Secondary battery and electronic device

Abstract

The invention relates to a secondary battery and electronic equipment, the secondary battery comprises a first pole piece and a second pole piece, the first pole piece comprises a first current collector, a first active layer and a first conductive piece, and the first current collector comprises a first polymer layer and first metal layers arranged on two opposite surfaces of the first polymer layer. The first current collector is provided with a first surface, the first surface comprises a first coating area and a first empty foil area which are connected, the first coating area is provided with a first active layer, and the first empty foil area is provided with a first conductive part. The first empty foil area is provided with a first hole, parts of the first conductive pieces extend into the first hole and abut against the two first metal layers, the number of the first pole pieces is multiple, and the multiple first conductive pieces are stacked and connected with the first pole lug. The first conductive part is provided with a second hole, and the second hole is located in the first hole when observed in the thickness direction of the first current collector. According to the secondary battery and the electronic equipment, the space of the tab area of the secondary battery can be saved.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] Secondary batteries, as the power source for electronic devices, are crucial for ensuring their normal operation. To improve the performance of secondary batteries, as shown in Figure 1, composite current collectors 1 are commonly used. Composite current collector 1 typically has a three-layer structure consisting of a metal layer 102, a polymer layer 101, and another metal layer 102. The current collector needs to be connected to the tab 3 for conductivity. To ensure conductivity between the two metal layers 102 of the composite current collector 1 and the tab 3, conductive elements 2 are usually roll-welded to the opposite surfaces of each composite current collector 1. Then, the multilayer conductive elements 2 are welded to the tab 3 (tab 3 transfer welding) to achieve conductivity between the two metal layers 102 of the composite current collector 1. 2 is connected to tab 3. If the position of tab 3 transfer welding overlaps with the position of roll welding, the polymer layer 101 of the multilayer composite current collector 1 will block the welding energy of tab 3 transfer welding, resulting in poor effect of tab 3 transfer welding. This can easily lead to cracking of tab 3, conductive part 2 and / or composite current collector 1, resulting in poor welding of tab 3 transfer welding. Therefore, the position of tab 3 transfer welding and the position of roll welding should not overlap. There needs to be a certain distance between them, but this will increase the space in the tab 3 area of ​​the secondary battery, causing the secondary battery to lose energy density. Summary of the Invention

[0003] The purpose of this application is to provide a secondary battery and electronic device that saves space in the tab area of ​​the secondary battery.

[0004] According to a first aspect of this application, a secondary battery is provided, comprising a first electrode and a second electrode stacked together, the first electrode and the second electrode having opposite polarities. The first electrode includes a first current collector, a first active layer, and a first conductive element. Along the thickness direction of the first current collector, the first current collector includes a first polymer layer and first metal layers disposed on opposite surfaces of the first polymer layer. The first current collector has a first surface, the first surface including a first coated area and a first empty foil area connected together. The first coated area is disposed of the first active layer, and the first empty foil area is disposed of the first conductive element. The first empty foil area is provided with a first hole, a portion of the first conductive element extending into the first hole and abutting against the two first metal layers. There are multiple first electrodes, and the first conductive elements of the multiple first electrodes are stacked and connected to a first electrode tab. The first conductive element is provided with a second hole, which is located within the first hole when viewed along the thickness direction of the first current collector.

[0005] In the above technical solution, along the thickness direction of the first current collector, the first current collector includes a first polymer layer and first metal layers disposed on opposite surfaces of the first polymer layer, which can improve the performance of the secondary battery. The first current collector has a first surface, which includes a first coated area and a first empty foil area connected together. The first coated area is provided with a first active layer, and the first empty foil area is provided with a first conductive element. The first empty foil area is provided with a first hole, and a portion of the first conductive element extends into the first hole and abuts against the two first metal layers, allowing the two first metal layers of the first current collector to conduct electricity with the first conductive element. There are multiple first electrodes, and multiple first conductive elements are stacked and connected to a first electrode tab. The two first metal layers of the first current collector can conduct electricity with the first electrode tab through the first conductive element. The first current collector of this application only needs to be provided with one first conductive element, and it is not necessary to provide conductive elements on both opposite surfaces of the first current collector. Therefore, the number of conductive elements can be reduced, thereby reducing the head space of the secondary battery and further improving the energy density of the secondary battery. Meanwhile, this application achieves self-riveting of the conductive element by having a portion of the first conductive element extend into the first hole and abut against the two first metal layers, thus improving the technical problems of complex processes and increased head thickness caused by adding riveting elements.

[0006] It should be noted that by increasing the width of the first tab, the contact area between the first tab and the first current collector can be increased, thereby expanding the current carrying capacity of the first tab. For secondary batteries with wound electrode structures, if the current carrying capacity is expanded by increasing the width of the first tab, the first tab will be thicker and harder after the width is increased, which is not conducive to the winding of the first electrode. However, this application can expand the current carrying capacity by increasing the width of the first conductive element. Since the thickness of the first conductive element in this application is less than the thickness of the first tab, the first conductive element will be less hard after the width is increased, and the impact on the winding of the first electrode will be smaller. Therefore, this application does not need to set an additional thin and wide conductive sheet between the first tab and the first current collector to expand the current carrying capacity.

[0007] It should be noted that the riveting method, which involves setting a riveting piece to penetrate the first conductive element and the first current collector, requires drilling holes in both elements before inserting the riveting piece into them. This process is relatively cumbersome, and the riveting piece fills the hole in the current collector. If the riveting piece does not have a hole for transmitting welding energy to the first electrode tab, the position of the first electrode tab cannot overlap with the position of the riveting piece, requiring a certain distance between them, which increases the space in the secondary battery electrode tab area. Furthermore, to secure the riveting piece to the first conductive element and the first current collector, one end of the riveting piece needs to protrude and abut against the surface of the first conductive element away from the first current collector, and the other end needs to protrude and abut against the surface of the first current collector away from the first conductive element. This increases the thickness of the riveting area between the first conductive element and the first current collector, potentially affecting the winding effect of the first electrode sheet. In this application, a portion of the first conductive element extends into the first hole of the first current collector, and the first conductive element has a second hole that overlaps with the first hole. This means that a portion of the first conductive element is connected through the first current collector using a riveting device to form a self-riveting structure. This eliminates the need for additional riveting components to connect the first conductive element and the first current collector, and also eliminates the need for drilling the first current collector, simplifying the operation. Furthermore, the second hole allows for the transmission of welding energy during the first electrode tab transfer welding, enabling the first electrode tab transfer welding position to overlap with the second hole position, saving space in the secondary battery electrode tab area. The self-riveting structure of the first conductive element and the first current collector in this application does not easily increase the thickness, which is beneficial for the winding of the first electrode sheet.

[0008] It should be noted that the coated area is the area where the current collector has an active layer, while the empty foil area is the area where the current collector does not have an active layer.

[0009] In some preferred embodiments, the first conductive element includes a first segment and a second segment connected together. The first segment is disposed in the first empty foil area, and the first segment can increase the contact area between the first conductive element and the first metal layer near the first surface, thereby improving the energy transmission efficiency between the first conductive element and the first metal layer near the first surface. The second segment is located in the first hole and abuts against the two first metal layers, and the second segment can assist in the connection and conduction of the two first metal layers of the first current collector. The second hole includes a first opening in the first segment and a channel in the second segment, and the first opening and the channel can be used for the first electrode adapter welding to transmit welding energy.

[0010] In some preferred embodiments, the first current collector has a second surface opposite to the first surface, the first hole penetrates through the first and second surfaces, and the first conductive element further includes a third segment connected to the second segment. The third segment is disposed on the second surface, and the third segment can increase the contact area between the first conductive element and the first metal layer near the second surface, thereby improving the energy transmission efficiency between the first conductive element and the first metal layer near the second surface. The second hole also includes a second opening located in the third segment, which can further facilitate the transmission of welding energy for the first electrode adapter welding.

[0011] In some preferred embodiments, multiple first conductive elements are connected to the first tab by welding (first tab transfer welding) to form a first solder mark. When viewed along the thickness direction of the first current collector, the projection of the first solder mark overlaps with at least a portion of the second hole. The welding energy of the first tab transfer welding can be transmitted through the second hole, so that the welding energy of the first tab transfer welding can be transmitted to multiple first conductive elements and / or multiple first current collectors, which can ensure the effect of the first tab transfer welding. At the same time, there is no need for a certain distance between the first solder mark and the second hole, which can save space in the first tab area of ​​the secondary battery.

[0012] In some preferred embodiments, the area of ​​the second hole along the thickness direction of the first current collector is S1, 0.1 mm. 2 ≤S1≤4mm 2 S1≥0.1mm 2 This design facilitates the passage of the first conductive element through the second hole and its contact with the two first metal layers, resulting in better connection strength and quality between the first current collector and the first conductive element. This also improves the manufacturing yield of the secondary battery. S1≤4mm 2 This increases the number of second holes and reduces the possibility of overlapping and conflict between adjacent second holes, thus improving the connection strength and quality between the first current collector and the first conductive element, and ultimately increasing the manufacturing yield of the secondary battery. Therefore, 0.1mm 2 ≤S1≤4mm 2 This allows for better connection quality between the first current collector and the first conductive element, while also improving the manufacturing yield of the secondary battery.

[0013] In some preferred embodiments, there are multiple second holes. Along the thickness direction of the first current collector, the sum of the areas of all the second holes is S2, and the overlap area between the first conductive element and the first current collector is S3, where 20% ≤ S2 / S3 ≤ 50%. S2 / S3 ≥ 20% ensures a more stable connection between the first conductive element and the first current collector. S2 / S3 ≤ 50% reduces the possibility of multiple overlapping second holes causing mutual conflict, thus ensuring a more stable connection between the first conductive element and the first current collector. Therefore, 20% ≤ S2 / S3 ≤ 50% ensures a more stable connection between the first conductive element and the first current collector.

[0014] In some preferred embodiments, when viewed along the thickness direction of the first current collector, the second hole is rhomboid in shape, which can improve the connection quality between the first conductive element and the first current collector.

[0015] In some preferred embodiments, when viewed along the thickness direction of the first current collector, the shape of the second hole can be a circle, an ellipse, a rectangle, or other polygons.

[0016] In some preferred embodiments, the thickness of the first segment is H1, where 10μm ≤ H1 ≤ 20μm. H1 ≥ 10μm facilitates the insertion of a portion of the first conductive element into the first hole and abutting against the two first metal layers, resulting in better connection strength and connection quality between the first current collector and the first conductive element. This also improves the energy transfer performance of the first conductive element from the first current collector. H1 ≤ 20μm reduces the likelihood of the first conductive element increasing the thickness of the secondary battery, thus reducing the possibility of significant volumetric energy density loss in the secondary battery. Therefore, 10μm ≤ H1 ≤ 20μm ensures good connection quality between the first current collector and the first conductive element while minimizing the possibility of significant volumetric energy density loss in the secondary battery.

[0017] In some preferred embodiments, the first coated area and the first empty foil area are connected along a first direction, and along a second direction, the width of the first segment is W1, 10mm≤W1≤20mm; the first direction, the second direction, and the thickness direction of the first current collector are perpendicular to each other. W1≥10mm is beneficial to improving the current carrying capacity of the first conductive element and to facilitating the connection between the first conductive element and the first electrode tab. During the manufacturing process, the first electrode needs to be carried along the second direction (e.g., coating and cold pressing processes), and W1≤20mm helps reduce the possibility of the first conductive element folding during the carrying process, thereby improving the carrying effect of the first electrode.

[0018] In some preferred embodiments, the thickness of the first current collector is H2, where 5μm≤H2≤20μm. This ensures the strength of the first current collector while reducing the possibility of the secondary battery losing a significant amount of volumetric energy density.

[0019] In some preferred embodiments, the thickness of the first metal layer is H3, where 0.5μm≤H3≤3μm. This ensures the strength and electrical connection of the first metal layer while reducing the possibility of the secondary battery losing a significant amount of volumetric energy density.

[0020] In some preferred embodiments, the first electrode is a positive electrode, the first conductive element is an aluminum foil, and the first metal layer is an aluminum layer. The first electrode is a positive electrode, meaning the current collector for the positive electrode uses a composite current collector. Compared to using a composite current collector for the negative electrode, this has advantages such as cost savings and ease of fabrication.

[0021] In some preferred embodiments, the second electrode includes a second current collector, a second active layer, and a second conductive element. Along the thickness direction of the second current collector, the second current collector includes a second polymer layer and second metal layers disposed on opposite surfaces of the second polymer layer, which can improve the performance of the secondary battery. The second current collector has a third surface, which includes a connected second coating area and a second empty foil area. The second coating area is provided with the second active layer, and the second empty foil area is provided with the second conductive element. The second empty foil area is provided with a third hole, and a portion of the second conductive element extends into the third hole and abuts against the two second metal layers, allowing the two second metal layers of the second current collector to conduct electricity with the second conductive element. Multiple second electrodes are available, and the second conductive elements of the multiple second electrodes are stacked and connected to second tabs. The two second metal layers of the second current collector can conduct electricity with the second tabs through the second conductive elements. The second conductive element has a fourth hole. Viewed along the thickness direction of the second current collector, the fourth hole is located inside the third hole. The fourth hole is a through hole, allowing it to pass through both the second conductive element and the second current collector. When the second conductive element is welded to the second tab (second tab transfer welding), and the position of the second tab transfer welding overlaps with the position of the fourth hole, the welding energy of the second tab transfer welding can be transmitted through the fourth hole. This can improve the problem of the second polymer layer of the multilayer second current collector blocking the welding energy of the second tab transfer welding, thus ensuring the effectiveness of the second tab transfer welding. Therefore, the position of the second tab transfer welding can overlap with the position of the fourth hole, and there is no need for a certain distance between them. This can save space in the second tab area of ​​the secondary battery and improve the energy density of the secondary battery.

[0022] Secondly, this application also proposes an electronic device including a secondary battery as described in any of the embodiments of the first aspect above.

[0023] In this application, only one first conductive element needs to be provided on one surface of the first current collector, eliminating the need to provide conductive elements on both opposite surfaces. This reduces the number of conductive elements, thereby reducing the thickness of the secondary battery and further improving its energy density. Furthermore, this application achieves self-rivetizing of the conductive element by having a portion of the first conductive element extend into the first hole and abut against the two first metal layers, thus overcoming the technical problems of increased process complexity and head thickness caused by adding riveting elements.

[0024] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0025] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the dimensions in the drawings do not constitute a limitation on scale.

[0026] Figure 1 is a schematic diagram of the connection between the composite current collector and the electrode tab in the prior art; Figure 2 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application; Figure 3 is a schematic diagram of the structure of an electrode assembly according to some embodiments of this application; Figure 4 is a schematic diagram of the connection between the first electrode and the first electrode tab when the first solder mark does not overlap with the second hole according to some embodiments of this application; Figure 5 is a schematic diagram of the connection between the first electrode and the first electrode tab when the first solder mark overlaps with the second hole according to some embodiments of this application; Figure 6 is a schematic diagram of the structure of the first current collector with the first hole according to some embodiments of this application; Figure 7 is a schematic diagram of the structure of the first current collector and the first conductive element according to some embodiments of this application; Figure 8 is an unfolded schematic diagram of the first electrode and the first electrode tab according to some embodiments of this application; Figure 9 is a schematic diagram of the structure of the electrode assembly according to some embodiments of this application; Figure 10 is a schematic diagram of the structure of the second current collector with the third hole according to some embodiments of this application.

[0027] Explanation of reference numerals in the attached drawings: 1. Composite current collector; 101. Polymer layer; 102. Metal layer; 2. Conductive component; 3. Electrode tab; 100. Secondary battery; 10. Housing; 20. Electrode assembly; 21. First electrode; 211. First current collector; 2111. First polymer layer; 2112. First metal layer; 2113. First pore; 212. First active layer; 213. First surface; 2131. First coating area; 2132. First empty foil area; 214. Second surface; 22. Second electrode; 221. Second current collector; 2211. Second polymer layer; 2212. Second metal layer; 2213. 222, Third hole; 223, Second active layer; 223, Third surface; 2231, Second coating area; 2232, Second empty foil area; 23, Separator; 24, First conductive element; 241, Second hole; 2411, First opening; 2412, Channel; 2413, Second opening; 242, First segment; 243, Second segment; 244, Third segment; 25, Second conductive element; 251, Fourth hole; 31, First tab; 311, First solder mark; 32, Second tab; 321, Second solder mark; X, Thickness direction of the first current collector; Y, Thickness direction of the second current collector; Z, First direction; M, Second direction. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0029] In this application, the reference to "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.

[0030] 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.

[0031] 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.

[0032] The term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components can exist in a state that is approximately perpendicular. For example, in numerical terms, perpendicularity can refer to the angle between two straight lines within the range of 90 ± 10°, the dihedral angle between two planes within the range of 90 ± 10°, or the angle between a straight line and a plane within the range of 90 ± 10°. The two components described as "perpendicular" do not have to be absolutely straight lines or planes; they can be approximately straight lines or planes. From a macroscopic perspective, if the overall direction of extension is straight or plane, the component can be considered a "straight line" or "plane".

[0033] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0034] In a first aspect, embodiments of this application provide a secondary battery 100. Referring to FIG2, the secondary battery 100 includes a housing 10, an electrode assembly 20, the housing 10 can accommodate the electrode assembly 20 and an electrolyte (not shown in the figure), and the electrolyte wets the electrode assembly 20 inside the housing 10.

[0035] In some embodiments, referring to Figures 3 and 4, the electrode assembly 20 includes a first electrode 21 and a second electrode 22 stacked together. The first electrode 21 and the second electrode 22 have opposite polarities and are wound together. A separator 23 is disposed between the first electrode 21 and the second electrode 22. The first electrode 21 includes a first current collector 211 and a first active layer 212. Along the thickness direction X of the first current collector, the first current collector 211 includes a first polymer layer 2111 and a first metal layer 2112 disposed on opposite surfaces of the first polymer layer 2111, which can improve the performance of the secondary battery 100. The current collector needs to be connected to the tab for conduction. To make the two first metal layers 2112 of the first current collector 211 conduct with the first tab 31, conductive elements are usually rolled-welded to the opposite two surfaces of each first current collector 211, and then the multi-layer conductive elements are welded to the first tab 31 (first tab 31 transfer welding) to achieve conduction between the two first metal layers 2112 of the first current collector 211 and the first tab 31. If the position of the first tab 31 transfer welding overlaps with the position of the roll welding, the first polymer layer 2111 of the multi-layer first current collector 211 will block the welding energy of the first tab 31 transfer welding, resulting in a poor effect of the first tab 31 transfer welding. This can easily lead to cracking of the first tab 31, the conductive elements and / or the first current collector 211, resulting in a poor weld of the first tab 31 transfer welding. Therefore, the position of the first tab 31 transfer welding cannot overlap with the position of the roll welding. The two need to be a certain distance apart, but this will increase the space of the first tab 31 area of ​​the secondary battery 100, causing the secondary battery 100 to lose energy density. On the other hand, in the prior art, conductive elements are respectively set on both sides of the first current collector 211, which increases the thickness of this area. In the subsequent transfer process, the superposition of multiple conductive elements will cause the head space of the secondary battery 100 to increase.

[0036] In other existing technologies, the connection between the conductive component and the current collector is achieved by adding a riveting component. This approach increases the difficulty of the process, and the independently added riveting component also increases the head space.

[0037] To solve the above problems, please refer to Figures 4 to 7. In this application, the first electrode 21 further includes a first conductive element 24. The first current collector 211 has a first surface 213, which includes a first coated area 2131 and a first empty foil area 2132 connected together. The first coated area 2131 is provided with a first active layer 212, and the first empty foil area 2132 is provided with the first conductive element 24. The first empty foil area 2132 is provided with a first hole 2113. A portion of the first conductive element 24 extends into the first hole 2113 and abuts against the two first metal layers 2112, allowing the two first metal layers 2112 of the first current collector 211 to conduct electricity with the first conductive element 24. There are multiple first electrodes 21, and the first conductive elements 24 of the multiple first electrodes 21 are stacked and connected to the first tab 31. The two first metal layers 2112 of the first current collector 211 can conduct electricity with the first tab 31 through the first conductive element 24. The first current collector 211 of this application only needs to have the first conductive element 24 on one surface, and it is not necessary to have conductive elements on both opposite surfaces of the first current collector 211. Therefore, the number of conductive elements can be reduced, thereby reducing the head space of the secondary battery 100 and further improving the energy density of the secondary battery 100.

[0038] It should be noted that by increasing the width of the first tab 31, the contact area between the first tab 31 and the first current collector 211 can be increased, thereby expanding the current carrying capacity of the first tab 31. For a secondary battery 100 with a wound electrode structure, if the current carrying capacity is expanded by increasing the width of the first tab 31, the first tab 31 is relatively thick, and the hardness of the first tab 31 after the width is increased, which is not conducive to the winding of the first electrode 21. However, this application can expand the current carrying capacity by increasing the width of the first conductive element 24. Since the thickness of the first conductive element 24 in this application is less than the thickness of the first tab 31, the hardness of the first conductive element 24 after the width is increased is smaller, and the impact on the winding of the first electrode 21 is smaller. Therefore, this application does not need to set an additional thin and wide conductive sheet between the first tab 31 and the first current collector 211 to expand the current carrying capacity.

[0039] It should be noted that the riveting method, which involves setting a riveting piece to pass through the first conductive element 24 and the first current collector 211, requires drilling holes in the first conductive element 24 and the first current collector 211 before inserting the riveting piece into these holes. This operation is rather cumbersome, and the riveting piece will fill the hole in the first current collector 211. If the riveting piece does not have a hole for the first tab 31 to transfer welding energy, the position of the first tab 31 cannot overlap with the position of the riveting piece, and the two need to be a certain distance apart, which will increase the space in the tab area of ​​the secondary battery 100. In addition, in order to secure the riveting to the first conductive element 24 and the first current collector 211, one end of the riveting needs to protrude and abut against the surface of the first conductive element 24 away from the first current collector 211, and the other end of the riveting needs to protrude and abut against the surface of the first current collector 211 away from the first conductive element 24. This will increase the thickness of the riveting area of ​​the first conductive element 24 and the first current collector 211, which may affect the winding effect of the first electrode 21. In this application, a portion of the first conductive element 24 extends into the first hole 2113 of the first current collector 211, and the first conductive element 24 is provided with a second hole 241 that overlaps with the first hole 2113. This means that a portion of the first conductive element 24 is connected through the first current collector 211 using a riveting device to form a self-riveting structure. This eliminates the need for additional riveting components to connect the first conductive element 24 and the first current collector 211, and eliminates the need for drilling the first current collector 211, simplifying the operation. Furthermore, the second hole 241 allows for the transfer of welding energy to the first electrode tab 31 during welding, enabling the welding position of the first electrode tab 31 to overlap with the position of the second hole 241, saving space in the electrode tab area of ​​the secondary battery 100. The self-riveting structure of the first conductive element 24 and the first current collector 211 in this application does not easily increase the thickness, which is beneficial for the winding of the first electrode sheet 21.

[0040] It should be noted that the coated area is the area where the current collector has an active layer, while the empty foil area is the area where the current collector does not have an active layer.

[0041] In some embodiments, the first conductive element 24 includes a first segment 242 and a second segment 243 connected together. The first segment 242 is disposed in the first empty foil area 2132. The first segment 242 can increase the contact area between the first conductive element 24 and the first metal layer 2112 near the first surface 213, thereby improving the energy transmission efficiency between the first conductive element 24 and the first metal layer 2112 near the first surface 213. The second segment 243 is located in the first hole 2113 and abuts against the two first metal layers 2112. The second segment 243 can assist in the connection and conduction of the two first metal layers 2112 of the first current collector 211. The second hole 241 includes a first opening 2411 located in the first segment 242 and a channel 2412 located in the second segment 243. The first opening 2411 and the channel 2412 can be used for the first electrode 31 to transfer welding energy.

[0042] In some embodiments, the first current collector 211 has a second surface 214 opposite to the first surface 213, and a first hole 2113 penetrates through the first surface 213 and the second surface 214. The first conductive element 24 further includes a third segment 244 connected to the second segment 243, the third segment 244 being disposed on the second surface 214. The third segment 244 can increase the contact area between the first conductive element 24 and the first metal layer 2112 near the second surface 214, thereby improving the energy transmission efficiency between the first conductive element 24 and the first metal layer 2112 near the second surface 214. The second hole 241 also includes a second opening 2413 located in the third segment 244, the second opening 2413 being further used for the first electrode 31 to transfer welding energy. When the first conductive element 24 is welded to the first tab 31 (first tab 31 transfer welding), and the position of the first tab 31 transfer welding overlaps with the position of the second hole 241, the welding energy of the first tab 31 transfer welding can be transmitted through the second hole 241. This can improve the problem that the first polymer layer 2111 of the multilayer first current collector 211 blocks the welding energy of the first tab 31 transfer welding, and can ensure the effect of the first tab 31 transfer welding. Therefore, the position of the first tab 31 transfer welding can overlap with the position of the second hole 241, and the two do not need to be a certain distance apart. This can save space in the area of ​​the first tab 31 of the secondary battery 100 and improve the energy density of the secondary battery 100.

[0043] In some embodiments, the thickness of the first segment 242 is H1, where 10μm ≤ H1 ≤ 20μm. H1 ≥ 10μm facilitates the insertion of a portion of the first conductive element 24 into the first hole 2113 and its contact with the two first metal layers 2112. This allows for better connection strength between the first current collector 211 and the first conductive element 24, resulting in better connection quality and improved energy transfer performance of the first conductive element 24. H1 ≤ 20μm reduces the likelihood of the first conductive element 24 increasing the thickness of the secondary battery 100, thus reducing the possibility of the secondary battery 100 losing significant volumetric energy density. Therefore, 10μm ≤ H1 ≤ 20μm ensures good connection quality between the first current collector 211 and the first conductive element 24, while also reducing the possibility of the secondary battery 100 losing significant volumetric energy density.

[0044] In some embodiments, the thickness of the first current collector 211 is H2, where 5μm≤H2≤20μm. This ensures the strength of the first current collector 211 and reduces the possibility of the secondary battery 100 losing a large volumetric energy density.

[0045] In some embodiments, the thickness of the first metal layer 2112 is H3, 0.5μm≤H3≤3μm, which can ensure the strength and electrical connection effect of the first metal layer 2112, while reducing the possibility of the secondary battery 100 losing a large volumetric energy density.

[0046] In some embodiments, referring to Figures 5 and 8, the first coating area 2131 and the first empty foil area 2132 are connected along the first direction Z and along the second direction M. The width of the first segment 242 is W1, 10mm≤W1≤20mm. The first direction Z, the second direction M, and the thickness direction of the first current collector 211 are perpendicular to each other. W1≥10mm is beneficial to improving the current carrying capacity of the first conductive element 24 and to facilitating the connection between the first conductive element 24 and the first electrode tab 31. During the manufacturing process, the first electrode 21 needs to be carried along the second direction M (e.g., coating and cold pressing processes). W1≤20mm is beneficial to reducing the possibility of the first conductive element 24 folding during the carrying process, thereby improving the carrying effect of the first electrode 21.

[0047] In some embodiments, referring to Figures 5 and 8, multiple first conductive elements 24 are connected to the first tab 31 by welding (first tab 31 transfer welding) to form a first solder mark 311. When viewed along the thickness direction X of the first current collector 211, the projection of the first solder mark 311 overlaps with at least a portion of the second hole 241. The welding energy of the first tab 31 transfer welding can be transmitted through the second hole 241, so that the welding energy of the first tab 31 transfer welding can be transmitted to multiple first conductive elements 24 and / or multiple first current collectors 211, which can ensure the effect of the first tab 31 transfer welding. At the same time, there is no need for a certain distance between the first solder mark 311 and the second hole 241, which can save space in the first tab 31 area of ​​the secondary battery 100.

[0048] In some embodiments, along the thickness direction X of the first current collector 211, the area of ​​the second hole 241 is S1, 0.1 mm. 2 ≤S1≤4mm 2 S1≥0.1mm 2 This allows a portion of the first conductive element 24 to pass through the second hole 241 and abut against the two first metal layers 2112, resulting in better connection tension between the first current collector 211 and the first conductive element 24, thus improving the connection quality and manufacturing yield of the secondary battery 100. S1≤4mm 2 This increases the number of second holes 241 and reduces the possibility of overlapping and conflict between adjacent second holes 241, thereby improving the connection strength between the first current collector 211 and the first conductive element 24, resulting in better connection quality and improving the manufacturing yield of the secondary battery 100. Therefore, 0.1mm 2 ≤S1≤4mm 2 This allows the first current collector 211 and the first conductive element 24 to have a better connection quality, and at the same time improves the manufacturing yield of the secondary battery 100.

[0049] In some embodiments, there are multiple second holes 241. Along the thickness direction X of the first current collector 211, the sum of the areas of all second holes 241 is S2, and the overlap area between the first conductive element 24 and the first current collector 211 is S3, where 20% ≤ S2 / S3 ≤ 50%. S2 / S3 ≥ 20% ensures a more stable connection between the first conductive element 24 and the first current collector 211. S2 / S3 ≤ 50% reduces the possibility of multiple overlapping second holes 241 causing mutual conflict, thus ensuring a more stable connection between the first conductive element 24 and the first current collector 211. Therefore, 20% ≤ S2 / S3 ≤ 50% ensures a more stable connection between the first conductive element 24 and the first current collector 211.

[0050] In some embodiments, when viewed along the thickness direction X of the first current collector 211, the second hole 241 is rhomboid in shape, which can improve the connection quality between the first conductive element 24 and the first current collector 211.

[0051] In some embodiments, when viewed along the thickness direction X of the first current collector 211, the shape of the second hole 241 can be a circle, an ellipse, a rectangle, or other polygons.

[0052] In some embodiments, the first electrode 21 is a positive electrode, the first conductive element 24 is an aluminum foil, and the first metal layer 2112 is an aluminum layer. The first electrode 21 is a positive electrode, that is, the current collector of the positive electrode adopts a composite current collector. Compared with the current collector of the negative electrode adopting a composite current collector, it has advantages such as cost saving and ease of preparation.

[0053] In some embodiments, referring to Figures 9 and 10, the second electrode 22 includes a second current collector 221, a second active layer 222, and a second conductive element 25. Along the thickness direction of the second current collector 221, the second current collector 221 includes a second polymer layer 2211 and second metal layers 2212 disposed on opposite surfaces of the second polymer layer 2211, which can improve the performance of the secondary battery 100. The second current collector 221 has a third surface 223, which includes a connected second coating area 2231 and a second empty foil area 2232. The second coating area 2231 is provided with the second active layer 222, and the second empty foil area 2232 is provided with the second conductive element 25. The second empty foil area 2232 is provided with a third hole 2213, and a portion of the second conductive element 25 extends into the third hole 2213 and abuts against the two second metal layers 2212, which allows the two second metal layers 2212 of the second current collector 221 to conduct with the second conductive element 25. There are multiple second electrode plates 22, and the second conductive elements 25 of the multiple second electrode plates 22 are stacked and connected to the second electrode tab 32. The two second metal layers 2212 of the second current collector 221 can be connected to the second electrode tab 32 through the second conductive elements 25. The second conductive element 25 is provided with a fourth hole 251. When viewed along the thickness direction Y of the second current collector 221, the fourth hole 251 is located inside the third hole 2213. The fourth hole 251 is a through hole, allowing the fourth hole 251 to pass through the second conductive element 25 and the second current collector 221. When the second conductive element 25 is welded to the second tab 32 (second tab 32 transfer welding), and the position of the second tab 32 transfer welding overlaps with the position of the fourth hole 251, the welding energy of the second tab 32 transfer welding can be transmitted through the fourth hole 251. This can improve the problem of the second polymer layer 2211 of the multilayer second current collector 221 blocking the welding energy of the second tab 32 transfer welding, and can ensure the effect of the second tab 32 transfer welding. Therefore, the position of the second tab 32 transfer welding can overlap with the position of the fourth hole 251, and there is no need for a certain distance between them. This can save space in the second tab 32 area of ​​the secondary battery 100 and improve the energy density of the secondary battery 100.

[0054] In some embodiments, a plurality of second conductive elements 25 are connected to the second tab 32 by welding (second tab 32 adapter welding) to form a second solder mark 321.

[0055] A second aspect of this application also provides an electronic device including a secondary battery 100 as described in any embodiment of the first aspect above. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, electronic devices include, but are not limited to, Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0056] Testing Section: 1. Tensile test of the connection between the first current collector and the first conductive element: Disassemble the secondary battery, remove the first tab, remove the first active layer of the first electrode, and obtain the connected first current collector and first conductive element. Use a tensile testing tool to prepare a test sample 100mm long and 15mm wide. Fix the portion of the first current collector and the first conductive element extending beyond the first current collector onto the test fixture of the high-speed rail tensile testing machine. The tensile speed is 50±0.5mm / min, and the tensile spacing is 50mm. The maximum tensile force after the first conductive element and the first current collector separate is taken as the connection tensile force.

[0057] 2. Volumetric energy density test of secondary batteries: Volumetric energy density of secondary batteries = battery capacity × discharge plateau / volume, with the basic unit being Wh / L.

[0058] 3. Manufacturing yield test of secondary batteries: Process yield (individual process) = Output quantity of this process / Output quantity of the previous process × 100% Total process yield = Yield of process 1 × Yield of process 2 × … × Yield of process X.

[0059] 4. Tensile test of the connection between the first electrode and the first tab: Disassemble the secondary battery and obtain the connected first electrode and the first tab. Use a special tensile cutting tool to make a test sample 100mm long and 15mm wide. Fix the first electrode and the portion of the first tab extending beyond the first electrode onto the test fixture of the high-speed rail tensile testing machine. The tensile speed is 50±0.5mm / min, and the tensile spacing is 50mm. The maximum tensile force after the first conductive element and the first current collector separate is taken as the connection tensile force.

[0060] Example 1 <Preparation of the first electrode>: The first electrode is a positive electrode. The positive electrode active materials lithium cobalt oxide (LiCoO2), carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt% and stirred evenly.

[0061] Polyethylene terephthalate (PET) is selected as the first polymer layer, with a thickness of 6 μm. A first metal layer of aluminum with a thickness of 1 μm is disposed on both surfaces of the first polymer layer to obtain a first current collector. The first current collector has a first surface, which includes a first coated area and a first empty foil area connected together. The aforementioned slurry is coated onto the surface of the first coated area and dried to obtain a first active layer. A first conductive element, which is aluminum foil, is disposed on the two opposite surfaces of the first empty foil area. The first empty foil area has a first hole, and the first conductive element has a second hole. Along the thickness direction of the first current collector, the second hole overlaps with the first hole. A portion of the first conductive element extends into the first hole and abuts against the two first metal layers. The first conductive element includes a first segment and a second segment connected together. The first segment is disposed in the first empty foil area, with a thickness H1 of 15 μm and a width W1 of 15 mm along a second direction. The second segment is located within the first hole and abuts against the two first metal layers. The second hole includes a first opening in the first segment and a channel in the second segment. The first current collector has a second surface opposite to the first surface, and a first hole penetrates both the first and second surfaces. The first conductive element also includes a third segment connected to the second segment, the third segment being disposed on the second surface, and the second hole further includes a second opening located in the third segment. Along the thickness direction of the first current collector, the area S1 of the second hole is 1 mm². 2 There are multiple second holes. Along the thickness direction of the first current collector, the sum of the areas of all the second holes is S2, and the overlap area between the first conductive element and the first current collector is S3. S2 / S3 = 30%.

[0062] <Preparation of negative electrode sheet>: The second electrode sheet is the negative electrode sheet. Graphite is used as the negative electrode active material. The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR) and the thickener sodium carboxymethyl cellulose (CMC) are mixed in a weight ratio of 96:2:2. Deionized water is added as a solvent to prepare a slurry with a solid content of 70wt% and stirred evenly.

[0063] Copper foil is selected as the second current collector. The above-mentioned slurry is coated on the surface of the second current collector, leaving an empty foil area. The slurry is dried to obtain a second electrode with a second active layer coated on its surface.

[0064] <Preparation of the diaphragm>: A porous polyethylene membrane is used as the substrate layer. A ceramic layer containing alumina ceramic and PVDF binder is coated on one side of the substrate layer as the diaphragm (CCS). The mass percentage of alumina ceramic in the ceramic layer is 95%.

[0065] <Electrolyte Preparation>: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent, dissolved, and mixed evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0066] <Preparation of the Secondary Battery>: An electrode assembly is obtained by sequentially stacking and winding a first electrode, a separator, and a second electrode. Multiple first electrodes are stacked and connected to a first tab. These multiple first conductive elements are connected to the first tab by welding (first tab transfer welding), forming a first weld mark. When viewed along the thickness direction of the first current collector, the projection of the first weld mark overlaps with a second hole. The electrode assembly is placed in an aluminum-plastic film housing, with the first tab extending out of the housing. After drying, electrolyte is injected. The secondary battery is obtained through vacuum sealing, settling, formation, capacity testing, degassing, and edge trimming.

[0067] The relevant parameters in Examples 1 to 13 are shown in Table 1 below.

[0068] Examples 1 to 5 differ only in the area S1 of the second hole.

[0069] Examples 1 and 6 to 9 differ only in S2 / S3. Specifically, along the thickness direction of the first current collector, the sum of the areas of all the second holes is S2, and the overlap area between the first conductive element and the first current collector is S3.

[0070] The only difference between Example 1 and Examples 10 to 13 is the thickness H1 of the first segment.

[0071] Table 1

[0072] According to Table 1 above, and in conjunction with Examples 1 to 5, the area of ​​the second hole along the thickness direction of the first current collector is S1. S1 ≥ 0.1 mm 2 This design facilitates the passage of the first conductive element through the second hole and its contact with the two first metal layers, resulting in better connection strength and quality between the first current collector and the first conductive element. This also improves the manufacturing yield of the secondary battery. S1≤4mm 2 This increases the number of second holes and reduces the possibility of overlapping and conflict between adjacent second holes, thus improving the connection strength and quality between the first current collector and the first conductive element, and ultimately increasing the manufacturing yield of the secondary battery. Therefore, 0.1mm 2 ≤S1≤4mm 2This allows for better connection quality between the first current collector and the first conductive element, while also improving the manufacturing yield of the secondary battery.

[0073] Based on Examples 1 and 6 to 9, the sum of the areas of all second holes along the thickness direction of the first current collector is S2, and the overlap area between the first conductive element and the first current collector is S3. S2 / S3 ≥ 20% ensures a relatively stable connection between the first conductive element and the first current collector. S2 / S3 ≤ 50% reduces the possibility of multiple overlapping second holes causing mutual conflict, further ensuring a relatively stable connection between the first conductive element and the first current collector. Therefore, 20% ≤ S2 / S3 ≤ 50% ensures a relatively stable connection between the first conductive element and the first current collector.

[0074] Based on Examples 1 and 10 to 13, the thickness of the first segment is H1. H1 ≥ 10 μm facilitates the insertion of the first conductive element into the first hole and its contact with the two first metal layers. This results in better connection strength between the first current collector and the first conductive element, leading to better connection quality and improved energy transfer performance of the first conductive element. H1 ≤ 20 μm reduces the likelihood of the first conductive element increasing the thickness of the secondary battery, thus reducing the possibility of significant volumetric energy density loss in the secondary battery. Therefore, 10 μm ≤ H1 ≤ 20 μm ensures good connection quality between the first current collector and the first conductive element while minimizing the possibility of significant volumetric energy density loss in the secondary battery.

[0075] The relevant parameters in Examples 1 and 14 are shown in Table 2 below.

[0076] When viewed along the thickness direction of the first current collector, the projection of the first solder mark in Example 1 overlaps with the second hole, while the projection of the first solder mark in Example 14 does not overlap with the second hole.

[0077] Table 2

[0078] According to Table 2 above, and in conjunction with Examples 1 and 14, when viewed along the thickness direction of the first current collector, the projection of the first solder mark overlaps with the second hole. The welding energy of the first tab transfer welding can be transmitted through the second hole, so that the welding energy of the first tab transfer welding can be transmitted to multiple first conductive parts and / or multiple first current collectors, which can ensure the effect of the first tab transfer welding. Therefore, the connection pull between the first electrode and the first tab can be improved. At the same time, there is no need for a certain distance between the first solder mark and the second hole, which can save space in the first tab area of ​​the secondary battery, thus improving the volumetric energy density of the secondary battery.

[0079] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A secondary battery, comprising a stacked first electrode and a second electrode, the first electrode and the second electrode having opposite polarities, the first electrode comprising a first current collector, a first active layer, and a first conductive element, wherein along the thickness direction of the first current collector, the first current collector comprises a first polymer layer and a first metal layer disposed on opposite surfaces of the first polymer layer; the first current collector has a first surface, the first surface comprising a first coated area and a first empty foil area connected together, the first coated area being disposed of the first active layer, and the first empty foil area being disposed of the first conductive element; characterized in that, The first empty foil area is provided with a first hole, a portion of the first conductive element extends into the first hole and abuts against the two first metal layers, there are multiple first electrode sheets, the first conductive elements of the multiple first electrode sheets are stacked and connected to the first electrode tab; the first conductive element is provided with a second hole, and when viewed along the thickness direction of the first current collector, the second hole is located in the first hole.

2. The secondary battery according to claim 1, characterized in that, The first conductive element includes a first segment and a second segment connected together. The first segment is disposed in the first empty foil area, and the second segment is located in the first hole and abuts against the two first metal layers. The second hole includes a first opening located in the first segment and a channel located in the second segment.

3. The secondary battery according to claim 2, characterized in that, The first current collector has a second surface opposite to the first surface, the first hole penetrates the first surface and the second surface, the first conductive element further includes a third segment connected to the second segment, the third segment is disposed on the second surface, and the second hole further includes a second opening located in the third segment.

4. The secondary battery according to any one of claims 1-3, characterized in that, Multiple first conductive elements are connected to the first electrode by welding to form a first solder mark. When viewed along the thickness direction of the first current collector, the projection of the first solder mark overlaps with at least a portion of the second hole.

5. The secondary battery according to claim 1, characterized in that, Along the thickness direction of the first current collector, the area of ​​the second hole is S1, 0.1 mm. 2 ≤S1≤4mm 2 .

6. The secondary battery according to claim 5, characterized in that, There are multiple second holes. Along the thickness direction of the first current collector, the sum of the areas of all the second holes is S2, and the overlap area between the first conductive element and the first current collector is S3, where 20% ≤ S2 / S3 ≤ 50%.

7. The secondary battery according to claim 1, characterized in that, Viewed along the thickness direction of the first current collector, the second hole has a rhomboid shape.

8. The secondary battery according to claim 2, characterized in that, The thickness of the first segment is H1, where 10μm≤H1≤20μm.

9. The secondary battery according to claim 2, characterized in that, The first coated area and the first empty foil area are connected along the first direction and along the second direction. The width of the first segment is W1, 10mm≤W1≤20mm. The first direction, the second direction and the thickness direction of the first current collector are perpendicular to each other.

10. The secondary battery according to claim 1, characterized in that, The thickness of the first current collector is H2, where 5μm≤H2≤20μm.

11. The secondary battery according to claim 10, characterized in that, The thickness of the first metal layer is H3, where 0.5μm≤H3≤3μm.

12. The secondary battery according to claim 1, characterized in that, The first electrode is a positive electrode, the first conductive element is an aluminum foil, and the first metal layer is an aluminum layer.

13. The secondary battery according to any one of claims 1 to 3, characterized in that, The second electrode includes a second current collector, a second active layer, and a second conductive element. Along the thickness direction of the second current collector, the second current collector includes a second polymer layer and a second metal layer disposed on opposite surfaces of the second polymer layer. The second current collector has a third surface, which includes a connected second coating area and a second empty foil area. The second coating area is provided with the second active layer, and the second empty foil area is provided with the second conductive element. The second empty foil area is provided with a third hole, and a portion of the second conductive element extends into the third hole and abuts against the two second metal layers. There are multiple second electrodes, and the second conductive elements of the multiple second electrodes are stacked and connected to a second electrode tab. The second conductive element is provided with a fourth hole. Viewed along the thickness direction of the second current collector, the fourth hole is located inside the third hole, and the fourth hole is a through hole.

14. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 13.

Images