Electrochemical device and electric equipment

Abstract

The embodiment of the present application provides an electrochemical device and an electric equipment. The electrochemical device comprises: a pole piece, the pole piece comprises a current collector, an active material layer and a tab connecting piece, in a pole piece unfolded state, the current collector comprises a first part and a second part along the width direction of the pole piece, the active material layer is arranged on the surface of the first part, the tab connecting piece overlaps the surface of the second part to form an overlapping area, the tab connecting piece is welded on the surface of the second part to form an electrical connection with the second part, along the length direction of the pole piece, the ratio of the welding mark area to the welding area is greater than or equal to 20%, and the ratio of the welding area length to the overlapping area length is greater than or equal to 60%.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and more particularly to an electrochemical device and electrical equipment. Background Technology

[0002] With the continuous development of technology, electrochemical devices (including but not limited to lithium-ion batteries, sodium-ion batteries, etc.) have been widely used, providing convenience for people to use tablet computers, mobile phones, electric vehicles, energy storage devices, and other devices.

[0003] In one type of electrochemical device in related technologies, it consists of a cathode electrode, an anode electrode, and a separating membrane disposed between the two. During its fabrication, tabs need to be electrically connected to the blank areas at the edges of the current collectors on the cathode and anode electrodes. Improving the fabrication yield is a technical problem that needs to be solved for this type of electrochemical device. Summary of the Invention

[0004] In view of this, embodiments of this application provide an electrochemical device and an electrical appliance to at least partially solve the above-mentioned problems.

[0005] According to a first aspect of the embodiments of this application, an electrochemical device is provided, comprising: an electrode, the electrode including a current collector, an active material layer, and a tab connecting piece. In the unfolded state of the electrode, the current collector includes a first part and a second part along the width direction of the electrode. The active material layer is disposed on the surface of the first part, and the second part is an empty foil area without an active material layer. The tab connecting piece overlaps with the surface of the second part to form an overlapping area. The tab connecting piece is welded to the surface of the second part to form an electrical connection with the second part. Along the length direction of the electrode, the ratio of the solder area to the solder area is greater than or equal to 20%, and the ratio of the length of the solder area to the length of the overlapping area is greater than or equal to 60%.

[0006] In this embodiment, the electrode includes a cathode electrode and an anode electrode. Since the cathode tab connecting piece of the electrochemical device is welded to the surface of the second part of the cathode current collector (i.e., the edge empty foil area on the cathode current collector), and the anode tab connecting piece of the anode electrode is welded to the surface of the second part of the anode current collector (i.e., the edge empty foil area on the anode current collector), when the cathode tab is led out from the cathode current collector in this application, it is no longer necessary to directly connect the cathode tab to the second part of the cathode current collector. Instead, it can be electrically connected to the cathode tab through the cathode tab connecting piece welded to the second part of the cathode current collector. When the anode tab is led out from the anode current collector in the application, it is no longer necessary to directly connect the anode tab to the second part of the anode current collector. Instead, it can be electrically connected to the anode tab through an anode tab connecting piece welded to the second part of the anode current collector. Based on this, when preparing the cathode electrode of the electrochemical device in this application, the cathode electrode is less likely to wrinkle when cold-pressed. Similarly, when preparing the anode electrode of the electrochemical device in this application, the anode electrode is less likely to wrinkle when cold-pressed. Therefore, by using such cathode and anode electrodes to manufacture the electrochemical device, the preparation yield of the electrochemical device can be effectively improved.

[0007] Furthermore, in the electrochemical device of this application, the ratio of the solder area to the welding area along the length of the electrode sheet is greater than or equal to 20%, which can ensure that the second part can form a stable weld with the tab connecting piece. Moreover, the ratio of the welding area length to the overlap area length is greater than or equal to 60%, which can ensure that the solder is evenly distributed in the welding area and the overlap area, avoiding the concentration of solder leading to excessive local strength or insufficient strength in other parts, and avoiding the processing difficulties caused by this.

[0008] Optionally, the electrode is a cathode electrode. The first part includes a first sub-part and a second sub-part connected to each other. The second sub-part is connected to the second part. An active material layer is disposed on the first sub-part, and an insulating layer is disposed on the second sub-part. Along the width direction of the electrode, the second part includes a first side close to the first sub-part and a second side away from the first sub-part. The tab connecting piece includes a first side close to the first sub-part and a second side away from the first sub-part. There is a gap between the tab connecting piece and the first sub-part, and the second side of the second part is located between the first side and the second side of the tab connecting piece.

[0009] In related technologies, one method to prevent wrinkling of the cathode electrode during cold pressing is to first cold press the cathode electrode with the cathode active material layer and insulating layer already in place. Before cold pressing, the edge foil area of ​​the cathode current collector is stretched to make the deformation degree of the edge foil area of ​​the cathode current collector and the insulating layer more consistent, thereby preventing wrinkling of the cathode electrode during subsequent cold pressing. However, while this can alleviate the wrinkling problem of the cathode electrode during cold pressing, it increases the cold pressing tension of the cathode electrode, making it prone to breakage during the cold pressing process and reducing the fabrication yield of the electrochemical device. In this embodiment, when the cathode tab is led out from the second part of the cathode current collector (i.e., the edge empty foil area of ​​the cathode current collector), it is no longer necessary to directly electrically connect the cathode tab to the second part of the cathode current collector. Instead, it can be electrically connected to the cathode tab through a cathode tab connecting piece welded to the second part of the cathode current collector. This eliminates the need to stretch the second part of the cathode current collector (i.e., the edge empty foil area of ​​the cathode current collector) before cold pressing the cathode electrode in the electrochemical device. This also improves the problem of wrinkling of the cathode electrode during subsequent cold pressing. Furthermore, since it is not necessary to stretch the second part of the cathode current collector (i.e., the edge empty foil area of ​​the cathode current collector), the cold pressing tension of the cathode electrode is reduced, thereby improving the problem of the cathode electrode easily breaking during the cold pressing process. Therefore, the fabrication yield of the electrochemical device can be improved. In addition, the insulating layer of this application can insulate and isolate the second sub-part and the anode electrode, effectively preventing short circuits between the cathode electrode and the anode electrode.

[0010] Optionally, along the width direction of the electrode sheet, the width d1 of the electrode tab connecting piece satisfies: 3mm≤d1≤25mm.

[0011] Taking the cathode electrode as an example, if the width d1 of the cathode tab connecting piece is too small, it is difficult to weld the cathode tab connecting piece to the second part of the cathode current collector during the fabrication of the electrochemical device. Conversely, if the width d1 of the cathode tab connecting piece is too large, the edges of the cathode tab connecting piece are prone to collapse during the fabrication of the cathode electrode, and accidental breakage of the cathode tab connecting piece is also possible. In this embodiment, the width of the cathode tab connecting piece satisfies the aforementioned value range (i.e., 3mm ≤ d1 ≤ 25mm), which effectively avoids both the disadvantages of an excessively small width and the disadvantages of an excessively large width, thus meeting the requirements of the electrochemical device and improving the fabrication yield of the electrochemical device.

[0012] Optionally, along the width direction of the electrode, the width d2 of the second part satisfies: 1mm≤d2≤20mm.

[0013] Taking the cathode electrode as an example, if the width of the second part of the cathode current collector is too small, it is difficult to guarantee the welding width during the fabrication of the electrochemical device, making it difficult to weld the cathode tab connecting piece to the second part of the cathode current collector. Conversely, if the width of the second part of the cathode current collector is too large, it is more prone to wrinkling after cold pressing during the cathode electrode fabrication process, easily increasing energy density loss and leading to increased costs. In this embodiment, the width of the second part of the cathode current collector satisfies the aforementioned value range, effectively avoiding both the drawbacks of an excessively small and excessively large width, thus meeting the requirements of the electrochemical device and improving the fabrication yield.

[0014] Optionally, along the width direction of the electrode, the width d3 of the insulating layer satisfies: 0.5mm≤d3≤5mm.

[0015] This embodiment uses an insulating layer with such a wide range of widths, which can effectively insulate and isolate the second sub-section of the cathode current collector from the anode electrode, preventing short circuits between the two, and meeting the usage requirements of the electrochemical device without adding extra costs.

[0016] Optionally, along the width direction of the electrode, the insulating layer includes a first side close to the first sub-part and a second side away from the first sub-part; if the first side of the electrode tab connecting piece is located on the insulating layer, the distance d4 between the first side of the electrode tab connecting piece and the second side of the insulating layer satisfies: 0mm≤d4≤8mm; or, if the first side of the electrode tab connecting piece is located on the second part, the distance d4 between the first side of the electrode tab connecting piece and the second side of the insulating layer satisfies: 0mm≤d4≤10mm.

[0017] Taking the cathode electrode as an example, when the first side of the cathode tab connecting piece is located on the insulating layer, it is equivalent to the first end of the cathode tab connecting piece extending beyond the first side of the second part of the cathode current collector in the opposite direction of the electrode width after the cathode tab connecting piece is welded to the second part of the cathode current collector. When the extension is too large (e.g., d4 > 8 mm), it can easily lead to an excessively thick electrochemical device. When the first side of the cathode tab connecting piece is located on the second part of the cathode current collector, and the distance between the first side of the cathode tab connecting piece and the second side of the insulating layer is too large (e.g., d4 > 10 mm), it is impossible to effectively solve the problem of folding after the second part of the cathode current collector is welded to the cathode tab connecting piece. In this embodiment, d4 satisfies the following value range, which can better avoid the disadvantage of the first end of the cathode tab connecting piece extending too far beyond the first side of the second part of the cathode current collector in the opposite direction of the electrode width, and can also better avoid the disadvantage of d4 being too large when the first side of the cathode tab connecting piece is located on the second part of the cathode current collector, thereby meeting the usage requirements of the electrochemical device and improving the preparation efficiency of the electrochemical device.

[0018] Optionally, the solder mark includes a first solder mark, which is formed when the second part is soldered to the tab connecting piece; along the width direction of the electrode piece, the first solder mark includes a first side close to the first sub-part and a second side away from the first sub-part; the second side of the first solder mark is located on the tab connecting piece, and there is a gap between the first solder mark and the first sub-part.

[0019] Taking the cathode electrode as an example, the second side of the first solder mark in this application is located on the cathode tab connecting piece, ensuring that the cathode tab connecting piece can form a stable solder connection with the second part of the cathode current collector.

[0020] Optionally, along the width direction of the electrode, the width d5 ​​of the first solder mark satisfies: 0.1mm≤d5≤10mm.

[0021] Taking the cathode electrode as an example, if the width d5 ​​of the first solder mark is too small (i.e., d5 < 0.1 mm), it is difficult to ensure that the welding pull force between the second part of the cathode current collector and the cathode tab connecting piece meets the requirements, resulting in the disadvantage of insufficient welding pull force. Conversely, if the width d5 ​​of the first solder mark is too large (i.e., d5 > 10 mm), welding becomes more difficult and additional costs are incurred. In this embodiment, the width d5 ​​of the first solder mark is within the aforementioned range (0.1 mm ≤ d5 ≤ 10 mm), which avoids both the disadvantages of an excessively small and excessively large width, thus meeting the requirements of the electrochemical device and improving the preparation yield of the electrochemical device.

[0022] Optionally, if the first side of the first solder mark is located on the second part, the distance d6 between the first side of the first solder mark and the first side of the electrode connecting piece satisfies: 0mm≤d6≤5mm; or, if the first side of the first solder mark is located on the electrode connecting piece, the distance d6 between the first side of the first solder mark and the first side of the electrode connecting piece satisfies: 0mm≤d6≤20mm.

[0023] Taking the cathode electrode as an example, when the first side of the first solder mark extends too far beyond the first side of the cathode tab connecting piece along the opposite direction of the electrode width (e.g., when the first side of the first solder mark is located on the second part of the cathode current collector, d6>5mm), there is a large portion without cathode active material. Therefore, the space ratio of the part that cannot provide energy is also large, resulting in serious energy density loss. This affects the subsequent electrical connection between the cathode tab and the cathode tab connecting piece (e.g., forming an electrical connection between the cathode tab and the cathode tab connecting piece by welding). In this process, the cathode tab connecting piece is also easily damaged, ultimately affecting the electrical performance of the electrochemical device. On the other hand, when the first side of the first solder mark extends too far beyond the first side of the cathode tab connecting piece along the width of the electrode width (e.g., when the first side of the first solder mark is located on the cathode tab connecting piece, d6>30mm), there is a situation where the unconstrained cathode tab connecting piece is too wide. This increases the process difficulty when preparing the cathode electrode and affects the preparation yield of the electrochemical device. By adopting such a range of values ​​for d6, this application can avoid the drawbacks that occur when the first side of the first solder mark extends too far beyond the first side of the cathode tab connecting piece in the opposite direction of the width of the electrode sheet, and also avoid the drawbacks that occur when the first side of the first solder mark extends too far beyond the first side of the cathode tab connecting piece in the width of the electrode sheet, thereby meeting the usage requirements of the electrochemical device and improving the preparation efficiency of the electrochemical device.

[0024] Optionally, if the first projection of the second side of the first solder mark on the tab connecting piece overlaps with the second projection of the second part on the tab connecting piece, then the distance d7 between the second side of the first solder mark and the second side of the second part satisfies: 0mm≤d7≤15mm; or, if the first projection of the second side of the first solder mark on the tab connecting piece does not overlap with the second projection of the second part on the tab connecting piece, then the distance d7 between the second side of the first solder mark and the second side of the second part satisfies: 0mm≤d7≤7mm.

[0025] Taking the cathode electrode as an example, when the first projection and the second projection overlap, the distance d7 between the second side of the first solder mark and the second side of the second part of the cathode current collector is too large (e.g., d7 > 15 mm when the first projection and the second projection overlap). That is, when the second side of the second part of the cathode current collector extends too far beyond the second side of the first solder mark along the width direction of the electrode, there is a situation where the second part of the cathode current collector in an unconstrained state is too wide. This increases the difficulty of the process in preparing the cathode electrode and affects the preparation yield of the electrochemical device. However, when the first projection and the second projection do not overlap... If the distance d7 between the second side of the first solder mark and the second side of the second part of the cathode current collector is too large (e.g., d7 > 7 mm when the first projection and the second projection do not overlap), that is, when the second side of the first solder mark extends too far beyond the second side of the second part of the cathode current collector along the width direction of the electrode, the energy density will be severely lost, affecting the subsequent electrical connection of the cathode tab and the cathode tab connecting piece (e.g., forming an electrical connection by welding the cathode tab and the cathode tab connecting piece). This process can also easily damage the cathode tab connecting piece, ultimately affecting the electrical performance of the manufactured electrochemical device. This application, by adopting such a range of d7 values, avoids both the drawbacks caused by the second side of the second part of the cathode current collector extending too far beyond the second side of the first solder mark along the width direction of the electrode and the drawbacks caused by the second side of the first solder mark extending too far beyond the second side of the second part of the cathode current collector along the width direction of the electrode, thereby meeting the usage requirements of the electrochemical device and improving the preparation efficiency of the electrochemical device.

[0026] Optionally, the electrochemical device further includes a tab, which is electrically connected to a tab connecting piece by welding, and a second solder mark is formed on the tab connecting piece; along the width direction of the electrode, the second solder mark includes a first side close to the first sub-part and a second side away from the first sub-part; wherein the distance d8 between the second side of the first solder mark and the first side of the second solder mark satisfies: 0mm < d8 ≤ 10mm.

[0027] Taking the cathode electrode as an example, when the cathode tab is electrically connected to the cathode tab connecting piece by welding, the second weld mark formed on the cathode tab connecting piece cannot overlap with the first weld mark. If they overlap, it will affect the welding effect between the cathode tab and the cathode tab connecting piece, reducing the welding pull. Furthermore, if the distance d8 between the second side of the first weld mark and the first side of the second weld mark is too large (e.g., d8 > 10 mm), it can easily affect the energy density of the electrochemical device. In this embodiment, by adopting such a range of d8 values, both the drawbacks caused by the overlap of the second and first weld marks and the drawbacks caused by an excessively large distance d8 between the second and first sides of the first weld mark can be avoided, thus meeting the usage requirements of the electrochemical device and improving the preparation efficiency of the electrochemical device.

[0028] Optionally, the welding pull force between the second part and the tab connecting piece is greater than or equal to 70N and less than or equal to 1000N.

[0029] If the welding pull force between the second part and the tab connecting piece is too small, the tab connecting piece is prone to detaching from the second part during the use of the electrochemical device; conversely, if the welding pull force between the second part and the tab connecting piece is too large, it affects the cost of manufacturing the electrochemical device. The welding pull force in this embodiment meets the aforementioned range, effectively avoiding both the drawbacks of insufficient and excessive welding pull force, thus meeting the requirements for use in the electrochemical device and improving the fabrication yield of the electrochemical device.

[0030] According to another aspect of the embodiments of this application, an electrical device is provided, which includes the electrochemical device described above.

[0031] The electrical device in this application embodiment includes the electrochemical device provided in the first aspect above. Since the electrochemical device has a high preparation yield, the preparation yield of the electrical device is also high. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0033] Figure 1 This is a schematic diagram of an example electrochemical device according to an embodiment of this application.

[0034] Figure 2 The preparation process of the cathode electrode of an electrochemical device according to an example in the related art.

[0035] Figure 3A This describes the preparation process of a cathode electrode in an example of an electrochemical device according to an embodiment of this application.

[0036] Figure 3B According to Figure 3A An enlarged schematic diagram of point T in the diagram.

[0037] Figure 4A This is a schematic cross-sectional view of the cathode electrode of an example electrochemical device according to an embodiment of this application, along the thickness direction.

[0038] Figure 4B This is a cross-sectional schematic diagram along the thickness direction of the cathode electrode of an electrochemical device according to another example of an embodiment of this application.

[0039] Figure 4C This is a cross-sectional schematic diagram along the thickness direction of the cathode electrode of an electrochemical device according to another example of an embodiment of this application.

[0040] Figure 5 This is a schematic diagram of an example of ultrasonic roll welding according to an embodiment of this application.

[0041] Figure 6 This is a schematic diagram of a first solder mark according to an example of an embodiment of this application.

[0042] Figure 7 This is a schematic diagram of a first solder mark, representing another example of an embodiment of this application.

[0043] Figure 8 This is a schematic diagram of a first solder mark according to another example of an embodiment of this application.

[0044] Figure 9 This is a schematic diagram of a first solder mark according to another example of an embodiment of this application.

[0045] Figure 10 This is a schematic diagram of an example electrical appliance according to an embodiment of this application. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0047] In the following description, the electrochemical device and electrical equipment in the embodiments of this application will be specifically described first, and then some relevant experimental examples and comparative examples will be given to illustrate the significant advantages of the electrochemical device and electrical equipment provided in the embodiments of this application compared with the prior art.

[0048] The specific implementation of the electrochemical device and electrical equipment according to the embodiments of this application is described below with reference to the accompanying drawings. It should be noted that, for ease of illustration, the structures in the following drawings are not necessarily drawn to scale.

[0049] It should be noted that in the embodiments of this application, lithium-ion batteries are used as an example of electrochemical device 10 to explain this application. However, the electrochemical device 10 of this application is not limited to lithium-ion batteries. For example, it can also be sodium-ion batteries, etc.

[0050] A first aspect of this application provides an electrochemical device comprising: an electrode, the electrode including a current collector, an active material layer, and a tab connecting piece; in an unfolded state, the current collector includes a first portion and a second portion along the width direction of the electrode; the active material layer is disposed on the surface of the first portion; the second portion is an empty foil area without an active material layer; the tab connecting piece overlaps with the surface of the second portion to form an overlapping area; the tab connecting piece is welded to the surface of the second portion to form an electrical connection with the second portion; along the length direction of the electrode, the ratio of the solder area to the solder area is greater than or equal to 20%, and the ratio of the length of the solder area to the length of the overlapping area is greater than or equal to 60%.

[0051] The electrodes of the electrochemical device of this application may include cathode electrodes and anode electrodes. In any optional embodiment of this application, when the electrode is a cathode electrode, the current collector is a cathode current collector, the active material layer is a cathode active material layer, the tab connecting piece is a cathode tab connecting piece, and the tab electrically connected to the tab connecting piece is a cathode tab; when the electrode is an anode electrode, the current collector is an anode current collector, the active material layer is an anode active material layer, the tab connecting piece is an anode tab connecting piece, and the tab electrically connected to the tab connecting piece is an anode tab. For ease of explanation of the electrochemical device in the embodiments of this application, the electrochemical device of this application mainly takes the cathode electrode as an example, and the anode electrode will not be described in detail below. Figures 1-9 Please provide an explanation. (Refer to...) Figures 1-9 As shown in the embodiments of this application, an exemplary electrochemical device 10 is disclosed, which includes: a cathode electrode 1, an anode electrode 2, a separator 3, a cathode tab 41, and an anode tab; the separator 3 is disposed between the cathode electrode 1 and the anode electrode 2; the cathode electrode 1 includes a cathode current collector 11, a cathode active material layer 12, and a cathode tab connecting piece 51. The cathode current collector 11 includes a first part and a second part along the width direction Y of the electrode. The cathode active material layer 12 is disposed on the surface of the first part of the cathode current collector. The second part of the cathode current collector is an empty foil area without the cathode active material layer 12. The cathode tab connecting piece 51 overlaps with the surface of the second part to form an overlapping area. The cathode tab connecting piece 51 is welded to the surface of the second part of the cathode current collector to form an electrical connection with the second part of the cathode current collector. The ratio of the solder area to the solder area is greater than or equal to 20%, and the ratio of the length of the solder area to the length of the overlapping area along the length direction of the electrode is greater than or equal to 60%.

[0052] In this embodiment, since the cathode tab connecting piece of the cathode electrode of the electrochemical device is welded to the surface of the second part of the cathode current collector (i.e., the edge empty foil area on the cathode current collector), when the cathode tab is led out from the cathode current collector in this application, it is no longer necessary to directly connect the cathode tab to the second part of the cathode current collector. Instead, it can be electrically connected to the cathode tab through the cathode tab connecting piece welded to the second part of the cathode current collector. Based on this, when preparing the cathode electrode of the electrochemical device in this application, the cathode electrode is less likely to wrinkle when cold pressing, which can effectively improve the preparation yield of the electrochemical device.

[0053] Optionally, refer to Figure 1 The electrochemical device 10 can be manufactured by winding a cathode electrode 1, a separator 3, and an anode electrode 2. It should be understood that this is for illustrative purposes only and should not be considered a limitation of this embodiment. Specifically, after being wound into the electrochemical device, the separator 3 is disposed between the cathode electrode 1 and the anode electrode 2, which can isolate the cathode electrode 1 and the anode electrode 2, prevent short circuits between the anode and cathode inside the electrochemical device, allow ions to pass through, and maintain the function of the electrolyte between the cathode electrode 1, the separator 3, and the anode electrode 2.

[0054] For ease of description, the first part of the cathode current collector will be referred to as the first part of the cathode current collector (labeled 111 in the figure) and the second part of the cathode current collector will be referred to as the second part of the cathode current collector (labeled 112 in the figure). In the cathode electrode 1 of this embodiment, the first part 111 and the second part 112 of the cathode current collector can be conductive foil.

[0055] In some embodiments, when the electrode is a cathode electrode 1, the first portion 111 of the cathode current collector includes a first sub-portion 1111 and a second sub-portion 1112 connected to each other. The second sub-portion 1112 is connected to the second portion 112 of the cathode current collector. The cathode active material layer 12 is disposed on the first sub-portion, and the second sub-portion is disposed on the insulating layer 13. Along the width direction Y of the electrode, the second portion 112 of the cathode current collector includes a first side close to the first sub-portion 1111 and a second side away from the first sub-portion 1111. The cathode tab connecting piece 51 includes a first side close to the first sub-portion 1111 and a second side away from the first sub-portion 1111. There is a gap between the cathode tab connecting piece 51 and the first sub-portion 1111, and the second side of the second portion 112 of the cathode current collector is located between the first side and the second side of the cathode tab connecting piece 51.

[0056] Specifically, in related technologies, one method to prevent wrinkling of the cathode electrode during cold pressing during cathode electrode fabrication is to first cold press the cathode electrode with the cathode active material layer and insulating layer already in place. Before cold pressing, the edge foil area of ​​the cathode current collector is stretched to make the deformation degree of the edge foil area of ​​the cathode current collector and the insulating layer more consistent, thereby preventing wrinkling of the cathode electrode during subsequent cold pressing. However, while this can alleviate the wrinkling problem of the cathode electrode during cold pressing, it increases the cold pressing tension of the cathode electrode, making it prone to breakage during the cold pressing process and reducing the fabrication yield of the electrochemical device.

[0057] In this embodiment, when the cathode tab 41 is led out from the second portion 112 of the cathode current collector 11 (i.e., the edge empty foil area of ​​the cathode current collector 11), it is no longer necessary to directly connect the cathode tab 41 to the second portion 112 of the cathode current collector. Instead, it can be electrically connected to the cathode tab 41 through the cathode tab connecting piece 51 welded to the second portion 112 of the cathode current collector. This means that when preparing the cathode electrode 1 of the electrochemical device 10, it is not necessary to stretch the second portion 112 of the cathode current collector 1 (i.e., the edge empty foil area of ​​the cathode current collector 11) before cold pressing the cathode electrode 1. This also improves the problem of the cathode electrode 1 wrinkling during subsequent cold pressing. Furthermore, since it is not necessary to stretch the second portion 112 of the cathode current collector 1 (i.e., the edge empty foil area of ​​the cathode current collector 11), the cold pressing tension of the cathode electrode 1 is reduced, thereby improving the problem of the cathode electrode 1 being prone to breakage during the cold pressing process. Therefore, the preparation efficiency of the electrochemical device can be improved.

[0058] The insulating layer 13 can insulate and isolate the second sub-part 1112 and the anode plate 2, and can effectively prevent short circuits between the cathode plate 1 and the anode plate 2.

[0059] Since the first part 111 of the cathode current collector can be a conductive foil, both the first sub-part 1111 and the second sub-part 1112 can be conductive foils. In the cathode current collector 11, the first sub-part 1111 and the second part 112 of the cathode current collector are respectively connected to both sides of the second sub-part 1112 along the width direction of the electrode.

[0060] Reference Figure 4A , Figure 4B , Figure 4C , showed Figure 3A A schematic diagram of the cross-section of the cathode electrode 1 along the thickness direction.

[0061] Figure 4A , Figure 4B , Figure 4CThe position of the cathode tab 41, which is electrically connected to the cathode tab connecting piece 51, is also schematically shown in the diagram. Figure 4A , Figure 4B , Figure 4C This is only used for illustrative purposes and is not intended to limit the scope of this embodiment.

[0062] The presence of a gap between the cathode tab connecting piece 51 and the first sub-part 1111 prevents the electrochemical device 10 from becoming too thick. Furthermore, since ions can pass through the separator 3 and the cathode active material layer 12 and the anode active material layer 22, but cannot pass through the cathode tab connecting piece 51 (which, as will be described below, can be a conductive foil, such as aluminum-plated foil), the gap between the cathode tab connecting piece 51 and the first part 111 of the cathode current collector prevents the cathode tab connecting piece 51 from being sandwiched between the cathode active material layer 12 (including the cathode active material) of the cathode electrode 1 and the anode active material layer 22 (including the anode active material) of the anode electrode 2, thus hindering the transport of ions between the cathode and anode.

[0063] The second side of the second part 112 of the cathode current collector is located between the first side of the cathode tab connecting piece 51 and the second side of the cathode tab connecting piece 51, which means that the cathode tab connecting piece 51 can be used as an extension of the second part 112 of the cathode current collector.

[0064] In this embodiment, the cathode tab 41 and anode tab 42 of the electrochemical device 10 can be located on the same side of the electrochemical device 10 or on different sides of the electrochemical device 10.

[0065] In this embodiment, the cathode active material layer 12 disposed on the first sub-part 1111 of the cathode electrode 1 includes a cathode active material, and the type of cathode active material is not limited here. For example, it can be lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, etc. In some embodiments, the cathode active material layer 12 can be a coating, that is, the cathode active material layer 12 is coated on the first sub-part 1111. This can ensure the structural stability of the cathode active material layer 12 disposed on the first sub-part 1111.

[0066] The following description, in conjunction with the preparation of the cathode electrode in related electrochemical devices, briefly illustrates the electrochemical device 10 in this embodiment. It should be understood that this description is for ease of understanding only and is not intended to limit the scope of this embodiment.

[0067] Reference Figure 2 The image illustrates the fabrication process of a cathode electrode 1' in an electrochemical device of the related art. In this example, the cathode active material layer and insulating layer of the cathode electrode are coatings applied to the cathode current collector. (Refer to...) Figure 2Structure A1 in the diagram is essentially multiple cathode plates without further processing (simply put, structure A1 is cut along the dotted line a1, and then cut along the dotted lines a2 and a3 respectively, thus separating structure A1 into four cathode plates 1'; this process will be explained in detail below). After coating the cathode active material layer 12' and the insulating layer 13' onto the cathode current collector 11', structure A1 is obtained. Structure A1 is then cold-pressed (for example, using a stepped roller (i.e., a special cold-pressing roller) adapted to structure A1. When using a stepped roller, different stepped roller sizes must be designed to match each different size of structure A1. For specific details, refer to the relevant technology for cold-pressing electrodes using stepped rollers, which will not be elaborated here). During the cold pressing process, the thickness of the empty foil area 14' at the edge of the cathode current collector 11' differs from the deformation degree of the coating area (i.e., the insulating layer 13' and the cathode active material layer 12'), which easily leads to wrinkling of structure A1 during the cold pressing process, i.e., wrinkling of the subsequently prepared cathode electrode 1'. Therefore, the empty foil area 14' at the edge is generally stretched first to make its deformation more uniform during the cold pressing process, thereby preventing wrinkling of the cathode electrode when the structure A1 is cold pressed later. After the stretching and cold pressing steps are completed, the cold-pressed structure A1 is cut along the dotted line a1 (for example, laser cutting technology can be used for cutting) to obtain two structures A2 (each structure A2 is equivalent to two cathode electrodes 1'). Then, the two structures A2 are cut along the dotted lines a2 and a3 respectively (for example, laser cutting technology can be used for cutting) to obtain the following... Figure 2 The four cathode plates 1' shown are illustrated. Later, when fabricating an electrochemical device using these final cathode plates 1', the cathode plates 1' can be wound together with a separator, anode plates, etc., and the edge empty foil area 14' can be electrically connected to the cathode tabs (e.g., by welding). The electrochemical device is thus successfully fabricated.

[0068] Correspondingly, in conjunction with the preparation of the cathode electrode 1 of the electrochemical device 10 in the embodiments of this application, the electrochemical device 10 in the embodiments of this application will be briefly described. It should be understood that this is only for the purpose of understanding and is not intended to limit the embodiments in any way.

[0069] Reference Figure 3A The preparation process of the cathode electrode 1 of an electrochemical device 10 in this embodiment is shown. Additionally, Figure 3B It shows Figure 3A An enlarged diagram of point T in the image. Figure 3A In this example shown, the cathode active material layer 12 and the insulating layer 13 of the cathode electrode 1 are coatings respectively applied to the first sub-part 1111 and the second sub-part 1112 of the cathode current collector 11. (Refer to...) Figure 3AStructure B1 in the diagram is essentially multiple unprocessed cathode plates 1 (simply put, structure A1 is cut along the dotted line b1, and then further cut along dotted lines b2 and b3, thus separating structure B1 into four cathode plates 1; this process will be explained in detail below). After coating the cathode active material layer 12 and the insulating layer 13 onto the cathode current collector 11, structure B1 is obtained. Structure B1 is then cold-pressed (the method of cold pressing here can be understood by referring to the relevant technology of cold pressing electrodes using cold pressing rollers, which will not be elaborated here). Comparison Figure 3A and Figure 2 As can be seen from structures B1 and A1, since the edge empty foil area of ​​structure B1 (which is also the second part 112 of the cathode current collector) does not need to be stretched before cold pressing, Figure 3A Compared to the middle structure B1 Figure 2 In structures A1 and B1, the width of the edge empty foil area of ​​the cathode current collector 11 is significantly reduced. After the cold pressing step, the cold-pressed structure B1 is cut along the dotted line b1 (e.g., laser cutting technology can be used) to obtain two structures B2. Cathode tab connecting pieces 51 are welded to the edge empty foil areas (i.e., the second part 112 of the cathode current collector) on both sides of structure B2, resulting in two structures B3 (each structure B3 is equivalent to two cathode plates 1). Then, the two structures B3 are cut along the dotted lines b2 and b3 respectively (e.g., laser cutting technology can be used) to obtain... Figure 3A The four cathode plates 1 shown (see also the other two) Figure 3B (Further understanding of the structure). Then, when preparing the electrochemical device 10 using the finally obtained cathode electrode 1, the cathode electrode 1 can be wound with the separator 3, the anode electrode 2, etc., and the cathode tab connecting piece 51 can be electrically connected to the cathode tab 41 (for example, by welding to form an electrical connection). The electrochemical device 10 is thus successfully prepared.

[0070] It should be understood that Figure 3A For easier schematic representation of the structure, the first weld mark 61 formed by welding the cathode tab connecting piece 51 to the second part 112 of the cathode current collector is omitted, while... Figure 3B The enlarged schematic diagram schematically shows the first solder mark 61. Figure 3A and Figure 3B This is not intended to limit the scope of this application.

[0071] In some optional embodiments, the second part 112 of the cathode current collector is a conductive foil, and the resistance R per square millimeter of the conductive foil (i.e., the second part 112 of the cathode current collector) satisfies: R < 20mΩ, which makes the second part 112 of the cathode current collector have good conductivity and meets the use requirements of the electrochemical device 10.

[0072] As mentioned above, the first sub-part 1111 and / or the second sub-part 1112 of the cathode current collector can also be conductive foil. For example, the resistance per square millimeter of the conductive foil of the first sub-part 1111 and / or the second sub-part 1112 is less than 20 mΩ, which also makes the first sub-part 1111 and / or the second sub-part 1112 have good conductivity and meet the needs of the electrochemical device 10.

[0073] In this embodiment, the second part 112 of the cathode current collector is welded to the cathode tab connecting piece 51, and the cathode tab 41 is electrically connected to the cathode tab connecting piece 51. The cathode tab connecting piece 51 can also be a conductive foil. Optionally, the resistance R per square millimeter of the cathode tab connecting piece 51 satisfies: R < 20mΩ, which makes the cathode tab connecting piece 51 have good conductivity and meets the usage requirements of the electrochemical device 10.

[0074] Optionally, when actually measuring the resistance R per square millimeter of the second part 112 of the cathode current collector or the cathode tab connecting piece 51 of the prepared electrochemical device 10, the electrochemical device 10 can be disassembled first, and then a clean part (i.e., the part without insulating material or cathode active material) of the second part 112 of the cathode current collector or the cathode tab connecting piece 51 can be taken and measured with a resistance tester. If it is not possible to take it, the insulating material or cathode active material attached to the second part 112 of the cathode current collector or the cathode tab connecting piece 51 can be washed away with organic solvents such as alcohol, and then the clean part after washing can be measured with a resistance tester. Alternatively, other methods can be used for measurement, and there are no restrictions here.

[0075] When the electrode is the cathode electrode 1, and the second part 112 of the cathode current collector and / or the cathode tab connecting piece 51 are made of conductive foil, this embodiment does not specifically limit the specific material of the conductive foil. It can be any material, provided that conductivity and structural strength are guaranteed. For example, conductive foil includes at least one of aluminum foil, aluminized foil, nickel foil, and nickel-plated foil. This type of conductive foil ensures the conductivity of the second part 112 of the cathode current collector and / or the cathode tab connecting piece 51 of the cathode electrode 1, meeting the requirements of the electrochemical device 10.

[0076] Optionally, when the conductive foil is aluminized foil, the aluminized foil includes at least one of the following: aluminum-plated foil on the surface of a polypropylene film and aluminum-plated foil on the surface of a polyethylene terephthalate film. These types of conductive foils can ensure the conductivity of the second portion 112 of the cathode current collector 1 and / or the cathode tab connecting piece 51, meeting the usage requirements of the electrochemical device 10.

[0077] Optionally, the second part 112 of the cathode current collector and the cathode tab connecting piece 5 in this application can be made of the same conductive foil or different conductive foils, and there is no limitation on this.

[0078] Optionally, the thickness L of the cathode tab connecting piece 51 satisfies: 4μm ≤ L ≤ 25μm. If the cathode tab connecting piece 51 is too thin, it increases the manufacturing difficulty of the cathode electrode 1 and leads to increased costs. Furthermore, its thinness results in lower strength, making it difficult to meet the structural strength requirements of the cathode electrode 1 and the cathode tab connecting piece 51. Conversely, if the cathode tab connecting piece 51 is too thick, it increases material costs and reduces the energy density gain of the electrochemical device 10. In this embodiment, the thickness L satisfies the above-mentioned range (i.e., 4μm ≤ L ≤ 25μm), which effectively avoids both the disadvantages of an excessively thin and excessively thick cathode tab connecting piece 51, thus meeting the usage requirements of the electrochemical device 10 and improving the fabrication yield of the electrochemical device 10. Optionally, based on 4μm ≤ L ≤ 25μm, the thickness L of the cathode tab connecting piece 51 satisfies: 5μm ≤ L ≤ 20μm. Within this preferred value range, the drawbacks of the cathode tab connecting piece 51 being too thin or too thick can be better avoided, thus meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10. Within the above-mentioned value range, L can be selected according to needs. For example, taking 5μm≤L≤20μm as an example, L can be 5μm, 7μm, 10μm, 15μm, 18μm, 20μm, etc., without specific limitations.

[0079] Optionally, when actually measuring the thickness L of the cathode tab connecting piece 51 of the prepared electrochemical device 10, the electrochemical device 10 can be disassembled first, and then the unwelded part of the cathode tab connecting piece 5 located between the first solder mark 61 and the second solder mark 62 (the first solder mark 61 and the second solder mark 62 will be introduced below) can be measured using a micrometer or ten-thousand-meter, or other methods can be used for measurement, which are not limited here.

[0080] Optionally, to ensure the strength of the cathode tab connecting piece 51, the fracture strength S of the cathode tab connecting piece 51 satisfies: 80MPa≤S≤800MPa. If the fracture strength of the cathode tab connecting piece 51 is too low, it is prone to breakage during the manufacturing process, increasing the difficulty of manufacturing the cathode electrode 1 and causing increased costs. Furthermore, too low a fracture strength also makes it difficult to meet the structural strength requirements of the cathode electrode 1 and the cathode tab connecting piece 51. Conversely, if the fracture strength S of the cathode tab connecting piece 51 is too high, it also increases the difficulty of manufacturing the cathode electrode 1 and causes increased costs. In this embodiment, the fracture strength S satisfies the above-mentioned range (i.e., 80MPa≤S≤800MPa), which effectively avoids both the disadvantages of too low and too high fracture strength of the cathode tab connecting piece 51, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10. Optionally, based on 80MPa≤S≤800MPa, the fracture strength S of the cathode tab connecting piece 51 satisfies: 100MPa≤S≤450MPa. Within this preferred value range, the drawbacks of excessively low or excessively high fracture strength of the cathode tab connecting piece 51 are better avoided, thus meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10. Within the above-mentioned value range, the fracture strength S of the cathode tab connecting piece 51 can be selected according to needs. For example, taking 100MPa≤S≤450MPa as an example, the fracture strength S can be 100MPa, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa, 400MPa, 450MPa, etc., without limitation.

[0081] Optionally, the thickness range of the second portion 112 of the cathode current collector 11 of the cathode electrode 1 can be the same as the thickness range of the cathode tab connecting piece 51, that is, the thickness range of the second portion 112 of the cathode current collector can be 4μm to 25μm, and more preferably 5μm to 20μm. The fracture strength range of the second portion 112 of the cathode current collector can be the same as the fracture strength range of the cathode tab connecting piece 51, that is, the fracture strength range of the second portion 112 of the cathode current collector can be 80MPa to 800MPa, and more preferably 100MPa to 450MPa.

[0082] Furthermore, when both the second part 112 of the cathode current collector and the cathode tab connecting piece 51 are conductive foils, the thickness of the second part 112 of the cathode current collector and the thickness of the cathode tab connecting piece 51 can be the same or different, and the breaking strength of the second part 112 of the cathode current collector and the breaking strength of the cathode tab connecting piece 51 can be the same or different.

[0083] Optionally, when the first sub-part 1111 and / or the second sub-part 1112 of the cathode current collector 11 of the cathode electrode 1 is a conductive foil, it can be made of the same material as the second sub-part 112 of the cathode current collector, and the thickness of the second sub-part 112 of the cathode current collector can satisfy the same range of values. That is, when the first sub-part 1111 and / or the second sub-part 1112 is a conductive foil, it can be at least one of aluminum foil, aluminized foil, nickel foil, and nickel-plated foil; and the aluminized foil includes at least one of aluminized foil on the surface of a polypropylene film and aluminized foil on the surface of a polyethylene terephthalate film; the thickness of the first sub-part 1111 and / or the second sub-part 1112 is in the range of 4 μm to 25 μm, preferably 5 μm to 20 μm; the tensile strength of the first sub-part 1111 and / or the second sub-part 1112 is in the range of 80 MPa to 800 MPa, preferably 100 MPa to 450 MPa, thereby meeting the corresponding usage requirements of the electrochemical device 10.

[0084] In this embodiment, the insulating layer 13 is disposed on the second sub-part 1112 of the cathode electrode 1. This embodiment does not specifically limit the material of the insulating layer 13; for example, it can be at least one of alumina or silicon oxide. Using an insulating layer 13 of such material to insulate and isolate the second sub-part 1112 and the anode electrode 2 can effectively prevent short circuits between the cathode electrode 1 and the anode electrode 2.

[0085] Optionally, the insulating layer 13 can be a coating (e.g., an alumina coating, a silicon oxide coating, etc.), that is, the insulating layer 13 is coated on the second sub-part 1112 of the cathode electrode 1. This ensures the structural stability of the insulating layer 13 disposed on the second sub-part 1112.

[0086] In this embodiment, along the width direction Y of the electrode, the width d3 of the insulating layer 13 satisfies: 0.5mm≤d3≤5mm.

[0087] Reference Figure 4A , Figure 4B , Figure 4CThe width d3 of the insulating layer 13 is also the distance d3 between the first side and the second side of the insulating layer 13 in the width direction Y of the electrode. In this embodiment, the insulating layer 13 with such a width range can effectively insulate and isolate the second sub-part 1112 of the cathode current collector 11 from the anode electrode 2, preventing short circuits between them. This does not increase the cost while meeting the usage requirements of the electrochemical device 10.

[0088] Optionally, for the cathode electrode 1, the width d3 of the insulating layer 13 is equal to the width of the second sub-part 1112 (i.e., the distance between the first side and the second side of the second sub-part 1112 along the width direction Y of the electrode). It can be understood that the first side of the second sub-part 1112 is the side of the second sub-part 1112 closer to the first sub-part 1111 along the width direction Y of the electrode; the second side of the second sub-part 1112 is the side of the second sub-part 1112 farther from the first sub-part 1111 along the width direction Y of the electrode.

[0089] In some optional embodiments of this application, the welding pull force between the second part of the current collector of the electrode and the electrode tab connecting piece is greater than or equal to 70N and less than or equal to 1000N.

[0090] For example, in some optional embodiments, when the electrode is a cathode electrode 1, the second part 112 of the cathode current collector and the cathode tab connecting piece 51 are welded together, and the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 satisfies: 70N≤F≤1000N. If the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 is too small, the cathode tab connecting piece 51 is prone to detaching from the second part 112 of the cathode current collector when using the electrochemical device 10; while if the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 is too large, it affects the cost of manufacturing the electrochemical device 10. In this embodiment, the welding pull force F satisfies the above-mentioned value range (i.e., 70N≤F≤1000N), which can effectively avoid the disadvantage of the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 being too small, and can also effectively avoid the disadvantage of the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 being too large, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0091] Optionally, based on 70N≤F≤1000N, the welding pull force F between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 satisfies: 150N≤F≤500N. Within this preferred value range, the disadvantages of insufficient welding pull force between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 are better avoided, as are the disadvantages of excessive welding pull force, thereby meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10.

[0092] Within the above range, the welding tensile force F can be selected according to the needs. For example, taking 150N≤F≤500N as an example, the welding tensile force F can be 150N, 200N, 300N, 350N, 400N, 500N, etc., without specific restrictions.

[0093] The method for testing the welding tensile force F can refer to relevant technologies and is not limited here. For example, an exemplary method for testing the welding tensile force F may be as follows: Take a sample of the welded cathode current collector second part 112 and cathode tab connecting piece 51 and place it into a tensile testing machine. Along the width direction Y of the electrode piece, the left and right clamps respectively clamp the cathode current collector second part 112 and cathode tab connecting piece 51, with the left and right clamps at a suitable distance (e.g., 20mm). Place the welding area (e.g., the first weld mark 61 mentioned below) in the middle of the left and right clamps. During the test, keep the left and right clamps from contacting the welding area (e.g., the first weld mark 61 mentioned below). Then, fix the left clamp and pull the right clamp away from the left clamp at a suitable speed (e.g., 1mm / s). After breaking, confirm whether the welding area is broken. If the welding area is broken, confirm the corresponding welding tensile force F. If the welding area is not broken, replace the sample and retest. Of course, this is only an example and not any limitation on the embodiment.

[0094] The fracture strength of the cathode tab connecting piece 51 can also be tested using a similar method to the welding tensile force F described above. Simply take an appropriate width for the cathode tab connecting piece 51 (e.g., 10 mm), clamp the cathode tab connecting piece 51 with the left and right clamps respectively, then fix the left clamp in place and pull the right clamp away from the left clamp at a suitable speed (e.g., 1 mm / s). The fracture strength of the cathode tab connecting piece 51 can then be tested. The method for testing the fracture strength of each part of the cathode current collector 11 can be deduced similarly, and will not be elaborated here. Of course, this is only an example and not a limitation on the embodiment.

[0095] In this embodiment, the welding between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 can be performed by any welding method, such as ultrasonic roll welding. (Refer to...) Figure 5 The diagram illustrates an ultrasonic roll welding method. First, the second part 112 of the cathode current collector partially overlaps with the cathode tab connecting piece 51 and is placed on a roll welding base 71. Then, the roll welding head 72 is aligned with the cathode tab connecting piece 51 and the second part 112 of the cathode current collector above the roll welding base 71 and ultrasonically welded. During the welding process, the roll welding head 72 emits high-frequency ultrasonic waves to the cathode tab connecting piece 51 and the second part 112 of the cathode current collector. When the roll welding head 72 applies pressure to both, the contact surfaces of the cathode tab connecting piece 51 and the second part 112 of the cathode current collector rub against each other, generating heat. This heat causes the welding position of the cathode tab connecting piece 51 and the second part 112 of the cathode current collector to melt, thus ultimately forming a welded connection between the cathode tab connecting piece 51 and the second part 112 of the cathode current collector. Of course, this is merely an example of an embodiment of this application and is not intended to limit the scope of this application.

[0096] In some optional embodiments, the solder mark includes a first solder mark 61. Taking the cathode electrode 1 as an example, in the electrochemical device 10, the first solder mark 61 is formed when the second part 112 of the cathode current collector is welded to the cathode tab connecting piece 51. Along the width direction Y of the electrode, the first solder mark 61 includes a first side close to the first sub-part 1111 and a second side away from the first sub-part 1111. The second side of the first solder mark 61 is located on the cathode tab connecting piece 51, and there is a gap between the first solder mark 61 and the first sub-part 1111.

[0097] Specifically, the second side of the first solder mark 61 is located on the cathode tab connecting piece 51, ensuring that the cathode tab connecting piece 51 can form a stable solder connection with the second part 112 of the cathode current collector. The first side of the first solder mark 61 can be located on the second part 112 of the cathode current collector or on the cathode tab connecting piece 51, and there is no limitation on this.

[0098] In this embodiment, the shape of the first solder mark 61 is not limited. For example Figure 6 , Figure 7 As shown, the first solder mark 61 can be a combination of multiple first sub-solder marks 611, with a spacing between each pair of adjacent first sub-solder marks 611. The first sub-solder mark 611 can be composed of multiple small solder dots of regular or irregular shapes; for example, the shape of the small solder dots can be a circle, rectangle, or other polygons, etc. Optionally, the shape of the first sub-solder mark 611 formed by the arrangement of small solder dots can be a parallelogram, rectangle (which can be a square), triangle, or other polygons, or it can be other irregular shapes. For example... Figure 6 As shown, the first sub-solder mark 611 has a rectangular shape composed of small solder dots, and the small solder dots are rectangular. Or, for example... Figure 7 As shown, each first sub-solder mark 611 can be a complete solder mark. No restrictions are imposed here.

[0099] For example Figure 8 , Figure 9 As shown, the first solder mark 61 can also be a continuous solder mark. This continuous solder mark can be a single, complete solder mark (a complete solder mark can be combined with...). Figure 9 (This will be understood, but will not be elaborated upon here). Alternatively, the continuous solder mark can also be composed of multiple small solder joints of regular or irregular shapes. For example, the shape of the small solder joints can be circular, rectangular, or other polygonal, etc. (This can be combined with...) Figure 8 (This is for illustrative purposes only and will not be elaborated upon here). No limitations are imposed in this embodiment.

[0100] In the electrochemical device of this application, when the electrode is in its unfolded state, the weld area formed by welding the tab connecting piece to the surface of the second part of the current collector of the electrode refers to the sum of the areas of all weld marks (i.e., small solder joints, complete weld marks, etc.) formed when the tab connecting piece is welded to the surface of the second part of the current collector of the electrode; the weld zone area refers to the area of ​​the smallest circumscribed region of all weld marks (i.e., small solder joints, complete weld marks, etc.) formed when the tab connecting piece is welded to the surface of the second part of the current collector of the electrode; the area overlapping the tab connecting piece with the surface of the second part is the overlap zone (i.e., the area of ​​the projection of the tab connecting piece onto the surface of the second part along the thickness direction of the electrode); the weld zone length refers to the maximum distance between the two ends of the weld zone along the length direction of the electrode; the overlap zone length refers to the distance between the two ends of the overlap zone along the length direction of the electrode. In this application, the ratio of the weld area to the weld zone area of ​​the electrode is greater than or equal to 20%; the ratio of the weld zone length to the overlap zone length is greater than or equal to 60%.

[0101] Therefore, for a cathode electrode 1, the solder area can refer to the sum of the areas of all solder marks (i.e., small solder joints, complete solder marks, etc.) included in the first solder mark 61 formed by welding the tab connecting piece to the second part of the current collector of the electrode. The welding area can refer to the area of ​​the smallest bounding rectangle region included in the first solder mark 61 (i.e., small solder joints, complete solder marks, etc.). In this application, the ratio of the solder area of ​​the electrode to the welding area is greater than or equal to 20%, and the ratio of the welding area length to the overlap area length is greater than or equal to 60%.

[0102] Taking the first solder mark 61 as an example, the solder mark area is the area of ​​the first solder mark 61. When the first solder mark 61 is a combination of multiple first sub-solder marks 611, and there is a gap between each pair of adjacent first sub-solder marks 611, the solder mark area (denoted as Sy1) is equal to the sum of the areas of each first sub-solder mark 611. Wherein, for Figure 6 Regarding the area of ​​each first sub-solder mark 611, since each first sub-solder mark 611 includes multiple small solder joints, therefore Figure 6 The area of ​​the first sub-solder mark 611 is the sum of the areas of each small solder joint in the first sub-solder mark 611; then... Figure 7 Taking the first sub-weld 611 as an example, where each sub-weld is a complete weld, the weld area Sy1 = s11 + s12 + s13 + s14 + s15 + s16 + s17 + s18, where s11, s12, s13, s14, s15, s16, s17, and s18 are the areas of each individual first sub-weld 611. However, for the case where the first weld 61 is a continuous weld, refer to... Figure 8 As shown, the continuous solder mark consists of multiple small solder joints, and the area of ​​the solder mark is equal to the sum of the areas of all the small solder joints; refer to Figure 9 As shown, this continuous solder mark constitutes a complete solder mark, and the area of ​​the solder mark is equal to the area of ​​the complete solder mark. (Refer to...) Figure 6 and Figure 7 As shown, the length of the overlapping area is equal to the length of the electrode sheet, and the length of the welding area is h1. At this time, the ratio of the length of the welding area to the length of the overlapping area is greater than 60%. (Refer to...) Figure 8 and Figure 9 As shown, the length of the overlapping area is equal to the length of the electrode at this time, and the length of the welding area is h1, which is also equal to the length of the electrode. At this time, the length of the welding area and the length of the overlapping area are equal to 60%.

[0103] Reference Figure 6 , Figure 7 , Figure 8 , Figure 9 In the example shown, the area of ​​the welding zone is denoted as Sz1, then Sz1 = h1 * d5, where h1 is the length of the minimum bounding rectangle (i.e., the length of the welding zone), and d5 is the width of the minimum bounding rectangle. Furthermore, as will be explained below, d5 is the width of the first solder mark 61, which is the distance between the first side and the second side of the first solder mark 61 along the width direction Y of the electrode sheet.

[0104] Let P be the ratio of the solder area to the area of ​​the solder zone. When the electrode is cathode electrode 1, ... Figure 7 and Figure 9 Examples of the following scenarios are provided: Figure 7In this context, P = Sy1 / Sz1 = (s11 + s12 + s13 + s14 + s15 + s16 + s17 + s18) / (h1 * d5) > 20%; therefore... Figure 9 In this case, P = Sy1 / Sz1 = (h1*d5) / (h1*d5) = 100% > 20%. Figure 6 and Figure 8 In the case of P>20%, the ratio of the length of the welding zone to the length of the overlapping zone should not be too small, and should be at least greater than or equal to 60%. This ensures that the weld marks are evenly distributed in the welding zone and the overlapping zone, avoiding the problem of concentrated weld marks leading to excessive local strength or insufficient strength in other parts, thus avoiding the disadvantages of difficult processing.

[0105] In this application, the ratio of the solder area to the area of ​​the soldering zone P>20%, and the ratio of the length of the soldering zone to the length of the overlapping zone is greater than or equal to 60%, which can meet the requirement of forming a stable weld on the surface of the second part of the electrode connecting piece of the electrochemical device.

[0106] In some alternative embodiments, refer to Figure 4A , Figure 4B , Figure 4C As shown, along the width direction Y of the electrode, the width d5 ​​of the first solder mark 61 satisfies: 0.1mm ≤ d5 ≤ 10mm. It can be understood that the width d5 ​​of the first solder mark 61 is also the distance between the first side and the second side of the first solder mark 61 along the width direction Y of the electrode. The width d5 ​​of the first solder mark 61 can also be considered in conjunction with... Figure 6 , Figure 7 , Figure 8 and Figure 9 To understand.

[0107] When the width d5 ​​of the first weld mark 61 is too small (i.e., d5 < 0.1 mm), it is difficult to ensure that the welding pull force between the second part 112 of the cathode current collector and the cathode tab connecting piece 51 meets the requirements, thus causing the aforementioned drawback of insufficient welding pull force F. When the width d5 ​​of the first weld mark 61 is too large (i.e., d5 > 10 mm), the welding is difficult and additional costs are increased. In this embodiment, the width d5 ​​of the first weld mark 61 is within the above-mentioned value range (0.1 mm ≤ d5 ≤ 10 mm), which avoids the drawbacks of the first weld mark 61 being too small or too large, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0108] Within the aforementioned range of values, the width d5 ​​of the first solder mark 61 can be selected as appropriate as needed. For example, taking 0.1mm≤d5≤10mm as an example, d5 can be 0.1mm, 1mm, 3mm, 5mm, 8mm, 10mm, etc., without specific restrictions.

[0109] In some alternative embodiments, refer to Figure 4A , Figure 4B , Figure 4C As shown, if the first side of the first solder mark 61 is located on the second part 112 of the cathode current collector, then the distance d6 between the first side of the first solder mark 61 and the first side of the cathode tab connecting piece 51 satisfies: 0mm≤d6≤5mm; or, if the first side of the first solder mark 61 is located on the cathode tab connecting piece 51, then the distance d6 between the first side of the first solder mark 61 and the first side of the cathode tab connecting piece 51 satisfies: 0mm≤d6≤20mm.

[0110] Specifically, refer to Figure 4B As shown, an example is illustrated where the first side of the first solder mark 61 is located on the second portion 112 of the cathode current collector (it should be noted that...). Figure 4B Although the first side of the first solder mark 61 does not contact the second part 112 of the cathode current collector, and there is a gap between them, Figure 4B The actual representation is that the first side of the first solder mark 61 is in direct contact with the second portion 112 of the cathode current collector so as to be located on the second portion 112 of the cathode current collector, thereby forming a weld between the cathode tab connecting piece 5 and the second portion 112 of the cathode current collector (this is shown here for ease of illustration and is not intended to limit the scope of this application). When the first side of the first solder mark 61 is located on the second portion 112 of the cathode current collector, it is equivalent to the first side of the first solder mark 61 extending beyond the first side of the cathode tab connecting piece 51 in the opposite direction to the width direction Y of the electrode sheet, and the first solder mark 61 covers the first side of the cathode tab connecting piece 51; see reference. Figure 4A and Figure 4C As shown, an example is shown where the first side of the first solder mark 61 is located on the cathode tab connecting piece 51. This is equivalent to the first side of the first solder mark 61 extending beyond the first side of the cathode tab connecting piece 51 along the width direction Y of the electrode piece. In this case, the first side of the cathode tab connecting piece 51 is not covered by the first solder mark 61, and the first side of the cathode tab connecting piece 51 can be in an unconstrained state, that is, the first side of the cathode tab connecting piece 51 is not welded to the second part 112 of the cathode current collector.

[0111] When the first side of the first solder mark 61 extends too far beyond the first side of the cathode tab connecting piece 51 along the opposite direction of the electrode width Y (for example, when the first side of the first solder mark 61 is located on the second part 112 of the cathode current collector, d6>5mm), there is a large portion without cathode active material. Therefore, the space ratio of the portion that cannot provide energy is also large, resulting in a serious loss of energy density. This affects the subsequent electrical connection between the cathode tab 41 and the cathode tab connecting piece 51 (for example, the cathode tab 41 and the cathode tab connecting piece 51 are electrically connected by welding). In this process, the cathode tab connecting piece 51 is also easily damaged, ultimately affecting the electrical performance of the electrochemical device 10. When the first side of the first solder mark 61 extends too far beyond the first side of the cathode tab connecting piece 51 along the width direction Y of the electrode (for example, when the first side of the first solder mark is located on the cathode tab connecting piece 51, d6>30mm), there is a situation where the unconstrained cathode tab connecting piece 51 is too wide. This increases the process difficulty when preparing the cathode electrode 1 and affects the preparation yield of the electrochemical device 10.

[0112] In this embodiment of the application, by adopting such a range of values ​​for d6, it is possible to avoid the drawbacks that occur when the first side of the first solder mark 61 extends too far beyond the first side of the cathode tab connecting piece 51 in the opposite direction of the width Y of the electrode sheet, and also to avoid the drawbacks that occur when the first side of the first solder mark 61 extends too far beyond the first side of the cathode tab connecting piece 51 in the width Y of the electrode sheet, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0113] Optionally, based on the aforementioned value range, if the first side of the first solder mark 61 is located on the second part 112 of the cathode current collector, then the distance d6 between the first side of the first solder mark 61 and the first side of the cathode tab connecting piece 51 satisfies: 0mm≤d6≤3mm; or, if the first side of the first solder mark 61 is located on the cathode tab connecting piece 51, then the distance d6 between the first side of the first solder mark 61 and the first side of the cathode tab connecting piece 51 satisfies: 0mm≤d6≤10mm. Within this preferred value range, the disadvantages caused by the first side of the first solder mark 61 extending too far beyond the first side of the cathode tab connecting piece 51 in the opposite direction of the electrode width can be avoided, thereby further meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10.

[0114] Within the aforementioned value range, d6 can be selected as an appropriate value as needed. For example, taking the first side of the first solder mark 61 as being located on the second part 112 of the cathode current collector, 0mm≤d6≤3mm, then d6 can be 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3.0mm, etc., without restriction. Taking the first side of the first solder mark 61 as being located on the cathode tab connecting piece 51, 0mm≤d6≤10mm, then d6 can be 0mm, 1mm, 3mm, 5mm, 7mm, 8mm, 10mm, etc., without restriction.

[0115] In some alternative embodiments, refer to Figure 4A , Figure 4B , Figure 4C As shown, if the first projection of the second side of the first solder mark 61 on the cathode tab connecting piece 51 overlaps with the second projection of the second part 112 of the cathode current collector on the cathode tab connecting piece 51, then the distance d7 between the second side of the first solder mark 61 and the second side of the second part 112 of the cathode current collector satisfies: 0mm≤d7≤15mm; or, if the first projection of the second side of the first solder mark 61 on the cathode tab connecting piece 51 does not overlap with the second projection of the second part 112 of the cathode current collector on the cathode tab connecting piece 51, then the distance d7 between the second side of the first solder mark 61 and the second side of the second part 112 of the cathode current collector satisfies: 0mm≤d7≤7mm.

[0116] It is easy to understand that the first projection can be the projection of the second side of the first solder mark 61 along the thickness direction of the cathode tab connecting piece 51 on the cathode tab connecting piece 51, and the second projection can be the projection of the second part 112 of the cathode current collector along the thickness direction of the cathode tab connecting piece 51 on the cathode tab connecting piece 51.

[0117] Reference Figure 4B and Figure 4C As shown, when the first projection and the second projection overlap, it is equivalent to the second side of the second portion 112 of the cathode current collector extending beyond the second side of the first solder mark 61 along the width direction of the electrode sheet. The second side of the second portion 112 of the cathode current collector is in an unconstrained state, that is, the second side of the second portion 112 of the cathode current collector is not welded to the cathode tab connecting piece 51; Refer to Figure 4A As shown, when the first projection and the second projection do not overlap, it is equivalent to the second side of the second part 112 of the cathode current collector not extending beyond the second side of the first solder mark 61 along the width direction of the electrode sheet, and the second side of the second part 112 of the cathode current collector forms a weld with the cathode tab connecting piece 51.

[0118] When the first projection and the second projection overlap, the distance d7 between the second side of the first solder mark 61 and the second side of the second portion 112 of the cathode current collector is too large (e.g., d7 > 15 mm when the first projection and the second projection overlap), that is, when the second side of the second portion 112 of the cathode current collector extends too far beyond the second side of the first solder mark 61 along the width direction of the electrode, there is a situation where the unconstrained second portion 112 of the cathode current collector is too wide. This increases the process difficulty in preparing the cathode electrode 1 and affects the preparation efficiency of the electrochemical device 10. When the first projection and the second projection do not overlap, the distance d7 between the second side of the first solder mark 61 and the second side of the second portion 112 of the cathode current collector is too large (e.g., d7 > 15 mm when the first projection and the second projection overlap). If the distance d7 between the two sides and the second side of the second part 112 of the cathode current collector is too large (for example, d7>7mm when the first projection and the second projection do not overlap), that is, when the second side of the first solder mark 61 extends too far beyond the second side of the second part 112 of the cathode current collector along the width direction of the electrode, the energy density loss will be severe, affecting the subsequent electrical connection of the cathode tab 41 and the cathode tab connecting piece 51 (for example, the cathode tab 41 and the cathode tab connecting piece 51 are electrically connected by welding). In this process, the cathode tab connecting piece 51 is also easily damaged, ultimately affecting the electrical performance of the manufactured electrochemical device 10.

[0119] In this embodiment of the application, by adopting such a range of values ​​for d7, it is possible to avoid the drawbacks that occur when the second side of the second portion 112 of the cathode current collector extends too far beyond the second side of the first solder mark 61 along the width direction of the electrode, and also to avoid the drawbacks that occur when the second side of the first solder mark 61 extends too far beyond the second side of the second portion 112 of the cathode current collector along the width direction of the electrode, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0120] Optionally, based on the aforementioned value range, if the first projection of the second side of the first solder mark 61 on the cathode tab connecting piece 51 overlaps with the second projection of the second part 112 of the cathode current collector on the cathode tab connecting piece 51, then the distance d7 between the second side of the first solder mark 61 and the second side of the second part 112 of the cathode current collector satisfies: 0mm≤d7≤10mm; or, if the first projection of the second side of the first solder mark 61 on the cathode tab connecting piece 51 does not overlap with the second projection of the second part 112 of the cathode current collector on the cathode tab connecting piece 51, then the distance d7 between the second side of the first solder mark 61 and the second side of the second part 112 of the cathode current collector satisfies: 0mm≤d7≤3mm. Within this preferred range of values, it is possible to avoid the drawbacks that occur when the second side of the second portion 112 of the cathode current collector extends too far beyond the second side of the first solder mark 61 along the width direction of the electrode, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0121] Within the aforementioned range, d7 can be selected as a suitable value as needed. For example, if the first and second projections overlap, and 0mm ≤ d7 ≤ 10mm, then d7 can be 0mm, 1mm, 3mm, 5mm, 8mm, 9mm, 10mm, etc., without specific restrictions. Conversely, if the first and second projections do not overlap, and 0mm ≤ d7 ≤ 3mm, then d7 can be 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, etc., without specific restrictions.

[0122] In some optional embodiments, the electrochemical device further includes tabs, which are electrically connected to the tab connecting pieces of the electrode by welding. Specifically, the electrochemical device also includes a housing, with the tabs extending out of the housing. Optionally, for the housing, the cathode electrode 1, the separator 3, and the anode electrode 2 can be disposed inside the housing, and the housing can protect them. Optionally, corresponding to the pouch cell, the housing can be made of a metal-plastic film, which can be a steel-plastic film, an aluminum-plastic film, etc. In any embodiment of this application, the electrode of the electrochemical device 10 can be the cathode electrode 1 and / or the anode electrode 2. When the electrode of the electrochemical device is the cathode electrode 1, the tab 4 that is electrically connected to the cathode tab connecting piece of the cathode electrode 1 by welding is the cathode tab; and when the electrode of the electrochemical device is the anode electrode 2, the tab 4 that is electrically connected to the anode tab connecting piece of the anode electrode 2 by welding is the anode tab.

[0123] Taking cathode electrode 1 as an example, and cathode tab 41 as an example, refer to... Figure 4A , Figure 4B , Figure 4C As shown, the cathode tab 41 is electrically connected to the cathode tab connecting piece 51 by welding, and a second solder mark 62 is formed on the cathode tab connecting piece 51; along the width direction Y of the electrode, the second solder mark 62 includes a first side close to the first sub-part 1111 and a second side away from the first sub-part 1111; wherein, the distance d8 between the second side of the first solder mark 61 and the first side of the second solder mark 62 satisfies: 0mm<d8≤10mm.

[0124] This application does not limit the specific welding process when the cathode tab 41 and the cathode tab connecting piece 51 are welded together. For example, the welding process can be a transfer welding, then the second weld mark 62 can be a transfer welding mark.

[0125] When the cathode tab 41 is electrically connected to the cathode tab connecting piece 51 by welding, the second weld mark 62 formed on the cathode tab connecting piece 51 cannot overlap with the first weld mark 61. If they overlap, it will affect the welding effect between the cathode tab 41 and the cathode tab connecting piece 51, reducing the welding pull. If the distance d8 between the second side of the first weld mark 61 and the first side of the second weld mark 62 is too large (e.g., d8 > 10 mm), it will easily affect the energy density of the electrochemical device 10. In this embodiment, by adopting such a range of d8 values, the disadvantages caused by the overlap of the second weld mark 62 and the first weld mark 61 can be avoided, as well as the disadvantages caused by the excessive distance d8 between the second side of the first weld mark 61 and the first side of the second weld mark 62. This satisfies the usage requirements of the electrochemical device 10 and improves the preparation efficiency of the electrochemical device 10.

[0126] Within the above range of values, d8 can also be selected as appropriate as needed. For example, if 0mm < d8 ≤ 10mm, then d8 can be 1mm, 3mm, 5mm, 7mm, 9mm, 10mm, etc., without specific restrictions.

[0127] In this embodiment, the width d1 of the cathode tab connecting piece 51 is not limited (refer to...). Figure 4A , Figure 4B , Figure 4C The width d1 of the cathode tab connecting piece 51 (i.e., the distance between the first side and the second side of the cathode tab connecting piece 51 along the width direction Y of the electrode) is sufficient to meet the requirements of the electrochemical device 10. In some optional embodiments, the width d1 of the cathode tab connecting piece 51 along the width direction Y of the electrode satisfies: 3mm ≤ d1 ≤ 25mm.

[0128] When the width d1 of the cathode tab connecting piece 51 is too small, it is difficult to weld the cathode tab connecting piece 51 to the second part 112 of the cathode current collector during the fabrication of the electrochemical device 10. When the width d1 of the cathode tab connecting piece 51 is too large, the edge of the cathode tab connecting piece 51 is prone to collapse during the fabrication of the cathode electrode 1, and it is also easy for the cathode tab connecting piece 51 to break accidentally. In this embodiment, the width of the cathode tab connecting piece 51 meets the above-mentioned value range (i.e., 3mm≤d1≤25mm), which can effectively avoid the disadvantages of the cathode tab connecting piece 51 being too small or too large, thereby meeting the usage requirements of the electrochemical device 10 and improving the fabrication yield of the electrochemical device 10.

[0129] Optionally, based on the condition that 3mm ≤ d1 ≤ 25mm, the width d1 of the cathode tab connecting piece 51 satisfies: 5mm ≤ d1 ≤ 25mm. Within this preferred value range, the disadvantages of the cathode tab connecting piece 51 being too narrow or too wide can be better avoided, thus meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10.

[0130] Within the above range of values, the width d1 of the cathode tab connecting piece 51 can be selected as appropriate as needed. For example, if 5mm≤d1≤25mm is taken as an example, then d1 can be 5mm, 10mm, 15mm, 18mm, 20mm, 23mm, 25mm, etc., and there is no restriction here.

[0131] In this embodiment, the width d2 of the second portion 112 of the cathode current collector 11 is not limited (refer to...). Figure 4A , Figure 4B , Figure 4C The width d2 of the second portion 112 of the cathode current collector (i.e., the distance between the first side and the second side of the second portion 112 of the cathode current collector along the width direction Y of the electrode) should meet the requirements of the electrochemical device 10. In some optional embodiments, the width d2 of the second portion 112 of the cathode current collector along the width direction Y of the electrode satisfies: 1mm ≤ d2 ≤ 20mm.

[0132] When the width of the second portion 112 of the cathode current collector is too small, it is difficult to guarantee the welding width during the fabrication of the electrochemical device 10, making it difficult to weld the cathode tab connecting piece 51 to the second portion 112 of the cathode current collector. Conversely, when the width of the second portion 112 of the cathode current collector is too large, it is more prone to wrinkling after cold pressing during the fabrication of the cathode electrode 1, which can increase energy density loss and thus increase costs. In this embodiment, the width of the second portion 112 of the cathode current collector satisfies the above-mentioned value range (i.e., 1mm ≤ d2 ≤ 20mm), which can effectively avoid the disadvantages of both excessively small and excessively large widths, thereby meeting the usage requirements of the electrochemical device 10 and improving the fabrication yield of the electrochemical device 10.

[0133] Optionally, based on the condition that 1mm ≤ d2 ≤ 20mm, the width d2 of the second part 112 of the cathode current collector satisfies: 1mm ≤ d2 ≤ 10mm. Within this preferred value range, the disadvantages of the second part 112 of the cathode current collector being too small or too large can be better avoided, thereby meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10.

[0134] Within the above range of values, the width d2 of the second part 112 of the cathode current collector can be selected as appropriate as needed. For example, taking 1mm≤d2≤10mm as an example, d2 can be 1mm, 3mm, 4mm, 5mm, 7mm, 8mm, 10mm, etc., without any restrictions.

[0135] In some alternative embodiments, refer to Figure 4A , Figure 4B , Figure 4C As shown, along the width direction Y of the electrode, the insulating layer 13 includes a first side close to the first sub-part 1111 and a second side away from the first sub-part 1111; if the first side of the cathode tab connecting piece 51 is located on the insulating layer 13, then the distance d4 between the first side of the cathode tab connecting piece 51 and the second side of the insulating layer 13 satisfies: 0mm≤d4≤8mm; or, if the first side of the cathode tab connecting piece 51 is located on the second part 112 of the cathode current collector, then the distance d4 between the first side of the cathode tab connecting piece 51 and the second side of the insulating layer 13 satisfies: 0mm≤d4≤10mm.

[0136] Specifically, refer to Figure 4CWhen the first side of the cathode tab connecting piece 51 is located on the insulating layer 13, it is equivalent to the first end of the cathode tab connecting piece 51 extending beyond the first side of the cathode current collector second part 112 in the opposite direction of the width direction Y of the electrode sheet after the cathode tab connecting piece 51 is welded to it. When it extends too far (e.g., d4 > 8 mm), it is easy to cause the thickness of the manufactured electrochemical device 10 to be too large; refer to Figure 4A and Figure 4B As shown, the first side of the cathode tab connecting piece 51 is located on the second part 112 of the cathode current collector. When the distance d4 between the first side of the cathode tab connecting piece 51 and the second side of the insulating layer 13 is too large (for example, d4 > 10 mm), the problem of folding after the second part 112 of the cathode current collector and the cathode tab connecting piece 51 are welded together cannot be effectively solved.

[0137] In this embodiment, d4 satisfies the above-mentioned value range, which can better avoid the disadvantage of the first end of the cathode tab connecting piece 51 extending too far beyond the first side of the second part 112 of the cathode current collector along the opposite direction of the width Y of the electrode, and can also better avoid the disadvantage of the first side of the cathode tab connecting piece 51 being located on the second part 112 of the cathode current collector and d4 being too large, thereby meeting the usage requirements of the electrochemical device 10 and improving the preparation efficiency of the electrochemical device 10.

[0138] A preferred embodiment is one where a gap exists between the first side of the cathode tab connecting piece 51 and the insulating layer 13 and the second portion 112 of the cathode current collector. Optionally, when the first side of the cathode tab connecting piece 51 is located on the second portion 112 of the cathode current collector, the gap d4 between the first side of the cathode tab connecting piece 51 and the second side of the insulating layer 13 satisfies: 0mm ≤ d4 ≤ 5mm. Within this preferred value range, the disadvantage of d4 being too large when the first side of the cathode tab connecting piece 51 is located on the second portion 112 of the cathode current collector is better avoided, thereby meeting the usage requirements of the electrochemical device 10 and further improving the preparation efficiency of the electrochemical device 10.

[0139] It is understood that the above content is only intended as some optional examples of the electrochemical device 10 in the embodiments of this application, and not as any limitation on the electrochemical device 10 in the embodiments of this application.

[0140] In this embodiment, the electrode includes a cathode electrode and an anode electrode. Since the cathode tab connecting piece of the electrochemical device is welded to the surface of the second part of the cathode current collector (i.e., the edge empty foil area on the cathode current collector), and the anode tab connecting piece of the anode electrode is welded to the surface of the second part of the anode current collector (i.e., the edge empty foil area on the anode current collector), when the cathode tab is led out from the cathode current collector in this application, it is no longer necessary to directly connect the cathode tab to the second part of the cathode current collector. Instead, it can be electrically connected to the cathode tab through the cathode tab connecting piece welded to the second part of the cathode current collector. When the anode tab is led out from the anode current collector in the application, it is no longer necessary to directly connect the anode tab to the second part of the anode current collector. Instead, it can be electrically connected to the anode tab through an anode tab connecting piece welded to the second part of the anode current collector. Based on this, when preparing the cathode electrode of the electrochemical device in this application, the cathode electrode is less likely to wrinkle when cold-pressed. Similarly, when preparing the anode electrode of the electrochemical device in this application, the anode electrode is less likely to wrinkle when cold-pressed. Therefore, by using such cathode and anode electrodes to manufacture the electrochemical device, the preparation yield of the electrochemical device can be effectively improved.

[0141] According to another aspect of the embodiments of this application, referring to Figure 10 The structural block diagram shows that this application provides an electrical device 20, which includes any of the electrochemical devices 10 provided above.

[0142] Specifically, the electrochemical device 10 can be used to supply power to various electrical components in the electrical equipment 20.

[0143] Since the electrical device 20 in this embodiment includes the electrochemical device 10 described above, and the electrochemical device 10 has a high yield, the electrical device 20 also has a high yield.

[0144] The following description, in conjunction with some actual embodiments of the electrochemical device 10 in this application and comparative examples of electrochemical devices in related technologies, will make it easier to see the beneficial effects of the electrochemical device 10 in this application compared to related technologies. In these comparative examples and embodiments, the electrochemical device is a lithium-ion battery as an example.

[0145] The electrochemical device of Comparative Example 1 has a conventional wound structure. The difference between Comparative Example 2 and Example 1 is that the ratio of the solder area to the area of ​​the soldering zone is less than 20%, and the ratio of the length of the soldering zone to the length of the overlapping zone is less than 60%. Due to the insufficient welding strength, the welding strength is unstable during the preparation of the electrochemical device, and the tab connecting piece and the second part of the cathode are partially separated, making it inconvenient to measure.

[0146] Example 1 is formed by winding the cathode electrode sheet of Example 1 in Table 1 and the anode electrode sheet of a conventional structure. In the cathode electrode sheet, the ratio of the solder area to the area of ​​the solder zone is greater than or equal to 20%, and the ratio of the length of the solder zone to the length of the overlap zone is greater than or equal to 60%, in order to meet the requirements for welding stability. Examples 2-16 are similar to Example 1. In addition, compared with Comparative Example 1, Examples 1-16 eliminated the stretching of the edge empty foil area of ​​the cathode current collector before cold pressing during the preparation of the cathode electrode sheet. Instead, cathode tab connecting pieces were welded onto the edge empty foil area of ​​the cathode current collector (i.e., the second part of the cathode current collector), and the step roller was eliminated during the cold pressing process. All other parameters were the same. In addition, compared with Comparative Example 1, Examples 1-18 eliminated the stretching of the edge empty foil area of ​​the cathode current collector before cold pressing during the preparation of the cathode electrode sheet. Instead, cathode tab connecting pieces were welded onto the edge empty foil area of ​​the cathode current collector (i.e., the second part of the cathode current collector), and the step roller was eliminated during the cold pressing process. All other parameters were the same. In Comparative Example 2, the experimental data could not be measured because the ratio of the solder area to the solder area and the ratio of the solder area length to the overlap area length did not meet the requirements.

[0147] The relevant data of the cathode plates of the electrochemical devices of Comparative Examples 1-2 and Examples 1-16 are shown in Table 1 below:

[0148] Table 1

[0149]

[0150] It should be noted that, for ease of viewing, in Table 1 above, in the column d4, negative numbers indicate the case where the first side of the cathode tab connecting piece 51 is located on the insulating layer 13 (taking d4 as -2mm in Table 1 as an example, that is: the first side of the cathode tab connecting piece 51 is located on the insulating layer 13, d4 = 2mm), while positive numbers indicate the case where the first side of the cathode tab connecting piece 51 is located on the second part 112 of the cathode current collector (taking d4 as 2mm in Table 1 as an example, that is: the first side of the cathode tab connecting piece 51 is located on the second part 112 of the cathode current collector). 2. (d4 = 2mm); In the d6 column, negative numbers indicate the case where the first side of the first solder mark 61 is located on the second part 112 of the cathode current collector (taking d6 = -3mm in Table 1 as an example, i.e., the first side of the first solder mark 61 is located on the second part 112 of the cathode current collector, d6 = 3mm), while positive numbers indicate the case where the first side of the first solder mark 61 is located on the cathode tab connecting piece 51 (taking d6 = 20mm in Table 1 as an example, i.e., the first side of the first solder mark 61 is located on the cathode tab connecting piece 51, d6 = 20mm). Additionally, in Table 1, "\" indicates "none," and the number of "★" indicates the degree of wrinkling; the more "★" there are, the more severe the wrinkling. Furthermore, for Embodiments 1-18, the tab folding ratio can refer to the ratio of the folding of the cathode tab connecting piece 51 and the second part 112 of the cathode current collector (which can be combined with...). Figure 3A , Figure 3B as well as Figure 4A , Figure 4B , Figure 4C (Understanding), while for Comparative Examples 1 and 2, the tab folding ratio can refer to the folding ratio of the edge empty foil area 14' (which can be combined with...). Figure 2 understand).

[0151] Analysis of the data in Table 1 above shows that the electrochemical device 10 in this application (i.e., Examples 1-18) significantly improves the wrinkling of the cathode electrode 1 after cold pressing and the folding of the tabs compared with the electrochemical devices in the related art. Therefore, by using such a cathode electrode 1 to make the electrochemical device 10, the preparation yield of the electrochemical device 10 can be effectively improved.

[0152] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc., mentioned in this application are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0153] It should be noted that the terms "a" and "a plurality of" used in this application are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0154] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the appended claims.

Claims

1. An electrochemical device, comprising: An electrode sheet includes a current collector, an active material layer, and a tab connecting piece. In the unfolded state, the current collector includes a first part and a second part along the width direction of the electrode sheet. The active material layer is disposed on the surface of the first part. The second part is an empty foil area without the active material layer. The tab connecting piece overlaps with the surface of the second part to form an overlapping area. The tab connecting piece is welded to the surface of the second part to form an electrical connection with the second part. Along the length direction of the electrode sheet, the ratio of the solder area to the solder area is greater than or equal to 20%, and the ratio of the length of the solder area to the length of the overlapping area is greater than or equal to 60%. Wherein, the electrode is a cathode electrode, the first part includes a first sub-part and a second sub-part connected to each other, the second sub-part is connected to the second part, the active material layer is disposed on the first sub-part, and an insulating layer is disposed on the second sub-part; Along the width direction of the electrode sheet, the second portion includes a first side close to the first sub-portion and a second side away from the first sub-portion, and the electrode tab connecting piece includes a first side close to the first sub-portion and a second side away from the first sub-portion; The tab connecting piece is spaced from the first sub-part, and the second side of the second part is located between the first side and the second side of the tab connecting piece.

2. The electrochemical device according to claim 1, wherein, Along the width direction of the electrode sheet, the width d1 of the electrode tab connecting piece satisfies: 3mm≤d1≤25mm.

3. The electrochemical device according to claim 1, wherein, Along the width direction of the electrode, the width d2 of the second part satisfies: 1mm≤d2≤20mm.

4. The electrochemical device according to claim 1, wherein, Along the width direction of the electrode, the width d3 of the insulating layer satisfies: 0.5mm≤d3≤5mm.

5. The electrochemical device according to claim 1, wherein, Along the width direction of the electrode sheet, the insulating layer includes a first side close to the first sub-part and a second side away from the first sub-part; If the first side of the tab connecting piece is located on the insulating layer, then the distance d4 between the first side of the tab connecting piece and the second side of the insulating layer satisfies: 0mm≤d4≤8mm; or, If the first side of the tab connecting piece is located on the second part, then the distance d4 between the first side of the tab connecting piece and the second side of the insulating layer satisfies: 0mm≤d4≤10mm.

6. The electrochemical device according to claim 1, wherein, The solder mark includes a first solder mark, which is formed when the second part is welded to the tab connecting piece; Along the width direction of the electrode sheet, the first solder mark includes a first side close to the first sub-part and a second side away from the first sub-part; The second side of the first solder mark is located on the tab connecting piece, and there is a gap between the first solder mark and the first sub-part.

7. The electrochemical device according to claim 6, wherein, Along the width direction of the electrode sheet, the width d5 ​​of the first solder mark satisfies: 0.1mm≤d5≤10mm.

8. The electrochemical device according to claim 6, wherein, If the first side of the first solder mark is located on the second part, then the distance d6 between the first side of the first solder mark and the first side of the electrode connecting piece satisfies: 0mm≤d6≤5mm; or, If the first side of the first solder mark is located on the tab connecting piece, then the distance d6 between the first side of the first solder mark and the first side of the tab connecting piece satisfies: 0mm≤d6≤20mm.

9. The electrochemical device according to claim 6, wherein, If the first projection of the second side of the first solder mark on the tab connecting piece overlaps with the second projection of the second part on the tab connecting piece, then the distance d7 between the second side of the first solder mark and the second side of the second part satisfies: 0mm≤d7≤15mm; or, If the first projection of the second side of the first solder mark on the tab connecting piece does not overlap with the second projection of the second part of the electrode on the tab connecting piece, then the distance d7 between the second side of the first solder mark and the second side of the second part satisfies: 0mm≤d7≤7mm.

10. The electrochemical device according to claim 6, wherein, The electrochemical device further includes an electrode tab, which is electrically connected to the electrode tab connecting piece by welding, and a second solder mark is formed on the electrode tab connecting piece; Along the width direction of the electrode sheet, the second solder mark includes a first side close to the first sub-part and a second side away from the first sub-part; Wherein, the distance d8 between the second side of the first solder mark and the first side of the second solder mark satisfies: 0mm<d8≤10mm.

11. The electrochemical device according to claim 1, wherein, The welding pull force between the second part and the electrode connecting piece is greater than or equal to 70N and less than or equal to 1000N.

12. An electrical appliance, comprising: The electrochemical device as described in any one of claims 1-11.

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