Foam, and secondary battery and battery box comprising same

Abstract

The present specification discloses a technology related to a foam comprising a foaming agent, an organic binder, and an inorganic filler and having a swelling stability index (SSI) of 0.100 to 1.450, wherein the SSI is defined as a ratio of an expansion rate and a compression rate derived from an initial thickness, a fully expanded thickness, and a compressed thickness of the foam. The foam has remarkable 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, secondary battery and battery box containing the same

[0001] In this specification, technology is disclosed regarding a foam, a secondary battery and battery box including said foam, and an electric device.

[0002]

[0003] 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.

[0004] 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.

[0005] Specifically, during the charging and discharging process, secondary batteries may experience thermal runaway, such as ignition or explosion, due to internal factors like electrolyte leakage, excessive gas generation, or internal short circuits, or due to external impact. In particular, when multiple secondary batteries are installed in a device, such as an electric vehicle, significant damage can occur due to thermal propagation; even if a fire or explosion occurs in only one battery, the fire or explosion can spread to adjacent batteries. Therefore, technology capable of preventing damage caused by thermal propagation and fire is required.

[0006]

[0007] The present specification aims to provide a foam that can ensure durability for long-term use by having excellent internal moisture retention capabilities even in environments with large temperature fluctuations, and can expect maximum foaming effects through foaming at a specific temperature, while also having excellent thickness expansion rates by foaming and the ability to maintain this state, thereby stably preventing heat propagation or thermal runaway.

[0008] In addition, the present specification aims to provide a secondary battery and a battery box 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.

[0009] In addition, the present specification aims to provide an electric device that ensures safety and allows a user to use it safely for a long period of time by including a secondary battery and / or battery box having excellent fire resistance and safety.

[0010]

[0011] [1] In one aspect, a foam comprising a foaming agent, an inorganic filler, and an organic binder is provided, wherein the foam has a swelling stability index (SSI) of 0.100 to 1.450 derived by the following formula 1.

[0012] [Equation 1]

[0013] SSI = (1-R S 2 ) / (1-R C )

[0014] In Equation 1 above, R S is the expansion rate, derived by Equation 2 below, and R C is derived as the compression ratio by the following Equation 3, and

[0015] [Equation 2]

[0016] R S = (TS - T i ) / T S

[0017] [Equation 3]

[0018] R C = (T S - T C ) / T S

[0019] In the above equations 2 and 3, T i is the initial thickness (cm) of the foam, and T S is the full expansion thickness (cm) of the foam, and T C is the compressed thickness (cm) of the foam after a pressure of 30 kPa is applied to the fully expanded foam for 30 seconds.

[0020] [2] In the foam of [1] above, the compression ratio may be greater than 0 and less than or equal to 0.64.

[0021] [3] In the foam of [1] and / or [2] above, foaming may begin at a temperature of 130°C or higher.

[0022] [4] In at least one of the foams [1] to [3] above, when the foam is foamed, the foaming agent may form a three-dimensional network structure having pores within an organic binder matrix, and the inorganic filler may be disposed within the organic binder matrix.

[0023] [5] In at least one of the foams [1] to [4] above, the foaming agent may be included in an amount of 40 to 60 parts by weight per 100 parts by weight of the foam.

[0024] [6] In at least one of the foams [1] to [5] above, the foaming agent may include one or more selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate and titanium silicate.

[0025] [7] In at least one of the foams [1] to [6] above, the foaming agent may include sodium silicate, and the sodium silicate may satisfy Formula 1 below.

[0026] [Equation 1]

[0027] 2 ≤ M S / M N ≤ 4.5

[0028] In the above Equation 1, 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.

[0029] [8] In at least one of the foams [1] to [7] above, the inorganic filler may have a plate-like structure.

[0030] [9] In at least one of the foams [1] to [8] above, the inorganic filler may be one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide and boehmite.

[0031]

[0010] In at least one of the foams [1] to [9] above, the inorganic filler may be included in an amount of 50 parts by weight or less per 100 parts by weight of the foaming composition.

[0032]

[0011] In at least one of the foams [1] to

[0010] above, the organic binder may form a matrix within the foam and be included in an amount of 50 parts by weight or less per 100 parts by weight of the foaming composition.

[0033]

[0012] In at least one foam of [1] to

[0011] above, the organic binder may comprise one or more selected from the group consisting of styrene-butadiene rubber; silicone rubber; nitrile rubber; polyester resin; cellulose resin; epoxy resin; phenolic resin; silicone resin; and urethane resin.

[0034]

[0013] In at least one of the foams [1] to

[0012] above, the organic binder may include an elastic binder and a reinforcing binder.

[0035]

[0014] In the foam of

[0013] above, 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, silicone resin and silicone rubber, and the reinforcing binder may comprise one or more selected from the group consisting of epoxy resin and phenolic resin.

[0036]

[0015] In another aspect, 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

[0014] , 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.

[0037]

[0016] In another aspect, a battery box is provided comprising: a plurality of secondary batteries; a housing in which the secondary batteries are accommodated; and a foam according to at least one of [1] to

[0014] , wherein the foam is positioned at one or more locations selected from between the plurality of secondary batteries, between the housing and the secondary batteries, and in a space other than the space in which the secondary batteries are accommodated within the housing.

[0038]

[0017] In another aspect, an electric device comprising a secondary battery according to

[0015] and / or a battery box according to

[0016] is provided.

[0039]

[0040] The foam according to the present specification has excellent internal moisture retention capabilities even in environments with large temperature fluctuations, thereby ensuring 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.

[0041] 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.

[0042] Furthermore, the electric device according to the present specification includes the secondary battery and / or battery box, which ensures fire resistance and safety through the control of thermal propagation and / or thermal runaway, thereby significantly reducing the risk of explosion and ensuring the safety of the user.

[0043]

[0044] FIG. 1 is a schematic diagram showing a cross-section of a foamed body before foaming according to the present specification.

[0045] FIG. 2 is a schematic diagram showing a cross-section of a foam after foaming according to the present specification.

[0046] Figure 3 is a diagram showing a method for measuring the rate of change in thickness of a foam.

[0047] FIG. 4 is a cross-sectional view of a secondary battery according to the present specification.

[0048] FIG. 5 is a cross-sectional view of a battery box according to the present specification.

[0049]

[0050] The advantages and features of the invention described herein and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the invention is complete and to fully inform those skilled in the art of the scope of the invention, and the invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0051] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0052] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0053] In this specification, when a part is described as including a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0054] In this specification, the description "A and / or B" means A, or B, or A and B.

[0055]

[0056] The foam, secondary battery, battery box, and electrical device 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.

[0057] Below, the above foam, secondary battery, battery box, and electrical device will be described in detail.

[0058]

[0059] foam

[0060] In one aspect, a foam comprising a foaming agent, an inorganic filler, and an organic binder is provided, wherein the foam has a swelling stability index (SSI) of 0.100 to 1.450 derived by the following formula 1.

[0061] [Equation 1]

[0062] SSI = (1-R S 2 ) / (1-R C )

[0063] In Equation 1 above, R S is the expansion rate, derived by Equation 2 below, and R C is derived as the compression ratio by the following Equation 3, and

[0064] [Equation 2]

[0065] R S = (T S - T i ) / T S

[0066] [Equation 3]

[0067] R C = (T S - T C ) / T S

[0068] In the above equations 2 and 3, T i is the initial thickness (cm) of the foam, and T Sis the full expansion thickness (cm) of the foam, and T C is the compressed thickness (cm) of the foam after a pressure of 30 kPa is applied to the fully expanded foam for 30 seconds.

[0069]

[0070] Foam expansion stability index

[0071] The above foam may include 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 level, 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 within the organic binder matrix to function to more firmly support the three-dimensional network structure.

[0073] The types and contents of the foaming agent, inorganic filler, and organic binder mentioned above are explained in more detail below.

[0074]

[0075] In one aspect, the foam may have an expansion stability index (SSI) defined by Equation 1 of 0.100 to 1.450. The expansion stability index is the ratio of the expansion rate to the compression rate and can be considered an indicator of how much the foam can expand and how stably it can maintain that expanded state. Typically, when a battery cell or box ignites, a large amount of gas is generated internally, resulting in a high temperature / high pressure state. In order to prevent heat transfer between adjacent cells and runaway phenomena in this state, the distance between internal cell components or between cells must be separated, and this separated state must withstand high pressure to prevent heat propagation / runaway and ensure safety.

[0076] The smaller the above expansion stability index—for example, when the expansion rate is large and the compression rate is small—the more effectively the function of preventing heat propagation to adjacent cells and thermal runaway can be performed when an event occurs in a battery cell or box, and thus it can serve as an indicator for determining whether safety can be guaranteed. Specifically, while a larger expansion rate contributes to safety by allowing greater separation between components or cells, even if the expansion is significant, if the cell or battery box cannot withstand the high pressure conditions and becomes compressed, thermal runaway cannot be effectively prevented. In this regard, it can be understood that a correction of the square of the expansion rate was applied to Equation 1 to reflect the influence of the compression rate and expansion rate on safety contribution. Furthermore, by analyzing the expansion rate and compression rate in Equation 1, it can be expected that the full expansion thickness has a complex effect on the expansion stability index, and that the degree of influence on the expansion stability index becomes stronger as the compression thickness decreases.

[0077] The above expansion stability index should be 1.450 or less to ensure safety, and preferably, it may be 1.400 or less, 1.350 or less, 1.300 or less, 1.250 or less, 1.200 or less, 1.150 or less, 1.100 or less, 1.050 or less, 1.000 or less, 0.950 or less, 0.900 or less, 0.850 or less, 0.800 or less, 0.750 or less, 0.700 or less, 0.650 or less, 0.600 or less, or 0.550 or less.

[0078] While it can be understood that safety is guaranteed as the above expansion stability index increases, if it exceeds a certain value—for example, if it is less than 0.100—it can be understood that the foam lacks ductility, and there may be problems such as cracks occurring in the foam before foaming or reduced long-term durability. Therefore, the above expansion stability index may be 0.130 or higher, and preferably 0.150 or higher, 0.170 or higher, 0.200 or higher, 0.230 or higher, 0.250 or higher, 0.270 or higher, 0.290 or higher, or 0.300 or higher.

[0079]

[0080] In addition, the compression ratio defined by the above Equation 3 may be greater than 0 and less than or equal to 0.64. The compression ratio may be a measure of how well the foam maintains its expanded thickness after full expansion, and a smaller expansion retention ratio indicates that it is less likely to deform under external forces, which can provide excellent protection against thermal runaway or heat propagation.

[0081] There may be various factors for reducing the above compression rate. The foam has a porous structure when expanded by foaming, and as a result, its thickness can easily decrease again due to external pressure. To prevent the thickness from decreasing again, for example, an inorganic filler is used, and the type, content, and shape of the inorganic filler can have an influence, thereby allowing the inorganic filler to be placed in the pores of a three-dimensional network structure, which can improve the ability to withstand the collapse of the pores.

[0082] As another example, the content and type of foaming agent can also have an effect. Depending on the foaming agent used, the expansion rate at which thickness increases by foaming at a specific temperature may differ, and consequently, the thickness and rigidity of the framework forming the three-dimensional network structure may be affected. This can also be influenced by the content of the foaming agent used.

[0083] As another example, the type and content of the organic binder can also play a role. The organic binder can be viewed as a supporting structure that forms the matrix, or basic framework, within the foam, and the rigidity of this supporting structure can lead to the rigidity of the three-dimensional network formed by foaming.

[0084] The compression ratio of the foam may be influenced by the factors mentioned above, and when all influences from these factors are taken into account, the foam may have a compression ratio greater than 0 and less than or equal to 0.64. Preferably, it may be greater than or equal to 0.01, greater than or equal to 0.03, or greater than or equal to 0.05, and may also be less than or equal to 0.62, less than or equal to 0.60, less than or equal to 0.58, or less than or equal to 0.55. In the case of the thickness change rate, the smaller it is, the more rigid it is, and the more effectively it can prevent heat propagation and thermal runaway. Meanwhile, a thickness change of 0 may be practically impossible to achieve, and a value of 0.01 or higher is preferably achievable. If a value greater than this is satisfied, it can be interpreted as meaning that the pore structure inside the foam is well formed and sufficient ductility is secured. In this case, the foam indirectly has sufficient ductility, which reduces the likelihood of cracking. Since sufficient ductility means that the foam retains moisture well, there may be advantages in terms of ensuring durability for long-term use.

[0085]

[0086] The expansion rate defined by the above Equation 2 may be 0.50 to 0.95, preferably 0.53 or higher, 0.55 or higher, 0.57 or higher, 0.60 or higher, or 0.63 or higher, and may also be 0.94 or lower, 0.93 or lower, 0.92 or lower, 0.91 or lower, or 0.90 or lower. The above expansion rate functions to separate the cell or cell member where ignition has occurred from the adjacent cell or cell member, and is more desirable as it increases; however, since safety cannot be ensured by the expansion rate alone, it is desirable to design the foam so as to satisfy the aforementioned expansion stability index.

[0087]

[0088] As described above, the expansion stability index of the above foam can be defined by the following Equation 1.

[0089] [Equation 1]

[0090] SSI = (1-R S 2 ) / (1-R C )

[0091] In Equation 1 above, R S is the expansion rate, derived by Equation 2 below, and R C is derived as the compression ratio by the following Equation 3, and

[0092] [Equation 2]

[0093] R S = (T S - T i ) / T S

[0094] [Equation 3]

[0095] R C = (T S - T C ) / T S

[0096] In the above equations 2 and 3, T i is the initial thickness (cm) of the foam, and T S is the full expansion thickness (cm) of the foam, and T C is the compressed thickness (cm) of the foam after a pressure of 30 kPa is applied to the fully expanded foam for 30 seconds.

[0097] FIG. 3 is a schematic diagram showing the process and apparatus for measuring the compression ratio to derive the expansion stability index. Hereinafter, the method for measuring the expansion ratio and compression ratio is described with reference to FIG. 3. First, the foam can be cut to a width and length of approximately 5 cm and a thickness of approximately 0.2 cm. At this time, the width, length, and thickness are arbitrarily designated for the convenience of measurement, and even if they are freely changed within the limits allowed by the apparatus, as long as the types and contents of the components constituting the foam do not differ, the expansion ratio and compression ratio can be derived without difference within the margin of error. At this time, the initial thickness (Ti) of the foam can be determined.

[0098] The above-described foam (10) can be placed on an insulating board (10b), and a heating plate (10a) is placed on the opposite side of the surface where the foam (10) contacts the insulating board (10b) to induce foaming of the foam (10). At this time, the positions of the heating plate (10a) and the insulating board (10b) are not fixed to the upper and lower positions, but can be arranged in such a way for the convenience of measurement; even if arranged differently, the same expansion rate can be obtained as long as the environment allows for foaming to be induced. When foaming is induced through the heating plate (10a), the foaming agent within the foam is 100% foamed, resulting in a 'completely expanded thickness (T S It is necessary to use a heating plate (10a) heated to a high temperature to achieve )'.

[0099] The above fully expanded thickness (T S ) may refer to the thickness of the foam just before it is completely expanded, no further expansion occurs even when heat is applied, deformation of the internal structure occurs, or combustion begins. Additionally, if the foam expands irregularly or unevenly when it expands, the completely expanded thickness may refer to the thickness of the thickest part of the expanded foam.

[0100] To achieve the above-mentioned full expansion thickness, for example, the heating plate (10a) may be heated to approximately 750°C or higher. Contact with the heating plate (10a) may be maintained for a sufficient time for foaming to occur, and may be maintained for approximately 30 seconds; provided that the foam is not combusted, the contact maintenance time may be appropriately adjusted. The thickness (T) of the foam (10) expanded by this series of processes H) is measured, and the above conditions may be appropriately modified as long as they result in the foam being fully expanded; for example, in the case of a heating plate, temperatures of 600°C or higher, 650°C or higher, or 700°C or higher may be applied, and in the case of contact time, 20 seconds or more, 25 seconds or more, or 30 seconds or more may be applied. By fully expanding the foam in this way, the fully expanded thickness (T S ) can be obtained.

[0101] The above-described foamed body (10) may be placed between substrates (10c). The substrate (10c) used at this time may include an aluminum board, but the material is not significant; any material with higher rigidity than the foamed body (10) and that does not deform when pressed may be appropriately substituted. After placing the foamed body (10) between the substrates (10c), a pressure of 30 kPa is applied in the thickness direction for 30 seconds, and after applying the pressure, the compression thickness (T) of the foamed body (10) C Measures ).

[0102] The initial thickness (T) measured above i ), full expansion thickness (T S ) and compression thickness (T C The thickness change rate can be derived by the above Equation 1 using ).

[0103]

[0104] The above foam may begin to foam and expand in volume at a temperature of 130°C or higher. The above foam is placed inside a secondary battery, etc., and when a specific heat / flame event occurs or the ambient temperature rises abnormally, it foams to separate the distance between internal components of the secondary battery, thereby preventing heat transfer or heat propagation. Accordingly, it may be desirable to ensure that foam does not foam in the temperature range where the battery operates normally and at a recoverable level even if there is an abnormal temperature rise, while foaming can begin in the temperature range before reaching the thermal runaway / transfer temperature where the temperature rises rapidly. In this regard, it may be desirable for foaming to begin at a temperature of 130°C to 150°C, and more preferably, it may be 133°C or higher, or 135°C or higher, and also 148°C or lower, or 145°C or lower.

[0105]

[0106] In one aspect, 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 achieved 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.

[0107]

[0108] Below, foaming agents, inorganic fillers, and organic binders capable of implementing the above-mentioned effects are described in detail.

[0109]

[0110] blowing agent

[0111] The above foaming 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 foaming 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 foaming agent is applied to the foam with such content, a sufficient foaming expansion rate can be achieved, and excellent durability of the three-dimensional network formed after foaming can be expected. This allows for the effective prevention of heat propagation and thermal runaway by separating the distance between the point of thermal event occurrence and other adjacent members and maintaining this separated distance for a certain period. Furthermore, 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.

[0112] The above foaming agent may include one or more selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, and titanium silicate.

[0113] 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.

[0114] The foaming agent may preferably include sodium silicate. The sodium silicate may satisfy Formula 4 below:

[0115] [Equation 4]

[0116] 2.0 ≤ M S / M N ≤ 4.5

[0117] 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.

[0118] In the above Equation 1, 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.

[0119]

[0120] Weapon filler

[0121] The above-mentioned inorganic filler may have a plate-like structure. While the thickness resulting from foam expansion and the ability to maintain this thickness may play an important role in the foam, such a rate of thickness change may lose its significance if the foam itself burns easily or has poor durability. Accordingly, by including the above-mentioned inorganic filler, the heat resistance or fire resistance of the foam can be significantly improved, and excellent mechanical strength can be secured. When the above-mentioned inorganic filler has a plate-like structure, there is an advantage in that it can optimally perform the function of supporting the pores of the three-dimensional network so that they are not compressed by external pressure after the foam is foamed.

[0122] The above inorganic filler may include one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, 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]

[0126] organic binder

[0127] 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.

[0128] 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, is prone to deformation not only at high temperatures of 50°C or higher but also at low temperatures of 0°C or lower, and does not exhibit a moisturizing effect, which limits the environments in which it can be utilized.

[0129] 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.

[0130] 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.

[0131] The above organic binder comprises: styrene-butadiene rubbers such as styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS), or modified rubbers thereof; silicone resins such as polydimethylsiloxane (PDMS), polymethylvinylsiloxane (PMVS), or phenyl-silicone rubber; nitrile rubbers 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; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, etc.; and cellulose resins 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 resins such as epoxy putty, bisphenol A diglycidyl ether (DGEBA), bisphenol F diglycidyl ether (DEGBF), and novolac epoxy; phenol resins; and urethane resins. Here, the silicone resin may include both resins commonly referred to as silicone resin and resins commonly referred to as silicone rubber.

[0132] 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.

[0133]

[0134] 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 resin, and the above reinforcing binder may include one or more selected from the group consisting of epoxy resin and phenolic resin.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] The above 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, for example.

[0140]

[0141] 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.

[0142] 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.

[0143] Exemplary application locations of the above foam will be described later.

[0144]

[0145] Foaming composition

[0146] In one aspect, a foaming composition comprising a foaming agent, an inorganic filler, an organic binder, and a solvent may be provided.

[0147] 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.

[0148] 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.

[0149] 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.

[0150]

[0151] secondary battery

[0152] In another aspect, 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 disposed at one or more locations selected from within the electrode assembly, between the electrode assembly and the battery case, and in 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 various combinations of the aforementioned configurations regarding the foam are applied.

[0153] 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.

[0154] 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.

[0155]

[0156] 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).

[0157] 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).

[0158] 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.

[0159] A secondary battery in which the above-described 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. This is achieved by preventing short circuits by increasing the distance between electrodes through sufficient expansion and maintaining the expanded state when a thermal event occurs within the secondary battery at each part, disconnecting electrode tabs and electrode leads, or destroying the battery case prematurely to prevent excessive energy accumulation.

[0160]

[0161] battery box

[0162] In another aspect, a battery box is provided comprising: a plurality of secondary batteries; a housing in which the secondary batteries are housed; and a foam, wherein the foam is positioned at 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 housed within the housing. Here, the foam may be a foam in which the aforementioned configurations regarding the foam are combined in various ways.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167]

[0168] 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.

[0169] 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).

[0170] 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.

[0171] 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.

[0172]

[0173] 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.

[0174]

[0175] Examples

[0176]

[0177] Example 1

[0178] 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, epoxy putty (3M, Scotch-Weld Epoxy Adhesive 2214, 100% solid content) and styrene-butadiene rubber (SBR) as organic binders to water and mixing them such that the weight ratio based on solid content was 40:20:20:20. 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.

[0179]

[0180] Example 2

[0181] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, epoxy-putty, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 50:20:15:15 based on solid content.

[0182]

[0183] Example 3

[0184] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, epoxy-putty, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 60:20:10:10 based on solid content.

[0185]

[0186] Comparative Example 1

[0187] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, epoxy-putty, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 20:20:30:30 based on solid content.

[0188]

[0189] Comparative Example 2

[0190] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, epoxy-putty, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 30:20:25:25 based on solid content.

[0191]

[0192] Comparative Example 3

[0193] A foam was produced in the same manner as in Example 1 above, except that sodium silicate, kaolin, epoxy-putty, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 80:10:5:5 based on solid content.

[0194]

[0195] Experimental Example 1

[0196] The foam prepared in the above examples and comparative examples 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) S ) was measured.

[0197] Next, the foamed foam (10) is placed between aluminum boards (10c), and a pressure of 30 kPa is applied in both directions in the thickness direction for 30 seconds, and then the compression thickness (T) of the foam (10) C ) was measured.

[0198] The measured thickness T above S Wow T C , and, initial thickness (T i Using 0.2 cm, the expansion rate (R S ) and compression ratio (R C ) was calculated, and the expansion stability index was derived and shown in Table 1 below.

[0199] Thickness after foaming, T H (cm) Thickness after compression, T C (cm) Expansion rate (R S )(T S -T i ) / T S Compression ratio (R C )(T S -T C ) / T S Expansion Stability Index (SSI) Example 1 0.78 0.67 0.74 40.14 10.520 Example 21 15 0.85 0.826 0.26 10.430 Example 31 42 0.96 0.85 90.324 0.388 Comparative Example 10.44 0.13 0.54 50.70 52.383 Comparative Example 20.51 0.18 0.60 80.64 71.786 Comparative Example 31 55 0.25 0.87 10.839 1.499

[0200]

[0201] Experimental Example 2: Evaluation of Heat Propagation Delay Effect

[0202] A foam (2T, 300mm x 100mm) prepared in the above example and comparative example was inserted between two secondary batteries. They were laminated by bonding them with double-sided tape to secure the sheets. For convenience, one secondary battery was named Cell A and the other secondary battery was named Cell B.

[0203] Afterwards, a heater (120 mm x 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 x 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 x 100 mm) was attached to that outer surface, and the laminate was fastened by applying pressure of 30 kPa.

[0204] After placing the above laminate into a SUS box (420 mm x 105 mm x 125 mm, thickness 10T) and sealing it, the heater was operated at a heating rate of 5 ℃ / min to induce thermal runaway in cell A, and at this time, the voltage and temperature of each cell were recorded.

[0205] 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 19 236 7275 Example 29 143 3342 Example 39 210 54962 Comparative Example 19 112 231 Comparative Example 29 11 41 50 Comparative Example 39 11 50 59

[0206] Referring to Table 2 above, it can be seen that in the case of Examples 1 to 3, where the expansion stability index is 0.100 to 1.450, the time required for heat propagation is more than 10 times longer compared to Comparative Examples 1 to 3, where the expansion stability index is small. The fact that the heat propagation time can be secured by more than 10 times in the event of a fire occurring during operation in an electric device powered by a secondary battery means that a level of safety directly related to the life of the user can be secured. It can be seen that by applying a foam that satisfies the above expansion stability index, a secondary battery or battery box with improved safety can be provided.

[0207]

[0208] [Explanation of the symbol]

[0209] 10, 110, 210: Foam

[0210] 11: Foaming agent

[0211] 12: Weapon Filler

[0212] 13: Organic binder

[0213] 14: Qi Gong

[0214] 10a: Heating plate

[0215] 10b: Insulation board

[0216] 10c: Substrate

[0217] 100: Secondary battery

[0218] 120: Battery case

[0219] 130: Electrode

[0220] 140: Septum

[0221] 150: Electrode tab

[0222] 160: Electrode Lead

[0223] 200: Battery box

[0224] 220: Housing

[0225] 230: Separator

Claims

1. A foam comprising a foaming agent, an inorganic filler, and an organic binder, The above foam is a foam having a Swelling Stability Index (SSI) of 0.100 to 1.450 derived by the following Formula 1: [Equation 1] SSI = (1-R S 2 ) / (1-R C ) In the above Equation 1, R S is the expansion rate, derived by Equation 2 below, and R C is derived as the compression ratio by the following Equation 3, and [Equation 2] R S = (T S - T i ) / T S [Equation 3] R C = (T S - T C ) / T S In the above equations 2 and 3, T i is the initial thickness (cm) of the foam above, and T S is the full expansion thickness (cm) of the above foam, and T C is the compressed thickness (cm) of the foam after a pressure of 30 kPa is applied to the fully expanded foam for 30 seconds.

2. In Claim 1, The above foam is, A foam having a compression ratio greater than 0 and less than or equal to 0.

64.

3. In Claim 1, The above foam is, A foam that begins to foam at a temperature of 130°C or higher.

4. In Claim 1, When the above foam is foamed, The above foaming agent forms a three-dimensional network structure having pores within an organic binder matrix, and The above-mentioned inorganic filler is a foam disposed within an organic binder matrix.

5. In Claim 1, The above foaming agent is, A foam comprising 40 to 60 parts by weight per 100 parts by weight of the above foam.

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

7. In Claim 1, The above foaming agent is, A foam comprising sodium silicate, wherein the sodium silicate satisfies Formula 4 below: [Equation 4] 2 ≤ 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.

8. In Claim 1, The above-mentioned weapon filler is, Foam having a plate-like structure.

9. 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, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and boehmite.

10. In Claim 1, The above-mentioned weapon filler is, A foam containing 50 parts by weight or less per 100 parts by weight of the above foam.

11. In Claim 1, The above organic binder is, A matrix is ​​formed within the above foam, and A foam containing 50 parts by weight or less per 100 parts by weight of the above foam.

12. In Claim 1, The above organic binder is, A foam comprising one or more selected from the group consisting of styrene-butadiene rubber; nitrile rubber; polyester resin; cellulose resin; epoxy resin; phenolic resin; silicone resin; and urethane resin.

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

14. In Claim 13, The above elastic binder is, It comprises one or more selected from the group consisting of styrene-butadiene rubber, nitrile rubber, polyester resin, cellulose resin, urethane resin, and silicone resin, and The above-mentioned reinforced binder is, A foam comprising one or more selected from the group consisting of epoxy resins and phenolic resins.

15. 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 a space other than the space in which the electrode assembly is accommodated within the battery case, in a secondary battery.

16. Multiple secondary batteries; A housing accommodating the above secondary battery; and A foam according to claim 1; comprising, The above foam is a battery box disposed at 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.

17. An electric device comprising at least one of a secondary battery according to claim 15 and a battery box according to claim 16.

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