Secondary battery self-foaming foam composite pad and manufacturing method therefor

Abstract

The present invention relates to a secondary battery safety pad between secondary battery cells / modules, and to a secondary battery self-foaming foam composite pad and a manufacturing method therefor, the pad having a porous structure with an expansion buffer characteristic for ensuring the safety of a secondary battery pack by preventing a fire occurring in a single cell from spreading to adjacent cells. The objectives of the present invention are to: provide a pad having an open-cell porous structure so as to be utilized as a heat dissipation path for discharging heat generated during normal operation; provide a heat-insulating fire-extinguishing foam having a porous structure with an expansion buffer characteristic and exhibiting a compression rate of a specific value or higher, so as to respond to volumetric expansion / contraction that inevitably occurs during battery use and swelling occurring over a lifespan; and enable a foam-shaped multifunctional safety composite pad to be manufactured utilizing foaming of a self-foaming flame retardant.

Description

Self-expanding foam composite pad for secondary batteries and its manufacturing method

[0001] The present invention relates to a secondary battery safety pad between secondary battery cells / modules, and to a self-expanding foam composite pad for secondary batteries having a pore structure with cushioning properties corresponding to secondary battery expansion, which prevents a fire occurring in a single cell from spreading to surrounding cells in preparation for heat generation / ignition occurring during secondary battery operation, thereby ensuring the safety of a secondary battery pack, and a method for manufacturing the same.

[0002] The lithium secondary battery market has expanded beyond powering small mobile electronic devices like cell phones and laptops to powering electric vehicles for long-distance driving, and now serves as the primary source of electrical energy in energy storage systems (ESS), which store and use surplus electricity generated through eco-friendly power generation as needed. In particular, lithium secondary battery systems based on non-aqueous electrolytes have made rapid progress, driven by their high operating voltages and high energy and output power.

[0003] However, in lithium secondary battery systems that use flammable organic solvents as electrolytes, there is always a risk of fire accidents due to mechanical and electrical misuse caused by various reasons during battery use.

[0004] In the case of medium- to large-sized battery systems as power sources for electric vehicles, ESS, etc., tens to thousands of single cells are integrated to meet high energy demands.

[0005] To respond to external shocks, it is common to group multiple cells together into a frame to form a module, and then bundle the modules together to form a battery pack that includes safety devices such as a BMS.

[0006] In situations where multiple batteries are packed in a limited space like this, the physical spacing between cells becomes closer, so when a fire occurs in a single cell, the possibility of a continuous explosion due to fire spreading to adjacent cells increases rapidly, making it more urgent to ensure the safety of secondary battery packs.

[0007] To minimize material and personal damage from ignition, it is crucial to prevent the thermal runaway spread of a battery fire as much as possible and secure evacuation time. One solution to this problem has been the introduction of a secondary battery safety composite pad.

[0008] This is based on the insulating properties provided by the safety composite pads located between cells and modules, and between modules, to prevent or delay as much as possible the heat generation and temperature increase caused by the fire from being transferred to adjacent cells, thereby preventing the expansion into a chain reaction of explosions in the battery pack, thereby buying time to respond to the fire and minimizing damage.

[0009] The present invention provides a self-foaming foam composite pad for a secondary battery and a method for manufacturing the same, which provides a foam-type pad with an open-cell porous structure that can be used as a heat dissipation path for dissipating heat generated in normal times, and provides an insulating fire extinguishing foam with an expansion cushioning property that exhibits a compression ratio of a specific value or higher so that it can respond to volume expansion / contraction that inevitably occurs during battery use and swelling according to lifespan, and aims to manufacture a multifunctional safety composite pad that implements a foam shape by utilizing the foaming phenomenon of a self-foaming flame retardant.

[0010] The present invention aims to provide an insulating / flame retardant safety composite pad that prevents or delays as much as possible the spread of a fire that occurs in a single cell to surrounding cells by being positioned between cells or between modules, thereby preventing a chain reaction of fire / explosion leading to a large fire, thereby ensuring the safety of a secondary battery pack.

[0011] The present invention aims to prevent pressure increase due to battery swelling by replacing the currently used expansion buffer battery pressure pad, thereby providing a safety composite pad including an insulation / flame retardant function, thereby minimizing the reduction in energy density of a battery pack due to the addition of components unrelated to energy generation, and more effectively improving thermal performance due to the reduction in heat generation due to the flame retardant / extinguishing function as well as the expansion buffer and insulation properties.

[0012] The present invention is characterized by a self-foaming foam flame retardant safety composite pad comprising a high compression characteristic including a high compression ratio surface pressure pad characteristic applied between cells to cope with pressure increase within the current cell, and a porous structure with expansion buffering characteristics.

[0013] The self-foaming foam composite pad for a secondary battery of the present invention is a multifunctional safety composite pad having a foam form manufactured by utilizing the foaming phenomenon of a polymer due to the addition of a flame retardant material during the manufacturing process.

[0014] (a). By introducing a flame retardant with foaming properties, it is possible to manufacture a composite pad in the form of a foam, thereby providing a compressibility (resistance to battery swelling) between cell pads and providing heat dissipation properties through heat dissipation to the outside by the pore structure within the polymer at all times.

[0015] (b). The original function of flame retardants is to ultimately provide extinguishing properties, and their technical features include direct reduction of calorific value through heat consumption in the thermal decomposition process unique to inorganic flame retardants and prevention of expansion of combustion through dilution of combustible gases generated by decomposition.

[0016] In the case of flame retardants based on metal compounds (such as hydroxides, carbonates, phosphates, and sulfur oxides), they decompose spontaneously due to heat as the temperature rises, accompanied by a gas release reaction. It is characteristic that most thermal decomposition reactions of metal compounds are endothermic reactions. As the temperature rises due to heat transfer from an external heat source, thermal decomposition of metal compounds occurs, and by directly taking away the generated heat, the heat energy transferred to the surroundings is reduced, thereby exhibiting flame retardant properties. In addition, the accompanying gas generation contributes to flame retardant properties by diluting the active radicals in the gas phase, which act as carriers of the chain reaction during the combustion process.

[0017] In the above process, it was confirmed that a foaming phenomenon occurred in the production of a silicone resin-based polymer composite without adding a foaming agent when a specific metal compound-based flame retardant was used, and as a result, it was confirmed that a functional foam-type safety pad with flame retardancy was successfully produced without additional addition of a foaming agent.

[0018] In addition, the structural improvement of the pores created by adding a second flame retardant was achieved, and the flame retardant properties of the composite pad were also improved, ultimately enabling the manufacture of a safety composite pad with excellent flame retardancy and expansion cushioning performance.

[0019] The self-foaming foam composite pad for a secondary battery of the present invention is characterized in that it is manufactured in the form of a foam having a pore structure with expansion buffering properties by forming a mixture based on a polymer resin and a self-foaming flame retardant into a predetermined shape and curing the mixture.

[0020] In addition, the self-foaming foam composite pad for a secondary battery of the present invention is characterized by further mixing a second flame retardant additive.

[0021] And in the self-foaming foam composite pad for secondary batteries of the present invention, the resin used as the matrix may be composed of a silicone resin, and the silicone resin may be a siloxane-based polydimethylsiloxane (PDMS; Poly DiMethyl Siloxane).

[0022] And in the self-foaming foam composite pad for secondary batteries of the present invention, the self-foaming flame retardant may be composed of a hydroxide-based flame retardant, and may be one or two or more of calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), or aluminum hydroxide (Al(OH)3).

[0023] And in the self-foaming foam composite pad for secondary batteries of the present invention, the second flame retardant additive may be composed of one or two or more of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), potassium phosphate tribasic (K3PO4), or calcium phosphate monobasic (Ca(H2PO4)2).

[0024] The method for manufacturing the self-foaming foam composite pad for secondary batteries of the present invention is as follows:

[0025] A resin mixture is created by mixing a self-foaming flame retardant and a second flame retardant additive into a matrix resin,

[0026] The above resin mixture is molded into a predetermined shape,

[0027] It is characterized by being manufactured through a process of hardening at a set temperature for a set period of time.

[0028] According to the present invention, by applying a combination of self-foaming flame retardants to the manufacture of a composite pad, an insulating fire extinguishing means between cells and modules of a secondary battery is provided in the form of a foam with a high compression ratio, thereby providing an insulating fire extinguishing means with excellent performance and possessing expansion buffering properties.

[0029] Accordingly, the present invention provides a functional safety composite pad as a replacement for an expansion buffer battery pressure pad used for the purpose of preventing pressure increase due to battery swelling, thereby minimizing the reduction in energy density of a battery pack due to the addition of components unrelated to energy generation, and providing a multifunctional safety composite pad having a foam form with improved thermal performance that is more effective by directly reducing heat generation due to flame retardancy / extinguishing function as well as expansion buffering and insulation properties.

[0030] Figure 1 is a drawing showing a method for manufacturing a self-foaming foam composite pad for a secondary battery of the present invention.

[0031] FIG. 2 is a cross-sectional view of a foam composite pad manufactured by including a calcium hydroxide flame retardant according to the present invention.

[0032] Figure 3 is a drawing showing the foaming form of the foam according to the hydroxide-based flame retardant component in the present invention.

[0033] Figure 4 is a cross-sectional view of a foam flame-retardant composite pad manufactured by including a hydroxide-based flame retardant and calcium phosphate according to the present invention.

[0034] Figure 5 is a cross-sectional view of a foam flame-retardant composite pad manufactured by including a hydroxide-based flame retardant and potassium triphosphate according to the present invention.

[0035] FIG. 6 is a drawing showing the change in initial expansion behavior according to the introduction of an additive in the present invention, where a shows the results of a manufacturing example that does not include tribasic potassium phosphate and monobasic calcium phosphate, and b and c show the results of a manufacturing example that includes tribasic potassium phosphate and monobasic calcium phosphate, respectively.

[0036] Fig. 7 is a drawing showing a foam composite pad after a heat transfer prevention test according to the present invention, where a represents the front side of the foam composite pad and b represents the back side.

[0037] Figure 8 is an image after a thermal transfer prevention test of a foam composite pad manufactured by adding potassium triphosphate according to the present invention, where a represents the front side of the foam composite pad and b represents the back side of the foam composite pad.

[0038] FIG. 9 is a drawing showing a foam composite pad manufactured by adding calcium phosphate according to the present invention, where a represents the front side of the foam composite pad and b represents the back side of the foam composite pad.

[0039] Figure 10 is a photographic image of a foam composite pad immediately after the end of a contact test according to the present invention.

[0040] Figure 11 is a drawing showing the results of monitoring the compression behavior of a foam composite pad using UTM in the present invention.

[0041] First, the terms used in this specification and claims are general terms selected based on their functions in various embodiments of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, legal or technical interpretations, and the emergence of new technologies. Furthermore, some terms may be arbitrarily selected by the applicant. These terms may be interpreted according to the meanings defined herein. In the absence of a specific definition, they may be interpreted based on the overall content of this specification and common technical knowledge in the relevant technical field.

[0042] In addition, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and therefore, there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0043] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "comprise" or "comprises" are intended to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0044] The self-foaming foam composite pad for a secondary battery of the present invention aims to manufacture a multifunctional safety composite pad having a foam form by utilizing the self-foaming phenomenon resulting from the introduction of a flame retardant.

[0045] The self-foaming foam composite pad for a secondary battery of the present invention can be manufactured in the form of a foam having excellent compressibility by mixing a polymer matrix that provides an elastic structure with heat resistance and flexibility, and a self-foaming flame retardant material for forming a porous structure for fire extinguishment and thermal runaway delay in the event of a fire, and for heat dissipation and expansion buffering functions.

[0046] The above polymer matrix is ​​composed of a silicone resin, and the silicone resin may be polydimethylsiloxane (PDMS; Poly DiMethyl Siloxane), which is a siloxane-based material with excellent heat resistance and flexibility.

[0047] The self-foaming flame retardant material is a material that exhibits a self-foaming phenomenon when used with a specific polymer matrix, and is typically a hydroxide-based flame retardant, and may be calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), and aluminum hydroxide (Al(OH)3), and may include two or more of these.

[0048] In addition, the self-foaming foam composite pad for secondary batteries of the present invention can further mix an additive for controlling viscosity.

[0049] In addition, the self-foaming foam composite pad for secondary batteries of the present invention can further mix a second flame retardant additive.

[0050] The second flame retardant additive may be a carbonate-based inorganic substance or a phosphoric acid-based inorganic substance.

[0051] More specifically, it may be calcium carbonate (CaCO3), magnesium carbonate (MgCO3), potassium phosphate tribasic (K3PO4), or calcium phosphate monobasic (Ca(H2PO4)2), and may include two or more of these.

[0052] This type of self-foaming foam composite pad for secondary batteries is

[0053] 10g of polymer resin and 6g to 10g of hydroxide-based foamable flame retardant are mixed, molded into a predetermined shape, and cured at 80℃ to 150℃ for a predetermined time to produce a foam.

[0054] In addition, 10g of polymer resin, 6g to 10g of hydroxide-based foamable flame retardant, and 1g to 2g of viscosity-controlling additive are mixed in a weight ratio, molded into a predetermined shape, and cured at 80℃ to 150℃ for a predetermined time to produce a foam form.

[0055] The above hydroxide-based foamable flame retardant may be composed of either calcium hydroxide or magnesium hydroxide or a mixture thereof.

[0056] Hereinafter, a method for manufacturing a self-foaming foam composite pad for a secondary battery of the present invention will be specifically described with reference to an embodiment illustrated in the attached drawing 1.

[0057] Figure 1 is a drawing showing the manufacturing process of the self-foaming foam composite pad for a secondary battery of the present invention.

[0058] The method for manufacturing the self-foaming foam composite pad of the present invention is as follows:

[0059] It can be manufactured by a process of adding the above-mentioned hydroxyl-based foamable flame retardant to a polymer matrix individually or simultaneously, mixing them uniformly, molding them into a predetermined shape, and curing them at a predetermined temperature for a predetermined period of time.

[0060] It can be manufactured by a process of adding a hydroxide-based foamable flame retardant and a viscosity-controlling additive to a polymer matrix, mixing them evenly, molding them into a predetermined shape using a doctor blade, and curing them at a predetermined temperature for a predetermined time.

[0061] The self-foaming foam composite pad of the present invention is as follows:

[0062] The technical features of the present invention include forming a foam structure without adding any other foaming agent by using a calcium hydroxide or magnesium hydroxide flame retardant with self-foaming properties, and inhibiting combustion by reducing the amount of heat generated through heat consumption during the thermal decomposition process and diluting combustible gases through gas generation. In addition, the foam is manufactured into a foam form with a porous structure through the foaming process, thereby providing a level of compressibility applicable as an inter-cell pad for battery swelling resistance, and providing heat dissipation properties by constantly dissipating heat to the outside through the porous structure within the composite pad.

[0063] The foam composite pad of the present invention is

[0064] It can be manufactured by mixing 10g of resin and 6g to 10g of calcium hydroxide or magnesium hydroxide in a weight ratio.

[0065] The foam composite pad of the present invention can be manufactured by mixing 10 g of resin and 6 g to 10 g of self-foaming flame retardants calcium hydroxide and magnesium hydroxide, molding the resin mixture into a predetermined size and shape, and curing it at a predetermined temperature of 80°C to 150°C for a predetermined period of time.

[0066] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by adding 6 to 10 g of calcium hydroxide or magnesium hydroxide to 10 g of resin, stirring at a speed of 100 rpm to 800 rpm for 10 to 120 seconds, molding to a thickness of 2 to 3 mm using a doctor blade, and curing at a temperature of 80°C to 150°C for 30 to 120 minutes.

[0067] The foam composite pad of the present invention is

[0068] It can be prepared by mixing 10g of resin and 6g to 10g of calcium hydroxide or magnesium hydroxide in a weight ratio, and adding 1g to 2g of a viscosity-controlling additive.

[0069] The foam composite pad of the present invention can be manufactured by mixing 10 g of resin, 6 g to 10 g of self-foaming flame retardants calcium hydroxide and magnesium hydroxide, and 1 g to 2 g of a viscosity-controlling additive in a weight ratio, molding the mixture into a predetermined size and shape, and curing it at 80°C to 150°C for a predetermined time.

[0070] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by adding 6 to 10 g of calcium hydroxide or magnesium hydroxide and 1 to 2 g of a viscosity-controlling additive to 10 g of resin, stirring at a speed of 100 rpm to 800 rpm for 10 to 120 seconds, molding to a thickness of 2 mm using a doctor blade, and curing at a temperature of 80°C to 150°C for 30 to 120 minutes.

[0071] In addition, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by adding a second flame retardant, calcium carbonate or magnesium carbonate.

[0072] According to this, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 6 g of calcium hydroxide, 1 g to 4 g of calcium carbonate, or 1 g to 5 g of magnesium carbonate, stirring as described above, molding, and then curing at a set temperature for a set period of time.

[0073] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 6 g of calcium hydroxide, 1 g to 4 g of calcium carbonate, and 1 g to 2 g of a viscosity-controlling additive in a weight ratio, stirring as described above, molding, and then curing at a set temperature for a set period of time.

[0074] In addition, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by adding a second flame retardant, tribasic potassium phosphate or monobasic calcium phosphate.

[0075] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 5 g of calcium hydroxide, 1 g to 5 g of monobasic calcium phosphate, or 1 g to 5 g of monobasic calcium phosphate, stirring and molding as described above, and then curing at a set temperature for a set period of time.

[0076] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 5 g of calcium hydroxide, 1 to 5 g of tribasic potassium phosphate or 1 to 5 g of monobasic calcium phosphate, and 1 to 2 g of a viscosity-controlling additive in a weight ratio, stirring as described above, molding, and then curing at a set temperature for a set period of time.

[0077] In addition, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by simultaneously adding second flame retardants, tribasic potassium phosphate and monobasic calcium phosphate.

[0078] According to this, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 6 g of calcium hydroxide and magnesium hydroxide, 1 g of monobasic calcium phosphate, and 3 g of tribasic potassium phosphate, stirring as described above, molding, and then curing at a set temperature for a set period of time.

[0079] Accordingly, the self-foaming foam composite pad for a secondary battery of the present invention can be manufactured by mixing 10 g of resin, 6 g of calcium hydroxide and magnesium hydroxide, 1 g of monobasic calcium phosphate, and 3 g of tribasic potassium phosphate, additionally mixing 1 g to 2 g of a viscosity-controlling additive in a weight ratio, stirring as described above, molding, and then curing at a set temperature for a set period of time.

[0080] The process performed to achieve this embodiment of the present invention is as follows.

[0081] As shown in Table 1, by adjusting the ratio of the polymer resin and the self-foaming flame retardant, a resin composition suitable for manufacturing a self-foaming foam composite pad between cells and modules can be manufactured, and a self-foaming foam composite pad having a pore structure with expansion buffering properties can be manufactured using the same.

[0082] (A). Manufacturing of polymer foam using self-foaming flame retardant

[0083] A polymer composite film can be manufactured by uniformly mixing PDMS resin and a curing agent, casting the mixture to a desired thickness, and curing it at a specific temperature for a specified period of time. This polymer composite film is transparent due to the absence of additives, and maintains its shape with no visible bubbles. Furthermore, the thickness of the manufactured film is not significantly different from that before curing, indicating that no foaming has occurred.

[0084] For reference, when a film was manufactured using a calcium carbonate flame retardant that lacks foaming ability, it was manufactured in the form of a white film, and no change in thickness was observed.

[0085] Here, prior to mixing the PDMS resin and the curing agent, calcium hydroxide (Ca(OH)2) was added at a specific ratio for the purpose of flame retardancy and mixed.

[0086] Calcium hydroxide (Ca(OH)2) was added to the matrix polymer at a specific ratio for the purpose of a flame retardant and mixed uniformly, and the mixture was cast to a desired thickness and cured at a specific temperature for a certain period of time. As a result, traces of bubble generation, which were formed like craters along with the progress of the foaming process, were observed on the surface, and when the cross-section was checked, a well-developed pore structure was observed, as shown in Fig. 2.

[0087] Figure 2 shows a cross-section of a foam composite pad manufactured by including a calcium hydroxide flame retardant.

[0088] Additionally, as thickness increase was observed, it was confirmed that a foam-like composite pad was formed.

[0089] As shown in Table 1, unlike the case where there is no change in thickness before and after curing, the presence or absence of foaming and the degree of foaming of the foam composite pad can be determined by the increase in the resulting thickness compared to the casting thickness.

[0090] The ratio of the thickness after curing to the casting thickness is expressed in the form of a foaming ratio (%).

[0091] Resin (g)Calcium hydroxide (g)Casting thickness (mm)Thickness after curing (mm)Foam ratio (%)11001.01.010021081.02.7270

[0092] (B). Difference in foam expansion rate according to the ratio of self-foaming flame retardant to resin

[0093] Flame-retardant foams were manufactured with different flame retardant contents while keeping the amount of resin fixed.

[0094] As a result of manufacturing a composite foam by varying the amount of calcium hydroxide added in the range of 4 to 10 g per 10 g of resin, when the amount of calcium hydroxide, a self-foaming flame retardant, was less than 5 g, the viscosity of the mixture was low and even in the manufactured foam, the density of the formed bubbles was low, so the compressibility of the composite foam was not good.

[0095] And as the content of self-foaming flame retardant increased, it was confirmed that the density of the mixture increased and the foaming rate showed an overall increasing trend.

[0096] Table 2 below is a graph showing the change in foaming ratio and viscosity according to the mixing ratio of calcium hydroxide.

[0097] Resin (g) Calcium hydroxide (g) Foaming rate (%) Viscosity 1100 100 ◎ 210 4180 ◎ 310 6220 ○ 410 8270 △ 510 10150 X

[0098] Meanwhile, when calcium hydroxide self-foaming and flame retardant were added in amounts of 9 g or more, the flowability of the resin and flame retardant mixture almost disappeared and it became stiff, making it difficult to form into a film. In addition, it was confirmed that the growth of bubbles was minimal even after curing and the compression ratio results were not good.

[0099] (C). Differences in the foaming form of resin compositions and foams (pads) manufactured using the same according to the type of self-foaming flame retardant.

[0100] (1) Use of hydroxide flame retardants alone

[0101] By utilizing the characteristics of hydroxide-based flame retardants that produce endothermic reactions and water molecules through thermal decomposition reactions at high temperatures, foam composite pads were manufactured for other hydroxide-based flame retardants, such as magnesium hydroxide (Mg(OH)2) and aluminum hydroxide (Al(OH)3).

[0102] After replacing the magnesium hydroxide flame retardant with the calcium hydroxide flame retardant, a foam pad was formed in a form almost identical to that of the case where the calcium hydroxide flame retardant was used. However, when comparing the cross-sections, the pore size was smaller than that of calcium hydroxide, and instead, the pore distribution was densely formed, enabling the production of high-density foam.

[0103] In the case of aluminum hydroxide flame retardants, unlike the foaming forms of the two previous flame retardants, the formation of bubbles was absolutely reduced when checking the cross-section, and the number and size of bubbles formed were also smaller than in the previous case. In the case of aluminum hydroxide, foaming progressed somewhat, but it did not form into a highly elastic foam.

[0104] Resin (g) Flame retardant type Flame retardant content (g) Foaming rate (%) Viscosity 110 Calcium hydroxide 8270△210 Magnesium hydroxide 8200○310 Aluminum hydroxide 8120○

[0105] Table 3 above is a graph showing the change in foaming degree according to the type of flame retardant. Figure 3 is a diagram showing the difference in foaming according to the flame retardant component, showing calcium hydroxide, magnesium hydroxide, and aluminum hydroxide.

[0106] (2) Mixture of two or more hydroxide flame retardants

[0107] The results of using calcium hydroxide and magnesium hydroxide flame retardants, which previously demonstrated foaming properties, simultaneously are shown in the table below.

[0108] The problem of excessive viscosity increase that occurred when only calcium hydroxide was used was alleviated, and it was confirmed that the foaming rate increased compared to when only magnesium hydroxide was used.

[0109] Resin (g) Flame retardant type Flame retardant content (g) Foaming rate (%) Viscosity 110 Calcium hydroxide 4250 ○ Magnesium hydroxide 4210 Calcium hydroxide 4190 ○ Aluminum hydroxide 4310 Calcium hydroxide 4170 ○ Aluminum hydroxide 4

[0110] Table 4 above is a graph showing changes in foaming rate and viscosity according to the composition of two types of flame retardants.

[0111] (D). Difference in foaming rate of resin composition and manufactured foam according to the content of additives for viscosity control.

[0112] During the foaming process using calcium hydroxide, a self-foaming flame retardant, an increase in the viscosity of the resin composition was observed. Since the increase in viscosity is a disadvantageous aspect in the current pad process, a viscosity-controlling additive was added to manufacture the foam composite pad.

[0113] As the additive content increased, the overall viscosity of the composition improved. Despite the addition of the additive, no significant decrease in foaming rate was observed. However, when the content exceeded a certain level (3g per 18g composition), curing did not occur under the same conditions, making pad manufacturing impossible. This confirmed the maximum viscosity control achieved through the viscosity-controlling additive.

[0114] Resin composition (g) Additive (g) Foaming rate (%) Viscosity 1180 270 △ 218 1270 ○ 3 18 2260 ○ 4 18 3 Not cured ◎

[0115] Table 5 above is a graph showing the relationship between foaming ratio and viscosity according to the composition ratio of viscosity-controlling additives.

[0116] (E). Difference in foaming rate according to curing temperature

[0117] It is known that the curing time can be shortened as the temperature increases during the curing process of silicone resin, and in the case of a foaming process accompanying curing as in the embodiment of the present invention, it was confirmed that changes in the foaming result occurred depending on the temperature.

[0118] Accordingly, the manufacturing of a foam composite pad was performed with the manufacturing temperature as a variable and the foaming rate was confirmed.

[0119] Manufacturing temperature (℃) Foaming ratio (%) 180 180 210 0 220 3120 270 415 0 230 Pore size: 1 ≫ 2 > 3 ≫ 4

[0120] Table 6 above is a graph showing the difference in foaming rate according to the manufacturing temperature. In general, as the temperature increases, curing progresses rapidly. However, at temperatures above 150℃, the pore size becomes smaller due to curing that progresses faster than the foaming speed, resulting in a tendency for the foaming rate to decrease. At temperatures below 80℃, the curing speed cannot keep up with the foaming speed, resulting in a low foaming rate. In addition, the size of the generated bubbles is also large, resulting in poor compression characteristics.

[0121] (F). Performance improvement of foam flame-retardant composite pads through the addition of a second flame retardant.

[0122] In order to improve performance such as fairness and compressive strength, an attempt was made to manufacture a foam flame-retardant composite pad by adding a second flame-retardant additive.

[0123] (1). Carbonate minerals

[0124] In order to compensate for the drawback of rapid increase in viscosity of resin composition when excessive addition of calcium hydroxide flame retardant content is made, a foam flame retardant composite pad was manufactured by replacing part of the composition with a carbonate-based inorganic flame retardant that has the same mechanism of providing flame retardant properties through thermal decomposition but is unrelated to foaming ability and has less negative effect on mixture viscosity.

[0125] (a) calcium carbonate (CaCO3)

[0126] Resin (g) Calcium hydroxide (g) Calcium carbonate (g) Foaming rate (%) Viscosity 11060220○21061250○31062250○41064260△51066200X

[0127] Table 7 above graphically illustrates the differences in the manufacturing process due to the addition of calcium carbonate. The foaming rate increased slightly with the addition of calcium carbonate, but an increase in the content of up to 4 g did not significantly affect the viscosity or final product of the mixture composition.

[0128] However, when the calcium carbonate content reached 6g, the viscosity increased rapidly, making pad manufacturing difficult, and the foaming rate also decreased again.

[0129] In the heat transfer prevention evaluation test, no decrease in performance was found due to the addition of calcium carbonate, indicating that the addition of calcium carbonate for viscosity control was successful.

[0130] (b) magnesium carbonate (MgCO3)

[0131] Resin (g) Calcium hydroxide (g) Magnesium carbonate (g) Foaming rate (%) Viscosity 11060220○21062250○31064250○41066260△51067200X

[0132] Table 8 above graphically illustrates the differences in the manufacturing process due to the addition of magnesium carbonate. The addition of magnesium carbonate was found to have a lesser effect on viscosity than calcium carbonate. As the magnesium carbonate content increased, the foaming degree increased, but as with calcium carbonate, a point was reached where both viscosity and foaming rate decreased simultaneously.

[0133] In an additional heat transfer evaluation experiment, the addition of magnesium carbonate did not show any decrease in performance, confirming that processability can be improved through the additional introduction of carbonate-based inorganic substances.

[0134] (2). Phosphoric acid minerals

[0135] In the process of manufacturing the above calcium hydroxide-based foam flame-retardant composite pad, it was confirmed that a difference in the foaming results occurred when a phosphoric acid-based inorganic flame retardant was included in the manufacturing process, and through this, it was intended to improve the foaming state and the performance of the pad.

[0136] (a) Calcium phosphate monobasic (Ca(H2PO4)2)

[0137] Resin (g) Calcium hydroxide (g) Monobasic calcium phosphate (g) Viscosity 11051◎21052◎31053○41055○Pore size: 4 ≫ 2 ≒ 3 > 1

[0138] Table 9 above is a graph showing the results of foam manufacturing according to the amount of calcium phosphate monobasic added, and Fig. 5 is a cross-sectional photograph image of a foam composite pad manufactured including calcium phosphate monobasic. As calcium phosphate monobasic was added, the pores were combined with each other during the pore formation stage, which resulted in an increase in the pore size. This is a factor that can positively affect the increase in compressibility, and it was found that there was a clear difference in the pore structure depending on the change in the amount added. In the sample with 5 g of calcium phosphate monobasic added, the pore size increased excessively, which negatively affected the stable foaming structure of the foam, and thus, it was confirmed that an appropriate amount of calcium phosphate monobasic additive was necessary.

[0139] Additionally, it was confirmed that viscosity problems at the mixture level did not significantly occur due to the addition of additives.

[0140] (b) potassium phosphate tribasic (K3PO4)

[0141] Resin (g) Calcium hydroxide (g) Tribasic potassium phosphate (g) Viscosity 11052◎21053◎31054○41055○ Pore size: 4 ≫ 3 > 1 ≒ 2

[0142] Table 10 above is a graph showing the change in viscosity according to the mixing ratio of potassium phosphate tribasic, and Fig. 5 shows a cross-sectional photographic image of a foam composite pad manufactured by including potassium phosphate tribasic. As a result of manufacturing a foam flame-retardant composite pad by adding potassium phosphate tribasic, (a). the size of open pore cells decreased and the cell size became uniform throughout, and (b). it was confirmed that as the pore wall film became thinner, the elasticity of the foam increased, showing excellent shock absorption behavior.

[0143] As shown in Table 10, as the content of potassium phosphate tribasic increased, the viscosity tended to increase slightly, but the difference was not large, and it was confirmed that the foaming rate and compression characteristics were clearly improved.

[0144] (c) Mixed application of two or more additional phosphoric acid flame retardants

[0145] Resin (g) Calcium hydroxide (g) Magnesium hydroxide (g) Tribasic potassium phosphate (g) Monobasic calcium phosphate (g) Viscosity 1106-31◎2103331◎

[0146] Table 11 above shows the results of changes according to the mixed use of basic flame retardants and additional flame retardants. When the two phosphate-based inorganic substances were mixed and used, the reduction in the cell size of the open pores was the same as when only potassium phosphate tribasic was applied. This was consistent with the results of applying potassium phosphate tribasic, which showed a more uniform pore distribution and thinner membranes. This confirmed that the individual characteristics were expressed independently as the two phosphate-based inorganic substances were added.

[0147] (G). Evaluation of insulation / flame retardant properties

[0148] To examine the practical applicability of the secondary battery composite pad, the following tests were conducted to evaluate the insulation and flame retardancy properties.

[0149] (1) Heat transfer prevention evaluation test using a gas torch

[0150] A test was conducted to evaluate whether the foam composite pad was damaged / destructed due to combustion and the temperature behind the composite pad by placing the foam flame-retardant composite pad vertically and placing the gas torch horizontally so that the flame was irradiated in a direction perpendicular to the foam, and then applying the flame at a distance where the flame did not directly touch the composite pad.

[0151] Here, Fig. 6 shows the results of the initial expansion behavior relaxation according to the presence or absence of the addition of a phosphate-based inorganic flame retardant. a is the result including only the basic flame retardant, a hydroxide-based flame retardant, Fig. b is the result with the addition of a phosphate-based inorganic substance, and c is the result with the application of a mixture of two or more types of a hydroxide-based flame retardant and a phosphate-based inorganic substance.

[0152] FIG. 8 and FIG. 9 show the results of a thermal transfer prevention test of a foam composite pad manufactured by adding one or more phosphoric acid-based inorganic flame retardants. FIG. 8(a) shows the front side of a foam composite pad with one type of phosphoric acid-based inorganic material added, and FIG. 8(b) shows the back side of a foam composite pad. FIG. 9(a) shows the front side of a foam composite pad with two or more types of phosphoric acid-based inorganic material added, and FIG. 9(b) shows the back side of a foam composite pad.

[0153] (A) Results of application of hydroxide flame retardants

[0154] For the foam composite pad containing the hydroxide-based flame retardant, it was confirmed in the thermal transfer prevention evaluation test that the composite pad maintained its overall shape without damage for a period exceeding 20 minutes.

[0155] However, as shown in Fig. 6a, it was observed that the back of the pad swelled in a hemispherical shape in the beginning (within 2 minutes), and cracks occurred starting from the swollen edge section during the shrinking process while cooling to room temperature after the test.

[0156] During the test process, the temperature on the back of the pad was measured and it was confirmed that initially, the temperature rose to around 400℃, and then after about 2 minutes, it was maintained at 320-350℃ without any significant temperature change.

[0157] (B) Results of additional application of hydroxide flame retardants and phosphate flame retardants

[0158] Compared to Fig. 6a when only a hydroxide-based flame retardant was used, the expansion behavior behind the torch ignition that occurred at the beginning of the test was weakened as shown in Fig. 6b, and the formation of cracks on the pad surface due to shrinkage after the test was noticeably reduced as shown in Fig. 7a. In particular, as shown in Fig. 7b, it can be confirmed that no cracks were observed at all on the back. In addition, no cracks were observed during the cooling process after the test as shown in Fig. 8b.

[0159] (C) Results of simultaneous application of two types of hydroxide flame retardants and phosphoric acid flame retardants

[0160] In the case of a foam pad containing two or more types of hydroxide-based flame retardants and phosphate-based inorganic flame retardants, the phenomenon in the gas torch test showed the same phenomenon as the foam pad with the phosphate-based inorganic flame retardants added, as shown in Fig. 6 c and Fig. 9 b, and the backside temperature measurement results confirmed that the temperature was maintained at 300 to 310°C without a significant change after about 2 minutes.

[0161] (2) Contact evaluation (UL94 simulation test)

[0162] A test was conducted to examine the combustion time and pattern after cutting the foam composite pad into a certain size and mounting it vertically and then applying a flame directly to the lower cut surface for 10 seconds.

[0163] Despite the exposure for 10 seconds, as shown in Fig. 10, no behavior related to ignition / combustion was observed, such as no combustion progressing except for soot at the bottom where the flame directly touched, confirming the excellent flame retardant properties.

[0164] Figure 10 is a drawing showing a foam composite pad after the end of the contact test.

[0165] (3) Shock absorption performance evaluation

[0166] In order to buffer the expansion due to swelling of secondary batteries, the shock absorption performance was evaluated by measuring the compression rate through the change in thickness according to the pressure applied.

[0167] After applying a certain amount of pressure to the foam composite pad, the compressibility was confirmed by measuring the thickness before and afterward. Multiple identical samples were prepared, measured, and the average value was taken. Furthermore, a universal testing machine (UTM) was used to monitor the applied pressure in real time as the thickness was compressed at a constant rate, thereby examining the compression-related behavior of the foam composite pad.

[0168] First, 1 kgf / cm through the press 2 By measuring the compressed thickness after applying pressure, the degree of compression is expressed as a percentage compared to the thickness before the test, and the results are shown in Table 12. It was confirmed that the compression ratio result was approximately 34%.

[0169] After applying the thickness pressure and voltage 1 st 3.061.982 nd 3.092.063 rd 3.112.064 th 3.022.01Average3.072.03Compression ratio (%)34.0

[0170] Additionally, after stacking multiple layers of samples and mounting them on the UTM, a constant rate of displacement was applied, and the resulting load was monitored. Figure 11 shows the results of monitoring the compression behavior of a foam composite pad using the UTM.

[0171] As shown in Fig. 11, it was confirmed that approximately 30% of the compressible thickness was initially compressed intensively, and thereafter the compression thickness and load showed linear behavior.

[0172] In the above embodiments of the present invention, calcium hydroxide, magnesium hydroxide, and aluminum hydroxide were described as examples of self-foaming flame retardants, hydroxide-based flame retardants, but the present invention is not limited thereto, and a self-foaming flame retardant composed of a specific polymer matrix and a material that exhibits a self-foaming phenomenon when used can be applied.

[0173] In addition, the present invention can expect the effect of a self-foaming foam composite pad manufactured as in the embodiment of the present invention by using a self-foaming flame retardant such as magnesium hydroxide or calcium hydroxide by configuring a hydroxide transition metal as a self-foaming flame retardant.

[0174] Here, the above-mentioned hydroxide transition metals may be composed of iron hydroxide, copper hydroxide, manganese hydroxide, nickel hydroxide, cobalt hydroxide, zinc hydroxide, etc.

[0175] In the above, the foam composite pad was manufactured at an optimal ratio for a preferred embodiment of the present invention, and the test results were presented and described as a foam composite pad manufactured at an optimal ratio. However, the present invention is not limited to the specific embodiment described above, and various modifications can be made by a person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the present invention.

Claims

1. In the insulating fire extinguishing pad for secondary batteries, A self-foaming foam composite pad for a secondary battery, which is manufactured by molding a mixture of a resin, a hardener, and a self-foaming flame retardant material into a predetermined shape and curing it to form a foam having a pore structure with expansion buffering properties.

2. A self-foaming foam composite pad for a secondary battery, wherein a viscosity-controlling additive is further mixed in the first paragraph.

3. A self-expanding foam composite pad for a secondary battery, wherein a second flame retardant additive is further mixed in the first paragraph.

4. In paragraph 1, A self-foaming foam composite pad for a secondary battery, wherein the self-foaming flame retardant is a hydroxide-based flame retardant and is composed of one or two or more of calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), or aluminum hydroxide (Al(OH)3).

5. In paragraph 3, A self-expanding foam composite pad for a secondary battery, wherein the second flame retardant additive is one or more of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), potassium phosphate tribasic (K3PO4), or calcium phosphate monobasic (Ca(H2PO4)2).

6. A self-foaming foam composite pad for a secondary battery, which is manufactured by mixing 10 g of a resin and a hardener with 6 g to 10 g of either calcium hydroxide or magnesium hydroxide or a mixture of the two, molding it into a predetermined shape, and curing it at 80°C to 150°C to produce a foam having a pore structure with expansion buffering properties.

7. Create a resin mixture by mixing a self-foaming flame retardant with the resin and hardener, The above resin mixture is molded into a predetermined shape, A method for manufacturing a self-foaming foam composite pad for a secondary battery, characterized in that it comprises a process of manufacturing by curing at a set temperature for a set period of time.

8. A method for manufacturing a self-foaming foam composite pad for a secondary battery, characterized in that in the 7th paragraph, the manufacturing temperature for curing the resin mixture is 80°C to 150°C.

9. A method for manufacturing a self-foaming foam composite pad for a secondary battery, further comprising a step of mixing a viscosity-controlling additive into the resin mixture in the 7th paragraph.

10. A method for manufacturing a self-foaming foam composite pad for a secondary battery, further comprising a step of mixing a second flame retardant additive into the resin mixture in the 7th paragraph.

11. In the 7th paragraph, the self-foaming flame retardant is a hydroxide-based flame retardant, and includes one or two or more of calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), or aluminum hydroxide (Al(OH)3), a method for manufacturing a self-foaming foam composite pad for a secondary battery.

12. A method for manufacturing a self-foaming foam composite pad for a secondary battery, wherein the second flame retardant additive comprises one or two or more of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), potassium phosphate tribasic (K3PO4), or calcium phosphate monobasic (Ca(H2PO4)2).

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