Improved safety of battery packs

Abstract

The present invention relates to a battery pack, and the battery pack can minimize the propagation of generated heat and flames to adjacent assemblies when thermal runaway occurs in any one of a plurality of cell stack assemblies housed therein, thereby improving safety against fire and explosion of the battery pack.

Description

[Technical field]

[0001] The present invention relates to a battery pack with improved safety.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0108524 dated August 29, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0003] Currently, commercial secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, etc. Among these, lithium secondary batteries are attracting attention due to their advantages over nickel-based secondary batteries, such as almost no memory effect, freedom in charging and discharging, a very low self-discharge rate, and high energy density.

[0004] Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as positive and negative active materials, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate, each coated with a positive electrode active material and a negative electrode active material, are disposed with a separator therebetween, and an exterior material, i.e., a battery case, that hermetically houses the electrode assembly together with an electrolyte.

[0005] Generally, lithium secondary batteries can be classified into can-type secondary batteries in which an electrode assembly is housed in a metal can and pouch-type secondary batteries in which an electrode assembly is housed in a pouch made of an aluminum laminate sheet, depending on the shape of the exterior material.

[0006] In recent years, secondary batteries have been widely used for driving and energy storage not only in small devices such as portable electronic devices but also in medium-sized and large devices such as automobiles and energy storage systems (ESS). The secondary batteries are provided in a battery pack and installed in the medium-sized and large devices. In this case, in order to increase the capacity and output of the battery pack, the battery pack includes a large number of secondary batteries which are electrically connected to each other. Here, a large number of secondary batteries may be housed inside one module case to form one battery module, and a large number of battery modules may be housed inside one pack case to form one battery pack.

[0007] Generally, when a secondary battery is used in an environment where the temperature is higher than the appropriate temperature, the performance of the secondary battery may be degraded, and in the worst case, there may be a risk of explosion or fire. In addition, when a battery pack is formed using a number of secondary batteries, the heat generated from the multiple secondary batteries is added together in a small space, and the temperature of the battery pack may rise more quickly and violently. In particular, battery packs for vehicles and battery packs for power storage devices, which are mainly used outdoors, are frequently exposed to direct sunlight and may be placed in severe high-temperature conditions such as in summer or in desert regions.

[0008] In addition, a battery pack is composed of a plurality of battery modules and a plurality of secondary batteries. When an abnormal condition occurs in some of the battery modules or secondary batteries constituting the battery pack, heat may be generated. Once heat is generated, the temperature of the battery may continuously rise and exceed a certain critical temperature, which may lead to a thermal runaway condition. When such thermal runaway occurs inside a battery module or battery pack in which a plurality of battery cells are stacked, it may induce an explosion or fire of the battery cells. In this case, the flame may spread to other battery cells that are operating normally, causing a chain reaction of explosions of the plurality of battery cells, which may damage the device in which the battery module / pack is installed and may expose the user to a safety accident risk. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 10-2022-0029941 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to provide a battery pack with improved safety by slowing the propagation of heat and / or flame between cells under conditions of heat generation or thermal runaway. [Means for solving the problem]

[0011] To solve the above-mentioned problems, In one embodiment, the present invention comprises: A battery pack containing a plurality of cell stack assemblies, a pack case including a base plate including a cell stack region in which a cell stack assembly is located, and a side pack frame extending vertically along an edge of the base plate and coupled to the base plate so as to surround the cell stack region; a pack case cover located on an upper portion of the cell stack assembly located in the cell stack region and coupled to an upper end portion of the pack case, The cell stack assembly includes an isolation member having an outer heat resistant plastic matrix; The separator is characterized in that no liquid droplets are formed even when the separator is in contact with a flame at 800 to 1,000° C. for 5 minutes or more.

[0012] In this case, the isolating member may include a sheet having a single layer structure in which a fibrous structure is dispersed in a heat-resistant plastic matrix.

[0013] The heat-resistant plastic matrix may contain one or more compounds selected from the group consisting of acrylonitrile-based resins, acrylic-based resins, benzimidazole-based resins, indoline-based resins, imide-based resins, amide-based resins, phenylene oxide-based resins, butylene terephthalate-based resins, and copolymer resins thereof.

[0014] The fiber structure may contain one or more of glass fiber, carbon fiber, and aramid fiber, and the content thereof may be adjusted to 5 to 40% by weight based on the total weight of the isolation member.

[0015] In addition, the isolation member provided on the upper surface of the cell stack assembly may include a plurality of exhaust ports.

[0016] In addition, a flame propagation prevention sheet may be provided between the pack case cover and the isolation member.

[0017] In this case, the flame propagation prevention sheet may be a silicate sheet composed of a silicate containing one or more elements selected from the group consisting of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

[0018] As an example, the flame spread prevention sheet may include one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and banded mica.

[0019] In addition, the isolation member may include a plurality of exhaust ports arranged perpendicular to the cell stacking direction of the cell stack assembly contained inside the pack case, and the flame propagation prevention sheet may have an exhaust area partially cut out along the exhaust ports of the isolation member.

[0020] Furthermore, the flame propagation prevention sheet may have an average thickness of 0.5 to 5.0 mm in order to be activated by pressure generated by gas and / or flame generated inside. Effect of the Invention

[0021] The battery pack according to the present invention has the advantage that when thermal runaway occurs in any one of the multiple cell stack assemblies contained therein, the propagation of the generated heat and resulting flames to an adjacent assembly can be minimized, thereby improving the safety of the battery pack against fire or explosion. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view illustrating a structure of a battery pack according to the present invention; [Diagram 2] 2 is a plan view showing an isolation member disposed on the upper surface of a cell stack assembly in accordance with the present invention. FIG. [Diagram 3] 1 is a plan view showing a flame propagation prevention sheet on an isolation member arranged on the upper surface of a cell stack assembly according to the present invention. [Figure 4] 4 is a cross-sectional view illustrating a method for discharging heat and / or flames generated inside a cell stack assembly housed in a battery pack according to the present invention during thermal runaway. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0024] However, this is not intended to limit the invention to any particular embodiment, but it should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0025] In the present invention, terms such as "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and may be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] In addition, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion in between. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion in between. In addition, in the present application, being "on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0027] The present invention will now be described in more detail.

[0028] <Battery pack> In one embodiment, the present invention comprises: A battery pack containing a plurality of cell stack assemblies, a pack case including a base plate including a cell stack region in which a cell stack assembly is located, and a side pack frame extending vertically along an edge of the base plate and coupled to the base plate so as to surround the cell stack region; a pack case cover located on an upper portion of the cell stack assembly located in the cell stack region and coupled to an upper end portion of the pack case, the side pack frame and the pack case cover include isolation members including a heat resistant plastic matrix therein; The separator is characterized in that no liquid droplets are formed even when the separator is in contact with a flame at 800 to 1,000° C. for 5 minutes or more.

[0029] The battery pack according to the present invention includes a plurality of cell stack assemblies, a pack case that houses the cell stack assemblies, and a pack case cover. The side pack frame and the pack case cover included in the pack case have a structure having an isolation member on the inside that does not form droplets even at a high temperature of 500° C. or more. As a result, the battery pack can prevent heat and / or flames from the cell stack assembly from propagating to an adjacent cell stack assembly when heat is generated or thermal runaway occurs in one of the plurality of cell stack assemblies, thereby preventing ignition and / or explosion of the battery pack.

[0030] 1 to 4 are a perspective view, a plan view and a cross-sectional view illustrating the structure of a battery pack 100 according to the present invention. Hereinafter, a more detailed description will be given with reference to FIGS.

[0031] The battery pack 100 of the present invention includes a cell stack assembly 110, a pack case 120 in which the cell stack assembly 110 is housed, and a pack case cover 130 (not shown).

[0032] The cell stack assembly 110 referred to in the present invention may eliminate a module frame configuration that surrounds and protects a cell stack in which multiple battery cells are stacked, and may include a configuration in which a bus bar frame and end plates are respectively attached to the front and rear surfaces of the cell stack on which electrode leads are formed.

[0033] In this case, the cell stack has a structure in which a plurality of battery cells are stacked, and each battery cell includes an electrode assembly therein, a pair of electrode leads electrically connected to the electrode assembly, and a battery case surrounding the electrode assembly such that the electrode leads are led out to the outside. The electrode leads may be led out to both sides of the battery case.

[0034] The bus bar frame includes bus bars electrically connected to the battery cells, and is closely coupled to the cell stack from the front and rear of the cell stack such that electrode leads of each battery cell included in the cell stack are connected to the bus bars.

[0035] In addition, the end plates are coupled to the bus bar frame to cover the bus bars in order to protect the bus bars and electrode leads from external impact, and the end plates gather and fix the battery cells included in the cell stack.

[0036] The cell stack assembly does not have a module frame configuration that surrounds and protects the cell stack as described above, but instead includes end plates that structurally fix the stacked battery cells and a bus bar frame that electrically connects the fixed battery cells, thereby offering the advantages of being able to more efficiently release heat generated in the multiple battery cells during charging and discharging, as well as reducing the unit weight of the cell stack.

[0037] Also, a plurality of the cell stack assemblies 110 may be provided in the battery pack. The plurality of cell stack assemblies 110 may be arranged in the left-right direction with their side surfaces facing each other. For example, the battery pack 100 may include at least two cell stack assemblies 110. In this case, the two cell stack assemblies 110 may be arranged in the left-right direction with their right and left sides facing each other.

[0038] The battery pack 100 also includes a pack case 120 including the cell stack assembly 110 described above, and a pack case cover 130 (not shown) coupled to the pack case to cover the top of the cell stack assembly 110 at the top of the pack case.

[0039] Here, the pack case 120 includes a base plate 121 disposed under the cell stack assembly 110 and including a cell stack region in which the cell stack assembly 110 is located. The base plate 121 may have a plate shape extending in a horizontal direction. Here, the horizontal direction refers to the surface direction of a flat ground. The base plate 121 may be made of a metal material having excellent mechanical rigidity.

[0040] In addition, a plurality of cell stack assemblies 110 may be positioned on the upper portion of the base plate 121. To this end, the base plate 121 may include a cell stack region in which the cell stack assemblies 110 are positioned, and side pack frames 122 extending vertically along the edges of the base plate 121 to surround the cell stack region may be coupled to each other to form a space for accommodating the cell stack assemblies 110.

[0041] The base plate 121 may function not only to provide a space for accommodating the cell stack assembly 110 thereunder, but also to function as a heat sink for dissipating heat generated in the cell stack assembly 110 to the outside. To this end, the base plate 121 may be provided with a cooling means (not shown) on the other side of the surface on which the cell stack assembly 110 is accommodated, such that a coolant such as cooling water or air can flow in contact with the cooling means, in order to remove heat generated from the cell stack assembly 110. In addition, the side pack frame 122 may be joined in a manner commonly applied in the art, for example, by friction stir welding.

[0042] The battery pack 100 also includes an isolation member 140 on the outside of the cell stack assembly 110 housed therein, in other words, on the outside of the cell stack assembly 110. Specifically, the battery pack 100 may include isolation members 140a and 140b on the inside of the side pack frame 122 and the pack case cover 130 excluding the base plate 121 functioning as a heat sink as shown in FIG. 1, i.e., between the side pack frame 122 and the cell stack assembly 110 and between the pack case cover 130 and the cell stack assembly 110, respectively.

[0043] Since the isolation member 140 contains a heat-resistant plastic matrix, if a thermal runaway occurs in any of the multiple cell stack assemblies contained therein, not only is there less damage caused by the generated heat or flames, but the transmission of the generated heat or flames from the cell stack assembly to an adjacent cell stack assembly can be minimized.

[0044] For this purpose, the isolation member 140 includes a heat-resistant plastic matrix that is little or not deformed at high temperatures. Here, "little or not deformed at high temperatures" may mean that there is no change in shape due to melting and / or carbonization at a temperature of 500°C or higher. More specifically, it may mean that there is no change in shape due to melting and / or carbonization of the material when the isolation member is left for a certain period of time or is exposed to heat at a temperature of 600°C or higher, 700°C or higher, or 600°C to 1,000°C. As an example, the isolation member may not form droplets due to melting of the heat-resistant plastic matrix or holes due to carbonization even when it is in contact with a flame of 800 to 1,000°C for 5 minutes or more, and more specifically, may not form droplets or holes due to carbonization even when it is in contact with a flame of 800 to 1,000°C for 5 minutes or more.

[0045] As described above, the heat-resistant plastic matrix may be applied without any particular limitation as long as it does not change in shape due to melting and / or carbonization at a temperature of 500°C or higher. Preferably, the heat-resistant plastic matrix may be applied with no change in shape due to melting and / or carbonization at a temperature of 800 to 1,000°C, taking into consideration the ignition and / or explosion temperature induced inside the cell stack assembly 110 during thermal runaway. For example, the heat-resistant plastic matrix may include one or more compounds selected from acrylonitrile-based resins, acrylic-based resins, benzimidazole-based resins, indoline-based resins, imide-based resins, amide-based resins, phenylene oxide-based resins, butylene terephthalate-based resins, and copolymer resins thereof. Here, the compound refers to a compound formed using a monomer such as acrylonitrile or acrylate, or a compound containing benzimidazole, indoline, imide, amide, phenylene oxide, butylene terephthalate, etc. in a repeating unit.

[0046] As an example, the heat-resistant plastic matrix may be a phenylene oxide-based resin such as polyphenylene oxide (PPO) or an amide-based resin such as nylon, which may be used alone or in combination. Here, the phenylene oxide-based resin and the amide-based resin may be used in the form of a homopolymer or in the form in which some of the repeating units are modified.

[0047] Also, the isolating members 140a and 140b may have a single-layered sheet shape in which a fiber structure is dispersed in a heat-resistant plastic matrix to provide the members with heat resistance and rigidity. In a conventional battery pack, a multi-layered member made of a metal oxide such as silicon oxide (SiO2) is provided inside a pack case to realize the heat resistance and rigidity of the module and / or cell stack assembly housed therein. In this case, an adhesive is applied between each layer to realize the multi-layered structure of the metal oxide, but since the adhesive is deformed when the module and / or cell stack assembly generates heat or experiences thermal runaway, there is a limit to preventing the heat or flame generated inside the battery pack from spreading to the adjacent module and / or cell stack assembly. However, the isolating members 140a and 140b of the present invention have a single-layered sheet shape in which a fiber structure is dispersed in a heat-resistant plastic matrix having high dimensional stability at high temperatures, and thus have the advantage of being able to realize sufficient heat resistance and rigidity without the need for an adhesive required for a multi-layered structure.

[0048] In this case, the fiber structure may include one or more of glass fiber (GF), carbon fiber (CF) and aramid fiber (AF). As one example, the fiber structure may include glass fiber (GF) that can improve the strength and elastic modulus of the heat-resistant plastic matrix and at the same time reinforce the insulating performance of the isolation member. The glass fiber is commercially available and may be E-glass, S-glass, etc., and may have a length of 3 to 6 mm and a diameter of 10 to 15 μm.

[0049] In addition, the fiber structure may be included in the isolating members 140a and 140b at a certain content in order to improve the heat resistance and mechanical properties of the isolating members 140a and 140b. Specifically, the fiber structure may be included in the isolating members 140a and 140b at a content of 5 to 40% by weight based on the total weight of the isolating members 140a and 140b, and more specifically, the fiber structure may be included in the isolating members 140a and 140b at a content of 5 to 35% by weight, 5 to 30% by weight, 5 to 15% by weight, 8 to 12% by weight, 10 to 20% by weight, 20 to 40% by weight, or 25 to 35% by weight based on the total weight of the isolating members 140a and 140b. By controlling the content of the fiber structure within the above range, the present invention can prevent the isolating members 140a and 140b from being insufficiently realized in heat resistance and rigidity due to a significantly low content, while preventing the isolating members 140a and 140b from being excessively increased in breaking strength, thereby preventing a decrease in resistance to external force when an external force is applied to the battery pack 100.

[0050] 2, the isolation member 140b provided on the inside of the pack case cover may include a plurality of exhaust ports 141, and the exhaust ports 141 may be positioned perpendicular to the cell stacking direction of the cell stack assembly 110 accommodated inside the pack case 120. The exhaust ports 141 may be provided in the form of through-holes over the entire surface of the isolation member 140b, and may provide a path for discharging heat, gas, and / or flames generated during abnormal operation such as heat generation or thermal runaway in any one of the plurality of cell stack assemblies provided inside the battery pack 100 to the outside.

[0051] Meanwhile, the battery pack 100 may further include a flame propagation prevention sheet 150 on the isolation member 140b disposed on the upper surface of the cell stack assembly 110. In this case, the flame propagation prevention sheet 150 may be made of an insulating material that does not deform even at high internal temperatures during abnormal operation of the battery pack 100. Specifically, the flame propagation prevention sheet 150 may be made of a silicate material that has high rigidity and insulating properties and combines excellent heat resistance and thermal insulation.

[0052] The silicate material referred to in the present invention is composed of silicate, and the silicate may be any silicate commonly used in the art without any particular limitation. Specifically, the silicate may contain one or more elements selected from the group consisting of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

[0053] Generally, silicate refers to a neutral salt in which hydrogen of silicic acid is replaced with other metal atoms, but in the present invention, silicates in which elements such as aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), etc. are substituted at the hydrogen site may be used to realize flame retardant and / or flame retardant effects, and layered silicates may be used in particular for flame retardancy.

[0054] For example, the silicates may include one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and banded mica.

[0055] As an example, the flame spread prevention sheet 150 may include a mica sheet. Mica is one of the rock-forming materials that constitute granite, and has excellent electrical insulation properties and has the property that its physical properties change very little when heated. The mica has excellent shape stability and insulation resistance even at high temperatures of 500 to 1,000°C. In addition, mica has excellent flame retardancy and does not produce smoke when burned or heated.

[0056] In addition, the flame spread prevention sheet 150 may be manufactured in a sheet shape by mixing scrap mica or crushed mica, which is a main component, with a binder (e.g., heat-resistant silicone) to form a large plate, and then cutting it to a suitable length to manufacture the sheet shape that matches the size of the electrode assembly, in order to manufacture the silicate, e.g., mica, in a sheet shape. However, the manufacturing method of the mica sheet is not limited thereto, and the mica sheet may be manufactured in various ways according to techniques commonly known in the art.

[0057] Here, "mainly as a component" can mean that the target component is contained in an amount of 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, 98 parts by weight or more, or 99 parts by weight or more per 100 parts by weight of the total substance.

[0058] As an example, the flame propagation prevention sheet 150 may contain 1 to 20 parts by weight of a binder with respect to 100 parts by weight of the total silicate.

[0059] The binder contained in the sheet may have excellent adhesion to silicates. Specifically, the binder may include at least one of polyolefins including polyethylene (PE), polypropylene (PP) or poly(ethylene-propylene) copolymers, polyamides including nylon, and heat-resistant silicones, but is not limited thereto.

[0060] Further, the flame propagation prevention sheet 150 may include an exhaust area 151 partially cut along the exhaust port 141 of the isolation member 140b disposed at the lower part as shown in FIG. 3. Specifically, referring to FIG. 4, the flame propagation prevention sheet 150 may provide a path for the exhaust area 151 to be closed during normal operation of the battery pack 100 in which thermal runaway occurs, and to be discharged to the outside together with the exhaust port 141 of the isolation member, without propagating heat, gas and / or flame generated from the cell stack assembly 110 in which thermal runaway occurs, to an assembly adjacent to the cell stack assembly 110 in which thermal runaway occurs, during abnormal operation of the battery pack 100 in which thermal runaway occurs. For this purpose, the exhaust area 151 may have shapes 151a and 151b partially cut along the exhaust port 141 of the isolation member 140b disposed at the lower part of the flame propagation prevention sheet 150. In this configuration, when heat, gas, and / or flame occurs inside the battery pack 100, the exhaust area 151 may invert onto the outer surface of the flame propagation prevention sheet 150 due to pressure from the heat, gas, and / or flame, inducing the external release of the heat, gas, and / or flame.

[0061] The battery pack according to the present invention has the above-mentioned configuration, and therefore has the advantage of being able to prevent the heat and / or flames from one of the multiple cell stack assemblies provided therein from spreading to an adjacent cell stack assembly when heat is generated or thermal runaway occurs in that one cell stack assembly, thereby improving the safety of the battery pack against fire or explosion.

[0062] The present invention will now be described in more detail with reference to examples and experimental examples.

[0063] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0064] <Examples 1 to 5 and Comparative Examples 1 to 3> A battery pack was prepared in which four cell stack assemblies, each containing ten pouch cells, were inserted into a pack case, two each horizontally and vertically. Each cell stack assembly was manufactured to have a structure including isolation members on the side and top as shown in Figure 1, and a flame propagation prevention sheet was installed on the isolation member on the top.

[0065] In this case, the i) type of heat-resistant plastic matrix, ii) type of fiber structure, iii) content of the fiber structure (based on the weight of the entire partition member), and iv) whether or not the isolation member includes a flame propagation prevention sheet were adjusted as follows.

[0066] The thermal runaway test results for the isolation member are shown in Table 1. In the thermal runaway test, the isolation member was fixed parallel to the ground, and a flame (internal temperature: 850±20°C) was vertically exposed to the bottom surface for 20 minutes, and the time it took for the morphological changes in the area exposed to the flame (whether or not droplets were formed due to the melting of the matrix or holes were formed) to occur was measured.

[0067] [Table 1]

[0068] <Comparative Example 4> A battery pack was manufactured in the same manner as in Example 1, except that a two-layered sheet including a rigid layer made of a mixture of polyimide and carbon fiber and a mica layer was used as the isolation member.

[0069] <Experimental Example> In order to evaluate the influence of a cell stack assembly housed in a battery pack according to the present invention on an adjacent assembly during thermal runaway, an internal fire was caused by inducing thermal runaway in one of the cell stack assemblies installed in each battery pack manufactured in the examples and comparative examples. Then, it was confirmed whether the flame generated in the cell stack assembly in which thermal runaway was induced spread to the adjacent cell stack assembly, and separately, the time it took for the adjacent cell stack assembly to ignite was measured.

[0070] Specifically, the battery packs manufactured in the examples and the comparative examples were all charged to an SOC of 100%. Then, a heating pad was attached to the bottom of any one of the four cell stack assemblies housed in the pack case, and the heating pad was heated to 800°C at a heating rate of 10°C / min to induce thermal runaway. At this time, a silicon heater (model name: SBH2012) manufactured by Hakkosha Co., Ltd. was used as the heating pad. When the heating pad started to heat up and the cell stack assembly to which the heating pad was attached ignited, it was confirmed whether the flame generated inside would spread to the adjacent cell stack assembly. Then, the time it took for the adjacent cell stack assembly to ignite was measured, and the results are shown in Table 2 below.

[0071] [Table 2]

[0072] As shown in Table 2 above, it can be seen that the battery pack according to the present invention has improved safety in the event of thermal runaway of the cell stack assembly. Specifically, it was confirmed that the battery pack of the embodiment releases flames generated inside the battery pack through the path provided by the isolation member (and the flame propagation prevention sheet) in the event of thermal runaway of the cell stack assembly, so that the flames do not propagate to assemblies adjacent to the assembly. It was also shown that the battery pack of the embodiment reduces heat propagation from the cell stack assembly in which thermal runaway is induced to adjacent assemblies, delaying ignition of the adjacent cell stack assemblies.

[0073] These results show that the battery pack according to the present invention can prevent the heat / flame of a cell stack assembly from spreading to an adjacent cell stack assembly when the cell stack assembly generates high temperatures or experiences thermal runaway, thereby improving the safety of the battery pack.

[0074] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or having ordinary knowledge in the art may make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as described in the claims below.

[0075] Therefore, the technical scope of the present invention is not limited to the contents described in the Summary of the Invention of the specification, but can be defined by the claims. [Explanation of symbols]

[0076] 100: Battery pack of the present invention 110: Cell stack assembly 120: Pack case 130: Pack case cover 121: Base plate 122: Side pack frame 140, 140a, 140b: Isolation members 141: Exhaust port 150: Flame propagation prevention sheet 151: Exhaust area 151a: Incision line 151b: Non-incision line

Claims

1. A battery pack containing a plurality of cell stack assemblies, a pack case including a base plate including a cell stack region in which the cell stack assembly is located, and a side pack frame extending vertically along an edge of the base plate and coupled to the base plate so as to surround the cell stack region; a pack case cover located on an upper portion of the cell stack assembly located in the cell stack region and coupled to an upper end of the pack case, the cell stack assembly includes an isolation member having an exterior heat resistant plastic matrix; The separator does not form droplets even when in contact with a flame at 800 to 1,000° C. for 5 minutes or more.

2. 2. The battery pack according to claim 1, wherein the heat-resistant plastic matrix includes one or more compounds selected from the group consisting of acrylonitrile-based resins, acrylic-based resins, benzimidazole-based resins, indoline-based resins, imide-based resins, amide-based resins, phenylene oxide-based resins, butylene terephthalate-based resins, and copolymer resins thereof.

3. The battery pack according to claim 1 or 2, wherein the isolating member comprises a sheet having a single layer structure in which a fibrous structure is dispersed in the heat-resistant plastic matrix.

4. 4. The battery pack according to claim 3, wherein the fiber structure is one or more of glass fiber, carbon fiber, and aramid fiber.

5. The battery pack according to claim 3 , wherein the fiber structure has a content of 5 to 40% by weight based on the total weight of the separator.

6. The battery pack according to claim 1 or 2, wherein the isolation member provided on the upper surface of the cell stack assembly includes a plurality of exhaust ports.

7. The battery pack according to claim 1 or 2, further comprising a flame propagation prevention sheet between the pack case cover and the isolation member.

8. 8. The battery pack according to claim 7, wherein the flame propagation prevention sheet is a silicate sheet made of a silicate containing one or more elements selected from the group consisting of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

9. 8. The battery pack according to claim 7, wherein the flame propagation prevention sheet includes one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and banded mica.

10. the isolation member includes a plurality of exhaust ports provided perpendicular to a cell stacking direction of the cell stack assembly housed inside the pack case, The battery pack according to claim 7 , wherein the flame propagation prevention sheet has an exhaust area partially cut along the exhaust port of the isolation member.

11. The battery pack according to claim 7, wherein the flame propagation prevention sheet has an average thickness of 0.5 to 5.0 mm.

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