Composite current collector and battery

Abstract

The utility model provides a composite current collector and a battery. The composite current collector comprises an aluminum foil and a copper foil, a composite material is arranged between the aluminum foil and the copper foil; the composite material at least comprises a polyimide base film or a polyethylene glycol terephthalate base film; one side of the aluminum foil is connected with one side of the polyimide base film or the polyethylene glycol terephthalate base film in an attached manner, and the other side of the polyimide base film or the polyethylene glycol terephthalate base film is connected with one side of the copper foil in an attached manner. Compared with the conventional current collector, the composite current collector has the advantages that the tensile strength is greatly improved, the problem of pole piece breakage is avoided, and the composite current collector is applied to the positive and negative pole pieces of the battery, so that the energy density of the battery is improved, and the capacity and the quality of the battery are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, and in particular to a composite current collector and a battery. Background Art

[0002] Currently, the market typically uses methods such as increasing the voltage system, thinning the diaphragm, and thinning the current collector to increase battery capacity. However, due to the insufficient tensile strength and elongation of the current collector, thinning the current collector has reached a bottleneck. The current collectors used in lithium-ion batteries are generally aluminum foil for the positive electrode current collector and copper foil for the negative electrode current collector. The assembly method basically involves evenly coating the active material on the current collector to form a pole piece. After the pole piece is cut into the required width for the battery, the pole piece is welded and wound. The pole piece welding uses aluminum ribbon for the positive electrode and nickel / copper ribbon for the negative electrode. These are ultrasonically welded to the bare foil area of ​​the pole piece to lead to the tab. During the assembly process, the tab is connected to the steel shell through resistance welding or laser welding. Among them, the tensile strength of the positive and negative current collectors is insufficient, which may cause the tab to break during battery cycling and lead to battery failure. The tensile strength of the current collector is too low, which may cause the tab to break during the manufacturing process and prevent normal production. The risk of battery charging and discharging breakage is extremely high and cannot be used normally. In addition, the battery energy density is low, which cannot increase the battery capacity. Utility Model Content

[0003] In view of this, the purpose of the present invention is to provide a composite current collector and a battery. Compared with conventional current collectors, the composite current collector greatly improves the tensile strength, eliminates the problem of electrode fragmentation, and, due to the small thickness of the composite current collector, improves the battery energy density, thereby greatly improving the battery capacity.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A composite current collector comprises aluminum foil and copper foil; a composite material is further provided between the aluminum foil and the copper foil; the composite material comprises at least a polyimide-based film; one side of the aluminum foil is bonded to one side of the polyimide-based film, and the other side of the polyimide-based film is bonded to one side of the copper foil.

[0006] Furthermore, a plurality of through holes are provided on the surface of the polyimide-based film, and the through holes are used for conducting connection between the aluminum foil and the copper foil.

[0007] Alternatively, the composite material at least includes a polyethylene terephthalate base film; one side of the aluminum foil is bonded to one side of the polyethylene terephthalate base film, and the other side of the polyethylene terephthalate base film is bonded to one side of the copper foil.

[0008] Furthermore, a plurality of through holes are provided on the surface of the polyethylene terephthalate base film, and the through holes are used for conducting connection between the aluminum foil and the copper foil.

[0009] In order to achieve the above purpose, the present invention also adopts the following technical solutions:

[0010] A battery comprises at least a positive electrode sheet and a negative electrode sheet; further comprises a composite current collector as described above; and further comprises active substances; the active substances comprise at least positive electrode active materials and negative electrode active materials.

[0011] The positive electrode sheet is formed by uniformly coating the positive electrode active material on the surface of the composite current collector; the negative electrode sheet is formed by uniformly coating the negative electrode active material on the surface of the composite current collector.

[0012] Furthermore, an empty foil gap with a preset distance is provided between the positive electrode plate and the negative electrode plate.

[0013] Furthermore, a positive electrode tab is provided in the overlapping area between the positive electrode sheet and the gap between the empty foil; and a negative electrode tab is provided in the overlapping area between the negative electrode sheet and the gap between the empty foil.

[0014] Furthermore, the battery further comprises a steel shell; the positive electrode tab is connected to the outer surface of the steel shell by laser welding; and the negative electrode tab is connected to the outer surface of the steel shell by laser welding.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The composite current collector and battery proposed in this utility model significantly improve the tensile strength and flexibility of the current collector by adding a composite material (polyimide or polyethylene terephthalate base film) between the aluminum foil and the copper foil, thereby enhancing the mechanical stability of the battery and extending its service life. Furthermore, the addition of the composite material acts as an isolation barrier, preventing direct contact between the aluminum and copper foils that could cause a short circuit, thereby improving battery safety. This composite current collector also enables a thinner current collector, thereby reducing the weight of the battery and increasing its energy density, allowing the battery to store more electrical energy for the same volume or weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a composite current collector according to a preferred embodiment of the present invention.

[0018] Figure 2 It is a side cross-sectional schematic diagram of a composite current collector after composite molding in a preferred embodiment of the present utility model.

[0019] Figure 3 This is a schematic diagram of a packaged battery according to a preferred embodiment of the present invention.

[0020] Figure 4This is a schematic structural diagram of a positive electrode sheet coated with positive electrode active material in a preferred embodiment of the present invention.

[0021] Among them, 100-composite current collector; 101-copper foil; 102-polyimide-based film; 103-aluminum foil; 200-battery; 201-steel shell; 202-positive electrode sheet; 203-positive electrode active material; 2021-positive electrode ear. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Example 1:

[0023] In a preferred embodiment, a composite current collector 100 includes an aluminum foil 103 and a copper foil 101; a composite material is also included between the aluminum foil 103 and the copper foil 101; the composite material includes at least a polyimide-based film 102; one side of the aluminum foil 103 is bonded and connected to one side of the polyimide-based film 102, and the other side of the polyimide-based film 102 is bonded and connected to one side of the copper foil 101.

[0024] Alternatively, the composite material at least includes a polyethylene terephthalate base film; one side of the aluminum foil 103 is bonded to one side of the polyethylene terephthalate base film, and the other side of the polyethylene terephthalate base film is bonded to one side of the copper foil 101 .

[0025] In this embodiment, please refer to Figure 1 , a schematic diagram of a preferred structure of a composite current collector 100, showing, from top to bottom: copper foil 101, polyimide-based film 102, and aluminum foil 103. Composite current collector 100 employs a sandwich-like structure, with aluminum foil 103 and copper foil 101 serving as conductive layers separated by a thin layer of polyimide-based film 102 or polyethylene terephthalate-based film material.

[0026] Preferably, Figure 2 Schematic side cross-section of a preferred structure of a composite current collector 100 after composite molding.

[0027] Polyimide has excellent thermal stability, maintaining stability at temperatures up to 300°C, making it suitable for applications in high-temperature environments. It also exhibits excellent resistance to chemical substances within the battery 200, such as the electrolyte, and is not susceptible to chemical reactions. It also has high insulating properties, providing a high level of electrical insulation, helping to prevent unauthorized current flow between current collectors.

[0028] Polyethylene terephthalate is relatively low in cost, which not only reduces the overall manufacturing cost of the battery 200 , but also has good tensile strength and flexibility, and can meet the requirements of the mechanical properties of the current collector.

[0029] Preferably, the thickness of the polyimide base film 102 or the polyethylene terephthalate base film can be in an extremely thin range of 0.001~0.002mm, and combined with a thinner metal foil, wherein the thickness of the copper foil 101 can be between 0.002~0.005mm, and the thickness of the aluminum foil 103 can be between 0.003~0.005mm, but not limited thereto. The composite current collector 100 formed is lighter and thinner, and can also be used to improve the energy density of the battery 200.

[0030] Furthermore, a plurality of through holes are provided on the surface of the polyimide base film 102, and the through holes are used for conducting connection between the aluminum foil 103 and the copper foil 101. Alternatively, a plurality of through holes are provided on the surface of the polyethylene terephthalate base film, and the through holes are used for conducting connection between the aluminum foil 103 and the copper foil 101.

[0031] It should be noted that the number, position, and size of the through-holes or through-holes on the base film can be flexibly set according to actual conditions and are not specifically limited in this embodiment. In this embodiment, a polyimide or polyethylene terephthalate base film material is used as a carrier, and uniform holes are pre-punched on its surface so that the aluminum foil 103 and the copper foil 101 can be firmly connected to the PI material through these holes to form an integral composite current collector 100. The composite current collector 100 has good mechanical strength and can serve as a reinforcement layer to increase the tensile strength of the current collector. In addition, it can withstand greater mechanical stress during the charge and discharge process of the battery 200.

[0032] In other embodiments, a nano-reinforcement material layer may be coated between the contact surface of the polyimide base film 102 or polyethylene terephthalate base film and the aluminum foil 103 or the copper foil 101 to enhance mechanical properties; the nano-reinforcement material layer is composed of carbon nanotubes, nanofibers or other reinforcing nanomaterials.

[0033] In this embodiment, a conductive adhesive layer may be coated on the surface of the aluminum foil 103 and the copper foil 101 to improve the bonding strength and conductivity; and to improve the bonding strength and conductivity between the current collector and the active material.

[0034] This embodiment may further include a thermal management functional layer coated on the outer side of the nano-enhanced material layer, which is used to adjust the temperature of the current collector and prevent the battery 200 from overheating.

[0035] This embodiment may further include a self-repairing functional layer coated on the outside of the conductive adhesive layer, which can self-repair tiny cracks or damages during the cycle of the battery 200 and extend the life of the battery 200.

[0036] This embodiment may further include a surface treatment layer coated on the outside of the thermal management functional layer or the self-repairing functional layer to improve the compatibility between the current collector and the electrolyte and reduce the interface impedance.

[0037] The thermal management functional layer is composed of phase change materials or other heat regulating materials, which can absorb or release heat to maintain the battery 200 within the optimal operating temperature range.

[0038] The self-repairing functional layer comprises a polymer or nanocomposite material having self-repairing capabilities, and is capable of repairing microscopic defects in response to stress or temperature changes during the battery 200 cycle.

[0039] The surface treatment layer uses an electrolyte-philic material or surface-modified nanoparticles to reduce the interface impedance between the current collector and the electrolyte, thereby improving the power output and cycle stability of the battery 200.

[0040] Through the thermal management functional layer, the thermal stability of the battery 200 is improved and the service life of the battery 200 is extended; the self-repair functional layer enhances the durability of the current collector and reduces the performance degradation caused by the expansion of micro cracks during the cycle; the surface treatment layer optimizes the interface contact between the current collector and the electrolyte, reduces the interface impedance, and improves the charge and discharge efficiency of the battery 200.

[0041] This embodiment significantly improves the tensile strength and ductility of the current collector, overcoming the mechanical performance bottleneck of the traditional current collector after thinning; through the combination of the conductive adhesive layer and the nano-reinforced material layer, the bonding force between the current collector and the active material and the cycle stability of the battery 200 are improved; the polyimide-based film 102 with a microporous structure increases the contact area between the current collector and the active material, thereby improving the energy density of the battery 200; the nano-reinforced material layer further enhances the structural stability and conductivity of the current collector, thereby improving the overall performance of the battery 200.

[0042] In summary, the lightweight composite current collector 100 reduces the weight of the battery 200 while maintaining good conductivity, allowing the battery 200 to store more electrical energy within the same volume or weight. It also significantly improves the tensile strength of the current collector, allowing the battery 200 to withstand greater mechanical stress, thereby improving the cycle life and reliability of the battery 200. Furthermore, the uniform pore design helps disperse current, reducing the risk of thermal runaway in the battery 200. Through the structural design of this embodiment, battery 200 manufacturers can achieve more efficient, thinner, and more cost-effective lithium-ion batteries 200 without sacrificing performance and safety. Example 2:

[0043] As attached Figure 3 FIG2 is a schematic diagram of a packaged finished battery 200 in a preferred embodiment, comprising at least a positive electrode sheet 202 and a negative electrode sheet; a composite current collector 100 as described above; and active materials. The active materials include at least a positive electrode active material 203 and a negative electrode active material. The positive electrode sheet 202 is formed by uniformly coating the positive electrode active material 203 on the surface of the composite current collector 100; and the negative electrode sheet is formed by uniformly coating the negative electrode active material on the surface of the composite current collector 100.

[0044] Preferably, as shown in the attached Figure 4 The figure shows a schematic diagram of the structure of a positive electrode sheet 202 coated with a positive electrode active material 203. The structure of the negative electrode sheet is similar to that of the positive electrode sheet 202. The positive electrode active material 203 may generally include lithium cobalt oxide (LiCoO2), a ternary material (such as LiNiMnCoO2, referred to as NMC), lithium iron phosphate (LiFePO4, referred to as LFP), etc. The negative electrode active material mainly includes graphite and silicon-carbon (Si-C) composite materials, etc., but is not limited to these.

[0045] In this embodiment, the composition ratio of the positive electrode active material 203 or the negative electrode active material is not specifically limited and can be adjusted based on actual conditions. For example, in the negative electrode active material, graphite typically accounts for the majority of the active material and can be mixed with other materials to improve performance. Silicon-carbon composite materials, by combining silicon (Si) with graphite, can increase the capacity and energy density of battery 200. The silicon content is typically low because silicon expands significantly during charge and discharge, potentially affecting cycle stability. Typical ratios range from 5% to 30%.

[0046] In a preferred embodiment,

[0047] Positive electrode: lithium cobalt oxide (or ternary, lithium iron) accounts for 70-90% of the total active material, and other additives (such as conductive agents, binders, etc.) account for the remaining proportion; negative electrode: graphite accounts for 60-90% of the total active material, and the proportion of silicon in the silicon-carbon composite material may be between 5-30%. The actual ingredient ratio needs to be determined through experiments and optimization by the battery 200 manufacturer to ensure that the performance of the battery 200 meets expectations.

[0048] Furthermore, an empty foil gap of a preset distance is provided between the positive electrode plate 202 and the negative electrode plate.

[0049] Preferably, when the positive electrode sheet 202 and the negative electrode sheet are coated with blank foil, a gap of 20±5 mm is reserved.

[0050] Furthermore, a positive electrode tab 2021 is provided in the overlapping area between the positive electrode sheet 202 and the gap between the empty foil; and a negative electrode tab is provided in the overlapping area between the negative electrode sheet and the gap between the empty foil.

[0051] Preferably, in the process flow of battery 200, the electrode sheets are first rolled and cut into small pieces; then the electrode sheets are wound, and during winding, the empty foil areas at the tails of the positive and negative electrode sheets are folded vertically along the edge of the material area to lead out to form the positive and negative electrode ears.

[0052] Furthermore, the battery 200 further includes a steel shell 201; the positive electrode tab 2021 is connected to the outer surface of the steel shell 201 by laser welding; and the negative electrode tab is connected to the outer surface of the steel shell 201 by laser welding.

[0053] During assembly, the negative electrode ear is connected to the steel shell 201 by laser welding on the outside, and then the core is rolled into the shell. The positive electrode ear is connected to the steel shell 201 by laser welding on the outside, and then the battery cell is filled with liquid and sealed to form a complete battery 200.

[0054] Preferably, the battery 200 may further include a cap, or the positive electrode tab and the cap may be connected by laser welding on the outside, but the present invention is not limited thereto.

[0055] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative use of the above terms does not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0056] In the description of the present invention, it should be understood that terms such as "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0058] Although the present invention has been described with reference to the above specific embodiments, it is apparent that those skilled in the art can make many substitutions, modifications, and variations based on the above. Therefore, all such substitutions, modifications, and variations are intended to fall within the spirit and scope of the appended claims.

Claims

1. A composite current collector comprising aluminum foil and copper foil; characterized in that: A composite material is also included between the aluminum foil and the copper foil; the composite material at least includes a polyimide-based film; One side of the aluminum foil is bonded to one side of the polyimide-based film, and the other side of the polyimide-based film is bonded to one side of the copper foil.

2. A composite current collector according to claim 1, characterized in that: A plurality of through holes are provided on the surface of the polyimide-based film, and the through holes are used for conducting connection between the aluminum foil and the copper foil.

3. A composite current collector according to claim 1, characterized in that: The composite material further comprises at least a polyethylene terephthalate base film; One side of the aluminum foil is bonded to one side of the polyethylene terephthalate base film, and the other side of the polyethylene terephthalate base film is bonded to one side of the copper foil.

4. A composite current collector according to claim 3, characterized in that: A plurality of through holes are provided on the surface of the polyethylene terephthalate base film, and the through holes are used for conducting connection between the aluminum foil and the copper foil.

5. A battery, characterized in that: At least comprising a positive electrode sheet and a negative electrode sheet; further comprising the composite current collector according to any one of claims 1 to 4, and further comprising: Active material; the active material includes at least a positive electrode active material and a negative electrode active material; The positive electrode sheet is formed by uniformly coating the positive electrode active material on the surface of the composite current collector; The negative electrode plate is formed by uniformly coating the negative electrode active material on the surface of a composite current collector.

6. A battery according to claim 5, characterized in that: An empty foil gap with a preset distance is provided between the positive electrode plate and the negative electrode plate.

7. A battery according to claim 6, characterized in that: A positive electrode tab is provided in the overlapping area between the positive electrode sheet and the empty foil; a negative electrode tab is provided in the overlapping area between the negative electrode sheet and the empty foil.

8. A battery according to claim 7, characterized in that: The battery further comprises a steel case; The positive electrode tab is connected to the outer surface of the steel shell by laser welding; the negative electrode tab is connected to the outer surface of the steel shell by laser welding.

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