Battery module and battery pack

Abstract

One embodiment of the present invention may provide a battery module that houses a plurality of secondary battery cells in a housing member, a flame retardant composite material between the plurality of secondary battery cells, the flame retardant composite material comprising a thermal insulation layer comprising an inorganic long fiber network and an organic binder, the inorganic long fiber network is formed by weaving a plurality of first fibers (weft yarns) arranged in a first direction and second fibers (warp yarns) arranged in a second direction crossing the first direction.

Description

Technical Field

[0001] The present invention relates to a battery module and a battery pack having improved safety. Background Art

[0002] Secondary batteries are easy to use depending on the product group and have electrical characteristics such as high energy density, so they are widely used not only in portable devices but also in electric vehicles (EV) or hybrid electric vehicles (HEV) driven by an electric drive source.

[0003] When a higher output voltage is required, multiple battery cells can be connected in series / parallel to form a battery pack. Generally, a battery module including at least one battery cell is first formed, and at least one such battery module and other components are added to form a battery pack or battery rack.

[0004] In addition, secondary batteries have the risk of catching fire when overheated, so ensuring safety is an important technical issue. When abnormal heating occurs due to various reasons such as overcharging, overcurrent, short circuit or physical impact, it may cause flames or fires, and eventually cause secondary batteries to explode due to thermal runaway. In the case of a battery module or battery pack including multiple secondary batteries, its stability problem becomes more serious.

[0005] In the past, in order to prevent the spread of flames, a cooling component for cooling or a box containing a thermal conductive additive was installed in the battery module. However, this is for cooling the heat generated when the battery is driven, and has the limitation that it cannot be used in the case of thermal runaway such as battery cell explosion.

[0006] As another prior art, a scheme of placing a highly fire-resistant material such as mica sheets or ceramic wool in a battery module has been proposed, but the material causes dust or debris in the battery module, which may cause a short circuit or failure, and thus there is a problem that the long-term stability of the battery module cannot be ensured. In addition, materials such as mica sheets or ceramic wool not only have a high specific gravity (density) but also have a low adhesive force, so the thickness of the adhesive must be applied thickly when stacked with a battery cell, which has limitations in terms of increasing the energy density of the battery module and achieving lightweight.

[0007] Therefore, it is necessary to develop a battery module that can suppress the spread of flames when a fire occurs in the battery module and ensure long-term stability. Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] According to one aspect of the present invention, a battery module including a flame retardant composite material can be provided, which can prevent the occurrence of short circuits due to dust or debris when the battery module operates normally and can suppress the spread of heat or flames when a fire occurs.

[0010] According to another aspect of the present invention, a battery module that can simultaneously achieve the effects of weight reduction and improved flame retardancy can be provided.

[0011] In addition, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and those skilled in the art can clearly understand other technical problems not mentioned from the following description.

[0012] (II) Technical solution

[0013] A battery module according to one embodiment of the present invention accommodates a plurality of secondary battery cells in a shell component, and a flame retardant composite material is located between the plurality of secondary battery cells, the flame retardant composite material includes an insulating layer comprising an inorganic long fiber network and an organic binder, the inorganic long fiber network being formed by weaving a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction with each other.

[0014] In one embodiment, the thermal insulation layer may further include an inorganic filler.

[0015] In one embodiment, in the thermal insulation layer, the inorganic filler may be evenly distributed in the inorganic long fiber network.

[0016] In one embodiment, the inorganic filler may include any one or both selected from heat absorbing materials or heat expanding materials.

[0017] In one embodiment, the thermal insulation layer may further include additives.

[0018] In one embodiment, the additive may include a flame retardant.

[0019] In one embodiment, the thermal insulation layer may include a plurality of unit thermal insulation layers.

[0020] In one embodiment, directions of the first fibers (weft yarns) of adjacent unit insulation layers in the plurality of unit insulation layers may be the same as or different from each other.

[0021] In one embodiment, the unit thermal insulation layer may further include an inorganic filler.

[0022] In one embodiment, the plurality of unit insulation layers may independently contain 40-80 wt % of inorganic long fibers, 10-30 wt % of organic binder, 1-15 wt % of inorganic filler and 5-20 wt % of additives relative to the total weight.

[0023] In one embodiment, the inorganic filler may have an average diameter of 1 to 50 μm.

[0024] In one embodiment, the heat absorbing material may include one or more selected from aluminum hydroxide, talc, calcium carbonate, diatomaceous earth, titanium oxide, zeolite or white carbon black.

[0025] In one embodiment, the thermal expansion material may include any one or two or more selected from mica (biotite, muscovite), vermiculite, kaolin, thermal expansion graphite, perlite, and bentonite.

[0026] In one embodiment, the inorganic long fibers may include glass long fibers.

[0027] In one embodiment, the organic binder may include a thermosetting resin, a thermoplastic resin, or a combination thereof.

[0028] In one embodiment, the flame retardant composite material may have a thickness of 0.12-40 mm.

[0029] In one embodiment, the secondary battery cell may include an electrode assembly in which a plurality of negative electrodes and positive electrodes are alternately stacked with a separator as a boundary, and a soft package outer material surrounding the electrode assembly.

[0030] A battery pack according to one embodiment of the present invention includes: a plurality of secondary battery cells; a flame retardant composite material located between the plurality of secondary battery cells; and a battery pack shell, the battery pack shell accommodating the plurality of secondary battery cells and the flame retardant composite material, wherein the flame retardant composite material includes an insulating layer comprising an inorganic long fiber network and an organic adhesive, the inorganic long fiber network being formed by weaving together a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction.

[0031] (III) Beneficial effects

[0032] According to one embodiment of the present invention, it is possible to prevent a short circuit caused by dust or debris from occurring when a battery module is operating normally.

[0033] According to one embodiment of the present invention, it is possible to suppress the spread of heat or flame when a battery module catches fire.

[0034] According to one embodiment of the present invention, the flame retardant composite material can have lightweight characteristics while achieving excellent flame retardancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is an exploded perspective view showing a battery module according to one embodiment of the present invention.

[0036] Figure 2 is a diagram showing a battery module according to one embodiment of the present invention.

[0037] Figure 3 is a diagram showing a battery pack according to one embodiment of the present invention.

[0038] Description of Reference Numerals

[0039] 10: Secondary battery cell 20: Casing member

[0040] 21: Bottom part 22: Side wall part

[0041] 23: Cover part 24: Compression part

[0042] 25: Busbar component 26: Front component

[0043] 27: Rear part 30: Flame retardant composite material

[0044] 40: Battery pack housing 41: Lower housing

[0045] 51: First partition 52: Second partition

[0046] 100: Battery module 200: Battery pack DETAILED DESCRIPTION

[0047] Unless otherwise specifically stated, the singular forms of the terms used in this specification may be construed as also including the plural forms.

[0048] The numerical range used in this specification includes the lower limit value and the upper limit value and all possible combinations of all values ​​within the range, all values ​​defined therein, and the upper and lower limits of the numerical range defined in different forms from each other. In this specification, unless otherwise specifically defined, values ​​outside the numerical range that may appear due to experimental errors or rounding of values ​​are also included in the defined numerical range.

[0049] The words “comprising” or “including” mentioned in this specification are open-ended statements with the same meaning as “having”, “containing”, “having”, “characterized by”, etc., and do not exclude elements, materials or processes not further listed.

[0050] The expressions "woven inorganic long fibers" or "woven inorganic long fiber network" mentioned in this specification refer to an inorganic long fiber network formed by weaving a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction.

[0051] Among the angles mentioned in this specification, + refers to the angle in the clockwise direction, and - refers to the angle in the counterclockwise direction.

[0052] The battery module according to the present invention accommodates a plurality of secondary battery cells in a shell component, and a flame retardant composite material is located between the plurality of secondary battery cells, the flame retardant composite material includes an insulating layer containing an inorganic long fiber network and an organic adhesive, the inorganic long fiber network being formed by weaving a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction with each other.

[0053] By having the above structural combination, it is possible to prevent the generation of dust and the resulting short circuit during normal operation of the battery module, and to effectively suppress the spread of heat or flames when a fire occurs.

[0054] Hereinafter, the flame retardant composite material will be described in detail.

[0055] <Flame-retardant composite material including thermal insulation layer>

[0056] The flame retardant composite material comprising a sheet molding compound (SMC) material containing an inorganic long fiber network and an organic adhesive has excellent thermal insulation, heat resistance and fire resistance, which can not only prevent the spread of high temperature and flame, but also maintain the original shape in a high temperature environment without physical or chemical deformation. In addition, the short circuit of the battery module caused by foreign matter can be prevented by minimizing the amount of dust generated by the flame retardant composite material. In addition, the flame retardant composite material has a low density (specific gravity), and when the flame retardant composite material is stacked with a secondary battery cell, the thickness of the adhesive applied between the secondary battery cell and the flame retardant composite material is minimized, thereby realizing a battery module with high stability and high energy density.

[0057] In one embodiment, the thermal insulation layer comprises an inorganic long fiber network formed by weaving a plurality of first fibers (weft yarns) arranged in a first direction and second fibers (warp yarns) arranged in a second direction intersecting the first direction, thereby providing excellent thermal insulation and structural stability that cannot be provided by existing inorganic short fibers, and effectively inhibiting the spread of heat or flame. In addition, the organic binder is evenly filled in the inorganic long fiber network formed by weaving, thereby achieving excellent bonding force and durability.

[0058] In a specific embodiment, the angle at which the first fiber (weft yarn) and the second fiber (warp yarn) cross can be 30° to 90°. By weaving within the above angle range to form an inorganic long fiber network, excellent thermal insulation and durability can be achieved. Specifically, the angle can be 45° to 90°, and more specifically, the angle can be 60° to 90°.

[0059] In one embodiment, the thermal insulation layer may further include an additive, and the additive may include a flame retardant.

[0060] By further including a flame retardant as an additive in the thermal insulation layer, the long-term stability of the flame retardant composite material can be further enhanced. The flame retardant can include an organic flame retardant, an inorganic flame retardant, or a combination thereof, and the organic flame retardant can include one or more selected from phosphorus-based flame retardants, boron-based flame retardants, halogen-based flame retardants, and nitrogen-based flame retardants.

[0061] Exemplarily, the phosphorus-based flame retardant may include a phosphate compound, a phosphonate compound, a phosphinate compound, a phosphine oxide compound, a phosphazene compound or a metal salt thereof. The boron-based flame retardant may include sodium polyborate, sodium borate, zinc borate, etc. The halogen-based flame retardant may include a bromine-based flame retardant or a chlorine-based flame retardant, and the bromine-based flame retardant may include decabromodiphenyl ethane, decabromodiphenyl ether, tetrabromobisphenol A, tetrabromobisphenol A-epoxy oligomer, brominated epoxy oligomer, etc. The chlorine-based flame retardant may include chlorinated paraffins, chlorinated polyethylene (CPE), aliphatic chlorine-based flame retardants, etc. The nitrogen-based flame retardant may include piperazine pyrophosphate, melamine polyphosphate, ammonium polyphosphate (APP), guanidine compounds, melamine compounds, etc.

[0062] The inorganic flame retardant may include magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony tetroxide, antimony pentoxide, sodium carbonate antimonate, metal antimony, antimony trichloride, antimony pentachloride, barium metaborate, zirconium oxide, zinc borate, zinc tartrate or a combination thereof. Advantageously, phosphorus-based flame retardants are preferred in terms of excellent flame retardancy and no release of toxic and harmful substances, but the present invention is not limited by the specific type of flame retardant.

[0063] In a specific embodiment, the thermal insulation layer may further include an inorganic filler. By further including an inorganic filler, the propagation of heat or flame can be more effectively suppressed, and the durability can be further improved. Specifically, when a fire occurs in a battery module, the temperature may rise to about 1200 ° C, and an explosion may be caused due to the increase in temperature and pressure inside the module. Therefore, by making the flame retardant composite material include a thermal insulation layer composed of a woven inorganic long fiber network, an organic binder and an inorganic filler, excellent thermal insulation and durability can be achieved, so that the propagation of heat or flame can be effectively suppressed. The inorganic filler can be evenly distributed on the inorganic long fiber network. Therefore, structural stability can be achieved in all temperature ranges, and long-term stability can be ensured by suppressing dust or debris generated by the inorganic filler. Among them, the inorganic filler is evenly distributed on the inorganic long fiber network and can refer to the inorganic filler being evenly distributed on the inorganic long fiber network.

[0064] The shape of the inorganic filler is not particularly limited, for example, it can be granular, fibrous, rod-shaped, spherical, plate-shaped, or sheet-shaped. Specifically, the shape of the inorganic filler can be granular. When the inorganic filler is granular, it can be more evenly distributed on the woven inorganic long fiber network, and can effectively inhibit the spread of heat or flame.

[0065] The inorganic filler can be used without restriction, as long as it can effectively prevent the spread of heat or flame in the thermal insulation layer and improve durability. For example, the inorganic filler can include any one or a mixture of two or more selected from metal hydroxides, mica (biotite, muscovite, sericite), metal oxides, metal carbonates, silicon dioxide, diatomaceous earth, dawsonite, barium sulfate, talc, clay, montmorillonite, bentonite, activated clay, sepiolite, imogolite, glass beads, silica-based hollow spheres, aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon hollow spheres, charcoal powder, potassium titanate, magnesium sulfate, lead zirconate titanate, zinc stearate, calcium stearate, aluminum borate, molybdenum sulfide, silicon carbide, stainless steel fiber, zinc borate, various magnetic powders, slag fiber, fly ash, and dewatered sludge. This is just an example and is not necessarily limited to this.

[0066] Preferably, the inorganic filler may include any one or both selected from an endothermic material or a thermal expansion material. The thermal insulation layer may include an endothermic material or a thermal expansion material as an inorganic filler, or may include both an endothermic material and a thermal expansion material as an inorganic filler. More preferably, when both an endothermic material and a thermal expansion material are included, the propagation of heat or flame can be effectively suppressed. At this time, the weight ratio of the endothermic material to the thermal expansion material may be 1:0.8 to 1.4. More specifically, the weight ratio of the endothermic material to the thermal expansion material may be 1:1 to 1.4.

[0067] The endothermic material may include any one or more selected from aluminum hydroxide, talc, calcium carbonate, diatomaceous earth, titanium oxide, zeolite or white carbon black, but is not necessarily limited thereto. The endothermic material may function as an endothermic material through a dehydration reaction, and may be used without restriction as long as it can quickly absorb high-temperature heat when a fire occurs in the module. Specifically, the endothermic material may start an endothermic reaction at a temperature above 110°C, and may exhibit an endothermic performance of more than 50% of the total endothermic performance within a temperature range of 110-150°C, for example, 50-80% of the endothermic performance. More specifically, the endothermic material may be aluminum hydroxide.

[0068] The thermal expansion material may include any one or more selected from mica (biotite, muscovite), vermiculite, kaolin, thermal expansion graphite, perlite, bentonite, but is not necessarily limited thereto. The thermal expansion material may be used without restriction as long as the space for heat or flame movement can be closed or the propagation of heat or flame can be prevented. Specifically, the thermal expansion material may be mica.

[0069] Preferably, the inorganic filler can use aluminum hydroxide and mica at the same time. When a fire occurs in the module, aluminum hydroxide quickly absorbs heat to suppress the temperature rise inside the battery module, while mica blocks the spread of flames, thereby achieving optimal performance.

[0070] In a specific embodiment, when the heat insulation layer is projected in a direction perpendicular to the surface, the cross-sectional area occupied by the inorganic filler on the woven inorganic long fiber network can be 80% or more. Within the above range, the propagation of heat or flame can be effectively suppressed, and excellent durability can be achieved. Specifically, the cross-sectional area can be 85% or more, and more specifically, 90% or more.

[0071] In a specific embodiment, the average diameter of the inorganic filler may be 1-50 μm. Within the above range, the inorganic filler is evenly distributed in the inorganic long fiber network, thereby achieving excellent thermal insulation and durability. Specifically, the average diameter of the inorganic filler may be 5-40 μm, more specifically 10-30 μm.

[0072] Specifically, the inorganic long fiber can be formed by weaving a plurality of first fibers (weft yarns) arranged in a first direction and a second fiber (warp yarn) arranged in a second direction intersecting the first direction. In a specific embodiment, the inorganic long fiber can be a glass long fiber. By including the glass long fiber, excellent thermal insulation and durability can be achieved, and the large area and reproducibility of the glass long fiber network can be easily achieved.

[0073] Furthermore, the long glass fibers may include fabrics in which fibers (yarns) are arranged in only one direction. As an example, the long glass fibers may use unidirectional fabrics, non-crimp fabrics, woven fabrics, etc., but are not limited thereto.

[0074] In a specific embodiment, the organic binder can improve the bonding force between the components contained in the thermal insulation layer such as the inorganic long fiber network and the inorganic filler, and can prevent dust and other debris from scattering to the outside of the flame retardant composite material. The organic binder can include a polymer resin having excellent heat resistance, flexibility and processability, and more specifically, the organic binder can include a thermosetting resin, a thermoplastic resin or a combination thereof. The thermoplastic resin may include, for example, any one selected from polyolefin resins such as polypropylene (PP), polyethylene (PE), polybutene, and polypentene, saturated polyester resins such as polyethylene terephthalate (PET), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), ethylene-vinylacetate (EVA), polycarbonate (PC), polyphenylene ether (PPE), (meth)acrylic resin ((meta)acrylate resin), polyamide (PA), polyvinyl chloride (PVC), novolak resin, polyisobutylene (PIB), and the like, or a mixture of two or more thereof. Exemplarily, the thermosetting resin may include any one selected from unsaturated polyester resin, epoxy resin, urea resin, melamine resin, phenolic resin, resorcinol resin and polyurethane (PU) or a mixture of two or more thereof. More specifically, the organic binder may be a polyamide resin, an unsaturated polyester resin or an epoxy resin.

[0075] <Flame-retardant composite material including more than one unit thermal insulation layer>

[0076] As another embodiment of the present invention, the heat insulation layer included in the flame retardant composite material may include a plurality of unit heat insulation layers.

[0077] For example, the heat insulating layer may include 1-100, 1-50, 1-30, 1-20, 1-10 or 1-5 unit heat insulating layers, but is not limited thereto.

[0078] Among them, each unit insulation layer may contain an inorganic long fiber network and an organic adhesive, wherein the inorganic long fiber network is formed by weaving a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction.

[0079] At this time, the directions of the first fibers (weft yarns) of the adjacent unit heat-insulating layers among the plurality of unit heat-insulating layers may be the same as or different from each other.

[0080] As an example, when the thermal insulation layer includes a first unit thermal insulation layer, a second unit thermal insulation layer connected to the first unit thermal insulation layer, and a third unit thermal insulation layer connected to the second unit thermal insulation layer, relative to a reference direction (0°) based on the first direction of the first fiber (weft yarn) arrangement of the first unit thermal insulation layer, the directions of arrangement of the first fibers (weft yarns) of the second unit thermal insulation layer and the third unit thermal insulation layer may be the same as or different from each other as the reference direction.

[0081] That is, the direction of the first fibers (weft yarns) of each unit heat-insulating layer can be freely selected within a range of 0° to ±180° with respect to the reference direction.

[0082] As a specific embodiment, the directions of the first fibers (weft yarns) of the adjacent unit insulation layers in the plurality of unit insulation layers may be different from each other.

[0083] By making the directions of the first fibers (weft yarns) of the adjacent unit heat insulating layers different from each other, the propagation of heat or flame can be more effectively suppressed.

[0084] As an example, when the arrangement directions of the first fibers (weft yarns) of each adjacent unit insulation layer are different from each other, the first fibers (weft yarns) of each unit insulation layer can be arranged at an angle greater than 0° and less than 90°, specifically an angle of 30° to 90°, and more specifically an angle of 45° to 90°.

[0085] The angle range is merely an example, and the present invention is not limited to the above angle range.

[0086] In a specific embodiment, the unit insulation layers may each further include an inorganic filler as a heat absorbing material. When the flame retardant composite material includes a first unit insulation layer, a second unit insulation layer, and a third unit insulation layer stacked in sequence, by including a heat absorbing material in the first unit insulation layer and the third unit insulation layer as the outer layer, heat can be quickly absorbed when a fire occurs in the module, thereby suppressing or delaying the temperature rise inside the battery module, and preventing thermal runaway from occurring in the early stage.

[0087] In a specific embodiment, the second unit heat insulation layer may further include an inorganic filler as a thermal expansion material. As described above, the first unit heat insulation layer or the third unit heat insulation layer including the heat absorbing material first absorbs the heat generated inside the module, thereby blocking the heat transfer to the adjacent secondary battery cells, and secondly, the second unit heat insulation layer including the thermal expansion material blocks the spread of flames, thereby achieving optimal performance.

[0088] In a specific embodiment, the total thickness of the flame retardant composite material may be 0.12-40 mm, 0.22-30 mm, 0.32-20 mm or 0.42-10 mm. More specifically, the thickness of the flame retardant composite material may be 0.3-5 mm, and further specifically 0.5-3 mm. The above thickness range is the minimum thickness range of the flame retardant composite material having an insulation layer including a plurality of unit insulation layers as described above. By making the flame retardant composite material have the above structure, the total thickness can be thinned, and the safety of the battery module can be ensured while achieving an increase in the energy density and lightweight of the battery module.

[0089] As described above, when the heat insulating layer included in the flame retardant composite material includes a plurality of unit heat insulating layers, the thickness of the unit heat insulating layer located inside may be thicker than the thickness of the unit heat insulating layer located on the outermost side, thereby achieving excellent durability.

[0090] For example, when the flame retardant composite material includes a first unit thermal insulation layer, a second unit thermal insulation layer, and a third unit thermal insulation layer stacked in sequence, the thickness (T2) of the second unit thermal insulation layer as an inner layer may be thicker than the thickness (T1) of the first unit thermal insulation layer and the thickness (T3) of the third unit thermal insulation layer as the outermost layer. Specifically, the thickness ratio of T2 to T1 may be 1.1:1 to 2:1, more specifically 1.3:1 to 2:1. In addition, the thickness ratio of T2 to T3 may be 1.1:1 to 2:1, more specifically 1.3:1 to 2:1.

[0091] In a specific embodiment, the multiple unit insulation layers may each independently contain 40-80 weight % of inorganic long fibers, 10-30 weight % of organic binders, 1-15 weight % of inorganic fillers, and 5-20 weight % of additives relative to the total weight. Specifically, the multiple unit insulation layers may each independently contain 50-80 weight % of inorganic long fibers, 12-18 weight % of organic binders, 2-8 weight % of inorganic fillers, and 10-20 weight % of additives relative to the total weight. More specifically, the multiple unit insulation layers may each independently contain 50-80 weight % of inorganic long fibers, 14-18 weight % of organic binders, and 4-8 weight % of inorganic fillers relative to the total weight. Within the above range, the spread of heat or flame can be effectively suppressed.

[0092] The additive may include a flame retardant. As described above, when any one of the plurality of secondary battery cells catches fire, the flame retardant may help prevent the flame from spreading to other adjacent secondary battery cells and may minimize damage to the heat insulation layer by the flame.

[0093] <Battery Module>

[0094] Hereinafter, a battery module according to an embodiment of the present invention will be described in detail.

[0095] In a specific embodiment, the battery module can accommodate a plurality of secondary battery cells in a shell component, and the secondary battery cells can include an electrode assembly in which a plurality of negative electrodes and positive electrodes are alternately stacked with a separator as a boundary, and a soft package outer packaging material surrounding the electrode assembly, and the flame retardant composite material can be located between the plurality of secondary battery cells.

[0096] like Figure 1 As shown, the battery module 100 accommodates a plurality of secondary battery cells 10 in a housing component 20. The secondary battery cell 10 is a secondary battery cell in which an electrode assembly in which negative electrodes and positive electrodes are alternately stacked with a separator as a boundary is inserted into an outer packaging material and filled with an electrolyte. The electrolyte may contain lithium salts such as LiPF6 and LiBF4 in an organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), but is not limited thereto. In addition, the electrolyte may be in a liquid, solid, or gel phase.

[0097] In a specific embodiment, the outer packaging material protects the electrode assembly and contains the electrolyte, and the outer packaging material may be a soft-pack outer packaging material. The soft-pack outer packaging material contains the electrode assembly and the electrolyte by sealing the electrode assembly from three or four sides. Generally, in a can-type battery, even if a flame is generated due to an explosion of a battery cell, etc., such a flame will not be exposed to the outside of the can, and in a soft-pack type secondary battery cell using a soft-pack outer packaging material, if an explosion occurs inside the battery cell, the soft-pack outer packaging material is destroyed and the flame is exposed to the outside of the soft pack, so that the flame and heat are easily transferred to adjacent batteries. Therefore, a battery module comprising a flame-retardant composite material according to a specific embodiment of the present invention can be effectively applied to a soft-pack type secondary battery cell.

[0098] A battery module can be formed by accommodating a plurality of the soft-pack type secondary battery cells 10 in a housing component 20. The housing component 20 can function as the main body of the battery module that accommodates the plurality of the secondary battery cells 10. In addition, the housing component 20 is a component that accommodates the plurality of secondary battery cells 10, and the housing component 20 can protect the secondary battery cells 10 while transmitting the electric energy generated by the secondary battery cells 10 to the outside, or can transmit the electric energy from the outside to the secondary battery cells 10.

[0099] For this purpose, the housing member 20 is not limited thereto, but for example, Figure 1 As shown, the housing component 20 may include a bottom component 21 and a side wall component 22, etc. The bottom component 21 may be provided with the plurality of secondary battery cells 10, and may support the plurality of secondary battery cells 10 provided in this manner. In addition, the bottom component 21 may be cooled by transferring the heat generated by the secondary battery cells 10 to an external radiator. In addition, the side wall component 22 forms the side of the housing component 20, and may also discharge the heat generated by the secondary battery cells 10 to the outside.

[0100] The shell component 20 may further include a cover component 23 disposed at the upper end of the side wall component 22, so as to be configured to protect the upper end of the secondary battery cell 10. In addition, the shell component 20 may include a front component 26 and a rear component 27 adjacent to the side wall component 22, so as to be configured to surround the plurality of secondary battery cells 10. In addition, the shell component 20 may be provided with additional components such as a bus bar component 25 that electrically connects the secondary battery cell to the outside. In addition, a compression component 24 may be provided on the inner side of the side wall component 22 to more firmly protect the secondary battery cell 10.

[0101] When any one of the plurality of secondary battery cells 10 accommodated in the module generates heat, the heat may be transferred to other adjacent secondary battery cells 10 , and a problem may occur in which other adjacent secondary battery cells 10 explode successively due to flames caused by explosion of any one secondary battery cell 10 .

[0102] In a specific embodiment of the present invention, in order to suppress or prevent the above-mentioned problems, as Figure 2 As shown, the flame retardant composite material 30 may be disposed between any one of the plurality of secondary battery cells 10 accommodated in the battery module and an adjacent secondary battery cell 10. The battery module 100 including the flame retardant composite material 30 may prevent heat and flame generated by any one of the secondary battery cells 10 from propagating to other adjacent secondary battery cells 10, thereby enhancing the safety of the battery module.

[0103] <Battery Pack>

[0104] Hereinafter, a battery pack according to an embodiment of the present invention will be described in detail. When describing the battery pack according to a specific embodiment of the present invention in detail, since the plurality of secondary battery cells and the flame retardant composite material included in the battery pack are the same or similar to the above, the detailed description is omitted.

[0105] A battery pack according to one embodiment of the present invention includes: a plurality of secondary battery cells; a flame retardant composite material located between the plurality of secondary battery cells; and a battery pack shell, the battery pack shell accommodating the plurality of secondary battery cells and the flame retardant composite material, wherein the flame retardant composite material includes an insulating layer comprising an inorganic long fiber network and an organic adhesive, the inorganic long fiber network being formed by weaving together a plurality of first fibers (weft yarns) arranged along a first direction and second fibers (warp yarns) arranged along a second direction intersecting the first direction.

[0106] As described above, when any one of a plurality of secondary battery cells generates heat or catches fire, a battery pack comprising a flame-retardant composite material that can inhibit the spread of heat and flame to other adjacent secondary battery cells can effectively block thermal runaway and chain explosion caused by overheating of the secondary battery cells, thereby significantly enhancing the safety of the battery pack.

[0107] In one embodiment, reference Figure 3The battery pack 200 may house a plurality of secondary battery cells 10 inside a battery pack case 40, the plurality of secondary battery cells 10 including a flame retardant composite material between adjacent secondary battery cells 10. The battery pack case 40 may include a lower case 41 housing the plurality of secondary battery cells 10 and an upper case (not shown) coupled to the lower case 41 and covering the plurality of secondary battery cells 10.

[0108] The lower housing 41 may include a lower plate located at the bottom of the plurality of secondary battery cells and a side wall extending from the edge of the lower plate and forming an internal space. The side wall may include a first side wall and a second side wall, wherein the first side wall is located at both ends of the first direction of the lower housing 41, for example Figure 3 The second side walls are located at two ends of the X direction, and the second side walls are located at two ends of a second direction perpendicular to the first direction, for example Figure 3 At both ends in the Y direction, the first side wall and the second side wall may be combined with each other to form four outer side surfaces of the battery pack housing 40.

[0109] The upper case (not shown) may be located above the plurality of secondary battery cells 10 accommodated in the internal space, and may protect the plurality of secondary battery cells 10 from external influences by being combined with the lower case 41. However, this is only described as one embodiment, and the lower plate and / or the upper case may be omitted to expose the upper and / or lower portions of the plurality of secondary battery cells 10.

[0110] The internal space may include a partition that protrudes from the lower plate at a predetermined height and divides the internal space of the battery pack housing 40. The partition may include a first partition 51 arranged in one direction and a plurality of second partitions 52 arranged perpendicular to the first partition 51 and spaced apart from each other. A plurality of secondary battery cells 10 may be accommodated in the plurality of internal spaces divided by the first partition 51 and the second partition 52. Therefore, at least two or more secondary battery cells 10 may be accommodated in the minimum unit accommodation space divided by the first partition 51 and the second partition 52. At this time, the plurality of secondary battery cells 10 accommodated in the internal space may be fixed to the lower housing 41 of the battery pack housing 40 by a bracket component.

[0111] An exhaust component (not shown) may be provided in the battery pack housing 40 so that the gas, flame and / or combustion material generated by the plurality of secondary battery cells 10 can be discharged to the outside of the battery pack 200. Such an exhaust component (not shown) may have a structure that is normally closed and opened when exhausting gas, etc. However, the exhaust component (not shown) may also be provided as an opening formed in the battery pack housing 40. The location and number of the exhaust component (not shown) may be variously changed as needed.

[0112] In order to make the gas, flame and / or burning material discharged from the plurality of secondary battery cells 10 easily move to the exhaust component (not shown), the interior of the battery pack housing 40 may be provided with an exhaust channel that allows the gas, flame and burning material to move to the exhaust component (not shown). As an example, the exhaust channel may be formed inside the side wall or inside the first partition 51 and the second partition 52, between the battery pack housing 40 and the plurality of secondary battery cells 10. The gas, flame, burning material, etc. transported through the exhaust channel can be quickly discharged to the outside through the exhaust component (not shown). Therefore, by minimizing the rapid spread of flames and heat and the secondary damage caused thereby, the stability of the battery pack can be further improved.

[0113] In one embodiment, the structure of the battery pack 200 is not limited and may have various forms. As an example, the battery pack 200 may have a plurality of secondary battery cells 10 and a flame retardant composite material ( Figure 1 The structure of the battery pack housing 40 is a structure such as a non-module battery pack (Cell to Pack) and a battery body integration (Cell to Body). Alternatively, a plurality of secondary battery cells 10 and a flame retardant composite material ( Figure 1 30) battery module ( Figure 1 100) may be housed inside the battery pack housing 40 to form the battery pack 200, but the present invention is not limited by the structure of the battery pack 200.

[0114] Hereinafter, the present invention will be described in detail by way of examples. However, the following examples are only used to illustrate the present invention, and the content of the present invention is not limited by the following examples. At this time, unless otherwise defined, the technical terms and scientific terms used have the meanings commonly understood by those skilled in the art to which the present invention belongs. In addition, the repeated description of the technical features and functions identical to those of the prior art is omitted.

[0115] (Example 1)

[0116] A flame retardant composite material including a heat insulation layer having a thickness of 1 mm was manufactured, wherein the heat insulation layer contained 50 wt % of woven glass long fibers, 20 wt % of unsaturated polyester, 13 wt % of aluminum hydroxide, and 17 wt % of a phosphorus-based flame retardant. At this time, the woven glass long fibers were woven glass long fibers in which a first fiber (weft yarn) and a second fiber (warp yarn) were crossed at 60°.

[0117] The flame retardant composite material is disposed between two adjacent battery cells, thereby preparing a battery module including the flame retardant composite material.

[0118] (Example 2)

[0119] A battery module similar to that of Example 1 was prepared, except that in Example 1, as the heat insulating layer, a heat insulating layer containing 67 wt % of woven glass long fibers, 13 wt % of unsaturated polyester, 9 wt % of aluminum hydroxide, and 11 wt % of a phosphorus-based flame retardant was used.

[0120] (Example 3)

[0121] A battery module similar to that of Example 1 was prepared, except that in Example 1, a heat insulating layer containing 67 wt % of woven glass long fibers, 15 wt % of unsaturated polyester, and 18 wt % of a phosphorus-based flame retardant was used as the heat insulating layer.

[0122] (Example 4)

[0123] A battery module identical to that of Example 1 was prepared, except that, in Example 1, a thermal insulation layer comprising 67 wt % of woven long glass fibers, 13 wt % of unsaturated polyester, 4 wt % of aluminum hydroxide, 5 wt % of mica, and 11 wt % of a phosphorus-based flame retardant was used as the thermal insulation layer.

[0124] (Example 5)

[0125] A flame-retardant composite material having a total thickness of 1 mm in which a plurality of unit insulation layers (a first unit insulation layer, a second unit insulation layer, and a third unit insulation layer) are sequentially stacked is prepared. Each unit insulation layer contains 67% by weight of woven glass long fibers, 13% by weight of unsaturated polyester, 9% by weight of aluminum hydroxide, and 11% by weight of a phosphorus-based flame retardant, and the woven glass long fibers are woven glass long fibers in which the first fibers (weft yarns) and the second fibers (warp yarns) are crossed at 60°. In addition, each unit insulation layer is stacked in such a manner that the angles between the first fibers (weft yarns) of each unit insulation layer disposed in contact with each other are the same.

[0126] The flame retardant composite material is disposed between two adjacent battery cells, thereby preparing a battery module including the flame retardant composite material.

[0127] (Example 6)

[0128] A battery module identical to that of Example 5 is prepared, except that, in Example 5, the first unit thermal insulation layer and the second unit thermal insulation layer are stacked so that the angle between the first fibers (weft yarns) of each of them is +45°, and the second unit thermal insulation layer and the third unit thermal insulation layer are stacked so that the angle between the first fibers (weft yarns) of each of them is -45°.

[0129] (Example 7)

[0130] The same battery module as in Example 6 was prepared, except that the components contained in each layer were changed in Example 6. Specifically, the same battery module as in Example 6 was prepared, except that the cell insulation layers each contained 30 wt% of woven glass long fibers, 61 wt% of unsaturated polyester, 4 wt% of aluminum hydroxide, and 5 wt% of mica.

[0131] (Example 8)

[0132] A battery module was prepared that was the same as that of Example 1 except that, in Example 1, as the heat insulating layer, a heat insulating layer including 80 wt % of woven glass long fibers, 13 wt % of unsaturated polyester, and 7 wt % of a bromine-based flame retardant was used.

[0133] (Example 9)

[0134] A battery module identical to that of Example 1 was prepared, except that, in Example 1, a thermal insulation layer comprising 67 wt % of woven long glass fibers, 13 wt % of epoxy resin, 4 wt % of aluminum hydroxide, 5 wt % of mica, and 11 wt % of a phosphorus-based flame retardant was used as a thermal insulation layer.

[0135] (Example 10)

[0136] The same battery module as in Example 1 was prepared, except that in Example 1, as the heat insulating layer, a fiber containing 67 wt % of woven glass long fibers, 13 wt % of nylon 6 (BASF, C60X1V30 Black), 4 wt % aluminum hydroxide, 5 wt % mica and 11 wt % phosphorus-based flame retardant.

[0137] (Example 11)

[0138] A battery module identical to that of Example 4 was manufactured, except that the total thickness of the flame retardant composite material was 40 mm.

[0139] (Example 12)

[0140] The same battery module as in Example 7 was prepared except that in Example 7, a flame retardant composite material having a total thickness of 0.5 mm was used in which the first unit heat insulating layer and the second unit heat insulating layer each having a thickness of 0.25 mm were sequentially stacked without including the third unit heat insulating layer.

[0141] (Comparative Example 1)

[0142] A battery module similar to that of Example 1 was prepared, except that, in Example 1, a heat insulating layer containing 5 wt % of polymethylsilsesquioxane and 95 wt % of mica was used as the heat insulating layer.

[0143] (Comparative Example 2)

[0144] A battery module similar to that of Example 1 was prepared, except that in Example 1, as the heat insulating layer, a heat insulating layer containing 45 wt % of glass short fibers, 18 wt % of unsaturated polyester, 16 wt % of aluminum hydroxide, and 21 wt % of a phosphorus-based flame retardant was used.

[0145] (Evaluation example)

[0146] Specific gravity: The specific gravity of the flame retardant composite material is measured according to the ISO1183-1 (2019) method.

[0147] Flame retardant grade: The flame retardant composite material was cut into samples of 5″×1 / 2″ and subjected to a UL94 Vertical Burn (V) test to evaluate the flame retardant properties of the flame retardant composite material.

[0148] Thermal insulation performance: A butane gas torch is placed 140 mm away from one side (front) of the flame retardant composite material. The torch is used to generate a flame, and one side (front) of the flame retardant composite material is heated to 1100-1200°C, and then the temperature of the back (back) of the flame retardant composite material as the other side is measured, and it is confirmed whether the flame retardant composite material has holes, thereby evaluating the thermal insulation effect. In the following Tables 1 and 3, when holes are generated in the flame retardant composite material, whether the flame spreads to the back is indicated by O, and when no holes are generated in the flame retardant composite material, whether the flame spreads to the back is indicated by X.

[0149] Evaluation of explosion: Referring to GB / T-38031 safety test, which is one of the safety tests for battery modules, the situation where any battery cell in the battery module has thermal runaway at above 1200°C is intentionally simulated. The thermal runaway phenomenon is allowed to continue for 30 minutes and whether the battery module explodes is confirmed. In Tables 1 to 3 below, when the battery module explodes, it is indicated by O, and when the battery module does not explode, it is indicated by X.

[0150] Evaluation of adhesive thickness: When the adhesive is applied to both sides of the flame retardant composite material, the required thickness of the adhesive is measured. The adhesive uses a double-sided tape including a substrate.

[0151] Evaluation of whether foreign matter is generated: The cleanliness of the battery module is evaluated according to the VDA 1.9 test method. Deionized water (DI water) is used as the solvent, and the solvent is sprayed into the battery module at a flow rate of 1.5L / min. At this time, a part of the components is disassembled so that the solvent can be sprayed into the inside of the module, and the cleanliness is evaluated separately. A total of 5.0L of solvent is sprayed inside the battery module for 4 minutes, and a total of 2.5L of solvent is sprayed outside the module for 1 minute. The solvent is discharged through the nozzle of the sprayer, the diameter of the nozzle is 2.5mm, and the distance between the battery module and the nozzle is set to a maximum of 15cm. The solvent sprayed on the battery module is passed through a filter to obtain foreign matter such as dust present in the battery module, and then the amount of foreign matter is measured. The filter is a polyester or polyamide filter with a mesh size of 20μm. In Tables 1 and 3 below, when the amount of foreign matter discharged from the battery module is 200ppm or more, it is expressed as O, and when the amount of foreign matter discharged from the battery module is less than 200ppm, it is expressed as X.

[0152] Evaluation of short circuit: The battery module was operated for 30 minutes in a normal working environment to confirm whether the module had a short circuit. In Tables 1 to 3 below, when a short circuit occurred in the battery module, it was indicated by O, and when no short circuit occurred in the battery module, it was indicated by X.

[0153] [Table 1]

[0154]

[0155] [Table 2]

[0156]

[0157] [Table 3]

[0158]

[0159]

[0160] As shown in Tables 1 to 3, in Examples 1 to 12, the back surface temperature in the blowtorch test is below 600°C, which has excellent thermal insulation effect, and even if the thermal runaway phenomenon lasts for 30 minutes, the battery module will not explode, and the battery module will not short-circuit under normal working conditions, so that it can operate stably.

[0161] Specifically, in Examples 2 and 3, even though the content of aluminum hydroxide decreases as the content of woven long glass fibers increases, a better thermal insulation effect than that of Example 1 is exhibited.

[0162] In Example 4, 4 wt % of aluminum hydroxide and 5 wt % of mica were used in combination as the inorganic filler, and it was confirmed that the heat insulation effect was superior to that of Examples 1 to 3.

[0163] In addition, in Example 6 and Example 7, a plurality of unit insulation layers are included, and the angles between the first fibers (weft yarns) of each unit insulation layer are adjusted and stacked, so that it can be confirmed that the insulation effect is excellent. Among them, the content of woven glass long fibers in Example 7 is 30% by weight, and the content of woven glass long fibers included is less than that in Example 6, and the insulation layer does not contain flame retardants. In the case of Example 7, the result of the blowtorch test, the back temperature is 567°C, which shows low insulation performance compared with Example 6, but unlike Comparative Example 2 containing glass short fibers, the flame does not spread to the back. In particular, unlike Comparative Examples 1 and 2, no explosion and short circuit of the battery module occurred in Example 7, thereby showing excellent long-term stability, and the specific gravity of the insulation layer is as low as 1.6g / cm 3 That is, by controlling the angles between the insulation layers of each unit, the specific gravity of the insulation layer can be minimized, which is not only conducive to achieving lightweight battery modules, but also can ensure good insulation effect and stability of the battery modules.

[0164] In the case of Example 8 in which the heat insulating layer does not contain an inorganic filler and contains a bromine-based flame retardant instead of a phosphorus-based flame retardant, the back surface temperature measured in the blowtorch test was 370°C, and no explosion or short circuit of the battery module occurred during stability evaluation. Even though the heat insulating layer does not contain an inorganic filler, since the content of the woven glass long fiber is increased to 80% by weight, excellent heat insulating properties are exhibited, and since the flame retardant composite material does not contain an inorganic filler, there is no dust generated from the inorganic filler, so long-term stability is improved.

[0165] Examples 9 and 10 are battery modules including heat insulating layers containing epoxy resin and nylon 6 as binder resins, respectively. In the case of using other types of polymer resins as binder resins instead of unsaturated polyester, the back surface temperatures measured during the blowtorch test were 365°C and 398°C, respectively, indicating excellent heat insulating properties, and no explosion or short circuit of the battery module occurred, confirming that the stability of the battery module was significantly improved.

[0166] Example 11, in which the total thickness of the flame-retardant composite material was 40 mm, also exhibited excellent thermal insulation performance and stability. In Example 12, even if the total thickness of the flame-retardant composite material was reduced to 0.5 mm, the back temperature measured during the blowtorch test was 590°C, and no explosion or short circuit of the battery module occurred during the stability evaluation. It was confirmed that by adjusting the angle between the first fibers (weft yarns) of each unit thermal insulation layer included in the flame-retardant composite material, a battery module that minimizes the volume occupied by the flame-retardant composite material in the battery module while maintaining safety and thermal insulation performance was achieved.

[0167] Therefore, in the flame retardant composite material according to one embodiment of the present invention, during the blowtorch test, the flame did not spread to the back side, thereby effectively blocking the flame from the front side of the flame retardant composite material to the back side, and there was less than 200ppm of foreign matter inside and outside the battery module. By significantly reducing the amount of dust generated from the flame retardant composite material, the problem of damage to the battery module caused by foreign matter can be eliminated. In addition, the measured thickness of the adhesive between the secondary battery cell and the flame retardant composite material is 0.2mm. By minimizing the thickness of the adhesive, the energy density per unit area and per unit volume of the battery module is increased, which helps to improve the performance of the battery module and can reduce the manufacturing cost of the battery module.

[0168] On the other hand, in Comparative Example 1, since the heat insulation layer does not contain woven inorganic long fibers and contains 95% by weight of mica, dust is generated, and more than 200 ppm of foreign matter exists in the battery module, so the battery explodes during operation, causing the battery module to fail to operate normally, and since the specific gravity is 2.4 g / cm 3 , so it is confirmed that it is not suitable for lightweighting when applied to electric vehicle batteries, etc. In addition, in order to adhere the flame retardant composite material between the secondary battery cells, the adhesive must be applied between the flame retardant composite material and the secondary battery cells with a thickness of 1 mm. Since the thickness of the adhesive of Comparative Example 1 is 5 times the thickness of the adhesive of Example 1, the energy density per unit area and the energy density per unit volume of the battery module are significantly reduced.

[0169] In Comparative Example 2, since the heat insulation layer contains short glass fibers instead of woven long glass fibers, the back temperature rises to 572°C in the blowtorch test, and the heat insulation effect is reduced compared to Examples 1 to 4 with the same thickness of the flame-retardant composite material, and even the flame spreads to the back of the flame-retardant composite material. When the thermal runaway phenomenon of the battery module according to Comparative Example 2 was allowed to continue for 30 minutes, a short circuit of the battery module occurred. Therefore, when the flame-retardant composite material of Comparative Example 2 was used, it was confirmed that the heat shielding and flame propagation blocking effects were significantly low.

[0170] The embodiments of the present invention are described above, but the present invention is not limited to the above embodiments, but can be implemented in various forms different from each other, and those skilled in the art of the present invention can understand that it can be implemented by other specific schemes without changing the technical ideas or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary and not restrictive in all aspects.

Claims

1. A battery module, the battery module accommodating a plurality of secondary battery cells in a housing member, The flame retardant composite material is located between the plurality of secondary battery cells, The flame retardant composite material includes a heat insulating layer including an inorganic long fiber network and an organic binder, wherein the inorganic long fiber network is formed by weaving a plurality of first fibers, ie, weft yarns, arranged in a first direction and second fibers, ie, warp yarns, arranged in a second direction crossing the first direction with each other.

2. The battery module according to claim 1, wherein: The heat-insulating layer further comprises an inorganic filler.

3. The battery module according to claim 2, wherein: In the thermal insulation layer, the inorganic filler is evenly distributed in the inorganic long fiber network.

4. The battery module according to claim 2, wherein: The inorganic filler comprises any one or both selected from heat absorbing materials and heat expanding materials.

5. The battery module according to claim 1, wherein: The thermal insulation layer further comprises an additive.

6. The battery module according to claim 5, wherein: The additives include flame retardants.

7. The battery module according to claim 1, wherein: The thermal insulation layer includes a plurality of unit thermal insulation layers.

8. The battery module according to claim 7, wherein: The directions of the first fibers, ie, weft yarns, of the adjacent unit insulation layers in the plurality of unit insulation layers are the same as or different from each other.

9. The battery module according to claim 7, wherein: The unit thermal insulation layer further includes an inorganic filler.

10. The battery module according to claim 7, wherein: The plurality of unit heat-insulating layers independently contain 40-80 wt % of inorganic long fibers, 10-30 wt % of organic binder, 1-15 wt % of inorganic filler and 5-20 wt % of additives relative to the total weight.

11. The battery module according to claim 2, wherein: The average diameter of the inorganic filler is 1-50 μm.

12. The battery module according to claim 4, wherein: The heat absorbing material comprises one or more selected from aluminum hydroxide, talc, calcium carbonate, diatomaceous earth, titanium oxide, zeolite or white carbon black.

13. The battery module according to claim 4, wherein: The thermal expansion material comprises any one or two or more selected from mica, vermiculite, kaolin, thermal expansion graphite, perlite, and bentonite.

14. The battery module according to claim 1, wherein: The inorganic long fibers include glass long fibers.

15. The battery module according to claim 1, wherein: The organic binder includes a thermosetting resin, a thermoplastic resin, or a combination thereof.

16. The battery module according to claim 1, wherein: The thickness of the flame retardant composite material is 0.12-40 mm.

17. The battery module according to claim 1, wherein: The secondary battery cell includes an electrode assembly in which a plurality of negative electrodes and positive electrodes are alternately stacked with a separator as a boundary, and a soft package outer material surrounding the electrode assembly.

18. A battery pack, comprising: a plurality of secondary battery cells; a flame retardant composite material, wherein the flame retardant composite material is located between the plurality of secondary battery cells; as well as a battery pack housing that accommodates the plurality of secondary battery cells and the flame-retardant composite material, The flame retardant composite material includes a heat-insulating layer comprising an inorganic long fiber network and an organic adhesive, wherein the inorganic long fiber network is formed by weaving a plurality of first fibers, i.e., weft yarns, arranged along a first direction and second fibers, i.e., warp yarns, arranged along a second direction intersecting the first direction.

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