Electrode sheet, battery cell, and electric device

Abstract

Embodiments of the present application relate to the technical field of batteries, and in particular disclose an electrode sheet, a battery cell, and an electric device. The electrode sheet comprises a current collector, a first transition layer, and a second transition layer, and the electrode sheet is provided with a welding portion. The current collector comprises a first metal layer, a support layer and a second metal layer that are arranged in a first direction. The first transition layer and the second transition layer are respectively connected to two sides of the current collector. The welding portion is located at the junction of the first transition layer and the first metal layer, and the welding portion is located at the junction of the second transition layer and the second metal layer; along the first direction, on one side of the first transition layer, the welding portion is embedded in the support layer to a depth of D1, on one side of the second transition layer, the welding portion is embedded in the support layer to a depth of D2, and the thickness of the support layer is H1; the ratios of D1 and D2 to the thickness of the support layer satisfy: 0.1≤(D1+D2) / H1≤0.8, D1 / H1≥0.05, and D2 / H1≥0.05. By means of the described structure, the range of the embedment depths of the welding portion in the support layer is optimized, reducing insufficient welding or over-welding of the welding portion.

Description

Electrode sheets, battery cells and electrical equipment

[0001] Cross-reference to related applications

[0002] This application claims priority to the earlier application filed on July 12, 2024 with the China National Intellectual Property Administration, application number 2024109389216, entitled "Electrode, Battery Cell and Electrical Equipment", the contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to an electrode, a battery cell, and an electrical device. Background Technology

[0004] Composite current collectors are sandwich-type electrodes composed of stacked metal, polymer, and metal structures, and have attracted widespread attention from battery developers. These current collectors use polymers as the electrode skeleton, thereby reducing the thickness of the metal layer. This electrode structure reduces metal burrs when the battery cell suffers mechanical damage, thus addressing the safety hazards currently associated with mechanical damage to battery cells.

[0005] In the process of realizing this application, the inventors discovered that the current composite current collector's metal-polymer-metal structure includes both metal and non-metal materials. When the current collector is ultrasonically welded with aluminum foil, the polymer layer cannot be well integrated with the metal, which easily leads to over-welding or incomplete welding. Summary of the Invention

[0006] The embodiments of this application aim to provide an electrode sheet, a battery cell, and an electrical device that can improve the current situation where over-welding or incomplete welding is easily generated when ultrasonically welding current collectors and aluminum foils.

[0007] To solve the above-mentioned technical problems, this application adopts the following technical solution:

[0008] In a first aspect, an electrode is provided, comprising a current collector, a first transition layer, and a second transition layer, wherein the electrode further comprises a welding portion. The current collector comprises a first metal layer, a support layer, and a second metal layer disposed along a first direction. The first transition layer is connected to the side of the first metal layer opposite to the support layer. The second transition layer is connected to the side of the second metal layer opposite to the support layer. The electrode further comprises a welding portion located at the connection between the first transition layer and the first metal layer, and at the connection between the second transition layer and the second metal layer. Along the first direction, on one side of the first transition layer, the welding portion is embedded in the support layer with a thickness D1; ​​on one side of the second transition layer, the welding portion is embedded in the support layer with a thickness D2; the thickness of the support layer is H1; the ratio of D1 and D2 to the thickness of the support layer satisfies: 0.1 ≤ (D1 + D2) / H1 ≤ 0.8, D1 / H1 ≥ 0.05, D2 / H1 ≥ 0.05.

[0009] In the above scheme, the welding portion is provided to weld the first transition layer and the second transition layer to the current collector. The first transition layer is welded to the first metal layer of the current collector, and the second transition layer is welded to the second metal layer of the current collector, facilitating fusion. The weld portion obtained after welding the electrode sheet is embedded towards the support layer. Furthermore, the thickness of the weld portion embedded in the support layer is optimized so that the thickness of the weld portion embedded in the support layer from both sides satisfies the following condition: 0.1 ≤ (D1+D2) / H1 ≤ 0.8. This reduces the phenomenon of insufficient welding caused by the weld portion being embedded too little when the ratio of the weld portion's thickness embedded in the support layer is less than 0.1, thus reducing the impact of weak welding on the electrode sheet. Alternatively, it reduces the phenomenon of over-welding caused by the weld portion being embedded too much when the ratio of the weld portion's thickness embedded in the support layer is greater than 0.8, thus reducing the impact of over-welding on the mechanical properties of the support layer and the electrode sheet. With D1 / H1≥0.05 and D2 / H1≥0.05, limiting the lower limits of D1 and D2 can reduce the possibility of insufficient welding due to an excessively small weld portion on one side.

[0010] In one or more embodiments, along the first direction, the ratio of D1 and D2 to the thickness of the support layer satisfies: 0.4 ≤ (D1 + D2) / H1 ≤ 0.6. This further reduces the possibility of incomplete or excessive soldering at the welded portion.

[0011] In one or more embodiments, the thickness of the support layer along the first direction is H1, the thickness of the first metal layer along the first direction is H2, and the thickness of the second metal layer along the first direction is H3. 4μm ≤ H1 ≤ 18.4μm, 0.8μm ≤ H2 ≤ 3μm, 0.8μm ≤ H3 ≤ 3μm; and 6.5μm ≤ H1 + H2 + H3 ≤ 20μm. This ensures that the support layer of the current collector has stable mechanical properties, and the provision of the first and second metal layers facilitates welding with the aforementioned first and second transition layers.

[0012] In one or more embodiments, along the first direction, the support layer, the first metal layer, and the second metal layer satisfy the following conditions: 13μm≤H1≤16μm, 1μm≤H2≤3μm, and 1μm≤H3≤3μm. This structure enables the current collector to have good mechanical properties and current carrying capacity.

[0013] In one or more embodiments, along the first direction, the thickness of the first transition layer is Z1, 8μm≤Z1≤20μm. The thickness of the second transition layer is Z2, 8μm≤Z2≤20μm. This reduces the thickness of the electrode and the space occupied.

[0014] In one or more embodiments, the width of the first transition layer is Z3, 10mm≤Z3≤20mm; the width of the second transition layer is Z4, 10mm≤Z4≤20mm. This reduces the width of the electrode and the space occupied.

[0015] In one or more embodiments, the welding portion is provided with a plurality of weld feet, which are arranged at point intervals within the area of ​​the welding portion; the ratio of the area of ​​the weld foot to the area of ​​the welding portion is B, where 0.3 ≤ B ≤ 0.7. When the ratio B is less than 0.3, the area of ​​the weld foot is too small relative to the area of ​​the welding portion, which can easily lead to a cold weld; when the ratio is greater than 0.7, the area of ​​the weld foot is too large relative to the area of ​​the welding portion, which can easily lead to an over-weld.

[0016] In one or more embodiments, along the second direction, the width D3 of the solder foot satisfies: 10μm ≤ D3 ≤ 50μm; the second direction is perpendicular to the first direction and extends along the length of the current collector. This reduces the occurrence of incomplete or excessive soldering of the solder foot.

[0017] In one or more embodiments, the projection of the first transition layer along the first direction at least partially coincides with the current collector, and the projection of the second transition layer along the first direction at least partially coincides with the current collector. The welding portion is located in the overlapping area of ​​the projections of the first transition layer, the current collector, and the second transition layer. This allows the welding portion to weld the first and second transition layers opposite to each other on both sides of the current collector, facilitating welding of the first and second transition layers to other external metal materials.

[0018] In one or more embodiments, on the electrode sheet, along the first direction, the thickness of the overlapping portion of the welded portion, the first transition layer, the current collector, and the second transition layer is A1; the thickness of the overlapping portion of the first transition layer, the current collector, and the second transition layer is A2; the difference between A1 and A2 is: 10μm ≤ A1 - A2 ≤ 30μm. Through the above structure, the portion of the electrode sheet with thickness A1 is made thicker, thereby improving the structural strength and stability of the electrode sheet.

[0019] In one or more embodiments, along the first direction, the current collector has an empty foil area in the region where the projections of the first transition layer and the second transition layer overlap, the empty foil area being used for soldering the first transition layer and / or the second transition layer.

[0020] In one or more embodiments, the length of the empty foil area along the second direction is K1, where 1mm ≤ K1 ≤ 5mm; the second direction is perpendicular to the first direction and extends along the length of the current collector. This leaves space for welding.

[0021] In one or more embodiments, the length of the empty foil area along the second direction is K1, where 2.5mm ≤ K1 ≤ 3.5mm. This further allows space for welding.

[0022] In one or more embodiments, the material of the support layer includes polypropylene, polyethylene, polyurethane, polyethylene terephthalate, etc., to give the support layer good mechanical properties.

[0023] In a second aspect, a battery cell is provided, including an electrode assembly, the electrode assembly including the aforementioned electrode sheet.

[0024] Thirdly, an electrical device is provided, including the aforementioned battery cell.

[0025] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0027] Figure 1 is a schematic diagram provided by one or more embodiments of this application;

[0028] Figure 2 is another schematic diagram provided by one or more embodiments of this application;

[0029] Figure 3 is another schematic diagram provided by one or more embodiments of this application;

[0030] Figure 4 is a schematic diagram of one of the test methods provided in this application.

[0031] The attached icons are numbered as follows:

[0032] Electrode, 1000; Current collector, 100; First metal layer, 110; Support layer, 120; Second metal layer, 130; First transition layer, 200; Second transition layer, 300; Welding part, 400; Welding foot part, 410; Empty foil area, 500; First direction, X; Second direction, Y. Embodiments of the present invention

[0033] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0034] It should be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component, or there may be one or more intermediate components in between. When a component is described as "connected to" or "welded" to another component, it can be directly connected / welded to the other component, or there may be one or more intermediate components in between.

[0035] In the description of the embodiments of this application, the technical terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application 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 the embodiments of this application.

[0036] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0037] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0039] In a first aspect, please refer to Figures 1 and 2. This application provides an electrode 1000, which includes a current collector 100, a first transition layer 200, and a second transition layer 300. Furthermore, the electrode 1000 is provided with a welding portion 400. The current collector 100 includes a first metal layer 110, a support layer 120, and a second metal layer 130 disposed along a first direction X. The first transition layer 200 is connected to the side of the first metal layer 110 opposite to the support layer 120. The second transition layer 300 is connected to the side of the second metal layer 130 opposite to the support layer 120. The welding portion 400 is located at the connection between the first transition layer 200 and the first metal layer 110, and at the connection between the second transition layer 300 and the second metal layer 130. Along the first direction X, on one side of the first transition layer 200, the welding portion 400 is embedded in the support layer 120 with a thickness of D1; on the other side of the second transition layer 300, the welding portion 400 is embedded in the support layer 120 with a thickness of D2, and the support layer 120 has a thickness of H1. The ratio of D1 and D2 to the thickness of the support layer 120 satisfies: 0.1 ≤ (D1 + D2) / H1 ≤ 0.8. By providing the welding portion 400, the first transition layer 200 and the second transition layer 300 are welded to the current collector 100, wherein the first transition layer 200 is welded to the first metal layer 110 of the current collector 100, and the second transition layer 300 is welded to the second metal layer 130 of the current collector 100, to facilitate fusion. The welded portion 400 obtained after welding the electrode 1000 will penetrate the first metal layer 110 and the second metal layer 130 from both sides and embed into the support layer 120. Furthermore, the thickness of the welded portion 400 embedded in the support layer 120 is optimized so that the thickness of the welded portion 400 embedded in the support layer 120 and the thickness of the support layer 120 itself satisfy: 0.1≤(D1+D2) / H1≤0.8. This reduces the phenomenon of incomplete welding caused by insufficient thickness of the welded portion 400 embedded in the support layer 120 when the ratio of the welded portion 400 embedded in the support layer 120 is less than 0.1, thus reducing the impact of weak welding on the electrode 1000. Alternatively, it reduces the phenomenon of over-welding caused by excessive thickness of the welded portion 400 embedded in the support layer 120 when the ratio of the welded portion 400 embedded in the support layer 120 is greater than 0.8, thus reducing the impact of over-welding on the mechanical properties of the support layer 120 and the electrode 1000. That is, when (D1+D2) / H1 is greater than 0.8, the welded part 400 is prone to over-welding, thereby damaging the mechanical properties of the support layer 120, increasing the resistance of the current collector 100, and reducing the current carrying capacity of the current collector 100; while when (D1+D2) / H1 is less than 0.1, the welded part 400 will not be connected to the support layer 120 after welding, which will easily lead to the phenomenon of poor welding, resulting in insufficient bonding strength between the first transition layer 200 and the second transition layer 300 and the current collector 100, reducing the current carrying capacity and mechanical properties of the current collector 100.

[0040] It should be further explained that the current collector 100 is a composite structure composed of multiple structures. The first metal layer 110 and the second metal layer 130 are made of the same material. On the one hand, this ensures the stable current carrying capacity of the electrode 1000, preventing uneven resistance due to different metal materials, which would affect current flow. On the other hand, the same metal material exhibits the same physical properties during welding, resulting in stable and efficient welding. In this application, the first transition layer 200 and the first metal layer 110 are welded together by roll welding, and the second transition layer 300 and the second metal layer 130 are welded together by roll welding. The advantages of this welding method are high welding efficiency. Roll welding is a solid-state welding method, where the metal is heated to a certain temperature, and pressure is applied by rollers to plastically deform the joint surface to create a metal bond. The internal resistance after welding is low, resulting in good conductivity of the electrode 1000. Optionally, the materials of the first metal layer 110 and the second metal layer 130 include aluminum, copper, etc. It is worth mentioning that the materials of the first transition layer 200 and the second transition layer 300 include aluminum and copper. In order to facilitate the welding between the first transition layer 200 and the first metal layer 110, and to facilitate the welding between the second transition layer 300 and the second metal layer 130, the materials of the first metal layer 110, the second metal layer 130, the first transition layer 200 and the second transition layer 300 are the same. This allows the first transition layer 200 and the first metal layer 110, as well as the second transition layer 300 and the second metal layer 130, to fuse together during the roll welding process, thereby ensuring current carrying capacity while improving welding efficiency.

[0041] In some preferred embodiments, along the first direction X, the thickness of the welded portion 400 embedded in the support layer 120 is D1, and the thickness of the welded portion 400 embedded in the support layer 120 is D2, where 0.1 ≤ (D1 + D2) / H1 ≤ 0.8. This further reduces the phenomenon of incomplete welding or over-welding in the welded portion 400. D1 / H1 ≥ 0.05, D2 / H1 ≥ 0.05. Through the above structure, in one or more embodiments of this application, embodiments with better current carrying capacity and better mechanical properties can be obtained, as detailed in the following analysis of the embodiments and comparative examples. This reduces the phenomenon of incomplete welding or over-welding in the welded portion 400, thereby reducing the impact of incomplete welding on the current carrying capacity of the current collector 100 due to insufficient connection strength between the current collector 100, the first transition layer 200, and the second transition layer 300, or reducing the impact of over-welding on the mechanical properties of the current collector 100 due to damage to the support layer 120 structure within the current collector 100. With D1 / H1≥0.05 and D2 / H1≥0.05, limiting the lower limits of D1 and D2 can reduce the possibility of insufficient welding due to an excessively small weld portion on one side.

[0042] For the current collector 100 described above, please refer to Figures 1 and 2. The thickness of the support layer 120 along the first direction X is H1, the thickness of the first metal layer 110 along the first direction X is H2, and the thickness of the second metal layer 130 along the first direction X is H3; 4μm≤H1≤18.4μm, 0.8μm≤H2≤3μm, 0.8μm≤H3≤3μm; and 6.5μm≤H1+H2+H3≤20μm. To ensure the mechanical properties of the current collector 100, the thickness of the support layer 120 is between 4 μm and 18.4 μm. If the thickness is too small, the support performance of the current collector 100 will be insufficient, and the current collector 100 will have poor stress resistance. If the thickness is too large, it will affect the volume of the current collector 100, resulting in an increase in the thickness of the electrode 1000. Alternatively, if the overall thickness of the current collector 100 is fixed, the thickness of the support layer 120 may occupy too much of the thickness of the current collector 100, resulting in a reduction in the thickness of the first metal layer 110 and the second metal layer 130. This may lead to a decrease in the current carrying capacity of the current collector 100 and an increase in resistance.

[0043] Preferably, please refer to Figures 1 and 2. Along the first direction X, the support layer 120, the first metal layer 110, and the second metal layer 130 satisfy the following conditions: 13μm≤H1≤16μm, 1μm≤H2≤3μm, and 1μm≤H3≤3μm. This further improves the mechanical properties of the support layer 120 and also enhances the electrical conductivity of the first metal layer 110 and the second metal layer 130.

[0044] In one or more embodiments of this application, please refer to Figures 1 and 2. For the first transition layer 200 and the second transition layer 300 described above, along the first direction X, the thickness of the first transition layer 200 is Z1, 8μm≤Z1≤20μm; the thickness of the second transition layer 300 is Z2, 8μm≤Z2≤20μm. The width of the first transition layer 200 is Z3, 10mm≤Z3≤20mm; the width of the second transition layer 300 is Z4, 10mm≤Z4≤20mm. It is worth noting that the thickness of the first transition layer 200 and the width of the second transition layer 300 disposed on both sides of the current collector 100 can be equal or unequal. When multiple electrodes 1000 need to be stacked, the overall thickness can be reduced by decreasing the thickness of the first transition layer 200 and / or the second transition layer 300 of adjacent electrodes 1000, thereby further improving space utilization.

[0045] In one or more embodiments of this application, please refer to Figures 1 and 2. The welding portion 400 is provided with a plurality of weld feet 410, which are arranged in a dotted pattern within the area of ​​the welding portion 400. The ratio of the area of ​​the weld foot 410 to the area of ​​the welding portion 400 is B, where 0.3 ≤ B ≤ 0.7. When the ratio B is less than 0.3, the area of ​​the weld foot 410 is too small relative to the area of ​​the welding portion 400, which can easily lead to incomplete soldering; when the ratio is greater than 0.7, the area of ​​the weld foot 410 is too large relative to the area of ​​the welding portion 400, which can easily lead to over-soldering. The weld feet 410 are located at the junctions of the first metal layer 110, the first transition layer 200, and at least a portion of the support layer 120, and at the junctions of the second metal layer 130, the second transition layer 300, and at least a portion of the support layer 120. The weld foot portion 410 can be cylindrical along the first direction X, with a diameter between 1 mm and 5 mm. Preferably, the diameter of the weld foot portion 410 is 2 mm, thereby improving the connection capability of the weld foot portion 410, enhancing the connection stability between the first transition layer 200 and the first metal layer 110, and improving the connection stability between the second transition layer 300 and the second metal layer 130. It is understood that the dotted, spaced weld foot portions 410, through embedding, cause deformation of the first transition layer 200 and / or the second transition layer 300 without overall compression, improving roll welding efficiency and reducing material waste. Furthermore, when the ratio B is less than or equal to 0.7, roll welding efficiency can be further improved, and roll welding costs reduced. Specifically, when the ratio B is greater than 0.7, on the one hand, it can lead to over-welding of the welded portion 400, and on the other hand, it requires increasing the number of weld foot portions 410. Therefore, during the roll welding process, the number of weld points used for rolling welding the weld foot portions 410 needs to be increased, thereby reducing roll welding efficiency.

[0046] Furthermore, along the second direction Y, the width D3 of the solder foot 410 satisfies: 10μm≤D3≤50μm; the second direction Y is perpendicular to the first direction X and extends along the length of the current collector 100. It should be noted that the width of the solder foot 410 in the second direction Y includes the distance between two adjacent solder feet 410, thereby preventing over-soldering caused by excessively close proximity between the two solder feet 410. With the above structure, when the width of the solder foot 410 is less than 10μm, over-soldering is likely to occur, affecting the mechanical properties of the current collector 100 and reducing its ability to withstand local stress; when the width of the solder foot 410 is greater than 50μm, incomplete soldering is likely to occur, affecting the connection stability between the current collector 100 and the first transition layer 200 and / or the second transition layer 300.

[0047] In one or more embodiments of this application, please refer to Figures 1 and 2. The projection of the first transition layer 200 along the first direction X at least partially coincides with the current collector 100, and the projection of the second transition layer 300 along the first direction X at least partially coincides with the current collector 100. The welding portion 400 is located in the overlapping area of ​​the projections of the first transition layer 200, the current collector 100, and the second transition layer 300. This allows the welding portion 400 to weld the first transition layer 200 and the second transition layer 300 to opposite sides of the current collector 100, facilitating welding of the first transition layer 200 and the second transition layer 300 to other external metal materials. It is understood that the projection of the first transition layer 200 along the first direction X at least partially coincides with the current collector 100, meaning that the first transition layer 200 in the first direction X is at least partially connected to the current collector 100, while in the second direction Y, the current collector 100 leaves other areas unconnected to the first transition layer 200 for other external parts to connect to the current collector 100, and the areas of the first transition layer 200 in the second direction Y that are not connected to the current collector 100 can be used to connect other metal materials; correspondingly, the projection of the second transition layer 300 along the first direction X at least partially coincides with the current collector 100, meaning that the second transition layer 300 in the first direction X is at least partially connected to the current collector 100, while in the second direction Y, the current collector 100 leaves other areas unconnected to the second transition layer 300 for other external parts to connect to the current collector 100, and the areas of the second transition layer 300 in the second direction Y that are not connected to the current collector 100 can be used to connect other metal materials. Optionally, the areas of the first transition layer 200 and the second transition layer 300 that are not connected to the current collector 100 can facilitate connection between multiple electrodes 1000.

[0048] In one or more embodiments of this application, please refer to 3. For the electrode 1000, along the first direction X, the thickness of the overlapping portion of the welding portion 400, the first transition layer 200, the current collector 100, and the second transition layer 300 is A1; the thickness of the overlapping portion of the first transition layer 200, the current collector 100, and the second transition layer 300 is A2; the difference between A1 and A2 is: 10μm≤A1-A2≤30μm. Through the above structure, the portion of the electrode 1000 with thickness A1 is made thicker, improving the structural strength and stability of the electrode 1000. Further explanation of the electrode 1000 in conjunction with the above structure: before the electrode 1000 is roll-welded, the thickness of the electrode 1000 is the sum of the thickness of the current collector 100, the thickness of the first transition layer 200, and the thickness of the second transition layer 300. After the electrode 1000 is rolled and welded, it is compressed by the rolling process. The weld foot 410 is embedded in the current collector 100, the first transition layer 200, and the second transition layer 300. This causes the first transition layer 200 and the second transition layer 300 to deform around the weld foot 410. Specifically, the difference between the thickness of the weld portion 400 and the thickness of the portion of the electrode 1000 outside the weld portion 400 is 10μm to 30μm, representing the deformation of the electrode 1000 before and after welding. With this structure, if the deformation is less than 10μm, it indicates insufficient thickness of the weld foot 410, which can easily lead to a cold weld; if the deformation is greater than 30μm, it indicates excessive thickness of the weld foot 410, which can easily lead to over-welding.

[0049] In one or more embodiments of this application, please refer to Figures 1 and 2. Along the first direction X, the current collector 100 has an empty foil area 500 in the region where the projections of the first transition layer 200 and the second transition layer 300 overlap. The empty foil area 500 is used for welding the first transition layer 200 and / or the second transition layer 300. By providing the empty foil area 500, roll welding and the application of other metal materials, such as aluminum foil, copper foil, etc., are facilitated. Specifically, the empty foil area 500 is an area that is not coated with other materials, thereby reducing the influence of coated materials on roll welding.

[0050] Optionally, along the second direction Y, see Figures 1 and 2. The length of the empty foil area 500 is K1, where 1mm ≤ K1 ≤ 5mm. The second direction Y is perpendicular to the first direction X and extends along the length of the current collector 100. This leaves more space for connecting other metal materials.

[0051] Preferably, along the second direction Y, see Figures 1 and 2. The length of the empty foil area 500 is K1, 2.5mm≤K1≤3.5mm. This allows for more space to be provided for the external connection of other metal materials while saving some space and reducing the volume and area occupied by the electrode 1000.

[0052] Optionally, the material of the support layer 120 includes polypropylene, polyethylene, polyurethane, polyethylene terephthalate, etc. This gives the support layer 120 good insulation properties, mechanical support properties, heat resistance, and wear resistance.

[0053] Based on one or more embodiments given above, this application specifically provides the following embodiments and comparative examples for testing. The testing methods include two methods: 1) By clamping the electrode 1000 in a high-speed rail tensile testing machine, with the two sides of the electrode 1000 having the welding portion 400 connected to the high-speed rail tensile testing machine, and setting the speed of the high-speed rail tensile testing machine to 50 mm / min, the tensile force that the welding portion 400 can withstand after welding is tested to obtain the "welding tensile force." The greater the welding tensile force, the stronger the mechanical properties of the embodiment or comparative example; 2) As shown in Figure 4, the electrode 1000 is connected to the same conductive element (the bottommost structure in Figure 4), one side of the welding portion 400 in the second direction Y is connected to the conductive element, and the welding portion 400 is symmetrically cut along the second direction Y into two identical "C"-shaped areas, and the two identical areas are respectively connected to the positive and negative terminals of the same circuit to form a conductive path. The "welding resistance" is measured by applying the same voltage between the positive and negative terminals of the conductive paths in each embodiment and comparative example. A lower welding resistance indicates a stronger current-carrying capacity of the embodiment. It is understood that the welding resistance is only a resistance value used in this test to represent the current-carrying capacity of the embodiment or comparative example, and not the actual resistance value of the embodiment or comparative example. It should be noted that the thickness of the first metal layer 110 and the second metal layer 130 of the current collector 100 in the following embodiments and comparative examples is 2 μm, and the thickness of the polymer layer is 15 μm.

[0054] Example 1: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.1; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0055] Example 2: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.3; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0056] Example 3: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.4; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0057] Example 4: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.5; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0058] Example 5: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0059] Example 6: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.8; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0060] Example 7: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.3.

[0061] Example 8: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.4.

[0062] Example 9: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.6.

[0063] Example 10: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.7.

[0064] Example 11: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.2.

[0065] Example 11: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.8.

[0066] Comparative Example 1: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.05; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0067] Comparative Example 2: The ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.9; the ratio of the area of ​​the weld foot 410 to the area of ​​the welded part 400 is 0.5.

[0068] Based on the above comparative examples and embodiments, the welding tensile force and welding resistance of the roller-welded electrode 1000 were measured and the results are shown in Table 1.

[0069] Table 1:

[0070] The ratio of the thickness of the embedded support layer to the thickness of the support layer (D1+D2) / H1, the ratio of the weld foot area to the weld area, the welding tensile force (N / 20mm), and the welding resistance (mΩ) are all calculated. Example 1: 0.1 0.5 2643; Example 2: 0.3 0.5 2841; Example 3: 0.4 0.5 2940; Example 4: 0.5 0.5 3035; Example 5: 0.6 0.5 2738; Example 6: 0.8 0.5 2640; Example 7: 0.6 0.3 1840; Example 8: 0.6 0.4 2050; Example 9: 0.6 0.6 2045; Example 10: 0.6 0.7 3035; Example 11: 0.6 0.2 1753; Example 12: 0.6 0.8 1652; Comparative Example 1: 0.05 0.5 1355; Comparative Example 2: 0.9 0.5 1160.

[0071] Through the above tests, it was found that in Comparative Example 1, when the ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is less than 0.1, the welding tensile force is low and the welding resistance is high. In Comparative Example 2, when the ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is greater than 0.8, the welding tensile force is low and the welding resistance is high. Comparing Examples 11 and 12 with any one of Examples 7 to 10, it can be seen that the ratio of the thickness of the welded part 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6. In Example 11, when the ratio of the weld foot 410 to the welded part 400 is less than 0.3, the mechanical properties are insufficient compared to any one of Examples 7 to 10, and the welding resistance is relatively high. In Example 12, when the ratio of the weld foot 410 to the welded part 400 is greater than 0.7, the mechanical properties are insufficient compared to any one of Examples 7 to 10, and the welding resistance is relatively high. Of the various embodiments provided in this application, Embodiments 4 and 10 are preferred embodiments, but this does not mean that the embodiments and preferred embodiments provided in this application are limited to the 12 embodiments described above. Specifically, a preferred embodiment can be obtained when the ratio of the thickness of the weld portion 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.5; the ratio of the area of ​​the weld foot portion 410 to the area of ​​the weld portion 400 is 0.5; or, the ratio of the thickness of the weld portion 400 embedded in the support layer 120 to the thickness of the support layer 120 is 0.6; and the ratio of the area of ​​the weld foot portion 410 to the area of ​​the weld portion 400 is 0.7. This results in the electrode 1000 obtaining better mechanical properties and current carrying capacity after roll welding.

[0072] In conjunction with the above, this application also provides a welding method for an electrode 1000, which is applied to the electrode 1000, the electrode 1000 including: a current collector 100, a first transition layer 200, a second transition layer 300 and an electrode tab, the method including: disposing the first transition layer 200 and the second transition layer 300 on both sides of the current collector 100; welding one end of the first transition layer 200 and / or one end of the second transition layer 300 to the current collector 100 by roll welding; welding the other end of the first transition layer 200 and / or the other end of the second transition layer 300 to the electrode tab by ultrasonic welding or spot welding.

[0073] In a second aspect, this application also provides a battery cell, the battery cell including an electrode assembly, the electrode assembly including the aforementioned electrode sheet 1000.

[0074] In a third aspect, this application also provides an electrical device, which includes a battery cell.

[0075] In this embodiment, an electrode 1000 is provided, comprising a current collector 100, a first transition layer 200, and a second transition layer 300. The electrode 1000 also includes a welding portion 400. The current collector 100 comprises a first metal layer 110, a support layer 120, and a second metal layer 130 disposed along a first direction X. The first transition layer 200 is connected to the side of the first metal layer 110 opposite to the support layer 120. The second transition layer 300 is connected to the side of the second metal layer 130 opposite to the support layer 120. The welding portion 400 is located at the connection between the first transition layer 200 and the first metal layer 110, and at the connection between the second transition layer 300 and the second metal layer 130. Along the first direction X, on one side of the first transition layer 200, the welding portion 400 is embedded in the support layer 120 with a thickness of D1; on the other side of the second transition layer 300, the welding portion 400 is embedded in the support layer 120 with a thickness of D2, and the thickness of the support layer 120 is H1. The ratio of D1 and D2 to the thickness of the support layer 120 satisfies: 0.1 ≤ (D1 + D2) / H1 ≤ 0.8. By providing the welding portion 400, the first transition layer 200 and the second transition layer 300 are welded to the current collector 100, wherein the first transition layer 200 is welded to the first metal layer 110 of the current collector 100, and the second transition layer 300 is welded to the second metal layer 130 of the current collector 100, to facilitate fusion. The welded portion 400 obtained after welding the electrode 1000 will be embedded into the support layer 120. Furthermore, the thickness of the welded portion 400 embedded in the support layer 120 is optimized so that the thickness of the welded portion 400 embedded in the support layer 120 from both sides of the support layer 120 and the thickness of the support layer 120 itself satisfy: 0.1≤(D1+D2) / H1≤0.8. This reduces the phenomenon of insufficient welding caused by the welded portion 400 being embedded in the support layer 120 when the ratio of the thickness of the welded portion 400 embedded in the support layer 120 is less than 0.1, thus reducing the impact of weak welding on the electrode 1000. Alternatively, it reduces the phenomenon of over-welding caused by the welded portion 400 being embedded in the support layer 120 when the ratio of the thickness of the welded portion 400 embedded in the support layer 120 is greater than 0.8, thus reducing the impact of over-welding on the mechanical properties of the support layer 120 on the electrode 1000.

[0076] Based on the same inventive concept, this application also provides a battery cell, which includes an electrode assembly, and the electrode assembly includes an electrode 1000. The electrode 1000 has the same structure and effect as the electrode 1000 mentioned above, and will not be described in detail here.

[0077] Based on the same inventive concept, this application also provides an electrical device, which includes a battery cell. The battery cell has the same structure and effect as the battery cell described above, and will not be described in detail here.

[0078] It should be noted that while preferred embodiments of this application are provided in the specification and accompanying drawings, this application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this application; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this application. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this application's specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An electrode sheet, characterized in that, The electrode includes: A current collector, the current collector comprising a first metal layer, a support layer, and a second metal layer disposed along a first direction; The first transition layer is connected to the side of the first metal layer opposite to the support layer; The second transition layer is connected to the side of the second metal layer opposite to the support layer; The electrode sheet is further provided with a welding part, which is located at the connection between the first transition layer and the first metal layer, and at the connection between the second transition layer and the second metal layer. Along the first direction, on one side of the first transition layer, the welding part is embedded in the support layer with a thickness of D1, and on one side of the second transition layer, the welding part is embedded in the support layer with a thickness of D2, and the thickness of the support layer is H1. The ratios of D1 and D2 to the thickness of the support layer satisfy the following conditions: 0.1 ≤ (D1 + D2) / H1 ≤ 0.8, D1 / H1 ≥ 0.05, D2 / H1 ≥ 0.

05.

2. The electrode sheet according to claim 1, characterized in that, Along the first direction, the ratio of D1 and D2 to the thickness of the support layer satisfies: 0.4≤(D1+D2) / H1≤0.

6.

3. The electrode sheet according to claim 1, characterized in that, The thickness of the support layer along the first direction is H1, the thickness of the first metal layer along the first direction is H2, and the thickness of the second metal layer along the first direction is H3. 4μm≤H1≤18.4μm, 0.8μm≤H2≤3μm, 0.8μm≤H3≤3μm; And 6.5μm≤H1+H2+H3≤20μm.

4. The electrode sheet according to claim 3, characterized in that, Along the first direction, the support layer, the first metal layer and the second metal layer satisfy: 13μm≤H1≤16μm, 1μm≤H2≤3μm, 1μm≤H3≤3μm.

5. The electrode sheet according to claim 1, characterized in that, Along the first direction, the thickness of the first transition layer is Z1, 8μm≤Z1≤20μm; The thickness of the second transition layer is Z2, where 8μm≤Z2≤20μm.

6. The electrode sheet according to claim 5, characterized in that, The width of the first transition layer is Z3, 10mm≤Z3≤20mm; The width of the second transition layer is Z4, 10mm≤Z4≤20mm.

7. The electrode sheet according to claim 1, characterized in that, The welding part is provided with multiple welding feet, and the multiple welding feet are arranged at point intervals within the area of ​​the welding part. The ratio of the area of ​​the weld foot to the area of ​​the welded part is B, where 0.3 ≤ B ≤ 0.

7.

8. The electrode sheet according to claim 7, characterized in that, Along the second direction, the width D3 of the weld leg satisfies: 10μm≤D3≤50μm; The second direction is perpendicular to the first direction and extends along the length of the current collector.

9. The electrode sheet according to any one of claims 1-8, characterized in that, The projection of the first transition layer along the first direction at least partially coincides with the current collector, the projection of the second transition layer along the first direction at least partially coincides with the current collector, and the welded portion is located in the overlapping area of ​​the projections of the first transition layer, the current collector, and the second transition layer.

10. The electrode sheet according to claim 9, characterized in that, Along the first direction, the thickness of the overlapping portion of the welded part, the first transition layer, the current collector, and the second transition layer is A1; the thickness of the overlapping portion of the first transition layer, the current collector, and the second transition layer is A2. The difference between A1 and A2 is: 10μm≤A1-A2≤30μm.

11. The electrode according to claim 10, characterized in that, Along the first direction, the current collector has an empty foil area in the region where the projections of the first transition layer and the second transition layer overlap, and the empty foil area is used for welding the first transition layer and / or the second transition layer.

12. The electrode sheet according to claim 11, characterized in that, Along the second direction, the length of the empty foil region is K1, where 1mm ≤ K1 ≤ 5mm; The second direction is perpendicular to the first direction and extends along the length of the current collector.

13. The electrode sheet according to claim 12, characterized in that, Along the second direction, the length of the empty foil area is K1, where 2.5mm ≤ K1 ≤ 3.5mm.

14. The electrode sheet according to any one of claims 1-8, characterized in that, The materials of the support layer include polypropylene, polyethylene, polyurethane, polyethylene terephthalate, etc.

15. A battery cell, characterized in that, It includes an electrode assembly, the electrode assembly comprising an electrode sheet as described in any one of claims 1 to 14.

16. An electrical appliance, characterized in that, Including the battery cell as described in claim 15.

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