Electrode assembly

Abstract

The present specification relates to an electrode assembly of good fire resistance and safety, the electrode assembly comprising a plurality of electrodes, and any one or more thereof is a foamable electrode. The foamable electrode comprises a current collector and a foam body positioned on at least one surface thereof, and the foam body comprises a foaming agent, an organic binder, and an inorganic filler, and has impact absorption energy density of 0.18 J / cm2 or greater and expansion rate (E) of 1.9 or greater calculated via equation 1 of the specification.

Description

electrode assembly

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196779 filed on December 26, 2024, Korean Patent Application No. 10-2025-0084739 filed on June 25, 2025, and Korean Patent Application No. 10-2025-0166731 filed on November 6, 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 an electrode assembly 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] In this specification, an electrode assembly with excellent fire resistance and thermal safety is provided by applying a foamed electrode to the electrode assembly, which can stably and effectively delay and / or block thermal propagation and thermal runaway even when a thermal event occurs.

[0012]

[0013] [1] In one embodiment, an electrode assembly comprising a plurality of electrodes, wherein at least one of the plurality of electrodes is a foamed electrode, and the foamed electrode comprises a current collector and a foam located on at least one surface of the current collector, and the foam comprises a foaming agent, an organic binder and an inorganic filler, and the foam has an impact absorption energy density of 0.18 J / cm² 2 The above is an electrode assembly provided, wherein the foam has an expansion rate (E) of 1.9 or higher derived by the following formula 1.

[0014] [Equation 1]

[0015] E = (T e - T i ) / T i

[0016] In the above Equation 1,

[0017] T iis the initial thickness (mm) of the foam above, and

[0018] T e is the full expansion thickness (mm) of the above foam.

[0019] [2] The present invention, in the electrode assembly of [1], wherein the foam has an Expansion Toughness Index (ETI) of 3.0 cm derived by the following Equation 2. 2 It can be more than / J.

[0020] [Equation 2]

[0021] ETI = E / F

[0022] In the above Equation 2,

[0023] 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.

[0024] [3] The present invention, in the electrode assembly of [2], wherein the expansion strength index (ETI) derived by Equation 2 is 3.0 cm 2 / J to 20.0cm 2 / J could be.

[0025] [4] In the present invention, in at least one electrode assembly among [1] to [3], the foamed electrode may be located at the outermost part of the electrode assembly.

[0026] [5] The present invention comprises at least one electrode assembly among [1] to [4], wherein the foamed electrode comprises two or more, and at least one of the foamed electrodes is located at one end of the electrode assembly, and at least one of the foamed electrodes is located at the other end of the electrode assembly.

[0027] [6] In the present invention, in at least one electrode assembly among [1] to [5], an electrode active material layer may be located on one side of the current collector of the foamed electrode, and the foam may be located on the other side.

[0028] [7] The present invention relates to at least one electrode assembly among [1] to [6], wherein the foam has an impact absorption energy density of 0.18 J / cm² 2 Up to 0.72 J / cm 2 And, the foam may have an expansion rate (E) derived by the above formula 1 of 1.9 to 7.0.

[0029] [8] In the present invention, in at least one electrode assembly of [1] to [7], 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.

[0030] [9] In the present invention, in at least one electrode assembly of [1] to [8], the organic binder may include an elastic binder and a reinforcing binder.

[0031]

[0010] In the electrode assembly of [9] above, the foam can satisfy K of Formula 3 below from 0.4 to 2.2.

[0032] [Equation 3]

[0033] K = B e / B r

[0034] In the above Equation 3,

[0035] B e is the mass percentage of the elastic binder based on the total weight of the foam, and B r is the mass percentage of the reinforcing binder based on the total weight of the foam.

[0036]

[0011] The present invention, in the electrode assembly of [9], the elastic binder comprises 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 reinforcing binder may comprise one or more selected from the group consisting of epoxy resin and phenolic resin.

[0037]

[0012] The present invention, in at least one electrode assembly among [1] to

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

[0038]

[0013] The present invention comprises at least one electrode assembly among [1] to

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

[0039] [Equation 4]

[0040] 2 ≤ M S / M N ≤ 4.5

[0041] In the above Equation 4,

[0042] 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.

[0043]

[0014] The present invention, in at least one electrode assembly among [1] to

[0013] , wherein the inorganic filler may include one or more selected from the group consisting of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide and boehmite.

[0044]

[0015] In the present invention, in at least one electrode assembly among [1] to

[0014] , the thickness of the foam may be 10 μm to 1000 μm.

[0045]

[0046] The electrode assembly according to the present specification includes a foamed electrode, thereby effectively delaying or preventing heat propagation and / or thermal runaway even when a thermal event occurs, and accordingly, fire resistance and safety can be significantly improved.

[0047] Specifically, the foam included in the foamed electrode can stably retain internal moisture even in environments with large temperature fluctuations, thereby ensuring the stability of the electrode assembly manufacturing process and guaranteeing durability for long-term use. In addition, the foam expands at a specific temperature, has a high thickness expansion rate, and can maintain the expanded state for a long time, thus preventing the transfer of heat and / or flame.

[0048]

[0049] Figure 1 is a schematic diagram showing a cross-section of a foam before foaming.

[0050] FIG. 2 is a schematic diagram showing a cross-section of a foam after foaming according to the present specification.

[0051] FIG. 3 is a schematic diagram showing the structure of an electrode assembly according to one embodiment.

[0052]

[0053] 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.

[0054] 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.

[0055] 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.

[0056]

[0057] The electrode assembly described in the specification includes at least one of the technical configurations described below, and may include any combination of technically feasible configurations among the technical configurations below.

[0058] First, I will explain the foamed electrode in detail.

[0059]

[0060] foamed electrode

[0061] The foamed electrode according to the present invention comprises a current collector and a foam disposed on at least one surface of the current collector. The foamed electrode comprises the foam, and when a thermal event such as an internal short circuit, external impact, or abnormal heat generation occurs in a secondary battery, the foam expands and its volume increases. As a result, the foamed electrode can perform the function of preventing heat from being transferred to an adjacent electrode within an electrode assembly, and further preventing heat or fire from being transferred to another adjacent secondary battery.

[0062] In one embodiment, the foam may be located on one side of the current collector of the foamed electrode, or on both sides of the current collector of the foamed electrode. For example, an electrode active material layer may be located on one side of the foamed electrode assembly, and the foam may be located on the other side.

[0063] In one embodiment, the foamed electrode may be located at the outermost edge of the electrode assembly. When the foamed electrode is located at the outermost edge of the electrode assembly, the foam expands during the foaming process, thereby securing a gap with adjacent secondary batteries. This effectively suppresses the transfer of heat or flames generated from a secondary battery that has caught fire to adjacent secondary batteries. In other words, by positioning the foam at the outer edge of the electrode assembly, the protective effect of the foamed electrode can be maximized. Furthermore, by positioning the foamed electrode at the outermost edge, where it has relatively little influence on battery capacity development, safety can be simultaneously ensured while minimizing battery capacity degradation.

[0064] In one embodiment, the electrode assembly may include a plurality of foamed electrodes. Specifically, the electrode assembly may include two or more foamed electrodes, at least one of which may be located at one end of the electrode assembly, and at least one of the foamed electrodes may be located at the other end of the electrode assembly. When the foamed electrodes are located at both ends of the electrode assembly, heat transfer to an adjacent secondary battery or another electrode can be effectively prevented even if a fire or abnormal heat generation occurs in the electrode assembly. Therefore, the safety of the electrode assembly can be improved by preventing large-scale accidents caused by thermal runaway.

[0065] Below, the above foam is described in more detail.

[0066]

[0067] foam

[0068] The foam according to the present invention comprises a foaming agent, an organic binder, and an inorganic filler, and has an impact absorption energy density of 0.18 J / cm² 2 The above is the case, and the expansion rate (E) derived by the following Equation 1 is 1.9 or higher.

[0069] [Equation 1]

[0070] E = (T e - T i ) / T i

[0071] In the above Equation 1,

[0072] T i is the initial thickness (mm) of the foam above, and

[0073] T e is the full expansion thickness (mm) of the above foam.

[0074] The above shock absorption energy density is the shock energy (J) required for fracture or breakage of the foam specimen measured through the Izod impact test (modified ASTM D256 method) divided by the cross-sectional area (cm²) of the foam 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.

[0075] 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 length of 5 cm and a thickness of approximately 0.2 mm is placed on an insulation board, and then a heating plate heated to 750°C is brought into contact with the side opposite to the 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 ).

[0076] The foam located on the assembly expands in volume when the temperature of the secondary battery rises above a certain temperature due to the occurrence of a specific event, and as a result, the distance between adjacent electrodes increases, which can prevent the transfer of heat or fire.

[0077] Furthermore, the foam described above possesses excellent fire resistance and heat resistance by comprising a foaming agent, an organic binder, and an inorganic filler. The foaming agent can play a role in delaying the temperature rise through latent heat as moisture vaporizes at high temperatures, and suppressing heat transfer by increasing the distance between cells through expansion. Additionally, the function of this foaming agent can be optimally realized when the organic binder and the inorganic filler work together. Specifically, the organic binder maintains the moisture contained in the foaming agent at a level above a certain threshold despite changes in the external environment, thereby ensuring the foaming phenomenon manifests stably. Moreover, the inorganic filler improves the durability of the foam, ensuring stability during long-term use, while contributing to the realization of a foam with flexibility and high strength.

[0078] Meanwhile, FIG. 1 is a schematic diagram showing a cross-section of a foamed body before foaming. Referring to FIG. 1, before the foamed body (10) is foamed, the organic binder (13) acts as a matrix, and the foaming agent (11) and inorganic filler (12) may have a structure filled within the organic binder matrix.

[0079] 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) still maintains the matrix, and the foaming agent (11) forms a three-dimensional network structure having pores (14). Additionally, the inorganic filler (12) can be dispersed within the pores (14) formed by the foaming agent (11) to more firmly support the three-dimensional network structure.

[0080] In one embodiment, the thickness of the foam may be 10 µm to 1000 µm. Specifically, the thickness of the foam may be 10 µm or more, 20 µm or more, 30 µm or more, 50 µm or more, 60 µm or more, 70 µm or more, 80 µm or more, 90 µm or more, 100 µm or more, or 150 µm or more. Additionally, the thickness of the foam may be 1000 µm or less, 900 µm or less, 800 µm or less, 700 µm or less, 500 µm or less, 400 µm or less, 300 µm or less, or 250 µm or less. The above numerical ranges may be combined with one another without limitation. When the thickness of the foam satisfies the above range, it is possible to prevent the energy density and performance of the electrode assembly from decreasing due to an excessive increase in the thickness of the foamed electrode, which is unrelated to capacity development. At the same time, when a thermal event occurs, the foam expands to effectively secure the gap between electrodes and block heat transfer, thereby suppressing the spread of thermal runaway and improving the safety of the electrode assembly.

[0081]

[0082] Shock absorption energy density and expansion rate

[0083] Typically, when an electrode assembly ignites, a large amount of gas is rapidly generated inside the secondary battery, placing the electrode assembly under high temperature and / or high pressure. In this situation, if heat is transferred to adjacent secondary batteries, a chain reaction of thermal runaway may occur, severely degrading the safety of the battery system.

[0084] To solve the above problem, the present invention provides a foamed electrode comprising a foam. Specifically, the foam of the foamed electrode is located within an electrode assembly to physically separate adjacent electrodes or, furthermore, adjacent secondary batteries, and stably maintains the separated state through expansion and buffering action of the foam even in high temperature and high pressure environments.

[0085] Accordingly, the foam according to the present invention can block or delay the direct conduction of heat to adjacent electrodes and / or batteries, and consequently, effectively prevent heat transfer between electrodes and / or batteries and the occurrence of sequential thermal runaway. Therefore, the present invention can significantly improve the thermal safety of an electrode assembly.

[0086] Specifically, the foam of the present invention satisfies an impact absorption energy density of 0.18 J / cm² or more and an expansion rate (E) calculated by the following formula (1) of 1.9 or more.

[0087] [Equation 1]

[0088] E = (T e - T i ) / T i

[0089] In the above Equation 1,

[0090] T i is the initial thickness (mm) of the foam above, and

[0091] T e is the full expansion thickness (mm) of the above foam.

[0092] As described above, by simultaneously satisfying the shock absorption energy density and expansion rate, the foam not only exhibits excellent durability and processability but also significantly improved fire resistance and thermal safety. Conversely, if the shock absorption energy density of the foam is 0.18 J / cm² 2 If the thickness expansion rate is less than 1.9, cracks or breakage may occur due to impact applied during the manufacturing process of the electrode assembly or during the transfer process. In addition, if the thickness expansion rate due to foaming is low, the heat propagation blocking effect may be insufficient, or if the expansion rate is not maintained stably, the heat blocking effect may be easily weakened, resulting in reduced thermal safety.

[0093] In particular, the foam according to the present invention is applied to an electrode assembly, and its thickness should not be excessively thick so that the energy density of the electrode assembly is not excessively reduced due to the foamed electrode. Nevertheless, in the event of a thermal event, sufficient spacing must be secured from adjacent electrodes or secondary batteries. In addition, the foam must possess durability that allows it to be maintained stably without damage even during repeated compression or winding processes during the manufacturing process of the electrode assembly.

[0094] Accordingly, the foam of the above-mentioned foamed electrode must secure a certain level of expandability while simultaneously possessing mechanical strength and flexibility, thereby providing an effective separation distance in the event of a thermal event, and enabling stable functioning during the manufacturing and operation processes of the electrode assembly.

[0095] In other words, the foam of the present invention simultaneously satisfies two numerical requirements—shock absorption energy density and expansion rate—thereby ensuring excellent durability and flexibility even under thin thickness conditions, thereby securing stability during the manufacturing process. Furthermore, through a sufficient thickness expansion rate, it effectively blocks heat propagation between adjacent electrodes and / or secondary batteries, and by stably maintaining the thickness after foaming even in high-temperature and high-pressure environments generated during ignition, it can significantly improve the thermal safety of the electrode assembly.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] The expansion rate (E) of the foam defined by Equation 1 above may be influenced by the factors mentioned above. When all influences from these factors are taken into account, the expansion rate (E) of the foam defined by Equation 1 above may be between 1.9 and 7.0. Specifically, the expansion rate (E) defined by Equation 1 above may be 1.9 or higher, 2.0 or higher, 2.1 or higher, 2.2 or higher, 2.3 or higher, 2.4 or higher, 2.5 or higher, 3.0 or higher, 3.5 or higher, 3.8 or higher, or 3.9 or higher. Additionally, the expansion rate (E) defined by Equation 1 above may be 7.0 or lower, 6.8 or lower, 6.5 or lower, 6.0 or lower, 5.5 or lower, 5.4 or lower, 5.3 or lower, 5.2 or lower, or 5.15 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 1.9 to 7.0, 2.3 to 7.0, or 2.3 to 5.5.

[0101] The above expansion rate performs the function of suppressing heat transfer by securing the distance between the electrode where ignition occurred and another adjacent electrode, and a larger value is desirable. However, it is difficult to ensure sufficient safety if the expansion rate is simply large. For example, even if the expansion rate is excessively large, if the shock absorption energy density is low, the foam may crack or break due to mechanical shock, and consequently, there is a risk that the separation function and heat blocking effect will be weakened.

[0102] Therefore, it is desirable for the foam to be designed to simultaneously satisfy the aforementioned range of shock absorption energy density. By satisfying these two physical properties—expansion rate and shock absorption energy density—in a balanced manner, the foam possesses sufficient mechanical stability even at a thin thickness, while effectively maintaining the distance between adjacent cells upon ignition to prevent thermal runaway diffusion.

[0103] In one embodiment, the shock absorption energy density of the foam is 0.18 J / cm²2 Up to 0.72 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 0.18 J / cm² 2 Above, 0.20 J / cm² 2 Above, 0.21 J / cm² 2 Above, 0.23 J / cm² 2 Above, 0.24 J / cm 2 Above, 0.25 J / cm² 2 Above, 0.28 J / cm² 2 Above, 0.30 J / cm² 2 Above, 0.35 J / cm² 2 Above, 0.38 J / cm² 2 Above, 0.40 J / cm² 2 Above, or 0.42 J / cm 2 It may be more than that. In addition, the shock absorption energy density is 0.72 J / cm² 2 Below, 0.70 J / cm² 2 Below, 0.68 J / cm² 2 Below, 0.66 J / cm² 2 Below, 0.65 J / cm 2 Less than 0.63 / cm 2 Below, 0.60 / cm 2 Less than 0.58 / cm 2 Less than 0.57 / cm 2 Less than, or 0.56 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 0.18 J / cm². 2 Up to 0.72 J / cm 2 , 0.20J / cm 2 Up to 0.70 J / cm 2 , or 0.23 J / cm 2 Up to 0.70 J / cm 2It may be possible. When the shock-absorbing energy density satisfies the above range, it is possible to prevent the foam from being damaged by shock or shaking that occurs during the electrode assembly manufacturing process, such as assembly, lamination, and winding. In addition, when the shock-absorbing energy density of the foam satisfies the above range, damage caused by the molding process of the electrode assembly and external shock can be prevented, and at the same time, the foamed thickness can be stably maintained even in a thermal runaway situation.

[0104]

[0105] Expansion strength index

[0106] In one embodiment, the foam has an Expansion Toughness Index (ETI) of 3.0 cm derived by the following Formula 2. 2 It can be more than / J.

[0107] [Equation 2]

[0108] ETI = E / F

[0109] In the above Equation 2,

[0110] 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.

[0111] The 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 of the expandable electrode can secure a thickness expansion of a certain amount or more during foaming while simultaneously maintaining shock resistance.

[0112] 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 3.0 cm 2In 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 electrodes and / or secondary batteries.

[0113] Specifically, the foam applied to the foamed electrode must not easily crack or break due to shocks or vibrations that may occur during movement or handling in the manufacturing process; therefore, it is necessary to possess sufficient durability to be used stably in the batch and molding processes. However, merely ensuring mechanical durability is not sufficient; it must exhibit an excellent thickness expansion rate during the foaming process when a thermal event occurs in order to secure a distance within the electrode assembly. Furthermore, this secured separation must be stably maintained even in high temperature and high pressure environments so that heat propagation and thermal runaway to adjacent electrodes and / or secondary batteries can be effectively prevented.

[0114] To evaluate this, the present invention introduces an expansion strength index that indicates the correlation between shock absorption energy density and expansion rate. A higher value of the expansion strength index signifies greater expansion of the foam at the same shock absorption energy density, while a lower value signifies a relatively higher shock absorption energy density at the same expansion rate. In particular, when the expansion strength index is sufficiently large, the foamed electrode can effectively expand to suppress heat propagation and thermal runaway to adjacent electrodes and / or electrode assemblies, even if the electrode assembly is exposed to an abnormal high-temperature and high-pressure environment. Therefore, the expansion strength index can function as a key performance indicator for ensuring the safety of a secondary battery system.

[0115] However, the above expansion strength index does not necessarily indicate an excellent value simply by increasing the expansion rate; if the impact resistance is low, making it difficult to handle during the manufacturing process or easily damaged by external impact, it is difficult to secure performance as a foam. Therefore, in the present invention, it was confirmed that when the expansion strength index calculated according to [Equation 2] satisfies a specific threshold value or higher, the foam can simultaneously secure mechanical durability and thermal safety. That is, the foam of the present invention can be optimally applied to electrode assemblies and can guarantee process stability and long-term reliability even in thin foamed electrode structures.

[0116] In one embodiment, the expansion strength index (ETI) derived by Equation 2 is 3.0 cm 2 It may be greater than / J. A foam having an expansion strength index satisfying the above range can exhibit sufficient thickness expansion without being easily damaged by impact or external force, thus providing excellent heat propagation blocking effects and stably maintaining thickness after foaming in high-temperature and high-pressure environments. Specifically, the above expansion strength index is 3.0cm 2 / J or more, 3.3cm 2 / J or more, 3.4cm 2 / J or more, 3.5cm 2 / J or more, 3.8cm 2 / J or more, 4.0cm 2 / J, 4.5cm 2 / J or more, 5.0cm 2 / J or more, 5.3cm 2 / J or more, 5.5cm 2 / J or more, 6.0cm 2 / J or more, 6.5cm 2 / J or larger, or 6.8cm 2 It can be more than / J.

[0117] 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 20.0 cm 2 / J Below, 19.5cm 2 / J Below, 19.0cm 2 / J Below, 18.5cm 2 / J Below, 18.3cm 2 / J or less, 18.0cm 2 / J Below, 17.9cm 2 / J Below, 17.5cm 2 / J Below, 17.4cm 2 / J or less, 15.0cm 2 / J or less, 13.0cm 2 / J or less, 12.5cm 2 / J or less, 12.0cm 2 / J or less, 11.5cm 2 / J or less, or 11.0cm 2 It may be less than / J.

[0118] The above numerical ranges can be combined without limitation. For example, the expansion strength index (ETI) derived by Equation 2 above is 3.0 cm 2 / J to 20.0cm 2 / J, 3.3cm 2 / J to 18.0cm 2 / J, or 3.5cm 2 / J to 17.5cm 2 / J could be.

[0119] 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 the safety of the pouch-type secondary battery.

[0120]

[0121] The foam described above may include a foaming agent, an inorganic filler, and an organic binder. Through the combination of these components, the foam can exhibit excellent fire resistance and heat resistance. The foaming agent increases the thickness of the foam by delaying the temperature rise through latent heat as moisture vaporizes at high temperatures and inducing expansion. The increased thickness can be stably maintained above a certain level, thereby effectively suppressing heat transfer. This effect is not achieved solely by the foaming agent; rather, it can be optimally realized by including the organic binder and inorganic filler together, which complement structural stability and durability. For example, by designing the foam so that the moisture contained in the foaming agent is maintained above a certain level even in the operating environment of a secondary battery, the foam can immediately expand in the event of a thermal event, thereby preventing heat transfer to the foamed electrode. At the same time, through the interaction between the inorganic filler and the organic binder, deformation or degradation is suppressed even during long-term use, enabling the realization of a foam that possesses both high flexibility and mechanical strength.

[0122]

[0123] Below, foaming agents, inorganic fillers, and organic binders capable of implementing the above-mentioned effects are described in detail.

[0124]

[0125] blowing agent

[0126] The blowing agent may be included in an amount of 20 to 90 parts by weight relative to 100 parts by weight of the foam. Preferably, the blowing agent may be included in an amount of 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, or 40 parts by weight or more, and may also be included in an amount of 90 parts by weight or less, 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, or 70 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 of time. 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.

[0127] 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.

[0128] 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.

[0129] The foaming agent may preferably include sodium silicate. The sodium silicate may satisfy Formula 4 below:

[0130] [Equation 4]

[0131] 2.0 ≤ M S / M N ≤ 4.5

[0132] 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.

[0133] 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.

[0134] In one embodiment, the foaming agent is foamed at a temperature of 130°C or higher, the foamed foaming agent forms a three-dimensional network structure having pores, and the inorganic filler may have a structure disposed within the pores.

[0135]

[0136] Weapon filler

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142]

[0143] organic binder

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150]

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] In one embodiment, the foam may satisfy K of Formula 3 below in a range of 0.4 to 2.2:

[0158] [Equation 3]

[0159] K = B e / B r

[0160] In the above Equation 3,

[0161] 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.

[0162] 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.

[0163] 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.

[0164]

[0165] 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.

[0166] 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.

[0167]

[0168] Hereinafter, an electrode assembly including the above-mentioned foamed electrode is described.

[0169]

[0170] electrode assembly

[0171] In one embodiment, an electrode assembly comprising a plurality of electrodes, wherein at least one of the plurality of electrodes is a foamed electrode, and the foamed electrode comprises a current collector and a foam located on at least one surface of the current collector.

[0172] The plurality of electrodes mentioned above may include foamed electrodes and electrodes that are not foamed electrodes. The electrode that is not a foamed electrode may refer to an electrode commonly used in the field of secondary batteries. The foamed electrode is an electrode containing a foam, and the electrode that is not a foamed electrode may refer to an electrode that does not contain a foam. The foamed electrode may include a foam and an electrode active material layer, and the electrode that is not a foamed electrode may include an electrode active material layer.

[0173] In one embodiment, the foamed electrode may be located at the outermost edge of the electrode assembly. When the foamed electrode is located at the outermost edge of the electrode assembly, a gap can be secured between it and an adjacent secondary battery during foaming, thereby preventing heat generated from a secondary battery that has caught fire from being transferred to an adjacent secondary battery. Furthermore, by placing the foamed electrode at the outermost edge, where it has relatively less influence on the development of the secondary battery capacity, safety can be improved while minimizing the degradation of the battery capacity.

[0174] In one embodiment, the electrode assembly may include a plurality of foamed electrodes. Specifically, the electrode assembly may include two or more foamed electrodes, at least one of the foamed electrodes may be located at one end of the electrode assembly, and at least one of the foamed electrodes may be located at the other end of the electrode assembly. When foamed electrodes are located at both ends of the electrode assembly, even if a fire or abnormal heat generation occurs in the secondary battery, the transfer of heat to adjacent secondary batteries or the surroundings can be blocked, thereby effectively preventing major accidents caused by thermal runaway.

[0175] Referring to FIG. 3, foam electrodes (110) may be positioned at both ends of the electrode assembly (100). According to another embodiment, foam electrodes (110) may be positioned on only one side of the electrode assembly (100) rather than on both sides. The foam electrode (110) may include a current collector (111), an electrode active material layer (112) formed on one side of the current collector (111), and a foam (113) located on the other side. Additionally, an electrode other than a foam electrode (not shown) and a separator (not shown) may be interposed between the foam electrodes (120).

[0176] In one embodiment, the electrode active material layer may include an electrode active material. The electrode may be classified into a positive electrode or a negative electrode, and accordingly, the electrode active material layer may be classified into a positive active material or a negative active material.

[0177] The above-mentioned positive electrode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a positive electrode active material used in the field. Specifically, the above-mentioned positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the above-mentioned lithium metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based oxide (e.g., LiNi1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 MnY2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 Examples include )O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are each atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc., and any one or more of these compounds may be included.

[0178] The above-mentioned negative electrode active material is a material capable of reversibly inserting / extracting lithium ions and may include at least one selected from the group consisting of carbon-based active materials, (meta)metal-based active materials, and lithium metal, and specifically may include at least one selected from carbon-based active materials and (meta)metal-based active materials. In this specification, the term (meta)metal-based active material may be a comprehensive expression encompassing both metal-based active materials and metal-based active materials.

[0179] The above carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and specifically may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0180] The above (quasi)metallic active material may include at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium with at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); lithium vanadium oxide; etc.

[0181] More specifically, the above (quasi)metallic active material may include a silicon-based active material.

[0182] The above silicon-based active material is silicon (Si) and silicon oxide (SiOx(O2)). <x<2)로 표시될 수 있음. 바람직하게는 SiO일 수 있음) 및 실리콘-탄소 복합체(Si / C Composite)로 이루어진 군에서 선택된 적어도 1종을 포함할 수 있다.

[0183] In one embodiment, the electrode active material layer may further include a binder and / or a conductive material. The binder is a component that assists in the binding of the active material and the conductive material, and the binding to the current collector, and specifically may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride.

[0184] The above conductive material may be used to assist and enhance conductivity in a secondary battery, and is not particularly limited as long as it possesses conductivity without causing chemical changes. Specifically, the above conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably may include carbon nanotubes in terms of enhancing conductivity.

[0185] In one embodiment, the electrode assembly may further include a separator, and the separator may be interposed between the plurality of electrodes.

[0186] As the above separator, a conventional porous polymer film used as a separator, such as a polyolefin-based polymer film made of ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, may be used alone or in a laminate thereof, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., may be used, but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0187]

[0188] 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.

[0189]

[0190] Example 1

[0191] (Manufacture of foam)

[0192] A foaming 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, solid content 100%) 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 foaming composition onto a substrate, a foamed body with a thickness of 200 μm was produced by drying in a drying oven at 60°C for 2 hours.

[0193] (Manufacture of foamed electrodes)

[0194] A foamed electrode was manufactured by fixing the above foam to the uncoated surface of a single-sided coated cathode using a small amount of styrene butadiene rubber (SBR) and rolling it. At this time, the foam can also be applied to a single-sided coated anode.

[0195]

[0196] Example 2

[0197] A foamed electrode was prepared 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 when preparing the foamed composition, with a weight ratio of 40:20:20:20 based on solid content.

[0198]

[0199] Example 3

[0200] A foamed electrode was prepared 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 when preparing the foamed composition, with a weight ratio of 60:20:10:10 based on solid content.

[0201]

[0202] Example 4

[0203] A foamed electrode was prepared in the same manner as in Example 1, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed when preparing the foamed composition, with a weight ratio of 60:20:13.5:6.5 based on solid content.

[0204]

[0205] Example 5

[0206] A foamed electrode was prepared in the same manner as in Example 1, except that sodium silicate, kaolin, styrene-butadiene rubber, and epoxy-putty were added to water and mixed when preparing the foamed composition, with a weight ratio of 60:20:6.5:13.5 based on solid content.

[0207]

[0208] Example 6

[0209] A foamed electrode was prepared 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 when preparing the foamed composition, with a weight ratio of 90:2.5:3.75:3.75 based on solid content.

[0210]

[0211] Comparative Example 1

[0212] A foamed electrode was prepared in the same manner as in Example 1, except that epoxy-putty was not added when preparing the foamed composition, and sodium silicate, kaolin, and styrene-butadiene rubber were added to water and mixed, with a weight ratio of 60:20:20 based on solid content.

[0213]

[0214] Comparative Example 2

[0215] A foamed electrode was prepared in the same manner as in Example 1, except that styrene-butadiene was not added when preparing the foamed composition, and sodium silicate, kaolin, and epoxy-putty were added to water and mixed, with a weight ratio of 60:20:20 based on solid content.

[0216]

[0217] Comparative Example 3

[0218] A foamed electrode was prepared 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 when preparing the foamed composition, with a weight ratio of 10:20:35:35 based on solid content.

[0219]

[0220] Comparative Example 4

[0221] A foamed electrode was prepared 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 when preparing the foamed composition, with a weight ratio of 95:2.5:1.25:1.25 based on solid content.

[0222]

[0223] Comparative Example 5

[0224] A foamed electrode was prepared in the same manner as in Example 1 above, except that acrylic resin was added instead of epoxy putty when preparing the foamed composition, and sodium silicate, kaolin, styrene-butadiene, and acrylic resin were added to water and mixed, with a weight ratio of 40:20:20:20 based on solid content.

[0225]

[0226] Comparative Example 6

[0227] A foamed electrode was prepared in the same manner as in Example 1 above, except that acrylic resin was added instead of epoxy putty when preparing the foamed composition, and sodium silicate, kaolin, styrene-butadiene, and acrylic resin were added to water and mixed, with a weight ratio of 60:20:10:10 based on solid content.

[0228]

[0229] Comparative Example 7

[0230] A foamed electrode was prepared in the same manner as in Example 1 above, except that carboxymethylcellulose was added instead of styrene-butadiene when preparing the foamed composition, and sodium silicate, kaolin, epoxy-putty, and carboxymethylcellulose were added to water and mixed, with a weight ratio of 40:20:20:20 based on solid content.

[0231]

[0232] Comparative Example 8

[0233] A foamed electrode was prepared in the same manner as in Example 1 above, except that carboxymethylcellulose was added instead of styrene-butadiene when preparing the foamed composition, and sodium silicate, kaolin, epoxy-putty, and carboxymethylcellulose were added to water and mixed, with a weight ratio of 60:20:10:10 based on solid content.

[0234]

[0235] 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

[0236]

[0237] Experimental Example 1: Measurement of Shock Absorption Energy Density

[0238] This experiment was conducted using a modified Izod impact test according to ASTM D256 standards to evaluate the relative impact resistance of polymer materials.

[0239] Specifically, five plate-shaped specimens each were prepared from the foams of Examples 1-6 and Comparative Examples 1-8, measuring 5 cm in width × 5 cm in length × 0.2 mm in thickness, 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] for a cross-sectional area of ​​0.10 cm² 2 Value calculated by dividing by (= 5cm × 0.02cm) (J / m²) 2 ) was used as an indicator of shock absorption energy density.

[0240] This test focused on evaluating the intrinsic impact resistance of the foam material by not applying a notch.

[0241] The measurement results are shown in Table 2 below.

[0242] Shock Absorption Energy Density (J / cm²) Example 10.66 Example 20.56 Example 30.44 Example 40.47 Example 50.43 Example 60.25 Comparative Example 10.16 Comparative Example 20.15 Comparative Example 30.75 Comparative Example 40.07 Comparative Example 50.13 Comparative Example 60.11 Comparative Example 70.12 Comparative Example 80.11

[0243]

[0244] Experimental Example 2: Measurement of Thickness Expansion Rate

[0245] The foams prepared in Experimental Examples 1-6 and Comparative Examples 1-8 were cut to a width and length of 5 cm and a thickness of 0.2 mm, respectively, and then placed on an insulating board. Subsequently, a heating plate heated to 750°C was placed on the opposite side of the insulating board and contact was maintained for 30 seconds to expand the foam, and the fully expanded thickness (T) of the expanded foam e ) was measured.

[0246] 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.

[0247] Initial thickness, T i (mm) Thickness after foaming, T e (mm) Expansion rate (E) (T e -T i ) / Ti Expansion Strength Index (ETI) (cm² / J) Example 10.20 30.6 8 2.35 3.56 Example 20.20 20.9 8 3.8 5 6.88 Example 30.20 21.1 24.5 4 10.32 Example 40.20 01.2 35.1 5 10.96 Example 50.20 11.1 54.7 2 10.98 Example 60.20 01.0 7 4.35 17.40 Comparative Example 10.20 10.5 7 1.8 4 11.50 Comparative Example 20.20 20.5 11.5 2 10.13 Comparative Example 30.20 30.2 20.0 8 40.11 Comparative Example 40.2020.672.3133.00 Comparative Example 50.2020.511.5211.69 Comparative Example 60.2000.772.8525.91 Comparative Example 70.2020.612.0216.83 Comparative Example 80.2000.843.2029.09

[0248] Experimental Example 3: Evaluation of Fairness and Heat Propagation Delay Effects

[0249] (1) Fairness evaluation

[0250] The foam of Examples 1-6 and Comparative Examples 1-8 prepared in Experimental Example 1 above was cut into sheets of 260 mm × 100 mm × 0.2 mm, and the test was performed by lifting the foam horizontally using a suction device and dropping it from a height of 1 m. If the foam 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 and is shown in Table 4 below.

[0251] Since shape retention and mechanical stability are important factors when moving or stacking foams to manufacture electrode assemblies, this experiment allows for the evaluation of durability to ensure the processability of the foam.

[0252]

[0253] (2) Evaluation of heat propagation delay effect

[0254] Subsequently, two secondary batteries were manufactured in which the foamed electrodes of Examples 1-6 and Comparative Example 3, which were judged as OK in the processability evaluation test, were located at both ends of the electrode assembly. For convenience, one secondary battery was named Cell A and the other secondary battery was named Cell B.

[0255] 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. Additionally, a thermocouple was attached between Cell A and Cell B, and also at the center of Cell B on the side that does not come into contact with Cell A. Then, Superwool insulation (10T, 300 mm × 100 mm) was attached to the outer surface opposite to the side in contact with Cell A and Cell B, and an aluminum plate (10T, 300 mm × 100 mm) was attached to that outer surface, and the structure was fastened into a laminate by applying pressure of 30 kPa.

[0256] 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.

[0257] 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 OK 3 1 7 6 4 5 Example 2 OK 3 2 1 1 8 8 6 Example 3 OK 3 3 1 5 9 1 2 6 Example 4 OK 3 5 1 6 9 1 3 4 Example 5 OK 3 3 1 6 5 1 3 2 Example 6 OK 3 6 1 4 7 1 1 Comparative Example 1 NG --- Comparative Example 2 NG --- Comparative Example 3 OK 3 1 4 7 1 6 Comparative Example 4 NG --- Comparative Example 5 NG --- Comparative Example 6 NG --- Comparative Example 7 NG --- Comparative Example 8 NG ---

[0258] Referring to Table 4 above, Examples 1 to 6, which have an impact absorption energy density of 0.18 J / cm² or higher and an expansion rate (E) derived by Equation 1 of 1.9 or higher, all showed no breakage in the processability evaluation. In addition, these examples showed a heat propagation delay effect of 45 seconds or more, confirming that they are significantly superior to Comparative Example 3, which has a heat propagation delay time of only 16 seconds.

[0259] Meanwhile, among Comparative Examples 1 to 8, only Comparative Example 3, which had an impact absorption energy density of 0.18 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 heat propagation delay time was only 16 seconds.

[0260]

[0261] [Explanation of the symbol]

[0262] 10, 113: Foam

[0263] 11: Foaming agent

[0264] 12: Weapon Filler

[0265] 13: Organic binder

[0266] 14: Qi Gong

[0267] 100: Electrode Zolbiche

[0268] 110: Foamed electrode

[0269] 111: Entire house

[0270] 112: Electrode active material layer

Claims

1. An electrode assembly comprising a plurality of electrodes, At least one of the above plurality of electrodes is a foamed electrode, and The above-mentioned foamed electrode comprises a current collector and a foam located on at least one surface of the current collector, and The above foam comprises a foaming agent, an organic binder, and an inorganic filler, and The above foam has a shock absorption energy density of 0.18 J / cm² 2 That is all, The above foam is an electrode assembly having an expansion rate (E) of 1.9 or higher 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 (mm) of the foam above, and T e is the full expansion thickness (mm) of the above foam.

2. In Claim 1, The above foam has an Expansion Toughness Index (ETI) of 3.0 cm, derived by the following Equation 2. 2 / J or more, electrode assembly: [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 3.0 cm derived by Equation 2. 2 / J to 20.0cm 2 / J person, electrode assembly.

4. In Claim 1, The above-mentioned foamed electrode is an electrode assembly located at the outermost edge of the above-mentioned electrode assembly.

5. In Claim 1, The above-mentioned foamed electrode includes two or more, and At least one of the above foamed electrodes is located at one end of the electrode assembly, and An electrode assembly in which at least one of the above foamed electrodes is located at the other end of the electrode assembly.

6. In Claim 1, An electrode active material layer is located on one side of the current collector of the above-mentioned foamed electrode, and An electrode assembly having the above foam located on the other side.

7. In Claim 1, The above foam has a shock absorption energy density of 0.18 J / cm² 2 Up to 0.72 J / cm 2 And, The above foam is an electrode assembly having an expansion rate (E) derived by the above formula 1 of 1.9 to 7.

0.

8. In Claim 1, The electrode assembly comprising the foaming agent in an amount of 20 to 90 parts by weight per 100 parts by weight of the foam.

9. In Claim 1, The above organic binder comprises an elastic binder and a reinforcing binder, forming an electrode assembly.

10. In Claim 9, The above foam is an electrode assembly 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 mass percentage of the elastic binder based on the total weight of the foam, and B r is the mass percentage of the reinforcing binder based on the total weight of the foam.

11. In Claim 9, The above elastic binder comprises 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 comprises one or more selected from the group consisting of epoxy resins and phenolic resins, an electrode assembly.

12. In Claim 1, The above foaming agent is, An electrode assembly comprising one or more selected from the group consisting of lithium silicate, potassium silicate, sodium silicate, potassium 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 an electrode assembly satisfying the following Formula 4: [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.

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

15. In Claim 1, An electrode assembly having a thickness of 10㎛ to 1000㎛ of the foam.

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