CN116648482A - Resin molded body and battery pack - Google Patents

Abstract

The resin molded body of the present application is a resin molded body which is attached to the outer periphery of one or more lithium ion secondary battery cells having safety valves or vent holes so as to cover at least the safety valves or vent holes, and is characterized in that the thermal conductivity (measurement temperature: 50 ℃) of the resin molded body measured by a one-way heat flow steady state comparison method according to JIS H7903:2008 is less than 1.0W/m.K, the thickness of the portion of the resin molded body covering the safety valves or vent holes is 0.5mm or more and 10.0mm or less, and the surface hardness of the resin molded body measured according to JIS K7215 and by a D-type durometer is 50 or more and 90 or less.

Description

Resin molded body and battery pack

Technical Field

The present application relates to a flame-resistant resin molded body and a battery pack using the resin molded body.

The present application claims priority from patent applications 2020-216366 and 2021 to patent applications 2021-201664 based on 25 th month of 2020 and 13 th month of 2021.

Background

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

For example, if a lithium ion secondary battery is overcharged or overdischarged, or is subjected to an unexpected impact to cause an internal short circuit or an external short circuit, thermal runaway may occur. The lithium ion secondary battery, which generates thermal runaway, increases the internal pressure of the battery due to the generation of gas. In this case, there is a possibility that the outer can breaks due to an increase in internal pressure, and therefore, a vent hole, a safety valve, and the like for exhausting air are provided in these batteries.

In addition, when thermal runaway occurs, there is a possibility that a fire may occur due to a overheated battery or the like, and in order to prevent ignition or burning, for example, in patent document 1, the surface of the battery is covered with a fireproof sheet.

However, high temperature/high pressure gas may be ejected from an exhaust hole or a safety valve provided to the lithium ion secondary battery where thermal runaway occurs and used for exhaust. As for the temperature, according to the description of non-patent document 1, there is a case where the instantaneous maximum temperature exceeds 999 ℃.

Accordingly, the fireproof sheet of patent document 1 is provided for the purpose of preventing flames (i.e., fireproof) from the high-temperature gas.

Patent document 1: japanese patent laid-open publication No. 2019-032923 (A)

Non-patent document 1: pine cone, pine cone and male traffic safety ring institute, nuclear, , general/traffic safety ring institute, number 135-138,2012 (pine cone, pine cone and male, forum lecture summary of the institute of traffic safety and environment/institute of traffic safety and environment 135-138,2012

However, with recent higher energy density batteries, the pressure of the gas discharged at the time of thermal runaway has significantly increased. Even the fire protection sheet of patent document 1 may be broken due to the high pressure of the gas. Specifically, for example, in the case of the fire-protection sheet made of fibers described in patent document 1, the mesh of the fibers is widened by the high pressure of the gas, and in the case of the fire-protection sheet made of resin, the fire-protection sheet is reduced in strength to be unable to withstand the high pressure in a softened state of the resin before combustion, and thus, in any case, through holes are formed in the fire-protection sheet, and there is a possibility that the high temperature/high pressure gas ejected from the through holes may spread to a part other than the fire-protection sheet (for example, an outer case accommodating a battery) and burn out.

In addition, there is also the following risk: air (oxygen) is supplied from the through-hole, and burning loss and flame spread of the battery itself are increased, which becomes a factor of thermal runaway of the adjacent normal lithium ion secondary battery.

Disclosure of Invention

The present application has been made in view of such a background, and an object thereof is to provide a resin molded body capable of suppressing ignition and burning loss even when high-temperature/high-pressure gas is discharged from a safety valve or a vent 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 resin molded body is attached.

In the present application, in order to achieve the above object, the following is constructed.

(1) The resin molded body according to the present application is attached to the outer periphery of at least one lithium ion secondary battery cell having a safety valve or vent hole so as to cover at least the safety valve or vent hole, wherein the thermal conductivity (measurement temperature: 50 ℃) of the resin molded body measured by a one-way heat flow steady state comparison method according to JIS H7903:2008 is less than 1.0W/m.K, the thickness of the portion of the resin molded body covering the safety valve or vent hole is 0.5mm or more and 10.0mm or less, and the surface hardness of the resin molded body measured according to JIS K7215 and using a D-type durometer is 50 or more and 90 or less.

According to the present application, since the resin molded body having the thermal conductivity, thickness, and surface hardness within the predetermined ranges is attached so as to cover the safety valve or the vent hole of the lithium ion secondary battery cell, even if the lithium ion secondary battery is thermally out of control, the penetration hole is not formed in the resin molded body by the high-temperature/high-pressure gas ejected from the safety valve or the vent hole, and the burning and burning due to the ejection of the high-temperature/high-pressure gas can be suppressed.

(2) In another embodiment of the resin molded body according to the present application, a thickness of a portion of the resin molded body covering the safety valve or the vent hole is 1.0mm or more.

(3) In another embodiment of the resin molded body according to the present application, the resin molded body includes a resin composition containing carbon fibers in an amount of 2 parts by mass or more and 70 parts by mass or less and a silane coupling agent in an amount of 0.3 parts by mass or more and 7.0 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

(4) In another embodiment of the resin molded article according to the present application, the resin composition further contains polytetrafluoroethylene in a range of 50 parts by mass or less per 100 parts by mass of the thermoplastic resin.

(5) In another embodiment of the resin molded body according to the present application, the glass fiber is contained in an amount of 9 to 80 parts by mass and the silane coupling agent is contained in an amount of 0.3 to 7.0 parts by mass based on 100 parts by mass of the thermoplastic resin.

(6) In another embodiment of the resin molded article according to the present application, the resin composition further contains carbon fibers in a range of 2 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

(7) In another embodiment of the resin molded article according to the present application, the thermoplastic resin is one or a mixture of two or more of polyphenylene sulfide, polyamide, polybutylene terephthalate, modified polyphenylene ether, and polycarbonate.

(8) The battery pack according to the present application includes one or more lithium ion secondary battery cells, and the resin molded body according to any one of (1) to (7) is attached to the outer periphery of the one or more lithium ion secondary battery cells.

(9) Another aspect of the present application provides a battery pack comprising: one or more lithium ion secondary battery cells each having a safety valve or a vent hole at one end face thereof; and a resin molded body that is disposed along the one end face of the lithium ion secondary battery cell and that covers the safety valve or the vent, the resin molded body being any one of (1) to (7).

As described above, according to the present application, since the resin molded body is attached so as to cover the safety valve or the vent hole of the lithium ion secondary battery cell, even if the lithium ion secondary battery is thermally out of control, the penetration hole is not formed in the resin molded body by the high-temperature/high-pressure gas ejected from the safety valve or the vent hole, and the burning and burning due to the ejection of the high-temperature/high-pressure gas can be suppressed.

Drawings

Fig. 1 is a perspective view of a lithium ion secondary battery cell to which a resin molded body according to an embodiment of the present application is attached.

Fig. 2 is a perspective view showing a resin molded body and a lithium ion secondary battery cell according to an embodiment of the present application.

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

Fig. 4 is a cross-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 application.

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

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 application.

Fig. 9 is a perspective view of a lithium ion secondary battery cell to which the resin 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 application.

Detailed Description

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

Fig. 1 is a perspective view of a lithium ion secondary battery cell to which a resin molded body according to an embodiment of the present application is attached.

The lithium ion secondary battery cell 1 is, for example, a rectangular battery cell, and a positive electrode terminal 3 and a negative electrode terminal 4 are provided on one end surface (upper surface in fig. 1) of an outer can 2 as a battery container, with a safety valve 5 provided therebetween.

The safety valve 5 operates when the internal pressure increases due to thermal runaway of the lithium ion secondary battery cell 1, and prevents the external can 2 from being ruptured by the high-temperature/high-pressure gas being discharged.

If the lithium ion secondary battery cell 1 is thermally out of control, there is a possibility that the lithium ion secondary battery cell may be ignited by overheating, and if the high-temperature/high-pressure gas ejected from the safety valve 5 rapidly spreads widely, it is difficult to prevent the ignition or the burning loss.

In this embodiment, therefore, as shown in fig. 2, 3, and fig. 4 which is a sectional view taken along line A-A of fig. 3, a sheet-like resin molded body 6 having flexibility is attached to the outer periphery of the lithium ion secondary battery cell 1 directly or via (via) an insulating sheet 7 so as to cover at least the safety valve 5.

When the insulating sheet 7 is provided, the portion of the insulating sheet 7 covering the safety valve 5 preferably abuts against the safety valve 5, but may not abut against the safety valve. In the case where the insulating sheet 7 is not provided, the portion of the resin molded body 6 covering the safety valve 5 preferably abuts against the safety valve 5, but may not abut against the safety valve.

In this embodiment, the insulating sheet 7 and the sheet-like resin molded body 6 are rectangular and have substantially the same size, and are attached so as to cover the upper surfaces of the rectangular lithium ion secondary battery cell 1 including the safety valve 5 and cover the upper portions of the front surface and the rear surface (left and right surfaces in fig. 4). However, the dimensions of the resin molded body 6 and the insulating sheet 7 may be different, the resin molded body 6 may be larger than the insulating sheet 7, and the insulating sheet 7 may be larger than the resin molded body 6. The two may be joined in advance.

The 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 led out by the side surfaces not covered with the insulating sheet 7 and the resin molded body 6.

The lithium ion secondary battery cell 1 provided with the insulating sheet 7 and the sheet-like resin molded body 6 is accommodated in an external case, not shown. In the outer case, the resin molded body 6 covering the upper portions of the front and rear surfaces of the lithium ion secondary battery cell 1 is pressed by the inner wall surface of the outer case, and the resin molded body 6 is held.

The resin molded body 6 of this embodiment is formed by molding and curing a resin composition described later, and the thermal conductivity (measurement temperature: 50 ℃) of the resin molded body 6 measured by a unidirectional heat flow steady state comparison method (SCHF) according to JIS H7903:2008 is less than 1.0W/m·k.

If the thermal conductivity is 1.0W/m·k or more, when the lithium ion secondary battery is thermally out of control, heat is conducted to a member (for example, an outer case accommodating the lithium ion secondary battery cell 1 covered with the sheet-shaped resin molded body 6) on the outer periphery of the resin molded body 6 via the resin molded body 6 by the high-temperature/high-pressure gas ejected from the safety valve or the vent hole, and the outer case may be melt deformed.

The lower the thermal conductivity, the more preferable, but the lower limit thereof is, for example, 0.1W/mK, and more preferably 0.01W/mK.

In this embodiment, the resin molded body 6 has a sheet shape with a uniform thickness, and the thickness of the sheet-shaped resin molded body 6 may be 0.5mm or more and 10.0mm or less, preferably 0.7mm or more and 5mm or less, and more preferably 1.0mm or more and 2mm or less. Although it is preferable that the thickness of the resin molded body 6 is uniform, the thickness of the other portion may not be within the above range as long as the thickness of the portion of the resin molded body 6 covering the safety valve 5 is within the above range.

If the thickness is less than 0.5mm, a through hole is formed in the resin molded body 6 by the high-temperature and high-pressure gas discharged from the safety valve 5, and the high-temperature and high-pressure gas is discharged from the through hole, so that the parts outside the lithium ion secondary battery cell 1 covered with the insulating sheet 7 and the sheet-shaped resin molded body 6 may be burned out and burned out. The through-holes serve as air (oxygen) supply ports, which may cause the lithium ion secondary battery cell 1 itself covered with the insulating sheet 7 and the sheet-like resin molded body 6 to be burned or burned.

If the thickness of the sheet-like resin molded body 6 is greater than 10.0mm, high-temperature and high-pressure gas can be blocked, that is, no through-holes are generated, but the resin molded body 6 tends to be large in size, and the molding process becomes complicated. Further, it is difficult to house the lithium ion secondary battery cell 1 in an existing exterior case for housing.

The surface hardness of the resin molded body 6 is preferably 50 to 90, measured by a D-type durometer in accordance with JIS K7215. If the surface hardness is less than 50, the resin molded body 6 may be broken or a penetration hole may be formed due to the high-temperature/high-pressure gas (in particular, the influence of pressure (ejection force)) ejected from the safety valve 5. If the surface hardness is more than 90, the sheet-like resin molded body 6 becomes brittle. Therefore, when a curvature is given to the resin molded body 6 and the resin molded body is attached to the lithium ion secondary battery cell 1, or when an unnecessary impact is applied to the resin molded body 6 due to high temperature/high pressure gas or the like discharged from the safety valve 5, the resin molded body 6 may be broken.

The resin molded body 6 is not limited to the resin composition described later, and may be a resin molded body obtained by molding and curing another resin composition as long as it is a resin that becomes a resin molded body according to the present application after curing. The resin molded article 6 is preferably not melted and dropped or through holes are generated by the heat of high temperature and high pressure gas unlike other resin molded articles which are not the resin molded articles of the present application.

The shape of the resin molded body 6 is not particularly limited, and may be any shape such as a rectangle or a circle as long as it can cover at least the surface (upper surface) to which the safety valve 5 and the vent are attached.

The resin molded body 6 of this embodiment includes a resin composition obtained by mixing a carbon fiber and a silane coupling agent with a thermoplastic resin. The resin composition contains carbon fibers in an amount of 2 to 70 parts by mass and a silane coupling agent in an amount of 0.3 to 7.0 parts by mass, based on 100 parts by mass of the thermoplastic resin. The resin composition may further contain Polytetrafluoroethylene (PTFE) in an amount of 3 to 50 parts by mass based on 100 parts by mass of the thermoplastic resin. In addition, the PTFE can improve chemical resistance, antifouling property, slidability, and the like of the resin composition.

The resin molded body 6 of the other embodiment contains a resin composition obtained by mixing a glass fiber and a silane coupling agent with a thermoplastic resin. The resin composition contains glass fibers in an amount of 9 to 80 parts by mass, and a silane coupling agent in an amount of 0.3 to 7.0 parts by mass, based on 100 parts by mass of the thermoplastic resin. The resin composition may contain carbon fibers in a range of 2 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the thermoplastic resin.

Examples of the thermoplastic resin include polyphenylene sulfide (PPS), polyamide, polybutylene terephthalate, modified polyphenylene ether, and polycarbonate, or a mixture of two or more thereof.

As PPS suitable for the thermoplastic resin of the resin composition, either of an oxidative crosslinking PPS in which the melt viscosity is increased by heat treatment in the presence of oxygen and a linear PPS in which the molecular weight is increased by adding lithium chloride, an organic acid salt, water, or the like to the polymerization system, while maintaining the linear state, can be used.

As the carbon fiber suitable for the resin composition, any one of PAN (polyacrylonitrile) based carbon fiber using acrylic fiber and pitch based carbon fiber using pitch can be used. In the present embodiment, pitch-based carbon fibers may be used as the carbon fibers.

The pitch-based carbon fibers include isotropic pitch-based carbon fibers and mesophase pitch-based carbon fibers, but any pitch-based carbon fibers may be used.

As an example of the shape of the carbon fiber used in the resin composition, the fiber diameter of the single fiber may be 1 to 20. Mu.m, the average fiber length may be 0.01 to 10mm, and the aspect ratio may be about 1.5 to 1300.

The silane coupling agent contained in the resin composition is a component imparting deformation resistance, and can suppress melting and falling of the resin composition during combustion, thereby further improving flame retardancy.

The silane coupling agent contained in the resin composition may preferably be, for example, 3-aminopropyl triethoxysilane or 3-glycidoxypropyl triethoxysilane.

The PTFE contained in the resin composition is preferably powdery PTFE. For example, a BET specific surface area of 0.5 to 5m having an average particle diameter of 10 to 30 μm can be used ² /g PTFE powder.

The resin composition preferably further contains carbon black as a colorant, polyolefin wax or stearyl alcohol as a mold release agent, hydrotalcite or zinc carbonate as a mold anticorrosive agent.

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

For example, PPS, carbon fiber, a silane coupling agent, PTFE, carbon black, polyolefin wax, a mold anticorrosive agent, and a mold release agent are charged into a biaxial extruder, and the kneading temperature is controlled to 270 ℃ or higher and 300 ℃ or lower, the screw rotation speed is controlled to 100rpm or higher and 300rpm or lower, and the kneading time is set to 30 minutes or higher and 60 minutes or lower, and the mixture is pelletized to form a particulate resin composition.

Then, the obtained resin composition is molded into a sheet shape having a desired thickness by a known molding method such as extrusion molding by an extruder or press molding by a press machine, whereby the resin molded body 6 can be produced.

As described above, in the present embodiment, since the resin molded body 6 is attached so as to cover the safety valve 5 of the lithium ion secondary battery cell 1, even if the lithium ion secondary battery is thermally out of control, the penetration holes are not formed in the resin molded body 6 by the high-temperature/high-pressure gas discharged from the safety valve 5, and the burning and burning due to the discharge of the high-temperature/high-pressure gas can be suppressed.

In the above embodiment, as described above, the insulating sheet 7 and the resin molded body 6 attached so as to cover the upper surface of the lithium ion secondary battery cell 1 and the upper portions of the front and rear surfaces are housed in the outer case. Therefore, the resin molded body 6 covering the front and rear surfaces of the lithium ion secondary battery cell 1 is pressed against the inner wall surface of the outer case, thereby holding the resin molded body 6.

In contrast, in another embodiment of the present application, as shown in fig. 5 corresponding to fig. 3, the resin molded body 6 may be fixed to the outer can 2 of the lithium ion secondary battery cell 1 by the adhesive tape 8. In fig. 5, the adhesive tape 8 is wound so as to cover the front and rear ends of the sheet-like resin molded body 6 of the lithium ion secondary battery cell 1 and the outer can 2 of the lithium ion secondary battery cell 1, thereby fixing the resin molded body 6 to the lithium ion secondary battery cell 1.

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

When the insulating sheet 7 and the resin molded body 6 are attached to the lithium ion secondary battery cell 1, tension may be applied so that the gap between the upper surface of the lithium ion secondary battery cell 1 and the insulating sheet 7 becomes small, and the insulating sheet and the resin molded body may be fixed by the adhesive tape 8.

This makes it possible to bring the insulating sheet 7 and the resin molded body 6 into close contact with the safety valve 5 on the upper surface of the lithium ion secondary battery cell 1, and thus it is possible to effectively suppress rapid diffusion of high-temperature and high-pressure gas ejected from the safety valve 5 due to thermal runaway of the lithium ion secondary battery.

The adhesive tape 8 is preferably an adhesive tape having an acrylic adhesive, a silicone adhesive, or the like applied to a polyimide film, since the adhesive tape having a silicone adhesive applied to a polyimide film is excellent in heat resistance.

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

In this embodiment, the paste composition 9 having excellent heat transfer property is coated on the entire outer peripheral surface of the lithium ion secondary battery cell 1.

The insulating sheet 7 and the sheet-like resin molded body 6 are attached via the paste composition 9 so as to cover the upper surface of the lithium ion secondary battery cell 1, the upper part of the front surface, and the upper part of the back surface.

By coating the outer peripheral surface of the lithium ion secondary battery cell 1 with the paste composition 9 having excellent heat transfer properties in this way, 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 overall heat distribution can be uniformized.

The paste composition 9 can coat the lithium ion secondary battery cell 1 as a coating member in accordance with the surface shape thereof, and thus can increase the contact area with the lithium ion secondary battery cell 1 as a heat source, and can significantly improve heat dissipation.

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

In the above embodiments, the resin molded body of the present application is applied to one lithium ion secondary battery cell 1, but it is needless to say that the resin molded body of the present application can also be applied 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, an insulating sheet 7 and a sheet-like resin molded body 6 are attached to a combined battery constituted by connecting a plurality of (four in this example) lithium ion secondary battery cells 1 with bus bars (bus bar), not shown, so as to cover the upper surfaces of the lithium ion secondary battery cells 1 and the upper parts of the front and rear surfaces of the lithium ion secondary battery cells 1 located at both ends.

As shown in fig. 10, for example, four lithium ion secondary battery cells 1 each having an insulating sheet 7 and a resin molded body 6 attached thereto are housed in a resin outer case 10 having a gas inlet 10a and a gas outlet 10b, and a battery pack 11 is configured.

(other embodiments)

In the above embodiment, the resin molded body is configured to cover the upper surface of the lithium ion secondary battery cell and the upper portions of the front surface and the rear surface, 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 outer case may be omitted.

In the above embodiments, the resin molded body is in the form of a sheet, but not limited to a sheet, and may be in the form of a strip as long as it can cover at least the safety valve of the lithium ion secondary battery cell, or may be in the form of a cap (bag, cup) that can cover the upper portion of the lithium ion secondary battery cell.

The resin molded body 6 in the case of a cap may cover the entire lithium ion secondary battery cell, or may cover only a part of the upper end where the safety valve or the vent hole is disposed. When the lid-shaped resin molded body 6 covers only a part of the upper end of the lithium ion secondary battery cell, the length of the part of the side surface of the lithium ion secondary battery cell that covers the upper end (upper surface) is preferably 2mm or more and 300mm or less, more preferably 10mm or more and 250mm or less, and still more preferably 15mm or more and 150mm or less. The resin molded body 6 having such a shape can be sufficiently adhered to the lithium ion secondary battery cell, and can be easily mounted.

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

The ribbon-shaped resin molded body may be wound in a spiral shape so as to cover substantially the entire outer peripheral surface of the lithium ion secondary battery cell (for example, so as to overlap at half a pitch), and the ends thereof may be fixed by an adhesive tape.

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

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

The above embodiments may be appropriately combined, for example, the sheet-like resin molded body 6 covering the lithium ion secondary battery cell 1 via the paste composition 9 of fig. 6 is attached and fixed to the paste composition 9 by the adhesive 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 paste composition 9 shown in fig. 6 and 7. In this case, the paste composition 9 may be coated between the adjacent two lithium ion secondary battery cells 1, or the paste composition 9 may not be coated.

In the above embodiments, the resin 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. In the case where the lithium ion secondary battery cell has both the safety valve and the vent hole, the resin molded body may be attached so as to cover both the safety valve and the vent hole.

In the above embodiments, the square lithium ion secondary battery cell was described, but the present application is of course also applicable to a cylindrical lithium ion secondary battery cell. The resin molded article according to each of the above embodiments is suitable for lithium ion secondary battery cells having a high energy density, specifically, for lithium ion secondary battery cells having an energy density of 300Wh/kg or more, and more preferably for lithium ion secondary battery cells having an energy density of 400Wh/kg or more.

Examples

In the following, as examples, resin molded articles were produced, and as physical properties thereof, hardness (surface hardness) and thermal conductivity were measured.

1. Raw material for producing resin composition

(1) Polyphenylene sulfide (PPS-1):

torilina (registered trademark) M2588 (TORAY INDUSTRIES, INC.)

(2) Polyphenylene sulfide (PPS-2):

SE-730 (DIC Corporation)

(3) Polyphenylene sulfide (PPS-3):

torilina (registered trademark) L2840 (TORAY INDUSTRIES, INC.)

(4) Polybutylene terephthalate (PBT-1):

5710N1TX (Mitsubishi Engineering-Plastics Corporation)

(5) Polybutylene terephthalate (PBT-2):

1494X02 (TORAY INDUSTRIES, INC.)

(6) Polyamide 6 (PA 6):

CM 1014V 0 (TORAY INDUSTRIES, INC.)

(7) Modified polyphenylene ether (mPE-1):

240Z (ASAHI KASEI CORPORATION)

(8) Modified polyphenylene ether (mPE-2):

644Z (ASAHI KASEI CORPORATION)

(9) Modified polyphenylene ether (mPE-3):

GN30 (Mitsubishi Engineering-Plastics Corporation)

(10) Polycarbonate (PC-1):

GV-3430R/QG0717VX (manufactured by TEIJIN LIMITED)

(11) Polycarbonate (PC-2):

MN4800Z/QM19047Z (manufactured by TEIJIN LIMITED)

(12) Carbon fiber:

donacarbon Milled (registered trademark) S-242 (Osaka Gas Chemicals Co., ltd.), pitch-based carbon fiber, average fiber length of 0.36mm, fiber diameter of 13 μm, aspect ratio of 28

(13) Glass fiber

Chopped Starand CS-3J-256 (manufactured by Nitto Boseki Co., ltd.), a cut length of 3mm, a fiber diameter of 11 μm, a silane-based treatment, a profile ratio of 1:1, a cross-sectional shape: round shape

(14) Polytetrafluoroethylene (PTFE):

fluon (registered trademark) L169E (manufactured by AGC Inc.), powder, average particle diameter 18 μm, BET specific surface area 2m ² /g

(15) Silane coupling agent (deformation resistance imparting agent):

KBE-903 (Shin-Etsu Chemical Co., ltd.), ignition point 98℃and minimum coating area 352m ² /g

(16) Carbon black (colorant):

BP880 (Cabot corporation)

(17) Polyolefin wax (release agent):

LICOWAX PE520 (manufactured by Clariant Chemicals Co.) at a drop point of 117 ℃ to 123 ℃ and a melt viscosity of 650 mPa.s (140 ℃)

(18) Zinc carbonate (mold anticorrosive):

2, seta (trade name), znCO ₃ (SEIDO CHEMICAL INDUSTRY CO., LTD.)

2. Preparation of resin composition and pelletization

The resin compositions of examples 1 to 13 of the present application were each formed by changing the type of thermoplastic resin and the mixing amount of PTFE, carbon fiber, glass fiber, silane coupling agent, mold release agent, coloring pigment and mold preservative with respect to the mass ratio (parts by mass) of thermoplastic resin 100. The compositions of the respective resin compositions of examples 1 to 13 of the present application are shown in Table 1. The respective components shown in table 1 were weighed, dried and mixed, and then pelletized using a twin-screw extruder, whereby the respective resin compositions of examples 1 to 13 of the present application were pelletized.

TABLE 1

3. Molding of resin molded article

Injection molding was performed using the resin compositions (pellets) of examples 1 to 13 of the present application to prepare sheet-like resin molded articles having the thicknesses shown in Table 1.

The molding conditions are as follows:

the temperature of the cylinder is 270-310 DEG C

The temperature of the injection head is 320 DEG C

The temperature of the die is 140 DEG C

4. Measurement of hardness and thermal conductivity

The obtained resin molded articles of examples 1 to 13 were used to measure hardness and thermal conductivity, respectively.

(1) Measurement of hardness:

hardness was measured according to JIS K7215.

(2) Measurement of thermal conductivity:

the thermal conductivity was measured according to JIS H7903:2008 by a one-way heat flow steady state comparison method at a measurement temperature of 50 ℃.

(3) Flame retardancy evaluation:

the flame retardancy of the resin molded articles of examples 1 to 13 of the present application was evaluated by a flame retardancy evaluation test simulating the ejection of high temperature/high pressure gas from a safety valve or vent hole of a lithium ion secondary battery due to thermal runaway of the lithium ion secondary battery. With respect to the test method, a 5580W burner was fixed vertically downward, a resin sheet 100 mm. Times.120 mm. Times.2 mm thick was prepared, and the resin sheet was placed in a horizontal manner with respect to the floor at a position 200mm from the burner fire.

The flame retardancy "failed" was determined when the flame retardant was burned before the resin sheet was deformed by 5mm or more in the vertical direction by igniting the burner, and the deformation amount was determined to be "failed" when the flame retardant was not burned even after the deformation was 5 mm.

The measurement results are shown in Table 1.

According to the results shown in examples 1 to 4 of the present application in Table 1, resin molded articles having a hardness of 62 to 88, a thermal conductivity of 0.41 to 0.82 (W/mK), excellent strength characteristics and low thermal conductivity were obtained by using resin compositions containing carbon fibers in an amount of 7.69 to 65.00 parts by mass and a silane coupling agent in an amount of 1.39 to 4.57 parts by mass based on 100 parts by mass of polyphenylene sulfide (thermoplastic resin).

Based on the results shown in examples 5 to 8 of the present application in Table 1, a resin molded article having a hardness of 65 to 69, a thermal conductivity of 0.36 to 0.53 (W/mK), excellent strength characteristics, and low thermal conductivity was obtained by using a resin composition in which the polyphenylene sulfide of example 1 of the present application was changed to polyamide 6, modified polyphenylene ether, and polybutylene terephthalate, and the silane coupling agent was changed to 0.77 parts by mass per 100 parts by mass of the changed polyamide 6, modified polyphenylene ether, and polybutylene terephthalate.

From the results shown in inventive example 9 of table 1, a resin composition containing 46.15 parts by mass of PTFE, 7.69 parts by mass of carbon fiber, and 0.77 part by mass of a silane coupling agent per 100 parts by mass of polyphenylene sulfide was used to obtain a resin molded article having a hardness of 67, a thermal conductivity of 0.44 (W/mK), excellent strength characteristics, and low thermal conductivity.

From the results shown in examples 10 to 13 of the present application in Table 1, resin molded articles having a hardness of 66 to 76, a thermal conductivity of 0.41 to 0.56 (W/mK), excellent strength characteristics, and low thermal conductivity were obtained by using resin compositions containing carbon fibers in an amount of 0 to 13.89 parts by mass, glass fibers in an amount of 9.92 to 79.37 parts by mass, and a silane coupling agent in an amount of 0.76 to 1.39 parts by mass, based on 100 parts by mass of the thermoplastic resin.

The resin molded articles of examples 1 to 13 of the present application were also acceptable in the flame retardancy evaluation test. Therefore, each resin molded body has sufficient flame retardancy when attached to the outer periphery of one or more lithium ion secondary battery cells having one or more safety valves or vent holes so as to cover at least the safety valves or vent holes.

In the above examples, the present application examples 10 to 13 each include a mold preservative, a mold release agent, and a colorant, but these mold preservatives, mold release agents, and colorants are not essential components in the resin composition constituting the resin molded article of the present application. Even if these mold preservatives, mold release agents and colorants are not contained, a resin molded article having excellent strength characteristics and low thermal conductivity can be obtained.

The contents of the mold preservative, the mold release agent, and the colorant in examples 10 to 13 of the present application in the above examples are examples, and the contents of the mold preservative, the mold release agent, and the colorant may be increased or decreased as needed to any amounts, and the contents are not limited.

The resin molded articles of each of the present application examples 20 to 28 described in table 2 were also subjected to flame retardancy evaluation simulating the ejection of high temperature/high pressure gas from the safety valve or vent hole of the lithium ion secondary battery due to thermal runaway of the lithium ion secondary battery.

TABLE 2

The resin molded articles of examples 20 to 28 of the present application were found to have a thermal conductivity (measurement temperature: 50 ℃) of less than 1.0W/mK, a thickness of 0.5mm or more and 10.0mm or less, measured according to JIS H7903:2008 by a one-way heat flow steady state comparison method, and a surface hardness of 50 or more and 90 or less, measured according to JIS K7215 by a D-type durometer, and therefore were found to be satisfactory in terms of flame retardancy as in examples 1 to 13 of the present application.

Symbol description

1. Lithium ion secondary battery cell

2. Outer can

3. Positive electrode terminal

4. Negative electrode terminal

5. Safety valve

6. Resin molded body

7. Insulating sheet

8. Adhesive tape

9. Paste composition

10. Outer casing

11. Battery pack

Claims (9)

1. A resin molded body 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, characterized in that,

the resin molded body has a thermal conductivity of less than 1.0W/mK measured according to JIS H7903:2008 and by a unidirectional heat flow steady state comparison method, wherein the measurement temperature is 50 ℃,

the thickness of the portion of the resin molded body covering the safety valve or the vent hole is 0.5mm or more and 10.0mm or less,

the surface hardness of the resin molded body measured according to JIS K7215 and by a D-type durometer is 50 to 90.

2. The resin molded body according to claim 1, wherein,

the thickness of the portion of the resin molded body covering the safety valve or the vent hole is 1.0mm or more.

3. The resin molded body according to claim 1 or 2, wherein,

the resin molded body contains a resin composition containing carbon fibers in an amount of 2 to 70 parts by mass and a silane coupling agent in an amount of 0.3 to 7.0 parts by mass, based on 100 parts by mass of a thermoplastic resin.

4. The resin molded body according to claim 3, wherein,

the resin composition further contains polytetrafluoroethylene in an amount of 50 parts by mass or less per 100 parts by mass of the thermoplastic resin.

5. The resin molded body according to claim 1 or 2, wherein,

the resin molded article comprises a resin composition containing 9 to 80 parts by mass of glass fibers and 0.3 to 7.0 parts by mass of a silane coupling agent per 100 parts by mass of a thermoplastic resin.

6. The resin molded body according to claim 5, wherein,

the resin composition further contains carbon fibers in a range of 2 to 70 parts by mass based on 100 parts by mass of the thermoplastic resin.

7. The resin molded body according to any one of claims 3 to 6, wherein,

the thermoplastic resin is any one or more than two of polyphenylene sulfide, polyamide, polybutylene terephthalate, modified polyphenyl ether and polycarbonate.

8. A battery pack comprising one or more lithium ion secondary battery cells, wherein the resin molded body according to any one of claims 1 to 7 is attached to the outer periphery of the one or more lithium ion secondary battery cells.

9. A battery pack, characterized by comprising: one or more lithium ion secondary battery cells each having a safety valve or a vent hole at one end face thereof; and a resin molded body that is disposed along the one end face of the lithium ion secondary battery cell and covers the safety valve or the vent, the resin molded body being the resin molded body according to any one of claims 1 to 7.