Electrode assembly and electrochemical device

Abstract

The utility model discloses an electrode assembly and electrochemical device. The utility model discloses an electrode assembly includes composite current collector, pole lug, conducting band and gum paper. Composite current collector includes the through area. Conducting band and pole lug are arranged respectively at both sides of composite current collector. Gum paper includes first area and second area who connects each other, along the thickness direction of composite current collector, the projection of first area is located at least partially in the through area, the projection of second area is located at least partially outside the through area, and the thickness of first area is greater than the thickness of second area. Through setting up the gum paper into the special-shaped gum paper of uneven thickness, the first area of thickness thicker is connected in the pole lug part corresponding to the through area, and the second area of thickness thinner is connected in the pole lug part outside the through area, to realize the complementation on the thickness, improve the flatness near the through area, thereby reduce the stress concentration of uneven position, and facilitate the subsequent packaging.

Description

Technical Field

[0001] This utility model relates to the field of electrochemical energy storage technology, specifically to an electrode assembly and an electrochemical device. Background Technology

[0002] To meet the demands for high energy density and safety, composite current collectors are increasingly being used. Composite current collectors incorporate a polymer material layer between two metal layers to enhance structural strength. However, the polymer material layer suffers from poor conductivity, necessitating the creation of a conductive zone. Furthermore, tabs and conductive strips are placed on either side of this zone to achieve bidirectional conductivity. In related technologies, the area near the conductive zone exhibits poor flatness. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an electrode assembly capable of improving the flatness near the conductive region.

[0004] This application also proposes an electrochemical device having the above-described electrode assembly.

[0005] An electrode assembly according to a first aspect of this application includes a composite current collector, a tab, a conductive strip, and adhesive tape. The composite current collector includes a conductive region extending through the composite current collector along its thickness direction. The conductive strip and the tab are respectively disposed on opposite sides of the composite current collector along its thickness direction, and the conductive strip is connected to the tab through the conductive region. The adhesive tape is connected to the side of the tab opposite to the composite current collector, and the adhesive tape includes a first region and a second region interconnected. Along the thickness direction of the composite current collector, the projection of the first region is at least partially located within the conductive region, and the projection of the second region is at least partially located outside the conductive region. The thickness of the first region is greater than the thickness of the second region.

[0006] The electrode assembly according to the embodiments of this application has at least the following beneficial effects: In the related art, since there is a conductive area in the composite current collector, after the tab on the conductive area is connected to the composite current collector, the part located in the conductive area will be recessed, and the part outside the conductive area will form a step compared to the part inside the conductive area, thereby making the adhesive paper on the tab uneven. The electrode assembly of the embodiments of this application sets the adhesive paper to be an irregularly shaped adhesive paper with uneven thickness. The thicker first area is connected to the tab part corresponding to the conductive area, and the thinner second area is connected to the tab part outside the conductive area, thereby achieving complementary thickness, improving the flatness near the conductive area, thereby reducing stress concentration at uneven positions, and facilitating subsequent encapsulation.

[0007] According to some embodiments of this application, the conductive area includes a conductive hole disposed within the composite current collector, and / or the conductive area includes a conductive groove communicating with the edge of the composite current collector along its width direction.

[0008] According to some embodiments of this application, the conductive area includes conductive holes and conductive grooves, and the conductive holes and conductive grooves are distributed at intervals along the width direction of the composite current collector.

[0009] According to some embodiments of this application, the adhesive tape includes two first regions, and a second region is connected between the two first regions. Along the thickness direction of the composite current collector, each of the through hole and the through groove is provided with one first region.

[0010] According to some embodiments of this application, the thickness of the first region is D1, the thickness of the second region is D2, the thickness of the composite current collector is D3, and -5μm≤(D1—(D2+D3))≤5μm.

[0011] According to some embodiments of this application, along the length direction of the composite current collector, the size of the adhesive tape is larger than the size of the electrode tab, and the two ends of the adhesive tape are connected to the composite current collector.

[0012] According to some embodiments of this application, the first region includes an interconnected base layer and an adhesive layer, the adhesive layer being bonded to the tab, and the base layer being connected to the side of the adhesive layer opposite to the tab; the second region includes the base layer.

[0013] According to some embodiments of this application, the thickness of the base layer is L1, where 2μm≤L1≤6μm.

[0014] According to some embodiments of this application, the thickness of the adhesive layer is L2, 10μm≤L1≤14μm.

[0015] According to some embodiments of this application, the electrode tab and the conductive strip are fixedly connected in the conductive area by welding.

[0016] An electrochemical device according to a second aspect embodiment of this application includes an electrode assembly as described in any one of the first aspect embodiments.

[0017] The electrochemical device according to the embodiments of this application has at least the following beneficial effects: In the related art, since there is a conductive area in the composite current collector, after the tab on the conductive area is connected to the composite current collector, the part located in the conductive area will be recessed, and the part outside the conductive area will form a step compared to the part inside the conductive area, thereby making the adhesive paper attached to the tab uneven. In the electrode assembly of the embodiments of this application, by setting the adhesive paper to be an irregularly shaped adhesive paper with uneven thickness, the thicker first area is connected to the tab part corresponding to the conductive area, and the thinner second area is connected to the tab part outside the conductive area, thereby achieving complementary thickness, improving the flatness near the conductive area, and improving the internal structural flatness of the electrochemical device using the electrode assembly.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a side view of the electrode assembly in the first embodiment of this application; Figure 2 This is a perspective view of the composite current collector of the electrode assembly in one embodiment of this application; Figure 3 This is a side view of the electrode assembly in the second embodiment of this application; Figure 4 This is a side view of an electrode assembly in the prior art.

[0020] Reference numerals: electrode assembly 100, composite current collector 101, electrode tab 102, conductive strip 103, adhesive tape 104, base layer 105, adhesive layer 106, conductive area 107, conductive hole 108, conductive groove 109, first area 110, second area 111. Detailed Implementation

[0021] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0022] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0023] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0024] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0025] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] In order to improve electrical conductivity, existing composite current collectors have a conductive region, but the flatness near the conductive region is poor. This application proposes an electrode assembly that can improve the flatness near the conductive region.

[0027] refer to Figures 1 to 3According to a first aspect embodiment of this application, an electrode assembly 100 includes a composite current collector 101, a tab 102, a conductive strip 103, and adhesive tape 104. The composite current collector 101 includes a conductive region 107 that extends through the composite current collector 101 along its thickness direction. The conductive strip 103 and the tab 102 are respectively disposed on opposite sides of the composite current collector 101 along its thickness direction, and the conductive strip 103 is connected to the tab 102 through the conductive region 107. The adhesive tape 104 is connected to the side of the tab 102 facing away from the composite current collector 101. The adhesive tape 104 includes a first region 110 and a second region 111 that are interconnected. Along the thickness direction of the composite current collector 101, the projection of the first region 110 is at least partially located within the conductive region 107, and the projection of the second region 111 is at least partially located outside the conductive region 107. The thickness of the first region 110 is greater than the thickness of the second region 111. In related technologies, because the composite current collector 101 has a conductive area 107, after the tab 102 on the conductive area 107 is connected to the composite current collector 101, the portion located inside the conductive area 107 will be recessed, and the portion outside the conductive area 107 will form a step compared to the portion inside the conductive area 107. This causes the adhesive tape 104 bonded to the tab 102 to become uneven (e.g., Figure 4 As shown in the figure, the electrode assembly 100 of this application embodiment is configured with an adhesive tape 104 of uneven thickness. The thicker first region 110 is connected to the tab 102 portion corresponding to the conductive region 107, and the thinner second region 111 is connected to the tab 102 portion outside the conductive region 107. This achieves complementary thickness, improves the flatness near the conductive region 107, reduces stress concentration at uneven positions, and facilitates subsequent encapsulation.

[0028] It should be noted that in some embodiments of this application, along the thickness direction of the composite current collector 101, the projection of the first region 110 is at least partially located within the conductive region 107, which can be achieved as follows: Figure 1 The portion shown is located outside the conductive area 107, or it can be completely located inside the conductive area 107. The portion located outside the conductive area 107 is for better connection to the surface of the composite current collector 101, thereby fixing the tab 102 to the composite current collector 101.

[0029] It should be noted that the composite current collector 101 specifically refers to a three-layer structure. The middle layer is usually composed of a polymer base film such as polypropylene or polyester resin, which gives the current collector high mechanical strength. The two sides of the middle layer are coated with conductive layers to achieve electrical conduction. Therefore, it is necessary to set the conductive area 107 to conduct electricity between the two sides of the composite current collector 101, and to set the tabs 102 and conductive strips 103 on both sides for connection.

[0030] It should be noted that in some embodiments, the conductive strip 103 is made of metal, and preferably the same metal is used as the conductive layer on both sides of the composite current collector 101, thereby reducing the potential difference between the two and improving the conductivity of the electrode assembly 100. The electrode assembly 100 of this application embodiment can be used for both anode and cathode sheets.

[0031] It should be noted that in some embodiments of this application, the adhesive tape 104 is bonded to the tab 102 and the composite current collector 101 connected to the tab 102, thereby fixing the tab 102. In some embodiments, when the electrode assembly 100 of this application is applied to a battery, a portion of the adhesive tape 104 can be bonded to the housing or encapsulation film, which can also fix the tab 102.

[0032] refer to Figure 1 and Figure 2 In some embodiments of this application, the conductive region 107 includes a through hole 108 disposed within the composite current collector 101, and / or, the conductive region 107 includes a through groove 109 communicating with the edge of the composite current collector 101 along its width direction. Both the through hole 108 and the through groove 109 have advantages. The hole structure allows the composite current collector 101 to maintain good mechanical strength, preventing edge warping, and the position design of the through hole 108 is more flexible. Conversely, the through groove 109 directly exposes the metal layers on both sides of the composite current collector 101, facilitating the connection between the tab 102 and the conductive strip 103 and reducing process complexity. In some embodiments of this application, the conductive region 107 may only have a through hole 108, or only a through groove 109, or as described above. Figure 2 The design of both the through hole 108 and the through groove 109 shown can be adjusted and selected according to process requirements.

[0033] It should be noted that the reference Figure 2 In some embodiments of this application, the through hole 108 and the through groove 109 can be square, or they can be round, elliptical, or other shapes. In order to prevent burrs from appearing, a chamfer structure can be provided on the inner wall edge of the through hole 108 and the through groove 109.

[0034] refer to Figure 2 In some embodiments of this application, the conductive area 107 includes a through hole 108 and a through groove 109, which are spaced apart along the width direction of the composite current collector 101. Simultaneously providing both the through hole 108 and the through groove 109 combines the advantages of both, increasing the connection area between the conductive strip 103 and the tab 102, improving structural stability, and allowing for simultaneous processing without requiring additional processing steps. For example, as... Figure 2As shown, the through hole 108 and the through groove 109 are flush with each other and have the same size along the length of the composite current collector 101. They can be processed using the same set of opening molds, which improves the consistency of the size and facilitates the processing of the first area 110 and the second area 111 of the adhesive tape 104 and its matching with the through hole 108. The equal and flush size along the length can also reduce the minimum size required for the adhesive tape 104 to cover the through area 107.

[0035] It should be noted that the reference Figure 3 In some embodiments of this application, multiple through holes 108 can be spaced apart along the width direction of the composite current collector 101. Correspondingly, a first region 110 can be provided above each through hole 108, and a second region 111 can be provided above the region between two through holes 108, thereby improving... Figure 3 The flatness of the electrode assembly 100 in the illustrated embodiment.

[0036] refer to Figure 1 In some embodiments of this application, the adhesive tape 104 includes two first regions 110, with a second region 111 connecting the two first regions 110. Along the thickness direction of the composite current collector 101, each of the through-hole 108 and the through-groove 109 is provided with a corresponding first region 110. This compensates for the thickness of both the through-hole 108 and the through-groove 109, and the connection between them by the thinner second region 111 makes the upper surface of the electrode assembly 100 ultimately appear as... Figure 1 The surface shown is relatively flat. It should be noted that both the through hole 108 and the through groove 109 have at least a portion of the first area 110 corresponding to them, including... Figure 1 The first region 110 corresponding to the through hole 108 shown has a portion extending out relative to the through hole 108. This portion of the first region 110 extending out relative to the through hole 108 can be used to connect the composite current collector 101, thereby fixing the tab 102. This also includes the case where the projection of the first region 110 along the thickness direction falls entirely within the through hole 108, in which case the adhesive tape 104 is completely connected to the tab 102. Since the edge of the tab 102 has a step relative to the composite current collector 101, the portion of the first region 110 extending out relative to the through hole 108 connecting to the upper surface of the composite current collector 101 does not increase the overall thickness.

[0037] refer to Figure 1In some embodiments of this application, the thickness of the first region 110 is D1, the thickness of the second region 111 is D2, and the thickness of the composite current collector 101 is D3, where -5μm ≤ (D1 - (D2 + D3)) ≤ 5μm. This design results in a small overall thickness difference between the regions containing the first region 110 and the second region 111, meaning the area where the adhesive tape 104 is applied is relatively flat. Ideally, the difference between the two should be zero, with a thickness deviation within 5μm. Specifically, this could be 0, 1μm, 2μm, 3μm, 4μm, or 5μm, or any two of the above values, resulting in a relatively flat surface for the electrode assembly 100. When the deviation exceeds 5μm, it leads to poor flatness consistency and localized over-thickness. It should be noted that, referring to... Figure 1 The total thickness of both regions actually includes the thickness of the tab 102, but the thickness of the tab 102 is rounded down in the difference calculation. Therefore, the difference between the thickness of the relatively thinner second region 111 and the thickness of the composite current collector 101 with the through hole 108, and the thickness of the first region 110 is controlled within a certain range. It should be noted that, for reference... Figure 1 In some embodiments of this application, when the first region 110 includes an interconnected base layer 105 and an adhesive layer 106, and the second region 111 includes the base layer 105, the thickness of the first region 110 is the thickness of the base layer 105 plus the thickness of the adhesive layer 106, and the thickness of the second region 111 is the thickness of the base layer 105.

[0038] In some embodiments of this application, along the length of the composite current collector 101, the size of the adhesive tape 104 is larger than the size of the tab 102, and both ends of the adhesive tape 104 are connected to the composite current collector 101. This allows the adhesive tape 104 to be directly bonded to the composite current collector 101 and the tab 102, thereby fixing the tab 102 and improving the battery's sealing, safety, and electrochemical performance. The adhesive tape 104 can also block the risk of short circuit between the metal tab 102 and the aluminum-plastic film, enhancing battery safety. This bonding method also allows the electrode assembly 100 to adapt to electrochemical devices with various structures.

[0039] refer to Figure 1In some embodiments of this application, the first region 110 includes a base layer 105 and an adhesive layer 106 interconnected. The adhesive layer 106 is bonded to the tab 102, and the base layer 105 is connected to the side of the adhesive layer 106 opposite to the tab 102. The second region 111 includes the base layer 105. The base layer 105 provides support for the adhesive tape 104, and the adhesive layer 106 provides adhesion for the adhesive tape 104. The first region 110 includes the base layer 105 and the adhesive layer 106, while the second region 111 only includes the base layer 105. This allows the thickness of the second region 111 to be less than that of the first region 110, and facilitates the processing and manufacturing of the adhesive tape 104. It only requires applying the adhesive layer 106 at intervals on the base layer 105 and then cutting, simplifying the process. In some embodiments, the second region 111 may include the adhesive layer 106 to improve the adhesion of the adhesive tape 104. This requires thinning the adhesive layer 106 in the second region 111 so that the thickness of the second region 111 is less than that of the first region 110.

[0040] It should be noted that in some embodiments of this application, the base layer 105 can be made of polymer materials such as polypropylene film, polyethylene, and polyvinyl chloride, providing mechanical strength, flexibility, and puncture resistance, while the adhesive layer 106 can be made of pressure-sensitive adhesive, silicone, etc.

[0041] refer to Figure 1 In some embodiments of this application, the thickness of the base layer 105 is L1, where 2μm ≤ L1 ≤ 6μm. Specifically, the dimensions of L1 can be 2μm, 2.5μm, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.1μm, 4.3μm, 4.5μm, 4.7μm, 4.9μm, 5μm, 5.5μm, 5.8μm, 6μm, or within any two of the above values. A suitable thickness of the base layer 105 can balance various requirements such as the mechanical strength of the adhesive tape 104 and the electrochemical performance of the electrode assembly 100. When the thickness of the base layer 105 is less than 2μm, the base layer 105 is too thin to provide sufficient insulation and support, which increases the risk of short circuit between the tab 102 and the external metal part, and cannot properly support the adhesive layer 106, and may crack during bending or processing. When the thickness of the base layer 105 is greater than 6 μm, the excessive thickness of the base layer 105 will increase the overall rigidity of the adhesive paper 104, resulting in greater mechanical stress during the charging and discharging process of the electrochemical device, which may lead to detachment. Furthermore, an excessively thick base layer 105 will occupy too much space, reducing the energy density of the electrochemical device. It should be noted that, preferably, in some embodiments of this application, the thickness of the base layer 105 is selected as 4 μm.

[0042] refer to Figure 1In some embodiments of this application, the thickness of the adhesive layer 106 is L2, where 10μm ≤ L1 ≤ 14μm. Specifically, the dimensions of L2 can be 10μm, 10.2μm, 10.4μm, 10.6μm, 10.8μm, 11μm, 11.5μm, 12μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13.7μm, 13.8μm, 13.9μm, 14μm, or within any two of the above values. A suitable adhesive layer 106 thickness can balance various requirements such as adhesive strength, electrochemical performance of electrode assembly 100, and safety performance. When the thickness of adhesive layer 106 is less than 10 μm, the adhesive layer 106 is too thin, which may lead to local missing adhesive, resulting in discontinuous bonding, low bonding strength, and also easily causing short circuit risk. When the thickness of adhesive layer 106 is greater than 14 μm, the adhesive layer 106 is too thick, which may cause bubbles or defects to easily form in the adhesive layer 106, which may also cause breakage and reduced bonding strength. In addition, an excessively thick adhesive layer 106 will occupy space in the electrochemical device and reduce energy density.

[0043] In some embodiments of this application, the tab 102 and the conductive strip 103 are fixedly connected in the conductive area 107 by welding. Welding makes the connection between the tab 102, the conductive strip 103 and the composite current collector 101 more stable and the processing technology is mature and efficient. Specifically, ultrasonic welding, resistance welding or a combination of two methods can be used to improve the welding effect of the tab 102.

[0044] The electrochemical device according to the second aspect of this application includes the electrode assembly 100 of any one of the first aspect embodiments. In the related art, since the composite current collector 101 has a conductive region 107, after the tab 102 on the conductive region 107 is connected to the composite current collector 101, the portion located inside the conductive region 107 will be recessed, and the portion outside the conductive region 107 will form a step compared to the portion inside the conductive region 107, thereby making the adhesive tape 104 bonded to the tab 102 uneven. The electrode assembly 100 of this application sets the adhesive tape 104 as an irregularly shaped adhesive tape 104 with uneven thickness. The thicker first region 110 is connected to the portion of the tab 102 corresponding to the conductive region 107, and the thinner second region 111 is connected to the portion of the tab 102 outside the conductive region 107, thereby achieving complementary thickness, improving the flatness near the conductive region 107, and improving the internal structural flatness of the electrochemical device using the electrode assembly 100.

[0045] The electrochemical device described in this application includes any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0046] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An electrode assembly, characterized in that, include: A composite current collector, the composite current collector including a conductive area, the conductive area penetrating the composite current collector along its thickness direction; Extreme ear; A conductive strip and the tab are respectively disposed on both sides of the composite current collector along its thickness direction, and the conductive strip is connected to the tab through the conductive area; The adhesive tape is attached to the side of the electrode opposite to the composite current collector. The adhesive tape includes a first region and a second region that are interconnected. Along the thickness direction of the composite current collector, the projection of the first region is at least partially located within the conductive region, and the projection of the second region is at least partially located outside the conductive region. The thickness of the first region is greater than the thickness of the second region.

2. The electrode assembly according to claim 1, characterized in that, The conductive area includes a conductive hole disposed within the composite current collector, and / or the conductive area includes a conductive groove communicating with the edge of the composite current collector along its width direction.

3. The electrode assembly according to claim 2, characterized in that, The conductive area includes conductive holes and conductive grooves, which are spaced apart along the width direction of the composite current collector.

4. The electrode assembly according to claim 3, characterized in that, The adhesive tape includes two first regions, and a second region is connected between the two first regions. Along the thickness direction of the composite current collector, each of the through hole and the through groove is provided with one first region.

5. The electrode assembly according to claim 1, characterized in that, The thickness of the first region is D1, the thickness of the second region is D2, and the thickness of the composite current collector is D3, -5μm≤(D1—(D2+D3))≤5μm.

6. The electrode assembly according to claim 1, characterized in that, Along the length of the composite current collector, the size of the adhesive tape is larger than the size of the electrode tab, and the two ends of the adhesive tape are connected to the composite current collector.

7. The electrode assembly according to claim 1, characterized in that, The first region includes an interconnected base layer and an adhesive layer, the adhesive layer being bonded to the tab, and the base layer being connected to the side of the adhesive layer opposite to the tab. The second region includes the base layer.

8. The electrode assembly according to claim 7, characterized in that, The thickness of the base layer is L1, where 2μm≤L1≤6μm.

9. The electrode assembly according to claim 7, characterized in that, The thickness of the adhesive layer is L2, 10μm≤L1≤14μm.

10. The electrode assembly according to claim 1, characterized in that, The electrode tab and the conductive strip are fixedly connected in the conductive area by welding.

11. An electrochemical device, characterized in that, Includes the electrode assembly according to any one of claims 1 to 10.

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