WO2025256316A1 - 极片及其制备方法、电极组件及二次电池 - Google Patents

极片及其制备方法、电极组件及二次电池

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Publication number
WO2025256316A1
WO2025256316A1 PCT/CN2025/094344 CN2025094344W WO2025256316A1 WO 2025256316 A1 WO2025256316 A1 WO 2025256316A1 CN 2025094344 W CN2025094344 W CN 2025094344W WO 2025256316 A1 WO2025256316 A1 WO 2025256316A1
Authority
WO
WIPO (PCT)
Prior art keywords
adhesive layer
tab
current collector
electrode
area
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/CN2025/094344
Other languages
English (en)
French (fr)
Inventor
金富懂
吴华
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ningde Amperex Technology Ltd
Original Assignee
Ningde Amperex Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ningde Amperex Technology Ltd filed Critical Ningde Amperex Technology Ltd
Publication of WO2025256316A1 publication Critical patent/WO2025256316A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H01M50/552—Terminals characterised by their shape
    • H01M50/553—Terminals adapted for prismatic, pouch or rectangular cells
    • H01M50/557—Plate-shaped terminals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of battery technology, and in particular to an electrode sheet and its preparation method, an electrode assembly, and a secondary battery.
  • the tabs which serve as a bridge connecting the battery to the external circuit, are usually made of metal.
  • the tabs are welded to the current collector inside the battery, which allows the tabs to conduct electricity with the electrode components inside the battery, thereby achieving the purpose of transmitting current.
  • a double-sided empty foil area is usually required on the current collector, with the welding head and welding seat contacting the current collector on both sides of the empty foil area for welding.
  • the welding of the tabs to the empty foil area of the current collector usually results in some welding burrs. These burrs can easily pierce the separator and cause short circuit failure of the positive and negative electrodes inside the secondary battery.
  • the purpose of this application is to provide an electrode sheet and its preparation method, an electrode assembly and a secondary battery, which aims to improve the problems of welding burrs and easy puncture of the separator on the electrode sheet.
  • an electrode sheet comprising a current collector, a first active material layer, and a tab.
  • the current collector has a first surface, the first active material layer is disposed on the first surface, the first surface has a first empty foil region, the tab is disposed in the first empty foil region, and the electrode sheet further comprises a first adhesive layer.
  • the tab has a first portion and a second portion connected together, the first adhesive layer is bonded between the first portion and the first empty foil region, the first portion is electrically connected to the first empty foil region, and the second portion is used for connecting to an external electronic device.
  • the surface of the first portion facing the first empty foil region has a recessed region, the recessed region having a plurality of embedding grooves, the embedding grooves being recessed relative to the second portion along the thickness direction of the tab, and the first adhesive layer being embedded in at least a portion of the embedding grooves.
  • the tab since the tab is directly bonded to the current collector via the first adhesive layer, it is not only convenient to operate but also eliminates welding burrs. It eliminates the need for tab adhesive in the tab or the first empty foil area, saving the space occupied by the tab adhesive and increasing the energy density of the secondary battery while reducing costs. Furthermore, the surface of the tab facing the first empty foil area has several embedding grooves. When the first adhesive layer is bonded between the tab and the first empty foil area, the first adhesive layer is embedded in at least part of the embedding grooves. The first adhesive layer can fill at least part of the gap between the tab and the current collector. The embedding grooves increase the bonding area between the first adhesive layer and the tab, reduce the relative movement between the tab and the current collector, and thus improve the connection strength between the current collector and the tab.
  • the current collector further has a second surface, and the first surface and the second surface are disposed opposite each other along the thickness direction of the current collector.
  • the electrode also has a second active material layer disposed on the second surface, and when viewed along the thickness direction of the current collector, the projection of the first empty foil area lies on the projection of the second active material layer. Since the electrode tab and the first empty foil area of the current collector are bonded and fixed by the first adhesive layer, no soldering socket or soldering head is required. Therefore, the second surface can be entirely disposed of with the second active material layer.
  • the single-sided empty foil area can make full use of the internal space of the secondary battery and improve the energy density of the secondary battery.
  • the first adhesive layer comprises at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin, or styrene-butadiene rubber. It exhibits excellent adhesive properties and chemical resistance, making it adaptable to various electrochemical reactions within the secondary battery.
  • the first adhesive layer comprises hot melt adhesive and/or pressure-sensitive adhesive and/or thermosetting adhesive.
  • the overlap area between the tab and the first empty foil area is S3
  • the overlap area between the recessed area and the first empty foil area is S4 , where 20% ⁇ S4 / S3 ⁇ 80%.
  • Sufficient recessed area increases the bonding area between the tab and the first adhesive layer, facilitating the embedding of the first adhesive layer into multiple embedding grooves. This, in turn, improves the connection strength between the tab and the current collector.
  • the length of the first empty foil area is L1
  • the length of the first adhesive layer is L2 , where 1mm ⁇ L1 - L2 ⁇ 5mm. This facilitates the tab being positioned in the first empty foil area along the width of the current collector, while simultaneously reserving a gap space of 1mm to 5mm in the width of the current collector to prevent direct adhesion between the first adhesive layer and the first active material layer, thereby reducing the impact of the first adhesive layer on the battery energy density.
  • the width of the first empty foil area is W1
  • the width of the first adhesive layer is W2 , where 0mm ⁇ W1 - W2 ⁇ 5mm.
  • This facilitates the placement of the tab in the first empty foil area along the length of the current collector, while also reserving a gap of 1mm to 5mm along the length of the current collector to prevent direct adhesion between the first adhesive layer and the first active material layer, reducing the impact of the first adhesive layer on the energy density of the secondary battery.
  • This not only facilitates the placement of the tab in the first empty foil area but also facilitates the adhesion and fixation of the tab to the current collector through the first adhesive layer.
  • the bonding length between the first adhesive layer and the first empty foil area is L3 , where 4mm ⁇ L3 ⁇ 24mm.
  • the bonding width between the first adhesive layer and the first empty foil area is W3 , where 4mm ⁇ W3 ⁇ 14mm. This increases the bonding area between the first adhesive layer and the first empty foil area, improves the connection strength, and simultaneously reduces the impact of the first adhesive layer on the energy density of the secondary battery.
  • the thickness of the first adhesive layer is T1 along the thickness direction of the current collector, where 2 ⁇ m ⁇ T1 ⁇ 50 ⁇ m. This can improve the connection strength while reducing the impact of the first adhesive layer on the energy density of the secondary battery. Furthermore, 15 ⁇ m ⁇ T1 ⁇ 25 ⁇ m can reduce the detachment of the tab protrusion from the current collector.
  • the length of the first adhesive layer is L2
  • the length of the recessed area is L4
  • the width of the first adhesive layer is W2
  • the width of the recessed area is W4
  • the width of the tab located on the first empty foil area is W5 , and 0mm ⁇ W2 - W4 ⁇ 5mm, 0 ⁇ W2 - W5 ⁇ 5mm.
  • the embedding groove includes an opening near the current collector and a bottom away from the current collector.
  • the width of the opening is W6 , 0.1mm ⁇ W6 ⁇ 1mm
  • the width of the bottom is W7 , 0.1mm ⁇ W7 ⁇ 1mm; W6 > W7 .
  • Limiting the width to 0.1mm to 1mm facilitates the embedding of the first adhesive layer, and a wider opening allows for easier embedding of the first adhesive layer from the opening to the bottom of the embedding groove during hot-pressing of the tab, the first adhesive layer, and the current collector.
  • the distance between two adjacent embedding slots is D, where 0.1mm ⁇ D ⁇ 1mm.
  • D the distance between two adjacent embedding slots.
  • a straight portion is formed between them. This straight portion facilitates the adhesion of the first adhesive layer, reduces air ingress between the first adhesive layer and the electrode tab, and minimizes air bubble formation.
  • the embedding slot design increases the bonding area and the friction between the first adhesive layer and the electrode tab. The combination of the straight portion and the embedding slot further enhances the connection strength between the first adhesive layer and the electrode tab.
  • the recess depth H of the embedding groove along the thickness direction of the first electrode is 10 ⁇ m ⁇ H ⁇ 50 ⁇ m. This facilitates the embedding of the first adhesive layer into the entire embedding groove, reduces the likelihood of the first adhesive layer detaching from the embedding groove, and the sufficient embedding depth improves the connection strength between the first adhesive layer and the electrode tab.
  • the contact area between the first adhesive layer and a single embedding groove is S1
  • the area of the single embedding groove is S2 , where 10% ⁇ S1 / S2 ⁇ 100%.
  • the embedding of the first adhesive layer into the embedding groove increases the bonding area between the first adhesive layer and the embedding groove, reduces the generation of air bubbles, and improves the bonding strength between the first adhesive layer and the tab .
  • the total number of embedding slots is M, and the number of embedding slots containing the first adhesive layer is N, where 10% ⁇ N/M ⁇ 100%.
  • the first adhesive layer is embedded in multiple embedding slots to increase the bonding area between the tab and the first adhesive layer.
  • this application also proposes an electrode assembly, including a separator and at least two electrodes as described in any of the embodiments of the first aspect above, wherein the at least two electrodes are a positive electrode and a negative electrode, and the positive electrode and the separator are stacked and wound around the negative electrode.
  • this application also proposes a secondary battery, including the electrode assembly as described in the second aspect above.
  • this application also proposes a method for preparing an electrode sheet as described in any of the embodiments of the first aspect above, comprising: providing a current collector having a first surface, coating the first surface with a first active material layer, and reserving a first empty foil area on the first surface; providing a first adhesive layer, bonding the first adhesive layer to the first empty foil area; providing an electrode tab having a plurality of embedding grooves, the embedding grooves of the electrode tab facing the first adhesive layer, bonding the electrode tab to the first adhesive layer, and pressing the electrode tab to the first adhesive layer such that the first adhesive layer is at least partially embedded in the embedding grooves.
  • Figure 1 is a schematic diagram of the structure of an electrode sheet according to an embodiment of this application.
  • Figure 2 is a magnified view of part A in Figure 1;
  • Figure 3 is a schematic diagram of the bonding of the electrode tab, the first adhesive layer and the current collector according to an embodiment of this application (the first adhesive layer is not pressed);
  • Figure 4 is a schematic diagram of the bonding of the tab, the first adhesive layer and the current collector according to an embodiment of this application (the state after the first adhesive layer is pressed).
  • Figure 5 is a schematic diagram of the bonding of the electrode tab, the first adhesive layer and the current collector according to an embodiment of this application;
  • Figure 6 is a schematic diagram of the bonding of the tab, the first adhesive layer and the current collector according to an embodiment of this application (viewed along the third direction Z);
  • Figure 7 is a schematic diagram of the structure of the electrode tab according to an embodiment of this application.
  • Figure 8 is a schematic diagram of the structure of the first adhesive layer according to an embodiment of this application.
  • Figure 9 is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application.
  • Figure 10 is a schematic diagram of the structure of the electrode assembly of the related technology.
  • Electrode 100. Electrode; 10. Current collector; 11. First surface; 111. First empty foil area; 12. Second surface; 13. Protrusion; 20. First active substance layer; 30. Tab; 31. First part; 32. Second part; 311. Recessed area; 312. Embedded groove; 321. Groove opening; 322. Groove bottom; 33. Straight section; 40. First adhesive layer; 50.
  • Second active substance layer 1000, Electrode assembly; 100a, Positive electrode sheet; 10a, Positive current collector; 11a, First positive electrode surface; 111a, First positive electrode empty foil region; 12a, Second positive electrode surface; 20a, First positive electrode active material layer; 50a, Second positive electrode active material layer; 30a, Positive electrode tab; 100b, negative electrode sheet; 10b, negative electrode current collector; 11b, first negative electrode surface; 111b, first negative electrode empty foil area; 12b, second negative electrode surface; 20b, first negative electrode active material layer; 50b, second negative electrode active material layer; 30b, negative electrode tab; 200.
  • the term "and/or” is merely a description of the relationship between related objects, indicating that three relationships can exist.
  • a and/or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.
  • the character "/" in this document generally indicates that the preceding and following related objects have an "or" relationship.
  • the tab 30 serves as a bridge connecting the secondary battery to the external circuit. It is usually made of metal.
  • the tab 30 is welded to the current collector 10 inside the secondary battery, which allows the tab 30 to conduct with the electrode assembly 1000 inside the secondary battery, thereby achieving the purpose of transmitting current.
  • a double-sided empty foil area (the empty foil area is the area on the current collector 10 where no active material layer is provided) is usually required on the positive electrode current collector 10a.
  • the welding socket contacts the positive electrode current collector 10a in one empty foil area, and the welding head welds the positive electrode tab 30a to the positive electrode current collector 10a in the other empty foil area.
  • the negative electrode 100b is usually configured similarly.
  • the welding of the positive electrode tab 30a to the positive electrode current collector 10a and the welding of the negative electrode tab 30b to the negative electrode current collector 10b usually results in some welding burrs. These burrs can easily pierce the separator 200, which can easily lead to short circuit failure of the positive electrode 100a and the negative electrode 100b inside the secondary battery.
  • a double layer of tab adhesive 400 is typically provided at the positive electrode tab 30a position. That is, a layer of tab adhesive 400 is provided on one side of the empty foil of the positive electrode current collector 10a, and a layer of tab adhesive 400 is also provided on the other side.
  • the negative electrode sheet 100b is treated similarly, with the double layer of tab adhesive 400 preventing burrs from puncturing the separator 200.
  • two layers of adhesive are required on the positive electrode 100a to reduce the impact of burrs at the negative electrode tab 30b on the positive electrode active material layer.
  • two layers of adhesive 300 are required on the negative electrode 100b to reduce the impact of burrs at the positive electrode tab 30a on the negative electrode active material layer.
  • the multiple layers of adhesive affect the energy density of the secondary battery.
  • an electrode 100 is a crucial component of a secondary battery.
  • the electrode 100 is typically divided into a positive electrode and a negative electrode. Both the positive and negative electrodes contain substances capable of electrochemical reactions. These substances work together with the electrolyte to achieve energy storage and release in the secondary battery.
  • Figure 1 which illustrates the structure of an electrode 100 according to some embodiments of this application, the electrode 100 includes a current collector 10, a first active material layer 20, tabs 30, and a first adhesive layer 40.
  • the first active material layer 20 is disposed on the current collector 10, and the tabs 30 are bonded to the current collector 10 via the first adhesive layer 40.
  • the aforementioned current collector 10 which serves as the conductive substrate of the electrode 100, it can be made of aluminum foil or copper foil with an integrally flat and strip-like structure.
  • the current collector 10 when the current collector 10 is the positive electrode current collector, aluminum foil can be used; when the current collector 10 is the negative electrode current collector, copper foil can be used.
  • Aluminum foil and copper foil have high conductivity, which can effectively reduce the internal resistance of the secondary battery and facilitate the improvement of the energy density and power density of the secondary battery.
  • aluminum foil and copper foil also have good mechanical strength, which can withstand the expansion and contraction of the secondary battery during charging and discharging, ensuring the stability and safety of the secondary battery.
  • the current collector 10 has a first surface 11 and a second surface 12 disposed opposite to each other.
  • the first active material layer 20 may be disposed on the first surface 11.
  • the electrode 100 also includes a second active material layer 50 disposed on the second surface 12.
  • the first active material layer 20 comprises an active material, a conductive agent, and a binder. These components are mixed and stirred until homogeneous, then coated onto the first surface 11 of the current collector 10 to obtain the first active material layer 20.
  • the active material can be selected from one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, and cobalt-free materials.
  • the active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, elemental silicon, silicon oxides, and silicon alloys.
  • the current collector 10 has areas without an active material layer.
  • the first surface 11 has a first empty foil area 111, which is the area on the current collector 10 without an active material layer.
  • the second surface 12 can also have a second empty foil area (not shown in the figures). This double-sided empty foil area facilitates the welding of the tab 30 to the current collector 10.
  • the entire second surface 12 can be coated with the second active material layer 50 to improve the energy density of the secondary battery.
  • the tab 30 can be electrically connected to the current collector 10 in the first empty foil area 111.
  • the aforementioned tab 30 serves as a bridge connecting the secondary battery to an external circuit, allowing the current flowing through the current collector 10 to be directed to the external circuit.
  • the tab 30 can have a flat structure, comprising a first portion 31 and a second portion 32 connected to each other.
  • the first portion 31 is disposed in the first empty foil area 111 and is electrically connected to the current collector 10.
  • the second portion 32 of the tab 30 extends beyond the current collector 10 and is used to connect to external electronic devices.
  • the tab 30 can be fixed to the first empty foil area 111 using adhesive.
  • the first adhesive layer 40 is bonded between the first empty foil area 111 and the first portion 31 of the tab 30, fixing the tab 30 to the current collector 10, and electrically connecting the first portion 31 to the first empty foil area 111. Since the tab 30 is directly bonded to the current collector 10 via the first adhesive layer 40, it is not only convenient to operate but also eliminates welding burrs. Therefore, there is no need to place tab adhesive on the tab 30 or the first empty foil area 111, saving the space occupied by tab adhesive and increasing the energy density of the secondary battery while reducing costs. Furthermore, conventional welding methods often fail to fully weld the overlapping portion of the tab 30 and the current collector 10, resulting in typically low welding strength. The first adhesive layer 40 of this application, however, can fully bond the overlapping portion of the tab 30 and the current collector 10 and fill at least part of the gap between them, resulting in a larger connection area and higher connection strength.
  • the surface of the tab 30 facing away from the first adhesive layer 40 can directly contact the separator 200, thereby improving space utilization and increasing the energy density of the secondary battery.
  • the second active material layer 50 is disposed on the second surface 12. Viewed along the thickness direction (third direction Z) of the current collector 10, the projection of the first empty foil area 111 lies on the projection of the second active material layer 50. Since the tab 30 and the first empty foil area 111 of the current collector 10 are bonded and fixed by the first adhesive layer 40, no soldering base or soldering head is required. Therefore, the second surface 12 can be entirely disposed of with the second active material layer 50.
  • the single-sided empty foil area configuration fully utilizes the internal space of the secondary battery, improving its energy density. Simultaneously, no welding burrs are generated on either the first surface 11 or the second surface 12, and neither the first surface 11 nor the second surface 12 requires tab adhesive. This not only fully utilizes space and further improves energy density but also reduces costs.
  • the surface of the first portion 31 facing the first empty foil area 111 has a recessed area 311, and the recessed area 311 is provided with a plurality of embedding grooves 312.
  • the recessed area 311 refers to the entire area provided with the embedding grooves 312, not just the location where the embedding grooves 312 are provided.
  • the area can be divided by the longest distance in the length and width directions of the distribution of the embedding grooves 312.
  • the embedding grooves 312 are recessed relative to the second portion 32.
  • the embedding grooves 312 can be formed on the tab 30 by laser processing or extrusion molding.
  • the first adhesive layer 40 When the first adhesive layer 40 is bonded between the tab 30 and the first empty foil area 111, the first adhesive layer 40 is embedded in at least part of the embedding grooves 312.
  • the provision of the embedding grooves 312 can increase the bonding area between the first adhesive layer 40 and the tab 30, thereby improving the connection strength between the current collector 10 and the tab 30.
  • the total number of embedding grooves 312 is M
  • the number of embedding grooves 312 in which the first adhesive layer 40 is embedded is N, where 10% ⁇ N/M ⁇ 100%.
  • the first adhesive layer 40 is embedded in multiple embedding grooves 312, increasing the bonding area between the tab 30 and the first adhesive layer 40. Furthermore, when the first adhesive layer 40 is embedded in the embedding grooves 312, the friction between the first adhesive layer 40 and the tab 30 can be increased, further improving the structural strength between the current collector 10 and the tab 30.
  • the contact area between the first adhesive layer 40 and the single embedding groove 312 is S1
  • the area of the single embedding groove 312 is S2 , where 10% ⁇ S1 / S2 ⁇ 100%.
  • the embedding of the first adhesive layer 40 into the embedding groove 312 increases the bonding area between the first adhesive layer 40 and the embedding groove 312. Sufficient bonding area improves the bonding strength between the first adhesive layer 40 and the tab 30.
  • S1 / S2 100% indicates that the first adhesive layer 40 is completely embedded in the single embedding groove 312, reducing the occurrence of air bubbles between the first adhesive layer 40 and the embedding groove 312, and improving the bonding strength.
  • protrusions 13 may also be provided on the first empty foil area 111 of the current collector 10.
  • Several protrusions 13 can be formed on the current collector 10 by methods such as extrusion molding.
  • the protrusions 13 can act as reinforcing ribs, increasing the strength of the current collector 10 in the first empty foil area 111 and reducing deformation and tearing of the first empty foil area 111.
  • the first adhesive layer 40 is bonded between the current collector 10 and the tab 30, the first adhesive layer 40 is also embedded between two adjacent protrusions 13, increasing the bonding area between the first adhesive layer 40 and the current collector 10, and improving the connection strength between the current collector 10 and the tab 30.
  • the protrusion 13 can be embedded in the insertion groove 312 of the tab 30, which can restrict the relative movement between the tab 30 and the current collector 10 and improve the connection strength between the tab 30 and the current collector 10.
  • a first adhesive layer 40 is present between the protrusion 13 and the insertion groove 312, and the first adhesive layer 40 simultaneously bonds the protrusion and the insertion groove 312; or, a portion of the protrusion 13 may directly contact the insertion groove 312 to achieve electrical connection between the tab 30 and the current collector 10.
  • the first empty foil area 111 can also be provided with several embedding grooves 312, and the first adhesive layer 40 is embedded in the embedding grooves 312 of the first empty foil area 111 to improve the bonding strength between the first adhesive layer 40 and the current collector 10.
  • the tab 30 has a protrusion 13 on its surface facing the first adhesive layer 40, and the protrusion 13 on the tab 30 is directly embedded in the first adhesive layer 40 to increase the bonding area between the tab 30 and the first adhesive layer 40 and improve the connection strength.
  • the first adhesive layer 40 includes thermosetting adhesive and/or pressure-sensitive adhesive and/or hot melt adhesive.
  • the first adhesive layer 40 can be made of hot melt adhesive.
  • the first adhesive layer 40 can be first bonded to the first empty foil area 111, and then the tab 30 can be bonded to the first adhesive layer 40 by hot pressing.
  • the hot pressing melts the first adhesive layer 40 and embeds it into the embedding groove 312. After the first adhesive layer 40 is cured, the tab 30 can be fixed to the current collector 10.
  • the first adhesive layer 40 can also be a thermosetting adhesive. After the first adhesive layer 40 is bonded to the first empty foil area 111, it is cured by hot pressing, so that the tab 30 is fixed to the current collector 10.
  • the first adhesive layer 40 can also be a pressure-sensitive adhesive. When pressing the tab 30, the first adhesive layer 40, and the current collector 10, the first adhesive layer 40 can be embedded in at least part of the embedding groove 312, and the first adhesive layer 40 can bond the current collector 10 and the tab 30. In some other embodiments, the first adhesive layer 40 can also be made of both hot melt adhesive and pressure-sensitive adhesive.
  • the first adhesive layer 40 can be of various types.
  • the first adhesive layer 40 includes at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin, or styrene-butadiene rubber.
  • the first adhesive layer 40 includes epoxy resin, which has excellent adhesive properties and chemical resistance, strong adhesion after immersion in liquid, and minimal swelling. It can adapt to various electrochemical reactions inside the secondary battery, and the epoxy resin can be cured by heating or reacting with a curing agent to form a robust first adhesive layer 40.
  • the first adhesive layer 40 is conductive, and when the first adhesive layer 40 is bonded between the tab 30 and the current collector 10, the tab 30 and the current collector 10 are electrically connected.
  • the first adhesive layer 40 includes conductive metal fillers such as silver, copper, and nickel, which makes the first adhesive layer 40 conductive and facilitates the electrical connection between the tab 30 and the current collector 10.
  • the material of the first adhesive layer 40 can be either an insulating material or a conductive adhesive.
  • the first adhesive layer 40 is a conductive adhesive.
  • the overlap area between the tab 30 and the first empty foil area 111 is S3
  • the overlap area between the recessed area 311 and the first empty foil area 111 is S4 , where 20% ⁇ S4 / S3 ⁇ 80%.
  • the recessed area 311 and the first empty foil area 111 have sufficient overlap area.
  • the sufficient area of the recessed area 311 can increase the bonding area between the tab 30 and the first adhesive layer 40, thereby improving the connection strength between the tab 30 and the current collector 10.
  • the sum of the areas of all the embedded grooves 312 can also be S4.
  • the size of the first empty foil area 111 if the size of the first empty foil area 111 is too large, it will affect the energy density of the battery; if the size of the first empty foil area 111 is too small, it will be difficult to accommodate the tab 30, which is not conducive to the bonding and fixing of the tab 30 and the current collector 10.
  • the size of the first adhesive layer 40 if the size of the first adhesive layer 40 is too small, it may lead to unstable adhesion with the current collector 10 or the tab 30. If the size of the first adhesive layer 40 is too large, it occupies a large space and is easy to adhere to the first active material layer 20, which will affect the energy density of the battery.
  • the length of the first empty foil area 111 is L1
  • the length of the first adhesive layer 40 is L2 . 1mm ⁇ L1 - L2 ⁇ 5mm , which facilitates the tab 30 to be disposed in the first empty foil area 111 in the width direction (second direction Y) of the current collector 10.
  • a gap space of 1mm to 5mm is reserved in the width direction (second direction Y) of the current collector 10 to prevent the first adhesive layer 40 from directly bonding with the first active material layer 20 and reduce the impact of the first adhesive layer 40 on the battery energy density.
  • the width of the first empty foil area 111 is W1
  • the width of the first adhesive layer 40 is W2 , 0mm ⁇ W1 - W2 ⁇ 5mm .
  • This facilitates the placement of the tab 30 in the first empty foil area 111 along the length direction (first direction X) of the current collector 10.
  • a gap space of 1mm to 5mm is reserved in the length direction (first direction X) of the current collector 10 to prevent the first adhesive layer 40 from directly bonding with the first active material layer 20, thereby reducing the impact of the first adhesive layer 40 on the energy density of the secondary battery.
  • This not only facilitates the placement of the tab 30 in the first empty foil area 111, but also facilitates the bonding and fixation of the tab 30 to the current collector 10 through the first adhesive layer 40.
  • the bonding length between the first adhesive layer 40 and the first empty foil area 111 is L3 , where 4mm ⁇ L3 ⁇ 24mm.
  • the bonding width between the first adhesive layer 40 and the first empty foil area 111 is W3 , where 4mm ⁇ W3 ⁇ 14mm.
  • the thickness of the first adhesive layer 40 if the thickness of the first adhesive layer 40 is too large, it will affect the energy density of the secondary battery; if the thickness of the first adhesive layer 40 is too small, it will easily lead to unstable adhesion between the tab 30 and the current collector 10, and may also make it difficult for the first adhesive layer 40 to be embedded in the embedding groove 312 of the tab 30.
  • the thickness of the first adhesive layer 40 is T1 , 2 ⁇ m ⁇ T1 ⁇ 50 ⁇ m .
  • the first adhesive layer 40 and the tab 30 When the current collector 10, the first adhesive layer 40 and the tab 30 are hot-pressed, the first adhesive layer 40 can be embedded in the embedding groove 312 of the tab 30, and the first adhesive layer 40 can stably bond the tab 30 and the current collector 10, which can improve the connection strength while reducing the impact of the first adhesive layer 40 on the energy density of the secondary battery.
  • 15 ⁇ m ⁇ T 1 ⁇ 25 ⁇ m where 15 ⁇ m to 25 ⁇ m is typically the finished thickness of the first adhesive layer 40.
  • 15 ⁇ m to 25 ⁇ m is typically the thickness after the rebound, which can reduce the tabs 30 from detaching from the current collector 10.
  • the length of the first adhesive layer 40 is L2
  • the length of the recessed area 311 is L4 , 0mm ⁇ L2 - L4 ⁇ 5mm .
  • the length of the first adhesive layer 40 can be the same as or greater than the length of the recessed area 311, so that the first adhesive layer 40 can be embedded in each embedding groove 312 of the recessed area 311.
  • the length of the recessed area 311 can be the same as or less than the length of the tab 30. When the length is the same as the tab 30, the bonding between the first adhesive layer 40 and the tab 30 is the same as the bonding between the first adhesive layer 40 and the recessed area 311.
  • the tab 30 does not occupy too much space, which is conducive to improving the energy density of the battery.
  • the first adhesive layer 40 can bond the recessed area 311 and part of the flat area of the tab 30 (the area without the embedded groove 312).
  • the first adhesive layer 40 and the tab 30 the bonding of the flat area is more compact, which can reduce the air entering between the first adhesive layer 40 and the tab 30 and reduce the generation of air bubbles.
  • the recessed area 311 has a larger friction and bonding area. The combination of the flat area and the recessed area 311 can further improve the connection strength between the tab 30 and the current collector 10.
  • the width of the first adhesive layer 40 is W2
  • the width of the recessed area 311 is W4 , where 0mm ⁇ W2 - W4 ⁇ 5mm.
  • the width of the tab 30 located in the first empty foil area 111 is W5 , where 0 ⁇ W2 - W5 ⁇ 5mm.
  • the width of the first adhesive layer 40 is greater than the width of the tab 30 located in the first empty foil area 111, allowing the first adhesive layer 40 to completely bond the tab 30, thus improving the bonding strength.
  • the embedding groove 312 when viewed along the length direction (first direction X) of the current collector 10, can be triangular, rectangular, trapezoidal, semi-circular, or arc-shaped, etc.; or the embedding groove 312 can be a groove with a strip-shaped structure, which can be set along the length direction of the tab 30, along the width direction of the tab 30, or along other directions, etc.; multiple embedding grooves 312 with strip-shaped structures can be arranged along the length direction of the tab 30, or along the width direction, etc.
  • the embedding groove 312 adopts a trapezoidal structure.
  • the embedding groove 312 includes a groove opening 321 and a groove bottom 322.
  • the groove opening 321 is located close to the current collector 10, while the groove bottom 322 is located away from the current collector 10.
  • the width of the groove opening 321 is W6 , for example, 0.1mm ⁇ W6 ⁇ 1mm, limiting the width to 0.1mm to 1mm to facilitate the embedding of the first adhesive layer.
  • the width of the groove bottom 322 is W7 , 0.1mm ⁇ W7 ⁇ 1mm, where W6 > W7 .
  • the groove 321 is wider, which makes it easier for the first adhesive layer 40 to be embedded from the groove 321 into the bottom 322 of the embedding groove 312 when hot pressing the tab 30, the first adhesive layer 40 and the current collector 10. As the width of the bottom 322 becomes smaller, the first adhesive layer 40 will be continuously squeezed during embedding and will stick tightly to the inner wall of the embedding groove 312, thereby improving the bonding strength.
  • the distance between two adjacent embedding grooves 312 is D, where 0.1mm ⁇ D ⁇ 1mm.
  • a straight portion 33 can be formed between them.
  • the straight portion 33 facilitates the bonding of the first adhesive layer 40, reduces air entry between the first adhesive layer 40 and the tab 30, and reduces air bubble generation.
  • the embedding groove 312 configuration increases the bonding area and the friction between the first adhesive layer 40 and the tab 30.
  • the combination of the straight portion 33 and the embedding groove 312 further improves the connection strength between the first adhesive layer 40 and the tab 30.
  • the first adhesive layer 40 may not be fully embedded in the embedding groove 312, resulting in a gap between the first adhesive layer 40 and the embedding groove 312, affecting the bonding quality. If the depth of the embedding groove 312 is too small, the amount of the first adhesive layer 40 embedded is insufficient, which is not enough to increase the connection area, resulting in poor effect on improving the connection strength.
  • the recess depth of the embedding groove 312 is H, 10 ⁇ m ⁇ H ⁇ 50 ⁇ m, which facilitates the first adhesive layer 40 to be embedded into the entire embedding groove 312, reduces the first adhesive layer 40 from falling out of the embedding groove 312, and the sufficient embedding depth improves the connection strength between the first adhesive layer 40 and the tab 30.
  • embodiments of this application also provide an electrode assembly 1000, including a separator 200 and at least two electrode sheets 100 as described in any of the embodiments of the first aspect above.
  • the at least two electrode sheets 100 are a positive electrode sheet 100a and a negative electrode sheet 100b, respectively.
  • the positive electrode sheet 100a, the separator 200, and the negative electrode sheet 100b are stacked or stacked and wound along the thickness direction (third direction Z).
  • the separator 200 is disposed between the positive electrode sheet 100a and the negative electrode sheet 100b to separate the two.
  • the positive electrode sheet 100a includes a positive current collector 10a, a first positive active material layer 20a, a second positive active material layer 50a, and a positive electrode tab 30a.
  • the positive current collector 10a has a first positive electrode surface 11a and a second positive electrode surface 12a.
  • the first positive electrode surface 11a may be provided with the first positive active material layer 20a
  • the second positive electrode surface 12a may be provided with the second positive active material layer 50a.
  • the first positive electrode surface 11a has a first positive electrode empty foil region 111a, and the positive electrode tab 30a can be bonded to the first positive electrode empty foil region 111a through the aforementioned first adhesive layer 40.
  • the negative electrode 100b includes a negative current collector 10b, a first negative active material layer 20b, a second negative active material layer 50b, and a negative electrode tab 30b.
  • the negative current collector 10b has a first negative electrode surface 11b and a second negative electrode surface 12b.
  • the first negative active material layer 20b is disposed on the first negative electrode surface 11b
  • the second negative active material layer 50b is disposed on the second negative electrode surface 12b.
  • the first positive active material layer 20a faces the second negative active material layer 50b.
  • a first negative empty foil region 111b is disposed on the second negative electrode surface 12b of the negative current collector 10b.
  • the negative electrode tab 30b can be bonded to the first negative empty foil region 111b through a first adhesive layer 40.
  • this application also proposes a secondary battery including an electrode assembly 1000 as described in any of the embodiments of the second aspect above.
  • this application also proposes a method for preparing an electrode 100 as described in any of the embodiments of the first aspect above, comprising: providing a current collector 10 having a first surface 11; coating the first surface 11 with a first active material layer 20 and reserving a first empty foil area 111 on the first surface 11; providing a first adhesive layer 40 and bonding the first adhesive layer 40 to the first empty foil area 111; providing an electrode tab 30 having a plurality of embedding grooves 312, the embedding grooves 312 of the electrode tab 30 facing the first adhesive layer 40, and bonding the electrode tab 30 to the first adhesive layer 40; and pressing the electrode tab 30 and the first adhesive layer 40 such that the first adhesive layer 40 is at least partially embedded in the embedding grooves 312.
  • the tab 30 is directly bonded to the current collector 10 via the first adhesive layer 40.
  • This method is not only convenient to operate but also eliminates welding burrs. It eliminates the need for tab adhesive on the tab 30 or the first empty foil area 111, saving space and increasing the energy density of the secondary battery while reducing costs.
  • the surface of the tab 30 facing the first empty foil area 111 has several embedding grooves 312.
  • the first adhesive layer 40 is bonded between the tab 30 and the first empty foil area 111, the first adhesive layer 40 is embedded in at least a portion of the embedding grooves 312.
  • the first adhesive layer 40 can fill at least a portion of the gap between the tab 30 and the current collector 10.
  • the embedding grooves 312 increase the bonding area between the first adhesive layer 40 and the tab 30, reducing the relative movement between the tab 30 and the current collector 10, thereby improving the connection strength between the current collector 10 and the tab 30.
  • Lithium iron phosphate (LiFePO4), acetylene black (Acetylene Black), and polyvinylidene fluoride (PVDF, weight-average molecular weight 5 ⁇ 105 ) were mixed in a mass ratio of 94:3:3.
  • N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred under vacuum until a homogeneous positive electrode slurry with a solid content of 75 wt% was obtained.
  • the positive electrode slurry was uniformly coated onto one surface of a 6 ⁇ m thick aluminum foil current collector and dried at 90 °C to obtain a positive electrode sheet with a single-sided coating of positive active material (80 ⁇ m thick).
  • the above steps were then repeated on the other surface of the aluminum foil, with a first empty foil area of 10 mm width and 22 mm length pre-reserved on one surface, resulting in a positive electrode sheet with a double-sided coating of positive active material.
  • An epoxy resin first adhesive layer is bonded to the first empty foil area.
  • the bonding width of the first adhesive layer in the first empty foil area is 8 mm, with a 1 mm gap reserved on each side from the positive electrode active material layer.
  • the bonding length is 21 mm, with a 1 mm gap reserved in the length direction from the positive electrode active material layer.
  • the thickness of the first adhesive layer is 20 ⁇ m.
  • An aluminum sheet is used as the positive electrode tab.
  • An embedding groove is formed on the positive electrode tab by mechanical pressing. Each embedding groove surrounds a recessed area on the surface of the positive electrode tab. The width of the recessed area is 4 mm, the width of the positive electrode tab is 6 mm, and the length of the recessed area on the first empty foil area is 18 mm, consistent with the length of the positive electrode tab on the first empty foil area. The length of the recessed area is less than the length of the first adhesive layer, with a difference of 3 mm.
  • the positive electrode tab and the current collector with the first adhesive layer are fixed by hot pressing.
  • the embedding groove of the positive electrode tab faces the first adhesive layer, and the embedding groove depth is 20 ⁇ m. During hot pressing, the first adhesive layer is embedded into the embedding groove.
  • Graphite powder negative electrode active material
  • conductive carbon black Super P
  • conductive agent conductive agent
  • SBR styrene-butadiene rubber
  • a second empty foil area 10 mm wide and 22 mm long, was left on the negative electrode sheet.
  • An epoxy resin first adhesive layer is bonded to the first empty foil area.
  • the bonding width of the first adhesive layer in the first empty foil area is 8mm, with a 1mm gap space reserved on each side from the negative electrode active material layer.
  • the bonding length is 21mm, with a 1mm gap space reserved in the length direction from the negative electrode active material layer.
  • the first adhesive layer is embedded in the embedding groove.
  • Nickel sheets are used as the negative electrode tabs.
  • Embedding grooves are formed on the negative electrode tabs using mechanical pressing. Each embedding groove surrounds a recessed area on the surface of the negative electrode tab. The width of the recessed area is 4 mm, the width of the negative electrode tab is 6 mm, and the length of the recessed area on the second empty foil area is 18 mm, consistent with the length of the negative electrode tab on the first empty foil area. The length of the recessed area is less than the length of the first adhesive layer, with a difference of 3 mm.
  • the negative electrode tab and the current collector with the first adhesive layer are fixed by hot pressing.
  • the embedding grooves of the negative electrode tab face the first adhesive layer, and the embedding groove depth is 20 ⁇ m. During hot pressing, the first adhesive layer is embedded into the embedding grooves.
  • ethylene carbonate, methyl ethyl carbonate and diethyl carbonate are mixed in a mass ratio of 30:50:20 to obtain an organic solution.
  • lithium hexafluorophosphate is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol/L.
  • the separator, positive electrode, separator, and negative electrode prepared above are stacked in sequence and wound to obtain an electrode assembly.
  • the electrode assembly is then hot-pressed at a pressure of 5 MPa and a temperature of 65°C for 10 seconds.
  • the electrode assembly is placed in an aluminum-plastic film packaging bag, with both the positive and negative electrode tabs extending from the top seal edge of the packaging bag. After removing moisture at 80°C, electrolyte is injected and the bag is sealed.
  • Drop test method The lithium-ion batteries were pretreated at 25°C and allowed to stand at room temperature for 60 minutes. The voltage of the lithium-ion batteries before the drop test was measured. The lithium-ion batteries were then placed in a fixture and dropped freely from a height of 1.5m using a drop device in the following sequence: head-tail-right head corner-right tail corner-left head corner-left tail corner (angle: 45 ⁇ 15°), repeated 6 times. After the drop test, the batteries were allowed to stand at room temperature for 24 hours, and the voltage of the lithium-ion batteries was measured and recorded. The appearance of the lithium-ion batteries was checked and photographed before and after the test. The criteria for passing the drop test were: no smoke, no leakage, and voltage drop ⁇ 30mV. 100 lithium-ion batteries were tested, and the number of batteries that passed the test was X, with a pass rate of X/100. The test results are shown in Table 1 below.
  • the first adhesive layer fills the gap between the electrode and the current collector, and the setting of the embedded groove makes the connection area between the electrode and the current collector larger, thereby improving the connection strength.
  • the positive electrode used two tab adhesives with a thickness of 8 ⁇ m and dimensions of 15*30 mm to cover the empty foil areas on both sides of the positive electrode tab, and a positive electrode adhesive sheet with a thickness of 8 ⁇ m and dimensions of 15 mm*30 mm to cover the position of the positive electrode active material layer corresponding to the negative electrode tab.

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Abstract

本申请涉及一种极片及其制备方法、电极组件及二次电池，包括集流体、第一活性物质层和极耳，集流体具有第一表面，第一活性物质层设置于第一表面，第一表面具有第一空箔区，极耳设置于第一空箔区，极片包括第一胶层。极耳具有相连接的第一部分和第二部分，第一胶层粘接于第一部分与第一空箔区之间，第二部分用于外接电子设备。第一部分面向第一空箔区的表面具有凹陷区，凹陷区凹设有若干嵌入槽，沿极耳的厚度方向，嵌入槽相对于第二部分凹陷，第一胶层嵌入至少部分嵌入槽。不存在焊接毛刺，因此不需要在极耳或第一空箔区设置极耳胶，省去了极耳胶所占用的空间，可在减少成本的同时提高二次电池的能量密度。

Description

极片及其制备方法、电极组件及二次电池
相关申请的交叉参考
本申请要求于2024年6月13日提交中国专利局，申请号为202410763571.4，发明名称为“极片及其制备方法、电极组件及二次电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电池技术领域，特别是涉及一种极片及其制备方法、电极组件及二次电池。
背景技术
极耳作为电池与外部电路电连接的桥梁，其通常采用金属材料制成，极耳与电池内部的集流体焊接，可使得极耳与电池内部的电极组件导通，从而达到传输电流的目的。
为便于极耳的焊接，集流体上通常需要设置双面空箔区，焊头和焊座分别在两侧空箔区与集流体接触焊接。然而，极耳与集流体空箔区的焊接，通常会出现部分焊接毛刺，该毛刺易刺穿隔离膜，易导致二次电池内部的正负极片短接失效。
发明内容
本申请的目的在于提供一种极片及其制备方法、电极组件及二次电池，旨在改善极片上易出现焊接毛刺、易刺穿隔离膜的问题。
根据本申请的第一方面，提供一种极片，包括集流体、第一活性物质层和极耳，集流体具有第一表面，第一活性物质层设置于第一表面，第一表面具有第一空箔区，极耳设置于第一空箔区，极片还包括第一胶层。极耳具有相连接的第一部分和第二部分，第一胶层粘接于第一部分与第一空箔区之间，第一部分与第一空箔区电连接，第一部分与第一空箔区电连接，第二部分用于外接电子设备。第一部分面向第一空箔区的表面具有凹陷区，凹陷区凹设有若干嵌入槽，沿极耳的厚度方向，嵌入槽相对于第二部分凹陷，第一胶层嵌入至少部分嵌入槽。
上述技术方案中，由于极耳是通过第一胶层与集流体直接粘接固定，不仅操作方便，而且不存在焊接毛刺，不需要在极耳或第一空箔区设置极耳胶，省去了极耳胶所占用的空间，可在减少成本的同时提高二次电池的能量密度。并且，极耳面向第一空箔区的表面具有若干嵌入槽，当第一胶层粘接于极耳与第一空箔区之间时，第一胶层嵌入至少部分嵌入槽。第一胶层可填充极耳与集流体之间的至少部分间隙，嵌入槽的设置可增大第一胶层与极耳的粘接面积，减少极耳与集流体的相对运动，进而提高集流体与极耳之间的连接强度。
在一些优选的实施方式中，集流体还具有第二表面，沿集流体的厚度方向，第一表面与第二表面相对设置。极片还具有第二活性物质层，第二活性物质层设置于第二表面，沿集流体的厚度方向观察，第一空箔区的投影位于第二活性物质层的投影上。由于极耳与集流体的第一空箔区是通过第一胶层粘接固定，不需要焊座以及焊头，因此第二表面可全部设置第二活性物质层，单面空箔区的设置，可充分利用二次电池的内部空间，提高二次电池的能量密度。
在一些优选的实施方式中，第一胶层包括环氧树脂、聚烯烃、聚苯乙烯、聚甲基丙烯酸甲酯、酚醛树脂或丁苯橡胶中的至少一种。具有优异的粘接性能以及耐化学腐蚀性，可适应二次电池内部的各类电化学反应。
在一些优选的实施方式中，第一胶层包括热熔胶和/或压敏胶和/或热固胶。
在一些优选的实施方式中，沿第一极片的厚度方向观察，极耳与第一空箔区的重叠面积为S3，凹陷区与第一空箔区的重叠面积为S4，20％≤S4/S3≤80％。足够的凹陷区面积可增大极耳与第一胶层的粘接面积，方便第一胶层嵌入多个嵌入槽。进而提高极耳与集流体之间的连接强度。
在一些优选的实施方式中，沿集流体的宽长度方向，第一空箔区的长度为L1，第一胶层的长度为L2，1mm≤L1-L2≤5mm。方便极耳在集流体宽度方向上设置于第一空箔区，同时在集流体的宽度方向上预留1mm至5mm的间隙空间，防止第一胶层与第一活性物质层直接粘接，减少第一胶层对电池能量密度的影响。
可选的，沿集流体的长度方向，第一空箔区的宽度为W1，第一胶层的宽度为W2，0mm≤W1-W2≤5mm。方便极耳在集流体长度方向上设置于第一空箔区，同时在集流体长度方向上预留1mm至5mm的间隙空间，防止第一胶层与第一活性物质层直接粘接，减少第一胶层对二次电池能量密度的影响，不仅便于极耳设置于第一空箔区，也便于极耳通过第一胶层与集流体粘接固定。
在一些优选的实施方式中，沿集流体的宽度方向，第一胶层与第一空箔区的粘接长度为L3，4mm≤L3≤24mm。沿集流体的长度方向，第一胶层与第一空箔区的粘接宽度为W3，4mm≤W3≤14mm，提高第一胶层与第一空箔区的粘接面积，提高连接强度，同时减少第一胶层对二次电池能量密度的影响。
可选的，沿集流体的厚度方向，第一胶层的厚度为T1，2μm≤T1≤50μm。可在提高连接强度的同时，减少第一胶层对二次电池能量密度的影响。进一步的，15μm≤T1≤25μm，可减少极耳凸起部脱离集流体。
在一些优选的实施方式中，沿集流体的长宽度方向，第一胶层的长度为L2，凹陷区的长度为L4，0mm≤L2-L4≤5mm。可选的，沿集流体的长度方向，第一胶层的宽度为W2，凹陷区的宽度为W4，极耳位于第一空箔区上的宽度为W5，0mm≤W2-W4≤5mm，0≤W2-W5≤5mm。
在一些优选的实施方式中，嵌入槽包括靠近集流体的槽口以及远离集流体的槽底。沿集流体的宽度方向，槽口的宽度为W6，0.1mm≤W6≤1mm，槽底的宽度为W7，0.1mm≤W7≤1mm；W6＞W7。限定宽度为0.1mm至1mm，便于第一胶层的嵌入，并且槽口的宽度更大，在热压极耳、第一胶层以及集流体时，可方便第一胶层自槽口嵌入至嵌入槽的槽底。
在一些优选的实施方式中，相邻两嵌入槽之间的距离为D，0.1mm≤D≤1mm。通过将相邻两嵌入槽间隔设置，可使得相邻两嵌入槽之间形成平直部分，平直部分利于第一胶层的粘接，可减少空气进入第一胶层与极耳之间，减少气泡产生嵌入槽的设置可提高粘接面积，增大第一胶层与极耳之间的摩擦力，平直部分与嵌入槽的结合，进一步提高第一胶层与极耳之间的连接强度。
在一些优选的实施方式中，沿第一极片的厚度方向，嵌入槽的凹陷深度H，10μm≤H≤50μm。便于第一胶层嵌入至整个嵌入槽，减少第一胶层从嵌入槽中脱出，并且足够的嵌入深度提高第一胶层与极耳之间的连接强度。
在一些优选的实施方式中，第一胶层与单个嵌入槽接触的面积为S1，单个嵌入槽的面积为S2，10％≤S1/S2≤100％。第一胶层嵌入嵌入槽增大了第一胶层与嵌入槽的粘接面积，减少气泡产生，提高第一胶层与极耳的粘接强度。
在一些优选的实施方式中，全部嵌入槽的数量为M，嵌入有第一胶层的嵌入槽数量为N，10％≤N/M≤100％。第一胶层嵌入多个嵌入槽，提高极耳与第一胶层的粘接面积。
第二方面，本申请还提出了一种电极组件，包括隔离膜以及至少两个如上述第一方面任一实施例的极片，至少两个极片分别为正极极片和负极极片，正极极片、隔离膜以负极极片层叠并卷绕设置。
第三方面，本申请还提出了一种二次电池，包括如上述第二方面的电极组件。
第四方面，本申请还提出了一种制备如上述第一方面任一实施例极片的方法，包括：提供集流体，集流体具有第一表面，对第一表面涂覆第一活性物质层，并在第一表面预留第一空箔区；提供第一胶层，将第一胶层粘接于第一空箔区；提供极耳，极耳具有若干嵌入槽，极耳的嵌入槽面向第一胶层，并将极耳与第一胶层粘接，压接极耳与第一胶层使得第一胶层至少部分嵌入嵌入槽中。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
一个或多个实施例通过与之对应的附图进行示例性说明，这些示例性说明并不构成对实施例的限定，附图中具有相同参考数字标号的元件表示为类似的元件，除非特别申明，附图中的尺寸不构成比例限制。
图1为本申请一实施例的极片的结构示意图；
图2为图1中A处的局部放大图；
图3为本申请一实施例的极耳、第一胶层以及集流体的粘接示意图(第一胶层未压接的状态)；
图4为本申请一实施例的极耳、第一胶层以及集流体的粘接示意图(第一胶层压接后的状态)；
图5为本申请一实施例的极耳、第一胶层以及集流体的粘接示意图；
图6为本申请一实施例的极耳、第一胶层以及集流体的粘接示意图(沿第三方向Z观察)；
图7为本申请一实施例的极耳的结构示意图；
图8为本申请一实施例的第一胶层的结构示意图；
图9为本申请一实施例的电极组件的结构示意图；
图10为相关技术的电极组件的结构示意图。
附图标记说明：
100、极片；
10、集流体；11、第一表面；111、第一空箔区；12、第二表面；13、凸起
部；
20、第一活性物质层；
30、极耳；31、第一部分；32、第二部分；311、凹陷区；312、嵌入槽；
321、槽口；322、槽底；33、平直部分；
40、第一胶层；
50、第二活性物质层；
1000、电极组件；
100a、正极极片；10a、正极集流体；11a、第一正极表面；111a、第一正
极空箔区；12a、第二正极表面；20a、第一正极活性物质层；50a、第二正极活性物质层；30a、正极极耳；
100b、负极极片；10b、负极集流体；11b、第一负极表面；111b、第一负
极空箔区；12b、第二负极表面；20b、第一负极活性物质层；50b、第二负极活性物质层；30b、负极极耳；
200、隔离膜；
300、极片胶；
X、第一方向；Y、第二方向；Z、第三方向。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。
在本申请中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
接下来，下面所采用的“上”、“下”、“顶”、“底”等表示方位或位置关系的名词，均是相对于第一方向X而言的。下面所描述的本申请不同实施例中所涉及的技术特征只要彼此之间未构成冲突就可以相互结合。
极耳30作为二次电池与外部电路电连接的桥梁，其通常采用金属材料制成，极耳30与二次电池内部的集流体10焊接，可使得极耳30与二次电池内部的电极组件1000导通，从而达到传输电流的目的。
请参照图10，为便于正极极耳30a的焊接，正极集流体10a上通常需要设置双面空箔区(空箔区为集流体10上未设置活性物质层的区域)，焊座在一侧空箔区与正极集流体10a接触，焊头在另一侧空箔区焊接正极极耳30a与正极集流体10a。负极极片100b通常也类似设置。
然而正极极耳30a与正极集流体10a的焊接以及负极极耳30b与负极集流体10b的焊接，通常会出现部分焊接毛刺，该毛刺易刺穿隔离膜200，易导致二次电池内部的正极极片100a与负极极片100b短接失效。
为降低隔离膜200被刺穿的风险，如图10所示，通常需要在正极极耳30a位置设置双层极耳胶400，也即在正极集流体10a的一侧空箔设置一道极耳胶400，另一侧同样设置极耳胶400。负极极片100b也是如此，双层极耳胶400的设置，防止毛刺刺穿隔离膜200。
并且，正极极片100a上同样需要设置两道极片胶，减少负极极耳30b位的毛刺对正极活性物质层的影响，负极极片100b同样需要设置两道极片胶300，以减少正极极耳30a位的毛刺对负极活性物质层的影响。然而，多道贴胶的设置，又影响了二次电池的能量密度。
为改善上述问题，第一方面，本申请的实施例提出了一种极片100，极片100是二次电池的重要组成部分，极片100通常分为正极极片和负极极片，正极极片和负极极片都具有能够进行电化学反应的物质，这些物质与电解液一起工作，实现二次电池的能量储存和释放。请参照图1，图1示出了本申请一些实施例的极片100的结构，该极片100包括集流体10、第一活性物质层20、极耳30以及第一胶层40。第一活性物质层20设置于集流体10上，极耳30通过第一胶层40与集流体10粘接。
对于上述集流体10，集流体10作为极片100的导电基材，其可采用整体扁平且呈条状结构的铝箔或铜箔。例如，当集流体10为正极集流体时，可采用铝箔，当集流体10为负极集流体时，可采用铜箔。铝箔和铜箔具有较高的导电性，可以有效地降低二次电池的内阻，便于提高二次电池的能量密度和功率密度。此外，铝箔和铜箔还具有较好的机械强度，可以承受二次电池在充放电过程中的膨胀和收缩，保证二次电池的稳定性和安全性。
沿集流体10的厚度方向(第三方向Z)，集流体10具有相对设置的第一表面11和第二表面12，上述第一活性物质层20可设置于第一表面11，在其他一些实施例中，极片100还包括第二活性物质层50，第二活性物质层设置于第二表面12。
对于上述第一活性物质层20，第一活性物质层20包括活性材料、导电剂以及粘接剂等，上述各材料组分混合后搅拌均匀，并涂覆于集流体10的第一表面11，从而得到第一活性物质层20。当极片100为正极极片时，活性材料可选自镍钴锰酸锂、钴酸锂、磷酸铁锂、镍钴锰酸锂、锰酸锂、磷酸锰铁锂、无钴材料中的一种或多种。当极片100为负极极片时，活性材料可选自石墨、软碳、硬碳、碳纤维、单质硅、硅氧化合物、硅合金中的一种或多种。
集流体10上具有未涂覆活性物质层的区域，例如，请参照图1至图3，第一表面11具有第一空箔区111，第一空箔区111为集流体10上未涂覆活性物质层的区域。第二表面12同样可设置第二空箔区(图中未标示)，双面空箔区设置，便于极耳30与集流体10的焊接，或者第二表面12全部涂覆第二活性物质层50，提高二次电池的能量密度。上述极耳30可在第一空箔区111与集流体10电连接。
对于上述极耳30，极耳30是二次电池与外部电路连接的桥梁，可将流经集流体10的电流导出至外部电路中。请参照图1至图3，极耳30可采用扁平结构，极耳30包括相连接的第一部分31和第二部分32，第一部分31设置于上述第一空箔区111，并且第一部分31与集流体10电连接，极耳30的第二部分32则超出集流体10，用于外接电子设备。本申请的实施例中，可采用胶粘的方式将极耳30固定于第一空箔区111。
对于上述第一胶层40，请参照图1至图3，第一胶层40粘接于第一空箔区111与极耳30的第一部分31之间，可将极耳30与集流体10固定，并且第一部分31与第一空箔区111电连接。由于极耳30是通过第一胶层40与集流体10直接粘接固定，不仅操作方便，而且不存在焊接毛刺，因此不需要在极耳30或第一空箔区111设置极耳胶，省去了极耳胶所占用的空间，可在减少成本的同时提高二次电池的能量密度。并且，常规的焊接方式，是难以将极耳30与集流体10重叠的部位进行全部焊接，其焊接强度通常较低，而本申请的第一胶层40可将极耳30与集流体10重叠的部分进行全部粘接，并可填充极耳30与集流体10之间的至少部分间隙，连接面积更大，连接强度更高。
其中，极耳30背离第一胶层40的表面可与隔离膜200直接接触，提高空间利用率，提高二次电池的能量密度。
请参照图1至图3，在一些实施例中，第二活性物质层50设置于第二表面12，沿集流体10的厚度方向(第三方向Z)观察，第一空箔区111的投影位于第二活性物质层50的投影上。由于极耳30与集流体10的第一空箔区111是通过第一胶层40粘接固定，不需要焊座以及焊头，因此第二表面12可全部设置第二活性物质层50，单面空箔区的设置，可充分利用二次电池的内部空间，提高二次电池的能量密度。同时，不论是第一表面11还是第二表面12，均不会产生焊接毛刺，第一表面11和第二表面12均不需要极耳胶，不仅充分利用空间，进一步提高能量密度，还可达到降低成本的作用。
在一些实施例中，请参照图1至图3，第一部分31面向第一空箔区111的表面具有凹陷区311，凹陷区311设置有若干嵌入槽312。参照图7，凹陷区311指的是设置有嵌入槽312的一整片区域，并不是仅仅设置有嵌入槽312的位置为凹陷区，可以以嵌入槽312的分布的长度方向和宽度方向的最长距离划分区域。沿极耳30的厚度方向(第三方向Z)，嵌入槽312相对于第二部分32凹陷。可通过激光处理或者挤压成形等方法在极耳30上形成嵌入槽312，当第一胶层40粘接于极耳30与第一空箔区111之间时，第一胶层40嵌入至少部分嵌入槽312。嵌入槽312的设置可增大第一胶层40与极耳30的粘接面积，进而提高集流体10与极耳30之间的连接强度。
在一些实施例中，全部嵌入槽312的数量为M，嵌入有第一胶层40的嵌入槽312数量为N，10％≤N/M≤100％，第一胶层40嵌入多个嵌入槽312，提高极耳30与第一胶层40的粘接面积。并且，当第一胶层40嵌入嵌入槽312后，可提高第一胶层40与极耳30之间的摩擦力，可进一步提高集流体10与极耳30之间的结构强度。
在一些实施例中，第一胶层40与单个嵌入槽312接触的面积为S1，单个嵌入槽312的面积为S2，10％≤S1/S2≤100％，第一胶层40嵌入嵌入槽312增大了第一胶层40与嵌入槽312的粘接面积，足够的粘接面积提高第一胶层40与极耳30的粘接强度。例如，S1/S2＝100％，即表明单个嵌入槽312中被第一胶层40全部嵌入，减少第一胶层40与嵌入槽312之间出现气泡，提高粘接强度。
在其他一些实施例中，请参照图4，也可在集流体10的第一空箔区111上设置凸起部13，可通过挤压成形等方法在集流体10上凸设出若干凸起部13，凸起部13可起到类似于加强筋的作用，可提高集流体10在第一空箔区111的强度，减少第一空箔区111的变形撕裂。当第一胶层40粘接于集流体10与极耳30之间时，第一胶层40同样嵌入相邻两个凸起部13之间，可提高第一胶层40与集流体10之间的粘接面积，提高集流体10与极耳30之间的连接强度。
可选的，凸起部13嵌入极耳30的嵌入槽312，可限制极耳30与集流体10的相对运动，提高极耳30与集流体10之间的连接强度。其中，当凸起部13嵌入嵌入槽312内时，凸起部13与嵌入槽312之间具有第一胶层40，第一胶层40同时粘接凸起部与嵌入槽312；或者，部分凸起部13与嵌入槽312直接接触，实现极耳30与集流体10的电连接。
类似的，第一空箔区111也可设置若干嵌入槽312，第一胶层40嵌入第一空箔区111的嵌入槽312，提高第一胶层40与集流体10的粘接强度。或者，极耳30面向第一胶层40的表面设置凸起部13，极耳30上的凸起部13直接嵌入第一胶层40，增大极耳30与第一胶层40的粘接面积，提高连接强度。
第一胶层40包括热固胶和/或压敏胶和/或热熔胶。
例如，第一胶层40可采用热熔胶，可首先将第一胶层40粘接于第一空箔区111，再通过热压的方式将极耳30与第一胶层40粘接，热压第一胶层40熔融并嵌入至嵌入槽312内，待第一胶层40固化后即可使得极耳30与集流体10相固定。
第一胶层40还可采用热固胶，将第一胶层40粘接第一空箔区111后，通过热压固化，使得极耳30与集流体10相固定。
第一胶层40也可采用压敏胶，压接极耳30、第一胶层40以及集流体10时，可使得第一胶层40嵌入至少部分嵌入槽312内，并且可使得第一胶层40粘接集流体10以及极耳30。在其他一些实施例中，第一胶层40也可同时采用热熔胶及压敏胶。
第一胶层40的种类可选择多种，例如，第一胶层40包括环氧树脂、聚烯烃、聚苯乙烯、聚甲基丙烯酸甲酯、酚醛树脂或丁苯橡胶中的至少一种。示例性的，第一胶层40包括环氧树脂，环氧树脂具有优异的粘接性能以及耐化学腐蚀性，泡液后粘接性能强并且溶胀小，可适应二次电池内部的各类电化学反应，并且环氧树脂可以通过加热或与固化剂反应进行固化，形成坚固的第一胶层40。
在一些实施例中，第一胶层40具有导电性，当第一胶层40粘接于极耳30与集流体10之间时，即使得极耳30与集流体10电连接。例如，第一胶层40中包括银、铜、镍等导电金属填充物，使得第一胶层40具备导电性，方便极耳30与集流体10的电连接。
需要说明，当极耳30部分穿过第一胶层40并与第一空箔区111接触时，第一胶层40的材料可选择绝缘材料，也可选择导电胶。当极耳30没有穿过第一胶层40时，第一胶层40为导电胶。
在一些实施例中，沿第一极片100的厚度方向(第三方向Z)观察，极耳30与第一空箔区111的重叠面积为S3，凹陷区311与第一空箔区111的重叠面积为S4，20％≤S4/S3≤80％。凹陷区311与第一空箔区111具有足够的重叠面积，当第一胶层40粘接于极耳30与集流体10之间时，足够的凹陷区311面积可增大极耳30与第一胶层40的粘接面积，进而提高极耳30与集流体10之间的连接强度。可选的，也可以全部嵌入槽312的面积之和为S4，全部嵌入槽312的面积占比较大时，会导致相邻两嵌入槽312之间的间隔较小，易导致极耳30强度不高。全部嵌入槽312的面积占比较小时，易导致第一胶层40难以嵌入至嵌入槽312，不利于提高粘接效果。选择20％≤S4/S3≤80％，可便于第一胶层40嵌入至嵌入槽312，提高连接强度。
对于上述第一空箔区111的尺寸，第一空箔区111的尺寸过大，影响电池的能量密度，第一空箔区111的尺寸过小，难以容纳极耳30，不利于极耳30与集流体10的粘接固定。
而对于第一胶层40的尺寸，第一胶层40的尺寸过小，可能会导致与集流体10或极耳30的粘接不稳定，第一胶层40的尺寸过大，占用的空间较大，并且易与第一活性物质层20粘接，影响电池的能量密度。
本申请的实施例中，请参照图5和图6，沿集流体10的宽度方向(第二方向Y)，第一空箔区111的长度为L1，第一胶层40的长度为L2，1mm≤L1-L2≤5mm，方便极耳30在集流体10宽度方向(第二方向Y)上设置于第一空箔区111，同时在集流体10的宽度方向(第二方向Y)上预留1mm至5mm的间隙空间，防止第一胶层40与第一活性物质层20直接粘接，减少第一胶层40对电池能量密度的影响。
沿集流体10的长度方向(第一方向X)，第一空箔区111的宽度为W1，第一胶层40的宽度为W2，0mm≤W1-W2≤5mm，方便极耳30在集流体10长度(第一方向X)方向上设置于第一空箔区111，同时在集流体10长度方向(第一方向X)上预留1mm至5mm的间隙空间，防止第一胶层40与第一活性物质层20直接粘接，减少第一胶层40对二次电池能量密度的影响，不仅便于极耳30设置于第一空箔区111，也便于极耳30通过第一胶层40与集流体10粘接固定。
可选的，沿集流体10的宽度方向(第二方向Y)，第一胶层40与第一空箔区111的粘接长度为L3，4mm≤L3≤24mm。沿集流体10的长度方向(第一方向X)，第一胶层40与第一空箔区111的粘接宽度为W3，4mm≤W3≤14mm。足够的粘接长度以及粘接宽度，提高第一胶层40与第一空箔区111的粘接面积，提高连接强度，同时减少第一胶层40对二次电池能量密度的影响。第一胶层40通常是整体与第一空箔区111粘接，第一胶层40的宽度W2即为第一胶层40与第一空箔区111的粘接宽度W3，也即W2＝W3。
对于第一胶层40的厚度，第一胶层40的厚度过大，影响二次电池的能量密度，第一胶层40的厚度过小，易导致极耳30与集流体10粘接不稳定，同时可能导致第一胶层40难以嵌入极耳30的嵌入槽312。本申请的实施例中，沿集流体10的厚度方向(第三方向Z)，第一胶层40的厚度为T1，2μm≤T1≤50μm，当热压集流体10、第一胶层40以及极耳30时，第一胶层40可嵌入极耳30的嵌入槽312，并能够使得第一胶层40稳定粘接极耳30以及集流体10，可在提高连接强度的同时，减少第一胶层40对二次电池能量密度的影响。
进一步的，15μm≤T1≤25μm，15μm至25μm通常为第一胶层40的成品厚度，在二次电池制备过程中存在高温环境，使得第一胶层40反弹，15μm至25μm通常为反弹后的厚度，可以减少极耳30从集流体10脱出。
在一些实施例中，请进一步参照图4，沿集流体10的宽度方向(第二方向Y)，第一胶层40的长度为L2，凹陷区311的长度为L4，0mm≤L2-L4≤5mm，第一胶层40的长度可与凹陷区311的长度一致或大于凹陷区311的长度，便于第一胶层40均能够嵌入凹陷区311的各嵌入槽312。凹陷区311的长度可与极耳30的长度一致或者小于极耳30的长度，当与极耳30的长度一致时，第一胶层40与极耳30的粘接即为与凹陷区311的粘接，极耳30不占用过多的空间，便于提高电池的能量密度；当小于极耳30的长度时，第一胶层40可粘接凹陷区311以及部分极耳30的平直区(未设置嵌入槽312的区域)，在压接集流体10、第一胶层40以及极耳30时，平直区粘接更致密，可减少空气进入第一胶层40与极耳30之间，减少气泡产生；而凹陷区311摩擦力及粘接面积更大，平直区与凹陷区311的结合，可进一步提高极耳30与集流体10的连接强度。
类似的，沿集流体10的长度方向(第一方向X)，第一胶层40的宽度为W2，凹陷区311的宽度为W4，0mm≤W2-W4≤5mm，在集流体10的长度方向(第一方向X)上，可便于第一胶层40均能够嵌入凹陷区311的各嵌入槽312。极耳30位于第一空箔区111上的宽度为W5，0≤W2-W5≤5mm，第一胶层40的宽度大于极耳30位于第一空箔区111的宽度，可使得第一胶层40将极耳30全部粘接，提高粘接强度。
对于嵌入槽312的形状，沿集流体10的长度方向(第一方向X)观察，嵌入槽312可采用三角形、矩形、梯形、半圆形或弧形等；或者嵌入槽312为条状结构的凹槽，条状结构可沿极耳30的长度方向设置，也可沿极耳30宽度方向设置，或者沿其他方向设置等；多个条状结构的嵌入槽312可沿极耳30的长度方向排列，也可沿宽度方向排列等。
示例性的，嵌入槽312采用梯形结构，请参照图3和图8，嵌入槽312包括槽口321和槽底322，槽口321靠近集流体10设置，槽底322则远离集流体10设置。沿集流体10的宽度方向(第二方向Y)，槽口321的宽度为W6，例如0.1mm≤W6≤1mm，限定宽度为0.1mm至1mm，方便第一胶层的嵌入。槽底322的宽度为W7，0.1mm≤W7≤1mm，其中，W6＞W7。槽口321的宽度更大，在热压极耳30、第一胶层40以及集流体10时，可方便第一胶层40自槽口321嵌入至嵌入槽312的槽底322，并且随着槽底322的宽度更小，第一胶层40在嵌入时会不断挤压，并紧贴嵌入槽312的内壁，进而提高粘接强度。
在一些实施例中，请参照图8，相邻两嵌入槽312之间的距离为D，0.1mm≤D≤1mm。通过将相邻两嵌入槽312之间间隔设置，可使得相邻两嵌入槽312之间形成平直部分33，平直部分33利于第一胶层40的粘接，可减少空气进入第一胶层40与极耳30之间，减少气泡产生嵌入槽312的设置可提高粘接面积，增大第一胶层40与极耳30之间的摩擦力，平直部分33与嵌入槽312的结合，进一步提高第一胶层40与极耳30之间的连接强度。
对于嵌入槽312的深度，嵌入槽312的深度过大，可能导致第一胶层40难以全部嵌入嵌入槽312，导致第一胶层40与嵌入槽312之间存在间隙，影响粘接质量。嵌入槽312的深度过小，第一胶层40嵌入第一胶层40的量不足，不足以增大连接面积，以致于提高连接强度的效果不佳。本申请的实施例中，沿第一极片100的厚度方向(第三方向Z)，嵌入槽312的凹陷深度为H，10μm≤H≤50μm，便于第一胶层40嵌入至整个嵌入槽312，减少第一胶层40从嵌入槽312中脱出，并且足够的嵌入深度提高第一胶层40与极耳30之间的连接强度。
第二方面，本申请的实施例还提出了一种电极组件1000，包括隔离膜200以及至少两个如上述第一方面任一实施例中所述的极片100。请参照图9，该至少两个极片100分别为正极极片100a和负极极片100b，正极极片100a、隔离膜200以及负极极片100b沿厚度方向(第三方向Z)层叠或者层叠并卷绕设置，隔离膜200设置于正极极片100a与负极极片100b之间，用于分隔二者。
在一些实施例中，请参照图9，正极极片100a包括正极集流体10a、第一正极活性物质层20a、第二正极活性物质层50a和正极极耳30a。沿正极集流体10a的厚度方向(第三方向Z)，正极集流体10a具有第一正极表面11a和第二正极表面12a，第一正极表面11a可设置第一正极活性物质层20a，第二正极表面12a可设置第二正极活性物质层50a。第一正极表面11a具有第一正极空箔区111a，正极极耳30a可通过上述第一胶层40粘接于第一正极空箔区111a。
负极极片100b包括负极集流体10b、第一负极活性物质层20b、第二负极活性物质层50b以及负极极耳30b。负极集流体10b具有第一负极表面11b和第二负极表面12b，第一负极活性物质层20b设置于第一负极表面11b，第二负极活性物质层50b设置于第二负极表面12b。第一正极活性物质层20a面向第二负极活性物质层50b设置，负极集流体10b的第二负极表面12b上设置有第一负极空箔区111b，负极极耳30b可通过第一胶层40粘接于第一负极空箔区111b。
请参照图9，由于正极极耳30a通过第一胶层40粘接于第一正极空箔区111a，正极极耳30a和/或第一正极空箔区111a处无需设置极耳胶，并且，沿第三方向Z，在第二正极活性物质层50a对应第一正极空箔区111a的位置也无需设置极片100胶。类似的，负极极耳30b和/或第一负极空箔区111b处无需设置极耳胶，沿第三方向Z，第一负极活性物质层20b对应第一负极空箔区111b的位置也无需设置极片胶，减少极耳胶以及两道极片胶，可节省空间，充分提高二次电池的能量密度。
可选的，沿第三方向Z，第一正极活性物质层20a对应第一负极空箔区111b的位置设置有极片胶300，可缓解此处的锂离子脱嵌，保证负极极片100b始终具有足够的余量嵌入正极极片100a脱嵌的锂离子，可缓解二次电池的析锂。还可在第一正极活性物质层20a上开设收容空间，极片胶300可设置于收容空间，减少极片胶300对极片厚度的影响，提高二次电池的能量密度。
第三方面，本申请还提出了一种二次电池，包括如上述第二方面任一实施例所述的电极组件1000。
第四方面，本申请还提出了一种制备如上述第一方面任一实施例极片100的方法，包括：提供集流体10，集流体10具有第一表面11，对第一表面11涂覆第一活性物质层20，并在第一表面11预留第一空箔区111；提供第一胶层40，将第一胶层40粘接于第一空箔区111；提供极耳30，极耳30具有若干嵌入槽312，极耳30的嵌入槽312面向第一胶层40，并将极耳30与第一胶层40粘接，压接极耳30与第一胶层40使得第一胶层40至少部分嵌入嵌入槽312中。
极耳30是通过第一胶层40与集流体10直接粘接固定，不仅操作方便，而且不存在焊接毛刺，不需要在极耳30或第一空箔区111设置极耳胶，省去了极耳胶所占用的空间，可在减少成本的同时提高二次电池的能量密度。并且，极耳30面向第一空箔区111的表面具有若干嵌入槽312，当第一胶层40粘接于极耳30与第一空箔区111之间时，第一胶层40嵌入至少部分嵌入槽312。第一胶层40可填充极耳30与集流体10之间的至少部分间隙，嵌入槽312的设置可增大第一胶层40与极耳30的粘接面积，减少极耳30与集流体10的相对运动，进而提高集流体10与极耳30之间的连接强度。
实验一：[锂离子电池的跌落测试]
实施例1：锂离子电池的制备
<正极极片的制备>
将正极活性材料磷酸铁锂、正极导电剂乙炔黑、正极粘结剂聚偏二氟乙烯(PVDF，重均分子量为5×105)按照质量比94:3:3进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，在真空搅拌机作用下搅拌至固含量为75wt％且体系均匀的正极浆料。将正极浆料均匀涂布在厚度为6um的正极集流体铝箔的一个表面上，90℃条件下烘干，得到单面涂布正极活性物质层(厚度80μm)的正极极片。之后，在该铝箔的另一个表面上重复以上步骤，并在铝箔的一个表面预留第一空箔区，第一空箔区宽度为10mm，长度为22mm，得到双面涂布正极活性物质层的正极极片。
在第一空箔区上粘接环氧树脂的第一胶层，第一胶层在第一空箔区的粘接宽度为8mm，两侧与正极活性物质层各预留1mm的间隙的空间，粘接长度为21mm，长度方向上与正极活性物质层预留1mm的间隙空间，第一胶层厚度为20μm。
采用铝片作为正极极耳，通过机械压接的方法在正极极耳上形成嵌入槽，各嵌入槽在正极极耳的表面围合形成凹陷区，凹陷区宽度为4mm，正极极耳宽度6mm，凹陷区在第一空箔区上的长度为18mm，与正极极耳在第一空箔区上的长度一致，凹陷区长度小于第一胶层长度，差值为3mm。将正极极耳与带有第一胶层的集流体通过热压固定。正极极耳的嵌入槽朝向第一胶层，嵌入槽深度为20μm，在热压固定时，第一胶层嵌入至嵌入槽中。
<负极极片的制备>
将负极活性材料石墨粉末、导电剂导电炭黑(Super P)、粘结剂丁苯橡胶(SBR)按照重量比97.5:1:1.5进行混合，然后加入去离子水作为溶剂，调配成固含量为50wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为5μm的负极集流体铜箔的一个表面上，110℃条件下烘干，得到负极活性物质重量为9.1mg/cm2单面负极极片。以上步骤完成后，即已完成负极极片的单面涂布。之后，在该负极极片的另一个表面上重复以上步骤，即得到双面涂布负极活性物质层的负极极片。在负极极片上预留出第二空箔区，第二空箔区宽度为10mm，长度为22mm。在第一空箔区上粘接环氧树脂的第一胶层，第一胶层在第一空箔区的粘接宽度为8mm，两侧与负极活性物质层各预留1mm的间隙的空间，粘接长度为21mm，长度方向上与负极活性物质层预留1mm的间隙空间，第一胶层嵌入至嵌入槽中。
采用镍片作为负极极耳，通过机械压接的方法在负极极耳上形成嵌入槽，各嵌入槽在负极极耳的表面围合形成凹陷区，凹陷区宽度为4mm，负极极耳宽度6mm，凹陷区在第二空箔区上的长度为18mm，与负极极耳在第一空箔区上的长度一致，凹陷区长度小于第一胶层长度，差值为3mm。将负极极耳与带有第一胶层的集流体通过热压固定。负极极耳的嵌入槽朝向第一胶层，嵌入槽深度为20μm，在热压固定时，第一胶层嵌入至嵌入槽中。
<隔离膜的制备>
以厚度为8μm的聚乙烯(PE)多孔薄膜作为隔离膜。
<电解液制备>
在干燥氩气气氛中，将碳酸乙烯酯、碳酸甲乙酯和碳酸二乙酯以质量比30:50:20混合得到有机溶液，然后向有机溶剂中加入锂盐六氟磷酸锂溶解并混合均匀，得到锂盐的浓度为1.15mol/L的电解液。
<锂离子电池的制备>
将上述制备得到的隔离膜、正极极片、隔离膜、负极极片按顺序叠好，卷绕得到电极组件，对电极组件进行热压，压力5MPa，温度65℃，保压时间10s。将电极组件放入包装袋铝塑膜中，并且上述正极极耳和负极极耳均从包装袋的顶封边伸出，在80℃下脱去水分后，注入电解液并封装。
对比例1，与实施例1不同的是，正极极耳与正极集流体焊接，负极极耳与负极集流体焊接。
跌落测试方法：将锂离子电池在25℃下进行预处理，常温环境中静置60min后，测试跌落测试前锂离子电池的电压；将锂离子电池装入夹具中，采用跌落设备按照如下顺序从距离地面1.5m的位置自由跌落：头-尾-头右角-尾右角-头左角-尾左角(角度：45±15°)，重复6轮。跌落结束后，常温静置24h，测量记录锂离子电池的电压，测试前后均检查锂离子电池的外观并拍照。跌落测试通过判断标准：不冒烟，不漏液，电压降<30mV。测试100个锂离子电池，通过测试的电池数量为X个，测试通过率为X/100。测试结果如下表1所示。
表1
根据上述表1，结合实施例1和对比例1、2可知，当极耳与集流体采用第一胶层粘接时，并且在极耳上设置嵌入槽时，其跌落测试通过率明显优于对比例1、2，对比例1中采用的是焊接，焊接毛刺易刺穿隔离膜，当锂离子电池出现跌落等碰撞时，更易导致毛刺刺穿隔离膜，以致于正负极片短接，导致锂离子电池失效。而实施例1中采用的是第一胶层粘接，不存在焊接毛刺，可有效降低隔离膜被刺穿的风险，进而提高锂离子电池的抗碰撞性能。
同时，焊接的方式难以将极耳与集流体重叠的部分全部焊接，连接面积较小，而粘接的方式可将极耳与集流体重叠的区域全部粘接，并且压紧后，第一胶层填充极耳与集流体之间的间隙，以及嵌入槽的设置使得极耳与集流体的连接面积更大，从而提高连接强度。
实验二：能量密度测试及抗拉强度测试
以上述实施例1以及对比例1的锂离子电池为例，对其进行能量密度测试。其中，对比例1中，正极采用厚度为8μm，以及长宽分别15*30的两片极耳胶覆盖正极极耳两侧的空箔区，以及采用厚度为8μm，长宽分别为15mm*30mm的正极极片胶覆盖正极活性物质层对应负极极耳的位置。负极则采用厚度为8μm，以及长宽分别14mm*28mm的两片极耳胶覆盖负极极耳两侧的空箔区，以及采用厚度为8μm，长宽分别为15mm*30mm的负极极片胶覆盖正极活性物质层对应负极极耳的位置。
实施例2至9中的相关参数如下表2所示。
能量密度测试方法：以上述制备方法制备出方形的锂离子电池，以1C的恒定电流对电池充电至4.2V，再以4.2V的恒定电压对电池充电至0.05C，以0.2C的恒定电流对电池放电至2.5V，记录放电能量E；测出方形电池的外形尺寸，并计算其体积，即为V；则能量密度W＝E/V。测试结果如下表2所示。
抗拉强度测试方法：拆解电池获得正极极片与负极极片，以正极极片为例，采用高铁拉力机将极耳固定在拉力机的下端，并将集流体固定在高铁拉力机的上端，保持两端在同一垂直面上，设置拉力机速度为50mm/min，拉动极耳与集流体，记录极耳与集流体拉开时的拉力F(单位为N)。
表2

结合上述表2，根据实施例1至9以及对比例1可知，当采用第一胶层粘接极耳以及集流体，并且极耳上设置嵌入槽时，其抗拉强度明显高于对比例1，这是因为第一胶层可嵌入至嵌入槽中，以限制第一胶层与极耳之间的相对运动，并且在压紧后，第一胶层可填充极耳与集流体之间的间隙，增大第一胶层与极耳之间的连接面积，进而提高极耳与集流体之间的抗拉强度。而焊接的方式难以将极耳与集流体的部分全部焊接，连接面积较小，以致于连接强度不高。
对比例2中，极耳为粘接设置，但没有设置嵌入槽，因此抗拉强度较低。
实施例1以及实施例3至9中，其抗拉强度优于实施例2，实施例1以及实施例3至9中，第一胶层的宽度均大于4mm，可提高极耳与集流体之间的连接面积，极耳提高连接强度。实施例1以及实施例3至8中，能量密度高于实施例9中，这可能是因为第一胶层宽度过大，易导致第一胶层直接粘接在活性物质层上，影响电池容量。并且，结合实施例8和实施例9，第一胶层的宽度对提高抗拉强度的效果也不明显，这可能是因为部分第一胶层粘接在活性物质层，以致于该部分的粘接效果不佳。因此，本申请中，第一胶层的宽度选择4mm≤W2≤14mm，也即第一胶层与第一空箔区的粘接宽度4mm≤W3≤14mm。
进一步的，实施例1以及实施例3至5中，其能量密度不仅高于实施例6至9，并且抗拉强度高于实施例2。实施例6至9，随着第一胶层宽度的增大，对提高抗拉强度的效果也越来越不明显，因第一胶层的宽度大于第一空箔区的宽度，部分第一胶层直接粘接在活性物质层，粘接在活性物质层的部分对提高连接强度的效果较小。而实施例1以及实施例3至5中，第一胶层宽度小于第一空箔区宽度，可减少与活性物质层的直接粘接，并且足够的宽度可提高连接强度，对能量密度的影响也较小。因此，本申请中，选择第一空箔区与第一胶层的宽度差为0mm≤W1-W2≤5mm。
以上所述仅为本申请的实施例，并非因此限制本申请的专利范围，凡是利用本申请说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本申请的专利保护范围内。

Claims (18)

  1. 一种极片，包括集流体、第一活性物质层和极耳，所述集流体具有第一表面，所述第一活性物质层设置于所述第一表面，所述第一表面具有第一空箔区，所述极耳设置于所述第一空箔区，其特征在于，所述极片还包括第一胶层；
    所述极耳具有相连接的第一部分和第二部分，所述第一胶层粘接于所述第一部分与所述第一空箔区之间，所述第一部分与所述第一空箔区电连接，所述第二部分用于外接电子设备；
    所述第一部分面向所述第一空箔区的表面具有凹陷区，所述凹陷区凹设有若干嵌入槽，沿所述极耳的厚度方向，所述嵌入槽相对于所述第二部分凹陷，所述第一胶层嵌入至少部分所述嵌入槽。
  2. 根据权利要求1所述的极片，其特征在于，所述集流体还具有第二表面，沿所述集流体的厚度方向，所述第一表面与所述第二表面相对设置；
    所述极片还具有第二活性物质层，所述第二活性物质层设置于所述第二表面，沿所述集流体的厚度方向观察，所述第一空箔区的投影位于所述第二活性物质层的投影上。
  3. 根据权利要求1所述的极片，其特征在于，所述第一胶层包括环氧树脂、聚烯烃、聚苯乙烯、聚甲基丙烯酸甲酯、酚醛树脂或丁苯橡胶中的至少一种。
  4. 根据权利要求1所述的极片，其特征在于，所述第一胶层包括热熔胶、压敏胶、热固胶中的至少一种。
  5. 根据权利要求1所述的极片，其特征在于，沿所述第一极片的厚度方向观察，所述极耳与所述第一空箔区的重叠面积为S3，所述凹陷区与所述第一空箔区的重叠面积为S4，20％≤S4/S3≤80％。
  6. 根据权利要求1所述的极片，其特征在于，沿所述集流体的宽度方向，所述第一空箔区的长度为L1，所述第一胶层的长度为L2，1mm≤L1-L2≤5mm；和/或，
    沿所述集流体的长度方向，所述第一空箔区的宽度为W1，所述第一胶层的宽度为W2，0mm≤W1-W2≤5mm。
  7. 根据权利要求1所述的极片，其特征在于，
    沿所述集流体的宽度方向，所述第一胶层与所述第一空箔区的粘接长度为L3，4mm≤L3≤24mm；
    沿所述集流体的长度方向，所述第一胶层与所述第一空箔区的粘接宽度为W3，4mm≤W3≤14mm。
  8. 根据权利要求1所述的极片，其特征在于，沿所述集流体的厚度方向，所述第一胶层的厚度为T1，2μm≤T1≤50μm。
  9. 根据权利要求8所述的极片，其特征在于，15μm≤T1≤25μm。
  10. 根据权利要求1所述的极片，其特征在于，
    沿所述集流体的宽度方向，所述第一胶层的长度为L2，所述凹陷区的长度为L4，0mm≤L2-L4≤5mm；和/或，
    沿所述集流体的长度方向，所述第一胶层的宽度为W2，所述凹陷区的宽度为W4，所述极耳位于所述第一空箔区上的宽度为W5，0mm≤W2-W4≤5mm，0≤W2-W5≤5mm。
  11. 根据权利要求1所述的极片，其特征在于，所述嵌入槽包括靠近所述集流体的槽口以及远离所述集流体的槽底；
    沿所述集流体的宽度方向，所述槽口的宽度为W6，0.1mm≤W6≤1mm所述槽底的宽度为W7，0.1mm≤W7≤1mm；W6＞W7。
  12. 根据权利要求1所述的极片，其特征在于，相邻两所述嵌入槽之间的距离为D，0.1mm≤D≤1mm。
  13. 根据权利要求1所述的极片，其特征在于，沿所述第一极片的厚度方向，所述嵌入槽的凹陷深度H，10μm≤H≤50μm。
  14. 根据权利要求1所述的极片，其特征在于，在单个所述嵌入槽中，所述第一胶层与单个所述嵌入槽的接触的面积为S1，单个所述嵌入槽的面积为S2，10％≤S1/S2≤100％。
  15. 根据权利要求1所述的极片，其特征在于，全部所述嵌入槽的数量为M，嵌入有所述第一胶层的嵌入槽数量为N，10％≤N/M≤100％。
  16. 一种电极组件，其特征在于，包括隔离膜以及如权利要求1至15中任一项所述的极片。
  17. 一种二次电池，其特征在于，包括如权利要求16所述的电极组件。
  18. 一种制备如权利要求1至15中任一项所述极片的方法，其特征在于，包括：
    提供集流体，所述集流体具有第一表面，对所述第一表面涂覆第一活性物质层，并在所述第一表面预留第一空箔区；
    提供第一胶层，将所述第一胶层粘接于所述第一空箔区；
    提供极耳，所述极耳具有若干嵌入槽，所述极耳的嵌入槽面向所述第一胶层，并将所述极耳与所述第一胶层粘接，压接所述极耳与所述第一胶层使得所述第一胶层至少部分嵌入所述嵌入槽中。
PCT/CN2025/094344 2024-06-13 2025-05-12 极片及其制备方法、电极组件及二次电池 Pending WO2025256316A1 (zh)

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