阅读说明：本技术 橡胶成型体及电池组 (Rubber molded body and battery pack ) 是由 芦田桂子 厨子敏博 于 2020-06-18 设计创作，主要内容包括：本发明涉及一种橡胶成型体,其附设于具有安全阀或排气孔的一个以上的锂离子二次电池芯的外周而至少覆盖所述安全阀或所述排气孔,根据JIS H7903：2008,利用单向热流稳态比较法测得的导热度(测定温度：33℃)小于1.0W/m·K,覆盖上述安全阀或上述排气孔的部分的厚度为0.3mm以上且10.0mm以下,基于JIS K6253,利用A型硬度计测得的表面硬度为50以上且90以下。(The present invention relates to a rubber molded body which is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a gas discharge hole so as to cover at least the safety valve or the gas discharge hole, and which has a shape of a sheet according to JIS H7903: 2008, a heat conductivity (measurement temperature: 33 ℃) measured by a one-way heat flow steady-state comparison method is less than 1.0W/mK, a thickness of a portion covering the safety valve or the exhaust hole is 0.3mm or more and 10.0mm or less, and a surface hardness measured by a type A durometer is 50 or more and 90 or less in accordance with JIS K6253.)

1. A rubber molded body which is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a gas discharge hole so as to cover at least the safety valve or the gas discharge hole,

according to JIS H7903: 2008, the heat conductivity measured by the unidirectional heat flow steady state comparison method is less than 1.0W/m.K, wherein the measurement temperature is 33 ℃,

the thickness of the portion covering the safety valve or the exhaust hole is 0.3mm to 10.0mm,

the surface hardness measured by a type A durometer is 50 or more and 90 or less in accordance with JIS K6253.

2. A rubber molded body which is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole so as to cover at least the safety valve or the vent hole,

the rubber molded body is formed and cured from a silicone rubber composition containing, per 100 parts by mass of organopolysiloxane, 10 to 100 parts by mass of powdered silica, 10 to 50 parts by mass of a layered silicate, 0.5 to 20 parts by mass of titanium oxide, and 4.0 to 14.0 parts by mass of a curing agent.

3. A rubber molded body which is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a gas discharge hole so as to cover at least the safety valve or the gas discharge hole,

the rubber molded body is obtained by molding and curing a silicone rubber composition containing, per 100 parts by mass of an organopolysiloxane, 10 to 100 parts by mass of a powdered silica, 10 to 50 parts by mass of a layered silicate, 0.5 to 20 parts by mass of a titanium oxide, and 4.0 to 14.0 parts by mass of a curing agent,

the rubber molded article was prepared according to JIS H7903: 2008, the heat conductivity measured by the unidirectional heat flow steady state comparison method is less than 1.0W/m.K, wherein the measurement temperature is 33 ℃,

the thickness of the portion of the rubber molded body covering the safety valve or the exhaust hole is 0.3mm to 10.0mm,

the rubber molded article has a surface hardness of 50 or more and 90 or less as measured by a type a durometer in accordance with JIS K6253.

4. The rubber molded article according to claim 1, wherein the elongation at the time of cutting of the rubber molded article is 80% or more and 500% or less.

5. The rubber molded article according to claim 2, wherein the elongation at the time of cutting of the rubber molded article is 80% or more and 500% or less.

6. A rubber molded article according to claim 3, wherein the elongation at the time of cutting of the rubber molded article is 80% or more and 500% or less.

7. The rubber molded body according to any one of claims 1 to 6, wherein the rubber molded body has a shape of a sheet, a belt or a cap.

8. An assembled battery comprising one or more lithium ion secondary battery cells, wherein the rubber molded article described in any one of claims 1 to 7 is attached to the outer periphery of the battery cells.

9. The battery pack according to claim 8, wherein at least a part of the outer peripheral surface of the lithium ion secondary battery cell is coated with a putty-like composition having thermal conductivity.

Technical Field

The present invention relates to a rubber molded article obtained by molding and curing a rubber composition, and a battery pack including a lithium ion secondary battery cell to which the rubber molded article is attached.

Background

In recent years, demand for lithium ion secondary batteries (hereinafter, also referred to as "batteries") has increased. On the other hand, with the progress of miniaturization and high energy density (energy density of 300Wh/kg or more), there is a risk of heat generation and high temperature depending on the usage. Therefore, the safety of the battery or the battery pack becomes more important.

For example, if a lithium ion secondary battery is overcharged or overdischarged, or is subjected to an accidental impact to cause an internal short circuit or an external short circuit, there is a risk of thermal runaway being induced. In a lithium ion secondary battery in which thermal runaway occurs, gas is generated to increase the internal pressure of the battery. In this case, the internal pressure may increase to cause breakage of the package can, and therefore, these batteries are provided with a vent hole for venting air, a safety valve, and the like.

In addition, when thermal runaway occurs, there is a risk of ignition due to an overheated battery or the like, and in order to prevent ignition and burnout, for example, in patent document 1, the surface of the battery is covered with an ignition preventing sheet.

However, high-temperature/high-pressure gas may be ejected from an exhaust hole or a safety valve provided in the lithium ion secondary battery, which has been subjected to thermal runaway, to exhaust the gas. According to the description of non-patent document 1, although the temperature is instantaneous, the maximum temperature may exceed 999 ℃.

Therefore, the fire-retardant sheet of patent document 1 is provided for protection against flames (i.e., fire-retardant) derived from the high-temperature gas.

[ patent document 1] Japanese patent application laid-open No. 2019-032923

[ non-patent document 1] pine village tree, pine island and male traffic safety environment institute forum lecture summary/traffic safety environment institute compile 135 + 138,2012 (pine village tree , pine island and male traffic safety ring environment institute フォーラム summarization/traffic safety ring environment institute compile 135 + 138,2012)

However, in recent years, as the energy density of batteries has increased, the pressure of gas discharged during thermal runaway has increased significantly. Due to the high pressure of the gas, the fireproof sheet of patent document 1 may be damaged. Specifically, for example, in the case of the flameproof sheet made of fibers described in patent document 1, the mesh of the fibers is expanded by the high pressure of the gas, and in the case of the flameproof sheet made of a resin, the strength of the flameproof sheet is reduced to such a level that the sheet cannot withstand the high pressure and is burnt out in a softened state of the resin before reaching a burning state, and therefore, in any case, there is a risk that: the flame-retardant sheet has a through-hole, and the high-temperature/high-pressure gas discharged from the through-hole burns a member other than the flame-retardant sheet (for example, a package case in which a battery is housed) to burn it, and finally burns it to a device or a vehicle in which the battery is mounted.

Also, there is a risk that: air (oxygen) is supplied from the through-hole, and the battery itself is burned or extended to cause thermal runaway of the adjacent normal lithium ion secondary battery.

Disclosure of Invention

The present invention has been made in view of the above-described background, and an object thereof is to provide a rubber molded article capable of suppressing scorching or burning even when high-temperature/high-pressure gas is ejected from a safety valve or an exhaust hole of a lithium ion secondary battery due to thermal runaway of the lithium ion secondary battery, and a battery pack including a lithium ion secondary battery cell to which the rubber molded article is attached.

To achieve the above object, the present invention is configured as follows.

(1) The rubber molded article of the present invention is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a gas discharge hole so as to cover at least the safety valve or the gas discharge hole, and is characterized in that the rubber molded article is a molded article obtained by molding a rubber composition according to JIS H7903: 2008, a heat conductivity (measurement temperature: 33 ℃) measured by a one-way heat flow steady-state comparison method is less than 1.0W/mK, a thickness of a portion covering the safety valve or the exhaust hole is 0.3mm or more and 10.0mm or less, and a surface hardness measured by a type A durometer is 50 or more and 90 or less in accordance with JIS K6253.

According to the present invention, since the rubber molded body having the heat conductivity, thickness, and surface hardness within the predetermined ranges is attached so as to cover the safety valve or the exhaust hole of the lithium ion secondary battery cell, even if the lithium ion secondary battery is thermally runaway, the rubber molded body can suppress burning and burnout due to ejection of high-temperature/high-pressure gas, and no through-hole is generated due to the high-temperature/high-pressure gas ejected from the safety valve or the exhaust hole.

(2) The rubber molded body is formed and cured from a silicone rubber composition containing, per 100 parts by mass of organopolysiloxane, 10 to 100 parts by mass of powdered silica, 10 to 50 parts by mass of a layered silicate, 0.5 to 20 parts by mass of titanium oxide, and 4.0 to 14.0 parts by mass of a curing agent, the powdered silica being attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or an exhaust hole and covering at least the safety valve or the exhaust hole.

According to the present invention, since the rubber molded body obtained by molding and curing the silicone rubber composition in a predetermined compounding ratio is attached so as to cover the safety valve or the exhaust hole of the lithium ion secondary battery cell, even if the lithium ion secondary battery is thermally runaway, the rubber molded body can be prevented from generating a through hole due to the high-temperature/high-pressure gas ejected from the safety valve or the exhaust hole, and burning and burnout due to the ejection of the high-temperature/high-pressure gas can be suppressed.

(3) The rubber molded body of the present invention is formed by molding and curing a silicone rubber composition containing, per 100 parts by mass of organopolysiloxane, 10 to 100 parts by mass of powdered silica, 10 to 50 parts by mass of a layered silicate, 0.5 to 20 parts by mass of titanium oxide, and 4.0 to 14.0 parts by mass of a curing agent, the powdered silica being attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or an exhaust hole and covering at least the safety valve or the exhaust hole,

the rubber molded article was prepared in accordance with JIS H7903: 2008, a heat conductivity (measurement temperature: 33 ℃) measured by a one-way heat flow steady state comparison method is less than 1.0W/m.K, a thickness of a portion of the rubber molded body covering the safety valve or the exhaust hole is 0.3mm or more and 10.0mm or less, and a surface hardness measured by a type A durometer based on JIS K6253 is 50 or more and 90 or less.

According to the present invention, since the rubber molded body is attached so as to cover the safety valve or the exhaust hole of the lithium ion secondary battery cell, the rubber molded body is molded and cured from the silicone rubber composition having a predetermined compounding ratio, and the heat conductivity, the thickness, and the surface hardness are within predetermined ranges, even if the lithium ion secondary battery is thermally out of control, the rubber molded body does not generate a through hole due to the high-temperature/high-pressure gas ejected from the safety valve or the exhaust hole, and the burning and burning caused by the ejection of the high-temperature/high-pressure gas can be suppressed.

(4) In a preferred embodiment of the rubber molded article of the present invention, the elongation at the time of cutting of the rubber molded article is 80% or more and 500% or less.

According to this embodiment, when the rubber molded body is attached to the lithium ion secondary battery cell, the rubber molded body is attached to the lithium ion secondary battery cell so that tension is applied to the rubber molded body in close contact with the safety valve or the exhaust hole of the lithium ion secondary battery cell, and the thickness of the portion covering the safety valve or the exhaust hole is maintained at a desired thickness.

(5) In another embodiment of the rubber molded article of the present invention, the rubber molded article has a sheet-like, belt-like or cap-like shape.

According to this embodiment, when the rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell so as to cover the safety valve or the exhaust hole, the rubber molded body can be attached in a preferable form according to the shape of the rubber molded body.

(6) The assembled battery of the present invention includes one or more lithium ion secondary battery cells in which the rubber molded body of any one of (1) to (5) is attached to the outer periphery.

According to the present invention, since the rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell so as to cover the safety valve or the exhaust hole, even if thermal runaway occurs in the lithium ion secondary battery, the rubber molded body can suppress the delay of burning or burnout of the battery pack due to the ejection of high-temperature/high-pressure gas, and the occurrence of a through hole due to the high-temperature/high-pressure gas ejected from the safety valve or the exhaust hole is prevented.

(7) In a preferred embodiment of the present invention, at least a part of the outer peripheral surface of the lithium ion secondary battery cell is coated with a putty-like composition having thermal conductivity.

The putty-like composition preferably has a thermal conductivity (W/m.K) of 1.5 or more and 16.0 or less.

According to this embodiment, since at least a part of the outer peripheral surface of the lithium ion secondary battery cell is coated with the putty-like composition having thermal conductivity, even if the lithium ion secondary battery generates heat due to thermal runaway, the heat can be effectively released to the outside of the lithium ion secondary battery cell, and overheating of the lithium ion secondary battery cell can be suppressed.

As described above, according to the present invention, since the rubber molded body is attached so as to cover the safety valve or the exhaust hole of the lithium ion secondary battery cell, even if thermal runaway of the lithium ion secondary battery occurs, the rubber molded body can suppress burning and burnout due to ejection of high-temperature/high-pressure gas, and a through hole is not generated due to the high-temperature/high-pressure gas ejected from the safety valve or the exhaust hole.

Drawings

Fig. 1 is a perspective view of a lithium-ion secondary battery cell with a rubber molded article according to an embodiment of the present invention attached thereto.

Fig. 2 is a perspective view showing a rubber molded article and a lithium-ion secondary battery cell according to an embodiment of the present invention.

Fig. 3 is a perspective view of a lithium-ion secondary battery cell to which the rubber molded body of fig. 2 is attached.

Fig. 4 is a sectional view taken along line a-a of fig. 3.

Fig. 5 is a perspective view corresponding to fig. 3 of another embodiment of the present invention.

Fig. 6 is a perspective view corresponding to fig. 3 of still another embodiment of the present invention.

Fig. 7 is a sectional view taken along line B-B of fig. 6.

Fig. 8 is a perspective view corresponding to fig. 2 of another embodiment of the present invention.

Fig. 9 is a perspective view of a lithium-ion secondary battery cell to which the rubber molded body of fig. 8 is attached.

Fig. 10 is a schematic configuration diagram of a battery pack according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

Fig. 1 is a perspective view of a lithium-ion secondary battery cell with a rubber molded article according to an embodiment of the present invention attached thereto.

The lithium ion secondary battery cell 1 is a square battery cell, and a positive electrode terminal 3 and a negative electrode terminal 4 are provided on the upper surface of a package can 2 as a battery container, and a safety valve 5 is provided therebetween.

When the lithium ion secondary battery cell 1 is thermally runaway and the internal pressure rises, the safety valve 5 is actuated to prevent the packaging can 2 from being broken due to the ejection of high-temperature/high-pressure gas.

When thermal runaway occurs in the lithium ion secondary battery cell 1, there is a risk of ignition due to overheating, and if the high-temperature/high-pressure gas ejected from the safety valve 5 is diffused in a wide range at once, it is difficult to prevent burning and burnout.

Therefore, in this embodiment, as shown in fig. 2, fig. 3, and fig. 4 which is a cross-sectional view taken along line a-a of fig. 3, a flexible sheet-like rubber molded body 6 is attached to the outer periphery of the lithium ion secondary battery cell 1 via an insulating sheet 7 so as to cover at least the safety valve 5.

In this embodiment, the insulating sheet 7 and the sheet-shaped rubber molded body 6 are both rectangular and have substantially the same size, and are attached so as to cover the upper surface including the safety valve 5 of the rectangular parallelepiped lithium ion secondary battery cell 1 and the upper portions of the front and rear surfaces (left and right surfaces in fig. 4).

Lead wires, not shown, connected to the positive electrode terminal 3 and the negative electrode terminal 4 of the lithium ion secondary battery cell 1 are drawn out through side surfaces not covered with the insulating sheet 7 and the rubber molded body 6.

The lithium ion secondary battery cell 1 provided with the insulating sheet 7 and the sheet-shaped rubber molded body 6 is housed in a packaging case, not shown. In the package case, the rubber molded body 6 covering the upper portions of the front and back surfaces of the lithium ion secondary battery cell 1 is pressed by the inner wall surface of the package case, thereby holding the rubber molded body 6.

The rubber molded body 6 of this embodiment is molded and cured from the following rubber composition, and the rubber molded body 6 is molded and cured according to JIS H7903: 2008, the heat conductivity (measurement temperature: 33 ℃ C.) measured by the single-direction heat flow steady-state comparison method (SCHF) is less than 1.0W/m.K.

If the thermal conductivity is 1.0W/m · K or more, when thermal runaway occurs in the lithium ion secondary battery, heat is conducted to the outer periphery of the rubber molded body 6 through the rubber molded body by high-temperature and high-pressure gas ejected from the safety valve or the exhaust hole, for example, a packing case containing the lithium ion secondary battery cell 1 covered with the disk rubber molded body 6, and the packing case is melted and deformed.

The lower the thermal conductivity, the better, the lower limit of 0.1W/m.K.

In the present embodiment, the thickness of the portion of the rubber molded body 6 covering the safety valve 5 is a sheet-like rubber molded body 6 having a uniform thickness, and the thickness of the sheet-like rubber molded body 6 is preferably 0.3mm or more and 10.0mm or less, more preferably 0.5mm or more and 5mm or less, and further preferably 0.7mm or more and 2mm or less.

If the thickness is less than 0.3mm, a through hole is formed in the rubber molded body 6 by the high-temperature/high-pressure gas discharged from the safety valve 5, and the high-temperature/high-pressure gas is discharged from the through hole, and burns to a part outside the lithium ion secondary battery cell 1 covered with the insulating sheet 7 and the sheet-like rubber molded body 6, thereby burning the same. The through-hole serves as a supply port for air (oxygen), and the burning and burnout of the lithium ion secondary battery cell 1 itself covered with the insulating sheet 7 and the sheet-like rubber molded body 6 are expanded.

If the thickness of the sheet-like rubber molded body 6 exceeds 10.0mm, high-temperature/high-pressure gas can be blocked, that is, no through-hole is generated, but the rubber molded body 6 becomes large in size and the molding process becomes complicated. Moreover, it is difficult to store the lithium ion secondary battery cell 1 in an existing package case.

The surface hardness of the rubber molded body 6 is preferably 50 or more and 90 or less, as measured by a type a durometer in accordance with JIS K6253. If the surface hardness is less than 50, the rubber molded body 6 is broken or a through hole is formed due to the high-temperature and high-pressure gas (particularly, the influence of the pressure (ejection force)) ejected from the safety valve 5. If the surface hardness exceeds 90, the sheet-shaped rubber molded body 6 becomes brittle, and therefore, when the sheet-shaped rubber molded body is attached to the lithium-ion secondary battery cell 1 so as to impart a curvature, the sheet-shaped rubber molded body is broken when an accidental impact such as a high-temperature high-pressure gas ejected from the safety valve 5 is received.

The rubber molded body 6 is not limited to the following rubber composition, and may be formed by molding and curing the rubber composition, and the rubber molded body 6 is preferable because it is not burned or a through hole is not generated by the heat of high-temperature/high-pressure gas as in the case of a resin molded body.

The rubber molded body 6 of this embodiment is formed and cured from a rubber composition containing a silicone rubber composition as a main component.

The silicone rubber composition suitable for the rubber molded body 6 contains, per 100 parts by mass of the organopolysiloxane, 10 to 100 parts by mass of powdered silica, 10 to 50 parts by mass of a layered silicate, 0.5 to 20 parts by mass of titanium oxide, and 4.0 to 14.0 parts by mass of a curing agent.

The organopolysiloxane is represented by the average unit formula: RaSiO (4-a)/2 (wherein R is a hydrocarbon group or a halogenated alkyl group; a is 1.95 to 2.05). Examples of the hydrocarbon group R include: alkyl groups such as methyl, ethyl, and propyl; alkenyl groups such as vinyl and allyl; cycloalkyl groups such as cyclohexyl; aralkyl groups such as β -phenylethyl; and aryl groups such as phenyl and tolyl. Examples of R of the halogenated alkyl group include a 3,3, 3-trifluoropropyl group, a 3-chloropropyl group and the like. In the case where the organopolysiloxane is cross-linked between molecules at the position of a hydrogen atom bonded to a silicon atom in the molecule using an organic peroxide and/or a platinum-based catalyst as a curing agent, it is preferable that the organopolysiloxane has at least 2 alkenyl groups bonded to silicon atoms in the molecule. Examples of the alkenyl group include: vinyl, allyl, propenyl, hexenyl, and the like. The molecule of the organopolysiloxane may be linear or branched.

Examples of the powdered silica include: dry silica such as fumed silica, and wet silica such as precipitated silica. Further, as the powdered silica, there can be mentioned: the surface of the dry-process silica or the wet-process silica is hydrophobized with an organochlorosilane, organoalkoxysilane, hexaorganodisilazane, organosiloxane oligomer, or the like. The powder silica preferably contains one or more of these, and more preferably contains a hydrophobized dry-process silica from the viewpoint of improving sinterability, and maintaining the shape of the rubber molded article without generating through-holes even when thermal runaway of the lithium ion secondary battery occurs and high-temperature/high-pressure gas is ejected from the safety valve.

Powder silica is prepared by passing JISK 6430: the specific surface area measured by the multipoint nitrogen adsorption method (BET method) of 2008 is preferably 50m²More than g. The primary median particle diameter of the powdered silica measured by a laser diffraction/scattering particle size distribution measuring apparatus is preferably 1 μm or more and 10 μm or less. From the viewpoint of flame resistance, the content of the powder silica in the silicone rubber composition is preferably 10 parts by mass or more and 100 parts by mass or less, and less than 10 parts by mass, based on 100 parts by mass of the organopolysiloxaneIn the amount of the component (b), a through-hole is formed in the rubber molded body 6 by the high-temperature/high-pressure gas discharged from the safety valve 5. When the amount exceeds 100 parts by mass, the surface hardness of the rubber molded body 6 becomes high and becomes brittle.

Examples of the layered silicate include: mica, montmorillonite, bentonite, illite, sepiolite, attapulgite (アレルバルダイト), amesite, hectorite, talc, fluorohectorite, saponite, aluminum bentonite, nontronite, stevensite, bentonite, vermiculite, fluorovermiculite, halloysite, and the like. The layered silicate preferably contains one or two or more of these, and more preferably contains mica from the viewpoint of improving sinterability while maintaining the lithium ion secondary battery. Examples of mica include: muscovite, biotite, phlogopite, and the like. The median particle diameter of the layered silicate measured by a laser diffraction/scattering particle size distribution measuring apparatus is preferably 1 μm or more and 100 μm or less. The median particle diameter of the layered silicate is preferably greater than the primary median particle diameter of the powdered silica. In order to improve sinterability and prevent the rubber molded body 6 from forming through-holes even when thermal runaway occurs in the lithium ion secondary battery and high-temperature/high-pressure gas is discharged from the safety valve 5, the content of the layered silicate in the silicone rubber composition is preferably 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the organopolysiloxane, from the viewpoint of flame resistance.

In addition, from the viewpoint of maintaining the shape of the rubber molded body 6 (maintaining the shape even when exposed to high temperatures), the content of the layered silicate in the silicone rubber composition is preferably larger than the content of the powder silica.

The silicone rubber composition contains titanium oxide as a heat resistance improver. The amount of titanium oxide is preferably in the range of 0.5 to 20 parts by mass, more preferably 1.0 to 10.0 parts by mass, per 100 parts by mass of organopolysiloxane. If the blending amount is less than 0.5 parts by mass, the heat resistance of the rubber molded article 6 is insufficient, and if it exceeds 20.0 parts by mass, the flame retardancy of the rubber molded article 6 is lowered.

In addition to titanium oxide, for example, metal oxides of iron oxide, silica, and zinc oxide may be used in combination, and graphite, aluminum, and the like may be used together with the metal oxides as the heat resistance improver.

The silicone rubber composition needs to be cured to a desired hardness, and therefore, the curing agent is contained in an amount of 4.0 parts by mass or more and 14.0 parts by mass or less per 100 parts by mass of the organopolysiloxane. If the amount is 4.0 parts by mass or less, the surface hardness of the rubber molded body 6 is insufficient, and the rubber molded body is likely to be broken when attached to the outer periphery of the lithium ion secondary battery cell 1, for example. If it exceeds 14.0 parts by mass, the rubber molded body 6 becomes brittle.

As the curing agent, an organic peroxide or platinum is preferable as a catalyst.

The rubber molded body 6 may be produced by a known production method.

For example, the above-mentioned materials may be mixed and kneaded, extruded into a sheet of a desired thickness, and subjected to primary vulcanization (conditions: 10 minutes at 120 ℃ C. or lower) or secondary vulcanization (conditions: 4 hours at 200 ℃ C.). The sheet-like material may be cut into a predetermined width to form a strip. Alternatively, the resin composition may be injection molded or press molded into a desired shape, and then subjected to primary vulcanization or secondary vulcanization to be cured.

When the elongation at break of the rubber molded body 6 is 80% or more and 500% or less, the elongation at break is preferably 100% or more and 350% or less in terms of applying tension to the outer periphery of the lithium ion secondary battery cell 1 when the rubber molded body 6 is attached so as to cover the safety valve 5.

When the elongation at the time of cutting is less than 80%, the rubber molded body 6 tends to break when it is attached so as to cover the safety valve 5, and when the elongation at the time of cutting exceeds 500%, the thickness of the rubber molded body 6 becomes thin, and a through hole tends to be easily generated by the ejection of high-temperature/high-pressure gas.

As described above, in the present embodiment, since the rubber molded body 6 is attached so as to cover the safety valve 5 of the lithium ion secondary battery cell 1, even if thermal runaway of the lithium ion secondary battery occurs, burning and burnout due to ejection of high-temperature/high-pressure gas can be suppressed in the rubber molded body 6, and a through hole is not generated due to the high-temperature/high-pressure gas ejected from the safety valve 5.

In the above embodiment, the insulating sheet 7 and the rubber molded body 6 are attached so as to cover the upper surface of the lithium ion secondary battery cell 1 and cover the upper portions of the front and back surfaces, and when the lithium ion secondary battery cell is accommodated in the package case as described above, the rubber molded body 6 covering the front and back surfaces of the lithium ion secondary battery cell 1 is pressed by the inner wall surface of the package case, thereby holding the rubber molded body 6.

In contrast, in another embodiment of the present invention, as shown in fig. 5 corresponding to fig. 3, the rubber molded body 6 may be fixed to the package can 2 of the lithium ion secondary battery cell 1 by the adhesive tape 8. In fig. 5, the rubber molded body 6 is fixed to the lithium ion secondary battery cell 1 by winding and bonding the adhesive tape 8 so as to straddle and cover each end of the front surface side and the back surface side of the sheet-shaped rubber molded body 6 of the lithium ion secondary battery cell 1 and the package can 2 of the lithium ion secondary battery cell 1.

This can suppress the positional displacement of the insulating sheet 7 and the rubber molded body 6 covering the lithium ion secondary battery cell 1.

When the insulating sheet 7 and the rubber molded body 6 are attached to the lithium ion secondary battery cell 1, the upper surface of the lithium ion secondary battery cell 1 and the insulating sheet 7 can be fixed by the tape 8 while applying tension so that the gap therebetween is reduced.

Accordingly, the insulating sheet 7 and the rubber molded body 6 can be brought into close contact with the safety valve 5 on the upper surface of the lithium ion secondary battery cell 1, and the instant diffusion of the high-temperature and high-pressure gas ejected from the safety valve 5 due to the thermal runaway of the lithium ion secondary battery can be effectively suppressed.

Further, since the rubber molded body 6 has rubber elasticity, even if high-pressure gas is immediately discharged from the safety valve 5, the pressure can be relaxed by expansion.

As the adhesive tape 8, an acrylic adhesive, a silicone adhesive, or the like coated with a polyimide film can be used, and among these, an adhesive tape coated with silicone as an adhesive on a polyimide film is preferable because it is excellent in heat resistance.

Fig. 6 is a perspective view corresponding to fig. 3 of another embodiment of the present invention, and fig. 7 is a sectional view taken along line B-B of fig. 6.

In this embodiment, the entire outer peripheral surface of the lithium ion secondary battery cell 1 is coated with the putty-like composition 9 having excellent thermal conductivity.

An insulating sheet 7 and a sheet-like rubber molding 6 are attached so as to cover the upper surface, the upper portion of the front surface, and the lower portion of the rear surface of the lithium ion secondary battery cell 1 with a putty-like composition 9 interposed therebetween.

By coating the outer peripheral surface of the lithium ion secondary battery cell 1 with the putty-like composition 9 having excellent thermal conductivity in this manner, even if the lithium ion secondary battery cell 1 generates heat due to thermal runaway, the heat can be efficiently conducted to the outside of the lithium ion secondary battery cell 1 to dissipate the heat, and the heat distribution in the entire lithium ion secondary battery cell 1 can be made uniform.

Since the putty-like composition 9 can be coated so as to follow the surface shape of the lithium ion secondary battery cell 1 as a member to be coated, the contact area with the lithium ion secondary battery cell 1 as a heat source can be increased, and the heat dissipation property can be significantly improved.

The thickness of the coated putty-like composition 9 is preferably 2mm or more and 5mm or less.

The range in which the putty-like composition 9 is coated may be the entire outer peripheral surface of the lithium-ion secondary battery cell 1 or may be a part thereof, as in the present embodiment. Preferably, the lithium ion secondary battery cell 1 is located directly above the safety valve 5.

That is, it is preferable that a layer of the putty-like composition 9 having excellent thermal conductivity and the rubber molded body 6 are laminated directly above the safety valve 5 of the lithium-ion secondary battery cell 1.

The putty-like composition having excellent thermal conductivity is preferably the following compositions (1) and (2).

(1) A composition comprising a liquid polymer, aluminum hydroxide, and a bentonite, wherein the content of the aluminum hydroxide is 150 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the liquid polymer, and the content of the bentonite is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the liquid polymer.

(2) A composition which is a thermally conductive putty composition comprising a base polymer and a thermally conductive filler, wherein the base polymer contains a liquid polymer having a hydroxyl group as a main component, and the thermally conductive filler is contained in an amount of 500 parts by mass or more and 3000 parts by mass or less per 100 parts by mass of the base polymer.

Here, "putty-like" means that the adhesive composition is prepared according to JIS a 5752: 1994 (measurement temperature: 23. + -. 3 ℃ C.) is a state corresponding to a needle penetration of 50mm or more and 160mm or less.

The term "liquid polymer" means a polymer that is in a liquid state at normal temperature and normal pressure (25 ℃ C., 1 atm). Examples of the liquid polymer include: liquid polyolefins such as liquid polybutadiene, liquid polyisoprene, liquid polybutene, and liquid ethylene-propylene copolymers; liquid silicone; liquid acrylic acid; liquid amine esters, and the like. The liquid polymer preferably contains one or more of these, and more preferably contains a liquid polyolefin. From the viewpoint of preventing the generation of halogen gas during combustion, the liquid polymer preferably contains no halogen element in the molecule.

The characteristics of the putty-like composition having excellent thermal conductivity of the above (1) are as follows:

(A) thermal conductivity (W/m.K): 1.5 to 3.5 inclusive

(B) Softness (needle penetration mm): 50 or more and 110 or less.

The characteristics of the putty-like composition having excellent thermal conductivity of the above (2) are as follows:

(A) thermal conductivity (W/m.K): 5.0 to 16.0 inclusive

(B) Softness (needle penetration mm): 60 to 160 inclusive.

In view of the heat dissipation performance (a) × (B) in consideration of the shape following property,

the heat dissipation performance of the above (1) is 150 or more and 314 or less,

the heat dissipation performance of the above (2) is 390 to 1036 inclusive.

One reason why the heat dissipation performance of (2) is superior to that of (1) is presumably that the heat dissipation performance is caused by the presence of hydroxyl groups.

The above embodiments are applied to one lithium ion secondary battery cell 1, but the present invention is applicable to a plurality of lithium ion secondary battery cells 1.

For example, as shown in fig. 8 and 9 corresponding to fig. 2 and 3, respectively, a plurality of, in this example, 4, lithium ion secondary battery cells 1 may be connected by unshown bus bars to form a battery pack, and the insulating sheet 7 and the sheet-like rubber molded body 6 may be attached to the battery pack so as to cover the upper surfaces of the lithium ion secondary battery cells 1 and also cover the upper front surface and the upper rear surface of the lithium ion secondary battery cells 1 located at both ends, respectively.

The battery pack 11 is configured by housing 4 lithium ion secondary battery cells 1 each having the insulating sheet 7 and the rubber molded body 6 attached thereto in a resin package case 10, for example, as shown in fig. 10.

(Another embodiment)

In the above embodiment, the rubber molded body is configured to cover the upper surface of the lithium ion secondary battery cell and the upper portions of the front and back surfaces, but may be configured to cover substantially the entire surface except for the lead portion of the lithium ion secondary battery cell. In this case, the package housing may be omitted.

In the above embodiments, the rubber molded body is in the form of a sheet, but is not limited to the sheet, and may be in the form of a band as long as it is a shape capable of covering at least the safety valve of the lithium ion secondary battery cell, or may be in the form of a cap capable of covering the upper portion of the lithium ion secondary battery cell.

When the rubber molded body is in the form of a band, the band-shaped rubber molded body may be wound around the lithium ion secondary battery cell so as to cover the safety valve, and the end portion of the band-shaped rubber molded body may be bonded and fixed by the adhesive tape.

Further, for example, a band-shaped rubber molded body may be spirally wound so as to overlap a half pitch, and an end portion thereof may be fixed with a tape so as to cover substantially the entire outer peripheral surface of the lithium ion secondary battery cell.

An adhesive layer may be formed on at least a part of one surface of the rubber molded body, for example, a peripheral edge portion of one surface, and the rubber molded body may be bonded and fixed to the lithium ion secondary battery cell.

In the above embodiments, the rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell via the insulating sheet, but as another embodiment of the present invention, the insulating sheet may be omitted.

The above embodiments may be combined as appropriate, and for example, the sheet-like rubber molded body 6 covering the lithium ion secondary battery cell 1 with the putty-like composition 9 of fig. 6 interposed therebetween may be bonded and fixed to the putty-like composition 9 by the tape 8 shown in fig. 5.

At least a part of the outer peripheral surfaces of the plurality of lithium ion secondary battery cells 1 shown in fig. 8 to 10 may be coated with the putty-like composition 9 shown in fig. 6 and 7. In this case, the putty composition 9 may be coated between the two adjacent lithium ion secondary battery cells 1 and 1, or the putty composition 9 may not be coated.

In the above embodiments, the rubber molded body is attached so as to cover the safety valve of the lithium ion secondary battery cell, but may be attached so as to cover the vent hole instead of the safety valve.

The above embodiments are described as being applied to a square lithium ion secondary battery cell, but it goes without saying that the present invention can be similarly applied to a cylindrical lithium ion secondary battery cell. The present invention is also applicable to a lithium ion secondary battery cell having a high energy density, specifically, a lithium ion secondary battery cell having an energy density of 300Wh/kg or more, more preferably 400Wh/kg or more.

[ notation ] to show

1: lithium ion secondary battery core

2: packaging can

3 positive terminal

4: negative terminal

5, safety valve

6 rubber molded body

7 insulating sheet

8: adhesive tape

9 putty-like composition

10: packaging shell

And 11, a battery pack.