Composite current collector, electrode sheet, battery, and electric device

Abstract

The present application relates to a composite current collector, an electrode sheet, a battery, and an electric device. The composite current collector comprises an insulating base and a conductive layer, wherein the conductive layer is disposed on two sides of the insulating base in the thickness direction of the insulating base; in a direction perpendicular to the thickness direction of the composite current collector, the composite current collector comprises an active substance supporting region and a tab connecting region, and the thickness of the insulating base in the tab connecting region is less than the thickness of the insulating base in the active substance supporting region; and the thickness of the conductive layer in the tab connecting region is greater than the thickness of the conductive layer in the active substance supporting region. The technical solution better facilitates an improvement in the degree of edge metallization of a composite current collector, thereby facilitating an improvement in the overcurrent effect of an electrode sheet in a tab connecting region when a tab is connected to the tab connecting region.

Description

Composite current collectors, pole pieces, batteries, and electrical equipment

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311010514.0, filed on August 11, 2023, entitled “Composite current collector, electrode, battery, and electrical equipment,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application relates to a composite current collector, a pole piece, a battery, and an electrical device. Background Art

[0004] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life and low environmental pollution.

[0005] Traditional lithium-ion batteries use copper foil and aluminum foil as conventional current collectors, which are widely used in lithium-ion batteries for current conduction and load support. In recent years, the requirements for high energy density and thermal runaway probability of lithium-ion batteries have become increasingly higher, and many studies have turned their attention to the application of composite current collectors.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a composite current collector, a pole piece, a battery, and an electrical device.

[0008] The embodiment of the present application is implemented as follows:

[0009] In the first aspect, the present invention provides a composite current collector, comprising: an insulating substrate; and a conductive layer; along the thickness direction of the insulating substrate, the conductive layer is arranged on both sides of the insulating substrate.

[0010] Along the direction perpendicular to the thickness of the composite current collector, the composite current collector includes an active material support area and a tab connection area. The thickness of the insulating substrate in the tab connection area is less than the thickness of the insulating substrate in the active material support area; the thickness of the conductive layer in the tab connection area is greater than the thickness of the conductive layer in the active material support area.

[0011] In the above technical solution, the thickness of the insulating substrate in the tab connection area is less than the thickness of the insulating substrate in the active material support area; the thickness of the conductive layer in the tab connection area is greater than the thickness of the conductive layer in the active material support area, which is more conducive to improving the edge metallization degree of the composite current collector, so that when the tab is connected to the tab connection area, it is beneficial to improve the overcurrent effect of the pole piece in the tab connection area.

[0012] In some optional embodiments, the thickness of the composite current collector is the same at all positions, the thickness of the insulating substrate in the active material support area is D1; ​​the thickness of the insulating substrate in the tab connection area is D3; D3<D1.

[0013] In the above technical solution, the thickness of the insulating substrate of the active material support area and the thickness of the insulating substrate of the tab connection area satisfy the above relationship, which is beneficial to improving the metallization degree of the tab connection area of ​​the composite current collector, so that when the tab is connected to the tab connection area, it is beneficial to improve the flow-through effect of the pole piece in the tab connection area.

[0014] In some optional embodiments, the thickness of the conductive layer in the tab connection area is D4; the thickness of the insulating base in the tab connection area is D3; the ratio of D4 to D3 is A, A≥1; optionally, 1≤A≤2.

[0015] Because the composite current collector's intermediate layer is a polymer and non-conductive, metal transfer welding is required for tab welding, which increases the welding failure rate and is also prone to failure at high battery rates. The above technical solution, by setting the thickness of the conductive layer in the tab connection area and the thickness of the insulating substrate in the tab connection area to meet the above relationship, greatly improves the metallization level of the tab connection area of ​​the composite current collector, can meet the requirements of ultrasonic direct welding, and thus can achieve the composite current collector without transfer welding, greatly broadening the application of the composite current collector. The above technical solution does not require transfer welding, can meet the high-rate charge and discharge requirements of the battery, and is conducive to meeting the more demanding requirements of battery thermal runaway.

[0016] In some optional embodiments, the thickness of the insulating substrate in the active material support area is D1; ​​the thickness of the insulating substrate in the tab connection area is D3; and the ratio of D1 to D3 is B, where B≥2.

[0017] In the above technical solution, by controlling the lower limit of the ratio of the thickness of the insulating substrate in the active material support area to the thickness of the insulating substrate in the tab connection area within the above range, the overall strength and ductility of the insulating substrate can be effectively controlled to meet both the manufacturing requirements and the overall mechanical performance requirements of the composite current collector; at the same time, the active material support area is maintained to have sufficient strength and ductility.

[0018] In some optional embodiments, the thickness of the insulating substrate of the active material supporting region is D1, 3 μm≤D1≤10 μm.

[0019] In the above technical solution, the thickness of the insulating substrate in the active material supporting region is set within the above range, which can make the composite current collector have good mechanical properties.

[0020] In some optional embodiments, the thickness of the conductive layer in the active material supporting region is D2, 0.5 μm≤D2≤1.5 μm.

[0021] In the above technical solution, the thickness of the conductive layer in the active material support region is set within the above range, which can make the composite current collector have a good flow-conducting effect.

[0022] In some optional embodiments, the thickness of the insulating substrate in the tab connection area is D3, D3≤3 μm; optionally, 1.5 μm≤D3≤3 μm.

[0023] In the above technical solution, the thickness of the insulating base of the tab connection area is set within the above range, which is conducive to achieving an excellent degree of metallization in the tab connection area, so that the tab connection area can meet the requirements of ultrasonic direct welding, so that the composite current collector can be directly welded without the need for transfer welding.

[0024] In some optional embodiments, the thickness of the conductive layer in the tab connection area is D4, D4 ≥ 1.5 μm; optionally, 1.5 μm ≤ D4 ≤ 4 μm.

[0025] In the above technical solution, the thickness of the conductive layer in the tab connection area is set within the above range, which is beneficial to increasing the strength performance of the composite current collector edge and reducing the probability of the composite current collector being cracked by rolling in subsequent battery manufacturing processes.

[0026] In some optional embodiments, the width of the tab connection area is L1, L1 ≥ 10 mm; optionally,

[0027] 10mm≤L1≤40mm.

[0028] In the above technical solution, by controlling the width of the tab connection area within the above range, not only the shortest tab requirement for electrode welding can be met, but also the length of the tab can be controlled, and the battery folding tab space design and the length requirement of the tab for winding can be met.

[0029] In some optional embodiments, a conductive material is added to the insulating substrate;

[0030] Optionally, the conductive material includes at least one of conductive carbon black, carbon nanotubes, acetylene black or carbon fibers.

[0031] In some optional embodiments, the added proportion of the conductive material accounts for 3%-10% of the mass of the insulating substrate in terms of mass percentage.

[0032] In the above technical solution, by controlling the addition ratio of the conductive material in the insulating base within the above range, it can not only meet the requirement of increasing welding conductivity and play a soldering effect, but also will not affect the mechanical properties of the insulating base due to excessive content.

[0033] In some optional embodiments, the material of the insulating substrate includes at least one of an organic polymer insulating material, an inorganic insulating material, or a composite material;

[0034] Optionally, the organic polymer insulating material includes at least one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber or polycarbonate;

[0035] Optionally, the inorganic insulating material includes at least one of aluminum oxide, silicon carbide or silicon dioxide;

[0036] Optionally, the composite material includes at least one of an epoxy resin glass fiber reinforced composite material or a polyester resin glass fiber reinforced composite material.

[0037] In some optional embodiments, the material of the conductive layer includes at least one of a metallic conductive material or a carbon-based conductive material;

[0038] Optionally, the metal conductive material includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy or aluminum-zirconium alloy;

[0039] Optionally, the carbon-based conductive material includes at least one of graphite, acetylene black, graphene or carbon nanotubes.

[0040] In a second aspect, an embodiment of the present application provides a pole piece, comprising the composite current collector provided in the first aspect.

[0041] In the above technical solution, the electrode can improve the preparation yield of the electrode by setting the composite current collector provided by the first aspect; applying it to the battery can help improve the cycle performance and energy density of the battery.

[0042] In a third aspect, an embodiment of the present application provides a battery, which includes the electrode provided in the second aspect.

[0043] In the above technical solution, the battery is provided with the pole piece provided by the second aspect, which is conducive to enabling the battery to obtain high energy density while meeting the high-rate fast charging requirements and obtaining a lower probability of thermal runaway.

[0044] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes the battery provided in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0046] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0047] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0048] FIG3 is an exploded view of the battery cell shown in FIG2 ;

[0049] FIG4 is a schematic diagram of a partial structure of an electrode assembly provided in some embodiments of the present application;

[0050] FIG5 is a schematic diagram of a partial structure of a positive electrode sheet provided in some embodiments of the present application;

[0051] FIG6 is a schematic structural diagram of a composite current collector provided in some embodiments of the present application;

[0052] FIG7 is another schematic structural diagram of a composite current collector provided in some embodiments of the present application;

[0053] FIG8 is a schematic structural diagram of a die head for preparing an insulating substrate provided in some embodiments of the present application;

[0054] FIG9 is a schematic structural diagram of an edge thinning device for producing a composite current collector insulating substrate according to some embodiments of the present application;

[0055] FIG10 is a schematic diagram of the structure of a composite current collector coated with a positive electrode active material layer provided in some embodiments of the present application.

[0056] Icons: Vehicle 1000; Battery 100; Controller 200; Motor 300; Housing 10; First portion 11; Second portion 12; Accommodation space 13; Battery cell 20; Housing 21; Electrode assembly 22; Electrode terminal 23; Pressure relief structure 24; Case 211; Cover 212; Positive electrode sheet 221; Negative electrode sheet 222; Separator 223; Positive current collector 2211; Positive active material layer 2212; Negative current collector 2221; Negative active material layer 2222. DETAILED DESCRIPTION

[0057] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0060] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application 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. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0061] In the description of the embodiments of this application, unless otherwise specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on specific circumstances.

[0062] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0063] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the heights, lengths, widths, and other dimensions of the various components in the embodiments of this application, as well as the overall heights, lengths, widths, and other dimensions of the integrated device shown in the drawings are merely illustrative and do not constitute any limitation on this application.

[0064] The composite current collector generally includes a non-conductive polymer in the middle layer and a metal conductor on the surface layer. The non-conductive polymer plays a structural support role; the metal conductor is used to provide electrons for the electrode active material and connect the tabs, that is, it plays the role of conduction and current collection, as well as the role of pole piece flow in the tab area.

[0065] However, the composite current collector's application is limited by the fact that it includes a non-conductive polymer intermediate layer. Research has found that the non-conductive nature of the polymer results in a low degree of metallization in the tab connection area at the edge of the composite current collector, resulting in a low flow rate of the composite current collector.

[0066] The embodiment of the present application provides a composite current collector, which includes: an insulating substrate; and a conductive layer; along the thickness direction of the insulating substrate, the conductive layer is arranged on both sides of the insulating substrate;

[0067] Along the direction perpendicular to the thickness of the composite current collector, the composite current collector includes an active material support area and a tab connection area. The thickness of the insulating substrate in the tab connection area is less than the thickness of the insulating substrate in the active material support area; the thickness of the conductive layer in the tab connection area is greater than the thickness of the conductive layer in the active material support area.

[0068] In the above technical solution, the thickness of the insulating substrate in the tab connection area is less than the thickness of the insulating substrate in the active material support area; the thickness of the conductive layer in the tab connection area is greater than the thickness of the conductive layer in the active material support area, which is more conducive to improving the edge metallization degree of the composite current collector, so that when the tab is connected to the tab connection area, it is beneficial to improve the overcurrent effect of the pole piece in the tab connection area.

[0069] The pole piece provided in the present application includes the aforementioned composite current collector.

[0070] By setting the composite current collector provided in the first aspect, the pole piece can improve the preparation yield of the pole piece; applying it in a battery can help improve the cycle performance and energy density of the battery.

[0071] The battery provided in the present application includes the aforementioned electrode. By setting the electrode provided in the second aspect, the battery is advantageously provided with a high energy density while meeting the high-rate fast charging requirements and obtaining a lower probability of thermal runaway.

[0072] An embodiment of the present application provides an electrical device including the aforementioned battery.

[0073] Refer to Figure 1, which is a structural schematic diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0074] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0075] In this application, battery 100 refers to a single physical module that includes one or more battery cells 20 to provide voltage and capacity. Battery 100 generally includes a housing 10 for enclosing one or more battery cells 20. Housing 10 prevents liquids or other foreign matter from affecting the charging or discharging of battery cells 20.

[0076] Referring to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application, the battery 100 may include a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to house the battery cell 20 and may have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other and together define a storage space 13 for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one end open, and the first portion 11 may be a plate-like structure, which overlaps the open side of the second portion 12 to form the housing 10 with the storage space 13. Alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12 to form the housing 10 with the storage space 13. Of course, the first portion 11 and the second portion 12 may have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0077] In the battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection. Mixed connection means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the case 10. Alternatively, multiple battery cells 20 can be first connected in series, in parallel, or in a mixed connection to form a module, and the multiple modules are then connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the case 10. The battery 100 can also include other structures. For example, the multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of the multiple battery cells 20.

[0078] Each battery cell 20 may be a lithium-ion battery, such as a secondary battery or a primary battery; it may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto.

[0079] Referring to Figure 3 , which is an exploded view of the battery cell 20 shown in Figure 2 , the battery cell 20 is the smallest unit that makes up the battery 100. The battery cell 20 may include a housing 21 , an electrode assembly 22 , and an electrolyte, with both the electrode assembly 22 and the electrolyte being housed within the housing 21 .

[0080] The outer shell 21 may include a shell 211 and a cover 212. The shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space of the battery cell 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, electrolyte and other components. The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211. Functional components such as electrode terminals 23 and pressure relief structures 24 can also be provided on the cover 212. A sealing ring can be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.

[0081] The shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell 211 and the cover 212 can be various, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance. A coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0082] Referring to Figure 4 , the electrode assembly 22 may be composed of a positive electrode sheet 221, a negative electrode sheet 222, and a separator 223. The separator 223 is located between the positive electrode sheet 221 and the negative electrode sheet 222 to provide isolation. The electrode assembly 22 may be a wound or laminated structure, but the present invention is not limited thereto.

[0083] 5 , the negative electrode sheet 222 includes a negative electrode current collector 2221 and a negative electrode active material layer 2222 . The negative electrode active material layer 2222 includes a negative electrode active material. The negative electrode active material includes at least one of graphite, silicon, silicon alloy, or tin alloy.

[0084] 5 , the positive electrode sheet 221 includes a positive electrode current collector 2211 and a positive electrode active material layer 2212 . The positive electrode active material layer 2212 includes a positive electrode active material.

[0085] In some embodiments of the present application, both the negative electrode current collector 2221 and the positive electrode current collector 2211 may be composite current collectors.

[0086] In some embodiments of the present application, a composite current collector includes an insulating substrate and a conductive layer. Along the thickness direction of the insulating substrate, the conductive layer is disposed on both sides of the insulating substrate. In a direction perpendicular to the thickness of the composite current collector, the composite current collector includes an active material support region and a tab connection region. The thickness of the insulating substrate in the tab connection region is thinner than that in the active material support region. The thickness of the conductive layer in the tab connection region is thicker than that in the active material support region.

[0087] In the above technical solution, the thickness of the insulating substrate in the tab connection area is less than the thickness of the insulating substrate in the active material support area; the thickness of the conductive layer in the tab connection area is greater than the thickness of the conductive layer in the active material support area, which is more conducive to improving the edge metallization degree of the composite current collector, so that when the tab is connected to the tab connection area, it is beneficial to improve the overcurrent effect of the pole piece in the tab connection area.

[0088] Furthermore, in some embodiments of the present application, the tab connection region refers to the region of the composite current collector used to connect to the tab, for example, the region of the current collector occupied by the tab when the tab is welded to the composite current collector. Furthermore, optionally, the tab connection region may be provided on one edge of the composite current collector, or on both edges of the composite current collector.

[0089] Further, referring to Figure 10 , in some embodiments of the present application, the active material support region refers to the region coated with the active material layer; for example, it can be the region coated with the positive electrode active material layer or the region coated with the negative electrode active material layer. Furthermore, optionally, the active material support region is disposed in the central region of the composite current collector.

[0090] Furthermore, in some embodiments of the present application, the aforementioned "thickness of the insulating base in the tab connection area" refers to the thickness of the area when the cross-sectional shape is regular (the thickness is the same at all locations within the area); when the cross-sectional shape is irregular (the thickness is not exactly the same at all locations within the area, or the thickness at all locations within the area varies gradually), the "thickness of the insulating base in the tab connection area" refers to the average thickness of the entire area. The "thickness" of other aforementioned areas also follows the above rules. For example, the "thickness of the conductive layer in the tab connection area" refers to the average thickness of the area when the cross-sectional shape is irregular.

[0091] Further, referring to Figure 6, in some embodiments of the present application, the thickness of the composite current collector is the same at all positions, the thickness of the insulating substrate in the active material support area (area H in Figure 6) is D1; ​​the thickness of the insulating substrate in the tab connection area (area J in Figure 6) is D3; D3<D1.

[0092] In the above technical solution, the thickness of the insulating substrate of the active material support area and the thickness of the insulating substrate of the tab connection area satisfy the above relationship, which is beneficial to improving the metallization degree of the tab connection area of ​​the composite current collector, so that when the tab is connected to the tab connection area, it is beneficial to improve the flow-through effect of the pole piece in the tab connection area.

[0093] Furthermore, conventional composite current collectors are usually designed with an integrated polymer support layer. The conductive layer and the polymer support layer are designed with a uniform thickness regardless of the active material bearing area or the tab area, which is usually manifested as the thickness of the support layer being greater than the thickness of the conductive layer. Since the base film of the support layer in the edge tab area is an insulator, the traditional ultrasonic direct welding method cannot weld the upper and lower conductive layers. It is usually necessary to use two pieces of transition metal foil to weld the upper and lower conductive layers respectively, and then the final pole piece and tab are ultrasonically welded to multiple tabs. Among them, transition welding also poses a huge challenge to the reliability of composite current collector welding. If the ultrasonic energy is too low, the metal layers cannot be effectively fused, resulting in a cold weld; if the ultrasonic energy is too large, it is easy to directly vibrate and crack the metal layer, which also affects the conductivity. This type of transition welding not only increases the welding failure rate, but is also prone to failure at high battery rates.

[0094] In some embodiments of the present application, referring to FIG6 , the thickness of the conductive layer in the tab connection area is D4; the thickness of the insulating base in the tab connection area is D3; and the ratio of D4 to D3 is A, where A≥1.

[0095] The above technical solution, by setting the thickness of the conductive layer in the tab connection area and the thickness of the insulating substrate in the tab connection area to meet the above relationship, greatly improves the metallization level of the tab connection area of ​​the composite current collector. For composite current collectors of common thicknesses (3.5μm to 11.5μm), it can meet the requirements of ultrasonic direct welding, thus achieving the composite current collector without the need for transfer welding, greatly broadening the application of the composite current collector. The above technical solution does not require transfer welding, greatly reducing the welding failure rate; it also effectively reduces the probability of failure at high battery rates, and is also conducive to meeting the more demanding battery thermal runaway requirements.

[0096] In other optional embodiments of the present application, only one side of the tab may be provided, and in this case, the composite current collector is only provided with a tab connection region on one side.

[0097] Further optionally, in some embodiments of the present application, 1≤A≤2.

[0098] Illustratively, in some embodiments of the present application, A is 1, A is 1.1, A is 1.2, A is 1.3, A is 1.4, A is 1.5, A is 1.6, A is 1.7, A is 1.8, A is 1.9, or A is 2.0; or A is a value within the range formed by any two of the above values.

[0099] Furthermore, in some embodiments of the present application, referring to FIG6 , the thickness of the insulating substrate in the active material support region is D1; ​​the thickness of the insulating substrate in the tab connection region is D3; and the ratio of D1 to D3 is B, where B≥2.

[0100] In the above technical solution, by controlling the lower limit of the ratio of the thickness of the insulating substrate in the active material support area to the thickness of the insulating substrate in the tab connection area within the above range, the overall strength and ductility of the insulating substrate can be effectively controlled to meet both the manufacturing requirements and the overall mechanical performance requirements of the composite current collector; at the same time, the active material support area is maintained to have sufficient strength and ductility.

[0101] Furthermore, in some embodiments of the present application, referring to FIG. 6 , the thickness of the insulating substrate in the active material support region is D1, and 3 μm≤D1≤10 μm.

[0102] In the above technical solution, the thickness of the insulating substrate in the active material supporting region is set within the above range, which can make the composite current collector have good mechanical properties.

[0103] Illustratively, in some embodiments of the present application, D1 is 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm; or D1 is a value within the range formed by any two of the above values.

[0104] Furthermore, in some embodiments of the present application, referring to FIG. 6 , the thickness of the conductive layer in the active material support region is D2, and 0.5 μm≤D2≤1.5 μm.

[0105] In the above technical solution, the thickness of the conductive layer in the active material support region is set within the above range, which can make the composite current collector have a good flow-conducting effect.

[0106] Illustratively, in some embodiments of the present application, D2 is 0.5 μm, 600 nm, 800 nm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or 1.5 μm; or D2 is a value within the range formed by any two of the above values.

[0107] Furthermore, in some embodiments of the present application, referring to FIG. 6 , the thickness of the insulating substrate in the tab connection region is D3, where D3 ≤ 3 μm.

[0108] In the above technical solution, the thickness of the insulating base of the tab connection area is set within the above range, which is conducive to achieving an excellent degree of metallization in the tab connection area, so that the tab connection area can meet the requirements of ultrasonic direct welding, so that the composite current collector can be directly welded without the need for transfer welding.

[0109] Further optionally, in some embodiments of the present application, 1.5 μm≤D3≤3 μm.

[0110] Illustratively, in some embodiments of the present application, D3 is 1.5 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.3 μm, 2.5 μm, 2.6 μm, 2.8 μm, or 3.0 μm; or D3 is a value within the range formed by any two of the above values.

[0111] Furthermore, after the composite current collector undergoes the coating process, the weld area is always exposed and directly contacts the equipment's drive roller system. Due to the speed difference between the equipment and the current collector, wear and scratches are easily generated at the interface between the weld area and the coating area. The submicron-level conductive layer is also easily damaged or even cracked, resulting in an increase in the electrode sheet's square resistance or even loss of conductivity. Such poorly welded or damaged electrodes must be removed during the battery manufacturing process, resulting in a decrease in process quality and an increase in manufacturing costs. If poorly welded or damaged conductive layers are not identified during the production process, they are susceptible to further corrosion from the electrolyte after entering the battery, leading to failure, increased degradation of cycle performance, and reliability issues. Furthermore, after traditional transfer welding, the height of the folded tabs of the composite current collector electrode increases by approximately 7mm, significantly reducing the battery's space utilization.

[0112] Furthermore, in some embodiments of the present application, referring to FIG. 6 , the thickness of the conductive layer in the tab connection region is D4, and D4 ≥ 1.5 μm.

[0113] In the above technical solution, the thickness of the conductive layer in the tab connection area is set within the above range, which helps to increase the strength of the composite current collector edge and reduce the probability of the composite current collector being cracked by rolling during subsequent battery manufacturing processes. It can also reduce the height of the composite current collector electrode, improving the space utilization of the battery.

[0114] Further optionally, in some embodiments of the present application, 1.5 μm≤D4≤4 μm.

[0115] Illustratively, in some embodiments of the present application, D4 is 1.5 μm, 1.8 μm, 2.0 μm, 2.5 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.5 μm, 3.8 μm, or 4.0 μm; or D4 is a value within the range formed by any two of the above values.

[0116] Furthermore, in some embodiments of the present application, the thicknesses of the conductive layers disposed on both sides of the insulating substrate may be selected to be the same; or the thicknesses of the conductive layers disposed on both sides of the insulating substrate may be selected to be different.

[0117] For example, in some embodiments of the present application, the thickness D4 of the conductive layer disposed in the insulating base tab connection region may be the same, for example, 1.5 μm; or different, 1.5 μm on one side and 2.0 μm on the other side.

[0118] For example, in some embodiments of the present application, the thickness D2 of the conductive layer of the active material support area provided on both sides of the insulating substrate may be the same, for example, both are 0.5 μm; or different, 0.5 μm on one side and 600 nm on the other side.

[0119] Furthermore, in some embodiments of the present application, the width of the tab connection area is L1, and L1 is ≥ 10 mm.

[0120] In the above technical solution, by controlling the width of the tab connection area within the above range, not only the shortest tab requirement for electrode welding can be met, but also the length of the tab can be controlled, and the battery folding tab space design and the length requirement of the tab for winding can be met.

[0121] Further optionally, in some embodiments of the present application, 10 mm ≤ L1 ≤ 40 mm.

[0122] Illustratively, in some embodiments of the present application, L1 is 10 mm, 12 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 38 mm, or 40 mm; or L1 is a value within the range formed by any two of the above values.

[0123] In some embodiments of the present application, the method for testing the length of the tab region is to perform a width test using a ruler.

[0124] Furthermore, in some embodiments of the present application, referring to FIG. 7 , a conductive material (black dots in FIG. 7 ) is added to the insulating substrate.

[0125] Furthermore, in some embodiments of the present application, the conductive material includes at least one of conductive carbon black, carbon nanotubes, acetylene black, or carbon fibers.

[0126] For example, in some embodiments of the present application, the conductive material is selected from any one of conductive carbon black, carbon nanotubes, acetylene black or carbon fibers; or in some embodiments of the present application, the conductive material is selected from a mixture of conductive carbon black and carbon nanotubes, and the two can be mixed in any mass ratio; or in some embodiments of the present application, the conductive material is selected from acetylene black, a mixture of acetylene black and carbon fibers, and the three can be mixed in any mass ratio; or in some embodiments of the present application, the conductive material is selected from a mixture of conductive carbon black, carbon nanotubes, acetylene black and carbon fibers, and the four can be mixed in any mass ratio.

[0127] Furthermore, in some embodiments of the present application, the added proportion of the conductive material accounts for 3%-10% of the mass of the insulating substrate in terms of mass percentage.

[0128] In the above technical solution, by controlling the addition ratio of the conductive material in the insulating base within the above range, it can not only meet the requirement of increasing welding conductivity and play a soldering effect, but also will not affect the mechanical properties of the insulating base due to excessive content.

[0129] Further optionally, in some embodiments of the present application, the added proportion of the conductive material accounts for 3.1%-9.9% of the mass of the insulating substrate in terms of mass percentage.

[0130] Illustratively, in some embodiments of the present application, the proportion of conductive material added is 3.2%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, or 9.5% of the mass of the insulating substrate, as a percentage by mass; or the proportion of conductive material added is a value within the range formed by any two of the above values.

[0131] In some embodiments of the present application, the testing method for the composition of the insulating base conductive material is: obtaining the percentage of trace element content through elemental ICP analysis.

[0132] Furthermore, in some embodiments of the present application, the material of the insulating substrate includes at least one of an organic polymer insulating material, an inorganic insulating material, or a composite material.

[0133] For example, in some embodiments of the present application, the material of the insulating base is selected from any one of an organic polymer insulating material, an inorganic insulating material or a composite material; or, in some embodiments of the present application, the material of the insulating base is selected from a mixture of an organic polymer insulating material and an inorganic insulating material, and the two can be mixed in any proportion; or, in some embodiments of the present application, the material of the insulating base is selected from a mixture of an organic polymer insulating material, an inorganic insulating material and a composite material, and the three can be mixed in any proportion.

[0134] Furthermore, in some embodiments of the present application, the organic polymer insulating material includes at least one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber or polycarbonate.

[0135] For example, in some embodiments of the present application, the organic polymer insulating material is selected from polyethylene, polypropylene or polystyrene; or in some embodiments of the present application, the organic polymer insulating material is selected from a mixture of polyformaldehyde and epoxy resin, and the two can be mixed in any proportion; or in some embodiments of the present application, the organic polymer insulating material is selected from a mixture of polytetrafluoroethylene, polyvinylidene fluoride and silicone rubber, and the three can be mixed in any proportion.

[0136] Furthermore, in some embodiments of the present application, the inorganic insulating material includes at least one of aluminum oxide, silicon carbide, or silicon dioxide.

[0137] For example, in some embodiments of the present application, the inorganic insulating material is selected from any one of aluminum oxide, silicon carbide or silicon dioxide; or in some embodiments of the present application, the inorganic insulating material is selected from a mixture of aluminum oxide and silicon carbide, and the two can be mixed in any proportion; or in some embodiments of the present application, the inorganic insulating material is selected from a mixture of aluminum oxide, silicon carbide and silicon dioxide, and the three can be mixed in any proportion.

[0138] Furthermore, in some embodiments of the present application, the composite material includes at least one of an epoxy resin glass fiber reinforced composite material or a polyester resin glass fiber reinforced composite material.

[0139] For example, in some embodiments of the present application, the composite material is selected from either epoxy resin glass fiber reinforced composite material or polyester resin glass fiber reinforced composite material; or in some embodiments of the present application, the composite material is selected from a mixture of epoxy resin glass fiber reinforced composite material and polyester resin glass fiber reinforced composite material, and the two can be mixed in any proportion.

[0140] Furthermore, in some embodiments of the present application, the material of the conductive layer includes at least one of a metal conductive material or a carbon-based conductive material.

[0141] For example, in some embodiments of the present application, the material of the conductive layer is selected from any one of metal conductive materials or carbon-based conductive materials; or the material of the conductive layer is selected from a mixture of metal conductive materials and carbon-based conductive materials, and the two can be mixed in any proportion.

[0142] Furthermore, in some embodiments of the present application, the metal conductive material includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, or aluminum-zirconium alloy.

[0143] For example, in some embodiments of the present application, the metal conductive material is selected from aluminum, copper or nickel; or in some embodiments of the present application, the metal conductive material is selected from a mixture of aluminum and copper, and the two can be mixed in any proportion.

[0144] Furthermore, in some embodiments of the present application, the carbon-based conductive material includes at least one of graphite, acetylene black, graphene, or carbon nanotubes.

[0145] For example, in some embodiments of the present application, the carbon-based conductive material is selected from any one of graphite, acetylene black, graphene or carbon nanotubes; or in some embodiments of the present application, the carbon-based conductive material is selected from a mixture of graphite and acetylene black, and the two can be mixed in any proportion; or in some embodiments of the present application, the carbon-based conductive material is selected from a mixture of graphite, acetylene black and graphene, and the three can be mixed in any proportion.

[0146] Furthermore, in some embodiments of the present application, the above-mentioned insulating substrate can be formed by co-extruding a film through a specially structured die head. For example, in some embodiments of the present application, FIG8 shows a dropper-shaped die head, which can be used to co-extrude a film through extrusion to form the above-mentioned insulating substrate.

[0147] Further, referring to Figure 9, in some embodiments of the present application, a multi-stage rolling and thinning device is added to the front section of the film drawing to roll the freshly extruded cast sheet into a thin sheet for film drawing, so that the insulating base forms a special structure in which the tab connection area is thinner and the active material support area is thicker.

[0148] Furthermore, in some embodiments of the present application, when a conductive material is added to the insulating base, the conductive material needs to be added in a corresponding mass percentage when the insulating base material masterbatch is melted to form the insulating base with the added conductive material in the above-mentioned special structure.

[0149] Furthermore, in some embodiments of the present application, the conductive layer may be formed on both sides of the insulating substrate by at least one of water electroplating, vapor deposition or chemical plating.

[0150] Further optionally, in some embodiments of the present application, the above-mentioned vapor deposition method can be physical vapor deposition; the physical vapor deposition method can be at least one of evaporation or sputtering; the evaporation method can be at least one of vacuum evaporation, thermal evaporation or electron beam evaporation; the sputtering method can be magnetron sputtering.

[0151] Furthermore, in some embodiments of the present application, the conductive layer in the edge tab connection area can be thickened by increasing the current in the edge area and the concentration distribution of the plating solution through the conductive method of water electroplating at both ends to increase the thickness, and the middle active material support area is thinned by anode shielding; optionally, the solution uses copper sulfate solution, and the anode is an insoluble anode plate to deposit metal.

[0152] Further optionally, in some embodiments of the present application, evaporation is used to achieve thickening of the conductive layer in the edge tab connection area; multiple evaporation methods can be adopted, and after the evaporation of the conductive layer in the middle area is completed, wire feeding evaporation is performed separately on the edge tab, and other areas do not adopt wire feeding and evaporation methods to thicken the edges.

[0153]

[0154] Some specific embodiments are listed below to better illustrate the present application.

[0155]

Preparation of insulating substrate

[0156] The die shown in Figure 8 is used for extrusion. The masterbatch or slice of the insulating base material is melted and extruded through the die shown in Figure 8 to form a thick cast sheet. The cast sheet is stretched by setting the transverse and longitudinal stretching ratios in different directions, first stretching in the longitudinal direction (MD direction) and then stretching in the transverse direction (TD direction). The edge tab area thinning treatment adopts the insulating base production edge thinning device shown in Figure 9. After the first stretching, a rolling device is added to further roll the thinned cast sheet into a film, and then it is stretched through multiple stages to finally form a film. The conductive material is added in the molten state of the slice or masterbatch, and then the film is co-extruded.

[0157]

Composite current collector preparation

[0158] The surface of the insulating substrate prepared above is cleaned; it is then placed in a vacuum plating chamber, and the high-purity metal wire in the metal evaporation chamber is melted and evaporated at a high temperature of 1600°C to 2000°C. The evaporated metal passes through the cooling system in the vacuum plating chamber and is finally deposited on the surfaces of both sides of the insulating substrate to form a conductive layer. The melting mechanism of the metal wire is composed of several independently controlled melting units arranged along the width direction of the insulating substrate (including an evaporation boat, a wire feeding mechanism, and a heating current circuit). The conductive layer of the edge tab connection area is thickened by only opening the wire feeding mechanism at the edge and closing the wire feeding mechanism in the middle, and then thickening it through multiple passes of evaporation.

[0159]

Composite current collector performance test

[0160] (1) The test method for the thickness of the insulating substrate / conductive layer is as follows: prepare a composite current collector cross-section sample using liquid nitrogen quenching or argon ion etching, observe the secondary electron phase morphology of the sample cross-section using a scanning electron microscope (1000-5000 times) and measure the thickness of the conductive layer and the supporting layer. The minimum resolution can reach the nanometer level.

[0161] (2) The test method for the strength and ductility of the composite current collector is as follows: the sample is cut into strips with a top width of 15 mm along the MD direction, and the strength and ductility of the tab connection area are tested. The results are shown in Table 2. In Table 2, the mean strength value is used to represent the strength of the tab connection area; the mean ductility value is used to represent the ductility of the tab connection area;

[0162] Intensity mean = sum of 10 sample intensity values / 10;

[0163] The average elongation is the sum of the elongation values ​​of 10 samples / 10.

[0164] Examples and Comparative Examples

[0165] A composite current collector is provided. The performance parameters of the composite current collectors of various embodiments or comparative examples are shown in Table 1.

[0166] In Table 1, D1 is the thickness of the insulating substrate in the active material support area;

[0167] D2 is the thickness of the conductive layer in the active material support area;

[0168] D3 is the thickness of the insulating base in the tab connection area;

[0169] D4 is the thickness of the conductive layer in the tab connection area;

[0170] The ratio of D4 to D3 is A;

[0171] The ratio of D1 to D3 is B.

[0172]

Lithium-ion battery preparation and testing

[0173] Through conventional battery coating process, positive electrode slurry or negative electrode slurry is coated on the surface of the current collector and dried at 100°C to obtain positive electrode sheets or negative electrode sheets. Tab connection areas of different widths are reserved on both sides of the sheet for welding metal tabs; the active material layer on the surface of the positive and negative electrode sheets is compacted through conventional battery cold pressing process, and the compaction density of the positive electrode sheet is set to 3.4g / cm 3 The compaction density of the negative electrode is set to 1.6g / cm 3 .

[0174] During cold pressing, the number of broken strips and tab cracks is collected, and one round of data is counted every 1000m.

[0175] Subsequently, the positive electrode sheet, separator, and negative electrode sheet were wound together into a bare cell using conventional battery manufacturing processes. Ultrasonic welding was then used to perform multi-layer welding of the positive and negative electrode tabs, eliminating the transfer welding process. The welding power was 4 kW to 6 kW, and the amplitude was 25 to 60 μm. Example 7 and Comparative Example 1 employed transfer welding, laminating two narrow current collectors along the base of the tab in the weld zone. The weld zone and the fixed-width substrate were then roller-welded together to form the integral tab.

[0176] In order to evaluate the reliability of multi-layer tab welding, the ultrasonic welding tensile force of the tab was evaluated.

[0177] (1) Use a high-speed rail tensile testing machine to measure the ultrasonic welding tensile force of multi-layer tabs.

[0178] The weld tension after multi-layer tab welding is measured using a high-speed rail tensile testing machine. Ultrasonic-welded tabs are cut along the base of the tabs and stretched at a speed of 5 mm / min. The maximum force at the point of weld failure is recorded as the weld tension (N).

[0179] (2) 32 samples were selected for testing, and samples of the batteries after welding were randomly selected. The mechanical bonding effect of the welding was evaluated by the average ultrasonic welding tensile force of the samples to determine whether there was a cold weld. The formula for calculating the mean tensile force and standard deviation is as follows:

[0180] Average welding tensile force = sum of welding tensile force values ​​of 32 samples / 32;

[0181] The effects of the composite current collectors of various embodiments and comparative examples on the welding results are shown in Table 2. The welding tension in Table 2 adopts the average value of the welding tension.

[0182] In order to evaluate the reliability of the single-layer tab welding using transfer welding in the comparative example, the single-layer transfer welding tensile force of the tab was evaluated.

[0183] (1) Use a high-speed rail tensile testing machine to measure the welding tensile force of a single-layer transfer tab.

[0184] A high-speed rail tensile testing machine was used to measure the weld tension after welding a single-layer tab. The tab was cut into fixed samples with a width of 50 mm along the diaphragm area, with a length suitable for testing. The sample was stretched at a speed of 5 mm / min, and the maximum force at the point of weld failure was recorded as the weld tension (N).

[0185] (2) 32 samples were selected for testing, and samples of the batteries after welding were randomly selected. The mechanical bonding effect of the welding was evaluated by the average welding tensile force of the samples to determine whether there was a cold weld. The calculation formula for the average tensile force and standard deviation is as follows:

[0186] The average welding tensile force = the sum of the welding tensile force values ​​of 32 samples / 32.

[0187] The welded battery cell is then placed in a battery casing and the electrolyte is injected (EC:EMC volume ratio is 3:7, LiPF6 is 1 mol / L), followed by sealing, formation and other processes to finally obtain a lithium-ion battery.

[0188] By collecting short-term DCR data of 10 batteries, the effect of different conductive layer thicknesses in the tab connection area on the battery DCR was observed.

[0189] (1) Use the battery test equipment to test the DCR test. The specific test method is as follows: adjust the battery capacity to 50% SOC, record the voltage V1, and obtain the voltage value V2 at 4C discharge current for 30S. DCR = (V1-V2) / 4C (discharge current)

[0190] DCR value = sum of DCR values ​​of 10 samples / 10;

[0191] (2) Temperature rise test: Before the battery cell is placed in the shell, the temperature sensing wire is glued to the ultrasonic welding position with Teflon tape, and then the package is injected with liquid. Under different current rates (3C, 4C, 5C), the temperature rise difference of the ultrasonic welding position is tested with a multi-channel thermometer to evaluate the fast charging effect.

[0192] The temperature rise value of the ultrasonic weld = the sum of the temperature rise values ​​of the ultrasonic welds of 10 samples / 10.

[0193] The lithium battery performance test results are shown in Table 2.

[0194] Table 1

[0195] Table 2

[0196] From Table 2 above, we can see that:

[0197] Comparative Example 1 is a conventional integrated composite current collector. Compared with Comparative Example 1, the discharge temperature rise at different rates of ultrasonic welding in the above-mentioned embodiments of the present application is better than that in Comparative Example 1. It can be seen that the composite current collector provided by the embodiments of the present application improves the flow of current through the electrode sheet in the tab connection area.

[0198] Furthermore, compared to Comparative Example 1, Examples 1-6 showed significantly improved welding tension. This is because the conventional composite current collector in Comparative Example 1 has a low degree of metallization in the tab connection area, making direct ultrasonic welding highly susceptible to cold welds, significantly reducing welding tension or even failing to weld. Direct welding was not feasible in Comparative Example 1, requiring transfer welding.

[0199] Furthermore, a comparison of Examples 2 to 6 shows that when the thickness D3 of the insulating substrate in the tab connection area is less than 1.5 μm, the elongation of the composite current collector tab connection area is low, which may cause cold press cracking and welding failure. When the thickness D3 of the insulating substrate in the tab connection area is greater than 3 μm, the overall strength and elongation of the tab connection area decrease, and the frequency of cold press cracking increases. Therefore, when 1.5 μm ≤ D3 ≤ 3 μm, the tab connection area has excellent strength and elongation, and high welding reliability.

[0200] Furthermore, the welding tension of Examples 8-11 was significantly improved compared to Comparative Example 1. This is because the conventional composite current collector in Comparative Example 1 has a low degree of metallization in the tab connection area, and direct ultrasonic welding is very likely to cause cold welds, resulting in a significant reduction in welding tension or even failure to weld.

[0201] Furthermore, by comparing Examples 8 to 11 with each other, it can be seen that when the ratio A of the thickness D4 of the conductive layer in the tab connection area to the thickness D3 of the insulating substrate in the tab connection area is less than 1, the elongation of the composite current collector tab connection area is low, which may cause cold pressing cracking and welding failure problems; when the ratio A of the thickness D4 of the conductive layer in the tab connection area to the thickness D3 of the insulating substrate in the tab connection area is greater than 2, the degree of metallization of the composite current collector tab connection area is too high, which can easily cause large deposition in the tab connection area and the generation of holes during the manufacturing stage. Although the overall strength is high and the temperature rise and welding tension at different rates are improved, the low elongation leads to a significant increase in the number of cold pressing cracks; therefore, when 1≤A≤2, the strength and elongation of the tab connection area are excellent, and the welding reliability is high; it can directly meet the needs of direct ultrasonic welding of the composite current collector and meet the discharge safety and reliability requirements of the battery at high rates.

[0202] Furthermore, by comparing Examples 12 to 17, it can be seen that when the amount of conductive material added to the insulating base is less than 3%, the temperature rise effect of the final battery cell at different rates is not improved; when the amount of conductive material added to the insulating base is greater than 10%, due to the excessive addition of conductive material, the overall elongation of the composite current collector decreases, the brittleness increases, the probability of cold press cracking increases, and the risk of welding failure increases. The increase in the problem of cold welding leads to an abnormal increase in the temperature rise of the battery cell. Therefore, when the proportion of conductive material added accounts for 3%-10% of the mass of the insulating base, the mechanical properties of the composite current collector are excellent, and the DCR of the battery and the temperature rise performance at different rates are improved.

[0203] The performance of Example 7 and Comparative Example 1 are compared, see Table 3 and Table 4.

[0204] Table 3

[0205] Table 4

[0206] From Table 4 above, we can see that:

[0207] Example 7 and Comparative Example 1 do not adopt direct ultrasonic welding, but adopt the traditional transfer welding method of composite current collector to make battery cells. Although the ratio A of the metal thickness D4 in the pole ear area / the polymer layer thickness D3 in the pole ear area in Example 7 of this scheme is less than 1, which may affect the cold pressing cracking, after selecting some areas to make battery cells, it is found that the metallization strength of the pole ear area of ​​Example 7 is high and the thickness of the polymer layer accounts for a small proportion, which improves the strength of the transfer welding and improves the overcurrent temperature rise compared with the traditional structure of the comparative example.

[0208] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A composite current collector, characterized in that: The composite current collector comprises: an insulating substrate; and A conductive layer; along the thickness direction of the insulating substrate, the conductive layer is arranged on both sides of the insulating substrate; Along a direction perpendicular to the thickness of the composite current collector, the composite current collector includes an active material support area and a tab connection area, the thickness of the insulating substrate of the tab connection area is less than the thickness of the insulating substrate of the active material support area; the thickness of the conductive layer of the tab connection area is greater than the thickness of the conductive layer of the active material support area.

2. The composite current collector according to claim 1, characterized in that: The thickness of the composite current collector is the same at all positions. The thickness of the insulating substrate in the active material support area is D1; ​​the thickness of the insulating substrate in the tab connection area is D3; D3<D1.

3. The composite current collector according to claim 1 or 2, characterized in that: The thickness of the conductive layer in the tab connection area is D4; the ratio of D4 to D3 is A, and A≥1.

4. The composite current collector according to any one of claims 1 to 3, characterized in that: 1≤A≤2。 5. The composite current collector according to any one of claims 1 to 4, characterized in that: The ratio of D1 to D3 is B, B≥2.

6. The composite current collector according to any one of claims 1 to 5, characterized in that: The thickness of the insulating substrate in the active material supporting area is D1, 3 μm≤D1≤10 μm.

7. The composite current collector according to any one of claims 1 to 6, characterized in that: The thickness of the conductive layer in the active material supporting area is D2, 0.5 μm≤D2≤1.5 μm.

8. The composite current collector according to any one of claims 1 to 7, characterized in that: The thickness of the insulating substrate in the tab connection area is D3, and D3≤3 μm.

9. The composite current collector according to claim 8, characterized in that: 1.5μm≤D3≤3μm.

10. The composite current collector according to any one of claims 1 to 9, characterized in that: The thickness of the conductive layer in the tab connection area is D4, and D4≥1.5 μm.

11. The composite current collector according to claim 10, characterized in that: 1.5μm≤D4≤4μm.

12. The composite current collector according to any one of claims 1 to 11, characterized in that: The width of the tab connection area is L1, and L1≥10 mm.

13. The composite current collector according to claim 12, characterized in that: 10mm≤L1≤40mm.

14. The composite current collector according to any one of claims 1 to 13, characterized in that: Conductive material is added into the insulating substrate.

15. The composite current collector according to claim 14, characterized in that: The conductive material includes at least one of conductive carbon black, carbon nanotubes, acetylene black or carbon fibers.

16. The composite current collector according to claim 15, characterized in that: In terms of mass percentage, the added proportion of the conductive material accounts for 3%-10% of the mass of the insulating substrate.

17. The composite current collector according to any one of claims 1 to 16, characterized in that: The material of the insulating substrate includes at least one of an organic polymer insulating material, an inorganic insulating material or a composite material.

18. The composite current collector according to claim 17, characterized in that: The organic polymer insulating material includes at least one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber or polycarbonate; and / or the inorganic insulating material includes at least one of aluminum oxide, silicon carbide or silicon dioxide; and / or the composite material includes at least one of epoxy resin glass fiber reinforced composite material or polyester resin glass fiber reinforced composite material.

19. The composite current collector according to any one of claims 1 to 18, characterized in that: The material of the conductive layer includes at least one of a metal conductive material or a carbon-based conductive material.

20. The composite current collector according to claim 19, characterized in that: The metal conductive material includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy or aluminum-zirconium alloy; and / or The carbon-based conductive material includes at least one of graphite, acetylene black, graphene or carbon nanotubes.

21. A pole piece, characterized in that: A composite current collector comprising any one of claims 1-20.

22. A battery, characterized in that: The battery comprises the pole piece according to claim 21.

23. An electrical equipment, characterized in that: The electrical device comprises the battery according to claim 22.

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