KR20240142053A - Silicone form pad having preventing thermal runaway function and, battery pack with the same - Google Patents

Abstract

The present invention relates to a silicone foam pad for delaying thermal runaway of a battery and a battery pack including the same. The purpose of the present invention is to provide a silicone foam pad for delaying thermal runaway of a battery and a battery pack including the same, which can delay the thermal runaway phenomenon of a battery cell even in a high temperature range of about 1300°C.
The present invention comprises a silicone foam structure including expanded graphite, and when a battery pack experiences thermal runaway, the silicone foam structure is maintained while the volume of the silicone foam pad expands due to the expanded graphite, thereby delaying the thermal runaway phenomenon for about 4 minutes or more even in a temperature range of 1,300°C.

Description

{Silicone form pad having preventing thermal runaway function and, battery pack with the same}

The present invention relates to a silicone foam pad for delaying battery thermal runaway and a battery pack including the same. The silicone foam pad is installed between battery cells to have a buffering function, and when the temperature of the battery cell rises, the foam structure is maintained and the volume is expanded, thereby preventing the thermal runaway phenomenon of the battery cell in a high temperature range of about 1,300°C, and a battery pack including the same.

Eco-friendly vehicles refer to electric vehicles and fuel cell vehicles that do not emit exhaust gases. Eco-friendly vehicles are equipped with a motor for driving and a battery to drive the motor.

In this way, the battery pack applied to an eco-friendly vehicle has a plurality of battery cells stacked within a case, and a buffer pad made of a foam member that can be stretched according to pressure (surface pressure) is placed between the battery cells.

A battery pack constructed as described above experiences a thermal runaway phenomenon when its temperature continuously rises due to manufacturing defects, incorrect handling or misuse of the cells, short-circuiting of some battery cells, etc., or when it is exposed to high temperatures from an external source and the temperature of the battery cells exceeds the critical temperature.

In addition, since the above battery cells are laminated in multiple pieces, there was a problem that if a thermal runaway phenomenon occurred in some battery cells, the thermal runaway phenomenon could spread to adjacent battery cells within a short period of time, leading to a disaster such as fire or explosion of the battery module or battery pack, which is a battery unit with a larger capacity than the battery cell.

In particular, when a thermal runaway phenomenon occurs, the battery cell generates a high temperature range of approximately 600℃ to 800℃, so the risk of fire increases further as surrounding combustibles are ignited due to such high temperatures.

In conventional battery packs for electric vehicles, a buffer pad made of urethane foam (PU foam) is installed between one battery cell and another adjacent battery cell to prevent thermal runaway phenomenon occurring in one battery cell from spreading to the other battery cell, that is, to delay/prevent thermal runaway propagation.

However, the above-mentioned urethane foam (PU foam), although it has a cushioning function that can be expanded according to pressure (surface pressure), has material characteristics of low heat resistance and low flame retardancy, so when the temperature of the battery rises, the foam decomposes in a lower temperature range (around 200°C) than the high temperature range where thermal runaway occurs, and there was a problem in that the required thermal runaway delay effect could not be expected.

In addition, as electric vehicles have become more widespread in recent years, electric vehicle fires have occurred more frequently, and as international standards for preventing such fires in electric vehicles have been strengthened, the verification conditions for batteries, i.e., the battery thermal runaway test conditions at 600℃ to 800℃, have been increased to approximately 1,300℃.

However, there were various problems, such as when a high temperature of about 1,300℃ is applied to one side of a pad installed in a conventional battery cell according to the strengthened verification conditions, a high temperature area of about 600℃ is created on the opposite side, and such high temperature causes surrounding combustibles to ignite, further increasing the risk of fire.

Publication of Patent Publication No. 10-2020-0106378 (2020.09.14) Patent Registration No. 10-1518189 (April 29, 2015) Publication of Patent Publication No. 10-2020-0141570 (2020.12.21) Patent Registration No. 10-2058194 (2019.12.16) Patent Registration No. 10-2425374 (2022.07.21) Patent Registration No. 10-2332128 (2021.11.24)

The purpose of the present invention is to provide a silicone foam pad for delaying battery thermal runaway, which can delay the thermal runaway phenomenon of a battery cell even in a high temperature range of about 1300℃, and a battery pack including the same.

The present invention provides a silicone foam pad for delaying battery thermal runaway, which has improved flame retardancy and thermal insulation properties by adding expanded graphite and has a predetermined CFD so that it can be applied to a battery pack while being formed into a foam structure, and a battery pack including the same.

The purpose of the present invention is to provide a silicon foam pad for delaying battery thermal runaway, in which a silicon foam pad including expanded graphite is installed between battery cells, so that when a thermal runaway phenomenon occurs in some battery cells, the propagation of the thermal runaway phenomenon to another neighboring battery cell can be delayed/prevented by volume expansion due to expanded graphite, and a battery pack including the same.

The present invention comprises a silicone foam structure including expanded graphite, and when a battery pack experiences thermal runaway, the silicone foam structure is maintained while the volume of the silicone foam pad is expanded by the expanded graphite, thereby delaying or preventing heat generated in one battery cell from being transmitted to another battery cell.

The present invention has a predetermined CFD even when expanded graphite is added, and since the volume increases due to the expanded graphite that begins to expand at 200℃ or higher, it has the effect of efficiently delaying the thermal runaway phenomenon of the battery cell. That is, the present invention simultaneously satisfies the predetermined requirements of CFD required for a battery pack and has characteristics corresponding to thermal runaway even when expanded graphite is added.

The present invention has the effect of providing excellent flame retardancy and thermal insulation properties because it is formed into a foam structure by setting the mixing ratio of the components and the foaming molding temperature while adding expanded graphite.

The present invention has the effect of delaying the thermal runaway phenomenon for about 4 minutes or more in a high temperature range of 1,300℃.

The present invention has the effect of maintaining the formability of a silicone foam pad more stably since gas discharge due to impurities in expanded graphite is achieved through pretreatment.

The present invention has the effect of improving the properties and quality of a silicone foam pad by further improving the dispersibility by limiting the powder particle size and reaction temperature expandability of expanded graphite.

The present invention has the effect of further improving self-extinguishing properties and heat diffusion delay effects by mixing a flame retardant filler and a platinum-based flame retardant composed of a phosphate-platinum complex, thereby increasing flame retardancy by the flame retardant filler and the platinum-based flame retardant, and forming a carbonized layer by the platinum-based flame retardant composed of a phosphate-platinum complex, thereby blocking oxygen and further lowering the oxygen concentration by generating graphite ash.

The present invention has many effects, such as improved thermal runaway delay performance in a high-temperature range of 800°C or higher, by providing a non-flammable film made of glass wool, glass fiber, aramid film, ceramic film, or mica film on one or both sides.

Figure 1 is an exemplary diagram showing the configuration of a battery pack including a silicone foam pad (buffer pad) for delaying battery thermal runaway according to the present invention.
Figure 2 is an exemplary diagram showing the configuration of a silicone foam pad for delaying battery thermal runaway according to the present invention.
Figure 3 is an example of the reaction mechanism of a platinum-based flame retardant according to the present invention.
Figure 4 is a photographic example showing the results according to Example 1 of the present invention.
Figure 5 is a photographic example showing the results according to Example 2 of the present invention.
Figure 6 is an example graph showing the results according to Example 3 of the present invention.
Figure 7 is an example graph showing the results according to Example 4 of the present invention.

The silicone foam pad for delaying battery thermal runaway according to the present invention is made of a silicone foam structure including expanded graphite, and when a battery pack experiences thermal runaway, the silicone foam structure is maintained while the volume of the silicone foam pad expands due to the expanded graphite, thereby delaying or preventing heat generated in one battery cell from spreading to another battery cell.

The silicone foam pad for delaying battery thermal runaway according to the present invention is

For 100 parts by weight of polyorganosiloxane,

5 to 50 parts by weight of flame retardant filler composed of aluminum hydroxide or magnesium hydroxide;

5 to 30 parts by weight of expanded graphite,

0.01 to 1.0 parts by weight of a platinum-based flame retardant comprising a phosphate-platinum complex;

It is designed to contain 0.0001 to 0.1 parts by weight of platinum catalyst.

The above polyorganosiloxane comprises 30 to 60 wt% of a first polydiorganosiloxane having at least two unsaturated hydrocarbon groups, 30 to 60 wt% of a second polydiorganosiloxane having one or two hydroxyl groups, 5 to 38 wt% of a third polydihydrogen siloxane having a hydrogen group at a terminal, and 0.2 to 20 wt% of a fourth polydihydrogen siloxane having at least two hydrogen groups.

The above first polydiorganosiloxane is selected from the group consisting of dimethyl siloxane having both molecular chain terminals blocked with dimethylvinylsiloxane groups, a dimethyl siloxane methyl phenylsiloxane copolymer having both molecular chain terminals blocked with dimethylvinylsiloxane groups, and a dimethyl siloxane and methyl trifluoropropyl siloxane copolymer having both molecular chain terminals blocked with dimethylvinylsiloxane groups, having a vinyl group content of 0.05 to 0.3 mmol/g and a viscosity at 25°C of 1,000 to 100,000 cps.

[Chemical Formula 1]

In the above [Chemical Formula 1], R1 is an unsubstituted or substituted group not containing an aliphatic unsaturated bond, preferably a monovalent hydrocarbon having 1 to 10 carbon atoms, particularly 1 to 5 carbon atoms, and examples thereof include a lower alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an aryl group such as a phenyl group, a xylyl group, a benzene group, a cycloalkyl group such as a cyclohexyl group, or a chloromethyl group, a cyanomethyl group, a 3,3,3,-trifluoropropyl group, etc. in which some or all of the hydrogen atoms of these groups are substituted with a halogen atom, a cyano group, etc., and n is 0 or a positive integer.

The above second polydiorganosiloxane is a dimethyl siloxane having both molecular chain terminals blocked with dimethylhydroxy siloxane groups, a dimethyl siloxane methyl phenyl siloxane copolymer having both molecular chain terminals blocked with dimethylhydroxy siloxane groups, and a dimethyl siloxane and methyl trifluoropropyl siloxane copolymer having both molecular chain terminals blocked with dimethylhydroxy siloxane groups, which does not contain an unsaturated hydrocarbon group and has a viscosity at 25°C of 100 to 200,000 cP.

[Chemical formula 2]

In the above [Chemical Formula 1], R1 is an unsubstituted or substituted group not containing an aliphatic unsaturated bond, preferably a monovalent hydrocarbon having 1 to 10 carbon atoms, particularly 1 to 5 carbon atoms, and examples thereof include a lower alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an aryl group such as a phenyl group, a xylyl group, a benzene group, a cycloalkyl group such as a cyclohexyl group, or a chloromethyl group, a cyanomethyl group, a 3,3,3-trifluoropropyl group, etc. in which some or all of the hydrogen atoms of these groups are substituted with a halogen atom, a cyano group, etc., and n is 0 or a positive integer.

The above third polydihydrogen siloxane is a dimethyl siloxane in which both molecular chain terminals are blocked with dimethylhydrogensiloxane groups, a dimethyl siloxane methyl phenyl siloxane copolymer in which both molecular chain terminals are blocked with dimethylhydrogensiloxane groups, and a dimethyl siloxane and methyl trifluoropropyl siloxane copolymer in which both molecular chain terminals are blocked with dimethylhydrogensiloxane groups, which does not contain an aliphatic unsaturated hydrocarbon group and has a viscosity at 25°C of 10 to 10,000 cP.

[Chemical Formula 3]

In the above [chemical formula 3], R1 is an unsubstituted or substituted group not containing an aliphatic unsaturated bond, preferably a monovalent hydrocarbon having 1 to 10 carbon atoms, particularly 1 to 5 carbon atoms, and examples thereof include a lower alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an aryl group such as a phenyl group, a xylyl group, a benzene group, a cycloalkyl group such as a cyclohexyl group, or a chloromethyl group, a cyanomethyl group, a 3,3,3,-trifluoropropyl group, etc., in which some or all of the hydrogen atoms of these groups are substituted with a halogen atom, a cyano group, etc., and n is 0 or a positive integer.

The above-mentioned fourth polydihydrogen siloxane is a copolymer of dimethylsiloxane and methylhydrogen siloxane, in which both terminals of the molecular chain are blocked with trimethylsiloxane groups, has at least two hydrogen atoms bonded to silicon atoms per molecule, contains 1 to 15 mol% of hydrogen groups based on the total organic group, and has a viscosity of 100 to 20,000 cP at 25°C.

[Chemical Formula 4]

In the above [chemical formula 4], R1 and R4 are unsubstituted or substituted groups not containing aliphatic unsaturated bonds and preferably monovalent hydrocarbons having 1 to 10 carbon atoms, particularly 1 to 5 carbon atoms, and examples thereof include lower alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, an aryl group such as a phenyl group, a xylyl group, a benzene group, a cycloalkyl group such as a cyclohexyl group, or a chloromethyl group, a cyanomethyl group, a 3,3,3-trifluoropropyl group, etc. in which some or all of the hydrogen atoms of these groups are substituted with a halogen atom, a cyano group, etc., and n and m are 0 or a positive integer.

The above flame retardant filler is aluminum hydroxide (ATH) or magnesium hydroxide ( ) and is used in an amount of 5 to 50 parts by weight, preferably about 5 to 30 parts by weight, per 100 parts by weight of polyorganosiloxane.

The above flame retardant filler is preferably aluminum hydroxide (ATH) having a particle size of 5 to 60 um, preferably 5 to 30 um.

The above aluminum hydroxide (ATH) has the function of improving the heat resistance of silicone foam by reducing the temperature rise and inhibiting the movement of combustion by causing an endothermic reaction when a fire occurs.

That is, the aluminum hydroxide has a structure in which water molecules are mixed between silica and, when heated, the water molecules burst out from the gaps in the silica, thereby generating non-combustible moisture and metal oxides as products of the combustion reaction, thereby blocking contact with oxygen, which is the cause of combustion, and further improving the heat insulating properties of the silicone foam.

The above aluminum hydroxide may not properly improve heat resistance when added in an amount less than 5 parts by weight, and may rapidly deteriorate the properties of the silicone foam (such as tear strength, stretch, tensile strength, etc.). Therefore, it is added within an appropriate range.

The above-mentioned expanded graphite has the function of improving the flame retardancy and thermal insulation of the silicone foam pad by increasing the volume of the silicone foam pad and generating ash when the temperature of the battery cell rises.

The above-mentioned expanded graphite does not expand at room temperature, but when exposed to temperatures above 200℃, it begins to peel (expand) faster than the initial volume, increasing the volume and forming a heat insulating layer, which is used to improve the flame retardancy and thermal insulation of the silicone foam pad.

When the above expanded graphite is exposed to temperatures above 200℃, graphite ash is generated, and the generated ash lowers the oxygen concentration, resulting in self-extinguishing properties and heat diffusion delay effects.

The above expanded graphite is preferably composed of particles (average particle size of about 250 to 350 μm) that pass through 50 mesh by about 65%. Expanded graphite having such an average particle size has excellent dispersibility when mixed with other components, thereby having the effect of making silicone foam molding more smoothly.

The above expanded graphite may be expanded graphite that begins to expand at 200°C or higher and has an expansion volume of about 180 cm3/g or higher, preferably about 200 cm3/g or higher, at 600°C.

In addition, it is preferable that the expanded graphite has neutral surface characteristics.

Expanded graphite having the above characteristics is added in an amount of 5 to 30 parts by weight, preferably about 5 to 20 parts by weight, and more preferably about 5 to 15 parts by weight, per 100 parts by weight of polyorganosiloxane.

At this time, if the expanded graphite is less than 5 parts by weight, there is a concern that the expandability of the silicone foam pad may decrease, resulting in insufficient expression of flame retardancy and non-flammability characteristics. If it exceeds 30 parts by weight, not only is it difficult to foam mold into a silicone foam structure, but also the expanded graphite is not sufficiently dispersed within the foamed silicone foam, resulting in a deterioration of physical properties. Therefore, it is added within an appropriate range.

In addition, it is preferable that the expanded graphite is pretreated so that gas is discharged by heat treatment. That is, the expanded graphite according to the present invention is preferably expanded graphite that has been heat-treated at less than 200°C, preferably within about 100°C to 180°C, for about 0.2 to 1 hour.

In this way, expanded graphite that has been heat-treated at a low temperature of less than 200℃ has the characteristic of enabling more stable molding of silicone foam pads, since unreacted or potentially generated gases are preemptively discharged through heat treatment during the silicone foam molding process.

That is, when a silicone foam molding process is performed by adding expanded graphite, which is usually flame retardant, a large amount of gas may be generated during the molding process due to impurities contained in the expanded graphite, which may inhibit the catalytic reaction in the silicone reaction mechanism, and this may cause the moldability of the silicone foam pad to deteriorate.

However, if expanded graphite is heat treated at a temperature below 200℃ for a specified period of time, gas generation due to impurities is significantly reduced, so that the phenomenon of reduced formability can be prevented in advance.

As described above, graphite has excellent dispersibility and allows for smooth molding of silicone foam pads even with limitations in average particle size and expansion volume. However, when pretreatment is performed concurrently, gas generation due to impurities is prevented, and even with a high addition amount of 30 parts by weight, excellent dispersibility and smooth or constant molding of silicone foam pads are achieved.

The above platinum-based flame retardant is added to improve the mechanical strength and heat resistance of silicone rubber while imparting flame retardancy, and is composed of a platinum-based flame retardant in which platinum is complexed with phosphate.

The platinum-based flame retardant composed of the above phosphate-platinum complex has the function of reinforcing the deterioration of the physical properties of silicone rubber, increasing the flame retardant effect, and delaying heat diffusion.

In particular, the platinum-based flame retardant composed of the phosphate-platinum complex forms a carbon layer (carbon film) by reacting with silicon (polysiloxane) when a thermal runaway phenomenon occurs, thereby further delaying heat diffusion between battery cells.

The above platinum-based flame retardant may be one selected from among Pt{P(CH ₃ ) ₃ } ₄ , Pt{P(C4H ₉ ) ₃ } ₄ , Pt{P(OCH ₃ ) ₃ } ₄ , Pt{P(OC ₆ H ₅ ) ₃ } ₃ , Pt{P(C ₆ H ₅ ) ₃ } ₃ , Pt{P(OC ₆ H ₅ ) ₃ } ₄ , Pt{P(C ₆ H ₅ ) ₃ } ₄ , Pt{P(C ₆ H ₅ )(C ₂ H ₅ ) ₂ } ₄ , Pt{P(OC ₆ H ₅ )(OC ₂ H ₅ ) ₂ } ₄ , Pt{P(C ₆ H ₅ ) ₂ (OC ₂ H ₅ )} _{4 .} there is.

In addition, a platinum-based flame retardant composed of the above phosphate-platinum complex may be used, for example, a platinum-based flame retardant according to the following [Chemical Formula 5].

[Chemical Formula 5]

FIG. 3 is a diagram illustrating an example of the reaction mechanism of a platinum-based flame retardant according to the present invention, wherein the mechanism in which trypheny phosphite (TPP) undergoes a radical addition reaction at the end of PDMS (polydimethyl siloxane) is illustrated. In this way, the platinum-based flame retardant according to the present invention forms a carbonized layer on the side of the silicone foam through addition reaction by thermal decomposition when the temperature of the battery cell rises, thereby blocking the supply/contact of oxygen and providing a function of delaying heat diffusion.

In addition, the platinum-based flame retardant according to the present invention forms a hard carbonized layer on the surface of the silicone foam, so that the volume of the silicone foam is expanded by the expanded graphite, and the carbonized layer formed on the surface maintains the silicone foam structure constant, thereby further delaying the thermal runaway propagation phenomenon.

In addition, the formation of a carbon layer of the platinum-based flame retardant as described above has the function of preventing the physical properties of silicone rubber from being deteriorated due to the addition of a flame retardant filler. That is, aluminum hydroxide (ATH) or magnesium hydroxide ( ) has excellent flame retardancy, but when high temperatures occur, the physical properties and heat resistance of silicone rubber may deteriorate.

However, the present invention comprises aluminum hydroxide (ATH) or magnesium hydroxide ( ) is mixed with a platinum-based flame retardant and a flame retardant filler, so that heat diffusion and decomposition of the foam are prevented by a carbon layer that is hardened and formed on the surface of the silicone side, thereby preventing the deterioration of the physical properties and heat resistance of the silicone rubber due to the addition of the flame retardant filler when a high temperature occurs.

The above platinum-based flame retardant is used in an amount of 0.01 to 1.0 parts by weight per 100 parts by weight of polyorganosiloxane, and preferably 0.01 to 0.5 parts by weight.

The above platinum-based flame retardant cannot be expected to improve flame retardancy if used in amounts less than 0.01 part by weight, and if added in amounts exceeding 1.0 part by weight, flame retardancy actually decreases, so it is added within an appropriate range.

In addition, the platinum-based flame retardant can be used by dispersing it in an organic solvent such as alcohol, isopropyl alcohol, benzene, or xylene.

The platinum-based catalyst is platinum or a platinum compound, and a known platinum-based catalyst used in the production of silicon is used. The platinum-based catalyst uses single platinum or a platinum compound. The platinum-based catalyst includes, for example, single platinum (Pt), H ₂ PtCl ₆ ·nH ₂ O, NaHPtCl ₆ ·nH ₂ O, KHPtCl ₆ ·nH ₂ O, NaPtCl ₆ ·nH ₂ O, K ₂ PtCl ₆ ·nH ₂ O, PtCl ₄ ·nH ₂ O, PtCl ₂ , NaPtCl ₄ ·nH ₂ O, and H ₂ PtCl ₄ ·nH ₂ O.

In addition, the present invention may further include 0.01 to 4.0 parts by weight of a silane coupling agent to further improve the dispersibility for expanded graphite. That is, the present invention may further include 0.01 to 4.0 parts by weight of a silane coupling agent per 100 parts by weight of polyorganosiloxane.

The above silane coupling agent is at least one silane having a Vinyl, Methacryl, Amino, Epoxy, Mercapto, Acryl group and Hexamethyldisilazane, and most preferably, a Vinyl-based silane (e.g., Vinyltrimethoxyethoxysilane) and a Methacryl-based silane (e.g., 3-Methacryloxypropyl trimethoxysilane) are used.

Such a silane coupling agent is mixed into the polyorganosiloxane before the expanded graphite is added during the compounding process, or the surface of the expanded graphite is coated by the reaction of the single functional group of the silane coupling agent with the expanded graphite by mixing, thereby increasing the dispersibility with the silicone polymer.

The present invention, which is formed as described above, forms a silicone foam pad by foaming at about 100°C to 140°C.

That is, conventional silicone foam (for example, silicone foam for preventing thermal runaway according to Patent Publication No. 10-2425374 and Patent Publication No. 10-2332128, which were applied for and registered by the applicant of the present invention) is designed to undergo foaming at a temperature of about 80℃ or higher and less than 100℃.

In the present invention, 5 to 50 parts by weight of a flame retardant filler, 5 to 30 parts by weight of expandable graphite, 0.01 to 1.0 parts by weight of a platinum-based flame retardant composed of a phosphate-platinum complex, and 0.0001 to 0.1 parts by weight of a platinum catalyst are compounded with respect to 100 parts by weight of polyorganosiloxane and then foamed. Therefore, when foaming is performed at a temperature of about 80°C or higher and less than 100°C, as in the case of a conventional silicone foam pad, the formability into a foam structure deteriorates due to low reactivity, resulting in a phenomenon in which the physical properties of the product are deteriorated, particularly, the CFD (compressive strength) is deteriorated. That is, the present invention is configured to form a silicone foam pad by foaming at a high temperature of about 100°C to 140°C, so that the problem of low reactivity caused by the addition of expandable graphite and the adjustment of the content of other components accordingly is resolved.

In this way, the silicone foam pad (20) of the present invention, which is foam-molded at a high temperature of about 100℃ to 140℃, is room temperature-curable and has a foam structure having a thickness of 1.0 to 15 mm, a hardness (ShoreOO) of 20 to 60, and a density of 0.20 to 0.45 (g/cm2), and has rubber elasticity, so that it is installed between battery cells to have a buffering function and a reverse runaway prevention function.

In addition, the silicone foam pad according to the present invention contains expanded graphite, so that when the temperature of the battery cell reaches 200°C, it begins to undergo an expansion reaction, and when it exceeds 1,000°C, it expands to about 1.5 (V) to 3 (V) with respect to the initial volume (V), thereby improving flame retardancy and thermal insulation, and thereby delaying the thermal runaway phenomenon.

In addition, since the foaming molding conditions (excluding temperature conditions) according to the compounding of the components according to the present invention are performed by known techniques, a detailed description thereof is omitted.

Figure 1 is an exemplary diagram showing the configuration of a battery pack including a silicone foam pad (buffer pad) for delaying battery thermal runaway according to the present invention.

The battery pack (100) according to the present invention comprises a battery module (30) with a silicone foam pad (20) positioned between a plurality of stacked battery cells (10) and provided in a case (40).

The above silicone foam pad (20) is configured to be foam-molded into a foam structure at about 100°C to 140°C, including 5 to 50 parts by weight of a flame-retardant filler made of aluminum hydroxide or magnesium hydroxide, 5 to 30 parts by weight of expanded graphite, 0.01 to 1.0 parts by weight of a platinum-based flame retardant made of a phosphate-platinum complex, and 0.0001 to 0.1 parts by weight of a platinum catalyst, with respect to 100 parts by weight of polyorganosiloxane.

In addition, the present invention may further include 0.01 to 4.0 parts by weight of a silane coupling agent per 100 parts by weight of polyorganosiloxane.

In addition, the silicone foam pad (20) for delaying battery thermal runaway according to the present invention may be configured to further include a fire-retardant film (21) on one or both sides, as shown in FIG. 2.

The above-mentioned non-combustible film (21) may be made of glass wool, aramid film, MICA film, ceramic film, asbestos, etc. In addition, the above-mentioned non-combustible film (21) may be made of a thickness of 50 um to 2000 um, preferably about 100 to 500 um.

The battery pack (100) of the present invention configured as described above has a silicone foam pad (20) having a foam structure and a thickness of 1.5 to 15 mm installed between the battery cells (10), so as to have an absorption capacity for shrinkage and expansion of the cells, that is, an elasticity/buffering function according to pressure (surface pressure), and in the event of a fire, the flame retardancy is increased by the expanded graphite and the flame retardant filler, and at the same time, the volume is increased by the expanded graphite, and a hard carbonized layer is formed on the surface by the platinum-based flame retardant composed of a phosphate-platinum complex in a chain manner, so as to have a function of delaying the spread of a thermal runaway phenomenon occurring in one battery cell to another battery cell.

That is, as shown in FIG. 5, the silicone foam pad (20) according to the present invention prevents expansion of the battery cell due to the high expansion force of the expanded graphite when a high temperature occurs and expands into the space created when the battery cell is destroyed, thereby delaying the reverse runaway phenomenon.

In Fig. 1, the unexplained reference numeral 50 denotes a cooling plate, 60 denotes a heat insulating foam, and 70 denotes a seal. The battery pack illustrated in Fig. 1 is merely an example, and the configuration of the battery pack according to the present invention is not limited to Fig. 1.

Example 1

The foaming formability according to the amount of expanded graphite added was tested, and the results are shown in Fig. 4. 10 wt%, 15 wt%, 20 wt%, and 25 wt% shown in Fig. 4 represent the amount of expanded graphite added, and the other components used were 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of a platinum-based flame retardant composed of a phosphate-platinum complex, and 0.01 parts by weight of a platinum catalyst, with respect to 100 parts by weight of polyorganosiloxane, and the foaming temperature was set to about 110°C.

At this time, the polyorganosiloxane means that it includes 42 wt% of a first polydiorganosiloxane having at least two unsaturated hydrocarbon groups, 42 wt% of a second polydiorganosiloxane having one or two hydroxyl groups, 10 wt% of a third polydihydrogen siloxane having a hydrogen group at a terminal, and 6 wt% of a fourth polydihydrogen siloxane having at least two hydrogen groups.

As shown in Fig. 4, it can be seen that all silicone foam pads with a foam structure were foam-molded regardless of the amount of expanded graphite added.

Example 2

After producing a specimen according to the mixing ratio in [Table 1], the expansion phenomenon according to direct heat (approximately 600℃, approximately 60 seconds) was observed, and the results are shown in Fig. 5.

[Table 1]

In [Table 1], the polyorganosiloxane used was the polyorganosiloxane according to Example 1.

As shown in Figure 5, it can be seen that as the amount of graphite added increases, a volume increase phenomenon due to expansion occurs.

Example 3

After producing specimens according to the mixing ratio in [Table 2], the thermal diffusion delay effect at 1,300℃ for the specimens was measured.

The above thermal diffusion delay effect was measured by installing insulation pads on both sides of a specimen (2 mm thick), processing a hole with a diameter of approximately 50 mm, applying heat of 1,300°C to one side, and measuring the temperature reached on the opposite side. The results are shown in Fig. 6.

[Table 2]

In [Table 2], the polyorganosiloxane used was the polyorganosiloxane according to Example 1.

As shown in Fig. 6, in the case of the control specimen without the addition of expanded graphite, the temperature reached on the opposite side rises to about 500°C in about 50 seconds, and the temperature then gradually increases and remains below about 600°C after 4 minutes (240 seconds).

It can be seen that the temperature of the opposite surfaces of specimens 1 and 2 according to the present invention is approximately 100°C after about 50 seconds, and is maintained below about 200°C even after 4 minutes (240 seconds).

That is, it can be seen that the present invention has the effect of efficiently delaying thermal runaway for more than 4 minutes in an ultra-high temperature region of 1,300℃ or higher where rapid thermal runaway phenomenon occurs. In particular, although not shown in Fig. 6, the temperature reached on the opposite side was maintained below about 220℃ even after 10 minutes.

Example 4

CFD (Compressive strength and Compression ratio) was measured for the specimens according to the mixing ratio in [Table 2] above. CFD (Compressive strength and Compression ratio) measurement was performed under the conditions in [Table 3] below (Experimental conditions for measuring CFD basic requirements), and the results are shown in [Table 4] and Fig. 7. (The test equipment used was Model 68YM-50: INSSTRON.)

The above CFD (compressive strength and compression ratio) is an important factor for stably supporting battery cells undergoing contraction/expansion, and must satisfy the basic requirements (compression ratio 13%: 0.03∼0.15 (kgf/㎠), compression ratio 45%: ∼0.67 (kgf/㎠), MAX COMPRESSION OVER 72%). That is, when the battery generates heat, the battery cells expand and the pads arranged between the battery cells contract (compress), and when the battery cools, the battery cells contract and the pads arranged between the battery cells expand (restore). In order for the battery cells to be stably supported by this contraction/expansion (restore) of the pads, the CFD (compressive strength and compression ratio) must be within the basic requirements.

[Table 3]

[Table 4]

As shown in [Table 4] and [Fig. 7], it can be seen that all of the specimens 1, 2, and the control specimen meet the basic requirements of CFD required for pads for battery cells.

In addition, although not shown in [Table 4] and [Fig. 7], all of the specimens 1, 2, and the control specimen had very excellent compression ratios, with MAX COMPRESSION OVER 82.10%, 80.02%, and 83.40%, respectively. This can be seen to be a very excellent compression ratio, considering that the compression ratio of the existing buffer pad placed in the battery pack is typically about 75%.

The present invention is not limited to the specific preferred embodiments described above, and anyone with ordinary skill in the art to which the present invention pertains may make various modifications without departing from the gist of the present invention claimed in the claims, and such modifications are within the scope of the claims.

In addition, since the terms described in the present invention are intended to distinguish one component from another and to aid in understanding the present invention, the components of the present invention are not limited by the terms described.

(10): Battery Cell (20): Silicone Foam Pad
(30) : Battery module (40) : Case
(50) : Cooling plate (60) : Heat insulation foam
(70) : Seal (100) : Battery Pack

Claims (8)

For 100 parts by weight of polyorganosiloxane,
5 to 50 parts by weight of flame retardant filler composed of aluminum hydroxide or magnesium hydroxide;
5 to 30 parts by weight of expanded graphite,
0.01 to 1.0 parts by weight of a platinum-based flame retardant comprising a phosphate-platinum complex;
A silicone foam pad for delaying battery thermal runaway, characterized in that it is foam-molded into a foam structure at a temperature of 100°C to 140°C, and contains 0.0001 to 0.1 weight part of a platinum catalyst.
In claim 1;
A silicone foam pad for delaying battery thermal runaway, characterized by expanded graphite having an average particle size of 250 to 350 μm.
In claim 2;
A silicone foam pad for delaying battery thermal runaway, characterized in that expanded graphite begins to expand at 200°C or higher and has an expansion volume of 180㎤/g or higher at 600°C.
In claim 3;
Expanded graphite is a silicone foam pad for delaying battery thermal runaway, characterized by having neutral surface properties.
In any one of claims 1 to 4;
A silicone foam pad for delaying battery thermal runaway, characterized in that the expanded graphite is expanded graphite heat-treated at 100℃ to 180℃ for 0.2 to 1 hour.
In claim 1;
The polyorganosiloxane comprises 30 to 60 wt% of a first polydiorganosiloxane having at least two unsaturated hydrocarbon groups, 30 to 60 wt% of a second polydiorganosiloxane having one or two hydroxyl groups, 5 to 38 wt% of a third polydihydrogen siloxane having a hydrogen group at a terminal, and 0.2 to 20 wt% of a fourth polydihydrogen siloxane having at least two hydrogen groups.
A silicone foam pad for delaying battery thermal runaway, characterized in that the platinum-based flame retardant composed of a phosphate-platinum complex is a platinum-based flame retardant according to [chemical formula 5].
[Chemical Formula 5]

A battery module with a silicon foam pad placed between a plurality of stacked battery cells is provided within the case.
A battery pack including a silicone foam pad for delaying battery thermal runaway, characterized in that the silicone foam pad is made of a silicone foam pad according to any one of claims 1 to 4.
In claim 7;
The silicone foam pad may be provided with a non-flammable film on one or both sides.
A battery pack including a silicone foam pad for delaying battery thermal runaway, characterized in that the above-mentioned fire-retardant film is one selected from glass wool, aramid film, MICA film, ceramic film, and asbestos.