Copper-aluminum composite connecting sheet and battery cover plate

Abstract

The invention belongs to the technical field of batteries, and discloses a copper-aluminum composite connecting piece and a battery cover plate, the copper-aluminum composite connecting piece comprises an aluminum area and a copper area, the copper area is connected with the aluminum area, a copper-aluminum boundary is formed between the aluminum area and the copper area, the aluminum area is welded with a pole, the copper area is welded with a negative tab, and the copper area is welded with a positive tab. The distance dimension between a boundary line, facing the copper-aluminum boundary line, of the connection welding printing area and the copper-aluminum boundary line in the first direction is X, and X is more than or equal to 4mm and less than or equal to 30mm. The use amount of copper materials is reduced, so that the cost is reduced, the weight is reduced, and the size of the connection welding printing area formed after the copper area and the negative tab are welded is limited, so that the situation that the distance between a boundary line, facing the copper-aluminum boundary line, of the connection welding printing area and the aluminum boundary line is too short is avoided; and an interface at the copper-aluminum boundary after welding is damaged, so that cracks are caused near the copper-aluminum boundary, the mechanical property is reduced, and the risk of fracture is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a copper-aluminum composite connecting sheet and a battery cover plate. Background Art

[0002] Lithium-ion batteries have the advantages of high energy, many cycles, and long storage time. They are widely used not only in portable electronic devices such as mobile phones, digital cameras, and laptops, but also in large and medium-sized electric devices such as electric vehicles, electric bicycles, and electric tools. Therefore, the performance requirements for lithium-ion batteries are getting higher and higher. Generally speaking, the structure of a lithium-ion battery includes a shell containing a pole group and a cover assembly that encapsulates the shell. The pole group includes a pole piece and a negative pole ear, and the negative pole ear is connected to the pole of the cover assembly through a connecting piece to achieve electrical connection.

[0003] The connecting piece is generally made of the same material as the negative electrode ear of the corresponding polarity to facilitate connection and welding. Since the positive electrode is generally aluminum and the negative electrode is generally copper, the connecting piece connected to the positive electrode is a pure aluminum piece, and the connecting piece connected to the negative electrode is a pure copper piece. However, since the cost and weight of copper are greater than those of aluminum, pure copper is used as the connecting piece, which not only increases the production cost, but also increases the overall weight of the lithium-ion battery, which does not conform to the principle of lightweight structural design. Summary of the invention

[0004] The object of the present invention is to provide a copper-aluminum composite connecting piece and a battery cover plate, which have low production cost and light weight and conform to the principle of lightweight structural design.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] Provided is a copper-aluminum composite connecting sheet, which is used to connect a negative electrode ear and an electrode column, and comprises an aluminum area and a copper area, wherein the copper area is connected to the aluminum area, and a copper-aluminum dividing line is formed between the aluminum area and the copper area, the aluminum area is welded to the electrode column, and the copper area is welded to the negative electrode ear, and a connection weld mark area for connecting the copper area and the negative electrode ear is formed;

[0007] A distance dimension along a first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line is X, and satisfies 4mm≤X≤30mm.

[0008] Optionally, when the copper area is laser welded to the negative electrode ear to form the connection weld mark area, a distance dimension X along the first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line satisfies 3mm≤X≤30mm.

[0009] Optionally, when the copper area is ultrasonically welded to the negative electrode ear to form the connection weld mark area, a distance dimension X along the first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line satisfies 1.5 mm≤X≤30 mm.

[0010] Optionally, a distance dimension along the first direction between a boundary line of the connecting weld mark area away from the copper-aluminum boundary line and a boundary line of the copper area away from the copper-aluminum boundary line is Y, and satisfies 4mm≤Y≤30mm.

[0011] Optionally, when the copper area is laser welded to the negative electrode ear to form the connecting weld mark area, the distance dimension Y along the first direction between the boundary line of the connecting weld mark area away from the copper-aluminum dividing line and the boundary line of the copper area away from the copper-aluminum dividing line satisfies 3mm≤Y≤30mm.

[0012] Optionally, when the copper area is ultrasonically welded to the negative electrode ear to form the connecting weld mark area, the distance dimension Y along the first direction between the boundary line of the connecting weld mark area away from the copper-aluminum dividing line and the boundary line of the copper area away from the copper-aluminum dividing line satisfies 2mm≤Y≤30mm.

[0013] Optionally, a distance dimension between a boundary line of the connection weld print area on either side along the second direction and a boundary line of the copper area adjacent thereto along the second direction is Z, and Z≥2 mm.

[0014] Optionally, the volume of the copper-aluminum composite connecting sheet is V, the total volume of the copper area is V1, and 0.1≤V1 / V≤0.6 is satisfied.

[0015] Optionally, the copper-aluminum composite connecting sheet includes a plurality of copper regions connected to the aluminum region, a volume of each copper region is V2, and 0.3≤V2 / V1≤0.7 is satisfied.

[0016] On the other hand, a battery cover is provided, wherein the battery cover comprises the copper-aluminum composite connecting sheet as described in any one of the above items.

[0017] Beneficial effects of the present invention:

[0018] The invention provides a copper-aluminum composite connecting sheet. The copper-aluminum composite connecting sheet is composed of a copper area and an aluminum area, and the copper area is connected to the negative electrode ear, and the aluminum area is connected to the pole. Compared with a traditional single copper connecting sheet, the use amount of copper material is reduced, thereby reducing the cost and reducing the weight. In addition, by limiting the distance dimension X between the boundary line of the connecting weld print area facing the copper-aluminum boundary line and the copper-aluminum boundary line along the first direction to satisfy 4mm≤X≤30mm, on the one hand, it is avoided that the distance between the boundary line of the connecting weld print area facing the copper-aluminum boundary line and the copper-aluminum boundary line is too short, resulting in the interface at the copper-aluminum boundary line being destroyed after welding, thereby causing cracks near the copper-aluminum boundary line, reducing the mechanical properties and increasing the risk of fracture. On the other hand, it is avoided that the distance between the boundary line of the connecting weld print area facing the copper-aluminum boundary line and the copper-aluminum boundary line is too long, resulting in more space occupied due to the increase in the size of the connecting sheet.

[0019] The present invention also provides a battery cover plate, which effectively controls the production cost and the weight of the finished product after assembly by applying the above-mentioned copper-aluminum composite connecting sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the connection between the copper-aluminum composite connecting piece and the pole ear provided by the present invention by laser welding to complete the final welding;

[0021] Figure 2 It is a schematic diagram of the connection between the copper-aluminum composite connecting sheet and the pole ear provided by the present invention by ultrasonic welding to complete the final welding;

[0022] Figure 3 It is a schematic diagram of the connection between the copper-aluminum composite connecting sheet and the pole ear provided by the present invention when pre-welding is completed by ultrasonic welding;

[0023] Figure 4 It is a schematic structural diagram of the copper-aluminum composite connecting piece provided by the present invention being a single copper area in the shape of a straight line;

[0024] Figure 5 It is a schematic structural diagram of the copper-aluminum composite connecting piece provided by the present invention being a double copper zone straight line shape;

[0025] Figure 6 It is a schematic structural diagram of the copper-aluminum composite connecting piece provided by the present invention being a single copper area convex shape;

[0026] Figure 7 The copper-aluminum composite connecting piece provided by the present invention is a schematic structural diagram of a single copper area in the shape of a Chinese character "X";

[0027] Figure 8 The present invention is a schematic diagram of the structure of a copper-aluminum composite connecting piece in a single copper area Z-shaped.

[0028] In the figure:

[0029] 100, negative electrode ear;

[0030] 1. Aluminum area;

[0031] 2. Copper area;

[0032] 3. Copper-aluminum dividing line;

[0033] 4. Connect the welding area;

[0034] 5. Pre-welding and welding mark. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0036] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0039] In the battery, since the negative electrode is copper, the connecting plate connected to it is generally a pure copper plate. The use of a pure copper connecting plate is not only heavy and does not conform to the design principle of lightweight structure, but also has a high material cost, resulting in a high production cost.

[0040] Therefore, in order to reduce the weight of the connecting piece, meet the design principle of lightweight structure, reduce production costs, and improve product competitiveness, this embodiment provides a copper-aluminum composite connecting piece for connecting the negative electrode ear and the pole.

[0041] like Figures 1 to 3 As shown, the copper-aluminum composite connecting sheet includes an aluminum area 1 and a copper area 2, the copper area 2 is connected to the aluminum area 1, and a copper-aluminum dividing line 3 is formed between the aluminum area 1 and the copper area 2, the aluminum area 1 is welded to the pole, the copper area 2 is welded to the negative electrode ear 100, and a connecting weld mark area 4 for connecting the copper area 2 and the negative electrode ear 100 is formed, and the distance dimension between the boundary line of the connecting weld mark area 4 toward the copper-aluminum dividing line 3 and the copper-aluminum dividing line 3 along the first direction is X, and satisfies 4mm≤X≤30mm.

[0042] The copper-aluminum composite connecting sheet is composed of a copper area 2 and an aluminum area 1, and the copper area 2 is connected to the negative electrode ear 100, and the aluminum area 1 is connected to the pole. Compared with a traditional single pure copper connecting sheet, the amount of copper material used is reduced, thereby reducing costs and reducing weight. In addition, by limiting the distance dimension X along the first direction between the boundary line of the connecting weld print area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 to satisfy 4mm≤X≤30mm, on the one hand, it is avoided that the distance between the boundary line of the connecting weld print area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is too short, resulting in the interface at the copper-aluminum boundary line 3 being destroyed due to being too close to the copper-aluminum boundary line 3 during welding, and cracks are caused near the copper-aluminum boundary line 3, resulting in a decrease in the mechanical properties of the copper-aluminum composite connecting sheet and an increased risk of fracture. On the other hand, it is avoided that the distance between the boundary line of the connecting weld print area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is too long, thereby increasing the size of the copper-aluminum composite connecting sheet and increasing the manufacturing cost.

[0043] Among them, Figures 4 to 8 As shown, the shape of the copper-aluminum composite connecting piece can be freely set according to the actual structural requirements, such as a straight line, a convex shape, a cross shape or a Z shape. And the copper-aluminum composite connecting piece can be used in the cover plate assembly of various types of batteries, such as the cover plate assembly of blade batteries, the cover plate assembly of square shell batteries or the cover plate assembly of large cylindrical batteries.

[0044] Alternatively, if Figure 1As shown, when the copper area 2 is laser welded with the negative electrode ear 100 to form a connection weld mark area 4, the distance dimension X between the boundary line of the connection weld mark area 4 facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction satisfies 3mm≤X≤30mm. By using laser welding to weld the copper area 2 and the negative electrode ear 100, compared with the traditional welding method, the heating area of ​​laser welding is very small, so the heat-affected zone is also very small, so it has a smaller deformation amplitude, and because the depth-to-width ratio of laser welding is large, that is, the welding depth is large and the width is small, which makes the welding have a higher welding strength after welding. At this time, for the connection weld mark area 4 formed by laser welding, the limitation of the distance dimension X between the boundary line of the connection weld mark area 4 facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction formed by laser welding can be relaxed to satisfy 3mm≤X≤30mm. This can prevent the distance between the boundary line of the connecting weld mark area 4 generated by laser welding toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 from being too short, resulting in the interface at the copper-aluminum boundary line 3 being destroyed due to being too close to the copper-aluminum boundary line 3 during welding, and causing cracks near the copper-aluminum boundary line 3, causing the mechanical properties of the copper-aluminum composite connecting piece to decrease and increasing the risk of fracture. On the other hand, it can prevent the distance between the boundary line of the connecting weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 from being too long, thereby increasing the size of the copper-aluminum composite connecting piece and increasing the production cost.

[0045] In this embodiment, the connection weld mark area 4 formed after laser welding is the final weld mark. In order to facilitate the laser welding operation and ensure the welding quality after laser welding, ultrasonic welding is required to perform pre-welding before laser welding, so as to play the role of closing the pole ear. At this time, a pre-welding mark 5 will be generated after ultrasonic welding. After the ultrasonic welding as a pre-welding is completed, laser welding is used to complete the final welding on the basis of the pre-welding mark 5. At this time, the connection weld mark area 4 formed by laser welding is located in the area of ​​the pre-welding mark 5. Among them, the distance dimension X between the boundary line of the connecting weld mark area 4 formed by laser welding toward the copper-aluminum dividing line 3 and the copper-aluminum dividing line 3 along the first direction can be any value between 3mm and 30mm or a range between any two values, for example, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, etc.

[0046] Alternatively, if Figure 2As shown, when the copper area 2 is ultrasonically welded to the negative electrode ear 100 and a connection weld mark area 4 is formed, the distance dimension X between the boundary line of the connection weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction satisfies 1.5mm≤X≤30mm. By using ultrasonic welding to weld the copper area 2 to the negative electrode ear 100, compared with the traditional welding method, ultrasonic welding can melt the metal surface in a short time through local tiny friction heat to form fusion between molecular layers, effectively reduce the deformation and stress concentration of the material, thereby obtaining higher welding strength, reducing the heat-affected zone that may occur in traditional welding and laser welding, thereby maintaining the original characteristics of the welding material to a great extent, and no open flame or arc discharge will be generated during the welding process, avoiding the risk of fire and explosion, and improving the safety of welding. At this time, the connection weld mark area 4 formed by ultrasonic welding can further relax the limitation of the distance dimension X between the boundary line of the connection weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction formed by ultrasonic welding, so that it satisfies 1.5mm≤X≤30mm. Thus, on the one hand, it is avoided that the distance between the boundary line of the connection weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is too short, resulting in the interface at the copper-aluminum boundary line 3 being destroyed due to being too close to the copper-aluminum boundary line 3 during welding, and cracks are caused near the copper-aluminum boundary line 3, resulting in the mechanical properties of the copper-aluminum composite connecting piece being reduced and the risk of fracture being increased. On the other hand, it is avoided that the distance between the boundary line of the connection weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is too long, thereby increasing the size of the copper-aluminum composite connecting piece and increasing the manufacturing cost.

[0047] In this embodiment, the connection weld mark area 4 formed by ultrasonic welding is the final weld mark. In order to facilitate the operation of ultrasonic welding and ensure the welding quality after ultrasonic welding, ultrasonic welding is also required to be pre-welded in advance before ultrasonic welding, so as to play the role of closing the pole ear. Figure 3As shown, after ultrasonic welding, multiple small pre-welding marks 5 with intervals are generated. After the pre-welding is completed, secondary welding is performed by ultrasonic welding to complete the final welding. At this time, the connection weld mark area 4 formed by ultrasonic welding covers multiple small pre-welding marks 5 with intervals. Among them, the distance dimension X between the boundary line of the connection weld mark area 4 toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction formed by ultrasonic welding can be any value between 1.5mm and 30mm or a range between any two values, such as 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, etc.

[0048] Optionally, a distance along the first direction between a boundary line connecting the weld mark area 4 away from the copper-aluminum boundary line 3 and a boundary line connecting the copper area 2 away from the copper-aluminum boundary line 3 is Y, and satisfies 4mm≤Y≤30mm. By setting the distance dimension along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 as Y, and limiting the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 to satisfy 4mm≤Y≤30mm, on the one hand, it is avoided that the distance between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is too small, resulting in a situation where part of the welding head of the welding equipment is located outside the welding area during the welding process, resulting in uneven force when part of the welding head exceeds the welding area, making the welding head easily damaged and reducing the service life of the welding head, and on the other hand, it is avoided that the distance between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is too large, thereby increasing the external dimensions of the copper-aluminum composite connecting piece and increasing the manufacturing cost.

[0049] Alternatively, if Figure 1As shown, when the copper area 2 is laser welded to the negative electrode ear 100 and a connection weld mark area 4 is formed, the distance dimension Y along the first direction between the boundary line of the connection weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 satisfies 3mm≤Y≤30mm. By laser welding the copper area 2 and the negative electrode ear 100, compared with the traditional welding method, the heating area of ​​laser welding is very small, so the heat-affected zone is also very small, so that the deformation amplitude is small, and because the depth-to-width ratio of laser welding is large, that is, the welding depth is large and the width is small, which makes the welding have a higher welding strength after welding. At this time, for the connecting weld mark area 4 formed by laser welding, the limitation on the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum dividing line 3 and the boundary line of the copper area 2 away from the copper-aluminum dividing line 3 formed by laser welding can be relaxed to satisfy 3mm≤Y≤30mm, thereby, on the one hand, avoiding the distance between the boundary line of the connecting weld mark area 4 away from the copper-aluminum dividing line 3 and the boundary line of the copper area 2 away from the copper-aluminum dividing line 3 being too small, resulting in the situation that part of the laser welding head of the laser welding equipment is located outside the welding area during the welding process, resulting in uneven force when part of the laser welding head exceeds the welding area, making the laser welding head easily damaged and reducing the service life of the laser welding head, and on the other hand, avoiding the distance between the boundary line of the connecting weld mark area 4 away from the copper-aluminum dividing line 3 and the boundary line of the copper area 2 away from the copper-aluminum dividing line 3 being too large, thereby increasing the external dimensions of the copper-aluminum composite connecting piece and increasing the production cost.

[0050] In this embodiment, the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 produced by laser welding and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 can be any value between 3mm and 30mm or a range between any two values, for example, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, etc.

[0051] Alternatively, if Figure 2As shown, when the copper area 2 is ultrasonically welded to the negative electrode ear 100 and a connection weld mark area 4 is formed, the distance dimension Y along the first direction between the boundary line of the connection weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 satisfies 2mm≤Y≤30mm. By using ultrasonic welding to weld the copper area 2 to the negative electrode ear 100, compared with the traditional welding method, ultrasonic welding can melt the metal surface in a short time through local tiny friction heat to form fusion between molecular layers, effectively reduce the deformation and stress concentration of the material, thereby obtaining higher welding strength, reducing the heat-affected area that may occur in traditional welding and laser welding, thereby maintaining the original characteristics of the welding material to a great extent, and no open flame or arc discharge will be generated during the welding process, avoiding the risk of fire and explosion, and improving the safety of welding. At this time, compared with the traditional welding and laser welding methods, the connection weld mark area 4 formed by ultrasonic welding can further relax the limitation of the distance dimension Y along the first direction between the boundary line of the connection weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3, so that it satisfies 2mm≤Y≤30mm, thereby avoiding, on the one hand, the distance between the boundary line of the connection weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 being too small, resulting in the situation that part of the ultrasonic welding head of the ultrasonic welding equipment is located outside the welding area during the welding process, resulting in uneven force on the ultrasonic welding head when part of the ultrasonic welding head exceeds the welding area, making the ultrasonic welding head easily damaged and reducing the service life of the ultrasonic welding head, and on the other hand, avoiding the distance between the boundary line of the connection weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 being too large, thereby increasing the external dimensions of the copper-aluminum composite connecting piece and increasing the production cost.

[0052] In this embodiment, the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 produced by ultrasonic welding can be any value between 2mm and 30mm or a range between any two values, for example 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, etc.

[0053] In order to ensure the reliability after welding by laser welding, as shown in Table 1, the dimension parameters of the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 are set, eight groups of embodiments and three groups of comparative examples are set to verify them, observe whether the interface at the copper-aluminum boundary line 3 is destroyed, whether cracks are found near the copper-aluminum boundary line 3, and finally test the mechanical properties of the copper-aluminum composite connecting sheet to determine that they fully meet the product requirements.

[0054] Table 1

[0055]

[0056] In Example 1, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 3 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 3 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0057] In Example 2, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 5 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 5 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0058] In Example 3, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 10 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 10 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0059] In Example 4, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 15 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 15 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0060] In Example 5, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 19 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 19 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0061] In Example 6, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 24 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 24 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0062] In Example 7, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 27 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 27 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0063] In Example 8, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 30 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 30 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0064] It can be seen from Examples 1 to 8 that when the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 satisfies the range of 3mm≤Y≤30mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 satisfies the range of 2mm≤Y≤30mm, at this time, it is more appropriate for the connecting weld mark area 4 to be located in the copper area 2, so that the copper-aluminum boundary line 3 will not be affected after welding, and during the welding process, the welding head will not exceed the welding area.

[0065] In Comparative Example 1, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 1 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 4 mm. After experimental verification, the interface at the copper-aluminum boundary line 3 was destroyed, cracks were found, and the mechanical properties were NG.

[0066] It can be seen from Comparative Example 1 that when the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is less than the minimum value in the range of 3mm≤Y≤30mm, it proves that the spacing between the connecting weld mark area 4 and the copper-aluminum boundary line 3 is too small, resulting in the hot zone involving the copper-aluminum boundary line 3 during welding, thereby causing the interface at the copper-aluminum boundary line 3 to be destroyed, cracks to be found, and the mechanical properties to be NG.

[0067] In Comparative Example 2, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 4 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 1 mm. After experimental verification, the interface at the copper-aluminum boundary line 3 was not damaged, no cracks were found, the mechanical properties were OK, and the welding head was damaged.

[0068] It can be seen from Comparative Example 2 that when the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 generated by laser welding that is away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 that is away from the copper-aluminum boundary line 3 is less than the minimum value in the range of 2mm≤Y≤30mm, it proves that the spacing between the boundary line of the connecting weld mark area 4 and the copper area 2 is too small, resulting in the situation that part of the welding head is located outside the welding area during the welding process, causing the welding head to be unevenly stressed and damaged.

[0069] In comparative example 3, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 35 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 35 mm. It has been verified by experiments that the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, the mechanical properties are OK, the size is too large, and the cost is high.

[0070] It can be seen from Comparative Example 3 that when the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is greater than the maximum value in the range of 3mm≤Y≤30mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by laser welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is greater than the maximum value in the range of 2mm≤Y≤30mm, at this time, although the interface at the copper-aluminum boundary line 3 is not destroyed, no cracks are found, and the mechanical properties are OK, the size of the copper-aluminum composite connecting piece is increased, which leads to an increase in cost.

[0071] In order to ensure the reliability after ultrasonic welding, as shown in Table 2, the dimension parameters of the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding and the copper-aluminum boundary line 3 and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 are set, eight groups of embodiments and three groups of comparative examples are set to verify them, observe whether the interface at the copper-aluminum boundary line 3 is destroyed, whether cracks are found near the copper-aluminum boundary line 3, and finally test the mechanical properties of the copper-aluminum composite connecting sheet to determine that they meet the product requirements.

[0072] Table 2

[0073]

[0074] In Example 9, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 1.5 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 2 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0075] In Example 10, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 3 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 3 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0076] In Example 11, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 5 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 5 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0077] In Example 12, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 10 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 10 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0078] In Example 13, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 15 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 15 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0079] In Example 14, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 20 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 20 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0080] In Example 15, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 25 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 25 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0081] In Example 16, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 30 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 30 mm. It has been verified by experiments that at this time, the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, and the mechanical properties are OK.

[0082] It can be seen from Examples 9 to 16 that when the distance dimension X between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 along the first direction satisfies the range of 1.5mm≤Y≤30mm, and the distance dimension Y between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 along the first direction satisfies the range of 2mm≤Y≤30mm, at this time, it is more appropriate for the connecting weld mark area 4 to be located in the copper area 2, so that the copper-aluminum boundary line 3 will not be affected after welding, and during the welding process, the welding head will not exceed the welding area.

[0083] In Comparative Example 4, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 1 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 3 mm. After experimental verification, the interface at the copper-aluminum boundary line 3 was destroyed, cracks were found, and the mechanical properties were NG.

[0084] It can be seen from Comparative Example 4 that when the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding toward the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is less than the minimum value in the range of 1.5mm≤Y≤30mm, it proves that the spacing between the connecting weld mark area 4 and the copper-aluminum boundary line 3 is too small, resulting in the hot zone involving the copper-aluminum boundary line 3 during welding, thereby causing the interface at the copper-aluminum boundary line 3 to be destroyed, cracks to be found, and the mechanical properties to be NG.

[0085] In comparative example 5, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 3 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 1.4 mm. After experimental verification, the interface at the copper-aluminum boundary line 3 was not damaged, no cracks were found, the mechanical properties were OK, and the welding head was damaged.

[0086] It can be seen from Comparative Example 5 that when the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 generated by ultrasonic welding that deviates from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 that deviates from the copper-aluminum boundary line 3 is less than the minimum value in the range of 2mm≤Y≤30mm, it proves that the spacing between the boundary line of the connecting weld mark area 4 and the copper area 2 is too small, resulting in the situation that part of the welding head is located outside the welding area during the welding process, causing the welding head to be unevenly stressed and damaged.

[0087] In comparative example 6, the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is set to 35 mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is set to 35 mm. It has been verified by experiments that the interface at the copper-aluminum boundary line 3 is not damaged, no cracks are found, the mechanical properties are OK, the size is too large, and the cost is high.

[0088] It can be seen from Comparative Example 6 that when the distance dimension X along the first direction between the boundary line of the connecting weld mark area 4 formed by ultrasonic welding facing the copper-aluminum boundary line 3 and the copper-aluminum boundary line 3 is greater than the maximum value in the range of 1.5mm≤Y≤30mm, and the distance dimension Y along the first direction between the boundary line of the connecting weld mark area 4 away from the copper-aluminum boundary line 3 and the boundary line of the copper area 2 away from the copper-aluminum boundary line 3 is greater than the maximum value in the range of 2mm≤Y≤30mm, at this time, although the interface at the copper-aluminum boundary line 3 is not destroyed, no cracks are found, and the mechanical properties are OK, the size of the copper-aluminum composite connecting sheet is increased, which leads to an increase in cost.

[0089] Alternatively, if Figure 1 to Figure 2As shown, the distance dimension between the boundary line connecting the weld mark area 4 along any side of the second direction and the boundary line of the copper area 2 adjacent thereto along the second direction is Z, and Z≥2mm is satisfied. By setting the distance dimension between the boundary line connecting the weld mark area 4 along any side of the second direction and the boundary line of the copper area 2 adjacent thereto along the second direction as Z, and making the distance dimension Z between the boundary line connecting the weld mark area 4 along any side of the second direction and the boundary line of the copper area 2 adjacent thereto along the second direction satisfy Z≥2mm, it is avoided that the distance between the boundary line connecting the weld mark area 4 along any side of the second direction and the boundary line of the copper area 2 adjacent thereto along the second direction is too small, resulting in a situation in which part of the welding head of the welding equipment is located outside the welding area during the welding process, resulting in uneven force on the welding head when part of the welding head exceeds the welding area, making the welding head easily damaged and reducing the service life of the welding head.

[0090] Optionally, the volume of the copper-aluminum composite connecting sheet is V, the total volume of the copper region 2 is V1, and 0.1≤V1 / V≤0.6 is satisfied. By setting the volume of the copper-aluminum composite connecting sheet to V, the total volume of the copper region 2 to V1, and making the ratio of the two satisfy 0.1≤V1 / V≤0.6, on the one hand, it is avoided that the total volume of the copper region 2 is too small, which increases the difficulty of welding with the negative electrode ear 100, and on the other hand, it is avoided that the total volume of the copper region 2 is too large, resulting in increased cost and weight.

[0091] Furthermore, the copper-aluminum composite connecting sheet is provided with a plurality of copper regions 2 connected to the aluminum region 1, and the volume of each copper region 2 is V2, and 0.3≤V2 / V1≤0.7 is satisfied. By setting the volume of each copper region 2 to V2, and making the ratio of the volume V2 of each copper region 2 to the total volume V1 of the copper region 2 satisfy 0.3≤V2 / V1≤0.7, on the one hand, it is avoided that the volume of the copper region 2 after splitting is too small, which increases the difficulty of welding with the negative electrode ear 100, and on the other hand, it is avoided that the total volume of the copper region 2 after splitting is too large, resulting in increased cost and weight.

[0092] In this embodiment, the optimal ratio between the volume of the split copper region 2 and the total volume of the plurality of copper regions 2 is 0.5, that is, the volumes of the split copper regions 2 are the same.

[0093] In this embodiment, a battery cover is also provided, the battery cover includes the copper-aluminum composite connecting piece mentioned above. The battery cover effectively controls the production cost and the weight of the finished product after assembly by using the copper-aluminum composite connecting piece mentioned above.

[0094] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A copper-aluminum composite connecting piece, which is used to connect the negative electrode ear and the pole, characterized in that: The copper-aluminum composite connecting sheet comprises an aluminum area and a copper area, the copper area is connected to the aluminum area, and a copper-aluminum boundary line is formed between the aluminum area and the copper area, the aluminum area is welded to the pole, and the copper area is welded to the negative electrode ear, and a connection weld mark area for connecting the copper area and the negative electrode ear is formed; A distance dimension along a first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line is X, and satisfies 4mm≤X≤30mm.

2. The copper-aluminum composite connecting sheet according to claim 1, characterized in that: When the copper area is laser welded to the negative electrode ear to form the connection weld mark area, a distance dimension X along the first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line satisfies 3mm≤X≤30mm.

3. The copper-aluminum composite connecting sheet according to claim 1, characterized in that: When the copper area is ultrasonically welded to the negative electrode ear to form the connection weld mark area, a distance dimension X along the first direction between a boundary line of the connection weld mark area toward the copper-aluminum boundary line and the copper-aluminum boundary line satisfies 1.5 mm≤X≤30 mm.

4. The copper-aluminum composite connecting sheet according to claim 1, characterized in that: A distance dimension along the first direction between a boundary line of the connecting weld mark area away from the copper-aluminum boundary line and a boundary line of the copper area away from the copper-aluminum boundary line is Y, and satisfies 4mm≤Y≤30mm.

5. The copper-aluminum composite connecting sheet according to claim 4, characterized in that: When the copper area is laser welded to the negative electrode ear to form the connecting weld mark area, the distance dimension Y along the first direction between the boundary line of the connecting weld mark area away from the copper-aluminum dividing line and the boundary line of the copper area away from the copper-aluminum dividing line satisfies 3mm≤Y≤30mm.

6. The copper-aluminum composite connecting sheet according to claim 4, characterized in that: When the copper area is ultrasonically welded to the negative electrode ear to form the connection weld mark area, the distance dimension Y along the first direction between the boundary line of the connection weld mark area away from the copper-aluminum dividing line and the boundary line of the copper area away from the copper-aluminum dividing line satisfies 2mm≤Y≤30mm.

7. The copper-aluminum composite connecting sheet according to claim 1, characterized in that: The distance dimension between the boundary line of the connection weld print area on either side along the second direction and the boundary line of the copper area adjacent thereto along the second direction is Z, and Z≥2mm.

8. The copper-aluminum composite connecting sheet according to claim 1, characterized in that: The volume of the copper-aluminum composite connecting sheet is V, the total volume of the copper area is V1, and 0.1≤V1 / V≤0.6 is satisfied.

9. The copper-aluminum composite connecting sheet according to claim 8, characterized in that: The copper-aluminum composite connecting sheet includes a plurality of copper regions connected to the aluminum region, the volume of each copper region is V2, and 0.3≤V2 / V1≤0.7 is satisfied.

10. A battery cover, characterized in that: The battery cover plate includes the copper-aluminum composite connecting sheet as described in any one of claims 1 to 9.

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