercapto groups, glycidoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, and amino groups. Epoxy groups may be included in epoxy-containing groups such as glycidoxy groups.

[0092] Examples of reactive groups used to modify the surface of the network structure with organic groups include halogens, amino groups, imino groups, carboxyl groups, alkoxyl groups, hydroxyl groups, alkyl groups, phenyl groups, alkyl group fluorides, and phenyl group fluorides. The network structure may have only one of these reactive groups, or two or more. Specifically, examples include organic silane compounds such as hexamethyldisilazane, hexamethyldisiloxane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, triethylmethoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, methyltrichlorosilane, and ethyltrichlorosilane. In addition, organic compounds such as carboxylic acids like acetic acid, formic acid, and succinic acid, and alkyl halides like methyl chloride can also be used.

[0093] (3-1-5. Solvent Replacement Process) The solvent replacement process is a process in which the solvent of the wet gel is replaced with a predetermined replacement solvent. In this process, the solvent of the wet gel is ultimately replaced with water. The solvent of the wet gel is replaced by placing the wet gel in any container and adding a sufficient amount of solvent to the container for the wet gel to be impregnated. At this time, heating can be used to improve the replacement efficiency. In the solvent replacement process, in order to maintain the desired structure of the wet gel, it is necessary to gradually replace the solvent of the wet gel from the solvent used in the mixing process to water. To do this, the solvent replacement process is divided into multiple steps. In the first solvent replacement step, a mixed solvent of the solvent used in the mixing process and water is used for solvent replacement. In the second and subsequent solvent replacement steps, the proportion of water in the mixed solvent of the solvent used in the mixing process and water is gradually increased to perform solvent replacement. In the final solvent replacement step, only water is used as the solvent for solvent replacement. If necessary, the solvent replacement process using only water as the solvent may be performed multiple times. The amount of solvent used in the mixing step in the wet gel should be 10% by mass or less relative to 100% by mass of the wet gel, and preferably 5% by mass or less, more preferably 2% by mass or less, from the viewpoint of easily maintaining a high thermal conductivity at room temperature. When replacing the solvent impregnating the wet gel in each solvent replacement step, any method can be used as long as the structure of the wet gel is maintained, for example, the solvent can be replaced by decantation or a transfer pump.

[0094] (3-1-6. Aging Process) Aging may be performed on the hydrogel after solvent replacement is complete, and the method in this case can be the same as the aging process described above. However, when aging the hydrogel by impregnating it with a solvent, water shall be used as the solvent.

[0095] (3-1-7. Washing Process) In the washing process, the wet gel obtained in the wet gelation process, maturation process, solvent replacement process, and modification process is washed to remove unreacted substances and by-products from each process. This washing can be repeated using, for example, water or an organic solvent. The washing efficiency can be improved by heating during this process. If the modification process and maturation process are performed after the solvent replacement process, and then the washing process is performed, the solvent replacement process should be performed again.

[0096] Various organic solvents can be used, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, methylene chloride, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid. These organic solvents may be used individually or in combination of two or more.

[0097] The amount of water or organic solvent used in the washing process can be sufficient to adequately replace the solvent in the wet gel and wash it thoroughly. Any washing method can be selected, such as decantation or sprinkling wash. The temperature environment in the washing process can be kept below the boiling point of the solvent used for washing; for example, when using hexane, the temperature can be raised to about 30-60°C.

[0098] (3-2. Second Synthesis Route) The following describes each step of the second synthesis route for the hydrogel of this embodiment.

[0099] (3-2-1. Mixing Process) The mixing process in the second synthesis route involves mixing the silicate source with water and an acidic ion exchange resin to remove alkali metal ions or alkaline earth metal ions from the silicate source and produce a silicate sol. The mixing process is carried out until the pH of the solution reaches 2 to 4, and the acidic ion exchange resin is removed by filtration or the solution is recovered by decantation.

[0100] Sources of silicate include sodium silicate, potassium silicate, and lithium silicate. Examples of sodium silicate include sodium silicate No. 1, sodium silicate No. 2, sodium silicate No. 3, or natural silicate minerals, and sodium metasilicate (Na). ２ SiO ３ ), sodium orthosilicate (Na ４ SiO ４ ), sodium disilicate (Na ２ Si ２ O ５ ), sodium tetrasilicate (Na ２ Si４ O ９ A solution of ) dissolved in caustic soda can be used. can also be used. Furthermore, natural silicate minerals, sodium metasilicate (Na) can be used. ２ SiO ３ ), sodium orthosilicate (Na ４ SiO ４ ), sodium disilicate (Na ２ Si ２ O ５ ), sodium tetrasilicate (Na ２ Si ４ O ９ ) may be an anhydrous form or a hydrate (for example, Na ２ SiO ３ 9H ２ O) is also acceptable.

[0101] The weight ratio of water to the silicate source should be, for example, 3 to 10 times. The amount of water used will be the amount of water contained in the hydrogel, and from the viewpoint of making it easier to maintain a high thermal conductivity at room temperature, it is preferable to use at least 3 times the amount of water. The acidic ion exchange resin is not particularly limited, but a strongly acidic ion exchange resin having a sulfonic acid group is preferred. Specific examples of acidic ion exchange resins include cation exchange resins SK1B-H, SK110-H, PK216-H, PK220-H manufactured by Mitsubishi Chemical Corporation, or cation exchange resins AMBERLITE IR120B-H, AMBERLITE IR124-H manufactured by DuPont. The acidic ion exchange resin may be washed with methanol before use. After washing until the methanol used for washing no longer discolors, it should be washed with water before use. The amount of acidic ion exchange resin used should be sufficient to remove alkali metal ions or alkaline earth metal ions contained in the silicate source, and the amount to be used should be determined from the ion exchange capacity of the acidic ion exchange resin.

[0102] (3-2-2. Gelation Process) The gelation process is the same as (3-1-2. Gelation Process).

[0103] By using a base catalyst, the condensation reaction of silicic acid in the sol can be accelerated, allowing the sol to gel in a shorter time.

[0104] (3-2-3. Maturation Process) The maturation process is the same as (3-1-3. Maturation Process). In this maturation process, the gel may be impregnated with water.

[0105] (3-2-4. Modification Step) The modification step is the same as (3-1-4. Modification Step). If the second synthesis route has a modification step, it is preferable to further include solvent replacement steps before and after the modification step. The modification step is the same as (3-1-5. Solvent Replacement Step). In the solvent replacement step before the modification step, it is preferable to gradually replace the water used in the mixing step with a mixed solvent of water and an organic solvent, and in the solvent replacement step after the modification step, it is preferable to gradually replace the solvent used in the modification step with water.

[0106] (3-2-5. Washing Process) The washing process is the same as (3-1-7. Washing Process).

[0107] (3-3. Third Synthesis Route) The following describes each step of the third synthesis route for the hydrogel of this embodiment.

[0108] (3-3-1. Mixing Process) The mixing process involves mixing aqueous silica sol with water to prepare the sol. Any aqueous silica sol can be used, but an example is "Snowtex" manufactured by Nissan Chemical Corporation. Any particle size and particle shape of silica particles in the aqueous silica sol can be used.

[0109] (3-3-2. Gelation Process) The gelation process is the same as (3-1-2. Gelation Process).

[0110] (3-3-3. Maturation Process) The maturation process is the same as (3-1-3. Maturation Process). In this maturation process, the gel may be impregnated with water.

[0111] (3-3-4. Modification Process) The modification process is the same as (3-2-4. Modification Process).

[0112] (3-3-5. Washing Process) The washing process is the same as (3-1-7. Washing Process).

[0113] (3-4. Fourth Synthesis Route) The following describes each step in the fourth synthesis route of the hydrogel of this embodiment.

[0114] (3-4-1. Mixing step) The mixing step is a process of preparing a sol by mixing a silicic acid source and water, similar to the second synthesis route.

[0115] (3-4-2. Gelation Process) The gelation process involves gelling the sol obtained in the mixing process and then maturing it to obtain a wet gel. In this process, a curing agent can be used to promote gelation. While known curing agents can be used, it is preferable to use at least one curing agent selected from acids, carbon dioxide, polyvalent metal salts, polyhydric alcohols, and acetate esters. The gelation reaction time can be controlled by the pH, concentration, temperature, and mixing rate of the reaction solution.

[0116] (3-4-3. Maturation Process) The maturation process is the same as (3-1-3. Maturation Process). In this maturation process, the gel may be impregnated with water.

[0117] (3-4-4. Modification Process) The modification process is the same as (3-2-4. Modification Process).

[0118] (3-4-5. Washing Process) The washing process is the same as (3-1-7. Washing Process).

[0119] [4. Method for Manufacturing a Spacer] One embodiment of the present invention is a method for manufacturing a spacer comprising an internal material. The manufacturing method includes, in this order, a manufacturing step for the internal material and a step for housing the internal material in an outer packaging material. From the viewpoint of increasing the burst pressure, the manufacturing method preferably further includes a sealing step for the outer packaging material. From the viewpoint of improving the thermal properties, the manufacturing method preferably includes a manufacturing step for the gel composition disclosed in "3. Method for Manufacturing a Gel Composition", and may be included in any of the above steps.

[0120] (4-1. Manufacturing process of encapsulating material) The encapsulating material preferably contains at least a sol composition or a gel composition, and may be the sol composition or gel composition itself (Aspect 1), a sol composition or gel composition in contact with a porous body (Aspect 2), or a sol composition or gel composition filled into a holding part (Aspect 3). This step is a step for manufacturing the encapsulating material. In the case of Aspect 1, the sol composition or gel composition described in "3. Method for manufacturing a gel composition" may be prepared and the encapsulating material may be manufactured. In the case of Aspect 2, the silica sol described in "3. Method for manufacturing a gel composition" may be impregnated into a porous body, or the prepared gel composition may be laminated onto a porous body to manufacture the encapsulating material. In the case of Aspect 3, the silica sol described in "3. Method for manufacturing a gel composition" may be filled into a holding part, or the prepared gel composition may be filled into a holding part to manufacture the encapsulating material.

[0121] (4-2. Process of housing the encapsulated material in the outer packaging material) This process involves housing the encapsulated material in the outer packaging material. The encapsulated material may be a gel composition prepared after housing a sol composition in the outer packaging material, or the prepared gel composition may be housing the outer packaging material. The outer packaging material may be a pair of independent sheets, a pair of partially sealed sheets, or a single sheet folded in half.

[0122] (4-3. Sealing Process of Outer Packaging) This process involves sealing the outer packaging containing the inner encapsulant. The inner encapsulant may be prepared from a sol composition into a gel composition after sealing the outer packaging, or the prepared gel composition may be contained in and sealed within the outer packaging. When sealing the outer packaging, it is preferable that the outer packaging includes a sealant resin layer. The sealant resin layers can be sealed by heat fusion. It is preferable that the outer packaging is sealed so that there are no gaps through which the contained inner encapsulant can leak out.

[0123] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0124] (1) The moisture adhering to the surface for measuring the liquid absorption rate was removed using filter paper, and the sample was prepared. Sample (thickness 2 mm, density 0.85 g / cm³) ３Three 50mm x 50mm test pieces were taken from the sample and their mass was measured. Water was placed in a polypropylene container (volume 1680 ml), and the test pieces were immersed for at least 15 minutes. After that, the test pieces were removed from the water, sandwiched between two sheets of dry filter paper (Advantec Toyo Co., Ltd., model No. 514A, thickness 0.32 mm, 150mm x 150mm), and a metal plate (Misumi Co., Ltd., made of SUS430, 150mm x 100mm x 10mm, 1.3 kg) was placed on top to compress them for 1 minute. After the compression was released, the mass of the test pieces was measured immediately. The pressure due to the 1.3 kg metal plate load was 0.05 kgf / cm². ２ This is appropriate. Another test specimen, removed from the water, was placed between two pieces of filter paper, and a metal plate and a load cell (Showa Sokki Co., Ltd., model number: RCD-50kN) were placed on top in that order. The load was adjusted to 125 kg using a vise press machine MP-001 (AS ONE Corporation). After compression for 1 minute, the compression was released and the mass of the test specimen was measured immediately. The pressure applied by the vise press machine was 5 kgf / cm². ２ This is reasonable. The liquid absorption rate of each test specimen was determined three times according to the following formulas, and the average value was calculated. [Liquid absorption rate 1 (%)] = (m2 - m1) / m1 × 100 ... (Formula A) [Liquid absorption rate 2 (%)] = (m3 - m1) / m1 × 100 ... (Formula B) [Ratio of liquid absorption rates] = [Liquid absorption rate 2] / [Liquid absorption rate 1] ... (Formula C) However, m1 is the mass (g) of the test specimen before liquid absorption. m2 is the mass (g) of the test specimen after liquid absorption under a load of 1.3 kg (0.05 kgf / cm²). ２ m3 is the mass (g) after compression with a load of 125 kg (5 kgf / cm²) on the test specimen after liquid absorption. ２ This is the mass (g) of the test specimen after compression.

[0125] (2) Thermal conductivity measurement The thermal conductivity of the spacer at 45°C is measured simultaneously with the spacer by heating a thermal resistance sheet, whose thermal conductivity has been evaluated in advance, to 45°C. When the temperature difference between the front and back of the thermal resistance sheet is Δt1 and the temperature difference between the front and back of the spacer is Δt2, the thermal conductivity of the spacer is calculated using the relationship formula "Δt1 × thermal conductivity of the thermal resistance sheet / Δt2". The difference in thickness between the spacer and the thermal resistance sheet is converted as appropriate. (3) Plateau time measurement The partition members made in each experimental example were evaluated for their heat insulation properties using a test apparatus as shown in Figure 12. Specifically, the partition member 1 was placed on a brass metal plate 403 with a thickness of 1 mm, and a brass metal block 402 with a thickness of 5 mm was set on top of the partition member 1. The metal plate 403, partition member 1, and metal block 402 were covered with heat insulating material 401, except for the lower part of the metal plate 403. Nitrogen gas heated to 300°C by two tube heaters 404 was blown onto the metal plate 403 from below, and the temperature of the metal block 402 located at the top of the partition member 1 was measured. The time during which the temperature of the metal block 402 measured in this heating test was maintained within the range of 100°C ± 5°C was measured as the plateau time.

[0126] (Example 1) In a 50 mL two-necked flask fitted with a reflux condenser and thermocouple, 20 g of tetraethoxysilane, 17.24 g of ethanol, 74.88 μL of 1 mol / L hydrochloric acid, and 1.730 g of water were weighed and stirred until homogeneous. Once the solution was homogeneous, it was heated while stirring until the internal temperature reached 60°C, and then heated and stirred for 1.5 hours after the internal temperature reached 60°C. After that, heating was stopped while continuing to stir, and when the internal temperature fell below 40°C, 4.326 g of water and 37.0 μL of 28% aqueous ammonia were added and stirred until homogeneous. This solution was poured into a polypropylene container without overflowing, another polypropylene container was placed on top, and it was left to stand at 25°C for 24 hours. After 24 hours, the obtained silica gel was placed in a polypropylene container, and an amount of deionized water / ethanol (25 / 75, v / v) sufficient to fully immerse the gel was added to the container, and it was left to stand at 25°C for 24 hours. Subsequently, the liquid in the container was removed by decantation, and an amount of deionized water / ethanol (50 / 50, v / v) sufficient to fully immerse the gel was added and left to stand at 25°C for 24 hours. Subsequently, the liquid in the container was removed by decantation, and an amount of deionized water / ethanol (75 / 25, v / v) sufficient to fully immerse the gel was added and left to stand at 25°C for 24 hours. Subsequently, the liquid in the container was removed by decantation, and an amount of deionized water sufficient to fully immerse the gel was added and left to stand at 25°C for 24 hours. Subsequently, the liquid in the container was removed by decantation, and an amount of deionized water sufficient to fully immerse the gel was added and left to stand at 25°C for 24 hours to obtain a silica hydrogel. In the liquid absorption rate measurement of the silica hydrogel, the ratio of [liquid absorption rate 2] to [liquid absorption rate 1] was 1.0. The 30% mass loss temperature of the silica hydrogel was 56.9°C. The mass loss rate of the silica hydrogel from 30°C to 100°C was 0.81 mass% / °C. The silica hydrogel was used as an encapsulant and placed between a pair of films containing a first resin layer consisting of a polyethylene terephthalate layer and a nylon layer, a metal layer consisting of an aluminum layer, and a sealant layer consisting of a polypropylene layer. The periphery was sealed to manufacture a spacer. The spacer had a thermal conductivity of λ at T°C. Ｔ is λ ４０ >λ １８０ It met the requirements.

[0127] (Example 2) Sodium silicate solution (approximately 38%, SiO₂) in a beaker ２ / Na ２ 10.6 g of silica gel (O ratio = 3.0-3.3) and 39.8 g of deionized water were added and stirred until homogeneous. Then, 50 mL of AMBERLITE IR120B H (DuPont), which had been washed sequentially with methanol and deionized water, was added and stirred with a mechanical stirrer until the pH reached 2-3, at which point stirring was stopped. The supernatant was collected by decantation. 1 M aqueous ammonia was added dropwise to the collected supernatant to adjust the pH of the solution to 4-5. This solution was poured into a polypropylene container without overflowing, another polypropylene container was placed on top, and the mixture was left to stand at 25°C for 24 hours. After 24 hours, the obtained silica gel was placed in a polypropylene container, an amount of deionized water sufficient to fully immerse the gel was added, and the mixture was left to stand at 25°C for 24 hours to obtain silica hydrogel. In the absorption rate measurement of the silica hydrogel, the ratio [absorption rate 2] / [absorption rate 1] was 1.0. The silica hydrogel was used as an encapsulant and placed between a pair of films containing a first resin layer (a polyethylene terephthalate layer and a nylon layer), a metal layer (an aluminum layer), and a sealant layer (a polypropylene layer), and the periphery was sealed to manufacture a spacer. The spacer has a thermal conductivity of λ at T°C. Ｔ is λ ４０ >λ １８０ It met the requirements.

[0128] (Example 3) Sodium silicate solution (approximately 37%, SiO₂) in a beaker ２ / Na ２24.5 g of (O ratio = 2.0-2.1) and 50.5 g of deionized water were added and stirred until homogeneous. Then, while stirring this solution, 23.8 mL of 7.3 M phosphoric acid aqueous solution was added dropwise and stirred until homogeneous. A porous material (120 mm x 65 mm, 1 mm thick) was impregnated into this solution for 5 minutes. The impregnated insulating paper was removed from the solution, the naturally dripping water droplets were removed, and it was placed in a polypropylene container. Then, to prevent the evaporation of moisture, the polypropylene container containing the porous material was placed in a resealable plastic bag and left to stand at 25°C for 24 hours to obtain a porous material impregnated with silica hydrogel. The porous material impregnated with silica hydrogel was used as an encapsulant and placed between a pair of films containing a first resin layer (polyethylene terephthalate layer and nylon layer), a metal layer (aluminum layer), and a sealant layer (polypropylene layer), and the periphery was sealed to manufacture a spacer. The S1 / (S1+S2) of the spacer in a plan view in the thickness direction was 0.82. S4 is 2350mm ２ The thermal conductivity ratio of the spacer was λ １８０ / λ ４０ The value was 0.23. The plateau time for the spacer was 825 seconds.

[0129] (Example 4) The spacer was manufactured under the same conditions as in Example 3, except that the size of the porous body was changed so that S1 / (S1+S2) in a plan view in the thickness direction of the spacer was 0.61, without changing the overall dimensions of the spacer. S4 was 4700 mm. ２ The compression deformation rate (MPa) of the spacer was 1.2 MPa or more, and the thickness change rate (dimensionless) was 0.87.

[0130] 1 Spacer 2 Encapsulating material 3 Holding part (tray-shaped member) 4 Composition part (heat transfer control layer) 5 Void layer 6 Outer material 7 Smallest rectangle surrounding the tray-shaped member 100 Battery pack 200 Single cell 210 Terminal 220 Terminal 300 Housing 400 Thermal insulation performance evaluation tester 401 Thermal insulation material 402 Metal block 403 Metal plate 404 Tube heater D Thickness direction

Claims

1. A spacer that separates a single cell from another component, wherein the thermal conductivity λ in the thickness direction at the average surface temperature T°C of the spacer is... Ｔ The following formula 1 is satisfied, the spacer includes an exterior material and an inner material housed in the exterior material, the inner material comprises a composition portion containing a liquid and a material that absorbs the liquid, and the material has a pressure of 0.05 kgf / cm². ２ When compressed for 1 minute, the liquid absorption rate is 5 kgf / cm² relative to a pressure of 1. ２ A spacer such that the ratio of liquid absorption rates when compressed for 1 minute satisfies the following equation 2. Equation 1: λ ４０ >λ １８０ Formula 2: [Liquid absorption rate 2] / [Liquid absorption rate 1]≧0.81 2. The spacer according to claim 1, wherein the spacer includes a sealing portion, and in a plan view from the thickness direction of the spacer, the area S1 of a first region where the exterior material and the composition portion overlap and the sealing portion is excluded, and the area S2 of a second region where the exterior material and the composition portion do not overlap and the sealing portion is excluded, satisfy the following formula 3, and the burst pressure of the spacer is 9.0 MPa or more. Formula 3: 0.60 ≤ S1 / (S1 + S2) ≤ 1.00 3. The spacer according to claim 1, wherein the compression deformation rate at which the thickness of the spacer in the thickness direction becomes 70% of that when not pressurized is 0.5 MPa or more.

4. λ in Equation 1 ４０ λ for １８０ The spacer according to claim 1, wherein the ratio is less than 0.

50.

5. The spacer according to claim 1, wherein the composition portion is a single molded body.

6. The spacer according to claim 1, wherein the composition portion comprises a material capable of chemically interacting with the liquid.

7. The spacer according to claim 1, wherein the composition portion comprises a gel composition.

8. The spacer according to claim 1, wherein the composition portion comprises a gel composition, and the 30% mass loss temperature of the gel composition is 40 to 125°C.

9. The spacer according to claim 1, wherein the composition portion comprises a gel composition, the gel composition comprises a polymer that holds a liquid, and the liquid content is more than 60% by mass and 99% by mass or less based on 100% by mass of the gel composition.

10. The composition portion comprises a gel composition, and the density of the gel composition at 25°C, as measured by the liquid weighing method, is 0.90 to 1.90 g / cm³. ３ The spacer according to claim 1 or 2.

11. The spacer according to claim 1 or 2, wherein the composition portion comprises a gel composition, and the gel composition comprises a polymer of a silicon-containing compound.

12. The composition part contains a gel composition, the gel composition contains a polymer of a silicon-containing compound, and the polymer of the silicon-containing compound contains siloxane units (Q units) represented by SiO ４／２ units, siloxane units (T units) represented by R １ SiO ３／２ units, siloxane units (D units) represented by R ２ R ３ SiO ２／２ units, and one or more units selected from the group consisting of siloxane units (M units) represented by R ４ R ５ R ６ SiO １／２ units (where R １ to R ６ each independently represent an alkyl group or an aryl group bonded to a silicon atom). When the molar percentages of the Q unit, the T unit, the D unit, and the M unit are Qx, Tx, Dx, and Mx, respectively, 80 ≦ Qx ≦ 100, 0 ≦ Tx ≦ 20, 0 ≦ Dx ≦ 20, 0 ≦ Mx ≦ 20, and Qx + Tx + Dx + Mx = 100 are satisfied. The spacer according to claim 1 or 2.

13. The spacer according to claim 1 or 2, wherein the encapsulating material further comprises a holding portion, the holding portion having an outer wall portion that contacts at least a portion of the outer peripheral end surface in the planar direction of the composition portion and extends in the thickness direction.

14. The spacer according to claim 1, wherein the exterior material includes a metal layer and the composition portion is in contact with the exterior material.

15. A battery pack comprising a single cell and the spacer described in claim 1 or 2.

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