Foam and secondary battery comprising same

Abstract

The present specification relates to a foam having excellent durability and fire resistance, the foam comprising a foaming agent, an inorganic filler, and an organic binder, wherein the foam has an impact absorption energy density of 0.20J / cm2 or more, and the expansion rate (E) derived from Equation 1 is 1.2 or more. The foam has excellent foaming expansion and ability to maintain an expanded state, stably preventing heat propagation or thermal runaway. A secondary battery and a battery box comprising the foam have excellent fire resistance and safety, making it possible to provide an electrical device capable of ensuring the safety of a user.

Description

Foam and secondary battery containing the same

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196780 filed on December 26, 2024, Korean Patent Application No. 10-2025-0084739 filed on June 25, 2025, Korean Patent Application No. 10-2025-0166732 filed on November 6, 2025, and Korean Patent Application No. 10-2025-0196378 filed on December 11, 2025, and all contents disclosed in said Korean patent application documents are incorporated herein as part of the specification.

[0003] Technology field

[0004] In this specification, technology relating to a foam and a secondary battery including said foam is disclosed.

[0005]

[0006] Secondary batteries are used in a wide range of fields, including small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and E-bikes, as well as large products requiring high output such as electric vehicles and hybrid vehicles, and power storage devices and backup power storage devices that store surplus power or renewable energy.

[0007] As the scope of applications for secondary batteries expands, demands for their safety are increasing. During the charging and discharging process, the temperature of the electrodes can rise rapidly, posing a risk of fire or explosion. For instance, if thermal runaway occurs in a secondary battery equipped in an electric vehicle, it can lead to a major fire or a series of explosions that affect adjacent vehicles, potentially resulting in casualties and property damage.

[0008] Specifically, during the charging and discharging process, secondary batteries may experience thermal runaway, such as ignition or explosion, due to internal factors or external impacts, including electrolyte leakage, excessive gas generation, and internal short circuits. In particular, when multiple secondary batteries are installed in a device, such as an electric vehicle, significant damage can occur due to thermal propagation, where a fire or explosion in only one battery spreads to adjacent batteries.

[0009] Therefore, technology is needed to prevent damage caused by heat propagation and fire.

[0010]

[0011] The present specification aims to provide a foam that ensures durability for long-term use by having excellent internal moisture retention capabilities even in environments with large temperature fluctuations, and allows for the expectation of maximum foaming effect through foaming at a specific temperature, while also having excellent thickness expansion rates due to foaming and the ability to maintain this state, thereby stably preventing heat propagation or thermal runaway.

[0012] In addition, the present specification aims to provide a secondary battery with excellent fire resistance and safety by including the foam, which can effectively delay or prevent heat propagation and thermal runaway even when a thermal event occurs.

[0013]

[0014] [1] In one embodiment, the foam comprises a blowing agent, an inorganic filler, and an organic binder, with an impact absorption energy density of 0.2 J / cm² 2 A foam is provided having an expansion rate (E) of 1.2 or more, derived by the following formula 1.

[0015] [Equation 1]

[0016] E = (T e - T i ) / T i

[0017] In the above Equation 1, T i is the initial thickness (cm) of the foam, and T e is the full expansion thickness (cm) of the above foam.

[0018] [2] The present invention relates to the foam of [1], wherein the Expansion Toughness Index (ETI) derived by the following Formula 2 is 2.0 cm 2 It can be more than / J.

[0019] [Equation 2]

[0020] ETI = E / F

[0021] In the above Equation 2,

[0022] E is the expansion rate, derived by Equation 1 above, and F is the shock absorption energy density (J / cm²) of the foam. 2 )am.

[0023] [3] The present invention relates to a foam of [1] and / or [2], wherein the expansion strength index (ETI) derived by Equation 2 is 2.0 cm 2 / J to 12.0cm 2 / J could be.

[0024] [4] The present invention relates to at least one foam of [1] to [3], wherein the shock absorption energy density is 0.20 J / cm² 2 Up to 0.75 J / cm 2 And, the expansion rate (E) derived by the above Equation 1 can be 1.2 to 5.0.

[0025] [5] In the present invention, in at least one of [1] to [4] foams, the foaming agent may be included in an amount of 20 to 90 parts by weight relative to 100 parts by weight of the foam.

[0026] [6] In the present invention, in at least one foam of [1] to [4], the organic binder may include an elastic binder and a reinforcing binder.

[0027] [7] In the foam of [6] above, the present invention may satisfy K of Formula 3 below from 0.4 to 2.2:

[0028] [Equation 3]

[0029] K = B e / B r

[0030] In the above Equation 3,

[0031] B e is the weight percentage of the elastic binder based on the total weight of the foam, and B r is the weight percentage of the reinforcing binder based on the total weight of the foam.

[0032] [8] In the foam of [6], the elastic binder may comprise one or more selected from the group consisting of styrene-butadiene rubber, nitrile rubber, polyester resin, cellulose resin, urethane resin and silicone rubber.

[0033] [9] In the foam of [6], the reinforcing binder may comprise one or more selected from the group consisting of epoxy resin and phenolic resin.

[0034]

[0010] The present invention may have a weight ratio of the inorganic filler and the foaming agent in at least one of [1] to [9], such that the weight ratio is 1:1 to 1:36.

[0035]

[0011] The present invention relates to at least one foam of [1] to

[0010] , wherein when the foam is foamed, the foaming agent forms a three-dimensional network structure having pores, and the inorganic filler may have a structure disposed within the pores.

[0036]

[0012] The present invention [1] to

[0011] , wherein at least one foam is provided, the foaming agent may include one or more selected from the group consisting of lithium silicate, potassium silicate, sodium silicate, zirconium silicate, magnesium silicate, and titanium silicate.

[0037]

[0013] The present invention comprises at least one foam of [1] to

[0012] , wherein the foaming agent comprises sodium silicate, and the sodium silicate may satisfy Formula 4 below.

[0038] [Equation 4]

[0039] 2.0 ≤ M S / M N ≤ 4.5

[0040] In the above Equation 4, M S is the molar ratio of SiO2 contained in the above sodium silicate, and M N This is the molar ratio of Na2O contained in the above sodium silicate.

[0041]

[0014] In the present invention, at least one foam of [1] to

[0013] may have a thickness of 0.1 mm to 100 mm.

[0042]

[0015] The present invention [1] to

[0014] , wherein at least one foam is provided, the inorganic filler may comprise one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide and boehmite.

[0043]

[0016] In another embodiment, a secondary battery is provided comprising: an electrode assembly including a plurality of electrodes; a battery case in which the electrode assembly is housed; and a foam according to at least one of [1] to

[0015] , wherein the foam is positioned at one or more locations selected from the interior of the electrode assembly, between the electrode assembly and the battery case, and a space other than the space in which the electrode assembly is housed within the battery case.

[0044]

[0045] The foam according to the present specification has excellent internal moisture retention capabilities even in environments with large temperature fluctuations, thereby ensuring processability during secondary battery manufacturing and durability for long-term use. Furthermore, while maximum foaming effect can be expected through foaming at a specific temperature, it exhibits excellent thickness expansion rates due to foaming and the ability to maintain this state, allowing for stable control of heat propagation or thermal runaway.

[0046] In addition, the secondary battery and / or battery box according to the present specification may have excellent fire resistance and safety by including the foam, thereby effectively delaying or preventing heat propagation and / or thermal runaway even when a thermal event occurs.

[0047]

[0048] FIG. 1 is a schematic diagram showing a cross-section of a foamed body before foaming according to the present specification.

[0049] FIG. 2 is a schematic diagram showing a cross-section of a foam after foaming according to the present specification.

[0050] Figure 3 is a diagram showing a method for measuring the expansion rate of a foam.

[0051] FIG. 4 is a cross-sectional view of a secondary battery according to the present specification.

[0052] FIG. 5 is a cross-sectional view of a battery box according to the present specification.

[0053]

[0054] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0055] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0056] In this specification, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0057]

[0058] The foam, secondary battery, and battery box described in this specification include at least one of the technical configurations described below, and may include any combination of technically feasible configurations among the technical configurations below.

[0059] Below, the above foam, secondary battery, and battery box will be described in detail.

[0060]

[0061] foam

[0062] In one aspect, a foam comprising a blowing agent, an inorganic filler, and an organic binder, having an impact absorption energy density of 0.20 J / cm² 2A foam is provided having an expansion rate (E) of 1.2 or more, derived by the following formula 1.

[0063] [Equation 1]

[0064] E = (T e - T i ) / T i

[0065] In the above Equation 1,

[0066] T i is the initial thickness (cm) of the foam above, and

[0067] T e is the full expansion thickness (cm) of the above foam.

[0068] The above shock absorption energy density is the shock energy (J) required for fracture or breakage of the specimen, measured through the Izod impact test (modified ASTM D256 method), divided by the cross-sectional area (cm²) of the specimen. 2 Value divided by ) (J / cm 2 It means ) and is an indicator representing the impact resistance per unit area of ​​the above foam.

[0069] The above expansion rate represents the degree of thickness increase after foaming the foam as a ratio to the initial thickness. Specifically, a foam cut to a width and depth of 5 cm and a thickness of 0.2 cm is placed on an insulation board, and then a heating plate heated to 750°C is brought into contact with the side opposite the positive / negative surface in contact with the insulation board for 30 seconds to induce foaming. After foaming is complete, the thickness of the foam (fully expanded thickness, T e Measure the initial thickness (T) before foaming. i Calculated according to the above Equation 1 by comparing with ).

[0070]

[0071] The above foam comprises a foaming agent, an inorganic filler, and an organic binder. FIG. 1 is a schematic diagram showing a cross-section of the foam before foaming. Referring to FIG. 1, before the foam (10) is foamed, the organic binder (13) may function as a matrix and may have a structure in which the foaming agent (11) and the inorganic filler (12) are filled within the organic binder matrix.

[0072] FIG. 2 is a schematic diagram showing a cross-section of a foam after foaming. Referring to FIG. 2, when the foam (10) is foamed at a temperature above a certain temperature, the organic binder (13) matrix maintains its matrix as is, while the foaming agent (11) forms a three-dimensional network structure having pores (14), and the inorganic filler (12) is dispersed inside the pores (14) formed by the foaming agent (11) to more firmly support the three-dimensional network structure.

[0073] In one embodiment, the thickness of the foam may be 0.1 mm to 100 mm. Specifically, the thickness of the foam may be 0.1 mm or more, 0.3 mm or more, 0.5 mm or more, or 1 mm or more. Additionally, the thickness of the foam may be 100 mm or less, 50 mm or less, 30 mm or less, 10 mm or less, 8 mm or less, 5 mm or less, 3 mm or less, or 2.5 mm or less. The above numerical ranges may be combined with each other without limitation. When the thickness of the foam satisfies the above range, it can effectively block heat transfer by expanding in the thickness direction when a thermal event occurs, without occupying an excessive volume within the internal space of the secondary battery or battery box.

[0074]

[0075] Shock absorption energy density and expansion rate

[0076] Typically, when a battery cell or battery box ignites, a large amount of gas is generated internally, placing the cell's interior under high temperature and pressure. Under these conditions, if heat is transferred between adjacent cells, a chain reaction of runaway failures may occur, which can severely compromise the safety of the entire battery system.

[0077] To solve these problems, the present invention provides a foam that separates internal cell members or cells at a certain distance using a foam, and ensures safety by preventing heat propagation and thermal runaway through the foam maintaining a separated state even in a high-pressure environment.

[0078] Specifically, the foam of the present invention has an impact absorption energy density of 0.2 J / cm² 2 The above conditions are satisfied, and the expansion rate derived by Equation (1) is 1.2 or higher. By simultaneously satisfying the shock absorption energy density and the expansion rate in this way, the foam not only has excellent durability and processability, but its fire resistance and thermal safety can also be significantly improved. Conversely, the shock absorption energy density of the foam is 0.2 J / cm² 2 If the thickness expansion rate is less than 1.2, cracks or damage may occur due to impacts during the secondary battery manufacturing process or during movement in the process. Additionally, if the thickness expansion rate due to foaming is low, the heat propagation blocking effect may be weak, or if the expansion rate cannot be maintained consistently, the heat blocking effect may be easily weakened, resulting in reduced thermal safety.

[0079] Accordingly, the foam of the present invention has a shock absorption energy density of 0.2 J / cm² 2By simultaneously satisfying the conditions of having an expansion rate of 1.2 or higher, high durability ensures stability during the manufacturing process, effectively blocks heat propagation between adjacent cells through a sufficient thickness expansion rate, and maintains the thickness stably after foaming even in a high-pressure environment that occurs during ignition, thereby improving the thermal safety of the battery system.

[0080] The expansion rate and shock absorption energy density of the above foam can be influenced by various factors. As the foam expands in the thickness direction during the foaming process, it forms a number of pore structures; however, a foam having such pore structures can easily undergo deformation in which its thickness decreases again due to external pressure. Therefore, in order to prevent the phenomenon of the thickness decreasing again after foaming, a configuration capable of supporting the pore structure so that it does not collapse is required.

[0081] For example, when inorganic fillers are included, the type, content, and shape of the inorganic fillers can affect the mechanical stability of the foam. When inorganic fillers are properly dispersed, they are placed inside the pores of the three-dimensional network structure formed during the foaming process, and can support the pores so that they do not easily collapse under external pressure. In this case, the content of the inorganic fillers can also affect the final expansion thickness of the foam. For instance, if the inorganic filler content is too low, the support strength of the pore structure is insufficient, which may reduce the thickness retention after foaming; conversely, if the inorganic filler content is excessively high, foaming may not occur sufficiently, which may reduce the expansion rate.

[0082] As another example, the type and content of the blowing agent can also affect the expansion rate and shock absorption energy density. Blowing agents generate gas as they decompose under specific temperature conditions, and the final expansion rate reached by the foam can vary depending on the decomposition temperature characteristics of the blowing agent. Furthermore, the size and distribution of pores formed vary depending on the type and content of the blowing agent, which in turn affects the thickness and rigidity of the framework forming the three-dimensional network structure.

[0083] As another example, the type and content of the organic binder can also affect the expansion rate and shock absorption energy density. The organic binder contributes to the mechanical strength of the foam prior to foaming. By forming a structure that supports inorganic particles and the blowing agent within the foam, the organic binder can reduce the failure rate caused by breakage during processes such as drops or impacts. Furthermore, the organic binder contributes to maintaining a matrix structure that allows for stable processing during foaming. Specifically, if the organic binder content is too low, the foamed structure becomes weak, increasing the risk of breakage due to impact; conversely, if the organic binder content is excessively high, the thickness expansion rate may not be sufficiently secured.

[0084] The expansion rate (E) defined by the above Equation 1 may be affected by the factors mentioned above. When all the effects of these factors are taken into account, the foam may have an expansion rate (E) defined by the above Equation 1 of 1.2 to 5.0. Specifically, the expansion rate defined by the above Equation 1 may be 1.2 or higher, 1.3 or higher, 1.4 or higher, 1.5 or higher, 2.0 or higher, 2.5 or higher, or 2.8 or higher. Additionally, the expansion rate (E) defined by the above Equation 1 may be 5.0 or lower, 4.5 or lower, 4.0 or lower, 3.5 or lower, or 3.4 or lower. The above numerical ranges may be combined without limitation. For example, the expansion rate (E) defined by the above Equation 1 may be 1.2 to 5.0, 1.4 to 5.0, 1.4 to 3.5, or 1.5 to 3.5.

[0085] The above expansion rate functions to separate the cell or cell member where ignition has occurred from the adjacent cell or cell member, and while a larger rate is desirable, safety cannot be ensured simply by having a large expansion rate, so it is desirable to design the foam to satisfy the aforementioned shock absorption energy density range.

[0086] In one embodiment, the shock absorption energy density is 0.20 J / cm² 2 Up to 0.75 J / cm 2 It may be. The above shock absorption energy density refers to the impact resistance per unit area of ​​the foam and may be an indicator representing the degree to which damage or cracking caused by external impact can be suppressed. Specifically, the above shock absorption energy density is 0.20 J / cm² 2 Above, 0.23 J / cm² 2 Above, 0.25 J / cm² 2 Above, 0.30 J / cm² 2 Above, 0.35 J / cm² 2 Above, 0.40 J / cm² 2 Above, or 0.45 J / cm 2It may be more than that. In addition, the shock absorption energy density is 0.75 J / cm² 2 Below, 0.70 J / cm 2 Below, 0.69 J / cm² 2 Below, 0.68 J / cm² 2 Below, 0.60 J / cm² 2 Below, 0.59 J / cm 2 Less than 0.58 / cm 2 Less than, or 0.55 J / cm² 2 It may be less than or equal to. The above numerical ranges may be combined without limitation. For example, the shock absorption energy density is 0.2 J / cm² 2 Up to 0.75 J / cm 2 , 0.2J / cm 2 Up to 0.69 J / cm 2 , 0.23J / cm 2 Up to 0.69 J / cm 2 , or 0.25 J / cm 2 Up to 0.69 J / cm 2 It may be possible. When the shock-absorbing energy density satisfies the above range, the foam can be prevented from being damaged by shocks or shaking that occur during the handling and assembly process of the battery cell manufacturing process. In addition, when the shock-absorbing energy density of the foam satisfies the above range, damage caused by external impact inside the battery box can be prevented, and at the same time, the foamed thickness can be stably maintained even in a thermal runaway situation.

[0087]

[0088] Expansion strength index

[0089] In one embodiment, the foam has an Expansion Toughness Index (ETI) of 2.0 cm derived by the following Formula 2. 2 It can be more than / J.

[0090] [Equation 2]

[0091] ETI = E / F

[0092] In the above Equation 2,

[0093] E is the expansion rate, derived by Equation 1 above, and F is the shock absorption energy density (J / cm²) of the foam. 2 )am.

[0094] The aforementioned Expansion Toughness Index (ETI) is the ratio of the expansion rate to the shock absorption energy density, and is a comprehensive indicator of thermal and mechanical stability that indicates whether the foam can maintain impact resistance while securing a thickness expansion of a certain amount or more during foaming.

[0095] When the composition and process conditions of the foam appropriately balance the shock absorption energy density and the expansion rate, the Expansion Strength Index (ETI), defined by Equation 2 below, can be secured above a specific threshold value. In particular, when the ETI is 2.0 cm 2 In the case of / J or higher, the foam can stably maintain its thickness after foaming in a high-temperature and high-pressure environment while securing sufficient impact resistance, so it can be said to have optimal conditions for preventing heat propagation and runaway between battery cells.

[0096] Specifically, since the foam must not break due to shock or shaking that occurs during movement or handling in the secondary battery manufacturing process, it is necessary to have sufficient durability to facilitate placement inside the cell or battery box. However, simply ensuring mechanical durability is not sufficient; it must exhibit an excellent thickness expansion rate during foaming to secure spacing between internal cell components or between cells, and this spacing must be maintained even in high temperature and high pressure environments to effectively prevent heat propagation to adjacent cells and thermal runaway.

[0097] The above expansion strength index indicates that a higher value signifies greater expansion of the foam relative to its shock absorption energy density, while a lower value signifies a relatively higher shock absorption energy density relative to the expansion rate. In particular, when the expansion strength index is sufficiently high, it can effectively suppress heat propagation to adjacent cells and thermal runaway even if abnormal high-temperature and high-pressure environments are created inside the battery cell or box, thereby serving as an important indicator to guarantee system safety.

[0098] However, the expansion strength index does not necessarily have an excellent value simply because the expansion rate is high; if the impact resistance is low, making it difficult to handle during the process, or if it is easily damaged by external impact, it is difficult to secure performance as a foam. Therefore, if the expansion strength index calculated according to Equation 2 above satisfies a specific threshold value or higher, the foam can be understood as being in a state where mechanical durability and thermal safety are simultaneously optimized.

[0099] In one embodiment, the expansion strength index (ETI) derived by Equation 2 is 2.0 cm 2 It may be greater than / J. This means that the foam can exhibit sufficient thickness expansion without being easily damaged by impact or external force, resulting in excellent heat propagation blocking effects between cells and the ability to stably maintain thickness after foaming in high-temperature and high-pressure environments. Specifically, the above expansion strength index is 2.0cm 2 / J or more, 2.5cm 2 / J or more, 3.0cm 2 / J or more, 3.3cm 2 / J or more, or 3.4cm 2 It can be more than / J.

[0100] Furthermore, while it can be understood that a higher expansion strength index ensures thermal safety, exceeding a certain value may result in reduced mechanical strength, potentially causing cracks in the foam prior to expansion or reduced long-term durability. Therefore, the expansion strength index is 12.0 cm 2 / J or less, 11.0cm 2 / J or less, 10.5cm 2 / J or less, 10.0cm 2 / J or less, 9.0cm 2 / J or less, 8.0cm 2 / J or less, 7.5cm 2 / J or less, or 7.0cm 2 It may be less than / J.

[0101] The above numerical ranges can be combined without limitation. For example, the expansion strength index (ETI) derived by Equation 2 above is 2.0 cm 2 / J to 12cm 2 / J, 3.0cm 2 / J to 12cm 2 / J, 3.3cm 2 / J to 11cm 2 / J, 3.3cm 2 / J to 10cm 2 / J or 3.3cm 2 / J to 7.0cm 2 / J could be.

[0102] Therefore, satisfying the above range of the expansion strength index serves as an important technical indicator that the foam possesses both durability and expansion characteristics sufficient to ensure battery safety.

[0103]

[0104] The foam may include a foaming agent, an inorganic filler, and an organic binder. By including these components, excellent fire resistance and heat resistance can be expected. The foaming agent has excellent ability to delay the temperature rise by latent heat as moisture vaporizes at high temperatures, increase the thickness of the foam through expansion, and maintain the increased thickness, thereby effectively suppressing heat transfer. This function can be optimally achieved by including the organic binder and the inorganic filler together. For example, by ensuring that the moisture contained in the foaming agent is maintained above a certain level even in the operating environment of a secondary battery, a foaming effect can be implemented in a timely manner when a thermal event occurs while the secondary battery and / or battery box is operating in an electrical device. This enables the realization of a flexible and high-strength foam with excellent durability and stability for long-term use.

[0105]

[0106] Below, foaming agents, inorganic fillers, and organic binders capable of implementing the above-mentioned effects are described in detail.

[0107]

[0108] blowing agent

[0109] The blowing agent may be included in an amount of 30 to 70 parts by weight relative to 100 parts by weight of the foam. Preferably, the blowing agent may be included in an amount of 33 parts by weight or more, 35 parts by weight or more, 37 parts by weight or more, or 40 parts by weight or more, and may also be included in an amount of 68 parts by weight or less, 65 parts by weight or less, 63 parts by weight or less, or 60 parts by weight or less. When the blowing agent is applied to the foam with such content, a sufficient foam expansion rate can be achieved, and excellent durability of the three-dimensional network formed after foaming can be expected. As a result, the blowing agent can effectively prevent heat propagation and thermal runaway by separating the distance between the point where a thermal event occurs and other adjacent members, and maintaining this separated distance for a certain period. In addition, since the content of the foaming agent can contribute to better withstanding potential damage to the foam during the process of placing and processing the foam in a secondary battery or battery box, it may be desirable to apply the above content.

[0110] The above foaming agent may include one or more selected from the group consisting of lithium silicate, potassium silicate, sodium silicate, zirconium silicate, magnesium silicate, and titanium silicate.

[0111] The aforementioned silicates, namely water glass, may be materials that undergo dehydration along with a polycondensation reaction caused by heat. The moisture generated in this way vaporizes and moves outward, which can cause foaming. That is, if the temperature of the foam rises abnormally, the foaming agent can expand the volume of the foam, thereby preventing heat propagation and improving safety.

[0112] The foaming agent may preferably include sodium silicate. The sodium silicate may satisfy Formula 4 below:

[0113] [Equation 4]

[0114] 2.0 ≤ M S / M N ≤ 4.5

[0115] In the above Equation 4, M S is the molar ratio of SiO2 contained in the above sodium silicate, and M N This is the molar ratio of Na2O contained in the above sodium silicate.

[0116] In the above Equation 4, M S / M N The value of may be 2.0 or greater, 2.5 or greater, or 3.0 or greater, and may also be 4.5 or less, 4.0 or less, or 3.5 or less. The above M S / M N If the value satisfies the above range, a foamed composition with excellent mechanical strength and foaming properties can be realized. In addition, when a sodium silicate satisfying the above range is applied, the foaming agent may have a specific strength to maintain the expanded thickness and may be desirable for achieving a sufficient foamed expansion thickness.

[0117]

[0118] Weapon filler

[0119] The above-mentioned weapon filler may have various forms, but is not limited thereto.

[0120] While the thickness resulting from foam expansion and the ability to stably maintain that thickness after foaming may play an important role in the above foam, such a rate of thickness change may lose its significance if the foam itself burns easily or lacks durability. Therefore, by including the inorganic filler, the above foam can significantly improve heat resistance and fire resistance and secure excellent mechanical strength.

[0121] In addition, inorganic fillers are sometimes depicted as having a plate-like structure, but this is merely a schematic representation to aid understanding. In reality, they can have various structures, including not only plate-like structures but also granular, fibrous, or irregular shapes, and these structures can effectively perform the function of supporting the three-dimensional network pores after foaming so that they are not compressed by external pressure.

[0122] The above inorganic filler may include one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, and boehmite.

[0123] The above inorganic filler may be included in an amount of 50 parts by weight or less per 100 parts by weight of the foam. Preferably, the above inorganic filler may be included in the foam in an amount of 40 parts by weight or less, 30 parts by weight or less, or 20 parts by weight or less, and may also be included in an amount of 5 parts by weight or more, 10 parts by weight or more, or 15 parts by weight or more.

[0124] When the above-mentioned type and content of the inorganic filler are satisfied, more desirable results can be obtained in optimally realizing the aforementioned expected effects intended to be obtained by introducing the inorganic filler.

[0125] In one embodiment, the weight ratio of the inorganic filler to the foaming agent may be 1:1 or more, 1:2 or more, or 1:3 or more, or the weight ratio of the inorganic filler to the foaming agent may be 1:36 or less, 1:30 or less, 1:20 or less, 1:10 or less, 1:7 or less, 1:5 or less, or 1:4 or less. The above numerical ranges may be combined with one another without limitation. For example, the weight ratio of the inorganic filler to the foaming agent may be 1:1 to 1:36, specifically 1:2 to 1:36, and more specifically 1:3 to 1:36. When the weight ratio of the inorganic filler to the foaming agent satisfies the above range, a foam with excellent thermal safety and processability can be realized, as both the expansion rate and shock absorption energy density are excellent.

[0126]

[0127] organic binder

[0128] The above organic binder can form a matrix that supports the entire foam inside the foam and can impart adhesive strength and flexibility to the foam. Although a self-standing foam can be manufactured using only a gel-state foaming agent and a sufficient foaming effect can be achieved, there is a problem that the durability and flexibility are poor, and the foam can be easily damaged during the process of processing the finished product after attaching it in place.

[0129] In order to improve the flexibility of the foam and eliminate its brittle nature, one may consider adding a moisturizer capable of holding moisture, such as glycerin. However, this type of moisturizer, such as glycerin, easily deforms at high temperatures above 50°C as well as at low temperatures below 0°C, and does not exhibit a moisturizing effect, which limits the environments in which it can be utilized.

[0130] To solve these problems, the foam may include an organic binder. By applying this, a foam with excellent adhesion and durability can be realized, and as a result, there is an advantage that the foam can be utilized even in high-temperature environments of 130°C or higher. In addition, the organic binder can improve adhesion between materials and between the foam and the member to which it is attached through hydrogen bonding with the inorganic filler and the foaming agent, and can improve the flexibility and elasticity of the foam.

[0131] The above organic binder may be included in an amount of 50 parts by weight or less per 100 parts by weight of the foam. Preferably, the above organic binder may be included in the foam in an amount of 40 parts by weight or less, 30 parts by weight or less, or 20 parts by weight or less, and may also be included in the foam in an amount of 5 parts by weight or more, 10 parts by weight or more, or 15 parts by weight or more.

[0132] The above organic binder is a styrene-butadiene-based rubber such as styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS), or modified rubbers thereof; a silicone rubber such as polydimethylsiloxane (PDMS), polymethylvinylsiloxane (PMVS), or phenyl-silicone rubber; a nitrile-based rubber such as nitrile-butadiene rubber (NBR), hydrogenated nitrile-butadiene rubber (HNBR), carboxylated nitrile-butadiene rubber, nitrile-butadiene rubber latex (NBR latex), or modified rubbers thereof; a polyester-based resin such as polyethylene terephthalate, polybutylene terephthalate, etc.; a cellulose-based resin such as cellulose acetate (CA), cellulose butyrate (CB), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), or hydroxypropylmethyl cellulose (HPMC); It may include one or more selected from the group consisting of epoxy-putty, epoxy resins such as bisphenol A diglycidyl ether (DGEBA), bisphenol F diglycidyl ether (DEGBF), and novolac epoxy; phenol resins; and urethane resins.

[0133] By including an organic binder satisfying the above content and type in the foam, the flexibility of the foam and the adhesive strength can be improved.

[0134]

[0135] Preferably, two or more types of the above organic binder may be applied, and the above organic binder may include an elastic binder and a reinforcing binder. The above elastic binder may include one or more selected from the group consisting of styrene-butadiene rubber, nitrile rubber, polyester resin, cellulose resin, urethane resin, and silicone rubber, and the above reinforcing binder may include one or more selected from the group consisting of epoxy resin and phenolic resin.

[0136] When a reinforcing binder is used in the above organic binder, a three-dimensional network structure can be formed upon drying, and this structure combines with the three-dimensional network structure formed as the foaming agent expands. In this case, the reinforcing binder and the foaming agent chemically form hydrogen bonds and structurally intertwine to form a more robust network structure, thereby preventing cracks from occurring in the foam.

[0137] In addition, elastic binders can compensate for the increased brittleness and reduced flexibility that may result from using reinforcing binders. That is, when two types of binders are used as described above, they can function more optimally for securing adhesion and flexibility, and can also have the effect of increasing durability.

[0138] Preferably, the reinforcing binder may be processed to include one or more additives such as a curing agent, silica, metal powder, or plasticizer, and in this case, it may be preferable to use epoxy putty. In addition, it may be preferable to use styrene-butadiene-based rubber as the elastic binder.

[0139] When two or more types of the above organic binders are included, each organic binder may be independently selected and applied appropriately within the aforementioned content range, but the content of the mixed organic binder may be applied so as not to exceed the above range.

[0140] In one embodiment, the elastic binder and the reinforcing binder may each be included in an amount of 5% by weight or more based on the total weight of the foam. When the content of the elastic binder and the reinforcing binder satisfies the above range, the flexibility and durability of the foam can be effectively improved simultaneously. As a result, the shock absorption energy density of the foam can be improved.

[0141] In one embodiment, the foam may satisfy K of Formula 3 below in a range of 0.4 to 2.2:

[0142] [Equation 3]

[0143] K = B e / B r

[0144] In the above Equation 3,

[0145] B e is the weight percentage of the elastic binder based on the total weight of the foam, and B r K is the weight percentage of the reinforcing binder based on the total weight of the foam. The K value is an indicator representing the mixing ratio of the elastic binder and the reinforcing binder within the foam, and the two binders work complementarily to optimize the mechanical properties and flexibility of the foam.

[0146] The value of K in Equation 3 above may be 0.40 or higher, 0.45 or higher, 0.5 or higher, or 0.8 or higher, and may be 2.2 or lower, 2.1 or lower, 2.0 or lower, or 1.5 or lower. The above numerical ranges may be combined with one another without limitation. For example, the above K may be 0.4 to 2.2, specifically 0.5 to 2.1, and more specifically 0.8 to 2.0. When the above K value satisfies the above range, the balance of the two binders is optimized so that the foam simultaneously secures impact resistance and flexibility, and can stably withstand external shocks and heat generated during the cell manufacturing process.

[0147] In one embodiment, the foam may further include additives to improve volume expansion rate and thermal insulation, and may further include one or more selected from vermiculite and perlite.

[0148]

[0149] The above foam is not subject to any particular restrictions on its shape. The foam may be in the form of a sheet, such as a foam pad; in this case, the sheet may refer to a self-supporting, independent sheet or a sheet coated on a specific substrate and attached to the substrate. Additionally, the shape of the sheet may be identical to the shape of various components within a secondary battery or battery box, or it may be formed to be smaller or larger than such components.

[0150] In addition, the foam can be molded to fit the shape of the space where it is to be applied. For example, if the foam is to be applied to the empty space remaining after the electrode assembly is accommodated inside a battery case, it can be molded to fit the shape of that space and applied; similarly, it can be molded to fit the shape of the space within the housing of a battery box. In this way, when the foam is not in the form of a sheet, the expansion rate and compression rate can be measured and derived by substituting them with the change in average diameter as the average of the major and minor axes.

[0151] Exemplary application locations of the above foam will be described later.

[0152]

[0153] Foaming composition

[0154] In one embodiment, a foaming composition comprising a foaming agent, an inorganic filler, an organic binder, and a solvent may be provided.

[0155] The above-mentioned foaming composition can serve as a raw material for manufacturing a foam, and a foam can be manufactured by coating the foaming composition onto a substrate and then removing the substrate, by extruding and then forming a sheet to produce a self-standing foam, or by directly coating the foam at the location where the foam is to be applied and removing the solvent.

[0156] The foaming agent, inorganic filler, and organic binder included in the above-mentioned foaming composition are the same as those described in the aforementioned foam, and the content can be understood as the solid content of the foaming composition.

[0157] The foaming composition may include a solvent. The solvent may include one or more selected from the group consisting of water, ethanol, methanol, ethyl acetate, and toluene, but may be applied without particular limitation as long as it can effectively disperse the foaming agent and the inorganic filler and dissolve or disperse the organic binder.

[0158]

[0159] secondary battery

[0160] In another embodiment, a secondary battery is provided comprising: an electrode assembly including a plurality of electrodes; a battery case in which the electrode assembly is housed; and a foam, wherein the foam is positioned at one or more locations selected from the interior of the electrode assembly, between the electrode assembly and the battery case, and a space other than the space in which the electrode assembly is housed within the battery case. Here, the foam may be a foam in which the aforementioned configurations relating to the foam are combined in various ways.

[0161] Although the above secondary battery (100) is described using a pouch-type secondary battery as an example in FIG. 4, there are no limitations on the shape of the secondary battery, and it can be applied to cylindrical secondary batteries and prismatic secondary batteries, and it can be applied to various form factors by adjusting the shape of the foam.

[0162] Here, the electrode (130) and diaphragm (140) of the secondary battery (100) may be a separator, a solid electrolyte membrane, and a liquid electrolyte, provided that they are applicable to this field of technology, they may be applied without special limitation.

[0163]

[0164] FIG. 4 illustrates an exemplary location where a foam can be applied within a secondary battery. Referring to FIG. 4, the secondary battery (100) includes a battery case (120) and an electrode assembly, the electrode assembly includes a plurality of electrodes (130), and a diaphragm (140) may be interposed between the electrodes. In the case of a non-aqueous electrolyte secondary battery, the diaphragm (140) may be a separator, and in the case of an all-solid-state secondary battery, it may be a solid electrolyte membrane. Additionally, the secondary battery (100) may also be provided with an electrode tab (150) and an electrode lead (160) that are drawn out from a current collector within the electrode (130) for electrical connection to the outside from the electrode (130).

[0165] In the above secondary battery (100), for example, as shown in FIG. 4, a foam (110) may be positioned at four locations. It may be placed between stack cells in which unit cells are stacked inside the electrode assembly, for example, between the positive electrode and the separator or between the negative electrode and the separator (② and ③ in FIG. 4), between the electrode assembly and the battery case (120) (① in FIG. 4), and in a space other than the space in which the electrode assembly is accommodated inside the battery case (120) (④ in FIG. 4).

[0166] In addition to the locations shown in FIG. 4, it may be applied. For example, a foam may be applied instead of the active material layer located on the outermost surface of the outermost electrode, and it may also be applied at the location where the electrode tab (150) and the electrode lead (160) are welded or at the connection point where the electrode tab (150) is drawn out from the electrode (130). Furthermore, if the secondary battery (100) is a pouch-type secondary battery, one of the laminated films inside the battery case (120) may be replaced or additionally laminated and used.

[0167] A secondary battery to which the above-described foam is applied in the aforementioned locations can prevent short circuits by widening the distance between electrodes or disconnecting electrode tabs and electrode leads by sufficiently expanding and maintaining the expanded state when a thermal event occurs within the secondary battery at each part. Furthermore, it has the advantage of ensuring safety by delaying or preventing thermal runaway and thermal propagation through actions such as prematurely destroying the battery case to prevent excessive energy accumulation.

[0168]

[0169] battery box

[0170] In another embodiment, a battery box is provided comprising: a plurality of secondary batteries; a housing in which the secondary batteries are accommodated; and a foam, wherein the foam is disposed in one or more locations selected from among the space between the plurality of secondary batteries, the space between the housing and the secondary batteries, and the space other than the space in which the secondary batteries are accommodated within the housing. Here, the foam may be a foam in which the aforementioned configurations relating to the foam are combined in various ways.

[0171] The above battery box may be composed of a larger number of secondary batteries so that the electrical capacity or voltage can be increased. Multiple secondary batteries may be arranged in a predetermined manner, for example, stacked in one direction, but the arrangement method of the secondary batteries is not particularly limited.

[0172] The above housing may be configured to accommodate a secondary battery and protect it from external contamination or impact. For example, the housing may have an enclosure shape, but the structure or shape of the housing is not particularly limited as long as it can accommodate the secondary battery.

[0173] Additionally, components that perform specific functions may be installed in the housing to ensure the operation or safety of the battery box. For example, a connector or busbar for energizing the secondary battery to the outside may be installed in the housing, and a vent plug for communicating the inside and outside of the housing may be installed.

[0174] The above battery box may be used to mean, for example, a battery module or a battery pack, and may encompass the form of a housing and an assembly of battery cells in which a plurality of secondary batteries are accommodated within the housing.

[0175]

[0176] FIG. 5 illustrates an exemplary location where a foam can be applied within a battery box. Referring to FIG. 5, the battery box (200) may have a structure in which a plurality of secondary batteries (100) are accommodated inside a housing (220), and a separator plate (230) for separating cell assemblies may be provided, but the separator plate (230) may be applied optionally.

[0177] In the battery box (200) above, a foam (210) may be placed in various locations, for example, as shown in FIG. 5. For example, it may be placed between the housing (220) and a plurality of secondary batteries (100) (①, ③ and ④ in FIG. 5), or between a plurality of secondary batteries (100) (② in FIG. 5).

[0178] Additionally, FIG. 5 is the simplest representation of the battery box (200), and although not shown in the drawing, if one wishes to place it in a space other than the space where the secondary battery (100) is housed within the housing (220) in addition to the aforementioned location, such as near the connector, bus bar, or vent plug, that is also sufficiently possible.

[0179] A battery box in which the above-mentioned foam is applied at the aforementioned location has the advantage of being able to delay or prevent thermal runaway and thermal propagation, thereby ensuring safety, by preventing the excessive accumulation of energy—such as by increasing the distance between cells or inducing disconnection of connectors or busbars—through sufficient expansion and maintenance of the expanded state when a thermal event occurs within the battery box at each part.

[0180]

[0181] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are merely examples to aid in understanding the invention and do not limit the scope of the invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of this description, and it is natural that such variations and modifications fall within the scope of the appended claims.

[0182]

[0183] Example 1

[0184] (Manufacture of foam)

[0185] A foamed composition was prepared by adding sodium silicate with a molar ratio of SiO2:Na2O of 3.2:1 as a foaming agent, kaolin as an inorganic filler, styrene-butadiene rubber (SBR) as an elastic binder among organic binders, and epoxy putty (3M, Scotch-Weld Epoxy Adhesive 2214, 100% solid content) as a reinforcing binder to water and mixing them such that the weight ratio based on solid content was 20:20:30:30. After bar-coating the composition onto a substrate, a sheet-shaped foam with a thickness of 0.2 cm was produced by drying in a drying oven at 60°C for 2 hours.

[0186]

[0187] Example 2

[0188] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 40:20:20:20.

[0189]

[0190] Example 3

[0191] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:10:10.

[0192]

[0193] Example 4

[0194] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:13.5:6.5.

[0195]

[0196] Example 5

[0197] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:6.5:13.5.

[0198]

[0199] Example 6

[0200] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 90:2.5:3.75:3.75.

[0201]

[0202] Comparative Example 1

[0203] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, and styrene-butadiene rubber were added to water and mixed without adding epoxy putty, and the weight ratio based on solid content was adjusted to 60:20:20.

[0204]

[0205] Comparative Example 2

[0206] A foam was produced in the same manner as in Example 1 above, except that styrene-butadiene was not added, and sodium silicate, kaolin, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:20.

[0207]

[0208] Comparative Example 3

[0209] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 10:20:35:35.

[0210]

[0211] Comparative Example 4

[0212] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed, with the weight ratio based on solid content adjusted to 95:2.5:1.25:1.25.

[0213]

[0214] Comparative Example 5

[0215] A foam was produced in the same manner as in Example 1 above, except that acrylic resin was added instead of epoxy putty, and sodium silicate, kaolin, styrene-butadiene, and acrylic resin were added to water and mixed, with the weight ratio based on solid content adjusted to 40:20:20:20.

[0216]

[0217] Comparative Example 6

[0218] A foam was produced in the same manner as in Example 1 above, except that acrylic resin was added instead of epoxy putty, and sodium silicate, kaolin, styrene-butadiene, and acrylic resin were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:10:10.

[0219]

[0220] Comparative Example 7

[0221] A foam was produced in the same manner as in Example 1 above, except that carboxymethylcellulose was added instead of styrene-butadiene, and sodium silicate, kaolin, epoxy-putty, and carboxymethylcellulose were added to water and mixed, with the weight ratio based on solid content adjusted to 40:20:20:20.

[0222]

[0223] Comparative Example 8

[0224] A foam was produced in the same manner as in Example 1 above, except that carboxymethylcellulose was added instead of styrene-butadiene, and sodium silicate, kaolin, epoxy-putty, and carboxymethylcellulose were added to water and mixed, with the weight ratio based on solid content adjusted to 60:20:10:10.

[0225] Foaming agent, inorganic filler, binder, sodium silicate, kaolin, SBR, epoxy-putty, acrylic resin, CMC Example 1 20203030--Example 2 40202020--Example 3 60201010--Example 4 602013.56.5--Example 5 60206.513.5--Example 6 902.53.753.75--Comparative Example 1 602020---Comparative Example 2 6020-20--Comparative Example 3 10203535--Comparative Example 4 952.51.251.25--Comparative Example 5 402020-20-Comparative Example 6 602010-10-Comparative Example 7 4020-20-20 Comparative Example 86020-10-10

[0226]

[0227] Experimental Example 1: Measurement of Shock Absorption Energy Density

[0228] This experiment was conducted using a modified Izod impact test according to ASTM D256 standards to evaluate the relative impact resistance of polymer materials.

[0229] Specifically, five plate-shaped specimens measuring 5 cm in width × 5 cm in length × 0.2 cm in thickness were prepared for each of the foams manufactured in Examples 1-6 and Comparative Examples 1-8, and no notches were applied to the specimens. While the specimens were fixed to vertical supports, the center was struck using an Izod-type pendulum hammer moving horizontally, and a constant energy of 22 J was applied to the hammer. At this time, whether the specimen fractured (or broke) and the energy (J) required upon fracture (or breakage) were recorded, and the average impact absorption energy (J) of the five specimens was calculated for each example and comparative example. This average value was calculated based on a cross-sectional area of ​​1.0 cm² of the specimen. 2 The value (J / cm²) calculated by dividing by (= 5cm × 0.2cm) was used as an indicator of shock absorption energy density.

[0230] This test focused on evaluating the intrinsic impact resistance of the foam material by not applying a notch.

[0231] The measurement results are shown in Table 2 below.

[0232] Shock Absorption Energy Density (J / cm²) Example 1 0.6899 Example 20.5873 Example 30.4678 Example 40.4951 Example 50.4555 Example 60.2589 Comparative Example 10.1675 Comparative Example 20.1587 Comparative Example 30.7897 Comparative Example 40.0733 Comparative Example 50.1336 Comparative Example 60.1147 Comparative Example 70.1312 Comparative Example 80.1189

[0233]

[0234] Experimental Example 2: Measurement of Thickness Expansion Rate

[0235] Each foam prepared in Examples 1-6 and Comparative Examples 1-8 above was cut to a width and length of 5 cm and a thickness of 0.2 cm, and then the cut foam was placed on an insulating board (10b) as shown in FIG. 3. Subsequently, a heating plate (10a) heated to 750°C was placed on the opposite side of the foam surface in contact with the insulating board (10b) and contact was maintained for 30 seconds to expand the foam (10), and the full expansion thickness (T) of the expanded foam (10) e ) was measured.

[0236] The measured thickness T above e , and, initial thickness (T i The expansion rate (E) was calculated using ), and the expansion strength index (ETI) was calculated by substituting it into Equation 2 as in the result of Experimental Example 1, and is shown in Table 3 below.

[0237] Initial thickness, T i (cm) Thickness after foaming, T e (cm) Expansion rate (E) (T e -T i) / Ti Expansion Strength Index (ETI) (cm² / J) Example 10.2000.48 1.40 2.029 Example 20.2010.61 2.03 3.456 Example 30.2020.85 3.216 862 Example 40.2010.88 3.386 827 Example 50.2020.83 3.116 828 Example 60.2000.76 2.8010.81 Comparative Example 10.2020.51 1.52 9.075 Comparative Example 20.2020.48 1.38 8.696 Comparative Example 30.2000.21 0.05 0.06 33 Comparative Example 40.2010.662.2831.105 Comparative Example 50.2020.400.987.335 Comparative Example 60.2010.511.5413.426 Comparative Example 70.2020.411.037.851 Comparative Example 80.2000.531.6513.877

[0238]

[0239] Experimental Example 3: Evaluation of Fairness and Heat Propagation Delay Effects

[0240] (1) Fairness evaluation

[0241] Each foam prepared in Examples 1-6 and Comparative Examples 1-8 was cut into a sheet measuring 260 mm × 100 mm × 2 mm, and then the test was performed by lifting the sheet horizontally using a suction device and dropping it from a height of 1 m. If the sheet broke, deformed, or was damaged after the drop, it was judged as NG, and conversely, if the shape was maintained after the drop, it was judged as OK.

[0242] This process evaluation allows for the assessment of durability to ensure the processability of the sheet, as shape retention and mechanical stability are critical factors when the sheet or pad is attached between cells or secured as an internal component of a module or pack.

[0243] (2) Evaluation of heat propagation delay effect

[0244] Subsequently, the foam (2T, 300mm × 100mm) of Examples 1-6 and Comparative Example 3, which were judged to be OK as a result of the processability evaluation test, was inserted between two secondary batteries. They were laminated by bonding them with double-sided tape to secure the sheets. At this time, for convenience, one secondary battery was named Cell A and the other secondary battery was named Cell B.

[0245] Subsequently, a heater (120 mm × 60 mm) was placed on cell A, a thermocouple was attached between the heater and cell A, and the heater was secured with polyimide tape. Then, Superwool insulation (10T, 300 mm × 100 mm) was attached to the outer surface opposite to the surface where the foam of cell A and cell B meet, and an aluminum plate (10T, 300 mm × 100 mm) was attached to the outer surface, and the structure was fastened into a laminate by applying pressure of 30 kPa.

[0246] The completed laminate was placed in a SUS box (internal dimensions: length 420 mm × width 125 mm × height 105 mm, thickness 10T) and sealed. Then, thermal runaway of the cell was induced using a heater, and the results were measured. Specifically, the heater was operated at a heating rate of 10℃ / s at room temperature (25℃) to heat the cell until it reached 625℃, and once it reached 625℃, the temperature was maintained. In addition, the elapsed time from when the heater reached 625℃ until the temperatures of Cell A and Cell B reached 250℃ was measured, and the results are shown in Table 4 below.

[0247] Processability Time to reach 250°C for Cell A (s) Time to reach 250°C for Cell B (s) Time required for heat propagation (s) Example 1 OK336633 Example 2 OK329462 Example 3 OK3211482 Example 4 OK31133102 Example 5 OK3212189 Example 6 OK3210371 Comparative Example 1 NG--- Comparative Example 2 NG--- Comparative Example 3 OK314312 Comparative Example 4 NG--- Comparative Example 5 NG--- Comparative Example 6 NG--- Comparative Example 7 NG--- Comparative Example 8 NG---

[0248] Referring to Table 4 above, it can be confirmed that Examples 1 to 6, which have an impact absorption energy density of 0.2 J / cm² or higher and an expansion rate of 1.2 or higher derived by Equation 1, all showed no deformation or breakage in the processability evaluation. Furthermore, these examples demonstrated an excellent thermal runaway delay effect, with the time required for heat propagation in the heat propagation suppression test being measured at 80 seconds or more.

[0249] On the other hand, among Comparative Examples 1 to 8, only Comparative Example 3, which had an impact absorption energy density of 0.2 J / cm² or higher, did not experience deformation or breakage in the processability evaluation, but it was confirmed that the thermal runaway delay effect was very low as the time required for heat propagation was only 12 seconds.

[0250]

[0251] [Explanation of the symbol]

[0252] 10, 110, 210: Foam

[0253] 11: Foaming agent

[0254] 12: Weapon Filler

[0255] 13: Organic binder

[0256] 14: Qi Gong

[0257] 10a: Heating plate

[0258] 10b: Insulation board

[0259] 100: Secondary battery

[0260] 120: Battery case

[0261] 130: Multiple electrodes

[0262] 140: Septum

[0263] 150: Electrode tab

[0264] 160: Electrode Lead

[0265] 200: Battery box

[0266] 220: Housing

[0267] 230: Separator

Claims

1. A foam comprising a foaming agent, an inorganic filler, and an organic binder, The above foam has a shock absorption energy density of 0.20 J / cm² 2 That is all, The above foam is a foam having an expansion rate (E) of 1.2 or more derived by the following Formula 1: [Equation 1] E = (T e - T i ) / T i In the above Equation 1, T i is the initial thickness (cm) of the foam above, and T e is the full expansion thickness (cm) of the above foam.

2. In Claim 1, The above foam has an Expansion Toughness Index (ETI) of 2.0 cm, derived by the following Equation 2. 2 / J Lee Sang-in, foam: [Equation 2] ETI = E / F In the above Equation 2, E is the expansion rate, derived by Equation 1 above, and F is the shock absorption energy density (J / cm²) of the foam. 2 )am.

3. In Claim 2, The above foam has an expansion strength index (ETI) of 2.0 cm derived by Equation 2. 2 / J to 12.0cm 2 / J-type, foam.

4. In Claim 1, The above foam has a shock absorption energy density of 0.20 J / cm² 2 Up to 0.75 J / cm 2 And, The above foam is a foam having an expansion rate (E) derived by the above formula 1 of 1.2 to 5.

0.

5. In Claim 1, The foam is a foam containing 20 to 90 parts by weight of the foam per 100 parts by weight of the foam.

6. In Claim 1, The above organic binder is a foam comprising an elastic binder and a reinforcing binder.

7. In Claim 6, The above foam is a foam satisfying K of Formula 3 below from 0.4 to 2.2: [Equation 3] K = B e / B r In the above Equation 3, B e is the weight percentage of the elastic binder based on the total weight of the foam, and B r is the weight percentage of the reinforcing binder based on the total weight of the foam.

8. In Claim 6, The above elastic binder is, A foam comprising one or more selected from the group consisting of styrene-butadiene rubber, nitrile rubber, polyester resin, cellulose resin, urethane resin, and silicone rubber.

9. In Claim 6, The above-mentioned reinforced binder is, A foam comprising one or more selected from the group consisting of epoxy resins and phenolic resins.

10. In Claim 1, A foam having a weight ratio of the above-mentioned inorganic filler and foaming agent of 1:1 to 1:

36.

11. In Claim 1, When the above foam is foamed, A foam having a three-dimensional network structure having pores, and an inorganic filler having a structure disposed within the pores.

12. In Claim 1, The above foaming agent is, A foam comprising one or more selected from the group consisting of lithium silicate, potassium silicate, sodium silicate, zirconium silicate, magnesium silicate, and titanium silicate.

13. In Claim 1, The above foaming agent includes sodium silicate, and The above sodium silicate is a foam satisfying Formula 4 below: [Equation 4] 2.0 ≤ M S / M N ≤ 4.5 In the above Equation 4, M S is the molar ratio of SiO2 contained in the above sodium silicate, and M N This is the molar ratio of Na2O contained in the above sodium silicate.

14. In Claim 1, A foam having a thickness of 0.1 mm to 100 mm.

15. In Claim 1, The above-mentioned weapon filler is, A foam comprising one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, and boehmite.

16. Electrode assembly comprising a plurality of electrodes; A battery case accommodating the above electrode assembly; and A foam according to claim 1; comprising, The foam is disposed in one or more locations selected from the interior of the electrode assembly, between the electrode assembly and the battery case, and the space other than the space in which the electrode assembly is accommodated within the battery case, in a secondary battery.

Images