Battery module

Abstract

A battery module comprising: a cell stack containing a plurality of battery cells; a flexible printed circuit board disposed on at least one surface of the cell stack; and a housing with an internal space in which the cell stack and the flexible printed circuit board are housed, wherein the flexible printed circuit board comprises a base substrate, a metal layer arranged on the base substrate and an insulating layer arranged on the metal layer, and the insulating layer includes a plurality of stacked polyimide layers and a first adhesive layer disposed between the adjacent polyimide layers.

Description

TECHNICAL FIELD

[0001] The following disclosure relates to a battery module with significantly improved insulation properties. BACKGROUND

[0002] In recent years, the secondary battery, which can be charged and discharged, has been widely used as a power source for a wireless mobile device and has attracted attention as a power source for an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (plug-in HEV), which are developed to solve problems such as air pollution caused by existing gasoline and diesel fossil fuel vehicles.

[0003] While small mobile devices use one to three battery cells per device, medium- and large-sized devices, such as automobiles, use a battery module or battery pack, which is created by electrically connecting a large number of battery cells, due to the need for high power and large capacity. Such a secondary battery may consist of a large number of battery cells connected in series to provide the power and capacity required for a specific device or appliance.

[0004] Although lithium secondary batteries have excellent electrical properties, they have poor safety. For example, abnormal operating conditions such as overcharging, overdischarging, high temperatures, or electrical short circuits in lithium secondary batteries will cause a decomposition reaction of battery components such as active materials and electrolytes, resulting in heat and gas generation. The resulting high temperature and high pressure conditions further accelerate the decomposition reaction, ultimately leading to ignition or explosion.

[0005] To avoid safety accidents, conventional medium and large battery modules or battery packs are equipped with a sensor that can measure the voltage and temperature of the battery cells, as well as a battery management system (BMS) that controls the battery based on the measured values.

[0006] However, the BMS is only a management system that detects risks and activates safety devices within the battery module or pack, and a fundamental solution to improve safety is still required.

[0007] The battery module of the present disclosure includes the flexible circuit board having excellent insulation properties, so that the battery module can have significantly improved insulation properties. SUMMARY

[0008] An embodiment of the present disclosure aims to provide a flexible printed circuit board (FPCB) having excellent insulation properties used in a battery module, and a battery module including the same.

[0009] Another embodiment of the present disclosure aims to provide a battery module with improved safety.

[0010] Another embodiment of the present disclosure aims to provide a battery module with a significantly reduced defect rate in a manufacturing process.

[0011] The battery module of the present disclosure can be used in a wide range of green technology applications, such as electric vehicles, battery charging stations, and solar and wind power generation using batteries. Furthermore, the battery module of the present disclosure can be used in green electric vehicles, hybrid vehicles, and the like to prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0012] In one general aspect, a battery module comprises: a cell stack containing a plurality of battery cells; a flexible circuit board disposed on at least one surface of the cell stack; and a housing having an internal receiving space in which the cell stack and the flexible circuit board are housed, wherein the flexible circuit board includes a base substrate, a metal layer disposed on the base substrate, and an insulating layer disposed on the metal layer, and the insulating layer includes a plurality of stacked polyimide layers and a first adhesive layer disposed between the adjacent polyimide layers.

[0013] In an exemplary embodiment, the sum of the thicknesses of the plurality of polyimide layers may be from 5 µm to 50 µm.

[0014] In an exemplary embodiment, the thickness of the first adhesive layer may be from 1 µm to 50 µm.

[0015] In an exemplary embodiment, the thickness of the insulating layer may be from 15 µm to 100 µm.

[0016] In an exemplary embodiment, the flexible printed circuit board may have a heat deflection temperature of 200°C or higher, measured according to ASTM D648, a breakdown voltage of 4000 V to 6000 V, measured according to ASTM D 3755, and a flame retardancy rating of V-1 or higher, rated according to the UL-94 VB flame retardancy standard.

[0017] In an exemplary embodiment, the insulating layer may have a structure in which two polyimide layers are stacked via the first adhesive layer.

[0018] In an exemplary embodiment, the thickness of each of the polyimide layers may be from 5 µm to 15 µm.

[0019] In an exemplary embodiment, the first adhesive layer may contain an adhesive and a flame retardant.

[0020] In an exemplary embodiment, the flame retardant may be at least one of an organic flame retardant, an inorganic flame retardant, or a combination thereof.

[0021] In an exemplary embodiment, the organic flame retardant may contain one or more selected from the group consisting of a phosphorus-based flame retardant, a nitrogen-based flame retardant, a phosphorus-nitrogen-based flame retardant, and a halogen-based flame retardant.

[0022] In an exemplary embodiment, the inorganic flame retardant may contain a metal oxide.

[0023] In an exemplary embodiment, the flexible circuit board may further include a second adhesive layer disposed between the base substrate and the metal layer.

[0024] In an exemplary embodiment, the flexible circuit board may further include a third adhesive layer disposed between the metal layer and the insulating layer.

[0025] In an exemplary embodiment, the base substrate may include an insulating material.

[0026] In an exemplary embodiment, the flexible circuit board may be arranged on the cell stack such that the insulating layer and the housing are opposite each other.

[0027] Further features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing a flexible printed circuit board included in a conventional battery module. Fig.2 is a cross-sectional view schematically showing a flexible printed circuit board according to an exemplary embodiment. Fig. 3 is a view explaining the principle of improving the insulation properties of a flexible printed circuit board according to an exemplary embodiment. Fig. 4 is a perspective view schematically showing a battery module according to an exemplary embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The exemplary embodiments described in the present specification may be modified in various forms, and the technology according to an exemplary embodiment is not limited to the exemplary embodiments described below. Furthermore, these exemplary embodiments are provided to more fully describe the present disclosure to those skilled in the art.

[0029] Unless the context clearly indicates otherwise, the singular forms used in the description and the appended claims may also include plural forms.

[0030] Furthermore, a numerical range used in this specification includes upper and lower limits and all values within those limits, increments logically derived from a shape and span of a defined range, all doubly bounded values, and all possible combinations of upper and lower limits within the numerical range defined in various forms. Unless expressly defined otherwise in this specification, values outside the numerical range that may occur due to experimental errors or rounded values are also included within the defined numerical range.

[0031] Furthermore, throughout this specification, unless expressly stated otherwise, “contains” a particular ingredient means the inclusion of other ingredients and not the exclusion of other ingredients.

[0032] When in this specification a part, such as a layer, film, region or plate, is referred to as being “on” or “over” another part, it may be “directly on” another part or there may be an intermediate part.

[0033] The terms "first," "second," and the like, as used in this specification, may be used to describe various components, but the components should not be limited by these terms. The terms are used only to distinguish one component from another.

[0034] According to a first aspect of the present disclosure, there is provided a battery module including: a cell stack including a plurality of battery cells; a flexible circuit board disposed on at least one surface of the cell stack; and a housing having an internal receiving space in which the cell stack and the flexible circuit board are housed, wherein the flexible circuit board includes a base substrate, a metal layer disposed on the base substrate, and an insulating layer disposed on the metal layer, and the insulating layer includes a plurality of stacked polyimide layers and a first adhesive layer disposed between the adjacent polyimide layers.

[0035] The battery module according to an exemplary embodiment of the present disclosure can ensure excellent insulation properties through the other polyimide layers even if a defect occurs in one of the plurality of polyimide layers. Since the insulation properties are maintained even if a defect occurs in all polyimide layers, unless the defect occurs at the same location in each layer, the possibility of ensuring excellent insulation properties can be significantly increased. Accordingly, the problem of safety deterioration due to the occurrence of a short circuit and the problem of an increased defect rate in the manufacturing process can be solved.

[0036] In an exemplary embodiment, a flexible printed circuit board is arranged on a cell stack such that an insulating layer having a structure in which a plurality of polyimide layers are stacked via a first adhesive layer faces a conductive component such as a casing, so that the insulating properties can be significantly improved without an additional insulating unit, thereby increasing the energy density per volume of the battery module.

[0037] In an exemplary embodiment, the insulating layer may include a plurality of polyimide layers and a first adhesive layer connecting each polyimide layer and an adjacent polyimide layer. That is, the insulating layer may include n polyimide layers and (n-1) first adhesive layers connecting each polyimide layer and an adjacent polyimide layer. For example, when the insulating layer includes two polyimide layers, the insulating layer may have a structure in which a polyimide layer, a first adhesive layer, and a polyimide layer are sequentially stacked, and when the insulating layer includes three polyimide layers, the insulating layer may have a structure in which a polyimide layer, a first adhesive layer, a polyimide layer, a first adhesive layer, and a polyimide layer are sequentially stacked.

[0038] In an exemplary embodiment, the sum of the thicknesses of the two or more polyimide layers may be 5 µm or more, 10 µm or more, 15 µm or more, 20 µm or more, 60 µm or less, 50 µm or less, or a value between the above values. For example, the sum of the thicknesses of the two or more polyimide layers may be from 5 µm to 60 µm, 10 µm to 60 µm, 15 µm to 55 µm, or 20 µm to 50 µm. If the thickness range described above is maintained, the battery module may have improved mechanical properties and thus also improved insulation properties.In particular, the battery module according to an exemplary embodiment has the above-described thickness range and includes the insulating layer including a plurality of polyimide layers, so that a phenomenon of cracking on the polyimide layer due to folding can be effectively suppressed, and as a result, significantly improved mechanical properties and insulation properties can be obtained.

[0039] In an exemplary embodiment, the thickness of the first adhesive layer may be 1 µm or more, 5 µm or more, 50 µm or less, 30 µm or less, 20 µm or less, or a value between the above-mentioned values. The thickness of the first adhesive layer may, for example, be from 1 µm to 50 µm, 1 µm to 30 µm, or 5 µm to 20 µm. In this case, the thickness of the first adhesive layer may refer to the total thickness of the first adhesive layer contained in the insulating layer. If the thickness range described above is maintained, the battery module may have improved mechanical properties and thus also improved insulating properties.

[0040] In an exemplary embodiment, the total thickness of the insulating layer may be 15 µm or more, 20 µm or more, 25 µm or more, 100 µm or less, 75 µm or less, 50 µm or less, or a value between the above values. For example, the total thickness of the insulating layer may be from 15 µm to 100 µm, 20 µm to 75 µm, 15 µm to 50 µm, or 25 µm to 50 µm. If the insulating layer meets the thickness range described above, the battery module may have improved mechanical properties and thus also improved insulating properties.

[0041] In an exemplary embodiment, the flexible printed circuit board may have a heat deflection temperature of 200°C or higher, measured according to ASTM D648, a breakdown voltage (BDA) of 4,000 V to 6,000 V, measured according to ASTM D149, and a flame retardancy rating of V-1 or higher, evaluated according to the UL-94 VB flame retardancy standard. When the flexible printed circuit board satisfies the heat deflection temperature, breakdown voltage, and flame retardancy rating described above, the battery module can exhibit significantly improved insulation properties, thereby effectively reducing the manufacturing defect rate of the battery module. In particular, since the flexible printed circuit board satisfies all of the above-described characteristics, the phenomenon of cracking on the polyimide layer due to folding can be effectively suppressed, and as a result, significantly improved mechanical properties and insulation properties can be obtained.

[0042] Specifically, the heat deflection temperature (HDT) of the flexible circuit board can be 150°C or higher, 180°C or higher, or 200°C or higher, and can be 800°C or lower, 700°C or lower, 600°C or lower, or a value between the above values, but is not limited to them. Since the flexible circuit board has excellent heat resistance at the heat deflection temperature in the above range, the safety of the flexible circuit board can be improved due to the excellent heat resistance even in a high-temperature environment during battery module operation. Furthermore, the possibility of damage to the flexible circuit board during manufacturing and use can be greatly reduced.

[0043] For example, the heat deflection temperature (HDT) may be measured according to ASTM D648, and in particular, the heat deflection temperature (HDT) may be a temperature at which the flexible circuit board is deformed by 0.25 mm when the flexible circuit board is placed on a fixture of a heat deflection tester (INSTRON CEAST, HV3S) and heated at a heating rate of 2 ± 0.2°C / min while applying a bending stress of 264 psi to the center.

[0044] Specifically, the breakdown voltage (BDV) of the flexible printed circuit board can be from 4 kV to 6 kV, 4.2 kV to 5.8 kV, or 4.5 kV to 5.5 kV. The breakdown voltage (BDV) can be measured according to ASTM D149, and specifically, the breakdown voltage (BDV) can be a voltage (kV) when a leakage current value is 5 mA, which is measured under a condition where the flexible printed circuit board is placed between electrodes of a withstand voltage tester (Model 19052, Chroma ATE Inc.) at room temperature (25°C), and then the applied voltage is increased to 5 kV / 10 sec.

[0045] In particular, the flame retardancy rating of the flexible printed circuit board is evaluated according to the UL-94 VB flame retardancy standard and may be V-1 or higher or V-0 or higher, and advantageously it may be 5 VB.

[0046] In an exemplary embodiment, the insulating layer may have a structure in which two polyimide layers are stacked over a first adhesive layer. In this case, the thickness of each polyimide layer may be 2.5 µm or more, 5 µm or more, 25 µm or less, 20 µm or less, 15 µm or less, or a value between the above values. For example, the thickness of each polyimide layer may be from 2.5 µm to 25 µm or 2.5 µm to 20 µm, and may be 5 µm to 15 µm from the viewpoint of improving the mechanical properties and insulation properties of the battery module.

[0047] In an exemplary embodiment, the plurality of polyimide layers included in the insulating layer may have the same or different properties, and it is preferable that the plurality of polyimide layers have the same properties from the viewpoint of improving the mechanical properties and the insulating properties of the battery module.

[0048] In an exemplary embodiment, the first adhesive layer may include an adhesive, and the adhesive may have adhesive properties achieved by heat compression. Any adhesive may be selected and used without limitation as long as it is an adhesive material used in the art. Examples of the adhesive material include a polymer or a combination of two or more polymers selected from the group consisting of an ethylene-vinyl acetate (EVA)-based polymer, an acrylic-based polymer, an epoxy-based polymer, an olefin-based polymer, a rubber-based polymer, an amide-based polymer, and a urethane-based polymer, but the adhesive material may be replaced with other components without departing from the scope of the present disclosure.

[0049] In an exemplary embodiment, the first adhesive layer may additionally contain a flame retardant, and thus may contain an adhesive and a flame retardant. Since the first adhesive layer additionally contains a flame retardant, a battery module with significantly improved thermal stability and insulation properties can be provided.

[0050] In an exemplary embodiment, the flame retardant may include an organic flame retardant, an inorganic flame retardant, or a combination thereof. The organic flame retardant may include one or more selected from the group consisting of a phosphorus-based flame retardant, a nitrogen-based flame retardant, a phosphorus-nitrogen-based flame retardant, and a halogen-based flame retardant, and the inorganic flame retardant may include a metal oxide.

[0051] Phosphorus-based flame retardants can include, for example, a phosphate compound, a phosphonate compound, a phosphinate compound, a phosphine oxide compound, a phosphazene compound, or a metal salt thereof. Nitrogen-based flame retardants can include piperazine pyrophosphate, melamine polyphosphate, ammonium polyphosphate (APP), melamine cyanurate, or a combination thereof. Halogen-based flame retardants can include decabromodiphenyl oxide, decabromodiphenyl ethane, decabromodiphenyl ether, tetrabromobisphenol A, a tetrabromobisphenol A epoxy oligomer, a brominated epoxy oligomer, octabromotrimethylphenylindane, ethylenebistetrabromophthalimide, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, or a combination thereof.The inorganic flame retardant may contain a metal oxide such as magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimony carbonate, metallic antimony, antimony trichloride, antimony pentachloride, barium metaborate, zirconium oxide, zinc borate, zinc stannate, or a combination thereof. For example, the flame retardant may contain a phosphorus-nitrogen-based flame retardant containing ammonium polyphosphate (APP) and an inorganic flame retardant containing aluminum hydroxide.

[0052] In an exemplary embodiment, the flexible printed circuit board may further include a second adhesive layer disposed between the base substrate and the metal layer to bond the base substrate and the metal layer. The thickness of the second adhesive layer may be from 1 µm to 50 µm, 10 µm to 50 µm, or 20 µm to 40 µm, but is not limited thereto. The adhesive used in the second adhesive layer may be the same as the adhesive used in the first adhesive layer described above, and a detailed description thereof is not required.

[0053] In an exemplary embodiment, the flexible printed circuit board may further include a third adhesive layer disposed between the metal layer and the insulating layer to bond the metal layer and the insulating layer. The thickness of the third adhesive layer may be from 1 µm to 50 µm, 1 µm to 30 µm, or 5 µm to 20 µm, but is not limited thereto. An adhesive used in the third adhesive layer may be the same as the adhesive used in the first adhesive layer described above, and a detailed description thereof is omitted.

[0054] In an exemplary embodiment, the base substrate may include an insulating material. The insulating material may be one or more selected from the group consisting of polyimide, polyamideimide, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid, polycarbonate, and polyarylate, and may in particular be polyimide. The thickness of the base substrate may be from 1 µm to 50 µm, 10 µm to 50 µm, or 20 µm to 40 µm, but is not limited thereto.

[0055] In an exemplary embodiment, the metal layer may include a conductor made of copper, silver, gold, or nickel, particularly copper in terms of electrical conductivity. The metal layer may be formed by a method known in the art, e.g., by forming a thin metal film on the base substrate (or the second adhesive layer) by a method such as deposition or coating and forming a pattern by photolithography. The thickness of the metal layer may be from 1 µm to 50 µm, 10 µm to 50 µm, or 20 µm to 50 µm, but is not limited thereto.

[0056] In an exemplary embodiment, the total thickness of the flexible circuit board is not limited as long as it satisfies the above-described thickness of the individual layers, and may be, for example, from 20 µm to 500 µm, 50 µm to 250 µm, or 50 µm to 200 µm.

[0057] In an exemplary embodiment, the flexible circuit board may be electrically connected to some or all of a plurality of battery cells and may be used to transmit information about the battery cells to a battery management system (BMS). In particular, the battery module may further comprise a sensor on the battery cell for measuring the voltage and / or temperature of the battery cell and a battery management system. The flexible circuit board may be electrically connected to the sensor or the battery management system and transmit the information (voltage and / or temperature) detected by the sensor to the battery management system.

[0058] In an exemplary embodiment, the casing included in the battery module may be designed to surround the entire cell stack. The material of the casing is not particularly limited as long as it is a material with excellent thermal conductivity, and may be, for example, an aluminum-based alloy. Examples of the aluminum alloy include an Al-Mg-based aluminum alloy, an Al-Mg-Si-based aluminum alloy, an Al-Si-based aluminum alloy, and an Al-Si-Cu-based aluminum alloy. The thickness of the casing may be on the order of 10 0 mm to 10 1 mm and, as a practical example, can be in the range of 1 mm to 30 mm, but is not limited to this.

[0059] In an exemplary embodiment, a battery pack may be formed by enclosing a battery cell stack and a flexible circuit board disposed on at least one surface of the battery cell stack in a package housing.

[0060] As described above, in the battery pack with the flexible printed circuit board according to an exemplary embodiment of the present disclosure, an insulating layer having a structure in which a plurality of polyimide layers are stacked via a first adhesive layer is disposed on at least one surface of the battery cell stack, so that significantly improved insulating properties can be achieved. In particular, the secondary battery pack can ensure excellent insulating properties through the other polyimide layers even if a defect occurs in one of the plurality of polyimide layers. Since the insulating properties are maintained even if a defect occurs in all the polyimide layers, unless the defect occurs at the same location in each layer, the possibility of achieving excellent insulating properties can be significantly increased.Accordingly, the problem of safety deterioration caused by short circuits and the increased defect rate in the manufacturing process can be solved. Since two or more polyimide layers are arranged on one side of a conductive component, such as a casing in a secondary battery, no additional insulation unit is required, allowing the battery pack to have high energy density while significantly improving insulation properties.

[0061] Each component included in the secondary battery pack according to a second aspect can be used in the same manner as each component included in the battery module according to the first aspect described above, and a detailed description thereof is omitted.

[0062] In an exemplary embodiment, the battery pack is not limited to one structure and may have various forms. For example, the battery pack may have a structure such as cell-to-pack, in which the battery cell stack and the flexible circuit board are directly housed in the package case, cell-to-body, or the like. In this case, the flexible circuit board may be arranged to face the package case to improve insulation performance. Alternatively, a battery module in which a battery cell stack and a flexible circuit board are housed in a case may be housed in a package case to form a battery pack.

[0063] In an exemplary embodiment, the pack housing may be configured to surround all battery cell stacks. The housing may be formed from a metal material to provide rigidity, but is not limited thereto. For example, at least a portion of the pack housing may be formed from aluminum to improve heat dissipation.

[0064] The present disclosure will be described in detail below with reference to the accompanying drawings. However, the description is merely exemplary, and the present disclosure is not limited to the specific embodiments described by way of example.

[0065] Fig. 1 is a view showing a cross-sectional structure of a flexible printed circuit board in a conventional battery module, and Fig. 2 is a view showing a cross-sectional structure of a flexible printed circuit board in a battery module or a battery pack. Fig.3 is a view explaining the principle of improving the insulation properties of a flexible printed circuit board according to an exemplary embodiment, and Fig. 4 is a view showing the structure of a battery module according to an exemplary embodiment.

[0066] Referring to Fig.1, the flexible printed circuit board included in the conventional battery module or pack comprises a base substrate 1; a metal layer 3 disposed on the base substrate 1; an insulating layer 5 formed of a single polyimide layer disposed on the metal layer 3; an adhesive layer 2 for bonding the base substrate 1 and the metal layer 3; and an adhesive layer 4 for bonding the metal layer 3 and the insulating layer 5. When the insulating layer 5 is damaged by the occurrence of pinholes or dents in the single polyimide layer, there is a significantly high possibility of a short circuit occurring between the metal layer 3 and a conductive member 200 such as a case of the battery module or a case of the secondary battery pack.

[0067] Referring to Fig.2, a flexible printed circuit board 100 included in the battery module or pack according to an exemplary embodiment includes: a base substrate 10; a metal layer 30 disposed on the base substrate 10; an insulating layer 50 having a structure in which two polyimide layers 51 and 53 disposed on the metal layer 30 are stacked via a first adhesive layer 52; a second adhesive layer 20 for bonding the base substrate 10 and the metal layer 30; and a third adhesive layer 40 for bonding the metal layer 30 and the insulating layer 50. Fig. 2 shows the flexible printed circuit board 100 with the insulating layer 50 in which the two polyimide layers 51 and 53 are stacked, but this is only an example and the present disclosure is not limited thereto. In addition, Fig.2 illustrates the flexible printed circuit board 100 with the second adhesive layer 20 and the third adhesive layer 40, but the present disclosure is not limited thereto and does not exclude other exemplary embodiments that do not include the second adhesive layer 20 and the third adhesive layer 40.

[0068] The battery module and the battery pack according to an exemplary embodiment include the flexible printed circuit board in which an insulating layer having a structure in which two or more polyimide layers are stacked is arranged to face a conductive component such as a casing of the battery module or a casing of the secondary battery pack, so that the possibility of a short circuit occurring between the conductive component and the metal layer can be significantly reduced. Accordingly, the present disclosure can provide a battery module and a battery pack with significantly improved insulation properties. As can be seen from Fig.3, even if a defect occurs at point A of the polyimide layer 51, excellent insulation properties can be maintained by the other polyimide layer 53. Even if a defect occurs at point B of the polyimide layer 53, excellent insulation properties can be maintained by the other polyimide layer 51. Even if a defect occurs simultaneously at point A of the polyimide layer 51 and point B of the polyimide layer 53, excellent insulation properties can be maintained unless the defect occurs at the same location in each layer and point A and point B are connected to each other. That is, the battery module and the battery pack according to an exemplary embodiment can have significantly improved insulation properties by significantly reducing the possibility of a short circuit between the conductive component 200 and the metal layer 30.

[0069] Referring to Fig. 4, the battery module according to an exemplary embodiment of the present disclosure includes: a battery cell stack 310 in which a plurality of battery cells are stacked; a housing 320 that houses the battery cell stack 310; a bus bar assembly disposed on one side of the housing 320 and electrically connected to the battery cells of the battery cell stack 310; and a sensor module 340 that interconnects the bus bar assembly and a flexible circuit board 100.

[0070] The battery cells of the battery cell stack 310 are stacked and arranged in one direction within the housing 320 and electrically connected to adjacent battery cells, wherein each battery cell can deliver or store electrical energy.

[0071] The plurality of battery cells contained in the battery cell stack 310 may be electrically connected to one another via the busbar assembly. The busbar assembly may be arranged such that at least a portion of the busbar assembly faces the battery cell stack 310 in a direction perpendicular to a cell stack direction.

[0072] The busbar assembly may include a busbar 332 that electrically connects one battery cell to another, and a busbar plate 331 that supports the busbar 332. The busbar plate 331 may be connected to a side plate 321 as a conductive member that electrically connects one or more electrode tabs 311 that project outward through outlet holes of the side plate 321. As known to those skilled in the art, the busbar plate 331 may be embedded in and connected to the side plate 321, with one side open to the outside. Furthermore, the busbar plate 331 disposed on the side plate 321 may be arranged to be mutually insulated from the adjacent busbar plate disposed on the same side plate.

[0073] The bus bar 332 may include a conductive material that is electrically connected to the electrode tabs 311 of the battery cells to electrically connect the plurality of battery cells. Various welding methods, including laser welding, may be used to connect the bus bar 332 to the lead tabs. However, the connection method is not limited to welding; any connection method capable of electrically connecting the two metallic materials may be used.

[0074] A battery module 300 may also include a sensor module 340 connected to the bus bar assembly. The sensor module 340 may include a temperature sensor, a voltage sensor, or the like. The sensor module 340 may detect a status of the battery cells and output the detected information to the exterior of the battery module 300.

[0075] The sensor module 340 may include a flexible circuit board 100 that connects a pair of bus bars 332 arranged on both sides in a direction in which the electrode tabs 311 extend, a connector 341 that transmits information such as the detected voltage and temperature to the outside, and a support part 342 that supports the flexible circuit board 100 and the connector 341.

[0076] The flexible circuit board 100 can transmit and receive electrical signals for detected information by being in contact with each bus bar plate 331 arranged along an outer surface of the side plate 321. Furthermore, the flexible circuit board 100 is fixed to the side plate 321 and the support member 342, so that stress applied to the flexible circuit board 100 can be dispersed and a lifting phenomenon can be prevented, thereby minimizing damage to the flexible circuit board 100.

[0077] As described above, the flexible printed circuit board 100 according to an exemplary embodiment of the present disclosure not only significantly reduces the possibility of a defect occurring due to deformation such as folding, but also maintains excellent insulation properties even when a defect occurs in the polyimide layer in the flexible printed circuit board 100. Accordingly, the failure rate of the battery module 300 due to a defect in the flexible printed circuit board 100 can be significantly reduced, and the safety of the battery module 300 can be improved with excellent durability even under high temperatures and high pressure.

[0078] Furthermore, the flexible circuit board 100 is arranged on the battery cell stack 310 such that the insulating layer of the flexible circuit board 100 faces the conductive component, e.g., a housing (not shown), so that the battery module 300 can have excellent insulation properties without providing an additional insulation unit, thereby significantly improving the energy density per volume of the battery module.

[0079] Below, examples of the present disclosure will be described in more detail with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It is obvious to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the present disclosure, and it is obvious that these modifications and changes are included in the appended claims. (Example 1)

[0080] A flexible printed circuit board, as in Fig.2 was fabricated. Specifically, a flexible copper foil laminate (Hanwha e-ssential Corporation, HGLS-S211EM) was used in which a base substrate 10 including a polyimide film with a thickness of 25 µm, a second adhesive layer 20 with a thickness of 30 µm, and a metal layer 30 including a thin copper foil with a thickness of 35 µm with a formed pattern were sequentially stacked. As for the polyimide layers 51 and 53, a first adhesive layer 52 and a third adhesive layer 40, and two polyimide film sheets (PI Advanced Materials Co. Ltd., GF100) each containing an adhesive layer containing an epoxy-based polymer having a thickness of 10 µm and disposed on a surface of a polyimide layer having a thickness of 12.5 µm were stacked on the metal layer 30 and used. (Example 2)

[0081] A flexible printed circuit board was manufactured in the same manner as in Example 1, except that a polyimide film was used in which the thickness of the two polyimide layers 51 and 53 was 30 µm each. (Example 3)

[0082] A flexible printed circuit board was manufactured in the same manner as in Example 1, except that a flame retardant containing ammonium polyphosphate (APP) and aluminum hydroxide (Al(OH)3) was additionally contained in the first adhesive layer 52. (Example 4)

[0083] A flexible printed circuit board was manufactured in the same manner as in Example 1, except that a polyimide layer having a thickness of 12.5 µm and an adhesive layer having a thickness of 10 µm were stacked in three layers to form an insulating layer. (Comparison example 1)

[0084] A flexible printed circuit board, as in Fig.1 was manufactured. Specifically, a flexible copper foil laminate (Hanwha e-ssential Corporation, HGLS-S211EM) was used in which a base substrate 1 including a polyimide film with a thickness of 25 µm, a second adhesive layer 2 with a thickness of 30 µm, and a metal layer 30 including a thin copper film with a thickness of 35 µm with a formed pattern were sequentially stacked, and as the adhesive layer 4 and the insulating layer 5, a polyimide film (PI Advanced Materials Co. Ltd, GF100) in which an adhesive layer 4 with a thickness of 10 µm was arranged on one surface of a polyimide insulating layer 5 with a thickness of 25 µm was used. (Valuation examples)

[0085] The heat resistance of the flexible printed circuit board was evaluated by measuring the heat deflection temperature (HDT) according to ASTM D648. Specifically, the heat deflection temperature (HDT) was evaluated by placing the flexible printed circuit board manufactured in each of the examples or comparative examples on a support of a heat distortion tester (INSTRON CEAST, HV3S) and measuring the temperature when the flexible printed circuit board was deformed by 0.25 mm at a heating rate of 2 ± 0.2 °C / min while applying a bending stress of 264 psi to the center.

[0086] The breakdown voltage of the flexible printed circuit board was measured according to ASTM D 3755. Specifically, the breakdown voltage (BDV) was measured under a condition where the flexible printed circuit board manufactured in each of the examples or comparative examples was placed between electrodes of a withstand voltage tester (Model 19052, Chroma ATE Inc.) at room temperature (25 °C), and the applied voltage was increased to 5 kV / 10 s, and a voltage (kV) at which a leakage current value was 5 mA was used.

[0087] The flame retardancy rating of the flexible printed circuit board was evaluated according to the flame retardancy standard UL-94 VB.

[0088] To evaluate the mechanical properties of the flexible printed circuit board, a bending test was conducted. Specifically, when a process of folding the flexible printed circuit board manufactured in each of the examples or comparative examples in half, applying a 5 kg load to the folded flexible printed circuit board, and then unfolding a folded portion was set as a cycle and the process was repeated, the number of times the measured leakage current began to exceed 10 mA after a DC voltage of 1,000 kV was applied was confirmed. At this time, the leakage current was measured using a leakage current tester (HIOKI, ST5540).

[0089] The evaluation results are shown in Table 1. [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Comparison example 1 Number of polyimide layers contained in the insulating layer 2 2 2 3 2 1 Thickness of the polyimide layer (µm) 12,5 30 12,5 12,5 7,5 25 Heat deflection temperature (°C) 270 270 270 270 270 270 Breakdown voltage (kV) 2,5 6 2,5 3,7 1,5 0,5 Flame retardancy assessment VO VO 5 VB V-0 V-0 VO Result of the bending test 64 times 32 times 64 times 76 times 92 times 64 times

[0090] As shown in Table 1, the flexible printed circuit boards of Examples 1 to 4 were found to have excellent breakdown voltage characteristics, and even when the bending stress was applied 40 times or more, a leakage current of 10 mA or less was recorded, which demonstrated that the flexible printed circuit boards of Examples 1 to 4 had excellent insulation properties. Specifically, in the case of Examples 1 and 3, the heat distortion temperature was measured at 270°C and the breakdown voltage was measured at 2.5 kV, and when the bending stress was repeated 64 times, the leakage current of the flexible printed circuit board exceeded 10 mA, and therefore, it was found that the flexible printed circuit board maintained excellent insulation properties even when deformed.

[0091] In particular, the flexible printed circuit board of Example 3, in which a flame retardant was additionally included in the first insulating layer, exhibited flame-retardant properties with a flame retardancy rating of 5 VB, which was higher than the flame retardancy rating (V-0) of the flexible printed circuit board of Example 1.

[0092] Furthermore, in the flexible printed circuit board of Example 5, in which the thickness of the polyimide layer was 7.5 µm, the bending test result was increased by 92 times compared to Example 1, thereby improving the mechanical properties, but the breakdown voltage was reduced to 1.5 kV because the thickness of the polyimide layer was thinner than that of Example 1.

[0093] In the flexible printed circuit board of Example 4, in which the number of polyimide layers in the insulating layer was increased to three, the breakdown voltage increased to 6 kV with increasing number of stacked polyimide layers and increasing total thickness of the insulating layer compared to Example 1, but the mechanical properties deteriorated with increasing thickness of the polyimide layer, as the bending test result decreased to 32 times.

[0094] In the flexible circuit board manufactured by the method of Example 2, since the polyimide layer was thicker than that of the flexible circuit board of Example 1, the total thickness of the insulating layer increased to 60 μm, and the breakdown voltage increased to 6 kV, but when the bending stress was repeated 32 times, the leakage current of the flexible circuit board increased rapidly due to cracking according to the increased thickness, resulting in slightly lower durability than that of Example 1.

[0095] On the other hand, in Comparative Example 1, in which the flexible circuit board included a layer of polyimide film, a significantly lower breakdown voltage (0.5 kV) was demonstrated compared to Example 1, even though the thickness of the polyimide layer was 25 μm. Defects such as pinholes, dents, and scratches that occur in a single layer of polyimide film were exposed on the surface of the flexible circuit board, resulting in a significant deterioration in the insulation properties. Therefore, it was found that when the flexible circuit board of Comparative Example 1 is applied to a battery module or secondary battery pack, there is a significantly high risk of a problem in which a short circuit occurs between the conductive component facing the insulating layer and the metal layer, resulting in a loss of insulation performance.

[0096] Accordingly, in the flexible printed circuit board included in the battery module according to the present disclosure, an insulating layer was formed by stacking two or more layers of polyimide films on a metal layer, so that the flexible printed circuit board had excellent insulating performance without providing an additional insulating unit. Even if a defect occurred in the polyimide layer, the insulating performance was maintained by the other polyimide layers, so that the insulating performance and the defect rate of the manufactured battery module were improved. In particular, since a flexible printed circuit board with excellent insulating properties is manufactured even when polyimide is stacked in two layers, the thickness of the flexible printed circuit board can be minimized, so that the capacity per unit volume of the battery module incorporating it can be improved.

[0097] As set forth above, the battery module of the present disclosure includes the flexible printed circuit board having excellent insulation properties, so that the battery module can have significantly improved insulation properties.

[0098] Furthermore, the battery module of the present disclosure can have significantly improved safety and a significantly lower defect rate in the manufacturing process.

[0099] Another aspect of the present invention relates to a battery module comprising: a cell stack containing a plurality of battery cells; a flexible circuit board arranged on at least one surface of the cell stack, wherein the flexible circuit board comprises a base substrate, a metal layer formed on the base substrate, and an insulating layer formed on the metal layer, wherein the insulating layer comprises a structure in which a plurality of polyimide layers are stacked via a first adhesive layer arranged between adjacent polyimide layers; and a housing that defines an internal space for accommodating the cell stack and the flexible printed circuit board.

[0100] The above description is merely an example of the application of the principles of the present disclosure, and other configurations may be incorporated without departing from the scope of the present disclosure. [Detailed description of the main elements] 1, 10 Base substrate 3, 30 metal layer 2, 4 adhesive layer 5.50 Insulation layer 20 Second adhesive layer 51, 53 polyimide layer 100 Flexible Printed Circuit Boards A, B Defect 310 battery cell stacks 320 housing 331 Busbar plate 340 sensor module 342 carrier part 40 Third adhesive layer 52 First adhesive layer 200 Conductive component 300 battery module 311 Electrode tongue 321 side plate 332 busbar 341 connectors

Claims

[1] A battery module comprising: a cell stack containing a plurality of battery cells; a flexible printed circuit board disposed on at least one surface of the cell stack; and a housing with an internal space in which the cell stack and the flexible printed circuit board are housed, wherein the flexible printed circuit board comprises a base substrate, a metal layer arranged on the base substrate and an insulating layer arranged on the metal layer, and the insulating layer includes a plurality of stacked polyimide layers and a first adhesive layer disposed between the adjacent polyimide layers. [2] The battery module according to claim 1, wherein the sum of the thicknesses of the plurality of polyimide layers is 5 µm to 50 µm. [3] Battery module according to one of claims 1 or 2, wherein the thickness of the first adhesive layer is 1 µm to 50 µm. [4] The battery module according to any one of claims 1 to 3, wherein the thickness of the insulating layer is 15 µm to 100 µm. [5] The battery module according to any one of claims 1 to 4, wherein the flexible printed circuit board has a heat distortion temperature of 200°C or higher as measured according to ASTM D648, a breakdown voltage of 4000 V to 6000 V as measured according to ASTM D 3755, and a flame retardancy rating of V-1 or higher as evaluated according to the flame retardancy standard UL-94 VB. [6] The battery module according to any one of claims 1 to 4, wherein the insulating layer has a structure in which two polyimide layers are stacked over the first adhesive layer. [7] The battery module according to any one of claims 1 to 6, wherein the thickness of each of the polyimide layers is 5 µm to 15 µm. [8] The battery module according to any one of claims 1 to 7, wherein the first adhesive layer contains an adhesive and a flame retardant. [9] The battery module according to any one of claims 1 to 8, wherein the flame retardant contains at least one of an organic flame retardant, an inorganic flame retardant, or a combination thereof. [10] The battery module according to any one of claims 1 to 9, wherein the organic flame retardant contains one or more selected from the group consisting of a phosphorus-based flame retardant, a nitrogen-based flame retardant, a phosphorus-nitrogen-based flame retardant, and a halogen-based flame retardant. [11] Battery module according to one of claims 1 to 10, wherein the inorganic flame retardant contains a metal oxide. [12] The battery module according to any one of claims 1 to 11, wherein the flexible circuit board further includes a second adhesive layer disposed between the base substrate and the metal layer. [13] The battery module according to any one of claims 1 to 12, wherein the flexible circuit board further includes a third adhesive layer disposed between the metal layer and the insulating layer. [14] The battery module according to any one of claims 1 to 13, wherein the base substrate contains an insulating material. [15] The battery module according to claim 1, wherein the flexible circuit board is arranged on the cell stack such that the insulating layer and the housing face each other.

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