Composite connecting sheet for battery cell and battery cell

Abstract

The invention relates to the technical field of batteries, in particular to a composite connecting piece for a battery cell and the battery cell. A composite connecting piece for a battery cell comprises a first structure or a second structure, the first structure comprises a laminated composite structure of a structure A and a metal layer structure, the structure A is selected from at least one of a composite metal foil and a polymer PTC film, and the second structure comprises a laminated composite structure of a plurality of composite metal foils. The composite metal foil comprises a polymeric membrane layer and conductive metal layers located on the surfaces of the two sides of the polymeric membrane layer. The composite connecting sheet is provided with an arrow-shaped fusing structure. The composite connecting piece for the battery cell has high current carrying capacity, utilizes the skin effect of current, has the overcurrent capacity 5-6 times that of pure metal with the same size, has a thermal safety turn-off function, has the high-flexibility physical characteristic, can realize 8C fast charging and no thermal runaway, and improves the volumetric specific energy of the battery cell by more than 2.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a composite connecting sheet for a battery cell and a battery cell. Background Art

[0002] With the application and promotion of new energy vehicles, the problem of charging resources is becoming increasingly tense. In order to improve the efficiency of charging piles and enhance the user's charging experience, the vehicle application end has put forward higher and higher requirements on the fast charging characteristics of power batteries. The next generation of charging capacity is expected to be increased to more than 8C.

[0003] The traditional battery cover and the winding core are connected by a copper-aluminum connector. Considering the fuse safety setting under high current conditions, the conventional copper-aluminum connector of the battery cell cannot simultaneously ensure high overcurrent and high current safety, as well as temperature rise control under fast charging conditions. This poses a great challenge to the thermal safety boundary and thermal application boundary control of the battery cell. Under fast charging conditions, the battery cell temperature rise is too high, which may accelerate the decay rate of the battery cell throughout its life cycle, and the thermal safety risk of the battery cell is greatly increased.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One object of the present invention is to provide a composite connecting sheet for a battery cell, so as to solve the problem that conventional battery cell connecting sheets in the prior art cannot simultaneously ensure high overcurrent and large current safety as well as temperature rise control under fast charging conditions.

[0006] Another object of the present invention is to provide a battery cell.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] A composite connecting sheet for a battery cell, the composite connecting sheet for a battery cell comprising a first structure or a second structure, the first structure comprising a stacked composite structure of a structure A and a metal layer structure, the structure A being selected from at least one of a composite metal foil and a polymer PTC film, the second structure comprising a stacked composite structure of multiple composite metal foils, the composite metal foil comprising a polymer film layer and a conductive metal layer located on both side surfaces of the polymer film layer; the composite connecting sheet is provided with an arrow-shaped fuse structure.

[0009] In some embodiments, the polymer film layer includes at least one of polyethylene terephthalate, polypropylene, nylon and polyimide.

[0010] In some embodiments, the conductive metal layer is at least one of a copper layer, an aluminum layer, and a nickel layer.

[0011] In some embodiments, the composite metal foil has a thickness of 3 to 500 μm, wherein the conductive metal layer has a thickness of 1 to 20 μm.

[0012] In some implementations, the metal layer structure is provided with the arrow-shaped fuse structure.

[0013] In some embodiments, the polymer PTC film includes a polymer material, a conductive agent and a filler, wherein the mass content of the polymer material is 5% to 80%, and the mass content of the conductive agent is 0.5% to 50%.

[0014] In some embodiments, the polymer material includes at least one of high-density polyethylene, epoxy resin and polyethylene wax.

[0015] In some embodiments, the conductive agent includes at least one of carbon black, metal wire, metal powder, carbon nanotubes, carbon fiber and graphene.

[0016] In some embodiments, the filler includes at least one of BaCO3, TiO2, BaTiO3, SrCO3, PbO, Pb3O4, Y2O3, Nb2O5, Al2O3, SiO2, TiO2, Mn(NO3)2 and Li2CO3.

[0017] In some embodiments, the filler includes, by weight, 55 to 65 parts of BaTiO3, 0.5 to 2 parts of BaCO3, 0.5 to 2 parts of PbO, 0.5 to 2 parts of Y2O3, 0.5 to 2 parts of Al2O3, and 0.5 to 2 parts of Li2CO3.

[0018] In some implementations, the polymer PTC film has a thickness of 0.1 to 2 mm.

[0019] In some embodiments, the metal layer structure includes a metal copper layer or a metal aluminum layer.

[0020] In some embodiments, the connection method between the A structure and the metal layer structure, and the connection method between the plurality of composite metal foils each independently include at least one of adhesive, riveting, ultrasonic welding and laser welding.

[0021] In some embodiments, the current capacity of the composite connecting sheet for the battery cell is 12 to 30 A / mm 2 .

[0022] A battery cell comprises the composite connecting sheet for the battery cell.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The composite connecting piece for the battery cell of the present invention has a high current carrying capacity. By utilizing the current "skin effect", its current carrying capacity is 5-6 times that of pure metal of the same size. The composite connecting piece has an arrow-shaped fuse structure, which can realize the thermal safety shutdown function. Under super-threshold current or super-threshold temperature conditions, the thermistor material part can be set to break the circuit at a certain temperature, greatly improving the Fuse startup accuracy. The melting temperature consistency accuracy of the composite connecting piece can be improved by 50% compared with the pure metal Fuse, ensuring the safety characteristics of the battery cell under super-threshold current. It has highly flexible physical characteristics, can achieve 8C fast charging, no thermal runaway, and the battery cell volume energy is increased by more than 2.5%.

[0025] (2) The battery cell of the present invention contains the above-mentioned composite connecting sheet. According to the same current carrying capacity, its thickness is 1 / 5 to 1 / 4 of the thickness of the conventional connecting sheet. The height of the assembled battery cell electrode sheet can be increased to more than 2.5% relative to the height of the conventional battery cell electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a schematic diagram of the structure of the composite connecting sheet in Example 1 of the present invention;

[0028] Figure 2 A schematic diagram of the structure of the battery cell in each embodiment 1 of the present invention;

[0029] Figure 3 Schematic diagram of the structure of the composite connecting sheet in Example 2 of the present invention, wherein (a) is a schematic top view, and (b) is a schematic front view;

[0030] Figure 4 Schematic diagram of the structure of the composite connecting sheet in Example 3 of the present invention, wherein (c) is a top view schematic diagram, and (d) is a front view schematic diagram.

[0031] Reference numerals:

[0032] 1-composite connecting piece, 101-composite metal foil, 1011-conductive metal layer, 1012-polymer film layer, 102-metal layer structure, 103-polymer PTC film, 104-arrow-shaped fuse structure, 2-shell, 3-cover plate pole, 4-pole piece stack, 5-pole ear. DETAILED DESCRIPTION

[0033] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0034] According to one aspect of the present invention, the present invention relates to a composite connecting sheet for a battery cell, the composite connecting sheet for a battery cell comprises a first structure or a second structure, the first structure comprises a stacked composite structure of a structure A and a metal layer structure, the structure A is selected from at least one of a composite metal foil and a polymer PTC film, the second structure comprises a stacked composite structure of multiple composite metal foils, the composite metal foil comprises a polymer film layer and a conductive metal layer located on both side surfaces of the polymer film layer; the composite connecting sheet is provided with an arrow-shaped fuse structure.

[0035] The composite connecting sheet for the battery cell of the present invention has high current carrying capacity and utilizes the current "skin effect". Its current carrying capacity is 5-6 times that of pure metal of the same size and has a thermal safety shutdown function. It also has highly flexible physical characteristics, can achieve 8C fast charging, no thermal runaway, and the battery cell volume energy ratio is increased by more than 2.5%.

[0036] The arrow-shaped fuse structure in the composite connecting piece of the present invention can break the circuit at a certain temperature when the thermistor material part is under super-threshold current or super-threshold temperature conditions, which greatly improves the fuse startup accuracy. The optimized composite thermistor connecting piece has a 50% higher consistency in the fuse temperature than the pure metal fuse, ensuring the safety characteristics of the battery cell under super-threshold current.

[0037] In some embodiments, the metal layer structure is provided with the arrow-shaped fuse structure. The arrow-shaped fuse structure refers to: a first notch and a second notch are respectively provided on two opposite long sides of the metal layer structure, the first notch and the second notch are arranged oppositely, the shapes of the first notch and the second notch are pentagonal, and the angles of the vertex angles of the first notch and the second notch relative to each other are 40° to 120°, for example, 40°, 60°, 70°, 80°, 90°, 100°, 120°, etc. The angles of each angle of the pentagon from the vertex angle are 45° to 120°, 120° to 160°, 90°, 90°, 120° to 160° in a counterclockwise direction. In some embodiments, the first notch and the second notch of the arrow-shaped fuse structure involved in each embodiment are the same size, the angle of the relative vertex angle is 90°, and the angles of each angle of the pentagon of the first notch and the second notch from the vertex angle are 90°, 135°, 90°, 90°, 135° in a counterclockwise direction.

[0038] In some embodiments, the polymer film layer includes at least one of polyethylene terephthalate (PET), polypropylene (PP), nylon and polyimide (PI).

[0039] In some embodiments, the conductive metal layer is at least one of a copper layer, an aluminum layer, and a nickel layer.

[0040] In some embodiments, the composite connecting sheet for the battery cell includes a positive composite connecting sheet and a negative composite connecting sheet.

[0041] In some embodiments, the composite metal foil includes Cu layer-PET layer-Cu layer, Cu layer-PP layer-Cu layer, Cu layer-PI layer-Cu layer, Al layer-PET layer-Al layer, Al layer-PP layer-Al layer, Al layer-nylon layer-Al layer, Al layer-PI layer-Al layer.

[0042] In some embodiments, the thickness of the composite metal foil is 3 to 500 μm, including but not limited to 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 90 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 500 μm, etc. Wherein, the thickness of the conductive metal layer is 1 to 20 μm, such as 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.

[0043] In some embodiments, the thickness of the Cu layer-PET layer-Cu layer is 3-300 μm, preferably 5-10 μm. In some embodiments, the thickness of the Al layer-PET layer-Al layer is 5-500 μm, preferably 8-15 μm.

[0044] In some embodiments, the composite metal foil has multiple layers, for example, 2 layers, 5 layers, 10 layers, 20 layers, 21 layers, 22 layers, 23 layers, 24 layers, 25 layers, 26 layers, 27 layers, 28 layers, 29 layers, 30 layers, 50 layers, etc.

[0045] In some embodiments, the polymer PTC film includes a polymer material, a conductive agent and a filler, wherein the mass content of the polymer material is 5% to 80%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, etc., or any range between the two. The mass content of the conductive agent is 0.5% to 50%, such as 0.5%, 1%, 2%, 5%, 10%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., or any range between the two.

[0046] In some embodiments, the polymer material includes at least one of high-density polyethylene, epoxy resin, and polyethylene wax, such as a combination of high-density polyethylene and epoxy resin, or a combination of epoxy resin and polyethylene wax.

[0047] In some embodiments, the conductive agent includes at least one of carbon black, metal wire, metal powder, carbon nanotube, carbon fiber and graphene, such as carbon black and carbon nanotube, carbon fiber and graphene, carbon black, carbon nanotube and graphene.

[0048] In some embodiments, the filler includes at least one of BaCO3, TiO2, BaTiO3, SrCO3, PbO, Pb3O4, Y2O3, Nb2O5, Al2O3, SiO2, TiO2, Mn(NO3)2 and Li2CO3, such as BaCO3 and TiO2, SrCO3 and PbO, Nb2O5, Al2O3 and SiO2, etc.

[0049] In some embodiments, the filler includes, by weight, 55 to 65 parts of BaTiO3, 0.5 to 2 parts of BaCO3, 0.5 to 2 parts of PbO, 0.5 to 2 parts of Y2O3, 0.5 to 2 parts of Al2O3, and 0.5 to 2 parts of Li2CO3. In some embodiments, BaTiO3 is 55, 58, 60, 63 or 65 parts, BaCO3 is 0.5, 0.8, 1, 1.2, 1.5, 1.8 or 2 parts, PbO is 0.5, 0.8, 1, 1.5, 1.8 or 2 parts, Y2O3 is 0.5, 0.8, 1, 1.2, 1.5, 1.8 or 2 parts, Al2O3 is 0.5, 0.8, 1, 1.2, 1.5, 1.8 or 2 parts, and Li2CO3 is 0.5, 0.8, 1, 1.2, 1.5, 1.8 or 2 parts.

[0050] In some embodiments, the polymer PTC film has a thickness of 0.1 to 2 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, etc.

[0051] In some embodiments, a method for preparing a polymer PTC film comprises: mixing a polymer material with an organic solvent, wherein the organic solvent comprises at least one of NMP, acetone, and xylene, to obtain a glue having a solid content of 8% to 12% (e.g., 8%, 9%, 10%, 11%, or 12%), adding a conductive agent and a filler, and stirring evenly to obtain a coating slurry, wherein the coating slurry has a fineness of 18 to 22 μm (e.g., 18 μm, 19 μm, 20 μm, or 21 μm), a viscosity of 2800 to 3300 cp (e.g., 2800 cp, 2900 cp, 3000 cp, or 3100 cp, etc.), and a solid content of 70% to 80% (e.g., 70%, 72%, 75%, or 80%, etc.); coating and drying the coating slurry at a drying temperature of 70 to 80° C. (e.g., 72° C., 75° C., or 80° C., etc.) to obtain a polymer PTC film.

[0052] In some embodiments, the preparation method of the polymer PTC film involved in the embodiment includes: mixing the polymer material with an organic solvent, the organic solvent is acetone, to obtain a glue solution with a solid content of 10%, and then adding a conductive agent and a filler, stirring evenly to obtain a coating slurry, the coating slurry has a fineness of 20μm, a viscosity of 3000cp, and a solid content of 75%, and the coating slurry is coated and dried at a drying temperature of 75°C to obtain a polymer PTC film.

[0053] In some embodiments, the metal layer structure includes a metal copper layer or a metal aluminum layer. The copper layer can be used to obtain a negative electrode connecting piece, and the aluminum layer can be used to obtain a positive electrode connecting piece.

[0054] In some embodiments, the connection method between the plurality of A structures and the plurality of metal layer structures, and the connection method between the plurality of composite metal foils each independently include at least one of adhesive, riveting, ultrasonic welding and laser welding. The present invention can connect and composite the layers by means of adhesive, riveting, ultrasonic welding and laser welding to obtain a connecting sheet.

[0055] In some embodiments, the current capacity of the composite connecting sheet for the battery cell is 12 to 30 A / mm 2 , for example 12A / mm 2 , 15A / mm 2 , 20A / mm 2 , 25A / mm 2 、30A / mm 2 Etc. The battery cell using this connecting sheet structure has a normal current capacity of ≥8C.

[0056] According to one aspect of the present invention, the present invention relates to a battery cell, comprising the above-mentioned composite connecting sheet for the battery cell.

[0057] According to the same current capacity, the thickness of the connecting piece of the present invention is 1 / 5 to 1 / 4 of the thickness of the conventional connecting piece, and the height of the assembled battery cell pole piece is increased by more than 2.5% compared with the height of the conventional battery cell pole piece.

[0058] In some embodiments, the battery cell of the present invention includes a shell and a pole sheet stack located inside the shell; a cover plate pole is provided on the back of the top cover plate of the shell, including a positive cover plate pole and a negative cover plate pole; the pole sheet stack includes a positive pole sheet stack and a negative pole sheet stack, the positive pole sheet stack is provided with a positive electrode ear, the negative pole sheet stack is provided with a negative electrode ear, the positive electrode ear is connected to the positive cover plate pole through a positive composite connecting piece, and the negative electrode ear is connected to the negative cover plate pole through a negative composite connecting piece.

[0059] The following is further explained in conjunction with specific embodiments and comparative examples.

[0060] Example 1

[0061] A battery cell, such as Figure 2 As shown, the cell size is 44.1*197*109.7, including a shell 2 and a pole piece stack 4 located inside. The cover plate of the shell 2 is provided with a cover plate pole 3. The pole piece stack 4 has positive and negative pole ears 5, and the positive and negative pole ears 5 are connected to the cover plate pole 3 through a composite connecting piece. The positive electrode adopts ternary NCM, and the negative electrode adopts 450mAh / g fast-charge graphite + nano silicon carbon. The stacked structure is assembled, with 211 positive stacks and 212 negative stacks. The battery pack has a total of 192 cells, with a total of 105.6kWh of electricity.

[0062] The battery cell includes a positive electrode composite connecting sheet 1 and a negative electrode composite connecting sheet 1, such as Figure 1 As shown, the positive electrode composite connecting sheet 1 adopts a laminated composite structure of multiple composite metal foils 101, and a single composite metal foil 101 includes a polymer film layer 1012 and a conductive metal layer 1011 located on both sides thereof, which is an Al layer-PET layer-Al layer. The thickness of a single composite metal foil 101 is 6 μm, and the number of layers is 100. The negative electrode composite connecting sheet 1 adopts a laminated composite structure of multiple composite metal foils 101, and a single composite metal foil 101 is a Cu layer-PET layer-Cu layer. The thickness of a single copper composite foil is 6 μm, and the number of layers is 100. The thickness of the positive electrode composite connecting sheet 1 is 0.63 mm, and the thickness of the negative electrode composite connecting sheet 1 is 0.63 mm. The positive electrode composite connecting sheet 1 and the negative electrode composite connecting sheet 1 are laser welded respectively. The composite metal foil has a high-precision thermal sensitive characteristic. When the temperature rises to a certain level, thermal expansion occurs, blocking the current, thereby having the traditional Fuse over-limit current shutdown function, which can ensure that under the condition of over-limit current, no thermal runaway safety problem occurs.

[0063] Example 2

[0064] A battery cell with a size of 44.1*197*109.7, including a shell 2 and a pole piece stack 4 located inside. The cover plate of the shell 2 is provided with a cover plate pole 3. The pole piece stack 4 has positive and negative pole ears 5. The positive and negative pole ears 5 are connected to the cover plate pole 3 through a composite connecting sheet. The positive electrode adopts ternary NCM, and the negative electrode adopts 450mAh / g fast-charge graphite + nano silicon carbon. The stacked structure is used for assembly. The number of positive electrode stacks is 211, and the number of negative electrode stacks is 212. The battery pack has a total of 192 cells, with a total power of 103kWh.

[0065] The battery cell includes a positive electrode composite connecting sheet 1 and a negative electrode composite connecting sheet 1, such as Figure 3 As shown, (a) represents a schematic diagram of a top view, and (b) represents a schematic diagram of a front view; the positive electrode composite connecting sheet 1 is a laminated composite structure of a polymer PTC film 103 and an aluminum metal layer structure 102, and the negative electrode composite connecting sheet 1 is a laminated composite structure of a polymer PTC film 103 and a copper metal layer structure 102, which are obtained by laser welding respectively. The polymer PTC film 103 includes a polymer material, a conductive agent and a filler, wherein the mass content of the polymer material is 55%, the mass content of the conductive agent is 35%, and the filler is 10%. In terms of mass fractions, the filler includes 60 parts of BaTiO3, 1 part of BaCO3, 1 part of PbO, 1 part of Y2O3, 1 part of Al2O3, and 1 part of Li2CO3; the polymer material is epoxy resin, and the conductive agent is carbon fiber. The thickness of the positive composite connecting sheet 1 is 1.0 mm, the thickness of the polymer PTC film 103 is 0.5 mm, the thickness of the negative composite connecting sheet 1 is 1.0 mm, and the thickness of the polymer PTC film 103 is 0.2 mm. The aluminum metal layer structure 102 and the copper metal layer structure 102 are respectively arranged with arrow-shaped fuse structures 104 (fuse functional structures).

[0066] Example 3

[0067] A battery cell with a size of 44.1*197*109.7, including a shell 2 and a pole piece stack 4 located inside. The cover plate of the shell 2 is provided with a cover plate pole 3. The pole piece stack 4 has positive and negative pole ears 5. The positive and negative pole ears 5 are connected to the cover plate pole 3 through a composite connecting sheet. The positive electrode adopts ternary NCM, and the negative electrode adopts 450mAh / g fast-charge graphite + nano silicon carbon. The stacked structure is used for assembly. The number of positive electrode stacks is 211, and the number of negative electrode stacks is 212. The battery pack has a total of 192 cells, with a total power of 103kWh.

[0068] The battery cell includes a positive electrode composite connecting sheet 1 and a negative electrode composite connecting sheet 1, such as Figure 4As shown, (c) represents a schematic diagram of a top view, and (d) represents a schematic diagram of a front view; the positive electrode composite connecting sheet 1 includes a composite structure in which a plurality of metal composite foils (Al layer-PET-Al layer), a polymer PTC film 103 and a metal layer structure 102 (Al layer) are stacked in sequence. The negative electrode composite connecting sheet 1 includes a composite structure in which a plurality of metal composite foils (Cu layer-PET-Cu layer), a polymer PTC film 103 and a metal layer structure 102 (Cu layer) are stacked in sequence. The composite connecting sheet 1 and the negative electrode composite connecting sheet 1 are obtained by laser welding, respectively. Among them, the polymer PTC film 103 includes a polymer material, a conductive agent and a filler, the mass content of the polymer material is 60%, the mass content of the conductive agent is 35%, and the filler is 5%. In terms of mass fractions, the filler includes 60 parts of BaTiO3, 1 part of BaCO3, 1 part of PbO, 1 part of Y2O3, 1 part of Al2O3, and 1 part of Li2CO3; the polymer material is polyethylene wax, and the conductive agent is graphene. The thickness of the positive electrode composite connecting sheet 1 is 1.5 mm, the thickness of the metal layer structure 102 (Al layer) is 1.0 mm, the thickness of the polymer PTC film 103 is 0.38 mm, the thickness of the single-layer composite metal foil 101 is 0.006 mm, the number of layers is 20, and the total thickness of the composite metal foil 101 is 0.12 mm; the total thickness of the negative electrode composite connecting sheet 1 is 1.2 mm, the thickness of the metal layer structure 102 (Cu layer) is 1.0 mm, the thickness of the polymer PTC film 103 is 0.14 mm, the thickness of the single-layer composite metal foil 101 is 0.006 mm, the number of layers is 10, and the total thickness of the composite metal foil 101 is 0.06 mm. The metal layer structure 102 (Al layer) of the positive electrode composite connecting sheet and the metal layer structure 102 (Cu layer) of the negative electrode composite connecting sheet are respectively arranged with an arrow-shaped fuse structure 104 (Fuse functional structure).

[0069] Example 4

[0070] A battery cell, which is different from Example 3 in that:

[0071] The polymer PTC film 103 includes a polymer material, a conductive agent and a filler. The mass content of the polymer material is 30%, the mass content of the conductive agent is 5%, and the filler is 65%. In terms of mass parts, the filler includes 55 parts of BaTiO3, 0.5 parts of BaCO3, 1.5 parts of PbO, 0.5 parts of Y2O3, 1.5 parts of Al2O3, and 2 parts of Li2CO3; the polymer material is epoxy resin, and the conductive agent is carbon fiber.

[0072] Example 5

[0073] A battery cell, which is different from Example 3 in that:

[0074] The polymer PTC film 103 includes a polymer material, a conductive agent and a filler. The mass content of the polymer material is 30%, the mass content of the conductive agent is 5%, and the filler is 65%. In terms of mass fractions, the filler includes 65 parts of BaTiO3, 2 parts of BaCO3, 0.5 parts of PbO, 1.5 parts of Y2O3, 0.5 parts of Al2O3, and 1.5 parts of Li2CO3; the polymer material is epoxy resin, and the conductive agent is carbon fiber.

[0075] Example 6

[0076] A battery cell, which is different from Example 3 in that:

[0077] The polymer PTC film 103 includes a polymer material, a conductive agent and a filler. The mass content of the polymer material is 50%, the mass content of the conductive agent is 45%, and the filler is 5%. The filler is SrCO3.

[0078] Comparative Example 1

[0079] A battery cell with a size of 44.1*197*109.7, a ternary NCM positive electrode, a 450mAh / g fast-charging graphite + nano silicon carbon negative electrode, and a laminated structure. The positive electrode laminates are 211 sheets, and the negative electrode is 212 sheets. The battery pack has a total of 192 cells, with a total power of 103kWh.

[0080] The traditional connecting piece structure is adopted. The thickness of the positive aluminum connecting piece is 1.5mm, and the thickness of the negative copper connecting piece is 1.2mm. The connecting pieces are all made of pure metal. The connecting piece cannot be equipped with a fuse function.

[0081] Comparative Example 2

[0082] A battery cell with a size of 44.1*197*109.7, a ternary NCM positive electrode, a 450mAh / g fast-charging graphite + nano silicon carbon negative electrode, and a laminated structure. The positive electrode laminates are 211 sheets, and the negative electrode is 212 sheets. The battery pack has a total of 192 cells, with a total power of 103kWh.

[0083] The traditional connecting piece structure is adopted. The thickness of the positive aluminum connecting piece is 1.5mm and the thickness of the negative copper connecting piece is 1.2mm. The connecting pieces are all made of pure metal. The connecting piece Fuse function is set by controlling the minimum cross-sectional size. Connecting piece arrangement Fuse function.

[0084] Experimental example

[0085] The performance of the battery cells of each embodiment and comparative example was tested, and the test results are shown in Table 1.

[0086] Table 1 Performance test results

[0087]

[0088] It can be seen from Table 1 that the composite connecting sheet for the battery cell of the present invention has a high current carrying capacity, utilizes the current "skin effect", has a strong current passing capacity, and has an excellent thermal safety shutdown function, can achieve 8C fast charging without thermal runaway, and the volume energy of the battery cell is increased by more than 2.5%.

[0089] In Comparative Example 1, in order to ensure high current, the connecting piece cannot be arranged with a fuse function, and thermal safety under over-limit current cannot be ensured, which creates a safety risk under the condition of over-limit current.

[0090] In Comparative Example 2, a Fuse structure is set to ensure the safety of over-limit current, and there is no over-current heating problem, but it cannot meet the high current carrying capacity.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite connecting sheet for a battery cell, characterized in that: The composite connecting sheet for the battery cell comprises a first structure or a second structure, wherein the first structure comprises a stacked composite structure of structure A and a metal layer structure, wherein structure A is selected from at least one of a composite metal foil and a polymer PTC film, and the second structure comprises a stacked composite structure of multiple composite metal foils, wherein the composite metal foil comprises a polymer film layer and a conductive metal layer located on both side surfaces of the polymer film layer; and the composite connecting sheet is provided with an arrow-shaped fuse structure.

2. The composite connecting sheet for battery cells according to claim 1, characterized in that: Contains at least one of the following features (1) to (4): (1) The polymer film layer includes at least one of polyethylene terephthalate, polypropylene, nylon and polyimide; (2) The conductive metal layer is at least one of a copper layer, an aluminum layer and a nickel layer; (3) The thickness of the composite metal foil is 3 to 500 μm, wherein the thickness of the conductive metal layer is 1 to 20 μm; (4) The metal layer structure is provided with the arrow-shaped fuse structure.

3. The composite connecting sheet for a battery cell according to claim 1, characterized in that: The polymer PTC film comprises a polymer material, a conductive agent and a filler, wherein the mass content of the polymer material is 5% to 80%, and the mass content of the conductive agent is 0.5% to 50%.

4. The composite connecting sheet for battery cells according to claim 3, characterized in that: Contains at least one of the following features (1) to (2): (1) The polymer material includes at least one of high-density polyethylene, epoxy resin and polyethylene wax; (2) The conductive agent includes at least one of carbon black, metal wire, metal powder, carbon nanotubes, carbon fiber and graphene; (3) The filler includes at least one of BaCO3, TiO2, BaTiO3, SrCO3, PbO, Pb3O4, Y2O3, Nb2O5, Al2O3, SiO2, TiO2, Mn(NO3)2 and Li2CO3.

5. The composite connecting sheet for battery cell according to claim 4, characterized in that: In terms of mass fractions, the filler includes 55-65 parts of BaTiO3, 0.5-2 parts of BaCO3, 0.5-2 parts of PbO, 0.5-2 parts of Y2O3, 0.5-2 parts of Al2O3, and 0.5-2 parts of Li2CO3.

6. The composite connecting sheet for battery cell according to claim 3, characterized in that: The thickness of the polymer PTC film is 0.1-2 mm.

7. The composite connecting sheet for a battery cell according to claim 1, characterized in that: The metal layer structure includes a metal copper layer or a metal aluminum layer.

8. The composite connecting sheet for a battery cell according to claim 1, characterized in that: The connection method between the A structure and the metal layer structure, and the connection method between the plurality of composite metal foils each independently include at least one of adhesive, riveting, ultrasonic welding and laser welding.

9. The composite connecting sheet for a battery cell according to claim 1, characterized in that: The current capacity of the composite connecting sheet for the battery core is 12 to 30 A / mm 2 .

10. A battery cell, characterized in that: The invention comprises the composite connecting sheet for a battery cell according to any one of claims 1 to 9.

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