A composite connector for battery cells and a battery cell

Abstract

This invention relates to the field of battery technology, specifically to a composite connector for battery cells and a battery cell. The composite connector for battery cells includes a first structure or a second structure. The first structure includes a laminated composite structure of structure A and a metal layer structure, wherein structure A is selected from at least one of composite metal foil and polymer PTC film. The second structure includes a laminated composite structure of multiple composite metal foils, wherein the composite metal foil includes a polymer film layer and conductive metal layers located on both sides of the polymer film layer. The composite connector is provided with an arrow-shaped fusion structure. The composite connector for battery cells of this invention has high current carrying capacity, utilizing the current "skin effect," its current carrying capacity is 5-6 times that of pure metal of the same size, and it has a thermal safety shutdown function. It also possesses highly flexible physical characteristics, enabling 8C fast charging, no thermal runaway, and an increase in battery cell volumetric energy density of more than 2.5%.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite connector for battery cells and a battery cell. Background Technology

[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 side has put forward increasingly higher requirements for the fast charging characteristics of power batteries. The next generation of charging capabilities is expected to be improved to 8C or above.

[0003] Traditional battery covers and cores are connected by copper-aluminum connectors. Considering fuse safety settings under high current conditions, conventional copper-aluminum connectors cannot simultaneously guarantee safety under high overcurrent and high current conditions, as well as temperature rise control under fast charging conditions. This poses a significant challenge to the control of the cell's thermal safety and thermal application boundaries. Under fast charging conditions, excessively high cell temperature rise may accelerate the cell's degradation rate throughout its lifespan, greatly increasing the cell's thermal safety risks.

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

[0005] One objective of this invention is to provide a composite connector for battery cells, thereby solving the problem that conventional battery cell connectors in the prior art cannot simultaneously ensure safety under high overcurrent and high current conditions 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 objectives of the present invention, the following technical solution is adopted:

[0008] A composite connector for battery cells includes a first structure or a second structure. The first structure includes a laminated composite structure of structure A and a metal layer structure. Structure A is selected from at least one of composite metal foil and polymer PTC film. The second structure includes a laminated composite structure of multiple composite metal foils. The composite metal foil includes a polymer film layer and conductive metal layers located on both sides of the polymer film layer. The composite connector is provided with an arrow-shaped fusion structure.

[0009] In some embodiments, the polymeric membrane layer comprises 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 thickness of the composite metal foil is 3 to 500 μm, wherein the thickness of the conductive metal layer is 1 to 20 μm.

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

[0013] In some embodiments, the polymeric PTC membrane comprises a polymeric material, a conductive agent, and a filler, wherein the polymeric material has a mass content of 5% to 80%, and the conductive agent has a mass content of 0.5% to 50%.

[0014] In some embodiments, the polymeric 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 selected from BaCO3, TiO2, BaTiO3, SrCO3, PbO, Pb3O4, Y2O3, Nb2O5, Al2O3, SiO2, TiO2, Mn(NO3)2, and Li2CO3.

[0017] In some embodiments, the filler comprises, by mass parts, 55-65 parts BaTiO3, 0.5-2 parts BaCO3, 0.5-2 parts PbO, 0.5-2 parts Y2O3, 0.5-2 parts Al2O3, and 0.5-2 parts Li2CO3.

[0018] In some embodiments, the thickness of the polymer PTC film is 0.1 to 2 mm.

[0019] In some embodiments, the metal layer structure includes a copper layer or an 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 includes at least one of adhesive, riveting, ultrasonic welding, and laser welding.

[0021] In some embodiments, the current-carrying capacity of the composite connector for the battery cell is 12–30 A / mm. 2 .

[0022] A battery cell, comprising the composite connecting piece for the battery cell.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The composite connector for the battery cell of the present invention has high current carrying capacity. Utilizing the current "skin effect", its overcurrent capacity is 5-6 times that of pure metal of the same size. The composite connector has an arrow-shaped fuse structure, which can realize thermal safety shutdown function. Under the conditions of over-threshold current or over-threshold temperature, the thermistor part can be disconnected at a fixed temperature, which greatly improves the start-up accuracy of the fuse. The fuse temperature consistency accuracy of the composite connector can be improved by 50% compared with pure metal fuse, ensuring the safety characteristics of the battery cell under over-threshold current. It has high flexibility physical characteristics, which can realize 8C fast charging, no thermal runaway, and increase the volumetric energy density of the battery cell by more than 2.5%.

[0025] (2) The battery cell of the present invention includes the above-mentioned composite connecting piece. According to the same current carrying capacity, its thickness is 1 / 5 to 1 / 4 of the thickness of the conventional connecting piece, and the height of the assembled battery cell electrode can be increased by more than 2.5% compared with the height of the conventional battery cell electrode. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the composite connecting piece in Embodiment 1 of the present invention;

[0028] Figure 2 Schematic diagrams of the battery cell structure in each embodiment 1 of the present invention;

[0029] Figure 3 This is a schematic diagram of the composite connecting piece in Embodiment 2 of the present invention, wherein (a) is a top view and (b) is a front view;

[0030] Figure 4 This is a schematic diagram of the composite connecting piece in Embodiment 3 of the present invention, wherein (c) represents a top view and (d) represents a front view.

[0031] Figure label:

[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 fusion structure, 2-Shell, 3-Cover plate pole, 4-Electrode laminate, 5-Electrode tab. Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0034] According to one aspect of the present invention, the present invention relates to a composite connector for battery cells, the composite connector for battery cells comprising a first structure or a second structure, the first structure comprising a laminated composite structure of structure A and a metal layer structure, wherein structure A is selected from at least one of composite metal foil and polymer PTC film, the second structure comprising a laminated composite structure of multiple composite metal foils, wherein the composite metal foil comprises a polymer film layer and conductive metal layers located on both sides of the polymer film layer; the composite connector is provided with an arrow-shaped fusion structure.

[0035] The composite connector for battery cells of the present invention has high current carrying capacity. Utilizing the current "skin effect", its current carrying capacity is 5-6 times that of pure metal of the same size. It also has thermal safety shutdown function and high flexibility physical characteristics, enabling 8C fast charging, no thermal runaway, and an increase in battery cell volumetric energy density of more than 2.5%.

[0036] The arrow-shaped fuse structure in the composite connector of this invention can break the circuit at a constant temperature in the thermistor material under conditions of over-threshold current or over-threshold temperature, which greatly improves the start-up accuracy of the fuse. The optimized composite thermistor connector has a 50% higher consistency accuracy in fuse temperature than pure metal fuse, ensuring the safety characteristics of the battery cell under over-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 respectively provided on two opposite long sides of the metal layer structure. The first and second notches are positioned opposite each other, and each notch is pentagonal in shape. The angle between the opposite apex angles of the first and second notches is 40°–120°, for example, 40°, 60°, 70°, 80°, 90°, 100°, 120°, etc. The angles of the pentagons, rotating counterclockwise from the apex, are 45°–120°, 120°–160°, 90°, 90°, 120°–160°, etc. In some embodiments, the first and second notches of the arrow-shaped fuse structure involved in each embodiment are the same size, the angle between their opposite apex angles is 90°, and the angles of the pentagons of the first and second notches, rotating counterclockwise from the apex, are 90°, 135°, 90°, 90°, 135°, etc.

[0038] In some embodiments, the polymeric membrane layer comprises 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 implementations, the composite connector for the battery cell includes a positive electrode composite connector and a negative electrode composite connector.

[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, and Al layer-PI layer-Al layer.

[0042] In some embodiments, the thickness of the composite metal foil is 3–500 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, and 500 μm. The thickness of the conductive metal layer is 1–20 μm, for example, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, and 20 μm.

[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, such as 2, 5, 10, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 50 layers, etc.

[0045] In some embodiments, the polymeric PTC membrane comprises a polymeric material, a conductive agent, and a filler. The polymeric material has a mass content of 5% to 80%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, or any value within a range of both. The conductive agent has a mass content of 0.5% to 50%, for example, 0.5%, 1%, 2%, 5%, 10%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within a range of both.

[0046] In some embodiments, the polymeric material includes at least one of high-density polyethylene, epoxy resin, and polyethylene wax. Examples include combinations of high-density polyethylene and epoxy resin, and combinations 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 nanotubes, carbon fibers, and graphene. Examples include carbon black and carbon nanotubes, carbon fibers and graphene, and carbon black, carbon nanotubes, and graphene.

[0048] In some embodiments, the filler includes at least one selected from BaCO3, TiO2, BaTiO3, SrCO3, PbO, Pb3O4, Y2O3, Nb2O5, Al2O3, SiO2, TiO2, Mn(NO3)2, and Li2CO3. Examples include BaCO3 and TiO2, SrCO3 and PbO, Nb2O5, Al2O3, and SiO2.

[0049] In some embodiments, the filler comprises, by mass parts, 55-65 parts BaTiO3, 0.5-2 parts BaCO3, 0.5-2 parts PbO, 0.5-2 parts Y2O3, 0.5-2 parts Al2O3, and 0.5-2 parts Li2CO3. In some embodiments, BaTiO3 is 55 parts, 58 parts, 60 parts, 63 parts, or 65 parts; BaCO3 is 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, or 2 parts; PbO is 0.5 parts, 0.8 parts, 1 part, 1.5 parts, 1.8 parts, or 2 parts; Y2O3 is 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, or 2 parts; Al2O3 is 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, or 2 parts; and Li2CO3 is 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, or 2 parts.

[0050] In some embodiments, the thickness of the polymer PTC film is 0.1 to 2 mm, such as 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, the method for preparing a polymeric PTC membrane includes: mixing a polymeric material with an organic solvent, the organic solvent including at least one of NMP, acetone, and xylene, to obtain a slurry with a solid content of 8% to 12% (e.g., 8%, 9%, 10%, 11%, 12%); adding a conductive agent and filler; stirring evenly to obtain a coating slurry with 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, 3100 cp, etc.), and a solid content of 70% to 80% (e.g., 70%, 72%, 75%, 80%, etc.); coating the slurry and drying it at a temperature of 70 to 80°C (e.g., 72°C, 75°C, or 80°C, etc.) to obtain a polymeric PTC membrane.

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

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

[0054] In some embodiments, the connection methods between the plurality of A structures and the plurality of metal layer structures, and the connection methods between the plurality of composite metal foils, each independently include at least one of adhesive, riveting, ultrasonic welding, and laser welding. This invention uses adhesive, riveting, ultrasonic welding, and laser welding to connect and composite the layers to obtain a connecting piece.

[0055] In some embodiments, the current-carrying capacity of the composite connector for the battery cell is 12–30 A / mm. 2 For example, 12A / mm 2 15A / mm 2 20A / mm 2 25A / mm 2 30A / mm 2 Cells using this connector structure have a conventional overcurrent capability of ≥8C.

[0056] According to one aspect of the present invention, the present invention relates to a battery cell comprising the aforementioned composite connecting piece for the battery cell.

[0057] For the same current carrying 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 cell electrode is increased by >2.5% compared with the height of the conventional cell electrode.

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

[0059] The following explanation, in conjunction with specific embodiments and comparative examples, further clarifies the situation.

[0060] Example 1

[0061] One type of battery cell, such as Figure 2 As shown, the cell dimensions are 44.1*197*109.7 mm, including a housing 2 and an internal electrode stack 4. A cover plate post 3 is located inside the cover plate of the housing 2. The electrode stack 4 has positive and negative tabs 5, which are connected to the cover plate post 3 via composite connecting pieces. The positive electrode uses ternary NCM, and the negative electrode uses 450mAh / g fast-charging graphite + nano-silicon carbon, assembled using a stacked structure. The positive electrode has 211 stacked plates, and the negative electrode has 212 stacked plates. The battery pack contains a total of 192 cells, with a total capacity of 105.6 kWh.

[0062] The battery cell includes a positive electrode composite connector 1 and a negative electrode composite connector 1, such as Figure 1 As shown, the positive electrode composite connector 1 adopts a multi-layer composite structure of multiple composite metal foils 101. Each composite metal foil 101 includes a polymer film layer 1012 and conductive metal layers 1011 on both sides thereof, which are Al layer-PET layer-Al layer. The thickness of a single composite metal foil 101 is 6μm, and the number of layers is 100. The negative electrode composite connector 1 also adopts a multi-layer composite structure of multiple composite metal foils 101. Each composite metal foil 101 is Cu layer-PET layer-Cu layer. The thickness of a single copper composite foil is 6μm, and the number of layers is 100. The thickness of both the positive and negative electrode composite connectors is 0.63mm. Both the positive and negative electrode composite connectors 1 are laser-welded. The composite metal foils possess high-precision thermosensitive properties. When the temperature rises to a certain level, thermal expansion occurs, blocking the current, thus possessing the overcurrent shutdown function of a traditional fuse. This ensures that thermal runaway safety issues do not occur under overcurrent conditions.

[0063] Example 2

[0064] A battery cell with dimensions of 44.1*197*109.7 mm includes a housing 2 and an internal electrode stack 4. A cover plate post 3 is disposed inside the cover plate of the housing 2. The electrode stack 4 has positive and negative tabs 5, which are connected to the cover plate post 3 via composite connecting pieces. The positive electrode uses ternary NCM, and the negative electrode uses 450mAh / g fast-charging graphite + nano-silicon carbon, assembled using a stacked structure. The positive electrode has 211 stacked plates, and the negative electrode has 212 stacked plates. The battery pack contains a total of 192 cells, with a total capacity of 103 kWh.

[0065] The battery cell includes a positive electrode composite connector 1 and a negative electrode composite connector 1, such as Figure 3 As shown, (a) represents a top view and (b) represents a front view. The positive electrode composite connector 1 is a laminated composite structure of a polymer PTC film 103 and an aluminum metal layer structure 102, and the negative electrode composite connector 1 is a laminated composite structure of a polymer PTC film 103 and a copper metal layer structure 102, respectively obtained by laser welding. The polymer PTC film 103 includes polymer materials, conductive agents, and fillers. The polymer material has a mass content of 55%, the conductive agent has a mass content of 35%, and the filler has a mass content of 10%. By mass parts, 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 electrode composite connector 1 is 1.0 mm, the thickness of the polymer PTC film 103 is 0.5 mm, the thickness of the negative electrode composite connector 1 is 1.0 mm, and the thickness of the polymer PTC film 103 is 0.2 mm. Arrow-shaped fusible structures 104 (fuse functional structures) are respectively arranged on the aluminum metal layer structure 102 and the copper metal layer structure 102.

[0066] Example 3

[0067] A battery cell with dimensions of 44.1*197*109.7 mm includes a housing 2 and an internal electrode stack 4. A cover plate post 3 is disposed inside the cover plate of the housing 2. The electrode stack 4 has positive and negative tabs 5, which are connected to the cover plate post 3 via composite connecting pieces. The positive electrode uses ternary NCM, and the negative electrode uses 450mAh / g fast-charging graphite + nano-silicon carbon, assembled using a stacked structure. The positive electrode has 211 stacked plates, and the negative electrode has 212 stacked plates. The battery pack contains a total of 192 cells, with a total capacity of 103 kWh.

[0068] The battery cell includes a positive electrode composite connector 1 and a negative electrode composite connector 1, such as Figure 4As shown, (c) represents a top view and (d) represents a front view. The positive electrode composite connector 1 comprises a composite structure in which multiple metal composite foils (Al layer-PET-Al layer), a polymer PTC film 103, and a metal layer structure 102 (Al layer) are stacked sequentially. The negative electrode composite connector 1 comprises a composite structure in which multiple metal composite foils (Cu layer-PET-Cu layer), a polymer PTC film 103, and a metal layer structure 102 (Cu layer) are stacked sequentially. The composite connector 1 and the negative electrode composite connector 1 are obtained by laser welding. The polymer PTC film 103 comprises a polymer material, a conductive agent, and a filler. The polymer material has a mass content of 60%, the conductive agent has a mass content of 35%, and the filler has a mass content of 5%. By mass parts, 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 positive electrode composite connector 1 has a thickness of 1.5 mm, a metal layer structure 102 (Al layer) thickness of 1.0 mm, a polymer PTC film 103 thickness of 0.38 mm, and a single-layer composite metal foil 101 thickness of 0.006 mm. There are 20 layers, and the total thickness of the composite metal foil 101 is 0.12 mm. The negative electrode composite connector 1 has a total thickness of 1.2 mm, a metal layer structure 102 (Cu layer) thickness of 1.0 mm, a polymer PTC film 103 thickness of 0.14 mm, and a single-layer composite metal foil 101 thickness of 0.006 mm. There are 10 layers, and the total thickness of the composite metal foil 101 is 0.06 mm. Arrow-shaped fusion structures 104 (fuse functional structures) are arranged on the metal layer structures 102 (Al layer) of the positive electrode composite connector and 102 (Cu layer) of the negative electrode composite connector.

[0069] Example 4

[0070] One type of battery cell differs from Example 3 in that:

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

[0072] Example 5

[0073] One type of battery cell differs from Example 3 in that:

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

[0075] Example 6

[0076] One type of battery cell differs from Example 3 in that:

[0077] The polymer PTC membrane 103 comprises polymeric material, conductive agent, and filler. The polymeric material has a mass content of 50%, the conductive agent has a mass content of 45%, and the filler has a mass content of 5%, which is SrCO3.

[0078] Comparative Example 1

[0079] A battery cell with dimensions of 44.1*197*109.7 mm uses ternary NCM for the positive electrode and 450mAh / g fast-charging graphite + nano-silicon carbon for the negative electrode. It is assembled using a stacked structure, with 211 positive electrode cells and 212 negative electrode cells. The battery pack contains a total of 192 cells and a total capacity of 103 kWh.

[0080] Using a traditional connector structure, the thickness of the positive electrode aluminum connector is 1.5mm, and the thickness of the negative electrode copper connector is 1.2mm. Both connectors are pure metal structures. The connectors cannot accommodate a fuse function.

[0081] Comparative Example 2

[0082] A battery cell with dimensions of 44.1*197*109.7 mm uses ternary NCM for the positive electrode and 450mAh / g fast-charging graphite + nano-silicon carbon for the negative electrode. It is assembled using a stacked structure, with 211 positive electrode cells and 212 negative electrode cells. The battery pack contains a total of 192 cells and a total capacity of 103 kWh.

[0083] A traditional connecting piece structure is adopted, with the positive electrode aluminum connecting piece having a thickness of 1.5mm and the negative electrode copper connecting piece having a thickness of 1.2mm. Both connecting pieces are pure metal structures. The connecting pieces are configured with a fuse function by controlling their minimum cross-sectional dimensions. The fuse function is implemented in the connecting piece arrangement.

[0084] Experimental Example

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

[0086] Table 1 Performance Test Results

[0087]

[0088] As shown in Table 1, the composite connector for the battery cell of the present invention has high current carrying capacity, utilizes the current "skin effect", has strong overcurrent capability, and has excellent thermal safety shutdown function, which can realize 8C fast charging without thermal runaway, and improve the volumetric energy density of the battery cell by more than 2.5%.

[0089] In Comparative Example 1, to ensure high current, the connecting piece cannot be equipped with a fuse function, which cannot ensure thermal safety under over-limit current conditions, resulting in safety risks under over-limit current conditions.

[0090] Comparative Example 2 uses a fuse structure to ensure overcurrent safety, which eliminates overcurrent heating issues but cannot meet high current carrying capacity requirements.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite connector for battery cells, characterized in that, The composite connector for the battery cell includes a first structure, which is a laminated composite structure of structure A and a metal layer structure. Structure A is selected from composite metal foil or composite metal foil and polymer PTC film. The composite metal foil includes a polymer film layer and conductive metal layers located on both sides of the polymer film layer. The metal layer structure is provided with an arrow-shaped fusion structure. The polymer film is at least one of polyethylene terephthalate, polypropylene, nylon, and polyimide; The polymer PTC membrane is composed of polymer materials, conductive agents, and fillers, wherein the mass content of the polymer materials is 5% to 80%, and the mass content of the conductive agents is 0.5% to 50%. The filler is composed of 55-65 parts BaTiO3, 0.5-2 parts BaCO3, 0.5-2 parts PbO, 0.5-2 parts Y2O3, 0.5-2 parts Al2O3 and 0.5-2 parts Li2CO3; The thickness of the conductive metal layer is 1~20μm; The conductive metal layer is at least one of copper, aluminum and nickel. The thickness of the composite metal foil is 3~500μm.

2. The composite connecting piece for battery cells according to claim 1, characterized in that, It includes 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 composite connector for battery cells according to claim 1, characterized in that, The thickness of the polymer PTC film is 0.1~2mm.

4. The composite connecting piece for battery cells according to claim 1, characterized in that, The metal layer structure includes a copper layer or an aluminum layer.

5. The composite connecting piece for battery cells according to claim 1, characterized in that, The connection method between the A structure and the metal layer structure includes at least one of adhesive, riveting, ultrasonic welding and laser welding.

6. The composite connecting piece for battery cells according to claim 1, characterized in that, The current handling capacity of the composite connector for the battery cell is 12~30A / mm. 2 .

7. A battery cell, characterized in that, The composite connecting piece for battery cells includes any one of claims 1 to 6.

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