Battery pack with improved safety

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 filed on August 29, 2022, and all the contents disclosed in the literature of the Korean patent application are included as part of this specification. 【Background Art】 【0003】 Currently, commercialized secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, etc. Among these, lithium secondary batteries have attracted attention because they have almost no memory effect, can be freely charged and discharged, have a very low self-discharge rate, and have a high energy density compared to nickel-based secondary batteries. 【0004】 Such lithium secondary batteries mainly use a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. A lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate coated with a positive electrode active material and a negative electrode active material, respectively, are disposed with a separator interposed therebetween, and an exterior material that hermetically stores the electrode assembly together with an electrolytic solution, that is, a battery case. 【0005】 Generally, lithium secondary batteries can be classified into a can-type secondary battery in which an electrode assembly is built in a metal can and a pouch-type secondary battery in which an electrode assembly is built in a pouch of an aluminum laminate sheet according to the shape of the exterior material. 【0006】 In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices, but also in medium- and large-scale devices such as automobiles and energy storage systems (ESS) for propulsion and energy storage. Secondary batteries are housed in battery packs and installed in medium- and large-scale devices. In this case, to increase the capacity and output of the battery pack, the battery pack contains numerous secondary batteries that are electrically connected to each other. Here, a large number of secondary batteries can be housed inside one module case to form one battery module, and a large number of battery modules can be housed inside one pack case to form one battery pack. 【0007】 Generally, secondary batteries can degrade in performance when used in environments with temperatures higher than their optimal level, and in severe cases, there is a risk of explosion or fire. Furthermore, when a battery pack is constructed using multiple secondary batteries, the heat generated by the numerous batteries in a confined space can accumulate, causing the battery pack's temperature to rise more rapidly and severely. In particular, vehicle battery packs and battery packs for power storage devices, which are primarily used outdoors, are frequently exposed to direct sunlight and may be subjected to harsh high-temperature conditions such as those experienced in summer or in desert regions. 【0008】 Furthermore, a battery pack is composed of multiple battery modules or multiple secondary batteries. If an abnormal condition occurs in some of the multiple battery modules or secondary batteries that make up the battery pack, heat may be generated. Once heat is generated, the battery temperature will continue to rise, exceeding a predetermined critical temperature, and may proceed to a continuous thermal runaway situation. If such a thermal runaway occurs inside a battery module or battery pack in which multiple battery cells are stacked, it may induce the explosion or ignition of battery cells. In this case, the flame may spread to other battery cells that are functioning normally, causing multiple battery cells to explode in a chain reaction, which may damage the device to which the battery module / pack is installed, and the user may be at risk of a safety accident. [Prior art documents] [Patent Documents] 【0009】 [Patent Document 1] Korean Published Patent No. 10-2022-0029941 [Overview of the Initiative] [Problems that the invention aims to solve] 【0010】 Therefore, the object of the present invention is to provide a battery pack in which safety is improved by delaying the propagation of heat and / or flames between cells under conditions of overheating or thermal runaway. [Means for solving the problem] 【0011】 In order to solve the above-mentioned problems, In one embodiment, the present invention is described as follows: A battery pack containing multiple cell stack assemblies, A pack case including a base plate containing a cell stack region in which a cell stack assembly is located, and a side pack frame that extends vertically along the edge of the base plate and is joined to surround the cell stack region, It includes a pack case cover located on top of the cell stack assembly in the cell stack region and coupled to the upper end of the pack case, The above cell stack assembly includes an isolation member on the outside containing a heat-resistant plastic matrix, The above-mentioned isolation member provides a battery pack characterized in that no droplets are formed even when in contact with a flame of 800 to 1,000°C for more than 5 minutes. 【0012】 In this case, the isolation member may include a single-layer sheet in which a fibrous structure is dispersed in a heat-resistant plastic matrix. 【0013】 The above heat-resistant plastic matrix may include one or more compounds from among acrylonitrile resins, acrylic resins, benzimidazole resins, indoline resins, imide resins, amide resins, phenylene oxide resins, butylene terephthalate resins, and copolymer resins thereof. 【0014】 Furthermore, the above-mentioned fiber structure may contain one or more of glass fibers, carbon fibers, and aramid fibers, and the content thereof can be adjusted to 5 to 40% by weight relative to the total weight of the isolation member. 【0015】 Furthermore, the isolation member provided on the upper surface of the cell stack assembly may include a plurality of exhaust ports. 【0016】 Furthermore, 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 from among silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F), and oxygen (O). 【0018】 As one example, the flame propagation prevention sheet described above may contain one or more of the following: muscovite, phengite, celadonite, paragonite, margalite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, tsinwaldite, and striped mica. 【0019】 Furthermore, the isolation member includes a plurality of exhaust ports provided perpendicular to the cell stacking direction of the cell stack assembly housed inside the pack case, and the flame propagation prevention sheet may have exhaust regions partially cut 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 operate due to the pressure generated by the gas and / or flame generated inside. 【Advantages of the Invention】 【0021】 When thermal runaway occurs in any of the plurality of cell stack assemblies housed inside the battery pack according to the present invention, the heat and flames generated thereby can be minimized from spreading to adjacent assemblies. Therefore, there is an advantage in that the safety against ignition and explosion of the battery pack is improved. 【Brief Description of the Drawings】 【0022】 [Figure 1] It is a perspective view showing the structure of the battery pack according to the present invention. [Figure 2] It is a plan view showing the isolation member arranged on the upper surface of the cell stack assembly according to the present invention. [Figure 3] It is a plan view showing the flame propagation prevention sheet on the isolation member arranged on the upper surface of the cell stack assembly according to the present invention. [Figure 4] It is a cross-sectional view schematically showing the method of discharging the heat and / or flame generated inside during thermal runaway of the cell stack assembly housed in the battery pack according to the present invention. 【Modes for Carrying Out the Invention】 【0023】 The present invention can be modified in various ways and can have various embodiments, so specific embodiments will be described in detail in the detailed description. 【0024】 However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. 【0025】 In the present invention, terms such as "includes" and "have" are intended to specify the presence of features, numbers, stages, operations, components, parts, or combinations thereof as described in the specification, and do not preemptively exclude the presence or possibility of adding one or more other features, numbers, stages, operations, components, parts, or combinations thereof. 【0026】 Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom. 【0027】 The present invention will be described in more detail below. 【0028】 <Battery Pack> In one embodiment, the present invention is described as follows: A battery pack containing multiple cell stack assemblies, A pack case including a base plate containing a cell stack region in which a cell stack assembly is located, and a side pack frame that extends vertically along the edge of the base plate and is joined to surround the cell stack region, It includes a pack case cover located on top of the cell stack assembly in the cell stack region and coupled to the upper end of the pack case, The above side pack frame and pack case cover include an isolation member containing a heat-resistant plastic matrix on the inside. The above-mentioned isolation member provides a battery pack characterized in that no droplets are formed even when in contact with a flame of 800 to 1,000°C for more than 5 minutes. 【0029】 The battery pack according to the present invention includes a plurality of cell stack assemblies, a pack case that houses them, and a pack case cover. In this case, the side pack frame and pack case cover contained in the pack case have a structure that includes an isolation member on the inside that prevents droplet formation even at high temperatures of 500°C or higher. As a result, the battery pack can suppress the propagation of heat and / or flames from any one of the plurality of cell stack assemblies to adjacent cell stack assemblies in the event of heat generation or thermal runaway, thereby suppressing the occurrence of ignition and / or explosion of the battery pack. 【0030】 Figures 1 to 4 are perspective views, plan views, and cross-sectional views illustrating the structure of the battery pack 100 according to the present invention. The following description will be made in more detail with reference to Figures 1 to 4. 【0031】 The battery pack 100 of the present invention includes a cell stack assembly 110, a pack case 120 and a pack case cover 130 (not shown) in which the cell stack assembly 110 is housed. 【0032】 The cell stack assembly 110 referred to in the present invention may include a configuration in which a module frame configuration surrounds and protects a cell stack in which multiple battery cells are stacked, and busbar frames and end plates are bonded to the front and rear surfaces on which electrode leads are formed in the cell stack, respectively. 【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 inside, 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 can be led out on both sides of the battery case, respectively. 【0034】 Furthermore, the busbar frame includes busbars that are electrically connected to the battery cells. The busbar frame is tightly coupled to the cell stack from the front and rear so that the electrode leads of each battery cell included in the cell stack are connected to the busbars. 【0035】 Furthermore, the end plate is coupled to the busbar frame to cover the busbars and electrode leads to protect them from external impacts. The end plate also gathers and secures each battery cell included in the cell stack. 【0036】 The above-described cell stack assembly eliminates the module frame configuration that surrounds and protects the cell stack as described above. Instead, it includes end plates that structurally fix the stacked battery cells and busbar frames that electrically connect the fixed battery cells. This has the advantage of not only allowing for more efficient dissipation of heat generated by multiple battery cells during charging and discharging, but also reducing the unit weight of the cell stack. 【0037】 Furthermore, a battery pack may be provided with a large number of the cell stack assemblies 110. The large number of cell stack assemblies 110 may be arranged in the left-right direction with their sides 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】 Furthermore, the battery pack 100 includes a pack case 120 containing the cell stack assembly 110 described above, and a pack case cover 130 (not shown) which is coupled to the pack case so as to cover the top of the cell stack assembly 110 at the top of the pack case. 【0039】 Here, the pack case 120 is positioned below the cell stack assembly 110 and includes a base plate 121 that includes the cell stack region in which the cell stack assembly 110 is located. The base plate 121 may have a plate shape that extends horizontally. Here, horizontal means in the direction of a flat ground surface. The base plate 121 may be made of a metal material with excellent mechanical rigidity. 【0040】 Furthermore, multiple cell stack assemblies 110 may be positioned on the upper part of the base plate 121. For this purpose, the base plate 121 includes a cell stack region in which the cell stack assemblies 110 are located, and side pack frames 122 extending vertically along the edge of the base plate 121 to surround the cell stack region are connected to each other, forming a space for accommodating the cell stack assemblies 110. 【0041】 The base plate 121 not only provides space for housing the cell stack assembly 110 at its bottom, but can also function as a heat sink to dissipate heat generated by the cell stack assembly 110 to the outside. For this purpose, the base plate 121 may be provided with cooling means (not shown) that allows a coolant such as cooling water or air to flow in contact with the other surface of the surface housing the cell stack assembly 110 in order to remove the heat generated from the cell stack assembly 110. Furthermore, the connection of the side pack frame 122 may be carried out in a manner commonly applied in the industry, for example, by friction stir welding. 【0042】 Furthermore, the battery pack 100 includes isolation members 140 on the outside of the cell stack assembly 110 housed inside, in other words, on the outside of the cell stack assembly 110. Specifically, the battery pack 100 may include isolation members 140a and 140b inside the side pack frame 122 and the pack case cover 130, excluding the base plate 121 which functions as a heat sink as shown in Figure 1, that is, 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 includes a heat-resistant plastic matrix, if thermal runaway occurs in any of the multiple cell stack assemblies housed inside, not only is damage from the generated heat and flames reduced, but the propagation of the generated heat and flames from that cell stack assembly to adjacent cell stack assemblies is minimized. 【0044】 For this purpose, the isolation member 140 includes a heat-resistant plastic matrix that undergoes little to no morphological deformation at high temperatures. Here, "little to no morphological deformation at high temperatures" may mean that there is no morphological change due to melting and / or carbonization at temperatures of 500°C or higher. More specifically, it may mean that there is no morphological change due to melting and / or carbonization of the material when left at or exposed to temperatures of 600°C or higher, 700°C or higher, or 600°C to 1,000°C for a certain period of time. 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 exposed to a flame of 800 to 1,000°C for 5 minutes or more, and specifically, it may not form droplets or holes due to carbonization even when exposed for 5 to 15 minutes or 8 to 12 minutes. 【0045】 Such heat-resistant plastic matrices can be applied without particular limitations as long as they do not undergo morphological changes due to melting and / or carbonization at temperatures above 500°C, as described above. However, preferably, considering the ignition and / or explosion temperature induced internally during thermal runaway of the cell stack assembly 110, those that do not undergo morphological changes due to melting and / or carbonization at temperatures between 800 and 1,000°C can be applied. For example, the above heat-resistant plastic matrix may contain one or more compounds from among acrylonitrile resins, acrylic resins, benzimidazole resins, indoline resins, imide resins, amide resins, phenylene oxide resins, butylene terephthalate resins, and copolymer resins thereof. Here, the above compounds refer to compounds formed using monomers such as acrylonitrile and acrylate, or compounds that repeatedly contain benzimidazole, indoline, imide, amide, phenylene oxide, butylene terephthalate, etc., within their units. 【0046】 As one example, the heat-resistant plastic matrix described above may be made by applying phenylene oxide resins such as polyphenylene oxide (PPO) or amide resins such as nylon, either alone or in combination. Here, the phenylene oxide resins and amide resins may be applied in homopolymer form or in a form in which some of the repeating units have been modified. 【0047】 Furthermore, the isolation members 140a and 140b may have a single-layer sheet structure in which a fibrous structure is dispersed in a heat-resistant plastic matrix in order to provide rigidity as well as heat resistance to the members. Conventional battery packs are equipped with multilayer members made of metal oxides such as silicon dioxide (SiO2) on the inside of the pack case in order to realize the heat resistance and rigidity of the modules and / or cell stack assemblies housed inside. In this case, adhesives are applied between each layer to realize the multilayer structure of metal oxides, but these adhesives deform when the modules and / or cell stack assemblies generate heat or experience thermal runaway, so there are limitations to preventing heat and flames generated inside the battery pack from propagating to adjacent modules and / or cell stack assemblies. However, the isolation members 140a and 140b of the present invention have the advantage of being able to realize sufficient heat resistance and rigidity while eliminating the adhesives required for multilayer structures, by having a single-layer sheet structure in which a fibrous structure is dispersed in a heat-resistant plastic matrix that has high morphological stability at high temperatures. 【0048】 In this case, the fiber structure may include one or more of the following: glass fiber (GF), carbon fiber (CF), and aramid fiber (AF). As one example, the fiber structure may include glass fiber (GF) which can improve the strength and elastic modulus of the heat-resistant plastic matrix and at the same time reinforce the insulation 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】 Furthermore, the above-mentioned fiber structure may be included in the isolation members 140a and 140b in a certain content to improve the heat resistance and mechanical properties of the isolation members 140a and 140b. Specifically, the above-mentioned fiber structure may be included in a content of 5 to 40% by weight relative to the total weight of the isolation members 140a and 140b, and more specifically, in 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 relative to the total weight of the isolation members 140a and 140b. By controlling the content of the fiber structure within the above range, the present invention can prevent the heat resistance and rigidity of the isolation members 140a and 140b from not being sufficiently realized due to an extremely low content, while preventing the breaking strength of the isolation members 140a and 140b from increasing due to an excessive content, thereby preventing a decrease in resistance to external forces when an external force is applied to the battery pack 100. 【0050】 Furthermore, the isolation member 140b provided on the inside of the pack case cover, as shown in Figure 2, includes 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 housed inside the pack case 120. The exhaust ports 141 may be provided in the form of through-holes across the entire surface of the isolation member 140b, and may provide a path for exhausting heat, gas and / or flames generated during abnormal operation in which any one of the plurality of cell stack assemblies housed inside the battery pack 100 generates heat or experiences thermal runaway. 【0051】 On the other hand, the battery pack 100 may further include a flame propagation prevention sheet 150 on top of the isolation member 140b positioned on the upper surface of the cell stack assembly 110. In this case, the flame propagation prevention sheet 150 may be made of a material that does not deform in shape even at high internal temperatures during abnormal operation of the battery pack 100 and has insulating properties. 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 heat insulation. 【0052】 The silicate materials referred to in this invention are composed of silicates, and the silicates can be applied without particular limitations as long as they are commonly used in the industry, but specifically, those containing one or more elements from silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F), and oxygen (O) can be used. 【0053】 Generally, silicates refer to neutral salts in which the hydrogen atoms of silicic acid are replaced with other metal atoms. However, in this invention, silicates in which elements such as aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), and potassium (K) are substituted in the hydrogen atom may be used to embody flame retardant and / or fire retardant effects, and layered silicates may be used in particular for flame retardancy. 【0054】 For example, the above-mentioned silicates may include one or more of the following: muscovite, phengite, celadonite, paragonite, margalite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, tinwaldite, and striped mica. 【0055】 As one example, the flame propagation prevention sheet 150 described above may include a mica sheet containing mica. Mica is one of the rock-forming materials that make up granite, and it has excellent electrical insulation properties and the characteristic of showing very little change in physical properties when heated. The mica described above has excellent dimensional stability and insulation resistance even at high temperatures of 500 to 1,000°C. In addition, mica has excellent flame retardancy and the characteristic of not producing smoke when burned or heated. 【0056】 Furthermore, the flame propagation prevention sheet 150 can be manufactured by mixing scrap mica or pulverized mica, which is the main component, with a binder (e.g., heat-resistant silicone) to form a large plate, and then cutting it to a suitable length to produce a sheet that matches the size of the electrode assembly. However, the method of manufacturing the mica sheet is not limited to this, and mica sheets can be manufactured in a variety of ways according to techniques commonly known in the industry. 【0057】 Here, "main component" may mean that the component in question is present 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 one example, the flame propagation prevention sheet 150 may contain 1 to 20 parts by weight of binder per 100 parts by weight of the total silicate. 【0059】 Furthermore, the binder included in the above sheet may be one that exhibits excellent adhesion to silicates. Specifically, the binder may include, but is not limited to, one or more of the following: polyethylene (PE), polypropylene (PP), poly(ethylene-propylene) copolymer, polyamide containing nylon, and heat-resistant silicone. 【0060】 Furthermore, as shown in Figure 3, the flame propagation prevention sheet 150 may include an exhaust region 151 that is partially cut along the exhaust port 141 of the isolation member 140b located at the bottom. Specifically, referring to Figure 4, the flame propagation prevention sheet 150 is sealed in a closed state when the battery pack 100 is operating normally, but when the battery pack 100 is operating abnormally and a thermal runaway occurs in the cell stack assembly 110, it may function to provide a path that prevents the heat, gas, and / or flame generated from the thermal runaway cell stack assembly 110 from propagating to adjacent assemblies and allows them to be released to the outside along with the exhaust port 141 of the isolation member. For this purpose, the exhaust region 151 may have forms 151a and 151b that are partially cut along the exhaust port 141 of the isolation member 140b located at the bottom of the flame propagation prevention sheet 150. In this configuration, when heat, gas, and / or flame are generated inside the battery pack 100, the exhaust area 151 may be inverted to the outer surface of the flame propagation prevention sheet 150 due to the pressure from the heat, gas, and / or flame, thereby inducing the release of the heat, gas, and / or flame to the outside. 【0061】 The battery pack according to the present invention, having the above-described configuration, has the advantage of improving the safety of the battery pack against ignition and explosion, as it can suppress the propagation of heat and / or flames from one of the multiple cell stack assemblies inside to adjacent cell stack assemblies in the event of heat generation or thermal runaway. 【0062】 The present invention will be described in more detail below with reference to examples and experimental examples. 【0063】 However, the following examples and experimental examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples. 【0064】 <Examples 1-5 and Comparative Examples 1-3> A battery pack was prepared with a structure in which four cell stack assemblies, each containing 10 pouch cells, were inserted into a pack case, two horizontally and two vertically. Each cell stack assembly was manufactured to have a structure including isolation members on the sides and top, as shown in Figure 1, and a flame propagation prevention sheet was introduced on the isolation member on the top. 【0065】 At this time, the following adjustments were made to the above-mentioned isolation member: i) the type of heat-resistant plastic matrix, ii) the type of fiber structure, iii) the content of the fiber structure (based on the total weight of the partition member), and iv) whether or not it included a flame propagation prevention sheet. 【0066】 Table 1 shows the results of the thermal runaway test on the isolation member described above. In this thermal runaway test, the isolation member was fixed parallel to the ground, and then a flame (internal temperature: 850±20℃) was applied vertically to its lower surface for 20 minutes. The time taken for morphological changes (presence or absence of droplet formation or hole formation due to matrix melting) to occur in the area in contact with the flame 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-layer sheet containing a rigid layer of polyimide mixed with carbon fibers and a mica layer was used as the isolation member. 【0069】 <Example of experiment> To evaluate the effect of a cell stack assembly housed in a battery pack according to the present invention on adjacent assemblies during thermal runaway, thermal runaway was induced in one of the cell stack assemblies mounted in each battery pack manufactured in the examples and comparative examples, causing internal ignition. Subsequently, it was confirmed whether the flame generated in the cell stack assembly where thermal runaway was induced propagated to an adjacent cell stack assembly, and separately, the time required for ignition to occur in the adjacent cell stack assembly was measured. 【0070】 Specifically, the battery packs manufactured in the examples and comparative examples were both charged to a State of Charge (SOC) of 100%. Then, a heating pad was attached to the bottom of one of the four cell stack assemblies housed in the pack case. The heating pad was then heated to 800°C at a rate of 10°C / min to induce thermal runaway. The heating pad used was a silicon heater (model name: SBH2012) manufactured by Hakko Co., Ltd. Once the heating pad began to heat up and the cell stack assembly to which the heating pad was attached ignited, it was checked whether the flame generated inside propagated to adjacent cell stack assemblies. The time taken for adjacent cell stack assemblies to ignite was then measured, and the results are shown in Table 2 below. 【0071】 [Table 2] 【0072】 As shown in Table 2 above, the battery pack according to the present invention provides improved safety during thermal runaway of the cell stack assembly. Specifically, in the battery pack of the embodiment, when thermal runaway occurs in the cell stack assembly, the flame generated inside is released through the path provided by the isolation member (and flame propagation prevention sheet), so it was confirmed that the flame does not propagate to assemblies adjacent to the assembly in question. Furthermore, it was shown that the battery pack of the embodiment reduces heat propagation from the cell stack assembly where thermal runaway is induced to adjacent assemblies, delaying the ignition of adjacent cell stack assemblies. 【0073】 These results show that the battery pack according to the present invention can suppress the propagation of heat / flames from a cell stack assembly to adjacent cell stack assemblies when the cell stack assembly overheats or experiences thermal runaway, thereby improving the safety of the battery pack. 【0074】 In the above, the preferred embodiments of the present invention have been described. However, those skilled in the art or those with ordinary knowledge in the technical field can understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the claims to be described later. 【0075】 Therefore, the technical scope of the present invention is not limited to the content described in the summary of the invention in the specification, and can be determined by the claims. 【Explanation of Reference Signs】 【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 member 141: Exhaust port 150: Flame propagation prevention sheet 151: Exhaust region 151a: Scoring line 151b: Non-scoring line

Claims

[Claim 1] A battery pack containing multiple cell stack assemblies, A pack case comprising a base plate including a cell stack region in which the cell stack assembly is located, and a side pack frame extending vertically along the edge of the base plate and joined thereto so as to surround the cell stack region, Includes a pack case cover located on the upper part of the cell stack assembly located in the cell stack region and coupled to the upper end of the pack case, The cell stack assembly includes an isolation member on the outside, which consists of a heat-resistant plastic matrix and a fiber structure. The aforementioned isolation member does not form droplets even when in contact with a flame of 800 to 1,000°C for more than 5 minutes. Between the pack case cover and the isolation member, an insulating flame propagation prevention sheet is provided. The isolation member includes a single-layer sheet in which a fibrous structure is dispersed in the heat-resistant plastic matrix. The aforementioned fiber structure is present in a battery pack having an content of 5 to 40% by weight relative to the total weight of the isolation member. [Claim 2] The battery pack according to claim 1, wherein the heat-resistant plastic matrix includes one or more compounds selected from acrylonitrile resins, acrylic resins, benzimidazole resins, indoline resins, imide resins, amide resins, phenylene oxide resins, butylene terephthalate resins, and copolymer resins thereof. [Claim 3] The battery pack according to claim 1 or 2, wherein the fiber structure is one or more of glass fibers, carbon fibers, and aramid fibers. [Claim 4] 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. [Claim 5] The battery pack according to claim 1 or 2, wherein the flame propagation prevention sheet is a silicate sheet composed of a silicate containing one or more elements from silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F), and oxygen (O). [Claim 6] The battery pack according to claim 1 or 2, wherein the flame propagation prevention sheet comprises one or more of the following: muscovite, phengite, celadonite, paragonite, margalite, phlogopite, biotite, annite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinwaldite, and striped mica. [Claim 7] The isolation member includes a plurality of exhaust ports provided so as to be perpendicular to the cell stacking direction of the cell stack assembly housed inside the pack case, The battery pack according to claim 1 or 2, wherein the flame propagation prevention sheet has an exhaust region that is partially cut along the exhaust port of the isolation member. [Claim 8] The battery pack according to claim 1 or 2, wherein the flame propagation prevention sheet has an average thickness of 0.5 to 5.0 mm.

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