JP7797782B2 - Partition member and battery pack - Google Patents

Description

The present invention relates to a partition member and a battery pack.

In recent years, secondary batteries have seen a rapid increase in use as power sources for vehicles and other devices. Research is underway to increase the energy density of secondary batteries in order to improve flexibility when installing them in limited spaces such as vehicles, and to extend the driving distance that can be traveled on a single charge. However, the safety of secondary batteries tends to be at odds with their energy density, and the higher the energy density of a secondary battery, the lower its safety tends to be. For example, in the case of secondary batteries installed in electric vehicles with driving ranges of several hundred kilometers, if the secondary battery is damaged by overcharging or an internal short circuit, the battery surface temperature can exceed several hundred degrees Celsius, sometimes reaching 1,000 degrees Celsius or more.

Secondary batteries used as power sources for vehicles, etc., are generally used as battery packs consisting of multiple cells. Therefore, if one of the cells in the battery pack is damaged and reaches the temperature range described above, the heat generated may damage adjacent cells, causing a chain reaction of damage that may spread to the entire battery pack. To prevent this chain reaction of damage between cells, various technologies have been proposed that install partition members between cells and cool damaged cells.

For example, there is a module in which a partition member made of a sheet-like bag filled with a coolant such as water is placed between unit cells (see, for example, Patent Document 1). This module efficiently transfers heat generated from adjacent unit cells to nearby units. In addition, if an adjacent unit cell is damaged and the battery surface becomes hot, the water in the bag is released from the opening, cooling the damaged battery. Another partition member is made of a sheet-like bag filled with a porous material impregnated with a coolant such as water (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2014-157747 JP 2011-108617 A

After detailed investigation of these conventional technologies, the inventors found the following problems. Specifically, the cells in a battery pack are subjected to confining pressure during battery assembly manufacturing. Furthermore, when a cell is charged, the electrodes inside the cell expand, causing the cell's casing to expand and press against adjacent components. Furthermore, repeated use of the cell causes gas to be generated from the electrolyte inside the cell, causing the cell to expand and exert pressure. For these reasons, the partition members installed between the cells are required to be pressure-resistant. However, the pressure-resistant properties of the partition members disclosed in Patent Documents 1 and 2 have not been fully investigated.

The inventors have proposed a partition member that includes a liquid-holding insulating material and an exterior housing that houses the insulating material. This partition member has the property of switching its thermal resistance around the temperature (opening temperature) at which the vapor pressure of the liquid exceeds the burst strength of the exterior housing. Below the opening temperature, the partition member exhibits low thermal resistance due to the liquid held inside the exterior housing, while above the opening temperature, the liquid evaporates and the remaining insulating material exhibits high thermal resistance. Due to this property, the partition member in contact with a cell that has experienced an abnormal temperature rise due to overcharging, internal short circuit, etc. opens, and its high thermal resistance suppresses heat conduction to adjacent cells. Meanwhile, the partition members between cells other than the abnormal cell have low thermal resistance, suppressing the temperature rise of each battery due to heat transfer from the abnormal cell.

Under the above circumstances, a partition member is required to have good elasticity and pressure resistance to absorb the expansion of the cells and maintain the performance of the cells under normal conditions. On the other hand, it is required to efficiently transfer heat generated from adjacent cells to nearby cells, and to prevent a chain reaction of temperature rises between the cells in abnormal conditions where an abnormal temperature rise in an adjacent cell could spread to the entire battery pack.
That is, an object of the present invention is to provide a partition member that can achieve high levels of performance required under normal conditions and performance required under abnormal conditions, and a battery pack using the partition member.

After extensive research to solve the above problems, the inventors discovered that the above problems could be solved by incorporating a layer that controls heat transfer and a layer that controls compressibility into the partition member of a battery pack, and thus completed the present invention. Specifically, the present invention is as follows:

[1] A partition member having a thickness direction and a surface direction perpendicular to the thickness direction, which separates cells in the thickness direction, or between cells and components other than cells, the partition member including a heat transfer control layer, a compressibility control layer, and an exterior body that houses these.
[2] A partition member described in [1] above, wherein the compressibility control layer is a tray-shaped member having a plurality of recesses, and the heat transfer control layer is composed of a paste containing at least one selected from the group consisting of heat-resistant particles and heat-resistant fibers and a liquid.
[3] The partition member according to the above [2], wherein the paste is filled in the recess of the tray-shaped member.
[4] The partition member according to [2] or [3] above, wherein the liquid is water.
[5] The partition member according to the above [1], wherein the compressibility control layer is a tray-shaped member having a plurality of recesses, and the heat transfer control layer is made of heat-resistant particles.
[6] The partition member according to any one of the above [2] to [5], wherein the tray-shaped member is made of a thermoplastic resin.
[7] The partition member according to the above [6], wherein the thermoplastic resin is an olefin-based resin.
[8] The partition member according to the above [7], wherein the olefin-based resin is polypropylene.
[9] The partition member according to any one of the above [2] to [8], wherein the heat-resistant particles are at least one selected from the group consisting of calcium silicate and zeolite.
[10] A battery pack including the partition member according to any one of [1] to [9] above and a plurality of unit cells.

The present invention provides a partition member and battery assembly that, under normal circumstances, exhibits good elasticity and pressure resistance, and can efficiently transfer heat generated from adjacent cells to nearby cells, while also preventing damage from spreading between cells in the event of an abnormality that could result in damage to adjacent cells and spreading to the entire battery assembly.

1 is a photograph showing one embodiment of the compressibility control layer of the present invention. FIG. 2 is a conceptual diagram showing an example of a partition member of the present invention. FIG. 10 is a conceptual diagram showing another example of the partition member of the present invention. 1 is a conceptual diagram showing a battery pack of the present invention. FIG. 2 is a plan view showing an example of a unit cell. FIG. 6 is a front view of the cell of FIG. 5 . FIG. 6 is a side view of the cell of FIG. 5 . FIG. 1 is a conceptual diagram of a heat insulation evaluation device.

An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below, and can be implemented with any modifications within the scope of the gist of the present invention.
In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also means "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is stated that "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[Partition member]
The partition member of the present invention has a thickness direction and a plane direction perpendicular to the thickness direction, and is a member that separates cells in the thickness direction or separates cells from components other than cells. Here, the "components other than cells" refers to, for example, a housing that has a bottom and four side surfaces and that houses the cells and the partition member that constitute the battery pack.
The partition member of the present invention includes a heat transfer control layer, a compressibility control layer, and an exterior body that houses them. A single partition member may contain a plurality of heat transfer control layers and a plurality of compressibility control layers.

<Heat transfer control layer>
The partition member of the present invention is characterized by having a heat transfer control layer. The heat transfer control layer is a layer that can efficiently transfer heat generated from adjacent cells to nearby cells under normal conditions and, in an abnormal condition, exhibits heat insulating properties and controls the transfer of heat to the adjacent cells. Specifically, heat-resistant particles or a paste of heat-resistant particles and a liquid (hereinafter, sometimes referred to as a "heat-resistant particle paste") is preferably used.
In the present invention, it is particularly preferable to use a heat-resistant particle paste. The liquid contained in the heat-resistant particle paste volatilizes when one of the cells generates abnormal heat, thereby absorbing the heat of vaporization from the surroundings and suppressing the temperature rise, and heat can also be released by escaping the volatilized gas.
On the other hand, a configuration may be adopted in which heat-resistant particles are used without using a liquid, and by combining the compressibility control layer and the exterior body to form a partition member, the partition member can absorb the expansion of the unit cells despite being a powder.In addition, the partition member has high pressure resistance and will not burst or otherwise occur when the unit cells expand.

(Heat-resistant particles and heat-resistant fibers)
The heat-resistant particles are not particularly limited as long as they achieve the effects of the present invention, but inorganic particles are preferred, such as silica particles, alumina particles, calcium silicate, zeolite, diatomaceous earth, shirasu balloons, 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 particularly preferred because they allow a larger amount of liquid to be contained within and between the particles.
Among the types of calcium silicate, xonotlite, tobermorite, wollastonite, and gyrolite are preferred, with gyrolite being particularly 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 are mainly magnesium silicate (including talc and sepiolite), montmorillonite, and kaolinite. The particle diameter of the heat-resistant particles is preferably 1/5 or less of the thickness of the heat transfer control layer. These heat-resistant particles can be used alone or in a mixture of multiple types.
The heat-resistant fiber is not particularly limited as long as it achieves the effects of the present invention, and examples thereof include glass fiber, alumina fiber, and rock wool. The fiber diameter of the heat-resistant fiber is preferably 1/5 or less of the thickness of the heat transfer control layer. These heat-resistant fibers can be used alone or in combination.
When the heat-resistant fiber is made into a paste with a liquid, the fiber diameter and fiber length are not particularly limited as long as they can be made into a paste. Generally, a relatively small fiber diameter and a relatively short fiber length are advantageous for making into a paste.
The heat-resistant particles and the heat-resistant fibers can also be used in combination.

(liquid)
The liquid for turning the particles into a paste may be any liquid that has thermal conductivity and can efficiently transfer heat generated from a cell to a neighboring cell, and preferably has a boiling point of 80°C or higher and 250°C or lower at normal pressure (1 atmosphere), more preferably 100°C or higher and 150°C or lower at normal pressure.
The liquid preferably contains at least one selected from the group consisting of water, alcohols, esters, ethers, ketones, hydrocarbons, fluorine-based compounds, and silicone-based oils. These may be used alone or as a mixture of two or more. Furthermore, water is particularly preferred as the liquid because of its large heat of vaporization and its general availability.

Alcohols that can be used in the liquid include alcohols containing 3 to 8 carbon atoms, such as propanol, isopropanol, butanol, benzyl alcohol, and phenylethyl alcohol; alkylene glycols, such as ethylene glycol and propylene glycol; and dihydric or higher alcohols, such as glycerin. These can be used alone or as a mixture of two or more.

Esters that can be used in liquids include alkyl aliphatic carboxylic acid esters, alkyl carbonate diesters, alkyl oxalic acid diesters, and fatty acid esters of ethylene glycol. These can be used alone or as a mixture of two or more.

Ethers that can be used in liquids include n-butyl ether, n-propyl ether, and isoamyl ether. These can be used alone or as a mixture of two or more.

Ketones that can be used in liquids include methyl ethyl ketone and diethyl ketone. These can be used alone or as a mixture of two or more.

Hydrocarbons that can be used as liquids include heptane, octane, nonane, decane, toluene, and xylene. These can be used alone or as a mixture of two or more.

Fluorine-based compounds that can be used in liquids include the refrigerants 1,1,2,2,3,3,4-heptafluorocyclopentane (HFC-c447ef) and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane (HFC-76-13sf). These can be used alone or as a mixture of two or more.

Examples of silicone-based oils that can be used in the liquid include modified silicone oils such as methylpolysiloxane, methylphenylpolysiloxane, cyclic methylsiloxane, and silicone polyether copolymers. These can be used alone or as a mixture of two or more types.

The liquid may also contain additives such as antifreeze, preservatives, pH adjusters, and surfactants. The surfactant can help adjust the compatibility of the heat-resistant particle paste or heat-resistant fiber paste when filling the tray-shaped member. The liquid may also contain a gelling agent to create a gel. The above additives can be used alone or as a mixture of two or more. The liquid is not limited to these additives, and can be added as needed.

The heat transfer control layer described above is enclosed within the exterior packaging, which will be described later. However, if a heat-resistant particle paste or powdered heat-resistant particles is used, it is preferable to have a member for holding them. This member is preferably a tray-shaped member that functions as the compressibility control layer, which will be described later.

<Compressibility control layer>
The compressibility control layer in the present invention is a layer that functions to absorb expansion due to normal charging of the unit cell, expansion due to deterioration of the unit cell, expansion when the battery is used at high temperatures, etc. Specifically, a tray-shaped member (hereinafter sometimes referred to as a "tray-shaped member") having multiple recesses as shown in FIG. 1 is exemplified. The presence of such recesses is preferable because it allows the aforementioned heat-resistant particles or heat-resistant particle paste to be held. Furthermore, the use of a compressibility control layer is preferable because it allows the compression characteristics to be controlled as a partition member while using heat-resistant particles, heat-resistant fibers, heat-resistant particle paste, and heat-resistant fiber paste.
That is, the tray-shaped member has the function of filling and holding heat-resistant particles or heat-resistant particle paste suitable as a heat transfer control layer in the recesses of the tray-shaped member, and also has the function of a compressibility control layer.
In the present invention, even in an embodiment in which a tray-shaped member is filled with a heat-resistant particle paste or the like, the tray-shaped member is defined as a compressibility control layer, and the heat-resistant particle paste or the like filled in the recesses is defined as a heat transfer control layer. The heat-resistant particles (powder) or heat-resistant particle paste may be filled so that the recesses of the tray-shaped member are completely filled (see FIG. 2), or may be filled to a portion of the depth of the recesses. It is also not necessary to fill all of the recesses with heat-resistant particles or heat-resistant particle paste. Furthermore, as long as the tray-shaped member and heat-resistant particles or the like are loaded into the exterior body, it is acceptable for the heat-resistant particles or the like to overflow from the recesses of the tray-shaped member (see FIG. 3).

The size of the recesses in the tray-shaped member is not particularly limited as long as the effects of the present invention are achieved. For example, when viewed from above, the area of the recesses relative to the total area of the tray-shaped member is preferably in the range of 5 to 99%, more preferably 10 to 95%, and even more preferably 20 to 90%. When the area of the recesses is equal to or greater than the above-mentioned lower limit, a sufficient amount of heat-resistant particle paste or the like can be retained within the recesses, thereby maintaining heat transfer control and heat insulation. On the other hand, when the area is equal to or less than the above-mentioned upper limit, sufficient strength of the tray-shaped member is ensured, and good elasticity is obtained. Furthermore, when the area is equal to or less than the above-mentioned upper limit, the internal pressure of the partition member is less likely to increase when pressurized, improving the pressure resistance of the partition member.
The depth of the recess is not particularly limited, but is preferably in the range of 0.1 to 20 mm, more preferably in the range of 0.5 to 10 mm, and even more preferably in the range of 0.8 to 7 mm. If the depth is equal to or greater than the lower limit, a sufficient amount of heat-resistant particle paste or the like can be retained in the recess, thereby maintaining heat transfer control and heat insulation effects. On the other hand, if the depth is equal to or less than the upper limit, sufficient strength of the tray-shaped member is ensured, good elasticity is obtained, and the battery pack can be made compact. Furthermore, if the depth is equal to or less than the upper limit, more expansion of the unit cells can be absorbed.

The shape of the recesses is not particularly limited either, and may be a square as shown in Fig. 1, a rectangular shape such as a rectangle or a diamond, or a circular shape, an elliptical shape, a honeycomb shape, etc. Furthermore, the recesses do not all have to have the same shape, and may be a combination of different shapes.
The number of recesses is also not particularly limited as long as it has the above-mentioned area ratio, and it is usually preferable that it is about 0.1 to 5 recesses per unit area (1 cm ² ), and more preferably 0.25 to 2 recesses.
The thickness of the tray-shaped member (sheet thickness) is preferably in the range of 50 to 1000 μm, and more preferably in the range of 100 to 500 μm. If the thickness of the tray-shaped member is equal to or greater than the lower limit, sufficient elasticity is obtained. On the other hand, if the thickness is equal to or less than the upper limit, the thickness of the partition member can be made thinner, which increases the proportion of the unit cells and improves energy efficiency. This also leads to a more compact battery pack.
The recess may also have through holes in the thickness direction of the member. The ratio of the area of the through holes to the area of the normal recess is preferably about 10 to 100%, and more preferably 50 to 90%. The presence of through holes makes it possible to hold a larger amount of heat-resistant particle paste, etc., and achieve better heat transfer control and heat insulation effects. When the ratio of the area of the through holes to the area of the normal recess is equal to or greater than the above lower limit, better heat transfer control and heat insulation effects are achieved, and when it is equal to or less than the above upper limit, the tray-shaped member is better able to hold the heat-resistant particle paste, etc.

The material for the tray-shaped member is preferably a thermoplastic resin, as it has good elasticity and excellent processability. Examples include olefin-based 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-based resins are preferred, with polypropylene being particularly preferred, in terms of versatility and cost. These resins may also contain heat-resistant fillers such as alumina particles and glass fiber.

There are no particular limitations on the method for manufacturing the tray-shaped member, but suitable methods include, for example, preparing a resin sheet such as polypropylene and vacuum molding or press molding it, or creating a mold for the tray-shaped member and pouring molten resin into it using injection molding.

<Exterior body>
The exterior body has a sealed peripheral portion, and the heat transfer control layer and compressibility control layer are housed in an internal space formed by the sealing. The exterior body is flexible and can deform in response to the expansion of the unit cells. Furthermore, the exterior body can return to its original state when the unit cells contract. Specifically, when the battery expands due to charging, the exterior body is compressed to absorb the expansion, and when the battery contracts due to discharging, the exterior body returns to its original state.
The outer casing may be a resin sheet, a resin film, or the like. For example, the heat transfer control layer and the compressibility control layer are sandwiched between two or two-folded resin sheets or resin films, and the peripheral portions of the outer casing where the two resin sheets or resin films come into contact are heat-sealed or glued together to seal the heat transfer control layer and the compressibility control layer.

The outer casing can be made of, for example, resin or metal. A laminate of metal foil and resin is preferred because of its high heat resistance and strength. A metal-resin laminate is preferably a laminate of three or more layers including a resin layer, a metal layer, and a resin sealant layer.

The metal constituting the metal foil is preferably at least one of aluminum, copper, tin, nickel, stainless steel, lead, tin-lead alloy, bronze, silver, iridium, and phosphor bronze. Specific examples include aluminum foil, copper foil, tin foil, nickel foil, stainless steel foil, lead foil, tin-lead alloy foil, bronze foil, silver foil, iridium foil, and phosphor bronze foil. Aluminum foil, copper foil, and nickel foil are particularly preferred, with aluminum foil being even more preferred.

At least one of thermosetting resins and thermoplastic resins can be used as the resin, with thermoplastic resins being particularly preferred. Examples of resins include polyethylene, polypropylene, polystyrene, nylon, acrylic, epoxy resin, polyurethane, polyether ether ketone, polyethylene terephthalate, polyphenyl sulfide, polycarbonate, and aramid. At least one selected from polypropylene, nylon, and polyethylene terephthalate is particularly preferred.

The thickness of the outer casing is not particularly limited, but is, for example, 5 μm to 200 μm. In the case of the above-mentioned laminate, the metal foil can be 3 μm to 50 μm thick, and the resin layer can be 2 μm to 150 μm thick. This allows the metal foil to exhibit its heat resistance and low water vapor permeability, while the resin improves sealing properties.

The heat transfer control layer and compressibility control layer may be sealed within the exterior body by joining the peripheral edges of two exterior bodies into a ring shape using heat fusion, adhesive, or the like. Alternatively, one exterior body may be folded and the peripheral edges joined using heat fusion, adhesive, or the like, thereby sealing the heat transfer control layer and compressibility control layer. It is preferable that the exterior body be flexible (elastic), but it may not be flexible.

It is preferable for the internal air pressure of the exterior body to be lower than the external air pressure in order to ensure a sufficiently high opening temperature. For this reason, it is particularly preferable to vacuum seal the exterior body.

[Battery assembly]
The battery pack of the present invention includes the partition member of the present invention and a plurality of cells. More specifically, as shown in Fig. 4, a plurality of cells 200 and partition members 1 that separate the cells 200 are stacked together, and are housed in, for example, a housing 300. The partition members 1 are provided at least between the cells 200 that make up the battery pack 100, preventing the cells 200 from contacting each other. The partition member can also be used as a partition member (1A) that separates the cells 200 from other components (the bottom of the housing in Fig. 4) in addition to separating the cells 200.

As described above, the partition member 1 comprises a heat transfer control layer, a compressibility control layer, and an exterior body that houses these. The compressive modulus of the partition member in the thickness direction is preferably in the range of 0.1 to 20 MPa. By setting the compressive modulus to 0.1 MPa or more, an appropriate stress can be applied to the single battery cells, enabling the single battery cells to be securely fixed. From the above perspectives, the compressive modulus is preferably 0.2 MPa or more, and more preferably 0.5 MPa or more. Meanwhile, the upper limit is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less, from the viewpoint of absorbing stresses due to swelling during charge and discharge, as well as expansion during deterioration over time, thereby enabling the cell to have a long life.
The compressive modulus (23°C) is generally a value measured in accordance with JIS K7181. However, in the present invention, the compressive modulus is evaluated by simply measuring the pressure and thickness of the partition member when pressure is applied so that the thickness of the partition member becomes approximately 95% to 50% of the thickness when no pressure is applied, and calculating the ratio to the thickness when no pressure is applied.
The partition member can be used as is to separate the cells or the cells from other components, but to make it easier to fix the cells when separating them from one another or from other components, adhesive or double-sided tape may be attached to the surface, or a piece of resin or the like may be attached to the surface.

[Single cell]
The unit cell is preferably a lithium ion secondary battery having a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, and an electrolyte. In addition to the lithium ion secondary battery, other secondary batteries such as a lithium ion all-solid-state battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc. may also be used.
Furthermore, the type of the cell may be a prismatic cell, a pouch-shaped cell, a cylindrical cell, or the like, and the present invention is applicable regardless of the type of battery.
Fig. 5 is a plan view showing an example of a cell 200 constituting a battery pack, Fig. 6 is a front view of the cell 200 shown in Fig. 5, and Fig. 7 is a right side view of the cell 200. The 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 the upper surface thereof.

The battery pack according to the present embodiment described above is applicable to battery packs mounted in, for example, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric heavy machinery, electric motorcycles, electrically assisted bicycles, ships, aircraft, trains, uninterruptible power supplies (UPSs), home energy storage systems, and storage battery systems for stabilizing power grids that utilize renewable energy sources such as wind, solar, tidal, and geothermal. However, the battery pack can also be used as a power source to supply power to devices other than the above-mentioned EVs.

(Evaluation method)
Evaluation method 1 (thermal insulation)
The heat insulating properties of the partition members produced in each example and comparative example were evaluated using a test device such as that shown in Fig. 8. Specifically, the partition member 1 was placed on a brass metal plate 403 having a thickness of 1 mm, and a brass metal block 402 having 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 a 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 located above the partition member 1 was measured.

Evaluation method 2 (compressive elastic modulus)
The thickness of the partition members produced in each example and comparative example was evaluated when a pressure of 1.4 MPa was applied in examples 1 to 4, and 1.5 MPa in comparative example 1, and the compressive elastic modulus was evaluated by calculating the ratio to the thickness when no pressure was applied.

Example 1
A tray-shaped member as shown in Figure 1 was fabricated by vacuum molding using a 0.3 mm thick polypropylene sheet. The shape of the lowest part of the recess was a square of 7.79 mm x 7.79 mm, and the depth was 2 mm. The area ratio of the recess in plan view to the total area was 61%. The tray-shaped member was 60 mm long and 120 mm wide.
Next, as shown in Figure 2, calcium silicate paste (heat-resistant particle paste 3) was filled into the recesses of the tray-shaped member 2, and the tray-shaped member 2 was placed inside an aluminum laminate film (containing resin layers of polyethylene terephthalate (outer) 0.012 mm thick, nylon (inner) 0.015 mm thick, and polypropylene (innermost) 0.06 mm thick) as an exterior body 4, and the resulting product was sealed (hermetically sealed) using a vacuum sealer to obtain a partition member. The overall thickness of the partition member was 2.5 mm.
The produced partition members were evaluated by the above-mentioned evaluation methods, and the evaluation results are shown in Table 1. The calcium silicate paste was prepared as follows.
(Calcium silicate paste)
0.87 g of calcium silicate was added to 9.13 g of water and mixed with a stirring rod at room temperature for 5 minutes to obtain a calcium silicate paste.

Example 2
A partition member was obtained in the same manner as in Example 1, except that a zeolite paste prepared by using 4.2 g of zeolite 13X and 5.3 g of water was used instead of calcium silicate in Example 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 3
A partition member was obtained in the same manner as in Example 1, except that a zeolite paste prepared by using 5.0 g of zeolite 4A and 5.3 g of water was used instead of calcium silicate in Example 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 4
A partition member was obtained in the same manner as in Example 1, except that calcium silicate powder was used instead of the calcium silicate paste in Example 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Comparative Example 1
A porous sheet (calcium silicate paper, length 118 mm, width 61 mm, thickness 1.8 mm) serving as a heat insulating material was placed within an aluminum laminate film (containing a 0.012 mm thick polyethylene terephthalate (outer), a 0.015 mm thick nylon (inner), and a 0.06 mm thick polypropylene (innermost) resin layer) serving as an exterior. After placing the heat insulating material within the exterior, it was saturated with 5.0 g of water and then sealed (hermetically sealed) using a vacuum degassing sealer to obtain a partition member. The overall thickness of the partition member was 2.0 mm. The results of evaluation similar to Example 1 are shown in Table 1.

As can be seen from Table 1, Examples 1 to 3 showed a slower temperature rise and a higher compressive modulus of elasticity than Comparative Example 1. Furthermore, the results of Example 4 show that even when only powder was used without liquid, the modulus of elasticity was equivalent to that of Comparative Example 1, which used water. In this way, it was confirmed that the partition member of the present invention exhibits the same effect as the conventional partition member (Comparative Example 1), even without the use of liquid.

The partition member of the present invention exhibits good elasticity and pressure resistance under normal conditions, and can efficiently transfer heat generated from adjacent cells to nearby cells. In addition, in the event of an abnormality where damage to adjacent cells could spread in a chain reaction to the entire battery pack, the partition member can prevent damage from spreading between cells.
Therefore, a battery pack using the partition member of the present invention is promising as a secondary battery that has a high energy density and is highly safe, for example as a power source for vehicles.

1 Partition member 2 Tray-shaped member (compressibility control layer)
3. Heat-resistant particle paste (heat transfer control layer)
4 Exterior body 100 Battery pack 200 Cell 210 Terminal 220 Terminal 300 Housing 400 Heat insulation evaluation tester 401 Heat insulating material 402 Metal block 403 Metal plate 404 Tube heater t Depth D of recess in tray-shaped member Thickness direction P Surface direction H Height direction W Width directions TC1, TC2, TC3 Thermocouple

Claims (13)

a partition member having a thickness direction and a plane direction perpendicular to the thickness direction, which separates cells in the thickness direction or separates cells from members other than the cells, the partition member including a heat transfer control layer, a compressibility control layer, and an exterior body that houses these;
The compressible control layer has a recess, and the ratio of the area of the recess to the total area is 5 to 99%. a partition member having a thickness direction and a plane direction perpendicular to the thickness direction, which separates cells in the thickness direction or separates cells from members other than the cells, the partition member including a heat transfer control layer, a compressibility control layer, and an exterior body that houses these;
The compressibility control layer has recesses, and the number of the recesses per unit area is 0.1 to 5. a partition member having a thickness direction and a plane direction perpendicular to the thickness direction, which separates cells in the thickness direction or separates cells from members other than the cells, the partition member including a heat transfer control layer, a compressibility control layer, and an exterior body that houses these;
the compressible control layer has a recess;
The partition member has a compressive elastic modulus of 0.1 to 20 MPa.
The compressive modulus of elasticity is determined by measuring the thickness of the partition member when pressure is applied so that the thickness of the partition member is 95% of the thickness when no pressure is applied, and expressing the ratio to the thickness when no pressure is applied. The partition member described in any one of claims 1 to 3, wherein the compressibility control layer is a tray-shaped member having multiple recesses, and the heat transfer control layer is composed of a paste containing at least one material selected from the group consisting of heat-resistant particles and heat-resistant fibers, and a liquid. The partition member according to claim 4, wherein the paste is filled into the recessed portion of the tray-shaped member. A partition member according to claim 4 or 5, wherein the liquid is water. The partition member described in any one of claims 1 to 3, wherein the compressibility control layer is a tray-shaped member having multiple recesses, and the heat transfer control layer is composed of at least one material selected from the group consisting of heat-resistant particles and heat-resistant fibers. The partition member according to any one of claims 4 to 7, wherein the tray-shaped member is made of a thermoplastic resin. A partition member according to any one of claims 1 to 8, wherein the recess has a depth in the thickness direction. The partition member according to claim 8 , wherein the thermoplastic resin is an olefin-based resin. The partition member according to claim 10, wherein the olefin-based resin is polypropylene. 12. The partition member according to claim 4, wherein the heat-resistant particles are at least one selected from the group consisting of calcium silicate and zeolite. A battery pack comprising the partition member according to any one of claims 1 to 12 and a plurality of unit cells.